Elastic, optoelectronic and photocatalytic properties of semiconducting CsNbO3: first principles insights.

The cubic phase of CsNbO3 (CNO) perovskite has been hypothesized to investigate the elastic, electronic, photocatalytic, and optical properties for various technological applications using first-principles method. The pressure dependent structural stability has been confirmed from computed elastic constants. Relatively high value of elastic moduli, large hardness and toughness suggested that CNO would be applicable to design industrial machineries. The ductile to brittle transition is noticed at 20 GPa. The indirect bandgap of CNO proclaims its suitability for photovoltaic and IR photodetector applications. The total and partial density of states are calculated to show in evidence the contribution of individual atomic orbitals in the formation of bands. The pressure changes orbitals hybridization which can be substantiated by the change in the bandgap. Strong covalency of the Nb-O bond and antibonding character of Cs-O have been anticipated by the Mulliken population analysis and by the contour maps of electron charge density. The low carrier effective mass and high mobility carriers predict the good electrical conductivity of the material. The calculated values of conduction and valance band edge potential illustrate the excellent water-splitting and environmental pollutants degradation properties of CNO.

Electric field and aging effects of uniaxial ferroelectrics Sr x Ba1-x Nb2O6 probed by Brillouin scattering.

Static and dynamic heterogeneity of disordered system is one of the current topics in materials science. In disordered ferroelectric materials with random fields, dynamic polar nanoregions (PNRs) appear at Burns temperature and freeze into nanodomain state below Curie temperature (T C). This state is very sensitive to external electric field and aging by which it gradually switches into macrodomain state. However, the role of PNRs in such states below T C is still a puzzling issue of materials science. Electric field and aging effects of uniaxial ferroelectric Sr x Ba1-x Nb2O6 (x = 0.40, SBN40) single crystals were studied using Brillouin scattering to clarify the critical nature of PNRs in domain states below T C. On field heating, a broad anomaly in longitudinal acoustic (LA) velocity at low temperature region was due to an incomplete alignment of nanodomains caused by the interaction between PNRs. A sharp anomaly near T C was attributed to the complete switching of nanodomain to macrodomain state owing to the lack of interaction among PNRs. After isothermal aging below T C, the noticeable increase of LA velocity was observed. It was unaffected by cyclic temperature measurements up to T C, and recovered to initial state outside of a narrow temperature range above and below aging temperature.

Role of polar nanoregions with weak random fields in Pb-based perovskite ferroelectrics.

In relaxor ferroelectrics, the role of randomly orientated polar nanoregions (PNRs) with weak random fields (RFs) is one of the most puzzling issues of materials science. The relaxation time of polarization fluctuations of PNRs, which manifests themselves as a central peak (CP) in inelastic light scattering, is the important physical quantity to understand the dynamics of PNRs. Here, the angular and temperature dependences of depolarized and polarized CPs in 0.44Pb(Mg1/3Nb2/3)O3-0.56PbTiO3 single crystals with weak RFs have been studied by Raman and Brillouin scattering, respectively. The CPs observed in Raman scattering show the very clear angular dependence which is consistent with the local tetragonal symmetry. It is different from the well-known local rhombohedral symmetry with strong RFs for Pb(Mg1/3Nb2/3)O3. In Brillouin scattering, depolarized and polarized CPs show two relaxation processes corresponding to transverse and longitudinal fluctuations of PNRs. The remarkable slowing down towards the Curie temperature was observed for transverse fluctuations in local tetragonal symmetry.

The teratogenic effects of imatinib mesylate on rat fetuses.

Imatinib mesylate, a selective tyrosine kinase inhibitor, is the first line treatment against chronic myelogenous leukemia and gastrointestinal stromal tumors. The aim of the present study is to investigate the effects of imatinib mesylate on the pregnant rats and their fetuses. Pregnant rats were divided into three groups; the first group served as a control group. The second and third groups were orally administered imatinib at doses of 36 mg/kg body weight or 54 mg/kg b.wt. on gestation days (SDs) 6 through 13 or SDs 13 through 19, respectively. All animals were sacrificed on the 20th day of gestation. Treatment with imatinib caused a reduction of maternal body weight gain, uterine and placental weights, increased rate of abortion and fetal resorptions. High dose of imatinib caused fetal congenital deformities represented in harelip, contraction of the fore limbs, and paralysis of the hind limbs, exencephaly, encephalocoele and distended abdominal wall, besides occurrence of wavy ribs and absence of other ribs in addition to skeletal growth retardation and lack of ossification of the most skeletal elements. The present work concluded that imatinib is teratogenic when given orally to pregnant rats at 54 mg/kg b.wt. and causes direct maternal or developmental toxicity.

Goldenhar syndrome - a case report.

Goldenhar syndrome is a developmental abnormality of 1st & 2nd branchial arch involving the craniofacial microsomia with ocular & vertebral abnormality. Though most of the cases are sporadic, some familial association is also found in autosomal dominant or recessive manner. Teratogenic effect of some toxic substances may lead to the condition. Ocular abnormalities are epibulbar dermoid, lipodermoid & coloboma. Otic defects are preauricular tags, microtia, anotia & conductive hearing loss. Cardio-pulmonary & genitourinary abnormalities are common associations. Here we have described the case of a 10 years old girl had ocular, auricular & vertebral changes consistent with Goldenhar syndrome, she was managed with multidisciplinary approach and she was symptomatically improved but corrective surgery was planned as schedule of respective department.

Multifocal skeletal tuberculosis in children.

Multifocal bone involvement is though rare but is reported from some countries where tuberculosis is endemic. Here we report a case of three years old boy was admitted in Bangabandhu Sheikh Mujib Medical University, Dhaka with the complaints of difficulty in walking ,low grade fever for six months, swelling over the back, elbow joint, knee joint and upper part of forearm and legs for two months. Family history of tuberculosis was positive. Mantoux test was 18 mm, ESR 85 mm in first hour, chest X-ray reveals right hilar lymphadenopathy, X-ray dorsolumber spine shows wedge shaped deformity in T11, L4 and with paravertebral collection from L2-L4. X-ray of legs, knee joint and forearms show multiple lytic lesions in shaft with periosteal reaction and cortical thickening. Ultrasonograph of whole abdomen shows psoas abscess. Culture of bone marrow aspirate reveals Mycobacterium tuberculosis. Patient was given an anti tubercular regimen with Rifampicin, Isoniazid, Pyrazinamide and Streptomycin for initial two months which to be followed by Rifampicin and Isoniazid for another 10 months.

Ontogeny of human fetal testicular apoptosis during first, second, and third trimesters of pregnancy.

During spermatogenesis in human adults, testicular germ cells proliferate, differentiate, and die by apoptosis. However, little is known about the temporal or spatial nature of this programmed cell death. Such information may be useful for understanding prenatal developmental biology as well as spermatogenesis during adulthood, particularly in the context of germ cell disorders. We undertook this study to determine 1) whether apoptosis occurred in a cell-specific fashion in the germ cell population and the supporting somatic cells; and 2) whether apoptosis varied with gestational age. We examined human fetal testicular tissues obtained from 17 karyotypically and structurally normal fetuses of mothers who underwent spontaneous or induced abortions. Three gestational ages were defined as follows: group A, 12-13 wk gestation (n = 5); group B, 20-22 wk gestation (n = 7); and group C, 37-40 wk gestation (n = 5). Morphology in conjunction with in situ end labeling was used to identify and quantify apoptotic nuclei in fetal gonadal tissues. The results of this study suggest that gonadal apoptosis occurred in germ cells, Sertoli cells, and Leydig cells at all gestational ages. Apoptotic death was highest in the Leydig cells, followed by germ cells and Sertoli cells. There was a significant positive correlation between the apoptosis of germ cells and Sertoli cells (P < 0.01) and a negative correlation between healthy germ cells and Sertoli cells (P < 0.001). There was also a negative correlation between the intratubular cell number and the gestational age. Specifically, the proportion of Sertoli cells decreased with gestational age, although there was no significant change in the germ cell in relation to gestational age. No such relationship was found in the Leydig cell population, all of which reside outside the seminiferous tubules. These results are the first to suggest that fetal testicular apoptosis begins in the first trimester, occurs in the three major cell types, and continues throughout pregnancy. Our data also suggest that in the fetal gonad, germ and Sertoli cell proliferation and death may be controlled by a genetic program distinct from that of the Leydig cells. This information is relevant to the understanding of abnormal spermatogenesis associated with infertility and to germ cell tumors in adult life.

