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Sample records for flexure necrosis due

  1. Assessing the extent of colon lengthening due to splenic flexure mobilization techniques: a cadaver study

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    Sergio Eduardo Alonso Araujo

    2012-09-01

    Full Text Available CONTEXT: Failure of a colorectal anastomosis represents a life-threatening complication of colorectal surgery. Splenic flexure mobilization may contribute to reduce the occurrence of anastomotic complications due to technical flaws. There are no published reports measuring the impact of splenic flexure mobilization on the length of mobilized colon viable to construct a safe colorectal anastomosis. OBJECTIVE: The aim of the present study was to determine the effect of two techniques for splenic flexure mobilization on colon lengthening during open left-sided colon surgery using a cadaver model. DESIGN: Anatomical dissections for left colectomy and colorectal anastomosis at the sacral promontory level were conducted in 20 fresh cadavers by the same team of four surgeons. The effect of partial and full splenic flexure mobilization on the extent of mobilized left colon segment was determined. SETTING: University of Sao Paulo Medical School, Sao Paulo, SP, Brazil. Tertiary medical institution and university hospital. PARTICIPANTS: A team of four surgeons operated on 20 fresh cadavers. RESULTS: The length of resected left colon enabling a tension-free colorectal anastomosis at the level of sacral promontory achieved without mobilizing the splenic flexure was 46.3 (35-81 cm. After partial mobilization of the splenic flexure, an additionally mobilized colon segment measuring 10.7 (2-30 cm was obtained. After full mobilization of the distal transverse colon, a mean 28.3 (10-65 cm segment was achieved. CONCLUSION: Splenic flexure mobilization techniques are associated to effective left colon lengthening for colorectal anastomosis. This result may contribute to decision-making during rectal surgery and low colorectal and coloanal anastomosis.

  2. Neurogenic pulmonary edema due to delayed radiation necrosis

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    Mani R

    2005-01-01

    Full Text Available Neurogenic pulmonary edema is oftten missed in the ICU setting as it is mistaken for pneumonia or ARDS. The case presented here illustrates how a high index of suspicion in the appropriate setting can lead to the diagnosis. The patient in this report developed acute-on-chronic cerebral edema due to radiation necrosis following gamma-knife radiation therapy for cerebral arteriovenous malformation.

  3. Penile strangulation and necrosis due to condom catheter.

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    Özkan, Heval S; İrkoren, Saime; Sivrioğlu, Nazan

    2015-06-01

    Condom catheters are often used in the management of male urinary incontinence, and are considered to be safe. As condom catheters are placed on the male genitalia, sometimes adequate care is not taken after placement owing to poor medical care of debilitated patients and feelings of embarrassment and shame. Similarly, sometimes the correct size of penile sheath is not used. Strangulation of penis due to condom catheter is a rare condition; only few such cases have been reported in the literature. Proper application and routine care of condom catheters are important in preventing this devastating complication especially in a neurologically debilitated population. We present a case of penile necrosis due to condom catheter. We will also discuss proper catheter care and treatment of possible complications.

  4. Symmetrical drug-related intertriginous and flexural exanthema due to ranitidine

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    Manikoth Payyanadan Binitha

    2014-01-01

    Full Text Available Symmetrical drug-related intertriginous and flexural exanthema (SDRIFE is an adverse drug reaction which has been reported to be caused by various drugs. In this report, we describe a case induced by ranitidine, a drug which has not been previously reported to cause SDRIFE.

  5. Bilateral breast necrosis due to local injection of fish oil.

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    Turk, Emin; Karagulle, Erdal; Koksal, Hande; Togan, Turhan; Erinanc, Ozgur Hilal; Dogru, Osman; Moray, Gokhan

    2013-01-01

    The breast is as aesthetically important as it is physiologically. Physicians and women have practiced various methods for breast aesthetics and augmentation. We report a female veterinarian who injected fish oil into her breast, which led to inflammation and necrosis of breast tissue. When all medical therapies failed, bilateral subcutaneous mastectomy was performed. We did not find a case in the literature where fish oil had been used for breast augmentation. However, we did find that many agents have been injected for breast augmentation, the results of which were tragic, just as the case presented herein.

  6. Reconstruction of the penis after necrosis due to circumcision burn.

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    Stefan, H

    1994-02-01

    Penile necrosis secondary to circumcision by an electrical scalpel in a 2 years and-2-months-old boy occurred. After healing of the electric burn only stumps of the erectile bodies and strictured urethral meatus remained. Penile shaft reconstruction by corpora mobilisation and detachment of the crura from the pubo-ischial rami was performed. This procedure gained 6 cm of a new length of the penis. To prevent readhesions to the pubo-ischial rami the penis was buried in a scrotal tunnel. Six months later the denuded shaft was resurfaced with one split-thickness skin graft and a zigzag seam on the ventral side was made. The patient voids with good stream, has spontaneous erections and nocturnal emissions. During 10 years of follow-up after the reconstruction two complications, namely a stricture of the urethra and a slight dorsal tethering of the penis caused by a scarred pubic skin were treated. The problems of reconstruction and resurfacing of the penis in childhood are discussed.

  7. A Methodology for Characterizing Gun Barrel Flexure due to Vehicle Motion

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    Mark Bundy

    2001-01-01

    Full Text Available Barrel centerline curvature is known to influence the location of projectile shot impacts. Superimposed on the unique manufactured barrel centerline is the flexed barrel shape that can occur prior to firing while the vehicle is on the move. In order to understand and quantify the effects of barrel flexure on gun accuracy, it is necessary to determine what combination of fundamental mode shapes is most likely to occur. A method to accomplish this task is described in this paper. The method is demonstrated by enumerating the 10 most likely flexed barrel shapes that were found to occur in a tank-mounted gun barrel while it traversed a bump course.

  8. Hemorrhagic necrosis due to peliosis hepatis: imaging findings and pathological correlation

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    Vignaux, O.; Legmann, P.; Bonnin, A. [Department of Radiology A, Cochin Hospital, Paris (France); Pinieux, G. de [Department of Pathology, Cochin Hospital, Paris (France); Chaussade, S.; Couturier, D. [Department of Gastroenterology, Cochin Hospital, Paris (France); Spaulding, C. [Department of Cardiology, Cochin Hospital, Paris (France)

    1999-04-01

    Peliosis hepatis is an uncommon liver condition characterized by blood-filled cavities. We report the CT, angiographic and MR features of a case of peliosis hepatis with no obvious etiology and spontaneously regressing hemorrhagic necrosis. Helical CT showed multiple peripheral low-density regions with foci of spontaneous high density suggesting the presence of blood component. On MR imaging, the multiple peripheral lesions were hypointense on T1-weighted and hyperdense on T2-weighted images, with bright foci on all sequences suggesting subacute blood. Angiography showed no evidence of tumor or vascular malformation; multiple nodular vascular lesions filling in the parenchymal phase and persisting in the venous phase suggested blood-filled cavities. Pathological examination showed blood-filled spaces with no endothelial lining, characteristic of the parenchymal type of peliosis. Knowledge of the imaging features of hemorrhagic necrosis due to peliosis hepatis is important since it can be responsive to antibiotic therapy. Furthermore, differentiating hemorrhagic necrosis from hepatic abscess avoids dangerous and sometimes fatal percutaneous drainage. (orig.) With 3 figs., 13 refs.

  9. Colon Necrosis Due to Sodium Polystyrene Sulfonate with and without Sorbitol: An Experimental Study in Rats

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    Ayoub, Isabelle; Oh, Man S.; Gupta, Raavi; McFarlane, Michael; Babinska, Anna; Salifu, Moro O.

    2015-01-01

    Introduction Based on a single rat study by Lillemoe et al, the consensus has been formed to implicate sorbitol rather than sodium polystyrene sulfonate (SPS) as the culprit for colon necrosis in humans treated with SPS and sorbitol. We tested the hypothesis that colon necrosis by sorbitol in the experiment was due to the high osmolality and volume of sorbitol rather than its chemical nature. Methods 26 rats underwent 5/6 nephrectomy. They were divided into 6 groups and given enema solutions under anesthesia (normal saline, 33% sorbitol, 33% mannitol, SPS in 33% sorbitol, SPS in normal saline, and SPS in distilled water). They were sacrificed after 48 hours of enema administration or earlier if they were very sick. The gross appearance of the colon was visually inspected, and then sliced colon tissues were examined under light microscopy. Results 1 rat from the sorbitol and 1 from the mannitol group had foci of ischemic colonic changes. The rats receiving SPS enema, in sorbitol, normal saline, distilled water, had crystal deposition with colonic necrosis and mucosal erosion. All the rats not given SPS survived until sacrificed at 48 h whereas 11 of 13 rats that received SPS in sorbitol, normal saline or distilled water died or were clearly dying and sacrificed sooner. There was no difference between sorbitol and mannitol when given without SPS. Conclusions In a surgical uremic rat model, SPS enema given alone or with sorbitol or mannitol seemed to cause colon necrosis and high mortality rate, whereas 33% sorbitol without SPS did not. PMID:26413782

  10. Transient flexural-and capillary-gravity waves due to disturbances in two-layer density-stratified fluid

    Institute of Scientific and Technical Information of China (English)

    LU Dong-qiang; SUN Cui-zhi

    2013-01-01

    Generation of the transient flexural-and capillary-gravity waves by impulsive disturbances in a two-layer fluid is investigated analytically.The upper fluid is covered by a thin elastic plate or by an inertial surface with the capillary effect.The density of each of the two immiscible layers is constant.The fluids are assumed to be inviscid and incompressible and the motion be irrotational.A point force on the surface and simple mass sources in the upper and lower fluid layers are considered.A linear system is established within the framework of potential theory.The integral solutions for the surface and interfacial waves are obtained by means of the Laplace-Fourier transform.A new representation for the dispersion relation of flexural-and capillary-gravity waves in a two-layer fluid is derived.The asymptotic representations of the wave motions are derived for large time with a fixed distance-to-time ratio with the Stokes and Scorer methods of stationary phase.It is shown that there are two different modes,namely the surface and interfacial wave modes.The wave systems observed depend on the relation between the observer's moving speed and the intrinsic minimal and maximal group velocities.

  11. Colonic necrosis and perforation due to calcium polystyrene sulfonate in a uraemic patient: a case report

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    Akagun, Tulin; Yazici, Halil; Gulluoglu, Mine G.; Yegen, Gulcin; Turkmen, Aydin

    2011-01-01

    Sodium or calcium polystyrene sulfonate (Kayexalate or analog) is an ion-exchange resin commonly used to treat hyperkalaemia in patients with chronic kidney disease. It is known to cause digestive complications, such as nausea, vomiting and constipation. Although rare, colonic necrosis and perforation are very severe complications associated with the medication. In this case report, we present a case of calcium polystyrene sulfonate-induced colonic necrosis and perforation to remind clinician...

  12. An Investigation of Energy Transmission Due to Flexural Wave Propagation in Lightweight, Built-Up Structures. Thesis

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    Mickol, John Douglas; Bernhard, R. J.

    1986-01-01

    A technique to measure flexural structure-borne noise intensity is investigated. Two accelerometers serve as transducers in this cross-spectral technique. The structure-borne sound power is obtained by two different techniques and compared. In the first method, a contour integral of intensity is performed from the values provided by the two-accelerometer intensity technique. In the second method, input power is calculated directly from the output of force and acceleration transducers. A plate and two beams were the subjects of the sound power comparisons. Excitation for the structures was either band-limited white noise or a deterministic signal similar to a swept sine. The two-accelerometer method was found to be sharply limited by near field and transducer spacing limitations. In addition, for the lightweight structures investigated, it was found that the probe inertia can have a significant influence on the power input to the structure. In addition to the experimental investigation of structure-borne sound energy, an extensive study of the point harmonically forced, point-damped beam boundary value problem was performed to gain insight into measurements of this nature. The intensity formulations were also incorporated into the finite element method. Intensity mappings were obtained analytically via finite element modeling of simple structures.

  13. Colonic necrosis and perforation due to calcium polystyrene sulfonate in a uraemic patient: a case report.

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    Akagun, Tulin; Yazici, Halil; Gulluoglu, Mine G; Yegen, Gulcin; Turkmen, Aydin

    2011-12-01

    Sodium or calcium polystyrene sulfonate (Kayexalate or analog) is an ion-exchange resin commonly used to treat hyperkalaemia in patients with chronic kidney disease. It is known to cause digestive complications, such as nausea, vomiting and constipation. Although rare, colonic necrosis and perforation are very severe complications associated with the medication. In this case report, we present a case of calcium polystyrene sulfonate-induced colonic necrosis and perforation to remind clinicians of this rare, but dangerous, toxicity associated with this commonly used medication.

  14. Colonic necrosis due to calcium polystyrene sulfonate (Kalimate) not suspended in sorbitol.

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    Castillo-Cejas, María Dolores; de-Torres-Ramírez, Inés; Alonso-Cotoner, Carmen

    2013-04-01

    Cation-exchange resins are used in the management of hyperkalemia, particularly in patients with end-stage renal disease. These resins were associated with gastrointestinal tract lesions, especially sodium polystyrene sulfonate (Kayexalate) mixed with sorbitol. We present a case of colonic necrosis after the administration of calcium polystyrene sulfonate (Kalimate) not suspended in sorbitol.

  15. Colonic necrosis due to calcium polystyrene sulfonate (Kalimate) not suspended in sorbitol

    OpenAIRE

    María Dolores Castillo-Cejas; Inés de Torres-Ramírez; Carmen Alonso-Cotoner

    2013-01-01

    Cation-exchange resins are used in the management of hyperkalemia, particularly in patients with end-stage renal disease. These resins were associated with gastrointestinal tract lesions, especially sodium polystyrene sulfonate (Kayexalate) mixed with sorbitol. We present a case of colonic necrosis after the administration of calcium polystyrene sulfonate (Kalimate) not suspended in sorbitol.

  16. Colonic necrosis due to calcium polystyrene sulfonate (Kalimate not suspended in sorbitol

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    María Dolores Castillo-Cejas

    2013-04-01

    Full Text Available Cation-exchange resins are used in the management of hyperkalemia, particularly in patients with end-stage renal disease. These resins were associated with gastrointestinal tract lesions, especially sodium polystyrene sulfonate (Kayexalate mixed with sorbitol. We present a case of colonic necrosis after the administration of calcium polystyrene sulfonate (Kalimate not suspended in sorbitol.

  17. Bilateral Atraumatic Avascular Necrosis of Both the Humeral and Femoral Heads due to the Corticosteroid Usage

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    Okkes Bilal

    2013-08-01

    Full Text Available Avascular necrosis is frequently associated with femoral head involvement and may also be observed in the knee joint, humeral head, wrist and foot. Avascular necrosis may also affect multiple joints. Bilateral involvement of both humeral and femoral heads is a rare condition in the same patient. A patient who complained about a sustained pain in both of his shoulders and hips for a few years applied to our outpatient clinic. The patient who had oral steroid treatment episodically was diagnosed with ulcerative colitis seven years ago. Arthroscopy-assisted decompression to the shoulder joints and core decompression to both hip joints were applied. The range of motions of both humeral and femoral joints was limited and painful prior to the surgical treatment. A follow-up after five years later showed that the patient's range of motions of joints was normal and no further treatment was necessary. [Arch Clin Exp Surg 2013; 2(4.000: 246-250

  18. Skin Necrosis with Oculomotor Nerve Palsy Due to a Hyaluronic Acid Filler Injection

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    Jae Il Lee

    2017-07-01

    Full Text Available Performing rhinoplasty using filler injections, which improve facial wrinkles or soft tissues, is relatively inexpensive. However, intravascular filler injections can cause severe complications, such as skin necrosis and visual loss. We describe a case of blepharoptosis and skin necrosis caused by augmentation rhinoplasty and we discuss the patient’s clinical progress. We describe the case of a 25-year-old female patient who experienced severe pain, blepharoptosis, and decreased visual acuity immediately after receiving a filler injection. Our case suggests that surgeons should be aware of nasal vascularity before performing an operation, and that they should avoid injecting fillers at a high pressure and/or in excessive amounts. Additionally, filler injections should be stopped if the patient complains of severe pain, and appropriate measures should be taken to prevent complications caused by intravascular filler injections.

  19. [Acute kidney failure due to kidney cortex necrosis. 2 clinical cases of surviving patients].

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    Fuenzalida, E

    1991-07-01

    A 22 year old female developed preeclampsia with fetal death in utero. After cesarean section she developed uterine inertia and acute hemorrhagic anemia complicated by sepsis, disseminated intravascular coagulation and total anuria for 4 weeks. She was treated with hemodialysis. The second patient, a 49 year old man developed sepsis and intravascular coagulation after a dog bite. Acute renal failure with a 3 week total anuria followed. He was initially treated with peritoneo dialysis. Renal biopsy showed evidence of renal cortical necrosis in both patients.

  20. Acute kidney injury, hyperbilirubinemia, and ischemic skin necrosis due to massive sulindac overdose.

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    Vaughn, John L; Shah, Kejal V; Ghossein, Maroun M; Meyer, William L; Kirkpatrick, Robert B

    2015-01-01

    Sulindac is a long-acting nonsteroidal anti-inflammatory drug (NSAID) widely used for the management of osteoarthritis, rheumatoid arthritis, ankylosing sponydlitis, and acute gouty arthritis. Reports of sulindac toxicity in the literature are rare. We report the case of a 22-year old male with a history of bipolar disorder who was brought to the emergency department after ingesting approximately 15 g of sulindac in a suicide attempt. He was found to have acute kidney injury and hyperbilirubinemia. Despite aggressive fluid resuscitation, his renal function progressively worsened requiring the initiation of hemodialysis. Ten days following ingestion of sulindac, he began to develop ischemic skin changes with a gangrenous appearance in his hands and feet. He continued to receive supportive treatment, and his acute kidney injury, hyperbillirubinemia, and ischemic skin necrosis eventually resolved. Clinicians should be aware of this long-acting NSAID and its ability to cause prolonged multisystem organ dysfunction.

  1. Shape memory alloy flexures

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    Bellouard, Yves; Clavel, Reymond

    2003-07-25

    Flexures are used in precision engineering where highly accurate, wear-free, smooth and repeatable motion is desired. Flexures are based on deformation of material to achieve a motion between elastically joined parts. They are used in a variety of precision mechanisms such as high-resolution balances or high accuracy optical positioning stages. Shape memory alloys (SMA) are an attractive option in designing flexures. Superelastic flexures can withstand larger deformations for the same weight as a conventional flexure. In addition, the damping properties of SMA, controllable through the phase transformation, offer new design opportunities for adaptive compliant mechanisms. The martensitic phase transformation can also be used to shift the natural frequency of flexures adding useful functionalities such as vibration rejection. This paper presents design principles of SMA flexures based on non-linear beam theory. Results show a good agreement between measured and predicted data. In addition, experimental results on phase transformation effects on damping behavior are also presented. Both, natural-frequency shift and increased damping were observed in bulk-micro machined flexures using the R-phase transformation. These results demonstrate the feasibility of natural-frequency-tunable flexures.

  2. Risk of tuberculosis in patients treated with tumor necrosis factor antagonists due to incomplete prevention of reactivation of latent infection.

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    Gómez-Reino, Juan J; Carmona, Loreto; Angel Descalzo, Miguel

    2007-06-15

    To evaluate the causes of new cases of active tuberculosis (ATB) in patients treated with tumor necrosis factor (TNF) antagonists included in the national registry BIOBADASER (Base de Datos de Productos Biológicos de la Sociedad Española de Reumatología) after the dissemination of recommendations to prevent reactivation of latent tuberculosis infection (LTBI). Incidence rate of ATB per 100,000 patient-years and 95% confidence intervals (95% CIs) were calculated in patients entering BIOBADASER after March 2002 and were stratified by compliance with recommendations (complete or incomplete). ATB rates in BIOBADASER were compared with the background rate and the rate in the rheumatoid arthritis cohort EMECAR (Estudio de la Morbilidad y Expresión Clínica de la Artritis Reumatoide) not treated with TNF antagonists. In addition, rates of ATB among patients treated with adalimumab, etanercept, and infliximab were estimated and compared only for treatments started after September 2003, when all 3 drugs became fully available. Following March 2002, a total of 5,198 patients treated with a TNF antagonist were registered in BIOBADASER. Fifteen ATB cases were noted (rate 172 per 100,000 patient-years, 95% CI 103-285). Recommendations were fully followed in 2,655 treatments. The probability of developing ATB was 7 times higher when recommendations were not followed (incidence rate ratio 7.09, 95% CI 1.60-64.69). Two-step tuberculosis skin test for LTBI was the major failure in complying with recommendations. New cases of ATB still occur in patients treated with all available TNF antagonists due to lack of compliance with recommendations to prevent reactivation of LTBI. Continuous evaluation of recommendations is required to improve clinical practice.

  3. Short Communication: Flexure delicacies

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    S. Henein

    2012-01-01

    Full Text Available Flexures are nowadays enjoying a new boom in numerous high-precision and extreme-environment applications. The paper presents some delicate issues concerning stiffness compensation, large reduction ratios, as well as rectilinear and circular movements in compliant mechanisms. Novel concrete technical solutions to these well-known issues are described, giving a glimpse into the vast and still largely unexploited potential of flexure mechanisms manufactured by wire-electrical-discharge machining.

  4. BIOPSY PROVEN ACUTE TUBULAR NECROSIS DUE TO RHABDOMYOLYSIS IN A DENGUE FEVER PATIENT: A CASE REPORT AND REVIEW OF LITERATURE

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    Liliany P. Repizo

    2014-01-01

    Full Text Available Renal histology results are very scarce in dengue-associated rhabdomyolysis patients developing acute kidney injury (AKI. We report a case of dengue fever-induced AKI associated to rhabdomyolysis with a renal biopsy showing acute tubular necrosis (ATN and renal deposition of myoglobin. A 28-year-old patient who presented dengue fever (DF complicated by severe AKI and rhabdomyolysis is described. The patient required hemodialysis for three weeks. A renal biopsy revealed ATN with positive staining for myoglobin in the renal tubuli. The patient was discharged with recovered renal function. In conclusion, this case report described a biopsy proven ATN associated to DF-induced rhabdomyolysis, in which renal deposition of myoglobin was demonstrated. We suggest that serum creatine phosphokinase should be monitored in DF patients to allow for an early diagnosis of rhabdomyolysis and the institution of renal protective measures.

  5. Flexural eczema versus atopic dermatitis

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    Jacob, Sharon E; Goldenberg, Alina; Nedorost, Susan

    2015-01-01

    Flexural eczema and atopic dermatitis are frequently synonymized. As respiratory atopy is rarely tested for and found in these patients, systematically equating a flexural distribution of dermatitis with atopic dermatitis may too frequently result in misclassified diagnoses and potentially missed...

  6. Avascular Necrosis

    Science.gov (United States)

    ... Medical conditions, such as sickle cell anemia and Gaucher's disease, also can cause diminished blood flow to bone. ... conditions associated with avascular necrosis include: Pancreatitis Diabetes Gaucher's disease HIV/AIDS Systemic lupus erythematosus Sickle cell anemia ...

  7. Ductility of Reinforced Concrete Structures in Flexure

    DEFF Research Database (Denmark)

    Hestbech, Lars

    2013-01-01

    In this thesis, a rotational capacity model for flexural reinforced concrete elements is presented. The model is based on the general assumption, that any other failure mode than bending is prevented by proper design. This includes failure due to shear, anchorage, concentrated loads etc. Likewise......, beams governed by failure described by Kani’s Valley are not covered by the presented model. Hence, the model is delimited to shear reinforced elements failing in flexure. The rotational capacity model is divided into the following calculation procedures. 1. A cross sectional analysis of the critical...... are not necessarily so. An example shows the applicability of the model and a parametric study shows the advantages of the model compared with code provisions. Finally, improvements of the compression zone modelling is performed in order to include a better performance when concrete crushing is the failure criterion...

  8. Flexural eczema versus atopic dermatitis.

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    Jacob, Sharon E; Goldenberg, Alina; Nedorost, Susan; Thyssen, Jacob P; Fonacier, Luz; Spiewak, Radoslaw

    2015-01-01

    Flexural eczema and atopic dermatitis are frequently synonymized. As respiratory atopy is rarely tested for and found in these patients, systematically equating a flexural distribution of dermatitis with atopic dermatitis may too frequently result in misclassified diagnoses and potentially missed opportunity for intervention toward improving patients' symptoms and quality of life. We present a critical review of the available evidence for the atopic dermatitis diagnosis and discuss the similarities between atopic dermatitis and allergic contact dermatitis. Because neither flexural predilection nor atopy is specific for atopic dermatitis, we conclude that the term atopic dermatitis is a misnomer and propose an etymologic reclassification of atopic dermatitis to "atopy-related" dermatitis. Allergic contact dermatitis can induce an atopic dermatitis-like phenotype, and thus, flexural dermatitis cannot be assumed as atopic without further testing. Patch testing should at least be considered in cases of chronic or recurrent eczema regardless of the working diagnosis.

  9. Elliptical flexure hinges

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    Smith, Stuart T.; Badami, Vivek G.; Dale, Jami S.; Xu, Ying

    1997-03-01

    This paper presents closed form equations based on a modification of those originally derived by Paros and Weisbord in 1965, for the mechanical compliance of a simple monolithic flexure hinge of elliptic cross section, the geometry of which is determined by the ratio ɛ of the major and minor axes. It is shown that these equations converge at ɛ=1 to the Paros and Weisbord equations for a hinge of circular section and at ɛ ⇒∞ to the equations predicted from simple beam bending theory for the compliance of a cantilever beam. These equations are then assessed by comparison with results from finite element analysis over a range of geometries typical of many hinge designs. Based on the finite element analysis, stress concentration factors for the elliptical hinge are also presented. As a further verification of these equations, a number of elliptical hinges were manufactured on a CNC milling machine. Experimental data were produced by applying a bending moment using dead weight loading and measuring subsequent angular deflections with a laser interferometer. In general, it was found that predictions for the compliance of elliptical hinges are likely to be within 12% for a range of geometries with the ratio βx(=t/2ax) between 0.06 and 0.2 and for values of ɛ between 1 and 10.

  10. High accuracy flexural hinge development

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    Santos, I.; Ortiz de Zárate, I.; Migliorero, G.

    2005-07-01

    This document provides a synthesis of the technical results obtained in the frame of the HAFHA (High Accuracy Flexural Hinge Assembly) development performed by SENER (in charge of design, development, manufacturing and testing at component and mechanism levels) with EADS Astrium as subcontractor (in charge of doing an inventory of candidate applications among existing and emerging projects, establishing the requirements and perform system level testing) under ESA contract. The purpose of this project has been to develop a competitive technology for a flexural pivot, usuable in highly accurate and dynamic pointing/scanning mechanisms. Compared with other solutions (e.g. magnetic or ball bearing technologies) flexural hinges are the appropriate technology for guiding with accuracy a mobile payload over a limited angular ranges around one rotation axes.

  11. Broadband cloaking for flexural waves

    CERN Document Server

    Zareei, Ahmad

    2016-01-01

    The governing equation for elastic waves in flexural plates is not form invariant, and hence designing a cloak for such waves faces a major challenge. Here, we present the design of a perfect broadband cloak for flexural waves through the use of a nonlinear transformation, and by matching term-by-term the original and transformed equations. For a readily achievable flexural cloak in a physical setting, we further present an approximate adoption of our perfect cloak under more restrictive physical constraints. Through direct simulation of the governing equations, we show that this cloak, as well, maintains a consistently high cloaking efficiency over a broad range of frequencies. The methodology developed here may be used for steering waves and designing cloaks in other physical systems with non form-invariant governing equations.

  12. Effect of flexural crack on plain concrete beam failure mechanism A numerical simulation

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    Abdoullah Namdar

    2016-03-01

    Full Text Available The flexural failure of plain concrete beam occurs along with development of flexural crack on beam. In this paper by using ABAQUS, mechanism failure of plain concrete beam under three steps have been simulated. The cracking moment has been analytically calculated and applied on the both sides of the fixed beam, and flexural crack has been simulated on beam. Displacement, von Mises, load reaction, displacementcrack length, von Mises-crack length and von Mises-displacement of beams have been graphical depicted. Results indicated that, the flexural crack governs beam mechanism failure and its effects on beam resistance failure. It has been found that the flexural crack in initial stage it developed slowly and changes to be fast at the final stage of collapsing beam due to reduction of the flexural resistance of beam. Increasing mechanical properties of concrete, collapse displacement is reduced.

  13. Static deformation modeling and analysis of flexure hinges made of a shape memory alloy

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    Du, Zhijiang; Yang, Miao; Dong, Wei; Zhang, Dan

    2016-11-01

    The flexure hinge is a key element in compliant mechanisms to achieve continuous motion; however the motion range of a flexure hinge is severely restricted by the material’s allowable strain. Due to the superelasticity effect, shape memory alloys (SMAs) can undergo much larger strain than other metals; this means that they are excellent candidates for the fabrication of flexure hinges with a large motion range. In this paper, a simple static deformation modeling approach is proposed for a flexure hinge made of a SMA. The superelastic behavior of the SMA is described by Brinson’s constitutive model. The flexure hinge is considered as a non-prismatic cantilever beam associated with geometrical and material nonlinearities. Govern equations of the flexure hinge are derived and solved numerically by applying the nonlinear bending theory of the Euler-Bernoulli beam. Experimental tests show that the proposed modeling approach can predict the deformation of the flexure hinge precisely; the maximum relative error is less than 6.5%. Based on the static deformation model, the motion capacity, the stiffness characteristic and the rotational error of the flexure hinge are also investigated. The results reveal that the flexure hinge made of a SMA has great potential to construct compliant mechanisms with a large motion range.

  14. Metal cap flexural transducers for air-coupled ultrasonics

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    Eriksson, T. J. R.; Dixon, S.; Ramadas, S. N.

    2015-03-01

    Ultrasonic generation and detection in fluids is inefficient due to the large difference in acoustic impedance between the piezoelectric element and the propagation medium, leading to large internal reflections and energy loss. One way of addressing the problem is to use a flexural transducer, which uses the bending modes in a thin plate or membrane. As the plate bends, it displaces the medium in front of it, hence producing sound waves. A piezoelectric flexural transducer can generate large amplitude displacements in fluid media for relatively low excitation voltages. Commercially available flexural transducers for air applications operate at 40 kHz, but there exists ultrasound applications that require significantly higher frequencies, e.g. flow measurements. Relatively little work has been done to date to understand the underlying physics of the flexural transducer, and hence how to design it to have specific properties suitable for particular applications. This paper investigates the potential of the flexural transducer and its operating principles. Two types of actuation methods are considerd: piezoelectric and electrodynamic. The piezoelectrically actuated transducer is more energy efficient and intrinsically safe, but the electrodynamic transducer has the advantage of being less sensitive to high temperature environments. The theory of vibrating plates is used to predict transducer frequency in addition to front face amplitude, which shows good correlation with experimental results.

  15. Flexural-Phonon Scattering Induced by Electrostatic Gating in Graphene

    DEFF Research Database (Denmark)

    Gunst, Tue; Kaasbjerg, Kristen; Brandbyge, Mads

    2017-01-01

    Graphene has an extremely high carrier mobility partly due to its planar mirror symmetry inhibiting scattering by the highly occupied acoustic flexural phonons. Electrostatic gating of a graphene device can break the planar mirror symmetry, yielding a coupling mechanism to the flexural phonons.......We examine the effect of the gate-induced one-phonon scattering on the mobility for several gate geometries and dielectric environments using first-principles calculations based on density functional theory and the Boltzmann equation. We demonstrate that this scattering mechanism can be a mobility...

  16. Synthesis and Optimisation of Large Stroke Flexure Hinges

    NARCIS (Netherlands)

    Grootens, Martijn; Aarts, Ronald; Brouwer, Dannis; Wenger, Philippe; Flores, Paulo

    2016-01-01

    Flexure hinges are advantageous for use in high-precision applications because of their lack of hysteresis, friction and backlash. However, their range of motion is limited due to increasing stresses and a decreasing support stiffness at large strokes. Currently available hinges are typically design

  17. Derivation of a poroelastic flexural shell model

    CERN Document Server

    Mikelic, Andro

    2015-01-01

    In this paper we investigate the limit behavior of the solution to quasi-static Biot's equations in thin poroelastic flexural shells as the thickness of the shell tends to zero and extend the results obtained for the poroelastic plate by Marciniak-Czochra and Mikeli\\'c. We choose Terzaghi's time corresponding to the shell thickness and obtain the strong convergence of the three-dimensional solid displacement, fluid pressure and total poroelastic stress to the solution of the new class of shell equations. The derived bending equation is coupled with the pressure equation and it contains the bending moment due to the variation in pore pressure across the shell thickness. The effective pressure equation is parabolic only in the normal direction. As additional terms it contains the time derivative of the middle-surface flexural strain. Derivation of the model presents an extension of the results on the derivation of classical linear elastic shells by Ciarlet and collaborators to the poroelastic shells case. The n...

  18. Flexural-slip during visco-elastic buckle folding

    Science.gov (United States)

    Damasceno, Davi R.; Eckert, Andreas; Liu, Xiaolong

    2017-07-01

    Flexural-slip is considered as an important mechanism during folding and a general conceptual and qualitative understanding has been provided by various field studies. However, quantitative evidence of the importance of the flexural-slip mechanism during fold evolution is sparse due to the lack of suitable strain markers. In this study, 2D finite element analysis is used to overcome these disadvantages and to simulate flexural-slip during visco-elastic buckle folding. Variations of single and multilayer layer fold configurations are investigated, showing that flexural-slip is most likely to occur in effective single layer buckle folds, where slip occurs between contacts of competent layers. Based on effective single layer buckle folds, the influence of the number of slip surfaces, the degree of mechanical coupling (based on the friction coefficient), and layer thickness, on the resulting slip distribution are investigated. The results are in agreement with the conceptual flexural-slip model and show that slip is initiated sequentially during the deformation history and is maximum along the central slip surface of the fold limb. The cumulative amount of slip increases as the number of slip surfaces is increased. For a lower degree of mechanical coupling increased slip results in different fold shapes, such as box folds, during buckling. In comparison with laboratory experiments, geometrical relationships and field observations, the numerical modeling results show similar slip magnitudes. It is concluded that flexural-slip should represent a significant contribution during buckle folding, affecting the resulting fold shape for increased amounts of slip.

  19. EFFECT OF FILLER LOADING ON PHYSICAL AND FLEXURAL PROPERTIES OF RAPESEED STEM/PP COMPOSITES

    Directory of Open Access Journals (Sweden)

    Seyed Majid Zabihzadeh

    2011-03-01

    Full Text Available The objective of the study is to develop a new filler for the production of natural filler thermoplastic composites using the waste rapeseed stalks. The long-term water absorption and thickness swelling behaviors and flexural properties of rapeseed filled polypropylene (PP composites were investigated. Three different contents of filler were tested: 30, 45, and 60 wt%. Results of long-term hygroscopic tests indicated that by the increase in filler content from 30% to 60%, water diffusion absorption and thickness swelling rate parameter increased. A swelling model developed by Shi and Gardner can be used to quantify the swelling rate. The increasing of filler content reduced the flexural strength of the rapeseed/PP composites significantly. In contrast to the flexural strength, the flexural modulus improved with increasing the filler content. The flexural properties of these composites were decreased after the water uptake, due to the effect of the water molecules.

  20. Effects of forming processing conditions on the flexural properties of bagasse and bamboo plastic composites

    Directory of Open Access Journals (Sweden)

    Shinichi Shibata

    2012-11-01

    Full Text Available The effects of processing conditions such as pressure, temperature, and holding time on the flexural properties of bagasse and bamboo biodegradable composites were investigated. Each sample of bagasse or bamboo was mixed with a corn-starch-based biodegradable resin and fabricated by a hot press forming method. The cross-sectional structure of the bagasse fiber was found to be porous and compressible, while that of bamboo was found to be more solid. The relationship between flexural strength, flexural modulus, and pressure in bagasse fiber was apparently different from that of bamboo due to the differences in the cross-sectional structure. In bagasse, the flexural strength and flexural modulus increased with the increase in pressure, whereas in bamboo those properties decreased. In bagasse, an increase in pressure made the fibers into a more compressed structure, increasing their flexural properties. In rigid bamboo, an increase in pressure caused the resin to extrude between fibers, and this resulted in lower flexural properties. At temperatures above 170 oC, the resin depolymerized thermally and the degree of polymerization decreased. Thus, the flexural modulus and strength decreased gradually with increase in holding temperature in both bagasse and bamboo composites. Furthermore, a maximum fiber volume fraction existed for both bagasse and bamboo plastic composites in the approximate range of 75% to 80%.

  1. Flexural modulus identification of thin polymer sheets

    Science.gov (United States)

    Gluhihs, S.; Kovalovs, A.; Tishkunovs, A.; Chate, A.

    2011-06-01

    The method of determination of the flexural Young's modulus is based on a solution to the problem of compression of a thin-walled cylindrical specimen by two parallel planes (TWCS method). This method was employed to calculate the flexural modulus for PET polymer compositions. The flexural modules received by TWCS method were verified by comparing the experimentally measured eigenfrequencies by Polytec vibrometer with numerical results from ANSYS program.

  2. Flexural modulus identification of thin polymer sheets

    Energy Technology Data Exchange (ETDEWEB)

    Gluhihs, S; Kovalovs, A; Tishkunovs, A; Chate, A, E-mail: s_gluhih@inbox.lv [Riga Technical University, Institute of Materials and Structures, Azenes 16/22, LV-1048, Riga (Latvia)

    2011-06-23

    The method of determination of the flexural Young's modulus is based on a solution to the problem of compression of a thin-walled cylindrical specimen by two parallel planes (TWCS method). This method was employed to calculate the flexural modulus for PET polymer compositions. The flexural modules received by TWCS method were verified by comparing the experimentally measured eigenfrequencies by Polytec vibrometer with numerical results from ANSYS program.

  3. Analysis of flexural wave cloaks

    Directory of Open Access Journals (Sweden)

    Alfonso Climente

    2016-12-01

    Full Text Available This work presents a comprehensive study of the cloak for bending waves theoretically proposed by Farhat et al. [see Phys. Rev. Lett. 103, 024301 (2009] and later on experimentally realized by Stenger et al. [see Phys. Rev. Lett. 108, 014301 (2012]. This study uses a semi-analytical approach, the multilayer scattering method, which is based in the Kirchoff-Love wave equation for flexural waves in thin plates. Our approach was unable to reproduce the predicted behavior of the theoretically proposed cloak. This disagreement is here explained in terms of the simplified wave equation employed in the cloak design, which employed unusual boundary conditions for the cloaking shell. However, our approach reproduces fairly well the measured displacement maps for the fabricated cloak, indicating the validity of our approach. Also, the cloak quality has been here analyzed using the so called averaged visibility and the scattering cross section. The results obtained from both analysis let us to conclude that there is room for further improvements of this type of flexural wave cloak by using better design procedures.

  4. Analysis of flexural wave cloaks

    Science.gov (United States)

    Climente, Alfonso; Torrent, Daniel; Sánchez-Dehesa, José

    2016-12-01

    This work presents a comprehensive study of the cloak for bending waves theoretically proposed by Farhat et al. [see Phys. Rev. Lett. 103, 024301 (2009)] and later on experimentally realized by Stenger et al. [see Phys. Rev. Lett. 108, 014301 (2012)]. This study uses a semi-analytical approach, the multilayer scattering method, which is based in the Kirchoff-Love wave equation for flexural waves in thin plates. Our approach was unable to reproduce the predicted behavior of the theoretically proposed cloak. This disagreement is here explained in terms of the simplified wave equation employed in the cloak design, which employed unusual boundary conditions for the cloaking shell. However, our approach reproduces fairly well the measured displacement maps for the fabricated cloak, indicating the validity of our approach. Also, the cloak quality has been here analyzed using the so called averaged visibility and the scattering cross section. The results obtained from both analysis let us to conclude that there is room for further improvements of this type of flexural wave cloak by using better design procedures.

  5. Design OF Flexure Bearing For Linear Compressor By Optimization Procedure Using FEA

    Directory of Open Access Journals (Sweden)

    Saurabh Malpani

    2012-05-01

    Full Text Available Bearing are used to allow the relative motion between two surfaces. A shaft has to rotate about its casing or a piston has to slide about the cylinder. Both requires relative motion to happened least rictional losses. The flexural bearing however ,offers a different approach in supporting the bearing surfaces. The elements of bearing surfaces are deformed on application of load to one of the surfaces, allowing the relative motion between the two surfaces on removal of the load ,the surfaces go back to their original position subjected tocondition that caused deformation of the bearing element due to pplied load is within the limit of elasticity. This eliminates the wear ,vibration and frictional losses. However ,the deformation has to be limited. The precision and micro machining applications and some medical applications very low relative motion. Hence, flexural bearing in this kind of application is a better. The present work is specific to the typical flexure bearing used in linear compressor. Since the flexural bearing designed procedure is not available, this paper proposes to the FEM as a tool to find the axial stiffness thatwould be offered by a typical flexure used in the linear compressor application for cryocooler. The cryocooler has a linear compressor use for compressing a gas with a typical displacement of 5 mm. The typical design has the flexural bearing with spiral cuts in the flexures. These spiral cuts allows each of the flexure to move itselfaxially on application of load in the axial direction. There are two states of flexures called stacks on either side of linear motor supporting a piston rod which moves the piston either side i.e. back and forth in gas displacer. As mentioned typical displacement of the piston is 5mm causing each of the flexure to get deformed by same amount. Since there is no any standard method available for alculating axial stiffness of bearing ,we haveconsider an example of disc.

  6. EXPERIMENTAL ANALYSIS OF FLEXURAL STRENGTH ON GLASS FIBER SANDWICH COMPOSITE BY VARYING Z-PINS PITCHES

    OpenAIRE

    Pravin*, Jeyapratha

    2016-01-01

    This paper ambit to evaluate the flexural strength of glass fiber sandwich panels with varying z-pins pitches. Failure of sandwich panel are delamination and core shear, to minimize the crack propagation, pins are inserted in z-direction, by varying pitches through its thickness. During the insertion of pin, may cause the material some damage. Despite the damage, flexural property does not affected due interpolation of pins. Although the experiment were pull out with a phenomenal results of z...

  7. Mechanisms of tumor cell necrosis.

    Science.gov (United States)

    Proskuryakov, Sergey Y; Gabai, Vladimir L

    2010-01-01

    Until recently, necrosis, unlike apoptosis, was considered as passive and unregulated form of cell death. However, during the last decade a number of experimental data demonstrated that, except under extreme conditions, necrosis may be a well-regulated process activated by rather specific physiological and pathological stimuli. In this review, we consider mechanisms and the role of necrosis in tumor cells. It became recently clear that the major player in necrotic cascade is a protein kinase RIP1, which can be activated by number of stumuli including TNF, TRAIL, and LPS, oxidative stress, or DNA damage (via poly-ADP-ribose polymerase). RIP1 kinase directly (or indirectly via another kinase JNK) transduces signal to mitochondria and causes specific damage (mitochondrial permeability transition). Mitochondrial collapse activates various proteases (e.g., calpains, cathepsin) and phospholipases, and eventually leads to plasma membrane destruction, a hallmark of necrotic cell death. Necrosis, in contrast to apoptosis, usually evokes powerful inflammatory response, which may participate in tumor regression during anticancer therapy. On the other hand, excessive spontaneous necrosis during tumor development may lead to more aggressive tumors due to stimulatory role of necrosis-induced inflammation on their growth.

  8. Flexure-based nanomagnetic actuators

    Science.gov (United States)

    Vasquez, Daniel James

    Nanometer-scale actuators powered through applied-magnetic fields have been designed, fabricated, and tested. These actuators consist of one or more ferromagnetic elements attached to a mechanical flexure. Two types of flexures were studied including a cantilever beam that is fixed on one end, and free on the other. The free end of the cantilever is attached to a, ferromagnetic element allowing a bending torque to be applied by a magnetic field. The second type of actuator design uses a set of torsion beams that are each anchored on one end, and attached to the magnetic element on the other end. The torsion beams are designed such that the application of a magnetic field will result in a twist along the long axis of the beam with little to no bending. The smallest fabricated and tested device is a cantilever-based ferromagnetic actuator that consists of a single 1.5-mum-long, 338-nm-wide, and 50-nm-thick nickel element, and a 2.2-mum-long, 110-nm-wide, and 30-nm-thick gold cantilever beam. A deflection of over 17° was measured for this actuator, while a similar one with a 10.1-mum long cantilever beam experienced measured deflections up to 57°. Torsion-based ferromagnetic actuators have been fabricated and tested with 110-nm-wide, and 50-rim-thick magnetic elements. Such magnetic elements contain only a single saturated magnetic domain. The ultimate scalability of ferromagnetic actuation is limited by the ability of thermal noise to affect the temporal stability of a nanometer-scale magnet. Theory to describe thermal noise and ultimate scalability of the ferromagnetic actuators has been developed. The size of the ferromagnetic actuators studied in this manuscript are smaller than most plant and animal cells. This enables the possibility of such actuators to manipulate a, living cell on an intracellular level. Other potential applications of such small actuators include MHz, to GHz frequency resonators, and tunable optical filters.

  9. Flexural-Phonon Scattering Induced by Electrostatic Gating in Graphene

    Science.gov (United States)

    Gunst, Tue; Kaasbjerg, Kristen; Brandbyge, Mads

    2017-01-01

    Graphene has an extremely high carrier mobility partly due to its planar mirror symmetry inhibiting scattering by the highly occupied acoustic flexural phonons. Electrostatic gating of a graphene device can break the planar mirror symmetry, yielding a coupling mechanism to the flexural phonons. We examine the effect of the gate-induced one-phonon scattering on the mobility for several gate geometries and dielectric environments using first-principles calculations based on density functional theory and the Boltzmann equation. We demonstrate that this scattering mechanism can be a mobility-limiting factor, and show how the carrier density and temperature scaling of the mobility depends on the electrostatic environment. Our findings may explain the high deformation potential for in-plane acoustic phonons extracted from experiments and, furthermore, suggest a direct relation between device symmetry and resulting mobility.

  10. Analysis of the flexural vibration of ship's tail shaft by transfer matrix method

    Institute of Scientific and Technical Information of China (English)

    JIA Xiao-jun; FAN Shi-dong

    2008-01-01

    A ship's tail shaft has serious flexural vibration due to the cantilevered nature of the propeller's blades. Analysis of the nature frequency of flexural vibration is vital to be able to provide effective shock absorption for a ship's tail shaft. A mathematic model of tail shaft flexural vibrations was built using the transfer matrix method. The nature frequency of flexural vibration for an electrically propelled ship's tail shaft was then analyzed, and an effective method for calculating it was proposed: a genetic algorithm (GA), which calculates the nature frequency of vibration of a system. Sample calculations, with comparisons by the Prohl method under conditions bearing isotropic support, showed this method to be practical. It should have significant impact on engineering design theory.

  11. Childhood flexural comedones: a new entity.

    Science.gov (United States)

    Larralde, Margarita; Abad, María Eugenia; Muñoz, Andrea Santos; Luna, Paula

    2007-07-01

    Comedones are usually found in acne and involve the seborrheic areas of the skin. Disseminated comedones can be found in other skin disorders. Flexural comedones are characterized by double orifices connected by a thin layer of epidermis that reveals the comedo content below it. To the best of our knowledge, flexural comedones have not been previously described as an entity. Our objective was to characterize this disorder. A cross-sectional descriptive study was performed from April 2004 to July 2006. We included 40 pediatric and adolescent patients with flexural comedones; 21 were female (52%), and 19 were male (48%) (mean age, 6.2 years). In 29 cases the lesions were single (72%) and in 32 cases (80%) unilateral. The lesions were located in the axilla in 88% of the patients. We performed biopsies of skin samples in 6 cases. To our knowledge, flexural comedones have not been previously described as an entity, and we felt that they deserved attention owing to the relative frequency of cases in our clinical practice. Because of its clinical appearance, flexural localization, and age distribution, we named this disorder childhood flexural comedones. Further investigation and follow-up of a larger number of patients is needed.

  12. Isostasy, flexure, and dynamic topography

    Science.gov (United States)

    Gvirtzman, Zohar; Faccenna, Claudio; Becker, Thorsten W.

    2016-06-01

    A fundamental scientific question is, what controls the Earth's topography? Although the theoretical principles of isostasy, flexure, and dynamic topography are widely discussed, the parameters needed to apply these principles are frequently not available. Isostatic factors controlling lithospheric buoyancy are frequently uncertain and non-isostatic factors, such as lithospheric bending towards subduction zones and dynamic topography, are hard to distinguish. The question discussed here is whether a set of simple rules that relate topography to lithospheric structure in various tectonic environments can be deduced in a way that missing parameters can be approximated; or does each area behave differently, making generalizations problematic. We contribute to this issue analyzing the Asia-Africa-Arabia-Europe domain following a top-down strategy. We compile a new crustal thickness map and remove the contribution of the crust from the observed elevation. Then, the challenge is to interpret the residual topography in terms of mantle lithosphere buoyancy and dynamics. Based on systematic relationships between tectonic environments and factors controlling topography, we argue that crustal buoyancy and mantle lithospheric density can be approximated from available geological data and that regions near mantle upwelling or downwelling are easily identified by their extreme residual topography. Yet, even for other areas, calculating lithospheric thickness from residual topography is problematic, because distinguishing variations in mantle lithosphere thickness from sub-lithospheric dynamics is difficult. Fortunately, the area studied here provides an opportunity to examine this issue. Based on the conjunction between the Afar Plume and the mid-ocean ridge in the nearby Gulf of Aden and southern Red Sea, we constrain the maximal amplitude of dynamic topography to ~ 1 km. This estimate is based on a narrow definition of dynamic topography that only includes sub

  13. A review on the flexural mode of graphene: lattice dynamics, thermal conduction, thermal expansion, elasticity and nanomechanical resonance.

    Science.gov (United States)

    Jiang, Jin-Wu; Wang, Bing-Shen; Wang, Jian-Sheng; Park, Harold S

    2015-03-04

    Single-layer graphene is so flexible that its flexural mode (also called the ZA mode, bending mode, or out-of-plane transverse acoustic mode) is important for its thermal and mechanical properties. Accordingly, this review focuses on exploring the relationship between the flexural mode and thermal and mechanical properties of graphene. We first survey the lattice dynamic properties of the flexural mode, where the rigid translational and rotational invariances play a crucial role. After that, we outline contributions from the flexural mode in four different physical properties or phenomena of graphene-its thermal conductivity, thermal expansion, Young's modulus and nanomechanical resonance. We explain how graphene's superior thermal conductivity is mainly due to its three acoustic phonon modes at room temperature, including the flexural mode. Its coefficient of thermal expansion is negative in a wide temperature range resulting from the particular vibration morphology of the flexural mode. We then describe how the Young's modulus of graphene can be extracted from its thermal fluctuations, which are dominated by the flexural mode. Finally, we discuss the effects of the flexural mode on graphene nanomechanical resonators, while also discussing how the essential properties of the resonators, including mass sensitivity and quality factor, can be enhanced.

  14. Flexural performance of woven hybrid composites

    Science.gov (United States)

    Maslinda, A. B.; Majid, M. S. Abdul; Dan-mallam, Y.; Mazawati, M.

    2016-07-01

    This paper describes the experimental investigation of the flexural performance of natural fiber reinforced polymer composites. Hybrid composites consist of interwoven kenaf/jute and kenaf/hemp fibers was prepared by infusion process using epoxy as polymer matrix. Woven kenaf, jute and hemp composites were also prepared for comparison. Both woven and hybrid composites were subjected to three point flexural test. From the result, bending resistance of hybrid kenaf/jute and kenaf/hemp composites was higher compared to their individual fiber. Hybridization with high strength fiber such as kenaf enhanced the capability of jute and hemp fibers to withstand bending load. Interlocking between yarns in woven fabric make pull out fibers nearly impossible and increase the flexural performance of the hybrid composites.

  15. Flexure and rheology of Pacific oceanic lithosphere

    Science.gov (United States)

    Hunter, Johnny; Watts, Tony

    2016-04-01

    The idea of a rigid lithosphere that supports loads through flexural isostasy was first postulated in the late 19th century. Since then, there has been much effort to investigate the spatial and temporal variation of the lithosphere's flexural rigidity, and to understand how these variations are linked to its rheology. We have used flexural modelling to first re-assess the variation in the rigidity of oceanic lithosphere with its age at the time of loading, and then to constrain mantle rheology by testing the predictions of laboratory-derived flow laws. A broken elastic plate model was used to model trench-normal, ensemble-averaged profiles of satellite-derived gravity at the trench-outer rise system of circum-Pacific subduction zones, where an inverse procedure was used to find the best-fit Te and loading conditions. The results show a first-order increase in Te with plate age, which is best fit by the depth to the 400 ± 35°C plate-cooling isotherm. Fits to the observed gravity are significantly improved by an elastic plate that weakens landward of the outer rise, which suggests that bending-induced plate weakening is a ubiquitous feature of circum-Pacific subduction zones. Two methods were used to constrain mantle rheology. In the first, the Te derived by modelling flexural observations was compared to the Te predicted by laboratory-derived yield strength envelopes. In the second, flexural observations were modelled using elastic-plastic plates with laboratory-derived, depth-dependent yield strength. The results show that flow laws for low-temperature plasticity of dry olivine provide a good fit to the observations at circum-Pacific subduction zones, but are much too strong to fit observations of flexure in the Hawaiian Islands region. We suggest that this discrepancy can be explained by differences in the timescale of loading combined with moderate thermal rejuvenation of the Hawaiian lithosphere.

  16. Rotation flexure with temperature controlled modal frequency

    Energy Technology Data Exchange (ETDEWEB)

    Salas, Theodore E.; Barney, Patrick S.; Ison, Aaron M.; Akau, Ronald L; Weir, Nathan

    2017-09-12

    A flexure bearing includes an inner race, an outer race, and a plurality of substantially planar radially extending blades coupled between the inner and outer race. The blades have a thickness that is thinner than a thickness of the inner and outer races. The inner race, outer race, and blades have substantially the same height. At least one heating element is coupled to the inner race and/or the outer race. The heating element is configured to apply heat to the race that it is coupled to in order to tune the flexure bearing.

  17. Reflection and refraction of flexural waves at geometric boundaries.

    Science.gov (United States)

    Evans, Arthur A; Levine, Alex J

    2013-07-19

    We present a theory of flexural wave propagation on elastic shells having nontrivial geometry and develop an analogy to geometric optics. The transport of momentum within the shell itself is anisotropic due to the curvature, and as such complex classical effects such as birefringence are generically found. We determine the equations of reflection and refraction of such waves at boundaries between different local geometries, showing that waves are totally internally reflected, especially at boundaries between regions of positive and negative Gaussian curvature. We verify these effects by using finite element simulations and discuss the ramifications of these effects for the statistical mechanics of thin curved materials.

  18. Fabrication and flexural strength of multi-layer alumina with aligned acicular pores

    Science.gov (United States)

    Park, Dong-Soo; Lee, Myoung-Won; Kim, Hai-Doo; Jung, Yeon-Gil

    2004-07-01

    Multi-layer alumina with alternating dense and porous layers with aligned acicular pores was successfully prepared by tape casting the slurry with chopped carbon fibers followed by pressureless sintering. As the content of the chopped carbon fiber increased, the open porosity was increased, in part due to impingement among the carbon fibers inside the sample. The three-point flexural strength of the sample with total porosity of 11% was approximately 80% that of a dense sample. However, a sample with a porous layer with 5% chopped carbon fiber exhibited only 60% flexural strength of the dense sample, in part due to a low degree of alignment among the chopped fibers.

  19. Free flexural radial vibrations of a thin circular cylindrical shell bearing added mass

    Directory of Open Access Journals (Sweden)

    Seregin Sergey Valer’evich

    2014-12-01

    Full Text Available The author comes up with a refined mathematical model contemplating that added mass facilitates interaction between coupled flexural and radial vibrations in the linear setting. The author has identified a higher splitting of the flexural frequency spectrum due to the presence of the added mass and the wave generation parameters that characterize the relative length and thickness of the shell. Within the framework of the shallow-shell theory, the influence of the small concentrated mass onto natural dynamic properties of the shell is exposed to research. The refined mathematical model was employed to identify that the added mass binds the coupled flexural shape of the circular cylindrical shell and facilitates interaction between low-frequency flexural vibrations and high-frequency radial vibrations. Moreover, radial vibrations act as a supplementary inertial link between coupled flexural shapes. Due to the availability of the exciting load, non-resonant areas, identified through the application of the traditional mathematical model, can be resonant in essence. The findings of this research must be considered in the course of the assessment of the dynamic strength of any shell structures designed. This refined finite-dimensional model, capable of recognizing radial vibrations, has generated the results that comply with numerical analyses and experimental data both quantitatively and qualitatively. Therefore, dynamic problems that have already been resolved may need refinement.

  20. Flexural strength and ductility of reinforced concrete beams

    OpenAIRE

    Kwan, AKH; Ho, JCM; Pam, HJ

    2002-01-01

    In the design of reinforced concrete beams, especially those made of high-strength concrete and those in earthquake-resistant structures, both the flexural strength and ductility need to be considered. From the numerical results obtained in a previous study on the post-peak behaviour and flexural ductility of reinforced concrete beams, the interrelation between the flexural strength and the flexural ductility that could be simultaneously achieved was evaluated and plotted in the form of chart...

  1. Flexural waves focusing through shunted piezoelectric patches

    Science.gov (United States)

    Yi, K.; Collet, M.; Ichchou, M.; Li, L.

    2016-07-01

    In this paper, we designed and analyzed a piezo-lens to focus flexural waves in thin plates. The piezo-lens is comprised of a host plate and piezoelectric arrays bonded on the surfaces of the plate. The piezoelectric patches are shunted with negative capacitance circuits. The effective refractive indexes inside the piezo-lens are designed to fit a hyperbolic secant distribution by tuning the negative capacitance values. A homogenized model of a piezo-mechanical system is adopted in the designing process of the piezo-lens. The wave focusing effect is studied by the finite element method. Numerical results show that the piezo-lens can focus flexural waves by bending their trajectories, and is effective in a large frequency band. The piezo-lens has the ability to focus flexural waves at different locations by tuning the shunting negative capacitance values. The piezo-lens is shown to be effective for flexural waves generated by different types of sources.

  2. Flexural Properties of Eastern Hardwood Pallet Parts

    Science.gov (United States)

    John A. McLeod; Marshall S. White; Paul A. Ifju; Philip A. Araman

    1991-01-01

    Accurate estimates of the flexural properties of pallet parts are critical to the safe, yet efficient, design of wood pallets. To develop more accurate data for hardwood pallet parts, 840 stringers and 2,520 deckboards, representing 14 hardwood species, were sampled from 35 mills distributed throughout the Eastern United States. The parts were sorted by species,...

  3. Psoriasis of the face and flexures.

    NARCIS (Netherlands)

    Kerkhof, P.C.M. van de; Murphy, G.M.; Austad, J.; Ljungberg, A.; Cambazard, F.; Duvold, L.B.

    2007-01-01

    Facial and flexural psoriasis may impair the quality of life of psoriatic patients considerably. For the adequate management of psoriasis it is important to pay attention to lesions at these sensitive sites, which require an approach different to that for lesions on other sites in several respects.

  4. Psoriasis of the face and flexures.

    NARCIS (Netherlands)

    Kerkhof, P.C.M. van de; Murphy, G.M.; Austad, J.; Ljungberg, A.; Cambazard, F.; Duvold, L.B.

    2007-01-01

    Facial and flexural psoriasis may impair the quality of life of psoriatic patients considerably. For the adequate management of psoriasis it is important to pay attention to lesions at these sensitive sites, which require an approach different to that for lesions on other sites in several respects.

  5. Flexural buckling of fire exposed aluminium columns

    NARCIS (Netherlands)

    Maljaars, J.; Twilt, L.; Soetens, F.

    2009-01-01

    In order to study buckling of fire exposed aluminium columns, a finite element model is developed. The results of this model are verified with experiments. Based on a parametric study with the finite element model, it is concluded that the simple calculation model for flexural buckling of fire expos

  6. Design and Performance Optimization of Large Stroke Spatial Flexures

    NARCIS (Netherlands)

    Wiersma, D.H.; Boer, S.E.; Aarts, R.G.K.M.; Brouwer, D.M.

    2013-01-01

    Flexure hinges inherently lose stiffness in supporting directions when deflected. In this paper a method is presented for optimizing the geometry of flexure hinges, which aims at maximizing supporting stiffnesses. In addition, the new ∞ -flexure hinge design is presented. The considered hinges are

  7. Effects of Reinforcement Geometry on Strength and Stiffness in Adhesively Bonded Steel-Timber Flexural Beams

    Directory of Open Access Journals (Sweden)

    Dave Smedley

    2012-07-01

    Full Text Available A finite element model is developed to analyse, as a function of volume fraction, the effects of reinforcement geometry and arrangement within a timber beam. The model is directly validated against experimental equivalents and found to never be mismatched by more than 8% in respect to yield strength predictions. Yield strength increases linearly as a function of increasing reinforcement volume fraction, while the flexural modulus follows more closely a power law regression fit. Reinforcement geometry and location of reinforcement are found to impact both the flexural properties of timber-steel composite beams and the changes due to an increase in volume fraction.

  8. Thin elastic shells with variable thickness for lithospheric flexure of one-plate planets

    CERN Document Server

    Beuthe, Mikael

    2007-01-01

    Planetary topography can either be modeled as a load supported by the lithosphere, or as a dynamical effect due to lithospheric flexure caused by mantle convection. In both cases the response of the lithosphere to external forces can be calculated with the theory of thin elastic plates or shells. On one-plate planets the spherical geometry of the lithospheric shell plays an important role in the flexure mechanism. So far the equations governing the deformations and stresses of a spherical shell have only been derived under the assumption of a shell of constant thickness. However local studies of gravity and topography data suggest large variations in the thickness of the lithosphere. In this article we obtain the scalar flexure equations governing the deformations of a thin spherical shell with variable thickness or variable Young's modulus. The resulting equations can be solved in succession, except for a system of two simultaneous equations, the solutions of which are the transverse deflection and an associ...

  9. Physical and theoretical modeling of rock slopes against block-flexure toppling failure

    Directory of Open Access Journals (Sweden)

    Mehdi Amini

    2015-12-01

    Full Text Available Block-flexure is the most common mode of toppling failure in natural and excavated rock slopes. In such failure, some rock blocks break due to tensile stresses and some overturn under their own weights and then all of them topple together. In this paper, first, a brief review of previous studies on toppling failures is presented. Then, the physical and mechanical properties of experimental modeling materials are summarized. Next, the physical modeling results of rock slopes with the potential of block-flexural toppling failures are explained and a new analytical solution is proposed for the stability analysis of such slopes. The results of this method are compared with the outcomes of the experiments. The comparative studies show that the proposed analytical approach is appropriate for the stability analysis of rock slopes against block-flexure toppling failure. Finally, a real case study is used for the practical verification of the suggested method.

  10. Effect of fiber loading on flexural strength of hybrid sisal/hemp-HDPE composites

    Science.gov (United States)

    Aggarwal, Lakshya; Sinha, Shishir; Gupta, V. K.

    2015-05-01

    The continuing demand for sustainable materials and increasing environmental concerns have led to intense research in the field of natural fiber reinforced composites. Natural fibers are favored over synthetic fibers as reinforcement due to positive environmental benefits such as raw material utilization at source and easy disposable of the biodegradable fiber. In the present work, we have investigated flexural behavior of hybrid natural fiber reinforced HDPE composites. The matrix comprises of 50-50 ratio of virgin and recycled HDPE and the content of fibers (sisal and hemp) in the composite is varied from 10 to 30%. The natural fibers were mercerized with NaOH solution and chemically treated with maleic anhydride. The flexural specimens were prepared by injection moulding process and the testing was conducted in accordance to ASTM D790 standards. It is revealed that the flexural strength of the hybrid composite increases with the increase in fibers content when compared to specimen containing 100% HDPE.

  11. Flexural Mie Resonances: Localized Surface Platonic Modes

    CERN Document Server

    Farhat, M; Chen, P Y; Salama, K N; Bagci, H

    2016-01-01

    Surface plasmons polaritons were thought to exist only in metals near their plasma frequencies. The concept of spoof plasmons extended the realms of plasmonics to domains such as radio frequencies, magnetism, or even acoustic waves. Here, we introduce the concept of localized surface platonic modes (SPMs). We demonstrate that they can be generated on a two-dimensional clamped (or stress-free) cylindrical surface, in a thin elastic plate, with subwavelength corrugations under excitation by an incident flexural plane wave. Our results show that the corrugated rigid surface is elastically equivalent to a cylindrical scatterer with negatively uniform and dispersive flexural rigidity. This, indeed, suggests that plasmonic-like platonic materials can be engineered with potential applications in various areas including earthquake sensing, or elastic imaging and cloaking.

  12. Flexural creep behaviour of jute polypropylene composites

    Science.gov (United States)

    Chandekar, Harichandra; Chaudhari, Vikas

    2016-09-01

    Present study is about the flexural creep behaviour of jute fabric reinforced polypropylene (Jute-PP) composites. The PP sheet and alkali treated jute fabric is stacked alternately and hot pressed in compression molding machine to get Jute-PP composite laminate. The flexural creep study is carried out on dynamic mechanical analyzer. The creep behaviour of the composite is modeled using four-parameter Burgers model. Short-term accelerated creep testing is conducted which is later used to predict long term creep behaviour. The feasibility of the construction of a master curve using the time-temperature superposition (TTS) principle to predict long term creep behavior of unreinforced PP and Jute-PP composite is investigated.

  13. Renal papillary necrosis

    Directory of Open Access Journals (Sweden)

    Stephen A. Geller

    2013-12-01

    Full Text Available In 1877, Dr. Nikolaus Friedreich (1825-1882; student of Virchow who became Professor of Pathology at Heidelberg and who also described Friedreich’s ataxia first described renal papillary necrosis (RPN in patients with prostatic hypertrophy and secondary hydronephrosis. Thereafter in 1937, Froboese and Günther emphasized the association of this entity with diabetes mellitus. These authors also observed renal papillary necrosis in cases of urinary tract obstruction even in the absence of diabetes mellitus.

