WorldWideScience

Sample records for cardiac acoustic-radiation-force-driven shear

  1. Cardiac shear-wave elastography using a transesophageal transducer: application to the mapping of thermal lesions in ultrasound transesophageal cardiac ablation

    Science.gov (United States)

    Kwiecinski, Wojciech; Bessière, Francis; Constanciel Colas, Elodie; Apoutou N'Djin, W.; Tanter, Mickaël; Lafon, Cyril; Pernot, Mathieu

    2015-10-01

    Heart rhythm disorders, such as atrial fibrillation or ventricular tachycardia can be treated by catheter-based thermal ablation. However, clinically available systems based on radio-frequency or cryothermal ablation suffer from limited energy penetration and the lack of lesion’s extent monitoring. An ultrasound-guided transesophageal device has recently successfully been used to perform High-Intensity Focused Ultrasound (HIFU) ablation in targeted regions of the heart in vivo. In this study we investigate the feasibility of a dual therapy and imaging approach on the same transesophageal device. We demonstrate in vivo that quantitative cardiac shear-wave elastography (SWE) can be performed with the device and we show on ex vivo samples that transesophageal SWE can map the extent of the HIFU lesions. First, SWE was validated with the transesophageal endoscope in one sheep in vivo. The stiffness of normal atrial and ventricular tissues has been assessed during the cardiac cycle (n=11 ) and mapped (n= 7 ). Second, HIFU ablation has been performed with the therapy-imaging transesophageal device in ex vivo chicken breast samples (n  =  3), then atrial (left, n= 2 ) and ventricular (left n=1 , right n=1 ) porcine heart tissues. SWE provided stiffness maps of the tissues before and after ablation. Areas of the lesions were obtained by tissue color change with gross pathology and compared to SWE. During the cardiac cycle stiffness varied from 0.5   ±   0.1 kPa to 6.0   ±   0.3 kPa in the atrium and from 1.3   ±   0.3 kPa to 13.5   ±   9.1 kPa in the ventricles. The thermal lesions were visible on all SWE maps performed after ablation. Shear modulus of the ablated zones increased to 16.3   ±   5.5 kPa (versus 4.4   ±   1.6 kPa before ablation) in the chicken breast, to 30.3   ±   10.3 kPa (versus 12.2   ±   4.3 kPa) in the atria and to 73.8   ±   13

  2. Cardiac shear-wave elastography using a transesophageal transducer: application to the mapping of thermal lesions in ultrasound transesophageal cardiac ablation.

    Science.gov (United States)

    Kwiecinski, Wojciech; Bessière, Francis; Colas, Elodie Constanciel; N'Djin, W Apoutou; Tanter, Mickaël; Lafon, Cyril; Pernot, Mathieu

    2015-10-21

    Heart rhythm disorders, such as atrial fibrillation or ventricular tachycardia can be treated by catheter-based thermal ablation. However, clinically available systems based on radio-frequency or cryothermal ablation suffer from limited energy penetration and the lack of lesion's extent monitoring. An ultrasound-guided transesophageal device has recently successfully been used to perform High-Intensity Focused Ultrasound (HIFU) ablation in targeted regions of the heart in vivo. In this study we investigate the feasibility of a dual therapy and imaging approach on the same transesophageal device. We demonstrate in vivo that quantitative cardiac shear-wave elastography (SWE) can be performed with the device and we show on ex vivo samples that transesophageal SWE can map the extent of the HIFU lesions. First, SWE was validated with the transesophageal endoscope in one sheep in vivo. The stiffness of normal atrial and ventricular tissues has been assessed during the cardiac cycle (n = 11) and mapped (n = 7). Second, HIFU ablation has been performed with the therapy-imaging transesophageal device in ex vivo chicken breast samples (n  =  3), then atrial (left, n = 2) and ventricular (left n = 1, right n = 1) porcine heart tissues. SWE provided stiffness maps of the tissues before and after ablation. Areas of the lesions were obtained by tissue color change with gross pathology and compared to SWE. During the cardiac cycle stiffness varied from 0.5   ±   0.1 kPa to 6.0   ±   0.3 kPa in the atrium and from 1.3   ±   0.3 kPa to 13.5   ±   9.1 kPa in the ventricles. The thermal lesions were visible on all SWE maps performed after ablation. Shear modulus of the ablated zones increased to 16.3   ±   5.5 kPa (versus 4.4   ±   1.6 kPa before ablation) in the chicken breast, to 30.3   ±   10.3 kPa (versus 12.2   ±   4.3 kPa) in the atria and to 73.8

  3. Lateral shear interferometry with holo shear lens

    Science.gov (United States)

    Joenathan, C.; Mohanty, R. K.; Sirohi, R. S.

    1984-12-01

    A simple method for obtaining lateral shear using holo shear lenses (HSL) has been discussed. This simple device which produces lateral shears in the orthogonal directions has been used for lens testing. The holo shear lens is placed at or near the focus of the lens to be tested. It has also been shown that HSL can be used in speckle shear interferometry as it performs both the functions of shearing and imaging.

  4. Cardiac arrest

    Science.gov (United States)

    ... Article.jsp. Accessed June 16, 2014. Myerburg RJ, Castellanos A. Approach to cardiac arrest and life-threatening ... PA: Elsevier Saunders; 2011:chap 63. Myerburg RJ, Castellanos A. Cardiac arrest and audden aardiac death. In: ...

  5. Cardiac Malpositions

    Energy Technology Data Exchange (ETDEWEB)

    Yoo, Shi Joon; Im, Chung Gie; Yeon, Kyung Mo; Hasn, Man Chung [Seoul National University College of Medicine, Seoul (Korea, Republic of)

    1979-06-15

    Cardiac Malposition refers to any position of the heart other than a left-sided heart in a situs solitus individual. Associated cardiac malformations are so complex that even angiocardiographic and autopsy studies may not afford an accurate information. Although the terms and classifications used to describe the internal cardiac anatomy and their arterial connections in cardiac malpositions differ and tend to be confusing, common agreement exists on the need for a segmental approach to diagnosis. Authors present 18 cases of cardiac malpositions in which cardiac catheterization and angiocardiography were done at the Department of Radiology, Seoul National University Hospital between 1971 and 1979. Authors analyzed the clinical, radiographic, operative and autopsy findings with the emphasis on the angiocardiographic findings. The results are as follows: 1. Among 18 cases with cardiac malpositions, 6 cases had dextrocardia with situs inversus, 9 cases had dextrocardia with situs solitus and 3 cases had levocardia with situs inversus. 2. There was no genuine exception to visceroatrial concordance rule. 3. Associated cardiac malpositions were variable and complex with a tendency of high association of transposition and double outlet varieties with dextrocardia in situs solitus and levocardia in situs inversus. Only one in 6 cases of dextrocardia with situs inversus had pure transposition. 4. In two cases associated pulmonary atresia was found at surgery which was not predicted by angiocardiography. 5. Because many of the associated complex lesions can be corrected surgically provided the diagnosis is accurate, the selective biplane angiocardiography with or without cineradiography is essential.

  6. Cardiac rehabilitation

    Science.gov (United States)

    ... attack or other heart problem. You might consider cardiac rehab if you have had: Heart attack Coronary heart disease (CHD) Heart failure Angina (chest pain) Heart or heart valve surgery Heart transplant Procedures such as angioplasty and stenting In some ...

  7. Cardiac CT

    Energy Technology Data Exchange (ETDEWEB)

    Dewey, Marc [Charite - Universitaetsmedizin Berlin (Germany). Inst. fuer Radiologie

    2011-07-01

    Computed tomography of the heart has become a highly accurate diagnostic modality that is attracting increasing attention. This extensively illustrated book aims to assist the reader in integrating cardiac CT into daily clinical practice, while also reviewing its current technical status and applications. Clear guidance is provided on the performance and interpretation of imaging using the latest technology, which offers greater coverage, better spatial resolution, and faster imaging. The specific features of scanners from all four main vendors, including those that have only recently become available, are presented. Among the wide range of applications and issues to be discussed are coronary artery bypass grafts, stents, plaques, and anomalies, cardiac valves, congenital and acquired heart disease, and radiation exposure. Upcoming clinical uses of cardiac CT, such as plaque imaging and functional assessment, are also explored. (orig.)

  8. Cardiac echinococcosis

    Directory of Open Access Journals (Sweden)

    Ivanović-Krstić Branislava A.

    2002-01-01

    Full Text Available Cardiac hydatid disease is rare. We report on an uncommon hydatid cyst localized in the right ventricular wall, right atrial wall tricuspid valve left atrium and pericard. A 33-year-old woman was treated for cough, fever and chest pain. Cardiac echocardiograpic examination revealed a round tumor (5.8 x 4 cm in the right ventricular free wall and two smaller cysts behind that tumor. There were cysts in right atrial wall and tricuspidal valve as well. Serologic tests for hydatidosis were positive. Computed tomography finding was consistent with diagnosis of hydatid cyst in lungs and right hylar part. Surgical treatment was rejected due to great risk of cardiac perforation. Medical treatment with albendazole was unsuccessful and the patient died due to systemic hydatid involvement of the lungs, liver and central nervous system.

  9. Reduced shear power spectrum

    Energy Technology Data Exchange (ETDEWEB)

    Dodelson, Scott; /Fermilab /Chicago U., Astron. Astrophys. Ctr. /Northwestern U.; Shapiro, Charles; /Chicago U. /KICP, Chicago; White, Martin J.; /UC, Berkeley, Astron.

    2005-08-01

    Measurements of ellipticities of background galaxies are sensitive to the reduced shear, the cosmic shear divided by (1-{kappa}) where {kappa} is the projected density field. They compute the difference between shear and reduced shear both analytically and with simulations. The difference becomes more important an smaller scales, and will impact cosmological parameter estimation from upcoming experiments. A simple recipe is presented to carry out the required correction.

  10. In vivo wall shear measurements within the developing zebrafish heart.

    Directory of Open Access Journals (Sweden)

    R Aidan Jamison

    Full Text Available Physical forces can influence the embryonic development of many tissues. Within the cardiovascular system shear forces resulting from blood flow are known to be one of the regulatory signals that shape the developing heart. A key challenge in investigating the role of shear forces in cardiac development is the ability to obtain shear force measurements in vivo. Utilising the zebrafish model system we have developed a methodology that allows the shear force within the developing embryonic heart to be determined. Accurate wall shear measurement requires two essential pieces of information; high-resolution velocity measurements near the heart wall and the location and orientation of the heart wall itself. We have applied high-speed brightfield imaging to capture time-lapse series of blood flow within the beating heart between 3 and 6 days post-fertilization. Cardiac-phase filtering is applied to these time-lapse images to remove the heart wall and other slow moving structures leaving only the red blood cell movement. Using particle image velocimetry to calculate the velocity of red blood cells in different regions within the heart, and using the signal-to-noise ratio of the cardiac-phase filtered images to determine the boundary of blood flow, and therefore the position of the heart wall, we have been able to generate the necessary information to measure wall shear in vivo. We describe the methodology required to measure shear in vivo and the application of this technique to the developing zebrafish heart. We identify a reduction in shear at the ventricular-bulbar valve between 3 and 6 days post-fertilization and demonstrate that the shear environment of the ventricle during systole is constantly developing towards a more uniform level.

  11. [Cardiac amyloidosis].

    Science.gov (United States)

    Hoyer, Caroline; Angermann, Christiane E; Knop, Stefan; Ertl, Georg; Störk, Stefan

    2008-03-15

    Amyloidoses are a heterogeneous group of multisystem disorders, which are characterized by an extracellular deposition of amyloid fibrils. Typically affected are the heart, liver, kidneys, and nervous system. More than half of the patients die due to cardiac involvement. Clinical signs of cardiac amyloidosis are edema of the lower limbs, hepatomegaly, ascites and elevated jugular vein pressure, frequently in combination with dyspnea. There can also be chest pain, probably due to microvessel disease. Dysfunction of the autonomous nervous system or arrhythmias may cause low blood pressure, dizziness, or recurrent syncope. The AL amyloidosis caused by the deposition of immunoglobulin light chains is the most common form. It can be performed by monoclonal gammopathy. The desirable treatment therapy consists of high-dose melphalan therapy twice followed by autologous stem cell transplantation. Due to the high peritransplantation mortality, selection of appropriate patients is mandatory. The ATTR amyloidosis is an autosomal dominant disorder caused by the amyloidogenic form of transthyretin, a plasmaprotein that is synthesized in the liver. Therefore, liver transplantation is the only curative therapy. The symptomatic treatment of cardiac amyloidosis is based on the current guidelines for chronic heart failure according to the patient's New York Heart Association (NYHA) state. Further types of amyloidosis with possible cardiac involvement comprise the senile systemic amyloidosis caused by the wild-type transthyretin, secondary amyloidosis after chronic systemic inflammation, and the beta(2)-microglobulin amyloidosis after long-term dialysis treatment. PMID:18344065

  12. Cardiac rhabdomyosarcoma

    OpenAIRE

    Chlumský, Jaromír; Holá, Dana; Hlaváček, Karel; Michal, Michal; Švec, Alexander; Špatenka, Jaroslav; Dušek, Jan

    2001-01-01

    Cardiac sarcoma is a very rare neoplasm and is difficult to diagnose. The case of a 51-year-old man with a left atrial tumour, locally recurrent three months after its surgical removal, is presented. Computed tomography showed metastatic spread to the lung parenchyma. On revised histology, the mass extirpated was a sarcoma. Because of the metastatic spread, further therapy was symptomatic only; the patient died 15 months after the first manifestation of his problems. Immunohistochemical stain...

  13. Cross Shear Roll Bonding

    DEFF Research Database (Denmark)

    Bay, Niels; Bjerregaard, Henrik; Petersen, Søren. B;

    1994-01-01

    The present paper describes an investigation of roll bonding an AlZn alloy to mild steel. Application of cross shear roll bonding, where the two equal sized rolls run with different peripheral speed, is shown to give better bond strength than conventional roll bonding. Improvements of up to 20......-23% in bond strength are found and full bond strength is obtained at a reduction of 50% whereas 65% is required in case of conventional roll bonding. Pseudo cross shear roll bonding, where the cross shear effect is obtained by running two equal sized rolls with different speed, gives the same results....

  14. Cardiac MRI in Athletes

    NARCIS (Netherlands)

    Luijkx, T.

    2012-01-01

    Cardiac magnetic resonance imaging (CMR) is often used in athletes to image cardiac anatomy and function and is increasingly requested in the context of screening for pathology that can cause sudden cardiac death (SCD). In this thesis, patterns of cardiac adaptation to sports are investigated with C

  15. Shear-resistant behavior of light composite shear wall

    Institute of Scientific and Technical Information of China (English)

    李升才; 董毓利

    2015-01-01

    Shear test results for a composite wall panel in a light composite structure system are compared with test results for shear walls in Japan. The analysis results show that this kind of composite wall panel works very well, and can be regarded as a solid panel. The composite wall panel with a hidden frame is essential for bringing its effect on shear resistance into full play. Comprehensive analysis of the shear-resistant behavior of the composite wall panel suggests that the shear of the composite shear wall panel can be controlled by the cracking strength of the web shearing diagonal crack.

  16. Shear-Resistant Behavior Analysis of Light Composite Shear Walls

    Institute of Scientific and Technical Information of China (English)

    李升才; 江见鲸; 于庆荣

    2002-01-01

    Shear test results for a composite wall panel in a light composite structure system are compared with test results for shear walls in Japan in this paper. The analysis results show that this kind of composite wall panel works very well, and can be regarded as a solid panel. The composite wall panel with a hidden frame is essential for bringing its effect on shear resistance into full play. Comprehensive analysis of the shear-resistant behavior of the composite wall panel suggests that the shear of the composite shear wall panel can be controlled by the cracking strength of the web shearing diagonal crack.

  17. Cardiac MR Elastography: Comparison with left ventricular pressure measurement

    OpenAIRE

    Samani Abbas; Hamm Bernd; Schnorr Jörg; Kaufels Nikola; Laule Michael; Elgeti Thomas; Braun Jürgen; Sack Ingolf

    2009-01-01

    Abstract Purpose of study To compare magnetic resonance elastography (MRE) with ventricular pressure changes in an animal model. Methods Three pigs of different cardiac physiology (weight, 25 to 53 kg; heart rate, 61 to 93 bpm; left ventricular [LV] end-diastolic volume, 35 to 70 ml) were subjected to invasive LV pressure measurement by catheter and noninvasive cardiac MRE. Cardiac MRE was performed in a short-axis view of the heart and applying a 48.3-Hz shear-wave stimulus. Relative changes...

  18. Cardiac perception and cardiac control. A review.

    Science.gov (United States)

    Carroll, D

    1977-12-01

    The evidence regarding specific cardiac perception and discrimination, and its relationship to voluntary cardiac control, is critically reviewed. Studies are considered in three sections, depending on the method used to assess cardiac perception: questionnaire assessment, discrimination procedures, and heartbeat tracking. The heartbeat tracking procedure would appear to suffer least from interpretative difficulties. Recommendations are made regarding the style of analysis used to assess heartbeat perception in such tracking tasks. PMID:348240

  19. Free volume under shear

    Science.gov (United States)

    Maiti, Moumita; Vinutha, H. A.; Sastry, Srikanth; Heussinger, Claus

    2015-10-01

    Using an athermal quasistatic simulation protocol, we study the distribution of free volumes in sheared hard-particle packings close to, but below, the random-close packing threshold. We show that under shear, and independent of volume fraction, the free volumes develop features similar to close-packed systems — particles self-organize in a manner as to mimick the isotropically jammed state. We compare athermally sheared packings with thermalized packings and show that thermalization leads to an erasure of these structural features. The temporal evolution in particular the opening-up and the closing of free-volume patches is associated with the single-particle dynamics, showing a crossover from ballistic to diffusive behavior.

  20. Mixing through shear instabilities

    CERN Document Server

    Brüggen, M

    2000-01-01

    In this paper we present the results of numerical simulations of the Kelvin-Helmholtz instability in a stratified shear layer. This shear instability is believed to be responsible for extra mixing in differentially rotating stellar interiors and is the prime candidate to explain the abundance anomalies observed in many rotating stars. All mixing prescriptions currently in use are based on phenomenological and heuristic estimates whose validity is often unclear. Using three-dimensional numerical simulations, we study the mixing efficiency as a function of the Richardson number and compare our results with some semi-analytical formalisms of mixing.

  1. Development of conjugate shear bands during bulk simple shearing

    Science.gov (United States)

    Harris, L. B.; Cobbold, P. R.

    In rocks possessing a strong planar fabric, shear bands of constant shear sense and oriented at an oblique angle to the foliation are considered by many authors to be characteristic of a non-coaxial bulk deformation history, whereas conjugate shear bands are considered to indicate coaxial shortening. However, in two areas where bulk deformation history appears to be non-coaxial (Cap Corse, Corsica and Ile de Groix, Brittany), conjugate shear bands are observed. In order to investigate this problem, experiments were performed by bulk simple shearing using Plasticine as a rock analogue. When slip between layers of the model is permitted, shear bands of normal-fault geometry form with both the same and opposite shear sense as the bulk simple shearing at approximately the same angle with the layering (40°) irrespective of layer orientation in the undeformed state (for initial orientations of 50, 30 and 15°). Shear bands are initially formed within individual layers and may propagate across layer interfaces when further movement along these is inhibited. The existence of conjugate shear bands in Corsica and Ile de Groix is therefore not incompatible with a model of bulk simple shearing for these two regions. In field studies, one should perhaps exercise care in using shear bands to determine the kind of motion or the sense of bulk shearing.

  2. Sheared solid materials

    Indian Academy of Sciences (India)

    Akira Onuki; Akira Furukawa; Akihiko Minami

    2005-05-01

    We present a time-dependent Ginzburg–Landau model of nonlinear elasticity in solid materials. We assume that the elastic energy density is a periodic function of the shear and tetragonal strains owing to the underlying lattice structure. With this new ingredient, solving the equations yields formation of dislocation dipoles or slips. In plastic flow high-density dislocations emerge at large strains to accumulate and grow into shear bands where the strains are localized. In addition to the elastic displacement, we also introduce the local free volume . For very small the defect structures are metastable and long-lived where the dislocations are pinned by the Peierls potential barrier. However, if the shear modulus decreases with increasing , accumulation of around dislocation cores eventually breaks the Peierls potential leading to slow relaxations in the stress and the free energy (aging). As another application of our scheme, we also study dislocation formation in two-phase alloys (coherency loss) under shear strains, where dislocations glide preferentially in the softer regions and are trapped at the interfaces.

  3. Cardiac sodium channelopathies

    NARCIS (Netherlands)

    A.S. Amin; A. Asghari-Roodsari; H.L. Tan

    2010-01-01

    Cardiac sodium channel are protein complexes that are expressed in the sarcolemma of cardiomyocytes to carry a large inward depolarizing current (I-Na) during phase 0 of the cardiac action potential. The importance of I-Na for normal cardiac electrical activity is reflected by the high incidence of

  4. Diffuse infiltrative cardiac tuberculosis

    International Nuclear Information System (INIS)

    We present the cardiac magnetic resonance images of an unusual form of cardiac tuberculosis. Nodular masses in a sheet-like distribution were seen to infiltrate the outer myocardium and pericardium along most of the cardiac chambers. The lesions showed significant resolution on antitubercular therapy

  5. Shear Thinning of Noncolloidal Suspensions

    Science.gov (United States)

    Vázquez-Quesada, Adolfo; Tanner, Roger I.; Ellero, Marco

    2016-09-01

    Shear thinning—a reduction in suspension viscosity with increasing shear rates—is understood to arise in colloidal systems from a decrease in the relative contribution of entropic forces. The shear-thinning phenomenon has also been often reported in experiments with noncolloidal systems at high volume fractions. However its origin is an open theoretical question and the behavior is difficult to reproduce in numerical simulations where shear thickening is typically observed instead. In this letter we propose a non-Newtonian model of interparticle lubrication forces to explain shear thinning in noncolloidal suspensions. We show that hidden shear-thinning effects of the suspending medium, which occur at shear rates orders of magnitude larger than the range investigated experimentally, lead to significant shear thinning of the overall suspension at much smaller shear rates. At high particle volume fractions the local shear rates experienced by the fluid situated in the narrow gaps between particles are much larger than the averaged shear rate of the whole suspension. This allows the suspending medium to probe its high-shear non-Newtonian regime and it means that the matrix fluid rheology must be considered over a wide range of shear rates.

  6. Plasticity Approach to Shear Design

    DEFF Research Database (Denmark)

    Hoang, Cao Linh; Nielsen, Mogens Peter

    1998-01-01

    -shear reinforced beams as well as in lightly shear reinforced beams. For such beams the shear strength is determined by the recently developed crack sliding model. This model is based upon the hypothesis that cracks can be transformed into yield lines, which have lower sliding resistance than yield lines formed...

  7. Cardiac tumours in children

    Directory of Open Access Journals (Sweden)

    Parsons Jonathan M

    2007-03-01

    Full Text Available Abstract Cardiac tumours are benign or malignant neoplasms arising primarily in the inner lining, muscle layer, or the surrounding pericardium of the heart. They can be primary or metastatic. Primary cardiac tumours are rare in paediatric practice with a prevalence of 0.0017 to 0.28 in autopsy series. In contrast, the incidence of cardiac tumours during foetal life has been reported to be approximately 0.14%. The vast majority of primary cardiac tumours in children are benign, whilst approximately 10% are malignant. Secondary malignant tumours are 10–20 times more prevalent than primary malignant tumours. Rhabdomyoma is the most common cardiac tumour during foetal life and childhood. It accounts for more than 60% of all primary cardiac tumours. The frequency and type of cardiac tumours in adults differ from those in children with 75% being benign and 25% being malignant. Myxomas are the most common primary tumours in adults constituting 40% of benign tumours. Sarcomas make up 75% of malignant cardiac masses. Echocardiography, Computing Tomography (CT and Magnetic Resonance Imaging (MRI of the heart are the main non-invasive diagnostic tools. Cardiac catheterisation is seldom necessary. Tumour biopsy with histological assessment remains the gold standard for confirmation of the diagnosis. Surgical resection of primary cardiac tumours should be considered to relieve symptoms and mechanical obstruction to blood flow. The outcome of surgical resection in symptomatic, non-myxomatous benign cardiac tumours is favourable. Patients with primary cardiac malignancies may benefit from palliative surgery but this approach should not be recommended for patients with metastatic cardiac tumours. Surgery, chemotherapy and radiotherapy may prolong survival. The prognosis for malignant primary cardiac tumours is generally extremely poor.

  8. The Elemental Shear Dynamo

    CERN Document Server

    McWilliams, James C

    2011-01-01

    A quasi-linear theory is presented for how randomly forced, barotropic velocity fluctuations cause an exponentially-growing, large-scale (mean) magnetic dynamo in the presence of a uniform shear flow, $\\vec{U} = S x \\vec{e}_y$. It is a "kinematic" theory for the growth of the mean magnetic energy from a small initial seed, neglecting the saturation effects of the Lorentz force. The quasi-linear approximation is most broadly justifiable by its correspondence with computational solutions of nonlinear magneto-hydrodynamics, and it is rigorously derived in the limit of large resistivity, $\\eta \\rightarrow \\infty$. Dynamo action occurs even without mean helicity in the forcing or flow, but random helicity variance is then essential. In a sufficiently large domain and with small wavenumber $k_z$ in the direction perpendicular to the mean shearing plane, a positive exponential growth rate $\\gamma$ can occur for arbitrary values of $\\eta$, the viscosity $\

  9. Gelation under shear

    Energy Technology Data Exchange (ETDEWEB)

    Butler, B.D.; Hanley, H.J.M.; Straty, G.C. [National Institute of Standards and Technology, Boulder, CO (United States); Muzny, C.D. [Univ. of Colorado, Boulder, CO (United States)

    1995-12-31

    An experimental small angle neutron scattering (SANS) study of dense silica gels, prepared from suspensions of 24 nm colloidal silica particles at several volume fractions {theta} is discussed. Provided that {theta}{approx_lt}0.18, the scattered intensity at small wave vectors q increases as the gelation proceeds, and the structure factor S(q, t {yields} {infinity}) of the gel exhibits apparent power law behavior. Power law behavior is also observed, even for samples with {theta}>0.18, when the gel is formed under an applied shear. Shear also enhances the diffraction maximum corresponding to the inter-particle contact distance of the gel. Difficulties encountered when trying to interpret SANS data from these dense systems are outlined. Results of computer simulations intended to mimic gel formation, including computations of S(q, t), are discussed. Comments on a method to extract a fractal dimension characterizing the gel are included.

  10. Mixing in sheared suspensions

    Science.gov (United States)

    Souzy, Mathieu; Abid, Nora Cherifa; Villermaux, Emmanuel; Metzger, Bloen

    2015-11-01

    Mixing occurs spontaneously in sheared suspensions, even at low Reynolds number. Under flow, successive collisions between particles deviate the laminar streamlines, and thus induce disturbances in the fluid phase, which produce very efficient mixing. We measure fluid velocity fields by performing high spatial resolution PIV experiments within a sheared suspension, and we numerically advect isolated scalar filaments in the flow using Diffusive Strip Method. Stretching law parameters are measured from the elongation of the filaments, and are used to fully characterize the process. The deformation statistics are found to be well modeled by a Langevin equation with multiplicative noise, which can be coupled with diffusion to infer the probability density function of the concentration in the medium.

  11. Shear Behavior of Concrete Beams Reinforced with GFRP Shear Reinforcement

    Directory of Open Access Journals (Sweden)

    Heecheul Kim

    2015-01-01

    Full Text Available This paper presents the shear capacities of concrete beams reinforced with glass fiber reinforced polymer (GFRP plates as shear reinforcement. To examine the shear performance, we manufactured and tested a total of eight specimens. Test variables included the GFRP strip-width-to-spacing ratio and type of opening array. The specimen with a GFRP plate with a 3×2 opening array showed the highest shear strength. From the test results, the shear strength increased as the strip-width-to-strip-spacing ratio increased. Also, we used the experimental results to evaluate whether the shear strength equations of ACI 318-14 and ACI 440.1R can be applied to the design of GFRP shear reinforcement. In the results, the ACI 440 equation underestimated the experimental results more than that of ACI 318.

  12. Micromechanics of shear banding

    Energy Technology Data Exchange (ETDEWEB)

    Gilman, J.J.

    1992-08-01

    Shear-banding is one of many instabilities observed during the plastic flow of solids. It is a consequence of the dislocation mechanism which makes plastic flow fundamentally inhomogeneous, and is exacerbated by local adiabatic heating. Dislocation lines tend to be clustered on sets of neighboring glide planes because they are heterogeneously generated; especially through the Koehler multiple-cross-glide mechanism. Factors that influence their mobilities also play a role. Strain-hardening decreases the mobilities within shear bands thereby tending to spread (delocalize) them. Strain-softening has the inverse effect. This paper reviews the micro-mechanisms of these phenomena. It will be shown that heat production is also a consequence of the heterogeneous nature of the microscopic flow, and that dislocation dipoles play an important role. They are often not directly observable, but their presence may be inferred from changes in thermal conductivity. It is argued that after deformation at low temperatures dipoles are distributed a la Pareto so there are many more small than large ones. Instability at upper yield point, the shapes of shear-band fronts, and mechanism of heat generation are also considered. It is shown that strain-rate acceleration plays a more important role than strain-rate itself in adiabatic instability.

  13. Stimulating endogenous cardiac regeneration

    Directory of Open Access Journals (Sweden)

    Amanda eFinan

    2015-09-01

    Full Text Available The healthy adult heart has a low turnover of cardiac myocytes. The renewal capacity, however, is augmented after cardiac injury. Participants in cardiac regeneration include cardiac myocytes themselves, cardiac progenitor cells, and peripheral stem cells, particularly from the bone marrow compartment. Cardiac progenitor cells and bone marrow stem cells are augmented after cardiac injury, migrate to the myocardium, and support regeneration. Depletion studies of these populations have demonstrated their necessary role in cardiac repair. However, the potential of these cells to completely regenerate the heart is limited. Efforts are now being focused on ways to augment these natural pathways to improve cardiac healing, primarily after ischemic injury but in other cardiac pathologies as well. Cell and gene therapy or pharmacological interventions are proposed mechanisms. Cell therapy has demonstrated modest results and has passed into clinical trials. However, the beneficial effects of cell therapy have primarily been their ability to produce paracrine effects on the cardiac tissue and recruit endogenous stem cell populations as opposed to direct cardiac regeneration. Gene therapy efforts have focused on prolonging or reactivating natural signaling pathways. Positive results have been demonstrated to activate the endogenous stem cell populations and are currently being tested in clinical trials. A potential new avenue may be to refine pharmacological treatments that are currently in place in the clinic. Evidence is mounting that drugs such as statins or beta blockers may alter endogenous stem cell activity. Understanding the effects of these drugs on stem cell repair while keeping in mind their primary function may strike a balance in myocardial healing. To maximize endogenous cardiac regeneration,a combination of these approaches couldameliorate the overall repair process to incorporate the participation ofmultiple cell players.

  14. In vivo vascular wall shear rate and circumferential strain of renal disease patients.

    Science.gov (United States)

    Park, Dae Woo; Kruger, Grant H; Rubin, Jonathan M; Hamilton, James; Gottschalk, Paul; Dodde, Robert E; Shih, Albert J; Weitzel, William F

    2013-02-01

    This study measures the vascular wall shear rate at the vessel edge using decorrelation based ultrasound speckle tracking. Results for nine healthy and eight renal disease subjects are presented. Additionally, the vascular wall shear rate and circumferential strain during physiologic pressure, pressure equalization and hyperemia are compared for five healthy and three renal disease subjects. The mean and maximum wall shear rates were measured during the cardiac cycle at the top and bottom wall edges. The healthy subjects had significantly higher mean and maximum vascular wall shear rate than the renal disease subjects. The key findings of this research were that the mean vascular wall shear rates and circumferential strain changes between physiologic pressure and hyperemia that was significantly different between healthy and renal disease subjects.

  15. Front tracking for shear bands in an antiplane shear model

    International Nuclear Information System (INIS)

    In this paper we describe a numerical algorithm for the study of shear band, formation and growth in two-dimensional antiplane shear. The constitutive model uses a non-associative flow rule. The numerical scheme is based on a Godunov method for updating the velocity, while the stress is updated via integration along particle paths. The scheme is coupled with a front tracking algorithm for careful evolution of the shear bands. The main challenges are the non-hyperbolicity of the shear band formation and growth (front tracking avoids the catastrophic effects of the loss of hyperbolicity in the Godunov-type numerical scheme), the existence of endpoints for the shear band (the tracked front does not separate the computational domain into disconnected regions), and the non-hyperbolic rate of growth of the shear band. We give examples of the success of the algorithm and show convergence tests. 69 refs., 13 figs

  16. Marketing cardiac CT programs.

    Science.gov (United States)

    Scott, Jason

    2010-01-01

    There are two components of cardiac CT discussed in this article: coronary artery calcium scoring (CACS) and coronary computed tomography angiography (CCTA).The distinctive advantages of each CT examination are outlined. In order to ensure a successful cardiac CT program, it is imperative that imaging facilities market their cardiac CT practices effectively in order to gain a competitive advantage in this valuable market share. If patients receive quality care by competent individuals, they are more likely to recommend the facility's cardiac CT program. Satisfied patients will also be more willing to come back for any further testing.

  17. The Elemental Shear Dynamo

    OpenAIRE

    Mcwilliams, James C.

    2011-01-01

    A quasi-linear theory is presented for how randomly forced, barotropic velocity fluctuations cause an exponentially-growing, large-scale (mean) magnetic dynamo in the presence of a uniform shear flow, $\\vec{U} = S x \\vec{e}_y$. It is a "kinematic" theory for the growth of the mean magnetic energy from a small initial seed, neglecting the saturation effects of the Lorentz force. The quasi-linear approximation is most broadly justifiable by its correspondence with computational solutions of non...

  18. Shear strength of non-shear reinforced concrete elements

    DEFF Research Database (Denmark)

    Hoang, Cao linh

    1997-01-01

    The paper deals with the plastic shear strength of non shear reinforced T-beams.The influence of an un-reinforced flange on the shear capacity is investigated by considering a failure mechanism involving crack sliding in the web and a kind of membrane action over an effective width of the flange....... The position of the crack in which sliding takes place is determined by the crack sliding model developed by Jin-Ping Zhang. The theoretical calculations are compared with test results reported in the literature. A good agreement has been found.A simplified method to calculate the shear capacity of T...

  19. Wall shear stress indicators in abnormal aortic geometries

    Science.gov (United States)

    Prahl Wittberg, Lisa; van Wyk, Stevin; Fuchs, Laszlo; Gutmark, Ephraim; Gutmark-Little, Iris

    2015-11-01

    Cardiovascular disease, such as atherosclerosis, occurs at specific locations in the arterial tree. Characterizing flow and forces at these locations is crucial to understanding the genesis of disease. Measures such as time average wall shear stress, oscillatory shear index, relative residence time and temporal wall shear stress gradients have been shown to identify plaque prone regions. The present paper examines these indices in three aortic geometries obtained from patients whose aortas are deformed due to a genetic pathology and compared to one normal geometry. This patient group is known to be prone to aortic dissection and our study aims to identify early indicators that will enable timely intervention. Data obtained from cardiac magnetic resonance imaging is used to reconstruct the aortic arch. The local unsteady flow characteristics are calculated, fully resolving the flow field throughout the entire cardiac cycle. The Quemada model is applied to account for the non-Newtonian properties of blood, an empirical model valid for different red blood cell loading. The impact of the deformed aortic geometries is analyzed to identify flow patterns that could lead to arterial disease at certain locations.

  20. Inductive shearing of drilling pipe

    Energy Technology Data Exchange (ETDEWEB)

    Ludtka, Gerard M.; Wilgen, John; Kisner, Roger; Mcintyre, Timothy

    2016-04-19

    Induction shearing may be used to cut a drillpipe at an undersea well. Electromagnetic rings may be built into a blow-out preventer (BOP) at the seafloor. The electromagnetic rings create a magnetic field through the drillpipe and may transfer sufficient energy to change the state of the metal drillpipe to shear the drillpipe. After shearing the drillpipe, the drillpipe may be sealed to prevent further leakage of well contents.

  1. Shear viscosity of nuclear matter

    International Nuclear Information System (INIS)

    This paper reports my recent study[1] on the shear viscosity of neutron-rich nuclear matter from a relaxation time approach. An isospin- and momentum-dependent interaction is used in the study. Dependence of density, temperature, and isospin asymmetry of nuclear matter on its shear viscosity have been discussed. Similar to the symmetry energy, the symmetry shear viscosity is defined and its density and temperature dependence are studied. (authors)

  2. Mathematical cardiac electrophysiology

    CERN Document Server

    Colli Franzone, Piero; Scacchi, Simone

    2014-01-01

    This book covers the main mathematical and numerical models in computational electrocardiology, ranging from microscopic membrane models of cardiac ionic channels to macroscopic bidomain, monodomain, eikonal models and cardiac source representations. These advanced multiscale and nonlinear models describe the cardiac bioelectrical activity from the cell level to the body surface and are employed in both the direct and inverse problems of electrocardiology. The book also covers advanced numerical techniques needed to efficiently carry out large-scale cardiac simulations, including time and space discretizations, decoupling and operator splitting techniques, parallel finite element solvers. These techniques are employed in 3D cardiac simulations illustrating the excitation mechanisms, the anisotropic effects on excitation and repolarization wavefronts, the morphology of electrograms in normal and pathological tissue and some reentry phenomena. The overall aim of the book is to present rigorously the mathematica...

  3. Biomaterials for cardiac regeneration

    CERN Document Server

    Ruel, Marc

    2015-01-01

    This book offers readers a comprehensive biomaterials-based approach to achieving clinically successful, functionally integrated vasculogenesis and myogenesis in the heart. Coverage is multidisciplinary, including the role of extracellular matrices in cardiac development, whole-heart tissue engineering, imaging the mechanisms and effects of biomaterial-based cardiac regeneration, and autologous bioengineered heart valves. Bringing current knowledge together into a single volume, this book provides a compendium to students and new researchers in the field and constitutes a platform to allow for future developments and collaborative approaches in biomaterials-based regenerative medicine, even beyond cardiac applications. This book also: Provides a valuable overview of the engineering of biomaterials for cardiac regeneration, including coverage of combined biomaterials and stem cells, as well as extracellular matrices Presents readers with multidisciplinary coverage of biomaterials for cardiac repair, including ...

  4. Bayesian Lensing Shear Measurement

    CERN Document Server

    Bernstein, Gary M

    2013-01-01

    We derive an estimator of weak gravitational lensing shear from background galaxy images that avoids noise-induced biases through a rigorous Bayesian treatment of the measurement. The Bayesian formalism requires a prior describing the (noiseless) distribution of the target galaxy population over some parameter space; this prior can be constructed from low-noise images of a subsample of the target population, attainable from long integrations of a fraction of the survey field. We find two ways to combine this exact treatment of noise with rigorous treatment of the effects of the instrumental point-spread function and sampling. The Bayesian model fitting (BMF) method assigns a likelihood of the pixel data to galaxy models (e.g. Sersic ellipses), and requires the unlensed distribution of galaxies over the model parameters as a prior. The Bayesian Fourier domain (BFD) method compresses galaxies to a small set of weighted moments calculated after PSF correction in Fourier space. It requires the unlensed distributi...

  5. [Cardiac evaluation before non-cardiac surgery].

    Science.gov (United States)

    Menzenbach, Jan; Boehm, Olaf

    2016-07-01

    Before non-cardiac surgery, evaluation of cardiac function is no frequent part of surgical treatment. European societies of anesthesiology and cardiology published consensus-guidelines in 2014 to present a reasonable approach for preoperative evaluation. This paper intends to differentiate the composite of perioperative risk and to display the guidelines methodical approach to handle it. Features to identify patients at risk from an ageing population with comorbidities, are the classification of surgical risk, functional capacity and risk indices. Application of diagnostic means, should be used adjusted to this risk estimation. Cardiac biomarkers are useful to discover risk of complications or mortality, that cannot be assessed by clinical signs. After preoperative optimization and perioperative cardiac protection, the observation of the postoperative period remains, to prohibit complications or even death. In consideration of limited resources of intensive care department, postoperative ward rounds beyond intensive care units are considered to be an appropriate instrument to avoid or recognize complications early to reduce postoperative mortality. PMID:27479258

  6. A Piezoelectric Shear Stress Sensor

    Science.gov (United States)

    Kim, Taeyang; Saini, Aditya; Kim, Jinwook; Gopalarathnam, Ashok; Zhu, Yong; Palmieri, Frank L.; Wohl, Christopher J.; Jiang, Xiaoning

    2016-01-01

    In this paper, a piezoelectric sensor with a floating element was developed for shear stress measurement. The piezoelectric sensor was designed to detect the pure shear stress suppressing effects of normal stress generated from the vortex lift-up by applying opposite poling vectors to the: piezoelectric elements. The sensor was first calibrated in the lab by applying shear forces and it showed high sensitivity to shear stress (=91.3 +/- 2.1 pC/Pa) due to the high piezoelectric coefficients of PMN-33%PT (d31=-1330 pC/N). The sensor also showed almost no sensitivity to normal stress (less than 1.2 pC/Pa) because of the electromechanical symmetry of the device. The usable frequency range of the sensor is 0-800 Hz. Keywords: Piezoelectric sensor, shear stress, floating element, electromechanical symmetry

  7. Cardiac metabolism and arrhythmias

    OpenAIRE

    Barth, Andreas S.; Tomaselli, Gordon F.

    2009-01-01

    Sudden cardiac death remains a leading cause of mortality in the Western world, accounting for up to 20% of all deaths in the U.S.1, 2 The major causes of sudden cardiac death in adults age 35 and older are coronary artery disease (70–80%) and dilated cardiomyopathy (10–15%).3 At the molecular level, a wide variety of mechanisms contribute to arrhythmias that cause sudden cardiac death, ranging from genetic predisposition (rare mutations and common polymorphisms in ion channels and structural...

  8. Comprehensive cardiac rehabilitation

    DEFF Research Database (Denmark)

    Kruse, Marie; Hochstrasser, Stefan; Zwisler, Ann-Dorthe O;

    2006-01-01

    OBJECTIVES: The costs of comprehensive cardiac rehabilitation are established and compared to the corresponding costs of usual care. The effect on health-related quality of life is analyzed. METHODS: An unprecedented and very detailed cost assessment was carried out, as no guidelines existed...... and may be as high as euro 1.877. CONCLUSIONS: Comprehensive cardiac rehabilitation is more costly than usual care, and the higher costs are not outweighed by a quality of life gain. Comprehensive cardiac rehabilitation is, therefore, not cost-effective....

  9. Cardiac Risk Assessment

    Science.gov (United States)

    ... to assess cardiac risk include: High-sensitivity C-reactive protein (hs-CRP) : Studies have shown that measuring ... LDL-C but does not respond to typical strategies to lower LDL-C such as diet, exercise, ...

  10. Sudden Cardiac Arrest

    Science.gov (United States)

    ... Heart Risk Factors & Prevention Heart Diseases & Disorders Atrial Fibrillation (AFib) Sudden Cardiac Arrest (SCA) SCA: Who's At Risk? Prevention of SCA What Causes SCA? SCA Awareness Atrial Flutter Heart Block Heart Failure Sick Sinus Syndrome Substances & Heart Rhythm Disorders Symptoms & ...

  11. Socially differentiated cardiac rehabilitation

    DEFF Research Database (Denmark)

    Meillier, Lucette Kirsten; Nielsen, Kirsten Melgaard; Larsen, Finn Breinholt;

    2012-01-01

    to a standard rehabilitation programme (SRP). If patients were identified as socially vulnerable, they were offered an extended version of the rehabilitation programme (ERP). Excluded patients were offered home visits by a cardiac nurse. Concordance principles were used in the individualised programme elements......%. Patients were equally distributed to the SRP and the ERP. No inequality was found in attendance and adherence among referred patients. Conclusions: It seems possible to overcome unequal referral, attendance, and adherence in cardiac rehabilitation by organisation of systematic screening and social......Aim: The comprehensive cardiac rehabilitation (CR) programme after myocardial infarction (MI) improves quality of life and results in reduced cardiac mortality and recurrence of MI. Hospitals worldwide face problems with low participation rates in rehabilitation programmes. Inequality...

  12. Cardiac arrest - cardiopulmonary resuscitation

    Institute of Scientific and Technical Information of China (English)

    Basri Lenjani; Besnik Elshani; Nehat Baftiu; Kelmend Pallaska; Kadir Hyseni; Njazi Gashi; Nexhbedin Karemani; Ilaz Bunjaku; Taxhidin Zaimi; Arianit Jakupi

    2014-01-01

    Objective:To investigate application of cardiopulmonary resuscitation(CPR) measures within the golden minutes inEurope.Methods:The material was taken from theUniversityClinical Center ofKosovo -EmergencyCentre inPristina, during the two(2) year period(2010-2011).The collected date belong to the patients with cardiac arrest have been recorded in the patients' log book protocol at the emergency clinic.Results:During the2010 to2011 in the emergency center of theCUCK inPristina have been treated a total of269 patients with cardiac arrest, of whom159 or59.1% have been treated in2010, and110 patients or40.9% in2011.Of the269 patients treated in the emergency centre,93 or34.6% have exited lethally in the emergency centre, and176 or 65.4% have been transferred to other clinics.In the total number of patients with cardiac arrest, males have dominated with186 cases, or69.1%.The average age of patients included in the survey was56.7 year oldSD±16.0 years.Of the269 patients with cardiac arrest, defibrillation has been applied for93 or34.6% of patients.In the outpatient settings defibrillation has been applied for3 or3.2% of patients.Patients were defibrillated with application of one to four shocks. Of27 cases with who have survived cardiac arrest, none of them have suffered cardiac arrest at home,3 or11.1% of them have suffered cardiac arrest on the street, and24 or88.9% of them have suffered cardiac arrest in the hospital.5 out of27 patients survived have ended with neurological impairment.Cardiac arrest cases were present during all days of the week, but frequently most reported cases have been onMonday with32.0% of cases, and onFriday with24.5% of cases. Conclusions:All survivors from cardiac arrest have received appropriate medical assistance within10 min from attack, which implies that if cardiac arrest occurs near an institution health care(with an opportunity to provide the emergent health care) the rate of survival is higher.

  13. Awareness in cardiac anesthesia.

    LENUS (Irish Health Repository)

    Serfontein, Leon

    2010-02-01

    Cardiac surgery represents a sub-group of patients at significantly increased risk of intraoperative awareness. Relatively few recent publications have targeted the topic of awareness in this group. The aim of this review is to identify areas of awareness research that may equally be extrapolated to cardiac anesthesia in the attempt to increase understanding of the nature and significance of this scenario and how to reduce it.

  14. Cardiac rehabilitation in Germany.

    Science.gov (United States)

    Karoff, Marthin; Held, Klaus; Bjarnason-Wehrens, Birna

    2007-02-01

    The purpose of this review is to give an overview of the rehabilitation measures provided for cardiac patients in Germany and to outline its legal basis and outcomes. In Germany the cardiac rehabilitation system is different from rehabilitation measures in other European countries. Cardiac rehabilitation in Germany since 1885 is based on specific laws and the regulations of insurance providers. Cardiac rehabilitation has predominantly been offered as an inpatient service, but has recently been complemented by outpatient services. A general agreement on the different indications for offering these two services has yet to be reached. Cardiac rehabilitation is mainly offered after an acute cardiac event and bypass surgery. It is also indicated in severe heart failure and special cases of percutaneous coronary intervention. Most patients are men (>65%) and the age at which events occur is increasing. The benefits obtained during the 3-4 weeks after an acute event, and confirmed in numerous studies, are often later lost under 'usual care' conditions. Many attempts have been made by rehabilitation institutions to improve this deficit by providing intensive aftercare. One instrument set up to achieve this is the nationwide institution currently comprising more than 6000 heart groups with approximately 120000 outpatients. After coronary artery bypass grafting or acute coronary syndrome cardiac rehabilitation can usually be started within 10 days. The multidisciplinary rehabilitation team consists of cardiologists, psychologists, exercise therapists, social workers, nutritionists and nurses. The positive effects of cardiac rehabilitation are also important economically, for example, for the improvement of secondary prevention and vocational integration. PMID:17301623

  15. Cardiac tumours in infancy

    OpenAIRE

    Yadava, O.P.

    2012-01-01

    Cardiac tumours in infancy are rare and are mostly benign with rhabdomyomas, fibromas and teratomas accounting for the majority. The presentation depends on size and location of the mass as they tend to cause cavity obstruction or arrhythmias. Most rhabdomyomas tend to regress spontaneously but fibromas and teratomas generally require surgical intervention for severe haemodynamic or arrhythmic complications. Other relatively rare cardiac tumours too are discussed along with an Indian perspect...

  16. Infected cardiac hydatid cyst

    OpenAIRE

    Ceviz, M; Becit, N; Kocak, H.

    2001-01-01

    A 24 year old woman presented with chest pain and palpitation. The presence of a semisolid mass—an echinococcal cyst or tumour—in the left ventricular apex was diagnosed by echocardiography, computed tomography, and magnetic resonance imaging. The infected cyst was seen at surgery. The cyst was removed successfully by using cardiopulmonary bypass with cross clamp.


Keywords: cardiac hydatid cyst; infected cardiac hydatid cyst

  17. Shear Profiles and Velocity Distribution in Dense Shear Granular Flow

    Institute of Scientific and Technical Information of China (English)

    WANG Deng-Ming; ZHOU You-He

    2009-01-01

    We perform DEM simulations to investigate the influence of the packing fraction γ on the,shape of mean tan-gential velocity profile in a 2D annular dense shear granular flow. There is a critical packing fraction γc. For γ < γc, the mean tangential velocity profile shows a roughly exponential decay from the shearing boundary and is almost invariant to the imposed shear rate. However, for γ γc, the tangential velocity profile exhibits a rate-dependence feature and changes from linear to nonlinear gradually with the increasing shear rate. Fhrther-more, the distributions of normalized tangential velocities at different positions along radial direction exhibit the Gaussian or the composite Gaussian distributing features.

  18. Improvement of Shear Wave Motion Detection Using Harmonic Imaging in Healthy Human Liver.

    Science.gov (United States)

    Amador, Carolina; Song, Pengfei; Meixner, Duane D; Chen, Shigao; Urban, Matthew W

    2016-05-01

    Quantification of liver elasticity is a major application of shear wave elasticity imaging (SWEI) to non-invasive assessment of liver fibrosis stages. SWEI measurements can be highly affected by ultrasound image quality. Ultrasound harmonic imaging has exhibited a significant improvement in ultrasound image quality as well as for SWEI measurements. This was previously illustrated in cardiac SWEI. The purpose of this study was to evaluate liver shear wave particle displacement detection and shear wave velocity (SWV) measurements with fundamental and filter-based harmonic ultrasound imaging. In a cohort of 17 patients with no history of liver disease, a 2.9-fold increase in maximum shear wave displacement, a 0.11 m/s decrease in the overall interquartile range and median SWV and a 17.6% increase in the success rate of SWV measurements were obtained when filter-based harmonic imaging was used instead of fundamental imaging. PMID:26803391

  19. Cardiac applications of optogenetics.

    Science.gov (United States)

    Ambrosi, Christina M; Klimas, Aleksandra; Yu, Jinzhu; Entcheva, Emilia

    2014-08-01

    In complex multicellular systems, such as the brain or the heart, the ability to selectively perturb and observe the response of individual components at the cellular level and with millisecond resolution in time, is essential for mechanistic understanding of function. Optogenetics uses genetic encoding of light sensitivity (by the expression of microbial opsins) to provide such capabilities for manipulation, recording, and control by light with cell specificity and high spatiotemporal resolution. As an optical approach, it is inherently scalable for remote and parallel interrogation of biological function at the tissue level; with implantable miniaturized devices, the technique is uniquely suitable for in vivo tracking of function, as illustrated by numerous applications in the brain. Its expansion into the cardiac area has been slow. Here, using examples from published research and original data, we focus on optogenetics applications to cardiac electrophysiology, specifically dealing with the ability to manipulate membrane voltage by light with implications for cardiac pacing, cardioversion, cell communication, and arrhythmia research, in general. We discuss gene and cell delivery methods of inscribing light sensitivity in cardiac tissue, functionality of the light-sensitive ion channels within different types of cardiac cells, utility in probing electrical coupling between different cell types, approaches and design solutions to all-optical electrophysiology by the combination of optogenetic sensors and actuators, and specific challenges in moving towards in vivo cardiac optogenetics.

  20. Shear Banding of Complex Fluids

    Science.gov (United States)

    Divoux, Thibaut; Fardin, Marc A.; Manneville, Sebastien; Lerouge, Sandra

    2016-01-01

    Even in simple geometries, many complex fluids display nontrivial flow fields, with regions where shear is concentrated. The possibility for such shear banding has been known for several decades, but in recent years, we have seen an upsurge in studies offering an ever-more precise understanding of the phenomenon. The development of new techniques to probe the flow on multiple scales with increasing spatial and temporal resolution has opened the possibility for a synthesis of the many phenomena that could only have been thought of separately before. In this review, we bring together recent research on shear banding in polymeric and soft glassy materials and highlight their similarities and disparities.

  1. SEDflume - High Shear Stress Flume

    Data.gov (United States)

    Federal Laboratory Consortium — The U.S. Army Corps of Engineers High Shear Stress flume (SEDflume) is designed for estimating erosion rates of fine-grained and mixed fine/coarse grained sediments...

  2. Grafted polymer under shear flow

    Science.gov (United States)

    Kumar, Sanjiv; Foster, Damien P.; Giri, Debaprasad; Kumar, Sanjay

    2016-04-01

    A self-attracting-self-avoiding walk model of polymer chain on a square lattice has been used to gain an insight into the behaviour of a polymer chain under shear flow in a slit of width L. Using exact enumeration technique, we show that at high temperature, the polymer acquires the extended state continuously increasing with shear stress. However, at low temperature the polymer exhibits two transitions: a transition from the coiled to the globule state and a transition to a stem-flower like state. For a chain of finite length, we obtained the exact monomer density distributions across the layers at different temperatures. The change in density profile with shear stress suggests that the polymer under shear flow can be used as a molecular gate with potential application as a sensor.

  3. Shear Banding of Complex Fluids

    OpenAIRE

    Divoux, Thibaut; Fardin, Marc-Antoine; Manneville, Sebastien; Lerouge, Sandra

    2015-01-01

    Even in simple geometries many complex fluids display non-trivial flow fields, with regions where shear is concentrated. The possibility for such shear banding has been known since several decades, but the recent years have seen an upsurge of studies offering an ever more precise understanding of the phenomenon. The development of new techniques to probe the flow on multiple scales and with increasing spatial and temporal resolution has opened the possibility for a synthesis of the many pheno...

  4. Estimation of the shear stress on the surface of an aortic valve leaflet.

    Science.gov (United States)

    Weston, M W; LaBorde, D V; Yoganathan, A P

    1999-01-01

    The limited durability of xenograft heart valves and the limited supply of allografts have sparked interest in tissue engineered replacement valves. A bioreactor for tissue engineered valves must operate at conditions that optimize the biosynthetic abilities of seeded cells while promoting their adherence to the leaflet matrix. An important parameter is shear stress, which is known to influence cellular behavior and may thus be crucial in bioreactor optimization. Therefore, an accurate estimate of the shear stress on the leaflet surface would not only improve our understanding of the mechanical environment of aortic valve leaflets, but it would also aid in bioreactor design. To estimate the shear stress on the leaflet surface, two-component laser-Doppler velocimetry measurements have been conducted inside a transparent polyurethane valve with a trileaflet structure similar to the native aortic valve. Steady flow rates of 7.5, 15.0, and 22.5 L/min were examined to cover the complete range possible during the cardiac cycle. The laminar shear stresses were calculated by linear regression of four axial velocity measurements near the surface of the leaflet. The maximum shear stress recorded was 79 dyne/cm2, in agreement with boundary layer theory and previous experimental and computational studies. This study has provided a range of shear stresses to be explored in bioreactor design and has defined a maximum shear stress at which cells must remain adherent upon a tissue engineered construct.