Adenocarcinoma in a continent colonic urinary reservoir.

We report the first case of an adenocarcinoma developing in a continent ileocolonic urinary reservoir. The tumor presented 7 years after the urinary diversion and more than 6 years after the resection of a Dukes' B lesion of the left colon. This report demonstrates that the colonic segment used for urinary diversion retains its malignant potential and that surveillance pouchoscopy should be performed in these patients.

Tunica vaginalis flap for the management of disabling Peyronie's disease: surgical technique, results, and complications.

OBJECTIVES: To discuss the surgical technique for tunica vaginalis flap (TVF) in the management of disabling Peyronie's disease and to evaluate the results and complications. METHODS: Twelve patients underwent the TVF technique. Through a scrotal incision, the most dependent part of the tunica was dissected from the testicle and epididymis. The flap measured at least 4 cm in width and its upper extremity was left attached to the cremasteric muscle. Subsequently, the flap was brought underneath a groin skin bridge to cover the dorsal penile defect. RESULTS: All patients were pain free. Seven patients (58.3%) were able to achieve a satisfactory erection with good vaginal penetration. Five patients (41.7%) were unable to perform sexually secondary to disabling chordee in 3 patients, glanular hypoesthesia in 1 patient, and venous leakage in 1 patient. CONCLUSIONS: TVF is an adequate alternative for correction of distortions of Peyronie's plaque in patients with disabling disease. TVF is at present our first choice in the management of this disease. If penetration is still impaired following recurrent curvature, a Nesbit ventral plication can be used as a secondary procedure.

A trans-reservoir technique for correction of ureterointestinal obstruction in continent urinary diversion.

Following construction of a continent colonic urinary reservoir, 5 uretero-colonic reimplantations became obstructed at the anastomotic site. In these obstructed units previous percutaneous balloon dilation and stent placement had failed and they were subsequently treated by a new reimplantation procedure. Preoperatively, in all ureteral units a percutaneous ureteral stent was inserted to facilitate intraoperative recognition of the ureteral meatus. The technique included a trans-reservoir approach, which allowed easy localization of the stent and anastomotic site. The ureter was dissected free from the intestinal wall and then was mobilized into the lumen of the reservoir. After excision of the scarred distal ureteral segment and spatulation of the proximal healthy ureter, a new direct mucosa-to-mucosa reimplantation was performed leaving the ureter stented. This trans-reservoir approach (occasionally done through an abdominal transverse muscle splitting incision) allows for shortening of the operation, and avoids the time-consuming and more complicated transabdominal lysis of adhesions. All newly reimplanted ureters (100%) showed evidence of adequate ureteral drainage without residual obstruction on followup excretory urography or furosemide renography up to 45 months postoperatively. The trans-reservoir approach for refractory ureteral reimplantation obstruction in continent colonic reservoirs has been associated with no morbidity or mortality, and facilitates the solution to a difficult clinical problem.

Derivation of closed-form expression for the cerebral circulation models.

Loops which occur due to anastomosing vascular networks, such as the circle of Willis, cannot be analyzed analytically using any of the published mathematical models. This paper presents the theoretical basis of a new model of the cerebral circulation loops which occur due to the circle of Willis. Equations of the model are presented and justified. The transmission line equations obtained from the linearized Navier-Stokes equations and the linearized dynamic deformation equations of the arterial wall are solved analytically to compute the hemodynamic parameters. A comparison of simulation result with experimental data shows that the agreement between experimental and theoretical results is satisfactory and more accurate than the numerical solution.

Hydrodynamic simulation of arterial networks which include compliant and rigid bypass grafts.

