Lead halide perovskite nanowires stabilized by block copolymers for Langmuir-Blodgett assembly

The rapid development of solar cells based on lead halide perovskites (LHPs) has prompted very active research activities in other closely-related fields. Colloidal nanostructures of such materials display superior optoelectronic properties. Especially, one-dimensional (1D) LHPs nanowires show anisotropic optical properties when they are highly oriented. However, the ionic nature makes them very sensitive to external environment, limiting their large scale practical applications. Here, we introduce an amphiphilic block copolymer, polystyrene-block-poly(4-vinylpyridine) (PS-P4VP), to chemically modify the surface of colloidal CsPbBr3 nanowires. The resulting core-shell nanowires show enhanced photoluminescent emission and good colloidal stability against water. Taking advantage of the stability enhancement, we further applied a modified Langmuir-Blodgett technique to assemble monolayers of highly aligned nanowires, and studied their anisotropic optical properties. [Figure not available: see fulltext.]

Perception and attitude towards work related ill-health and use of dust mask among crushers of selected quarry (crushed stone) industry in Ebonyi State: effect of health education

Background: Quarry industry has become a major means of livelihood in Ebonyi state, but insufficient data exists on their operations and use of control measures like dust mask, with no serious attempt at comprehensive health education. The study sought to assess the effect of health education on the perception and attitude towards work related ill-health, and use of dust mask among crushers of selected quarry industry.Methodology: The study was conducted in the crush stone sites in Abakaliki and environs as the study group, while sites in Ishiagu, Ikenyi and Iyioge Ukwagba were the control group. Study population was 104 crushers, dust mask was provided at all sites, but health education (didactic lectures, demonstrations and interactive sections) for 8weeks was for the study group. Post-intervention evaluations were done at 3 and 6 months. Data was obtained using interviewer administered semi structured questionnaires, tally sheets and bimonthly forms, and analysed using SPSS (16.0) and Mathcad 7.Result: Health education was followed with: significant improvement in the proportion with good perception of work-related ill-health (P<0.00003) in the study group, but not in the control (P<0.639); more significant improvement in the proportion with good perception of dust mask in the study (P<0.00003) than control (P<0.004) group; lesser improvements in attitudes and significant improvement in the proportion that always wore dust mask, 6% to 24% (P<0.003) in the study group.Conclusion: Sustained periodic health education by government and private sectors is necessary, with training on dust mask usage, greater availability and provision of water-cooled caps.Keywords: Quarry Crushers, Ill-health, Dust Mask, Health Education, Ebony

Evidence Propagation and Consensus Formation in Noisy Environments

We study the effectiveness of consensus formation in multi-agent systems where there is both belief updating based on direct evidence and also belief combination between agents. In particular, we consider the scenario in which a population of agents collaborate on the best-of-n problem where the aim is to reach a consensus about which is the best (alternatively, true) state from amongst a set of states, each with a different quality value (or level of evidence). Agents' beliefs are represented within Dempster-Shafer theory by mass functions and we investigate the macro-level properties of four well-known belief combination operators for this multi-agent consensus formation problem: Dempster's rule, Yager's rule, Dubois & Prade's operator and the averaging operator. The convergence properties of the operators are considered and simulation experiments are conducted for different evidence rates and noise levels. Results show that a combination of updating on direct evidence and belief combination between agents results in better consensus to the best state than does evidence updating alone. We also find that in this framework the operators are robust to noise. Broadly, Yager's rule is shown to be the better operator under various parameter values, i.e. convergence to the best state, robustness to noise, and scalability.Comment: 13th international conference on Scalable Uncertainty Managemen

Investigation of a novel composite sorbent for improved sorption characteristic

Novel composite sorbents are developed. Strontium chloride (SrCl2) is selected whereas expanded natural graphite and nanoparticle i.e. carbon coated nickel are integrated as the additive with different densities for the better heat transfer and sorption performance. Thermal properties such as thermal diffusivity and conductivity are investigated by the laser flash method. The sorption performance is tested by the unit which is especially designed. It is indicated that the highest thermal diffusivity could reach 2.242 mm2\ub7s-1 when the density is 1000 kg\ub7m-3 and testing temperature is 20oC. For different testing temperature and density, the thermal diffusivity range from 1.3 mm2\ub7s-1 to 2.242 mm2\ub7s-1. Also worth noting that the highest thermal conductivity could reach 2.5 mm2\ub7s-1 for the environmental temperature. One paramount factor i.e. the global conversion rate of the novel composite SrCl2 is compared and analyzed under different working conditions. It can be found that the higher desorption temperature results in the faster variation of the global conversion rate. In addition, It takes about 15 minutes and 40 minutes to finish the reaction SrCl2 8-1 and 1-0 when the desorption temperature is 180oC and 130oC, respectively. For sorption process, it is indicated that the global conversion rate varies faster with the increase of the sorption temperature. When the global conversion is 0.7, it takes about 14 to 28 minutes when sorption temperature range from -5oC to 15oC

Methods for Analyzing the Role of DNA Methylation and Chromatin Structure in Regulating T Lymphocyte Gene Expression

