Low physiologic oxygen tensions reduce proliferation and differentiation of human multipotent mesenchymal stromal cells

Directory of Open Access Journals (Sweden)

Handgretinger Rupert

2010-01-01

Full Text Available Abstract Background Human multipotent mesenchymal stromal cells (MSC can be isolated from various tissues including bone marrow. Here, MSC participate as bone lining cells in the formation of the hematopoietic stem cell niche. In this compartment, the oxygen tension is low and oxygen partial pressure is estimated to range from 1% to 7%. We analyzed the effect of low oxygen tensions on human MSC cultured with platelet-lysate supplemented media and assessed proliferation, morphology, chromosomal stability, immunophenotype and plasticity. Results After transferring MSC from atmospheric oxygen levels of 21% to 1%, HIF-1α expression was induced, indicating efficient oxygen reduction. Simultaneously, MSC exhibited a significantly different morphology with shorter extensions and broader cell bodies. MSC did not proliferate as rapidly as under 21% oxygen and accumulated in G1 phase. The immunophenotype, however, was unaffected. Hypoxic stress as well as free oxygen radicals may affect chromosomal stability. However, no chromosomal abnormalities in human MSC under either culture condition were detected using high-resolution matrix-based comparative genomic hybridization. Reduced oxygen tension severely impaired adipogenic and osteogenic differentiation of human MSC. Elevation of oxygen from 1% to 3% restored osteogenic differentiation. Conclusion Physiologic oxygen tension during in vitro culture of human MSC slows down cell cycle progression and differentiation. Under physiological conditions this may keep a proportion of MSC in a resting state. Further studies are needed to analyze these aspects of MSC in tissue regeneration.

A Method for Combined Retinal Vascular and Tissue Oxygen Tension Imaging.

Science.gov (United States)

Felder, Anthony E; Wanek, Justin; Tan, Michael R; Blair, Norman P; Shahidi, Mahnaz

2017-09-06

The retina requires adequate oxygenation to maintain cellular metabolism and visual function. Inner retinal oxygen metabolism is directly related to retinal vascular oxygen tension (PO 2 ) and inner retinal oxygen extraction fraction (OEF), whereas outer retinal oxygen consumption (QO 2 ) relies on oxygen availability by the choroid and is contingent upon retinal tissue oxygen tension (tPO 2 ) gradients across the retinal depth. Thus far, these oxygenation and metabolic parameters have been measured independently by different techniques in separate animals, precluding a comprehensive and correlative assessment of retinal oxygenation and metabolism dynamics. The purpose of the current study is to report an innovative optical system for dual oxyphor phosphorescence lifetime imaging to near-simultaneously measure retinal vascular PO 2 and tPO 2 in rats. The use of a new oxyphor with different spectral characteristics allowed differentiation of phosphorescence signals from the retinal vasculature and tissue. Concurrent measurements of retinal arterial and venous PO 2 , tPO 2 through the retinal depth, inner retinal OEF, and outer retinal QO 2 were demonstrated, permitting a correlative assessment of retinal oxygenation and metabolism. Future application of this method can be used to investigate the relations among retinal oxygen content, extraction and metabolism under pathologic conditions and thus advance knowledge of retinal hypoxia pathophysiology.

A method for volumetric retinal tissue oxygen tension imaging.

Science.gov (United States)

Felder, Anthony E; Wanek, Justin; Teng, Pang-Yu; Blair, Norman P; Shahidi, Mahnaz

2018-01-01

Inadequate retinal oxygenation occurs in many vision-threatening retinal diseases, including diabetic retinopathy, retinal vascular occlusions, and age-related macular degeneration. Therefore, techniques that assess retinal oxygenation are necessary to understand retinal physiology in health and disease. The purpose of the current study is to report a method for the three-dimensional (3D) imaging of retinal tissue oxygen tension (tPO 2 ) in rats. Imaging was performed in Long Evans pigmented rats under systemic normoxia (N = 6) or hypoxia (N = 3). A vertical laser line was horizontally scanned on the retina and a series of optical section phase-delayed phosphorescence images were acquired. From these images, phosphorescence volumes at each phase delay were constructed and a 3D retinal tPO 2 volume was generated. Retinal tPO 2 volumes were quantitatively analyzed by generating retinal depth profiles of mean tPO 2 (M tPO2 ) and the spatial variation of tPO 2 (SV tPO2 ). The effects of systemic condition (normoxia/hypoxia) and retinal depth on M tPO2 and SV tPO2 were determined by mixed linear model. Each 3D retinal tPO 2 volume was approximately 500 × 750 × 200 μm (horizontal × vertical × depth) and consisted of 45 en face tPO 2 images through the retinal depth. M tPO2 at the chorioretinal interface was significantly correlated with systemic arterial oxygen tension (P = 0.007; N = 9). There were significant effects of both systemic condition and retinal depth on M tPO2 and SV tPO2 , such that both were lower under hypoxia than normoxia and higher in the outer retina than inner retina (P < 0.001). For the first time, 3D imaging of retinal tPO 2 was demonstrated, with potential future application for assessment of physiological alterations in animal models of retinal diseases.

Oxygen tension regulates the osteogenic, chondrogenic and endochondral phenotype of bone marrow derived mesenchymal stem cells

Energy Technology Data Exchange (ETDEWEB)

Sheehy, Eamon J.; Buckley, Conor T. [Trinity Centre for Bioengineering, School of Engineering, Trinity College Dublin, Dublin 2 (Ireland); Kelly, Daniel J., E-mail: kellyd9@tcd.ie [Trinity Centre for Bioengineering, School of Engineering, Trinity College Dublin, Dublin 2 (Ireland)

2012-01-06

Highlights: Black-Right-Pointing-Pointer Expansion in low oxygen enhances MSC proliferation and osteogenesis. Black-Right-Pointing-Pointer Differentiation in low oxygen enhances chondrogenesis and suppresses hypertrophy. Black-Right-Pointing-Pointer Oxygen can regulate the MSC phenotype for use in tissue engineering applications. -- Abstract: The local oxygen tension is a key regulator of the fate of mesenchymal stem cells (MSCs). The objective of this study was to investigate the effect of a low oxygen tension during expansion and differentiation on the proliferation kinetics as well as the subsequent osteogenic and chondrogenic potential of MSCs. We first hypothesised that expansion in a low oxygen tension (5% pO{sub 2}) would improve both the subsequent osteogenic and chondrogenic potential of MSCs compared to expansion in a normoxic environment (20% pO{sub 2}). Furthermore, we hypothesised that chondrogenic differentiation in a low oxygen environment would suppress hypertrophy of MSCs cultured in both pellets and hydrogels used in tissue engineering strategies. MSCs expanded at 5% pO{sub 2} proliferated faster forming larger colonies, resulting in higher cell yields. Expansion at 5% pO{sub 2} also enhanced subsequent osteogenesis of MSCs, whereas differentiation at 5% pO{sub 2} was found to be a more potent promoter of chondrogenesis than expansion at 5% pO{sub 2}. Greater collagen accumulation, and more intense staining for collagen types I and X, was observed in pellets maintained at 20% pO{sub 2} compared to 5% pO{sub 2}. Both pellets and hydrogels stained more intensely for type II collagen when undergoing chondrogenesis in a low oxygen environment. Differentiation at 5% pO{sub 2} also appeared to inhibit hypertrophy in both pellets and hydrogels, as demonstrated by reduced collagen type X and Alizarin Red staining and alkaline phosphatase activity. This study demonstrates that the local oxygen environment can be manipulated in vitro to either stabilise a

Matrix forming characteristics of inner and outer human meniscus cells on 3D collagen scaffolds under normal and low oxygen tensions.

Science.gov (United States)

Croutze, Roger; Jomha, Nadr; Uludag, Hasan; Adesida, Adetola

2013-12-13

Limited intrinsic healing potential of the meniscus and a strong correlation between meniscal injury and osteoarthritis have prompted investigation of surgical repair options, including the implantation of functional bioengineered constructs. Cell-based constructs appear promising, however the generation of meniscal constructs is complicated by the presence of diverse cell populations within this heterogeneous tissue and gaps in the information concerning their response to manipulation of oxygen tension during cell culture. Four human lateral menisci were harvested from patients undergoing total knee replacement. Inner and outer meniscal fibrochondrocytes (MFCs) were expanded to passage 3 in growth medium supplemented with basic fibroblast growth factor (FGF-2), then embedded in porous collagen type I scaffolds and chondrogenically stimulated with transforming growth factor β3 (TGF-β3) under 21% (normal or normoxic) or 3% (hypoxic) oxygen tension for 21 days. Following scaffold culture, constructs were analyzed biochemically for glycosaminoglycan production, histologically for deposition of extracellular matrix (ECM), as well as at the molecular level for expression of characteristic mRNA transcripts. Constructs cultured under normal oxygen tension expressed higher levels of collagen type II (p = 0.05), aggrecan (p oxygen tension. There was no significant difference in expression of these genes between scaffolds seeded with MFCs isolated from inner or outer regions of the tissue following 21 days chondrogenic stimulation (p > 0.05). Cells isolated from inner and outer regions of the human meniscus demonstrated equivalent differentiation potential toward chondrogenic phenotype and ECM production. Oxygen tension played a key role in modulating the redifferentiation of meniscal fibrochondrocytes on a 3D collagen scaffold in vitro.

In vivo mitochondrial oxygen tension measured by a delayed fluorescence lifetime technique

NARCIS (Netherlands)

Mik, Egbert G.; Johannes, Tanja; Zuurbier, Coert J.; Heinen, Andre; Houben-Weerts, Judith H. P. M.; Balestra, Gianmarco M.; Stap, Jan; Beek, Johan F.; Ince, Can

2008-01-01

Mitochondrial oxygen tension (mitoPO(2)) is a key parameter for cellular function, which is considered to be affected under various pathophysiological circumstances. Although many techniques for assessing in vivo oxygenation are available, no technique for measuring mitoPO(2) in vivo exists. Here we

Impact of low oxygen tension on stemness, proliferation and differentiation potential of human adipose-derived stem cells

Energy Technology Data Exchange (ETDEWEB)

Choi, Jane Ru; Pingguan-Murphy, Belinda; Wan Abas, Wan Abu Bakar [Department of Biomedical Engineering, Faculty of Engineering, University of Malaya, Lembah Pantai, 50603 Kuala Lumpur (Malaysia); Noor Azmi, Mat Adenan; Omar, Siti Zawiah [Department of Obstetrics and Gynaecology, Faculty of Medicine, University of Malaya, Lembah Pantai, 50603 Kuala Lumpur (Malaysia); Chua, Kien Hui [Department of Physiology, Faculty of Medicine, Universiti Kebangsaan Malaysia, Jalan Raja Muda Abdul Aziz, 50300 Kuala Lumpur (Malaysia); Wan Safwani, Wan Kamarul Zaman, E-mail: wansafwani@um.edu.my [Department of Biomedical Engineering, Faculty of Engineering, University of Malaya, Lembah Pantai, 50603 Kuala Lumpur (Malaysia)

2014-05-30

Highlights: • Hypoxia maintains the stemness of adipose-derived stem cells (ASCs). • ASCs show an increased proliferation rate under low oxygen tension. • Oxygen level as low as 2% enhances the chondrogenic differentiation potential of ASCs. • HIF-1α may regulate the proliferation and differentiation activities of ASCs under hypoxia. - Abstract: Adipose-derived stem cells (ASCs) have been found adapted to a specific niche with low oxygen tension (hypoxia) in the body. As an important component of this niche, oxygen tension has been known to play a critical role in the maintenance of stem cell characteristics. However, the effect of O{sub 2} tension on their functional properties has not been well determined. In this study, we investigated the effects of O{sub 2} tension on ASCs stemness, differentiation and proliferation ability. Human ASCs were cultured under normoxia (21% O{sub 2}) and hypoxia (2% O{sub 2}). We found that hypoxia increased ASC stemness marker expression and proliferation rate without altering their morphology and surface markers. Low oxygen tension further enhances the chondrogenic differentiation ability, but reduces both adipogenic and osteogenic differentiation potential. These results might be correlated with the increased expression of HIF-1α under hypoxia. Taken together, we suggest that growing ASCs under 2% O{sub 2} tension may be important in expanding ASCs effectively while maintaining their functional properties for clinical therapy, particularly for the treatment of cartilage defects.

[Long-term expansion of multipotent mesenchymal stromal cells under reduced oxygen tension].

Science.gov (United States)

Rylova, Iu V; Buravkova, L B

2013-01-01

We have shown that the decrease in oxygen tension in the culture medium of multipotent mesenchymal stromal cells (MMSCs) results in a short-term reduction in the proportion of CD73(+)-cells in the population, without effecting the number of cells expressing other constitutive surface markers (CD90 and CD105). In this case, the heterogeneity of the cell population declined: large spread cells disappeared. The proliferative activity of MMSCs significantly increased and remained stable in conditions in which the oxygen content was close to the tissue oxygen levels (5% O2). At lower oxygen concentration, proliferative activity of the cells gradually reduced from passages 3-4. The increase in proliferative activity was not accompanied by increased expression of telomerase gene indicateding the alsance of cell transformation. However, genome-wide analysis of MMSC gene expression level revealed changes in expression of cyclins (CCND2 and PCNA), regulatory subunit cyclin-dependent kinase (CKS2) and an inhibitor of cyclin-dependent kinase (CDKN2C), regulating the cell cycle, which is obviously facilitated the increase in the proliferative capacity of cells at lower oxygen tension.

Control of oxygen tension recapitulates zone-specific functions in human liver microphysiology systems.

Science.gov (United States)

Lee-Montiel, Felipe T; George, Subin M; Gough, Albert H; Sharma, Anup D; Wu, Juanfang; DeBiasio, Richard; Vernetti, Lawrence A; Taylor, D Lansing

2017-10-01

This article describes our next generation human Liver Acinus MicroPhysiology System (LAMPS). The key demonstration of this study was that Zone 1 and Zone 3 microenvironments can be established by controlling the oxygen tension in individual devices over the range of ca. 3 to 13%. The oxygen tension was computationally modeled using input on the microfluidic device dimensions, numbers of cells, oxygen consumption rates of hepatocytes, the diffusion coefficients of oxygen in different materials and the flow rate of media in the MicroPhysiology System (MPS). In addition, the oxygen tension was measured using a ratiometric imaging method with the oxygen sensitive dye, Tris(2,2'-bipyridyl) dichlororuthenium(II) hexahydrate (RTDP) and the oxygen insensitive dye, Alexa 488. The Zone 1 biased functions of oxidative phosphorylation, albumin and urea secretion and Zone 3 biased functions of glycolysis, α1AT secretion, Cyp2E1 expression and acetaminophen toxicity were demonstrated in the respective Zone 1 and Zone 3 MicroPhysiology System. Further improvements in the Liver Acinus MicroPhysiology System included improved performance of selected nonparenchymal cells, the inclusion of a porcine liver extracellular matrix to model the Space of Disse, as well as an improved media to support both hepatocytes and non-parenchymal cells. In its current form, the Liver Acinus MicroPhysiology System is most amenable to low to medium throughput, acute through chronic studies, including liver disease models, prioritizing compounds for preclinical studies, optimizing chemistry in structure activity relationship (SAR) projects, as well as in rising dose studies for initial dose ranging. Impact statement Oxygen zonation is a critical aspect of liver functions. A human microphysiology system is needed to investigate the impact of zonation on a wide range of liver functions that can be experimentally manipulated. Because oxygen zonation has such diverse physiological effects in the liver, we

Oxygen Tension Regulates Human Mesenchymal Stem Cell Paracrine Functions.

Science.gov (United States)

Paquet, Joseph; Deschepper, Mickael; Moya, Adrien; Logeart-Avramoglou, Delphine; Boisson-Vidal, Catherine; Petite, Hervé

2015-07-01

: Mesenchymal stem cells (MSCs) have captured the attention and research endeavors of the scientific world because of their differentiation potential. However, there is accumulating evidence suggesting that the beneficial effects of MSCs are predominantly due to the multitude of bioactive mediators secreted by these cells. Because the paracrine potential of MSCs is closely related to their microenvironment, the present study investigated and characterized select aspects of the human MSC (hMSC) secretome and assessed its in vitro and in vivo bioactivity as a function of oxygen tension, specifically near anoxia (0.1% O2) and hypoxia (5% O2), conditions that reflect the environment to which MSCs are exposed during MSC-based therapies in vivo. In contrast to supernatant conditioned media (CM) obtained from hMSCs cultured at either 5% or 21% of O2, CM from hMSCs cultured under near anoxia exhibited significantly (p mesenchymal stem cell (hMSC) secretome and assessed its in vitro and in vivo biological bioactivity as a function of oxygen tension, specifically near anoxia (0.1% O2) and hypoxia (5% O2), conditions that reflect the environment to which MSCs are exposed during MSC-based therapies in vivo. The present study provided the first evidence of a shift of the hMSC cytokine signature induced by oxygen tension, particularly near anoxia (0.1% O2). Conditioned media obtained from hMSCs cultured under near anoxia exhibited significantly enhanced chemotactic and proangiogenic properties and a significant decrease in the inflammatory mediator content. These findings provide new evidence that elucidates aspects of great importance for the use of MSCs in regenerative medicine, could contribute to improving the efficacy of such therapies, and most importantly highlighted the interest in using conditioned media in therapeutic modalities. ©AlphaMed Press.

Evaluation of multi-exponential curve fitting analysis of oxygen-quenched phosphorescence decay traces for recovering microvascular oxygen tension histograms

NARCIS (Netherlands)

Bezemer, Rick; Faber, Dirk J.; Almac, Emre; Kalkman, Jeroen; Legrand, Matthieu; Heger, Michal; Ince, Can

2010-01-01

Although it is generally accepted that oxygen-quenched phosphorescence decay traces can be analyzed using the exponential series method (ESM), its application until now has been limited to a few (patho)physiological studies, probably because the reliability of the recovered oxygen tension (pO(2))

Low Oxygen Tension Enhances Expression of Myogenic Genes When Human Myoblasts Are Activated from G0 Arrest

DEFF Research Database (Denmark)

Sellathurai, Jeeva; Nielsen, Joachim; Hejbøl, Eva Kildall

2016-01-01

-PCR, immunocytochemistry and western blot. RESULTS AND CONCLUSIONS: We found an increase in proliferation rate of myoblasts when activated at a low oxygen tension (1% O2) compared to 21% O2. In addition, the gene expression studies showed up regulation of the myogenesis related genes PAX3, PAX7, MYOD, MYOG (myogenin), MET......, NCAM, DES (desmin), MEF2A, MEF2C and CDH15 (M-cadherin), however, the fraction of DES and MYOD positive cells was not increased by low oxygen tension, indicating that 1% O2 may not have a functional effect on the myogenic response. Furthermore, the expression of genes involved in the TGFβ, Notch...... and Wnt signaling pathways were also up regulated in low oxygen tension. The differences in gene expression were most pronounced at day one after activation from G0-arrest, thus the initial activation of myoblasts seemed most sensitive to changes in oxygen tension. Protein expression of HES1 and β...

"Tissue oxygen tension, a determinant of resistance to infection and ...

African Journals Online (AJOL)

"Tissue oxygen tension, a determinant of resistance to infection and healing" - An Inaugural Lecture. K Jönsson. Abstract. An Inaugural Lecture Given in the University of Zimbabwe on 21 June 2001. Full Text: EMAIL FULL TEXT EMAIL FULL TEXT · DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT.

Cerebral interstitial tissue oxygen tension, pH, HCO3, CO2.

Science.gov (United States)

Charbel, F T; Hoffman, W E; Misra, M; Hannigan, K; Ausman, J I

1997-10-01

There are many techniques for monitoring the injured brain following trauma, subarachnoid hemorrhage, or surgery. It is thought that the major determinants for recovery of injured cerebral tissue are oxygen, glucose delivery, and the clearance of metabolites. These factors, at optimal levels, are probably responsible for the regaining of neuronal functions. These parameters are in turn dependent on the tissue's blood flow and metabolism. We have been using a single, compact, polyethylene sensor, the Paratrend 7 for the measurement of cerebral oxygen tension, CO2, pH, and temperature. This sensor is designed for continuous blood gas analysis to aid in monitoring neurosurgical patients, both during surgery and in the intensive care unit. Using the Paratrend 7 sensor, we found the normal range of values to be: PO2 33 +/- 11 mm Hg; PCO2 48 +/- 7 mm Hg; pH 7.19 +/- 0.11. Critical measurements are considered to be tissue PO2 60 mm Hg, and pH effective method of measuring tissue cerebral oxygen tension, along with carbon dioxide levels, pH, and temperature.

Oxygen tension is a determinant of the matrix-forming phenotype of cultured human meniscal fibrochondrocytes.

Directory of Open Access Journals (Sweden)

Adetola B Adesida

Full Text Available BACKGROUND: Meniscal cartilage displays a poor repair capacity, especially when injury is located in the avascular region of the tissue. Cell-based tissue engineering strategies to generate functional meniscus substitutes is a promising approach to treat meniscus injuries. Meniscus fibrochondrocytes (MFC can be used in this approach. However, MFC are unable to retain their phenotype when expanded in culture. In this study, we explored the effect of oxygen tension on MFC expansion and on their matrix-forming phenotype. METHODOLOGY/PRINCIPAL FINDINGS: MFC were isolated from human menisci followed by basic fibroblast growth factor (FGF-2 mediated cell expansion in monolayer culture under normoxia (21%O(2 or hypoxia (3%O(2. Normoxia and hypoxia expanded MFC were seeded on to a collagen scaffold. The MFC seeded scaffolds (constructs were cultured in a serum free chondrogenic medium for 3 weeks under normoxia and hypoxia. Constructs containing normoxia-expanded MFC were subsequently cultured under normoxia while those formed from hypoxia-expanded MFC were subsequently cultured under hypoxia. After 3 weeks of in vitro culture, the constructs were assessed biochemically, histologically and for gene expression via real-time reverse transcription-PCR assays. The results showed that constructs under normoxia produced a matrix with enhanced mRNA ratio (3.5-fold higher; p<0.001 of collagen type II to I. This was confirmed by enhanced deposition of collagen II using immuno-histochemistry. Furthermore, the constructs under hypoxia produced a matrix with higher mRNA ratio of aggrecan to versican (3.5-fold, p<0.05. However, both constructs had the same capacity to produce a glycosaminoglycan (GAG -specific extracellular matrix. CONCLUSIONS: Our data provide evidence that oxygen tension is a key player in determining the matrix phenotype of cultured MFC. These findings suggest that the use of normal and low oxygen tension during MFC expansion and subsequent neo

Bladder urine oxygen tension for assessing renal medullary oxygenation in rabbits: experimental and modeling studies

OpenAIRE

Sgouralis, Ioannis; Kett, Michelle M.; Ow, Connie P. C.; Abdelkader, Amany; Layton, Anita T.; Gardiner, Bruce S.; Smith, David W.; Lankadeva, Yugeesh R.; Evans, Roger G.

2016-01-01

Oxygen tension (Po2) of urine in the bladder could be used to monitor risk of acute kidney injury if it varies with medullary Po2. Therefore, we examined this relationship and characterized oxygen diffusion across walls of the ureter and bladder in anesthetized rabbits. A computational model was then developed to predict medullary Po2 from bladder urine Po2. Both intravenous infusion of [Phe2,Ile3,Orn8]-vasopressin and infusion of NG-nitro-l-arginine reduced urinary Po2 and medullary Po2 (8–1...

Oxygen Tension Regulates Human Mesenchymal Stem Cell Paracrine Functions

OpenAIRE

Paquet, Joseph; Deschepper, Mickael; Moya, Adrien; Logeart-Avramoglou, Delphine; Boisson-Vidal, Catherine; Petite, Hervé

2015-01-01

This study examined the shift of the human mesenchymal stem cell (hMSC) cytokine signature induced by oxygen tension. Conditioned media obtained from hMSCs cultured under near anoxia exhibited significantly enhanced chemotactic and proangiogenic properties and a significant decrease in the inflammatory mediator content. These results elucidate important aspects of using MSCs in regenerative medicine, contribute to improving the efficacy of such therapies, and highlight the interest in using c...

Enhanced proliferation and dopaminergic differentiation of ventral mesencephalic precursor cells by synergistic effect of FGF2 and reduced oxygen tension

DEFF Research Database (Denmark)

Jensen, Pia; Gramsbergen, Jan-Bert; Zimmer, Jens

2011-01-01

Effective numerical expansion of dopaminergic precursors might overcome the limited availability of transplantable cells in replacement strategies for Parkinson's disease. Here we investigated the effect of fibroblast growth factor-2 (FGF2) and FGF8 on expansion and dopaminergic differentiation o...... enzyme activity, which may explain the elevated dopamine levels. Our findings demonstrate that modulation of oxygen tension is a recognizable factor for in vitro expansion and dopaminergic differentiation of rat embryonic midbrain precursor cells....... of rat embryonic ventral mesencephalic neuroblasts cultured at high (20%) and low (3%) oxygen tension. More cells incorporated bromodeoxyuridine in cultures expanded at low as compared to high oxygen tension, and after 6 days of differentiation there were significantly more neuronal cells in low than......, switching FGF2-expanded cultures from low to high oxygen tension during the last two days of differentiation significantly enhanced dopamine release and intracellular dopamine levels as compared to all other treatment groups. In addition, the short-term exposure to high oxygen enhanced in situ assessed TH...

The Role of Oxygen Tension in Penile Erection and Its Relationship to Erectile Dysfunction

Directory of Open Access Journals (Sweden)

Jong-Kwan Park

2004-01-01

Full Text Available The corpus cavernosum of the penis is one of the few vascular beds in which there is a change in oxygen tension with function (blood PO2 25-40mm Hg in the flaccid state, and 90-100mm Hg in the erect state. This change in oxygen tension exposes the components of the corpus cavernosum to a variety of cytokines, humoral, vasoactive, and growth factors which may affect the structure and function of the endothelial cells, smooth muscle cells, neurons and extracellular matrix. Among these cell types, endothelial cells are the first line of defense to blood-borne stress and can affect the underlying smooth muscle via paracrine mechanisms. Impotence is defined as the inability to obtain or sustain an erection sufficient for vaginal penetration and can result from a variety of pathological conditions, vascular disease, endocrine disease, neurological disease, and psychogenic disorders. The penis is a vascular organ and as such is susceptible to the effects of vascular diseases. This review will discuss the basic etiology of erection and vasculogenic erectile dysfunction and explore the role oxygen tension in regulating various cellular and humoral factors as well as trabecular structure and function.

Development of bovine embryos cultured in CR1aa and IVD101 media using different oxygen tensions and culture systems.

Science.gov (United States)

Somfai, Tamás; Inaba, Yasushi; Aikawa, Yoshio; Ohtake, Masaki; Kobayashi, Shuji; Konishi, Kazuyuki; Nagai, Takashi; Imai, Kei

2010-12-01

The aim of the present study was to optimise the culture conditions for the in vitro production of bovine embryos. The development of in vitro fertilised bovine oocytes in CR1aa supplemented with 5% calf serum and IVD101 culture media were compared using traditional microdrops and Well of the Well (WOW) culture systems either under 5% or 20% oxygen tension. After 7 days of culture, a significantly higher blastocyst formation rate was obtained for embryos cultured in CR1aa medium compared to those cultured in IVD101, irrespective of O2 tensions and culture systems. The blastocyst formation in IVD101 was suppressed under 20% O2 compared to 5% O2 . Despite their similar total cell numbers, higher rates of inner cell mass (ICM) cells were observed in blastocysts developed in IVD101 medium than in those developed in CR1aa, irrespective of O2 tensions. There was no significant difference in blastocyst formation, total, ICM and trophectoderm (TE) cell numbers between embryos obtained by microdrop and WOW culture systems irrespective of the culture media and O2 tensions used. In conclusion, CR1aa resulted in higher blastocyst formation rates irrespective of O2 tension, whereas IVD101 supported blastocyst formation only under low O2 levels but enhanced the proliferation of ICM cells.

Cerebral Microcirculation and Oxygen Tension in the Human Secondary Cortex

Science.gov (United States)

Linninger, A. A.; Gould, I. G.; Marinnan, T.; Hsu, C.-Y.; Chojecki, M.; Alaraj, A.

2013-01-01

The three-dimensional spatial arrangement of the cortical microcirculatory system is critical for understanding oxygen exchange between blood vessels and brain cells. A three-dimensional computer model of a 3 × 3 × 3 mm3 subsection of the human secondary cortex was constructed to quantify oxygen advection in the microcirculation, tissue oxygen perfusion, and consumption in the human cortex. This computer model accounts for all arterial, capillary and venous blood vessels of the cerebral microvascular bed as well as brain tissue occupying the extravascular space. Microvessels were assembled with optimization algorithms emulating angiogenic growth; a realistic capillary bed was built with space filling procedures. The extravascular tissue was modeled as a porous medium supplied with oxygen by advection–diffusion to match normal metabolic oxygen demand. The resulting synthetic computer generated network matches prior measured morphometrics and fractal patterns of the cortical microvasculature. This morphologically accurate, physiologically consistent, multi-scale computer network of the cerebral microcirculation predicts the oxygen exchange of cortical blood vessels with the surrounding gray matter. Oxygen tension subject to blood pressure and flow conditions were computed and validated for the blood as well as brain tissue. Oxygen gradients along arterioles, capillaries and veins agreed with in vivo trends observed recently in imaging studies within experimental tolerances and uncertainty. PMID:23842693

Enhanced dopaminergic differentiation of human neural stem cells by synergistic effect of Bcl-xL and reduced oxygen tension

DEFF Research Database (Denmark)

Krabbe, Christina; Courtois, Elise; Jensen, Pia

2009-01-01

Neural stem cells constitute a promising source of cells for transplantation in Parkinson's disease, but a protocol for controlled dopaminergic differentiation is not yet available. Here we investigated the effect of the anti-apoptotic protein Bcl-x(L) and oxygen tension on dopaminergic different......Neural stem cells constitute a promising source of cells for transplantation in Parkinson's disease, but a protocol for controlled dopaminergic differentiation is not yet available. Here we investigated the effect of the anti-apoptotic protein Bcl-x(L) and oxygen tension on dopaminergic...... days at 20% oxygen, hVMbcl-x(L) cultures contained proportionally more tyrosine hydroxylase(TH)-positive cells than hVM1 control cultures. This difference was significantly potentiated from 11 +/- 0.8% to 17.2 +/- 0.2% of total cells when the oxygen tension was lowered to 3%. Immunocytochemistry and Q...

Influence of hyperoxia on the number of nucleated cells and oxygen tension in rat bone marrow after whole-body irradiation

International Nuclear Information System (INIS)

Zima, M.; Vodicka, I.

1987-01-01

The cell number in the femur bone marrow of rats determined three days after X-ray or gamma irradiation is inversely proportional to the dose while oxygen tension in the marrow shows direct dependence on the dose. With fractionation of the lethal dose of gamma radiation (9 Gy) into two doses with different time intervals between them, a greater number of bone marrow cells and a smaller oxygen tension are reached on the 3rd day after the second dose, reflecting the extent of bone marrow repair. A short-term hyperoxia (95% O 2 + 5% CO 2 ) lasting 20 min from the end of exposure compared with the euoxic conditions induced, on the 3rd day after the second fraction, a nonsignificant but reproducible increase in the marrow cell number and a decrease in partial oxygen tension in the distal part of femur marrow. The results obtained testify that immediate short-term hyperoxia facilitates regeneration of the marrow and that a greater number of cells accompanied by greater metabolic activity and oxygen consumption decrease the partial oxygen tension measured on the 3rd day following the last exposure. (author). 7 figs., 16 refs

Indomethacin lowers optic nerve oxygen tension and reduces the effect of carbonic anhydrase inhibition and carbon dioxide breathing

DEFF Research Database (Denmark)

Pedersen, D B; Eysteinsson, T; Stefánsson, E

2004-01-01

Prostaglandins are important in blood flow regulation. Carbon dioxide (CO(2)) breathing and carbonic anhydrase inhibition increase the oxygen tension in the retina and optic nerve. To study the mechanism of this effect and the role of cyclo-oxygenase in the regulation of optic nerve oxygen tension...... (ONPO(2)), the authors investigated how indomethacin affects ONPO(2) and the ONPO(2) increases caused by CO(2) breathing and carbonic anhydrase inhibition in the pig....

Microcomputer-based system for registration of oxygen tension in peripheral muscle.

Science.gov (United States)

Odman, S; Bratt, H; Erlandsson, I; Sjögren, L

1986-01-01

For registration of oxygen tension fields in peripheral muscle a microcomputer based system was designed on the M6800 microprocessor. The system was designed to record the signals from a multiwire oxygen electrode, MDO, which is a multiwire electrode for measuring oxygen on the surface of an organ. The system contained patient safety isolation unit built on optocopplers and the upper frequency limit was 0.64 Hz. Collected data were corrected for drift and temperature changes during the measurement by using pre- and after calibrations and a linear compensation technique. Measure drift of the electrodes were proved to be linear and thus the drift could be compensated for. The system was tested in an experiment on pig. To study the distribution of oxygen statistically mean, standard deviation, skewness and curtosis were calculated. To see changes or differences between histograms a Kolmogorv-Smirnov test was used.

[Effect of different oxygen tension on the cytoskeleton remodeling of goat temporomandibular joint disc cells].

Science.gov (United States)

Xiaolan, He; Guangjie, Bao; Linglu, Sun; Xue, Zhang; Shanying, Bao; Hong, Kang

2017-08-01

Objective The effect of different oxygen tensions on the cytoskeleton remodeling of goat temporomandibular joint (TMJ) disc cells were investigated. Methods Goat TMJ disc cells were cultured under normoxia (21% O₂) and hypoxia (2%, 4%, and 8% O₂). Toluidine blue, picrosirius red, and type Ⅰ collagen immunocytochemical staining were performed to observe the changes in cell phenotype under different oxygen levels. Immunofluorescent staining and real-time reverse transcription-polymerase chain reaction analysis were then performed to identify actin, tubulin, and vimentin in the cultured disc cells. Results TMJ disc cells still displayed fibroblast characteristics under different oxygen levels and their cytoskeletons had regular arrangement. The fluorescence intensities of actin and vimentin were lowest at 4% O₂(P0.05). Actin mRNA levels were considerably decreased at 2% O₂ and 4% O₂ in hypoxic conditions, while actin mRNA expression was highest in 21% O₂. Tubulin mRNA levels considerably increased at 2% O₂, while tubulin mRNA expression was lowest in 8% O₂ (Plevels among these oxygen levels (Poxygen tensions, and 2% O₂ may be the optimal oxygen level required to proliferate TMJ disc cells.

Characterization and validation of noninvasive oxygen tension measurements in human glioma xenografts by 19F-MR relaxometry

International Nuclear Information System (INIS)

Sanden, Boudewijn P.J. van der; Heerschap, Arend; Simonetti, Arjan W.; Rijken, Paul F.J.W.; Peters, Hans P.W.; Stbeen, Georg; Kogel, Albert J. van der

1999-01-01

Purpose: The aim of this study was to characterize and to validate noninvasive 19 F-magnetic resonance relaxometry for the measurement of oxygen tensions in human glioma xenografts in nude mice. The following three questions were addressed: 1. When perfluorocarbon compounds (PFCs) are administrated intravenously, which tumor regions are assessed by 19 F-MR relaxometry? 2. Are oxygen tension as detected by 19 F-MR relaxometry (pO 2/relaxo ) comparable to Eppendorf O 2 -electrode measurements (pO 2/electrode )? 3. Can 19 F-MR relaxometry be used to detect oxygen tension changes in tumor tissue during carbogen breathing? Methods and Materials: Slice-selective 19 F-MR relaxometry was carried out with perfluoro-15-crown-5-ether as oxygen sensor. The PFC was injected i.v. 3 days before the 19 F-MR experiments. Two datasets were acquired before and two after the start of carbogen breathing. The distribution of PFCs and necrotic areas were analyzed in 19 F-Spin Echo (SE) density MR images and T 2 -weighted 1 H-SE MR images, respectively. One day after the MR investigations, oxygen tensions were measured by oxygen electrodes in the same slice along two perpendicular tracks. These measurements were followed by (immuno)histochemical analysis of the 2D distribution of perfused microvessels, hypoxic cells, necrotic areas, and macrophages. Results: The PFCs mainly became sequestered in perfused regions at the tumor periphery; thus, 19 F-MR relaxometry probed mean oxygen tensions in these regions throughout the selected MR slice. In perfused regions of the tumor, mean pO 2/relaxo values were comparable to mean pO 2/electrode values, and varied from 0.03 to 9 mmHg. Median pO 2/electrode values of both tracks were lower than mean pO 2/relaxo values, because low pO 2/electrode values that originate from hypoxic and necrotic areas were also included in calculations of median pO 2/electrode values. After 8-min carbogen breathing, the average pO 2/relaxo increase was 3.3 ± 0.8 (SEM

Effect of body position and oxygen tension on foramen ovale recruitment.

Science.gov (United States)

Moses, Kayla L; Beshish, Arij G; Heinowski, Nicole; Baker, Kim R; Pegelow, David F; Eldridge, Marlowe W; Bates, Melissa L

2015-01-01

While there is an increased prevalence of stroke at altitude in individuals who are considered to be low risk for thrombotic events, it is uncertain how venous thrombi reach the brain. The patent foramen ovale (PFO) is a recruitable intracardiac shunt between the right and left atrium. We aimed to determine whether body position and oxygen tension affect blood flow through the PFO in healthy adults. We hypothesized that hypoxia and body positions that promote right atrial filling would independently recruit the PFO. Subjects with a PFO (n = 11) performed 11 trials, combining four different fractions of inhaled oxygen (FiO₂) (1.0, 0.21, 0.15, and 0.10) and three positions (upright, supine, and 45° head down), with the exception of FiO₂ = 0.10, while 45° head down. After 5 min in each position, breathing the prescribed oxygen tension, saline bubbles were injected into an antecubital vein and a four-chamber echocardiogram was obtained to evaluate PFO recruitment. We observed a high incidence of PFO recruitment in all conditions, with increased recruitment in response to severe hypoxia and some contribution of body position at moderate levels of hypoxia. We suspect that increased pulmonary vascular pressure, secondary to hypoxia-induced pulmonary vasoconstriction, increased right atrial pressure enough to recruit the PFO. Additionally, we hypothesize that the minor increase in breathing resistance that was added by the mouthpiece, used during experimental trials, affected intrathoracic pressure and venous return sufficiently to recruit the PFO. Copyright © 2015 the American Physiological Society.

Methyl sterol and cyclopropane fatty acid composition of Methylococcus capsulatus grown at low oxygen tensions

Science.gov (United States)

Jahnke, L. L.; Nichols, P. D.

1986-01-01

The sterol and fatty acid concentrations for M. capsulatus grown in fed-batch cultures over a wide range of oxygen tensions (0.1-10.6 percent) and at a constant methane level are evaluated. The analyses reveal that the biomass decreases as oxygen levels are lowered; the sterol concentration increases when the oxygen range is between 0.5-1.1 percent and decreases when the oxygen range is below 0.5 percent; and the amount of monounsaturated C16 decreases and the concentration of cyclopropane fatty acids increases after oxygen is reduced. It is noted that growth and membrane synthesis occur at low oxygen concentrations and that the synthesis of membrane lipids responds to growth conditions.

Indomethacin decreases optic nerve oxygen tension by a mechanism other than cyclo-oxygenase inhibition

DEFF Research Database (Denmark)

Noergaard, M Hove; Pedersen, D Bach; Bang, K

2008-01-01

We investigated the effect of several Non-Steroidal Anti-Inflammatory Drugs (NSAIDs), on the preoptic nerve oxygen tension (ONPO2), as indomethacin previously has demonstrated a strong decreasing effect on ONPO2. We tested whether these NSAIDs, like indomethacin, also reduce the increasing effect...

BIOELECTRIC POTENTIALS IN HALICYSTIS : VII. THE EFFECTS OF LOW OXYGEN TENSION.

Science.gov (United States)

Blinks, L R; Darsie, M L; Skow, R K

1938-11-20

The potential difference across the protoplasm of impaled cells of Halicystis is not affected by increase of oxygen tension in equilibrium with the sea water, nor with decrease down to about 1/10 its tension in the air (2 per cent O(2) in N(2)). When bubbling of 2 per cent O(2) is stopped, the P.D. drifts downward, to be restored on stirring the sea water, or rebubbling the gas. Bubbling 0.2 per cent O(2) causes the P.D. to drop to 20 mv. or less; 1.1 per cent O(2) to about 50 mv. Restoration of 2 per cent or higher O(2) causes recovery to 70 or 80 mv. often with a preliminary cusp which decreases the P.D. before it rises. Perfusion of aerated sea water through the vacuole is just as effective in restoring the P.D. as external aeration, indicating that the direction of the oxygen gradient is not significant. Low O(2) tension also inhibits the reversed, negative P.D. produced by adding NH(4)Cl to sea water, 0.2 per cent O(2) bringing this P.D. back to the same low positive values found without ammonia. Restoration of 2 per cent O(2) or air, restores this latent negativity. At slightly below the threshold for ammonia reversal, low O(2) may induce a temporary negativity when first bubbled, and a negative cusp may occur on aeration before positive P.D. is regained. This may be due to a decreased consumption of ammonia, or to intermediate pH changes. The locus of the P.D. alteration was tested by applying increased KCl concentrations to the cell exterior; the large cusps produced in aerated solutions become greatly decreased when the P.D. has fallen in 0.2 per cent O(2). This indicates that the originally high relative mobility or concentration of K(+) ion has approached that of Na(+) in the external protoplasmic surface under reduced O(2) tension. Results obtained with sulfate sea water indicate that Na(+) mobility approaches that of SO(4) (-) in 0.2 per cent O(2). P.D. measurements alone cannot tell whether this is due to an increase of the slower ion or a decrease of

Oxygen Exposure Resulting in Arterial Oxygen Tensions Above the Protocol Goal Was Associated With Worse Clinical Outcomes in Acute Respiratory Distress Syndrome.

Science.gov (United States)

Aggarwal, Neil R; Brower, Roy G; Hager, David N; Thompson, B Taylor; Netzer, Giora; Shanholtz, Carl; Lagakos, Adrian; Checkley, William

2018-04-01

High fractions of inspired oxygen may augment lung damage to exacerbate lung injury in patients with acute respiratory distress syndrome. Participants enrolled in Acute Respiratory Distress Syndrome Network trials had a goal partial pressure of oxygen in arterial blood range of 55-80 mm Hg, yet the effect of oxygen exposure above this arterial oxygen tension range on clinical outcomes is unknown. We sought to determine if oxygen exposure that resulted in a partial pressure of oxygen in arterial blood above goal (> 80 mm Hg) was associated with worse outcomes in patients with acute respiratory distress syndrome. Longitudinal analysis of data collected in these trials. Ten clinical trials conducted at Acute Respiratory Distress Syndrome Network hospitals between 1996 and 2013. Critically ill patients with acute respiratory distress syndrome. None. We defined above goal oxygen exposure as the difference between the fraction of inspired oxygen and 0.5 whenever the fraction of inspired oxygen was above 0.5 and when the partial pressure of oxygen in arterial blood was above 80 mm Hg. We then summed above goal oxygen exposures in the first five days to calculate a cumulative above goal oxygen exposure. We determined the effect of a cumulative 5-day above goal oxygen exposure on mortality prior to discharge home at 90 days. Among 2,994 participants (mean age, 51.3 yr; 54% male) with a study-entry partial pressure of oxygen in arterial blood/fraction of inspired oxygen that met acute respiratory distress syndrome criteria, average cumulative above goal oxygen exposure was 0.24 fraction of inspired oxygen-days (interquartile range, 0-0.38). Participants with above goal oxygen exposure were more likely to die (adjusted interquartile range odds ratio, 1.20; 95% CI, 1.11-1.31) and have lower ventilator-free days (adjusted interquartile range mean difference of -0.83; 95% CI, -1.18 to -0.48) and lower hospital-free days (adjusted interquartile range mean difference of -1.38; 95

Multibreath alveolar oxygen tension imaging.

Science.gov (United States)

Clapp, Justin; Hamedani, Hooman; Kadlecek, Stephen; Xin, Yi; Shaghaghi, Hoora; Siddiqui, Sarmad; Rossman, Milton D; Rizi, Rahim R

2016-10-01

This study tested the ability of a multibreath hyperpolarized HP (3) He MRI protocol to increase the accuracy of regional alveolar oxygen tension (PA O2 ) measurements by lessening the influence of gas-flow artifacts. Conventional single-breath PA O2 measurement has been susceptible to error induced by intervoxel gas flow, particularly when used to study subjects with moderate-to-severe chronic obstructive pulmonary disease (COPD). Both single-breath and multibreath PA O2 imaging schemes were implemented in seven human subjects (one healthy, three asymptomatic smokers, and three COPD). The number and location of voxels with nonphysiologic PA O2 values generated by intervoxel gas flow were compared between the two protocols. The multibreath scheme resulted in a significantly lower total percentage of nonphysiologic PA O2 values (6.0%) than the single-breath scheme (13.7%) (P = 0.006). PA O2 maps showed several patterns of gas-flow artifacts that were present in the single-breath protocol but mitigated by the multibreath approach. Multibreath imaging also allowed for the analysis of slow-filling areas that presented no signal after a single breath. A multibreath approach enhances the accuracy and completeness of noninvasive PA O2 measurement by significantly lessening the proportion of nonphysiologic values generated by intervoxel gas flow. Magn Reson Med 76:1092-1101, 2016. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.

Navigating the Tensions of Innovative Assessment and Pedagogy in Higher Education

Directory of Open Access Journals (Sweden)

Jennifer Lock

2018-04-01

Full Text Available Innovative practice in a classroom adds challenges and tensions to programs and institutional structures in higher education. With the recent emphasis on curricula reform, there is a great focus on assessment and pedagogical practices to support student learning. To illustrate the tensions arising from these efforts, we present four pedagogical and assessment innovation approaches using both Shulman’s (2005 Signature Pedagogies and Tatar’s (2007 Design Tensions frameworks. The four approaches include problem-based learning, game-based learning, case-based learning, and technology-enhanced learning. A narrative for each approach examines and addresses tensions using Shulman’s (2005 surface, deep and implicit structures. We argue that there is an interconnected complexity and conflicting visions among the micro- (e.g., classroom or practicum, meso- (e.g., program, and macro- (e.g., institution levels. We acknowledge that dynamic tensions continually exist and needs to be thoughtfully navigated in support of innovative assessment and pedagogies in higher education. Dans l’enseignement supérieur, les pratiques innovatrices en salle de classe ajoutent des défis et des tensions aux programmes et aux structures institutionnelles. Suite à l’importance accrue récemment attachée à la réforme des programmes d’études, l’accent est mis sur l’évaluation et les pratiques pédagogiques pour soutenir l’apprentissage des étudiants. Afin d’illustrer les tensions qui découlent de ces efforts, nous présentons quatre approches de pédagogie et d’évaluation innovatrices qui font appel à la fois aux cadres de Shulman, Signature Pedagogies (2005, et à ceux de Tatar, Design Tensions (2007. Les quatre approches comprennent l’apprentissage par problèmes, l’apprentissage fondé sur le jeu, l’apprentissage basé sur des cas et l’apprentissage amélioré par les technologies. Chaque approche est examinée et traite des tensions

Oxygen Tension Beneath Scleral Lenses of Different Clearances.

Science.gov (United States)

Giasson, Claude J; Morency, Jeanne; Melillo, Marc; Michaud, Langis

2017-04-01

To evaluate the relative partial pressure in oxygen (pO2) at the corneal surface under Boston XO2 scleral lenses (SL) fitted with targeted clearances of 200 and 400 μm (SL200 and SL400). During this prospective study, the right eyes of eight normal subjects were fitted with SL200 and SL400. Clearance, validated after 5 minutes of wear with an optical coherence tomograph, was used with lens thicknesses to calculate transmissibility and estimate pO2. Corneal pO2s were measured with an oxygen electrode after 5 minutes of (1) corneal exposure to calibrating gases with various pO2 or of (2) SL wear. Decays in pO2 were modeled to an exponential. Linear regression between exponent k of these decays and calibrating gas pO2s allowed for the calculation of corneal pO2 under SL. Differences between pO2s beneath SL200 and SL400 were tested with a mixed ANOVA. The estimated transmissibility based on thicknesses and clearances (239.7 ± 34.7; 434.5 ± 33.2 μm) predicted a corneal pO2 of 8.52 ± 0.51 and 6.37 ± 0.28% for SL200 and SL400. These values were close to measured pO2: 9.07 ± 0.86 and 6.19 ± 0.87% (mean ± SEM) (P time, an 18-mm scleral lens fitted with a 400-μm clearance reduces the oxygen tension available to the cornea by 30% compared to a similar lens fitted with a 200-μm clearance after 5 minutes of wear.

Membrane culture and reduced oxygen tension enhances cartilage matrix formation from equine cord blood mesenchymal stromal cells in vitro.

Science.gov (United States)

Co, C; Vickaryous, M K; Koch, T G

2014-03-01

Ongoing research is aimed at increasing cartilage tissue yield and quality from multipotent mesenchymal stromal cells (MSC) for the purpose of treating cartilage damage in horses. Low oxygen culture has been shown to enhance chondrogenesis, and novel membrane culture has been proposed to increase tissue yield and homogeneity. The objective of this study was to evaluate and compare the effect of reduced oxygen and membrane culture during in vitro chondrogenesis of equine cord blood (CB) MSC. CB-MSC (n = 5 foals) were expanded at 21% oxygen prior to 3-week differentiation in membrane or pellet culture at 5% and 21% oxygen. Assessment included histological examination (H&E, toluidine Blue, immunohistochemistry (IHC) for collagen type I and II), protein quantification by hydroxyproline assay and dimethylmethylene assay, and mRNA analysis for collagen IA1, collagen IIA1, collagen XA1, HIF1α and Sox9. Among treatment groups, 5% membrane culture produced neocartilage most closely resembling hyaline cartilage. Membrane culture resulted in increased wet mass, homogenous matrix morphology and an increase in total collagen content, while 5% oxygen culture resulted in higher GAG and type II collagen content. No significant differences were observed for mRNA analysis. Membrane culture at 5% oxygen produces a comparatively larger amount of higher quality neocartilage. Matrix homogeneity is attributed to a uniform diffusion gradient and reduced surface tension. Membrane culture holds promise for scale-up for therapeutic purposes, for cellular preconditioning prior to cytotherapeutic applications, and for modeling system for gas-dependent chondrogenic differentiation studies. Crown Copyright © 2014. Published by Elsevier Ltd. All rights reserved.

Tensions in Higher Education Leadership: Towards a Multi-Level Model of Leadership Practice

Science.gov (United States)

Bolden, Richard; Petrov, Georgy; Gosling, Jonathan

2008-01-01

UK higher education is undergoing a period of significant change that generates a series of tensions and difficulties for universities and university leaders. This paper explores these tensions through analysis of findings from a study comprising 152 semi-structured face-to-face interviews in 12 UK universities. Building on from theories of…

Oxygen tension measurements of tumors growing in mice

International Nuclear Information System (INIS)

Adam, Markus F.; Dorie, Mary Jo; Brown, J. Martin

1999-01-01

Purpose: Clinical studies using the Eppendorf histograph have shown that patients whose tumors have a low pO 2 have worse local control after radiotherapy, and have higher metastatic rates. Because preclinical studies of methods of overcoming, or exploiting, hypoxia generally use transplanted tumors in mice, we have compared the oxygenation of mouse tumors with human tumors to determine the appropriateness of the transplanted mouse model for such preclinical studies. Methods and Materials: We evaluated the oxygenation status of subcutaneous (s.c.) tissue and of 12 intradermally (i.d.)- and 7 s.c.-growing mouse or human transplanted tumors in mice using the Eppendorf histograph, and compared the values obtained with measurements of human head and neck nodes. Results: The normal tissue pO 2 profile of air-breathing mice showed a nearly Gaussian distribution (38.2 ± 14.9 mmHg). Breathing 10% O 2 or carbogen resulted in dramatic changes in normal tissue oxygenation. Tumors growing intradermally in the back of air-breathing mice were extremely hypoxic and resistant to expected changes in oxygenation (carbogen breathing, size, and use of anesthetics). Tumors growing s.c. in the foot showed higher oxygen profiles with marked changes in oxygenation when exposing the animals to different levels of oxygen. However, the oxygenation of the mouse tumors transplanted in either site was only a fraction of that of the majority of human tumors. Conclusion: Experimental mouse tumors are markedly hypoxic, with median values of 10-20% of those of human tumors. Hence, mouse tumors are probably good models for the most hypoxic human tumors that respond poorly to radiotherapy; however, caution has to be exercised in extrapolating data from mouse to man

Unusual Growth Phase and Oxygen Tension Regulation of Oxidative Stress Protection Enzymes, Catalase and Superoxide Dismutase, in the Phytopathogen Xanthomonas oryzae pv. oryzae

OpenAIRE

Chamnongpol, S.; Mongkolsuk, S.; Vattanaviboon, P.; Fuangthong, M.

1995-01-01

The enzymes catalase and superoxide dismutase play major roles in protecting phytopathogenic bacteria from oxidative stress. In Xanthomonas species, these enzymes are regulated by both growth phase and oxygen tension. The highest enzyme levels were detected within 1 h of growth. Continued growth resulted in a decline of both enzyme activities. High oxygen tension was an inducing signal for both enzyme activities. An 80,000-Da monofunctional catalase and a manganese superoxide dismutase were t...

Measuring oxygen tension modulation, induced by a new pre-radiotherapy therapeutic, in a mammary window chamber mouse model

Science.gov (United States)

Schafer, Rachel; Gmitro, Arthur F.

2015-03-01

Tumor regions under hypoxic or low oxygen conditions respond less effectively to many treatment strategies, including radiation therapy. A novel investigational therapeutic, NVX-108 (NuvOx Pharma), has been developed to increase delivery of oxygen through the use of a nano-emulsion of dodecofluoropentane. By raising pO2 levels prior to delivering radiation, treatment efficacy may be improved. To aid in evaluating the novel drug, oxygen tension was quantitatively measured, spatially and temporally, to record the effect of administrating NVX-108 in an orthotopic mammary window chamber mouse model of breast cancer. The oxygen tension was measured through the use of an oxygen-sensitive coating, comprised of phosphorescent platinum porphyrin dye embedded in a polystyrene matrix. The coating, applied to the surface of the coverslip of the window chamber through spin coating, is placed in contact with the mammary fat pad to record the oxygenation status of the surface tissue layer. Prior to implantation of the window chamber, a tumor is grown in the SCID mouse model by injection of MCF-7 cells into the mammary fat pad. Two-dimensional spatial distributions of the pO2 levels were obtained through conversion of measured maps of phosphorescent lifetime. The resulting information on the spatial and temporal variation of the induced oxygen modulation could provide valuable insight into the optimal timing between administration of NVX-108 and radiation treatment to provide the most effective treatment outcome.

Oxygen tension and prediction of the radiation response. Polarographic study in human breast cancer

International Nuclear Information System (INIS)

Pappova, N.; Siracka, E.

1982-01-01

Serial polarographic measurement of the tissue oxygen tension (pO 2 ) was made in the course of fractionated irradiation (preoperative or sole treatment) of advanced breast cancer in 24 patients. In responsive tumors an increase in pO 2 appeared sooner before expressive tumor size reduction became noticeable. Repeated recording of unchanged pO 2 values proved to be a good prognostic indicator of local failure. The study made on this tumor model showed that serial polarographic pO 2 determinations with suitable electrodes causing minimal trauma and providing consistent and reproductive data about changes in tumor microcirculation and oxygenation may enlarge the scale of indicators of radiation response. (author)

Adverse effects of reduced oxygen tension on the proliferative capacity of rat kidney and insulin-secreting cell lines involve DNA damage and stress responses

International Nuclear Information System (INIS)

Chen Jianhua; Jones, R. Huw; Tarry-Adkins, Jane; Smith, Noel H.; Ozanne, Susan E.

2008-01-01

Standard cell culture conditions do not reflect the physiological environment in terms of oxygen tension (20% vs 3%). The effects of lowering oxygen tension on cell proliferation in culture can be beneficial as well as detrimental depending on the cell line studied, but the molecular mechanism underlying such effects is not fully understood. We observed that the proliferative capacity of the rat cell lines NRK and INS-1 was inhibited when cultured under 3% oxygen as compared to 20% oxygen. Suppression of proliferation in NRK cells was accompanied by induction of DNA double strand breaks whereas in INS-1 cells it was accompanied by up-regulation of p53 and p27. Although Sirt1 was up-regulated in both cell lines by 3% oxygen the effects on antioxidant enzymes (MnSOD, CuZnSOD and catalase) were cell line specific. Marked up-regulation of heme oxygenase-1 (HO-1) was detected in both NRK and INS-1 cells when cultured in 3% oxygen. HO-1 expression can be readily induced by exposure to hydrogen peroxide in culture. These results suggest that reduced oxygen tension suppresses the proliferative capacity of these two cell lines through a stress response that is similar to an oxidative stress response but the molecular events that lead to the reduced cell proliferation are cell line specific

Arterial oxygen tension and pulmonary ventilation in horses placed in the Anderson Sling suspension system after a period of lateral recumbency and anaesthetised with constant rate infusions of romifidine and ketamine.

Science.gov (United States)

François, I; Lalèyê, F-X; Micat, M; Benredouane, K; Portier, K

2014-09-01

Some controversy exists over whether or not horses' recovery and cardiopulmonary function are affected by suspension in slings. To measure arterial oxygen tension and pulmonary ventilation in anaesthetised horses placed in a standing position in an Anderson Sling (AS) after a period of right lateral recumbency (RLR). Randomised crossover experimental study. Six Standardbred horses were anaesthetised twice. Catheters were inserted into the right jugular vein and the left carotid artery. After premedication with romifidine, anaesthesia was induced with diazepam and ketamine. Following 50 min in RLR, horses were maintained in either RLR or AS for an additional 60 min through to recovery. Anaesthesia was maintained i.v. with a constant rate infusion of romifidine and ketamine. Heart rate, respiratory rate, mean arterial pressure, expiratory tidal volume, minute volumes and end tidal CO2 were monitored continuously. Venous and arterial bloods were sampled for lactate concentration, creatine kinase activity and blood gas analysis before premedication, after induction, every 20 min for 100 min, as soon as the horse was standing (TR), and 24 h later. The data were averaged within 2 anaesthetic periods: P1, 0-20 min; and P2, 40-100 min. During P2, horses in the RLR group had lower arterial oxygen tension (P = 0.001), higher alveolar-arterial oxygen tension gradient (P = 0.005), higher respiratory rate (P = 0.04) and higher minute volumes (P = 0.04) than horses in the AS group. Arterial CO2 tension and mean arterial pressure increased in the AS group during P2 (P = 0.01 and 0.02 respectively). The recoveries were judged better in the AS group than in the RLR group (P = 0.01). During TR, lactate were higher in the RLR group than in the AS group (P = 0.007). Creatine kinase activities were higher in the AS group at 24 h vs. TR (P = 0.02). Anderson Sling suspension after a period of recumbency improves cardiopulmonary function and recovery quality in horses and

Intraoperative transfusion threshold and tissue oxygenation

DEFF Research Database (Denmark)

Nielsen, K; Dahl, B; Johansson, P I

2012-01-01

Transfusion with allogeneic red blood cells (RBCs) may be needed to maintain oxygen delivery during major surgery, but the appropriate haemoglobin (Hb) concentration threshold has not been well established. We hypothesised that a higher level of Hb would be associated with improved subcutaneous...... oxygen tension during major spinal surgery....

Exogenous and endogenous angiotensin-II decrease renal cortical oxygen tension in conscious rats by limiting renal blood flow

NARCIS (Netherlands)

Emans, Tonja W.; Janssen, Ben J.; Pinkham, Maximilian I.; Ow, Connie P. C.; Evans, Roger G.; Joles, Jaap A.; Malpas, Simon C.; Krediet, C. T. Paul; Koeners, Maarten P.

