Mining Twitter to Assess the Opioid Crisis

https://scholar.dsu.edu/research-symposium/1009/thumbnail.jp

Reflected Backward Stochastic Differential Equations Driven by L\'{e}vy Process

In this paper, we deal with a class of reflected backward stochastic differential equations associated to the subdifferential operator of a lower semi-continuous convex function driven by Teugels martingales associated with L\'{e}vy process. We obtain the existence and uniqueness of solutions to these equations by means of the penalization method. As its application, we give a probabilistic interpretation for the solutions of a class of partial differential-integral inclusions.Comment: 14 page

FBSDEs with time delayed generators:L-P-solutions, differentiability, representation formulas and path regularity

AbstractWe extend the work of Delong and Imkeller (2010) [6,7] concerning backward stochastic differential equations with time delayed generators (delay BSDEs). We give moment and a priori estimates in general Lp-spaces and provide sufficient conditions for the solution of a delay BSDE to exist in Lp. We introduce decoupled systems of SDEs and delay BSDEs (delay FBSDEs) and give sufficient conditions for their variational differentiability. We connect these variational derivatives to the Malliavin derivatives of delay FBSDEs via the usual representation formulas. We conclude with several path regularity results, in particular we extend the classic L2-path regularity to delay FBSDEs

Highly Enhanced Concentration and Stability of Reactive Ce^3+ on Doped CeO_2 Surface Revealed In Operando

Trivalent cerium ions in CeO_2 are the key active species in a wide range of catalytic and electro-catalytic reactions. We employed ambient pressure X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy to quantify simultaneously the concentration of the reactive Ce^3+ species on the surface and in the bulk of Sm-doped CeO_2(100) in hundreds of millitorr of H2–H2O gas mixtures. Under relatively oxidizing conditions, when the bulk cerium is almost entirely in the 4+ oxidation state, the surface concentration of the reduced Ce^3+ species can be over 180 times the bulk concentration. Furthermore, in stark contrast to the bulk, the surface’s 3+ oxidation state is also highly stable, with concentration almost independent of temperature and oxygen partial pressure. Our thermodynamic measurements reveal that the difference between the bulk and surface partial molar entropies plays a key role in this stabilization. The high concentration and stability of reactive surface Ce^3+ over wide ranges of temperature and oxygen partial pressure may be responsible for the high activity of doped ceria in many pollution-control and energy-conversion reactions, under conditions at which Ce^3+ is not abundant in the bulk

On Markovian solutions to Markov Chain BSDEs

We study (backward) stochastic differential equations with noise coming from a finite state Markov chain. We show that, for the solutions of these equations to be `Markovian', in the sense that they are deterministic functions of the state of the underlying chain, the integrand must be of a specific form. This allows us to connect these equations to coupled systems of ODEs, and hence to give fast numerical methods for the evaluation of Markov-Chain BSDEs

A Direct Substrate-Substrate Interaction Found in the Kinase Domain of the Bifunctional Enzyme, 6-Phosphofructo-2-kinase/Fructose-2,6-bisphosphatase

To understand the molecular basis of a phosphoryl transfer reaction catalyzed by the 6-phosphofructo-2-kinase domain of the hypoxia-inducible bifunctional enzyme 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFKFB3), the crystal structures of PFKFB3{radical dot}AMPPCP{radical dot}fructose-6-phosphate and PFKFB3{radical dot}ADP{radical dot}phosphoenolpyruvate complexes were determined to 2.7 Å and 2.25 Å resolution, respectively. Kinetic studies on the wild-type and site-directed mutant proteins were carried out to confirm the structural observations. The experimentally varied liganding states in the active pocket cause no significant conformational changes. In the pseudo-substrate complex, a strong direct interaction between AMPPCP and fructose-6-phosphate (Fru-6-P) is found. By virtue of this direct substrate-substrate interaction, Fru-6-P is aligned with AMPPCP in an orientation and proximity most suitable for a direct transfer of the γ-phosphate moiety to 2-OH of Fru-6-P. The three key atoms involved in the phosphoryl transfer, the β,γ-phosphate bridge oxygen atom, the γ-phosphorus atom, and the 2-OH group are positioned in a single line, suggesting a direct phosphoryl transfer without formation of a phosphoenzyme intermediate. In addition, the distance between 2-OH and γ-phosphorus allows the γ-phosphate oxygen atoms to serve as a general base catalyst to induce an associative phosphoryl transfer mechanism. The site-directed mutant study and inhibition kinetics suggest that this reaction will be catalyzed most efficiently by the protein when the substrates bind to the active pocket in an ordered manner in which ATP binds first. © 2007 Elsevier Ltd. All rights reserved