  5. Experimental observation of shear thickening oscillation

    DEFF Research Database (Denmark)

    Nagahiro, Shin-ichiro; Nakanishi, Hiizu; Mitarai, Namiko

    2013-01-01

    We report experimental observations of the shear thickening oscillation, i.e. the spontaneous macroscopic oscillation in the shear flow of severe shear thickening fluid. Using a density-matched starch-water mixture, in the cylindrical shear flow of a few centimeters flow width, we observed that w...

  6. Pediatric cardiac postoperative care

    Directory of Open Access Journals (Sweden)

    Auler Jr. José Otávio Costa

    2002-01-01

    Full Text Available The Heart Institute of the University of São Paulo, Medical School is a referral center for the treatment of congenital heart diseases of neonates and infants. In the recent years, the excellent surgical results obtained in our institution may be in part due to modern anesthetic care and to postoperative care based on well-structured protocols. The purpose of this article is to review unique aspects of neonate cardiovascular physiology, the impact of extracorporeal circulation on postoperative evolution, and the prescription for pharmacological support of acute cardiac dysfunction based on our cardiac unit protocols. The main causes of low cardiac output after surgical correction of heart congenital disease are reviewed, and methods of treatment and support are proposed as derived from the relevant literature and our protocols.

  7. The cardiac anxiety questionnaire: cross-validation among cardiac inpatients

    NARCIS (Netherlands)

    Beek, M.H. van; Oude Voshaar, R.C.; Deelen, F.M. van; Balkom, A.J. van; Pop, G.A.; Speckens, A.E.

    2012-01-01

    OBJECTIVE: General anxiety symptoms are common in patients with cardiac disease and considered to have an adverse effect on cardiac prognosis. The role of specific cardiac anxiety, however, is still unknown. The aim of this study is to examine the factor structure, reliability, and validity of the D

  8. THE CARDIAC ANXIETY QUESTIONNAIRE : CROSS-VALIDATION AMONG CARDIAC INPATIENTS

    NARCIS (Netherlands)

    van Beek, M. H. C. T.; Voshaar, R. C. Oude; van Deelen, F. M.; van Balkom, A. J. L. M.; Pop, G.; Speckens, A. E. M.

    2012-01-01

    Objective: General anxiety symptoms are common in patients with cardiac disease and considered to have an adverse effect on cardiac prognosis. The role of specific cardiac anxiety, however, is still unknown. The aim of this study is to examine the factor structure, reliability, and validity of the D

  9. Giant Cardiac Cavernous Hemangioma.

    Science.gov (United States)

    Unger, Eric; Costic, Joseph; Laub, Glenn

    2015-07-01

    We report the case of an asymptomatic giant cardiac cavernous hemangioma in a 71-year-old man. The intracardiac mass was discovered incidentally during surveillance for his prostate cancer; however, the patient initially declined intervention. On presentation to our institution 7 years later, the lesion had enlarged significantly, and the patient consented to excision. At surgery, an 8 × 6.5 × 4.8 cm intracardiac mass located on the inferior heart border was excised with an intact capsule through a median sternotomy approach. The patient had an uneventful postoperative course. We discuss the diagnostic workup, treatment, and characteristics of this rare cardiac tumor. PMID:26140782

  10. Bicontinuous Microemulsions under Steady Shear Flow

    OpenAIRE

    Kodama, Hiroya; Komura, Shigeyuki

    1997-01-01

    Dynamic response of microemulsions to shear deformation on the basis of two-order-parameter time dependent Ginzburg-Landau model is investigated by means of cell dynamical system approach. Time evolution of anisotropic factor and excess shear stress under steady shear flow is studied by changing shear rate and total amount of surfactant. As the surfactant concentration is increased, overshoot peak height of the anisotropic factor increases whereas that of the excess shear stress is almost unc...

  11. Perioperative management of cardiac disease.

    Science.gov (United States)

    Aresti, N A; Malik, A A; Ihsan, K M; Aftab, S M E; Khan, W S

    2014-01-01

    Pre-existing cardiac disease contributes significantly to morbidity and mortality amongst patients undergoing non cardiac surgery. Patients with pre-existing cardiac disease or with risk factors for it, have as much as a 3.9% risk of suffering a major perioperative cardiac event (Lee et al 1999, Devereaux 2005). Furthermore, the incidence of perioperative myocardial infarction (MI) is increased 10 to 50 fold in patients with previous coronary events (Jassal 2008).

  12. The cardiac malpositions.

    Science.gov (United States)

    Perloff, Joseph K

    2011-11-01

    Dextrocardia was known in the 17th century and was 1 of the first congenital malformations of the heart to be recognized. Fifty years elapsed before Matthew Baillie published his account of complete transposition in a human of the thoracic and abdominal viscera to the opposite side from what is natural. In 1858, Thomas Peacock stated that "the heart may be congenitally misplaced in various ways, occupying either an unusual position within the thorax, or being situated external to that cavity." In 1915, Maude Abbott described ectopia cordis, and Richard Paltauf's remarkable illustrations distinguished the various types of dextrocardia. In 1928, the first useful classification of the cardiac malpositions was proposed, and in 1966, Elliott et al's radiologic classification set the stage for clinical recognition. The first section of this review deals with the 3 basic cardiac malpositions in the presence of bilateral asymmetry. The second section deals with cardiac malpositions in the presence of bilateral left-sidedness or right-sidedness. Previous publications on cardiac malpositions are replete with an arcane vocabulary that confounds rather than clarifies. Even if the terms themselves are understood, inherent complexity weighs against clarity. This review was designed as a guided tour of an unfamiliar subject.

  13. Hepato-cardiac disorders

    Institute of Scientific and Technical Information of China (English)

    Yasser; Mahrous; Fouad; Reem; Yehia

    2014-01-01

    Understanding the mutual relationship between the liver and the heart is important for both hepatologists and cardiologists. Hepato-cardiac diseases can be classified into heart diseases affecting the liver, liver diseases affecting the heart, and conditions affecting the heart and the liver at the same time. Differential diagnoses of liver injury are extremely important in a cardiologist’s clinical practice calling for collaboration between cardiologists and hepatologists due to the many other diseases that can affect the liver and mimic haemodynamic injury. Acute and chronic heart failure may lead to acute ischemic hepatitis or chronic congestive hepatopathy. Treatment in these cases should be directed to the primary heart disease. In patients with advanced liver disease, cirrhotic cardiomyopathy may develop including hemodynamic changes, diastolic and systolic dysfunctions, reduced cardiac performance and electrophysiological abnormalities. Cardiac evaluation is important for patients with liver diseases especially before and after liver transplantation. Liver transplantation may lead to the improvement of all cardiac changes and the reversal of cirrhotic cardiomyopathy. There are systemic diseases that may affect both the liver and the heart concomitantly including congenital, metabolic and inflammatory diseases as well as alcoholism. This review highlights these hepatocardiac diseases

  14. Cardiac effects of vasopressin.

    Science.gov (United States)

    Pelletier, Jean-Sébastien; Dicken, Bryan; Bigam, David; Cheung, Po-Yin

    2014-07-01

    Vasopressin is an essential hormone involved in the maintenance of cardiovascular homeostasis. It has been in use therapeutically for many decades, with an emphasis on its vasoconstrictive and antidiuretic properties. However, this hormone has a ubiquitous influence and has specific effects on the heart. Although difficult to separate from its powerful vascular effects in the clinical setting, a better understanding of vasopressin's direct cardiac effects could lead to its more effective clinical use for a variety of shock states by maximizing its therapeutic benefit. The cardiac-specific effects of vasopressin are complex and require further elucidation. Complicating our understanding include the various receptors and secondary messengers involved in vasopressin's effects, which may lead to various results based on differing doses and varying environmental conditions. Thus, there have been contradictory reports on vasopressin's action on the coronary vasculature and on its effect on inotropy. However, beneficial results have been found and warrant further study to expand the potential therapeutic role of vasopressin. This review outlines the effect of vasopressin on the coronary vasculature, cardiac contractility, and on hypertrophy and cardioprotection. These cardiac-specific effects of vasopressin represent an interesting area for further study for potentially important therapeutic benefits. PMID:24621650

  15. Cardiac potassium channel subtypes

    DEFF Research Database (Denmark)

    Schmitt, Nicole; Grunnet, Morten; Olesen, Søren-Peter

    2014-01-01

    About 10 distinct potassium channels in the heart are involved in shaping the action potential. Some of the K(+) channels are primarily responsible for early repolarization, whereas others drive late repolarization and still others are open throughout the cardiac cycle. Three main K(+) channels...

  16. Cardiac pacemaker power sources

    International Nuclear Information System (INIS)

    A review of chemical and radioisotope batteries used in cardiac pacemakers is presented. The battery systems are examined in terms of longevity, reliability, cost, size and shape, energy density, weight, internal resistance versus time, end-of-life voltage, chemical compatibility, and potential failure mechanisms

  17. Grouted Connections with Shear Keys

    DEFF Research Database (Denmark)

    Pedersen, Ronnie; Jørgensen, M. B.; Damkilde, Lars;

    2012-01-01

    This paper presents a finite element model in the software package ABAQUS in which a reliable analysis of grouted pile-to-sleeve connections with shear keys is the particular purpose. The model is calibrated to experimental results and a consistent set of input parameters is estimated so that dif......This paper presents a finite element model in the software package ABAQUS in which a reliable analysis of grouted pile-to-sleeve connections with shear keys is the particular purpose. The model is calibrated to experimental results and a consistent set of input parameters is estimated so...

  18. Shear loading of costal cartilage

    CERN Document Server

    Subit, Damien

    2014-01-01

    A series of tests were performed on a single post-mortem human subject at various length scales. First, tabletop tests were performed. Next, the ribs and intercostal muscles were tested with the view to characterize the load transfer between the ribs. Finally, the costal cartilage was tested under shear loading, as it plays an important in the transfer of the load between the ribs and the sternum. This paper reports the results of dynamic shear loading tests performed on three samples of costal cartilage harvested from a single post-mortem human subject, as well as the quantification of the effective Young's modulus estimated from the amount of cartilage calcification.

  19. Cosmic Shear Bias and Calibration in Cosmic Shear Studies

    CERN Document Server

    Taylor, A N

    2016-01-01

    With the advent of large-scale weak lensing surveys there is a need to understand how realistic, scale-dependent systematics bias cosmic shear and dark energy measurements, and how they can be removed. Here we describe how spatial variations in the amplitude and orientation of realistic image distortions convolve with the measured shear field, mixing the even-parity convergence and odd-parity modes, and bias the shear power spectrum. Many of these biases can be removed by calibration to external data, the survey itself, or by modelling in simulations. The uncertainty in the calibration must be marginalised over and we calculate how this propagates into parameter estimation, degrading the dark energy Figure-of-Merit. We find that noise-like biases affect dark energy measurements the most, while spikes in the bias power have the least impact, reflecting their correlation with the effect of cosmological parameters. We argue that in order to remove systematic biases in cosmic shear surveys and maintain statistica...

  20. Shear resistance of beams based on the effective shear depth

    NARCIS (Netherlands)

    Pruijssers, A.F.

    1986-01-01

    Despite extensive experimental and theoretical studies the shear resistance of beams with longitudinal reinforcement is described by empirical expressions. A reliable empirical formula is derived by Rafla [10]. This formula is based on 442 experimental results. In this report no experiments are desc

  1. Active Control of Shear Thickening in Suspensions

    CERN Document Server

    Lin, Neil Y C; Cates, Michael E; Sun, Jin; Cohen, Itai

    2016-01-01

    Shear thickening, an increase of viscosity with shear rate, is a ubiquitous phenomena in suspended materials that has implications for broad technological applications. Controlling this thickening behavior remains a major challenge and has led to empirical strategies ranging from altering the particle surfaces and shape to modifying the solvent properties. However, none of these methods allow for active control of flow properties during shear itself. Here, we demonstrate that by strategic imposition of a high-frequency and low-amplitude shear perturbation orthogonal to the primary shearing flow, we can largely eradicate shear thickening. The orthogonal shear effectively becomes a regulator for controlling thickening in the suspension, allowing the viscosity to be reduced by up to two decades on demand. In a separate setup, we show that such effects can be induced by simply agitating the sample transversely to the primary shear direction. Overall, the ability of in situ manipulation of shear thickening paves a...

  2. Models for providing shear resistance of reinforced concrete elements subjected to shear

    OpenAIRE

    Klemen, Eva

    2015-01-01

    Shear resistance of reinforced concrete elements subjected to shear were analyzed in this thesis. Firstly, shear stresses in reinforced concrete and influences which are important to determine shear resitance are presented. Later different procedures for determining shear resistance of members without and with shear reinforcement in Slovenian standard SIST EN 1992-1-1 and in model direction fib Model Code 2010 are discussed, respectively. Furher different analitical models on whic...

  3. Shear-affected depletion interaction

    NARCIS (Netherlands)

    July, C.; Kleshchanok, D.; Lang, P.R.

    2012-01-01

    We investigate the influence of flow fields on the strength of the depletion interaction caused by disc-shaped depletants. At low mass concentration of discs, it is possible to continuously decrease the depth of the depletion potential by increasing the applied shear rate until the depletion force i

  4. Cardiac fusion and complex congenital cardiac defects in thoracopagus twins: diagnostic value of cardiac CT

    Energy Technology Data Exchange (ETDEWEB)

    Goo, Hyun Woo [University of Ulsan College of Medicine, Asan Medical Center, Department of Radiology and Research Institute of Radiology, Seoul (Korea, Republic of); Park, Jeong-Jun [University of Ulsan College of Medicine, Asan Medical Center, Department of Pediatric Cardiac Surgery, Seoul (Korea, Republic of); Kim, Ellen Ai-Rhan [University of Ulsan College of Medicine, Asan Medical Center, Division of Neonatology, Department of Pediatrics, Seoul (Korea, Republic of); Won, Hye-Sung [University of Ulsan College of Medicine, Asan Medical Center, Department of Obstetrics and Gynecology, Seoul (Korea, Republic of)

    2014-09-15

    Most thoracopagus twins present with cardiac fusion and associated congenital cardiac defects, and assessment of this anatomy is of critical importance in determining patient care and outcome. Cardiac CT with electrocardiographic triggering provides an accurate and quick morphological assessment of both intracardiac and extracardiac structures in newborns, making it the best imaging modality to assess thoracopagus twins during the neonatal period. In this case report, we highlight the diagnostic value of cardiac CT in thoracopagus twins with an interatrial channel and complex congenital cardiac defects. (orig.)

  5. Zipper and freeway shear zone junctions

    Science.gov (United States)

    Passchier, Cees; Platt, John

    2016-04-01

    Ductile shear zones are usually presented as isolated planar high-strain domains in a less deformed wall rock, characterised by shear sense indicators such as characteristic deflected foliation traces. Many shear zones, however, form branched systems and if movement on such branches is contemporaneous, the resulting geometry can be complicated and lead to unusual fabric geometries in the wall rock. For Y-shaped shear zone junctions with three simultaneously operating branches, and with slip directions at a high angle to the branch line, eight basic types of shear zone triple junctions are possible, divided into three groups. The simplest type, called freeway junctions, have similar shear sense on all three branches. If shear sense is different on the three branches, this can lead to space problems. Some of these junctions have shear zone branches that join to form a single branch, named zipper junctions, or a single shear zone which splits to form two, known as wedge junctions. Closing zipper junctions are most unusual, since they form a non-active high-strain zone with opposite deflection of foliations. Shear zipper and shear wedge junctions have two shear zones with similar shear sense, and one with the opposite sense. All categories of shear zone junctions show characteristic flow patterns in the shear zone and its wall rock. Shear zone junctions with slip directions normal to the branch line can easily be studied, since ideal sections of shear sense indicators lie in the plane normal to the shear zone branches and the branch line. Expanding the model to allow slip oblique and parallel to the branch line in a full 3D setting gives rise to a large number of geometries in three main groups. Slip directions can be parallel on all branches but oblique to the branch line: two slip directions can be parallel and a third oblique, or all three branches can have slip in different directions. Such more complex shear zone junctions cannot be studied to advantage in a

  6. Review of the Shearing Process for Sheet Steels and Its Effect on Sheared-Edge Stretching

    Science.gov (United States)

    Levy, B. S.; Van Tyne, C. J.

    2012-07-01

    Failure in sheared-edge stretching often limits the use of advanced high-strength steel sheets in automotive applications. The present study analyzes data in the literature from laboratory experiments on both the shearing process and the characteristics of sheared edges. Shearing produces a surface with regions of rollover, burnish, fracture, and burr. The effect of clearance and tensile strength on the shear face characteristics is quantified. Higher strength, lower ductility steels exhibit an increase in percent fracture region. The shearing process also creates a zone of deformation adjacent to the shear face called the shear-affected zone (SAZ). From an analysis of data in the literature, it is concluded that deformation in the SAZ is the dominant factor in controlling failure during sheared-edge stretching. The characteristics of the shear face are generally important for failures during sheared-edge stretching only as there is a correlation between the characteristics of the shear face and the characteristics of the SAZ. The effect of the shear burr on shear-edge stretching is also related to a correlation with the characteristics of the SAZ. In reviewing the literature, many shearing variables that could affect sheared-edge stretching limits are not identified or if identified, not quantified. It is likely that some of these variables could affect subsequent sheared-edge stretching limits.

  7. Sudden Cardiac Death

    Directory of Open Access Journals (Sweden)

    Yipsy María Gutiérrez Báez

    2015-09-01

    Full Text Available Since the second half of the twentieth century, dying suddenly due to heart-related problems has become the main health issue in all countries where infectious diseases are not prevalent. Sudden death from cardiac causes is an important global health problem. Major databases were searched for the leading causes of sudden cardiac death. It has been demonstrated that there is a group of hereditary diseases with structural alterations or without apparent organic cause that explains many cases of sudden death in young people, whether related or not to physical exertion. Certain population groups are at higher risk for this disease. They are relatively easy to identify and can be the target of primary prevention measures.

  8. Inherited cardiac disease

    Directory of Open Access Journals (Sweden)

    Philippe Charron

    2012-06-01

    Full Text Available Major advances have been achieved over the two last decades in the field of genetic cardiovascular diseases, not only through increased recognition and understanding of underlying molecular defects but also through rapid translation of knowledge into clinical practice. Genetic counseling and organization of cardiac family screening has become part of the medical management of these diseases, and these should be performed systematically unless an acquired cause has been diagnosed...

  9. Cardiac Tissue Engineering

    OpenAIRE

    MILICA RADISIC; GORDANA VUNJAK-NOVAKOVIC

    2009-01-01

    We hypothesized that clinically sized (1-5 mm thick),compact cardiac constructs containing physiologically high density of viable cells (~108 cells/cm3) can be engineered in vitro by using biomimetic culture systems capable of providing oxygen transport and electrical stimulation, designed to mimic those in native heart. This hypothesis was tested by culturing rat heart cells on polymer scaffolds, either with perfusion of culture medium (physiologic interstitial velocity, supplementation of p...

  10. Cardiac developmental toxicity

    OpenAIRE

    Mahler, Gretchen J.; Jonathan T Butcher

    2011-01-01

    Congenital heart disease is a highly prevalent problem with mostly unknown origins. Many cases of CHD likely involve an environmental exposure coupled with genetic susceptibility, but practical and ethical considerations make nongenetic causes of CHD difficult to assess in humans. The development of the heart is highly conserved across all vertebrate species, making animal models an excellent option for screening potential cardiac teratogens. This review will discuss exposures known to cause ...

  11. Cardiac hybrid imaging

    Energy Technology Data Exchange (ETDEWEB)

    Gaemperli, Oliver [University Hospital Zurich, Cardiac Imaging, Zurich (Switzerland); University Hospital Zurich, Nuclear Cardiology, Cardiovascular Center, Zurich (Switzerland); Kaufmann, Philipp A. [University Hospital Zurich, Cardiac Imaging, Zurich (Switzerland); Alkadhi, Hatem [University Hospital Zurich, Institute of Diagnostic and Interventional Radiology, Zurich (Switzerland)

    2014-05-15

    Hybrid cardiac single photon emission computed tomography (SPECT)/CT imaging allows combined assessment of anatomical and functional aspects of cardiac disease. In coronary artery disease (CAD), hybrid SPECT/CT imaging allows detection of coronary artery stenosis and myocardial perfusion abnormalities. The clinical value of hybrid imaging has been documented in several subsets of patients. In selected groups of patients, hybrid imaging improves the diagnostic accuracy to detect CAD compared to the single imaging techniques. Additionally, this approach facilitates functional interrogation of coronary stenoses and guidance with regard to revascularization procedures. Moreover, the anatomical information obtained from CT coronary angiography or coronary artery calcium scores (CACS) adds prognostic information over perfusion data from SPECT. The use of cardiac hybrid imaging has been favoured by the dissemination of dedicated hybrid systems and the release of dedicated image fusion software, which allow simple patient throughput for hybrid SPECT/CT studies. Further technological improvements such as more efficient detector technology to allow for low-radiation protocols, ultra-fast image acquisition and improved low-noise image reconstruction algorithms will be instrumental to further promote hybrid SPECT/CT in research and clinical practice. (orig.)

  12. Developments in Plasticity Approach to Shear

    DEFF Research Database (Denmark)

    Hoang, Cao Linh; Nielsen, Mogens Peter

    1999-01-01

    The paper deals with plastic methods applied to shear design of reinforced concrete beams. Emphasis is put on the recently developed crack sliding model applicable to non-shear reinforced and lightly shear reinforced beams and slabs. The model, which is an upper bound plasticity approach, takes...

  13. Shear instability of a gyroid diblock copolymer

    DEFF Research Database (Denmark)

    Eskimergen, Rüya; Mortensen, Kell; Vigild, Martin Etchells

    2005-01-01

    -induced destabilization is discussed in relation to analogous observations on shear-induced order-to-order and disorder-to-order transitions observed in related block copolymer systems and in microemulsions. It is discussed whether these phenomena originate in shear-reduced fluctuations or shear-induced dislocations....

  14. Indeterminacy of Spatiotemporal Cardiac Alternans

    CERN Document Server

    Zhao, Xiaopeng

    2007-01-01

    Cardiac alternans, a beat-to-beat alternation in action potential duration (at the cellular level) or in ECG morphology (at the whole heart level), is a marker of ventricular fibrillation, a fatal heart rhythm that kills hundreds of thousands of people in the US each year. Investigating cardiac alternans may lead to a better understanding of the mechanisms of cardiac arrhythmias and eventually better algorithms for the prediction and prevention of such dreadful diseases. In paced cardiac tissue, alternans develops under increasingly shorter pacing period. Existing experimental and theoretical studies adopt the assumption that alternans in homogeneous cardiac tissue is exclusively determined by the pacing period. In contrast, we find that, when calcium-driven alternans develops in cardiac fibers, it may take different spatiotemporal patterns depending on the pacing history. Because there coexist multiple alternans solutions for a given pacing period, the alternans pattern on a fiber becomes unpredictable. Usin...

  15. An overview of cardiac morphogenesis.

    Science.gov (United States)

    Schleich, Jean-Marc; Abdulla, Tariq; Summers, Ron; Houyel, Lucile

    2013-11-01

    Accurate knowledge of normal cardiac development is essential for properly understanding the morphogenesis of congenital cardiac malformations that represent the most common congenital anomaly in newborns. The heart is the first organ to function during embryonic development and is fully formed at 8 weeks of gestation. Recent studies stemming from molecular genetics have allowed specification of the role of cellular precursors in the field of heart development. In this article we review the different steps of heart development, focusing on the processes of alignment and septation. We also show, as often as possible, the links between abnormalities of cardiac development and the main congenital heart defects. The development of animal models has permitted the unraveling of many mechanisms that potentially lead to cardiac malformations. A next step towards a better knowledge of cardiac development could be multiscale cardiac modelling. PMID:24138816

  16. Statistical Model of Extreme Shear

    DEFF Research Database (Denmark)

    Larsen, Gunner Chr.; Hansen, Kurt Schaldemose

    2004-01-01

    In order to continue cost-optimisation of modern large wind turbines, it is important to continously increase the knowledge on wind field parameters relevant to design loads. This paper presents a general statistical model that offers site-specific prediction of the probability density function...... (PDF) of turbulence driven short-term extreme wind shear events, conditioned on the mean wind speed, for an arbitrary recurrence period. The model is based on an asymptotic expansion, and only a few and easily accessible parameters are needed as input. The model of the extreme PDF is supplemented...... by a model that, on a statistically consistent basis, describe the most likely spatial shape of an extreme wind shear event. Predictions from the model have been compared with results from an extreme value data analysis, based on a large number of high-sampled full-scale time series measurements...

  17. Sudden Cardiac Death in Athletes.

    Science.gov (United States)

    Wasfy, Meagan M; Hutter, Adolph M; Weiner, Rory B

    2016-01-01

    There are clear health benefits to exercise; even so, patients with cardiac conditions who engage in exercise and athletic competition may on rare occasion experience sudden cardiac death (SCD). This article reviews the epidemiology and common causes of SCD in specific athlete populations. There is ongoing debate about the optimal mechanism for SCD prevention, specifically regarding the inclusion of the ECG and/or cardiac imaging in routine preparticipation sports evaluation. This controversy and contemporary screening recommendations are also reviewed. PMID:27486488

  18. Shear viscosity of nuclear matter

    CERN Document Server

    Magner, A G; Grygoriev, U V; Plujko, V A

    2016-01-01

    Shear viscosity $\\eta$ is calculated for the nuclear matter described as a system of interacting nucleons with the van der Waals (VDW) equation of state. The Boltzmann-Vlasov kinetic equation is solved in terms of the plane waves of the collective overdamped motion. In the frequent collision regime, the shear viscosity depends on the particle number density $n$ through the mean-field parameter $a$ which describes attractive forces in the VDW equation. In the temperature region $T=15\\div 40$~MeV, a ratio of the shear viscosity to the entropy density $s$ is smaller than 1 at the nucleon number density $n =(0.5\\div 1.5)\\,n^{}_0$, where $n^{}_0=0.16\\,$fm$^{-3}$ is the particle density of equilibrium nuclear matter at zero temperature. A minimum of the $\\eta/s$ ratio takes place somewhere in a vicinity of the critical point of the VDW system. Large values of $\\eta/s\\gg 1$ are however found in both the low density, $n\\ll n^{}_0$, and high density, $n>2n^{}_0$, regions. This makes the ideal hydrodynamic approach ina...

  19. Haptic Edge Detection Through Shear

    Science.gov (United States)

    Platkiewicz, Jonathan; Lipson, Hod; Hayward, Vincent

    2016-01-01

    Most tactile sensors are based on the assumption that touch depends on measuring pressure. However, the pressure distribution at the surface of a tactile sensor cannot be acquired directly and must be inferred from the deformation field induced by the touched object in the sensor medium. Currently, there is no consensus as to which components of strain are most informative for tactile sensing. Here, we propose that shape-related tactile information is more suitably recovered from shear strain than normal strain. Based on a contact mechanics analysis, we demonstrate that the elastic behavior of a haptic probe provides a robust edge detection mechanism when shear strain is sensed. We used a jamming-based robot gripper as a tactile sensor to empirically validate that shear strain processing gives accurate edge information that is invariant to changes in pressure, as predicted by the contact mechanics study. This result has implications for the design of effective tactile sensors as well as for the understanding of the early somatosensory processing in mammals. PMID:27009331

  20. Kinematics and shear heat pattern of ductile simple shear zones with `slip boundary condition'

    Science.gov (United States)

    Mulchrone, Kieran F.; Mukherjee, Soumyajit

    2016-04-01

    Extrusion by Poiseuille flow and simple shear of hot lower crust has been deciphered from large hot orogens, and partial-slip boundary condition has been encountered in analogue models. Shear heat and velocity profiles are deduced from a simplified form of Navier-Stokes equation for simple shear together with extrusive Poiseuille flow and slip boundary condition for Newtonian viscous rheology. A higher velocity at the upper boundary of the shear zone promotes higher slip velocity at the lower boundary. The other parameters that affect the slip are viscosity and thickness of the shear zone and the resultant pressure gradient that drives extrusion. In the partial-slip case, depending on flow parameters (resultant pressure gradient, density and viscosity) and thickness of the shear zone, the velocity profiles can curve and indicate opposite shear senses. The corresponding shear heat profiles can indicate temperature maximum inside shear zones near either boundaries of the shear zone, or equidistant from them.

  1. Case Report: Penetrating Cardiac Injury

    Directory of Open Access Journals (Sweden)

    Adem Grbolar

    2013-10-01

    Full Text Available Summary: Penetrating cardiac injurys caused by gunshots and penetrating tools have high mortality rates. The way of injury, how the cardiac area is effected and the presence of cardiac tamponadecauses mortality in different rates. However the better treatment quality of hospitals, increasingoperative techniques, and internel care unit quality has not been change during the years. Searching the literature, we want to present a 42 years old male patient whowas injured by knife and had a 1 cm skin wound on chest with cardiac tamponade. After sternotomy a 7 cm laseration was observed in heart. Cardioraphy was performed.

  2. Shear Strength of Reinforced Concrete Shear Walls under Eccentric Tensile Axial Force

    OpenAIRE

    MIZOGUCHI, Mitsuo; ARAI, Yasuyuki; Hosoya, Koji

    2002-01-01

    Six reinforced concrete shear wall models were built and tested to investigate effects of cyclic lateral loading and an eccentric tensile axial force on their shear strength behavior. The following are confirmed from this test result. When the elongation at the bottom of the boundary column on the compression side for a lateral force is small, the shear strength of shear walls subjected to a tensile axial force at the boundary column can be evaluated by conventional shear strenght equations, ...

  3. Continuous shear - a method for studying material elements passing a stationary shear plane

    DEFF Research Database (Denmark)

    Lindegren, Maria; Wiwe, Birgitte; Wanheim, Tarras

    2003-01-01

    circumferential groove. Normally shear in metal forming processes is of another nature, namely where the material elements move through a stationary shear zone, often of small width. In this paper a method enabling the simulation of this situation is presented. A tool for continuous shear has beeen manufactured...... and tested with AlMgSil and copper. The sheared material has thereafter been tested n plane strain compression with different orientation concerning the angle between the shear plane and the compression direction....

  4. Magnetic shear. II - Hale region 17244

    International Nuclear Information System (INIS)

    A B-gamma(delta) sunspot group with growing delta-spots of trailing polarity shows evidence in H-alpha filament structure of a transition from a state of weak magnetic shear to a state of strong shear. The shear develops in the chromosphere and transition region to the corona overlying the photospheric magnetic neutral line separating the delta-spots from the leading polarity at a time when the delta-spots are undergoing rapid growth. Several major flares occur along the sheared portion of the neutral line following the shear development. Other segments of the neutral line far removed from the delta-spots show similar evidence of shear in the H-alpha filament structure and in C IV velocity patterns as well. These quiescent regions of shear are relatively steady or decaying with time and show very little related activity. 11 references

  5. Antifibrinolytics in cardiac surgery

    Directory of Open Access Journals (Sweden)

    Achal Dhir

    2013-01-01

    Full Text Available Cardiac surgery exerts a significant strain on the blood bank services and is a model example in which a multi-modal blood-conservation strategy is recommended. Significant bleeding during cardiac surgery, enough to cause re-exploration and/or blood transfusion, increases morbidity and mortality. Hyper-fibrinolysis is one of the important contributors to increased bleeding. This knowledge has led to the use of anti-fibrinolytic agents especially in procedures performed under cardiopulmonary bypass. Nothing has been more controversial in recent times than the aprotinin controversy. Since the withdrawal of aprotinin from the world market, the choice of antifibrinolytic agents has been limited to lysine analogues either tranexamic acid (TA or epsilon amino caproic acid (EACA. While proponents of aprotinin still argue against its non-availability. Health Canada has approved its use, albeit under very strict regulations. Antifibrinolytic agents are not without side effects and act like double-edged swords, the stronger the anti-fibrinolytic activity, the more serious the side effects. Aprotinin is the strongest in reducing blood loss, blood transfusion, and possibly, return to the operating room after cardiac surgery. EACA is the least effective, while TA is somewhere in between. Additionally, aprotinin has been implicated in increased mortality and maximum side effects. TA has been shown to increase seizure activity, whereas, EACA seems to have the least side effects. Apparently, these agents do not differentiate between pathological and physiological fibrinolysis and prevent all forms of fibrinolysis leading to possible thrombotic side effects. It would seem prudent to select the right agent knowing its risk-benefit profile for a given patient, under the given circumstances.

  6. Cardiac arrest – cardiopulmonary resuscitation

    Directory of Open Access Journals (Sweden)

    Basri Lenjani

    2014-01-01

    Conclusions: All survivors from cardiac arrest have received appropriate medical assistance within 10 min from attack, which implies that if cardiac arrest occurs near an institution health care (with an opportunity to provide the emergent health care the rate of survival is higher.

  7. Leadership in cardiac surgery.

    Science.gov (United States)

    Rao, Christopher; Patel, Vanash; Ibrahim, Michael; Ahmed, Kamran; Wong, Kathie A; Darzi, Ara; von Segesser, Ludwig K; Athanasiou, Thanos

    2011-06-01

    Despite the efficacy of cardiac surgery, less invasive interventions with more uncertain long-term outcomes are increasingly challenging surgery as first-line treatment for several congenital, degenerative and ischemic cardiac diseases. The specialty must evolve if it is to ensure its future relevance. More importantly, it must evolve to ensure that future patients have access to treatments with proven long-term effectiveness. This cannot be achieved without dynamic leadership; however, our contention is that this is not enough. The demands of a modern surgical career and the importance of the task at hand are such that the serendipitous emergence of traditional charismatic leadership cannot be relied upon to deliver necessary change. We advocate systematic analysis and strategic leadership at a local, national and international level in four key areas: Clinical Care, Research, Education and Training, and Stakeholder Engagement. While we anticipate that exceptional individuals will continue to shape the future of our specialty, the creation of robust structures to deliver collective leadership in these key areas is of paramount importance. PMID:20884217

  8. Interventional cardiac catheterization.

    Science.gov (United States)

    Pihkala, J; Nykanen, D; Freedom, R M; Benson, L N

    1999-04-01

    Over the past decade, transcatheter interventions have become increasingly important in the treatment of patients with congenital heart lesions. These procedures may be broadly grouped as dilations (e.g., septostomy, valvuloplasty, angioplasty, and endovascular stenting) or as closures (e.g., vascular embolization and device closure of defects). Balloon valvuloplasty has become the treatment of choice for patients in all age groups with simple valvar pulmonic stenosis and, although not curative, seems at least comparable to surgery for congenital aortic stenosis in newborns to young adults. Balloon angioplasty is successfully applied to a wide range of aortic, pulmonary artery, and venous stenoses. Stents are useful in dilating lesions of which the intrinsic elasticity results in vessel recoil after balloon dilation alone. Catheter-delivered coils are used to embolize a wide range of arterial, venous, and prosthetic vascular connections. Although some devices remain investigational, they have been successfully used for closure of many arterial ducts and atrial and ventricular septal defects. In the therapy for patients with complex CHD, best results may be achieved by combining cardiac surgery with interventional catheterization. The cooperation among interventional cardiologists and cardiac surgeons was highlighted in a report of an algorithm to manage patients with tetralogy of Fallot or pulmonary atresia with diminutive pulmonary arteries, involving balloon dilation, coil embolization of collaterals, and intraoperative stent placement. In this setting, well-planned catheterization procedures have an important role in reducing the overall number of procedures that patients may require over a lifetime, with improved outcomes.

  9. Ictal Cardiac Ryhthym Abnormalities.

    Science.gov (United States)

    Ali, Rushna

    2016-01-01

    Cardiac rhythm abnormalities in the context of epilepsy are a well-known phenomenon. However, they are under-recognized and often missed. The pathophysiology of these events is unclear. Bradycardia and asystole are preceded by seizure onset suggesting ictal propagation into the cortex impacting cardiac autonomic function, and the insula and amygdala being possible culprits. Sudden unexpected death in epilepsy (SUDEP) refers to the unanticipated death of a patient with epilepsy not related to status epilepticus, trauma, drowning, or suicide. Frequent refractory generalized tonic-clonic seizures, anti-epileptic polytherapy, and prolonged duration of epilepsy are some of the commonly identified risk factors for SUDEP. However, the most consistent risk factor out of these is an increased frequency of generalized tonic-clonic seizures (GTC). Prevention of SUDEP is extremely important in patients with chronic, generalized epilepsy. Since increased frequency of GTCS is the most consistently reported risk factor for SUDEP, effective seizure control is the most important preventive strategy. PMID:27347227

  10. Pneumothorax in cardiac pacing

    DEFF Research Database (Denmark)

    Kirkfeldt, Rikke Esberg; Johansen, Jens Brock; Nohr, Ellen Aagaard;

    2012-01-01

    AIM: To identify risk factors for pneumothorax treated with a chest tube after cardiac pacing device implantation in a population-based cohort.METHODS AND RESULTS: A nationwide cohort study was performed based on data on 28 860 patients from the Danish Pacemaker Register, which included all Danish...... patients who received their first pacemaker (PM) or cardiac resynchronization device from 1997 to 2008. Multiple logistic regression was used to estimate adjusted odds ratios (aOR) with 95% confidence intervals for the association between risk factors and pneumothorax treated with a chest tube. The median...... age was 77 years (25th and 75th percentile: 69-84) and 55% were male (n = 15 785). A total of 190 patients (0.66%) were treated for pneumothorax, which was more often in women [aOR 1.9 (1.4-2.6)], and in patients with age >80 years [aOR 1.4 (1.0-1.9)], a prior history of chronic obstructive pulmonary...

  11. Punching shear capacity of reinforced concrete slabs with headed shear studs

    DEFF Research Database (Denmark)

    Hoang, Linh Cao; Pop, Anamaria

    2015-01-01

    Punching shear in slabs is analogous to shear in beams. Despite this similarity, current design codes provide distinctly different methods for the design of shear reinforcement in the two situations. For example, the Eurocode method for beam shear design is founded on the theory of rigid plasticity....... To design shear reinforcement in slabs, on the other hand, the engineer must settle for an empirical equation. The aim of the study reported is to demonstrate that it is possible in a simple manner to design shear reinforcement in slabs based on the same rigid-plasticity foundation as for beam shear design....... For this purpose, an extension of the upper-bound crack sliding model is proposed. This involves analysis of sliding mechanisms in yield lines developed both within and outside the zone with shear reinforcement. Various types of headed shear studs were considered. The results obtained using the model were compared...

  12. Magnetogenesis through Relativistic Velocity Shear

    Science.gov (United States)

    Miller, Evan

    Magnetic fields at all scales are prevalent in our universe. However, current cosmological models predict that initially the universe was bereft of large-scale fields. Standard magnetohydrodynamics (MHD) does not permit magnetogenesis; in the MHD Faraday's law, the change in magnetic field B depends on B itself. Thus if B is initially zero, it will remain zero for all time. A more accurate physical model is needed to explain the origins of the galactic-scale magnetic fields observed today. In this thesis, I explore two velocity-driven mechanisms for magnetogenesis in 2-fluid plasma. The first is a novel kinematic 'battery' arising from convection of vorticity. A coupling between thermal and plasma oscillations, this non-relativistic mechanism can operate in flows that are incompressible, quasi-neutral and barotropic. The second mechanism results from inclusion of thermal effects in relativistic shear flow instabilities. In such flows, parallel perturbations are ubiquitously unstable at small scales, with growth rates of order with the plasma frequency over a defined range of parameter-space. Of these two processes, instabilities seem far more likely to account for galactic magnetic fields. Stable kinematic effects will, at best, be comparable to an ideal Biermann battery, which is suspected to be orders of magnitude too weak to produce the observed galactic fields. On the other hand, instabilities grow until saturation is reached, a topic that has yet to be explored in detail on cosmological scales. In addition to investigating these magnetogenesis sources, I derive a general dispersion relation for three dimensional, warm, two species plasma with discontinuous shear flow. The mathematics of relativistic plasma, sheared-flow instability and the Biermann battery are also discussed.

  13. Affect intensity and cardiac arousal.

    Science.gov (United States)

    Blascovich, J; Brennan, K; Tomaka, J; Kelsey, R M; Hughes, P; Coad, M L; Adlin, R

    1992-07-01

    Relationships between affect intensity and basal, evoked, and perceived cardiac arousal were investigated in 3 experiments. Affect intensity was assessed using Larsen and Diener's (1987) Affect Intensity Measure (AIM). Cardiac arousal was evoked with exercise in the 1st study and with mental arithmetic in the 2nd and 3rd. Perceived cardiac arousal was measured under optimal conditions using a standard heartbeat discrimination procedure. Women as a group scored higher on the AIM. Affect intensity was unrelated to basal or evoked cardiac arousal and was negatively related to perceived cardiac arousal in all 3 studies. Data suggest that affect intensity, although unrelated to actual physiological arousal, is negatively related to the accuracy with which individuals perceive their own arousal. Results are discussed within the context of an expanded arousal-regulation model (Blascovich, 1990). PMID:1494983

  14. Magnetorheological Shear Flow Near Jamming

    Science.gov (United States)

    Vågberg, Daniel; Tighe, Brian

    2015-03-01

    Flow in magnetorheological (MR) fluids and systems near jamming both display hallmarks of complex fluid rheology, including yield stresses and shear thinning viscosities. They are also tunable, which means that both phenomena can be used as a switching mechanism in ``smart'' fluids, i.e. fluids where properties can be tuned rapidly and reversibly by changing external parameters. We use numerical simulations to investigate the rheological properties of MR fluids close to the jamming transition as a function of the applied field and volume fraction. We are especially interested in the crossover region where both phenomena are needed to describe the observed dynamics. Funded by the Dutch Organization for Scientific Research (NWO).

  15. Mixing in shear thinning fluids

    Directory of Open Access Journals (Sweden)

    H. Ameur

    2012-06-01

    Full Text Available In the present study, a CFD characterization of the flow generated by curved-blade impellers in a cylindrical unbaffled vessel was carried out. The tank diameter was 300 mm, with a flat bottom. The liquid height was equal to the vessel diameter. The fluids simulated have a shear thinning behavior. Analyses concern the effect of the impeller speed, the fluid rheology and the number of impeller blades on the induced flow patterns and the power consumption. The predictions were compared with literature data and a satisfactory agreement was found.

  16. Shear-Induced Reactive Gelation.

    Science.gov (United States)

    Brand, Bastian; Morbidelli, Massimo; Soos, Miroslav

    2015-11-24

    In this work, we describe a method for the production of porous polymer materials in the form of particles characterized by narrow pore size distribution using the principle of shear-induced reactive gelation. Poly(styrene-co-divinylbenzene) primary particles with diameter ranging from 80 to 200 nm are used as building blocks, which are assembled into fractal-like clusters when exposed to high shear rates generated in a microchannel. It was found that independent of the primary particle size, it is possible to modulate the internal structure of formed fractal-like aggregates having fractal dimension ranging from 2.4 to 2.7 by varying the residence time in the microchannel. Thermally induced postpolymerization was used to increase the mechanical resilience of such formed clusters. Primary particle interpenetration was observed by SEM and confirmed by light scattering resulting in an increase of fractal dimension. Nitrogen sorption measurements and mercury porosimetry confirmed formation of a porous material with surface area ranging from 20 to 40 m(2)/g characterized by porosity of 70% and narrow pore size distribution with an average diameter around 700 nm without the presence of any micropores. The strong perfusive character of the synthesized material was confirmed by the existence of a plateau of the height equivalent to a theoretical plate measured at high reduced velocities using a chromatographic column packed with the synthesized microclusters. PMID:26488233

  17. Local Gravitational Instability of Magnetized Shear Flows

    CERN Document Server

    Howes, G G; McWilliams, J C; Howes, Gregory G.; Cowley, Steven C.; Williams, James C. Mc

    2001-01-01

    The effect of magnetic shear and shear flow on local gravitationally induced instabilities is investigated. A simple model is constructed allowing for an arbitrary entropy gradient and a shear plasma flow in the Boussinesq approximation. A transformation to shearing magnetic coordinates achieves a model with plasma flow along the magnetic field lines where the coordinate lines are coincident with the field lines. The solution for the normal modes of the system depends on two parameters: the Alfven Mach number of the plasma flow and the entropy gradient. The behavior of the unstable normal modes of this system is summarized by a stability diagram. Important characteristics of this stability diagram are the following: magnetic shear is stabilizing and the entropy gradient must exceed a threshold value for unstable mode growth to occur; flow acts to suppress mode growth in a substantially unstable regime as expected, yet near marginal stability it can lessen the stabilizing effect of magnetic shear and enhance t...

  18. Interfacial Slip in Sheared Polymer Blends

    OpenAIRE

    Lo, Tak Shing; Mihajlovic, Maja; Shnidman, Yitzhak; Li, Wentao; Gersappe, Dilip

    2004-01-01

    We have developed a dynamic self-consistent field theory, without any adjustable parameters, for unentangled polymer blends under shear. Our model accounts for the interaction between polymers, and enables one to compute the evolution of the local rheology, microstructure and the conformations of the polymer chains under shear self-consistently. We use this model to study the interfacial dynamics in sheared polymer blends and make a quantitative comparison between this model and Molecular Dyn...

  19. Periodic Exponential Shear of Complex Fluids

    OpenAIRE

    Kalelkar, Chirag; McKinley, Gareth

    2012-01-01

    We define a class of flows with exponential kinematics termed Periodic Exponential Shear (PES) flow which involve periodic exponential stretching of fluid elements along with their rotation. We exhibit analytical and numerical results for PES flow by using the Oldroyd-B model for viscoelastic fluids. We calculate the growth in the shear and the normal stresses analytically as well as demonstrate that repeated application of the flow leads to stable oscillatory shear and normal stresses. We de...

  20. Shear wall experiments and design in Japan

    Energy Technology Data Exchange (ETDEWEB)

    Park, Y.J.; Hofmayer, C.

    1994-12-01

    This paper summarizes the results of recent survey studies on the available experimental data bases and design codes/standards for reinforced concrete (RC) shear wall structures in Japan. Information related to the seismic design of RC reactor buildings and containment structures was emphasized in the survey. The seismic requirements for concrete structures, particularly those related to shear strength design, are outlined. Detailed descriptions are presented on the development of Japanese shear wall equations, design requirements for containment structures, and ductility requirements.

  1. Dynamo efficiency with shear in helical turbulence .

    OpenAIRE

    Leprovost, Nicolas; Kim, Eun-Jin

    2009-01-01

    To elucidate the influence of shear flow on the generation of magnetic fields through the modification of turbulence property, we consider the case where a large-scale magnetic field is parallel to a large-scale shear flow without direct interaction between the two in the kinematic limit where the magnetic field does not backreact on the velocity. By nonperturbatively incorporating the effect of shear in a helically forced turbulence, we show that turbulence intensity and turbulent transport ...

  2. Physics of Cardiac Arrhythmogenesis

    Science.gov (United States)

    Karma, Alain

    2013-04-01

    A normal heartbeat is orchestrated by the stable propagation of an excitation wave that produces an orderly contraction. In contrast, wave turbulence in the ventricles, clinically known as ventricular fibrillation (VF), stops the heart from pumping and is lethal without prompt defibrillation. I review experimental, computational, and theoretical studies that have shed light on complex dynamical phenomena linked to the initiation, maintenance, and control of wave turbulence. I first discuss advances made to understand the precursor state to a reentrant arrhythmia where the refractory period of cardiac tissue becomes spatiotemporally disordered; this is known as an arrhythmogenic tissue substrate. I describe observed patterns of transmembrane voltage and intracellular calcium signaling that can contribute to this substrate, and symmetry breaking instabilities to explain their formation. I then survey mechanisms of wave turbulence and discuss novel methods that exploit electrical pacing stimuli to control precursor patterns and low-energy pulsed electric fields to control turbulence.

  3. Design of a Pulsatile Flow Facility to Evaluate Thrombogenic Potential of Implantable Cardiac Devices

    OpenAIRE

    Arjunon, Sivakkumar; Ardana, Pablo Hidalgo; Saikrishnan, Neelakantan; Madhani, Shalv; Foster, Brent; Glezer, Ari; Yoganathan, Ajit P.

    2015-01-01

    Due to expensive nature of clinical trials, implantable cardiac devices should first be extensively characterized in vitro. Prosthetic heart valves (PHVs), an important class of these devices, have been shown to be associated with thromboembolic complications. Although various in vitro systems have been designed to quantify blood-cell damage and platelet activation caused by nonphysiological hemodynamic shear stresses in these PHVs, very few systems attempt to characterize both blood damage a...

  4. Mediastinitis after cardiac transplantation

    Directory of Open Access Journals (Sweden)

    Noedir A. G. Stolf

    2000-05-01

    Full Text Available OBJECTIVE: Assessment of incidence and behavior of mediastinitis after cardiac transplantation. METHODS: From 1985 to 1999, 214 cardiac transplantations were performed, 12 (5.6% of the transplanted patients developed confirmed mediastinitis. Patient's ages ranged from 42 to 66 years (mean of 52.3±10.0 years and 10 (83.3% patients were males. Seven (58.3% patients showed sternal stability on palpation, 4 (33.3% patients had pleural empyema, and 2 (16.7% patients did not show purulent secretion draining through the wound. RESULTS: Staphylococcus aureus was the infectious agent identified in the wound secretion or in the mediastinum, or both, in 8 (66.7% patients. Staphylococcus epidermidis was identified in 2 (16.7% patients, Enterococcus faecalis in 1 (8.3% patient, and the cause of mediastinitis could not be determined in 1 (8.3% patient. Surgical treatment was performed on an emergency basis, and the extension of the débridement varied with local conditions. In 2 (16.7% patients, we chose to leave the surgical wound open and performed daily dressings with granulated sugar. Total sternal resection was performed in only 1 (8.3% patient. Out of this series, 5 (41.7% patients died, and the causes of death were related to the infection. Autopsy revealed persistence of mediastinitis in 1 (8.3% patient. CONCLUSION: Promptness in diagnosing mediastinitis and precocious surgical drainage have changed the natural evolution of this disease. Nevertheless, observance of the basic precepts of prophylaxis of infection is still the best way to treat mediastinitis.

  5. Platelets and cardiac arrhythmia

    Directory of Open Access Journals (Sweden)

    Jonas S De Jong

    2010-12-01

    Full Text Available Sudden cardiac death remains one of the most prevalent modes of death in industrialized countries, and myocardial ischemia due to thrombotic coronary occlusion is its primary cause. The role of platelets in the occurrence of SCD extends beyond coronary flow impairment by clot formation. Here we review the substances released by platelets during clot formation and their arrhythmic properties. Platelet products are released from three types of platelet granules: dense core granules, alpha-granules, and platelet lysosomes. The physiologic properties of dense granule products are of special interest as a potential source of arrhythmic substances. They are released readily upon activation and contain high concentrations of serotonin, histamine, purines, pyrimidines, and ions such as calcium and magnesium. Potential arrhythmic mechanisms of these substances, e.g. serotonin and high energy phosphates, include induction of coronary constriction, calcium overloading, and induction of delayed after-depolarizations. Alpha-granules produce thromboxanes and other arachidonic acid products with many potential arrhythmic effects mediated by interference with cardiac sodium, calcium and potassium channels. Alpha-granules also contain hundreds of proteins that could potentially serve as ligands to receptors on cardiomyocytes. Lysosomal products probably do not have an important arrhythmic effect. Platelet products and ischemia can induce coronary permeability, thereby enhancing interaction with surrounding cardiomyocytes. Antiplatelet therapy is known to improve survival after myocardial infarction. Although an important part of this effect results from prevention of coronary clot formation, there is evidence to suggest that antiplatelet therapy also induces anti-arrhythmic effects during ischemia by preventing the release of platelet activation products.

  6. ON WALL SHEAR STRESS OF ARTERY

    Institute of Scientific and Technical Information of China (English)

    Liu Zhao-rong; Liu Bao-yu; Qin Kai-rong

    2003-01-01

    In this paper, a method was proposed that the wall shear stress of artery could be determined by measuring the centerline axial velocity and radial motion of arterial wall simultaneously.The method is simple in application and can get higher precision when it is used to determine the shear stress of arterial wall in vivo.As an example, the shear stress distribution in periodic oscillatory flow of human carotid was calculated and discussed.The computed results show that the shear stress distribution at any given instant is almost uniform and will be zero at the centerline and tends to maximum at the vessel wall.

  7. Determination of arterial wall shear stress

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The arteries can remodel their structure and function to adapt themselves to the mechanical environment. In various factors that lead to vascular remodeling, the shear stress on the arterial wall induced by the blood flow is of great importance. However, there are many technique difficulties in measuring the wall shear stress directly at present. In this paper, through analyzing the pulsatile blood flow in arteries, a method has been proposed that can determine the wall shear stress quantitatively by measuring the velocity on the arterial axis, and that provides a necessary means to discuss the influence of arterial wall shear stress on vascular remodeling.

  8. Periodically sheared 2D Yukawa systems

    Energy Technology Data Exchange (ETDEWEB)

    Kovács, Anikó Zsuzsa [Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Hungarian Academy of Sciences, Konkoly-Thege Miklós str. 29-33, H-1121 Budapest (Hungary); Hartmann, Peter [Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Hungarian Academy of Sciences, Konkoly-Thege Miklós str. 29-33, H-1121 Budapest (Hungary); Center for Astrophysics, Space Physics and Engineering Research (CASPER), One Bear Place 97310, Baylor University, Waco, Texas 76798 (United States); Donkó, Zoltán [Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Hungarian Academy of Sciences, Konkoly-Thege Miklós str. 29-33, H-1121 Budapest (Hungary); Physics Department, Boston College, Chestnut Hill, Massachusetts 20467 (United States)

    2015-10-15

    We present non-equilibrium molecular dynamics simulation studies on the dynamic (complex) shear viscosity of a 2D Yukawa system. We have identified a non-monotonic frequency dependence of the viscosity at high frequencies and shear rates, an energy absorption maximum (local resonance) at the Einstein frequency of the system at medium shear rates, an enhanced collective wave activity, when the excitation is near the plateau frequency of the longitudinal wave dispersion, and the emergence of significant configurational anisotropy at small frequencies and high shear rates.

  9. Cyclic Shearing Deformation Behavior of Saturated Clays

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The apparatus for static and dynamic universal triaxial and torsional shear soil testing is employed to perform stress-controlled cyclic single-direction torsional shear tests and two-direction coupled shear tests under unconsolidated-undrained conditions. Through a series of tests on saturated clay, the effects of initial shear stress and stress reversal on the clay's strain-stress behavior are examined, and the behavior of pore water pressure is studied. The experimental results indicate that the patterns of stress-strain relations are distinctly influenced by the initial shear stress in the cyclic single-direction shear tests. When the initial shear stress is large and no stress reversal occurs, the predominant deformation behavior is characterized by an accumulative effect. When the initial shear stress is zero and symmetrical cyclic stress occurs, the predominant deformation behavior is characterized by a cyclic effect. The pore water pressure fluctuates around the confining pressure with the increase of cycle number. It seems that the fluctuating amplitude increases with the increase of the cyclic stress. But a buildup of pore water pressure does not occur. The deformations of clay samples under the complex initial and the cyclic coupled stress conditions include the normal deviatoric deformation and horizontal shear deformation, the average deformation and cyclic deformation. A general strain failure criterion taking into account these deformations is recommended and is proved more stable and suitable compared to the strain failure criteria currently used.

