Catalyctic reduction of nitric oxide by carbon monoxide and copper loaded granular activated carbon in the presence of oxygen

The reduction reaction of nitric oxide (NO) by carbon monoxide (CO), and granular activated carbon (GAC) in the presence and absence of oxygen was studied in a fixed bed catalytic reactor. The conversion of NO as a function of reaction temperature was evaluated for various reductant to NO ratios and space velocities. The results show that oxygen enhanced the NO+CO reaction over copper (Cu) ion exchanged ZSM-5. About 60% NO conversion to nitrogen (N2) was obtained at 400°C and 2,000 v/v/hr. This result is consistent with the hypothesis that CO is an intermediate in the soot-NO reaction. The apparent mechanism seems to be the soot-O2 reaction produces CO on the surface, the CO diffuses into the catalyst pores where it preferentially reacts with NO to produce carbon dioxide (CO2) and N2. The overall observation is that soot or GAC in the presence of oxygen reduces NO to N2 and CO2 if a Cu containing catalyst is present. One observes that Cu ion dispersed in GAC in the presence of 10% oxygen promotes the formation of CO at a relatively low temperature. This is followed by essentially complete NO conversion to N2 at 600°C and 2,000 v/v/hr and 20,000 v/v/hr. At 450°C, 95% NO is converted to N2 at 2,000 v/v/hr-. The reaction rate of NO conversion to N2 decreases with increasing space velocity with either CO or carbon black as the reducing materials. Based on the results presented here, additional research on the catalytic reduction of NO by CO on the results presented here, additional research on the catalytic reduction of NO by CO and copper loaded GAC in the presence of O2, at higher space velocities between 50,000 and 100,000 v/v/hr is warranted. Effect of water on the two reactions is also needed to be studied

Precheck Sequence Based False Base Station Detection During Handover: A Physical Layer Based Security Scheme

False Base Station (FBS) attack has been a severe security problem for the cellular network since 2G era. During handover, the user equipment (UE) periodically receives state information from surrounding base stations (BSs) and uploads it to the source BS. The source BS compares the uploaded signal power and shifts UE to another BS that can provide the strongest signal. An FBS can transmit signal with the proper power and attract UE to connect to it. In this paper, based on the 3GPP standard, a Precheck Sequence-based Detection (PSD) Scheme is proposed to secure the transition of legal base station (LBS) for UE. This scheme first analyzes the structure of received signals in blocks and symbols. Several additional symbols are added to the current signal sequence for verification. By designing a long table of symbol sequence, every UE which needs handover will be allocated a specific sequence from this table. The simulation results show that the performance of this PSD Scheme is better than that of any existing ones, even when a specific transmit power is designed for FBS

Black-Box Variational Inference Converges

We provide the first convergence guarantee for full black-box variational inference (BBVI), also known as Monte Carlo variational inference. While preliminary investigations worked on simplified versions of BBVI (e.g., bounded domain, bounded support, only optimizing for the scale, and such), our setup does not need any such algorithmic modifications. Our results hold for log-smooth posterior densities with and without strong log-concavity and the location-scale variational family. Also, our analysis reveals that certain algorithm design choices commonly employed in practice, particularly, nonlinear parameterizations of the scale of the variational approximation, can result in suboptimal convergence rates. Fortunately, running BBVI with proximal stochastic gradient descent fixes these limitations, and thus achieves the strongest known convergence rate guarantees. We evaluate this theoretical insight by comparing proximal SGD against other standard implementations of BBVI on large-scale Bayesian inference problems.Comment: under revie

Cognitively diagnostic analysis using the G-DINA model in R

Cognitive diagnosis models (CDMs) have increasingly been applied in education and other fields. This article provides an overview of a widely used CDM, namely, the G-DINA model, and demonstrates a hands-on example of using multiple R packages for a series of CDM analyses. This overview involves a step-by-step illustration and explanation of performing Q-matrix evaluation, CDM calibration, model fit evaluation, item diagnosticity investigation, classification reliability examination, and the result presentation and visualization. Some limitations of conducting CDM analysis in R are also discusse

Research Progress on Improving the Survival Rate and Extending the Storage Period of Lactic Acid Bacteria through Vacuum Freeze-Drying

The survival rate and storage period of lactic acid bacteria (LAB) are affected by numerous factors in the vacuum freeze-drying process. Hence, optimizing the freeze-drying process and storage conditions is an effective method to improve the survival rate and prolong the storage period of LAB. This paper reviews the factors that influence the survival rate of LAB during the vacuum freeze-drying process and explores how to optimize the freeze-drying process and storage conditions to improve the survival rate and extend the storage period of LAB. We expect that this review will provide a basis and reference for the preparation of lyophilized LAB formulations with high activity and good storage stability

STAT4 deficiency reduces obesity-induced insulin resistance and adipose tissue inflammation