  14. Flexural Free Vibrations of Multistep Nonuniform Beams

    Directory of Open Access Journals (Sweden)

    Guojin Tan

    2016-01-01

    Full Text Available This paper presents an exact approach to investigate the flexural free vibrations of multistep nonuniform beams. Firstly, one-step beam with moment of inertia and mass per unit length varying as I(x=α11+βxr+4 and m(x=α21+βxr was studied. By using appropriate transformations, the differential equation for flexural free vibration of one-step beam with variable cross section is reduced to a four-order differential equation with constant coefficients. According to different types of roots for the characteristic equation of four-order differential equation with constant coefficients, two kinds of modal shape functions are obtained, and the general solutions for flexural free vibration of one-step beam with variable cross section are presented. An exact approach to solve the natural frequencies and modal shapes of multistep beam with variable cross section is presented by using transfer matrix method, the exact general solutions of one-step beam, and iterative method. Numerical examples reveal that the calculated frequencies and modal shapes are in good agreement with the finite element method (FEM, which demonstrates the solutions of present method are exact ones.

  15. Tachykinin receptors in the equine pelvic flexure.

    Science.gov (United States)

    Sonea, I M; Wilson, D V; Bowker, R M; Robinson, N E

    1997-07-01

    Tachykinins, of which substance P (SP) is the prototype, are neuropeptides which are widely distributed in the nervous systems. In the equine gut, SP is present in enteric nerves and is a powerful constrictor of enteric muscle; in other species, SP is also known to have potent vasodilatory and pro-inflammatory effects. The specific effects of SP are determined by the subtype of receptor present in the target tissue. There are 3 known subtypes of tachykinin receptors, distinguished by their relative affinities for SP and other tachykinins. The distribution of SP binding sites in the equine pelvic flexure was determined using 125I-Bolton Hunter SP (I-BHSP) autoradiography. Most I-BHSP binding sites were determined to be saturable and specific, therefore presumably representing tachykinin receptors. The greatest degree of I-BHSP binding occurred over very small vessels, and over the muscularis mucosae; I-BHSP binding was also intense over the circular muscle of the muscularis externa and mucosa, and present, although less intense, over the longitudinal muscle of the muscularis externa. Competition of I-BHSP with specific receptor agonists for binding sites in the equine pelvic flexure were used to determine the subtypes of tachykinin receptors present. The neurokinin-1 receptor subtype predominated in the equine pelvic flexure, followed by the neurokinin-3 receptor subtype.

  16. Effect of zinc oxide on flexural and physical properties of PMMA composites

    Science.gov (United States)

    Hamad, Wan Nur Fadilla Wan; Abdullah, Abdul Manaf; Mohamad, Dasmawati

    2016-12-01

    Polymethylmethacrylate (PMMA) is the most widely accepted material in maxillofacial implants due to its superior advantages. The material used for craniofacial implant should have good mechanical and antibacterial properties to withstand forces and eliminate infection. A study was conducted to prepare PMMA incorporated with β-tricalcium phosphate (β -TCP) filler and zinc oxide as an antibacterial agent at different compositions and investigate the flexural properties of the produced PMMA/β- TCP/ZnOcomposites. Pure PMMA as control,15 % β -TCP filled, 15% β -TCPwith 2.5% ZnO filled as well as15% β -TCPwith5% ZnOfilled PMMA were prepared. PMMA were mixed together with β -TCP and zinc oxide manually according to the percentages specified until it has reached the homogeneous state. Flexural specimens were prepared by casting the paste in silicone mould which has been fabricated using 3D printed flexural template. The number of samples was n=7 for each composition. Statistical analysis of One Way ANOVA was employed to compare the flexural properties of each samples. Flexural strength of pure PMMA,15 % β -TCP filled, 15% β -TCP with 2.5% ZnO filled as well as 15% β -TCP with 5% ZnO filled PMMA were 60.79, 46.75, 38.72 and 41.49 MPa respectively. The addition of either β- TCP or β- TCP with ZnO decreased the flexural properties and it showed significant differences as compared to pure PMMA (p0.05).

  17. Source illusion devices for flexural Lamb waves using elastic metasurfaces

    CERN Document Server

    Liu, Yongquan; Liu, Fu; Diba, Owen; Lamb, Alistair; Li, Jensen

    2016-01-01

    Metamaterials with the transformation method has greatly promoted the development in achieving invisibility and illusion for various classical waves. However, the requirement of tailor-made bulk materials and extreme constitutive parameters associated to illusion designs hampers its further progress. Inspired by recent demonstrations of metasurfaces in achieving reduced versions of electromagnetic cloaks, we propose and experimentally demonstrate source illusion devices to manipulate flexural waves using metasurfaces. The approach is particularly useful for elastic waves due to the lack of form-invariance in usual transformation methods. We demonstrate metasurfaces for shifting, transforming and splitting a point source with "space-coiling" structures. The effects are found to be broadband and robust against a change of source position, with agreement from numerical simulations and Huygens-Fresnel theory. The proposed approach provides an avenue to generically manipulate guided elastic waves in solids, and is...

  18. THE EFFECT OF FLY ASH ON FLEXURAL CAPACITY CONCRETE BEAMS

    Directory of Open Access Journals (Sweden)

    Amir Mohammad Amiri

    2016-06-01

    Full Text Available This paper presents the flexural response of Reinforced Geopolymer Concrete (RGPC beam. A commercial finite element (FE software ABAQUS has been used to perform a structural behavior of RGPC beam. Using parameters such: stress, strain, Young’s modulus, and Poisson’s ratio obtained from experimental results, a beam model has been simulated in ABAQUS. The results from experimental test and ABAQUS simulation were compared. Due to friction forces at the supports and loading rollers; slip occurring, the actual deflection of RGPC beam from experimental test results were slightly different from the results of ABAQUS. And there is good agreement between the crack patterns of fly-ash based geopolymer concrete generated by FE analysis using ABAQUS, and those in experimental data.

  19. Modeling of the flexural behavior of ceramic-matrix composites

    Science.gov (United States)

    Kuo, Wen-Shyong; Chou, Tsu-Wei

    1990-01-01

    This paper examines the effects of matrix cracking and fiber breakage on the flexural behavior of ceramic composite beams. A model has been proposed to represent the damage evolution of the beam, of which the matrix fracture strain is smaller than that of the fibers. Close form solutions of the critical loads for the initiation of matrix cracking and fiber breakage in the tension side of the beam have been found. The effects of thermal residual stresses and fiber/matrix debonding have been taken into account. The initial deviation of the load-deflection curve from linearity is due to matrix cracking, while fiber breakages are responsible for the drop in the load carrying capacity of the beam. The proportional limit as well as the nonlinear behavior of the beam deflection have been identified. The growth of the damaged zone has also been predicted. A three-point bending case is given as a numerical example.

  20. Subcutaneous encapsulated fat necrosis

    DEFF Research Database (Denmark)

    Aydin, Dogu; Berg, Jais O

    2016-01-01

    We have described subcutaneous encapsulated fat necrosis, which is benign, usually asymptomatic and underreported. Images have only been published on two earlier occasions, in which the necrotic nodules appear "pearly" than the cloudy yellow surface in present case. The presented image may help f...... future surgeons to establish the diagnosis peroperatively....

  1. FLEXURAL TOUGHNESS OF STEEL FIBER REINFORCED CONCRETE

    Directory of Open Access Journals (Sweden)

    Fehmi ÇİVİCİ

    2006-02-01

    Full Text Available Fiber concrete is a composite material which has mechanical and physical characteristics unlike plain concrete. One of the important mechanical characteristics of fiber concrete is its energy absorbing capability. This characteristics which is also called toughness, is defined as the total area under the load-deflection curve. A number of composite characteristics such as crack resistance, ductility and impact resistance are related to the energy absorbtion capacity. According to ASTM C 1018 and JSCE SF-4 the calculation of toughness is determined by uniaxial flexural testing. Fiber concrete is often used in plates such as bridge decks, airport pavements, parking areas, subjected to cavitation and erosion. In this paper, toughness has been determined according to ASTM C 1018 and JSCE SF-4 methods by testing beam specimens. Energy absorbing capacities of plain and steel fiber reinforced concrete has been compared by evaluating the results of two methods. Also plain and steel fiber reinforced plate specimens behaviors subjected to biaxial flexure are compared by the loaddeflection curves of each specimen.

  2. Flexure and isostasy of lunar mascons

    Science.gov (United States)

    Peters, S. T. M.; Foing, B. H.

    2009-04-01

    A mascon is a region of a planet's or moon's crust that contains an excess positive gravity anomaly, indicating the presence of additional mass in this area. Mascons on the Moon coincide with the locations of circular basins and hence a related origin for both is likely. The formation of a circular basin includes the excavation of the upper parts of the crust and subsequent upwelling of the lower parts as a result of isostatic compensation [1]. Afterwards, filling of the basins by mare basalts leads to concentrations of dense rocks and is hence suggested as the origin of the mascon. The present day presence of mascons indicates that there was no subsequent isostasy leading to downward migration of the moho and that they are hence supported by an elastic layer on the surface of the Moon. The interaction between mascons and this elastic shell is the main topic of our modeling. Since they were discovered by Muller and Sjogren (1968), the origin of mascons and their interaction with the crust became clearer. As we point out below, several questions have however remained unsolved. Our contribution includes the usage of recent gravity and topography models that have not been applied in mascon studies yet. Mascons act like a dense load on the lunar lithosphere and hence flexure it. Flexure profiles of circular basins have been made by previous authors [2], however, only a single-layered crust was considered until now. Our modeling includes the two-layered crustal model preferred by Wieczorek and Phillips (1997) which explains the gravity to topography ratios of the lunar highlands. On the hand of previously existing data it has been suggested that rings of negative gravity anomalies surround the mascons [3]. Whereas this observation was first questionable, prereleases of the high-resolution KAGUYA gravity measurements recently clearly confirmed the presence of these features. Part of our modeling focuses on the location and extent of the negative anomalies in respect to

  3. RESIDUAL FLEXURAL STRENGTH OF RECYCLED BRICK AGGREGATE CONCRETE EXPOSED TO HIGH TEMPERATURES

    Directory of Open Access Journals (Sweden)

    Kasi Rekha

    2015-12-01

    Full Text Available The practice of using crushed brick in concrete is picking up due to its value addition to the mechanical properties of concrete. In the present experimental investigation the brick from the demolition waste is used as a coarse aggregate to study the flexural behaviour of recycled brick aggregate (RBA concrete after exposure to high temperatures. The recycled brick aggregate is replaced to granite aggregate up to 25% by its volume to produce RBA concrete. Beam specimens of size 100mm × 100mm × 500mm were used to study the flexural strength (modulus of rupture of both RBA concrete and granite aggregate (GA concrete. Both the concretes were heated to desired temperatures from 100oC to 1000oC in an interval of 100oC for three hours in bogie hearth furnace. The residual flexural strengths of both heated RBA and GA concretes were presented in this research to study the performance of RBAconcrete at high temperatures. The RBA concrete performed better than that of GA concrete in flexure at high temperatures by exhibiting higher residual strength.

  4. Flexural Properties of PLA Components Under Various Test Condition Manufactured by 3D Printer

    Science.gov (United States)

    Jaya Christiyan, K. G.; Chandrasekhar, U.; Venkateswarlu, K.

    2016-10-01

    Rapid Prototyping (RP) technologies have emerged as a fabrication method to obtain engineering components in the resent past. Desktop 3D printing, also referred as an additive layer manufacturing technology is a powerful method of RP technique that can fabricate 3 dimensional engineering components. In this method, 3D digital data is converted into real product. In the present investigation, Polylactic Acid (PLA) was considered as a starting material. Flexural strength of PLA material was evaluated using 3-point bend test, as per ASTM D790 standard. Specimens with flat (0°) and vertical (90°) orientation were considered. Moreover, layer thicknesses of 0.2, 0.25, and 0.3 mm were considered. To fabricate these specimens, printing speed of 38 and 52 mm/s was maintained. Nozzle diameter of 0.4 mm with 40 % of infill density were used. Based on the experimental results, it was observed that 0° orientation, 38 mm/s printing speed, and 0.2 mm layer thickness resulted maximum flexural strength, as compared to all other specimens. The improved flexural strength was due to the lower layer thickness (0.2 mm) specimens, as compared with other specimens made of 0.25 and 0.30 mm layer thicknesses. It was concluded that flexural strength properties were greatly influenced by lower the layer thickness, printing speed, and orientation.

  5. Isolated varices over hepatic flexure colon indicating superior mesenteric venous thrombosis caused by uncinate pancreatic head cancer- a case report

    Institute of Scientific and Technical Information of China (English)

    Yu-Pin Ho; Chun-Jung Lin; Ming-Yao Su; Jeng-Hwei Tseng; Cheng-Tang Chiu; Pang-Chi Chen

    2005-01-01

    Very rare cases of varices involving right side colon were reported. Most of them were due to cirrhotic portal hypertension or other primary causes. No report case contributed to pancreatic cancer. Here, we reported a case of uncinate pancreatic cancer with the initial finding of isolated hepatic flexure colon varices. Following studies confirmed isolated varices involving hepatic flexure colon due to pancreatic cancer with occlusion of superior mesenteric vein. From this report, superior mesenteric vein occlusion caused by uncinate pancreatic head cancer should be considered as a differential diagnosis of colon varices.

  6. Performance evaluation of HSC beams with low flexural reinforcement

    Directory of Open Access Journals (Sweden)

    T.M. Elrakib

    2013-04-01

    Full Text Available The main objective of the current research is to establish experimental data for minimum flexural reinforcement, ρmin, of high strength concrete (HSC rectangular beams. Nine full-scale singly reinforced beams with flexural reinforcement ratios varying from 50% to 100% of the minimum limit specified by the ACI 363R-35were tested in flexure. Concrete compressive strengths of 52, 73 and 96.5 MPa were used. The test results including crack patterns, deflections and strains in the tensile flexural steel bars show that a 25% reduction of the ACI 363R-35 limit for the ρmin would result in a satisfactory flexural beam behavior with a reserve flexural parameter (Py,/Pcr ⩾ 1.29 and a displacement ductility index λΔ > 5 for all concrete grades which may lead to good savings in the amount of the flexural reinforcement. Also, it was noted that the displacement ductility index λΔ increased as the concrete compressive strength increased for the same ratio (ρ/ρmin up to 75 MPa and then decreases as fcu increases. For the same concrete compressive strength with low values of flexural reinforcement ratio, ρ, the displacement ductility index λΔ increased as ρ increased. The experimental results of this study were compared with the limits specified by available codes and researches.

  7. LOADS INFLUENCE ANALYSIS ON NOVEL HIGH PRECISION FLEXURE PARALLEL POSITIONER

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    A large workspace flexure parallel positioner system is developed, which can attain sub-micron scale accuracy over cubic centimeter motion range for utilizing novel wide-range flexure hinges instead of the conventional mechanism joints. Flexure hinges eliminate backlash and friction, but on the other hand their deformation caused by initial loads influences the positioning accuracy greatly, so discussions about loads' influence analysis on this flexure parallel positioner is very necessary. The stiffness model of the whole mechanism is presented via stiffness assembly method based on the stiffness model of individual flexure hinge. And the analysis results are validated by the finite element analysis (FEA) simulation and experiment tests, which provide essential data to the practical application of this positioner system.

  8. Continuum Mechanics of Beam and Plate Flexure

    DEFF Research Database (Denmark)

    Jönsson, Jeppe

    This text has been written and used during the spring of 1995 for a course on flexural mechanics of beams and plates at Aalborg University. The idea has been to concentrate on basic principles of the theories, which are of importance to the modern structural engineer. Today's structural engineer...... must be acquainted with the classic beam and plate theories, when reading manuals and using modern software tools such as the finite element method. Each chapter includes supplementary theory and derivations enabling consultation of the notes also at a later stage of study. A preliminary chapter...... analysis of beam structures is presented and includes both upper and lower-bound solution techniques. The remaining chapters are devoted to plates. The classic elastic plate theories are presented. The plastic yield line theory for plates is presented including both upper and lower-bound techniques...

  9. Continuum Mechanics of Beam and Plate Flexure

    DEFF Research Database (Denmark)

    Jönsson, Jeppe

    This text has been written and used during the spring of 1995 for a course on flexural mechanics of beams and plates at Aalborg University. The idea has been to concentrate on basic principles of the theories, which are of importance to the modern structural engineer. Today's structural engineer...... must be acquainted with the classic beam and plate theories, when reading manuals and using modern software tools such as the finite element method. Each chapter includes supplementary theory and derivations enabling consultation of the notes also at a later stage of study. A preliminary chapter...... introduces the modern notation used in textbooks and in research today. It further gives an introduction to three-dimensional continuum mechanics of elastic bodies and the related principles of virtual work. The ideas to give the students a basic understanding of the stresses and strains, the equilibrium...

  10. Tissue necrosis following intramuscular diclofenac injection

    Directory of Open Access Journals (Sweden)

    Feyzi Çelik

    2010-09-01

    Full Text Available Following intramuscular drug injections, livedoid dermati-tis (also known as embolia cutis medicamentosa or NicolauSyndrome, characterized by pain, skin discoloration,and cutaneous necrosis, may rarely be observed. In thepresent study, we present a 32-year-old male patient whodeveloped Nicolau Syndrome after intramuscular injec-tion of single-dose diclofenac sodium 75 mg due to renalcolic pain. The physical examination revealed skin discol-oration in his left gluteal region, and a skin necrosis. Caseis very interesting because of rarely.

  11. Renal Papillary Necrosis: Role of Radiology

    Science.gov (United States)

    Pandya, Vaidehi K.

    2016-01-01

    Renal Papillary Necrosis (RPN) is idefined as Ischemic necrobiosis of the papilla in the medulla of the kidneys. Variety of etiological factors are recognized which cause papillary necrosis, such as analgesic nephropathy, diabetes mellitus, urinary obstruction and sickle cell haemoglobinopathy. The early diagnosis of RPN is important to improve prognosis and reduce morbidity. Radiological Imaging offers early diagnosis and can guide prompt treatment of papillary necrosis and can minimize a decline in renal function. Here we report three cases of RPN with typical imaging findings. One of them was diabetic and hypertensive female with recurrent Urinary tract Infections and other was a male with no known co-morbidity. Both of them were diagnosed to have renal papillary necrosis on CT scan and were managed operatively and conservatively, respectively. Third case was a healthy female being investigated to be renal donor for her son. Here RPN was an incidental finding and was treated conservatively. Thus CT scan could detect it pre-operatively and complications due to transplantation of a kidney with papillary necrosis were avoided. So, we want to emphasize the importance of Radiology, particularly CT scanning in detection of RPN and to guide early and prompt treatment. PMID:26894147

  12. Flexural strength and microhardness of anterior composites after accelerated aging

    Science.gov (United States)

    Pala, Kanşad; Tuncer, Safa; Demirci, Mustafa; Öznurhan, Fatih; Serim, Merve

    2017-01-01

    Background This study aimed to evaluate the flexural strength and microhardness of three different anterior composites after 10 000 thermocycles. Material and Methods The mechanical properties of a nano-fill composite (Filtek Ultimate Universal Restorative (FUR) (Enamel)), a nano-hybrid composite (Clearfil Majesty ES2 (ES2) (Enamel)), and a micro-hybrid composite (G Aenial Anterior (GAA)) were investigated in this study. For the microhardness test, 8-mm diameter and 2-mm thickness composite discs were used (n = 10), and for the flexural strength test, 25x2x2 mm bar-shaped specimens were prepared (n = 13). The specimens were tested at 24 h and after 10 000 thermocycles. Data were analyzed using two-way analysis of variance and the post-hoc Tukey test (p .05). Pearson correlation analysis revealed that there was a negative relationship between the mean hardness and flexural strength values (correlation coefficient = -0.367, p = .043). After 10 000 thermocycles, microhardness values of each material and flexural strength of ES2 and GAA decreased significantly according to 24 h. Conclusions The nano-fill composite FUR displayed significantly higher microhardness values. However, each resin composite was statistically similar for flexural strength values. Ten thousand thermocycles significantly affected microhardness and flexural strength. Key words:Flexural strength, microhardness, anterior composites. PMID:28298986

  13. Effect of electrospun nanofibers on flexural properties of fiberglass composites

    Science.gov (United States)

    White, Fatima T.

    In the present study, sintered electrospun TEOS nanofibers were interleaved in S2 fiberglass woven fabric layers, and composite panels were fabricated using the heated vacuum assisted resin transfer molding (H-VARTM) process. Cured panels were water jet cut to obtain the flexural test coupons. Flexural coupons were then tested using ASTM D7264 standard. The mechanical properties such as flexural strength, ultimate flexural failure strains, flexural modulus, and fiber volume fraction were measured. The S-2 fiberglass composite with the sintered TEOS electrospun nanofibers displayed lower flexural stiffness and strength as compared to the composites that were fabricated using S-2 fiberglass composite without the TEOS electrospun nanofibers. The present study also indicated that the composites fabricated with sintered TEOS electrospun nanofibers have larger failure strains as compared to the ones that were fabricated without the presence of electrospun nanofibers. The study indicates that the nanoengineered composites have better energy absorbing mechanism under flexural loading as compared to conventional fiberglass composites without presence of nanofibers.

  14. A large workspace flexure hinge-based parallel manipulator system

    Institute of Scientific and Technical Information of China (English)

    Dong Wei; Du Zhijiang; Sun Lining

    2005-01-01

    Parallel manipulator systems as promising precision devices are used widely in current researches. A novel large workspace flexure parallel manipulator system utilizing wide-range flexure hinges as passive joints is proposed in this paper, which can attain sub-micron-scale precision over the cubic centimeter motion range. This paper introduces the mechanical system architecture based on the wide-range flexure hinges, analyzes the kinematics via stiffness matrices, presents the control system configuration and control strategy, and finally gives the system performance test results.

  15. Thermoelastic dissipation in MEMS/NEMS flexural mode resonators.

    Science.gov (United States)

    Yan, Jize; Seshia, Ashwin A

    2009-02-01

    Understanding the energy dissipation mechanisms in single-crystal silicon MEMS/NEMS resonators are particularly important to maximizing an important figure of merit relevant for miniature sensor and signal processing applications: the Quality factor (Q) of resonance. This paper discusses thermoelastic dissipation (TED) as the dominant internal-friction mechanism in flexural mode MEMS/NEMS resonators. Criteria for optimizing the geometrical design of flexural mode MEMS/NEMS resonators are theoretically established with a view towards minimizing the TED for single-crystal silicon MEMS/NEMS flexural mode resonators.

  16. Flexure bearing support, with particular application to stirling machines

    Science.gov (United States)

    Beckett, Carl D.; Lauhala, Victor C.; Neely, Ron; Penswick, Laurence B.; Ritter, Darren C.; Nelson, Richard L.; Wimer, Burnell P.

    1996-01-01

    The use of flexures in the form of flat spiral springs cut from sheet metal materials provides support for coaxial nonrotating linear reciprocating members in power conversion machinery, such as Stirling cycle engines or heat pumps. They permit operation with little or no rubbing contact or other wear mechanisms. The relatively movable members include one member having a hollow interior structure within which the flexures are located. The flexures permit limited axial movement between the interconnected members, but prevent adverse rotational movement and radial displacement from their desired coaxial positions.

  17. Sensitivity Analysis of MEMS Flexure FET with Multiple Gates

    Directory of Open Access Journals (Sweden)

    K.Spandana

    2016-02-01

    Full Text Available This paper deals with the design and modelling of Flexure FET and the FETs are the one of the important fundamental devices in electronic devices.. In this paper we are going analyse one of the MEMS Flexure Gate Field Effect Transistors. Here we will design gate of the FLEXURE FET with different type of materials and with different structure and we made the comparison between all the structures. We apply pull-in voltage to the Gate with respect to the change in the gate voltage the respective displacement of the gate changes which reflect the change in the drain current and sensitivity.

  18. Synthesis and stiffness modeling of XYZ flexure parallel mechanisms with large-motion and decoupled kinematic structure

    Institute of Scientific and Technical Information of China (English)

    Xueyan TANG; IMing CHEN

    2009-01-01

    This paper systematically studies structure synthesis and dimension optimization of XYZ flexure parallel mechanisms (FPMs) with large-motion and decoupled kinematic structure. Different from structure synthesis of rigid-body mechanisms, structure synthesis of flexure mechanisms is constrained by the limitations inherent in flexure mechanisms. These limitations are investigated and summarized as the structure constraints. With consideration of these structure constraints, the configurations of the decoupled XYZ-FPMs are synthesized using the Screw Theory. The synthesized XYZ-FPMs also possess large motion range, due to integration of a new type of large-motion prismatic joint designed in this paper. The stiffness models of the synthesized XYZ-FPMs are formulated. A 3-PPP XYZ-FPM is developed as the case of the studies of structure synthesis and stiffness modeling.

  19. Exploratory flexural power flow measurements on a bar

    Science.gov (United States)

    Vanderwal, H. M. M.

    1990-05-01

    Exploratory experiments in a bar with an absorptive termination were performed. The bar was excited in a transversal direction. The flexural power flow in the bar was measured at various positions, applying the two transducer technique (2TT) and the four transducer technique (4TT). The separation distance between the accelerometers was varied. The power flow at the excitation point was determined from a force and an acceleration measurement (Fv). When comparing the 2TT power flow with the 4TT or Fv power flow, the discretization error (i.e. the error due to a finite accelerometer separation) is an important parameter, particularly for separations larger than one sixth of a wavelength. In order to quantify the effect of this error, a prediction of the measured power flows on the basis of an analytical solution of the bending wave equation for the far field is performed. For most cases a good agreement is found between the predicted and the measured power flow ratios (i.e. 4TT/2TT and 2TT/Fv). However, for accelerometer separations smaller than about one sixth of a wavelength, a larger scatter is observed in the power flow data, measured with the 4TT, due to loss of significant digits. This effect may result in limitations for multiple transducer techniques in two or three dimensional structures.

  20. Acute retinal necrosis

    Directory of Open Access Journals (Sweden)

    Hugo Hernán Ocampo

    2009-12-01

    Full Text Available Purpose: Clinical features in a case of acute retinal necrosis are described as well as its diagnostic approach and response to early treatment. Methods: This is a descriptive and retrospective study case report of a 26 year old male patient who arrived to the emergency room with a three day history of sudden visual loss in the right eye (RE. At initial evaluation a visual acuity of hand movements in the RE, 20/15 in the left eye (LE and a right relative afferent pupillary defect were found. Fundoscopy revealed profuse soft exudates and hemorrhages involving posterior pole, inferior hemiretina and superotemporal periphery. Infectious workup and fluoresceinic angiography were made and positive serologies for herpes virus types 1 and 2, without HIV, were found. A diagnosis of acute retinal necrosis was made and treatment with intravenous valgancyclovir for two weeks and intra-vitreous triamcinolone for severe vasculitis, was given. Then a 3 months treatment with oral antiviral agents was prescribed. Results: Patient’s evolution showed improvement with treatment and at two and a half months of follow up, visual acuity was 20/50 in the right eye, normal slit lamp examination, tonometry of 12 mm Hg and fundoscopy improved when compared to initial pictures.Conclusions: A high index of suspicion is needed for diagnosing ARN taking into account clinical findings. Prompt intravenous and intra-vitreous treatments are needed to achieve good clinical and functional outcomes and to avoid central nervous system complications.

  1. Analysis of flexural wave propagation in poroelastic composite ...

    African Journals Online (AJOL)

    DR OKE

    of flexural vibrations of poroelastic composite hollow cylinder is obtained. ... The equations of motion of a homogeneous, isotropic poroelastic solid (Biot 1956) in the presence of dissipation b are: 2. 2. 11. 12. 2 ...... Vibration and Control, Vol.

  2. predicting flexural strength river gravel using multi ravel using multi ...

    African Journals Online (AJOL)

    eobe

    s building a multi-layer perception neural network model which uses expe layer perception neural ..... using flexural testing machine. 3.2.2 Regression Model ... Training the network (learning) could be supervised or unsupervised training.

  3. Notch flexure hinges: An effective theory

    Science.gov (United States)

    Tseytlin, Yakov M.

    2002-09-01

    This article presents effective tractable equations for rotational compliance (stiffness) of a simple monolithic flexure hinge with circular (radius R and crosspiece thickness t), elliptical [at semiaxis ax, ay, elliptical ratio epsilon (=ax/ay)] and other cross sections. These equations and the method by inverse conformal mapping of circular approximating contour used to derive them are different from the known and widely used theoretical equations originally derived in 1965 by Paros and Weisbord for circular notch hinges. Later it was found that the circular hinge represents the worst case error between known theoretical and finite element models. The conformal mapping equations data presented in this article are likely to be much closer (within less than 10%) to the finite element analysis and experimental data than other theoretical equations. In particular this is the case for circular notch hinges at relative thickness beta(=t/2R) in the range 0.01 to 0.3 and for elliptical hinges at the elliptical ratio epsilon=1 to 10. The derived general equation is common for all types of notch hinges whose profiles can be approximated by two shifted contiguous circles and includes material parameters with Young's modulus and Poisson's ratio. The latter is totally omitted in known theoretical solutions by other authors. New tractable equations are derived from the general equation on the basis of trigonometric functions' simplified series expansion in certain ranges of hinge crosspiece relative thickness. The corresponding graphs are presented. Experimental data were received by holographic interference and autocollimator measurement.

  4. Flexural vibrations of finite composite poroelastic cylinders

    Indian Academy of Sciences (India)

    Sandhya Rani Bandari; Srisailam Aleti; Malla Reddy Perati

    2015-04-01

    This paper deals with the flexural vibrations of composite poroelastic solid cylinder consisting of two cylinders that are bonded end to end. Poroelastic materials of the two cylinders are different. The frequency equations for pervious and impervious surfaces are obtained in the framework of Biot’s theory of wave propagation in poroelastic solids. The gauge invariance property is used to eliminate one arbitrary constant in the solution of the problem. This would lower the number of boundary conditions actually required. If the wavelength is infinite, frequency equations are degenerated as product of two determinants pertaining to extensional vibrations and shear vibrations. In this case, it is seen that the nature of the surface does not have any influence over shear vibrations unlike in the case of extensional vibrations. For illustration purpose, three composite cylinders are considered and then discussed. Of the three, two are sandstone cylinders and the third one is resulted when a cylindrical bone is implanted with Titanium. In either case, phase velocity is computed against aspect ratios.

  5. Flexural testing of weld site and HVOF coating characteristics

    CERN Document Server

    Yilbas, Bekir Sami; Sahin, Ahmet

    2014-01-01

    This book provides fundamental understanding and practical application of characteristics of flexural motion in the assessment of the weld size and coating thickness. Some formulations of heat transfer and flexural motion are introduced while displacement and load correlation are used to estimate elastic modules and the size of the heat affected zone as well as the coating thickness. The case studies presented give a practical understanding of weld size and coating thickness characterizations.

  6. Modeling the Flexural Carrying Capacity of Corroded RC Beam

    Institute of Scientific and Technical Information of China (English)

    WANG Xiao-hui; LIU Xi-la

    2008-01-01

    Considering the change of bond strength between corroded steel and concrete, flexural carrying ca-pacity of corroded reinforced concrete (RC) beam was calculated. On the basis of the condition of equilibriumof forces and compatibility of deformations for the whole beam, a model for the prediction of flexural carryingcapacity of the corroded RC beam was proposed. Comparison of the model's predictions with the experimentalresults published in the literature shows the practicality of the proposed method.

  7. Thermal noise of a gram-scale cantilever flexure

    CERN Document Server

    Nguyen, Thanh T-H; Miller, John; Mow-Lowry, Conor M; Goßler, Stefan; Shaddock, Daniel A; McClelland, David E

    2015-01-01

    Measured thermal noise displacement spectra from low frequency to $3\\,$kHz of Niobium and Aluminium flexures are presented. With a simple thermal noise model dominated by structural and thermoelastic losses, the agreement between the theory and measurement has been robust. The thermal noise spectra were recorded up to an order of magnitude below and above the fundamental resonance, with the fundamental resonances for both Aluminium and Niobium flexures within the range of $50\\,$Hz to $300\\,$Hz

  8. Flexural Strength of Glass and Polyethylene Fiber Combined with Three Different Composites

    Directory of Open Access Journals (Sweden)

    Sharafeddin F.

    2013-03-01

    Full Text Available tatement of Problem: The flexure of the fiber- reinforced composites (FRC which can be generally used instead of fixed metal- framework prostheses have been more advocated due to the enormous demands for the conservative and esthetic restoration. The flexure of the fiber should be well-fitted to its covering composite. No study has been reported the comparison of the combination of glass and polyethylene fiber with particulate filled composite and fiber reinforced composite yet.Purpose: This study compared the flexural strength of two types of fibers combined with three types of composites.Materials and Method: Sixty-six specimens were prepared in a split mold (25×2×2 mm. The specimens were divided into six groups according to the type of resin and the fiber (N = 11: group 1: Z250 composite + Polyethylene fiber; group 2: Build It composite + Polyethylene fiber; group 3: Nulite F composite+ Polyethylene fiber; group 4: glass fiber + Z250 composite; group 5: glass fiber + Build-It composite and group 6: glass fiber + Nulite F. The mean flexural strengths (MPa values were determined in a 3-point bending test at a crosshead speed of 1 mm/min by a universal testing machine (Zwick/Roell Z020, Germany. The results were statistically analyzed, using one and two- way ANOVA and LSD post-hoc tests (p< 0.05.Results: The highest flexural strength was registered for glass fiber in combination with Z250 composite (500 MPa and the lowest for polyethylene fiber in combination with Build-It composite (188 MPa. One-way ANOVA test revealed that there was no statistically significant difference between polyethylene fiber combinations (p= 0.62 but there was a significant difference between glass fiber combinations (p= 0.0001. Two-way ANOVA revealed that the fiber type had a significant effect on flexural strength (p= 0.0001.Conclusion: The choice of fiber and composite type was shown to have a significant positive influence on the flexural properties of the

  9. Intrinsic low pass filtering improves signal-to-noise ratio in critical-point flexure biosensors

    Energy Technology Data Exchange (ETDEWEB)

    Jain, Ankit; Alam, Muhammad Ashraful, E-mail: alam@purdue.edu [School of ECE, Purdue University, West Lafayette, Indiana 47906 (United States)

    2014-08-25

    A flexure biosensor consists of a suspended beam and a fixed bottom electrode. The adsorption of the target biomolecules on the beam changes its stiffness and results in change of beam's deflection. It is now well established that the sensitivity of sensor is maximized close to the pull-in instability point, where effective stiffness of the beam vanishes. The question: “Do the signal-to-noise ratio (SNR) and the limit-of-detection (LOD) also improve close to the instability point?”, however remains unanswered. In this article, we systematically analyze the noise response to evaluate SNR and establish LOD of critical-point flexure sensors. We find that a flexure sensor acts like an effective low pass filter close to the instability point due to its relatively small resonance frequency, and rejects high frequency noise, leading to improved SNR and LOD. We believe that our conclusions should establish the uniqueness and the technological relevance of critical-point biosensors.

  10. Three-degree-of-freedom flexure-based manipulator for high-resolution spatial micromanipulation

    Science.gov (United States)

    Speich, John E.; Goldfarb, Michael

    1998-10-01

    Flexure-based compliant mechanism design enables the development of revolute joint manipulators without the backlash or Coulomb friction that impede precision position and especially force control. Additionally, due to scaling effects, the adverse consequences of Coulomb friction are exacerbated at small scales. Conventional approaches to compliant mechanism design impose several limitations, however, such as severely limited ranges of motion, poor kinematic behavior, and significant deformation under multi- axis loading. The authors have developed a new type of compliant mechanism that enables the implementation of spatially-loaded revolute joint manipulators with well- behaved kinematic characteristics and without the backlash and stick-slip behavior that would otherwise impede precision control. The primary innovation in the design is the split-tube flexure, a unique small-scale revolute joint that exhibits a considerably larger range of motion and significantly better multi-axis revolute joint characteristics than a conventional flexure. Specifically, the compliant manipulator has an approximately spherical workspace two centimeters in diameter, yet is structurally rigid along non-actuated axes. Data from the small-scale manipulator demonstrates that positioning resolution is limited by digital quantization and sensor noise, and not by more fundamental physical limitations, such as backlash or Coulomb friction.

  11. The LINC-NIRVANA fringe and flexure tracker: an update of the opto-mechanical system

    Science.gov (United States)

    Zuther, Jens; Eckart, Andreas; Bertram, Thomas; Horrobin, Matthew; Lindhorst, Bettina; Lindhorst, Uwe; Moser, Lydia; Rost, Steffen; Straubmeier, Christian; Tremou, Evangelia; Wank, Imke

    2010-07-01

    LINC-NIRVANA (LN) is a German/Italian interferometric beam combiner camera for the Large Binocular Telescope. Due to homothetic imaging, LN will make use of an exceptionally large field-of-view. As part of LN, the Fringe-and-Flexure-Tracker system (FFTS) will provide real-time, closed-loop measurement and correction of pistonic and flexure signals induced by the atmosphere and inside the telescope-instrument system. Such compensation is essential for achieving coherent light combination over substantial time intervals (~ 10min.). The FFTS is composed of a dedicated near-infrared detector, which can be positioned by three linear stages within the curved focal plane of LN. The system is divided into a cryogenic (detector) and ambient (linear stages) temperature environment, which are isolated from each other by a moving baffle. We give an overview of the current design and implementation stage of the FFTS opto-mechanical and electronic components. We present recent important updates of the system, including the development of separated channels for the tracking of piston and flexure. Furthermore, the inclusion of dispersive elements will allow for the correction of atmospheric differential refraction, as well as the induction of artificial dispersion to better exploit the observational-conditions parameter space (air mass, brightness).

  12. Ice shelf flexures modeled with a 2-D elastic flow line model

    Directory of Open Access Journals (Sweden)

    Y. V. Konovalov

    2011-10-01

    Full Text Available Ice shelf flexures modeling was performed using a 2-D finite-difference elastic model, which takes into account sub-ice-shelf sea water flow. The sub-ice water flow was described by the wave equation for the sub-ice-shelf pressure perturbations (Holdsworth and Glynn, 1978. In the model ice shelf flexures result from variations in ocean pressure due to changes in prescribed sea levels. The numerical experiments were performed for a flow line down one of the fast flowing ice streams of the Academy of Sciences Ice Cap. The profile includes a part of the adjacent ice shelf. The numerical experiments were carried out for harmonic incoming pressure perturbations P' and the ice shelf flexures were obtained for a wide spectrum of the pressure perturbations frequencies, ranging from tidal periods down to periods of a few seconds (0.004..0.02 Hz. The amplitudes of the ice shelf deflections obtained by the model achieve a maxima at about T ≈ 165 s in concordance with previous investigations of the impact of waves on Antarctic ice shelves (Bromirski et al., 2010. The explanation of the effect is found in the solution of the corresponding eigenvalue problem revealing the existence of a resonance at these high frequencies.

  13. Flexural Toughness Characteristics of Steel Synthetic Fibers-Lightweight Aggregate Concrete

    Directory of Open Access Journals (Sweden)

    Rajai

    2016-06-01

    Full Text Available In general, the steel synthetic fibers improve the durability of concrete by providing crackarresting mechanism and minimizing it’s possible to cracking. In this study, an experimental program was undertaken to investigate the effect of steel synthetic fibers content volume fractions on the compressive, tensile, modulus of elasticity, and flexural toughness of lightweight aggregate concrete (LAWC. The tested specimens were divided into five groups based on steel synthetic fibers content volume fractions (0, 0.3, 0.6, 0.9 and 1.2%. The experimental results show that steel synthetic fibers content volume fractions considerably enhanced the mechanical properties of concrete in terms of compressive strength (2.8 for 0.3% fiber to 11.3% for 1.2% fiber, splitting tensile strength (3.9 for 0.3% fiber to 35.9% for 1.2% fiber, and flexural strength (21.8 for 0.3% fiber to 56.8% for 1.2% fiber. Also, the tested results show that the flexural toughness indexes and post-cracking toughness especially on the first crack and failure deflections were extensively enhanced by the addition of fibers. The improvement in post-cracking toughness could be due to the crack arresting effect of steel synthetic fibers because it continued to exhibit residual strength after the first crack creation and needed higher energy for the fiber pull out.

  14. Flexural fatigue life prediction of closed hat-section using materially nonlinear axial fatigue characteristics

    Science.gov (United States)

    Razzaq, Zia

    1989-01-01

    Straight or curved hat-section members are often used as structural stiffeners in aircraft. For instance, they are employed as stiffeners for the dorsal skin as well as in the aerial refueling adjacent area structure in F-106 aircraft. The flanges of the hat-section are connected to the aircraft skin. Thus, the portion of the skin closing the hat-section interacts with the section itself when resisting the stresses due to service loads. The flexural fatigue life of such a closed section is estimated using materially nonlinear axial fatigue characteristics. It should be recognized that when a structural shape is subjected to bending, the fatigue life at the neutral axis is infinity since the normal stresses are zero at that location. Conversely, the fatigue life at the extreme fibers where the normal bending stresses are maximum can be expected to be finite. Thus, different fatigue life estimates can be visualized at various distances from the neural axis. The problem becomes compounded further when significant portions away from the neutral axis are stressed into plastic range. A theoretical analysis of the closed hat-section subjected to flexural cyclic loading is first conducted. The axial fatigue characteristics together with the related axial fatigue life formula and its inverted form given by Manson and Muralidharan are adopted for an aluminum alloy used in aircraft construction. A closed-form expression for predicting the flexural fatigue life is then derived for the closed hat-section including materially nonlinear action. A computer program is written to conduct a study of the variables such as the thicknesses of the hat-section and the skin, and the type of alloy used. The study has provided a fundamental understanding of the flexural fatigue life characteristics of a practical structural component used in aircraft when materially nonlinear action is present.

  15. Application of bamboo for flexural and shear reinforcement in concrete beams

    Science.gov (United States)

    Schneider, Nathan Alan

    As the developing world is industrializing and people migrate to cities, the need for infrastructure is growing quickly and concrete has become one of the most widely used construction materials. One poor construction practice observed widely across the developing world is the minimal use of reinforcement for concrete structures due to the high cost of steel. As a low-cost, high-performance material with good mechanical properties, bamboo has been investigated as an alternative to steel for reinforcing concrete. The goal of this research is to add to the knowledge base of bamboo reinforced concrete (BRC) by investigating a unique stirrup design and testing the lap-splicing of flexural bamboo reinforcement in concrete beams. Component tests on the mechanical properties of Moso bamboo (Phyllostachys edulis) were performed, including tensile tests and pull-out tests. The results of the component tests were used to design and construct 13 BRC beams which were tested under monotonic gravity loading in 3 and 4-point bending tests. Three types of beams were designed and tested, including shear controlled, flexure controlled, and lap-spliced flexure controlled beams. The test results indicated that bamboo stirrups increased unreinforced concrete beam shear capacities by up to 259%. The flexural bamboo increased beam capacities by up to 242% with an optimal reinforcement ratio of up to 3.9%, assuming sufficient shear capacity. Limitations of the bamboo reinforcement included water absorption as well as poor bonding capability to the concrete. The test results show that bamboo is a viable alternative to steel as tensile reinforcement for concrete as it increases the ultimate capacity of the concrete, allows for high deflections and cracks, and provides warning of impending structural failure.

  16. Avascular Necrosis of the Capitate

    OpenAIRE

    Bekele, Wosen; Escobedo, Eva; Allen, Robert

    2011-01-01

    Avascular necrosis of the capitate is a rare entity. The most common reported etiology is trauma. We report a case of avascular necrosis of the capitate in a patient with chronic wrist pain that began after a single episode of remote trauma.

  17. Ageing effect on swell, shrinkage and flexural strength of sand and waste marble powder stabilized expansive soil

    Directory of Open Access Journals (Sweden)

    Oncu Serife

    2016-01-01

    Full Text Available Expansive soils in semi-arid climates must be mitigated to minimize potential structural damage to the overlying structures due to swell-shrink behavior caused by climatic changes. The expansive soil in this study was amended by sand which reduced the swell-shrink potential significantly. As a secondary additive, a waste by product of construction industry was selected, marble powder. Recycling this material would minimize its accumulation and covering a large space in landfill areas. In this study, waste material was assessed as a possible partial replacement for sand and due to its high calcite content, curing effect on its cementitious characteristic was also evaluated. It was observed that for mitigating the swell-shrink potential, 10% marble powder by dry mass was the optimum amount which was observed to gain improved characteristics with curing. The flexural strength, however, slightly reduced with marble powder addition, the soil mixture displayed a brittle behavior. Therefore the utilization of this material is recommended to be restricted to soils exposed to lower flexural loads, such as light traffic. The correlation between shrinkage strains and flexural strength parameters suggested herein, could be a potential empirical approach to predict the flexural strength based on shrinkage behavior.

  18. Flexural-torsional buckling behavior of aluminum alloy beams

    Institute of Scientific and Technical Information of China (English)

    Xiaonong GUO; Zhe XIONG; Zuyan SHEN

    2015-01-01

    This paper presents an investigation on the flexural-torsional buckling behavior of aluminum alloy beams (AAB). First, based on the tests of 14 aluminum alloy beams under concentrated loads, the failure pattern, load- deformation curves, bearing capacity and flexural-torsional buckling factor are studied. It is found that all the beam specimens collapsed in the flexuml-torsional buckling with excessive deformation pattern. Moreover, the span, loading location and slenderness ratio influence the flexural-torsional buckling capacity of beams significantly. Secondly, besides the experiments, a finite element method (FEM) analysis on the flexural-torsional buckling behavior of AAB is also conducted. The main parameters in the FEM analysis are initial imperfection, material property, cross-section and loading scheme. According to the analytical results, it is indicated that the FEM is reasonable to capture mechanical behavior of AAB. Finally, on the basis of the experimental and analytical results, theoretical formulae to estimate the flexural- torsional buckling capacity of AAB are proposed, which could improve the application of present codes for AAB.

  19. Mandibular bone necrosis after use of paraformaldehyde-containing paste

    Science.gov (United States)

    Lee, Chi-hwan; Choi, Yoorina

    2016-01-01

    Paraformaldehyde has been used in the past as a pulpotomy agent. However, it has a severe cytotoxic effect and may cause alveolar bone necrosis. Depulpin, a devitalizing agent containing 49% paraformaldehyde, is no longer used frequently due to its severe side effects. In the two cases described in the present study, Depulpin was used as a devitalizing agent during root canal treatment. It caused a gradual loss of sensibility in adjacent teeth, gingival necrosis, and osteomyelitis. This case report demonstrates the serious side effects of using a paraformaldehyde-containing paste as a devitalizing agent for pulp, particularly mandibular bone necrosis. PMID:27847756

  20. Influence of Carbon & Glass Fiber Reinforcements on Flexural Strength of Epoxy Matrix Polymer Hybrid Composites

    Directory of Open Access Journals (Sweden)

    T.D. Jagannatha

    2015-04-01

    Full Text Available Hybrid composite materials are more attracted by the engineers because of their properties like stiffness and high specific strength which leads to the potential application in the area of aerospace, marine and automobile sectors. In the present investigation, the flexural strength and flexural modulus of carbon and glass fibers reinforced epoxy hybrid composites were studied. The vacuum bagging technique was adopted for the fabrication of polymer hybrid composite materials. The hardness, flexural strength and flexural modulus of the hybrid composites were determined as per ASTM standards. The hardness, flexural strength and flexural modulus were improved as the fiber reinforcement contents increased in the epoxy matrix material.

  1. Tensile and Flexural Properties of Ultra High Toughness Cemontious Composite

    Institute of Scientific and Technical Information of China (English)

    LI Hedong; XU Shilang; Christopher K Y Leung

    2009-01-01

    The tensile and flexural properties of polyvinyl alcohol(PVA)fiber reinforced ultra high toughness cementitious composite(UHTCC)were investigated.The composite,tested at the age of 14 d,28 d and 56 d,shows extremely remarkable pseudo strain hardening behavior,saturated mul-tiple cracking and ultra high ultimate strain capacity above 4%under uniaxial loading.Also,the cor-responding crack widths are controlled under 50 μm even at 56 days age.In the third point bending tests on thin plate specimens,the composite shows ultra high flexural ductility and multiple cracking on the tension surface.The high ultimate flexural strength/first tensile strength ratio of about 5 verifies the pseudo strain hardening behavior of UHTCC.SEM observation on fracture surfaces provides in-direct evidence of optimal design for the composite.

  2. Flexural and Impact Resistance of FRC/Bamboo Laminate

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The flexural and impact resistance of a newly developed FRC/bamboo laminate have been investigated. The laminate considered in this study was combined with reformed bamboo plate and extruded fiber reinforced cementitious (FRC)sheet. Innovated from the raw bamboo, reformed bamboo showed high tensile strength and high strength to weight ratio. It can not only remarkably strengthen the FRC sheet but also reduce the total weight of the laminate. Flexural and impact load, broken energy, deflection and duration were measured. Test results showed that the flexural strength value for the laminate can be improved to greater than 90 MPa, while the impact resistance is increased more than 10 times for the laminate when compared with the FRC sheet only.

  3. Flexural Fatigue Behavior of Polypropylene Fiber Reinforeed Segment Conerete

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The influence of polypropylene fiber on the flexural fatigue performance of high- strength concrete (HSC), which could be used as cover of reinforcement of segment, was investigate by three-point load bending tests. Also, the flexural fatigue equations of high-strength concrete with and without polypropylene fiber were established through test analysis. The experimental results indicate that the addition of polypropylene fiber can improve the static bending strength of segment concrete, and the important is that it can markedly increase the flexural fatigue performance of the HSC subjected to cyclic bending load. Especially when with 1.37 kg/m3 addition of the fiber was corporate with silica fume and slag powder, the fatigue life of the HSC can be increased by 43.4% compared to that of the segment concrete without fiber,silica fume and slag.

  4. Pengaruh Penggunaan Serat Baja Terhadap Flexural Toughness Reactive Powder Concrete

    Directory of Open Access Journals (Sweden)

    Widodo Kushartomo

    2016-08-01

    Full Text Available This research present flexural toughness behavior of local steel fiber reinforced reactive powder concrete produced with different steel fibers volume fraction and aspect ratio. Prismatic concrete specimens of 100 x 100 x 350 mm were prepared with and without steel fiber. Steel fiber was used of 0% (control, 1,0%, 1,5%, and 2,0% by volume and 75, 100 and 125 as aspect ratio. Specimens were de-molded after 24 hours and cured in water until 3 days, after that the speciments were cure by steam curing for 8 hours at 90°C. Flexural toughness of the prisms has been defined at 28 day old. The result show that the effects of fibre volume and aspec ratio on flexural toughness of reactive powder concrete are very significant.

  5. Flexural strength of acrylic resins polymerized by different cycles

    Directory of Open Access Journals (Sweden)

    Débora Barros Barbosa

    2007-10-01

    Full Text Available Despite the large number of studies addressing the effect of microwave polymerization on the properties of acrylic resin, this method has received limited clinical acceptance. This study evaluated the influence of microwave polymerization on the flexural strength of a denture base resin. A conventional heat-polymerized (Clássico, a microwave-polymerized (Onda-Cryl and a autopolymerizing acrylic (Jet resins were used. Five groups were established, according to polymerization cycles: A, B and C (Onda-Cryl, short cycle - 500W/3 min, long - 90W/13 min + 500W/90 sec, and manufacturing microwave cycle - 320W/3 min + 0W/3 min + 720W/3 min; T (Clássico, water bath cycle - 74ºC/9h and Q (Jet, press chamber cycle - 50ºC/15 min at 2 bar. Ten specimens (65 x 10 x 3.3mm were prepared for each cycle. The flexural strength of the five groups was measured using a three-point bending test at a cross-head speed of 5 mm/min. Flexural strength values were analyzed by one-way ANOVA and the Tukey's test was performed to identify the groups that were significantly different at 5% level. The microwave-polymerized groups showed the highest means (p<0.05 for flexural strength (MPa (A = 106.97 ± 5.31; B = 107.57 ± 3.99; C = 109.63 ± 5.19, and there were no significant differences among them. The heat-polymerized group (T showed the lowest flexural strength means (84.40 ± 1.68, and differ significantly from all groups. The specimens of a microwavable denture base resin could be polymerized by different microwave cycles without risk of decreasing the flexural strength.

  6. [The asterisk sign and adult ischemic femur head necrosis].

    Science.gov (United States)

    Dihlmann, W; Heller, M

    1985-04-01

    The asterisk sign is a stellate density, which is seen normally in the femoral head on computed tomography. It is due to the demonstration of the trabeculae in the femoral head. In adult ischaemic necrosis of the femoral head, there are characteristic changes in the asterisk sign at an early stage, even before there is collapse of the head. The changes are described and the indications for performing CT of the hip for diagnosing adult ischaemic necrosis are discussed.

  7. Characterization of flexure hinges for the French watt balance experiment

    Directory of Open Access Journals (Sweden)

    Pinot Patrick

    2014-01-01

    Full Text Available In the French watt balance experiment, the translation and rotation functions must have no backlash, no friction, nor the need for lubricants. In addition errors in position and movement must be below 100 nm. Flexure hinges can meet all of these criteria. Different materials, profile shapes and machining techniques have been studied. The flexure pivots have been characterized using three techniques: 1 an optical microscope and, if necessary, a SEM to observe the surface inhomogeneities; 2 a mass comparator to determine the bending stiffness of unloaded pivots; 3 a loaded beam oscillating freely under vacuum to study the dynamic behavior of loaded pivots.

  8. Flexural waves induced by electro-impulse deicing forces

    Science.gov (United States)

    Gien, P. H.

    1990-01-01

    The generation, reflection and propagation of flexural waves created by electroimpulsive deicing forces are demonstrated both experimentally and analytically in a thin circular plate and a thin semicylindrical shell. Analytical prediction of these waves with finite element models shows good correlation with acceleration and displacement measurements at discrete points on the structures studied. However, sensitivity to spurious flexural waves resulting from the spatial discretization of the structures is shown to be significant. Consideration is also given to composite structures as an extension of these studies.

  9. Characterization of flexure hinges for the French watt balance experiment

    Science.gov (United States)

    Pinot, Patrick; Genevès, Gérard

    2014-08-01

    In the French watt balance experiment, the translation and rotation functions must have no backlash, no friction, nor the need for lubricants. In addition errors in position and movement must be below 100 nm. Flexure hinges can meet all of these criteria. Different materials, profile shapes and machining techniques have been studied. The flexure pivots have been characterized using three techniques: 1) an optical microscope and, if necessary, a SEM to observe the surface inhomogeneities; 2) a mass comparator to determine the bending stiffness of unloaded pivots; 3) a loaded beam oscillating freely under vacuum to study the dynamic behavior of loaded pivots.

  10. Intestinal necrosis in young patient due to arterial tumour embolism

    DEFF Research Database (Denmark)

    Dahle, Einar; Gögenur, Ismail; Nørgaard, Peter

    2012-01-01

    A patient in the thirties, currently undergoing chemotherapy for metastatic osteosarcoma diagnosed 3 years earlier, was admitted with in the emergency department with abdominal pain. Laparoscopic surgery revealed severe inflammation and an abscess. 18 cm of small intestine was removed because of ...

  11. Experimental research and finite element analysis of bridge piers failed in flexure-shear modes

    Institute of Scientific and Technical Information of China (English)

    Sun Zhiguo; Si Bingjun; Wang Dongsheng; Guo Xun

    2008-01-01

    In recent earthquakes,a large number of reinforced concrete (RC) bridges were severely damaged due to mixed flexure-shear failure modes of the bridge piers.An integrated experimental and finite element (FE) analysis study is described in this paper to study the seismic performance of the bridge piers that failed in flexure-shear modes.In the first part,a nonlinear cyclic loading test on six RC bridge piers with circular cross sections is carried out experimentally.The damage states,ductility and energy dissipation parameters,stiffness degradation and shear strength of the piers are studied and compared with each other.The experimental results suggest that all the piers exhibit stable flexural response at displacement ductilities up to four before exhibiting brittle shear failure.The ultimate performance of the piers is dominated by shear capacity due to significant shear cracking,and in some cases,rupturing of spiral bars.In the second part,modeling approaches describing the hysteretic behavior of the piers are investigated by using ANSYS software.A set of models with different parameters is selected and evaluated through comparison with experimental results.The influences of the shear retention coefficients between concrete cracks,the Bauschinger effect in longitudinal reinforcement,the bond-slip relationship between the longitudinal reinforcement and the concrete and the concrete failure surface on the simulated hysteretie curves are discussed.Then,a modified analysis model is presented and its accuracy is verified by comparing the simulated results with experimental ones.This research uses models available in commercial FE codes and is intended for researchers and engineers interested in using ANSYS software to predict the hysteretic behavior of reinforced concrete structures.

  12. Experimental research and finite element analysis of bridge piers failed in flexure-shear modes

    Science.gov (United States)

    Sun, Zhiguo; Si, Bingjun; Wang, Dongsheng; Guo, Xun

    2008-12-01

    In recent earthquakes, a large number of reinforced concrete (RC) bridges were severely damaged due to mixed flexure-shear failure modes of the bridge piers. An integrated experimental and finite element (FE) analysis study is described in this paper to study the seismic performance of the bridge piers that failed in flexure-shear modes. In the first part, a nonlinear cyclic loading test on six RC bridge piers with circular cross sections is carried out experimentally. The damage states, ductility and energy dissipation parameters, stiffness degradation and shear strength of the piers are studied and compared with each other. The experimental results suggest that all the piers exhibit stable flexural response at displacement ductilities up to four before exhibiting brittle shear failure. The ultimate performance of the piers is dominated by shear capacity due to significant shear cracking, and in some cases, rupturing of spiral bars. In the second part, modeling approaches describing the hysteretic behavior of the piers are investigated by using ANSYS software. A set of models with different parameters is selected and evaluated through comparison with experimental results. The influences of the shear retention coefficients between concrete cracks, the Bauschinger effect in longitudinal reinforcement, the bond-slip relationship between the longitudinal reinforcement and the concrete and the concrete failure surface on the simulated hysteretic curves are discussed. Then, a modified analysis model is presented and its accuracy is verified by comparing the simulated results with experimental ones. This research uses models available in commercial FE codes and is intended for researchers and engineers interested in using ANSYS software to predict the hysteretic behavior of reinforced concrete structures.

  13. Flexural strength and Weibull analysis of a microhybrid and a nanofill composite evaluated by 3- and 4-point bending tests.

    Science.gov (United States)

    Rodrigues, Sinval A; Ferracane, Jack L; Della Bona, Alvaro

    2008-03-01

    The aim of the present study was to evaluate the flexural strength and the Weibull modulus of a microhybrid and a nanofill composite by means of 3- and 4-point bending tests. Thirty specimens of Filtek Z250 (3M/ESPE) and Filtek Supreme (3M/ESPE) were prepared for each test according to the ISO 4049/2000 specification. After 24h in distilled water at 37 degrees C the specimens were submitted to 3- and 4-point bending tests using a universal testing machine DL2000 (EMIC) with a crosshead speed of 1 mm/min. Flexural strength data were calculated and submitted to Student's t-test (alpha=0.05) and Weibull statistics. The fractured surfaces were analyzed based on fractographic principles. The two composites had equivalent strength in both test methods. However, the test designs significantly affected the flexural strength of the microhybrid and the nanofill composites. Weibull modulus (m) of Supreme was similar with both tests, while for Z250, a higher m was observed with the 3-point bending test. Critical flaws were most often associated with the specimen's surface (up to 90%) and were characterized as surface scratches/grooves, non-uniform distribution of phases, inclusions and voids. Flexural strength as measured by the 3-point bending test is higher than by the 4-point bending test, due to the smaller flaw containing area involved in the former. Despite the large difference in average filler size between the composites, the volume fraction of the filler in both materials is similar, which was probably the reason for similar mean flexural strength values and fracture behavior.

  14. Flexure of the Indian plate and intraplate earthquakes

    Indian Academy of Sciences (India)

    Roger Bilham; Rebecca Bendick; Kali Wallace

    2003-09-01

    The flexural bulge in central India resulting from India's collision with Tibet has a wavelength of approximately 670 km. It is manifest topographically and in the free-air gravity anomaly and the geoid. Calculations of the stress distribution within a flexed Indian plate reveal spatial variations throughout the depth of the plate and also a function of distance from the Himalaya. The wave- length (and therefore local gradient) of stress variation is a function of the effective elastic thickness of the plate, estimates of which have been proposed to lie in the range 40-120 km. The imposition of this stress field on the northward moving Indian plate appears fundamental to explaining the current distribution of intraplate earthquakes and their mechanisms. The current study highlights an outer trough south of the flexural bulge in central India where surface stresses are double the contiguous compressional stresses to the north and south. The Bhuj, Latur and Koyna earthquakes and numerous other recent reverse faulting events occurred in this compressional setting. The N/S spatial gradient of stress exceeds 2 bars/km near the flexural bulge. The overall flexural stress distribution provides a physical basis for earthquake hazard mapping and suggests that areas of central India where no historic earthquakes are recorded may yet be the locus of future damaging events.

  15. Effect of silica coating on flexural strength of fiber posts

    NARCIS (Netherlands)

    Valandro, LF; Ozcan, M; de Melo, RM; Galhano, GAP; Baldissara, P; Scotti, R; Bottino, MA

    2006-01-01

    Purpose: Fiber-reinforced composite (FRC) posts can be air-abraded to obtain good attachment to the resin cement. This study tested the effect of silica coating on the flexural strength of carbon, opaque, and translucent quartz FRC posts. Materials and Methods: Six experimental groups of FRC posts (

  16. Substructural Identification of Flexural Rigidity for Beam-Like Structures

    Directory of Open Access Journals (Sweden)

    Ki-Young Koo

    2015-01-01

    Full Text Available This study proposes a novel substructural identification method based on the Bernoulli-Euler beam theory with a single variable optimization scheme to estimate the flexural rigidity of a beam-like structure such as a bridge deck, which is one of the major structural integrity indices of a structure. In ordinary bridges, the boundary condition of a superstructure can be significantly altered by aging and environmental variations, and the actual boundary conditions are generally unknown or difficult to be estimated correctly. To efficiently bypass the problems related to boundary conditions, a substructural identification method is proposed to evaluate the flexural rigidity regardless of the actual boundary conditions by isolating an identification region within the internal substructure. The proposed method is very simple and effective as it utilizes the single variable optimization based on the transfer function formulated utilizing Bernoulli Euler beam theory for the inverse analysis to obtain the flexural rigidity. This novel method is also rigorously investigated by applying it for estimating the flexural rigidity of a simply supported beam model with different boundary conditions, a concrete plate-girder bridge model with different length of an internal substructure, a cantilever-type wind turbine tower structure with different type of excitation, and a steel box-girder bridge model with internal structural damages.

  17. Effect of Finger Joint on Flexural Strength of Teak Wood

    Directory of Open Access Journals (Sweden)

    Bharatesh A. Danawade

    2014-01-01

    Full Text Available This paper presents the flexural properties of rectangular Burma teak wood beam without finger joint and with finger joint. Finger joints enable full utilization of wood. Finger jointing technique is also used to eliminate wood defects which weaken the strength of wood. This paper considers finger joint as defined defect and its effect on the flexural strength is determined. Teakwood is hard and heavy, seasons rapidly and has good durability. The specimens were studied under three point bending test. Both edge wise and flat wise tests were carried out. It is observed that Burma teakwood beam without finger joint is stronger than beams with finger joints. Because of finger jointing the flexural strength reduces. It can be concluded that the strength loss can improved upon by selecting suitable geometry of finger joint and a suitable adhesive. It is recognized that further studies are necessary on jointing techniques of wood and type of adhesive so as to equal the flexural strength properties of clear teak wood beams.

  18. Strengthening of Steel Columns under Load: Torsional-Flexural Buckling

    Directory of Open Access Journals (Sweden)

    Martin Vild

    2016-01-01

    Full Text Available The paper presents experimental and numerical research into the strengthening of steel columns under load using welded plates. So far, the experimental research in this field has been limited mostly to flexural buckling of columns and the preload had low effect on the column load resistance. This paper focuses on the local buckling and torsional-flexural buckling of columns. Three sets of three columns each were tested. Two sets corresponding to the base section (D and strengthened section (E were tested without preloading and were used for comparison. Columns from set (F were first preloaded to the load corresponding to the half of the load resistance of the base section (D. Then the columns were strengthened and after they cooled, they were loaded to failure. The columns strengthened under load (F had similar average resistance as the columns welded without preloading (E, meaning the preload affects even members susceptible to local buckling and torsional-flexural buckling only slightly. This is the same behaviour as of the tested columns from previous research into flexural buckling. The study includes results gained from finite element models of the problem created in ANSYS software. The results obtained from the experiments and numerical simulations were compared.

  19. On mechanical properties of planar flexure hinges of compliant mechanisms

    Directory of Open Access Journals (Sweden)

    F. Dirksen

    2011-06-01

    Full Text Available The synthesis of compliant mechanisms yield optimized topologies that combine several stiff parts with highly elastic flexure hinges. The hinges are often represented in finite element analysis by a single node (one-node hinge leaving doubts on the physical meaning as well as an uncertainty in the manufacturing process.

    To overcome this one-node hinge problem of optimized compliant mechanisms' topologies, one-node hinges need to be replaced by real flexure hinges providing desired deflection range and the ability to bear internal loads without failure. Therefore, several common types of planar flexure hinges with different geometries are characterized and categorized in this work providing a comprehensive guide with explicit analytical expressions to replace one-node hinges effectively.

    Analytical expressions on displacements, stresses, maximum elastic deformations, bending stiffness, center of rotation and first natural frequencies are derived in this work. Numerical simulations and experimental studies are performed validating the analytical results. More importance is given to practice-oriented flexure hinge types in terms of cost-saving manufacturability, i.e. circular notch type hinges and rectangular leaf type hinges.