  10. Metoclopramide-induced cardiac arrest

    Directory of Open Access Journals (Sweden)

    Martha M. Rumore

    2011-11-01

    Full Text Available The authors report a case of cardiac arrest in a patient receiving intravenous (IV metoclopramide and review the pertinent literature. A 62-year-old morbidly obese female admitted for a gastric sleeve procedure, developed cardiac arrest within one minute of receiving metoclopramide 10 mg via slow intravenous (IV injection. Bradycardia at 4 beats/min immediately appeared, progressing rapidly to asystole. Chest compressions restored vital function. Electrocardiogram (ECG revealed ST depression indicative of myocardial injury. Following intubation, the patient was transferred to the intensive care unit. Various cardiac dysrrhythmias including supraventricular tachycardia (SVT associated with hypertension and atrial fibrillation occurred. Following IV esmolol and metoprolol, the patient reverted to normal sinus rhythm. Repeat ECGs revealed ST depression resolution without pre-admission changes. Metoclopramide is a non-specific dopamine receptor antagonist. Seven cases of cardiac arrest and one of sinus arrest with metoclopramide were found in the literature. The metoclopramide prescribing information does not list precautions or adverse drug reactions (ADRs related to cardiac arrest. The reaction is not dose related but may relate to the IV administration route. Coronary artery disease was the sole risk factor identified. According to Naranjo, the association was possible. Other reports of cardiac arrest, severe bradycardia, and SVT were reviewed. In one case, five separate IV doses of 10 mg metoclopramide were immediately followed by asystole repeatedly. The mechanism(s underlying metoclopramide’s cardiac arrest-inducing effects is unknown. Structural similarities to procainamide may play a role. In view of eight previous cases of cardiac arrest from metoclopramide having been reported, further elucidation of this ADR and patient monitoring is needed. Our report should alert clinicians to monitor patients and remain diligent in surveillance and

  11. Shear Thickening in Concentrated Soft Sphere Colloidal Suspensions: A Shear Induced Phase Transition

    Directory of Open Access Journals (Sweden)

    Joachim Kaldasch

    2015-01-01

    Full Text Available A model of shear thickening in dense suspensions of Brownian soft sphere colloidal particles is established. It suggests that shear thickening in soft sphere suspensions can be interpreted as a shear induced phase transition. Based on a Landau model of the coagulation transition of stabilized colloidal particles, taking the coupling between order parameter fluctuations and the local strain-field into account, the model suggests the occurrence of clusters of coagulated particles (subcritical bubbles by applying a continuous shear perturbation. The critical shear stress of shear thickening in soft sphere suspensions is derived while reversible shear thickening and irreversible shear thickening have the same origin. The comparison of the theory with an experimental investigation of electrically stabilized colloidal suspensions confirms the presented approach.

  12. Epigenetic regulation in cardiac fibrosis

    Institute of Scientific and Technical Information of China (English)

    Li-Ming; Yu; Yong; Xu

    2015-01-01

    Cardiac fibrosis represents an adoptive response in the heart exposed to various stress cues. While resolution of the fibrogenic response heralds normalization of heart function, persistent fibrogenesis is usually associated with progressive loss of heart function and eventually heart failure. Cardiac fibrosis is regulated by a myriad of factors that converge on the transcription of genes encoding extracellular matrix proteins, a process the epigenetic machinery plays a pivotal role. In this minireview, we summarize recent advances regarding the epigenetic regulation of cardiac fibrosis focusing on the role of histone and DNA modifications and non-coding RNAs.

  13. Cardiac perioperative complications in noncardiac surgery

    OpenAIRE

    Radovanović Dragana; Kolak Radmila; Stokić Aleksandar; Radovanović Zoran; Jovanović Gordana

    2008-01-01

    Anesthesiologists are confronted with an increasing population of patients undergoing noncardiac surgery who are at risk for cardiac complications in the perioperative period. Perioperative cardiac complications are responsible for significant mortality and morbidity. The aim of the present study was to determine the incidence of perioperative (operative and postoperative) cardiac complications and correlations between the incidence of perioperative cardiac complications and type of surgical ...

  14. Cardiac Mechano-Gated Ion Channels and Arrhythmias.

    Science.gov (United States)

    Peyronnet, Rémi; Nerbonne, Jeanne M; Kohl, Peter

    2016-01-22

    Mechanical forces will have been omnipresent since the origin of life, and living organisms have evolved mechanisms to sense, interpret, and respond to mechanical stimuli. The cardiovascular system in general, and the heart in particular, is exposed to constantly changing mechanical signals, including stretch, compression, bending, and shear. The heart adjusts its performance to the mechanical environment, modifying electrical, mechanical, metabolic, and structural properties over a range of time scales. Many of the underlying regulatory processes are encoded intracardially and are, thus, maintained even in heart transplant recipients. Although mechanosensitivity of heart rhythm has been described in the medical literature for over a century, its molecular mechanisms are incompletely understood. Thanks to modern biophysical and molecular technologies, the roles of mechanical forces in cardiac biology are being explored in more detail, and detailed mechanisms of mechanotransduction have started to emerge. Mechano-gated ion channels are cardiac mechanoreceptors. They give rise to mechano-electric feedback, thought to contribute to normal function, disease development, and, potentially, therapeutic interventions. In this review, we focus on acute mechanical effects on cardiac electrophysiology, explore molecular candidates underlying observed responses, and discuss their pharmaceutical regulation. From this, we identify open research questions and highlight emerging technologies that may help in addressing them.

  15. Shear Behavior of Reinforced Concrete Shear Walls under Tensile Axial Force with Eccentricity

    OpenAIRE

    MIZOGUCHI, Mitsuo; ARAI, Yasuyuki; KUCHIJI, Hideki

    2000-01-01

    A lateral loading test of six reinforced concrete shear walls subjected to an eccentric tensile axial force was carried out to examine their shear behavior. Next facts ware confirmed on the shear strength of the walls subjected to an eccentric tensile axial force. The test results can be evaluat by the shear strength equation [2] considering axial tensile stress. The calculated values given by the (AIJ "Design Guidelines for Earthquake Resistant Reinforced Concrete Buildings Based on Inelasti...

  16. Shear Behavior Of Reinforced High-Strength Concrete Beams Without Shear Reinforcement

    OpenAIRE

    Wafa, Faisal F.

    1994-01-01

    Eighteen rectangular singly reinforced high-strength concrete beams without web reinforcement were tested in combined shear and flexure. The main variables were the longitudinal steel reinforcement ratio and the shear-span to effective depth ratio. The uniaxial compressive strength of concrete was about 93 MPa (13,500 psi). The experimental shear capacities were compared with the shear capacities predicted by different empirical equations presented in literatures. Two empirical equations have...

  17. Inverse Magnetic/Shear Catalysis

    CERN Document Server

    McInnes, Brett

    2015-01-01

    It is well known that very large magnetic fields are generated when the Quark-Gluon Plasma is formed during peripheral heavy-ion collisions. Lattice, holographic, and other studies strongly suggest that these fields may, for observationally relevant field values, induce ``inverse magnetic catalysis'', signalled by a lowering of the critical temperature for the chiral/deconfinement transition. The theoretical basis of this effect has recently attracted much attention; yet so far these investigations have not included another, equally dramatic consequence of the peripheral collision geometry: the QGP acquires a large angular momentum vector, parallel to the magnetic field. Here we use holographic techniques to argue that the angular momentum can also, independently, have an effect on transition temperatures, and we obtain a rough estimate of the relative effects of the presence of both a magnetic field and an angular momentum density. We find that the shearing angular momentum reinforces the effect of the magne...

  18. Shear Viscosity from Lattice QCD

    CERN Document Server

    Mages, Simon W; Fodor, Zoltán; Schäfer, Andreas; Szabó, Kálmán

    2015-01-01

    Understanding of the transport properties of the the quark-gluon plasma is becoming increasingly important to describe current measurements at heavy ion collisions. This work reports on recent efforts to determine the shear viscosity h in the deconfined phase from lattice QCD. The main focus is on the integration of the Wilson flow in the analysis to get a better handle on the infrared behaviour of the spectral function which is relevant for transport. It is carried out at finite Wilson flow time, which eliminates the dependence on the lattice spacing. Eventually, a new continuum limit has to be carried out which sends the new regulator introduced by finite flow time to zero. Also the non-perturbative renormalization strategy applied for the energy momentum tensor is discussed. At the end some quenched results for temperatures up to 4 : 5 T c are presented

  19. Robot-assisted cardiac surgery.

    Science.gov (United States)

    Ishikawa, Norihiko; Watanabe, Go

    2015-01-01

    Recognition of the significant advantages of minimizing surgical trauma has resulted in the development of minimally invasive surgical procedures. Endoscopic surgery offers patients the benefits of minimally invasive surgery, and surgical robots have enhanced the ability and precision of surgeons. Consequently, technological advances have facilitated totally endoscopic robotic cardiac surgery, which has allowed surgeons to operate endoscopically rather than through a median sternotomy during cardiac surgery. Thus, repairs for structural heart conditions, including mitral valve plasty, atrial septal defect closure, multivessel minimally invasive direct coronary artery bypass grafting (MIDCAB), and totally endoscopic coronary artery bypass graft surgery (CABG), can be totally endoscopic. Robot-assisted cardiac surgery as minimally invasive cardiac surgery is reviewed. PMID:26134073

  20. Recent developments in cardiac pacing.

    Science.gov (United States)

    Rodak, D J

    1995-10-01

    Indications for cardiac pacing continue to expand. Pacing to improve functional capacity, which is now common, relies on careful patient selection and technical improvements, such as complex software algorithms and diagnostic capabilities.

  1. Robotic Applications in Cardiac Surgery

    Directory of Open Access Journals (Sweden)

    Alan P. Kypson

    2008-11-01

    Full Text Available Traditionally, cardiac surgery has been performed through a median sternotomy, which allows the surgeon generous access to the heart and surrounding great vessels. As a paradigm shift in the size and location of incisions occurs in cardiac surgery, new methods have been developed to allow the surgeon the same amount of dexterity and accessibility to the heart in confined spaces and in a less invasive manner. Initially, long instruments without pivot points were used, however, more recent robotic telemanipulation systems have been applied that allow for improved dexterity, enabling the surgeon to perform cardiac surgery from a distance not previously possible. In this rapidly evolving field, we review the recent history and clinical results of using robotics in cardiac surgery.

  2. Dynamics of colloidal crystals in shear flow

    NARCIS (Netherlands)

    Derks, D.; Wu, Y.L.; van Blaaderen, A.; Imhof, A.

    2009-01-01

    We investigate particle dynamics in nearly hard sphere colloidal crystals submitted to a steady shear flow. Both the fluctuations of single colloids and the collective motion of crystalline layers as a whole are studied by using a home-built counter rotating shear cell in combination with confocal m

  3. On the shear instability of fluid interfaces

    OpenAIRE

    Alexakis, A.; Young, Y; Rosner, R

    2001-01-01

    We examine the linear stability of fluid interfaces subjected to a shear flow. Our main object is to generalize previous work to arbitrary Atwood number, and to allow for surface tension and weak compressibility. The motivation derives from instances in astrophysical systems where mixing across material interfaces driven by shear flows may significantly affect the dynamical evolution of these systems.

  4. Cardiac Biomarkers in Hyperthyroid Cats

    OpenAIRE

    Sangster, Jodi Kirsten

    2013-01-01

    Background: Hyperthyroidism has substantial effects on the circulatory system. The cardiac biomarkers NT-proBNP and troponin I (cTNI) have proven useful in identifying cats with myocardial disease but have not been as extensively investigated in hyperthyroidism.Hypothesis: Plasma NT-proBNP and cTNI concentrations are higher in cats with primary cardiac disease than in cats with hyperthyroidism and higher in cats with hyperthyroidism than in healthy control cats.Animals: Twenty-three hyperthyr...

  5. Cardiac manifestations in systemic sclerosis

    Institute of Scientific and Technical Information of China (English)

    Sevdalina; Lambova

    2014-01-01

    Primary cardiac involvement, which develops as a direct consequence of systemic sclerosis(SSc), may manifest as myocardial damage, fibrosis of the conduction system, pericardial and, less frequently, as valvular disease. In addition, cardiac complications in SSc may develop as a secondary phenomenon due to pulmonary arterial hypertension and kidney pathology. The prevalence of primary cardiac involvement in SSc is variable and difficult to determine because of the diversity of cardiac manifestations, the presence of subclinical periods, the type of diagnostic tools applied, and the diversity of patient populations. When clinically manifested, cardiac involvement is thought to be an important prognostic factor. Profound microvascular disease is a pathognomonic feature of SSc, as both vasospasm and structural alterations are present. Such alterations are thought to predict macrovascular atherosclerosis over time. There are contradictory reports regarding the prevalence of atherosclerosis in SSc. According to some authors, the prevalence of atherosclerosis of the large epicardial coronary arteries is similar to that of the general population, in contrast with other rheumatic diseases such as rheumatoid arthritis and systemic lupus erythematosus. However, the level of inflammation in SSc is inferior. Thus, the atherosclerotic process may not be as aggressive and not easily detectable in smaller studies. Echocardiography(especially tissue Doppler imaging), single-photon emission computed tomography, magnetic resonance imaging and cardiac computed tomography are sensitive techniques for earlier detection of both structural and functional scleroderma-related cardiac pathologies. Screening for subclinical cardiac involvement via modern, sensitive tools provides an opportunity for early diagnosis and treatment, which is of crucial importance for a positive outcome.

  6. Computational Modeling of Cardiac Electromechanics

    OpenAIRE

    Krishnamoorthi, Shankarjee

    2013-01-01

    Cardiac arrhythmias are a leading cause of death worldwide. Notably, the electrophysiologiy and microstructural requirements for a fatal ventricular arrhythmia remain incompletely understood, thereby the treatment remains largely empirical. Standard antiarrhythmic drug therapy has failed to reduce, and in some instances has increased, the incidence of Sudden Cardiac Death (SCD). Hence, a more complete understanding of the mechanisms that foment a fatal arrhythmia is needed and computational m...

  7. Current trends in cardiac rehabilitation

    OpenAIRE

    Dafoe, W; Huston, P

    1997-01-01

    Cardiac rehabilitation can reduce mortality and morbidity for patients with many types of cardiac disease cost-effectively, yet is generally underutilized. Rehabilitation is helpful not only for patients who have had a myocardial infarction but also for those with stable angina or congestive heart failure or those who have undergone myocardial revascularization procedures, a heart transplant or heart valve surgery. The beneficial effects of rehabilitation include a reduction in the rate of de...

  8. An overview of cardiac morphogenesis.

    OpenAIRE

    Schleich, Jean-Marc; Abdulla, Tariq; Summers, Ron; Houyel, Lucile

    2013-01-01

    International audience Accurate knowledge of normal cardiac development is essential for properly understanding the morphogenesis of congenital cardiac malformations that represent the most common congenital anomaly in newborns. The heart is the first organ to function during embryonic development and is fully formed at 8 weeks of gestation. Recent studies stemming from molecular genetics have allowed specification of the role of cellular precursors in the field of heart development. In th...

  9. Physiological and pathological cardiac hypertrophy.

    Science.gov (United States)

    Shimizu, Ippei; Minamino, Tohru

    2016-08-01

    The heart must continuously pump blood to supply the body with oxygen and nutrients. To maintain the high energy consumption required by this role, the heart is equipped with multiple complex biological systems that allow adaptation to changes of systemic demand. The processes of growth (hypertrophy), angiogenesis, and metabolic plasticity are critically involved in maintenance of cardiac homeostasis. Cardiac hypertrophy is classified as physiological when it is associated with normal cardiac function or as pathological when associated with cardiac dysfunction. Physiological hypertrophy of the heart occurs in response to normal growth of children or during pregnancy, as well as in athletes. In contrast, pathological hypertrophy is induced by factors such as prolonged and abnormal hemodynamic stress, due to hypertension, myocardial infarction etc. Pathological hypertrophy is associated with fibrosis, capillary rarefaction, increased production of pro-inflammatory cytokines, and cellular dysfunction (impairment of signaling, suppression of autophagy, and abnormal cardiomyocyte/non-cardiomyocyte interactions), as well as undesirable epigenetic changes, with these complex responses leading to maladaptive cardiac remodeling and heart failure. This review describes the key molecules and cellular responses involved in physiological/pathological cardiac hypertrophy. PMID:27262674

  10. FGF21 and cardiac physiopathology

    Directory of Open Access Journals (Sweden)

    Anna ePlanavila

    2015-08-01

    Full Text Available The heart is not traditionally considered either a target or a site of fibroblast growth factor-21 (FGF21 production. However, recent findings indicate that FGF21 can act as a cardiomyokine; that is, it is produced by cardiac cells at significant levels and acts in an autocrine manner on the heart itself. The heart is sensitive to the effects of FGF21, both systemic and locally generated, owing to the expression in cardiomyocytes of β-Klotho, the key co-receptor known to confer specific responsiveness to FGF21 action. FGF21 has been demonstrated to protect against cardiac hypertrophy, cardiac inflammation, and oxidative stress. FGF21 expression in the heart is induced in response to cardiac insults, such as experimental cardiac hypertrophy and myocardial infarction in rodents, as well as in failing human hearts. Intracellular mechanisms involving PPARα and Sirt1 mediate transcriptional regulation of the FGF21 gene in response to exogenous stimuli. In humans, circulating FGF21 levels are elevated in coronary heart disease and atherosclerosis, and are associated with a higher risk of cardiovascular events in patients with type 2 diabetes. These findings provide new insights into the role of FGF21 in the heart and may offer potential therapeutic strategies for cardiac disease.

  11. [Stem cells and cardiac regeneration].

    Science.gov (United States)

    Perez Millan, Maria Ines; Lorenti, Alicia

    2006-01-01

    Stem cells are defined by virtue of their functional attributes: absence of tissue specific differentitated markers, capable of proliferation, able to self-maintain the population, able to produce a large number of differentiated, functional progeny, able to regenerate the tissue after injury. Cell therapy is an alternative for the treatment of several diseases, like cardiac diseases (cell cardiomyoplasty). A variety of stem cells could be used for cardiac repair: from cardiac and extracardiac sources. Each cell type has its own profile of advantages, limitations, and practicability issues in specific clinical settings. Differentiation of bone marrow stem cells to cardiomyocyte-like cells have been observed under different culture conditions. The presence of resident cardiac stem cell population capable of differentiation into cardiomyocyte or vascular lineage suggests that these cells could be used for cardiac tissue repair, and represent a great promise for clinical application. Stem cells mobilization by cytokines may also offer a strategy for cardiac regeneration. The use of stem cells (embryonic and adult) may hold the key to replacing cells lost in many devastating diseases. This potential benefit is a major focus for stem cell research.

  12. Cardiac Regeneration and Stem Cells.

    Science.gov (United States)

    Zhang, Yiqiang; Mignone, John; MacLellan, W Robb

    2015-10-01

    After decades of believing the heart loses the ability to regenerate soon after birth, numerous studies are now reporting that the adult heart may indeed be capable of regeneration, although the magnitude of new cardiac myocyte formation varies greatly. While this debate has energized the field of cardiac regeneration and led to a dramatic increase in our understanding of cardiac growth and repair, it has left much confusion in the field as to the prospects of regenerating the heart. Studies applying modern techniques of genetic lineage tracing and carbon-14 dating have begun to establish limits on the amount of endogenous regeneration after cardiac injury, but the underlying cellular mechanisms of this regeneration remained unclear. These same studies have also revealed an astonishing capacity for cardiac repair early in life that is largely lost with adult differentiation and maturation. Regardless, this renewed focus on cardiac regeneration as a therapeutic goal holds great promise as a novel strategy to address the leading cause of death in the developed world.

  13. Cardiac involvement in myotonic dystrophy

    DEFF Research Database (Denmark)

    Lund, Marie; Diaz, Lars Jorge; Ranthe, Mattis Flyvholm;

    2014-01-01

    genetic testing for DM1. Information on incident cardiac diseases was obtained from the NPR. We estimated standardized incidence ratios (SIRs) of cardiac disease compared with the background population, overall and according to selected diagnostic subgroups (cardiomyopathy, heart failure, conduction...... disorders, arrhythmias, and device implantation). In the DM cohort, SIR for any cardiac disease was 3.42 [95% confidence interval (CI) 3.01-3.86]; for a cardiac disease belonging to the selected subgroups 6.91 (95% CI: 5.93-8.01) and for other cardiac disease 2.59 (95% CI: 2.03-3.25). For a cardiac disease...... belonging to the selected subgroups, the risk was particularly high in the first year after DM diagnosis [SIR 15.4 (95% CI: 10.9-21.3)] but remained significantly elevated in subsequent years [SIR 6.07 (95% CI: 5.11-7.16]). The risk was higher in young cohort members [e.g. 20-39 years: SIR 18.1 (95% CI: 12...

  14. Cardiac imaging. A multimodality approach

    Energy Technology Data Exchange (ETDEWEB)

    Thelen, Manfred [Johannes Gutenberg University Hospital, Mainz (Germany); Erbel, Raimund [University Hospital Essen (Germany). Dept. of Cardiology; Kreitner, Karl-Friedrich [Johannes Gutenberg University Hospital, Mainz (Germany). Clinic and Polyclinic for Diagnostic and Interventional Radiology; Barkhausen, Joerg (eds.) [University Hospital Schleswig-Holstein, Luebeck (Germany). Dept. of Radiology and Nuclear Medicine

    2009-07-01

    An excellent atlas on modern diagnostic imaging of the heart Written by an interdisciplinary team of experts, Cardiac Imaging: A Multimodality Approach features an in-depth introduction to all current imaging modalities for the diagnostic assessment of the heart as well as a clinical overview of cardiac diseases and main indications for cardiac imaging. With a particular emphasis on CT and MRI, the first part of the atlas also covers conventional radiography, echocardiography, angiography and nuclear medicine imaging. Leading specialists demonstrate the latest advances in the field, and compare the strengths and weaknesses of each modality. The book's second part features clinical chapters on heart defects, endocarditis, coronary heart disease, cardiomyopathies, myocarditis, cardiac tumors, pericardial diseases, pulmonary vascular diseases, and diseases of the thoracic aorta. The authors address anatomy, pathophysiology, and clinical features, and evaluate the various diagnostic options. Key features: - Highly regarded experts in cardiology and radiology off er image-based teaching of the latest techniques - Readers learn how to decide which modality to use for which indication - Visually highlighted tables and essential points allow for easy navigation through the text - More than 600 outstanding images show up-to-date technology and current imaging protocols Cardiac Imaging: A Multimodality Approach is a must-have desk reference for cardiologists and radiologists in practice, as well as a study guide for residents in both fields. It will also appeal to cardiac surgeons, general practitioners, and medical physicists with a special interest in imaging of the heart. (orig.)

  15. Experimental study on the adiabatic shear bands

    International Nuclear Information System (INIS)

    Four martensitic steels (Z50CDV5 steel, 28CND8 steel, 35NCDV16 steel and 4340 steel) with different hardness between 190 and 600 Hsub(B) (Brinell hardness), have been studied by means of dynamic compressive tests on split Hopkinson pressure bar. Microscopic observations show that the fracture are associated to the development of adiabatic shear bands (except 4340 steel with 190 Hsub(B) hardness). By means of tests for which the deformation is stopped at predetermined levels, the measurement of shear and hardness inside the band and the matrix indicates the chronology of this phenomenon: first the localization of shear, followed by the formation of adiabatic shear band and ultimatly crack initiation and propagation. These results correlated with few simulations by finite elements have permitted to suggest two mecanisms of deformation leading to the formation of adiabatic shear bands in this specific test

  16. Sheared Ising models in three dimensions

    Science.gov (United States)

    Hucht, Alfred; Angst, Sebastian

    2013-03-01

    The nonequilibrium phase transition in sheared three-dimensional Ising models is investigated using Monte Carlo simulations in two different geometries corresponding to different shear normals [A. Hucht and S. Angst, EPL 100, 20003 (2012)]. We demonstrate that in the high shear limit both systems undergo a strongly anisotropic phase transition at exactly known critical temperatures Tc which depend on the direction of the shear normal. Using dimensional analysis, we determine the anisotropy exponent θ = 2 as well as the correlation length exponents ν∥ = 1 and ν⊥ = 1 / 2 . These results are verified by simulations, though considerable corrections to scaling are found. The correlation functions perpendicular to the shear direction can be calculated exactly and show Ornstein-Zernike behavior. Supported by CAPES-DAAD through PROBRAL as well as by the German Research Society (DFG) through SFB 616 ``Energy Dissipation at Surfaces.''

  17. Numerical analysis of cross shear plate rolling

    DEFF Research Database (Denmark)

    Zhang, Wenqi; Bay, Niels

    1997-01-01

    The rolling process is widely applied for industrial production of metal plates. In conventional plate rolling the two work rolls are rotating at the same peripheral speed. By introducing a specific difference in the speed of the two work rolls, cross shear rolling is introduced forming a central...... shear zone between the forward and backward slip zones in the deformation zone thus lowering the rolling load. A numerical analysis of the cross shear rolling process is carried out based on the slab method adopting Wanheim and Bay's general friction model. The pressure distribution along the contact...... are in the roll gap, the position and the size of the shear zone and the rolling load are calculated. Experimental results are presented verifying the calculations. The numerical analysis facilitates a better understanding of the mechanics in cross shear plate rolling....

  18. Squirming through shear-thinning fluids

    CERN Document Server

    Datt, Charu; Elfring, Gwynn J; Pak, On Shun

    2015-01-01

    Many microorganisms find themselves immersed in fluids displaying non-Newtonian rheological properties such as viscoelasticity and shear-thinning viscosity. The effects of viscoelasticity on swimming at low Reynolds numbers have already received considerable attention, but much less is known about swimming in shear-thinning fluids. A general understanding of the fundamental question of how shear-thinning rheology influences swimming still remains elusive. To probe this question further, we study a spherical squirmer in a shear-thinning fluid using a combination of asymptotic analysis and numerical simulations. Shear-thinning rheology is found to affect a squirming swimmer in nontrivial and surprising ways; we predict and show instances of both faster and slower swimming depending on the surface actuation of the squirmer. We also illustrate that while a drag and thrust decomposition can provide insights into swimming in Newtonian fluids, extending this intuition to problems in complex media can prove problemat...

  19. Trapped Electron Precession Shear Induced Fluctuation Decorrelation

    International Nuclear Information System (INIS)

    We consider the effects of trapped electron precession shear on the microturbulence. In a similar way the strong E x B shear reduces the radial correlation length of ambient fluctuations, the radial variation of the trapped electron precession frequency can reduce the radial correlation length of fluctuations associated with trapped electrons. In reversed shear plasmas, with the explicit dependence of the trapped electron precession shearing rate on B(subscript)theta, the sharp radial gradient of T(subscript)e due to local electron heating inside qmin can make the precession shearing mechanism more effective, and reduce the electron thermal transport constructing a positive feedback loop for the T(subscript)e barrier formation

  20. Simple shear of deformable square objects

    Science.gov (United States)

    Treagus, Susan H.; Lan, Labao

    2003-12-01

    Finite element models of square objects in a contrasting matrix in simple shear show that the objects deform to a variety of shapes. For a range of viscosity contrasts, we catalogue the changing shapes and orientations of objects in progressive simple shear. At moderate simple shear ( γ=1.5), the shapes are virtually indistinguishable from those in equivalent pure shear models with the same bulk strain ( RS=4), examined in a previous study. In theory, differences would be expected, especially for very stiff objects or at very large strain. In all our simple shear models, relatively competent square objects become asymmetric barrel shapes with concave shortened edges, similar to some types of boudin. Incompetent objects develop shapes surprisingly similar to mica fish described in mylonites.

  1. Quantitative imaging of nonlinear shear modulus by combining static elastography and shear wave elastography.

    Science.gov (United States)

    Latorre-Ossa, Heldmuth; Gennisson, Jean-Luc; De Brosses, Emilie; Tanter, Mickaël

    2012-04-01

    The study of new tissue mechanical properties such as shear nonlinearity could lead to better tissue characterization and clinical diagnosis. This work proposes a method combining static elastography and shear wave elastography to derive the nonlinear shear modulus by applying the acoustoelasticity theory in quasi-incompressible soft solids. Results demonstrate that by applying a moderate static stress at the surface of the investigated medium, and by following the quantitative evolution of its shear modulus, it is possible to accurately and quantitatively recover the local Landau (A) coefficient characterizing the shear nonlinearity of soft tissues.

  2. Risk factors and the effect of cardiac resynchronization therapy on cardiac and non-cardiac mortality in MADIT-CRT

    DEFF Research Database (Denmark)

    Perkiomaki, Juha S; Ruwald, Anne-Christine; Kutyifa, Valentina;

    2015-01-01

    causes, 108 (63.9%) deemed cardiac, and 61 (36.1%) non-cardiac. In multivariate analysis, increased baseline creatinine was significantly associated with both cardiac and non-cardiac deaths [hazard ratio (HR) 2.97, P ...AIMS: To understand modes of death and factors associated with the risk for cardiac and non-cardiac deaths in patients with cardiac resynchronization therapy with implantable cardioverter-defibrillator (CRT-D) vs. implantable cardioverter-defibrillator (ICD) therapy, which may help clarify...... the action and limitations of cardiac resynchronization therapy (CRT) in relieving myocardial dysfunction. METHODS AND RESULTS: In Multicenter Automatic Defibrillator Implantation Trial-Cardiac Resynchronization Therapy (MADIT-CRT), during 4 years of follow-up, 169 (9.3%) of 1820 patients died of known...

  3. Cardiac output during exercise

    DEFF Research Database (Denmark)

    Siebenmann, C; Rasmussen, P.; Sørensen, H.;

    2015-01-01

    Several techniques assessing cardiac output (Q) during exercise are available. The extent to which the measurements obtained from each respective technique compares to one another, however, is unclear. We quantified Q simultaneously using four methods: the Fick method with blood obtained from...... the right atrium (Q(Fick-M)), Innocor (inert gas rebreathing; Q(Inn)), Physioflow (impedance cardiography; Q(Phys)), and Nexfin (pulse contour analysis; Q(Pulse)) in 12 male subjects during incremental cycling exercise to exhaustion in normoxia and hypoxia (FiO2  = 12%). While all four methods reported...... a progressive increase in Q with exercise intensity, the slopes of the Q/oxygen uptake (VO2) relationship differed by up to 50% between methods in both normoxia [4.9 ± 0.3, 3.9 ± 0.2, 6.0 ± 0.4, 4.8 ± 0.2 L/min per L/min (mean ± SE) for Q(Fick-M), Q(Inn), QP hys and Q(Pulse), respectively; P = 0...

  4. Inverse magnetic/shear catalysis

    Science.gov (United States)

    McInnes, Brett

    2016-05-01

    It is well known that very large magnetic fields are generated when the Quark-Gluon Plasma is formed during peripheral heavy-ion collisions. Lattice, holographic, and other studies strongly suggest that these fields may, for observationally relevant field values, induce "inverse magnetic catalysis", signalled by a lowering of the critical temperature for the chiral/deconfinement transition. The theoretical basis of this effect has recently attracted much attention; yet so far these investigations have not included another, equally dramatic consequence of the peripheral collision geometry: the QGP acquires a large angular momentum vector, parallel to the magnetic field. Here we use holographic techniques to argue that the angular momentum can also, independently, have an effect on transition temperatures, and we obtain a rough estimate of the relative effects of the presence of both a magnetic field and an angular momentum density. We find that the shearing angular momentum reinforces the effect of the magnetic field at low values of the baryonic chemical potential, but that it can actually decrease that effect at high chemical potentials.

  5. IMAGE ANALYSIS FOR MODELLING SHEAR BEHAVIOUR

    Directory of Open Access Journals (Sweden)

    Philippe Lopez

    2011-05-01

    Full Text Available Through laboratory research performed over the past ten years, many of the critical links between fracture characteristics and hydromechanical and mechanical behaviour have been made for individual fractures. One of the remaining challenges at the laboratory scale is to directly link fracture morphology of shear behaviour with changes in stress and shear direction. A series of laboratory experiments were performed on cement mortar replicas of a granite sample with a natural fracture perpendicular to the axis of the core. Results show that there is a strong relationship between the fracture's geometry and its mechanical behaviour under shear stress and the resulting damage. Image analysis, geostatistical, stereological and directional data techniques are applied in combination to experimental data. The results highlight the role of geometric characteristics of the fracture surfaces (surface roughness, size, shape, locations and orientations of asperities to be damaged in shear behaviour. A notable improvement in shear understanding is that shear behaviour is controlled by the apparent dip in the shear direction of elementary facets forming the fracture.

  6. Patch in Cardiac Surgery

    Directory of Open Access Journals (Sweden)

    Alireza Alizadeh Ghavidel

    2014-06-01

    Full Text Available Introduction: Excessive bleeding presents a risk for the patient in cardiovascular surgery. Local haemostatic agents are of great value to reduce bleeding and related complications. TachoSil (Nycomed, Linz, Austria is a sterile, haemostatic agent that consists of an equine collagen patchcoated with human fibrinogen and thrombin. This study evaluated the safety and efficacy of TachoSil compared to conventional technique.Methods: Forty-two patients scheduled for open heart surgeries, were entered to this study from August 2010 to May 2011. After primary haemostatic measures, patients divided in two groups based on surgeon’s judgment. Group A: 20 patients for whom TachoSil was applied and group B: 22 patients that conventional method using Surgicel (13 patients or wait and see method (9 cases, were performed in order to control the bleeding. In group A, 10 patients were male with mean age of 56.95±15.67 years and in group B, 9 cases were male with mean age of 49.95±14.41 years. In case group 70% (14/20 of the surgeries were redo surgeries versus 100% (22/22 in control group.Results: Baseline characteristics were similar in both groups. In TachoSil group 75% of patients required transfusion versus 90.90% in group B (P=0.03.Most transfusions consisted of packed red blood cell; 2±1.13 units in group A versus 3.11±1.44 in group B (P=0.01, however there were no significant differences between two groups regarding the mean total volume of intra and post-operative bleeding. Re-exploration was required in 10% in group A versus 13.63% in group B (P=0.67.Conclusion: TachoSil may act as a superior alternative in different types of cardiac surgery in order to control the bleeding and therefore reducing transfusion requirement.

  7. Cardiac output monitoring

    Directory of Open Access Journals (Sweden)

    Mathews Lailu

    2008-01-01

    Full Text Available Minimally invasive and non-invasive methods of estimation of cardiac output (CO were developed to overcome the limitations of invasive nature of pulmonary artery catheterization (PAC and direct Fick method used for the measurement of stroke volume (SV. The important minimally invasive techniques available are: oesophageal Doppler monitoring (ODM, the derivative Fick method (using partial carbon dioxide (CO 2 breathing, transpulmonary thermodilution, lithium indicator dilution, pulse contour and pulse power analysis. Impedance cardiography is probably the only non-invasive technique in true sense. It provides information about haemodynamic status without the risk, cost and skill associated with the other invasive or minimally invasive techniques. It is important to understand what is really being measured and what assumptions and calculations have been incorporated with respect to a monitoring device. Understanding the basic principles of the above techniques as well as their advantages and limitations may be useful. In addition, the clinical validation of new techniques is necessary to convince that these new tools provide reliable measurements. In this review the physics behind the working of ODM, partial CO 2 breathing, transpulmonary thermodilution and lithium dilution techniques are dealt with. The physical and the physiological aspects underlying the pulse contour and pulse power analyses, various pulse contour techniques, their development, advantages and limitations are also covered. The principle of thoracic bioimpedance along with computation of CO from changes in thoracic impedance is explained. The purpose of the review is to help us minimize the dogmatic nature of practice favouring one technique or the other.

  8. Fan-structure waves in shear ruptures

    Science.gov (United States)

    Tarasov, Boris

    2016-04-01

    This presentation introduces a recently identified shear rupture mechanism providing a paradoxical feature of hard rocks - the possibility of shear rupture propagation through the highly confined intact rock mass at shear stress levels significantly less than frictional strength. According to the fan-mechanism the shear rupture propagation is associated with consecutive creation of small slabs in the fracture tip which, due to rotation caused by shear displacement of the fracture interfaces, form a fan-structure representing the fracture head. The fan-head combines such unique features as: extremely low shear resistance (below the frictional strength), self-sustaining stress intensification in the rupture tip (providing easy formation of new slabs), and self-unbalancing conditions in the fan-head (making the failure process inevitably spontaneous and violent). An important feature of the fan-mechanism is the fact that for the initial formation of the fan-structure an enhanced local shear stress is required, however, after completion of the fan-structure it can propagate as a dynamic wave through intact rock mass at shear stresses below the frictional strength. Paradoxically low shear strength of pristine rocks provided by the fan-mechanism determines the correspondingly low transient strength of the lithosphere, which favours generation of new earthquake faults in the intact rock mass adjoining pre-existing faults in preference to frictional stick-slip instability along these faults. The new approach reveals an alternative role of pre-existing faults in earthquake activity: they represent local stress concentrates in pristine rock adjoining the fault where special conditions for the fan-mechanism nucleation are created, while further dynamic propagation of the new fault (earthquake) occurs at low field stresses even below the frictional strength.

  9. Shear Reinforcements in the Reinforced Concrete Beams

    Directory of Open Access Journals (Sweden)

    Moayyad M. Al-Nasra

    2013-10-01

    Full Text Available - This study focuses on the use of different types of shear reinforcement in the reinforced concrete beams. Four different types of shear reinforcement are investigated; traditional stirrups, welded swimmer bars, bolted swimmer bars, and u-link bolted swimmer bars. Beam shear strength as well as beam deflection are the main two factors considered in this study. Shear failure in reinforced concrete beams is one of the most undesirable modes of failure due to its rapid progression. This sudden type of failure made it necessary to explore more effective ways to design these beams for shear. The reinforced concrete beams show different behavior at the failure stage in shear compare to the bending, which is considered to be unsafe mode of failure. The diagonal cracks that develop due to excess shear forces are considerably wider than the flexural cracks. The cost and safety of shear reinforcement in reinforced concrete beams led to the study of other alternatives. Swimmer bar system is a new type of shear reinforcement. It is a small inclined bars, with its both ends bent horizontally for a short distance and welded or bolted to both top and bottom flexural steel reinforcement. Regardless of the number of swimmer bars used in each inclined plane, the swimmer bars form plane-crack interceptor system instead of bar-crack interceptor system when stirrups are used. Several reinforced concrete beams were carefully prepared and tested in the lab. The results of these tests will be presented and discussed. The deflection of each beam is also measured at incrementally increased applied load.

  10. Computed tomography of cardiac pseudotumors and neoplasms.

    Science.gov (United States)

    Anavekar, Nandan S; Bonnichsen, Crystal R; Foley, Thomas A; Morris, Michael F; Martinez, Matthew W; Williamson, Eric E; Glockner, James F; Miller, Dylan V; Breen, Jerome F; Araoz, Philip A

    2010-07-01

    Important features of cardiac masses can be clearly delineated on cardiac computed tomography (CT) imaging. This modality is useful in identifying the presence of a mass, its relationship with cardiac and extracardiac structures, and the features that distinguish one type of mass from another. A multimodality approach to the evaluation of cardiac tumors is advocated, with the use of echocardiography, CT imaging and magnetic resonance imaging as appropriately indicated. In this article, various cardiac masses are described, including pseudotumors and true cardiac neoplasms, and the CT imaging findings that may be useful in distinguishing these rare entities are presented. PMID:20705174

  11. Shear viscosity of liquid mixtures: Mass dependence

    International Nuclear Information System (INIS)

    Expressions for zeroth, second, and fourth sum rules of transverse stress autocorrelation function of two component fluid have been derived. These sum rules and Mori's memory function formalism have been used to study shear viscosity of Ar-Kr and isotopic mixtures. It has been found that theoretical result is in good agreement with the computer simulation result for the Ar-Kr mixture. The mass dependence of shear viscosity for different mole fraction shows that deviation from ideal linear model comes even from mass difference in two species of fluid mixture. At higher mass ratio shear viscosity of mixture is not explained by any of the emperical model. (author)

  12. Cardiac Penetrating Injuries and Pseudoaneurysm

    Institute of Scientific and Technical Information of China (English)

    CHEN Shifeng

    2002-01-01

    Objective To discuss the early diagnosis and treatment of cardiac penetrating injuries and pseudoaneurysm. Methods 18 cases of cardiac penetrating injuries, in which 2 cases were complicated with pseudoaneurysm, were diagnosed by emergency operation and color Doppler echocardiography between May 1973 and Dec. 2001 in our hospital. The basis for emergency operation is the injured path locating in cardiac dangerous zone, severe shock or pericardial tamponade. ResultsAmong 18 cases of this study, 17 cases underwent emergency operation. During the operation, 11 cases were found injured in right ventricle, 2 cases were found injured in right atrium, 1 case was found injured in pulmonary artery,4 cases were found injured in left ventricle, 2 cases were found complicated with pseudoaneurysm. 17cases underwent cardiac repair including 1 case of rupture of aneurysm. 1 case underwent elective aneurysm resection. In whole group, 15 cases survived(83.33% ), 3 cases died( 16.67%). The cause of death is mainly hemorrhagic shock. Conclusion Highly suspicious cardiac penetrating injuries or hemopericaridium should undergo direct operative exploration. Pseudoaneurysm should be resected early,which can prevent severe complications.

  13. Vitamin D and Cardiac Differentiation.

    Science.gov (United States)

    Kim, Irene M; Norris, Keith C; Artaza, Jorge N

    2016-01-01

    Calcitriol (1,25-dihydroxycholecalciferol or 1,25-D3) is the hormonally active metabolite of vitamin D. Experimental studies of vitamin D receptors and 1,25-D3 establish calcitriol to be a critical regulator of the structure and function of the heart. Clinical studies link vitamin D deficiency with cardiovascular disease (CVD). Emerging evidence demonstrates that calcitriol is highly involved in CVD-related signaling pathways, particularly the Wnt signaling pathway. Addition of 1,25-D3 to cardiomyocyte cells and examination of its effects on cardiomyocytes and mainly Wnt11 signaling allowed the specific characterization of the role of calcitriol in cardiac differentiation. 1,25-D3 is demonstrated to: (i) inhibit cell proliferation without promoting apoptosis; (ii) decrease expression of genes related to the regulation of the cell cycle; (iii) promote formation of cardiomyotubes; (iv) induce expression of casein kinase-1-α1, a negative regulator of the canonical Wnt signaling pathway; and (v) increase expression of noncanonical Wnt11, which has been recognized to induce cardiac differentiation during embryonic development and in adult cells. Thus, it appears that vitamin D promotes cardiac differentiation through negative modulation of the canonical Wnt signaling pathway and upregulation of noncanonical Wnt11 expression. Future work to elucidate the role(s) of vitamin D in cardiovascular disorders will hopefully lead to improvement and potentially prevention of CVD, including abnormal cardiac differentiation in settings such as postinfarction cardiac remodeling. PMID:26827957

  14. Cardiac factors in orthostatic hypotension

    Science.gov (United States)

    Löllgen, H.; Dirschedl, P.; Koppenhagen, K.; Klein, K. E.

    Cardiac function is determined by preload, afterload, heart rate and contractility. During orthostatic stress, the footward blood shift is compensated for by an increase of afterload. LBNP is widely used to analyze effects of volume displacement during orthostatic stress. Comparisons of invasive ( right heart catheterization) and non-invasive approach (echocardiography) yielded similar changes. Preload and afterload change with graded LBNP, heart rate increases, and stroke volume and cardiac output decrease. Thus, the working point on the left ventricular function curve is shifted to the left and downward, similar to hypovolemia. However, position on the Frank-Starling curve, the unchanged ejection fraction, and the constant Vcf indicate a normal contractile state during LBNP. A decrease of arterial oxygen partial pressure during LBNP shwos impaired ventilation/perfusion ratio. Finally, LBNP induced cardiac and hemodynamic changes can be effectively countermeasured by dihydroergotamine, a potent venoconstrictor. Comparison of floating catheter data with that of echocardiography resulted in close correlation for cardiac output and stroke volume. In addition, cardiac dimensions changed in a similar way during LBNP. From our findings, echocardiography as a non-invasive procedure can reliably used in LBNP and orthostatic stress tests. Some informations can be obtained on borderline values indicating collaps or orthostatic syncope. Early fainters can be differentiated from late fainters by stroke volume changes.

  15. Animal models of cardiac cachexia.

    Science.gov (United States)

    Molinari, Francesca; Malara, Natalia; Mollace, Vincenzo; Rosano, Giuseppe; Ferraro, Elisabetta

    2016-09-15

    Cachexia is the loss of body weight associated with several chronic diseases including chronic heart failure (CHF). The cachectic condition is mainly due to loss of skeletal muscle mass and adipose tissue depletion. The majority of experimental in vivo studies on cachexia rely on animal models of cancer cachexia while a reliable and appropriate model for cardiac cachexia has not yet been established. A critical issue in generating a cardiac cachexia model is that genetic modifications or pharmacological treatments impairing the heart functionality and used to obtain the heart failure model might likely impair the skeletal muscle, this also being a striated muscle and sharing with the myocardium several molecular and physiological mechanisms. On the other hand, often, the induction of heart damage in the several existing models of heart failure does not necessarily lead to skeletal muscle loss and cachexia. Here we describe the main features of cardiac cachexia and illustrate some animal models proposed for cardiac cachexia studies; they include the genetic calsequestrin and Dahl salt-sensitive models, the monocrotaline model and the surgical models obtained by left anterior descending (LAD) ligation, transverse aortic constriction (TAC) and ascending aortic banding. The availability of a specific animal model for cardiac cachexia is a crucial issue since, besides the common aspects of cachexia in the different syndromes, each disease has some peculiarities in its etiology and pathophysiology leading to cachexia. Such peculiarities need to be unraveled in order to find new targets for effective therapies. PMID:27317993

  16. Epicardial Lineages and Cardiac Repair

    Directory of Open Access Journals (Sweden)

    Manvendra K. Singh

    2013-08-01

    Full Text Available The death of cardiac myocytes resulting from myocardial infarction is a major cause of heart failure worldwide. Effective therapies for regenerating lost cardiac myocytes are lacking. Recently, the epicardium has been implicated as a source of inflammatory cytokines, growth factors and progenitor cells that modulate the response to myocardial injury. During embryonic development, epicardially-derived cells have the potential to differentiate into multiple cardiac lineages, including fibroblasts, vascular smooth muscle and potentially other cell types. In the healthy adult heart, epicardial cells are thought to be generally quiescent. However, injury of the adult heart results in reactivation of a developmental gene program in the epicardium, which leads to increased epicardial cell proliferation and differentiation of epicardium-derived cells (EPDCs into various cardiac lineages. Recent work suggests that epicardial reactivation after injury is accompanied by, and contributes to, a robust inflammatory response. In this review, we describe the current status of research related to epicardial biology in cardiac development and regeneration, highlighting important recent discoveries and ongoing controversies.

  17. Cardiac perioperative complications in noncardiac surgery

    Directory of Open Access Journals (Sweden)

    Radovanović Dragana

    2008-01-01

    Full Text Available Anesthesiologists are confronted with an increasing population of patients undergoing noncardiac surgery who are at risk for cardiac complications in the perioperative period. Perioperative cardiac complications are responsible for significant mortality and morbidity. The aim of the present study was to determine the incidence of perioperative (operative and postoperative cardiac complications and correlations between the incidence of perioperative cardiac complications and type of surgical procedure, age, presence of concurrent diseases. A total of 100 patients with cardiac diseases undergoing noncardiac surgery were included in the prospective study (Group A 50 patients undergoing intraperitoneal surgery and Group B 50 patients undergoing breast and thyroid surgery. The patients were followed up during the perioperative period and after surgery until leaving hospital to assess the occurrence of cardiac events. Cardiac complications (systemic arterial hypertension, systemic arterial hypotension, abnormalities of cardiac conduction and cardiac rhythm, perioperative myocardial ischemia and acute myocardial infarction occurred in 64% of the patients. One of the 100 patients (1% had postoperative myocardial infarction which was fatal. Systemic arterial hypertension occurred in 57% of patients intraoperatively and 33% postoperatively, abnormalities of cardiac rhythm in 31% of patients intraoperatively and 17% postoperatively, perioperative myocardial ischemia in 23% of patients intraoperatively and 11% of postoperatively. The most often cardiac complications were systemic arterial hypertension, abnormalities of cardiac rhythm and perioperative myocardial ischemia. Factors independently associated with the incidence of cardiac complications included the type of surgical procedure, advanced age, duration of anaesthesia and surgery, abnormal preoperative electrocardiogram, abnormal preoperative chest radiography and diabetes.

  18. Electrophysiological Cardiac Modeling: A Review.

    Science.gov (United States)

    Beheshti, Mohammadali; Umapathy, Karthikeyan; Krishnan, Sridhar

    2016-01-01

    Cardiac electrophysiological modeling in conjunction with experimental and clinical findings has contributed to better understanding of electrophysiological phenomena in various species. As our knowledge on underlying electrical, mechanical, and chemical processes has improved over time, mathematical models of the cardiac electrophysiology have become more realistic and detailed. These models have provided a testbed for various hypotheses and conditions that may not be easy to implement experimentally. In addition to the limitations in experimentally validating various scenarios implemented by the models, one of the major obstacles for these models is computational complexity. However, the ever-increasing computational power of supercomputers facilitates the clinical application of cardiac electrophysiological models. The potential clinical applications include testing and predicting effects of pharmaceutical agents and performing patient-specific ablation and defibrillation. A review of studies involving these models and their major findings are provided.

  19. Mesoscale Elucidation of Biofilm Shear Behavior

    CERN Document Server

    Barai, Pallab; Mukherjee, Partha P

    2015-01-01

    Formation of bacterial colonies as biofilm on the surface/interface of various objects has the potential to impact not only human health and disease but also energy and environmental considerations. Biofilms can be regarded as soft materials, and comprehension of their shear response to external forces is a key element to the fundamental understanding. A mesoscale model has been presented in this article based on digitization of a biofilm microstructure. Its response under externally applied shear load is analyzed. Strain stiffening type behavior is readily observed under high strain loads due to the unfolding of chains within soft polymeric substrate. Sustained shear loading of the biofilm network results in strain localization along the diagonal direction. Rupture of the soft polymeric matrix can potentially reduce the intercellular interaction between the bacterial cells. Evolution of stiffness within the biofilm network under shear reveals two regions: a) initial increase in stiffness due to strain stiffe...

  20. Localization in inelastic rate dependent shearing deformations

    KAUST Repository

    Katsaounis, Theodoros

    2016-09-04

    Metals deformed at high strain rates can exhibit failure through formation of shear bands, a phenomenon often attributed to Hadamard instability and localization of the strain into an emerging coherent structure. We verify formation of shear bands for a nonlinear model exhibiting strain softening and strain rate sensitivity. The effects of strain softening and strain rate sensitivity are first assessed by linearized analysis, in- dicating that the combined effect leads to Turing instability. For the nonlinear model a class of self-similar solutions is constructed, that depicts a coherent localizing struc- ture and the formation of a shear band. This solution is associated to a heteroclinic orbit of a dynamical system. The orbit is constructed numerically and yields explicit shear localizing solutions.

  1. Wall Shear Rates in Taylor Vortex Flow

    Directory of Open Access Journals (Sweden)

    V. Sobolik

    2011-01-01

    Full Text Available Wall shear rate and its axial and azimuthal components were evaluated in stable Taylor vortices. The measurements were carried out in a broad interval of Taylor numbers (52-725 and several gap width (R1/R2 = 0.5 – 0.8 by two three-segment electrodiffusion probes and three single probes flush mounted in the wall of the outer fixed cylinder. The axial distribution of wall shear rate components was obtained by sweeping the vortices along the probes using a slow axial flow. The experimental results were verified by CFD simulations. The knowledge of local wall shear rates and its fluctuations is of primordial interest for industrial applications like tangential filtration, membrane reactors and bioreactors containing shear sensitive cells.

  2. Low Shear Strength and Shear-Induced Failure in Ti3SiC2

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Shear strength and shear-induced Hertzian contact damage in Ti3SiC2 were investigated using double-notched-beamspecimen and steel spherical indenter, respectively. The shear strength of 40 MPa that was only about 10% of bendingstrength was obtained for this novel ceramic. The SEM fractograph of specimens failed in shear test indicated acombination of intergranular and transgranular fracture. Under a contact load, plastic indent without cone crackcould be formed on the surface of Ti3SiC2 sample. Optical observation on side view showed half-circle cracks aroundthe damage zone below the indent, and the crack shape was consistent with the contrail of the principal shearingstress. The low shear strength and the shearing-activated intergranular sliding were confirmed being the key factorsfor failure in Ti3SiC2.

  3. Resistive interchange instability in reversed shear tokamaks

    Energy Technology Data Exchange (ETDEWEB)

    Furukawa, Masaru; Nakamura, Yuji; Wakatani, Masahiro [Graduate School of Energy Science, Kyoto University, Uji, Kyoto (Japan)

    1999-04-01

    Resistive interchange modes become unstable due to the magnetic shear reversal in tokamaks. In the present paper, the parameter dependences, such as q (safety factor) profile and the magnetic surface shape are clarified for improving the stability, using the local stability criterion. It is shown that a significant reduction of the beta limit is obtained for the JT-60U reversed shear configuration with internal transport barrier, since the local pressure gradient increases. (author)

  4. Assessment of Shear Strength in Silty Soils

    Directory of Open Access Journals (Sweden)

    Stefaniak Katarzyna

    2015-06-01

    Full Text Available The article presents a comparison of shear strength values in silty soils from the area of Poznań, determined based on selected Nkt values recommended in literature, with values of shear strength established on the basis of Nkt values recommended by the author. Analysed silty soils are characterized by the carbonate cementation zone, which made it possible to compare selected empirical coefficients both in normally consolidated and overconsolidated soils

  5. Liquid migration in sheared unsaturated granular media

    OpenAIRE

    Mani, Roman; Kadau, Dirk; Herrmann, Hans J.

    2012-01-01

    We show how liquid migrates in sheared unsaturated granular media using a grain scale model for capillary bridges. Liquid is redistributed to neighboring contacts after rupture of individual capillary bridges leading to redistribution of liquid on large scales. The liquid profile evolution coincides with a recently developed continuum description for liquid migration in shear bands. The velocity profiles which are linked to the migration of liquid as well as the density profiles of wet and dr...

  6. Dynamo quenching due to shear flow

    OpenAIRE

    Leprovost, Nicolas; Kim, Eun-Jin

    2008-01-01

    We provide a theory of dynamo ($\\alpha$ effect) and momentum transport in three-dimensional magnetohydrodynamics. For the first time, we show that the $\\alpha$ effect is severely reduced by the shear even in the absence of magnetic field. The $\\alpha$ effect is further suppressed by magnetic fields well below equipartition (with the large-scale flow) with different scalings depending on the relative strength of shear and magnetic field. The turbulent viscosity is also found to be significantl...

  7. Complications after cardiac implantable electronic device implantations

    DEFF Research Database (Denmark)

    Kirkfeldt, Rikke Esberg; Johansen, Jens Brock; Nohr, Ellen Aagaard;

    2013-01-01

    Complications after cardiac implantable electronic device (CIED) treatment, including permanent pacemakers (PMs), cardiac resynchronization therapy devices with defibrillators (CRT-Ds) or without (CRT-Ps), and implantable cardioverter defibrillators (ICDs), are associated with increased patient...