Signal transducer and activator of transcription (STAT) 4 is one of the seven members of the STAT family. STAT4 has a prominent role in mediating interleukin-12-induced T-helper cell type 1 lineage differentiation. T cells are key players in the maintenance of adipose tissue (AT) inflammation. The role of STAT4 in obesity and AT inflammation is unknown. We sought to determine the role of STAT4 in AT inflammation in obesity-induced insulin resistance. We studied STAT4-null mice on the C57Bl6/J background. We have found that STAT4(-/-)C57Bl6/J mice develop high-fat diet-induced obesity (DIO) similar to wild-type controls, but that they have significantly improved insulin sensitivity and better glucose tolerance. Using flow cytometry and real-time PCR, we show that STAT4(-/-) mice with DIO produce significantly reduced numbers of inflammatory cytokines and chemokines in adipocytes, have reduced numbers of CD8(+) cells, and display increased alternative (M2) macrophage polarization. CD8(+) cells, but not CD4(+) cells, from STAT4(-/-) mice displayed reduced in vitro migration. Also, we found that adipocyte inflammation is reduced and insulin signaling is improved in STAT4(-/-) mice with DIO. We have identified STAT4 as a key contributor to insulin resistance and AT inflammation in DIO. Targeting STAT4 activation could be a novel approach to reducing AT inflammation and insulin resistance in obesity

Spectroscopic Evidence for Interfacial Charge Separation and Recombination in Graphene-MoS2 Vertical Heterostructures

Vertical van der Waals (vdW) heterostructures consisting of graphene (Gr) and transition metal dichalcogenides (TMDs) have created a fascinating platform for exploring optical and electronic properties in the two-dimensional limit. Previous study has revealed the ultrafast formation of interfacial excitons and the exciton dynamics in the Gr/MoS2 heterostructure. However, a fully understanding of interfacial charge separation and the subsequent dynamics in graphene-based heterostructures remains elusive. Here, we investigate the carrier dynamics of Gr-MoS2 (including Gr/MoS2 and MoS2/Gr stacking sequences) heterostructures under different photoexcitation energies and stacking sequences by comprehensive ultrafast means, including time-resolved terahertz spectroscopy (TRTS), terahertz emission spectroscopy (TES) and transient absorption spectroscopy (TAS). We demonstrate that the Gr/MoS2 heterostructure generates hot electron injection from graphene into the MoS2 layer with photoexcitation of sub-A-exciton of MoS2, while the interfacial charge separation in the MoS2/Gr could be partially blocked by the electric field of substrate. Charge transfer (CT) occurs in same directions for the Gr-MoS2 heterostructures with opposite stacking order, resulting in the opposite orientations of the interfacial photocurrent, as directly demonstrated by the terahertz (THz) emission. Moreover, we demonstrate that the recombination time of interfacial charges after CT is on a timescale of 18 ps to 1 ns, depending on the density of defect states in MoS2 layer. This work provides a comprehensive and unambiguous picture of the interfacial charge dynamics of graphene-based heterostructures, which is essential for developing Gr/TMDs based optoelectronic devices.Comment: 23 pages, 5 Figure

Effects of chloride ions in acid-catalyzed biomass dehydration reactions in polar aprotic solvents

The use of polar aprotic solvents in acid-catalyzed biomass conversion reactions can lead to improved reaction rates and selectivities. We show that further increases in catalyst performance in polar aprotic solvents can be achieved through the addition of inorganic salts, specifically chlorides. Reaction kinetics studies of the Brønsted acid-catalyzed dehydration of fructose to hydroxymethylfurfural (HMF) show that the use of catalytic concentrations of chloride salts leads to a 10-fold increase in reactivity. Furthermore, increased HMF yields can be achieved using polar aprotic solvents mixed with chlorides. Ab initio molecular dynamics simulations (AIMD) show that highly localized negative charge on Cl− allows the chloride anion to more readily approach and stabilize the oxocarbenium ion that forms and the deprotonation transition state. High concentrations of polar aprotic solvents form local hydrophilic environments near the reactive hydroxyl group which stabilize both the proton and chloride anions and promote the dehydration of fructose

12-Lipoxygenase Inhibitor Improves Functions of Cytokine-Treated Human Islets and Type 2 Diabetic Islets

Context: The 12-lipoxygenase (12-LO) pathway produces proinflammatory metabolites, and its activation is implicated in islet inflammation associated with type 1 and type 2 diabetes (T2D). Objectives: We aimed to test the efficacy of ML355, a highly selective, small molecule inhibitor of 12-LO, for the preservation of islet function. Design: Human islets from nondiabetic donors were incubated with a mixture of tumor necrosis factor α , interluekin-1β, and interferon-γ to model islet inflammation. Cytokine-treated islets and human islets from T2D donors were incubated in the presence and absence of ML355. Setting: In vitro study. Participants: Human islets from organ donors aged >20 years of both sexes and any race were used. T2D status was defined from either medical history or most recent hemoglobin A1c value >6.5%. Intervention: Glucose stimulation. Main Outcome Measures: Static and dynamic insulin secretion and oxygen consumption rate (OCR). Results: ML355 prevented the reduction of insulin secretion and OCR in cytokine-treated human islets and improved both parameters in human islets from T2D donors. Conclusions: ML355 was efficacious in improving human islet function after cytokine treatment and in T2D islets in vitro. The study suggests that the blockade of the 12-LO pathway may serve as a target for both form of diabetes and provides the basis for further study of this small molecule inhibitor in vivo