  20. Post-facelift flap necrosis treatment using charged polystyrene microspheres

    Science.gov (United States)

    Weissman, Oren; Farber, Nimrod; Remer, Eric; Tessone, Ariel; Trivizki, Omer; Bank, Jonathan; Winkler, Eyal; Zilinsky, Isaac; Haik, Josef

    2013-01-01

    BACKGROUND: Flap necrosis following facial rhytidectomy constitutes a vexing and grievous complication to the patient and the surgeon. Treatment modalities that can expedite wound healing and re-epithelialization rates are highly desired. OBJECTIVES: To assess wound healing and re-epithelialization rates of open wounds following postrhytidectomy flap necrosis treated with commercially available charged polystyrene microspheres (Polyheal-1, Polyheal Ltd, Israel). METHODS: Flap necrosis following rhytidectomy with open wounds in three female patients were treated using dressings soaked with Polyheal-1. Wound closure rates were documented. RESULTS: The wounds demonstrated both accelerated granulation tissue formation and rapid re-epithelialization rates. No complications or side effects were encountered. CONCLUSIONS: Charged polystyrene microspheres may offer a new and efficacious way to treat open wounds due to flap necrosis following facial rhytidectomy. Further research with larger patient numbers is still needed to verify these findings. PMID:24431937

  1. [A case report of progressive penile necrosis].

    Science.gov (United States)

    Haba, Tomomi; Koike, Hiroshi

    2014-05-01

    The penis is provided with blood by multiple arteries. Penile necrosis is uncommon. Penile necrosis sporadically occurs in patients with progressive diabetes mellitus and/or end stage renal failure. Penile necrosis is often considered a poor prognostic feature. We present a case of penile necrosis in a patient with mild diabetes mellitus.

  2. Flexural strength and fracture toughness of dental core ceramics.

    Science.gov (United States)

    Yilmaz, Handan; Aydin, Cemal; Gul, Basak E

    2007-08-01

    Many different strengthened all-ceramic core materials are available. In vitro study of their mechanical properties, such as flexural strength and fracture toughness, is necessary before they are used clinically. The purpose of this study was to evaluate and compare the mechanical properties of 6 commonly used all-ceramic core materials using biaxial flexural strength and indentation fracture toughness tests. Specimens of 6 ceramic core materials (Finesse, Cergo, IPS Empress, In-Ceram Alumina, In-Ceram Zirconia, and Cercon Zirconia) were fabricated (n=25) with a diameter of 15 mm and width of 1.2 +/- 0.2 mm. For each group, the specimens were tested to compare their biaxial flexural strength (piston on 3 balls) (n=15), Weibull modulus, and indentation fracture toughness (n=10) (IF method). The data were analyzed with 1-way ANOVA test (a=.05). The Tamhane multiple comparison test was used for post hoc analysis. Mean (SD) of biaxial flexural strength values (MPa) and Weibull modulus (m) results were: Finesse (F): 88.04 (31.61), m=3.17; Cergo (C): 94.97 (13.62), m=7.94; IPS Empress (E): 101.18 (13.49), m=10.13; In-Ceram Alumina (ICA): 341.80 (61.13), m=6.96; In-Ceram Zirconia (ICZ): 541.80 (61.10), m=10.17; and Cercon Zirconia (CZ): 1140.89 (121.33), m=13.26. The indentation fracture toughness results showed that there were significant differences between the tested ceramics. The highest fracture toughness values (MPa x m(0.5)) were obtained with the zirconia-based ceramic core materials. Significant differences were found in strength and toughness values of the materials evaluated. Cercon Zirconia core material showed high values of biaxial flexural strength and indentation fracture toughness when compared to the other ceramics studied.

  3. Contour accuracy improvement of a flexure-based micro-motion stage for tracking repetitive trajectory

    Science.gov (United States)

    Jia, Shi; Jiang, Yao; Li, Tiemin; Du, Yunsong

    2017-01-01

    Flexure-based micro-motion mechanisms have been widely utilized in modern precision industry due to their inherent merits, while model uncertainty, uncertain nonlinearity, and cross-coupling effect will obviously deteriorate their contour accuracy, especially in the high-speed application. This paper aims at improving the contouring performance of a flexure-based micro-motion stage utilized for tracking repetitive trajectories. The dynamic characteristic of the micro-motion stage is first studied and modeled as a second-order system, which is identified through an open-loop sinusoidal sweeping test. Then the iterative learning control (ILC) scheme is utilized to improve the tracking performance of individual axis of the stage. A nonlinear cross-coupled iterative learning control (CCILC) scheme is proposed to reduce the coupling effect among each axis, and thus improves contour accuracy of the stage. The nonlinear gain function incorporated into the CCILC controller can effectively avoid amplifying the non-recurring disturbances and noises in the iterations, which can further improve the stage's contour accuracy in high-speed motion. Comparative experiments between traditional PID, ILC, ILC & CCILC, and the proposed ILC & nonlinear CCILC are carried out on the micro-motion stage to track circular and square trajectories. The results demonstrate that the proposed control scheme outperforms other control schemes much in improving the stage's contour accuracy in high-speed motion. The study in this paper provides a practically effective technique for the flexure-based micro-motion stage in high-speed contouring motion.

  4. Polytopic idiopathetic epiphysis-necrosis

    Energy Technology Data Exchange (ETDEWEB)

    Strohmeyer, G.; Burkhart, A.

    1987-09-01

    As early as 1985 a 43-old male patient was found suffering of an idiopathetic hip joint necrosis, which in October 1985 had to be treated, at the left hand side, with an inflecting osteotomy of the femur and in June 1986, at the right hand side, by means of a cementfree totalendoprotesis. The X-ray examination of both shoulder joints, May 1987, necessitated by a painful restriction of movement, revealed an additional humerus joint necrosis at stage IV according to Ficat and Arlet.

  5. Time-Dependent Flexural Deformation Beneath the Emperor Seamounts

    Science.gov (United States)

    Wessel, P.; Watts, A. B.; Kim, S. S.

    2014-12-01

    The Hawaii-Emperor seamount chain stretches over 6000 km from the Big Island of Hawaii to the subduction cusp off Kamchatka and represents a near-continuous record of hotspot volcanism since the Late Cretaceous. The load of these seamounts and islands has caused the underlying lithosphere to deform, developing a flexural flanking moat that is now largely filled with volcanoclastic sediments. Because the age differences between the seafloor and the seamounts vary by an order of magnitude or more along the chain, the Hawaii-Emperor chain and surrounding area is considered a natural laboratory for lithospheric flexure and has been studied extensively in order to infer the rheology of the oceanic lithosphere. While most investigations have focused on the Hawaiian Islands and proximal seamounts (where data sets are more complete, including seismic reflection and refraction, swath bathymetry and even mapping and dating of drowned reef terraces), far fewer studies have examined the flexural deformation beneath the remote Emperor chain. Preliminary analysis of satellite altimetry data shows the flexural moats to be associated with very large negative gravity anomalies relative to the magnitudes of the positive anomalies over the loads, suggesting considerable viscous or viscoelastic relaxation since the loads were emplaced 50-80 Myr ago. In our study, we will attempt to model the Emperor seamount chain load as a superposition of individual elliptical Gaussian seamounts with separate loading histories. We use Optimal Robust Separation (ORS) techniques to extract the seamount load from the regional background bathymetry and partition the residual load into a set of individual volcanoes. The crustal age grid and available seamount dates are used to construct a temporal loading model and evaluate the flexural response of the lithosphere beneath the Emperor seamounts. We explore a variety of rheological models and loading scenarios that are compatible with the inferred load

  6. Implication of snail in metabolic stress-induced necrosis.

    Directory of Open Access Journals (Sweden)

    Cho Hee Kim

    Full Text Available BACKGROUND: Necrosis, a type of cell death accompanied by the rupture of the plasma membrane, promotes tumor progression and aggressiveness by releasing the pro-inflammatory and angiogenic cytokine high mobility group box 1. It is commonly found in the core region of solid tumors due to hypoxia and glucose depletion (GD resulting from insufficient vascularization. Thus, metabolic stress-induced necrosis has important clinical implications for tumor development; however, its regulatory mechanisms have been poorly investigated. METHODOLOGY/PRINCIPAL FINDINGS: Here, we show that the transcription factor Snail, a key regulator of epithelial-mesenchymal transition, is induced in a reactive oxygen species (ROS-dependent manner in both two-dimensional culture of cancer cells, including A549, HepG2, and MDA-MB-231, in response to GD and the inner regions of a multicellular tumor spheroid system, an in vitro model of solid tumors and of human tumors. Snail short hairpin (sh RNA inhibited metabolic stress-induced necrosis in two-dimensional cell culture and in multicellular tumor spheroid system. Snail shRNA-mediated necrosis inhibition appeared to be linked to its ability to suppress metabolic stress-induced mitochondrial ROS production, loss of mitochondrial membrane potential, and mitochondrial permeability transition, which are the primary events that trigger necrosis. CONCLUSIONS/SIGNIFICANCE: Taken together, our findings demonstrate that Snail is implicated in metabolic stress-induced necrosis, providing a new function for Snail in tumor progression.

  7. Internal-Notched Flexure Test for Measurement of Mode II Delamination Resistance of Fibre-Reinforced Polymers

    Directory of Open Access Journals (Sweden)

    Chengye Fan

    2013-01-01

    Full Text Available This paper introduces a new test, method, named internal-notched flexure (INF test, that is designed to measure the critical energy release rate of fibre-reinforced polymers for delamination growth in shear mode (mode II. The INF test generates stable delamination growth, with a monotonic increase of load and displacement in a nearly linear fashion. Values of the mode II delamination toughness were deduced using experimental compliance fitting method. Good repeatability of the results was obtained. Compared with the end-notched flexure (ENF test using the same material, the INF test yielded higher delamination resistance, possibly due to the bridging fibres found between fracture surfaces of the INF test specimens.

  8. Localized surface plate modes via flexural Mie resonances

    KAUST Repository

    Farhat, M.

    2017-05-11

    Surface-plasmon polaritons are naturally generated upon excitation of metals with high-frequency electromagnetic waves. However, the concept of spoof plasmons has made it possible to generate plasmoniclike effects in microwave electrodynamics, magnetics, and even acoustics. Similarly, in this paper, the concept of localized surface plate modes (SPMs) is introduced. It is demonstrated that SPMs can be generated on a two-dimensional (clamped or stress-free) cylindrical surface with subwavelength corrugations, which resides on a thin elastic plate, under excitation by an incident flexural plane wave. Numerical characterization of this corrugated rigid structure shows that it is elastically equivalent to a cylindrical scatterer with dispersive but uniformly negative flexural rigidity. This, indeed, suggests that plasmoniclike elastic materials can be engineered with potential applications in various areas including earthquake sensing and elastic imaging and cloaking.

  9. Enhanced flexural wave sensing by adaptive gradient-index metamaterials

    Science.gov (United States)

    Chen, Y. Y.; Zhu, R.; Barnhart, M. V.; Huang, G. L.

    2016-10-01

    Increasing sensitivity and signal to noise ratios of conventional wave sensors is an interesting topic in structural health monitoring, medical imaging, aerospace and nuclear instrumentation. Here, we report the concept of a gradient piezoelectric self-sensing system by integrating shunting circuitry into conventional sensors. By tuning circuit elements properly, both the quality and quantity of the flexural wave measurement data can be significantly increased for new adaptive sensing applications. Through analytical, numerical and experimental studies, we demonstrate that a metamaterial-based sensing system (MBSS) with gradient bending stiffness can be designed by connecting gradient negative capacitance circuits to an array of piezoelectric patches (sensors). Furthermore, we demonstrate that the proposed system can achieve more than two orders of magnitude amplification of flexural wave signals to overcome the detection limit. This research encompasses fundamental advancements in the MBSS with improved performance and functionalities, and will yield significant advances for a range of applications.

  10. The LINC-NIRVANA fringe and flexure tracker: laboratory tests

    Science.gov (United States)

    Tremou, Evangelia; Eckart, Andreas; Horrobin, Matthew; Lindhorst, Bettina; Moser, Lydia; Rost, Steffen; Smajic, Semir; Straubmeier, Christian; Wank, Imke; Zuther, Jens; Bertram, Thomas

    2010-07-01

    LINC-NIRVANA is the NIR homothetic imaging camera for the Large Binocular Telescope (LBT). In close cooperation with the Adaptive Optics systems of LINC-NIRVANA the Fringe and Flexure Tracking System (FFTS) is a fundamental component to ensure a complete and time-stable wavefront correction at the position of the science detector in order to allow for long integration times at interferometric angular resolutions. In this contribution, we present the design and the realization of the ongoing FFTS laboratory tests, taking into account the system requirements. We have to sample the large Field of View and to follow the reference source during science observations to an accuracy of less than 2 microns. In particular, important tests such as cooling tests of cryogenic components and tip - tilt test (the repeatability and the precision under the different inclinations) are presented. The system parameters such as internal flexure and precision are discussed.

  11. Flexural Strength and Behavior of Polypropylene Fiber Reinforced Concrete Beams

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The strength and deformation characteristics of polypropylene fiber reinforced concrete (PFRC) beams were investigated by four-point bending procedures in this paper.Two kinds of polypropylene fibers with different fiber contents (0.2%, 0.5%, 1.0% and 1.5%) by volume were used in the beam, which measured 100×100 mm with a span of 300 mm.It was found that the strength of the reinforced concrete beams was significantly decreased,whereas the flexural toughness was improved,compared to those unreinforced concrete beams.Geometry properties and volume contents of polypropylene fiber were considered to be important factors for improving the flexural toughness.Moreover,the composite mechanism between polypropylene fiber and concrete was analyzed and discussed.

  12. Flexural analysis of palm fiber reinforced hybrid polymer matrix composite

    Science.gov (United States)

    Venkatachalam, G.; Gautham Shankar, A.; Raghav, Dasarath; Santhosh Kiran, R.; Mahesh, Bhargav; Kumar, Krishna

    2015-07-01

    Uncertainty in availability of fossil fuels in the future and global warming increased the need for more environment friendly materials. In this work, an attempt is made to fabricate a hybrid polymer matrix composite. The blend is a mixture of General Purpose Resin and Cashew Nut Shell Liquid, a natural resin extracted from cashew plant. Palm fiber, which has high strength, is used as reinforcement material. The fiber is treated with alkali (NaOH) solution to increase its strength and adhesiveness. Parametric study of flexure strength is carried out by varying alkali concentration, duration of alkali treatment and fiber volume. Taguchi L9 Orthogonal array is followed in the design of experiments procedure for simplification. With the help of ANOVA technique, regression equations are obtained which gives the level of influence of each parameter on the flexure strength of the composite.

  13. Enhanced flexural wave sensing by adaptive gradient-index metamaterials

    Science.gov (United States)

    Chen, Y. Y.; Zhu, R.; Barnhart, M. V.; Huang, G. L.

    2016-01-01

    Increasing sensitivity and signal to noise ratios of conventional wave sensors is an interesting topic in structural health monitoring, medical imaging, aerospace and nuclear instrumentation. Here, we report the concept of a gradient piezoelectric self-sensing system by integrating shunting circuitry into conventional sensors. By tuning circuit elements properly, both the quality and quantity of the flexural wave measurement data can be significantly increased for new adaptive sensing applications. Through analytical, numerical and experimental studies, we demonstrate that a metamaterial-based sensing system (MBSS) with gradient bending stiffness can be designed by connecting gradient negative capacitance circuits to an array of piezoelectric patches (sensors). Furthermore, we demonstrate that the proposed system can achieve more than two orders of magnitude amplification of flexural wave signals to overcome the detection limit. This research encompasses fundamental advancements in the MBSS with improved performance and functionalities, and will yield significant advances for a range of applications. PMID:27748379

  14. Controlling flexural waves in semi-infinite platonic crystals

    CERN Document Server

    Haslinger, Stewart G; Movchan, Alexander B; Jones, Ian S; Craster, Richard V

    2016-01-01

    We address the problem of scattering and transmission of a plane flexural wave through a semi-infinite array of point scatterers/resonators, which take a variety of physically interesting forms. The mathematical model accounts for several classes of point defects, including mass-spring resonators attached to the top surface of the flexural plate and their limiting case of concentrated point masses. We also analyse the special case of resonators attached to opposite faces of the plate. The problem is reduced to a functional equation of the Wiener-Hopf type, whose kernel varies with the type of scatterer considered. A novel approach, which stems from the direct connection between the kernel function of the semi-infinite system and the quasi-periodic Green's functions for corresponding infinite systems, is used to identify special frequency regimes. We thereby demonstrate dynamically anisotropic wave effects in semi-infinite platonic crystals, with particular attention paid to designing systems to exhibit dynami...

  15. Novel parameter-based flexure bearing design method

    Science.gov (United States)

    Amoedo, Simon; Thebaud, Edouard; Gschwendtner, Michael; White, David

    2016-06-01

    A parameter study was carried out on the design variables of a flexure bearing to be used in a Stirling engine with a fixed axial displacement and a fixed outer diameter. A design method was developed in order to assist identification of the optimum bearing configuration. This was achieved through a parameter study of the bearing carried out with ANSYS®. The parameters varied were the number and the width of the arms, the thickness of the bearing, the eccentricity, the size of the starting and ending holes, and the turn angle of the spiral. Comparison was made between the different designs in terms of axial and radial stiffness, the natural frequency, and the maximum induced stresses. Moreover, the Finite Element Analysis (FEA) was compared to theoretical results for a given design. The results led to a graphical design method which assists the selection of flexure bearing geometrical parameters based on pre-determined geometric and material constraints.

  16. Flexural Vibration Characteristics of Initially Stressed Composite Plates

    Directory of Open Access Journals (Sweden)

    Rupesh Daripa

    2010-01-01

    Full Text Available The influence of localised in-plane load on the flexural vibration characteristics of isotropic and composite plates have been studied using a four-noded shear flexible high precision plate bending finite element. First, the critical buckling loads of such plates subjected to partial or concentrated compressive loads were calculated, then the linear and nonlinear flexural vibration frequencies were obtained. Limited parametric study was carried out to study the influences of location and distribution of tensile or compressive in-plane load on the vibration frequencies of such plates.Defence Science Journal, 2010, 60(1, pp.106-111, DOI:http://dx.doi.org/10.14429/dsj.60.117

  17. Flexural Properties of WeftKnitted Fabric Reinforced Composites

    Institute of Scientific and Technical Information of China (English)

    龙海如; 冯勋伟

    2001-01-01

    Several different kinds of weft knitted fabrics from glass fiber yarns were used as reinforcement to make fabric/polyester composite laminates. Flexural tests were carried out to examine stress- deflection process and compare the mechanical properties in course and wale directions of these composites. The experimental results indicate that the numbers of load-bearing yarn in course and wale direction and the fabric density are the main factors influencing the ultimate tensile strength and initial elastic modulus of specimens.

  18. Weakened Flexural Strength of Nanocrystalline Nanoporous Gold by Grain Refinement.

    Science.gov (United States)

    Gwak, Eun-Ji; Kim, Ju-Young

    2016-04-13

    High density of grain boundaries in solid materials generally leads to high strength because grain boundaries act as strong obstacles to dislocation activity. We find that the flexural strength of nanoporous gold of grain size 206 nm is 33.6% lower than that of grain size 238 μm. We prepared three gold-silver precursor alloys, well-annealed, prestrained, and high-energy ball-milled, from which nanoporous gold samples were obtained by the same free-corrosion dealloying process. Ligaments of the same size are formed regardless of precursor alloys, and microstructural aspects of precursor alloys such as crystallographic orientation and grain size is preserved in the dealloying process. While the nanoindentation hardness of three nanoporous golds is independent of microstructural variation, flexural strength of nanocrystalline nanoporous gold is significantly lower than that of nanoporous golds with much larger grain size. We investigate weakening mechanisms of grain boundaries in nanocrystalline nanoporous gold, leading to weakening of flexural strength.

  19. Experimental Evaluation of Three Designs of Electrodynamic Flexural Transducers

    Science.gov (United States)

    Eriksson, Tobias J. R.; Laws, Michael; Kang, Lei; Fan, Yichao; Ramadas, Sivaram N.; Dixon, Steve

    2016-01-01

    Three designs for electrodynamic flexural transducers (EDFT) for air-coupled ultrasonics are presented and compared. An all-metal housing was used for robustness, which makes the designs more suitable for industrial applications. The housing is designed such that there is a thin metal plate at the front, with a fundamental flexural vibration mode at ∼50 kHz. By using a flexural resonance mode, good coupling to the load medium was achieved without the use of matching layers. The front radiating plate is actuated electrodynamically by a spiral coil inside the transducer, which produces an induced magnetic field when an AC current is applied to it. The transducers operate without the use of piezoelectric materials, which can simplify manufacturing and prolong the lifetime of the transducers, as well as open up possibilities for high-temperature applications. The results show that different designs perform best for the generation and reception of ultrasound. All three designs produced large acoustic pressure outputs, with a recorded sound pressure level (SPL) above 120 dB at a 40 cm distance from the highest output transducer. The sensitivity of the transducers was low, however, with single shot signal-to-noise ratio (SNR)≃15 dB in transmit–receive mode, with transmitter and receiver 40 cm apart. PMID:27571075

  20. Asymmetric Flexural-gravity Lumps in Nonuniform Media

    CERN Document Server

    Liang, Yong

    2014-01-01

    Here we show that asymmetric fully-localized flexural-gravity lumps can propagate on the surface of an inviscid and irrotational fluid covered by a variable-thickness elastic material, provided that the thickness varies only in one direction and has a local minimum. We derive and present equations governing the evolution of the envelope of flexural-gravity wave packets allowing the flexing material to have small variations in the transverse (to propagation) direction. We show that the governing equation belongs to the general family of Davey-Stewartson equations, but with an extra term in the surface evolution equation that accounts for the variable thickness of the elastic cover. We then use an iterative Newton-Raphson scheme, with a numerical continuation procedure via Lagrange interpolation, in a search to find fully-localized solutions of this system of equations. We show that if the elastic sheet thickness has (at least) a local minimum, flexural-gravity lumps can propagate near the minimum thickness, an...

  1. Edge chipping and flexural resistance of monolithic ceramics☆

    Science.gov (United States)

    Zhang, Yu; Lee, James J.-W.; Srikanth, Ramanathan; Lawn, Brian R.

    2014-01-01

    Objective Test the hypothesis that monolithic ceramics can be developed with combined esthetics and superior fracture resistance to circumvent processing and performance drawbacks of traditional all-ceramic crowns and fixed-dental-prostheses consisting of a hard and strong core with an esthetic porcelain veneer. Specifically, to demonstrate that monolithic prostheses can be produced with a much reduced susceptibility to fracture. Methods Protocols were applied for quantifying resistance to chipping as well as resistance to flexural failure in two classes of dental ceramic, microstructurally-modified zirconias and lithium disilicate glass–ceramics. A sharp indenter was used to induce chips near the edges of flat-layer specimens, and the results compared with predictions from a critical load equation. The critical loads required to produce cementation surface failure in monolithic specimens bonded to dentin were computed from established flexural strength relations and the predictions validated with experimental data. Results Monolithic zirconias have superior chipping and flexural fracture resistance relative to their veneered counterparts. While they have superior esthetics, glass–ceramics exhibit lower strength but higher chip fracture resistance relative to porcelain-veneered zirconias. Significance The study suggests a promising future for new and improved monolithic ceramic restorations, with combined durability and acceptable esthetics. PMID:24139756

  2. LINC-NIRVANA: optical elements of the fringe and flexure tracker

    Science.gov (United States)

    Zuther, Jens; Eckart, Andreas; Bertram, Thomas; Horrobin, Matthew; Lindhorst, Bettina; Lindhorst, Uwe; Pott, Jörg-Uwe; Rauch, Christoph; Rost, Steffen; Smajic, Semir; Straubmeier, Christian; Wank, Imke; Beckmann, Udo; Lenzen, Rainer; Tremou, Evangelia

    2012-07-01

    LINC-NIRVANA (LN) is a German /Italian interferometric beam combiner camera for the Large Binocular Telescope. Due to homothetic imaging, LN will make use of an exceptionally large field-of-view. As part of LN, the Fringe-and-Flexure-Tracker system (FFTS) will provide real-time, closed-loop measurement and correction of pistonic and flexure signals induced by the atmosphere and inside the telescope-instrument system. Such compensation is essential for achieving coherent light combination over substantial time intervals (~10min.). The FFTS is composed of a dedicated near-infrared detector, which can be positioned by three linear stages within the curved focal plane of LN. The system is divided into a cryogenic (detector) and ambient (linear stages) temperature environment, which are isolated from each other by a moving baffie. We give an overview of the current design and implementation stage of the FFTS opto-mechanical components. The optical components represent an update of the original design to assess slow image motion induced by the LN instrument separately.

  3. High resolution space quartz-flexure accelerometer based on capacitive sensing and electrostatic control technology.

    Science.gov (United States)

    Tian, W; Wu, S C; Zhou, Z B; Qu, S B; Bai, Y Z; Luo, J

    2012-09-01

    High precision accelerometer plays an important role in space scientific and technical applications. A quartz-flexure accelerometer operating in low frequency range, having a resolution of better than 1 ng/Hz(1/2), has been designed based on advanced capacitive sensing and electrostatic control technologies. A high precision capacitance displacement transducer with a resolution of better than 2 × 10(-6) pF/Hz(1/2) above 0.1 Hz, is used to measure the motion of the proof mass, and the mechanical stiffness of the spring oscillator is compensated by adjusting the voltage between the proof mass and the electrodes to induce a proper negative electrostatic stiffness, which increases the mechanical sensitivity and also suppresses the position measurement noise down to 3 × 10(-10) g/Hz(1/2) at 0.1 Hz. A high resolution analog-to-digital converter is used to directly readout the feedback voltage applied on the electrodes in order to suppress the action noise to 4 × 10(-10) g/Hz(1/2) at 0.1 Hz. A prototype of the quartz-flexure accelerometer has been developed and tested, and the preliminary experimental result shows that its resolution comes to about 8 ng/Hz(1/2) at 0.1 Hz, which is mainly limited by its mechanical thermal noise due to low quality factor.

  4. Effect of resin and type of surface treatment on the flexural strength of cracked feldspathic porcelain

    Directory of Open Access Journals (Sweden)

    Kermanshah Hamid

    2015-05-01

    Full Text Available Background and Aims: Porcelain restorations are often ground for clinical adjustment and this removes the surface glaze layer and introduces flaws that can grow in wet environments due to stress-corrosion, reduce the strength of porcelain and limit restoration lifetime. The aim of this study was to introduce some surface treatment methods to control the flaws of ceramic restorations external surface and improve their strength.   Materials and Methods: 40 feldspathic discs were prepared and divided into 4 groups (n=10: not indented (group 1 and others indented by vickers with 29.4 N and received different treatments: no treatment (group 2, polished (group 3 and polished-silane-resin (group 4. Biaxial flexural strength of discs was tested after water storage. Data were analyzed using one-way ANOVA .   Results: The mean flexural strength of specimens in group 1 (134.49±12.60, 2 (94.81±15.41, 3 (89.20±16.22 and 4 (80.67±12.01 were measured. Group 1 (not indented revealed significantly higher strength (P<0.001 than that of indented groups (2, 3 and 4 . There was no significant difference between group 2 (no treatment and 3 or 4 (treated and between treatment methods (3 and 4 (P=0.136.   Conclusion: The strength of porcelains is dependent on presence of cracks. With the limitations of this study, none of the treatment methods could strengthen the cracked ceramic.

  5. Walled-off pancreatic necrosis

    Institute of Scientific and Technical Information of China (English)

    Michael; Stamatakos; Charikleia; Stefanaki; Konstantinos; Kontzoglou; Spyros; Stergiopoulos; Georgios; Giannopoulos; Michael; Safioleas

    2010-01-01

    Walled-off pancreatic necrosis (WOPN), formerly known as pancreatic abscess is a late complication of acute pancreatitis. It can be lethal, even though it is rare. This critical review provides an overview of the continually expanding knowledge about WOPN, by review of current data from references identified in Medline and PubMed, to September 2009, using key words, such as WOPN, infected pseudocyst, severe pancreatitis, pancreatic abscess, acute necrotizing pancreatitis (ANP), pancreas, inflammation and al...

  6. RIP Kinases Initiate Programmed Necrosis

    Institute of Scientific and Technical Information of China (English)

    Lorenzo Galluzzi; Oliver Kepp; Guido Kroemer

    2009-01-01

    Some lethal stimuli can induce either apoptosis or necrosis, depending on the cell type and/or experimental setting. Until recently,the molecular bases of this phenomenon were largely unknown. Now, two members of the receptor-interacting serine-threonine kinase (RIP) family, RIP1 and RIP3, have been demonstrated to control the switch between apoptotic and necrotic cell death.Some mechanistic details, however, remain controversial.

  7. Licensed DNA Vaccines against Infectious Hematopoietic Necrosis Virus (IHNV).

    Science.gov (United States)

    Alonso, Marta; Leong, Jo-Ann C

    2013-04-01

    This article reviews some of the recent patents on DNA vaccines against fish viruses, in particular against the novirhabdovirus infectious hematopoitic necrosis virus (IHNV). Although very effective in protecting fish against IHNV, only one DNA vaccine has been approved to date for use in Canada. In Europe and in US, its commercialization is restricted due to safety concerns.

  8. A high performance all-organic flexural piezo-FET and nanogenerator via nanoscale soft-interface strain modulation.

    Science.gov (United States)

    Dhakras, Dipti; Gawli, Yogesh; Chhatre, Shraddha; Wadgaonkar, Prakash; Ogale, Satishchandra

    2014-11-07

    Flexural strain fields are encountered in a wide variety of situations and invite novel device designs for their effective use in sensing, actuating, as well as energy harvesting (nanogenerator) applications. In this work we demonstrate an interesting all-organic device design comprising an electrospun P(VDF-TrFE) fiber-mat built directly on a conducting PANI film, which is also grown on a flexible PET substrate, for flexural piezo-FET and nanogenerator applications. Orders of magnitude stronger modulation of electrical transport in PANI film is realized in this device as compared to the case of a similar device but with a uniform spin-coated P(VDF-TrFE) film. We find that in the flexural mode of operation, the interaction between the laterally modulated nanoscale strain field distributions created by the fibers and the applied coherent strain field strongly influences the carrier transport in PANI. The transport modulation is suggested to occur due to strain-induced conformational changes in P(VDF-TrFE) leading to changes in carrier localization-delocalization. We further show that the fiber-mat based device system also works as an efficient nanogenerator capable of delivering power for low power applications.

  9. FLEXURAL-GRAVITY WAVES DUE TO TRANSIENT DISTURBANCES IN AN INVISCID FLUID OF FINITE DEPTH

    Institute of Scientific and Technical Information of China (English)

    LU Dong-qiang; LE Jia-chun; DAI Shi-qiang

    2008-01-01

    The dynamic response of an ice-covered fluid to transient disturbances was analytically investigated by means of integral transforms and the generalized method of stationary phase. The initially quiescent fluid of finite depth was assumed to be inviscid, incompressible, and homogenous. The thin ice-cover was modeled as a homogeneous elastic plate. The disturbances were idealized as the fundamental singularities. A linearized initial-boundary-value problem was formulated within the framework of potential flow. The perturbed flow was decomposed into the regular and the singular components. An image system was introduced for the singular part to meet the boundary condition at the flat bottom. The solutions in integral form for the vertical deflexion at the ice-water interface were obtained by means of a joint Laplace-Fourier transform. The asymptotic representations of the wave motion were explicitly derived for large time with a fixed distance-to-time ratio. The effects of the finite depth of fluid on the resultant wave patterns were discussed in detail. As the depth increases from zero, the critical wave number and the minimal group velocity first increase to their peak values and then decrease to constants.

  10. The effect of nanoclay filler loading on the flexural strength of fiber-reinforced composites

    Directory of Open Access Journals (Sweden)

    Vajihesadat Mortazavi

    2012-01-01

    Results: For groups with the same concentration of nanoparticles, PMMA-grafted filler-loaded group showed significantly higher flexural strength, except for 0.2% wt. For groups that contain PMMA-grafted nanoclay fillers, the 2% wt had the highest flexural strength value with significant difference to other subgroups. 1% wt and 2% wt showed significantly higher values compared to control (P 0.05. Flexural modulus of 2%, 5% wt PMMA-grafted and 0.5%, 1%, 2%, 5% wt unmodified nanoclay particles-loaded subgroups decreased significantly compared to control group (P < 0.05. Conclusions: PMMA-grafted nanoclay filler loading may enhance the flexural strength of FRCs. Addition of unmodified nanoparticles cannot significantly improve the flexural strength of FRCs. Addition of both unmodified and PMMA-grafted nanoclay particles in some concentrations decreased the flexural modulus.

  11. A Rare Cause of Acute Abdomen: Idiopathic Isolated Cecal Necrosis

    Directory of Open Access Journals (Sweden)

    Ender Özer

    2015-03-01

    Full Text Available Idiopathic isolated cecal necrosis is a clinical problem characterized by right-sided inferior abdominal pain. It is rarely seen, develops due to decreased blood flow to the colon and, imitates acute appendicitis. Its clinical signs are similar to many illnesses causing sensitivity in the right inferior quadrant and, the diagnosis is generally determined during surgery. An 86-year-old male patient presented with the complaints of abdominal pain, trichiniasis, nausea and vomiting. Surgical intervention was decided when physical examination and laboratory results were taken into consideration. After diagnostic laparoscopy, right hemicolectomy was performed because of cecal necrosis. While the mortality and morbidity rates for ischemic bowel disease are high, prognosis for early diagnosed patients with isolated cecal necrosis is better, provided that timely surgical treatment is decided.

  12. Targeting of regulated necrosis in kidney disease.

    Science.gov (United States)

    Martin-Sanchez, Diego; Poveda, Jonay; Fontecha-Barriuso, Miguel; Ruiz-Andres, Olga; Sanchez-Niño, María Dolores; Ruiz-Ortega, Marta; Ortiz, Alberto; Sanz, Ana Belén

    2017-06-21

    The term acute tubular necrosis was thought to represent a misnomer derived from morphological studies of human necropsies and necrosis was thought to represent an unregulated passive form of cell death which was not amenable to therapeutic manipulation. Recent advances have improved our understanding of cell death in acute kidney injury. First, apoptosis results in cell loss, but does not trigger an inflammatory response. However, clumsy attempts at interfering with apoptosis (e.g. certain caspase inhibitors) may trigger necrosis and, thus, inflammation-mediated kidney injury. Second, and most revolutionary, the concept of regulated necrosis emerged. Several modalities of regulated necrosis were described, such as necroptosis, ferroptosis, pyroptosis and mitochondria permeability transition regulated necrosis. Similar to apoptosis, regulated necrosis is modulated by specific molecules that behave as therapeutic targets. Contrary to apoptosis, regulated necrosis may be extremely pro-inflammatory and, importantly for kidney transplantation, immunogenic. Furthermore, regulated necrosis may trigger synchronized necrosis, in which all cells within a given tubule die in a synchronized manner. We now review the different modalities of regulated necrosis, the evidence for a role in diverse forms of kidney injury and the new opportunities for therapeutic intervention. Copyright © 2017 Sociedad Española de Nefrología. Published by Elsevier España, S.L.U. All rights reserved.

  13. Design principle of high-precision flexure mechanisms based on parasitic-motion compensation

    Science.gov (United States)

    Li, Shouzhong; Yu, Jingjun

    2014-07-01

    In design of flexure mechanism, diminishing the parasitic-motion is a key point to improve the accuracy. However, most of existing topics concentrate on improving the accuracy of linear-motion flexure mechanisms via compensating the parasitic error, but few research the multi-dimensional flexure mechanisms. A general design principle and method for high-precision flexure mechanisms based on the parasitic-motion compensation is presented, and the proposed method can compensate the parasitic rotation in company with translation, or the parasitic translation in company with rotation, or both. The crucial step for the method is that the parasitic motion of a flexure mechanism is formulated and evaluated in terms of its compliance. The overall compliance matrix of a general flexure mechanism is formulated by using screw theory firstly, then the criteria for the parasitic motions is introduced by analyzing the characteristics of the resultant compliance matrix as well as with aid of the concept of instantaneous rotation center. Subsequently, a compliance-based compensation approach for reducing parasitic-motion is addressed as the most important part. The design principles and procedure are further discussed to help with improving the accuracy of flexure mechanisms, and case studies are provided to illustrate this method. Finally, an analytical verification is provided to demonstrate that the symmetry design philosophy widely used in flexure design can effectively improve accuracy in terms of the proposed method. The proposed compensation method can be well used to diminish the parasitic-motion of multi-dimensional flexure mechanisms.

  14. Experimental determination of optimum dielectric strength of Turmeric fiber reinforced polyester composites using flexural properties

    Directory of Open Access Journals (Sweden)

    K. Murali Mohan Rao

    2009-10-01

    Full Text Available The present investigation puts forward new natural fiber turmeric to be used in the preparation of turmeric fiber reinforced polyester (FRP composites. The dielectric strength of the composites shown decrease in trend with increase in volume fraction of fiber with appreciable reduction in their weight. There was clear fall in the density of the composites with increase in fiber volume fraction. The optimum value of dielectric strength was determined with flexural strength, flexural modulus and specific flexural strength, specific flexural modulus against percentage volume fraction of fiber from the graphs.

  15. RING-TENSILE-STRENGTH AND FLEXURE-STRENGTH CORRELATIONS OF SEA ICE.

    Science.gov (United States)

    SEA ICE, MECHANICAL PROPERTIES), TENSILE PROPERTIES, SALINITY, TEMPERATURE, ICE, FLEXURAL STRENGTH , CORRELATION TECHNIQUES, ACCURACY, SAMPLING, THICKNESS, PREDICTIONS, ANTARCTIC REGIONS, LOADS(FORCES)

  16. On the significance of microtubule flexural behavior in cytoskeletal mechanics.

    Directory of Open Access Journals (Sweden)

    Mehrdad Mehrbod

    Full Text Available Quantitative description of cell mechanics has challenged biological scientists for the past two decades. Various structural models have been attempted to analyze the structure of the cytoskeleton. One important aspect that has been largely ignored in all these modeling approaches is related to the flexural and buckling behavior of microtubular filaments. The objective of this paper is to explore the influence of this flexural and buckling behavior in cytoskeletal mechanics.In vitro the microtubules are observed to buckle in the first mode, reminiscent of a free, simply-supported beam. In vivo images of microtubules, however, indicate that the buckling mostly occurs in higher modes. This buckling mode switch takes place mostly because of the lateral support of microtubules via their connections to actin and intermediate filaments. These lateral loads are exerted throughout the microtubule length and yield a considerable bending behavior that, unless properly accounted for, would produce erroneous results in the modeling and analysis of the cytoskeletal mechanics.One of the promising attempts towards mechanical modeling of the cytoskeleton is the tensegrity model, which simplifies the complex network of cytoskeletal filaments into a combination merely of tension-bearing actin filaments and compression-bearing microtubules. Interestingly, this discrete model can qualitatively explain many experimental observations in cell mechanics. However, evidence suggests that the simplicity of this model may undermine the accuracy of its predictions, given the model's underlying assumption that "every single member bears solely either tensile or compressive behavior," i.e. neglecting the flexural behavior of the microtubule filaments. We invoke an anisotropic continuum model for microtubules and compare the bending energy stored in a single microtubule with its axial strain energy at the verge of buckling. Our results suggest that the bending energy can

  17. Flexural Behavior of Aluminum Honeycomb Core Sandwich Structure

    Science.gov (United States)

    Matta, Vidyasagar; Kumar, J. Suresh; Venkataraviteja, Duddu; Reddy, Guggulla Bharath Kumar

    2017-05-01

    This project is concerned with the fabrication and flexural testing of aluminium honey comb sandwich structure which is a special case of composite materials that is fabricated by attaching two thin but stiff skins to a light weight but thick core. The core material is normally low density material but its high thickness provide the sandwich composite with high bonding stiffness. Honeycomb core are classified into two types based on the materials and structures. Hexagonal shape has a unique properties i.e has more bonding strength and less formation time based on the cell size and sheet thickness. Sandwich structure exhibit different properties such as high load bearing capacity at low weight and has excellent thermal insulation. By considering the above properties it has tendency to minimize the structural problem. So honey comb sandwich structure is choosed. The core structure has a different applications such as aircraft, ship interiors, construction industries. As there is no proper research on strength characteristics of sandwich structure. So, we use light weight material to desire the strength. There are different parameters involved in this structure i.e cell size, sheet thickness and core height. In this project we considered 3 level of comparison among the 3 different parameters cell size of 4, 6 and 8 mm, sheet thickness of 0.3, 0.5 and 0.7 mm, and core height of 20,25 and 30 mm. In order to reduce the number of experiment we use taguchi design of experiment, and we select the L8 orthogonal array is the best array for this type of situation, which clearly identifies the parameters by independent of material weight to support this we add the minitab software, to identify the main effective plots and regression equation which involves the individual response and corresponding parameters. Aluminium material is used for the fabrication of Honeycomb sandwich structure among the various grades of aluminium we consider the AL6061 which is light weight material

  18. Intrinsic embedded sensors for polymeric mechatronics: flexure and force sensing.

    Science.gov (United States)

    Jentoft, Leif P; Dollar, Aaron M; Wagner, Christopher R; Howe, Robert D

    2014-02-25

    While polymeric fabrication processes, including recent advances in additive manufacturing, have revolutionized manufacturing, little work has been done on effective sensing elements compatible with and embedded within polymeric structures. In this paper, we describe the development and evaluation of two important sensing modalities for embedding in polymeric mechatronic and robotic mechanisms: multi-axis flexure joint angle sensing utilizing IR phototransistors, and a small (12 mm), three-axis force sensing via embedded silicon strain gages with similar performance characteristics as an equally sized metal element based sensor.

  19. Intrinsic Embedded Sensors for Polymeric Mechatronics: Flexure and Force Sensing

    Directory of Open Access Journals (Sweden)

    Leif P. Jentoft

    2014-02-01

    Full Text Available While polymeric fabrication processes, including recent advances in additive manufacturing, have revolutionized manufacturing, little work has been done on effective sensing elements compatible with and embedded within polymeric structures. In this paper, we describe the development and evaluation of two important sensing modalities for embedding in polymeric mechatronic and robotic mechanisms: multi-axis flexure joint angle sensing utilizing IR phototransistors, and a small (12 mm, three-axis force sensing via embedded silicon strain gages with similar performance characteristics as an equally sized metal element based sensor.

  20. Long wavelength gravity anomalies over India: Crustal and lithospheric structures and its flexure

    Science.gov (United States)

    Tiwari, V. M.; Ravi Kumar, M.; Mishra, D. C.

    2013-07-01

    crustal thicknesses under the Vindhyan and the Ganga basins are attributed to the lithospheric flexure of the Indian plate due to Himalaya. Crustal bulge due to lithospheric flexure is well reflected in isostatic Moho based on flexural model of average effective elastic thickness of ˜40 km. Lithospheric flexure causes high heat flow that is aided by large crustal scale fault system of mobile belts and their extensions northwards in this section, which may be responsible for lower crustal bulk density in the northern part. A low density and high thermal regime in north India north of the SMB compared to south India, however does not conform to the high S-wave velocity in the northern part and thus it is attributed to changes in composition between the northern and the southern parts indicating a reworked lithosphere. Some of the long wavelength gravity anomalies along the east and the west coasts of India are attributed to the intrusives that caused the breakup of India from Antarctica, and Africa, Madagascar and Seychelles along the east and the west coasts of India, respectively.

  1. Flexure bearing compressor in the one watt linear (OWL) envelope

    Science.gov (United States)

    Rühlich, I.; Mai, M.; Wiedmann, Th.; Rosenhagen, C.

    2007-04-01

    For high performance IR detectors the split linear cooler is a preferred solution. High reliability, low induced vibration and low audible noise are major benefits of such coolers. Today, most linear coolers are qualified for MTTF of 8,000h or above. It is a strong customer desire to further reduce the maintenance costs on system level with significantly higher cooler lifetime. Increased cooler MTTF figures are also needed for IR applications with high lifetime requirements like missile warning applications, border surveillance or homeland security applications. AIM developed a Moving Magnet Flexure Bearing compressor to meet a MTTF of minimum 20,000h. The compressor has a full flexure bearing support on both sides of the driving mechanism. In the assembly process of the compressor an automated alignment process is used to achieve the necessary accuracy. Thus, side-forces on the pistons are minimized during operation, which significantly reduces the wear-out. In order to reduce the outgassing potential most of the internal junctions are welded and the use of all non-metallic components is minimized. The outline dimensions comply with the SADA2 requirements in length and diameter. Further, when operated with a 1/2" SADA type coldfinger, the cooler meets all specified performance data for SADA2. The compressor can be combined with different Stirling type coldfingers and also with the AIM Pulse Tube coldfinger, which gives increased lifetime potential up to 50,000h MTTF. Technical details and performance data of the new compressor are shown.

  2. Flexural Strength of Functionally Graded Nanotube Reinforced Sandwich Spherical Panel

    Science.gov (United States)

    Mahapatra, Trupti R.; Mehar, Kulmani; Panda, Subrata K.; Dewangan, S.; Dash, Sushmita

    2017-02-01

    The flexural behaviour of the functionally graded sandwich spherical panel under uniform thermal environment has been investigated in the present work. The face sheets of the sandwich structure are made by the functionally graded carbon nanotube reinforced material and the core face is made by the isotropic and homogeneous material. The material properties of both the fiber and matrix are assumed to be temperature dependent. The sandwich panel model is developed in the framework of the first order shear deformation theory and the governing equation of motion is derived using the variational principle. For the discretization purpose a suitable shell element has been employed from the ANSYS library and the responses are computed using a parametric design language (APDL) coding. The performance and accuracy of the developed model has been established through the convergence and validation by comparing the obtained results with previously published results. Finally, the influence of different geometrical parameters and material properties on the flexural behaviour of the sandwich spherical panel in thermal environment has been investigated through various numerical illustrations and discussed in details.

  3. Investigation of the elastic modulus, tensile and flexural strength of five skull simulant materials for impact testing of a forensic skin/skull/brain model.

    Science.gov (United States)

    Falland-Cheung, Lisa; Waddell, J Neil; Chun Li, Kai; Tong, Darryl; Brunton, Paul

    2017-04-01

    Conducting in vitro research for forensic, impact and injury simulation modelling generally involves the use of a skull simulant with mechanical properties similar to those found in the human skull. For this study epoxy resin, fibre filled epoxy resin, 3D-printing filaments (PETG, PLA) and self-cure acrylic denture base resin were used to fabricate the specimens (n=20 per material group), according to ISO 527-2 IBB and ISO20795-1. Tensile and flexural testing in a universal testing machine was used to measure their tensile/flexural elastic modulus and strength. The results showed that the epoxy resin and fibre filled epoxy resin had similar tensile elastic moduli (no statistical significant difference) with lower values observed for the other materials. The fibre filled epoxy resin had a considerably higher flexural elastic modulus and strength, possibly attributed to the presence of fibres. Of the simulants tested, epoxy resin had an elastic modulus and flexural strength close to that of mean human skull values reported in the literature, and thus can be considered as a suitable skull simulant for a skin/skull/brain model for lower impact forces that do not exceed the fracture stress. For higher impact forces a 3D printing filament (PLA) may be a more suitable skull simulant material, due to its closer match to fracture stresses found in human skull bone. Influencing factors were also anisotropy, heterogeneity and viscoelasticity of human skull bone and simulant specimens. Copyright © 2017 Elsevier Ltd. All rights reserved.

  4. Tailoring of fiber-reinforced cementitious composites (FRCC) for flexural strength and reliability

    Science.gov (United States)

    Obla, Karthikeyan Hariya

    models. In Part II of the thesis an investigation on the use of fibers for reduction of MOR variability of cementitious materials is reported. Specifically, the concept of lowering the sensitivity of MOR to flaw size based on fiber bridging is confirmed with experimental studies of flexural strength of mesh reinforced mortar beams. Variability of composite properties due to variability introduced by fiber itself was identified, and techniques in controlling such variability were introduced. In this connection, the influence of viscosity of the fresh mix on fiber dispersion uniformity was investigated.

  5. Fatigue behavior of dental resin composites: flexural fatigue in vitro versus 6 years in vivo

    NARCIS (Netherlands)

    Garcia-Godoy, F.; Frankenberger, R.; Lohbauer, U.; Feilzer, A.J.; Krämer, N.

    2012-01-01

    Objectives: To evaluate fatigue behavior of direct resin composite restorations (Tetric Ceram vs. Grandio) in vitro and in vivo over an observation period of 6 years. Methods: For the in vitro part, Young's moduli (YM) were calculated and both initial (FS: flexural strength) and fatigue flexural

  6. A comparison of flexural strengths of polymer (SBR and PVA modified, roller compacted concrete

    Directory of Open Access Journals (Sweden)

    John N. Karadelis

    2015-09-01

    Full Text Available This brief article aims to reveal the flexural performance, including the equivalent flexural strength of PVA (Polyvinyl Alcohol modified concrete by comparing it primarily with that of SBR (Styrene Butadiene Rubber concrete. This data article is directly related to Karadelis and Lin [6].

  7. A comparison of flexural strengths of polymer (SBR and PVA) modified, roller compacted concrete.

    Science.gov (United States)

    Karadelis, John N; Lin, Yougui

    2015-09-01

    This brief article aims to reveal the flexural performance, including the equivalent flexural strength of PVA (Polyvinyl Alcohol) modified concrete by comparing it primarily with that of SBR (Styrene Butadiene Rubber) concrete. This data article is directly related to Karadelis and Lin [6].

  8. A comparison of flexural strengths of polymer (SBR and PVA) modified, roller compacted concrete

    OpenAIRE

    Karadelis, John N.; Lin, Yougui

    2015-01-01

    This brief article aims to reveal the flexural performance, including the equivalent flexural strength of PVA (Polyvinyl Alcohol) modified concrete by comparing it primarily with that of SBR (Styrene Butadiene Rubber) concrete. This data article is directly related to Karadelis and Lin [6].

  9. The influence of resin flexural modulus on the magnitude of ceramic strengthening.

    LENUS (Irish Health Repository)

    Fleming, Garry J P

    2012-07-01

    The aim was to determine the magnitude of ceramic resin-strengthening with resin-based materials with varying flexural moduli using a regression technique to assess the theoretical strengthening at a \\'zero\\' resin-coating thickness. The hypothesis tested was that experimentally, increasing resin flexural modulus results in increased resin-strengthening observed at a theoretical \\'zero\\' resin-coating thickness.

  10. Fatigue behavior of dental resin composites: flexural fatigue in vitro versus 6 years in vivo

    NARCIS (Netherlands)

    F. Garcia-Godoy; R. Frankenberger; U. Lohbauer; A.J. Feilzer; N. Krämer

    2012-01-01

    Objectives: To evaluate fatigue behavior of direct resin composite restorations (Tetric Ceram vs. Grandio) in vitro and in vivo over an observation period of 6 years. Methods: For the in vitro part, Young's moduli (YM) were calculated and both initial (FS: flexural strength) and fatigue flexural str

  11. A Symbolic Formulation for Analytical Compliance Analysis and Synthesis of Flexure Mechanisms.

    Science.gov (United States)

    Su, Hai-Jun; Shi, Hongliang; Yu, Jingjun

    2012-05-01

    This paper presents a symbolic formulation for analytical compliance analysis and synthesis of flexure mechanisms with serial, parallel, or hybrid topologies. Our approach is based on the screw theory that characterizes flexure deformations with motion twists and loadings with force wrenches. In this work, we first derive a symbolic formulation of the compliance and stiffness matrices for commonly used flexure elements, flexure joints, and simple chains. Elements of these matrices are all explicit functions of flexure parameters. To analyze a general flexure mechanism, we subdivide it into multiple structural modules, which we identify as serial, parallel, or hybrid chains. We then analyze each module with the known flexure structures in the library. At last, we use a bottom-up approach to obtain the compliance/stiffness matrix for the overall mechanism. This is done by taking appropriate coordinate transformation of twists and wrenches in space. Four practical examples are provided to demonstrate the approach. A numerical example is employed to compare analytical compliance models against a finite element model. The results show that the errors are sufficiently small (2%, compared with finite element (FE) model), if the range of motion is limited to linear deformations. This work provides a systematical approach for compliance analysis and synthesis of general flexure mechanisms. The symbolic formulation enables subsequent design tasks, such as compliance synthesis or sensitivity analysis.

  12. Infectious haematopoietic necrosis virus: Chapter 2

    Science.gov (United States)

    Leong, Jo-Ann; Kurath, Gael

    2017-01-01

    Infectious haematopoietic necrosis virus (IHNV) is a Rhabdovirus that causes significant disease in Pacific salmon (Oncorhynchus spp.), Atlantic salmon (Salmo salar), and rainbow and steelhead trout (O. mykiss). IHNV causes necrosis of the haematopoietic tissues, and consequently it was named infectious haematopoietic necrosis. This virus is waterborne and may transmit horizontally and vertically through virus associated with seminal and ovarian fluids. The clinical signs of disease and diagnosis; pathology; pathophysiology; and control strategies against IHNV are discussed.

  13. Totally robotic single-position 'flip' arm technique for splenic flexure mobilizations and low anterior resections.

    Science.gov (United States)

    Obias, Vincent; Sanchez, Caroline; Nam, Arthur; Montenegro, Grace; Makhoul, Rami

    2011-06-01

    Using the da Vinci robot in low anterior resection (LAR) has not been widely adopted due to limited range of motion of the robotic arms and the need to move the robot during operations. Our technique uses all three arms for both the splenic flexure and the pelvis, but with only one docking position. The robot is placed to the left of the patient. The camera port is 3 cm to the right of the umbilicus. Arm 1 is placed in the RLQ. Arm 2 is placed midepigastric. Arm 3 is placed in the LLQ. Arm 3 starts off on the left side of the robot, on the same side as Arm 1 aimed cephalad. During mobilization of colon and splenic flexure, Arms 2 and 3 help retract the colon while Arm 1 dissects. Our pelvic dissection begins with Arm 3 "flipped" to the right side of the robot and redocked to the same left sided port aimed caudally. The robot does not need to be repositioned and the patient does not need to be moved. The pelvic dissection can now be done in the standard fashion. Our early experience includes four patients: two LARs and two left hemicolectomies. Mean operative time = 347 minutes, docking time = 20 minutes, and robotic surgical time = 195 minutes. Two complications occurred: post-operative ileus and high ostomy output. Mean LOS = 5. The robotic "flip" arm technique allows the surgeon to fully utilize all the robotic arms in LAR, which is unique versus other techniques. Copyright © 2011 John Wiley & Sons, Ltd.

  14. Flexural Behavior of Continuous Bubbled Reinforced Reactive Powder Concrete Flat Slab

    Directory of Open Access Journals (Sweden)

    Mohammad Redha K. Mahmood

    2017-05-01

    Full Text Available This paper presents an experimental investigation on flexural behavior of continuous bubbled reinforced Reactive Powder Concrete (RPC flat slabs. Bubbled slab is one of the various types of voided slabs. It consist of bubbles placed inside a concrete slab which will reduce the self-weight of the structure by about 35% (Tina Lai 2009. On the other hand, using RPC make it possible for structural member to have smaller dimensions due to the great strength of this type of concrete. In this study these two method are used to increase the building spaces dimensions by reducing self-weigh of the structure by using bubbled slabs and to decrease the structural members' dimensions by using RPC have been investigated together. To study the flexural behavior of continuous bubbled flat slabs such as the ultimate load carrying capacity, central deflection and slabs crack pattern at the ultimate load, seven types of slabs were tested. The parameters of the study were type of concrete (RPC and Normal Concrete (NC, bubbles diameter to slab thickness ratio (D/t of (0.6 and 0.7, type of loading (distributed and line load and solid slab. The test results show that the crack pattern and ultimate load capacity as well as maximum deflection depends on all of the mentioned parameters, were by increasing (D/t ratio the ultimate load capacity increases about (7.36%, 5.46% and 16.52% for RPC slabs under distributed load, line load and NC slabs, respectively. The solid slab increases the ultimate load about (4.05% compare to bubbled slab. Also, the line load decreases the ultimate load compare to distributed load by (3.45-5.16% for different (D/t ratio, and using the NC also decreases the ultimate load compare to RPC by (48-52.13% for different (D/t ratio

  15. RENAL PAPYLAR NECROSIS - RADIOLOGICAL PRESENTATION

    Directory of Open Access Journals (Sweden)

    Rade R. Babic

    2003-10-01

    Full Text Available Renal papylar necrosis is rare disease. It is diagnosed by intravenous urography. Radio-logical presentation is patognomonical: necrotis focus of the papila, on the urogram is visualised as a punctiformne, blot spot of the iodine contrast, or the depots of the iodine contrast are spread from the edge of fornix to the renal medulla as a ribbon-like or needle-shaped formations, apear-ing in a late phase of illness like a crebs legs or feeler, sometimes convergning in the oreol or in ring-shaped formation, while necrotic sequestar is resorbed formating the cavity filled by iodine contrast, which has trigonal shape with the lateral basis, or necrotican sequestar can be removed with the channel system obstruction, presenting with the picture of ureterohydronephrosis, caused by the organic concrement. In the late stadium of the desease necrotic cavity can present with calcified wall and it can be diagnoses also at the native radiogram of the urotract.

  16. Flexure fatigue testing of 90 deg graphite/epoxy composites

    Science.gov (United States)

    Peck, Ann Nancy W.

    1995-01-01

    A great deal of research has been performed characterizing the in-plane fiber-dominated properties, under both static and fatigue loading, of advanced composite materials. To the author's knowledge, no study has been performed to date investigating fatigue characteristics in the transverse direction. This information is important in the design of bonded composite airframe structure where repeated, cyclic out-of-plane bending may occur. Recent tests characterizing skin/stringer debond failures in reinforced composite panels where the dominant loading in the skin is flexure along the edge of the frame indicate failure initiated either in the skin or else the flange, near the flange tip. When failure initiated in the skin, transverse matrix cracks formed in the surface skin ply closest to the flange and either initiated delaminations or created matrix cracks in the next lower ply, which in turn initiated delaminations. When failure initiated in the flanges, transverse cracks formed in the flange angle ply closest to the skin and initiated delamination. In no configuration did failure propagate through the adhesive bond layer. For the examined skin/flange configurations, the maximum transverse tension stress at failure correlates very well with the transverse tension strength of the composites. Transverse tension strength (static) data of graphite epoxy composites have been shown to vary with the volume of material stressed. As the volume of material stressed increased, the strength decreased. A volumetric scaling law based on Weibull statistics can be used to predict the transverse strength measurements. The volume dependence reflects the presence of inherent flaws in the microstructure of the lamina. A similar approach may be taken to determine a volume scale effect on the transverse tension fatigue behavior of graphite/epoxy composites. The objective of this work is to generate transverse tension strength and fatigue S-N characteristics for composite materials using

  17. Experimental and theoretical assessment of flexural properties of hybrid natural fibre composites

    DEFF Research Database (Denmark)

    Raghavalu Thirumalai, Durai Prabhakaran; Toftegaard, Helmuth Langmaack; Markussen, Christen Malte

    2014-01-01

    The concept of hybridization of natural fibre composites with synthetic fibres is attracting increasing scientific attention. The present study addresses the flexural properties of hybrid flax/glass/epoxy composites to demonstrate the potential benefits of hybridization. The study covers both...... experimental and theoretical assessments. Composite laminates with different hybrid fibre mixing ratios and different layer configurations were manufactured, and their volumetric composition and flexural properties were measured. The relationship between volume fractions in the composites is shown to be well...... predicted as a function of the hybrid fibre mixing ratio. The flexural modulus of the composites is theoretically assessed by using micromechanical models and laminate theory. The model predictions are compared with the experimentally determined flexural properties. Both approaches show that the flexural...

  18. Effect of Anatase Titanium Dioxide Nanoparticles on the Flexural Strength of Heat Cured Poly Methyl Methacrylate Resins: An In-Vitro Study.

    Science.gov (United States)

    Nazirkar, Girish; Bhanushali, Shilpa; Singh, Shailendra; Pattanaik, Bikash; Raj, Naveen

    2014-12-01

    Poly methyl methacrylate (PMMA) resin is the most widely used material for fabrication of dentures since 1937 as it exhibits adequate physical, mechanical and esthetic properties. But one of the major problems faced using this material is that, it is highly prone to plaque accumulation due to surface porosities and its food retentive properties. This in turn increases the bacterial activity causing denture stomatitis. In efforts to impart antimicrobial property to these resins, various nanoparticles (NP) have been incorporated viz. Silver, Zirconia oxide, Titanium dioxide (TiO2), Silica dioxide (SiO2) etc. However, as additives they can affect the mechanical properties of the final product. Therefore, the aim of the present study was to evaluate and compare the effect of different concentration of TiO2 NP on the flexural strength of PMMA resins. Specimens made from heat polymerizing resin (DPI) without NP were used as a control group (Group A). The two experimental groups, (Group B and Group C) had 0.5 and 1 % concentration of TiO2 NP respectively. The specimens were stored in 37 °C distilled water for 50 ± 2 h. A three-point bending test for flexural strength measurement was conducted following ADA specification no. 12. The maximum mean flexural strength (90.65 MPa) belonged to the control group; and acrylic resin with 1 % TiO2 NP demonstrated the minimum mean flexural strength (76.38 MPa). But, the values of all the three groups exceeded the ADA Specification level of 65 MPa. Conclusion may be drawn from the present study that addition of TiO2 NP into acrylic resin can adversely affect the flexural strength of the final product and is directly proportional to the concentration of NP.

  19. Ice-Shelf Tidal Flexure and Subglacial Pressure Variations

    Science.gov (United States)

    Walker, Ryan T.; Parizek, Byron R.; Alley, Richard B.; Anandakrishnan, Sridhar; Riverman, Kiya L.; Christianson, Knut

    2013-01-01

    We develop a model of an ice shelf-ice stream system as a viscoelastic beam partially supported by an elastic foundation. When bed rock near the grounding line acts as a fulcrum, leverage from the ice shelf dropping at low tide can cause significant (approx 1 cm) uplift in the first few kilometers of grounded ice.This uplift and the corresponding depression at high tide lead to basal pressure variations of sufficient magnitude to influence subglacial hydrology.Tidal flexure may thus affect basal lubrication, sediment flow, and till strength, all of which are significant factors in ice-stream dynamics and grounding-line stability. Under certain circumstances, our results suggest the possibility of seawater being drawn into the subglacial water system. The presence of sea water beneath grounded ice would significantly change the radar reflectivity of the grounding zone and complicate the interpretation of grounded versus floating ice based on ice-penetrating radar observations.

  20. [Splenic flexure and irritable colon syndromes: conjugate conditions].

    Science.gov (United States)

    Osipenko, M F; Bikbulatova, E A; Mut-Gusaim, V I

    2008-01-01

    To investigate phenotypical and clinical characteristics in individuals with high fixation of the splenic angle (HFSA). The study group included 82 patients with HFSA, the comparison group--76 patients with irritable colon syndrome (ICS), control group--19 patients without colon pathology. the results of the following examinations were analysed: the disease history, detailed intestinal investigation, rectal sensitivity, constitution, connective tissue weakness, vegetative dysfunction and regulation. HFSA is encountered mainly in persons with hyperstenic constitution. Some HFSA patients have pain on the left side--splenic flexure syndrome (SFS). The pain corresponds most to clinical criteria of irritable colon syndrome diagnosis and is accompanied with reduced threshold of pain sensitivity to balloon extension. Provoking factors of the symptoms are stress situations in childhood. SFS can be considered as a variant of ICS arising in HFSA. The treatment should be based on the principles of ICS treatment.

  1. The LINC-NIRVANA fringe and flexure tracker control system

    Science.gov (United States)

    Rost, Steffen; Eckart, Andreas; Horrobin, Matthew; Lindhorst, Bettina; Rauch, Christoph; Smajic, Semir; Straubmeier, Christian; Tremou, Evangelia; Wank, Imke; Zuther, Jens; Pott, Jörg-Uwe

    2012-07-01

    We present the latest status of the control system of the LN (LINC-NIRVANA) FFTS (Fringe and Flexure Tracker System) for the LBT. The software concept integrates the sensor data and control of the various subsystems and provides the interaction with the whole LN instrument. Varying conditions and multiple configurations for observations imply a flexible interconnection of the control loops for the hardware manipulators with respect to the time-critical data analysis of the fringe detection. In this contribution details of the implementation of the algorithms on a real-time Linux PC are given. By considering the results from simulations of the system dynamics, lab experiments, atmospheric simulations, and telescope characterization the optimal parameter setup for an observation can be chosen and basic techniques for adaption to changing conditions can be derived.

  2. Free flexural vibration of functionally graded size-dependent nanoplates

    CERN Document Server

    Natarajan, S; Thangavel, M

    2012-01-01

    In this paper, the linear free flexural vibration behaviour of functionally graded (FG) size-dependent nanoplates are investigated using the finite element method. The field variables are approximated by non-uniform rational B-splines. The size-dependent FG nanoplate is investigated by using Eringen's differential form of nonlocal elasticity theory. The material properties are assumed to vary only in the thickness direction and the effective properties for FG nanoplate are computed using Mori-Tanaka homogenization scheme. The accuracy of the present formulation is tested considering the problems for which solutions are available. A detailed numerical study is carried out to examine the effect of material gradient index, the characteristic internal length, the plate thickness, the plate aspect ratio and the boundary conditions on the global response of FG nanoplate.

  3. Flexural Behavior of Posttensioned Flat Plates Depending on Tendon Layout

    Directory of Open Access Journals (Sweden)

    Min Sook Kim

    2016-01-01

    Full Text Available This paper discusses the experimental results on the flexural behavior and deflections of posttensioned concrete flat plates depending on tendon layout. One reinforced concrete flat plate and two posttensioned concrete flat plates were manufactured and tested. One-way posttensioning layout and two-way posttensioning layout were considered in this paper. The load-deflection behavior and modes of crack are presented from the test results. Posttension systems effectively controlled crack and deflection. One-way and two-way posttensioning layouts both showed similar maximum load. However, serviceability improved with two-way posttensioning layout compared to one-way posttensioning layout. Also, the yield-line theory was applied to predict the ultimate load for the posttensioned flat plates. The comparison between the test results and estimation by yield-line analysis generally showed good agreement.

