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  1. Sodium bicarbonate-based hydration prevents contrast-induced nephropathy: a meta-analysis

    Directory of Open Access Journals (Sweden)

    Tamhane Umesh

    2009-05-01

    Full Text Available Abstract Background Contrast-induced nephropathy is the leading cause of in-hospital acute renal failure. This side effect of contrast agents leads to increased morbidity, mortality, and health costs. Ensuring adequate hydration prior to contrast exposure is highly effective at preventing this complication, although the optimal hydration strategy to prevent contrast-induced nephropathy still remains an unresolved issue. Former meta-analyses and several recent studies have shown conflicting results regarding the protective effect of sodium bicarbonate. The objective of this study was to assess the effectiveness of normal saline versus sodium bicarbonate for prevention of contrast-induced nephropathy. Methods The study searched MEDLINE, EMBASE, Cochrane databases, International Pharmaceutical Abstracts database, ISI Web of Science (until 15 December 2008, and conference proceedings for randomized controlled trials that compared normal saline with sodium bicarbonate-based hydration regimen regarding contrast-induced nephropathy. Random-effects models were used to calculate summary odds ratios. Results A total of 17 trials including 2,633 subjects were pooled. Pre-procedural hydration with sodium bicarbonate was associated with a significant decrease in the rate of contrast-induced nephropathy (odds ratios 0.52; 95% confidence interval 0.34–0.80, P = 0.003. Number needed to treat to prevent one case of contrast-induced nephropathy was 16 (95% confidence interval 10–34. No significant differences in the rates of post-procedure hemodialysis (P = 0.20 or death (P = 0.53 was observed. Conclusion Sodium bicarbonate-based hydration was found to be superior to normal saline in prevention of contrast-induced nephropathy in this updated meta-analysis.

  2. Impact of left ventricular end diastolic pressure guided hydration on prevention of contrast induced nephropathy post cardiac catheterization

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    Sherif Wagdy Ayad

    2015-12-01

    Conclusions: LVEDP-guided hydration is superior to standard hydration in prevention of CIN. Hydration can be done based on LVFP in patients with pre-procedure normal LVF and in patients with pre-procedure elevated LVFP but not in those patients with inconclusive LVFP in which hydration should be guided by the invasively measured LVEDP.

  3. Contrast-induced nephropathy: risks, pathogenetic, prevention

    International Nuclear Information System (INIS)

    Paskalev, D.; Balev, B.

    2006-01-01

    Full text: The aim of the presentation is to review the contrast induced nephropathy ? nature, mechanisms of development, risk factors. Summary of the most important ways of prevention, diagnostics and treatment. The definition of CIN according the European Association of Urogenital Radiology is: 'A condition, in which renal function is impaired (elevation of serum creatinine with more than 25% or 44 μmol/l above the initial level) due to intravasal application of contrast media (CM) within 3 days following the application and when no other etiology factors are present'. We summarize the main risk factors of developing CIN - renal failure, diabetic nephropathy, dehydration, congestive heart failure, high blood pressure, age above 70 yrs, nephrotoxic medicines. The most effective ways of preventing CIN are the good hydratation of the patients and the usage of low-osmolar or iso-osmolar CM. Therapeutic treatment is with no proven preventive effect and currently is not routinely recommended. An early hem dialysis does not decrease the risk level of CIN development in patients with chronic renal failure (CRF). In such patients complete elimination of CM is achieved only after several hem dialyses. Hem filtration reliably decreases the risk of CIN in CRF patients, but is expensive and not widely available. We present a case from our hospital of a patient with diabetic nephropathy, who developed CIN following a coronary angiography

  4. Guideline adherence for identification and hydration of high-risk hospital patients for contrast-induced nephropathy.

    NARCIS (Netherlands)

    Schilp, J.; Blok, C. de; Langelaan, M.; Spreeuwenberg, P.; Wagner, C.

    2014-01-01

    Background: Contrast-induced nephropathy (CIN) is a common cause of acute renal failure in hospital patients. To prevent CIN, identification and hydration of high-risk patients is important. Prevention of CIN by hydration of high-risk patients was one of the themes to be implemented in the Dutch

  5. Guideline adherence for identification and hydration of high-risk hospital patients for contrast-induced nephropathy

    NARCIS (Netherlands)

    Schilp, J.; de Blok, C.; Langelaan, M.; Spreeuwenberg, P.; Wagner, C.

    2014-01-01

    Background: Contrast-induced nephropathy (CIN) is a common cause of acute renal failure in hospital patients. To prevent CIN, identification and hydration of high-risk patients is important. Prevention of CIN by hydration of high-risk patients was one of the themes to be implemented in the Dutch

  6. Nonpharmacological Strategies to Prevent Contrast-Induced Acute Kidney Injury

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    Paweena Susantitaphong

    2014-01-01

    Full Text Available Contrast-induced AKI (CI-AKI has been one of the leading causes for hospital-acquired AKI and is associated with independent risk for adverse clinical outcomes including morbidity and mortality. The aim of this review is to provide a brief summary of the studies that focus on nonpharmacological strategies to prevent CI-AKI, including routine identification of at-risk patients, use of appropriate hydration regimens, withdrawal of nephrotoxic drugs, selection of low-osmolar contrast media or isoosmolar contrast media, and using the minimum volume of contrast media as possible. There is no need to schedule dialysis in relation to injection of contrast media or injection of contrast agent in relation to dialysis program. Hemodialysis cannot protect the poorly functioning kidney against CI-AKI.

  7. Effect of atorvastatin on preventing contrast-induced nephropathy

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    Zhang Dongya; Zhu Jing; Chen Jianchang; Xu Weiting; Luo Xiaoyu; Zhao Liangping

    2011-01-01

    Objective: To study the effects of atorvastatin on contrast-induced renal function and urinary protein change in patients undergoing diagnostic and therapeutic coronary intervention. Methods: Two hundred and forty-six patients who underwent coronary angiography or percutaneous coronary intervention (PCI) were randomized to receive atorvastatin (40 mg, qn, n=123) or no atorvastatin (n=123) treatment 3 days before coronary angiography. All patients received hydrated therapy. Serum creatinine (Scr), urinary αl-microglobulin (α l -MG), and urinary albumin (mALB) were checked for evidence of tubular or glomerular damage at start, and 36 to 48 hours after the administration of a radiocontrast agent. High-sensitive C-reactive protein (hsCRP) levels, urinary α l -MG/ urinary creatinine(Ucr) and mALB/ Ucr were also assessed at the same time. Creatinine clearance(Ccr) was calculated according to Cockcroft-Gault formulas basing on serum creatinine. Results: (1) In the control group and atorvastatin-treated group, comparison with the value before coronary angiography or PCI, urinary α l -MG/ Ucr, mALB/ Ucr, Scr and hsCRP significantly increased from 36 to 48 hours after angiography or PCI (P l -MG/ Ucr significantly increased at the 2nd day after angiography or PCI in the control group (P<0.05), incidence of contrast induced nephropathy (CIN) significantly increased too (8.13% vs 0.81%, P<0.05). Conclusions: Contrast media induces light renal function damage. Pretreatment with atorvastatin 40 mg/qn for 3 days could significantly reduce procedural inflammatory reaction and prevent contrast-induced nephropathy. (authors)

  8. Effect of atorvastatin on preventing contrast-induced nephropathy

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    Dongya, Zhang; Jing, Zhu; Jianchang, Chen; Weiting, Xu; Xiaoyu, Luo; Liangping, Zhao [Dept of Cardiology, the Second Hospital Affiliated to Soochow University, Suzhou (China)

    2011-03-15

    Objective: To study the effects of atorvastatin on contrast-induced renal function and urinary protein change in patients undergoing diagnostic and therapeutic coronary intervention. Methods: Two hundred and forty-six patients who underwent coronary angiography or percutaneous coronary intervention (PCI) were randomized to receive atorvastatin (40 mg, qn, n=123) or no atorvastatin (n=123) treatment 3 days before coronary angiography. All patients received hydrated therapy. Serum creatinine (Scr), urinary {alpha}l-microglobulin ({alpha}{sub l}-MG), and urinary albumin (mALB) were checked for evidence of tubular or glomerular damage at start, and 36 to 48 hours after the administration of a radiocontrast agent. High-sensitive C-reactive protein (hsCRP) levels, urinary {alpha}{sub l}-MG/ urinary creatinine(Ucr) and mALB/ Ucr were also assessed at the same time. Creatinine clearance(Ccr) was calculated according to Cockcroft-Gault formulas basing on serum creatinine. Results: (1) In the control group and atorvastatin-treated group, comparison with the value before coronary angiography or PCI, urinary {alpha}{sub l}-MG/ Ucr, mALB/ Ucr, Scr and hsCRP significantly increased from 36 to 48 hours after angiography or PCI (P<0.05). Ccr significantly decreased from 36 to 48 hours after angiography or PCI (P<0.05). (2) Compared the atorvastatin-treated group, the values of hsCRP, urinary {alpha}{sub l}-MG/ Ucr significantly increased at the 2nd day after angiography or PCI in the control group (P<0.05), incidence of contrast induced nephropathy (CIN) significantly increased too (8.13% vs 0.81%, P<0.05). Conclusions: Contrast media induces light renal function damage. Pretreatment with atorvastatin 40 mg/qn for 3 days could significantly reduce procedural inflammatory reaction and prevent contrast-induced nephropathy. (authors)

  9. Prevention of contrast-induced nephropathy by use of bicarbonate solution: preliminary results and literature review.

    Science.gov (United States)

    Silva, Ricardo Gonçalves da; Silva, Nelson Gonçalves da; Lucchesi, Fabiano; Burdmann, Emmanuel A

    2010-01-01

    The incidence of contrast-induced nephropathy has increased simultaneously with the increase in contrast medium use in diagnostic and interventional procedures. The incidence of contrast-induced nephropathy in the general population is low, but increases exponentially in patients with risk factors, such as diabetes and chronic kidney disease. Several strategies have been used in order to prevent contrast-induced nephropathy. The most efficient strategies are saline hydration (0.9% or 0.45%), use of low-or iso-osmolality contrast medium, and sodium bicarbonate infusion. The aim of this study was to review the pertinent literature and to assess the efficacy of hydration with 1.3% sodium bicarbonate compared with hydration with 0.9% saline solution in preventing contrast-induced nephropathy in high-risk patients. A systematic search of the literature was conducted in PubMed by using the following keywords: bicarbonate, nephropathy, contrast medium, and acute kidney failure. In addition, 27 patients with diabetes and/or chronic kidney disease, diagnosed with some kind of cancer were randomized for study. None of the patients developed contrast-induced nephropathy characterized as a 0.5 mg/ dL-increase and/or a relative 25%-increase in baseline creatinine. The literature review strongly suggested that sodium bicarbonate is effective in preventing contrast-induced nephropathy. Regarding the randomized study, saline solution and bicarbonate solution had similar efficacy in preventing contrast-induced nephropathy. However, the small number of patients does not allow definite conclusions.

  10. Sodium bicarbonate versus isotonic saline solution to prevent contrast-induced nephropathy : a systematic review and meta-analysis.

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    Zapata-Chica, Carlos Andres; Bello Marquez, Diana; Serna-Higuita, Lina Maria; Nieto-Ríos, John Fredy; Casas-Arroyave, Fabian David; Donado-Gómez, Jorge Hernando

    2015-09-30

    Contrast-induced nephropathy is one of the main causes of acute kidney injury and increased hospital-acquired morbidity and mortality. The use of sodium bicarbonate for nephroprotection has emerged as a preventative strategy; however, its efficacy is controversial compared to other strategies, such as hydration using 0.9% saline solution. To compare the effectiveness of sodium bicarbonate vs. hydration using 0.9% saline solution to prevent contrast-induced acute kidney injury. A systematic review of studies registered in the COCHRANE, PUBMED, MEDLINE, LILACS, SCIELO and EMBASE databases was conducted. Randomized controlled studies that evaluated the use of 0.9% saline solution vs. sodium bicarbonate to prevent contrast-induced nephropathy were included. A total of 22 studies (5,686 patients) were included. Sodium bicarbonate did not decrease the risk of contrast-induced nephropathy (RD= 0.00; 95% CI= -0.02 to 0.03; p= 0.83; I(2)= 0%). No significant differences were found in the demand for renal replacement therapy (RD= 0.00; 95% CI= -0.01 to 0-01; I(2)= 0%; p= 0.99) or in mortality (RD= -0.00; 95% CI= -0.001 to 0.001; I(2)= 0%; p= 0.51). Sodium bicarbonate administration is not superior to the use of 0.9% saline solution for preventing contrast-induced nephropathy in patients with risk factors, nor is it better at reducing mortality or the need for renal replacement therapy.

  11. Prevention of Contrast-Induced Nephropathy in STEMI Patients Undergoing Primary Percutaneous Coronary Intervention

    DEFF Research Database (Denmark)

    Busch, Sarah Victoria Ekeløf; Jensen, Svend Eggert; Rosenberg, Jacob

    2012-01-01

    -acetylcysteine, one study of early and late hydration regimens, one study of recombinant human brain natriuretic peptide and one study comparing a low-osmolar contrast agent with an iso-osmolar contrast agent. Results: Recombinant human brain natriuretic peptide and the regimens of hydration significantly reduced...... the incidence of CIN and administration of N-acetylcysteine in one of the six studies significantly reduced the occurrence of CIN. The iso-osmolar contrast agent was not proven to be superior to the low-osmolar contrast agent in terms of preventing CIN. Conclusion: Preliminary studies are promising but further......Objective: To evaluate the current prophylactic strategies against CIN in patients with STEMI treated by primary percutaneous coronary intervention. Background: Contrast-induced nephropathy (CIN) is the third leading course of acute renal failure and a recognized complication to cardiac...

  12. Atorvastatin and prevention of contrast induced nephropathy following coronary angiography

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    Peyman Bidram

    2015-01-01

    Full Text Available Background: Contrast induced nephropathy (CIN is one of the most common complications after radiographic procedures using intravascular radiocontrast media. The aim of the current study was to assess the effect of atorvastatin on prevention of CIN in patients undergoing coronary angiography. Materials and Methods: In a clinical trial study, 200 patients referred for angiography were randomly divided into two groups of using 80 mg atorvastatin and placebo before the procedure. Furthermore, 100 patients who were under chronic treatment of statins were included as the third group. Serum creatinine (Scr levels before and after the procedure were evaluated and incidence of CIN (post-procedural Scr of >0.5 mg/dl or >25% from baseline was assessed. Results: Mean age of the participants was 60.06 ± 0.69 years and 276 (92% were male. There were no significant differences between group with respect to age and gender. In pre-operation atorvastatin, placebo and long term statin groups, the incidence of CIN was 1%, 2% and 1%, and mean changes of Glomerular filtration rate (GFR was 3.68 ± 1.32, −0.77 ± 1.21 and 1.37 ± 0.86; and mean changes of creatinine (Cr was −0.05 ± 0.02, 0.02 ± 0.02 and −0.01 ± 0.01 respectively. (P = 0.776, 0.026 and 0.041 respectively. In pre-operation atorvastatin group, Cr decreased, and GFR increased significantly (P = 0.019 and 0.007 respectively. Conclusion: pre-operation short term high dose atorvastatin use was associated with a significant decrease in serum Cr level and increase in GFR after angiography.

  13. [Vitamin C+sodium bicarbonate versus sodium bicarbonate alone in preventing contrast-induced nephropathy].

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    Laroussi, L; Triki, M; Ibn Elhaj, Z; Ben Halima, A; Boukhris, M; Ben Amara, W; Keskes, H; Kraiem, S; Lahidheb, D; Marrakchi, S; Kammoun, I; Addad, F; Kachboura, S

    2017-09-01

    Contrast-induced nephropathy (CIN) is a common and severe complication in interventional cardiology. The aim of our study was to compare the incidence of contrast-induced nephropathy in two accelerated hydration protocols: the first one by the serum bicarbonate and the second combining the serum bicarbonate and oral vitamin C. This is a multicenter prospective, randomized study conducted between October 2012 and May 2013, including 160 patients. The mean age of our study population was 60.8±9.3 years (36-83 years). The two study groups were comparable in terms of cardiovascular risk factors, concomitant medication, and baseline serum creatinine. The CIN incidence was 6.3% in the vitamin C group and 10% in the control group (P=0.38). No significant difference was observed in terms of CIN incidence between the different subgroups analyzed. According to our study, ascorbic acid administered orally as part of an accelerated hydration protocol does not reduce the incidence of CIN. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

  14. Na/K citrate versus sodium bicarbonate in prevention of contrast-induced nephropathy

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    Sameh Mohamed Abouzeid

    2016-01-01

    Full Text Available Contrast-induced nephropathy (CIN is one of the important complications of radiographic procedures, especially in patients with chronic kidney disease. It is also one of the common causes of acute kidney injury. The pathogenesis is postulated to be the effect of oxygen- free radicals and hyperosmolar stress on the renal medulla. It is reported that the production of superoxide is most active at acid environment. K/Na citrate is well known as a urine alkalini- zation medium, and this has been evaluated earlier with standard hydration for reduction of CIN and was stated to be efficient. We aimed to determine the efficacy of Na/K citrate in reducing the frequency of CIN in comparison to sodium bicarbonate in patients after coronary angiography. Two hundred and ten patients with renal dysfunction [estimated glomerular filtration rate (eGFR, 60 mL/min/1.73 m2or less] who underwent elective or emergency coronary angiography (CAG with/without percutaneous coronary intervention (PCI at our institution were enrolled into the study. The patients were randomized into two groups, Group 1-Taking Na/K citrate and Group 2-Taking sodium bicarbonate. Radiographic contrast agent iohexol was used. Change in creatinine, percent change in creatinine, percent change in eGFR, change in serum potassium, and urine pH were all compared between the two groups. There was no significant difference for prevention of CIN when comparing the Na/K citrate with sodium bicarbonate solution in patients exposed to CAG with or without PCI. Mean absolute change in eGFR after 48 h after administration of contrast between sodium bicarbonate group and Na/K citrate group was −0.60 ± 1.58 versus −0.71 ± 1.38. Serum potassium decreased postprocedure in the sodium bicarbonate group than in the citrate group (3.90 ± 0.33 vs. 4.14 ± 0.39. Both agents are equally effective in reducing the incidence of CIN, but the citrate would possibly be a safer option for patients at risk of

  15. Haemodynamic-guided fluid administration for the prevention of contrast-induced acute kidney injury: the POSEIDON randomised controlled trial.

    Science.gov (United States)

    Brar, Somjot S; Aharonian, Vicken; Mansukhani, Prakash; Moore, Naing; Shen, Albert Y-J; Jorgensen, Michael; Dua, Aman; Short, Lindsay; Kane, Kevin

    2014-05-24

    trial is registered with ClinicalTrials.gov, number NCT01218828. Contrast-induced acute kidney injury occurred less frequently in patients in the left ventricular end-diastolic pressure-guided group (6·7% [12/178]) than in the control group (16·3% [28/172]; relative risk 0·41, 95% CI 0·22-0·79; p=0·005). Hydration treatment was terminated prematurely because of shortness of breath in three patients in each group. Left ventricular end-diastolic pressure-guided fluid administration seems to be safe and effective in preventing contrast-induced acute kidney injury in patients undergoing cardiac catheterisation. Kaiser Permanente Southern California regional research committee grant. Copyright © 2014 Elsevier Ltd. All rights reserved.

  16. Contrast-induced nephropathy and its prevention: What do we really know from evidence-based findings?

    LENUS (Irish Health Repository)

    Reddan, Donald

    2010-03-12

    INTRODUCTION: Contrast-induced acute kidney injury, also referred to as contrast-induced nephropathy (CIN), is a potentially serious renal complication associated with the use of iodinated contrast media (CM) in patients at risk. With the dramatic growth in contrast-enhanced imaging services worldwide, including procedures involving exposure to iodinated CM, efforts to reduce the occurrence of CIN have received considerable attention in recent years. To date, these efforts have met with little success since the 12% prevalence of CIN today remains unchanged from 2 decades ago. METHODS: We conducted a systematic literature review of the most recent evidence available from published reports of contemporary (2000-2008) prospective, randomized, controlled trials that have investigated CIN either by comparing CM or by comparing preventive strategies. The objective was to critically review the findings in light of several aspects of study design and then to establish a set of parameters for consideration in the planning of future CIN trials so as to optimize the strength of evidence obtained. RESULTS: Whether future CIN trials are investigating comparative CM nephrotoxicity or dealing with prophylactic strategies for risk reduction, the complexities that must be addressed include a standardized definition of CIN, appropriate timing of SCr measurements with timing standardized for all subjects in a given study population, awareness of study population risk profile, hydration protocols, and pharmacological prophylactic strategies. CONCLUSIONS: Large, well-designed trials (ideally with hard clinical outcome measures) that consider all the complexities involved in CIN and its prevention are needed before the clinical community has the evidence-based direction required for optimized patient care.

  17. Sodium Bicarbonate-Ascorbic Acid Combination for Prevention of Contrast-Induced Nephropathy in Chronic Kidney Disease Patients Undergoing Catheterization.

    Science.gov (United States)

    Komiyama, Kota; Ashikaga, Takashi; Inagaki, Dai; Miyabe, Tomonori; Arai, Marina; Yoshida, Kiyotaka; Miyazawa, Satoshi; Nakada, Akihiro; Kawamura, Iwanari; Masuda, Shinichiro; Nagamine, Sho; Hojo, Rintaro; Aoyama, Yuya; Tsuchiyama, Takaaki; Fukamizu, Seiji; Shibui, Takashi; Sakurada, Harumizu

    2017-01-25

    Sodium bicarbonate and ascorbic acid have been proposed to prevent contrast-induced nephropathy (CIN). The present study evaluated the effect of their combined use on CIN incidence.Methods and Results:We prospectively enrolled 429 patients with chronic kidney disease (CKD: baseline estimated glomerular filtration rate <60 mL/min/1.73 m 2 ) prior to elective coronary catheterization. CIN was defined as absolute (≥0.5 mg/dL) or relative (≥25%) increase in serum creatinine within 72 h. In the saline hydration (n=218) and combined sodium bicarbonate+ascorbic acid (n=211) groups, a total of 1,500-2,500 mL 0.9% saline was given before and after the procedure. In addition, the combination group received 20 mEq sodium bicarbonate and 3 g ascorbic acid i.v. before the procedure, followed by 2 g ascorbic acid after the procedure and a further 2 g after 12 h. There were no significant differences between the basic characteristics and contrast volume in the 2 groups. CIN occurred in 19 patients (8.7%) in the saline group, and in 6 patients (2.8%) in the combined treatment group (P=0.008). Combined sodium bicarbonate and ascorbic acid could prevent CIN following catheterization in CKD patients.

  18. Prevention of contrast induced nephropathy with sodium bicarbonate (the PROMEC study

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    John Fredy Nieto-Ríos

    2014-09-01

    Full Text Available Introduction: Contrast-induced nephropathy is a common complication of radiographic procedures. Different measures have been used to avoid this damage, but the evidence is controversial. New investigations are required to clarify it. We investigated the efficacy and safety of sodium bicarbonate solution compared with sodium chloride solution to prevent contrast induced nephropathy in patients with or at risk of renal dysfunction. Methods: A prospective, single-center, randomized clinical trial conducted from May 1, 2007 to February 8, 2008. Inpatients in a tertiary center, scheduled to undergo a procedure with the nonionic radiographic contrast agent iohexol. There were 220 patients with serum creatinine levels of at least 1.2 mg/dL (106.1 µmol/L and/or type 2 diabetics, who were randomized to receive an infusion of sodium chloride (n = 113 or sodium bicarbonate (n = 107 before and after contrast dye administration. The intervention were "A" group received 1 ml/kg/hour of normal saline solution, starting 12 hours before and continuing 12 hours after iohexol contrast. "B" group received 3 ml/kg of sodium bicarbonate solution (150 mEq/L one hour prior to procedure and then drip rate was decreased to 1 ml/kg/hour until 6 hours post procedure. Our main outcome measure was change in serum creatinine. Results: The mean creatinine value after the procedure was 1.26 mg/dL in the saline group and 1.22 mg/dL in the bicarbonate group (mean difference: 0.036; CI 95%: -0.16 to 0.23, p = 0.865. The diagnosis of contrast-induced nephropathy, defined by increase in serum creatinine on 25% or more within 2 days after administration of radiographic contrast, was done in twelve patients (12% in the bicarbonate group and eighth patients (7.1% in the saline group (RR: 1.68, CI 95%: 0.72 to 3.94. Conclusion: Our investigation showed that there were no differences between normal saline solution (extended infusion vs. bicarbonate solution for nephroprotection.

  19. Evaluation of N-acetylcysteine for the prevention of contrast-induced nephropathy

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    Sara K. Richter

    2015-06-01

    Full Text Available Background: Contrast-induced nephropathy (CIN remains a leading cause of acute renal failure in hospitalized patients. N-Acetylcysteine has been studied previously for the prevention of CIN, resulting in mixed findings. Objective: The objective of this study was to determine the impact of N-acetylcysteine on the development of CIN in order to guide its use at community, teaching hospitals. Methods: Patients admitted between January 1 and December 31, 2011, receiving intravenous radiocontrast dye were included if they were compliant with two or more of the following conditions: baseline serum creatinine >1.2 mg/dL or estimated creatinine clearance <50 mL/min, age ≥75 years, diabetes mellitus, heart failure, or hypertension. The primary outcome was the difference in the proportion of patients in each group (N-acetylcysteine or no N-acetylcysteine who developed CIN, which was defined as a ≥0.5 mg/dL increase in serum creatinine or a ≥25% increase in serum creatinine within 12–96 hours post-exposure to contrast. Results: A total of 302 patients were included, 151 who received N-acetylcysteine and 151 who did not receive N-acetylcysteine. Patients who received N-acetylcysteine had significantly worse renal function at baseline than those who did not receive N-acetylcysteine (mean pre-contrast serum creatinine, 1.41 vs. 0.95 mg/dL, p<0.0001. A lower proportion of patients developing CIN was observed between those who received N-acetylcysteine and those who did not receive N-acetylcysteine (10.2% vs. 21.8%, p=0.0428. Conclusions: The use of N-acetylcysteine was likely associated with a reduced incidence of CIN in patients at risk for CIN development. Based on these results, hospitals may benefit from the development of a protocol to guide the appropriate use of N-acetylcysteine.

  20. Usefulness of Sodium Bicarbonate for the Prevention of Contrast-Induced Nephropathy in Patients Undergoing Cardiac Resynchronization Therapy.

    Science.gov (United States)

    Alonso, Pau; Sanz, Jorge; García-Orts, Ana; Reina, Samuel; Jiménez, Sonia; Osca, Joaquín; Cano, Oscar; Andrés, Ana; Sancho-Tello, María José; Martínez, Luis

    2017-11-01

    The use of contrast media during cardiac resynchronization therapy (CRT) devices implantation is associated with the risk of contrast-induced nephropathy (CIN). The aim of this study was to evaluate the possible beneficial role of periprocedural intravenous volume expansion with isotonic saline and sodium bicarbonate solution in patients who undergo CRT implantation. Eligible patients were randomly assigned in a 1:1 ratio to receive hydration plus one-sixth molar sodium bicarbonate (study group) or not (control group). Primary end point was CIN incidence. Secondary end points were (1) a combined end point of death, heart transplantation, or hospitalization for heart failure at 12 months, (2) incidence of death, and (3) the need for renal replacement therapy at 12 months. Final analysis was performed with 93 patients. In the hydration group CIN incidence was significantly reduced related to control group (0% vs 11%, p = 0.02). There was a trend to reduce the combined end point in hydration group (12.5% vs 22%, p = 0.14). Finally, CIN incidence was related to a higher 12 months mortality (25% vs 7%, p = 0.03). In conclusion, CIN incidence was 11% in a nonselected population of patients receiving a CRT device. CIN appearance could be reduced by using a hydration protocol based on sodium bicarbonate and isotonic saline. Copyright © 2017 Elsevier Inc. All rights reserved.

  1. Efficacy of atorvastatin on the prevention of contrast-induced acute kidney injury: a meta-analysis

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    Liu L

    2018-03-01

    Full Text Available Ling-Yun Liu,1 Yang Liu,2 Mei-Yan Wu,2 Yan-Yan Sun,3 Fu-Zhe Ma2 1Department of Andrology, 2Department of Nephrology, the First Hospital of Jilin University, 3Department of Nephrology, the Fourth Hospital of Jilin University, Changchun, China Background: Results of studies on the efficacy of atorvastatin pretreatment on reducing the prevalence of contrast-induced acute kidney injury (CIAKI in patients undergoing coronary angiography (CAG or percutaneous coronary intervention (PCI have been controversial.Objective: We undertook a meta-analysis to evaluate the efficacy of atorvastatin on contrast-induced nephropathy (CIN after CAG or PCI.Materials and methods: We undertook a systematic search of electronic databases (PubMed, Embase, and the Cochrane Library up to June 2017. A meta-analysis was carried out including randomized controlled trials (RCTs that compared atorvastatin pretreatment with pretreatment with a low-dose statin or placebo for CIAKI prevention in patients undergoing CAG. The main endpoint was CIN prevalence.Results: Nine RCTs were included in our meta-analysis. Atorvastatin pretreatment reduced the prevalence of CIN significantly (odds ratio [OR] 0.46; 95% confidence interval [95% CI] 0.27–0.79; p=0.004. The benefit of high-dose atorvastatin pretreatment was consistent when compared with the control group (OR 0.45; 95% CI 0.21–0.95; p=0.04.Conclusion: At high doses, atorvastatin pretreatment was associated with a significant reduction in the prevalence of CIAKI in patients undergoing CAG. Pretreatment with high-dose atorvastatin could be employed to prevent CIAKI. Keywords: atorvastatin, contrast-induced acute kidney injury, coronary angiography, percutaneous coronary intervention, contrast-induced nephropathy, meta-analysis

  2. Effect of sodium bicarbonate on the prevention of contrast induced nephropathy in patients undergoing coronary angiography

    International Nuclear Information System (INIS)

    Isono, Tsuyoshi; Kamihata, Hiroshi; Seno, Takeshi; Manabe, Kenichi; Moriguchi, Akira; Yurugi, Takatomi; Iwasaka, Toshiji; Motohiro, Masayuki

    2007-01-01

    Contrast induced nephropathy (CIN) remains a common complication of coronary angiography (CAG) and is associated with significant morbidity and mortality. Although a previous study reported pretreatment with sodium bicarbonate is more effective than sodium chloride for prophylaxis of CIN, this has not been a universal finding and the long-term effects of sodium bicarbonate on CIN have not been studied before. We performed a prospective, single-center, randomized trial to investigate whether CIN can be avoided by sodium bicarbonate in patients with chronic renal failure. Eighty patients with chronic renal failure (defined as serum creatinine concentration (SCr), >1.1 mg per deciliter), who were undergoing CAG, were enrolled in this study. We assigned them to either sodium chloride plus sodium bicarbonate (Group B: n=35) or sodium chloride alone (Group C: n=45). In all patients, an infusion of sodium chloride of 1 ml/kg per hour was given between 12 hours before and after the procedure. In Group B, sodium bicarbonate infusion of 1 ml/kg per hour continued from 3 hours before procedure to 6 hours after procedure, changing from sodium chloride at 1 ml/kg per hour. SCr was measured at baseline, day 1, day 2 and 1 month after the procedure. CIN was defined as a 25% increase in SCr from baseline value, or an absolute increase of at least 0.5 mg/dl, which appears within 2 days after CAG. No differences in age, sex and contrast volume were observed between the two groups. SCr at baseline was not significantly different in the two groups (Group B: 1.41±0.32 versus Group C: 1.50±0.38 mg/dl). SCr at day 2 was significantly lower in Group B than Group C (1.44±0.38 versus 1.60±0.5 mg/dl, p<0.05) and 1 month (1.28±0.27 versus 1.49±0.55 mg/dl, p<0.05). CIN occurred in 9 patients (20%) in Group C but in only 2 (6%) in Group B (p=0.03). Sodium chloride plus sodium bicarbonate is more effective than sodium chloride alone for prophylaxis of CIN and can help retain long

  3. Short term high dose atorvastatin for the prevention of contrast-induced nephropathy in patients undergoing computed tomography angiography

    Directory of Open Access Journals (Sweden)

    Hamid Sanei

    2014-09-01

    Full Text Available BACKGROUND: Statins are shown effective by some studies in preventing contrast-induced nephropathy (CIN. We evaluated the effectiveness of atorvastatin in the prevention of CIN in computed tomography angiography (CTA candidates. METHODS: This study was conducted on patients referring for elective CTA with normal renal function. Patients received atorvastatin (80 mg/day or placebo from 24 h before to 48 h after administration of the contrast material. Serum creatinine was measured before and 48 h after contrast material injection. CIN was defined as an increase in serum creatinine level of ≥ 0.5 mg/dl or ≥ 25% of the baseline creatinine. RESULTS: A total of 236 patients completed the study; 115 atorvastatin, 121 placebo, mean age = 58.40 ± 9.80 year, 68.6% male. Serum creatinine increased after contrast material injection in both the atorvastatin (1.00 ± 0.16-1.02 ± 0.15 mg/dl, P = 0.017 and placebo groups (1.03 ± 0.17-1.08 ± 0.18 mg/dl, P < 0.001. Controlling for age, gender, comorbidities, drug history, and baseline serum creatinine level, patients who received atorvastatin experienced less increase in serum creatinine after contrast material injection (beta = 0.127, P = 0.034. However, there was no difference between the atorvastatin and placebo groups in the incidence of CIN (4.3 vs. 5.0%, P = 0.535. CONCLUSION: In patients undergoing CTA, a short-term treatment with high dose atorvastatin is effective in preventing contrast-induced renal dysfunction, in terms of less increase in serum creatinine level after contrast material injection. Further trials including larger sample of patients and longer follow-ups are warranted.   Keywords: Kidney Diseases, Multidetector Computed Tomography, Contrast Media, Hydroxymethylglutaryl-CoA Reductase Inhibitors, Atorvastatin 

  4. The use of nitrates in the prevention of contrast-induced nephropathy in patients hospitalized after undergoing percutaneous coronary intervention.

    Science.gov (United States)

    Peguero, Julio G; Cornielle, Vertilio; Gomez, Sabas I; Issa, Omar M; Heimowitz, Todd B; Santana, Orlando; Goldszer, Robert C; Lamas, Gervasio A

    2014-05-01

    Contrast-induced nephropathy (CIN) is a significant cause of morbidity and mortality and effective strategies for its prevention are greatly needed. The purpose of this retrospective, single-center study was to investigate whether nitrate use during percutaneous coronary artery intervention reduces the incidence of CIN. Chart review of all individuals who underwent percutaneous coronary intervention (PCI) from April 2010 to March 2011 was done. Included in the study were patients who were admitted to the hospital after percutaneous coronary artery intervention and had baseline and follow-up creatinine measured. Patients with end-stage renal disease requiring dialysis and those patients with insufficient information to calculate Mehran score were excluded. There were 199 patients who met the eligibility criteria for inclusion in this study. In the identified population, postprocedure renal function was compared between 112 patients who received nitrates prior to coronary intervention and 87 who did not. Baseline characteristics were similar between the 2 groups. Contrast-induced nephropathy was defined as either a 25% or a 0.5 mg/dL, or greater, increase in serum creatinine during the first 48 to 72 hours after contrast exposure. Overall, 43 (21.6%) patients developed CIN post-PCI. Of the patients who received nitrates, 15.2% developed renal impairment when compared to 29.9% in those who did not (odds ratio [OR] = 0.42, 95% confidence interval [CI] 0.21-0.84, P = .014). Multivariate logistic regression analysis demonstrated that nitrate use was independently correlated with a reduction in the development of contrast nephropathy (OR = 0.334, 95% CI 0.157-0.709, P = .004). Additionally, of the various methods of nitrate administration, intravenous infusion was shown to be the most efficacious route in preventing renal impairment (OR = 0.42, 95% CI 0.20-0.90, P = .03). In conclusion, the use of nitrates prior to PCI, particularly intravenous nitroglycerin infusion, may

  5. Sodium bicarbonate for the prevention of contrast induced nephropathy: A meta-analysis of published clinical trials

    International Nuclear Information System (INIS)

    Kunadian, Vijayalakshmi; Zaman, Azfar; Spyridopoulos, Ioakim; Qiu, Weiliang

    2011-01-01

    Background: Contrast induced nephropathy (CIN) is a serious but rare complication following contrast based procedures. Sodium bicarbonate (NaHCO 3 ) has been postulated to prevent CIN by various mechanisms. However, the outcomes following sodium bicarbonate administration to prevent CIN have been inconsistent. Methods: A meta-analysis of published randomized clinical trials to determine if the administration of sodium bicarbonate is superior to sodium chloride among patients with chronic renal failure undergoing catheterization and interventional procedures in preventing CIN was performed. Results: Data were combined across seven published clinical trials consisting of 1734 patients. There were no significant differences in the baseline characteristics between the NaHCO 3 and NaCl groups except patients in the bicarbonate group were heavier (P = 0.04). The odds ratio (OR) for the development of contrast nephropathy for NaHCO 3 versus NaCl was 0.33 (95% confidence interval [CI] 0.16-0.69; P = 0.003). Heterogeneity and publication bias were detectable with P-values 0.01 and 0.0005 respectively. There was no difference between the NaHCO 3 group and the NaCl group in the occurrence of death [OR 0.6; 95% CI (0.26-1.41); P = 0.24], congestive heart failure [OR 0.85; 95% CI (0.32-2.24); P = 0.74] and the requirement for renal replacement therapy [OR 0.56; 95% CI (0.22-1.41); P = 0.22]. Conclusion: This meta-analysis demonstrates that based on currently available randomized trials, the administration of NaHCO 3 is superior to the administration of NaCl alone in the prevention of CIN among patients with moderate to severe chronic kidney disease. However, further controlled clinical trials are needed due to significant study heterogeneity and publication bias.

  6. Sodium bicarbonate for the prevention of contrast induced nephropathy: A meta-analysis of published clinical trials

    Energy Technology Data Exchange (ETDEWEB)

    Kunadian, Vijayalakshmi, E-mail: kunadianvijay@aol.com [Cardiothoracic Centre, Freeman Hospital, Newcastle upon Tyne Hospitals, NHS Foundation Trust/Newcastle University, Newcastle upon Tyne (United Kingdom); Zaman, Azfar, E-mail: Azfar.Zaman@nuth.nhs.uk [Cardiothoracic Centre, Freeman Hospital, Newcastle upon Tyne Hospitals, NHS Foundation Trust/Newcastle University, Newcastle upon Tyne (United Kingdom); Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne (United Kingdom); Spyridopoulos, Ioakim [Cardiothoracic Centre, Freeman Hospital, Newcastle upon Tyne Hospitals, NHS Foundation Trust/Newcastle University, Newcastle upon Tyne (United Kingdom); Institute of Human Genetics, Newcastle University, Newcastle upon Tyne (United Kingdom); Qiu, Weiliang [Channing Laboratory, Department of Medicine, Brigham and Women' s Hospital/Harvard Medical School, Boston, MA, United States of America (United States)

    2011-07-15

    Background: Contrast induced nephropathy (CIN) is a serious but rare complication following contrast based procedures. Sodium bicarbonate (NaHCO{sub 3}) has been postulated to prevent CIN by various mechanisms. However, the outcomes following sodium bicarbonate administration to prevent CIN have been inconsistent. Methods: A meta-analysis of published randomized clinical trials to determine if the administration of sodium bicarbonate is superior to sodium chloride among patients with chronic renal failure undergoing catheterization and interventional procedures in preventing CIN was performed. Results: Data were combined across seven published clinical trials consisting of 1734 patients. There were no significant differences in the baseline characteristics between the NaHCO{sub 3} and NaCl groups except patients in the bicarbonate group were heavier (P = 0.04). The odds ratio (OR) for the development of contrast nephropathy for NaHCO{sub 3} versus NaCl was 0.33 (95% confidence interval [CI] 0.16-0.69; P = 0.003). Heterogeneity and publication bias were detectable with P-values 0.01 and 0.0005 respectively. There was no difference between the NaHCO{sub 3} group and the NaCl group in the occurrence of death [OR 0.6; 95% CI (0.26-1.41); P = 0.24], congestive heart failure [OR 0.85; 95% CI (0.32-2.24); P = 0.74] and the requirement for renal replacement therapy [OR 0.56; 95% CI (0.22-1.41); P = 0.22]. Conclusion: This meta-analysis demonstrates that based on currently available randomized trials, the administration of NaHCO{sub 3} is superior to the administration of NaCl alone in the prevention of CIN among patients with moderate to severe chronic kidney disease. However, further controlled clinical trials are needed due to significant study heterogeneity and publication bias.

  7. Prevention of contrast-induced nephropathy with single bolus erythropoietin in patients with diabetic kidney disease: A randomized controlled trial.

    Science.gov (United States)

    Shema-Didi, Lilach; Kristal, Batya; Eizenberg, Sarit; Marzuq, Nabil; Sussan, Majdy; Feldman-Idov, Yulie; Ofir, Pnina; Atar, Shaul

    2016-04-01

    Contrast-induced-nephropathy (CIN) is associated with poor outcomes, thus prevention of CIN may be of clinical value. Erythropoietin (EPO) has been shown to elicit tissue-protective effects in experimental models and in clinical studies of acute kidney injury. We therefore evaluated its effectiveness for prevention of CIN after coronary angiography (CA) ± percutaneous coronary intervention (PCI) in diabetic patients with chronic kidney disease. A prospective, randomized, controlled trial was carried out in 138 diabetic patients with eGFR <60 mL/min who underwent non-urgent CA ± PCI. Patients received normal saline and n-acetyl cysteine before CA, with or without 50,000 U of EPO administered 30 min prior to CA. CIN was defined as an increase in serum creatinine of at least 0.5 mg/dL during the first 2 days after exposure to contrast media. Primary outcome was the incidence of CIN. Secondary outcomes were the sensitivity and positive predictive value (PPV) of Cystatin C (CC) and Neutrophil-gelatinase-associated-lipocalin (NGAL) for diagnosis of CIN. The observed incidence of CIN was 8.7%, significantly lower than the expected for such high-risk population. The administration of EPO prior to CA did not reduce the incidence of CIN (9.7% vs. 7.6%, P = 0.65). CC and NGAL demonstrated a low sensitivity (16.6%) and low PPV (6.7 and 33.3%, respectively) for detecting CIN. The administration of EPO prior to CA did not reduce the incidence of CIN. Additional prospective research with a larger sample size and in other patient categories is essential to further define the potential protective effect of EPO on prevention of CIN. © 2015 Asian Pacific Society of Nephrology.

  8. Do intravenous N-acetylcysteine and sodium bicarbonate prevent high osmolal contrast-induced acute kidney injury? A randomized controlled trial.

    Directory of Open Access Journals (Sweden)

    Antonio Jose Inda-Filho

    Full Text Available N-acetylcysteine (NAC or sodium bicarbonate (NaHCO3, singly or combined, inconsistently prevent patients exposed to radiographic contrast media from developing contrast-induced acute kidney injury (CI-AKI.We asked whether intravenous isotonic saline and either NaHCO3 in 5% dextrose or else a high dose of NAC in 5% dextrose prevent CI-AKI in outpatients exposed to high-osmolal iodinated contrast medium more than does saline alone.This completed prospective, parallel, superiority, open-label, controlled, computer-randomized, single-center, Brazilian trial (NCT01612013 hydrated 500 adult outpatients (214 at high risk of developing CI-AKI exposed to ioxitalamate during elective coronary angiography and ventriculography. From 1 hour before through 6 hours after exposure, 126 patients (group 1 received a high dose of NAC and saline, 125 (group 2 received NaHCO3 and saline, 124 (group 3 received both treatments, and 125 (group 4 received only saline.Groups were similar with respect to age, gender, weight, pre-existing renal dysfunction, hypertension, medication, and baseline serum creatinine and serum cystatin C, but diabetes mellitus was significantly less prevalent in group 1. CI-AKI incidence 72 hours after exposure to contrast medium was 51.4% (257/500, measured as serum creatinine > (baseline+0.3 mg/dL and/or serum cystatin C > (1.1 · baseline, and 7.6% (38/500, measured as both serum creatinine and serum cystatin C > (baseline+0.3 mg/dL or > (1.25 · baseline. CI-AKI incidence measured less sensitively was similar among groups. Measured more sensitively, incidence in group 1 was significantly (p<0.05 lower than in groups 2 and 3 but not group 4; adjustment for confounding by infused volume equalized incidence in groups 1 and 3.We found no evidence that intravenous isotonic saline and either NaHCO3 or else a high dose of NAC prevent CI-AKI in outpatients exposed to high osmolal iodinated contrast medium more than does saline alone

  9. N-acetylcysteine and other preventive measures for contrast-induced nephropathy in the intensive care unit

    NARCIS (Netherlands)

    Schultz, Marcus J.; Baas, Marije C.; van der Sluijs, Hans P.; Stamkot, G. André; Smit, Watske

    2006-01-01

    The increase in diagnostic imaging procedures that require infusion of intravenous radiographic contrast has led to a parallel increase in the incidence of contrast-induced nephropathy (CIN). Since CIN accounts for a significant increase of hospital-acquired renal failure, length of stay and

  10. A network meta-analysis on randomized trials focusing on the preventive effect of statins on contrast-induced nephropathy

    DEFF Research Database (Denmark)

    Peruzzi, Mariangela; De Luca, Leonardo; Thomsen, Henrik S

    2014-01-01

    -analysis. Randomized trials focusing on statins were searched and pooled with random-effect odds ratios. A total of 14 trials (6,160 patients) were included, focusing on atorvastatin (high/low dose), rosuvastatin (high dose), simvastatin (high/low dose), and placebo or no statin therapy before contrast administration....... The risk of contrast-induced nephropathy was reduced by atorvastatin high dose and rosuvastatin high dose, with no difference between these two agents. Results for atorvastatin low dose and simvastatin (high/low dose) in comparison to placebo were inconclusive. Atorvastatin and rosuvastatin administered...

  11. Prevention of Contrast-Induced AKI: A Review of Published Trials and the Design of the Prevention of Serious Adverse Events following Angiography (PRESERVE) Trial

    Science.gov (United States)

    Gallagher, Martin; Kaufman, James; Cass, Alan; Parikh, Chirag R.; Chertow, Glenn M.; Shunk, Kendrick A.; McCullough, Peter A.; Fine, Michael J.; Mor, Maria K.; Lew, Robert A.; Huang, Grant D.; Conner, Todd A.; Brophy, Mary T.; Lee, Joanne; Soliva, Susan; Palevsky, Paul M.

    2013-01-01

    Summary Contrast-induced AKI (CI-AKI) is a common condition associated with serious, adverse outcomes. CI-AKI may be preventable because its risk factors are well characterized and the timing of renal insult is commonly known in advance. Intravenous (IV) fluids and N-acetylcysteine (NAC) are two of the most widely studied preventive measures for CI-AKI. Despite a multitude of clinical trials and meta-analyses, the most effective type of IV fluid (sodium bicarbonate versus sodium chloride) and the benefit of NAC remain unclear. Careful review of published trials of these interventions reveals design limitations that contributed to their inconclusive findings. Such design limitations include the enrollment of small numbers of patients, increasing the risk for type I and type II statistical errors; the use of surrogate primary endpoints defined by small increments in serum creatinine, which are associated with, but not necessarily causally related to serious, adverse, patient-centered outcomes; and the inclusion of low-risk patients with intact baseline kidney function, yielding low event rates and reduced generalizability to a higher-risk population. The Prevention of Serious Adverse Events following Angiography (PRESERVE) trial is a randomized, double-blind, multicenter trial that will enroll 8680 high-risk patients undergoing coronary or noncoronary angiography to compare the effectiveness of IV isotonic sodium bicarbonate versus IV isotonic sodium chloride and oral NAC versus oral placebo for the prevention of serious, adverse outcomes associated with CI-AKI. This article discusses key methodological issues of past trials investigating IV fluids and NAC and how they informed the design of the PRESERVE trial. PMID:23660180

  12. Impact of minimum contrast media volumes during elective percutaneous coronary intervention for prevention of contrast-induced nephropathy in patients with stable coronary artery disease.

    Science.gov (United States)

    Ebisawa, Soichiro; Kurita, Tairo; Tanaka, Nobuyoshi; Nasu, Kenya; Kimura, Masashi; Ito, Tatsuya; Kinoshita, Yoshihisa; Tsuchikane, Etsuo; Terashima, Mitsuyasu; Suzuki, Takahiko

    2016-01-01

    Contrast-induced nephropathy (CIN) is an important complication following percutaneous coronary intervention (PCI). The clinical importance of a minimum contrast media volume (CMV) for PCI to prevent CIN has not been well evaluated. The purpose of this study was to evaluate the impact of minimum CMV to prevent CIN after PCI. In this study, 2052 consecutive patients who underwent elective PCI in our institute were analyzed. We divided patients into two groups according to CMV: a minimum CMV PCI group [CMV ≤50 ml (n = 94)] and a non-minimum CMV PCI group [CMV >50 ml (n = 1958)]. CIN occurred in 160 (7.8 %) patients. The incidence of CIN was significantly lower in the minimum CMV PCI group than in the non-minimum CMV PCI group (2.1 vs. 8.1 %; P = 0.03). According to multivariate analysis, elderly patients and diabetes mellitus patients were at high risk of developing CIN in this study population. When analyzing only high-risk patients, the incidence of CIN was also significantly lower in the minimum CMV group than in the non-minimum CMV group (2.6 vs. 10.3 %; P = 0.03). Minimum CMV PCI could reduce the incidence of CIN, particularly in high-risk patients; as such, defining the minimum CMV clinical cut-off values may be useful for the prevention of CIN.

  13. Hydrate prevention in petroleum production sub sea system

    Energy Technology Data Exchange (ETDEWEB)

    Rodrigues, Paula L.F.; Rocha, Humberto A.R. [Universidade Estacio de Sa (UNESA), Rio de Janeiro, RJ (Brazil); Rodrigues, Antonio P. [Universidade Federal do Rio Grande do Norte (UFRN), Natal, RN (Brazil)

    2012-07-01

    In spite of the merits of the several hydrate prevention techniques used nowadays, such as: chemical product injection for inhibition and use of thick thermal insulate lines; hydrates per times happen and they are responsible for considerable production losses. Depressurization techniques can be used so much for prevention as in the remediation. Some hydrate removal techniques need a rig or vessel, resources not readily available and with high cost, reason that limits such techniques just for remediation and not for prevention. In the present work it is proposed and described an innovative depressurization system, remote and resident, for hydrate prevention and removal, applicable as for individual sub sea wells as for grouped wells by manifold. Based on low cost jet pumps, without movable parts and with a high reliability, this technique allows hydrate prevention or remediation in a fast and remote way, operated from the production unit. The power fluid line and fluid return line can be integrated in the same umbilical or annulus line structure, without significant increase in the construction costs and installation. It is not necessary to wait for expensive resource mobilization, sometimes not available quickly, such as: vessels or rigs. It still reduces the chemical product consumption and permits to depressurized stopped lines. Other additional advantage, depressurization procedure can be used in the well starting, removing fluid until riser emptying. (author)

  14. Contrast induced nephropathy

    DEFF Research Database (Denmark)

    Stacul, Fulvio; van der Molen, Aart J; Reimer, Peter

    2011-01-01

    PURPOSE: The Contrast Media Safety Committee (CMSC) of the European Society of Urogenital Radiology (ESUR) has updated its 1999 guidelines on contrast medium-induced nephropathy (CIN). AREAS COVERED: Topics reviewed include the definition of CIN, the choice of contrast medium, the prophylactic me....../min/1.73 m (2) is CIN risk threshold for intravenous contrast medium. • Hydration with either saline or sodium bicarbonate reduces CIN incidence. • Patients with eGFR = 60 ml/min/1.73 m (2) receiving contrast medium can continue metformin normally....

  15. Efficacy of short-term high-dose statin in preventing contrast-induced nephropathy: a meta-analysis of seven randomized controlled trials.

    Directory of Open Access Journals (Sweden)

    Yongchuan Li

    Full Text Available A few studies focused on statin therapy as specific prophylactic measures of contrast-induced nephropathy have been published with conflicting results. In this meta-analysis of randomized controlled trials, we aimed to assess the effectiveness of short-term high-dose statin treatment for the prevention of CIN and clinical outcomes and re-evaluate of the potential benefits of statin therapy.We searched PubMed, OVID, EMBASE, Web of science and the Cochrane Central Register of Controlled Trials databases for randomized controlled trials comparing short-term high-dose statin treatment versus low-dose statin treatment or placebo for preventing CIN. Our outcome measures were the risk of CIN within 2-5 days after contrast administration and need for dialysis.Seven randomized controlled trials with a total of 1,399 patients were identified and analyzed. The overall results based on fixed-effect model showed that the use of short-term high-dose statin treatment was associated with a significant reduction in risk of CIN (RR =0.51, 95% CI 0.34-0.76, p =0.001; I(2 = 0%. The incidence of acute renal failure requiring dialysis was not significant different after the use of statin (RR = 0.33, 95% CI 0.05-2.10, p = 0.24; I(2 = 0%. The use of statin was not associated with a significant decrease in the plasma C-reactive protein level (SMD -0.64, 95% CI: -1.57 to 0.29, P = 0.18, I(2 = 97%.Although this meta-analysis supports the use of statin to reduce the incidence of CIN, it must be considered in the context of variable patient demographics. Only a limited recommendation can be made in favour of the use of statin based on current data. Considering the limitations of included studies, a large, well designed trial that incorporates the evaluation of clinically relevant outcomes in participants with different underlying risks of CIN is required to more adequately assess the role for statin in CIN prevention.

  16. Prevention of Contrast-Induced Nephropathy With N-Acetylcysteine or Sodium Bicarbonate in Patients With ST-Segment-Myocardial Infarction

    DEFF Research Database (Denmark)

    Thayssen, Per; Lassen, Jens Flensted; Jensen, Svend Eggert

    2014-01-01

    (CINSTEMI) trial. Patients were randomly assigned in a 1:1:1:1 ratio to receive hydration with sodium chloride together with 1 of 4 prophylactic regimes (1) N-acetylcysteine (NAC), (2) sodium bicarbonate (NaHCO3) infusion, (3) NAC in combination with NaHCO3, or (4) hydration with sodium chloride infusion...... not reduce the rate of CIN significantly compared with hydration with intravenous sodium chloride infusion alone (20.1% versus 20.1% versus 20.8% versus 26.5%; P=NS). However, an increase in serum creatinine >25% from the baseline value to 30 day was significantly lower in patients treated with combined NAC...

  17. Contrast-induced nephropathy after computed tomography

    Directory of Open Access Journals (Sweden)

    Luciano da Silva Selistre

    2015-03-01

    Full Text Available Introduction: Contrast induced nephropathy is the third most prevalent preventable cause of acute kidney injury in hospitalized patients. It defined as an absolute increase in serum creatinine ≥ 0.5 mg/dL and relative ≥ 25% increase. Objective: We studied the risk factors to intravenous injection contrast nephropathy after computed tomography. Methods: We studied 400 patients prospectively. Results: The incidence of contrast induced nephropathy, with an absolute or a relative increase were 4.0% and 13.9%, respectively. Diabetes and cardiac failure were independent risk factors for CIN a relative increase de serum creatinine (O.R.: 3.5 [95% CI: 1.92-6.36], p < 0.01, 2.61 [95% CI: 1.14-6.03%], p < 0.05, respectively. Conclusions: We showed association between uses of intravenous injection contrast after computed tomography with acute injury renal, notably with diabetes and heart failure.

  18. Reducing the Risks for Contrast-Induced Nephropathy

    International Nuclear Information System (INIS)

    Stacul, Fulvio

    2005-01-01

    Contrast-induced nephropathy (CIN) is one of the most serious adverse events associated with the use of contrast media (CM). Patients who develop this complication can have increased morbidity, higher rates of mortality, lengthy hospital stays, and poor long-term outcomes. Although CIN cannot be eliminated, the chances of developing this condition can be reduced by using appropriate prevention strategies. An important first step to reduce the chance of CIN is to identify risk factors associated with this condition. Patients with a previously elevated serum creatinine level, especially when secondary to diabetic nephropathy, are at great risk for developing CIN. Other patient-related risk factors include concurrent use of nephrotoxic medications, dehydration, congestive heart failure, age greater than 70 years, and probably the presence of diabetes mellitus even if serum creatinine is normal. Adequate hydration is widely accepted as an important prophylactic measure for preventing CIN, but the optimal hydration regimen is still debatable. The risk of CIN increases with greater doses of CM, as well as with the type of CM used. A high-osmolar CM poses a greater risk of CIN than does a low-osmolar CM and, as recent but limited data suggest, the use of an iso-osmolar CM is less nephrotoxic than a low-osmolar CM in patients with renal impairment following intra-arterial procedures, although this finding needs to be verified in future clinical studies. Pharmacologic agents such as calcium channel blockers, dopamine, atrial natriuretic peptide, fenoldopam, prostaglandin E1, and endothelin receptor antagonist have not been proven effective against CIN development. Controversies still exist on the possible effectiveness of theophylline and N-acetylcysteine. Simple strategies for the prevention of CIN in at-risk patients are reviewed and unproven interventions are discussed

  19. Hydration for the prevention of contrast medium-induced nephropathy. An update

    International Nuclear Information System (INIS)

    Heinrich, M.; Uder, M.

    2006-01-01

    Contrast medium-induced nephropathy (CIN) continues to be one of the most common causes of hospital-acquired acute renal failure. Since most of the clinical studies on the prophylactic use of different drugs to prevent CIN produced disappointing results, hydration remains the mainstay of prophylaxis. A number of recent prospective randomized trials provided further evidence of the effectiveness of hydration and relevant information regarding the optimization of hydration protocols. It was shown that a bolus hydration solely during examination is not sufficient to prevent CIN. In addition, isotonic 0.9% saline was superior to the commonly used halfisotonic 0.45% saline in another trial. An outpatient hydration protocol including oral hydration before the examination followed by forced intravenous hydration over 6 hrs. beginning 30 to 60 min. prior to examination seems to be comparable to the usual hydration over 24 hrs. Another hydration protocol, which could also be very attractive especially for outpatients, included the infusion of sodium bicarbonate. In a recent trial, hydration with sodium bicarbonate, given as a bolus for 1 hr. prior to examination followed by an infusion for 6 hrs. after examination, was more effective than hydration with sodium chloride for the prophylaxis of CIN. However, there is still a lack of large-scale, multi-center trials comparing different hydration protocols and investigating their influence on clinically relevant endpoints such as mortality or the need for dialysis. (orig.)

  20. Preventive effect of pretreatment with intravenous nicorandil on contrast-induced nephropathy in patients with renal dysfunction undergoing coronary angiography (PRINCIPLE Study).

    Science.gov (United States)

    Ko, Young-Guk; Lee, Byoung-Kwon; Kang, Woong Chol; Moon, Jae-Youn; Cho, Yun Hyeong; Choi, Seong Hun; Hong, Myeong-Ki; Jang, Yangsoo; Kim, Jong-Youn; Min, Pil-Ki; Kwon, Hyuck-Moon

    2013-07-01

    To investigate the effect of pretreatment with intravenous nicorandil on the incidence of contrast-induced nephropathy (CIN) in patients with renal dysfunction undergoing coronary angiography. This randomized controlled multicenter study enrolled a total of 166 patients (nicorandil n=81; control n=85) with an estimated glomerular filtration rate 0.5 mg/dL increase or >25% rise in serum creatinine (SCr) concentration within 48 hours of contrast exposure compared to baseline. The final analysis included 149 patients (nicorandil n=73; control n=76). The baseline characteristics and the total volume of the used contrast (Iodixanol, 125.6±69.1 mL vs. 126.9±74.6 mL, p=0.916) were similar between the two groups. The incidence of CIN also did not differ between the nicorandil and control groups (6.8% vs. 6.6%, p=0.794). There was no difference between the two groups in the relative change in SCr from baseline to peak level within 48 hours after coronary angiography (-1.58±24.07% vs. 0.96±17.49%, p=0.464), although the nicorandil group showed less absolute change in SCr than the control group (-0.01±0.43 mg/mL vs. 0.02±0.31 mg/mL, p=0.005). Prophylactic intravenous infusion of nicorandil did not decrease the incidence of CIN in patients with renal dysfunction undergoing coronary angiography.

  1. Prevenção de nefrotoxicidade por contraste com solução de bicarbonato: resultados preliminares e revisão da literatura Prevention of contrast-induced nephropathy by use of bicarbonate solution: preliminary results and literature review

    Directory of Open Access Journals (Sweden)

    Ricardo Gonçalves da Silva

    2010-09-01

    contrast medium use in diagnostic and interventional procedures. The incidence of contrast-induced nephropathy in the general population is low, but increases exponentially in patients with risk factors, such as diabetes and chronic kidney disease. Several strategies have been used in order to prevent contrast-induced nephropathy. The most efficient strategies are saline hydration (0.9% or 0.45%, use of low-or iso-osmolality contrast medium, and sodium bicarbonate infusion. OBJECTIVE: The aim of this study was to review the pertinent literature and to assess the efficacy of hydration with 1.3% sodium bicarbonate compared with hydration with 0.9% saline solution in preventing contrastinduced nephropathy in high-risk patients. MATERIAL AND METHODS: A systematic search of the literature was conducted in PubMed by using the following keywords: bicarbonate, nephropathy, contrast medium, and acute kidney failure. In addition, 27 patients with diabetes and/or chronic kidney disease, diagnosed with some kind of cancer were randomized for study. RESULTS: None of the patients developed contrast-induced nephropathy characterized as a 0.5 mg/ dL-increase and/or a relative 25%-increase in baseline creatinine. CONCLUSIONS: The literature review strongly suggested that sodium bicarbonate is effective in preventing contrast-induced nephropathy. Regarding the randomized study, saline solution and bicarbonate solution had similar efficacy in preventing contrast-induced nephropathy. However, the small number of patients does not allow definite conclusions.

  2. Current concepts of contrast-induced nephropathy: A brief review

    Directory of Open Access Journals (Sweden)

    Chao-Fu Chang

    2013-12-01

    Full Text Available Contrast-induced nephropathy (CIN is a common hospital-acquired acute kidney injury. Published studies on this condition have dramatically increased in recent years. This article aims to provide a brief literature review. English articles published from 1983 to 2012 were retrieved from PubMed by searching using the term “contrast-induced nephropathy.” Patients with CIN were associated with increased resource utilization, prolonged hospital stay, and increased long-term mortality. CIN is defined as a ≥0.5 mg/dL rise in serum creatinine or a 25% increase, assessed within 48–72 hours after administration of contrast medium (CM. All patients receiving CM should be evaluated for their CIN risk, especially preexisting kidney disease. The CM should be prewarmed to 37 °C and injected at the lowest possible dose. Repeat injection within 72 hours should be avoided. Either iso-osmolar CM or low-osmolar CM, except ioxaglate or iohexol, can be used in all patients. Iso-osmolar CM iodixanol may be a better choice for high-risk patients with chronic kidney disease requiring intra-arterial administration. Nephrotoxic drugs should be stopped 2 days prior to when the patient undergoes a procedure. All patients receiving CM should be at an optimal volume status. Parenteral isotonic saline without any diuretic should be started 12 hours prior to CM at a rate of 1 mL/kg/h and continued for 24 hours if there is no contraindication. In patients who require shorter volume supplement periods or are at a higher risk, bicarbonate infusion (154 mEq/L, 3 mL/kg/h for 1 hour bolus prior to CM, followed by 1 mL/kg/h for 6 hours may be used as an alternative to isotonic saline. Oral N-acetylcysteine (600 mg bid, starting on the day prior to the procedure together with parenteral hydration is suggested for patients at risk. Hemodialysis/hemofiltration is only considered in chronic kidney disease stage 4/5 patients when an access is available. The other medications

  3. The efficacy of N-acetylcysteine plus sodium bicarbonate in the prevention of contrast-induced nephropathy after cardiac catheterization and percutaneous coronary intervention: A meta-analysis of randomized controlled trials.

    Science.gov (United States)

    Zhao, Shi-Jie; Zhong, Zhao-Shuang; Qi, Guo-Xian; Tian, Wen

    2016-10-15

    The efficacy of combining use of N-acetylcysteine (NAC) and sodium bicarbonate (SOB) in the prevention of contrast-induced nephropathy (CIN) after cardiac catheterization and percutaneous coronary intervention (PCI) is unclear. All relevant studies that compared the effect of combining the use of NAC and SOB with individual use on CIN in patients undergoing cardiac catheterization and PCI were identified by searching the databases including Pubmed, Embase, Cochrane Library, and Web of Science without time and language limitation. Only randomized controlled trials (RCTs) with full-text published were considered. Sixteen RCTs involving 4432 cases were included into this meta-analysis. The results showed there were no additional benefit in reduction of CIN in COM group (COM versus NAC: RR 0.85, 95% CI 0.70-1.03, P=0.103; COM versus SOB: RR 0.91, 95% CI 0.71-1.16, P=0.449), even in patients with diabetes mellitus (COM versus NAC: RR 1.11, 95% CI 0.71-1.75, P=0.646; COM versus SOB: RR 1.06, 95% CI 0.45-2.47, P=0.893), undergoing PCI procedure (COM versus NAC: RR0.76, 95% CI 0.39-1.47, P=0.411; COM versus SOB: RR0.96, 95% CI 0.65-1.40, P=0.814), or with baseline renal dysfunction (COM versus NAC: RR 0.89, 95% CI 0.70-1.14, P=0.366; COM versus SOB: RR 0.95, 95% CI 0.67-1.36, P=0.788). The present study demonstrated combining use of NAC and SOB was not significantly superior to individual use method in the prevention of CIN after cardiac catheterization and PCI. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  4. Safety of contrast media. Focus on contrast-induced nephropathy (CIN)

    International Nuclear Information System (INIS)

    Kuwatsuru, Ryohei

    2011-01-01

    Despite advances in imaging diagnosis, contrast media still play an important role in diagnosing the existence of the disease, demonstrating the extent of disease, and determining the perfusion of the disease, which is important to make a differential diagnosis. However, the administration of contrast media may cause contrast-induced nephropathy (CIN), especially in patients with renal impairment. It is estimated that 20-30% of patients with renal impairment who received contrast media develop CIN. Though the precise cause of CIN currently remains unknown, almost all injected contrast media are excreted through the kidney and the effects of contrast media on the kidney are easily understood. As CIN is the most common cause of death due to complications after receiving contrast media, prevention of CIN is important. There are several known risk factors for CIN. Patients with renal impairment, diabetes mellitus, and dehydration are at high risk for CIN. Furthermore, a high osmolar contrast media, excessive amount of contrast media, and ionic contrast media are also risk factors for CIN. CIN can be prevented in several ways. Certain drugs seem to be useful to prevent CIN, while others are harmful. Hydration is useful to prevent CIN, although there is no widely acceptable hydration method to prevent CIN. Both sodium bicarbonate and N-acetylcysteine are promising candidates for prevention of CIN. There are few reports to study CIN after intravenous administration, although reports of CIN after percutaneous cardiac intervention (PCI) and angiography are well recognized. In clinical situations, intravenous administration of contrast media is common. Therefore, a study of CIN after intravenous administration of contrast media should be performed. (author)

  5. Remote Ischemic Preconditioning To Reduce Contrast-Induced Nephropathy: A Randomized Controlled Trial

    NARCIS (Netherlands)

    Menting, T.P.; Sterenborg, T.B.; Waal, Y.R. de; Donders, R.; Wever, K.E.; Lemson, M.S.; Vliet, J.A. van der; Wetzels, J.F.M.; Schultze Kool, L.J.; Warle, M.C.

    2015-01-01

    BACKGROUND: Despite the increasing use of pre- and post-hydration protocols and low osmolar instead of high osmolar iodine containing contrast media, the incidence of contrast induced nephropathy (CIN) is still significant. There is evidence that contrast media cause ischemia reperfusion injury of

  6. Contrast induced nephropathy after transcatheter aortic valve implantation

    Directory of Open Access Journals (Sweden)

    D. L. Kranin

    2017-01-01

    Full Text Available Background: Aortic stenosis ranks the third in the structure of all cardiovascular diseases, conceding only to arterial hypertension and coronary heart disease. Transcatheter aortic valve implantation (TAVI is a promising area of interventional endovascular surgery that enables to provide surgical care to a significant group of the patients with severe aortal stenosis.Aim: To assess the efficacy of prevention of the contrast induced nephropathy (CIN in patients who underwent TAVI under general anesthesia.Materials and methods: We evaluated incidence of CIN in 19 patients who underwent surgery for aortic valve stenosis under general anesthesia with hemodilution and intravenous magnesium sulfate 1 g before administration of the contrast.Results: Laboratory signs of nephropathy within the first 72 hours after the intervention were found in 8/19 (42.1% of patients. In 4 (50% of patients with CIN, its risk had been very high, in 3 (38%, high, and in 1 (12%, moderate. The results obtained are compatible with the contrast-induced acute kidney injury risk estimated from the Mehran-Barrett-Parfrey scale.Conclusion: The used technique of hemodilution and magnesium-based prevention can be considered a safe method of CIN prophylaxis in TAVI patients.

  7. Hydrate formation in drilling fluids: prevention and countering; Formacao de hidratos em fluidos de perfuracao: prevencao e controle

    Energy Technology Data Exchange (ETDEWEB)

    Villas Boas, Mario Barbosa [PETROBRAS, Macae, RJ (Brazil). Distrito de Perfuracao do Sudeste. Setor de Fluidos de Perfuracao

    1988-12-31

    The possibility of hydrates forming during deep water well drilling is analyzed under conditions typical of the state of Rio de Janeiro`s coastal ocean bed. Relying on an extensive review of technical literature, an effort has been made to ascertain the conditions which favor the occurrence of such hydrates in gas-contaminated water-based drilling muds. Based on this study, methods are proposed for preventing and countering this problem. (author) 58 refs., 10 figs.

  8. Contrast-induced encephalopathy following cardiac catheterization.

    Science.gov (United States)

    Spina, Roberto; Simon, Neil; Markus, Romesh; Muller, David Wm; Kathir, Krishna

    2017-08-01

    To describe the epidemiology, pathophysiology, clinical presentation, and management of contrast-induced encephalopathy (CIE) following cardiac catheterization. CIE is an acute, reversible neurological disturbance directly attributable to the intra-arterial administration of iodinated contrast medium. The PubMed database was searched and all cases in the literature were retrieved and reviewed. 52 reports of CIE following cardiac catheterization were found. Encephalopathy, motor and sensory disturbances, vision disturbance, opthalmoplegia, aphasia, and seizures have been reported. Transient cortical blindness is the most commonly reported neurological syndrome, occurring in approximately 50% of cases. The putative mechanism involves disruption of the blood brain barrier and direct neuronal injury. Contrast-induced transient vasoconstriction has also been implicated. Symptoms typically appear within minutes to hours of contrast administration and resolve entirely within 24-48 hr. Risk factors may include hypertension, diabetes mellitus, renal impairment, the administration of large volumes of iodinated contrast, percutaneous coronary intervention or selective angiography of internal mammary grafts, and previous adverse reaction to iodinated contrast. Characteristic findings on cerebral imaging include cortical and sub-cortical contrast enhancement on computed tomography (CT). Imaging findings in CIE may mimic subarachnoid hemorrhage or cerebral ischemia; the Hounsfield scale on CT and the apparent diffusion coefficient on magnetic resonance imaging (MRI) are useful imaging tools in distinguishing these entities. In some cases, brain imaging is normal. Prognosis is excellent with supportive management alone. CIE tends to recur, although re-challenge with iodinated contrast without adverse effects has been documented. CIE is an important clinical entity to consider in the differential diagnosis of stroke following cardiac catheterization. Given that prognosis is

  9. Antithrombin III Protects Against Contrast-Induced Nephropathy

    Directory of Open Access Journals (Sweden)

    Zeyuan Lu

    2017-03-01

    Full Text Available We previously reported that insufficiency of antithrombin III (ATIII, the major anti-coagulation molecule in vivo, exacerbated renal ischemia-reperfusion injury in animal models and possibly humans. In the present study, we investigated the relationship between ATIII level and contrast induced nephropathy (CIN in patients and examined therapeutic effect of ATIII on CIN in Sprague-Dawley rats. Patients with low ATIII activity presented a higher incidence of acute kidney injury (AKI following coronary angiography. ATIII (500 μg/kg was intravenously injected before or after the induction of AKI in rats. Our data demonstrated ATIII significantly attenuated the elevation of serum creatinine, blood urea nitrogen, and renal histological injury. The beneficial effects of ATIII were accompanied by diminished renal inflammatory response, oxidative stress, cell apoptosis and improved renal blood flow in rats. In conclusion, ATIII appears to attenuate CIN through inhibiting inflammation, oxidative stress, apoptosis and improving renal blood flow. ATIII administration may represent a promising strategy for the prevention and treatment of contrast-induced AKI.

  10. Numerical simulation of an alternative to prevent hydrates formation in a bypass section

    Energy Technology Data Exchange (ETDEWEB)

    Almeida, Lucilla Coelho; Oliveira Junior, Joao Americo Aguirre; Fonte, Clarissa Bergman [Engineering Simulation and Scientific Software Ltda. (ESSS), Florianopolis, SC (Brazil); Silva, Fabricio Soares da; Moraes, Carlos Alberto Capela [Petroleo Brasileiro S.A. (PETROBRAS), Rio de Janeiro, RJ (Brazil)

    2012-07-01

    This work presents the use of Computational Fluid Dynamics to evaluate the feasibility of MEG (monoethylene glycol) injection as an alternative to prevent hydrate formation in a bypass section, present in an inlet module of a separation device of a subsea separation system. As the bypass section is open to the main pipeline, MEG will probably be dragged due to secondary flows generated by the main flow stream. The MEG removal rate is estimated, as well as the internal heat transfer between the currents and the heat loss to the external environment in order to estimate the temperature in the equipment. In a first step, the MEG removal was evaluated considering the heat transfer between the liquid phase (composed of water, oil and MEG) and the gas phase as well as the heat transfer by forced convection to the external environment. In a second step, the influence of a thermal insulation layer around the bypass line, reducing the heat loss to the external environment, was studied. Both simulations (with or without thermal insulation) showed the establishment of secondary flows in the open connection between the main line and bypass line, promoting the removal of MEG from the bypass section and enabling other components of the liquid phase and/or gas to enter in the bypass line. This MEG removal is faster when thermal isolation was considered, due to the fact that higher temperatures are established in the bypass, maintaining the liquid phase with lower densities and viscosities. With regard to temperature, the insulation was able to keep higher temperatures at the bypass line than those obtained without insulation, indicating that the combination of MEG injection and thermal insulation may be able to avoid the critical condition for hydrate formation. (author)

  11. Contrast-induced nephrotoxicity: possible synergistic effect of stress hyperglycemia.

    LENUS (Irish Health Repository)

    O'Donnell, David H

    2010-07-01

    Oxidative stress on the renal tubules has been implicated as a mechanism of injury in both stress hyperglycemia and contrast-induced nephrotoxicity. The purpose of this study was to determine whether the combination of these effects has a synergistic effect on accentuating renal tubular apoptosis and therefore increasing the risk of contrast-induced nephrotoxicity.