Exploring the Molecular and Metabolic Factors Contributing to the Adaptation of Maize Seedlings to Nitrate Limitation

Crop production on soils containing sub-optimal levels of nitrogen (N) severely compromises yield potential. The development of plant varieties displaying high N use efficiency (NUE) will optimize N fertilizer use and reduce the environmental damage caused by excess N application. Maize is one of the most important crops cultivated worldwide. Identification of the genotypes with an enhanced NUE in the field is both time and resource consuming and sometime is difficult due to the regulation in the biotechnology programs. Identification of traits associated with adaptation to N limitation at an early vegetative stage which could reflect NUE at maturity is in need. We developed a hydroponic growth system and used it to test two genotypes that were different in their NUE at maturity under N limitation. One genotype SRG-200 showed a higher NUE than the other genotype SRG-100 and we used its hybrid SRG-150 as a reference for NUE. A number of phenotypic, molecular, and metabolic factors were tested using these three genetic lines at an early vegetative stage to determine which of these could be more indicative of predicting improved NUE at an early seedling stage. These include a transcriptional analysis which showed that the higher NUE in SRG-200 genotype is associated with higher transcript levels for the genes involved in nitrate transport, N assimilation, and GS and that the SRG-200 genotype maintained higher sugar content in leaves. Those identified in this study could be useful indicators for selecting promising maize lines at early stages to help develop elite varieties showing an enhanced NUE

Crystal structure of the hypoxia-inducible form of 6-phosphofructo-2- kinase/fructose-2,6-bisphosphatase (PFKFB3): A possible new target for cancer therapy

The hypoxia-inducible form of 6-phosphofructo-2-kinase/fructose-2,6- bisphosphatase (PFKFB3) plays a crucial role in the progression of cancerous cells by enabling their glycolytic pathways even under severe hypoxic conditions. To understand its structural architecture and to provide a molecular scaffold for the design of new cancer therapeutics, the crystal structure of the human form was determined. The structure at 2.1 Å resolution shows that the overall folding and functional dimerization are very similar to those of the liver (PFKFB1) and testis (PFKFB4) forms, as expected from sequence homology. However, in this structure, the N-terminal regulatory domain is revealed for the first time among the PFKFB isoforms. With a β-hairpin structure, the N terminus interacts with the 2-Pase domain to secure binding of fructose-6-phosphate to the active pocket, slowing down the release of fructose-6-phosphate from the phosphoenzyme intermediate product complex. The C-terminal regulatory domain is mostly disordered, leaving the active pocket of the fructose-2,6-bisphosphatase domain wide open. The active pocket of the 6-phosphofructo-2-kinase domain has a more rigid conformation, allowing independent bindings of substrates, fructose-6-phosphate and ATP, with higher affinities than other isoforms. Intriguingly, the structure shows an EDTA molecule bound to the fructose-6-phosphate site of the 6-phosphofructo-2-kinase active pocket despite its unfavorable liganding concentration, suggesting a high affinity. EDTA is not removable from the site with fructose-6-P alone but is with both ATP and fructose-6-P or with fructose-2,6-bisphosphate. This finding suggests that a molecule in which EDTA is covalently linked to ADP is a good starting molecule for the development of new cancer-therapeutic molecules. © 2006 by The American Society for Biochemistry and Molecular Biology, Inc

Effects of green manure crops and mulching technology on reduction in herbicide and fertilizer use during rice cultivation in Korea

Green manure crops are primarily used in environmentally friendly agricultural practices to reduce the application of chemical fertilizer and herbicide. In this study, a two-year field experiment was conducted to evaluate the effects of paper and plastic mulching with hairy vetch alone or in combination with barley on weed control and rice yield. In addition, treatment effects on soil redox potential (Eh) and the concentration of ammonium (NH4+) in rice paddy were investigated. The results showed that plastic film (10 or 20 μm) and paper mulching with hairy vetch alone had no significant effects on weed density and rice yield when compared with conventional practice (herbicide and fertilizer application) during the first year. However, during the second year, plastic film (20 μm) with partial tillage of hairy vetch alone increased rice yield and decreased weed occurence; but barley and hairy vetch mixture showed opposite trends. Plastic film mulching led to a decrease in soil redox potential, mainly due to the decomposition of soil organic matter. In addition, plastic film mulching increased NH4+-N contents in rice paddy soil. These results suggest that the combination of plastic film with hairy vetch and barley mixture can be used in rice fields to reduce the use of chemical fertilizer and herbicide.Keywords: Green manure, hairy vetch, mulching, rice, weed co