Spin and valley dependent electronic transport in molybdenum disulfide considering up to the second order k-dependent terms: a more exact solution.

Previous studies of electronic transport in molybdenum disulfide (MoS2) are restricted to the first order approximation of the Hamiltonian. In this paper, to obtain more exact results, we firstly present an analytical solution for the Hamiltonian of MoS2 when terms up to the second order (quadratic k-dependent) of the Hamiltonian are taken into account. Our analytical solution is easily applicable to study the transport properties of any single and multi-junctions of MoS2. Then, we propose a device composed of two ferromagnetic barriers with anti-parallel exchange fields and we show that this device has interesting properties such as spin and valley filtering with perfect spin and valley polarizations. Using this device, we can easily switch both spin and valley polarizations to their opposite polarizations only by using electric voltage, which is of fundamental importance in quantum computation and the next generation of logic devices.

Generation of large spin and valley currents in a quantum pump based on molybdenum disulfide.

Generation of large currents, versatile functionality, and simple structures are of fundamental importance in the development of adiabatic quantum pump devices with nanoscale dimensions. In the present study, we propose an adiabatic quantum pump with a simple structure based on molybdenum disulfide, MoS2, to generate large spin and valley resolved currents. We show that pure and fully polarized spin and valley currents can be easily generated by employing two potential gates and using an exchange magnetic field. Unlike graphene and silicene, in order to induce a valley resolved current in MoS2, one does not need to induce strain and apply an electric field. The spin and valley resolved currents are completely coupled together, so that the spin up (down) current is exactly equal to the valley K(K') current. Hence, we can detect the valley resolved current by utilizing more straightforward and simple methods used for the detection of spin resolved currents. The other prominent feature of this proposed pump is its large current, which is two and three orders of magnitude larger than the maximum current of similar pump structures based on silicene and graphene, respectively. The results of this study are promising for the fabrication of quantum pumps with large spin and valley resolved currents, which opens up the possibility of further development of spintronics and valleytronics in 2D nanostructures.

Controllable quantum valley pumping with high current in a silicene junction.

We propose an efficient scheme for the generation and control of both pure and fully polarized valley currents in a silicene-based junction, using adiabatic quantum pumping. The pure and fully polarized valley currents are induced using ferromagnetic proximity and the application of a perpendicular electric field. We show that the valley polarized current can easily be switched from valley K to valley [Formula: see text] and vice versa, simply by reversing the direction of the electric field. Thus, the valley current is controllable electrically. Compared to the methods proposed for generation of valley current by quantum pumping in graphene, which are based on inducing strain on its sheet, our method is very simple and can be easily utilized in practical applications. Also, we show that the magnitude of pumped current in a silicene-based junction is roughly one order of magnitude greater than that of graphene. In addition to valley-related currents, our pump scheme can be used on its own to generate pure and fully polarized spin currents. A comparison between weak and strong adiabatic regimes is given, and the effects of some structural parameters that can significantly affect the pumping currents and polarizations are discussed.

Brain metastasis from gastrointestinal cancers: a systematic review.

BACKGROUND: Brain metastases (BM) from the gastrointestinal tract (GIT) cancers are relatively rare. Despite those advances in diagnostic and treatment options, life expectancy and quality of life in these patients are still poor. In this review, we present an overview of the studies which have been previously performed as well as a comprehensive strategy for the assessment and treatment of BM from the GIT cancers. METHOD: To obtain information on brain metastases from GIT, we performed a systematic review of Medline, EMBASE and the Cochrane Central Register of Controlled Trials (CENTRAL). The collected data included patient characteristics, primary tumor data and brain metastases data. RESULT: In our search of the literature, we found 74 studies between 1980 and 2011, which included 2538 patients with brain metastases originated from gastrointestinal cancer. Analysis of available data showed that among 2538 patients who had brain metastases from GIT, a total of 116 patients (4.57%) had esophageal cancer, 148 patients (5.83%) had gastric cancer, 233 patients (9.18%) had liver cancer, 13 patients had pancreas cancer (0.52%) and 2028 patients (79.90%) had colorectal cancer. The total median age of the patients was 58.9 years. CONCLUSION: Brain metastases have been considered the most common structural neurological complication of systemic cancer. Due to poor prognosis they influence the survival rate as well as the quality of life of the patients. The treatment of cerebral metastasis depends on the patients' situation and the decisions of the treating physicians. The early awareness of a probable metastasis from GI to the brain will have a great influence on treatment outcomes as well as the survival rate and the quality-of-life of the patients.