  12. Contrast-Induced Nephropathy in Patients Undergoing Percutaneous Coronary Intervention

    Directory of Open Access Journals (Sweden)

    Sana Shoukat

    2010-01-01

    Full Text Available Contrast Induced Nephropathy (CIN is a feared complication of numerous radiological procedures that expose patients to contrast media. The most notorious of these procedures is percutaneous coronary intervention (PCI. Not only is this a leading cause of morbidity and mortality, but it also adds to increased costs in high risk patients undergoing PCI. It is thought to result from direct cytotoxicity and hemodynamic challenge to renal tissue. CIN is defined as an increase in serum creatinine by either ≥0.5 mg/dL or by ≥25% from baseline within the first 2-3 days after contrast administration, after other causes of renal impairment have been excluded. The incidence is considerably higher in diabetics, elderly and patients with pre-existing renal disease when compared to the general population. The nephrotoxic potential of various contrast agents must be evaluated completely, with prevention as the mainstay of focus as no effective treatment exists. The purpose of this article is to examine the pathophysiology, risk factors, and clinical course of CIN, as well as the most recent studies dealing with its prevention and potential therapeutic interventions, especially during PCI. The role of gadolinium as an alternative to iodinated contrast is also discussed.

  13. Hidratação com bicarbonato de sódio não previne a nefropatia de contraste: ensaio clínico multicêntrico Hydration with sodium bicarbonate does not prevent contrast nephropathy: a multicenter clinical trial

    Directory of Open Access Journals (Sweden)

    Vitor O. Gomes

    2012-12-01

    Full Text Available FUNDAMENTO: A exposição ao meio de contraste radiográfico pode causar comprometimento agudo da função renal. Há evidências limitadas e conflitantes de que a hidratação com bicarbonato de sódio previne a Nefropatia Induzida por Contraste (NIC em pacientes submetidos a cateterismo cardíaco. OBJETIVO: O presente estudo teve como objetivo determinar se o bicarbonato de sódio é superior à hidratação com soro fisiológico para evitar a nefropatia em pacientes de risco submetidos a cateterismo cardíaco. MÉTODOS: Trezentos e um pacientes submetidos a intervenção coronariana percutânea ou angiografia coronariana com creatinina sérica > 1,2 mg/dL ou Taxa de Filtração Glomerular (TFG BACKGROUND: Radiographic contrast media exposition can cause acute renal function impairment. There is limited and conflicting evidence that hydration with sodium bicarbonate prevents contrast-induced nephropathy (CIN in patients undergoing cardiac catheterization. OBJECTIVE: The present study was aimed at determining whether sodium bicarbonate is superior to hydration with saline to prevent nephropathy in patients at risk undergoing cardiac catheterization. METHODS: Three hundred and one patients undergoing coronary angiography or percutaneous coronary intervention with serum creatinine > 1.2mg/dL or glomerular filtration rate (GFR < 50ml/min were randomized to receive hydration with sodium bicarbonate starting 1 hour before the procedure and 6 hours after the procedure, or hydration with 0.9% saline. CIN was defined as an increase of 0.5mg/dL in creatinine in 48h RESULTS: Eighteen patients (5.9% developed contrast induced nephropathy: 9 patients in the bicarbonate group (6.1% and 9 patients in the saline group (6.0%, p = 0.97. The change in serum creatinine was similar in both groups, 0.01 ± 0.26 mg/dL in the bicarbonate group and 0.01 ± 0.35 mg/dL in the saline group, p = 0.9. No statistical difference was observed between the change in glomerular

  14. Hidratação com bicarbonato de sódio não previne a nefropatia de contraste: ensaio clínico multicêntrico Hydration with sodium bicarbonate does not prevent contrast nephropathy: a multicenter clinical trial

    Directory of Open Access Journals (Sweden)

    Vitor O. Gomes

    2012-01-01

    Full Text Available FUNDAMENTO: A exposição ao meio de contraste radiográfico pode causar comprometimento agudo da função renal. Há evidências limitadas e conflitantes de que a hidratação com bicarbonato de sódio previne a Nefropatia Induzida por Contraste (NIC em pacientes submetidos a cateterismo cardíaco. OBJETIVO: O presente estudo teve como objetivo determinar se o bicarbonato de sódio é superior à hidratação com soro fisiológico para evitar a nefropatia em pacientes de risco submetidos a cateterismo cardíaco. MÉTODOS: Trezentos e um pacientes submetidos a intervenção coronariana percutânea ou angiografia coronariana com creatinina sérica > 1,2 mg/dL ou Taxa de Filtração Glomerular (TFG BACKGROUND: Radiographic contrast media exposition can cause acute renal function impairment. There is limited and conflicting evidence that hydration with sodium bicarbonate prevents contrast-induced nephropathy (CIN in patients undergoing cardiac catheterization. OBJECTIVE: The present study was aimed at determining whether sodium bicarbonate is superior to hydration with saline to prevent nephropathy in patients at risk undergoing cardiac catheterization. METHODS: Three hundred and one patients undergoing coronary angiography or percutaneous coronary intervention with serum creatinine > 1.2mg/dL or glomerular filtration rate (GFR < 50ml/min were randomized to receive hydration with sodium bicarbonate starting 1 hour before the procedure and 6 hours after the procedure, or hydration with 0.9% saline. CIN was defined as an increase of 0.5mg/dL in creatinine in 48h RESULTS: Eighteen patients (5.9% developed contrast induced nephropathy: 9 patients in the bicarbonate group (6.1% and 9 patients in the saline group (6.0%, p = 0.97. The change in serum creatinine was similar in both groups, 0.01 ± 0.26 mg/dL in the bicarbonate group and 0.01 ± 0.35 mg/dL in the saline group, p = 0.9. No statistical difference was observed between the change in glomerular

  15. Preprocedural Prediction Model for Contrast-Induced Nephropathy Patients.

    Science.gov (United States)

    Yin, Wen-Jun; Yi, Yi-Hu; Guan, Xiao-Feng; Zhou, Ling-Yun; Wang, Jiang-Lin; Li, Dai-Yang; Zuo, Xiao-Cong

    2017-02-03

    Several models have been developed for prediction of contrast-induced nephropathy (CIN); however, they only contain patients receiving intra-arterial contrast media for coronary angiographic procedures, which represent a small proportion of all contrast procedures. In addition, most of them evaluate radiological interventional procedure-related variables. So it is necessary for us to develop a model for prediction of CIN before radiological procedures among patients administered contrast media. A total of 8800 patients undergoing contrast administration were randomly assigned in a 4:1 ratio to development and validation data sets. CIN was defined as an increase of 25% and/or 0.5 mg/dL in serum creatinine within 72 hours above the baseline value. Preprocedural clinical variables were used to develop the prediction model from the training data set by the machine learning method of random forest, and 5-fold cross-validation was used to evaluate the prediction accuracies of the model. Finally we tested this model in the validation data set. The incidence of CIN was 13.38%. We built a prediction model with 13 preprocedural variables selected from 83 variables. The model obtained an area under the receiver-operating characteristic (ROC) curve (AUC) of 0.907 and gave prediction accuracy of 80.8%, sensitivity of 82.7%, specificity of 78.8%, and Matthews correlation coefficient of 61.5%. For the first time, 3 new factors are included in the model: the decreased sodium concentration, the INR value, and the preprocedural glucose level. The newly established model shows excellent predictive ability of CIN development and thereby provides preventative measures for CIN. © 2017 The Authors. Published on behalf of the American Heart Association, Inc., by Wiley Blackwell.

  16. Contrast-induced nephropathy following intravenous urography with Iopromid

    International Nuclear Information System (INIS)

    Krysteva, R.; Andreev, E.; Kirojcheva, M.; Kundurdzhiev, A.; Kiperova, B.

    1997-01-01

    In retrospective studies the incidence of contrast-induced nephropathy is less than 1 per cent, while in prospective ones it may reach up to 10 per cent. Thirty-nine patients (9 men and 30 women at mean age 46.6 ± 16.5 years, range 15 - 75) undergo prospective study by iv urography with Iopramid (Ultravist 370) administered at mean dose 0.9 ± 0.1 ml/kg b.w. The patients are distributed in 3 groups: group I - with normal renal function free of diabetes mellitus (33 cases), group II - with normal renal function and diabetes mellitus, group III - with renal failure free of diabetes mellitus (plasma creatinine concentration (Pcr) > 140 μmol/l). Pcr is evaluated prior to (baseline) and 48 hours after urography. Dehydration is precluded and none of the patients is given nephrotoxic drugs. In group I Pcr shows a more than 25 per cent increase in 4 patients, but remains below 140 μmol/l. In 2 patients of the same group Pcr levels exceed the reference values: from 51 to 205, and from 105 to 196 μmol/l in two women aged 70 and 74 years, respectively. Renal function impairment is reversible, with Pcr returning to normal within a week. In groups II and III no changes in Pcr level are noted. A slight elevation of serum creatinine pointing to contrast-induced nephrotoxicity is documented in 4 patients with previously normal renal function. A reversible renal failure is observed in two instances. The obtained results demonstrate an incidence rate of contrast-induced nephropathy amounting to 15.4 per cent, or in 6/39 patients (author)

  17. [Skin hydration and hydrating products].

    Science.gov (United States)

    Duplan, H; Nocera, T

    2018-05-01

    One of the skin's principal functions is to protect the body against its environment by maintaining an effective epidermal barrier, not only against external factors, but also to prevent water loss from the body. Indeed, water homeostasis is vital for the normal physiological functioning of skin. Hydration levels affect not only visible microscopic parameters such as the suppleness and softness of skin, but also molecular parameters, enzyme activities and cellular signalling within the epidermis. The body is continually losing some of its water, but this phenomenon is limited and the optimal hydration gradient in skin is ensured via a set of sophisticated regulatory processes that rely on the functional and dynamic properties of the uppermost level of the skin consisting of the stratum corneum. The present article brings together data recently acquired in the fields of skin hydration and the characterisation of dehydrated or dry skin, whether through study of the regulatory processes involved or as a result of changes in the techniques used for in situ measurement, and thus in optimisation of management. Copyright © 2018. Published by Elsevier Masson SAS.

  18. Risk score for contrast induced nephropathy following percutaneous coronary intervention

    International Nuclear Information System (INIS)

    Ghani, Amal Abdel; Tohamy, Khalid Y.

    2009-01-01

    Contrast-induced nephropathy (CIN) is an important cause of acute renal failure. Identification of risk factors of CIN and creating a simple risk scoring for CIN after percutaneous coronary intervention (PCI) is important. A prospective single center study was conducted in Kuwait chest disease hospital. All patients admitted to chest disease hospital for PCI from March to May 2005 were included in the study. Total of 247 patients were randomly assigned for the development dataset and 100 for the validation set using the simple random method. The overall occurrence of CIN in the development set was 5.52%. Using multivariate analysis; basal Serum creatinine, shock, female gender, multivessel PCI, and diabetes mellitus were identified as risk factors. Scores assigned to different variables yielded basal creatinine > 115 micron mol/L with the highest score(7), followed by shock (3), female gender, multivessel PCI and diabetes mellitus had the same score (2). Patients were further risk stratified into low risk score ( 1 2). The developed CIN model demonstrated good discriminative power in the validation population. In conclusion, use of a simple risk score for CIN can predict the probability of CIN after PCI; this however needs further validation in larger multicenter trials. (author)

  19. Contrast-induced nephropathy in patients with chronic kidney disease and peripheral arterial disease

    International Nuclear Information System (INIS)

    Kroneberger, Christian; Enzweiler, Christian N; Schmidt-Lucke, Andre; Rückert, Ralph-Ingo; Teichgräber, Ulf; Franiel, Tobias

    2015-01-01

    The risk for contrast-induced nephropathy (CIN) after intra-arterial application of an iodine-based contrast material is unknown for patients with chronic kidney disease (CKD) and peripheral arterial disease (PAD). To investigate the incidence of CIN in patients with CKD and PAD. This retrospective study was approved by the local ethics committee. One hundred and twenty patients with 128 procedures (73 with baseline eGFR in the range of 45–60 mL/min/1.73m 2 , 55 with eGFR < 45 mL/min/1.73m 2 ) were evaluated. All patients received intra-arterially an iodine-based low-osmolar contrast material (CM) after adequate intravenous hydration with isotonic NaCl 0.9% solution. CIN was defined as an increase in serum creatinine of more than 44 μmol/L within 4 days. The influence of patient-related risk factors (age, weight, body mass index, eGFR, serum creatinine, hypertension, diabetes mellitus, coronary heart disease, heart failure) and therapy-related risk factors (amount of CM, nephrotoxic drugs, number of CM applications) on CIN were examined. CIN developed in 0% (0/73) of procedures in patients with PAD and an eGFR in the range of 45–60 mL/min/1.73m 2 and in 10.9% (6/55) of procedures in patients with an eGFR <45 mL/min/1.73m 2 . No risk factor significantly influenced the development of CIN, although baseline serum creatinine (P = 0.06) and baseline eGFR (P = 0.10) showed a considerable dependency. Patients with an eGFR in the range of 45–60 mL/min/1.73m 2 and PAD seem not at risk for CIN after intra-arterial CM application and adequate hydration. Whereas, an eGFR < 45 mL/min/1.73m 2 correlated with a risk of 10.9% for a CIN

  20. Gas hydrates

    Digital Repository Service at National Institute of Oceanography (India)

    Ramprasad, T.

    , not all of them are white like snow. Some hydrates from the deep Gulf of Mexico are richly colored in shades of yellow, orange, or even red. The ice-like masses are beautiful, and contrast with the dull gray of deep sea muds. Hydrates from the Blake... volcanoes and associated gas hydrates: Marine Geology, v. 167, p. 29-42. Milkov, A.V. and R. Sassen, 2001a, Estimate of gas hydrate resource, northwestern Gulf of Mexico continental slope: Marine Geology, v. 179, pp. 71-83. Milkov, A.V., Sassen, R...

  1. Factors affecting the incidence of contrast-induced nephropathy in patients undergoing computed tomography.

    Science.gov (United States)

    Heras Benito, M; Garrido Blázquez, M; Gómez Sanz, Y; Bernardez Mardomingo, M; Ruiz Cacho, J; Rodríguez Recio, F J; Fernández-Reyes Luis, M J

    2018-05-17

    To analyze the incidence of contrast-induced nephropathy in a cohort of patients undergoing computed tomography (CT) with intravenous iodinated contrast material. To evaluate the efficacy of N-acetylcysteine in preventing contrast-induced nephropathy. This prospective observational study was carried out in the months comprising March 2016 through July 2016. We selected the first five patients scheduled to undergo CT examination each day who agreed to participate and signed the informed consent form. We recorded patients' cardiovascular histories, chronic treatments, and indications for the CT examination. We measured blood levels of creatinine and urea before and after the CT examination. We used the Modification of Diet in Renal Disease (MDRD-4) equation to estimate the glomerular filtration rate. We analyzed the type and dose of contrast material. We recorded whether N-acetylcysteine was administered before the CT examination. We used SPSS 15.0 ® to compare means and proportions. Statistical significance was set at p < 0.05. No incidents of contrast-induced nephropathy were detected in any of the 202 patients included [mean age, 63.92 ± 12 years (range 22-87); 57.4% male; 21.8% diabetic; 39.6% hypertensive; 87.1% had MDRD4 ≥ 60 ml/min/1.73 m 2 (89.45 ± 14, range 62.36-134.14) and 12.9% had MDRD4 < 60 ml/min/1.73 m 2 (45.38 ± 11, range 9.16-58.90)]. The most common indication for CT examinations was oncologic (81.2%). The only contrast agent administered was iopamidol; the mean dose was 107.83 ± 11 ml (range 70-140). The mean interval between pre-CT and post-CT laboratory tests was 4.06 ± 1 days. Only 13 patients received N-acetylcysteine; 9 of these had MDRD < 60 ml/min/1.73 m 2 and 4 had MDRD4 ≥ 60 ml/min/1.73 m 2 (p = 0.000). The incidence of contrast-induced nephropathy was not significant in patients with glomerular filtration rates greater than 30 ml/min/1.73 m 2 : these favorable results might be due to

  2. Ad libitum fluid intake does not prevent dehydration in suboptimally hydrated young soccer players during a training session of a summer camp.

    Science.gov (United States)

    Arnaoutis, Giannis; Kavouras, Stavros A; Kotsis, Yiannis P; Tsekouras, Yiannis E; Makrillos, Michalis; Bardis, Costas N

    2013-06-01

    There is a lack of studies concerning hydration status of young athletes exercising in the heat. To assess preexercise hydration status in young soccer players during a summer sports camp and to evaluate body- water balance after soccer training sessions. Initial hydration status was assessed in 107 young male soccer players (age 11-16 yr) during the 2nd day of the camp. Seventy-two athletes agreed to be monitored during 2 more training sessions (3rd and 5th days of the camp) to calculate dehydration via changes in body weight, while water drinking was allowed ad libitum. Hydration status was assessed via urine specific gravity (USG), urine color, and changes in total body weight. Mean environmental temperature and humidity were 27.2 ± 2 °C and 57% ± 9%, respectively. According to USG values, 95 of 107 of the players were hypohydrated (USG ≥ 1.020) before practice. The prevalence of dehydration observed was maintained on both days, with 95.8% and 97.2% of the players being dehydrated after the training sessions on the 3rd and 5th days, respectively. Despite fluid availability, 54 of the 66 (81.8%) dehydrated players reduced their body weight (-0.35 ± 0.04 kg) as a response to training, while 74.6% (47 out of the 63) further reduced their body weight (-0.22 ± 0.03 kg) after training on the 5th day. Approximately 90% of the young soccer players who began exercising under warm weather conditions were hypohydrated, while drinking ad libitum during practice did not prevent further dehydration in already dehydrated players.

  3. Fluid hydration to prevent post-ERCP pancreatitis in average- to high-risk patients receiving prophylactic rectal NSAIDs (FLUYT trial): study protocol for a randomized controlled trial.

    Science.gov (United States)

    Smeets, Xavier J N M; da Costa, David W; Fockens, Paul; Mulder, Chris J J; Timmer, Robin; Kievit, Wietske; Zegers, Marieke; Bruno, Marco J; Besselink, Marc G H; Vleggaar, Frank P; van der Hulst, Rene W M; Poen, Alexander C; Heine, Gerbrand D N; Venneman, Niels G; Kolkman, Jeroen J; Baak, Lubbertus C; Römkens, Tessa E H; van Dijk, Sven M; Hallensleben, Nora D L; van de Vrie, Wim; Seerden, Tom C J; Tan, Adriaan C I T L; Voorburg, Annet M C J; Poley, Jan-Werner; Witteman, Ben J; Bhalla, Abha; Hadithi, Muhammed; Thijs, Willem J; Schwartz, Matthijs P; Vrolijk, Jan Maarten; Verdonk, Robert C; van Delft, Foke; Keulemans, Yolande; van Goor, Harry; Drenth, Joost P H; van Geenen, Erwin J M

    2018-04-02

    Post-endoscopic retrograde cholangiopancreatography (ERCP) pancreatitis (PEP) is the most common complication of ERCP and may run a severe course. Evidence suggests that vigorous periprocedural hydration can prevent PEP, but studies to date have significant methodological drawbacks. Importantly, evidence for its added value in patients already receiving prophylactic rectal non-steroidal anti-inflammatory drugs (NSAIDs) is lacking and the cost-effectiveness of the approach has not been investigated. We hypothesize that combination therapy of rectal NSAIDs and periprocedural hydration would significantly lower the incidence of post-ERCP pancreatitis compared to rectal NSAIDs alone in moderate- to high-risk patients undergoing ERCP. The FLUYT trial is a multicenter, parallel group, open label, superiority randomized controlled trial. A total of 826 moderate- to high-risk patients undergoing ERCP that receive prophylactic rectal NSAIDs will be randomized to a control group (no fluids or normal saline with a maximum of 1.5 mL/kg/h and 3 L/24 h) or intervention group (lactated Ringer's solution with 20 mL/kg over 60 min at start of ERCP, followed by 3 mL/kg/h for 8 h thereafter). The primary endpoint is the incidence of post-ERCP pancreatitis. Secondary endpoints include PEP severity, hydration-related complications, and cost-effectiveness. The FLUYT trial design, including hydration schedule, fluid type, and sample size, maximize its power of identifying a potential difference in post-ERCP pancreatitis incidence in patients receiving prophylactic rectal NSAIDs. EudraCT: 2015-000829-37 . Registered on 18 February 2015. 13659155 . Registered on 18 May 2015.

  4. Hydrate prevention during formation test of gas in deep water; Prevencao de formacao de hidratos durante teste de formacao de poco de gas em lamina d'agua profunda

    Energy Technology Data Exchange (ETDEWEB)

    Rodrigues, Renato Cunha [PETROBRAS, Rio de Janeiro, RJ (Brazil)

    2008-07-01

    This work shows a scenery of formation test in deep water, for a well of gas, for which, there were made simulations with objective of identifying possible pairs of points (Pressure x Temperature), favorable to the hydrates formation. Besides, they were made comparisons of the values obtained in the simulation with the values registered during the formation test for the well Alfa of the field Beta. Of ownership of those information, we made an evaluation of the real needs of injection of inhibitors with intention of preventing the hydrates formation in each phase of the test. In an including way, the work has as objective recommends the volumes of hydrates inhibitors to be injected in each phase of a test of formation of well of gas in deep water, in way to assure that the operations are made without there is risk of hydrates formation. (author)

  5. Chloral Hydrate

    Science.gov (United States)

    ... if you are allergic to chloral hydrate, aspirin, tartrazine (a yellow dye in some processed foods and ... in, tightly closed, and out of reach of children. Store it at room temperature, away from excess ...

  6. Contrast-induced acute kidney injury: how much contrast is safe?

    LENUS (Irish Health Repository)

    Keaney, John J

    2013-02-14

    Iodinated contrast media (CM) are used in many investigations that a patient may undergo during the course of an in-patient stay. For the vast majority of patients, exposure to CM has no sequelae; however, in a small percentage, it can result in a worsening in renal function termed contrast-induced acute kidney injury (CI-AKI). CI-AKI is one of the leading causes of in-hospital renal dysfunction. It is associated with a significant increase in morbidity and mortality as well as an increased length of hospital stay and costs. Unfortunately, the results of extensive research into pharmacological inventions to prevent CI-AKI remain disappointing. In this article, we briefly outline the pathophysiological mechanisms by which iodinated CM may cause CI-AKI and discuss the evidence for reducing CI-AKI by limiting contrast volumes. In particular, we review the data surrounding the use of contrast volume to glomerular filtration rate ratios, which can be used by clinicians to effectively lower the incidence of CI-AKI in their patients.

  7. Thermodynamic inhibitor performance extender that, effectively and economically prevent hydrate formation in the oil field production systems

    Energy Technology Data Exchange (ETDEWEB)

    Allenson, Stephen; Johnston, Angela [Nalco Energy Services, Sugar Land, TX (United States)

    2008-07-01

    This paper presents the development of a new additive that was developed to improve the effectiveness of the treatment two to four fold when added to the thermodynamic hydrate inhibitor (THI). Consequently, the THI/additive treatment can now enable the system to handle two to four times the amount of water production or can allow treatment of the same amount of water at half to quarter the dosage of THI. This new additive extends the performance of the THI and allows for a significant increase in production or a significant drop in the amount of THI usage with a corresponding drop in cost. This paper will further discuss the overall process of THI enhancement and will present several case studies where the enhanced THI has been successfully applied. (author)

  8. Oxidative stress caused by activation of NADPH oxidase 4 promotes contrast-induced acute kidney injury.

    Directory of Open Access Journals (Sweden)

    Bo Young Jeong

    Full Text Available Contrast-induced acute kidney injury (CIAKI is a leading cause of acute kidney injury following radiographic procedures. Intrarenal oxidative stress plays a critical role in CIAKI. Nicotinamide adenine dinucleotide 3-phosphate (NADPH oxidases (Noxs are important sources of reactive oxygen species (ROS. Among the various types of Noxs, Nox4 is expressed predominantly in the kidney in rodents. Here, we evaluated the role of Nox4 and benefit of Nox4 inhibition on CIAKI using in vivo and in vitro models. HK-2 cells were treated with iohexol, with or without Nox4 knockdown, or the most specific Nox1/4 inhibitor (GKT137831. Effects of Nox4 inhibition on CIAKI mice were examined. Expression of Nox4 in HK-2 cells was significantly increased following iohexol exposure. Silencing of Nox4 rescued the production of ROS, downregulated pro-inflammatory markers (particularly phospho-p38 implicated in CIAKI, and reduced Bax and caspase 3/7 activity, which resulted in increased cellular survival in iohexol-treated HK-2 cells. Pretreatment with GKT137831 replicated these effects by decreasing levels of phospho-p38. In a CIAKI mouse model, even though the improvement of plasma blood urea nitrogen was unclear, pretreatment with GKT137831 resulted in preserved structure, reduced expression of 8-hydroxy-2'-deoxyguanosine (8OHdG and kidney injury molecule-1 (KIM-1, and reduced number of TUNEL (terminal deoxynucleotidyl transferase dUTP nick end labeling-positive cells. These results suggest Nox4 as a key source of reactive oxygen species responsible for CIAKI and provide a novel potential option for prevention of CIAKI.

  9. Type I anaphylactic reaction due to contrast induced angioedema causing neck swelling: the role of sitting fiberoptic bronchoscopy in emergent intubation

    Directory of Open Access Journals (Sweden)

    Ali Dabbagh

    2016-07-01

    Full Text Available Contrast induced angioedema is a rapidly progressive state involving a number of organ systems including the upper airway tract; which is usually a type I anaphylactic reaction also known as immediate hypersensitivity reaction. Prompt preservation of the respiratory tract is the cornerstone of this situation. The use of fiberoptic bronchoscope for tracheal intubation though very helpful, has some special considerations due to the anatomic distortions created by edema.This manuscript describes a patient with contrast induced angioedema managed successfully. Serum levels of IgE were highly increased during the first hours after the event; while serum levels of complement were normal. However, rapid airway management and prophylactic intubation saved the patient and prevented the possible aftermath of airway obstruction.Keywords: airway management; type I anaphylactic reaction, angioedema; fiberoptic bronchoscope.Conflict of interest: none of the authors has any conflict of interest.

  10. Alcohol cosurfactants in hydrate antiagglomeration.

    Science.gov (United States)

    York, J Dalton; Firoozabadi, Abbas

    2008-08-28

    Because of availability, as well as economical and environmental considerations, natural gas is projected to be the premium fuel of the 21st century. Natural gas production involves risk of the shut down of onshore and offshore operations because of blockage from hydrates formed from coproduced water and hydrate-forming species in natural gas. Industry practice has been usage of thermodynamic inhibitors such as alcohols often in significant amounts, which have undesirable environmental and safety impacts. Thermodynamic inhibitors affect bulk-phase properties and inhibit hydrate formation. An alternative is changing surface properties through usage of polymers and surfactants, effective at 0.5 to 3 weight % of coproduced water. One group of low dosage hydrate inhibitors (LDHI) are kinetic inhibitors, which affect nucleation rate and growth. A second group of LDHI are antiagglomerants, which prevent agglomeration of small hydrate crystallites. Despite great potential, work on hydrate antiagglomeration is very limited. This work centers on the effect of small amounts of alcohol cosurfactant in mixtures of two vastly different antiagglomerants. We use a model oil, water, and tetrahydrofuran as a hydrate-forming species. Results show that alcohol cosurfactants may help with antiagglomeration when traditional antiagglomerants alone are ineffective. Specifically, as low as 0.5 wt. % methanol cosurfactant used in this study is shown to be effective in antiagglomeration. Without the cosurfactant there will be agglomeration independent of the AA concentration. To our knowledge, this is the first report of alcohol cosurfactants in hydrate antiagglomerants. It is also shown that a rhamnolipid biosurfactant is effective down to only 0.5 wt. % in such mixtures, yet a quaternary ammonium chloride salt, i. e., quat, results in hydrate slurries down to 0.01 wt. %. However, biochemical surfactants are less toxic and biodegradable, and thus their use may prove beneficial even if at

  11. Hyper-alkalinization without hyper-hydration for the prevention of high-dose methotrexate acute nephrotoxicity in patients with osteosarcoma.

    Science.gov (United States)

    Mir, Olivier; Ropert, Stanislas; Babinet, Antoine; Alexandre, Jérôme; Larousserie, Frédérique; Durand, Jean-Philippe; Enkaoua, Eric; Anract, Philippe; Goldwasser, François

    2010-11-01

    To evaluate the reliability and renal safety of an original schedule of high-dose methotrexate (HDMTX) administration with hyper-alkalinization, and without hyper-hydration. Patients with osteosarcoma received HDMTX (8-12 g/m(2)) as a 4-h infusion. Hypertonic 8.4% sodium bicarbonate was infused prior to HDMTX, then once daily for 3 days. Methotrexate serum concentrations were measured at hour 4 (Cmax), hour 24, hour 48, and hour 72. Urinary pH was measured on each miction. Serum creatinine was assessed on days 1, 3, and 8. Twenty-six patients (median age: 18 years, range: 15-25) received a total of 344 cycles of HDMTX, including 16 patients treated in an outpatient basis. Urinary pH remained constantly higher than 7.5 in all patients. Grade 1 creatininemia toxicity was observed in 31 cycles (9%), and grade 2 creatinine toxicity was observed in one patient. No episode of acute severe nephrotoxicity was observed. No significant worsening was observed in serum creatinine and calculated creatinine clearance from baseline to the end of therapy (P = 0.74). The main extra-renal toxicity was alkalinization-related hypokalemia from H48. No re-hospitalization was required. Hyper-alkalinization appears an efficient and reliable method to prevent the acute renal toxicity of HDMTX and allows its safe administration in the outpatient setting.

  12. Suspension hydration of C3S [tricalcium silicate] at constant pH. II. Effect of previously formed hydrates and of additives

    NARCIS (Netherlands)

    McCurdy, K.G.; Stein, H.N.

    1973-01-01

    A retardation shown by the hydration of C3S at pH=11.5 can be prevented if before the addition of C3S there are present hydrate particles in the aqueous medium. These hydrate particles probably have the composition CSHn. This indicates a hydrate CSHn, precipitated from solution, as the retarding

  13. Fire extinction utilizing carbon dioxide hydrate

    Energy Technology Data Exchange (ETDEWEB)

    Hatakeyama, T.; Aida, E.; Yokomori, T.; Ohmura, R.; Ueda, T. [Keio Univ., Hiyoshi, Kohoku-ku, Yokohama (Japan)

    2008-07-01

    Clathrate hydrates formed with nonflammable gases may be suitable for use as fire extinguishing agents because dissociation of the hydrates results in the temperature decrease in the combustion field and the nonflammable gases released from the dissociated hydrates prevent the supply of the oxygen to the combustion field. This paper discussed experiments in which ordinary ice and dry ice were used to evaluate the performance of CO{sub 2} hydrate as a fire extinguishing agent. The paper described the apparatus and procedure for the preparation of CO{sub 2} hydrate crystals. A schematic of the reactor to form CO{sub 2} hydrate and a photograph of CO{sub 2} hydrate crystal formed in the study were also presented. Other illustrations, photographs, and tables that were presented included a schematic diagram of the experimental apparatus used for the flame extinction experiments; a photograph of CO{sub 2} hydrate powder; sequential video graphs of the flame extinction by the supply of CO{sub 2} hydrate crystals to the methanol pool flame and the relevant illustration; and heat of CO{sub 2} hydrate dissociation, water vaporization and sublimation of dry ice. It was concluded that the critical mass of the CO{sub 2} hydrate required to extinguish a flame was much less than that of ordinary ice, indicating the superiority of CO{sub 2} hydrate to the ice. In addition, the experiments also revealed that the size of the CO{sub 2} hydrate particles had a significant effect on the performance of flame extinction. 5 refs., 2 tabs., 7 figs.

  14. Randomized trial of one-hour sodium bicarbonate vs standard periprocedural saline hydration in chronic kidney disease patients undergoing cardiovascular contrast procedures.

    Directory of Open Access Journals (Sweden)

    Judith Kooiman

    Full Text Available Guidelines advise periprocedural saline hydration for prevention of contrast induced-acute kidney injury (CI-AKI. We analysed whether 1-hour sodium bicarbonate hydration administered solely prior to intra-arterial contrast exposure is non-inferior to standard periprocedural saline hydration in chronic kidney disease (CKD patients undergoing elective cardiovascular diagnostic or interventional contrast procedures.We performed an open-label multicentre non-inferiority trial between 2011-2014. Patients were randomized to 1 hour pre-procedure sodium bicarbonate hydration (250 ml 1.4%, N = 168 or 4-12 hours saline hydration (1000 ml 0.9%, N = 165 prior to and following contrast administration (2000 ml of saline total. Primary outcome was the relative serum creatinine increase (% 48-96 hours post contrast exposure. Secondary outcomes were: incidence of CI-AKI (serum creatinine increase>25% or >44μmol/L, recovery of renal function, the need for dialysis, and hospital costs within two months follow-up.Mean relative creatinine increase was 3.1% (95%CI 0.9 to 5.2% in the bicarbonate and 1.1% (95%CI -1.2 to 3.5% in the saline arm, mean difference 1.9% (95%CI -1.2 to 5.1%, p-non-inferiority <0.001. CI-AKI occurred in 11 (6.7% patients randomized to sodium bicarbonate and 12 (7.5% to saline (p = 0.79. Renal function did not fully recover in 40.0% and 44.4% of CI-AKI patients, respectively (p = 0.84. No patient required dialysis. Mean costs for preventive hydration and clinical preparation for the contrast procedure were $1158 for sodium bicarbonate vs. $1561 for saline (p < 0.001.Short hydration with sodium bicarbonate prior to elective cardiovascular diagnostic or therapeutic contrast procedures is non-inferior to standard periprocedural saline hydration in CKD patients with respect to renal safety and results in considerable healthcare savings.Netherlands Trial Register (http://www.trialregister.nl/trialreg/index.asp, Nr NTR2699.

  15. Randomized trial of one-hour sodium bicarbonate vs standard periprocedural saline hydration in chronic kidney disease patients undergoing cardiovascular contrast procedures.

    Science.gov (United States)

    Kooiman, Judith; de Vries, Jean-Paul P M; Van der Heyden, Jan; Sijpkens, Yvo W J; van Dijkman, Paul R M; Wever, Jan J; van Overhagen, Hans; Vahl, Antonie C; Aarts, Nico; Verberk-Jonkers, Iris J A M; Brulez, Harald F H; Hamming, Jaap F; van der Molen, Aart J; Cannegieter, Suzanne C; Putter, Hein; van den Hout, Wilbert B; Kilicsoy, Inci; Rabelink, Ton J; Huisman, Menno V

    2018-01-01

    Guidelines advise periprocedural saline hydration for prevention of contrast induced-acute kidney injury (CI-AKI). We analysed whether 1-hour sodium bicarbonate hydration administered solely prior to intra-arterial contrast exposure is non-inferior to standard periprocedural saline hydration in chronic kidney disease (CKD) patients undergoing elective cardiovascular diagnostic or interventional contrast procedures. We performed an open-label multicentre non-inferiority trial between 2011-2014. Patients were randomized to 1 hour pre-procedure sodium bicarbonate hydration (250 ml 1.4%, N = 168) or 4-12 hours saline hydration (1000 ml 0.9%, N = 165) prior to and following contrast administration (2000 ml of saline total). Primary outcome was the relative serum creatinine increase (%) 48-96 hours post contrast exposure. Secondary outcomes were: incidence of CI-AKI (serum creatinine increase>25% or >44μmol/L), recovery of renal function, the need for dialysis, and hospital costs within two months follow-up. Mean relative creatinine increase was 3.1% (95%CI 0.9 to 5.2%) in the bicarbonate and 1.1% (95%CI -1.2 to 3.5%) in the saline arm, mean difference 1.9% (95%CI -1.2 to 5.1%, p-non-inferiority <0.001). CI-AKI occurred in 11 (6.7%) patients randomized to sodium bicarbonate and 12 (7.5%) to saline (p = 0.79). Renal function did not fully recover in 40.0% and 44.4% of CI-AKI patients, respectively (p = 0.84). No patient required dialysis. Mean costs for preventive hydration and clinical preparation for the contrast procedure were $1158 for sodium bicarbonate vs. $1561 for saline (p < 0.001). Short hydration with sodium bicarbonate prior to elective cardiovascular diagnostic or therapeutic contrast procedures is non-inferior to standard periprocedural saline hydration in CKD patients with respect to renal safety and results in considerable healthcare savings. Netherlands Trial Register (http://www.trialregister.nl/trialreg/index.asp), Nr NTR2699.

  16. Artificial Hydration and Nutrition

    Science.gov (United States)

    ... Crisis Situations Pets and Animals myhealthfinder Food and Nutrition Healthy Food Choices Weight Loss and Diet Plans ... Your Health Resources Healthcare Management Artificial Hydration and Nutrition Artificial Hydration and Nutrition Share Print Patients who ...

  17. Valsartan Protects Against Contrast-Induced Acute Kidney Injury in Rats by Inhibiting Endoplasmic Reticulum Stress-Induced Apoptosis.

    Science.gov (United States)

    Sun, Yan; Peng, Ping-An; Ma, Yue; Liu, Xiao-Li; Yu, Yi; Jia, Shuo; Xu, Xiao-Han; Wu, Si-Jing; Zhou, Yu-Jie

    2017-01-01

    Contrast-induced acute kidney injury (CI-AKI) is a serious complication of the administration of iodinated contrast media (CM) for diagnostic and interventional cardiovascular procedures and is associated with substantial morbidity and mortality. While the preventative measures can mitigate the risk of CI-AKI, there remains a need for novel and effective therapeutic approaches. The pathogenesis of CI-AKI is complex and not completely understood. CM-induced renal tubular cell apoptosis caused by the activation of endoplasmic reticulum (ER) stress is involved in CIAKI. We previously demonstrated that valsartan alleviated CM-induced human renal tubular cell apoptosis by inhibiting ER stress in vitro. However, the nephroprotective effect of valsartan on CI-AKI in vivo has not been investigated. Therefore, the aim of this study was to explore the protective effect of valsartan in a rat model of CI-AKI by measuring the amelioration of renal damage and the changes in ER stressrelated biomarkers. Our results showed that the radiocontrast agent meglumine diatrizoate caused significant renal insufficiency, renin-angiotensin system (RAS) activation, and renal tubular apoptosis by triggering ER stress through activation of glucose-regulated protein 78 (GRP78), activating transcription factor 4 (ATF4), caspase 12, CCAAT/enhancer-binding protein-homologous protein (CHOP) and c-Jun N-terminal protein kinase (JNK) (Pvalsartan significantly alleviated renal dysfunction, pathological injury, and apoptosis along with the inhibition of ER stressrelated biomarkers (PValsartan could protect against meglumine diatrizoate-induced kidney injury in rats by inhibiting the ER stress-induced apoptosis, making it a promising strategy for preventing CI-AKI. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

  18. Risk factors and incidence of contrast induced nephropathy following coronary intervention

    Directory of Open Access Journals (Sweden)

    Yoga Yuniadi

    2008-06-01

    Full Text Available Contrast induced nephropathy (CIN is one of important complication of contrast media administration. Its incidence and risk factors among Indonesian patients undergoing coronary intervention has not been reported yet. CIN was defined as increasing of serum creatinine by 0.5 mg/dl or more in the third day following contrast media exposure. Of 312 patients undergoing coronary intervention, 25% developed CIN. Patient-related risk factors comprised of hypertension, diabetes mellitus, NYHA class, proteinuria, serum creatinine > 1.5 mg/dl and ejection fraction ≤ 35%. Contrast-related risk factors comprised of contrast media volume > 300 ml, contrast media type. However, our final model demonstrated that only hypertension [Hazard ratio (HR = 2.89, 95% confidence intrval (CI = 1.78 to 4.71, P = 0.000], diabetes mellitus (HR = 3.09, 95% CI = 1.89 to 5.06, P = 0.000, ejection fraction (EF ≤ 35% (HR = 2.92; 95% CI = 1.72 to 4.96; P = 0.000, total contrast volume > 300 ml (HR = 7.73; 95% CI = 3.09 to 19.37; P = 0.000 and proteinuria (HR = 14.96; 95% CI = 3.45 to 64.86; P = 0.000 were independent risk factors of CIN. In conclusion, CIN developed in 25% of patients undergoing coronary intervention. The independent risk factors of CIN included hypertension, diabetes mellitus, EF ≤ 35%, contrast volume > 300 ml and proteinuria. (Med J Indones 2008; 17: 131-7Keywords: contrast induced nephropathy, coronary intervention

  19. Report: Fourth International Conference on Gas Hydrates, held at Yokohama, Japan, 19-23 May 2002

    Digital Repository Service at National Institute of Oceanography (India)

    Karisiddaiah, S.M.

    formations, while Dr. L. Stern presented ne insights into the phenomena of anomalous or self- preservation of gas hydrates. JOUR.GEOL.SOC.INDIA, VOL.61, JAN. 2001 Posters on hydrate formation and prevention in pipelines and hydrate based...-1 REPORT ON THE 4TH INTERNATIONAL CONFERENCE ON GAS HYDRATES The fourth International Conference on Gas Hydrates was recently held at Yokohama, Japan, between 19-23 May 2002 following the earlier conferences held in USA (1993...

  20. Contrast-induced acute kidney injury in children with cardiovascular defects – results of a pilot study

    Directory of Open Access Journals (Sweden)

    Daria Tomczyk

    2016-12-01

    Full Text Available Introduction: Contrast-induced nephropathy – acute kidney injury is an acquired kidney injury that is an important factor in short- and long-term cardiovascular complications. Contrast-induced nephropathy – acute kidney injury continues to be diagnosed based on serum creatinine level. Serum creatinine, however, is a delayed indicator of contrast-induced nephropathy, as its levels typically peak between 1 and 3 days following contrast exposure. Currently, more sensitive biomarkers of kidney injury are sought, with human neutrophil lipocalin (also known as neutrophil gelatinase-associated lipocalin highlighted in literature as a troponin-like biomarker of early nephropathy. Aim of the study: Changes in serum and urine neutrophil gelatinase-associated lipocalin levels were assessed in children with congenital heart diseases, following a scheduled cardiac catheterization procedure. Material and methods: The group studied comprised 16 patients. The neutrophil gelatinaseassociated lipocalin and creatinine levels, along with urine and serum neutrophil gelatinase-associated lipocalin/creatinine ratio were evaluated five times at different time intervals from the procedure. The group did not vary in respect of kidney function, preprocedure management, and volume expansion (hydration therapy prior to the procedure. Results: In the assessed material, median neutrophil gelatinase-associated lipocalin rose as early as 2 hours after exposure to contrast as compared with baseline [median = 28.2 ng/mL (Quartile 1 = 22.8 – Quartile 3 = 33.77 vs. median = 25.87 ng/mL (Quartile 1 = 19.4 – Quartile 3 = 29.6]. Serum neutrophil gelatinase-associated lipocalin level peaked in hour 6 of our study: median – 30.6 ng/mL (Quartile 1 = 22.32 – Quartile 3 = 42.17, then reverting to normal. Urine neutrophil gelatinaseassociated lipocalin peaked in hour 24 of the study, subsequently dropping below baseline in hour 48

  1. Basics of development of gas hydrate deposits

    Energy Technology Data Exchange (ETDEWEB)

    Makogon, Yuri F.; Holditch, Stephen A.; Makogon, Taras Y.

    2005-07-01

    Natural gas hydrate deposits could possibly be an important energy resource during this century. However, many problems associated with producing these deposits must first be solved. The industry must develop new technologies to produce the gas, to forecast possible tectonic cataclysms in regions of gas hydrate accumulations, and to prevent damage to the environment. These global issues must be addressed by every company or country who wants to produce gas hydrate deposits. Cooperative research between industry and universities can lead to technology breakthroughs in coming years. This paper reviews the Messoyakha field and the Blake Ridge and Nankai areas to explain a methodology for estimating how much gas might be producible from gas hydrate deposits (GHDs) under various conditions. The Messoyakha field is located on land, while the Blake Ridge and Nankai areas are offshore. Messoyakha is the first and the only GHD where gas production from hydrates has reached commercial flow rates. The Blake Ridge GHD has been studied for 20 years and 11 wells have been drilled to collect gas-hydrate samples. The potential resources of gas (gas in place) from Blake Ridge is estimated at 37.7Oe10{sup 12} m{sup 3} (1.330 Tcf) in hydrate form and 19.3Oe10{sup 12}m{sup 3} (681 Bcf) [5] in free gas. To estimate how much of the potential resource can be produced we need a thorough understanding of both the geologic and the thermodynamic characteristics of the formations. (Author)

  2. Contrast induced nephropathy in hypertensive patients after elective percutaneous coronary intervention

    Science.gov (United States)

    Aryfa Andra, Cut; Khairul, Andi; Aria Arina, Cut; Mukhtar, Zulfikri; Nyak Kaoy, Isfanuddin

    2018-03-01

    Contrast induced nephropathy (CIN) is the third lead cause of hospital acquired renal failure and was associated with significant morbidity and mortality. We hypothesized that hypertension is an independent risk factor for the development of CIN in patients undergoing elective percutaneous coronary intervention (PCI). The case-control method was used, 138 patients scheduled for elective PCI. We measured serum creatinine at baseline and after 24 hours of the procedure. CIN was defined as arising in serum creatinine of at least 44 μmol/l (0,5 mg/dl) or 25% rise from baseline. All patients received low osmolality nonionic contrast during PCI. Hypertension was defined as self-reported a history of treated or untreated diagnosed high blood pressure. One hundred thirty-eight patients (74,6%) were male, and 35 patients (25,4%) were female. Among the 138 patients, 86 (62,3%) were hypertensive patients whereas 52 (37,7%) were nonhypertensive patients. There was no difference in baseline serum creatinine levels and the amount of contrast media in patient with and without CIN. CIN developed in 42 patients, 39 patients (92,9%) were hypertensive compared to 3 patients (7,1%) without hypertension with p value < 0,05. (Odds ratio 16,8, 95% CI 4.542 - 62,412). This study showed that hypertension was a risk factor for the development of CIN

  3. Incidence of contrast-induced nephropathy in hospitalised patients with cancer

    Energy Technology Data Exchange (ETDEWEB)

    Cicin, Irfan; Erdogan, Bulent; Gulsen, Emrah; Uzunoglu, Sernaz; Kodaz, Hilmi [Trakya University, Department of Medical Oncology, Faculty of Medicine, Edirne (Turkey); Sut, Necdet [Trakya University, Department of Biostatistics, Faculty of Medicine, Edirne (Turkey); Turkmen, Esma [Trakya University, Department of Medical Oncology, Faculty of Medicine, Edirne (Turkey); Trakya Ueniversitesi Hastanesi Medikal Onkoloji Bilim Dali, Edirne (Turkey); Ustundag, Sedat [Trakya University, Department of Nephrology, Faculty of Medicine, Edirne (Turkey)

    2014-01-15

    To determine the frequency of and possible factors related to contrast-induced nephropathy (CIN) in hospitalised patients with cancer. Ninety adult patients were enrolled. Patients with risk factors for acute renal failure were excluded. Blood samples were examined the day before contrast-enhanced computed tomography (CT) and serially for 3 days thereafter. CIN was defined as an increase in serum creatinine (Cr) of 0.5 mg/dl or more, or elevation of Cr to 25 % over baseline. Relationships between CIN and possible risk factors were investigated. CIN was detected in 18/90 (20 %) patients. CIN developed in 25.5 % patients who underwent chemotherapy and in 11 % patients who did not (P = 0.1). CIN more frequently developed in patients who had undergone CT within 45 days after the last chemotherapy (P = 0.005); it was also an independent risk factor (P = 0.017). CIN was significantly more after treatment with bevacizumab/irinotecan (P = 0.021) and in patients with hypertension (P = 0.044). The incidence of CIN after CT in hospitalised oncological patients was 20 %. CIN developed 4.5-times more frequently in patients with cancer who had undergone recent chemotherapy. Hypertension and the combination of bevacizumab/irinotecan may be additional risk factors for CIN development. (orig.)

  4. Lansoprazole halts contrast induced nephropathy through activation of Nrf2 pathway in rats.

    Science.gov (United States)

    Khaleel, Sahar A; Alzokaky, Amany A; Raslan, Nahed A; Alwakeel, Asmaa I; Abd El-Aziz, Heba G; Abd-Allah, Adel R

    2017-05-25

    Contrast-induced nephropathy (CIN) is an important cause of acute kidney injury characterized by significant mortality and morbidity. To date, there is no successful protective regimen for CIN especially in poor kidney function patients. Lansoprazole has been shown to exert antioxidant action through induction of nuclear factor-erythroid 2-related factor 2 (Nrf2) pathway. The aim of the present study is to investigate the potential of lansoprazole to activate Nrf2 pathway in the kidney and consequently to protect against oxidative stress induced by iodinated contrast media. Lansoprazole, at a dose of 100 mg/kg, showed a significant induction of Nrf2 mRNA after 3 h. Administration of contrast media induced significant increase in serum creatinine and blood urea nitrogen, histological deterioration, and reduction in total antioxidant capacity. Moreover, it instigated the defensive Nrf2 gene expression and immunoreactivity. In addition, there were overexpression of HO-1, caspase 3, p53 and IL6 genes and downregulation of Bcl2 gene. Pre-treatment with lansoprazole (100 mg/kg) ameliorated the nephrotoxicity parameters and oxidative stress, improved histological lesions, and hijacked apoptotic and inflammatory markers that were provoked by contrast media. In conclusion, lansoprazole attenuates experimental CIN which might be due to activation of Nrf2 antioxidant defence pathway. These findings highlight the potential benefit of incorporating lansoprazole in the protective regimen against CIN especially for susceptible patients. Copyright © 2017 Elsevier B.V. All rights reserved.

  5. Contrast-Induced Nephropathy Is Less Common in Patients with Good Coronary Collateral Circulation.

    Science.gov (United States)

    Avci, Eyup; Yildirim, Tarik; Kadi, Hasan

    2017-10-01

    Contrast-induced nephropathy (CIN) is a typically reversible type of acute renal failure that develops after exposure to contrast agents; underlying endothelial dysfunction is thought to be an important risk factor for CIN. Although the mechanism of coronary collateral circulation (CCC) is not fully understood, a pivotal role of the endothelium has been reported in many studies. The aim of this study was to investigate whether there is a relationship between CCC and CIN. Patients with at least one occluded major coronary artery and blood creatinine analyses performed before and on the second day after angiography were included in the study. CIN was defined as a 25% or greater elevation of creatinine on the second day after exposure to the contrast agent. Collateral grading was performed according to the Rentrop classification. Patients were grouped according to whether they developed CIN or not, i.e., CIN(-) and CIN(+) group. A total of 214 patients who met the inclusion criteria were included in the study. CIN was diagnosed in 43 patients (20.1%) in the study population. Good CCC was identified in 112 patients (65.5%) in the CIN(-) group, whereas it was identified in 13 patients (30.2%) in the CIN(+) group. In the CIN(-) group, good CCC was significantly more frequent ( p Good collateral circulation was associated with a lower frequency of CIN, and poor collateral circulation was an independent predictor of CIN.

  6. Gas hydrate in nature

    Science.gov (United States)

    Ruppel, Carolyn D.

    2018-01-17

    Gas hydrate is a naturally occurring, ice-like substance that forms when water and gas combine under high pressure and at moderate temperatures. Methane is the most common gas present in gas hydrate, although other gases may also be included in hydrate structures, particularly in areas close to conventional oil and gas reservoirs. Gas hydrate is widespread in ocean-bottom sediments at water depths greater than 300–500 meters (m; 984–1,640 feet [ft]) and is also present in areas with permanently frozen ground (permafrost). Several countries are evaluating gas hydrate as a possible energy resource in deepwater or permafrost settings. Gas hydrate is also under investigation to determine how environmental change may affect these deposits.

  7. Gas hydrate nucleation

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-12-31

    The overall aim of the project was to gain more knowledge about the kinetics of gas hydrate formation especially the early growth phase. Knowledge of kinetics of gas hydrate formation is important and measurements of gas hydrate particle size and concentration can contribute to improve this knowledge. An experimental setup for carrying out experimental studies of the nucleation and growth of gas hydrates has been constructed and tested. Multi wavelength extinction (MWE) was the experimental technique selected for obtaining particle diameter and concentration. The principle behind MWE is described as well as turbidity spectrum analysis that in an initial stage of the project was considered as an alternative experimental technique. Details of the experimental setup and its operation are outlined. The measuring cell consists of a 1 litre horizontal tube sustaining pressures up to 200 bar. Laser light for particle size determination can be applied through sapphire windows. A description of the various auxiliary equipment and of another gas hydrate cell used in the study are given. A computer program for simulation and analysis of gas hydrate experiments is based on the gas hydrate kinetics model proposed by Skovborg and Rasmussen (1993). Initial measurements showed that knowledge of the refractive index of gas hydrates was important in order to use MWE. An experimental determination of the refractive index of methane and natural gas hydrate is described. The test experiments performed with MWE on collectives of gas hydrate particles and experiments with ethane, methane and natural gas hydrate are discussed. Gas hydrate particles initially seem to grow mainly in size and at latter stages in number. (EG) EFP-94; 41 refs.

  8. Gas hydrate nucleation

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-12-31

    The overall aim of the project was to gain more knowledge about the kinetics of gas hydrate formation especially the early growth phase. Knowledge of kinetics of gas hydrate formation is important and measurements of gas hydrate particle size and concentration can contribute to improve this knowledge. An experimental setup for carrying out experimental studies of the nucleation and growth of gas hydrates has been constructed and tested. Multi wavelength extinction (MWE) was the experimental technique selected for obtaining particle diameter and concentration. The principle behind MWE is described as well as turbidity spectrum analysis that in an initial stage of the project was considered as an alternative experimental technique. Details of the experimental setup and its operation are outlined. The measuring cell consists of a 1 litre horizontal tube sustaining pressures up to 200 bar. Laser light for particle size determination can be applied through sapphire windows. A description of the various auxiliary equipment and of another gas hydrate cell used in the study are given. A computer program for simulation and analysis of gas hydrate experiments is based on the gas hydrate kinetics model proposed by Skovborg and Rasmussen (1993). Initial measurements showed that knowledge of the refractive index of gas hydrates was important in order to use MWE. An experimental determination of the refractive index of methane and natural gas hydrate is described. The test experiments performed with MWE on collectives of gas hydrate particles and experiments with ethane, methane and natural gas hydrate are discussed. Gas hydrate particles initially seem to grow mainly in size and at latter stages in number. (EG) EFP-94; 41 refs.

  9. Coronary artery calcification scores improve contrast-induced nephropathy risk assessment in chronic kidney disease patients.

    Science.gov (United States)

    Osugi, Naohiro; Suzuki, Susumu; Shibata, Yohei; Tatami, Yosuke; Harata, Shingo; Ota, Tomoyuki; Hayashi, Mutsuharu; Yasuda, Yoshinari; Ishii, Hideki; Shimizu, Atsuya; Murohara, Toyoaki

    2017-06-01

    Coronary artery calcification (CAC) is an independent predictor of cardiovascular morbidity and mortality in chronic kidney disease (CKD) patients. The aim of the present study was to evaluate the predictive value of CAC scores for the incidence of contrast-induced nephropathy (CIN) after cardiac catheterization in non-dialyzed CKD patients. The present study evaluated a total of 140 CKD patients who underwent cardiac catheterization. Patients were stratified into two groups based on the optimal cut-off value of the CAC score, which was graded by a non-triggered, routine diagnostic chest computed tomography scan: CAC score ≥8 (high CAC group); and CAC score 10 % in the baseline serum cystatin C level at 24 h after contrast administration. The mean estimated glomerular filtration rate levels were 41.1 mL/min/1.73 m 2 , and the mean contrast dose administered was 37.5 mL. Patients with high CAC scores exhibited a higher incidence of CIN than patients with low CAC scores (25.5 vs. 3.2 %, p < 0.001). After multivariate adjustment for confounders, the CAC score predicted CIN (odds ratio 1.68, 95 % confidence interval 1.28-2.21, p < 0.001). Moreover, the C-index for CIN prediction significantly increased when the CAC scores were added to the Mehran risk score (0.855 vs. 0.760, p = 0.023). CAC scores, as evaluated using semi-quantitative methods, are a simple and powerful predictor of CIN. Incorporating the CAC score in the Mehran risk score significantly improved the predictive ability to predict CIN incidence.

  10. A comparison of definitions of contrast-induced nephropathy in patients with normal serum creatinine

    Directory of Open Access Journals (Sweden)

    Mohammad Reza Khatami

    2016-01-01

    Full Text Available Contrast-induced nephropathy (CIN is the third leading cause of acute kidney injury in hospitalized patients. The prevalence of CIN is reported to range from 0% to 50%, depending not only on patient condition and the procedure used but also the definition of CIN applied. We aimed to determine the best diagnostic indicator of CIN in patients with normal serum creatinine. This study included 206 patients with normal serum creatinine who underwent coronary angiography/angioplasty. Serum creatinine level and glomerular filtration rate (GFR were measured before and on the second and fifth days after contrast administration. The incidence of CIN based on a 25% increase in serum creatinine was calculated and compared with the incidence based on a 25% decrease in GFR or an increase of at least 0.5 mg/dL in serum creatinine. Of 206 patients, 127 were male (61.7% and 79 were female (38.3%; the mean age was 59.56 ± 10.3 years. The prevalence of CIN was 30% based on a 25% increase in serum creatinine, 23% based on a 25% decrease in GFR (P <0.012 and 3.8% based on a serum creatinine increase of at least 0.5 mg/dL (P <0.0001. The serum creatinine levels remained within the normal range in the majority of patients with CIN based on the different definitions. In patients with normal serum creatinine, the absolute increase in serum creatinine may describe the prevalence of CIN more accurately than the relative increase in serum creatinine or relative decrease in GFR.

  11. The potential use of biomarkers in predicting contrast-induced acute kidney injury

    Directory of Open Access Journals (Sweden)

    Andreucci M

    2016-09-01

    Full Text Available Michele Andreucci,1 Teresa Faga,1 Eleonora Riccio,2 Massimo Sabbatini,2 Antonio Pisani,2 Ashour Michael,1 1Department of Health Sciences, University “Magna Graecia” of Catanzaro, Catanzaro, 2Department of Public Health, University of Naples Federico II, Naples, Italy Abstract: Contrast-induced acute kidney injury (CI-AKI is a problem associated with the use of iodinated contrast media, causing kidney dysfunction in patients with preexisting renal failure. It accounts for 12% of all hospital-acquired kidney failure and increases the length of hospitalization, a situation that is worsening with increasing numbers of patients with comorbidities, including those requiring cardiovascular interventional procedures. So far, its diagnosis has relied upon the rise in creatinine levels, which is a late marker of kidney damage and is believed to be inadequate. Therefore, there is an urgent need for biomarkers that can detect CI-AKI sooner and more reliably. In recent years, many new biomarkers have been characterized for AKI, and these are discussed particularly with their use in known CI-AKI models and studies and include neutrophil gelatinase-associated lipocalin, cystatin C (Cys-C, kidney injury molecule-1, interleukin-18, N-acetyl-β-d-glucosaminidase, and L-type fatty acid-binding protein (L-FABP. The potential of miRNA and metabolomic technology is also mentioned. Early detection of CI-AKI may lead to early intervention and therefore improve patient outcome, and in future any one or a combination of several of these markers together with development in technology for their analysis may prove effective in this respect. Keywords: radiocontrast media, acute renal failure, markers, renal injury

  12. A novel approach to contrast-induced nephrotoxicity: the melatonergic agent agomelatine

    Science.gov (United States)

    Karaman, Adem; Diyarbakir, Busra; Kose, Duygu; Özbek-Bilgin, Asli; Topcu, Atilla; Gundogdu, Cemal; Durur-Karakaya, Afak; Bayraktutan, Zafer; Alper, Fatih

    2016-01-01

    Objective: To study the potential nephroprotective role of agomelatine in rat renal tissue in cases of contrast-induced nephrotoxicity (CIN). The drug's action on the antioxidant system and proinflammatory cytokines, superoxide dismutase (SOD) activity, levels of glutathione (GSH) and malondialdehyde (MDA) and the gene expression of interleukin-6 (IL-6), tumour necrosis factor (TNF)-α and nuclear factor kappa B (NF-κB) was measured. Tubular necrosis and hyaline and haemorrhagic casts were also histopathologically evaluated. Methods: The institutional ethics and local animal care committees approved the study. Eight groups of six rats were put on the following drug regimens: Group 1: healthy controls, Group 2: GLY (glycerol), Group 3: CM (contrast media—iohexol 10 ml kg−1), Group 4: GLY+CM, Group 5: CM+AGO20 (agomelatine 20 mg kg−1), Group 6: GLY+CM+AGO20, Group 7: CM+AGO40 (agomelatine 40 mg kg−1) and Group 8: GLY+CM+AGO40. The groups were evaluated by one-way analysis of variance and Duncan's multiple comparison test. Results: Agomelatine administration significantly improved the serum levels of blood urea nitrogen (BUN) and creatinine, SOD activity, GSH and MDA. The use of agomelatine had substantial downregulatory consequences on TNF-α, NF-κB and IL-6 messenger RNA levels. Mild-to-severe hyaline and haemorrhagic casts and tubular necrosis were observed in all groups, except in the healthy group. The histopathological scores were better in the agomelatine treatment groups. Conclusion: Agomelatine has nephroprotective effects against CIN in rats. This effect can be attributed to its properties of reducing oxidative stress and inhibiting the secretion of proinflammatory cytokines (NF-κB, TNF-α and IL-6). Advances in knowledge: CIN is one of the most important adverse effects of radiological procedures. Renal failure, diabetes, malignancy, old age and non-steroidal anti-inflammatory drug use pose the risk of CIN in patients. Several

  13. Detection of Occupancy Differences in Methane Gas Hydrates by Raman Spectroscopy

    DEFF Research Database (Denmark)

    Hansen, Susanne Brunsgaard; Berg, Rolf W.; Stenby, Erling Halfdan

    2004-01-01

    of reservoir fluids due to plugging. Methods to prevent hydrate formation are in use, e.g. by injection of inhibitors. From environmental and security points of view an easy way to detect hydrate formation is of interest. We have tried to detect methane hydrate formation by use of Raman spectroscopy....

  14. Hydration rate of obsidian.

    Science.gov (United States)

    Friedman, I; Long, W

    1976-01-30

    The hydration rates of 12 obsidian samples of different chemical compositions were measured at temperatures from 95 degrees to 245 degrees C. An expression relating hydration rate to temperature was derived for each sample. The SiO(2) content and refractive index are related to the hydration rate, as are the CaO, MgO, and original water contents. With this information it is possible to calculate the hydration rate of a sample from its silica content, refractive index, or chemical index and a knowledge of the effective temperature at which the hydration occurred. The effective hydration temperature can be either measured or approximated from weather records. Rates have been calculated by both methods, and the results show that weather records can give a good approximation to the true EHT, particularly in tropical and subtropical climates. If one determines the EHT by any of the methods suggested, and also measures or knows the rate of hydration of the particular obsidian used, it should be possible to carry out absolute dating to +/- 10 percent of the true age over periods as short as several years and as long as millions of years.

  15. A randomized controlled trial comparing hydration therapy to additional hemodialysis or N-acetylcysteine for the prevention of contrast medium-induced nephropathy: the Dialysis-versus-Diuresis (DVD) Trial.

    Science.gov (United States)

    Reinecke, H; Fobker, M; Wellmann, J; Becke, B; Fleiter, J; Heitmeyer, C; Breithardt, G; Hense, H-W; Schaefer, R M

    2007-03-01

    Contrast medium-induced nephropathy (CIN) is a serious complication with increasing frequency and an unfavorable prognosis. Previous analyses of surrogate parameters have suggested beneficial effects of hemodialysis that are assessed in this randomized clinical trial. We performed a prospective single-center trial in 424 consecutive patients with serum creatinine concentrations between 1.3- 3.5 mg/dl who underwent elective coronary angiography. Patients were randomized to one of three treatment strategies with all patients receiving pre- and postprocedural hydration: One group received no additional therapy, patients in the second group were hemodialyzed once, and the third group received oral N-acetylcysteine. The frequency of CIN (defined as an increase in serum creatinine>or=0.5 mg/dl) from 48 to 72 h after catheterization was 6.1% in the hydration-only group, 15.9% with hemodialysis treatment, and 5.3% in the N-ACC group (intention-to-treat analysis; P=0.008). There were no differences between the treatment groups with regard to increased (>or=0.5 mg/dl) serum creatinine concentrations after 30-60 days (4.8%, 5.1%, and 3.1%, respectively; P=0.700). Analyses of long-term follow-up (range 63 to 1316 days) by Cox regressions models of the study groups found quite similar survival rates (P=0.500). In contrast to other (retrospective) studies, long-term survival of patients with vs those without CIN within 72 h was not different, but patients who still had elevated creatinine concentrations at 30-60 days suffered from a markedly higher 2-year mortality (46% vs 17%, P=0.002). In conclusion, hemodialysis in addition to hydration therapy for the prevention of CIN provided no evidence for any outcome benefit but evidence for probable harm. Increased creatinine concentrations at 30-60 days, but not within 72 h, were associated with markedly reduced long-term survival.

  16. Topological modeling of methane hydrate crystallization from low to high water cut emulsion systems

    OpenAIRE

    Melchuna , Aline; Cameirão , Ana; Herri , Jean-Michel; Glénat , Philippe

    2016-01-01

    International audience; Hydrate formation and remediation in oil flowlines facilities represent a major concern for oil industry in respect of capital and operational costs. It is necessary to have a better understanding on the hydrate formation process to be more efficient in hydrate prevention, especially in respect to additive dosage. This work is a contribution to enhance the knowledge of hydrate formation at high water cuts, by introducing new techniques of analysis in the Archimede flow...

  17. The Effect of Hyperuricemia on the Rate of Contrast-Induced Nephropathy in Patients with Coronary Angiography

    Directory of Open Access Journals (Sweden)

    Hossein Vakili

    2016-10-01

    Full Text Available Introduction: There is little information about the relationship between hyperuricemia and contrast induced nephropathy. The present study aimed to evaluate the relationship between hyperuricemia and contrast induced nephropathy among patients, who had undergone coronary angiography.Methods: In the current study, 200 consecutive patients with coronary artery disease, who underwent coronary angiography in Modarres hospital, were enrolled. According to the available data, the upper limit normal level of uric acid was defined as 7 mg/dl in males and 6.5 mg/dl in females. By increasing level of serum creatinine to 0.5 mg/dl (or 25% enhancement from basic level of creatinine during 48 hours of introduction of contrast agent, diagnosis of Contrast Induced Nephropathy (CIN was established. The relationship between hyperuricemia and CIN was then assessed.Results: There is a significant difference between normouricemic patients and hyperuricemic patients, in aspect of weight (P = 0.011 and uric acid (P = 0.001; however, other quantitative and qualitative variables including age, volume of contract agent, creatinine level after angiography, hemoglobin level, gender, arterial access type, number of involved vessels, were insignificant between the two groups (P > 0.05. Moreover, as an essential finding, CIN was shown in 9% of normouricemic patients and 10% of hyperuricemic  patients with no significant difference between the two groups (P = 0.6.Conclusions: Our study suggests that hyperuricemia may not significantly increase the rate of the contrast-induced nephropathy in patients, who had undergone angiography

  18. Methane Hydrates: Chapter 8

    Science.gov (United States)

    Boswell, Ray; Yamamoto, Koji; Lee, Sung-Rock; Collett, Timothy S.; Kumar, Pushpendra; Dallimore, Scott

    2008-01-01

    Gas hydrate is a solid, naturally occurring substance consisting predominantly of methane gas and water. Recent scientific drilling programs in Japan, Canada, the United States, Korea and India have demonstrated that gas hydrate occurs broadly and in a variety of forms in shallow sediments of the outer continental shelves and in Arctic regions. Field, laboratory and numerical modelling studies conducted to date indicate that gas can be extracted from gas hydrates with existing production technologies, particularly for those deposits in which the gas hydrate exists as pore-filling grains at high saturation in sand-rich reservoirs. A series of regional resource assessments indicate that substantial volumes of gas hydrate likely exist in sand-rich deposits. Recent field programs in Japan, Canada and in the United States have demonstrated the technical viability of methane extraction from gas-hydrate-bearing sand reservoirs and have investigated a range of potential production scenarios. At present, basic reservoir depressurisation shows the greatest promise and can be conducted using primarily standard industry equipment and procedures. Depressurisation is expected to be the foundation of future production systems; additional processes, such as thermal stimulation, mechanical stimulation and chemical injection, will likely also be integrated as dictated by local geological and other conditions. An innovative carbon dioxide and methane swapping technology is also being studied as a method to produce gas from select gas hydrate deposits. In addition, substantial additional volumes of gas hydrate have been found in dense arrays of grain-displacing veins and nodules in fine-grained, clay-dominated sediments; however, to date, no field tests, and very limited numerical modelling, have been conducted with regard to the production potential of such accumulations. Work remains to further refine: (1) the marine resource volumes within potential accumulations that can be

  19. Atorvastatin attenuates experimental contrast-induced acute kidney injury: a role for TLR4/MyD88 signaling pathway.

    Science.gov (United States)

    Yue, Rongzheng; Zuo, Chuan; Zeng, Jing; Su, Baihai; Tao, Ye; Huang, Songmin; Zeng, Rui

    2017-11-01

    To investigate the protective effect of different atorvastatin doses on contrast-induced acute kidney injury and the related mechanism. Healthy male Sprague-Dawley (SD) rats were randomly divided into the blank control group, experimental control group and different-dose atorvastatin groups. A rat model of contrast-induced acute kidney injury was established. We detected changes in serum creatinine (Scr) and blood urea nitrogen (BUN) before and after model establishment, observed and scored renal tubular injury, analyzed rat renal cell apoptosis, and measure the expression of signal pathway proteins and downstream inflammatory factors. After contrast agent injection, the Scr and BUN levels of the experimental control group were significantly increased, the different doses applied in the atorvastatin group significantly reduced the Scr and BUN levels (p atorvastatin doses have protective effects on contrast-induced acute renal tubular injury in rats, possibly by targeting TLR4, suppressing TLR4 expression, regulating the TLR4/Myd88 signaling pathway, and inhibiting the expression of downstream inflammatory factors.

  20. Atorvastatin attenuates contrast-induced nephropathy by modulating inflammatory responses through the regulation of JNK/p38/Hsp27 expression

    Directory of Open Access Journals (Sweden)

    Xuyu He

    2016-05-01

    Our study demonstrates that high-dosage atorvastatin treatment attenuates both the inflammatory processes and apoptosis in contrast-induced acute kidney injury, and that the JNK/p38 MAPK pathway participates in the contrast-induced apoptosis of renal tubular cells. Finally, atorvastatin reduces CIN by suppression of apoptosis, which may be through inhibition of JNK/p38 MAPK pathways.

  1. THz characterization of hydrated and anhydrous materials

    Science.gov (United States)

    Sokolnikov, Andre

    2011-06-01

    The characterization of anhydrous and hydrated forms of materials is of great importance to science and industry. Water content poses difficulties for successful identification of the material structure by THz radiation. However, biological tissues and hydrated forms of nonorganic substances still may be investigated by THz radiation. This paper outlines the range of possibilities of the above characterization, as well as provides analysis of the physical mechanism that allows or prevents penetration of THz waves through the substance. THz-TDS is used to measure the parameters of the characterization of anhydrous and hydrated forms of organic and nonorganic samples. Mathematical methods (such as prediction models of time-series analysis) are used to help identifying the absorption coefficient and other parameters of interest. The discovered dependencies allow designing techniques for material identification/characterization (e.g. of drugs, explosives, etc. that may have water content). The results are provided.

  2. Irrigation port hydration in phacoemulsification surgery

    Directory of Open Access Journals (Sweden)

    Suzuki H

    2018-01-01

    Full Text Available Hisaharu Suzuki,1 Yoichiro Masuda,2 Yuki Hamajima,1 Hiroshi Takahashi3 1Department of Ophthalmology, Nippon Medical School Musashikosugi Hospital, Kawasaki City, Kanagawa, 2Department of Ophthalmology, The Jikei University, Katsushika Medical Center, Tokyo, 3Department of Ophthalmology, Nippon Medical School, Tokyo, Japan Background: In most cases, hydration is performed by water injection into the stromal tissue with a needle. The technique is simple, however it is sometimes troublesome.Purpose: We describe a simple technique for hydrating the corneal stroma in cataract surgery using an irrigation port.Patients and methods: The technique began by pushing the irrigation port against the corneal stroma for a few seconds during phacoemulsification, which generated edema in the corneal incision that subsequently prevented leakage. This procedure is called the hydration using irrigation port (HYUIP technique. A total of 60 eyes were randomized and placed in two groups, 30 eyes underwent surgeries using the HYUIP technique (HYUIP group and 30 eyes underwent surgeries without the HYUIP technique (control. The three points evaluated during each surgery included 1 the occurrence of anterior chamber collapse during the pulling out of the I/A tip after inserting the intraocular lens, 2 the need for conventional hydration, and 3 watertight completion at the end stage of surgery.Results: The anterior chamber collapse and the need for conventional hydration were significantly smaller in the HYUIP group compared to the control group. Regarding the self-sealing completion, no significant difference was observed between the two groups.Conclusion: The HYUIP technique is an effective method for creating self-sealing wound. In addition, this technique helps to prevent anterior chamber collapse. Keywords: cataract surgery, hydration, irrigation and aspiration, phacoemulsification, wound, self-sealing 

  3. Lack of Serum Creatinine Decrease After Coronary Angiography Despite Prophylactic Hydration After Routine Coronary Angiography/Angioplasty in Stable Angina Patients--Pilot Study.

    Science.gov (United States)

    Burchardt, Pawel; Rzezniczak, Janusz; Synowiec, Tomasz; Angerer, Dariusz; Palasz, Anna; Zurawski, Jakub

    2016-01-01

    To prevent contrast induced renal dysfunction a periprocedural prophylactic hydration is applied. Due to dilution it should cause a drop in serum creatinine concentration (SCR). Surprisingly, no reduction in SCR after contrast admission is found in up to 25% of patients as early as 12-18 hours after coronary angiography/angioplasty. This study aims to find a clinical explanation as well as predict circumstances for this phenomenon. Retrospective clinical and laboratory data was used from 341 patients who underwent elective coronary angiography/angioplasty, received a prophylactic hydration, and had serum creatinine concentration measured prior to, and 12-18 hours after invasive procedure with iodine contrast administration. To exclude an improper hydration due to no creatinine decrease, the number of red blood cells was analysed as well as hemoglobin and hematocrit in blood donations collected during the study time points. The resulting lack of serum creatinine reduction could be explained by dehydration (measured by increase in number of RBC, HGB and HCT) only in 13.5% , 10.8%, and 20% of cases, respectively. Any form of abnormal glucose metabolism combined with either baseline serum creatinine concentration creatinine clearance >86.77 mL/min, or GFR by CKD EPI >80.08 mL/min/1.73 m2, or GFR by MDRD >74.48 mL/min/1.73 m2 were the predictors for no creatinine decrease at outcome. Additionally, it was demonstrated that the lack of creatinine decrease was more often observed among those patients whose initial renal function was better than in the subjects with reduction of SCR. This observation requires further prospective investigation on extended group of patients. © 2016 The Author(s) Published by S. Karger AG, Basel.