  8. Sudden Cardiac Arrest (SCA) Risk Assessment

    Science.gov (United States)

    ... Find a Specialist Share Twitter Facebook SCA Risk Assessment Sudden Cardiac Arrest (SCA) occurs abruptly and without ... of all ages and health conditions. Start Risk Assessment The Sudden Cardiac Arrest (SCA) Risk Assessment Tool ...

  9. An update on insertable cardiac monitors

    DEFF Research Database (Denmark)

    Olsen, Flemming J; Biering-Sørensen, Tor; Krieger, Derk W

    2015-01-01

    Continuous cardiac rhythm monitoring has undergone compelling progress over the past decades. Cardiac monitoring has emerged from 12-lead electrocardiograms being performed at the discretion of the treating physician to in-hospital telemetry, Holter monitoring, prolonged external event monitoring...

  10. Shear induced structures in crystallizing cocoa butter

    Science.gov (United States)

    Mazzanti, Gianfranco; Guthrie, Sarah E.; Sirota, Eric B.; Marangoni, Alejandro G.; Idziak, Stefan H. J.

    2004-03-01

    Cocoa butter is the main structural component of chocolate and many cosmetics. It crystallizes in several polymorphs, called phases I to VI. We used Synchrotron X-ray diffraction to study the effect of shear on its crystallization. A previously unreported phase (phase X) was found and a crystallization path through phase IV under shear was observed. Samples were crystallized under shear from the melt in temperature controlled Couette cells, at final crystallization temperatures of 17.5^oC, 20^oC and 22.5^oC in Beamline X10A of NSLS. The formation of phase X was observed at low shear rates (90 s-1) and low crystallization temperature (17.5^oC), but was absent at high shear (720 s-1) and high temperature (20^oC). The d-spacing and melting point suggest that this new phase is a mixture rich on two of the three major components of cocoa butter. We also found that, contrary to previous reports, the transition from phase II to phase V can happen through the intermediate phase IV, at high shear rates and temperature.

  11. The Radiation Hydrodynamics of Relativistic Shear Flows

    Science.gov (United States)

    Coughlin, Eric R.; Begelman, Mitchell C.

    2016-07-01

    We present a method for analyzing the interaction between radiation and matter in regions of intense, relativistic shear that can arise in many astrophysical situations. We show that there is a simple velocity profile that should be manifested in regions of large shear that have “lost memory” of their boundary conditions, and we use this self-similar velocity profile to construct the surface of last scattering, or the τ ≃ 1 surface, as viewed from any comoving point within the flow. We demonstrate that a simple treatment of scattering from this τ ≃ 1 surface exactly conserves photon number, and we derive the rate at which the radiation field is heated due to the shear present in the flow. The components of the comoving radiation energy–momentum tensor are calculated, and we show that they have relatively simple, approximate forms that interpolate between the viscous (small shear) and streaming (large shear) limits. We put our expression for the energy–momentum tensor in a covariant form that does not depend on the explicit velocity profile within the fluid and, therefore, represents a natural means for analyzing general, radiation-dominated, relativistic shear flows.

  12. Behavior of Tilted Angle Shear Connectors.

    Directory of Open Access Journals (Sweden)

    Koosha Khorramian

    Full Text Available According to recent researches, angle shear connectors are appropriate to transfer longitudinal shear forces across the steel-concrete interface. Angle steel profile has been used in different positions as L-shaped or C-shaped shear connectors. The application of angle shear connectors in tilted positions is of interest in this study. This study investigates the behaviour of tilted-shaped angle shear connectors under monotonic loading using experimental push out tests. Eight push-out specimens are tested to investigate the effects of different angle parameters on the ultimate load capacity of connectors. Two different tilted angles of 112.5 and 135 degrees between the angle leg and steel beam are considered. In addition, angle sizes and lengths are varied. Two different failure modes were observed consisting of concrete crushing-splitting and connector fracture. By increasing the size of connector, the maximum load increased for most cases. In general, the 135 degrees tilted angle shear connectors have a higher strength and stiffness than the 112.5 degrees type.

  13. Analysis of shear banding in twelve materials

    Science.gov (United States)

    Batra, R. C.; Kim, C. H.

    The problem of the initiation and growth of shear bands in 12 different materials, namely, OFHC copper, Cartridge brass, Nickel 200, Armco IF (interstitial free) iron, Carpenter electric iron, 1006 steel, 2024-T351 aluminum, 7039 aluminum, low alloy steel, S-7 tool steel, Tungsten alloy, and Depleted Uranium (DU -0.75 Ti) is studied with the objectives of finding out when a shear band initiates, and upon what parameters does the band width depend. The nonlinear coupled partial differential equations governing the overall simple shearing deformations of a thermally softening viscoplastic block are analyzed. It is assumed that the thermomechanical response of these materials can be adequately represented by the Johnson-Cook law, and the only inhomogeneity present in the block is the variation in its thickness. The effect of the defect size on the initiation and subsequent growth of the band is also studied. It is found that, for each one of these 12 materials, the deformation has become nonhomogeneous by the time the maximum shear stress occurs. Also the band width, computed when the shear stress has dropped to 85 percent of its peak value, does not correlate well with the thermal conductivity of the material. The band begins to grow rapidly when the shear stress has dropped to 90 percent of its maximum value.

  14. Elevated sensitivity to cardiac ischemia in proteinuric rats is independent of adverse cardiac remodeling

    NARCIS (Netherlands)

    Szymanski, Mariusz K.; Hillege, Hans L.; Danser, A. H. Jan; Garrelds, Ingrid M.; Schoemaker, Regien G.

    2013-01-01

    Objectives: Chronic renal dysfunction severely increases cardiovascular risk. Adverse cardiac remodeling is suggested to play a major role as predisposition for increased cardiac ischemic vulnerability. The aim of the present study was to examine the role of adverse cardiac remodeling in cardiac sen

  15. [Cardiac output monitoring by impedance cardiography in cardiac surgery].

    Science.gov (United States)

    Shimizu, H; Seki, S; Mizuguchi, A; Tsuchida, H; Watanabe, H; Namiki, A

    1990-04-01

    The cardiac output monitoring by impedance cardiography, NCCOM3, was evaluated in adult patients (n = 12) who were subjected to coronary artery bypass grafting. Values of cardiac output measured by impedance cardiography were compared to those by the thermodilution method. Changes of base impedance level used as an index of thoracic fluid volume were also investigated before and after cardiopulmonary bypass (CPB). Correlation coefficient (r) of the values obtained by thermodilution with impedance cardiography was 0.79 and the mean difference was 1.29 +/- 16.9 (SD)% during induction of anesthesia. During the operation, r was 0.83 and the mean difference was -14.6 +/- 18.7%. The measurement by impedance cardiography could be carried out through the operation except when electro-cautery was used. Base impedance level before CPB was significantly lower as compared with that after CPB. There was a negative correlation between the base impedance level and central venous pressure (CVP). No patients showed any signs suggesting lung edema and all the values of CVP, pulmonary artery pressure and blood gas analysis were within normal ranges. From the result of this study, it was concluded that cardiac output monitoring by impedance cardiography was useful in cardiac surgery, but further detailed examinations will be necessary on the relationship between the numerical values of base impedance and the clinical state of the patients. PMID:2362347

  16. Health Literacy Predicts Cardiac Knowledge Gains in Cardiac Rehabilitation Participants

    Science.gov (United States)

    Mattson, Colleen C.; Rawson, Katherine; Hughes, Joel W.; Waechter, Donna; Rosneck, James

    2015-01-01

    Objective: Health literacy is increasingly recognised as a potentially important patient characteristic related to patient education efforts. We evaluated whether health literacy would predict gains in knowledge after completion of patient education in cardiac rehabilitation. Method: This was a re-post observational analysis study design based on…

  17. Regulation of Cardiac Hypertrophy: the nuclear option

    OpenAIRE

    Kuster, Diederik

    2011-01-01

    textabstractCardiac hypertrophy is the response of the heart to an increased workload. After myocardial infarction (MI) the surviving muscle tissue has to work harder to maintain cardiac output. This sustained increase in workload leads to cardiac hypertrophy. Despite its apparent appropriateness, cardiac hypertrophy is an independent risk factor for the development of heart failure and is therefore called pathological hypertrophy. That hypertrophy is not bad per se, is illustrated by the hyp...

  18. Shear time dependent viscosity of polystyrene-ethylacrylate based shear thickening fluid

    Science.gov (United States)

    Chen, Qian; Xuan, Shouhu; Jiang, Wanquan; Cao, Saisai; Gong, Xinglong

    2016-04-01

    In this study, the influence of the shear rate and shear time on the transient viscosity of polystyrene-ethylacrylate based shear thickening fluid (STF) is investigated. If the shear rate is stepwise changed, it is found that both the viscosity and critical shear rate are affected by the shear time. Above the critical shear rate, the viscosity of the STF with larger power law exponent (n) increases faster. However, the viscosity tends to decrease when the shear time is long enough. This phenomenon can be responsible for the reversible structure buildup and the break-down process. An effective volume fraction (EVF) mechanism is proposed to analyze the shear time dependent viscosity and it is found that viscosity changes in proportion to EVF. To further clarify the structure evolution, a structural kinetic model is studied because the structural kinetic parameter (λ) could describe the variation in the effective volume fraction. The theoretical results of the structural kinetic model agree well with the experimental results. With this model, the change in viscosity and EVF can be speculated from the variation of λ and then the structure evolution can be better illustrated.

  19. Shear Stress in MR Fluid with Small Shear Deformation in Bctlattic Structure

    Institute of Scientific and Technical Information of China (English)

    LIU Lisheng; RUAN Zhongwei; ZHAI Pengcheng; ZHANG Qingjie

    2008-01-01

    A theoretical model based on BCT lattice structure was developed.Resultant force in the BCT lattice structure was deduced,following the interaction force of two kinds of magnetic particles.According to empirical FroHlich-Kennelly law,the relationship between the magnetic induction and the magnetic field was discussed,and a predictive formula of shear stresses of the BCT lattice structure model was established for the case of small shear deformation.Compared with the experimental data for different particle volume fractions,the theoretical results of the shear stress indicate the effects of the saturation magnetization and the external magnetic field on the shear stress.

  20. Cell-Activation by Shear Stresses in Abdominal Aortic Aneurysms (AAA)

    Science.gov (United States)

    Salsac, Anne-Virginie; Sparks, Steven; Chomaz, Jean-Marc; Lasheras, Juan C.

    2003-11-01

    Increasing experimental evidence indicates that low and oscillatory shear stresses promote proliferative, thrombotic, adhesive and inflammatory-mediated degenerative conditions throughout the wall of the aorta. These degenerative conditions have been shown to be involved in the pathogenesis of AAAs, a permanent, localized dilatation of the abdominal aorta. The purpose of this study is to measure both the magnitude and the duration of the shear stresses acting on both the arterial walls and on the blood cells inside AAAs, and to characterize their changes as the AAA enlarges. We conducted a parametric in-vitro study of the pulsatile blood flow in elastic models of AAAs while systematically varying the blood flow parameters, and the geometry of the aneurysm's bulging. The instantaneous flow characteristic inside the AAA was measured using DPIV at a sampling rate of 15 Hertz. A "cell-activation parameter" defined as the integral of the product of the magnitude of the shear stress and the time during which the stress acts was computed along each of the blood cell pathlines. The Lagrangian tracking of the blood cells shows that a large majority of them are subjected first to very high level of shear-induced "cell-activation" while later on they are entrained in regions of stasis where their residence time can increase up to several cardiac cycles. This cell-activation followed by the entrainment in low shear regions creates the optimal cell-adhesive and inflammatory-mediated degenerative conditions that are postulated to play an important role in the etiology and progressive enlargement of AAAs.

  1. Transthoracic Cardiac Acoustic Radiation Force Impulse Imaging

    Science.gov (United States)

    Bradway, David Pierson

    This dissertation investigates the feasibility of a real-time transthoracic Acoustic Radiation Force Impulse (ARFI) imaging system to measure myocardial function non-invasively in clinical setting. Heart failure is an important cardiovascular disease and contributes to the leading cause of death for developed countries. Patients exhibiting heart failure with a low left ventricular ejection fraction (LVEF) can often be identified by clinicians, but patients with preserved LVEF might be undetected if they do not exhibit other signs and symptoms of heart failure. These cases motivate development of transthoracic ARFI imaging to aid the early diagnosis of the structural and functional heart abnormalities leading to heart failure. M-Mode ARFI imaging utilizes ultrasonic radiation force to displace tissue several micrometers in the direction of wave propagation. Conventional ultrasound tracks the response of the tissue to the force. This measurement is repeated rapidly at a location through the cardiac cycle, measuring timing and relative changes in myocardial stiffness. ARFI imaging was previously shown capable of measuring myocardial properties and function via invasive open-chest and intracardiac approaches. The prototype imaging system described in this dissertation is capable of rapid acquisition, processing, and display of ARFI images and shear wave elasticity imaging (SWEI) movies. Also presented is a rigorous safety analysis, including finite element method (FEM) simulations of tissue heating, hydrophone intensity and mechanical index (MI) measurements, and thermocouple transducer face heating measurements. For the pulse sequences used in later animal and clinical studies, results from the safety analysis indicates that transthoracic ARFI imaging can be safely applied at rates and levels realizable on the prototype ARFI imaging system. Preliminary data are presented from in vivo trials studying changes in myocardial stiffness occurring under normal and abnormal

  2. MRI of cardiac rhabdomyoma in the fetus

    Energy Technology Data Exchange (ETDEWEB)

    Kivelitz, Dietmar E.; Muehler, Matthias [Institut fuer Radiologie, Medizinische Fakultaet, Humboldt-Universitaet zu Berlin, Charite, Schumannstrasse 20/21, 10098, Berlin (Germany); Rake, Annett; Chaoui, Rabih [Klinik fuer Gynaekologie und Geburtshilfe, Medizinische Fakultaet, Humboldt-Universitaet zu Berlin, Charite, Schumannstrasse 20/21, 10098, Berlin (Germany); Scheer, Ianina [Klinik fuer Strahlenheilkunde, Abteilung Paediatrische Radiologie, Medizinische Fakultaet, Humboldt-Universitaet zu Berlin, Charite, Schumannstrasse 20/21, 10098, Berlin (Germany)

    2004-08-01

    Primary cardiac tumors are rarely diagnosed in utero and are usually seen on prenatal echocardiography. Cardiac rhabdomyomata can be associated with tuberous sclerosis. Prenatal MRI can be performed to assess associated malformations. This case report illustrates the ability of fetal MRI to image cardiac rhabdomyata and compares it with prenatal and postnatal echocardiography. (orig.)

  3. Regulation of Cardiac Hypertrophy: the nuclear option

    NARCIS (Netherlands)

    D.W.D. Kuster (Diederik)

    2011-01-01

    textabstractCardiac hypertrophy is the response of the heart to an increased workload. After myocardial infarction (MI) the surviving muscle tissue has to work harder to maintain cardiac output. This sustained increase in workload leads to cardiac hypertrophy. Despite its apparent appropriateness, c

  4. Childhood cancer survivors: cardiac disease & social outcomes

    NARCIS (Netherlands)

    E.A.M. Feijen

    2015-01-01

    The thesis is divided in two parts; Cardiac health problems and healthcare consumption & social outcomes in CCS. The general aims of part 1 creates optimal conditions for the evaluation of cardiac events in 5-year childhood cancer survivors, evaluation of the long term risk of cardiac events, and to

  5. Cardiac tumors: optimal cardiac MR sequences and spectrum of imaging appearances.

    LENUS (Irish Health Repository)

    O'Donnell, David H

    2012-02-01

    OBJECTIVE: This article reviews the optimal cardiac MRI sequences for and the spectrum of imaging appearances of cardiac tumors. CONCLUSION: Recent technologic advances in cardiac MRI have resulted in the rapid acquisition of images of the heart with high spatial and temporal resolution and excellent myocardial tissue characterization. Cardiac MRI provides optimal assessment of the location, functional characteristics, and soft-tissue features of cardiac tumors, allowing accurate differentiation of benign and malignant lesions.

  6. Development of the Shear Bands in Saturated Soil

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    This paper describes the development of shear bands in saturated soil under simple shear using a matching technique at the moving boundary of a shear band, and it is shown that the development of shear bands is affected by the coupling strain rate and pore pressure of material. Some numerical solutions have been presented.

  7. Cardiac connexins and impulse propagation

    NARCIS (Netherlands)

    J.A. Jansen; T.A.B. van Veen; J.M.T. de Bakker; H.V.M. van Rijen

    2010-01-01

    Gap junctions form the intercellular pathway for cell-to-cell transmission of the cardiac impulse from its site of origin, the sinoatrial node, along the atria, the atrioventricular conduction system to the ventricular myocardium. The component parts of gap junctions are proteins called connexins (C

  8. Cardiac abnormalities after subarachnoid hemorrhage

    NARCIS (Netherlands)

    Bilt, I.A.C. van der

    2016-01-01

    Aneurysmal subarachnoid hemorrhage(aSAH) is a devastating neurological disease. During the course of the aSAH several neurological and medical complications may occur. Cardiac abnormalities after aSAH are observed often and resemble stress cardiomyopathy or Tako-tsubo cardiomyopathy(Broken Heart Syn

  9. Molecular therapies for cardiac arrhythmias

    NARCIS (Netherlands)

    G.J.J. Boink

    2013-01-01

    Despite the ongoing advances in pharmacology, devices and surgical approaches to treat heart rhythm disturbances, arrhythmias are still a significant cause of death and morbidity. With the introduction of gene and cell therapy, new avenues have arrived for the local modulation of cardiac disease. Th

  10. Historical highlights in cardiac pacing.

    Science.gov (United States)

    Geddes, L A

    1990-01-01

    The benchmarks in cardiac pacing are identified, beginning with F. Steiner (1871), who rhythmically stimulated the chloroform-arrested hearts of 3 horses, 1 donkey, 10 dogs, 14 cats, and 8 rabbits. The chloroform-arrested heart in human subjects was paced by T. Greene in the following year (1872) in the UK. In 1882, H. Ziemssen in Germany applied cardiac pacing to a 42-year old woman who had a large defect in the anterior left chest wall subsequent to resection of an enchondroma. Intentional cardiac pacing did not occur until 1932, when A.A. Hyman in the US demonstrated that cardiac pacing could be clinically practical. Hyman made a batteryless pacemaker for delivery in induction shock stimuli (60-120/min) to the atria. His pacemaker was powered by a hand-wound, spring-driven generator which provided 6 min of pacemaking without rewinding. Closed-chest ventricular pacing was introduced in the US in 1952 by P.M. Zoll et al. Zoll (1956) also introduced closed-chest ventricular defibrillation. W.L. Weirich et al. (1958) demonstrated that direct-heart stimulation in closed-chest patients could be achieved with slender wire electrodes. S. Furman and J.B. Schwedel (1959) developed a monopolar catheter electrode for ventricular pacing in man. In the same year, W. Greatbatch and W.M. Chardack developed the implantable pacemaker. PMID:18238328

  11. Cardiac resynchronization therapy in China

    Institute of Scientific and Technical Information of China (English)

    Wei HUA

    2006-01-01

    @@ Congestive heart failure (HF) is a major and growing public health problem. The therapeutic approach includes non-pharmacological measures, pharmacological therapy,mechanical devices, and surgery. Despite the benefits of optimal pharmacologic therapy, the prognosis is still not ideal. At this time, cardiac resynchronization therapy (CRT)has gained wide acceptance as an alternative treatment for HF patients with conduction delay.1

  12. Cardiac pacemakers and nuclear batteries

    International Nuclear Information System (INIS)

    Following the introduction giving the indications for cardiac pacemaker therapy with special regard to the use of pacemakers powered by nuclear batteries, reference is made to the resulting radiation exposure of the patient. The activities of the Federal Health Office in this field such as recommendations and surveys including the entire Federal Republic are outlined. (orig.)

  13. CARDIAC TRANSPLANTATION: AN ANESTHETIC CHALLENGE

    OpenAIRE

    Premalatha; Jayaraman,

    2014-01-01

    : Heart transplantation has emerged as the definitive therapy for patients with end-stage cardiomyopathy. The two most common forms of cardiac disease that lead to transplantation are ischemic cardiomyopathy and dilated cardiomyopathy, which together comprise approximately 90% of cases. The other less common forms of heart disease include viral cardiomyopathy, infiltrative cardiomyopathy, postpartum cardiomyopathy, valvular heart disease and congenital heart disease

  14. Epidural analgesia for cardiac surgery

    NARCIS (Netherlands)

    V. Svircevic; M.M. Passier; A.P. Nierich; D. van Dijk; C.J. Kalkman; G.J. van der Heijden

    2013-01-01

    Background A combination of general anaesthesia (GA) with thoracic epidural analgesia (TEA) may have a beneficial effect on clinical outcomes by reducing the risk of perioperative complications after cardiac surgery. Objectives The objective of this review was to determine the impact of perioperativ

  15. Magnetic Resonance Elastography as a Method for the Assessment of Effective Myocardial Stiffness throughout the Cardiac Cycle

    OpenAIRE

    Kolipaka, Arunark; Araoz, Philip A; McGee, Kiaran P.; Manduca, Armando; Ehman, Richard L.

    2010-01-01

    Magnetic resonance elastography (MRE) is a noninvasive technique in which images of externally generated waves propagating in tissue are used to measure stiffness. The first aim is to determine, from a range of driver configurations the optimal driver for the purpose of generating waves within the heart in vivo. The second aim is to quantify the shear stiffness of normal myocardium throughout the cardiac cycle using MRE and to compare MRE stiffness to left ventricular (LV) chamber pressure in...

  16. Measurement of wall shear stress in chick embryonic heart using optical coherence tomography

    Science.gov (United States)

    Ma, Zhenhe; Dou, Shidan; Zhao, Yuqian; Wang, Yi; Suo, Yanyan; Wang, Fengwen

    2015-03-01

    The cardiac development is a complicated process affected by genetic and environmental factors. Wall shear stress (WSS) is one of the components which have been proved to influence the morphogenesis during early stages of cardiac development. To study the mechanism, WSS measurement is a step with significant importance. WSS is caused by blood flow imposed on the inner surface of the heart wall and it can be determined by calculating velocity gradients of blood flow in a direction perpendicular to the wall. However, the WSS of the early stage embryonic heart is difficult to measure since the embryonic heart is tiny and beating fast. Optical coherence tomography (OCT) is a non-invasive imaging modality with high spatial and temporal resolution, which is uniquely suitable for the study of early stage embryonic heart development. In this paper, we introduce a method to measure the WSS of early stage chick embryonic heart based on high speed spectral domain optical coherence tomography (SDOCT). 4D (x,y,z,t) scan was performed on the outflow tract (OFT) of HH18 (~3 days of incubation) chick embryonic heart. After phase synchronization, OFT boundary segmentation, and OFT center line calculation, Doppler angle of the blood flow in the OFT can be achieved (This method has been described in previous publications). Combining with the Doppler OCT results, we calculate absolute blood flow velocity distribution in the OFT. The boundary of the OFT was segmented at each cross-sectional structural image, then geometrical center of the OFT can be calculated. Thus, the gradients of blood flow in radial direction can be calculated. This velocity gradient near the wall is termed wall shear rate and the WSS value is proportional to the wall shear rate. Based on this method, the WSS at different heart beating phase are compare. The result demonstrates that OCT is capable of early stage chicken embryonic heart WSS study.

  17. Dilute rigid dumbbell suspensions in large-amplitude oscillatory shear flow: Shear stress response

    Science.gov (United States)

    Bird, R. B.; Giacomin, A. J.; Schmalzer, A. M.; Aumnate, C.

    2014-02-01

    We examine the simplest relevant molecular model for large-amplitude shear (LAOS) flow of a polymeric liquid: the suspension of rigid dumbbells in a Newtonian solvent. We find explicit analytical expressions for the shear rate amplitude and frequency dependences of the first and third harmonics of the alternating shear stress response. We include a detailed comparison of these predictions with the corresponding results for the simplest relevant continuum model: the corotational Maxwell model. We find that the responses of both models are qualitatively similar. The rigid dumbbell model relies entirely on the dumbbell orientation to explain the viscoelastic response of the polymeric liquid, including the higher harmonics in large-amplitude oscillatory shear flow. Our analysis employs the general method of Bird and Armstrong ["Time-dependent flows of dilute solutions of rodlike macromolecules," J. Chem. Phys. 56, 3680 (1972)] for analyzing the behavior of the rigid dumbbell model in any unsteady shear flow. We derive the first three terms of the deviation of the orientational distribution function from the equilibrium state. Then, after getting the "paren functions," we use these for evaluating the shear stress for LAOS flow. We find the shapes of the shear stress versus shear rate loops predicted to be reasonable.

  18. Phase Coexistence of Complex Fluids in Shear Flow

    OpenAIRE

    Olmsted, Peter D; Lu, C-Y David

    1999-01-01

    We present some results of recent calculations of rigid rod-like particles in shear flow, based on the Doi model. This is an ideal model system for exhibiting the generic behavior of shear-thinning fluids (polymer solutions, wormlike micelles, surfactant solutions, liquid crystals) in shear flow. We present calculations of phase coexistence under shear among weakly-aligned (paranematic) and strongly-aligned phases, including alignment in the shear plane and in the vorticity direction (log-rol...

  19. Monotonic direct simple shear tests on sand under multidirectional loading

    OpenAIRE

    Li, Yao; Yang, Yunming; Yu, Hai-Sui; Roberts, Gethin Wyn

    2016-01-01

    Stress–strain responses of Leighton Buzzard sand are investigated under bidirectional shear. The tests are conducted by using the variable direction dynamic cyclic simple shear (VDDCSS), which is manufactured by Global Digital Systems (GDS) Instruments Ltd., U.K. Soil samples are anisotropically consolidated under a vertical normal stress and horizontal shear stress and then sheared in undrained conditions by applying a horizontal shear stress acting along a different direction from the conso...

  20. Molecular Dynamics Simulation of Shear Moduli for Coulomb Crystals

    CERN Document Server

    Horowitz, C J

    2008-01-01

    Torsional (shear) oscillations of neutron stars may have been observed in quasiperiodic oscillations of Magnetar Giant Flares. The frequencies of these modes depend on the shear modulus of neutron star crust. We calculate the shear modulus of Coulomb crystals from molecular dynamics simulations. We find that electron screening reduces the shear modulus by about 10% compared to previous Ogata et al. results. Our MD simulations can be extended to calculate the effects of impurities and or polycrystalline structures on the shear modulus.

  1. Analytical theory of forced rotating sheared turbulence: The Parallel case

    OpenAIRE

    Leprovost, Nicolas; Kim, Eun-Jin

    2008-01-01

    Forced turbulence combined with the effect of rotation and shear flow is studied. In a previous paper [N. Leprovost and E. J. Kim, Phys. Rev. E 78, 016301 (2008)], we considered the case where the shear and the rotation are perpendicular. Here, we consider the complementary case of parallel rotation and shear, elucidating how rotation and flow shear influence the generation of shear flow (e.g., the direction of energy cascade), turbulence level, transport of particles, and momentum. We show t...

  2. Shear-Driven Reconnection in Kinetic Models

    Science.gov (United States)

    Black, C.; Antiochos, S. K.; Germaschewski, K.; Karpen, J. T.; DeVore, C. R.; Bessho, N.

    2015-12-01

    The explosive energy release in solar eruptive phenomena is believed to be due to magnetic reconnection. In the standard model for coronal mass ejections (CME) and/or solar flares, the free energy for the event resides in the strongly sheared magnetic field of a filament channel. The pre-eruption force balance consists of an upward force due to the magnetic pressure of the sheared field countered by a downward tension due to overlying unsheared field. Magnetic reconnection disrupts this force balance; therefore, it is critical for understanding CME/flare initiation, to model the onset of reconnection driven by the build-up of magnetic shear. In MHD simulations, the application of a magnetic-field shear is a trivial matter. However, kinetic effects are dominant in the diffusion region and thus, it is important to examine this process with PIC simulations as well. The implementation of such a driver in PIC methods is challenging, however, and indicates the necessity of a true multiscale model for such processes in the solar environment. The field must be sheared self-consistently and indirectly to prevent the generation of waves that destroy the desired system. Plasma instabilities can arise nonetheless. In the work presented here, we show that we can control this instability and generate a predicted out-of-plane magnetic flux. This material is based upon work supported by the National Science Foundation under Award No. AGS-1331356.

  3. Review article: Cosmology with cosmic shear observations

    CERN Document Server

    Kilbinger, Martin

    2014-01-01

    Cosmic shear is the distortion of images of distant galaxies due to weak gravitational lensing by the large-scale structure in the Universe. Such images are coherently deformed by the tidal field of matter inhomogeneities along the line of sight. By measuring galaxy shape correlations, we can study the properties and evolution of structure on large scales as well as the geometry of the Universe. Thus, cosmic shear has become a powerful probe into the nature of dark matter and the origin of the current accelerated expansion of the Universe. Over the last years, cosmic shear has evolved into a reliable and robust cosmological probe, providing measurements of the expansion history of the Universe and the growth of its structure. We review here the principles of weak gravitational lensing and show how cosmic shear is interpreted in a cosmological context. Then we give an overview of weak-lensing measurements, and present the main observational cosmic-shear results since it was discovered 15 years ago, as well as ...

  4. Delayed shear enhancement in mesoscale atmospheric dispersion

    Energy Technology Data Exchange (ETDEWEB)

    Moran, M.D. [Atmospheric Environment Service, Ontario (Canada); Pielke, R.A. [Colorado State Univ., Fort Collins, CO (United States)

    1994-12-31

    Mesoscale atmospheric dispersion (MAD) is more complicated than smaller-scale dispersion because the mean wind field can no longer be considered steady or horizontally homogeneous over mesoscale time and space scales. Wind shear also plays a much more important role on the mesoscale: horizontal dispersion can be enhanced and often dominated by vertical wind shear on these scales through the interaction of horizontal differential advection and vertical mixing. Just over 30 years ago, Pasquill suggested that this interaction need not be simultaneous and that the combination of differential horizontal advection with delayed or subsequent vertical mixing could maintain effective horizontal diffusion in spite of temporal or spatial reductions in boundary-layer turbulence intensity. This two-step mechanism has not received much attention since then, but a recent analysis of observations from and numerical simulations of two mesoscale tracer experiments suggests that delayed shear enhancement can play an important role in MAD. This paper presents an overview of this analysis, with particular emphasis on the influence of resolvable vertical shear on MAD in these two case studies and the contributions made by delayed shear enhancement.

  5. COMPUTATIONAL APPROACH TO PREDICT SOIL SHEAR STRENGTH

    Directory of Open Access Journals (Sweden)

    Rajeev Jain,

    2010-08-01

    Full Text Available The paper presents an artificial neural network technique to predict the shear strength parameters of medium compressibility soil, which influenced by basic properties of soil in unconsolidated undrained conditions. Obviously obtained the undisturbed samples of soil to determination of shear strength parameters is a tedious work. Commercial software’s MATLAB-7 was used for this study. Triaxial shear tests were conducted to obtain these parameters at different water contents and densities. The results were used to predict the strength parameters. A set of 198 experimental results were used to construct the ANN model out of which 120 for training , 39 for validation and 39 for testing or prediction of shear strength parameters ( Cohesion & Angle of internal friction were used. The correlation between the basic properties and shear strength parameters were obtained from the trained neural network. For trained the feed forward ANN models: multilayer perceptrons and radial basis function neural network, followings parameters were considered as input data – the compaction energy, degree of saturation, dry density and C & ф were output parameter. The regression coefficient and MSEwere 0.94, 0.76 and 0.0642, 0.253 respectively. In addition, the experimental results were compared to MLPN and RBF networks predicted results. It was concluded that the performance of the multilayer perceptron feed forward neural network model with three hidden layers is better than radial basis function neural network model.

  6. The radiation hydrodynamics of relativistic shear flows

    CERN Document Server

    Coughlin, Eric R

    2016-01-01

    We present a method for analyzing the interaction between radiation and matter in regions of intense, relativistic shear that can arise in many astrophysical situations. We show that there is a simple velocity profile that should be manifested in regions of large shear that have "lost memory" of their boundary conditions, and we use this self-similar velocity profile to construct the surface of last scattering, or $\\tau \\simeq 1$ surface, as viewed from any comoving point within the flow. We demonstrate that a simple treatment of scattering from this $\\tau \\simeq 1$ surface exactly conserves photon number, and derive the rate at which the radiation field is heated due to the shear present in the flow. The components of the comoving radiation energy-momentum tensor are calculated, and we show that they have relatively simple, approximate forms that interpolate between the viscous (small shear) and streaming (large shear) limits. We put our expression for the energy-momentum tensor in a covariant form that does...

  7. Pressure-shear experiments on granular materials.

    Energy Technology Data Exchange (ETDEWEB)

    Reinhart, William Dodd (Sandia National Laboratories, Albuquerque, NM); Thornhill, Tom Finley, III (, Sandia National Laboratories, Albuquerque, NM); Vogler, Tracy John; Alexander, C. Scott (Sandia National Laboratories, Albuquerque, NM)

    2011-10-01

    Pressure-shear experiments were performed on granular tungsten carbide and sand using a newly-refurbished slotted barrel gun. The sample is a thin layer of the granular material sandwiched between driver and anvil plates that remain elastic. Because of the obliquity, impact generates both a longitudinal wave, which compresses the sample, and a shear wave that probes the strength of the sample. Laser velocity interferometry is employed to measure the velocity history of the free surface of the anvil. Since the driver and anvil remain elastic, analysis of the results is, in principal, straightforward. Experiments were performed at pressures up to nearly 2 GPa using titanium plates and at higher pressure using zirconium plates. Those done with the titanium plates produced values of shear stress of 0.1-0.2 GPa, with the value increasing with pressure. On the other hand, those experiments conducted with zirconia anvils display results that may be related to slipping at an interface and shear stresses mostly at 0.1 GPa or less. Recovered samples display much greater particle fracture than is observed in planar loading, suggesting that shearing is a very effective mechanism for comminution of the grains.

  8. Shear melting of confined solid monolayer films

    Energy Technology Data Exchange (ETDEWEB)

    Schoen, M. (Institut fuer Experimentalphysik, Naturwissenschaftliche Fakultaet, Universitaet Witten/Herdecke, Stockumer Str. 10, D-5810 Witten (Germany)); Diestler, D.J. (Richard B. Wetherill Laboratory of Chemistry, Purdue University, West Lafayette, Indiana 47907 (United States)); Cushman, J.H. (Lilly Hall of Life Sciences, Purdue University, West Lafayette, Indiana 47907 (United States))

    1993-03-01

    Strain-induced melting of solid phases in a prototypal slit pore [a monatomic fluid constrained between two plane-parallel walls made up like atoms fixed in the configuration of the (100) plane of the face-centered cubic lattice] is investigated by Monte Carlo calculations in the isostress-isostrain'' ensemble where the thermodynamic state of the pore phase is uniquely determined by a fixed number of molecules, constant load or normal stress and constant temperature. If the walls are properly aligned laterally, a commensurate solid phase can form epitaxially. Moving the walls out of alignment (shear strain) creates a distorted solid, which reacts (shear stress) by tending to realign the walls. If the shear strain is increased beyond a critical value, the solid begins to melt. However, melting is a continuous transition which does not immediately lead to a normal liquid, but rather a disordered phase that sustains a non-negligible shear stress. Shear melting is contrasted to ordinary melting at constant normal stress, which appears to be a first-order transition.

  9. On Shearing Fluids with Homogeneous Densities

    CERN Document Server

    Srivastava, D C; Kumar, Rajesh

    2016-01-01

    In this paper, we study shearing spherically symmetric homogeneous density fluids in comoving coordinates. It is found that the expansion of the four-velocity of a perfect fluid is homogeneous, whereas its shear is generated by an arbitrary function of time M(t), related to the mass function of the distribution. This function is found to bear a functional relationship with density. The field equations are reduced to two coupled first order ordinary differential equations for the metric coefficients, g 11 and g 22. We have explored a class of solutions assuming that M is a linear function of the density. This class embodies, as a subcase, the complete class of shear-free solutions. We have discussed the off quoted work of Kustaanheimo (1947) and have noted that it deals with shear-free fluids having anisotropic pressure. It is shown that the anisotropy of the fluid is characterized by an arbitrary function of time. We have discussed some issues of historical priorities and credentials related to shear-free sol...

  10. A Refined Shear Deformation Plate Theory

    Science.gov (United States)

    Liu, Yucheng

    2011-04-01

    An improved higher-order shear deformation theory of plates is presented in this paper. The theory is developed from the transverse shear deformation theory presented by Ambartsumian [11]. The present plate theory contains kinematics of higher-order displacement field of plates, a system of higher-order differential equilibrium equations in terms of the three generalized displacements of bending plates, and a system of boundary conditions at each edge of plate boundaries. The present shear deformation theory of plates is validated by applying it to solve torsional plates and simply supported plates. The obtained solutions using the present theory are compared with the solutions of other shear-deformation theories. A good agreement is achieved through these comparisons and the advantages of the present theory are clearly verified. The shear deformation plate theory presented here can be applied to the analysis of laminated composite plates to better predict their dynamic and static behaviors. The proposed theory should also be supplemented to the theory of finite element analysis for developing new shell elements.

  11. Hydrodynamic theory of tissue shear flow

    CERN Document Server

    Popović, Marko; Merkel, Matthias; Etournay, Raphaël; Eaton, Suzanne; Jülicher, Frank; Salbreux, Guillaume

    2016-01-01

    We propose a hydrodynamic theory to describe shear flows in developing epithelial tissues. We introduce hydrodynamic fields corresponding to state properties of constituent cells as well as a contribution to overall tissue shear flow due to rearrangements in cell network topology. We then construct a constitutive equation for the shear rate due to topological rearrangements. We identify a novel rheological behaviour resulting from memory effects in the tissue. We show that anisotropic deformation of tissue and cells can arise from two distinct active cellular processes: generation of active stress in the tissue, and actively driven cellular rearrangements. These two active processes result in distinct cellular and tissue shape changes, depending on boundary conditions applied on the tissue. Our findings have consequences for the understanding of tissue morphogenesis during development.

  12. Shear and Turbulence Effects on Lidar Measurements

    DEFF Research Database (Denmark)

    Courtney, Michael; Sathe, Ameya; Gayle Nygaard, Nicolai

    Wind lidars are now used extensively for wind resource measurements. It is known that lidar wind speed measure-ments are affected by both turbulence and wind shear. This report explains the mechanisms behind these sensitivities. For turbulence, it is found that errors in the scalar mean speed...... are usually only small. However, particularly in re-spect of a lidar calibration procedure, turbulence induced errors in the cup anemometer speed are seen to be signifi-cantly larger. Wind shear is shown to induce measurement errors both due to possible imperfections in the lidar sensing height and due...... to the averaging of a non-linear speed profile. Both effects in combination have to be included when modelling the lidar error. Attempts to evaluate the lidar error from ex-perimental data have not been successful probably due to a lack of detailed knowledge of both the wind shear and the actual lidar sensing...

  13. Shear viscosity in magnetized neutron star crust

    CERN Document Server

    Ofengeim, D D

    2015-01-01

    The electron shear viscosity due to Coulomb scattering of degenerate electrons by atomic nuclei throughout a magnetized neutron star crust is calculated. The theory is based on the shear viscosity coefficient calculated neglecting magnetic fields but taking into account gaseous, liquid and solid states of atomic nuclei, multiphonon scattering processes, and finite sizes of the nuclei albeit neglecting the effects of electron band structure. The effects of strong magnetic fields are included in the relaxation time approximation with the effective electron relaxation time taken from the field-free theory. The viscosity in a magnetized matter is described by five shear viscosity coefficients. They are calculated and their dependence on the magnetic field and other parameters of dense matter is analyzed. Possible applications and open problems are outlined.

  14. Magnetic shear. III - Hale region 17255

    International Nuclear Information System (INIS)

    Hale active region 17255, which in many respects was the most vigorous active region observed during the first operational period of SMM, appears to lie between two large areas of flow (observed in C IV) converging toward the major axis of the region. In the 6-day period from November 6-12, 1980, the major axis of the region rotates by about 25 deg. Several segments of the magnetic neutral line show C IV flow velocities of opposite sign on either side of the neutral line. Those segments whose orientation is favorable for measuring velocity components parallel to the neutral line show evidence that such flow is present, which is interpreted as evidence for magnetic shear. This, together with other evidence, suggests that magnetic shear is widespread in this region, as in the two previous regions studied. It is concluded that magnetic shear is often associated with flaring activity but is not a sufficient condition for flaring to occur. 8 references

  15. On shear rheology of gel propellants

    Energy Technology Data Exchange (ETDEWEB)

    Rahimi, Shai; Peretz, Arie [RAFAEL, MANOR Propulsion and Explosive Systems Division, Haifa (Israel); Natan, Benveniste [Faculty of Aerospace Engineering, Technion - Israel Institute of Technology, Haifa (Israel)

    2007-04-15

    Selected fuel, oxidizer and simulant gels were prepared and rheologically characterized using a rotational rheometer. For fuel gelation both organic and inorganic gellants were utilized, whereas oxidizers and simulants were gelled with addition of silica and polysaccharides, respectively. The generalized Herschel-Bulkley constitutive model was found to most adequately represent the gels studied. Hydrazine-based fuels, gelled with polysaccharides, were characterized as shear-thinning pseudoplastic fluids with low shear yield stress, whereas inhibited red-fuming nitric acid (IRFNA) and hydrogen peroxide oxidizers, gelled with silica, were characterized as yield thixotropic fluids with significant shear yield stress. Creep tests were conducted on two rheological types of gels with different gellant content and the results were fitted by Burgers-Kelvin viscoelastic constitutive model. The effect of temperature on the rheological properties of gel propellant simulants was also investigated. A general rheological classification of gel propellants and simulants is proposed. (Abstract Copyright [2007], Wiley Periodicals, Inc.)

  16. Wind Shear Target Echo Modeling and Simulation

    Directory of Open Access Journals (Sweden)

    Xiaoyang Liu

    2015-01-01

    Full Text Available Wind shear is a dangerous atmospheric phenomenon in aviation. Wind shear is defined as a sudden change of speed or direction of the wind. In order to analyze the influence of wind shear on the efficiency of the airplane, this paper proposes a mathematical model of point target rain echo and weather target signal echo based on Doppler effect. The wind field model is developed in this paper, and the antenna model is also studied by using Bessel function. The spectrum distribution of symmetric and asymmetric wind fields is researched by using the mathematical model proposed in this paper. The simulation results are in accordance with radial velocity component, and the simulation results also confirm the correctness of the established model of antenna.

  17. Structural relaxation monitored by instantaneous shear modulus

    DEFF Research Database (Denmark)

    Olsen, Niels Boye; Dyre, Jeppe; Christensen, Tage Emil

    1998-01-01

    time definition based on a recently proposed expression for the relaxation time, where G [infinity] reflects the fictive temperature. All parameters entering the reduced time were determined from independent measurements of the frequency-dependent shear modulus of the equilibrium liquid.......This paper reports on aging of the silicone oil MS704 for sudden changes of temperature from 210.5 to 209.0 K and from 207.5 to 209.0 K studied by continuously monitoring the instantaneous shear modulus G [infinity]. The results are interpreted within the Tool-Narayanaswamy formalism with a reduced...

  18. Shear reinforced beams in autoclaved aerated concrete

    DEFF Research Database (Denmark)

    Cornelius, Thomas

    2010-01-01

    Shear behaviour in concrete materials is very well documented, for normal density concrete materials. In this paper results of various tests on low density concrete materials like aerated autoclaved concrete (in the following denoted aircrete) will be presented and analyzed for different combinat......Shear behaviour in concrete materials is very well documented, for normal density concrete materials. In this paper results of various tests on low density concrete materials like aerated autoclaved concrete (in the following denoted aircrete) will be presented and analyzed for different...

  19. Encoding of Memory in Sheared Amorphous Solids

    Science.gov (United States)

    Fiocco, Davide; Foffi, Giuseppe; Sastry, Srikanth

    2014-01-01

    We show that memory can be encoded in a model amorphous solid subjected to athermal oscillatory shear deformations, and in an analogous spin model with disordered interactions, sharing the feature of a deformable energy landscape. When these systems are subjected to oscillatory shear deformation, they retain memory of the deformation amplitude imposed in the training phase, when the amplitude is below a "localization" threshold. Remarkably, multiple persistent memories can be stored using such an athermal, noise-free, protocol. The possibility of such memory is shown to be linked to the presence of plastic deformations and associated limit cycles traversed by the system, which exhibit avalanche statistics also seen in related contexts.

  20. Shear viscosity coefficient of liquid lanthanides

    International Nuclear Information System (INIS)

    Present paper deals with the computation of shear viscosity coefficient (η) of liquid lanthanides. The effective pair potential v(r) is calculated through our newly constructed model potential. The Pair distribution function g(r) is calculated from PYHS reference system. To see the influence of local field correction function, Hartree (H), Tailor (T) and Sarkar et al (S) local field correction function are used. Present results are compared with available experimental as well as theoretical data. Lastly, we found that our newly constructed model potential successfully explains the shear viscosity coefficient (η) of liquid lanthanides

  1. Enhancing Rotational Diffusion Using Oscillatory Shear

    Science.gov (United States)

    Leahy, Brian D.; Cheng, Xiang; Ong, Desmond C.; Liddell-Watson, Chekesha; Cohen, Itai

    2013-05-01

    Taylor dispersion—shear-induced enhancement of translational diffusion—is an important phenomenon with applications ranging from pharmacology to geology. Through experiments and simulations, we show that rotational diffusion is also enhanced for anisotropic particles in oscillatory shear. This enhancement arises from variations in the particle’s rotation (Jeffery orbit) and depends on the strain amplitude, rate, and particle aspect ratio in a manner that is distinct from the translational diffusion. This separate tunability of translational and rotational diffusion opens the door to new techniques for controlling positions and orientations of suspended anisotropic colloids.

  2. Enhancing Rotational Diffusion Using Oscillatory Shear

    KAUST Repository

    Leahy, Brian D.

    2013-05-29

    Taylor dispersion - shear-induced enhancement of translational diffusion - is an important phenomenon with applications ranging from pharmacology to geology. Through experiments and simulations, we show that rotational diffusion is also enhanced for anisotropic particles in oscillatory shear. This enhancement arises from variations in the particle\\'s rotation (Jeffery orbit) and depends on the strain amplitude, rate, and particle aspect ratio in a manner that is distinct from the translational diffusion. This separate tunability of translational and rotational diffusion opens the door to new techniques for controlling positions and orientations of suspended anisotropic colloids. © 2013 American Physical Society.

  3. Halo abundances and shear in void models

    DEFF Research Database (Denmark)

    Alonso, David; García-Bellido, Juan; Haugbølle, Troels;

    2012-01-01

    We study the non-linear gravitational collapse of dark matter into halos through numerical N-body simulations of Lemaitre-Tolman-Bondi void models. We extend the halo mass function formalism to these models in a consistent way. This extension not only compares well with the simulated data at all...... times and radii, but it also gives interesting clues about the impact of the background shear on the growth of perturbations. Our results give hints about the possibility of constraining the background shear via cluster number counts, which could then give rise to strong constraints on general...

  4. Nutritional Status and Cardiac Autophagy

    Directory of Open Access Journals (Sweden)

    Jihyun Ahn

    2013-02-01

    Full Text Available Autophagy is necessary for the degradation of long-lasting proteins and nonfunctional organelles, and is activated to promote cellular survival. However, overactivation of autophagy may deplete essential molecules and organelles responsible for cellular survival. Lifelong calorie restriction by 40% has been shown to increase the cardiac expression of autophagic markers, which suggests that it may have a cardioprotective effect by decreasing oxidative damage brought on by aging and cardiovascular diseases. Although cardiac autophagy is critical to regulating protein quality and maintaining cellular function and survival, increased or excessive autophagy may have deleterious effects on the heart under some circumstances, including pressure overload-induced heart failure. The importance of autophagy has been shown in nutrient supply and preservation of energy in times of limitation, such as ischemia. Some studies have suggested that a transition from obesity to metabolic syndrome may involve progressive changes in myocardial inflammation, mitochondrial dysfunction, fibrosis, apoptosis, and myocardial autophagy.

  5. [Cardiac support and replacement therapies].

    Science.gov (United States)

    Lotz, Christopher; Roewer, Norbert; Muellenbach, Ralf M

    2016-09-01

    Circulatory support represents an integral part within the treatment of the critically ill patient. Sophisticated pharmacologic regimens help to maintain systemic perfusion pressure by increasing vascular tone as well as mediating positive inotropic effects. Besides the administration of catecholamines and phosphodiesterase-III-inhibitors, in particular the administration of levosimendan represents a promising alternative during low-cardiac-output. Nevertheless, sufficient evidence demonstrating a survival benefit for any pharmacologic regimen is nonexistent. In case pharmacological measures do not suffice mechanical cardiopulmonary support (MCS) may be used. MCS may be used during cardiopulmonary resuscitation or a "low-cardiac-output-syndrome" as bridging towards decision, recovery or long-term support. Venoarterial extracorporeal membrane oxygenation (vaECMO) may take over cardiopulmonary function and may improve survival as well as neurological outcome after cardiogenic shock or cardiopulmonary resuscitation. PMID:27631451

  6. Heart fields and cardiac morphogenesis.

    Science.gov (United States)

    Kelly, Robert G; Buckingham, Margaret E; Moorman, Antoon F

    2014-10-01

    In this review, we focus on two important steps in the formation of the embryonic heart: (i) the progressive addition of late differentiating progenitor cells from the second heart field that drives heart tube extension during looping morphogenesis, and (ii) the emergence of patterned proliferation within the embryonic myocardium that generates distinct cardiac chambers. During the transition between these steps, the major site of proliferation switches from progenitor cells outside the early heart to proliferation within the embryonic myocardium. The second heart field and ballooning morphogenesis concepts have major repercussions on our understanding of human heart development and disease. In particular, they provide a framework to dissect the origin of congenital heart defects and the regulation of myocardial proliferation and differentiation of relevance for cardiac repair.

  7. A dynamic jamming point for shear thickening suspensions

    Science.gov (United States)

    Brown, Eric; Jaeger, Heinrich

    2008-11-01

    Densely packed suspensions can shear thicken, in which the viscosity increases with shear rate. We performed rheometry measurements on two model systems: corn starch in water and glass spheres in oils. In both systems we observed shear thickening up to a critical packing fraction φc (=0.55 for spherical grains) above which the flow abruptly transitions to shear thinning. The viscosity and yield stress diverge as power laws at φc. Extrapolating the dynamic ranges of shear rate and stress in the shear thickening regime up to φc suggests a finite change in shear stress with zero change in shear rate. This is a dynamic analog to the jamming point with a yield stress at zero shear rate.

  8. Exponential Shear Flow of Linear, Entangled Polymeric Liquids

    DEFF Research Database (Denmark)

    Neergaard, Jesper; Park, Kyungho; Venerus, David C.;

    2000-01-01

    A previously proposed reptation model is used to interpret exponential shear flow data taken on an entangled polystyrenesolution. Both shear and normal stress measurements are made during exponential shear using mechanical means. The model iscapable of explaining all trends seen in the data......, and suggests a novel analysis of the data. This analysis demonstrates thatexponential shearing flow is no more capable of stretching polymer chains than is inception of steady shear at comparableinstantaneous shear rates. In fact, all exponential shear flow stresses measured are bounded quantitatively...... by stressmeasurements taken during inception of steady shear. Information taken from the model about chain stretching suggests thatnormal stress measurements are strong indications of stretching, whereas shear stress measurements are indicative of bothchain stretching and segment orientation....

  9. Shear zones between rock units with no relative movement

    DEFF Research Database (Denmark)

    Koyi, Hemin; Schmeling, Harro; Burchardt, Steffi;

    2013-01-01

    a partially molten magma body (stoping). From the fluid dynamics perspective these shear zones can be regarded as low Reynolds number deformation zones within the wake of a body moving through a viscous medium. While compact moving bodies (aspect ratio 1:1:1) generate axial symmetric (cone like) shear zones......Shear zones are normally viewed as relatively narrow deformation zones that accommodate relative displacement between two "blocks" that have moved past each other in opposite directions. This study reports localized zones of shear between adjacent blocks that have not moved past each other...... or wakes, elongated bodies (vertical plates or horizontal rod-like bodies) produce tabular shear zones or wakes. Unlike conventional shear zones across which shear indicators usually display consistent symmetries, shear indicators on either side of the shear zone or wake reported here show reverse...

  10. Shear zones between rock units with no relative movement

    DEFF Research Database (Denmark)

    Koyi, H.; Schmeling, H.; Burchardt, S.;

    2012-01-01

    magma body (stoping). From the fluid dynamics point of view these shear zones can be regarded as the low Reynolds number deformation zones within the wake of a body moving through a viscous medium. While compact (aspect ratio 1:1:1) moving bodies generate axial symmetric (cone like) shear zones......Shear zones are normally viewed as relatively narrow deformation zones that accommodate relative displacement between two "blocks" that have moved past each other in opposite directions. This study reports localized zones of shear between adjacent blocks that have not moved past each other......, elongated bodies (vertical plates or horizontal rod-like bodies) produce tabular shear zones. Unlike conventional shear zones across which shear indicators ideally display consistent symmetries, shear indicators on either sides of the shear zone reported here show reverse kinematics. Thus profiles exhibit...

