Dielectric anomalies and spiral magnetic order in CoCr2O4

We have investigated the structural, magnetic, thermodynamic, and dielectric properties of polycrystalline CoCr$_2$O$_4$, an insulating spinel exhibiting both ferrimagnetic and spiral magnetic structures. Below $T_c$ = 94 K the sample develops long-range ferrimagnetic order, and we attribute a sharp phase transition at $T_N$ $\approx$ 25 K with the onset of long-range spiral magnetic order. Neutron measurements confirm that while the structure remains cubic at 80 K and at 11 K; there is complex magnetic ordering by 11 K. Density functional theory supports the view of a ferrimagnetic semiconductor with magnetic interactions consistent with non-collinear ordering. Capacitance measurements on CoCr$_2$O$_4$, show a sharp decrease in the dielectric constant at $T_N$, but also an anomaly showing thermal hysteresis falling between approximately $T$ = 50 K and $T$ = 57 K. We tentatively attribute the appearance of this higher temperature dielectric anomaly to the development of \textit{short-range} spiral magnetic order, and discuss these results in the context of utilizing dielectric spectroscopy to investigate non-collinear short-range magnetic structures.Comment: & Figure

A density-matching approach for optimization under uncertainty

Modern computers enable methods for design optimization that account for uncertainty in the system - so-called optimization under uncertainty (OUU). We propose a metric for OUU that measures the distance between a designer-specified probability density function of the system response (the target) and the system response's density function at a given design. We study an OUU formulation that minimizes this distance metric over all designs. We discretize the objective function with numerical quadrature, and we approximate the response density function with a Gaussian kernel density estimate. We offer heuristics for addressing issues that arise in this formulation, and we apply the approach to a CFD-based airfoil shape optimization problem. We qualitatively compare the density-matching approach to a multi-objective robust design optimization to gain insight into the method.This research was funded through a Dorothy Hodgkin Postgraduate Award, which is jointly sponsored by the Engineering and Physical Sciences Research Council (EPSRC) (UK) and Rolls-Royce plc. The first author would like to acknowledge the financial assistance provided by the Center for Turbulence Research at Stanford University and St. Edmund's College, Cambridge. The authors would like to thank Shahrokh Shahpar of Rolls-Royce plc for his advice on various aspects of this work. The authors also thank the reviewers for their suggestions and comments, which improved the overall quality of this manuscript. The second author's work is supported by the U.S. Department of Energy Office of Science, Office of Advanced Scientific Computing Research, Applied Mathematics program under Award Number DE-SC-0011077.This is the final version of the article. It first appeared from Elsevier via https://doi.org/10.1016/j.cma.2016.03.00

Intermediation and Value Creation in an Incomplete Market: Implications for Securitization

This paper studies the impact of financial innovations on real investment decisions. We model an incomplete market economy comprised of firms, investors and an intermediary. The firms face unique investment opportunities that are not spanned by the traded securities in the financial market, and thus, cannot be priced uniquely using the no-arbitrage principle. The specific innovation we consider is securitization; the intermediary buys claims from the firms that are fully backed by cash flows from the new projects, pools these claims together, and then issues tranches of secondary securities to the investors. We first derive necessary and sufficient conditions under which pooling provides value enhancement and the prices paid to the firms are acceptable to them compared to the no-investment option or the option of forming alternative pools. We find that there is a unique pool that is sustainable, and may or may not consist of all projects in the intermediary’s consideration set. We then determine the optimal design of tranches, fully backed by the asset pool, to be sold to different investor classes. We determine the general structure of the tranches. The new securities created by the intermediary could have up to three components, one that is a marketable claim, one that represents the arbitrage opportunities available in the market due to special ability to design and sell securities to a subset of investors, and a third component that is the rest of the asset pool which is sold at a price which does not exceed arbitrage based bounds to investors. The presence of these three components in the tranching solution has direct bearing upon the size of the asset pool, and therefore value creation due to financing additional projects

Intermediation and Value Creation in an Incomplete Market: Implications for Securitization

This paper studies the impact of financial innovations on real investment decisions. We model an incomplete market economy comprised of firms, investors and an intermediary. The firms face unique investment opportunities that are not spanned by the securities traded in the financial market, and thus, cannot be priced uniquely using the no-arbitrage principle. The specific innovation we consider is securitization: the intermediary buys claims from the firms that are fully backed by cash flows from the new projects, pools these claims together, and then issues tranches of secondary securities to the investors. We first derive necessary and sufficient conditions under which pooling provides value enhancement from the new projects that are undertaken, and the prices paid to the firms are acceptable to them compared to the no-investment option or the option of forming alternative pools. We find that there is a unique pool that is sustainable, and which may or may not consist of all projects in the intermediary’s consideration set

Citrullinemia type 1: genetic diagnosis and prenatal diagnosis in subsequent pregnancy

Citrullinemia type 1 was diagnosed by tandem mass spectrometry in a full term male neonate who presented with an acute catastrophic collapse on the 3rd day of life. Both parents were identified to be carriers for the exon 15 p Gly390Arg mutation in the argininosuccinate synthetase gene located at chromosome 9q34.1. Chorionic villus sampling and prenatal genetic testing in the subsequent pregnancy revealed an affected fetus resulting in termination of pregnancy

Effect of sustained released metformin therapy on phenotypic and biochemical markers of insulin resistance in polycystic ovary syndrome in South Indian women

Background: Polycystic ovary syndrome (PCOS) is the most common endocrine disorder in young women. Insulin resistance (IR) may play a substantial part in the pathogenesis of PCOS, which leads to type 2 diabetes mellitus (T2DM), cardiovascular disorders and ovarian cancer. Metformin is an insulin sensitizing agent, however its role in PCOS is still controversial.Methods: Sixty women newly diagnosed with PCOS and healthy age matched controls between 18 to 45 years were enrolled after obtaining informed consent. Women in the PCOS group were started on metformin-SR 1gram orally, which was then increased to 1.5 grams after two weeks and continued for 6 months. Fasting blood sugar (FBS), fasting insulin (FI), SHBG, TT, free androgen index (FAI), homeostatic model assessment of Insulin resistance (HOMA-IR), homeostatic model assessment of β- cell function (HOMA-B), homeostatic model assessment of Insulin sensitivity (HOMA-S) and quantitative insulin sensitivity check index (QUICKI) were measured in the control group as well as PCOS group before and after metformin therapy.Results: After six months of metformin-SR therapy, PCOS group showed significant reduction in FI, HOMA-IR, HOMA- β, HOMA-S QUICKI, TT and FAI and significant increase in SHBG levels.Conclusions: Six months of metformin-SR therapy favorably altered markers of IR, TT, SHBG, anovulation and hyperandrogenism in normoglycemic women with PCOS

Secure Code Update for Embedded Devices via Proofs of Secure Erasure

Abstract. Remote attestation is the process of verifying internal state of a remote embedded device. It is an important component of many security protocols and applications. Although previously proposed re-mote attestation techniques assisted by specialized secure hardware are effective, they not yet viable for low-cost embedded devices. One no-table alternative is software-based attestation, that is both less costly and more efficient. However, recent results identified weaknesses in some proposed software-based methods, thus showing that security of remote software attestation remains a challenge. Inspired by these developments, this paper explores an approach that relies neither on secure hardware nor on tight timing constraints typi-cal of software-based technqiques. By taking advantage of the bounded memory/storage model of low-cost embedded devices and assuming a small amount of read-only memory (ROM), our approach involves a new primitive – Proofs of Secure Erasure (PoSE-s). We also show that, even though it is effective and provably secure, PoSE-based attestation is not cheap. However, it is particularly well-suited and practical for two other related tasks: secure code update and secure memory/storage erasure. We consider several flavors of PoSE-based protocols and demonstrate their feasibility in the context of existing commodity embedded devices.