  4. Experimental Investigation into the Combustion Characteristics of Propane Hydrates in Porous Media

    Directory of Open Access Journals (Sweden)

    Xiang-Ru Chen

    2015-02-01

    Full Text Available The combustion characteristics of both pure propane hydrates and the mixtures of hydrates and quartz sands were investigated by combustion experiments. The flame propagation, flame appearance, burning time and temperature in different hydrate layers were studied. For pure propane hydrate combustion, the initial flame falls in the “premixed” category. The flame propagates very rapidly, mainly as a result of burnt gas expansion. The flame finally self-extinguishes with some proportion of hydrates remaining unburned. For the hydrate-sand mixture combustion, the flame takes the form of many tiny discontinuous flames appearing and disappearing at different locations. The burn lasts for a much shorter amount of time than pure hydrate combustion. High porosity and high hydrate saturation is beneficial to the combustion. The hydrate combustion is the combustion of propane gas resulting from the dissociation of the hydrates. In both combustion test scenarios, the hydrate-dissociated water plays a key role in the fire extinction, because it is the main resistance that restrains the heat transfer from the flame to the hydrates and that prevents the hydrate-dissociated gas from releasing into the combustion zone.

  5. Contrast-induced enphropathy in patients undergoing intravenous contrast-enhanced computed tomography in Korea; A multi-institutional study in 101487 patients

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Joong Yub [Medical Research Collaborating Center, Seoul National University Hospital, Seoul National University College of Medicine, Seoul (Korea, Republic of); Cho, Jeong Yeon [Dept. of Radiology, Seoul National University College of Medicine, Seoul (Korea, Republic of); Jeong, Yong Yeon [Dept. of Radiology, Chonnam National University Hwasun Hospital, Chonnam National University Medical School, Hwasun (Korea, Republic of); and others

    2014-08-15

    To evaluate the prevalence of known risk factors for contrast-induced nephropathy (CIN) and their association with the actual occurrence of CIN in patients undergoing intravenous contrast-enhanced computed tomography (CECT) in Korea. Patients who underwent CECT in 2008 were identified in the electronic medical records of 16 tertiary hospitals of Korea. Data on demographics, comorbidities, prescriptions and laboratory test results of patients were collected following a standard data extraction protocol. The baseline renal function was assessed using the estimated glomerular filtration rate (eGFR). We identified the prevalence of risk factors along the eGFR strata and evaluated their influence on the incidence of CIN, defined as a 0.5 mg/dL or 25% increase in serum creatinine after CECT. Of 432425 CECT examinations in 272136 patients, 140838 examinations in 101487 patients met the eligibility criteria for analysis. The mean age of the participants was 57.9 ± 15.5 years; 25.1% of the patients were older than 70 years. The prevalence of diabetes mellitus was 11.9%, of hypertension 13.7%, of gout 0.55% and of heart failure was 1.7%. Preventive measures were used in 40238 CECT examinations (28.6%). The prevalence of risk factors and use of preventive measures increased as the renal function became worse. A CIN was occurred after 3103 (2.2%) CECT examinations, revealing a significant association with decreased eGFR, diabetes mellitus, and congestive heart failure after adjustment. Risk factors for CIN are prevalent among the patients undergoing CECT. Preventive measures were seemingly underutilized and a system is needed to improve preventive care.

  6. Preventing Pressure Sores

    Medline Plus

    Full Text Available ... L Sarah Harrison, OT Anne Bryden, OT The Role of the Social Worker after Spinal Cord Injury ... do to prevent pressure sores? play_arrow What role does diet and hydration play in preventing pressure ...

  7. HYDRATE CORE DRILLING TESTS

    Energy Technology Data Exchange (ETDEWEB)

    John H. Cohen; Thomas E. Williams; Ali G. Kadaster; Bill V. Liddell

    2002-11-01

    The ''Methane Hydrate Production from Alaskan Permafrost'' project is a three-year endeavor being conducted by Maurer Technology Inc. (MTI), Noble, and Anadarko Petroleum, in partnership with the U.S. DOE National Energy Technology Laboratory (NETL). The project's goal is to build on previous and ongoing R&D in the area of onshore hydrate deposition. The project team plans to design and implement a program to safely and economically drill, core and produce gas from arctic hydrates. The current work scope includes drilling and coring one well on Anadarko leases in FY 2003 during the winter drilling season. A specially built on-site core analysis laboratory will be used to determine some of the physical characteristics of the hydrates and surrounding rock. Prior to going to the field, the project team designed and conducted a controlled series of coring tests for simulating coring of hydrate formations. A variety of equipment and procedures were tested and modified to develop a practical solution for this special application. This Topical Report summarizes these coring tests. A special facility was designed and installed at MTI's Drilling Research Center (DRC) in Houston and used to conduct coring tests. Equipment and procedures were tested by cutting cores from frozen mixtures of sand and water supported by casing and designed to simulate hydrate formations. Tests were conducted with chilled drilling fluids. Tests showed that frozen core can be washed out and reduced in size by the action of the drilling fluid. Washing of the core by the drilling fluid caused a reduction in core diameter, making core recovery very difficult (if not impossible). One successful solution was to drill the last 6 inches of core dry (without fluid circulation). These tests demonstrated that it will be difficult to capture core when drilling in permafrost or hydrates without implementing certain safeguards. Among the coring tests was a simulated hydrate

  8. Use of conivaptan to allow aggressive hydration to prevent tumor lysis syndrome in a pediatric patient with large-cell lymphoma and SIADH.

    Science.gov (United States)

    Rianthavorn, Pornpimol; Cain, Joan P; Turman, Martin A

    2008-08-01

    The available treatment options for hyponatremia secondary to SIADH are limited and not completely effective. Conivaptan is a vasopressin 1a and 2 receptor antagonist recently approved by the US Food and Drug Administration (FDA) for treating euvolemic and hypervolemic hyponatremia in adult patients. However, data on efficacy and safety of conivaptan in pediatrics are limited. We report a case of a 13-year-old boy with extensively metastasized anaplastic large-cell lymphoma. He also developed hyponatremia due to syndrome of inappropriate antidiuretic hormone secretion (SIADH) prior to chemotherapy initiation. SIADH management in this case was complicated when fluid restriction was not safely attainable. Conivaptan played a significant role in this situation by allowing provision of a large amount of intravenous fluid prior to and during induction chemotherapy. It proved to be an important component in preventing uric acid nephropathy/tumor lysis syndrome. Conivaptan induced free-water clearance as indicated by increased urine output and decreased urine osmolality. The patient responded to conivaptan without any adverse effects.

  9. Molecular analysis of petroleum derived compounds that adsorb onto gas hydrate surfaces

    International Nuclear Information System (INIS)

    Borgund, Anna E.; Hoiland, Sylvi; Barth, Tanja; Fotland, Per; Askvik, Kjell M.

    2009-01-01

    Field observations have shown that some streams of water, gas and crude oil do not form gas hydrate plugs during petroleum production even when operating within thermodynamic conditions for hydrate formation. Also, when studied under controlled laboratory conditions, some oils are found to form hydrate dispersed systems whereas others form plugs. Oils with low tendency to form hydrate plugs are believed to contain natural hydrate plug inhibiting components (NICs) that adsorb onto the hydrate surface, making them less water-wet and preventing the particles from agglomerating into large hydrate clusters. The molecular structure of the NICs is currently unknown. In this work, hydrate adsorbing components were extracted from crude oils using freon hydrates as an extraction phase. The fractions were found to be enriched in polar material, and more polar material is associated with hydrates generated in biodegraded crude oils than in non-biodegraded oils. Various fractionation schemes and analytical techniques have been applied in the search for molecular characterisation. The average molecular weights were found to be approximately 500 g/mole. GC-MS chromatograms show a large UCM (Unresolved Complex Mixture). Thus, GC-MS has a limited potential for identification of compounds. A commercial biosurfactant was used as a model compound in the search for similar structures in the extracts. The results from analysis of the hydrate adsorbing components suggest that the type and structure are more important for hydrate morphology than the amount of material adsorbed.

  10. Nephroprotective Effects of N-Acetylcysteine Amide against Contrast-Induced Nephropathy through Upregulating Thioredoxin-1, Inhibiting ASK1/p38MAPK Pathway, and Suppressing Oxidative Stress and Apoptosis in Rats

    Directory of Open Access Journals (Sweden)

    Xuezhong Gong

    2016-01-01

    Full Text Available Contrast-induced nephropathy (CIN is a leading cause of hospital-acquired acute kidney injury (AKI due to apoptosis induced in renal tubular cells. Our previous study demonstrated the novel N-acetylcysteine amide (NACA; the amide form of N-acetyl cysteine (NAC prevented renal tubular cells from contrast-induced apoptosis through inhibiting p38 MAPK pathway in vitro. In the present study, we aimed to compare the efficacies of NACA and NAC in preventing CIN in a well-established rat model and investigate whether thioredoxin-1 (Trx1 and apoptosis signal-regulating kinase 1 (ASK1 act as the potential activator for p38 MAPK. NACA significantly attenuated elevations of serum creatinine, blood urea nitrogen, and biomarkers of AKI. At equimolar concentration, NACA was more effective than NAC in reducing histological changes of renal tubular injuries. NACA attenuated activation of p38 MAPK signal, reduced oxidative stress, and diminished apoptosis. Furthermore, we demonstrated that contrast exposure resulted in Trx1 downregulation and increased ASK1/p38 MAPK phosphorylation, which could be reversed by NACA and NAC. To our knowledge, this is the first report that Trx1 and ASK1 are involved in CIN. Our study highlights a renal protective role of NACA against CIN through modulating Trx1 and ASK1/p38 MAPK pathway to result in the inhibition of apoptosis among renal cells.

  11. Zirconium molybdate hydrate precipitates in spent nuclear fuel reprocessing

    International Nuclear Information System (INIS)

    Magnaldo, A.; Noire, M.H.; Esbelin, E.; Dancausse, J.P.; Picart, S.

    2004-01-01

    This paper presents through 2 posters a general overview studies realised by CEA teams on deposits observed in the La Hague plant dissolution facilities. Their main constituents are metallic debris bound together with zirconium molybdate hydrate. A comprehensive study of zirconium molybdate hydrate formation included nucleation and growth kinetics was developed. Fouling mechanisms were consequently explained as influenced by the operation conditions. Pu insertion was also overviewed. Its behaviour is important when curative and preventive chemical treatments are considered. (authors)

  12. Is hypoalbuminemia a prognostic risk factor for contrast-induced nephropathy in peritoneal dialysis patients?

    Directory of Open Access Journals (Sweden)

    Hassan K

    2014-10-01

    /dL should be monitored carefully when exposed to ICM. Serum albumin level may be considered a potential therapeutic target in the prevention of CIN and preservation of RRF in PD patients. Keywords: peritoneal dialysis, renal function, iodine radio-contrast media, iodine contrast media-induced nephropathy

  13. Radiologists' knowledge and perceptions of the impact of contrast-induced nephropathy and its risk factors when performing computed tomography examinations: A survey of European radiologists

    International Nuclear Information System (INIS)

    Reddan, Donal; Fishman, Elliot K.

    2008-01-01

    Background: The past decade has seen a proliferation in the number of CT procedures. As increasing numbers of elderly patients with multiple comorbidities undergo contrast media (CM)-enhanced procedures, more patients are at risk for contrast-induced nephropathy (CIN). Objectives: To understand whether radiologists are sufficiently aware of the incidence, impact and risk factors of CIN, and whether they are taking sufficient measures to prevent CIN among patients undergoing CT. Materials and methods: A telephone or online survey was conducted in 2005 with 509 radiologists from 10 European countries. Participants had a minimum of 3 years' experience and performed at least 50 CT scans per week. Results: Most (88%) radiologists believed that CIN is an important issue. While 45% identify that a patient is experiencing CIN when the serum creatinine level increases >25% (0.5 mg/dL) from baseline within 48 h, the remainder used criteria that might lead to significant under-diagnosis. Most (72%) radiologists believed that CIN is associated with increased morbidity; 56% did not believe that it is associated with increased mortality. Most respondents agreed that pre-existing renal impairment (97%), dehydration (90%) and diabetes (89%) were risk factors for CIN; however, 26%, 30% and 46%, respectively, did not identify advanced age, CM dose or congestive cardiac failure as risk factors. Only 7% of radiologists thought they were always made aware of CIN associated with their cases and 28% never consulted a nephrologist to discuss patients at risk of CIN or who had developed CIN. Conclusion: There is highly variable awareness of the definition, impact and risk factors for CIN among European radiologists. Data regarding the importance of CIN in CT are limited. Improved efforts are required to better educate radiologists and referring physicians and to institute appropriate protocols to identify at-risk patients and prevent CIN

  14. Radiologists' knowledge and perceptions of the impact of contrast-induced nephropathy and its risk factors when performing computed tomography examinations: A survey of European radiologists

    Energy Technology Data Exchange (ETDEWEB)

    Reddan, Donal [University College Galway Hospitals, Unit 7, Merlin Park Hospital, Galway (Ireland)], E-mail: donal.reddan@mailn.hse.ie; Fishman, Elliot K. [Johns Hopkins Hospital, Baltimore, MD (United States)

    2008-05-15

    Background: The past decade has seen a proliferation in the number of CT procedures. As increasing numbers of elderly patients with multiple comorbidities undergo contrast media (CM)-enhanced procedures, more patients are at risk for contrast-induced nephropathy (CIN). Objectives: To understand whether radiologists are sufficiently aware of the incidence, impact and risk factors of CIN, and whether they are taking sufficient measures to prevent CIN among patients undergoing CT. Materials and methods: A telephone or online survey was conducted in 2005 with 509 radiologists from 10 European countries. Participants had a minimum of 3 years' experience and performed at least 50 CT scans per week. Results: Most (88%) radiologists believed that CIN is an important issue. While 45% identify that a patient is experiencing CIN when the serum creatinine level increases >25% (0.5 mg/dL) from baseline within 48 h, the remainder used criteria that might lead to significant under-diagnosis. Most (72%) radiologists believed that CIN is associated with increased morbidity; 56% did not believe that it is associated with increased mortality. Most respondents agreed that pre-existing renal impairment (97%), dehydration (90%) and diabetes (89%) were risk factors for CIN; however, 26%, 30% and 46%, respectively, did not identify advanced age, CM dose or congestive cardiac failure as risk factors. Only 7% of radiologists thought they were always made aware of CIN associated with their cases and 28% never consulted a nephrologist to discuss patients at risk of CIN or who had developed CIN. Conclusion: There is highly variable awareness of the definition, impact and risk factors for CIN among European radiologists. Data regarding the importance of CIN in CT are limited. Improved efforts are required to better educate radiologists and referring physicians and to institute appropriate protocols to identify at-risk patients and prevent CIN.

  15. A prospective study on the risk of contrast induced nephropathy in the patients who underwent contrast-enhanced CT examination

    International Nuclear Information System (INIS)

    Zhang Baocui; Zhang Yudong; Zhao Kai; Wang Xiaoying; Jiang Xuexiang

    2013-01-01

    Objective: To investigate the incidence of contrast induced nephropathy (CIN) among different patient groups after contrast agent injection. Methods: A total of 1243 patients were included in this study (male = 694, female = 549). The SCr level one week before and 72 hours after the CT examination and the incidence of CIN were recorded and comparison was made among groups according to sex, age, body mass index (BMI), the history of high blood pressure (HBP), diabetes mellitus (DM), chronic kidney disease (CKD), chronic heart failure (CHF), tumor, nephrotoxicity drug (NTD) usage. The frequency, type, dose and injection velocity of the contrast media (CM) were also recorded. Multivariate predictors of CIN were identified by Logistic regression using step-wise selection with entry and exit criteria of P 1). Conclusion: Women, age ≥ 75 years, LOCM, NTD, tumor, and the frequency of using CM more than once per month were more likely to develop CIN. (authors)

  16. A prediction method of natural gas hydrate formation in deepwater gas well and its application

    Directory of Open Access Journals (Sweden)

    Yanli Guo

    2016-09-01

    Full Text Available To prevent the deposition of natural gas hydrate in deepwater gas well, the hydrate formation area in wellbore must be predicted. Herein, by comparing four prediction methods of temperature in pipe with field data and comparing five prediction methods of hydrate formation with experiment data, a method based on OLGA & PVTsim for predicting the hydrate formation area in wellbore was proposed. Meanwhile, The hydrate formation under the conditions of steady production, throttling and shut-in was predicted by using this method based on a well data in the South China Sea. The results indicate that the hydrate formation area decreases with the increase of gas production, inhibitor concentrations and the thickness of insulation materials and increases with the increase of thermal conductivity of insulation materials and shutdown time. Throttling effect causes a plunge in temperature and pressure in wellbore, thus leading to an increase of hydrate formation area.

  17. Historical methane hydrate project review

    Science.gov (United States)

    Collett, Timothy; Bahk, Jang-Jun; Frye, Matt; Goldberg, Dave; Husebo, Jarle; Koh, Carolyn; Malone, Mitch; Shipp, Craig; Torres, Marta

    2013-01-01

    In 1995, U.S. Geological Survey made the first systematic assessment of the volume of natural gas stored in the hydrate accumulations of the United States. That study, along with numerous other studies, has shown that the amount of gas stored as methane hydrates in the world greatly exceeds the volume of known conventional gas resources. However, gas hydrates represent both a scientific and technical challenge and much remains to be learned about their characteristics and occurrence in nature. Methane hydrate research in recent years has mostly focused on: (1) documenting the geologic parameters that control the occurrence and stability of gas hydrates in nature, (2) assessing the volume of natural gas stored within various gas hydrate accumulations, (3) analyzing the production response and characteristics of methane hydrates, (4) identifying and predicting natural and induced environmental and climate impacts of natural gas hydrates, and (5) analyzing the effects of methane hydrate on drilling safety.Methane hydrates are naturally occurring crystalline substances composed of water and gas, in which a solid water-­‐lattice holds gas molecules in a cage-­‐like structure. The gas and water becomes a solid under specific temperature and pressure conditions within the Earth, called the hydrate stability zone. Other factors that control the presence of methane hydrate in nature include the source of the gas included within the hydrates, the physical and chemical controls on the migration of gas with a sedimentary basin containing methane hydrates, the availability of the water also included in the hydrate structure, and the presence of a suitable host sediment or “reservoir”. The geologic controls on the occurrence of gas hydrates have become collectively known as the “methane hydrate petroleum system”, which has become the focus of numerous hydrate research programs.Recognizing the importance of methane hydrate research and the need for a coordinated

  18. Overview: Nucleation of clathrate hydrates.

    Science.gov (United States)

    Warrier, Pramod; Khan, M Naveed; Srivastava, Vishal; Maupin, C Mark; Koh, Carolyn A

    2016-12-07

    Molecular level knowledge of nucleation and growth of clathrate hydrates is of importance for advancing fundamental understanding on the nature of water and hydrophobic hydrate formers, and their interactions that result in the formation of ice-like solids at temperatures higher than the ice-point. The stochastic nature and the inability to probe the small length and time scales associated with the nucleation process make it very difficult to experimentally determine the molecular level changes that lead to the nucleation event. Conversely, for this reason, there have been increasing efforts to obtain this information using molecular simulations. Accurate knowledge of how and when hydrate structures nucleate will be tremendously beneficial for the development of sustainable hydrate management strategies in oil and gas flowlines, as well as for their application in energy storage and recovery, gas separation, carbon sequestration, seawater desalination, and refrigeration. This article reviews various aspects of hydrate nucleation. First, properties of supercooled water and ice nucleation are reviewed briefly due to their apparent similarity to hydrates. Hydrate nucleation is then reviewed starting from macroscopic observations as obtained from experiments in laboratories and operations in industries, followed by various hydrate nucleation hypotheses and hydrate nucleation driving force calculations based on the classical nucleation theory. Finally, molecular simulations on hydrate nucleation are discussed in detail followed by potential future research directions.

  19. Formation of submarine gas hydrates

    Energy Technology Data Exchange (ETDEWEB)

    Soloviev, V.; Ginsburg, G.D. (Reserch Institute of Geology and Mineral Resources of the Ocean ' ' VNII Okeangeologia' ' , St. Petersburg (Russian Federation))

    1994-03-01

    Submarine gas hydrates have been discoverd in the course of deep-sea drilling (DSDP and ODP) and bottom sampling in many offshore regions. This paper reports on expeditions carried out in the Black, Caspian and Okhotsk Seas. Gas hydrate accumulations were discovered and investigated in all these areas. The data and an analysis of the results of the deep-sea drilling programme suggest that the infiltration of gas-bearing fluids is a necessary condition for gas hydrate accumulation. This is confirmed by geological observations at three scale levels. Firstly, hydrates in cores are usually associated with comparatively coarse-grained, permeable sediments as well as voids and fractures. Secondly, hydrate accumulations are controlled by permeable geological structures, i.e. faults, diapirs, mud volcanos as well as layered sequences. Thirdly, in the worldwide scale, hydrate accumulations are characteristic of continental slopes and rises and intra-continental seas where submarine seepages also are widespread. Both biogenic and catagenic gas may occur, and the gas sources may be located at various distances from the accumulation. Gas hydrates presumably originate from water-dissolved gas. The possibility of a transition from dissolved gas into hydrate is confirmed by experimental data. Shallow gas hydrate accumulations associated with gas-bearing fluid plumes are the most convenient features for the study of submarine hydrate formation in general. These accumulations are known from the Black, Caspian and Okhotsk Seas, the Gulf of Mexico and off northern California. (au) (24 refs.)

  20. Overview: Nucleation of clathrate hydrates

    Science.gov (United States)

    Warrier, Pramod; Khan, M. Naveed; Srivastava, Vishal; Maupin, C. Mark; Koh, Carolyn A.

    2016-12-01

    Molecular level knowledge of nucleation and growth of clathrate hydrates is of importance for advancing fundamental understanding on the nature of water and hydrophobic hydrate formers, and their interactions that result in the formation of ice-like solids at temperatures higher than the ice-point. The stochastic nature and the inability to probe the small length and time scales associated with the nucleation process make it very difficult to experimentally determine the molecular level changes that lead to the nucleation event. Conversely, for this reason, there have been increasing efforts to obtain this information using molecular simulations. Accurate knowledge of how and when hydrate structures nucleate will be tremendously beneficial for the development of sustainable hydrate management strategies in oil and gas flowlines, as well as for their application in energy storage and recovery, gas separation, carbon sequestration, seawater desalination, and refrigeration. This article reviews various aspects of hydrate nucleation. First, properties of supercooled water and ice nucleation are reviewed briefly due to their apparent similarity to hydrates. Hydrate nucleation is then reviewed starting from macroscopic observations as obtained from experiments in laboratories and operations in industries, followed by various hydrate nucleation hypotheses and hydrate nucleation driving force calculations based on the classical nucleation theory. Finally, molecular simulations on hydrate nucleation are discussed in detail followed by potential future research directions.

  1. Dehydration behaviour of hydrates

    Energy Technology Data Exchange (ETDEWEB)

    Dette, S.S.; Stelzer, T.; Jones, M.J.; Ulrich, J. [Martin-Luther-Universitaet Halle-Wittenberg, Zentrum fuer Ingenieurwissenschaften, Verfahrenstechnik/TVT, 06099 Halle (Germany)

    2010-07-15

    Immersing a crystalline solvate in a suitable anti-solvent can induce phase transformation to solvent-free solid phase. In certain cases the solvent-mediated phase transition results in the generation of hollow, tubular structures. Both the tube dimensions of sodium-2-keto-L-gulonate anhydrate (skga) and the dehydration kinetics of sodium-2-keto-L-gulonate monohydrate (skgm) can be modified by the antisolvent employed. An explanation for the variable dehydration behaviour of skgm in the antisolvents is presented here. Furthermore, other crystalline hydrates were dehydrated in dry methanol. Providing an operational window can be found, any hydrate material could possibly find use in the production of tubes (micro- or nanotubes for different applications). The experimental conditions selected (dry methanol as antisolvent, dehydration temperature at 25 C) for the dehydration did not lead to the anhydrate tube growth for all hydrates investigated. Based upon the results presented here a first hypothesis is presented to explain this effect. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  2. Methane Recycling During Burial of Methane Hydrate-Bearing Sediments

    Science.gov (United States)

    You, K.; Flemings, P. B.

    2017-12-01

    We quantitatively investigate the integral processes of methane hydrate formation from local microbial methane generation, burial of methane hydrate with sedimentation, and methane recycling at the base of the hydrate stability zone (BHSZ) with a multiphase multicomponent numerical model. Methane recycling happens in cycles, and there is not a steady state. Each cycle starts with free gas accumulation from hydrate dissociation below the BHSZ. This free gas flows upward under buoyancy, elevates the hydrate saturation and capillary entry pressure at the BHSZ, and this prevents more free gas flowing in. Later as this layer with elevated hydrate saturation is buried and dissociated, the large amount of free gas newly released and accumulated below rapidly intrudes into the hydrate stability zone, drives rapid hydrate formation and creates three-phase (gas, liquid and hydrate) equilibrium above the BHSZ. The gas front retreats to below the BHSZ until all the free gas is depleted. The shallowest depth that the free gas reaches in one cycle moves toward seafloor as more and more methane is accumulated to the BHSZ with time. More methane is stored above the BHSZ in the form of concentrated hydrate in sediments with relatively uniform pore throat, and/or with greater compressibility. It is more difficult to initiate methane recycling in passive continental margins where the sedimentation rate is low, and in sediments with low organic matter content and/or methanogenesis reaction rate. The presence of a permeable layer can store methane for significant periods of time without recycling. In a 2D system where the seafloor dips rapidly, the updip gas flow along the BHSZ transports more methane toward topographic highs where methane gas and elevated hydrate saturation intrude deeper into the hydrate stability zone within one cycle. This could lead to intermittent gas venting at seafloor at the topographic highs. This study provides insights on many phenomenon associated with

  3. Clinical study on orofacial photonic hydration using phototherapy and biomaterials

    Science.gov (United States)

    Lizarelli, Rosane F. Z.; Grandi, Natália D. P.; Florez, Fernando L. E.; Grecco, Clovis; Lopes, Luciana A.

    2015-06-01

    Skin hydration is important to prevent aging and dysfunction of orofacial system. Nowadays, it is known that cutaneous system is linked to muscle system, then every dentist need to treat healthy facial skin, as lips, keeping orofacial functions healthy. Thirty-two patients were treated using laser and led therapy single or associated to biomaterials (dermo-cosmetics) searching for the best protocol to promote skin hydration. Using a peace of equipment to measure electric impedance, percentage of water and oil from skin, before and after different treatments were analyzed. Statistic tests using 5% and 0.1% of significance were applied and results showed that light could improve hydration of epidermis layer of facial skin. Considering just light effect, using infrared laser followed by blue led system is more effective to hydration than just blue led system application. Considering dermo-cosmetic and light, the association between both presented the best result.

  4. A study on dehydration of rare earth chloride hydrate

    International Nuclear Information System (INIS)

    Cho, Yong Zun; Eun, Hee Chul; Son, Sung Mo; Lee, Tae Kyo; Hwang, Taek Sung

    2012-01-01

    The dehydration schemes of rare earth (La, Ce, Nd, Pr, Sm. Eu, Gd, Y) chloride hydrates was investigated by using a dehydration apparatus. To prevent the formation of the rare earth oxychlorides, the operation temperature was changed step by step (80→150→230 degree C) based on the TGA (thermo-gravimetric analysis) results of the rare earth chloride hydrates. A vacuum pump and preheated Ar gas were used to effectively remove the evaporated moisture and maintain an inert condition in the dehydration apparatus. The dehydration temperature of the rare earth chloride hydrate was increased when the atomic number of the rare earth nuclide was increased. The content of the moisture in the rare earth chloride hydrate was decreased below 10% in the dehydration apparatus.

  5. Contrast induced nephropathy

    DEFF Research Database (Denmark)

    Stacul, Fulvio; van der Molen, Aart J; Reimer, Peter

    2011-01-01

    PURPOSE: The Contrast Media Safety Committee (CMSC) of the European Society of Urogenital Radiology (ESUR) has updated its 1999 guidelines on contrast medium-induced nephropathy (CIN). AREAS COVERED: Topics reviewed include the definition of CIN, the choice of contrast medium, the prophylactic me...

  6. Accuracy of point-of-care serum creatinine devices for detecting patients at risk of contrast-induced nephropathy: a critical overview.

    Science.gov (United States)

    Martínez Lomakin, Felipe; Tobar, Catalina

    2014-12-01

    Contrast-induced nephropathy (CIN) is a common event in hospitals, with reported incidences ranging from 1 to 30%. Patients with underlying kidney disease have an increased risk of developing CIN. Point-of-care (POC) creatinine devices are handheld devices capable of providing quantitative data on a patient's kidney function that could be useful in stratifying preventive measures. This overview aims to synthesize the current evidence on diagnostic accuracy and clinical utility of POC creatinine devices in detecting patients at risk of CIN. Five databases were searched for diagnostic accuracy studies or clinical trials that evaluated the usefulness of POC devices in detecting patients at risk of CIN. Selected articles were critically appraised to assess their individual risk of bias by the use of standard criteria; 13 studies were found that addressed the diagnostic accuracy or clinical utility of POC creatinine devices. Most studies incurred a moderate to high risk of bias. Overall concordance between POC devices and reference standards (clinical laboratory procedures) was found to be moderate, with 95% limits of agreement often lying between -35.4 and +35.4 µmol/L (-0.4 and +0.4 mg/dL). Concordance was shown to decrease with worsening kidney function. Data on the clinical utility of these devices were limited, but a significant reduction in time to diagnosis was reported in two studies. Overall, POC creatinine devices showed a moderate concordance with standard clinical laboratory creatinine measurements. Several biases could have induced optimism in these estimations. Results obtained from these devices may be unreliable in cases of severe kidney failure. Randomized trials are needed to address the clinical utility of these devices.

  7. Gas hydrate cool storage system

    Science.gov (United States)

    Ternes, M.P.; Kedl, R.J.

    1984-09-12

    The invention presented relates to the development of a process utilizing a gas hydrate as a cool storage medium for alleviating electric load demands during peak usage periods. Several objectives of the invention are mentioned concerning the formation of the gas hydrate as storage material in a thermal energy storage system within a heat pump cycle system. The gas hydrate was formed using a refrigerant in water and an example with R-12 refrigerant is included. (BCS)

  8. THERMODYNAMIC MODEL OF GAS HYDRATES

    OpenAIRE

    Недоступ, В. И.; Недоступ, О. В.

    2015-01-01

    The interest to gas hydrates grows last years. Therefore working out of reliable settlement-theoretical methods of definition of their properties is necessary. The thermodynamic model of gas hydrates in which the central place occupies a behaviour of guest molecule in cell is described. The equations of interaction of molecule hydrate formative gas with cell are received, and also an enthalpy and energy of output of molecule from a cell are determined. The equation for calculation of thermody...

  9. Novel understanding of calcium silicate hydrate from dilute hydration

    KAUST Repository

    Zhang, Lina; Yamauchi, Kazuo; Li, Zongjin; Zhang, Xixiang; Ma, Hongyan; Ge, Shenguang

    2017-01-01

    The perspective of calcium silicate hydrate (C-S-H) is still confronting various debates due to its intrinsic complicated structure and properties after decades of studies. In this study, hydration at dilute suspension of w/s equaling to 10

  10. Anemia and the risk of contrast-induced nephropathy in patients with renal insufficiency undergoing contrast-enhanced MDCT

    International Nuclear Information System (INIS)

    Murakami, Ryusuke; Kumita, Shin-ichiro; Hayashi, Hiromitsu; Sugizaki, Ken-ichi; Okazaki, Emi; Kiriyama, Tomonari; Hakozaki, Kenta; Tani, Hitomi; Miki, Izumi; Takeda, Minako

    2013-01-01

    Purpose: The purpose of this study was to assess the effect of anemia on the incidence of contrast-induced nephropathy (CIN) in patients with renal impairment undergoing MDCT. Materials and methods: Institutional review board approval was waived for this retrospective review of 843 patients with stable renal insufficiency (eGFR between 15 and 60 mL/min) who had undergone contrast-enhanced MDCT. Baseline hematocrit and hemoglobin values were measured. Serum creatinine (SCr) was assessed at the baseline and at 48–72 h after contrast administration. Results: The overall incidence of CIN in the patient population with renal insufficiency was 6.9%. CIN developed in 7.8% (54 of 695) of anemic patients, and in 2.8% (4 of 148) of non-anemic patients (P = .027). After adjustment for confounders, low hemoglobin and low hematocrit values remained independent predictors of CIN (odds ratio 4.6, 95% CI 1.0–20.5, P = .046). Conclusions: Anemia is associated with a higher incidence of CIN in patients with renal insufficiency. Anemia is a potentially modifiable risk factor for CIN, and has an unfavorable impact on prognosis in patients with renal insufficiency undergoing contrast-enhanced MDCT

  11. Anemia and the risk of contrast-induced nephropathy in patients with renal insufficiency undergoing contrast-enhanced MDCT

    Energy Technology Data Exchange (ETDEWEB)

    Murakami, Ryusuke, E-mail: rywakana@nms.ac.jp; Kumita, Shin-ichiro; Hayashi, Hiromitsu; Sugizaki, Ken-ichi; Okazaki, Emi; Kiriyama, Tomonari; Hakozaki, Kenta; Tani, Hitomi; Miki, Izumi; Takeda, Minako

    2013-10-01

    Purpose: The purpose of this study was to assess the effect of anemia on the incidence of contrast-induced nephropathy (CIN) in patients with renal impairment undergoing MDCT. Materials and methods: Institutional review board approval was waived for this retrospective review of 843 patients with stable renal insufficiency (eGFR between 15 and 60 mL/min) who had undergone contrast-enhanced MDCT. Baseline hematocrit and hemoglobin values were measured. Serum creatinine (SCr) was assessed at the baseline and at 48–72 h after contrast administration. Results: The overall incidence of CIN in the patient population with renal insufficiency was 6.9%. CIN developed in 7.8% (54 of 695) of anemic patients, and in 2.8% (4 of 148) of non-anemic patients (P = .027). After adjustment for confounders, low hemoglobin and low hematocrit values remained independent predictors of CIN (odds ratio 4.6, 95% CI 1.0–20.5, P = .046). Conclusions: Anemia is associated with a higher incidence of CIN in patients with renal insufficiency. Anemia is a potentially modifiable risk factor for CIN, and has an unfavorable impact on prognosis in patients with renal insufficiency undergoing contrast-enhanced MDCT.

  12. Nefropatía por contraste en el síndrome coronario agudo Contrast induced nephropathy in acute coronary syndrome

    Directory of Open Access Journals (Sweden)

    Mariana Carnevalini

    2011-10-01

    Full Text Available La nefropatía inducida por contraste (NIC es una de las causas más frecuentes de insuficiencia renal en pacientes internados. En el síndrome coronario agudo (SCA, la presencia de NIC aumenta la morbimortalidad. Las medidas de profilaxis y los factores de riesgo intervinientes de NIC en SCA no han sido determinados con exactitud. El objetivo de este estudio fue evaluar la incidencia de NIC y los factores asociados a su desarrollo en pacientes ingresados en unidad coronaria con requerimiento de cinecoronariografía (CCG. Se realizó un estudio de cohorte retrospectivo. Se incluyeron pacientes consecutivos cursando SCA estudiados con CCG dentro de las 72 horas de su admisión. Se definió NIC al aumento del 25% del valor de creatinina a las 48 h sobre el nivel basal de ingreso. El período de inclusión fue entre el 1° de enero de 2004 hasta el 30 de junio de 2010. Se analizaron 125 casos. La incidencia de NIC fue del 10.4% (n = 13. En el análisis multivariado, los factores asociados independientemente a su desarrollo fueron la edad [OR 1.05 (IC 95% 1.004 - 1.11 p = 0.034], la angioplastia a múltiple vaso [OR 2.2 (IC 95% 1.07 - 4.8, p = 0.03] y el volumen de contraste utilizado [OR 1.007 (IC 95% 1.001 - 1.01, p = 0.014].Contrast induced nephropathy (CIN is one of the most frequent causes of acute renal failure in hospitalized patients. It is associated with an increase in morbidity and mortality in patients hospitalized for acute coronary syndrome (ACS undergoing percutaneous coronary intervention (PCI. Risk factors and prevention strategies are not well defined. The aim of this study was to assess the incidence and clinical risk factors associated to the development of contrast induced nephropathy in patients hospitalized for ACS. In a retrospective cohort we analyzed consecutive patients hospitalized for ACS undergoing urgent PCI within 72 hours from the admission. CIN was defined as a 25% increase of creatinine levels from baseline at 48

  13. Hydrate-CASM for modeling Methane Hydrate-Bearing Sediments

    Science.gov (United States)

    De La Fuente Ruiz, M.; Vaunat, J.; Marin Moreno, H.

    2017-12-01

    A clear understanding of the geomechanical behavior of methane hydrate-bearing sediments (MHBS) is crucial to assess the stability of the seafloor and submarine infrastructures to human and natural loading changes. Here we present the Hydrate-CASM, a new elastoplastic constitutive model to predict the geomechanical behavior of MHBS. Our model employs the critical state model CASM (Clay and Sand Model) because of its flexibility in describing the shape of the yield surface and its proven ability to predict the mechanical behavior of sands, the most commercially viable hydrate reservoirs. The model considers MHBS as a deformable elastoplastic continuum, and hydrate-related changes in the stress-strain behavior are predicted by a densification mechanism. The densification attributes the mechanical contribution of hydrate to; a reduction of the available void ratio; a decrease of the swelling line slope; and an increase of the volumetric yield stress. It is described by experimentally derived physical parameters except from the swelling slope coefficient that requires empirical calibration. The Hydrate-CASM is validated against published triaxial laboratory tests performed at different confinement stresses, hydrate saturations, and hydrate morphologies. During the validation, we focused on capturing the mechanical behavior of the host sediment and consider perturbations of the sediment's mechanical properties that could result from the sample preparation. Our model successfully captures the experimentally observed influence of hydrate saturation in the magnitude and trend of the stiffness, shear strength, and dilatancy of MHBS. Hence, we propose that hydrate-related densification changes might be a major factor controlling the geomechanical response of MHBS.

  14. Ductile flow of methane hydrate

    Science.gov (United States)

    Durham, W.B.; Stern, L.A.; Kirby, S.H.

    2003-01-01

    Compressional creep tests (i.e., constant applied stress) conducted on pure, polycrystalline methane hydrate over the temperature range 260-287 K and confining pressures of 50-100 MPa show this material to be extraordinarily strong compared to other icy compounds. The contrast with hexagonal water ice, sometimes used as a proxy for gas hydrate properties, is impressive: over the thermal range where both are solid, methane hydrate is as much as 40 times stronger than ice at a given strain rate. The specific mechanical response of naturally occurring methane hydrate in sediments to environmental changes is expected to be dependent on the distribution of the hydrate phase within the formation - whether arranged structurally between and (or) cementing sediments grains versus passively in pore space within a sediment framework. If hydrate is in the former mode, the very high strength of methane hydrate implies a significantly greater strain-energy release upon decomposition and subsequent failure of hydrate-cemented formations than previously expected.

  15. New generation LDHI with an improved environmental profile[Low dosage hydrate inhibitors

    Energy Technology Data Exchange (ETDEWEB)

    Fu, Bob; Houston, Christopher; Spratt, Tony

    2005-07-01

    A new generation of low dosage hydrate inhibitors has been developed. These inhibitors are specially designed and synthesized in the laboratory in order to achieve a high level of performance as hydrate inhibitors and to improve their environmental profiles. These new inhibitors have been extensively evaluated in the laboratory using high pressure rocking cells. They function like anti-agglomerants by preventing the formation of large hydrate crystals or agglomerates. The resulting hydrate crystals are extremely tiny and finely dispersed in the hydrocarbon stream. In addition to controlling the hydrate crystal growth, these novel molecules demonstrate the ability to extend the induction time to onset of hydrate formation. When compared to the previous generations, the improved performance as well as the favorable environmental characteristics further expand the window for LDHI applications in the fields. (Author)

  16. Prevention

    DEFF Research Database (Denmark)

    Halken, S; Høst, A

    2001-01-01

    , breastfeeding should be encouraged for 4-6 months. In high-risk infants a documented extensively hydrolysed formula is recommended if exclusive breastfeeding is not possible for the first 4 months of life. There is no evidence for preventive dietary intervention neither during pregnancy nor lactation...... populations. These theories remain to be documented in proper, controlled and prospective studies. Breastfeeding and the late introduction of solid foods (>4 months) is associated with a reduced risk of food allergy, atopic dermatitis, and recurrent wheezing and asthma in early childhood. In all infants....... Preventive dietary restrictions after the age of 4-6 months are not scientifically documented....

  17. Flow assurance intervention, hydrates remediation

    Energy Technology Data Exchange (ETDEWEB)

    Mancini, Christopher S. [Oceaneering International Inc., Houston, TX (United States)

    2012-07-01

    This paper addresses the issues of removing hydrates in sub sea flow lines and associated equipment with an Remotely Operated Vehicle (ROV) of opportunity and a multi-service-vessel (MSV). The paper is split into three topics: the equipment used with the ROV, assessing the interface points and handling fluids produced from drawing down the pressure. Each section is explained thoroughly and backed up with real world experience. The equipment section details information from actual jobs performed and why the particular components were utilized. The system is generally contained in an ROV mounted skid. Pumps are utilized to draw down the pressure inside the hydrated section of equipment, removing one of the three necessary components for hydrates formation. Once the section is pumped down, several options exist for handling the fluids pumped out of the system: pumping to surface, re-injection into the well, or injection into an operating flow line. This method of hydrates remediation is both economical and timely. Hydrate blockages form in low temperatures and high pressures. Reducing the pressure or increasing the temperature so the conditions lie to the right of the hydrate dissociation curve will slowly decompose the blockage. Depressurization and the use of MEG or methanol will give favorable conditions to remove the hydrate plug. Oceaneering has the capabilities to remove hydrates using the FRS in conjunction with an installation vessel to dispose of the gas and fluid removed from the flow line. Hydrate remediation techniques should be implemented into the initial design to reduce costs later. The cost of stopped production combined with the day rate for equipment needed for hydrate removal outweighs the costs if no technique is utilized. (author)

  18. Contrast induced nephropathy in patients undergoing intravenous (IV) contrast enhanced computed tomography (CECT) and the relationship with risk factors: a meta-analysis

    NARCIS (Netherlands)

    Moos, Shira I.; van Vemde, David N. H.; Stoker, Jaap; Bipat, Shandra

    2013-01-01

    To summarize the incidence of contrast-induced nephropathy (CIN) and associations between CIN incidence and risk factors in patients undergoing intravenous contrast-enhanced computed tomography (CECT) with low- or iso-osmolar iodinated contrast medium. This review is performed in accordance with the

  19. Risk factors for contrast-induced nephropathy and their association with mortality in patients with blunt splenic injuries.

    Science.gov (United States)

    Hsieh, Ting-Min; Tsai, Tzu-Hsien; Liu, Yueh-Wei; Hsieh, Ching-Hua

    2016-11-01

    Although angioembolization increases the success rate of non-operative management in patients with blunt splenic injuries (BSI), the issue of contrast-induced nephropathy (CIN) due to serial administration of contrast medium remains unclear. We aimed to examine the risk factors of CIN and their clinical effect on mortality in patients with BSI. We retrospectively studied the complete data on 377 trauma patients with BSI who survived more than 48 h between July 2003 and June 2015. CIN was defined as the relative (≥25%) or absolute (≥0.5 mg/dL) increase in serum creatinine within 48 h after contrast administration. A multivariate logistic regression analysis was conducted to identify the independent predictors of CIN and mortality. CIN was independently associated with body mass index (BMI) ≥ 30 kg/m 2 (odds ratio [OR]: 3.25, 95% confidence interval [CI]: 1.20-8.76), injury severity score (ISS) ≥ 25 (OR: 6.08, 95% CI: 2.76-13.53), and 24-h hemoglobin (Hb) < 10 g/dL (OR: 3.16, 95% CI: 1.46-6.81). CIN (OR: 19.04, 95% CI: 6.15-58.94) and diabetes (OR: 3.43, 95% CI: 1.04-11.26) were also identified as independent predictors for mortality. In this study, we found that BMI ≥ 30 kg/m 2 , ISS ≥ 25, and 24-h Hb < 10 g/dL were independent risk factors for the occurrence of CIN in patients with BSI. However, angioembolization was not identified to be an independent risk factor for CIN. In addition, CIN and diabetes mellitus were identified as independent risk factors for mortality in patients with BSI. Copyright © 2016 IJS Publishing Group Ltd. Published by Elsevier Ltd. All rights reserved.

  20. Na+/Ca2+ exchange inhibitor, KB-R7943, attenuates contrast-induced acute 
kidney injury.

    Science.gov (United States)

    Yang, Dingwei; Yang, Dingping; Jia, Ruhan; Tan, Jin

    2013-01-01

    Intracellular Ca2+ overload is considered to be a key factor in contrast-induced acute kidney injury (CI-AKI). The Na+/Ca2+ exchanger (NCX) system is one of the main pathways of intracellular Ca2+ overload. We investigated the effects of KB-R7943, an inhibitor of the reverse mode of NCX, on CI-AKI in a rat model. Rats were divided into control group, CI-AKI group and pretreatment groups (with KB-R7943 dose of 5 or 10 mg/kg). CI-AKI was induced by diatrizoate administration in rats with cholesterol-supplemented diet for 8 weeks. Renal function and renal hemodynamics were determined 1 day following contrast medium administration. Renal histopathology was observed by light microscope. Renal tubular apoptosis was examined by TUNEL. Renal endothelin-1 (ET-1) was measured by radioimmunoassay. Renal malondialdehyde (MDA) and catalase (CAT) were measured as oxidative markers. Levels of serum creatinine (Scr), renal ET-1, MDA and CAT, and resistance index (RI) of renal blood vessels increased significantly in CI-AKI rats. The 
increases in Scr and RI of renal blood vessels induced by diatrizoate were suppressed significantly and 
dose-dependently by pretreatment with KB-R7943. Histopathological and TUNEL results showed that 
the contrast medium-induced severe renal tubular 
necrosis and apoptosis were significantly and dose-dependently attenuated by KB-R7943. KB-R7943 significantly suppressed the increment of renal ET-1 content and MDA and CAT level induced by contrast medium administration. Activation of the reverse mode of NCX, followed by ET-1 overproduction and increased oxidative stress, seems to play an important role in the pathogenesis of CI-AKI. The inhibitor of the reverse mode of NCX, KB-R7943, has renoprotective effects on CI-AKI.

  1. Calcium Aluminate Cement Hydration Model

    Directory of Open Access Journals (Sweden)

    Matusinović, T.

    2011-01-01

    Full Text Available Calcium aluminate cement (AC is a very versatile special cement used for specific applications. As the hydration of AC is highly temperature dependent, yielding structurally different hydration products that continuously alter material properties, a good knowledge of thermal properties at early stages of hydration is essential. The kinetics of AC hydration is a complex process and the use of single mechanisms models cannot describe the rate of hydration during the whole stage.This paper examines the influence of temperature (ϑ=5–20 °C and water-to-cement mass ratio (mH /mAC = 0.4; 0.5 and 1.0 on hydration of commercial iron-rich AC ISTRA 40 (producer: Istra Cement, Pula, Croatia, which is a part of CALUCEM group, Figs 1–3. The flow rate of heat generation of cement pastes as a result of the hydration reactions was measured with differential microcalorimeter. Chemically bonded water in the hydrated cement samples was determined by thermo-gravimetry.Far less heat is liberated when cement and water come in contact for the first time, Fig. 1, than in the case for portland cement (PC. Higher water-to-cement ratio increases the heat evolved at later ages (Fig. 3 due to higher quantity of water available for hydration. A significant effect of the water-to-cement ratio on the hydration rate and hydration degree showed the importance of water as being the limiting reactant that slows down the reaction early. A simplified stoichiometric model of early age AC hydration (eq. (8 based on reaction schemes of principal minerals, nominally CA, C12A7 and C4AF (Table 1, was employed. Hydration kinetics after the induction period (ϑ < 20 °C had been successfully described (Fig. 4 and Table 2 by a proposed model (eq. (23 which simultaneously comprised three main mechanisms: nucleation and growth, interaction at phase boundary, and mass transfer. In the proposed kinetic model the nucleation and growth is proportional to the amount of reacted minerals (eq

  2. Shifting Focus: From Hydration for Performance to Hydration for Health.

    Science.gov (United States)

    Perrier, Erica T

    2017-01-01

    Over the past 10 years, literature on hydration biomarkers has evolved considerably - from (de)hydration assessment towards a more global definition of biomarkers of hydration in daily life. This shift in thinking about hydration markers was largely driven by investigating the differences that existed between otherwise healthy individuals whose habitual, ad-libitum drinking habits differ, and by identifying physiological changes in low-volume drinkers who subsequently increase their water intake. Aside from obvious differences in urinary volume and concentration, a growing body of evidence is emerging that links differences in fluid intake with small, but biologically significant, differences in vasopressin (copeptin), glomerular filtration rate, and markers of metabolic dysfunction or disease. Taken together, these pieces of the puzzle begin to form a picture of how much water intake should be considered adequate for health, and represent a shifting focus from hydration for performance, toward hydration for health outcomes. This narrative review outlines the key areas of research in which the global hydration process - including water intake, urinary hydration markers, and vasopressin - has been associated with health outcomes, focusing on kidney and metabolic endpoints. It will also provide a commentary on how various hydration biomarkers may be used in hydration for health assessment. Finally, if adequate water intake can play a role in maintaining health, how might we tell if we are drinking enough? Urine output is easily measured, and can take into account differences in daily physical activity, climate, dietary solute load, and other factors that influence daily water needs. Today, targets have been proposed for urine osmolality, specific gravity, and color that may be used by researchers, clinicians, and individuals as simple indicators of optimal hydration. However, there remain a large number of incomplete or unanswered research questions regarding the

  3. The temperature hydration kinetics

    Directory of Open Access Journals (Sweden)

    Mircea Oroian

    2017-07-01

    Full Text Available The aim of this study is to evaluate the hydration kinetics of lentil seeds (Lens culinaris in water at different temperatures (25, 32.5, 40, 55, 70 and 80 °C for assessing the adequacy of models for describing the absorption phenomena during soaking. The diffusion coefficient values were calculated using Fick’s model for spherical and hemispherical geometries and the values were in the range of 10−6 m2/s. The experimental data were fitted to Peleg, Sigmoidal, Weibull and Exponential models. The models adequacy was determined using regression coefficients (R2, root mean square error (RMSE and reduced chi-square (χ2. The Peleg model is the suitable one for predicting the experimental data. Temperature had a positive and significant effect on the water absorption capacities and absorption was an endothermic process.

  4. Modelling the effects of waste components on cement hydration

    NARCIS (Netherlands)

    van Eijk, R.J.; Brouwers, Jos

    2000-01-01

    Ordinary Portland Cement (OPC) is often used for the Solidification/Stabilization (S/S) of waste containing heavy metals and salts. These waste componenents will precipitate in the form of insoluble compounds onto unreacted cement clinker grains preventing further hydration. In this study the long

  5. Protecting exposed tissues with external ultrasonic super-hydration.

    Science.gov (United States)

    Silberg, Barry Neil

    2006-01-01

    The author contends that a technique preventing dehydration of exposed tissues, such as external ultrasonic super-hydration, will result in a lower morbidity rate, decreasing deep tissue pain, susceptibility to infection, fat necrosis, wound dehiscence, and improving recovery times. He discusses how he uses this technique in his aesthetic surgery practice.

  6. Influence of Physical Activity and Ambient Temperature on Hydration: The European Hydration Research Study (EHRS

    Directory of Open Access Journals (Sweden)

    Ricardo Mora-Rodriguez

    2016-04-01

    Full Text Available This study explored the effects of physical activity (PA and ambient temperature on water turnover and hydration status. Five-hundred seventy three healthy men and women (aged 20–60 years from Spain, Greece and Germany self-reported PA, registered all food and beverage intake, and collected 24-h urine during seven consecutive days. Fasting blood samples were collected at the onset and end of the study. Food moisture was assessed using nutritional software to account for all water intake which was subtracted from daily urine volume to allow calculation of non-renal water loss (i.e., mostly sweating. Hydration status was assessed by urine and blood osmolality. A negative association was seen between ambient temperature and PA (r = −0.277; p < 0.001. Lower PA with high temperatures did not prevent increased non-renal water losses (i.e., sweating and elevated urine and blood osmolality (r = 0.218 to 0.163 all p < 0.001. When summer and winter data were combined PA was negatively associated with urine osmolality (r = −0.153; p = 0.001. Our data suggest that environmental heat acts to reduce voluntary PA but this is not sufficient to prevent moderate dehydration (increased osmolality. On the other hand, increased PA is associated with improved hydration status (i.e., lower urine and blood osmolality.

  7. Impact of benazepril on contrast-induced acute kidney injury for patients with mild to moderate renal insufficiency undergoing percutaneous coronary intervention.

    Science.gov (United States)

    Li, Xi-ming; Cong, Hong-liang; Li, Ting-ting; He, Li-jun; Zhou, Yu-jie

    2011-07-01

    The role of angiotensin-converting enzyme inhibitors (ACEI) in contrast-induced acute kidney injury (CI-AKI) is controversial. Some studies pointed out that it was effective in the prevention of CI-AKI, while some concluded that it was one risk for CI-AKI, especially for patients with pre-existing renal impairment. The purpose of this study was to assess the influence of benazepril administration on the development of CI-AKI in patients with mild to moderate renal insufficiency undergoing coronary intervention. One hundred and fourteen patients with mild to moderate impairment of renal function were enrolled before coronary angioplasty, who were randomly assigned to benazepril group (n = 52) and control group (n = 62). In the benazepril group, the patients received benazepril tablets 10 mg per day at least for 3 days before procedure. CI-AKI was defined as an increase of ≥ 25% in creatinine over the baseline value or increase of 0.5 mg/L within 72 hours of angioplasty. Patients were well matched with no significant differences at baseline in all measured parameters between two groups. The incidence of CI-AKI was lower by 64% in the benazepril group compared with control group but without statistical significance (3.45% vs. 9.68%, P = 0.506). Compared with benazepril group, estimated glomerular filtration rate (eGFR) level significantly decreased from (70.64 ± 16.38) ml · min⁻¹·1.73 m⁻² to (67.30 ± 11.99) ml · min⁻¹·1.73 m⁻² in control group (P = 0.038). There was no significant difference for the post-procedure decreased eGFR from baseline (ΔeGFR) between two groups (benazepril group (0.67 ± 12.67) ml · min⁻¹·1.73 m⁻² vs. control group (-3.33 ± 12.39) ml · min⁻¹·1.73 m⁻², P = 0.092). In diabetic subgroup analysis, ΔeGFR in benazepril group was slightly lower than that in the control group, but the difference was not statistically significant. Benazepril has a protective effect on mild to moderate impairment of renal function

  8. Relationship Between the Urine Flow Rate and Risk of Contrast-Induced Nephropathy After Emergent Percutaneous Coronary Intervention.

    Science.gov (United States)

    Liu, Yong; Lin, Lixia; Li, Yun; Li, Hualong; Wu, Deng-Xuan; Zhao, Jian-bin; Lian, Dan; Zhou, Yingling; Liu, Yuanhui; Ye, Piao; Ran, Peng; Duan, Chongyang; Chen, Shiqun; Chen, Pingyan; Xian, Ying; Chen, Jiyan; Tan, Ning

    2015-12-01

    A low urine flow rate is a marker of acute kidney injury. However, it is unclear whether a high urine flow rate is associated with a reduced risk of contrast-induced nephropathy (CIN) in high-risk patients. We conducted this study to evaluate the predictive value of the urine flow rate for the risk of CIN following emergent percutaneous coronary intervention (PCI). We prospectively examined 308 patients undergoing emergent PCI who provided consent. The predictive value of the 24-hour postprocedural urine flow rate, adjusted by weight (UR/W, mL/kg/h) and divided into quartiles, for the risk of CIN was assessed using multivariate logistic regression analysis. The cumulative incidence of CIN was 24.4%. In particular, CIN was observed in 29.5%, 19.5%, 16.7%, and 32.0% of cases in the UR/W quartile (Q)-1 (≤0.94  mL/kg/h), Q2 (0.94-1.30  mL/kg/h), Q3 (1.30-1.71  mL/kg/h), and Q4 (≥1.71  mL/kg/h), respectively. Moreover, in-hospital death was noted in 7.7%, 3.9%, 5.1%, and 5.3% of patients in Q1, Q2, Q3, and Q4, respectively. After adjusting for potential confounding predictors, multivariate analysis indicated that compared with the moderate urine flow rate quartiles (Q2 + Q3), a high urine flow rate (Q4) (odds ratio [OR], 2.69; 95% confidence interval [CI], 1.27-5.68; P = 0.010) and low urine flow rate (Q1) (OR, 2.23; 95% CI, 1.03-4.82; P = 0.041) were significantly associated with an increased risk of CIN. Moreover, a moderate urine flow rate (0.94-1.71  mL/kg/h) was significantly associated with a decreased risk of mortality. Our data suggest that higher and lower urine flow rates were significantly associated with an increased risk of CIN after emergent PCI, and a moderate urine flow rate (0.94-1.71  mL/kg/h) may be associated with a decreased risk of CIN with a good long-term prognosis after emergent PCI.

  9. Obsidian hydration dates glacial loading?

    Science.gov (United States)

    Friedman, I; Pierce, K L; Obradovich, J D; Long, W D

    1973-05-18

    Three different groups of hydration rinds have been measured on thin sections of obsidian from Obsidian Cliff, Yellowstone National Park, Wyoming. The average thickness of the thickest (oldest) group of hydration rinds is 16.3 micrometers and can be related to the original emplacement of the flow 176,000 years ago (potassium-argon age). In addition to these original surfaces, most thin sections show cracks and surfaces which have average hydration rind thicknesses of 14.5 and 7.9 micrometers. These later two hydration rinds compare closely in thickness with those on obsidian pebbles in the Bull Lake and Pinedale terminal moraines in the West Yellowstone Basin, which are 14 to 15 and 7 to 8 micrometers thick, respectively. The later cracks are thought to have been formed by glacial loading during the Bull Lake and Pinedale glaciations, when an estimated 800 meters of ice covered the Obsidian Cliff flow.

  10. Hydration water and microstructure in calcium silicate and aluminate hydrates

    International Nuclear Information System (INIS)

    Fratini, Emiliano; Ridi, Francesca; Chen, Sow-Hsin; Baglioni, Piero

    2006-01-01

    Understanding the state of the hydration water and the microstructure development in a cement paste is likely to be the key for the improvement of its ultimate strength and durability. In order to distinguish and characterize the reacted and unreacted water, the single-particle dynamics of water molecules in hydrated calcium silicates (C 3 S, C 2 S) and aluminates (C 3 A, C 4 AF) were studied by quasi-elastic neutron scattering, QENS. The time evolution of the immobile fraction represents the hydration kinetics and the mobile fraction follows a non-Debye relaxation. Less sophisticated, but more accessible and cheaper techniques, like differential scanning calorimetry, DSC, and near-infrared spectroscopy, NIR, were validated through QENS results and they allow one to easily and quantitatively follow the cement hydration kinetics and can be widely applied on a laboratory scale to understand the effect of additives (i.e., superplasticizers, cellulosic derivatives, etc) on the thermodynamics of the hydration process. DSC provides information on the free water index and on the activation energy involved in the hydration process while the NIR band at 7000 cm -1 monitors, at a molecular level, the increase of the surface-interacting water. We report as an example the effect of two classes of additives widely used in the cement industry: superplasticizers, SPs, and cellulose derivatives. SPs interact at the solid surface, leading to a consistent increment of the activation energy for the processes of nucleation and growth of the hydrated phases. In contrast, the cellulosic additives do not affect the nucleation and growth activation energy, but cause a significant increment in the water availability: in other words the hydration process is more efficient without any modification of the solid/liquid interaction, as also evidenced by the 1 H-NMR. Additional information is obtained by scanning electron microscopy (SEM), ultra small angle neutron scattering (USANS) and wide

  11. Hydration dependent dynamics in RNA

    International Nuclear Information System (INIS)

    Olsen, Greg L.; Bardaro, Michael F.; Echodu, Dorothy C.; Drobny, Gary P.; Varani, Gabriele

    2009-01-01

    The essential role played by local and collective motions in RNA function has led to a growing interest in the characterization of RNA dynamics. Recent investigations have revealed that even relatively simple RNAs experience complex motions over multiple time scales covering the entire ms-ps motional range. In this work, we use deuterium solid-state NMR to systematically investigate motions in HIV-1 TAR RNA as a function of hydration. We probe dynamics at three uridine residues in different structural environments ranging from helical to completely unrestrained. We observe distinct and substantial changes in 2 H solid-state relaxation times and lineshapes at each site as hydration levels increase. By comparing solid-state and solution state 13 C relaxation measurements, we establish that ns-μs motions that may be indicative of collective dynamics suddenly arise in the RNA as hydration reaches a critical point coincident with the onset of bulk hydration. Beyond that point, we observe smaller changes in relaxation rates and lineshapes in these highly hydrated solid samples, compared to the dramatic activation of motion occurring at moderate hydration

  12. First Study of Poly(3-Methylene-2-Pyrrolidone) as a Kinetic Hydrate Inhibitor

    DEFF Research Database (Denmark)

    Abrahamsen, Eirin; Heyns, Ingrid Marié; von Solms, Nicolas

    2017-01-01

    Formation of gas hydrates is a problem in the petroleum industry where the gas hydrates can cause blockage of the flowlines. Kinetic hydrate inhibitors (KHIs) are water-soluble polymers, sometimes used in combination synergistically or with non-polymeric synergists, that are used to prevent gas h...... are preferable in KHI polymers as long as they are water-soluble at hydrate-forming temperatures.......Formation of gas hydrates is a problem in the petroleum industry where the gas hydrates can cause blockage of the flowlines. Kinetic hydrate inhibitors (KHIs) are water-soluble polymers, sometimes used in combination synergistically or with non-polymeric synergists, that are used to prevent gas...... hydrate blockages. They have been used in the field successfully since 1995. In this paper, we present the first KHI results for the polymer, poly(3-methylene-2-pyrrolidone) (P(3M2P)), which is structurally similar to poly(N-vinylpyrrolidone) (PVP), one of the first KHIs to be discovered. 3M2P polymers...

  13. Mechanism of gypsum hydration

    Directory of Open Access Journals (Sweden)

    Pacheco, G.

    1991-06-01

    Full Text Available There is an hypothesis that the mechanism o f gypsum hydration and dehydration is performed through two simultaneous phenomena. In this study we try to clear up this phenomenon using chlorides as accelerators or a mixture of ethanol-methanol as retarders to carry out the gypsum setting. Natural Mexican gypsum samples and a hemihydrate prepared in the laboratory are used. The following analytical techniques are used: MO, DRX, DTA, TG and DTG. In agreement with the obtained results, it can be concluded: that colloid formation depends on the action of accelerators or retarders and the crystals are a consequence of the quantity of hemihydrate formed.

    En el mecanismo de hidratación y deshidratación del yeso existe la hipótesis de que éste se efectúa por dos fenómenos simultáneos. Este estudio intenta esclarecer estos fenómenos, empleando: cloruros como aceleradores o mezcla etanol-metanol como retardadores para efectuar el fraguado del yeso. Se emplean muestras de yeso de origen natural mexicano y hemihydrate preparado en laboratorio; se utilizan técnicas analíticas: MO, DRX, DTA, TG y DTG. De acuerdo a los resultados obtenidos se puede deducir: que la formación del coloide depende de la acción de los agentes aceleradores o retardadores y que los cristales son consecuencia de la cantidad de hemihidrato formado.

  14. Acoustical method of whole-body hydration status monitoring

    Science.gov (United States)

    Sarvazyan, A. P.; Tsyuryupa, S. N.; Calhoun, M.; Utter, A.

    2016-07-01

    An acoustical handheld hydration monitor (HM) for assessing the water balance of the human body was developed. Dehydration is a critical public health problem. Many elderly over age of 65 are particularly vulnerable as are infants and young children. Given that dehydration is both preventable and reversible, the need for an easy-to-perform method for the detection of water imbalance is of the utmost clinical importance. The HM is based on an experimental fact that ultrasound velocity in muscle is a linear function of water content and can be referenced to the hydration status of the body. Studies on the validity of HM for the assessment of whole-body hydration status were conducted in the Appalachian State University, USA, on healthy young adults and on elderly subjects residing at an assisted living facility. The HM was able to track changes in total body water during periods of acute dehydration and rehydration in athletes and day-to-day and diurnal variability of hydration in elderly. Results of human studies indicate that HM has a potential to become an efficient tool for detecting abnormal changes in the body hydration status.

  15. Reconsideration on Hydration of Sodium Ion: From Micro-Hydration to Bulk Hydration

    Science.gov (United States)

    Yongquan, Zhou; Chunhui, Fang; Yan, Fang; Fayan, Zhu; Haiwen, Ge; Hongyan, Liu

    2017-12-01

    Micro hydration structures of the sodium ion, [Na(H2O) n ]+, n = 1-12, were probed by density functional theory (DFT) at B3LYP/aug-cc-pVDZ level in both gaseous and aqueous phase. The predicted equilibrium sodium-oxygen distance of 0.240 nm at the present level of theory. The four-, five- and six-coordinated cluster can transform from each other at the ambient condition. The analysis of the successive water binding energy and natural charge population (NBO) on Na+ clearly shows that the influence of Na+ on the surrounding water molecules goes beyond the first hydration shell with the hydration number of 6. The Car-Parrinello molecular dynamic simulation shows that only the first hydration sphere can be found, and the hydration number of Na+ is 5.2 and the hydration distance ( r Na-O) is 0.235 nm. All our simulations mentioned in the present paper show an excellent agreement with the diffraction result from X-ray scattering study.

  16. A high yield process for hydrate formation

    Energy Technology Data Exchange (ETDEWEB)

    Giavarini, C.; Maccioni, F. [Univ. of Roma La Sapienza, Roma (Italy). Dept. of Chemical Engineering

    2008-07-01

    Due to the large quantities of natural gas stored in deep ocean hydrates, hydrate reservoirs are a substantial energy resource. Hydrates concentrate methane by as much as a factor of 164. As such, several natural gas transportation and storage systems using gas hydrates have been studied, and many of them are nearing practical use. In these systems, the hydrate is produced as a slurry by a spray process at approximately 7 megapascal (MPa), and then shaped into pellets. The use of a spray process, instead of a conventional stirred vessel is necessary in order to reach high hydrate concentrations in the hydrate-ice system. This paper presented a new procedure to produce a bulk of concentrated methane hydrate in a static traditional reactor at moderate pressure, controlling pressure and temperature in the interval between ice melting and the hydrate equilibrium curve. This paper discussed the experimental procedure which included formation of methane hydrate at approximately 5 MPa and 2 degrees Celsius in a reaction calorimeter at a volume of two liters. Results were also discussed. It was concluded that the procedure seemed suitable for the development of a gas hydrate storage and transport technology. It was found that the spray procedure took more time, but could be sped up and made continuous by using two vessels, one for hydrate formation and the other for hydrate concentration. The advantage was the production of a concentrated hydrate, using a simpler equipment and working at lower pressures respect to the spray process. 9 refs., 5 figs.

  17. Clinker mineral hydration at reduced relative humidities

    DEFF Research Database (Denmark)

    Jensen, Ole Mejlhede; Hansen, Per Freiesleben; Lachowski, Eric E.

    1999-01-01

    and experimental data are presented showing that C(3)A can hydrate at lower humidities than either C3S or C2S. It is suggested that the initiation of hydration during exposure to water vapour is nucleation controlled. When C(3)A hydrates at low humidity, the characteristic hydration product is C(3)AH(6......Vapour phase hydration of purl cement clinker minerals at reduced relative humidities is described. This is relevant to modern high performance concrete that may self-desiccate during hydration and is also relevant to the quality of the cement during storage. Both the oretical considerations...

  18. Storage capacity of hydrogen in gas hydrates

    International Nuclear Information System (INIS)

    Tsuda, Takaaki; Ogata, Kyohei; Hashimoto, Shunsuke; Sugahara, Takeshi; Sato, Hiroshi; Ohgaki, Kazunari

    2010-01-01

    The storage capacity of H 2 in the THF, THT, and furan hydrates was studied by p-V-T measurements. We confirmed that the storage and release processes of H 2 in all hydrates could be performed reversibly by pressure swing without destroying of hydrate cages. H 2 absorption in both THT and furan hydrates is much faster than THF hydrate in spite of same unit-cell structure. On the other hand, the storage amounts of H 2 are coincident in the all additive hydrates and would reach at about 1.0 mass% asymptotically.

  19. Gas hydrates forming and decomposition conditions analysis

    Directory of Open Access Journals (Sweden)

    А. М. Павленко

    2017-07-01

    Full Text Available The concept of gas hydrates has been defined; their brief description has been given; factors that affect the formation and decomposition of the hydrates have been reported; their distribution, structure and thermodynamic conditions determining the gas hydrates formation disposition in gas pipelines have been considered. Advantages and disadvantages of the known methods for removing gas hydrate plugs in the pipeline have been analyzed, the necessity of their further studies has been proved. In addition to the negative impact on the process of gas extraction, the hydrates properties make it possible to outline the following possible fields of their industrial use: obtaining ultrahigh pressures in confined spaces at the hydrate decomposition; separating hydrocarbon mixtures by successive transfer of individual components through the hydrate given the mode; obtaining cold due to heat absorption at the hydrate decomposition; elimination of the open gas fountain by means of hydrate plugs in the bore hole of the gushing gasser; seawater desalination, based on the hydrate ability to only bind water molecules into the solid state; wastewater purification; gas storage in the hydrate state; dispersion of high temperature fog and clouds by means of hydrates; water-hydrates emulsion injection into the productive strata to raise the oil recovery factor; obtaining cold in the gas processing to cool the gas, etc.

  20. Implications of hydration depletion in the in vitro starch digestibility of white bread crumb and crust.

    Science.gov (United States)

    Martínez, Mario M; Román, Laura; Gómez, Manuel

    2018-01-15

    The objective of this study was to provide understanding about the efficacy of decreasing dough hydration to slow down starch digestibility in white bread. Breads were made with 45 (low hydration bread, LHB), 60 (intermediate hydration bread, IHB) and 75% (high hydration bread, HHB) water (flour basis). A hydration depletion down to 45%, which is close to the minimum hydration found in commercially available white bread, did not prevent the starch in the crumb from complete gelatinization. However, LHB and IHB crumbs were more resistant to physical breakdown during in vitro digestion than HHB crumbs, resulting in a 96.81% increase of slowly digestible starch (SDS) from 75 to 45% dough hydration. The degree of gelatinization in crust samples was significantly reduced with a depletion in the dough hydration, ranging from 29.90 to 44.36%, which led to an increase of SDS from 7.41 in HHB to 13.78% in LHB (bread basis). Copyright © 2017 Elsevier Ltd. All rights reserved.

  1. Permeability of sediment cores from methane hydrate deposit in the Eastern Nankai Trough, Japan

    Science.gov (United States)

    Konno, Y.; Yoneda, J.; Egawa, K.; Ito, T.; Jin, Y.; Kida, M.; Suzuki, K.; Nakatsuka, Y.; Nagao, J.

    2013-12-01

    Effective and absolute permeability are key parameters for gas production from methane-hydrate-bearing sandy sediments. Effective and/or absolute permeability have been measured using methane-hydrate-bearing sandy cores and clayey and silty cores recovered from Daini Atsumi Knoll in the Eastern Nankai Trough during the 2012 JOGMEC/JAPEX Pressure coring operation. Liquid-nitrogen-immersed cores were prepared by rapid depressurization of pressure cores recovered by a pressure coring system referred to as the Hybrid PCS. Cores were shaped cylindrically on a lathe with spraying of liquid nitrogen to prevent hydrate dissociation. Permeability was measured by a flooding test or a pressure relaxation method under near in-situ pressure and temperature conditions. Measured effective permeability of hydrate-bearing sediments is less than tens of md, which are order of magnitude less than absolute permeability. Absolute permeability of clayey cores is approximately tens of μd, which would perform a sealing function as cap rocks. Permeability reduction due to a swelling effect was observed for a silty core during flooding test of pure water mimicking hydrate-dissociation-water. Swelling effect may cause production formation damage especially at a later stage of gas production from methane hydrate deposits. This study was financially supported by the Research Consortium for Methane Hydrate Resources in Japan (MH21 Research Consortium) that carries out Japan's Methane Hydrate R&D Program conducted by the Ministry of Economy, Trade and Industry (METI).

  2. Methods to determine hydration states of minerals and cement hydrates

    Energy Technology Data Exchange (ETDEWEB)

    Baquerizo, Luis G., E-mail: luis.baquerizoibarra@holcim.com [Innovation, Holcim Technology Ltd., CH-5113 Holderbank (Switzerland); Matschei, Thomas [Innovation, Holcim Technology Ltd., CH-5113 Holderbank (Switzerland); Scrivener, Karen L. [Laboratory of Construction Materials, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne (Switzerland); Saeidpour, Mahsa; Thorell, Alva; Wadsö, Lars [Building Materials, Lund University, Box 124, 221 000 Lund (Sweden)

    2014-11-15

    This paper describes a novel approach to the quantitative investigation of the impact of varying relative humidity (RH) and temperature on the structure and thermodynamic properties of salts and crystalline cement hydrates in different hydration states (i.e. varying molar water contents). The multi-method approach developed here is capable of deriving physico-chemical boundary conditions and the thermodynamic properties of hydrated phases, many of which are currently missing from or insufficiently reported in the literature. As an example the approach was applied to monosulfoaluminate, a phase typically found in hydrated cement pastes. New data on the dehydration and rehydration of monosulfoaluminate are presented. Some of the methods used were validated with the system Na{sub 2}SO{sub 4}–H{sub 2}O and new data related to the absorption of water by anhydrous sodium sulfate are presented. The methodology and data reported here should permit better modeling of the volume stability of cementitious systems exposed to various different climatic conditions.

  3. Methods to determine hydration states of minerals and cement hydrates

    International Nuclear Information System (INIS)

    Baquerizo, Luis G.; Matschei, Thomas; Scrivener, Karen L.; Saeidpour, Mahsa; Thorell, Alva; Wadsö, Lars

    2014-01-01

    This paper describes a novel approach to the quantitative investigation of the impact of varying relative humidity (RH) and temperature on the structure and thermodynamic properties of salts and crystalline cement hydrates in different hydration states (i.e. varying molar water contents). The multi-method approach developed here is capable of deriving physico-chemical boundary conditions and the thermodynamic properties of hydrated phases, many of which are currently missing from or insufficiently reported in the literature. As an example the approach was applied to monosulfoaluminate, a phase typically found in hydrated cement pastes. New data on the dehydration and rehydration of monosulfoaluminate are presented. Some of the methods used were validated with the system Na 2 SO 4 –H 2 O and new data related to the absorption of water by anhydrous sodium sulfate are presented. The methodology and data reported here should permit better modeling of the volume stability of cementitious systems exposed to various different climatic conditions

  4. Novel understanding of calcium silicate hydrate from dilute hydration

    KAUST Repository

    Zhang, Lina

    2017-05-13

    The perspective of calcium silicate hydrate (C-S-H) is still confronting various debates due to its intrinsic complicated structure and properties after decades of studies. In this study, hydration at dilute suspension of w/s equaling to 10 was conducted for tricalcium silicate (C3S) to interpret long-term hydration process and investigate the formation, structure and properties of C-S-H. Based on results from XRD, IR, SEM, NMR and so forth, loose and dense clusters of C-S-H with analogous C/S ratio were obtained along with the corresponding chemical formulae proposed as Ca5Si4O13∙6.2H2O. Crystalline structure inside C-S-H was observed by TEM, which was allocated at the foil-like proportion as well as the edge of wrinkles of the product. The long-term hydration process of C3S in dilute suspension could be sketchily described as migration of calcium hydroxide and in-situ growth of C-S-H with equilibrium silicon in aqueous solution relatively constant and calcium varied.

