How good can monolayer MoS₂ transistors be?

Monolayer molybdenum disulfide (MoS(2)), unlike its bulk form, is a direct band gap semiconductor with a band gap of 1.8 eV. Recently, field-effect transistors have been demonstrated experimentally using a mechanically exfoliated MoS(2) monolayer, showing promising potential for next generation electronics. Here we project the ultimate performance limit of MoS(2) transistors by using nonequilibrium Green's function based quantum transport simulations. Our simulation results show that the strength of MoS(2) transistors lies in large ON-OFF current ratio (>10(10)), immunity to short channel effects (drain-induced barrier lowering ～10 mV/V), and abrupt switching (subthreshold swing as low as 60 mV/decade). Our comparison of monolayer MoS(2) transistors to the state-of-the-art III-V materials based transistors, reveals that while MoS(2) transistors may not be ideal for high-performance applications due to heavier electron effective mass (m = 0.45 m(0)) and a lower mobility, they can be an attractive alternative for low power applications thanks to the large band gap and the excellent electrostatic integrity inherent in a two-dimensional system.     

An aetiological profile of short stature in the Indian subcontinent

To determine whether the genetic background of the insulin-producing beta cells of the pancreas contributes to autoimmune diabetes susceptibility, we have used a model of the disease based on transferring spleen cells from nonobese diabetic (NOD) <--> C57BL/6 (B6) embryo aggregation (EA) chimeras into B6 and NOD irradiated mice. Insulitis and diabetes could be induced into both B6 and NOD hosts, albeit with low incidence. Cyclophosphamide (CY) treatment, known to accelerate diabetes in prediabetic NOD mice, was found to increase diabetes incidence up to 50-60% in both B6 and NOD mice reconstituted with chimeric splenocytes, while diabetes did not occur in CY-treated B6 mice reconstituted with B6 splenocytes. We conclude that the genetic make-up of the target organ does not affect the final stage of the pathogenesis of insulin-dependent diabetes mellitus.     

Interleukin-6 in the fever and multiorgan crisis of pheochromocytoma

A 31-y-old black man with neurofibromatosis, alcoholism and hypertension was admitted because of abdominal pain, hematemesis and cough. In the hospital he had prolonged fever and developed a multiorgan crisis. Despite thorough investigation, no infectious cause for fever was found. Urinary catecholamines and metabolites were markedly elevated. Computerized tomography revealed a mass abutting the left kidney. A diagnosis of pheochromocytoma was made, and as soon as treatment with phenoxybenzamine and propranolol was begun, the fever resolved. Serum interleukin-6 (IL-6) concentration was initially elevated, decreased after the start of adrenergic blockade, and gradually fell to an undetectable level after surgery. These observations suggest that interleukin-6 might have been causally related to the patient's fever and possibly the multiorgan crisis.     

Turbulence-Driven Tearing Modes in Inhomogeneous Magnetized Plasma

The effects of density inhomogeneity in the nonlinear growth of tearing modes in the presence of background density, electrostatic and magnetic fluctuations are investigated. The nonlinear interaction is assumed to occur in the inner layer of the tearing mode, where the fields and their variations are greatest. Our results demonstrate that turbulence-generated dissipative effects replace the collisional resistivity as the driving force of the tearing mode. The inhomogeneity introduces a real frequency to the nonlinear tearing mode, as well as new unstable tearing-mode–related drift waves.     

Reversible unfolding of the major fraction of ovalbumin by guanidine hydrochloride

The guanidine hydrochloride induced unfolding of the major fraction of ovalbumin (i.e. A1 which contains two phosphate groups and constitutes about 77% of the total protein) was investigated systematically by difference spectran and viscosity measurements. As judged by the intrinsic viscosity (3.9 ml/g), the native protein conformation is compact and globular. Difference spectral results showed extensive disruption of the native structure by guanidine hydrochloride with and without 0.1 M beta-mercaptoethanol were 31.1 and 27.0 ml/g. These and optical rotation results indicated that the denatured protein existed in a cross-linked random coil conformation in 6 M guanidine hydrochloride alone. Strikingly, in contrast to whole ovalbumin, the denaturation of its A1 fraction by guanidine hydrochloride was fully reversible and obeyed first-order kinetic law under different experimental condit ions of pH, temperature, and the denaturant concentration. The monotonic variation of deltaH for the unfolding of ovalbumin A1 by guanidine hydrochloride with temperature, the coincidence of the two transition curves obtained by measuring two independent properties (namely reduced viscosity and difference in light absorption at 288 nm (or 293 nm) as a function of the denaturant concentration, and finally the adherence of the unfolding as well as refolding reactions to first-order kinetic law suggested that the transition of ovalbumin. A1 can reasonably be approximated by a two-state mode. Analysis of the equilibrium data obtained at pH 7.0 and 25 degrees C according to Aune and Tanford (Aune, K.C.,and Tanford, C. (1969), Biochemistry 8, 4586) showed that 12 additional binding sites for the denaturant with an association constant of 1.12 were freshly exposed by the unfolding process and that the native protein was marginally more stable (approximately 6 kcal/mol) than its unfolded form even under native condition. The temperature dependence of the equilibrium constant for the unfolding of ovalbumin A1 by guanidine hydrochloride which was studied in the range 10-60 degrees C at pH 7.0 can be described by assigning the following values of the thermodynamic parameters for the unfolding process: deltaH = 52 kcal/mol at 25 degrees C; deltaS = 153 cal deg-1 mol-1 at 25 degrees C; and delta Cp = 2700 +/- 400 cal deg-1 mol-1.     