  4. CT Scan Mapping of Splenic Flexure in Relation to Spleen and its Clinical Implications.

    Science.gov (United States)

    Saber, Alan A; Dervishaj, Ornela; Aida, Samer S; Christos, Paul J; Dakhel, Mahmoud

    2016-05-01

    Splenic flexure mobilization is a challenging step during left colon resection. The maneuver places the spleen at risk for injury. To minimize this risk, we conducted this study for CT scan mapping of splenic flexure in relation to the spleen. One hundred and sixty CT scans of abdomen were reviewed. The level of the splenic flexure was determined in relation to hilum and lower pole of spleen. These levels were compared with patient demographics. Statistical analysis was performed using Fisher's exact test. The splenic flexure was above the hilum of the spleen in 95 patients (67.86%), at the splenic hilum level in 11 patents (7.88%), between the hilum and lower pole of the spleen in 12 (8.57%), at the lower pole of the spleen in 15 (10.7%) patients and 7 (5%) patients has a splenic flexure that lied below the lower pole of the spleen. Patient demographics showed no statistical significance in regard to splenic flexure location. Splenic flexure lies above the hilum of the spleen in majority of patients. This should be considered as part of operative strategies for left colon resection.

  5. Comparative study of flexural strength test methods on CAD/CAM Y-TZP dental ceramics

    Science.gov (United States)

    Xu, Yongxiang; Han, Jianmin; Lin, Hong; An, Linan

    2015-01-01

    Clinically, fractures are the main cause of computer-aided design and computer-aided manufacturing (CAD/CAM) 3 mol%-yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) all-ceramic dental restorations failure because of repetitive occlusal loading. The goal of this work is to study the effect of test methods and specimen’s size on the flexural strength of five ceramic products. Both bi-axial flexure test (BI) and uni-axial flexure tests (UNI), including three-point flexure test (3PF) and four-point flexure test (4PF), are used in this study. For all five products, the flexural strength is as follows: BI > 3PF > 4PF. Furthermore, specimens with smaller size (3PF-s) have higher values than the bigger ones (3PF). The difference between BI and UNI resulted from the edge flaws in ceramic specimens. The relationship between different UNI (including 3PF-s, 3PF and 4PF) can be explained according to Weibull statistical fracture theory. BI is recommended to evaluate the flexural strength of CAD/CAM Y-TZP dental ceramics. PMID:26816646

  6. NANO-BEARING: THE DESIGN OF A NEW TYPE OF AIR BEARING WITH FLEXURE STRUCTURE

    Institute of Scientific and Technical Information of China (English)

    KO Pui Hang; DU Ruxu

    2007-01-01

    A new type of air bearing with flexure structure is introduced. The new bearing is designed for precision mechanical engineering devices such as mechanical watch movement. The new design uses the flexure structure to provide 3D damping to absorb shocks from all directions. Two designs are presented: one has 12 T-shape slots in the radian direction while the other has 8 spiral slots in the radian direction. Both designs have flexure mountings on the axial directions. Based on the finite element analysis (FEA), the new bearing can reduce the vibration (displacement) by as much as 8.37% and hence, can better protect the shafts.

  7. Controlling thermal and electrical properties of graphene by strain-engineering its flexural phonons

    Science.gov (United States)

    Conley, Hiram; Nicholl, Ryan; Bolotin, Kirill

    2014-03-01

    We explore the effects of flexural phonons on the thermal and electrical properties of graphene. To control the amplitude of flexural phonons, we developed a technique to engineer uniform mechanical strain between 0 and 1% in suspended graphene. We determine the level of strain, thermal conductivity and carrier mobility of graphene through a combination of mechanical resonance and electrical transport measurements. Depending on strain, we find significant changes in the thermal expansion coefficient, thermal conductivity, and carrier mobility of suspended graphene. These changes are consistent with the expected contribution of flexural phonons.

  8. Geometrical design parameters for journal bearings with flexure pads and compliant liners

    DEFF Research Database (Denmark)

    Thomsen, Kim; Klit, Peder

    2012-01-01

    A hydrodynamic journal bearing utilizing flexure pads with a compliant liner is studied and its performance enhanced through a parametric study. The main geometrical dimensions are varied and the affect on pad performance is analyzed. This will put more knowledge into the design and function...... of flexure pads. uidelines are given to the design of the pads and are also covering the polymer liner. It is found that the use of flexure pads is an attractive alternative to pivoted pads. Pivot contact-related failure modes are eliminated and load capacity is not restricted by the force that can...

  9. EFFECT OF NANOPOWDER ADDITION ON THE FLEXURAL STRENGTH OF ALUMINA CERAMIC - A WEIBULL MODEL ANALYSIS

    Directory of Open Access Journals (Sweden)

    Daidong Guo

    2016-05-01

    Full Text Available Alumina ceramics were prepared either with micrometer-sized alumina powder (MAP or with the addition of nanometer-sized alumina powder (NAP. The density, crystalline phase, flexural strength and the fracture surface of the two ceramics were measured and compared. Emphasis has been put on the influence of nanopowder addition on the flexural strength of Al₂O₃ ceramic. The analysis based on the Weibull distribution model suggests the distribution of the flexural strength of the NAP ceramic is more concentrated than that of the MAP ceramic. Therefore, the NAP ceramics will be more stable and reliable in real applications.

  10. Detection of disbonds in foam composite assemblies using flexural waves and shearography

    Science.gov (United States)

    Lamboul, B.; Giraudo, O.; Osmont, D.

    2015-03-01

    This paper presents a method based on the generation of low frequency flexural waves for the detection of disbonds in foam composite assemblies. An imaging procedure based on the shearography technique is proposed for the fast generation of images suitable for nondestructive testing analysis. The method is assessed with calibrated disbond defects in a composite foam core sandwich. The role of local flexural resonances for obtaining clear defect signatures is studied and highlighted using complementary Laser vibrometry data. The minimum defect size for detection is associated with the conditions for exciting the first flexural mode in the defect region.

  11. Prediction of Flexural Strength of Concretes Containing Silica Fume and Styrene-Butadiene Rubber (SBR) with an Empirical Model

    Science.gov (United States)

    Shafieyzadeh, M.

    2015-12-01

    In the flexural test, the theoretical maximum tensile stress at the bottom fiber of a test beam is known as the modulus of rupture or flexural strength. This work deals with the effects of Silica Fume and Styrene-Butadiene Latex (SBR) on flexural strength of concrete. An extensive experimentation was carried out to determine the effects of silica fume and SBR on flexural strength of concrete. Two water-binder ratios and several percentages of silica fume and SBR were considered. Abrams' Law, which was originally formulated for conventional concrete containing cement as the only cementations material, is used for prediction of flexural strength of these concretes. The aim of this work is to construct an empirical model to predict the flexural strength of silica fume-SBR concretes using concrete ingredients and time of curing in water. Also, the obtained results for flexural strength tests have been compared with predicted results.

  12. Gravity-based model for regional flexure induced by crustal loading by the 14-km-thick Mississippi delta

    Science.gov (United States)

    Ajala, R. A.; Mann, P.

    2016-12-01

    We used gravity data constrained by deep-penetration seismic reflection lines to determine the crustal structure beneath the Mississippi delta, the seventh-largest deltaic accumulation on Earth. The observed gravity anomaly at the margin consist of a high of 50 mGal over the shelf with a low of -27 mGal at a landward distance of 250 km, a low of -18 mGal at a seaward distance of 136 km, and another high of 23 mGal at a seaward distance of 178 km from the shelf edge. The gravity high is centered over the thickest part of the delta, much of which has been deposited since the Miocene. The elastic thickness of the underlying crust is estimated by comparing the amplitude and wavelength of the observed gravity anomaly to the predicted anomaly based on simple elastic plate models. The process-oriented gravity modeling approach has been used to flexurally backstrip the sediments and add the present-day water depth to obtain the total tectonic subsidence (TTS). The gravity effect due to the initial rift structure obtained from the TTS known as the "rifting anomaly" and sediment loading called the "sedimentation anomaly" are used to compute the present-day gravity anomaly. The best fit result is for a margin which sediments were deposited on thinned transitional crust with an elastic thickness of 48 km. Results from flexural modeling show that top of basement has been flexed up to 8 km over a lateral distance of more than 500 km by the deltaic load. The map-view shape of the uplifted rim with a predicted, maximum topographic expression of 40 m is egg-shaped with its northern, more narrow tip crossing the Mississippi Valley near Memphis, its northwestern part running parallel to the northern Ouachita Mountains, its western part tracking parallel to the Mexia-Balcones fault system of Texas, and its eastern edge parallel to the west coast of Florida. While the overall magnitude of the topographic flexure is low, delta-related flexure may have contributed to the Miocene

  13. Acute Necrotizing Esophagitis Followed by Duodenal Necrosis.

    Science.gov (United States)

    Del Hierro, Piedad Magdalena

    2011-12-01

    Acute Necrotizing Esophagitis is an uncommon pathology, characterized by endoscopic finding of diffuse black coloration in esophageal mucosa and histological presence of necrosis in patients with upper gastrointestinal bleeding. The first case of acute necrotizing esophagitis followed by duodenal necrosis, in 81 years old woman with a positive history of Type 2 Diabetes Mellitus, Hypertension, and usual intake of Nonsteroidal Anti-inflammatory drugs, is reported. Although its etiology remains unknown, the duodenal necrosis suggests that ischemia could be the main cause given that the branches off the celiac axis provide common blood supply to the distal esophageal and duodenal tissue. The massive gastroesophagic reflux and NSAID intake could be involved.

  14. Post-pancreatitis Fat Necrosis Mimicking Carcinomatosis.

    Science.gov (United States)

    Smith, Joshua P; Arnoletti, J Pablo; Varadarajulu, Shyam; Morgan, Desiree E

    2008-01-01

    Acute pancreatitis can result in retroperitoneal fat necrosis, typically occurring in the peripancreatic region, with extension into the transverse mesocolon, omentum and mesenteric root. When evaluated with contrast enhanced computed tomography (CECT), acute peripancreatic post necrotic collections typically become lower in attenuation over time, and often appear as homogeneous fluid collections. Saponification as a complication of fat necrosis in patients with acute pancreatitis is a well recognized clinical entity. While retroperitonal fat necrosis is commonly seen on CECT, saponification is not a prominent imaging feature. We present a case of acute pancreatitis complicated by extensive saponification of fat throughout the retroperitoneum and peritoneal lining, mimicking carcinomatosis.

  15. ROLE OF THE MITOCHONDRION IN PROGRAMMED NECROSIS

    Directory of Open Access Journals (Sweden)

    Christopher eBaines

    2010-11-01

    Full Text Available In contrast to the programmed nature of apoptosis and autophagy, necrotic cell death has always been believed to be a random, uncontrolled process that leads to the accidental death of the cell. This dogma, however, is being challenged and the concept of necrosis also being programmed is gaining ground. In particular, mitochondria appear to play a pivotal role in the mediation of programmed necrosis. The purpose of this review, therefore, is to appraise the current concepts regarding the signaling mechanisms of programmed necrosis, with specific attention to the contribution of mitochondria to this process.

  16. Influence of moisture absorption on the flexural properties of composites made of epoxy resin reinforced with low-content iron particles

    Indian Academy of Sciences (India)

    E SIDERIDIS; J VENETIS; E KYRIAZI; V KYTOPOULOS

    2017-08-01

    In this work, the effect of moisture absorption on the mechanical properties of particulate composite materials isstudied. Moisture absorption constitutes a main parameter affecting the thermomechanical behaviour of composites, since itcauses plasticization of the polymer matrix with a concurrent swelling. In the present work, the influence of water absorptionon the flexural properties of particle-reinforced composites was thoroughly investigated. It was found that during the processof moisture absorption there exists a variation of the flexural properties closely related to the degradation of the mechanicalbehaviour of the composite, as well as the percentage amount of moisture absorbed. Experiments were carried out withcomposite made of epoxy resin reinforced with low-content iron particles. The variation of ultimate stress, breaking strain,deflection, elastic modulus and Poisson ratio due to water absorption was examined.

  17. A case of spontaneous myocardial necrosis and cerebral ischemic lesions in a laboratory beagle dog.

    Science.gov (United States)

    Matsushita, Kohei; Kohara, Yukari; Ito, Yuko; Yoshikawa, Tsuyoshi; Sato, Makoto; Kitaura, Keisuke; Matsumoto, Satoshi

    2015-10-01

    A beagle dog treated with saline as a control animal in a preclinical study was euthanized due to sudden systemic deterioration. On histopathological examination, contraction band necrosis of myocardial cells was observed widely in the left ventricular wall, including the papillary muscle and apex, and observed slightly in the ventricular septum and left atrium. In the brain, necrosis was observed in neurons and glia of the cerebral cortex, hippocampal pyramidal cells, glial cells of the rostral commissure and Purkinje cells of the cerebellar vermis. It is highly probable that the marked systemic deterioration was caused by cardiac dysfunction due to the spontaneous contraction band necrosis of the myocardial cells, although the pathogenesis of the myocardial lesions remains unclear. Given the distribution of neuronal necrosis in the brain, it is likely that these lesions resulted from the ischemia responsible for acute cardiac failure.

  18. Pharm GKB: Acute necrosis of liver NOS [PharmGKB

    Lifescience Database Archive (English)

    Full Text Available MeSH: Massive Hepatic Necrosis (D047508) SnoMedCT: Acute necrosis of liver NOS (197273006) UMLS: C0001364 (C...000011090) Common Searches Search Medline Plus Search CTD Pharm GKB: Acute necrosis of liver NOS ...

  19. A colonic splenic flexure tumour presenting as an empyema thoracis: a case report.

    LENUS (Irish Health Repository)

    Murphy, K

    2009-01-01

    The case report describes the rare presentation of a 79-year-old patient with a locally perforated splenic flexure tumour of the colon presenting with an apparent empyema thoracis in the absence of abdominal signs or symptoms.

  20. Wear and flexural strength comparisons of alumina/feldspar resin infiltrated dental composites.

    Science.gov (United States)

    Le Roux, A R; Lachman, N; Walker, M; Botha, T

    2008-11-01

    Incorporating a feldspar chemical bond between alumina filler particles is expected to increase the wear-resistant and flexural strength properties. An investigation was carried out to evaluate the influence of the feldspar chemical bonding between alumina filler particles on wear and flexural strength of experimental alumina/feldspar dental composites. It was hypothesized that wear resistance and flexural strength would be significantly increased with increased feldspar mass. Alumina was chemically sintered and bonded with 30% and 60% feldspar mass, silanized and infiltrated with UDMA resin to prepare the dental restorative composite material. Higher wear-resistant characteristics resulted with increased feldspar mass of up to 60% (p 0.05). Feldspar chemical bonding between the alumina particles may improve on the wear-resistance and flexural strength of alumina/feldspar composites.

  1. Flexural Strength of Acrylic Resin Denture Bases Processed by Two Different Methods

    Directory of Open Access Journals (Sweden)

    Jafar Gharechahi

    2014-09-01

    Full Text Available Background and aims. The aim of this study was to compare flexural strength of specimens processed by conventional and injection-molding techniques. Materials and methods. Conventional pressure-packed PMMA was used for conventional pressure-packed and injection-molded PMMA was used for injection-molding techniques. After processing, 15 specimens were stored in distilled water at room temperature until measured. Three-point flexural strength test was carried out. Statistical analysis was carried out by SPSS using t-test. Statistical significance was defined at P<0.05. Results. Flexural strength of injection-polymerized acrylic resin specimens was higher than that of theconventional method (P=0.006. This difference was statistically significant (P=0.006. Conclusion. Within the limitations of this study, flexural strength of acrylic resin specimens was influenced by the mold-ing technique.

  2. ASYMPTOTIC ANALYSIS OF DYNAMIC PROBLEMS FOR LINEARLY ELASTICSHELLS JUSTIFICATION OF EQUATIONS FOR DYNAMIC FLEXURAL SHELLS

    Institute of Scientific and Technical Information of China (English)

    肖黎明

    2001-01-01

    Under certain conditions, starting from the three-dimensional dynamic equations of elastic shells the author gives the justification of dynamic equations of flexural shells by means of themethod of asymptotic analysis.

  3. Flexural strength of acrylic resin denture bases processed by two different methods.

    Science.gov (United States)

    Gharechahi, Jafar; Asadzadeh, Nafiseh; Shahabian, Foad; Gharechahi, Maryam

    2014-01-01

    Background and aims. The aim of this study was to compare flexural strength of specimens processed by conventional and injection-molding techniques. Materials and methods. Conventional pressure-packed PMMA was used for conventional pressure-packed and injection-molded PMMA was used for injection-molding techniques. After processing, 15 specimens were stored in distilled water at room temperature until measured. Three-point flexural strength test was carried out. Statistical analysis was carried out by SPSS using t-test. Statistical significance was defined at P<0.05. Results. Flexural strength of injection-polymerized acrylic resin specimens was higher than that of the conventional method (P=0.006). This difference was statistically significant (P=0.006). Conclusion. Within the limitations of this study, flexural strength of acrylic resin specimens was influenced by the molding technique.

  4. Stiffness Analysis of Corrugated Flexure Beam Used in Compliant Mechanisms

    Institute of Scientific and Technical Information of China (English)

    WANG Nianfeng; LIANG Xiaohe; ZHANG Xianmin

    2015-01-01

    Conventional flexible joints generally have limited range of motion and high stress concentration. To overcome these shortcomings, corrugated flexure beam(CF beam) is designed because of its large flexibility obtained from longer overall length on the same span. The successful design of compliant mechanisms using CF beam requires manipulation of the stiffnesses as the design variables. Empirical equations of the CF beam stiffness components, except of the torsional stiffness, are obtained by curve-fitting method. The application ranges of all the parameters in each empirical equation are also discussed. The ratio of off-axis to axial stiffness is considered as a key characteristic of an effective compliant joint. And parameter study shows that the radius of semi-circular segment and the length of straight segment contribute most to the ratio. At last, CF beam is used to design translational and rotational flexible joints, which also verifies the validity of the empirical equations. CF beam with large flexibility is presented, and empirical equations of its stiffness are proposed to facilitate the design of flexible joint with large range of motion.

  5. Polymerization Shrinkage and Flexural Modulus of Flowable Dental Composites

    Directory of Open Access Journals (Sweden)

    Janaína Cavalcanti Xavier

    2010-09-01

    Full Text Available Linear polymerization shrinkage (LPS, flexural strength (FS and modulus of elasticity (ME of low-viscosity resin composites (Admira Flow™, Grandio Flow™/VOCO; Filtek Z350 Flow™/3M ESPE; Tetric Flow™/Ivoclar-Vivadent was evaluated using a well-established conventional micro-hybrid composite as a standard (Filtek Z250™/3M ESPE. For the measurement of LPS, composites were applied to a cylindrical metallic mould and polymerized (n = 8. The gap formed at the resin/mould interface was observed using SEM (1500×. For FS and ME, specimens were prepared according to the ISO 4049 specifications (n = 10. Statistical analysis of the data was performed with one-way ANOVA and the Tukey test. The conventional resin presented significantly lower LPS associated with high FS and ME, but only the ME values of the conventional resin differed significantly from the low-viscosity composites. The relationship between ME and LPS of low-viscosity resin composites when used as restorative material is a critical factor in contraction stress relief and marginal leakage.

  6. CYCLIC TEMPERATURE LOADING RESIDUAL FLEXURAL STRENGHT OF REFRACTORY SLABS

    Directory of Open Access Journals (Sweden)

    Ondřej Holčapek

    2017-05-01

    Full Text Available This paper describes the effect of cyclic elevated temperature loading on refractory slabs made from high performance, fibre reinforced cement composite. Slabs were produced from aluminous cement-based composites, reinforced by different dosages of basalt fibres. The composite investigated in this study had self-compacting characteristics. The slabs used were exposed to different thermal loading – 600 °C, 1000 °C, six times applied 600 °C and 1000 °C. Then, flexural strength was investigated in all groups of slabs, including group reference slabs with no thermal loading. The results show that the appropriate combination of aluminous cement, natural basalt aggregate, fine filler and basalt fibres in dosage 1.00% of volume is able to successfully resist to cyclic temperature loading. Tensile strength in bending of these slabs (after cyclic temperature loading at 600 °C achieved 6.0 MPa. It was demonstrated that it is possible to use this composite for high extensive conditions in real industrial conditions.

  7. Moulding and shielding flexural waves in elastic plates

    Science.gov (United States)

    Antonakakis, T.; Craster, R. V.; Guenneau, S.

    2014-03-01

    Platonic crystals (PlCs) are the elastic plate analogue of the photonic crystals widely used in optics, and are thin structured elastic plates along which flexural waves cannot propagate within certain stop band frequency intervals. The practical importance of PlCs is twofold: These can be used either in the design of microstructured acoustic metamaterials or as an approximate model for surface elastic waves propagating in meter scale seismic metamaterials. Here, we make use of the band spectrum of PlCs created by an array of either very small or densely packed clamped circles to achieve surface wave reflectors at very large wavelengths, a flat lens, a waveguide effect, a directive antenna near the stop band frequencies. The limit in which the circles reduce to points is particularly appealing as there is an exact dispersion relation available so the origin of these phenomena can be explained and interpreted using Fourier series and high-frequency homogenization (HFH). We then enlarge the radius of clamped circles, which both makes the zero-frequency stop band up to five times wider and flattens the dispersion curves. Here, HFH notably captures the essence of localized modes, one of which appears in the zero-frequency stop band and is used in the design of a highly directive waveguide.

  8. Imaging Tumor Necrosis with Ferumoxytol.

    Directory of Open Access Journals (Sweden)

    Maryam Aghighi

    high T1 signal in areas of tumor necrosis and low signal in areas of intracellularly compartmentalized iron.Differential T1- and T2-enhancement patterns of USPIO in tumors enable conclusions about their intracellular and extracellular location. This information can be used to characterize the composition of the tumor microenvironment.

  9. Genetics of Infantile Bilateral Striatal Necrosis

    Directory of Open Access Journals (Sweden)

    J Gordon Millichap

    2006-09-01

    Full Text Available The gene mutation causing autosomal recessive infantile bilateral striatal necrosis (IBSN was identified in eight consanguineous Israeli Bedouin families, in a study at Schneider Children’s Medical Center, Petah Tikva, Israel, and other centers.

  10. Hypoplasia of exocrine pancreas with myocardial necrosis

    Institute of Scientific and Technical Information of China (English)

    Xiang Sheng Zhang; Xin Xiu Xu; Yan Zhang; Sbu Hua Wu

    2000-01-01

    AIM To study the clinical and pathological features of hypoplasia of exocrine pancreas with myocardialnecrosis.METHODS One ease of hypoplasia of exocrine pancreas with myocardial necrosis was autopsied. Theclinical signs and pathological changes were analyzed.RESULTS A 15-month-old boy with hypoplasia of exocrine pancreas was reported. The main clinicalfeatures were steatorrhea and marked underdevelopment. He died of acute heart failure afterhospitalization. Autopsy showed that there were aplasia of exocrine portion and fatty metaplasia ofpancreas, the myocardium revealed focal necrosis and sear formation.CONCLUSION Atrophy of exocrine pancreas and myocardial necrosis exist at the same time, suggestingthat there may be some relationship between them. It was likely that the damaged pancreatic tissue releasedsome active materials that may harm the myocardium or decrease pancreatic juice that results in lack ofnutrient and myocardial necrosis.

  11. Electron in the field of flexural vibrations of a membrane: Quantum time, magnetic oscillations, and coherence breaking

    Science.gov (United States)

    Gornyi, I. V.; Dmitriev, A. P.; Mirlin, A. D.; Protopopov, I. V.

    2016-08-01

    We have studied the motion of an electron in a membrane under the influence of flexural vibrations with a correlator that decreases upon an increase in the distance in accordance with the law r-2η. We have conducted a detailed consideration of the case with η < 1/2, in which the perturbation theory is inapplicable, even for an arbitrarily weak interaction. It is shown that, in this case, reciprocal quantum time 1/τ q is proportional to g 1/(1-η) T (2-η)/(2-2η), where g is the electron-phonon interaction constant and T is the temperature. The method developed here is applied for calculating the electron density of states in a magnetic field perpendicular to the membrane. In particular, it is shown that the Landau levels in the regime with ω c τ q » 1 have a Gaussian shape with a width that depends on the magnetic field as B η. In addition, we calculate the time τφ of dephasing of the electron wave function that emerges due to the interaction with flexural phonons for η < 1/2. It has been shown that, in several temperature intervals, quantity 1/τφ can be expressed by various power functions of the electron-phonon interaction constant, temperature, and electron energy.

  12. Influence of Specimen Preparation and Test Methods on the Flexural Strength Results of Monolithic Zirconia Materials

    OpenAIRE

    Christine Schatz; Monika Strickstrock; Malgorzata Roos; Daniel Edelhoff; Marlis Eichberger; Isabella-Maria Zylla; Bogna Stawarczyk

    2016-01-01

    The aim of this work was to evaluate the influence of specimen preparation and test method on the flexural strength results of monolithic zirconia. Different monolithic zirconia materials (Ceramill Zolid (Amann Girrbach, Koblach, Austria), Zenostar ZrTranslucent (Wieland Dental, Pforzheim, Germany), and DD Bio zx2 (Dental Direkt, Spenge, Germany)) were tested with three different methods: 3-point, 4-point, and biaxial flexural strength. Additionally, different specimen preparation methods wer...

  13. Influence of specimen preparation and test methods on the flexural strength results of monolithic zirconia materials

    OpenAIRE

    Schatz, Christine; Strickstrock, Monika; Roos, Malgorzata; Edelhoff, Daniel; Eichberger, Marlis; Zylla, Isabella-Maria; Stawarczyk, Bogna

    2016-01-01

    The aim of this work was to evaluate the influence of specimen preparation and test method on the flexural strength results of monolithic zirconia. Different monolithic zirconia materials (Ceramill Zolid (Amann Girrbach, Koblach, Austria), Zenostar ZrTranslucent (Wieland Dental, Pforzheim, Germany), and DD Bio zx2 (Dental Direkt, Spenge, Germany)) were tested with three different methods: 3-point, 4-point, and biaxial flexural strength. Additionally, different specimen preparation methods wer...

  14. Effects of forming processing conditions on the flexural properties of bagasse and bamboo plastic composites

    OpenAIRE

    2012-01-01

    The effects of processing conditions such as pressure, temperature, and holding time on the flexural properties of bagasse and bamboo biodegradable composites were investigated. Each sample of bagasse or bamboo was mixed with a corn-starch-based biodegradable resin and fabricated by a hot press forming method. The cross-sectional structure of the bagasse fiber was found to be porous and compressible, while that of bamboo was found to be more solid. The relationship between flexural strength, ...

  15. Blockage, trapping and waveguide modes for flexural waves in a semi-infinite double grating

    CERN Document Server

    Jones, Ian S; Movchan, Alexander B

    2015-01-01

    The paper presents a novel view on the scattering of a flexural wave in a Kirchhoff plate by a semi-infinite discrete system. Blocking and channelling of flexural waves are of special interest. A quasi-periodic two-source Green's function is used in the analysis of the waveguide modes. An additional "effective waveguide" approximation has been constructed. Comparisons are presented for these two methods in addition to an analytical solution for a finite truncated system.

  16. Modeling and analysis of circular flexural-vibration-mode piezoelectric transformer.

    Science.gov (United States)

    Huang, Yihua; Huang, Wei

    2010-12-01

    We propose a circular flexural-vibration-mode piezoelectric transformer and perform a theoretical analysis of the transformer. An equivalent circuit is derived from the equations of piezoelectricity and the Hamilton's principle. With this equivalent circuit, the voltage gain ratio, input impedance, and the efficiency of the circular flexural-vibration-mode piezoelectric transformer can be determined. The basic behavior of the transformer is shown by numerical results.

  17. The Flexural Behavior of Denture Base Reinforced by Different Contents of Ultrahigh-Modulus Polyethylene Fiber

    Institute of Scientific and Technical Information of China (English)

    XU Dong-xuan; CHENG Xiang-rong; ZHANG Yu-feng; WANG Jun; CHENG Han-ting

    2003-01-01

    Denture base made from acrylic resin (polymethyl methacrylate,PMMA) was reinforced by different contents of ultrahigh-modulus polyethylene fiber (UHMPEF).The flexural strength of the denture base was tested,the failure modes and microstructures were investigated with a scanning electron microscope(SEM).The results indicate that 3.5wt%UHMPEF increased the ultimate flexural strength of the denture base.

  18. EXPERIMENTAL RESEARCH OF EFFICIENCY OF DISPERSE REINFORCEMENT OF STRETCHED ZONE OF FLEXURAL CONCRETE ELEMENTS

    OpenAIRE

    V. S. Izotov, R. Kh. Mukhametrakhimov, L. S. Sаbitov

    2011-01-01

    Problem statement. The method of disperse reinforcement of flexural concrete elements by fiber introduction in concrete stretched zone is described.Results and conclusions. The method provides more efficient use and economy of disperse rein-forcement, materials consumption reduction at the maintenance of specified flexural strength, high impact elasticity, and fracture strength. The comparative assessment of disperse reinforcement efficiency for two types of metal fibers is given at reinforce...

  19. Prediction of Mean and Design Fatigue Lives of Self Compacting Concrete Beams in Flexure

    Science.gov (United States)

    Goel, S.; Singh, S. P.; Singh, P.; Kaushik, S. K.

    2012-02-01

    In this paper, result of an investigation conducted to study the flexural fatigue characteristics of self compacting concrete (SCC) beams in flexure are presented. An experimental programme was planned in which approximately 60 SCC beam specimens of size 100 × 100 × 500 mm were tested under flexural fatigue loading. Approximately 45 static flexural tests were also conducted to facilitate fatigue testing. The flexural fatigue and static flexural strength tests were conducted on a 100 kN servo-controlled actuator. The fatigue life data thus obtained have been used to establish the probability distributions of fatigue life of SCC using two-parameter Weibull distribution. The parameters of the Weibull distribution have been obtained by different methods of analysis. Using the distribution parameters, the mean and design fatigue lives of SCC have been estimated and compared with Normally vibrated concrete (NVC), the data for which have been taken from literature. It has been observed that SCC exhibits higher mean and design fatigue lives compared to NVC.

  20. Flexural behavior of bonded post-tensioned concrete beams under strand corrosion

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xuhui [College of Civil Engineering and Mechanics, Xiangtan University, 411105 Xiangtan (China); School of Civil Engineering and Architecture, Changsha University of Science & Technology, 410114 Changsha (China); Industry Key Laboratory of Traffic Infrastructure Security Risk Management (CSUST), 410114 Changsha (China); Wang, Lei, E-mail: leiwlei@hotmail.com [School of Civil Engineering and Architecture, Changsha University of Science & Technology, 410114 Changsha (China); Industry Key Laboratory of Traffic Infrastructure Security Risk Management (CSUST), 410114 Changsha (China); Zhang, Jianren; Ma, Yafei [School of Civil Engineering and Architecture, Changsha University of Science & Technology, 410114 Changsha (China); Industry Key Laboratory of Traffic Infrastructure Security Risk Management (CSUST), 410114 Changsha (China); Liu, Yongming [School for Engineering of Matter, Transport and Energy, Arizona State University, 85281 Tempe, AZ (United States)

    2017-03-15

    Highlights: • Flexural behavior of bonded PT beams with strand corrosion is experimental tested. • Cracking, stiffness, ultimate strength, failure & ductility of beams are clarified. • A coefficient is proposed to measure incompatible strain between strand & concrete. - Abstract: An experimental test is performed to investigate the flexural behavior of bonded post-tensioned concrete beams under strand corrosion. Eight beams are designed and subjected to accelerated method to different corrosion levels. The initial stiffness of beams is observed by cyclic loading-unloading test during the corrosion procedure. Corrosion effects on concrete cracking, post-cracking stiffness, ultimate strength, failure mode and ductility are then clarified by the flexural test. And, a coefficient is introduced to quantify the incompatible strain between corroded strand and concrete. Results show that the prestress force loss of strand has almost the linear relation with corrosion loss. Strand corrosion affects slightly the initial stiffness of beam before flexural cracking, but degrades significantly the post-cracking stiffness of beam as the corrosion loss exceeds 27.0%. Slight corrosion of strand has little effects on beams flexural behavior. The severe corrosion, however, decreases the number of crack, changes the failure mode form the concrete crushing to strand rupture, degrades the ductility and the ultimate strength of beams, and leads to the incompatible strain between strand and concrete. In the present test, the incompatible strain decreases about 20% of the flexural strength as the corrosion loss exceeds 27.0%.

  1. An experimental study on flexural strength enhancement of concrete by means of small steel fibers

    Directory of Open Access Journals (Sweden)

    Abdoullah Namdar

    2013-10-01

    Full Text Available Cost effective improvement of the mechanical performances of structural materials is an important goal in construction industry. To improve the flexural strength of plain concrete so as to reduce construction costs, the addition of fibers to the concrete mixture can be adopted. The addition of small steel fibers with different lengths and proportion have experimentally been analyzed in terms of concrete flexural strength enhancement. The main objectives of the present study are related to the evaluation of the influence of steel fibers design on the increase of concrete flexural characteristics and on the mode of failure. Two types of beams have been investigated. The force level, deflection and time to failure of beams have been measured. The shear crack, flexural crack and intermediate shear-flexural crack have been studied. The steel fiber content controlled crack morphology. Flexural strength and time to failure of fiber reinforce concrete could be further enhanced if, instead of smooth steel fibers, corrugated fibers were used.

  2. Understanding the drivers for the development of design rules for the synthesis of cylindrical flexures

    Directory of Open Access Journals (Sweden)

    M. J. Telleria

    2012-04-01

    Full Text Available Cylindrical flexures (CFs, defined as flexures with only one finite radius of curvature loaded normal to the plane of curvature, present an interesting research direction in compliant mechanisms. CFs are constructed out of a cylindrical stock which leads to geometry, manufacturability, and compatibility advantages. Synthesis rules must be developed to design these new systems effectively. Current knowledge in flexure design pertains to straight-beam flexures or curved flexures loaded along the plane of curvature. CFs present a challenge because their mechanics differ from those of straight beams, and although their modelling has been researched thoroughly it has yet to be distilled into element and system creation rules. This paper uses models and finite element analysis to demonstrate that current design rules for straight-beam flexures are insufficient and inadequate for the design of CF systems. The presented discussion will show that CFs differ both at the element and systems levels, and therefore future research will focus on developing the three components of the building block approach: (i reworking of element mechanics models to reveal the parameters which cause the kinematics of the curved beam to differ from those of the straight beam, (ii development of a visual stiffness representation, and (iii formation of system creation rules.

  3. 3D Seismic Flexure Analysis for Subsurface Fault Detection and Fracture Characterization

    Science.gov (United States)

    Di, Haibin; Gao, Dengliang

    2017-03-01

    Seismic flexure is a new geometric attribute with the potential of delineating subtle faults and fractures from three-dimensional (3D) seismic surveys, especially those overlooked by the popular discontinuity and curvature attributes. Although the concept of flexure and its related algorithms have been published in the literature, the attribute has not been sufficiently applied to subsurface fault detection and fracture characterization. This paper provides a comprehensive study of the flexure attribute, including its definition, computation, as well as geologic implications for evaluating the fundamental fracture properties that are essential to fracture characterization and network modeling in the subsurface, through applications to the fractured reservoir at Teapot Dome, Wyoming (USA). Specifically, flexure measures the third-order variation of the geometry of a seismic reflector and is dependent on the measuring direction in 3D space; among all possible directions, flexure is considered most useful when extracted perpendicular to the orientation of dominant deformation; and flexure offers new insights into qualitative/quantitative fracture characterization, with its magnitude indicating the intensity of faulting and fracturing, its azimuth defining the orientation of most-likely fracture trends, and its sign differentiating the sense of displacement of faults and fractures.

  4. Effect of test method on flexural strength of recent dental ceramics.

    Science.gov (United States)

    Jin, Jingyue; Takahashi, Hidekazu; Iwasaki, Naohiko

    2004-12-01

    The purpose of the present study was to evaluate the relationships among three flexural strengths of recent dental ceramics using 3-point and 4-point bending tests and biaxial flexural test. Three brands of porcelain for veneering (d.SIGN, Supper porcelain AAA, Vintage Hallo), two injectable ceramics (Empress 2, OPC 3G), and one castable ceramic (Crys-Cera) were used. Twenty bar-shaped and 10 disc-shaped specimens of each ceramic type were prepared according to manufacturers' instructions, polished, and subjected to 3-point and 4-point bending tests and biaxial flexural test, respectively. Three flexural strengths for each ceramics were compared using one-way analysis of variance and Tukey comparison, and also investigated by Weibull analysis. The biaxial flexural strength and 3-point bending strength of all ceramics, except OPC 3G and Crys-Cera, were significantly greater than the corresponding 4-point bending strength. As for OPC 3G and Crys-Cera, their biaxial flexural strengths were significantly greater than their 3-point bending strengths, which is contrary to the other ceramics. The Weibull moduli ranged from 6.6 to 20.8. The Weibull moduli of examined ceramics, except Crys-cera, were statistically insignificant regardless of test methods.

  5. Flexural Properties of E Glass and TR50S Carbon Fiber Reinforced Epoxy Hybrid Composites

    Science.gov (United States)

    Dong, Chensong; Sudarisman; Davies, Ian J.

    2013-01-01

    A study on the flexural properties of E glass and TR50S carbon fiber reinforced hybrid composites is presented in this paper. Specimens were made by the hand lay-up process in an intra-ply configuration with varying degrees of glass fibers added to the surface of a carbon laminate. These specimens were then tested in the three-point bend configuration in accordance with ASTM D790-07 at three span-to-depth ratios: 16, 32, and 64. The failure modes were examined under an optical microscope. The flexural behavior was also simulated by finite element analysis, and the flexural modulus, flexural strength, and strain to failure were calculated. It is shown that although span-to-depth ratio shows an influence on the stress-strain relationship, it has no effect on the failure mode. The majority of specimens failed by either in-plane or out-of-plane local buckling followed by kinking and splitting at the compressive GFRP side and matrix cracking combined with fiber breakage at the CFRP tensile face. It is shown that positive hybrid effects exist for the flexural strengths of most of the hybrid configurations. The hybrid effect is noted to be more obvious when the hybrid ratio is small, which may be attributed to the relative position of the GFRP layer(s) with respect to the neutral plane. In contrast to this, flexural modulus seems to obey the rule of mixtures equation.

  6. Design Considerations of a Slit Diaphragm Flexure Used in a Precision Mirror Gimbal

    Energy Technology Data Exchange (ETDEWEB)

    Cox, B. C., Kaufman, M. I.

    2011-09-01

    Two precision mirror gimbals were designed using slit diaphragm flexures to provide two-axis precision mirror alignment in space-limited applications. Both gimbals are currently in use in diagnostics at the National Ignition Facility: one design in the Gamma Reaction History (GRH) diagnostic and the other in the Neutron Imaging System (NIS) diagnostic. The GRH gimbal has an adjustment sensitivity of 0.1 mrad about both axes and a total adjustment capability of ±6°; the NIS gimbal has an adjustment sensitivity of 0.8 μrad about both axes and a total adjustment range of ±3°. Both slit diaphragm flexures were electro-discharge machined out of high-strength titanium and utilize stainless steel stiffeners. The stiffener-flexure design results in adjustment axes with excellent orthogonality and centering with respect to the mirror in a single stage; a typical two-axis gimbal flexure requires two stages. Finite element analyses are presented for both flexure designs, and a design optimization of the GRH flexure is discussed.

  7. Design considerations of a slit diaphragm flexure used in a precision mirror gimbal

    Science.gov (United States)

    Cox, Brian; Kaufman, Morris

    2011-09-01

    Two precision mirror gimbals were designed using slit diaphragm flexures to provide two-axis precision mirror alignment in space-limited applications. Both gimbals are currently in use in diagnostics at the National Ignition Facility: one design in the Gamma Reaction History (GRH) diagnostic and the other in the Neutron Imaging System (NIS) diagnostic. The GRH gimbal has an adjustment sensitivity of 0.1 mrad about both axes and a total adjustment capability of +/-6° the NIS gimbal has an adjustment sensitivity of 0.8 μrad about both axes and a total adjustment range of +/-3°. Both slit diaphragm flexures were electro-discharge machined out of high-strength titanium and utilize stainless steel stiffeners. The stiffener-flexure design results in adjustment axes with excellent orthogonality and centering with respect to the mirror in a single stage; a typical two-axis gimbal flexure requires two stages. Finite element analyses are presented for both flexure designs, and a design optimization of the GRH flexure is discussed.

  8. Compliance and control characteristics of an additive manufactured-flexure stage

    Energy Technology Data Exchange (ETDEWEB)

    Lee, ChaBum; Tarbutton, Joshua A. [Department of Mechanical Engineering, University of South Carolina, 300 Main St., Columbia, South Carolina 29208 (United States)

    2015-04-15

    This paper presents a compliance and positioning control characteristics of additive manufactured-nanopositioning system consisted of the flexure mechanism and voice coil motor (VCM). The double compound notch type flexure stage was designed to utilize the elastic deformation of two symmetrical four-bar mechanisms to provide a millimeter-level working range. Additive manufacturing (AM) process, stereolithography, was used to fabricate the flexure stage. The AM stage was inspected by using 3D X-ray computerized tomography scanner: air-voids and shape irregularity. The compliance, open-loop resonance peak, and damping ratio of the AM stage were measured 0.317 mm/N, 80 Hz, and 0.19, respectively. The AM stage was proportional-integral-derivative positioning feedback-controlled and the capacitive type sensor was used to measure the displacement. As a result, the AM flexure mechanism was successfully 25 nm positioning controlled within 500 μm range. The resonance peak was found approximately at 280 Hz in closed-loop. This research showed that the AM flexure mechanism and the VCM can provide millimeter range with high precision and can be a good alternative to an expensive metal-based flexure mechanism and piezoelectric transducer.

  9. Effect of Banana Fibers on the Compressive and Flexural Strength of Compressed Earth Blocks

    Directory of Open Access Journals (Sweden)

    Marwan Mostafa

    2015-03-01

    Full Text Available Sustainable development of the built environment in developing countries is a major challenge in the 21st century. The use of local materials in construction of buildings is one of the potential ways to support sustainable development in both urban and rural areas. Building with Compressed Earthen Blocks (CEBs is becoming more popular due to their low cost and relative abundance of materials. The proposed Green-Compressed Earth Block (GCEB consists of ordinary CEB ingredients plus Banana fibers, which will be the focus of this study. Banana fibers are widely available worldwide as agricultural waste from Banana cultivation. Banana fibers are environmentally friendly and present important attributes, such as low density, light weight, low cost, high tensile strength, as well as being water and fire resistant. This kind of waste has a greater chance of being utilized for different application in construction and building materials. This focused on the use of banana fiber and its effect on the compressive and flexural strength in CEB. The deflection at the mid-span of the blocks studied was calculated using the Linear Variable Differential Transformer (LVDT. The results of this study will highlight general trends in the strength properties of different soil mixes for CEBs. These efforts are necessary to ensure that GCEB technology becomes more widely accepted in the world of building materials and is considered a reliable option for providing low-cost housing.

  10. A piezoelectric motor using flexural vibration of a thin piezoelectric membrane.

    Science.gov (United States)

    Lamberti, N; Iula, A; Pappalardo, M

    1998-01-01

    This paper describes a new implementation of a disk-type piezoelectric motor, whose stator is a commercial available piezomembrane composed of a nickel alloy disk to which a piezoceramic disk is bonded. The two disks are concentric, and the total thickness is very small. Ultrasonic motors are based on the concept of driving a rotor by mechanical vibration excited on a stator, via the piezoelectric effect. The rotor is in contact with the stator, and the driving force is the frictional force between rotor and stator. To transform the mechanical vibration of the stator in the rotor rotation, a traveling wave must be excited on the stator surface. The proposed motor can be regarded as a disk-type, single wavelength motor in which the traveling wave is due to the natural flexural vibration of the piezomembrane at low frequency. The behavior of the stator is analyzed both theoretically, by using the theory of isotropic and homogeneous vibrating plates, and by means of a commercial finite element computer code, finding a good agreement with the experimental results. The main features of the motor are very small thickness, appreciable torque, and high speed, obtained with low input power at low voltage; the intended application is to substitute the moving-coil in analogic instrumentation.

  11. Evaluation of Relative Sensitivity of SAW and Flexural Plate Wave Devices for Atmospheric Sensing

    Science.gov (United States)

    White, Richard M.; Black, Justin; Chen, Bryan

    1998-01-01

    The objective of this project is to evaluate the suitability of the ultrasonic flexural plate wave (FPW) device as the detector in a gas chromatograph (GC). Of particular interest is the detection of nitrous oxide (N2O). From experimental results we conclude analyte detection is achieved through two mechanisms: changes in gas density, and mass loading of the device membrane due to the sorption of gas molecules. Reducing the dead volume of the FPW chamber increased the FPW response. A comparison of the FPW response to that of the surface acoustic wave (SAW) detector provided with the GC (made by MSI, Microsensor Technologies, Inc.), shows that for unseparated N2O in N2, the FPW exhibits a sensitivity that is at least 550 times greater than that of the SAW device. A Porapak Q column was found to separate N2O from its carrier gas, N2 or He. With the Porapak Q column, a coated FPW detected 1 ppm N2O in N2 or He, with a response magnitude of 7 Hz. A coated SAW exhibited a response of 25 Hz to pure N2O. The minimal detectable N2O concentrations of the sensors were not evaluated.

  12. Tectonic Evolution of Bell Regio, Venus: Regional Stress, Lithospheric Flexure, and Edifice Stresses

    Science.gov (United States)

    Rogers, P. G.; Zuber, M. T.

    1996-03-01

    Analyses of the tectonic features associated with large volcanoes provide important insight into the relationship between volcanic and tectonic processes and the stress state of a planet's crust over time, and provide constraints on the local and regional geologic evolution. This investigation focuses on the tectonism and volcanism of Bell Regio, a major highland uplift n Venus. The stress environments and resulting tectonic features associated with the major volcanic edifices in this region are examined using Magellan ynthetic aperture radar (SAR) images and altimeter measurements of topography. The major volcanoes of Bell Regio, Tepev Mons and the "Eastern Volcanic Center" (EVC), exhibit tectonic characteristics that are unique relative to other volcanic edifices on Venus. The most prominent distinctions are the lack of large rift zones within the overall highland uplift and the presence of radial tectonic and concentric fractures associated with the major edifices. This study examines the regional stress field in Bell Regio through analysis of structural features believed to be a consequence of lithospheric flexure due to volcanic loading and tectonic features that likely resulted from edifice stresses associated with magma chamber inflation.

  13. Failure Predictions of Out-of-Autoclave Sandwich Joints with Delaminations Under Flexure Loads

    Science.gov (United States)

    Nordendale, Nikolas A.; Goyal, Vinay K.; Lundgren, Eric C.; Patel, Dhruv N.; Farrokh, Babak; Jones, Justin; Fischetti, Grace; Segal, Kenneth N.

    2015-01-01

    An analysis and a test program was conducted to investigate the damage tolerance of composite sandwich joints. The joints contained a single circular delamination between the face-sheet and the doubler. The coupons were fabricated through out-of-autoclave (OOA) processes, a technology NASA is investigating for joining large composite sections. The four-point bend flexure test was used to induce compression loading into the side of the joint where the delamination was placed. The compression side was chosen since it tends to be one of the most critical loads in launch vehicles. Autoclave cure was used to manufacture the composite sandwich sections, while the doubler was co-bonded onto the sandwich face-sheet using an OOA process after sandwich panels were cured. A building block approach was adopted to characterize the mechanical properties of the joint material, including the fracture toughness between the doubler and face-sheet. Twelve four-point-bend samples were tested, six in the sandwich core ribbon orientation and six in sandwich core cross-ribbon direction. Analysis predicted failure initiation and propagation at the pre-delaminated location, consistent with experimental observations. A building block approach using fracture analyses methods predicted failure loads in close agreement with tests. This investigation demonstrated a small strength reduction due to a flaw of significant size compared to the width of the sample. Therefore, concerns of bonding an OOA material to an in-autoclave material was mitigated for the geometries, materials, and load configurations considered.

  14. Flexural and diametral tensile strength of composite resins

    Directory of Open Access Journals (Sweden)

    Álvaro Della Bona

    2008-03-01

    Full Text Available This study evaluated the flexural strength (sf and the diametral tensile strength (st of light-cured composite resins, testing the hypothesis that there is a positive relation between these properties. Twenty specimens were fabricated for each material (Filtek Z250- 3M-Espe; AM- Amelogen, Ultradent; VE- Vit-l-escence, Ultradent; EX- Esthet-X, Dentsply/Caulk, following ISO 4049 and ANSI/ADA 27 specifications and the manufacturers’ instructions. For the st test, cylindrical shaped (4 mm x 6 mm specimens (n = 10 were placed with their long axes perpendicular to the applied compressive load at a crosshead speed of 1.0 mm/min. The sf was measured using the 3-point bending test, in which bar shaped specimens (n = 10 were tested at a crosshead speed of 0.5 mm/min. Both tests were performed in a universal testing machine (EMIC 2000 recording the fracture load (N. Strength values (MPa were calculated and statistically analyzed by ANOVA and Tukey (a = 0.05. The mean and standard deviation values (MPa were Z250-45.06 ± 5.7; AM-35.61 ± 5.4; VE-34.45 ± 7.8; and EX-42.87 ± 6.6 for st; and Z250-126.52 ± 3.3; AM-87.75 ± 3.8; VE-104.66 ± 4.4; and EX-119.48 ± 2.1 for sf. EX and Z250 showed higher st and sf values than the other materials evaluated (p < 0.05, which followed a decreasing trend of mean values. The results confirmed the study hypothesis, showing a positive relation between the material properties examined.

  15. Comparative Analysis of the Flexural Stiffness of Pinniped Vibrissae.

    Directory of Open Access Journals (Sweden)

    Carly C Ginter Summarell

    Full Text Available Vibrissae are important components of the mammalian tactile sensory system and are used to detect vibrotactile stimuli in the environment. Pinnipeds have the largest and most highly innervated vibrissae among mammals, and the hair shafts function as a biomechanical filter spanning the environmental stimuli and the neural mechanoreceptors deep in the follicle-sinus complex. Therefore, the material properties of these structures are critical in transferring vibrotactile information to the peripheral nervous system. Vibrissae were tested as cantilever beams and their flexural stiffness (EI was measured to test the hypotheses that the shape of beaded vibrissae reduces EI and that vibrissae are anisotropic. EI was measured at two locations on each vibrissa, 25% and 50% of the overall length, and at two orientations to the point force. EI differed in orientations that were normal to each other, indicating a functional anisotropy. Since vibrissae taper from base to tip, the second moment of area (I was lower at 50% than 25% of total length. The anterior orientation exhibited greater EI values at both locations compared to the dorsal orientation for all species. Smooth vibrissae were generally stiffer than beaded vibrissae. The profiles of beaded vibrissae are known to decrease the amplitude of vibrations when protruded into a flow field. The lower EI values of beaded vibrissae, along with the reduced vibrations, may function to enhance the sensitivity of mechanoreceptors to detection of small changes in flow from swimming prey by increasing the signal to noise ratio. This study builds upon previous morphological and hydrodynamic analyses of vibrissae and is the first comparative study of the mechanical properties of pinniped vibrissae.

  16. Topographic mapping of biological specimens: flexure and curvature characterization

    Science.gov (United States)

    Baron, William S.; Baron, Sandra F.

    2004-07-01

    Shape quantification of tissue and biomaterials can be central to many studies and applications in bioengineering and biomechanics. Often, shape is mapped with photogrammetry or projected light techniques that provide XYZ point cloud data, and shape is quantified using derived flexure and curvature calculations based on the point cloud data. Accordingly, the accuracy of the calculated curvature depends on the properties of the point cloud data set. In this study, we present a curvature variability prediction (CVP) software model that predicts the distribution, i.e., the standard deviation, of curvature measurements associated with surface topography point cloud data properties. The CVP model point cloud data input variables include XYZ noise, sampling density, and map extent. The CVP model outputs the curvature variability statistic in order to assess performance in the curvature domain. Representative point cloud data properties are obtained from an automated biological specimen video topographer, the BioSpecVT (ver. 1.02) (Vision Metrics, Inc.,). The BioSpecVT uses a calibrated, structured light pattern to support automated computer vision feature extraction software for precisely converting video images of biological specimens, within seconds, into three dimensional point cloud data. In representative sample point cloud data obtained with the BioSpecVT, sampling density is about 11 pts/mm2 for an XYZ mapping volume encompassing about 16 mm x 13.5 mm x 18.5 mm, average XY per point variability is about +/-2 μm, and Z axis variability is about +/-40 μm (50% level) with a Gaussian distribution. A theoretical study with the CVP model shows that for derived point cloud data properties, curvature mapping accuracy increases, i.e. measurement variability decreases, when curvature increases from about 30 m-1 to 137 m-1. This computed result is consistent with the Z axis noise becoming less significant as the measured depth increases across an approximately fixed XY

  17. Colonic Necrosis in a 4-Year-Old with Hyperlipidemic Acute Pancreatitis

    Directory of Open Access Journals (Sweden)

    Tiffany J. Patton

    2016-01-01

    Full Text Available Here we report the case of a 4-year-old male with severe acute pancreatitis due to hyperlipidemia, who presented with abdominal pain, metabolic abnormalities, and colonic necrosis. This colonic complication was secondary to the extension of a large peripancreatic fluid collection causing direct serosal autodigestion by pancreatic enzymes. Two weeks following the initial presentation, the peripancreatic fluid collection developed into a mature pancreatic pseudocyst, which was percutaneously drained. To our knowledge, this is the youngest documented pediatric case of colonic necrosis due to severe pancreatitis and the first descriptive pediatric case of a colonic complication due to hyperlipidemia-induced acute pancreatitis.

  18. Determination of Dynamic Flexural Tensile Strength of Thermally Treated Laurentian Granite Using Semi-Circular Specimens

    Science.gov (United States)

    Yin, Tubing; Wang, Pin; Li, Xibing; Wu, Bangbiao; Tao, Ming; Shu, Ronghua

    2016-10-01

    To understand the effects of increasing temperature and loading rate on the flexural tensile strength of Laurentian granite, dynamic flexural tensile strength experiments were carried out by means of a semi-circular bend specimen with a modified split Hopkinson pressure bar system. The tests were performed at different loading rates, specimens were treated from room temperature up to 850 °C, and a high-speed camera was utilized to monitor the failure process of the specimen. For samples in the same temperature group, a loading rate dependence of the flexural tensile strength was observed; it increased consistently with the increase of loading rate. Temperature effects on rock mechanical properties were investigated from the microscopic viewpoint, and the dynamic flexural tensile strength decreased with the treatment temperature. A formula relating dynamic flexural tensile strength to loading rate and temperature is presented to quantify the results. It was found that the change regulation of the dynamic flexural tensile strength of rock is very similar to that of its crack growth along with the increase of loading rate, which indicates that the essence of rock failure is the initiation and propagation of the internal cracks. Compared with our earlier work on dynamic tensile tests using the Brazilian test, it was observed that the flexural tensile strength is higher than the tensile strength. Non-local failure theory can be adopted to explain this discrepancy at low temperature conditions, but it is no longer effective at high temperatures. Under high loading rates, rock failure is initiated at the centre of the half circular disc, and finally it is separated completely into two equal parts.

  19. Flexural rigidity evolvement laws of reinforced concrete beams strengthened with carbon fiber laminates

    Institute of Scientific and Technical Information of China (English)

    NIU Peng-zhi; HUANG Pei-yan; DENG Jun; HAN Qiang

    2007-01-01

    Extensive research has shown that externally bonded carbon fiber reinforced polymer (CFRP) laminates are particularly suitable for improving the fatigue behavior of reinforced concrete (RC) beams. This paper presents the research on flexural rigidity evolvement laws by testing 14 simple-supported RC beams strengthened with carbon fiber laminates (CFL) under cyclic load, and 2 under monotone load as a reference. The cyclic load tests revealed the peak load applied onto the surface of a supported RC beam strengthened with CFL is linear to the logarithm of its fatigue life, and the flexural rigidity evolvement undergoes three distinct phases: a rapid decrease from the start to about 5% of the fatigue life; an even development from 5% to about 99% of the fatigue life; and a succedent rapid decrease to failure. When the ratio of fatigue cycles to the fatigue life is within 0.05 to 0.99, the flexural rigidity varies linearly with the ratio. The peak load does not affect the flexural rigidity evolvement if it is not high enough to make the main reinforcements yield. The dependences of the flexural rigidity of specimens formed in the same group upon their fatigue cycles normalized by fatigue life are almost coincident. This implies the flexural rigidity may be a material parameter independent of the stress level. These relationships of flexural rigidity to fatigue cycles, and fatigue life may be able to provide some hints for fatigue design and fatigue life evaluation of RC member strengthened with CFL; nevertheless the findings still need verifying by more experiments.

  20. Correlation between flexural and indirect tensile strength of resin composite cements.

    Science.gov (United States)

    Cassina, Gianluca; Fischer, Jens; Rohr, Nadja

    2016-11-04

    To evaluate a potential correlation between flexural strength and indirect tensile strength in assessing the mechanical strength of resin composite cements. Flexural strength (n = 5) and indirect tensile strength (n = 5) of 7 resin composite cements (RelyX Unicem 2 Automix [RXU], Panavia SA [PSA], Clearfil SA [CSA], Panavia F2.0 [PF2], Multilink Implant [MLI], DuoCem [DCM], Panavia 21 [P21]) were determined. Specimens were either auto-polymerized or dual-cured (except P21) and stored in water at 37 °C for 1 day prior to measurement. Flexural and indirect tensile strength of 4 cements (RXU, PSA, PF2, MLI) was additionally measured directly after curing and after 96 h water storage at 37 °C. Except for PF2, dual-cured specimens achieved higher flexural strength than auto-polymerized specimens. In the indirect tensile strength test differences in auto-polymerized and dual-cured specimens were only detected for RXU and DCM. A general non-linear correlation was found between flexural and indirect tensile strength values. However, strength values of auto-polymerized and dual-cured specimens did not generally correlate. Flexural strength and indirect tensile strength of resin composite cements are correlated. At high strength values the indirect tensile test is less sensitive than the flexural test. The results suggest that the indirect tensile test may only be recommended as a screening test especially for low or medium strength resin composite cements.

  1. Hyperglycemia Increases Susceptibility to Ischemic Necrosis

    Directory of Open Access Journals (Sweden)

    D. Lévigne

    2013-01-01

    Full Text Available Diabetic patients are at risk for spontaneous foot ulcers, chronic wounds, infections, and tissue necrosis. Current theories suggest that the development and progression of diabetic foot ulcers are mainly caused by arteriosclerosis and peripheral neuropathy. Tissue necrosis plays a primordial role in the progression of diabetic foot ulcers but the underlying mechanisms are poorly understood. The aim of the present study was to investigate the effects of hyperglycemia per se on the susceptibility of ischemic tissue to necrosis, using a critical ischemic hind limb animal model. We inflicted the same degree of ischemia in both euglycemic and streptozotocin-induced hyperglycemic rats by resecting the external iliac, the femoral, and the saphenous arteries. Postoperative laser Doppler flowmetry of the ischemic feet showed the same degree of reduction in skin perfusion in both hyperglycemic and euglycemic animals. Nevertheless, we found a significantly higher rate of limb necrosis in hyperglycemic rats compared to euglycemic rats (71% versus 29%, resp.. In this study, we revealed that hyperglycemia per se increases the susceptibility to limb necrosis in ischemic conditions. Our results may help to better understand the physiopathology of progressive diabetic wounds and underline the importance of strict glycemic control in patients with critical limb ischemia.

  2. Bilateral acute retinal necrosis after herpetic meningitis

    Directory of Open Access Journals (Sweden)

    Katsura T

    2012-04-01

    Full Text Available Keisho Hirota1,2, Masayuki Akimoto1,3, Toshiaki Katsura21Department of Ophthalmology, Kyoto Medical Center, National Hospital Organization, 2Internal Medicine, Kyoto Medical Center, 3Clinical Research Center, Kyoto Medical Center, Kyoto, JapanPurpose: The report of a case of bilateral acute retinal necrosis after herpetic meningitis.Case report: A 47-year-old man was admitted with the chief complaint of persistent high fever and transient loss of consciousness. Although his general condition improved after intravenous acyclovir administration, the patient presented with visual loss in both eyes 4 days after admission. Visual acuity in his right eye was 20/200 and his left eye had light perception alone. Both eyes showed panretinal arteritis diagnosed as acute retinal necrosis. Panretinal photocoagulation was performed for both eyes. Progression of retinal detachment was prevented in both eyes; however, visual acuity of the left eye was totally lost because of neovascular glaucoma. Visual acuity of the right eye recovered to 20/20.Conclusion: Although cases of bilateral acute retinal necrosis have been reported after herpetic encephalitis, this condition is rare after herpetic meningitis. Prophylactic acyclovir therapy and early panretinal photocoagulation may prevent retinal detachment and improve the prognosis. Neurologists and ophthalmologists should be aware that not only herpetic encephalitis but also herpetic meningitis can lead to acute retinal necrosis within a very short interval.Keywords: acute retinal necrosis, herpetic meningitis, herpes simplex, varicella zoster virus

  3. Post-partum bilateral renal cortical necrosis in antiphospholipid syndrome and systemic lupus erythematosus

    Directory of Open Access Journals (Sweden)

    Venkat Sainaresh Vellanki

    2013-01-01

    Full Text Available In the presence of systemic lupus erythematosus or related autoimmune disorders, antiphospholipid syndrome (APS is termed secondary APS. Pregnancy-related renal failure due to SAPS is rarely reported in the literature. We present the case of a young primgravida woman with bilateral renal cortical necrosis due to secondary APS in late pregnancy.

  4. Extrapancreatic necrosis without pancreatic parenchymal necrosis : a separate entity in necrotising pancreatitis?

    NARCIS (Netherlands)

    Bakker, Olaf J.; van Santvoort, Hjalmar; Besselink, Marc G. H.; Boermeester, Marja A.; van Eijck, Casper; Dejong, Kees; van Goor, Harry; Hofker, Hendrik; Ali, Usama Ahmed; Gooszen, Hein G.; Bollen, Thomas L.

    2013-01-01

    Objective In the revised Atlanta classification of acute pancreatitis, the term necrotising pancreatitis also refers to patients with only extrapancreatic fat necrosis without pancreatic parenchymal necrosis (EXPN), as determined on contrast-enhanced CT (CECT). Patients with EXPN are thought to have

  5. [The effect of tumor necrosis factor alpha on hepatic necrosis in viral hepatitis].

    Science.gov (United States)

    Yu, Y; Si, C; Lang, Z

    1996-01-01

    In order to investigate the effect of tumor necrosis factor alpha (TNF alpha) on hepatocyte necrosis in viral hepatitis, TNF alpha with or without D-galactosamine (D-Gal) was injected into the abdominal cavity of rats. No effect was observed after injection of TNF alpha alone. After injection of TNF alpha with D-Gal, the total bilirubin level in rat blood increased and hepatocyte necrosis appeared (P hepatic tissue were stained with anti-TNF alpha McAb by using ABC immunohistochemistry method. It was found that more severe the hepatocyte necrosis, more the positive cells expressing TNF alpha. There were more TNF alpha positive cells in the tissue of severe hepatitis. These results suggested that TNF alpha is a mediator in hepatocyte necrosis.

  6. Flexural strength and hardness of direct and indirect composites

    Directory of Open Access Journals (Sweden)

    Márcia Borba

    2009-03-01

    Full Text Available The objective of this study was to evaluate the flexural strength (σf and hardness (H of direct and indirect composites, testing the hypotheses that direct resin composites produce higher σf and H values than indirect composites and that these properties are positively related. Ten bar-shaped specimens (25 mm x 2 mm x 2 mm were fabricated for each direct [D250 - Filtek Z250 (3M-Espe and D350 - Filtek Z350 (3M-Espe] and indirect [ISin - Sinfony (3M-Espe and IVM - VitaVM LC (Vita Zahnfabrik] materials, according to the manufacturer's instructions and ISO4049 specifications. The σf was tested in three-point bending using a universal testing machine (EMIC DL 2000 at a crosshead speed of 0.5 mm/min (ISO4049. Knoop hardness (H was measured on the specimens' fragments resultant from the σf test and calculated as H = 14.2P/l², where P is the applied load (0.1 kg; dwell time = 15 s and l is the longest diagonal of the diamond shaped indent (ASTM E384. The data were statistically analyzed using Anova and Tukey tests (α = 0.05. The mean σf and standard deviation values (MPa and statistical grouping were: D250 - 135.4 ± 17.6a; D350 - 123.7 ± 11.1b; ISin - 98.4 ± 6.4c; IVM - 73.1 ± 4.9d. The mean H and standard deviation values (kg/mm² and statistical grouping were: D250 - 98.12 ± 1.8a; D350 - 86.5 ± 1.9b; ISin - 28.3 ± 0.9c; IVM - 30.8 ± 1.0c. The direct composite systems examined produce higher mean σf and H values than the indirect composites, and the mean values of these properties were positively correlated (r = 0.91, confirming the study hypotheses.

  7. In vitro evaluation of flexural strength of different brands of expansion screws

    Directory of Open Access Journals (Sweden)

    Kádna Fernanda Mendes de Oliveira

    2012-06-01

    Full Text Available OBJECTIVE: The objective of this study was to compare the flexural strength of the stems of three maxillary expanders screws of Morelli, Forestadent and Dentaurum brands. METHODS: The sample consisted of nine expander screws (totalizing of 36 stems, three from each brand, all stainless steel and 12 mm of expansion capacity. The stems of the expander screws were cut with cutting pliers close to the weld region with screw body, then fixed in a universal testing machine Instron 4411 for tests of bending resistance of three points. The ultimate strength in kgF exerted by the machine to bend the stem of the 5 mm screw was recorded and the flexural strength was calculated using a mathematical formula. During the flexural strength test it was verified the modulus of elasticity of the stems by means of Bluehill 2 software. The flexural strength data were subjected to ANOVA with one criterion and Tukey's test, with significance level of 5%. RESULTS: Forestadent screw brand showed the greatest bending strength, significantly higher than Dentaurum. Morelli showed the lowest resistance. CONCLUSION: The flexural strength of the screws varied according to the brand. Forestadent screw showed the greatest resistance and Morelli the lowest. All the three screws were found adequate for use in procedures for rapid maxillary expansion.

  8. Acute Retinal Necrosis Presenting in Developmentally-delayed Patients with Neonatal Encephalitis: A Case Series and Literature Review.

