Supersymmetry versus Gauge Symmetry on the Heterotic Landscape

One of the goals of the landscape program in string theory is to extract information about the space of string vacua in the form of statistical correlations between phenomenological features that are otherwise uncorrelated in field theory. Such correlations would thus represent predictions of string theory that hold independently of a vacuum-selection principle. In this paper, we study statistical correlations between two features which are likely to be central to any potential description of nature at high energy scales: gauge symmetries and spacetime supersymmetry. We analyze correlations between these two kinds of symmetry within the context of perturbative heterotic string vacua, and find a number of striking features. We find, for example, that the degree of spacetime supersymmetry is strongly correlated with the probabilities of realizing certain gauge groups, with unbroken supersymmetry at the string scale tending to favor gauge-group factors with larger rank. We also find that nearly half of the heterotic landscape is non-supersymmetric and yet tachyon-free at tree level; indeed, less than a quarter of the tree-level heterotic landscape exhibits any supersymmetry at all at the string scale.Comment: 29 pages, LaTeX, 4 figures, 7 table

Reductive Biotransformation of Ethyl Acetoacetate: A Comparative Studies using Free and Immobilized Whole Yeast Cells

Bioreduction of ethyl acetoacetate with free and immobilized yeast whole cell was achieved by using water and sucrose combination. After detachment from immobilized beads under basic condition, the corresponding ethyl(S)-(+)-3-hydroxybutanoate was isolated with 98 to 100% yield. Immobilized beads of yeast whole cell were prepared at different temperature which affects the morphology and physiology of the beads for the diffusion of the enzyme, which shown the maximum conversion of the substrate to products as compared to the free yeast whole cell

Gas–liquid flow in stirred reactors: Trailing vortices and gas accumulation behind impeller blades

In a gas–liquid stirred reactor, gas tends to accumulate in low-pressure regions behind the impeller blades. Such gas accumulation significantly alters impeller performance characteristics. We have computationally investigated gas–liquid flow generated by a Rushton (disc) turbine. Rotating Rushton turbine generates trailing vortices behind the blades, which influence the gas accumulation in the impeller region. Characteristics of these trailing vortices were first investigated by considering a model problem of flow over a single impeller blade. Predicted results were compared with the published experimental data. Circulation velocity and turbulent kinetic energy of the trailing vortices were found to scale with blade tip velocity. Several numerical experiments were carried out to understand interaction of gas bubbles and trailing vortices. Gas–liquid flow in stirred vessel was then simulated by extending the computational snapshot approach of Ranade and Dometti (Chem. Engng Res. Des., 74, 476–484, 1996). The approach was able to capture the main features of gas–liquid flow in stirred vessels. The detailed analysis of predicted results with reference to experimental data and the results obtained for flow over a single impeller blade will be useful for extending the scope of computational fluid dynamics (CFD) based tools for engineering gas–liquid stirred reactors

Channel routing optimization using a genetic algorithm

A modified approach for the application of Genetic Algorithm (GA) to the Channel Routing Problem has been proposed. The code based on the algorithm proposed in [1] has been implemented for the GA procedures of Initial Population Generation, Crossover, Mutation and Selection. A few improvements over the existing work have been made and the results so far obtained have been encouraging. Further experimentation is being done on the algorithm and other ideas generated during the development of the code are being implemented for faster convergence of the algorithm and for generation of more efficient results. Also application of variations of the GA technique like Vector GA and even other computationally intelligent techniques like Particle Swarm Optimization to the channel routing problem is being thought of

Comparison of the spatial QRS-T angle derived from digital ECGs recorded using conventional electrode placement with that derived from Mason-Likar electrode position

Background: The spatial QRS-T angle is ideally derived from orthogonal leads. We compared the spatial QRS-T angle derived from orthogonal leads reconstructed from digital 12-lead ECGs and from digital Holter ECGs recorded with the Mason-Likar (M-L) electrode positions. Methods and results: Orthogonal leads were constructed by the inverse Dower method and used to calculate spatial QRS-T angle by (1) a vector method and (2) a net amplitude method, in 100 volunteers. Spatial QRS-T angles from standard and M-L ECGs differed significantly (57° ± 18° vs 48° ± 20° respectively using net amplitude method and 53° ± 28° vs 48° ± 23° respectively by vector method; p < 0.001). Difference in amplitudes in leads V4–V6 was also observed between Holter and standard ECGs, probably due to a difference in electrical potential at the central terminal. Conclusion: Mean spatial QRS-T angles derived from standard and M-L lead systems differed by 5°–9°. Though statistically significant, these differences may not be clinically significant

Virtual-Source based accurate model for predicting noise behavior at high frequencies in nanoscale PMOS SOI transistors

Complementary Metal Oxide Semiconductor (CMOS) technology at the nanometre scale is an excellent platform to implement monolithically integratedsystems because of the low cost of manufacturing and ease of integration. Newly developed CMOS Silicon on Insulator (SOI) transistors that are currentlydeveloped are suitable for use in radio frequency circuits. They find applications in many areas such as 5G telecommunication systems, high speed Wi-Fi andairport body-scanners. Unfortunately, the models for CMOS SOI transistors that are currently used in these circuits are inaccurate because of their complexity.The models currently used require the optimization of more than 200 variables. This paper aims to accurately create a scalable model of a P-type MOS transistorusing a Virtual Source (VS) model with much less complexity. The VS model’s DC characteristics will require the optimization of only ten parameters and issupplemented with parasitic resistances, inductances and capacitances to accurately predict behaviour at radio frequencies. These parameters were optimizedtwo at a time using a multivariate optimization algorithm while fixing the remaining parameter’s values within a certain range. A simulation of the voltage andcurrent at the drain of the transistor was performed and the resulting I-V curves were plotted. A frequency simulation was also conducted in order to test thehigh frequency performance of the MOSFET. A typical I-V characteristic curve for a PMOS was obtained with no change in shape when the transistor widthwas scaled. The model’s performance under high frequencies also matched those displayed by a standard 45nm PMOS. The I-V characteristic plots that wereobtained displayed the general behaviour of a p-type MOSFET under those voltage conditions. This demonstrates that the Virtual source model is able topredict the general behaviour of the I-V characteristic curves of the p-type MOSFET as well as function properly at high frequencies typically seen in RFcircuits