Kinetic Arrest of Field-Temperature Induced First Order Phase Transition in Quasi- One Dimensional Spin System Ca3Co2O6

We have found that the geometrically frustrated spin chain compound Ca3Co2O6 belonging to Ising like universality class with uniaxial anisotropy shows kinetic arrest of first order intermediate phase (IP) to ferrimagnetic (FIM) transition. In this system, dc magnetization measurements followed by different protocols suggest the coexistence of high temperature IP with equilibrium FIM phase in low temperature. Formation of metastable state due to hindered first order transition has also been probed through cooling and heating in unequal field (CHUF) protocol. Kinetically arrested high temperature IP appears to persist down to almost the spin freezing temperature in this system.Comment: Kinetic arrest of first order magnetic transition in spin chain compound Ca3Co2O

Dynamic Labyrinthine Pattern in an Active Liquid Film

We report the generation of a dynamic labyrinthine pattern in an active alcohol film. A dynamic labyrinthine pattern is formed along the contact line of air/pentanol/aqueous three phases. The contact line shows a clear time-dependent change with regard to both perimeter and area of a domain. An autocorrelation analysis of time-development of the dynamics of the perimeter and area revealed a strong geometric correlation between neighboring patterns. The pattern showed autoregressive behavior. The behavior of the dynamic pattern is strikingly different from those of stationary labyrinthine patterns. The essential aspects of the observed dynamic pattern are reproduced by a diffusion-controlled geometric model

The rapid decline of the prompt emission in Gamma-Ray Bursts

Many gamma ray bursts (GRBs) have been observed with the Burst-Alert and X-Ray telescopes of the Swift satellite. The successive `pulses' of these GRBs end with a fast decline and a fast spectral softening, until they are overtaken by another pulse, or the last pulse's decline is overtaken by a less rapidly-varying `afterglow'. The fast decline-phase has been attributed, in the currently-explored standard fireball model of GRBs, to `high-latitude' synchrotron emission from a collision of two conical shells. This high latitude emission does not explain the observed spectral softening. In contrast, the temporal behaviour and the spectral evolution during the fast-decline phase agree with the predictions of the cannonball model of GRBs.Comment: Four added figures comparing the evolution of the inferred effective photon spectral index during the fast decline phase of the prompt emission in 14 selected Swift GRBS and the cannonball (CB) model predictio

Extending the bounds of performance in E-mode p-channel GaN MOSHFETs

An investigation of the distribution of the electric field within a normally-off p-channel heterostructure field-effect transistor in GaN, explains why a high |Vth| requires a reduction of the thickness of oxide and the GaN channel layer. The trade-off between on-current |Ion| and |Vth|, responsible for the poor |ION| in E-mode devices is overcome with an additional cap AlGaN layer that modulates the electric field in itself and the oxide. A record |Ion| of 50-60 mA/mm is achieved with a |Vth| greater than |-2| V in the designed E-mode p-channel MOSHFET, which is more than double that in a conventional device

An E-mode p-channel GaN MOSHFET for a CMOS compatible PMIC

The operation principle of a low power E-mode p-channel GaN MOSHFET is explained via TCAD simulations. The challenges of achieving negative threshold voltage with the scaling of gate length are addressed by adjusting the mole fraction of an AlGaN cap layer beneath the gate. An inverter consisting of the proposed p-channel GaN MOSHFET with a gate length of 025 μm shows promise of a CMOS compatible Power Management IC in the MHz range

A p-channel GaN heterostructure tunnel FET with high ON/OFF current ratio

A novel mechanism to achieve a nonambipolar tunnel FET (TFET) is proposed in this paper. The method relies on polarization charge induced in semiconductors, such as group III nitrides, to enhance the electric field across the junction and facilitate unidirectional tunneling based on the polarity of the applied gate bias. This also enables enhanced control over the tunneling distance, reducing it significantly in comparison to a conventional TFET. The proposed p-channel device implemented in a novel vertical GaN nanowire geometry facilitates a reduction of footprint while still maintaining comparable performance to that of conventional E-mode p-channel devices in GaN. This opens up possibilities for E-mode p-channel GaN devices

An Innovative Technique of Liquid Purity Analysis and Its Application to Analysis of Water Concentration in Alcohol-Water Mixtures and Studies on Change of Activation Energies of the Mixtures

The activation energy of a liquid molecule and hence its viscosity coefficient changes with addition of contaminants to the original liquid. This forms the basis of a new technology for analysis of purity of the liquid. We discovered that concentration of certain contaminants such as water in alcohol or vice versa can be uniquely and accurately determined in a short time (about 10-15 minutes) using a simple and yet innovative technique that only requires measurement of time of flow of the impure liquid (say, water-alcohol mixture) and distilled water through a simple viscometer designed and constructed for this purpose. We find that the viscosity coefficient μ of alcohol increased almost linearly with water concentration at a rate that depends on the type of alcohol and water concentration. We determined the increase of activation energy of alcohol molecules with increase of water concentration. This increase also depends on type of alcohol. Our detailed investigation on alcohol-water mixtures for both ethyl and methyl alcohol along with discussion on possible future potential application of such a simple, yet very reliable inexpensive technique for liquid purity analysis is presented. A comparison is made of our present method with other methods on the accuracies, problems and reliability of impurity analysis. A part of the quantum theory of viscosity of liquid mixtures that is in the developmental stage in order to explain some of the observed properties is presented

Crack roughness and avalanche precursors in the random fuse model

We analyze the scaling of the crack roughness and of avalanche precursors in the two dimensional random fuse model by numerical simulations, employing large system sizes and extensive sample averaging. We find that the crack roughness exhibits anomalous scaling, as recently observed in experiments. The roughness exponents ($\zeta$, $\zeta_{loc}$) and the global width distributions are found to be universal with respect to the lattice geometry. Failure is preceded by avalanche precursors whose distribution follows a power law up to a cutoff size. While the characteristic avalanche size scales as $s_0 \sim L^D$, with a universal fractal dimension $D$, the distribution exponent $\tau$ differs slightly for triangular and diamond lattices and, in both cases, it is larger than the mean-field (fiber bundle) value $\tau=5/2$

An ultralow power 3-terminal memory device with write capability in the off-state

In this work, we demonstrated a room temperature fabricated ZnO/Ta 2 O 5 transistor for low power compute-in-memory application. By writing during the off-state, the device programmed for compute-in-memory shows power consumption in nW. By using variable pulse amplitudes for SET/RESET allows control of the on/off ratio of resistance states without affecting power consumption. Benchmarked against other ReRAMs the device shows a competitive 8 nJ per transition, which allows a reduction of power consumption in comparison to a filamentary device