  11. Monotonic shear and shear fatigue of foam-core composite sandwich structures

    Energy Technology Data Exchange (ETDEWEB)

    Liu, L.; Song, H.; Holmes, J.W. [Georgia Institute of Technology, School of Aerospace Eng., Materials and Advanced Structure Testing Lab., Atlanta, Georgia (United States)

    2006-07-01

    Details of a new test apparatus that allows direct shear testing of sandwich structures is discussed. In addition to monotonic and cyclic shear, the apparatus allows studying the shear-creep behavior of various sandwich structures and can be extended to investigate lap-joints and adhesive joints. The test apparatus can accommodate sandwich panels as large as 400 mm x 400 mm. In proof-of-concept experiments, the apparatus was used to investigate the effect of loading history on the ambient temperature monotonic shear and shear fatigue life of sandwich composites with a PVC foam core and fiberglass/epoxy face sheets. The fatigue experiments were performed at a loading frequency of 1 Hz and a stress ratio between 0.16 and 0.19. During fatigue, a progressive degradation in shear modulus occurs as well as considerable stress-strain hysteresis. Damage accumulated by the cycle-by-cycle extension of cracks along the face-sheet/core interface and shear-related damage to the PVC foam core. (au)

  12. Acute shear stress direction dictates adherent cell remodeling and verifies shear profile of spinning disk assays

    International Nuclear Information System (INIS)

    Several methods have been developed to quantify population level changes in cell attachment strength given its large heterogeneity. One such method is the rotating disk chamber or ‘spinning disk’ in which a range of shear forces are applied to attached cells to quantify detachment force, i.e. attachment strength, which can be heterogeneous within cell populations. However, computing the exact force vectors that act upon cells is complicated by complex flow fields and variable cell morphologies. Recent observations suggest that cells may remodel their morphology and align during acute shear exposure, but contrary to intuition, shear is not orthogonal to the radial direction. Here we theoretically derive the magnitude and direction of applied shear and demonstrate that cells, under certain physiological conditions, align in this direction within minutes. Shear force magnitude is also experimentally verified which validates that for spread cells shear forces and not torque or drag dominate in this assay, and demonstrates that the applied force per cell area is largely independent of initial morphology. These findings suggest that direct quantified comparison of the effects of shear on a wide array of cell types and conditions can be made with confidence using this assay without the need for computational or numerical modeling. (paper)

  13. A new method for shear wave speed estimation in shear wave elastography.

    Science.gov (United States)

    Engel, Aaron J; Bashford, Gregory R

    2015-12-01

    Visualization of mechanical properties of tissue can aid in noninvasive pathology diagnosis. Shear wave elastography (SWE) measures the elastic properties of soft tissues by estimation of local shear wave propagation speed. In this paper, a new robust method for estimation of shear wave speed is introduced which has the potential for simplifying continuous filtering and real-time elasticity processing. Shear waves were generated by external mechanical excitation and imaged at a high frame rate. Three homogeneous phantoms of varying elastic moduli and one inclusion phantom were imaged. Waves propagating in separate directions were filtered and shear wave speed was estimated by inversion of the 1-D first-order wave equation. Final 2-D shear wave speed maps were constructed by weighted averaging of estimates from opposite traveling directions. Shear wave speed results for phantoms with gelatin concentrations of 5%, 7%, and 9% were 1.52 ± 0.10 m/s, 1.86 ± 0.10 m/s, and 2.37 ± 0.15 m/s, respectively, which were consistent with estimates computed from three other conventional methods, as well as compression tests done with a commercial texture analyzer. The method was shown to be able to reconstruct a 2-D speed map of an inclusion phantom with good image quality and variance comparable to conventional methods. Suggestions for further work are given. PMID:26670851

  14. Application of in situ direct shear device to shear strength measurement of rockfill materials

    Institute of Scientific and Technical Information of China (English)

    Si-hong LIU

    2009-01-01

    A simplified in situ direct shear test (DST) was developed for measuring the shear strength of soils in fields.In this test,a latticed shearing frame replaces the upper half of the shear box used in the conventional direct shear box test.The latticed shearing frame is directly embedded in the ground to be tested after a construction process and is pulled with a flexible chain while a constant dead load is applied to the sample in the shearing frame.This simplified in situ DST has been validated by comparing its results with those of triaxial tests on samples with parallel gradations under normal stresses less than 100 kPa.In this study,the DST was further validated by carrying out tests on samples with the same gradations,rather than on samples with parallel gradations,under normal stresses up to 880 kPa.In addition,the DST was performed inside fills in two applications.

  15. Cardiac Biomarkers in Hyperthyroid Cats

    OpenAIRE

    Sangster, J.K.; Panciera, D L; Abbott, J.A.; Zimmerman, K.C.; Lantis, A.C.

    2013-01-01

    Background Hyperthyroidism has substantial effects on the circulatory system. The cardiac biomarkers NT‐proBNP and troponin I (cTNI) have proven useful in identifying cats with myocardial disease but have not been extensively investigated in hyperthyroidism. Hypothesis Plasma NT‐proBNP and cTNI concentrations are higher in cats with primary myocardial disease than in cats with hyperthyroidism and higher in cats with hyperthyroidism than in healthy control cats. Animals Twenty‐three hyperthyro...

  16. Historical perspectives of cardiac electrophysiology.

    Science.gov (United States)

    Lüderitz, Berndt

    2009-01-01

    The diagnosis and treatment of clinical electrophysiology has a long and fascinating history. From earliest times, no clinical symptom impressed the patient (and the physician) more than an irregular heart beat. Although ancient Chinese pulse theory laid the foundation for the study of arrhythmias and clinical electrophysiology in the 5th century BC, the most significant breakthrough in the identification and treatment of cardiac arrhythmias first occurred in this century. In the last decades, our knowledge of electrophysiology and pharmacology has increased exponentially. The enormous clinical significance of cardiac rhythm disturbances has favored these advances. On the one hand, patients live longer and thus are more likely to experience arrhythmias. On the other hand, circulatory problems of the cardiac vessels have increased enormously, and this has been identified as the primary cause of cardiac rhythm disorders. Coronary heart disease has become not just the most significant disease of all, based on the statistics for cause of death. Arrhythmias are the main complication of ischemic heart disease, and they have been directly linked to the frequently arrhythmogenic sudden death syndrome, which is now presumed to be an avoidable "electrical accident" of the heart. A retrospective look--often charming in its own right--may not only make it easier to sort through the copious details of this field and so become oriented in this universe of important and less important facts: it may also provide the observer with a chronological vantage point from which to view the subject. The study of clinical electrophysiology is no dry compendium of facts and figures, but rather a dynamic field of study evolving out of the competition between various ideas, intentions and theories. PMID:19196616

  17. Cardiac Biomarkers and Cycling Race

    OpenAIRE

    Caroline Le Goff, Jean-François Kaux, Sébastien Goffaux, Etienne Cavalier

    2015-01-01

    In cycling as in other types of strenuous exercise, there exists a risk of sudden death. It is important both to understand its causes and to see if the behavior of certain biomarkers might highlight athletes at risk. Many reports describe changes in biomarkers after strenuous exercise (Nie et al., 2011), but interpreting these changes, and notably distinguishing normal physiological responses from pathological changes, is not easy. Here we have focused on the kinetics of different cardiac bi...

  18. Functiogenesis of cardiac pacemaker activity.

    Science.gov (United States)

    Sakai, Tetsuro; Kamino, Kohtaro

    2016-07-01

    Throughout our investigations on the ontogenesis of the electrophysiological events in early embryonic chick hearts, using optical techniques to record membrane potential probed with voltage-sensitive dyes, we have introduced a novel concept of "functiogenesis" corresponding to "morphogenesis". This article gives an account of the framework of "functiogenesis", focusing on the cardiac pacemaker function and the functional organization of the pacemaking area. PMID:26719289

  19. Cardiac involvement in tuberous sclerosis.

    OpenAIRE

    Mühler, E G; Turniski-Harder, V; Engelhardt, W.; von Bernuth, G

    1994-01-01

    OBJECTIVE--To assess the incidence, importance, and history of cardiac involvement in infants and children with tuberous sclerosis. DESIGN--Prospective study; clinical examination, sector and Doppler echocardiography, standard and ambulatory electrocardiography. SETTING--A tertiary referral centre. PATIENTS--21 patients with tuberous sclerosis aged 1 day to 16 years (mean 6.3 years); follow up investigations were available in 14 cases (10 retrospective, 4 prospective; mean follow up 4.3 years...

  20. Cardiac autonomic nerve distribution and arrhythmia

    Institute of Scientific and Technical Information of China (English)

    Quan Liu; Dongmei Chen; Yonggang Wang; Xin Zhao; Yang Zheng

    2012-01-01

    OBJECTIVE: To analyze the distribution characteristics of cardiac autonomic nerves and to explore the correlation between cardiac autonomic nerve distribution and arrhythmia.DATA RETRIEVAL: A computer-based retrieval was performed for papers examining the distribution of cardiac autonomic nerves, using "heart, autonomic nerve, sympathetic nerve, vagus nerve, nerve distribution, rhythm and atrial fibrillation" as the key words.SELECTION CRITERIA: A total of 165 studies examining the distribution of cardiac autonomic nerve were screened, and 46 of them were eventually included.MAIN OUTCOME MEASURES: The distribution and characteristics of cardiac autonomic nerves were observed, and immunohistochemical staining was applied to determine the levels of tyrosine hydroxylase and acetylcholine transferase (main markers of cardiac autonomic nerve distribution). In addition, the correlation between cardiac autonomic nerve distribution and cardiac arrhythmia was investigated.RESULTS: Cardiac autonomic nerves were reported to exhibit a disordered distribution in different sites, mainly at the surface of the cardiac atrium and pulmonary vein, forming a ganglia plexus. The distribution of the pulmonary vein autonomic nerve was prominent at the proximal end rather than the distal end, at the upper left rather than the lower right, at the epicardial membrane rather than the endocardial membrane, at the left atrium rather than the right atrium, and at the posterior wall rather than the anterior wall. The main markers used for cardiac autonomic nerves were tyrosine hydroxylase and acetylcholine transferase. Protein gene product 9.5 was used to label the immunoreactive nerve distribution, and the distribution density of autonomic nerves was determined using a computer-aided morphometric analysis system.CONCLUSION: The uneven distribution of the cardiac autonomic nerves is the leading cause of the occurrence of arrhythmia, and the cardiac autonomic nerves play an important role in the

  1. Sudden cardiac death risk stratification.

    Science.gov (United States)

    Deyell, Marc W; Krahn, Andrew D; Goldberger, Jeffrey J

    2015-06-01

    Arrhythmic sudden cardiac death (SCD) may be caused by ventricular tachycardia/fibrillation or pulseless electric activity/asystole. Effective risk stratification to identify patients at risk of arrhythmic SCD is essential for targeting our healthcare and research resources to tackle this important public health issue. Although our understanding of SCD because of pulseless electric activity/asystole is growing, the overwhelming majority of research in risk stratification has focused on SCD-ventricular tachycardia/ventricular fibrillation. This review focuses on existing and novel risk stratification tools for SCD-ventricular tachycardia/ventricular fibrillation. For patients with left ventricular dysfunction or myocardial infarction, advances in imaging, measures of cardiac autonomic function, and measures of repolarization have shown considerable promise in refining risk. Yet the majority of SCD-ventricular tachycardia/ventricular fibrillation occurs in patients without known cardiac disease. Biomarkers and novel imaging techniques may provide further risk stratification in the general population beyond traditional risk stratification for coronary artery disease alone. Despite these advances, significant challenges in risk stratification remain that must be overcome before a meaningful impact on SCD can be realized.

  2. Review Article of Cardiac Amyloidosis

    Directory of Open Access Journals (Sweden)

    Jittiporn PURATTANAMAL

    2010-06-01

    Full Text Available Cardiac amyloidosis is a term that means the deposit of abnormal proteins in the myocardium leading to global thickening of the heart walls. The clinical character is that of infiltrative cardiomyopathy. AL amyloidosis is the most common type that involves cardiac failure. Cardiac amyloid precedes clinical congestive heart failure, especially right-sided heart failure. Laboratory investigations have identified the amyloid fibril proteins deposited in the organ tissues. Immunofixation tests are the most sensitive that recognize the paraprotein mean light chain protein or immunoglobulin subtype deposit. Prognosis is poor if AL amyloidosis is untreated. Treatment of systemic involvement in AL amyloidosis is via chemotherapy such as melphalan and prednisolone. UK experts have reported the results of treatment in AL amyloidosis. Regardless of the use of adjunctive chemotherapy, the five-year survival after heart transplantation was generally poorer for AL (20 % at five years, but similar for non-AL amyloidosis (64 % at five years, than heart transplants in other cases. Progression of the systemic disease contributed to increased mortality. A specific treatment that increases the chances of survival is unknown.

  3. Cardiac MRI in restrictive cardiomyopathy

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, A. [Department of Cardiovascular Radiology, All India Institute of Medical Sciences, Ansari Nagar, Delhi (India); Singh Gulati, G., E-mail: gulatigurpreet@rediffmail.com [Department of Cardiovascular Radiology, All India Institute of Medical Sciences, Ansari Nagar, Delhi (India); Seth, S. [Department of Cardiology, All India Institute of Medical Sciences, Ansari Nagar, Delhi (India); Sharma, S. [Department of Cardiovascular Radiology, All India Institute of Medical Sciences, Ansari Nagar, Delhi (India)

    2012-02-15

    Restrictive cardiomyopathy (RCM) is a specific group of heart muscle disorders characterized by inadequate ventricular relaxation during diastole. This leads to diastolic dysfunction with relative preservation of systolic function. Although short axis systolic function is usually preserved in RCM, the long axis systolic function may be severely impaired. Confirmation of diagnosis and information regarding aetiology, extent of myocardial damage, and response to treatment requires imaging. Importantly, differentiation from constrictive pericarditis (CCP) is needed, as only the latter is managed surgically. Echocardiography is the initial cardiac imaging technique but cannot reliably suggest a tissue diagnosis; although recent advances, especially tissue Doppler imaging and spectral tracking, have improved its ability to differentiate RCM from CCP. Cardiac catheterization is the reference standard, but is invasive, two-dimensional, and does not aid myocardial characterization. Cardiac magnetic resonance (CMR) is a versatile technique providing anatomical, morphological and functional information. In recent years, it has been shown to provide important information regarding disease mechanisms, and also been found useful to guide treatment, assess its outcome and predict patient prognosis. This review describes the CMR features of RCM, appearances in various diseases, its overall role in patient management, and how it compares with other imaging techniques.

  4. Laboratory Investigation on Shear Behavior of Rock Joints and a New Peak Shear Strength Criterion

    Science.gov (United States)

    Zhang, Xiaobo; Jiang, Qinghui; Chen, Na; Wei, Wei; Feng, Xixia

    2016-09-01

    In this study, shear tests on artificial rock joints with different roughness were conducted under five normal stress levels. Test results showed that the shear strength of rock joints had a positive correlation with roughness and the applied normal stress. Observation of joint specimens after shear tests indicated that asperity damage was mainly located in the steep areas facing the shear direction. The damaged joint surfaces tend to be rough, which implies that tensile failure plays an important role in shear behavior. As a result of the anisotropic characteristic of joint roughness, two quantitative 2D roughness parameters, i.e., the revised root-mean-square of asperity angle tan-1( Z 2r) and the maximum contact coefficient C m, were proposed considering the shear direction. The proposed roughness parameters can capture the difference of roughness in forward and reverse directions along a single joint profile. The normalized tensile strength and the proposed roughness parameters were used to perform a rational derivation of peak dilatancy angle. A negative exponential-type function was found to be appropriate to model the peak dilatancy angle. Using the new model of peak dilatancy angle, we obtained a new criterion for peak shear strength of rock joints. The good agreement between test results and predicted results by the new criterion indicated that the proposed criterion is capable of estimating the peak shear strength of rock joints. Comparisons between the new criterion and published models from available literature revealed that the proposed criterion has a good accuracy for predicting the peak shear strength of joints investigated in this study.

  5. Numerical Simulation of Tripolar Vortex in Dusty Plasma with Sheared Flow and Sheared Magnetic Field

    Institute of Scientific and Technical Information of China (English)

    Wang Ge; Chen Yinhua; Tan Liwei

    2005-01-01

    This article presents a study we have made of one class of coherent structures of the tripolar vortex. Considering the sheared flow and sheared magnetic field which are common in the thermonuclear plasma and space plasma, we have simulated the dynamics of the tripolar vortex.The results show that the tripolar vortex is largely stable in most cases, but a strongly sheared magnetic field will make the structure less stable, and lead it to decays into single vortices with the large space scale. These results are consistent with findings from former research about the dipolar vortex.

  6. Instabilities in Pulsating Pipe Flow of Shear-Thinning and Shear-Thickening Fluids

    OpenAIRE

    Sadrizadeh, Sasan

    2012-01-01

    In this study, we have considered the modal and non-modal stability of fluids with shear-dependent viscosity flowing in a rigid straight pipe. A second order finite-difference code is used for the simulation of pipe flow in the cylindrical coordinate system. The Carreau-Yasuda model where the rheological parameters vary in the range of 0.3 < n < 1.5 and 0.1 < λ < 100 is represents the viscosity of shear- thinning and shear thickening fluids. Variation of the periodic pulsatile for...

  7. Analysis of shear test method for composite laminates

    Science.gov (United States)

    Bergner, H. W., Jr.; Davis, J. G., Jr.; Herakovich, C. T.

    1977-01-01

    An elastic plane stress finite element analysis of the stress distributions in four flat test specimens for in-plane shear response of composite materials subjected to mechanical or thermal loads is presented. The shear test specimens investigated include: slotted coupon, cross beam, losipescu, and rail shear. Results are presented in the form of normalized shear contour plots for all three in-plane stess components. It is shown that the cross beam, losipescu, and rail shear specimens have stress distributions which are more than adequate for determining linear shear behavior of composite materials. Laminate properties, core effects, and fixture configurations are among the factors which were found to influence the stress distributions.

  8. Self-organization in circular shear layers

    DEFF Research Database (Denmark)

    Bergeron, K.; Coutsias, E.A.; Lynov, Jens-Peter;

    1996-01-01

    Experiments on forced circular shear layers performed in both magnetized plasmas and in rotating fluids reveal qualitatively similar self-organization processes leading to the formation of patterns of coherent vortical structures with varying complexity. In this paper results are presented from...

  9. Red blood cell in simple shear flow

    Science.gov (United States)

    Chien, Wei; Hew, Yayu; Chen, Yeng-Long

    2013-03-01

    The dynamics of red blood cells (RBC) in blood flow is critical for oxygen transport, and it also influences inflammation (white blood cells), thrombosis (platelets), and circulatory tumor migration. The physical properties of a RBC can be captured by modeling RBC as lipid membrane linked to a cytoskeletal spectrin network that encapsulates cytoplasm rich in hemoglobin, with bi-concave equilibrium shape. Depending on the shear force, RBC elasticity, membrane viscosity, and cytoplasm viscosity, RBC can undergo tumbling, tank-treading, or oscillatory motion. We investigate the dynamic state diagram of RBC in shear and pressure-driven flow using a combined immersed boundary-lattice Boltzmann method with a multi-scale RBC model that accurately captures the experimentally established RBC force-deformation relation. It is found that the tumbling (TU) to tank-treading (TT) transition occurs as shear rate increases for cytoplasm/outer fluid viscosity ratio smaller than 0.67. The TU frequency is found to be half of the TT frequency, in agreement with experiment observations. Larger viscosity ratios lead to the disappearance of stable TT phase and unstable complex dynamics, including the oscillation of the symmetry axis of the bi-concave shape perpendicular to the flow direction. The dependence on RBC bending rigidity, shear modulus, the order of membrane spectrin network and fluid field in the unstable region will also be discussed.

  10. Shear-free boundary in Stokes flow

    OpenAIRE

    Amaranath, T.; S. D. Nigam; Palaniappan, D.

    1996-01-01

    A theorem of Harper for axially symmetric flow past a sphere which is a stream surface, and is also shear-free, is extended to flow past a doubly-body ð”… consisting of two unequal, orthogonally intersecting spheres. Several illustrative examples are given. An analogue of Faxen's law for a double-body is observed.

  11. Axisymmetric Toroidal Equilibrium with Sheared Toroidal Flows

    Institute of Scientific and Technical Information of China (English)

    石秉仁

    2002-01-01

    Problem of the axisymmetric toroidal equilibrium with pure sheared toroidal flow is involved. For standard tokamak equilibrium, general approximate solutions are analytically pursued for arbitrary current profile and non-circular cross-section. Equilibrium properties including the flow-induced density asymmetry are analyzed.

  12. Equilibrium states of homogeneous sheared compressible turbulence

    Science.gov (United States)

    Riahi, M.; Lili, T.

    2011-06-01

    Equilibrium states of homogeneous compressible turbulence subjected to rapid shear is studied using rapid distortion theory (RDT). The purpose of this study is to determine the numerical solutions of unsteady linearized equations governing double correlations spectra evolution. In this work, RDT code developed by authors solves these equations for compressible homogeneous shear flows. Numerical integration of these equations is carried out using a second-order simple and accurate scheme. The two Mach numbers relevant to homogeneous shear flow are the turbulent Mach number Mt, given by the root mean square turbulent velocity fluctuations divided by the speed of sound, and the gradient Mach number Mg which is the mean shear rate times the transverse integral scale of the turbulence divided by the speed of sound. Validation of this code is performed by comparing RDT results with direct numerical simulation (DNS) of [A. Simone, G.N. Coleman, and C. Cambon, Fluid Mech. 330, 307 (1997)] and [S. Sarkar, J. Fluid Mech. 282, 163 (1995)] for various values of initial gradient Mach number Mg0. It was found that RDT is valid for small values of the non-dimensional times St (St 10) in particular for large values of Mg0. This essential feature justifies the resort to RDT in order to determine equilibrium states in the compressible regime.

  13. Equilibrium states of homogeneous sheared compressible turbulence

    Directory of Open Access Journals (Sweden)

    M. Riahi

    2011-06-01

    Full Text Available Equilibrium states of homogeneous compressible turbulence subjected to rapid shear is studied using rapid distortion theory (RDT. The purpose of this study is to determine the numerical solutions of unsteady linearized equations governing double correlations spectra evolution. In this work, RDT code developed by authors solves these equations for compressible homogeneous shear flows. Numerical integration of these equations is carried out using a second-order simple and accurate scheme. The two Mach numbers relevant to homogeneous shear flow are the turbulent Mach number Mt, given by the root mean square turbulent velocity fluctuations divided by the speed of sound, and the gradient Mach number Mg which is the mean shear rate times the transverse integral scale of the turbulence divided by the speed of sound. Validation of this code is performed by comparing RDT results with direct numerical simulation (DNS of [A. Simone, G.N. Coleman, and C. Cambon, Fluid Mech. 330, 307 (1997] and [S. Sarkar, J. Fluid Mech. 282, 163 (1995] for various values of initial gradient Mach number Mg0. It was found that RDT is valid for small values of the non-dimensional times St (St 10 in particular for large values of Mg0. This essential feature justifies the resort to RDT in order to determine equilibrium states in the compressible regime.

  14. Shear adhesion strength of aligned electrospun nanofibers.

    Science.gov (United States)

    Najem, Johnny F; Wong, Shing-Chung; Ji, Guang

    2014-09-01

    Inspiration from nature such as insects' foot hairs motivates scientists to fabricate nanoscale cylindrical solids that allow tens of millions of contact points per unit area with material substrates. In this paper, we present a simple yet robust method for fabricating directionally sensitive shear adhesive laminates. By using aligned electrospun nylon-6, we create dry adhesives, as a succession of our previous work on measuring adhesion energies between two single free-standing electrospun polymer fibers in cross-cylinder geometry, randomly oriented membranes and substrate, and peel forces between aligned fibers and substrate. The synthetic aligned cylindrical solids in this study are electrically insulating and show a maximal Mode II shear adhesion strength of 27 N/cm(2) on a glass slide. This measured value, for the purpose of comparison, is 270% of that reported from gecko feet. The Mode II shear adhesion strength, based on a commonly known "dead-weight" test, is 97-fold greater than the Mode I (normal) adhesion strength of the same. The data indicate a strong shear binding on and easy normal lifting off. Anisotropic adhesion (Mode II/Mode I) is pronounced. The size and surface boundary effects, crystallinity, and bending stiffness of fibers are used to understand these electrospun nanofibers, which vastly differ from otherwise known adhesive technologies. The anisotropic strength distribution is attributed to a decreasing fiber diameter and an optimized laminate thickness, which, in turn, influences the bending stiffness and solid-state "wettability" of points of contact between nanofibers and surface asperities.

  15. Electrorheological Effects at High Shear Rate

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Much attention has been given to electrorheological (ER) fluids because of the ER effect, which has been described by a large number of researchers as a notable increase in the apparent viscosity of a fluid upon the application of an electric field. The description of ER effects is, however, not accurate at high shear rates. To clarify the discrepancy, we analyze and compute the apparent viscosity as a function of shear rate for ER fluid flow between rotating coaxial cylinders in the presence of an electric field. The theoretical predictions show that the increase of electric intensity contributes little to the apparent viscosity enhancement at high shear rates, while ER effects for ER fluids with a higher polarization rate still exist and ER devices possess controllability in this regime. Description of the ER effect by the apparent viscosity leads to an unrealistic conclusion that ER effects disappear at high shear rates, because the apparent viscosity of ER fluids approaches the value for Newtonian fluids. Therefore, it is concluded that the proper description of ER effects, i.e., one that holds uniformly for any strain rate when ER effects exist, is manifested by a remarkable increase in the extra stress rather than in the apparent viscosity of ER fluids.

  16. Shearing DNA for genomic library construction.

    Science.gov (United States)

    Hengen, P N

    1997-07-01

    Methods and reagents is a unique monthly column that highlights current discussion in the newsgroup bionet.molibio.methds-reagnts, available on the internet. This month's column discusses the pros and cons of various techniques used to shear DNA for shotgun cloning. For details on how to partake in the newsgroup, see the accompanying box. PMID:9255070

  17. Shear deformation in thick auxetic plates

    International Nuclear Information System (INIS)

    This paper aims to understand the effect of auxeticity on shear deformation in thick plates. Three models for the shear correction factor of plates as a function of Poisson’s ratio were proposed: an analytical model, a cubic fit model and a modified model. Of these three, the cubic fit model exhibits the best accuracy over the entire range of Poisson’s ratio from −1 to 0.5. The extent of shear deformation is herein investigated using the example of uniformly loaded circular plates. It was found that the maximum deformation of such plates based on Mindlin theory approximates to those according to Kirchhoff theory when the Poisson’s ratio of the plate material is highly negative. When the Poisson’s ratio of the plate material is −1 and the edge of the plate is simply supported, the calculation of the maximum deflection by Mindlin theory simplifies into that by Kirchhoff theory. These results suggest that auxeticity reduces shear deformation in thick plates, permitting the use of classical plate theory for thick plates only if the plate material is highly auxetic. (paper)

  18. Evaluation of Known or Suspected Cardiac Sarcoidosis.

    Science.gov (United States)

    Blankstein, Ron; Waller, Alfonso H

    2016-03-01

    Sarcoidosis is a multisystem disorder of unknown cause, and cardiac sarcoidosis affects at least 25% of patients and accounts for substantial mortality and morbidity from this disease. Cardiac sarcoidosis may present with heart failure, left ventricular systolic dysfunction, AV block, atrial or ventricular arrhythmias, and sudden cardiac death. Cardiac involvement can be challenging to detect and diagnose because of the focal nature of the disease, as well as the fact that clinical criteria have limited diagnostic accuracy. Nevertheless, the diagnosis of cardiac sarcoidosis can be enhanced by integrating both clinical and imaging findings. This article reviews the various roles that different imaging modalities provide in the evaluation and management of patients with known or suspected cardiac sarcoidosis. PMID:26926267

  19. Sensing Cardiac Electrical Activity With a Cardiac Myocyte--Targeted Optogenetic Voltage Indicator

    NARCIS (Netherlands)

    Chang Liao, Mei-Ling; de Boer, Teun P; Mutoh, Hiroki; Raad, Nour; Richter, Claudia; Wagner, Eva; Downie, Bryan R; Unsöld, Bernhard; Arooj, Iqra; Streckfuss-Bömeke, Katrin; Döker, Stephan; Luther, Stefan; Guan, Kaomei; Wagner, Stefan; Lehnart, Stephan E; Maier, Lars S; Stühmer, Walter; Wettwer, Erich; van Veen, Toon; Morlock, Michael M; Knöpfel, Thomas; Zimmermann, Wolfram-Hubertus

    2015-01-01

    RATIONALE: Monitoring and controlling cardiac myocyte activity with optogenetic tools offer exciting possibilities for fundamental and translational cardiovascular research. Genetically encoded voltage indicators may be particularly attractive for minimal invasive and repeated assessments of cardiac

  20. Spurious Shear in Weak Lensing with LSST

    Energy Technology Data Exchange (ETDEWEB)

    Chang, C.; Kahn, S.M.; Jernigan, J.G.; Peterson, J.R.; AlSayyad, Y.; Ahmad, Z.; Bankert, J.; Bard, D.; Connolly, A.; Gibson, R.R.; Gilmore, K.; Grace, E.; Hannel, M.; Hodge, M.A.; Jee, M.J.; Jones, L.; Krughoff, S.; Lorenz, S.; Marshall, P.J.; Marshall, S.; Meert, A.

    2012-09-19

    The complete 10-year survey from the Large Synoptic Survey Telescope (LSST) will image {approx} 20,000 square degrees of sky in six filter bands every few nights, bringing the final survey depth to r {approx} 27.5, with over 4 billion well measured galaxies. To take full advantage of this unprecedented statistical power, the systematic errors associated with weak lensing measurements need to be controlled to a level similar to the statistical errors. This work is the first attempt to quantitatively estimate the absolute level and statistical properties of the systematic errors on weak lensing shear measurements due to the most important physical effects in the LSST system via high fidelity ray-tracing simulations. We identify and isolate the different sources of algorithm-independent, additive systematic errors on shear measurements for LSST and predict their impact on the final cosmic shear measurements using conventional weak lensing analysis techniques. We find that the main source of the errors comes from an inability to adequately characterise the atmospheric point spread function (PSF) due to its high frequency spatial variation on angular scales smaller than {approx} 10{prime} in the single short exposures, which propagates into a spurious shear correlation function at the 10{sup -4}-10{sup -3} level on these scales. With the large multi-epoch dataset that will be acquired by LSST, the stochastic errors average out, bringing the final spurious shear correlation function to a level very close to the statistical errors. Our results imply that the cosmological constraints from LSST will not be severely limited by these algorithm-independent, additive systematic effects.

  1. Methods in pharmacology: measurement of cardiac output

    OpenAIRE

    Geerts, Bart F; Aarts, Leon P; Jansen, Jos R.

    2011-01-01

    Many methods of cardiac output measurement have been developed, but the number of methods useful for human pharmacological studies is limited. The ‘holy grail’ for the measurement of cardiac output would be a method that is accurate, precise, operator independent, fast responding, non-invasive, continuous, easy to use, cheap and safe. This method does not exist today. In this review on cardiac output methods used in pharmacology, the Fick principle, indicator dilution techniques, arterial pul...

  2. Cardiac tumours simulating collagen vascular disease.

    OpenAIRE

    Fitzpatrick, A. P.; Lanham, J. G.; Doyle, D V

    1986-01-01

    Cardiac tumours can mimic collagen vascular disease and they are often accompanied by profound systemic upset. Both benign and malignant tumours may present in this way. Three cases of cardiac tumour, two malignant and one benign, are reported with just such a presentation. A review of fifteen similar case reports showed that a spectrum of different collagen vascular diseases was diagnosed and treated before the true diagnosis emerged. In half of these cases the cardiac tumour was only diagno...

  3. Disseminated cysticercosis with pulmonary and cardiac involvement

    OpenAIRE

    Jain Bharat; Sankhe Shilpa; Agrawal Mukta; Naphade Prashant

    2010-01-01

    Pulmonary and cardiac involvement by cysticercosis is extremely rare, and is usually asymptomatic. We report the case of a 19-year-old boy who presented with a history of headache and vomiting and was found to have disseminated cysticercosis with pulmonary and cardiac involvement; the emphasis is on the rare occurrence of pulmonary, cardiac, pancreatic, intraocular, and extradural spinal canal involvement in the same patient. This case demonstrates the extent to which cysticercosis can be dis...

  4. Electrocardiographically Determination of Cardiac Enlargements in Dogs

    OpenAIRE

    Gönül, Remzi; OR, Mehmet Erman; DODURKA, Tamer

    2002-01-01

    In this study, the electrocardiographic parameters necessary to determine cardiac enlargements and to establish and distinguish such complaints from each other in the early stage in dogs with circulatory problems were assessed. The material of the study consisted of 33 dogs 1.5-15 years of age with cardiac enlargements determined from 140 dogs suspected of having cardiac disease based on clinical, radiographic and electrocardiographic analyses. In these dogs, 12 cases of left atrial hypert...

  5. Test and Analysis of a New Ductile Shear Connection Design for RC Shear Walls

    DEFF Research Database (Denmark)

    Sørensen, Jesper Harrild; Hoang, Linh Cao; Olesen, John Forbes;

    2016-01-01

    This paper presents a new and construction-friendly shear connection for assembly of precast reinforced concrete shear wall elements. In the proposed design, the precast elements have indented interfaces and are connected by a narrow zone grouted with mortar and reinforced with overlapping U......-bar loops. Contrary to the classical shear connections, the planes of the U-bar loops are here parallel to the plane of the wall elements. This feature enables a construction-friendly installation of the elements without the risk of rebars clashing. The core of mortar inside each U-bar loop is reinforced...... with a transverse double T-headed bar to ensure transfer of tension between the overlapping U-bars. Push-off tests show that a significantly ductile load-displacement response can be obtained by the new solution as compared to the performance of the conventional keyed shear connection design. The influence...

  6. [Out-of-hospital cardiac arrest].

    Science.gov (United States)

    Virkkunen, Ilkka; Hoppu, Sanna; Kämäräinen, Antti

    2011-01-01

    Cardiac arrest as the first symptom of coronary artery disease is not uncommon. Some of previously healthy people with sudden cardiac arrest may be saved by effective resuscitation and post-resuscitative therapy. The majority of cardiac arrest patients experience the cardiac arrest outside of the hospital, in which case early recognition of lifelessness, commencement of basic life support and entry to professional care without delay are the prerequisites for recovery. After the heart has started beating again, the clinical picture of post-resuscitation syndrome must be recognized and appropriate treatment utilized. PMID:22204143

  7. Detecting deterministic dy namics of cardiac rhythm

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Under the acceptable hypothesis that cardiac rhythm is an approximately deterministic process with a small scale noise component, an available way is provided to construct a model that can reflect its prominent dynamics of the deterministic component. When applied to the analysis of 19 heart rate data sets, three main findings are stated. The obtained model can reflect prominent dynamics of the deterministic component of cardiac rhythm; cardiac chaos is stated in a reliable way; dynamical noise plays an important role in the generation of complex cardiac rhythm.``

  8. Molecular origins of higher harmonics in large-amplitude oscillatory shear flow: Shear stress response

    Science.gov (United States)

    Gilbert, P. H.; Giacomin, A. J.

    2016-10-01

    Recent work has focused on deepening our understanding of the molecular origins of the higher harmonics that arise in the shear stress response of polymeric liquids in large-amplitude oscillatory shear flow. For instance, these higher harmonics have been explained by just considering the orientation distribution of rigid dumbbells suspended in a Newtonian solvent. These dumbbells, when in dilute suspension, form the simplest relevant molecular model of polymer viscoelasticity, and this model specifically neglects interactions between the polymer molecules [R. B. Bird et al., "Dilute rigid dumbbell suspensions in large-amplitude oscillatory shear flow: Shear stress response," J. Chem. Phys. 140, 074904 (2014)]. In this paper, we explore these interactions by examining the Curtiss-Bird model, a kinetic molecular theory designed specifically to account for the restricted motions that arise when polymer chains are concentrated, thus interacting and specifically, entangled. We begin our comparison using a heretofore ignored explicit analytical solution [X.-J. Fan and R. B. Bird, "A kinetic theory for polymer melts. VI. Calculation of additional material functions," J. Non-Newtonian Fluid Mech. 15, 341 (1984)]. For concentrated systems, the chain motion transverse to the chain axis is more restricted than along the axis. This anisotropy is described by the link tension coefficient, ɛ, for which several special cases arise: ɛ = 0 corresponds to reptation, ɛ > 1/8 to rod-climbing, 1/5 ≤ ɛ ≤ 3/4 to reasonable predictions for shear-thinning in steady simple shear flow, and ɛ = 1 to the dilute solution without hydrodynamic interaction. In this paper, we examine the shapes of the shear stress versus shear rate loops for the special cases ɛ = (" separators=" 0 , 1 / 8 , 3 / 8 , 1 ) , and we compare these with those of rigid dumbbell and reptation model predictions.

  9. Insulation Impact on Shear Strength of Screw Connections and Shear Strength of Diaphragms

    OpenAIRE

    Lease, Adam R.

    2005-01-01

    Several thousand tests throughout the world have been conducted on the shear strength of screw connections in cold-formed steel, however, little to no research has been conducted on how various thicknesses of insulation placed between two sheets of steel, such as a steel panel and structural supporting member, affects a screw's shear strength. Elemental tests were conducted as part of this study at Virginia Tech where rolled fiberglass insulation was placed between two pieces of steel connec...

  10. 42 CFR 410.49 - Cardiac rehabilitation program and intensive cardiac rehabilitation program: Conditions of coverage.

    Science.gov (United States)

    2010-10-01

    ... and intensive cardiac rehabilitation program: Conditions of coverage. (a) Definitions. As used in this... 42 Public Health 2 2010-10-01 2010-10-01 false Cardiac rehabilitation program and intensive cardiac rehabilitation program: Conditions of coverage. 410.49 Section 410.49 Public Health CENTERS...

  11. Tumors of the cardiac conduction system: are they an explanation for otherwise unexplained sudden cardiac death?

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    @@ Cardiac tumors are well described in the literature. The first reports of cardiac tumors date back hundreds of years.The prevalence of primary cardiac tumors at autopsy ranges from 0.001% to 0.3% with secondary tumors more common than in primary tumors.

  12. Molecular Origins of Higher Harmonics in Large-Amplitude Oscillatory Shear Flow: Shear Stress Response

    Science.gov (United States)

    Gilbert, Peter; Giacomin, A. Jeffrey; Schmalzer, Andrew; Bird, R. B.

    Recent work has focused on understanding the molecular origins of higher harmonics that arise in the shear stress response of polymeric liquids in large-amplitude oscillatory shear flow. These higher harmonics have been explained using only the orientation distribution of a dilute suspension of rigid dumbbells in a Newtonian fluid, which neglects molecular interactions and is the simplest relevant molecular model of polymer viscoelasticity [R.B. Bird et al., J Chem Phys, 140, 074904 (2014)]. We explore these molecular interactions by examining the Curtiss-Bird model, a kinetic molecular theory that accounts for restricted polymer motions arising when chains are concentrated [Fan and Bird, JNNFM, 15, 341 (1984)]. For concentrated systems, the chain motion transverse to the chain axis is more restricted than along the axis. This anisotropy is described by the link tension coefficient, ɛ, for which several special cases arise: ɛ =0 corresponds to reptation, ɛ > 1 1 8 8 to rod-climbing, 1 1 2 2 >= ɛ >= 3 3 4 4 to reasonable shear-thinning predictions in steady simple shear flow, and ɛ =1 to a dilute solution of chains. We examine the shapes of the shear stress versus shear rate loops for the special cases, ɛ = 0 , 1 0 , 1 8 , 3 3 8 8 8 , 3 3 8 8 , 1 , of the Curtiss-Bird model, and we compare these with those of rigid dumbbell and reptation model predictions.

  13. Amorphous silicon under mechanical shear deformations: Shear velocity and temperature effects

    Science.gov (United States)

    Kerrache, Ali; Mousseau, Normand; Lewis, Laurent J.

    2011-04-01

    Mechanical shear deformations lead, in some cases, to effects similar to those resulting from ion irradiation. Here we characterize the effects of shear velocity and temperature on amorphous silicon (a-Si) modeled using classical molecular-dynamics simulations based on the empirical environment-dependent interatomic potential (EDIP). With increasing shear velocity at low temperature, we find a systematic increase in the internal strain leading to the rapid appearance of structural defects (fivefold-coordinated atoms). The impacts of externally applied strain can be almost fully compensated by increasing the temperature, allowing the system to respond more rapidly to the deformation. In particular, we find opposite power-law relations between the temperature and the shear velocity and the deformation energy. The spatial distribution of defects is also found to depend strongly on temperature and strain velocity. For low temperature or high shear velocity, defects are concentrated in a few atomic layers near the center of the cell, while with increasing temperature or decreasing shear velocity, they spread slowly throughout the full simulation cell. This complex behavior can be related to the structure of the energy landscape and the existence of a continuous energy-barrier distribution.

  14. Influence of material properties on the sheared impact process of shear-cap in squib valve

    International Nuclear Information System (INIS)

    Background: Squib valve is a key valve in the new generation nuclear power plant, which has not been localized and the research on the failure process of shear-cap is necessary. Purpose: This research aims to study the influence of material on the failure process of shear-cap in squib valve. Methods: The finite element method is used to simulate the shear-caps' sheared process of different materials-Inconel 690, 304 stainless steel and 321 stainless steel. Results: As a result, the failure time and the final speed of piston are shown at each impact speed. Conclusions: The shear-cap of Inconel 690 is hardest to shear. A method to get the critical impact speed in the open process of valve is proposed. It can be found that the residual kinetic energy of the piston has the common feature and is 25% of the initial kinetic energy. Piston's final speed has a linear relationship to its initial speed for all three materials. (authors)

  15. Adaptive Estimation of Intravascular Shear Rate Based on Parameter Optimization

    Science.gov (United States)

    Nitta, Naotaka; Takeda, Naoto

    2008-05-01

    The relationships between the intravascular wall shear stress, controlled by flow dynamics, and the progress of arteriosclerosis plaque have been clarified by various studies. Since the shear stress is determined by the viscosity coefficient and shear rate, both factors must be estimated accurately. In this paper, an adaptive method for improving the accuracy of quantitative shear rate estimation was investigated. First, the parameter dependence of the estimated shear rate was investigated in terms of the differential window width and the number of averaged velocity profiles based on simulation and experimental data, and then the shear rate calculation was optimized. The optimized result revealed that the proposed adaptive method of shear rate estimation was effective for improving the accuracy of shear rate calculation.

  16. Disentangling the role of structure and friction in shear jamming

    Science.gov (United States)

    Vinutha, H. A.; Sastry, Srikanth

    2016-06-01

    Amorphous sphere packings have been intensely investigated to understand mechanical and flow behaviour of dense granular matter and to explore universal aspects of the jamming transition, from fluid to structurally arrested states. Considerable recent research has focused on anisotropic packings of frictional grains generated by shear deformation leading to shear jamming, occurring below the jamming density for isotropic packings of frictionless grains. Here, with the aim of disentangling the role of shear-deformation-induced structures and friction in generating shear jamming, we computationally study sheared assemblies of frictionless spheres, over a wide range of densities. We demonstrate that shear deformation alone leads to the emergence of geometric features characteristic of jammed packings, with the increase of shear strain. We also show that such emergent geometry, together with friction, leads to mechanically stable, shear-jammed, packings above a threshold density that lies well below the isotropic jamming point.

  17. Flexible Micropost Arrays for Shear Stress Measurement

    Science.gov (United States)

    Wohl, Christopher J.; Palmieri, Frank L.; Hopkins, John W.; Jackson, Allen M.; Connell, John W.; Lin, Yi; Cisotto, Alexxandra A.

    2015-01-01

    Increased fuel costs, heightened environmental protection requirements, and noise abatement continue to place drag reduction at the forefront of aerospace research priorities. Unfortunately, shortfalls still exist in the fundamental understanding of boundary-layer airflow over aerodynamic surfaces, especially regarding drag arising from skin friction. For example, there is insufficient availability of instrumentation to adequately characterize complex flows with strong pressure gradients, heat transfer, wall mass flux, three-dimensionality, separation, shock waves, and transient phenomena. One example is the acoustic liner efficacy on aircraft engine nacelle walls. Active measurement of shear stress in boundary layer airflow would enable a better understanding of how aircraft structure and flight dynamics affect skin friction. Current shear stress measurement techniques suffer from reliability, complexity, and airflow disruption, thereby compromising resultant shear stress data. The state-of-the-art for shear stress sensing uses indirect or direct measurement techniques. Indirect measurements (e.g., hot-wire, heat flux gages, oil interferometry, laser Doppler anemometry, small scale pressure drag surfaces, i.e., fences) require intricate knowledge of the studied flow, restrictive instrument arrangements, large surface areas, flow disruption, or seeding material; with smaller, higher bandwidth probes under development. Direct measurements involve strain displacement of a sensor element and require no prior knowledge of the flow. Unfortunately, conventional "floating" recessed components for direct measurements are mm to cm in size. Whispering gallery mode devices and Fiber Bragg Gratings are examples of recent additions to this type of sensor with much smaller (?m) sensor components. Direct detection techniques are often single point measurements and difficult to calibrate and implement in wind tunnel experiments. In addition, the wiring, packaging, and installation

  18. Turbulent transport across shear layers in magnetically confined plasmas

    International Nuclear Information System (INIS)

    Shear layers modify the turbulence in diverse ways and do not only suppress it. A spatial-temporal investigation of gyrofluid simulations in comparison with experiments allows to identify further details of the transport process across shear layers. Blobs in and outside a shear layer merge, thereby exchange particles and heat and subsequently break up. Via this mechanism particles and heat are transported radially across shear layers. Turbulence spreading is the immanent mechanism behind this process

  19. Shear viscosity for a moderately dense granular binary mixture

    OpenAIRE

    Garzo, Vicente; Montanero, Jose Maria

    2003-01-01

    The shear viscosity for a moderately dense granular binary mixture of smooth hard spheres undergoing uniform shear flow is determined. The basis for the analysis is the Enskog kinetic equation, solved first analytically by the Chapman-Enskog method up to first order in the shear rate for unforced systems as well as for systems driven by a Gaussian thermostat. As in the elastic case, practical evaluation requires a Sonine polynomial approximation. In the leading order, we determine the shear v...

  20. Hysteresis and Lubrication in Shear Thickening of Cornstarch Suspensions

    OpenAIRE

    Chu, Clarence E.; Groman, Joel A.; Sieber, Hannah L.; Miller, James G.; Okamoto, Ruth J.; Katz, Jonathan I.

    2014-01-01

    Aqueous and brine suspensions of corn starch show striking discontinuous shear thickening. We have found that a suspension shear-thickened throughout may remain in the jammed thickened state as the strain rate is reduced, but an unjamming front may propagate from any unjammed regions. Transient shear thickening is observed at strain rates below the thickening threshold, and above it the stress fluctuates. The jammed shear-thickened state may persist to low strain rates, with stresses resembli...

  1. Reynolds stresses from hydrodynamic turbulence with shear and rotation

    OpenAIRE

    Snellman, J. E.; Käpylä, P. J.; Korpi, M. J.; Liljeström, A. J.

    2009-01-01

    To study the Reynolds stresses which describe turbulent momentum transport from turbulence affected by large-scale shear and rotation. Three-dimensional numerical simulations are used to study turbulent transport under the influences of large-scale shear and rotation in homogeneous, isotropically forced turbulence. We study three cases: one with only shear, and two others where in addition to shear, rotation is present. These cases differ by the angle (0 or 90\\degr) the rotation vector makes ...

  2. Shear Strength of R/C Beams with Spiral Reinforcement

    OpenAIRE

    市之瀬, 敏勝; 横尾, 慎一; イチノセ, トシカツ; Ichinose, Toshikatsu

    1992-01-01

    Based on the upper bound theorem, the shear strength of R/C beams with spiral reinforcement is discussed considering its pitch. Three dimensional failure pattern is considered. Conclusions are as follows : (1) Spiral reinforcement is more liable to yield than closed shear reinforcement if their pitch is the same ; (2) The shear strength of R/C beams with usual amount of spiral reinforcement is similar to that with the same amount of closed shear reinforcement. The difference appears when the ...

  3. Analytical theory of forced rotating sheared turbulence: The perpendicular case

    OpenAIRE

    Leprovost, Nicolas; Kim, Eun-Jin

    2008-01-01

    Rotation and shear flows are ubiquitous features of many astrophysical and geophysical bodies. To understand their origin and effect on turbulent transport in these systems, we consider a forced turbulence and investigate the combined effect of rotation and shear flow on the turbulence properties. Specifically, we study how rotation and flow shear influence the generation of shear flow (e.g., the direction of energy cascade), turbulence level, transport of particles and momentum, and the anis...

  4. ECLS in Pediatric Cardiac Patients

    Science.gov (United States)

    Di Nardo, Matteo; MacLaren, Graeme; Marano, Marco; Cecchetti, Corrado; Bernaschi, Paola; Amodeo, Antonio

    2016-01-01

    Extracorporeal life support (ECLS) is an important device in the management of children with severe refractory cardiac and or pulmonary failure. Actually, two forms of ECLS are available for neonates and children: extracorporeal membrane oxygenation (ECMO) and use of a ventricular assist device (VAD). Both these techniques have their own advantages and disadvantages. The intra-aortic balloon pump is another ECLS device that has been successfully used in larger children, adolescents, and adults, but has found limited applicability in smaller children. In this review, we will present the “state of art” of ECMO in neonate and children with heart failure. ECMO is commonly used in a variety of settings to provide support to critically ill patients with cardiac disease. However, a strict selection of patients and timing of intervention should be performed to avoid the increase in mortality and morbidity of these patients. Therefore, every attempt should be done to start ECLS “urgently” rather than “emergently,” before the presence of dysfunction of end organs or circulatory collapse. Even though exciting progress is being made in the development of VADs for long-term mechanical support in children, ECMO remains the mainstay of mechanical circulatory support in children with complex anatomy, particularly those needing rapid resuscitation and those with a functionally univentricular circulation. With the increase in familiarity with ECMO, new indications have been added, such as extracorporeal cardiopulmonary resuscitation (ECPR). The literature supporting ECPR is increasing in children. Reasonable survival rates have been achieved after initiation of support during active compressions of the chest following in-hospital cardiac arrest. Contraindications to ECLS have reduced in the last 5 years and many centers support patients with functionally univentricular circulations. Improved results have been recently achieved in this complex subset of patients. PMID

  5. EVALUATION OF NEONATAL CARDIAC MURMURS

    Directory of Open Access Journals (Sweden)

    Somaiah

    2014-09-01

    Full Text Available Cardiovascular malformations are the most common cause of congenital malformations, the diagnosis of which requires a close observation in the neonatal period. Early recognition of CHD is important in the neonatal period, as many of them may be fatal if undiagnosed and may require immediate intervention. The objectives of this study are to study the epidemiology of neonatal cardiac murmurs, to identify clinical characteristics which differentiate pathological murmur from functional murmurs and to assess the reliability of clinical evaluation in diagnosing CHD. Method of study included all neonates admitted to the NICU, postnatal ward, attending pediatric OPD or neonatal follow up clinic and were detected to have cardiac murmurs. It was a cross sectional study over a period of 16months. A clinical diagnosis was made based on history and clinical examination. Then Chest X-ray and ECG, Echocardiography was done in all neonates for confirmation of the diagnosis. These neonates were again examined daily till they were in hospital and during the follow-up visit at 6 weeks. The results of 70 neonates in this study conducted over a period of 24 months included the incidence of cardiac murmurs among intramural neonates which was 13.5 for 1000 live births. Most frequent symptom was fast breathing in 10(14.3% cases. VSD was the most common diagnosis clinically in 23 (33% babies. The most frequent Echo diagnosis was acyanotic complex congenital heart disease in 25(36% cases followed by 12(17% cases each of VSD and ASD respectively. Overall in our study 77.1% (54cases of the murmurs were diagnosed correctly and confirmed by Echocardiography The study concluded that it is possible to make clinical diagnosis in many cases of congenital heart diseases, the functional murmurs could be differentiated from those arising from structural heart disease and evaluation of the infants based only on murmurs, few congenital heart diseases can be missed.

  6. Cerebral oximetry in cardiac anesthesia

    Science.gov (United States)

    Vretzakis, George; Georgopoulou, Stauroula; Stamoulis, Konstantinos; Stamatiou, Georgia; Tsakiridis, Kosmas; Katsikogianis, Nikolaos; Kougioumtzi, Ioanna; Machairiotis, Nikolaos; Tsiouda, Theodora; Mpakas, Andreas; Beleveslis, Thomas; Koletas, Alexander; Siminelakis, Stavros N.; Zarogoulidis, Konstantinos

    2014-01-01

    Cerebral oximetry based on near-infrared spectroscopy (NIRS) is increasingly used during the perioperative period of cardiovascular operations. It is a noninvasive technology that can monitor the regional oxygen saturation of the frontal cortex. Current literature indicates that it can stratify patients preoperatively according their risk. Intraoperatively, it provides continuous information about brain oxygenation and allows the use of brain as sentinel organ indexing overall organ perfusion and injury. This review focuses on the clinical validity and applicability of this monitor for cardiac surgical patients. PMID:24672700

  7. Cardiac leiomyosarcoma, a case report

    DEFF Research Database (Denmark)

    Andersen, Rikke; Kristensen, Bjarne W; Gill, Sabine

    2013-01-01

    In this case report we present the history of a patient admitted with recurrent pulmonary edema. Transesophageal chocardiography showed a tumour in the left atrium, occluding the ostium of the mitral valve and mimicking intermittent mitral stenosis. Cardiac surgery followed by pathological...... examination revealed that the tumour was a leiomyosarcoma. Images from the echocardiography as well as the pathological findings are shown and discussed. The present case report illustrates that atrial tumors comprise also sarcomas, suggesting the use of careful, rapid diagnostic procedures and treatment...

  8. Cardiac imaging: does radiation matter?

    Science.gov (United States)

    Einstein, Andrew J.; Knuuti, Juhani

    2012-01-01

    The use of ionizing radiation in cardiovascular imaging has generated considerable discussion. Radiation should not be considered in isolation, but rather in the context of a careful examination of the benefits, risks, and costs of cardiovascular imaging. Such consideration requires an understanding of some fundamental aspects of the biology, physics, epidemiology, and terminology germane to radiation, as well as principles of radiological protection. This paper offers a concise, contemporary perspective on these areas by addressing pertinent questions relating to radiation and its application to cardiac imaging. PMID:21828062

  9. Autologous Transfusion in Cardiac Surgery

    Directory of Open Access Journals (Sweden)

    Radmehr H

    2003-11-01

    Full Text Available Preoperative autologous blood donation is commonly used to reduce exposure to homologous blood transfusions among patients undergoing elective cardiac surgery. The aim of this study was to evaluate the effect of autologous transfusion on patients' hematocryte value, intra and postoperative blood loss, hospitalization time, the development of infective complications and other factors. Materials and Methods: Between June 2001 to April 2002, 208 patients were underwent cardiac surgery in cardiac surgery ward in Imam Khomeini Medical Center. One or more blood units donate from 104 Patients before cardiopulmonary bypass and heparin injection, and transfused to them after CPB and Protamin injection (autologous Group, group 1. 104 patients underwent cardiac surgery routinely (control group, group 2."nResults: Mean of age was 55.9±8.6 in group 1 and 56.6±9.3 in group 2 (P=NS. 73 male and 31 females were in group 1 and 79 males and 25 females were in group 2 (P=NS. Smoking, familial history, hyperlipidemia, diabetes mellitus, renal failure, hypertension, stroke, and history of myocardial infarction was similar in two groups."nSeverity of angina, urgency operation, number vessels disease, duration of cardiopulmonary bypass, duration of aortic cross clamp time, use of internal thoracic artery graft, and number of grafts was similar in both groups. Mean of bleeding post operation was 548 cc in group 1 and 803 cc in-group 2 (P=0.003. Bleeding that need to operation was 1.8% in group 1 and 8.6% in group 2 (P=0.002. Wound infection, mediastinitis, renal failure, ventilatory prolonged, stroke, need to Intra-aortic Balloon Pump (IABP, intraoperative bleeding, and hospital stay was similar in both groups. Mean of extubationt time was 10.2 hours in group 1 and 14.8 hours in group 2 (P=0.001."nConclusion: Preoperative and intra-operative donations are safe and continue to contribute uniquely to blood conservation, providing important options in comprehensive

  10. [Acute cardiac failure in pheochromocytoma.

    DEFF Research Database (Denmark)

    Jønler, Morten; Munk, Kim

    2008-01-01

    Pheochromocytoma (P) is an endocrine catecholamine-secreting tumor. Classical symptoms like hypertension, attacks of sweating, palpitations, headache and palor are related to catecholamine discharge. We provide a case of P in a 71 year-old man presenting with acute cardiac failure, severe reduction...... in left ventricular function and elevated myocardial enzymes. No coronary stenoses were found. The myocardium regained nearly normal systolic function in one and a half month. A renal P was laparoscopicaly removed. We discuss the pathophysiology of catecholamine cardiomyopathy. Udgivelsesdato: 2008-Jun-2...