Colour M-mode superiority in evaluation of improvement in myocardial performance indices following successful percutaneous coronary intervention (PCI).

AIM: This study aimed at evaluating the early effects of successful elective percutaneous coronary intervention (PCI) on systolic and diastolic function. METHODS: We consecutively studied the systolic and diastolic function in 21 patients with stable coronary artery disease (CAD) and left ventricular ejection fraction (LVEF) > 40% before and 48 hours after successful elective PCI. RESULTS: Tei index and systolic indices (LVEF, regional wall motion abnormality score, tricuspid annular plane systolic excursion and peak systolic velocity of mitral and tricuspid annulus) did not change significantly. Among the diastolic indices, only velocity propagation (Vp) improved significantly (from 42.9 ± 10.8 to 51.8 ± 10.7, p-value = 0.008) following PCI. Diastolic velocities, E/A ratio, deceleration time (DT), early and late diastolic velocities of mitral annulus in TDI, pulmonary vein systolic (PVs) and diastolic flow velocity (PVd) did not show significant improvement. CONCLUSION: Propagation velocity of mitral inflow was the earliest index to recover following successful PCI in patients with stable CAD.

Electronic properties of a defected ring-shaped quantum dot array.

In this paper we present a theoretical study of an array of circularly arranged quantum dots with a rectangular Kronig-Penney potential in the presence of a perpendicular magnetic field. For a perfect array of dots, an analytical formula for energy dispersion is derived. We also study the effects of disorder on the energy spectrum and persistent tunneling current. The effects of electron-electron interaction are then investigated for both perfect and defected arrays. We show that the period of Aharonov-Bohm oscillations is fractional for interacting electrons confined in a perfect array. In contrast, for a defected array, we find a critical value of electron-electron interaction strength at which a transition occurs from an integer to a fractional period of Aharonov-Bohm oscillations. Moreover, it is shown that the persistent current of weakly interacting electrons confined in a defected array is greater than the current of non- or strongly interacting electrons.

Inhibitory effect of Crocus sativus (saffron) on histamine (H1) receptors of guinea pig tracheal chains.

The inhibitory effects of aqueous-ethanolic extracts of Crocus sativus (Iridaceae), on histamine (H1) receptors was examined on tracheal chains of guinea pigs. The effects of three concentrations of aqueous-ethanolic extract, 10 nM chlorpheniramine, and saline on histamine (H1) receptors were tested on three groups of guinea pig tracheal chains as follows; incubated trachea with: 1) indomethacin, 2) indomethacin, propranolol, and atropine and 3) indomethacin and propranolol. The EC50 (effective concentration of histamine causing 50% of maximum response) obtained in the presence of chlorpheniramine and all concentrations of the extract in all three groups were significantly greater than those of saline (p<0.05 to p<0.001) except low concentration of the extract in groups 1 and 3. The EC50 obtained in the presence of two higher concentrations of extract in group 2 were greater than group 1 and 3 (p<0.05 to p<0.001). Maximum response obtained in the presence of two higher concentrations of extract in group 2 were greater than those of group 1 and group 3 (p<0.001 for all cases). There were parallel right ward shift in concentration response curves obtained in the presence of only low and medium concentrations of the extract in group 2 compared to the those of saline. These results indicated an inhibitory effect of Crocus sativus at histamine H1 receptors.

The role of an interdisciplinary transplant team on living donation kidney transplantation program.