    Science.gov (United States)

    Okafor, Kingsley; Lu, Jonathan; Thinda, Sumeer; Schwab, Ivan; Morse, Lawrence S; Park, Susanna S; Moshiri, Ala

    2016-05-18

    We report three cases of patients with developmental-delay from neonatal herpetic encephalitis and/or meningitis who presented years later with acute retinal necrosis due to herpes simplex virus. The diagnosis was delayed in all cases due to the patients' inability to verbalize their ocular complaints and cooperate with eye examinations. This case series documents the clinical course, pathophysiologic mechanism, and treatment of acute retinal necrosis in this patient population. Clinicians should understand the importance of prudent consideration of acute retinal necrosis in patients with a history of neonatal herpetic encephalitis and/or meningitis presenting with a red eye.

  9. Cumulative Effect of Crumb Rubber and Steel Fiber on the Flexural Toughness of Concrete

    Directory of Open Access Journals (Sweden)

    B. H. Abu Bakar

    2017-02-01

    Full Text Available Concrete properties, such as toughness and ductility, are enhanced to resist different impacts or blast loads. Rubberized concrete, which could be considered a green material, is produced from recycled waste tires grinded into different crumb rubber particle sizes and mixed with concrete. In this study, the behavior of rubberized steel fiber-reinforced concrete is investigated. Flexural performance of concrete beams (400×100×100 mm manufactured from plain, steel fiber, crumb rubber and combination crumb rubber and steel fiber are also evaluated. Similarly, concrete slabs (500×500×50 mm are also tested under flexural loading. Flexural performance of the SFRRC mixtures was significantly enhanced. The toughness and maximum deflection of specimens with rubber were considerably improved. Steel fiber/crumb rubber-reinforced concrete can be used for practical application, which requires further studies.

  10. Adaptive Kalman Filter of Transfer Alignment with Un-modeled Wing Flexure of Aircraft

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The alignment accuracy of the strap-down inertial navigation system (SINS) of airborne weapon is greatly degraded by the dynamic wing flexure of the aircraft. An adaptive Kalman filter uses innovation sequences based on the maximum likelihood estimated criterion to adapt the system noise covariance matrix and the measurement noise covariance matrix on line, which is used to estimate the misalignment if the model of wing flexure of the aircraft is unknown. From a number of simulations, it is shown that the accuracy of the adaptive Kalman filter is better than the conventional Kalman filter, and the erroneous misalignment models of the wing flexure of aircraft will cause bad estimation results of Kalman filter using attitude match method.

  11. Effect of polymerization cycles on flexural strengths and microhardness of different denture base materials.

    Science.gov (United States)

    Gungor, Hasan; Gundogdu, Mustafa; Alkurt, Murat; Yesil Duymus, Zeynep

    2017-01-13

    The purpose of this study was to evaluate the effect of different polymerization cycles on the flexural strengths and microhardness of two denture base materials (Meliodent and Paladent). Heat-polymerized acrylic resin specimens (65.0 mm long×10.0 mm wide×2.5 mm in height) were prepared using different short and long polymerization cycles. After the specimens had been polymerized, they were stored in distilled water at 37±1°C for 24 h. Flexural strength test was performed at a cross-head speed of 5 mm/min and Vickers microhardness was measured. Data were analyzed with a 1-way analysis of variance followed by Tukey test, and Student t-test (α=0.05). The flexural strengths and microhardness were significantly different between Meliodent and Paladent (pmicrohardness (p<0.05). Polymerization with G cycle may be suggested for Meliodent and H cycle may be suggested for Paladent.

  12. Processing, structure and flexural strength of CNT and carbon fibre reinforced, epoxy-matrix hybrid composite

    Indian Academy of Sciences (India)

    K Chandra Shekar; M Sai Priya; P K Subramanian; Anil Kumar; B Anjaneya Prasad; N Eswara Prasad

    2014-05-01

    Advanced materials such as continuous fibre-reinforced polymer matrix composites offer significant enhancements in variety of properties, as compared to their bulk, monolithic counterparts. These properties include primarily the tensile stress, flexural stress and fracture parameters. However, till date, there are hardly any scientific studies reported on carbon fibre (Cf) and carbon nanotube (CNT) reinforced hybrid epoxy matrix composites (unidirectional). The present work is an attempt to bring out the flexural strength properties along with a detailed investigation in the synthesis of reinforced hybrid composite. In this present study, the importance of alignment of fibre is comprehensively evaluated and reported. The results obtained are discussed in terms of material characteristics, microstructure and mode of failure under flexural (3-point bend) loading. The study reveals the material exhibiting exceptionally high strength values and declaring itself as a material with high strength to weight ratio when compared to other competing polymer matrix composites (PMCs); as a novel structural material for aeronautical and aerospace applications.

  13. Flexural-torsional buckling analysis of angle-bar stiffened plates

    Energy Technology Data Exchange (ETDEWEB)

    Ahmad, Rahbar Ranji [Amirkabir University of Technology, Tehran (Iran, Islamic Republic of)

    2015-09-15

    The interaction of flexural-torsional buckling modes is critical for stiffened plates with asymmetric stiffeners. However, this interaction is ignored in all design rules because it is complex to characterize. In the literature, the presence of an attached plate is ignored, and stiffened plate is treated as an ordinary asymmetric beam. In the flexural buckling mode, stiffener and the attached plate buckle together; in the torsional buckling mode, the attached plate cannot freely rotate with stiffener. Basic equations of the flexural-torsional buckling modes are deduced based on hybrid beam concept and a new strain distribution assumption for sideway bending of stiffeners. Elastic buckling stresses of different angle-bar stiffened plates are calculated and compared with those generated by the Finite element method (FEM) and those available in the literature. The present method has better agreements with FEM.

  14. Cyclic loading effect on the flexural properties of commercial mdf and particleboard panels

    Directory of Open Access Journals (Sweden)

    Cláudio Henrique Soares Del Menezzi

    2011-09-01

    Full Text Available This paper aimed at evaluating the effect of fatigue through different loading cycles (20,0000; 40,000 and 80,000 cycles on deflection and flexural properties of commercial MDF and particleboard panels. A 2.2 seconds (0.45 Hz cyclic loading was employed and the applied load about 25% of modulus of rupture was used. After the tests, final deflection (with load, residual deflection (without load and flexural properties of the panels were evaluated. According to the results, the flexural properties for both kinds of panels were not affected by the loading cycles tested. However, it was identified that the MDF residual deflection was affected between 20,000 and 80,000 loading cycles.

  15. Flexural fatigue characteristics of steel fiber reinforced recycled aggregate concrete (SFRRAC

    Directory of Open Access Journals (Sweden)

    Heeralal M.

    2009-01-01

    Full Text Available This research work is aimed at investigating the flexural fatigue behavior of Steel Fiber Reinforced Recycled Aggregate Concrete (SFRRAC. This study gains importance in view of the wide potential for demolished concrete to serve as a source of quality aggregate feed stock in a variety of structural and non-structural applications. This is a continuation of a series of investigations being conducted aimed at optimizing the utilization of recycled aggregate concrete in rigid pavements. A total of 72 standard flexure specimens of 100mm x 100mm x 450mm were cast and tested for flexure under both static and fatigue loading. The parameters of the investigation included the different replacements of recycled aggregate in natural aggregate, presence of steel fiber and different stress levels. The study showed that the recycled aggregates can be used in rigid pavements also and the inclusion of fibers can benefit the fatigue performance of recycled aggregate concrete.

  16. Effects of Core Softness and Bimodularity of Fibreglass Layers on Flexural Stiffness of Polymer Sandwich Structures

    Directory of Open Access Journals (Sweden)

    Šuba Oldřich

    2017-01-01

    Full Text Available This paper deals with the study of the flexural stiffness of the sandwich structures based on fibreglass and polymeric foams. The influence of geometrical and material parameters on the resulting effective flexural stiffness of the sandwich structure is being studied experimentally, analytically and by using FEM models. The effective modulus of elasticity of the sandwich-structured element is being studied and its theoretical and model dependencies on the flexibility of the foam core and bimodularity of the fibreglass layers are being investigated. The achieved results are compared with the experimentally observed values. This study shows that it is necessary to pay special attention to the issue of flexural stiffness of the walls when designing sandwich shell products in order to prevent possible failures in the practical applications of these types of structures.

  17. FLEXURAL PROPERTIES OF ALKALINE TREATED SUGAR PALM FIBRE REINFORCED EPOXY COMPOSITES

    Directory of Open Access Journals (Sweden)

    D. Bachtiar

    2010-06-01

    Full Text Available A study of the effect of alkaline treatment on the flexural properties of sugar palm fibre reinforced epoxy composites is presented in this paper. The composites were reinforced with 10% weight fraction of the fibres. The fibres were treated using sodium hydroxide (NaOH with 0.25 M and 0.5 M concentration solution for 1 hour, 4 hours and 8 hours soaking time. The purpose of treating fibres with alkali was to enhance the interfacial bonding between matrix and fibre surfaces. The maximum flexural strength occurred at 0.25 M NaOH solution with 1 hour of soaking time, i.e 96.71 MPa, improving by 24.41% from untreated fibre composite. But, the maximum flexural modulus took place at 0.5 M NaOH solution with 4 hours soaking time, i.e. 6948 MPa, improving by 148% from untreated composite.

  18. Bevacizumab as a treatment option for radiation-induced cerebral necrosis

    Energy Technology Data Exchange (ETDEWEB)

    Matuschek, Christiane; Boelke, Edwin; Budach, Wilfried [Univ. Hospital Duesseldorf (Germany). Dept. of Radiation Oncology; Nawatny, Jens [Univ. Hospital Duesseldorf (Germany). Dept. of Radiology; Hoffmann, Thomas K. [Duisburg-Essen Univ., Essen (Germany). Dept. of Otorhinolaryngology; Peiper, Matthias; Orth, Klaus [Hospital Essen-Sued, Essen (Germany). Dept. of Surgery; Gerber, Peter Arne [Univ. Hospital Duesseldorf (Germany). Dept. of Dermatology; Rusnak, Ethelyn [State Univ. of New York, Buffalo, NY (United States). Dept. of Anesthesiology; Lammering, Guido [Univ. Hospital Duesseldorf (Germany). Dept. of Radiation Oncology; MAASTRO Clinic, Maastricht (Netherlands). Radiation Oncology

    2011-02-15

    Radiation necrosis of normal CNS tissue represents one of the main risk factors of brain irradiation, occurring more frequently and earlier at higher total doses and higher doses per fraction. At present, it is believed that the necrosis results due to increasing capillary permeability caused by cytokine release leading to extracellular edema. This process is sustained by endothelial dysfunction, tissue hypoxia, and subsequent necrosis. Consequently, blocking the vascular endothelial growth factor (VEGF) at an early stage could be an option to reduce the development of radiation necrosis by decreasing the vascular permeability. This might help to reverse the pathological mechanisms, improve the symptoms and prevent further progression. A patient with radiation-induced necrosis was treated with an anti-VEGF antibody (bevacizumab), in whom neurologic signs and symptoms improved in accordance with a decrease in T1-weighted fluid-attenuated inversion recovery signals. Our case report together with the current literature suggests bevacizumab as a treatment option for patients with symptoms and radiological signs of cerebral necrosis induced by radiotherapy. (orig.)

  19. Acute esophageal necrosis caused by alcohol abuse

    Institute of Scientific and Technical Information of China (English)

    Tetsu Endo; Juichi Sakamoto; Ken Sato; Miyako Takimoto; Koji Shimaya; Tatsuya Mikami; Akihiro Munakata; Tadashi Shimoyama; Shinsaku Fukuda

    2005-01-01

    Acute esophageal necrosis (AEN) is extremely rare and the pathogenesis of this is still unknown. We report a case of AEN caused by alcohol abuse. In our case, the main pathogenesis could be accounted for low systemic perfusion caused by severe alcoholic lactic acidosis. After the healing of AEN, balloon dilatation was effective to manage the stricture.

  20. [Acral necrosis as a complication of urosepsis].

    Science.gov (United States)

    Blarer, J; Pfister, D; Jandali, A R; Gutzeit, A; John, H; Horstmann, M

    2014-06-01

    Sepsis is the third most common cause of death in Germany. Every fourth patient with sepsis has urosepsis. Even if substantial therapeutic progress has been made, sepsis remains a severe condition with high morbidity and mortality that requires rapid interdisciplinary measures. Besides life-threatening complications, acral necrosis as presented here can occur as a result of disseminated intravascular coagulation and severe microcirculatory disorders.

  1. A comparison on the flexural strength of a new dental porcelain (D.} Dentin with Vita company Dentin porcelain (VMK 68N

    Directory of Open Access Journals (Sweden)

    Ghahramanloo A.

    2004-06-01

    Full Text Available Statement of Problem: Dental porcelain is one of the best materials ever used in dentistry. Excellent tissue"ncompatibility, esthetics, very low solubility in oral fluids, high compressive strength, and the lowest bacterial"nplaque accumulation on the glazed porcelain are some of its advantages. Porcelain brittleness due to its low"ntensile strength, impact strength and the occlusal attrition of opposing teeth enamel are some of its"ndisadvantages. The most important mechanical properties of dental porcelains are their flexural strength that is"nthe ability of a porcelain to resist fracture when loaded from above. Different ways have been proposed to"neliminate porcelain brittleness and develop its flexural strength, among which baking porcelain on a metal"nframework is more commonly used."nPurpose: Considering that restoration and replacement of teeth by porcelain fused to metal restorations is still"nthe most commonly used technique, the aim of the present study was to measure the flexural strength of a"nporcelain bonded to metal powder, D4 Dentin, and to compare it with Vita Dentin powder."nMaterials and Methods: In this experimental study, a stainless steel box, 25x5x2mm was made according to"nISO 6872: 1995 (E Standard and filled with D4 Dentin powder and Vita Dentin (VMK 68N and baked in"nVita furnace. Then 10 blocks of D^ Dentin and 10 of Vita Dentin were made. Samples were placed on the"nthree point bending test machine and force was applied the middle of each block. To analyze the data, t-"nstudent test and co-variance analysis were used."nResults: Mean flexural strength of D4 Dentin was 53.40±1.35 MPa and that of Vita Dentin was 53.86+7.38"nMPa. The difference was not statistically significant."nConclusion: According to ISO 6872: 1995 (E standard, the flexural strength of all D4 Dentin samples were"ngreater than 50 Mpa.

  2. Biaxial flexural strength of Turkom-Cera core compared to two other all-ceramic systems

    Directory of Open Access Journals (Sweden)

    Bandar Mohammed Abdullah Al-Makramani

    2010-12-01

    Full Text Available Advances in all-ceramic systems have established predictable means of providing metal-free aesthetic and biocompatible materials. These materials must have sufficient strength to be a practical treatment alternative for the fabrication of crowns and fixed partial dentures. OBJECTIVES: The aim of this study was to compare the biaxial flexural strength of three core ceramic materials. MATERIAL AND METHODS: Three groups of 10 disc-shaped specimens (16 mm diameter x 1.2 mm thickness - in accordance with ISO-6872, 1995 were made from the following ceramic materials: Turkom-Cera Fused Alumina [(Turkom-Ceramic (M Sdn Bhd, Puchong, Selangor, Malaysia], In-Ceram (Vita Zahnfabrik, Bad Säckingen, Baden-Württemberg, Germany and Vitadur-N (Vita Zahnfabrik, Bad Säckingen, Baden-Württemberg, Germany, which were sintered according to the manufacturer's recommendations. The specimens were subjected to biaxial flexural strength test in an universal testing machine at a crosshead speed of 0.5 mm/min. The definitive fracture load was recorded for each specimen and the biaxial flexural strength was calculated from an equation in accordance with ISO-6872. RESULTS: The mean biaxial flexural strength values were: Turkom-Cera: 506.8±87.01 MPa, In-Ceram: 347.4±28.83 MPa and Vitadur-N: 128.7±12.72 MPa. The results were analyzed by the Levene's test and Dunnett's T3 post-hoc test (SPSS software V11.5.0 for Windows, SPSS, Chicago, IL, USA at a preset significance level of 5% because of unequal group variances (P<0.001. There was statistically significant difference between the three core ceramics (P<0.05. Turkom-Cera showed the highest biaxial flexural strength, followed by In-Ceram and Vitadur-N. CONCLUSIONS: Turkom-Cera core had significantly higher flexural strength than In-Ceram and Vitadur-N ceramic core materials.

  3. Flexural resistance of heat-pressed and CAD-CAM lithium disilicate with different translucencies.

    Science.gov (United States)

    Fabian Fonzar, Riccardo; Carrabba, Michele; Sedda, Maurizio; Ferrari, Marco; Goracci, Cecilia; Vichi, Alessandro

    2017-01-01

    To compare flexural strength of CAD-CAM and heat-pressed lithium disilicate. For Pressed specimens (Group A), acrylate polymer blocks were cut with a saw in bars shape. Sprueing, investing and preheating procedures were carried out following manufacturer's instructions. IPS e.max Press ingots (Ivoclar-Vivadent) were divided into subgroups (n=15) according to translucency: A.1=HT-A3; A.2=MT-A3; A.3=LT-A3; A.4=MO2. Ingots were then pressed following manufacturer's instructions. For CAD-CAM specimens (Group B) blocks of IPS e.max CAD (Ivoclar-Vivadent) were divided into subgroups: B.1=HT-A3; B.2=MT-A3; B.3=LT-A3; B.4=MO2. Specimens (n=15) were obtained by cutting the blocks with a saw. Final crystallization was performed following manufacturer's instructions. Both Press and CAD specimens were polished and finished with silica carbide papers of increasing grit. Final dimensions of the specimens were 4.0±0.2mm, 1.2±0.2mm, and 16.0±0.2mm. Specimens were tested using a three-point bending test. Flexural strength, Weibull modulus, and Weibull characteristic strength were calculated. Flexural strength data were statistically analyzed. The overall means of Press and CAD specimens did not differ significantly. Within the Press group different translucencies were found to have similar flexural strength. Within the CAD group, statistically significant differences emerged among the tested translucencies (pCAD formulations can be based on different criteria than flexural resistance. Within each formulation, for IPS e.max Press translucency does not affect the flexural strength while for IPS e.max CAD it is an influential factor. Copyright © 2016 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  4. Effect of cavity preparation on the flexural strengths of acrylic resin repairs

    Directory of Open Access Journals (Sweden)

    Safa Salim Elhadiry

    2010-12-01

    Full Text Available OBJECTIVE: To investigate the effect of cavity preparation on the flexural strength of heat-curing denture resin when repaired with an auto-curing resin. MATERIAL AND METHODS: Ninety-six rectangular specimens (64x10x2.5 mm prepared from heat-curing denture base resin (Meliodent were randomly divided into four groups before repair. One group was left intact as control. Each repair specimen was sectioned into two; one group was repaired using the conventional repair method (Group 1. Two groups had an additional transverse cavity (2x3.5x21.5 mm prepared prior to the repair; one repaired with (Group 2 and one without glass-fiber reinforcement (Group 3. A three-point flexural bending test according to the ISO 1567:1999 specification8 for denture base polymers was carried out on all groups after 1, 7 and 30 days of water immersion. Statistical analysis was carried out using two-way ANOVA, Kruskal Wallis and post-hoc Mann Whitney tests. RESULTS: The highest flexural strength was observed in the control group. Control and conventional repairs group (Group 1 showed reduction in the flexural strength 30 days after water immersion. No significant change in the strength was observed for Groups 2 and 3 where the repair joints were similarly prepared with additional transverse cavity. CONCLUSION: Repaired specimens showed lower flexural strength values than intact heat-curing resin. Cavity preparation had no significant effect on the flexural strength of repair with water immersion.

  5. Comparison of porcelain surface and flexural strength obtained by microwave and conventional oven glazing.

    Science.gov (United States)

    Prasad, Soni; Monaco, Edward A; Kim, Hyeongil; Davis, Elaine L; Brewer, Jane D

    2009-01-01

    Although the superior qualities of microwave technology are common knowledge in the industry, effects of microwave glazing of dental ceramics have not been investigated. The purpose of this study was to investigate the surface roughness and flexural strength achieved by glazing porcelain specimens in a conventional and microwave oven. Thirty specimens of each type of porcelain (Omega 900 and IPS d.Sign) were fabricated and sintered in a conventional oven. The specimens were further divided into 3 groups (n=10): hand polished (using diamond rotary ceramic polishers), microwave glazed, and conventional oven glazed. Each specimen was evaluated for surface roughness using a profilometer. The flexural strength of each specimen was measured using a universal testing machine. A 2-way ANOVA and Tukey HSD post hoc analysis were used to determine significant intergroup differences in surface roughness (alpha=.05). Flexural strength results were also analyzed using 2-way ANOVA, and the Weibull modulus was determined for each of the 6 groups. The surfaces of the specimens were subjectively evaluated for cracks and porosities using a scanning electron microscope (SEM). A significant difference in surface roughness was found among the surface treatments (P=.02). Follow-up tests showed a significant difference in surface roughness between oven-glazed and microwave-glazed treatments (P=.02). There was a significant difference in flexural strength between the 2 porcelains (Pmicrowave-glazed group was the highest (1.9) as compared to the other groups. The surface character of microwave-glazed porcelain was superior to oven-glazed porcelain. Omega 900 had an overall higher flexural strength than IPS d.Sign. Weibull distributions of flexural strengths for Omega 900 oven-glazed and microwave-glazed specimens were similar. SEM analysis demonstrated a greater number of surface voids and imperfections in IPS d. Sign as compared to Omega 900.

  6. Acute esophageal necrosis: a rare syndrome.

    Science.gov (United States)

    Gurvits, Grigoriy E; Shapsis, Alexander; Lau, Nancy; Gualtieri, Nicholas; Robilotti, James G

    2007-01-01

    Acute esophageal necrosis, which presents as a black esophagus on endoscopy, is a rare disorder that is poorly described in the medical literature. In this study, we analyze all cases reported to date to define risk factors, clinical presentation, endoscopic features, histologic appearance, treatment, complications, outcome and etiopathogenesis of the disease and to describe a distinct medical syndrome and propose a staging system. We searched Medline and PubMed from January 1965 to February 2006 for English-language articles using the key words "acute esophageal necrosis," "necrotizing esophagitis," and "black esophagus." A total of 88 patients were reported in the literature during the 40 years, 70 men and 16 women with an average age of 67 years. Patients were generally admitted for gastrointestinal bleeding and cardiovascular event/shock. Patients presented with hematemesis and melena in more than 70% of the cases. Upper endoscopy showed black, diffusely necrotic esophageal mucosa predominantly affecting the distal third of the organ. Necrosis was confirmed histologically in most cases. Complications included strictures or stenoses, mediastinitis/abscesses, and perforations. Overall mortality was 31.8%. This study provides a structured approach to identifying risk factors, diagnosis, and pathogenesis of the acute esophageal necrosis. Risk factors include age, male sex, cardiovascular disease, hemodynamic compromise, gastric outlet obstruction, alcohol ingestion, malnutrition, diabetes, renal insufficiency, hypoxemia, hypercoagulable state, and trauma. Mechanism of damage is usually multifactorial secondary to ischemic compromise, acute gastric outlet obstruction, and malnutrition. Overall, acute esophageal necrosis should be viewed as a poor prognostic factor, associated with high mortality from the underlying clinical disease.

  7. Flexural waves in fluid-filled tubes subject to axial impact

    OpenAIRE

    2008-01-01

    We experimentally studied the propagation of coupled fluid stress waves and tube flexural waves generated through projectile impact along the axis of a water-filled tube. We tested mild steel tubes, 38–40 mm inner diameter and wall thicknesses of 0.8 mm, 6.4 mm, and 12.7 mm. A steel impactor was accelerated using an air cannon and struck a polycarbonate buffer placed on top of the water surface within the tube. Elastic flexural waves were observed for impact speeds of 5–10 m/s and plastic wav...

  8. Omnidirectional refractive devices for flexural waves based on graded phononic crystals

    Energy Technology Data Exchange (ETDEWEB)

    Torrent, Daniel, E-mail: daniel.torrent@iemn.univ-lille1.fr; Pennec, Yan; Djafari-Rouhani, Bahram [Institut d' Electronique, de Microléctronique et de Nanotechnologie, UMR CNRS 8520, Université de Lille 1, 59655 Villeneuve d' Ascq (France)

    2014-12-14

    Different omnidirectional refractive devices for flexural waves in thin plates are proposed and numerically analyzed. Their realization is explained by means phononic crystal plates, where a previously developed homogenization theory is employed for the design of graded index refractive devices. These devices consist of a circular cluster of inclusions with a properly designed gradient in their radius. With this approach, the Luneburg and Maxwell lenses and a family of beam splitters for flexural waves are proposed and analyzed. Results show that these devices work properly in a broadband frequency region, being therefore an efficient approach for the design of refractive devices specially interesting for nano-scale applications.

  9. Flexural vibration band gaps in thin plates with two-dimensional binary locally resonant structures

    Institute of Scientific and Technical Information of China (English)

    Yu Dian-Long; Wang Gang; Liu Yao-Zong; Wen Ji-Hong; Qiu Jing

    2006-01-01

    The complete flexural vibration band gaps are studied in the thin plates with two-dimensional binary locally resonant structures, i.e. the composite plate consisting of soft rubber cylindrical inclusions periodically placed in a host material. Numerical simulations show that the low-frequency gaps of flexural wave exist in the thin plates. The width of the first gap decreases monotonically as the matrix density increases. The frequency response of the finite periodic thin plates is simulated by the finite element method, which provides attenuations of over 20dB in the frequency range of the band gaps. The findings will be significant in the application of phononic crystals.

  10. Effect of Nanoclay on the Flexural Creep Behavior of Wood/Plastic Composites

    Science.gov (United States)

    Kord, B.; Sheykholeslami, A.; Najafi, A.

    2016-01-01

    The effect of nanoclay on the short-term flexural creep behavior of polypropylene/wood flour composites was investigated. The results obtained showed that the flexural strength and modulus increased with contentt of nanoclay up to 3 phc and then decreased. The fractional deflection and relative creep decreased with increasing content of nanoclay. X-ray diffraction patterns and transmission electron microscopy revealed that the nanocomposites formed were intercalated. Morphological findings testified that the samples containing 3 phc of nanoclay had the highest degree of intercalation and dispersion.

  11. A flexure-based wrist for needle-sized surgical robots

    Science.gov (United States)

    Losey, Dylan P.; York, Peter A.; Swaney, Philip J.; Burgner, Jessica; Webster, Robert J.

    2013-03-01

    We present a novel flexure-based wrist design intended for use with needle-sized robotic manipulators. It is designed to be mounted at the tip of a traditional surgical needle, deployed through an endoscope working channel, or attached to the tip of a concentric tube robot. In all these applications, the wrist enables dexterity in small spaces. The wrist consists of two stacked flexure joints that are actuated by thin pull wires. In this paper we present the design of the wrist, its kinematics, and an experimental evaluation of the relationship between actuation force and tip displacement conducted using a scale model.

  12. Keratocyte loss in Acanihamoeba Keratitis: Phagocytosis, necrosis or apoptosis?

    Directory of Open Access Journals (Sweden)

    Vemuganti Geeta

    2000-01-01

    Full Text Available Purpose: Pathogenesis of Acanthamoeba keratitis involves breakdown of epithelial barrier, stromal invasion by Acanthamoeba, loss of keratocytes, inflammatory response and finally stromal necrosis. The loss of keratocytes, believed to be due to the phagocytic activity of the parasite, occurs disproportionate to and independent of the parasite load, thereby suggesting additional modes of cell loss. To test our hypothesis that the loss of keratocytes in Acanthamoeba keratitis is due to apoptosis, we did both histology and histochemistry on the corneal tissues. Methods: Routine Haematoxylin and Eosin, Gomori′s Methenamine Silver and Periodic acid Schiff stained sections of five corneal tissues from penetrating keratoplasty and eviscerated eyes were reviewed. TUNEL staining was done for morphological detection of apoptosis in three cases, using formalin-fixed, paraffin-processed tissues. Results: Histological changes were epithelial ulceration, loss of keratocytes in all layers, inflammation in anterior two-thirds of the stroma with necrosis, and deeper quiet stroma. Acanthamoeba trophozoites were found in the anterior stroma while the cysts were more in the deeper stroma, with minimal or no inflammatory response. TUNEL staining was positive in keratocytic nuclei in all layers. Conclusions: This study demonstrates that one of the modes of keratocyte loss in Acanthamoeba keratitis is by apoptosis, possibly in addition to the necrotic process and phagocytic activity of the parasite. The death of inflammatory cells also appears to be mediated by apoptosis.

  13. Analytical theory of flexural behavior of concrete beam reinforced with textile-combined steel

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Textile-reinforced concrete (TRC) is a new high performance cementitious composite material,which not only has superior corrosion resistance but also can effectively limit the development of concrete cracks and make the crack width and spacing of concrete become smaller.However,due to the brittle feature of fiber materials,the TRC structural member has no distinct failure symptom when it arrives at its ultimate load.At the same time,ordinary reinforced concrete (RC) elements have large dead weight and can not efficiently restrict the expansion of the main crack of structures because of the restriction of their special cover thickness.In order to overcome the disadvantages of both the TRC and the RC,a new architecture reinforced with textile-combined steel is proposed in this study,making full use of the advantages of the above two structures.The cover concrete at the tension zone of an RC element is partially replaced with TRC and thus the steel reinforcements replaced with textiles are subtracted.Compared with the old one,the new structure has less dead weight and has the merits of service safety and good durability.The flexural development process of the proper beam with this new structure is investigated in this paper and based on the plane section assumption,analytical equations are derived by using nonlinear analysis theory,including the load-carrying capacity at different stages and moment-curvature relationship and mid-span deflection during the entire loading process.Comparison between the calculated and the experimental results reveals satisfactory agreement and thus verifies the feasibility of the equations.

  14. [The effect of core veneer thickness ratio on the flexural strength of diatomite-based dental ceramic].

    Science.gov (United States)

    Jiang, Jie; Zhang, Xin; Gao, Mei-qin; Zhang, Fei-min; Lu, Xiao-li

    2015-06-01

    To evaluate the effect of different core veneer thickness ratios on the flexural strength and failure mode of bilayered diatomite-based dental ceramics. Diatomite-based dental ceramics blocks (16 mm×5.4 mm×1 mm) were sintered with different thickness of veneer porcelains: 0 mm (group A), 0.6 mm (group B), 0.8 mm (group C) and 1.0 mm (group D). Flexural strength was detected and scanning electron microscope was used to observe the interface microstructure. Statistical analysis was performed using SPSS 17.0 software package. With the increase of the thickness of the veneer porcelain, flexural strength of group C showed highest flexural strength up to (277.24±5.47) MPa. Different core veneer thickness ratios can significantly influence the flexural strength of bilayered diatomite-based dental ceramics. Supported by Science and Technology Projects of Nantong City (HS2013010).

  15. Continuum Plate Theory and Atomistic Modeling to Find the Flexural Rigidity of a Graphene Sheet Interacting with a Substrate

    Directory of Open Access Journals (Sweden)

    M. W. Roberts

    2010-01-01

    Full Text Available Using a combination of continuum modeling, atomistic simulations, and numerical optimization, we estimate the flexural rigidity of a graphene sheet. We consider a rectangular sheet that is initially parallel to a rigid substrate. The sheet interacts with the substrate by van der Waals forces and deflects in response to loading on a pair of opposite edges. To estimate the flexural rigidity, we model the graphene sheet as a continuum and numerically solve an appropriate differential equation for the transverse deflection. This solution depends on the flexural rigidity. We then use an optimization procedure to find the value of the flexural rigidity that minimizes the difference between the numerical solutions and the deflections predicted by atomistic simulations. This procedure predicts a flexural rigidity of 0.26 nN nm=1.62 eV.

  16. Regulated necrosis and its implications in toxicology.

    Science.gov (United States)

    Aki, Toshihiko; Funakoshi, Takeshi; Uemura, Koichi

    2015-07-03

    Recent research developments have revealed that caspase-dependent apoptosis is not the sole form of regulated cell death. Caspase-independent, but genetically regulated, forms of cell death include pyroptosis, necroptosis, parthanatos, and the recently discovered ferroptosis and autosis. Importantly, regulated necrosis can be modulated by small molecule inhibitors/activators, confirming the cell autonomous mechanism of these forms of cell death. The success of small molecule-mediated manipulation of regulated necrosis has produced great changes in the field of cell death research, and has also brought about significant changes in the fields of pharmacology as well as toxicology. In this review, we intend to summarize the modes of regulated cell death other than apoptosis, and discuss their implications in toxicology.

  17. Pancreatic Necrosis Associated with Preeclampsia-Eclampsia

    Directory of Open Access Journals (Sweden)

    Parmar MS

    2004-03-01

    Full Text Available CONTEXT: Acute pancreatitis during pregnancy is rare and commonly occurs in association with biliary disease. Preeclampsia is associated with microvascular abnormalities that may involve cerebral, placental, hepatic, renal and splanchnic circulation and rarely can cause acute pancreatitis. CASE REPORT: A case of acute pancreatitis in a patient with preeclampsia-eclampsia where the diagnosis was missed initially that resulted in a protracted course and development of organized pancreatic necrosis. The pancreatic necrosis resolved with conservative management over 8 weeks. CONCLUSIONS: The development of severe hypoalbuminemia, out of proportion to proteinuria, hypocalcemia and findings of capillary leak should alert the physician to search for other inflammatory causes, including acute pancreatitis so that early and effective management be given to avoid complications.

  18. Rapid repair of severely earthquake-damaged bridge piers with flexural-shear failure mode

    Science.gov (United States)

    Sun, Zhiguo; Wang, Dongsheng; Du, Xiuli; Si, Bingjun

    2011-12-01

    An experimental study was conducted to investigate the feasibility of a proposed rapid repair technique for severely earthquake-damaged bridge piers with flexural-shear failure mode. Six circular pier specimens were first tested to severe damage in flexural-shear mode and repaired using early-strength concrete with high-fluidity and carbon fiber reinforced polymers (CFRP). After about four days, the repaired specimens were tested to failure again. The seismic behavior of the repaired specimens was evaluated and compared to the original specimens. Test results indicate that the proposed repair technique is highly effective. Both shear strength and lateral displacement of the repaired piers increased when compared to the original specimens, and the failure mechanism of the piers shifted from flexural-shear failure to ductile flexural failure. Finally, a simple design model based on the Seible formulation for post-earthquake repair design was compared to the experimental results. It is concluded that the design equation for bridge pier strengthening before an earthquake could be applicable to seismic repairs after an earthquake if the shear strength contribution of the spiral bars in the repaired piers is disregarded and 1.5 times more FRP sheets is provided.

  19. Occlusal force, electromyographic activity of masticatory muscles and mandibular flexure of subjects with different facial types

    Directory of Open Access Journals (Sweden)

    William Custodio

    2011-08-01

    Full Text Available OBJECTIVE: The aim of this study was to evaluate whether vertical facial patterns influence maximal occlusal force (MOF, masticatory muscle electromyographic (EMG activity, and medial mandibular flexure (MMF. MATERIAL AND METHODS: Seventy-eight dentate subjects were divided into 3 groups by Ricketts's analysis: brachyfacial, mesofacial and dolychofacial. Maximum occlusal force in the molar region was bilaterally measured with a force transducer. The electromyographic activities of the masseter and anterior temporal muscles were recorded during maximal voluntary clenching. Medial mandibular flexure was calculated by subtracting the intermolar distance of maximum opening or protrusion from the distance in the rest position. The data were analyzed using ANOVA followed by Tukey's HSD test. The significance level was set at 5%. RESULTS: Data on maximum occlusal force showed that shorter faces had higher occlusal forces (P<0.0001. Brachyfacial subjects presented higher levels of masseter electromyographic activity and medial mandibular flexure, followed by the mesofacial and dolychofacial groups. Additionally, dolychofacial subjects showed significantly lower electromyographic temporalis activities (P<0.05. CONCLUSION: Within the limitations of the study, it may be concluded that maximum occlusal force, masticatory muscle activity and medial mandibular flexure were influenced by the vertical facial pattern.

  20. Evaluation of the flexural strength of carbon, quartz, and glass fiber-based posts

    Directory of Open Access Journals (Sweden)

    Sita Rama Raju

    2014-01-01

    Full Text Available Objectives: This study was done to evaluate the flexural strength of carbon, quartz, and glass fiber posts by means of three-point bending test. Materials and Methods: Thirty pre-fabricated fiber posts were used and divided into three groups. Group I carbon fiber posts (C-Post, group II quartz fiber post (Aestheti Plus, group III glass fiber post (Para Post White Ten posts (N = 10 were used for each experimental group and were measured with digital caliper before test accomplishment. The fracture load of post specimens was measured, and flexural strength was obtained by the formula using S = 8FL/pd 3 . The values in Kgf/mm 2 were obtained and calculated to Mpa and submitted to ANOVA (a = 0.01 and to the Tukey′s test. Results: The mean values of flexural strength show that group II quartz fiber posts (666 MPa are significantly higher than group I carbon fiber (614 MPa and group III glass fiber (575 MPa. C onclusion: Hence, this study concluded that quartz fiber post showed significantly higher flexural strength values. Further scope of this study lies in the evaluation and evolution of a restorative materials used for post and core preparation, which have modulus of elasticity in harmony with that of dentin and near-natural esthetic appearance.

  1. 6 W Full-Flexure-Bearing Stirling Cryocooler for the Cryosystem Program

    Science.gov (United States)

    Benschop, A. A. J.; Bruins, P. C.; Mullié, J. C.; Meijers, M.; Helmonds, H.; Trollier, T.

    2004-06-01

    In February 2002, ASTRIUM selected AL/DTA for the delivery of the vial freezers for the ESA / CRYOSYSTEM project. The CRYOSYSTEM is a set of facilities for ultra-rapid cooling, preservation and storage of biological samples and protein crystals at -180°C on-board the ISS. While selecting the cooler for this program, AL/DTA recognised that THALES' moving magnet flexure-bearing coolers offer the reliability required for space programs, for a price that is far below what is usual for space cryocoolers. Based on the cold finger of the existing LSF9320 cryocooler (5.6 W at 80 K for 150 W input), THALES has developed a cold finger with flexure-bearing support of the displacer. Combined with the moving magnet flexure-bearing compressor, this offers a very long lifetime and a very high reliability. The paper describes the development of the flexure-bearing supported displacer, which has an extra driving rod to increase its efficiency compared with conventional free displacer fingers. The efficiency optimisation and mass reduction has led to a cooler with a total mass (including heat-sinking and EMI shield) of 7.8 kg, with a cooling power of 6.6 W at 75 K for 100 W input. The results of the ongoing space qualification program will be discussed.

  2. Optimization of release locations for small self-stress large stiffness flexure mechanisms

    NARCIS (Netherlands)

    Brouwer, D.M.; Boer, S.E.; Meijaard, J.P.; Aarts, R.G.K.M.

    2013-01-01

    In overconstrained mechanisms inherent alignment errors cause self-stress. The level of stress can be reduced by inserting flexure releases making the mechanism exactly constrained. The location and orientation of releases can be optimized for a combination of minimum self-stress and maximum stiffne

  3. Fluoride release, recharge and flexural properties of polymethylmethacrylate containing fluoridated glass fillers.

    Science.gov (United States)

    Al-Bakri, I A; Swain, M V; Naoum, S J; Al-Omari, W M; Martin, E; Ellakwa, A

    2014-06-01

    The purpose of this study was to investigate the effect of fluoridated glass fillers on fluoride release, recharge and the flexural properties of modified polymethylmethacrylate (PMMA). Specimens of PMMA denture base material with various loading of fluoridated glass fillers (0%, 1%, 2.5%, 5% and 10% by weight) were prepared. Flexural properties were evaluated on rectangular specimens (n = 10) aged in deionized water after 24 hours, 1 and 3 months. Disc specimens (n = 10) were aged for 43 days in deionized water and lactic acid (pH 4.0) and fluoride release was measured at numerous intervals. After ageing, specimens were recharged and fluoride re-release was recorded at 1, 3 and 7 days after recharge. Samples containing 2.5%, 5% and 10% glass fillers showed significantly (p glass fillers specimens. All experimental specimens exhibited fluoride release in both media. The flexural strength of specimens decreased in proportion to the percentage filler inclusion with the modulus of elasticity values remaining within ISO Standard 1567. The modified PMMA with fluoridated glass fillers has the ability to release and re-release fluoride ion. Flexural strength decreased as glass filler uploading increased. © 2014 Australian Dental Association.

  4. AN ACCURATE MODEL FOR CALCULATING CORRECTION OF PATH FLEXURE OF SATELLITE SIGNALS

    Institute of Scientific and Technical Information of China (English)

    LiYanxing; HuXinkang; ShuaiPing; ZhangZhongfu

    2003-01-01

    The propagation path of satellite signals in the atmosphere is a curve thus it,is very difficult to calculate its flexure correction accurately, a strict calculating expressions has so far not been derived. In this study, the flexure correction of the refraction curve is divided into two parts and their strict calculating expressions are derived. By use of the standard atmospheric model, the accurate flexure correction of the refraction curve is calculated for different zenith distance Z. On this basis, a calculation model is structured. This model is very simple in structure, convenient in use and high in accuracy. When Z is smaller than 85°,the accuracy of the correction exceeds 0.06mm. The flexure correction is basically proportional to tan2Z and increases rapidly with the increase of Z When Z>50°,the correction is smaller than 0.5 mm and can be neglected. When Z>50°, the correction must be made. When Z is 85°, 88° and 89° , the corrections are 198mm, 8.911m and 28.497 km, respectively. The calculation results shows that the correction estimate by Hopfield is correct when Z≤80°, but too small when Z=89°. The expression in this paper is applicable to any satellite.

  5. AN ACCURATE MODEL FOR CALCULATING CORRECTION OF PATH FLEXURE OF SATELLITE SIGNALS

    Institute of Scientific and Technical Information of China (English)

    Li Yanxing; Hu Xinkang; Shuai Ping; Zhang Zhongfu

    2003-01-01

    The propagation path of satellite signals in the atmosphere is a curve thus it.is very difficult to calculate its flexure correction accurately, a strict calculating expressions has so far not been derived. In this study, the flexure correction of the refraction curve is divided into two parts and their strict calculating expressions are derived. By use of the standard atmospheric model, the accurate flexure correction of the refraction curve is calculated for different zenith distance Z. On this basis, a calculation model is structured. This model is very simple in structure, convenient in use and high in accuracy. When Z is smaller than 85°, the accuracy of the correction exceeds 0.06 mm. The flexure correction is basically proportional to tan2Z and increases rapidly with the increase of Z When Z>50°,the correction is smaller than 0.5 mm and can be neglected.When Z>50°, the correction must be made. When Z is 85° , 88° and 89° , the corrections are 198mm, 8. 911 m and 28. 497 km, respectively. The calculation results shows that the correction estimate by Hopfield is correct when Z≤80 °, but too small when Z=89°. The expression in this paper is applicable to any satellite.

  6. Compressive and flexural strength of expanded perlite aggregate mortar subjected to high temperatures

    Science.gov (United States)

    Zulkifeli, Muhamad Faqrul Hisham bin Mohd; Saman@Hj Mohamed, Hamidah binti Mohd

    2017-08-01

    Work on thermal resistant of outer structures of buildings is one of the solution to reduce death, damages and properties loss in fire cases. Structures protected with thermal resistant materials can delay or avoid failure and collapse during fire. Hence, establishment of skin cladding with advance materials to protect the structure of buildings is a necessary action. Expanded perlite is a good insulation material which can be used as aggregate replacement in mortar. This study is to study on mortar mechanical properties of flexural and compressive strength subjected to elevated temperatures using expanded perlite aggregate (EPA). This study involved experimental work which was developing mortar with sand replacement by volume of 0%, 10%, 20%, 30% and 40% of EPA and cured for 56 days. The mortars then exposed to 200°C, 400 °C, 700 °C and 1000 °C. Flexural and compressive strength of the mortar were tested. The tests showed that there were increased of flexural and compressive strength at 200°C, and constantly decreased when subjected to 400°C, 700°C and 1000 °C. There were also variation of strengths at different percentages of EPA replacement. Highest compressive strength and flexural strength recorded were both at 200 °C with 65.52 MPa and 21.34 MPa respectively. The study conclude that by using EPA as aggregate replacement was ineffective below elevated temperatures but increased the performance of the mortar at elevated temperatures.

  7. Influence of hydrofluoric acid concentration on the flexural strength of a feldspathic ceramic.

    Science.gov (United States)

    Venturini, Andressa B; Prochnow, Catina; May, Liliana G; Bottino, Marco C; Felipe Valandro, Luiz

    2015-08-01

    This study evaluated the effects of etching with increasing hydrofluoric (HF) acid concentrations on the roughness and flexural strength of a feldspathic ceramic. One hundred and fifty ceramic specimens (14×4×1.2 mm(2)) were produced from ceramic blocks (VitaBlocks Mark II). All specimens were polished, chamfered and sonically cleaned in isopropyl alcohol. Specimens were randomly divided into 5 groups (n=30): SC (control) no ceramic surface etching; HF1, HF3, HF5 and HF10 ceramic surface etching for 60s with 1%, 3%, 5% and 10% HF acid concentrations, respectively. Profilometry was performed in all specimens to evaluate roughness prior to flexural strength testing. Data were analyzed using one-way ANOVA and Tukey׳s test (α=0.05). Weibull module (m) and characteristic stress (σc) were also determined. HF acid etching, regardless of the concentration used, led to significantly rougher surfaces than the control (pAcid etching significantly reduced the mean flexural strength when compared with the control (143.3 MPa). Weibull modulus of the groups was similar, except for the HF5 group that was higher compared to HF3. Flexural strength was similarly affected by the different HF acid concentrations tested, but roughness increased higher the acid concentration. Ceramic etching led to a significant reduction in strength when compared to the untreated ceramic, regardless of its concentration.

  8. Studies on the flexural and thermomechanical properties of woven carbon/nanoclay-epoxy laminates

    Energy Technology Data Exchange (ETDEWEB)

    Chowdhury, F.H. [Center for Advanced Materials, Tuskegee University, Tuskegee, AL 36088 (United States); Hosur, M.V. [Center for Advanced Materials, Tuskegee University, Tuskegee, AL 36088 (United States)]. E-mail: mhosur@gmail.com; Jeelani, S. [Center for Advanced Materials, Tuskegee University, Tuskegee, AL 36088 (United States)

    2006-04-15

    A systematic study was carried out to investigate the effects of nanoclay particles on flexural and thermal properties of woven carbon fiber reinforced polymer matrix composites. Different weight percentages of Nanomer[reg] I-28E nanoclay, a surface modified montmorillonite mineral, were dispersed in SC-15 epoxy using sonication route. The nanophased epoxy was then used to manufacture 6000 fiber tow-plain weave carbon/epoxy nanocomposites using vacuum assisted resin infusion molding (VARIM) process. Effect of post curing on these samples was also investigated. Three-point bend flexure and dynamic mechanical analysis (DMA) studies were carried out on eight and three layered samples, respectively. Maximum improvements in flexural strength and modulus were found for 2 wt.% nanoclay reinforced composites. Failure surface analysis of flexure samples was carried out by scanning electron microscopy (SEM) analysis. Dynamic mechanical analysis showed enhancement in thermomechanical properties. Glass transition temperature, T {sub g} of room temperature cured and thermally post cured samples showed an improvement of about 9 and 13 deg. C, respectively for 2 wt.% nanoclay loading.

  9. Corrections for shear and rotatory inertia on flexural vibrations of beams

    NARCIS (Netherlands)

    Nederveen, C.J.; Schwarzl, F.R.

    1964-01-01

    Different correction formulae for the influence of shear and rotatory inertia on flexural vibrations of freely supported beams are compared with the exact solution. It appears that in most cases a simple formula is sufficient because of the appearance of a constant which is not accurately known, viz

  10. Flexural and tensile bond strength, related via a stochastic numerical approach

    NARCIS (Netherlands)

    Pluijm, R. van der

    1998-01-01

    The flexural strength of masonry parallel to the bed joint depends on the geometry of the cross section, tensile bond strength, fracture energy, stiffness of units and of mortar joints. In experiments, tensile bond strength and fracture energy determined on relatively small specimens, show a large s

  11. Effect of mechanical cycling on the flexural strength of densely sintered ceramics

    NARCIS (Netherlands)

    Itinoche, Koiti Marco; Ozcan, Mudu; Bottino, Marco Antonio; Oyafuso, Denise

    2006-01-01

    Objectives. The aim of this study was to evaluate the effect of mechanical cycling on the biaxial flexural strength of two densely sintered ceramic materials. Methods. Disc shaped zirconia (In-Ceram Zirconia) and high alumina (Procera AllCeram) ceramic specimens (diameter: 15 min and thickness: 1.2

  12. Exact Constraint Design of a Two-Degree of Freedom Flexure-Based Mechanism

    NARCIS (Netherlands)

    Brouwer, Dannis Michel; Folkersma, Ger; Boer, Steven; Aarts, Ronald G.K.M.

    2013-01-01

    We present the exact constraint design of a two degrees of freedom cross-flexure-based stage that combines a large workspace to footprint ratio with high vibration mode frequencies. To maximize unwanted vibration mode frequencies the mechanism is an assembly of optimized parts. To ensure a

  13. Coupling of flexural and longitudinal wave motion in a periodic structure with asymmetrically arranged transverse beams

    DEFF Research Database (Denmark)

    Friis, Lars; Ohlrich, Mogens

    2005-01-01

    In this paper we investigate the coupling of flexural and longitudinal wave motions in a waveguide with structural side branches attached at regular intervals. The analysis is based on periodic structure theory, and considers wave transmission in a fully tricoupled and semidefinite periodic...

  14. Flexural performance of foam concrete containing pulverized bone as partial replacement of cement

    Directory of Open Access Journals (Sweden)

    Efe Ikponmwosa

    2014-01-01

    Full Text Available This paper presents the results of a study conducted to investigate the flexural behaviour of foam concrete containing pulverised bone as partial replacement of cement. A total of sixty reinforced beams (150×150×750 mm were used to investigate the flexural behaviour of the specimens. For reinforcement of the beams, hot-rolled, deformed 10-mm-diameter bars with yield and ultimate stresses of 478.10 N/mm2 and 710.81 N/mm2 respectively were used. The cement constituent of the mix was partly replaced with up to 20% of pulverised bone. The flexural parameters investigated are crack formation and its pattern, failure mode, ul timate load, theoretical and experimental ultimate moments, deflection and stiffness. From the results of this investigation, it is concluded that the provision of the design standard in relation to shear and flexural design of beams can be considered as adequate for the design of reinforced foam concrete. It is further concluded that the stiffness is not affected by the inclusion of pulverised bone in the mix at up to 15% cement replacement level , and neither is the deflection pattern of the uncracked sections of the specimens affected by the inclusion of pulverised bone. The bending moments of the specimens,however, decreased with increase in pulverised bone.

  15. Mechanical and thermal cycling effects on the flexural strength of glass ceramics fused to titanium

    NARCIS (Netherlands)

    Vasquez, Vanessa; Ozcan, Mutlu; Nishioka, Renato; Souza, Rodrigo; Mesquita, Alfredo; Pavanelli, Carlos

    2008-01-01

    This study evaluated the effects of mechanical and thermal cycling on the flexural strength (ISO 9693) of three brands of ceramics fused to commercially pure titanium (cpTi). Metallic frameworks of 25 x 3 x 0.5 mm dimensions (N = 84) were cast in cpTi, followed by 150-mu m aluminum oxide airborne pa

  16. Coupling of Flexural and Longitudinal Damped Vibration in a Two-Layered Beam

    Directory of Open Access Journals (Sweden)

    F. Pourroy

    1998-01-01

    Full Text Available In dynamics, the effect of varying the constitutive materials’ thickness of a two-layered beam is investigated. Resonance frequencies and damping variations are determined. It is shown that for specific thicknesses the coupling of longitudinal and flexural vibrations influences the global modal damping ratio significantly.

  17. Performance optimization of large stroke flexure hinges for high stiffness and eigenfrequency

    NARCIS (Netherlands)

    Gunnink, K.; Aarts, R.G.K.M.; Brouwer, D.M.

    2013-01-01

    Two flexure hinge types are optimized for high support stiffness and high first unwanted eigenfrequency for two different working ranges, ±5.7° and ±20°. We show how multiple performance specifications lead to different designs with different performance. The optimization uses efficient parameterize

  18. Research on differences and correlation between tensile, compression and flexural moduli of cement stabilized macadam

    Directory of Open Access Journals (Sweden)

    Yi Yang

    2017-07-01

    Full Text Available In order to reveal the differences and conversion relations between the tensile, compressive and flexural moduli of cement stabilized macadam, in this paper, we develop a new test method for measuring three moduli simultaneously. By using the materials testing system, we test three moduli of the cement stabilized macadam under different loading rates, propose a flexural modulus calculation formula which considers the shearing effect, reveal the change rules of the tensile, compression and flexural moduli with the loading rate and establish the conversion relationships between the three moduli. The results indicate that: three moduli become larger with the increase of the loading rate, showing a power function pattern; with the shear effect considered, the flexural modulus is increased by 47% approximately over that in the current test method; the tensile and compression moduli of cement stabilized macadam are significantly different. Therefore, if only the compression modulus is used as the structural design parameter of asphalt pavement, there will be a great deviation in the analysis of the load response. In order to achieve scientific design and calculation, the appropriate design parameters should be chosen based on the actual stress state at each point inside the pavement structure.

  19. Flexural Strength Evaluation of Reinforced Concrete Members with Ultra High Performance Concrete

    Directory of Open Access Journals (Sweden)

    Baek-Il Bae

    2016-01-01

    Full Text Available Flexural strength evaluation models for steel fiber reinforced ultra high strength concrete were suggested and evaluated with test results. Suggested flexural strength models were composed of compression stress blocks and tension stress blocks. Rectangular stress block, triangular stress block, and real distribution shape of stress were used on compression side. Under tension, rectangular stress block distributed to whole area of tension side and partial area of tension side was used. The last model for tension side is realistic stress distribution. All these models were verified with test result which was carried out in this study. Test was conducted by four-point loading with 2,000 kN actuator for slender beam specimen. Additional verifications were carried out with previous researches on flexural strength of steel fiber reinforced concrete or ultra high strength concrete. Total of 21 test specimens were evaluated. As a result of comparison for flexural strength of section, neutral axis depth at ultimate state, models with triangular compression stress block, and strain-softening type tension stress block can be used as exact solution for ultra high performance concrete. For the conservative and convenient design of section, modified rectangular stress block model can be used with strain softening type tension stress block.

  20. An In vitro Evaluation of Flexural Bond Strength of Indirect Composites Fused to Metal.

    Science.gov (United States)

    Sunitha, N; Ariga, Padma; Jain, Ashish R; Philip, Jacob Mathew

    2013-06-01

    With the advent of newer indirect composite resin materials for crown and bridge prosthesis, it has become imperative to evaluate their strength to serve as long term replacements as a substitute to metal ceramic restorations. This study aimed to evaluate and compare the flexural bond strength of three composite resin veneering material to metal, cured by different methods. Specimen were fabricated with pattern resin by duplicating it with machined metal die and divided into three groups. Three composite resin materials were used in this study. Group (A) received Adoro, Group (B) received Targis and Group (C) received Tescera. The bond strength of all specimens was tested with Lloyd's universal testing machine under three point loading. The highest values for fracture resistance were displayed by light, heat and pressure cured composites followed by composites cured using a temperature of 104 °C and composites with curing temperature of 95 °C. The results indicate that there is a significant difference between the three groups, with the Tescera group specimens exhibiting the highest flexural bond strength. Of the other two groups, Adoro group exhibited higher flexural bond strength than Targis group. The results of this study suggest that Tescera group with curing temperature of 130 °C and pressure of 80 Psi, cured with metal halide unit exhibited the highest flexural bond strength when compared to Adoro and Targis groups.

  1. Long-Term Flexural Behaviors of GFRP Reinforced Concrete Beams Exposed to Accelerated Aging Exposure Conditions

    Directory of Open Access Journals (Sweden)

    Yeonho Park

    2014-06-01

    Full Text Available This study investigates the impact of accelerated aging conditions on the long-term flexural behavior and ductility of reinforced concrete (RC members with glass fiber-reinforced polymer (GFRP bars (RC-GFRP specimen and steel bars (RC-steel specimen. A total of thirty six specimens were designed with different amounts of reinforcement with three types of reinforcing bars (i.e., helically wrapped GFRP, sand-coated surface GFRP and steel. Eighteen specimens were subjected to sustained loads and accelerated aging conditions (i.e., 47 °C and 80% relative humidity in a chamber. The flexural behavior of specimens under 300-day exposure was compared to that of the companion specimens without experiencing accelerated aging conditions. Results indicate that the accelerated aging conditions reduced flexural capacity in not only RC-steel, but also RC-GFRP specimens, with different rates of reduction. Different types of GFRP reinforcement exhibited different rates of degradation of the flexural capacity when embedded in concrete under the same exposure conditions. Several existing models were compared with experimental results for predicting the deflection and deformability index for specimens. Bischoff and Gross’s model exhibited an excellent prediction of the time-dependent deflections. Except for the deformability index proposed by Jaeger, there was no general trend related to the aging duration. This study recommends the need for further investigation on the prediction of the deformability index.

  2. Mechanical and thermal cycling effects on the flexural strength of glass ceramics fused to titanium

    NARCIS (Netherlands)

    Vasquez, Vanessa; Ozcan, Mutlu; Nishioka, Renato; Souza, Rodrigo; Mesquita, Alfredo; Pavanelli, Carlos

    This study evaluated the effects of mechanical and thermal cycling on the flexural strength (ISO 9693) of three brands of ceramics fused to commercially pure titanium (cpTi). Metallic frameworks of 25 x 3 x 0.5 mm dimensions (N = 84) were cast in cpTi, followed by 150-mu m aluminum oxide airborne

  3. Flexural strength and the probability of failure of cold isostatic pressed zirconia core ceramics.

    Science.gov (United States)

    Siarampi, Eleni; Kontonasaki, Eleana; Papadopoulou, Lambrini; Kantiranis, Nikolaos; Zorba, Triantafillia; Paraskevopoulos, Konstantinos M; Koidis, Petros

    2012-08-01

    The flexural strength of zirconia core ceramics must predictably withstand the high stresses developed during oral function. The in-depth interpretation of strength parameters and the probability of failure during clinical performance could assist the clinician in selecting the optimum materials while planning treatment. The purpose of this study was to evaluate the flexural strength based on survival probability and Weibull statistical analysis of 2 zirconia cores for ceramic restorations. Twenty bar-shaped specimens were milled from 2 core ceramics, IPS e.max ZirCAD and Wieland ZENO Zr, and were loaded until fracture according to ISO 6872 (3-point bending test). An independent samples t test was used to assess significant differences of fracture strength (α=.05). Weibull statistical analysis of the flexural strength data provided 2 parameter estimates: Weibull modulus (m) and characteristic strength (σ(0)). The fractured surfaces of the specimens were evaluated by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The investigation of the crystallographic state of the materials was performed with x-ray diffraction analysis (XRD) and Fourier transform infrared (FTIR) spectroscopy. Higher mean flexural strength (Pstrength of WZ ceramics was associated with a lower m and more voids in their microstructure. These findings suggest a greater scattering of strength values and a flaw distribution that are expected to increase failure probability. Copyright © 2012 The Editorial Council of the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved.

  4. [Avascular necrosis of the femoral head].

    Science.gov (United States)

    Porubský, Peter; Trč, Tomáš; Havlas, Vojtěch; Smetana, Pavel

    Avascular necrosis of the femoral head in adults is not common, but not too rare diseases. In orthopedic practice, it is one of the diseases that are causing implantation of hip replacement at a relatively early age. In the early detection and initiation of therapy can delay the implantation of prosthesis for several years, which is certainly more convenient for the patient and beneficial. This article is intended to acquaint the reader with the basic diagnostic procedures and therapy.

  5. Black esophagus: Acute esophageal necrosis syndrome

    Institute of Scientific and Technical Information of China (English)

    Grigoriy; E; Gurvits

    2010-01-01

    Acute esophageal necrosis (AEN), commonly referred to as "black esophagus", is a rare clinical entity arising from a combination of ischemic insult seen in hemodynamic compromise and low-flow states, corrosive injury from gastric contents in the setting of esophago-gastroparesis and gastric outlet obstruction, and decreased function of mucosal barrier systems and reparative mechanisms present in malnourished and debilitated physical states. AEN may arise in the setting of multiorgan dysfunction, hypoperfusi...

  6. Avascular necrosis of a vertebral body

    Institute of Scientific and Technical Information of China (English)

    HUANG Sheng-li; SHI Wei; HE Xi-jing

    2009-01-01

    @@ Avascular necrosis of a vertebral body,a relatively uncommon entity,is caused by malicgnancy,infection,radiation,systemic stemid treatment,trauma,and the ike.1 Vertebral osteonecrosis induced by trauma is called Kümmell's disease,because it was initially described by Hermann KLimmell of Germany in 1891.2 This paper reported a young female with posttraumatic vertebral osteonecrosis and analyzed the causes.She was treated by thoracoscopic Surgery successfully.

  7. Characterizetion of Flexural Strength, Warpage and Shrinkage of Polypropylene-Nanoclay-Nanocomposites Blend with Gigantochloa Scortechinii.

    Science.gov (United States)

    Khamis, S. Z.; Othman, M. H.; Hasan, S.; Ibrahim, M. H. I.

    2017-08-01

    This paper presents the characterization of Flexural Strength, Warpage and Shrinkage of reinforcement gigantochloa scortechinii fibre. The content of fiber were fixed at 0 wt.%, 3 wt.% and 6 wt.% in uniform increased. The selected injection moulding processing conditions were packing pressure, melt temperature, screw speed and filling time. The quality factors that need to be improved upon the characterization were flexural strength, warpage and shrinkage. This research started by drying the Gigantochloa Scortechinii fibres at 120°C. After that, 3 wt.% of the fibres were mixed with 81 wt.% of polypropylene, 15 wt.% of polypropylene grafted maleic anhydride (compatibilizer) and 1 wt. % of nanoclay. Samples with 6 wt.% of fibers were also prepared for comparison purpose. The mixing process was performed by using Brabender Lab-Compounder KETSE 20/40 and the pallets were produced using used Brabender® pelletizer with diameters of 1 to 4 mm. The optimisation process was accomplished by adopting the Taguchi L9 orthogonal array method. According to the results, for 0 wt.% GS, the flexural strength is 30.0082 MPa, the warpage is 0.0030000 mm and the shrinkage is 0.0003830 mm at packing pressure 40%, melt temperature 165°C, filled time 2 seconds and screw speed 35%. For the result 3 wt.% GS, the flexural strength is 32.2477 MPa, the warpage is 0.006670 mm and the shrinkage is 0.0003830 mm at packing pressure is 35%, melt temperature 165°C, filled times is 1 seconds and screw speed is 30%. While for the 6 wt.% GS, the results of the flexural strength is 36.9084 MPa, the warpage is 0.0066700 mm and the shrinkage is 0.0003830 mm at packing pressure is 35%, melt temperature 165°C, filled time is 2 seconds and screw speed is 30%. The existence of Gigantochloa Scortechinii fibre was also proven to effect significantly towards flexural strength with 6% increasing value ordering from 0 wt.% GS to 6 wt.% GS. while, the warpage value increasing from 0.003000 mm to 0.00667 mm and

  8. The role of tumour necrosis factor alpha and soluble tumour necrosis factor alpha receptors in the symptomatology of schizophrenia.

    Science.gov (United States)

    Turhan, Levent; Batmaz, Sedat; Kocbiyik, Sibel; Soygur, Arif Haldun

    2016-07-01

    Background Immunological mechanisms may be responsible for the development and maintenance of schizophrenia symptoms. Aim The aim of this study is to measure tumour necrosis factor-alpha (TNF-α), soluble tumour necrosis factor-alpha receptor I (sTNF-αRI), and soluble tumour necrosis factor-alpha receptor II (sTNF-αRII) levels in patients with schizophrenia and healthy individuals, and to determine their relationship with the symptoms of schizophrenia. Methods Serum TNF-α, sTNF-αRI and sTNF-αRII levels were measured. The Positive and Negative Syndrome Scale (PANSS) was administered for patients with schizophrenia (n = 35), and the results were compared with healthy controls (n = 30). Hierarchical regression analyses were undertaken to predict the levels of TNF-α, sTNF-αRI and sTNF-αRII. Results No significant difference was observed in TNF-α levels, but sTNF-αRI and sTNF-αRII levels were lower in patients with schizophrenia. Serum sTNF-αRI and sTNF-αRII levels were found to be negatively correlated with the negative subscale score of the PANSS, and sTNF-αRI levels were also negatively correlated with the total score of the PANSS. Smoking, gender, body mass index were not correlated with TNF-α and sTNF-α receptor levels. Conclusions These results suggest that there may be a change in anti-inflammatory response in patients with schizophrenia due to sTNF-αRI and sTNF-αRII levels. The study also supports low levels of TNF activity in schizophrenia patients with negative symptoms.

  9. Rin4 Causes Hybrid Necrosis and Race-Specific Resistance in an Interspecific Lettuce Hybrid

    NARCIS (Netherlands)

    Jeuken, M.J.W.; Zhang, N.; McHale, L.K.; Pelgrom, K.T.B.; Boer, den E.; Lindhout, P.; Michelmore, R.; Visser, R.G.F.; Niks, R.E.

    2009-01-01

    Some inter- and intraspecific crosses may result in reduced viability or sterility in the offspring, often due to genetic incompatibilities resulting from interactions between two or more loci. Hybrid necrosis is a postzygotic genetic incompatibility that is phenotypically manifested as necrotic les

  10. Severe glandular tularemia in a patient treated with anti-tumour necrosis factor for psoriatic arthritis

    Directory of Open Access Journals (Sweden)

    Ruxandra Calin

    2017-07-01

    Full Text Available A case of severe glandular tularemia in a patient receiving anti-tumour necrosis factor (TNF therapy is reported here. The patient required prolonged treatment with doxycycline–ciprofloxacin due to early relapse after ciprofloxacin was stopped. Tularemia may have a more severe course in patients receiving anti-TNF. This may thus be an indication for more aggressive treatment.