2016-01-01

Our understanding of the mechanisms underlying the role of hypoxia in the initiation and progression of renal disease remains rudimentary. We have developed a method that allows wireless measurement of renal tissue oxygen tension in unrestrained rats. This method provides stable and continuous

Oxygen tension regulates the miRNA profile and bioactivity of exosomes released from extravillous trophoblast cells - Liquid biopsies for monitoring complications of pregnancy.

Directory of Open Access Journals (Sweden)

Grace Truong

Full Text Available Our understanding of how cells communicate has undergone a paradigm shift since the recent recognition of the role of exosomes in intercellular signaling. In this study, we investigated whether oxygen tension alters the exosome release and miRNA profile from extravillous trophoblast (EVT cells, modifying their bioactivity on endothelial cells (EC. Furthermore, we have established the exosomal miRNA profile at early gestation in women who develop pre-eclampsia (PE and spontaneous preterm birth (SPTB. HTR-8/SVneo cells were used as an EVT model. The effect of oxygen tension (i.e. 8% and 1% oxygen on exosome release was quantified using nanocrystals (Qdot® coupled to CD63 by fluorescence NTA. A real-time, live-cell imaging system (Incucyte™ was used to establish the effect of exosomes on EC. Plasma samples were obtained at early gestation (<18 weeks and classified according to pregnancy outcomes. An Illumina TrueSeq Small RNA kit was used to construct a small RNA library from exosomal RNA obtained from EVT and plasma samples. The number of exosomes was significantly higher in EVT cultured under 1% compared to 8% oxygen. In total, 741 miRNA were identified in exosomes from EVT. Bioinformatic analysis revealed that these miRNA were associated with cell migration and cytokine production. Interestingly, exosomes isolated from EVT cultured at 8% oxygen increased EC migration, whilst exosomes cultured at 1% oxygen decreased EC migration. These changes were inversely proportional to TNF-α released from EC. Finally, we have identified a set of unique miRNAs in exosomes from EVT cultured at 1% oxygen and exosomes isolated from the circulation of mothers at early gestation, who later developed PE and SPTB. We suggest that aberrant exosomal signalling by placental cells is a common aetiological factor in pregnancy complications characterised by incomplete SpA remodeling and is therefore a clinically relevant biomarker of pregnancy complications.

Effect of supplemental oxygen versus dobutamine administration on liver oxygen tension in dPP-guided normovolemic pigs.

Science.gov (United States)

Pestel, G; Fukui, K; Hager, H; Kurz, A; Hiltebrand, L

2009-01-01

Difference in pulse pressure (dPP) confirms adequate intravascular filling as a prerequisite for tissue perfusion. We hypothesized that both oxygen and dobutamine increase liver tissue oxygen tension (ptO(2)). Eight anesthetized pigs received dPP-guided fluid management. Hepatic pO(2) was measured with Clark-type electrodes placed subcapsularly, and on the liver surface. Pigs received: (1) supplemental oxygen (F(i)O(2) 1.0); (2) dobutamine 2.5 microg/kg/min, and (3) dobutamine 5 microg/kg/min. Data were analyzed using repeated-measures ANOVA followed by a Tukey post-test for multiple comparisons. ptO(2 )measured subcapsularly and at the liver surface were compared using the Bland-Altman plot. Variation in F(i)O(2) changed local hepatic tissue ptO(2) [subcapsular measurement: 39 +/- 12 (F(i)O(2) 0.3), 89 +/- 35 mm Hg (F(i)O(2) 1.0, p = 0.01 vs. F(i)O(2) 0.3), 44 +/- 10 mm Hg (F(i)O(2) 0.3, p = 0.05 vs. F(i)O(2) 1.0); surface measurement: 52 +/- 35 (F(i)O(2) 0.3), 112 +/- 24 mm Hg (F(i)O(2) 1.0, p = 0.001 vs. F(i)O(2) 0.3), 54 +/- 24 mm Hg (F(i)O(2) 0.3, p = 0.001 vs. F(i)O(2) 1.0)]. Surface measurements were widely scattered compared to subcapsular measurements (bias: -15 mm Hg, precision: 76.3 mm Hg). Dobutamine did not affect hepatic oxygenation. Supplemental oxygen increased hepatic tissue pO(2) while dobutamine did not. Although less invasive, the use of surface measurements is discouraged. Copyright 2009 S. Karger AG, Basel.

IVF/ICSI outcomes after culture of human embryos at low oxygen tension: a meta-analysis

Directory of Open Access Journals (Sweden)

Gomes Sobrinho David B

2011-11-01

Full Text Available Abstract Background Improved pregnancy, implantation, and birth rates have been reported after the use of reduced O2 concentration during embryo culture, mainly due to a reduction of the cumulative detrimental effects of reactive oxygen species. However, some studies have failed to report any positive effects. The objective of this meta-analysis was to evaluate the effect of a low-O2 environment on IVF/intracytoplasmic sperm injection (ICSI outcomes. Methods All available published and ongoing randomised trials that compared the effects of low (~5%; OC~5 and atmospheric (~20%; OC~20 oxygen concentrations on IVF/ICSI outcomes were included. Search strategies included online surveys of databases from 1980 to 2011. The outcomes measured were fertilisation rate, implantation rate and ongoing pregnancy rates. The fixed effects model was used to calculate the odds ratio. Results Seven studies were included in this analysis. The pooled fertilisation rate did not differ significantly (P = 0.54 between the group of oocytes cultured at low O2 tension and the group at atmospheric O2 tension. Concerning all cycles, the implantation (P = 0.06 and ongoing pregnancy (P = 0.051 rates were not significantly different between the group receiving transferred sets containing only OC~5 embryos and the group receiving transferred sets with only OC~20 embryos. In a meta-analysis performed for only those trials in which embryos were transferred on day 2/3, implantation (P = 0.63 and ongoing pregnancy (P = 0.19 rates were not significantly different between the groups. In contrast, when a meta-analysis was performed using only trials in which embryos were transferred on days 5 and 6 (at the blastocyst stage, the group with transferred sets of only OC~5 embryos showed a statistically significantly higher implantation rate (P = 0.006 than the group receiving transferred sets with only OC~20 embryos, although the ongoing pregnancy (P = 0.19 rates were not significantly

Reactive oxygen species-driven HIF1α triggers accelerated glycolysis in endothelial cells exposed to low oxygen tension

International Nuclear Information System (INIS)

Paik, Jin-Young; Jung, Kyung-Ho; Lee, Jin-Hee; Park, Jin-Won; Lee, Kyung-Han

2017-01-01

Endothelial cells and their metabolic state regulate glucose transport into underlying tissues. Here, we show that low oxygen tension stimulates human umbilical vein endothelial cell 18 F–fluorodeoxyglucose ( 18 F–FDG) uptake and lactate production. This was accompanied by augmented hexokinase activity and membrane Glut-1, and increased accumulation of hypoxia-inducible factor-1α (HIF1α). Restoration of oxygen reversed the metabolic effect, but this was blocked by HIF1α stabilization. Hypoxia-stimulated 18 F–FDG uptake was completely abrogated by silencing of HIF1α expression or by a specific inhibitor. There was a rapid and marked increase of reactive oxygen species (ROS) by hypoxia, and ROS scavenging or NADPH oxidase inhibition completely abolished hypoxia-stimulated HIF1α and 18 F–FDG accumulation, placing ROS production upstream of HIF1α signaling. Hypoxia-stimulated HIF1α and 18 F–FDG accumulation was blocked by the protein kinase C (PKC) inhibitor, staurosporine. The phosphatidylinositol 3-kinase (PI3K) inhibitor, wortmannin, blocked hypoxia-stimulated 18 F–FDG uptake and attenuated hypoxia-responsive element binding of HIF1α without influencing its accumulation. Thus, ROS-driven HIF1α accumulation, along with PKC and PI3K signaling, play a key role in triggering accelerated glycolysis in endothelial cells under hypoxia, thereby contributing to 18 F–FDG transport.

Bladder urine oxygen tension for assessing renal medullary oxygenation in rabbits: experimental and modeling studies

Science.gov (United States)

Sgouralis, Ioannis; Kett, Michelle M.; Ow, Connie P. C.; Abdelkader, Amany; Layton, Anita T.; Gardiner, Bruce S.; Smith, David W.; Lankadeva, Yugeesh R.

2016-01-01

Oxygen tension (Po2) of urine in the bladder could be used to monitor risk of acute kidney injury if it varies with medullary Po2. Therefore, we examined this relationship and characterized oxygen diffusion across walls of the ureter and bladder in anesthetized rabbits. A computational model was then developed to predict medullary Po2 from bladder urine Po2. Both intravenous infusion of [Phe2,Ile3,Orn8]-vasopressin and infusion of NG-nitro-l-arginine reduced urinary Po2 and medullary Po2 (8–17%), yet had opposite effects on renal blood flow and urine flow. Changes in bladder urine Po2 during these stimuli correlated strongly with changes in medullary Po2 (within-rabbit r2 = 0.87–0.90). Differences in the Po2 of saline infused into the ureter close to the kidney could be detected in the bladder, although this was diminished at lesser ureteric flow. Diffusion of oxygen across the wall of the bladder was very slow, so it was not considered in the computational model. The model predicts Po2 in the pelvic ureter (presumed to reflect medullary Po2) from known values of bladder urine Po2, urine flow, and arterial Po2. Simulations suggest that, across a physiological range of urine flow in anesthetized rabbits (0.1–0.5 ml/min for a single kidney), a change in bladder urine Po2 explains 10–50% of the change in pelvic urine/medullary Po2. Thus, it is possible to infer changes in medullary Po2 from changes in urinary Po2, so urinary Po2 may have utility as a real-time biomarker of risk of acute kidney injury. PMID:27385734

Postnatal follow-up of the oxygenation index, arterial to alveolar oxygen tension ratio and alveolar arterial oxygen tension difference values in neonates with the respiratory distress syndrome treated with conventional ventilatory support.

Science.gov (United States)

Atanasov, A; Despotova-Toleva, L

1997-01-01

Recent development of sophisticated intensive care technique for use in newborn infants with the respiratory distress syndrome (RDS) has resulted in changes in the therapeutic strategies and moved the problem of neonatal survival into the realm of new therapeutic realities. At present, the mechanical ventilation methods form an integral part of the intensive care strategy of infants with RDS. They have come to the forefront of infant care because of their successful use in ventilatory support and children survival where other therapeutic modalities have failed. The present prospective observational longitudinal study was designed to assess the real-time convenience, reliability and accuracy of the changes in the oxygenation index (OI), arterial-to-alveolar oxygen tension ratio (a/A PO2) and alveolar-arterial oxygen gradient (A-a)DO2 in ventilator-dependent neonates with RDS, to analyze their feasibility and potential information yield in oxygen inhalation therapy as well as their prognostic implications and predictive value. Twenty neonates with RDS, heralded by respiratory failure which necessitated the initiation of oxygen inhalation therapy and ventilatory support within 24 hours of birth, were enrolled in the study. Ten of the infants survived and the remaining ten died. OI, (a/A PO2) and (A-a)DO2 were followed up sequentially and thoroughly analyzed as the primary outcome measures of the study. The indices were calculated on the basis of the complete monitoring of the ventilatory equipment parameters and acid-base status carried out on an hourly basis. Our results show that: 1. The combination of three indexes (OI, (a/A)PO2 and (A-a)DO2 we propose is a useful discriminating predictor of neonatal lung maturity reflecting arterial blood gas status in ventilator-dependent neonates with RDS. 2. The indices detect the efficacy of the modern conventional ventilatory support with real-time convenience and reliable accuracy forming the cornerstone of clinical decision

The relationship between alveolar oxygen tension and the single-breath carbon monoxide diffusing capacity.

Science.gov (United States)

Kanner, R E; Crapo, R O

1986-04-01

The effects of alveolar oxygen tension (PAO2) on the single-breath carbon monoxide diffusing capacity (DLCO) were quantified and a factor was derived to accommodate for differences in PAO2 over commonly encountered altitudes and/or varying concentrations of oxygen in the test gas mixture (FIO2) We performed duplicate measurements of DLCO in 7 normal subjects with 6 different oxygen fractions (0.176, 0.196, 0.211, 0.22, 0.25, and 0.27). The PAO2 for each test was measured as the PO2 in the alveolar gas sample bag. DLCO varied inversely with PAO2 and changed by 0.35% for each mmHg change in PAO2 (r = -0.62, p less than 0.001). At an FIO2 of 0.25, PAO2 varied between subjects and was highly correlated with each subject's residual volume to total lung capacity ratio (r = -0.84, p less than 0.001). We suggest that laboratories can adjust the measured DLCO when PAO2 is not congruent to 120 mmHg by the following formula: DLCO (corrected = DLCO (measured) x [1.0 + 0.0035 (PAO2 - 120)].

Matrix stiffness and oxigen tension modulate epigenetic conversion of mouse dermal fibroblasts into insulin producing cells.

Directory of Open Access Journals (Sweden)

Alessandro Zenobi

2017-05-01

Full Text Available In vivo, cells are surrounded by a three-dimensional (3-D organization of supporting matrix, neighboring cells and a gradient of chemical and mechanical signals (Antoni, et al., 2015. However, the present understanding of many biological processes is mainly based on two-dimensional (2-D systems that typically provides a static environment. In the present study, we tested two different 3-D culture systems and apply them to the epigenetic conversion of mouse dermal fibroblasts into insulin producing-cells (Pennarossa, et al., 2013; Brevini, et al., 2015, combining also the use of two oxygen tensions. In particular, cells were differentiated using the Polytetrafluoroethylene micro-bioreactor (PTFE and the Polyacrylamide (PAA gels with different stiffness (1 kPa; 4 kPa, maintained either in the standard 20% or in the more physiological 5% oxygen tensions. Standard differentiation performed on plastic substrates was assessed as a control. Cell morphology (Fig.1A, insulin expression and release were analyzed to evaluate the role of both stiffness and oxygen tension in the process. The results obtained showed that 1 kPa PAA gel and PTFE system induced a significantly higher insulin expression and release than plastic and 4 kPa PAA gel, especially in low oxygen condition (Fig.1B. Furthermore, comparing the efficiency of the two systems tested, 1 kPa PAA gel ensured a higher insulin transcription than PTFE (Fig.1C. Recent studies show the direct influence of substrates on lineage commitment and cell differentiation (Engler, et al., 2006; Evans, et al., 2009. The evidence here presented confirm that the use of an appropriate stiffness (similar to the pancreatic tissue, combined with a physiological oxygen tension, promote β-cell differentiation, with beneficial effects on cell functional activity and insulin release. The present results highlight the importance of 3-D cell rearrangement and oxigen tension to promote in vitro epigenetic conversion of

Towards a quantitative understanding of oxygen tension and cell density evolution in fibrin hydrogels.

Science.gov (United States)

Demol, Jan; Lambrechts, Dennis; Geris, Liesbet; Schrooten, Jan; Van Oosterwyck, Hans

2011-01-01

The in vitro culture of hydrogel-based constructs above a critical size is accompanied by problems of unequal cell distribution when diffusion is the primary mode of oxygen transfer. In this study, an experimentally-informed mathematical model was developed to relate cell proliferation and death inside fibrin hydrogels to the local oxygen tension in a quantitative manner. The predictive capacity of the resulting model was tested by comparing its outcomes to the density, distribution and viability of human periosteum derived cells (hPDCs) that were cultured inside fibrin hydrogels in vitro. The model was able to reproduce important experimental findings, such as the formation of a multilayered cell sheet at the hydrogel periphery and the occurrence of a cell density gradient throughout the hydrogel. In addition, the model demonstrated that cell culture in fibrin hydrogels can lead to complete anoxia in the centre of the hydrogel for realistic values of oxygen diffusion and consumption. A sensitivity analysis also identified these two parameters, together with the proliferation parameters of the encapsulated cells, as the governing parameters for the occurrence of anoxia. In conclusion, this study indicates that mathematical models can help to better understand oxygen transport limitations and its influence on cell behaviour during the in vitro culture of cell-seeded hydrogels. Copyright © 2010 Elsevier Ltd. All rights reserved.

Exogenous and endogenous angiotensin‐II decrease renal cortical oxygen tension in conscious rats by limiting renal blood flow

Science.gov (United States)

Emans, Tonja W.; Janssen, Ben J.; Pinkham, Maximilian I.; Ow, Connie P. C.; Evans, Roger G.; Joles, Jaap A.; Malpas, Simon C.; Krediet, C. T. Paul

2016-01-01

Key points Our understanding of the mechanisms underlying the role of hypoxia in the initiation and progression of renal disease remains rudimentary.We have developed a method that allows wireless measurement of renal tissue oxygen tension in unrestrained rats.This method provides stable and continuous measurements of cortical tissue oxygen tension (PO2) for more than 2 weeks and can reproducibly detect acute changes in cortical oxygenation.Exogenous angiotensin‐II reduced renal cortical tissue PO2 more than equi‐pressor doses of phenylephrine, probably because it reduced renal oxygen delivery more than did phenylephrine.Activation of the endogenous renin–angiotensin system in transgenic Cyp1a1Ren2 rats reduced cortical tissue PO2; in this model renal hypoxia precedes the development of structural pathology and can be reversed acutely by an angiotensin‐II receptor type 1 antagonist.Angiotensin‐II promotes renal hypoxia, which may in turn contribute to its pathological effects during development of chronic kidney disease. Abstract We hypothesised that both exogenous and endogenous angiotensin‐II (AngII) can decrease the partial pressure of oxygen (PO2) in the renal cortex of unrestrained rats, which might in turn contribute to the progression of chronic kidney disease. Rats were instrumented with telemeters equipped with a carbon paste electrode for continuous measurement of renal cortical tissue PO2. The method reproducibly detected acute changes in cortical oxygenation induced by systemic hyperoxia and hypoxia. In conscious rats, renal cortical PO2 was dose‐dependently reduced by intravenous AngII. Reductions in PO2 were significantly greater than those induced by equi‐pressor doses of phenylephrine. In anaesthetised rats, renal oxygen consumption was not affected, and filtration fraction was increased only in the AngII infused animals. Oxygen delivery decreased by 50% after infusion of AngII and renal blood flow (RBF) fell by 3.3 ml min−1

Mixomics analysis of Bacillus subtilis: effect of oxygen availability on riboflavin production.

Science.gov (United States)

Hu, Junlang; Lei, Pan; Mohsin, Ali; Liu, Xiaoyun; Huang, Mingzhi; Li, Liang; Hu, Jianhua; Hang, Haifeng; Zhuang, Yingping; Guo, Meijin

2017-09-12

Riboflavin, an intermediate of primary metabolism, is one kind of important food additive with high economic value. The microbial cell factory Bacillus subtilis has already been proven to possess significant importance for the food industry and have become one of the most widely used riboflavin-producing strains. In the practical fermentation processes, a sharp decrease in riboflavin production is encountered along with a decrease in the dissolved oxygen (DO) tension. Influence of this oxygen availability on riboflavin biosynthesis through carbon central metabolic pathways in B. subtilis is unknown so far. Therefore the unveiled effective metabolic pathways were still an unaccomplished task till present research work. In this paper, the microscopic regulation mechanisms of B. subtilis grown under different dissolved oxygen tensions were studied by integrating 13 C metabolic flux analysis, metabolomics and transcriptomics. It was revealed that the glucose metabolic flux through pentose phosphate (PP) pathway was lower as being confirmed by smaller pool sizes of metabolites in PP pathway and lower expression amount of ykgB at transcriptional level. The latter encodes 6-phosphogluconolactonase (6-PGL) under low DO tension. In response to low DO tension in broth, the glucose metabolic flux through Embden-Meyerhof-Parnas (EMP) pathway was higher and the gene, alsS, encoding for acetolactate synthase was significantly activated that may result due to lower ATP concentration and higher NADH/NAD + ratio. Moreover, ResE, a membrane-anchored protein that is capable of oxygen regulated phosphorylase activity, and ResD, a regulatory protein that can be phosphorylated and dephosphorylated by ResE, were considered as DO tension sensor and transcriptional regulator respectively. This study shows that integration of transcriptomics, 13 C metabolic flux analysis and metabolomics analysis provides a comprehensive understanding of biosynthesized riboflavin's regulatory mechanisms in

Cross-Border Higher Education: Global and Local Tensions within Competition and Economic Development

Science.gov (United States)

Owens, Taya L.; Lane, Jason E.

2014-01-01

In this chapter, the authors explore various types of cross-border higher education, considering equity and quality issues within these developments. With a particular focus on international branch campuses, the authors discuss the ways in which global competition for knowledge and economic development interact with tensions at the local level.

Oxygen, nitric oxide and articular cartilage

Directory of Open Access Journals (Sweden)

B Fermor

2007-04-01

Full Text Available Molecular oxygen is required for the production of nitric oxide (NO, a pro-inflammatory mediator that is associated with osteoarthritis and rheumatoid arthritis. To date there has been little consideration of the role of oxygen tension in the regulation of nitric oxide production associated with arthritis. Oxygen tension may be particularly relevant to articular cartilage since it is avascular and therefore exists at a reduced oxygen tension. The superficial zone exists at approximately 6% O2, while the deep zone exists at less than 1% O2. Furthermore, oxygen tension can alter matrix synthesis, and the material properties of articular cartilage in vitro.The increase in nitric oxide associated with arthritis can be caused by pro-inflammatory cytokines and mechanical stress. Oxygen tension significantly alters endogenous NO production in articular cartilage, as well as the stimulation of NO in response to both mechanical loading and pro-inflammatory cytokines. Mechanical loading and pro-inflammatory cytokines also increase the production of prostaglandin E2 (PGE2. There is a complex interaction between NO and PGE2, and oxygen tension can alter this interaction. These findings suggest that the relatively low levels of oxygen within the joint may have significant influences on the metabolic activity, and inflammatory response of cartilage as compared to ambient levels. A better understanding of the role of oxygen in the production of inflammatory mediators in response to mechanical loading, or pro-inflammatory cytokines, may aid in the development of strategies for therapeutic intervention in arthritis.

Modelling of L-valine Repeated Fed-batch Fermentation Process Taking into Account the Dissolved Oxygen Tension

Directory of Open Access Journals (Sweden)

Tzanko Georgiev

2009-03-01

Full Text Available This article deals with synthesis of dynamic unstructured model of variable volume fed-batch fermentation process with intensive droppings for L-valine production. The presented approach of the investigation includes the following main procedures: description of the process by generalized stoichiometric equations; preliminary data processing and calculation of specific rates for main kinetic variables; identification of the specific rates takes into account the dissolved oxygen tension; establishment and optimisation of dynamic model of the process; simulation researches. MATLAB is used as a research environment.

Optic nerve oxygenation

DEFF Research Database (Denmark)

Stefánsson, Einar; Pedersen, Daniella Bach; Jensen, Peter Koch

2005-01-01

The oxygen tension of the optic nerve is regulated by the intraocular pressure and systemic blood pressure, the resistance in the blood vessels and oxygen consumption of the tissue. The oxygen tension is autoregulated and moderate changes in intraocular pressure or blood pressure do not affect...... the optic nerve oxygen tension. If the intraocular pressure is increased above 40 mmHg or the ocular perfusion pressure decreased below 50 mmHg the autoregulation is overwhelmed and the optic nerve becomes hypoxic. A disturbance in oxidative metabolism in the cytochromes of the optic nerve can be seen...... at similar levels of perfusion pressure. The levels of perfusion pressure that lead to optic nerve hypoxia in the laboratory correspond remarkably well to the levels that increase the risk of glaucomatous optic nerve atrophy in human glaucoma patients. The risk for progressive optic nerve atrophy in human...

Exogenous and endogenous angiotensin-II decrease renal cortical oxygen tension in conscious rats by limiting renal blood flow.

Science.gov (United States)

Emans, Tonja W; Janssen, Ben J; Pinkham, Maximilian I; Ow, Connie P C; Evans, Roger G; Joles, Jaap A; Malpas, Simon C; Krediet, C T Paul; Koeners, Maarten P

2016-11-01

Our understanding of the mechanisms underlying the role of hypoxia in the initiation and progression of renal disease remains rudimentary. We have developed a method that allows wireless measurement of renal tissue oxygen tension in unrestrained rats. This method provides stable and continuous measurements of cortical tissue oxygen tension (PO2) for more than 2 weeks and can reproducibly detect acute changes in cortical oxygenation. Exogenous angiotensin-II reduced renal cortical tissue PO2 more than equi-pressor doses of phenylephrine, probably because it reduced renal oxygen delivery more than did phenylephrine. Activation of the endogenous renin-angiotensin system in transgenic Cyp1a1Ren2 rats reduced cortical tissue PO2; in this model renal hypoxia precedes the development of structural pathology and can be reversed acutely by an angiotensin-II receptor type 1 antagonist. Angiotensin-II promotes renal hypoxia, which may in turn contribute to its pathological effects during development of chronic kidney disease. We hypothesised that both exogenous and endogenous angiotensin-II (AngII) can decrease the partial pressure of oxygen (PO2) in the renal cortex of unrestrained rats, which might in turn contribute to the progression of chronic kidney disease. Rats were instrumented with telemeters equipped with a carbon paste electrode for continuous measurement of renal cortical tissue PO2. The method reproducibly detected acute changes in cortical oxygenation induced by systemic hyperoxia and hypoxia. In conscious rats, renal cortical PO2 was dose-dependently reduced by intravenous AngII. Reductions in PO2 were significantly greater than those induced by equi-pressor doses of phenylephrine. In anaesthetised rats, renal oxygen consumption was not affected, and filtration fraction was increased only in the AngII infused animals. Oxygen delivery decreased by 50% after infusion of AngII and renal blood flow (RBF) fell by 3.3 ml min -1 . Equi-pressor infusion of

Diet-induced weight loss decreases adipose tissue oxygen tension with parallel changes in adipose tissue phenotype and insulin sensitivity in overweight humans

NARCIS (Netherlands)

Vink, R.G.; Roumans, N.J.; Čajlaković, M.; Cleutjens, J.P.M.; Boekschoten, M.V.; Fazelzadeh, P.; Vogel, M.A.A.; Blaak, E.E.; Mariman, E.C.; Baak, van M.A.; Goossens, G.H.

2017-01-01

Background/objectives: Although adipose tissue (AT) hypoxia is present in rodent models of obesity, evidence for this in humans is limited. Here, we investigated the effects of diet-induced weight loss (WL) on abdominal subcutaneous AT oxygen tension (pO 2), AT blood flow (ATBF), AT capillary

Comparison of Preterm and Term Wharton's Jelly-Derived Mesenchymal Stem Cell Properties in Different Oxygen Tensions.

Science.gov (United States)

Balgi-Agarwal, Saloni; Winter, Caitlyn; Corral, Alexis; Mustafa, Shamimunisa B; Hornsby, Peter; Moreira, Alvaro

2018-06-27

Mesenchymal stem cells (MSCs) have shown promise as therapeutic agents in treating morbidities associated with premature birth. MSCs derived from the human umbilical cord are easy to isolate and have low immunogenicity and a robust ability to secrete paracrine factors. To date, there are no studies evaluating preterm versus term umbilical cord tissue-derived MSCs. Therefore, our aim was twofold: (1) to compare stem cell properties in preterm versus term MSCs and (2) to examine the impact of oxygen tension on stem cell behavior. Umbilical cord tissue was obtained from 5 preterm and 5 term neonates. The cells were isolated and characterized as MSCs in accordance with the International Society for Cellular Therapy. We exposed MSCs to different oxygen tensions to examine the impact of environmental factors on cell performance. We studied the following stem cell properties: (i) motility, (ii) proliferation, (iii) senescence, (iv) cell viability, (v) colony-forming unit efficiency, and (vi) inflammatory cytokine expression. Under normoxia (21% O2), cells from preterm and term infants had similar properties. Under hypoxic conditions (1% O2), term MSCs had better cell proliferation; however, cells exposed to hyperoxia (90% O2) had the slowest motility and lowest cell viability (p cytokine expression between the groups. The term cells demonstrated more colony-forming efficiency than the preterm cells. In sum, our preliminary findings suggest that MSCs derived from term and preterm umbilical cords have similar characteristics, offering the potential of future autologous/allogeneic MSC transplants in neonates. © 2018 S. Karger AG, Basel.

Modification of the radiation response of pig skin by manipulation of tissue oxygen tension using anesthetics and administration of BW12C

International Nuclear Information System (INIS)

van den Aardweg, G.J.; Hopewell, J.W.; Barnes, D.W.; Sansom, J.M.; Nethersell, A.B.

1989-01-01

The importance of tissue oxygen tension on radiosensitivity was studied by examining modifications in the incidence of moist desquamation in pig skin after irradiation with strontium-90 plaques. The effects were analyzed using quantal dose-response data and comparisons were made using ED50 values for moist desquamation. Under standard anesthetic conditions of 2% halothane, approximately 70% oxygen, and approximately 30% nitrous oxide, the ED50 value (+/- SE) for moist desquamation was 27.32 +/- 0.52 Gy with no significant variation in radiosensitivity between dorsal, lateral, and ventral skin sites on the flank. Irradiation with 2% halothane and air increased the ED50 to 31.25 +/- 0.94 Gy, primarily due to an increased radioresistance of the dorsal sites. When combined with BW12C, a drug which binds oxygen selectively to hemoglobin and hence reduced the oxygen availability to tissues, a further increase in the ED50 values was observed. This was approximately 39 Gy with BW12C concentrations of 30 mg/kg and 50 mg/kg b.w. of BW12C, indicating a dose modification factor (DMF) of approximately 1.26. However, when animals were breathing the standard gas mixture, this DMF was reduced to 1.15 for 30 mg/kg of BW12C, indicating that a higher level of oxygen partly counteracted the effects of the drug in these studies with BW12C. The greatest variability in radiosensitivity was seen in the dorsal fields. This suggested complex physiological adaptation, a phenomenon that might also explain the absence of any modification of the radiation response when 100 mg/kg of BW12C was used

Closed Loop Control of Oxygen Delivery and Oxygen Generation

Science.gov (United States)

2017-08-01

were used for this study and were connected via a USB cable to allow communication. The ventilator was modified to allow closed loop control of oxygen...connected via a USB cable to allow communication. The ventilator was modified to allow closed loop control of oxygen based on the oxygen saturation...2017-4119, 28 Aug 2017. oximetry (SpO2) and intermittent arterial blood sampling for arterial oxygen tension (partial pressure of oxygen [PaO2]) and

Localized increase of tissue oxygen tension by magnetic targeted drug delivery

Science.gov (United States)

Liong, Celine; Ortiz, Daniel; Ao-ieong, Eilleen; Navati, Mahantesh S.; Friedman, Joel M.; Cabrales, Pedro

2014-07-01

Hypoxia is the major hindrance to successful radiation therapy of tumors. Attempts to increase the oxygen (O2) tension (PO2) of tissue by delivering more O2 have been clinically disappointing, largely due to the way O2 is transported and released by the hemoglobin (Hb) within the red blood cells (RBCs). Systemic manipulation of O2 transport increases vascular resistance due to metabolic autoregulation of blood flow to prevent over oxygenation. This study investigates a new technology to increase O2 delivery to a target tissue by decreasing the Hb-O2 affinity of the blood circulating within the targeted tissue. As the Hb-O2 affinity decreases, the tissue PO2 to satisfy tissue O2 metabolic needs increases without increasing O2 delivery or extraction. Paramagnetic nanoparticles (PMNPs), synthetized using gadolinium oxide, were coated with the cell permeable Hb allosteric effector L35 (3,5-trichlorophenylureido-phenoxy-methylpropionic acid). L35 decreases Hb affinity for O2 and favors the release of O2. The L35-coated PMNPs (L35-PMNPs) were intravenously infused (10 mg kg-1) to hamsters instrumented with the dorsal window chamber model. A magnetic field of 3 mT was applied to localize the effects of the L35-PMNPs to the window chamber. Systemic O2 transport characteristics and microvascular tissue oxygenation were measured after administration of L35-PMNPs with and without magnetic field. The tissue PO2 in untreated control animals was 25.2 mmHg. L35-PMNPs without magnetic field decreased tissue PO2 to 23.4 mmHg, increased blood pressure, and reduced blood flow, largely due to systemic modification of Hb-O2 affinity. L35-PMNPs with magnetic field increased tissue PO2 to 27.9 mmHg, without systemic or microhemodynamic changes. These results indicate that localized modification of Hb-O2 affinity can increase PO2 of target tissue without affecting systemic O2 delivery or triggering O2 autoregulation mechanisms. This technology can be used to treat local hypoxia and to

Oxygen dependency of porfiromycin cytotoxicity

International Nuclear Information System (INIS)

Marshall, R.S.; Rauth, A.M.

1987-01-01

The authors determined the oxygen dependency of toxicity for the bioreductive alkylating agents mitomycin C (MMC) and porfiromycin (PM) to investigate whether the toxicities of these agents increase in the range of oxygen tensions over which cells become increasingly radioresistant. In the present work the oxygen dependency of PM in CHO cells was determined by assaying survival as a function of time of exposure to 1.0 μg/ml PM under various known levels of oxygen. While PM demonstrated preferential hypoxic cell toxicity, aerobic cell survival was reduced ten-fold after five hours of exposure. Conversely, PM toxicity after a five hour hypoxic exposure to <0.001% oxygen appeared to be greater than that observed for similar MMC exposures, suggesting that PM may be more selective than MMC in killing hypoxic rather than aerobic cells. The authors are currently investigating this preferential toxicity in two human cell lines, one of which is resistant to these agents. At present, these observations suggest that PM may be more effective than MMC at destroying tumour cells in regions of intermediate and low oxygen tensions which may survive radiotherapy, though the range of oxygen tensions which mediate toxicity is similar for both agents

The role of tissue oxygen tension in the control of local blood flow in the microcirculation of skeletal muscles

DEFF Research Database (Denmark)

Ngo, Thuc Anh

2010-01-01

In the microcirculation blood flow is highly regulated dependent on the metabolic activity of the tissues. Among several mechanisms, mechanisms involved in the coupling of changes in tissue oxygen tension due to changes in the metabolic activity of the tissue play an important role. In the systemic...... (inhibitor of KATP channels) in the superfusate abolished both vasodilatation and constriction to low and high oxygen superfusate, indicating that KATP channels are involved in both hypoxic vasodilatation and hyperoxic vasoconstriction. Red blood cells (RBCs) have been proposed to release ATP and...... as in the intact blood-perfused arteriole. This indicates that RBCs are not essential for hypoxic vasodilatation. In addition several potential pathways were evaluated. Application of DPCPX (inhibitor of adenosine A1 and A2 receptors) and L-NAME (inhibitor of NO-synthase) did not affect vasomotor responses to low...

Discrepancies between measured changes of radiobiological hypoxic fraction and oxygen tension monitoring using two assay systems

International Nuclear Information System (INIS)

Sasai, K.; Brown, J.M.

1994-01-01

This study was conducted to assess the ability of computerized pO 2 histography to measure changes in tumor oxygenation produced by low oxygen breathing. Female syngeneic C3H/Km mice bearing SCC VII/St carcinomas were used in these experiments. Changes in tumor oxygenation produced by the mice breathing 10% oxygen were assessed with computerized pO2 histography, 3 H-misonidazole binding, and the paired survival curve assay of radiosensitivity. The hypoxic cell fraction of the tumors in mice breathing 10% oxygen was 3.1 times higher than that of tumors in mice breathing normal air determined by an in vivo-in vitro clonogenic assay. Binding of radiolabeled misonidazole to the tumors in mice breathing 10% oxygen was also significantly higher than that to tumors in mice breathing normal air (p 2 value for the tumor. The number of pO 2 readings lower than 5 mmHg in the tumor was not affected by the 10% oxygen breathing. These findings indicate that increases in radiobiological hypoxic fraction produced by lower blood oxygen levels may not correlate well with the results of polarographic measurements of tumor pO 2 levels. 29 refs., 4 figs., 1 tab

Near-simultaneous hemoglobin saturation and oxygen tension maps in mouse brain using an AOTF microscope.

Science.gov (United States)

Shonat, R D; Wachman, E S; Niu, W; Koretsky, A P; Farkas, D L

1997-09-01

A newly developed microscope using acousto-optic tunable filters (AOTFs) was used to generate in vivo hemoglobin saturation (SO2) and oxygen tension (PO2) maps in the cerebral cortex of mice. SO2 maps were generated from the spectral analysis of reflected absorbance images collected at different wavelengths, and PO2 maps were generated from the phosphorescence lifetimes of an injected palladium-porphyrin compound using a frequency-domain measurement. As the inspiratory O2 was stepped from hypoxia (10% O2), through normoxia (21% O2), to hyperoxia (60% O2), measured SO2 and PO2 levels rose accordingly and predictably throughout. A plot of SO2 versus PO2 in different arterial and venous regions of the pial vessels conformed to the sigmoidal shape of the oxygen-hemoglobin dissociation curve, providing further validation of the two mapping procedures. The study demonstrates the versatility of the AOTF microscope for in vivo physiologic investigation, allowing for the generation of nearly simultaneous SO2 and PO2 maps in the cerebral cortex, and the frequency-domain detection of phosphorescence lifetimes. This class of study opens up exciting new possibilities for investigating the dynamics of hemoglobin and O2 binding during functional activation of neuronal tissues.

Higher cerebral oxygen saturation may provide higher urinary output during continuous regional cerebral perfusion

Directory of Open Access Journals (Sweden)

Tomoyasu Takahiro

2008-10-01

Full Text Available Abstract Objective We examined the hypothesis that higher cerebral oxygen saturation (rSO2 during RCP is correlated with urinary output. Methods Between December 2002 and August 2006, 12 patients aged 3 to 61 days and weighing 2.6 to 3.4 kg underwent aortic arch repair with RCP. Urinary output and rSO2 were analyzed retrospectively. Data were assigned to either of 2 groups according to their corresponding rSO2: Group A (rSO2 ≦ 75% and Group B (rSO2 Results Seven and 5 patients were assigned to Group A and Group B, respectively. Group A was characterized by mean radial arterial pressure (37.9 ± 9.6 vs 45.8 ± 7.8 mmHg; P = 0.14 and femoral arterial pressure (6.7 ± 6.1 vs 20.8 ± 14.6 mmHg; P = 0.09 compared to Group B. However, higher urinary output during CPB (1.03 ± 1.18 vs 0.10 ± 0.15 ml·kg-1·h-1; P = 0.03. Furthermore our results indicate that a higher dose of Chlorpromazine was used in Group A (2.9 ± 1.4 vs 1.7 ± 1.0 mg/kg; P = 0.03. Conclusion Higher cerebral oxygenation may provide higher urinary output due to higher renal blood flow through collateral circulation.

Effects of Dissolved Oxygen Concentration and Iron Addition on Immediate-early Gene Expression of Magnetospirillum gryphiswaldense MSR-1

DEFF Research Database (Denmark)

Zhuang, Shiwen; Anyaogu, Diana Chinyere; Kasama, Takeshi

2017-01-01

in cultures at 0.5% O2 compared to those at higher oxygen tensions. Moreover, expression of katG (catalase-peroxidase gene) and feoB2 (ferrous transport protein B2 gene) was reduced markedly by iron addition, regardless of oxygen conditions. The data provides a greater understanding of molecular response...

Critical oxygen tension and the effect of hypoxia on the oxygen consumption of the striped catfish, Pangasius hypophthaimos (Pangasiidae)

DEFF Research Database (Denmark)

Lefevre, S.; Bayley, Mark; Wang, Tobias

2008-01-01

The striped catfish (Pangasius hypophthalmus) is an air-breathing teleost that uses a modified swim bladder for aerial gas exchange. Pangasius is of enormous importance for aquaculture industry in the Mekong Delta(Vietnam), but little is known about its physiology. We have initiated a series...... consumption (VO2), measured with intermittent closed respirometry, was 67.8 ± 5.1 mLO2/kg/h when the fish were maintained without access to air at 27 °C. The critical oxygen tension (Pcrit) at these conditions was 57.9 ± 8.9 mmHg (N = 7). The metabolic response to aquatic hypoxia was studied in fish subjected....... The ontogenetic effect of environmental PO2 on metabolism is currently under investigation with fish being reared in 30%, 60% and 100% saturation. Data on resting VO2and Pcrit will be presented and discussed for these animals....

Oxygen Modulates Human Decidual Natural Killer Cell Surface Receptor Expression and Interactions with Trophoblasts1

Science.gov (United States)

Wallace, Alison E.; Goulwara, Sonu S.; Whitley, Guy S.; Cartwright, Judith E.

2014-01-01

Decidual natural killer (dNK) cells have been shown to both promote and inhibit trophoblast behavior important for decidual remodeling in pregnancy and have a distinct phenotype compared to peripheral blood NK cells. We investigated whether different levels of oxygen tension, mimicking the physiological conditions of the decidua in early pregnancy, altered cell surface receptor expression and activity of dNK cells and their interactions with trophoblast. dNK cells were isolated from terminated first-trimester pregnancies and cultured in oxygen tensions of 3%, 10%, and 21% for 24 h. Cell surface receptor expression was examined by flow cytometry, and the effects of secreted factors in conditioned medium (CM) on the trophoblast cell line SGHPL-4 were assessed in vitro. SGHPL-4 cells treated with dNK cell CM incubated in oxygen tensions of 10% were significantly more invasive (P cells treated with dNK cell CM incubated in oxygen tensions of 3% or 21%. After 24 h, a lower percentage of dNK cells expressed CD56 at 21% oxygen (P cells expressed NKG2D at 10% oxygen (P oxygen tensions, with large patient variation. This study demonstrates dNK cell phenotype and secreted factors are modulated by oxygen tension, which induces changes in trophoblast invasion and endovascular-like differentiation. Alterations in dNK cell surface receptor expression and secreted factors at different oxygen tensions may represent regulation of function within the decidua during the first trimester of pregnancy. PMID:25232021

The Effective Lifetime of ACSR Full Tension Splice Connector Operated at Higher Temperature

International Nuclear Information System (INIS)

Wang, Jy-An John; Lara-Curzio, Edgar; King Jr, Thomas J.; Graziano, Joe; Chan, John; Goodwin, Tip

2009-01-01

This paper is to address the issues related to integrity of ACSR full tension splice connectors operated at high temperatures. A protocol of integrating analytical and experimental approaches to evaluate the integrity of a full tension single-stage splice connector (SSC) assembly during service at high operating temperature was developed. Based on the developed protocol the effective lifetime evaluation was demonstrated with ACSR Drake conductor SSC systems. The investigation indicates that thermal cycling temperature and frequency, conductor cable tension loading, and the compressive residual stress field within a SSC system have significant impact on the SSC integrity and the associated effective lifetime

Simultaneous Monitoring of Vascular Oxygenation and Tissue Oxygen Tension of Breast Tumors Under Hyperbaric Oxygen Exposure

Science.gov (United States)

2008-04-01

28. Alagoz, T., R. Buller, B. Anderson, K. Terrell , R...and oxygenation Ann . New Acad. Sci. 838 29–45 Chapman J D, Stobbe C C, Arnfield M R, Santus R, Lee J and McPhee M S 1991 Oxygen dependency of tumor

Oxygen tension and riboflavin gradients cooperatively regulate the migration of Shewanella oneidensis MR-1 revealed by a hydrogel-based microfluidic device

Directory of Open Access Journals (Sweden)

Beum Jun Kim

2016-09-01

Full Text Available Shewanella oneidensis (S. oneidensis is a model bacterial strain for studies of bioelectrochemical systems (BESs. It has two extracellular electron transfer pathways: 1 shuttling electrons via an excreted mediator riboflavin; and 2 direct contact between the c-type cytochromes at the cell membrane and the electrode. Despite the extensive use of S. oneidensis in bioelectrochemical systems such as microbial fuel cells and biosensors, many basic microbiology questions about S. oneidensis in the context of BES remain unanswered. Here, we present studies of motility and chemotaxis of S. oneidensis under well controlled concentration gradients of two electron acceptors, oxygen and oxidized form of riboflavin (flavin+ using a newly developed microfluidic platform. Experimental results demonstrate that either oxygen or flavin+ is a chemoattractant to S. oneidensis. The chemotactic tendency of S. oneidensis in a flavin+ concentration gradient is significantly enhanced in an anaerobic in contrast to an aerobic condition. Furthermore, either a low oxygen tension or a high flavin+ concentration considerably enhances the speed of S. oneidensis. This work presents a robust microfluidic platform for generating oxygen and/or flavin+ gradients in an aqueous environment, and demonstrates that two important electron acceptors, oxygen and oxidized riboflavin, cooperatively regulate S. oneidensis migration patterns. The microfluidic tools presented as well as the knowledge gained in this work can be used to guide the future design of BESs for efficient electron production.

Oxygen sensing and conducted vasomotor responses in mouse cremaster arterioles in situ

DEFF Research Database (Denmark)

Ngo, Thuc Anh; Jensen, Lars Jørn; Riemann, Mads Achen

2010-01-01

.0 +/- 4.9 mum) when changing from high (PO(2) = 242.5 +/- 13.3 mm Hg) to low (PO(2) = 22.5 +/- 4.8 mm Hg) oxygen tension as seen in the intact cremaster circulation (DeltaD = 18.7 +/- 1.0 mum). Blockade of NO synthases by L: -NAME and adenosine receptors by DPCPX had no effects on vasomotor responses...... to low or high oxygen. Induction of localized low (PO(2) = 23.3 +/- 5.7 mmHg) or high (PO(2) = 300.0 +/- 25.7 mm Hg) oxygen tension caused vasodilatation or -constriction locally and at a site 1,000 mum upstream (distantly). Glibenclamide blocker of ATP-sensitive K(+) channels inhibited vasodilatation...... and -constriction to low (PO(2) = 16.0 +/- 6.4 mm Hg) and high (PO(2) = 337.4 +/- 12.8 mm Hg) oxygen tension. 1) ATP-sensitive K(+) channels seem to mediate, at least in part, vasodilatation and vasoconstriction to low and high oxygen tension; 2) Red blood cells are not necessary for inducing vasodilatation...

Oxygenation measurement by multi-wavelength oxygen-dependent phosphorescence and delayed fluorescence: catchment depth and application in intact heart

NARCIS (Netherlands)

Balestra, Gianmarco M.; Aalders, Maurice C. G.; Specht, Patricia A. C.; Ince, Can; Mik, Egbert G.

2015-01-01

Oxygen delivery and metabolism represent key factors for organ function in health and disease. We describe the optical key characteristics of a technique to comprehensively measure oxygen tension (PO(2)) in myocardium, using oxygen-dependent quenching of phosphorescence and delayed fluorescence of

Development of pulmonary vascular response to oxygen

International Nuclear Information System (INIS)

Morin, F.C. III; Egan, E.A.; Ferguson, W.; Lundgren, C.E.

1988-01-01

The ability of the pulmonary circulation of the fetal lamb to respond to a rise in oxygen tension was studied from 94 to 146 days of gestation. The unanesthetized ewe breathed room air at normal atmospheric pressure, followed by 100% oxygen at three atmospheres absolute pressure in a hyperbaric chamber. In eleven near-term lambs, fetal arterial oxygen tension (Pa O 2 ) increased from 25 to 55 Torr, which increased the proportion or right ventricular output distributed to the fetal lungs from 8 to 59%. In five very immature lambs fetal Pa O 2 increased from 27 to 174 Torr, but the proportion of right ventricular output distributed to the lung did not change. In five of the near-term lambs, pulmonary blood flow was measured. For each measurement of the distribution of blood flow, approximately 8 x 10 5 spheres of 15-μm diameter, labeled with either 153 Gd, 113 Sn, 103 Ru, 95 Nb, or 46 Sc were injected. It increased from 34 to 298 ml · kg fetal wt -1 · min -1 , an 8.8-fold increase. The authors conclude that the pulmonary circulation of the fetal lamb does not respond to an increase in oxygen tension before 101 days of gestation; however, near term an increase in oxygen tension alone can induce the entire increase in pulmonary blood flow that normally occurs after the onset of breathing at birth

Measurement of brain oxygenation changes using dynamic T1-weighted imaging

DEFF Research Database (Denmark)

Haddock, Bryan; Larsson, Henrik B W; Hansen, Adam E

2013-01-01

Magnetic resonance imaging (MRI) has proven useful in evaluating oxygenation in several types of tissue and blood. This study evaluates brain tissue oxygenation changes between normoxia and hyperoxia in healthy subjects using dynamic T1 and T2*-weighted imaging sequences. The change in FiO2 induced...... by hyperoxia caused a significant decrease in T1. A model to determine changes in tissue oxygen tension from the T1-weighted MRI signal is presented based on previous findings that T1 is sensitive to oxygen tension whereas T2* is sensitive to blood saturation. The two sequences produce results with different...... regional and temporal dynamics. These differences combined with results from simulations of the T1 signal intensities, indicate an increase in extravascular oxygen tension during hyperoxia. This study concludes that T1 and T2* responses to FiO2 serve as independent biomarkers of oxygen physiology...

Intervention of oxygen-control ability to radiation sensitivity, cell aging and cell transformation

International Nuclear Information System (INIS)

Yoshii, Hanako; Watanabe, Masami

2009-01-01

Oxygen is essential for life, and cells have therefore developed numerous adaptive responses to oxygen change. Here, we examined the difference in oxygen-control functions of human (HE), mouse (ME), and Syrian hamster embryo (SHE) cells cultured under different oxygen conditions (0.5%, 2% and 20%), and also examined whether oxygen tensions contributed to cellular lifespan and transformation. HE cells had their replicative lifespan slightly extended under hypoxic (0.5% and 2% oxygen) conditions, but were not immortalized under any of the oxygen concentrations. On the other hand, although ME cells cultured under 20% oxygen tension decreased their proliferation potency temporarily at early stage, all rodent cells were immortalized and acquired anchorage-independency, regardless of oxygen tension. These results suggest that cellular oxygen control function is related to sensitivities cellular immortalization and transformation. To understand intervention of oxygen control ability on cellular immortalization and transformation, we examined the intracellular oxidative level, mitochondria functions and radiation sensitivity. Intracellular oxidative levels of hypoxically cultured rodent cells were significantly enhanced. Mitochondrial membrane potential was altered depend on oxygen tensions, but the change was not parallel to mitochondria number in rodent cells. ME cells were particularly sensitive to oxygen change, and showed a clear oxygen effect on the X-ray survival. However, there was no difference in frequency of radiation-induced micronuclei between HE and ME cells. These results suggest that the response to oxygen change differs markedly in HE and rodent cells. (author)

Effect of low oxygen tension on the biological characteristics of human bone marrow mesenchymal stem cells.

Science.gov (United States)

Kim, Dae Seong; Ko, Young Jong; Lee, Myoung Woo; Park, Hyun Jin; Park, Yoo Jin; Kim, Dong-Ik; Sung, Ki Woong; Koo, Hong Hoe; Yoo, Keon Hee

2016-11-01

Culture of mesenchymal stem cells (MSCs) under ambient conditions does not replicate the low oxygen environment of normal physiological or pathological states and can result in cellular impairment during culture. To overcome these limitations, we explored the effect of hypoxia (1 % O 2 ) on the biological characteristics of MSCs over the course of different culture periods. The following biological characteristics were examined in human bone marrow-derived MSCs cultured under hypoxia for 8 weeks: proliferation rate, morphology, cell size, senescence, immunophenotypic characteristics, and the expression levels of stemness-associated factors and cytokine and chemokine genes. MSCs cultured under hypoxia for approximately 2 weeks showed increased proliferation and viability. During long-term culture, hypoxia delayed phenotypic changes in MSCs, such as increased cell volume, altered morphology, and the expression of senescence-associated-β-gal, without altering their characteristic immunophenotypic characteristics. Furthermore, hypoxia increased the expression of stemness and chemokine-related genes, including OCT4 and CXCR7, and did not decrease the expression of KLF4, C-MYC, CCL2, CXCL9, CXCL10, and CXCR4 compared with levels in cells cultured under normoxia. In conclusion, low oxygen tension improved the biological characteristics of MSCs during ex vivo expansion. These data suggest that hypoxic culture could be a useful method for increasing the efficacy of MSC cell therapies.

Variations in tumour oxygen tension (pO2) during accelerated radiotherapy of head and neck carcinoma

International Nuclear Information System (INIS)

Guichard, M.; Eschwege, F.; Luboinski, B.; Wibault, P.; Weeger, P.; Lusinchi, A.; Lartigau, E.

1998-01-01

The study was performed to assess the effect of accelerated radiotherapy on oxygenation of primary tumours and metastatic nodes in patients with advanced head and neck tumours. In 14 patients with head and neck tumour, oxygen tension (pO 2 ) was evaluated in normal tissues and tumours (primary tumour or metastatic neck node) before (0 Gy) and after 2 weeks (32 Gy) of accelerated radiotherapy (70 Gy in 3.5 weeks, with three daily fractions). Radiotherapy was combined with carbogen breathing in 5 patients. pO 2 was measured using a polarographic technique. For pooled normal tissues, median pO 2 was 38 mmHg before treatment and 46 mmHg after 2 weeks. For tumours, very low values ( 2 12 mmHg before treatment versus 26 mmHg after 2 weeks, P 2 was 44 mmHg at 2 weeks, compared with 13.5 mmHg before treatment (P=0.05). Very low pO 2 values, corresponding to tumour hypoxia, were found in the tumours (primary and metastatic neck nodes) prior to accelerated treatment. During the first 2 weeks of accelerated treatment, an increase in median pO 2 was found in nine of the 14 tumours, together with a decrease in the frequency of very low values. (Copyright (c) 1998 Elsevier Science B.V., Amsterdam. All rights reserved.)

Inadequate cerebral oxygen delivery and central fatigue during strenuous exercise

DEFF Research Database (Denmark)

Nybo, Lars; Rasmussen, Peter

2007-01-01

Under resting conditions, the brain is protected against hypoxia because cerebral blood flow increases when the arterial oxygen tension becomes low. However, during strenuous exercise, hyperventilation lowers the arterial carbon dioxide tension and blunts the increase in cerebral blood flow, which...... can lead to an inadequate oxygen delivery to the brain and contribute to the development of fatigue....

Quantifying oxygen in paper-based cell cultures with luminescent thin film sensors.

Science.gov (United States)

Boyce, Matthew W; Kenney, Rachael M; Truong, Andrew S; Lockett, Matthew R

2016-04-01

Paper-based scaffolds are an attractive material for generating 3D tissue-like cultures because paper is readily available and does not require specialized equipment to pattern, cut, or use. By controlling the exchange of fresh culture medium with the paper-based scaffolds, we can engineer diffusion-dominated environments similar to those found in spheroids or solid tumors. Oxygen tension directly regulates cellular phenotype and invasiveness through hypoxia-inducible transcription factors and also has chemotactic properties. To date, gradients of oxygen generated in the paper-based cultures have relied on cellular response-based readouts. In this work, we prepared a luminescent thin film capable of quantifying oxygen tensions in apposed cell-containing paper-based scaffolds. The oxygen sensors, which are polystyrene films containing a Pd(II) tetrakis(pentafluorophenyl)porphyrin dye, are photostable, stable in culture conditions, and not cytotoxic. They have a linear response for oxygen tensions ranging from 0 to 160 mmHg O2, and a Stern-Volmer constant (K sv) of 0.239 ± 0.003 mmHg O2 (-1). We used these oxygen-sensing films to measure the spatial and temporal changes in oxygen tension for paper-based cultures containing a breast cancer line that was engineered to constitutively express a fluorescent protein. By acquiring images of the oxygen-sensing film and the fluorescently labeled cells, we were able to approximate the oxygen consumption rates of the cells in our cultures.

Is oxygen availability a limiting factor for in vitro folliculogenesis?

Directory of Open Access Journals (Sweden)

Riccardo Talevi

Full Text Available Transplantation of ovarian tissue for the preservation of fertility in oncological patients is becoming an accepted clinical practice. However, the risk of re-introducing tumour cells at transplantation has stirred an increased interest for complete in vitro folliculogenesis. This has not yet been achieved in humans possibly for the lack of knowledge on the environmental milieu that orchestrates folliculogenesis in vivo. The main aim of this study was to investigate the effect of oxygen availability on follicle health and growth during in vitro culture of ovarian tissue strips. To this end, a model was developed to predict the dissolved oxygen concentration in tissue under varying culture conditions. Ovarian cortical strips of bovine, adopted as an animal model, and human tissue were cultured in conventional (CD and gas permeable (PD dishes under different media column heights and gaseous oxygen tensions for 3, 6 and 9 days. Follicle quality, activation of primordial follicles to the primary stage, and progression to the secondary stage were analysed through histology. Follicle viability was assessed through a live-dead assay at the confocal scanning laser microscope. Findings showed a higher follicle quality and viability after culture of bovine ovarian strips in PD in adequate medium height and oxygen tensions. The best culture conditions found in the bovine were adopted for human ovarian strip culture and promoted a higher follicle quality, viability and progression. Overall, data demonstrated that modulation of oxygen availability in tissue plays a key role in maintaining follicles' health and their ability to survive and progress to the secondary stage during ovarian tissue in vitro culture. Such culture conditions could increase the yield of healthy secondary follicles for subsequent dissection and individual culture to obtain competent oocytes.

Density and surface tension of ionic liquids.

Science.gov (United States)

Kolbeck, C; Lehmann, J; Lovelock, K R J; Cremer, T; Paape, N; Wasserscheid, P; Fröba, A P; Maier, F; Steinrück, H-P

2010-12-30

We measured the density and surface tension of 9 bis[(trifluoromethyl)sulfonyl]imide ([Tf(2)N](-))-based and 12 1-methyl-3-octylimidazolium ([C(8)C(1)Im](+))-based ionic liquids (ILs) with the vibrating tube and the pendant drop method, respectively. This comprehensive set of ILs was chosen to probe the influence of the cations and anions on density and surface tension. When the alkyl chain length in the [C(n)C(1)Im][Tf(2)N] series (n = 1, 2, 4, 6, 8, 10, 12) is increased, a decrease in density is observed. The surface tension initially also decreases but reaches a plateau for alkyl chain lengths greater than n = 8. Functionalizing the alkyl chains with ethylene glycol groups results in a higher density as well as a higher surface tension. For the dependence of density and surface tension on the chemical nature of the anion, relations are only found for subgroups of the studied ILs. Density and surface tension values are discussed with respect to intermolecular interactions and surface composition as determined by angle-resolved X-ray photoelectron spectroscopy (ARXPS). The absence of nonvolatile surface-active contaminants was proven by ARXPS.

The Neuroprotection Effect of Oxygen Therapy: A Systematic Review ...

African Journals Online (AJOL)

2018-04-04

Apr 4, 2018 ... investigating the neuroprotective effect of oxygen, but the outcomes as well as ...... Neuroprotective gases – Fantasy or reality for clinical use? Prog .... of oxygen on brain tissue oxygen tension in children with severe traumatic ...

Oxygen-controlled automated neural differentiation of mouse embryonic stem cells.

Science.gov (United States)

Mondragon-Teran, Paul; Tostoes, Rui; Mason, Chris; Lye, Gary J; Veraitch, Farlan S

2013-03-01

Automation and oxygen tension control are two tools that provide significant improvements to the reproducibility and efficiency of stem cell production processes. the aim of this study was to establish a novel automation platform capable of controlling oxygen tension during both the cell-culture and liquid-handling steps of neural differentiation processes. We built a bespoke automation platform, which enclosed a liquid-handling platform in a sterile, oxygen-controlled environment. An airtight connection was used to transfer cell culture plates to and from an automated oxygen-controlled incubator. Our results demonstrate that our system yielded comparable cell numbers, viabilities, metabolism profiles and differentiation efficiencies when compared with traditional manual processes. Interestingly, eliminating exposure to ambient conditions during the liquid-handling stage resulted in significant improvements in the yield of MAP2-positive neural cells, indicating that this level of control can improve differentiation processes. This article describes, for the first time, an automation platform capable of maintaining oxygen tension control during both the cell-culture and liquid-handling stages of a 2D embryonic stem cell differentiation process.

[Case of tension pneumothorax associated with asthma attack during general anesthesia].

Science.gov (United States)

Komasawa, Nobuyasu; Ueki, Ryusuke; Kusuyama, Kazuki; Okano, Yukari; Tatara, Tsuneo; Tashiro, Chikara

2010-05-01

We report a case of tension pneumothorax associated with asthma attack during general anesthesia. An 86-year-old woman with dementia underwent cataract surgery under general anesthesia. At 70 min after the start of operation, airway pressure suddenly increased from 19 to 28 cm HO2O. In spite of bag ventilation with 100% oxygen, Sp(O2) decreased to 81%. Chest-Xp showed typical image of tension pneumothorax. Chest drainage was immediately performed, after which Pa(O2) recovered soon. She was extubated on postoperative day 1 without any neurological disorder. Hyperinflation of fragile alveoli by mechanical ventilation was likely a cause of tension pneumothorax.

Encouraging effects of a short-term, adapted Nordic diet intervention on skin microvascular function and skin oxygen tension in younger and older adults.

Science.gov (United States)

Rogerson, David; McNeill, Scott; Könönen, Heidi; Klonizakis, Markos

2018-05-01

The microvascular benefits of regional diets appear in the literature; however, little is known about Nordic-type diets. We investigated the effects of a short-term, adapted, Nordic diet on microvascular function in younger and older individuals at rest and during activity. Thirteen young (mean age: 28 y; standard deviation: 5 y) and 15 older (mean age: 68 y; standard deviation: 6 y) participants consumed a modified Nordic diet for 4 wk. Laser Doppler flowmetry and transcutaneous oxygen monitoring were used to assess cutaneous microvascular function and oxygen tension pre- and postintervention; blood pressure, body mass, body fat percentage, ratings of perceived exertion, and peak heart rate during activity were examined concurrently. Axon-mediated vasodilation improved in older participants (1.17 [0.30] to 1.30 [0.30]; P Nordic diet might improve microvascular health. Copyright © 2017 Elsevier Inc. All rights reserved.

Bilateral tension pneumothorax related to acupuncture.

Science.gov (United States)

Tagami, Rumi; Moriya, Takashi; Kinoshita, Kosaku; Tanjoh, Katsuhisa

2013-06-01

We report on a patient with a rare case of bilateral tension pneumothorax that occurred after acupuncture. A 69-year-old large-bodied man, who otherwise had no risk factors for spontaneous pneumothorax, presented with chest pressure, cold sweats and shortness of breath. Immediately after bilateral pneumothorax had been identified on a chest radiograph in the emergency room, his blood pressure and percutaneous oxygen saturation suddenly decreased to 78 mm Hg and 86%, respectively. We confirmed deterioration in his cardiopulmonary status and diagnosed bilateral tension pneumothorax. We punctured his chest bilaterally and inserted chest tubes for drainage. His vital signs promptly recovered. After the bilateral puncture and drainage, we learnt that he had been treated with acupuncture on his upper back. We finally diagnosed a bilateral tension pneumothorax based on the symptoms that appeared 8 h after the acupuncture. Because the patient had no risk factors for spontaneous pneumothorax, no alternative diagnosis was proposed. We recommend that patients receiving acupuncture around the chest wall must be adequately informed of the possibility of complications and expected symptoms, as a definitive diagnosis can be difficult without complete information.

Patients with tension-type headaches feel stigmatized

Directory of Open Access Journals (Sweden)

Sanjay Prakash

2016-01-01

Full Text Available The author, a sufferer of tension-type headache (TTH, believes that the word "tension" in "tension-type headache" carries a social stigma and that patients do not accept a diagnosis of TTH readily. TTH is the most common primary headache disorder. The disability of TTH as a burden of society is greater than that of migraine. Absenteeism because of TTH is higher than that due to migraine. However, patients with TTH do not go for consultation. Even the prevalence of new daily persistent headache (NDPH is 12 times higher at the headache clinic than that of chronic TTH (CTTH. These points hint that TTH patients probably do not want to visit the clinic. The author believes that it could be because of the stigma attached to "tension." Herein, the author has noted the first responses given by 50 consecutive patients with TTH when they were told that they had been suffering from TTH. The first answer of 64% of patients with TTH was "I do not have any tension/stress ." This denial is similar to the denial declared by patients with depression. Depression and tension are similar in the sense that both are considered as a signs of personal weakness. Such a preconception in the society creates a stigma, and patients deny the diagnosis, conceal symptoms, and become reluctant to seek help and treatment.

Oxygen tension in human tumours measured with polarographic needle electrodes and its relationship to vascular density, necrosis and hypoxia

International Nuclear Information System (INIS)

Lyng, Heidi; Sundfoer, Kolbein; Rofstad, Einar K.

1997-01-01

Background and purpose: The use of polarographic needle electrodes for measurement of oxygen tension (pO 2 ) in tumours requires documentation of the validity of the method. In the present work the pO 2 values measured polarographically with the Eppendorf pO 2 histograph in human tumours were compared with the histological appearance of the tumour tissue, i.e. vascular density, fraction of necrosis and fraction of hypoxic tissue, to investigate whether the measurements reflected the expected pO 2 . Materials and methods: The pO 2 was measured in cervix tumours in patients and in human melanoma xenografted tumours in athymic mice. Vascular density was determined in the cervix tumours by histological analysis of biopsies from the pO 2 measurement tracks. Fraction of necrosis and fraction of hypoxic tissue, i.e. tissue binding the hypoxia marker pimonidazole, were determined in the melanomas by analysis of histological sections from the tumour planes in which the pO 2 measurements were performed. Results: The pO 2 distributions showed large intratumour heterogeneity. In cervix tumours, tumour regions with vascular density (vascular length per unit tissue volume) in the range of 47-77 mm/mm 3 showed higher pO 2 than tumour regions with vascular density in the range of 20-47 mm/mm 3 , which in turn showed higher pO 2 than tumour regions with vascular density in the range of 0-20 mm/mm 3 . In melanomas, tumour regions in which necrosis and hypoxia constituted more than 50% of the tissue showed lower pO 2 than other tumour regions. Conclusions: The pO 2 measured in the tumours was consistent with the histological appearance of the tissue in which the measurements were performed, suggesting that reliable pO 2 distributions of tumours can be obtained with polarographic needle electrodes

"We Have to Learn from Both Sciences": Dilemmas and Tension Concerning Higher Education of Wichí Youth in the Province of Salta (Argentina)

Science.gov (United States)

Ossola, María Macarena

2017-01-01

This article analyzes the tension generated by the admission of Wichí youths to higher education in the province of Salta (Argentina). The main goal is to show how access to higher education generates continuities and discontinuities in the indigenous social organization. The article is based on ethnographic fieldwork that examined how young Wichí…

Radiosensitization of mouse skin by oxygen and depletion of glutathione

International Nuclear Information System (INIS)

Stevens, Graham; Joiner, Michael; Joiner, Barbara; Johns, Helen; Denekamp, Juliana

1995-01-01

Purpose: To determine the oxygen enhancement ratio (OER) and shape of the oxygen sensitization curve of mouse foot skin, the extent to which glutathione (GSH) depletion radiosensitized skin, and the dependence of such sensitization on the ambient oxygen tension. Methods and Materials: The feet of WHT mice were irradiated with single doses of 240 kVp x-rays while mice were exposed to carbogen or gases with oxygen/nitrogen mixtures containing 8-100% O 2 . The anoxic response was obtained by occluding the blood supply to the leg of anesthetized mice with a tourniquet, surrounding the foot with nitrogen, and allowing the mice to breathe 10% O 2 . Further experiments were performed to assess the efficacy of this method to obtain an anoxic response. Radiosensitivity of skin was assessed using the acute skin-reaction assay. Glutathione levels were modified using two schedules of dl-buthionine sulphoximine (BSO) and diethylmaleate (DEM), which were considered to produce extensive and intermediate levels of GSH depletion in the skin of the foot during irradiation. Results: Carbogen caused the greatest radiosensitization of skin, with a reproducible enhancement of 2.2 relative to the anoxic response. The OER of 2.2 is lower than other reports for mouse skin. This may indicate that the extremes of oxygenation were not produced, although there was no direct evidence for this. When skin radiosensitivity was plotted against the logarithm of the oxygen tension in the ambient gas, a sigmoid curve with a K value of 17-21% O 2 in the ambient gas was obtained. Depletion of GSH caused minimal radiosensitization when skin was irradiated under anoxic or well-oxygenated conditions. Radiosensitization by GSH depletion was maximal at intermediate oxygen tensions of 10-21% O 2 in the ambient gas. Increasing the extent of GSH depletion led to increasing radiosensitization, with sensitization enhancement ratios of 1.2 and 1.1, respectively, for extensive and intermediate levels of GSH

Oxygen transfer rate during the production of alginate by Azotobacter vinelandii under oxygen-limited and non oxygen-limited conditions

Directory of Open Access Journals (Sweden)

Peña Carlos F

2011-02-01

Full Text Available Abstract Background The oxygen transfer rate (OTR and dissolved oxygen tension (DOT play an important role in determining alginate production and its composition; however, no systematic study has been reported about the independent influence of the OTR and DOT. In this paper, we report a study about alginate production and the evolution of the molecular mass of the polymer produced by a wild-type A. vinelandii strain ATCC 9046, in terms of the maximum oxygen transfer rate (OTRmax in cultures where the dissolved oxygen tension (DOT was kept constant. Results The results revealed that in the two dissolved oxygen conditions evaluated, strictly controlled by gas blending at 0.5 and 5% DOT, an increase in the agitation rate (from 300 to 700 rpm caused a significant increase in the OTRmax (from 17 to 100 mmol L-1 h-1 for DOT of 5% and from 6 to 70 mmol L-1 h-1 for DOT of 0.5%. This increase in the OTRmax improved alginate production, as well as the specific alginate production rate (SAPR, reaching a maximal alginate concentration of 3.1 g L-1 and a SAPR of 0.031 g alg g biom-1 h-1 in the cultures at OTRmax of 100 mmol L-1 h-1. In contrast, the mean molecular mass (MMM of the alginate isolated from cultures developed under non-oxygen limited conditions increased by decreasing the OTRmax, reaching a maximal of 550 kDa at an OTRmax of 17 mmol L-1 h-1 . However, in the cultures developed under oxygen limitation (0.5% DOT, the MMM of the polymer was practically the same (around 200 kDa at 300 and 700 rpm, and this remained constant throughout the cultivation. Conclusions Overall, our results showed that under oxygen-limited and non oxygen-limited conditions, alginate production and its molecular mass are linked to the OTRmax, independently of the DOT of the culture.

Hyperbaric oxygen and radiotherapy

International Nuclear Information System (INIS)

Mayer, R.; Hamilton-Farrell, M.R.; Kleij, A.J. van der

2005-01-01

Background: Hyperbaric oxygen (HBO) therapy is the inhalation of 100% oxygen at a pressure of at least 1.5 atmospheres absolute (150 kPa). It uses oxygen as a drug by dissolving it in the plasma and delivering it to the tissues independent of hemoglobin. For a variety of organ systems, HBO is known to promote new vessel growth into areas with reduced oxygen tension due to poor vascularity, and therewith promotes wound healing and recovery of radiation-injured tissue. Furthermore, tumors may be sensitized to irradiation by raising intratumoral oxygen tensions. Methods: A network of hyperbaric facilities exists in Europe, and a number of clinical studies are ongoing. The intergovernmental framework COST B14 action 'Hyperbaric Oxygen Therapy' started in 1999. The main goal of the Working Group Oncology is preparation and actual implementation of prospective study protocols in the field of HBO and radiation oncology in Europe. Results: In this paper a short overview on HBO is given and the following randomized clinical studies are presented: (a) reirradiation of recurrent squamous cell carcinoma of the head and neck after HBO sensitization; (b) role of HBO in enhancing radiosensitivity on glioblastoma multiforme; (c) osseointegration in irradiated patients; adjunctive HBO to prevent implant failures; (d) the role of HBO in the treatment of late irradiation sequelae in the pelvic region. The two radiosensitization protocols (a, b) allow a time interval between HBO and subsequent irradiation of 10-20 min. Conclusion: Recruitment of centers and patients is being strongly encouraged, detailed information is given on www.oxynet.org. (orig.)

L-lysine escinat, thiotriazolin, gordox and mydocalm influence on oxygen tension in the intestinal wall and acid-base balance and limited proteolysis in intestinal venous blood in terms of intraabdominal hypertension modeling

Directory of Open Access Journals (Sweden)

Sapegin V.I.

2014-11-01

Full Text Available In acute experiments on rabbits there were studied changes in oxygen tension in the intestinal wall tissues, acid-base balance and limited proteolysis and its inhibitors in intestinal venous blood, protective action of L-lysine escinat (0,15 mg/kg / single dose, thiotriazolin (25 mg/kg / single dose, aprotinin (gordox (10,000 units/kg / single dose in sequential modeling of standard levels increasing of intra-abdominal hypertension (IAH — 50, 100, 150, 200, 250, 300, 350 m H2O, and also of tolperison (mydocalm (5 mg/kg / single dose on modeling of stable 3-hour IAH 200 m H2O. The IAH modeling was performed by means of stand of our construction. Under the influence of IAH the compensated metabolic acidosis in intestinal venous blood with a compensative hyperpnoe develops, decline of oxygen tension in tissues and activating of a limited proteolysis as well as decline of its inhibitors activity in intestinal venous blood occur. By the degree of metabolic acidosis prevention investigational preparations were distributed as follows gordox > thiotriazolin = L-lysine escinat = mydocalm, and by prevention of decline of oxygen tension in tissues — thiotriazolin > L-lysine escinat > mydocalm > gordox, it is is connected with different rate of methabolic products excretion into the blood, due to the influence on blood circulation and transcapilary exchange. By the degree of prevention of proteolytic activity and inhibitory potential changes, investigational preparations were distributed as follows: gordox > mydocalm > thiotriazolin > L-lysine escinat, this is connected with inhibition of proteolysis in gordox, and in other ones – with reduction of ischemic damage of tissues. Owing to different mechanism of action thiotriazolin, L-lysine escinat and mydocalm may be simultaneously recommended for a conservative treatment of patients with intraabdominal hypertension syndrome.

Simultaneous Monitoring of Vascular Oxygenation and Tissue Oxygen Tension of Breast Tumors Under Hyperbaric Oxygen Exposure

National Research Council Canada - National Science Library

Xia, Mengna

2005-01-01

The goals of the study in the first stage are 1) to develop a mathematic model by which we can derive tumor blood flow and metabolic rate of oxygen from hemoglobin concentration during interventions, 2...

The tension of framed membranes from computer simulations

DEFF Research Database (Denmark)

Hamkens, Daniel; Jeppesen, Claus; Ipsen, John H.

2018-01-01

the membranes display power-law characteristics for the equation of state, while higher tension levels includes both an extended linear (elastic) as well as a highly non-linear stretching regime. For semi-flexible membranes a transition from extended to buckled conformations takes place at negative frame......Abstract.: We have analyzed the behavior of a randomly triangulated, self-avoiding surface model of a flexible, fluid membrane subject to a circular boundary by Wang-Landau Monte Carlo computer simulation techniques. The dependence of the canonical free energy and frame tension on the frame area...... is obtained for flexible membranes. It is shown that for low bending rigidities the framed membrane is only stable above a threshold tension, suggesting a discontinuous transition from the collapsed (branched polymer) state to a finite tension extended state. In a tension range above this threshold tension...

Transcriptional and metabolic response of recombinant Escherichia coli to spatial dissolved oxygen tension gradients simulated in a scale-down system.

Science.gov (United States)

Lara, Alvaro R; Leal, Lidia; Flores, Noemí; Gosset, Guillermo; Bolívar, Francisco; Ramírez, Octavio T

2006-02-05

Escherichia coli, expressing recombinant green fluorescent protein (GFP), was subjected to dissolved oxygen tension (DOT) oscillations in a two-compartment system for simulating gradients that can occur in large-scale bioreactors. Cells were continuously circulated between the anaerobic (0% DOT) and aerobic (10% DOT) vessels of the scale-down system to mimic an overall circulation time of 50 s, and a mean residence time in the anaerobic and aerobic compartments of 33 and 17 s, respectively. Transcription levels of mixed acid fermentation genes (ldhA, poxB, frdD, ackA, adhE, pflD, and fdhF), measured by quantitative RT-PCR, increased between 1.5- to over 6-fold under oscillatory DOT compared to aerobic cultures (constant 10% DOT). In addition, the transcription level of fumB increased whereas it decreased for sucA and sucB, suggesting that the tricarboxylic acid cycle was functioning as two open branches. Gene transcription levels revealed that cytrochrome bd, which has higher affinity to oxygen but lower energy efficiency, was preferred over cytochrome bO3 in oscillatory DOT cultures. Post-transcriptional processing limited heterologous protein production in the scale-down system, as inferred from similar gfp transcription but 19% lower GFP concentration compared to aerobic cultures. Simulated DOT gradients also affected the transcription of genes of the glyoxylate shunt (aceA), of global regulators of aerobic and anaerobic metabolism (fnr, arcA, and arcB), and other relevant genes (luxS, sodA, fumA, and sdhB). Transcriptional changes explained the observed alterations in overall stoichiometric and kinetic parameters, and production of ethanol and organic acids. Differences in transcription levels between aerobic and anaerobic compartments were also observed, indicating that E. coli can respond very fast to intermittent DOT conditions. The transcriptional responses of E. coli to DOT gradients reported here are useful for establishing rational scale-up criteria and

[Effects of gap junction blocking on the oxygen partial pressure in acupoints of the bladder meridian].

Science.gov (United States)

Wang, Qi; Yu, Wei-Chang; Jiang, Hong-Zhi; Chen, Sheng-Li; Zhang, Ming-Min; Kong, E-Sheng; Huang, Guang-Ying

2010-12-01

To explore the relation between gap junction and meridian phenomenon. The oxygen partial pressure in acupoints [see text for formula] and in their corresponding non-acupoints of the Bladder Meridian was observed with the needle-type tissue oxygen tension sensor in the gap junction blocking goats by 1-Heptanol injection and the Connexin 43 (Cx43) gene knockout mice. (1) The oxygen partial pressure in acupoints of Bladder Meridian on goats was higher than that in non-acupoints after 1-Heptanol injection with significant differences between them (both P oxygen partial pressure in acupoints of Bladder Meridian on goats increased significantly after injecting 1-Heptanol as compare with that either injecting normal saline or injecting nothing with significant differences between them (all P oxygen partial pressure in acupoints of the Bladder Meridian was significantly higher than that in the non-acupoint controls in Cx43 wild type (WT) mice (all P oxygen partial pressure between acupoints and non-acupoint controls showed no significant differences (all P > 0.05). (4) In acupoints, the oxygen partial pressure in Cx43 WT mice was significantly higher than that in Cx43 HT mice (all P 0.05). Gap junction maybe the essential factor in signal transduction of acupuncture.

Prediction of inspired oxygen fraction for targeted arterial oxygen tension following open heart surgery in non-smoking and smoking patients.

Science.gov (United States)

Bou-Khalil, Pierre; Zeineldine, Salah; Chatburn, Robert; Ayyoub, Chakib; Elkhatib, Farouk; Bou-Akl, Imad; El-Khatib, Mohamad

2017-10-01

Simple and accurate expressions describing the P a O 2 -F i O 2 relationship in mechanically ventilated patients are lacking. The current study aims to validate a novel mathematical expression for accurate prediction of the fraction of inspired oxygen that will result in a targeted arterial oxygen tension in non-smoking and smoking patients receiving mechanical ventilation following open heart surgeries. One hundred P a O 2 -F i O 2 data pairs were obtained from 25 non-smoking patients mechanically ventilated following open heart surgeries. One data pair was collected at each of F i O 2 of 40, 60, 80, and 100% while maintaining same mechanical ventilation support settings. Similarly, another 100 hundred P a O 2 -F i O 2 data pairs were obtained from 25 smoking patients mechanically ventilated following open heart surgeries. The utility of the new mathematical expression in accurately describing the P a O 2 -F i O 2 relationship in these patients was assessed by the regression and Bland-Altman analyses. Significant correlations were seen between the true and estimated F i O 2 values in non-smoking (r 2  = 0.9424; p < 0.05) and smoking (r 2  = 0.9466; p < 0.05) patients. Tight biases between the true and estimated F i O 2 values for non-smoking (3.1%) and smoking (4.1%) patients were observed. Also, significant correlations were seen between the true and estimated P a O 2 /F i O 2 ratios in non-smoking (r 2  = 0.9530; p < 0.05) and smoking (r 2  = 0.9675; p < 0.05) patients. Tight biases between the true and estimated P a O 2 /F i O 2 ratios for non-smoking (-18 mmHg) and smoking (-16 mmHg) patients were also observed. The new mathematical expression for the description of the P a O 2 -F i O 2 relationship is valid and accurate in non-smoking and smoking patients who are receiving mechanical ventilation for post cardiac surgery.

Capillary-oxygenation-level-dependent near-infrared spectrometry in frontal lobe of humans

NARCIS (Netherlands)

Rasmussen, Peter; Dawson, Ellen A.; Nybo, Lars; van Lieshout, Johannes J.; Secher, Niels H.; Gjedde, Albert

2007-01-01

Brain function requires oxygen and maintenance of brain capillary oxygenation is important. We evaluated how faithfully frontal lobe near-infrared spectroscopy (NIRS) follows haemoglobin saturation (SCap) and how calculated mitochondrial oxygen tension (PMitoO2) influences motor performance. Twelve

Cerebral oxygenation is reduced during hyperthermic exercise in humans

DEFF Research Database (Denmark)

Rasmussen, Peter; Nybo, Lars; Volianitis, S.

2010-01-01

Abstract Aim: Cerebral mitochondrial oxygen tension (P(mito)O(2)) is elevated during moderate exercise, while it is reduced when exercise becomes strenuous, reflecting an elevated cerebral metabolic rate for oxygen (CMRO(2)) combined with hyperventilation-induced attenuation of cerebral blood flo...

With medium-chain triglycerides, higher and faster oxygen radical production by stimulated polymorphonuclear leukocytes occurs.

Science.gov (United States)

Kruimel, J W; Naber, A H; Curfs, J H; Wenker, M A; Jansen, J B

2000-01-01

Parenteral lipid emulsions are suspected of suppressing the immune function. However, study results are contradictory and mainly concern the conventional long-chain triglyceride emulsions. Polymorphonuclear leukocytes were preincubated with parenteral lipid emulsions. The influence of the lipid emulsions on the production of oxygen radicals by these stimulated leukocytes was studied by measuring chemiluminescence. Three different parenteral lipid emulsions were tested: long-chain triglycerides, a physical mixture of medium- and long-chain triglycerides, and structured triglycerides. Structured triglycerides consist of triglycerides where the medium- and long-chain fatty acids are attached to the same glycerol molecule. Stimulated polymorphonuclear leukocytes preincubated with the physical mixture of medium- and long-chain triglycerides showed higher levels of oxygen radicals (p triglycerides or structured triglycerides. Additional studies indicated that differences in results of various lipid emulsions were not caused by differences in emulsifier. The overall production of oxygen radicals was significantly lower after preincubation with the three lipid emulsions compared with controls without lipid emulsion. A physical mixture of medium- and long-chain triglycerides induced faster production of oxygen radicals, resulting in higher levels of oxygen radicals, compared with long-chain triglycerides or structured triglycerides. This can be detrimental in cases where oxygen radicals play either a pathogenic role or a beneficial one, such as when rapid phagocytosis and killing of bacteria is needed. The observed lower production of oxygen radicals by polymorphonuclear leukocytes in the presence of parenteral lipid emulsions may result in immunosuppression by these lipids.

Oxygen status during haemodialysis. The Cord-Group

DEFF Research Database (Denmark)

Nielsen, A L; Jensen, H Æ; Hegbrant, J

1995-01-01

Hypoxia during haemodialysis, mainly acetate, has been reported several times. In our study we have monitored oxygen status during 258 bicarbonate haemodialyses. A significant drop below 80 mmHg in mean oxygen tension occurred. Mean oxygen saturation reflected this drop but did not reach levels...... below 90%. The mean oxygen concentration was on the whole critical low, though slightly increasing during each haemodialysis session due to ultrafiltration. It is concluded that both hypoxia and hypoxaemia do occur during bicarbonate haemodialysis. To a group of patients generally having limited cardiac...... reserves, a poor oxygen status is a potentially serious complication to haemodialysis. Monitoring oxygen status is thus advisable....

Effect of epidural blockade and oxygen therapy on changes in subcutaneous oxygen tension after abdominal surgery

DEFF Research Database (Denmark)

Rosenberg, J; Pedersen, U; Erichsen, C J

1994-01-01

The effect of oxygen therapy (37% by face mask) and epidural local anesthetic blockade (9 ml 0.5% bupivacaine at Th9-11 level) on wound oxygenation was evaluated in eight otherwise healthy patients undergoing elective colorectal resection. The patients were monitored continuously for subcutaneous...... without epidural blockade and 15 (10-20) min with blockade (P surgery....

Modifiers of hemoglobin/oxygen affinity as sensitizers of tumors to radiation

International Nuclear Information System (INIS)

Hirst, D.G.; Wood, P.J.

1987-01-01

A powerful mechanism in the control of oxygen delivery to tissues is the allosteric modification of hemoglobin. Increased or decreased release of oxygen can be achieved by altering the affinity of hemoglobin for oxygen. Several studies have shown that tumor radiosensitivity is dependent on this relationship. The authors studied affinity changes produced in two distinctly different ways. Tumor bearing mice were given isovolemic exchange blood transfusions with the blood from donor mice which had been exposed to abnormal oxygen tensions, leading to increased or slightly decreased levels of 2,3-diphosphoglycerate (2,3 DPG) in their blood. When the recipient mice were irradiated, those receiving the blood with higher 2,3 DPG levels showed greater tumor sensitivity to radiation. An alternative strategy is the use of drugs which directly alter hemoglobin/oxygen affinity. The authors studied three antihyperlipoproteinemia drugs, all of which have produced markedly reduced affinities in vivo. Preliminary data indicate that the radiosensitization produced by at least one of these compounds is less than would have been expected from the 2,3 DPG experiments

Tension Headache

Science.gov (United States)

... tight band around your head. A tension headache (tension-type headache) is the most common type of headache, and ... Headache after a head injury, especially if the headache gets worse ... tension or stress. But research suggests muscle contraction isn't the ...

Membrane tension regulates clathrin-coated pit dynamics

Science.gov (United States)

Liu, Allen

2014-03-01

Intracellular organization depends on close communication between the extracellular environment and a network of cytoskeleton filaments. The interactions between cytoskeletal filaments and the plasma membrane lead to changes in membrane tension that in turns help regulate biological processes. Endocytosis is thought to be stimulated by low membrane tension and the removal of membrane increases membrane tension. While it is appreciated that the opposing effects of exocytosis and endocytosis have on keeping plasma membrane tension to a set point, it is not clear how membrane tension affects the dynamics of clathrin-coated pits (CCPs), the individual functional units of clathrin-mediated endocytosis. Furthermore, although it was recently shown that actin dynamics counteracts membrane tension during CCP formation, it is not clear what roles plasma membrane tension plays during CCP initiation. Based on the notion that plasma membrane tension is increased when the membrane area increases during cell spreading, we designed micro-patterned surfaces of different sizes to control the cell spreading sizes. Total internal reflection fluorescence microscopy of living cells and high content image analysis were used to quantify the dynamics of CCPs. We found that there is an increased proportion of CCPs with short (<20s) lifetime for cells on larger patterns. Interestingly, cells on larger patterns have higher CCP initiation density, an effect unexpected based on the conventional view of decreasing endocytosis with increasing membrane tension. Furthermore, by analyzing the intensity profiles of CCPs that were longer-lived, we found CCP intensity decreases with increasing cell size, indicating that the CCPs are smaller with increasing membrane tension. Finally, disruption of actin dynamics significantly increased the number of short-lived CCPs, but also decreased CCP initiation rate. Together, our study reveals new mechanistic insights into how plasma membrane tension regulates

Deep breathing exercises with positive expiratory pressure at a higher rate improve oxygenation in the early period after cardiac surgery--a randomised controlled trial.

Science.gov (United States)

Urell, Charlotte; Emtner, Margareta; Hedenström, Hans; Tenling, Arne; Breidenskog, Marie; Westerdahl, Elisabeth

2011-07-01

In addition to early mobilisation, a variety of breathing exercises are used to prevent postoperative pulmonary complications after cardiac surgery. The optimal duration of the treatment is not well evaluated. The aim of this study was to determine the effect of 30 versus 10 deep breaths hourly, while awake, with positive expiratory pressure on oxygenation and pulmonary function the first days after cardiac surgery. A total of 181 patients, undergoing cardiac surgery, were randomised into a treatment group, performing 30 deep breaths hourly the first postoperative days, or into a control group performing 10 deep breaths hourly. The main outcome measurement arterial blood gases and the secondary outcome pulmonary function, evaluated with spirometry, were determined on the second postoperative day. Preoperatively, both study groups were similar in terms of age, SpO(2), forced expiratory volume in 1s and New York Heart Association classification. On the second postoperative day, arterial oxygen tension (PaO(2)) was 8.9 ± 1.7 kPa in the treatment group and 8.1 ± 1.4 kPa in the control group (p = 0.004). Arterial oxygen saturation (SaO(2)) was 92.7 ± 3.7% in the treatment group and 91.1 ± 3.8% in the control group (p = 0.016). There were no differences in measured lung function between the groups or in compliance to the breathing exercises. Compliance was 65% of possible breathing sessions. A significantly increased oxygenation was found in patients performing 30 deep breaths the first two postoperative days compared with control patients performing 10 deep breaths hourly. These results support the implementation of a higher rate of deep breathing exercises in the initial phase after cardiac surgery. Copyright © 2010 European Association for Cardio-Thoracic Surgery. Published by Elsevier B.V. All rights reserved.

Spontaneous calcium waves in Bergman glia increase with age and hypoxia and may reduce tissue oxygen.

Science.gov (United States)

Mathiesen, Claus; Brazhe, Alexey; Thomsen, Kirsten; Lauritzen, Martin

2013-02-01

Glial calcium (Ca(2+)) waves constitute a means to spread signals between glial cells and to neighboring neurons and blood vessels. These waves occur spontaneously in Bergmann glia (BG) of the mouse cerebellar cortex in vivo. Here, we tested three hypotheses: (1) aging and reduced blood oxygen saturation alters wave activity; (2) glial Ca(2+) waves change cerebral oxygen metabolism; and (3) neuronal and glial wave activity is correlated. We used two-photon microscopy in the cerebellar cortexes of adult (8- to 15-week-old) and aging (48- to 80-week-old) ketamine-anesthetized mice after bolus loading with OGB-1/AM and SR101. We report that the occurrence of spontaneous waves is 20 times more frequent in the cerebellar cortex of aging as compared with adult mice, which correlated with a reduction in resting brain oxygen tension. In adult mice, spontaneous glial wave activity increased on reducing resting brain oxygen tension, and ATP-evoked glial waves reduced the tissue O(2) tension. Finally, although spontaneous Purkinje cell (PC) activity was not associated with increased glia wave activity, spontaneous glial waves did affect intracellular Ca(2+) activity in PCs. The increased wave activity during aging, as well as low resting brain oxygen tension, suggests a relationship between glial waves, brain energy homeostasis, and pathology.

Cerebral oxygenation and metabolism during exercise following three months of endurance training in healthy overweight males

DEFF Research Database (Denmark)

Seifert, T; Rasmussen, P; Brassard, P

2009-01-01

/(glucose + (1/2) lactate); OCI], changes in mitochondrial oxygen tension (DeltaP(Mito)O(2)) and the cerebral metabolic rate of oxygen (CMRO(2)) were calculated. For all subjects, resting OCI was higher at the 3-mo follow-up (6.3 +/- 1.3 compared with 4.7 +/- 0.9 at baseline, mean +/- SD; P ... with a lower plasma epinephrine concentration (P Mito)O(2) (-22 mmHg) decreased (P ... +/- 53 micromol x 100 x g(-1) min(-1) (P Mito)O(2) (-7 +/- 13 mmHg) did not decrease significantly from rest and when compared with values before training (P

Changes in the metabolic footprint of placental explant-conditioned medium cultured in different oxygen tensions from placentas of small for gestational age and normal pregnancies.

LENUS (Irish Health Repository)

Horgan, R P

2012-01-31

Being born small for gestational age (SGA) confers significantly increased risks of perinatal morbidity and mortality. Accumulating evidence suggests that an SGA fetus results from a poorly perfused and abnormally developed placenta. Some of the placental features seen in SGA, such as abnormal cell turnover and impaired nutrient transport, can be reproduced by culture of placental explants in hypoxic conditions. Metabolic footprinting offers a hypothesis-generating strategy to investigate factors absorbed by and released from this tissue in vitro. Previously, metabolic footprinting of the conditioned culture media has identified differences in placental explants cultured under normoxic and hypoxic conditions and between normal pregnancies and those complicated by pre-eclampsia. In this study we aimed to examine the differences in the metabolic footprint of placental villous explants cultured at different oxygen (O(2)) tensions between women who deliver an SGA baby (n = 9) and those from normal controls (n = 8). Placental villous explants from cases and controls were cultured for 96 h in 1% (hypoxic), 6% (normoxic) and 20% (hyperoxic) O(2). Metabolic footprints were analysed by Ultra Performance Liquid Chromatography coupled to an electrospray hybrid LTQ-Orbitrap Mass Spectrometry (UPLC-MS). 574 metabolite features showed significant difference between SGA and normal at one or more of the oxygen tensions. SGA explant media cultured under hypoxic conditions was observed, on a univariate level, to exhibit the same metabolic signature as controls cultured under normoxic conditions in 49% of the metabolites of interest, suggesting that SGA tissue is acclimatised to hypoxic conditions in vivo. No such behaviour was observed under hyperoxic culture conditions. Glycerophospholipid and tryptophan metabolism were highlighted as areas of particular interest.

The Integrity of ACSR Full Tension Single-Stage Splice Connector at Higher Operation Temperature

Energy Technology Data Exchange (ETDEWEB)

Wang, Jy-An John [ORNL; Lara-Curzio, Edgar [ORNL; King Jr, Thomas J [ORNL

2008-10-01

Due to increases in power demand and limited investment in new infrastructure, existing overhead power transmission lines often need to operate at temperatures higher than those used for the original design criteria. This has led to the accelerated aging and degradation of splice connectors. It is manifested by the formation of hot-spots that have been revealed by infrared imaging during inspection. The implications of connector aging is two-fold: (1) significant increases in resistivity of the splice connector (i.e., less efficient transmission of electricity) and (2) significant reductions in the connector clamping strength, which could ultimately result in separation of the power transmission line at the joint. Therefore, the splice connector appears to be the weakest link in electric power transmission lines. This report presents a protocol for integrating analytical and experimental approaches to evaluate the integrity of full tension single-stage splice connector assemblies and the associated effective lifetime at high operating temperature.

Speaker and Observer Perceptions of Physical Tension during Stuttering.

Science.gov (United States)

Tichenor, Seth; Leslie, Paula; Shaiman, Susan; Yaruss, J Scott

2017-01-01

Speech-language pathologists routinely assess physical tension during evaluation of those who stutter. If speakers experience tension that is not visible to clinicians, then judgments of severity may be inaccurate. This study addressed this potential discrepancy by comparing judgments of tension by people who stutter and expert clinicians to determine if clinicians could accurately identify the speakers' experience of physical tension. Ten adults who stutter were audio-video recorded in two speaking samples. Two board-certified specialists in fluency evaluated the samples using the Stuttering Severity Instrument-4 and a checklist adapted for this study. Speakers rated their tension using the same forms, and then discussed their experiences in a qualitative interview so that themes related to physical tension could be identified. The degree of tension reported by speakers was higher than that observed by specialists. Tension in parts of the body that were less visible to the observer (chest, abdomen, throat) was reported more by speakers than by specialists. The thematic analysis revealed that speakers' experience of tension changes over time and that these changes may be related to speakers' acceptance of stuttering. The lack of agreement between speaker and specialist perceptions of tension suggests that using self-reports is a necessary component for supporting the accurate diagnosis of tension in stuttering. © 2018 S. Karger AG, Basel.

The effect of oxygen tension on porcine embryonic development is dependent on embryo type

DEFF Research Database (Denmark)

Booth, Paul; Holm, Peter; Callesen, Henrik

2005-01-01

of the embryos prior to culture--a study was performed to examine the effect of O2 tension during culture on three different types of porcine embryos, namely: in vivo flushed embryos, and in vitro matured oocytes either fertilized in vitro or parthenogenetically activated. In vivo embryos (n=208) were flushed...... supplemented with 10% calf serum until day 7. The gas environment for IVM/IVF was 5% CO2 in air, while that for IVC was either 5% CO2 in air or 5% O2, 5% CO2 and 90% N2. Low O2 tension increased both day 7 blastocyst rates (high versus low O2, respectively; 9.3+/-2.9%: 26/280; 23.9+/-4.2%: 71/293; P...

Muscle trigger point therapy in tension-type headache.

Science.gov (United States)

Alonso-Blanco, Cristina; de-la-Llave-Rincón, Ana Isabel; Fernández-de-las-Peñas, César

2012-03-01

Recent evidence suggests that active trigger points (TrPs) in neck and shoulder muscles contribute to tension-type headache. Active TrPs within the suboccipital, upper trapezius, sternocleidomastoid, temporalis, superior oblique and lateral rectus muscles have been associated with chronic and episodic tension-type headache forms. It seems that the pain profile of this headache may be provoked by referred pain from active TrPs in the posterior cervical, head and shoulder muscles. In fact, the presence of active TrPs has been related to a higher degree of sensitization in tension-type headache. Different therapeutic approaches are proposed for proper TrP management. Preliminary evidence indicates that inactivation of TrPs may be effective for the management of tension-type headache, particularly in a subgroup of patients who may respond positively to this approach. Different treatment approaches targeted to TrP inactivation are discussed in the current paper, focusing on tension-type headache. New studies are needed to further delineate the relationship between muscle TrP inactivation and tension-type headache.

Radiosensitizers and the oxygen effects in mammalian cells

International Nuclear Information System (INIS)

Millar, B.C.; Fielden, E.M.; Steele, J.J.

1979-01-01

The survival curves for Chinese Hamster cells irradiated under various oxygen tensions have been determined. The variation in OER with oxygen concentration shows two distinct components. Between 1.4 and 7.0 μM the OER is constant with a value of 1.9. Experiments with nitroaromatic radiosensitizers in combination with low concentrations of oxygen show that they can all mimic the 'low concentration' oxygen effect. Of the compounds tested only misonidazole can apparently mimic the 'high concentration' oxygen effect although the full OER cannot be obtained with the authors cell line because of toxicity by the sensitizer. (Auth.)

Radiosensitivity of Hela cells in various O2 concentrations and consideration of oxygen effect in radiotherapy

International Nuclear Information System (INIS)

Kuroda, Yoshikazu; Nyunoya, Koichiro

1979-01-01

The aim of this paper is the study of the radiosensitivity of HeLa cells in vitro in various oxygen concentrations and the consideration of the utilization of oxygen effect in radiation therapy, based on the data of HeLa cells and tumor oxygen tension. Survival curves of HeLa cells are found to be exponential as a function of radiation dose and the radiosensitivity is dependent on oxygen tension of culture medium. Relative radiosensitivity decreases remarkably at low level of oxygen, especially under 9 mmHg pO 2 . The utilization of oxygen effect in radiation may be useful in hyperbaric oxygen inhalation and not useful under local tissue hypoxia induced by tourniquet application. Reoxygenation occurs with shrinkage of tumor after irradiation and this phenomenon will diminish the value of hyperbaric oxygen in radiation therapy. (author)

The concentration of oxygen dissolved in tissues at the time of irradiation as a factor in radiotherapy

International Nuclear Information System (INIS)

Gray, L.H.; Conger, A.D.; Ebert, M.; Hornsey, S.; Scott, O.C.A.

1984-01-01

The sensitivity of tumour cells to X rays has been shown to be about three times as great when irradiated in a well-oxygenated medium as under anoxic conditions. The manner in which sensitivity depends on oxygen tension closely resembles that found by other workers for plant and insect tissues. The sensitivity of the tumour cells to fast neutron radiation is only slightly affected by oxygen tension. Consideration is given to the supply of oxygen to tissues as a factor in radiotherapy, and it is concluded on the basis of existing knowledge that in certain circumstances the effectiveness of X-ray treatment might be increased if the patient were breathing oxygen at the time of irradiation

Internationalization and Global Tension: Lessons From History

Science.gov (United States)

Altbach, Philip G.; de Wit, Hans

2015-01-01

Increasing political and military tension in several parts of the world will inevitably affect international higher education. Nationalist, religious, and ideological conflicts challenge the original ideas of international cooperation and exchange in higher education as promoters of peace and mutual understanding and of global engagement. Since…

Increase of tumor oxygen tension and potentiation of radiation effects using pentoxifylline, vinpocetine and ticlopidine hydrochloride

International Nuclear Information System (INIS)

Amano, Morikazu; Monzen, Hajime; Suzuki, Takatoshi; Hasegawa, Takeo

2004-01-01

The effects of pentoxifylline (PTX), vinpocetine (VPT) and ticlopidine hydrochloride (TCD), each drug commonly used for vascular disorders in humans, on the pO 2 in SCC-7 (squamous cell carcinoma) tumors of C3H/HeJ mice on the radioresponse of SCC-7 tumors were investigated. When the SCC-7 implanted in the leg of C3H/HeJ mice grew about 100 mm 3 , the effects of PTX, VPT and TCD on the increase oxygen tension in the tumor was determined with polarography. The mice were injected intraperitoneally (ip) with 5 ml/kg PTX, 5 ml/kg VPT, or 10 ml/kg TCD, the tumor pO 2 increased slowly, peaked about 20-50 min postinjection, and returned to its original level in 60-80 min. When the C3H/HeJ mice bearing SCC-7 tumors in the legs were injected ip with 5 ml/kg PTX, 5 ml/kg VPT or 10 ml/kg TCD and tumors were X-irradiated 30 min later, the radiation induced growth delay of the tumor was greater than that caused by X-irradiation alone. The results in the present study, PTX, VPT and TCD increase the tumor pO 2 in rodent tumors strongly suggest that each drug may be useful for increasing the radiosensitivity of human tumor. (author)

Coulomb string tension, asymptotic string tension, and the gluon chain

OpenAIRE

Greensite, Jeff; Szczepaniak, Adam P.

2014-01-01

We compute, via numerical simulations, the non-perturbative Coulomb potential of pure SU(3) gauge theory in Coulomb gauge. We find that that the Coulomb potential scales nicely in accordance with asymptotic freedom, that the Coulomb potential is linear in the infrared, and that the Coulomb string tension is about four times larger than the asymptotic string tension. We explain how it is possible that the asymptotic string tension can be lower than the Coulomb string tension by a factor of four.

Identification of subgroups of patients with tension type headache with higher widespread pressure pain hyperalgesia.

Science.gov (United States)

Fernández-de-Las-Peñas, César; Benito-González, Elena; Palacios-Ceña, María; Wang, Kelun; Castaldo, Matteo; Arendt-Nielsen, Lars

2017-12-01

Identification of subgroups of patients with different levels of sensitization and clinical features can help to identify groups at risk and the development of better therapeutic strategies. The aim of this study was to identify subgroups of patients with tension type headache (TTH) with different levels of sensitization, clinical pain features, and psychological outcomes. A total of 197 individuals with TTH participated. Headache intensity, frequency, and duration and medication intake were collected with a 4-weeks diary. Pressure pain thresholds were assessed bilaterally over the temporalis muscle, C5-C6 joint, second metacarpal and tibialis anterior muscle to determine widespread pressure pain hyperalgesia. The Hospital Anxiety and Depression Scale assessed anxiety and depression. The State-Trait Anxiety Inventory evaluated the state and trait levels of anxiety. The Headache Disability Inventory evaluated the burden of headache. Health-related quality of life was determined with the SF-36 questionnaire. Groups were considered as positive (three or more criteria) or negative (less than three criteria) on a clinical prediction rule: headache duration patients with TTH with higher sensitization, higher chronicity of headaches and worse quality of life but lower frequency and duration of headache episodes. This subgroup of individuals with TTH may need particular attention and specific therapeutic programs for avoiding potential chronification.

Oxygen dynamics around buried lesser sandeels Ammodytes tobianus (Linnaeus 1785): mode of ventilation and oxygen requirements

DEFF Research Database (Denmark)

Behrens, Jane W; Stahl, Henrik J; Steffensen, John F

2007-01-01

The oxygen environment around buried sandeels (Ammodytes tobianus) was monitored by planar optodes. The oxygen penetration depth at the sediment interface was only a few mm. Thus fish, typically buried at 1-4 cm depth, were generally in anoxic sediment. However, they induced an advective transport...... down along the body, referred to as ;plume ventilation'. Yet, within approximately 30 min the oxic plume was replenished by oxygen-depleted water from the gills. The potential for cutaneous respiration by the buried fish was thus of no quantitative importance. Calculations derived by three independent...... methods (each with N=3) revealed that the oxygen uptake of sandeel buried for 6-7 h was 40-50% of previous estimates on resting respirometry of non-buried fish, indicating lower O(2) requirements during burial on a diurnal timescale. Buried fish exposed to decreasing oxygen tensions gradually approached...

Ion release from magnesium materials in physiological solutions under different oxygen tensions.

Science.gov (United States)

Feyerabend, Frank; Drücker, Heiko; Laipple, Daniel; Vogt, Carla; Stekker, Michael; Hort, Norbert; Willumeit, Regine

2012-01-01

Although magnesium as degradable biomaterial already showed clinical proof of concepts, the design of new alloys requires predictive in vitro methods, which are still lacking. Incubation under cell culture conditions to obtain "physiological" corrosion may be a solution. The aim of this study was to analyse the influence of different solutions, addition of proteins and of oxygen availability on the corrosion of different magnesium materials (pure Mg, WE43, and E11) with different surface finishing. Oxygen content in solution, pH, osmolality and ion release were determined. Corrosion led to a reduction of oxygen in solution. The influence of oxygen on pH was enhanced by proteins, while osmolality was not influenced. Magnesium ion release was solution-dependent and enhanced in the initial phase by proteins with delayed release of alloying elements. The main corrosion product formed was magnesium carbonate. Therefore, cell culture conditions are proposed as first step toward physiological corrosion.

Reduced muscle activation during exercise related to brain oxygenation and metabolism in humans

DEFF Research Database (Denmark)

Rasmussen, Peter; Nielsen, Jannie; Overgaard, M

2010-01-01

Maximal exercise may be limited by central fatigue defined as an inability of the central nervous system to fully recruit the involved muscles. This study evaluated whether a reduction in the cerebral oxygen-to-carbohydrate index (OCI) and in the cerebral mitochondrial oxygen tension relate to th...... indicating that reduced cerebral oxygenation may play a role in the development of central fatigue and may be an exercise capacity limiting factor.......Maximal exercise may be limited by central fatigue defined as an inability of the central nervous system to fully recruit the involved muscles. This study evaluated whether a reduction in the cerebral oxygen-to-carbohydrate index (OCI) and in the cerebral mitochondrial oxygen tension relate...... of perceived exertion (RPE), arm maximal voluntary force (MVC), and voluntary activation of elbow flexor muscles assessed with transcranial magnetic stimulation. Low intensity exercise did not produce any indication of central fatigue or marked cerebral metabolic deviations. Exercise in hypoxia (0.10) reduced...

Macrophages Under Low Oxygen Culture Conditions Respond to Ion Parametric Resonance Magnetic Fields

Science.gov (United States)

Macrophages, when entering inflamed tissue, encounter low oxygen tension due to the impairment of blood supply and/or the massive infiltration of cells that consume oxygen. Previously, we showed that such macrophages release more bacteriotoxic hydrogen peroxide (H202) when expose...

Effects of Changes in Arterial Carbon Dioxide and Oxygen Partial Pressures on Cerebral Oximeter Performance.

Science.gov (United States)

Schober, Andrew; Feiner, John R; Bickler, Philip E; Rollins, Mark D

2018-01-01

Cerebral oximetry (cerebral oxygen saturation; ScO2) is used to noninvasively monitor cerebral oxygenation. ScO2 readings are based on the fraction of reduced and oxidized hemoglobin as an indirect estimate of brain tissue oxygenation and assume a static ratio of arterial to venous intracranial blood. Conditions that alter cerebral blood flow, such as acute changes in PaCO2, may decrease accuracy. We assessed the performance of two commercial cerebral oximeters across a range of oxygen concentrations during normocapnia and hypocapnia. Casmed FORE-SIGHT Elite (CAS Medical Systems, Inc., USA) and Covidien INVOS 5100C (Covidien, USA) oximeter sensors were placed on 12 healthy volunteers. The fractional inspired oxygen tension was varied to achieve seven steady-state levels including hypoxic and hyperoxic PaO2 values. ScO2 and simultaneous arterial and jugular venous blood gas measurements were obtained with both normocapnia and hypocapnia. Oximeter bias was calculated as the difference between the ScO2 and reference saturation using manufacturer-specified weighting ratios from the arterial and venous samples. FORE-SIGHT Elite bias was greater during hypocapnia as compared with normocapnia (4 ± 9% vs. 0 ± 6%; P oxygen saturation and mixed venous oxygen tension, as well as increased oxygen extraction across fractional inspired oxygen tension levels (P oxygen extraction (P < 0.0001). Changes in PaCO2 affect cerebral oximeter accuracy, and increased bias occurs with hypocapnia. Decreased accuracy may represent an incorrect assumption of a static arterial-venous blood fraction. Understanding cerebral oximetry limitations is especially important in patients at risk for hypoxia-induced brain injury, where PaCO2 may be purposefully altered.

Necessary Tension in Marine Risers Tension des colonnes montantes en mer

Directory of Open Access Journals (Sweden)

Lubinski A.

2006-11-01

Full Text Available The tension governing transverse static and dynamic deflections in a riser is not the actual tension but the so-called « effective tension » The concept of effective tension and effective compression is thoroughly explained, and means for calculating effective forces are given. Numerical examples are worked out for risers whose length is between 152 m (520 ft and 920 m (3020 ft. The reciprocal of maximum bending moment of the vicinity of the hall joint is plotted versus the effective tension of the ball joint. Bending moments used were obtained through use of static and dynamic computer programs applied ta a variety of conditions of wave loading, use or non-use of buoyant moterial sleeves, etc. The most important parameters affecting riser performance are the effective La tension régissant les déflections transversales statiques et dynamiques d'une colonne montante n'est pas la tension réelle mais ce qu'on appelle « la tension effective ». Le concept de tension ou de compression effective est expliqué en détail et la façon de calculer les forces effectives est indiquée dans cet article. Des exemples numériques sont développés pour des colonnes montantes de longueur comprise entre 152 m (520 ft et 920 m (3 020 ft. On a tracé la courbe de l'inverse du moment fléchissant en fonction de la tension effective à l'articulation. Les moments fléchissants utilisés ont été calculés par ordinateur en utilisant des programmes dynamiques et statiques pour des conditions variées d'action des vagues, la colonne montante étant ou non munie de manchettes de flottabilité, etc. Les deux paramètres les plus importants qui affectent le bon comportement d'une colonne montante sont la tension effective et la charge latérale.

Length and elasticity of side reins affect rein tension at trot.

Science.gov (United States)

Clayton, Hilary M; Larson, Britt; Kaiser, LeeAnn J; Lavagnino, Michael

2011-06-01

This study investigated the horse's contribution to tension in the reins. The experimental hypotheses were that tension in side reins (1) increases biphasically in each trot stride, (2) changes inversely with rein length, and (3) changes with elasticity of the reins. Eight riding horses trotted in hand at consistent speed in a straight line wearing a bit and bridle and three types of side reins (inelastic, stiff elastic, compliant elastic) were evaluated in random order at long, neutral, and short lengths. Strain gauge transducers (240 Hz) measured minimal, maximal and mean rein tension, rate of loading and impulse. The effects of rein type and length were evaluated using ANOVA with Bonferroni post hoc tests. Rein tension oscillated in a regular pattern with a peak during each diagonal stance phase. Within each rein type, minimal, maximal and mean tensions were higher with shorter reins. At neutral or short lengths, minimal tension increased and maximal tension decreased with elasticity of the reins. Short, inelastic reins had the highest maximal tension and rate of loading. Since the tension variables respond differently to rein elasticity at different lengths, it is recommended that a set of variables representing different aspects of rein tension should be reported. Copyright © 2010 Elsevier Ltd. All rights reserved.

Depression, automatic thoughts, alexithymia, and assertiveness in patients with tension-type headache.

Science.gov (United States)

Yücel, Basak; Kora, Kaan; Ozyalçín, Süleyman; Alçalar, Nilüfer; Ozdemir, Ozay; Yücel, Aysen

2002-03-01

The role of psychological factors related to headache has long been a focus of investigation. The aim of this study was to evaluate depression, automatic thoughts, alexithymia, and assertiveness in persons with tension-type headache and to compare the results with those from healthy controls. One hundred five subjects with tension-type headache (according to the criteria of the International Headache Society classification) and 70 controls were studied. The Beck Depression Inventory, Automatic Thoughts Scale, Toronto Alexithymia Scale, and Rathus Assertiveness Schedule were administered to both groups. Sociodemographic variables and headache features were evaluated via a semistructured scale. Compared with healthy controls, the subjects with headache had significantly higher scores on measures of depression, automatic thoughts, and alexithymia and lower scores on assertiveness. Subjects with chronic tension-type headache had higher depression and automatic thoughts scores than those with episodic tension-type headache. These findings suggested that persons with tension-type headache have high depression scores and also may have difficulty with expression of their emotions. Headache frequency appears to influence the likelihood of coexisting depression.

Stimulation of growth of the human gastric pathogen Helicobacter pylori by atmospheric level of oxygen under high carbon dioxide tension

Directory of Open Access Journals (Sweden)

Lee Na

2011-05-01

Full Text Available Abstract Background Helicobacter pylori (Hp, a human pathogen that is associated with gastritis, peptic ulcer, and gastric cancer, has been considered a microaerophile, but there is no general consensus about its specific O2 requirements. A clear understanding of Hp physiology is needed to elucidate the pathogenic mechanism(s of Hp infection. Results We cultured Hp under a range of O2 levels with or without 10% CO2 and evaluated growth profiles, morphology, intracellular pH, and energy metabolism. We found that, in the presence of 10% CO2, the normal atmospheric level of O2 inhibited Hp growth at low density but stimulated growth at a higher density. Field emission scanning electron microscopy and fluorescence microscopy of Hp cells cultured under 20% O2 tension revealed live spiral-shaped bacteria with outer membrane vesicles on a rugged cell surface, which became smooth during the stationary phase. Fermentation products including acetate, lactate, and succinate were detected in cell culture media grown under microaerobic conditions, but not under the aerobic condition. CO2 deprivation for less than 24 h did not markedly change cytoplasmic or periplasmic pH, suggesting that cellular pH homeostasis alone cannot account for the capnophilic nature of Hp. Further, CO2 deprivation significantly increased intracellular levels of ppGpp and ATP but significantly decreased cellular mRNA levels, suggesting induction of the stringent response. Conclusions We conclude, unlike previous reports, that H. pylori may be a capnophilic aerobe whose growth is promoted by atmospheric oxygen levels in the presence of 10% CO2. Our data also suggest that buffering of intracellular pH alone cannot account for the CO2 requirement of H. pylori and that CO2 deprivation initiates the stringent response in H. pylori. Our findings may provide new insight into the physiology of this fastidious human pathogen.

Effects of Cyanate and 2,3-Diphosphoglycerate on Sickling RELATIONSHIP TO OXYGENATION

Science.gov (United States)

Jensen, Michael; Bunn, H. Franklin; Halikas, George; Kan, Yuet Wai; Nathan, David G.

1973-01-01

Cyanate and 2,3-diphosphoglycerate (2,3-DPG) both influence the oxygen affinity of hemoglobin. The studies presented here concern the effects of these compounds on the sickling phenomenon. The inhibitory effect of cyanate on sickling is largely due to the fact that it increases the percentage of oxyhemoglobin S at a given oxygen tension. In addition, cyanate inhibits sickling by a mechanism that is independent of oxygenation. In this paper, we have demonstrated that the viscosity of carbamylated sickle blood was lower than that of non-carbamylated controls at the same oxygen saturation. Furthermore, carbamylation resulted in an increase in the minimum concentration of deoxy-sickle hemoglobin required for gelation. Like cyanate, 2,3-DPG affected sickling of intact erythrocytes by two mechanisms. Since 2,3-DPG decreases the percentage of oxyhemoglobin S at a given oxygen tension, sickling is enhanced. In addition, 2,3-DPG had a direct effect. When the intracellular 2,3-DPG concentration was increased in vitro, a greater percentage of cells were sickled at a given oxygen saturation. Conversely, sickling was inhibited in cells in which 2,3-DPG was artificially lowered. These data indicate that the enhancement of sickling by 2,3-DPG is in part independent of its influence on oxygen affinity. PMID:4729047

Optimal oxygen saturation in premature infants

Directory of Open Access Journals (Sweden)

Meayoung Chang

2011-09-01

Full Text Available There is a delicate balance between too little and too much supplemental oxygen exposure in premature infants. Since underuse and overuse of supplemental oxygen can harm premature infants, oxygen saturation levels must be monitored and kept at less than 95% to prevent reactive oxygen species-related diseases, such as retinopathy of prematurity and bronchopulmonary dysplasia. At the same time, desaturation below 80 to 85% must be avoided to prevent adverse consequences, such as cerebral palsy. It is still unclear what range of oxygen saturation is appropriate for premature infants; however, until the results of further studies are available, a reasonable target for pulse oxygen saturation (SpO2 is 90 to 93% with an intermittent review of the correlation between SpO2 and the partial pressure of arterial oxygen tension (PaO2. Because optimal oxygenation depends on individuals at the bedside making ongoing adjustments, each unit must define an optimal target range and set alarm limits according to their own equipment or conditions. All staff must be aware of these values and adjust the concentration of supplemental oxygen frequently.

Myosin II dynamics are regulated by tension in intercalating cells.

Science.gov (United States)

Fernandez-Gonzalez, Rodrigo; Simoes, Sérgio de Matos; Röper, Jens-Christian; Eaton, Suzanne; Zallen, Jennifer A

2009-11-01

Axis elongation in Drosophila occurs through polarized cell rearrangements driven by actomyosin contractility. Myosin II promotes neighbor exchange through the contraction of single cell boundaries, while the contraction of myosin II structures spanning multiple pairs of cells leads to rosette formation. Here we show that multicellular actomyosin cables form at a higher frequency than expected by chance, indicating that cable assembly is an active process. Multicellular cables are sites of increased mechanical tension as measured by laser ablation. Fluorescence recovery after photobleaching experiments show that myosin II is stabilized at the cortex in regions of increased tension. Myosin II is recruited in response to an ectopic force and relieving tension leads to a rapid loss of myosin, indicating that tension is necessary and sufficient for cortical myosin localization. These results demonstrate that myosin II dynamics are regulated by tension in a positive feedback loop that leads to multicellular actomyosin cable formation and efficient tissue elongation.

Tension pneumothorax accompanied by type A aortic dissection.