  5. Impacts of Hydrate Distribution on the Hydro-Thermo-Mechanical Properties of Hydrate-Bearing Sediments

    Science.gov (United States)

    Dai, S.; Seol, Y.

    2015-12-01

    In general, hydrate makes the sediments hydraulically less conductive, thermally more conductive, and mechanically stronger; yet the dependency of these physical properties on hydrate saturation varies with hydrate distribution and morphology. Hydrate distribution in sediments may cause the bulk physical properties of their host sediments varying several orders of magnitude even with the same amount of hydrate. In natural sediments, hydrate morphology is inherently governed by the burial depth and the grain size of the host sediments. Compare with patchy hydrate, uniformly distributed hydrate is more destructive to fluid flow, yet leads to higher gas and water permeability during hydrate dissociation due to the easiness of forming percolation paths. Water and hydrate have similar thermal conductivity values; the bulk thermal conductivity of hydrate-bearing sediments depends critically on gas-phase saturation. 60% of gas saturation may result in evident thermal conductivity drop and hinder further gas production. Sediments with patchy hydrate yield lower stiffness than that with cementing hydrate but higher stiffness than that with pore filling and loading bearing hydrate. Besides hydrate distribution, the stress state and loading history also play an important role in the mechanical behavior of hydrate-bearing sediments.

  6. Nephrogenic systemic fibrosis versus contrast-induced nephropathy: risks and benefits of contrast-enhanced MR and CT in renally impaired patients

    DEFF Research Database (Denmark)

    Martin, Diego R; Semelka, Richard C; Chapman, Arlene

    2009-01-01

    -sectional imaging modality. Factors to consider include the relative risks of the contrast agent. Other factors include the relative procedural risks, including radiation risks and the relative expected diagnostic yield of the examination technique (12). In this review we describe both nephrogenic systemic fibrosis...... and contrast-induced nephropathy to compare the implications with regard to relative risks and benefits of contrast-enhanced MRI or CT in patients with impaired renal function. J. Magn. Reson. Imaging 2009;30:1350-1356. (c) 2009 Wiley-Liss, Inc....

  7. Is Br2 hydration hydrophobic?

    Science.gov (United States)

    Alcaraz-Torres, A; Gamboa-Suárez, A; Bernal-Uruchurtu, M I

    2017-02-28

    The spectroscopic properties of bromine in aqueous systems suggest it can behave as either hydrophilic or hydrophobic solute. In small water clusters, the halogen bond and the hydrogen-halogen interaction are responsible for its specific way of binding. In water hydrates, it is efficiently hosted by two different cages forming the crystal structure and it has been frequently assumed that there is little or no interaction between the guest and the host. Bromine in liquid solution poses a challenging question due to its non-negligible solubility and the large blue shift measured in its absorption spectra. Using a refined semi-empirical force field, PM3-PIF, we performed a Born-Oppenheimer molecular dynamics study of bromine in liquid water. Here we present a detailed study in which we retrieved the most representative hydration structures in terms of the most frequent positions around bromine and the most common water orientations. Albeit being an approximate description of the total hydration phenomenon, it captures the contribution of the leading molecular interactions in form of the recurrent structures. Our findings confirm that the spectroscopic signature is mainly caused by the closest neighbors. The dynamics of the whole first hydration shell strongly suggests that the external molecules in that structure effectively isolate the bulk from the presence of bromine. The solvation structure fluctuates from a hydrophilic to a hydrophobic-like environment along the studied trajectory.

  8. Hydration modeling of calcium sulphates

    NARCIS (Netherlands)

    de Korte, A.C.J.; Brouwers, H.J.H.; Al-Mattarneh, Hashem; Mustapha, Kamal N.; Nuruddin, Muhd Fadhil

    2008-01-01

    The CEMHYD3D model has been extended at the University of Twente in the last ten years [1,2]. At present the cement hydration model is extended for the use of gypsum. Although gypsum was present in the model already, the model was not suitable for high contents of gypsum and did not include the

  9. Prospective evaluation of the development of contrast-induced nephropathy in patients with acute coronary syndrome undergoing rotational coronary angiography vs. conventional coronary angiography: CINERAMA study

    Directory of Open Access Journals (Sweden)

    Diego Fernández-Rodríguez

    2018-03-01

    Full Text Available Introduction and objectives: Rotational coronary angiography (RCA requires less contrast to be administered and can prevent the onset of contrast-induced nephropathy (CIN during invasive coronary procedures. The aim of the study is to evaluate the impact of RCA on CIN (increase in serum creatinine ≥0.5 mg/dL or ≥25% after an acute coronary syndrome. Methods: From April to September 2016, patients suffering acute coronary syndromes who underwent diagnostic coronary angiography, with the possibility of ad hoc coronary angioplasty, were prospectively enrolled. At the operator's discretion, patients underwent RCA or conventional coronary angiography (CCA. CIN (primary endpoint, as well as analytical, angiographic and clinical endpoints, were compared between groups. Results: Of the 235 patients enrolled, 116 patients received RCA and 119 patients received CCA. The RCA group was composed of older patients (64.0 ± 11.8 years vs. 59.7 ± 12.1 years; p = 0.006, a higher proportion of women (44.8 vs. 17.6%; p < 0.001, patients with a lower estimated glomerular filtration rate (76 ± 25 vs. 86 ± 27 ml/min/1.73 m2; p = 0.001, and patients who underwent fewer coronary angioplasties (p < 0.001 compared with the CCA group. Furthermore, the RCA group, received less contrast (113 ± 92 vs. 169 ± 103 ml; p < 0.001, including in diagnostic procedures (54 ± 24 vs. 85 ± 56 ml; p < 0.001 and diagnostic-therapeutic procedures (174 ± 64 vs. 205 ± 98 ml; p = 0.049 compared with the CCA group. The RCA group presented less CIN (4.3 vs. 22.7%; p < 0.001 compared to the CCA group, and this finding was maintained in the regression analysis (Adjusted relative risk: 0.868; 95% CI: 0.794–0.949; p = 0.002. There were no differences in clinical endpoints between the groups. Conclusions: RCA was associated

  10. HYDRATION AND TEMPERATURE IN TENNIS - A PRACTICAL REVIEW

    OpenAIRE

    Mark S. Kovacs

    2006-01-01

    Competitive tennis is typically played in warm and hot environments. Because hypohydration will impair tennis performance and increases the risk of heat injury, consumption of appropriate fluid levels is necessary to prevent dehydration and enhance performance. The majority of research in this area has focused on continuous aerobic activity - unlike tennis, which has average points lasting less than ten seconds with rest periods dispersed between each work period. For this reason, hydration a...

  11. Observed gas hydrate morphologies in marine sediment

    Energy Technology Data Exchange (ETDEWEB)

    Holland, M.; Schultheiss, P.; Roberts, J.; Druce, M. [Geotek Ltd., Daventry, Northamptonshire (United Kingdom)

    2008-07-01

    The morphology of gas hydrate in marine sediments determines the basic physical properties of the sediment-hydrate matrix and provides information regarding the formation of gas hydrate deposits, and the nature of the disruption that will occur on dissociation. Small-scale morphology is useful in estimating the concentrations of gas hydrate from geophysical data. It is also important for predicting their response to climate change or commercial production. Many remote techniques for gas hydrate detection and quantification depend on hydrate morphology. In this study, morphology of gas hydrate was examined in HYACINTH pressure cores from recent seagoing expeditions. Visual and infrared observations from non-pressurized cores were also used. The expeditions and pressure core analysis were described in detail. This paper described the difference between two types of gas hydrate morphologies, notably pore-filling and grain-displacing. Last, the paper addressed the impact of hydrate morphology. It was concluded that a detailed morphology of gas hydrate is an essential component for a full understanding of the past, present, and future of any gas hydrate environment. 14 refs., 4 figs.

  12. Seismic reflections associated with submarine gas hydrates

    Energy Technology Data Exchange (ETDEWEB)

    Andreassen, K

    1996-12-31

    Gas hydrates are often suggested as a future energy resource. This doctoral thesis improves the understanding of the concentration and distribution of natural submarine gas hydrates. The presence of these hydrates are commonly inferred from strong bottom simulating reflection (BSR). To investigate the nature of BSR, this work uses seismic studies of hydrate-related BSRs at two different locations, one where gas hydrates are accepted to exist and interpreted to be very extensive (in the Beaufort Sea), the other with good velocity data and downhole logs available (offshore Oregon). To ascertain the presence of free gas under the BSR, prestack offset data must supplement near-vertical incidence seismic data. A tentative model for physical properties of sediments partially saturated with gas hydrate and free gas is presented. This model, together with drilling information and seismic data containing the BSR beneath the Oregon margin and the Beaufort Sea, made it possible to better understand when to apply the amplitude-versus-offset (AVO) method to constrain BSR gas hydrate and gas models. Distribution of natural gas hydrates offshore Norway and Svalbard is discussed and interpreted as reflections from the base of gas hydrate-bearing sediments, overlying sediments containing free gas. Gas hydrates inferred to exist at the Norwegian-Svalbard continental margin correlate well with Cenozoic depocenters, and the associated gas is assumed to be mainly biogenic. Parts of that margin have a high potential for natural gas hydrates of both biogenic and thermogenic origin. 235 refs., 86 figs., 4 tabs.

  13. Seismic reflections associated with submarine gas hydrates

    Energy Technology Data Exchange (ETDEWEB)

    Andreassen, K.

    1995-12-31

    Gas hydrates are often suggested as a future energy resource. This doctoral thesis improves the understanding of the concentration and distribution of natural submarine gas hydrates. The presence of these hydrates are commonly inferred from strong bottom simulating reflection (BSR). To investigate the nature of BSR, this work uses seismic studies of hydrate-related BSRs at two different locations, one where gas hydrates are accepted to exist and interpreted to be very extensive (in the Beaufort Sea), the other with good velocity data and downhole logs available (offshore Oregon). To ascertain the presence of free gas under the BSR, prestack offset data must supplement near-vertical incidence seismic data. A tentative model for physical properties of sediments partially saturated with gas hydrate and free gas is presented. This model, together with drilling information and seismic data containing the BSR beneath the Oregon margin and the Beaufort Sea, made it possible to better understand when to apply the amplitude-versus-offset (AVO) method to constrain BSR gas hydrate and gas models. Distribution of natural gas hydrates offshore Norway and Svalbard is discussed and interpreted as reflections from the base of gas hydrate-bearing sediments, overlying sediments containing free gas. Gas hydrates inferred to exist at the Norwegian-Svalbard continental margin correlate well with Cenozoic depocenters, and the associated gas is assumed to be mainly biogenic. Parts of that margin have a high potential for natural gas hydrates of both biogenic and thermogenic origin. 235 refs., 86 figs., 4 tabs.

  14. Influence of fluorosurfactants on hydrate formation rates

    Energy Technology Data Exchange (ETDEWEB)

    Kim, C.U.; Jeong, K.E.; Chae, H.J.; Jeong, S.Y. [Korea Reasearch Inst. of Chemical Technology, Alternative Chemicals/Fuel Research Center, Yuseong-Gu, Daejon (Korea, Republic of)

    2008-07-01

    Gas hydrates, or clathrates, are ice-like solids that forms when natural gas is in contact with liquid water or ice under high pressure and low temperature. There is significant interest in studying the storage and transportation of gas in the form of hydrates. However, a critical problem impacting the industrial application of gas hydrates for storage and transportation of natural gas is the slow formation rate of natural gas hydrate. Researchers have previously reported on the promotion effect of some additives on gas hydrate formation and hydrate gas content. Fluorosurfactants are significantly superior to nonfluorinated surfactants in wetting action, as well as stability in harsh environments, both thermal and chemical. This paper discussed an experimental investigation into the effects of fluorosurfactants with different ionic types on the formation of methane hydrate. The surfactants used were FSN-100 of DuPont Zonyl as non-ionic surfactant and FC-143 of DuPont as anionic surfactant. The paper discussed the experimental apparatus for methane hydrate formation. It also discussed hydrate formation kinetics and the series of hydrate formation experiments that were conducted in the presence of fluorosurfactants. Last, the paper explored the results of the study. It was concluded that anionic fluorosurfactant of FC-143 had a better promoting effect on methane hydrate formation compared with nonionic surfactant of FSN-100. 8 refs., 2 tabs., 2 figs.

  15. Gas hydrates in gas storage caverns; Gashydrate bei der Gaskavernenspeicherung

    Energy Technology Data Exchange (ETDEWEB)

    Groenefeld, P. [Kavernen Bau- und Betriebs-GmbH, Hannover (Germany)

    1997-12-31

    Given appropriate pressure and temperature conditions the storage of natural gas in salt caverns can lead to the formation of gas hydrates in the producing well or aboveground operating facilities. This is attributable to the stored gas becoming more or less saturated with water vapour. The present contribution describes the humidity, pressure, and temperature conditions conducive to gas hydrate formation. It also deals with the reduction of the gas removal capacity resulting from gas hydrate formation, and possible measures for preventing hydrate formation such as injection of glycol, the reduction of water vapour absorption from the cavern sump, and dewatering of the cavern sump. (MSK) [Deutsch] Bei der Speicherung von Erdgas in Salzkavernen kann es unter entsprechenden Druck- und Temperaturverhaeltnissen zur Gashydratbildung in den Foerdersonden oder obertaegigen Betriebseinrichtungen kommen, weil sich das eingelagerte Gas mehr oder weniger mit Wasserdampf aufsaettigt. Im Folgenden werden die Feuchtigkeits-, Druck- und Temperaturbedingungen, die zur Hydratbildung fuehren erlaeutert. Ebenso werden die Verringerung der Auslagerungskapazitaet durch die Hydratbildung, Massnahmen zur Verhinderung der Hydratbildung wie die Injektion von Glykol, die Verringerung der Wasserdampfaufnahme aus dem Kavernensumpf und die Entwaesserung der Kavernensumpfs selbst beschrieben.

  16. Prolonged carotid sinus reflex is a risk factor for contrast-induced nephropathy following carotid artery stenting.

    Science.gov (United States)

    Kato, T; Sakai, H; Tsujimoto, M; Nishimura, Y

    2011-03-01

    Although many studies have demonstrated that CIN is associated with in-hospital and long-term mortality, the incidence of CIN following CAS is unclear. We investigated the incidence of CIN, defined as an increase from a baseline creatinine value of at least 0.5 mg/dL or 25% within 72 hours of contrast administration, and we also examined renal function in the late phase after CAS. We examined 80 patients who underwent CAS between April 2005 and December 2009. Clinical background, laboratory data, contrast volume, and clinical course were collected and analyzed. The incidence of CIN was 8.8% (7/80), and no patients required hemodialysis. In the group that developed CIN, prolonged CSR after CAS was found in 57.1% (4/7) of cases; this incidence differed significantly (P = .001) from that in the group without development of CIN. Neither preoperative renal function, contrast volume, nor history was related to the incidence of CIN, while on multivariate analysis, prolonged CSR was found to be an independent risk factor for CIN. The incidence of elevation in creatinine values at 6 months after CAS was 8.2% (6/73). All patients who developed delayed renal impairment had pre-existing CKD; this finding differed significantly (P = .04) from that in the group without development of delayed renal impairment. Because patients who develop prolonged CSR after CAS are at increased risk of perioperative major adverse clinical events including CIN, patients at high risk for this condition should be carefully managed to prevent increased morbidity and mortality.

  17. Hydrates plugs dissociation in pipelines; Dissociation des bouchons d'hydrates de gaz dans les conduites petrolieres sous-marines

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen Hong, D.

    2005-03-15

    Natural gas hydrates plugs cause problems during drilling, well operations, production, transportation and processing of oil and gas. Especially, it is a very serious problem in off-shore oil transportation where low temperature and high pressure become more and more favourable to gas hydrate formation as the new production wells are more and more deeper. Up to now, although many studies have been developed concerning the possibility of preventing pipe plugging, there is limited information in open literature on hydrate plugs dissociation and all models in literature are numerically complicated. In this study, hydrate plugs are formed from water in n-dodecane mixture with addition of a dispersant E102B in two different experimental apparatus in order to obtain hydrates plugs with different sizes (diameter of 7, 10.75 and 12 cm). Then, the plugs are dissociated by the method of two-sided depressurization. In this paper, we propose a numerical model which describes the dissociation of gas hydrate plugs in pipelines. The numerical model, which is constructed for cylindrical coordinates and for two-sided pressurization, is based on enthalpy method. We present also an approximate analytical model which has an average error 2.7 % in comparison with the numerical model. The excellent agreement between our experimental results, literature data and the two models shows that the models give a good prediction independently of the pipeline diameter, plug porosity and gas. The simplicity of the analytical model will make it easier in industrial applications. (author)

  18. Hydration and temperature in tennis - a practical review.

    Science.gov (United States)

    Kovacs, Mark S

    2006-03-01

    Competitive tennis is typically played in warm and hot environments. Because hypohydration will impair tennis performance and increases the risk of heat injury, consumption of appropriate fluid levels is necessary to prevent dehydration and enhance performance. The majority of research in this area has focused on continuous aerobic activity - unlike tennis, which has average points lasting less than ten seconds with rest periods dispersed between each work period. For this reason, hydration and temperature regulation methods need to be specific to the activity. Tennis players can sweat more than 2.5 L·h(-1) and replace fluids at a slower rate during matches than in practice. Latter stages of matches and tournaments are when tennis players are more susceptible to temperature and hydration related problems. Sodium (Na(+)) depletion, not potassium (K(+)), is a key electrolyte in tennis related muscle cramps. However, psychological and competitive factors also contribute. CHO drinks have been shown to promote fluid absorption to a greater degree than water alone, but no performance benefits have been shown in tennis players in short matches. It is advisable to consume a CHO beverage if practice or matches are scheduled longer than 90-120 minutes. Key PointsAlthough substantial research has been performed on temperature and hydration concerns in aerobic activities, there is little information with regard to tennis performance and safetyTennis athletes should be on an individualized hydration schedule, consuming greater than 200ml of fluid every changeover (approximately 15 minutes).Optimum hydration and temperature regulation will reduce the chance of tennis related muscle cramps and performance decrements.

  19. The optimal definition of contrast-induced acute kidney injury for prediction of inpatient mortality in patients undergoing percutaneous coronary interventions.

    Science.gov (United States)

    Parsh, Jessica; Seth, Milan; Briguori, Carlo; Grossman, Paul; Solomon, Richard; Gurm, Hitinder S

    2016-05-01

    It is unknown which definition of contrast-induced acute kidney injury (CI-AKI) in the setting of percutaneous coronary interventions is best associated with inpatient mortality and whether this association is stable across patients with various preprocedural serum creatinine (SCr) values. We applied logistic regression models to multiple CI-AKI definitions used by the Kidney Disease Improving Global Outcomes guidelines and previously published studies to examine the impact of preprocedural SCr on a candidate definition's correlation with the adverse outcome of inpatient mortality. We used likelihood ratio tests to examine candidate definitions and identify those where association with inpatient mortality remained constant regardless of preprocedural SCr. These definitions were assessed for specificity, sensitivity, and positive and negative predictive values to identify an optimal definition. Our study cohort included 119,554 patients who underwent percutaneous coronary intervention in Michigan between 2010 and 2014. Most commonly used definitions were not associated with inpatient mortality in a constant fashion across various preprocedural SCr values. Of the 266 candidate definitions examined, 16 definition's association with inpatient mortality was not significantly altered by preprocedural SCr. Contrast-induced acute kidney injury defined as an absolute increase of SCr ≥0.3 mg/dL and a relative SCr increase ≥50% was selected as the optimal candidate using Perkins and Shisterman decision theoretic optimality criteria and was highly predictive of and specific for inpatient mortality. We identified the optimal definition for CI-AKI to be an absolute increase in SCr ≥0.3 mg/dL and a relative SCr increase ≥50%. Further work is needed to validate this definition in independent studies and to establish its utility for clinical trials and quality improvement efforts. Copyright © 2016 Elsevier Inc. All rights reserved.

  20. Clinker mineral hydration at reduced relative humidities

    DEFF Research Database (Denmark)

    Jensen, Ole Mejlhede

    1998-01-01

    This report deals with gas phase hydration of pure cement clinker minerals at reduced relative humidities. This is an important subject in relation to modern high performance concrete which may self-desiccate during hydration. In addition the subject has relevance to storage stability where...... prehydration may occur. In the report both theoretical considerations and experimental data are presented. It is suggested that the initiation of hydration during water vapour exposure is nucleation controlled....

  1. Thermal conductivity of hydrate-bearing sediments

    Science.gov (United States)

    Cortes, Douglas D.; Martin, Ana I.; Yun, Tae Sup; Francisca, Franco M.; Santamarina, J. Carlos; Ruppel, Carolyn D.

    2009-01-01

    A thorough understanding of the thermal conductivity of hydrate-bearing sediments is necessary for evaluating phase transformation processes that would accompany energy production from gas hydrate deposits and for estimating regional heat flow based on the observed depth to the base of the gas hydrate stability zone. The coexistence of multiple phases (gas hydrate, liquid and gas pore fill, and solid sediment grains) and their complex spatial arrangement hinder the a priori prediction of the thermal conductivity of hydrate-bearing sediments. Previous studies have been unable to capture the full parameter space covered by variations in grain size, specific surface, degree of saturation, nature of pore filling material, and effective stress for hydrate-bearing samples. Here we report on systematic measurements of the thermal conductivity of air dry, water- and tetrohydrofuran (THF)-saturated, and THF hydrate–saturated sand and clay samples at vertical effective stress of 0.05 to 1 MPa (corresponding to depths as great as 100 m below seafloor). Results reveal that the bulk thermal conductivity of the samples in every case reflects a complex interplay among particle size, effective stress, porosity, and fluid-versus-hydrate filled pore spaces. The thermal conductivity of THF hydrate–bearing soils increases upon hydrate formation although the thermal conductivities of THF solution and THF hydrate are almost the same. Several mechanisms can contribute to this effect including cryogenic suction during hydrate crystal growth and the ensuing porosity reduction in the surrounding sediment, increased mean effective stress due to hydrate formation under zero lateral strain conditions, and decreased interface thermal impedance as grain-liquid interfaces are transformed into grain-hydrate interfaces.

  2. Comparing effectiveness of rhamnolipid biosurfactant with a quaternary ammonium salt surfactant for hydrate anti-agglomeration.

    Science.gov (United States)

    York, J Dalton; Firoozabadi, Abbas

    2008-01-24

    Natural gas is projected to be the premium fuel of the 21st century because of availability, as well as economical and environmental considerations. Natural gas is coproduced with water from the subsurface forming gas hydrates. Hydrate formation may result in shutdown of onshore and offshore operations. Industry practice has been usage of alcohols--which have undesirable environmental impacts--to affect bulk-phase properties and inhibit hydrate formation. An alternative to alcohols is changing the surface properties through usage of polymers and surfactants, effective at 0.5-3 wt % of coproduced water. One group of low-dosage hydrate inhibitors (LDHI) are kinetic inhibitors, which affect nucleation rate and growth. A second group of LDHI are anti-agglomerants, which prevent agglomeration of small hydrate crystallites. Despite great potential, reported work on hydrate anti-agglomeration is very limited. In this paper, our focus is on the use of two vastly different surfactants as anti-agglomerants. We use a model oil, water, and tetrahydrofuran as a hydrate-forming species. We examine the effectiveness of a quaternary ammonium salt (i.e., quat). Visual observation measurements show that a small concentration of the quat (0.01%) can prevent agglomeration. However, a quat is not a green chemical and therefore may be undesirable. We show that a rhamnolipid biosurfactant can be effective to a concentration of 0.05 wt %. One difference between the two surfactants is the stability of the water-in-oil emulsions created. The biosurfactant forms a less stable emulsion, which makes it very desirable for hydrate application.

  3. Physical Properties of Gas Hydrates: A Review

    Energy Technology Data Exchange (ETDEWEB)

    Gabitto, Jorge [Prairie View A& M University; Tsouris, Costas [ORNL

    2010-01-01

    Methane gas hydrates in sediments have been studied by several investigators as a possible future energy resource. Recent hydrate reserves have been estimated at approximately 1016?m3 of methane gas worldwide at standard temperature and pressure conditions. In situ dissociation of natural gas hydrate is necessary in order to commercially exploit the resource from the natural-gas-hydrate-bearing sediment. The presence of gas hydrates in sediments dramatically alters some of the normal physical properties of the sediment. These changes can be detected by field measurements and by down-hole logs. An understanding of the physical properties of hydrate-bearing sediments is necessary for interpretation of geophysical data collected in field settings, borehole, and slope stability analyses; reservoir simulation; and production models. This work reviews information available in literature related to the physical properties of sediments containing gas hydrates. A brief review of the physical properties of bulk gas hydrates is included. Detection methods, morphology, and relevant physical properties of gas-hydrate-bearing sediments are also discussed.

  4. Accelerated hydration of high silica cements

    International Nuclear Information System (INIS)

    Walker, Colin; Yui, Mikazu

    2012-01-01

    Current Japanese designs for high level radioactive waste (HLW) repositories anticipate the use of both bentonite (buffer and backfill material) and cement based materials. Using hydrated Ordinary Portland Cement (OPC) as a grouting material is undesirable because the associated high pH buffer will have an undisputed detrimental effect on the performance of the bentonite buffer and backfill and of the host rock by changing its porosity. Instead, hydrated low pH cement (LopHC) grouting materials are being developed to provide a pH inferior or equal to 11 to reduce these detrimental effects. LopHC grouting materials use mixtures of superfine OPC (SOPC) clinker and silica fume (SF), and are referred as high silica cements (HSC). The focus of the present study was to identify the development of the unhydrated and hydrated mineral assemblage and the solution chemistry during the hydration of HSC. Since hydration experiments of cementitious materials are notably slow, a ball mill was used to accelerate hydration. This was done for two reasons. Firstly, to develop a method to rapidly hydrate cement based materials without the need for higher temperatures (which can alter the mineral assemblage), and secondly, to ensure that the end point of hydration was reached in a reasonable time frame and so to realize the final mineralogy and solution chemistry of hydrated HSC

  5. Microstructure of natural hydrate host sediments

    International Nuclear Information System (INIS)

    Jones, K.W.; Kerkar, P.B.; Mahajan, D.; Lindquist, W.B.; Feng, H.

    2007-01-01

    There is worldwide interest in the study of natural gas hydrate because of its potential impact on world energy resources, control on seafloor stability, significance as a drilling hazard and probable impact on climate as a reservoir of a major greenhouse gas. Gas hydrates can (a) be free floating in the sediment matrix (b) contact, but do not cement, existing sediment grains, or (c) actually cement and stiffen the bulk sediment. Seismic surveys, often used to prospect for hydrates over a large area, can provide knowledge of the location of large hydrate concentrations because the hydrates within the sediment pores modify seismic properties. The ability to image a sample at the grain scale and to determine the porosity, permeability and seismic profile is of great interest since these parameters can help in determining the location of hydrates with certainty. We report here on an investigation of the structure of methane hydrate sediments at the grain-size scale using the synchrotron radiation-based computed microtomography (CMT) technique. Work has started on the measurements of the changes occurring as tetrahydrofuran hydrate, a surrogate for methane hydrate, is formed in the sediment

  6. Side Effects of Radiographic Contrast Media: Pathogenesis, Risk Factors, and Prevention

    Directory of Open Access Journals (Sweden)

    Michele Andreucci

    2014-01-01

    Full Text Available Radiocontrast media (RCM are medical drugs used to improve the visibility of internal organs and structures in X-ray based imaging techniques. They may have side effects ranging from itching to a life-threatening emergency, known as contrast-induced nephropathy (CIN. We define CIN as acute renal failure occurring within 24–72 hrs of exposure to RCM that cannot be attributed to other causes. It usually occurs in patients with preexisting renal impairment and diabetes. The mechanisms underlying CIN include reduction in medullary blood flow leading to hypoxia and direct tubule cell damage and the formation of reactive oxygen species. Identification of patients at high risk for CIN is important. We have reviewed the risk factors and procedures for prevention, providing a long list of references enabling readers a deep evaluation of them both. The first rule to follow in patients at risk of CIN undergoing radiographic procedure is monitoring renal function by measuring serum creatinine and calculating the eGFR before and once daily for 5 days after the procedure. It is advised to discontinue potentially nephrotoxic medications, to choose radiocontrast media at lowest dosage, and to encourage oral or intravenous hydration. In high-risk patients N-acetylcysteine may also be given.

  7. Side Effects of Radiographic Contrast Media: Pathogenesis, Risk Factors, and Prevention

    Science.gov (United States)

    Tasanarong, Adis

    2014-01-01

    Radiocontrast media (RCM) are medical drugs used to improve the visibility of internal organs and structures in X-ray based imaging techniques. They may have side effects ranging from itching to a life-threatening emergency, known as contrast-induced nephropathy (CIN). We define CIN as acute renal failure occurring within 24–72 hrs of exposure to RCM that cannot be attributed to other causes. It usually occurs in patients with preexisting renal impairment and diabetes. The mechanisms underlying CIN include reduction in medullary blood flow leading to hypoxia and direct tubule cell damage and the formation of reactive oxygen species. Identification of patients at high risk for CIN is important. We have reviewed the risk factors and procedures for prevention, providing a long list of references enabling readers a deep evaluation of them both. The first rule to follow in patients at risk of CIN undergoing radiographic procedure is monitoring renal function by measuring serum creatinine and calculating the eGFR before and once daily for 5 days after the procedure. It is advised to discontinue potentially nephrotoxic medications, to choose radiocontrast media at lowest dosage, and to encourage oral or intravenous hydration. In high-risk patients N-acetylcysteine may also be given. PMID:24895606

  8. Application of empirical hydration distribution functions around polar atoms for assessing hydration structures of proteins

    International Nuclear Information System (INIS)

    Matsuoka, Daisuke; Nakasako, Masayoshi

    2013-01-01

    Highlights: ► Empirical distribution functions of water molecules in protein hydration are made. ► The functions measure how hydrogen-bond geometry in hydration deviate from ideal. ► The functions assess experimentally identified hydration structures of protein. - Abstract: To quantitatively characterize hydrogen-bond geometry in local hydration structures of proteins, we constructed a set of empirical hydration distribution functions (EHDFs) around polar protein atoms in the main and side chains of 11 types of hydrophilic amino acids (D. Matsuoka, M. Nakasako, Journal of Physical Chemistry B 113 (2009) 11274). The functions are the ensemble average of possible hydration patterns around the polar atoms, and describe the anisotropic deviations from ideal hydrogen bond geometry. In addition, we defined probability distribution function of hydration water molecules (PDFH) over the hydrophilic surface of a protein as the sum of EHDFs of solvent accessible polar protein atoms. The functions envelop most of hydration sites identified in crystal structures of proteins (D. Matsuoka, M. Nakasako, Journal of Physical Chemistry B 114 (2010) 4652). Here we propose the application of EHDFs and PDFHs for assessing crystallographically identified hydration structures of proteins. First, hydration water molecules are classified with respect to the geometry in hydrogen bonds in referring EHDFs. Difference Fourier electron density map weighted by PDFH of protein is proposed to identify easily density peaks as candidates of hydration water molecules. A computer program implementing those ideas was developed and used for assessing hydration structures of proteins

  9. Waters of Hydration of Cupric Hydrates: A Comparison between Heating and Absorbance Methods

    Science.gov (United States)

    Barlag, Rebecca; Nyasulu, Frazier

    2011-01-01

    The empirical formulas of four cupric hydrates are determined by measuring the absorbance in aqueous solution. The Beer-Lambert Law is verified by constructing a calibration curve of absorbance versus known Cu[superscript 2+](aq) concentration. A solution of the unknown hydrate is prepared by using 0.2-0.3 g of hydrate, and water is added such…

  10. Hydration in soccer: a review

    Directory of Open Access Journals (Sweden)

    Monteiro Cristiano Ralo

    2003-01-01

    Full Text Available Hydration should be considered before, during and after the exercise. This review intends to approach the main points of hydration process in soccer. The replacement of fluids during exercise is proportional to some factors, such as: exercise intensity; climatic conditions; the athlete's acclimatization; the athlete's physical conditioning; physiologic individual characteristics and the player's biomechanics. Performance is improved when players ingest not only water but also carbohydrate. The rates that carbohydrate and water are absorbed by the organism are limited by the rates of gastric emptying and intestinal absorption. The composition of drinks offered to the players should be influenced by the relative importance of the need of supplying carbohydrates or water; it should be remembered that the depletion of carbohydrate can result in fatigue and decrease of performance, but it is not usually a life-threatening condition. The addition of carbohydrate in these drinks increases the concentrations of blood glucose, increases the use of external fuel through the increase of the glucose oxidation in the muscles and it spares muscle glycogen. So, the ingestion of carbohydrate before and during the exercise can delay the emergence of fatigue and increase the players' performance. Several tactics can be used to avoid dehydration, like hyperhydration before exercise and player's acclimatization. The ideal situation to restore the player's fluid losses is between the sessions of exercises. Since soccer is a sport with quite peculiar characteristics related to hydration, the players should be concerned and educated about the importance of fluid ingestion before, during and after the exercise.

  11. Gas Hydrates | Alaska Division of Geological & Geophysical Surveys

    Science.gov (United States)

    Preliminary Report - Cascadia Margin Gas Hydrates, Volume 204 Initial Report Mallik 2002 GSC Bulletin 585 : Scientific results from the Mallik 2002 gas hydrate production well program Offshore gas hydrate sample

  12. Simulation and Characterization of Methane Hydrate Formation

    Science.gov (United States)

    Dhakal, S.; Gupta, I.

    2017-12-01

    The ever rising global energy demand dictates human endeavor to explore and exploit new and innovative energy sources. As conventional oil and gas reserves deplete, we are constantly looking for newer sources for sustainable energy. Gas hydrates have long been discussed as the next big energy resource to the earth. Its global occurrence and vast quantity of natural gas stored is one of the main reasons for such interest in its study and exploration. Gas hydrates are solid crystalline substances with trapped molecules of gas inside cage-like crystals of water molecules. Gases such as methane, ethane, propane and carbon dioxide can form hydrates but in natural state, methane hydrates are the most common. Subsurface geological conditions with high pressure and low temperature favor the formation and stability of gas hydrates. While the occurrence and potential of gas hydrates as energy source has long been studied, there are still gaps in knowledge, especially in the quantitative research of gas hydrate formation and reservoir characterization. This study is focused on exploring and understanding the geological setting in which gas hydrates are formed and the subsequent changes in rock characteristics as they are deposited. It involves the numerical simulation of methane gas flow through fault to form hydrates. The models are representative of the subsurface geologic setting of Gulf of Mexico with a fault through layers of shale and sandstone. Hydrate formation simulated is of thermogenic origin. The simulations are conducted using TOUGH+HYDRATE, a numerical code developed at the Lawrence Berkley National Laboratory for modeling multiphase flow through porous medium. Simulation results predict that as the gas hydrates form in the pores of the model, the porosity, permeability and other rock properties are altered. Preliminary simulation results have shown that hydrates begin to form in the fault zone and gradually in the sandstone layers. The increase in hydrate

  13. Formation rate of natural gas hydrate

    Energy Technology Data Exchange (ETDEWEB)

    Mork, Marit

    2002-07-01

    The rate of methane hydrate and natural gas hydrate formation was measured in a 9.5 litre stirred tank reactor of standard design. The experiments were performed to better understand the performance and scale-up of a reactor for continuous production of natural gas hydrates. The hydrate formation rate was measured at steady-state conditions at pressures between 70 and 90 bar and temperatures between 7 and 15 deg C. Between 44 and 56 % of the gas continuously supplied to the reactor was converted to hydrate. The experimental results show that the rate of hydrate formation is strongly influenced by gas injection rate and pressure. The effect of stirring rate is less significant and subcooling has no observable effect on the formation rate. Hydrate crystal concentration and gas composition do not influence the hydrate formation rate. Observations of produced hydrate crystals indicate that the crystals are elongated, about 5 micron in diameter and 10 micron long. Analysis of the results shows that the rate of hydrate formation is dominated by gas-liquid mass transfer. A mass transfer model, the bubble-to-crystal model, was developed for the hydrate formation rate in a continuous stirred tank reactor, given in terms of concentration driving force and an overall mass transfer coefficient. The driving force is the difference between the gas concentration at the gas-liquid interface and at the hydrate crystal surface. These concentrations correspond to the solubility of gas in water at experimental temperature and pressure and the solubility of gas at hydrate equilibrium temperature and experimental pressure, respectively. The overall mass transfer coefficient is expressed in terms of superficial gas velocity and impeller power consumption, parameters commonly used in study of stirred tank reactors. Experiments and modeling show that the stirred tank reactor has a considerable potential for increased production capacity. However, at higher hydrate production rates the

  14. Free energy of hydration of niobium oxide

    International Nuclear Information System (INIS)

    Plodinec, M.J.

    1996-01-01

    Some of the glasses being formulated by SRTC researchers contain niobium oxide. In this report, the free energy of hydration of the oxide is calculated from the free energies of formation of the oxide, the hydroxide, and water. This value can be used in calculations of the free energy of hydration of glasses containing niobium

  15. Investigations into surfactant/gas hydrate relationship

    Energy Technology Data Exchange (ETDEWEB)

    Rogers, Rudy; Zhang, Guochang; Dearman, Jennifer; Woods, Charles [Swalm School of Chemical Engineering, Mississippi State University, Mississippi State, MS 39762 (United States)

    2007-03-15

    Gas hydrates have unique physical properties portending useful industrial applications of gas storage, gas separation, or water desalination. When gas hydrates were found in the early 1990s to occur naturally and abundantly in seafloors, three other primary interests and concerns emerged: potential new energy source, climate threat from their greenhouse gases, and seafloor instabilities. This paper presents research showing how anionic synthetic surfactants helped develop an industrial gas hydrate storage process for natural gas and how naturally-occurring in-situ anionic biosurfactants influence the formation and placement of gas hydrates in ocean sediments. The catalytic effects, mechanisms, and surface specificities imparted by synthetic surfactants in the gas storage process and imparted by biosurfactants in porous media are discussed. The Bacillus subtilis bacterium that is indigenous to gas hydrate mounds in the Gulf of Mexico was cultured in the laboratory. Its biosurfactant was separated and found to catalyze gas hydrates in porous media. The experiments indicate that seafloor-biosurfactants can be produced rapidly in-situ to achieve threshold concentrations whereby hydrates are promoted. The biosurfactants accumulate and promote hydrate formation on specific mineral surfaces such as sodium montmorillonite. (author)

  16. 75 FR 9886 - Methane Hydrate Advisory Committee

    Science.gov (United States)

    2010-03-04

    ... DEPARTMENT OF ENERGY Methane Hydrate Advisory Committee AGENCY: Department of Energy, Office of Fossil Energy. ACTION: Notice of open meeting. SUMMARY: This notice announces a meeting of the Methane... the Committee: The purpose of the Methane Hydrate Advisory Committee is to provide advice on potential...

  17. Raman Spectroscopic Studies of Methane Gas Hydrates

    DEFF Research Database (Denmark)

    Hansen, Susanne Brunsgaard; Berg, Rolf W.

    2009-01-01

    A brief review of the Raman spectroscopic studies of methane gas hydrates is given, supported by some new measurements done in our laboratory.......A brief review of the Raman spectroscopic studies of methane gas hydrates is given, supported by some new measurements done in our laboratory....

  18. Multicomponent modelling of Portland cement hydration reactions

    NARCIS (Netherlands)

    Ukrainczyk, N.; Koenders, E.A.B.; Van Breugel, K.

    2012-01-01

    The prospect of cement and concrete technologies depends on more in depth understanding of cement hydration reactions. Hydration reaction models simulate the development of the microstructures that can finally be used to estimate the cement based material properties that influence performance and

  19. METHANE HYDRATE PRODUCTION FROM ALASKAN PERMAFROST

    Energy Technology Data Exchange (ETDEWEB)

    Donn McGuire; Steve Runyon; Richard Sigal; Bill Liddell; Thomas Williams; George Moridis

    2005-02-01

    Natural-gas hydrates have been encountered beneath the permafrost and considered a nuisance by the oil and gas industry for years. Engineers working in Russia, Canada and the USA have documented numerous drilling problems, including kicks and uncontrolled gas releases, in arctic regions. Information has been generated in laboratory studies pertaining to the extent, volume, chemistry and phase behavior of gas hydrates. Scientists studying hydrate potential agree that the potential is great--on the North Slope of Alaska alone, it has been estimated at 590 TCF. However, little information has been obtained on physical samples taken from actual rock containing hydrates. This gas-hydrate project is in the final stages of a cost-shared partnership between Maurer Technology, Noble Corporation, Anadarko Petroleum, and the U.S. Department of Energy's Methane Hydrate R&D program. The purpose of the project is to build on previous and ongoing R&D in the area of onshore hydrate deposition to identify, quantify and predict production potential for hydrates located on the North Slope of Alaska. Hot Ice No. 1 was planned to test the Ugnu and West Sak sequences for gas hydrates and a concomitant free gas accumulation on Anadarko's 100% working interest acreage in section 30 of Township 9N, Range 8E of the Harrison Bay quadrangle of the North Slope of Alaska. The Ugnu and West Sak intervals are favorably positioned in the hydrate-stability zone over an area extending from Anadarko's acreage westward to the vicinity of the aforementioned gas-hydrate occurrences. This suggests that a large, north-to-south trending gas-hydrate accumulation may exist in that area. The presence of gas shows in the Ugnu and West Sak reservoirs in wells situated eastward and down dip of the Hot Ice location indicate that a free-gas accumulation may be trapped by gas hydrates. The Hot Ice No. 1 well was designed to core from the surface to the base of the West Sak interval using the

  20. Clinically Significant Contrast Induced Acute Kidney Injury after Non-Emergent Cardiac Catheterization - Risk Factors and Impact on Length of Hospital Stay

    International Nuclear Information System (INIS)

    Kashif, W.; Yaqub, S.; Khawaja, A.

    2013-01-01

    Objective: To evaluate the frequency and risk factors associated with clinically significant contrast-induced nephropathy (CIN) in patients undergoing non-emergent coronary angiography. Study Design: Descriptive study. Place and Duration of Study: The Aga Khan University Hospital, Karachi, from January 2005 to December 2007. Methodology: Case records of patients who underwent coronary angiography with a serum creatinine of >= 1.5 mg/dl at the time of procedure were evaluated. Clinically significant contrast induced nephropathy (CSCIN) was defined as either doubling of serum creatinine from baseline value within a week following the procedure or need for emergency hemodialysis after the procedure. Results: One hundred and sixteen patients met the inclusion criteria. Mean age was 64.0 +- 11.5 years, 72% were males. Overall prevalence of CIN was 17% (rise of serum creatinine by A= 0.5 mg/dl) while that of clinically significant CIN (CSCIN) was 9.5% (11 patients). Patients with CSCIN had significantly lower left ventricular ejection fraction (p = 0.03, OR: 0.24; 95% CI = 0.06 A= 0.91) and higher prevalence of cerebrovascular disease (p < 0.001, OR: 14.66; 95% CI = 3.30 - 65.08). Mean baseline serum creatinine was significantly higher, 3.0 +- 1.5 vs. 2.0 +- 1.1 mg/dl (p = 0.03, OR: 1.47; 95% CI = 1.03 - 2.11) whereas mean GFR estimated by Cockcroft-Gault formula was significantly lower at 25 +- 7.4 vs. 41.0 +- 14.6 ml/minute (p = 0.001, OR = 0.89, 95% CI = 0.84 A= 0.95) at the time of procedure in patients with CSCIN. Mean length of hospital stay was significantly higher in this group compared to those without CIN, 9.0 +- 5.1 vs. 3.0 +- 3.2 days (p = 0.001, OR = 1.31, 95% CI = 1.12 - 1.54). Multivariate analysis revealed low GFR (p = 0.001, OR = 0.88; 95% CI = 0.82 - 0.95) and low ejection fraction (p = 0.03, OR = 0.20; 95% CI = 0.04 - 0.91) to be independent factors associated with CSCIN. No significant differences were noted between the two groups in patients with

  1. Polyethylene glycol drilling fluid for drilling in marine gas hydrates-bearing sediments: an experimental study

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, G.; Liu, T.; Ning, F.; Tu, Y.; Zhang, L.; Yu, Y.; Kuang, L. [China University of Geosciences, Faculty of Engineering, Wuhan (China)

    2011-07-01

    Shale inhibition, low-temperature performance, the ability to prevent calcium and magnesium-ion pollution, and hydrate inhibition of polyethylene glycol drilling fluid were each tested with conventional drilling-fluid test equipment and an experimental gas-hydrate integrated simulation system developed by our laboratory. The results of these tests show that drilling fluid with a formulation of artificial seawater, 3% bentonite, 0.3% Na{sub 2}CO{sub 3}, 10% polyethylene glycol, 20% NaCl, 4% SMP-2, 1% LV-PAC, 0.5% NaOH and 1% PVP K-90 performs well in shale swelling and gas hydrate inhibition. It also shows satisfactory rheological properties and lubrication at temperature ranges from -8 {sup o}C to 15 {sup o}C. The PVP K-90, a kinetic hydrate inhibitor, can effectively inhibit gas hydrate aggregations at a dose of 1 wt%. This finding demonstrates that a drilling fluid with a high addition of NaCl and a low addition of PVP K-90 is suitable for drilling in natural marine gas-hydrate-bearing sediments. (authors)

  2. Polyethylene Glycol Drilling Fluid for Drilling in Marine Gas Hydrates-Bearing Sediments: An Experimental Study

    Directory of Open Access Journals (Sweden)

    Lixin Kuang

    2011-01-01

    Full Text Available Shale inhibition, low-temperature performance, the ability to prevent calcium and magnesium-ion pollution, and hydrate inhibition of polyethylene glycol drilling fluid were each tested with conventional drilling-fluid test equipment and an experimental gas-hydrate integrated simulation system developed by our laboratory. The results of these tests show that drilling fluid with a formulation of artificial seawater, 3% bentonite, 0.3% Na2CO3, 10% polyethylene glycol, 20% NaCl, 4% SMP-2, 1% LV-PAC, 0.5% NaOH and 1% PVP K-90 performs well in shale swelling and gas hydrate inhibition. It also shows satisfactory rheological properties and lubrication at temperature ranges from −8 °C to 15 °C. The PVP K-90, a kinetic hydrate inhibitor, can effectively inhibit gas hydrate aggregations at a dose of 1 wt%. This finding demonstrates that a drilling fluid with a high addition of NaCl and a low addition of PVP K-90 is suitable for drilling in natural marine gas-hydrate-bearing sediments.

  3. Experimental Setup to Characterize Bentonite Hydration Processes

    International Nuclear Information System (INIS)

    Bru, A.; Casero, D.; Pastor, J. M.

    2001-01-01

    We present an experimental setup to follow-up the hydration process of a bentonite. Clay samples, of 2 cm x 12 cm x 12 cm, were made and introduced in a Hele-Shaw cell with two PMM windows and two steel frames. In hydration experiments, a fluid enters by an orifice in the frame, located both at the top and the bottom of the cell, to perform hydration in both senses. To get a uniform hydration we place a diffuser near the orifice. Volume influxes in hydration cells are registered in time. The evolution of the developed interface was recorded on a videotape. The video cameras was fixed to a holder so that the vertical direction in the monitor was the same as the direction of the larger extension of the cell. (Author) 6 refs

  4. Volume of hydration in terminal cancer patients.

    Science.gov (United States)

    Bruera, E; Belzile, M; Watanabe, S; Fainsinger, R L

    1996-03-01

    In this retrospective study we reviewed the volume and modality of hydration of consecutive series of terminal cancer patients in two different settings. In a palliative care unit 203/290 admitted patients received subcutaneous hydration for 12 +/- 8 days at a daily volume of 1015 +/- 135 ml/day. At the cancer center, 30 consecutive similar patients received intravenous hydration for 11.5 +/- 5 days (P > 0.2) but at a daily volume of 2080 +/- 720 ml/day (P palliative care unit patients required discontinuation of hydration because of complications. Hypodermoclysis was administered mainly as a continuous infusion, an overnight infusion, or in one to three 1-h boluses in 62 (31%), 98 (48%) and 43 (21%) patients, respectively. Our findings suggest that, in some settings, patients may be receiving excessive volumes of hydration by less comfortable routes such as the intravenous route. Increased education and research in this area are badly needed.

  5. Hydration shells exchange charge with their protein

    DEFF Research Database (Denmark)

    Abitan, Haim; Lindgård, Per-Anker; Nielsen, Bjørn Gilbert

    2010-01-01

    . In our experiments, the amplitude of an ultrasonic pressure wave is gradually increased (0–20 atm) while we simultaneously measure the Raman spectra from the hydrated protein (β-lactoglobulin and lysozyme). We detected two types of spectral changes: first, up to 70% increase in the intensity......Investigation of the interaction between a protein and its hydration shells is an experimental and theoretical challenge. Here, we used ultrasonic pressure waves in aqueous solutions of a protein to explore the conformational states of the protein and its interaction with its hydration shells...... the presence of an ultrasonic pressure, a protein and its hydration shells are in thermodynamic and charge equilibrium, i.e. a protein and its hydration shells exchange charges. The ultrasonic wave disrupts these equilibria which are regained within 30–45 min after the ultrasonic pressure is shut off....

  6. METHANE HYDRATE PRODUCTION FROM ALASKAN PERMAFROST

    Energy Technology Data Exchange (ETDEWEB)

    Thomas E. Williams; Keith Millheim; Bill Liddell

    2005-03-01

    Natural-gas hydrates have been encountered beneath the permafrost and considered a nuisance by the oil and gas industry for years. Oil-field engineers working in Russia, Canada and the USA have documented numerous drilling problems, including kicks and uncontrolled gas releases, in Arctic regions. Information has been generated in laboratory studies pertaining to the extent, volume, chemistry and phase behavior of gas hydrates. Scientists studying hydrates agree that the potential is great--on the North Slope of Alaska alone, it has been estimated at 590 TCF. However, little information has been obtained on physical samples taken from actual rock containing hydrates. This gas-hydrate project is a cost-shared partnership between Maurer Technology, Anadarko Petroleum, Noble Corporation, and the U.S. Department of Energy's Methane Hydrate R&D program. The purpose of the project is to build on previous and ongoing R&D in the area of onshore hydrate deposition to help identify, quantify and predict production potential for hydrates located on the North Slope of Alaska. As part of the project work scope, team members drilled and cored the HOT ICE No. 1 on Anadarko leases beginning in January 2003 and completed in March 2004. Due to scheduling constraints imposed by the Arctic drilling season, operations at the site were suspended between April 21, 2003 and January 30, 2004. An on-site core analysis laboratory was designed, constructed and used for determining physical characteristics of frozen core immediately after it was retrieved from the well. The well was drilled from a new and innovative Anadarko Arctic Platform that has a greatly reduced footprint and environmental impact. Final efforts of the project were to correlate geology, geophysics, logs, and drilling and production data and provide this information to scientists for future hydrate operations. Unfortunately, no gas hydrates were encountered in this well; however, a wealth of information was generated

  7. Geometric changes of parotid glands caused by hydration during chemoradiotherapy

    International Nuclear Information System (INIS)

    Kager, Petronella M.; Weerdenburg, Sanne C. C. van; Kranen, Simon R. van; Beek, Suzanne van; Lamers-Kuijper, Elisabeth A.; Heemsbergen, Wilma D.; Hamming-Vrieze, Olga; Remeijer, Peter

    2015-01-01

    Plan adaptation during the course of (chemo)radiotherapy of H&N cancer requires repeat CT scanning to capture anatomy changes such as parotid gland shrinkage. Hydration, applied to prevent nephrotoxicity from cisplatin, could temporarily alter the hydrogen balance and hence the captured anatomy. The aim of this study was to determine geometric changes of parotid glands as function of hydration during chemoradiotherapy compared to a control group treated with radiotherapy only. This study included an experimental group (n = 19) receiving chemoradiotherapy, and a control group (n = 19) receiving radiotherapy only. Chemoradiotherapy patients received cisplatin with 9 l of saline solution during hydration in the first, fourth and seventh week. The delineations of the parotid glands on the planning CT scan were automatically propagated to Cone Beam CT scans using deformable image registration. Relative volume and position of the parotid glands were determined at the second chemotherapy cycle (week four) and at fraction 35. When saline solution was administrated, the volume temporarily increased on the first day (7.2 %, p < 0.001), second day (10.8 %, p < 0.001) and third day (7.0 %, p = 0.016). The gland positions shifted lateral, the distance between glands increased on the first day with 1.5 mm (p < 0.001), on the second day 2.2 mm (p < 0.001). At fraction 35, with both groups the mean shrinkage was 24 % ± 11 % (1SD) and the mean medial distance between the parotid glands decreased by 0.47 cm ± 0.27 cm. Hydration significantly modulates parotid gland geometry. Unless, in the context of adaptive RT, a repeat CT scan is timed during a chemotherapy cycle, these effects are of minor clinical relevance

  8. A New Risk Factor Profile for Contrast-Induced Acute Kidney Injury in Patients Who Underwent an Emergency Percutaneous Coronary Intervention.

    Science.gov (United States)

    Yuan, Ying; Qiu, Hong; Song, Lei; Hu, Xiaoying; Luo, Tong; Zhao, Xueyan; Zhang, Jun; Wu, Yuan; Qiao, Shubin; Yang, Yuejin; Gao, Runlin

    2018-07-01

    We developed a new risk factor profile for contrast-induced acute kidney injury (CI-AKI) under a new definition in patients who underwent an emergency percutaneous coronary intervention (PCI). Consecutive patients (n = 1061) who underwent an emergency PCI were divided into a derivation group (n = 761) and a validation group (n = 300). The rates of CI-AKI were 23.5% (definition 1: serum creatinine [SCr] increase ≥25% in 72 hours), 4.3% (definition 2: SCr increase ≥44.2 μmol/L in 72 hours), and 7.0% (definition 3: SCr increase ≥44.2 μmol/L in 7 days). Due to the high sensitivity of definition 1 and the high rate of missed cases for late diagnosis of CI-AKI under definition 2, definition 3 was used in the study. The risk factor profile included body surface area 15.00 × 10 9 /L ( P = .047), estimated glomerular filtration rate 133 μmol/L ( P = .007), intra-aortic balloon pump application ( P = .006), and diuretics administration ( P risk factor profile of CI-AKI under a new CI-AKI definition in emergency PCI patients is easily applicable with a useful predictive value.

  9. Assessing the Risk of Contrast-Induced Nephropathy Using a Finger Stick Analysis in Recalls from Breast Screening: The CINFIBS Explorative Study.

    Science.gov (United States)

    Houben, I P L; van Berlo, C J L Y; Bekers, O; Nijssen, E C; Lobbes, M B I; Wildberger, J E

    2017-01-01

    To evaluate whether a handheld point-of-care (POC) device is able to predict and discriminate patients at potential risk of contrast-induced nephropathy (CIN) prior to iodine-based contrast media delivery. Between December 2014 and June 2016, women undergoing contrast-enhanced spectral mammography (CESM) with an iodine-based contrast agent were asked to have their risk of CIN assessed by a dedicated POC device (StatSensor CREAT) and a risk factor questionnaire based on national guidelines. Prior to contrast injection, a venous blood sample was drawn to compare the results of POC with regular laboratory testing. A total of 351 patients were included; 344 were finally categorized as low risk patients by blood creatinine evaluation. Seven patients had a eGFR below 60 ml/min/1.73 m 2 , necessitating additional preparation prior to contrast delivery. The POC device failed to categorize six out of seven patients (86%), leading to (at that stage) unwanted contrast administration. Two patients subsequently developed CIN after 2-5 days, which was self-limiting after 30 days. The POC device tested was not able to reliably assess impairment of renal function in our patient cohort undergoing CESM. Consequently, we still consider classic clinical laboratory testing preferable in patients at potential risk for developing CIN.

  10. Assessing the Risk of Contrast-Induced Nephropathy Using a Finger Stick Analysis in Recalls from Breast Screening: The CINFIBS Explorative Study

    Directory of Open Access Journals (Sweden)

    I. P. L. Houben

    2017-01-01

    Full Text Available Purpose. To evaluate whether a handheld point-of-care (POC device is able to predict and discriminate patients at potential risk of contrast-induced nephropathy (CIN prior to iodine-based contrast media delivery. Methods and Materials. Between December 2014 and June 2016, women undergoing contrast-enhanced spectral mammography (CESM with an iodine-based contrast agent were asked to have their risk of CIN assessed by a dedicated POC device (StatSensor CREAT and a risk factor questionnaire based on national guidelines. Prior to contrast injection, a venous blood sample was drawn to compare the results of POC with regular laboratory testing. Results. A total of 351 patients were included; 344 were finally categorized as low risk patients by blood creatinine evaluation. Seven patients had a eGFR below 60 ml/min/1.73 m2, necessitating additional preparation prior to contrast delivery. The POC device failed to categorize six out of seven patients (86%, leading to (at that stage unwanted contrast administration. Two patients subsequently developed CIN after 2–5 days, which was self-limiting after 30 days. Conclusion. The POC device tested was not able to reliably assess impairment of renal function in our patient cohort undergoing CESM. Consequently, we still consider classic clinical laboratory testing preferable in patients at potential risk for developing CIN.

  11. Impact of an Early Decrease in Systolic Blood Pressure on The Risk of Contrast-Induced Nephropathy after Percutaneous Coronary Intervention.

    Science.gov (United States)

    Li, Hualong; Huang, Shuijin; He, Yiting; Liu, Yong; Liu, Yuanhui; Chen, Jiyan; Zhou, Yingling; Tan, Ning; Duan, Chongyang; Chen, Pingyan

    2016-02-01

    The early postprocedural period was thought to be the rush hour of contrast media excretion, causing rapid and prolonged renal hypoperfusion, which was the critical time window for contrast-induced nephropathy (CIN). 349 consecutive patients were enrolled into the study. The relation between an early postprocedural decrease in systolic blood pressure (SBP) and the risk of CIN was assessed using multivariate logistic regression. A postprocedural decrease in SBP was observed in 63% of patients and CIN developed in 28 (8.0%) patients. The CIN group had a lower postprocedural SBP (114.5±13.5 vs. 123.7±15.6mmHg, P=0.003) and a greater postprocedural decrease in SBP (16.2±19.1 vs. 5.9±18.7mmHg, P=0.005) than the no-CIN group. ROC analysis revealed that the optimum cutoff value for the SBP decrease in detecting CIN was >10mmHg (sensitivity 60.7%, specificity 59.5%, AUC=0.66). Multivariate logistic regression analysis found that a postprocedural decrease in SBP >10mmHg was a significant independent predictor of CIN (OR 2.368, 95%CI: 1.043-5.379, P=0.039), after adjustment for other risk factors. An early moderate postprocedural decrease in SBP may increase the risk of CIN in patients undergoing PCI. Copyright © 2015. Published by Elsevier B.V.

  12. Gas Hydrate Storage of Natural Gas

    Energy Technology Data Exchange (ETDEWEB)

    Rudy Rogers; John Etheridge

    2006-03-31

    Environmental and economic benefits could accrue from a safe, above-ground, natural-gas storage process allowing electric power plants to utilize natural gas for peak load demands; numerous other applications of a gas storage process exist. A laboratory study conducted in 1999 to determine the feasibility of a gas-hydrates storage process looked promising. The subsequent scale-up of the process was designed to preserve important features of the laboratory apparatus: (1) symmetry of hydrate accumulation, (2) favorable surface area to volume ratio, (3) heat exchanger surfaces serving as hydrate adsorption surfaces, (4) refrigeration system to remove heat liberated from bulk hydrate formation, (5) rapid hydrate formation in a non-stirred system, (6) hydrate self-packing, and (7) heat-exchanger/adsorption plates serving dual purposes to add or extract energy for hydrate formation or decomposition. The hydrate formation/storage/decomposition Proof-of-Concept (POC) pressure vessel and supporting equipment were designed, constructed, and tested. This final report details the design of the scaled POC gas-hydrate storage process, some comments on its fabrication and installation, checkout of the equipment, procedures for conducting the experimental tests, and the test results. The design, construction, and installation of the equipment were on budget target, as was the tests that were subsequently conducted. The budget proposed was met. The primary goal of storing 5000-scf of natural gas in the gas hydrates was exceeded in the final test, as 5289-scf of gas storage was achieved in 54.33 hours. After this 54.33-hour period, as pressure in the formation vessel declined, additional gas went into the hydrates until equilibrium pressure/temperature was reached, so that ultimately more than the 5289-scf storage was achieved. The time required to store the 5000-scf (48.1 hours of operating time) was longer than designed. The lower gas hydrate formation rate is attributed to a

  13. Can hydrate dissolution experiments predict the fate of a natural hydrate system?

    Energy Technology Data Exchange (ETDEWEB)

    Hester, K.C.; Peltzer, E.T.; Dunk, R.M.; Walz, P.M.; Brewer, P.G. [Monterey Bay Aquarium Research Inst., Moss Landing, CA (United States); Dendy Sloan, E. [Colorado School of Mines, Golden, CO (United States). Center for Hydrate Research

    2008-07-01

    Gas hydrates are naturally occurring compounds found in permafrost regions and in oceans. In the natural environment, sufficient temperature and pressure conditions for hydrate formation exist over a significant portion of the ocean. However, in addition to pressure and temperature, the chemical potential of the gas in the hydrate must be equal to the surrounding waters. If the concentration of the gas in surrounding water is under-saturated with respect to the gas in the hydrate, the hydrate will dissolve to drive the system towards chemical equilibrium. This paper presented a dissolution study of exposed hydrate from outcrops at Barkley Canyon, located off Vancouver Island, British Columbia. A previous field experiment on synthetic methane hydrate samples had demonstrated that mass transfer controlled dissolution in under-saturated seawater. However, seafloor hydrate outcrops have been shown to have significant longevity compared to expected dissolution rates based upon convective boundary layer diffusion calculations. An in-situ dissolution experiment was performed on two distinct natural hydrate fabrics in order to help resolve this apparent disconnect between the dissolution rates of synthetic and natural hydrate. The paper presented a map of Barkley Canyon and discussed the field measurements and methods for the study. Exposed outcrops of gas hydrates were cored using a specially constructed stainless steel coring device and a hydraulic ram was located inside the corer. Hydrate samples were cored directly using the a manipulator arm and then injected into a sampling cell. The hydrate was then added to an open mesh exposure container, which allowed for exposure to ambient benthic currents with minimal disturbance. As well, in order to observe the slow dissolution of the hydrate in seawater at Barkley Canyon, time-lapse photography was employed. Last, the paper presented the results of the hydrate fabric porosities and hydrate dissolution rates. It was

  14. The method of predicting the process of condensation of moisture and hydrate formation in the gas pipeline

    OpenAIRE

    Хвостова, Олена Вікторівна

    2014-01-01

    The problem of ensuring the required value of one of the natural gas quality indicators during its transportation to the consumer - moisture content is considered in the paper. The method for predicting possible moisture condensation and hydrate formation processes in gas pipelines considering mixing gas flows with different moisture content was developed.Predicting the moisture condensation and hydrate formation in gas pipelines is an actual task since a timely prevention of these processes ...

  15. Hydration Properties of Ground Granulated Blast-Furnace Slag (GGBS Under Different Hydration Environments

    Directory of Open Access Journals (Sweden)

    Shuhua LIU

    2017-02-01

    Full Text Available The hydration properties of various cementitious materials containing Ground Granulated Blast-furnace Slag (GGBS, two alkali-activated slag cements (AAS-1 and AAS-2 in which sodium silicate and sodium hydroxide act as alkaline activators respectively, supersulfated cement (SSC and slag Portland cement(PSC, are compared with ordinary Portland cement (OPC to investigate the effect of activating environment on the hydration properties in this study by determining the compressive strength of the pastes, the hydration heat of binders within 96 hours, and the hydration products at age of 28 days. The results show that C-S-H gels are the main hydrated products for all cementitious systems containing GGBS. Ca(OH2 is the hydration products of OPC and PSC paste. However, ettringite and gypsum crystals instead of Ca(OH2 are detected in SSC paste. Additionally, tobermorite, a crystalline C-S-H, and calcite are hydrated products in AAS-1. Tobermorite, cowlesite and calcite are hydrated products of AAS-2 as well. Based on strength results, AAS-1 paste exhibits the highest compressive strength followed by POC, PSC, SSC in order at all testing ages and AAS-2 give the lowest compressive strength except for the early age at 3 days, which is higher than SSC but still lower than PSC. From hydration heat analysis, alkalinity in the reaction solution is a vital factor influencing the initial hydration rate and the initial hydration rate from higher to lower is AAS-2, AAS-1, OPC, PSC and SSC. Although AAS possesses a faster reaction rate in the initial hours, cumulative hydration heat of AAS is comparably lower than that of OPC, but higher than those of PSC and SSC in turn, which indicates that the hydration heat of clinkers is much higher than that of slag.DOI: http://dx.doi.org/10.5755/j01.ms.23.1.14934

  16. Calcium and magnesium silicate hydrates

    International Nuclear Information System (INIS)

    Lothenbach, B.; L'Hopital, E.; Nied, D.; Achiedo, G.; Dauzeres, A.

    2015-01-01

    Deep geological disposals are planed to discard long-lived intermediate-level and high-level radioactive wastes. Clay-based geological barriers are expected to limit the ingress of groundwater and to reduce the mobility of radioelements. In the interaction zone between the cement and the clay based material alteration can occur. Magnesium silicate hydrates (M-S-H) have been observed due to the reaction of magnesium sulfate containing groundwater with cements or in the interaction zone between low-pH type cement and clays. M-S-H samples synthesized in the laboratory showed that M-S-H has a variable composition within 0.7 ≤ Mg/Si ≤ 1.5. TEM/EDS analyses show an homogeneous gel with no defined structure. IR and 29 Si NMR data reveal a higher polymerization degree of the silica network in M-S-H compared to calcium silicate hydrates (C-S-H). The presence of mainly Q 3 silicate tetrahedrons in M-S-H indicates a sheet like or a triple-chain silica structure while C-S-H is characterised by single chain-structure. The clear difference in the silica structure and the larger ionic radius of Ca 2+ (1.1 Angstrom) compared to Mg 2+ (0.8 Angstrom) make the formation of an extended solid solution between M-S-H and C-S-H gel improbable. In fact, the analyses of synthetic samples containing both magnesium and calcium in various ratios indicate the formation of separate M-S-H and C-S-H gels with no or very little uptake of magnesium in CS-H or calcium in M-S-H

  17. Detection and Production of Methane Hydrate

    Energy Technology Data Exchange (ETDEWEB)

    George Hirasaki; Walter Chapman; Gerald Dickens; Colin Zelt; Brandon Dugan; Kishore Mohanty; Priyank Jaiswal

    2011-12-31

    This project seeks to understand regional differences in gas hydrate systems from the perspective of as an energy resource, geohazard, and long-term climate influence. Specifically, the effort will: (1) collect data and conceptual models that targets causes of gas hydrate variance, (2) construct numerical models that explain and predict regional-scale gas hydrate differences in 2-dimensions with minimal 'free parameters', (3) simulate hydrocarbon production from various gas hydrate systems to establish promising resource characteristics, (4) perturb different gas hydrate systems to assess potential impacts of hot fluids on seafloor stability and well stability, and (5) develop geophysical approaches that enable remote quantification of gas hydrate heterogeneities so that they can be characterized with minimal costly drilling. Our integrated program takes advantage of the fact that we have a close working team comprised of experts in distinct disciplines. The expected outcomes of this project are improved exploration and production technology for production of natural gas from methane hydrates and improved safety through understanding of seafloor and well bore stability in the presence of hydrates. The scope of this project was to more fully characterize, understand, and appreciate fundamental differences in the amount and distribution of gas hydrate and how this would affect the production potential of a hydrate accumulation in the marine environment. The effort combines existing information from locations in the ocean that are dominated by low permeability sediments with small amounts of high permeability sediments, one permafrost location where extensive hydrates exist in reservoir quality rocks and other locations deemed by mutual agreement of DOE and Rice to be appropriate. The initial ocean locations were Blake Ridge, Hydrate Ridge, Peru Margin and GOM. The permafrost location was Mallik. Although the ultimate goal of the project was to understand

  18. Gas hydrate exploration activities in Korea

    Energy Technology Data Exchange (ETDEWEB)

    Keun-Pil Park, K.P. [Korea Inst. of Geoscience and Mineral Resources, Gas Hydrate R and D Organization, Ministry of Knowledge Economy, Yuseong-gu, Daejeon (Korea, Republic of)

    2008-07-01

    Korea's first gas hydrate research project was launched in 1996 to study the gas hydrate potential in the Ulleung Basin of the East Sea. It involved a series of laboratory experiments followed by a preliminary offshore seismic survey and regional reconnaissance geophysical and marine geological surveys. The bottom simulating reflector (BSR) was interpreted to show wide area distribution in the southern part of the Ulleung Basin, and its average burial depth was 187 m below the sea floor in the East Sea. A three-phase 10-year National Gas Hydrate Development Program was launched in 2004 to estimate the potential reserves in the East Sea. It will involve drilling to identify natural gas hydrates and to determine the most optimized production methods. Drilling sites were proposed based on five indicators that imply gas hydrate occurrence, notably BSR, gas vent, enhanced seismic reflection, acoustic blanking and gas seeping structure. The UBGH-X-01 gas hydrate expedition in the East Sea Ulleung Basin involved 5 logging while drilling (LWD) surveys at three high priority sites. One wire line logging was implemented at the site of the UBGH09. A total 334 m of non-pressurized conventional cores and 16 pressure cores were obtained in late 2007. The UBGH-X-01 was successfully completed, recovering many natural samples of gas hydrate from 3 coring sites in the East Sea. 7 refs., 12 figs.

  19. Gas Hydrates Research Programs: An International Review

    Energy Technology Data Exchange (ETDEWEB)

    Jorge Gabitto; Maria Barrufet

    2009-12-09

    Gas hydrates sediments have the potential of providing a huge amount of natural gas for human use. Hydrate sediments have been found in many different regions where the required temperature and pressure conditions have been satisfied. Resource exploitation is related to the safe dissociation of the gas hydrate sediments. Basic depressurization techniques and thermal stimulation processes have been tried in pilot efforts to exploit the resource. There is a growing interest in gas hydrates all over the world due to the inevitable decline of oil and gas reserves. Many different countries are interested in this valuable resource. Unsurprisingly, developed countries with limited energy resources have taken the lead in worldwide gas hydrates research and exploration. The goal of this research project is to collect information in order to record and evaluate the relative strengths and goals of the different gas hydrates programs throughout the world. A thorough literature search about gas hydrates research activities has been conducted. The main participants in the research effort have been identified and summaries of their past and present activities reported. An evaluation section discussing present and future research activities has also been included.

  20. Creation of technological bases of struggle with generation of natural gas hydrates

    International Nuclear Information System (INIS)

    Asadov, M.M.; Alieva, S.A.

    2005-01-01

    Chemical technological access, permitting directed of intensify processes prevention of gas hydrates during motion of the gas-liquid current of natural gas in the borehole cavity of natural gas-borehole cavity have been engineered. Determined technological regimes of gas current conditioning, permitting create nonequilibrium state providing condition for reversible process

  1. Infrared spectroscopic measurement of skin hydration and sebum levels and comparison to corneometer and sebumeter

    NARCIS (Netherlands)

    Ezerskaia, A.; Pereira, S.F.; Urbach, Paul; Varghese, Babu; Popp, Jürgen; Tuchin, Valery V.; Matthews, Dennis L.; Pavone, Francesco S.

    2016-01-01

    Skin health characterized by a system of water and lipids in Stratum Corneum provide protection from harmful external elements and prevent trans-epidermal water loss. Skin hydration (moisture) and sebum (skin surface lipids) are considered to be important factors in skin health; a right balance

  2. Supramolecular Organization of Nonstoichiometric Drug Hydrates: Dapsone

    Science.gov (United States)

    Braun, Doris E.; Griesser, Ulrich J.

    2018-01-01

    The observed moisture- and temperature dependent transformations of the dapsone (4,4′-diaminodiphenyl sulfone, DDS) 0. 33-hydrate were correlated to its structure and the number and strength of the water-DDS intermolecular interactions. A combination of characterization techniques was used, including thermal analysis (hot-stage microscopy, differential scanning calorimetry and thermogravimetric analysis), gravimetric moisture sorption/desorption studies and variable humidity powder X-ray diffraction, along with computational modeling (crystal structure prediction and pair-wise intermolecular energy calculations). Depending on the relative humidity the hydrate contains between 0 and 0.33 molecules of water per molecule DDS. The crystal structure is retained upon dehydration indicating that DDS hydrate shows a non-stoichiometric (de)hydration behavior. Unexpectedly, the water molecules are not located in structural channels but at isolated-sites of the host framework, which is counterintuitively for a hydrate with non-stoichiometric behavior. The water-DDS interactions were estimated to be weaker than water-host interactions that are commonly observed in stoichiometric hydrates and the lattice energies of the isomorphic dehydration product (hydrate structure without water molecules) and (form III) differ only by ~1 kJ mol−1. The computational generation of hypothetical monohydrates confirms that the hydrate with the unusual DDS:water ratio of 3:1 is more stable than a feasible monohydrate structure. Overall, this study highlights that a deeper understanding of the formation of hydrates with non-stoichiometric behavior requires a multidisciplinary approach including suitable experimental and computational methods providing a firm basis for the development and manufacturing of high quality drug products. PMID:29520359

  3. Methane hydrate stability and anthropogenic climate change

    Directory of Open Access Journals (Sweden)

    D. Archer

    2007-07-01

    Full Text Available Methane frozen into hydrate makes up a large reservoir of potentially volatile carbon below the sea floor and associated with permafrost soils. This reservoir intuitively seems precarious, because hydrate ice floats in water, and melts at Earth surface conditions. The hydrate reservoir is so large that if 10% of the methane were released to the atmosphere within a few years, it would have an impact on the Earth's radiation budget equivalent to a factor of 10 increase in atmospheric CO2.

    Hydrates are releasing methane to the atmosphere today in response to anthropogenic warming, for example along the Arctic coastline of Siberia. However most of the hydrates are located at depths in soils and ocean sediments where anthropogenic warming and any possible methane release will take place over time scales of millennia. Individual catastrophic releases like landslides and pockmark explosions are too small to reach a sizable fraction of the hydrates. The carbon isotopic excursion at the end of the Paleocene has been interpreted as the release of thousands of Gton C, possibly from hydrates, but the time scale of the release appears to have been thousands of years, chronic rather than catastrophic.

    The potential climate impact in the coming century from hydrate methane release is speculative but could be comparable to climate feedbacks from the terrestrial biosphere and from peat, significant but not catastrophic. On geologic timescales, it is conceivable that hydrates could release as much carbon to the atmosphere/ocean system as we do by fossil fuel combustion.