  11. Introduction to noninvasive cardiac mapping.

    Science.gov (United States)

    Bear, Laura; Cuculich, Phillip S; Bernus, Olivier; Efimov, Igor; Dubois, Rémi

    2015-03-01

    From the dawn of the twentieth century, the electrocardiogram (ECG) has revolutionized the way clinical cardiology has been practiced, and it has become the cornerstone of modern medicine today. Driven by clinical and research needs for a more precise understanding of cardiac electrophysiology beyond traditional ECG, inverse solution electrocardiography has been developed, tested, and validated. This article outlines the important progress from ECG development, through more extensive measurement of body surface potentials, and the fundamental leap to solving the inverse problem of electrocardiography, with a focus on mathematical methods and experimental validation. PMID:25784020

  12. 10.2.Cardiac arrhythmias

    Institute of Scientific and Technical Information of China (English)

    1993-01-01

    930257 Electrophysiologic study of reperfu-sion arrhythmias.YIN Hong (尹红),et al.Af-fil Hosp,Shandong Med Univ,Jinan.Chin CirJ 1993;8(1):37—39.Twenty dogs of experimental ischemic reper-fusion were studied with a three-dimensionalmapping system of cardiac electric activity andmultiple—level myocardial recordings by bipolarplunge—needle electrodes.27% of the nonsus-tained ventricular tachycardia (NSVT) of intra-mural reentry occurred in the ischemic subendo-

  13. Control over colloidal crystallization by shear and electric fields

    NARCIS (Netherlands)

    Wu, Y.L.

    2007-01-01

    We used shear flow and an electric field to control colloidal crystallization. The structures were examined in situ with confocal microscopy. For experiments under shear, a new parallel plate shear cell was designed. It had a zero-velocity plane that was stationary with respect to the microscope. Th

  14. Seismic behavior of semi-supported steel shear walls

    DEFF Research Database (Denmark)

    Jahanpour, A.; Jönsson, J.; Moharrami, H.

    2012-01-01

    During the recent past decade semi-supported steel shear walls (SSSW) have been introduced as an alternative to the traditional type of steel plate shear walls. In this system the shear wall does not connect directly to the main columns of the building frame; instead it is connected to a pair...

  15. Shear effects on crystalline structures of poly(L-lactide)

    DEFF Research Database (Denmark)

    Xiao, Peitao; Li, Hongfei; Huang, Shaoyong;

    2013-01-01

    The shearing effects of sheared polymer melts on their finally formed crystalline structures of poly(L-lactide) (PLLA) were investigated by means of small angle X-ray scattering (SAXS) and wide angle X-ray diffraction (WAXD). The results of WAXD prove that shear has no effects on the crystal stru...

  16. Assessment of cardiac sympathetic nerve integrity with positron emission tomography

    Energy Technology Data Exchange (ETDEWEB)

    Raffel, David M. E-mail: raffel@umich.edu; Wieland, Donald M

    2001-07-01

    The autonomic nervous system plays a critical role in the regulation of cardiac function. Abnormalities of cardiac innervation have been implicated in the pathophysiology of many heart diseases, including sudden cardiac death and congestive heart failure. In an effort to provide clinicians with the ability to regionally map cardiac innervation, several radiotracers for imaging cardiac sympathetic neurons have been developed. This paper reviews the development of neuronal imaging agents and discusses their emerging role in the noninvasive assessment of cardiac sympathetic innervation.

  17. The Cardiac Conduction System: Generation and Conduction of the Cardiac Impulse.

    Science.gov (United States)

    Kennedy, Alan; Finlay, Dewar D; Guldenring, Daniel; Bond, Raymond; Moran, Kieran; McLaughlin, James

    2016-09-01

    In this article, the authors outline the key components behind the automated generation of the cardiac impulses and the effect these impulses have on cardiac myocytes. Also, a description of the key components of the normal cardiac conduction system is provided, including the sinoatrial node, the atrioventricular node, the His bundle, the bundle branches, and the Purkinje network. Finally, an outline of how each stage of the cardiac conduction system is represented on the electrocardiogram is described, allowing the reader of the electrocardiogram to translate background information about the normal cardiac conduction system to everyday clinical practice. PMID:27484656

  18. Hyperscaling violation and the shear diffusion constant

    Science.gov (United States)

    Kolekar, Kedar S.; Mukherjee, Debangshu; Narayan, K.

    2016-09-01

    We consider holographic theories in bulk (d + 1)-dimensions with Lifshitz and hyperscaling violating exponents z , θ at finite temperature. By studying shear gravitational modes in the near-horizon region given certain self-consistent approximations, we obtain the corresponding shear diffusion constant on an appropriately defined stretched horizon, adapting the analysis of Kovtun, Son and Starinets. For generic exponents with d - z - θ > - 1, we find that the diffusion constant has power law scaling with the temperature, motivating us to guess a universal relation for the viscosity bound. When the exponents satisfy d - z - θ = - 1, we find logarithmic behaviour. This relation is equivalent to z = 2 +deff where deff =di - θ is the effective boundary spatial dimension (and di = d - 1 the actual spatial dimension). It is satisfied by the exponents in hyperscaling violating theories arising from null reductions of highly boosted black branes, and we comment on the corresponding analysis in that context.

  19. Turbulent Shear Layers in Supersonic Flow

    CERN Document Server

    Smits, Alexander J

    2006-01-01

    A good understanding of turbulent compressible flows is essential to the design and operation of high-speed vehicles. Such flows occur, for example, in the external flow over the surfaces of supersonic aircraft, and in the internal flow through the engines. Our ability to predict the aerodynamic lift, drag, propulsion and maneuverability of high-speed vehicles is crucially dependent on our knowledge of turbulent shear layers, and our understanding of their behavior in the presence of shock waves and regions of changing pressure. Turbulent Shear Layers in Supersonic Flow provides a comprehensive introduction to the field, and helps provide a basis for future work in this area. Wherever possible we use the available experimental work, and the results from numerical simulations to illustrate and develop a physical understanding of turbulent compressible flows.

  20. Stochastically driven instability in rotating shear flows

    CERN Document Server

    Mukhopadhyay, Banibrata

    2012-01-01

    Origin of hydrodynamic turbulence in rotating shear flows is investigated. The particular emphasis is the flows whose angular velocity decreases but specific angular momentum increases with increasing radial coordinate. Such flows are Rayleigh stable, but must be turbulent in order to explain observed data. Such a mismatch between the linear theory and observations/experiments is more severe when any hydromagnetic/magnetohydrodynamic instability and then the corresponding turbulence therein is ruled out. The present work explores the effect of stochastic noise on such hydrodynamic flows. We essentially concentrate on a small section of such a flow which is nothing but a plane shear flow supplemented by the Coriolis effect. This also mimics a small section of an astrophysical accretion disk. It is found that such stochastically driven flows exhibit large temporal and spatial correlations of perturbation velocities, and hence large energy dissipations of perturbation, which presumably generate instability. A ra...

  1. MECHANICAL BEHAVIOR OF AMORPHOUS POLYMERS IN SHEAR

    Institute of Scientific and Technical Information of China (English)

    张赟; 黄筑平

    2004-01-01

    Based on the non-equilibrium thermodynamic theory, a new thermo-viscoelastic constitutive model for an incompressible material is proposed. This model can be considered as a kind of generalization of the non-Gaussian network theory in rubber elasticity to include the viscous and the thermal effects. A set of second rank tensorial internal variables was introduced, and in order to adequately describe the evolution of these internal variables, a new expression of the Helmholtz free energy was suggested. The mechanical behavior of the thermo-viscoelastic material under simple shear deformation was studied, and the "viscous dissipation induced" anisotropy due to the change of orientation distribution of molecular chains was examined. Influences of strain rate and thermal softening produced by the viscous dissipation on the shear stress were also discussed. Finally, the model predictions were compared with the experimental results performed by G'Sell et al., thus the validity of the proposed model is verified.

  2. Bulk and shear viscosity in Hagedorn fluid

    Energy Technology Data Exchange (ETDEWEB)

    Tawfik, A.; Wahba, M. [Egyptian Center for Theoretical Physics (ECTP), MTI University, Faculty of Engineering, Cairo (Egypt)

    2010-11-15

    Assuming that the Hagedorn fluid composed of known particles and resonances with masses m <2 GeV obeys the first-order theory (Eckart) of relativistic fluid, we discuss the transport properties of QCD confined phase. Based on the relativistic kinetic theory formulated under the relaxation time approximation, expressions for bulk and shear viscosity in thermal medium of hadron resonances are derived. The relaxation time in the Hagedorn dynamical fluid exclusively takes into account the decay and eventually van der Waals processes. We comment on the in-medium thermal effects on bulk and shear viscosity and averaged relaxation time with and without the excluded-volume approach. As an application of these results, we suggest the dynamics of heavy-ion collisions, non-equilibrium thermodynamics and the cosmological models, which require thermo- and hydro-dynamics equations of state. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  3. Bulk and Shear Viscosity in Hagedorn Fluid

    CERN Document Server

    Tawfik, A

    2010-01-01

    Assuming that the Hagedorn fluid composed of known particles and resonances with masses $m<2\\,$GeV obeys the {\\it first-order} theory (Eckart) of relativistic fluid, we discuss the transport properties of QCD confined phase. Based on the relativistic kinetic theory formulated under the relaxation time approximation, expressions for bulk and shear viscosity in thermal medium are derived. The relaxation time in the Hagedorn dynamical fluid exclusively takes into account the decay and eventually van der Waals processes. We comment on the {\\it in-medium} thermal effects on bulk and shear viscosities and averaged relaxation time with and without the excluded-volume approach. As an application of these results, we suggest the dynamics of heavy-ion collisions, non-equlibrium thermodynamics and the cosmological models, which require thermo and hydrodynamics equations of state.

  4. Static inelastic analysis of RC shear walls

    Institute of Scientific and Technical Information of China (English)

    陈勤; 钱稼茹

    2002-01-01

    A macro-model of a reinforced concrete (RC) shear wall is developed for static inelastic analysis. The model iscomposed of RC column elements and RC membrane elements. The column elements are used to model the boundary zone andthe membrane elements are used to model the wall panel. Various types of constitutive relationships of concrete could beadopted for the two kinds of elements. To perform analysis, the wall is divided into layers along its height. Two adjacent layersare connected with a rigid beam. There are only three unknown displacement components for each layer. A method called singledegree of freedom compensation is adopted to solve the peak value of the capacity curve. The post-peak stage analysis isperformed using a forced iteration approach. The macro-model developed in the study and the complete process analysismethodology are verified by the experimental and static inelastic analytical results of four RC shear wall specimens.

  5. Hierarchical probabilistic inference of cosmic shear

    CERN Document Server

    Schneider, Michael D; Marshall, Philip J; Dawson, William A; Meyers, Joshua; Bard, Deborah J; Lang, Dustin

    2014-01-01

    Point estimators for the shearing of galaxy images induced by gravitational lensing involve a complex inverse problem in the presence of noise, pixelization, and model uncertainties. We present a probabilistic forward modeling approach to gravitational lensing inference that has the potential to mitigate the biased inferences in most common point estimators and is practical for upcoming lensing surveys. The first part of our statistical framework requires specification of a likelihood function for the pixel data in an imaging survey given parameterized models for the galaxies in the images. We derive the lensing shear posterior by marginalizing over all intrinsic galaxy properties that contribute to the pixel data (i.e., not limited to galaxy ellipticities) and learn the distributions for the intrinsic galaxy properties via hierarchical inference with a suitably flexible conditional probabilitiy distribution specification. We use importance sampling to separate the modeling of small imaging areas from the glo...

  6. Undulatory swimming in shear-thinning fluids

    CERN Document Server

    Gagnon, David A; Arratia, Paulo E

    2014-01-01

    The swimming behaviour of microorganisms can be strongly influenced by the rheology of their fluid environment. In this manuscript, we experimentally investigate the effects of shear-thinning viscosity on the swimming behaviour of an undulatory swimmer, the nematode Caenorhabditis elegans. Tracking methods are used to measure the swimmer's kinematic data (including propulsion speed) and velocity fields. We find that shear-thinning viscosity modifies the velocity fields produced by the swimming nematode but does not modify the nematode's speed and beating kinematics. Velocimetry data show significant enhancement in local vorticity and circulation, and an increase in fluid velocity near the nematode's tail, compared to Newtonian fluids of similar effective viscosity. These findings are in good agreement with recent theoretical and numerical results.

  7. Flexible magnetic filaments in a shear flow

    Energy Technology Data Exchange (ETDEWEB)

    Cebers, Andrejs [Institute of Physics, University of Latvia, Salaspils-1 LV-2169 (Latvia)]. E-mail: aceb@tesla.sal.lv

    2006-05-15

    By flexible magnetic filament model its behavior under the simultaneous action of the shear flow and the magnetic field is investigated. It is found that for magnetoelastic numbers larger as the critical value, which depends on the shear rate, the periodic regime is established. For the values of the magnetoelastic number close to the critical the periodical regime is characterized by a rather slow development of the buckling instability due to the action of magnetic torques with the subsequent stage of the fast straightening of the filament. For the magnetoelastic numbers below the critical slightly bent shape of the filament orientated along the flow is established. The application of the results for the description of the viscoelasticity of the magnetorheological suspensions is discussed.

  8. Drop impact of shear thickening liquids

    CERN Document Server

    Boyer, Francois; Dijksman, J Frits; Lohse, Detlef

    2013-01-01

    The impact of drops of concentrated non-Brownian suspensions (cornstarch and polystyrene spheres) onto a solid surface is investigated experimentally. The spreading dynamics and maxi- mal deformation of the droplet of such shear thickening liquids are found to be markedly different from the impact of Newtonian drops. A particularly striking observation is that the maximal de- formation is independent of the drop velocity and that the deformation suddenly stops during the impact phase. Both observations are due to the shear-thickening rheology of the suspensions, as is theoretically explained from a balance between the kinetic energy and the viscously-dissipated en- ergy, from which we establish a scaling relation between drop maximal deformation and rheological parameters of concentrated suspensions.

  9. Implications of Orientation in Sheared Cocoa Butter

    Science.gov (United States)

    Guthrie, Sarah E.; Mazzanti, Gianfranco; Marangoni, Alejandro; Idziak, Stefan H. J.

    2004-03-01

    We will present x-ray and mechanical studies of oriented phases of cocoa butter. The structural elements of foods play an important role in determining such things as quality and shelf stability. The specific structure and properties of cocoa butter, however, are complicated due to the ability of the cocoa butter to form crystals in six polymorphic forms. Recent work has shown that the application of shear not only accelerates the transitions to more stable polymorphs, but also causes orientation of the crystallites[1]. The implications of orientation on the structures formed under conditions of shear and cooling will be described using x-ray diffraction and mechanical measurements. 1 G. Mazzanti, S. E. Guthrie, E. B. Sirota et al., Crystal Growth & Design 3 (5), 721 (2003).

  10. Direct measurement of shear properties of microfibers

    Energy Technology Data Exchange (ETDEWEB)

    Behlow, H.; Saini, D.; Durham, L.; Simpson, J.; Skove, M. J.; Rao, A. M. [Department of Physics and Astronomy, and Clemson Nanomaterials Center, Clemson University, Clemson, South Carolina 29634 (United States); Oliveira, L. [School of Materials Science and Engineering, Clemson University, Clemson, South Carolina 29634 (United States); Serkiz, S. M. [Department of Physics and Astronomy, and Clemson Nanomaterials Center, Clemson University, Clemson, South Carolina 29634 (United States); Savannah River National Laboratory, Aiken, South Carolina 29808 (United States)

    2014-09-15

    As novel fibers with enhanced mechanical properties continue to be synthesized and developed, the ability to easily and accurately characterize these materials becomes increasingly important. Here we present a design for an inexpensive tabletop instrument to measure shear modulus (G) and other longitudinal shear properties of a micrometer-sized monofilament fiber sample, such as nonlinearities and hysteresis. This automated system applies twist to the sample and measures the resulting torque using a sensitive optical detector that tracks a torsion reference. The accuracy of the instrument was verified by measuring G for high purity copper and tungsten fibers, for which G is well known. Two industrially important fibers, IM7 carbon fiber and Kevlar{sup ®} 119, were also characterized with this system and were found to have G = 16.5 ± 2.1 and 2.42 ± 0.32 GPa, respectively.

  11. Shear viscosity, cavitation and hydrodynamics at LHC

    Energy Technology Data Exchange (ETDEWEB)

    Bhatt, Jitesh R., E-mail: jeet@prl.res.in [Theoretical Physics Division, Physical Research Laboratory, Navrangpura, Ahmedabad 380 009 (India); Mishra, Hiranmaya, E-mail: hm@prl.res.in [Theoretical Physics Division, Physical Research Laboratory, Navrangpura, Ahmedabad 380 009 (India); Sreekanth, V., E-mail: skv@prl.res.in [Theoretical Physics Division, Physical Research Laboratory, Navrangpura, Ahmedabad 380 009 (India)

    2011-10-25

    We study evolution of quark-gluon matter in the ultrarelativistic heavy-ion collisions within the frame work of relativistic second-order viscous hydrodynamics. In particular, by using the various prescriptions of a temperature-dependent shear viscosity to the entropy ratio, we show that the hydrodynamic description of the relativistic fluid becomes invalid due to the phenomenon of cavitation. For most of the initial conditions relevant for LHC, the cavitation sets in very early stage. The cavitation in this case is entirely driven by the large values of shear viscosity. Moreover we also demonstrate that the conformal terms used in equations of the relativistic dissipative hydrodynamic can influence the cavitation time.

  12. Shear viscosity, cavitation and hydrodynamics at LHC

    CERN Document Server

    Bhatt, Jitesh R; Sreekanth, V

    2011-01-01

    We study evolution of quark-gluon matter in the ultrarelativistic heavy-ion collisions within the frame work of relativistic second-order viscous hydrodynamics. In particular, by using the various prescriptions of a temperature-dependent shear viscosity to the entropy ratio, we show that the hydrodynamic description of the relativistic fluid become invalid due to the phenomenon of cavitation. For most of the initial conditions relevant for LHC, the cavitation sets in very early during the evolution of the hydrodynamics in time $\\lesssim 2 $fm/c. The cavitation in this case is entirely driven by the large values of shear viscosity. Moreover we also demonstrate that the conformal term used in equations of the relativistic dissipative hydrodynamic can influence the cavitation time.

  13. Shear instabilities in shallow-water magnetohydrodynamics

    CERN Document Server

    Mak, Julian; Hughes, D W

    2016-01-01

    Within the framework of shallow-water magnetohydrodynamics, we investigate the linear instability of horizontal shear flows, influenced by an aligned magnetic field and stratification. Various classical instability results, such as H{\\o}iland's growth rate bound and Howard's semi-circle theorem, are extended to this shallow-water system for quite general profiles. Two specific piecewise-constant velocity profiles, the vortex sheet and the rectangular jet, are studied analytically and asymptotically; it is found that the magnetic field and stratification (as measured by the Froude number) are generally both stabilising, but weak instabilities can be found at arbitrarily large Froude number. Numerical solutions are computed for corresponding smooth velocity profiles, the hyperbolic-tangent shear layer and the Bickley jet, for a uniform background field. A generalisation of the long-wave asymptotic analysis of Drazin & Howard (1962) is employed in order to understand the instability characteristics for both ...

  14. Reynolds stress and shear flow generation

    DEFF Research Database (Denmark)

    Korsholm, Søren Bang; Michelsen, Poul; Naulin, V.;

    2001-01-01

    treatment of the pseudo-Reynolds stress, we present analytical and numerical results which demonstrate that the Reynolds stress in a plasma, indeed, generates a poloidal shear flow. The numerical simulations are performed both in a drift wave turbulence regime and a resistive interchange turbulence regime......The so-called Reynolds stress may give a measure of the self-consistent flow generation in turbulent fluids and plasmas by the small-scale turbulent fluctuations. A measurement of the Reynolds stress can thus help to predict flows, e.g. shear flows in plasmas. This may assist the understanding of...... improved confinement scenarios such as H-mode confinement regimes. However, the determination of the Reynolds stress requires measurements of the plasma potential, a task that is difficult in general and nearly impossible in hot plasmas in large devices. In this work we investigate an alternative method...

  15. Shear capacity of high-strength concrete beams with their point of inflection within the shear span

    OpenAIRE

    Islam, MS; Pam, HJ; Kwan, AKH

    1998-01-01

    The shear strength of concrete does not increase in proportion with the concrete grade. Thus, when high-strength concrete is used in place of normal-strength concrete, the shear capacity of the structure could become critical. In the study presented, the effect of concrete strength on the shear capacity of concrete beams was investigated. As previous research on normal-strength concrete beams has shown that the presence of an inflection point within the shear span can significantly influence ...

  16. Shear modulus of the neutron star crust

    International Nuclear Information System (INIS)

    Complete text of publication follows. The shear modulus of the solid neutron star crust is calculated by the thermodynamic perturbation theory, taking into account ion motion. At given density, the crust is modelled as a body-centred cubic Coulomb crystal of fully ionized atomic nuclei of one type with the uniform charge-compensating electron background. Classic and quantum regimes of ion motion are considered. The calculations in the classic temperature range agree well with previous Monte Carlo simulations. At these temperatures, the shear modulus is given by the sum of a positive contribution due to the static lattice and a negative / T contribution due to the ion motion. The quantum calculations are performed for the first time. The main result is that at low temperatures the contribution to the shear modulus due to the ion motion saturates at a constant value, associated with zero-point ion vibrations. Such behaviour is qualitatively similar to the zero-point ion motion contribution to the crystal energy. The quantum effects may be important for lighter elements at higher densities, where the ion plasma temperature is not entirely negligible compared to the typical Coulomb ion interaction energy. Additionally, the correction to the static lattice shear modulus due to the electron gas polarizability is evaluated. This effect is taken into account in the formalism of the dielectric function. Static zero temperature dielectric function of degenerate relativistic electron gas obtained in the Random Phase Approximation is used. The results of numerical calculations are approximated by convenient fitting formulae. They should be used for precise neutron star oscillation modelling, a rapidly developing branch of stellar seismology. This work was partially supported by the Russian Foundation for Basic Research (grant 11-02-00253-a), by the State Program 'Leading Scientific Schools of Russian Federation' (grant NSh 3769.2010.2) and by the Ministry of Education and

  17. Stent implantation influence wall shear stress evolution

    Science.gov (United States)

    Bernad, S. I.; Totorean, A. F.; Bosioc, A. I.; Petre, I.; Bernad, E. S.

    2016-06-01

    Local hemodynamic factors are known affect the natural history of the restenosis critically after coronary stenting of atherosclerosis. Stent-induced flows disturbance magnitude dependent directly on the strut design. The impact of flow alterations around struts vary as the strut geometrical parameters change. Our results provide data regarding the hemodynamic parameters for the blood flow in both stenosed and stented coronary artery under physiological conditions, namely wall shear stress and pressure drop.

  18. Shear modulus titration in crystalline colloidal suspensions

    OpenAIRE

    Palberg, Thomas; Kottal, Johannes; Bitzer, Franz; Simon, Rolf; Würth, Mathias; Leiderer, Paul

    1995-01-01

    We present the first direct experimental access to the actual surface charge number Z of colloidal particles under conditions of strong electrostatic interaction. We further calculate a renormalized charge number Z *(Z) using the modified DLVO approximation and the dependence of the shear modulus G(Z*) on the concentration of neutral electrolyte ns. The excellent agreement of predicted and measured values provides an experimental verification of the renormalization concept under variation of ...

  19. Shear adhesion strength of aligned electrospun nanofibers.

    Science.gov (United States)

    Najem, Johnny F; Wong, Shing-Chung; Ji, Guang

    2014-09-01

    Inspiration from nature such as insects' foot hairs motivates scientists to fabricate nanoscale cylindrical solids that allow tens of millions of contact points per unit area with material substrates. In this paper, we present a simple yet robust method for fabricating directionally sensitive shear adhesive laminates. By using aligned electrospun nylon-6, we create dry adhesives, as a succession of our previous work on measuring adhesion energies between two single free-standing electrospun polymer fibers in cross-cylinder geometry, randomly oriented membranes and substrate, and peel forces between aligned fibers and substrate. The synthetic aligned cylindrical solids in this study are electrically insulating and show a maximal Mode II shear adhesion strength of 27 N/cm(2) on a glass slide. This measured value, for the purpose of comparison, is 270% of that reported from gecko feet. The Mode II shear adhesion strength, based on a commonly known "dead-weight" test, is 97-fold greater than the Mode I (normal) adhesion strength of the same. The data indicate a strong shear binding on and easy normal lifting off. Anisotropic adhesion (Mode II/Mode I) is pronounced. The size and surface boundary effects, crystallinity, and bending stiffness of fibers are used to understand these electrospun nanofibers, which vastly differ from otherwise known adhesive technologies. The anisotropic strength distribution is attributed to a decreasing fiber diameter and an optimized laminate thickness, which, in turn, influences the bending stiffness and solid-state "wettability" of points of contact between nanofibers and surface asperities. PMID:25105533

  20. Stochastically driven instability in rotating shear flows

    International Nuclear Information System (INIS)

    The origin of hydrodynamic turbulence in rotating shear flows is investigated, with particular emphasis on the flows whose angular velocity decreases but whose specific angular momentum increases with the increasing radial coordinate. Such flows are Rayleigh stable, but must be turbulent in order to explain the observed data. Such a mismatch between the linear theory and the observations/experiments is more severe when any hydromagnetic/magnetohydrodynamic instability and then the corresponding turbulence therein is ruled out. This work explores the effect of stochastic noise on such hydrodynamic flows. We essentially concentrate on a small section of such a flow, which is nothing but a plane shear flow supplemented by the Coriolis effect. This also mimics a small section of an astrophysical accretion disc. It is found that such stochastically driven flows exhibit large temporal and spatial correlations of perturbation velocities and hence large energy dissipations of perturbation, which presumably generate the instability. A range of angular velocity (Ω) profiles of the background flow, starting from that of a constant specific angular momentum (λ = Ωr2; r being the radial coordinate) to a constant circular velocity (vϕ = Ωr), is explored. However, all the background angular velocities exhibit identical growth and roughness exponents of their perturbations, revealing a unique universality class for the stochastically forced hydrodynamics of rotating shear flows. This work, to the best of our knowledge, is the first attempt to understand the origin of instability and turbulence in three-dimensional Rayleigh stable rotating shear flows by introducing additive noise to the underlying linearized governing equations. This has important implications to resolve the turbulence problem in astrophysical hydrodynamic flows such as accretion discs. (paper)

  1. An implementation of Bayesian lensing shear measurement

    Science.gov (United States)

    Sheldon, Erin S.

    2014-10-01

    The Bayesian gravitational shear estimation algorithm developed by Bernstein & Armstrong can potentially be used to overcome multiplicative noise bias and recover shear using very low signal-to-noise ratio (S/N) galaxy images. In that work, the authors confirmed that the method is nearly unbiased in a simplified demonstration, but no test was performed on images with realistic pixel noise. Here, I present a full implementation for fitting models to galaxy images, including the effects of a point spread function (PSF) and pixelization. I tested the implementation using simulated galaxy images modelled as Sérsic profiles with n = 1 (exponential) and n = 4 (De Vaucouleurs'), convolved with a PSF and a flat pixel response function. I used a round Gaussian model for the PSF to avoid potential PSF-fitting errors. I simulated galaxies with mean observed, post-PSF full width at half-maximum equal to approximately 1.2 times that of the PSF, with lognormal scatter. I also drew fluxes from a lognormal distribution. I produced independent simulations, each with pixel noise tuned to produce different mean S/N ranging from 10-1000. I applied a constant shear to all images. I fitted the simulated images to a model with the true Sérsic index to avoid modelling biases. I recovered the input shear with fractional error Δg/g < 2 × 10-3 in all cases. In these controlled conditions, and in the absence of other multiplicative errors, this implementation is sufficiently unbiased for current surveys and approaches the requirements for planned surveys.

  2. Localized shear generates three-dimensional chaos

    OpenAIRE

    Smith, Lachlan D.; Rudman, Murray; Lester, Daniel R.; Metcalfe, Guy

    2016-01-01

    Understanding the mechanisms that control 3D fluid transport is central to many processes including mixing, chemical reaction and biological activity. Here a novel mechanism for 3D transport is uncovered where fluid particles are kicked between streamlines near a localized shear, which occurs in many flows and materials. This results in 3D transport similar to Resonance Induced Dispersion (RID); the new mechanism is more rapid and mutually incompatible with RID. We explore its governing impac...

  3. Motional Effect on Wall Shear Stresses

    DEFF Research Database (Denmark)

    Kock, Samuel Alberg; Torben Fründ, Ernst; Yong Kim, Won

    Atherosclerosis is the leading cause of death and severe disability. Wall Shear Stress (WSS), the stress exerted on vessel walls by the flowing blood is a key factor in the development of atherosclerosis. Computational Fluid Dynamics (CFD) is widely used for WSS estimations. Most CFD simulations...... are based on static models to ease computational burden leading to inaccurate estimations. The aim of this work was to estimate the effect of vessel wall deformations (expansion and bending) on WSS levels....

  4. Excitation of fundamental shear horizontal wave by using face-shear (d36) piezoelectric ceramics

    Science.gov (United States)

    Miao, Hongchen; Dong, Shuxiang; Li, Faxin

    2016-05-01

    The fundamental shear horizontal (SH0) wave in plate-like structures is extremely useful for non-destructive testing (NDT) and structural health monitoring (SHM) as it is non-dispersive. However, currently, the SH0 wave is usually excited by electromagnetic acoustic transducers (EMAT) whose energy conversion efficiency is fairly low. The face-shear ( d 36 ) mode piezoelectrics is more promising for SH0 wave excitation, but this mode cannot appear in conventional piezoelectric ceramics. Recently, by modifying the symmetry of poled PbZr1-xTixO3 (PZT) ceramics via ferroelastic domain engineering, we realized the face-shear d 36 mode in both soft and hard PZT ceramics. In this work, we further improved the face-shear properties of PZT-4 and PZT-5H ceramics via lateral compression under elevated temperature. It was found that when bonded on a 1 mm-thick aluminum plate, the d 36 type PZT-4 exhibited better face-shear performance than PZT-5H. We then successfully excite SH0 wave in the aluminum plate using a face-shear PZT-4 square patch and receive the wave using a face-shear 0.72[Pb(Mg1/3Nb2/3)O3]-0.28[PbTiO3] (PMN-PT) patch. The frequency response and directionality of the excited SH0 wave were also investigated. The SH0 wave can be dominated over the Lamb waves (S0 and A0 waves) from 160 kHz to 280 kHz. The wave amplitude reaches its maxima along the two main directions (0° and 90°). The amplitude can keep over 80% of the maxima when the deviate angle is less than 30°, while it vanishes quickly at the 45° direction. The excited SH0 wave using piezoelectric ceramics could be very promising in the fields of NDT and SHM.

  5. Cardiac cell proliferation assessed by EdU, a novel analysis of cardiac regeneration.

    Science.gov (United States)

    Zeng, Bin; Tong, Suiyang; Ren, Xiaofeng; Xia, Hao

    2016-08-01

    Emerging evidence suggests that mammalian hearts maintain the capacity for cardiac regeneration. Rapid and sensitive identification of cardiac cellular proliferation is prerequisite for understanding the underlying mechanisms and strategies of cardiac regeneration. The following immunologically related markers of cardiac cells were analyzed: cardiac transcription factors Nkx2.5 and Gata 4; specific marker of cardiomyocytes TnT; endothelial cell marker CD31; vascular smooth muscle marker smooth muscle myosin IgG; cardiac resident stem cells markers IsL1, Tbx18, and Wt1. Markers were co-localized in cardiac tissues of embryonic, neonatal, adult, and pathological samples by 5-ethynyl-2'-deoxyuridine (EdU) staining. EdU was also used to label isolated neonatal cardiomyocytes in vitro. EdU robustly labeled proliferating cells in vitro and in vivo, co-immunostaining with different cardiac cells markers. EdU can rapidly and sensitively label proliferating cardiac cells in developmental and pathological states. Cardiac cell proliferation assessed by EdU is a novel analytical tool for investigating the mechanism and strategies of cardiac regeneration in response to injury. PMID:25480318

  6. Cardiac hydatid cyst revealed by ventricular tachycardia

    OpenAIRE

    Ibn Elhadj, Zied; Boukhris, Marouane; Kammoun, Ikram; Halima, Afef Ben; Addad, Faouzi; Kachboura, Salem

    2013-01-01

    Hydatid disease is a human parasitic infestation caused by the larval stage of Echinococcus Granulosus. The liver and the lungs are the most common locations. Cardiac involvement is rare and accounts for 0.5–2% of all hydatid disease. We report an unusual presentation of cardiac hydatid cyst revealed by ventricular tachycardia in a patient with a history of cerebral hydatid cyst.

  7. Acute cardiac failure in neuroleptic malignant syndrome.

    LENUS (Irish Health Repository)

    Sparrow, Patrick

    2012-02-03

    We present a case of rapid onset acute cardiac failure developing as part of neuroleptic malignant syndrome in a 35-year-old woman following treatment with thioridazine and lithium. Post mortem histology of cardiac and skeletal muscle showed similar changes of focal cellular necrosis and vacuolation suggesting a common disease process.

  8. Cardiac MRI of the athlete's heart

    NARCIS (Netherlands)

    Prakken, N.H.J.

    2010-01-01

    The increase in pre-participation cardiovascular screening using the Lausanne protocol will ultimately lead to an increased use of cardiac MRI and MDCT in the cardiovascular work-up of athletes. The role of cardiac MRI is well established in the evaluation of cardiomyopathies, myocarditis, aortic st

  9. The Western Denmark Cardiac Computed Tomography Registry

    DEFF Research Database (Denmark)

    Nielsen, Lene Hüche; Nørgaard, Bjarne Linde; Tilsted, Hans Henrik;

    2015-01-01

    BACKGROUND: As a subregistry to the Western Denmark Heart Registry (WDHR), the Western Denmark Cardiac Computed Tomography Registry (WDHR-CCTR) is a clinical database established in 2008 to monitor and improve the quality of cardiac computed tomography (CT) in Western Denmark. OBJECTIVE: We...

  10. Fetal cardiac interventions: clinical and experimental research.

    Science.gov (United States)

    Yuan, Shi-Min; Humuruola, Gulimila

    2016-01-01

    Fetal cardiac interventions for congenital heart diseases may alleviate heart dysfunction, prevent them evolving into hypoplastic left heart syndrome, achieve biventricular outcome and improve fetal survival. Candidates for clinical fetal cardiac interventions are now restricted to cases of critical aortic valve stenosis with evolving hypoplastic left heart syndrome, pulmonary atresia with an intact ventricular septum and evolving hypoplastic right heart syndrome, and hypoplastic left heart syndrome with an intact or highly restrictive atrial septum as well as fetal heart block. The therapeutic options are advocated as prenatal aortic valvuloplasty, pulmonary valvuloplasty, creation of interatrial communication and fetal cardiac pacing. Experimental research on fetal cardiac intervention involves technical modifications of catheter-based cardiac clinical interventions and open fetal cardiac bypass that cannot be applied in human fetuses for the time being. Clinical fetal cardiac interventions are plausible for midgestation fetuses with the above-mentioned congenital heart defects. The technical success, biventricular outcome and fetal survival are continuously being improved in the conditions of the sophisticated multidisciplinary team, equipment, techniques and postnatal care. Experimental research is laying the foundations and may open new fields for catheter-based clinical techniques. In the present article, the clinical therapeutic options and experimental fetal cardiac interventions are described. PMID:27279868

  11. Is fetal cardiac function gender dependent?

    NARCIS (Netherlands)

    Clur, S. A. B.; Rengerink, K. Oude; Mol, B. W.; Ottenkamp, J.; Bilardo, C. M.

    2011-01-01

    Introduction An increased nuchal translucency (NT) is more common in males. A delayed diastolic cardiac function maturation has been proposed to explain this and the reported gender-related differences in ductus venosus (DV) flow. Objective To investigate gender-related differences in fetal cardiac

  12. Is fetal cardiac function gender dependent?

    NARCIS (Netherlands)

    S.A.B. Clur; K. Oude Rengerink; B.W. Mol; J. Ottenkamp; C.M. Bilardo

    2011-01-01

    An increased nuchal translucency (NT) is more common in males. A delayed diastolic cardiac function maturation has been proposed to explain this and the reported gender-related differences in ductus venosus (DV) flow. To investigate gender-related differences in fetal cardiac function. One hundred a

  13. Preoperative respiratory physical therapy in cardiac surgery

    NARCIS (Netherlands)

    Hulzebos, H.J.

    2006-01-01

    Cardiac surgery is one of the most common surgical procedures and accounts for more resources expended in cardiovascular medicine than any other single procedure. Because cardiac surgery involves sternal incision and cardiopulmonary bypass, patients usually have a restricted respiratory function in

  14. Cardiac Diseases in People with Intellectual Disability

    Science.gov (United States)

    van den Akker, M.; Maaskant, M. A.; van der Meijden, R. J. M.

    2006-01-01

    Background: In people with ID there is more morbidity than in the general population, including cardiac diseases. Dutch figures on this subject are scarce. Methods: Descriptive study of the prevalence of cardiac diseases in 436 residential clients in Echt, the Netherlands, and comparisons between men and women, age groups, and level and aetiology…

  15. Coagulopathy and hemostatic monitoring in cardiac surgery

    DEFF Research Database (Denmark)

    Johansson, Pär I; Sølbeck, Sacha; Genet, Gustav;

    2012-01-01

    Cardiac surgery with cardiopulmonary bypass (CPB) causes severe derangements in the hemostatic system, which in turn puts the patient at risks of microvascular bleeding. Excessive transfusion and surgical re-exploration after cardiac surgery are potentially associated with a number of adverse...

  16. Athletes at Risk for Sudden Cardiac Death

    Science.gov (United States)

    Subasic, Kim

    2010-01-01

    High school athletes represent the largest group of individuals affected by sudden cardiac death, with an estimated incidence of once or twice per week. Structural cardiovascular abnormalities are the most frequent cause of sudden cardiac death. Athletes participating in basketball, football, track, soccer, baseball, and swimming were found to…

  17. CARDIAC SIZE IN THE SUPINE CHESTFILM

    NARCIS (Netherlands)

    VANDERJAGT, EJ; SMITS, HJ

    1992-01-01

    The aim of this study was to find a normal value for the cardiac size in the supine position because such a standard is hardly known in the literature. Cardiac size in the erect and supine positions were compared in 165 patients in whom both chest radiographs were performed prior to kidney transplan

  18. Using the Trajectory Framework: reconceptualizing cardiac illness.

    Science.gov (United States)

    Hawthorne, M H

    1991-01-01

    Cardiac disease is known to be the leading cause of premature morbidity and mortality in the United States. Nursing management of cardiac illnesses, as such, is a primary concern for most practicing nurses. Dramatic changes in cardiac patient populations and associated technology available for treatment indicate a need to reconceptualize the nature of cardiac illness and to consider alternative approaches to guide the care of these patients. Traditional care, to a large degree, has focused upon acute illness, consequently limiting needed attention to the increasing group of patients suffering chronic illness and disability. In the present paper, the major changes in the cardiac patient population and in utilization of available technology are presented. The application of the Corbin and Strauss trajectory framework as an appropriate and useful framework for conceptualizing cardiac illness and care is then discussed. Five characteristics of the framework which render the model particularly well suited to address cardiac care are identified and discussed. These characteristics are: 1) comprehensiveness of care, 2) patient-centered care, 3) gender issues in care, 4) family-focused care, 5) technology and cardiac care. PMID:1763241

  19. Cardiac arrhythmia classification using autoregressive modeling

    OpenAIRE

    Srinivasan Narayanan; Ge Dingfei; Krishnan Shankar M

    2002-01-01

    Abstract Background Computer-assisted arrhythmia recognition is critical for the management of cardiac disorders. Various techniques have been utilized to classify arrhythmias. Generally, these techniques classify two or three arrhythmias or have significantly large processing times. A simpler autoregressive modeling (AR) technique is proposed to classify normal sinus rhythm (NSR) and various cardiac arrhythmias including atrial premature contraction (APC), premature ventricular contraction (...

  20. Conditional shape models for cardiac motion estimation

    DEFF Research Database (Denmark)

    Metz, C.T.; Baka, N.; Kirisli, H.A.;

    2010-01-01

    We propose a conditional statistical shape model to predict patient specific cardiac motion from the 3D end-diastolic CTA scan. The model is built from 4D CTA sequences by combining atlas based segmentation and 4D registration. Cardiac motion estimation is, for example, relevant in the dynamic al...

  1. Drugs, QTc prolongation and sudden cardiac death

    NARCIS (Netherlands)

    S.M.J.M. Straus (Sabine)

    2005-01-01

    textabstract__Abstract__ The term sudden cardiac death pertains to an unexpected death from cardiac causes within a short time period and has been described throughout history. The ancient Egyptians inscribed on the tomb of a nobleman some 4500 years ago that he had died suddenly and without appare

  2. Clinical study of cardiac diseases during pregnancy

    Directory of Open Access Journals (Sweden)

    Amitha Vijay Kamat

    2016-03-01

    Conclusions: Cardiac diseases in pregnancy constitute high risk pregnancy and require special attention during antepartum, intrapartum and postpartum period. Rheumatic heart disease was the major contribution of cardiac diseases in pregnancy and is seen to be associated with increased maternal morbidity. [Int J Reprod Contracept Obstet Gynecol 2016; 5(3.000: 855-859

  3. Primary cardiac hemangioendothelioma: a case report

    Institute of Scientific and Technical Information of China (English)

    WANG Li-feng; LIU Ming; ZHU Hong; HAN Wei; HU Cheng-yi; QI Ji-ping; MEI Huan-lin; GE Re-le; ZHOU Min

    2006-01-01

    @@ Primary cardiac hemangioendothelioma is extremely rare.1-3 Up to now less than twenty cases have been reported in English literature, the data about this kind of cardiac tumors are scanty. In this report, a case of a huge hemangio-endothelioma that arose from the right atrium and was successfully resected is presented.

  4. Cardiac manifestations of inborn errors of metabolism.

    NARCIS (Netherlands)

    Evangeliou, A.; Papadopoulou-Legbelou, K.; Daphnis, E.; Ganotakis, E.; Vavouranakis, I.; Michailidou, H.; Hitoglou-Makedou, A.; Nicolaidou, P.; Wevers, R.A.; Varlamis, G.

    2007-01-01

    AIM: The aim of the study was to investigate the frequency and type of cardiac manifestations in a defined group of patients with inborn errors of metabolism. This paper also explores the key role of cardiac manifestations in the diagnosis of inborn errors of metabolism in daily practice. METHODS: O

  5. Ultrasound Imaging in Teaching Cardiac Physiology

    Science.gov (United States)

    Johnson, Christopher D.; Montgomery, Laura E. A.; Quinn, Joe G.; Roe, Sean M.; Stewart, Michael T.; Tansey, Etain A.

    2016-01-01

    This laboratory session provides hands-on experience for students to visualize the beating human heart with ultrasound imaging. Simple views are obtained from which students can directly measure important cardiac dimensions in systole and diastole. This allows students to derive, from first principles, important measures of cardiac function, such…

  6. Stem cell sources for cardiac regeneration

    NARCIS (Netherlands)

    Roccio, M.; Goumans, M. J.; Sluijter, J. P. G.; Doevendans, P. A.

    2008-01-01

    Cell-based cardiac repair has the ambitious aim to replace the malfunctioning cardiac muscle developed after myocardial infarction, with new contractile cardiomyocytes and vessels. Different stem cell populations have been intensively studied in the last decade as a potential source of new cardiomyo

  7. Cardiac Vagal Regulation and Early Peer Status

    Science.gov (United States)

    Graziano, Paulo A.; Keane, Susan P.; Calkins, Susan D.

    2007-01-01

    A sample of 341 5 1/2-year-old children participating in an ongoing longitudinal study was the focus of a study on the relation between cardiac vagal regulation and peer status. To assess cardiac vagal regulation, resting measures of respiratory sinus arrhythmia (RSA) and RSA change (suppression) to 3 cognitively and emotionally challenging tasks…

  8. Spurious Shear in Weak Lensing with LSST

    CERN Document Server

    Chang, C; Jernigan, J G; Peterson, J R; AlSayyad, Y; Ahmad, Z; Bankert, J; Bard, D; Connolly, A; Gibson, R R; Gilmore, K; Grace, E; Hannel, M; Hodge, M A; Jee, M J; Jones, L; Krughoff, S; Lorenz, S; Marshall, P J; Marshall, S; Meert, A; Nagarajan, S; Peng, E; Rasmussen, A P; Shmakova, M; Sylvestre, N; Todd, N; Young, M

    2012-01-01

    The Large Synoptic Survey Telescope (LSST) is one of the most powerful ground-based weak lensing survey telescopes in the upcoming decade. The complete 10-year survey will image $\\sim$ 20,000 square degrees of sky in six filter bands every few nights, bringing the final survey depth to $r\\sim27.5$, with over 4 billion well measured galaxies. To take full advantage of this unprecedented statistical power, the systematic errors associated with weak lensing measurements need to be controlled to a level similar to the statistical errors. This work is the first attempt to quantitatively estimate the absolute level and statistical properties of the systematic errors on weak lensing shear measurements due to the most important physical effects in the LSST system via high fidelity ray-tracing simulations. We identify and isolate the different sources of \\textit{additive} systematic errors on shear measurements for LSST and predict their impact on the final cosmic shear measurements using conventional weak lensing ana...

  9. Shear sensitive silicon piezoresistive tactile sensor prototype

    Science.gov (United States)

    Wang, Lin; Beebe, David J.

    1998-09-01

    Shear sensing ability it important in many fields such as robotics, rehabilitation, teleoperation and human computer interfaces. A shear sensitive tactile sensor prototype is developed based on the principles of the piezoresistive effect in silicon, and using microfabrication technology. Analogous to the conventional silicon piezoresistive pressure sensor, piezoresistive resistors embedded in a silicon diaphragm are used to sense stress change. An additional mesa is fabricated on the top of the diaphragm and serves to transform an applied force to a stress. Both the shear and normal components of the force are resolved by measuring the resistance changes of the four resistors placed at the corners of a prism mesa. The prototype is tested both statically and dynamically when a spatial force of 0 - 300 gram is applied. Good linearity (R > 0.98) and high repeatability are observed. In this paper, the force sensing mechanism and force determination approach are described. The fabrication process is presented. The preliminary testing results are presented and discussed.

  10. Horizontal Shear Wave Imaging of Large Optics

    Energy Technology Data Exchange (ETDEWEB)

    Quarry, M J

    2007-09-05

    When complete the National Ignition Facility (NIF) will be the world's largest and most energetic laser and will be capable of achieving for the first time fusion ignition in the laboratory. Detecting optics features within the laser beamlines and sizing them at diameters of 0.1 mm to 10 mm allows timely decisions concerning refurbishment and will help with the routine operation of the system. Horizontally polarized shear waves at 10 MHz were shown to accurately detect, locate, and size features created by laser operations from 0.5 mm to 8 mm by placing sensors at the edge of the optic. The shear wave technique utilizes highly directed beams. The outer edge of an optic can be covered with shear wave transducers on four sides. Each transducer sends a pulse into the optic and any damage reflects the pulse back to the transmitter. The transducers are multiplexed, and the collected time waveforms are enveloped and replicated across the width of the element. Multiplying the data sets from four directions produces a map of reflected amplitude to the fourth power, which images the surface of the optic. Surface area can be measured directly from the image, and maximum depth was shown to be correlated to maximum amplitude of the reflected waveform.

  11. Shear modulus of neutron star crust

    CERN Document Server

    Baiko, D A

    2011-01-01

    Shear modulus of solid neutron star crust is calculated by thermodynamic perturbation theory taking into account ion motion. At given density the crust is modelled as a body-centered cubic Coulomb crystal of fully ionized atomic nuclei of one type with the uniform charge-compensating electron background. Classic and quantum regimes of ion motion are considered. The calculations in the classic temperature range agree well with previous Monte Carlo simulations. At these temperatures the shear modulus is given by the sum of a positive contribution due to the static lattice and a negative $\\propto T$ contribution due to the ion motion. The quantum calculations are performed for the first time. The main result is that at low temperatures the contribution to the shear modulus due to the ion motion saturates at a constant value, associated with zero-point ion vibrations. Such behavior is qualitatively similar to the zero-point ion motion contribution to the crystal energy. The quantum effects may be important for li...

  12. Shear modulus of neutron star crust

    Science.gov (United States)

    Baiko, D. A.

    2011-09-01

    The shear modulus of solid neutron star crust is calculated by the thermodynamic perturbation theory, taking into account ion motion. At a given density, the crust is modelled as a body-centred cubic Coulomb crystal of fully ionized atomic nuclei of one type with a uniform charge-compensating electron background. Classic and quantum regimes of ion motion are considered. The calculations in the classic temperature range agree well with previous Monte Carlo simulations. At these temperatures, the shear modulus is given by the sum of a positive contribution due to the static lattice and a negative ∝ T contribution due to the ion motion. The quantum calculations are performed for the first time. The main result is that at low temperatures the contribution to the shear modulus due to the ion motion saturates at a constant value, associated with zero-point ion vibrations. Such behaviour is qualitatively similar to the zero-point ion motion contribution to the crystal energy. The quantum effects may be important for lighter elements at higher densities, where the ion plasma temperature is not entirely negligible compared to the typical Coulomb ion interaction energy. The results of numerical calculations are approximated by convenient fitting formulae. They should be used for precise neutron star oscillation modelling, a rapidly developing branch of stellar seismology.

  13. Singular eigenfunctions for shearing fluids I

    Energy Technology Data Exchange (ETDEWEB)

    Balmforth, N.J.; Morrison, P.J.

    1995-02-01

    The authors construct singular eigenfunctions corresponding to the continuous spectrum of eigenvalues for shear flow in a channel. These modes are irregular as a result of a singularity in the eigenvalue problem at the critical layer of each mode. They consider flows with monotonic shear, so there is only a single critical layer for each mode. They then solve the initial-value problem to establish that these continuum modes, together with any discrete, growing/decaying pairs of modes, comprise a complete basis. They also view the problem within the framework of Hamiltonian theory. In that context, the singular solutions can be viewed as the kernel of an integral, canonical transformation that allows us to write the fluid system, an infinite-dimensional Hamiltonian system, in action-angle form. This yields an expression for the energy in terms of the continuum modes and provides a means for attaching a characteristic signature (sign) to the energy associate with each eigenfunction. They follow on to consider shear-flow stability within the Hamiltonian framework. Next, the authors show the equivalence of integral superpositions of the singular eigenfunctions with the solution derived with Laplace transform techniques. In the long-time limit, such superpositions have decaying integral averages across the channel, revealing phase mixing or continuum damping. Under some conditions, this decay is exponential and is then the fluid analogue of Landau damping. Finally, the authors discuss the energetics of continuum damping.

  14. Cardiac cachexia: hic et nunc

    Science.gov (United States)

    Loncar, Goran; Springer, Jochen; Anker, Markus; Doehner, Wolfram

    2016-01-01

    Abstract Cardiac cachexia (CC) is the clinical entity at the end of the chronic natural course of heart failure (HF). Despite the efforts, even the most recent definition of cardiac cachexia has been challenged, more precisely, the addition of new criteria on top of obligatory weight loss. The pathophysiology of CC is complex and multifactorial. A better understanding of pathophysiological pathways in body wasting will contribute to establish potentially novel treatment strategies. The complex biochemical network related with CC and HF pathophysiology underlines that a single biomarker cannot reflect all of the features of the disease. Biomarkers that could pick up the changes in body composition before they convey into clinical manifestations of CC would be of great importance. The development of preventive and therapeutic strategies against cachexia, sarcopenia, and wasting disorders is perceived as an urgent need by healthcare professionals. The treatment of body wasting remains an unresolved challenge to this day. As CC is a multifactorial disorder, it is unlikely that any single agent will be completely effective in treating this condition. Among all investigated therapeutic strategies, aerobic exercise training in HF patients is the most proved to counteract skeletal muscle wasting and is recommended by treatment guidelines for HF. PMID:27386168

  15. Cardiac cachexia: hic et nunc.

    Science.gov (United States)

    Loncar, Goran; Springer, Jochen; Anker, Markus; Doehner, Wolfram; Lainscak, Mitja

    2016-06-01

    Cardiac cachexia (CC) is the clinical entity at the end of the chronic natural course of heart failure (HF). Despite the efforts, even the most recent definition of cardiac cachexia has been challenged, more precisely, the addition of new criteria on top of obligatory weight loss. The pathophysiology of CC is complex and multifactorial. A better understanding of pathophysiological pathways in body wasting will contribute to establish potentially novel treatment strategies. The complex biochemical network related with CC and HF pathophysiology underlines that a single biomarker cannot reflect all of the features of the disease. Biomarkers that could pick up the changes in body composition before they convey into clinical manifestations of CC would be of great importance. The development of preventive and therapeutic strategies against cachexia, sarcopenia, and wasting disorders is perceived as an urgent need by healthcare professionals. The treatment of body wasting remains an unresolved challenge to this day. As CC is a multifactorial disorder, it is unlikely that any single agent will be completely effective in treating this condition. Among all investigated therapeutic strategies, aerobic exercise training in HF patients is the most proved to counteract skeletal muscle wasting and is recommended by treatment guidelines for HF. PMID:27386168

  16. Cardiac involvement in rheumatoid arthritis

    Directory of Open Access Journals (Sweden)

    V. De Gennaro Colonna

    2011-06-01

    Full Text Available Rheumatoid arthritis (RA is a systemic disease of unknown etiology characterized by a chronic inflammatory process mainly leading to destruction of synovial membrane of small and major diarthrodial joints. The prevalence of RA within the general adult population is about 1% and female subjects in fertile age result mostly involved. It’s an invalidating disease, associated with changes in life quality and a reduced life expectancy. Moreover, we can observe an increased mortality rate in this population early after the onset of the disease. The mortality excess can be partially due to infective, gastrointestinal, renal or pulmonary complications and malignancy (mainly lung cancer and non- Hodgkin lymphoma. Among extra-articular complications, cardiovascular (CV involvement represents one of the leading causes of morbidity and mortality. Every cardiac structure can be affected by different pathogenic pathways: heart valves, conduction system, myocardium, endocardium, pericardium and coronary arteries. Consequently, different clinical manifestations can be detected, including: pericarditis, myocarditis, myocardial fibrosis, arrhythmias, alterations of conduction system, coronaropathies and ischemic cardiopathy, valvular disease, pulmonary hypertension and heart failure. Considering that early cardiac involvement negatively affects the prognosis, it is mandatory to identify high CV risk RA patients to better define long-term management of this population.

  17. [Technologies for cardiac valve prostheses].

    Science.gov (United States)

    Nakano, Kiyoharu

    2009-07-01

    To show the technological development of cardiac valve prostheses, a historical review of both mechanical and biological valve prostheses and a current overview of modern cardiac valve devices are provided. Scince the 1st implantation of Starr-Edwards ball valve in 1960, both mechanical and biological valve prostheses have advanced. The valve design, the material of the leaflet and the hausing of mechanical prostheses have improved. Currently, the majority of the mechanical prostheses are bileaflet tilting disc valves made of pyrolytic carbon, which is antithromboembolic. However, anticoagulation therapy with warfarin is still required. As for the bioprostheses, although the fixation and anti-mineralization methods of the tissues improved, the durability of these valves is still limited. For the material of the current biological valves, the porcine aortic valve or bovine pericardium are used. The tissues are fixed by non-pressure or low-pressure method in glutaraldehyde solution. A stented and non-stented valves are available. Epoch-making events in this field are the implantation of new bioprosthetic valves using tissue engineering methods and the development of the transcatheter valve replacement therapies.