Science.gov (United States)

Hifumi, Toru; Kiriu, Nobuaki; Inoue, Junichi; Koido, Yuichi

2012-11-09

A 51-year-old man was brought to the emergency room because of a sudden onset of severe dysponea. On presentation, his blood pressure was 94/55 mm Hg. Oxygen saturation was 86% while he was receiving 10 l/min oxygen through a non-rebreather mask. On physical examination, no jugular venous distention was noted, but breath sounds over the left lung were diminished. A bedside chest radiograph showed left tension pneumothorax, for which urgent needle decompression followed by chest thoracostomy was performed. Ventricular tachycardia developed, but a biphasic shock at 120 J immediately restored normal sinus rhythm. His vital signs, however, did not improve. A CT scan of the chest showed type A aortic dissection with bullae in the upper lobe of the left lung. He had an emergency operation for distal aortic arch displacement and was discharged on the 37th day of hospitalisation.

Simultaneous sampling of tissue oxygenation and oxygen consumption in skeletal muscle.

Science.gov (United States)

Nugent, William H; Song, Bjorn K; Pittman, Roland N; Golub, Aleksander S

2016-05-01

Under physiologic conditions, microvascular oxygen delivery appears to be well matched to oxygen consumption in respiring tissues. We present a technique to measure interstitial oxygen tension (PISFO2) and oxygen consumption (VO2) under steady-state conditions, as well as during the transitions from rest to activity and back. Phosphorescence Quenching Microscopy (PQM) was employed with pneumatic compression cycling to achieve 1 to 10 Hz sampling rates of interstitial PO2 and simultaneous recurrent sampling of VO2 (3/min) in the exteriorized rat spinotrapezius muscle. The compression pressure was optimized to 120-130 mmHg without adverse effect on the tissue preparation. A cycle of 5s compression followed by 15s recovery yielded a resting VO2 of 0.98 ± 0.03 ml O2/100 cm(3)min while preserving microvascular oxygen delivery. The measurement system was then used to assess VO2 dependence on PISFO2 at rest and further tested under conditions of isometric muscle contraction to demonstrate a robust ability to monitor the on-kinetics of tissue respiration and the compensatory changes in PISFO2 during contraction and recovery. The temporal and spatial resolution of this approach is well suited to studies seeking to characterize microvascular oxygen supply and demand in thin tissues. Copyright © 2015 Elsevier Inc. All rights reserved.

Aversive tension in female adolescents with Anorexia Nervosa: a controlled ecological momentary assessment using smartphones.

Science.gov (United States)

Kolar, David R; Hammerle, Florian; Jenetzky, Ekkehart; Huss, Michael; Bürger, Arne

2016-04-12

Current models of Anorexia Nervosa (AN) emphasize the role of emotion regulation. Aversive tension, described as a state of intense arousal and negative valence, is considered to be a link between emotional events and disordered eating. Recent research focused only on adult patients, and mainly general emotion regulation traits were studied. However, the momentary occurrence of aversive tension, particularly in adolescents with AN, has not been previously studied. 20 female adolescents with AN in outpatient treatment and 20 healthy adolescents aged 12 to 19 years participated in an ecological momentary assessment using their smartphones. Current states of aversive tension and events were assessed hourly for two consecutive weekdays. Mean and maximum values of aversive tension were compared. Multilevel analyses were computed to test the influence of time and reported events on aversive tension. The effect of reported events on subsequent changes of aversive tension in patients with AN were additionally tested in a multilevel model. AN patients showed higher mean and maximum levels of aversive tension. In a multilevel model, reported food intake was associated with higher levels of aversive tension in the AN group, whereas reported school or sport-related events were not linked to specific states of aversive tension. After food intake, subsequent increases of aversive tension were diminished and decreases of aversive tension were induced in adolescents with AN. Aversive tension may play a substantial role in the psychopathology of AN, particular in relation with food intake. Therefore, treatment should consider aversive tension as a possible intervening variable during refeeding. Our findings encourage further research on aversive tension and its link to disordered eating. German register of clinical trials (DRKS): DRKS00005228 (Date of registration: September 2, 2013).

Surface Tension Measurements with a Smartphone

Science.gov (United States)

Goy, Nicolas-Alexandre; Denis, Zakari; Lavaud, Maxime; Grolleau, Adrian; Dufour, Nicolas; Deblais, Antoine; Delabre, Ulysse

2017-01-01

Smartphones are increasingly used in higher education and at university in mechanics, acoustics, and even thermodynamics as they offer a unique way to do simple science experiments. In this article, we show how smartphones can be used in fluid mechanics to measure surface tension of various liquids, which could help students understand the concept…

Optimizing the calculation of DM,CO and VC via the single breath single oxygen tension DLCO/NO method.

Science.gov (United States)

Coffman, Kirsten E; Taylor, Bryan J; Carlson, Alex R; Wentz, Robert J; Johnson, Bruce D

2016-01-15

Alveolar-capillary membrane conductance (D(M,CO)) and pulmonary-capillary blood volume (V(C)) are calculated via lung diffusing capacity for carbon monoxide (DL(CO)) and nitric oxide (DL(NO)) using the single breath, single oxygen tension (single-FiO2) method. However, two calculation parameters, the reaction rate of carbon monoxide with blood (θ(CO)) and the D(M,NO)/D(M,CO) ratio (α-ratio), are controversial. This study systematically determined optimal θ(CO) and α-ratio values to be used in the single-FiO2 method that yielded the most similar D(M,CO) and V(C) values compared to the 'gold-standard' multiple-FiO2 method. Eleven healthy subjects performed single breath DL(CO)/DL(NO) maneuvers at rest and during exercise. D(M,CO) and V(C) were calculated via the single-FiO2 and multiple-FiO2 methods by implementing seven θ(CO) equations and a range of previously reported α-ratios. The RP θ(CO) equation (Reeves, R.B., Park, H.K., 1992. Respiration Physiology 88 1-21) and an α-ratio of 4.0-4.4 yielded DM,CO and VC values that were most similar between methods. The RP θ(CO) equation and an experimental α-ratio should be used in future studies. Copyright © 2015 Elsevier B.V. All rights reserved.

Differential oxygen dynamics in two diverse Dunning prostate R3327 rat tumor sublines (MAT-Lu and HI) with respect to growth and respiratory challenge

International Nuclear Information System (INIS)

Zhao Dawen; Constantinescu, Anca; Hahn, Eric W.; Mason, Ralph P.

2002-01-01

Purpose: Since hypoxia may influence tumor response to therapy and prognosis, we have compared oxygenation of tumors known to exhibit differential growth rate and tissue differentiation. Methods and Materials: Regional tumor oxygen tension was measured using 19 F nuclear magnetic resonance echo planar imaging relaxometry of hexafluorobenzene, which provided dynamic maps with respect to respiratory intervention. Investigations used two Dunning prostate R3327 rat tumor sublines: the fast growing, highly metastatic MAT-Lu and the moderately well-differentiated, slower growing HI. Results: Both sublines showed significantly higher oxygen tension in smaller tumors ( 3 ) than in larger tumors (>3.5 cm 3 ). Pooled data showed that MAT-Lu tumors exhibited greater hypoxia compared with the size-matched HI tumors (p 2 for tumors of both sublines (p 2 , while those in the MAT-Lu tumors showed little response to respiratory intervention. Conclusions: These results concur with hypotheses that hypoxia is related to tumor growth rate and degree of differentiation. Under baseline conditions, the differences were subtle. However, response to respiratory intervention revealed highly significant differences, which, if held valid in the clinic, could have prognostic value

Dissolved oxygen concentration in the medium during cell culture: Defects and improvements.

Science.gov (United States)

Zhang, Kuan; Zhao, Tong; Huang, Xin; He, Yunlin; Zhou, Yanzhao; Wu, Liying; Wu, Kuiwu; Fan, Ming; Zhu, Lingling

2016-03-01

In vitro cell culture has provided a useful model to study the effects of oxygen on cellular behavior. However, it remains unknown whether the in vitro operations themselves affect the medium oxygen levels and the living states of cells. In addition, a prevailing controversy is whether reactive oxygen species (ROS) production is induced by continuous hypoxia or reoxygenation. In this study, we have measured the effects of different types of cell culture containers and the oxygen environment where medium replacement takes place on the actual oxygen tension in the medium. We found that the deviations of oxygen concentrations in the medium are much greater in 25-cm(2) flasks than in 24-well plates and 35-mm dishes. The dissolved oxygen concentrations in the medium were increased after medium replacement in normoxia, but remained unchanged in glove boxes in which the oxygen tension remained at a low level (11.4, 5.7, and 0.5% O2 ). We also found that medium replacement in normoxia increased the number of ROS-positive cells and reduced the cell viability; meanwhile, medium replacement in a glove box did not produce the above effects. Therefore, we conclude that the use of 25-cm(2) flasks should be avoided and demonstrate that continuous hypoxia does not produce ROS, whereas the reoxygenation that occurs during the harvesting of cells leads to ROS and induces cell death. © 2015 International Federation for Cell Biology.

Prompt meningeal reconstruction mediated by oxygen-sensitive AKAP12 scaffolding protein after central nervous system injury

Science.gov (United States)

Cha, Jong-Ho; Wee, Hee-Jun; Seo, Ji Hae; Ahn, Bum Ju; Park, Ji-Hyeon; Yang, Jun-Mo; Lee, Sae-Won; Lee, Ok-Hee; Lee, Hyo-Jong; Gelman, Irwin H.; Arai, Ken; Lo, Eng H.; Kim, Kyu-Won

2015-01-01

The meninges forms a critical epithelial barrier, which protects the central nervous system (CNS), and therefore its prompt reconstruction after CNS injury is essential for reducing neuronal damage. Meningeal cells migrate into the lesion site after undergoing an epithelial-mesenchymal transition (EMT) and repair the impaired meninges. However, the molecular mechanisms of meningeal EMT remain largely undefined. Here we show that TGF-β1 and retinoic acid (RA) released from the meninges, together with oxygen tension, could constitute the mechanism for rapid meningeal reconstruction. AKAP12 is an effector of this mechanism, and its expression in meningeal cells is regulated by integrated upstream signals composed of TGF-β1, RA and oxygen tension. Functionally, AKAP12 modulates meningeal EMT by regulating the TGF-β1-non-Smad-SNAI1 signalling pathway. Collectively, TGF-β1, RA and oxygen tension can modulate the dynamic change in AKAP12 expression, causing prompt meningeal reconstruction after CNS injury by regulating the transition between the epithelial and mesenchymal states of meningeal cells. PMID:25229625

Cerebral oxygenation decreases during exercise in humans with beta-adrenergic blockade

DEFF Research Database (Denmark)

Seifert, T.; Rasmussen, P.; Secher, Niels H.

2009-01-01

AIM: Beta-blockers reduce exercise capacity by attenuated increase in cardiac output, but it remains unknown whether performance also relates to attenuated cerebral oxygenation. METHODS: Acting as their own controls, eight healthy subjects performed a continuous incremental cycle test to exhaustion...... attenuated the increase in cardiac output of consequence for cerebral perfusion and oxygenation. We suggest that a decrease in cerebral oxygenation limits exercise capacity Udgivelsesdato: 2009/7...... with or without administration of the non-selective beta-blocker propranolol. Changes in cerebral blood flow velocity were measured with transcranial Doppler ultrasound and those in cerebral oxygenation were evaluated using near-infrared spectroscopy and the calculated cerebral mitochondrial oxygen tension...

Reduced-Gravity Measurements of the Effect of Oxygen on Properties of Zirconium

Science.gov (United States)

Zhao, J.; Lee, J.; Wunderlich, R.; Fecht, H.-J.; Schneider, S.; SanSoucie, M.; Rogers, J.; Hyers, R.

2016-01-01

The influence of oxygen on the thermophysical properties of zirconium is being investigated using MSL-EML (Material Science Laboratory - Electromagnetic Levitator) on ISS (International Space Station) in collaboration with NASA, ESA (European Space Agency), and DLR (German Aerospace Center). Zirconium samples with different oxygen concentrations will be put into multiple melt cycles, during which the density, viscosity, surface tension, heat capacity, and electric conductivity will be measured at various undercooled temperatures. The facility check-up of MSL-EML and the first set of melting experiments have been successfully performed in 2015. The first zirconium sample will be tested near the end of 2015. As part of ground support activities, the thermophysical properties of zirconium and ZrO were measured using a ground-based electrostatic levitator located at the NASA Marshall Space Flight Center. The influence of oxygen on the measured surface tension was evaluated. The results of this research will serve as reference data for those measured in ISS.

Tension-induced vesicle fusion: pathways and pore dynamics

DEFF Research Database (Denmark)

Shillcock, Julian C.

2008-01-01

and eventually opens a pore to complete the fusion process. In pathway II, at higher tension, a stalk is formed during the fusion process that is then transformed by transmembrane pore formation into a fusion pore. Whereas the latter pathway II resembles stalk pathways as observed in other simulation studies......, fusion pathway I, which does not involve any stalk formation, has not been described previously to the best of our knowledge. A statistical analysis of the various processes shows that fusion is the dominant pathway for releasing the tension of the vesicles. The functional dependence of the observed...

Effects of motexafin gadolinium on tumor oxygenation and cellular oxygen consumption

International Nuclear Information System (INIS)

Donnelly, E.T.; Liu, Y.; Rockwell, S.; Magda, D.

2003-01-01

Full text: Recent work in our laboratory showed that motexafin gadolinium (MGd, Xcytrin), a drug currently in Phase III clinical trials as an adjuvant to radiation therapy, modulates the oxygen tensions in EMT6 tumors. The median pO 2 increased from the control value of 1.5±0.4 mmHg to 7.4 ± 3.8 mmHg six hours after treatment with 40 μmol/kg MGd and the percentage of severely hypoxic readings in the tumors ( 7 plateau phase EMT6 cells in 3 mL Dulbecco's Modified Eagle's Medium supplemented with 10% dialyzed fetal bovine serum, which contains no ascorbic acid. In the absence of ascorbic acid, 100 μM MGd did not alter the cellular oxygen consumption rate for EMT6 cells significantly. Marked inhibition of cellular oxygen consumption was observed when cells were incubated with 100 μM MGd in medium supplemented with equimolar ascorbic acid (a 31.5% decrease in consumption was observed after 6 hours of treatment). The 5% mannitol vehicle solution with equimolar ascorbic acid had no discernible effect on cellular oxygen consumption. Ascorbic acid may facilitate cellular uptake of MGd via the intermediate formation of a MGd-oxalate complex. These studies suggest that changes in cellular oxygen consumption could contribute to the changes in tumor oxygenation seen after administration of MGd. These experiments were supported by Pharmacyclics and training grant T32CA09085 from the NIH (E.T.D.). We thank Dr. Raymond Russell for allowing us to use his oxygen electrode apparatus

Higher levels of cardiovascular fitness are associated with better executive function and prefrontal oxygenation in younger and older women

Directory of Open Access Journals (Sweden)

Olivier eDupuy

2015-02-01

Full Text Available Aim: Many studies have suggested that physical exercise training improves cognition and more selectively executive functions. There is a growing interest to clarify the neurophysiological mechanisms that underlie this effect. The aim of the current study was to evaluate the neurophysiological changes in cerebral oxygenation associated with physical fitness level and executive functions. Method: In this study, 22 younger and 36 older women underwent a maximal graded continuous test (i.e., O2max in order to classifyassign them into a fitness group (higher vs. lower fit. All participants completed neuropsychological paper and pencil testing and a computerized Stroop task (which contained executive and non-executive conditions in which the change in pPrefrontal cortex oxygenation change was evaluated in all participants with a near infrared spectroscopy (NIRS. system during a computerized Stroop task (which contains executive and non-executive conditions. Results: Our findings revealed a Fitness x Condition interaction (p < .05 such that higher fit women scored better on measures of executive functions than lower fit women. In comparison to lower fit women, higher fit women had faster reaction times in the switching (executiveExecutive condition of the computerized Stroop task. No significant effect was observed ion the non-executive condition of the test and no interactions were found with age. In measures of cerebral oxygenation (ΔHbT and ΔHbO2, we found a main effect of fitness on cerebral oxygenation during the Stroop task such that only high fit women demonstrated a significant increase in the right inferior frontal gyrus. Discussion/Conclusion:Higher fit individuals who demonstrate better cardiorespiratory functions (as measured by O2max show faster reaction times and greater cerebral oxygenation in the right inferior frontal gyrus than women with lower fitness levels. The lack of interaction with age, suggests that good

Developing a Customized Perfusion Bioreactor Prototype with Controlled Positional Variability in Oxygen Partial Pressure for Bone and Cartilage Tissue Engineering.

Science.gov (United States)

Lee, Poh Soo; Eckert, Hagen; Hess, Ricarda; Gelinsky, Michael; Rancourt, Derrick; Krawetz, Roman; Cuniberti, Gianaurelio; Scharnweber, Dieter

2017-05-01

Skeletal development is a multistep process that involves the complex interplay of multiple cell types at different stages of development. Besides biochemical and physical cues, oxygen tension also plays a pivotal role in influencing cell fate during skeletal development. At physiological conditions, bone cells generally reside in a relatively oxygenated environment whereas chondrocytes reside in a hypoxic environment. However, it is technically challenging to achieve such defined, yet diverse oxygen distribution on traditional in vitro cultivation platforms. Instead, engineered osteochondral constructs are commonly cultivated in a homogeneous, stable environment. In this study, we describe a customized perfusion bioreactor having stable positional variability in oxygen tension at defined regions. Further, engineered collagen constructs were coaxed into adopting the shape and dimensions of defined cultivation platforms that were precasted in 1.5% agarose bedding. After cultivating murine embryonic stem cells that were embedded in collagen constructs for 50 days, mineralized constructs of specific dimensions and a stable structural integrity were achieved. The end-products, specifically constructs cultivated without chondroitin sulfate A (CSA), showed a significant increase in mechanical stiffness compared with their initial gel-like constructs. More importantly, the localization of osteochondral cell types was specific and corresponded to the oxygen tension gradient generated in the bioreactor. In addition, CSA in complementary with low oxygen tension was also found to be a potent inducer of chondrogenesis in this system. In summary, we have demonstrated a customized perfusion bioreactor prototype that is capable of generating a more dynamic, yet specific cultivation environment that could support propagation of multiple osteochondral lineages within a single engineered construct in vitro. Our system opens up new possibilities for in vitro research on human

Reactor vessel stud tensioner

International Nuclear Information System (INIS)

Malandra, L.J.; Beer, R.W.; Salton, R.B.; Spiegelman, S.R.; Cognevich, M.L.

1982-01-01

A quick-acting stud tensioner, for facilitating the loosening or tightening of a stud nut on a reactor vessel stud, has gripper jaws which when the tensioner is lowered into engagement with the upper end of the stud are moved inwards to grip the upper end and which when the tensioner is lifted move outward to release the upper end. (author)

Efficient synthesis of tension modulation in strings and membranes based on energy estimation.

Science.gov (United States)

Avanzini, Federico; Marogna, Riccardo; Bank, Balázs

2012-01-01

String and membrane vibrations cannot be considered as linear above a certain amplitude due to the variation in string or membrane tension. A relevant special case is when the tension is spatially constant and varies in time only in dependence of the overall string length or membrane surface. The most apparent perceptual effect of this tension modulation phenomenon is the exponential decay of pitch in time. Pitch glides due to tension modulation are an important timbral characteristic of several musical instruments, including the electric guitar and tom-tom drum, and many ethnic instruments. This paper presents a unified formulation to the tension modulation problem for one-dimensional (1-D) (string) and two-dimensional (2-D) (membrane) cases. In addition, it shows that the short-time average of the tension variation, which is responsible for pitch glides, is approximately proportional to the system energy. This proportionality allows the efficient physics-based sound synthesis of pitch glides. The proposed models require only slightly more computational resources than linear models as opposed to earlier tension-modulated models of higher complexity. © 2012 Acoustical Society of America.

Pericellular oxygen monitoring with integrated sensor chips for reproducible cell culture experiments.

Science.gov (United States)

Kieninger, J; Aravindalochanan, K; Sandvik, J A; Pettersen, E O; Urban, G A

2014-04-01

Here we present an application, in two tumour cell lines, based on the Sensing Cell Culture Flask system as a cell culture monitoring tool for pericellular oxygen sensing. T-47D (human breast cancer) and T98G (human brain cancer) cells were cultured either in atmospheric air or in a glove-box set at 4% oxygen, in both cases with 5% CO2 in the gas phase. Pericellular oxygen tension was measured with the help of an integrated sensor chip comprising oxygen sensor arrays. Obtained results illustrate variation of pericellular oxygen tension in attached cells covered by stagnant medium. Independent of incubation conditions, low pericellular oxygen concentration levels, usually associated with hypoxia, were found in dense cell cultures. Respiration alone brought pericellular oxygen concentration down to levels which could activate hypoxia-sensing regulatory processes in cultures believed to be aerobic. Cells in culture believed to experience conditions of mild hypoxia may, in reality, experience severe hypoxia. This would lead to incorrect assumptions and suggests that pericellular oxygen concentration readings are of great importance to obtain reproducible results when dealing with hypoxic and normoxic (aerobic) incubation conditions. The Sensing Cell Culture Flask system allows continuous monitoring of pericellular oxygen concentration with outstanding long-term stability and no need for recalibration during cell culture experiments. The sensor is integrated into the flask bottom, thus in direct contact with attached cells. No additional equipment needs to be inserted into the flask during culturing. Transparency of the electrochemical sensor chip allows optical inspection of cells attached on top of the sensor. © 2014 John Wiley & Sons Ltd.

Validation of the protoporphyrin IX-triplet state lifetime technique for mitochondrial oxygen measurements in the skin

NARCIS (Netherlands)

F.A. Harms (Floor A.); S.I.A. Bodmer (Sander I. A.); N.J.H. Raat (Nicolaas); R.J. Stolker (Robert); E.G. Mik (Egbert)

2012-01-01

textabstractMitochondrial oxygen tension can be measured in vivo by means of oxygen-dependent quenching of delayed fluorescence of protoporphyrin IX (PpIX). Here we demonstrate that mitochondrial PO2 (mitoPO2) can be measured in the skin of a rat after topical application of the PpIX precursor

Effects of the kinematic viscosity and surface tension on the bubble take-off period in a catalase-hydrogen peroxide system.

Science.gov (United States)

Sasaki, Satoshi; Iida, Yoshinori

2009-06-01

The effect of kinematic viscosity and surface tension of the solution was investigated by adding catalase, glucose oxidase, or glucose on the bubble movement in a catalase-hydrogen peroxide system. The kinematic viscosity was measured using a Cannon-Fenske kinematic viscometer. The surface tension of the solution was measured by the Wilhelmy method using a self-made apparatus. The effects of the hole diameter/cell wall thickness, catalase concentration, glucose concentration, and glucose oxidase concentration on the kinematic viscosity, surface tension, and bubble take-off period were investigated. With our system, the effects of the changes in the solution materiality on the bubble take-off period were proven to be very small in comparison to the change in the oxygen-producing rate.

Constraining brane tension using rotation curves of galaxies

Science.gov (United States)

García-Aspeitia, Miguel A.; Rodríguez-Meza, Mario A.

2018-04-01

We present in this work a study of brane theory phenomenology focusing on the brane tension parameter, which is the main observable of the theory. We show the modifications steaming from the presence of branes in the rotation curves of spiral galaxies for three well known dark matter density profiles: Pseudo isothermal, Navarro-Frenk-White and Burkert dark matter density profiles. We estimate the brane tension parameter using a sample of high resolution observed rotation curves of low surface brightness spiral galaxies and a synthetic rotation curve for the three density profiles. Also, the fittings using the brane theory model of the rotation curves are compared with standard Newtonian models. We found that Navarro-Frenk-White model prefers lower values of the brane tension parameter, on the average λ ∼ 0.73 × 10‑3eV4, therefore showing clear brane effects. Burkert case does prefer higher values of the tension parameter, on the average λ ∼ 0.93 eV4 ‑ 46 eV4, i.e., negligible brane effects. Whereas pseudo isothermal is an intermediate case. Due to the low densities found in the galactic medium it is almost impossible to find evidence of the presence of extra dimensions. In this context, we found that our results show weaker bounds to the brane tension values in comparison with other bounds found previously, as the lower value found for dwarf stars composed of a polytropic equation of state, λ ≈ 104 MeV4.

General definition of gravitational tension

International Nuclear Information System (INIS)

Harmark, T.; Obers, N.A.

2004-01-01

In this note we give a general definition of the gravitational tension in a given asymptotically translationally-invariant spatial direction of a space-time. The tension is defined via the extrinsic curvature in analogy with the Hawking-Horowitz definition of energy. We show the consistency with the ADM tension formulas for asymptotically-flat space-times, in particular for Kaluza-Klein black hole solutions. Moreover, we apply the general tension formula to near-extremal branes, constituting a check for non-asymptotically flat space-times. (author)

Structural design significance of tension-tension fatigue data on composites

Science.gov (United States)

Grimes, G. C.

1977-01-01

Constant cycle tension-tension fatigue and related static tension data have been generated on six single composite material/orientation combinations and twenty-one hybrid composite material/orientation combinations. Anomalies are related to the temperature rise and stopped interval creep, whereas endurance limit stresses (runouts) are associated with static proportional limit values, when they occur, and internal damage. The significance of these room temperature-dry data on the design allowables and weight of aerodynamic structueres is discussed. Such structures are helicopter rotor blades and wing and horizontal stabilizer lower surfaces. Typical criteria for turning these data into preliminary allowables are shown, as are examples of such allowables developed from the data. These values are then compared to those that might be used if the structures were made of metal.

Tension type headache

Directory of Open Access Journals (Sweden)

Debashish Chowdhury

2012-01-01

Full Text Available Tension type headaches are common in clinical practice. Earlier known by various names, the diagnosis has had psychological connotations. Recent evidence has helped clarify the neurobiological basis and the disorder is increasingly considered more in the preview of neurologists. The classification, clinical features, differential diagnosis and treatment of tension type headache are discussed in this paper.

Surface density profile and surface tension of the one-component classical plasma

International Nuclear Information System (INIS)

Ballone, P.; Senatore, G.; Trieste Univ.; Tosi, M.P.; Oxford Univ.

1982-08-01

The density profile and the interfacial tension of two classical plasmas in equilibrium at different densities are evaluated in the square-density-gradient approximation. For equilibrium in the absence of applied external voltage, the profile is oscillatory in the higher-density plasma and the interfacial tension is positive. The amplitude and phase of these oscillations and the magnitude of the interfacial tension are related to the width of the background profile. Approximate representations of the equilibrium profile by matching of its asymptotic forms are analyzed. A comparison with computer simulation data and a critical discussion of a local-density theory are also presented. (author)

Tumour oxygen dynamics measured simultaneously by near-infrared spectroscopy and 19F magnetic resonance imaging in rats

International Nuclear Information System (INIS)

Xia Mengna; Kodibagkar, Vikram; Liu Hanli; Mason, Ralph P

2006-01-01

Simultaneous near-infrared spectroscopy (NIRS) and magnetic resonance imaging (MRI) were used to investigate the correlation between tumour vascular oxygenation and tissue oxygen tension dynamics in rat breast 13762NF tumours with respect to hyperoxic gas breathing. NIRS directly detected global variations in the oxygenated haemoglobin concentration (Δ[HbO 2 ]) within tumours and oxygen tension (pO 2 ) maps were achieved using 19 F MRI of the reporter molecule hexafluorobenzene. Multiple correlations were examined between rates and magnitudes of vascular (Δ[HbO 2 ]) and tissue (pO 2 ) responses. Significant correlations were found between response to oxygen and carbogen breathing using either modality. Comparison of results for the two methods showed a correlation between the vascular perfusion rate ratio and the mean pO 2 values (R 2 > 0.7). The initial rates of increase of Δ[HbO 2 ] and the slope of dynamic pO 2 response, d(pO 2 )/dt, of well-oxygenated voxels in response to hyperoxic challenge were also correlated. These results demonstrate the feasibility of simultaneous measurements using NIRS and MRI. As expected, the rate of pO 2 response to oxygen is primarily dependent upon the well perfused rather than poorly perfused vasculature

Resistance to small plastic strains during martensite tempering under tension

Energy Technology Data Exchange (ETDEWEB)

Zabil' skij, V.V.; Sarrak, V.I. (AN SSSR, Sverdlovsk. Inst. Fiziki Metallov)

1982-11-01

The mechanism of plastic deformation of martensite of a series of hardened steels (N18, 20KhG, 50KhFA and others) during tempering under tension and the role of residual internal microstresses and phase transformations are studied. It is shown that martensite low resistance to small plastic deformations during tempering under tension which is usually associated with phase transformations depends as well on the level of residual internal microstresses in the martensite structure. The decrease of resistance to deformation in the course of the decomposition of a solid solution is due to weakening of martensitic matrix because of carbon departure from the solid solution and carbide coarsening. An assumption is made that martensite plastic deformation during tempering under tension is realized at the expense of the directed microplastic deformation in the regions of higher concentration of internal stresses.

On relation between the quark-gluon bag surface tension and the colour tube string tension

International Nuclear Information System (INIS)

Bugaev, K.A.; Zinovjev, G.M.

2010-01-01

We revisit the bag phenomenology of deconfining phase transition aiming to replenish it by introducing systematically the bag surface tension. Comparing the free energies of such bags and the strings confining the static quark-antiquark pair, we express the string tension in terms of the bag surface tension and the bulk pressure in order to estimate the bag characteristics using the lattice QCD (LQCD) data. Our analysis of the bag entropy density demonstrates that the surface tension coefficient is amazingly negative at the cross-over (continuous transition). The approach developed allows us to naturally account for an origin of a pronounced maximum (observed in the LQCD studies) in the behaviour of heavy quark-antiquark pair entropy. The vicinity of the (tri-)critical endpoint is also analyzed to clarify the meaning of vanishing surface tension coefficient.

Effects of targeting lower versus higher arterial oxygen saturations on death or disability in preterm infants.

Science.gov (United States)

Askie, Lisa M; Darlow, Brian A; Davis, Peter G; Finer, Neil; Stenson, Ben; Vento, Maximo; Whyte, Robin

2017-04-11

The use of supplemental oxygen in the care of extremely preterm infants has been common practice since the 1940s. Despite this, there is little agreement regarding which oxygen saturation (SpO₂) ranges to target to maximise short- or long-term growth and development, while minimising harms. There are two opposing concerns. Lower oxygen levels (targeting SpO₂ at 90% or less) may impair neurodevelopment or result in death. Higher oxygen levels (targeting SpO₂ greater than 90%) may increase severe retinopathy of prematurity or chronic lung disease.The use of pulse oximetry to non-invasively assess neonatal SpO₂ levels has been widespread since the 1990s. Until recently there were no randomised controlled trials (RCTs) that had assessed whether it is better to target higher or lower oxygen saturation levels in extremely preterm infants, from birth or soon thereafter. As a result, there is significant international practice variation and uncertainty remains as to the most appropriate range to target oxygen saturation levels in preterm and low birth weight infants. 1. What are the effects of targeting lower versus higher oxygen saturation ranges on death or major neonatal and infant morbidities, or both, in extremely preterm infants?2. Do these effects differ in different types of infants, including those born at a very early gestational age, or in those who are outborn, without antenatal corticosteroid coverage, of male sex, small for gestational age or of multiple birth, or by mode of delivery? We used the standard search strategy of Cochrane Neonatal to search the Cochrane Central Register of Controlled Trials (CENTRAL 2016, Issue 4), MEDLINE via PubMed (1966 to 11 April 2016), Embase (1980 to 11 April 2016) and CINAHL (1982 to 11 April 2016). We also searched clinical trials databases, conference proceedings and the reference lists of retrieved articles for randomised controlled trials. Randomised controlled trials that enrolled babies born at less than 28

Inverse Regulation of Early and Late Chondrogenic Differentiation by Oxygen Tension Provides Cues for Stem Cell-Based Cartilage Tissue Engineering

Directory of Open Access Journals (Sweden)

Sophie Portron

2015-01-01

Full Text Available Background/Aims: Multipotent stem/stromal cells (MSC are considered promising for cartilage tissue engineering. However, chondrogenic differentiation of MSC can ultimately lead to the formation of hypertrophic chondrocytes responsible for the calcification of cartilage. To prevent the production of this calcified matrix at the articular site, the late hypertrophic differentiation of MSCs must be carefully controlled. Given that articular cartilage is avascular, we hypothesized that in addition to its stimulatory role in the early differentiation of chondrogenic cells, hypoxia may prevent their late hypertrophic conversion. Methods: Early and late chondrogenic differentiation were evaluated using human adipose MSC and murine ATDC5 cells cultured under either normoxic (21%O2 or hypoxic (5%O2 conditions. To investigate the effect of hypoxia on late chondrogenic differentiation, the transcriptional activity of hypoxia-inducible factor-1alpha (HIF-1α and HIF-2α were evaluated using the NoShift DNA-binding assay and through modulation of their activity (chemical inhibitor, RNA interference. Results: Our data demonstrate that low oxygen tension not only stimulates the early chondrogenic commitment of two complementary models of chondrogenic cells, but also inhibits their hypertrophic differentiation. Conclusion: These results suggest that hypoxia can be used as an instrumental tool to prevent the formation of a calcified matrix in MSC-based cartilage tissue engineering.

Oxygen diffusion coefficient in isolated chicken red and white skeletal muscle fibers in ontogenesis.

Science.gov (United States)

Baranov, V I; Belichenko, V M; Shoshenko, C A

2000-09-01

Oxygen diffusion from medium to cultured isolated muscle fibers from red gastrocnemius muscle (deep part) (RGM) and white pectoralis muscle (WPM) of embryonic and postnatal chickens (about 6 months) was explored. The intracellular effective O(2) diffusion coefficient (D(i)) in muscle fiber was calculated from a model of a cylindrical fiber with a uniform distribution of an oxygen sink based on these experimentally measured parameters: critical tension of O(2) (PO(2)) on the surface of a fiber, specific rate of O(2) consumption by a weight unit of muscle fibers (;VO(2)), and average diameter of muscle fibers. The results document the rapid hypertrophic growth of RGM fibers when compared to WPM fibers in the second half of the embryonic period and the higher values of;VO(2) and critical PO(2) during the ontogenetic period under study. The oxygen D(i) in RGM fibers of embryos and 1-day chickens was two to three times higher than observed for WPM fibers. For senior chickens, the oxygen D(i) value in RGM and WPM fibers does not differ. The D(i) of O(2) in both RGM and WPM fibers increased from 1.4-2.7 x 10(-8) to 90-95 x 10(-8) cm(2)/s with an ontogenetic increase in fiber diameter from 7. 5 to 67.0 microm. At all stages the oxygen D(i) values in RGM and WPM fibers are significantly lower than the O(2) diffusion coefficient in water: for 11-day embryos they are 889 and 1714 times lower and for adult individuals 25 and 27 times lower, respectively. Why oxygen D(i) values in RGM and WPM fibers are so low and why they are gradually increasing during the course of hypertrophic ontogenetic growth are still unclear. Copyright 2000 Academic Press.

Strength and stiffness of uniaxially tensioned reinforced concrete panels subjected to membrane shear. Technical report

International Nuclear Information System (INIS)

Hilmy, S.I.; White, R.N.; Gergely, P.

1982-06-01

This report presents experimental and analytical results on internal pressurization effects and seismic shear effects in a concrete containment vessel that is cracked by tension in one direction only. The experimental program, which was restricted to 6 in. thick flat specimens with two-way reinforcement, included establishment of (a) extensional stiffness for uniaxially tensioned specimens stressed to 0.6fy, and (b) shear strength and stiffness of these cracked specimens with tension levels ranging from 0 to 0.9fy; values were about 10 to 15 percent higher than in similar biaxially tensioned specimens. Eleven (11) specimens were tested (6 in monotonic shear and 5 in reversing cyclic shear)

Thermal Characteristics of Plastic Film Tension in Roll-to-Roll Gravure Printed Electronics

Directory of Open Access Journals (Sweden)

Kui He

2018-02-01

Full Text Available In the printing section of a roll-to-roll gravure printed electronics machine, the plastic film tension is directly associated with the product quality. The temperature distribution of the plastic film in the printing section is non-uniform, because of the higher drying temperature and the lower room temperature. Furthermore, the drying temperature and the room temperature are not constants in industrial production. As the plastic film is sensitive to temperature, the temperature of the plastic film will affects the web tension in the printing section. In this paper, the thermal characteristics of the plastic film tension in roll-to-roll gravure printed electronics are studied in order to help to improve the product quality. First, the tension model including the factor of temperature is derived based on the law of mass conservation. Then, some simulations and experiments are carried out in order to in-depth research the effects of the drying temperature and room temperature based on the relations between system inputs and outputs. The results show that the drying temperature and room temperature have significant influences on the web tension. The research on the thermal characteristics of plastic film tension would benefit the tension control accuracy for further study.

Endothelial cell respiration is affected by the oxygen tension during shear exposure: role of mitochondrial peroxynitrite.

Science.gov (United States)

Jones, Charles I; Han, Zhaosheng; Presley, Tennille; Varadharaj, Saradhadevi; Zweier, Jay L; Ilangovan, Govindasamy; Alevriadou, B Rita

2008-07-01

Cultured vascular endothelial cell (EC) exposure to steady laminar shear stress results in peroxynitrite (ONOO(-)) formation intramitochondrially and inactivation of the electron transport chain. We examined whether the "hyperoxic state" of 21% O(2), compared with more physiological O(2) tensions (Po(2)), increases the shear-induced nitric oxide (NO) synthesis and mitochondrial superoxide (O(2)(*-)) generation leading to ONOO(-) formation and suppression of respiration. Electron paramagnetic resonance oximetry was used to measure O(2) consumption rates of bovine aortic ECs sheared (10 dyn/cm(2), 30 min) at 5%, 10%, or 21% O(2) or left static at 5% or 21% O(2). Respiration was inhibited to a greater extent when ECs were sheared at 21% O(2) than at lower Po(2) or left static at different Po(2). Flow in the presence of an endothelial NO synthase (eNOS) inhibitor or a ONOO(-) scavenger abolished the inhibitory effect. EC transfection with an adenovirus that expresses manganese superoxide dismutase in mitochondria, and not a control virus, blocked the inhibitory effect. Intracellular and mitochondrial O(2)(*-) production was higher in ECs sheared at 21% than at 5% O(2), as determined by dihydroethidium and MitoSOX red fluorescence, respectively, and the latter was, at least in part, NO-dependent. Accumulation of NO metabolites in media of ECs sheared at 21% O(2) was modestly increased compared with ECs sheared at lower Po(2), suggesting that eNOS activity may be higher at 21% O(2). Hence, the hyperoxia of in vitro EC flow studies, via increased NO and mitochondrial O(2)(*-) production, leads to enhanced ONOO(-) formation intramitochondrially and suppression of respiration.

In vitro synthesis of tensioned synoviocyte bioscaffolds for meniscal fibrocartilage tissue engineering.

Science.gov (United States)

Warnock, Jennifer J; Baker, Lindsay; Ballard, George A; Ott, Jesse

2013-12-03

Meniscal injury is a common cause of lameness in the dog. Tissue engineered bioscaffolds may be a treatment option for meniscal incompetency, and ideally would possess meniscus- like extracellular matrix (ECM) and withstand meniscal tensile hoop strains. Synovium may be a useful cell source for meniscal tissue engineering because of its natural role in meniscal deficiency and its in vitro chondrogenic potential. The objective of this study is to compare meniscal -like extracellular matrix content of hyperconfluent synoviocyte cell sheets ("HCS") and hyperconfluent synoviocyte sheets which have been tensioned over wire hoops (tensioned synoviocyte bioscaffolds, "TSB") and cultured for 1 month. Long term culture with tension resulted in higher GAG concentration, higher chondrogenic index, higher collagen concentration, and type II collagen immunoreactivity in TSB versus HCS. Both HCS and TSB were immunoreactive for type I collagen, however, HCS had mild, patchy intracellular immunoreactivity while TSB had diffuse moderate immunoreactivity over the entire bisocaffold. The tissue architecture was markedly different between TSB and HCS, with TSB containing collagen organized in bands and sheets. Both HCS and TSB expressed alpha smooth muscle actin and displayed active contractile behavior. Double stranded DNA content was not different between TSB and HCS, while cell viability decreased in TSB. Long term culture of synoviocytes with tension improved meniscal- like extra cellular matrix components, specifically, the total collagen content, including type I and II collagen, and increased GAG content relative to HCS. Future research is warranted to investigate the potential of TSB for meniscal tissue engineering.

Response of notched AS4/PEEK laminates to tension/compression loading

Science.gov (United States)

Simonds, Robert A.; Stinchcomb, Wayne W.

1989-01-01

Fatigue life, damage-initiation and propagation, and residual strength data are presently examined to ascertain the response of notched AS4/PEEK specimens to fully reversed tension/compression loading. Stiffness measurements made during the low-level fatigue history show that compression stiffness and tension stiffness degrade throughout the fatigue life. Damage to specimens fatigued at higher cyclic stresses developed primarily in the direction perpendicular to the loading. As in the case of specimens fatigued at lower stress levels, residual compressive stress decreased with damage development.

Mixed oxygen ion/electron-conducting ceramics for oxygen separation

Energy Technology Data Exchange (ETDEWEB)

Stevenson, J.W.; Armstrong, T.R.; Armstrong, B.L. [Pacific Northwest National Lab., Richland, WA (United States)

1996-08-01

Mixed oxygen ion and electron-conducting ceramics are unique materials that can passively separate high purity oxygen from air. Oxygen ions move through a fully dense ceramic in response to an oxygen concentration gradient, charge-compensated by an electron flux in the opposite direction. Compositions in the system La{sub 1{minus}x}M{sub x}Co{sub 1{minus}y{minus}z}Fe{sub y}N{sub z}O{sub 3{minus}{delta}}, perovskites where M=Sr, Ca, and Ba, and N=Mn, Ni, Cu, Ti, and Al, have been prepared and their electrical, oxygen permeation, oxygen vacancy equilibria, and catalytic properties evaluated. Tubular forms, disks, and asymmetric membrane structures, a thin dense layer on a porous support of the same composition, have been fabricated for testing purposes. In an oxygen partial gradient, the passive oxygen flux through fully dense structures was highly dependent on composition. An increase in oxygen permeation with increased temperature is attributed to both enhanced oxygen vacancy mobility and higher vacancy populations. Highly acceptor-doped compositions resulted in oxygen ion mobilities more than an order of magnitude higher than yttria-stabilized zirconia. The mixed conducting ceramics have been utilized in a membrane reactor configuration to upgrade methane to ethane and ethylene. Conditions were established to balance selectivity and throughput in a catalytic membrane reactor constructed from mixed conducting ceramics.

Characterization of hemodynamics and oxygenation in the renal cortex of rats

Science.gov (United States)

Grosenick, Dirk; Wabnitz, Heidrun; Macdonald, Rainer; Niendorf, Thoralf; Cantow, Kathleen; Flemming, Bert; Arakelyan, Karen; Seeliger, Erdmann

2015-03-01

We have performed a pre-clinical study on 13 rats to investigate the potential of near-infrared spectroscopy for quantification of hemoglobin concentration and oxygen saturation of hemoglobin in the renal cortex of small animals. These measurements were combined with laser-Doppler fluxmetry and a fluorescence quenching technique for quantification of tissue oxygen tension. Hemoglobin concentration and oxygen saturation were determined from experimental data by a Monte Carlo model. The methods were applied to investigate and compare temporal changes during several types of interventions such as arterial and venous occlusions, as well as hyperoxia, hypoxia and hypercapnia induced by different mixtures of the inspired gas.

Liquid oxygen liquid acquisition device bubble point tests with high pressure lox at elevated temperatures

Science.gov (United States)

Jurns, J. M.; Hartwig, J. W.

2012-04-01

When transferring propellant in space, it is most efficient to transfer single phase liquid from a propellant tank to an engine. In earth's gravity field or under acceleration, propellant transfer is fairly simple. However, in low gravity, withdrawing single-phase fluid becomes a challenge. A variety of propellant management devices (PMDs) are used to ensure single-phase flow. One type of PMD, a liquid acquisition device (LAD) takes advantage of capillary flow and surface tension to acquire liquid. The present work reports on testing with liquid oxygen (LOX) at elevated pressures (and thus temperatures) (maximum pressure 1724 kPa and maximum temperature 122 K) as part of NASA's continuing cryogenic LAD development program. These tests evaluate LAD performance for LOX stored in higher pressure vessels that may be used in propellant systems using pressure fed engines. Test data shows a significant drop in LAD bubble point values at higher liquid temperatures, consistent with lower liquid surface tension at those temperatures. Test data also indicates that there are no first order effects of helium solubility in LOX on LAD bubble point prediction. Test results here extend the range of data for LOX fluid conditions, and provide insight into factors affecting predicting LAD bubble point pressures.

Soft-tissue tension total knee arthroplasty.

Science.gov (United States)

Asano, Hiroshi; Hoshino, Akiho; Wilton, Tim J

2004-08-01

It is far from clear how best to define the proper strength of soft-tissue tensioning in total knee arthroplasty (TKA). We attached a torque driver to the Monogram balancer/tensor device and measured soft-tissue tension in full extension and 90 degrees flexion during TKA. In our surgical procedure, when we felt proper soft-tissue tension was being applied, the mean distraction force was noted to be 126N in extension and 121N in flexion. There was no significant correlation between soft-tissue tension and the postoperative flexion angle finally achieved. To the best of our knowledge, this is the first study to assess the actual distraction forces in relation to soft-tissue tension in TKA. Further study may reveal the most appropriate forces to achieve proper soft-tissue tension in the wide variety of circumstances presenting at knee arthroplasty.

Cutaneous respirometry by dynamic measurement of mitochondrial oxygen tension for monitoring mitochondrial function in vivo.

Science.gov (United States)

Harms, Floor A; Voorbeijtel, Wilhelmina J; Bodmer, Sander I A; Raat, Nicolaas J H; Mik, Egbert G

2013-09-01

Progress in diagnosis and treatment of mitochondrial dysfunction in chronic and acute disease could greatly benefit from techniques for monitoring of mitochondrial function in vivo. In this study we demonstrate the feasibility of in vivo respirometry in skin. Mitochondrial oxygen measurements by means of oxygen-dependent delayed fluorescence of protoporphyrin IX are shown to provide a robust basis for measurement of local oxygen disappearance rate (ODR). The fundamental principles behind the technology are described, together with an analysis method for retrievel of respirometry data. The feasibility and reproducibility of this clinically useful approach are demonstrated in a series of rats. Copyright © 2012 Elsevier B.V. All rights reserved.

Temperature and oxygenation during organ preservation: friends or foes?

Science.gov (United States)

Gilbo, Nicholas; Monbaliu, Diethard

2017-06-01

The liberalization of donor selection criteria in organ transplantation, with the increased use of suboptimal grafts, has stimulated interest in ischemia-reperfusion injury prevention and graft reconditioning. Organ preservation technologies are changing considerably, mostly through the reintroduction of dynamic machine preservation. Here, we review the current evidence on the role of temperature and oxygenation during dynamic machine preservation. A large but complex body of evidence exists and comparative studies are few. Oxygenation seems to support an advantageous effect in hypothermic machine preservation and is mandatory in normothermic machine preservation, although in the latter, supraphysiological oxygen tensions should be avoided. High-risk grafts, such as suboptimal organs, may optimally benefit from oxygenated perfusion conditions that support metabolism and activate mechanisms of repair such as subnormothermic machine preservation, controlled oxygenated rewarming, and normothermic machine preservation. For lower risk grafts, oxygenation during hypothermic machine preservation may sufficiently reduce injuries and recharge the cellular energy to secure functional recovery after transplantation. The relationship between temperature and oxygenation in organ preservation is more complex than physiological laws would suggest. Rather than one default perfusion temperature/oxygenation standard, perfusion protocols should be tailored for specific needs of grafts of different quality.

Phenylephrine Decreases Vascular Tension in Goat Arteries in Specific Circumstances.

Directory of Open Access Journals (Sweden)

Renu R Raj

Full Text Available Phenylephrine (PE causes vasoconstriction through alpha adrenergic receptors. PE-induced vasodilatation has also been reported earlier in pre-constricted vessels. Here we demonstrate in spiral strips of goat arteries that addition of PE can decrease tone even from base-line levels (i.e. not pre-constricted and show that this process requires nitric oxide (NO and alpha adrenergic stimulation, but is cGMP-independent. Under control conditions, PE caused vasoconstriction, but under conditions where NO levels are higher, as with L-Arginine or sodium nitroprusside, PE decreased vessel tension. L-Arginine/PE combination was not able to decrease tension when alpha adrenoceptors were blocked with Phentolamine or endothelial nitric oxide synthase (eNOS was blocked with Nω-Nitro-L-arginine (L-NNA. Propranolol, a beta blocker, was unable to prevent the reduction in tension by the L-Arginine/PE combination. Adrenaline and noradrenaline (and not isoproterenol also reduced vessel tension in the presence of L-Arginine. Even when NO levels were not enhanced, relieving NO from having to stimulate the enzyme soluble guanylyl cyclase (sGC (either by using sGC blockers, namely ODQ or methylene blue, or by enhancing cGMP levels (with sildenafil which by negative feedback probably inhibits sGC led to PE-induced reduction of vascular tension. PMA-phorbol myristate acetate-an agonist which stimulates Protein Kinase C was able to prevent the ability of PE to reduce vascular tension in a high NO environment. Our conclusion is that PE reduces vascular tension through alpha adrenoceptors if there is excess NO availability to activate a putative pathway. Though the reduction of vessel tone by PE is dependent on NO, it is independent of cGMP. Prior treatment with PMA or PE itself can prevent further PE-induced reduction of tension in a high NO environment. The results here suggest, counter-intuitively, that alpha blockers may be of help in the treatment of septic shock

[Effect of hemodilution with 10% hydroxyethyl starch solution (MW 200,000/9.5) on the flow properties of blood, arterial blood gases and conjunctival oxygen partial pressure in patients with cerebral infarct].

Science.gov (United States)

Staedt, U; Hütt, M; Herrmann, B; Seufzer, U; Leweling, H

1989-06-01

Hemorheological parameters, arterial blood gases and conjunctival oxygen tension were measured in 15 patients with acute ischemic stroke and compared with values obtained in an age matched reference group. Since the conjunctival capillary bed is perfused by the ophthalmic artery, it reflects the oxygen delivery to the areas supplied by the internal carotid artery. Measurements of conjunctival oxygen tension are simple and safe. Patients with acute ischemic stroke showed a lowered conjunctival oxygen tension; this holds true especially to the ipsilateral side, i.e. the side where the attack occurred, and to a lesser extent to the other side. By contrast, the ratio of arterial/conjunctival pO2 was disturbed only on the ipsilateral side. Furthermore, these patients had pathologically elevated values for red cell aggregation, whole blood and plasma viscosity. After infusing 500 ml 10% middle-molecular-weight hydroxyethyl starch (10% HAES-steril) and phlebotomy (250 ml) blood fluidity was normalized, although the hematokrit was only slightly reduced. Arterial pO2 improved slightly while pCO2 remained unchanged. Conjunctival oxygen tension improved by 30% on the ipsilateral and by 10% on the contralateral side, the ipsilateral values always remaining significantly lower. The ratio conjunctival/arterial pO2 raised only on the ipsilateral side where it was below the reference range before hemodilution. In addition to the well known improvement of blood fluidity and augmentation of cerebral blood flow following hemodilution in patients with acute ischemic stroke, there seems to be an increase in oxygen supply in the territories of both internal carotid arteries, especially on the ipsilateral side as indicated by the values of conjunctival oxygen tension and the ratio of conjunctival to arterial pO2.

Spontaneous tension haemopneumothorax

OpenAIRE

Patterson, Benjamin Oliver; Itam, Sarah; Probst, Fey

2008-01-01

Abstract We present a patient with sudden onset progressive shortness of breath and no history of trauma, who rapidly became haemodynamically compromised with a pneumothorax and pleural effusion seen on chest radiograph. He was treated for spontaneous tension pneumothorax but this was soon revealed to be a tension haemopneumothorax. He underwent urgent thoracotomy after persistent bleeding to explore an apical vascular abnormality seen on CT scanning. To our knowledge this is the first such c...

A hybrid multibreath wash-in wash-out lung function quantification scheme in human subjects using hyperpolarized 3 He MRI for simultaneous assessment of specific ventilation, alveolar oxygen tension, oxygen uptake, and air trapping.

Science.gov (United States)

Hamedani, Hooman; Kadlecek, Stephen; Xin, Yi; Siddiqui, Sarmad; Gatens, Heather; Naji, Joseph; Ishii, Masaru; Cereda, Maurizio; Rossman, Milton; Rizi, Rahim

2017-08-01

To present a method for simultaneous acquisition of alveolar oxygen tension (P A O 2 ), specific ventilation (SV), and apparent diffusion coefficient (ADC) of hyperpolarized (HP) gas in the human lung, allowing reinterpretation of the P A O 2 and SV maps to produce a map of oxygen uptake (R). An imaging scheme was designed with a series of identical normoxic HP gas wash-in breaths to measure ADC, SV, P A O 2 , and R in less than 2 min. Signal dynamics were fit to an iterative recursive model that regionally solved for these parameters. This measurement was successfully performed in 12 subjects classified in three healthy, smoker, and chronic obstructive pulmonary disease (COPD) cohorts. The overall whole lung ADC, SV, P A O 2 , and R in healthy, smoker, and COPD subjects was 0.20 ± 0.03 cm 2 /s, 0.39 ± 0.06,113 ± 2 Torr, and 1.55 ± 0.35 Torr/s, respectively, in healthy subjects; 0.21 ± 0.03 cm 2 /s, 0.33 ± 0.06, 115.9 ± 4 Torr, and 0.97 ± 0.2 Torr/s, respectively, in smokers; and 0.25 ± 0.06 cm 2 /s, 0.23 ± 0.08, 114.8 ± 6.0Torr, and 0.94 ± 0.12 Torr/s, respectively, in subjects with COPD. Hetrogeneity of SV, P A O 2 , and R were indicators of both smoking-related changes and disease, and the severity of the disease correlated with the degree of this heterogeneity. Subjects with symptoms showed reduced oxygen uptake and specific ventilation. High-resolution, nearly coregistered and quantitative measures of lung function and structure were obtained with less than 1 L of HP gas. This hybrid multibreath technique produced measures of lung function that revealed clear differences among the cohorts and subjects and were confirmed by correlations with global lung measurements. Magn Reson Med 78:611-624, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

Tension headache.

Science.gov (United States)

Ziegler, D K

1978-05-01

Headache is an extremely common symptom, and many headaches undoubtedly have a relationship to stressful situations. The clear definition, however, of a "tension headache" complex and its differentiation from migraine in some patients is difficult. The problems are in the identification of a specific headache pattern induced by stress or "tension" and the relationship of the symptom to involuntary contraction of neck and scalp muscles. Treatment consists of analgesics and occasionally mild tranquilizers. Psychotherapy consists of reassurance and often other supportive measures, including modification of life styles. Various feedback techniques have been reported of value, but their superiority to suggestion and hypnosis is still problematic.

Adult and newborn rat inner retinal oxygenation during carbogen and 100% oxygen breathing. Comparison using magnetic resonance imaging delta Po2 mapping.

Science.gov (United States)

Berkowitz, B A

1996-09-01

To test the hypothesis that breathing carbogen (95% O2-5% CO2) oxygenates the inner retina better than breathing 100% oxygen using an magnetic resonance imaging (MRI) method that noninvasively measures inner retinal oxygenation in normal adult and newborn rats. Urethane-anesthetized adult and newborn (day 18) rats were studied. Sequential images were acquired in room air combined with either 100% oxygen or carbogen breathing. Normalized vitreous signal intensity changes were converted to oxygen tension changes (delta PO2) either on a pixel-by-pixel basis or in specific regions of interest. Systemic levels of hyperoxia during carbogen or 100% oxygen breathing were not significantly different (P > 0.05). In the adult rat, a significant difference (P = 0.017) was found in the preretinal vitreous delta PO2 during the breathing of either carbogen (130 +/- 9 mm Hg, mean +/- SEM; n = 5) or 100% oxygen (88 +/- 16 mm Hg; n = 5). Agreement was found between the MRI-determined delta PO2 values and literature oxygen microelectrodes data. In the newborn rat, significant differences (P delta PO2 were found during carbogen (164 +/- 23 mm Hg; n = 3) and oxygen breathing (91 +/- 8 mm Hg; n = 3). MRI delta PO2 mapping demonstrated for the first time that in the normal adult and newborn rat eye, carbogen breathing oxygenates the inner retina better than 100% oxygen breathing.

Tensions in Distributed Leadership

Science.gov (United States)

Ho, Jeanne; Ng, David

2017-01-01

Purpose: This article proposes the utility of using activity theory as an analytical lens to examine the theoretical construct of distributed leadership, specifically to illuminate tensions encountered by leaders and how they resolved these tensions. Research Method: The study adopted the naturalistic inquiry approach of a case study of an…

Surface tension effects on vertical upward annular flows in a small diameter pipe

Energy Technology Data Exchange (ETDEWEB)

Sadatomi, Michio, E-mail: sadatomi@mech.kumamoto-u.ac.jp [Dept. of Advanced Mechanical Systems, Kumamoto Univ., 39-1, Kurokami 2-chome, Chuou-ku, Kumamoto 860-8555 (Japan); Kawahara, Akimaro [Dept. of Advanced Mechanical Systems, Kumamoto Univ., 39-1, Kurokami 2-chome, Chuou-ku, Kumamoto 860-8555 (Japan); Suzuki, Aruta [Plant Design & Engineering Dept., Environment, Energy & Plant Headquarters, Hitachi Zosen Corporation, 7-89, Nankokita 1-chome, Suminoe-ku, Osaka, 559-8559 (Japan)

2016-12-15

Highlights: • Surface tension effects were clarified on annular flow in a small diameter pipe. • The mean liquid film thickness became thinner with decreasing of surface tension. • The liquid droplet fraction and the interfacial shear stress became higher with it. • New prediction methods for the above parameters were developed and validated. - Abstract: Experiments were conducted to study the surface tension effects on vertical upward annular flows in a 5 mm I.D. pipe using water and low surface tension water with a little surfactant as the test liquid and air as the test gas. Firstly, the experimental results on the mean liquid film thickness, the liquid droplet fraction and the interfacial shear stress in annular flows together with some flow pictures are presented to clarify the surface tension effects. From these, the followings are clarified: In the low surface tension case, the liquid film surface becomes rough, the liquid film thickness thin, the liquid droplet fraction high, and the interfacial shear stress high. Secondary, correlations in literatures for the respective parameters are tested against the present data. The test results show that no correlation for the respective parameters could predict well the present data. Thus, correlations are revised by accounting for the surface tension effects. The results of the experiments, the correlations tests and their revisions mentioned above are presented in the present paper.

A numerical study on seismic response of self-centring precast segmental columns at different post-tensioning forces

Directory of Open Access Journals (Sweden)

Ehsan Nikbakht

Full Text Available Precast bridge columns have shown increasing demand over the past few years due to the advantages of such columns when compared against conventional bridge columns, particularly due to the fact that precast bridge columns can be constructed off site and erected in a short period of time. The present study analytically investigates the behaviour of self-centring precast segmental bridge columns under nonlinear-static and pseudo-dynamic loading at different prestressing strand levels. Self-centring segmental columns are composed of prefabricated reinforced concrete segments which are connected by central post-tensioning (PT strands. The present study develops a three dimensional (3D nonlinear finite element model for hybrid post-tensioned precast segmental bridge columns. The model is subjected to constant axial loading and lateral reverse cyclic loading. The lateral force displacement results of the analysed columns show good agreement with the experimental response of the columns. Bonded post-tensioned segmental columns at 25%, 40% and 70% prestressing strand stress levels are analysed and compared with an emulative monolithic conventional column. The columns with a higher initial prestressing strand levels show greater initial stiffness and strength but show higher stiffness reduction at large drifts. In the time-history analysis, the column samples are subjected to different earthquake records to investigate the effect post-tensioning force levels on their lateral seismic response in low and higher seismicity zones. The results indicate that, for low seismicity zones, post-tensioned segmental columns with a higher initial stress level deflect lower lateral peak displacement. However, in higher seismicity zones, applying a high initial stress level should be avoided for precast segmental self-centring columns with low energy dissipation capacity.