During the last decades, the disparity between the organ supply and the demand for kidney transplantation in Europe has led to consider living donors as a more acceptable option. In the last 7 years, we have established an interdisciplinary supporting transplant team to increase the rate of living donation. After 2001, the new interdisciplinary transplant team consisted of a transplant surgeon, a nephrologist, a pediatrician, a radiologist, a psychologist, a transplant coordinator, and a transplant nurse. We performed a prospective analysis to examine the effect of implementing this team on our living donation program. Demographic data, the annual number of procedures, the duration of waiting, and the cold ischemia time were evaluated among brain-dead and living donors. From January 2002 until December 2008, the number of patients who were annually on the waiting list increased 42% (from 377 to 536 patients). Consequently, the number of the total kidney transplants increased from 81 to 120 with an annual median of 98 cases. By implementing the interdisciplinary transplant team, a significant increase of living kidney donors was observed: from 18 to 42 cases; median = 27). In the last 7 years, a total number of 796 kidney transplants have been performed: 567 from brain-dead and 229 from living donors. In 2001, the waiting list times for recipients who received grafts from brain-dead versus living donors were 1356 versus 615 days respectively. Compared with 2008, the duration on the waiting list decreased significantly for patients receiving a living donor graft, whereas there was a slight increase for the patients in the brain-dead group: brain death versus living donors: 1407 versus 305 days. The interdisciplinary approach has also reduced the cold ischemia time for the living donor recipients: 3 hours and 42 minutes in 2001 versus 2 hours and 50 minutes in 2008. During the last years, by implementing an interdisciplinary transplant team, supporting living donor procedures has produce a gradual increase in the number of kidney transplants from living donors with a remarkable decrease in waiting and cold ischemia times, the latter presumably influencing graft quality.

Critical care management of potential organ donors: our current standard.

Caring for a brain dead potential organ donor requires a shift in critical care from the extensive treatment of increased intracranial pressure towards strategies to maintain donor organ function. Suboptimal, unstandardized critical care management of organ donors, however, is one of the main reasons for insufficient organ procurement. The pathophysiological changes following brain death entail a high incidence of complications including hemodynamic instability, endocrine and metabolic disturbances, and disruption of internal homeostasis that jeopardize potentially transplantable organs. Strategies for the management of organ donors exist and consist of the normalization of donor physiology. This has resulted in standardized efforts to improve the critical care delivered to potential organ donors, increasing not only the number, but also the quality of suitable organs and aiming at an optimal outcome for the recipients. In this review, we discuss the pathophysiological changes associated with brain death and present the current guidelines at our department, which are optimized based on available literature.

A single center experience of combined liver kidney transplantation.