  18. Cardiac Rehabilitation in Older Adults.

    Science.gov (United States)

    Schopfer, David W; Forman, Daniel E

    2016-09-01

    The biology of aging and the pathophysiology of cardiovascular disease (CVD) overlap, with the effect that CVD is endemic in the growing population of older adults. Moreover, CVD in older adults is usually complicated by age-related complexities, including multimorbidity, polypharmacy, frailty, and other intricacies that add to the risks of ambiguous symptoms, deconditioning, iatrogenesis, falls, disability, and other challenges. Cardiac rehabilitation (CR) is a comprehensive lifestyle program that can have particular benefit for older patients with cardiovascular conditions. Although CR was originally designed primarily as an exercise training program for younger adults after a myocardial infarction or coronary artery bypass surgery, it has evolved as a comprehensive lifestyle program (promoting physical activity as well as education, diet, risk reduction, and adherence) for a broader range of CVD (coronary heart disease, heart failure, and valvular heart disease). It provides a valuable opportunity to address and moderate many of the challenges pertinent for the large and growing population of older adults with CVD. Cardiac rehabilitation promotes physical function (cardiorespiratory fitness as well as strength and balance) that helps overcome disease and deconditioning as well as related vulnerabilities such as disability, frailty, and falls. Similarly, CR facilitates education, monitoring, and guidance to reduce iatrogenesis and promote adherence. Furthermore, CR fosters cognition, socialization, and independence in older patients. Yet despite all its conceptual benefits, CR is significantly underused in older populations. This review discusses benefits and the paradoxical underuse of CR, as well as evolving models of care that may achieve greater application and efficacy. PMID:27297002

  19. Lipid partitioning during cardiac stress.

    Science.gov (United States)

    Kolwicz, Stephen C

    2016-10-01

    It is well documented that fatty acids serve as the primary fuel substrate for the contracting myocardium. However, extensive research has identified significant changes in the myocardial oxidation of fatty acids during acute or chronic cardiac stress. As a result, the redistribution or partitioning of fatty acids due to metabolic derangements could have biological implications. Fatty acids can be stored as triacylglycerols, serve as critical components for biosynthesis of phospholipid membranes, and form the potent signaling molecules, diacylglycerol and ceramides. Therefore, the contribution of lipid metabolism to health and disease is more intricate than a balance of uptake and oxidation. In this review, the available data regarding alterations that occur in endogenous cardiac lipid pathways during the pathological stressors of ischemia-reperfusion and pathological hypertrophy/heart failure are highlighted. In addition, changes in endogenous lipids observed in exercise training models are presented for comparison. This article is part of a Special Issue entitled: Heart Lipid Metabolism edited by G.D. Lopaschuk. PMID:27040509

  20. A comparison between magnetic shear and flare shear in a well-observed M-class flare

    Institute of Scientific and Technical Information of China (English)

    Tuan-Hui Zhou; Hai-Sheng Ji

    2009-01-01

    We give an extensive multi-wavelength analysis of an eruptive M1.0/1N class solar flare, which occurred in the active region NOAA 10044 on 2002 July 26. Our empha-sis is on the relationship between magnetic shear and flare shear. Flare shear is defined as the angle formed between the line connecting the centroids of the two ribbons of the flare and the line perpendicular to the magnetic neutral line. The magnetic shear is computed from vector magnetograms observed at Big Bear Solar Observatory (BBSO), while the flare shear is computed from Transition Region and Coronal Explorer (TRACE) 1700A images. By a detailed comparison, we find that: 1) The magnetic shear and the flare shear of this event are basically consistent, as judged from the directions of the transverse mag-netic field and the line connecting the two ribbons' centroids. 2) During the period of the enhancement of magnetic shear, flare shear had a fast increase followed by a fluctuated decrease. 3) When the magnetic shear stopped its enhancement, the fluctuated decreasing behavior of the flare shear became very smooth. 4) Hard X-ray (HXR) spikes are well correlated with the unshearing peaks on the time profile of the rate of change of the flare shear. We give a discussion of the above phenomena.

  1. Gene transfer to promote cardiac regeneration.

    Science.gov (United States)

    Collesi, Chiara; Giacca, Mauro

    2016-12-01

    There is an impelling need to develop new therapeutic strategies for patients with myocardial infarction and heart failure. Leading from the large quantity of new information gathered over the last few years on the mechanisms controlling cardiomyocyte proliferation during embryonic and fetal life, it is now possible to devise innovative therapies based on cardiac gene transfer. Different protein-coding genes controlling cell cycle progression or cardiomyocyte specification and differentiation, along with microRNA mimics and inhibitors regulating pre-natal and early post-natal cell proliferation, are amenable to transformation in potential therapeutics for cardiac regeneration. These gene therapy approaches are conceptually revolutionary, since they are aimed at stimulating the intrinsic potential of differentiated cardiac cells to proliferate, rather than relying on the implantation of exogenously expanded cells to achieve tissue regeneration. For efficient and prolonged cardiac gene transfer, vectors based on the Adeno-Associated Virus stand as safe, efficient and reliable tools for cardiac gene therapy applications.

  2. Gender differences in cardiac hypertrophic remodeling.

    Science.gov (United States)

    Patrizio, Mario; Marano, Giuseppe

    2016-01-01

    Cardiac remodeling is a complex process that occurs in response to different types of cardiac injury such as ischemia and hypertension, and that involves cardiomyocytes, fibroblasts, vascular smooth muscle cells, vascular endothelial cells, and inflammatory cells. The end result is cardiomyocyte hypertrophy, fibrosis, inflammation, vascular, and electrophysiological remodeling. This paper reviews a large number of studies on the influence of gender on pathological cardiac remodeling and shows how sex differences result in different clinical outcomes and therapeutic responses, with males which generally develop greater cardiac remodeling responses than females. Although estrogens appear to have an important role in attenuating adverse cardiac remodeling, the mechanisms through which gender modulates myocardial remodeling remain to be identified. PMID:27364397

  3. Cardiac, Skeletal, and smooth muscle mitochondrial respiration

    DEFF Research Database (Denmark)

    Park, Song-Young; Gifford, Jayson R; Andtbacka, Robert H I;

    2014-01-01

    Unlike cardiac and skeletal muscle, little is known about vascular smooth muscle mitochondrial function. Therefore, this study examined mitochondrial respiratory rates in the smooth muscle of healthy human feed arteries and compared with that of healthy cardiac and skeletal muscle. Cardiac......, skeletal, and smooth muscle was harvested from a total of 22 subjects (53±6 yrs) and mitochondrial respiration assessed in permeabilized fibers. Complex I+II, state 3 respiration, an index of oxidative phosphorylation capacity, fell progressively from cardiac, skeletal, to smooth muscle (54±1; 39±4; 15......±1 pmol•s(-1)•mg (-1), pmitochondrial density, also fell progressively from cardiac, skeletal, to smooth muscle (222±13; 115±2; 48±2 umol•g(-1)•min(-1), p

  4. A neonatal blueprint for cardiac regeneration

    Directory of Open Access Journals (Sweden)

    Enzo R. Porrello

    2014-11-01

    Full Text Available Adult mammals undergo minimal regeneration following cardiac injury, which severely compromises cardiac function and contributes to the ongoing burden of heart failure. In contrast, the mammalian heart retains a transient capacity for cardiac regeneration during fetal and early neonatal life. Recent studies have established the importance of several evolutionarily conserved mechanisms for heart regeneration in lower vertebrates and neonatal mammals including induction of cardiomyocyte proliferation, epicardial cell activation, angiogenesis, extracellular matrix deposition and immune cell infiltration. In this review, we provide an up-to-date account of the molecular and cellular basis for cardiac regeneration in lower vertebrates and neonatal mammals. The historical context for these recent findings and their ramifications for the future development of cardiac regenerative therapies are also discussed.

  5. Drawing Recognition for Automatic Dimensioning of Shear-Walls

    Institute of Scientific and Technical Information of China (English)

    任爱珠; 喻强; 许云

    2002-01-01

    In computer-aided structural design, the drawing of shear-walls cannot be easily automated; however, dimensioning of the shear-walls provides a method to automate the drawing. This paper presents a drawing recognition method for automatic dimensioning of shear-walls. The regional relationship method includes a graphic shape template library that can learn new shear-wall shapes. The automatic dimensioning of shear-walls is then realized by matching the templates. The regional relationship method for graph recognition effectively describes the topological relationships for graphs to significantly increase the recognition efficiency.

  6. Granular dynamic shear strength and its influencing factors

    Institute of Scientific and Technical Information of China (English)

    吴爱祥; 孙业志

    2002-01-01

    The granular dynamic shear strength is the same as that of the static one in nature, as found from numerous experiments and investigations. The shear strength is equal to the sum of the internal frictional force and the cohesive force. The influences of type, shape, size distribution, pore ratio, moisture content and variation of vibration velocity on the dynamic shear strength of granules were studied. Based on numerous vibration shear experiments, the authors investigate the mechanism of dynamic shear strength in granules in terms of the fundamental principle and the relevant theory of modern tribology.

  7. Seismic Behavior of Dual Function Slitted Shear Wall

    Institute of Scientific and Technical Information of China (English)

    叶列平; 康胜

    2001-01-01

    The concept of seismic structural control was used to design a new type reinforced concrete shear wall, the dual function slitted shear wall. Connectors are installed in vertical slits in the slitted shear wall to provide the dual function slitted shear wall with greater stiffness and capacity for small and moderate earthquake intensities. The wall becomes a slitted wall with the ductile flexure failure mode when the connectors fail during severe earthquakes. Seven specimens were tested to study the seismic behavior of the dual function slitted shear wall, The results showed that the connector controlled function well and provided better seismic behavior.

  8. Fluid migration in ductile shear zones

    Science.gov (United States)

    Fusseis, Florian; Menegon, Luca

    2014-05-01

    Fluid migration in metamorphic environments depends on a dynamically evolving permeable pore space, which was rarely characterised in detail. The data-base behind our understanding of the 4-dimensional transport properties of metamorphic rocks is therefore fragmentary at best, which leaves conceptual models poorly supported. Generally, it seems established that deformation is a major driver of permeability generation during regional metamorphism, and evidence for metamorphic fluids being channelled in large scale shear zones has been found in all depth segments of the continental crust. When strain localizes in ductile shear zones, the microfabric is modified until a steady state mylonite is formed that supports large deformations. A dynamic porosity that evolves during mylonitisation controls the distinct transport pathways along which fluid interacts with the rock. This dynamic porosity is controlled by a limited number of mechanisms, which are intrinsically linked to the metamorphic evolution of the rock during its deformational overprint. Many mid- and lower-crustal mylonites comprise polyphase mixtures of micron-sized grains that show evidence for deformation by dissolution/precipitation-assisted viscous grain boundary sliding. The establishment of these mineral mixtures is a critical process, where monomineralic layers are dispersed and grain growth is inhibited by the heterogeneous nucleation of secondary mineral phases at triple junctions. Here we show evidence from three different mid- and lower-crustal shear zones indicating that heterogeneous nucleation occurs in creep cavities. Micro- and nanotomographic observations show that creep cavities provide the dominant form of porosity in these ultramylonites. They control a "granular fluid pump" that directs fluid migration and hence mass transport. The granular fluid pump operates on the grain scale driven by viscous grain boundary sliding, and requires only small amounts of fluid. The spatial arrangement of

  9. Nucleation in a Sheared Liquid Binary Mixture.

    Science.gov (United States)

    Min, Kyung-Yang

    When a binary liquid mixture of lutidine plus water (LW) is quenched to a temperature T and is exposed to a continuous shear rate S, the result is a steady-state droplet distribution. This steady state can be probed by measuring the unscattered intensity I_{f}, or the scattered intensity I_{s}, as a function of delta T and S. In the experiments described here, S is fixed and delta T is varied in a step-wise fashion. The absence of hysteresis was probed in two separate experiments: First, I_{f} was measured as a function of S for a given delta T. Next, I_{f} was measured as a function of delta T for a given S. In either case, the hysteresis associated with the shear-free nucleation is absent. In addition, a flow-history dependent hysteresis was studied. In the 2-dimensional parameter space consisting of S and delta T, the onset of nucleation uniquely determines a cloud point line. A plot of the cloud point line exhibits two segments of different slopes with a cross-over near the temperature corresponding to the Becker-Doring limit. The classical picture of a free energy barrier was reformulated to explain this cross-over behavior. Next, photon correlation spectroscopy was used to study the dependence of the transient nucleation behavior on the initial states. A unique feature of this study is that this initial state can be conveniently adjusted by varying the shear rate S to which the mixture is initially exposed. The shear is then turned off, and the number density N(t), as well as the mean radius of the growing droplets, is monitored as a function of time. It was possible to measure the droplet density at a very early stage of phase separation where the nucleation rate J was close to zero. The measurement reveals that N(t) depends critically on the initial state of the metastable system. When the shear is large enough to rupture the droplets as small as the critical size, N(t) increases very slowly. Measurements of the nucleation rates vs. the square of the

  10. A multi-shear perfusion bioreactor for investigating shear stress effects in endothelial cell constructs.

    Science.gov (United States)

    Rotenberg, Menahem Y; Ruvinov, Emil; Armoza, Anna; Cohen, Smadar

    2012-08-01

    Tissue engineering research is increasingly relying on the use of advanced cultivation technologies that provide rigorously-controlled cell microenvironments. Herein, we describe the features of a micro-fabricated Multi-Shear Perfusion Bioreactor (MSPB) designed to deliver up to six different levels of physiologically-relevant shear stresses (1-13 dyne cm(-2)) to six cell constructs simultaneously, during a single run. To attain a homogeneous fluid flow within each construct, flow-distributing nets photo-etched with a set of openings for fluid flow were placed up- and down-stream from each construct. Human umbilical vein endothelial cells (HUVECs) seeded in alginate scaffolds within the MSPB and subjected to three different levels of shear stress for 24 h, responded accordingly by expressing three different levels of the membranal marker Intercellular Adhesion Molecule 1 (ICAM-1) and the phosphorylated endothelial nitric oxide synthetase (eNOS). A longer period of cultivation, 17 d, under two different levels of shear stress resulted in different lengths of cell sprouts within the constructs. Collectively, the HUVEC behaviour within the different constructs confirms the feasibility of using the MSPB system for simultaneously imposing different shear stress levels, and for validating the flow regime in the bioreactor vessel as assessed by the computational fluid dynamic (CFD) model. PMID:22622237

  11. Shear Capacity of C-Shaped and L-Shaped Angle Shear Connectors

    Science.gov (United States)

    Tahmasbi, Farzad; Maleki, Shervin; Shariati, Mahdi; Ramli Sulong, N. H.; Tahir, M. M.

    2016-01-01

    This paper investigates the behaviour of C-shaped and L-shaped angle shear connectors embedded in solid concrete slabs. An effective finite element model is proposed to simulate the push out tests of these shear connectors that encompass nonlinear material behaviour, large displacement and damage plasticity. The finite element models are validated against test results. Parametric studies using this nonlinear model are performed to investigate the variations in concrete strength and connector dimensions. The finite element analyses also confirm the test results that increasing the length of shear connector increases their shear strength proportionately. It is observed that the maximum stress in L-shaped angle connectors takes place in the weld attachment to the beam, whereas in the C-shaped angle connectors, it is in the attached leg. The location of maximum concrete compressive damage is rendered in each case. Finally, a new equation for prediction of the shear capacity of C-shaped angle connectors is proposed. PMID:27478894

  12. Stiffness matrix for beams with shear deformation and warping torsion

    Energy Technology Data Exchange (ETDEWEB)

    Schramm, K.; Pilkey, W. [Univ. of Virginia, Charlottesville, VA (United States)

    1995-12-31

    A beam model which considers the warping effect in beams with arbitrary cross sections is discussed. This model takes into account bending, shear, and warping torsion. The derivation builds on a result in beam theory that, if shear is considered, for arbitrary cross sections the deflections in the different coordinate directions are not uncoupled as has been widely assumed. This conclusion follows from the calculation of the shear coefficients from an elasticity solution using an energy formulation. The shear coefficients form a symmetric tensor. The principal axes for this tensor are called principal shear axes. In Reference 2 structural matrices for the shear problem are derived using these shear coefficients. This paper extends these matrices to warping torsion. St. Venant`s semi-inverse method is applied to calculate warping shear stresses. The usual assumptions of the beam theory are made. The material is linear elastic. The loads may consist of shear forces, axial loads and twisting moments. Small deformations are considered. The cross section of the beam can be of arbitrary shape, thin-walled or solid. A deformation coefficient matrix is calculated which describes the relations between the deformations and the different load cases such as shear, torsion, and warping torsion. Numerical results for warping shear stresses and deformations are given. Also, a method to derive a stiffness matrix for a beam of arbitrary cross section under combined loading including warping torsion is presented.

  13. Atomic structure of amorphous shear bands in boron carbide.

    Science.gov (United States)

    Reddy, K Madhav; Liu, P; Hirata, A; Fujita, T; Chen, M W

    2013-01-01

    Amorphous shear bands are the main deformation and failure mode of super-hard boron carbide subjected to shock loading and high pressures at room temperature. Nevertheless, the formation mechanisms of the amorphous shear bands remain a long-standing scientific curiosity mainly because of the lack of experimental structure information of the disordered shear bands, comprising light elements of carbon and boron only. Here we report the atomic structure of the amorphous shear bands in boron carbide characterized by state-of-the-art aberration-corrected transmission electron microscopy. Distorted icosahedra, displaced from the crystalline matrix, were observed in nano-sized amorphous bands that produce dislocation-like local shear strains. These experimental results provide direct experimental evidence that the formation of amorphous shear bands in boron carbide results from the disassembly of the icosahedra, driven by shear stresses.

  14. Systematic tests for position-dependent additive shear bias

    CERN Document Server

    van Uitert, Edo

    2016-01-01

    We present new tests to identify stationary position-dependent additive shear biases in weak gravitational lensing data sets. These tests are important diagnostics for currently ongoing and planned cosmic shear surveys, as such biases induce coherent shear patterns that can mimic and potentially bias the cosmic shear signal. The central idea of these tests is to determine the average ellipticity of all galaxies with shape measurements in a grid in the pixel plane. The distribution of the absolute values of these averaged ellipticities can be compared to randomized catalogues; a difference points to systematics in the data. In addition, we introduce a method to quantify the spatial correlation of the additive bias, which suppresses the contribution from cosmic shear and therefore eases the identification of a position-dependent additive shear bias in the data. We apply these tests to the publicly available shear catalogues from the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS) and the Kilo Degree Su...

  15. Shear behavior of sand-expanded polystyrene beads lightweight fills

    Institute of Scientific and Technical Information of China (English)

    邓安; 肖杨

    2008-01-01

    Through direct shear and triaxial compression tests, effects of expanded polystyrene (EPS) mass ratios in sand-EPS mixtures and stress status on materials’ shear behavior were investigated. Hyperbolic curves were used to fit relationship between shear stress and shear displacement. The shear behavior is marginally associated with the EPS ratios and normal/confining stresses. Increases of EPS ratios and decreases of normal/confining stresses result in shear strength decreases. The shapes of Mohr-Coulomb’s envelope include linear and piecewise linear types, which are basically determined by the EPS ratio. Such difference is thought related to the embedding or apparent cohesion effect under relatively high EPS ratio conditions. Shear strength parameters can be used for further modeling and design purposes.

  16. Magnetic shear. IV - Hale regions 16740, 16815, and 16850

    International Nuclear Information System (INIS)

    Dopplergrams made in C IV 1548 A are studied for evidence of velocity shear near H-alpha dark filaments and for large-scale flow convergent on active regions. The three regions studied support earlier conclusions that shear is a common property of active regions and that active regions may be the foci of converging plasma flow. Flow patterns near filaments show divergence or convergence as well as shear. Also the sense of the shear can be either cyclonic or anticyclonic. No preference is noted for convergence or divergence or for a particular sense of shear, and there appears to be no correlation between the sense of the shear and the sign of the velocity gradient normal to the filament. The close association of H-alpha dark filaments with shear lines leads to the suggestion that the filaments may arise from a cooling instability induced by the Bernoulli effect. 12 references

  17. Shear-accelerated crystallization in a supercooled atomic liquid.

    Science.gov (United States)

    Shao, Zhen; Singer, Jonathan P; Liu, Yanhui; Liu, Ze; Li, Huiping; Gopinadhan, Manesh; O'Hern, Corey S; Schroers, Jan; Osuji, Chinedum O

    2015-02-01

    A bulk metallic glass forming alloy is subjected to shear flow in its supercooled state by compression of a short rod to produce a flat disk. The resulting material exhibits enhanced crystallization kinetics during isothermal annealing as reflected in the decrease of the crystallization time relative to the nondeformed case. The transition from quiescent to shear-accelerated crystallization is linked to strain accumulated during shear flow above a critical shear rate γ̇(c)≈0.3 s(-1) which corresponds to Péclet number, Pe∼O(1). The observation of shear-accelerated crystallization in an atomic system at modest shear rates is uncommon. It is made possible here by the substantial viscosity of the supercooled liquid which increases strongly with temperature in the approach to the glass transition. We may therefore anticipate the encounter of nontrivial shear-related effects during thermoplastic deformation of similar systems.

  18. Shear crack formation and propagation in reinforced Engineered Cementitious Composites

    DEFF Research Database (Denmark)

    Paegle, Ieva; Fischer, Gregor

    2011-01-01

    This paper describes an experimental investigation of the shear behaviour of beams consisting of steel reinforced Engineered Cementitious Composites (R/ECC). Based on the strain hardening and multiple cracking behaviour of ECC, this study investigates the extent to which ECC influences the shear...... capacity of beams loaded primarily in shear. The experimental program consists of ECC with short randomly distributed polyvinyl alcohol (PVA) fiber beams with different stirrup arrangements and conventional reinforced concrete (R/C) counterparts for comparison. The shear crack formation mechanism of ECC...... is investigated in detail and can be characterized by an opening and sliding of the crack. Photogrammetry was utilized to monitor the shear deformations of the specimens. Multiple shear cracking and strain hardening of ECC was observed under shear loading and based upon photogrammetric results fundamental...

  19. Phenomenon of transformed adiabatic shear band surrounded by deformed adiabatic shear band of ductile metal

    Institute of Scientific and Technical Information of China (English)

    WANG Xue-bin

    2008-01-01

    The coexistent phenomenon of deformed and transformed adiabatic shear bands(ASBs) of ductile metal was analyzed using the JOHNSON-COOK model and gradient-dependent plasticity(GDP). The effects of melting point, density, heat capacity and work to heat conversion factor were investigated. Higher work to heat conversion factor, lower density, lower heat capacity and higher melting point lead to wider transformed ASB and higher local plastic shear deformation between deformed and transformed ASBs. Higher work to heat conversion factor, lower density, lower heat capacity and lower melting point cause higher local plastic shear deformation in the deformed ASB. Three reasons for the scatter in experimental data on the ASB width were pointed out and the advantages of the work were discussed. If the transformed ASB width is used to back-calculate the internal length parameter in the GDP, undoubtedly, the parameter will be extremely underestimated.

  20. Measurement of surface shear stress vector distribution using shear-sensitive liquid crystal coatings

    Institute of Scientific and Technical Information of China (English)

    Ji-Song Zhao; Peter Scholz; Liang-Xian Gu

    2012-01-01

    The global wall shear stress measurement technique using shear-sensitive liquid crystal (SSLC) is extended to wind tunnel measurements.Simple and common everyday equipment is used in the measurement; in particular a tungsten-halogen light bulb provides illumination and a saturation of SSLC coating color change with time is found.Spatial wall shear stress distributions of several typical flows are obtained using this technique,including wall-jet flow,vortex flow generated by a delta wing and junction flow behind a thin cylinder,although the magnitudes are not fully calibrated.The results demonstrate that SSLC technique can be extended to wind tunnel measurements with no complicated facilities used.

  1. INFLUENCE OF MIMIC CARDIAC RATE ON HYDRODYNAMICS OF DIFFERENT MECHANICAL PROSTHETIC CARDIAC VALVES IN VITRO

    Institute of Scientific and Technical Information of China (English)

    Yin-ping Chu; Jin-lian Cheng; Ru-kun Chen; Yu-bo Fan; Fang Pu

    2005-01-01

    Objective To assess the influence of mimic cardiac rate on hydrodynamics of different mechanical prosthetic cardiac valves.Methods US-made CarboMedics bileaflet valve, China-made Jiuling bileaflet valve and C-L tilting disc valve were tested via a pulsatile flow simulator in the aortic position. Testing conditions were set at mimic cardiac rates of 55 bpm, 75 bpm, 100bpm with a constant mimic cardiac output of 4 L/min. The mean pressure differences (△P), leakage volumes (LEV) and closing volumes (CLV) across each valve, and effective orifice areas (EOA) were analyzed.Results Within physiological range, △p, LEV, and CLV decreased as mimic cardiac rate increased, with a large extent of variance. EOA increased along with an increase in mimic cardiac rate. It was a different response in terms of cardiac rate alteration for different types of mechanical prosthetic cardiac valves.Conclusion Mimic cardiac rate change affects hydrodynamics of mechanical prosthetic cardiac valves. Within physiological range, the hydrodynamic of prosthetic bileaflet valve is better than that of tilting disc valve.

  2. Monitoring of thermal therapy based on shear modulus changes: I. shear wave thermometry.

    Science.gov (United States)

    Arnal, Bastien; Pernot, Mathieu; Tanter, Mickael

    2011-02-01

    The clinical applicability of high-intensity focused ultrasound (HIFU) for noninvasive therapy is today hampered by the lack of robust and real-time monitoring of tissue damage during treatment. The goal of this study is to show that the estimation of local tissue elasticity from shear wave imaging (SWI) can lead to the 2-D mapping of temperature changes during HIFU treatments. This new concept of shear wave thermometry is experimentally implemented here using conventional ultrasonic imaging probes. HIFU treatment and monitoring were, respectively, performed using a confocal setup consisting of a 2.5-MHz single-element transducer focused at 30 mm on ex vivo samples and an 8-MHz ultrasound diagnostic probe. Thermocouple measurements and ultrasound-based thermometry were used as a gold standard technique and were combined with SWI on the same device. The SWI sequences consisted of 2 successive shear waves induced at different lateral positions. Each wave was created using 100-μs pushing beams at 3 depths. The shear wave propagation was acquired at 17,000 frames/s, from which the elasticity map was recovered. HIFU sonications were interleaved with fast imaging acquisitions, allowing a duty cycle of more than 90%. Elasticity and temperature mapping was achieved every 3 s, leading to realtime monitoring of the treatment. Tissue stiffness was found to decrease in the focal zone for temperatures up to 43°C. Ultrasound-based temperature estimation was highly correlated to stiffness variation maps (r² = 0.91 to 0.97). A reversible calibration phase of the changes of elasticity with temperature can be made locally using sighting shots. This calibration process allows for the derivation of temperature maps from shear wave imaging. Compared with conventional ultrasound-based approaches, shear wave thermometry is found to be much more robust to motion artifacts. PMID:21342822

  3. Analytical solution of transverse shear strain vibration of gas detonation loaded tube near second critical speed (shear group velocity)

    International Nuclear Information System (INIS)

    Analytical solution of transverse shear strain vibration of a tube caused by internal gaseous detonation near the second critical speed (shear group velocity) is not reported in the literature. It is performed based on a steady state model and first order shear deformation theories (model I and II) in this paper, and the results are verified through comparison with the finite element results reported in the literature. There are no known experimental ways of directly measuring dynamic transverse shear strain and only theoretical results and numerical data are available. The finite element method is very time consuming compared with the analytical solution. It is shown in this paper that the resonance phenomenon of the transverse shear strain vibration near the second critical speed can be predicted by steady state model and first order shear deformation theories. The first order shear deformation theory (model II) has a good agreement with finite element results in prediction of dynamic amplification factors and critical speeds.

  4. Fibre-reinforced plastic composites - Determination of the in-plane shear stress/shear strain response, including the in-plane shear modulus and strength, by the plus or minus 45 degree tension test method

    CERN Document Server

    International Organization for Standardization. Geneva

    1997-01-01

    Fibre-reinforced plastic composites - Determination of the in-plane shear stress/shear strain response, including the in-plane shear modulus and strength, by the plus or minus 45 degree tension test method

  5. Hypokalemia and sudden cardiac death

    DEFF Research Database (Denmark)

    Kjeldsen, Keld

    2010-01-01

    Worldwide, approximately three million people suffer sudden cardiac death annually. These deaths often emerge from a complex interplay of substrates and triggers. Disturbed potassium homeostasis among heart cells is an example of such a trigger. Thus, hypokalemia and, also, more transient...... was found in 24% of hospitalized patients. Hypokalemia is associated with increased risk of arrhythmia in patients with cardiovascular disease, as well as increased all-cause mortality, cardiovascular mortality and heart failure mortality by up to 10-fold. Long-term potassium homeostasis depends on renal...... capacity for potassium exchange. In cardiovascular patients, hypokalemia is often caused by nonpotassium-sparing diuretics, insufficient potassium intake and a shift of potassium into stores by increased potassium uptake stimulated by catecholamines, beta-adrenoceptor agonists and insulin. Interestingly...

  6. Evolution of thermal ion transport barriers in reversed shear/optimised shear plasmas

    International Nuclear Information System (INIS)

    The effects of the magnetic and ExB rotation shears on the thermal ion transport in advanced tokamak scenarios are analyzed through the predictive modelling of the evolution of internal transport barriers. Such a modelling is performed with an experimentally validated L-mode thermal diffusivity completed with a semi-empirical shear correction which is based on simple theoretical arguments from turbulence studies. A multi-machine test of the model on relevant discharges from the ITER Data Base (TFTR, DIII-D and JET) is presented. (author)

  7. Cardiac Rehabilitation: Improving Function and Reducing Risk.

    Science.gov (United States)

    Servey, Jessica T; Stephens, Mark

    2016-07-01

    Cardiac rehabilitation is a comprehensive multidisciplinary program individually tailored to the needs of patients with cardiovascular disease. The overall goals focus on improving daily function and reducing cardiovascular risk factors. Cardiac rehabilitation includes interventions aimed at lowering blood pressure and improving lipid and diabetes mellitus control, with tobacco cessation, behavioral counseling, and graded physical activity. The physical activity component typically involves 36 sessions over 12 weeks, during which patients participate in supervised exercise under cardiac monitoring. There are also intensive programs that include up to 72 sessions lasting up to 18 weeks, although these programs are not widely available. Additional components of cardiac rehabilitation include counseling on nutrition, screening for and managing depression, and assuring up-to-date immunizations. Cardiac rehabilitation is covered by Medicare and recommended for patients following myocardial infarction, bypass surgery, and stent placement, and for patients with heart failure, stable angina, and several other conditions. Despite proven benefits in mortality rates, depression, functional capacity, and medication adherence, rates of referral for cardiac rehabilitation are suboptimal. Groups less likely to be referred are older adults, women, patients who do not speak English, and persons living in areas where cardiac rehabilitation is not locally available. Additionally, primary care physicians refer patients less often than cardiologists and cardiothoracic surgeons. PMID:27386722

  8. MRS: a noninvasive window into cardiac metabolism.

    Science.gov (United States)

    van Ewijk, Petronella A; Schrauwen-Hinderling, Vera B; Bekkers, Sebastiaan C A M; Glatz, Jan F C; Wildberger, Joachim E; Kooi, M Eline

    2015-07-01

    A well-functioning heart requires a constant supply of a balanced mixture of nutrients to be used for the production of adequate amounts of adenosine triphosphate, which is the main energy source for most cellular functions. Defects in cardiac energy metabolism are linked to several myocardial disorders. MRS can be used to study in vivo changes in cardiac metabolism noninvasively. MR techniques allow repeated measurements, so that disease progression and the response to treatment or to a lifestyle intervention can be monitored. It has also been shown that MRS can predict clinical heart failure and death. This article focuses on in vivo MRS to assess cardiac metabolism in humans and experimental animals, as experimental animals are often used to investigate the mechanisms underlying the development of metabolic diseases. Various MR techniques, such as cardiac (31) P-MRS, (1) H-MRS, hyperpolarized (13) C-MRS and Dixon MRI, are described. A short overview of current and emerging applications is given. Cardiac MRS is a promising technique for the investigation of the relationship between cardiac metabolism and cardiac disease. However, further optimization of scan time and signal-to-noise ratio is required before broad clinical application. In this respect, the ongoing development of advanced shimming algorithms, radiofrequency pulses, pulse sequences, (multichannel) detection coils, the use of hyperpolarized nuclei and scanning at higher magnetic field strengths offer future perspective for clinical applications of MRS. PMID:26010681

  9. Dynamics of flexible fibers in shear flow

    Energy Technology Data Exchange (ETDEWEB)

    Słowicka, Agnieszka M.; Wajnryb, Eligiusz; Ekiel-Jeżewska, Maria L., E-mail: mekiel@ippt.pan.pl [Institute of Fundamental Technological Research, Polish Academy of Sciences, Pawińskiego 5b, 02-106 Warsaw (Poland)

    2015-09-28

    Dynamics of flexible non-Brownian fibers in shear flow at low-Reynolds-number are analyzed numerically for a wide range of the ratios A of the fiber bending force to the viscous drag force. Initially, the fibers are aligned with the flow, and later they move in the plane perpendicular to the flow vorticity. A surprisingly rich spectrum of different modes is observed when the value of A is systematically changed, with sharp transitions between coiled and straightening out modes, period-doubling bifurcations from periodic to migrating solutions, irregular dynamics, and chaos.

  10. Shear viscosity of a hadronic gas mixture

    OpenAIRE

    Itakura, Kazunori; Morimatsu, Osamu; Otomo, Hiroshi

    2007-01-01

    We discuss in detail the shear viscosity coefficient eta and the viscosity to entropy density ratio eta/s of a hadronic gas comprised of pions and nucleons. In particular, we study the effects of baryon chemical potential on eta and eta/s. We solve the relativistic quantum Boltzmann equations with binary collisions (pi pi, pi N, and NN) for a state slightly deviated from thermal equilibrium at temperature T and baryon chemical potential mu. The use of phenomenological amplitudes in the collis...

  11. Shear forces in molecularly thin films

    Energy Technology Data Exchange (ETDEWEB)

    Schoen, M. (Universitaet Witten-Herdecke, Stockumer Strasse (Germany, F.R.)); Rhykerd, C.L. Jr.; Diestler, D.J.; Cushman, J.H. (Purdue Univ., West Lafayette, IN (USA))

    1989-09-15

    Monte Carlo and molecular dynamics methods have been used to study the shearing behavior of an atomic fluid between two plane-parallel solid surfaces having the face-centered cubic (100) structure. A distorted, face-centered cubic solid can form epitaxially between surfaces that are separated by distances of one to five atomic diameters. Under these conditions a critical stress must be overcome to initiate sliding of the surfaces over one another at fixed separation, temperature, and chemical potential. As sliding begins, a layer of solid exits the space between the surfaces and the remaining layers become fluid. 18 refs., 2 figs.

  12. Propagation of waves in shear flows

    CERN Document Server

    Fabrikant, A L

    1998-01-01

    The state of the art in a theory of oscillatory and wave phenomena in hydrodynamical flows is presented in this book. A unified approach is used for waves of different physical origins. A characteristic feature of this approach is that hydrodynamical phenomena are considered in terms of physics; that is, the complement of the conventionally employed formal mathematical approach. Some physical concepts such as wave energy and momentum in a moving fluid are analysed, taking into account induced mean flow. The physical mechanisms responsible for hydrodynamic instability of shear flows are conside

  13. Plasticity Approach to HSC Shear Wall Design

    DEFF Research Database (Denmark)

    Liu, Lunying; Nielsen, Mogens Peter

    1998-01-01

    of concrete. The reduced strength is named the effective strength. The paper describes simple lower bound solutions. They consist of pure strut action or strut action combined with diagonal compression fields outside the struts. Near moment maximum and near supports the stress fields are modified to save...... to 140 MPa and reinforcement yield strengths up to 1420 MPa. The work was carried out as a Ph.D. study by the first author, the second author supervising the study.Keywords: shear wall, plasticity, strut and tie, load-carrying capacity, concrete, reinforcement....

  14. KIDNEY TRANSPLANTATION FROM DONORS AFTER CARDIAC DEATH

    Directory of Open Access Journals (Sweden)

    R.L. Rozental

    2012-01-01

    Full Text Available From 668 kidney transplantations performed during the period 2000–2005 68 grafts were recovered from donors after cardiac death and 176 from donors with confirmed brain death. Early results (number of primarily non-functioning grafts, rates of delayed graft function and acute rejections were similar in both groups. 5-year patient survival was 85% from donors after cardiac death and 88% from donors with confirmed brain death. 5-year graft survival was 77% and 85%, respectively. Results showed that the use of kidney grafts recovered from donors after cardiac death is valuable additional source of donor organs. 

  15. A rare case of primary cardiac lymphoma.

    Science.gov (United States)

    Khan-Kheil, Ayisha Mehtab; Mustafa, Hanif Muhammad; Anand, Dhakshinamurthy Vijay; Banerjee, Prithwish

    2015-01-01

    A 71-year-old man presented with shortness of breath and tachycardia along with systemic symptoms of weight loss and lethargy. A pulmonary embolus was the initial suspected diagnosis but through extensive investigations a rarer cause of his symptoms was identified. This case demonstrates the importance of cardiac imaging in the assessment and non-invasive tissue characterisation of a suspected cardiac tumour; in our case, this was subsequently confirmed by careful histological/immunocytochemical evaluation of the pericardial effusion as a primary cardiac B-cell non-Hodgkin's lymphoma, thus enabling appropriate management leading to an excellent clinical outcome. PMID:26538249

  16. Cardiac and Respiratory Disease in Aged Horses.

    Science.gov (United States)

    Marr, Celia M

    2016-08-01

    Respiratory and cardiac diseases are common in older horses. Advancing age is a specific risk factor for cardiac murmurs and these are more likely in males and small horses. Airway inflammation is the most common respiratory diagnosis. Recurrent airway obstruction can lead to irreversible structural change and bronchiectasis; with chronic hypoxia, right heart dysfunction and failure can develop. Valvular heart disease most often affects the aortic and/or the mitral valve. Management of comorbidity is an essential element of the therapeutic approach to cardiac and respiratory disease in older equids.

  17. Cardiac Amyloidosis Presenting With Cardiogenic Shock.

    Science.gov (United States)

    Afzal, Ashwad; Brener, Sorin J; Narula, Navneet; Worku, Berhane; Gulkarov, Iosif

    2016-01-01

    Cardiac amyloidosis is an infiltrative disorder of the myocardium. It is the result of one of 4 types of amyloidosis: primary systemic (immunoglobulin light chain), secondary, familial (hereditary), or senile. Cardiac amyloidosis ultimately causes congestive heart failure due to irreversible restrictive cardiomyopathy. Because of the rapid progression of the disease, early recognition and determination of underlying etiology are important for tailored therapy. Current interventions range from conservative heart failure management to autologous stem cell and heart transplantation. We present a case of cardiac amyloidosis accompanying undiagnosed multiple myeloma to illustrate the rapid progression of the disease and the complexities of diagnosing and treating this disorder. PMID:26177555

  18. Cardiac carcinoid: tricuspid delayed hyperenhancement on cardiac 64-slice multidetector CT and magnetic resonance imaging.

    LENUS (Irish Health Repository)

    Martos, R

    2012-02-01

    INTRODUCTION: Carcinoid heart disease is a rare condition in adults. Its diagnosis can be easily missed in a patient presenting to a primary care setting. We revised the advantages of using coronary multidetector computed tomography (MDCT) and cardiac magnetic resonance imaging (MRI) in diagnosing this condition. MATERIALS AND METHODS: We studied a 65-year-old patient with carcinoid heart disease and right heart failure using transthoracic Doppler-echocardiogram, cardiac MDCT and MRI. Cardiac echocardiogram revealed marked thickening and retraction of the tricuspid leaflets with dilated right atrium and ventricle. Cardiac MDCT and MRI demonstrated fixation and retraction of the tricuspid leaflets with delayed contrast hyperenhancement of the tricuspid annulus. CONCLUSION: This case demonstrates fascinating imaging findings of cardiac carcinoid disease and highlights the increasing utility of contrast-enhanced MRI and cardiac MDCT in the diagnosis of this interesting condition.

  19. IS CONSANGUINEOUS MARRIAGE RESPONSIBLE FOR CONGENITAL CARDIAC AND EXTRA-CARDIAC ANOMALIES?

    OpenAIRE

    Nutan Nalini; Sudha

    2016-01-01

    BACKGROUND This article is about the stillbirth in which we found significant numbers of cardiac as well as extracardiac defects, in combination or separately. In this article, we would like to emphasize the anomalies found in consanguineous marriages. AIM To correlate the prevalence of cardiac as well as extracardiac anomalies in consanguineous marriages. Especially, here we would like to focus on the cardiac lesions. MATERIAL AND METHOD The study was ca...

  20. Far-from-equilibrium sheared colloidal liquids: Disentangling relaxation, advection, and shear-induced diffusion

    KAUST Repository

    Lin, Neil Y. C.

    2013-12-01

    Using high-speed confocal microscopy, we measure the particle positions in a colloidal suspension under large-amplitude oscillatory shear. Using the particle positions, we quantify the in situ anisotropy of the pair-correlation function, a measure of the Brownian stress. From these data we find two distinct types of responses as the system crosses over from equilibrium to far-from-equilibrium states. The first is a nonlinear amplitude saturation that arises from shear-induced advection, while the second is a linear frequency saturation due to competition between suspension relaxation and shear rate. In spite of their different underlying mechanisms, we show that all the data can be scaled onto a master curve that spans the equilibrium and far-from-equilibrium regimes, linking small-amplitude oscillatory to continuous shear. This observation illustrates a colloidal analog of the Cox-Merz rule and its microscopic underpinning. Brownian dynamics simulations show that interparticle interactions are sufficient for generating both experimentally observed saturations. © 2013 American Physical Society.

  1. From supersonic shear wave imaging to full-field optical coherence shear wave elastography

    Science.gov (United States)

    Nahas, Amir; Tanter, Mickaël; Nguyen, Thu-Mai; Chassot, Jean-Marie; Fink, Mathias; Claude Boccara, A.

    2013-12-01

    Elasticity maps of tissue have proved to be particularly useful in providing complementary contrast to ultrasonic imaging, e.g., for cancer diagnosis at the millimeter scale. Optical coherence tomography (OCT) offers an endogenous contrast based on singly backscattered optical waves. Adding complementary contrast to OCT images by recording elasticity maps could also be valuable in improving OCT-based diagnosis at the microscopic scale. Static elastography has been successfully coupled with full-field OCT (FF-OCT) in order to realize both micrometer-scale sectioning and elasticity maps. Nevertheless, static elastography presents a number of drawbacks, mainly when stiffness quantification is required. Here, we describe the combination of two methods: transient elastography, based on speed measurements of shear waves induced by ultrasonic radiation forces, and FF-OCT, an en face OCT approach using an incoherent light source. The use of an ultrafast ultrasonic scanner and an ultrafast camera working at 10,000 to 30,000 images/s made it possible to follow shear wave propagation with both modalities. As expected, FF-OCT is found to be much more sensitive than ultrafast ultrasound to tiny shear vibrations (a few nanometers and micrometers, respectively). Stiffness assessed in gel phantoms and an ex vivo rat brain by FF-OCT is found to be in good agreement with ultrasound shear wave elastography.

  2. Tensile-shear correlations obtained from shear punch test technique using a modified experimental approach

    Science.gov (United States)

    Karthik, V.; Visweswaran, P.; Vijayraghavan, A.; Kasiviswanathan, K. V.; Raj, Baldev

    2009-09-01

    Shear punch testing has been a very useful technique for evaluating mechanical properties of irradiated alloys using a very small volume of material. The load-displacement data is influenced by the compliance of the fixture components. This paper describes a modified experimental approach where the compliances of the punch and die components are eliminated. The analysis of the load-displacement data using the modified setup for various alloys like low carbon steel, SS316, modified 9Cr-1Mo, 2.25Cr-1Mo indicate that the shear yield strength evaluated at 0.2% offset of normalized displacement relates to the tensile YS as per the Von Mises yield relation ( σys = 1.73 τys). A universal correlation of type UTS = mτmax where m is a function of strain hardening exponent, is seen to be obeyed for all the materials in this study. The use of analytical models developed for blanking process are explored for evaluating strain hardening exponent from the load-displacement data. This study is directed towards rationalizing the tensile-shear empirical correlations for a more reliable prediction of tensile properties from shear punch tests.

  3. Shear Behaviour of Reinforced Concrete Members without Shear Reinforcement: a New Look at an Old Problem

    NARCIS (Netherlands)

    Yang, Y.

    2014-01-01

    Shear loading on structures has been recognized as one of the most relevant actions determining structural safety since the 19th century. In the case of reinforced concrete structures, despite the great efforts that have been made through experimental and theoretical research over many years, the na

  4. Acceleration Statistics in Rotating and Sheared Turbulence

    Science.gov (United States)

    Jacobitz, Frank; Schneider, Kai; Bos, Wouter; Farge, Marie

    2012-11-01

    Acceleration statistics are of fundamental interest in turbulence ranging from theoretical questions to modeling of dispersion processes. Direct numerical simulations of sheared and rotating homogeneous turbulence are performed with different ratios of Coriolis parameter to shear rate. The statistics of Lagrangian and Eulerian acceleration are studied with a particular focus on the influence of the rotation ratio and also on the scale dependence of the statistics. The probability density functions (pdfs) of both Lagrangian and Eulerian acceleration show a strong and similar influence on the rotation ratio. The flatness further quantifies its influence and yields values close to three for strong rotation. For moderate and vanishing rotation, the flatness of the Eulerian acceleration is larger than that of the Lagrangian acceleration, contrary to previous results for isotropic turbulence. A wavelet-based scale-dependent analysis shows that the flatness of both Eulerian and Lagrangian acceleration increases as scale decreases. For strong rotation, the Eulerian acceleration is more intermittent than the Lagrangian acceleration, while the opposite result is obtained for moderate rotation.

  5. Nonlinear stability of relativistic sheared planar jets

    CERN Document Server

    Perucho, M; Hanasz, M

    2005-01-01

    The linear and non-linear stability of sheared, relativistic planar jets is studied by means of linear stability analysis and numerical hydrodynamical simulations. Our results extend the previous Kelvin-Hemlholtz stability studies for relativistic, planar jets in the vortex sheet approximation performed by Perucho et al. (2004a,b) by including a shear layer between the jet and the external medium and more general perturbations. The models considered span a wide range of Lorentz factors ($2.5-20$) and internal energies ($0.08 c^2-60 c^2$) and are classified into three classes according to the main characteristics of their long-term, non-linear evolution. We observe a clear separation of these three groups in a relativistic Mach-number Lorentz-factor plane. Jets with a low Lorentz factor and small relativistic Mach number are disrupted after saturation. Those with a large Lorentz factor and large relativistic Mach number are the stablest, due to the appearance of short wavelength resonant modes which generate l...

  6. An Implementation of Bayesian Lensing Shear Measurement

    CERN Document Server

    Sheldon, Erin S

    2014-01-01

    The Bayesian gravitational shear estimation algorithm developed by Bernstein and Armstrong (2014) can potentially be used to overcome noise bias and recover shear using very low signal-to-noise ratio (S/N) galaxy images. In that work the authors confirmed the method is sufficiently unbiased for planned surveys (fractional error less than 2 x 10^{-3}) in a simplified demonstration, but no test was performed on images. Here I present a full implementation for fitting models to galaxy images, including the effects of a point spread function (PSF) and pixelization. I tested the implementation using simulated galaxy images modeled as Sersic profiles with n=1 (exponential) and n=4 (De Vaucouleurs'), convolved with a PSF and a flat pixel response function. I used a round Gaussian model for the PSF to avoid potential PSF-fitting errors. I simulated galaxies with mean observed, post-PSF full-width at half maximum equal to approximately 1.2 times that of the PSF, with log-normal scatter. I also drew fluxes from a log-n...

  7. Resonant instability of supersonic shear layers

    Science.gov (United States)

    Tam, C. K. W.; Lele, S. K.

    1990-01-01

    A computer simulation of possible resonant instability of a supersonic shear layer is carried out. The resonance of two acoustic duct modes of the flow induced by periodic Mach waves generated by a wavy wall is sought. Results of the simulations are reported. Simulations are unable to document a resonant instability and the mixing characteristics remain unchanged. Possible weakness of the present simulations are discussed. A second set of simulations involving a mixing layer separating a supersonic and a subsonic stream were performed. A wavy wall placed adjacent to the supersonic stream to produce a set of periodic Mach waves terminating at the shear layer is modelled. The entire flow field is similar to that of an imperfectly expanded supersonic jet discharging into a subsonic coflowing stream for which enhanced mixing due to the onset of screech (feedback instability) is known to occur. The purpose of these simulations is to see if enhanced mixing and feedback instability would, indeed, take place. Some evidence of feedback oscillations is found in the simulated flow.

  8. Simulations of Reversed Shear Configuration in EAST

    Institute of Scientific and Technical Information of China (English)

    NIU Xingping; WU Bin

    2007-01-01

    The reversed shear (RS) mode is one of the advanced configurations being considered in EAST.Predictive simulations of EAST reversed shear configuration are carried out using an 1.5D equilibrium evolution code.In order to have the desired monotonic q-profile during a tokamak discharge,a successful preparation phase is required.In our simulation,the plasma current is ramped up from 100 kA to a flat-top maximum of 1.0 MA for four seconds.An ICRH power of 1 MW is applied until the plasma shape is formed at the moment of 4 s,and then the power is raised to 3 MW.A LHCD power of 3.5 MW is applied from is to optimize the plasma current density profile.A series of simulations are performed to study the influence of the time of applying the auxiliary heating on the plasma parameters.Based on these simulations,a scheme is proposed and tested for the control of the safety factor profile,which is very useful in real time profile control in tokamak experiments.

  9. Hyperscaling violation and the shear diffusion constant

    CERN Document Server

    Kolekar, Kedar S; Narayan, K

    2016-01-01

    We consider holographic theories in bulk $(d+1)$-dimensions with Lifshitz and hyperscaling violating exponents $z,\\theta$ at finite temperature. By studying shear gravitational modes in the near-horizon region given certain self-consistent approximations, we obtain the corresponding shear diffusion constant on an appropriately defined stretched horizon, adapting the analysis of Kovtun, Son and Starinets. For generic exponents with $d-z-\\theta>-1$, we find that the diffusion constant has power law scaling with the temperature, motivating us to guess a universal relation for the viscosity bound. When the exponents satisfy $d-z-\\theta=-1$, we find logarithmic behaviour. This relation is equivalent to $z=2+d_{eff}$ where $d_{eff}=d_i-\\theta$ is the effective boundary spatial dimension (and $d_i=d-1$ the actual spatial dimension). It is satisfied by the exponents in hyperscaling violating theories arising from null reductions of highly boosted black branes, and we comment on the corresponding analysis in that cont...

  10. Shearing of Materials with Intermittent Joints

    Science.gov (United States)

    Gerolymatou, Eleni; Triantafyllidis, Theodoros

    2016-07-01

    The strength of fractures is much lower as a rule than that of intact rock. As a result they play a controlling part in the mechanical behaviour in general and the failure in particular of rock mass. Though a large volume of experimental data is available on the shear resistance of joints, as well as on the propagation of single cracks, the same is not true for the mechanical behaviour of intermittent joints. The experimental data available in this case are limited and the strength of rock mass with intermittent joints is usually modelled using averaged values of cohesion or assuming the fractures to be continuous. In the present work, the results of simple shear tests on a series of gypsum specimens with pre-existing cracks are presented. Twelve different crack orientations and two normal stresses were tested. The hypothesis of averaged cohesion and the theory of fracture mechanics are used to reproduce the results. It is found that fracture mechanics provides a more suitable model for the experimental results, especially when crack interaction is taken into account.

  11. Anisotropy and Heterogeneity Interaction in Shear Zones

    Science.gov (United States)

    Dabrowski, M.; Schmid, D. W.

    2009-04-01

    Rocks are heterogeneous on many different scales and deformation may introduce a coexistence of heterogeneity and anisotropy in shear zones. A competent inclusion embedded in a laminated matrix is a typical example. Indisputably, the presence of a mechanical heterogeneity leads to a flow perturbation and consequently to a deflection of the lamination in its vicinity. Assuming a passive response of the matrix phase, the pattern formation around rigid objects has been modeled in two and three dimensions using analytical solutions. Yet, the laminas may be mechanically distinct, leading to an effectively anisotropic rheology of the matrix. The feedback of an evolving matrix structure on the inclusion motion cannot be precluded in this case. In our study elliptical inclusions of varying aspect ratios are embedded in a laminated linear viscous host and subject to a large simple shear deformation in finite element numerical simulations. Increasing the viscosity ratio of the weak and strong lamina significantly changes the pattern characteristics in the matrix. The structural evolution around an inclusion proves to have a major impact on the inclusion motion, leading to the stabilization of elongated inclusions at antithetic orientations. We provide a comparison of two different modeling approaches. In the first approach discrete layers are introduced in the matrix and the large strain evolution of individual minute layers is resolved. Next, the matrix is modeled as an anisotropic medium using an evolving director field that locally describes the anisotropy direction. The length scale of layering can be restored in this model using the micropolar medium formulation.

  12. Shear-induced instabilities in layered liquids

    Science.gov (United States)

    Auernhammer, Günter K.; Brand, Helmut R.; Pleiner, Harald

    2002-12-01

    Motivated by the experimentally observed shear-induced destabilization and reorientation of smectic-A-like systems, we consider an extended formulation of smectic-A hydrodynamics. We include both, the smectic layering (via the layer displacement u and the layer normal pcirc) and the director ncirc of the underlying nematic order in our macroscopic hydrodynamic description and allow both directions to differ in nonequilibrium situations. In an homeotropically aligned sample the nematic director does couple to an applied simple shear, whereas the smectic layering stays unchanged. This difference leads to a finite (but usually small) angle between ncirc and pcirc, which we find to be equivalent to an effective dilatation of the layers. This effective dilatation leads, above a certain threshold, to an undulation instability of the layers. We generalize our earlier approach [G. K. Auernhammer, H. R. Brand, and H. Pleiner, Rheol. Acta 39, 215 (2000)] and include the cross couplings with the velocity field and the order parameters for orientational and positional order and show how the order parameters interact with the undulation instability. We explore the influence of various material parameters on the instability. Comparing our results to recent experiments and molecular dynamic simulations, we find a good qualitative agreement.

  13. Determination of arterial wall shear stress

    Institute of Scientific and Technical Information of China (English)

    LIU; Zhaorong

    2001-01-01

    [1]Langille, B. L., 7Donnell, F., Reductions in arterial diameter produced by chronic decreases in blood flow are endothelium-dependent, Science, 1986, 231: 405—407.[2]Langer, R., Vacanti, J. P., Tissue engineering, Science, 1993, 260: 920—926.[3]Kamiya, A., Togawa, T., Adaptive regulation of wall shear stress to flow change in the canine carotid artery, Am. J. Physiol. (Heart Circ. Physiol.), 1980, 239: H14—H21.[4]Fung, Y. C., Biomechanics: Motion, Flow, Stress, and Growth, New York: Springer-Verlag, 1990.[5]Liu, S. Q., Biomechanical basis of vascular tissue engineering, Critical Reviews in Biomedical Engineering, 1999, 27: 75—148.[6]Ando, J., Kamiya, A., Blood flow and vascular endothelium cell function, Frontiers Med. Biological Eng., 1993, 5: 245—264.[7]Ku, D. N., Giddens, D. P., Zarins, D. K. et al., Pulsatile flow and atherosclerosis in the human carotid bifurcation-positive correlation between plaque location and low and oscillating shear stress, Atherosclerosis, 1985, 5: 293—302.[8]Liu Zhaorong, Li Xixi, Theory and Method on Hemodynamics (in Chinese), Shanghai: Fudan University Press, 1997.