Tension pneumocephalus: Mount Fuji sign

Directory of Open Access Journals (Sweden)

Pulastya Sanyal

2015-01-01

Full Text Available A 13-year-old male was operated for a space occupying lesion in the brain. A noncontrast computed tomography scan done in the late postoperative period showed massive subdural air collection causing compression of bilateral frontal lobes with widening of interhemispheric fissure and the frontal lobes acquiring a peak like configuration - causing tension pneumocephalus-"Mount Fuji sign." Tension pneumocephalus occurs when air enters the extradural or intradural spaces in sufficient volume to exert a mass or pressure effect on the brain, leading to brain herniation. Tension pneumocephalus is a surgical emergency, which needs immediate intervention in the form of decompression of the cranial cavity by a burr hole or needle aspiration. The Mount Fuji sign differentiates tension pneumocephalus from pneumocephalus.

Mimicking physiological O2 tension in the female reproductive tract improves Assisted Reproduction outcomes in pig.

Science.gov (United States)

García-Martínez, S; Sánchez-Hurtado, M A; Gutiérrez, H; Sánchez-Margallo, F M; Romar, R; Latorre, R; Coy, P; López-Albors, O

2018-02-27

48hpi, cleavage was evaluated under the stereomicroscope. Finally, at 180hpi, development to the blastocyst stage was quantified, blastocyst morphology was assessed, and embryos were fixed and stained to count the mean cell number per blastocyst. The mean O2 content within the pig oviduct and uterus was always lower than in ambient air. The average O2 percentage was higher in gilts (10.0%) than in sows (7.6%) (p number of cells in embryos cultured under the low O2 concentration (88.9 ± 5.9) was observed compared to those cultured under 20% O2 (59.0 ± 5.0) (p < 0.05). None. Although minimally invasive surgery was used the effect of anaesthesia and manipulations on O2 tension within the organs are unknown. Using physiological oxygen concentrations in IVF/EC could improve ART outcomes. This study was funded by Spanish Ministry of Economy and Competitiveness (MINECO) and European Regional Development Fund (FEDER). Grants AGL2012-40180-C03-01 and AGL2015-66341-R. The authors declare no conflict of interest.

Uniaxial Tension Test of Slender Reinforced Early Age Concrete Members

Directory of Open Access Journals (Sweden)

Wenbo Zhang

2011-08-01

Full Text Available The present study aims to obtain the tensile properties of early age concrete based on a uniaxial tension test employing RC slender members. First, the paper shows that concrete strain is equal to the strain of rebar at the mid-span of the RC member. The tensile Young’s modulus and the strain capacity of early age concrete are estimated using strain measurements. The experiment indicated that the tensile Young’s modulus at an early age is higher than the compressive modulus. This observation was similar to one found in a previous investigation which used a direct tension test of early age concrete. Moreover, the paper describes how an empirical equation for mature concrete can be applied to the relation between uniaxial tensile strength and splitting tensile strength even in early age concrete. Based on a uniaxial tension test, the paper proposes an empirical equation for the relationship between standard bond stresses and relative slip.

Experimental and theoretical studies of oxygen gradients in rat pial microvessels

OpenAIRE

Sharan, Maithili; Vovenko, Eugene P; Vadapalli, Arjun; Popel, Aleksander S; Pittman, Roland N

2008-01-01

Using modified oxygen needle microelectrodes and intravital videomicroscopy, measurements were made of tissue oxygen tension (PO2) profiles near cortical arterioles and transmural PO2 gradients in the pial arterioles of the rat. Under control conditions, the transmural PO2 gradient averaged 1.17 ± 0.06 mm Hg/μm (mean ± s.e., n = 40). Local arteriolar dilation resulted in a marked decrease in the transmural PO2 gradient to 0.68 ± 0.04 mm Hg/μm (P < 0.001, n = 38). The major finding of this stu...

Effects of in vitro low oxygen tension preconditioning of adipose stromal cells on their in vivo chondrogenic potential: application in cartilage tissue repair.

Directory of Open Access Journals (Sweden)

Sophie Portron

Full Text Available PURPOSE: Multipotent stromal cell (MSC-based regenerative strategy has shown promise for the repair of cartilage, an avascular tissue in which cells experience hypoxia. Hypoxia is known to promote the early chondrogenic differentiation of MSC. The aim of our study was therefore to determine whether low oxygen tension could be used to enhance the regenerative potential of MSC for cartilage repair. METHODS: MSC from rabbit or human adipose stromal cells (ASC were preconditioned in vitro in control or chondrogenic (ITS and TGF-β medium and in 21 or 5% O2. Chondrogenic commitment was monitored by measuring COL2A1 and ACAN expression (real-time PCR. Preconditioned rabbit and human ASC were then incorporated into an Si-HPMC hydrogel and injected (i into rabbit articular cartilage defects for 18 weeks or (ii subcutaneously into nude mice for five weeks. The newly formed tissue was qualitatively and quantitatively evaluated by cartilage-specific immunohistological staining and scoring. The phenotype of ASC cultured in a monolayer or within Si-HPMC in control or chondrogenic medium and in 21 or 5% O2 was finally evaluated using real-time PCR. RESULTS/CONCLUSIONS: 5% O2 increased the in vitro expression of chondrogenic markers in ASC cultured in induction medium. Cells implanted within Si-HPMC hydrogel and preconditioned in chondrogenic medium formed a cartilaginous tissue, regardless of the level of oxygen. In addition, the 3D in vitro culture of ASC within Si-HPMC hydrogel was found to reinforce the pro-chondrogenic effects of the induction medium and 5% O2. These data together indicate that although 5% O2 enhances the in vitro chondrogenic differentiation of ASC, it does not enhance their in vivo chondrogenesis. These results also highlight the in vivo chondrogenic potential of ASC and their potential value in cartilage repair.

Shape accuracy optimization for cable-rib tension deployable antenna structure with tensioned cables

Science.gov (United States)

Liu, Ruiwei; Guo, Hongwei; Liu, Rongqiang; Wang, Hongxiang; Tang, Dewei; Song, Xiaoke

2017-11-01

Shape accuracy is of substantial importance in deployable structures as the demand for large-scale deployable structures in various fields, especially in aerospace engineering, increases. The main purpose of this paper is to present a shape accuracy optimization method to find the optimal pretensions for the desired shape of cable-rib tension deployable antenna structure with tensioned cables. First, an analysis model of the deployable structure is established by using finite element method. In this model, geometrical nonlinearity is considered for the cable element and beam element. Flexible deformations of the deployable structure under the action of cable network and tensioned cables are subsequently analyzed separately. Moreover, the influence of pretension of tensioned cables on natural frequencies is studied. Based on the results, a genetic algorithm is used to find a set of reasonable pretension and thus minimize structural deformation under the first natural frequency constraint. Finally, numerical simulations are presented to analyze the deployable structure under two kinds of constraints. Results show that the shape accuracy and natural frequencies of deployable structure can be effectively improved by pretension optimization.

Spontaneous tension haemopneumothorax.

Science.gov (United States)

Patterson, Benjamin Oliver; Itam, Sarah; Probst, Fey

2008-10-31

We present a patient with sudden onset progressive shortness of breath and no history of trauma, who rapidly became haemodynamically compromised with a pneumothorax and pleural effusion seen on chest radiograph. He was treated for spontaneous tension pneumothorax but this was soon revealed to be a tension haemopneumothorax. He underwent urgent thoracotomy after persistent bleeding to explore an apical vascular abnormality seen on CT scanning. To our knowledge this is the first such case reported.Aetiology and current approach to spontaneous haemothorax are discussed briefly.

Correlation of cutaneous tension distribution and tissue oxygenation with acute external tissue expansion

Directory of Open Access Journals (Sweden)

Marquardt C

2009-11-01

Full Text Available Abstract Today, the biomechanical fundamentals of skin expansion are based on viscoelastic models of the skin. Although many studies have been conducted in vitro, analyses performed in vivo are rare. Here, we present in vivo measurements of the expansion at the skin surface as well as measurement of the corresponding intracutaneous oxygen partial pressure. In our study the average skin stretching was 24%, with a standard deviation of 11%, excluding age or gender dependency. The measurement of intracutaneous oxygen partial pressure produced strong inter-individual fluctuations, including initial values at the beginning of the measurement, as well as varying individual patient reactions to expansion of the skin. Taken together, we propose that even large defect wounds can be closed successfully using the mass displacement caused by expansion especially in areas where soft, voluminous tissue layers are present.

Silicon fertilization and soil water tensions on rice development and yield

Directory of Open Access Journals (Sweden)

Jakeline R. de Oliveira

2016-02-01

Full Text Available ABSTRACT The cultivation of upland rice (Oryza sativa in Brazil occurs mainly in the Cerrado, a region with adverse weather conditions. The use of silicon in its cultivation becomes important, since this nutrient provides higher rigidity, lower transpiration and higher resistance to dry spells in rice plants. The objective of the present study was to evaluate the effect of silicon fertilization and soil water tensions on upland rice development and yield in a Cerrado Oxisol. A 5 x 5 fractionated factorial with five soil water tensions (0, 15, 30, 45 and 60 kPa and five silicon doses (0, 120, 240, 480 and 960 mg dm-3 was used, which were distributed in a randomized block design, with four replicates. Plant height, number of tillers, number of panicles, number of grains per panicle, numbers of full and empty grains and percentage of empty grains were evaluated. Silicon fertilization promotes increased tillering in rice plants at the dose of 960 mg dm-3. The numbers of tillers and panicles decreased with the application of silicon up to the doses of 460 and 490 mg dm-3, respectively. The increase in soil water tensions reduced plant height and the number of full grains, and increased the percentage of empty grains of upland rice.

Efficiency of Photosynthesis in a Chl d-Utilizing Cyanobacterium is Comparable to or Higher than that in Chl a-Utilizing Oxygenic Species

Science.gov (United States)

Mielke, S. P.; Kiang, N. Y.; Blankenship, R. E.; Gunner, M. R.; Mauzerall, D.

2011-01-01

The cyanobacterium Acaryochloris marina uses chlorophyll d to carry out oxygenic photosynthesis in environments depleted in visible and enhanced in lower-energy, far-red light. However, the extent to which low photon energies limit the efficiency of oxygenic photochemistry in A. marina is not known. Here, we report the first direct measurements of the energy-storage efficiency of the photosynthetic light reactions in A. marina whole cells,and find it is comparable to or higher than that in typical, chlorophyll a-utilizing oxygenic species. This finding indicates that oxygenic photosynthesis is not fundamentally limited at the photon energies employed by A. marina, and therefore is potentially viable in even longer-wavelength light environments.

Spontaneous tension haemopneumothorax

Directory of Open Access Journals (Sweden)

Itam Sarah

2008-10-01

Full Text Available Abstract We present a patient with sudden onset progressive shortness of breath and no history of trauma, who rapidly became haemodynamically compromised with a pneumothorax and pleural effusion seen on chest radiograph. He was treated for spontaneous tension pneumothorax but this was soon revealed to be a tension haemopneumothorax. He underwent urgent thoracotomy after persistent bleeding to explore an apical vascular abnormality seen on CT scanning. To our knowledge this is the first such case reported. Aetiology and current approach to spontaneous haemothorax are discussed briefly.

Additive influence of extracellular pH, oxygen tension, and pressure on invasiveness and survival of human osteosarcoma cells

Directory of Open Access Journals (Sweden)

Takao eMatsubara

2013-07-01

Full Text Available BACKGROUND/PURPOSE:The effects of chemical and physical interactions in the microenvironment of solid tumors have not been fully elucidated. We hypothesized that acidosis, hypoxia, and elevated interstitial fluid pressure (eIFP have additive effects on tumor cell biology and lead to more aggressive behavior during tumor progression. We investigated this phenomenon using 3 human osteosarcoma cell lines and a novel in vitro cell culture apparatus. MATERIALS AND METHODS:U2OS, SaOS, and MG63 cell lines were cultured in media adjusted to various pH levels, oxygen tension (hypoxia 2% O2, normoxia 20% O2, and hydrostatic gauge pressure (0 or 50 mm Hg. Growth rate, apoptosis, cell cycle parameters, and expression of mRNA for proteins associated with invasiveness and tumor microenvironment (CA IX, VEGF-A, HIF-1A, MMP-9, and TIMP-2 were analyzed. Levels of CA IX, HIF-1α, and MMP-9 were measured using immunofluorescence. The effect of pH on invasiveness was evaluated in a Matrigel chamber assay.RESULTS: Within the acidic–hypoxic–pressurized conditions that simulate the microenvironment at a tumor’s center, invasive genes were upregulated, but the cell cycle was downregulated. The combined influence of acidosis, hypoxia, and IFP promoted invasiveness and angiogenesis to a greater extent than did pH, pO2, or eIFP individually. Significant cell death after brief exposure to acidic conditions occurred in each cell line during acclimation to acidic media, while prolonged exposure to acidic media resulted in reduced cell death. Furthermore, 48-hour exposure to acidic conditions promoted tumor invasiveness in the Matrigel assay. CONCLUSION: Our findings demonstrate that tumor microenvironmental parameters—particularly pH, pO2, and eIFP—additively influence tumor proliferation, invasion, metabolism, and viability to enhance cell survival.

Initial tension loss in cerclage cables.

Science.gov (United States)

Ménard, Jérémie; Émard, Maxime; Canet, Fanny; Brailovski, Vladimir; Petit, Yvan; Laflamme, George Y

2013-10-01

Cerclage cables, frequently used in the management of fractures and osteotomies, are associated with a high failure rate and significant loosening during surgery. This study compared the capacity to maintain tension of different types of orthopaedic cable systems. Multifilament Cobalt-Chrome (CoCr) cables with four different crimp/clamp devices (DePuy, Stryker, Zimmer and Smith&Nephew) and one non-metallic Nylon (Ny) cable from Kinamed were instrumented with a load cell to measure tension during insertion. Significant tension loss was observed with crimping for all cables (Ptensioner led to an additional unexpected tension loss (CoCr-DePuy: 18%, CoCr-Stryker: 29%, CoCr-Smith&Nephew: 33%, Ny: 46%, and CoCr-Zimmer: 52%). The simple CoCr (DePuy) cable system outperformed the more sophisticated locking devices due to its significantly better ability to prevent tension loss. Copyright © 2013 Elsevier Inc. All rights reserved.

The role of size in synchronous air breathing of Hoplosternum littorale.

Science.gov (United States)

Sloman, Katherine A; Sloman, Richard D; De Boeck, Gudrun; Scott, Graham R; Iftikar, Fathima I; Wood, Chris M; Almeida-Val, Vera M F; Val, Adalberto L

2009-01-01

Synchronized air breathing may have evolved as a way of minimizing the predation risk known to be associated with air breathing in fish. Little is known about how the size of individuals affects synchronized air breathing and whether some individuals are required to surface earlier than necessary in support of conspecifics, while others delay air intake. Here, the air-breathing behavior of Hoplosternum littorale held in groups or in isolation was investigated in relation to body mass, oxygen tensions, and a variety of other physiological parameters (plasma lactate, hepatic glycogen, hematocrit, hemoglobin, and size of heart, branchial basket, liver, and air-breathing organ [ABO]). A mass-specific relationship with oxygen tension of first surfacing was seen when fish were held in isolation; smaller individuals surfaced at higher oxygen tensions. However, this relationship was lost when the same individuals were held in social groups of four, where synchronous air breathing was observed. In isolation, 62% of fish first surfaced at an oxygen tension lower than the calculated P(crit) (8.13 kPa), but in the group environment this was reduced to 38% of individuals. Higher oxygen tensions at first surfacing in the group environment were related to higher levels of activity rather than any of the physiological parameters measured. In fish held in isolation but denied access to the water surface for 12 h before behavioral testing, there was no mass-specific relationship with oxygen tension at first surfacing. Larger individuals with a greater capacity to store air in their ABOs may, therefore, remain in hypoxic waters for longer periods than smaller individuals when held in isolation unless prior access to the air is prevented. This study highlights how social interaction can affect air-breathing behaviors and the importance of considering both behavioral and physiological responses of fish to hypoxia to understand the survival mechanisms they employ.

The Role of Oxygen Sensors, Hydroxylases, and HIF in Cardiac Function and Disease

Directory of Open Access Journals (Sweden)

W. H. Davin Townley-Tilson

2015-01-01

Full Text Available Ischemic heart disease is the leading cause of death worldwide. Oxygen-sensing proteins are critical components of the physiological response to hypoxia and reperfusion injury, but the role of oxygen and oxygen-mediated effects is complex in that they can be cardioprotective or deleterious to the cardiac tissue. Over 200 oxygen-sensing proteins mediate the effects of oxygen tension and use oxygen as a substrate for posttranslational modification of other proteins. Hydroxylases are an essential component of these oxygen-sensing proteins. While a major role of hydroxylases is regulating the transcription factor HIF, we investigate the increasing scope of hydroxylase substrates. This review discusses the importance of oxygen-mediated effects in the heart as well as how the field of oxygen-sensing proteins is expanding, providing a more complete picture into how these enzymes play a multifaceted role in cardiac function and disease. We also review how oxygen-sensing proteins and hydroxylase function could prove to be invaluable in drug design and therapeutic targets for heart disease.

Toward a general psychological model of tension and suspense.

Science.gov (United States)

Lehne, Moritz; Koelsch, Stefan

2015-01-01

Tension and suspense are powerful emotional experiences that occur in a wide variety of contexts (e.g., in music, film, literature, and everyday life). The omnipresence of tension and suspense suggests that they build on very basic cognitive and affective mechanisms. However, the psychological underpinnings of tension experiences remain largely unexplained, and tension and suspense are rarely discussed from a general, domain-independent perspective. In this paper, we argue that tension experiences in different contexts (e.g., musical tension or suspense in a movie) build on the same underlying psychological processes. We discuss key components of tension experiences and propose a domain-independent model of tension and suspense. According to this model, tension experiences originate from states of conflict, instability, dissonance, or uncertainty that trigger predictive processes directed at future events of emotional significance. We also discuss possible neural mechanisms underlying tension and suspense. The model provides a theoretical framework that can inform future empirical research on tension phenomena.

The impact of including spatially longitudinal heterogeneities of vessel oxygen content and vascular fraction in 3D tumor oxygenation models on predicted radiation sensitivity.

Science.gov (United States)

Lagerlöf, Jakob H; Kindblom, Jon; Bernhardt, Peter

2014-04-01

Oxygen distribution models have been used to analyze the influences of oxygen tensions on tissue response after radiotherapy. These distributions are often generated assuming constant oxygen tension in the blood vessels. However, as red blood cells progress through the vessels, oxygen is continuously released into the plasma and the surrounding tissue, resulting in longitudinally varying oxygen levels in the blood vessels. In the present study, the authors investigated whether a tumor oxygenation model that incorporated longitudinally varying oxygen levels would provide different predictions of necrotic fractions and radiosensitivity compared to commonly used models with a constant oxygen pressure. Our models simulated oxygen diffusion based on a Green's function approach and oxygen consumption according to the Michaelis-Menten equation. The authors constructed tumor models with different vascular fractions (VFs), from which they generated depth oxygenation curves and a look-up table of oxygen pressure gradients. The authors evaluated models of spherical tumors of various sizes, from 1 to 10(4) mg. The authors compared the results from a model with constant vessel oxygen (CVO) pressure to those from models with longitudinal variations in oxygen saturation and either a constant VF (CVF) or variable VF (VVF) within the tumor tissue. The authors monitored the necrotic fractions, defined as tumor regions with an oxygen pressure below 1 mmHg. Tumor radiation sensitivity was expressed as D99, the homogeneous radiation dose required for a tumor control probability of 0.99. In the CVO saturation model, no necrosis was observed, and decreasing the VF could only decrease the D99 by up to 10%. Furthermore, the D99 vs VF dependence was similar for different tumor masses. Compared to the CVO model, the extended CVF and VVF models provided clearly different results, including pronounced effects of VF and tumor size on the necrotic fraction and D99, necrotic fractions ranging

Tension type headaches: a review

African Journals Online (AJOL)

Location of the pain:There is often a typical location for tension- type headaches, as ... Cranial nerve abnormalities, including papilloedema. • Signs of ... peripheral and central mechanisms underlie tension-type ... Physiotherapy has been shown to be an effective management option for .... Acupuncture in primary headache.

Post-tensioning system surveillance program

International Nuclear Information System (INIS)

Drew, G.E.

1979-01-01

Nuclear power plant containment structure post-tensioning system tendon surveillance program is described in detail. Data collected over three yearly post-tensioning system Surveillance Programs is presented and evaluated to correlate anticipated stress losses with actual losses. In addition corrosion protected system performance is analyzed

The study and design of tension controller

Science.gov (United States)

Jun, G.; Lamei, X.

2018-02-01

Tension control is a wide used technology in areas such as textiles, paper and plastic films. In this article, the tension control system release and winding process is analyzed and the mathematical model of tension control system is established, and a high performance tension controller is designed. In hardware design, STM32F130 single chip microcomputer is used as the control core, which has the characteristics of fast running speed and rich peripheral features. In software design, μC/OS-II operating system is introduced to improve the efficiency of single chip microcomputer, and enhance the independence of each module, and make development and maintenance more convenient. The taper tension control is adopted in the winding part, which can effectively solve the problem of rolling shrinkage. The results show that the tension controller has the characteristics of simple structure, easy operation and stable performance.

End-Tidal CO2 Tension Is Predictive of Effective Nocturnal Oxygen Therapy in Patients with Chronic Heart Failure and Central Sleep Apnea.

Science.gov (United States)

Sugimura, Koichiro; Shinozaki, Tsuyoshi; Fukui, Shigefumi; Ogawa, Hiromasa; Shimokawa, Hiroaki

2016-05-01

Central sleep apnea (CSA) is characterized by recurring cycles of crescendo-decrescendo ventilation during sleep, and enhances sympathetic nerve activity. Thus CSA has a prognostic impact in patients with chronic heart failure (CHF). Although nocturnal oxygen (O2) therapy decreases frequency of CSA and improves functional exercise capacity, it is also known that some non-responders to the therapy exist. We thus aimed to identify predictors of responders to nocturnal O2 therapy in CHF patients with CSA. In 12 CHF patients with CSA hospitalized at our department, sleep study was performed at 2 consecutive nights. Patients nasally inhaled O2 at either the first or second night in a randomized manner. To predict the percentage reduction in apnea-hypopnea index (%ΔAHI) in response to the nocturnal O2 therapy, we performed multiple regression analysis with a stepwise method with variables including age, brain-natriuretic peptide, circulation time, baseline AHI, hypercapnic ventilatory response and end-tidal carbon dioxide tension (PETCO2). Nocturnal O2 therapy significantly decreased AHI (from 32 ± 13 /h to 12 ± 10 /h, P 50% reduction of AHI), with 88.9% of sensitivity and 66.7% of specificity. In conclusion, PETCO2 is useful to predict the efficacy of O2 therapy in CHF patients with CSA, providing important information to the current nocturnal O2 therapy.

Tension and robustness in multitasking cellular networks.

Directory of Open Access Journals (Sweden)

Jeffrey V Wong

Full Text Available Cellular networks multitask by exhibiting distinct, context-dependent dynamics. However, network states (parameters that generate a particular dynamic are often sub-optimal for others, defining a source of "tension" between them. Though multitasking is pervasive, it is not clear where tension arises, what consequences it has, and how it is resolved. We developed a generic computational framework to examine the source and consequences of tension between pairs of dynamics exhibited by the well-studied RB-E2F switch regulating cell cycle entry. We found that tension arose from task-dependent shifts in parameters associated with network modules. Although parameter sets common to distinct dynamics did exist, tension reduced both their accessibility and resilience to perturbation, indicating a trade-off between "one-size-fits-all" solutions and robustness. With high tension, robustness can be preserved by dynamic shifting of modules, enabling the network to toggle between tasks, and by increasing network complexity, in this case by gene duplication. We propose that tension is a general constraint on the architecture and operation of multitasking biological networks. To this end, our work provides a framework to quantify the extent of tension between any network dynamics and how it affects network robustness. Such analysis would suggest new ways to interfere with network elements to elucidate the design principles of cellular networks.

A theoretical evaluation of the oxygen concentration in a corrosion-fatigue crack

International Nuclear Information System (INIS)

Turnbull, A.

1981-01-01

The oxygen concentration in a corrosion-fatigue crack has been evaluated theoretically by assuming that oxygen was consumed by cathodic reduction on the walls of the crack and mass transport occurred by diffusion and advection (forced convection), with the latter resulting from the sinusoidal variation of the displacement of the crack walls. By using parameters relevant to a compact tension specimen, the time-dependent distribution of the oxygen concentration in the crack was calculated as a function of ΔK (the range of the stress intensity factor), R-value (minimum load/maximum load), frequency, crack length, and electrode potential. The influence of advection was to significantly enhance the mass transport of oxygen in the crack compared with ''diffusion-only'' even at low frequencies and low ΔK. Regions in the crack were identified in which advection dominance or diffusion dominance of the mass transport of oxygen occurred

Mentoring Preservice Teachers: Identifying Tensions and Possible Resolutions

Science.gov (United States)

Hudson, Peter; Hudson, Sue

2018-01-01

Tensions can occur in the mentor-mentee relationship during school-based professional experiences that require problem solving. What are the tensions for mentor teachers in preservice teacher education and how might these tensions be resolved? This qualitative study collected data from 31 high school mentor teachers about tensions experienced with…

The difference in passive tension applied to the muscles composing the hamstrings - Comparison among muscles using ultrasound shear wave elastography.

Science.gov (United States)

Nakamura, Masatoshi; Hasegawa, Satoshi; Umegaki, Hiroki; Nishishita, Satoru; Kobayashi, Takuya; Fujita, Kosuke; Tanaka, Hiroki; Ibuki, Satoko; Ichihashi, Noriaki

2016-08-01

Hamstring muscle strain is one of the most common injuries in sports. Therefore, to investigate the factors influencing hamstring strain, the differences in passive tension applied to the hamstring muscles at the same knee and hip positions as during terminal swing phase would be useful information. In addition, passive tension applied to the hamstrings could change with anterior or posterior tilt of the pelvis. The aims of this study were to investigate the difference in passive tension applied to the individual muscles composing the hamstrings during passive elongation, and to investigate the effect of pelvic position on passive tension. Fifteen healthy men volunteered for this study. The subject lay supine with the angle of the trunk axis to the femur of their dominant leg at 70° and the knee angle of the dominant leg fixed at 30° flexion. In three pelvic positions ("Non-Tilt", "Anterior-Tilt" and "Posterior-Tilt"), the shear elastic modulus of each muscle composing the hamstrings (semitendinosus, semimembranosus, and biceps femoris) was measured using an ultrasound shear wave elastography. The shear elastic modulus of semimembranosus was significantly higher than the others. Shear elastic modulus of the hamstrings in Anterior-Tilt was significantly higher than in Posterior-Tilt. Passive tension applied to semimembranosus is higher than the other muscles when the hamstring muscle is passively elongated, and passive tension applied to the hamstrings increases with anterior tilt of the pelvis. Copyright © 2016 Elsevier Ltd. All rights reserved.

Delayed Tension Pneumothorax - Identification and Treatment in Traumatic Bronchial Injury: An Interesting Presentation.

Science.gov (United States)

Gupta, Amit; Rattan, Amulya; Kumar, Sunil; Rathi, Vinita

2017-09-01

A 13-year-old girl, who did not receive any treatment for few hours following Road Traffic Injury (RTI), reported to the Casualty Department and found to have patent airway with clinically normal C spine, air-hunger (RR 42/minute), trachea deviated to left, distended neck veins and absent breath sounds on the right side. The chest X-ray she carried, done immediately after the injury, showed right sided tension pneumothorax. She was put on oxygen at 11 L/minute and an Intercostal chest tube drainage (ICD) was inserted on right side. Her oxygen saturation (40%) failed to improve. ICD bag showed continuous bubbling and air entry remained absent on the right side. An urgent right thoracotomy was done which revealed right main bronchus tear; the tear was repaired using interrupted Prolene ® sutures. Patient recovered well and was discharged 10 days later in a stable condition.

Comparison Between Cerebral Tissue Oxygen Tension and Energy Metabolism in Experimental Subdural Hematoma

DEFF Research Database (Denmark)

Nielsen, Troels Halfeld; Engell, Susanne I; Johnsen, Rikke Aagaard

2011-01-01

BACKGROUND: An experimental swine model (n = 7) simulating an acute subdural hematoma (ASDH) was employed (1) to explore the relation between the brain tissue oxygenation (PbtO(2)) and the regional cerebral energy metabolism as obtained by microdialysis, and (2) to define the lowest level of PbtO(2...

Whole-brain blood flow and oxygen metabolism in the rat after halothane anesthesia

Energy Technology Data Exchange (ETDEWEB)

Gjedde, A; Hindfeldt, B [Cerebrovascular Research Center, Department of Neurology, The New York Hospital-Cornell Medical Center, New York, U.S.A.; Department of Neurology, University Hospital, Lund, Sweden)

1975-01-01

A recent modification of the Kety-Schmidt wash-out technique for /sup 133/xenon was used to measure whole-brain flow (CBF) and oxygen consumption (CMRsub(o2)) 1 to 4 hours after termination of halothane anesthesia in 15 Wistar rats. In this 3-hour experimental period, mean CBF and CMRsub(o2) were reduced to 29 and 43 percent of control values, respectively. CBF and CMRsub(o2) determined at the beginning and end of the experimental period were not significantly different from each other. Cerebral venous O/sub 2/ tension was significantly higher than in the control group, supporting recent suggestions of a primary, intrinsic effect of halothane on the homeostatic control of this variable. It is concluded that halothane is not useful for cerebral metabolic studies in the rat.

Detection of cerebral arterial gas embolism using regional cerebral oxygen saturation, quantitative electroencephalography, and brain oxygen tension in the swine

NARCIS (Netherlands)

Weenink, R. P.; Hollmann, M. W.; Stevens, M. F.; Kager, J.; van Gulik, T. M.; van Hulst, R. A.

2014-01-01

Cerebral air emboli occur as a complication of invasive medical procedures. The sensitivity of cerebral monitoring methods for the detection of air emboli is not known. This study investigates the utility of electroencephalography and non-invasively measured cerebral oxygen saturation in the

Perceiving the affordance of string tension for power strokes in badminton: expertise allows effective use of all string tensions.

Science.gov (United States)

Zhu, Qin

2013-01-01

Affordances mean opportunities for action. These affordances are important for sports performance and relevant to the abilities developed by skilled athletes. In racquet sports such as badminton, different players prefer widely different string tension because it is believed to provide opportunities for effective strokes. The current study examined whether badminton players can perceive the affordance of string tension for power strokes and whether the perception of affordance itself changed as a function of skill level. The results showed that string tension constrained the striking performance of both novice and recreational players, but not of expert players. When perceptual capability was assessed, perceptual mode did not affect perception of the optimal string tension. Skilled players successfully perceived the affordance of string tension, but only experts were concerned about saving energy. Our findings demonstrated that perception of the affordance of string tension in badminton was determined by action abilities. Furthermore, experts could adjust the action to maintain a superior level of performance based on the perception of affordance.

Composite resin reinforced with pre-tensioned fibers: a three-dimensional finite element study on stress distribution.

Science.gov (United States)

Jie, Lin; Shinya, Akikazu; Lassila, Lippo V J; Vallittu, Pekka K

2013-01-01

Pre-tensioned construction material is utilized in engineering applications of high strength demands. The purpose of this study was to evaluate the effect of the pre-tensioning fibers of fiber-reinforced composite (FRC) using three-dimensional finite element (FE) analysis. The 3D FE models of particulate composite resin (CR), FRC and composite resin reinforced with pre-tensioned fibers (PRE-T-FRC) were constructed. The uniaxial three-point bending test was simulated using FE analysis to calculate the principal stress distribution. In the FRC and PRE-T-FRC, stresses were higher than CR, and they were located in the fiber. However, the maximum principal stress value at the composite of PRE-T-FRC was lower than the FRC and CR. Composite resin reinforced with pre-tensioned fibers was advantageous for stress distribution and lowering the stress at the composite itself. Experimental studies on physical properties of pre-tensioned FRC are encouraged to be conducted.

The partial pressure of oxygen affects biomarkers of oxidative stress in cultured rainbow trout (Oncorhynchus mykiss) hepatocytes.

Science.gov (United States)

Finne, E F; Olsvik, P A; Berntssen, M H G; Hylland, K; Tollefsen, K E

2008-09-01

Oxidative stress, the imbalance between production of reactive oxygen species and the cellular detoxification of these reactive compounds, is believed to be involved in the pathology of various diseases. Several biomarkers for oxidative stress have been proposed to serve as tools in toxicological and ecotoxicological research. Not only may exposure to various pro-oxidants create conditions of cellular oxidative stress, but hyperoxic conditions may also increase the production of reactive oxygen species. The objective of the current study was to determine the extent to which differences in oxygen partial pressure would affect biomarkers of oxidative stress in a primary culture of hepatocytes from rainbow trout (Oncorhynchus mykiss). Membrane integrity, metabolic activity, levels of total and oxidized glutathione (tGSH/GSSG) was determined, as well as mRNA expression levels of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), glutathione reductase (GSSG-R), gamma-glutamyl-cystein synthetase (GCS) and thioredoxin (TRX). The results show that different biomarkers of oxidative stress are affected when the cell culture is exposed to atmospheric oxygen, and that changes such as increased GSSG content and induction of GSSG-R and GSH-Px can be reduced by culturing the cells under lower oxygen tension. Oxygen tension may thus influence results of in vitro based cell research and is particularly important when assessing parameters in the antioxidant defence system. Further research is needed to establish the magnitude of this effect in different cellular systems.

Tension waves in tethered satellite cables

Science.gov (United States)

Lallman, F. J.

1984-01-01

A one-degree-of-freedom simulation of the Tethered Satellite System (TSS) was programmed using a distributed system model of the tether based on the one-dimensional wave equation. This model represents the time varying tension profile along the tether as the sum of two traveling waves of tension moving in opposite directions. A control loop was devised which combines a deployment rate command with the measured tension at the deployer to produce a smooth, stable rate of deployment of the subsatellite. Simulation results show a buildup of periodic bursts of high frequency oscillation in tension. This report covers the mathematical modelling and simulation results and explains the reason for the observed oscillations. The design of a possible vibration damping device is discussed.

Modeling and experimental methods to predict oxygen distribution in bone defects following cell transplantation.

Science.gov (United States)

Heylman, Christopher M; Santoso, Sharon; Krebs, Melissa D; Saidel, Gerald M; Alsberg, Eben; Muschler, George F

2014-04-01

We have developed a mathematical model that allows simulation of oxygen distribution in a bone defect as a tool to explore the likely effects of local changes in cell concentration, defect size or geometry, local oxygen delivery with oxygen-generating biomaterials (OGBs), and changes in the rate of oxygen consumption by cells within a defect. Experimental data for the oxygen release rate from an OGB and the oxygen consumption rate of a transplanted cell population are incorporated into the model. With these data, model simulations allow prediction of spatiotemporal oxygen concentration within a given defect and the sensitivity of oxygen tension to changes in critical variables. This information may help to minimize the number of experiments in animal models that determine the optimal combinations of cells, scaffolds, and OGBs in the design of current and future bone regeneration strategies. Bone marrow-derived nucleated cell data suggest that oxygen consumption is dependent on oxygen concentration. OGB oxygen release is shown to be a time-dependent function that must be measured for accurate simulation. Simulations quantify the dependency of oxygen gradients in an avascular defect on cell concentration, cell oxygen consumption rate, OGB oxygen generation rate, and OGB geometry.

Influence of copper high-tension lines on plants and soils

Energy Technology Data Exchange (ETDEWEB)

Kraal, H.; Ernst, W.

1976-09-01

The copper contents of plants and soils were determined in relation to the distance from copper high-tension lines. In the vicinity of the cables clayey and fenny soils had demonstrably higher copper contents, due to corrosion of the cables, than regions 20 m and more outside the high-tension lines. On these soils, however, copper accumulation in the plants was low in comparison with those from a sandy soil, although this soil itself showed no copper increase in relation to the cables. The contaminated plants may present a risk of poisoning for sheep within a 20 m distance on both sides of the cables. No changes in plant species composition and in the copper tolerance of Agrostis tenuis were observed.

Vented versus unvented chest seals for treatment of pneumothorax and prevention of tension pneumothorax in a swine model.

Science.gov (United States)

Kheirabadi, Bijan S; Terrazas, Irasema B; Koller, Alexandra; Allen, Paul B; Klemcke, Harold G; Convertino, Victor A; Dubick, Michael A; Gerhardt, Robert T; Blackbourne, Lorne H

2013-07-01

Unvented chest seals (CSs) are currently recommended for the management of penetrating thoracic injuries in the battlefield. Since no supporting data exist, we compared the efficacy of a preferred unvented with that of a vented CS in a novel swine model of pneumothorax (PTx). An open chest wound was created in the left thorax of spontaneously air-breathing anesthetized pigs (n = 8). A CS was applied over the injury, then tension PTx was induced by incremental air injections (0.2 L) into the pleural cavity via a cannula that was also used to measure intrapleural pressure (IP). Both CS were tested on each pig in series. Tidal volume (V(T)), respiratory rate, IP, heart rate, mean arterial pressure, cardiac output, central venous pressure, pulmonary arterial pressure, venous and peripheral oxygen saturations (SvO2, SpO2) were recorded. Tension PTx was defined as a mean IP equal to or greater than +1 mm Hg plus significant (20-30%) deviation in baseline levels of the previously mentioned parameters and confirmed by chest x-ray study. PaO2 and PaCo2 were also measured. PTx produced immediate breathing difficulty and significant rises in IP and pulmonary arterial pressure and falls in V(T), SpO2, and SvO2. Both CSs returned these parameters to near baseline within 5 minutes of application. After vented CS was applied, serial air injections up to 2 L resulted in no significant change in the previously mentioned parameters. After unvented CS application, progressive deterioration of all respiratory parameters and onset of tension PTx were observed in all subjects after approximately 1.4-L air injection. Both vented and unvented CSs provided immediate improvements in breathing and blood oxygenation in our model of penetrating thoracic trauma. However, in the presence of ongoing intrapleural air accumulation, the unvented CS led to tension PTx, hypoxemia, and possible respiratory arrest, while the vented CS prevented these outcomes.

Effects of acetazolamide on cerebral blood flow and brain tissue oxygenation

DEFF Research Database (Denmark)

Lassen, N A; Friberg, L; Kastrup, J

1987-01-01

Oral administration of 1 g of acetazolamide to 8 normal subjects studied at sea level and in normoxia caused an acute increase in cerebral blood flow (CBF). During the subsequent prolonged oral treatment with 1 g of acetazolamide daily, CBF returned to normal within 2 days. The alveolar CO2 tension...... decreased gradually to 70% of the control value, indicating hyperventilation. At sea level hyperventilation will not increase brain oxygenation significantly in normal man, as the arterial oxygen content only increases minimally, while CBF is unchanged. At high altitude the beneficial effects...... of acetazolamide on the symptoms of acute mountain sickness may well be due to an improved oxygen supply to the brain, as hyperventilation will, at the low ambient PO2, cause a significant increase of the arterial oxygen content, while CBF presumably is unaffected by the drug. During hypoxia at high altitude...

Effects of whole body UV-irradiation on oxygen delivery from the erythrocyte

International Nuclear Information System (INIS)

Humpeler, E.; Mairbaeurl, H.; Hoenigsmann, H.

1982-01-01

In 16 healthy caucasian volunteers (mean age: 22.2 years) the influence of whole body UV-irradiation on the oxygen transport properties of erythrocytes was investigated. Four hours after irradiation with UV (using the minimal erythema dose, MED) no variation of haemoglobin concentration, hematocrit, mean corpuscular haemoglobin concentration, pH or standard bicarbonate could be found, whereas inorganic plasma phosphate (Psub(i)), calcium, the intraerythrocytic 2,3-diphosphoglycerate (2,3-DPG), the activity of erythrocytic phosphofructokinase (PFK) and pyruvatekinase (PK) increased significantly. The half saturation tension of oxygen (P 50 -value) tended to increase. The increase of Psub(i) causes - via a stimulation of the glycolytic pathway - an increase in 2,3-DPG concentration and thus results in a shift of the oxygen dissociation curve. It is therefore possible to enhance tissue oxygenation by whole body UV-irradiation. (orig.)

Low Oxygen Modulates Multiple Signaling Pathways, Increasing Self-Renewal, While Decreasing Differentiation, Senescence, and Apoptosis in Stromal MIAMI Cells

Science.gov (United States)

Rios, Carmen; D'Ippolito, Gianluca; Curtis, Kevin M.; Delcroix, Gaëtan J.-R.; Gomez, Lourdes A.; El Hokayem, Jimmy; Rieger, Megan; Parrondo, Ricardo; de las Pozas, Alicia; Perez-Stable, Carlos; Howard, Guy A.

2016-01-01

Human bone marrow multipotent mesenchymal stromal cell (hMSC) number decreases with aging. Subpopulations of hMSCs can differentiate into cells found in bone, vasculature, cartilage, gut, and other tissues and participate in their repair. Maintaining throughout adult life such cell subpopulations should help prevent or delay the onset of age-related degenerative conditions. Low oxygen tension, the physiological environment in progenitor cell-rich regions of the bone marrow microarchitecture, stimulates the self-renewal of marrow-isolated adult multilineage inducible (MIAMI) cells and expression of Sox2, Nanog, Oct4a nuclear accumulation, Notch intracellular domain, notch target genes, neuronal transcriptional repressor element 1 (RE1)-silencing transcription factor (REST), and hypoxia-inducible factor-1 alpha (HIF-1α), and additionally, by decreasing the expression of (i) the proapoptotic proteins, apoptosis-inducing factor (AIF) and Bak, and (ii) senescence-associated p53 expression and β-galactosidase activity. Furthermore, low oxygen increases canonical Wnt pathway signaling coreceptor Lrp5 expression, and PI3K/Akt pathway activation. Lrp5 inhibition decreases self-renewal marker Sox2 mRNA, Oct4a nuclear accumulation, and cell numbers. Wortmannin-mediated PI3K/Akt pathway inhibition leads to increased osteoblastic differentiation at both low and high oxygen tension. We demonstrate that low oxygen stimulates a complex signaling network involving PI3K/Akt, Notch, and canonical Wnt pathways, which mediate the observed increase in nuclear Oct4a and REST, with simultaneous decrease in p53, AIF, and Bak. Collectively, these pathway activations contribute to increased self-renewal with concomitant decreased differentiation, cell cycle arrest, apoptosis, and/or senescence in MIAMI cells. Importantly, the PI3K/Akt pathway plays a central mechanistic role in the oxygen tension-regulated self-renewal versus osteoblastic differentiation of progenitor cells. PMID:27059084

Influence of oxygen levels on chondrogenesis of porcine mesenchymal stem cells cultured in polycaprolactone scaffolds.

Science.gov (United States)

Rodenas-Rochina, Joaquin; Kelly, Daniel J; Gómez Ribelles, Jose Luis; Lebourg, Myriam

2017-06-01

Chondrogenesis of mesenchymal stem cells (MSCs) is known to be regulated by a number of environmental factors, including local oxygen levels. The hypothesis of this study is that the response of MSCs to hypoxia is dependent on the physical and chemical characteristics of the substrate used. The objective of this study was to explore how different modifications to polycaprolactone (PCL) scaffolds influenced the response of MSCs to hypoxia. PCL, PCL-hyaluronic acid (HA), and PCL-Bioglass ® (BG) scaffolds were seeded with MSCs derived from bone marrow and cultured for 35 days under normoxic or low oxygen conditions, and the resulting biochemical properties of the MSC laden construct were assessed. Low oxygen tension has a positive effect over cell proliferation and macromolecules biosynthesis. Furthermore, hypoxia enhanced the distribution of collagen and glycosaminoglycans (GAGs) deposition through the scaffold. On the other hand, MSCs displayed certain material dependent responses to hypoxia. Low oxygen tension had a positive effect on cell proliferation in BG and HA scaffolds, but only a positive effect on GAGs synthesis in PCL and HA scaffolds. In conclusion, hypoxia increased cell viability and expression of chondrogenic markers but the cell response was modulated by the type of scaffold used. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1684-1691, 2017. © 2017 Wiley Periodicals, Inc.

Urinary incontinence - tension-free vaginal tape

Science.gov (United States)

... ency/article/007377.htm Urinary incontinence - tension-free vaginal tape To use the sharing features on this page, please enable JavaScript. Placement of tension-free vaginal tape is surgery to help control stress urinary ...

Oxygen distribution in tumors: A qualitative analysis and modeling study providing a novel Monte Carlo approach

International Nuclear Information System (INIS)

Lagerlöf, Jakob H.; Kindblom, Jon; Bernhardt, Peter

2014-01-01

end, due to anoxia, but smaller tumors showed undisturbed oxygen distributions. The six different models with correlated parameters generated three classes of oxygen distributions. The first was a hypothetical, negative covariance between vessel proximity and pO 2 (VPO-C scenario); the second was a hypothetical positive covariance between vessel proximity and pO 2 (VPO+C scenario); and the third was the hypothesis of no correlation between vessel proximity and pO 2 (UP scenario). The VPO-C scenario produced a distinctly different oxygen distribution than the two other scenarios. The shape of the VPO-C scenario was similar to that of the nonvariable DOC model, and the larger the tumor, the greater the similarity between the two models. For all simulations, the mean oxygen tension decreased and the hypoxic fraction increased with tumor size. The absorbed dose required for definitive tumor control was highest for the VPO+C scenario, followed by the UP and VPO-C scenarios. Conclusions: A novel MC algorithm was presented which simulated oxygen distributions and radiation response for various biological parameter values. The analysis showed that the VPO-C scenario generated a clearly different oxygen distribution from the VPO+C scenario; the former exhibited a lower hypoxic fraction and higher radiosensitivity. In future studies, this modeling approach might be valuable for qualitative analyses of factors that affect oxygen distribution as well as analyses of specific experimental and clinical situations

On Surface Tension for Compact Stars R. Sharma & S. D. Maharaj

Indian Academy of Sciences (India)

Abstract. In an earlier analysis it was demonstrated that general rel- ativity gives higher values of surface tension in strange stars with quark matter than neutron stars.We generate the modified Tolman–Oppenheimer–. Volkoff equation to incorporate anisotropic matter and use this to show that pressure anisotropy provides ...

Damage development in woven fabric composites during tension-tension fatigue

DEFF Research Database (Denmark)

Hansen, U.

1999-01-01

of the operating fatigue damage mechanism(s). Fatigue leads to a degradation of material properties. Consequently, in connection with impact induced local stress raisers, fatigue produces continuously changing non-uniform stress fields because of stress redistribution effects. Other models addressing evolution...... of fatigue damage in composite materials have not been able to simulate evolving nonuniform stress fields. Therefore. in the second part of this paper, an analytical/numerical approach capable of addressing these issues is also proposed.......Impacted woven fabric composites were tested in tension-tension fatigue. In contrast to results from static testing, the effects of low energy impact damage in a fatigue environment were found to be the critical element leading to failure of the specimen. This difference emphasizes the need...

The Effect of String Tension Variation on the Perceived Pitch of a Classical Guitar

Directory of Open Access Journals (Sweden)

Wanda Jadwiga Lewis

2014-09-01

Full Text Available Actual motion of a vibrating guitar string is a superposition of many possible shapes (modes in which it could vibrate. Each of these modes has a corresponding frequency, and the lowest frequency is associated with a shape idealised as a single wave, referred to as the fundamental mode. The other contributing modes, each with their own progressively higher frequency, are referred to as overtones, or harmonics. By attaching a string to a medium (a soundboard capable of a response to the vibrating string, sound waves are generated. The sound heard is dominated by the fundamental mode, ‘coloured’ by contributions from the overtones, as explained by the classical theory of vibration. The classical theory, however, assumes that the string tension remains constant during vibration, and this cannot be strictly true; when considering just the fundamental mode, string tension will reach two maximum changes, as it oscillates up and down. These changes, occurring twice during the fundamental period match the frequency of the octave higher, 1st overtone. It is therefore plausible to think that the changing tension effect, through increased force on the bridge and, therefore, greater soundboard deflection, could be amplifying the colouring effect of (at least the 1st overtone. In this paper, we examine the possible influence of string tension variation on tonal response of a classical guitar. We use a perturbation model based on the classical result for a string in general vibration in conjunction with a novel method of assessment of plucking force that incorporates the engineering concept of geometric stiffness, to assess the magnitude of the normal force exerted by the string on the bridge. The results of our model show that the effect of tension variation is significantly smaller than that due to the installed initial static tension, and affects predominantly the force contribution arising from the fundamental mode. We, therefore, conclude that string

Synthesis of ZnO nanoparticles for oil-water interfacial tension reduction in enhanced oil recovery

Science.gov (United States)

Soleimani, Hassan; Baig, Mirza Khurram; Yahya, Noorhana; Khodapanah, Leila; Sabet, Maziyar; Demiral, Birol M. R.; Burda, Marek

2018-02-01

Nanoparticles show potential use in applications associated with upstream oil and gas engineering to increase the performance of numerous methods such as wettability alteration, interfacial tension reduction, thermal conductivity and enhanced oil recovery operations. Surface tension optimization is an important parameter in enhanced oil recovery. Current work focuses on the new economical method of surface tension optimization of ZnO nanofluids for oil-water interfacial tension reduction in enhanced oil recovery. In this paper, zinc oxide (ZnO) nanocrystallites were prepared using the chemical route and explored for enhanced oil recovery (EOR). Adsorption of ZnO nanoparticles (NPs) on calcite (111) surface was investigated using the adsorption locator module of Materials Studio software. It was found that ZnO nanoparticles show maximum adsorption energy of - 253 kcal/mol. The adsorption of ZnO on the rock surface changes the wettability which results in capillary force reduction and consequently increasing EOR. The nanofluids have been prepared by varying the concentration of ZnO nanoparticles to find the optimum value for surface tension. The surface tension (ST) was calculated with different concentration of ZnO nanoparticles using the pendant drop method. The results show a maximum value of ST 35.57 mN/m at 0.3 wt% of ZnO NPs. It was found that the nanofluid with highest surface tension (0.3 wt%) resulted in higher recovery efficiency. The highest recovery factor of 11.82% at 0.3 wt% is due to the oil/water interfacial tension reduction and wettability alteration.

No oxygen delivery limitation in hepatic encephalopathy

DEFF Research Database (Denmark)

Gjedde, Albert; Keiding, Susanne; Vilstrup, Hendrik

2010-01-01

to choose between cause and effect in three groups of volunteers, including healthy control subjects (HC), patients with cirrhosis of the liver without hepatic encephalopathy (CL), and patients with cirrhosis with acute hepatic encephalopathy. Compared to HC subjects, blood flow and energy metabolism had......Hepatic encephalopathy is a condition of reduced brain functioning in which both blood flow and brain energy metabolism declined. It is not known whether blood flow or metabolism is the primary limiting factor of brain function in this condition. We used calculations of mitochondrial oxygen tension...

Direct measurement of local oxygen concentration in the bone marrow of live animals

Science.gov (United States)

Spencer, Joel A.; Ferraro, Francesca; Roussakis, Emmanuel; Klein, Alyssa; Wu, Juwell; Runnels, Judith M.; Zaher, Walid; Mortensen, Luke J.; Alt, Clemens; Turcotte, Raphaël; Yusuf, Rushdia; Côté, Daniel; Vinogradov, Sergei A.; Scadden, David T.; Lin, Charles P.

2014-04-01

Characterization of how the microenvironment, or niche, regulates stem cell activity is central to understanding stem cell biology and to developing strategies for the therapeutic manipulation of stem cells. Low oxygen tension (hypoxia) is commonly thought to be a shared niche characteristic in maintaining quiescence in multiple stem cell types. However, support for the existence of a hypoxic niche has largely come from indirect evidence such as proteomic analysis, expression of hypoxia inducible factor-1α (Hif-1α) and related genes, and staining with surrogate hypoxic markers (for example, pimonidazole). Here we perform direct in vivo measurements of local oxygen tension (pO2) in the bone marrow of live mice. Using two-photon phosphorescence lifetime microscopy, we determined the absolute pO2 of the bone marrow to be quite low (hypoxic as it is perfused with small arteries that are often positive for the marker nestin. These pO2 values change markedly after radiation and chemotherapy, pointing to the role of stress in altering the stem cell metabolic microenvironment.

[Observation on changes of oxygen partial pressure in the deep tissues along the large intestine meridian during acupuncture in healthy subjects].

Science.gov (United States)

Chen, Ming; Hu, Xiang-long; Wu, Zu-xing

2010-06-01

To observe changes of the partial oxygen pressure in the deep tissues along the Large Intestine Meridian (LIM) during acupuncture stimulation, so as to reveal the characteristics of energy metabolism in the tissues along the LIM. Thirty-one healthy volunteer subjects were enlisted in the present study. Partial oxygen pressure (POP) in the tissues (at a depth of about 1.5 cm) of acupoints Binao (LI 14), Shouwuli (LI 13), Shousanli (LI 10), 2 non-acupoints [the midpoints between Quchi (LI 11) and LI 14, and between Yangxi (LI 5) and LI 11) of the LIM, and 10 non-meridian points, 1.5-2.0 cm lateral and medial to each of the tested points of the LIM was detected before, during and after electroacupuncture (EA) stimulation of Hegu (LI 4) by using a tissue oxygen tension needle-like sensor. In normal condition, the POP values in the deep tissues along the LIM were significantly higher than those of the non-meridian control points on its bilateral sides. During and after EA of Hegu (LI 4), the POP levels decreased significantly in the deep tissues along the LIM in comparison with pre-EA (P 0.05). POP is significantly higher in the deep tissues along the LIM of healthy subjects under normal conditions, which can be downregulated by EA of Hegu (LI 4), suggesting an increase of both the utilization rate of oxygen and energy metabolism after EA.

Assessment and reduction of diaphragmatic tension during hiatal hernia repair.

Science.gov (United States)

Bradley, Daniel Davila; Louie, Brian E; Farivar, Alexander S; Wilshire, Candice L; Baik, Peter U; Aye, Ralph W

2015-04-01

During hiatal hernia repair there are two vectors of tension: axial and radial. An optimal repair minimizes the tension along these vectors. Radial tension is not easily recognized. There are no simple maneuvers like measuring length that facilitate assessment of radial tension. The aims of this project were to: (1) establish a simple intraoperative method to evaluate baseline tension of the diaphragmatic hiatal muscle closure; and, (2) assess if tension is reduced by relaxing maneuvers and if so, to what degree. Diaphragmatic characteristics and tension were assessed during hiatal hernia repair with a tension gage. We compared tension measured after hiatal dissection and after relaxing maneuvers were performed. Sixty-four patients (29 M:35F) underwent laparoscopic hiatal hernia repair. Baseline hiatal width was 2.84 cm and tension 13.6 dag. There was a positive correlation between hiatal width and tension (r = 0.55) but the strength of association was low (r (2) = 0.31). Four different hiatal shapes (slit, teardrop, "D", and oval) were identified and appear to influence tension and the need for relaxing incision. Tension was reduced by 35.8 % after a left pleurotomy (12 patients); by 46.2 % after a right crural relaxing incision (15 patients); and by 56.1 % if both maneuvers were performed (6 patients). Tension on the diaphragmatic hiatus can be measured with a novel device. There was a limited correlation with width of the hiatal opening. Relaxing maneuvers such as a left pleurotomy or a right crural relaxing incision reduced tension. Longer term follow-up will determine whether outcomes are improved by quantifying and reducing radial tension.

MR Imaging-derived Oxygen-Hemoglobin Dissociation Curves and Fetal-Placental Oxygen-Hemoglobin Affinities.

Science.gov (United States)

Avni, Reut; Golani, Ofra; Akselrod-Ballin, Ayelet; Cohen, Yonni; Biton, Inbal; Garbow, Joel R; Neeman, Michal

2016-07-01

Purpose To generate magnetic resonance (MR) imaging-derived, oxygen-hemoglobin dissociation curves and to map fetal-placental oxygen-hemoglobin affinity in pregnant mice noninvasively by combining blood oxygen level-dependent (BOLD) T2* and oxygen-weighted T1 contrast mechanisms under different respiration challenges. Materials and Methods All procedures were approved by the Weizmann Institutional Animal Care and Use Committee. Pregnant mice were analyzed with MR imaging at 9.4 T on embryonic days 14.5 (eight dams and 58 fetuses; imprinting control region ICR strain) and 17.5 (21 dams and 158 fetuses) under respiration challenges ranging from hyperoxia to hypoxia (10 levels of oxygenation, 100%-10%; total imaging time, 100 minutes). A shorter protocol with normoxia to hyperoxia was also performed (five levels of oxygenation, 20%-100%; total imaging time, 60 minutes). Fast spin-echo anatomic images were obtained, followed by sequential acquisition of three-dimensional gradient-echo T2*- and T1-weighted images. Automated registration was applied to align regions of interest of the entire placenta, fetal liver, and maternal liver. Results were compared by using a two-tailed unpaired Student t test. R1 and R2* values were derived for each tissue. MR imaging-based oxygen-hemoglobin dissociation curves were constructed by nonlinear least square fitting of 1 minus the change in R2*divided by R2*at baseline as a function of R1 to a sigmoid-shaped curve. The apparent P50 (oxygen tension at which hemoglobin is 50% saturated) value was derived from the curves, calculated as the R1 scaled value (x) at which the change in R2* divided by R2*at baseline scaled (y) equals 0.5. Results The apparent P50 values were significantly lower in fetal liver than in maternal liver for both gestation stages (day 14.5: 21% ± 5 [P = .04] and day 17.5: 41% ± 7 [P hemoglobin dissociation curves with a shorter protocol that excluded the hypoxic periods was demonstrated. Conclusion MR imaging

Tourniquet pressures: strap width and tensioning system widths.

Science.gov (United States)

Wall, Piper L; Coughlin, Ohmar; Rometti, Mary; Birkholz, Sarah; Gildemaster, Yvonne; Grulke, Lisa; Sahr, Sheryl; Buising, Charisse M

2014-01-01

Pressure distribution over tourniquet width is a determinant of pressure needed for arterial occlusion. Different width tensioning systems could result in arterial occlusion pressure differences among nonelastic strap designs of equal width. Ratcheting Medical Tourniquets (RMTs; m2 inc., http://www.ratcheting buckles.com) with a 1.9 cm-wide (Tactical RMT) or 2.3 cm-wide (Mass Casualty RMT) ladder were directly compared (16 recipients, 16 thighs and 16 upper arms for each tourniquetx2). Then, RMTs were retrospectively compared with the windlass Combat Application Tourniquet (C-A-T ["CAT"], http://combattourniquet.com) with a 2.5 cm-wide internal tensioning strap. Pressure was measured with an air-filled No. 1 neonatal blood pressure cuff under each 3.8 cm-wide tourniquet. RMT circumferential pressure distribution was not uniform. Tactical RMT pressures were not higher, and there were no differences between the RMTs in the effectiveness, ease of use ("97% easy"), or discomfort. However, a difference did occur regarding tooth skipping of the pawl during ratchet advancement: it occurred in 1 of 64 Tactical RMT applications versus 27 of 64 Mass Casualty RMT applications. CAT and RMT occlusion pressures were frequently over 300 mmHg. RMT arm occlusion pressures (175-397 mmHg), however, were lower than RMT thigh occlusion pressures (197-562 mmHg). RMT effectiveness was better with 99% reached occlusion and 1% lost occlusion over 1 minute versus the CAT with 95% reached occlusion and 28% lost occlusion over 1 minute. RMT muscle tension changes (up to 232 mmHg) and pressure losses over 1 minute (24±11 mmHg arm under strap to 40±12 mmHg thigh under ladder) suggest more occlusion losses may have occurred if tourniquet duration was extended. The narrower tensioning system Tactical RMT has better performance characteristics than the Mass Casualty RMT. The 3.8 cm-wide RMTs have some pressure and effectiveness similarities and differences compared with the CAT. Clinically

Effect of cold work on creep properties of oxygen-free copper

International Nuclear Information System (INIS)

Martinsson, Aasa; Andersson-Oestling, Henrik C.M.