  11. Sol-gel derived bioactive coating on zirconia: Effect on flexural strength and cell proliferation.

    Science.gov (United States)

    Shahramian, Khalil; Leminen, Heidi; Meretoja, Ville; Linderbäck, Paula; Kangasniemi, Ilkka; Lassila, Lippo; Abdulmajeed, Aous; Närhi, Timo

    2016-09-07

    The purpose of this study was to evaluate the effect of sol-gel derived bioactive coatings on the biaxial flexural strength and fibroblast proliferation of zirconia, aimed to be used as an implant abutment material. Yttrium stabilized zirconia disc-shaped specimens were cut, ground, sintered, and finally cleansed ultrasonically in each of acetone and ethanol for 5 minutes. Three experimental groups (n = 15) were fabricated, zirconia with sol-gel derived titania (TiO2 ) coating, zirconia with sol-gel derived zirconia (ZrO2 ) coating, and non-coated zirconia as a control. The surfaces of the specimens were analyzed through images taken using a scanning electron microscope (SEM), and a non-contact tapping mode atomic force microscope (AFM) was used to record the surface topography and roughness of the coated specimens. Biaxial flexural strength values were determined using the piston-on-three ball technique. Human gingival fibroblast proliferation on the surface of the specimens was evaluated using AlamarBlue assay™. Data were analyzed using a one-way analysis of variance (ANOVA) followed by Tukey's post-hoc test. Additionally, the biaxial flexural strength data was also statistically analyzed with the Weibull distribution. The biaxial flexural strength of zirconia specimens was unaffected (p > 0.05). Weibull modulus of TiO2 coated and ZrO2 coated groups (5.7 and 5.4, respectively) were lower than the control (8.0). Specimens coated with ZrO2 showed significantly lower fibroblast proliferation compared to other groups (p sol-gel derived coatings have no influence on the flexural strength of zirconia. ZrO2 coated specimens showed significantly lower cell proliferation after 12 days than TiO2 coated or non-coated control. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2016.

  12. Water Sorption and Flexural Strength of Thermoplastic and Conventional Heat-Polymerized Acrylic Resins

    Directory of Open Access Journals (Sweden)

    Mohammad Ali Hemmati

    2016-01-01

    Full Text Available Objectives: The aim of this study was to assess and compare the water sorption and flexural strength of thermoplastic and conventional acrylic resins.Materials and Methods: Water sorption and flexural strength were compared between a thermoplastic modified polymethyl methacrylate (PMMA denture base resin (group A and a heat-polymerized PMMA acrylic resin (group B as the control group (n=10. A three-point bending test was carried out for flexural strength testing. For water sorption test, 10 disc-shaped samples were prepared. After desiccating, the samples were weighed and immersed in distilled water for seven days. Then, they were weighed again, and desiccated for the second and third times. Differences between the mean values in the two groups were analyzed using Student's t-test.Results: The mean value of water sorption was 14.74±1.36 μg/mm3 in group A, and 19.11±0.90 μg/mm3 in group B; this difference was statistically significant (P< 0.001. The mean value of flexural strength was 88.21±8.63 MPa in group A and 77.77±9.49 MPa in group B. A significant difference was observed between the two groups (P= 0.019.Conclusion: Flexural strength of group A was significantly higher than that of group B, and its water sorption was significantly lower. Thus, thermoplastic resins can be a suitable alternative to conventional PMMA acrylic resins as denture base materials.

  13. Evaluation of the Flexural Strength of Interim Restorative Materials in Fixed Prosthodontics.

    Science.gov (United States)

    Mehrpour, Hanieh; Farjood, Ehsan; Giti, Rashin; Barfi Ghasrdashti, Alireza; Heidari, Hossein

    2016-09-01

    Mechanical properties of interim restorations are considered as important factors specially when selecting materials for long-term application or for patients with para-functional habits. Flexural strength is one of the most important components of these restorations. The purpose of this study was to compare the flexural strength of five interim restorative materials. Fifty identical samples sized 25×2×2-mm were made from five interim materials (TempSpan; Protemp 4, Unifast III, Trim, and Revotek LC) according to ADA specification #27. The specimens were stored in artificial saliva for 2 weeks and then thermocycled for 2500 cycles (5-55˚C). A standard three-point bending test was conducted on the specimens with a universal testing machine at a crosshead speed of 0.75mm/min. Data were analyzed by using one-way ANOVA and Tamhane's post-hoc tests to measure the flexural strength of temporary materials. One of the bis-acryl resins (TempSpan) showed the highest, and the light polymerized resin (Revotek LC) showed the lowest flexural strength. The mean values of flexural strength (MPa) for the examined materials were as follow: TempSpan=120.00, Protemp 4=113.00, Unifast III=64.20, Trim= 63.73 and Revotek LC=47.16. There were significant differences between all materials except Trim and Unifast III which did not show any statistical significant difference. Bis-acryl resins were statistically superior to traditional methacrylate and light-cured resins. Therefore, application of bis-acryl resins should be deliberated in patients with heavy occlusion and in cases that need long-term use of interim restorations.

  14. Biaxial flexural strength of Turkom-Cera core compared to two other all-ceramic systems.

    Science.gov (United States)

    Al-Makramani, Bandar Mohammed Abdullah; Razak, Abdul Aziz Abdul; Abu-Hassan, Mohamed Ibrahim

    2010-12-01

    Advances in all-ceramic systems have established predictable means of providing metal-free aesthetic and biocompatible materials. These materials must have sufficient strength to be a practical treatment alternative for the fabrication of crowns and fixed partial dentures. The aim of this study was to compare the biaxial flexural strength of three core ceramic materials. Three groups of 10 disc-shaped specimens (16 mm diameter x 1.2 mm thickness - in accordance with ISO-6872, 1995) were made from the following ceramic materials: Turkom-Cera Fused Alumina [(Turkom-Ceramic (M) Sdn Bhd, Puchong, Selangor, Malaysia)], In-Ceram (Vita Zahnfabrik, Bad Säckingen, Baden-Württemberg, Germany) and Vitadur-N (Vita Zahnfabrik, Bad Säckingen, Baden-Württemberg, Germany), which were sintered according to the manufacturer's recommendations. The specimens were subjected to biaxial flexural strength test in an universal testing machine at a crosshead speed of 0.5 mm/min. The definitive fracture load was recorded for each specimen and the biaxial flexural strength was calculated from an equation in accordance with ISO-6872. The mean biaxial flexural strength values were: Turkom-Cera: 506.8 ± 87.01 MPa, In-Ceram: 347.4 ± 28.83 MPa and Vitadur-N: 128.7 ± 12.72 MPa. The results were analyzed by the Levene's test and Dunnett's T3 post-hoc test (SPSS software V11.5.0 for Windows, SPSS, Chicago, IL, USA ) at a preset significance level of 5% because of unequal group variances (Pcore ceramics (Pstrength, followed by In-Ceram and Vitadur-N. Turkom-Cera core had significantly higher flexural strength than In-Ceram and Vitadur-N ceramic core materials.

  15. Foot Skin Ischemic Necrosis following Heel Prick in a Newborn

    Directory of Open Access Journals (Sweden)

    Esad Koklu

    2013-01-01

    Full Text Available There are only a few reports on side effects after heel prick in neonates although heel prick has been performed all over the world for many years. The medicine staff had obtained only a drop of blood by pricking the baby’s heel using a lancet without compressing the heel or foot to measure his blood glucose level 3 hours after birth. However he developed a severe and hemorrhagic skin reaction on his entire left foot, beginning 30 minutes after obtaining the drop of blood by pricking the baby’s heel using a lancet. The lesion, which was treated with topical mupirocin and povidone-iodine solution daily, slowly decreased in size and had almost fully resolved within 3 weeks. He was healthy and 9 months old at the time of writing this paper. We herein report a case of foot skin ischemic necrosis following heel prick in a newborn. To our knowledge this patient is the first case of foot skin ischemic necrosis due to heel prick in newborns.

  16. Partial Necrosis of the Mandibular Proximal Segment Following Transoral Vertical Ramus Osteotomy.

    Science.gov (United States)

    Kim, Somi; Kim, Sang Yoon; Kim, Gi-Jung; Jung, Hwi-Dong; Jung, Young-Soo

    2014-05-01

    Transoral vertical ramus osteotomy (TOVRO) procedure can result in a variety of complications. Complications commonly reported include extensive bleeding due to major blood vessel injury, unpredictable fracture, postoperative infection, neurosensory deficit related Inferior alveolar nerve, insufficient osteosynthesis, and temporomandibular joint problem. The authors describe a case of partial necrosis of the mandibular proximal segment following TOVRO, a rarely reported complication. A 37-year-old otherwise healthy woman underwent Lefort l osteotomy and TOVRO to correct mandibular prognathism. Postoperatively, she developed pain and swelling in the right submandibular region and was found to have a partial necrosis of proximal segment.

  17. Experimental Study on Flexural Behavior of Post-Tensioning Bonded Partially Prestressed Ultra-High Strength Concrete Beams

    Institute of Scientific and Technical Information of China (English)

    Jinqing Jia; Gang Meng

    2015-01-01

    This paper presents the results of four partially prestressed ultra⁃high strength concrete beams in flexure. The test results are used to evaluate the effects of prestressing tendon depth and area on flexure behavior of specimen beams. The test results indicate that:the cracking load, yielding load, peak load and stiffness post⁃cracking of specimen beams are enhanced by reducing prestressing tendon depth or increasing prestressing tendon area, and the flexural ductility is improved by increasing prestressing tendon depth or reducing prestressing tendon area. The effect of complex reinforcement index considering the strength of the equivalence principle and the reinforcement position on loading levels under serviceability limit state, flexural strength and displacement ductility factor are studied. The influence coefficient of prestressing tendon kp is introduced in the complex reinforcement index. As the complex reinforcement index increases, the loading levels under serviceability limit state and flexural strength increases linearly, and the displacement ductility factor decreases linearly. The test results also verify the conventional beam flexural theory based on the plane cross⁃section assumption for predicting ultimate flexural strength of partially prestressed ultra⁃high strength concrete beams is valid. After the introduction of the coefficient kp , the calculation method of cracks in code for design of concrete structure in china are appropriated for the specimen beams.

  18. [Necrosis in fingers and toes following local anaesthesia with adrenaline--an urban legend?].

    Science.gov (United States)

    Finsen, Vilhjalmur

    2013-09-17

    It is often maintained that a local anaesthetic (usually lidocaine) with adrenaline must not be used in fingers and toes because it may cause necrosis due to vascular spasm in end arteries. This review article is an attempt to find evidence to support this warning. Relevant literature was found by means of searches in PubMed limited downwards to 1946 and in EMBASE from 1980 to 2012, and in reference lists. Five review articles on finger necrosis following local anaesthesia concluded that lidocaine with adrenaline does not entail a risk of ischaemic injury. One article found 48 reported cases of finger necrosis in the period 1880 to 2000. Most were from the first half of the 1900s, and none involved lidocaine. Gangrene of part of the finger tip has subsequently been described in one patient with Raynaud's syndrome. No cases of necrosis have been described in a large number of reported accidents in which EpiPen injections contained the same quantity of adrenaline as is found in 60 ml lidocaine with adrenaline. Over a quarter of a million reports have been made of operations on feet, hands, fingers and toes anaesthetised with lidocaine with adrenaline without resulting necrosis. There are no grounds for the warning against using lidocaine with adrenaline in fingers and toes. This anaesthetic offers considerable practical advantages. Care should be taken with infected fingers or fingers with poor circulation.

  19. Bone marrow necrosis in systemic lupus erythematous patient

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    Cláudia Hilbig

    2017-01-01

    Full Text Available The hematological manifestations of systemic lupus erythematous (SLE are causes of morbidity and increased risk of mortality. Young patient, female, with SLE and antiphospholipid syndrome (APS had severe pancytopenia after urinary tract infection. A biopsy of the bone marrow (BM showed necrosis and fibrosis. The most common pathophysiological mechanism for pancytopenia is the production of peripheral antibodies. However, pancytopenia with BM aplasia or necrosis is rare. BM necrosis is more common with neoplastic diseases, severe infections or sickle cell anemia but is also reported for patients with SLE. It is seen more rarely in patients with primary APS. Changes in the BM microcirculation lead to ischemia and subsequent necrosis. The main complications are pancytopenia and embolism. BM necrosis has been appointed in few clinical studies as a possible cause for pancytopenia in SLE patients. Among the findings, BM necrosis was present in 19% of the patients. BM necrosis is a relatively rare and poor prognosis entity.

  20. Effect of Preheating and Precooling on the Flexural Strength and Modulus of Elasticity of Nanohybrid and Silorane-based Composite

    Directory of Open Access Journals (Sweden)

    Farahnaz Sharafeddin

    2015-09-01

    Full Text Available Statement of the Problem: Composite resin may be used in different temperatures; it is crucial to determine the effect of temperature on mechanical properties of nanohybrid and silorane-based composite. Purpose: This in vitro study compared the flexural strength and modulus of elasticity of nanohybrid and silorane-based resin composite, at 4˚C, room temperature (25˚C, and 45˚C. Materials and Method: In this experimental study, 60 specimens were prepared in a metal split mold (2×2×25mm. Two different resin composites, Filtek Z250 XT (3M/ ESPE and Filtek P90 (3M/ESPE, were evaluated. The material were inserted into split molds at room temperature, 4˚C or 45˚C and cured with LED (1200 mW/cm2 for 20 seconds in four points (n=10. Then, a three-point bending test was performed using a universal testing machine at a crosshead speed of 0.5 mm/min for measuring the flexural strength and flexural modulus of samples. The data were analyzed by the two-way ANOVA and Tukey test (p< 0.05. Results: The mean highest flexural strength was observed at 45˚C, showing statistically significant difference with flexural strength at 4˚C (p= 0.0001 and 25˚C (p= 0.003 regardless of the type of resin composite. The flexural modulus at 45˚C was highest, showing the statistically significant difference with flexural modulus at 4˚C (p= 0.0001 and 25˚C (p= 0.002. The flexural modulus was statistically different between nanohybrid and silorane-based resin composite (p= 0.01 in 25˚C and 45˚C, but there were no statistically significant differences between flexural strength of Filtek Z250 XT and Filtek P90 regardless of the temperatures (p= 0.062. Conclusion: Preheating the resin composite at 45˚C improves flexural strength and modulus of nanohybrid and silorane-based resin composite. However, flexural strength and modulus of the tested materials were not affected by precooling. The flexural modulus of nanohybrid resin composite was significantly higher than

  1. Mastectomy skin flap necrosis: challenges and solutions

    Directory of Open Access Journals (Sweden)

    Robertson SA

    2017-03-01

    Full Text Available Stuart A Robertson,1 Johann A Jeevaratnam,2 Avi Agrawal,2 Ramsey I Cutress,3,4 1Department of Surgery, University Hospital Coventry and Warwickshire NHS Trust, Coventry, 2Department of Breast Surgery, Portsmouth Hospitals NHS Trust, Cosham, Portsmouth, 3Department of Breast Surgery, University Hospital Southampton NHS Foundation Trust, Princess Anne Hospital, 4Somers Cancer Research UK Centre, Southampton General Hospital Southampton, UK Introduction: Mastectomy skin flap necrosis (MSFN has a reported incidence of 5%–30% in the literature. It is often a significant and underappreciated problem. The aim of this article was to review the associated challenges and possible solutions. Methods: A MEDLINE search was performed using the search term “mastectomy skin flap necrosis”. Titles and abstracts from peer-reviewed publications were screened for relevance. Results: MSFN is a common complication and may present as partial- or full-thickness necrosis. Predictive patient risk factors include smoking, diabetes, obesity, radiotherapy, previous scars and severe medical comorbidity. MSFN leads to a number of challenges, including wound management problems, delays to adjuvant therapy, esthetic compromise, implant extrusion, patient distress and financial loss. Careful preoperative planning and meticulous surgical technique may reduce the incidence of MSFN. A number of intraoperative techniques are available to try and predict skin flaps at risk of MSFN. MSFN may be managed operatively or nonoperatively. Early intervention may reduce the morbidity of MSFN in selected cases. Topical nitroglycerin ointment may be beneficial in reducing MSFN following immediate reconstruction, but the evidence base is still limited. Conclusion: MSFN can result in considerable challenges for the patient and the health care service. This review discusses the management options for this problem. Keywords: mastectomy, flap, necrosis, complication, breast surgery

  2. Apoptosis and Necrosis in the Liver

    Science.gov (United States)

    Guicciardi, Maria Eugenia; Malhi, Harmeet; Mott, Justin L.; Gores, Gregory J.

    2013-01-01

    Because of its unique function and anatomical location, the liver is exposed to a multitude of toxins and xenobiotics, including medications and alcohol, as well as to infection by hepatotropic viruses, and therefore, is highly susceptible to tissue injury. Cell death in the liver occurs mainly by apoptosis or necrosis, with apoptosis also being the physiologic route to eliminate damaged or infected cells and to maintain tissue homeostasis. Liver cells, especially hepatocytes and cholangiocytes, are particularly susceptible to death receptor-mediated apoptosis, given the ubiquitous expression of the death receptors in the organ. In a quite unique way, death receptor-induced apoptosis in these cells is mediated by both mitochondrial and lysosomal permeabilization. Signaling between the endoplasmic reticulum and the mitochondria promotes hepatocyte apoptosis in response to excessive free fatty acid generation during the metabolic syndrome. These cell death pathways are partially regulated by microRNAs. Necrosis in the liver is generally associated with acute injury (i.e., ischemia/reperfusion injury) and has been long considered an unregulated process. Recently, a new form of “programmed” necrosis (named necroptosis) has been described: the role of necroptosis in the liver has yet to be explored. However, the minimal expression of a key player in this process in the liver suggests this form of cell death may be uncommon in liver diseases. Because apoptosis is a key feature of so many diseases of the liver, therapeutic modulation of liver cell death holds promise. An updated overview of these concepts is given in this article. PMID:23720337

  3. Medication error - Inadvertent high dose intradermal cloxacillin induced skin necrosis

    Directory of Open Access Journals (Sweden)

    Adithan Surendiran

    2012-01-01

    Full Text Available Medication error is one of the important causes of preventable adverse drug reactions. It can occur in the form of administration of a wrong drug, in the wrong dose, to the wrong patient, in an unsuitable dosage form, for the wrong duration or by using an inappropriate route of administration. Intradermal skin testing for cloxacillin hypersensitivity is done at low doses to check for drug allergy. In this report, three patients were given 50 times higher dose of cloxacillin than recommended for skin testing, resulting in pain and necrosis at the site of injection. The error occurred due to wrong dilution of the drug as done by a nursing intern. Some reasons for this could be overtime working, under trained staff, unsupervised nursing interns, complicated and unclear protocols, interpersonal communication gap between health care professionals and also poor availability of ideal resources. Pharmacovigilance centers must alert health care professionals about the significance of reporting medication errors through bulletins and journals.

  4. Effect of thermocycling on the flexural strength of porcelain laminate veneers

    Directory of Open Access Journals (Sweden)

    Subramanian Deepa

    2008-01-01

    Full Text Available Aim: The aim of this study was to examine the impact of thermocycling on the flexural strength and development of surface flaws on the glazed surface of porcelain laminate veneer restorations with and without resin luting cement. Materials and Methods: 80 Vitadur alpha dentin porcelain discs (10 mm diameter, 0.9 mm thickness were glazed on one side and divided into two groups: A (porcelain laminate veneer only without resin luting cement and B (porcelain laminate veneer luted with resin cement, each containing 40 discs. The discs in groups A and B were then thermocycled at different temperatures and were subjected to SEM analysis to evaluate the effect of thermocycling on crack propagation. Mean flexural strength was determined by using the ball-on-ring test. Student′s t -test was used to find out the difference between strength values of the thermocycled porcelain discs and discs luted with resin cement. Results: SEM analysis revealed crack propagation in the subgroups subjected to extremes of temperature, i.e., 4 ± 1°C, 37 ± 1°C and 4 ± 1°C, 65 ± 1°C in the porcelain laminate veneers luted with resin cement. Flexural strength analysis revealed superior flexural strength for porcelain laminate veneers: 88.58 ± 6.94 Mpa when compared to porcelain laminate veneers luted with resin cement: 8.42 ± 2.60 MPa. Results were tabulated and statistically analyzed using Student′s t -test. Conclusion: Laminate veneer specimens exhibited greater flexural strength than those which were luted with resin cements. Laminate veneer specimens luted with resin cement and subjected to extremes of temperature, 4 ± 1°C and 37 ± 1°C and 4 ± 1°C and 65 ± 1°C, showed a marked decrease in flexural strength. After thermocycling at extremes of temperature, laminate veneer specimens luted with resin cement showed crack propagation. Fit of laminate veneers cannot / should not be compensated by the thickness of luting agent.

  5. Comparative Evaluation of Flexural Strength of Provisional Crown and Bridge Materials-An Invitro Study.

    Science.gov (United States)

    Singh, Ankita; Garg, Sandeep

    2016-08-01

    Provisional restorations serve a key role as a functional and esthetic try-in for the design of the final prosthesis. During selection of materials for this restoration, clinicians must consider physical properties, ease of handling, cost and patient satisfaction and approval. To evaluate and compare the flexural strength of provisional crown and bridge materials available commercially. This in-vitro study was done to compare the flexural strength of six temporary crown and bridge materials available commercially at 24 hours, 8 days and after repair. Three poly methyl methacrylate based materials (DPI, SC10 and Trulon) and three bis-acrylic based composite resins (Protemp, Cooltemp and Luxatemp) were selected. A total of 72 specimens of dimensions 64mm×10mm×2.5mm were prepared from these materials (12 from each material) and divided into two groups (n=36). Specimens were stored in artificial saliva and were fractured after 24 hours and 8 days using Universal Testing Machine. The fractured samples from the 8 days study were then subjected to repair. A uniform space of 2mm and a 450 bevel was maintained for all the repaired samples for better distribution of forces. Flexural strength of these repaired samples was recorded using the same machine. RESULTs were recorded and statistically analysed by one-way Anova and Post hoc tests. RESULTs revealed that there was decrease in flexural strength for all the materials tested from 24 hours to 8 days, though flexural strength between poly methyl methacrylate and bis-acrylic resins was similar at 24 hours and 8 days time interval. A substantial decrease was noticed in the strength of bis-acrylic composite resins after repair. From the current study it can be suggested that though there is decrease in flexural strength for all the materials from 24 hours to 8 days, both can be used to fabricate the provisional restorations. However, in the event of a fracture of a bis-acrylic provisional restoration, it may be more

  6. Distal extremity necrosis in captive birds.

    Science.gov (United States)

    Calle, P P; Montali, R J; Janssen, D L; Stoskopf, M K; Strandberg, J D

    1982-10-01

    The necropsy files of the National Zoological Park and Baltimore Zoological Society were reviewed for cases of distal extremity necrosis (DEN) in birds. Nineteen cases of DEN occurred following either trauma or frostbite. Six birds developed an apparently primary type of DEN in which no predisposing factors were obvious clinically. The toes and feet were most commonly involved, and in several cases the beak was also affected. Some pathologic evidence is provided that certain cardiovascular lesions may predispose birds to DEN by compromising circulation of the extremities.

  7. Comparative evaluation of compressive strength and flexural strength of conventional core materials with nanohybrid composite resin core material an in vitro study.

    Science.gov (United States)

    Jayanthi, Narasimha; Vinod, V

    2013-09-01

    Several dental materials have been used for core build-up procedures. Most of these materials were not specifically developed for this purpose, but as a consequence of their properties, have found application in core build-up procedures. Improvements in composites and the development of nanocomposites have led to their use as a core build up material due to their superior mechanical properties, optical properties and ease of handling. However it is not clear if they have better mechanical properties than the conventional core build up materials like amalgam, GIC and dual cure composite core build up material. The strength of the core material is very important and this study was undertaken to compare the mechanical properties of materials used for direct core foundations. The differences between the compressive strength and flexural strength of Filtek Z350 nanocomposite with conventional core build up materials like Amalgam, Vitremer GIC and Fluorocore were tested. Cylindrical plexi glass split molds of dimension 6 ± 1 mm [height] x4 ± 1 mm [diameter] were used to fabricate 15 samples of each core material for testing the compressive strength and rectangular plexi glass split molds of dimension 25 ± 1 mm [length] x 2 ± 1 mm[height] x2 ± 1 mm [width] used for fabricating samples for flexural strength. The samples were stored a water bath at 250 °C for 24 h before testing. The samples were tested using a Universal Instron testing machine. The results of the study showed that Fluorocore had the highest compressive strength and flexural strength followed by Filtek Z350 [nanocomposite] Amalgam had the least flexural strength and Vitremer GIC had the least compressive strength. Thus flurocore and nanocomposite are stronger than other core build up materials and hence should be preferred over other conventional core build up materials in extensively damaged teeth.

  8. A structural model for the flexural mechanics of nonwoven tissue engineering scaffolds.

    Science.gov (United States)

    Engelmayr, George C; Sacks, Michael S

    2006-08-01

    The development of methods to predict the strength and stiffness of biomaterials used in tissue engineering is critical for load-bearing applications in which the essential functional requirements are primarily mechanical. We previously quantified changes in the effective stiffness (E) of needled nonwoven polyglycolic acid (PGA) and poly-L-lactic acid (PLLA) scaffolds due to tissue formation and scaffold degradation under three-point bending. Toward predicting these changes, we present a structural model for E of a needled nonwoven scaffold in flexure. The model accounted for the number and orientation of fibers within a representative volume element of the scaffold demarcated by the needling process. The spring-like effective stiffness of the curved fibers was calculated using the sinusoidal fiber shapes. Structural and mechanical properties of PGA and PLLA fibers and PGA, PLLA, and 50:50 PGA/PLLA scaffolds were measured and compared with model predictions. To verify the general predictive capability, the predicted dependence of E on fiber diameter was compared with experimental measurements. Needled nonwoven scaffolds were found to exhibit distinct preferred (PD) and cross-preferred (XD) fiber directions, with an E ratio (PD/XD) of approximately 3:1. The good agreement between the predicted and experimental dependence of E on fiber diameter (R2 = 0.987) suggests that the structural model can be used to design scaffolds with E values more similar to native soft tissues. A comparison with previous results for cell-seeded scaffolds (Engelmayr, G. C., Jr., et al., 2005, Biomaterials, 26(2), pp. 175-187) suggests, for the first time, that the primary mechanical effect of collagen deposition is an increase in the number of fiber-fiber bond points yielding effectively stiffer scaffold fibers. This finding indicated that the effects of tissue deposition on needled nonwoven scaffold mechanics do not follow a rule-of-mixtures behavior. These important results underscore

  9. Acute fatal acetaminophen overdose without liver necrosis.

    Science.gov (United States)

    Singer, Peter P; Jones, Graham R; Bannach, Bernard G; Denmark, Lloyd

    2007-07-01

    Two unusual cases of suicidal overdose of acetaminophen (paracetamol) without the usual extensive centrilobular necrosis of the liver are reported. Both cases were subjected to comprehensive drug screening by immunoassay, and a combination of gas chromatography with mass spectrometry, nitrogen detection, and electron capture detection. Acetaminophen was detected in both cases. No other drugs were detected in case #1, and only a small amount of olanzapine (<0.1 mg/L) was detected in case #2. No anatomical cause of death was identified in either case. If untreated, the normal outcome of a large acetaminophen overdose would be massive hepatic necrosis with delayed death and low blood and tissue acetaminophen concentrations. In contrast, particularly high postmortem acetaminophen concentrations were measured in both our cases with little hepatic tissue damage. For case #1, femoral blood acetaminophen 1280 mg/L, vitreous 878 mg/L, and liver 729 mg/kg; in case #2, cardiac blood 1220 mg/L, vitreous 779 mg/L, liver 3260 mg/kg, and gastric 11,500 mg/500 g. Acetaminophen was measured using high performance liquid chromatography with UV detection (254 nm) using 3-hydroxyacetanilide as the internal standard. The very high concentrations of acetaminophen is these cases but relatively little hepatic damage suggests an alternative, possibly cardiac, mechanism of death.

  10. Mastectomy skin flap necrosis: challenges and solutions

    Science.gov (United States)

    Robertson, Stuart A; Jeevaratnam, Johann A; Agrawal, Avi; Cutress, Ramsey I

    2017-01-01

    Introduction Mastectomy skin flap necrosis (MSFN) has a reported incidence of 5%–30% in the literature. It is often a significant and underappreciated problem. The aim of this article was to review the associated challenges and possible solutions. Methods A MEDLINE search was performed using the search term “mastectomy skin flap necrosis”. Titles and abstracts from peer-reviewed publications were screened for relevance. Results MSFN is a common complication and may present as partial- or full-thickness necrosis. Predictive patient risk factors include smoking, diabetes, obesity, radiotherapy, previous scars and severe medical comorbidity. MSFN leads to a number of challenges, including wound management problems, delays to adjuvant therapy, esthetic compromise, implant extrusion, patient distress and financial loss. Careful preoperative planning and meticulous surgical technique may reduce the incidence of MSFN. A number of intraoperative techniques are available to try and predict skin flaps at risk of MSFN. MSFN may be managed operatively or nonoperatively. Early intervention may reduce the morbidity of MSFN in selected cases. Topical nitroglycerin ointment may be beneficial in reducing MSFN following immediate reconstruction, but the evidence base is still limited. Conclusion MSFN can result in considerable challenges for the patient and the health care service. This review discusses the management options for this problem. PMID:28331365

  11. TWO-DIMENSIONAL APPROXIMATION OF EIGENVALUE PROBLEMS IN SHELL THEORY: FLEXURAL SHELLS

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The eigenvalue problem for a thin linearly elastic shell, of thickness 2e, clamped along its lateral surface is considered. Under the geometric assumption on the middle surface of the shell that the space of inextensional displacements is non-trivial, the authors obtain, as ε→0,the eigenvalue problem for the two-dimensional"flexural shell"model if the dimension of the space is infinite. If the space is finite dimensional, the limits of the eigenvalues could belong to the spectra of both flexural and membrane shells. The method consists of rescaling the variables and studying the problem over a fixed domain. The principal difficulty lies in obtaining suitable a priori estimates for the scaled eigenvalues.

  12. Experimental investigation of laser surface processing of flexure silicon nitride ceramic

    Institute of Scientific and Technical Information of China (English)

    SUN Li; A. P. MALSHE; JIANG Wen-ping; P. H. MCCLUSKEY

    2006-01-01

    A continuous wave carbon dioxide (CO2) laser (λ=10.6μm) was employed to treat the surface of Si3N4 MOR (modulus of rupture) bars. The effects of the CO2 laser process on physical and mechanical properties of ground Si3N4 samples were investigated. Scanning electron microscopy (SEM) analysis shows that the area occupied by cavities and fracture is decreased by about 49.4% after laser treatments. Cross-sectional metallography results indicate that the secondary YSiAlON phase in the Si3N4 ceramic is softened/melted and flowed into the defects. Four-point bending tests show that the flexural strength of the treated samples is improved to 10.9%. Fractographic analysis show that the fracture origins move from the surface to subsurface. It is concluded that laser surface processing have significant effects on fracture behavior of flexure Si3N4 ceramic.

  13. Ice-Shelf Flexure and Tidal Forcing of Bindschadler Ice Stream, West Antarctica

    Science.gov (United States)

    Walker, Ryan T.; Parizek, Bryron R.; Alley, Richard B.; Brunt, Kelly M.; Anandakrishnan, Sridhar

    2014-01-01

    Viscoelastic models of ice-shelf flexure and ice-stream velocity perturbations are combined into a single efficient flowline model to study tidal forcing of grounded ice. The magnitude and timing of icestream response to tidally driven changes in hydrostatic pressure and/or basal drag are found to depend significantly on bed rheology, with only a perfectly plastic bed allowing instantaneous velocity response at the grounding line. The model can reasonably reproduce GPS observations near the grounding zone of Bindschadler Ice Stream (formerly Ice Stream D) on semidiurnal time scales; however, other forcings such as tidally driven ice-shelf slope transverse to the flowline and flexurally driven till deformation must also be considered if diurnal motion is to be matched

  14. Analysis of the Flexure Behavior and Compressive Strength of Fly Ash Core Sandwiched Composite Material

    Directory of Open Access Journals (Sweden)

    Vijaykumar H.K

    2014-07-01

    Full Text Available In this paper, commercially available Fly Ash and Epoxy is used for the core material, woven glass fabric as reinforcing skin material, epoxy as matrix/adhesive materials used in this study for the construction of sandwich composite. Analysis is carried out on different proportions of epoxy and fly ash sandwiched composite material for determining the flexural strength and compressive strength, three different proportions of epoxy and fly ash used for the study. Those are 65%-35% (65% by weight fly ash and 35% by weight epoxy resin composite material, 60%-40% and 55%-45% composite material. 60%-40% composite material specimen shows better results in the entire test carried out i.e. Flexure and Compression. The complete experimental results are discussed and presented in this paper.

  15. Determining the optimum topology of composites by the flexural stiffness criterion

    Directory of Open Access Journals (Sweden)

    Vasile MOGA

    2012-06-01

    Full Text Available An important stage in designing of pieces made of composite materials consists of establishing the composite topology in such a way that it has certain properties needed in exploitation. The paper presents the mathematical apparatus and the calculation programme for establishing the optimum thickness of the composite groups so that it should have certain imposed (given flexural stiffness. The method is applicable to all types of laminate composites, no matter of the cladding or matrix nature. The direct problem consists in determining the thickness of the groups and composite, minimising the bar mass, for an imposed (given flexural stiffness, knowing the densities and elasticity modules of the groups. The indirect problem consists in determining the maximum stiffness, the thickness of the groups and composite for a given (imposed mass, knowing the densities and elasticity modules of the groups. The presented programmes offer to the producer of this kind of materials the possibility to quickly establish the optimum topology.

  16. An Analytical Approach for Synthesizing Line Actuation Spaces of Parallel Flexure Mechanisms.

    Science.gov (United States)

    Yu, Jingjun; Li, Shouzhong; Qiu, Chen

    2013-12-01

    In this study, we present an analytical approach for synthesizing line actuation spaces of a parallel flexure mechanism (PFM) that can help designers to arrange linear actuators within the PFM in a correct and optimal way. On the basis of screw theory and upon an assumption of small deformations, an important synthesis criterion stated as "any actuation space of a flexure mechanism is always linearly independent of its constraint space" has been derived and disclosed for the first time. Guided by this criterion, a general synthesis process for the line actuation spaces of PFMs is introduced and demonstrated with several selective examples. The proposed synthesis criterion and process will enable designers to (i) systematically formulate line actuation spaces in the format of screw systems; (ii) likely yield a multiple solution to actuation spaces; and (iii) potentially determine an optimal result from those alternatives for actuator placement.

  17. Design of Flexure-based Precision Transmission Mechanisms using Screw Theory

    Energy Technology Data Exchange (ETDEWEB)

    Hopkins, J B; Panas, R M

    2011-02-07

    This paper enables the synthesis of flexure-based transmission mechanisms that possess multiple decoupled inputs and outputs of any type (e.g. rotations, translations, and/or screw motions), which are linked by designer-specified transmission ratios. A comprehensive library of geometric shapes is utilized from which every feasible concept that possesses the desired transmission characteristics may be rapidly conceptualized and compared before an optimal concept is selected. These geometric shapes represent the rigorous mathematics of screw theory and uniquely link a body's desired motions to the flexible constraints that enable those motions. This paper's impact is most significant to the design of nano-positioners, microscopy stages, optical mounts, and sensors. A flexure-based microscopy stage was designed, fabricated, and tested to demonstrate the utility of the theory.

  18. Flexural, Impact Properties and Sem Analysis of Bamboo and Glass Fiber Reinforced Polyester Hybrid Composites

    Directory of Open Access Journals (Sweden)

    Raghavendra Rao. H

    2014-08-01

    Full Text Available The Flexural, Impact properties and Scanning electron microscope analysis of Bamboo/glass fibers Reinforced polyester Hybrid composites were studied. The effect of alkali treatment of the bamboo fibers on these properties was also studied. It was observed that the Flexural, impact properties of the hybrid composite increase with glass fiber content. These properties found to be higher when alkali treated bamboo fibers were used in the hybrid composites. The elimination of amorphous hemi-cellulose with alkali treated leading to higher crystallinity of the bamboo fibers with alkali treatment may be responsible for these observations. The author investigated the interfacial bonding between Glass/Bamboo reinforced polyester composites. The effect of alkali treatment on the bonding between Glass/Bamboo composites was also studied.

  19. Tensile and Flexural Properties of Cement Composites Reinforced with Flax Nonwoven Fabrics

    Directory of Open Access Journals (Sweden)

    Josep Claramunt

    2017-02-01

    Full Text Available The aim of this study is to develop a process to produce high-performance cement-based composites reinforced with flax nonwoven fabrics, analyzing the influence of the fabric structure—thickness and entanglement—on mechanical behavior under flexural and tensile loadings. For this purpose, composite with flax nonwoven fabrics with different thicknesses were first prepared and their cement infiltration was evaluated with backscattered electron (BSE images. The nonwoven fabrics with the optimized thickness were then subjected to a water treatment to improve their stability to humid environments and the fiber-matrix adhesion. For a fixed thickness, the effect of the nonwoven entanglement on the mechanical behavior was evaluated under flexural and direct tension tests. The obtained results indicate that the flax nonwoven fabric reinforcement leads to cement composites with substantial enhancement of ductility.

  20. Tensile and Flexural Properties of Cement Composites Reinforced with Flax Nonwoven Fabrics

    Science.gov (United States)

    Claramunt, Josep; Ventura, Heura; Fernández-Carrasco, Lucía J; Ardanuy, Mònica

    2017-01-01

    The aim of this study is to develop a process to produce high-performance cement-based composites reinforced with flax nonwoven fabrics, analyzing the influence of the fabric structure—thickness and entanglement—on mechanical behavior under flexural and tensile loadings. For this purpose, composite with flax nonwoven fabrics with different thicknesses were first prepared and their cement infiltration was evaluated with backscattered electron (BSE) images. The nonwoven fabrics with the optimized thickness were then subjected to a water treatment to improve their stability to humid environments and the fiber-matrix adhesion. For a fixed thickness, the effect of the nonwoven entanglement on the mechanical behavior was evaluated under flexural and direct tension tests. The obtained results indicate that the flax nonwoven fabric reinforcement leads to cement composites with substantial enhancement of ductility. PMID:28772573

  1. Some comments on the experimental behavior of FRC beams in flexure

    Science.gov (United States)

    Campione, Giuseppe; La Mendola, Lidia; Mangiavillano, Maria Letizia; Papia, Maurizio

    2008-07-01

    In the present paper the experimental results, recently obtained by the authors, regarding the monotonic and the cyclic flexural response of normal and high-strength concrete beams reinforced with steel bars and discontinuous fibers, are shown. From the experimental results, all referred to low values of shear-to-depth ratios, it emerges clearly that the shear failure is brittle especially under cyclic actions highlighting the role of the fibers in the flexural behavior of the beams. The cyclic action produces a significant decay in the stiffness and in the strength capacity of the beams, and the addition of fibers reduces these negative effects. Form theoretical point of view good agreement can be found utilizing the recent analytical model proposed by the authors.

  2. Flexural strengthening of Reinforced Concrete (RC) Beams Retrofitted with Corrugated Glass Fiber Reinforced Polymer (GFRP) Laminates

    Science.gov (United States)

    Aravind, N.; Samanta, Amiya K.; Roy, Dilip Kr. Singha; Thanikal, Joseph V.

    2015-01-01

    Strengthening the structural members of old buildings using advanced materials is a contemporary research in the field of repairs and rehabilitation. Many researchers used plain Glass Fiber Reinforced Polymer (GFRP) sheets for strengthening Reinforced Concrete (RC) beams. In this research work, rectangular corrugated GFRP laminates were used for strengthening RC beams to achieve higher flexural strength and load carrying capacity. Type and dimensions of corrugated profile were selected based on preliminary study using ANSYS software. A total of twenty one beams were tested to study the load carrying capacity of control specimens and beams strengthened with plain sheets and corrugated laminates using epoxy resin. This paper presents the experimental and theoretical study on flexural strengthening of Reinforced Concrete (RC) beams using corrugated GFRP laminates and the results are compared. Mathematical models were developed based on the experimental data and then the models were validated.

  3. Thermal Flexure Measurement and Inverse Characterization for a Tri-layer Thin Plate

    Institute of Scientific and Technical Information of China (English)

    HuaLu; Alireza Shirazi; Ahmad Varvani-Farahani

    2011-01-01

    The paper presents a new study on a tri-layer thin plate.Shadow moiré implemented with an advanced phase unwrapping technique is employed to obtain actual flexural deformation of a real-life plate sample subjected to thermal loads.An analytical model is re-formulated to provide the plate with global closed-form solutions of the plate deflection as well as the interfacial stress and strain.With the measurements and the solutions available,an inverse iterative approach is developed to evaluate and maximize the correlation between the measured and the predicted thermal flexure,leading to ascertained materials' constitutive and thermal behaviour.The inverse search algorithm starts with estimated ranges of material property parameters and progressively updates them to finally approach the respective true values.The established model solutions along with the optimized material properties matrix enable an accurate evaluation of the interfacial stresses/strains for the specific plate sample.

  4. Effects of aluminum oxide addition on the flexural strength, surface hardness, and roughness of heat-polymerized acrylic resin

    Directory of Open Access Journals (Sweden)

    Mahroo Vojdani

    2012-09-01

    Conclusion: Reinforcement of the conventional heat-cured acrylic resin with 2.5 wt% Al2O3 powder significantly increased its flexural strength and hardness with no adverse effects on the surface roughness.

  5. ASYMPTOTIC ANALYSIS OF DYNAMIC??PROBLEMS FOR LINEARLY ELASTICSHELLS—JUSTIFICATION OF EQUATIONS???FOR DYNAMIC FLEXURAL SHELLS

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Under certain conditions, starting from the three-dimensional dynamic equations of elastic shells the author gives the justification of dynamic equations of flexural shells by means of the method of asymptotic analysis.

  6. Heat treatment of a direct composite resin: influence on flexural strength

    Directory of Open Access Journals (Sweden)

    Caroline Lumi Miyazaki

    2009-09-01

    Full Text Available The purpose of this study was to evaluate the flexural strength of a direct composite, for indirect application, that received heat treatment, with or without investment. One indirect composite was used for comparison. For determination of the heat treatment temperature, thermogravimetric analysis (TGA and differential scanning calorimetry (DSC were performed, considering the initial weight loss temperature and glass transition temperature (Tg. Then, after photoactivation (600 mW/cm² - 40 s, the specimens (10 x 2 x 2 mm were heat-treated following these conditions: 170ºC for 5, 10 or 15 min, embedded or not embedded in investment. Flexural strength was assessed as a means to evaluate the influence of different heat treatment periods and investment embedding on mechanical properties. The data were analyzed by ANOVA and Tukey's test (α = 0.05. TGA showed an initial weight loss temperature of 180ºC and DSC showed a Tg value of 157°C. Heat treatment was conducted in an oven (Flli Manfredi, Italy, after 37°C storage for 48 h. Flexural strength was evaluated after 120 h at 37°C storage. The results showed that different periods and investment embedding presented similar statistical values. Nevertheless, the direct composite resin with treatments presented higher values (178.7 MPa compared to the indirect composite resin (146.0 MPa and the same direct composite submitted to photoactivation only (151.7 MPa. Within the limitations of this study, it could be concluded that the heat treatment increased the flexural strength of the direct composite studied, leading to higher mechanical strength compared to the indirect composite.

  7. Sandblasting Effect on Flexural Strength and Fracture Resistance of Two Zirconia with Two Cross Sectional Areas

    Directory of Open Access Journals (Sweden)

    Juan Norberto Calvo Ramírez

    2015-08-01

    Full Text Available Background: Yttrium stabilized zirconia a ceramic material currently considered as an “aesthetic” alternative in fixed partial denture. Clinical studies they have shown micro fractures in the area of the connectors, detachment or “chipping” ceramic coating and also the difficulties in fitting for her cementing. Objective: To establish the influence of sandblasting on flexural strength and fracture toughness of two Yttrium stabilized zirconia with two cross- sectional areas. Material and methods: Two materials were tested VITA Inceram YZ and IPS e.max ZirCAD, for each material was obtained 20 bars of 25mm in length, 2x2mm±0.02 width and height and 20 bars of 3x3mm±0.03 width and height. The samples were sintered; ten samples of each group were subjected to surface treatment with sandblasting. Each specimen was loaded to fracture in a Universal Testing Machine with a transverse head speed of 1±0.5mm/min. The data were analysed with the t student test. Results: The zirconia e.max ZirCAD has the highest flexural strength (1232.78 MPa and the load-bearing fracture (802.74N. Surface treatment VITA Inceram YZ had a higher flexural strength (906.85 MPa and supported a major load 565,55N. The test t student indicated statistically significant differences in the group IPS e.max ZirCAD when it is sandblasting, so much in the resistance to the flexion, since in the maximum load up to the fracture in both areas. There were no statistically significant differences between two ceramics, it having considered both cross-section areas and surface treatment (with and without sandblasting. Conclusions: Sandblasting, the values flexural strength and fracture toughness of the two ceramics in the two areas of cross section significantly decreasing.  

  8. Effect of thermocycling on the flexural strength of porcelain laminate veneers

    OpenAIRE

    Subramanian Deepa; Sivagami G; Sendhilnathan D; Rajmohan C

    2008-01-01

    Aim: The aim of this study was to examine the impact of thermocycling on the flexural strength and development of surface flaws on the glazed surface of porcelain laminate veneer restorations with and without resin luting cement. Materials and Methods: 80 Vitadur alpha dentin porcelain discs (10 mm diameter, 0.9 mm thickness) were glazed on one side and divided into two groups: A (porcelain laminate veneer only without resin luting cement) and B (porcelain laminate veneer luted with resin ce...

  9. Asymmetric flexural behavior from bamboo's functionally graded hierarchical structure: underlying mechanisms.

    Science.gov (United States)

    Habibi, Meisam K; Samaei, Arash T; Gheshlaghi, Behnam; Lu, Jian; Lu, Yang

    2015-04-01

    As one of the most renewable resources on Earth, bamboo has recently attracted increasing interest for its promising applications in sustainable structural purposes. Its superior mechanical properties arising from the unique functionally-graded (FG) hierarchical structure also make bamboo an excellent candidate for bio-mimicking purposes in advanced material design. However, despite its well-documented, impressive mechanical characteristics, the intriguing asymmetry in flexural behavior of bamboo, alongside its underlying mechanisms, has not yet been fully understood. Here, we used multi-scale mechanical characterizations assisted with advanced environmental scanning electron microscopy (ESEM) to investigate the asymmetric flexural responses of natural bamboo (Phyllostachys edulis) strips under different loading configurations, during "elastic bending" and "fracture failure" stages, with their respective deformation mechanisms at microstructural level. Results showed that the gradient distribution of the vascular bundles along the thickness direction is mainly responsible for the exhibited asymmetry, whereas the hierarchical fiber/parenchyma cellular structure plays a critical role in alternating the dominant factors for determining the distinctly different failure mechanisms. A numerical model has been likewise adopted to validate the effective flexural moduli of bamboo strips as a function of their FG parameters, while additional experiments on uniaxial loading of bamboo specimens were performed to assess the tension-compression asymmetry, for further understanding of the microstructure evolution of bamboo's outer and innermost layers under different bending states. This work could provide insights to help the processing of novel bamboo-based composites and enable the bio-inspired design of advanced structural materials with desired flexural behavior.

  10. Performance of the LINC NIRVANA fringe and flexure tracker at delivery

    Science.gov (United States)

    Horrobin, Matthew; Eckart, Andreas; Beckmann, Udo; Connot, Claus; Dierkes, Jens; Lindhorst, Bettina; Nußbaum, Edmund; Rost, Steffen; Smajić, Semir; Straubmeier, Christian; Wank, Imke; Bertram, Thomas; Pott, Jörg-Uwe

    2014-07-01

    The LINC-NIRVANA Fringe and Flexure Tracking System has nearly completed assembly in the lab in Cologne, and will soon be ready for shipment and integration into the full LINC-NIRVANA system at MPIA Heidelberg. This paper provides an overview of the final assembly and testing phase in Cologne, concentrating on those aspects that directly affect instrument performance, including the detector performance and stability of the detector positioning system.

  11. Minimum bar size for flexure testing of irradiated SiC/SiC composite

    Energy Technology Data Exchange (ETDEWEB)

    Youngblood, G.E.; Jones, R.H. [Pacific Northwest National Lab., Richland, WA (United States)

    1998-03-01

    This report covers material presented at the IEA/Jupiter Joint International Workshop on SiC/SiC Composites for Fusion structural Applications held in conjunction with ICFRM-8, Sendai, Japan, Oct. 23-24, 1997. The minimum bar size for 4-point flexure testing of SiC/SiC composite recommended by PNNL for irradiation effects studies is 30 {times} 6 {times} 2 mm{sup 3} with a span-to-depth ratio of 10/1.

  12. Predicting the shear–flexural strength of slender reinforced concrete T and I shaped beams

    OpenAIRE

    Cladera Bohigas, Antoni; Marí Bernat, Antonio Ricardo; Ribas González, Carlos Rodrigo; Bairán García, Jesús Miguel; Oller Ibars, Eva

    2015-01-01

    A mechanical model previously developed by the authors for the prediction of the shear flexural strength of slender reinforced concrete beams with rectangular cross-section with or without stirrups has been extended to beams with T and I cross-sections. The effects of the section shape on each shear transfer action have been identified and incorporated into the corresponding equations. General expressions for strength verification and transverse reinforcement design have been derived. The con...

  13. The flexural stiffness of superficial neuromasts in the zebrafish (Danio rerio) lateral line.

    Science.gov (United States)

    McHenry, Matthew J; van Netten, Sietse M

    2007-12-01

    Superficial neuromasts are structures that detect water flow on the surface of the body of fish and amphibians. As a component of the lateral line system, these receptors are distributed along the body, where they sense flow patterns that mediate a wide variety of behaviors. Their ability to detect flow is governed by their structural properties, yet the micromechanics of superficial neuromasts are not well understood. The aim of this study was to examine these mechanics in zebrafish (Danio rerio) larvae by measuring the flexural stiffness of individual neuromasts. Each neuromast possesses a gelatinous cupula that is anchored to hair cells by kinocilia. Using quasi-static bending tests of the proximal region of the cupula, we found that flexural stiffness is proportional to the number of hair cells, and consequently the number of kinocilia, within a neuromast. From this relationship, the flexural stiffness of an individual kinocilium was found to be 2.4 x 10(-20) N m2. Using this value, we estimate that the 11 kinocilia in an average cupula generate more than four-fifths of the total flexural stiffness in the proximal region. The relatively minor contribution of the cupular matrix may be attributed to its highly compliant material composition (Young's modulus of approximately 21 Pa). The distal tip of the cupula is entirely composed of this material and is consequently predicted to be at least an order of magnitude more flexible than the proximal region. These findings suggest that the transduction of flow by a superficial neuromast depends on structural dynamics that are dominated by the number and height of kinocilia.

  14. Flexural Toughness Characteristics of Steel Synthetic Fibers-Lightweight Aggregate Concrete

    OpenAIRE

    2016-01-01

    In general, the steel synthetic fibers improve the durability of concrete by providing crackarresting mechanism and minimizing it’s possible to cracking. In this study, an experimental program was undertaken to investigate the effect of steel synthetic fibers content volume fractions on the compressive, tensile, modulus of elasticity, and flexural toughness of lightweight aggregate concrete (LAWC). The tested specimens were divided into five groups based on steel synthetic fibers conten...

  15. A colonic splenic flexure tumour presenting as an empyema thoracis: a case report

    Directory of Open Access Journals (Sweden)

    Murphy K

    2009-01-01

    Full Text Available Abstract Introduction The case report describes the rare presentation of a 79-year-old patient with a locally perforated splenic flexure tumour of the colon presenting with an apparent empyema thoracis in the absence of abdominal signs or symptoms. Case presentation Initial presentation was with a non-productive cough, anorexia and general malaise. An admission chest X-ray and subsequent computed tomographic image of the thorax showed a loculated pleural effusion consistent with an empyema. The computed tomography also showed a thickened splenic flexure. Thoracotomy was performed and a defect in the diaphragm was revealed after the abscess had been evacuated. A laparotomy was carried out at which point a tumour of the splenic flexure of the colon was found to be invading the spleen and locally perforated with subsequent collection in communication with the thorax. The tumour and spleen were resected and a transverse end colostomy was fashioned. Conclusion One must consider the diagnosis of pathology inferior to the diaphragm when an apparent empyema thoracis is encountered even in the absence of clinical signs or symptoms.

  16. Research on new-style flexure supports method for large-aperture transport mirror mounting

    Science.gov (United States)

    Quan, Xusong; Zhang, Zheng; Xiong, Zhao; Wang, Hui; Yuan, Xiaodong; Liu, Changchun

    2016-10-01

    In high-power solid-state laser facility (SG-III), focusing laser beams into the target center with precision better than 50 microns (RMS) is dependent on the stringent specifications of thousands of large-aperture transport mirror units and is a huge challenge on the surface aberration control of mirrors. The current mirror's mounting techniques with screw fastening loads has several engineering conundrums - low control precision for loads (higher scatter even +/-30%), and low assembly-rectification efficiency ( 100 screws). To improve the current screw-fastening method, a new-style flexure supports method, which has a wonderful performance on uniform control of the external loads and only uses 30 screws, is proposed to mount the mirror (size: 610mm×440mm×85mm). With theoretical modeling and FEM analysis, the impacts of mounting loads on mirror's surface aberrations are analyzed and discussed in detail, and the flexure supports system is designed. Finally, with experimental research and case studies, the proposed flexure supports method shows a powerful performance on even control precision of external loads with scatter even less than +/-10%, which is a promising mounting process to replace the threaded fasteners mounting the large-aperture optics. These improvements can lay a foundation for mounting process consistency, robustness, and assembly-rectification efficiency of large optical component.

  17. Effect of the bur grit size on the flexural strength of a glass-ceramic

    Directory of Open Access Journals (Sweden)

    P. P. Kist

    Full Text Available Abstract The purpose of the present study was to determine the biaxial flexural strength (BFS of a CAD/CAM leucite reinforced glass-ceramic ground by diamond burs of different grit sizes and the influence of surface roughness on the BFS. For this, 104 plates were obtained from CAD/CAM ceramic blocks and divided into 4 groups (n = 26, according to bur grit size: extra-fine, fine, medium and coarse. Roughness parameters (Ra, RyMax were measured, and plates were kept dry for 7 days. The flexural test was carried out and BFS was calculated. Ra, RyMax and BFS data were subjected to analysis of variance and post-hoc test. Weibull analysis was used to compare characteristic strength and Weibull modulus. Regression analysis was performed for BFS vs. Ra and RyMax. When burs with coarse grit were used, higher surface roughness values were found, causing a negative effect on the ceramic BFS (117 MPa for extra-fine, and 83 MPa for coarse. Correlation (r between surface roughness and BFS was 0.78 for RyMax and 0.73 for Ra. Increases in diamond grit size have a significant negative effect on the BFS of leucite-reinforced glass-ceramics, suggesting that grinding of sintered glass-ceramic should be performed using burs with the finest grit possible in order to minimize internal surface flaws and maximize flexural strength.

  18. Flexural behaviour of reinforced concrete beams with discrete steel – polypropylene fibres

    Directory of Open Access Journals (Sweden)

    Amizah Wan Jusoh Wan

    2017-01-01

    Full Text Available This paper discusses the experimental results on the flexural test of concrete containing different proportions of steel fibre (SF and polypropylene fibre (PPF. The flexural test was carried out under 4-point bending load and followed the relevant standards to FRC. Hooked-end deformed SF fibre with 60 mm length and fibrillated virgin PPF fibre with 19 mm length were used in this study. Meanwhile, the concrete was designed for high strength concrete of C60. The mixture included both single SF and PPF, and also the combination of both fibres; Control beam (PC, beam with 75%SF, beam with 75%SF + 25%PPF and beam with 25%PPF. The total fibre volume fraction (Vf was fixed at 1.5%. The experimental results show that the percentage proportion of combined SF-PPF at 75-25% had the best performance for its flexural capacity. Mixture with single PPF was also found not effective in delaying the onset of tension cracks and to increase the tensile strength of the concrete. Experimental result also shows beam with 75%SF +25%PPF had their structural stiffness improved the most as compared with the others. For the compressive strength, beam with 75%SF + 25%PPF also revealed comparable performance with the control for high strength composite concrete.

  19. Methods to Analyze Flexural Buckling of the Consequent Slabbed Rock Slope under Top Loading

    Directory of Open Access Journals (Sweden)

    Hongyan Liu

    2016-01-01

    Full Text Available The consequent slabbed rock slope is prone to flexural buckling failure under its self-weight and top loading. However, nearly none of the existing studies consider the effect of the top loading on the slope flexural critical buckling height (CBH. Therefore, on the basis of Euler’s Method and the flexural buckling failure mode of the consequent slabbed rock slope, the calculation method of the CBH of the vertical slabbed rock slope under the self-weight is firstly proposed, and then it is extended to that of the consequent slabbed rock slope. The effect of slope dip angle, friction angle, and cohesion between the neighboring rock slabs and rock elastic modulus on the slope CBH is discussed. Secondly, the calculation method of the CBH of the consequent slabbed rock slope under its self-weight and top loading is proposed according to the superposition principle. Finally, on the basis of the hypothesis that the rock mechanical behavior obeys the statistical damage model, the effect of the rock mechanical parameters n and ε0 on the slope CBH is studied. The results show that the rock strength has much effect on the slope CBH. If the rock is supposed to be a linear elastic body without failure in Euler’s Method, the result from it is the maximum of the slope CBH.

  20. COMPARISON OF ELASTIC OF POROUS CORDIERITE BY FLEXURE AND DYNAMIC TEST METHODS

    Energy Technology Data Exchange (ETDEWEB)

    Stafford, Randall [Cummins, Inc; Golovin, K. B. [Cummins, Inc; Dickinson, A. [Cummins, Inc; Watkins, Thomas R [ORNL; Shyam, Amit [ORNL; Lara-Curzio, Edgar [ORNL

    2012-01-01

    Previous work showed differences in apparent elastic modulus between mechanical flexure testing and resonance methods. Flexure tests have been conducted using non-contact optical systems to directly measure deflection for calculation of elastic modulus. Dynamic test methods for elastic modulus measurement were conducted on the same material for comparison. The results show significant difference in the apparent elastic modulus for static flexure versus dynamic methods. The significance of the difference in apparent elastic modulus on thermal stress and the hypotheses for these differences will be discussed. Dynamic measurement (resonance) and static measurement (mechanical) produce different values for elastic modulus of porous cordierite ceramic. The elastic modulus from resonance is a measure of the material response at very low strain which is different from the material response in a mechanical test with relatively large strain. The apparent elastic moduli for dynamic versus static test methods in this study are different by a factor of two. This result has significant impact on calculated stress and life in an aftertreatment component.

  1. Flexural and Thermal Properties of Novel Energy Conservation Slotted Reinforced Concrete Beams

    Directory of Open Access Journals (Sweden)

    Gao Ma

    2016-01-01

    Full Text Available Conventional solid reinforced concrete (RC beams were modified to slotted beams for consideration as thermal insulation structural components. The slotted beam consisted of an outer and an inner beam, respectively, with a slot located near the middle of the beam along its width direction for filling thermal insulation material. Flexural and thermal behavior of the slotted beams were investigated. Three RC reference solid beams and six slotted beams were fabricated and tested under four-point bending tests. The test results indicated that the failure mode of both slotted beams and the solid beams was flexural failure. However, the damage process of the slotted beams was different from that of the solid beams at the final loading stage. The moment curvature analysis indicated that the tensile reinforcement ratio of the outer and inner beams had an important effect on the flexural behavior, especially the ductility of the slotted beams. Thermal study indicated that the heat transfer coefficient of the slotted beam was greatly reduced and the thermal inertia factor increased a lot, compared with the solid beam. In addition, FE simulation results showed that a new frame structure using slotted beams exhibited obvious and attractive thermal insulation property.

  2. Laparoscopic radical lymph node dissection for advanced colon cancer close to the hepatic flexure.

    Science.gov (United States)

    Uematsu, Dai; Akiyama, Gaku; Sugihara, Takehiko; Magishi, Akiko; Yamaguchi, Takuya; Sano, Takayuki

    2017-02-01

    Complete mesocolic excision is currently recognized as a standard procedure for colon cancer. Gastroepiploic, infrapyloric, and superficial pancreatic head lymph node metastases in the gastrocolic ligament have been reported for colon cancer close to the hepatic flexure. We sought to investigate metastases in the gastrocolic ligament in colon cancer close to the hepatic flexure. This was a single-center retrospective study. All patients with T2 or deeper invasive colon cancer in the relevant tumor location who underwent laparoscopic right hemicolectomy or extended right hemicolectomy at our institution between 1 April 2011 and 31 March 2015 were included. Lymph node dissection in the gastrocolic ligament was performed in 35 cases. Complications occurred in 11 patients (31%) and were grades I and II according to the Clavien-Dindo classification. Lymph node metastases in the gastrocolic ligament were found in only three patients (9%). Each metastasis was larger than 9 mm. Metastases in the gastrocolic ligament occurred in 9% of patients with T2 or deeper invasive colon cancer close to the hepatic flexure. Laparoscopy was feasible and useful during gastrocolic ligament resection. This study included a small sample and lacked an extended follow-up. Further studies are needed to determine the clinical relevance of this finding, particularly in terms of recurrence and long-term survival. © 2016 Japan Society for Endoscopic Surgery, Asia Endosurgery Task Force and John Wiley & Sons Australia, Ltd.

  3. A novel constrained H2 optimization algorithm for mechatronics design in flexure-linked biaxial gantry.

    Science.gov (United States)

    Ma, Jun; Chen, Si-Lu; Kamaldin, Nazir; Teo, Chek Sing; Tay, Arthur; Mamun, Abdullah Al; Tan, Kok Kiong

    2017-08-18

    The biaxial gantry is widely used in many industrial processes that require high precision Cartesian motion. The conventional rigid-link version suffers from breaking down of joints if any de-synchronization between the two carriages occurs. To prevent above potential risk, a flexure-linked biaxial gantry is designed to allow a small rotation angle of the cross-arm. Nevertheless, the chattering of control signals and inappropriate design of the flexure joint will possibly induce resonant modes of the end-effector. Thus, in this work, the design requirements in terms of tracking accuracy, biaxial synchronization, and resonant mode suppression are achieved by integrated optimization of the stiffness of flexures and PID controller parameters for a class of point-to-point reference trajectories with same dynamics but different steps. From here, an H2 optimization problem with defined constraints is formulated, and an efficient iterative solver is proposed by hybridizing direct computation of constrained projection gradient and line search of optimal step. Comparative experimental results obtained on the testbed are presented to verify the effectiveness of the proposed method. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

  4. FLEXURAL PROPERTIES AND ORTHOTROPIC SWELLING BEHAVIOR OF BAGASSE/THERMOPLASTIC COMPOSITES

    Directory of Open Access Journals (Sweden)

    Seyed Majid Zabihzadeh

    2010-05-01

    Full Text Available The flexural properties of commercial bagasse-filled polyethylene (PE and polypropylene (PP composites were determined as a function of strain rate at room temperature. The applied strain rates were 1.5 ×10-4, 3.75×10-4, 7.5×10-4, and 1.5×10-3 s-1. The flexural modulus tended to increase linearly for the two types of composites with the logarithm of strain rate. The bending strength of polypropylene composite also behaved in a similar manner, but the polyethylene composite exhibited different behavior in which the MOR values of polyethylene composite didn’t alter appreciably as a function of strain rate. The flexural response of a polypropylene-based composite was found to exhibit higher dependency on strain rate than a polyethylene-based composite. Water absorption of both composites followed the kinetics of a Fickian diffusion process. Water absorption and dimensional instability of PE-based composites were lower than those of PP-based composites. The highest swelling took place in the thickness of the samples, followed by the width and length, respectively.

  5. A new hybrid piezo-actuated compliant mechanism with self-tuned flexure arm

    Science.gov (United States)

    Ling, Mingxiang; Cao, Junyi

    2017-04-01

    Recent interests and demands for developing video-rate atomic force microscopes, high-throughput probe-based nanofabrication and high-frequency vibration generator for assisted-machining are increasingly posing new challenges for designing high-bandwidth and large-range piezo-actuated compliant mechanisms. The previous studies mainly focused on making the trade-off between natural frequency and motion range by designing a proper topology. Differing from the previous works, this paper attempts to break the deadlock by employing both piezo-stacks and piezoelectric patches to actuate compliant mechanisms. In this method, piezo-stacks provide an actuating force similar to the traditional way, while piezoelectric patches are bonded on the surface of the flexure arms in compliant mechanisms. These `active' laminaes are used to further actuate the hosting flexural beam by inducing strains on the interface and then give additional bending moments to the flexural arms, which enlarge the output displacement of the compliant mechanism while without the sacrifice of natural frequency. An analytical formulation is established to illustrate the new driving principle and the compound static behaviour of a specific hybrid piezo-actuated multistage compliant mechanism. Initial prototype is also manufactured and experimentally testing is conducted to verify the feasibility of the method.

  6. COMPUTATION OF FLEXURAL PROPERTIES OF HA/PLLA COMPOSITE USING A CELL MODEL APPROACH

    Institute of Scientific and Technical Information of China (English)

    Fan Jianping; Tang Chak-Yin; Tsui C.P.

    2006-01-01

    A three-dimensional finite element analysis was conducted to evaluate the feasibility of predicting the flexural properties of hydroxyapatite-reinforced poly-L-lactide acid (HA/PLLA)biocomposite using three different schemes. The scheme 1, originated from a beam analysis, was used to determine the flexural modulus analytically while the scheme 2 and 3 were designed to have different loading and boundary conditions using a finite element cell modeling approach.An empirical approach using Chow's formula and experimental data were used for comparison with the predicted results. In order to reduce the computational time and save the storage space involved in determining the effect of varying particle volume fractions on the flexural properties of HA/PLLA, a superelement technique was applied. The results using the scheme 3 and the Chow's formula were found to be in reasonable agreement with experimental results over the range of particle volume fraction. In addition to the Chow's formula, local stress distribution and the failure processes in HA/PLLA were simulated using the finite element technique.