TCP-Cherry for satellite IP networks: Analytical model and performance evaluation

TCP-Cherry is a novel TCP congestion control scheme that we devised for ensuring high performance over satellite IP networks and the alikes which are characterized by long propagation delays and high link errors. In TCP-Cherry, two new algorithms, Fast-Forward Start and First-Aid Recovery, have been proposed for congestion control. Our algorithms use supplement segments, i.e., low-priority segments to probe the available bandwidth in the network for the TCP connections along with carrying new data blocks. In this paper, we present our new congestion control scheme, TCP-Cherry and devise an analytical model for it. Our major contributions in this paper include the analytical model and equations for performance evaluation, validation of the analytical model through comparison between analytical and simulation results and devising a guideline to tune the buffer related parameters both at the sender as well as the receiver ends for optimum throughput performance. Experiments show that simulation results and the calculated throughput from our analytical model match quite closely, thereby verifying the appropriateness of the model. In addition, from analysis of simulation results, we discover that a buffer size at the receiver, rwnd, that is around four times maxcwnd, or the maximum congestion window at the sender side, is likely to maintain high throughput over a wide range of operating conditions.     

High-frequency performance projections for ballistic carbon-nanotube transistors

A quasi-static approach is combined with a theory of ballistic nanotransistors to assess the high-frequency performance potential of carbon-nanotube field-effect transistors. A simple equivalent circuit, which applies in the ballistic limit of operation, is developed for the intrinsic device, and then employed to determine the behavior of the unity-current-gain frequency (f/sub T/) with gate voltage. The circuit is shown to reduce to the expected forms in the so-called "MOS" and "bipolar" limits. The f/sub T/ is shown to approach a maximum value of v/sub F//2/spl pi/L/spl ap/130 GHz/L (/spl mu/m) at high gate voltage, where v/sub F/ is the nanotube's Fermi velocity and L is the channel length, and to fall at low gate voltage due to the presence of source and drain electrostatic capacitances. The impact of the gate electrostatic capacitance on the f/sub T/ is also discussed. Numerical simulations on a "MOSFET-like" or "bulk-switched" carbon-nanotube transistor are shown to support the conclusions.     

Experimental Evidence of Chiral Ferrimagnetism in Amorphous GdCo Films

Inversion symmetry breaking has become a vital research area in modern magnetism with phenomena including the Rashba effect, spin Hall effect, and the Dzyaloshinskii–Moriya interaction (DMI)—a vector spin exchange. The latter one may stabilize chiral spin textures with topologically nontrivial properties, such as Skyrmions. So far, chiral spin textures have mainly been studied in helimagnets and thin ferromagnets with heavy‐element capping. Here, the concept of chirality driven by interfacial DMI is generalized to complex multicomponent systems and demonstrated on the example of chiral ferrimagnetism in amorphous GdCo films. Utilizing Lorentz microscopy and X‐ray magnetic circular dichroism spectroscopy, and tailoring thickness, capping, and rare‐earth composition, reveal that 2 nm thick GdCo films preserve ferrimagnetism and stabilize chiral domain walls. The type of chiral domain walls depends on the rare‐earth composition/saturation magnetization, enabling a possible temperature control of the intrinsic properties of ferrimagnetic domain walls.     

Confocal light absorption and scattering spectroscopic microscopy

We have developed a novel optical method for observing submicrometer intracellular structures in living cells, which is called confocal light absorption and scattering spectroscopic (CLASS) microscopy. It combines confocal microscopy, a well-established high-resolution microscopic technique, with light-scattering spectroscopy. CLASS microscopy requires no exogenous labels and is capable of imaging and continuously monitoring individual viable cells, enabling the observation of cell and organelle functioning at scales of the order of 100 nm.