2009-03-01

Spent nuclear fuel is in Sweden planned to be disposed by encapsulating in waste packages consisting of a cast iron insert surrounded by a copper canister. The cast iron is load bearing and the copper canister gives corrosion protection. The waste package is heavy. Throughout the manufacturing process from the extrusion/pierce-and-draw manufacturing to the final placement in the repository, the copper is subjected to handling which could introduce cold work in the material. It is well known that the creep properties of engineering materials at higher temperatures are affected by cold working. The study includes creep testing of four series of cold worked, oxygen-free, phosphorus doped copper (Cu-OFP) at 75 deg C. The results are compared to reference series for as series of copper cold worked in tension (12 and 24 %) and two series cold worked in compression (12 % parallel to creep load axis and 15 % perpendicular to creep load axis) were tested. The results show that pre-straining in tension of copper leads to prolonged creep life at 75 deg C. The creep rate and ductility are reduced. The influence on the creep properties increases with the amount of cold work. Cold work in compression applied along the creep load axis has no effect on the creep life or the creep rate. Nonetheless the ductility is still impaired. However, cold work in compression applied perpendicular to the creep load direction has a positive effect on the creep life. Cold work in both tension and compression results in a pronounced reduction of the initial creep strain, which is the strain obtained from the beginning of the loading until full creep load is achieved. Yet the area reduction is unaffected by the degree of cold work

Gene expression profiles in relation to tension and dissociation in borderline personality disorder.

Directory of Open Access Journals (Sweden)

Christian Schmahl

Full Text Available The biological underpinnings of borderline personality disorder (BPD and its psychopathology including states of aversive tension and dissociation is poorly understood. Our goal was to examine transcriptional changes associated with states of tension or dissociation within individual patients in a pilot study. Dissociation is not only a critical symptom of BPD but has also been associated with higher risk for self-mutilation and depression. We conducted a whole blood gene expression profile analysis using quantitative PCR in 31 female inpatients with BPD. For each individual, two samples were drawn during a state of high tension and dissociation, while two samples were drawn at non-tension states. There was no association between gene expression and tension states. However, we could show that Interleukin-6 was positively correlated to dissociation scores, whereas Guanine nucleotide-binding protein G(s subunit alpha isoforms, Mitogen-activated protein kinase 3 and 8, Guanine nucleotide-binding protein G(i subunit alpha-2, Beta-arrestin-1 and 2, and Cyclic AMP-responsive element-binding protein were negatively correlated to dissociation. Our data point to a potential association of dissociation levels with the expression of genes involved in immune system regulation as well as cellular signalling/second-messenger systems. Major limitations of the study are the the possibly heterogeneous cell proportions in whole blood and the heterogeneous medication.

Oxygen, a Key Factor Regulating Cell Behavior during Neurogenesis and Cerebral Diseases.

Science.gov (United States)

Zhang, Kuan; Zhu, Lingling; Fan, Ming

2011-01-01

Oxygen is vital to maintain the normal functions of almost all the organs, especially for brain which is one of the heaviest oxygen consumers in the body. The important roles of oxygen on the brain are not only reflected in the development, but also showed in the pathological processes of many cerebral diseases. In the current review, we summarized the oxygen levels in brain tissues tested by real-time measurements during the embryonic and adult neurogenesis, the cerebral diseases, or in the hyperbaric/hypobaric oxygen environment. Oxygen concentration is low in fetal brain (0.076-7.6 mmHg) and in adult brain (11.4-53.2 mmHg), decreased during stroke, and increased in hyperbaric oxygen environment. In addition, we reviewed the effects of oxygen tensions on the behaviors of neural stem cells (NSCs) in vitro cultures at different oxygen concentration (15.2-152 mmHg) and in vivo niche during different pathological states and in hyperbaric/hypobaric oxygen environment. Moderate hypoxia (22.8-76 mmHg) can promote the proliferation of NSCs and enhance the differentiation of NSCs into the TH-positive neurons. Next, we briefly presented the oxygen-sensitive molecular mechanisms regulating NSCs proliferation and differentiation recently found including the Notch, Bone morphogenetic protein and Wnt pathways. Finally, the future perspectives about the roles of oxygen on brain and NSCs were given.

Oxygen, a key factor regulating cell behaviour during neurogenesis and cerebral diseases

Directory of Open Access Journals (Sweden)

Kuan eZhang

2011-04-01

Full Text Available Oxygen is vital to maintain the normal functions of alomost all the organs, especially for brain which is one of the heaviest oxygen consumers in the body. The important roles of oxygen on the brain are not only reflected in the development, but also showed in the pathological processes of many cerebral diseases. In the current review, we summarized the oxygen levels in brain tissues tested by real-time measurements during the embryonic and adult neurogenesis, the cerebral diseases or in the hyperbaric/hypobaric oxygen environment. Oxygen concentration is low in fetal brain (0.01%- 1% and in adult brain (1.5%-7%, decreased during stroke, and increased in hyperbaric oxygen environment. In addition, we reviewed the effects of oxygen tensions on the behaviors of neural stem cells (NSCs in vitro cultures at different oxygen concentration (2%-20% and in vivo niche during different pathological states and in hyperbaric/hypobaric oxygen environment. Moderate hypoxia (3%-10% is known can promote the proliferation of NSCs and enhance the differentiation of NSCs into the TH-positive neurons. Next, we briefly presented the oxygen-sensitive molecular mechanisms regulating NSCs proliferation and differentiation recently found including the Notch, BMP and Wnt pathways. Finally, the future perspectives about the roles of oxygen on brain and NSCs were given.

Traumatic tension pneumocephalus: Two case reports

Directory of Open Access Journals (Sweden)

Abubaker Al-Aieb

2017-01-01

Conclusions: These are two rare cases with posttraumatic tension pneumocephalus treated conservatively with a favorable outcome. Early diagnosis of tension pneumocephalus is a crucial step to facilitate early recovery; however, the associated injuries need attention as they could influence the hospital course.

Oxygen-tension measurements - The first step towards prevention and early detection of anastomotic leakage

NARCIS (Netherlands)

Tanase, D.; French, P.J.; Komen, N.; Kleinrensink, G.J.; Jeekel, J.; Lange, J.F.; Draaijer, A.

2007-01-01

Many patients still die every year as a result of anastomotic leakage after surgery. The medical world needs an objective aid to detect leakage during surgery and during the critical recovery period. We propose a miniature measurement system to detect adequate tissue oxygenation pre- and

Exploratory experimental investigations on post-tensioned structural glass beams

DEFF Research Database (Denmark)

Louter, C.; Nielsen, Jens Henrik; Belis, J.

2013-01-01

This paper discusses two projects on post-tensioned glass beams, performed at EPFL and DTU, respectively. In these projects small scale glass beams (length of 1.5m and 1m) are post-tensioned by means of steel threaded rods tensioned at the beam ends. The purpose of post-tensioning glass beams...

Tumor Oxygen Dynamics: Correlation of In Vivo MRI with Histological Findings

Directory of Open Access Journals (Sweden)

Dawen Zhao

2003-07-01

Full Text Available Tumor oxygenation has long been recognized as a significant factor influencing cancer therapy. We recently established a novel magnetic resonance in vivo approach to measuring regional tumor oxygen tension, FREDOM (Fluorocarbon Relaxometry Using Echo Planar Imaging for Dynamic Oxygen Mapping, using hexafluorobenzene (HFB as the reporter molecule. We have now investigated oxygen dynamics in the two Dunning prostate R3327 rat tumor sublines, AT1 and H. FREDOM revealed considerable intratumoral heterogeneity in the distribution of pO2 values in both sublines. The anaplastic fastergrowing AT1 tumors were more hypoxic compared with the size-matched, well-differentiated, and slower-growing H tumors. Respiratory challenge with oxygen produced significant increases in mean and median pO2 in all the H tumors (P3 cm3. Immunohistochemical studies using the hypoxia marker, pimonidazole, and the vascular endothelial cell marker, CD31, confirmed that the H tumors had more extensive vasculature and less hypoxia than the AT1 tumors. These results further validate the utilization of FREDOM to monitor tumor oxygenation and concur with the hypothesis that the level of hypoxia is related to tumor growth rate and poor vascularity.

Tension pneumothorax, is it a really life-threatening condition?

Science.gov (United States)

2013-01-01

Background Tension pneumothorax is a life-threatening occurrence that is infrequently the consequence of spontaneous pneumothorax. The aim of this study was to identify the risk factors for the development of tension pneumothorax and its effect on clinical outcomes. Methods We reviewed patients who were admitted with spontaneous pneumothorax between August 1, 2003 and December 31, 2011. Electronic medical records and the radiological findings were reviewed with chest x-ray and high-resolution computed tomography scans that were retrieved from the Picture Archiving Communication System. Results Out of the 370 patients included in this study, tension pneumothorax developed in 60 (16.2%). The bullae were larger in patients with tension pneumothorax than in those without (23.8 ± 16.2 mm vs 16.1 ± 19.1 mm; P = 0.007). In addition, the incidence of tension pneumothorax increased with the lung bulla size. Fibrotic adhesion was more prevalent in the tension pneumothorax group than in that without (P = 0.000). The bullae were large in patients with fibrotic adhesion than in those without adhesion (35.0 ± 22.3 mm vs 10.4 ± 11.5 mm; P = 0.000). On multivariate analysis, the size of bullae (odds ratio (OR) = 1.03, P = 0.001) and fibrotic adhesion (OR = 10.76, P = 0.000) were risk factors of tension pneumothorax. Hospital mortality was 3.3% in the tension pneumothorax group and it was not significantly different from those patients without tension pneunothorax (P = 0.252). Conclusions Tension pneumothorax is not uncommon, but clinically fatal tension pneumothorax is extremely rare. The size of the lung bullae and fibrotic adhesion contributes to the development of tension pneumothorax. PMID:24128176

Rapid cable tension estimation using dynamic and mechanical properties

Science.gov (United States)

Martínez-Castro, Rosana E.; Jang, Shinae; Christenson, Richard E.

2016-04-01

Main tension elements are critical to the overall stability of cable-supported bridges. A dependable and rapid determination of cable tension is desired to assess the state of a cable-supported bridge and evaluate its operability. A portable smart sensor setup is presented to reduce post-processing time and deployment complexity while reliably determining cable tension using dynamic characteristics extracted from spectral analysis. A self-recording accelerometer is coupled with a single-board microcomputer that communicates wirelessly with a remote host computer. The portable smart sensing device is designed such that additional algorithms, sensors and controlling devices for various monitoring applications can be installed and operated for additional structural assessment. The tension-estimating algorithms are based on taut string theory and expand to consider bending stiffness. The successful combination of cable properties allows the use of a cable's dynamic behavior to determine tension force. The tension-estimating algorithms are experimentally validated on a through-arch steel bridge subject to ambient vibration induced by passing traffic. The tension estimation is determined in well agreement with previously determined tension values for the structure.

Psychosocial factors associated with migraine and tension-type headache in medical students

DEFF Research Database (Denmark)

Lebedeva, Elena R; Kobzeva, Natalia R; Gilev, Denis V

2017-01-01

BACKGROUND: In our previous study of workers, blood donors and medical students, students stood out with a higher 1-year prevalence of migraine (28%) and tension-type headache (TTH) (74%). General factors associated with headache were common for all groups except low physical activity. The hypoth...

Frontal lobe oxygenation is maintained during hypotension following propofol-fentanyl anesthesia

DEFF Research Database (Denmark)

Nissen, P.; Lieshout, J.J. van; Nielsen, H.B.

2009-01-01

Near-infrared spectroscopy (NIRS) assesses cerebral oxygen saturation (Sco2) as a balance between cerebral oxygen delivery and consumption. In 71 patients, we evaluated whether marked reduction in mean arterial pressure (MAP) during propofol-fentanyl anesthesia induction affects frontal lobe Sco2....... The NIRS-determined arm muscle oxygenation (Smo2), heart rate (HR), and cardiac output (CO) were monitored, endtidal carbon dioxide tension was controlled at 3.5 to 4.5 kPa, and central blood volume was maintained. Before anesthesia, the median (range) MAP, HR, and CO were 93 mm Hg (61-126 mm Hg), 76 beats......, the median (range) NIRS-determined Smo2 also decreased (73% [54%-94%] to 71% [52%-87%]), whereas Sco2 increased from 67% (46%-93%) to 74% (48%-95%) (P anesthesia induction, variables recovered and remained at preanesthetic levels during surgery. The findings...

[P300 potential in chldren with psychogenic nonepileptic events and tension headache].

Science.gov (United States)

Steczkowska, Małgorzata; Stolarska-Weryńska, Urszula; Fiederer, Krystyna; Kaciński, Marek

2016-01-01

Psychotherapy is being used as the primary treatment in nonepileptic psychogenic seizures and tension headaches in children. Children's intelectual functioning is related to certain endogenous neurophysiological parameters. The goal of this study was to establish whether the endogenous potential P300 is different in children with nonepileptic psychogenic events and with tension headaches, and whether it changes under the influence of the cognitive-behavioral psychotherapy. The study included a group of 47 children: 20 with nonepileptic psychogenic seizures (18 girls and 2 boys), aged 11.09-17.11 years, and 27 children with tension headache (25 girls and 2 boys), aged 10.11-17.11 years. The P300 potential was induced using an auditory stimulus. The reaction time, the amount of mistakes and the percentage of attention focus was measured in all children. All children attended 8-10 psychotherapy sessions. The P300 potential was registered before and after the course of therapy, and additionally in both cycles also after a 3 minutes hyperventilation. Medium P300 parameters were closer to normal in the group of children with tension headaches rather than in the group with nonepileptic seizures. The shorter was the reaction time in the first measurement, the higher the attention score and the shorter the reaction time in the second measurement - this was visible in the results of children with nonepileptic seizures, in contrast to children with tension headaches. The use of hyperventilation caused a noticeable extension of the reaction time in the P300 measurement, with other components unchanged (mistake count and percentage of attention focus). The endogenous potential P300 does vary, although on a statistically insignificant level, in groups of children with tension headaches and nonepileptic seizures.

The Equilibrium Spreading Tension of Pulmonary Surfactant

OpenAIRE

Dagan, Maayan P.; Hall, Stephen B.

2015-01-01

Monomolecular films at an air/water interface coexist at the equilibrium spreading tension (γe) with the bulk phase from which they form. For individual phospholipids, γe is single-valued, and separates conditions at which hydrated vesicles adsorb from tensions at which overcompressed monolayers collapse. With pulmonary surfactant, isotherms show that monolayers compressed on the surface of bubbles coexist with the three-dimensional collapsed phase over a range of surface tensions. γe therefo...

Tension perturbations of black brane spacetimes

International Nuclear Information System (INIS)

Traschen, Jennie; Fox, Daniel

2004-01-01

We consider black brane spacetimes that have at least one spatial translation Killing field that is tangent to the brane. A new parameter, the tension of a spacetime, is defined. The tension parameter is associated with spatial translations in much the same way that the ADM mass is associated with the time translation Killing field. In this work, we explore the implications of the spatial translation symmetry for small perturbations around a background black brane. For static-charged black branes we derive a law which relates the tension perturbation to the surface gravity times the change in the horizon area, plus terms that involve variations in the charges and currents. We find that as a black brane evaporates the tension decreases. We also give a simple derivation of a first law for black brane spacetimes. These constructions hold when the background stress-energy is governed by a Hamiltonian, and the results include arbitrary perturbative stress-energy sources

Measurement for Surface Tension of Aqueous Inorganic Salt

Directory of Open Access Journals (Sweden)

Jiming Wen

2018-03-01

Full Text Available Bubble columns are effective means of filtration in filtered containment venting systems. Here, the surface tension has a significant influence on bubble size distribution and bubble deformation, which have a strong impact on the behavior of the bubble column. The influence of aqueous inorganic compounds on the surface tension depends on the electrolytic activity, Debye length, entropy of ion hydration, and surface deficiencies or excess. In this work, the surface tensions of same specific aqueous solutions have been measured by different methods including platinum plate method, platinum ring method, and maximum bubble pressure method. The measured surface tensions of both sodium hydroxide and sodium thiosulfate are less than that of water. As solution temperature ranges from 20 to 75°C, the surface tension of 0.5 mol/L sodium hydroxide solution decreases from 71 to 55 mN/m while that of 1 mol/L solution decreases from 60 to 45 mN/m. Similarly during the same temperature range, the surface tension of 0.5 mol/L sodium thiosulfate decreases from 70 to 38 mN/m, and that of 1 mol/L sodium thiosulfate is between 68 and 36 mN/m. The analysis for the influence mechanism of aqueous inorganic on surface tension is provided. In addition, experimental results show that the surface tension of solid aerosol suspension liquid has no obvious difference from that of distilled water.

Tending the tensions in co-creation

DEFF Research Database (Denmark)

Phillips, Professor MSO Louise; Nordentoft, Helle Merete; Pedersen, Lektor Christina Hee

-for-granted positive value. In the panel we de-romanticise “co-creation” and explore how it is enacted in particular organisational contexts, concentrating on context-specific tensions arising in the meeting between different knowledge forms and interests. These include tensions BETWEEN dialogic views of knowledge co-creation...

Surface tension in soap films: revisiting a classic demonstration

International Nuclear Information System (INIS)

Behroozi, F

2010-01-01

We revisit a classic demonstration for surface tension in soap films and introduce a more striking variation of it. The demonstration shows how the film, pulling uniformly and normally on a loose string, transforms it into a circular arc under tension. The relationship between the surface tension and the string tension is analysed and presented in a useful graphical form. (letters and comments)

Surface tension in soap films: revisiting a classic demonstration

Energy Technology Data Exchange (ETDEWEB)

Behroozi, F [Department of Physics, University of Northern Iowa, Cedar Falls, IA 50614 (United States)], E-mail: behroozi@uni.edu

2010-01-15

We revisit a classic demonstration for surface tension in soap films and introduce a more striking variation of it. The demonstration shows how the film, pulling uniformly and normally on a loose string, transforms it into a circular arc under tension. The relationship between the surface tension and the string tension is analysed and presented in a useful graphical form. (letters and comments)

Bending Under Tension Test with Direct Friction Measurement

DEFF Research Database (Denmark)

Andreasen, Jan Lasson; Olsson, David Dam; Chodnikiewicz, K.

2006-01-01

A special Bending-Under-Tension (BUT) transducer has been developed in which friction around the tool radius can be directly measured when drawing a plane sheet strip around a cylindrical tool-pin under constant back tension. The front tension, back tension and torque on the tool-pin are all...... measured directly, thus enabling accurate measurement of friction and direct determination of lubricant film breakdown for varying normal pressure, sliding speed, tool radius and tool preheat temperature. The transducer is applied in an experimental investigation focusing on limits of lubrication...

Kinetics of the oxygen effect in yeast irradiated in dry and wet conditions

International Nuclear Information System (INIS)

Kiefer, J.; Schoepfer, F.; Luggen-Hoelscher, J.

1981-01-01

There are indications that the radiobiological oxygen-effect consists of more than one component: in dry bacterial spores three different classes can be separated depending on exposure- and after-treatment conditions, the dependence of the oxygen-enhancement ratio (OER) on oxygen concentration shows breaks in various systems, and it has been suggested that type O and type N damage are localized in different parts of the cells. These questions were studied in the simple eucaryote Saccharomyces cerevisiae using two approaches: the dependence of OER on oxygen tension was determined both for survivial and mutation induction. Since a forward mutation was used a haploid strain had to be employed in this case. In order to assess whether also in yeast cells more than one component may exist, the techniques originally developed for bacterial spores were adapted for dried diploid yeast cells. The results show that the dependence on oxygen concentration is the same for survival and mutation within error limits, implicating DNA as the main target and that also in our system three classes of oxygen dependent damage exist

Magnetic tension and gravitational collapse

International Nuclear Information System (INIS)

Tsagas, Christos G

2006-01-01

The gravitational collapse of a magnetized medium is investigated by studying qualitatively the convergence of a timelike family of non-geodesic worldlines in the presence of a magnetic field. Focusing on the field's tension, we illustrate how the winding of the magnetic forcelines due to the fluid's rotation assists the collapse, while shear-like distortions in the distribution of the field's gradients resist contraction. We also show that the relativistic coupling between magnetism and geometry, together with the tension properties of the field, lead to a magneto-curvature stress that opposes the collapse. This tension stress grows stronger with increasing curvature distortion, which means that it could potentially dominate over the gravitational pull of the matter. If this happens, a converging family of non-geodesic worldlines can be prevented from focusing without violating the standard energy conditions

[Reduced muscular oxygen tension and nerve impulse transmission from antishock hose. Reduction of oxygen tension in the tibial muscle and impulse transmission in the peroneal nerve from pneumatic -1 pressure from antishock hose].

Science.gov (United States)

Willy, C; Völker, H U; Weber, F; Albert, U; Sterk, J; Helm, M; Gerngross, H; Thomas, A

1998-07-01

The aim of the study was to assess, whether the pneumatic pressure of an antishock-trouser (AST) of 20-40 mm Hg induces a decreased oxygenation of the anterior tibial muscle and attenuates muscular response potential (MRP) of n. peronaeus profundus? Among 22 normotensive, healthy volunteers the AST were tested by applying pressure values between 0 and 100 mm Hg and measuring the intracompartmental pressure, the muscular oxygen pressure as well as the MRP by electroneurographic means within a period of 6 hours. The median initial intracompartmental pressure value of the m. tibialis anterior was 12.0 mm Hg (Q25%/Q75%: 8.9/17.3), the muscular oxygen pressure 14.8 mm Hg (Q25%/Q75%: 11.5/22.0). Transmission of the pneumatic AST-leg segment pressure to the muscle: 97.7% (Q25%/Q75%: 89.2/99.8). Already in the low AST pressure field (20-40 mm Hg) a severe hypoxia occurred in one case. A reduction of MRP was noticed at an AST pressure rate of 10 mm Hg. In 5 of 6 cases AST pressure values of 60 mm Hg led to pathological pO2-values within 5-20 minutes. Almost without exception AST-pressure rates < 60 mm Hg resulted in an anoxia of the muscle and loss of the MRP. We should demand that the AST are only applied with models where the pressure generated within the single segments can be controlled by pressure gauge. The application of the AST seems to be justified for polytraumatised in severe haemorrhagic shock where the risk of a local tissue ischemia with systemical consequences must deliberately be accepted.

The optimum tension for bridging sutures in transosseous-equivalent rotator cuff repair: a cadaveric biomechanical study.

Science.gov (United States)

Park, Ji Soon; McGarry, Michelle H; Campbell, Sean T; Seo, Hyuk Jun; Lee, Yeon Soo; Kim, Sae Hoon; Lee, Thay Q; Oh, Joo Han

2015-09-01

Transosseous-equivalent (TOE) rotator cuff repair can increase contact area and contact pressure between the repaired cuff tendon and bony footprint and can show higher ultimate loads to failure and smaller gap formation compared with other repair techniques. However, it has been suggested that medial rotator cuff failure after TOE repair may result from increased bridging suture tension. To determine optimum bridging suture tension in TOE repair by evaluating footprint contact and construct failure characteristics at different tensions. Controlled laboratory study. A total of 18 fresh-frozen cadaveric shoulders, randomly divided into 3 groups, were constructed with a TOE configuration using the same medial suture anchor and placing a Tekscan sensing pad between the repaired rotator cuff tendon and footprint. Nine of the 18 shoulders were used to measure footprint contact characteristics. With use of the Tekscan measurement system, the contact pressure and area between the rotator cuff tendon and greater tuberosity were quantified for bridging suture tensions of 60, 90, and 120 N with glenohumeral abduction angles of 0° and 30° and humeral rotation angles of 30° (internal), 0°, and 30° (external). TOE constructs of all 18 shoulders then underwent construct failure testing (cyclic loading and load to failure) to determine the yield load, ultimate load, stiffness, hysteresis, strain, and failure mode at 60 and 120 N of tension. As bridging suture tension increased, contact force, contact pressure, and peak pressure increased significantly at all positions (P .05 for all). Increasing bridging suture tension to over 90 N did not improve contact area but did increase contact force and pressure. Bridging suture tension did not significantly affect ultimate failure loads. Considering the risks of overtensioning bridging sutures, it may be clinically more beneficial to keep bridging suture tension below 90 N. © 2015 The Author(s).

Analytical description of concentration dependence of surface tension in multicomponent systems

Energy Technology Data Exchange (ETDEWEB)

Dadashev, R; Kutuev, R [Complex Science Research Institute of the Science Academy of the Chechen Republic, 21 Staropromisl. shosse, Grozny 364096 (Russian Federation); Elimkhanov, D [Science Academy of the Chechen Republic (Russian Federation)], E-mail: edzhabrail@mail.ru

2008-02-15

From the basic fundamental thermodynamic expressions the equation of isotherms of the surface tension of a ternary system is received. Various assumptions concerning the concentration dependence of molar areas are usually made when the equation is derived. The dependence of the molar areas is calculated as an additive function of the structure of a volumetric phase or the structure of a surface layer. To define the concentration dependence of the molar areas we used a stricter thermodynamic expression offered by Butler. In the received equation the dependence of molar areas on the structure of the solution is taken into account. Therefore, the equation can be applied for the calculation of surface tension over a wide concentration range of the components. Unlike the known expressions, the equation includes the surface tension properties of lateral binary systems, which makes the accuracy of the calculated values considerably higher. Thus, among the advantages of the offered equation we can point out the mathematical simplicity of the received equation and the fact that the equation includes physical parameters the experimental definition of which does not present any special difficulties.

Ultrasound Findings in Tension Pneumothorax: A Case Report.

Science.gov (United States)

Inocencio, Maxine; Childs, Jeannine; Chilstrom, Mikaela L; Berona, Kristin

2017-06-01

Delayed recognition of tension pneumothorax can lead to a mortality of 31% to 91%. However, the classic physical examination findings of tracheal deviation and distended neck veins are poorly sensitive in the diagnosis of tension pneumothorax. Point-of-care ultrasound is accurate in identifying the presence of pneumothorax, but sonographic findings of tension pneumothorax are less well described. We report the case of a 21-year-old man with sudden-onset left-sided chest pain. He was clinically stable without hypoxia or hypotension, and the initial chest x-ray study showed a large pneumothorax without mediastinal shift. While the patient was awaiting tube thoracostomy, a point-of-care ultrasound demonstrated findings of mediastinal shift and a dilated inferior vena cava (IVC) concerning for tension physiology, even though the patient remained hemodynamically stable. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: This case demonstrates a unique clinical scenario of ultrasound evidence of tension physiology in a clinically stable patient. Although this patient was well appearing without hypotension, respiratory distress, tracheal deviation, or distended neck veins, point-of-care ultrasound revealed mediastinal shift and a plethoric IVC. Given that the classic clinical signs of tension pneumothorax are not uniformly present, this case shows how point-of-care ultrasound may diagnose tension pneumothorax before clinical decompensation. Published by Elsevier Inc.

Tension and relaxation in the individual.

Science.gov (United States)

Newbury, C R

1979-06-01

Increasing materialism in society is resulting in more wide spread nervous tension in all age groups. While some degree of nervous tension is necessary in everyday living, its adverse effects require that we must learn to bring it under control. Total tension is shown to have two components: a controllable element arising from factors in the environment and the inbuilt uncontrollable residue which is basic in the individual temperament. The effects of excessive or uncontrolled stress can be classified as 1) emotional reactions such as neurotic behaviour (anxiety hypochondria, hysteria, phobia, depression obsessions and compulsions) or psychotic behaviour and 2) psychosomatic reactions (nervous asthma, headache, insomnia, heart attack). Nervous energy can be wastefully expended by such factors as loss of temper, wrong attitudes to work, job frustration and marital strains. Relaxation is the only positive way to control undesirable nervous tension and its techniques require to be learned. A number of techniques (progressive relaxation, differential relaxation, hypnosis, the use of biofeedback, Yoga and Transcendental Meditation) are described and their application to dental practice is discussed.

Filamin A Mediates Wound Closure by Promoting Elastic Deformation and Maintenance of Tension in the Collagen Matrix

Science.gov (United States)

Mohammadi, Hamid; Pinto, Vanessa I.; Wang, Yongqiang; Hinz, Boris; Janmey, Paul A.; McCulloch, Christopher A.

2016-01-01

Cell-mediated remodeling and wound closure are critical for efficient wound healing, but the contribution of actin-binding proteins to contraction of the extracellular matrix is not defined. We examined the role of filamin A (FLNa), an actin filament cross-linking protein, in wound contraction and maintenance of matrix tension. Conditional deletion of FLNa in fibroblasts in mice was associated with ~ 4 day delay of full-thickness skin wound contraction compared with wild-type (WT) mice. We modeled the healing wound matrix using cultured fibroblasts plated on grid-supported collagen gels that create lateral boundaries, which are analogues to wound margins. In contrast to WT cells, FLNa knockdown (KD) cells could not completely maintain tension when matrix compaction was resisted by boundaries, which manifested as relaxed matrix tension. Similarly, WT cells on cross-linked collagen, which requires higher levels of sustained tension, exhibited approximately fivefold larger deformation fields and approximately twofold greater fiber alignment compared with FLNa KD cells. Maintenance of boundary-resisted tension markedly influenced the elongation of cell extensions: in WT cells, the number (~50%) and length (~300%) of cell extensions were greater than FLNa KD cells. We conclude that FLNa is required for wound contraction, in part by enabling elastic deformation and maintenance of tension in the matrix. PMID:26134946

OPTIMUM, CRITICAL AND THRESHOLD VALUES FOR WATER OXYGENATION FOR MULLETS (MUGILIDAE AND FLATFISHES (PLEURONECTIDAE IN ONTOGENESIS

Directory of Open Access Journals (Sweden)

P. Shekk

2014-12-01

Full Text Available Purpose. To determine the optimum, critical, and threshold values of water oxygenation for embryos, larvae and fingerlings of mullets and flatfishes under different temperature conditions. Methodology. Oxygen consumption was studied in chronic experiments with «interrupted flow» method with automatic fixation of dissolved oxygen in water with the aid of an oxygen sensor and automatic, continuous recording of the obtained results. «Critical» (Pcrit., and the «threshold» (Pthr. oxygen tension in the water have been determined. Findings. Under optimum conditions, the normal embryogenesis of mullets and flatfish to the gastrulation stage, provided 90–130% oxygen saturation. The critical content was 80–85%, the threshold – 65–70% of the saturation. At the stage of «movable embryo» depending on water temperature and fish species, the optimum range of water oxygenation was within 70‒127.1%. The most tolerant to oxygen deficiency was flounder Platichthys luscus (Pcrit – 25.4–27,5; Pthr. – 20.5–22.5%, the least resistant to hypoxia was striped mullet Mugil серhalus (Pcrit. – 50–60; Pthr. – 35–40%. The limits of the critical and threshold concentration of dissolved oxygen directly depended on the temperature and salinity, at which embryogenesis occurred. An increase in water temperature and salinity resulted in an increase in critical and threshold values for oxygen tension embryos. Mullet and flatfish fingerlings in all stages of development had a high tolerance to hypoxia, which increased as they grew. They were resistant to the oversaturation of water with oxygen. The most demanding for the oxygen regime are larvae and fingerlings of striped mullet and Liza aurata. Hypoxia tolerance of Psetta maeoticus (Psetta maeoticus and flounder at all stages of development is very high. The fingerlings of these species can endure reduction of the dissolved oxygen in water to 2.10 and 1.65 mgO2/dm3 respectively for a long time

Emergency percutaneous needle decompression for tension pneumoperitoneum

Directory of Open Access Journals (Sweden)

Körner Markus

2011-05-01

Full Text Available Abstract Background Tension pneumoperitoneum as a complication of iatrogenic bowel perforation during endoscopy is a dramatic condition in which intraperitoneal air under pressure causes hemodynamic and ventilatory compromise. Like tension pneumothorax, urgent intervention is required. Immediate surgical decompression though is not always possible due to the limitations of the preclinical management and sometimes to capacity constraints of medical staff and equipment in the clinic. Methods This is a retrospective analysis of cases of pneumoperitoneum and tension pneumoperitoneum due to iatrogenic bowel perforation. All patients admitted to our surgical department between January 2005 and October 2010 were included. Tension pneumoperitoneum was diagnosed in those patients presenting signs of hemodynamic and ventilatory compromise in addition to abdominal distension. Results Between January 2005 and October 2010 eleven patients with iatrogenic bowel perforation were admitted to our surgical department. The mean time between perforation and admission was 36 ± 14 hrs (range 30 min - 130 hrs, between ER admission and begin of the operation 3 hrs and 15 min ± 47 min (range 60 min - 9 hrs. Three out of eleven patients had clinical signs of tension pneumoperitoneum. In those patients emergency percutaneous needle decompression was performed with a 16G venous catheter. This improved significantly the patients' condition (stabilization of vital signs, reducing jugular vein congestion, bridging the time to the start of the operation. Conclusions Hemodynamical and respiratory compromise in addition to abdominal distension shortly after endoscopy are strongly suggestive of tension pneumoperitoneum due to iatrogenic bowel perforation. This is a rare but life threatening condition and it can be managed in a preclinical and clinical setting with emergency percutaneous needle decompression like tension pneumothorax. Emergency percutaneous decompression is no

[Diagnostic and therapy of tension-type headache].

Science.gov (United States)

Straube, A

2014-08-01

Episodic headache of the tension type is the most prevalent primary headache with a lifetime prevalence of about 78 %. Clinical characteristics are a dull, moderate, holocephalic headache without accompanying autonomic or vegetative symptoms. The episodic tension-type headache often lasts only 30 min up to a maximum of a few days. In contrast to this clinically often undemanding headache, chronic tension-type headache can cause considerable disability in patients. The 1-year prevalence is 1-3 % of the population. All therapy strategies combine nonpharmaceutical therapy such as education of the patient, regular aerobic exercise, and psychological treatment (e.g., Jacobson's progressive muscle relaxation etc.) with pharmaceutical treatment such as tricyclic antidepressants or combined serotonergic and noradrenergic antidepressants. Combination therapy has been proven to be more effective than singular strategies; however, the chronic tension-type headache still poses a therapeutic problem.

Migraine and tension-type headache triggers in a Greek population

Directory of Open Access Journals (Sweden)

Vasilios Constantinides

2015-08-01

Full Text Available Migraine and tension type headache are the two most common primary headaches. The purpose of this study was to detect differences in clinical characteristics and headache triggers and in a Greek cohort of 51 migraineurs and 12 patients with tension-type headache. (TTH Migraine patients had a significantly lower age at headache onset and frequency, higher mean visual analogue scale (VAS and greater maximum duration of headache episodes compared to TTH patients. They did not differ from (TTH patients in quality of headache, laterality of pain, way of headache installation and progression and temporal pattern of headaches. Nausea, vomiting and phonophobia were more frequent in migraine. Triggering of headaches by dietary factors was associated with migraine, whereas there was no difference between the two groups in any of the other headache triggers. Stress, both physical and psychological, were particularly common in both patient groups.

Yeast alter micro-oxygenation of wine: oxygen consumption and aldehyde production.

Science.gov (United States)

Han, Guomin; Webb, Michael R; Richter, Chandra; Parsons, Jessica; Waterhouse, Andrew L

2017-08-01

Micro-oxygenation (MOx) is a common winemaking treatment used to improve red wine color development and diminish vegetal aroma, amongst other effects. It is commonly applied to wine immediately after yeast fermentation (phase 1) or later, during aging (phase 2). Although most winemakers avoid MOx during malolactic (ML) fermentation, it is often not possible to avoid because ML bacteria are often present during phase 1 MOx treatment. We investigated the effect of common yeast and bacteria on the outcome of micro-oxygenation. Compared to sterile filtered wine, Saccharomyces cerevisiae inoculation significantly increased oxygen consumption, keeping dissolved oxygen in wine below 30 µg L -1 during micro-oxygenation, whereas Oenococcus oeni inoculation was not associated with a significant impact on the concentration of dissolved oxygen. The unfiltered baseline wine also had both present, although with much higher populations of bacteria and consumed oxygen. The yeast-treated wine yielded much higher levels of acetaldehyde, rising from 4.3 to 29 mg L -1 during micro-oxygenation, whereas no significant difference was found between the bacteria-treated wine and the filtered control. The unfiltered wine exhibited rapid oxygen consumption but no additional acetaldehyde, as well as reduced pyruvate. Analysis of the acetaldehyde-glycerol acetal levels showed a good correlation with acetaldehyde concentrations. The production of acetaldehyde is a key outcome of MOx and it is dramatically increased in the presence of yeast, although it is possibly counteracted by the metabolism of O. oeni bacteria. Additional controlled experiments are necessary to clarify the interaction of yeast and bacteria during MOx treatments. Analysis of the glycerol acetals may be useful as a proxy for acetaldehyde levels. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

Prediction of tension-type headache risk in adolescents

Directory of Open Access Journals (Sweden)

K. A. Stepanchenko

2016-08-01

Full Text Available Tension-type headache is the actual problem of adolescent neurology, which is associated with the prevalence of the disease, the tendency of the disease to the chronic course and a negative impact on performance in education, work capacity and quality of patients’ life. The aim. To develop a method for prediction of tension-type headache occurrence in adolescents. Materials and methods. 2342 adolescent boys and girls at the age of 13-17 years in schools of Kharkiv were examined. We used questionnaire to identify the headache. A group of adolescents with tension-type headache - 1430 people (61.1% was selected. The control group included 246 healthy adolescents. Possible risk factors for tension-type headache formation were divided into 4 groups: genetic, biomedical, psychosocial and social. Mathematical prediction of tension-type headache risk in adolescents was performed using the method of intensive indicators normalization of E.N. Shigan, which was based on probabilistic Bayesian’s method. The result was presented in the form of prognostic coefficients. Results. The most informative risk factors for tension-type headache development were the diseases, from which the teenager suffered after 1 year (sleep disorders, gastrointestinal diseases, autonomic disorders in the family history, traumatic brain injury, physical inactivity, poor adaptation of the patient in the kindergarten and school, stresses. Diagnostic scale has been developed to predict the risk of tension-type headache. It includes 23 prognostic factors with their gradation and meaning of integrated risk indicator, depending on individual factor strength influence. The risk of tension-type headache development ranged from 25,27 to 81,43 values of prognostic coefficient (low probability (25,27-43,99, the average probability (43,99-62,71 and high probability (62,71- 81,43. Conclusion. The study of tension-type headache risk factors, which were obtained by using an assessed and

Planck and the local Universe: quantifying the tension

CERN Document Server

Verde, Licia; Protopapas, Pavlos

2013-01-01

We use the latest Planck constraints, and in particular constraints on the derived parameters (Hubble constant and age of the Universe) for the local universe and compare them with local measurements of the same quantities. We propose a way to quantify whether cosmological parameters constraints from two different experiments are in tension or not. Our statistic, T, is an evidence ratio and therefore can be interpreted with the widely used Jeffrey's scale. We find that in the framework of the LCDM model, the Planck inferred two dimensional, joint, posterior distribution for the Hubble constant and age of the Universe is in "strong" tension with the local measurements; the odds being ~ 1:50. We explore several possibilities for explaining this tension and examine the consequences both in terms of unknown errors and deviations from the LCDM model. In some one-parameter LCDM model extensions, tension is reduced whereas in other extensions, tension is instead increased. In particular, small total neutrino masses ...

Effects of surface tension on tray point efficiencies

Energy Technology Data Exchange (ETDEWEB)

Chen, G.X.; Afacan, A.; Chuang, K.T. (Alberta Univ., Edmonton, AB (Canada))

1994-08-01

Sieve tray efficiencies for the distillation of methanol/water, acetic acid/water, and cyclohexane/n-heptane mixtures were measured as a function of composition under fixed vapor and liquid rates in a 0.15 m diameter distillation column. The three binary distillation systems used in the study had a wide range of surface tensions measured as a function of composition. From the efficiencies measured, the number of vapor- and liquid-phase transfer units (Ng and Nl) was determined and the effects of surface tension on Ng and Nl were identified. To further verify the results obtained from the distillation column, bubble sizes in froths for air/water, air/methanol, and air/(water + surfactant) systems with different surface tensions were measured. The results show that surface tension has a significant effect on tray efficiency and the number of transfer units. Bubble sizes in the tray froths were mainly determined by surface tension, and bubble breakup and coalescence occur in the froths. 45 refs., 15 figs., 1 tab.

Accounting for oxygen in the renal cortex: a computational study of factors that predispose the cortex to hypoxia.

Science.gov (United States)

Lee, Chang-Joon; Gardiner, Bruce S; Ngo, Jennifer P; Kar, Saptarshi; Evans, Roger G; Smith, David W

2017-08-01

We develop a pseudo-three-dimensional model of oxygen transport for the renal cortex of the rat, incorporating both the axial and radial geometry of the preglomerular circulation and quantitative information regarding the surface areas and transport from the vasculature and renal corpuscles. The computational model was validated by simulating four sets of published experimental studies of renal oxygenation in rats. Under the control conditions, the predicted cortical tissue oxygen tension ([Formula: see text]) or microvascular oxygen tension (µPo 2 ) were within ±1 SE of the mean value observed experimentally. The predicted [Formula: see text] or µPo 2 in response to ischemia-reperfusion injury, acute hemodilution, blockade of nitric oxide synthase, or uncoupling mitochondrial respiration, were within ±2 SE observed experimentally. We performed a sensitivity analysis of the key model parameters to assess their individual or combined impact on the predicted [Formula: see text] and µPo 2 The model parameters analyzed were as follows: 1 ) the major determinants of renal oxygen delivery ([Formula: see text]) (arterial blood Po 2 , hemoglobin concentration, and renal blood flow); 2 ) the major determinants of renal oxygen consumption (V̇o 2 ) [glomerular filtration rate (GFR) and the efficiency of oxygen utilization for sodium reabsorption (β)]; and 3) peritubular capillary surface area (PCSA). Reductions in PCSA by 50% were found to profoundly increase the sensitivity of [Formula: see text] and µPo 2 to the major the determinants of [Formula: see text] and V̇o 2 The increasing likelihood of hypoxia with decreasing PCSA provides a potential explanation for the increased risk of acute kidney injury in some experimental animals and for patients with chronic kidney disease. Copyright © 2017 the American Physiological Society.

Experimental studies on radiation effects under high pressure oxygen

Energy Technology Data Exchange (ETDEWEB)

Fujimura, E [Osaka Univ. (Japan). School of Dentistry

1974-06-01

The effect of oxygen tension on the radiosensitivity of tumor cells is well known, but its clinical application for radiotherapy is not yet established. Rabbits with V x 2 carcinoma in the maxilla were irradiated by /sup 60/Co under high pressure oxygen (experimental group), and compared with those treated in air (control group). For the purpose of examining the clinical effects of high pressure oxygen, an experiment was made in vivo. The following items were compared respectively: a) Tumor regression effect b) Tumor clearance rate c) Survival days d) Half size reduction time e) Inhibition of DNA synthesis in the tumor tissue. Results obtained were as follows: a) 56 per cent of animals showed tumor regression in the experimental group, whereas it occured 26 per cent in the control group. b) 53 per cent of animals showed tumor disappearance in the experimental group, while it was observed only in 13 per cent in the control group. c) Only 2 of 30 rabbits irradiated in air survived over 180 days, whereas 11 of 30 rabbits survived meanwhile in the group irradiated under high pressure oxygen. d) About 11 days were necessary to reduce the tumor size by half after irradiation in the group under high pressure oxygen, while it took 17 days in the group treated in normal air. e) DNA synthesis was inhibited more prominently in the group irradiated under high pressure oxygen in normal air.

Critical Pedagogy, Internationalisation, and a Third Space: Cultural Tensions Revealed in Students' Discourse

Science.gov (United States)

Pitts, Margaret Jane; Brooks, Catherine F.

2017-01-01

Set within the context of a global pursuit towards the internationalisation of higher education, this paper critically examines student discourse in a globally connected classroom between learners in the USA and Singapore. It makes salient some of the cultural assumptions and tensions that undergird students' discourse in collaborative…

Modeling the oxygen microheterogeneity of tumors for photodynamic therapy dosimetry

Science.gov (United States)

Pogue, Brian W.; Paulsen, Keith D.; O'Hara, Julia A.; Hoopes, P. Jack; Swartz, Harold

2000-03-01

Photodynamic theory of tumors uses optical excitation of a sensitizing drug within tissue to produce large deposits of singlet oxygen, which are thought to ultimately cause the tumor destruction. Predicting dose deposition of singlet oxygen in vivo is challenging because measurement of this species in vivo is not easily achieved. But it is possible to follow the concentration of oxygen in vivo, and so measuring the oxygen concentration transients during PDT may provide a viable method of estimating the delivered dose of singlet oxygen. However modeling the microscopic heterogeneity of the oxygen distribution within a tumor is non-trivial, and predicting the microscopic dose deposition requires further study, but this study present the framework and initial calibration needed or modeling oxygen transport in complex geometries. Computational modeling with finite elements provides a versatile structure within which oxygen diffusion and consumption can be modeled within realistic tissue geometries. This study develops the basic tools required to simulate a tumor region, and examines the role of (i) oxygen supply and consumption rates, (ii) inter- capillary spacing, (iii) photosensitizer distribution, and (iv) differences between simulated tumors and those derived directly from histology. The result of these calculations indicate that realistic tumor tissue capillary networks can be simulated using the finite element method, without excessive computational burden for 2D regions near 1 mm2, and 3D regions near 0.1mm3. These simulations can provide fundamental information about tissue and ways to implement appropriate oxygen measurements. These calculations suggest that photodynamic therapy produces the majority of singlet oxygen in and near the blood vessels, because these are the sites of highest oxygen tension. These calculations support the concept that tumor vascular regions are the major targets for PDT dose deposition.

An automatic tension measurement system of MWPC wires

International Nuclear Information System (INIS)

D'Antone, I.; Lolli, M.; Torromeo, G.

1992-01-01

An electronic system is presented for automatic mechanical tension measurement to test wire chambers. The developed system works in the tension range from 50 g to 300 g; this large working range is obtained by using a microcontroller that performs a digital control on the bridge of an oscillator containing the wire of which the tension has to be measured. The microcontroller automatically brings the system towards the oscillation condition and subsequently, measuring the frequency, it evaluates, displays and sends to a host computer the value of the mechanical tension of the wires. The system is precise and allows fast measurements. A description of the hardware and software design is given. (orig.)

The Influence of Backpack Weight and Hip Belt Tension on Movement and Loading in the Pelvis and Lower Limbs during Walking

Directory of Open Access Journals (Sweden)

Katja Oberhofer

2018-01-01

Full Text Available The introduction of hip belts to backpacks has caused a shift of loading from the spine to the hips with reported improvements in musculoskeletal comfort. Yet the effects of different hip belt tensions on gait biomechanics remain largely unknown. The goal of this study was to assess the influence of backpack weight and hip belt tension on gait biomechanics. Data from optical motion capture and ground reaction forces (GRF during walking were acquired in nine healthy male subjects (age 28.0 ± 3.9 years. Six configurations of a commercial backpack were analyzed, that is, 15 kg, 20 kg, and 25 kg loading with 30 N and 120 N hip belt tension. Joint ranges of motion (ROM, peak GRF, and joint moments during gait were analyzed for significant differences by repeated measures of ANOVA with Bonferroni post hoc comparison. Increased loading led to a significant reduction of knee flexion-extension ROM as well as pelvis rotational ROM. No statistically significant effect of hip belt tension magnitudes on gait dynamics was found at any backpack weight, yet there was a trend of increased pelvis ROM in the transverse plane with higher hip belt tension at 25 kg loading. Further research is needed to elucidate the optimum hip belt tension magnitudes for different loading weights to reduce the risks of injury especially with higher loading.

Gastrothorax or tension pneumothorax: A diagnostic dilemma

Directory of Open Access Journals (Sweden)

Singh Sarvesh

2011-01-01

Full Text Available Gastrothorax, a rare complication following thoracoabdominal aortic aneurysm repair, is reported. The clinical features of a gastrothorax and tension pneumothorax are similar and thus, a gastrothorax can masquerade as a tension pneumothorax. The diagnosis is made by a high level of clinical suspicion, chest X-ray shows a distended stomach with air fluid levels and a computerised tomography is useful in assessing the diaphragm and establishing the positions of the various intra-abdominal organs. Also, the risk of an intercostal drainage tube placement and the role of nasogastric tube in avoiding the development of a tension gastrothorax is highlighted.

Cerebral blood flow response to changes in arterial carbon dioxide tension during hypothermic cardiopulmonary bypass in children

International Nuclear Information System (INIS)

Kern, F.H.; Ungerleider, R.M.; Quill, T.J.; Baldwin, B.; White, W.D.; Reves, J.G.; Greeley, W.J.

1991-01-01

We examined the relationship of changes in partial pressure of carbon dioxide on cerebral blood flow responsiveness in 20 pediatric patients undergoing hypothermic cardiopulmonary bypass. Cerebral blood flow was measured during steady-state hypothermic cardiopulmonary bypass with the use of xenon 133 clearance methodology at two different arterial carbon dioxide tensions. During these measurements there was no significant change in mean arterial pressure, nasopharyngeal temperature, pump flow rate, or hematocrit value. Cerebral blood flow was found to be significantly greater at higher arterial carbon dioxide tensions (p less than 0.01), so that for every millimeter of mercury rise in arterial carbon dioxide tension there was a 1.2 ml.100 gm-1.min-1 increase in cerebral blood flow. Two factors, deep hypothermia (18 degrees to 22 degrees C) and reduced age (less than 1 year), diminished the effect carbon dioxide had on cerebral blood flow responsiveness but did not eliminate it. We conclude that cerebral blood flow remains responsive to changes in arterial carbon dioxide tension during hypothermic cardiopulmonary bypass in infants and children; that is, increasing arterial carbon dioxide tension will independently increase cerebral blood flow

Tension Hydrothorax Related to Disseminated Endometriosis

Directory of Open Access Journals (Sweden)

AnnaKate Deal, MD

2016-01-01

Full Text Available We present the case of a 34-year-old woman presenting to the emergency department (ED with dyspnea, cough, and fever. She was found to have a tension hydrothorax and was treated with ultrasound-guided thoracentesis in the ED. Subsequent inpatient evaluation showed the patient had disseminated endometriosis. Tension hydrothorax has not been previously described in the literature as a complication of this disease.

Surface tension effect on the mechanical properties of nanomaterials measured by atomic force microscopy

Science.gov (United States)

Cuenot, Stéphane; Frétigny, Christian; Demoustier-Champagne, Sophie; Nysten, Bernard

2004-04-01

The effect of reduced size on the elastic properties measured on silver and lead nanowires and on polypyrrole nanotubes with an outer diameter ranging between 30 and 250 nm is presented and discussed. Resonant-contact atomic force microscopy (AFM) is used to measure their apparent elastic modulus. The measured modulus of the nanomaterials with smaller diameters is significantly higher than that of the larger ones. The latter is comparable to the macroscopic modulus of the materials. The increase of the apparent elastic modulus for the smaller diameters is attributed to surface tension effects. The surface tension of the probed material may be experimentally determined from these AFM measurements.

Rein tension acceptance in young horses in a voluntary test situation.

Science.gov (United States)

Christensen, J W; Zharkikh, T L; Antoine, A; Malmkvist, J

2011-03-01

During riding, horses are frequently exposed to pressure from the rider, e.g. through the bit and reins, but few studies have investigated at which point rein tension becomes uncomfortable for the horse. To investigate how much rein tension young inexperienced horses are willing to accept in order to obtain a food reward; whether the tension acceptance changes during 3 consecutive test days; and whether rein tension correlates with the expression of conflict behaviour and heart rate. Pressure-naïve horses will apply only little rein tension in the first voluntary trial, but their acceptance will gradually increase. High levels of rein tension will lead to expression of conflict behaviour and increases in heart rate. Fifteen 2-year-old, bridle-naïve mares were encouraged to stretch their head forward (across a 0.95 m high metal bar) to obtain a food reward in a voluntary test situation. On each test day, each horse was exposed to 2 control sessions (loose reins), an intermediate and a short rein session (1 min/session). Rein tension, heart rate and behaviour were recorded. The horses applied significantly more tension on the first day (mean rein tension: 10.2 N), compared to the second and third test day (Day 2: 6.0 and Day 3: 5.7 N). The horses showed significantly more conflict behaviour in the short rein treatment. There was no treatment effect on heart rate. The horses applied the highest rein tension on the first day, and apparently learned to avoid the tension, rather than habituate to it. Rein tension correlated with expression of conflict behaviour, indicating that the horses found the tension aversive. Further studies should focus on the correlation between rein tension and conflict behaviour in ridden horses. © 2010 EVJ Ltd.

Surface tension of liquid Al-Cu binary alloys.

OpenAIRE

Schmitz, Julianna; Brillo, Jürgen; Egry, Ivan; Schmid-Fetzer, Rainer

2009-01-01

Surface tension data of liquid Al–Cu binary alloys have been measured contactlessly using the technique of electromagnetic levitation. A digital CMOS-camera (400 fps) recorded image sequences of the oscillating liquid sample and surface tensions were determined from analysis of the frequency spectra. Measurements were performed for samples covering the entire range of composition and precise data were obtained in a broad temperature range. It was found that the surface tensions can ...

Effect of Membrane Tension on the Electric Field and Dipole Potential of Lipid Bilayer Membrane

Science.gov (United States)

Warshaviak, Dora Toledo; Muellner, Michael J.; Chachisvilis, Mirianas

2011-01-01

The dipole potential of lipid bilayer membrane controls the difference in permeability of the membrane to oppositely charged ions. We have combined molecular dynamics (MD) simulations and experimental studies to determine changes in electric field and electrostatic potential of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) lipid bilayer in response to applied membrane tension. MD simulations based on CHARMM36 force field showed that electrostatic potential of DOPC bilayer decreases by ~45 mV in the physiologically relevant range of membrane tension values (0 to 15 dyn/cm). The electrostatic field exhibits a peak (~0.8×109 V/m) near the water/lipid interface which shifts by 0.9 Å towards the bilayer center at 15 dyn/cm. Maximum membrane tension of 15 dyn/cm caused 6.4% increase in area per lipid, 4.7% decrease in bilayer thickness and 1.4% increase in the volume of the bilayer. Dipole-potential sensitive fluorescent probes were used to detect membrane tension induced changes in DOPC vesicles exposed to osmotic stress. Experiments confirmed that dipole potential of DOPC bilayer decreases at higher membrane tensions. These results are suggestive of a potentially new mechanosensing mechanism by which mechanically induced structural changes in the lipid bilayer membrane could modulate the function of membrane proteins by altering electrostatic interactions and energetics of protein conformational states. PMID:21722624

Embracing Tensions in Feminist Organizational Communication Pedagogies

Science.gov (United States)

Linabary, Jasmine R.; Long, Ziyu; Mouton, Ashton; Rao, Ranjani L.; Buzzanell, Patrice M.

2017-01-01

Feminist pedagogies hold potential to create more inclusive and transformative classrooms. Adopting a tension-centered approach, we draw on our individual and collective reflections on the design and instruction of a multi-section undergraduate organizational communication course to build an autoethnographic account of the tensions associated with…

Tension Pneumothorax following an Accidental Kerosene Poisoning ...

African Journals Online (AJOL)

Tension pneumothorax is a rare complication following an accidental kerosene poisoning. In such situation, a bed-side needle thoracocentesis is performed because of its potential of becoming fatal; hence its clinical importance. A case of 15 month old boy with tension pneumothorax following accidental kerosene ...

It's a Long Way down: The Underlying Tensions in the Education Export Industry

Science.gov (United States)

Marginson, Simon

2011-01-01

The stellar rise of the education export industry in Australian higher education, and the even more spectacular downturn now occurring, mask underlying tensions that have long dogged the industry and prevented it from improving quality or achieving long-term sustainability. The international education programme has been unbalanced by the drive for…

A novel approach to pipeline tensioner modeling

Energy Technology Data Exchange (ETDEWEB)

O' Grady, Robert; Ilie, Daniel; Lane, Michael [MCS Software Division, Galway (Ireland)

2009-07-01

As subsea pipeline developments continue to move into deep and ultra-deep water locations, there is an increasing need for the accurate prediction of expected pipeline fatigue life. A significant factor that must be considered as part of this process is the fatigue damage sustained by the pipeline during installation. The magnitude of this installation-related damage is governed by a number of different agents, one of which is the dynamic behavior of the tensioner systems during pipe-laying operations. There are a variety of traditional finite element methods for representing dynamic tensioner behavior. These existing methods, while basic in nature, have been proven to provide adequate forecasts in terms of the dynamic variation in typical installation parameters such as top tension and sagbend/overbend strain. However due to the simplicity of these current approaches, some of them tend to over-estimate the frequency of tensioner pay out/in under dynamic loading. This excessive level of pay out/in motion results in the prediction of additional stress cycles at certain roller beds, which in turn leads to the prediction of unrealistic fatigue damage to the pipeline. This unwarranted fatigue damage then equates to an over-conservative value for the accumulated damage experienced by a pipeline weld during installation, and so leads to a reduction in the estimated fatigue life for the pipeline. This paper describes a novel approach to tensioner modeling which allows for greater control over the velocity of dynamic tensioner pay out/in and so provides a more accurate estimation of fatigue damage experienced by the pipeline during installation. The paper reports on a case study, as outlined in the proceeding section, in which a comparison is made between results from this new tensioner model and from a more conventional approach. The comparison considers typical installation parameters as well as an in-depth look at the predicted fatigue damage for the two methods

Nitric oxide formation from the reaction of nitrite with carp and rabbit hemoglobin at intermediate oxygen saturations

DEFF Research Database (Denmark)

Jensen, Frank Bo

2008-01-01

The nitrite reductase activity of deoxyhemoglobin has received much recent interest because the nitric oxide produced in this reaction may participate in blood flow regulation during hypoxia. The present study used spectral deconvolution to characterize the reaction of nitrite with carp and rabbit...... hemoglobin at different constant oxygen tensions that generate the full range of physiological relevant oxygen saturations. Carp is a hypoxia-tolerant species with very high hemoglobin oxygen affinity, and the high R-state character and low redox potential of the hemoglobin is hypothesized to promote...... NO generation from nitrite. The reaction of nitrite with deoxyhemoglobin leads to a 1 : 1 formation of nitrosylhemoglobin and methemoglobin in both species. At intermediate oxygen saturations, the reaction with deoxyhemoglobin is clearly favored over that with oxyhemoglobin, and the oxyhemoglobin reaction...

Normobaric pulmonary oxygen toxicity : experimental studies on the mechanism of the protective role of endotoxin and the role of surfactant.

NARCIS (Netherlands)

J. Klein (Jan)

1991-01-01

textabstractAdministration of above-ambient oxygen tensions, necessary for treatment of severe hypoxemia caused by respiratory failure or acute lung injury, is potentially toxic for the lungs. This thesis is based on six articles dealing with this topic: one review article and five articles

Effect of potential attraction term on surface tension of ionic liquids

Science.gov (United States)

Vaziri, N.; Khordad, R.; Rezaei, G.

2018-03-01

In this work, we have studied the effect of attraction term of molecular potential on surface tension of ionic liquids (ILs). For this purpose, we have introduced two different potential models to obtain analytical expressions for the surface tension of ILs. The introduced potential models have different attraction terms. The obtained surface tensions in this work have been compared with other theoretical methods and also experimental data. Using the calculated surface tension, the sound velocity is also estimated. We have studied the structural effects on the surface tensions of imidazolium-based ionic liquids. It is found that the cation alkyl chain length and the anion size play important roles to the surface tension of the selected ionic liquids. The calculated surface tensions show a good harmony with experimental data. It is clear that the attraction term of molecular potential has an important role on surface tension and sound velocity of our system.