  7. Glass fiber reinforced plastics within the fringe and flexure tracker of LINC-NIRVANA

    Science.gov (United States)

    Smajic, Semir; Eckart, A.; Horrobin, M.; Lindhorst, B.; Pott, J.-U.; Rauch, C.; Rost, S.; Straubmeier, C.; Tremou, E.; Wank, I.; Zuther, J.

    2012-07-01

    The Fringe and Flexure Tracking System (FFTS) is meant to monitor and correct atmospheric piston varia­ tion and instrumental vibrations and flexure during near-infrared interferometric image acquisition of LING­ NIRVANA. In close work with the adaptive optics system the FFTS enables homothetic imaging for the Large Binocular Telescope. One of the main problems we had to face is the connection between the cryogenic upper part of the instrument, e.g. detector head, and the lower ambient temperature part. In this ambient temperature part the moving stages are situated that move the detector head in the given field of view (FOV). We show how we solved this problem using the versatile material glass fiber reinforced plastics (GFRP's) and report in what way this material can be worked. We discuss in detail the exquisite characteristics of this material which we use to combine the cryogenic and ambient environments to a fully working system. The main characteristics that we focus on are the low temperature conduction and the tensile strength of the GFRP's. The low temperature conduction is needed to allow for a low heat-exchange between the cryogenic and ambient part whereas the tensile strength is needed to support heavy structures like the baffle motor and to allow for a minimum of flexure for the detector head. Additionally, we discuss the way we attached the GFRP to the remaining parts of the FFTS using a two component encapsulant.

  8. Fuzzy sets predict flexural strength and density of silicon nitride ceramics

    Science.gov (United States)

    Cios, Krzysztof J.; Sztandera, Leszek M.; Baaklini, George Y.; Vary, Alex

    1993-01-01

    In this work, we utilize fuzzy sets theory to evaluate and make predictions of flexural strength and density of NASA 6Y silicon nitride ceramic. Processing variables of milling time, sintering time, and sintering nitrogen pressure are used as an input to the fuzzy system. Flexural strength and density are the output parameters of the system. Data from 273 Si3N4 modulus of rupture bars tested at room temperature and 135 bars tested at 1370 C are used in this study. Generalized mean operator and Hamming distance are utilized to build the fuzzy predictive model. The maximum test error for density does not exceed 3.3 percent, and for flexural strength 7.1 percent, as compared with the errors of 1.72 percent and 11.34 percent obtained by using neural networks, respectively. These results demonstrate that fuzzy sets theory can be incorporated into the process of designing materials, such as ceramics, especially for assessing more complex relationships between the processing variables and parameters, like strength, which are governed by randomness of manufacturing processes.

  9. An Experimental Study on Strengthening of Reinforced Concrete Flexural Members using Steel Wire Mesh

    Directory of Open Access Journals (Sweden)

    Al Saadi Hamza Salim Mohammed

    2017-01-01

    Full Text Available One of the major challenges and contemporary research in the field of structural engineering is strengthening of existing structural elements using readily available materials in the market. Several investigations were conducted on strengthening of various structural components using traditional and advanced materials. Many researchers tried to enhance the reinforced concrete (RC beams strength using steel plate, Glass and Carbon Fibre Reinforced Polymers (GFRP & CFRP. For the reason that high weight to the strength ratio and compatibility in strength between FRP composites and steel bars, steel plates and GFRP and CFRP composites are not used for strengthening works practically. Hence, in this present work the suitability of using wire mesh for the purpose of strengthening the RC flexural members is studied by conducting experimental works. New technique of strengthening system using wire mesh with a view to improve sectional properties and subsequently flexural strength of RC beams is adopted in this work. The results for experimental and theoretical analysis were compared and found that good correlation exists between them. The experimental results indicate that RC beams strengthened with steel wire mesh are easy technique for strengthening of existing flexural members.

  10. An experimental approach for the determination of axial and flexural wavenumbers in circular exponentially tapered bars

    Science.gov (United States)

    Kalkowski, Michał K.; Muggleton, Jen M.; Rustighi, Emiliano

    2017-03-01

    Whilst the dynamics of tapered structures have been extensively studied numerically and analytically, very few experimental results have been presented to date. The main aim of this paper is to derive and demonstrate an experimental method enabling both axial and flexural wavenumbers in exponentially tapered bars to be estimated. Our particular interest in this type of tapering is motivated by its occurrence in naturally grown structures such as tree roots, with an outlook towards remote root mapping. Decomposing a dynamic response into a sum of contributing waves, we propose a method in which two independent wavenumbers can be calculated from five equispaced measurements. The approach was demonstrated in an experiment on a freely suspended wooden specimen supported by theoretical modelling. For axial waves we used the well-established elementary rod theory, whereas for flexural waves we build a piecewise uniform model based on the Timoshenko beam theory. The estimates calculated from the experimental data were compared with the analytical and numerical results and showed good agreement. The limitations of the method include an appropriate choice of sensor spacing, the effect of sensor misalignments and the assumption of small wavenumber variation for flexural waves.

  11. Scanning near-field lithography with high precision flexure orientation stage control

    Science.gov (United States)

    Qin, Jin; Zhang, Liang; Tan, Haosen; Wang, Liang

    2017-09-01

    A new design of an orientation stage for scanning near-field lithography is presented based on flexure hinges. Employing flexure mechanisms in place of rigid-body mechanisms is one of the most promising techniques to efficiently implement high precision motion and avoid problems caused by friction. For near-field scanning lithography with evanescent wave, best resolution can be achieved in contact mode. However, if the mask is fixed on a rigid stage, contact friction will deteriorate the lithography surface. To reduce friction while maintaining good contact between the mask and the substrate, the mask should be held with high lateral stiffness and low torsion stiffness. This design can hold the mask in place during the scanning process and achieve passive alignment. Circular flexure hinges, whose parameters are determined by motion requirements based on Schotborgh's equation, are used as the basic unit of the stage to achieve passive alignment by compensating motions from elastic deformation. A finite-element analysis is performed to verify this property of the stage. With the aid of this stage, 21 nm resolution is achieved in static near-field lithography and 18 nm line-width in scanning near-field lithography.

  12. WATER UPTAKE AND FLEXURAL PROPERTIES OF NATURAL FILLER/HDPE COMPOSITES

    Directory of Open Access Journals (Sweden)

    Seyed Majid Zabihzadeh

    2010-02-01

    Full Text Available Composites of flour from different lignocellulosic sources with high-density polyethylene were prepared, and their water absorption and flexural properties were studied. Flour samples from loblolly pine, hybrid Euro-American poplar, and wheat straw were mixed with the polymer at 35 wt % lignocellulosics content and either zero or 2% compatibilizer. Water absorption tests were carried out on injection-molded specimens for temperatures of 30, 45, 60, and 75°C. Results indicated a significant difference among different lignocellulosic types, of which wheat straw composites exhibited the highest and the pine composites showed the lowest water absorption values. The composites with 2% MAPE showed lower water absorption compare to the composites without MAPE. This indicates that the compatibilizer plays an important role to repel the water molecules. For all four temperature conditions, rising temperature increased water absorption significantly. Composites with poplar had the highest flexural strength and modulus. Adding compatibilizer to the composites boosted the flexural properties by improving the adhesion between natural filler and the polymer matrix.

  13. Water Sorption and Flexural Strength of Thermoplastic and Conventional Heat-Polymerized Acrylic Resins

    Science.gov (United States)

    Hemmati, Mohammad Ali; Vafaee, Fariborz

    2015-01-01

    Objectives: The aim of this study was to assess and compare the water sorption and flexural strength of thermoplastic and conventional acrylic resins. Materials and Methods: Water sorption and flexural strength were compared between a thermoplastic modified polymethyl methacrylate (PMMA) denture base resin (group A) and a heat-polymerized PMMA acrylic resin (group B) as the control group (n=10). A three-point bending test was carried out for flexural strength testing. For water sorption test, 10 disc-shaped samples were prepared. After desiccating, the samples were weighed and immersed in distilled water for seven days. Then, they were weighed again, and desiccated for the second and third times. Differences between the mean values in the two groups were analyzed using Student’s t-test. Results: The mean value of water sorption was 14.74±1.36 μg/mm3 in group A, and 19.11±0.90 μg/mm3 in group B; this difference was statistically significant (PPMMA acrylic resins as denture base materials. PMID:26877737

  14. Effect of flexural phonons on the hole states in single-layer black phosphorus

    Science.gov (United States)

    Brener, S.; Rudenko, A. N.; Katsnelson, M. I.

    2017-01-01

    Flexural thermal fluctuations in crystalline membranes affect the band structure of the carriers, which leads to an exponential density-of-states (DOS) tail beyond the unperturbed band edge. We present a theoretical description of this tail for a particular case of holes in single-layer black phosphorus, a material which exhibits an extremely anisotropic quasi-one-dimensional dispersion (my/mx≫1 ) and, as a result, an enhanced Van Hove singularity at the valence band top. The material parameters are determined by ab initio calculations and then are used for quantitative estimation of the effect of two-phonon (flexural) processes have on the charge carrier DOS. It is shown that unlike the isotropic case, the physics is determined by the phonons with wave vectors of the order of q*, where q* determines the crossover between harmonic and anharmonic behavior of the flexural phonons. The spectral density of the holes in single-layer black phosphorus at finite temperatures is calculated.

  15. Static flexural properties of hedgehog spines conditioned in coupled temperature and relative humidity environments.

    Science.gov (United States)

    Kennedy, Emily B; Hsiung, Bor-Kai; Swift, Nathan B; Tan, Kwek-Tze

    2017-11-01

    Hedgehogs are agile climbers, scaling trees and plants to heights exceeding 10m while foraging insects. Hedgehog spines (a.k.a. quills) provide fall protection by absorbing shock and could offer insights for the design of lightweight, material-efficient, impact-resistant structures. There has been some study of flexural properties of hedgehog spines, but an understanding of how this keratinous biological material is affected by various temperature and relative humidity treatments, or how spine color (multicolored vs. white) affects mechanics, is lacking. To bridge this gap in the literature, we use three-point bending to analyze the effect of temperature, humidity, spine color, and their interactions on flexural strength and modulus of hedgehog spines. We also compare specific strength and stiffness of hedgehog spines to conventional engineered materials. We find hedgehog spine flexural properties can be finely tuned by modifying environmental conditioning parameters. White spines tend to be stronger and stiffer than multicolored spines. Finally, for most temperature and humidity conditioning parameters, hedgehog spines are ounce for ounce stronger than 201 stainless steel rods of the same diameter but as pliable as styrene rods with a slightly larger diameter. This unique combination of strength and elasticity makes hedgehog spines exemplary shock absorbers, and a suitable reference model for biomimicry. Copyright © 2017 Elsevier Ltd. All rights reserved.

  16. ORIENTATION AND POSITION EFFECTS OF A LOCAL HETEROGENEITY ON FLEXURAL VIBRATION FREQUENCIES IN WOODEN BEAMS

    Directory of Open Access Journals (Sweden)

    Mehran Roohnia

    2015-06-01

    Full Text Available Studying the influence of defect on the dynamic behavior of wood in order to detect the local heterogeneities is of great importance in non-destructive testing of wood. The natural heterogeneities in wood are oriented in a volume. However, onedimensional models are still used in dynamic characterization of wooden beams. The aim of this study was to experimentally investigate the effects of the orientation and position of an artificial defect on the flexural vibration frequencies. Different batches of Fagus orientalis specimens were drilled in the radial direction at five positions along the specimen. Dynamic tests in free flexural vibration were performed on the specimens before and after drilling both in the longitudinal-radial (LR and longitudinal-tangential (LT bending plan. The behavior in free flexural vibration was found to be different depending on the position and orientation of heterogeneity. When the drilling axis lies in the bending plane (LR, the weakening of frequency was maximal at the location of an antinode of vibration. On the contrary, the frequency offset was maximal in the place of a vibration node when the drilling axis was orthogonal to the bending plane (LT.

  17. On the effect of elastic nonlinearity on aquatic propulsion caused by propagating flexural waves

    CERN Document Server

    Krylov, Victor V

    2016-01-01

    In the present paper, the initial theoretical results on wave-like aquatic propulsion of marine craft by propagating flexural waves are reported. Recent experimental investigations of small model boats propelled by propagating flexural waves carried out by the present author and his co-workers demonstrated viability of this type of propulsion as an alternative to a well-known screw propeller. In the attempts of theoretical explanation of the obtained experimental results using the theory of Lighthill for fish locomotion, it was found that this theory predicts zero thrust for such model boats, which is in contradiction with the results of the experiments. One should note in this connection that the theory developed by Lighthill assumes that the amplitudes of propulsive waves created by fish body motion grow from zero on the front (at fish heads) to their maximum values at the tails. This is consistent with fish body motion in nature, but is not compatible with the behaviour of localised flexural waves used for...

  18. Effect of metal chloride solutions on coloration and biaxial flexural strength of yttria-stabilized zirconia

    Science.gov (United States)

    Oh, Gye-Jeong; Lee, Kwangmin; Lee, Doh-Jae; Lim, Hyun-Pil; Yun, Kwi-Dug; Ban, Jae-Sam; Lee, Kyung-Ku; Fisher, John G.; Park, Sang-Won

    2012-10-01

    The effect of three kinds of transition metal dopants on the color and biaxial flexural strength of zirconia ceramics for dental applications was evaluated. Presintered zirconia discs were colored through immersion in aqueous chromium, molybdenum and vanadium chloride solutions and then sintered at 1450 °C. The color of the doped specimens was measured using a digital spectrophotometer. For biaxial flexural strength measurements, specimens infiltrated with 0.3 wt% of each aqueous chloride solution were used. Uncolored discs were used as a control. Zirconia specimens infiltrated with chromium, molybdenum and vanadium chloride solutions were dark brown, light yellow and dark yellow, respectively. CIE L*, a*, and b* values of all the chromium-doped specimens and the specimens infiltrated with 0.1 wt% molybdenum chloride solution were in the range of values for natural teeth. The biaxial flexural strengths of the three kinds of metal chloride groups were similar to the uncolored group. These results suggest that chromium and molybdenum dopants can be used as colorants to fabricate tooth colored zirconia ceramic restorations.

  19. Topography of Beethoven and Tolstoj Basins, Mercury: Implications for Lithospheric Flexure

    Science.gov (United States)

    Andre, S. L.; Watters, T. R.

    2005-12-01

    Interior structures of two mercurian basins, Beethoven and Tolstoj, are characterized using topography derived from Mariner 10 stereo images. The topography of the two mercurian basins is similar to that of lunar mare-filled basins, such as Serenitatis. In addition to topography, the tectonic features within Beethoven and Tolstoj basins are compared to those of lunar basins. Beethoven and Tolstoj basins exhibit little evidence of deformation compared to Caloris basin and their lunar counterparts. Well-developed basin-concentric wrinkle ridges and arcuate graben are characteristic of many lunar basins and are thought to result from lithospheric flexure in response to the superisostatic load from the mare basalts. The presence of wrinkle ridges in the floor of Caloris basin suggests that the basin interior has undergone compression, possibly the result of subsidence of the interior fill. Because both Beethoven and Tolstoj lack basin-concentric wrinkle ridges and arcuate graben, we suggest that either Mercury's elastic lithosphere was too strong for significant lithospheric flexure and subsidence to occur, or the basin fill material provides little density contrast and thus exerts little net load on the mercurian lithosphere. Compositional evidence from color-derived parameter images of Tolstoj basin indicates that the basin fill has an FeO abundance comparable to that of average mercurian crust. This suggests that the basin fill has a similar density to the surrounding crustal material and that the load may be insufficient to induce flexure.

  20. An appropriate relationship between flexural strength and compressive strength of palm kernel shell conc

    Directory of Open Access Journals (Sweden)

    Ibrahim Tunde Yusuf

    2016-06-01

    Full Text Available This paper presents the determination of an appropriate compressive–flexural strength model of palm kernel shell concrete (PKSC. The direct and indirect Ultrasonic Pulse Velocity (UPV measurements, with respective to mechanical properties of compression (cube and flexural (slab elements, of concrete at various mixes and water/cement (w/c ratios were made. A total of 225 cubes and 15 slabs of the PKSC were casted for nominal mixes of 1:1:1, 1:1:2 and 1:11/2:3, and varying (w/c ratios of 0.3–0.7 at interval of 0.1. The test elements were cured for 3, 7, 14, 28, 56 and 91 days in water at laboratory temperature. The elements were then subjected to nondestructive testing using the Pundit apparatus for determination of direct ultrasonic wave velocity and the elastic modulus at the various ages. The cubes were subsequently subjected to destructive compressive test. The 28-day compressive strength–UPV and strength–age statistical relationships at w/c ratio of 0.5 determined from the velocity–strength data set in linear, power, logarithm, exponential and polynomial trend forms. The polynomial trend line in the form y = aln(x at R2 value of 0.989, found appropriate, among others, was proposed for the formulation of the compressive strength–flexural strength model of PKSC at w/c ratio of 0.5.

  1. The São Vicente earthquake of 2008 April and seismicity in the continental shelf off SE Brazil: further evidence for flexural stresses

    Science.gov (United States)

    Assumpção, M.; Dourado, J. C.; Ribotta, L. C.; Mohriak, W. U.; Dias, Fábio L.; Barbosa, J. R.

    2011-12-01

    The continental margin and shelf of most stable intraplate regions tend to be relatively more seismically active than the continental interior. In the southeast continental margin of Brazil, a seismic zone extends from Rio Grande do Sul to Espírito Santo, with seismic activity occurring mainly along the continental slope and suggesting a close relationship with flexural stresses caused by the weight of the sediments. In this region, earthquakes with magnitudes larger than 5 mb occur every 20-25 yr, on average. The focal mechanism solutions of previous earthquakes in this zone indicated reverse faulting on planes dipping approximately 45° with horizontal P-axes. The recent 5.2 mb earthquake of 2008 April 23 occurred 125 km south of São Vicente and was well recorded by many stations in SE Brazil, as well as at teleseismic distances in North America and Africa. Its focal depth was 17 km, locating the hypocentre in the lower crust. A well-determined focal mechanism solution shows one vertical nodal plane and one subhorizontal nodal plane. The P- and T-axes exhibit large dips, which were confirmed by a regional moment tensor inversion. This unusual orientation of the fault mechanism can be attributed to a rotation of the principal stress directions in the lower crust caused by flexural effects due to the load of recent sedimentation.

  2. The influence of self-compacting steel fibre reinforced concrete infill on the flexure strength and ductility of masonry walls

    OpenAIRE

    Oliveira, Luiz António Pereira de; Bernardo, Luís Filipe Almeida

    2010-01-01

    This paper presents an experimental study on the influence of longitudinal reinforcement ratio and steel fibre volume in self-compacting concrete infill on the strength and ductility of reinforced masonry walls subjected to flexure. Flexure tests were performed as four-point bending tests on twelve walls. The analysis of the concrete infill contribution to the walls capacity is made considering recent recommendations for steel fibre reinforced concrete design. A ductility...

  3. Effect of casein phosphopeptide-amorphous calcium phosphate on the flexural strength of enamel-dentin complex following extracoronal bleaching

    Directory of Open Access Journals (Sweden)

    Diatri Nari Ratih

    2015-03-01

    Full Text Available Background: Bleaching can affect the mechanical properties of enamel-dentin complex, such as flexural strength. Casein phosphopeptide-amorphus calcium phosphate (CPP-ACP is often used following bleaching treatment to reduce hypersensitivity and to increase demineralization of tooth. Purpose: The purpose of the study was to investigate the effect of CPP-ACP on the flexural strength of enamel-dentin complex following extracoronal bleaching. Methods: Forty-eight enamel-dentin plates (size 8 x 2 x 3 mm were randomly assigned into 6 groups, each consisted of 8 samples. Group 1, no bleaching and immersed in artificial saliva. Group 2, no bleaching, CPP-ACP application only. Group 3, bleaching using 15% carbamide peroxide. Group 4, similar to group 3, except application of CPP-ACP for the times between bleaching. Group 5, bleaching with 40% hydrogen peroxide. Group 6, similar to group 5, except application of CPP-ACP for the times between bleaching. Flexural strength of each enamel-dentin plate was tested by threepoint bending test using universal testing machine. Results: The results showed that 15% carbamide peroxide and 40% hydrogen peroxide significantly reduced flexural strength of enamel-dentin (216.25±26.44 MPa and 206.67±32.07 MPa respectively. Conversely, application of CPP-ACP following both bleachings increased flexural strength (266.75± 28.27MPa and 254.58±36.59 MPa respectively. A two-way Anova revealed that extracoronal bleaching agents significantly reduced flexural strength (p<0.05. Conclusion: Extracoronal bleaching agents reduce flexural strength, whereas application of CPP-ACP following bleaching either with 15% carbamide peroxide or 40% hydrogen peroxide can increase the flexural strength of enamel-dentin complex.

  4. Influence of flexural fatigue on chloride threshold value for the corrosion of steels in Ca(OH){sub 2} solutions

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Linhua, E-mail: hhulhjiang@gmail.com [College of Mechanics and Materials, Hohai University, 1 Xikang Rd., Nanjing, 210098 (China); Hydraulic Engineering Research Center for New Materials and Protection, Jiangsu Province, 1 Xikang Rd., Nanjing, 210098 (China); Liu, Hao; Wang, Yongliang; Zhang, Yan; Song, Zijian; Xu, Jinxia; Jin, Ming; Jiang, Peng; Xu, Yi; Gao, Hailang [College of Mechanics and Materials, Hohai University, 1 Xikang Rd., Nanjing, 210098 (China)

    2015-08-15

    The flexural fatigue was enforced on reinforced concrete beam with stress level of 0.6 and different fatigue life cycles. Steels removed from the beams were soaked in the saturated Ca(OH){sub 2} solution, which was used as a simulated concrete pore solution. The NaCl solution was chosen as the source of chloride ions. The Chloride Threshold Values (CTV) were detected by combining the open-circuit potentials (E{sub corr}) with the corrosion current densities (i{sub corr}), which were obtained by electrochemical impedance spectroscopy (EIS). The changes of microstructure caused by the flexural fatigue were observed by scanning electron microscopy (SEM). The results showed that as the fatigue cycle times increased, the CTV decreased under a certain stress level and range of fatigue life cycles. The grains became finer and cracks appeared on the surface of the steels. While the capacitive arcs under no flexural fatigue decreased gradually with the addition of chloride ions, the ones under flexural fatigue presented no regularity. Cracks at the surface were expanded because of sustaining flexural fatigue, which degenerated the later resistance to chloride ions of the steels. - Highlights: • The influence of flexural fatigue on chloride threshold value was examined. • The chloride threshold values vary with different fatigue life cycles. • The corrosion behavior depends on the surface integrity of the steels.

  5. The effect of zirconia on flexural strength of IPS Empress 2 ceramic

    Directory of Open Access Journals (Sweden)

    Kermanshah H

    2007-06-01

    Full Text Available Background and Aim: All ceramic, inlay-retained resin bonded fixed partial denture is a conservative method for replacement of missing teeth, because of minimal tooth reduction. The connector between the retainer and the pontic is the weak point of these bridges. Reinforcement of ceramic core will increase the clinical longevity. The aim of this study was to determine the effect of zirconia on flexural strength of IPS Empress 2 core ceramic.Materials and Methods: In this experimental in vitro study, twenty eight bar shape specimens (17´3.1´3.1 mm were made of four different materials: (1 Slip casting in-ceram alumina core (control group (2 Hot-pressed lithium disilicate core ceramic (IPS Empress 2 (3 IPS Empress 2 with cosmopost (zirconia post inserted longitudinally in the center of the bar (4 IPS Empress 2 with cosmopost (zirconia post inserted longitudinally in bottom of the bar. Specimens were subjected to three-point flexure loading with the span of 15mm, at a cross-head speed of 0.5 mm/min. Failure loads were recorded and analyzed using one-way ANOVA and Tomhane Post-hoc tests and p<0.05 was set as the level of significance. Fractured surfaces were then observed by scanning electron microscope (SEM. Four additional samples were made as the third group, and zirconia-IPS interface was observed by SEM before fracture.Results: Mean values and standard deviations of three point flexural strengths of groups 1 to 4, were: 378.4±44.6, 258.6±27.5, 144.3±51.7, 230±22.3 MPa respectively. All the groups were statistically different from each other (P<0.05, except groups 2 and 4. The flexural strengths of groups 2, 3, 4 were significantly lower than group 1. Group 3 had the lowest flexural strength. SEM analysis showed that the initiated cracks propagated in the interface of zirconia post and IPS Empress 2 ceramic.Conclusion: Based on the results of this study, inserting zirconia post (cosmopost in IPS Empress 2 ceramic does not reinforce all

  6. Tectonosedimentary evolution model of an intracontinental flexural (foreland) basin for paleoclimatic research

    Science.gov (United States)

    Fang, Xiaomin; Wang, Jiuyi; Zhang, Weilin; Zan, Jinbo; Song, Chunhui; Yan, Maodu; Appel, Erwin; Zhang, Tao; Wu, Fuli; Yang, Yibo; Lu, Yin

    2016-10-01

    Intracontinental flexural (foreland) basin sediments are now frequently used as archives for detailed paleoclimatic and sedimentary environmental reconstruction, fossil and stratigraphic correlation, and tectonic evolution and uplift of basin and orogen. However, sedimentologic characteristics vary considerably in time-space with the evolution of flexural basin, apt to cause misinterpretation of climatic change and stratigraphic correlation. Based on high resolution fossil mammal and magnetostratigraphic constraints and sedimentary facies analysis, here we took the Linxia Basin at the front of the NE Tibetan Plateau as a case to demonstrate and figure out a model how sedimentology and stratigraphy vary temporospatially with the evolution of such flexural basin. The results show that the Linxia Basin is a type intracontinental foreland basin subjected to two phases of flexural deformation exerted by the West Qin Ling (Mts.) and NE Tibetan Plateau to the south. Phase I began latest at the beginning of the Miocene (23.3 Ma), indicated by a balanced fast flexural subsidence and mostly fine sediment infilling giving rise to the early underlying unconformity. It manifests as an obvious sediment wedge with high filling rate, thickening toward mountains and an occurrence of a mountains-parallel big river - shallow lake system along the foredeep, suggesting a less high mountain topography. In the late Phase I, from ~ 13 Ma to 8 Ma, the subsidence and thickening rates began to decrease, accompanied by faults and deformation propagating gradually into the basin, causing gradual basinward migration of the foredeep and its accompanying river-lake system. Since ~ 8 Ma in Phase II, the West Qin Ling and NE Tibetan began to uplift rapidly and thrust/load onto the Linxia Basin, causing strong mountain erosion, thrust-fold belt propagation and basin overfilling. This forced the mountains-parallel river - lake system to turn to the mountains-perpendicular alluvial - braided river

  7. Nodular regenerative hyperplasia, portal vein thrombosis, and avascular hip necrosis due to hyperhomocysteinaemia

    OpenAIRE

    2005-01-01

    A male patient with portal hypertension, portal vein thrombosis, spontaneous splenorenal shunt formation, and encephalopathy, thought to have post-hepatitis B cirrhosis, is described. His condition deteriorated and necessitated liver transplantation. In the explant liver, nodular regenerative hyperplasia with pronounced vascular lesions both in portal venules and in arterioles was found instead of classical cirrhosis. Two years post-transplant he developed bilateral ischaemic femur head necro...

  8. Gemcitabine-Induced Extensive Skin Necrosis

    Directory of Open Access Journals (Sweden)

    Sara D'epiro

    2012-01-01

    Full Text Available An 82-year-old woman presented with oedema and extensive necrotic ulcerative lesions on the back side of her lower limbs, emerging after the second cycle of chemotherapy consisting of Gemcitabine for metastatic pancreatic cancer. The absence of any convincing argument in favor of cardiovascular or autoimmune disease led us to attribute the onset of skin necrosis to chemotherapy administration. Although skin ischemia has also been described as a paraneoplastic syndrome, in this case we could observe a temporal and causal relationship to Gemcitabine infusion. Recently, this drug has been associated with important vascular side effects; its vascular toxicity is in fact higher than previously estimated. To our knowledge, careful attention should be reserved to neoplastic patients candidated to Gemcitabine administration, especially if previously affected by arterial vascular disease, venous thromboembolism, or collagenoses.

  9. Determination of the elastic and stiffness characteristics of cross-laminated timber plates from flexural wave velocity measurements

    Science.gov (United States)

    Santoni, Andrea; Schoenwald, Stefan; Van Damme, Bart; Fausti, Patrizio

    2017-07-01

    Cross-laminated timber (CLT) is an engineered wood with good structural properties and it is also economically competitive with the traditional building construction materials. However, due to its low volume density combined with its high stiffness, it does not provide sufficient sound insulation, thus it is necessary to develop specific acoustic treatments in order to increase the noise reduction performance. The material's mechanical properties are required as input data to perform the vibro-acoustic analyses necessary during the design process. In this paper the elastic constants of a CLT plate are derived by fitting the real component of the experimental flexural wave velocity with Mindlin's dispersion relation for thick plates, neglecting the influence of the plate's size and boundary conditions. Furthermore, its apparent elastic and stiffness properties are derived from the same set of experimental data, for the plate considered to be thin. Under this latter assumption the orthotropic behaviour of an equivalent thin CLT plate is described by using an elliptic model and verified with experimental results.

  10. Impact strength and flexural properties enhancement of methacrylate silane treated oil palm mesocarp fiber reinforced biodegradable hybrid composites.

    Science.gov (United States)

    Eng, Chern Chiet; Ibrahim, Nor Azowa; Zainuddin, Norhazlin; Ariffin, Hidayah; Yunus, Wan Md Zin Wan

    2014-01-01

    Natural fiber as reinforcement filler in polymer composites is an attractive approach due to being fully biodegradable and cheap. However, incompatibility between hydrophilic natural fiber and hydrophobic polymer matrix restricts the application. The current studies focus on the effects of incorporation of silane treated OPMF into polylactic acid (PLA)/polycaprolactone (PCL)/nanoclay/OPMF hybrid composites. The composites were prepared by melt blending technique and characterize the composites with Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). FTIR spectra indicated that peak shifting occurs when silane treated OPMF was incorporated into hybrid composites. Based on mechanical properties results, incorporation of silane treated OPMF enhances the mechanical properties of unmodified OPMF hybrid composites with the enhancement of flexural and impact strength being 17.60% and 48.43%, respectively, at 10% fiber loading. TGA thermogram shows that incorporation of silane treated OPMF did not show increment in thermal properties of hybrid composites. SEM micrographs revealed that silane treated OPMF hybrid composites show good fiber/matrix adhesion as fiber is still embedded in the matrix and no cavity is present on the surface. Water absorption test shows that addition of less hydrophilic silane treated OPMF successfully reduces the water uptake of hybrid composites.

  11. The role of nonlinear torsional contributions on the stability of flexural-torsional oscillations of open-cross section beams

    Science.gov (United States)

    Di Egidio, Angelo; Contento, Alessandro; Vestroni, Fabrizio

    2015-12-01

    An open-cross section thin-walled beam model, already developed by the authors, has been conveniently simplified while maintaining the capacity of accounting for the significant nonlinear warping effects. For a technical range of geometrical and mechanical characteristics of the beam, the response is characterized by the torsional curvature prevailing over the flexural ones. A Galerkin discretization is performed by using a suitable expansion of displacements based on shape functions. The attention is focused on the dynamic response of the beam to a harmonic force, applied at the free end of the cantilever beam. The excitation is directed along the symmetry axis of the beam section. The stability of the one-component oscillations has been investigated using the analytical model, showing the importance of the internal resonances due to the nonlinear warping coupling terms. Comparison with the results provided by a computational finite element model has been performed. The good agreement among the results of the analytical and the computational models confirms the effectiveness of the simplified model of a nonlinear open-cross section thin-walled beam and overall the important role of the warping and of the torsional elongation in the study of the one-component dynamic oscillations and their stability.

  12. Impact Strength and Flexural Properties Enhancement of Methacrylate Silane Treated Oil Palm Mesocarp Fiber Reinforced Biodegradable Hybrid Composites

    Directory of Open Access Journals (Sweden)

    Chern Chiet Eng

    2014-01-01

    Full Text Available Natural fiber as reinforcement filler in polymer composites is an attractive approach due to being fully biodegradable and cheap. However, incompatibility between hydrophilic natural fiber and hydrophobic polymer matrix restricts the application. The current studies focus on the effects of incorporation of silane treated OPMF into polylactic acid (PLA/polycaprolactone (PCL/nanoclay/OPMF hybrid composites. The composites were prepared by melt blending technique and characterize the composites with Fourier transform infrared spectroscopy (FTIR, thermogravimetric analysis (TGA, and scanning electron microscopy (SEM. FTIR spectra indicated that peak shifting occurs when silane treated OPMF was incorporated into hybrid composites. Based on mechanical properties results, incorporation of silane treated OPMF enhances the mechanical properties of unmodified OPMF hybrid composites with the enhancement of flexural and impact strength being 17.60% and 48.43%, respectively, at 10% fiber loading. TGA thermogram shows that incorporation of silane treated OPMF did not show increment in thermal properties of hybrid composites. SEM micrographs revealed that silane treated OPMF hybrid composites show good fiber/matrix adhesion as fiber is still embedded in the matrix and no cavity is present on the surface. Water absorption test shows that addition of less hydrophilic silane treated OPMF successfully reduces the water uptake of hybrid composites.

  13. A comparison study on the flexural strength and compressive strength of four resin-modified luting glass ionomer cements.

    Science.gov (United States)

    Li, Yuan; Lin, Hong; Zheng, Gang; Zhang, Xuehui; Xu, Yongxiang

    2015-01-01

    The purpose of this study is to compare the differences in flexural strength and compressive strength between four resin-modified luting glass ionomer cements that are commonly used in clinics. Furthermore, this study investigates the influence of curing mode on the flexural strength and compressive strength of dual-cured resin-modified glass ionomer cements. Initially, flexural strength and compressive strength test specimens were prepared for RL, NR, GCP, and GCC. The RL group and NR group were cured by the light-curing mode and chemical-curing mode. Five specimens were prepared for each test group, and the flexural strength and compressive strength of each were measured. Data were analyzed by one-way ANOVA with SPSS 13.0. Furthermore, the fracture morphology of the flexural specimens was observed by SEM. The result of the mean flexural strength of each group is as follows: the NR light-cured group > NR chemically-cured group > GCP > RL light-cured group > GCC > RL chemically-cured group. More specifically, the flexural strength of the NR light-cured group ((42.903±4.242) MPa) is significantly higher (P NR chemically-cured group > NR light-cured group > GCC > RL light-cured group > RL chemically-cured group. Although the compressive strengths of the NR and GCP groups are higher than those of the GCC and RL groups, there are no significant differences (P>0.05) between NR and GCP, and no significant differences between GCC and RL. Furthermore, there are no significant differences (P>0.05) between the two curing modes on NR and RL. From the present study, it can be concluded that NR has superior flexural strength and compressive strength compared to the other three materials. Additionally, the curing mode can affect the flexural strength of dual-cured RMGIC because with the light-curing mode, the flexural strength is higher than with the chemical-curing mode. Therefore, light curing is an essential procedure when using dual-cured RMGIC in clinics.

  14. Necrosis: a specific form of programmed cell death?

    Science.gov (United States)

    Proskuryakov, Sergey Ya; Konoplyannikov, Anatoli G; Gabai, Vladimir L

    2003-02-01

    For a long time necrosis was considered as an alternative to programmed cell death, apoptosis. Indeed, necrosis has distinct morphological features and it is accompanied by rapid permeabilization of plasma membrane. However, recent data indicate that, in contrast to necrosis caused by very extreme conditions, there are many examples when this form of cell death may be a normal physiological and regulated (programmed) event. Various stimuli (e.g., cytokines, ischemia, heat, irradiation, pathogens) can cause both apoptosis and necrosis in the same cell population. Furthermore, signaling pathways, such as death receptors, kinase cascades, and mitochondria, participate in both processes, and by modulating these pathways, it is possible to switch between apoptosis and necrosis. Moreover, antiapoptotic mechanisms (e.g., Bcl-2/Bcl-x proteins, heat shock proteins) are equally effective in protection against apoptosis and necrosis. Therefore, necrosis, along with apoptosis, appears to be a specific form of execution phase of programmed cell death, and there are several examples of necrosis during embryogenesis, a normal tissue renewal, and immune response. However, the consequences of necrotic and apoptotic cell death for a whole organism are quite different. In the case of necrosis, cytosolic constituents that spill into extracellular space through damaged plasma membrane may provoke inflammatory response; during apoptosis these products are safely isolated by membranes and then are consumed by macrophages. The inflammatory response caused by necrosis, however, may have obvious adaptive significance (i.e., emergence of a strong immune response) under some pathological conditions (such as cancer and infection). On the other hand, disturbance of a fine balance between necrosis and apoptosis may be a key element in development of some diseases.

  15. Rin4 causes hybrid necrosis and race-specific resistance in an interspecific lettuce hybrid.

    Science.gov (United States)

    Jeuken, Marieke J W; Zhang, Ningwen W; McHale, Leah K; Pelgrom, Koen; den Boer, Erik; Lindhout, Pim; Michelmore, Richard W; Visser, Richard G F; Niks, Rients E

    2009-10-01

    Some inter- and intraspecific crosses may result in reduced viability or sterility in the offspring, often due to genetic incompatibilities resulting from interactions between two or more loci. Hybrid necrosis is a postzygotic genetic incompatibility that is phenotypically manifested as necrotic lesions on the plant. We observed hybrid necrosis in interspecific lettuce (Lactuca sativa and Lactuca saligna) hybrids that correlated with resistance to downy mildew. Segregation analysis revealed a specific allelic combination at two interacting loci to be responsible. The allelic interaction had two consequences: (1) a quantitative temperature-dependent autoimmunity reaction leading to necrotic lesions, lethality, and quantitative resistance to an otherwise virulent race of Bremia lactucae; and (2) a qualitative temperature-independent race-specific resistance to an avirulent race of B. lactucae. We demonstrated by transient expression and silencing experiments that one of the two interacting genes was Rin4. In Arabidopsis thaliana, RIN4 is known to interact with multiple R gene products, and their interactions result in hypersensitive resistance to Pseudomonas syringae. Site-directed mutation studies on the necrosis-eliciting allele of Rin4 in lettuce showed that three residues were critical for hybrid necrosis.

  16. MRI Brain Tumor Segmentation and Necrosis Detection Using Adaptive Sobolev Snakes

    Science.gov (United States)

    Nakhmani, Arie; Kikinis, Ron; Tannenbaum, Allen

    2014-01-01

    Brain tumor segmentation in brain MRI volumes is used in neurosurgical planning and illness staging. It is important to explore the tumor shape and necrosis regions at different points of time to evaluate the disease progression. We propose an algorithm for semi-automatic tumor segmentation and necrosis detection. Our algorithm consists of three parts: conversion of MRI volume to a probability space based on the on-line learned model, tumor probability density estimation, and adaptive segmentation in the probability space. We use manually selected acceptance and rejection classes on a single MRI slice to learn the background and foreground statistical models. Then, we propagate this model to all MRI slices to compute the most probable regions of the tumor. Anisotropic 3D diffusion is used to estimate the probability density. Finally, the estimated density is segmented by the Sobolev active contour (snake) algorithm to select smoothed regions of the maximum tumor probability. The segmentation approach is robust to noise and not very sensitive to the manual initialization in the volumes tested. Also, it is appropriate for low contrast imagery. The irregular necrosis regions are detected by using the outliers of the probability distribution inside the segmented region. The necrosis regions of small width are removed due to a high probability of noisy measurements. The MRI volume segmentation results obtained by our algorithm are very similar to expert manual segmentation. PMID:25302005

  17. Sex determination from the mandibular ramus flexure of Koreans by discrimination function analysis using three-dimensional mandible models.

    Science.gov (United States)

    Lin, Chenghe; Jiao, Benzheng; Liu, Shanshan; Guan, Feng; Chung, Nak-Eun; Han, Seung-Ho; Lee, U-Young

    2014-03-01

    It has been known that mandible ramus flexure is an important morphologic trait for sex determination. However, it will be unavailable when mandible is incomplete or fragmented. Therefore, the anthropometric analysis on incomplete or fragmented mandible becomes more important. The aim of this study is to investigate the sex-discriminant potential of mandible ramus flexure on the Korean three-dimensional (3D) mandible models with anthropometric analysis. The sample consists of 240 three dimensional mandibular models obtained from Korean population (M:F; 120:120, mean age 46.2 y), collected by The Catholic Institute for Applied Anatomy, The Catholic University of Korea. Anthropometric information about 11 metric was taken with Mimics, anthropometry libraries toolkit. These parameters were subjected to different discriminant function analyses using SPSS 17.0. Univariate analyses showed that the resubstitution accuracies for sex determination range from 50.4 to 77.1%. Mandibular flexure upper border (MFUB), maximum ramus vertical height (MRVH), and upper ramus vertical height (URVH) expressed the greatest dimorphism, 72.1 to 77.1%. Bivariate analyses indicated that the combination of MFUB and MRVH hold even higher resubstitution accuracy of 81.7%. Furthermore, the direct and stepwise discriminant analyses with the variables on the upper ramus above flexure could predict sex in 83.3 and 85.0%, respectively. When all variables of mandibular ramus flexure were input in stepwise discriminant analysis, the resubstitution accuracy arrived as high as 88.8%. Therefore, we concluded that the upper ramus above flexure hold the larger potentials than the mandibular ramus flexure itself to predict sexes, and that the equations in bivariate and multivariate analysis from our study will be helpful for sex determination on Korean population in forensic science and law.

  18. Effect of microwave postpolymerization treatment on residual monomer content and the flexural strength of autopolymerizing reline resin

    Directory of Open Access Journals (Sweden)

    Patil Padmakar

    2009-01-01

    Full Text Available Background : Microwave postpolymerization has been suggested as a method to improve the flexural strength of an autopolymerizing denture reline resin. However, the effect of microwave postpolymerization on the residual monomer content and its influence on flexural strength have not been investigated. Objectives : This study analyzed the effect of microwave postpolymerization on the residual monomer content and its influence on the flexural strength of an autopolymerizing reline resin (Denture Liner. Materials and Methods : A total of 70 specimens (64 Χ 10 Χ 3.3 mm were polymerized according to the manufacturer′s instructions and divided into 7 groups (n = 10. Control group specimens were not subjectedto any further processing. Before testing, the specimens were subjected to postpolymerization in a microwave oven using different power (550 and 650 W and time (3, 4, and 5 min settings. Two specimens of each group were then manually ground into fine powder and samples extracted from the specimens using reflux method. The samples were then subjected to gas chromatography for residual monomer determination in area%. Eight specimens were subjected to a three-point bending device with a span of 50 mm and crosshead speed of 5 mm/min, and the flexural strength was determined in MPa. Data analyses included Student′s t-test and one-way analysis of variance. Results : For the Denture Liner reline resin, the residual monomer content decreased and the flexural strength increased significantly with the application of microwave irradiation using different time/power combinations. The specimens with the lowest residual monomer content were the similar specimens which presented with the highest flexural strength. Conclusion : Microwave postpolymerization irradiation can be an effective method for increasing the flexural strength of denture liner (at 650 W for 5 min by reducing the residual monomer content by further polymerization at free radical sites.

  19. [Calcium polystyrene sulfonate induced colonic necrosis in patient with chronic kidney disease].

    Science.gov (United States)

    Lee, Sung Hoa; Kim, Sung Jung; Kim, Go Eun; Lee, Woo Jin; Hong, Won Ki; Baik, Gwang Ho; Choi, Young Hee; Kim, Dong Joon

    2010-04-01

    A 63-year-old woman was admitted due to right upper quadrant abdominal pain. She was going through hemodialysis due to end stage renal disease and taking calcium polystyrene sulfonate orally and rectally due to hyperkalemia. Colonoscopy showed a circular ulcerative mass on the proximal ascending colon. Biopsy specimen from the mass showed inflammation and necrotic debris. It also revealed basophilic angulated crystals which were adherent to the ulcer bed and normal mucosa. These crystals were morphologically consistent with calcium polystyrene sulfonate. She was diagnosed with calcium polystyrene phosphate induced colonic necrosis and improved with conservative treatment.

  20. Black esophagus (acute esophageal necrosis) after spinal anesthesia.

    Science.gov (United States)

    Román Fernández, A; López Álvarez, A; Fossati Puertas, S; Areán González, I; Varela García, O; Viaño López, P M

    2014-01-01

    Acute esophagic necrosis or black esophagus is an uncommon clinical entity that owes its name to the endoscopic view of the necrotic esophageal mucosa. It is always related with a critical medical condition and usually has an ischemic etiology. We report the first case of acute esophageal necrosis after a spinal anesthetic for partial hip joint arthroplasty. We discuss the underlying pathophysiological mechanisms.

  1. Lymphoma associated bone marrow necrosis with raised anticardiolipin antibody.

    Science.gov (United States)

    Murphy, P T; Sivakumaran, M; Casey, M C; Liddicoat, A; Wood, J K

    1998-05-01

    A case of high grade B cell lymphoma presented with bone marrow necrosis, followed by development of extensive marrow fibrosis, the evolution of which was documented by serial magnetic resonance imaging and bone marrow trephine histology. A markedly raised anticardiolipin antibody titre at diagnosis suggests that lymphoma associated antiphospholipid syndrome may have contributed to the aetiology of the bone marrow necrosis.

  2. [Cortisone-induced humerus head necrosis in acute myeloid leukemia: cartilage-preserving arthroscopic spongioplasty].

    Science.gov (United States)

    Heid, A; Dickschas, J; Schoeffl, V

    2013-02-01

    Osteonecrosis is a long known side effect in patients receiving cortisone or chemotherapy. A young patient was diagnosed with acute myeloid leukemia (AML) in 2005. After receiving combined cortisone and chemotherapy the patient was in complete remission. In 2007 a total hip replacement was necessary due to femoral head necrosis. Years after the joint replacement the patient reported acute shoulder pain without trauma. In this article an alternative procedure to an endoprothesis in a young patient with a humeral head osteonecrosis is presented.

  3. The role of surgery in a case of diffuse mucormycosis with haematemesis and gastric necrosis

    OpenAIRE

    Bini, R.; Addeo, A; Maganuco, L; Fontana, D; Viora, T.; Leli, R.

    2014-01-01

    Mucormycosis is a life threatening condition caused by invasion of fungi of the order Mucorales. Gastrointestinal invasion is very rare and often lethal, particularly in disseminated mucormycosis. We present the case of a 26-year-old woman from North Africa with type 2 diabetes who, after a cholecystectomy, developed unexplained septic shock and haematemesis due to gastric necrosis. Computed tomography (CT) revealed a disseminated fungal invasion of the lungs, kidney and paranasal sinuses. A ...

  4. Therapeutic approaches for tumor necrosis factor inhibition

    Directory of Open Access Journals (Sweden)

    Maria Letícia de Castro Barbosa

    2011-09-01

    Full Text Available Tumor necrosis factor (TNF consists of an inflammatory cytokine essential for homeostasis and organism defense. Despite its physiological relevance, both increased biosynthesis and release of TNF lead to the exacerbation of inflammatory and oxidative responses, which are related to the pathogenesis of a host of diseases of an inflammatory, autoimmune and/or infectious nature. In this context, effective therapeutic approaches for the modulation of TNF have been the focus of research efforts. Approximately one million individuals worldwide have been treated with biotechnological inhibitors of this cytokine, the so-called anti-TNF biopharmaceuticals. However, given the high risk of infection and the limitations related to cost and administration routes, new therapeutic approaches aimed at biological targets that directly or indirectly modulate the production and/or activation of TNF appear promising alternatives for the discovery of new anti-inflammatory and immunomodulatory orally active drugs and are therefore discussed in this paper.O fator de necrose tumoral (do inglês, tumor necrosis factor - TNF consiste em uma citocina inflamatória essencial para a homeostase e defesa do organismo. A despeito de sua relevância fisiológica, o aumento da biossíntese e liberação do TNF conduzem à exacerbação das respostas inflamatória e oxidativa, as quais estão relacionadas à patogênese de várias doenças de natureza inflamatória, auto-imune e/ou infecciosa. A busca por abordagens terapêuticas eficientes na modulação do TNF tem sido alvo de diversos esforços de pesquisa. Aproximadamente um milhão de pessoas ao redor do mundo já foi tratado com inibidores biotecnológicos desta citocina, os chamados biofármacos anti-TNF. Entretanto, em face ao elevado risco de infecções e as limitações relacionadas ao custo e a via de administração, novas abordagens terapêuticas com foco em alvos que modulem, de forma direta ou indireta, a produ

  5. Weibull analysis and flexural strength of hot-pressed core and veneered ceramic structures.

    Science.gov (United States)

    Bona, Alvaro Della; Anusavice, Kenneth J; DeHoff, Paul H

    2003-11-01

    To test the hypothesis that the Weibull moduli of single- and multilayer ceramics are controlled primarily by the structural reliability of the core ceramic.Methods. Seven groups of 20 bar specimens (25 x 4 x 1.2 mm) were made from the following materials: (1) IPS Empress--a hot-pressed (HP) leucite-based core ceramic; (2) IPS Empress2--a HP lithia-based core ceramic; (3 and 7) Evision--a HP lithia-based core ceramic (ES); (4) IPS Empress2 body--a glass veneer; (5) ES (1.1 mm thick) plus a glaze layer (0.1 mm); and (6) ES (0.8 mm thick) plus veneer (0.3 mm) and glaze (0.1 mm). Each specimen was subjected to four-point flexure loading at a cross-head speed of 0.5 mm/min while immersed in distilled water at 37 degrees C, except for Group 7 that was tested in a dry environment. Failure loads were recorded and the fracture surfaces were examined using SEM. ANOVA and Duncan's multiple range test were used for statistical analysis. No significant differences were found between the mean flexural strength values of Groups 2, 3, 5, and 6 or between Groups 1 and 4 (p>0.05). However, significant differences were found for dry (Group 7) and wet (Groups 1-6) conditions. Glazing had no significant effect on the flexural strength or Weibull modulus. The strength and Weibull modulus of the ES ceramic were similar to those of Groups 5 and 6. The structural reliability of veneered core ceramic is controlled primarily by that of the core ceramic.

  6. Stress optimization of leaf-spring crossed flexure pivots for an active Gurney flap mechanism

    Science.gov (United States)

    Freire Gómez, Jon; Booker, Julian D.; Mellor, Phil H.

    2015-04-01

    The EU's Green Rotorcraft programme is pursuing the development of a functional and airworthy Active Gurney Flap (AGF) for a full-scale helicopter rotor blade. Interest in the development of this `smart adaptive rotor blade' technology lies in its potential to provide a number of aerodynamic benefits, which would in turn translate into a reduction in fuel consumption and noise levels. The AGF mechanism selected employs leaf-spring crossed flexure pivots. These provide important advantages over bearings as they are not susceptible to seizing and do not require maintenance (i.e. lubrication or cleaning). A baseline design of this mechanism was successfully tested both in a fatigue rig and in a 2D wind tunnel environment at flight-representative deployment schedules. For full validation, a flight test would also be required. However, the severity of the in-flight loading conditions would likely compromise the mechanical integrity of the pivots' leaf-springs in their current form. This paper investigates the scope for stress reduction through three-dimensional shape optimization of the leaf-springs of a generic crossed flexure pivot. To this end, a procedure combining a linear strain energy formulation, a parametric leaf-spring profile definition and a series of optimization algorithms is employed. The resulting optimized leaf-springs are proven to be not only independent of the angular rotation at which the pivot operates, but also linearly scalable to leaf-springs of any length, minimum thickness and width. Validated using non-linear finite element analysis, the results show very significant stress reductions relative to pivots with constant cross section leaf-springs, of up to as much as 30% for the specific pivot configuration employed in the AGF mechanism. It is concluded that shape optimization offers great potential for reducing stress in crossed flexure pivots and, consequently, for extending their fatigue life and/or rotational range.

  7. Flexural anisotropy in the continental lithosphere: How robust are our estimates?

    Science.gov (United States)

    Kalnins, Lara; Simons, Frederik; Kirby, Jon; Wang, Dong; Olhede, Sofia

    2015-04-01

    In addition to considering the magnitude and lateral variation of the long-term strength of the lithosphere, we must also consider its directional variation, its anisotropy. Many geological materials and processes are themselves anisotropic; this might lead to a natural expectation of widespread anisotropy in lithosphere strength, which both modulates and is modulated by many key tectonic processes. Cratons, with their long, complex geological histories, and orogenic belts, the result of extremely anisotropy processes, might seem especially likely to show anisotropy in their flexural rigidity. The observed coherence between gravity and topography remains the most popular metric for the analysis of flexural rigidity, and, indeed, it is frequently anisotropic. However, does this correspond to anisotropy in the actual mechanical strength of the lithosphere? Using coherence, we should only reject the null hypothesis of isotropy when there is significant anisotropy in both the observed coherence and the resulting flexural strength. In addition, the anisotropy should not arise purely from marginal (in the statistical sense) anisotropy in the topography and gravity data themselves. We use wholly isotropic synthetic models to test two common methods for estimating coherence, multitapers and wavelets, and find widespread spurious anisotropy using both methods. Using a series of statistical and geophysical tests developed to identify and remove such spurious directionality, our global reanalysis shows sparse evidence for meaningful anisotropy in the mechanical strength of the lithosphere. Although the geological argument for anisotropy in these regions and its role in tectonic cycles remains highly plausible, this anisotropy has not yet been convincingly verified by any cross-spectral method.

  8. Molecular Mechanism of Apoptosis and Necrosis

    Directory of Open Access Journals (Sweden)

    Gulfidan Coskun

    2011-06-01

    Full Text Available Organismal homeostasis depends on an intricate balance between cell death and renewal. Apoptosis is a process of programmed cell death that plays a critical role in some normal and pathologic conditions beginning from embryologic development and ends at death. Apoptosis is initiated by morphological changes at the cell membrane, surface organels and nucleus. Apoptosis starts with death signals coming from outside or inside of the cell and continue to activate the mechanisms of apoptosis via cell death receptor or mitochondrial pathways. During apoptosis a group proteases are activated which cause DNA fragmentation, cytoplasmic shrinkage and membrane blebbing. Apoptotic cells divide into apoptotic bodies and then these apoptotic bodies are removed from tissue by phagocytes and adjacent cells In contrast to the “programmed” nature of apoptosis, necrotic cell death has always been believed to be a random, uncontrolled process that leads to death of the cell. Also necrosis, which is an other type of cell death, came to be used to describe pathologic cell death which cause inflamation. [Archives Medical Review Journal 2011; 20(3.000: 145-158

  9. DUAL RECIPROCITY BOUNDARY ELEMENT METHOD FOR FLEXURAL WAVES IN THIN PLATE WITH CUTOUT

    Institute of Scientific and Technical Information of China (English)

    GAO Suo-wen; WANG Yue-sheng; ZHANG Zi-mao; MA Xing-rui

    2005-01-01

    The theoretical analysis and numerical calculation of scattering of elastic waves and dynamic stress concentrations in the thin plate with the cutout was studied using dual reciprocity boundary element method (DRM). Based on the work equivalent law, the dual reciprocity boundary integral equations for flexural waves in the thin plate were established using static fundamental solution. As illustration, numerical results for the dynamic stress concentration factors in the thin plate with a circular hole are given.The results obtained demonstrate good agreement with other reported results and show high accuracy.

  10. Moho depth derived from gravity and magnetic data in the Southern Atlas Flexure (Algeria)

    Science.gov (United States)

    Meliani, O.; Bourmatte, A.; Hamoudi, M.; Haddoum, H.; Quesnel, Y.

    2016-09-01

    Existing aeromagnetic and gravity data were used to study the structure of the Southern Atlas Flexure (SAF) in Algeria. Forward and inverse numerical modelings were applied, giving access to the depth of the Moho and the Curie depth in this area. Our results suggest a maximum crustal thickness of about 48 km, and a Curie depth of about 20 km. We then discuss the implications of those results on the regional structure of the SAF, also using cross-sections built using 2D-geological modeling.

  11. Extensional and Flexural Waves in a Thin-Walled Graphite/Epoxy Tube

    Science.gov (United States)

    Prosser, William H.; Gorman, Michael R.; Dorighi, John

    1992-01-01

    Simulated acoustic emission signals were induced in a thin-walled graphite/epoxy tube by means of lead breaks (Hsu-Neilsen source). The tube is of similar material and layup to be used by NASA in fabricating the struts of Space Station Freedom. The resulting waveforms were detected by broad band ultrasonic transducers and digitized. Measurements of the velocities of the extensional and flexural modes were made for propagation directions along the tube axis (0 degrees), around the tube circumference (90 degrees) and at an angle of 45 degrees. These velocities were found to be in agreement with classical plate theory.

  12. Effect of different housing retaining materials on the flexural strength of an acrylic resin overdenture base.

    Science.gov (United States)

    Ozkir, Serhat Emre; Yilmaz, Burak

    2017-04-03

    An attachment housing inside an overdenture may weaken the acrylic resin base. The type of housing retaining material may affect the strength of the housing retaining material-acrylic resin base assembly. The effect of different housing retaining materials on the strength of acrylic resin base is unknown. The purpose of this in vitro study was to evaluate the effects of different materials used to retain the housing on the flexural strength of a poly(methyl methacrylate) (PMMA) resin base. Sixty PMMA specimens (64×10×4 mm) were prepared with a clearance inside to allow the insertion of overdenture housings. Five different materials were used for housing orientation: an autopolymerizing composite resin, an acrylic resin reline material, a heat-polymerized PMMA, an autopolymerizing PMMA (n=10), and a control group (n=10) were prepared without any preparation or housing. The specimens were thermocycled 5000 times between 5°C and 55°C. The flexural strength data were analyzed by an analysis of variance using the maximum likelihood estimation method to eliminate the needs for normality within the groups and for equality of variances between the groups. If statistically significant, resolution of the significance factor was obtained by pairwise comparisons using the Tukey adjustment (α=.05). The fracture values were statistically significantly higher (Pmaterial (26.78 ±6.72 MPa), the acrylic resin reline material (16.94 ±4.38 MPa), the Ufigel (16.07 ±3.40 MPa), and the autopolymerizing composite resin (19.37 ±3.13 MPa). Heat- and autopolymerizing PMMA groups were significantly different from acrylic resin-based hard reline materials (Pmaterial except for one of the hard reline groups, which separated from the PMMA. The tested retaining materials significantly reduced the flexural strength of PMMA denture base. The flexural strength of the resin base with housing was significantly higher when PMMA-based retaining materials were used than when acrylic resin

  13. Woven Hybrid Composites - Tensile and Flexural Properties of Jute Mat Fibres with Epoxy Composites

    Science.gov (United States)

    Gopal, P.; Bupesh Raja, V. K.; Chandrasekaran, M.; Dhanasekaran, C.

    2017-03-01

    The jute mat fibers are fabricated with several layers of fiber with opposite orientation in addition with coconut shell powder and resins. In current trends, metallic components are replaced by natural fibers because of the inherent properties such as light in weight, easy to fabricate, less cost and easy availability. This material has high strength and withstands the load. In this investigation the plates are made without stitching the fiber. The result of tensile strength and flexural strength are compared with nano material (coconut shell powder).

  14. Lithospheric flexure and sedimentary basin evolution: depositional cycles in the steer's head model

    Science.gov (United States)

    Moore, James; Watts, Tony

    2016-04-01

    Backstripping studies of biostratigraphic data from deep wells show that sediment loading is one of the main factors controlling the subsidence and uplift history of sedimentary basins. Previous studies based on single layer models of elastic and viscoelastic plates overlying an inviscid fluid have shown that sediment loading, together with a tectonic subsidence that decreases exponentially with time, can explain the large-scale 'architecture' of rift-type basins and, in some cases, details of their internal stratigraphy such as onlap and offlap patterns. One problem with these so-called 'steer's head' models is that they were based on a simple rheological model in which the long-term strength of the lithosphere increased with thermal age. Recent oceanic flexure studies, however, reveal that the long-term strength of the lithosphere depends not only on thermal age, but also load age. We have used the thermal structure based on plate cooling models, together with recent experimentally-derived flow laws, to compute the viscosity structure of the lithosphere and a new analytical model to compute the flexure of a multilayer viscoelastic plate by a trapezoid-shaped sediment load at different times since basin initiation. The combination of basin subsidence and viscoelastic flexural response results in the fluctuation of the depositional surface with time. If we define the nondimensional number Dw= τm/τt, where τm is the Maxwell time constant and τt is the thermal time constant, we find that for Dw>1 the flexure approximates that of a viscoelastic plate and is dominated by "offlapping" stratigraphy, with the basin edges evolving through shallow marine facies; though erosion late in the basin formation prevents much of this from being recorded in the stratigraphy. Interestingly Dw~1 produces a basin in which onlap dominates its early evolution while offlap dominates its later evolution with an unconformity separating the two different stratal patterns. This case lends

  15. Finite Element Calculation of the Flexural Stiffness of Corroded RC Eccentric Compressive Members

    Institute of Scientific and Technical Information of China (English)

    ZHANG Hua; WEI Jun; PAN Qiao; HUANG Ying

    2010-01-01

    A finite element calculation model of corroded RC eccentric compressive members was build using finite element software ANSYS. The model considers the decline of mechanical properties and the effective section of a corroded steel bar, as well as the deterioration of bond character between corroded reinforcement and concrete. The reliability of the finite element model was evaluated by comparing the results of the finite element calculation with the data from experiments. Based on the finite element analysis results, the influence of corrosion degree, the diameter change of the longitudinal reinforcing bars and the spacing change of stirrups on the flexural stiffness were calculated and analyzed.

  16. Experimental Investigation on Flexural Performance of Masonry Walls Reinforced with GFRP

    Institute of Scientific and Technical Information of China (English)

    LIU Jifu; LIU Ming; SONG Yupu

    2007-01-01

    This paper presents the results of a test program for flexure reinforcing characteristics of gless fiber-rein forced polymer(GFRP) sheets bonded to masonry beams. A total of eight specimens subjected to monotonic four-point bending were tested up to failure. These specimens were constructed with two different bond patterns. Six of these specimens were reinforced by using GFRP sheets prior to testing, and the remaining two were not reinforced. The test results indicate a significant increase in both load-bearing capacity and ductile performance of the reinforced walls over the unreinforced ones.

  17. Stroboscopic interferometry for characterization and improvement of flexural plate-wave transducers

    Science.gov (United States)

    Rembe, Christian; Caton, Pamela; White, Richard M.; Muller, Richard S.

    2001-10-01

    We describe an improved stroboscopic interferometer system making possible static-deformation measurements of MEMS structures as well as motion measurements at frequencies up to 1MHz. The time resolution of the system is determined by the width of the strobed laser pulse. To demonstrate high-frequency measurement capabilities, we investigate acoustic waves on a flexural plate-wave micropump developed at the Berkeley Sensor & Actuator Center. We also characterize the micropump with a commercial micro scanning vibrometer (Polytec). The results are compared and different features of the two systems are discussed.

  18. Biaxial Flexural Strength and Estimation of Size on the Strength Properties of FRP Composites

    Directory of Open Access Journals (Sweden)

    M. N. Saraf

    1990-04-01

    Full Text Available Fibre reinforced plastics (FRP are widely used as structural materials. For designing structural components, a designer is provided with data based on unidirectional testing. But in real structural applications the component is subjected to multiaxial stress throughout the material. Hence a multiaxial test is a better gauge of the behaviour of FRP components in service. In the present paper a ring-on-ring method was adopted which produces biaxial flexural stress on the FRP specimen. Wubull's statistical weakest link theory was applied to standardize the complexity and to assess the reliability of the results.

  19. FLEXURAL VIBRATIONS BAND GAPS IN PERIODIC BEAMS INCLUDING ROTARY INERTIA AND SHEAR DEFORMATION EFFECTS

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    With the idea of the phononic crystals, the beams with periodic structure are designed.Flexural vibration through such periodic beams composed of two kinds of materials is studied. The emphasis is laid on the effects of rotary inertia and shear deformation. Based on the vibration equation, plane wave expansion method is provided. The acceleration frequency responses of such beams with finite structure are simulated by the finite element method. The frequency ranges of sharp drops in the calculated acceleration frequency response curves are in good agreement with those in the band structures. The findings will be significant in the application of the periodic beams.

  20. Skull Flexure from Blast Waves: A Mechanism for Brain Injury with Implications for Helmet Design

    Energy Technology Data Exchange (ETDEWEB)

    Moss, W C; King, M J; Blackman, E G

    2009-04-30

    Traumatic brain injury [TBI] has become a signature injury of current military conflicts, with debilitating, costly, and long-lasting effects. Although mechanisms by which head impacts cause TBI have been well-researched, the mechanisms by which blasts cause TBI are not understood. From numerical hydrodynamic simulations, we have discovered that non-lethal blasts can induce sufficient skull flexure to generate potentially damaging loads in the brain, even without a head impact. The possibility that this mechanism may contribute to TBI has implications for injury diagnosis and armor design.

  1. Generation, Diffraction and Radiation of Subsonic Flexural Waves on Membranes and Plates: Observations of Structural and Acoustical Wavefields.

    Science.gov (United States)

    Matula, Thomas John

    Electromagnetic acoustic wave transducers (EMATs) are described for generating low-frequency tone bursts on metalized membranes in air and elastic plates in water. Bursts on the membrane have phase velocities much less than the speed of sound in the surrounding air and are accompanied by plane evanescent waves. The frequency and time-domain responses of the EMAT and the dependence on gap spacing between the coupling coil and the membrane were studied. Wave -number selective optical and capacitive probes were used to measure the wave properties. Versions of these transducers are insensitive to long wavelength motion of the membrane. Diffraction of the burst by a sharp edge in air was observed as a function of the gap between the membrane and a razor edge. The scattered pressure decreases exponentially with increasing gap as expected from an approximate analysis of edge diffraction of evanescent waves. In related work an EMAT is used to generate 28 kHz tone bursts of bending waves on an aluminum plate. The bursts propagate down into water where the surrounding wavefield is probed. Observations described indicate that there occurs a branching of energy as the wave crosses the air-water interface. Radiation from subsonic flexural plate waves due to the discontinuity in fluid -loading is observed. It is partially analogous to the transition radiation of fast charged particles crossing a dielectric interface. The angular radiation pattern resembles that of a line quadrupole. Near the interface there exists an interference between the two energy branches in water that produces a series of pressure nulls. The pressure nulls are associated with a pi phase change in the wavefield and are indicators of wavefront dislocations. A computation of the wavefield in an unbounded fluid due to a line-moment excitation of a plate is comparable with the null pattern observed but differs in certain details.