  4. Skin hydration of the heel with fissure in patients with diabetes: a cross-sectional observational study

    Directory of Open Access Journals (Sweden)

    Oe M

    2018-06-01

    Full Text Available Makoto Oe,1 Kimie Takehara,2 Hiroshi Noguchi,3 Yumiko Ohashi,4 Mayu Fukuda,1 Takashi Kadowaki,5 Hiromi Sanada1,6 1Global Nursing Research Center, 2Department of Advanced Nursing Technology, 3Department of Life Support Technology (Molten, Graduate School of Medicine, The University of Tokyo, 4Department of Nursing, The University of Tokyo Hospital, 5Department of Diabetes and Metabolic Diseases, 6Department of Gerontological Nursing/Wound Care Management, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan Purpose: Foot fissure should be prevented in patients with diabetes due to the likelihood of subsequent diabetic ulcer. The purpose of this study was to investigate a cutoff point for skin hydration with fissure and the factors associated with low skin hydration in patients with diabetes. Subjects and methods: Subjects were patients with diabetes who visited the diabetic foot clinic and were evaluated for skin hydration on the heel between April 2008 and March 2015. Information about fissure, skin hydration, age, sex, autonomic neuropathy, angiopathy, and tinea pedis were collected from the medical charts. Skin hydration on the heel was measured using a moisture checker. Skin hydration was compared between heels with and without fissure, and a cutoff for skin hydration with fissure was determined using receiver operating characteristic analysis. Based on the determined cutoff, factors associated with lower skin hydration were analyzed using logistic regression analysis. Results: Participants comprised 693 patients. Mean±SD age was 66.8±10.8 years, and 57.0% of subjects were male. The frequency of fissures on the heels was 10.4%. Area under the receiver operating characteristic curve for skin hydration in the presence of fissure was 0.717. Twenty percent was selected as the cutoff point, offering sensitivity of 0.478 and specificity of 0.819. Logistic regression analysis showed correlations between three factors (male sex, tinea

  5. Tapping methane hydrates for unconventional natural gas

    Science.gov (United States)

    Ruppel, Carolyn

    2007-01-01

    Methane hydrate is an icelike form of concentrated methane and water found in the sediments of permafrost regions and marine continental margins at depths far shallower than conventional oil and gas. Despite their relative accessibility and widespread occurrence, methane hydrates have never been tapped to meet increasing global energy demands. With rising natural gas prices, production from these unconventional gas deposits is becoming economically viable, particularly in permafrost areas already being exploited for conventional oil and gas. This article provides an overview of gas hydrate occurrence, resource assessment, exploration, production technologies, renewability, and future challenges.

  6. On the electrolytic generation of hydrated electron

    International Nuclear Information System (INIS)

    Ghosh Mazumdar, A.S.; Guha, S.N.

    1975-01-01

    Investigations on the electrolytic generation of hydrated electron in oxygenated as well as oxygen-free solutions at different pH were undertaken. Since sup(-e)aq is known to react rapidly with O 2 yielding the transient O 2 - ion, the latter was looked for through its interaction with phosphite ions resulting in their oxidation near the cathode. It appears from the results that in electrolytic processes, the primary electron (esup(-)sub(cathode)) probably reacts directly with reactive solutes like oxygen, bypassing the hydration step. Data obtained in oxygen-free solutions, however, support the possible formation of hydrated electron at least in alkaline solutions. (author)

  7. Experimental Investigation of Effect on Hydrate Formation in Spray Reactor

    Directory of Open Access Journals (Sweden)

    Jianzhong Zhao

    2015-01-01

    Full Text Available The effects of reaction condition on hydrate formation were conducted in spray reactor. The temperature, pressure, and gas volume of reaction on hydrate formation were measured in pure water and SDS solutions at different temperature and pressure with a high-pressure experimental rig for hydrate formation. The experimental data and result reveal that additives could improve the hydrate formation rate and gas storage capacity. Temperature and pressure can restrict the hydrate formation. Lower temperature and higher pressure can promote hydrate formation, but they can increase production cost. So these factors should be considered synthetically. The investigation will promote the advance of gas storage technology in hydrates.

  8. Gas hydrate concentration and characteristics within Hydrate Ridge inferred from multicomponent seismic reflection data

    Science.gov (United States)

    Kumar, Dhananjay; Sen, Mrinal K.; Bangs, Nathan L.

    2007-12-01

    A seismic experiment composed of streamer and ocean bottom seismometer (OBS) surveys was conducted in the summer of 2002 at southern Hydrate Ridge, offshore Oregon, to map the gas hydrate distribution within the hydrate stability zone. Gas hydrate concentrations within the reservoir can be estimated with P wave velocity (Vp); however, we can further constrain gas hydrate concentrations using S wave velocity (Vs), and use Vs through its relationship to Vp (Vp/Vs) to reveal additional details such as gas hydrate form within the matrix (i.e., hydrate cements the grains, becomes part of the matrix frame or floats in pore space). Both Vp and Vs can be derived simultaneously by inverting multicomponent seismic data. In this study, we use OBS data to estimate seismic velocities where both gas hydrate and free gas are present in the shallow sediments. Once Vp and Vs are estimated, they are simultaneously matched with modeled velocities to estimate the gas hydrate concentration. We model Vp using an equation based on a modification of Wood's equation that incorporates an appropriate rock physics model and Vs using an empirical relation. The gas hydrate concentration is estimated to be up to 7% of the rock volume, or 12% of the pore space. However, Vp and Vs do not always fit the model simultaneously. Vp can vary substantially more than Vs. Thus we conclude that a model, in which higher concentrations of hydrate do not affect shear stiffness, is more appropriate. Results suggest gas hydrates form within the pore space of the sediments and become part of the rock framework in our survey area.

  9. A Hydrate Database: Vital to the Technical Community

    Directory of Open Access Journals (Sweden)

    D Sloan

    2007-06-01

    Full Text Available Natural gas hydrates may contain more energy than all the combined other fossil fuels, causing hydrates to be a potentially vital aspect of both energy and climate change. This article is an overview of the motivation, history, and future of hydrate data management using a CODATA vehicle to connect international hydrate databases. The basis is an introduction to the Gas Hydrate Markup Language (GHML to connect various hydrate databases. The accompanying four articles on laboratory hydrate data by Smith et al., on field hydrate data by L?wner et al., on hydrate modeling by Wang et al., and on construction of a Chinese gas hydrate system by Xiao et al. provide details of GHML in their respective areas.

  10. The predictive value of the product of contrast medium volume and urinary albumin/creatinine ratio in contrast-induced acute kidney injury.

    Science.gov (United States)

    Wang, Chunrui; Ma, Shuai; Deng, Bo; Lu, Jianxin; Shen, Wei; Jin, Bo; Shi, Haiming; Ding, Feng

    2017-11-01

    Preexisting renal impairment and the amount of contrast media are the most important risk factors for contrast-induced acute kidney injury (CI-AKI). We aimed to investigate whether the product of contrast medium volume and urinary albumin/creatinine ratio (CMV × UACR) would be a better predictor of CI-AKI in patients undergoing nonemergency coronary interventions. This was a prospective single-center observational study, and 912 consecutive patients who were exposed to contrast media during coronary interventions were investigated prospectively. CI-AKI is defined as a 44.2 μmol/L rise in serum creatinine or a 25% increase, assessed within 48 h after administration of contrast media in the absence of other causes. Fifty patients (5.48%) developed CI-AKI. The urinary albumin/creatinine ratio (UACR) (OR = 1.002, 95% CI = 1.000-1.003, p = .012) and contrast medium volume (CMV) (OR = 1.008, 95% CI = 1.001-1.014, p = .017) were independent risk factors for the development of CI-AKI. The area under the ROC curve of CMV, UACR and CMV × UACR were 0.662 (95% CI = 0.584-0.741, p < .001), 0.761 (95% CI = 0.674-0.847, p < .001) and 0.808 (95% CI = 0.747-0.896, p < .001), respectively. The cutoff value of CMV × UACR to predict CI-AKI was 1186.2, with 80.0% sensitivity and 62.2% specificity. The product of CMV and UACR (CMV × UACR) might be a predictor of CI-AKI in patients undergoing nonemergency coronary interventions, which was superior to CMV or UACR alone.

  11. [Contrast-induced nephropathy in patients at risk of renal failure undergoing computed tomography: systematic review and meta-analysis of randomized controlled trials].

    Science.gov (United States)

    Arana, Estanislao; Catalá-López, Ferrán

    2010-09-11

    We evaluated and quantified by meta-analysis techniques the incidence of contrast-induced nephropathy (CIN) in patients at risk undergoing computed tomography (CT). We conducted a systematic review of randomized controlled clinical trials designated to evaluate the nephrotoxicity related to iso-osmolar contrast media (IOCM) compared to low-osmolar contrast media (LOCM). Main electronic databases searched included PubMed/MEDLINE, EMBASE, ISI Web of Knowledge and Virtual Health Library (BVS-BIREME), as well as abstracts presented at related scientific societies meetings. Prior to data extraction, definitions of nephrotoxicity and risk population were established. Besides meta-analysis, the global agreement between CIN definitions was evaluated with Mantel-Haenszel stratified test. Five studies were included with 716 randomized patients. When CIN was defined as increased serum creatinine (SCr)>or=25%, the relative risk (RR) was 0.71 (CI95%: 0.40-1.26)-in favor of IOCM-and when it was defined as SCr>or=0.5mg/dL it showed a RR 1.48 (CI95%: 0.37-5.87)-favoring LOCM-in the four studies used this criterion. Mantel-Haenszel stratified test was chi2=2.51 (p=0.8). In patients with renal failure undergoing CT there is a similar risk of CIN with the administration of any contrast media studied. CIN incidence depends on the chosen criteria and is lower with the definition of SCr>or=0.5mg/dL at 24-72h. No agreement was found between CIN definitions were adopted. Copyright © 2009 Elsevier España, S.L. All rights reserved.

  12. Comparative Effect of Contrast Media Type on the Incidence of Contrast-Induced Nephropathy: A Systematic Review and Meta-analysis.

    Science.gov (United States)

    Eng, John; Wilson, Renee F; Subramaniam, Rathan M; Zhang, Allen; Suarez-Cuervo, Catalina; Turban, Sharon; Choi, Michael J; Sherrod, Cheryl; Hutfless, Susan; Iyoha, Emmanuel E; Bass, Eric B

    2016-03-15

    Iodine contrast media are essential components of many imaging procedures. An important potential side effect is contrast-induced nephropathy (CIN). To compare CIN risk for contrast media within and between osmolality classes in patients receiving diagnostic or therapeutic imaging procedures. PubMed, EMBASE, Cochrane Library, Clinical Trials.gov, and Scopus through June 2015. Randomized, controlled trials that reported CIN-related outcomes in patients receiving low-osmolar contrast media (LOCM) or iso-osmolar contrast media for imaging. Independent study selection and quality assessment by 2 reviewers and dual extraction of study characteristics and results. None of the 5 studies that compared types of LOCM reported a statistically significant or clinically important difference among study groups, but the strength of evidence was low. Twenty-five randomized, controlled trials found a slight reduction in CIN risk with the iso-osmolar contrast media agent iodixanol compared with a diverse group of LOCM that just reached statistical significance in a meta-analysis (pooled relative risk, 0.80 [95% CI, 0.65 to 0.99]; P = 0.045). This comparison's strength of evidence was moderate. In a meta regression of randomized, controlled trials of iodixanol, no relationship was found between route of administration and comparative CIN risk. Few studies compared LOCM. Procedural details about contrast administration were not uniformly reported. Few studies specified clinical indications or severity of baseline renal impairment. No differences were found in CIN risk among types of LOCM. Iodixanol had a slightly lower risk for CIN than LOCM, but the lower risk did not exceed a criterion for clinical importance. Agency for Healthcare Research and Quality.

  13. Contrast induced-acute kidney injury following peripheral angiography with carbon dioxide versus iodinated contrast media: A meta-analysis and systematic review of current literature.

    Science.gov (United States)

    Ghumman, Saad S; Weinerman, Jonathan; Khan, Aazib; Cheema, Mubeen S; Garcia, Marlene; Levin, Daniel; Suri, Rajeev; Prasad, Anand

    2017-09-01

    We conducted a meta-analysis to compare the incidence of acute kidney injury (AKI) with carbon dioxide (CO 2 ) versus iodinated contrast media (ICM). Contrast induced-acute kidney injury (CI-AKI) is a known complication following endovascular procedures with ICM. CO 2 has been employed as an alternative imaging medium as it is nontoxic to the kidneys. Search of indexed databases was performed and 1,732 references were retrieved. Eight studies (7 observational, 1 Randomized Controlled Trial) formed the meta-analysis. Primary outcome was AKI. Fixed effect model was used when possible in addition to analysis of publication bias. In this meta-analysis, 677 patients underwent 754 peripheral angiographic procedures. Compared with ICM, CO 2 was associated with a decreased incidence of AKI (4.3% vs. 11.1%; OR 0.465, 95% CI: 0.218-0.992; P = 0.048). Subgroup analysis of four studies that included granular data for patients with chronic kidney disease (CKD) did not demonstrate a decreased incidence of AKI with CO 2 (4.1% vs. 10.0%; OR 0.449, 95% CI: 0.165-1.221, P = 0.117). Patients undergoing CO 2 angiography experienced a higher number of nonrenal events including limb/abdominal pain (11 vs. 0; P = 0.001) and nausea/vomiting (9 vs. 1; P = 0.006). In comparison to ICM, CO 2 use is associated with a modestly reduced rate of AKI with more frequent adverse nonrenal events. In studies that use CO 2 as the primary imaging agent, the average incidence of AKI remained high at 6.2%-supporting the concept that factors other than renal toxicity from ICM may contribute to renal impairment following peripheral angiography. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  14. Contrast induced nephropathy in patients undergoing intravenous (IV) contrast enhanced computed tomography (CECT) and the relationship with risk factors: a meta-analysis.

    Science.gov (United States)

    Moos, Shira I; van Vemde, David N H; Stoker, Jaap; Bipat, Shandra

    2013-09-01

    To summarize the incidence of contrast-induced nephropathy (CIN) and associations between CIN incidence and risk factors in patients undergoing intravenous contrast-enhanced computed tomography (CECT) with low- or iso-osmolar iodinated contrast medium. This review is performed in accordance with the preferred reporting items in systematic reviews and meta-analysis (PRISMA) guidelines. We searched the MEDLINE, EMBASE and Cochrane databases from 2002 till November 2012. Two reviewers included papers and extracted data. The pooled data were analysed by either fixed or random-effects approach depending on heterogeneity defined as the I(2) index. 42 articles with 18,790 patients (mean age 61.5 years (range: 38-83 years)) were included. The mean baseline eGFR was 59.8 mL/min and ranged from 4 to 256 mL/min. Of all patients 45.0% had an estimated glomerular filtration rate (eGFR)65 years and use of non-steroidal anti-inflammatory drugs (NSAID's) with odds ratios of 1.73 (95%CI: 1.06-2.82), 1.87 (95%CI: 1.55-2.26), 1.79 (95%CI: 1.03-3.11), 1.95 (95%CI: 1.02-3.70) and 2.32 (95%CI: 1.04-5.19), respectively while hypertension, anaemia and CFH were not associated (p=0.13, p=0.38, p=0.40). The mean incidence of CIN after intravenous iodinated CECT was low and associated with renal insufficiency, diabetes, presence of malignancy, old age and NSAID's use. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

  15. Predictive Value of CHA2DS2-VASC Score for Contrast-Induced Nephropathy After Percutaneous Coronary Intervention for Acute Coronary Syndrome.

    Science.gov (United States)

    Kurtul, Alparslan; Yarlioglues, Mikail; Duran, Mustafa

    2017-03-15

    The CHA2DS2-VASC score, used for embolic risk stratification in atrial fibrillation (AF), has been reported recently to predict adverse clinical outcomes in patients with acute coronary syndrome (ACS), regardless of having AF. We investigated the correlation between the CHA2DS2-VASC score and contrast-induced nephropathy (CIN) in patients with ACS who underwent urgent percutaneous coronary intervention (PCI). A total of 1,408 patients were enrolled in the study. The CHA2DS2-VASC score was calculated for each patient. Based on the receiver operating characteristic analysis, the study population was divided into 2 groups: CHA2DS2-VASC score ≤3 group (n = 944) and CHA2DS2-VASC score ≥4 group (n = 464). Patients were then reallocated to 2 groups according to the presence or absence of CIN. CIN was defined as a rise in serum creatinine >0.5 mg/dl or >25% increase in baseline within 72 hours after PCI. Overall, 159 cases (11.3%) of CIN were diagnosed. Receiver operating characteristic curve analysis revealed good diagnostic value of CHA2DS2-VASC score in predicting CIN (area under the curve 0.769, 95% confidence interval 0.733 to 0.805; p high score had a higher frequency of CIN (23.9% vs 5.1%; p <0.001), and multivariate analysis identified the CHA2DS2-VASC score of ≥4 as an independent predictor of CIN. In conclusion, CHA2DS2-VASC score can be used as a new, simple, and reliable tool to predict CIN in patients with ACS who underwent urgent PCI. Copyright © 2016 Elsevier Inc. All rights reserved.

  16. Exogenous origin of hydration on asteroid (16) Psyche: the role of hydrated asteroid families

    Science.gov (United States)

    Avdellidou, C.; Delbo', M.; Fienga, A.

    2018-04-01

    Asteroid (16) Psyche, which for a long time was the largest M-type with no detection of hydration features in its spectrum, was recently discovered to have a weak 3-μm band and thus it was eventually added to the group of hydrated asteroids. Its relatively high density, in combination with the high radar albedo, led researchers to classify the asteroid as a metallic object. It is believed that it is possibly a core of a differentiated body, a remnant of `hit-and-run' collisions. The detection of hydration is, in principle, inconsistent with a pure metallic origin for this body. Here, we consider the scenario in which the hydration on its surface is exogenous and was delivered by hydrated impactors. We show that impacting asteroids that belong to families whose members have the 3-μm band can deliver hydrated material to Psyche. We developed a collisional model with which we test all dark carbonaceous asteroid families, which contain hydrated members. We find that the major source of hydrated impactors is the family of Themis, with a total implanted mass on Psyche of the order of ˜1014 kg. However, the hydrated fraction could be only a few per cent of the implanted mass, as the water content in carbonaceous chondrite meteorites, the best analogue for the Themis asteroid family, is typically a few per cent of their mass.

  17. Oceanic hydrates: more questions than answers

    International Nuclear Information System (INIS)

    Laherrere, Jean

    2000-01-01

    Methane hydrates create problems by blocking pipelines and casing; they are also accused of contributing to environmental problems (e.g. global warming). Methane hydrates are also found in permafrost areas and in oceanic sediments where the necessary temperature and pressure for stability occur. Claims for the widespread occurrence in thick oceanic deposits are unfounded: apparently indirect evidence from seismic reflectors, seismic hydrocarbon indicators, logs and free samples is unreliable. At one time, hydrate was seen as a static, biogenic, continuous, huge resource but that view is changing to one of a dynamic, overpressurised, discontinuous and unreliable resource. Only Japan and India are currently showing any serious interest in hydrates. Academic research has raised more questions than answers. It is suggested that more hard exploratory evidence rather than theoretical study is required

  18. Vibrational dynamics of hydration water in amylose

    CERN Document Server

    Cavatorta, F; Albanese, G; Angelini, N

    2002-01-01

    We present a study of the dynamical properties of hydration water associated with amylose helices, based on low-temperature vibrational spectra collected using the TOSCA inelastic spectrometer at ISIS. The structural constraints of the polysaccharidic chains favour the formation of a high-density structure for water, which has been suggested by Imberty and Perez on the basis of conformational analysis. According to this model, hydration water can only enter the pores formed by six adjacent helices and completely fills the pores at a hydration level of about 0.27-g water/g dry amylose. Our measurements show that the dynamical behaviour of hydration water is similar to that observed in high-density amorphous ice. (orig.)

  19. Separation of water through gas hydrate formation

    DEFF Research Database (Denmark)

    Boch Andersen, Torben; Thomsen, Kaj

    2009-01-01

    Gas hydrate is normally recognized as a troublemaker in the oil and gas industry. However, gas hydrate has some interesting possibilities when used in connection with separation of water. Nordic Sugar has investigated the possibility of using gas hydrates for concentration of sugar juice. The goal...... of the project was to formulate an alternative separation concept, which can replace the traditional water evaporation process in the sugar production. Work with the separation concept showed that gas hydrates can be used for water separation. The process is not suitable for sugar production because of large...... volumes and the needs for high pressure. The process could be interesting for concentration of heat sensitive, high value products...

  20. Hydration states of AFm cement phases

    Energy Technology Data Exchange (ETDEWEB)

    Baquerizo, Luis G., E-mail: luis.baquerizoibarra@holcim.com [Innovation, Holcim Technology Ltd., CH-5113 Holderbank (Switzerland); Matschei, Thomas [Innovation, Holcim Technology Ltd., CH-5113 Holderbank (Switzerland); Scrivener, Karen L. [Laboratory of Construction Materials, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne (Switzerland); Saeidpour, Mahsa; Wadsö, Lars [Building Materials, Lund University, Box 124, 221 000 Lund (Sweden)

    2015-07-15

    The AFm phase, one of the main products formed during the hydration of Portland and calcium aluminate cement based systems, belongs to the layered double hydrate (LDH) family having positively charged layers and water plus charge-balancing anions in the interlayer. It is known that these phases present different hydration states (i.e. varying water content) depending on the relative humidity (RH), temperature and anion type, which might be linked to volume changes (swelling and shrinkage). Unfortunately the stability conditions of these phases are insufficiently reported. This paper presents novel experimental results on the different hydration states of the most important AFm phases: monocarboaluminate, hemicarboaluminate, strätlingite, hydroxy-AFm and monosulfoaluminate, and the thermodynamic properties associated with changes in their water content during absorption/desorption. This data opens the possibility to model the response of cementitious systems during drying and wetting and to engineer systems more resistant to harsh external conditions.

  1. ConocoPhillips Gas Hydrate Production Test

    Energy Technology Data Exchange (ETDEWEB)

    Schoderbek, David [ConocoPhillips Co., Houston, TX (United States); Farrell, Helen [ConocoPhillips Co., Houston, TX (United States); Howard, James [ConocoPhillips Co., Houston, TX (United States); Raterman, Kevin [ConocoPhillips Co., Houston, TX (United States); Silpngarmlert, Suntichai [ConocoPhillips Co., Houston, TX (United States); Martin, Kenneth [ConocoPhillips Co., Houston, TX (United States); Smith, Bruce [ConocoPhillips Co., Houston, TX (United States); Klein, Perry [ConocoPhillips Co., Houston, TX (United States)

    2013-06-30

    Work began on the ConocoPhillips Gas Hydrates Production Test (DOE award number DE-NT0006553) on October 1, 2008. This final report summarizes the entire project from January 1, 2011 to June 30, 2013.

  2. Hydrate Control for Gas Storage Operations

    Energy Technology Data Exchange (ETDEWEB)

    Jeffrey Savidge

    2008-10-31

    The overall objective of this project was to identify low cost hydrate control options to help mitigate and solve hydrate problems that occur in moderate and high pressure natural gas storage field operations. The study includes data on a number of flow configurations, fluids and control options that are common in natural gas storage field flow lines. The final phase of this work brings together data and experience from the hydrate flow test facility and multiple field and operator sources. It includes a compilation of basic information on operating conditions as well as candidate field separation options. Lastly the work is integrated with the work with the initial work to provide a comprehensive view of gas storage field hydrate control for field operations and storage field personnel.

  3. METHANE HYDRATE PRODUCTION FROM ALASKAN PERMAFROST

    Energy Technology Data Exchange (ETDEWEB)

    Ali Kadaster; Bill Liddell; Tommy Thompson; Thomas Williams; Michael Niedermayr

    2005-02-01

    Natural-gas hydrates have been encountered beneath the permafrost and considered a nuisance by the oil and gas industry for years. Engineers working in Russia, Canada and the USA have documented numerous drilling problems, including kicks and uncontrolled gas releases, in arctic regions. Information has been generated in laboratory studies pertaining to the extent, volume, chemistry and phase behavior of gas hydrates. Scientists studying hydrate potential agree that the potential is great--on the North Slope of Alaska alone, it has been estimated at 590 TCF. However, little information has been obtained on physical samples taken from actual rock containing hydrates. This gas-hydrate project was a cost-shared partnership between Maurer Technology, Noble Corporation, Anadarko Petroleum, and the U.S. Department of Energy's Methane Hydrate R&D program. The purpose of the project is to build on previous and ongoing R&D in the area of onshore hydrate deposition to identify, quantify and predict production potential for hydrates located on the North Slope of Alaska. The work scope included drilling and coring a well (Hot Ice No. 1) on Anadarko leases beginning in FY 2003 and completed in 2004. During the first drilling season, operations were conducted at the site between January 28, 2003 to April 30, 2003. The well was spudded and drilled to a depth of 1403 ft. Due to the onset of warmer weather, work was then suspended for the season. Operations at the site were continued after the tundra was re-opened the following season. Between January 12, 2004 and March 19, 2004, the well was drilled and cored to a final depth of 2300 ft. An on-site core analysis laboratory was built and implemented for determining physical characteristics of the hydrates and surrounding rock. The well was drilled from a new Anadarko Arctic Platform that has a minimal footprint and environmental impact. Final efforts of the project are to correlate geology, geophysics, logs, and drilling and

  4. Importance of the rate of hydration of pharmaceutical preparations of guar gum; a new in vitro monitoring method.

    Science.gov (United States)

    Ellis, P R; Morris, E R

    1991-05-01

    Dietary supplements of guar gum are known to improve blood glucose control in diabetic patients. The efficacy of guar is probably dependent mainly upon its capacity to hydrate rapidly and thus to increase viscosity in the small intestine post-prandially. Measurement of the rate of hydration in vitro might therefore be a useful index of the effectiveness of guar formulations. A simple method for monitoring the hydration rate of guar gum has been developed, which involves measuring the changes in viscosity at discrete time intervals over a period of 5 h using a Brookfield RVT rotoviscometer. Six different samples of guar gum (four pharmaceutical preparations and two food grades of guar flour) were hydrated in sealed glass jars rotated at 6 rev min-1 in order to prevent particle aggregation. Marked differences in hydration rate and ultimate (maximum) viscosity between the different guar samples were observed. Three of the four pharmaceutical preparations were lower in viscosity than the food grades of guar flour during the first 60 min of hydration. Two of the preparations hydrated so slowly that even after 5 h they attained viscosity levels of only 60% of their ultimate viscosity. These results may explain why some guar gum preparations are clinically ineffective.

  5. Supramolecular Organization of Nonstoichiometric Drug Hydrates: Dapsone

    Directory of Open Access Journals (Sweden)

    Doris E. Braun

    2018-02-01

    Full Text Available The observed moisture- and temperature dependent transformations of the dapsone (4,4′-diaminodiphenyl sulfone, DDS 0. 33-hydrate were correlated to its structure and the number and strength of the water-DDS intermolecular interactions. A combination of characterization techniques was used, including thermal analysis (hot-stage microscopy, differential scanning calorimetry and thermogravimetric analysis, gravimetric moisture sorption/desorption studies and variable humidity powder X-ray diffraction, along with computational modeling (crystal structure prediction and pair-wise intermolecular energy calculations. Depending on the relative humidity the hydrate contains between 0 and 0.33 molecules of water per molecule DDS. The crystal structure is retained upon dehydration indicating that DDS hydrate shows a non-stoichiometric (dehydration behavior. Unexpectedly, the water molecules are not located in structural channels but at isolated-sites of the host framework, which is counterintuitively for a hydrate with non-stoichiometric behavior. The water-DDS interactions were estimated to be weaker than water-host interactions that are commonly observed in stoichiometric hydrates and the lattice energies of the isomorphic dehydration product (hydrate structure without water molecules and (form III differ only by ~1 kJ mol−1. The computational generation of hypothetical monohydrates confirms that the hydrate with the unusual DDS:water ratio of 3:1 is more stable than a feasible monohydrate structure. Overall, this study highlights that a deeper understanding of the formation of hydrates with non-stoichiometric behavior requires a multidisciplinary approach including suitable experimental and computational methods providing a firm basis for the development and manufacturing of high quality drug products.

  6. Preservation of methane hydrate at 1 atm

    Science.gov (United States)

    Stern, L.A.; Circone, S.; Kirby, S.H.; Durham, W.B.

    2001-01-01

    A "pressure-release" method that enables reproducible bulk preservation of pure, porous, methane hydrate at conditions 50 to 75 K above its equilibrium T (193 K) at 1 atm is refined. The amount of hydrate preserved by this method appears to be greatly in excess of that reported in the previous citations, and is likely the result of a mechanism different from ice shielding.

  7. In Situ Raman Analyses of Natural Gas and Gas Hydrates at Hydrate Ridge, Oregon

    Science.gov (United States)

    Peltzer, E. T.; White, S. N.; Dunk, R. M.; Brewer, P. G.; Sherman, A. D.; Schmidt, K.; Hester, K. C.; Sloan, E. D.

    2004-12-01

    During a July 2004 cruise to Hydrate Ridge, Oregon, MBARI's sea-going laser Raman spectrometer was used to obtain in situ Raman spectra of natural gas hydrates and natural gas venting from the seafloor. This was the first in situ analysis of gas hydrates on the seafloor. The hydrate spectra were compared to laboratory analyses performed at the Center for Hydrate Research, Colorado School of Mines. The natural gas spectra were compared to MBARI gas chromatography (GC) analyses of gas samples collected at the same site. DORISS (Deep Ocean Raman In Situ Spectrometer) is a laboratory model laser Raman spectrometer from Kaiser Optical Systems, Inc modified at MBARI for deployment in the deep ocean. It has been successfully deployed to depths as great as 3600 m. Different sampling optics provide flexibility in adapting the instrument to a particular target of interest. An immersion optic was used to analyze natural gas venting from the seafloor at South Hydrate Ridge ( ˜780 m depth). An open-bottomed cube was placed over the vent to collect the gas. The immersion optic penetrated the side of the cube as did a small heater used to dissociate any hydrate formed during sample collection. To analyze solid hydrates at both South and North Hydrate Ridge ( ˜590 m depth), chunks of hydrate were excavated from the seafloor and collected in a glass cylinder with a mesh top. A stand-off optic was used to analyze the hydrate inside the cylinder. Due to the partial opacity of the hydrate and the small focal volume of the sampling optic, a precision underwater positioner (PUP) was used to focus the laser spot onto the hydrate. PUP is a stand-alone system with three degrees-of-freedom, capable of moving the DORISS probe head with a precision of 0.1 mm. In situ Raman analyses of the gas indicate that it is primarily methane. This is verified by GC analyses of samples collected from the same site. Other minor constituents (such as CO2 and higher hydrocarbons) are present but may be in

  8. Feasibility of using phase change materials to control the heat of hydration in massive concrete structures.

    Science.gov (United States)

    Choi, Won-Chang; Khil, Bae-Soo; Chae, Young-Seok; Liang, Qi-Bo; Yun, Hyun-Do

    2014-01-01

    This paper presents experimental results that can be applied to select a possible phase change material (PCM), such as a latent heat material (LHM), to control the hydration heat in mass concrete structures. Five experimental tests (microconduction, simplified adiabatic temperature rise, heat, and compressive strength tests) were conducted to select the most desirable LHM out of seven types of inorganic PCM used in cement mortar and to determine the most suitable mix design. The results of these experimental tests were used to assess the feasibility of using PCM to reduce hydration heat in mass concrete that was examined. The experimental results show that cement mortar containing barium- [Ba(OH)2 · 8H2O] based PCM has the lowest amount of total hydration heat of the cement pastes. The barium-based PCM provides good latent heat properties that help to prevent volume change and microcracks caused by thermal stress in mass concrete.

  9. Feasibility of Using Phase Change Materials to Control the Heat of Hydration in Massive Concrete Structures

    Directory of Open Access Journals (Sweden)

    Won-Chang Choi

    2014-01-01

    Full Text Available This paper presents experimental results that can be applied to select a possible phase change material (PCM, such as a latent heat material (LHM, to control the hydration heat in mass concrete structures. Five experimental tests (microconduction, simplified adiabatic temperature rise, heat, and compressive strength tests were conducted to select the most desirable LHM out of seven types of inorganic PCM used in cement mortar and to determine the most suitable mix design. The results of these experimental tests were used to assess the feasibility of using PCM to reduce hydration heat in mass concrete that was examined. The experimental results show that cement mortar containing barium- [Ba(OH2·8H2O] based PCM has the lowest amount of total hydration heat of the cement pastes. The barium-based PCM provides good latent heat properties that help to prevent volume change and microcracks caused by thermal stress in mass concrete.

  10. Infrared spectroscopic measurement of skin hydration and sebum levels and comparison to corneometer and sebumeter

    Science.gov (United States)

    Ezerskaia, Anna; Pereira, S. F.; Urbach, H. P.; Varghese, Babu

    2016-05-01

    Skin health characterized by a system of water and lipids in Stratum Corneum provide protection from harmful external elements and prevent trans-epidermal water loss. Skin hydration (moisture) and sebum (skin surface lipids) are considered to be important factors in skin health; a right balance between these components is an indication of skin health and plays a central role in protecting and preserving skin integrity. In this manuscript we present an infrared spectroscopic method for simultaneous and quantitative measurement of skin hydration and sebum levels utilizing differential detection with three wavelengths 1720, 1750, and 1770 nm, corresponding to the lipid vibrational bands that lie "in between" the prominent water absorption bands. The skin sebum and hydration values on the forehead under natural conditions and its variations to external stimuli were measured using our experimental set-up. The experimental results obtained with the optical set-up show good correlation with the results obtained with the commercially available instruments Corneometer and Sebumeter.

  11. Effects of excipients on hydrate formation in wet masses containing theophylline

    DEFF Research Database (Denmark)

    Airaksinen, Sari; Luukkonen, Pirjo; Jørgensen, Anna

    2003-01-01

    its dissolution rate. The aim of this study was to investigate whether excipients, such as alpha-lactose monohydrate or the highly water absorbing silicified microcrystalline cellulose (SMCC) can influence the hydrate formation of theophylline. In particular, the aim was to study if SMCC offers...... protection against the formation of theophylline monohydrate relative to alpha-lactose monohydrate in wet masses after an overnight equilibration and the stability of final granules during controlled storage. In addition, the aim was to study the use of spectroscopic methods to identify hydrate formation...... in the formulations containing excipients. Off-line evaluation of materials was performed using X-ray powder diffractometry, near infrared and Raman spectroscopy. alpha-Lactose monohydrate with minimal water absorbing potential was not able to prevent but enhanced hydrate formation of theophylline. Even though SMCC...

  12. Hydration Status of Adult Population of Yazd

    Directory of Open Access Journals (Sweden)

    MH Lotfi

    2008-07-01

    Full Text Available Introduction: Water is an essential nutrient for life. It comprises 75% of total body weight in infants,60% in adult males and 50% in adult females. Decrease in body water is commonly known as dehydration. Acute or chronic dehydration is a common condition in some population groups, especialy the elderly and those who participate in physical activity in warm enviroments. Potential consequences of dehydration include constipation,urinary tract and respiratory infection,urinary stone disease and there might also be an association between a low habitual fluid intake and some carcinomas,cardiovascular disease and diabetes. Many indices have been investigated to establish their role as markers of dehydration status. Body mass changes,blood indices,urine indices and bioelectrical impedance analysis have been used most widely, but current evidence and opinion tend to favour urine indices as the most convenient and sensitive methods. Methods: This cross sectional study was done for estimating the prevalence of dehydration in adult population(students,nurses,officials,workersin Yazd. These persons were selected randomly. Urine samples of two hundred and thirty persons were obtained at 10-12 AM,and urine specific gravity measured by refractometer (all of the samplesand dip stick (some samples. Finding: According to this study,96.7% of our population had some degree of dehydration.69.7% of them were significantly dehydrated(urine SG>1020 and 4.8% of them were severely dehydrated (urine SG>1030 and the mean specific gravity was 1021±5/65. This study evaluated other factors that could probably indicate hydration status like urine colour, type of drink,frequency of urination and frequency of thirst per day. Conclusion: High percentage of our population were dehydrated which was not correlated to the type of drink but was correlated to urine colour, frequency of urination and frequency of thirst. So, regular monitoring of urine to keep if clear or light

  13. The importance of hydration in wound healing: reinvigorating the clinical perspective.

    Science.gov (United States)

    Ousey, K; Cutting, K F; Rogers, A A; Rippon, M G

    2016-03-01

    Balancing skin hydration levels is important as any disruption in skin integrity will result in disturbance of the dermal water balance. The discovery that a moist environment actively supports the healing response when compared with a dry environment highlights the importance of water and good hydration levels for optimal healing. The benefits of 'wet' or 'hyper-hydrated' wound healing appear similar to those offered by moist over a dry environment. This suggests that the presence of free water may not be detrimental to healing, but any adverse effects of wound fluid on tissues is more likely related to the biological components contained within chronic wound exudate, for example elevated protease levels. Appropriate dressings applied to wounds must not only be able to absorb the exudate, but also retain this excess fluid together with its protease solutes, while concurrently preventing desiccation. This is particularly important in the case of chronic wounds where peri-wound skin barrier properties are compromised and there is increased permeation across the injured skin. This review discusses the importance of appropriate levels of hydration in skin, with a particular focus on the need for optimal hydration levels for effective healing. Declaration of interest: This paper was supported by Paul Hartmann Ltd. The authors have provided consultative services to Paul Hartmann Ltd.

  14. The influence of Na2O on the hydration of C3A II. Suspension hydration

    NARCIS (Netherlands)

    Spierings, G.A.C.M.; Stein, H.N.

    1976-01-01

    The influence of Na2O on the hydration of C3A was studied in suspensions from the start of the reaction onwards. The heat evolution rate in very early stages of the hydration, measured at varying NaOH concentrations, and SEM, indicate that at NaOH concentrations larger then 0.1 M the reaction

  15. Distinguishing between hydrated, partially hydrated or unhydrated clinker in hardened concrete using microscopy

    NARCIS (Netherlands)

    Valcke, S.L.A.; Rooij, M.R. de; Visser, J.H.M.; Nijland, T.G.

    2010-01-01

    Hydration of clinker particles is since long a topic of interest in both designing and optimizing cement composition and its quantity used in concrete. The interest for carefully observing and also quantifying the type or stage of clinker hydration in hardened cement paste is twofold. Firstly, the

  16. Methane hydrate dissociation using inverted five-spot water flooding method in cubic hydrate simulator

    International Nuclear Information System (INIS)

    Li, Gang; Li, Xiao-Sen; Li, Bo; Wang, Yi

    2014-01-01

    The combination forms of the hydrate dissociation methods in different well systems are divided into 6 main patterns. Dissociation processes of methane hydrate in porous media using the inverted five-spot water flooding method (Pattern 4) are investigated by the experimental observation and numerical simulation. In situ methane hydrate is synthesized in the Cubic Hydrate Simulator (CHS), a 5.832-L cubic reactor. A center vertical well is used as the hot water injection well, while the four vertical wells at the corner are the gas and water production wells. The gas production begins simultaneously with the hot water injection, while after approximately 20 min of compression, the water begins to be produced. One of the common characteristics of the inverted five-spot water flooding method is that both the gas and water production rates decrease with the reduction of the hydrate dissociation rate. The evaluation of the energy efficiency ratio might indicate the inverted five-spot water flooding as a promising gas producing method from the hydrate reservoir. - Highlights: • A three-dimensional 5.8-L cubic pressure vessel is developed. • Gas production of hydrate using inverted five-spot flooding method is studied. • Water/gas production rate and energy efficiency ratio are evaluated. • Temperature distributions of numerical simulation and experiment agree well. • Hydrate dissociation process is a moving boundary problem in this study

  17. Contrast induced nephropathy in patients undergoing intravenous (IV) contrast enhanced computed tomography (CECT) and the relationship with risk factors: A meta-analysis

    Energy Technology Data Exchange (ETDEWEB)

    Moos, Shira I., E-mail: s.i.moos@amc.uva.nl; Vemde, David N.H. van; Stoker, Jaap; Bipat, Shandra

    2013-09-15

    Purpose: To summarize the incidence of contrast-induced nephropathy (CIN) and associations between CIN incidence and risk factors in patients undergoing intravenous contrast-enhanced computed tomography (CECT) with low- or iso-osmolar iodinated contrast medium. Methods: This review is performed in accordance with the preferred reporting items in systematic reviews and meta-analysis (PRISMA) guidelines. We searched the MEDLINE, EMBASE and Cochrane databases from 2002 till November 2012. Two reviewers included papers and extracted data. The pooled data were analysed by either fixed or random-effects approach depending on heterogeneity defined as the I{sup 2} index. Results: 42 articles with 18,790 patients (mean age 61.5 years (range: 38–83 years)) were included. The mean baseline eGFR was 59.8 mL/min and ranged from 4 to 256 mL/min. Of all patients 45.0% had an estimated glomerular filtration rate (eGFR) < 60 mL/min, 55.2% had hypertension; 20.2% had diabetes mellitus (DM) and 6.5% had congestive heart failure (CHF). The overall pooled CIN incidence, defined as a SCr increase of ≥25% or ≥0.5 mg/dL, was 4.96% (95%CI: 3.79–6.47). Data analysis showed associations between CIN and the presence of renal insufficiency, DM, malignancy, age > 65 years and use of non-steroidal anti-inflammatory drugs (NSAID's) with odds ratios of 1.73 (95%CI: 1.06–2.82), 1.87 (95%CI: 1.55–2.26), 1.79 (95%CI: 1.03–3.11), 1.95 (95%CI: 1.02–3.70) and 2.32 (95%CI: 1.04–5.19), respectively while hypertension, anaemia and CFH were not associated (p = 0.13, p = 0.38, p = 0.40). Conclusion: The mean incidence of CIN after intravenous iodinated CECT was low and associated with renal insufficiency, diabetes, presence of malignancy, old age and NSAID's use.

  18. Controls on Gas Hydrate Formation and Dissociation

    Energy Technology Data Exchange (ETDEWEB)

    Miriam Kastner; Ian MacDonald

    2006-03-03

    The main objectives of the project were to monitor, characterize, and quantify in situ the rates of formation and dissociation of methane hydrates at and near the seafloor in the northern Gulf of Mexico, with a focus on the Bush Hill seafloor hydrate mound; to record the linkages between physical and chemical parameters of the deposits over the course of one year, by emphasizing the response of the hydrate mound to temperature and chemical perturbations; and to document the seafloor and water column environmental impacts of hydrate formation and dissociation. For these, monitoring the dynamics of gas hydrate formation and dissociation was required. The objectives were achieved by an integrated field and laboratory scientific study, particularly by monitoring in situ formation and dissociation of the outcropping gas hydrate mound and of the associated gas-rich sediments. In addition to monitoring with the MOSQUITOs, fluid flow rates and temperature, continuously sampling in situ pore fluids for the chemistry, and imaging the hydrate mound, pore fluids from cores, peepers and gas hydrate samples from the mound were as well sampled and analyzed for chemical and isotopic compositions. In order to determine the impact of gas hydrate dissociation and/or methane venting across the seafloor on the ocean and atmosphere, the overlying seawater was sampled and thoroughly analyzed chemically and for methane C isotope ratios. At Bush hill the pore fluid chemistry varies significantly over short distances as well as within some of the specific sites monitored for 440 days, and gas venting is primarily focused. The pore fluid chemistry in the tub-warm and mussel shell fields clearly documented active gas hydrate and authigenic carbonate formation during the monitoring period. The advecting fluid is depleted in sulfate, Ca Mg, and Sr and is rich in methane; at the main vent sites the fluid is methane supersaturated, thus bubble plumes form. The subsurface hydrology exhibits both

  19. Hydration of urea and alkylated urea derivatives

    Science.gov (United States)

    Kaatze, Udo

    2018-01-01

    Compressibility data and broadband dielectric spectra of aqueous solutions of urea and some of its alkylated derivatives have been evaluated to yield their numbers Nh of hydration water molecules per molecule of solute. Nh values in a broad range of solute concentrations are discussed and are compared to hydration numbers of other relevant molecules and organic ions. Consistent with previous results, it is found that urea differs from other solutes in its unusually small hydration number, corresponding to just one third of the estimated number of nearest neighbor molecules. This remarkable hydration behavior is explained by the large density φH of hydrogen bonding abilities offered by the urea molecule. In terms of currently discussed models of reorientational motions and allied dynamics in water and related associating liquids, the large density φH causes a relaxation time close to that of undisturbed water with most parts of water encircling the solute. Therefore only a small part of disturbed ("hydration") water is left around each urea molecule. Adding alkyl groups to the basic molecule leads to Nh values which, within the series of n-alkylurea derivatives, progressively increase with the number of methyl groups per solute. With n-butylurea, Nh from dielectric spectra, in conformity with many other organic solutes, slightly exceeds the number of nearest neighbors. Compared to such Nh values, hydration numbers from compressibility data are substantially smaller, disclosing incorrect assumptions in the formula commonly used to interpret the experimental compressibilities. Similar to other series of organic solutes, effects of isomerization have been found with alkylated urea derivatives, indicating that factors other than the predominating density φH of hydrogen bond abilities contribute also to the hydration properties.

  20. Hydrates on tap: scientists say natural gas hydrates may be tough nut to crack

    Energy Technology Data Exchange (ETDEWEB)

    Mahoney, J.

    2001-12-01

    Gas hydrates are methane molecules trapped in cages of water molecules, yielding a substance with a slushy, sherbet-like consistency. Drilling for hydrates is similar to conventional oil and gas drilling, however, the secret to economic production still remains hidden. Hydrates exist in abundance in such places as deep ocean floor and below ground in some polar regions. The real challenge lies in producing gas from this resource, inasmuch as there is no existing technology for production of gas specifically from methane hydrates. This paper describes an international research program, involving a five-country partnership to spud the first of three wells into the permafrost of the Mackenzie River Delta in the Northwest Territories. The project, worth about $15 million, has brought together public funding and expertise from Japan, Germany, India as well as the Canadian and US Geological Surveys and the US Dept. of Energy in an effort to gain information on the production response of gas hydrates. The operator of the project is Japan Petroleum Exploration Company of Canada, a subsidiary of Japan National Oil Corporation. Since Japan is poor in domestic hydrocarbon resources, but is surrounded by deep water that contains potential for gas hydrates, Japan has a great deal riding on the success of this project. Germany and the United States are also very much interested. Current thinking is that gas is in contact with the hydrates and that it should be possible to develop a free gas reservoir as if it were a conventional deposit. As the free gas is drawn off, the pressure is reduced on the hydrates in contact with it , the hydrates dissociate from the gas and replenish the conventional reservoir. So far this is still only a theory, but it appears to be a sensible approach to hydrate production. 1 photo.

  1. Experimental Determination of Refractive Index of Gas Hydrates

    DEFF Research Database (Denmark)

    Bylov, Martin; Rasmussen, Peter

    1997-01-01

    . For methane hydrate (structure I) the refractive index was found to be 1.346 and for natural gas hydrate (structure II) it was found to be 1.350. The measurements further suggest that the gas hydrate growth rate increases if the water has formed hydrates before. The induction time, on the other hand, seems......The refractive indexes of methane hydrate and natural gas hydrate have been experimentally determined. The refractive indexes were determined in an indirect manner making use of the fact that two non-absorbing materials will have the same refractive index if they cannot be distinguished visually...

  2. Development of hydrate risk quantification in oil and gas production

    Science.gov (United States)

    Chaudhari, Piyush N.

    Subsea flowlines that transport hydrocarbons from wellhead to the processing facility face issues from solid deposits such as hydrates, waxes, asphaltenes, etc. The solid deposits not only affect the production but also pose a safety concern; thus, flow assurance is significantly important in designing and operating subsea oil and gas production. In most subsea oil and gas operations, gas hydrates form at high pressure and low temperature conditions, causing the risk of plugging flowlines, with a undesirable impact on production. Over the years, the oil and gas industry has shifted their perspective from hydrate avoidance to hydrate management given several parameters such as production facility, production chemistry, economic and environmental concerns. Thus, understanding the level of hydrate risk associated with subsea flowlines is an important in developing efficient hydrate management techniques. In the past, hydrate formation models were developed for various flow-systems (e.g., oil dominated, water dominated, and gas dominated) present in the oil and gas production. The objective of this research is to extend the application of the present hydrate prediction models for assessing the hydrate risk associated with subsea flowlines that are prone to hydrate formation. It involves a novel approach for developing quantitative hydrate risk models based on the conceptual models built from the qualitative knowledge obtained from experimental studies. A comprehensive hydrate risk model, that ranks the hydrate risk associated with the subsea production system as a function of time, hydrates, and several other parameters, which account for inertial, viscous, interfacial forces acting on the flow-system, is developed for oil dominated and condensate systems. The hydrate plugging risk for water dominated systems is successfully modeled using The Colorado School of Mines Hydrate Flow Assurance Tool (CSMHyFAST). It is found that CSMHyFAST can be used as a screening tool in

  3. METHANE HYDRATE PRODUCTION FROM ALASKAN PERMAFROST

    Energy Technology Data Exchange (ETDEWEB)

    Richard Sigal; Kent Newsham; Thomas Williams; Barry Freifeld; Timothy Kneafsey; Carl Sondergeld; Shandra Rai; Jonathan Kwan; Stephen Kirby; Robert Kleinberg; Doug Griffin

    2005-02-01

    Natural-gas hydrates have been encountered beneath the permafrost and considered a nuisance by the oil and gas industry for years. Engineers working in Russia, Canada and the USA have documented numerous drilling problems, including kicks and uncontrolled gas releases, in arctic regions. Information has been generated in laboratory studies pertaining to the extent, volume, chemistry and phase behavior of gas hydrates. Scientists studying hydrate potential agree that the potential is great--on the North Slope of Alaska alone, it has been estimated at 590 TCF. However, little information has been obtained on physical samples taken from actual rock containing hydrates. The work scope drilled and cored a well The Hot Ice No. 1 on Anadarko leases beginning in FY 2003 and completed in 2004. An on-site core analysis laboratory was built and utilized for determining the physical characteristics of the hydrates and surrounding rock. The well was drilled from a new Anadarko Arctic Platform that has a minimal footprint and environmental impact. The final efforts of the project are to correlate geology, geophysics, logs, and drilling and production data and provide this information to scientists developing reservoir models. No gas hydrates were encountered in this well; however, a wealth of information was generated and is contained in this report. The Hot Ice No. 1 well was drilled from the surface to a measured depth of 2300 ft. There was almost 100% core recovery from the bottom of surface casing at 107 ft to total depth. Based on the best estimate of the bottom of the methane hydrate stability zone (which used new data obtained from Hot Ice No. 1 and new analysis of data from adjacent wells), core was recovered over its complete range. Approximately 580 ft of porous, mostly frozen, sandstone and 155 of conglomerate were recovered in the Ugnu Formation and approximately 215 ft of porous sandstone were recovered in the West Sak Formation. There were gas shows in the bottom

  4. Dietary water affects human skin hydration and biomechanics

    Directory of Open Access Journals (Sweden)

    Palma L

    2015-08-01

    Full Text Available Lídia Palma,1 Liliana Tavares Marques,1 Julia Bujan,2,3 Luís Monteiro Rodrigues1,4 1CBIOS – Research Center for Health Science and Technologies, Universidade Lusófona, Campo Grande, Lisboa, Portugal; 2Department of Medicine and Medical Specialities, Universidad de Alcalá de Henares, Madrid, Spain; 3CIBER-BBN, Madrid, España, Spain; 4Department of Pharmacological Sciences, School of Pharmacy, Universidade de Lisboa, Lisboa, Portugal Abstract: It is generally assumed that dietary water might be beneficial for the health, especially in dermatological (age preventing terms. The present study was designed to quantify the impact of dietary water on major indicators of skin physiology. A total of 49 healthy females (mean 24.5±4.3 years were selected and characterized in terms of their dietary daily habits, especially focused in water consumption, by a Food Frequency Questionnaire. This allowed two groups to be set – Group 1 consuming less than 3,200 mL/day (n=38, and Group 2 consuming more than 3,200 mL/day (n=11. Approximately 2 L of water were added to the daily diet of Group 2 individuals for 1 month to quantify the impact of this surplus in their skin physiology. Measurements involving epidermal superficial and deep hydration, transepidermal water loss, and several biomechanical descriptors were taken at day 0 (T0, 15 (T1, and 30 (T2 in several anatomical sites (face, upper limb, and leg. This stress test (2 L/day for 30 days significantly modified superficial and deep skin hydration, especially in Group 1. The same impact was registered with the most relevant biomechanical descriptors. Thus, in this study, it is clear that higher water inputs in regular diet might positively impact normal skin physiology, in particular in those individuals with lower daily water consumptions. Keywords: dietary water, water consume, skin hydration, TEWL, skin biomechanics

  5. Experimental investigation of methane release from hydrate formation in sandstone through both hydrate dissociation and CO{sub 2} sequestration

    Energy Technology Data Exchange (ETDEWEB)

    Husebo, J.; Graue, A.; Kvamme, B. [Bergen Univ., Bergen (Norway). Dept. of Physics and Technology; Stevens, J.; Howard, J.J. [ConocoPhillips, Ponca City, OK (United States); Baldwin, B.A. [Green Country Petrophysics LLC, Dewey, OK (United States)

    2008-07-01

    Large amounts of natural gas trapped in hydrate reservoirs are found in Arctic regions and in deep offshore locations around the world. Natural gas production from hydrate deposits offer significant potential for future energy needs. However, research is needed in order to propose potential production schemes for natural gas hydrates. Natural gas molecules can be freed from hydrate structured cages by depressurization, by heating and by exposing the hydrate to a substance that will form a thermodynamically more stable hydrate structure. This paper provided a comparison of two approaches for releasing methane from methane hydrate in porous sandstone. The study scope covered the dissociation rate of methane hydrate in porous media through depressurization, and also referred to previous work done on producing methane from hydrates in sandstone while sequestering carbon dioxide (CO{sub 2}). The study was conducted in a laboratory setting. The paper discussed the experimental design which included the placing of a pressure- and temperature-controlled sample holder inside the bore of a magnetic resonance imager. The experimental procedures were then outlined, with reference to hydrate formation; carbon dioxide sequestration; hydrate dissociation experiments with constant volume; and hydrate dissociation experiments at constant pressure. The constant volume experiments demonstrated that in order to dissociate a large amount of hydrate, the initial depressurization had to be significantly lower than the hydrate stability pressure. 9 refs., 9 figs.

  6. Strength Estimation for Hydrate-Bearing Sediments From Direct Shear Tests of Hydrate-Bearing Sand and Silt

    Science.gov (United States)

    Liu, Zhichao; Dai, Sheng; Ning, Fulong; Peng, Li; Wei, Houzhen; Wei, Changfu

    2018-01-01

    Safe and economic methane gas production, as well as the replacement of methane while sequestering carbon in natural hydrate deposits, requires enhanced geomechanical understanding of the strength and volume responses of hydrate-bearing sediments during shear. This study employs a custom-made apparatus to investigate the mechanical and volumetric behaviors of carbon dioxide hydrate-bearing sediments subjected to direct shear. The results show that both peak and residual strengths increase with increased hydrate saturation and vertical stress. Hydrate contributes mainly the cohesion and dilatancy constraint to the peak strength of hydrate-bearing sediments. The postpeak strength reduction is more evident and brittle in specimens with higher hydrate saturation and under lower stress. Significant strength reduction after shear failure is expected in silty sediments with high hydrate saturation Sh ≥ 0.65. Hydrate contribution to the residual strength is mainly by increasing cohesion at low hydrate saturation and friction at high hydrate saturation. Stress state and hydrate saturation are dominating both the stiffness and the strength of hydrate-bearing sediments; thus, a wave velocity-based peak strength prediction model is proposed and validated, which allows for precise estimation of the shear strength of hydrate-bearing sediments through acoustic logging data. This method is advantageous to geomechanical simulators, particularly when the experimental strength data of natural samples are not available.

  7. Hydraulic and Mechanical Effects from Gas Hydrate Conversion and Secondary Gas Hydrate Formation during Injection of CO2 into CH4-Hydrate-Bearing Sediments

    Science.gov (United States)

    Bigalke, N.; Deusner, C.; Kossel, E.; Schicks, J. M.; Spangenberg, E.; Priegnitz, M.; Heeschen, K. U.; Abendroth, S.; Thaler, J.; Haeckel, M.

    2014-12-01

    The injection of CO2 into CH4-hydrate-bearing sediments has the potential to drive natural gas production and simultaneously sequester CO2 by hydrate conversion. The process aims at maintaining the in situ hydrate saturation and structure and causing limited impact on soil hydraulic properties and geomechanical stability. However, to increase hydrate conversion yields and rates it must potentially be assisted by thermal stimulation or depressurization. Further, secondary formation of CO2-rich hydrates from pore water and injected CO2 enhances hydrate conversion and CH4 production yields [1]. Technical stimulation and secondary hydrate formation add significant complexity to the bulk conversion process resulting in spatial and temporal effects on hydraulic and geomechanical properties that cannot be predicted by current reservoir simulation codes. In a combined experimental and numerical approach, it is our objective to elucidate both hydraulic and mechanical effects of CO2 injection and CH4-CO2-hydrate conversion in CH4-hydrate bearing soils. For the experimental approach we used various high-pressure flow-through systems equipped with different online and in situ monitoring tools (e.g. Raman microscopy, MRI and ERT). One particular focus was the design of triaxial cell experimental systems, which enable us to study sample behavior even during large deformations and particle flow. We present results from various flow-through high-pressure experimental studies on different scales, which indicate that hydraulic and geomechanical properties of hydrate-bearing sediments are drastically altered during and after injection of CO2. We discuss the results in light of the competing processes of hydrate dissociation, hydrate conversion and secondary hydrate formation. Our results will also contribute to the understanding of effects of temperature and pressure changes leading to dissociation of gas hydrates in ocean and permafrost systems. [1] Deusner C, Bigalke N, Kossel E

  8. First-principles elasticity of monocarboaluminate hydrates

    KAUST Repository

    Moon, J.

    2014-07-01

    The elasticity of monocarboaluminate hydrates, 3CaO·Al2O3·CaCO3·xH2O (x = 11 or 8), has been investigated by first-principles calculations. Previous experimental study revealed that the fully hydrated monocarboaluminate (x = 11) exhibits exceptionally low compressibility compared to other reported calcium aluminate hydrates. This stiff hydration product can contribute to the strength of concrete made with Portland cements containing calcium carbonates. In this study, full elastic tensors and mechanical properties of the crystal structures with different water contents (x = 11 or 8) are computed by first-principles methods based on density functional theory. The results indicate that the compressibility of monocarboaluminate is highly dependent on the water content in the interlayer region. The structure also becomes more isotropic with the addition of water molecules in this region. Since the monocarboaluminate is a key hydration product of limestone added cement, elasticity of the crystal is important to understand its mechanical impact on concrete. Besides, it is put forth that this theoretical calculation will be useful in predicting the elastic properties of other complex cementitous materials and the influence of ion exchange on compressibility.

  9. Effect of overpressure on gas hydrate distribution

    Energy Technology Data Exchange (ETDEWEB)

    Bhatnagar, G.; Chapman, W.G.; Hirasaki, G.J. [Rice Univ., Houston, TX (United States). Dept. of Chemical and Biomolecular Engineering; Dickens, G.R.; Dugan, B. [Rice Univ., Houston, TX (United States). Dept. of Earth Sciences

    2008-07-01

    Natural gas hydrate systems can be characterized by high sedimentation rates and/or low permeability sediments, which can lead to pore pressure higher than hydrostatic. This paper discussed a study that examined this effect of overpressure on gas hydrate and free gas distribution in marine sediments. A one-dimensional numerical model that coupled sedimentation, fluid flow, and gas hydrate formation was utilized. In order to quantify the relative importance of sedimentation rates and low permeability sediments, a dimensionless sedimentation-compaction group (scN) was defined, that compared the absolute permeability of the sediments to the sedimentation rate. Higher values of scN mean higher permeability or low sedimentation rate which generally yield hydrostatic pore pressure while lower values of scN normally create pore pressure greater than hydrostatic. The paper discussed non-hydrostatic consolidation in gas hydrate systems, including mass balances; constitutive relationships; normalized variables; and dimensionless groups. A numerical solution to the problem was presented. It was concluded that simulation results demonstrated that decreasing scN not only increased pore pressure above hydrostatic values, but also lowered the lithostatic stress gradient and gas hydrate saturation. This occurred because overpressure resulted in lower effective stress, causing higher porosity and lower bulk density of the sediment. 16 refs., 5 figs., 1 appendix.

  10. First-principles elasticity of monocarboaluminate hydrates

    KAUST Repository

    Moon, J.; Yoon, S.; Wentzcovitch, R. M.; Monteiro, P. J. M.

    2014-01-01

    The elasticity of monocarboaluminate hydrates, 3CaO·Al2O3·CaCO3·xH2O (x = 11 or 8), has been investigated by first-principles calculations. Previous experimental study revealed that the fully hydrated monocarboaluminate (x = 11) exhibits exceptionally low compressibility compared to other reported calcium aluminate hydrates. This stiff hydration product can contribute to the strength of concrete made with Portland cements containing calcium carbonates. In this study, full elastic tensors and mechanical properties of the crystal structures with different water contents (x = 11 or 8) are computed by first-principles methods based on density functional theory. The results indicate that the compressibility of monocarboaluminate is highly dependent on the water content in the interlayer region. The structure also becomes more isotropic with the addition of water molecules in this region. Since the monocarboaluminate is a key hydration product of limestone added cement, elasticity of the crystal is important to understand its mechanical impact on concrete. Besides, it is put forth that this theoretical calculation will be useful in predicting the elastic properties of other complex cementitous materials and the influence of ion exchange on compressibility.

  11. Methane hydrates in quaternary climate change

    International Nuclear Information System (INIS)

    Kennett, J. P.; Hill, T. M.; Behl, R. J.

    2005-01-01

    The hydrate reservoir in marine sediments is known to contain a large volume of exchangeable carbon stored as solid methane hydrate and associated free gas. This reservoir has been shown to be potentially unstable in response to changing intermediate water temperature and sea level (pressure). Evidence continues to grow for past episodes of major methane release at times of climatic warming. Yet few studies of late Quaternary climate change include methane hydrates as an integral part of the global climate system, in spite of the largest known oscillations at this time in sea level and upper ocean temperature changes for the Cenozoic or earlier, conditions that favor instability of the methane hydrate reservoir. Abrupt increases in atmospheric methane recorded in polar ice cores are widely believed to have resulted, not from ocean-floor methane degassing, but instead from continental wetland activation, a hypothesis thus far unsupported by geological data. Furthermore, as part of this Wetland Methane Hypothesis, the abrupt methane increases have been seen as a response to climatic warming rather than contributing significantly to the change. An alternative view (formulated as the Clathrate Gun Hypothesis) is that the speed, magnitude and timing of abrupt climate change in the recent geologic past are consistent with the process of major degassing of methane hydrates. We summarize aspects of this hypothesis here and needs to test this hypothesis. (Author)

  12. Blue LED irradiation to hydration of skin

    Science.gov (United States)

    Menezes, Priscila F. C.; Requena, Michelle B.; Lizarelli, Rosane F., Z.; Bagnato, Vanderlei S.

    2015-06-01

    Blue LED system irradiation shows many important properties on skin as: bacterial decontamination, degradation of endogenous skin chromophores and biostimulation. In this clinical study we prove that the blue light improves the skin hydration. In the literature none authors reports this biological property on skin. Then this study aims to discuss the role of blue light in the skin hydration. Twenty patients were selected to this study with age between 25-35 years old and phototype I, II and III. A defined area from forearm was pre determined (A = 4.0 cm2). The study was randomized in two treatment groups using one blue light device (power of 5.3mW and irradiance of 10.8mW/cm2). The first treatment group was irradiated with 3J/cm2 (277seconds) and the second with 6J/cm2 (555 seconds). The skin hydration evaluations were done using a corneometer. The measurements were collected in 7, 14, 21 and 30 days, during the treatment. Statistical test of ANOVA, Tukey and T-Student were applied considering 5% of significance. In conclusion, both doses were able to improve the skin hydration; however, 6J/cm2 has kept this hydration for 30 days.

  13. Effects of Nanosilica on Early Age Stages of Cement Hydration

    Directory of Open Access Journals (Sweden)

    Forood Torabian Isfahani

    2017-01-01

    Full Text Available Effects of nanosilica on cement hydration have been broadly investigated in the literature and early age cement hydration, as a whole, has been mainly considered, disregarding the substages of the hydration. The hydration of cement is characterized by different substages and nanosilica effect on the hydration could be a result of diverse, even contradictory, behavior of nanosilica in individual stages of the hydration. In this study, effects of nanosilica on different substages of cement hydration are investigated. Isothermal calorimetry results show that at early ages (initial 72 hours the effects of nanosilica depend on the phenomenon by which the hydration is governed: when the hydration is chemically controlled, that is, during initial reaction, dormant period, and acceleratory period, the hydration rate is accelerated by adding nanosilica; when the hydration is governed by diffusion process, that is, during postacceleratory period, the hydration rate is decelerated by adding nanosilica. The Thermal Gravimetric Analysis on the samples at the hardened state (after 28 days of curing reveals that, after adding nanosilica, the hydration degree slightly increased compared to the plain paste.

  14. Morphology studies on gas hydrates interacting with silica gel

    Energy Technology Data Exchange (ETDEWEB)

    Beltran, J.; Servio, P. [McGill Univ., Montreal, PQ (Canada). Dept. of Chemical Engineering

    2008-07-01

    Clathrate hydrates or gas hydrates are non-stoichiometric, crystalline compounds that form when small molecules come in contact with water at certain temperatures and pressures. Natural gas hydrates are found in the ocean bottom and in permafrost regions. It is thought that the amount of energy stored in natural hydrates is at least twice that of all other fossil fuels combined. In addition, trapping carbon dioxide as a hydrate in the bottom of the ocean has been suggested as an alternative means of reducing atmospheric carbon dioxide levels. Naturally occurring clathrates are found in close interaction with fine grained particles of very small mean pore diameters. Even though an increasing amount of hydrate equilibrium data for small diameter porous media has become available, the morphological behavior of hydrates subject to such conditions is yet to be explored. This paper presented a study that visually examined hydrate formation and decomposition of gas hydrates while interacting with fine grains of silica gel. The study showed still frames from high-resolution video recordings for hydrate formation and decomposition. The paper discussed the experiment including the apparatus as well as the results of hydrate formation and hydrate dissociation. This study enabled for the first time to observe clathrate morphology while hydrates interacted closely with fine grain particles with small mean pore diameters. 9 refs., 8 figs.

  15. Methane hydrates in nature - Current knowledge and challenges

    Science.gov (United States)

    Collett, Timothy S.

    2014-01-01

    Recognizing the importance of methane hydrate research and the need for a coordinated effort, the United States Congress enacted the Methane Hydrate Research and Development Act of 2000. At the same time, the Ministry of International Trade and Industry in Japan launched a research program to develop plans for a methane hydrate exploratory drilling project in the Nankai Trough. India, China, the Republic of Korea, and other nations also have established large methane hydrate research and development programs. Government-funded scientific research drilling expeditions and production test studies have provided a wealth of information on the occurrence of methane hydrates in nature. Numerous studies have shown that the amount of gas stored as methane hydrates in the world may exceed the volume of known organic carbon sources. However, methane hydrates represent both a scientific and technical challenge, and much remains to be learned about their characteristics and occurrence in nature. Methane hydrate research in recent years has mostly focused on: (1) documenting the geologic parameters that control the occurrence and stability of methane hydrates in nature, (2) assessing the volume of natural gas stored within various methane hydrate accumulations, (3) analyzing the production response and characteristics of methane hydrates, (4) identifying and predicting natural and induced environmental and climate impacts of natural methane hydrates, (5) analyzing the methane hydrate role as a geohazard, (6) establishing the means to detect and characterize methane hydrate accumulations using geologic and geophysical data, and (7) establishing the thermodynamic phase equilibrium properties of methane hydrates as a function of temperature, pressure, and gas composition. The U.S. Department of Energy (DOE) and the Consortium for Ocean Leadership (COL) combined their efforts in 2012 to assess the contributions that scientific drilling has made and could continue to make to advance

  16. Fuel cell membrane hydration and fluid metering

    Science.gov (United States)

    Jones, Daniel O.; Walsh, Michael M.

    1999-01-01

    A hydration system includes fuel cell fluid flow plate(s) and injection port(s). Each plate has flow channel(s) with respective inlet(s) for receiving respective portion(s) of a given stream of reactant fluid for a fuel cell. Each injection port injects a portion of liquid water directly into its respective flow channel in order to mix its respective portion of liquid water with the corresponding portion of the stream. This serves to hydrate at least corresponding part(s) of a given membrane of the corresponding fuel cell(s). The hydration system may be augmented by a metering system including flow regulator(s). Each flow regulator meters an injecting at inlet(s) of each plate of respective portions of liquid into respective portion(s) of a given stream of fluid by corresponding injection port(s).

  17. Hydration dynamics of hyaluronan and dextran.

    Science.gov (United States)

    Hunger, Johannes; Bernecker, Anja; Bakker, Huib J; Bonn, Mischa; Richter, Ralf P

    2012-07-03

    Hyaluronan is a polysaccharide, which is ubiquitous in vertebrates and has been reported to be strongly hydrated in a biological environment. We study the hydration of hyaluronan in solution using the rotational dynamics of water as a probe. We measure these dynamics with polarization-resolved femtosecond-infrared and terahertz time-domain spectroscopies. Both experiments reveal that a subensemble of water molecules is slowed down in aqueous solutions of hyaluronan amounting to ∼15 water molecules per disaccharide unit. This quantity is consistent with what would be expected for the first hydration shell. Comparison of these results to the water dynamics in aqueous dextran solution, a structurally similar polysaccharide, yields remarkably similar results. This suggests that the observed interaction with water is a common feature for hydrophilic polysaccharides and is not specific to hyaluronan. Copyright © 2012 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  18. Multicavity SCRF calculation of ion hydration energies

    International Nuclear Information System (INIS)

    Diercksen, B.H.F.; Karelson, M.; Tamm, T.

    1994-01-01

    The hydration energies of the proton, hydroxyl ion, and several inorganic ions were calculated using the multicavity self-consistent reaction field (MCa SCRF) method developed for the quantum-mechanical modeling of rotationally or flexible systems in dielectric media. The ionic complexes H 3 O + (H2O) 4 , OH - (H2O) 4 , NH + 4 (H2O) 4 , and Hal - (H2O) 4 , where Hal = F, Cl, or Br, have been studied. Each complex was divided between five spheres, corresponding to the central ion and four water molecules in their first coordination sphere, respectively. Each cavity was surrounded by a polarizable medium with the dielectric permittivity of water at room temperature (80). The ionic hydration energies of ions were divided into specific and nonspecific parts. After accounting for the cavity-formation energy using scaled particle theory, good agreement between the total calculated and experimental hydration energies was obtained for all ions studied

  19. Thermal expansion properties of calcium aluminate hydrates

    International Nuclear Information System (INIS)

    Song, Tae Woong

    1986-01-01

    In order to eliminate the effect of impurities and aggregates on the thermomechanical properties of the various calcium aluminate hydrates, and to prepare clinkers in which all calcium aluminates are mixed homogeneously, chemically pure CaO and Al 2 O 3 were weighed, blended and heated in various conditions. After quantitative X-ray diffractometry(QXRD), the synthesized clinker was hydrated and cured under the conditions of 30 deg C, W/C=0.5, relative humidity> 90% respectively during 24 hours. And then differential thermal analysis(DTA), thermogravimetry(TG), micro calorimetry, thermomechanical analysis(TMA) and scanning electron microanalysis(SEM) were applied to examine the thermal properties of samples containing, calcium aluminate hydrates in various quantity. (Author)

  20. Relaxation mechanism of the hydrated electron.

    Science.gov (United States)

    Elkins, Madeline H; Williams, Holly L; Shreve, Alexander T; Neumark, Daniel M

    2013-12-20

    The relaxation dynamics of the photoexcited hydrated electron have been subject to conflicting interpretations. Here, we report time-resolved photoelectron spectra of hydrated electrons in a liquid microjet with the aim of clarifying ambiguities from previous experiments. A sequence of three ultrashort laser pulses (~100 femtosecond duration) successively created hydrated electrons by charge-transfer-to-solvent excitation of dissolved anions, electronically excited these electrons via the s→p transition, and then ejected them into vacuum. Two distinct transient signals were observed. One was assigned to the initially excited p-state with a lifetime of ~75 femtoseconds, and the other, with a lifetime of ~400 femtoseconds, was attributed to s-state electrons just after internal conversion in a nonequilibrated solvent environment. These assignments support the nonadiabatic relaxation model.

  1. Impact of high dose versus low dose atorvastatin on contrast induced nephropathy in diabetic patients with acute coronary syndrome undergoing early percutaneous coronary intervention

    Directory of Open Access Journals (Sweden)

    Haitham Galal

    2015-12-01

    Conclusion: No significant difference between high and low doses of atorvastatin in preventing CIN in diabetic patients with normal or mild renal impairment presenting with acute coronary syndrome who underwent early PCI.

  2. Chemical alteration of cement hydrates by dissolution

    International Nuclear Information System (INIS)

    Sugiyama, Daisuke; Fujita, Tomonari; Nakanishi, Kiyoshi

    2000-01-01

    Cementitious material is a potential waste packaging and backfilling material for the radioactive waste disposal, and is expected to provide both physical and chemical containment. In particular, the sorption of radionuclides onto cementitious material and the ability to provide a high pH condition are very important parameters when considering the release of radionuclides from radioactive wastes. For the long term, in the geological disposal environment, cement hydrates will be altered by, for example, dissolution, chemical reaction with ions in the groundwater, and hydrothermal reaction. Once the composition or crystallinity of the constituent minerals of a cement hydrate is changed by these processes, the pH of the repository buffered by cementitious material and its sorption ability might be affected. However, the mechanism of cement alteration is not yet fully understood. In this study, leaching experiments of some candidate cements for radioactive waste disposal were carried out. Hydrated Ordinary Portland Cement (OPC), Blast Furnace Slag blended cement (OPC/BFS) and Highly containing Flyash and Silicafume Cement (HFSC) samples were contacted with distilled water at liquid:solid ratios of 10:1, 100:1 and 1000:1 at room temperature for 200 days. In the case of OPC, Ca(OH) 2 dissolved at high liquid:solid ratios. The specific surface area of all cement samples increased by leaching process. This might be caused by further hydration and change of composition of constituent minerals. A model is presented which predicts the leaching of cement hydrates and the mineral composition in the hydrated cement solid phase, including the incongruent dissolution of CSH gel phases and congruent dissolution of Ca(OH) 2 , Ettringite and Hydrotalcite. Experimental results of dissolution of Ca-O-H and Ca-Si-O-H phases were well predicted by this model. (author)

  3. Ground movements associated with gas hydrate production

    International Nuclear Information System (INIS)

    Siriwardane, H.J.; Kutuk, B.