Substrate stiffness and oxygen as regulators of stem cell differentiation during skeletal tissue regeneration: a mechanobiological model.

Directory of Open Access Journals (Sweden)

Darren Paul Burke

Full Text Available Extrinsic mechanical signals have been implicated as key regulators of mesenchymal stem cell (MSC differentiation. It has been possible to test different hypotheses for mechano-regulated MSC differentiation by attempting to simulate regenerative events such as bone fracture repair, where repeatable spatial and temporal patterns of tissue differentiation occur. More recently, in vitro studies have identified other environmental cues such as substrate stiffness and oxygen tension as key regulators of MSC differentiation; however it remains unclear if and how such cues determine stem cell fate in vivo. As part of this study, a computational model was developed to test the hypothesis that substrate stiffness and oxygen tension regulate stem cell differentiation during fracture healing. Rather than assuming mechanical signals act directly on stem cells to determine their differentiation pathway, it is postulated that they act indirectly to regulate angiogenesis and hence partially determine the local oxygen environment within a regenerating tissue. Chondrogenesis of MSCs was hypothesized to occur in low oxygen regions, while in well vascularised regions of the regenerating tissue a soft local substrate was hypothesised to facilitate adipogenesis while a stiff substrate facilitated osteogenesis. Predictions from the model were compared to both experimental data and to predictions of a well established computational mechanobiological model where tissue differentiation is assumed to be regulated directly by the local mechanical environment. The model predicted all the major events of fracture repair, including cartilaginous bridging, endosteal and periosteal bony bridging and bone remodelling. It therefore provides support for the hypothesis that substrate stiffness and oxygen play a key role in regulating MSC fate during regenerative events such as fracture healing.

Tension Stiffened and Tendon Actuated Manipulator

Science.gov (United States)

Doggett, William R. (Inventor); Dorsey, John T. (Inventor); Ganoe, George G. (Inventor); King, Bruce D. (Inventor); Jones, Thomas C. (Inventor); Mercer, Charles D. (Inventor); Corbin, Cole K. (Inventor)

2015-01-01

A tension stiffened and tendon actuated manipulator is provided performing robotic-like movements when acquiring a payload. The manipulator design can be adapted for use in-space, lunar or other planetary installations as it is readily configurable for acquiring and precisely manipulating a payload in both a zero-g environment and in an environment with a gravity field. The manipulator includes a plurality of link arms, a hinge connecting adjacent link arms together to allow the adjacent link arms to rotate relative to each other and a cable actuation and tensioning system provided between adjacent link arms. The cable actuation and tensioning system includes a spreader arm and a plurality of driven and non-driven elements attached to the link arms and the spreader arm. At least one cable is routed around the driven and non-driven elements for actuating the hinge.

Limitations of potentiometric oxygen sensors operating at low oxygen levels

DEFF Research Database (Denmark)

Lund, Anders; Jacobsen, Torben; Hansen, Karin Vels

2011-01-01

The electrochemical processes that limit the range of oxygen partial pressures in which potentiometric oxygen sensors can be used, were analysed using a theoretical and an experimental approach. Electrochemical impedance spectroscopy was performed on porous Pt/yttria stabilised zirconia (YSZ......) electrodes between 10−6 and 0.2 bar and at temperatures between 500 and 950 °C. The flow of oxide ions and electron holes through a sensor cell, with a YSZ electrolyte, were calculated under similar conditions. The oxygen permeation of the sensor cell was insignificant at an oxygen partial pressure of 10......−6 bar for an inlet flow rate higher than 2 L h−1 between 600 and 800 °C. The polarisation resistance measured between 10−6 and 10−4 bar was found to be inversely proportional to the oxygen partial pressure, nearly temperature independent and inversely proportional to the inlet gas flow rate, which shows...

Muscular tension and body posture in relation to voice handicap and voice quality in teachers with persistent voice complaints.

Science.gov (United States)

Kooijman, P G C; de Jong, F I C R S; Oudes, M J; Huinck, W; van Acht, H; Graamans, K

2005-01-01

The aim of this study was to investigate the relationship between extrinsic laryngeal muscular hypertonicity and deviant body posture on the one hand and voice handicap and voice quality on the other hand in teachers with persistent voice complaints and a history of voice-related absenteeism. The study group consisted of 25 female teachers. A voice therapist assessed extrinsic laryngeal muscular tension and a physical therapist assessed body posture. The assessed parameters were clustered in categories. The parameters in the different categories represent the same function. Further a tension/posture index was created, which is the summation of the different parameters. The different parameters and the index were related to the Voice Handicap Index (VHI) and the Dysphonia Severity Index (DSI). The scores of the VHI and the individual parameters differ significantly except for the posterior weight bearing and tension of the sternocleidomastoid muscle. There was also a significant difference between the individual parameters and the DSI, except for tension of the cricothyroid muscle and posterior weight bearing. The score of the tension/posture index correlates significantly with both the VHI and the DSI. In a linear regression analysis, the combination of hypertonicity of the sternocleidomastoid, the geniohyoid muscles and posterior weight bearing is the most important predictor for a high voice handicap. The combination of hypertonicity of the geniohyoid muscle, posterior weight bearing, high position of the hyoid bone, hypertonicity of the cricothyroid muscle and anteroposition of the head is the most important predictor for a low DSI score. The results of this study show the higher the score of the index, the higher the score of the voice handicap and the worse the voice quality is. Moreover, the results are indicative for the importance of assessment of muscular tension and body posture in the diagnosis of voice disorders.

Muscle tissue oxygenation, pressure, electrical, and mechanical responses during dynamic and static voluntary contractions

DEFF Research Database (Denmark)

Vedsted, Pernille; Blangsted, Anne Katrine; Søgaard, Karen

2006-01-01

tension (rTO(2)) would be larger during dynamic (DYN) than intermittent static (IST) low force contractions; and that (2) oxygen tension would remain lower in the resting periods subsequent to DYN as compared to those following IST. Eight subjects performed elbow flexions with identical time......-tension products: (1) DYN as a 20 degrees elbow movement of 2 s concentric and 2 s eccentric followed by a 4 s rest; and (2) IST with a 4 s contraction followed by a 4 s rest. Each session was performed for 1 min at 10 and 20% of the maximal voluntary contraction (MVC). The force, bipolar surface EMG, MMG, IMP, rTO......, respectively), and a similar picture was seen for the eccentric phase. However, no differences were seen in rTO(2) in either the contraction or the rest periods. In a prolonged rest period (8 s) after the sessions, DYN but not IST showed rTO(2) above baseline level. In conclusion, rTO(2) in DYN and IST were...

Parachute Cord Tension Sensor

Data.gov (United States)

National Aeronautics and Space Administration — To design and fabricate a light weight (few oz), very small (~2 inch length) parachute cord tension sensor demonstrator device.A major challenge for the CPAS (The...

Tension-filled Governance?

DEFF Research Database (Denmark)

Celik, Tim Holst

on the statesituated tension-filled functional relationship between legitimation and accumulation, the study both historically and theoretically reworks this approach and reapplies it for the post-1970s/1990s governance period. It asks whether and to what extent governance has served as a distinctive post- 1970s/1990s...

Focal adhesions, stress fibers and mechanical tension

Energy Technology Data Exchange (ETDEWEB)

Burridge, Keith, E-mail: Keith_Burridge@med.unc.edu [Department of Cell Biology and Physiology, and Lineberger Comprehensive Cancer Center, 12-016 Lineberger, CB#7295, University of North Carolina, Chapel Hill, NC (United States); Guilluy, Christophe, E-mail: christophe.guilluy@univ-nantes.fr [Inserm UMR-S1087, CNRS UMR-C6291, L' institut du Thorax, and Université de Nantes, Nantes (France)

2016-04-10

Stress fibers and focal adhesions are complex protein arrays that produce, transmit and sense mechanical tension. Evidence accumulated over many years led to the conclusion that mechanical tension generated within stress fibers contributes to the assembly of both stress fibers themselves and their associated focal adhesions. However, several lines of evidence have recently been presented against this model. Here we discuss the evidence for and against the role of mechanical tension in driving the assembly of these structures. We also consider how their assembly is influenced by the rigidity of the substratum to which cells are adhering. Finally, we discuss the recently identified connections between stress fibers and the nucleus, and the roles that these may play, both in cell migration and regulating nuclear function. - Highlights: • The different types of stress fiber and focal adhesion are described. • We discuss the controversy about tension and assembly of these structures. • We describe the different models used to investigate assembly of these structures. • The influence of substratum rigidity is discussed. • Stress fiber connections to the nucleus are reviewed.

The law of corresponding states and surface tension of metals

International Nuclear Information System (INIS)

Digilov, R.

2001-01-01

Full Text: Surface tension of liquid metals is one of fundamental and most important quantities in theory and practice of material processing and its temperature dependence leads to the well-known Marangoni convection. Although currently methods are sufficiently precise to measure the surface tension, there are uncertainties in experimental data and its temperature dependence mainly due to impurity, which even a trace of it strongly affects the results of measurements. The theoretical treatment from the first principles is unwieldy and not always permits one to calculate the surface tension with certainty. Another active research field deals with empirical correlation between the surface tension and bulk thermodynamic properties, which we interpret as a simple consequence of the law of corresponding states. In order to relate the surface tension and to bulk properties of liquid metals the reduced formula is derived by scaling with the melting point T m (0) at p = 0 and atomic volume Ω 0 2/3 at T = 0 K as macroscopic parameters for scaling ε and a characterizing the interatomic potential in metals. The reduced surface tension and the reduced surface entropy obtained in high temperature limit are discussed and compared with the experiment. The reduced temperature coefficient of the surface tension found is a universal constant for the metals of the same structure. It is shown that pressure dependence of the surface tension, so called baric coefficient of the surface tension, can be described by pressure dependence of scaling parameters T m (p) and Ω 0 (p). (author)

Influence on cervical MR imaging by tension. Comparison between the picture quality of cervical MR image and tension

International Nuclear Information System (INIS)

Iseki, Tadahiro; Okano, Tamotsu; Kanou, Norio; Tanaka, Kazuharu; Kawasaki, Kouichi; Kawachi, Toshiaki

2003-01-01

In our first report, we compared influence on cervical MR image (C-MRI) by fear and anxiety on between the first time and experienced patients, in which the significant difference was not seen between those patients. Then, the present study, we made a comparison of the picture sharpness of C-MRI on between patients who were in states of tension and not, and on among tense patients by several causes. Our study showed the tendency which the good quality pictures were easy to be obtained in the experienced patients who were tensely and the poor quality pictures were in the patients who were not, which could not demonstrated the statistical significant difference. However, as compared the respective cause which induces tension with the picture sharpness, the patients with tenses caused by MR device showed to be difficult to be obtained the good quality pictures. The present study suggested that ''unsuitable tension'', which was overstrung due to fear and anxiety from MR device, was difficult to obtain good quality picture of C-MRI, and that ''suitable tension'', with which could be kept still during the examination, was easy to do it. (author)

Tensions between Teams and Their Leaders

Directory of Open Access Journals (Sweden)

J. David Johnson

2016-10-01

Full Text Available The intersection of teamwork and leadership results in tensions, dilemmas, and paradoxes for both individuals and for institutions such as simultaneously empowering individuals at the same time it frustrates them when our naive, cultural understanding of leadership centralizes power and values leaders who can impose their will and vision on others. Perhaps the fundamental paradox of teamwork and leadership is that the more leadership is focused on an individual the less likely a team’s potential will be realized. Six specific domains where tensions arise are: at team boundaries; culture; who is in charge, rationality/cognition; diversity; and collaborations. Three approaches - clarifying different levels of analysis, temporal factors, and overarching concepts - to resolving tensions are discussed. New conceptions of leadership and the importance of the larger cultural frame within which they are embedded are needed for the management of technology and innovation.

Oxygen delivery and consumption during on-bypass cabg in htea and central analgesia

Directory of Open Access Journals (Sweden)

Віталій Олексійович Собокарь

2015-04-01

Full Text Available Objective. Despite some advantages, the use of high thoracic epidural anesthesia (HTEA during on-bypass cardiac surgery may be discouraged by fear of adverse hemodynamic effects and associated disturbances of oxygen delivery.Aim. To compare oxygen delivery and consumption during on-bypass coronary artery bypass grafting in settings of HTEA and central analgesia (CA.Methods. 132 patients were assigned into two groups – study group (n=85, where the surgery was performed under HTEA and control group (n=47 - where the surgery was carried out under CA. Using data of transesophageal cardiac ultrasound and blood oximetry blood oxygen delivery (DO2, oxygen consumption (VO2, oxygen extraction coefficient (CEO2 were calculated at four stages of the surgery: after induction, sternotomy, cardiopulmonary bypass and at the end of the surgery.Results. In the initial stages of the surgery DO2 and VO2 were reduced relative to reference values with a tendency to increase in the course of the operation and achievement of the normal or supernormal level (VO2, study group in the final stage. The decrease was due to moderate hypodynamic circulation and hemodilution. After sternotomy DO2 in the study group was higher than that of the control: 356 (279; 458 vs 317±89 ml·min-1·m-2, (р=0,021. After cardiopulmonary bypass oxygen saturation of venous blood (SatvO2, in the study group was 71 ± 9 % compared with 68 ± 10 % in the control group. At the end of the surgery SatvO2 in the study group was 71 (66; 75 vs 59 (53; 70 % in the control (р = 0,005 and oxygen tension of venous blood (РvО2 was correspondingly 39 ± 6 and 33 (30; 38 mm Hg (р = 0,027. Despite the decrease in DO2 and VO2, oxygen extraction indices - CEO2, pvO2, SatvO2, and remained within the reference range, except that of the control group at the end of the surgery. Furthermore, at no stage lactate rise or acid-base deviations was observed in the both groups.Conclusions. In patients operated

Bending Under Tension Test with Direct Friction Measurement

DEFF Research Database (Denmark)

Andreasen, Jan Lasson; Olsson, David Dam; Chodnikiewicz, K.

2004-01-01

A special BUT-transducer has been developed in which friction around the tool radius can be directly measured when drawing a plane sheet strip around a cylindrical tool-pin under constant back tension. The front tension, back tension and torque on the tool-pin are all measured directly, thus...... enabling accurate measurement of friction and direct determination of lubricant film breakdown for varying normal pressure, sliding speed, tool radius and tool preheat temperature. The transducer is applied in an experimental investigation focusing on limits of lubrication in drawing of stainless steel...

Automated wireless monitoring system for cable tension using smart sensors

Science.gov (United States)

Sim, Sung-Han; Li, Jian; Jo, Hongki; Park, Jongwoong; Cho, Soojin; Spencer, Billie F.; Yun, Chung-Bang

2013-04-01

Cables are critical load carrying members of cable-stayed bridges; monitoring tension forces of the cables provides valuable information for SHM of the cable-stayed bridges. Monitoring systems for the cable tension can be efficiently realized using wireless smart sensors in conjunction with vibration-based cable tension estimation approaches. This study develops an automated cable tension monitoring system using MEMSIC's Imote2 smart sensors. An embedded data processing strategy is implemented on the Imote2-based wireless sensor network to calculate cable tensions using a vibration-based method, significantly reducing the wireless data transmission and associated power consumption. The autonomous operation of the monitoring system is achieved by AutoMonitor, a high-level coordinator application provided by the Illinois SHM Project Services Toolsuite. The monitoring system also features power harvesting enabled by solar panels attached to each sensor node and AutoMonitor for charging control. The proposed wireless system has been deployed on the Jindo Bridge, a cable-stayed bridge located in South Korea. Tension forces are autonomously monitored for 12 cables in the east, land side of the bridge, proving the validity and potential of the presented tension monitoring system for real-world applications.

Changes in Oxygen Partial Pressure in the Vitreous Body and Arterial Blood of Rabbits Depending on Oxygen Concentration in Inspired Mixture.

Science.gov (United States)

Amkhanitskaya, L I; Nikolaeva, G V; Sokolova, N A

2015-07-01

We demonstrated that the vitreous body of one-month-old rabbits becomes a "reservoir" for storage and accumulation of oxygen after exposure to additional oxygenation of the organism (O2 concentrations in inspired gas mixture were 40, 60, 85, and 99%). The higher was O2 concentration in inspired mixture, the higher was oxygen saturation of the blood and vitreous body. O2 concentration of 40% was relatively safe for eye tissues. O2 concentration >60% induced oxygen accumulation in the vitreous body, which can be a provoking factor for the development of oxygen-induced pathologies.

Corrosion resistance of grouted post-tensioning systems : [summary].

Science.gov (United States)

2013-08-01

The increased popularity of post-tensioned bridge construction in the United States has led to concerns about corrosion and its impact on the life cycle of these bridges. Although the vast majority of post-tensioned bridges in the United States have ...

Job-related tension, self-esteem and psychological distress in rehabilitation professionals.

Science.gov (United States)

Flett, R; Biggs, H; Alpass, F

1995-06-01

We examined perceptions of job-related tension among a non-random sample of 52 New Zealand rehabilitation service providers. We considered the relations between job tension and psychological distress and the extent to which feelings of self-esteem moderated this relationship. Major findings are that (a) there is a consistent positive relationship between job tension and general psychological distress; (b) there is a consistent negative relationship between self-esteem and both job tension and general distress; (c) self-esteem moderates the effect of job tension on general distress in that high levels of job tension were associated with increases in psychological distress among respondents with low self-esteem while among respondents with high-self esteem, job-related tension had little negative impact on feelings of psychological distress. Despite a number of limitations, the findings have a number of important implications for professional functioning among rehabilitation service providers and highlight the need for appropriate staff development and training initiatives which focus specifically on service provider wellbeing.

Dependence of nitrite oxidation on nitrite and oxygen in low-oxygen seawater

Science.gov (United States)

Sun, Xin; Ji, Qixing; Jayakumar, Amal; Ward, Bess B.

2017-08-01

Nitrite oxidation is an essential step in transformations of fixed nitrogen. The physiology of nitrite oxidizing bacteria (NOB) implies that the rates of nitrite oxidation should be controlled by concentration of their substrate, nitrite, and the terminal electron acceptor, oxygen. The sensitivities of nitrite oxidation to oxygen and nitrite concentrations were investigated using 15N tracer incubations in the Eastern Tropical North Pacific. Nitrite stimulated nitrite oxidation under low in situ nitrite conditions, following Michaelis-Menten kinetics, indicating that nitrite was the limiting substrate. The nitrite half-saturation constant (Ks = 0.254 ± 0.161 μM) was 1-3 orders of magnitude lower than in cultivated NOB, indicating higher affinity of marine NOB for nitrite. The highest rates of nitrite oxidation were measured in the oxygen depleted zone (ODZ), and were partially inhibited by additions of oxygen. This oxygen sensitivity suggests that ODZ specialist NOB, adapted to low-oxygen conditions, are responsible for apparently anaerobic nitrite oxidation.

Systematic instrumental errors between oxygen saturation analysers in fetal blood during deep hypoxemia.

Science.gov (United States)

Porath, M; Sinha, P; Dudenhausen, J W; Luttkus, A K

2001-05-01

During a study of artificially produced deep hypoxemia in fetal cord blood, systematic errors of three different oxygen saturation analysers were evaluated against a reference CO oximeter. The oxygen tensions (PO2) of 83 pre-heparinized fetal blood samples from umbilical veins were reduced by tonometry to 1.3 kPa (10 mm Hg) and 2.7 kPa (20 mm Hg). The oxygen saturation (SO2) was determined (n=1328) on a reference CO oximeter (ABL625, Radiometer Copenhagen) and on three tested instruments (two CO oximeters: Chiron865, Bayer Diagnostics; ABL700, Radiometer Copenhagen, and a portable blood gas analyser, i-STAT, Abbott). The CO oximeters measure the oxyhemoglobin and the reduced hemoglobin fractions by absorption spectrophotometry. The i-STAT system calculates the oxygen saturation from the measured pH, PO2, and PCO2. The measurements were performed in duplicate. Statistical evaluation focused on the differences between duplicate measurements and on systematic instrumental errors in oxygen saturation analysis compared to the reference CO oximeter. After tonometry, the median saturation dropped to 32.9% at a PO2=2.7 kPa (20 mm Hg), defined as saturation range 1, and to 10% SO2 at a PO2=1.3 kPa (10 mm Hg), defined as range 2. With decreasing SO2, all devices showed an increased difference between duplicate measurements. ABL625 and ABL700 showed the closest agreement between instruments (0.25% SO2 bias at saturation range 1 and -0.33% SO2 bias at saturation range 2). Chiron865 indicated higher saturation values than ABL 625 (3.07% SO2 bias at saturation range 1 and 2.28% SO2 bias at saturation range 2). Calculated saturation values (i-STAT) were more than 30% lower than the measured values of ABL625. The disagreement among CO oximeters was small but increasing under deep hypoxemia. Calculation found unacceptably low saturation.

Experimental and analytical study of oxygen depletion in stirred cell suspensions

International Nuclear Information System (INIS)

Whillans, D.W.; Rauth, A.M.

1980-01-01

The determination and maintenance of constant low but non-zero levels of oxygen is critical in the study of the radiation chemical interactions of nitroimidazoles in mammalian cells in vitro. As well, many of these chemicals have increased toxicity toward hypoxic compared to aerobic cells, although absolute hypoxia probably is not required. Both of these phenomena must be investigated in systems where significant consumption of oxygen takes place, either through radiation depletion or by cellular metabolism. In this paper an analysis has been made of the form of oxygen depletion in stirred cell suspensions with overlying gas phase, and it has been found to conform to the relationship (C[t] - C/sub infinity/) = (C[0] - C/sub infinity/) exp(-k 1 t), where C/sub infinity/ = C/sub g/ - R/k 1 . Here C[t] is the oxygen tension throughout the solution; C/sub g/, the equivalent level in the overlying gas phase; R (concentration units per sec), the depletion rate; k 1 (sec/sup -1/), a physical constant independent of oxygen concentration and depletion rate; and C/sub infinity/, the oxygen level in solution approached at long times. This relationship has been confirmed in detail using a Clark-type oxygen sensor and a high-stability amplifier design due to Koch. Since oxygen levels down to a few hundred parts per million can be determined with accuracy, it has been possible to measure precisely the oxygen levels present in our experimental systems. Implications of these results for the interpretation of data obtained in stirred cell suspension with overlying gas phase under conditions of consumption are discussed

Tensioned Fabric Structures with Surface in the Form of Chen-Gackstatter

Directory of Open Access Journals (Sweden)

Yee Hooi Min

2016-01-01

Full Text Available Form-finding has to be carried out for tensioned fabric structure in order to determine the initial equilibrium shape under prescribed support condition and prestress pattern. Tensioned fabric structures are normally designed to be in the form of equal tensioned surface. Tensioned fabric structure is highly suited to be used for realizing surfaces of complex or new forms. However, research study on a new form as a tensioned fabric structure has not attracted much attention. Another source of inspiration minimal surface which could be adopted as form for tensioned fabric structure is very crucial. The aim of this study is to propose initial equilibrium shape of tensioned fabric structures in the form of Chen-Gackstatter. Computational form-finding using nonlinear analysis method is used to determine the Chen-Gackstatter form of uniformly stressed surfaces. A tensioned fabric structure must curve equally in opposite directions to give the resulting surface a three dimensional stability. In an anticlastic doubly curved surface, the sum of all positive and all negative curvatures is zero. This study provides an alternative choice for structural designer to consider the Chen-Gackstatter applied in tensioned fabric structures. The results on factors affecting initial equilibrium shape can serve as a reference for proper selection of surface parameter for achieving a structurally viable surface.

On the Problem of Determining Aggregation Numbers from Surface Tension Measurements.

Science.gov (United States)

Rusanov, Anatoly I

2017-11-07

In view of the recent discovery of variable aggregation numbers in the vicinity of the critical micelle concentration (CMC), the mass-action-law theory of the surface tension isotherm of a micellar solution with variable aggregation numbers is formulated both for nonionic and ionic surfactants. It is shown that the shape of the surface tension isotherm should be concave in the logarithmic scale above the CMC. Considering a change in the isotherm slope at the CMC apparent break point, the problems of determining the aggregation number for nonionic micelles and the degree of counterion binding for ionic micelles are discussed. In case of the aggregation number variability near the CMC, finding the aggregation number above the CMC apparent break point is considered and a computational scheme is elaborated, requiring a higher precision for experiment. Some experimental data from the literature are analyzed, and the method of estimating the degree of counterion binding is improved.

Inclusion and Participation: Working with the Tensions

Directory of Open Access Journals (Sweden)

Gideon Calder

2011-12-01

Full Text Available Democracy is crucially about inclusion: a theory of democracy must account for who is to be included in the democratic process, how, and on what terms. Inclusion, if conceived democratically, is fraught with tensions. This article identifies three such tensions, arising respectively in: (i the inauguration of the democratic public; (ii enabling equal participation; and (iii the relationship between instrumental and non-instrumental accounts of democracy’s value. In each case, I argue, rather than seeking somehow to dissolve or avoid such tensions, theories of democracy should allow us to live with their implications reflexively: to work with them. Such tensions are counter-democratic to the extent that they derail what Nancy Fraser calls “participatory parity,” under which citizens count as “full partners in social interaction.” But the extent to which they do this is not itself dependent on points of paradox in the very idea of inclusion. Such parity relies on complex factors, social and economic, which democratic institutions and procedures will not by themselves address. To achieve full democratic inclusion we must already have addressed such factors; no account of democracy itself, however finely-tuned, will do this.

Utilization of Renewable Oxygenates as Gasoline Blending Components

Energy Technology Data Exchange (ETDEWEB)

Yanowitz, J.; Christensen, E.; McCormick, R. L.

2011-08-01

This report reviews the use of higher alcohols and several cellulose-derived oxygenates as blend components in gasoline. Material compatibility issues are expected to be less severe for neat higher alcohols than for fuel-grade ethanol. Very little data exist on how blending higher alcohols or other oxygenates with gasoline affects ASTM Standard D4814 properties. Under the Clean Air Act, fuels used in the United States must be 'substantially similar' to fuels used in certification of cars for emission compliance. Waivers for the addition of higher alcohols at concentrations up to 3.7 wt% oxygen have been granted. Limited emission testing on pre-Tier 1 vehicles and research engines suggests that higher alcohols will reduce emissions of CO and organics, while NOx emissions will stay the same or increase. Most oxygenates can be used as octane improvers for standard gasoline stocks. The properties of 2-methyltetrahydrofuran, dimethylfuran, 2-methylfuran, methyl pentanoate and ethyl pentanoate suggest that they may function well as low-concentration blends with gasoline in standard vehicles and in higher concentrations in flex fuel vehicles.

33 CFR 147.809 - Mars Tension Leg Platform safety zone.

Science.gov (United States)

2010-07-01

... 33 Navigation and Navigable Waters 2 2010-07-01 2010-07-01 false Mars Tension Leg Platform safety... SECURITY (CONTINUED) OUTER CONTINENTAL SHELF ACTIVITIES SAFETY ZONES § 147.809 Mars Tension Leg Platform safety zone. (a) Description. The Mars Tension Leg Platform (Mars TLP) is located at position 28°10′10.29...

Tension bulla: a cause of reversible pulmonary hypertension.

Science.gov (United States)

Waxman, Michael J; Waxman, Jacob D; Forman, John M

2015-01-01

A tension pneumothorax represents a medical emergency warranting urgent diagnosis and treatment. A rapidly expanding bulla may resemble the same clinical presentation but requires an entirely different treatment. A 53-year-old woman presented with increasing shortness of breath and her physical examination and chest x-ray were interpreted as showing a tension pneumothorax. A chest tube was placed which did not resolve the process. Placement of a second chest tube was likewise unsuccessful. A chest CT was then performed and was interpreted as showing an unresolved tension pneumothorax, despite seemingly adequate placement of the 2 chest tubes. Further review of the CT showed the border of a giant bulla and a tentative diagnosis was made of a rapidly expanding bulla with tension physiology. Echocardiogram revealed significant pulmonary hypertension. The bulla was surgically excised, the patient had marked improvement in her clinical symptoms and signs, and echocardiographic follow-up showed complete resolution of the pulmonary hypertension.

Genotype tunes pancreatic ductal adenocarcinoma tissue tension to induce matricellular fibrosis and tumor progression

DEFF Research Database (Denmark)

Laklai, Hanane; Miroshnikova, Yekaterina A.; Pickup, Michael W.

2016-01-01

by increasing matricellular fibrosis and tissue tension. In contrast, epithelial STAT3 ablation attenuated tumor progression by reducing the stromal stiffening and epithelial contractility induced by loss of TGF-β signaling. In PDAC patient biopsies, higher matricellular protein and activated STAT3 were......Fibrosis compromises pancreatic ductal carcinoma (PDAC) treatment and contributes to patient mortality, yet antistromal therapies are controversial. We found that human PDACs with impaired epithelial transforming growth factor-β (TGF-β) signaling have high epithelial STAT3 activity and develop...... stiff, matricellular-enriched fibrosis associated with high epithelial tension and shorter patient survival. In several KRAS-driven mouse models, both the loss of TGF-β signaling and elevated β1-integrin mechanosignaling engaged a positive feedback loop whereby STAT3 signaling promotes tumor progression...

Leadership. Using Creative Tension.

Science.gov (United States)

Cook, David L.

1986-01-01

Leadership involves maintaining a balance of the variables which comprise leadership. Love and fear, types of power, success and effectiveness, and driving and restraining forces are discussed as sources of the creative tension a leader uses to influence others. (MT)

Surface tension of H2O and D2O

International Nuclear Information System (INIS)

Vargaftik, N.B.; Voljak, L.D.; Volkov, B.N.

1975-01-01

There is a great number of works on surface tension of clean water (H 2 O) at temperatures up to 100 deg C and very few above the boiling point. Works on surface tension of heavy water (D 2 O) are insufficient. A review of works on surface tension of both kinds of water is given

A wireless smart sensor network for automated monitoring of cable tension

International Nuclear Information System (INIS)

Sim, Sung-Han; Cho, Soojin; Li, Jian; Jo, Hongki; Park, Jong-Woong; Jung, Hyung-Jo; Spencer Jr, Billie F

2014-01-01

As cables are primary load carrying members in cable-stayed bridges, monitoring the tension forces of the cables provides valuable information regarding structural soundness. Incorporating wireless smart sensors with vibration-based tension estimation methods provides an efficient means of autonomous long-term monitoring of cable tensions. This study develops a wireless cable tension monitoring system using MEMSIC’s Imote2 smart sensors. The monitoring system features autonomous operation, sustainable energy harvesting and power consumption, and remote access using the internet. To obtain the tension force, an in-network data processing strategy associated with the vibration-based tension estimation method is implemented on the Imote2-based sensor network, significantly reducing the wireless data transmission and the power consumption. The proposed monitoring system has been deployed and validated on the Jindo Bridge, a cable-stayed bridge located in South Korea. (paper)

A wireless smart sensor network for automated monitoring of cable tension

Science.gov (United States)

Sim, Sung-Han; Li, Jian; Jo, Hongki; Park, Jong-Woong; Cho, Soojin; Spencer, Billie F., Jr.; Jung, Hyung-Jo

2014-02-01

As cables are primary load carrying members in cable-stayed bridges, monitoring the tension forces of the cables provides valuable information regarding structural soundness. Incorporating wireless smart sensors with vibration-based tension estimation methods provides an efficient means of autonomous long-term monitoring of cable tensions. This study develops a wireless cable tension monitoring system using MEMSIC’s Imote2 smart sensors. The monitoring system features autonomous operation, sustainable energy harvesting and power consumption, and remote access using the internet. To obtain the tension force, an in-network data processing strategy associated with the vibration-based tension estimation method is implemented on the Imote2-based sensor network, significantly reducing the wireless data transmission and the power consumption. The proposed monitoring system has been deployed and validated on the Jindo Bridge, a cable-stayed bridge located in South Korea.

Kinetic therapy improves oxygenation in critically ill pediatric patients.

Science.gov (United States)

Schultz, Theresa Ryan; Lin, Richard; Francis, Barbara A; Hales, Roberta L; Colborn, Shawn; Napoli, Linda A; Helfaer, Mark A

2005-07-01

To compare changes in oxygenation after manual turning and percussion (standard therapy) and after automated rotation and percussion (kinetic therapy). Randomized crossover trial. General and cardiac pediatric intensive care units. Intubated and mechanically ventilated pediatric patients who had an arterial catheter and no contraindications to using a PediDyne bed. Patients were placed on a PediDyne bed (Kinetic Concepts) and received 18 hrs blocks of standard and kinetic therapy in an order determined by randomization. Arterial blood gases were measured every 2 hrs during each phase of therapy. Oxygenation index and arterial-alveolar oxygen tension difference [P(A-a)O(2)] were calculated. Indexes calculated at baseline and after each 18-hr phase of therapy were analyzed. Fifty patients were enrolled. Data from 15 patients were either not collected or not used due to reasons that included violation of protocol and inability to tolerate the therapies in the study. Indexes of oxygenation were not normally distributed and were compared using Wilcoxon signed rank testing. Both therapies led to improvements in oxygenation, but only those from kinetic therapy achieved statistical significance. In patients receiving kinetic therapy first, median oxygenation index decreased from 7.4 to 6.19 (p = .015). The median P(A-a)O(2) decreased from 165.2 to 126.4 (p = .023). There were continued improvements in oxygenation after the subsequent period of standard therapy, with the median oxygenation index decreasing to 5.52 and median P(A-a)O(2) decreasing to 116.0, but these changes were not significant (p = .365 and .121, respectively). When standard therapy was first, the median oxygenation index decreased from 8.83 to 8.71 and the median P(a-a)o(2) decreased from 195.4 to 186.6. Neither change was significant. Median oxygenation index after the subsequent period of kinetic therapy was significantly lower (7.91, p = .044) and median P(A-a)O(2) trended lower (143.4, p = .077

Strain Capacity of Reinforced Concrete Members Subjected to Uniaxial Tension

DEFF Research Database (Denmark)

Hagsten, Lars German; Rasmussen, Annette Beedholm; Fisker, Jakob

2017-01-01

The aim of this paper is to set up a method to determine the strain capacity of tension bars of reinforced concrete (RC) subjected to pure tension. Due to the interaction between reinforcement and concrete and due to the presence of cracks, the stresses in both reinforcement and concrete...... are varying along the length of the tension bar. The strain capacity of the tension bar is seen as the average strain in the reinforcement at the load level corresponding to the ultimate stress capacity of the reinforcement at the cracks. The result of the approach is in overall good agreement when comparing...

Effects on behaviour and rein tension on horses ridden with or without martingales and rein inserts.

Science.gov (United States)

Heleski, C R; McGreevy, P D; Kaiser, L J; Lavagnino, M; Tans, E; Bello, N; Clayton, H M

2009-07-01

Unsteady hand position can cause discomfort to the horse, potentially leading to conflict behaviours (CB) such as head tossing or tail lashing. Some instructors feel that martingales or elastic rein inserts can reduce discomfort caused by inexperienced and unsteady hands. Others consider these devices to be inappropriate 'crutches'. Four horses and nine riders were tested under three conditions in random order: plain reins, adjustable training martingales (TM), and elasticised rein inserts (RI). Rein-tension data (7s) and behavioural data (30s) were collected in each direction. Rein-tension data were collected via strain-gauge transducers. Behavioural data were assessed using an ethogram of defined behaviours. No differences in the number of CB were observed. Mean rein tension for TM was higher than that of RI or controls. Relative to the withers, the head was lower for horses ridden with martingales. Carefully fitted martingales may have a place in riding schools that teach novices.

Which patients with moderate hypoxemia benefit from long-term oxygen therapy? Ways forward

Directory of Open Access Journals (Sweden)

Ekström M

2018-01-01

Full Text Available Magnus Ekström,1 Thomas Ringbaek2 1Department of Respiratory Medicine and Allergology, Skåne University Hospital, Lund University, Lund, Sweden; 2Respiratory Department, Hvidovre Hospital, Copenhagen, Denmark Abstract: Long-term oxygen therapy (LTOT improves prognosis in patients with COPD and chronic severe hypoxemia. The efficacy in moderate hypoxemia (tension of arterial oxygen; on air, 7.4−8.0 kPa was questioned by a recent large trial. We reviewed the evidence to date (five randomized trials; 1,191 participants, all with COPD. Based on the current evidence, the survival time may be improved in patients with moderate hypoxemia with secondary polycythemia or right-sided heart failure, but not in the absence of these signs. Clinically, LTOT is not indicated in moderate hypoxemia except in the few patients with polycythemia or signs of right-sided heart failure, which may reflect more chronic and severe hypoxemia. Keywords: survival, oxygen therapy, hypoxemia, COPD

Tension in the recent Type Ia supernovae datasets

International Nuclear Information System (INIS)

Wei, Hao

2010-01-01

In the present work, we investigate the tension in the recent Type Ia supernovae (SNIa) datasets Constitution and Union. We show that they are in tension not only with the observations of the cosmic microwave background (CMB) anisotropy and the baryon acoustic oscillations (BAO), but also with other SNIa datasets such as Davis and SNLS. Then, we find the main sources responsible for the tension. Further, we make this more robust by employing the method of random truncation. Based on the results of this work, we suggest two truncated versions of the Union and Constitution datasets, namely the UnionT and ConstitutionT SNIa samples, whose behaviors are more regular.

The oxygen effect and cellular adaptation

International Nuclear Information System (INIS)

Meshcherikova, V.V.; Vajnson, A.A.; Yarmonenko, S.P.

1979-01-01

The radiomodifying effect of oxygen was shown to depend on the level of cellular oxygenation prior to irradiation. Acute hypoxia created at the time of irradiation protects previously normally oxygenated cells with DMF approximately 1.4 times larger than that of cells cultured for 24 hours under conditions of mild hypoxia. It is suggested that a decrease in the radioprotective effect of acute hypoxia on chronically hypoxic cells is correlated with an appreciable decrease in the rate of oxygen consumption by these cells, due to which the oxygen concentration near the intracellular targets in chronically hypoxic cells may be higher than in normal cells under conditions of poor oxygenation

Tensions in implementing the “energy-conservation/carbon-reduction” policy in Taiwanese culture

International Nuclear Information System (INIS)

Chiu, Mei-Shiu

2013-01-01

The aim of this study is to investigate the Taiwanese public's perceptions of tensions between the implementation of an energy policy and the practice of traditional culture. The energy policy calls for public actions to conserve energy and reduce carbon emissions. The research participants are 94 people, selected by balancing sexes, ages, and residential areas, from a wide range of vocations. The research data were collected by semi-structured interview with the participants individually. Interview questions were designed to elicit the participants' constructs, beliefs, behaviours, and tensions in relation to energy policy and traditional culture. Data analysis was performed based on a qualitative methodology by the procedure of open coding, theme finding, constant comparison, and theory generation. The analysis identifies four tensions: (1) tensions in knowledge bases between energy conservation and carbon reduction, (2) tensions in lifestyles between having and being, (3) tensions in social systems between authority and conformity, and (4) tensions in creation boundaries between technology and nature. The themes underlying the four tensions are uncertainty, pleasure, power, and control, respectively. Solutions to the four tensions may include practical knowledge, pragmatic idealism, hierarchical collaboration, and sustainable innovation. - Highlights: ► Tensions occur between energy policy and traditional culture. ► Tensions occur in knowledge, life, society, and creation in Taiwan. ► The themes of the four tensions are uncertainty, pleasure, power, and control

Spontaneous calcium waves in Bergman glia increase with age and hypoxia and may reduce tissue oxygen

DEFF Research Database (Denmark)

Mathiesen, Claus; Brazhe, Alexey; Thomsen, Kirsten Joan

2013-01-01

Glial calcium (Ca(2+)) waves constitute a means to spread signals between glial cells and to neighboring neurons and blood vessels. These waves occur spontaneously in Bergmann glia (BG) of the mouse cerebellar cortex in vivo. Here, we tested three hypotheses: (1) aging and reduced blood oxygen sa...... activity during aging, as well as low resting brain oxygen tension, suggests a relationship between glial waves, brain energy homeostasis, and pathology.......Glial calcium (Ca(2+)) waves constitute a means to spread signals between glial cells and to neighboring neurons and blood vessels. These waves occur spontaneously in Bergmann glia (BG) of the mouse cerebellar cortex in vivo. Here, we tested three hypotheses: (1) aging and reduced blood oxygen...... saturation alters wave activity; (2) glial Ca(2+) waves change cerebral oxygen metabolism; and (3) neuronal and glial wave activity is correlated. We used two-photon microscopy in the cerebellar cortexes of adult (8- to 15-week-old) and aging (48- to 80-week-old) ketamine-anesthetized mice after bolus...

Width and string tension of the flux tube in SU(2) lattice gauge theory at high temperature

Science.gov (United States)

Chagdaa, S.; Galsandorj, E.; Laermann, E.; Purev, B.

2018-02-01

We study the profiles of the flux tube between a static quark and an antiquark in quenched SU(2) lattice gauge theory at temperatures around the deconfinement phase transition. The physical width of the flux tube and the string tension have been determined from the transverse profiles and the q\\bar{q} potential, respectively. Exploiting the computational power of a GPU accelerator in our flux tube investigation, we achieve much higher statistics through which we can increase the signal to noise ratio of our observables in the simulation. This has allowed the investigation of larger lattices as well as larger separations between the quarks than in our previous work. The improved accuracy gives us better results for the width and the string tension. The physical width of the flux tube increases with the temperature up to around T c while keeping its increasing dependence on the q\\bar{q} separation. The string tension results are compared for two different sizes of the lattice. As the lattice becomes larger and finer together with the improved precision, the temperature dependent string tension tends to have a smaller value than the previous one.

Rein tension acceptance in young horses in a voluntary test situation

DEFF Research Database (Denmark)

Christensen, Janne Winther; zharkikh, T.L.; Antoine, A.

2011-01-01

Reasons for performing the study: During riding, horses are frequently exposed to pressure from the rider, e.g. through the bit and reins, but few studies have investigated at which point rein tension becomes uncomfortable for the horse. Objectives: To investigate how much rein tension young...... inexperienced horses are willing to accept in order to obtain a food reward; whether the tension acceptance changes during 3 consecutive test days; and whether rein tension correlates with the expression of conflict behaviour and heart rate. Hypotheses: Pressure-naïve horses will apply only little rein tension...... in the first voluntary trial, but their acceptance will gradually increase. High levels of rein tension will lead to expression of conflict behaviour and increases in heart rate. Methods: Fifteen 2-year-old, bridle-naïve mares were encouraged to stretch their head forward (across a 0.95 m high metal bar...

Tensions in the Parent and Adult Child Relationship: Links to Solidarity and Ambivalence

Science.gov (United States)

Birditt, Kira S.; Miller, Laura M.; Fingerman, Karen L.; Lefkowitz, Eva S.

2009-01-01

Tensions are normative in the parent and adult child relationship, but there is little research on the topics that cause the most tension or whether tensions are associated with overall relationship quality. Adult sons and daughters, aged 22 to 49, and their mothers and fathers (N = 158 families, 474 individuals) reported the intensity of different tension topics and relationship quality (solidarity and ambivalence) with one another. Tensions varied between and within families by generation, gender and age of offspring. In comparison to tensions regarding individual issues, tensions regarding the relationship were associated with lower affective solidarity and greater ambivalence. Findings are consistent with the developmental schism hypothesis, which indicates that parent-child tensions are common and are the result of discrepancies in developmental needs which vary by generation, gender, and age. PMID:19485648

Radiation dose optimization in pediatric temporal bone computed tomography: influence of tube tension on image contrast and image quality

International Nuclear Information System (INIS)

Nauer, Claude Bertrand; Zubler, Christoph; Weisstanner, Christian; Stieger, Christof; Senn, Pascal; Arnold, Andreas

2012-01-01

The purpose of this experimental study was to investigate the effect of tube tension reduction on image contrast and image quality in pediatric temporal bone computed tomography (CT). Seven lamb heads with infant-equivalent sizes were scanned repeatedly, using four tube tensions from 140 to 80 kV while the CT-Dose Index (CTDI) was held constant. Scanning was repeated with four CTDI values from 30 to 3 mGy. Image contrast was calculated for the middle ear as the Hounsfield unit (HU) difference between bone and air and for the inner ear as the HU difference between bone and fluid. The influence of tube tension on high-contrast detail delineation was evaluated using a phantom. The subjective image quality of eight middle and inner ear structures was assessed using a 4-point scale (scores 1-2 = insufficient; scores 3-4 = sufficient). Middle and inner ear contrast showed a near linear increase with tube tension reduction (r = -0.94/-0.88) and was highest at 80 kV. Tube tension had no influence on spatial resolution. Subjective image quality analysis showed significantly better scoring at lower tube tensions, with highest image quality at 80 kV. However, image quality improvement was most relevant for low-dose scans. Image contrast in the temporal bone is significantly higher at low tube tensions, leading to a better subjective image quality. Highest contrast and best quality were found at 80 kV. This image quality improvement might be utilized to further reduce the radiation dose in pediatric low-dose CT protocols. (orig.)

Oxygen as a factor in eukaryote evolution - Some effects of low levels of oxygen on Saccharomyces cerevisiae

Science.gov (United States)

Jahnke, L.; Klein, H. P.

1979-01-01

A comparative study of the effects of varying levels of oxygen on some of the metabolic functions of the primitive eukaryote, Saccharomyces cerevisiae, has shown that these cells are responsive to very low levels of oxygen: the level of palmitoyl-Co A desaturase was greatly enhanced by only 0.03 vol % oxygen. Similarly, an acetyl-CoA synthetase associated predominantly with anaerobic growth was stimulated by as little as 0.1% oxygen, while an isoenzyme correlated with aerobic growth was maximally active at much higher oxygen levels (greater than 1%). Closely following this latter pattern were three mitochondrial enzymes that attained maximal activity only under atmospheric levels of oxygen.

Specific toxicity of 5-thio-D-glucose to hypoxic cells

International Nuclear Information System (INIS)

Schulz, R.J.; Bongiorni, P.

1984-01-01

The toxicity of 5-thio-D-glucose (5TG) to mammalian cells in culture has been studied with respect to oxygen tension, concentration, and temperature. At 37 0 C and at 5 mM concentration of the drug in normal growth medium, survival is 10 -3 for 4-hr exposure to 5 ppm O 2 ; this increases to 0.5 for 24-hr exposure to 200 ppm O 2 . The relationship between survival and oxygen tension is nonlinear with the greatest change occurring between 50 and 100 ppm. The drug is essentially nontoxic to aerated cells. Drug toxicity increases with concentration up to about 5 mM at which point a plateau is reached. The effect of elevated temperature is to reduce the time required to obtain a specific level of survival, but temperatures as high as 42 0 C had only a slight effect on drug toxicity for oxygen tensions higher than 100 ppm. The effect of D-glucose on the toxicity of 5TG was studied, and an inverse relationship was established. At D-glucose concentrations greater than 20 mM the toxicity of 5TG was nullified regardless of oxygen tension or 5TG concentration

Cellular control of connective tissue matrix tension.

Science.gov (United States)

Langevin, Helene M; Nedergaard, Maiken; Howe, Alan K

2013-08-01

The biomechanical behavior of connective tissue in response to stretching is generally attributed to the molecular composition and organization of its extracellular matrix. It also is becoming apparent that fibroblasts play an active role in regulating connective tissue tension. In response to static stretching of the tissue, fibroblasts expand within minutes by actively remodeling their cytoskeleton. This dynamic change in fibroblast shape contributes to the drop in tissue tension that occurs during viscoelastic relaxation. We propose that this response of fibroblasts plays a role in regulating extracellular fluid flow into the tissue, and protects against swelling when the matrix is stretched. This article reviews the evidence supporting possible mechanisms underlying this response including autocrine purinergic signaling. We also discuss fibroblast regulation of connective tissue tension with respect to lymphatic flow, immune function, and cancer. Copyright © 2013 Wiley Periodicals, Inc.

Cavitation during hot tension testing of Ti-6Al-4V

International Nuclear Information System (INIS)

Semiatin, S.L.; Ghosh, A.K.; Shell, E.B.; Simon, M.P.

1998-01-01

Cavity initiation, growth, and coalescence phenomena during the hot tension testing of Ti-6Al-4V with several different transformed β-microstructures were established to obtain an understanding of the failure process during subtransus hot working. Samples with either a colony-type microstructure (containing grain-boundary α) or a martensitic, acicular α-microstructure were pulled to failure at strain rates between 0.01 and 3 s -1 and various subtransus temperatures ranging from 540 to 955 C. Metallographic analysis of sectioned tension samples with colony microstructures revealed that cavity initiation occurred at very low strains (< or∼0.2) irrespective of strain rate at temperatures below 900 C due to an apparent incompatibility of deformation between the grain-boundary α-layer and the Widmanstatten side plates. Initiation strains were somewhat higher (∝0.2-0.5) for samples with the acicular α-microstructure tested at temperatures below 900 C; however, failure was still intergranular. Subsequent cavity growth was more rapid for colony microstructures than that for the martensitic α-microstructure at these temperatures. Above 900 C, however, substantially higher cavity initiation strains and lower cavity growth rates were obtained for both microstructures. These latter behaviors were ascribed to the presence of a large volume fraction of ductile β-phase and moderate values of the strain-rate sensitivity of the flow stress, respectively. (orig.)

Theory and development of fluorescence-based optochemical oxygen sensors: oxygen optodes.

Science.gov (United States)

Opitz, N; Lübbers, D W

1987-01-01

range of PO2 values, resulting in a higher resolution. Use of suitable polymer alloys as indicator matrices can even enhance oxygen sensitivity; therefore, the application of optodes for trace analysis of oxygen might be possible, especially with regard to the application of highly oxygen-sensitive phosphorescent indicators. Finally, owing to the reversibility of fluorescence quenching, monitoring of oxygen by fluorescence optical sensors allows a continuous and remote control of biomedical parameters as well as regulation of biotechnological processes.(ABSTRACT TRUNCATED AT 400 WORDS)

Exploring the tensions of being and becoming a medical educator.

Science.gov (United States)

Sethi, Ahsan; Ajjawi, Rola; McAleer, Sean; Schofield, Susie

2017-03-23

Previous studies have identified tensions medical faculty encounter in their roles but not specifically those with a qualification in medical education. It is likely that those with postgraduate qualifications may face additional tensions (i.e., internal or external conflicts or concerns) from differentiation by others, greater responsibilities and translational work against the status quo. This study explores the complex and multi-faceted tensions of educators with qualifications in medical education at various stages in their career. The data described were collected in 2013-14 as part of a larger, three-phase mixed-methods research study employing a constructivist grounded theory analytic approach to understand identity formation among medical educators. The over-arching theoretical framework for the study was Communities of Practice. Thirty-six educators who had undertaken or were undertaking a postgraduate qualification in medical education took part in semi-structured interviews. Participants expressed multiple tensions associated with both becoming and being a healthcare educator. Educational roles had to be juggled with clinical work, challenging their work-life balance. Medical education was regarded as having lower prestige, and therefore pay, than other healthcare career tracks. Medical education is a vast speciality, making it difficult as a generalist to keep up-to-date in all its areas. Interestingly, the graduates with extensive experience in education reported no fears, rather asserting that the qualification gave them job variety. This is the first detailed study exploring the tensions of educators with postgraduate qualifications in medical education. It complements and extends the findings of the previous studies by identifying tensions common as well as specific to active students and graduates. These tensions may lead to detachment, cynicism and a weak sense of identity among healthcare educators. Postgraduate programmes in medical education

Conducting Qualitative Data Analysis: Managing Dynamic Tensions within

Science.gov (United States)

Chenail, Ronald J.

2012-01-01

In the third of a series of "how-to" essays on conducting qualitative data analysis, Ron Chenail examines the dynamic tensions within the process of qualitative data analysis that qualitative researchers must manage in order to produce credible and creative results. These tensions include (a) the qualities of the data and the qualitative data…

Coupled Interfacial Tension and Phase Behavior Model Based on Micellar Curvatures

KAUST Repository

Torrealba, V. A.

2017-11-08

This article introduces a consistent and robust model that predicts interfacial tensions for all microemulsion Winsor types and overall compositions. The model incorporates film bending arguments and Huh\\'s equation and is coupled to phase behavior so that simultaneous tuning of both interfacial tension (IFT) and phase behavior is possible. The oil-water interfacial tension and characteristic length are shown to be related to each other through the hydrophilic-lipophilic deviation (HLD). The phase behavior is tied to the micelle curvatures, without the need for using the net average curvature (NAC). The interfacial tension model is related to solubilization ratios in order to introduce a coupled interfacial tension-phase behavior model for all phase environments. The approach predicts two- and three-phase interfacial tensions and phase behavior (i.e., tie lines and tie triangles) for changes in composition and HLD input parameters, such as temperature, pressure, surfactant structure, and oil equivalent alkane carbon number. Comparisons to experimental data show excellent fits and predictive capability.

Monitoring hemodynamics and oxygenation of the kidney in rats by a combined near-infrared spectroscopy and invasive probe approach

Science.gov (United States)

Grosenick, Dirk; Cantow, Kathleen; Arakelyan, Karen; Wabnitz, Heidrun; Flemming, Bert; Skalweit, Angela; Ladwig, Mechthild; Macdonald, Rainer; Niendorf, Thoralf; Seeliger, Erdmann

2015-07-01

We have developed a hybrid approach to investigate the dynamics of perfusion and oxygenation in the kidney of rats under pathophysiologically relevant conditions. Our approach combines near-infrared spectroscopy to quantify hemoglobin concentration and oxygen saturation in the renal cortex, and an invasive probe method for measuring total renal blood flow by an ultrasonic probe, perfusion by laser-Doppler fluxmetry, and tissue oxygen tension via fluorescence quenching. Hemoglobin concentration and oxygen saturation were determined from experimental data by a Monte Carlo model. The hybrid approach was applied to investigate and compare temporal changes during several types of interventions such as arterial and venous occlusions, as well as hyperoxia, hypoxia and hypercapnia induced by different mixtures of the inspired gas. The approach was also applied to study the effects of the x-ray contrast medium iodixanol on the kidney.

Quantifying the BICEP2-Planck tension over gravitational waves.

Science.gov (United States)

Smith, Kendrick M; Dvorkin, Cora; Boyle, Latham; Turok, Neil; Halpern, Mark; Hinshaw, Gary; Gold, Ben

2014-07-18

The recent BICEP2 measurement of B-mode polarization in the cosmic microwave background (r = 0.2(-0.05)(+0.07)), a possible indication of primordial gravity waves, appears to be in tension with the upper limit from WMAP (r < 0.13 at 95% C.L.) and Planck (r < 0.11 at 95% C.L.). We carefully quantify the level of tension and show that it is very significant (around 0.1% unlikely) when the observed deficit of large-scale temperature power is taken into account. We show that measurements of TE and EE power spectra in the near future will discriminate between the hypotheses that this tension is either a statistical fluke or a sign of new physics. We also discuss extensions of the standard cosmological model that relieve the tension and some novel ways to constrain them.

Modeling of surface tension effects in venturi scrubbing

Science.gov (United States)

Ott, Robert M.; Wu, Tatsu K. L.; Crowder, Jerry W.

A modified model of venturi scrubber performance has been developed that addresses two effects of liquid surface tension: its effect on droplet size and its effect on particle penetration into the droplet. The predictions of the model indicate that, in general, collection efficiency increases with a decrease in liquid surface tension, but the range over which this increase is significant depends on the particle size and on the scrubber operating parameters. The predictions further indicate that the increases in collection efficiency are almost totally due to the effect of liquid surface tension on the mean droplet size, and that the collection efficiency is not significantly affected by the ability of the particle to penetrate the droplet.

Tensions related to implementation of postgraduate degree projects in specialist nursing education.

Science.gov (United States)

German Millberg, Lena; Berg, Linda; Lindström, Irma; Petzäll, Kerstin; Öhlén, Joakim

2011-04-01

In conjunction with the introduction of the Bologna process in Sweden, specialist nursing education programmes were moved up to the second cycle of higher education with the opportunity to take a one-year master's degree, which also meant that students would undertake a degree project carrying 15 ECTS. The purpose of this study was to examine the introduction of postgraduate degree projects on the second-cycle level into Swedish specialist nursing programmes in accordance with the Bologna process. Five universities were involved and the study design took the form of action research. Problem formulation, planning, evaluation and follow-up with reflection led to new actions over a period of 2 1/2 years. Through a review of local curriculum documents, the implementation of a postgraduate degree project was monitored and these reviews, together with field notes, were analysed by means of constant comparative analysis. The results revealed a variety of tensions that arose when postgraduate degree projects were introduced, taking the form of differing views on the relationship between research, clinical development, specific professional objectives and academic objectives. These tensions were reflected in six areas of change. In summary, it can be noted that implementation of the postgraduate degree projects highlighted tensions related to basic views of learning. Copyright © 2010 Elsevier Ltd. All rights reserved.

Hypoxia Induces a Metabolic Shift and Enhances the Stemness and Expansion of Cochlear Spiral Ganglion Stem/Progenitor Cells

Directory of Open Access Journals (Sweden)

Hsin-Chien Chen

2015-01-01

Full Text Available Previously, we demonstrated that hypoxia (1% O2 enhances stemness markers and expands the cell numbers of cochlear stem/progenitor cells (SPCs. In this study, we further investigated the long-term effect of hypoxia on stemness and the bioenergetic status of cochlear spiral ganglion SPCs cultured at low oxygen tensions. Spiral ganglion SPCs were obtained from postnatal day 1 CBA/CaJ mouse pups. The measurement of oxygen consumption rate, extracellular acidification rate (ECAR, and intracellular adenosine triphosphate levels corresponding to 20% and 5% oxygen concentrations was determined using a Seahorse XF extracellular flux analyzer. After low oxygen tension cultivation for 21 days, the mean size of the hypoxia-expanded neurospheres was significantly increased at 5% O2; this correlated with high-level expression of hypoxia-inducible factor-1 alpha (Hif-1α, proliferating cell nuclear antigen (PCNA, cyclin D1, Abcg2, nestin, and Nanog proteins but downregulated expression of p27 compared to that in a normoxic condition. Low oxygen tension cultivation tended to increase the side population fraction, with a significant difference found at 5% O2 compared to that at 20% O2. In addition, hypoxia induced a metabolic energy shift of SPCs toward higher basal ECARs and higher maximum mitochondrial respiratory capacity but lower proton leak than under normoxia, where the SPC metabolism was switched toward glycolysis in long-term hypoxic cultivation.

Superiority of Transcutaneous Oxygen Tension Measurements in Predicting Limb Salvage After Below-the-Knee Angioplasty: A Prospective Trial in Diabetic Patients With Critical Limb Ischemia

International Nuclear Information System (INIS)

Redlich, Ulf; Xiong, Yan Y.; Pech, Maciej; Tautenhahn, Jörg; Halloul, Zuhir; Lobmann, Ralf; Adolf, Daniela; Ricke, Jens; Dudeck, Oliver

2011-01-01

Purpose: To assess postprocedural angiograms, the ankle–brachial index (ABI), and transcutaneous oxygen tension (TcPO 2 ) to predict outcome after infrageniculate angioplasty (PTA) in diabetic patients with critical limb ischemia (CLI) scheduled for amputation. Materials and Methods: PTA was performed in 28 diabetic patients with CLI confined to infrapopliteal vessels. We recorded patency of crural vessels, including the vascular supply of the foot as well as the ABI and TcPO 2 of the foot. Results: Technical success rate was 92.9% (n = 26), and limb-salvage rate at 12 months was 60.7% (n = 17). The number of patent straight vessels above and below the level of the malleoli increased significantly in patients avoiding amputation. Amputation was unnecessary in 88.2% (n = 15) patients when patency of at least one tibial artery was achieved. In 72.7% (n = 8) of patients, patency of the peroneal artery alone was not sufficient for limb salvage. ABI was of no predictive value for limb salvage. TcPO 2 values increased significantly only in patients not requiring amputation (P = 0.015). In patients with only one tibial artery supplying the foot or only a patent peroneal artery in postprocedural angiograms, TcPO 2 was capable of reliably predicting the outcome. Conclusion: Below-the-knee PTA as an isolated part of therapy was effective to prevent major amputation in more than a half of diabetic patients with CLI. TcPO 2 was a valid predictor for limb salvage, even when angiographic outcome criteria failed.