  2. Necrosis, a regulated mechanism of cell death La necrosis, un mecanismo regulado de muerte celular

    Directory of Open Access Journals (Sweden)

    Mauricio Rojas López

    2010-05-01

    Full Text Available

    Three types of cellular death have been defined by morphological and biochemical criteria: apoptosis, necrosis and autophagy. Apoptosis is a regulated cell death, mainly mediated by caspases; autophagy induces degradation of intracellular damaged organelles through the formation of vesicles that fuse with hydrolytic vacuoles.

     

    Necrosis has been traditionally defined by the rupture the cytoplasmic membrane with subsequent release of intracellular material, triggering localized inflammatory Intrinsic cellular activities and the events preceding cellular collapse are critical to determine the type of tissue damage.

     

    The fact that all three types of cellular death can coexist in any organ and tissue with different availabilities of ATP, suggests that necrosis can be conceived as an active event and that to some extent it may be regulated. Alterations in the structure of proteins and in the

  3. Flexural and bond strengths of relined denture polymers assessed by four-point bending tests and Weibull analysis.

    Science.gov (United States)

    Polyzois, Gregory L; Lagouvardos, Panagiotis E; Frangou, Maria J

    2012-06-01

    The aim of this study was to (1) investigate the flexural strengths of three denture resins i.e. heat, photopolymerised and microwaved and how it was affected by relining with auto- and visible light-polymerised hard reliners, (2) investigate the bond strengths between denture resins and hard reliners and (3) interpret the results of both tests by utilising Weibull analysis. Specimens (65 × 10 × 2.5 mm) from denture resins, relined and bonded combinations were tested using a four-point bending test in a universal testing machine and a crosshead speed of 5 mm/min. Ten specimens for each bulk resin and denture resin-reliner combination for a total of 150 were tested. Statistical analysis indicated significant differences between bulk materials (p < 0.001) and between reliners (p < 0.001) for flexural and bond strength tests. was concluded that (1) the four-point flexural strength was different between the denture base materials, (2) flexure strength between bulk and relined or between relined with autopolymerised and photopolymerised bases was different, (3) flexural strength among relined denture bases was different and (4) bond strengths among relined denture bases were different. © 2011 The Gerodontology Society and John Wiley & Sons A/S.

  4. Reinforcement of Aluminum Oxide Filler on the Flexural Strength of Different Types of Denture Base Resins: An In vitro Study.

    Science.gov (United States)

    Dhole, Rohit I; Srivatsa, G; Shetty, Rohit; Huddar, Dayanand; Sankeshwari, Banashree; Chopade, Swapnil

    2017-04-01

    Acrylic resins have been used extensively for the fabrication of denture bases because of their aesthetic qualities, ease of manipulation and repairability. Flexural fatigue of the denture base has been shown to be a factor in the clinical failure of polymethyl methacrylate resin dentures. Also, the fracture can result from impact, fatigue or degradation of the base material. Hence, there is a need to increase the strength of denture base resins. To evaluate the effect of reinforcing alumina oxide filler on the flexural strength of different acrylic resins. A total of 180 acrylic specimens were fabricated, which were divided into three groups self cure acrylic resin (SC), conventional heat cure resin (HC) and high strength heat cure resin (HI). Each group was divided into four subgroups i.e., control group and the specimens of the remaining three groups were reinforced with aluminum oxide (Al2O3) powder by 5%, 10% and 15% by weight. Specimens were stored in distilled water for one week; flexural strength was tested by universal testing machine. Results were analysed by one-way analysis of variance and post-hoc Tukey paired group comparison tests. Flexural strength of SC increased by 9%, 13% and 19%, Flexural strength of HC increased by 8%, 15% and 19% and that of HI increased by 21%, 26% and 29% compared to control group by adding 5%,10% and 15% of alumina filler (p-value lead to more clinical success.

  5. Multi-objective optimization of flexure hinge mechanism considering thermal–mechanical coupling deformation and natural frequency

    Directory of Open Access Journals (Sweden)

    Lufan Zhang

    2017-01-01

    Full Text Available Flexure hinge mechanism plays a key part in realization of terminal nano-positioning. The performance of flexure hinge mechanism is determined by its positioning design. Based on the actual working conditions, its finite element model is built and calculated in ANSYS. Moreover, change trends of deformation and natural frequency with positioning design parameters are revealed. And sensitivity analysis is performed for exploration response to these parameters. These parameters are used to build four objective functions. To solve it conveniently, the multi-objective optimization problem is transferred to the form of single-objective function with constraints. An optimal mechanism is obtained by an optimization method combining ANSYS with MATLAB. Finite element numerical simulation has been carried out to demonstrate the superiority of the optimal flexure hinge mechanism, and the superiority can be further verified by experiment. Measurements and tests have been conducted at varying accelerations, velocities, and displacements, to quantify and characterize the amount of acceleration responses obtained from flexure hinge mechanism before and after optimization. Both time- and frequency-domain analyses of experimental data show that the optimal flexure hinge mechanism has superior effectiveness. It will provide a basic for realizing high acceleration and high precision positioning of macro–micro motion platform.

  6. Genetic ablation of soluble tumor necrosis factor with preservation of membrane tumor necrosis factor is associated with neuroprotection after focal cerebral ischemia

    DEFF Research Database (Denmark)

    Madsen, Pernille M; Clausen, Bettina H; Degn, Matilda;

    2016-01-01

    Microglia respond to focal cerebral ischemia by increasing their production of the neuromodulatory cytokine tumor necrosis factor, which exists both as membrane-anchored tumor necrosis factor and as cleaved soluble tumor necrosis factor forms. We previously demonstrated that tumor necrosis factor...

  7. [Torsion and necrosis of epiploic appendices of the large bowel].

    Science.gov (United States)

    Timofeev, M E; Fedorov, E D; Krechetova, A P; Shapoval'iants, S G

    2014-01-01

    The features of the clinical symptoms was studied, the possibility of laparoscopy in modern diagnosis and treatment of epiploic appendices torsion and necrosis of the large bowel was assessed in the article. It was done the retrospective analysis of the medical records of 87 patients with a diagnosis of epiploic appendices torsion and necrosis of the large bowel. The patients had laparoscopic operations in our hospital in the period from January 1995 to December 2012. The clinical picture, laboratory and instrumental datas in cases of epiploic appendices torsion and necrosis were scarce and nonspecific. An abdominal pain preferentially localized in the lower divisions was the main symptom (97.7%). The instrumental methods did not allow to diagnose the torsion and necrosis of epiploic appendices in the majority of cases and all these techniques were used for the differential diagnosis with other diseases. The assumption of the presence of appendices torsion and necrosis occured just in 34.5% of cases before the operation. Diagnosis of epiploic appendices torsion and necrosis present significant difficulties on prehospital and preoperative stages. The diagnostic laparoscopy is the method of choice in unclear situations and it allows to diagnose the torsion and necrosis of epiploic appendices in 96.6% of cases. Successful surgical treatment by using laparoscopic approach is possible in 90.8% of cases.

  8. Tumor necrosis factor interaction with gold nanoparticles

    Science.gov (United States)

    Tsai, De-Hao; Elzey, Sherrie; Delrio, Frank W.; Keene, Athena M.; Tyner, Katherine M.; Clogston, Jeffrey D.; Maccuspie, Robert I.; Guha, Suvajyoti; Zachariah, Michael R.; Hackley, Vincent A.

    2012-05-01

    We report on a systematic investigation of molecular conjugation of tumor necrosis factor-α (TNF) protein onto gold nanoparticles (AuNPs) and the subsequent binding behavior to its antibody (anti-TNF). We employ a combination of physical and spectroscopic characterization methods, including electrospray-differential mobility analysis, dynamic light scattering, polyacrylamide gel electrophoresis, attenuated total reflectance-Fourier transform infrared spectroscopy, fluorescence assay, and enzyme-linked immunosorbent assay. The native TNF used in this study exists in the active homotrimer configuration prior to conjugation. After binding to AuNPs, the maximum surface density of TNF is (0.09 +/- 0.02) nm-2 with a binding constant of 3 × 106 (mol L-1)-1. Dodecyl sulfate ions induce desorption of monomeric TNF from the AuNP surface, indicating a relatively weak intermolecular binding within the AuNP-bound TNF trimers. Anti-TNF binds to both TNF-conjugated and citrate-stabilized AuNPs, showing that non-specific binding is significant. Based on the number of anti-TNF molecules adsorbed, a substantially higher binding affinity was observed for the TNF-conjugated surface. The inclusion of thiolated polyethylene glycol (SH-PEG) on the AuNPs inhibits the binding of anti-TNF, and the amount of inhibition is related to the number ratio of surface bound SH-PEG to TNF and the way in which the ligands are introduced. This study highlights the challenges in quantitatively characterizing complex hybrid nanoscale conjugates, and provides insight on TNF-AuNP formation and activity.We report on a systematic investigation of molecular conjugation of tumor necrosis factor-α (TNF) protein onto gold nanoparticles (AuNPs) and the subsequent binding behavior to its antibody (anti-TNF). We employ a combination of physical and spectroscopic characterization methods, including electrospray-differential mobility analysis, dynamic light scattering, polyacrylamide gel electrophoresis

  9. Metabolic epidermal necrosis-hepatocutaneous syndrome.

    Science.gov (United States)

    Byrne, K P

    1999-11-01

    It is clear that cutaneous lesions of metabolic epidermal necrosis in the dog can occur either with a demonstrable glucagon-secreting tumor or with hepatic disease without any detectable glucagonoma. Additional clinical case reports of the disease in cats are needed to better characterize the disease in this species. The lesions of NME-MEN may not represent a specific physiological mechanism of cutaneous disease but instead a pathophysiological process that can be triggered by several systemic metabolic abnormalities. The fact that NME is observed in association with a variety of conditions supports the theory that an overall metabolic derangement results in the rash. The prognosis for canine MEN is poor; however, some affected dogs have been maintained for many months with dietary management. High-quality protein diets such as Hill's Prescription Diet a/d (Hill's Pet Products) or other "recovery" diets may be helpful. Zinc and essential fatty acid supplementation may help some patients. Dietary supplementation with cooked egg yolks may be helpful. It is prudent to avoid corticosteroids in these cases, as development of diabetes mellitus worsens the prognosis. Histopathological examination of the pancreas coupled with determination of plasma glucagon may help define the characteristics of GS versus HS in dogs. It is possible that some dogs diagnosed with MEN-HS may have an undetected pancreatic tumor. Although the hepatic ultrasound findings in dogs with MEN-HS are becoming well characterized, it is possible for dogs with pancreatic neuroendocrine tumors to also have abnormal hepatic ultrasonography. As the presence of MEN and hepatic disease does not necessarily rule out the presence of a pancreatic tumor, prospective studies correlating plasma glucagon levels with pancreatic histopathology in cases of MEN-GS versus MEN-HS seem warranted.

  10. Data characterizing flexural properties of Al/Al2O3 syntactic foam core metal matrix sandwich

    Directory of Open Access Journals (Sweden)

    Mohammed Yaseer Omar

    2015-12-01

    Full Text Available Microstructural observations and flexural property datasets are provided for aluminum alloy matrix syntactic foam core sandwich composites. The tests are conducted in three-point bending configuration. The data supplied includes methods used for conducting microscopy and mechanical testing. Raw load–displacement data, which is used to plot stress–strain graphs, obtained during the flexural test is also included. Images from a DSLR camera are stitched together to form a detailed failure sequencing video. Failure of specimens is captured in sequential images using a digital camera. These images are stitched together to develop a video for visualization of failure mechanisms. Calculations are also included for a theoretical model that is used to estimate the flexural properties of the syntactic foam core sandwich.

  11. Maximum-likelihood estimation of lithospheric flexural rigidity, initial-loading fraction, and load correlation, under isotropy

    CERN Document Server

    Simons, Frederik J

    2012-01-01

    Topography and gravity are geophysical fields whose joint statistical structure derives from interface-loading processes modulated by the underlying mechanics of isostatic and flexural compensation in the shallow lithosphere. Under this dual statistical-mechanistic viewpoint an estimation problem can be formulated where the knowns are topography and gravity and the principal unknown the elastic flexural rigidity of the lithosphere. In the guise of an equivalent "effective elastic thickness", this important, geographically varying, structural parameter has been the subject of many interpretative studies, but precisely how well it is known or how best it can be found from the data, abundant nonetheless, has remained contentious and unresolved throughout the last few decades of dedicated study. The popular methods whereby admittance or coherence, both spectral measures of the relation between gravity and topography, are inverted for the flexural rigidity, have revealed themselves to have insufficient power to in...

  12. Influence of Annealing Methods on the Magnetic Properties and Flexural Strength of Iron-OER Soft Magnetic Composites

    Directory of Open Access Journals (Sweden)

    Ling Xiao

    2016-01-01

    Full Text Available This study aims at investigating high flexural strength iron-OER soft magnetic composites (SMCs for active magnetic bearings (AMBs. Iron powders were firstly coated with oxide layer by the passivation process at room temperature. The effect of annealing methods on the static performance, magnetic properties, and flexural strength of SMCs was studied. The results showed that the significant improvements of permeability, magnetic loss, and flexural strength were presented by increasing the bonding number between iron surface and resin and using the two-step annealing method. In addition, the effect of pore shape and angle on the behavior of material fracture has been studied by FEM and the analysis was validated by experimental results.

  13. The influence of nickel slag aggregate concentration to compressive and flexural strength on fly ash-based geopolymer composite

    Science.gov (United States)

    Sujiono, E. H.; Setiawan, A.; Husain, H.; Irhamsyah, A.; Samnur, S.; Subaer, S.

    2016-04-01

    Fly ash-based geopolymer with nickel slag aggregate has been successfully produced. Fly ash and nickel slag were obtained from Bosowa Jeneponto Power Plant and PT. Vale Indonesia, respectively. This research aims to investigate the influence of nickel slag concentration to compressive strength, flexural strength, and microstructure of geopolymer composite. The increment of nickel slag aggregate on fly ash was relative to the weight of samples. Geopolymer composite were synthesized by using alkali activated method, cured at temperature of 70 °C for 1 hour. The resulting composites were left at room temperature for 14 days, before compressive and flexural strength were performed. The results showed that the addition of nickel slag aggregate was found to increase the compressive strength of the material. The optimum compressive strength was 14.81 MPa with the addition of 10% aggregate. The optimum flexural strength was 2.63 MPa with the addition of 15% aggregate.

  14. Measurement of mechanical quality factors of polymers in flexural vibration for high-power ultrasonic application.

    Science.gov (United States)

    Wu, Jiang; Mizuno, Yosuke; Tabaru, Marie; Nakamura, Kentaro

    2016-07-01

    A method for measuring the mechanical quality factor (Q factor) of materials in large-amplitude flexural vibrations was devised on the basis of the original definition of the Q factor. The Q factor, the ratio of the reactive energy to the dissipated energy, was calculated from the vibration velocity distribution. The bar thickness was selected considering the effect of the thickness on the estimation error. In the experimental setup, a 1-mm-thick polymer-based bar was used as a sample and fixed on the top of a longitudinal transducer. Using transducers of different lengths, flexural waves in the frequency range of 20-90kHz were generated on the bar. The vibration strain in the experiment reached 0.06%. According to the Bernoulli-Euler model, the reactive energy and dissipated energy were estimated from the vertical velocity distribution on the bar, and the Q factors were measured as the driving frequency and strain were varied. The experimental results showed that the Q factors decrease as the driving frequencies and strains increase. At a frequency of 28.30kHz, the Q factor of poly(phenylene sulfide) (PPS) reached approximately 460 when the strain was smaller than 0.005%. PPS exhibited a much higher Q factor than the other tested polymers, which implies that it is a potentially applicable material as the elastomer for high-power ultrasonic devices.

  15. Damping of flexural vibration using low-density, low-wave-speed media

    Science.gov (United States)

    Varanasi, Kripa K.; Nayfeh, Samir A.

    2006-04-01

    Significant damping of structural vibration can be attained by coupling to the structure a low-density medium (such as a powder or foam) in which the speed of sound propagation is relatively low. We describe a set of experiments in which flexural vibration of aluminum beams over a broad frequency range is damped by introduction of a layer of lossy low-wave-speed foam. At frequencies high enough to set up standing waves through the thickness of the foam, loss factors as high as 0.05 can be obtained with a foam layer whose mass is 3.9% of that of the beam. We model the foam as a continuum in which waves of dilatation and distortion can propagate, obtain approximate solutions for the frequency response of the system by means of a modal expansion, and find that the predictions are in close agreement with the measured responses. Finally, we develop a simple approximation for the system loss factor based on the complex wavenumber associated with flexural vibration in an infinite beam.

  16. Time-domain flexural wave intensity estimation in orthotropic Kirchhoff plates

    Science.gov (United States)

    Halkyard, C. R.; Masson, P.

    2016-04-01

    In this paper, a method for estimating the vibrational energy flow associated with the flexural vibration of an orthotropic Kirchhoff plate, in the time-domain, is presented. The approach is based on the plane propagating wave solution to the equation of motion, and uses a Fourier series approximation of the wave field. The various linear and angular velocities, shear forces and moments that are needed to calculate the energy flow are estimated by digitally filtering and combining the outputs of an array of sensors. A similar approach is used to reconstruct the local wave field to provide an estimate of the wave propagation direction. The theoretical basis of the approach is described, and design considerations for the sensor array and for the filters used for parameter estimation are discussed. Simulations are presented for plane flexural waves and for transient transverse point force excitation of a range of orthotropic plates having different material properties, using a simulated array of velocity sensors. These simulations show that the method can provide accurate estimates of the magnitude and direction of the vibrational energy flow, as well as of the propagation direction of a single wave train or 'burst', provided that the sensor array is sufficiently distant from the excitation point. This is consistent with preliminary experimental measurements, also presented in this paper, performed on a composite orthotropic plate.

  17. Flexural behavior of Sisal/Castor oil-Based Polyurethane and Sisal/Phenolic Composites

    Directory of Open Access Journals (Sweden)

    Andressa Cecília Milanese

    2012-04-01

    Full Text Available Natural fibers used as reinforcement of polymeric composites are interesting research subjects in polymer technology. Nowadays, these materials are being considered as a way to reinforce timber structures improvement. Fibers with larger structural applications are glass and carbon fibers, however, the use of natural fibers is an economic alternative and present many advantages such as biodegradability and having its origin from a renewable source. Castor oil, a triglyceride vegetable with hydroxyl groups, was reacted with 4,4' methylene diphenyl diisocyanate (MDI to produce the polyurethane matrix. The composites were prepared by compress molding at room temperature using woven sisal fiber as a reinforcement, with and without thermal treatment (at 60 ºC for 72 hours to the fabrics before the composites molding process. The present paper presents the preparation and a flexural caracterization of sisal/polyurethane and sisal/phenolic composites by using the three-point bending. The sisal fibers moisture content influence on the flexural behaviour was also analyzed. Experimental results showed a higher stiffness for the sisal/phenolic composite (11.2 MPa followed by the sisal/polyurethane (3.7 MPa, respectively.

  18. A Single Mooring System with Sag-Extensibility and Flexural Rigidity Applied to Offshore Platform

    Institute of Scientific and Technical Information of China (English)

    M.-C.Tsai; Hsien Hua Lee; Jun-Yen Lee; S.-S.Hsiao

    2013-01-01

    Floating platform system has been extensively used in ocean exploitation,particularly for a tension-leg platform (TLP) system in deep water.Most of the TLPs are multi-mooring systems,where multi-joints are connected to the tension-legs so that the platform is not allowed to twist freely and may subject to enormous force induced by large incident waves in the weak-direction of the structure.This study aims to exploit a single moored offshore platform system that may attract less force and can be operated with less effort.In our analysis,in addition to mechanical properties of the tether,two important properties are also taken into consideration for the single mooring tether with expanded cross sectional dimension and utilization of stronger material,namely,the sag-extensibility and the flexural rigidity.Finally,the dynamic structural behavior produced by the mechanical effects on the new system is investigated and compared with that of traditional design while the wave-structure interactions of large body are also accounted for.Our study finds that the neglect of sag-extensibility or the flexural rigidity of large,strong mooring cable may result in a conservative but not necessarily safe design.

  19. Opto-mechanical design of the G-CLEF flexure control camera system

    Science.gov (United States)

    Oh, Jae Sok; Park, Chan; Kim, Jihun; Kim, Kang-Min; Chun, Moo-Young; Yu, Young Sam; Lee, Sungho; Nah, Jakyoung; Park, Sung-Joon; Szentgyorgyi, Andrew; McMuldroch, Stuart; Norton, Timothy; Podgorski, William; Evans, Ian; Mueller, Mark; Uomoto, Alan; Crane, Jeffrey; Hare, Tyson

    2016-08-01

    The GMT-Consortium Large Earth Finder (G-CLEF) is the very first light instrument of the Giant Magellan Telescope (GMT). The G-CLEF is a fiber feed, optical band echelle spectrograph that is capable of extremely precise radial velocity measurement. KASI (Korea Astronomy and Space Science Institute) is responsible for Flexure Control Camera (FCC) included in the G-CLEF Front End Assembly (GCFEA). The FCC is a kind of guide camera, which monitors the field images focused on a fiber mirror to control the flexure and the focus errors within the GCFEA. The FCC consists of five optical components: a collimator including triple lenses for producing a pupil, neutral density filters allowing us to use much brighter star as a target or a guide, a tent prism as a focus analyzer for measuring the focus offset at the fiber mirror, a reimaging camera with three pair of lenses for focusing the beam on a CCD focal plane, and a CCD detector for capturing the image on the fiber mirror. In this article, we present the optical and mechanical FCC designs which have been modified after the PDR in April 2015.

  20. Damage detection of flexural structural systems using damage index method – Experimental

    Directory of Open Access Journals (Sweden)

    Atef Eraky

    2015-09-01

    Full Text Available In the framework of structural health monitoring, continuous dynamic records are essential for good judgment of structures. Overall degradation of structures can be obtained with reasonable accuracy using various system identification techniques. It is however, challenging to obtain precisely the position and size of local damages. The current research focuses on Damage Index Method (DIM as a tool for determining local damages occurred in flexural structural elements. The DIM technique depends on comparing modal strain energies of structures at different degradation stages. Self-made computer module was developed to encounter DIM for damage detection. First, the method was verified experimentally. Simply supported steel beam of 1500 mm (length, 50 mm (width and 6 mm (thickness, in addition to steel plate of area 930 × 910 mm and 3 mm (thickness was implemented in the experimental program. Both the beam and plate were subjected to different damage configurations. Collected acceleration time history was processed and used to verify the adequacy of DIM in identifying damages in the used physical models. Numerical parametric study was also conducted on a variety of beams and plates with various damage degrees and locations. It was noticed that both the experimental and numerical results showed good agreement in identifying damages in flexural structural elements.

  1. Current trends and controversies in the management of patients with splenic flexure tumours

    Directory of Open Access Journals (Sweden)

    Chan DS

    2013-03-01

    Full Text Available Aim: There exists a variation in practice in the management of tumours around the splenic flexure. We aim to determine the current opinion regarding the management of these tumours. Methods: An anonymised 10-part online questionnaire was sent to all members of the Association of Coloproctology of Great Britain and Ireland (ACPGBI. Results: The response rate was 24% (111/464 with approximately half of respondents performing laparoscopic surgery. Electively, an extended right hemicolectomy is the preferred option by 63% of respondents followed by left hemicolectomy (23% and segmental resection (14%. The upper sigmoid and rectosigmoid is the preferred site of anastomosis by 90% and 10% of respondents respectively. There were no significant differences in the type of operations performed by surgeons who practice laparoscopic or open surgery (p=0.10. A hand-sewn end-to-end anastomosis is most commonly performed (51% followed by a stapled side-to-side (36% and a stapled end-to-end (13% technique. Extended right hemicolectomy is also the preferred option in obstructing tumours. Of surgeons who perform segmental resections, 27% perform an on-table lavage and 9% perform a defunctioning stoma. Internal herniation following laparoscopic resection was only reported by a handful of surgeons. Conclusion: Opinion and practice in the management of patients with tumours around the splenic flexure are divided. Further trials are indicated to determine the best practice.

  2. Exact analytical solution of shear-induced flexural vibration of functionally graded piezoelectric beam

    Science.gov (United States)

    Sharma, Pankaj; Parashar, Sandeep Kumar

    2016-05-01

    The priority of this paper is to obtain the exact analytical solution for free flexural vibration of FGPM beam actuated using the d15 effect. In piezoelectric actuators, the potential use of d15 effect has been of particular interest for engineering applications since shear piezoelectric coefficient d15 is much higher than the other piezoelectric coupling constants d31 and d33. The applications of shear actuators are to induce and control the flexural vibrations of beams and plates. In this study, a modified Timoshenko beam theory is used where electric potential is assumed to vary sinusoidaly along the thickness direction. The material properties are assumed to be graded across the thickness in accordance with power law distribution. Hamilton`s principle is employed to obtain the equations of motion along with the associated boundary conditions for FGPM beams. Exact analytical solution is derived thus obtained equations of motion. Results for clamped-clamped and clamped-free boundary conditions are presented. The presented result and method shell serve as benchmark for comparing the results obtained from the other approximate methods.

  3. Flexural Fillet Geometry Optimization for Design of Force Transducers Used in Aeronautics Testing

    Science.gov (United States)

    Lynn, Keith C.; Dixon, Genevieve

    2015-01-01

    Force transducer designs used in the ground testing aeronautics community have seen minimal change over the last few decades. With increased focus on data quality and long-term performance capabilities over the life of these instruments, it is critical to investigate new methods that improve these designs. One area of focus in the past few years at NASA has been on the design of the flexural elements of traditional force balance transducers. Many of the heritage balances that have been heavily used over the last few decades have started to develop fatigue cracks. The recent focus on the flexural design of traditional single-piece force balances revolves around the design of these elements such that stress concentrations are minimized, with the overall goal of increasing the fatigue life of the balance. Recent research in the area of using conic shaped fillets in the highly stressed regions of traditional force balances will be discussed, with preliminary numerical and experimental data results. A case study will be presented which discusses integration of this knowledge into a new high-capacity semi-span force balance.

  4. Injection moulding of long glass fibre reinforced polyamide 6-6: guidelines to improve flexural properties

    Directory of Open Access Journals (Sweden)

    2007-07-01

    Full Text Available Based on a previous optimisation of set-up parameters for injection moulding of polyamide 6-6 (PA 6-6 reinforced with 40-wt% of 10 mm long glass fibre, the aim of this paper is to define suitable guidelines to further improve the mechanical performances of PA 6-6/glass long fibre thermoplastic (LFT injection mouldings. Different solutions have been considered: screw and non-return valve design modification so as to adapt them to LFT processing, increase of the initial fibre content (up to 50 wt% and length (up to 25 mm in the LFT pellets. Using a LFT dedicated plasticating unit has allowed decreasing the fibre breakage amount by about 80% at the nozzle exit, however without improving the flexural properties. Increasing the initial fibre content has logically permitted to improve the flexural properties. Increasing the initial fibre length has not brought any improvement of the properties and has even amplified the structural heterogeneities and anisotropy of the parts. These trends have been explained on the basis of cavity pressure records highlighting significantly different rheological behaviours, and of resulting residual fibre lengths and through-the-thickness fibre orientation profiles modifications.

  5. Acoustic streaming induced by ultrasonic flexural vibrations and associated enhancement of convective heat transfer.

    Science.gov (United States)

    Loh, Byoung-Gook; Hyun, Sinjae; Ro, Paul I; Kleinstreuer, Clement

    2002-02-01

    Acoustic streaming induced by ultrasonic flexural vibrations and the associated convection enhancement are investigated. Acoustic streaming pattern, streaming velocity, and associated heat transfer characteristics are experimentally observed. Moreover, analytical analysis based on Nyborg's formulation is performed along with computational fluid dynamics (CFD) simulation using a numerical solver CFX 4.3. Two distinctive acoustic streaming patterns in half-wavelength of the flexural vibrations are observed, which agree well with the theory. However, acoustic streaming velocities obtained from CFD simulation, based on the incompressible flow assumption, exceed the theoretically estimated velocity by a factor ranging from 10 to 100, depending upon the location along the beam. Both CFD simulation and analytical analysis reveal that the acoustic streaming velocity is proportional to the square of the vibration amplitude and the wavelength of the vibrating beam that decreases with the excitation frequency. It is observed that the streaming velocity decreases with the excitation frequency. Also, with an open-ended channel, a substantial increase in streaming velocity is observed from CFD simulations. Using acoustic streaming, a temperature drop of 40 degrees C with a vibration amplitude of 25 microm at 28.4 kHz is experimentally achieved.

  6. Influence of translucence/opacity and shade in the flexural strength of lithium disilicate ceramics

    Science.gov (United States)

    Santos, Mila Oliveira; do Amaral, Flávia Lucisano Botelho; França, Fabiana Mantovani Gomes; Basting, Roberta Tarkany

    2015-01-01

    Background: Lithium disilicate ceramic system consists of glass ceramic ingots with different grades of translucence which may influence its flexural strength. Aims: To assess the three-point flexural strength of the different lithium disilicate-based ceramic ingots (IPS e.max Press/Ivoclar Vivadent) with different levels of translucence and shade. Materials and Methods: Six groups of ceramic ingots were selected to represent different levels of translucence and shade (HTA1, HTBL2, LTA2, LTB2, MO2, and HO). They measured 25 mm × 5 mm × 2 mm (n = 10), according to ISO 6872 specifications, and tested on a universal test machine (EMIC). Statistical Analysis Used: A one-way analysis of variance (ANOVA) was used (α = 0.05). Results: The results (in MPa) were: HTA1 = 392.98; HTBL2 = 390.74; LTA2 = 390.46; LTB2 = 389.92; MO2 = 390.43; HO = 391.96. ANOVA showed no significant difference among groups (P = 0.1528). Conclusions: Different levels of translucence, opacity and shade of ingots did not affect their mechanical strength, and the use of these ceramics should be guided by the esthetic demands of each clinical situation. PMID:26430304

  7. Flexural Strengthening of RC Slabs Using a Hybrid FRP-UHPC System Including Shear Connector

    Directory of Open Access Journals (Sweden)

    Jiho Moon

    2017-01-01

    Full Text Available A polymeric hybrid composite system made of UHPC and CFRP was proposed as a retrofit system to enhance flexural strength and ductility of RC slabs. While the effectiveness of the proposed system was confirmed previously through testing three full-scale one-way slabs having two continuous spans, the slabs retrofitted with the hybrid system failed in shear. This sudden shear failure would stem from the excessive enhancement of the flexural strength over the shear strength. In this study, shear connectors were installed between the hybrid system and a RC slab. Using simple beam, only positive moment section was examined. Two full-scale RC slabs were cast and tested to failure: the first as a control and the second using this new strengthening technique. The proposed strengthening system increased the ultimate load carrying capacity of the slab by 70%, the stiffness by 60%, and toughness by 128%. The efficiency of shear connectors on ductile behavior of the retrofitted slab was also confirmed. After the UHPC top is separated from the slab, the shear connector transfer shear load and the slab system were in force equilibrium by compression in UHPC and tension in CFRP.

  8. Flexural Strengthening of RC Slabs with Prestressed CFRP Strips Using Different Anchorage Systems

    Directory of Open Access Journals (Sweden)

    José Sena-Cruz

    2015-10-01

    Full Text Available Externally Bonded Reinforcement (EBR technique has been widely used for flexural strengthening of concrete structures by using carbon fiber-reinforced polymers (CFRP. EBR technique offers several structural advantages when the CFRP material is prestressed. This paper presents an experimental and numerical study on reinforced (RC slabs strengthened in flexure with prestressed CFRP strips as a structural strengthening system. The strips are applied as an externally bonded reinforcement (EBR and anchored with either a mechanical or a gradient anchorage. The former foresees metallic anchorage plates fixed to the concrete substrate, while the latter is based on an accelerated epoxy resin curing followed by a segment-wise prestress force decrease at the strip ends. Both anchorage systems, in combination with different CFRP strip geometries, were subjected to static loading tests. It could be demonstrated that the composite strip’s performance is better exploited when prestressing is used, with slightly higher overall load carrying capacities for mechanical anchorages than for the gradient anchorage. The performed investigations by means of a cross-section analysis supported the experimental observation that in case a mechanical anchorage is used, progressive strip debonding changes the fully bonded configuration to an unbonded end-anchored system. The inclusion of defined debonding criteria for both the anchorage zones and free length between the anchorage regions allowed to precisely capture the ultimate loading forces.

  9. Flexural wave attenuation in a sandwich beam with viscoelastic periodic cores

    Science.gov (United States)

    Guo, Zhiwei; Sheng, Meiping; Pan, Jie

    2017-07-01

    The flexural-wave attenuation performance of traditional constraint-layer damping in a sandwich beam is improved by using periodic constrained-layer damping (PCLD), where the monolithic viscoelastic core is replaced with two periodically alternating viscoelastic cores. Closed-form solutions of the wave propagation constants of the infinite periodic sandwich beam and the forced response of the corresponding finite sandwich structure are theoretically derived, providing computational support on the analysis of attenuation characteristics. In a sandwich beam with PCLD, the flexural waves can be attenuated by both Bragg scattering effect and damping effect, where the attenuation level is mainly dominated by Bragg scattering in the band-gaps and by damping in the pass-bands. Affected by these two effects, when the parameters of periodic cores are properly selected, a sandwich beam with PCLD can effectively reduce vibrations of much lower frequencies than that with traditional constrained-layer damping. The effects of the parameters of viscoelastic periodic cores on band-gap properties are also discussed, showing that the average attenuation in the desired frequency band can be maximized by tuning the length ratio and core thickness to proper values. The research in this paper could possibly provide useful information for the researches and engineers to design damping structures.

  10. Polymerization shrinkage, flexural and compression properties of low-shrinkage dental resin composites.

    Science.gov (United States)

    Park, Jeong-Kil; Lee, Geun-Ho; Kim, Jong-Hwa; Park, Mi-Gyoung; Ko, Ching-Chang; Kim, Hyung-Il; Kwon, Yong Hoon

    2014-01-01

    This study evaluated the polymerization shrinkage, flexural and compressive properties of low-shrinkage resin composites. For the study, four methacrylate-based and one silorane-based resin composites were light cured using three different light-curing units (LCUs) and their polymerization shrinkage, flexural (strength (FS) and modulus (FM)) and compressive (strength (CS) and modulus (CM)) properties were evaluated. Data were statistically analyzed using ANOVA and a post-hoc Tukey test. The polymerization shrinkage ranged approximately 7.6-14.2 μm for 2-mm thick specimens depending on the resin product and LCU. Filtek LS showed the least shrinkage while the rest shrank approximately 13.2-14.2 μm. However, Filtek LS showed the greatest shrinkage difference for the used LCUs. FS and CS of the tested specimens ranged 96.2-152.1 MPa and 239.2-288.4 MPa, respectively, depending on the resin product and LCU. The highest and lowest FS and FM were recorded for the methacrylate-based resin composites. Among the specimens, Filtek LS showed the lowest CS and CM.

  11. Determination of tensile and compressive moduli of laminae in unidirectionally reinforced laminate by flexural tests

    Science.gov (United States)

    Kuklinski, Mariusz

    2017-03-01

    The Euler-Bernoulli beam theory is widely used in engineering despite of various simplifications. One of which, that do matters in this article, is neglecting the difference between tensile and compressive moduli. Experimental tests reveal that for fibre reinforced composites tensile moduli are generally greater than compressive ones. This paper presents the results of testing the laminate composed of four unidirectionally glass reinforced laminae separated by layers of glass mat. The specimens were subjected to flexural, tensile and compressive loading in order to calculate corresponding moduli of elasticity. The results were compared using equations of Classical Beam Theory. Knowing the tensile and compressive moduli of glass mat reinforced laminae and performing flexural tests of laminate it is possible to calculate the tensile and compressive moduli of unidirectionally glass reinforced laminae. The experimental data taken into calculations correspond to linear normal strains of 0.0005 and 0.0025. The experimental data are consistent with results of calculations within acceptable margin of tolerance.

  12. Study on Flexural Behaviour of Ternary Blended Reinforced Self Compacting Concrete Beam with Conventional RCC Beam

    Science.gov (United States)

    Marshaline Seles, M.; Suryanarayanan, R.; Vivek, S. S.; Dhinakaran, G.

    2017-07-01

    The conventional concrete when used for structures having dense congested reinforcement, the problems such as external compaction and vibration needs special attention. In such case, the self compacting concrete (SCC) which has the properties like flow ability, passing and filling ability would be an obvious answer. All those SCC flow behavior was governed by EFNARC specifications. In present study, the combination type of SCC was prepared by replacing cement with silica fume (SF) and metakaolin (MK) along with optimum dosages of chemical admixtures. From the fresh property test, cube compressive strength and cylinder split tensile strength, optimum ternary mix was obtained. In order to study the flexural behavior, the optimum ternary mix was taken in which beam specimens of size 1200 mm x 100 mm x 200 mm was designed as singly reinforced section according to IS: 456-2000, Limit state method. Finally the comparative experimental analysis was made between conventional RCC and SCC beams of same grade in terms of flexural strength namely yield load & ultimate load, load- deflection curve, crack size and pattern respectively.

  13. Flexural Behavior of RC Members Using Externally Bonded Aluminum-Glass Fiber Composite Beams

    Directory of Open Access Journals (Sweden)

    Ki-Nam Hong

    2014-03-01

    Full Text Available This study concerns improvement of flexural stiffness/strength of concrete members reinforced with externally bonded, aluminum-glass fiber composite (AGC beams. An experimental program, consisting of seven reinforced concrete slabs and seven reinforced concrete beams strengthened in flexure with AGC beams, was initiated under four-point bending in order to evaluate three parameters: the cross-sectional shape of the AGC beam, the glass fiber fabric array, and the installation of fasteners. The load-deflection response, strain distribution along the longitudinal axis of the beam, and associated failure modes of the tested specimens were recorded. It was observed that the AGC beam led to an increase of the initial cracking load, yielding load of the tension steels and peak load. On the other hand, the ductility of some specimens strengthened was reduced by more than 50%. The A-type AGC beam was more efficient in slab specimens than in beam specimens and the B-type was more suitable for beam specimens than for slabs.

  14. Flexural Capability of Patterned Transparent Conductive Substrate by Performing Electrical Measurements and Stress Simulations

    Directory of Open Access Journals (Sweden)

    Chang-Chun Lee

    2016-10-01

    Full Text Available The suitability of stacked thin films for next-generation display technology was analyzed based on their properties and geometrical designs to evaluate the mechanical reliability of transparent conducting thin films utilized in flexural displays. In general, the high bending stress induced by various operation conditions is a major concern regarding the mechanical reliability of indium–tin–oxide (ITO films deposited on polyethylene terephthalate (PET substrates; mechanical reliability is commonly used to estimate the flexibility of displays. However, the pattern effect is rarely investigated to estimate the mechanical reliability of ITO/PET films. Thus, this study examined the flexible content of patterned ITO/PET films with two different line widths by conducting bending tests and sheet resistance measurements. Moreover, a stress–strain simulation enabled by finite element analysis was performed on the patterned ITO/PET to explore the stress impact of stacked film structures under various levels of flexural load. Results show that the design of the ITO/PET film can be applied in developing mechanically reliable flexible electronics.

  15. Comparative Study on Flexural Strengthening of RC Beams using CFRP Laminate by Different Techniques

    Science.gov (United States)

    Jeevan, N.; Jagannatha Reddy, H. N.

    2017-08-01

    This paper presents a detailed study on flexural behaviour of RC beams strengthened using Carbon Fiber Reinforced Polymer (CFRP) laminate. A detailed study was made on strengthened beam using Externally Bonded Laminate (EBL) and Internally Bonded Laminate (IBL) techniques. In IBL technique the laminate is sandwiched between the layers of epoxy mounted on the cover portion by the groove. The beams were designed as under-reinforced section. Totally six beams were casted, out of this two beams were control beams. Strengthened beams were divided into two sets (IBL and EBL) of two beams each. The main aim of this work is to delay the debonding failure in order to enhance the ultimate load carrying capacity for strengthened beams. Four-point bending flexural tests were conducted on specimens up to failure. The experimental results illustrate that, the strengthened beams significantly increases the cracking, working and ultimate load when compared with control beams. IBL technique shows the significant increase in the debonding strain by delaying the beam from debonding failure which in turn enhances the ultimate load by almost 73% compared with control beam and 39% with EBL technique. All the deflection values from the experiments are within the limit of codal provisions. The IBL technique was emerged as the better strengthening technique, which increases almost 41% of working load (Pw) compared with strengthening codes.

  16. Analysis and enhancement of flexural wave stop bands in 2D periodic plates

    Energy Technology Data Exchange (ETDEWEB)

    Song, Yubao [Laboratory of Science and Technology on Integrated Logistics Support, National University of Defense Technology, 410073 Changsha (China); The Marcus Wallenberg Laboratory for Sound and Vibration Research, KTH – The Royal Institute of Technology, SE-100 44 Stockholm (Sweden); Feng, Leping [The Marcus Wallenberg Laboratory for Sound and Vibration Research, KTH – The Royal Institute of Technology, SE-100 44 Stockholm (Sweden); Wen, Jihong, E-mail: wenjihong_nudt1@vip.sina.com [Laboratory of Science and Technology on Integrated Logistics Support, National University of Defense Technology, 410073 Changsha (China); Yu, Dianlong; Wen, Xisen [Laboratory of Science and Technology on Integrated Logistics Support, National University of Defense Technology, 410073 Changsha (China)

    2015-07-17

    The band structure and enhancement of flexural wave stop bands in a 2D periodic plate are investigated. A unified method for analysing and designing the stop band of the plates with various attached structures is proposed. The effect of attached structures is considered based on their equivalent parameters (added equivalent mass and equivalent moment of inertia). The influences of the equivalent parameters on the band structures are studied. Three cases are considered: adding pure equivalent mass, pure equivalent moment of inertia and the combination of these two. The stop bands are enhanced via the multi interaction between the host plate and the attached structure. The enhancement pattern is determined, and several ways to obtain a wider combined stop band are presented. The frequency response functions of corresponding finite periodic plates are calculated to verify the stop bands and their enhancement in a number of typical cases. - Highlights: • A unified method for studying the stop band of the plates with various simplified attached structures is proposed. • The enhancement of flexural wave stop bands in a 2D phononic plate is investigated. • The stop bands are widened via multi interaction between the host plate and the attached structure. • The enhancement pattern is determined and several ways to get a wider stop band are presented.

  17. Force-Sensing Actuator with a Compliant Flexure-Type Joint for a Robotic Manipulator

    Directory of Open Access Journals (Sweden)

    Mathieu Grossard

    2015-12-01

    Full Text Available This paper deals with the mechatronic design of a novel self-sensing motor-to-joint transmission to be used for the actuation of robotic dexterous manipulators. Backdrivability, mechanical simplicity and efficient flexure joint structures are key concepts that have guided the mechanical design rationale to provide the actuator with force sensing capabilities. Indeed, a self-sensing characteristic is achieved by the specific design of high-resolution cable-driven actuators based on a DC motor, a ball-screw and a monolithic compliant anti-rotation system together with a novel flexure pivot providing a frictionless mechanical structure. That novel compliant pivot with a large angular range and a small center shift has been conceived of to provide the inter-phalangeal rotational degree of freedom of the fingers’ joints to be used for integration in a multi-fingered robotic gripper. Simultaneously, it helps to remove friction at the joint level of the mechanism. Experimental tests carried out on a prototype show an accurate matching between the model and the real behavior. Overall, this mechatronic design contributes to the improvement of the manipulation skills of robotic grippers, thanks to the combination of high performance mechanics, high sensitivity to external forces and compliance control capability.

  18. Detection of acute hepatopancreatic necrosis disease (AHPND) in Mexico.

    Science.gov (United States)

    Nunan, Linda; Lightner, Donald; Pantoja, Carlos; Gomez-Jimenez, Silvia

    2014-08-21

    Acute hepatopancreatic necrosis disease (AHPND), which has also been referred to as early mortality syndrome (EMS), initially emerged as a destructive disease of cultured shrimp species in Asia in 2009. The pathogen associated with the disease, Vibrio parahaemolyticus, subsequently spread to the Western Hemisphere and emerged in Mexico in early 2013. The spread to the Western Hemisphere is a major concern to shrimp producers in the region. To date, the only peer-reviewed published method for determining whether mortalities are due to AHPND is through histological examination. A novel PCR detection method was employed to assess samples from Mexico in order to confirm the presence of the pathogen in this country. This manuscript details the detection methods used to confirm the presence of AHPND in Mexico. Both immersion and per os challenge studies were used to expose the Penaeus vannamei to the bacteria in order to induce the disease. Histological analysis confirmed AHPND status following the challenge studies. Also provided are the details of the molecular test by PCR that was used for screening candidate V. parahaemolyticus isolates. A rapid PCR assay for detection of AHPND may help with early detection and help prevent the spread of AHPND to other countries.

  19. Acute Esophageal Necrosis: An Uncommon Cause of Hematemesis

    Directory of Open Access Journals (Sweden)

    George Sarin Zacharia

    2014-07-01

    Full Text Available Acute esophageal necrosis or black esophagus is an uncommon clinical entity, diagnosed at the upper gastrointestinal endoscopy with the presence of strikingly black necrotic esophagus. Very often no definite etiology will be identified even though a large list of potential associations has been postulated. Upper gastrointestinal bleeding is the most common clinical presentation, others being epigastric pain, retrosternal chest discomfort and dysphagia. Only about a hundred cases of acute esophageal necrosis have been described in medical literature till this date. We report a case of acute esophageal necrosis in an elderly female who had presented with hematemesis.

  20. Challenges With the Diagnosis and Treatment of Cerebral Radiation Necrosis

    Energy Technology Data Exchange (ETDEWEB)

    Chao, Samuel T., E-mail: chaos@ccf.org [Department of Radiation Oncology, Cleveland Clinic, Cleveland, Ohio (United States); Rose Ella Burkhardt Brain Tumor and Neuro-oncology Center, Cleveland Clinic, Cleveland, Ohio (United States); Ahluwalia, Manmeet S. [Department of Medical Oncology, Cleveland Clinic, Cleveland, Ohio (United States); Rose Ella Burkhardt Brain Tumor and Neuro-oncology Center, Cleveland Clinic, Cleveland, Ohio (United States); Barnett, Gene H. [Department of Neurosurgery, Cleveland Clinic, Cleveland, Ohio (United States); Rose Ella Burkhardt Brain Tumor and Neuro-oncology Center, Cleveland Clinic, Cleveland, Ohio (United States); Stevens, Glen H.J. [Department of Neurology, Cleveland Clinic, Cleveland, Ohio (United States); Rose Ella Burkhardt Brain Tumor and Neuro-oncology Center, Cleveland Clinic, Cleveland, Ohio (United States); Murphy, Erin S. [Department of Radiation Oncology, Cleveland Clinic, Cleveland, Ohio (United States); Rose Ella Burkhardt Brain Tumor and Neuro-oncology Center, Cleveland Clinic, Cleveland, Ohio (United States); Stockham, Abigail L. [Department of Radiation Oncology, Cleveland Clinic, Cleveland, Ohio (United States); Shiue, Kevin [Case Western Reserve University School of Medicine, Cleveland, Ohio (United States); Suh, John H. [Department of Radiation Oncology, Cleveland Clinic, Cleveland, Ohio (United States); Rose Ella Burkhardt Brain Tumor and Neuro-oncology Center, Cleveland Clinic, Cleveland, Ohio (United States)

    2013-11-01

    The incidence of radiation necrosis has increased secondary to greater use of combined modality therapy for brain tumors and stereotactic radiosurgery. Given that its characteristics on standard imaging are no different that tumor recurrence, it is difficult to diagnose without use of more sophisticated imaging and nuclear medicine scans, although the accuracy of such scans is controversial. Historically, treatment had been limited to steroids, hyperbaric oxygen, anticoagulants, and surgical resection. A recent prospective randomized study has confirmed the efficacy of bevacizumab in treating radiation necrosis. Novel therapies include using focused interstitial laser thermal therapy. This article will review the diagnosis and treatment of radiation necrosis.

  1. Avascular necrosis of the femoral head presenting as trochanteric bursitis.

    Science.gov (United States)

    Mandell, B F

    1990-01-01

    Five patients are described with avascular necrosis of the femoral head who presented with ipsilateral trochanteric bursitis, in the absence of clearcut hip joint disease. Avascular necrosis was indicated by magnetic resonance imaging. It is suggested that clinical trochanteric bursitis, especially when refractory to local corticosteroid treatment, may be the initial sign of hip disease. In the patient with risk factor(s) for avascular necrosis that diagnosis should be considered and evaluated with appropriate studies, such as magnetic resonance imaging, to prevent weight bearing at an early stage and permit possible surgical decompression in the hope of postponing or obviating the need for total hip replacement. PMID:2241294

  2. Differentiation of radiation necrosis from glioblastoma recurrence after radiotherapy

    Institute of Scientific and Technical Information of China (English)

    Chrissa Sioka; Anastasia Zikou; Anna Goussia; Spyridon Tsiouris; Loucas G Astrakas; Athanassios P Kyritsis

    2016-01-01

    The standard treatment of glioblastoma, the most common type of primary-brain-tumor, involves radiotherapy with concomitant temozolomide chemotherapy. A patient with glioblastoma, post radiotherapy developed magnatic resonance imaging (MRI) changes consistent with either radiation-induced tumor necrosis or tumor recurrence. Perfusion MRI was suggestive of radiation necrosis, but magnetic resonance spectroscopy and99mTc-Tetrofosmin single photon emission computed tomography was indicative of tumor recurrence. Positron emission tomography scan was not available. Tumor recurrence was documented by biopsy. Several advanced imaging methods are available to differentiate tumor recurrence from radiation necrosis in glioblastoma patients. However, in inconclusive cases, brain biopsy should be performed for deifnite diagnosis.

  3. FADD: an endogenous inhibitor of RIP3-driven regulated necrosis

    Institute of Scientific and Technical Information of China (English)

    Lorenzo Galluzzi; Oliver Kepp; Guido Kroemer

    2011-01-01

    Thanks to the work of multiple laboratories worldwide,the classical dichotomy postulating that apoptosis and necrosis would constitute diametrically opposed cell death subroutines has recently been dismissed [1].Thus,approximately in the same year when immunogenic instances of apoptosis were first characterized [2],the traditional belief that necrosis would represent a merely accidental,unregulated cell death modality has been definitely abandoned [3].This has fueled an intense wave of research,advancing our understanding of the molecular mechanisms and pathophysiological implications of regulated necrosis [4,5].

  4. Practical quantification of necrosis in histological whole-slide images.

    Science.gov (United States)

    Homeyer, André; Schenk, Andrea; Arlt, Janine; Dahmen, Uta; Dirsch, Olaf; Hahn, Horst K

    2013-06-01

    Since the histological quantification of necrosis is a common task in medical research and practice, we evaluate different image analysis methods for quantifying necrosis in whole-slide images. In a practical usage scenario, we assess the impact of different classification algorithms and feature sets on both accuracy and computation time. We show how a well-chosen combination of multiresolution features and an efficient postprocessing step enables the accurate quantification necrosis in gigapixel images in less than a minute. The results are general enough to be applied to other areas of histological image analysis as well.

  5. Flexural strength and microstructure of two lithium disilicate glass ceramics for CAD/CAM restoration in the dental clinic

    Directory of Open Access Journals (Sweden)

    Suk-Ho Kang

    2013-08-01

    Full Text Available Objectives There has been a growing interest in glass ceramic systems with good esthetics, high fracture resistance and bonding durability, and simplified fabrication techniques using CAD/CAM. The aim of this study is to compare flexural strength before and after heat treatment of two lithium disilicate CAD/CAM blocks, IPS e.max CAD (Ivoclar Vivadent and Rosetta SM (Hass, and to observe their crystalline structures. Materials and Methods Biaxial flexural strength was tested according to ISO 6872 with 20 disc form specimens sliced from each block before and after heat treatment. Also, the crystalline structures were observed using field-emission scanning microscopy (FE-SEM, Hitachi and x-ray diffraction (XRD, Rigaku analysis. The mean values of the biaxial flexural strength were analyzed by the Mann-Whitney U test at a significance level of p = 0.05. Results There were no statistically significant differences in flexural strength between IPS e.max CAD and Rosetta SM either before heat treatment or after heat treatment. For both ceramics, the initial flexural strength greatly increased after heat treatment, with significant differences (p < 0.05. The FE-SEM images presented similar patterns of crystalline structure in the two ceramics. In the XRD analysis, they also had similar patterns, presenting high peak positions corresponding to the standard lithium metasilicate and lithium disilicate at each stage of heat treatment. Conclusions IPS e.max CAD and Rosetta SM showed no significant differences in flexural strength. They had a similar crystalline pattern and molecular composition.

  6. Evaluation of Flexural Strength of Thermocycled Interim Resin Materials Used in Prosthetic Rehabilitation- An In-vitro Study

    Science.gov (United States)

    Kadiyala, Krishna Kishore; Anne, Gopinadh; Anche, Sampath Chowdary; Chiramana, Sandeep; Muvva, Suresh Babu; Zakkula, Srujana; Jyothula, Ravi Rakesh Dev

    2016-01-01

    Introduction Provisional restoration is an analytical component of fixed prosthodontics serving as a ground plan for the design of fixed dental prosthesis. Flexural strength is critical in case of long standing fixed dental prosthesis, to appreciate success of full mouth rehabilitation cases and temporomandibular joint dysfunction therapies. Aim The present study was to evaluate the flexural strength of different provisional restorative resins used for prosthetic rehabilitation. Materials and Methods Forty identical samples (n=10 for each material) measuring 25mm×2mm×2mm according to ADA/ANSI specification no. 27 were fabricated using autopolymerizing Poly Methyl Methacrylate (PMMA) (Group A); heat activated PMMA (Group B); autopolymerizing Bis-GMA composite resin (Group C) and light activated Urethane Dimethacrylate Resin (UDMA) (Group D). For 14 days all these samples were stored in artificial saliva. Ten samples from each material were subjected to thermal cycling for 2500 cycles (5°C to 55°C). Later, a standard three point bending test was conducted on all the specimens with a universal testing machine at a crosshead speed of 0.75mm/min. Statistical analysis used included Kruskal-Wallis and Mann-Whitney U test. Results The mean flexural strength of specimens confirmed higher flexural strength for Group C (102.98 Mpa) followed by Group B (91.86 Mpa), Group A (79.13 Mpa) and Group D (60.01 Mpa). There were significant differences between any two materials tested (p <0.05). Comparison between mean flexural strength values between four groups revealed significant difference between the interim materials (p <0.05). Conclusion The greatest flexural strength was observed for Bis-GMA composite resins followed by heat cure methacrylate resins, autopolymerizing methacrylate resins and was least for light cure resins. While fabricating provisional restorations, these greater values should be considered for better outcome of the treatment. PMID:27790588

  7. [Skin necrosis with vitamin K antagonists: An imbalance between coagulant and anticoagulant factors].

    Science.gov (United States)

    Vildy, S; Osmaeva, K; Closs-Prophette, F; Maillard, H

    2017-02-01

    Skin necrosis with vitamin k antagonists are rare. They affect more frequently middle-aged and obese women, often within 10 days after initiating of treatment. They occur most often in a context of thrombophilia. An 18-year-old obese woman was treated with heparin and fluindione for a lower limb deep venous thrombosis. On day 5, the patient presented fever and skin necrosis, which extended rapidly. We identified an activated protein C resistance and a major inflammatory syndrome related to Mycoplasma pneumoniae infection. The outcome was favorable after discontinuation of the fluindione, introduction of heparin and vitamin K, despite amputation of a toe. Skin necrosis is due to a transient hypercoagulable state during the initiation of vitamin K antagonist treatment due to an imbalance between pro- and anticoagulant factors. In our case, it was caused by an activated protein C resistance and an inflammatory syndrome. Copyright © 2016 Société Nationale Française de Médecine Interne (SNFMI). Published by Elsevier SAS. All rights reserved.

  8. Comparative evaluation of impact and flexural strength of four commercially available flexible denture base materials: an in vitro study.

    Science.gov (United States)

    Abhay, Pande Neelam; Karishma, Shori

    2013-12-01

    Poly-methyl methacrylate is a rigid material. It is generally observed that the impact and flexural strength of this material is not satisfactory and that is reflected in the continuous efforts to improve these mechanical properties. Hence there was a serious need to make another material which could overcome the limitations of the existing materials and could have better properties, like thermoplastic materials. The study was aimed to evaluate and compare the impact strength and the flexural strength of four different flexible denture base materials (thermoplastic denture base resins) with the conventional denture base material (high impact polymethyl-methacrylate). Two, machine made master moulds of metal blocks according to the size of sample holder of the equipment were prepared to test the impact and flexural strength. Total 40 samples, 10 for each group of flexible denture base materials namely: De-flex (Deflex, United Kingdom), Lucitone FRS (Densply, Germany), Valplast (Novoblast, USA), and Bre-flex (Bredent, Germany) in specially designed flask by injection molded process. For different flexible materials, the time, temperature and pressure for injecting the materials were followed as per the manufacturer's instructions. Total 20 samples for control (Trevelon denture base materials) were prepared by compression moulded process, for each test. ANOVA test was applied to calculate p value. Unpaired t test was applied to calculate t-value. Tukey-Kramer multiple test was provided for comparison between the groups for flexural and impact strength. From the statistical analysis, it was found that, the impact strength of Group III (Valplast) was found to be the highest than all other groups and nearer to the control group. Whereas Group IV (Bre-flex) had the maximum flexural strength. The flexural strength of Group I (De-flex) was lowest than all other groups and nearer to control group. The values were found to be statistically significant but clinically non

  9. Experimental study on slow flexural waves around the defect modes in a phononic crystal beam using fiber Bragg gratings

    Science.gov (United States)

    Chuang, Kuo-Chih; Zhang, Zhi-Qiang; Wang, Hua-Xin

    2016-12-01

    This work experimentally studies influences of the point defect modes on the group velocity of flexural waves in a phononic crystal Timoshenko beam. Using the transfer matrix method with a supercell technique, the band structures and the group velocities around the defect modes are theoretically obtained. Particularly, to demonstrate the existence of the localized defect modes inside the band gaps, a high-sensitivity fiber Bragg grating sensing system is set up and the displacement transmittance is measured. Slow propagation of flexural waves via defect coupling in the phononic crystal beam is then experimentally demonstrated with Hanning windowed tone burst excitations.

  10. Eyelid Necrosis and Secondary Cicatrical Ectropion Secondary to Levamisole-Associated Vasculitis.

    Science.gov (United States)

    Ramesh, Sathyadeepak; Sobti, Deepak; Mancini, Ronald

    2015-09-21

    A 56-year-old female presented with eyelid necrosis secondary to systemic levamisole-induced vasculitis. Skin biopsy revealed necrotic epidermis with small-vessel thrombosis, fibrinoid reaction, and neutrophilic infiltration of vessel walls in the dermis with +pANCA. She was treated with plasmapheresis and steroids. Six months later, she developed severe, symptomatic cicatrical ectropion with marked anterior lamellar shortage and middle lamellar contracture. Scar release in the middle lamellar plane with lateral tarsal strip procedures was performed, with full-thickness skin grafts from the upper eyelids. She remained fully epithelialized postoperatively with improvement in symptoms, although she incomplete graft take due to her eyelid necrosis and compromised dermal blood supply.

  11. Kyrieleis plaques associated with Herpes Simplex Virus type 1 acute retinal necrosis

    Directory of Open Access Journals (Sweden)

    Neha Goel

    2016-04-01

    Full Text Available We report the case of a 55-year-old immunocompetent male who presented with features typical of acute retinal necrosis (ARN. Polymerase chain reaction of the aqueous tap was positive for Herpes Simplex Virus (HSV – 1. Following therapy with intravenous Acyclovir, followed by oral Acyclovir and steroids, there was marked improvement in the visual acuity and clinical picture. At one week after initiation of treatment, Kyrieleis plaques were observed in the retinal arteries. They became more prominent despite resolution of the vitritis, retinal necrosis and vasculitis and persisted till six weeks of follow-up, when fluorescein angiography was performed. The appearance of this segmental retinal periarteritis also known as Kyrieleis plaques has not been described in ARN due to HSV-1 earlier.

  12. Hepatic Necrosis and Degenerative Myopathy Associated with Cassava Feeding in Pigs

    Directory of Open Access Journals (Sweden)

    Gloria Daniel-Igwe

    2014-01-01

    Full Text Available Forty-three deaths were recorded among pigs fed boiled cassava meal at a private piggery over a period of two years. There were signs of sudden death in some cases with blood exuding from the external nares, vomiting, muscular weakness and pain or reluctance to move, emaciation, and stunted growth. The necropsy lesions included skeletal and cardiac muscle degeneration and necrosis, icterus, hepatic necrosis, and oedema of the dependent parts. The deaths and clinical signs are thought to be due to a non cyanide toxic principle in cassava, possibly the coumarins (scopoletin, which is found in high levels in cassava diet even after heat treatment. Therefore, the use of proper processing technology to obtain cassava products of high quality is recommended.

  13. Renal papillary necrosis and pyelonephritis accompanying fenoprofen therapy.

    Science.gov (United States)

    Husserl, F E; Lange, R K; Kantrow, C M

    1979-10-26

    Renal papillary necrosis occurred after fenoprofen calcium administration in a patient with systemic lupus erythematosus and urinary tract infection. Possible mechanisms of renal damage may be hypersensitivity, decreased blood flow, and decreased production of a prostaglandin E-like substance.

  14. Acute esophageal necrosis and liver pathology, a rare combination

    Institute of Scientific and Technical Information of China (English)

    Amir Maqbul Khan; Rangit Hundal; Vijaya Ramaswamy; Mark Korsten; Sunil Dhuper

    2004-01-01

    Acute esophageal necrosis (AEN) or "black esophagus" is a clinical condition found at endoscopy. It is a rare entity the exact etiology of which remains unknown. We describe of liver cirrhosis and hepatic encephalopathy.

  15. The Link Between Oxidative Stress Response and Tumor Necrosis ...

    African Journals Online (AJOL)

    The Link Between Oxidative Stress Response and Tumor Necrosis Factor-Alpha ... Also, to investigate how this can affect normal hepatic tissues. ... A complex relationship exists between the thyroid gland and the liver in health and disease.

  16. Computerized tomography analysis of aceptic necrosis of the femoral head

    Energy Technology Data Exchange (ETDEWEB)

    Ichioka, Yoshiaki; Masuda, Takeshi; Matsuno, Takeo; Hasegawa, Isao; Sugano, Hiroki; Konno, Takushi.

    1988-03-01

    Computerized tomography (CT) findings of the normal femoral head in 14 patients with unilateral aceptic necrosis of the femoral head (ANF) and in healthy adults were analyzed for early diagnostic significance. CT appearance of the bone trabeculae fell into normal finding, diffuse sclerosis, and mottled sclerosis. The development of necrosis during the process was accompanied by diffuse sclerosis, suggesting that diffuse sclerosis is an early CT appearance in the case of ANF. In a three-dimensional quantification of the necrotic area for 20 patients before rotational osteotomy of the femoral head, deformation of the femoral head after the surgery was found to frequently result from 50 % or more of the necrotic area in the femoral head, irrespective of the size of necrosis on the surface of the femoral head. This suggested the influence of the three-dimensional spread of necrosis on the intensity of the femoral head. (Namekawa, K.).

  17. Skin and Neourethral Necrosis in Staged Hypospadias Repair

    OpenAIRE

    2016-01-01

    Complications in hypospadias surgery are not uncommon however penile skin or flap necrosis is rarely reported. Ischemia of the flap or graft is a major complication in two stage repair of hypospadias. A 2-year old boy with proximal penile hypospadias, operated earlier for chordee correction and urethral plate formation with a preputial flap, presented for stage 2 repair. Ten days after surgery patient developed skin and neourethral necrosis. Early debridement was done followed by coverage wit...

  18. Skin and Neourethral Necrosis in Staged Hypospadias Repair

    Directory of Open Access Journals (Sweden)

    Alireza Mirshemirani

    2016-05-01

    Full Text Available Complications in hypospadias surgery are not uncommon however penile skin or flap necrosis is rarely reported. Ischemia of the flap or graft is a major complication in two stage repair of hypospadias. A 2-year old boy with proximal penile hypospadias, operated earlier for chordee correction and urethral plate formation with a preputial flap, presented for stage 2 repair. Ten days after surgery patient developed skin and neourethral necrosis. Early debridement was done followed by coverage with scrotal flaps.

  19. Skin and Neourethral Necrosis in Staged Hypospadias Repair.

    Science.gov (United States)

    Mirshemirani, Alireza; Mahdavi, Alireza; Sarafi, Mehdi

    2016-01-01

    Complications in hypospadias surgery are not uncommon however penile skin or flap necrosis is rarely reported. Ischemia of the flap or graft is a major complication in two stage repair of hypospadias. A 2-year old boy with proximal penile hypospadias, operated earlier for chordee correction and urethral plate formation with a preputial flap, presented for stage 2 repair. Ten days after surgery patient developed skin and neourethral necrosis. Early debridement was done followed by coverage with scrotal flaps.

  20. Caseous Necrosis of Mitral Annulus: A Rare Cause of Stroke

    Directory of Open Access Journals (Sweden)

    Jérôme Corre

    2013-01-01

    Full Text Available The current report describes a rare case of a caseous necrosis presenting as a pseudotumor in ventricle, revealed by stroke. Cerebral MRI, showing multiples lacunes, evocates a cardioembolic mechanism. Transthoracic and transesophageal echocardiography demonstrate a large hyperechogenic mass fixed to the posterior mitral valve and annulus while thoracic tomography revealed a fully calcified lesion, at the mitral annulus, evocative of caseus necrosis. Medical therapy was preferred (anticoagulation, because of her age and the decaying nature of surgery.