    1992-03-01

    This report deals with a study directed towards a modeling effort on production related ground movements and subsidence resulting from hydrate dissociation. The goal of this research study was to evaluate whether there could be subsidence related problems that could be an impediment to hydrate production. During the production of gas from a hydrate reservoir, it is expected that porous reservoir matrix becomes more compressible which may cause reservoir compression (compaction) under the influence of overburden weight. The overburden deformations can propagate its influence upwards causing subsidence near the surface where production equipment will be located. In the present study, the reservoir compaction is modeled by using the conventional ''stress equilibrium'' approach. In this approach, the overburden strata move under the influence of body force (i.e. self weight) in response to the ''cavity'' generated by reservoir depletion. The present study is expected to provide a ''lower bound'' solution to the subsidence caused by hydrate reservoir depletion. The reservoir compaction anticipated during hydrate production was modeled by using the finite element method, which is a powerful computer modeling technique. The ground movements at the reservoir roof (i.e. reservoir compression) cause additional stresses and disturbance in the overburden strata. In this study, the reservoir compaction was modeled by using the conventional ''stress equilibrium'' approach. In this approach, the overburden strata move under the influence of body force (i.e. self weight) in response to the ''cavity'' generated by reservoir depletion. The resulting stresses and ground movements were computed by using the finite element method. Based on the parameters used in this investigation, the maximum ground subsidence could vary anywhere from 0.50 to 6.50 inches depending on the overburden depth and the size of the depleted hydrate reservoir

  4. Dietary water affects human skin hydration and biomechanics.

    Science.gov (United States)

    Palma, Lídia; Marques, Liliana Tavares; Bujan, Julia; Rodrigues, Luís Monteiro

    2015-01-01

    It is generally assumed that dietary water might be beneficial for the health, especially in dermatological (age preventing) terms. The present study was designed to quantify the impact of dietary water on major indicators of skin physiology. A total of 49 healthy females (mean 24.5±4.3 years) were selected and characterized in terms of their dietary daily habits, especially focused in water consumption, by a Food Frequency Questionnaire. This allowed two groups to be set - Group 1 consuming less than 3,200 mL/day (n=38), and Group 2 consuming more than 3,200 mL/day (n=11). Approximately 2 L of water were added to the daily diet of Group 2 individuals for 1 month to quantify the impact of this surplus in their skin physiology. Measurements involving epidermal superficial and deep hydration, transepidermal water loss, and several biomechanical descriptors were taken at day 0 (T0), 15 (T1), and 30 (T2) in several anatomical sites (face, upper limb, and leg). This stress test (2 L/day for 30 days) significantly modified superficial and deep skin hydration, especially in Group 1. The same impact was registered with the most relevant biomechanical descriptors. Thus, in this study, it is clear that higher water inputs in regular diet might positively impact normal skin physiology, in particular in those individuals with lower daily water consumptions.

  5. HYDRATION AND TEMPERATURE IN TENNIS - A PRACTICAL REVIEW

    Directory of Open Access Journals (Sweden)

    Mark S. Kovacs

    2006-03-01

    Full Text Available Competitive tennis is typically played in warm and hot environments. Because hypohydration will impair tennis performance and increases the risk of heat injury, consumption of appropriate fluid levels is necessary to prevent dehydration and enhance performance. The majority of research in this area has focused on continuous aerobic activity - unlike tennis, which has average points lasting less than ten seconds with rest periods dispersed between each work period. For this reason, hydration and temperature regulation methods need to be specific to the activity. Tennis players can sweat more than 2.5 L·h-1 and replace fluids at a slower rate during matches than in practice. Latter stages of matches and tournaments are when tennis players are more susceptible to temperature and hydration related problems. Sodium (Na+ depletion, not potassium (K+, is a key electrolyte in tennis related muscle cramps. However, psychological and competitive factors also contribute. CHO drinks have been shown to promote fluid absorption to a greater degree than water alone, but no performance benefits have been shown in tennis players in short matches. It is advisable to consume a CHO beverage if practice or matches are scheduled longer than 90-120 minutes.

  6. Hydration and nutrition knowledge in adolescent swimmers. Does water intake affect urine hydration markers after swimming?

    Directory of Open Access Journals (Sweden)

    Cesare Altavilla

    2017-12-01

    Full Text Available Little data exists regarding nutritional knowledge and hydration in adolescent swimmers. The aim of this study was to assess the level of nutrition and hydration knowledge and to describe the fluid balance in adolescent swimmers during training. A study was carried out with a cross-sectional descriptive part and a longitudinal part with repeated measurements over five swimming sessions. Eighty-six adolescent swimmers completed a questionnaire to assess their sport nutrition and hydration knowledge. Fluid balance and urine hydration markers were studied during training. Swimmers showed a limited nutrition knowledge (33.26 % ± SD 12.59 and meagre hydration knowledge (28.61 % ± SD 28.59. Females showed lower scores than male swimmers in nutrition and hydration knowledge. Based on urine specific gravity, swimmers started the training close to the euhydrated threshold (1.019 g/mL ± SD 0.008. Although urine specific gravity and urine colour were reduced after the training, there were minimal changes in body mass (-0.12 Kg ± SD 0.31. Sweat loss (2.67 g/min ± SD 3.23 and the net changes in the fluid balance (-0.22 % ± SD 0.59 were low. The poor knowledge in nutrition and hydration encountered in the swimmers can justify the development of a strategy to incorporate nutritional education programmes for this group. Body water deficit from swimming activity seems to be easily replaced with the water intake to maintain hydration. After the training, the urine of swimmers was diluted regardless of their water intake. Dilution of urine did not reflect real hydration state in swimming.

  7. Thermal decomposition of uranyl sulphate hydrate

    International Nuclear Information System (INIS)

    Sato, T.; Ozawa, F.; Ikoma, S.

    1980-01-01

    The thermal decomposition of uranyl sulphate hydrate (UO 2 SO 4 .3H 2 O) has been investigated by thermogravimetry, differential thermal analysis, X-ray diffraction and infrared spectrophotometry. As a result, it is concluded that uranyl sulphate hydrate decomposes thermally: UO 2 SO 4 .3H 2 O → UO 2 SO 4 .xH 2 O(2.5 = 2 SO 4 . 2H 2 O → UO 2 SO 4 .H 2 O → UO 2 SO 4 → α-UO 2 SO 4 → β-UO 2 SO 4 → U 3 O 8 . (author)

  8. Nanostructure of Calcium Silicate Hydrates in Cements

    KAUST Repository

    Skinner, L. B.; Chae, S. R.; Benmore, C. J.; Wenk, H. R.; Monteiro, P. J. M.

    2010-01-01

    Calcium silicate hydrate (CSH) is the major volume phase in the matrix of Portland cement concrete. Total x-ray scattering measurements with synchrotron x rays on synthetic CSH(I) shows nanocrystalline ordering with a particle diameter of 3.5(5) nm, similar to a size-broadened 1.1 nm tobermorite crystal structure. The CSH component in hydrated tricalcium silicate is found to be similar to CSH(I). Only a slight bend and additional disorder within the CaO sheets is required to explain its nanocrystalline structure. © 2010 The American Physical Society.

  9. Nanostructure of Calcium Silicate Hydrates in Cements

    KAUST Repository

    Skinner, L. B.

    2010-05-11

    Calcium silicate hydrate (CSH) is the major volume phase in the matrix of Portland cement concrete. Total x-ray scattering measurements with synchrotron x rays on synthetic CSH(I) shows nanocrystalline ordering with a particle diameter of 3.5(5) nm, similar to a size-broadened 1.1 nm tobermorite crystal structure. The CSH component in hydrated tricalcium silicate is found to be similar to CSH(I). Only a slight bend and additional disorder within the CaO sheets is required to explain its nanocrystalline structure. © 2010 The American Physical Society.

  10. Spectral Decomposition and Other Seismic Attributes for Gas Hydrate Prospecting

    Energy Technology Data Exchange (ETDEWEB)

    McConnell, Dan

    2018-02-25

    Studying the sediments at the base of gas hydrate stability is ideal for determining the seismic response to gas hydrate saturation. First, assuming gas migration to the shallow section, this area is more likely to have concentrated gas hydrate because it encompasses the zone in which upward moving buoyant gas transitions to form immobile gas hydrate deposits. Second, this zone is interesting because these areas have the potential to show a hydrate filled zone and a gas filled zone within the same sediments. Third, the fundamental measurement within seismic data is impedance contrasts between velocity*density layers. High saturation gas hydrates and free gas inhabit opposite ends of these measurements making the study of this zone ideal for investigating the seismic characteristics of gas hydrate and, hence, the investigation of other seismic attributes that may indicate gas hydrate fill.

  11. The rates measurement of methane hydrate formation and dissociation using micro-drilling system application for gas hydrate exploration

    Energy Technology Data Exchange (ETDEWEB)

    Bin Dou [Engineering Faculty, China Univ. of Geosciences, Wuhan (China)]|[Inst. of Petroleum Engineering, Technology Univ. of Clausthal (Germany); Reinicke, K.M. [Inst. of Petroleum Engineering, Technology Univ. of Clausthal (Germany); Guosheng Jiang; Xiang Wu; Fulong Ning [Engineering Faculty, China Univ. of Geosciences, Wuhan (China)

    2006-07-01

    When drilling through gas hydrate bearing formations, the energy supplied by virtue of the drilling process may lead to a destabilization of the hydrates surrounding the wellbore. Therefore, as the number of oil and gas fields being development in deepwater and onshore arctic environments increases, greater emphasis should be placed on quantifying the risks, gas hydrates pose to drilling operations. The qualification of these risks requires a comprehensive understanding of gas hydrate-formation and dissociation as a result of drilling induced processes. To develop the required understanding of gas hydrat formation and dissociation, the authors conducted laboratory experiments by using a micro-drilling system, to study the dissociation rates of methane hydrates contained in a tank reactor. The test facility used is a development of China University of Geosciences. The rates of methane hydrate formation and dissociation in the tank reactor were measured at steady-state conditions at pressures ranging from 0.1 to 25 MPa and temperatures ranging from -5 to 20 C. The experimental results show that the rate of hydrate formation is strongly influenced by the fluid system used to form the hydrates, pressure and temperature, with the influence of the temperature on methane hydrate dissociation being stronger than that of the pressure. Drilling speed, drilling fluids and hydrate dissociation inhibitors were also shown to influence hydrate dissociation rate. The derived results have been used to predict hydrate drilling stability for several drilling fluid systems.

  12. Marine Gas Hydrates - An Untapped Non-conventional Energy ...

    Indian Academy of Sciences (India)

    Table of contents. Marine Gas Hydrates - An Untapped Non-conventional Energy Resource · Slide 2 · Slide 3 · Slide 4 · Gas Hydrate Stability Zone · Slide 6 · Slide 7 · Exploration of gas hydrates (seismic) · Characteristics of BSR · Slide 10 · Slide 11 · Slide 12 · Slide 13 · Slide 14 · Slide 15 · Distribution of Gas Hydrates in KG ...

  13. Hydrate bearing clayey sediments: Formation and gas production concepts

    KAUST Repository

    Jang, Jaewon; Santamarina, Carlos

    2016-01-01

    Hydro-thermo-chemo and mechanically coupled processes determine hydrate morphology and control gas production from hydrate-bearing sediments. Force balance, together with mass and energy conservation analyses anchored in published data provide robust asymptotic solutions that reflect governing processes in hydrate systems. Results demonstrate that hydrate segregation in clayey sediments results in a two-material system whereby hydrate lenses are surrounded by hydrate-free water-saturated clay. Hydrate saturation can reach ≈2% by concentrating the excess dissolved gas in the pore water and ≈20% from metabolizable carbon. Higher hydrate saturations are often found in natural sediments and imply methane transport by advection or diffusion processes. Hydrate dissociation is a strongly endothermic event; the available latent heat in a reservoir can sustain significant hydrate dissociation without triggering ice formation during depressurization. The volume of hydrate expands 2-to-4 times upon dissociation or CO2single bondCH4 replacement. Volume expansion can be controlled to maintain lenses open and to create new open mode discontinuities that favor gas recovery. Pore size is the most critical sediment parameter for hydrate formation and gas recovery and is controlled by the smallest grains in a sediment. Therefore any characterization must carefully consider the amount of fines and their associated mineralogy.

  14. Standardization and software infrastructure for gas hydrate data communications

    Energy Technology Data Exchange (ETDEWEB)

    Kroenlein, K.; Chirico, R.D.; Kazakov, A.; Frenkel, M. [National Inst. of Standards and Technology, Boulder, CO (United States). Physical and Chemical Properties Div.; Lowner, R. [GeoForschungsZentrum Potsdam (Germany); Wang, W. [Chinese Academy of Science, Beijing (China). Computer Network Information Center; Smith, T. [MIT Systems, Flushing, NY (United States); Sloan, E.D. [Colorado School of Mines, Golden, CO (United States). Centre for Hydrate Research

    2008-07-01

    The perceived value of gas hydrates as an energy resource for the future has led to extensive hydrate research studies and experiments. The hydrate deposits are widely dispersed throughout the world, and many countries are now investigating methods of extracting gas hydrate resources. This paper described a gas hydrates markup language (GHML) developed as an international standard for data transfer and storage within the gas hydrates community. The language is related to a hydrates database developed to facilitate a greater understanding of naturally occurring hydrate interactions with geophysical processes, and aid in the development of hydrate technologies for resource recovery and storage. Recent updates to the GHML included the addition of ThermoML, a communication standard for thermodynamic data into the GHML schema. The standard will be used to represent all gas hydrates thermodynamic data. A new element for the description of crystal structures has also been developed, as well as a guided data capture tool. The tool is available free of charge and is publicly licensed for use by gas hydrate data producers. A web service has also been provided to ensure that access to GHML files for gas hydrates and data files are available for users. It was concluded that the tool will help to ensure data quality assurance for the conversion of data and meta-data within the database. 28 refs., 9 figs.

  15. Small angle X-ray scattering from hydrating tricalcium silicate

    International Nuclear Information System (INIS)

    Vollet, D.

    1983-01-01

    The small-angle X-ray scattering technique was used to study the structural evolution of hydrated tricalcium silicate at room temperature. The changes in specific area of the associated porosity and the evolution of density fluctuations in the solid hydrated phase were deduced from the scattering data. A correlation of these variations with the hydration mechanism is tried. (Author) [pt

  16. Hydrate bearing clayey sediments: Formation and gas production concepts

    KAUST Repository

    Jang, Jaewon

    2016-06-20

    Hydro-thermo-chemo and mechanically coupled processes determine hydrate morphology and control gas production from hydrate-bearing sediments. Force balance, together with mass and energy conservation analyses anchored in published data provide robust asymptotic solutions that reflect governing processes in hydrate systems. Results demonstrate that hydrate segregation in clayey sediments results in a two-material system whereby hydrate lenses are surrounded by hydrate-free water-saturated clay. Hydrate saturation can reach ≈2% by concentrating the excess dissolved gas in the pore water and ≈20% from metabolizable carbon. Higher hydrate saturations are often found in natural sediments and imply methane transport by advection or diffusion processes. Hydrate dissociation is a strongly endothermic event; the available latent heat in a reservoir can sustain significant hydrate dissociation without triggering ice formation during depressurization. The volume of hydrate expands 2-to-4 times upon dissociation or CO2single bondCH4 replacement. Volume expansion can be controlled to maintain lenses open and to create new open mode discontinuities that favor gas recovery. Pore size is the most critical sediment parameter for hydrate formation and gas recovery and is controlled by the smallest grains in a sediment. Therefore any characterization must carefully consider the amount of fines and their associated mineralogy.

  17. Obsidian Hydration Dating in the Undergraduate Curriculum.

    Science.gov (United States)

    Manche, Emanuel P.; Lakatos, Stephen

    1986-01-01

    Provides an overview of obsidian hydration dating for the instructor by presenting: (1) principles of the method; (2) procedures; (3) applications; and (4) limitations. The theory of the method and one or more laboratory exercises can be easily introduced into the undergraduate geology curriculum. (JN)

  18. Gas hydrate resource quantification in Uruguay

    International Nuclear Information System (INIS)

    Tomasini, J.; De Santa Ana, H.; Veroslavsky, G.

    2012-01-01

    The gas hydrates are crystalline solids formed by natural gas (mostly methane) and water, which are stable in thermobaric conditions given under high pressures and low temperatures. These conditions are given in permafrost zones and continental margin basins offshore in the nature

  19. Pentagonal dodecahedron methane hydrate cage and methanol ...

    Indian Academy of Sciences (India)

    methane hydrate in sea bed near continental margin and underneath of permafrost ... clathrate structure,6,7 IR spectroscopy analysis of vibra- tional form of guest .... Hydrogen (H71) of the hydroxyl group of methanol is found to have formed ...

  20. A new approach to model mixed hydrates

    Czech Academy of Sciences Publication Activity Database

    Hielscher, S.; Vinš, Václav; Jäger, A.; Hrubý, Jan; Breitkopf, C.; Span, R.

    2018-01-01

    Roč. 459, March (2018), s. 170-185 ISSN 0378-3812 R&D Projects: GA ČR(CZ) GA17-08218S Institutional support: RVO:61388998 Keywords : gas hydrate * mixture * modeling Subject RIV: BJ - Thermodynamics Impact factor: 2.473, year: 2016 https://www.sciencedirect.com/science/article/pii/S0378381217304983

  1. [Terminal phase hydration, pain and delirium

    DEFF Research Database (Denmark)

    Heick, A.

    2009-01-01

    Hydration of the terminal patient may relieve confusion and complaints of "dry mouth". But it may worsen oedema of the brain, lungs, and extremities, worsen terminal rattling and cause a need for frequent changing of diapers. The decision of whether and how to treat a dying patient with fluids...

  2. Hydration dynamics near a model protein surface

    International Nuclear Information System (INIS)

    Russo, Daniela; Hura, Greg; Head-Gordon, Teresa

    2003-01-01

    The evolution of water dynamics from dilute to very high concentration solutions of a prototypical hydrophobic amino acid with its polar backbone, N-acetyl-leucine-methylamide (NALMA), is studied by quasi-elastic neutron scattering and molecular dynamics simulation for both the completely deuterated and completely hydrogenated leucine monomer. We observe several unexpected features in the dynamics of these biological solutions under ambient conditions. The NALMA dynamics shows evidence of de Gennes narrowing, an indication of coherent long timescale structural relaxation dynamics. The translational water dynamics are analyzed in a first approximation with a jump diffusion model. At the highest solute concentrations, the hydration water dynamics is significantly suppressed and characterized by a long residential time and a slow diffusion coefficient. The analysis of the more dilute concentration solutions takes into account the results of the 2.0M solution as a model of the first hydration shell. Subtracting the first hydration layer based on the 2.0M spectra, the translational diffusion dynamics is still suppressed, although the rotational relaxation time and residential time are converged to bulk-water values. Molecular dynamics analysis shows spatially heterogeneous dynamics at high concentration that becomes homogeneous at more dilute concentrations. We discuss the hydration dynamics results of this model protein system in the context of glassy systems, protein function, and protein-protein interfaces

  3. A positron annihilation study of hydrated DNA

    DEFF Research Database (Denmark)

    Warman, J. M.; Eldrup, Morten Mostgaard

    1986-01-01

    Positron annihilation measurements are reported for hydrated DNA as a function of water content and as a function of temperature (20 to -180.degree. C) for samples containing 10 and 50% wt of water. The ortho-positronium mean lifetime and its intensity show distinct variations with the degree...

  4. Gold(III)-Catalyzed Hydration of Phenylacetylene

    Science.gov (United States)

    Leslie, J. Michelle; Tzeel, Benjamin A.

    2016-01-01

    A guided inquiry-based experiment exploring the regioselectivity of the hydration of phenylacetylene is described. The experiment uses an acidic gold(III) catalyst in a benign methanol/water solvent system to introduce students to alkyne chemistry and key principles of green chemistry. The experiment can be easily completed in approximately 2 h,…

  5. [Terminal phase hydration, pain and delirium

    DEFF Research Database (Denmark)

    Heick, A.

    2009-01-01

    Hydration of the terminal patient may relieve confusion and complaints of "dry mouth". But it may worsen oedema of the brain, lungs, and extremities, worsen terminal rattling and cause a need for frequent changing of diapers. The decision of whether and how to treat a dying patient with fluids sh...

  6. Alkali binding in hydrated Portland cement paste

    NARCIS (Netherlands)

    Chen, Wei; Brouwers, Jos

    2010-01-01

    The alkali-binding capacity of C–S–H in hydrated Portland cement pastes is addressed in this study. The amount of bound alkalis in C–S–H is computed based on the alkali partition theories firstly proposed by Taylor (1987) and later further developed by Brouwers and Van Eijk (2003). Experimental data

  7. A review of minodronic acid hydrate for the treatment of osteoporosis

    Directory of Open Access Journals (Sweden)

    Tanishima S

    2013-02-01

    Full Text Available Shinji Tanishima, Yasuo MorioDepartment of Orthopedic Surgery, Misasa Onsen Hospital, Misasa, Tottori, JapanAbstract: Minodronic acid hydrate was the first bisphosphonate developed and approved for osteoporosis treatment in Japan. With regard to inhibition of bone resorption, minodronic acid hydrate is 1000 times more effective than etidronic acid and 10–100 times more effective than alendronic acid. Clinical trials conducted to date have focused on postmenopausal female patients suffering from primary osteoporosis. In these trials, 1 mg of oral minodronic acid hydrate was administrated once daily, and a significant increase was observed in lumbar-spine and hip-joint bone density 1–2 years after administration. All markers of bone metabolism urinary collagen type 1 cross-linked N-telopeptide, urinary free deoxypyridinoline, serum bone alkaline phosphatase, and serum osteocalcin were decreased. The incidence rate of new vertebral and nonvertebral fractures was also decreased. Therefore, effectiveness in fracture prevention was confirmed. A form of minodronic acid (50 mg requiring once-monthly administration has been developed and is currently being used clinically. A comparative study between this new formulation and once-daily minodronic acid (1 mg showed no significant differences between the two formulations in terms of improvement rates in lumbar-spine and hip-joint bone density, changes in bone metabolism markers, or incidence of side effects. This indicates the noninferiority of the monthly formulation. Side effects such as osteonecrosis of the jaw or atypical femoral fractures were not reported with other bisphosphonates, although it is believed that these side effects may emerge as future studies continue to be conducted. On the basis of studies conducted to date, minodronic acid hydrate is considered effective for improving bone density and preventing fractures. We anticipate further investigations in the future

  8. Clathrate Hydrates for Thermal Energy Storage in Buildings: Overview of Proper Hydrate-Forming Compounds

    Directory of Open Access Journals (Sweden)

    Beatrice Castellani

    2014-09-01

    Full Text Available Increasing energy costs are at the origin of the great progress in the field of phase change materials (PCMs. The present work aims at studying the application of clathrate hydrates as PCMs in buildings. Clathrate hydrates are crystalline structures in which guest molecules are enclosed in the crystal lattice of water molecules. Clathrate hydrates can form also at ambient pressure and present a high latent heat, and for this reason, they are good candidates for being used as PCMs. The parameter that makes a PCM suitable to be used in buildings is, first of all, a melting temperature at about 25 °C. The paper provides an overview of groups of clathrate hydrates, whose physical and chemical characteristics could meet the requirements needed for their application in buildings. Simulations with a dynamic building simulation tool are carried out to evaluate the performance of clathrate hydrates in enhancing thermal comfort through the moderation of summer temperature swings and, therefore, in reducing energy consumption. Simulations suggest that clathrate hydrates have a potential in terms of improvement of indoor thermal comfort and a reduction of energy consumption for cooling. Cooling effects of 0.5 °C and reduced overheating hours of up to 1.1% are predicted.

  9. Enthalpy of dissociation and hydration number of methane hydrate from the Clapeyron equation

    International Nuclear Information System (INIS)

    Anderson, Graydon K.

    2004-01-01

    The enthalpies of the reactions in which methane hydrate is dissociated to methane vapor and either (1) water, or (2) ice are determined by a new analysis using the Clapeyron equation. The difference in enthalpies of the two reactions is used to infer the hydration number at the quadruple point where hydrate, ice, liquid water, and methane vapor coexist. By appropriate corrections, the hydration number at points removed from the quadruple point is also determined. The most important feature of the new analysis is the direct use of the Clapeyron equation. The method avoids the use of certain simplifying assumptions that have compromised the accuracy of previous analyses in which the Clausius-Clapeyron equation was used. The analysis takes into account the finite volumes of all phases, the non-ideality of the vapor phase, and the solubility of methane in water. The results show that the enthalpy of dissociation and hydration number are constant within experimental error over the entire (hydrate, liquid, vapor) coexistence region. The results are more accurate than but entirely consistent with almost all previous studies

  10. Direct measurement of methane hydrate composition along the hydrate equilibrium boundary

    Science.gov (United States)

    Circone, S.; Kirby, S.H.; Stern, L.A.

    2005-01-01

    The composition of methane hydrate, namely nW for CH 4??nWH2O, was directly measured along the hydrate equilibrium boundary under conditions of excess methane gas. Pressure and temperature conditions ranged from 1.9 to 9.7 MPa and 263 to 285 K. Within experimental error, there is no change in hydrate composition with increasing pressure along the equilibrium boundary, but nW may show a slight systematic decrease away from this boundary. A hydrate stoichiometry of n W = 5.81-6.10 H2O describes the entire range of measured values, with an average composition of CH4??5.99(??0.07) H2O along the equilibrium boundary. These results, consistent with previously measured values, are discussed with respect to the widely ranging values obtained by thermodynamic analysis. The relatively constant composition of methane hydrate over the geologically relevant pressure and temperature range investigated suggests that in situ methane hydrate compositions may be estimated with some confidence. ?? 2005 American Chemical Society.

  11. MORPHOLOGY OF METHANE HYDRATE HOST SEDIMENTS

    International Nuclear Information System (INIS)

    JONES, K.W.; FENG, H.; TOMOV, S.; WINTER, W.J.; EATON, M.; MAHAJAN, D.

    2004-01-01

    Results from simulated experiments in several laboratories show that host sediments influence hydrate formation in accord with known heterogeneity of host sediments at sites of gas hydrate occurrence (1). For example, in Mackenzie Delta, NWT Canada (Mallik 2L-38 well), coarser-grained units (pore-filling model) are found whereas in the Gulf of Mexico, the found hydrate samples do not appear to be lithologically controlled. We have initiated a systematic study of sediments, initially focusing on samples from various depths at a specific site, to establish a correlation with hydrate occurrence (or variations thereof) to establish differences in their microstructure, porosity, and other associated properties. The synchrotron computed microtomography (CMT) set-up at the X-27A tomography beam line at the National Synchrotron Light Source (NSLS), Brookhaven National Laboratory was used as a tool to study sediments from Blake Ridge at three sub bottom depths of 0.2, 50, and 667 meters. Results from the tomographic analysis of the deepest sample (667 m) are presented here to illustrate how tomography can be used to obtain new insights into the structures of methane hydrate host sediments. The investigation shows the internal grain/pore space resolution in the microstructure and a 3-D visualization of the connecting pathways obtained following data segmentation into pore space and grains within the sediment sample. The analysis gives the sample porosity, specific surface area, mean particle size, and tortuosity, as well. An earlier report on the experimental program has been given by Mahajan et al. (2)

  12. Infrared spectroscopic measurement of skin hydration and sebum levels and comparison to corneometer and sebumeter

    OpenAIRE

    Ezerskaia, A.; Pereira, S.F.; Urbach, Paul; Varghese, Babu; Popp, Jürgen; Tuchin, Valery V.; Matthews, Dennis L.; Pavone, Francesco S.

    2016-01-01

    Skin health characterized by a system of water and lipids in Stratum Corneum provide protection from harmful external elements and prevent trans-epidermal water loss. Skin hydration (moisture) and sebum (skin surface lipids) are considered to be important factors in skin health; a right balance between these components is an indication of skin health and plays a central role in protecting and preserving skin integrity. In this manuscript we present an infrared spectroscopic method for simulta...

  13. Inter-and intra-individual differences in skin hydration and surface lipids measured with mid-infrared spectroscopy

    NARCIS (Netherlands)

    Ezerskaia, A.; Pereira, S.F.; Urbach, Paul; Varghese, Babu; Coté, Gerard L.

    2016-01-01

    Skin health is characterized by heterogeneous system of water and lipids in upper layers providing protection from external environment and preventing loss of vital components of the body. Skin hydration (moisture) and sebum (skin surface lipids) are considered to be important factors in skin

  14. The structure of hydrate bearing fine grained marine sediments

    Energy Technology Data Exchange (ETDEWEB)

    Priest, J.; Kingston, E.; Clayton, C. [Southampton Univ., Highfield (United Kingdom). School of Civil Engineering and the Environment; Schultheiss, P.; Druce, M. [Geotek Ltd., Daventry (United Kingdom)

    2008-07-01

    This paper discussed the structure of naturally occurring methane gas hydrates in fine-grained sediments from core samples recovered using in situ pressures from the eastern margin of the Indian Ocean. High resolution X-ray computed tomography (CT) images were taken of gas hydrate cores. The hydrate structure was examined and comparisons were made between low resolution X-ray images obtained on the cores prior to sub-sectioning and depressurization procedures. The X-ray images showed the presence of high-angle, sub-parallel veins within the recovered sediments. The scans indicated that the hydrates occurred as fracture filing veins throughout the core. Fracture orientation was predominantly sub-vertical. Thick millimetric hydrate veins were composed of sub-millimetric veins with variations in fracture angle. The analysis indicated that hydrate formation was episodic in nature and subject to changes in the stress regime. Results of the study showed that depressurization and subsequent freezing alter the structure of the sediment even when the gas hydrate has not been altered. A large proportion of the hydrate survived when outside of its stability region. The self-preserving behaviour of the hydrate was attributed to the endothermic nature of gas hydrate dissociation. It was concluded that the accurate physical characterization of gas hydrates can only be conducted when the core section remains under in situ stress conditions. 13 refs., 9 figs.

  15. Carbon dioxide hydrate formation in a fixed-bed reactor

    Energy Technology Data Exchange (ETDEWEB)

    Fan, S.; Lang, X. [South China Univ. of Technology, Guangzhou (China). Key Laboratory of Enhanced Heat Transfer and Energy Conservation; Wang, Y.; Liang, D. [Chinese Academy of Sciences, Guangzhou (China). Guangzhou Inst. of Energy Conversion and Guangzhou Center of Natural Gas Hydrate; Sun, X.; Jurcik, B. [Air Liquide Laboratories, Tsukuba (Japan)

    2008-07-01

    Gas hydrates are thermodynamically stable at high pressures and near the freezing temperature of pure water. Methane hydrates occur naturally in sediments in the deep oceans and permafrost regions and constitute an extensive hydrocarbon reservoir. Carbon dioxide (CO{sub 2}) hydrates are of interest as a medium for marine sequestration of anthropogenic carbon dioxide. Sequestering CO{sub 2} as hydrate has potential advantages over most methods proposed for marine CO{sub 2} sequestration. Because this technique requires a shallower depth of injection when compared with other ocean sequestration methods, the costs of CO{sub 2} hydrate sequestration may be lower. Many studies have successfully used different continuous reactor designs to produce CO{sub 2} hydrates in both laboratory and field settings. This paper discussed a study that involved the design and construction of a fixed-bed reactor for simulation of hydrate formation system. Water, river sands and carbon dioxide were used to simulate the seep kind of hydrate formation. Carbon dioxide gas was distributed as small bubbles to enter from the bottom of the fixed-bed reactor. The paper discussed the experimental data and presented a diagram of the gas hydrate reactor system. The morphology as well as the reaction characters of CO{sub 2} hydrate was presented in detail. The results were discussed in terms of experimental phenomena and hydrate formation rate. A mathematical model was proposed for describing the process. 17 refs., 7 figs.

  16. Indian National Gas Hydrate Program Expedition 01 report

    Science.gov (United States)

    Collett, Timothy S.; Riedel, M.; Boswell, R.; Presley, J.; Kumar, P.; Sathe, A.; Sethi, A.; Lall, M.V.; ,

    2015-01-01

    Gas hydrate is a naturally occurring “ice-like” combination of natural gas and water that has the potential to serve as an immense resource of natural gas from the world’s oceans and polar regions. However, gas-hydrate recovery is both a scientific and a technical challenge and much remains to be learned about the geologic, engineering, and economic factors controlling the ultimate energy resource potential of gas hydrate. The amount of natural gas contained in the world’s gas-hydrate accumulations is enormous, but these estimates are speculative and range over three orders of magnitude from about 2,800 to 8,000,000 trillion cubic meters of gas. By comparison, conventional natural gas accumulations (reserves and undiscovered, technically recoverable resources) for the world are estimated at approximately 440 trillion cubic meters. Gas recovery from gas hydrate is hindered because the gas is in a solid form and because gas hydrate commonly occurs in remote Arctic and deep marine environments. Proposed methods of gas recovery from gas hydrate generally deal with disassociating or “melting” in situ gas hydrate by heating the reservoir beyond the temperature of gas-hydrate formation, or decreasing the reservoir pressure below hydrate equilibrium. The pace of energy-related gas hydrate assessment projects has accelerated over the past several years.

  17. Origins of hydration differences in homochiral and racemic crystals of aspartic acid.

    Science.gov (United States)

    Juliano, Thomas R; Korter, Timothy M

    2015-02-26

    The propensity for crystalline hydrates of organic molecules to form is related to the strength of the interactions between molecules, including the chiral composition of the molecular solids. Specifically, homochiral versus racemic crystalline samples can exhibit distinct differences in their ability to form energetically stable hydrates. The focus of the current study is a comparison of the crystal structures and intermolecular forces found in solid-state L-aspartic acid, DL-aspartic acid, and L-aspartic acid monohydrate. The absence of experimental evidence for the DL-aspartic acid monohydrate is considered here in terms of the enhanced thermodynamic stability of the DL-aspartic acid anhydrate crystal as compared to the L-aspartic acid anhydrate as revealed through solid-state density functional theory calculations and terahertz spectroscopic measurements. The results indicate that anhydrous DL-aspartic acid is the more stable solid, not due to intermolecular forces alone but also due to the improved conformations of the molecules within the racemic solid. Hemihydrated and monohydrated forms of DL-aspartic acid have been computationally evaluated, and in each case, the hydrates produce destabilized aspartic acid conformations that prevent DL-aspartic acid hydrate formation from occurring.

  18. Natural gas hydrates. Experimental techniques and their applications

    Energy Technology Data Exchange (ETDEWEB)

    Ye, Yuguang; Liu, Changling (eds.) [Qingdao Institute of Marine Geology (China). Gas Hydrate Laboratory

    2013-07-01

    Focuses on gas hydrate experiment in laboratory. Intends to provide practical significant parameters for gas hydrate exploration and exploitation in the oceanic and permafrost environments. Consists of different themes that present up-to-date information on hydrate experiments. ''Natural Gas Hydrates: Experimental Techniques and Their Applications'' attempts to broadly integrate the most recent knowledge in the fields of hydrate experimental techniques in the laboratory. The book examines various experimental techniques in order to provide useful parameters for gas hydrate exploration and exploitation. It provides experimental techniques for gas hydrates, including the detection techniques, the thermo-physical properties, permeability and mechanical properties, geochemical abnormalities, stability and dissociation kinetics, exploitation conditions, as well as modern measurement technologies etc.

  19. Terahertz Time Domain Spectroscopy for Structure-II Gas Hydrates

    DEFF Research Database (Denmark)

    Takeya, Kei; Zhang, Caihong; Kawayama, Iwao

    2009-01-01

    For the nondestructive inspection of gas hydrates, terahertz (THz) time-domain spectroscopy (TDS) was applied to tetrahydrofuran (THF) hydrate and propane hydrate. The absorption of propane hydrate monotonically increases with frequency, similar to the case of ice, while THF hydrate has...... a characteristic broad absorption peak at 0.5 THz corresponding to the dipole moment of THF molecules. The refractive indices of THF and propane hydrates are 1.725 and 1.775 at 1 THz, respectively, and show a slight but clear difference from the refractive index of ice (1.79). THz-TDS is a potentially useful...... technique for the ondestructive inspection of gas hydrates. # 2009 The Japan Society of Applied Physics...

  20. Comparative Assessment of Advanced Gay Hydrate Production Methods

    Energy Technology Data Exchange (ETDEWEB)

    M. D. White; B. P. McGrail; S. K. Wurstner

    2009-06-30

    Displacing natural gas and petroleum with carbon dioxide is a proven technology for producing conventional geologic hydrocarbon reservoirs, and producing additional yields from abandoned or partially produced petroleum reservoirs. Extending this concept to natural gas hydrate production offers the potential to enhance gas hydrate recovery with concomitant permanent geologic sequestration. Numerical simulation was used to assess a suite of carbon dioxide injection techniques for producing gas hydrates from a variety of geologic deposit types. Secondary hydrate formation was found to inhibit contact of the injected CO{sub 2} regardless of injectate phase state, thus diminishing the exchange rate due to pore clogging and hydrate zone bypass of the injected fluids. Additional work is needed to develop methods of artificially introducing high-permeability pathways in gas hydrate zones if injection of CO{sub 2} in either gas, liquid, or micro-emulsion form is to be more effective in enhancing gas hydrate production rates.

  1. Characterization of un-hydrated and hydrated BioAggregate™ and MTA Angelus™.

    Science.gov (United States)

    Camilleri, J; Sorrentino, F; Damidot, D

    2015-04-01

    BioAggregate™ is a novel material introduced for use as a root-end filling material. It is tricalcium silicate-based, free of aluminium and uses tantalum oxide as radiopacifier. BioAggregate contains additives to enhance the material performance. The purpose of this research was to characterize the un-hydrated and hydrated forms of BioAggregate using a combination of techniques, verify whether the additives if present affect the properties of the set material and compare these properties to those of MTA Angelus™. Un-hydrated and hydrated BioAggregate and MTA Angelus were assessed. Un-hydrated cement was tested for chemical composition, specific surface area, mineralogy and kinetics of hydration. The set material was investigated for mineralogy, microstructure and bioactivity. Scanning electron microscopy, X-ray energy dispersive spectroscopic analysis, X-ray fluorescence spectroscopy, X-ray diffraction and isothermal calorimetry were employed. The specific surface area was investigated using a gas adsorption method with nitrogen as the probe. BioAggregate was composed of tricalcium silicate, tantalum oxide, calcium phosphate and silicon dioxide and was free of aluminium. On hydration, the tricalcium silicate produced calcium silicate hydrate and calcium hydroxide. The former was deposited around the cement grains, while the latter reacted with the silicon dioxide to form additional calcium silicate hydrate. This resulted in reduction of calcium hydroxide in the aged cement. MTA Angelus reacted in a similar fashion; however, since it contained no additives, the calcium hydroxide was still present in the aged cement. Bioactivity was demonstrated by deposition of hydroxyapatite. BioAggregate exhibited a high specific surface area. Nevertheless, the reactivity determined by isothermal calorimetry appeared to be slow compared to MTA Angelus. The tantalum oxide as opposed to bismuth oxide was inert, and tantalum was not leached in solution. BioAggregate exhibited

  2. In-situ gas hydrate hydrate saturation estimated from various well logs at the Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope

    Science.gov (United States)

    Lee, M.W.; Collett, T.S.

    2011-01-01

    In 2006, the U.S. Geological Survey (USGS) completed detailed analysis and interpretation of available 2-D and 3-D seismic data and proposed a viable method for identifying sub-permafrost gas hydrate prospects within the gas hydrate stability zone in the Milne Point area of northern Alaska. To validate the predictions of the USGS and to acquire critical reservoir data needed to develop a long-term production testing program, a well was drilled at the Mount Elbert prospect in February, 2007. Numerous well log data and cores were acquired to estimate in-situ gas hydrate saturations and reservoir properties.Gas hydrate saturations were estimated from various well logs such as nuclear magnetic resonance (NMR), P- and S-wave velocity, and electrical resistivity logs along with pore-water salinity. Gas hydrate saturations from the NMR log agree well with those estimated from P- and S-wave velocity data. Because of the low salinity of the connate water and the low formation temperature, the resistivity of connate water is comparable to that of shale. Therefore, the effect of clay should be accounted for to accurately estimate gas hydrate saturations from the resistivity data. Two highly gas hydrate-saturated intervals are identified - an upper ???43 ft zone with an average gas hydrate saturation of 54% and a lower ???53 ft zone with an average gas hydrate saturation of 50%; both zones reach a maximum of about 75% saturation. ?? 2009.

  3. LABORATORY STRATEGIES FOR HYDRATE FORMATION IN FINE-GRAINED SEDIMENTS

    KAUST Repository

    Lei, L.; Santamarina, Carlos

    2018-01-01

    Fine‐grained sediments limit hydrate nucleation, shift the phase boundary and hinder gas supply. Laboratory experiments in this study explore different strategies to overcome these challenges, including the use of a more soluble guest molecule rather than methane, grain‐scale gas‐storage within porous diatoms, ice‐to‐hydrate transformation to grow lenses at predefined locations, forced gas injection into water saturated sediments, and long‐term guest molecule transport. Tomographic images, thermal and pressure data provide rich information on hydrate formation and morphology. Results show that hydrate formation is inherently displacive in fine‐grained sediments; lenses are thicker and closer to each other in compressible, high specific surface area sediments subjected to low effective stress. Temperature and pressure trajectories follow a shifted phase boundary that is consistent with capillary effects. Exo‐pore growth results in freshly formed hydrate with a striped and porous structure; this open structure becomes an effective pathway for gas transport to the growing hydrate front. Ice‐to‐hydrate transformation goes through a liquid stage at pre‐melt temperatures; then, capillarity and cryogenic suction compete, and some water becomes imbibed into the sediment faster than hydrate reformation. The geometry of hydrate lenses and the internal hydrate structure continue evolving long after the exothermal response to hydrate formation has completely decayed. Multiple time‐dependent processes occur during hydrate formation, including gas, water and heat transport, sediment compressibility, reaction rate and the stochastic nucleation process. Hydrate formation strategies conceived for this study highlight the inherent difficulties in emulating hydrate formation in fine‐grained sediments within the relatively short time‐scale available for laboratory experiments.

  4. Modeling dissociation behaviour of methane hydrate in porous soil media

    Energy Technology Data Exchange (ETDEWEB)

    Jayasinghe, A.G.; Grozic, J.L.H. [Calgary Univ., AB (Canada). Dept. of Civil Engineering

    2008-07-01

    Gas hydrates, or clathrates, exist in the form of crystalline solid structures of hydrogen bonded water molecules where the lattice cages are occupied by guest gas molecules. Methane gas hydrates are the most common. As such, hydrate bearing sediments are considered to be a potential future energy resource. Gas hydrates also function as a source or sink for atmospheric methane, which may influence global warming. The authors emphasized that an understanding of the behaviour of soils containing gas hydrates is necessary in order to develop ways of recovering the vast gas resources that exist in the form of hydrates, particularly since hydrates are also suspected to be a potential factor in the initiation and propagation of submarine slope failures. Gas hydrate dissociation occurs when water and gas are released, resulting in an increase in pore fluid pressure, thereby causing significant reductions in effective stress leading to sediment failure. Dissociation may occur as a result of pressure reductions or increases in temperature. This study focused on the strength and deformation behaviour of hydrate bearing soils associated with temperature induced dissociation. Modeling the dissociation behavior of hydrates in porous soil media involves an understanding of the geomechanics of hydrate dissociation. This paper addressed the issue of coupling the hydrate dissociation problem with the soil deformation problem. A mathematical framework was constructed in which the thermally stimulated hydrate dissociation process in porous soil media under undrained conditions was considered with conduction heat transfer. It was concluded that a knowledge of geomechanical response of hydrate bearing sediments will enable better estimates of benefits and risks associated with the recovery process, thereby ensuring safe and economical exploration. 20 refs., 1 fig., 1 appendix.

  5. LABORATORY STRATEGIES FOR HYDRATE FORMATION IN FINE-GRAINED SEDIMENTS

    KAUST Repository

    Lei, L.

    2018-04-02

    Fine‐grained sediments limit hydrate nucleation, shift the phase boundary and hinder gas supply. Laboratory experiments in this study explore different strategies to overcome these challenges, including the use of a more soluble guest molecule rather than methane, grain‐scale gas‐storage within porous diatoms, ice‐to‐hydrate transformation to grow lenses at predefined locations, forced gas injection into water saturated sediments, and long‐term guest molecule transport. Tomographic images, thermal and pressure data provide rich information on hydrate formation and morphology. Results show that hydrate formation is inherently displacive in fine‐grained sediments; lenses are thicker and closer to each other in compressible, high specific surface area sediments subjected to low effective stress. Temperature and pressure trajectories follow a shifted phase boundary that is consistent with capillary effects. Exo‐pore growth results in freshly formed hydrate with a striped and porous structure; this open structure becomes an effective pathway for gas transport to the growing hydrate front. Ice‐to‐hydrate transformation goes through a liquid stage at pre‐melt temperatures; then, capillarity and cryogenic suction compete, and some water becomes imbibed into the sediment faster than hydrate reformation. The geometry of hydrate lenses and the internal hydrate structure continue evolving long after the exothermal response to hydrate formation has completely decayed. Multiple time‐dependent processes occur during hydrate formation, including gas, water and heat transport, sediment compressibility, reaction rate and the stochastic nucleation process. Hydrate formation strategies conceived for this study highlight the inherent difficulties in emulating hydrate formation in fine‐grained sediments within the relatively short time‐scale available for laboratory experiments.

  6. FY1995 molecular control technology for mining of methane-gas-hydrate; 1995 nendo methane hydrate no bunshi seigyo mining

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-03-01

    The objectives of the investigation are as follows: 1) developing a method to control formation/dissociation of methane-gas-hydrate, 2) developing a technology to displace methane gas by CO{sub 2} in methane-gas-hydrate deposit, 3) developing a technology to produce methane gas from the deposit efficiently. The final purpose of the project is to create new mining industry that solves both the problems of energy and global environment. 1) Clustering of water molecules is found to play the key role in the methane gas hydrate formation. 2) Equilibrium properties and kinetics of gas hydrates formation and dissociation in bulk-scale gas-hydrate are clarified in the practical environmental conditions. 3) Particle size of hydrate deposit influences the formation and dissociation of bulk-scale gas-hydrate crystal. 4) Mass transfer between gas and liquid phase in turbulent bubbly flow is a function of bubble diameter. The mass transfer depends on interfacial dynamics. (NEDO)

  7. Geologic implications of gas hydrates in the offshore of India: results of the National Gas Hydrate Program Expedition 01

    Science.gov (United States)

    Collett, Timothy S.; Boswell, Ray; Cochran, J.R.; Kumar, Pushpendra; Lall, Malcolm; Mazumdar, Aninda; Ramana, Mangipudi Venkata; Ramprasad, Tammisetti; Riedel, Michael; Sain, Kalachand; Sathe, Arun Vasant; Vishwanath, Krishna

    2014-01-01

    The Indian National Gas Hydrate Program Expedition 01 (NGHP-01) is designed to study the occurrence of gas hydrate along the passive continental margin of the Indian Peninsula and in the Andaman convergent margin, with special emphasis on understanding the geologic and geochemical controls on the occurrence of gas hydrate in these two diverse settings. The NGHP-01 expedition established the presence of gas hydrates in the Krishna-Godavari and Mahanadi Basins, and the Andaman Sea. The expedition discovered in the Krishna-Godavari Basin one of the thickest gas hydrate accumulations ever documented, in the Andaman Sea one of the thickest and deepest gas hydrate stability zones in the world, and established the existence of a fully developed gas hydrate petroleum system in all three basins.

  8. Prevention of cisplatin nephrotoxicity

    Directory of Open Access Journals (Sweden)

    Hayati Fatemeh

    2016-01-01

    Full Text Available Cisplatin has a well-established role in the treatment of broad spectrum of malignancies; however its use is limited because of cisplatin-induced nephrotoxicity (CIN which can be progressive in more than 50% of cases. The most important risk factors for CIN include higher doses of cisplatin, previous cisplatin chemotherapy, underlying kidney damage and concurrent treatment with other potential nephrotoxin agents, such as aminoglycosides, nonsteroidal anti-inflammatory agents, or iodinated contrast media. Different strategies have been offered to diminish or prevent nephrotoxicity of cisplatin. The standard approach for prevention of CIN is the administration of lower doses of cisplatin in combination with full intravenous hydration prior and after cisplatin administration. Cisplatin-induced oxidative stress in the kidney may be prevented by natural antioxidant compounds. The results of this review show that many strategies for prevention of CIN exist, however, attention to the administration of these agent for CIN is necessary.

  9. Spatial resolution of gas hydrate and permeability changes from ERT data in LARS simulating the Mallik gas hydrate production test

    Science.gov (United States)

    Priegnitz, Mike; Thaler, Jan; Spangenberg, Erik; Schicks, Judith M.; Abendroth, Sven

    2014-05-01

    The German gas hydrate project SUGAR studies innovative methods and approaches to be applied in the production of methane from hydrate-bearing reservoirs. To enable laboratory studies in pilot scale, a large reservoir simulator (LARS) was realized allowing for the formation and dissociation of gas hydrates under simulated in-situ conditions. LARS is equipped with a series of sensors. This includes a cylindrical electrical resistance tomography (ERT) array composed of 25 electrode rings featuring 15 electrodes each. The high-resolution ERT array is used to monitor the spatial distribution of the electrical resistivity during hydrate formation and dissociation experiments over time. As the present phases of poorly conducting sediment, well conducting pore fluid, non-conducting hydrates, and isolating free gas cover a wide range of electrical properties, ERT measurements enable us to monitor the spatial distribution of these phases during the experiments. In order to investigate the hydrate dissociation and the resulting fluid flow, we simulated a hydrate production test in LARS that was based on the Mallik gas hydrate production test (see abstract Heeschen et al., this volume). At first, a hydrate phase was produced from methane saturated saline water. During the two months of gas hydrate production we measured the electrical properties within the sediment sample every four hours. These data were used to establish a routine estimating both the local degrees of hydrate saturation and the resulting local permeabilities in the sediment's pore space from the measured resistivity data. The final gas hydrate saturation filled 89.5% of the total pore space. During hydrate dissociation, ERT data do not allow for a quantitative determination of free gas and remaining gas hydrates since both phases are electrically isolating. However, changes are resolved in the spatial distribution of the conducting liquid and the isolating phase with gas being the only mobile isolating phase

  10. Obsidian hydration dating of volcanic events

    Science.gov (United States)

    Friedman, I.; Obradovich, J.

    1981-01-01

    Obsidian hydration dating of volcanic events had been compared with ages of the same events determined by the 14C and KAr methods at several localities. The localities, ranging in age from 1200 to over 1 million yr, include Newberry Craters, Oregon; Coso Hot Springs, California; Salton Sea, California; Yellowstone National Park, Wyoming; and Mineral Range, Utah. In most cases the agreement is quite good. A number of factors including volcanic glass composition and exposuretemperature history must be known in order to relate hydration thickness to age. The effect of composition can be determined from chemical analysis or the refractive index of the glass. Exposure-temperature history requires a number of considerations enumerated in this paper. ?? 1981.

  11. Experimental techniques for cement hydration studies

    Directory of Open Access Journals (Sweden)

    Andreas Luttge

    2011-10-01

    Full Text Available Cement hydration kinetics is a complex problem of dissolution, nucleation and growth that is still not well understood, particularly in a quantitative way. While cement systems are unique in certain aspects they are also comparable to natural mineral systems. Therefore, geochemistry and particularly the study of mineral dissolution and growth may be able to provide insight and methods that can be utilized in cement hydration research. Here, we review mainly what is not known or what is currently used and applied in a problematic way. Examples are the typical Avrami approach, the application of Transition State Theory (TST to overall reaction kinetics and the problem of reactive surface area. Finally, we suggest an integrated approach that combines vertical scanning interferometry (VSI with other sophisticated analytical techniques such as atomic force microscopy (AFM and theoretical model calculations based on a stochastic treatment.

  12. Limitation of biocompatibility of hydrated nanocrystalline hydroxyapatite

    Science.gov (United States)

    Minaychev, V. V.; Teleshev, A. T.; Gorshenev, V. N.; Yakovleva, M. A.; Fomichev, V. A.; Pankratov, A. S.; Menshikh, K. A.; Fadeev, R. S.; Fadeeva, I. S.; Senotov, A. S.; Kobyakova, M. I.; Yurasova, Yu B.; Akatov, V. S.

    2018-04-01

    Nanostructured hydroxyapatite (HA) in the form of hydrated paste is considered to be a promising material for a minor-invasive surgical curing of bone tissue injure. However questions about adhesion of cells on this material and its biocompatibility still remain. In this study biocompatibility of paste-formed nanosized HA (nano-HA) by in vitro methods is investigated. Nano-HA (particles sized about 20 nm) was synthesized under conditions of mechano-acoustic activation of an aqueous reaction mixture of ammonium hydrophosphate and calcium nitrate. It was ascertained that nanocrystalline paste was not cytotoxic although limitation of adhesion, spreading and growth of the cells on its surface was revealed. The results obtained point on the need of modification of hydrated nano-HA in the aims of increasing its biocompatibility and osteoplastic potential.

  13. Predicting hydration energies for multivalent ions

    DEFF Research Database (Denmark)

    Andersson, Martin Peter; Stipp, Susan Louise Svane

    2014-01-01

    We have predicted the free energy of hydration for 40 monovalent and multivalent cations and anions using density functional theory and the implicit solvent model COnductor like Screening MOdel for Real Solvents (COSMO-RS) at the Becke-Perdew (BP)/Triple zeta valence with polarization functions...... (TZVP) level. Agreement with experimental data for monovalent and divalent ions is good and shows no significant systematic errors. Predictions are noticeably better than with standard COSMO. The agreement with experimental data for trivalent and tetravalent ions is slightly worse and shows systematic...... errors. Our results indicate that quantum chemical calculations combined with COSMO-RS solvent treatment is a reliable method for treating multivalent ions in solution, provided one hydration shell of explicit water molecules is included for metal cations. The accuracy is not high enough to allow...

  14. Advances in understanding hydration of Portland cement

    International Nuclear Information System (INIS)

    Scrivener, Karen L.; Juilland, Patrick; Monteiro, Paulo J.M.

    2015-01-01

    Progress in understanding hydration is summarized. Evidence supports the geochemistry dissolution theory as an explanation for the induction period, in preference to the inhibiting layer theory. The growth of C–S–H is the principal factor controlling the main heat evolution peak. Electron microscopy indicates that C–S–H “needles” grow from the surface of grains. At the peak, the surface is covered, but deceleration cannot be attributed to diffusion control. The shoulder peak comes from renewed reaction of C 3 A after depletion of sulfate in solution, but release of sulfate absorbed on C–S–H means that ettringite continues to form. After several days space becomes the major factor controlling hydration. The use of new analytical technique is improving our knowledge of the action of superplasticizers and leading to the design of molecules for different applications. Atomistic modeling is becoming a topic of increasing interest. Recent publications in this area are reviewed

  15. Phosphate vibrations as reporters of DNA hydration

    Science.gov (United States)

    Corcelli, Steven

    The asymmetric phosphate stretch vibrational frequency is extraordinarily sensitive to its local solvent environment. Using density functional theory calculations on the model compound dimethyl phosphate, the asymmetric phosphate stretch vibrational frequency was found to shift linearly with the magnitude of an electric field along the symmetry axis of the PO2 moiety (i.e. the asymmetric phosphate stretch is an excellent linear vibrational Stark effect probe). With this linear relationship established, asymmetric phosphate stretch vibrational frequencies were computed during the course of a molecular dynamics simulation of fully hydrated DNA. Moreover, contributions to shifts in the frequencies from subpopulations of water molecules (e.g. backbone, minor groove, major groove, etc.) were calculated to reveal how phosphate vibrations report the onset of DNA hydration in experiments that vary the relative humidity of non-condensing (dry) DNA samples.

  16. Advances in understanding hydration of Portland cement

    Energy Technology Data Exchange (ETDEWEB)

    Scrivener, Karen L., E-mail: Karen.scrivener@epfl.ch [Laboratory of Construction Materials, Ecole Polytechnique Fédérale de Lausanne, 1015 (Switzerland); Juilland, Patrick [Sika Technology AG, Zürich (Switzerland); Monteiro, Paulo J.M. [Department of Civil and Environmental Engineering, University of California at Berkeley (United States)

    2015-12-15

    Progress in understanding hydration is summarized. Evidence supports the geochemistry dissolution theory as an explanation for the induction period, in preference to the inhibiting layer theory. The growth of C–S–H is the principal factor controlling the main heat evolution peak. Electron microscopy indicates that C–S–H “needles” grow from the surface of grains. At the peak, the surface is covered, but deceleration cannot be attributed to diffusion control. The shoulder peak comes from renewed reaction of C{sub 3}A after depletion of sulfate in solution, but release of sulfate absorbed on C–S–H means that ettringite continues to form. After several days space becomes the major factor controlling hydration. The use of new analytical technique is improving our knowledge of the action of superplasticizers and leading to the design of molecules for different applications. Atomistic modeling is becoming a topic of increasing interest. Recent publications in this area are reviewed.

  17. Modelling porewater chemistry in hydrated Portland cement

    International Nuclear Information System (INIS)

    Berner, U.R.

    1987-01-01

    Extensive employment of concrete is foreseen in radioactive waste repositories. A prerequisite for modelling the interactions between concrete and formation waters is characterization of the concrete system. Available experimental data from high pressure squeezing of cement pore-water indicate that, besides the high pH due to alkali hydroxide dissolution, cement composition itself influences the solubility determining solid phases. A model which simulates the hydration of Portland cement assuming complete hydration of the main clinker minerals is presented. The model also includes parameters describing the reactions between the cement and blending agents. Comparison with measured pore-water data generally gives a consistent picture and, as expected, the model gives correct predictions for pure Portland cements. For blended cements, the required additional parameters can, to some extent, be derived from pore-water analysis. 14 references, 1 figure, 4 tables

  18. Propane hydrate nucleation: Experimental investigation and correlation

    DEFF Research Database (Denmark)

    Jensen, Lars; Thomsen, Kaj; von Solms, Nicolas

    2008-01-01

    supersaturation region. The experiments showed that the gas dissolution rate rather than the induction time of propane hydrate is influenced by a change in agitation. This was especially valid at high stirring rates when the water surface was severely disturbed.Addition of polyvinylpyrrolidone (PVP......) to the aqueous phase was found to reduce the gas dissolution rate slightly. However the induction times were prolonged quite substantially upon addition of PVP.The induction time data were correlated using a newly developed induction time model based on crystallization theory also capable of taking into account...... the presence of additives. In most cases reasonable agreement between the data and the model could be obtained. The results revealed that especially the effective surface energy between propane hydrate and water is likely to change when the stirring rate varies from very high to low. The prolongation...

  19. Non-invasive measurement of corneal hydration.

    Science.gov (United States)

    March, W F; Bauer, N J

    2001-01-01

    To investigate the feasibility of a confocal Raman spectroscopic technique for the noncontact assessment of corneal hydration in vivo in two legally blind subjects. A laser beam (632.8 nm; 15 mJ) was maintained on the cornea using a microscope objective lens (25x magnification, NA=0.5, f=10 mm) both for focusing the incident light as well as collecting the Raman backscattered light, in a 180 degrees backscatter configuration. An optical fiber, acting as the confocal pinhole for elimination of light from out-of-focus places, was coupled to a spectrometer that dispersed the collected light onto a sensitive array-detector for rapid spectral data acquisition over a range from 2,890 to 3,590 cm(-1). Raman spectra were recorded from the anterior 100 to 150 microm of the cornea over a period of time before and after topical application of a mild dehydrating solution. The ratio between the amplitudes of the signals at 3,400 cm(-1) (OH-vibrational mode of water) and 2,940 cm(-1) (CH-vibrational mode of proteins) was used as a measure of corneal hydration. High signal-to-noise ratio (SNR 25) Raman spectra were obtained from the human corneas using 15 mJ of laser light energy. Qualitative changes in the hydration of the anterior-most part of the corneas could be observed as a result of the dehydrating agent. Confocal Raman spectroscopy could potentially be applied clinically as a noncontact tool for the assessment of corneal hydration in vivo.

  20. Hydration benefits to courtship feeding in crickets

    OpenAIRE

    Ivy, T. M.; Johnson, J. C.; Sakaluk, S. K.

    1999-01-01

    The spermatophore transferred by male decorated crickets (Gryllodes sigillatus) at mating includes a large gelatinous spermatophylax that the female consumes after copulation. Although previous studies have shown that G. sigillatus females gain no nutritional benefits from consuming food gifts, there may be other benefits to their consumption. We examined potential hydration benefits to females by experimentally manipulating both the availability of water and the number of food gifts that fem...

  1. Unraveling halide hydration: A high dilution approach.

    Science.gov (United States)

    Migliorati, Valentina; Sessa, Francesco; Aquilanti, Giuliana; D'Angelo, Paola

    2014-07-28

    The hydration properties of halide aqua ions have been investigated combining classical Molecular Dynamics (MD) with Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy. Three halide-water interaction potentials recently developed [M. M. Reif and P. H. Hünenberger, J. Chem. Phys. 134, 144104 (2011)], along with three plausible choices for the value of the absolute hydration free energy of the proton (ΔG [minus sign in circle symbol]hyd[H+]), have been checked for their capability to properly describe the structural properties of halide aqueous solutions, by comparing the MD structural results with EXAFS experimental data. A very good agreement between theory and experiment has been obtained with one parameter set, namely LE, thus strengthening preliminary evidences for a ΔG [minus sign in circle symbol]hyd[H] value of -1100 kJ mol(-1) [M. M. Reif and P. H. Hünenberger, J. Chem. Phys. 134, 144104 (2011)]. The Cl(-), Br(-), and I(-) ions have been found to form an unstructured and disordered first hydration shell in aqueous solution, with a broad distribution of instantaneous coordination numbers. Conversely, the F(-) ion shows more ordered and defined first solvation shell, with only two statistically relevant coordination geometries (six and sevenfold complexes). Our thorough investigation on the effect of halide ions on the microscopic structure of water highlights that the perturbation induced by the Cl(-), Br(-), and I(-) ions does not extend beyond the ion first hydration shell, and the structure of water in the F(-) second shell is also substantially unaffected by the ion.

  2. Reservoir Models for Gas Hydrate Numerical Simulation

    Science.gov (United States)

    Boswell, R.

    2016-12-01

    Scientific and industrial drilling programs have now providing detailed information on gas hydrate systems that will increasingly be the subject of field experiments. The need to carefully plan these programs requires reliable prediction of reservoir response to hydrate dissociation. Currently, a major emphasis in gas hydrate modeling is the integration of thermodynamic/hydrologic phenomena with geomechanical response for both reservoir and bounding strata. However, also critical to the ultimate success of these efforts is the appropriate development of input geologic models, including several emerging issues, including (1) reservoir heterogeneity, (2) understanding of the initial petrophysical characteristics of the system (reservoirs and seals), the dynamic evolution of those characteristics during active dissociation, and the interdependency of petrophysical parameters and (3) the nature of reservoir boundaries. Heterogeneity is ubiquitous aspect of every natural reservoir, and appropriate characterization is vital. However, heterogeneity is not random. Vertical variation can be evaluated with core and well log data; however, core data often are challenged by incomplete recovery. Well logs also provide interpretation challenges, particularly where reservoirs are thinly-bedded due to limitation in vertical resolution. This imprecision will extend to any petrophysical measurements that are derived from evaluation of log data. Extrapolation of log data laterally is also complex, and should be supported by geologic mapping. Key petrophysical parameters include porosity, permeability and it many aspects, and water saturation. Field data collected to date suggest that the degree of hydrate saturation is strongly controlled by/dependant upon reservoir quality and that the ratio of free to bound water in the remaining pore space is likely also controlled by reservoir quality. Further, those parameters will also evolve during dissociation, and not necessary in a simple

  3. The combined effect of thermodynamic promoters tetrahydrofuran and cyclopentane on the kinetics of flue gas hydrate formation

    DEFF Research Database (Denmark)

    Daraboina, Nagu; von Solms, Nicolas

    2015-01-01

    ) hydrate formation using a rocking cell apparatus. Hydrate formation and decomposition kinetics were investigated by constant cooling (hydrate nucleation temperature) and isothermal (hydrate nucleation time) methods. Improved (synergistic) hydrate formation kinetics (hydrate nucleation and growth) were...... of these two promoters is favorable both thermodynamically and kinetically for hydrate formation from flue gas....

  4. Experimental solid state NMR of gas hydrates : problems and solutions

    Energy Technology Data Exchange (ETDEWEB)

    Moudrakovski, I.; Lu, H.; Ripmeester, J. [National Research Council of Canada, Ottawa, ON (Canada). Steacie Inst. for Molecular Sciences; Kumar, R.; Susilo, R. [British Columbia Univ., Vancouver, BC (Canada). Dept. of Chemical and Biological Engineering; Luzi, M. [GeoForschungsZentrum Potsdam, Potsdam (Germany)

    2008-07-01

    Solid State NMR is a suitable spectroscopic technique for hydrate research for several reasons, including its capability to distinguish between different structural types of hydrates, its quantitative nature and potential for both in-situ and time resolved experiments. This study illustrated the applications of solid state NMR for compositional and structural studies of clathrate hydrates, with particular emphasis on experimental techniques and potential ways to overcome technical difficulties. In order to use the method to its full capacity, some instrumental developments are needed to adapt it to the specific experimental requirements of hydrate studies, such as very low temperatures and high pressures. This presentation discussed the quantification of the Carbon-13 spectra with examples from natural and synthetic hydrates prepared from multi-component mixtures of hydrocarbons. The main approach used for the first two examples was Carbon-13 NMR with Magic Angle Spinning (MAS) at -100 degrees C. The detailed characterization of mixed hydrogen hydrates required low temperature hydrogen MAS. The quantification problems encountered during these experiments were also discussed. The purpose of these recent experimental developments was to prompt wider application of Solid State NMR in hydrate research. NMR proved to be a viable method for analyzing the composition and structure of multi-component mixed gas hydrates; characterizing natural gas hydrates; and, evaluating the formation conditions and properties of mixed hydrogen hydrates. The limitations of the method were highlighted and sensible choices of experimental conditions and techniques that ensure accurate results were discussed. 34 refs., 10 figs.

  5. Effect of Gemini-type surfactant on methane hydrate formation

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, K.E.; Park, J.M.; Kim, C.U.; Chae, H.J.; Jeong, S.Y. [Korea Research Inst. of Chemical Technology, Jang-Dong, Yuseong-Gu, Daejeon (Korea, Republic of)

    2008-07-01

    Natural gas hydrates are formed from water and natural gas molecules at particular temperatures and pressures that become ice-like inclusion compounds. Gas hydrates offer several benefits such as energy resource potential and high storage capacity of natural gas in the form of hydrates. However, the application of natural gas hydrates has been deterred by its low formation rate and low conversion ratio of water into hydrate resulting in low actual storage capacity. This paper presented an experimental study to determine the effect of adding a novel Gemini-type surfactant on methane hydrate formation. The experimental study was described with reference to the properties of prepared diols and properties of prepared disulfonates. Gemini surfactant is the family of surfactant molecules possessing more than one hydrophobic tail and hydrophilic head group. They generally have better surface-active properties than conventional surfactants of equal chain length. The paper presented the results of the study in terms of the reactions of diols with propane sultone; storage capacity of hydrate formed with and without surfactant; and methane hydrate formation with and without disulfonate. It was concluded that the methane hydrate formation was accelerated by the addition of novel anionic Gemini-type surfactants and that hydrate formation was influenced by the surfactant concentration and alkyl chain length. For a given concentration, the surfactant with the highest chain length demonstrated the highest formation rate and storage capacity. 5 refs., 3 tabs., 4 figs.

  6. Carbon dioxide gas hydrates accumulation in freezing and frozen sediments

    Energy Technology Data Exchange (ETDEWEB)

    Chuvilin, E.; Guryeva, O. [Moscow State Univ., Moscow (Russian Federation). Dept. of Geology

    2008-07-01

    Carbon dioxide (CO{sub 2}) hydrates and methane hydrates can be formed, and exist under natural conditions. The permafrost area has been considered as an environment for the potential disposal of CO{sub 2}. The favorable factors for preserving CO{sub 2} in liquid and gas hydrate states in frozen sediments and under permafrost horizons are great thickness of frozen sediments; low permeability in comparison with thawed sediments; and favourable conditions for hydrates formation. Therefore, research on the formation and existence conditions of CO{sub 2} gas hydrates in permafrost and under permafrost sediments are of great importance for estimation of CO{sub 2} disposal conditions in permafrost, and for working out specific sequestration schemes. This paper presented the results of an experimental study on the process of carbon dioxide (CO{sub 2}) gas hydrates formation in the porous media of sediments under positive and negative temperatures. Sediment samples of various compositions including those selected in the permafrost area were used. The research was conducted in a special pressure chamber, which allowed to monitor pressure and temperature. The study used the monitoring results in order to make quantitative estimation of the kinetics of CO{sub 2} hydrates accumulation in the model sediments. Results were presented in terms of kinetics of CO{sub 2} hydrates accumulation in the porous media at positive and negative temperatures; kinetics of CO{sub 2} hydrates accumulation in various porous media; gas hydrate-former influence on kinetics of hydrates accumulation in frozen sediments; and influence of freezing on CO{sub 2} hydrates accumulation in porous media. It was concluded that hydrate accumulation took an active place in porous media not only under positive, but also under high negative temperatures, when the water was mainly in the form of ice in porous media. 27 refs., 3 tabs., 5 figs.

  7. Polymorphism in Br2 clathrate hydrates.

    Science.gov (United States)

    Goldschleger, I U; Kerenskaya, G; Janda, K C; Apkarian, V A

    2008-02-07

    The structure and composition of bromine clathrate hydrate has been controversial for more than 170 years due to the large variation of its observed stoichiometries. Several different crystal structures were proposed before 1997 when Udachin et al. (Udachin, K. A.; Enright, G. D.; Ratcliffe, C. I.; Ripmeester, J. A. J. Am. Chem. Soc. 1997, 119, 11481) concluded that Br2 forms only the tetragonal structure (TS-I). We show polymorphism in Br2 clathrate hydrates by identifying two distinct crystal structures through optical microscopy and resonant Raman spectroscopy on single crystals. After growing TS-I crystals from a liquid bromine-water solution, upon dropping the temperature slightly below -7 degrees C, new crystals of cubic morphology form. The new crystals, which have a limited thermal stability range, are assigned to the CS-II structure. The two structures are clearly distinguished by the resonant Raman spectra of the enclathrated Br2, which show long overtone progressions and allow the extraction of accurate vibrational parameters: omega(e) = 321.2 +/- 0.1 cm(-1) and omega(e)x(e) = 0.82 +/- 0.05 cm(-1) in TS-I and omega(e) = 317.5 +/- 0.1 cm(-1) and omega(e)x(e) = 0.70 +/- 0.1 cm(-1) in CS-II. On the basis of structural analysis, the discovery of the CS-II crystals implies stability of a large class of bromine hydrate structures and, therefore, polymorphism.

  8. The economics of exploiting gas hydrates

    International Nuclear Information System (INIS)

    Döpke, Lena-Katharina; Requate, Till

    2014-01-01

    We investigate the optimal exploitation of methane hydrates, a recent discovery of methane resources under the sea floor, mainly located along the continental margins. Combustion of methane (releasing CO2) and leakage through blow-outs (releasing CH4) contribute to the accumulation of greenhouse gases. A second externality arises since removing solid gas hydrates from the sea bottom destabilizes continental margins and thus increases the risk of marine earthquakes. We show that in such a model three regimes can occur: i) resource exploitation will be stopped in finite time, and some of the resource will stay in situ, ii) the resource will be used up completely in finite time, and iii) the resource will be exhausted in infinite time. We also show how to internalize the externalities by policy instruments. - Highlights: • We set up a model of optimal has hydrate exploitation • We incorporate to types of damages: contribution to global warming and geo-hazards • We characterize optimal exploitation paths and study decentralization with an exploitation tax. • Three regimes can occur: • i) exploitation in finite time and some of the stock remaining in situ, • ii) exploitation in finite time and the resource will be exhausted, • iii) exploitation and exhaustion in infinite time

  9. Raman spectroscopic studies of hydrogen clathrate hydrates.

    Science.gov (United States)

    Strobel, Timothy A; Sloan, E Dendy; Koh, Carolyn A

    2009-01-07

    Raman spectroscopic measurements of simple hydrogen and tetrahydrofuran+hydrogen sII clathrate hydrates have been performed. Both the roton and vibron bands illuminate interesting quantum dynamics of enclathrated H(2) molecules. The complex vibron region of the Raman spectrum has been interpreted by observing the change in population of these bands with temperature, measuring the absolute H(2) content as a function of pressure, and with D(2) isotopic substitution. Quadruple occupancy of the large sII clathrate cavity shows the highest H(2) vibrational frequency, followed by triple and double occupancies. Singly occupied small cavities display the lowest vibrational frequency. The vibrational frequencies of H(2) within all cavity environments are redshifted from the free gas phase value. At 76 K, the progression from ortho- to para-H(2) occurs over a relatively slow time period (days). The rotational degeneracy of H(2) molecules within the clathrate cavities is lifted, observed directly in splitting of the para-H(2) roton band. Raman spectra from H(2) and D(2) hydrates suggest that the occupancy patterns between the two hydrates are analogous, increasing confidence that D(2) is a suitable substitute for H(2). The measurements suggest that Raman is an effective and convenient method to determine the relative occupancy of hydrogen molecules in different clathrate cavities.

  10. Electronic structure calculations of calcium silicate hydrates

    International Nuclear Information System (INIS)

    Sterne, P.A.; Meike, A.

    1995-11-01

    Many phases in the calcium-silicate-hydrate system can develop in cement exposed over long periods of time to temperatures above 25 C. As a consequence, chemical reactions involving these phases can affect the relative humidity and water chemistry of a radioactive waste repository that contains significant amounts of cement. In order to predict and simulate these chemical reactions, the authors are developing an internally consistent database of crystalline Ca-Si-hydrate structures. The results of first principles electronic structure calculations on two such phases, wollastonite (CaSiO 3 ) and xonotlite (Ca 6 Si 6 O 17 (OH) 2 ), are reported here. The calculated ground state properties are in very good agreement with experiment, providing equilibrium lattice parameters within about 1--1.4% of the experimentally reported values. The roles of the different types of oxygen atoms, which are fundamental to understanding the energetics of crystalline Ca-Si-hydrates are briefly discussed in terms of their electronic state densities. The good agreement with experiment for the lattice parameters and the consistency of the electronic density of states features for the two structures demonstrate the applicability of these electronic structure methods in calculating the fundamental properties of these phases

  11. Intermolecular Hydrogen Transfer in Isobutane Hydrate

    Directory of Open Access Journals (Sweden)

    Takeshi Sugahara

    2012-05-01

    Full Text Available Electron spin resonance (ESR spectra of butyl radicals induced with γ-ray irradiation in the simple isobutane (2-methylpropane hydrate (prepared with deuterated water were investigated. Isothermal annealing results of the γ-ray-irradiated isobutane hydrate reveal that the isobutyl radical in a large cage withdraws a hydrogen atom from the isobutane molecule through shared hexagonal-faces of adjacent large cages. During this “hydrogen picking” process, the isobutyl radical is apparently transformed into a tert-butyl radical, while the sum of isobutyl and tert-butyl radicals remains constant. The apparent transformation from isobutyl to tert-butyl radicals is an irreversible first-order reaction and the activation energy was estimated to be 35 ± 3 kJ/mol, which was in agreement with the activation energy (39 ± 5 kJ/mol of hydrogen picking in the γ-ray-irradiated propane hydrate with deuterated water.

  12. Magnetic behavior of cobalt bromide hydrates including a deuterated form

    Energy Technology Data Exchange (ETDEWEB)

    DeFotis, G.C., E-mail: gxdefo@wm.edu; Hampton, A.S.; Van Dongen, M.J.; Komatsu, C.H.; DeSanto, C.L.; Davis, C.M.