The effect of oxygen tension in the sediment on the behaviour of waste radionuclides at the NEA Atlantic dumpsite

International Nuclear Information System (INIS)

Rutgers van der Loeff, M.M.; Waijers, D.A.

1985-01-01

Predictions of the transport and fate of waste radionuclides at the NEA Atlantic dumpsite require a knowledge of the behaviour of these nuclides within the sediment. Since redox conditions are known to influence the mobility of many elements in deep-sea sediments, we have investigated the speciation of some trace elements in relation to the dissolved oxygen concentration in sediments from the dumpsite. Dissolved oxygen in these sediments penetrates mostly between 50 and 100 cm, although at topographic highs and on hillsides oxygen penetrates more than 2 m into the sediment because of the special hydrodynamic and sedimentological conditions there. Remobilization at lowered redox potentials below the depth where oxygen reaches zero causes an upward diffusive transport of Mn and the manganese-associated trace metals Co and Ni. Whether this diagenetic mobilization influences other elements such as rare earth elements and actinides as well, remains to be investigated. Under normal sedimentological condition this mobilization can not be expected to return radioactivity to the water column through an oxidized sediment layer of 50 cm. However, burial of radioactivity to depths beyond the reach of deep burrowing organisms can be significantly delayed. Kd values (solid/dissolved partition coefficients) of redox sensitive elements vary over orders of magnitude and are inappropriate to model the behaviour of these elements in sediments with redox gradients

Method for the determination of oxygen consumption rates and diffusion coefficients in multicellular spheroids

OpenAIRE

Mueller-Klieser, W.

1984-01-01

A method has been developed for the quantitative evaluation of oxygen tension (PO2) distributions in multicellular spheroids measured with O2-sensitive microelectrodes. The experimental data showed that multicellular tumor spheroids in stirred growth media were characterized by a diffusion-depleted zone surrounding the spheroids. This zone was elicited by an unstirred layer of medium next to the spheroid leading to a continuous decrease in the PO2 values from the bulk medium towards the spher...

Surface tension anomalies in room temperature ionic liquids-acetone solutions

Science.gov (United States)

Abe, Hiroshi; Murata, Keisuke; Kiyokawa, Shota; Yoshimura, Yukihiro

2018-05-01

Surface tension anomalies were observed in room temperature ionic liquid (RTIL)-acetone solutions. The RTILs are 1-alkyl-3-methylimidazorium iodide with [Cnmim][I] in a [Cnmim][I]-x mol% acetone. The maximum value of the surface tension appeared at 40 mol% acetone, although density decreased monotonically with an increase in acetone concentration. A small alkyl chain length effect of the Cnmim+ cations was observed in the surface tension. By the Gibbs adsorption isotherm, it was found that I- anion-mediated surface structure became dominant above 40 mol%. In the different [Cnmim][TFSI]-acetone mixtures, normal decay of the surface tension was observed on the acetone concentration scale, where TFSI- is bis(trifluoromethanesulfonyl)imide.

Transitions of tethered chain molecules under tension.

Science.gov (United States)

Luettmer-Strathmann, Jutta; Binder, Kurt

2014-09-21

An applied tension force changes the equilibrium conformations of a polymer chain tethered to a planar substrate and thus affects the adsorption transition as well as the coil-globule and crystallization transitions. Conversely, solvent quality and surface attraction are reflected in equilibrium force-extension curves that can be measured in experiments. To investigate these effects theoretically, we study tethered chains under tension with Wang-Landau simulations of a bond-fluctuation lattice model. Applying our model to pulling experiments on biological molecules we obtain a good description of experimental data in the intermediate force range, where universal features dominate and finite size effects are small. For tethered chains in poor solvent, we observe the predicted two-phase coexistence at transitions from the globule to stretched conformations and also discover direct transitions from crystalline to stretched conformations. A phase portrait for finite chains constructed by evaluating the density of states for a broad range of solvent conditions and tensions shows how increasing tension leads to a disappearance of the globular phase. For chains in good solvents tethered to hard and attractive surfaces we find the predicted scaling with the chain length in the low-force regime and show that our results are well described by an analytical, independent-bond approximation for the bond-fluctuation model for the highest tensions. Finally, for a hard or slightly attractive surface the stretching of a tethered chain is a conformational change that does not correspond to a phase transition. However, when the surface attraction is sufficient to adsorb a chain it will undergo a desorption transition at a critical value of the applied force. Our results for force-induced desorption show the transition to be discontinuous with partially desorbed conformations in the coexistence region.

Effect of hypothermia on radiosensitization

International Nuclear Information System (INIS)

Nias, A.H.W.; Perry, P.; Photiou, A.; Reghebi, K.

1986-01-01

The blood supply and oxygen tension have been measured in C3H mouse mammary tumours under hypothermia and hyperbaric oxygen, and the enhancement of radiosensitivity by hyperbaric oxygen has been estimated in mice irradiated at different temperatures with and without anaesthesia. Measurement of xenon-133 clearance showed that the blood supply of a tumour tended to increase when anaesthetized mice became hypothermic. Oxygen cathode data showed that the oxygen tension tended to be relatively higher in tumours and lower in subcutaneous tissue when mice exposed to hyperbaric oxygen became hypothermic under anaesthesia. Hyperbaric oxygen enhanced the radiation response of the tumour in terms of an increase in regrowth delay by a factor of 1.7 when the mice had been anaesthetized, whether or not they became hypothermic. A lower factor of 1.4 was obtained without anaesthesia although induced hypothermia increased the response to a small extent. The authors conclude that anaesthesia and hypothermia affect oxygen metabolism in tumours by different mechanisms. (author)

Surface Tension Flows inside Surfactant-Added Poly(dimethylsiloxane Microstructures with Velocity-Dependent Contact Angles

Directory of Open Access Journals (Sweden)

Jyh Jian Chen

2014-03-01

Full Text Available Filling of liquid samples is realized in a microfluidic device with applications including analytical systems, biomedical devices, and systems for fundamental research. The filling of a disk-shaped polydimethylsiloxane (PDMS microchamber by liquid is analyzed with reference to microstructures with inlets and outlets. The microstructures are fabricated using a PDMS molding process with an SU-8 mold. During the filling, the motion of the gas-liquid interface is determined by the competition among inertia, adhesion, and surface tension. A single ramp model with velocity-dependent contact angles is implemented for the accurate calculation of surface tension forces in a three-dimensional volume-of-fluid based model. The effects of the parameters of this functional form are investigated. The influences of non-dimensional parameters, such as the Reynolds number and the Weber number, both determined by the inlet velocity, on the flow characteristics are also examined. An oxygen-plasma-treated PDMS substrate is utilized, and the microstructure is modified to be hydrophilic. Flow experiments are conducted into both hydrophilic and hydrophobic PDMS microstructures. Under a hydrophobic wall condition, numerical simulations with imposed boundary conditions of static and dynamic contact angles can successfully predict the moving of the meniscus compared with experimental measurements. However, for a hydrophilic wall, accurate agreement between numerical and experimental results is obvious as the dynamic contact angles were implemented.

Computationally fast estimation of muscle tension for realtime bio-feedback.

Science.gov (United States)

Murai, Akihiko; Kurosaki, Kosuke; Yamane, Katsu; Nakamura, Yoshihiko

2009-01-01

In this paper, we propose a method for realtime estimation of whole-body muscle tensions. The main problem of muscle tension estimation is that there are infinite number of solutions to realize a particular joint torque due to the actuation redundancy. Numerical optimization techniques, e.g. quadratic programming, are often employed to obtain a unique solution, but they are usually computationally expensive. For example, our implementation of quadratic programming takes about 0.17 sec per frame on the musculoskeletal model with 274 elements, which is far from realtime computation. Here, we propose to reduce the computational cost by using EMG data and by reducing the number of unknowns in the optimization. First, we compute the tensions of muscles with surface EMG data based on a biological muscle data, which is a very efficient process. We also assume that their synergists have the same activity levels and compute their tensions with the same model. Tensions of the remaining muscles are then computed using quadratic programming, but the number of unknowns is significantly reduced by assuming that the muscles in the same heteronymous group have the same activity level. The proposed method realizes realtime estimation and visualization of the whole-body muscle tensions that can be applied to sports training and rehabilitation.

POSTOPERATIVE URINARY RETENTION AND EARLY REPOSITION OF TENSION-FREE VAGINAL TAPE

Directory of Open Access Journals (Sweden)

Marijan Lužnik

2003-12-01

Full Text Available Background. The purpose of this article is to show a possible method of treatment of postoperative urinary retention after an initial tension-free vaginal tape.Methods. From December 1999 to May 2003 we performed one hundred TVT procedures at our department, among them five women had postoperative urinary retention evaluated with catheterization. Revision and reposition of tension-free vaginal tape were performed if retention of urine was over 100 ml.Results. Urinary retention after an initial tension-free vaginal tape was successfully treated by early reposition of tension-free vaginal tape. This resulted in immediate residualfree voiding and continence, which remained unchanged at 6 week and 3 month follow-up.Conclusions. Postoperative urinary retention may be treated by reposition instead of dissection or elongation of the tension-free vaginal tape.

Radiation dose optimization in pediatric temporal bone computed tomography: influence of tube tension on image contrast and image quality.

Science.gov (United States)

Nauer, Claude Bertrand; Zubler, Christoph; Weisstanner, Christian; Stieger, Christof; Senn, Pascal; Arnold, Andreas

2012-03-01

The purpose of this experimental study was to investigate the effect of tube tension reduction on image contrast and image quality in pediatric temporal bone computed tomography (CT). Seven lamb heads with infant-equivalent sizes were scanned repeatedly, using four tube tensions from 140 to 80 kV while the CT-Dose Index (CTDI) was held constant. Scanning was repeated with four CTDI values from 30 to 3 mGy. Image contrast was calculated for the middle ear as the Hounsfield unit (HU) difference between bone and air and for the inner ear as the HU difference between bone and fluid. The influence of tube tension on high-contrast detail delineation was evaluated using a phantom. The subjective image quality of eight middle and inner ear structures was assessed using a 4-point scale (scores 1-2 = insufficient; scores 3-4 = sufficient). Middle and inner ear contrast showed a near linear increase with tube tension reduction (r = -0.94/-0.88) and was highest at 80 kV. Tube tension had no influence on spatial resolution. Subjective image quality analysis showed significantly better scoring at lower tube tensions, with highest image quality at 80 kV. However, image quality improvement was most relevant for low-dose scans. Image contrast in the temporal bone is significantly higher at low tube tensions, leading to a better subjective image quality. Highest contrast and best quality were found at 80 kV. This image quality improvement might be utilized to further reduce the radiation dose in pediatric low-dose CT protocols.

The tension as perturbative parameter in string theory

International Nuclear Information System (INIS)

Gamboa, J.

1990-01-01

We propose an approach to string theory where the zero theory is the null string. We find an explicit form of the propagator for the null string in the momentum space. We show that considering the tension as perturbative parameter, the perturbative series is completely summable and we find the propagator of the bosonic open string with tension T. (author) [pt

A computational study of the effect of capillary network anastomoses and tortuosity on oxygen transport.

Science.gov (United States)

Goldman, D; Popel, A S

2000-09-21

The objective of this study was to investigate the effects of capillary network anastomoses and tortuosity on oxygen transport in skeletal muscle, as well as the importance of muscle fibers in determining the arrangement of parallel capillaries. Countercurrent flow and random capillary blockage (e.g. by white blood cells) were also studied. A general computational model was constructed to simulate oxygen transport from a network of blood vessels within a rectangular volume of tissue. A geometric model of the capillary network structure, based on hexagonally packed muscle fibers, was constructed to produce networks of straight unbranched capillaries, capillaries with anastomoses, and capillaries with tortuosity, in order to examine the effects of these geometric properties. Quantities examined included the tissue oxygen tension and the capillary oxyhemoglobin saturation. The computational model included a two-phase simulation of blood flow. Appropriate parameters were chosen for working hamster cheek-pouch retractor muscle. Our calculations showed that the muscle-fiber geometry was important in reducing oxygen transport heterogeneity, as was countercurrent flow. Tortuosity was found to increase tissue oxygenation, especially when combined with anastomoses. In the absence of tortuosity, anastomoses had little effect on oxygen transport under normal conditions, but significantly improved transport when vessel blockages were present. Copyright 2000 Academic Press.

Surface tension and density of Si-Ge melts

Science.gov (United States)

Ricci, Enrica; Amore, Stefano; Giuranno, Donatella; Novakovic, Rada; Tuissi, Ausonio; Sobczak, Natalia; Nowak, Rafal; Korpala, Bartłomiej; Bruzda, Grzegorz

2014-06-01

In this work, the surface tension and density of Si-Ge liquid alloys were determined by the pendant drop method. Over the range of measurements, both properties show a linear temperature dependence and a nonlinear concentration dependence. Indeed, the density decreases with increasing silicon content exhibiting positive deviation from ideality, while the surface tension increases and deviates negatively with respect to the ideal solution model. Taking into account the Si-Ge phase diagram, a simple lens type, the surface tension behavior of the Si-Ge liquid alloys was analyzed in the framework of the Quasi-Chemical Approximation for the Regular Solutions model. The new experimental results were compared with a few data available in the literature, obtained by the containerless method.

Rein tension during canter

NARCIS (Netherlands)

Egenvall, Agneta; Eisersiö, Marie; Rhodin, Marie; van Weeren, P.R.; Roepstorff, Lars

2015-01-01

Riders generally use reins as a means for communication with the horse. At present, the signalling pattern is poorly understood. The aim of this study was to illustrate and analyse the rein tension patterns in a number of rider/horse combinations across a variety of exercises in the canter gait. Our

On innovation patterns and value-tensions in public services

DEFF Research Database (Denmark)

Fuglsang, Lars; Rønning, Rolf

2015-01-01

to the possibility of intertwined innovation patterns. Focusing public sector services, this paper agues that intertwined innovation patterns emerge within public services as a response to value-tensions. Values can be defined as measures for beneficial behaviour that guide innovation. Value-tensions in public...... services include tensions between the political, economic, communal, aesthetic and intellectual values. The contribution of the paper to service innovation research is the emphasis on the concept of intertwined innovation patterns, such as the intertwinement of science driven and task driven innovation....... Further, the paper contributes by pinpointing how varied values guide innovation in public services....

The Effects of Synthetic Cannabinoids on Alveolar-Arterial Oxygen Gradient

Directory of Open Access Journals (Sweden)

Egemen Kucuk

2016-09-01

Full Text Available Aim: Synthetic cannabinoids are chemicals that produce several marijuana-like effects in humans. Aim of this study is to investigate the effects of synthetic cannabinoids on to alveolar-arterial oxygen gradient. Material and Method: A total of 112 patients, who admitted directly to emergency clinic with synthetic cannabinoid usage, were determined between February 2014 and August 2014. Blood gases of 41 patients were determined as arterial blood gases on room air, and included in to study. Patients were evaluated according to age, sex, decade, partial pressure of arterial oxygen, partial pressure of arterial carbon dioxide, pH, bicarbonate, metabolic status, age consistent expected alveolar-arterial oxygen gradient and calculated alveolar-arterial oxygen gradient. Results: Synthetic cannabinoid using was higher in males, mean age of patients was 23.32±6.14 years. Number of patients in the third decade were significantly higher than the other decades. The calculated alveolar-arterial oxygen gradient value of patients was significantly higher than age consistent expected alveolar-arterial oxygen gradient value. Respiratory acidosis, was significantly higher than the other types of the metabolic disorders. The best cutoff point for calculated alveolar-arterial oxygen gradient was 12.70, with sensitivity of 90% and specifity of 85%. Area under curve was 0.70 for calculated alveolar-arterial oxygen gradient. Discussion: The value of alveolar-arterial oxygen gradient has been increased due to synthetic cannabinoid usage. This can be used as a supportive parameter in the diagnosis of synthetic cannabinoid usage.

Tension-induced binding of semiflexible biopolymers

Science.gov (United States)

Benetatos, Panayotis; von der Heydt, Alice; Zippelius, Annette

2015-03-01

We investigate theoretically the effect of polymer tension on the collective behaviour of reversible cross-links. We use a model of two parallel-aligned, weakly-bending wormlike chains with a regularly spaced sequence of binding sites subjected to a tensile force. Reversible cross-links attach and detach at the binding sites with an affinity controlled by a chemical potential. In a mean-field approach, we calculate the free energy of the system and we show the emergence of a free energy barrier which controls the reversible (un)binding. The tension affects the conformational entropy of the chains which competes with the binding energy of the cross-links. This competition gives rise to a sudden increase in the fraction of bound sites as the polymer tension increases. The force-induced first-order transition in the number of cross-links implies a sudden force-induced stiffening of the effective stretching modulus of the polymers. This mechanism may be relevant to the formation and stress-induced strengthening of stress fibers in the cytoskeleton. We acknowledge support by the Deutsche Forschungsgemeinschaft (DFG) via grant SFB-937/A1.

Tension-induced binding of semiflexible biopolymers

International Nuclear Information System (INIS)

Benetatos, Panayotis; Heydt, Alice von der; Zippelius, Annette

2014-01-01

We investigate theoretically the effect of polymer tension on the collective behavior of reversibly binding cross-links. For this purpose, we employ a model of two weakly bending wormlike chains aligned in parallel by a tensile force, with a sequence of inter-chain binding sites regularly spaced along the contours. Reversible cross-links attach and detach at the sites with an affinity controlled by a chemical potential. In a mean-field approach, we calculate the free energy of the system and find the emergence of a free-energy barrier which controls the reversible (un)binding. The tension affects the conformational entropy of the chains which competes with the binding energy of the cross-links. This competition gives rise to a sudden increase in the fraction of bound sites as the tension increases. We show that this transition is related to the cross-over between weak and strong localization of a directed polymer in a pinning potential. The cross-over to the strongly bound state can be interpreted as a mechanism for force-stiffening which exceeds the capabilities of single-chain elasticity and thus available only to reversibly cross-linked polymers. (paper)

Comparison of the OxyMask and Venturi mask in the delivery of supplemental oxygen: Pilot study in oxygen-dependent patients

Science.gov (United States)

Beecroft, Jaime M; Hanly, Patrick J

2006-01-01

BACKGROUND: The OxyMask (Southmedic Inc, Canada) is a new face mask for oxygen delivery that uses a small ‘diffuser’ to concentrate and direct oxygen toward the mouth and nose. The authors hypothesized that this unique design would enable the OxyMask to deliver oxygen more efficiently than a Venturi mask (Hudson RCI, USA) in patients with chronic hypoxemia. METHODS: Oxygen-dependent patients with chronic, stable respiratory disease were recruited to compare the OxyMask and Venturi mask in a randomized, single-blind, cross-over design. Baseline blood oxygen saturation (SaO2) was established breathing room air, followed in a random order by supplemental oxygen through the OxyMask or Venturi mask. Oxygen delivery was titrated to maintain SaO2 4% to 5% and 8% to 9% above baseline for two separate 30 min periods of stable breathing. Oxygen flow rate, partial pressure of inspired and expired oxygen (PO2) and carbon dioxide (PCO2), minute ventilation, heart rate, nasal and oral breathing, SaO2 and transcutaneous PCO2 were collected continuously. The study was repeated following alterations to the OxyMask design, which improved clearance of carbon dioxide. RESULTS: Thirteen patients, aged 28 to 79 years, were studied initially using the original OxyMask. Oxygen flow rate was lower, inspired PO2 was higher and expired PO2 was lower while using the OxyMask. Minute ventilation and inspired and expired PCO2 were significantly higher while using the OxyMask, whereas transcutaneous PCO2, heart rate and the ratio of nasal to oral breathing did not change significantly throughout the study. Following modification of the OxyMask, 13 additional patients, aged 18 to 79 years, were studied using the same protocol. The modified OxyMask provided a higher inspired PO2 at a lower flow rate, without evidence of carbon dioxide retention. CONCLUSIONS: Oxygen is delivered safely and more efficiently by the OxyMask than by the Venturi mask in stable oxygen-dependent patients. PMID:16896425

The effects of combined elastic- and free-weight tension vs. free-weight tension on one-repetition maximum strength in the bench press.

Science.gov (United States)

Bellar, David M; Muller, Matthew D; Barkley, Jacob E; Kim, Chul-Ho; Ida, Keisuke; Ryan, Edward J; Bliss, Mathew V; Glickman, Ellen L

2011-02-01

The present study investigated the effects of training combining elastic tension, free weights, and the bench press. Eleven college-aged men (untrained) in the bench press participated in the 13-week study. The participants were first given instructions and then practiced the bench press, followed by a one-repetition maximum (1RM) test of baseline strength. Subjects were then trained in the bench press for 3 weeks to allow for the beginning of neural adaptation. After another 1RM test, participants were assigned to 1 of 2 conditions for the next 3 weeks of training: 85% Free-Weight Tension, 15% Elastic Tension (BAND), or 100% Free-Weight Tension (STAND). After 3 weeks of training and a third 1RM max test, participants switched treatments, under which they completed the final 3 weeks of training and the fourth 1RM test. Analysis via analysis of covariance revealed a significant (p ≤ 0.05) main effect for time and interaction effect for Treatment (BAND vs. STAND). Subsequent analysis via paired-samples t-test revealed the BAND condition was significantly better (p = 0.05) at producing raw gains in 1RM strength. (BAND 9.95 ± 3.7 kg vs. STAND 7.56 ± 2.8 kg). These results suggest that the addition of elastic tension to the bench press may be an effective method of increasing strength.

A Computational Study of Richtmyer-Meshkov Instability with Surface Tension

Science.gov (United States)

Francois, Marianne; Velechovsky, Jan; Jibben, Zach; Masser, Thomas; LANL Collaboration

2017-11-01

We have added the capability to model surface tension in our adaptive mesh refinement compressible flow solver, xRage. Our surface tension capability employs the continuum surface force to model surface tension and the height function method to compute curvatures. We have verified our model implementation for the static and oscillating droplets test cases and the linear regime of the Rayleigh-Taylor instability. With this newly added capability, we have performed a numerical study of the effects of surface tension on single-mode and multi-mode Richtmyer-Meshkov instability. This work was performed under the auspices of the National Nuclear Security Administration of the U.S. Department of Energy at Los Alamos National Laboratory under Contract No. DE-AC52 - 06NA25396.

The Challenges and Future of Public Higher Education Leadership in Kenya

Science.gov (United States)

Odhiambo, George

2014-01-01

This article discusses some of the key challenges and points of tension pertaining to leadership in higher education in Kenya. Effective leadership approaches are discussed including an exploration of why effective leadership is more important in Kenyan public higher education now than ever. Given the complex context within which public higher…

The effect of temperature and oxygen content on coal burnout

Energy Technology Data Exchange (ETDEWEB)

K. Milenkova; A.G. Borrego; D. Alvarez; J. Xiberta; R. Menendez [Instituto Nacional del Carbon, CSIC, Oviedo (Spain)

2003-07-01

In this study chars from six coals differing in rank and maceral composition have been prepared at 1100 and 1300{sup o}C in a drop tube reactor using four oxygen concentrations (0, 2.5, 10 and 21% oxygen). Char burnout, reactivity, morphology and optical texture have been considered in an attempt to understand the effect of temperature and oxygen concentration in relation to coal characteristics. Temperature has shown to have a different effect on conversion depending on coal rank. The high volatile coals showed similar conversions at 1100 and 1300{sup o}C at the various atmospheres tested, whereas higher rank coals showed higher conversions at 1300 than at 1100{sup o}C. The presence of oxygen in the reacting gas appears to have two opposite effects on coal combustion. On the one hand it prevents swelling and devolatilisation and on the other it enhances combustion. The burnout will depend on which process dominates. In addition, this effect appears to be temperature dependant and the inhibiting effect of oxygen on coal devolatilisation has shown to be higher at higher temperature, since at low temperature it only affects the lowest ranked coals. The presence of oxygen also affects the structure of carbonaceous material since the lower the oxygen concentration the higher the anisotropy development. The difference in temperature separating the two series of experiments (1000 and 1300{sup o}C) did not have a positive effect on the conversion of coals yielding highly porous chars whereas for coals yielding more dense structures higher conversions were achieved at higher temperatures. 7 refs., 5 figs., 1 tab.

Proceedings of the colloquium: The response of liquids to dynamic tension

International Nuclear Information System (INIS)

Jones, A.V.

1978-01-01

The contributed papers are: - Tension pulses in a liquid column; - A generalized cavitationn model for liquids; - Transmission of a tension pulse through water; - Current status of the equation of state in Lagrangian codes; - The effects of the reflection of an underwater shock at a free surface; - The calculation of the propagation of tension and recompaction waves

Spreading of oil films on water in the surface tension regime

Energy Technology Data Exchange (ETDEWEB)

Camp, D.W.

1985-01-01

Surface tension forces will cause an oil to spread over water if the tension of the oil film (the summed surface and interfacial tensions for bulk oil films, or the equilibrium spreading tension for monomolecular films) is less than the surface tension of water. For oil films spreading in a 40 cm long channel, measurements are made of leading edge position and lateral profiles of film thickness, velocity, and tension as a function of time. Measurements of the tension profiles, important for evaluating proposed theories, is made possible by the development of a new technique based on the Wilhelmy method. The oils studied were silicones, fatty acids and alcohols, and mixtures of surfactants in otherwise nonspreading oils. The single-component oils show an acceleration zone connecting a slow-moving inner region with a fast-moving leading monolayer. The dependence of film tension on film thickness for spreading single-component oils often differs from that at equilibrium. The mixtures show a bulk oil film configuration which extends to the leading edge and have velocity profiles which increase smoothly. The theoretical framework, similarity transformation, and asymptotic solutions of Foda and Cox for single-component oils were shown to be valid. An analysis of spreading surfactant-oil mixtures is developed which allows them to be treated under this framework. An easily-used semi-empirical model is proposed which allows them to be treated under this framework. An easily-used semi-empirical model is proposed which allows accurate prediction of detailed spreading behavior for any spreading oil.

Fatigue in tension perpendicular to the grain

DEFF Research Database (Denmark)

Clorius, Christian Odin; Pedersen, Martin Bo Uhre; Hoffmeyer, Preben

1999-01-01

Traditinally fatigue resistance is quantified as number of cycles to failure at a given stress level. A previous study by the authors showed that fatigue in compression parallel to the grain is governed partly by duration of load and partly by an effect of loading, i.e. a combination of a creep...... mechanism and a mechanism connected to damage introduce in the loading sequences. The purpose of the present study is to disentangle the effect of duration of load from the effect of load oscillation in fatigue in tension perpendicular to the grain. Fatigue experiments are made on small specimens...... and on dowel type joints with slotted in steel plates. In series of ten, the small specimens are taken to fatigue failure in uniform tension at square wave shaped load cycles at 0.01 Hz and 0.1 Hz. In order to test the predictive validity of the result from the small tension specimens, fatigue experiments...

Fatigue In Tension Perpendicular to the Grain

DEFF Research Database (Denmark)

Clorius, Christian Odin; Pedersen, Martin Uhre; Hoffmeyer, Preben

2004-01-01

Traditionally fatigue resistance is quantified as number of cycles to failure at a given stress level. A previous study by the authors showed that fatigue in compression parallel to the grain is governed partly by duration of load and partly by an effect of loading, i.e. a combination of a creep...... mechanism and a mechanism connected to damage introduced in the loading sequences. The purpose of the present study is to disentangle the effect of duration of load from the effect of load oscillation in fatigue in tension perpendicular to the grain. Fatigue experiments are made on small specimens...... and on dowel type joints with slotted in steel plates. In series of ten, the small specimens are taken to fatigue failure in uniform tension at square wave shaped load cycles at 0.01 Hz and 0.1 Hz. In arder to test the predictive validity of the result from the small tension specimens, fatigue experiments...

Surface tension of normal and heavy water

International Nuclear Information System (INIS)

Straub, J.; Rosner, N.; Grigull, V.

1980-01-01

A Skeleton Table and simple interpolation equation for the surface tension of light water was developed by the Working Group III of the International Association for the Properties of Steam and is recommended as an International Standard. The Skeleton Table is based on all known measurements of the surface tension and individual data were weighted corresponding to the accuracy of the measurements. The form of the interpolation equation is based on a physical concept. It represents an extension of van der Waals-equation, where the exponent conforms to the 'Scaling Laws'. In addition for application purposes simple relations for the Laplace-coefficient and for the density difference between the liquid and gaseous phases of light water are given. The same form of interpolation equation for the surface tension can be used for heavy water, for which the coefficients are given. However, this equation is based only on a single set of data. (orig.) [de

Modeling combined tension-shear failure of ductile materials

International Nuclear Information System (INIS)

Partom, Y

2014-01-01

Failure of ductile materials is usually expressed in terms of effective plastic strain. Ductile materials can fail by two different failure modes, shear failure and tensile failure. Under dynamic loading shear failure has to do with shear localization and formation of adiabatic shear bands. In these bands plastic strain rate is very high, dissipative heating is extensive, and shear strength is lost. Shear localization starts at a certain value of effective plastic strain, when thermal softening overcomes strain hardening. Shear failure is therefore represented in terms of effective plastic strain. On the other hand, tensile failure comes about by void growth under tension. For voids in a tension field there is a threshold state of the remote field for which voids grow spontaneously (cavitation), and the material there fails. Cavitation depends on the remote field stress components and on the flow stress. In this way failure in tension is related to shear strength and to failure in shear. Here we first evaluate the cavitation threshold for different remote field situations, using 2D numerical simulations with a hydro code. We then use the results to compute examples of rate dependent tension-shear failure of a ductile material.

Level of physical activity, well-being, stress and self-rated health in persons with migraine and co-existing tension-type headache and neck pain

DEFF Research Database (Denmark)

Krøll, Lotte Skytte; Hammarlund, Catharina Sjödahl; Westergaard, Maria Lurenda

2017-01-01

where questionnaires on physical activity, psychological well-being, perceived stress and self-rated health were completed by 148 persons with migraine and 100 healthy controls matched by sex and average age. Semi-structured interviews were conducted to assess characteristics of migraine, tension......-existing tension-type headache and neck pain in a clinic-based sample, b) the level of physical activity, psychological well-being, perceived stress and self-rated health in persons with migraine and co-existing tension-type headache and neck pain compared to healthy controls, c) the perceived ability of persons...... well-being, higher level of perceived stress and poorer self-rated health compared to healthy controls. They reported reduced ability to perform physical activity owing to migraine (high degree), tension-type headache (moderate degree) and neck pain (low degree). The most burdensome condition...

Curvature dependence of the electrolytic liquid-liquid interfacial tension

NARCIS (Netherlands)

Bier, Markus; de Graaf, J.; Zwanikken, J.W.; van Roij, R.H.H.G.

2009-01-01

The interfacial tension of a liquid droplet surrounded by another liquid in the presence of microscopic ions is studied as a function of the droplet radius. An analytical expression for the interfacial tension is obtained within a linear Poisson–Boltzmann theory and compared with numerical results

Coefficient of friction of dry slash pine and southern red oak on three tension-grip facings

Science.gov (United States)

Truett J. Lemoine; Peter Koch

1974-01-01

A urethane material proved to have nine times higher static friction coefficient (0.9) than smooth steel (0.1) on radial and tangential wood surfaces pulled parallel to the grain. It is probably superior to 220-grit garnet paper or sand coatings for tension-grip facings in lumber testing machines.

Indirect coupling of phosphate release to de novo tension generation during muscle contraction.

Science.gov (United States)

Davis, J S; Rodgers, M E

1995-01-01

A key question in muscle contraction is how tension generation is coupled to the chemistry of the actomyosin ATPase. Biochemical and mechanochemical experiments link tension generation to a change in structure associated with phosphate release. Length-jump and temperature-jump experiments, on the other hand, implicate phase 2slow, a significantly faster, markedly strain-sensitive kinetic process in tension generation. We use a laser temperature jump to probe the kinetics and mechanism of tension generation in skinned rabbit psoas fibers--an appropriate method since both phosphate release and phase 2slow are readily perturbed by temperature. Kinetics characteristic of the structural change associated with phosphate release are observed only when phosphate is added to fibers. When present, it causes a reduction in fiber tension; otherwise, no force is generated when it is perturbed. We therefore exclude this step from tension generation. The kinetics of de novo tension generation by the temperature-jump equivalent of phase 2slow appear unaffected by phosphate binding. We therefore propose that phosphate release is indirectly coupled to de novo tension generation via a steady-state flux through an irreversible step. We conclude that tension generation occurs in the absence of chemical change as the result of an entropy-driven transition between strongly bound crossbridges in the actomyosin-ADP state. The mechanism resembles the operation of a clock, with phosphate release providing the energy to tension the spring, and the irreversible step functions as the escapement mechanism, which is followed in turn by tension generation as the movement of the hands. Images Fig. 6 PMID:7479824

Methodology for the analysis of self-tensioned wooden structural floors

Directory of Open Access Journals (Sweden)

F. Suárez-Riestra

2017-09-01

Full Text Available It is described a self-tensioning system constituted by a force multiplying device which, attached to the supports of the ends of the structural element, is able to convert the vertical resultant from the gravitatonial actions into an effective tensioning action, through the movement that was induced by a set of rods. The self-tensioning system is able to offer a high performance, thanks to the beneficial effect of the opposite deflection generated by the tensioning, in proportion to the increasing of the gravitational action. This allows to design long-span timber ribbed floors using reduced depths. The complexity of calculation due to the non-linearity of the system can be obviated with the methodology of analysis developed in the article. In order to illustrate the advantages of the self-tensioning system and the methodology of analysis which were developed, six cases of ribbed floors have been analysed, with spans of 9, 12 and 15 m and variable using loads of 3,00 kN/m2 and 5,00 kN/m2.

The effects of viscosity, surface tension, and flow rate on gasoil-water flow pattern in microchannels

Energy Technology Data Exchange (ETDEWEB)

Boogar, Rahman Sadeghi; Gheshlaghi, Reza; Mahdavi, Mahmood Akhavan [Ferdowsi University of Mashhad, Mashhad (Iran, Islamic Republic of)

2013-01-15

A microchannel was fabricated with glass tubes to investigate the effect of viscosity, surface tension, and flow rate on the liquid-liquid two-phase flow regime. Water and gasoil were selected as aqueous and organic working fluids, respectively. The two fluids were injected into the microchannel and created either slug or parallel profile depending on the applied conditions. The range of Reynolds and capillary numbers was chosen in such a way that neither inertia nor interfacial tension forces were negligible. Xanthan gum was used to increase viscosity and Triton X-100 (TX-100) and Sodium Dodecyl Sulfate (SDS) were used to reduce the interfacial tension. The results demonstrated that higher value of viscosity and flow rate increased interfacial area, but slug flow regime remained unchanged. The two surfactants showed different effects on the flow regime and interfacial area. Addition of TX-100 did not change the slug flow but decreased the interfacial area. In contrast, addition of SDS increased interfacial area by decreasing the slug’s length in the low concentrations and by switching from slug to parallel regime at high concentrations.

Feasibility Study on Tension Estimation Technique for Hanger Cables Using the FE Model-Based System Identification Method

Directory of Open Access Journals (Sweden)

Kyu-Sik Park

2015-01-01

Full Text Available Hanger cables in suspension bridges are partly constrained by horizontal clamps. So, existing tension estimation methods based on a single cable model are prone to higher errors as the cable gets shorter, making it more sensitive to flexural rigidity. Therefore, inverse analysis and system identification methods based on finite element models are suggested recently. In this paper, the applicability of system identification methods is investigated using the hanger cables of Gwang-An bridge. The test results show that the inverse analysis and systemic identification methods based on finite element models are more reliable than the existing string theory and linear regression method for calculating the tension in terms of natural frequency errors. However, the estimation error of tension can be varied according to the accuracy of finite element model in model based methods. In particular, the boundary conditions affect the results more profoundly when the cable gets shorter. Therefore, it is important to identify the boundary conditions through experiment if it is possible. The FE model-based tension estimation method using system identification method can take various boundary conditions into account. Also, since it is not sensitive to the number of natural frequency inputs, the availability of this system is high.

Managing Tensions Between New and Existing Business Models

DEFF Research Database (Denmark)

Sund, Kristian J.; Bogers, Marcel; Villarroel Fernandez, Juan Andrei

2016-01-01

Exploring new business models may be a good way to stay competitive, but doing so can create tensions internally, in areas such as organizational structure and competition for resources. Companies exploring business model innovation may not recognize the inevitability of these tensions and thus b...... be poorly prepared to manage them. But understanding these issues may lessen some of the organizational challenges associated with business model innovation....

Contact angle control of sessile drops on a tensioned web

Science.gov (United States)

Park, Janghoon; Kim, Dongguk; Lee, Changwoo

2018-04-01

In this study, the influence of the change of tension applied to flexible and thin web substrate on the contact angle of sessile drop in roll-to-roll system was investigated. Graphene oxide and deionized water solutions were used in the experiments. Tension was changed to 29, 49, and 69 N, and the casting distance of the micropipette and the material was set to 10, 20, and 40 mm, and the droplet volume was set to 10, 20, and 30 μL, respectively. Statistical analysis of three variables and analysis of the variance methodology showed that the casting distance was most significant for the contact angle change, and the most interesting tension variable was also affected. The change in tension caused the maximum contact angle to change by 5.5°. The tension was not uniform in the width direction. When the droplet was applied in the same direction in the width direction, it was confirmed that the tension unevenness had great influence on the contact angle up to 11°. Finally, the casting distance, which has a large effect on the contact angle, was calibrated in the width direction to reduce the width direction contact angle deviation to 1%. This study can be applied to fine patterning research using continuous inkjet printing and aerosol jet printing, which are roll-to-roll processes based on droplet handling.

Corrosion characteristics of post-tensioning strands in ungrouted ducts : summary.

Science.gov (United States)

2011-01-01

To prevent corrosion of post-tensioning strands, FDOT construction specifications currently require post-tensioning ducts to be grouted within seven calendar days of strand installation. This period challenges construction schedules on large projects...

Measurement of calcium influx in tethered rings of rabbit aorta under tension

International Nuclear Information System (INIS)

Gleason, M.M.; Ratz, P.H.; Flaim, S.F.

1985-01-01

Calcium (Ca) influx in vascular smooth muscle is routinely measured in untethered preparations not under passive stretch, and Ca influx data are correlated with data for steady-state isometric tension obtained under parallel conditions from tethered preparations under passive stretch. The validity of this method was tested by simultaneous measurement of Ca influx and tension in tethered rings of rabbit thoracic aorta. Ca influx ( 45 Ca 3-min pulse) and tension were measured at 3 and 30 min after norepinephrine (NE) or KCl and under control (no agonist) conditions. Active tension was significantly altered by variations in passive tension. Ca influx was unaffected by passive tension under control, NE, or KCl conditions, and results were similar at 3 and 30 min. The results confirm the validity of correlating Ca influx data from untethered rings with steady-state contractile response data obtained from tethered rings under similar experimental conditions

Quantitative evaluation of the mitochondrial proteomes of Drosophila melanogaster adapted to extreme oxygen conditions.

Directory of Open Access Journals (Sweden)

Songyue Yin

Full Text Available Mitochondria are the primary organelles that consume oxygen and provide energy for cellular activities. To investigate the mitochondrial mechanisms underlying adaptation to extreme oxygen conditions, we generated Drosophila strains that could survive in low- or high-oxygen environments (LOF or HOF, respectively, examined their mitochondria at the ultrastructural level via transmission electron microscopy, studied the activity of their respiratory chain complexes, and quantitatively analyzed the protein abundance responses of the mitochondrial proteomes using Isobaric tag for relative and absolute quantitation (iTRAQ. A total of 718 proteins were identified with high confidence, and 55 and 75 mitochondrial proteins displayed significant differences in abundance in LOF and HOF, respectively, compared with the control flies. Importantly, these differentially expressed mitochondrial proteins are primarily involved in respiration, calcium regulation, the oxidative response, and mitochondrial protein translation. A correlation analysis of the changes in the levels of the mRNAs corresponding to differentially regulated mitochondrial proteins revealed two sets of proteins with different modes of regulation (transcriptional vs. post-transcriptional in both LOF and HOF. We believe that these findings will not only enhance our understanding of the mechanisms underlying adaptation to extreme oxygen conditions in Drosophila but also provide a clue in studying human disease induced by altered oxygen tension in tissues and cells.

The Recalibration of Neoliberalisation: Repoliticising Higher Education Policy in Hong Kong

Science.gov (United States)

Lo, William Yat Wai

2017-01-01

This article analyses a recent policy change in higher education in Hong Kong to determine the significance of politics in the conceptual understanding of higher education governance. To achieve this objective, the article examines the tension between the global agenda, which is characterised by neoliberal ideology and practices, and local needs,…

String tensions for lattice gauge theories in 2+1 dimensions

International Nuclear Information System (INIS)

Ambjoern, J.; Hey, A.J.G.; Otto, S.

1982-01-01

Compact U(1) and SU(2) lattice gauge theories in 3 euclidean dimensions are studied by standard Monte Carlo techniques. The question of extracting reliable string tensions from these theories is examined in detail, including a comparison of the Monte Carlo Wilson loop data with weak coupling predictions and a careful error analysis: our conclusions are rather different from those of previous investigations of these theories. In the case of U(1) theory, we find that only a tiny range of β values can possibly be relevant for extracting a string tension and we are unable to convincingly demonstrate the expected exponential dependence of the string tension on β. For the SU(2) theory we are able to determine, albeit with rather large errors, a string tension from a study of Wilson loops. (orig.)

Creating Tension in Writing.

Science.gov (United States)

Folta, Bernarr

This paper discusses the rationale and teaching methods for a six-week unit, for a high school freshman English Class, on perception, semantics, and writing, which places special focus on developing tension in student writing. The first four objectives of the course focus on perception and the next two focus on semantics. The seventh…

Surface tension modelling of liquid Cd-Sn-Zn alloys

Science.gov (United States)

Fima, Przemyslaw; Novakovic, Rada

2018-06-01

The thermodynamic model in conjunction with Butler equation and the geometric models were used for the surface tension calculation of Cd-Sn-Zn liquid alloys. Good agreement was found between the experimental data for limiting binaries and model calculations performed with Butler model. In the case of ternary alloys, the surface tension variation with Cd content is better reproduced in the case of alloys lying on vertical sections defined by high Sn to Zn molar fraction ratio. The calculated surface tension is in relatively good agreement with the available experimental data. In addition, the surface segregation of liquid ternary Cd-Sn-Zn and constituent binaries has also been calculated.

On the Minimum Cable Tensions for the Cable-Based Parallel Robots

Directory of Open Access Journals (Sweden)

Peng Liu

2014-01-01

Full Text Available This paper investigates the minimum cable tension distributions in the workspace for cable-based parallel robots to find out more information on the stability. First, the kinematic model of a cable-based parallel robot is derived based on the wrench matrix. Then, a noniterative polynomial-based optimization algorithm with the proper optimal objective function is presented based on the convex optimization theory, in which the minimum cable tension at any pose is determined. Additionally, three performance indices are proposed to show the distributions of the minimum cable tensions in a specified region of the workspace. An important thing is that the three performance indices can be used to evaluate the stability of the cable-based parallel robots. Furthermore, a new workspace, the Specified Minimum Cable Tension Workspace (SMCTW, is introduced, within which all the minimum tensions exceed a specified value, therefore meeting the specified stability requirement. Finally, a camera robot parallel driven by four cables for aerial panoramic photographing is selected to illustrate the distributions of the minimum cable tensions in the workspace and the relationship between the three performance indices and the stability.

Formation et stabilisation des émulsions inverses eau de mer-pétrole. Rôle de la tension et de la viscosité d'interface Formation and Stabilization of Reverse Seawater-Oil Emulsions. Role of Tension and Interfacial Viscosity

Directory of Open Access Journals (Sweden)

Desmaison M.

2006-11-01

Full Text Available On a étudié l'évolution au cours du temps de la tension et de la viscosité à l'interface d'un pétrole brut arabe léger et d'eau de mer reconstituée. D'une valeur initiale moyenne de 18 mNm-1, la tension interfaciale s'abaisse au niveau de 1 mNm-1 après 40 jours de contact. L'influence de l'oxygène et de la lumière, l'action des antioxydants et le rôle des constituants isolés du pétrole montrent que cette évolution est due à une oxydation photochimique de composés de la fraction aromatique. Inversement, la viscosité interfaciale augmente avec le temps selon une allure exponentielle. Cette évolution est liée à la présence d'asphaltènes dont les structures s'organisent au cours du temps. La superposition de ces deux phénomènes entraîne la formation et la stabilisation des émulsions inverses, dites mousses au chocolat que l'on observe lors des déversements accidentels de pétrole en mer. This article examines the evolution in time of the tension and interfacial viscosity of the Arabian Light crude oil reconstituted seawater interface. From an initial level of 18 mNm-1, the interfacial tension decreases to 1 mNm-1 after 40 days of contact. The influence of oxygen and light, the effect of antioxidants and the rote of constituents isolated from the oil show that this evolution is due to photochemical oxidation of compounds in the aromatic fraction. On the contrary, interfacial viscosity increases at an exponential rate with time. This evolution is linked to the presence of asphaltenes having structures which become organized with time. The combined effect of these two phenomena causes the formation and stabilization of reverse emulsions, called chocolate mousse, which are seen during accidental offshore oil spills.

Recombination and detachment in oxygen discharges: the role of metastable oxygen molecules

International Nuclear Information System (INIS)

Gudmundsson, J T

2004-01-01

A global (volume averaged) model of oxygen discharges is used to study the transition from a recombination dominated discharge to a detachment dominated discharge. The model includes the metastable oxygen molecules O 2 (a 1 Δ g ) and O 2 (b 1 Σ g + ) and the three Herzberg states O 2 (A 3 Σ u + , A' 3 Δ u , c 1 Σ u - ). Dissociative attachment of the oxygen molecule in the ground state O 2 ( 3 Σ g - ) and the metastable oxygen molecule O 2 (a 1 Δ g ) are the dominating channels for creation of the negative oxygen ion O - . At high pressures, dissociative attachment of the Herzberg states contributes significantly to the creation of the negative oxygen ion, O - . The detachment by a collision of the metastable oxygen molecule O 2 (b 1 Σ g + ) with the oxygen ion, O - , is a significant loss process for the O - at pressures above 10 mTorr. Its contribution to the loss is more significant at a lower applied power, but at the higher pressures it is always significant. Detachment by collision with O( 3 P) is also an important loss mechanism for O - . We find that ion-ion recombination is the dominating loss process for negative ions in oxygen discharges at low pressures and calculate the critical pressure where the contributions of recombination reactions and detachment reactions are equal. This critical pressure depends on the applied power, increases with applied power and is in the range 5-14 mTorr in the pressure and power range investigated

Local deformation method for measuring element tension in space deployable structures

Directory of Open Access Journals (Sweden)

Belov Sergey

2017-01-01

Full Text Available The article describes the local deformation method to determine the tension of cord and thin membrane elements in space deployable structure as antenna reflector. Possible measuring instrument model, analytical and numerical solutions and experimental results are presented. The boundary effects on measurement results of metallic mesh reflector surface tension are estimated. The study case depicting non-uniform reflector surface tension is considered.

Cerebral oxygenation and energy metabolism in bacterial meningitis

DEFF Research Database (Denmark)

Larsen, Lykke

Introduction: In a recent retrospective study of patients with severe bacterial meningitis we demonstrated that cerebral oxidative metabolism was affected in approximately 50% of the cases. An increase of lactate/pyruvate (LP) ratio above the upper normal limit, defined according to according...... bacterial meningitis; secondly to examine whether it is correct to separate the diagnosis of cerebral ischemia from mitochondrial dysfunction based exclusively on the biochemical pattern obtained during intracerebral microdialysis. Method: A prospective clinical study including patients with severe...... community acquired bacterial meningitis admitted to the Department of Infectious Diseases, Odense University Hospital, during the period January 2014 to June 2016. We relate data from measurements of brain tissue oxygen tension (PbtO2) to simultaneously recorded data reflecting cerebral cytoplasmic redox...

33 CFR 147.817 - Sir Douglas Morpeth Tension Leg Platform safety zone.

Science.gov (United States)

2010-07-01

... 33 Navigation and Navigable Waters 2 2010-07-01 2010-07-01 false Sir Douglas Morpeth Tension Leg... HOMELAND SECURITY (CONTINUED) OUTER CONTINENTAL SHELF ACTIVITIES SAFETY ZONES § 147.817 Sir Douglas Morpeth Tension Leg Platform safety zone. (a) Description. The Sir Douglas Morpeth Tension Leg Platform (Morpeth...

Ethical tensions: A qualitative systematic review of new graduate perceptions.

Science.gov (United States)

Hazelwood, Tori; Murray, Carolyn M; Baker, Amy; Stanley, Mandy

2017-01-01

New graduate transition into the workforce is challenging and can involve managing ethical tensions. Ethical tensions cause new graduates to doubt their capabilities due to their lack of experience. To support new graduates, we need to know what these ethical tensions are. To explore the ethical tensions perceived to occur in practice for new graduate health professionals. This qualitative systematic review involved a search of five databases (Medline, EMBASE, AMED, CINAHL and Scopus) which resulted in the retrieval of 3554 papers. After the two-phased screening process, eight studies were identified that met the inclusion criteria and had rich data on the review question. Articles were read several times, critically appraised and analysed through thematic analysis. Ethical considerations: No ethical approval was required for the systematic review. The review was conducted following well-established reporting guidelines enabling transparency and rigour. Studies originated from Australia, United States, Iran and China. One study included speech pathologists and seven were with nurses. Four themes included the following: (1) enduring an unknown workplace culture that generates uncertainty without support for new graduates; (2) being vulnerable because of distress from bullying, exclusion and being a scapegoat; (3) constraining systems and institutional restrictions that cause dilemmas; and (4) experiencing disillusionment from lost ideals about ethical practice. This review has brought to light the vulnerability of new graduates to negative workplace culture and collegial incivility. In addition, new graduates are subjected to ethical tensions created by institutional constraints which can create dilemmas and uncertainties through practice that does not align with what they anticipated. Understanding ethical tensions experienced by new graduates enables provision of informed support. There needs to be considerable cultural change for orientation and socialisation of

The Seven Deadly Tensions of Health-Related Human Information Behavior

Directory of Open Access Journals (Sweden)

J. David Johnson

2015-08-01

Full Text Available Tensions are a ubiquitous feature of social life and are manifested in a number of particular forms: contradictory logics, competing demands, clashes of ideas, contradictions, dialectics, irony, paradoxes, and/or dilemmas. This essay aims to explore in detail tensions surrounding seven common findings of the information seeking literature relating to: interpersonal communication, accessibility, level of skill, individual preferences, psychological limits, inertia, and costs. Our incomplete understanding of these tensions can lead us to suggest resolutions that do not recognize their underlying dualities. Human information behavior stands at the intersection of many important theoretical and policy issues (e.g., personalized medicine. Policy makers need to be more attuned to these basic tensions of information seeking recognizing the real human limits they represent to informing the public. So, even if you build a great information system, people will not necessarily use it because of the force of these underlying tensions. While rationality rules systems, irrationality rules people. The proliferation of navigator roles over the last several years is actually a hopeful sign: recognition that people need a human interface to inform them about our ever more complex health care systems.

Evaluation of tension stiffening effect on the crack width calculation of flexural RC members

Directory of Open Access Journals (Sweden)

Said M. Allam

2013-06-01

Full Text Available Building codes consider the tension stiffening when calculating the crack width of the flexural members. A simple analytical procedure is proposed for the determination of forces, stresses and strains acting on a reinforced concrete section subjected to flexure considering the concrete contribution in tension up to tensile concrete strain corresponding to the cracking strength of concrete. This analytical method gives the minimum value (lower bound of tension stiffening. Also, a commercial Finite Element Program (ABAQUS 2007 was used to perform non-linear analysis in order to evaluate the total contribution of the tensioned concrete in carrying loads which may be considered as the upper bound of tension stiffening. In addition, a comparison is carried out among the different codes using four reinforced concrete rectangular models to compare and evaluate the tension stiffening with proposed analytical lower bound tension stiffening and upper bound as obtained by ABAQUS. The models include different percentages of flexural steel ratio. The comparison revealed that the codes’ equations always consider tension stiffening lying between lower and upper bound of tension stiffening proposed in this study. Also, the study showed that the tension stiffening decreases with the increase of the percentage of the flexural reinforcement ratio.

Contact Angles and Surface Tension of Germanium-Silicon Melts

Science.gov (United States)

Croell, A.; Kaiser, N.; Cobb, S.; Szofran, F. R.; Volz, M.; Rose, M. Franklin (Technical Monitor)

2001-01-01

Precise knowledge of material parameters is more and more important for improving crystal growth processes. Two important parameters are the contact (wetting) angle and the surface tension, determining meniscus shapes and surface-tension driven flows in a variety of methods (Czochralski, EFG, floating-zone, detached Bridgman growth). The sessile drop technique allows the measurement of both parameters simultaneously and has been used to measure the contact angles and the surface tension of Ge(1-x)Si(x) (0 less than or equal to x less than or equal to 1.3) alloys on various substrate materials. Fused quartz, Sapphire, glassy carbon, graphite, SiC, carbon-based aerogel, pyrolytic boron nitride (pBN), AIN, Si3N4, and polycrystalline CVD diamond were used as substrate materials. In addition, the effect of different cleaning procedures and surface treatments on the wetting behavior were investigated. Measurements were performed both under dynamic vacuum and gas atmospheres (argon or forming gas), with temperatures up to 1100 C. In some experiments, the sample was processed for longer times, up to a week, to investigate any changes of the contact angle and/or surface tension due to slow reactions with the substrate. For pure Ge, stable contact angles were found for carbon-based substrates and for pBN, for Ge(1-x)Si(x) only for pBN. The highest wetting angles were found for pBN substrates with angles around 170deg. For the surface tension of Ge, the most reliable values resulted in gamma(T) = (591- 0.077 (T-T(sub m)) 10(exp -3)N/m. The temperature dependence of the surface tension showed similar values for Ge(1-x)Si(x), around -0.08 x 10(exp -3)N/m K, and a compositional dependence of 2.2 x 10(exp -3)N/m at%Si.

Tensions within Teaching: An Autoethnography of an American Teacher

Science.gov (United States)

Tuura, Brianne Marie

2012-01-01

This dissertation examines the personal transformation of an American teacher as she becomes aware of the social, political, and economic tensions that exist within the American school system and the affects these tensions have on her ability to teach. As the researcher becomes more aware of power structures surrounding her, the reader is enabled…

An Investigation of Corrosion Mitigation Strategies for Aging Post-Tensioned Cables

Science.gov (United States)

2017-01-01

for Aging Post- Tensioned Cables Ernest L. Miller, Barry C. White, Richard W. Haskins, Robert M. Ebeling, and James A. Evans Information Technology...approach walls) using post- tensioning (PT) seven-wire strand cables is a common approach. In the Portland District, for example, 10% of the projects...hydraulic structures by post- tensioned ground anchorage, appreciable loss of capacity in seven-wire strand cables due to corrosion is a reason for concern

An Investigation of Corrosion Mitigation Strategies for Aging Post Tensioned Cables

Science.gov (United States)

2017-01-01

for Aging Post- Tensioned Cables Ernest L. Miller, Barry C. White, Richard W. Haskins, Robert M. Ebeling, and James A. Evans Information Technology...approach walls) using post- tensioning (PT) seven-wire strand cables is a common approach. In the Portland District, for example, 10% of the projects...hydraulic structures by post- tensioned ground anchorage, appreciable loss of capacity in seven-wire strand cables due to corrosion is a reason for concern

Anterior cruciate ligament graft tensioning. Is the maximal sustained one-handed pull technique reproducible?

Directory of Open Access Journals (Sweden)

Hirpara Kieran M

2011-07-01

Full Text Available Abstract Background Tensioning of anterior cruciate ligament (ACL reconstruction grafts affects the clinical outcome of the procedure. As yet, no consensus has been reached regarding the optimum initial tension in an ACL graft. Most surgeons rely on the maximal sustained one-handed pull technique for graft tension. We aim to determine if this technique is reproducible from patient to patient. Findings We created a device to simulate ACL reconstruction surgery using Ilizarov components and porcine flexor tendons. Six experienced ACL reconstruction surgeons volunteered to tension porcine grafts using the device to see if they could produce a consistent tension. None of the surgeons involved were able to accurately reproduce graft tension over a series of repeat trials. Conclusions We conclude that the maximal sustained one-handed pull technique of ACL graft tensioning is not reproducible from trial to trial. We also conclude that the initial tension placed on an ACL graft varies from surgeon to surgeon.

Anterior cruciate ligament graft tensioning. Is the maximal sustained one-handed pull technique reproducible?

LENUS (Irish Health Repository)

O'Neill, Barry J

2011-07-20

Abstract Background Tensioning of anterior cruciate ligament (ACL) reconstruction grafts affects the clinical outcome of the procedure. As yet, no consensus has been reached regarding the optimum initial tension in an ACL graft. Most surgeons rely on the maximal sustained one-handed pull technique for graft tension. We aim to determine if this technique is reproducible from patient to patient. Findings We created a device to simulate ACL reconstruction surgery using Ilizarov components and porcine flexor tendons. Six experienced ACL reconstruction surgeons volunteered to tension porcine grafts using the device to see if they could produce a consistent tension. None of the surgeons involved were able to accurately reproduce graft tension over a series of repeat trials. Conclusions We conclude that the maximal sustained one-handed pull technique of ACL graft tensioning is not reproducible from trial to trial. We also conclude that the initial tension placed on an ACL graft varies from surgeon to surgeon.

Stress measurement and bolt tensioning by ultrasonic methods

International Nuclear Information System (INIS)

Smith, J.F.; Greiner, J.D.

1980-01-01

In the past decade, a new technique has been developed for measuring tensile stresses in solids. This ultrasonic technique has been used thus far primarily for measuring fastener tension. The precision of measurement is routinely to 2-3% and, with special care, to approx. 1%. The method is insensitive to the frictional losses which plague tensioning by torque wrench. Though the approach is relatively new, it promises a wide range of applicability

Stress Measurement and Bolt Tensioning by Ultrasonic Methods

Science.gov (United States)

Smith, J. F.; Greiner, John D.

1980-07-01

In the past decade, a new technique has been developed for measuring tensile stresses in solids. This ultrasonic technique has been used thus far primarily for measuring fastener tension. The precision of measurement is routinely to 2-3% and, with special care, to ˜1%. The method is insensitive to the frictional losses which plague tensioning by torque wrench. Though the approach is relatively new, it promises a wide range of applicability.

Prediction of surface tension of binary mixtures with the parachor method

Directory of Open Access Journals (Sweden)

Němec Tomáš

2015-01-01

Full Text Available The parachor method for the estimation of the surface tension of binary mixtures is modified by considering temperature-dependent values of the parachor parameters. The temperature dependence is calculated by a least-squares fit of pure-solvent surface tension data to the binary parachor equation utilizing the Peng-Robinson equation of state for the calculation of equilibrium densities. A very good agreement between experimental binary surface tension data and the predictions of the modified parachor method are found for the case of the mixtures of carbon dioxide and butane, benzene, and cyclohexane, respectively. The surface tension is also predicted for three refrigerant mixtures, i.e. propane, isobutane, and chlorodifluoromethane, with carbon dioxide.

Transitional Failure of Carbon Nanotube Systems under a Combination of Tension and Torsion