Supersymmetric RG flows and Janus from type II orbifold compactification

We study holographic RG flow solutions within four-dimensional $N=4$ gauged supergravity obtained from type IIA and IIB string theories compactified on $T^6/\mathbb{Z}_2\times \mathbb{Z}_2$ orbifold with gauge, geometric and non-geometric fluxes. In type IIB non-geometric compactifications, the resulting gauged supergravity has $ISO(3)\times ISO(3)$ gauge group and admits an $N=4$ $AdS_4$ vacuum dual to an $N=4$ superconformal field theory (SCFT) in three dimensions. We study various supersymmetric RG flows from this $N=4$ SCFT to $N=4$ and $N=1$ non-conformal field theories in the IR. The flows preserving $N=4$ supersymmetry are driven by relevant operators of dimensions $\Delta =1,2$ or alternatively by one of these relevant operators, dual to the dilaton, and irrelevant operators of dimensions $\Delta=4$ while the $N=1$ flows in addition involve marginal deformations. Most of the flows can be obtained analytically. We also give examples of supersymmetric Janus solutions preserving $N=4$ and $N=1$ supersymmetries. These solutions should describe two-dimensional conformal defects within the dual $N=4$ SCFT. Geometric compactifications of type IIA theory give rise to $N=4$ gauged supergravity with $ISO(3)\ltimes U(1)^6$ gauge group. In this case, the resulting gauged supergravity admits an $N=1$ $AdS_4$ vacuum. We also numerically study possible $N=1$ RG flows to non-conformal field theories in this case.Comment: 32 pages, 5 figures, typos corrected and references adde

Optimal first-passage time in gene regulatory networks

The inherent probabilistic nature of the biochemical reactions, and low copy number of species can lead to stochasticity in gene expression across identical cells. As a result, after induction of gene expression, the time at which a specific protein count is reached is stochastic as well. Therefore events taking place at a critical protein level will see stochasticity in their timing. First-passage time (FPT), the time at which a stochastic process hits a critical threshold, provides a framework to model such events. Here, we investigate stochasticity in FPT. Particularly, we consider events for which controlling stochasticity is advantageous. As a possible regulatory mechanism, we also investigate effect of auto-regulation, where the transcription rate of gene depends on protein count, on stochasticity of FPT. Specifically, we investigate for an optimal auto-regulation which minimizes stochasticity in FPT, given fixed mean FPT and threshold. For this purpose, we model the gene expression at a single cell level. We find analytic formulas for statistical moments of the FPT in terms of model parameters. Moreover, we examine the gene expression model with auto-regulation. Interestingly, our results show that the stochasticity in FPT, for a fixed mean, is minimized when the transcription rate is independent of protein count. Further, we discuss the results in context of lysis time of an \textit{E. coli} cell infected by a $\lambda$ phage virus. An optimal lysis time provides evolutionary advantage to the $\lambda$ phage, suggesting a possible regulation to minimize its stochasticity. Our results indicate that there is no auto-regulation of the protein responsible for lysis. Moreover, congruent to experimental evidences, our analysis predicts that the expression of the lysis protein should have a small burst size.Comment: 8 pages, 3 figures, Submitted to Conference on Decision and Control 201

TECHNICAL EFFICIENCY OF THE LONGLINE FISHERY IN HAWAII: AN APPLICATION OF A STOCHASTIC PRODUCTION FRONTIER

This paper examines the level and determinants of technical efficiency for a sample of domestic longline fishing vessels operating in Hawaii in 1993. The data on per-trip costs and revenues, fishing targets, vessel ownership, experience and education level of fishermen, vessel size, and vessel age are analyzed using a translog stochastic production frontier, including a model for vessel-specific technical inefficiencies. Output elasticities, marginal productivities of inputs, and returns to scale are also examined. The technical inefficiency effects are found to be highly significant in explaining the levels of and variation in vessel revenues. The mean technical efficiency for the sample vessels is estimated to be 84%. Vessels that target swordfish, and those varying target by season, set, or trip, tend to be less efficient than those vessels targeting tuna and those mixing targets in all trips. Owner-operated vessels seem to be more efficient than those operated by hired captains. The experience of fishermen has a strong positive influence on technical efficiency. Although insignificant, vessel size and fishermen's education level have a positive influence, and vessel age has a negative influence on vessel efficiency.Resource /Energy Economics and Policy,

Impact of Land Irrigability Classes on Crop Productivity in Canal Command Area of Gujarat: An Economic Analysis

The impact of land irrigability classes on crop productivity has been reported based on the survey of Mahi right bank (MRB), Ukai-Kakrapar right bank (UKRB) and Kakrapar left bank (KLB) canal command areas of the Gujarat state. The multi-stage random sampling method was used to select the farmers. The MRB and UKRB areas have five different soils environment in terms of land irrigability classes, while the KLB area has only three soils environment. The major crops grown in the UKRB are sugarcane, rice, cotton and pigeon pea, while sugarcane and rice are the major crops in the KLB. Similarly, in the MRB, rice, pearl millet, groundnut, wheat and tobacco crops occupy 95 per cent of the total irrigated area. The study has revealed that farmers have violated the recommended cropping pattern and are growing high water-requiring crops, irrespective of their suitability to land. In the land irrigability classes III, IV and V, cultivation of sugarcane and rice has led to waterlogging and secondary salinization problems, and reduction in crop yields. Hence, the cultivation of lower irrigability classes with minimum use of major inputs is not an advisable proposition. It would be better if crops are selected according to land irrigability classes which might result in a higher production with lower unit cost of production in the command areas under the study.Agricultural and Food Policy,

Enclaves, Social Capital and the City

This thesis focuses on the migration, settlement, and adaption of communities and their impacts on the transformation of host cities in the United States. I will borrow a social science term “enclave” to describe the uniqueness of these communities. Apart from the media and public at large, academic literature also portrays ambiguity about enclaves. Academic researchers and commentators of varying theoretical orientation differ in their views about enclaves. Some regard them positively, others regard them poorly and a few are unconcerned. Those steeped in the Chicago sociological tradition and the 'melting pot' perspective tends to view enclaves as cultural ghettos, obstructing the assimilation of ethnics;^1 whereas others inspired by European theoretical traditions and multicultural perspectives regard enclaves as expressions of cultural pluralism and sites of social capital formation.^2 However, little attention has been attributed toward the involvement of these self-sufficient, minority communities with the larger society. One important outcome of the thesis should thus be a theory or model that predicts or describes how to enable effective engagement (i.e., which mechanism to use, and how) in any particular situation. As a student of architecture I can provide such insight. Architecture requires more than the creative manipulation and coordination of material, technology, and environment. It is colored by the engagement of territory, culture, and structure. Examining society and enclaves with such lens enables me to identify the mechanisms for engagement