    2017-04-15

    The magnetic properties of little examined CoBr{sub 2}• 2H{sub 2}O and new CoBr{sub 2}• H{sub 2}O and CoBr{sub 2}• D{sub 2}O are studied. Curie-Weiss fits, χ{sub M}=C/(T-θ), yield θ of −9.9, 9.4 and 10.0 K, respectively, over a 30–80 K linear range for each. Higher temperature data are fit assuming two moderately separated low lying Kramers doublets, with exchange accounted for in a mean-field approximation. Susceptibility maxima appear at 9.5, 15.4 and 15.5 K, with χ{sub max} of 0.163, 0.375 and 0.435 emu/mol, respectively. Antiferromagnetic ordering is estimated to occur at 9.0, 13.7 and 13.8 K, in the same order. The ratio T{sub c}/T{sub max} is 0.95, 0.89 and 0.89, respectively, suggesting little low dimensional magnetic character in singly hydrated systems. Data at lower temperatures for the dihydrate are fit with an antiferromagnetic 3D-Ising model. For singly hydrated systems the large size of χ{sub max} prevents this; weakened interchain antiferromagnetic interactions yield enhanced susceptibility maxima. Magnetization data exhibit field induced transitions near 13.5 kG for the dihydrate, and near 6.5 kG for singly hydrated systems with enhanced hysteresis. These transitions are interpreted as metamagnetic in nature. - Highlights: • CoBr{sub 2}• 2H{sub 2}O has a larger susceptibility maximum at lower temperature than CoCl{sub 2}• 2H{sub 2}O. • Enhanced antiferromagnetic susceptibility maxima occur in CoBr{sub 2}·H{sub 2}O and CoBr{sub 2}• D{sub 2}O. • Metamagnetic transitions occur at much lower fields in monohydrates than dehydrate. • Interchain antiferromagnetic exchange is weaker in monohydrates than dehydrate. • CoBr{sub 2}• H{sub 2}O exhibit spin glass behavior similar to that seen previously in CoCl{sub 2}·H{sub 2}O.

  13. Impact of Compound Hydrate Dynamics on Phase Boundary Changes

    Science.gov (United States)

    Osegovic, J. P.; Max, M. D.

    2006-12-01

    Compound hydrate reactions are affected by the local concentration of hydrate forming materials (HFM). The relationship between HFM composition and the phase boundary is as significant as temperature and pressure. Selective uptake and sequestration of preferred hydrate formers (PF) has wide ranging implications for the state and potential use of natural hydrate formation, including impact on climate. Rising mineralizing fluids of hydrate formers (such as those that occur on Earth and are postulated to exist elsewhere in the solar system) will sequester PF before methane, resulting in a positive relationship between depth and BTU content as ethane and propane are removed before methane. In industrial settings the role of preferred formers can separate gases. When depressurizing gas hydrate to release the stored gas, the hydrate initial composition will set the decomposition phase boundary because the supporting solution takes on the composition of the hydrate phase. In other settings where hydrate is formed, transported, and then dissociated, similar effects can control the process. The behavior of compound hydrate systems can primarily fit into three categories: 1) In classically closed systems, all the material that can form hydrate is isolated, such as in a sealed laboratory vessel. In such systems, formation and decomposition are reversible processes with observed hysteresis related to mass or heat transfer limitations, or the order and magnitude in which individual hydrate forming gases are taken up from the mixture and subsequently released. 2) Kinetically closed systems are exposed to a solution mass flow across a hydrate mass. These systems can have multiple P-T phase boundaries based on the local conditions at each face of the hydrate mass. A portion of hydrate that is exposed to fresh mineralizing solution will contain more preferred hydrate formers than another portion that is exposed to a partially depleted solution. Examples of kinetically closed

  14. Inter- and intra-individual differences in skin hydration and surface lipids measured with mid-infrared spectroscopy

    Science.gov (United States)

    Ezerskaia, A.; Pereira, S. F.; Urbach, H. P.; Varghese, B.

    2016-03-01

    Skin health is characterized by heterogeneous system of water and lipids in upper layers providing protection from external environment and preventing loss of vital components of the body. Skin hydration (moisture) and sebum (skin surface lipids) are considered to be important factors in skin health; a right balance between these components is an indication of healthy skin and plays a central role in protecting and preserving skin integrity. In this manuscript we present inter- and intra-individual variation in skin hydration and surface lipids measured with a home-built experimental prototype based on infrared spectroscopy. Results show good agreement with measurements performed by commercially available instruments Corneometer and Sebumeter used for skin hydration and sebum measurements respectively.

  15. Impact of iso-osmolar versus low-osmolar contrast agents on contrast-induced nephropathy and tissue reperfusion in unselected patients with ST-segment elevation myocardial infarction undergoing primary percutaneous coronary intervention (from the Contrast Media and Nephrotoxicity Following Primary Angioplasty for Acute Myocardial Infarction [CONTRAST-AMI] Trial).

    Science.gov (United States)

    Bolognese, Leonardo; Falsini, Giovanni; Schwenke, Carsten; Grotti, Simone; Limbruno, Ugo; Liistro, Francesco; Carrera, Arcangelo; Angioli, Paolo; Picchi, Andrea; Ducci, Kenneth; Pierli, Carlo

    2012-01-01

    Conflicting data have been reported on the effects of low-osmolar and iso-osmolar contrast media on contrast-induced acute kidney injury (CI-AKI). In particular, no clinical trial has yet focused on the effect of contemporary contrast media on CI-AKI, epicardial flow, and microcirculatory function in patients with ST-segment elevation acute myocardial infarction who undergo primary percutaneous coronary intervention. The Contrast Media and Nephrotoxicity Following Coronary Revascularization by Angioplasty for Acute Myocardial Infarction (CONTRAST-AMI) trial is a prospective, randomized, single-blind, parallel-group, noninferiority study aiming to evaluate the effects of the low-osmolar contrast medium iopromide compared to the iso-osmolar agent iodixanol on CI-AKI and tissue-level perfusion in patients with ST-segment elevation acute myocardial infarction. Four hundred seventy-five consecutive, unselected patients who underwent primary percutaneous coronary intervention were randomized to iopromide (n = 239) or iodixanol (n = 236). All patients received high-dose N-acetylcysteine and hydration. The primary end point was the proportion of patients with serum creatinine (sCr) increases ≥25% from baseline to 72 hours. Secondary end points were Thrombolysis In Myocardial Infarction (TIMI) myocardial perfusion grade, increase in sCr ≥50%, increase in sCr ≥0.5 or ≥1 mg/dl, and 1-month major adverse cardiac events. The primary end point occurred in 10% of the iopromide group and in 13% of the iodixanol group (95% confidence interval -9% to 3%, p for noninferiority = 0.0002). A TIMI myocardial perfusion grade of 0 or 1 was present in 14% of patients in the 2 groups. No differences between the 2 groups were found in any of the secondary analyses of sCr increase. No significant difference in 1-month major adverse cardiac events was found (8% vs 6%, p = 0.37). In conclusion, in a population of unselected patients with ST-segment elevation acute myocardial infarction

  16. Protein Hydration Thermodynamics: The Influence of Flexibility and Salt on Hydrophobin II Hydration.

    Science.gov (United States)

    Remsing, Richard C; Xi, Erte; Patel, Amish J

    2018-04-05

    The solubility of proteins and other macromolecular solutes plays an important role in numerous biological, chemical, and medicinal processes. An important determinant of protein solubility is the solvation free energy of the protein, which quantifies the overall strength of the interactions between the protein and the aqueous solution that surrounds it. Here we present an all-atom explicit-solvent computational framework for the rapid estimation of protein solvation free energies. Using this framework, we estimate the hydration free energy of hydrophobin II, an amphiphilic fungal protein, in a computationally efficient manner. We further explore how the protein hydration free energy is influenced by enhancing flexibility and by the addition of sodium chloride, and find that it increases in both cases, making protein hydration less favorable.

  17. Indian continental margin gas hydrate prospects : results of the Indian National Gas Hydrate Program (NGHP) expedition 01

    Energy Technology Data Exchange (ETDEWEB)

    Collett, T [United States Geological Survey, Denver, CO (United States); Riedel, M. [McGill Univ., Montreal, PQ (Canada). Dept. of Earth and Planetary Sciences; Cochran, J.R. [Columbia Univ., Palisades, NY (United States). Lamont Doherty Earth Observatory; Boswell, R. [United States Dept. of Energy, Morgantown, WV (United States). National Energy Technology Lab; Kumar, P. [Pushpendra Kumar Oil and Natural Gas Corp. Ltd., Mumbai (India). Inst. of Engineering and Ocean Technology; Sathe, A.V. [Oil and Natural Gas Corp. Ltd., Uttaranchal (India). KDM Inst. of Petroleum Exploration

    2008-07-01

    The geologic occurrence of gas hydrate deposits along the continental margins of India were investigated in the first expedition of the Indian National Gas Hydrate Program (NGHP). The objective was to determine the regional context and characteristics of the gas hydrate deposits through scientific ocean drilling, logging, and analytical activities. A research drill ship was the platform for the drilling operation. The geological and geophysical studies revealed 2 geologically distinct areas with inferred gas hydrate occurrences, notably the passive continental margins of the Indian Peninsula and along the Andaman convergent margin. The NGHP Expedition 01 focused on understanding the geologic and geochemical controls on the occurrence of gas hydrate in these 2 diverse settings. The study established the presence of gas hydrates in Krishna-Godavari, Mahanadi and Andaman basins. Site 10 in the Krishna-Godavari Basin was discovered to be the one of the richest gas hydrate accumulations yet documented, while site 17 in the Andaman Sea had the thickest and deepest gas hydrate stability zone yet known. The existence of a fully-developed gas hydrate system in the Mahanadi Basin was also discovered. Most of the gas hydrate occurrences discovered during this expedition appeared to contain mostly methane which was generated by microbial processes. However, there was also evidence of a thermal origin for a portion of the gas within the hydrates of the Mahanadi Basin and the Andaman offshore area. Gas hydrate in the Krishna-Godavari Basin appeared to be closely associated with large scale structural features, in which the flux of gas through local fracture systems, generated by the regional stress regime, controlled the occurrence of gas hydrate. 3 refs., 1 tab., 2 figs.

  18. Focus on the Development of Natural Gas Hydrate in China

    Directory of Open Access Journals (Sweden)

    Zhongfu Tan

    2016-05-01

    Full Text Available Natural gas hydrate, also known as combustible ice, and mainly composed of methane, is identified as a potential clean energy for the 21st century. Due to its large reserves, gas hydrate can ease problems caused by energy resource shortage and has gained attention around the world. In this paper, we focus on the exploration and development of gas hydrate as well as discussing its status and future development trend in China and abroad. We then analyze its opportunities and challenges in China from four aspects, resource, technology, economy and policy, with five forces model and Politics Economics Society Technology method. The results show China has abundance gas hydrate resource; however, backward technologies and inadequate investment have seriously hindered the future development of gas hydrate; thus, China should establish relevant cooperation framework and intuitional arrangement to attract more investment as well as breaking through technical difficulties to commercialization gas hydrate as soon as possible.

  19. Raman studies of methane-ethane hydrate metastability.

    Science.gov (United States)

    Ohno, Hiroshi; Strobel, Timothy A; Dec, Steven F; Sloan, E Dendy; Koh, Carolyn A

    2009-03-05

    The interconversion of methane-ethane hydrate from metastable to stable structures was studied using Raman spectroscopy. sI and sII hydrates were synthesized from methane-ethane gas mixtures of 65% or 93% methane in ethane and water, both with and without the kinetic hydrate inhibitor, poly(N-vinylcaprolactam). The observed faster structural conversion rate in the higher methane concentration atmosphere can be explained in terms of the differences in driving force (difference in chemical potential of water in sI and sII hydrates) and kinetics (mass transfer of gas and water rearrangement). The kinetic hydrate inhibitor increased the conversion rate at 65% methane in ethane (sI is thermodynamically stable) but retards the rate at 93% methane in ethane (sII is thermodynamically stable), implying there is a complex interaction between the polymer, water, and hydrate guests at crystal surfaces.

  20. Enzyme hydration, activity and flexibility : A neutron scattering approach

    International Nuclear Information System (INIS)

    Kurkal-Siebert, V.; Finney, J.L.; Daniel, R.M.; Smith, Jeremy C.

    2006-01-01

    Recent measurements have demonstrated enzyme activity at hydrations as low as 3%. The question of whether the hydration-induced enzyme flexibility is important for activity is addressed by performing picosecond dynamic neutron scattering experiments on pig liver esterase powders at various temperatures as well as solutions. At all temperatures and hydrations investigated here, significant quasielastic scattering intensity is found in the protein, indicating the presence of anharmonic, diffusive motion. As the hydration increases a temperature-dependent dynamical transition appears and strengthens involving additional diffusive motion. At low temperature, increasing hydration resulted in lower flexibility of the enzyme. At higher temperatures, systems containing sufficient number of water molecules interacting with the protein exhibit increased flexibility. The implication of these results is that, although the additional hydration-induced diffusive motion and flexibility at high temperatures in the enzyme detected here may be related to increased activity, they are not required for the enzyme to function

  1. Thermal conductivity measurements in unsaturated hydrate-bearing sediments

    Science.gov (United States)

    Dai, Sheng; Cha, Jong-Ho; Rosenbaum, Eilis J.; Zhang, Wu; Seol, Yongkoo

    2015-08-01

    Current database on the thermal properties of hydrate-bearing sediments remains limited and has not been able to capture their consequential changes during gas production where vigorous phase changes occur in this unsaturated system. This study uses the transient plane source (TPS) technique to measure the thermal conductivity of methane hydrate-bearing sediments with various hydrate/water/gas saturations. We propose a simplified method to obtain thermal properties from single-sided TPS signatures. Results reveal that both volume fraction and distribution of the pore constituents govern the thermal conductivity of unsaturated specimens. Thermal conductivity hysteresis is observed due to water redistribution and fabric change caused by hydrate formation and dissociation. Measured thermal conductivity increases evidently when hydrate saturation Sh > 30-40%, shifting upward from the geometric mean model prediction to a Pythagorean mixing model. These observations envisage a significant drop in sediment thermal conductivity when residual hydrate/water saturation falls below ~40%, hindering further gas production.

  2. Dissolution mechanisms of CO2 hydrate droplets in deep seawaters

    International Nuclear Information System (INIS)

    Gabitto, Jorge; Tsouris, Costas

    2006-01-01

    Carbon dioxide dissolution at intermediate ocean depths was studied using physical and mass transfer models. Particle density and hydrate layer thickness were determined using existing field data. Pseudo-homogeneous and heterogeneous mass transfer models were proposed to study the dissolution process. Pseudo-homogeneous models do not seem to represent the dissolution process well. Although heterogeneous models interpret the physical behavior better, unresolved issues related to hydrate dissolution still remain. For example, solid hydrate forms on one side of the hydrate film while it dissolves on the other. Dissolution is a complex process that comprises at least two sequential steps. The global process is controlled by mass transfer inside the hydrate layer or by a dissolution reaction at the hydrate-water interface

  3. Natural gas storage in hydrates with the presence of promoters

    International Nuclear Information System (INIS)

    Sun Zhigao; Wang Ruzhu; Ma Rongsheng; Guo Kaihua; Fan Shuanshi

    2003-01-01

    Hydrate technology is being developed for the storage and transport of natural gas. Micellar surfectant solutions were found to increase the gas hydrate formation rate and storage capacity. An anionic surfactant, a nonionic surfactant, their mixtures and cyclopentane were used to improve the hydrate formation of a synthetic natural gas (methane=92.05 mol%, ethane=4.96 mol%, propane=2.99 mol%) in a quiescent system in this work. The effect of an anionic surfactant (sodium dodecyl sulfate) on natural gas storage in hydrates is more pronounced compared to the effect of a nonionic surfactant (dodecyl polysaccharide glycoside). Cyclopentane could reduce hydrate formation induction time but could not improve the hydrate formation rate and storage capacity

  4. Development of salt hydrate eutectics as latent heat storage for air conditioning and cooling

    International Nuclear Information System (INIS)

    Efimova, Anastasia; Pinnau, Sebastian; Mischke, Matthias; Breitkopf, Cornelia; Ruck, Michael; Schmidt, Peer

    2014-01-01

    Graphical abstract: - Highlights: • Inorganic salt hydrates. • Latent heat thermal energy storage. • Thermal behavior of melting and crystallization. • Cycling stability. • Nucleation. - Abstract: Sustainable air conditioning systems require heat reservoirs that operate between 4 and 20 °C. A systematic search for binary and ternary eutectics of inorganic salts and salt hydrates with melting temperatures in this temperature regime and with high enthalpies of fusion has been performed by means of differential scanning calorimetry (DSC). Promising results were obtained for the pseudo-ternary system Zn(NO 3 ) 2 ·6H 2 O, Mn(NO 3 ) 2 ·4H 2 O, and KNO 3 with the melting temperature range 18–21 °C and the enthalpy of fusion of about 110 kJ kg −1 . Suitable nucleating and thickening agents have been found and tested to prevent the mixture from supercooling and phase separation

  5. Obsidian hydration profiles measured by sputter-induced optical emission.

    Science.gov (United States)

    Tsong, I S; Houser, C A; Yusef, N A; Messier, R F; White, W B; Michels, J W

    1978-07-28

    The variation of concentrations of hydrogen, sodium, potassium, lithium, calcium, magnesium, silicon, and aluminum as a function of depth in the hydration layer of obsidian artifacts has been determined by sputter-induced optical emission. The surface hydration is accompanied by dealkalization, and there is a buildup of alkaline earths, calcium and magnesium in the outermost layers. These results have clarified the phenomena underlying the obsidian hydration dating technique.

  6. [Laser Raman Spectroscopy and Its Application in Gas Hydrate Studies].

    Science.gov (United States)

    Fu, Juan; Wu, Neng-you; Lu, Hai-long; Wu, Dai-dai; Su, Qiu-cheng

    2015-11-01

    Gas hydrates are important potential energy resources. Microstructural characterization of gas hydrate can provide information to study the mechanism of gas hydrate formation and to support the exploitation and application of gas hydrate technology. This article systemly introduces the basic principle of laser Raman spectroscopy and summarizes its application in gas hydrate studies. Based on Raman results, not only can the information about gas composition and structural type be deduced, but also the occupancies of large and small cages and even hydration number can be calculated from the relative intensities of Raman peaks. By using the in-situ analytical technology, laser Raman specstropy can be applied to characterize the formation and decomposition processes of gas hydrate at microscale, for example the enclathration and leaving of gas molecules into/from its cages, to monitor the changes in gas concentration and gas solubility during hydrate formation and decomposition, and to identify phase changes in the study system. Laser Raman in-situ analytical technology has also been used in determination of hydrate structure and understanding its changing process under the conditions of ultra high pressure. Deep-sea in-situ Raman spectrometer can be employed for the in-situ analysis of the structures of natural gas hydrate and their formation environment. Raman imaging technology can be applied to specify the characteristics of crystallization and gas distribution over hydrate surface. With the development of laser Raman technology and its combination with other instruments, it will become more powerful and play a more significant role in the microscopic study of gas hydrate.

  7. Characteristics of Methane Hydrate Formation in Artificial and Natural Media

    OpenAIRE

    Peng Zhang; Qingbai Wu; Yuzhong Yang

    2013-01-01

    The formation of methane hydrate in two significantly different media was investigated, using silica gel as an artificial medium and loess as a natural medium. The methane hydrate formation was observed through the depletion of water in the matrix, measured via the matrix potential and the relationship between the matrix potential and the water content was determined using established equations. The velocity of methane hydrate nucleation slowed over the course of the reaction, as it relied on...

  8. Small angle neutron scattering from hydrated cement pastes

    International Nuclear Information System (INIS)

    Sabine, T.M.; Bertram, W.K.; Aldridge, L.P.

    1996-01-01

    Small angle neutron scattering (SANS) was used to study the microstructure of hydrating cement made with, and without silica fume. Some significant differences were found between the SANS spectra of pastes made from OPC (ordinary Portland cement) and DSP (made with silica fume and superplasticiser). The SANS spectra are interpreted in terms of scattering from simple particles. Particle growth was monitored during hydration and it was found that the growth correlated with the heat of hydration of the cement

  9. Nuclear Well Log Properties of Natural Gas Hydrate Reservoirs

    Science.gov (United States)

    Burchwell, A.; Cook, A.

    2015-12-01

    Characterizing gas hydrate in a reservoir typically involves a full suite of geophysical well logs. The most common method involves using resistivity measurements to quantify the decrease in electrically conductive water when replaced with gas hydrate. Compressional velocity measurements are also used because the gas hydrate significantly strengthens the moduli of the sediment. At many gas hydrate sites, nuclear well logs, which include the photoelectric effect, formation sigma, carbon/oxygen ratio and neutron porosity, are also collected but often not used. In fact, the nuclear response of a gas hydrate reservoir is not known. In this research we will focus on the nuclear log response in gas hydrate reservoirs at the Mallik Field at the Mackenzie Delta, Northwest Territories, Canada, and the Gas Hydrate Joint Industry Project Leg 2 sites in the northern Gulf of Mexico. Nuclear logs may add increased robustness to the investigation into the properties of gas hydrates and some types of logs may offer an opportunity to distinguish between gas hydrate and permafrost. For example, a true formation sigma log measures the thermal neutron capture cross section of a formation and pore constituents; it is especially sensitive to hydrogen and chlorine in the pore space. Chlorine has a high absorption potential, and is used to determine the amount of saline water within pore spaces. Gas hydrate offers a difference in elemental composition compared to water-saturated intervals. Thus, in permafrost areas, the carbon/oxygen ratio may vary between gas hydrate and permafrost, due to the increase of carbon in gas hydrate accumulations. At the Mallik site, we observe a hydrate-bearing sand (1085-1107 m) above a water-bearing sand (1107-1140 m), which was confirmed through core samples and mud gas analysis. We observe a decrease in the photoelectric absorption of ~0.5 barnes/e-, as well as an increase in the formation sigma readings of ~5 capture units in the water-bearing sand as

  10. Impact of welan gum on tricalcium aluminate–gypsum hydration

    International Nuclear Information System (INIS)

    Ma Lei; Zhao Qinglin; Yao Chukang; Zhou Mingkai

    2012-01-01

    The retarding effect of welan gum on tricalcium aluminate–gypsum hydration, as a partial system of ordinary Portland cement (OPC) hydration, was investigated with several methods. The tricalcium aluminate–gypsum hydration behavior in the presence or absence of welan gum was researched by field emission gun scanning electron microscopy, X-ray diffraction and zeta potential analysis. Meanwhile, we studied the surface electrochemical properties and adsorption characteristics of welan gum by utilizing a zeta potential analyzer and UV–VIS absorption spectrophotometer. By adding welan gum, the morphology change of ettringite and retardation of hydration stages in tricalcium aluminate–gypsum system was observed. Moreover, we detected the adsorption behavior and zeta potential inversion of tricalcium aluminate and ettringite, as well as a rapid decrease in the zeta potential of tricalcium aluminate–gypsum system. The reduction on nucleation rate of ettringite and hydration activity of C 3 A was also demonstrated. Thus, through the adsorption effect, welan gum induces a retarding behavior in tricalcium aluminate–gypsum hydration. Highlights: ► Adsorption characteristics of welan gum on C 3 A and ettringite have been studied. ► C 3 A–gypsum hydration behavior and the hydration products are examined in L/S = 3. ► Welan gum retards the process of C 3 A–gypsum hydration. ► The addition of welan gum changes the nucleation growth of ettringite.

  11. Geomechanical Performance of Hydrate-Bearing Sediment in Offshore Environments

    Energy Technology Data Exchange (ETDEWEB)

    Stephen Holditch; Tad Patzek; Jonny Rutqvist; George Moridis; Richard Plumb

    2008-03-31

    The objective of this multi-year, multi-institutional research project was to develop the knowledge base and quantitative predictive capability for the description of geomechanical performance of hydrate-bearing sediments (hereafter referred to as HBS) in oceanic environments. The focus was on the determination of the envelope of hydrate stability under conditions typical of those related to the construction and operation of offshore platforms. We have developed a robust numerical simulator of hydrate behavior in geologic media by coupling a reservoir model with a commercial geomechanical code. We also investigated the geomechanical behavior of oceanic HBS using pore-scale models (conceptual and mathematical) of fluid flow, stress analysis, and damage propagation. The objective of the UC Berkeley work was to develop a grain-scale model of hydrate-bearing sediments. Hydrate dissociation alters the strength of HBS. In particular, transformation of hydrate clusters into gas and liquid water weakens the skeleton and, simultaneously, reduces the effective stress by increasing the pore pressure. The large-scale objective of the study is evaluation of geomechanical stability of offshore oil and gas production infrastructure. At Lawrence Berkeley National Laboratory (LBNL), we have developed the numerical model TOUGH + Hydrate + FLAC3D to evaluate how the formation and disassociation of hydrates in seafloor sediments affects seafloor stability. Several technical papers were published using results from this model. LBNL also developed laboratory equipment and methods to produce realistic laboratory samples of sediments containing gas hydrates so that mechanical properties could be measured in the laboratory. These properties are required to run TOUGH + Hydrate + FLAC3D to evaluate seafloor stability issues. At Texas A&M University we performed a detailed literature review to determine what gas hydrate formation properties had been measured and reported in the literature. We

  12. Hydration of Portoguese cements, measurement and modelling of chemical shrinkage

    DEFF Research Database (Denmark)

    Maia, Lino; Geiker, Mette Rica; Figueiras, Joaquim A.

    2008-01-01

    form of the dispersion model. The development of hydration varied between the investigated cements; based on the measured data the degree of hydration after 24 h hydration at 20 C varied between 40 and 50%. This should be taken into account when comparing properties of concrete made from the different......Development of cement hydration was studied by measuring the chemical shrinkage of pastes. Five types of Portuguese Portland cement were used in cement pastes with . Chemical shrinkage was measured by gravimetry and dilatometry. In gravimeters results were recorded automatically during at least...

  13. Ethylene Separation via Hydrate Formation in W/O Emulsions

    Directory of Open Access Journals (Sweden)

    Yong Pan

    2015-05-01

    Full Text Available An hybrid absorption-hydration method was adopted to recover C2H4 from C2H4/CH4 binary gas mixtures and the hydrate formation conditions of C2H4/CH4 mixtures was studied experimentally in diesel in water (w/o emulsions. Span 20 at a concentration of 1.0 wt% in the aqueous phase was added to form water in diesel emulsions before hydrate formation and then hydrate in diesel slurry was separated after hydrate formation. The influences of initial gas-liquid volume ratio (53–142, pressure (3.4–5.4 MPa, temperature (274.15–278.15 K, water cuts (10–30 vol%, and the mole fraction of C2H4 in feed gas (13.19–80.44 mol% upon the C2H4 separation efficiency were systematically investigated. The experimental results show that ethylene can be enriched in hydrate slurry phase with high separation factor (S and recovery ratio (R. Most hydrate formation finished in 20 min, after that, the hydrate formation rate became very slow. The conclusion is useful for determining the suitable operation conditions when adopting an absorption-hydration method to separate C2H4/CH4.

  14. Methane Production and Carbon Capture by Hydrate Swapping

    DEFF Research Database (Denmark)

    Mu, Liang; von Solms, Nicolas

    2017-01-01

    There are essentially two different approaches to producing methane from natural gas hydrate reservoirs, either bring the hydrate out of its thermodynamic stability region or expose the hydrate to a substance that will form a more stable hydrate structure, forcing an in situ swapping of the trapped...... experimental runs were performed to examine the influence of operating conditions on methane production by CO2/(CO2 + N2) injection in the temperature range of 274.15–277.15 K and 7.039–10.107 MPa pressure. Our results show that the use of the (CO2 + N2) binary gas mixture is advantageous compared to the use...

  15. HYDRATION AND MICROSTRUCTURE OF BLENDED CEMENT WITH SODIUM POLYSTYRENE SULFONATE

    Directory of Open Access Journals (Sweden)

    Weifeng Li

    2017-03-01

    Full Text Available Polystyrene foamed plastic wastes are a kind of environmental pollutant. It could be recycled in cement industry as a chemical agent. In this paper, the effects of sodium polystyrene sulfonate (SPS on the hydration and microstructure of blended cement were investigated by calorimetry, X-ray diffraction (XRD, scanning electron microscopy (SEM and mercury intrusion porosimetry (MIP. SPS slightly delayed the hydration of alite and decreased its hydration degree. SPS did not change the phase compositions during hydration. SPS changed the morphology of ettringite (AFt and decreased the pore volumes and the sizes of pores.

  16. Effects of various vehicles on skin hydration in vivo.

    Science.gov (United States)

    Wiedersberg, S; Leopold, C S; Guy, R H

    2009-01-01

    The stratum corneum, the outermost layer of the skin, regulates the passive loss of water to the environment. Furthermore, it is well accepted that drug penetration is influenced by skin hydration, which may be manipulated by the application of moisturizing or oleaginous vehicles. Measurements of transepidermal water loss (TEWL), and of skin hydration using a corneometer, were used to assess the effect of different vehicles on stratum corneum barrier function in vivo in human volunteers. A microemulsion significantly increased skin hydration relative to a reference vehicle based on medium chain triglycerides; in contrast, Transcutol(R) lowered skin hydration. TEWL measurements confirmed these observations. Copyright 2009 S. Karger AG, Basel.

  17. Hydrated electron: a destroyer of perfluorinated carboxylates?

    International Nuclear Information System (INIS)

    Huang Li; Dong Wenbo; Hou Huiqi

    2006-01-01

    As a class, perfluorinated carboxylate (PFCA) was ranked among the most prominent organohalogen contaminants in environment with respect to thermal, chemical and biological inertness. Hydrated electron (e aq - ), a highly reactive and strongly reductive species, has been reported to readily decompose perfluoroaromatic compounds via intermolecular electron transfer process in aqueous solution. Question then arose: what would happen if perfluorinated carboxylates encountered with hydrated electron? Original laboratory trial on the interaction between F(CF 2 ) n COO - (n=1, 3, 7) and hydrated electron was attempted by using laser flash photolysis technique in this research work. Abundant hydrated electron (e aq - ) could be produced by photolysis of 1.25 x 10 -4 M K 4 Fe(CN) 6 in nitrogen saturated water. In the presence of F(CF 2 ) n COO - (n=1, 3, 7), the decay of e aq - was observed to enhance dramatically, indicating e aq - was able to attack PFCAs. On addition of perfluorinated carboxylates, the loss of e aq - was mainly due to the following channels. By mixing the solution of K 4 Fe(CN) 6 with excess K 3 Fe(CN) 6 and PFCAs, e aq - turned to decayed corresponding to mixed first- and second-order kinetics. Rate constants for the reactions of e aq - with PFCAs could be then easily determined by monitoring the decay of e aq - absorption at 690 nm. Since perfluorinated carboxylates were salts, the influence of ionic strength on k 3 was examined systematically by carrying out experiments of varying ionic strength ranging from 0.009 up to 0.102 M by adding NaClO 4 . In this manner, the second order rate constants for e-aq with CF 3 COO - , C 3 F 7 COO - , C 7 F 15 COO - were derived to be (1.9±0.2) x 10 6 M -1 S -1 (μ=0), (7.1±0.2) x 10 6 M -1 S -1 (μ=0) and (1.7±0.5) x10 7 M -1 S -1 (μ=0.009 M) respectively. Apparently, the length of F(CF 2 ) n group exerted substantial influence on the rate constant. Further study on byproducts analysis by ion chromatography

  18. Life Origination Hydrate Hypothesis (LOH-Hypothesis

    Directory of Open Access Journals (Sweden)

    Victor Ostrovskii

    2012-01-01

    Full Text Available The paper develops the Life Origination Hydrate Hypothesis (LOH-hypothesis, according to which living-matter simplest elements (LMSEs, which are N-bases, riboses, nucleosides, nucleotides, DNA- and RNA-like molecules, amino-acids, and proto-cells repeatedly originated on the basis of thermodynamically controlled, natural, and inevitable processes governed by universal physical and chemical laws from CH4, niters, and phosphates under the Earth's surface or seabed within the crystal cavities of the honeycomb methane-hydrate structure at low temperatures; the chemical processes passed slowly through all successive chemical steps in the direction that is determined by a gradual decrease in the Gibbs free energy of reacting systems. The hypothesis formulation method is based on the thermodynamic directedness of natural movement and consists ofan attempt to mentally backtrack on the progression of nature and thus reveal principal milestones alongits route. The changes in Gibbs free energy are estimated for different steps of the living-matter origination process; special attention is paid to the processes of proto-cell formation. Just the occurrence of the gas-hydrate periodic honeycomb matrix filled with LMSEs almost completely in its final state accounts for size limitation in the DNA functional groups and the nonrandom location of N-bases in the DNA chains. The slowness of the low-temperature chemical transformations and their “thermodynamic front” guide the gross process of living matter origination and its successive steps. It is shown that the hypothesis is thermodynamically justified and testable and that many observed natural phenomena count in its favor.

  19. A DFT-based comparative equilibrium study of thermal dehydration and hydrolysis of CaCl2 hydrates and MgCl2 hydrates for seasonal heat storage

    NARCIS (Netherlands)

    Pathak, A.D.; Gaastra-Nedea, S.V.; Zondag, H.A.; Rindt, C.C.M.; Smeulders, D.M.J.

    2016-01-01

    Salt hydrates store solar energy in chemical form via a reversible dehydration–hydration reaction. However, as a side reaction to dehydration, hydrolysis (HCl formation) may occur in chloride based salt hydrates (specially in MgCl2 hydrates), affecting the durability of the storage system. The

  20. Withholding hydration and nutrition in newborns.

    Science.gov (United States)

    Porta, Nicolas; Frader, Joel

    2007-01-01

    In the twenty-first century, decisions to withhold or withdraw life-supporting measures commonly precede death in the neonatal intensive care unit without major ethical controversy. However, caregivers often feel much greater turmoil with regard to stopping medical hydration and nutrition than they do when considering discontinuation of mechanical ventilation or circulatory support. Nevertheless, forgoing medical fluids and food represents a morally acceptable option as part of a carefully developed palliative care plan considering the infant's prognosis and the burdens of continued treatment. Decisions to stop any form of life support should focus on the clinical circumstances, not the means used to sustain life.

  1. Well log characterization of natural gas-hydrates

    Science.gov (United States)

    Collett, Timothy S.; Lee, Myung W.

    2012-01-01

    In the last 25 years there have been significant advancements in the use of well-logging tools to acquire detailed information on the occurrence of gas hydrates in nature: whereas wireline electrical resistivity and acoustic logs were formerly used to identify gas-hydrate occurrences in wells drilled in Arctic permafrost environments, more advanced wireline and logging-while-drilling (LWD) tools are now routinely used to examine the petrophysical nature of gas-hydrate reservoirs and the distribution and concentration of gas hydrates within various complex reservoir systems. Resistivity- and acoustic-logging tools are the most widely used for estimating the gas-hydrate content (i.e., reservoir saturations) in various sediment types and geologic settings. Recent integrated sediment coring and well-log studies have confirmed that electrical-resistivity and acoustic-velocity data can yield accurate gas-hydrate saturations in sediment grain-supported (isotropic) systems such as sand reservoirs, but more advanced log-analysis models are required to characterize gas hydrate in fractured (anisotropic) reservoir systems. New well-logging tools designed to make directionally oriented acoustic and propagation-resistivity log measurements provide the data needed to analyze the acoustic and electrical anisotropic properties of both highly interbedded and fracture-dominated gas-hydrate reservoirs. Advancements in nuclear magnetic resonance (NMR) logging and wireline formation testing (WFT) also allow for the characterization of gas hydrate at the pore scale. Integrated NMR and formation testing studies from northern Canada and Alaska have yielded valuable insight into how gas hydrates are physically distributed in sediments and the occurrence and nature of pore fluids(i.e., free water along with clay- and capillary-bound water) in gas-hydrate-bearing reservoirs. Information on the distribution of gas hydrate at the pore scale has provided invaluable insight on the mechanisms

  2. Investigating the Metastability of Clathrate Hydrates for Energy Storage

    Energy Technology Data Exchange (ETDEWEB)

    Koh, Carolyn Ann [Colorado School of Mines, Golden, CO (United States)

    2014-11-18

    Important breakthrough discoveries have been achieved from the DOE award on the key processes controlling the synthesis and structure-property relations of clathrate hydrates, which are critical to the development of clathrate hydrates as energy storage materials. Key achievements include: (i) the discovery of key clathrate hydrate building blocks (stable and metastable) leading to clathrate hydrate nucleation and growth; (ii) development of a rapid clathrate hydrate synthesis route via a seeding mechanism; (iii) synthesis-structure relations of H2 + CH4/CO2 binary hydrates to control thermodynamic requirements for energy storage and sequestration applications; (iv) discovery of a new metastable phase present during clathrate hydrate structural transitions. The success of our research to-date is demonstrated by the significant papers we have published in high impact journals, including Science, Angewandte Chemie, J. Am. Chem. Soc. Intellectual Merits of Project Accomplishments: The intellectual merits of the project accomplishments are significant and transformative, in which the fundamental coupled computational and experimental program has provided new and critical understanding on the key processes controlling the nucleation, growth, and thermodynamics of clathrate hydrates containing hydrogen, methane, carbon dioxide, and other guest molecules for energy storage. Key examples of the intellectual merits of the accomplishments include: the first discovery of the nucleation pathways and dominant stable and metastable structures leading to clathrate hydrate formation; the discovery and experimental confirmation of new metastable clathrate hydrate structures; the development of new synthesis methods for controlling clathrate hydrate formation and enclathration of molecular hydrogen. Broader Impacts of Project Accomplishments: The molecular investigations performed in this project on the synthesis (nucleation & growth)-structure-stability relations of clathrate

  3. Free energy landscape and molecular pathways of gas hydrate nucleation

    International Nuclear Information System (INIS)

    Bi, Yuanfei; Porras, Anna; Li, Tianshu

    2016-01-01

    Despite the significance of gas hydrates in diverse areas, a quantitative knowledge of hydrate formation at a molecular level is missing. The impediment to acquiring this understanding is primarily attributed to the stochastic nature and ultra-fine scales of nucleation events, posing a great challenge for both experiment and simulation to explore hydrate nucleation. Here we employ advanced molecular simulation methods, including forward flux sampling (FFS), p B histogram analysis, and backward flux sampling, to overcome the limit of direct molecular simulation for exploring both the free energy landscape and molecular pathways of hydrate nucleation. First we test the half-cage order parameter (H-COP) which we developed for driving FFS, through conducting the p B histogram analysis. Our results indeed show that H-COP describes well the reaction coordinates of hydrate nucleation. Through the verified order parameter, we then directly compute the free energy landscape for hydrate nucleation by combining both forward and backward flux sampling. The calculated stationary distribution density, which is obtained independently of nucleation theory, is found to fit well against the classical nucleation theory (CNT). Subsequent analysis of the obtained large ensemble of hydrate nucleation trajectories show that although on average, hydrate formation is facilitated by a two-step like mechanism involving a gradual transition from an amorphous to a crystalline structure, there also exist nucleation pathways where hydrate crystallizes directly, without going through the amorphous stage. The CNT-like free energy profile and the structural diversity suggest the existence of multiple active transition pathways for hydrate nucleation, and possibly also imply the near degeneracy in their free energy profiles among different pathways. Our results thus bring a new perspective to the long standing question of how hydrates crystallize.

  4. Free energy landscape and molecular pathways of gas hydrate nucleation.

    Science.gov (United States)

    Bi, Yuanfei; Porras, Anna; Li, Tianshu

    2016-12-07

    Despite the significance of gas hydrates in diverse areas, a quantitative knowledge of hydrate formation at a molecular level is missing. The impediment to acquiring this understanding is primarily attributed to the stochastic nature and ultra-fine scales of nucleation events, posing a great challenge for both experiment and simulation to explore hydrate nucleation. Here we employ advanced molecular simulation methods, including forward flux sampling (FFS), p B histogram analysis, and backward flux sampling, to overcome the limit of direct molecular simulation for exploring both the free energy landscape and molecular pathways of hydrate nucleation. First we test the half-cage order parameter (H-COP) which we developed for driving FFS, through conducting the p B histogram analysis. Our results indeed show that H-COP describes well the reaction coordinates of hydrate nucleation. Through the verified order parameter, we then directly compute the free energy landscape for hydrate nucleation by combining both forward and backward flux sampling. The calculated stationary distribution density, which is obtained independently of nucleation theory, is found to fit well against the classical nucleation theory (CNT). Subsequent analysis of the obtained large ensemble of hydrate nucleation trajectories show that although on average, hydrate formation is facilitated by a two-step like mechanism involving a gradual transition from an amorphous to a crystalline structure, there also exist nucleation pathways where hydrate crystallizes directly, without going through the amorphous stage. The CNT-like free energy profile and the structural diversity suggest the existence of multiple active transition pathways for hydrate nucleation, and possibly also imply the near degeneracy in their free energy profiles among different pathways. Our results thus bring a new perspective to the long standing question of how hydrates crystallize.

  5. Free energy landscape and molecular pathways of gas hydrate nucleation

    Energy Technology Data Exchange (ETDEWEB)

    Bi, Yuanfei; Porras, Anna; Li, Tianshu, E-mail: tsli@gwu.edu [Department of Civil and Environmental Engineering, George Washington University, Washington DC 20052 (United States)

    2016-12-07

    Despite the significance of gas hydrates in diverse areas, a quantitative knowledge of hydrate formation at a molecular level is missing. The impediment to acquiring this understanding is primarily attributed to the stochastic nature and ultra-fine scales of nucleation events, posing a great challenge for both experiment and simulation to explore hydrate nucleation. Here we employ advanced molecular simulation methods, including forward flux sampling (FFS), p{sub B} histogram analysis, and backward flux sampling, to overcome the limit of direct molecular simulation for exploring both the free energy landscape and molecular pathways of hydrate nucleation. First we test the half-cage order parameter (H-COP) which we developed for driving FFS, through conducting the p{sub B} histogram analysis. Our results indeed show that H-COP describes well the reaction coordinates of hydrate nucleation. Through the verified order parameter, we then directly compute the free energy landscape for hydrate nucleation by combining both forward and backward flux sampling. The calculated stationary distribution density, which is obtained independently of nucleation theory, is found to fit well against the classical nucleation theory (CNT). Subsequent analysis of the obtained large ensemble of hydrate nucleation trajectories show that although on average, hydrate formation is facilitated by a two-step like mechanism involving a gradual transition from an amorphous to a crystalline structure, there also exist nucleation pathways where hydrate crystallizes directly, without going through the amorphous stage. The CNT-like free energy profile and the structural diversity suggest the existence of multiple active transition pathways for hydrate nucleation, and possibly also imply the near degeneracy in their free energy profiles among different pathways. Our results thus bring a new perspective to the long standing question of how hydrates crystallize.

  6. Behaviour of gas production from type 3 hydrate reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Pooladi-Darvish, M. [Calgary Univ., AB (Canada). Dept. of Chemical and Petroleum Engineering]|[Fekete Associates Inc., Calgary, AB (Canada); Zatsepina, O. [Calgary Univ., AB (Canada). Dept. of Chemical and Petroleum Engineering; Hong, H. [Fekete Associates Inc., Calgary, AB (Canada)

    2008-07-01

    The possible role of gas hydrates as a potential energy resource was discussed with particular reference to methods for estimating the rate of gas production from hydrate reservoirs under different operating conditions. This paper presented several numerical simulations studies of gas production from type 3 hydrate reservoirs in 1-D and 2-D geometries. Type 3 reservoirs include gas production from hydrate-reservoirs that lie totally within the hydrate stability zone and are sandwiched by impermeable layers on top and bottom. The purpose of this study was to better understand hydrate decomposition by depressurization. The study questioned whether 1-D modeling of type 3 hydrate reservoirs is a reasonable approximation. It also determined whether gas rate increases or decreases with time. The important reservoir characteristics for determining the rate of gas production were identified. Last, the study determined how competition between fluid and heat flow affects hydrate decomposition. This paper also described the relation and interaction between the heat and fluid flow mechanisms in depressurization of type 3 hydrate reservoirs. All results of 1-D and 2-D numerical simulation and analyses were generated using the STARS simulator. It was shown that the rate of gas production depends on the initial pressure/temperature conditions and permeability of the hydrate bearing formation. A high peak rate may be achieved under favourable conditions, but this peak rate is obtained after an initial period where the rate of gas production increases with time. The heat transfer in the direction perpendicular to the direction of fluid flow is significant, requiring 2D modeling. The hydraulic diffusivity is low because of the low permeability of hydrate-bearing formations. This could result in competition between heat and fluid flow, thereby influencing the behaviour of decomposition. 6 refs., 3 tabs., 12 figs.

  7. Nasogastric Hydration in Infants with Bronchiolitis Less Than 2 Months of Age.

    Science.gov (United States)

    Oakley, Ed; Bata, Sonny; Rengasamy, Sharmila; Krieser, David; Cheek, John; Jachno, Kim; Babl, Franz E

    2016-11-01

    To determine whether nasogastric hydration can be used in infants less than 2 months of age with bronchiolitis, and characterize the adverse events profile of these infants compared with infants given intravenous (IV) fluid hydration. A descriptive retrospective cohort study of children with bronchiolitis under 2 months of age admitted for hydration at 3 centers over 3 bronchiolitis seasons was done. We determined type of hydration (nasogastric vs IV fluid hydration) and adverse events, intensive care unit admission, and respiratory support. Of 491 infants under 2 months of age admitted with bronchiolitis, 211 (43%) received nonoral hydration: 146 (69%) via nasogastric hydration and 65 (31%) via IV fluid hydration. Adverse events occurred in 27.4% (nasogastric hydration) and 23.1% (IV fluid hydration), difference of 4.3%; 95%CI (-8.2 to 16.9), P = .51. The majority of adverse events were desaturations (21.9% nasogastric hydration vs 21.5% IV fluid hydration, difference 0.4%; [-11.7 to 12.4], P = .95). There were no pulmonary aspirations in either group. Apneas and bradycardias were similar in each group. IV fluid hydration use was positively associated with intensive care unit admission (38.5% IV fluid hydration vs 19.9% nasogastric hydration; difference 18.6%, [5.1-32.1], P = .004); and use of ventilation support (27.7% IV fluid hydration vs 15.1% nasogastric hydration; difference 12.6 [0.3-23], P = .03). Fewer infants changed from nasogastric hydration to IV fluid hydration than from IV fluid hydration to nasogastric hydration (12.3% vs 47.7%; difference -35.4% [-49 to -22], P hydration can be used in the majority of young infants admitted with bronchiolitis. Nasogastric hydration and IV fluid hydration had similar rates of complications. Copyright © 2016 Elsevier Inc. All rights reserved.

  8. A unified approach for description of gas hydrate formation kinetics in the presence of kinetic promoters in gas hydrate converters

    International Nuclear Information System (INIS)

    ZareNezhad, Bahman; Varaminian, Farshad

    2013-01-01

    Highlights: • A unified kinetic model for description of promoted and non-promoted gas hydrate formation processes is presented. • Effects of impeller speed, promoter concentration and different kinetic promoters are investigated. • A unique region of gas hydrate formation is identified regarding gas hydrate formation processes. • The proposed model is useful for understanding the behavior of gas hydrate formation processes and design of GTH converters. - Abstract: The kinetic promoters have found wide applications in enhancing the rate of energy conversion and storage via gas hydrate formation processes. Effects of different kinetic promoters such as anionic surfactants sodium dodecyl sulfate (SDS), dodecylbenzene sulfonic acid (DBSA), and sodium dodecyl benzene sulfonate (SDBS); cationic surfactants, Cetyl trimethyl ammonium bromide (CTAB), dodecyl trimethyl ammonium bromide (DTAB) and non-ionic surfactants, alkylpolyglucoside (APG), dodecyl polysaccharide glycoside (DPG), TritonX-100 (TX100) on methane (CH 4 ), ethane (C 2 H 6 ) and propane (C 3 H 8 ) gas hydrate formation processes are investigated in this work. A macroscopic kinetic model based on the time variations of reaction chemical potential is also presented for global description of gas hydrate formation processes. Experimental gas hydrate formation data are employed to validate the proposed kinetic model. Effects of promoter’s concentrations and agitation intensities on the gas consumption profiles are also investigated. A universal correlation and a unified kinetic map have been proposed for macroscopic description of gas hydrate formation kinetics in the presence or absence of kinetic promoters. According to the presented unified kinetic map, a unique region of gas hydrate formation is identified for the first time. For negligible amounts of kinetic promoters, the presented region disappears and approaches to a unique path at high agitation intensities. The presented unified approach is

  9. Prospects of gas hydrate presence in the Chukchi sea

    Directory of Open Access Journals (Sweden)

    Т. В. Матвеева

    2017-08-01

    Full Text Available The purpose of this study is to forecast the scale and distribution character of gas hydrate stability zone in the Chukchi Sea under simulated natural conditions and basing on these results to estimate resource potential of gas hydrates within this area. Three types of stability zone have been identified. A forecast map of gas hydrate environment and potentially gas hydrate-bearing water areas in the Chukchi Sea has been plotted to a scale of 1:5 000 000. Mapping of gas hydrate stability zone allowed to give a justified forecast based on currently available data on geologic, fluid dynamic, cryogenic, geothermal and pressure-temperature conditions of gas hydrate formation in the Chukchi Sea. It is the first forecast of such kind that focuses on formation conditions for hydrates of various types and compositions in the Arctic seas offshore Russia. Potential amount of gas, stored beneath the Chukchi Sea in the form of hydrates, is estimated based on mapping of their stability zone and falls into the interval of 7·1011-11.8·1013 m3.

  10. Exploring the solid-form landscape of pharmaceutical hydrates

    DEFF Research Database (Denmark)

    Raijada, Dharaben Kaushikkumar; Bond, Andrew; Larsen, Flemming Hofmann

    2013-01-01

    To understand the transformation pathways amongst anhydrate/hydrate solid forms of sodium naproxen and to highlight the importance of a polymorphic dihydrate within this context.......To understand the transformation pathways amongst anhydrate/hydrate solid forms of sodium naproxen and to highlight the importance of a polymorphic dihydrate within this context....

  11. Hydration behaviour of synthetic saponite at variable relative humidity

    Indian Academy of Sciences (India)

    Hydration behaviour of synthetic saponite was examined by X-ray powder diffraction simulation at various relative humidities (RH). The basal spacing of the Ca-saponite increased stepwise with increase in RH. The (00) reflections observed reflect single or dual hydration states of smectite. Quasi-rational, intermediate, or ...

  12. The effect of stereochemistry on carbohydrate hydration in aqueous solutions

    NARCIS (Netherlands)

    Galema, Saskia Alexandra

    1992-01-01

    Although-carbohydrates are widely used, not much is known about the stereochemical aspects of hydration of carbohydrates. For D-aldohexoses, for example, there are eight different stereoisomers. Just how the hydroxy topology of a carbohydrate molecule influences the hydration behaviour in water is

  13. Spectroscopic determination of optimal hydration time of zircon surface

    Energy Technology Data Exchange (ETDEWEB)

    Ordonez R, E. [ININ, Departamento de Quimica, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico); Garcia R, G. [Instituto Tecnologico de Toluca, Division de Estudios del Posgrado, Av. Tecnologico s/n, Ex-Rancho La Virgen, 52140 Metepec, Estado de Mexico (Mexico); Garcia G, N., E-mail: eduardo.ordonez@inin.gob.m [Universidad Autonoma del Estado de Mexico, Facultad de Quimica, Av. Colon y Av. Tollocan, 50180 Toluca, Estado de Mexico (Mexico)

    2010-07-01

    When a mineral surface is immersed in an aqueous solution, it develops and electric charge produced by the amphoteric dissociation of hydroxyl groups created by the hydration of the solid surface. This is one influential surface property. The complete hydration process takes a time which is specific for each mineral species. The knowledge of the aqueous solution contact time for complete surface hydration is mandatory for further surface phenomena studies. This study deals with the optimal hydration time of the raw zircon (ZrSiO{sub 4}) surface comparing the classical potentiometric titrations with a fluorescence spectroscopy technique. The latter is easy and rea liable as it demands only one sample batch to determine the optimal time to ensure a total hydration of the zircon surface. The analytical results of neutron activation analysis showed the presence of trace quantities of Dy{sup 3+}, Eu{sup 3+} and Er{sup 3} in the bulk of zircon. The Dy{sup 3+} is structured in the zircon crystalline lattice and undergoes the same chemical reactions as zircon. Furthermore, the Dy{sup 3+} has a good fluorescent response whose intensity is enhanced by hydration molecules. The results show that, according to the potentiometric analysis, the hydration process for each batch (at least 8 sample batches) takes around 2 h, while the spectrometric method indicates only 5 minutes from only one batch. Both methods showed that the zircon surface have a 16 h optimal hydration time. (Author)

  14. Spectroscopic determination of optimal hydration time of zircon surface

    International Nuclear Information System (INIS)

    Ordonez R, E.; Garcia R, G.; Garcia G, N.

    2010-01-01

    When a mineral surface is immersed in an aqueous solution, it develops and electric charge produced by the amphoteric dissociation of hydroxyl groups created by the hydration of the solid surface. This is one influential surface property. The complete hydration process takes a time which is specific for each mineral species. The knowledge of the aqueous solution contact time for complete surface hydration is mandatory for further surface phenomena studies. This study deals with the optimal hydration time of the raw zircon (ZrSiO 4 ) surface comparing the classical potentiometric titrations with a fluorescence spectroscopy technique. The latter is easy and rea liable as it demands only one sample batch to determine the optimal time to ensure a total hydration of the zircon surface. The analytical results of neutron activation analysis showed the presence of trace quantities of Dy 3+ , Eu 3+ and Er 3 in the bulk of zircon. The Dy 3+ is structured in the zircon crystalline lattice and undergoes the same chemical reactions as zircon. Furthermore, the Dy 3+ has a good fluorescent response whose intensity is enhanced by hydration molecules. The results show that, according to the potentiometric analysis, the hydration process for each batch (at least 8 sample batches) takes around 2 h, while the spectrometric method indicates only 5 minutes from only one batch. Both methods showed that the zircon surface have a 16 h optimal hydration time. (Author)

  15. Evaluation of Nutritional Status and Hydration in Patients on Chronic ...

    African Journals Online (AJOL)

    Background: Nutrition and hydration of the dialysis patients have major influences on the outcomes of chronic hemodialysis. Purpose: To characterize the states of nutrition and hydration in patients on chronic hemodialysis at Jos University Teaching Hospital (JUTH) and to evaluate the usefulness of measurements by ...

  16. Phase equilibrium condition of marine carbon dioxide hydrate

    International Nuclear Information System (INIS)

    Sun, Shi-Cai; Liu, Chang-Ling; Ye, Yu-Guang

    2013-01-01

    Highlights: ► CO 2 hydrate phase equilibrium was studied in simulated marine sediments. ► CO 2 hydrate equilibrium temperature in NaCl and submarine pore water was depressed. ► Coarse-grained silica sand does not affect CO 2 hydrate phase equilibrium. ► The relationship between equilibrium temperature and freezing point was discussed. - Abstract: The phase equilibrium of ocean carbon dioxide hydrate should be understood for ocean storage of carbon dioxide. In this paper, the isochoric multi-step heating dissociation method was employed to investigate the phase equilibrium of carbon dioxide hydrate in a variety of systems (NaCl solution, submarine pore water, silica sand + NaCl solution mixture). The experimental results show that the depression in the phase equilibrium temperature of carbon dioxide hydrate in NaCl solution is caused mainly by Cl − ion. The relationship between the equilibrium temperature and freezing point in NaCl solution was discussed. The phase equilibrium temperature of carbon dioxide hydrate in submarine pore water is shifted by −1.1 K to lower temperature region than that in pure water. However, the phase equilibrium temperature of carbon dioxide hydrate in mixture samples of coarsed-grained silica sand and NaCl solution is in agreement with that in NaCl solution with corresponding concentrations. The relationship between the equilibrium temperature and freezing point in mixture samples was also discussed.

  17. Unexpected Hydration of a Triple Bond During DNA Synthesis

    DEFF Research Database (Denmark)

    Fatthalla, Maha I.; Pedersen, Erik B.

    2016-01-01

    acidic conditions, polarizes the triple bond in the intercalator and this makes hydration of the triple bond possible during the DNA synthesis and an oligonucleotide with 1-(indol-3-yl)-2-(pyren-1-yl)ethanone as the intercalator is formed. Insertion of the unhydrated and hydrated linker systems gave...

  18. Solubility data for cement hydrate phases (25oC)

    International Nuclear Information System (INIS)

    Atkins, M.; Glasser, F.P.; Kindness, A.; Macphee, D.E.

    1991-05-01

    Solubility measurements were performed on most of the more thermodynamically-stable cement hydrate phases, at 25 o C. The results for each hydrate phase are summarised in the form of datasheets. Solubility properties are discussed, and where possible a K sp value is calculated. The data are compared with the data in the literature. (author)

  19. Potential natural gas hydrates resources in Indian Offshore areas

    Digital Repository Service at National Institute of Oceanography (India)

    Sethi, A.K.; Sathe, A.V.; Ramana, M.V.

    (geophysical proxies of gas hydrates). A qualitative map prepared based on the inferred BSRs brought out a deepwater area of about 80,000 sq.km unto 3000 m isobath as favourable for gas hydrate occurrence. Methodology for reprocessing of seismic data...

  20. Gas hydrate inhibition by perturbation of liquid water structure

    Science.gov (United States)

    Sa, Jeong-Hoon; Kwak, Gye-Hoon; Han, Kunwoo; Ahn, Docheon; Lee, Kun-Hong

    2015-06-01

    Natural gas hydrates are icy crystalline materials that contain hydrocarbons, which are the primary energy source for this civilization. The abundance of naturally occurring gas hydrates leads to a growing interest in exploitation. Despite their potential as energy resources and in industrial applications, there is insufficient understanding of hydrate kinetics, which hinders the utilization of these invaluable resources. Perturbation of liquid water structure by solutes has been proposed to be a key process in hydrate inhibition, but this hypothesis remains unproven. Here, we report the direct observation of the perturbation of the liquid water structure induced by amino acids using polarized Raman spectroscopy, and its influence on gas hydrate nucleation and growth kinetics. Amino acids with hydrophilic and/or electrically charged side chains disrupted the water structure and thus provided effective hydrate inhibition. The strong correlation between the extent of perturbation by amino acids and their inhibition performance constitutes convincing evidence for the perturbation inhibition mechanism. The present findings bring the practical applications of gas hydrates significantly closer, and provide a new perspective on the freezing and melting phenomena of naturally occurring gas hydrates.

  1. Putting the Deep Biosphere and Gas Hydrates on the Map

    Science.gov (United States)

    Sikorski, Janelle J.; Briggs, Brandon R.

    2016-01-01

    Microbial processes in the deep biosphere affect marine sediments, such as the formation of gas hydrate deposits. Gas hydrate deposits offer a large source of natural gas with the potential to augment energy reserves and affect climate and seafloor stability. Despite the significant interdependence between life and geology in the ocean, coverage…

  2. NMR Studies of Protein Hydration and Protein-Ligand Interactions

    Science.gov (United States)

    Chong, Yuan

    Water on the surface of a protein is called hydration water. Hydration water is known to play a crucial role in a variety of biological processes including protein folding, enzymatic activation, and drug binding. Although the significance of hydration water has been recognized, the underlying mechanism remains far from being understood. This dissertation employs a unique in-situ nuclear magnetic resonance (NMR) technique to study the mechanism of protein hydration and the role of hydration in alcohol-protein interactions. Water isotherms in proteins are measured at different temperatures via the in-situ NMR technique. Water is found to interact differently with hydrophilic and hydrophobic groups on the protein. Water adsorption on hydrophilic groups is hardly affected by the temperature, while water adsorption on hydrophobic groups strongly depends on the temperature around 10 C, below which the adsorption is substantially reduced. This effect is induced by the dramatic decrease in the protein flexibility below 10 C. Furthermore, nanosecond to microsecond protein dynamics and the free energy, enthalpy, and entropy of protein hydration are studied as a function of hydration level and temperature. A crossover at 10 C in protein dynamics and thermodynamics is revealed. The effect of water at hydrophilic groups on protein dynamics and thermodynamics shows little temperature dependence, whereas water at hydrophobic groups has stronger effect above 10 C. In addition, I investigate the role of water in alcohol binding to the protein using the in-situ NMR detection. The isotherms of alcohols are first measured on dry proteins, then on proteins with a series of controlled hydration levels. The free energy, enthalpy, and entropy of alcohol binding are also determined. Two distinct types of alcohol binding are identified. On the one hand, alcohols can directly bind to a few specific sites on the protein. This type of binding is independent of temperature and can be

  3. Changes in hydration status of elite Olympic class sailors in different climates and the effects of different fluid replacement beverages

    Science.gov (United States)

    2013-01-01

    Background Olympic class sailing poses physiological challenges similar to other endurance sports such as cycling or running, with sport specific challenges of limited access to nutrition and hydration during competition. As changes in hydration status can impair sports performance, examining fluid consumption patterns and fluid/electrolyte requirements of Olympic class sailors is necessary to develop specific recommendations for these elite athletes. The purpose of this study was to examine if Olympic class sailors could maintain hydration status with self-regulated fluid consumption in cold conditions and the effect of fixed fluid intake on hydration status in warm conditions. Methods In our cold condition study (CCS), 11 elite Olympic class sailors were provided ad libitum access to three different drinks. Crystal Light (control, C); Gatorade (experimental control, G); and customized sailing-specific Infinit (experimental, IN) (1.0:0.22 CHO:PRO), were provided on three separate training days in cold 7.1°C [4.2 – 11.3]. Our warm condition study (WCS) examined the effect of fixed fluid intake (11.5 mL.kg.-1.h-1) of C, G and heat-specific experimental Infinit (INW)(1.0:0.074 CHO:PRO) on the hydration status of eight elite Olympic Laser class sailors in 19.5°C [17.0 - 23.3]. Both studies used a completely random design. Results In CCS, participants consumed 802 ± 91, 924 ± 137 and 707 ± 152 mL of fluid in each group respectively. This did not change urine specific gravity, but did lead to a main effect for time for body mass (p warm condition training, hydration status was maintained by preventing changes in body mass and urine specific gravity. PMID:23432855

  4. Theoretical description of biomolecular hydration - Application to A-DNA

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, A.E.; Hummer, G. [Los Alamos National Laboratory, NM (United States); Soumpasis, D.M. [Max Planck Inst. for Biophysical Chemistry, Goettingen (Germany)

    1994-12-31

    The local density of water molecules around a biomolecule is constructed from calculated two- and three-points correlation functions of polar solvents in water using a Potential-of-Mean-Force (PMF) expansion. As a simple approximation, the hydration of all polar (including charged) groups in a biomolecule is represented by the hydration of water oxygen in bulk water, and the effect of non-polar groups on hydration are neglected, except for excluded volume effects. Pair and triplet correlation functions are calculated by molecular dynamics simulations. We present calculations of the structural hydration for ideal A-DNA molecules with sequences [d(CG){sub 5}]{sub 2} and [d(C{sub 5}G{sub 5})]{sub 2}. We find that this method can accurately reproduce the hydration patterns of A-DNA observed in neutron diffraction experiments on oriented DNA fibers.

  5. Seismic-Scale Rock Physics of Methane Hydrate

    Energy Technology Data Exchange (ETDEWEB)

    Amos Nur

    2009-01-08

    We quantify natural methane hydrate reservoirs by generating synthetic seismic traces and comparing them to real seismic data: if the synthetic matches the observed data, then the reservoir properties and conditions used in synthetic modeling might be the same as the actual, in-situ reservoir conditions. This approach is model-based: it uses rock physics equations that link the porosity and mineralogy of the host sediment, pressure, and hydrate saturation, and the resulting elastic-wave velocity and density. One result of such seismic forward modeling is a catalogue of seismic reflections of methane hydrate which can serve as a field guide to hydrate identification from real seismic data. We verify this approach using field data from known hydrate deposits.

  6. Gas hydrate phase equilibria measurement techniques and phase rule considerations

    International Nuclear Information System (INIS)

    Beltran, Juan G.; Bruusgaard, Hallvard; Servio, Phillip

    2012-01-01

    Highlights: → Inconsistencies found in hydrate literature. → Clarification to the number of variables needed to satisfy and justify equilibrium data. → Application of phase rule to mixed hydrate systems. → Thermodynamically consistent format to present data. - Abstract: A brief review of the Gibbs phase rule for non-reacting systems and its correct application to clathrate hydrates is presented. Clarification is provided for a common mistake found in hydrate phase-equilibria literature, whereby initial compositions are used as intensive variables to satisfy the Gibbs phase rule instead of the equilibrium values. The system of (methane + carbon dioxide + water) under (hydrate + liquid + vapor) equilibrium is used as a case study to illustrate key points and suggestions to improve experimental techniques are proposed.

  7. Hydration of Portland cement with additions of calcium sulfoaluminates

    International Nuclear Information System (INIS)

    Le Saoût, Gwenn; Lothenbach, Barbara; Hori, Akihiro; Higuchi, Takayuki; Winnefeld, Frank

    2013-01-01

    The effect of mineral additions based on calcium aluminates on the hydration mechanism of ordinary Portland cement (OPC) was investigated using isothermal calorimetry, thermal analysis, X-ray diffraction, scanning electron microscopy, solid state nuclear magnetic resonance and pore solution analysis. Results show that the addition of a calcium sulfoaluminate cement (CSA) to the OPC does not affect the hydration mechanism of alite but controls the aluminate dissolution. In the second blend investigated, a rapid setting cement, the amorphous calcium aluminate reacts very fast to ettringite. The release of aluminum ions strongly retards the hydration of alite but the C–S–H has a similar composition as in OPC with no additional Al to Si substitution. As in CSA–OPC, the aluminate hydration is controlled by the availability of sulfates. The coupling of thermodynamic modeling with the kinetic equations predicts the amount of hydrates and pore solution compositions as a function of time and validates the model in these systems.

  8. Thermal Stability and Proton Conductivity of Rare Earth Orthophosphate Hydrates

    DEFF Research Database (Denmark)

    Anfimova, Tatiana; Li, Qingfeng; Jensen, Jens Oluf

    2014-01-01

    as the rhabdophane structure is preserved. The bound hydrate water is accommodated in the rhabdophane structure and is stable at temperatures of up to 650 oC. The thermal stability of the hydrate water and the phosphate structure are of significance for the proton conductivity. The LaPO4·0.6H2O and NdPO4•0.5H2O......Hydrated orthophosphate powders of three rare earth metals, lanthanum, neodymium and gadolinium, were prepared and studied as potential proton conducting materials for intermediate temperature electrochemical applications. The phosphates undergo a transformation from the rhabdophane structure...... to the monazite structure upon dehydration. The thermal stability of the hydrate is studied and found to contain water of two types, physically adsorbed and structurally bound hydrate water. The adsorbed water is correlated to the specific surface area and can be reversibly recovered when dehydrated as long...

  9. Water Dynamics in the Hydration Shells of Biomolecules

    Science.gov (United States)

    2017-01-01

    The structure and function of biomolecules are strongly influenced by their hydration shells. Structural fluctuations and molecular excitations of hydrating water molecules cover a broad range in space and time, from individual water molecules to larger pools and from femtosecond to microsecond time scales. Recent progress in theory and molecular dynamics simulations as well as in ultrafast vibrational spectroscopy has led to new and detailed insight into fluctuations of water structure, elementary water motions, electric fields at hydrated biointerfaces, and processes of vibrational relaxation and energy dissipation. Here, we review recent advances in both theory and experiment, focusing on hydrated DNA, proteins, and phospholipids, and compare dynamics in the hydration shells to bulk water. PMID:28248491

  10. Theoretical description of biomolecular hydration - Application to A-DNA

    International Nuclear Information System (INIS)

    Garcia, A.E.; Hummer, G.; Soumpasis, D.M.

    1994-01-01

    The local density of water molecules around a biomolecule is constructed from calculated two- and three-points correlation functions of polar solvents in water using a Potential-of-Mean-Force (PMF) expansion. As a simple approximation, the hydration of all polar (including charged) groups in a biomolecule is represented by the hydration of water oxygen in bulk water, and the effect of non-polar groups on hydration are neglected, except for excluded volume effects. Pair and triplet correlation functions are calculated by molecular dynamics simulations. We present calculations of the structural hydration for ideal A-DNA molecules with sequences [d(CG) 5 ] 2 and [d(C 5 G 5 )] 2 . We find that this method can accurately reproduce the hydration patterns of A-DNA observed in neutron diffraction experiments on oriented DNA fibers

  11. Acute Kidney Injury by Radiographic Contrast Media: Pathogenesis and Prevention

    Science.gov (United States)

    Faga, Teresa; Pisani, Antonio; Michael, Ashour

    2014-01-01

    It is well known that iodinated radiographic contrast media may cause kidney dysfunction, particularly in patients with preexisting renal impairment associated with diabetes. This dysfunction, when severe, will cause acute renal failure (ARF). We may define contrast-induced Acute Kidney Injury (AKI) as ARF occurring within 24–72 hrs after the intravascular injection of iodinated radiographic contrast media that cannot be attributed to other causes. The mechanisms underlying contrast media nephrotoxicity have not been fully elucidated and may be due to several factors, including renal ischaemia, particularly in the renal medulla, the formation of reactive oxygen species (ROS), reduction of nitric oxide (NO) production, and tubular epithelial and vascular endothelial injury. However, contrast-induced AKI can be prevented, but in order to do so, we need to know the risk factors. We have reviewed the risk factors for contrast-induced AKI and measures for its prevention, providing a long list of references enabling readers to deeply evaluate them both. PMID:25197639

  12. The Effect of Compaction Force on the Transition to Hydrate of Anhydrous Aripiprazole.

    Science.gov (United States)

    Togo, Taichiro; Taniguchi, Toshiya; Nakata, Yoshitaka

    2018-01-01

    Aripiprazole (APZ) is used to treat schizophrenia and is administered as a tablet containing the anhydrous form of APZ. In this study, the effect of compaction force on the crystal form transition was investigated. The crystalline state was observed by X-ray diffraction (XRD). APZ Anhydrous Form II was compacted into tablets. The XRD intensity of anhydrous APZ became lower with higher compressive force. The degree of crystallinity decreased with the compaction force. The powder and the compacted tablets of anhydrous APZ were stored for one week under 60°C and 75% relative humidity. The powder showed no crystal form transition after storage. For the tablets, however, XRD peaks of APZ hydrate were observed after storage. The tablets compacted with higher force showed the higher XRD diffraction intensity of hydrate form. We concluded that the crystallinity reduction of APZ Anhydrous Form II by compaction caused and accelerated the transition to hydrate under high temperature and humidity conditions. In order to manufacture crystallographically stable tablets containing anhydrous APZ, it is important to prevent this crystallinity reduction during compaction.

  13. India National Gas Hydrate Program Expedition 02 Technical Contributions

    Science.gov (United States)

    Collett, T. S.; Kumar, P.; Shukla, K. M.; Nagalingam, J.; Lall, M. V.; Yamada, Y.; Schultheiss, P. J.; Holland, M.; Waite, W. F.

    2017-12-01

    The National Gas Hydrate Program Expedition 02 (NGHP-02) was conducted from 3-March-2015 to 28-July-2015 off the eastern coast of India. The primary objective of this expedition was the exploration and discovery of highly saturated gas hydrate occurrences in sand reservoirs that would be targets of future production testing. The first 2 months of the expedition were dedicated to logging while drilling (LWD) operations with a total of 25 holes being drilled and logged. The next 3 months were dedicated to coring operations at 10 of the most promising sites. NGHP-02 downhole logging, coring and formation pressure testing have confirmed the presence of large, highly saturated, gas hydrate accumulations in coarse-grained sand-rich depositional systems throughout the Krishna-Godavari Basin within the regions defined during NGHP-02 as Area-B, Area-C, and Area-E. The nature of the discovered gas hydrate occurrences closely matched pre-drill predictions, confirming the project developed depositional models for the sand-rich depositional facies in the Krishna-Godavari and Mahanadi Basins. The existence of a fully developed gas hydrate petroleum system was established in Area-C of the Krishna-Godavari Basin with the discovery of a large slope-basin interconnected depositional system, including a sand-rich, gas-hydrate-bearing channel-levee prospect at Sites NGHP-02-08 and -09. The acquisition of closely spaced LWD and core holes in the Area-B L1 Block gas hydrate accumulation have provided one of the most complete three-dimensional petrophysical-based views of any known gas hydrate reservoir system in the world. It was concluded that Area-B and Area-C in the area of the greater Krishna-Godavari Basin contain important world-class gas hydrate accumulations and represent ideal sites for consideration of future gas hydrate production testing.

  14. Skin Hydration Assessment through Modern Non-Invasive Bioengineering Technologies.

    Science.gov (United States)

    Constantin, Maria-Magdalena; Poenaru, Elena; Poenaru, Calin; Constantin, Traian

    2014-03-01

    Non-invasive bioengineering technologies continuously discovered and developed in recent decades provide a significant input to research development and remarkably contribute to the improvement of medical education and care to our patients. Assessing skin hydration by using the capacitance method for a group of patients with allergic contact dermatitis versus healthy subjects, before and after applying a moisturiser (assessing the immediate and long-term effectiveness of hydration). For both groups, but especially for the patients with dry skin, there was a clear improvement of hydration, statistically significant after applying the moisturiser. In the case of the patients with allergic contact dermatitis, hydration was at a maximum immediately after the first application, and then maintained an increased level after 7 and 28 days, respectively. In the healthy subjects, the increase in hydration was lower, but progressive. The moisturiser determined an increase in hydration for all age groups, but those who showed the most obvious effect were the young adults (18-29 years old) with an increase of 19.9%.The maintenance effect of hydration lasted for 28 days, while the improvement was important for allergic skin (17.1%) and significant for healthy skin (10.9%). The assessment of epidermal hydration performed by using the corneometer showed very good hydration of the stratum corneum for both groups studied, with immediate and long-term effect. This study also showed that the degree of skin hydration was inversely proportional with age. The corneometer is easy to use, efficient and widely utilised in international studies for measurements in healthy or pathological conditions, for quantitative assessment of the effectiveness of various preparations intended for application to the skin surface, under well-controlled and standardised conditions.

  15. Reflective terahertz (THz) imaging: system calibration using hydration phantoms

    Science.gov (United States)

    Bajwa, Neha; Garritano, James; Lee, Yoon Kyung; Tewari, Priyamvada; Sung, Shijun; Maccabi, Ashkan; Nowroozi, Bryan; Babakhanian, Meghedi; Sanghvi, Sajan; Singh, Rahul; Grundfest, Warren; Taylor, Zachary

    2013-02-01

    Terahertz (THz) hydration sensing continues to gain traction in the medical imaging community due to its unparalleled sensitivity to tissue water content. Rapid and accurate detection of fluid shifts following induction of thermal skin burns as well as remote corneal hydration sensing have been previously demonstrated in vivo using reflective, pulsed THz imaging. The hydration contrast sensing capabilities of this technology were recently confirmed in a parallel 7 Tesla Magnetic Resonance (MR) imaging study, in which burn areas are associated with increases in local mobile water content. Successful clinical translation of THz sensing, however, still requires quantitative assessments of system performance measurements, specifically hydration concentration sensitivity, with tissue substitutes. This research aims to calibrate the sensitivity of a novel, reflective THz system to tissue water content through the use of hydration phantoms for quantitative comparisons of THz hydration imagery.Gelatin phantoms were identified as an appropriate tissue-mimicking model for reflective THz applications, and gel composition, comprising mixtures of water and protein, was varied between 83% to 95% hydration, a physiologically relevant range. A comparison of four series of gelatin phantom studies demonstrated a positive linear relationship between THz reflectivity and water concentration, with statistically significant hydration sensitivities (p hydration). The THz-phantom interaction is simulated with a three-layer model using the Transfer Matrix Method with agreement in hydration trends. Having demonstrated the ability to accurately and noninvasively measure water content in tissue equivalent targets with high sensitivity, reflective THz imaging is explored as a potential tool for early detection and intervention of corneal pathologies.

  16. Advanced Gas Hydrate Reservoir Modeling Using Rock Physics

    Energy Technology Data Exchange (ETDEWEB)

    McConnell, Daniel

    2017-12-30

    Prospecting for high saturation gas hydrate deposits can be greatly aided with improved approaches to seismic interpretation and especially if sets of seismic attributes can be shown as diagnostic or direct hydrocarbon indicators for high saturation gas hydrates in sands that would be of most interest for gas hydrate production.