  14. Coupling effects in multiphase free shear flows

    International Nuclear Information System (INIS)

    The primary goal of this research program is to examine the effects of two-way multiphase coupling on the development of organized vortex structures in free shear flows and the resultant multiphase dispersion. Previous research studies have determined that one-way coupled particle dispersion in free shear flows is strongly dependent on the vortex structures present in these flows and their interactions as well as the ratio of the particle aerodynamic response time to the time scale of the dominant vortex structures. Current research efforts are directed towards exploring the effects that two-way momentum, mass and energy coupling have on the multiphase dispersion processes previously uncovered. These efforts involve analytical, numerical and experimental investigations. Recent analytical and numerical results indicate that momentum coupling effects can significantly alter the global stability and potentially the large scale features of the multiphase flow field. These multiphase coupling effects may have significant importance with regard to predicting the performance of many energy conversion systems

  15. Viscous shear heating instabilities in a 1-D viscoelastic shear zone

    Science.gov (United States)

    Homburg, J. M.; Coon, E. T.; Spiegelman, M.; Kelemen, P. B.; Hirth, G.

    2010-12-01

    Viscous shear instabilities may provide a possible mechanism for some intermediate depth earthquakes where high confining pressure makes it difficult to achieve frictional failure. While many studies have explored the feedback between temperature-dependent strain rate and strain-rate dependent shear heating (e.g. Braeck and Podladchikov, 2007), most have used thermal anomalies to initiate a shear instability or have imposed a low viscosity region in their model domain (John et al., 2009). By contrast, Kelemen and Hirth (2007) relied on an initial grain size contrast between a predetermined fine-grained shear zone and coarse grained host rock to initiate an instability. This choice is supported by observations of numerous fine grained ductile shear zones in shallow mantle massifs as well as the possibility that annealed fine grained fault gouge, formed at oceanic transforms, subduction related thrusts and ‘outer rise’ faults, could be carried below the brittle/ductile transition by subduction. Improving upon the work of Kelemen and Hirth (2007), we have developed a 1-D numerical model that describes the behavior of a Maxwell viscoelastic body with the rheology of dry olivine being driven at a constant velocity at its boundary. We include diffusion and dislocation creep, dislocation accommodated grain boundary sliding, and low-temperature plasticity (Peierls mechanism). Initial results suggest that including low-temperature plasticity inhibits the ability of the system to undergo an instability, similar to the results of Kameyama et al. (1999). This is due to increased deformation in the background allowing more shear heating to take place, and thus softening the system prior to reaching the peak stress. However if the applied strain rate is high enough (e.g. greater than 0.5 x 10-11 s-1 for a domain size of 2 km, an 8 m wide shear zone, a background grain size of 1 mm, a shear zone grain size of 150 μm, and an initial temperature of 650°C) dramatic

  16. Shear banding deformation in Cu/Ta nano-multilayers

    International Nuclear Information System (INIS)

    Highlights: → Formation of shear bands in Cu/Ta multilayers is layer thickness dependent. → Unique layer-morphology with prevalent mismatched laminate structure was observed. → A new physical mechanism that dominates shear band formation is suggested. - Abstract: Nanoscale Cu/Ta multilayers with individual layer thickness ranging from 3 to 70 nm were deformed under nanoindentation at room temperature. Shear bands can be observed only when individual layer thickness is reduced to 9 nm or below, indicating formation of shear bands in the Cu/Ta multilayers is layer thickness dependent. By observing the cross sectional transmission electron microscope images of the indentation fabricated through focused ion beam technique, shear banding deformation causing a unique layer-morphology with prevalent mismatched laminate structure has been reported for the first time. By capturing and analyzing a series of typical indentation-induced deformed microstructures, a new physical mechanism of shear banding behavior in metallic nano-multilayers is suggested.

  17. Effects of shear elasticity on sea bed scattering: numerical examples.

    Science.gov (United States)

    Ivakin, A N; Jackson, D R

    1998-01-01

    It is known that marine sediments can support both compressional and shear waves. However, published work on scattering from irregular elastic media has not examined the influence of shear on sea bed scattering in detail. A perturbation model previously developed by the authors for joint roughness-volume scattering is used to study the effects of elasticity for three sea bed types: sedimentary rock, sand with high shear speed, and sand with "normal" shear wave speed. Both bistatic and monostatic cases are considered. For sedimentary rock it is found that shear elasticity tends to increase the importance of volume scattering and decrease the importance of roughness scattering relative to the fluid case. Shear effects are shown to be small for sands.

  18. Transport Bifurcation Induced by Sheared Toroidal Flow in Tokamak Plasmas

    CERN Document Server

    Highcock, E G; Parra, F I; Schekochihin, A A; Roach, C M; Cowley, S C

    2011-01-01

    First-principles numerical simulations are used to describe a transport bifurcation in a differentially rotating tokamak plasma. Such a bifurcation is more probable in a region of zero magnetic shear, where the component of the sheared toroidal flow that is perpendicular to the magnetic field has the strongest suppressing effect on the turbulence, than one of finite magnetic shear. Where the magnetic shear is zero, there are no growing linear eigenmodes at any finite value of flow shear. However, subcritical turbulence can be sustained, owing to the transient growth of modes driven by the ion temperature gradient (ITG) and the parallel velocity gradient (PVG). Nonetheless, in a parameter space containing a wide range of temperature gradients and velocity shears, there is a sizeable window where all turbulence is suppressed. Combined with the relatively low transport of momentum by collisional (neoclassical) mechanisms, this produces the conditions for a bifurcation from low to high temperature and velocity gr...

  19. Investigation into ferrofluid magnetoviscous effects under an oscillating shear flow

    Energy Technology Data Exchange (ETDEWEB)

    Pinho, M., E-mail: marcos.pinho.etu@univ-lemans.fr [LAUM - Laboratoire d' Acoustique de l' Universite du Maine UMR CNRS 6613 (France); Brouard, B.; Genevaux, J.M. [LAUM - Laboratoire d' Acoustique de l' Universite du Maine UMR CNRS 6613 (France); Dauchez, N. [LISMMA - Institut Superieur de Mecanique de Paris (SUPMECA), 93407 Saint Ouen (France); Volkova, O. [Centre de micro et nanorheometrie, Universite de Nice-Sophia Antipolis, Parc Valrose, 06108 Nice-cedex2 (France); Meziere, H.; Collas, P. [LAUM - Laboratoire d' Acoustique de l' Universite du Maine UMR CNRS 6613 (France)

    2011-10-15

    The use of ferrofluid seals in mechanical systems can lead to viscous damping that affects their dynamic behavior. This paper describes an investigation into local viscous properties in the case of an axial harmonic force. The influence of magnetic field level, shear stress amplitude and frequency are studied. Even for ferrofluid particles in a highly saturated magnetic field, it is shown that viscosity increases with magnetic intensity, decreases with the frequency of harmonic excitation and is not sensitive to shear rate amplitude. Viscosity is lower for oscillatory flows than for steady flows. - Highlights: > Extension of the magnetoviscous effect of ferrofluids to the oscillatory shear flow. > Influence of magnetic field level, shear stress amplitude and frequency is studied. > Ferrofluid viscosity is lower for oscillatory than for steady flow shearing. > Ferrofluid viscosity is not sensitive to shear rate amplitude. > Negative-viscosity effect occurs even for a null magnetic field.

  20. A void coalescence model for combined tension and shear

    Science.gov (United States)

    Butcher, C.; Chen, Z. T.

    2009-03-01

    The influence of shear loading on damage development in Gurson-based models has long been neglected resulting in inadequate fracture strain predictions at low triaxiality where shear effects become significant. The plastic limit-load fracture criterion used in advanced Gurson models neglects the influence of shear loading and overestimates the fracture strain and porosity at low triaxiality. In this paper, we extend the recently proposed shear damage model of Xue [1] to provide a stronger physical foundation by removing the simplifying assumptions. Then we directly modify the plastic limit-load fracture criterion by coupling with the extended shear damage model to account for shear weakening and failure of the intervoid ligament in void coalescence. We apply the modified plastic limit-load criterion to predict the necking of sheet tensile specimens and find very good agreement with the available experimental results.

  1. Shear Strengthening of Reinforced Concrete Beams Using GFRP Wraps

    Directory of Open Access Journals (Sweden)

    M. A. A. Saafan

    2006-01-01

    Full Text Available The objective of the experimental work described in this paper was to investigate the efficiency of GFRP composites in strengthening simply supported reinforced concrete beams designed with insufficient shear capacity. Using the hand lay-up technique, successive layers of a woven fiberglass fabric were bonded along the shear span to increase the shear capacity and to avoid catastrophic premature failure modes. The strengthened beams were fabricated with no web reinforcement to explore the efficiency of the proposed strengthening technique using the results of control beams with closed stirrups as a  web reinforcement. The test results of 18 beams are reported, addressing the influence of different shear strengthening schemes and variable longitudinal reinforcement ratios on the structural behavior. The results indicated that significant increases in the shear strength and improvements in the overall structural behavior of beams with insufficient shear capacity could be achieved by proper application of GFRP wraps.

  2. Quantification in non-invasive cardiac imaging: CT and MR

    OpenAIRE

    Rossi, Alexia

    2013-01-01

    markdownabstract__Abstract__ The diagnosis and management of cardiac disease require a precise assessment of morphological and functional cardiac parameters. This thesis is divided in three parts. Part I emphasizes the role of cardiac computed tomography (CT) in the diagnosis of patients with ischemic heart disease. Part 2 describes the role of cardiac magnetic resonance (CMR) and cardiac CT in the diagnosis, interventional planning, and follow-up of patients with aortic valve stenosis. Part ...

  3. Evaluating the Cancer Therapeutic Potential of Cardiac Glycosides

    OpenAIRE

    José Manuel Calderón-Montaño; Estefanía Burgos-Morón; Manuel Luis Orta; Dolores Maldonado-Navas; Irene García-Domínguez; Miguel López-Lázaro

    2014-01-01

    Cardiac glycosides, also known as cardiotonic steroids, are a group of natural products that share a steroid-like structure with an unsaturated lactone ring and the ability to induce cardiotonic effects mediated by a selective inhibition of the Na+/K+-ATPase. Cardiac glycosides have been used for many years in the treatment of cardiac congestion and some types of cardiac arrhythmias. Recent data suggest that cardiac glycosides may also be useful in the treatment of cancer. These compounds typ...

  4. Thallium cardiac stressing by esophageal pacing

    Energy Technology Data Exchange (ETDEWEB)

    Allen, M.L.; Vacek, J.L.; Preston, D.F.; Robinson, R.G.; Feldkamp, M.J. (Univ. of Kansas Medical Center, Kansas City (USA))

    1989-09-01

    Forty-three patients were examined with the transesophageal pacing method of cardiac stressing and thallium imaging. Transesophageal cardiac pacing, using a pill electrode or a permanent pacemaker lead, is a safe alternative for patients who are physically unable to exercise. Prior studies suggest that transvenous right atrial pacing with thallium injection is equivalent to physical exercise thallium studies in the detection of coronary artery disease. The esophageal pacing bipolar electrode similarly increases heart rate without the necessity of transvenous pacing or fluoroscopy and without the adverse side effects often seen when using pharmacologic stressing agents (i.e., dipyridamole). The results compare well with cardiac catheterization, echocardiographic, and electrocardiographic results. Cardiac paced stress testing requires no sedation, is performed on an out-patient basis, and causes little if any discomfort for the patient.

  5. National Cardiac Device Surveillance Program Database

    Data.gov (United States)

    Department of Veterans Affairs — The National Cardiac Device Surveillance Program Database supports the Eastern Pacemaker Surveillance Center (EPSC) staff in its function of monitoring some 11,000...

  6. Cardiac sympathetic neuronal imaging using PET

    Energy Technology Data Exchange (ETDEWEB)

    Lautamaeki, Riikka; Tipre, Dnyanesh [Johns Hopkins University, Division of Nuclear Medicine, Russell H. Morgan Department of Radiology and Radiological Science, Baltimore, MD (United States); Bengel, Frank M. [Johns Hopkins University, Division of Nuclear Medicine, Russell H. Morgan Department of Radiology and Radiological Science, Baltimore, MD (United States); Cardiovascular Nuclear Medicine, Baltimore, MD (United States)

    2007-06-15

    Balance of the autonomic nervous system is essential for adequate cardiac performance, and alterations seem to play a key role in the development and progression of various cardiac diseases. PET imaging of the cardiac autonomic nervous system has advanced extensively in recent years, and multiple pre- and postsynaptic tracers have been introduced. The high spatial and temporal resolution of PET enables noninvasive quantification of neurophysiologic processes at the tissue level. Ligands for catecholamine receptors, along with radiolabeled catecholamines and catecholamine analogs, have been applied to determine involvement of sympathetic dysinnervation at different stages of heart diseases such as ischemia, heart failure, and arrhythmia. This review summarizes the recent findings in neurocardiological PET imaging. Experimental studies with several radioligands and clinical findings in cardiac dysautonomias are discussed. (orig.)

  7. Cardiac Computed Tomography (Multidetector CT, or MDCT)

    Science.gov (United States)

    ... Blood Pressure Tools & Resources Stroke More Cardiac Computed Tomography (Multidetector CT, or MDCT) Updated:Sep 3,2015 What is Computerized Tomography (CT)? CT is a noninvasive test that uses ...

  8. Cardiac assessment of African hedgehogs (Atelerix albiventris).

    Science.gov (United States)

    Black, Peter A; Marshall, Cecilia; Seyfried, Alice W; Bartin, Anne M

    2011-03-01

    Cardiomyopathy is a common finding in captive African hedgehogs (Atelerix albiventris) at postmortem exam. To date, treatment attempts have been mostly empirical and unrewarding. The objective of this study was to determine reference cardiac values for captive African hedgehogs based on echocardiogram, electrocardiogram (ECG), and radiographs. Adult African hedgehogs with no clinical signs of cardiac disease (n = 13) were selected. Each animal was anesthetized with isoflurane via facemask and an echocardiogram, ECG, and radiographs were performed. Standard measurements were taken and the descriptive statistics performed. Values were comparable to limited data available in other hedgehog species and other similar-sized exotic species. Two animals were removed from consideration of reference values due to valvular defects that were considered significant. These data are the first establishing cardiac parameters in normal African hedgehogs using radiographic cardiac measurement, echocardiogram, and ECG. Evaluating animals with possible cardiomyopathy may allow for earlier diagnosis and more successful treatment. PMID:22946370

  9. Chronic cough following cardiac transplantation: vagal Mitempfindung?

    OpenAIRE

    Hammond, R R; Ebers, G C

    1992-01-01

    Since operation a cardiac transplant recipient has suffered from chronic, non-productive but intense coughing spells triggered by stimulation of the right external ear. This demonstrates the unusual phenomenon of acquired aberrant sensory referral.

  10. MicroRNAs in cardiac arrhythmia

    DEFF Research Database (Denmark)

    Hedley, Paula L; Carlsen, Anting L; Christiansen, Kasper M;

    2014-01-01

    Long QT syndrome (LQTS) is a genetic cardiac condition associated with prolonged ventricular repolarization, primarily a result of perturbations in cardiac ion channels, which predisposes individuals to life-threatening arrhythmias. Using DNA screening and sequencing methods, over 700 different...... LQTS-causing mutations have been identified in 13 genes worldwide. Despite this, the genetic cause of 30-50% of LQTS is presently unknown. MicroRNAs (miRNAs) are small (∼ 22 nucleotides) noncoding RNAs which post-transcriptionally regulate gene expression by binding complementary sequences within...... cardiovascular diseases. MiR-1 and MiR-133A are the most abundant miRNAs in the heart and have both been reported to regulate cardiac ion channels. We hypothesized that, as a consequence of their role in regulating cardiac ion channels, genetic variation in the genes which encode MiR-1 and MiR-133A might explain...

  11. Automated Segmentation of Cardiac Magnetic Resonance Images

    DEFF Research Database (Denmark)

    Stegmann, Mikkel Bille; Nilsson, Jens Chr.; Grønning, Bjørn A.

    2001-01-01

    Magnetic resonance imaging (MRI) has been shown to be an accurate and precise technique to assess cardiac volumes and function in a non-invasive manner and is generally considered to be the current gold-standard for cardiac imaging [1]. Measurement of ventricular volumes, muscle mass and function...... is based on determination of the left-ventricular endocardial and epicardial borders. Since manual border detection is laborious, automated segmentation is highly desirable as a fast, objective and reproducible alternative. Automated segmentation will thus enhance comparability between and within cardiac...... studies and increase accuracy by allowing acquisition of thinner MRI-slices. This abstract demonstrates that statistical models of shape and appearance, namely the deformable models: Active Appearance Models, can successfully segment cardiac MRIs....

  12. Nanomaterials for Cardiac Tissue Engineering Application

    Institute of Scientific and Technical Information of China (English)

    Yachen Zhang; Yong Tang; Ying Wang; Liying Zhang

    2011-01-01

    In recent years, the emerging cardiac tissue engineering provides a new therapeutic method for heart diseases. And in the tissue engineering, the scaffold material which can mimic the structure of the extracellular matrix properly is a key factor. The rapid expansion of nano-scaffolds during the past ten years has led to new perspectives and advances in biomedical research as well as in clinical practice. Here we search articles published in recent years extensively on cardiac tissue engineering scaffold materials and nanotechnology. And we review the traditional scaffold materials and the advances of the nano-scaffolds in cardiac tissue engineering. A thorough understanding of the nano-scaffolds would enable us to better exploit technologies to research the ideal scaffold material, and promote the cardiac tissue engineering using in the clinical practice as soon as possible.

  13. Unveiling nonischemic cardiomyopathies with cardiac magnetic resonance.

    Science.gov (United States)

    Aggarwal, Niti R; Peterson, Tyler J; Young, Phillip M; Araoz, Philip A; Glockner, James; Mankad, Sunil V; Williamson, Eric E

    2014-02-01

    Cardiomyopathy is defined as a heterogeneous group of myocardial disorders with mechanical or electrical dysfunction. Identification of the etiology is important for accurate diagnosis, treatment and prognosis, but continues to be challenging. The ability of cardiac MRI to non-invasively obtain 3D-images of unparalleled resolution without radiation exposure and to provide tissue characterization gives it a distinct advantage over any other diagnostic tool used for evaluation of cardiomyopathies. Cardiac MRI can accurately visualize cardiac morphology and function and also help identify myocardial edema, infiltration and fibrosis. It has emerged as an important diagnostic and prognostic tool in tertiary care centers for work up of patients with non-ischemic cardiomyopathies. This review covers the role of cardiac MRI in evaluation of nonischemic cardiomyopathies, particularly in the context of other diagnostic and prognostic imaging modalities. PMID:24417294

  14. Acute kidney injury after pediatric cardiac surgery

    OpenAIRE

    Sarvesh Pal Singh

    2016-01-01

    Acute kidney injury is a common complication after pediatric cardiac surgery. The definition, staging, risk factors, biomarkers and management of acute kidney injury in children is detailed in the following review article.

  15. Incidental Cardiac Findings on Thoracic Imaging.

    LENUS (Irish Health Repository)

    Kok, Hong Kuan

    2013-02-07

    The cardiac structures are well seen on nongated thoracic computed tomography studies in the investigation and follow-up of cardiopulmonary disease. A wide variety of findings can be incidentally picked up on careful evaluation of the pericardium, cardiac chambers, valves, and great vessels. Some of these findings may represent benign variants, whereas others may have more profound clinical importance. Furthermore, the expansion of interventional and surgical practice has led to the development and placement of new cardiac stents, implantable pacemaker devices, and prosthetic valves with which the practicing radiologist should be familiar. We present a collection of common incidental cardiac findings that can be readily identified on thoracic computed tomography studies and briefly discuss their clinical relevance.

  16. Leadless Cardiac Pacemakers: Back to the Future.

    Science.gov (United States)

    Miller, Marc A; Neuzil, Petr; Dukkipati, Srinivas R; Reddy, Vivek Y

    2015-09-01

    Despite significant advances in battery longevity, lead performance, and programming features since the first implanted permanent pacemaker was developed, the basic design of cardiac pacemakers has remained relatively unchanged over the past 50 years. Because of inherent limitations in their design, conventional (transvenous) pacemakers are prone to multiple potential short- and long-term complications. Accordingly, there has been intense interest in a system able to provide the symptomatic and potentially lifesaving therapies of cardiac pacemakers while mitigating many of the risks associated with their weakest link-the transvenous lead. Leadless cardiac pacing represents the future of cardiac pacing systems, similar to the transition that occurred from the use of epicardial pacing systems to the familiar transvenous systems of today. This review summarizes the current evidence and potential benefits of leadless pacing systems, which are either commercially available (in Europe) or under clinical investigation. PMID:26337997

  17. Nonbiopsy Diagnosis of Cardiac Transthyretin Amyloidosis

    NARCIS (Netherlands)

    Gillmore, Julian D.; Maurer, Mathew S.; Falk, Rodney H.; Merlini, Giampaolo; Damy, Thibaud; Dispenzieri, Angela; Wechalekar, Ashutosh D.; Berk, John L.; Quarta, Candida C.; Grogan, Martha; Lachmann, Helen J.; Bokhari, Sabahat; Castano, Adam; Dorbala, Sharmila; Johnson, Geoff B.; Glaudemans, Andor W. J. M.; Rezk, Tamer; Fontana, Marianna; Palladini, Giovanni; Milani, Paolo; Guidalotti, Pierluigi L.; Flatman, Katarina; Lane, Thirusha; Vonberg, Frederick W.; Whelan, Carol J.; Moon, James C.; Ruberg, Frederick L.; Miller, Edward J.; Hutt, David F.; Hazenberg, Bouke P.; Rapezzi, Claudio; Hawkins, Philip N.

    2016-01-01

    Background-Cardiac transthyretin (ATTR) amyloidosis is a progressive and fatal cardiomyopathy for which several promising therapies are in development. The diagnosis is frequently delayed or missed because of the limited specificity of echocardiography and the traditional requirement for histologica

  18. Cardiac regeneration: different cells same goal

    NARCIS (Netherlands)

    P. Barnett; M.J.B. van den Hoff

    2011-01-01

    Cardiovascular diseases are the leading cause of mortality, morbidity, hospitalization and impaired quality of life. In most, if not all, pathologic cardiac ischemia ensues triggering a succession of events leading to massive death of cardiomyocytes, fibroblast and extracellular matrix accumulation,

  19. Development of Shear Connections in Steelconcrete Composite Structures

    OpenAIRE

    Biegus Antoni; Lorenc Wojciech

    2015-01-01

    Different types of shear connectors and modelling techniques are presented. Basic research conducted or presented after year 2000 is taken into consideration, following the idea of concrete dowel implemented in the form of perfobond strip at the beginning of the 1980s by F. Leonhardt. The latest research in the field of continuous shear connectors applied in bridges is highlited with special focus at the composite dowel shear connection, as it seems to be the most modern solution being strong...

  20. Buckling and failure characteristics of graphite-polyimide shear panels

    Science.gov (United States)

    Shuart, M. J.; Hagaman, J. A.

    1983-01-01

    The buckling and failure characteristics of unstiffened, blade stiffened, and hat stiffened graphite-polyimide shear panels are described. The picture frame shear test is used to obtain shear stress-strain data at room temperature and at 316 deg C. The experimental results are compared with a linear buckling analysis, and the specimen failure modes are described. The effect of the 316 deg C test temperature on panel behavior are discussed.

  1. Crystallization of amorphous silicon induced by mechanical shear deformations

    OpenAIRE

    Kerrache, Ali; Mousseau, Normand; Lewis, Laurent J.

    2011-01-01

    We have investigated the response of amorphous silicon (a-Si), in particular crystallization, to external mechanical shear deformations using classical molecular dynamics (MD) simulations and the empirical Environment Dependent Inter-atomic Potential (EDIP) [Phys. Rev. B 56, 8542 (1997)]. In agreement with previous results we find that, at low shear velocity and low temperature, shear deformations increase disorder and defect density. At high temperatures, however, the deformations are found ...

  2. Segregation by thermal diffusion in granular shear flows

    OpenAIRE

    Garzó, Vicente; Reyes, Francisco Vega

    2010-01-01

    Segregation by thermal diffusion of an intruder immersed in a sheared granular gas is analyzed from the (inelastic) Boltzmann equation. Segregation is induced by the presence of a temperature gradient orthogonal to the shear flow plane and parallel to gravity. We show that, like in analogous systems without shear, the segregation criterion yields a transition between upwards segregation and downwards segregation. The form of the phase diagrams is illustrated in detail showing that they depend...

  3. Rheological properties for inelastic Maxwell mixtures under shear flow

    OpenAIRE

    Garzo, Vicente; Trizac, Emmanuel

    2009-01-01

    The Boltzmann equation for inelastic Maxwell models is considered to determine the rheological properties in a granular binary mixture in the simple shear flow state. The transport coefficients (shear viscosity and viscometric functions) are {\\em exactly} evaluated in terms of the coefficients of restitution, the (reduced) shear rate and the parameters of the mixture (particle masses, diameters and concentration). The results show that in general, for a given value of the coefficients of rest...

  4. Low-n shear Alfven spectra in axisymmetric toroidal plasmas

    International Nuclear Information System (INIS)

    In toroidal plasmas, the toroidal magnetic field is nonuniform over a magnetic surface and causes coupling of different poloidal harmonics. It is shown both analytically and numerically that the toroidicity not only breaks up the shear Alfven continuous spectrum, but also creates new, discrete, toroidicity-induced shear Alfven eigenmodes with frequencies inside the continuum gaps. Potential applications of the low-n toroidicity-induced shear Alfven eigenmodes on plasma heating and instabilities are addressed. 17 refs., 4 figs

  5. Fractal Description of the Shearing-Surface of Tools

    Institute of Scientific and Technical Information of China (English)

    WANG Bing-cheng; JING Chang; REN Zhao-hui; REN Li-yi

    2004-01-01

    In this paper, the basic methods are introduced to calculate the fractal dimensions of the shearing surface of some tools. The fractal dimension of the shearing surface of experimental sampling is obtained and the fractal characteristics are also discussed. We can apply the fractal method to identify types of tools used by burglars and to do the job of individual recognition. New theories and methods are provided to measure and process the shearing surface profile of tools.

  6. Shear-induced assembly of lambda-phage DNA.

    OpenAIRE

    Haber, C.; Wirtz, D

    2000-01-01

    Recombinant DNA technology, which is based on the assembly of DNA fragments, forms the backbone of biological and biomedical research. Here we demonstrate that a uniform shear flow can induce and control the assembly of lambda-phage DNA molecules: increasing shear rates form integral DNA multimers of increasing molecular weight. Spontaneous assembly and grouping of end-blunted lambda-phage DNA molecules are negligible. It is suggested that shear-induced DNA assembly is caused by increasing th...

  7. On the nature of shear thinning in nanoscopically confined films

    OpenAIRE

    Manias, E; Bitsanis, I.; Hadziioannou, G.; Brinke, G. ten

    1996-01-01

    Non-Equilibrium Molecular Dynamics (NEMD) computer simulations were employed to study films in nanometer confinements under shear. Focusing on the response of the viscosity, we found that nearly all the shear thinning takes place inside the solid-oligomer interface and that the adsorbed layers are more viscous than the middle part of the films. Moreover, the shear thinning inside the interfacial area is determined by the wall affinity and is largely insensitive to changes of the film thicknes...

  8. Seismic damage analysis including inelastic shear-flexure interaction

    OpenAIRE

    Mergos, P.E.; Kappos, A. J.

    2010-01-01

    The paper focusses on seismic damage analysis of reinforced concrete (R/C) members, accounting for shear-flexure interaction in the inelastic range. A finite element of the beam-column type for the seismic analysis of R/C structures is first briefly described. The analytical model consists of two distributed flexibility sub-elements which interact throughout the analysis to simulate inelastic flexural and shear response. The finite element accounts for shear strength degradation with inelasti...

  9. On the route to shear jamming, are fragile states real?

    OpenAIRE

    Zhang, Ling; Zheng, Jie; Jie ZHANG

    2015-01-01

    Starting from an unjammed initial state, applying shear to a granular material of a fixed packing fraction below $\\phi_J$, i.e. the isotropic jamming density of frictionless spheres can produce shear jamming states, as have been discovered recently. In addition, it has also been discovered that the system will first experience a bulk fragile state before evolving into a shear jammed state. Due to the existence of friction between the system and the third dimension in the previous studies, it ...

  10. Shear induced electrical behaviour of conductive polymer composites

    OpenAIRE

    Stary, Zdenek; Krückel, Johannes; Schubert, Dirk W.

    2013-01-01

    The time-dependent electrical resistance of polymethylmethacrylate containing carbon black was measured under oscillatory shear in the molten state. The electrical signal was oscillating exactly at the doubled frequency of the oscillatory shear deformation. Moreover, the experimental results gave a hint to the development of conductive structures in polymer melts under shear deformation. It was shown that the flow induced destruction of conductive paths dominates over the flow induced build-u...

  11. Inherent Shear-Dilatation Coexistence in Metallic Glass

    Institute of Scientific and Technical Information of China (English)

    JIANG Min-Qiang; JIANG Si-Yue; DAI Lan-Hong

    2009-01-01

    Shear deformation can induce normal stress or hydrostatic stress in metallic glasses [Nature Mater. 2 (2003) 449, Intermetallics 14 (2006) 1033]. We perform the bulk deformation of three-dimensional Cu46Zr54 metallic glass (MG) and Cu single crystal model systems using molecular dynamics simulation. The results indicate that hydrostatic stress can incur shear stress in MG, but not in crystal. The resultant pronounced asymmetry between tension and compression originates from this inherent shear-dilatation coexistence in MG.

  12. Time-dependent rheological behavior of natural polysaccharide xanthan gum solutions in interrupted shear and step-incremental/reductional shear flow fields

    Science.gov (United States)

    Lee, Ji-Seok; Song, Ki-Won

    2015-11-01

    The objective of the present study is to systematically elucidate the time-dependent rheological behavior of concentrated xanthan gum systems in complicated step-shear flow fields. Using a strain-controlled rheometer (ARES), step-shear flow behaviors of a concentrated xanthan gum model solution have been experimentally investigated in interrupted shear flow fields with a various combination of different shear rates, shearing times and rest times, and step-incremental and step-reductional shear flow fields with various shearing times. The main findings obtained from this study are summarized as follows. (i) In interrupted shear flow fields, the shear stress is sharply increased until reaching the maximum stress at an initial stage of shearing times, and then a stress decay towards a steady state is observed as the shearing time is increased in both start-up shear flow fields. The shear stress is suddenly decreased immediately after the imposed shear rate is stopped, and then slowly decayed during the period of a rest time. (ii) As an increase in rest time, the difference in the maximum stress values between the two start-up shear flow fields is decreased whereas the shearing time exerts a slight influence on this behavior. (iii) In step-incremental shear flow fields, after passing through the maximum stress, structural destruction causes a stress decay behavior towards a steady state as an increase in shearing time in each step shear flow region. The time needed to reach the maximum stress value is shortened as an increase in step-increased shear rate. (iv) In step-reductional shear flow fields, after passing through the minimum stress, structural recovery induces a stress growth behavior towards an equilibrium state as an increase in shearing time in each step shear flow region. The time needed to reach the minimum stress value is lengthened as a decrease in step-decreased shear rate.

  13. Nanomaterials for Cardiac Myocyte Tissue Engineering

    OpenAIRE

    Rodolfo Amezcua; Ajay Shirolkar; Carolyn Fraze; David A. Stout

    2016-01-01

    Since their synthesizing introduction to the research community, nanomaterials have infiltrated almost every corner of science and engineering. Over the last decade, one such field has begun to look at using nanomaterials for beneficial applications in tissue engineering, specifically, cardiac tissue engineering. During a myocardial infarction, part of the cardiac muscle, or myocardium, is deprived of blood. Therefore, the lack of oxygen destroys cardiomyocytes, leaving dead tissue and possib...

  14. Haemochromatosis presenting as congestive cardiac failure.

    OpenAIRE

    Porter, J; Cary, N; Schofield, P

    1995-01-01

    A 24 year old man with congestive cardiac failure was found to have grossly increased transferrin saturations, raised serum ferritin, and an iron-laden myocardium on biopsy. Initial treatment with the iron chelator desferrioxamine was replaced by weekly venesection. He was placed on the cardiac transplant list because of severe left ventricular dysfunction but was later removed because his symptoms and function improved. He remains well with few symptoms and is maintained on regular venesecti...

  15. Mortality and Embolic Potential of Cardiac Tumors

    OpenAIRE

    Ricardo Ribeiro Dias; Fábio Fernandes; Félix José Alvarez Ramires; Charles Mady; Cícero Piva de Albuquerque; Fábio Biscegli Jatene

    2014-01-01

    Background: Cardiac tumors are rare, mostly benign with high embolic potential. Objectives: To correlate the histological type of cardiac masses with their embolic potential, implantation site and long term follow up in patients undergoing surgery. Methods: Between January 1986 and December 2011, we retrospectively analyzed 185 consecutive patients who underwent excision of intracardiac mass (119 females, mean age 48±20 years). In 145 patients, the left atrium was the origin site. 72% wer...

  16. Mitochondrial Protein Dynamics in Cardiac Remodeling

    OpenAIRE

    Lau, Edward

    2014-01-01

    The cardiac mitochondrial proteome contains ~1,500 distinct proteins that carry out necessary metabolic and energetic processes in the heart. To sustain cardiac function, the mitochondrial proteome must be maintained in constant renewal, or turnover, especially under stress conditions. Disruptions of protein turnover can lead to protein damage and proteotoxicity, a hallmark of many heart disease etiologies. Current quantitative proteomics experiments largely focus on the measurement of the st...

  17. MANAGEMENT OF ALLOSENSITIZED CARDIAC TRANSPLANT CANDIDATES

    OpenAIRE

    Velez, Mauricio; Johnson, Maryl R.

    2009-01-01

    Cardiac transplantation remains the best treatment in advanced heart failure patients with a high risk of death. However, an inadequate supply of donor hearts decreases the likelihood of transplantation for many patients. Ventricular assist devices (VAD) are being increasingly used as a bridge to transplant in patients who may not survive long enough to receive a heart. This expansion in VAD use has been associated with increasing rates of allosensitization in cardiac transplant candidates. A...

  18. Laparoscopic cholecystectomy in a cardiac transplant recipient

    OpenAIRE

    Pandya, Seema R.; Saloni Paranjape

    2014-01-01

    An increasing number of cardiac transplants are being carried out around the world. With increasing longevity, these patients present a unique challenge to non-transplant anesthesiologists for a variety of transplant related or incidental surgeries. The general considerations related to a cardiac transplant recipient are the physiological and pharmacological problems of allograft denervation, the side-effects of immunosuppression, the risk of infection and the potential for rejection. A thoro...

  19. Sexual Dysfunction before and after Cardiac Rehabilitation

    OpenAIRE

    Jörg Schumann; Zellweger, Michael J.; Marcello Di Valentino; Simone Piazzalonga; Andreas Hoffmann

    2010-01-01

    Background. The aim of this study was to assess sexual function before and after cardiac rehabilitation in relation to medical variables. Methods. Analysis of patients participating in a 12-week exercise-based outpatient cardiac rehabilitation program (OCR) between April 1999 and December 2007. Exercise capacity (ExC) and quality of life including sexual function were assessed before and after OCR. Results. Complete data were available in 896 male patients. No sexual activity at all was indic...

  20. Preoperative respiratory physical therapy in cardiac surgery

    OpenAIRE

    Hulzebos, H.J.

    2006-01-01

    Cardiac surgery is one of the most common surgical procedures and accounts for more resources expended in cardiovascular medicine than any other single procedure. Because cardiac surgery involves sternal incision and cardiopulmonary bypass, patients usually have a restricted respiratory function in the postoperative period. Moreover, anesthesia and analgesia affect respiratory function during and after the surgical intervention, causing changes in lung volume, diaphragmatic dysfunction, respi...

  1. Acute leukaemoid reaction following cardiac surgery

    Directory of Open Access Journals (Sweden)

    Webb Stephen T

    2007-01-01

    Full Text Available Abstract Chronic myelomonocytic leukaemia is an atypical myeloproliferative disorder with a natural history of progression to acute myeloid leukaemia, a complex and poorly understood response by the bone marrow to stress. Cardiac surgery activates many inflammatory cascades and may precipitate a systemic inflammatory response syndrome. We present a case of undiagnosed chronic myelomonocytic leukaemia who developed rapidly fatal multi-organ dysfunction following cardiac surgery due to an acute leukaemoid reaction.

  2. Remote monitoring of cardiac implantable electronic devices

    OpenAIRE

    Lappegård, Knut Tore

    2015-01-01

    Seminario desarrollado en la Segunda Conferencia Internacional de Comunicación en Salud, celebrada el 23 de octubre de 2015 en la Universidad Carlos III de Madrid Cardiac implantable electronic devices (CIEDs) are used with increasing frequency for the diagnosis and treatment of cardiac arrhythmias. In Europe, a total number of 550,000 pacemakers and 180,000 defibrillators were implanted in 2014. Follow-up of these patients is a large challenge to the health system and requires a substanti...

  3. Mechanical Thrombectomy for Stroke After Cardiac Surgery.

    Science.gov (United States)

    Madeira, Márcio; Martins, Catarina; Koukoulis, Giovanna; Marques, Marta; Reis, João; Abecassis, Miguel

    2016-08-01

    Stroke after cardiac surgery remains a devastating complication and its treatment options are limited. Systemic fibrinolysis is a relative contraindication, because it raises the risk of systemic hemorrhage. Endovascular therapy, mechanical thrombectomy, and intra-arterial fibrinolysis have emerged as safer options. We present three patients who developed strokes following cardiac surgery who underwent successful mechanical thrombectomy and review the literature on this subject. doi: 10.1111/jocs.12776 (J Card Surg 2016;31:517-520). PMID:27282492

  4. Mitochondria in cardiac hypertrophy and heart failure

    OpenAIRE

    Rosca, Mariana G.; Tandler, Bernard; Hoppel, Charles L.

    2012-01-01

    Heart failure (HF) frequently is the unfavorable outcome of pathological heart hypertrophy. In contrast to physiological cardiac hypertrophy, which occurs in response to exercise and leads to full adaptation of contractility to the increased wall stress, pathological hypertrophy occurs in response to volume or pressure overload, ultimately leading to contractile dysfunction and HF. Because cardiac hypertrophy impairs the relationship between ATP demand and production, mitochondrial bioenerget...

  5. Stem cell sources for cardiac regeneration.

    Science.gov (United States)

    Roccio, M; Goumans, M J; Sluijter, J P G; Doevendans, P A

    2008-03-01

    Cell-based cardiac repair has the ambitious aim to replace the malfunctioning cardiac muscle developed after myocardial infarction, with new contractile cardiomyocytes and vessels. Different stem cell populations have been intensively studied in the last decade as a potential source of new cardiomyocytes to ameliorate the injured myocardium, compensate for the loss of ventricular mass and contractility and eventually restore cardiac function. An array of cell types has been explored in this respect, including skeletal muscle, bone marrow derived stem cells, embryonic stem cells (ESC) and more recently cardiac progenitor cells. The best-studied cell types are mouse and human ESC cells, which have undisputedly been demonstrated to differentiate into cardiomyocyte and vascular lineages and have been of great help to understand the differentiation process of pluripotent cells. However, due to their immunogenicity, risk of tumor development and the ethical challenge arising from their embryonic origin, they do not provide a suitable cell source for a regenerative therapy approach. A better option, overcoming ethical and allogenicity problems, seems to be provided by bone marrow derived cells and by the recently identified cardiac precursors. This report will overview current knowledge on these different cell types and their application in cardiac regeneration and address issues like implementation of delivery methods, including tissue engineering approaches that need to be developed alongside.

  6. Surface Electrocardiogram Predictors of Sudden Cardiac Arrest

    Science.gov (United States)

    Abdelghani, Samy A.; Rosenthal, Todd M.; Morin, Daniel P.

    2016-01-01

    Background: Heart disease is a major cause of death in industrialized nations, with approximately 50% of these deaths attributable to sudden cardiac arrest. If patients at high risk for sudden cardiac arrest can be identified, their odds of surviving fatal arrhythmias can be significantly improved through prophylactic implantable cardioverter defibrillator placement. This review summarizes the current knowledge pertaining to surface electrocardiogram (ECG) predictors of sudden cardiac arrest. Methods: We conducted a literature review focused on methods of predicting sudden cardiac arrest through noninvasive electrocardiographic testing. Results: Several electrocardiographic-based methods of risk stratification of sudden cardiac arrest have been studied, including QT prolongation, QRS duration, fragmented QRS complexes, early repolarization, Holter monitoring, heart rate variability, heart rate turbulence, signal-averaged ECG, T wave alternans, and T-peak to T-end. These ECG findings have shown variable effectiveness as screening tools. Conclusion: At this time, no individual ECG finding has been found to be able to adequately stratify patients with regard to risk for sudden cardiac arrest. However, one or more of these candidate surface ECG parameters may become useful components of future multifactorial risk stratification calculators. PMID:27660578

  7. Role of Circulating Fibrocytes in Cardiac Fibrosis

    Institute of Scientific and Technical Information of China (English)

    Rong-Jie Lin; Zi-Zhuo Su; Shu-Min Liang; Yu-Yang Chen; Xiao-Rong Shu; Ru-Qiong Nie; Jing-Feng Wang

    2016-01-01

    Objective: It is revealed that circulating fibrocytes are elevated in patients/animals with cardiac fibrosis, and this review aims to provide an introduction to circulating fibrocytes and their role in cardiac fibrosis.Data Sources: This review is based on the data from 1994 to present obtained from PubMed.The search terms were "circulating fibrocytes" and "cardiac fibrosis".Study Selection: Articles and critical reviews, which are related to circulating fibrocytes and cardiac fibrosis, were selected.Results: Circulating fibrocytes, which are derived from hematopoietic stem cells, represent a subset of peripheral blood mononuclear cells exhibiting mixed morphological and molecular characteristics ofhematopoietic and mesenchymal cells (CD34+/CD45+/collagen I+).They can produce extracellular matrix and many cytokines.It is shown that circulating fibrocytes participate in many fibrotic diseases, including cardiac fibrosis.Evidence accumulated in recent years shows that aging individuals and patients with hypertension, heart failure, coronary heart disease, and atrial fibrillation have more circulating fibrocytes in peripheral blood and/or heart tissue, and this elevation of circulating fibrocytes is correlated with the degree of fibrosis in the hearts.Conclusions: Circulating fibrocytes are effector cells in cardiac fibrosis.

  8. Stem cells for cardiac repair: an introduction

    Institute of Scientific and Technical Information of China (English)

    Bastiaan C du Pr(e); Pieter A Doevendans; Linda W van Laake

    2013-01-01

    Cardiovascular disease is a major cause of morbidity and mortality throughout the world. Most cardiovascular diseases, such as ischemic heart disease and cardiomyopathy, are associated with loss of functional cardiomyocytes. Unfortunately, the heart has a limited regenerative capacity and is not able to replace these cardiomyocytes once lost. In recent years, stem cells have been put forward as a potential source for cardiac regeneration. Pre-clinical studies that use stem cell-derived cardiac cells show promising results. The mechanisms, though, are not well understood, results have been variable, sometimes transient in the long term, and often without a mechanistic explanation. There are still several major hurdles to be taken. Stem cell-derived cardiac cells should resemble original cardiac cell types and be able to integrate in the damaged heart. Integration requires administration of stem cell-derived cardiac cells at the right time using the right mode of delivery. Once delivered, transplanted cells need vascularization, electrophysiological coupling with the injured heart, and prevention of immunological rejection. Finally, stem cell therapy needs to be safe, reproducible, and affordable. In this review, we will give an introduction to the principles of stem cell based cardiac repair.

  9. Epigenetic mechanisms in cardiac development and disease

    Institute of Scientific and Technical Information of China (English)

    Marcus Vallaster; Caroline Dacwag Vallaster; Sean M. Wu

    2012-01-01

    During mammalian development,cardiac specification and ultimately lineage commitment to a specific cardiac cell type is accomplished by the action of specific transcription factors (TFs) and their meticulous control on an epigenetic level.In this review,we detail how cardiacspecific TFs function in concert with nucleosome remodeling and histone-modifying enzymes to regulate a diverse network of genes required for processes such as cell growth and proliferation,or epithelial to mesenchymal transition (EMT),for instance.We provide examples of how several cardiac TFs,such as Nkx2.5,WHSC1,Tbx5,and Tbx1,which are associated with developmental and congenital heart defects,are required for the recruitment of histone modifiers,such as Jarid2,p300,and Ash21,and components of ATP-dependent remodeling enzymes like Brg1,Baf60c,and Baf180.Binding of these TFs to their respective sites at cardiac genes coincides with a distinct pattern of histone marks,indicating that the precise regulation of cardiac gene networks is orchestrated by interactions between TFs and epigenetic modifiers.Furthermore,we speculate that an epigenetic signature,comprised of TF occupancy,histone modifications,and overall chromatin organization,is an underlying mechanism that governs cardiac morphogenesis and disease.

  10. Telocytes in cardiac regeneration and repair.

    Science.gov (United States)

    Bei, Yihua; Zhou, Qiulian; Sun, Qi; Xiao, Junjie

    2016-07-01

    Telocytes (TCs) are a novel type of stromal cells reported by Popescu's group in 2010. The unique feature that distinguishes TCs from other "classical" stromal cells is their extremely long and thin telopodes (Tps). As evidenced by electron microscopy, TCs are widely distributed in almost all tissues and organs. TCs contribute to form a three-dimensional interstitial network and play as active regulators in intercellular communication via homocellular/heterocellular junctions or shed vesicles. Interestingly, increasing evidence suggests the potential role of TCs in regenerative medicine. Although the heart retains some limited endogenous regenerative capacity, cardiac regenerative and repair response is however insufficient to make up the loss of cardiomyocytes upon injury. Developing novel strategies to increase cardiomyocyte renewal and repair is of great importance for the treatment of cardiac diseases. In this review, we focus on the role of TCs in cardiac regeneration and repair. We particularly describe the intercellular communication between TCs and cardiomyocytes, stem/progenitor cells, endothelial cells, and fibroblasts. Also, we discuss the current knowledge about TCs in cardiac repair after myocardial injury, as well as their potential roles in cardiac development and aging. TC-based therapy or TC-derived exosome delivery might be used as novel therapeutic strategies to promote cardiac regeneration and repair. PMID:26826525

  11. Development of Shear Connections in Steelconcrete Composite Structures

    Directory of Open Access Journals (Sweden)

    Biegus Antoni

    2015-03-01

    Full Text Available Different types of shear connectors and modelling techniques are presented. Basic research conducted or presented after year 2000 is taken into consideration, following the idea of concrete dowel implemented in the form of perfobond strip at the beginning of the 1980s by F. Leonhardt. The latest research in the field of continuous shear connectors applied in bridges is highlited with special focus at the composite dowel shear connection, as it seems to be the most modern solution being strongly introduced to the industry. Final shape of composite dowel shear connection is presented.

  12. Vibrational shear flow of anisotropic viscoelastic fluid with small amplitudes

    Institute of Scientific and Technical Information of China (English)

    韩式方

    2008-01-01

    Using the constitutive equation of co-rotational derivative type for anisotropic viscoelastic fluid-liquid crystalline(LC),polymer liquids was developed.Two relaxation times are introduced in the equation:λn represents relaxation of the normal-symmetric stress components;λs represents relaxation of the shear-unsymmetric stress components.A vibrational rotating flow in gap between cylinders with small amplitudes is studied for the anisotropic viscoelastic fluid-liquid crystalline polymer.The time-dependent constitutive equation are linearized with respect to parameter of small amplitude.For the normal-symmetric part of stress tensor analytical expression of the shear stress is obtained by the constitutive equation.The complex viscosity,complex shear modulus,dynamic and imaginary viscosities,storage modulus and loss modulus are obtained for the normal-symmetric stress case which are defined by the common shear rate.For the shear-unsymmetric stress part,two shear stresses are obtained thus two complex viscosities and two complex shear modulus(i.e.first and second one) are given by the constitutive equation which are defined by rotating shear rate introduced by author.The dynamic and imaginary viscosities,storage modulus and loss modulus are given for each complex viscosities and complex shear modulus.Using the constituive equation the rotating flow with small amplitudes in gap between two coaxial cylinders is studied.

  13. Notes on shear viscosity bound violation in anisotropic models

    CERN Document Server

    Ge, Xian-Hui

    2015-01-01

    The shear viscosity bound violation in Einstein gravity for anisotropic black branes is discussed, with the aim of constraining the deviation of the shear viscosity-entropy density ratio from the shear viscosity bound using causality and thermodynamics analysis. The results show that no stringent constraints can be imposed. The diffusion bound in anisotropic phases is also studied. Ultimately, it is concluded that shear viscosity violation always occurs in cases where the equation of motion of the metric fluctuations cannot be written in a form identical to that of the minimally coupled massless scalar fields.

  14. Single low shear stress results in atherosclerosis in vivo

    Institute of Scientific and Technical Information of China (English)

    HUANG Rong-guo; LIU Hou-qi; YANG Xiang-qun; ZHANG Chuan-sen; KANG Bin; JIANG Zong-lai

    2005-01-01

    Objective: Whether single low shear stress can result in atherosclerosis without hyperliposis-diet in vivo or not is unknown. Methods: Based on an electromagnetic blood flow meter and a method to determine the pulsatile shear stress from blood flow rate waveform and its software,we developed an in vivo pulsatile blood flow rate-shear stress determining system.The left external carotid arteries of 20 adult New Zealand white rabbits were ligated and the rabbits were fed with a standard chow for 2,4,8 or 12 weeks,then the common carotid arteries of 2 sides in each rabbit were harvested for morphologic test. Results: The ligation reduced pulsatile shear stress of left common carotid significantly,for example,τmean changed from(21.16±7.17) dynes/cm2 to(3.13±2.28) dynes/cm2(p=2.176E-21),meanwhile,the pulsatile shear stress of right common carotid did not change significantly,which lasted more than 12 weeks.Atherosclerotic plaques were found after 8 and 12 weeks in pulsatile-low-shear-stress left(not normal-shear-stress right) common carotid arteries.Conclusion:Single pulsatile low shear stress can result in atherosclerosis.It supports the pulsatile low shear stress(not hypolipidemia) is the key risk factor for atherosclerosis.

  15. Aerosol penetration through a seismically loaded shear wall

    International Nuclear Information System (INIS)

    An experimental study was performed to measure the aerosol penetration through a reinforced concrete shear wall after simulated seismic damage. Static load-cycle testing, to stress levels sufficient to induce visible shear cracking, was used to simulate the earthquake loading. Air permeability tests were performed both before and after the simulated seismic loading damaged the structure. Aerosol penetration measurements were conducted on the cracked shear wall structure using 0.10 μm monodisperse particles. The measured aerosol number penetration through the cracked shear wall was 0.5%. 7 refs

  16. Shear wave elastography with a new reliability indicator

    Science.gov (United States)

    Dong, Yi

    2016-01-01

    Non-invasive methods for liver stiffness assessment have been introduced over recent years. Of these, two main methods for estimating liver fibrosis using ultrasound elastography have become established in clinical practice: shear wave elastography and quasi-static or strain elastography. Shear waves are waves with a motion perpendicular (lateral) to the direction of the generating force. Shear waves travel relatively slowly (between 1 and 10 m/s). The stiffness of the liver tissue can be assessed based on shear wave velocity (the stiffness increases with the speed). The European Federation of Societies for Ultrasound in Medicine and Biology has published Guidelines and Recommendations that describe these technologies and provide recommendations for their clinical use. Most of the data available to date has been published using the Fibroscan (Echosens, France), point shear wave speed measurement using an acoustic radiation force impulse (Siemens, Germany) and 2D shear wave elastography using the Aixplorer (SuperSonic Imagine, France). More recently, also other manufacturers have introduced shear wave elastography technology into the market. A comparison of data obtained using different techniques for shear wave propagation and velocity measurement is of key interest for future studies, recommendations and guidelines. Here, we present a recently introduced shear wave elastography technology from Hitachi and discuss its reproducibility and comparability to the already established technologies. PMID:27679731

  17. Three dimensional simulations of the parallel velocity shear instability

    International Nuclear Information System (INIS)

    The authors have performed fully nonlinear three-dimensional fluid simulations of the electrostatic parallel velocity shear instability as applied to a tokamak edge plasma. In the present study a source terms in the parallel momentum equation drives the sheared parallel flow. Studied are the effects of magnetic shear on the turbulence of the mode and the associated fluctuation levels. The inclusion of the nonlinear polarization drift in the perpendicular dynamics is found to significantly affect the final nonlinear state. Dependence of the anomalous momentum transport on the magnetic shear and the gyroradius parameter, associated with the polarization drift, are presented

  18. Compression Enhanced Shear Yield Stress of Electrorheological Fluid

    Institute of Scientific and Technical Information of China (English)

    ZHANG Min-Liang; TIAN Yu; JIANG Ji-Le; ZHU Xu-Li; MENG Yong-Gang; WEN Shi-Zhu

    2009-01-01

    @@ Shear tests of an electrorheological fluid with pre-applied electric field and compression along the field direction are carried out. The results show that pre-compressions can increase the shear yield stress up to ten times. Under the same external electric field strength, a higher compressive strain corresponds to a larger shear yield stress enhancement but with slight current density decrease, which shows that the particle interaction potentials are not increased by compressions but the compression-induced chain aggregation dominates the shear yield stress improvement. This pre-compression technique might be useful [or developing high performance flexible ER or magnetorheological couplings.

  19. Large-scale direct shear testing of geocell reinforced soil

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The tests on the shear property of geocell reinforced soils were carried out by using large-scale direct shear equipment with shear-box-dimensions of 500 mm×500 mm×400 mm (length×width×height).Three types of specimens,silty gravel soil,geoceli reinforced silty gravel soil and geoceli reinforood cement stabilizing silty gravel soil were used to investigate the shear stress-displacement behavior,the shear strength and the strengthening mechanism of geocell reinforced soils.The comparisons of large-scale shear test with triaxial compression test for the same type of soil were conducted to evaluate the influences of testing method on the shear strength as well.The test results show that the unreinforced soil and geocell reinforced soil give similar nonlinear features on the behavior of shear stress and displacement.The geocell reinforced cement stabilizing soil has a quasi-elastic characteristic in the case of normal stress coming up to 1.0 GPa.The tests with the reinforcement of geocell result in an increase of 244% in cohesion,and the tests with the geocell and the cement stabilization result in an increase of 10 times in cohesion compared with the unreinforced soil.The friction angle does not change markedly.The geocell reinforcement develops a large amount of cohesion on the shear strength of soils.

  20. Analytical large deformation shear strength for bolted rough discontinuous rock

    Institute of Scientific and Technical Information of China (English)

    LIU Bo(刘波); TAO Long-guang(陶龙光); YUE Zhong-qi(岳中琦)

    2004-01-01

    Presented a new analytical model for studying the shear-tensile large deformation behavior near the vicinity of joint interface for bolted rough discontinuous rock, and presented the formulation estimating global shear strength for bolted joints under shearing-tensile loads. The analytical strength curves of bolts contribution on reinforced discontinuous rocks as the function of joint displacements or deformation angle of a bolt at rock joints was obtained. Based on Barton's equation on JRC roughness profiles, the theoretical shearing strength of bolted rough joints was also established. Test results on bolted granite and marble specimen confirm the validity of the analytical approach.