The conditions required to produce an ideal bypass graft have not yet been determined. In order to understand the hemodynamic impact of bypass grafts on cardiovascular function, a hydrodynamic model for the part of the human arterial network below the renal arteries has been constructed. The results from this physical model were used to validate a digital computer model of the arterial network developed by the authors, that incorporated loops which occur due to bypass grafts. The hydrodynamic model was designed to study the interaction between an arterial stenosis and bypass graft and, in particular, the effect of the compliance of the graft on their function. In the model, similarity laws have been maintained with regard to geometry, viscosity, peripheral resistance, wall elastic properties, pulse shape, and blood flow rate. Measured and predicted pressure and flow wave-forms showed an increase in their mean and peak values for the healthy leg when the bypass graft was closed. There was also a severe pressure drop across the stenosis and a marked decrease in mean and pulsatile flow in the stenotic leg. The stenosis in the hydrodynamic model produced similar behaviour to published results obtained on animals. When the graft was open, the agreement between our experimental and theoretical model was within 5% and both the pressure and flow waves were almost similar at the maxima and minima in both legs. Although the arterial system is non-linear, the non-linearities are shown to be of insignificant magnitude and therefore, we have concluded that the pressure flow relationship is essentially linear. The effect of the degree of compliance of the graft and the 'steal' phenomenon due to the graft have been investigated. It was found that there were no significant differences in the flow delivery between the compliant graft and stiff graft. Also, there was no 'steal'. Thus the compliance of the graft is not a significant factor in promoting its patency.

Urological aspects of hemicorporectomy.

The indications for hemicorporectomy are few. However, with improvements in surgical techniques, anaesthesia and post-operative surgical care, hemicorporectomy may again become a reasonable treatment for certain patients with malignancies of the pelvis. A 2-stage procedure is described which consists of an initial staging celiotomy with urinary and faecal diversions. A non-refluxing colon conduit is the preferred form of urinary diversion. The hemicorporectomy is performed approximately 2 weeks later. No complications were encountered in the post-operative period. Our experience and a review of the literature suggest that hemicorporectomy is a reasonable salvage procedure for certain patients with pelvic malignancies.

Haemodynamic model of a unilateral iliac stenosis with an aortoiliac bypass.

A hydrodynamic model for the part of the human arterial network below the renal arteries has been constructed using specially fabricated distensible tubes and a pulsatile pump to simulate an aortoiliac bypass. The experiments and the computer model indicated that no 'steal' occurred due to the insertion of the bypass graft. Also, the results showed that the length of the stenosis had a non-systematic apparent effect on the physiological significance of the obstruction and that the kinetic power represented only a small percentage of the total power. The total power efficiency of the bypass graft was unaffected by its elastic properties. The experimental investigation also indicated that the pressure drop across the stenosis was considerably larger than the drop calculated using the Poiseuille flow relationship when the stenosis was severe. Therefore, a critical arterial stenosis value cannot be defined as an obstruction of a constant percentage reduction of luminal area. It varies directly with the effective cross-sectional area and inversely with the flow rate. The value of angiography in assessing the functional significance of any arterial stenosis is therefore limited. A better method for evaluation requires quantitative measurements of local blood pressure and blood flow, not only at rest, but also under conditions creating augmented flows due to exercise.

[Continent urinary diversion with the Florida pouch]. / Dérivation urinaire continente à l'aide de la poche de Floride.

Continent urinary diversion (Florida Pouch) has been performed on 151 patients. The surgical technique utilizes a detubularized extended right colon segment, a doubly-plicated segment of ileum and a non-tunneled uretero-intestinal anastomosis. Mortality rate was 1.3%. Early and late complication rates have been minimal. 2.8% were incontinent. No radiographic renal damage has been noted and electrolyte abnormalities have not been a problem. The procedure is highly recommended to those surgeons performing continent urinary diversions.

Theoretical model for assessing haemodynamics in arterial networks which include bypass grafts.

The paper presents a theoretical model which can be used to simulate a vascular network which includes loops and bypass grafts, a feature not possible with previous models. Using the linearised Navier-Stokes equations, the linearised equation of a uniform thick-walled viscoelastic tube, and the equation of continuity, the model is applied to a vascular network which includes a bypass graft. This method represents each segment of an artery or graft by a four-terminal-network whose A, B, C, D parameters are functions of the frequency and physical characteristics of the segment. The model predicts the flow and pressure waveforms at any point in the human arterial network very accurately when compared with data obtained from normal patients, patients with arterial stenoses and for hypertensive patients. The model also gives results which are in close agreement with hydraulic experimental data for the input impedance of systems with bypass loops.