With advancements in the operative techniques, patient survival following liver transplantation (LTx) has increased substantially. This has led to the acceleration of pre-existing kidney disease because of immunosuppressive nephrotoxicity making additional kidney transplantation (KTx) inevitable. On the other hand, in a growing number of patients on the waiting list to receive liver, long waiting time has resulted in adverse effect of decompensated liver on the kidney function. During the last two decades, the transplant community has considered combined liver kidney transplantation (CLKTx) to overcome this problem. The aim of our study is to present an overview of our experience as well as a review of the literature in CLKTx and to discuss the controversy in this regard. All performed CLKTx (n = 22) at our institution as well as all available reported case series focusing on CLKTx are extracted. The references of the manuscripts were cross-checked to implement further articles into the review. The analyzed parameters include demographic data, indication for LTx and KTx, duration on the waiting list, Model for End-Stage Liver Disease (MELD) score, Child-Turcotte-Pugh (CTP) score, immunosuppressive regimen, post-transplant complications, graft and patient survival, and cause of death. From 1988 to 2009, a total of 22 CLKTx were performed at our institution. The median age of the patients at the time of CLKTx was 44.8 (range: 4.5-58.3 yr). The indications for LTx were liver cirrhosis, hyperoxaluria type 1, polycystic liver disease, primary or secondary sclerosing cholangitis, malignant hepatic epithelioid hemangioendothelioma, cystinosis, and congenital biliary fibrosis. The KTx indications were end-stage renal disease of various causes, hyperoxaluria type 1, polycystic kidney disease, and cystinosis. The mean follow-up duration for CLKTx patients were 4.6 +/- 3.5 yr (range: 0.5-12 yr). Overall, the most important encountered complications were sepsis (n = 8), liver failure leading to retransplantation (n = 4), liver rejection (n = 3), and kidney rejection (n = 1). The overall patient survival rate was 80%. Review of the literature showed that from 1984 to 2008, 3536 CLKTx cases were reported. The main indications for CLKTx were oxalosis of both organs, liver cirrhosis and chronic renal failure, polycystic liver and kidney disease, and liver cirrhosis along with hepatorenal syndrome (HRS). The most common encountered complications following CLKTx were infection, bleeding, biliary complications, retransplantation of the liver, acute hepatic artery thrombosis, and retransplantation of the kidney. From the available data regarding the need for post-operative dialysis (n = 673), a total of 175 recipients (26%) required hemodialysis. During the follow-up period, 154 episodes of liver rejection (4.3%) and 113 episodes of kidney rejection (3.2%) occurred. The cumulative 1, 2, 3, and 5 yr survival of both organs were 78.2%, 74.4%, 62.4%, and 60.9%, respectively. Additionally, the cumulative 1, 2, 3, and 5 yr patient survival were 84.9%, 52.8%, 45.4%, and 42.6%, respectively. The total number of reported deaths was 181 of 2808 cases (6.4%), from them the cause of death in 99 (55%) cases was sepsis. It can be concluded that there is still no definitive evidence of better graft and patient survival in CLKTx recipients when compared with LTx alone because of the complexity of the exact definition of irreversible kidney function in LTx candidates. Additionally, CLKTx is better to be performed earlier than isolated LTx and KTx leading to the avoidance of deterioration of clinical status, high rate of graft loss, and mortality. Shorter graft ischemia time and more effective immunosuppressive regimens can reduce the incidence of graft malfunctioning in CLKTx patients. Providing a model to reliably determine the need for CLKTx seems necessary. Such a model can be shaped based upon new and precise markers of renal function, and modification of MELD system.

Frequency of inter- and intraventricular dyssynchrony in patients with heart failure according to QRS width.

AIMS: Cardiac resynchronization therapy (CRT) is an effective treatment for heart failure patients with prolongation of QRS duration. Despite careful patient selection, some do not respond to CRT based on QRS complex duration. We sought to evaluate the presence of left ventricular dyssynchrony using tissue Doppler imaging (TDI) according to QRS duration in heart failure patients. METHODS AND RESULTS: Ninety-nine patients (mean age 52.6 +/- 15.3 years) with severe heart failure [left ventricular (LV) ejection fraction, <35%] were prospectively evaluated. On the basis of QRS width, the patients were divided into two groups. Forty-eight patients (48.5%) had a normal QRS duration (<120 ms), Group I, and 51 (51.5%) had a prolonged QRS duration, Group II. All patients underwent echocardiography coupled with TDI. Spectral displays of six basal and six middle LV segments with pulsed-wave TDI were obtained to assess the time to peak systolic point from R-wave on electrocardiogram (Ts). The standard deviation of Ts (Ts-SD) and the maximal temporal difference of Ts (Ts-diff) were measured. Interventricular dyssynchrony [defined as the presence of an interventricular mechanical delay (IVMD) >40 ms] and intra-LV mechanical delays (defined as Ts-SD >33.4 ms and Ts-diff >100 ms) were correlated with the QRS width and morphology. We found a greater IVMD in Group II patients, compared with patients in Group I (42.5 +/- 22.3 vs. 26.8 +/- 21, respectively, P < 0.001). Intraventricular dyssynchrony defined as Ts-SD > or =33.4 ms was found in 45.1% of patients in Group II compared with 23% of patients in Group I (P = 0.03). Similarly, the Ts-diff was prolonged in Group II patients compared with Group I (P = 0.02). By linear regression analysis, a weak relation was found between Ts-SD and QRS duration (P = 0.055). A substantial portion of patients with prolonged QRS did not exhibit ventricular dyssynchrony defined either as total asynchrony index > or =33.4 ms or as IVMD >40 ms. CONCLUSION: A substantial proportion of patients with prolonged QRS (32.1%) did not exhibit inter- or intraventricular dyssynchrony, which may represent a limitation in identifying the ideal QRS interval for the selection of patients for CRT.