    A large 3D seismic data set in the deep water Eastern Gulf of Mexico was screened for gas hydrates using a set of techniques and seismic signatures that were developed and proven in the Central deepwater Gulf of Mexico in the DOE Gulf of Mexico Joint Industry Project JIP Leg II in 2009 and recently confirmed with coring in 2017.

    A large gas hydrate deposit is interpreted in the data where gas has migrated from one of the few deep seated faults plumbing the Jurassic hydrocarbon source into the gas hydrate stability zone. The gas hydrate deposit lies within a flat-lying within Pliocene Mississippi Fan channel that was deposited outboard in a deep abyssal environment. The uniform architecture of the channel aided the evaluation of a set of seismic attributes that relate to attenuation and thin-bed energy that could be diagnostic of gas hydrates. Frequency attributes derived from spectral decomposition also proved to be direct hydrocarbon indicators by pseudo-thickness that could be only be reconciled by substituting gas hydrate in the pore space. The study emphasizes that gas hydrate exploration and reservoir characterization benefits from a seismic thin bed approach.

  17. Ultrasonic sound speed of hydrating calcium sulphate hemihydrate; part 2, the correlation of sound velocity to hydration degree

    NARCIS (Netherlands)

    de Korte, A.C.J.; Brouwers, Jos; Fischer, H.B; Matthes, C.; Beuthan, C.

    2011-01-01

    In this article the sound velocity through a mix is correlated to the hydration degree of the mix. Models are presented predicting the sound velocity through fresh slurries and hardened products. These two states correspond to the starting and finishing point of the hydration process. The present

  18. Ultrasonic sound speed of hydrating calcium sulphate hemihydrate; Part 2, The correlation of sound velocity to hydration degree

    NARCIS (Netherlands)

    Korte, de A.C.J.; Brouwers, H.J.H.; Fischer, H.B.; Mattes, Chr.; Beutha, C.

    2011-01-01

    In this article the sound velocity through a mix is correlated to the hydration degree of the mix. Models are presented predicting the sound velocity through fresh slurries and hardened products. These two states correspond to the starting and finishing point of the hydration process. The present

  19. Geologic implications of gas hydrates in the offshore of India: Results of the National Gas Hydrate Program Expedition 01

    Digital Repository Service at National Institute of Oceanography (India)

    Collett, T.S.; Boswell, R.; Cochran, J.R.; Kumar, P.; Lall, M.; Mazumdar, A.; Ramana, M.V.; Ramprasad, T.; Riedel, M.; Sain, K.; Sathe, A.V.; Vishwanath, K.; NGHP Expedition 01 Scientific Party

    in Japan (Tsujii et al., 2009) and in the Gulf of Mexico (Boswell et al., 2012a) and the pace of gas-hydrate energy-assessment projects continues to accelerate. Beyond a future energy resource, gas hydrates may in some cases represent a significant...

  20. A new aluminium-hydrate species in hydrated Portland cements characterized by 27Al and 29Si MAS NMR spectroscopy

    International Nuclear Information System (INIS)

    Andersen, Morten Daugaard; Jakobsen, Hans J.; Skibsted, Jorgen

    2006-01-01

    Recent 27 Al MAS NMR studies of hydrated Portland cements and calcium-silicate-hydrate (C-S-H) phases have shown a resonance from Al in octahedral coordination, which cannot be assigned to the well-known aluminate species in hydrated Portland cements. This resonance, which exhibits the isotropic chemical shift δ iso = 5.0 ppm and the quadrupole product parameter P Q = 1.2 MHz, has been characterized in detail by 27 Al MAS and 27 Al{ 1 H} CP/MAS NMR for different hydrated white Portland cements and C-S-H phases. These experiments demonstrate that the resonance originates from an amorphous or disordered aluminate hydrate which contains Al(OH) 6 3- or O x Al(OH) 6-x (3+x)- units. The formation of the new aluminate hydrate is related to the formation of C-S-H at ambient temperatures, however, it decomposes by thermal treatment at temperatures of 70-90 o C. From the experiments in this work it is proposed that the new aluminate hydrate is either an amorphous/disordered aluminate hydroxide or a calcium aluminate hydrate, produced as a separate phase or as a nanostructured surface precipitate on the C-S-H phase. Finally, the possibilities of Al 3+ for Ca 2+ substitution in the principal layers and interlayers of the C-S-H structure are discussed

  1. Face Masks for Noninvasive Ventilation: Fit, Excess Skin Hydration, and Pressure Ulcers.

    Science.gov (United States)

    Visscher, Marty O; White, Cynthia C; Jones, Jennifer M; Cahill, Thomas; Jones, Donna C; Pan, Brian S

    2015-11-01

    Pressure ulcers (stages III and IV) are serious safety events (ie, never events). Healthcare institutions are no longer reimbursed for costs to care for affected patients. Medical devices are the leading cause of pediatric pressure ulcers. Face masks for noninvasive ventilation were associated with a high percentage of pressure ulcers at our institution. A prospective cohort study investigated factors contributing to pressure ulcer development in 50 subjects using face masks for noninvasive ventilation. Color imaging, 3-dimensional surface imaging, and skin hydration measurements were used to identify early skin compromise and evaluate 3 interventions to reduce trauma: (1) a silicone foam dressing, (2) a water/polyethylene oxide hydrogel dressing, and (3) a flexible cloth mask. A novel mask fit technique was used to examine the impact of fit on the potential for skin compromise. Fifty subjects age 10.4 ± 9.1 y participated with color images for 22, hydration for 34, and mask fit analysis for 16. Of these, 69% had diagnoses associated with craniofacial anomalies. Stage I pressure ulcers were the most common injury. Skin hydration difference was 317 ± 29 for sites with erythema versus 75 ± 28 for sites without erythema (P skin erythema and pressure ulcers. This fit method is currently being utilized to select best-fit masks from available options, to identify the potential areas of increased tissue pressure, and to prevent skin injuries and their complications. Improvement of mask fit is an important priority for improving respiratory outcomes. Strategies to maintain normal skin hydration are important for protecting tissue integrity. Copyright © 2015 by Daedalus Enterprises.

  2. A coupled THMC model of a heating and hydration laboratory experiment in unsaturated compacted FEBEX bentonite

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, L.; Samper, J.; Montenegro, L.; Fernandez, A.M.

    2010-05-01

    Unsaturated compacted bentonite is foreseen by several countries as a backfill and sealing material in high-level radioactive waste repositories. The strong interplays between thermal (T), hydrodynamic (H), mechanical (M) and chemical (C) processes during the hydration stage of a repository call for fully coupled THMC models. Validation of such THMC models is prevented by the lack of comprehensive THMC experiments and the difficulties of experimental methods to measure accurately the chemical composition of bentonite porewater. We present here a non-isothermal multiphase flow and multicomponent reactive solute transport model for a deformable medium of a heating and hydration experiment performed on a sample of compacted FEBEX bentonite. Besides standard solute transport and geochemical processes, the model accounts for solute cross diffusion and thermal and chemical osmosis. Bentonite swelling is solved with a state-surface approach. The THM model is calibrated with transient temperature, water content and porosity data measured at the end of the experiment. The reactive transport model is calibrated with porewater chemical data derived from aqueous extract data. Model results confirm that thermal osmosis is relevant for the hydration of FEBEX bentonite while chemical osmosis can be safely neglected. Dilution and evaporation are the main processes controlling the concentration of conservative species. Dissolved cations are mostly affected by calcite dissolution-precipitation and cation exchange reactions. Dissolved sulphate is controlled by gypsum/anhydrite dissolution-precipitation. pH is mostly buffered by protonation/deprotonation via surface complexation. Computed concentrations agree well with inferred aqueous extract data at all sections except near the hydration boundary where cation data are affected by a sampling artifact. The fit of Cl{sup -} data is excellent except for the data near the heater. The largest deviations of the model from inferred aqueous

  3. Hydration Status and Fluid Balance of Elite European Youth Soccer Players during Consecutive Training Sessions.

    Science.gov (United States)

    Phillips, Saun M; Sykes, Dave; Gibson, Neil

    2014-12-01

    The objective of the study was to investigate the hydration status and fluid balance of elite European youth soccer players during three consecutive training sessions. Fourteen males (age 16.9 ± 0.8 years, height 1.79 ± 0.06 m, body mass (BM) 70.6 ± 5.0 kg) had their hydration status assessed from first morning urine samples (baseline) and pre- and post-training using urine specific gravity (USG) measures, and their fluid balance calculated from pre- to post-training BM change, corrected for fluid intake and urine output. Most participants were hypohydrated upon waking (USG >1.020; 77% on days 1 and 3, and 62% on day 2). There was no significant difference between first morning and pre-training USG (p = 0.11) and no influence of training session (p = 0.34) or time (pre- vs. post-training; p = 0.16) on USG. Significant BM loss occurred in sessions 1-3 (0.69 ± 0.22, 0.42 ± 0.25, and 0.38 ± 0.30 kg respectively, p sessions 1-3 was 425 ± 185, 355 ± 161, and 247 ± 157 ml, respectively (p sessions. Body mass loss, fluid intake, and USG measures showed large inter-individual variation. Elite young European soccer players likely wake and present for training hypohydrated, when a USG threshold of 1.020 is applied. When training in a cool environment with ad libitum access to fluid, replacing ~71% of sweat losses results in minimal hypohydration (training appears to prevent excessive (≥2% BM) dehydration, as advised by current fluid intake guidelines. Current fluid intake guidelines appear applicable for elite European youth soccer players training in a cool environment. Key PointsThe paper demonstrates a notable inter-participant variation in first morning, pre- and post-training hydration status and fluid balance of elite young European soccer players.On average, elite young European soccer players are hypohydrated upon waking and remain hypohydrated before and after training.Elite young European soccer players display varied fluid intake volumes during training

  4. Manufacture of Methane Hydrate using Carbon Nano Tubes

    International Nuclear Information System (INIS)

    Park, Sung Seek

    2010-02-01

    Methane hydrate is formed by physical binding between water molecule and gas such as methane, ethane, propane, or carbon dioxide, etc., which is captured in the cavities of water molecule under the specific temperature and pressure. More than 99% of naturally produced methane hydrate consists of methane, and is widely dispersed in the continental slope and continental Shelf of the Pacific and the Atlantic, the Antarctica etc. The reserve of fossil fuel is 500 billion carbon ton and the reserve of methane is 360 million carbon ton. The reserve of gas hydrate is more than 1 trillion carbon ton, which is twice the fossil fuel. Therefore, natural gas hydrate as a kind of gas hydrate is expected to replace fossil fuel as new energy source of 21st century. Also 1 m 3 hydrate of pure methane can be decomposed to the maximum of 216 m 3 methane at standard condition. If these characteristics of hydrate are reversely utilized, natural gas is fixed into water in the form of hydrate solid. Therefore, the hydrate is considered to be a great way to transport and store natural gas in large quantity. Especially the transportation cost is known to be 18∼25% less than the liquefied transportation. However, when natural gas hydrate is artificially formed, its reaction time may be too long and the gas consumption in water becomes relatively low, because the reaction rate between water and gas is low. Therefore, for the practical purpose in the application, the present investigation focuses on the rapid production of hydrates and increases gas consumption by adding MWCNT and NaCl into pure water. The results show that the equilibrium pressure in seawater is more higher than that in pure water, and methane hydrate could be formed rapidly during pressurization if the subcooling is maintained at 9K or above in seawater and 8K or above in pure water, respectively. Also, amount of consumed gas volume in pure water is more higher that in seawater at the same experimental conditions

  5. Moessbauer study of hydrated iron sulfates

    International Nuclear Information System (INIS)

    Araujo, S.I.; Danon, J.; Iannarella, L.

    1991-01-01

    The hydrated iron sulfates amarantite Fe(SO sub(4))(OH).3H sub(2)O, copiapite (Mg,Al)Fe sup(3+) sub(4)(SO sub(4)) sub(6)(OH) sub(2).20H sub(2)O and ungemachite K sub(3)Na sub(9)Fe(SO sub(4)) sub(6)(OH) sub(3).9H sub(2)O were studied by Moessbauer Spectroscopy (MS) in connection with Differential Scanning Calorimetry (DSC). The effect of the dehydration on the hyperfine parameters at the Fe sites was investigated. For amarantite, the Moessbauer spectrum remained practically unchanged, while the Fe sup(3+) quadrupole splittings for copiapite and ungemachite increased. The Fe sup(2+) quadrupole splitting of ungemachite was also unchanged. We have found out the anisotropy of the recoiless absorption probability for the sup(57)Fe Moessbauer gamma ray in amarantite. The three minerals were found to be highly hygroscopic after the dehydration consequent of the DSC measurements. (author)

  6. DNA under Force: Mechanics, Electrostatics, and Hydration

    Directory of Open Access Journals (Sweden)

    Jingqiang Li

    2015-02-01

    Full Text Available Quantifying the basic intra- and inter-molecular forces of DNA has helped us to better understand and further predict the behavior of DNA. Single molecule technique elucidates the mechanics of DNA under applied external forces, sometimes under extreme forces. On the other hand, ensemble studies of DNA molecular force allow us to extend our understanding of DNA molecules under other forces such as electrostatic and hydration forces. Using a variety of techniques, we can have a comprehensive understanding of DNA molecular forces, which is crucial in unraveling the complex DNA functions in living cells as well as in designing a system that utilizes the unique properties of DNA in nanotechnology.

  7. Irradiation effects in hydrated zirconium molybdate

    Energy Technology Data Exchange (ETDEWEB)

    Fourdrin, C., E-mail: chloe.fourdrin@polytechnique.edu [CEA Saclay, DEN/DANS/DPC/SECR/LSRM, 91 191 Gif-sur-Yvette (France); CEA Saclay, DSM/IRAMIS/SIS2M-UMR 3299/Lrad, 91 191 Gif-sur-Yvette (France); Esnouf, S. [CEA Saclay, DSM/IRAMIS/SIS2M-UMR 3299/Lrad, 91 191 Gif-sur-Yvette (France); Dauvois, V. [CEA Saclay, DEN/DANS/DPC/SECR/LSRM, 91 191 Gif-sur-Yvette (France); Renault, J.-P. [CEA Saclay, DSM/IRAMIS/SIS2M-UMR 3299/Lrad, 91 191 Gif-sur-Yvette (France); Venault, L. [CEN Valrho, DEN/DRCP/SCPS/LC2A, 30 207 Bagnols-sur-Ceze (France); Tabarant, M. [CEA Saclay, DEN/DANS/DPC/LRSI, 91 191 Gif-sur-Yvette (France); Durand, D. [CEA Saclay, DEN/DANS/DPC/SECR/LSRM, 91 191 Gif-sur-Yvette (France); Cheniere, A. [CEA Saclay, DEN/DANS/DPC/LRSI, 91 191 Gif-sur-Yvette (France); Lamouroux-Lucas, C. [CEA Saclay, DEN/DANS/DPC/SECR/LSRM, 91 191 Gif-sur-Yvette (France); Cochin, F. [AREVA NC Tour, AREVA, 92 084 Paris La Defense cedex (France)

    2012-07-15

    Hydrated zirconium molybdate is a precipitate formed during the process of spent nuclear fuel dissolution. In order to study the radiation stability of this material, we performed gamma and electron irradiation in a dose range of 10-100 kGy. XRD patterns showed that the crystalline structure is not affected by irradiation. However, the yellow original sample exhibits a blue-grey color after exposure. The resulting samples were analyzed by means of EPR and diffuse reflectance spectroscopy. Two sites for trapped electrons were evidenced leading to a d{sup 1} configuration responsible for the observed coloration. Moreover, a third defect corresponding to a hole trapped on oxygen was observed after electron irradiation at low temperature.

  8. Dehydration of hydrated low-temperature tar

    Energy Technology Data Exchange (ETDEWEB)

    Yoshida, T

    1949-01-01

    Yoshida examined the mechanism of the dehydration of hydrated low-temperature tar with a microscope. The tar containing free carbon and coal dust is so stable that the removal of the above substances and water by a physical method is very difficult. Addition of light oil produced by fractionation of low-temperature tar facilitates the operations. Yoshida tried using the separate acid, neutral, and basic components of the light oil; the acid oil proved to be most effective. For many reasons it is convenient to use light oil as it is. In this method the quantity of light oil required is 2 to 3 times that of tar. But in supplementing the centrifugal method, the quantity of light oil needed might be only half the amount of tar.

  9. Characterizing heterogeneous dynamics at hydrated electrode surfaces

    Science.gov (United States)

    Willard, Adam P.; Limmer, David T.; Madden, Paul A.; Chandler, David

    2013-05-01

    In models of Pt 111 and Pt 100 surfaces in water, motions of molecules in the first hydration layer are spatially and temporally correlated. To interpret these collective motions, we apply quantitative measures of dynamic heterogeneity that are standard tools for considering glassy systems. Specifically, we carry out an analysis in terms of mobility fields and distributions of persistence times and exchange times. In so doing, we show that dynamics in these systems is facilitated by transient disorder in frustrated two-dimensional hydrogen bonding networks. The frustration is the result of unfavorable geometry imposed by strong metal-water bonding. The geometry depends upon the structure of the underlying metal surface. Dynamic heterogeneity of water on the Pt 111 surface is therefore qualitatively different than that for water on the Pt 100 surface. In both cases, statistics of this ad-layer dynamic heterogeneity responds asymmetrically to applied voltage.

  10. Characterizing heterogeneous dynamics at hydrated electrode surfaces.

    Science.gov (United States)

    Willard, Adam P; Limmer, David T; Madden, Paul A; Chandler, David

    2013-05-14

    In models of Pt 111 and Pt 100 surfaces in water, motions of molecules in the first hydration layer are spatially and temporally correlated. To interpret these collective motions, we apply quantitative measures of dynamic heterogeneity that are standard tools for considering glassy systems. Specifically, we carry out an analysis in terms of mobility fields and distributions of persistence times and exchange times. In so doing, we show that dynamics in these systems is facilitated by transient disorder in frustrated two-dimensional hydrogen bonding networks. The frustration is the result of unfavorable geometry imposed by strong metal-water bonding. The geometry depends upon the structure of the underlying metal surface. Dynamic heterogeneity of water on the Pt 111 surface is therefore qualitatively different than that for water on the Pt 100 surface. In both cases, statistics of this ad-layer dynamic heterogeneity responds asymmetrically to applied voltage.

  11. High-pressure structures of methane hydrate

    International Nuclear Information System (INIS)

    Hirai, H; Uchihara, Y; Fujihisa, H; Sakashita, M; Katoh, E; Aoki, K; Yamamoto, Y; Nagashima, K; Yagi, T

    2002-01-01

    Three high-pressure structures of methane hydrate, a hexagonal structure (str. A) and two orthorhombic structures (str. B and str. C), were found by in situ x-ray diffractometry and Raman spectroscopy. The well-known structure I (str. I) decomposed into str. A and fluid at 0.8 GPa. Str. A transformed into str. B at 1.6 GPa, and str. B further transformed into str. C at 2.1 GPa which survived above 7.8 GPa. The fluid solidified as ice VI at 1.4 GPa, and the ice VI transformed to ice VII at 2.1 GPa. The bulk moduli, K 0 , for str. I, str. A, and str. C were calculated to be 7.4, 9.8, and 25.0 GPa, respectively

  12. Hydration Structure of the Quaternary Ammonium Cations

    KAUST Repository

    Babiaczyk, Wojtek Iwo

    2010-11-25

    Two indicators of the hydropathicity of small solutes are introduced and tested by molecular dynamics simulations. These indicators are defined as probabilities of the orientation of water molecules\\' dipoles and hydrogen bond vectors, conditional on a generalized distance from the solute suitable for arbitrarily shaped molecules. Using conditional probabilities, it is possible to distinguish features of the distributions in close proximity of the solute. These regions contain the most significant information on the hydration structure but cannot be adequately represented by using, as is usually done, joint distance-angle probability densities. Our calculations show that using our indicators a relative hydropathicity scale for the interesting test set of the quaternary ammonium cations can be roughly determined. © 2010 American Chemical Society.

  13. Balancing Accuracy and Computational Efficiency for Ternary Gas Hydrate Systems

    Science.gov (United States)

    White, M. D.

    2011-12-01

    Geologic accumulations of natural gas hydrates hold vast organic carbon reserves, which have the potential of meeting global energy needs for decades. Estimates of vast amounts of global natural gas hydrate deposits make them an attractive unconventional energy resource. As with other unconventional energy resources, the challenge is to economically produce the natural gas fuel. The gas hydrate challenge is principally technical. Meeting that challenge will require innovation, but more importantly, scientific research to understand the resource and its characteristics in porous media. Producing natural gas from gas hydrate deposits requires releasing CH4 from solid gas hydrate. The conventional way to release CH4 is to dissociate the hydrate by changing the pressure and temperature conditions to those where the hydrate is unstable. The guest-molecule exchange technology releases CH4 by replacing it with a more thermodynamically stable molecule (e.g., CO2, N2). This technology has three advantageous: 1) it sequesters greenhouse gas, 2) it releases energy via an exothermic reaction, and 3) it retains the hydraulic and mechanical stability of the hydrate reservoir. Numerical simulation of the production of gas hydrates from geologic deposits requires accounting for coupled processes: multifluid flow, mobile and immobile phase appearances and disappearances, heat transfer, and multicomponent thermodynamics. The ternary gas hydrate system comprises five components (i.e., H2O, CH4, CO2, N2, and salt) and the potential for six phases (i.e., aqueous, liquid CO2, gas, hydrate, ice, and precipitated salt). The equation of state for ternary hydrate systems has three requirements: 1) phase occurrence, 2) phase composition, and 3) phase properties. Numerical simulation of the production of geologic accumulations of gas hydrates have historically suffered from relatively slow execution times, compared with other multifluid, porous media systems, due to strong nonlinearities and

  14. Contrast induced hyperthyroidism due to iodine excess

    OpenAIRE

    Mushtaq, Usman; Price, Timothy; Laddipeerla, Narsing; Townsend, Amanda; Broadbridge, Vy

    2009-01-01

    Iodine induced hyperthyroidism is a thyrotoxic condition caused by exposure to excessive iodine. Historically this type of hyperthyroidism has been described in areas of iodine deficiency. With advances in medicine, iodine induced hyperthyroidism has been observed following the use of drugs containing iodine—for example, amiodarone, and contrast agents used in radiological imaging. In elderly patients it is frequently difficult to diagnose and control contrast related hyperthyroidism, as most...

  15. Precise structural analysis of methane hydrate by neutron diffraction

    International Nuclear Information System (INIS)

    Igawa, Naoki; Hoshikawa, Akinori; Ishii, Yoshinobu

    2006-01-01

    Methane hydrate has attracted great interest as an energy resource to replace natural gas since this material is deposited in the seafloor and the deposits are estimated to exceed those of natural gas. Understanding the physical proprieties, such as the temperature dependence of the crystal structure, helps to specify the optimum environmental temperature and pressure during drilling, transport, and storage of methane hydrate. Clathrate hydrates consisted of encaging atomic and/or molecular species as a guest and host water formed by a hydrogen bonding. Although many studies on the clathrate hydrate including methane hydrate were reported, no detailed crystallographic property has yet been cleared. We focused on the motion of methane in the clathrate hydrate by the neutron diffraction. The crystal structure of the methane hydrate was analyzed by the applying the combination of the Rietveld refinement and the maximum entropy method (MEM) to neutron powder diffraction. Temperature dependence of the scattering-length density distribution maps revealed that the motion of methane molecules differs between the shapes of dodecahedron and tetrakaidecahedron. (author)

  16. CLATHRATE HYDRATES FORMATION IN SHORT-PERIOD COMETS

    International Nuclear Information System (INIS)

    Marboeuf, Ulysse; Mousis, Olivier; Petit, Jean-Marc; Schmitt, Bernard

    2010-01-01

    The initial composition of current models of cometary nuclei is only based on two forms of ice: crystalline ice for long-period comets and amorphous ice for short-period comets. A third form of ice, i.e., clathrate hydrate, could exist within the short-period cometary nuclei, but the area of formation of this crystalline structure in these objects has never been studied. Here, we show that the thermodynamic conditions in the interior of short-period comets allow the existence of clathrate hydrates in Halley-type comets. We show that their existence is viable in the Jupiter family comets only when the equilibrium pressure of CO clathrate hydrate is at least 1 order of magnitude lower than the usually assumed theoretical value. We calculate that the amount of volatiles that could be trapped in the clathrate hydrate layer may be orders of magnitude greater than the daily amount of gas released at the surface of the nucleus at perihelion. The formation and the destruction of the clathrate hydrate cages could then explain the diversity of composition of volatiles observed in comets, as well as some pre-perihelion outbursts. We finally show that the potential clathrate hydrate layer in comet 67P/Churyumov-Gerasimenko would, unfortunately, be deep inside the nucleus, out of reach of the Rosetta lander. However, such a clathrate hydrate layer would show up by the gas composition of the coma.

  17. Experimental setting for assessing mechanical strength of gas hydrate pellet

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, S.J.; Choi, J.H.; Koh, B.H. [Dongguk Univ., Phil-dong, Chung-gu, Seoul (Korea, Republic of). Dept. of Mechanical Engineering

    2008-07-01

    Due to the constant increase in global demand for clean energy, natural gas production from stranded medium and small size gas wells has drawn significant interest. Because the ocean transport of natural gas in the form of solid hydrate pellets (NGHP) has been estimated to be economically feasible, several efforts have been made to develop a total NGHP ocean transport chain. The investigation of mechanical strength of solid-form hydrate pellet has been an important task in fully exploiting the benefit of gas hydrate in the perspective of mass transportation and storage. This paper provided the results of a preliminary study regarding the assessment of mechanical properties of the gas hydrate pellet. The preliminary study suggested some of the key issues regarding formation and strength of gas hydrate pellets. Instead of utilizing the gas hydrate pellet, the study focused on a preliminary test setup for developing the ice pellet which was readily applied to the gas hydrate pellet in the future. The paper described the pelletization of ice powder as well as the experimental setup. Several photographs were illustrated, including samples of ice pellets; compression test for ice pellet using air press and load cell; and the initiation of crack in the cross section of an ice pellet. It was found that mechanical strength, especially, compression strength was not significantly affected by different level of press-forming force up to a certain level. 4 refs., 1 tab., 4 figs.

  18. The effect of hydrate promoters on gas uptake.

    Science.gov (United States)

    Xu, Chun-Gang; Yu, Yi-Song; Ding, Ya-Long; Cai, Jing; Li, Xiao-Sen

    2017-08-16

    Gas hydrate technology is considered as a promising technology in the fields of gas storage and transportation, gas separation and purification, seawater desalination, and phase-change thermal energy storage. However, to date, the technology is still not commercially used mainly due to the low gas hydrate formation rate and the low gas uptake. In this study, the effect of hydrate promoters on gas uptake was systematically studied and analyzed based on hydrate-based CH 4 storage and CO 2 capture from CO 2 /H 2 gas mixture experiments. Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR) and gas chromatography (GC) were employed to analyze the microstructures and gas compositions. The results indicate that the effect of the hydrate promoter on the gas uptake depends on the physical and chemical properties of the promoter and gas. A strong polar ionic promoter is not helpful towards obtaining the ideal gas uptake because a dense hydrate layer is easily formed at the gas-liquid interface, which hinders gas diffusion from the gas phase to the bulk solution. For a weak polar or non-polar promoter, the gas uptake depends on the dissolution characteristics among the different substances in the system. The lower the mutual solubility among the substances co-existing in the system, the higher the independence among the substances in the system; this is so that each phase has an equal chance to occupy the hydrate cages without or with small interactions, finally leading to a relatively high gas uptake.

  19. Influence of limestone on the hydration of Portland cements

    International Nuclear Information System (INIS)

    Lothenbach, Barbara; Le Saout, Gwenn; Gallucci, Emmanuel; Scrivener, Karen

    2008-01-01

    The influence of the presence of limestone on the hydration of Portland cement was investigated. Blending of Portland cement with limestone was found to influence the hydrate assemblage of the hydrated cement. Thermodynamic calculations as well as experimental observations indicated that in the presence of limestone, monocarbonate instead of monosulfate was stable. Thermodynamic modelling showed that the stabilisation of monocarbonate in the presence of limestone indirectly stabilised ettringite leading to a corresponding increase of the total volume of the hydrate phase and a decrease of porosity. The measured difference in porosity between the 'limestone-free' cement, which contained less than 0.3% CO 2 , and a cement containing 4% limestone, however, was much smaller than calculated. Coupling of thermodynamic modelling with a set of kinetic equations which described the dissolution of the clinker, predicted quantitatively the amount of hydrates. The quantities of ettringite, portlandite and amorphous phase as determined by TGA and XRD agreed well with the calculated amounts of these phases after different periods of time. The findings in this paper show that changes in the bulk composition of hydrating cements can be followed by coupled thermodynamic models. Comparison between experimental and modelled data helps to understand in more detail the dominating processes during cement hydration

  20. Characteristics of Methane Hydrate Formation in Artificial and Natural Media

    Directory of Open Access Journals (Sweden)

    Qingbai Wu

    2013-03-01

    Full Text Available The formation of methane hydrate in two significantly different media was investigated, using silica gel as an artificial medium and loess as a natural medium. The methane hydrate formation was observed through the depletion of water in the matrix, measured via the matrix potential and the relationship between the matrix potential and the water content was determined using established equations. The velocity of methane hydrate nucleation slowed over the course of the reaction, as it relied on water transfer to the hydrate surfaces with lower Gibbs free energy after nucleation. Significant differences in the reactions in the two types of media arose from differences in the water retention capacity and lithology of media due to the internal surface area and pore size distributions. Compared with methane hydrate formation in silica gel, the reaction in loess was much slower and formed far less methane hydrate. The results of this study will advance the understanding of how the properties of the environment affect the formation of gas hydrates in nature.

  1. Structural and hydration properties of amorphous tricalcium silicate

    International Nuclear Information System (INIS)

    Mori, K.; Fukunaga, T.; Shiraishi, Y.; Iwase, K.; Xu, Q.; Oishi, K.; Yatsuyanagi, K.; Yonemura, M.; Itoh, K.; Sugiyama, M.; Ishigaki, T.; Kamiyama, T.; Kawai, M.

    2006-01-01

    Mechanical milling was carried out to synthesize amorphous tricalcium silicate (Ca 3 SiO 5 ) sample, where Ca 3 SiO 5 is the most principal component of Portland cement. The partial phase transformation from the crystalline to the amorphous state was observed by X-ray and neutron diffractions. Moreover, it was found that the structural distortion on the Ca-O correlation exists in the milled Ca 3 SiO 5 . The hydration of the milled Ca 3 SiO 5 with D 2 O proceeds as follows: the formation of hydration products such as Ca(OD) 2 rapidly occurs in the early hydration stage, and then proceeds slowly after about 15 h. The induction time for the hydration of the milled Ca 3 SiO 5 is approximately one half shorter than that for the hydration of the unmilled one. This result means that the mechanical milling brings about the chemical activity of Ca 3 SiO 5 for hydration, and may be particularly useful for increasing the reactivity in the early hydration stage

  2. Electrochemical stability of ionic clathrate hydrates and their structural consideration

    International Nuclear Information System (INIS)

    Lee, Wonhee; Lim, Dongwook; Lee, Huen

    2013-01-01

    Although electrochemical stability is an essential factor in relation to the potential applications of ionic clathrate hydrates to solid electrolytes, most studies regarding the proton conductors have focused on their ionic conductivity and thermal stability. Solid electrolytes in various electrochemical devices have to endure the applied potentials; thus, we examined the linear sweep voltammograms of various tetraalkylammonium hydroxide hydrates in order to shed light on the trend of electrochemical stability depending on the hydrate structure. We revealed that the electrochemical stability of Me 4 NOH hydrates is mainly affected by both their ionic concentration and cage occupancy. In particular, the true clathrate structures of β-Me 4 NOH hydrates are more electrochemically stable than their α-forms that possess partially broken hydrogen bonds. We also observed that the binary THF–Pr 4 NOH and pure Bu 4 NOH clathrate hydrates exhibit greater electrochemical stability than those of pure Me 4 NOH hydrates having lower or similar ionic concentrations. These results are considered to arise from the fact that each of the Pr 4 N + and Bu 4 N + ions occupies an extended space comprising four cages, which leads to stabilization of the larger unit, whereas a Me 4 N + ion is completely included only in one cage

  3. Ab initio modelling of methane hydrate thermophysical properties.

    Science.gov (United States)

    Jendi, Z M; Servio, P; Rey, A D

    2016-04-21

    The key thermophysical properties of methane hydrate were determined using ab initio modelling. Using density functional theory, the second-order elastic constants, heat capacity, compressibility, and thermal expansion coefficient were calculated. A wide and relevant range of pressure-temperature conditions were considered, and the structures were assessed for stability using the mean square displacement and radial distribution functions. Methane hydrate was found to be elastically isotropic with a linear dependence of the bulk modulus on pressure. Equally significant, multi-body interactions were found to be important in hydrates, and water-water interactions appear to strongly influence compressibility like in ice Ih. While the heat capacity of hydrate was found to be higher than that of ice, the thermal expansion coefficient was significantly lower, most likely due to the lower rigidity of hydrates. The mean square displacement gave important insight into stability, heat capacity, and elastic moduli, and the radial distribution functions further confirmed stability. The presented results provide a much needed atomistic thermoelastic characterization of methane hydrates and are essential input for the large-scale applications of hydrate detection and production.

  4. Influence of Lithium Carbonate on C3A Hydration

    Directory of Open Access Journals (Sweden)

    Weiwei Han

    2018-01-01

    Full Text Available Lithium salts, known to ameliorate the effects of alkali-silica reaction, can make significant effects on cement setting. However, the mechanism of effects on cement hydration, especially the hydration of C3A which is critical for initial setting time of cement, is rarely reported. In this study, the development of pH value of pore solution, conductivity, thermodynamics, and mineralogical composition during hydration of C3A with or without Li2CO3 are investigated. The results demonstrate that Li2CO3 promotes C3A hydration through high alkalinity, due to higher activity of lithium ion than that of calcium ion in the solution and carbonation of C3A hydration products resulted from Li2CO3. Li2CO3 favors the C3A hydration in C3A-CaSO4·2H2O-Ca(OH2-H2O hydration system and affects the mineralogical variation of the ettringite phase(s.

  5. Extended duration of prehydration does not prevent nephrotoxicity or delayed drug elimination in high-dose methotrexate infusions

    DEFF Research Database (Denmark)

    Mikkelsen, Torben Stamm; Mamoudou, Aissata Diop; Tuckuviene, Ruta

    2014-01-01

    Alkalized hydration is used as supportive care to prevent renal toxicity during infusions with high-dose methotrexate (HDMTX). In children with acute lymphoblastic leukemia (ALL), the hydration is commonly initiated 4 hours before start of the methotrexate (MTX) infusion. To test if longer durati...

  6. Hydration behaviors of calcium silicate-based biomaterials.

    Science.gov (United States)

    Lee, Yuan-Ling; Wang, Wen-Hsi; Lin, Feng-Huie; Lin, Chun-Pin

    2017-06-01

    Calcium silicate (CS)-based biomaterials, such as mineral trioxide aggregate (MTA), have become the most popular and convincing material used in restorative endodontic treatments. However, the commercially available CS-based biomaterials all contain different minor additives, which may affect their hydration behaviors and material properties. The purpose of this study was to evaluate the hydration behavior of CS-based biomaterials with/without minor additives. A novel CS-based biomaterial with a simplified composition, without mineral oxides as minor additives, was produced. The characteristics of this biomaterial during hydration were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectrometry. The hydration behaviors of commercially available gray and white MTAs with mineral oxide as minor additives were also evaluated for reference. For all three test materials, the XRD analysis revealed similar diffraction patterns after hydration, but MTAs presented a significant decrease in the intensities of Bi 2 O 3 -related peaks. SEM results demonstrated similar porous microstructures with some hexagonal and facetted crystals on the outer surfaces. In addition, compared to CS with a simplified composition, the FTIR plot indicated that hydrated MTAs with mineral oxides were better for the polymerization of calcium silicate hydrate (CSH), presenting Si-O band shifting to higher wave numbers, and contained more water crystals within CSH, presenting sharper bands for O-H bending. Mineral oxides might not result in significant changes in the crystal phases or microstructures during the hydration of CS-based biomaterials, but these compounds affected the hydration behavior at the molecular level. Copyright © 2016. Published by Elsevier B.V.

  7. Phase behavior of methane hydrate in silica sand

    International Nuclear Information System (INIS)

    Sun, Shi-Cai; Liu, Chang-Ling; Ye, Yu-Guang; Liu, Yu-Feng

    2014-01-01

    Highlights: • Hydrate p-T trace in coarse-grained sediment is consistent with that in bulk water. • Fine-grained sediment affects hydrate equilibrium for the depressed water activity. • Hydrate equilibrium in sediment is related to the pore size distribution. • The application of hydrate equilibrium in sediment depends on the actual condition. -- Abstract: Two kinds of silica sand powder with different particle size were used to investigate the phase behavior of methane hydrate bearing sediment. In coarse-grained silica sand, the measured temperature and pressure range was (281.1 to 284.2) K and (5.9 to 7.8) MPa, respectively. In fine-grained silica sand, the measured temperature and pressure range was (281.5 to 289.5) K and (7.3 to 16.0) MPa, respectively. The results show that the effect of coarse-grained silica sand on methane hydrate phase equilibrium can be ignored; however, the effect of fine-grained silica sand on methane hydrate phase equilibrium is significant, which is attributed to the depression of water activity caused by the hydrophilicity and negatively charged characteristic of silica particle as well as the pore capillary pressure. Besides, the analysis of experimental results using the Gibbs–Thomson equation shows that methane hydrate phase equilibrium is related to the pore size distribution of silica sand. Consequently, for the correct application of phase equilibrium data of hydrate bearing sediment, the geological condition and engineering requirement should be taken into consideration in gas production, resource evaluation, etc

  8. On the hydration and conformation of cocaine in solution

    Science.gov (United States)

    Gillams, Richard J.; Lorenz, Christian D.; McLain, Sylvia E.

    2017-05-01

    In order to develop theories relating to the mechanism through which cocaine can diffuse across the blood-brain barrier, it is important to understand the interplay between the hydration of the molecule and the adopted conformation. Here key differences in the hydration of cocaine hydrochloride (CHC) and freebase cocaine (CFB) are highlighted on the atomic scale in solution, through the use of molecular dynamics simulations. By adopting different conformations, CHC and CFB experience differing hydration environments. The interplay between these two factors may account for the vast difference in solubility of these two molecules.

  9. Gas hydrate dissociation prolongs acidification of the Anthropocene oceans

    OpenAIRE

    Boudreau, B.P.; Luo, Y.; Meysman, F.J.R.; Middelburg, J

    2015-01-01

    Anthropogenic warming of the oceans can release methane (CH4) currently stored in sediments as gas hydrates. This CH4 will be oxidized to CO2, thus increasing the acidification of the oceans. We employ a biogeochemical model of the multimillennial carbon cycle to determine the evolution of the oceanic dissolved carbonate system over the next 13?kyr in response to CO2 from gas hydrates, combined with a reasonable scenario for long-term anthropogenic CO2 emissions. Hydrate-derived CO2 will appr...

  10. An international effort to compare gas hydrate reservoir simulators

    Energy Technology Data Exchange (ETDEWEB)

    Wilder, J.W. [Akron Univ., Akron, OH (United States). Dept. of Theoretical and Applied Math; Moridis, G.J. [California Univ., Berkely, CA (United States). Earth Sciences Div., Lawrence Berkely National Lab.; Wilson, S.J. [Ryder Scott Co., Denver, CO (United States); Kurihara, M. [Japan Oil Engineering Co. Ltd., Tokyo (Japan); White, M.D. [Pacific Northwest National Laboratory Hydrology Group, Richland, WA (United States); Masuda, Y. [Tokyo Univ., Tokyo (Japan). Dept. of Geosystem Engineering; Anderson, B.J. [National Energy Technology Lab., Morgantown, WV (United States)]|[West Virginia Univ., Morgantown, WV (United States). Dept. of Chemical Engineering; Collett, T.S. [United States Geological Survey, Denver, CO (United States); Hunter, R.B. [ASRC Energy Services, Anchorage, AK (United States); Narita, H. [National Inst. of Advanced Industrial Science and Technology, MEthane hydrate Research Lab., Sapporo (Japan); Pooladi-Darvish, M. [Fekete Associates Inc., Calgary, AB (Canada); Rose, K.; Boswell, R. [National Energy Technology Lab., Morgantown, WV (United States)

    2008-07-01

    In this study, 5 different gas hydrate production scenarios were modeled by the CMG STARS, HydateResSim, MH-21 HYDRES, STOMP-HYD and the TOUGH+HYDRATE reservoir simulators for comparative purposes. The 5 problems ranged in complexity from 1 to 3 dimensional with radial symmetry, and in horizontal dimensions of 20 meters to 1 kilometer. The scenarios included (1) a base case with non-isothermal multi-fluid transition to equilibrium, (2) a base case with gas hydrate (closed-domain hydrate dissociation), (3) dissociation in a 1-D open domain, (4) gas hydrate dissociation in a one-dimensional radial domain, similarity solutions, (5) gas hydrate dissociation in a two-dimensional radial domain. The purpose of the study was to compare the world's leading gas hydrate reservoir simulators in an effort to improve the simulation capability of experimental and naturally occurring gas hydrate accumulations. The problem description and simulation results were presented for each scenario. The results of the first scenario indicated very close agreement among the simulators, suggesting that all address the basics of mass and heat transfer, as well as overall process of gas hydrate dissociation. The third scenario produced the initial divergence among the simulators. Other differences were noted in both scenario 4 and 5, resulting in significant corrections to algorithms within several of the simulators. The authors noted that it is unlikely that these improvements would have been identified without this comparative study due to a lack of real world data for validation purposes. It was concluded that the solution for gas hydrate production involves a combination of highly coupled fluid, heat and mass transport equations combined with the potential for formation or disappearance of multiple solid phases in the system. The physical and chemical properties of the rocks containing the gas hydrate depend on the amount of gas hydrate present in the system. Each modeling and

  11. Hydration numbers of trivalent lanthanide and actinide ions

    International Nuclear Information System (INIS)

    David, F.; Fourest, B.; Duplessis, J.

    1987-01-01

    Investigations on the structure of actinide aquo ions and determination of hydration numbers have to be studied, essentially, through radiochemical methods. They measured the transport numbers, diffusion coefficient D by the open end capillary method and ionic mobility u by electrophoresis. Both methods show a discontinuity in the transport number corresponding to the crystallographic radius of Eu 3+ or Bk 3+ ion. They deduced the volume of the actinide aquo ions, and the coordination number in the primary sphere. From calculations of the electrostriction phenomenon in the vicinity of central ion, they obtained effective volume of the water molecules and the dynamic hydration number corresponding to the second hydration sphere

  12. State of hydration and electrical conductance of ichthyotic skin

    OpenAIRE

    A B Gupta; Manisha Bhattacharya; B Haldar

    1990-01-01

    Dry skin of twelve subjects suffering from ichthyosis vulgaris and the efficacy of a moisturiser-Cotaryl were quantitatively assessed by measuring the skin surface hydration and high frequency (3.5 MHz) electrical conductance of skin. The state of hydration and conductance of ichthyotic skin were 86.9 + 24.6 and 11.0 + 5.7 micro-mho respectively, being much less-compared to 132. 0 + 5.3 and 72.5 + 54.0 micro-mho ofnormal subjects. The moisturiser increased the state of hydration and also the ...

  13. Examination of Hydrate Formation Methods: Trying to Create Representative Samples

    Energy Technology Data Exchange (ETDEWEB)

    Kneafsey, T.J.; Rees, E.V.L.; Nakagawa, S.; Kwon, T.-H.

    2011-04-01

    Forming representative gas hydrate-bearing laboratory samples is important so that the properties of these materials may be measured, while controlling the composition and other variables. Natural samples are rare, and have often experienced pressure and temperature changes that may affect the property to be measured [Waite et al., 2008]. Forming methane hydrate samples in the laboratory has been done a number of ways, each having advantages and disadvantages. The ice-to-hydrate method [Stern et al., 1996], contacts melting ice with methane at the appropriate pressure to form hydrate. The hydrate can then be crushed and mixed with mineral grains under controlled conditions, and then compacted to create laboratory samples of methane hydrate in a mineral medium. The hydrate in these samples will be part of the load-bearing frame of the medium. In the excess gas method [Handa and Stupin, 1992], water is distributed throughout a mineral medium (e.g. packed moist sand, drained sand, moistened silica gel, other porous media) and the mixture is brought to hydrate-stable conditions (chilled and pressurized with gas), allowing hydrate to form. This method typically produces grain-cementing hydrate from pendular water in sand [Waite et al., 2004]. In the dissolved gas method [Tohidi et al., 2002], water with sufficient dissolved guest molecules is brought to hydrate-stable conditions where hydrate forms. In the laboratory, this is can be done by pre-dissolving the gas of interest in water and then introducing it to the sample under the appropriate conditions. With this method, it is easier to form hydrate from more soluble gases such as carbon dioxide. It is thought that this method more closely simulates the way most natural gas hydrate has formed. Laboratory implementation, however, is difficult, and sample formation is prohibitively time consuming [Minagawa et al., 2005; Spangenberg and Kulenkampff, 2005]. In another version of this technique, a specified quantity of gas

  14. Methane hydrate synthesis from ice: Influence of pressurization and ethanol on optimizing formation rates and hydrate yield

    Science.gov (United States)

    Chen, Po-Chun.; Huang, Wuu-Liang; Stern, Laura A.

    2010-01-01

    Polycrystalline methane gas hydrate (MGH) was synthesized using an ice-seeding method to investigate the influence of pressurization and ethanol on the hydrate formation rate and gas yield of the resulting samples. When the reactor is pressurized with CH4 gas without external heating, methane hydrate can be formed from ice grains with yields up to 25% under otherwise static conditions. The rapid temperature rise caused by pressurization partially melts the granular ice, which reacts with methane to form hydrate rinds around the ice grains. The heat generated by the exothermic reaction of methane hydrate formation buffers the sample temperature near the melting point of ice for enough time to allow for continuous hydrate growth at high rates. Surprisingly, faster rates and higher yields of methane hydrate were found in runs with lower initial temperatures, slower rates of pressurization, higher porosity of the granular ice samples, or mixtures with sediments. The addition of ethanol also dramatically enhanced the formation of polycrystalline MGH. This study demonstrates that polycrystalline MGH with varied physical properties suitable for different laboratory tests can be manufactured by controlling synthesis procedures or parameters. Subsequent dissociation experiments using a gas collection apparatus and flowmeter confirmed high methane saturation (CH 4·2O, with n = 5.82 ± 0.03) in the MGH. Dissociation rates of the various samples synthesized at diverse conditions may be fitted to different rate laws, including zero and first order.

  15. Changes in structure and preferential cage occupancy of ethane hydrate and ethane-methane mixed gas hydrate under high pressure

    International Nuclear Information System (INIS)

    Hirai, H; Takahara, N; Kawamura, T; Yamamoto, Y; Yagi, T

    2010-01-01

    Structural changes and preferential cage occupancies were examined for ethane hydrate and ethane-methane mixed gas hydrates with five compositions in a pressure range of 0.2 to 2.8 GPa at room temperature. X-ray diffractometry and Raman spectroscopy showed the following structural changes. The initial structure, structure I (sI), of ethane hydrate was retained up to 2.1 GPa without any structural change. For the mixed hydrates, sI was widely distributed throughout the region examined except for the methane-rich and lower pressure regions, where sII and sH appeared. Above 2.1 GPa ethane hydrate and all of the mixed hydrates decomposed into ice VI and ethane fluid or methane-ethane fluid, respectively. The Raman study revealed that occupation of the small cages by ethane molecules occurred above 0.1 GPa in ethane hydrate and continued up to decomposition at 2.1 GPa, although it was thought that ethane molecules were contained only in the large cage.

  16. Hydrate-Bearing Clayey Sediments: Morphology, Physical Properties, Production and Engineering/Geological Implications

    Energy Technology Data Exchange (ETDEWEB)

    Dai, Sheng [Georgia Tech Research Corporation, Atlanta, GA (United States); Santamarina, J. Carlos [King Abdulaziz Univ., Jeddah (Saudi Arabia)

    2017-12-30

    Fine-grained sediments host more than 90 percent of global gas hydrate accumulation. However, hydrate formation in clay-dominated sediments is less understood and characterized than other types of hydrate occurrence. There is an inadequate understanding of hydrate formation mechanisms, segregation structures, hydrate lens topology, system connectivity, and physical macro-scale properties of clay-dominated hydrate-bearing sediments. This situation hinders further analyses of the global carbon budget as well as engineering challenges/solutions related to hydrate instability and production. This project studies hydrate-bearing clay-dominated sediments with emphasis on the enhanced fundamental understanding of hydrate formation and resulting morphology, the development laboratory techniques to emulate natural hydrate formations, the assessment of analytical tools to predict physical properties, the evaluation of engineering and geological implications, and the advanced understanding of gas production potential from finegrained sediments.

  17. Energy from gas hydrates - assessing the opportunities and challenges for Canada: report of the expert panel on gas hydrates

    International Nuclear Information System (INIS)

    2008-09-01

    Gas hydrates form when water and natural gas combine at low temperatures and high pressures in regions of permafrost and in marine subseafloor sediments. Estimates suggest that the total amount of natural gas bound in hydrate form may exceed all conventional gas resources, or even the amount of all combined hydrocarbon energy. Gas from gas hydrate could provide a potentially vast new source of energy to offset declining supplies of conventional natural gas in North America and to provide greater energy security for countries such as Japan and India that have limited domestic sources. However, complex issues would need to be addressed if gas hydrate were to become a large part of the energy future of Canada. Natural Resources Canada asked the Council of Canadian Academies to assemble a panel of experts to examine the challenges for an acceptable operational extraction of gas hydrates in Canada. This report presented an overview of relevant contextual background, including some basic science; the medium-term outlook for supply and demand in markets for natural gas; broad environmental issues related to gas hydrate in its natural state and as a fuel; and an overview of Canada's contribution to knowledge about gas hydrate in the context of ongoing international research activity. The report also presented current information on the subject and what would be required to delineate and quantify the resource. Techniques for extracting gas from gas hydrate were also outlined. The report also addressed safety issues related to gas hydrate dissociation during drilling operations or release into the atmosphere; the environmental issues associated with potential leakage of methane into the atmosphere and with the large volumes of water produced during gas hydrate dissociation; and jurisdictional and local community issues that would need to be resolved in order to proceed with the commercial exploitation of gas hydrate. It was concluded that there does not appear to be

  18. Using intravoxel incoherent motion MR imaging to study the renal pathophysiological process of contrast-induced acute kidney injury in rats: Comparison with conventional DWI and arterial spin labelling

    Energy Technology Data Exchange (ETDEWEB)

    Liang, Long; Zhang, Bin [Guangdong General Hospital/Guangdong Academy of Medical Sciences, Department of Radiology, Guangzhou, Guangdong Province (China); Southern Medical University, Graduate College, Guangzhou (China); Chen, Wen-bo; Liang, Chang-hong; Zhang, Shui-xing [Guangdong General Hospital/Guangdong Academy of Medical Sciences, Department of Radiology, Guangzhou, Guangdong Province (China); Chan, Kannie W.Y.; Li, Yu-guo; Liu, Guan-shu [The Johns Hopkins University School of Medicine, Russell H. Morgan Department of Radiology and Radiological Sciences, Division of MR Research, Baltimore, MD (United States)

    2016-06-15

    To investigate the potential of intravoxel incoherent motion (IVIM) to assess the renal pathophysiological process in contrast-induced acute kidney injury (CIAKI). Twenty-seven rats were induced with CIAKI model, six rats were imaged longitudinally at 24 h prior to and 30 min, 12, 24, 48, 72 and 96 h after administration; three rats were randomly chosen from the rest for serum creatinine and histological studies. D, f, D* and ADC were calculated from IVIM, and renal blood flow (RBF) was obtained from arterial spin labelling (ASL). A progressive reduction in D and ADC was observed in cortex (CO) by 3.07 and 8.62 % at 30 min, and by 25.77 and 28.16 % at 48 h, respectively. A similar change in outer medulla (OM) and inner medulla (IM) was observed at a later time point (12-72 h). D values were strongly correlated with ADC (r = 0.885). As perfusion measurement, a significant decrease was shown for f in 12-48 h and an increase in 72-96 h. A slightly different trend was found for D*, which was decreased by 26.02, 21.78 and 10.19 % in CO, OM and IM, respectively, at 30 min. f and D* were strongly correlated with RBF in the cortex (r = 0.768, r = 0.67), but not in the medulla. IVIM is an effective imaging tool for monitoring progress in renal pathophysiology undergoing CIAKI. (orig.)

  19. Contrast-induced nephropathy in patients with diabetes mellitus between iso- and low-osmolar contrast media: A meta-analysis of full-text prospective, randomized controlled trials.

    Science.gov (United States)

    Han, Xiao-Fang; Zhang, Xin-Xiu; Liu, Ke-Mei; Tan, Hua; Zhang, Qiu

    2018-01-01

    This study was conducted to compare iso-osmolar contrast medium, iodixanol, with low-osmolar contrast media (LOCM) for assessing contrast-induced nephropathy (CIN) incidence, exclusively in the diabetic population. A systematic search was conducted for full-text, prospective, randomized controlled trials (RCTs). The primary outcome was incidence of CIN. Medline, Cochrane Central Register of Controlled Trials, and other sources were searched until May 31, 2017. Twelve RCTs finally met the search criteria. Iodixanol did not significantly reduce the risk of CIN (risk ratio [RR]: 0.72, 95% confidence interval (CI): [0.49, 1.04], p = 0.08). However, there was significantly reduced risk of CIN when iodixanol was compared to a LOCM agent iohexol (RR: 0.32, 95% CI [0.12, 0.89]). There were no differences between iodixanol and the other non-iohexol LOCM (RR: 0.92, 95% CI [0.68, 1.25]). In diabetic populations, iodixanol is not associated with a significant reduction of CIN risk. Iodixanol is associated with a reduced risk of CIN compared with iohexol, whereas no significant difference between iodixanol and other LOCM could be found.

  20. Geo-scientific investigations of gas-hydrates in India

    Digital Repository Service at National Institute of Oceanography (India)

    Sain, K.; Gupta, H.; Mazumdar, A.; Bhaumik, A.K.; Bhowmick, P.K.

    The best solution to meet India's overwhelming energy requirement is to tap the nuclear and solar power to the maximum extent possible. Another feasible major energy resource is gas-hydrates (crystalline substances of methane and water) that have...

  1. A Review of the Methane Hydrate Program in Japan

    Directory of Open Access Journals (Sweden)

    Ai Oyama

    2017-09-01

    Full Text Available In this paper, methane hydrate R&D in Japan was examined in the context of Japan’s evolving energy policies. Methane hydrates have been studied extensively in Japanese national R&D programs since 1993, with the goal of utilizing them as an energy resource. Currently, the Research Consortium for Methane Hydrate Resources in Japan (MH 21 is in the third phase of a project that began in early 2002. Based on publicly available reports and other publications, and presentations made at the ten International Workshops for Methane Hydrate Research and Development, we have attempted to provide a timeline and a succinct summary of the major technical accomplishments of MH 21 during project Phases 1, 2, and 3.

  2. Methane Hydrate in Confined Spaces: An Alternative Storage System.

    Science.gov (United States)

    Borchardt, Lars; Casco, Mirian Elizabeth; Silvestre-Albero, Joaquin

    2018-03-14

    Methane hydrate inheres the great potential to be a nature-inspired alternative for chemical energy storage, as it allows to store large amounts of methane in a dense solid phase. The embedment of methane hydrate in the confined environment of porous materials can be capitalized for potential applications as its physicochemical properties, such as the formation kinetics or pressure and temperature stability, are significantly changed compared to the bulk system. We review this topic from a materials scientific perspective by considering porous carbons, silica, clays, zeolites, and polymers as host structures for methane hydrate formation. We discuss the contribution of advanced characterization techniques and theoretical simulations towards the elucidation of the methane hydrate formation and dissociation process within the confined space. We outline the scientific challenges this system is currently facing and look on possible future applications for this technology. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Development of a CB Resistant Durable, Flexible Hydration System

    National Research Council Canada - National Science Library

    Hall, Peyton W; Zeller, Frank T; Bulluck, John W; Dingus, Michael L

    2002-01-01

    A durable, flexible hydration system resistant to contamination by contact with VX, GD, and HD chemical agents, as well as damage by the decontaminants sodium hypochlorite and DS-2 is being developed for aviator use...

  4. Methane hydrates and the future of natural gas

    Science.gov (United States)

    Ruppel, Carolyn

    2011-01-01

    For decades, gas hydrates have been discussed as a potential resource, particularly for countries with limited access to conventional hydrocarbons or a strategic interest in establishing alternative, unconventional gas reserves. Methane has never been produced from gas hydrates at a commercial scale and, barring major changes in the economics of natural gas supply and demand, commercial production at a large scale is considered unlikely to commence within the next 15 years. Given the overall uncertainty still associated with gas hydrates as a potential resource, they have not been included in the EPPA model in MITEI’s Future of Natural Gas report. Still, gas hydrates remain a potentially large methane resource and must necessarily be included in any consideration of the natural gas supply beyond two decades from now.

  5. Research opportunities in salt hydrates for thermal energy storage

    Science.gov (United States)

    Braunstein, J.

    1983-11-01

    The state of the art of salt hydrates as phase change materials for low temperature thermal energy storage is reviewed. Phase equilibria, nucleation behavior and melting kinetics of the commonly used hydrate are summarized. The development of efficient, reliable inexpensive systems based on phase change materials, especially salt hydrates for the storage (and retrieval) of thermal energy for residential heating is outlined. The use of phase change material thermal energy storage systems is not yet widespread. Additional basic research is needed in the areas of crystallization and melting kinetics, prediction of phase behavior in ternary systems, thermal diffusion in salt hydrate systems, and in the physical properties pertinent to nonequilibrium and equilibrium transformations in these systems.

  6. Maximum Recoverable Gas from Hydrate Bearing Sediments by Depressurization

    KAUST Repository

    Terzariol, Marco

    2017-11-13

    The estimation of gas production rates from hydrate bearing sediments requires complex numerical simulations. This manuscript presents a set of simple and robust analytical solutions to estimate the maximum depressurization-driven recoverable gas. These limiting-equilibrium solutions are established when the dissociation front reaches steady state conditions and ceases to expand further. Analytical solutions show the relevance of (1) relative permeabilities between the hydrate free sediment, the hydrate bearing sediment, and the aquitard layers, and (2) the extent of depressurization in terms of the fluid pressures at the well, at the phase boundary, and in the far field. Close form solutions for the size of the produced zone allow for expeditious financial analyses; results highlight the need for innovative production strategies in order to make hydrate accumulations an economically-viable energy resource. Horizontal directional drilling and multi-wellpoint seafloor dewatering installations may lead to advantageous production strategies in shallow seafloor reservoirs.

  7. Positron annihilation probing for the hydratation rate of cement paste

    International Nuclear Information System (INIS)

    Myllylae, R.; Karras, M.

    1975-01-01

    Positron annihilation has been found to be a possible probe for the exponential hydratation of cement paste. Both lifetime and Doppler line broadening measurements revealed the hydratation rate. With the aid of increased stability in the lifetime spectrometer it has been possible to extend the measuring sensitivity over a period of several weeks. Two main lifetimes, tau 1 = 480 +- 20 psec and tau 2 = 2.1 +- 0.1 nsec, were observed to be constant during the hydratation. The intensity of the 2.1 nsec component changed from 4 to 8% after 47 days, and simultaneously the annihilation line narrowed from 2.6 to 2.4 keV. This behaviour has been interpreted as an increase in positronium formation. The possible practical applications of positron annihilation radiation as a hydratation probe has been evaluated for use in a concrete laboratory and even for regular construction work. (orig.) [de

  8. Dissociation behavior of methane gas hydrate in porous media

    Energy Technology Data Exchange (ETDEWEB)

    Qiang, C.; Yu-gang, Y.; Chang-ling, L. [Ministry of Land and Resources, Quindao (China). Qingdao Inst. of Marine Geology; Qing-guo, M. [Qingdao Univ. College of Chemical Engineering and Environment, Shandong, Qingdao (China)

    2008-07-01

    Gas hydrates are ice-like compounds that form by natural gas and water and are considered to be a new energy resource. In order to make good use of this resource, it is important to know the hydrate dissociation process. This paper discussed an investigation of methane hydrate dissociation through a simulation experiment. The paper discussed the gas hydrates dissociation experiment including the apparatus and experiment equipment, including methane gas supply; reaction cell; temperature controller; pressure maintainer; and gas flow meter. The paper also presented the method and material including iso-volumetric dissociation and normal pressure dissociation. Last, results and discussion of the results were presented. A comparison of five different particle sizes did not reveal any obvious effects that were related to the porous media, mostly likely because the particle size was too large. 15 refs., 2 tabs., 4 figs.

  9. Infrared spectroscopy for monitoring gas hydrates in aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Dobbs, G.T.; Luzinova, Y.; Mizaikoff, B. [Georgia Inst. of Technology, Atlanta, GA (United States). School of Chemistry and Biochemistry; Raichlin, Y.; Katzir, A. [Tel-Aviv Univ., Tel-Aviv (Israel). Shool of Physics and Astronomy

    2008-07-01

    This paper introduced the first principles for monitoring gas hydrate formation and dissociation in aqueous solution by evaluating state-responsive infrared (IR) absorption features of water with fiberoptic evanescent field spectroscopy. A first order linear functional relationship was also derived according to Lambert Beer's law in order to quantify the percentage gas hydrate within the volume of water probed via the evanescent field. In addition, spectroscopic studies evaluating seafloor sediments collected from a gas hydrate site in the Gulf of Mexico revealed minimal spectral interferences from sediment matrix components. As such, evanescent field sensing strategies were established as a promising perspective for monitoring the dynamics of gas hydrates in oceanic environments. 21 refs., 5 figs.

  10. Thermal Regeneration of Sulfuric Acid Hydrates after Irradiation

    Science.gov (United States)

    Loeffler, Mark J.; Hudson, Reggie L.

    2012-01-01

    In an attempt to more completely understand the surface chemistry of the jovian icy satellites, we have investigated the effect of heating on two irradiated crystalline sulfuric acid hydrates, H2SO4 4H2O and H2SO4 H2O. At temperatures relevant to Europa and the warmer jovian satellites, post-irradiation heating recrystallized the amorphized samples and increased the intensities of the remaining hydrate's infrared absorptions. This thermal regeneration of the original hydrates was nearly 100% efficient, indicating that over geological times, thermally-induced phase transitions enhanced by temperature fluctuations will reform a large fraction of crystalline hydrated sulfuric acid that is destroyed by radiation processing. The work described is the first demonstration of the competition between radiation-induced amorphization and thermally-induced recrystallization in icy ionic solids relevant to the outer Solar System.

  11. Maximum Recoverable Gas from Hydrate Bearing Sediments by Depressurization

    KAUST Repository

    Terzariol, Marco; Goldsztein, G.; Santamarina, Carlos

    2017-01-01

    financial analyses; results highlight the need for innovative production strategies in order to make hydrate accumulations an economically-viable energy resource. Horizontal directional drilling and multi-wellpoint seafloor dewatering installations may lead

  12. Skin hydration in nursing home residents using disposable bed baths.

    Science.gov (United States)

    Gillis, Katrin; Tency, Inge; Roelant, Ella; Laureys, Sarina; Devriendt, Hendrik; Lips, Dirk

    2016-01-01

    The objective of this study was to evaluate a new way for applying bed baths and reducing the risk for dry skin by comparing the effect of two washing methods on skin hydration. A cluster randomized trial was conducted. Skin hydration was measured before and after implementation of disposable wash gloves, using a MoistureMeter SC at three skin sites. Total skin hydration did not differ between residents at the start of the study in both groups. After implementation, the post minus pre hydration scores were higher for the intervention group than the control group at all skin sites. However, the difference was only significant at cheek site. The use of disposable wash gloves does not increase the risk for dry skin in comparison with traditional washing methods. These results may encourage the introduction of disposable wash gloves as an innovation in daily skin care practice. Copyright © 2016 Elsevier Inc. All rights reserved.

  13. Influence of Liquid Paraffin, White Soft Paraffin and Initial Hydration ...

    African Journals Online (AJOL)

    hydrated white soft paraffin on the viscosity of a cream formulated with a corticosteroid. Methods: The formulations were prepared via homogenization with variable velocity in the range 3300 - 4000 rpm. Individual series of preparations contained the ...

  14. Early hydration cement Effect of admixtures superplasticizers

    Directory of Open Access Journals (Sweden)

    Puertas, F.

    2001-06-01

    Full Text Available Early hydration of portland cement with superplasticizer admixtures of different nature has been studied. These admixtures were: one based on melamine synthetic, other based on vinyl copolymer and other based on polyacrylate copolymers. The dosage of the formers were constant (1% weigth of cement and for the third, the influence of admixture dosage was also evaluated, giving dosage values among 1-0.3%. The pastes obtained were studied by conduction calorimetry, XRD and FTIR. Also the apparent fluidity was determined by "Minislump" test. The main results obtained were: a superplasticizers admixtures used, regardless of their nature and for the polycarboxilate one the dosage, retard the silicate hydration (specially, alite phase, b The ettringite formation is affected by the nature of the admixture. cA relationship between the dosage of admixture based on polycarboxilates and the time at the acceleration has been established. A lineal relation (y = 11.03 + 16.05x was obtained. From these results is possible to know, in function of dosage admixture, the time when the masive hydration products and the setting times are produced. Also the total heat releases in these reactions is independent of the nature and dosage of admixture, saying that in all cases the reactions are the same.

    En el presente trabajo se ha estudiado la hidratación inicial de un cemento portland aditivado con superplastificantes de diferente naturaleza. Dichos aditivos fueron: uno basado en melaminas sintéticas, otro en copolímeros vinilicos y otro en policarboxilatos. La dosificación de los dos primeros se fijó constante en 1% en peso con relación al cemento, mientras que para el tercero se evaluó, también, la influencia de la dosificación, tomando proporciones desde el 1% hasta el 0,3%. Las pastas obtenidas se estudiaron por: calorimetría de conducción, DRX y FTIR. También se determinó la fluidez de la pasta a través del ensayo del "Minislump ". Los

  15. A multivariable model for predicting the frictional behaviour and hydration of the human skin.

    Science.gov (United States)

    Veijgen, N K; van der Heide, E; Masen, M A

    2013-08-01

    The frictional characteristics of skin-object interactions are important when handling objects, in the assessment of perception and comfort of products and materials and in the origins and prevention of skin injuries. In this study, based on statistical methods, a quantitative model is developed that describes the friction behaviour of human skin as a function of the subject characteristics, contact conditions, the properties of the counter material as well as environmental conditions. Although the frictional behaviour of human skin is a multivariable problem, in literature the variables that are associated with skin friction have been studied using univariable methods. In this work, multivariable models for the static and dynamic coefficients of friction as well as for the hydration of the skin are presented. A total of 634 skin-friction measurements were performed using a recently developed tribometer. Using a statistical analysis, previously defined potential influential variables were linked to the static and dynamic coefficient of friction and to the hydration of the skin, resulting in three predictive quantitative models that descibe the friction behaviour and the hydration of human skin respectively. Increased dynamic coefficients of friction were obtained from older subjects, on the index finger, with materials with a higher surface energy at higher room temperatures, whereas lower dynamic coefficients of friction were obtained at lower skin temperatures, on the temple with rougher contact materials. The static coefficient of friction increased with higher skin hydration, increasing age, on the index finger, with materials with a higher surface energy and at higher ambient temperatures. The hydration of the skin was associated with the skin temperature, anatomical location, presence of hair on the skin and the relative air humidity. Predictive models have been derived for the static and dynamic coefficient of friction using a multivariable approach. These

  16. Investigation of Methane Hydrate Formation in a Recirculating Flow Loop: Modeling of the Kinetics and Tests of Efficiency of Chemical Additives on Hydrate Inhibition Étude de la formation de l'hydrate de méthane dans une conduite de recirculation : modélisation de la cinétique et tests d'efficacité d'additifs chimiques inhibiteurs d'hydrates de gaz

    Directory of Open Access Journals (Sweden)

    Peytavy J. L.

    2006-12-01

    Full Text Available Gas hydrates can be formed when light gases, such as the components of natural gas, come into contact with water under particular conditions of temperature and pressure. These solid compounds give rise to problems in natural gas and oil industry because they can plug pipelines and process equipment. To prevent hydrate formation methanol and glycols are commonly and extensively used as inhibitors. Today, the thermodynamic equilibria of hydrate formation are well known, but the kinetics of gas hydrate formation and growth has to be studied in order to find means of controlling these processes and to explore the mechanisms for hydrate formation that follows non equilibrium laws. The present work deals with the kinetics of methane hydrate formation studied in a laboratory loop where the liquid blend saturated with methane is circulated up to a pressure of 75 bar. Pressure is maintained at a constant value during experimental runs by means of methane gas make-up. First the effects of pressure (35-75 bar, liquid velocity (0. 5-3 m/s, liquid cooling temperature ramp (2-15°C/h, and liquid hydrocarbon amount (0-96%, on hydrate formation kinetics are investigated. Then a new method is proposed to predict firstly the thermodynamic conditions (pressure and temperature at the maximum values of the growth rate of methane hydrate and secondly the methane hydrate growth rate. A good agreement is found between calculated and experimental data. Finally the evaluation of the efficiency of some kinetic additives and some surfactants developed to avoid either nucleation or crystal growth and agglomeration of methane hydrates is tested based on the proposed experimental procedure. Les hydrates de gaz des composés légers du gaz naturel se forment lorsque ceux-ci entrent en contact avec l'eau dans certaines conditions de température et de pression. Ces composés solides sont nuisibles pour les industries gazière et pétrolière car des bouchons solides peuvent

  17. Development of an offshore gas field - investigation of hydrate and paraffin formation potential with regard to flow assurance; Entwicklung eines Offshore-Gasfeldes: Hydrat- und Paraffinuntersuchungen zur Sicherstellung der kontinuierlichen Produktion

    Energy Technology Data Exchange (ETDEWEB)

    Zettlitzer, M.; Busch, M. [RWE Dea AG, Wietze (Germany)

    2005-11-01

    During the production of offshore gas fields, raw gas from a number of production wells is usually led to a platform or - for reservoirs located close to shore - even transported as wet gas to an onshore gas treatment plant. The pipelines are located at the sea bottom, resulting in significant cooling of the raw gas with subsequent potential for the formation of hydrates and/or precipitation of paraffin on the pipeline walls. In order to safeguard continuous production, additional installations and/or dosage of chemicals would possibly be required. On the basis of gas and condensate samples from production tests, the formation potential for paraffins was experimentally investigated while the hydrate formation potential was assessed by simulations. The very small volume of condensate available (2-3 ml of each sample) formed a special challenge and limited the number of possible analytical investigations. Nevertheless, wax appearance temperature of five condensates under investigation could successfully be determined by a combination of gas-chromatographic and rheological measurements. Two of the three gas-bearing layers turned out to produce dry gas so that paraffin problems can be excluded. However, according to the simulations, hydrate formation at temperatures {<=}+20 C has to be expected under the formation pressure of about 200 bars. The third layer contains a gas condensate, causing paraffin precipitation at {<=}0 C and forming hydrate in a temperature range similar to that of the other two sands. Hence, precautions have to taken to prevent hydrate formation in all field lines containing wet gas. Furthermore, the paraffin precipitation potential has to be taken into account in the subsequent low-temperature gas-treatment plant. (orig.)

  18. HEC influence on cement hydration measured by conductometry

    OpenAIRE

    Pourchez , Jérémie; Grosseau , Philippe; Guyonnet , René; Ruot , Bertrand

    2006-01-01

    International audience; Cellulose ethers are of universal use in factory-made mortars, though their influences on mortar properties at a molecular scale are poorly understood. Recent studies dealt with the influence of hydroxyethylmethyl cellulose (HEMC) and hydroxypropylmethyl cellulose (HPMC) molecular parameters on cement hydration. It was concluded that the degree of substitution is the most relevant factor on cement hydration kinetics, contrary to the molecular weight. Nevertheless, the ...

  19. Monitoring membrane hydration with 2-(dimethylamino)-6-acylnaphtalenes fluorescent probes

    DEFF Research Database (Denmark)

    Bagatolli, Luis

    2015-01-01

    of LAURDAN and PRODAN are exquisitely sensitive to cholesterol effects, allowing interpretations that correlate changes in membrane packing with membrane hydration. Different membrane model systems as well as innate biological membranes have been studied with this family of probes allowing interesting...... comparative studies. This chapter presents a short historical overview about these fluorescent reporters, discusses on different models proposed to explain their sensitivity to membrane hydration, and includes relevant examples from experiments performed in artificial and biological membranes....

  20. Transport of hydrate slurry at high water cut

    OpenAIRE

    Melchuna , Aline; Cameirão , Ana; Herri , Jean-Michel; Ouabbas , Yamina; Glenat , Philippe

    2014-01-01

    Poster; International audience; Oil transportation in pipelines at the end of field production life implies to flow high quantities of water which represents the dominant phase. The process of crystallization of gas hydrates in this system needs to be studied and compared to the opposite one widely studied in the literature where water is the dispersed phase. The laboratory is equipped with the Archimede flow loop where the hydrate crystallization and transport are monitored. The flow loop is...

  1. Formation of nitric acid hydrates - A chemical equilibrium approach

    Science.gov (United States)

    Smith, Roland H.

    1990-01-01

    Published data are used to calculate equilibrium constants for reactions of the formation of nitric acid hydrates over the temperature range 190 to 205 K. Standard enthalpies of formation and standard entropies are calculated for the tri- and mono-hydrates. These are shown to be in reasonable agreement with earlier calorimetric measurements. The formation of nitric acid trihydrate in the polar stratosphere is discussed in terms of these equilibrium constants.

  2. Life Origination Hydrate Theory (LOH-Theory) and Mitosis and Replication Hydrate Theory (MRH-Theory): three-dimensional PC validation

    Science.gov (United States)

    Kadyshevich, E. A.; Dzyabchenko, A. V.; Ostrovskii, V. E.

    2014-04-01

    Size compatibility of the CH4-hydrate structure II and multi-component DNA fragments is confirmed by three-dimensional simulation; it is validation of the Life Origination Hydrate Theory (LOH-Theory).

  3. Gas Hydrate-Sediment Morphologies Revealed by Pressure Core Analysis

    Science.gov (United States)

    Holland, M.; Schultheiss, P.; Roberts, J.; Druce, M.

    2006-12-01

    Analysis of HYACINTH pressure cores collected on IODP Expedition 311 and NGHP Expedition 1 showed gas hydrate layers, lenses, and veins contained in fine-grained sediments as well as gas hydrate contained in coarse-grained layers. Pressure cores were recovered from sediments on the Cascadia Margin off the North American West Coast and in the Krishna-Godavari Basin in the Western Bay of Bengal in water depths of 800- 1400 meters. Recovered cores were transferred to laboratory chambers without loss of pressure and nondestructive measurements were made at in situ pressures and controlled temperatures. Gamma density, P-wave velocity, and X-ray images showed evidence of grain-displacing and pore-filling gas hydrate in the cores. Data highlights include X-ray images of fine-grained sediment c