Chromatin structure, determined in part by DNA methylation, is established during differentiation and prevents expression of genes unnecessary for the function of a given cell type. We reported that DNA methylation and chromatin structure contributes to lymphoid-specific ITGAL (CD11a) and PRF1 (perforin) expression. We used bisulfite sequencing to compare methylation patterns in the ITGAL promoter and 5' flanking region of T cells and fibroblasts, and in the PRF1 promoter and upstream enhancer of CD4+ and CD8+ T cells with fibroblasts. The effects of methylation on promoter function were tested using regional methylation of reporter constructs, and confirmed by DNA methyltransferase inhibition. The relationship between DNA methylation and chromatin structure was analyzed by DNaseI hypersensitivity. Herein we described the methods and results in greater detail

Phase transitions and critical behavior of black branes in canonical ensemble

We study the thermodynamics and phase structure of asymptotically flat non-dilatonic as well as dilatonic black branes in a cavity in arbitrary dimensions ($D$). We consider the canonical ensemble and so the charge inside the cavity and the temperature at the wall are fixed. We analyze the stability of the black brane equilibrium states and derive the phase structures. For the zero charge case we find an analog of Hawking-Page phase transition for these black branes in arbitrary dimensions. When the charge is non-zero, we find that below a critical value of the charge, the phase diagram has a line of first-order phase transition in a certain range of temperatures which ends up at a second order phase transition point (critical point) as the charge attains the critical value. We calculate the critical exponents at that critical point. Although our discussion is mainly concerned with the non-dilatonic branes, we show how it easily carries over to the dilatonic branes as well.Comment: 37 pages, 6 figures, the validity of using the effective action discussed, references adde

Antioxidant capacity of some plants foods and beverages consumed in the eastern region of Nigeria

Today plant foods and beverages are receiving more scientific attention because of their potential to curb the effect of free radicals in the human system. The present study reports on the antioxidant potentials of some plants foods and beverages consumed in the Eastern Region of Nigeria. The study made use of the ferric reducing antioxidant power, phenolic and the flavonoid contents assays to assess the quality of the antioxidant potentials of the plant foods and beverages. Of the different classes of foods analyzed the following showed high antioxidant potentials: coffee for beverages, star apple for fruits, thyme for vegetable and spices, and raices for alcoholic beverages. Generally the vegetables and spices registered the highest antioxidant properties. The results obtained in this study could help consumers’ choice based on the antioxidant capacity of the samples analyzed.Keywords: Antioxidant, phenolic, ferric reducing antioxidant power, flavonoids, plant foods.doi: 10.4314/ajtcam.v8i4.

Phase structure of black branes in grand canonical ensemble

This is a companion paper of our previous work [1] where we studied the thermodynamics and phase structure of asymptotically flat black $p$-branes in a cavity in arbitrary dimensions $D$ in a canonical ensemble. In this work we study the thermodynamics and phase structure of the same in a grand canonical ensemble. Since the boundary data in two cases are different (for the grand canonical ensemble boundary potential is fixed instead of the charge as in canonical ensemble) the stability analysis and the phase structure in the two cases are quite different. In particular, we find that there exists an analog of one-variable analysis as in canonical ensemble, which gives the same stability condition as the rather complicated known (but generalized from black holes to the present case) two-variable analysis. When certain condition for the fixed potential is satisfied, the phase structure of charged black $p$-branes is in some sense similar to that of the zero charge black $p$-branes in canonical ensemble up to a certain temperature. The new feature in the present case is that above this temperature, unlike the zero-charge case, the stable brane phase no longer exists and `hot flat space' is the stable phase here. In the grand canonical ensemble there is an analog of Hawking-Page transition, even for the charged black $p$-brane, as opposed to the canonical ensemble. Our study applies to non-dilatonic as well as dilatonic black $p$-branes in $D$ space-time dimensions.Comment: 32 pages, 2 figures, various points refined, discussion expanded, references updated, typos corrected, published in JHEP 1105:091,201

Spatially-resolved electronic and vibronic properties of single diamondoid molecules

Diamondoids are a unique form of carbon nanostructure best described as hydrogen-terminated diamond molecules. Their diamond-cage structures and tetrahedral sp3 hybrid bonding create new possibilities for tuning electronic band gaps, optical properties, thermal transport, and mechanical strength at the nanoscale. The recently-discovered higher diamondoids (each containing more than three diamond cells) have thus generated much excitement in regards to their potential versatility as nanoscale devices. Despite this excitement, however, very little is known about the properties of isolated diamondoids on metal surfaces, a very relevant system for molecular electronics. Here we report the first molecular scale study of individual tetramantane diamondoids on Au(111) using scanning tunneling microscopy and spectroscopy. We find that both the diamondoid electronic structure and electron-vibrational coupling exhibit unique spatial distributions characterized by pronounced line nodes across the molecular surfaces. Ab-initio pseudopotential density functional calculations reveal that the observed dominant electronic and vibronic properties of diamondoids are determined by surface hydrogen terminations, a feature having important implications for designing diamondoid-based molecular devices.Comment: 16 pages, 4 figures. to appear in Nature Material

All-optical fiber anemometer based on laser heated fiber Bragg gratings

2010-2011 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe