Genetic and Molecular Analysis of Islet-and Liver-Enriched Transcription Factors in Metabolism and Development

Maturity-onset diabetes of the young (MODY) are monogenic forms of type 2 diabetes that are characterized by an early disease-onset, autosomal dominant inheritance, and defects in insulin secretion. Genetic studies have identified mutations in at least six genes associated with different forms of MODY. The majority of the MODY subtypes are caused by mutations in transcription factors that include hepatocyte nuclear factor (HNF)-4α,HNF-1α, PDX-1, HNF-1β, and NEURO-D1/BETA-2. In addition, genetic defects in the glucokinase gene, the glucose sensor of the pancreatic β-cells, and the insulin gene also lead to impaired glucose tolerance. Using molecular and genetic approaches, we demonstrated that the MODY genes are functionally related and form an integrated transcriptional network that plays an essential role in development and in different metabolic pathways

Finding a large submatrix of a Gaussian random matrix

We consider the problem of finding a k × k submatrix of an n × n matrix with i.i.d. standard Gaussian entries, which has a large average entry. It was shown in [Bhamidi, Dey and Nobel (2012)] using nonconstructive methods that the largest average value of a k × k submatrix is 2(1 + o(1))√log n/k, with high probability (w.h.p.), when k = O(log n/log log n). In the same paper, evidence was provided that a natural greedy algorithm called the Largest Average Submatrix (LAS) for a constant k should produce a matrix with average entry at most (1 + o(1))√2 log n/k, namely approximately √2 smaller than the global optimum, though no formal proof of this fact was provided. In this paper, we show that the average entry of the matrix produced by the LAS algorithm is indeed (1 + o(1))√2 log n/k w.h.p. when k is constant and n grows. Then, by drawing an analogy with the problem of finding cliques in random graphs, we propose a simple greedy algorithm which produces a k × k matrix with asymptotically the same average value (1 + o(1))√2 log n/k w.h.p., for k = o(log n). Since the greedy algorithm is the best known algorithm for finding _cliques in random graphs, it is tempting to believe that beating the factor √2 performance gap suffered by both algorithms might be very challenging. Surprisingly, we construct a very simple algorithm which produces a k × k matrix with average value (1 + ok(1) + o(1))(4/3)√2 log n/k for k = o((log n)[superscript 1.5]), that is, with the asymptotic factor 4/3 when k grows. To get an insight into the algorithmic hardness of this problem, and motivated by methods originating in the theory of spin glasses, we conduct the so-called expected overlap analysis of matrices with average value asymptotically (1 + o(1))α√2 log n/k for a fixed value α ∈ [1, √2]. The overlap corresponds to the number of common rows and the number of common columns for pairs of matrices achieving this value (see the paper for details). We discover numerically _an intriguing phase transition at α∗ 52/(33) ≈ 1.3608 . . . ∈ [4/3, √2]: when α α∗, appropriately defined. We conjecture that the OGP observed for α > α∗ also marks the onset of the algorithmic hardness—no polynomial time algorithm exists for finding matrices with average value at least (1 + o(1))α√2 log n/k, when α > α∗ and k is a mildly growing function of n

Electrospun polyvinyl alcohol/carbon dioxide modified polyethyleneimine composite nanofiber scaffolds

A novel biocompatible polyvinyl alcohol/carbon dioxide modified polyethyleneimine (PVA/PEI-CO2) composite nanofiber was fabricated by a green and facile protocol, which reduces the cytotoxicity of PEI through the surface modification of the PEI with CO2. The 13C NMR spectrum, elemental analysis, and TGA show that CO2 has been incorporated in the PEI surface resulting in a relatively stable structure. The resulting PVA/PEI-CO2 composite nanofibers have been characterized by attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), contact angle, and scanning electron microscopy (SEM). The results show that the average diameters of the nanofibers range from 265 ± 53 nm to 423 ± 80 nm. The cytotoxicity of PVA/PEI-CO2 composite nanofibers was assessed by cytotoxicity evaluation using the growth and cell proliferation of normal mice Schwann cells. SEM and the MTT assay demonstrated the promotion of cell growth and proliferation on the PVA/PEI-CO2 composite scaffold. It suggests that PEI-CO2 can have tremendous potential applications in biological material research

A preliminary assessment of the economic impact of desertification in Nambia

The present report is the result of a study commissioned by the Desert Ecological Research Unit of Namibia in conjunction with the Ministries of Environment and Agriculture, as part of the preparation for a National Workshop on Desertification held from 4th-7th July 1994. The object of the study was to assist in the development of a framework for understanding and assessing the economic costs and factors involved in desertification, as a basis for further research and action to be undertaken in the context of a national programme to combat desertification. The study is based on the findings of a number of regional case studies and data available at national level about the socioeconomic and biophysical aspects of land degradation