541 research outputs found
Coherence in amalgamated algebra along an ideal
Let be a ring homomorphism and let be an ideal of
. In this paper, we investigate the transfert of the property of coherence
to the amalgamation . We provide necessary and sufficient
conditions for to be a coherent ring
Development of a novel corrugated polyvinylidene difluoride membrane via improved imprinting technique for membrane distillation
© 2019 by the authors. Membrane distillation (MD) is an attractive technology for desalination, mainly because its performance that is almost independent of feed solute concentration as opposed to the reverse osmosis process. However, its widespread application is still limited by the low water flux, low wetting resistance and high scaling vulnerability. This study focuses on addressing those limitations by developing a novel corrugated polyvinylidene difluoride (PVDF) membrane via an improved imprinting technique for MD. Corrugations on the membrane surface are designed to offer an effective surface area and at the same time act as a turbulence promoter to induce hydrodynamic by reducing temperature polarization. Results show that imprinting of spacer could help to induce surface corrugation. Pore defect could be minimized by employing a dual layer membrane. In short term run experiment, the corrugated membrane shows a flux of 23.1 Lm-2h-1 and a salt rejection of > 99%, higher than the referenced flat membrane (flux of 18.0 Lm-2h_asuf and similar rejection). The flux advantage can be ascribed by the larger effective surface area of the membrane coupled with larger pore size. The flux advantage could be maintained in the long-term operation of 50 h at a value of 8.6 Lm-2h-1. However, the flux performance slightly deteriorates over time mainly due to wetting and scaling. An attempt to overcome this limitation should be a focus of the future study, especially by exploring the role of cross-flow velocity in combination with the corrugated surface in inducing local mixing and enhancing system performance
Secondary Organic Aerosol Formation from the β-Pinene+NO3 System: Effect of Humidity and Peroxy Radical Fate
The formation of secondary organic aerosol (SOA) from the oxidation of β-pinene via nitrate radicals is investigated in the Georgia Tech Environmental Chamber (GTEC) facility. Aerosol yields are determined for experiments performed under both dry (relative humidity (RH) \u3c 2 %) and humid (RH = 50 % and RH = 70 %) conditions. To probe the effects of peroxy radical (RO2) fate on aerosol formation, RO2 + NO3 dominant and RO2 + HO2 dominant experiments are performed. Gas-phase organic nitrate species (with molecular weights of 215, 229, 231, and 245 amu, which likely correspond to molecular formulas of C10H17NO4, C10H15NO5, C10H17NO5, and C10H15NO6, respectively) are detected by chemical ionization mass spectrometry (CIMS) and their formation mechanisms are proposed. The NO+ (at m/z 30) and NO2+ (at m/z 46) ions contribute about 11 % to the combined organics and nitrate signals in the typical aerosol mass spectrum, with the NO+ : NO2+ ratio ranging from 4.8 to 10.2 in all experiments conducted. The SOA yields in the RO2 + NO3 dominant and RO2 + HO2 dominant experiments are comparable. For a wide range of organic mass loadings (5.1–216.1 μg m−3), the aerosol mass yield is calculated to be 27.0–104.1 %. Although humidity does not appear to affect SOA yields, there is evidence of particle-phase hydrolysis of organic nitrates, which are estimated to compose 45–74 % of the organic aerosol. The extent of organic nitrate hydrolysis is significantly lower than that observed in previous studies on photooxidation of volatile organic compounds in the presence of NOx. It is estimated that about 90 and 10 % of the organic nitrates formed from the β-pinene+NO3 reaction are primary organic nitrates and tertiary organic nitrates, respectively. While the primary organic nitrates do not appear to hydrolyze, the tertiary organic nitrates undergo hydrolysis with a lifetime of 3–4.5 h. Results from this laboratory chamber study provide the fundamental data to evaluate the contributions of monoterpene + NO3 reaction to ambient organic aerosol measured in the southeastern United States, including the Southern Oxidant and Aerosol Study (SOAS) and the Southeastern Center for Air Pollution and Epidemiology (SCAPE) study
Predictors of subjective well-being among older Ghanaians
Background: Later years of life are accompanied by many physical, emotional and environmental changes which may impact on the well-being of the individual. Many factors are known to influence the subjectivewell-being of older adults, but most, if not all of this information was the result of studies in the Western world. This study aimed at obtaining and documenting the predictors of subjective well-being (SWB) among older Ghanaians.Methods: Data for the study was obtained from the WHO SAGE study. The single item measure of life satisfaction was used to determine subjective wellbeing. Descriptive statistics as well as logistic regression analysis were carried out to determine the predictors of SWB.Results: A total of 4724 individuals aged 50 years and above responded to the questionnaires. Of these 50.4% were males. Following multivariate logistic regression analysis, age, sex, educational level, income and ethnicbackground were found to significantly affect the SWB of older Ghanaians. Being male was associated with higher level of SWB (OR=1.68; CI: 1.39 – 2.03). For those 50 years and above, being younger (50-59 years) was also associated with a high level of SWB (OR=17.72; CI: 10.13-30.98). Earning a low income and having low educational level were both associatedwith low levels of SWB (OR=0.304; CI: 0.22-0.42; and OR=0.47; CI: 0.37-0.60 respectively). Ewes (p=0.027), Grumas (p=0.002) and Mole-Dagbons (p=0.04) had significantly higher SWB compared to the other ethnic groups.Conclusion: Among older Ghanaians, factors that positively influence SWB are younger age, male sex, high educational level and high income.Keywords: Subjective well-being, Life satisfaction, Older Ghanaians, SAGE study, Predictor
Quantum Size Effects on the Chemical Sensing Performance of Two-Dimensional Semiconductors
We investigate the role of quantum confinement on the performance of gas
sensors based on two-dimensional InAs membranes. Pd-decorated InAs membranes
configured as H2 sensors are shown to exhibit strong thickness dependence, with
~100x enhancement in the sensor response as the thickness is reduced from 48 to
8 nm. Through detailed experiments and modeling, the thickness scaling trend is
attributed to the quantization of electrons which favorably alters both the
position and the transport properties of charge carriers; thus making them more
susceptible to surface phenomena
Increased Oxidative Burden Associated with Traffic Component of Ambient Particulate Matter at Roadside and Urban Background Schools Sites in London
As the incidence of respiratory and allergic symptoms has been reported to be increased in children attending schools in close proximity to busy roads, it was hypothesised that PM from roadside schools would display enhanced oxidative potential (OP). Two consecutive one-week air quality monitoring campaigns were conducted at seven school sampling sites, reflecting roadside and urban background in London. Chemical characteristics of size fractionated particulate matter (PM) samples were related to the capacity to drive biological oxidation reactions in a synthetic respiratory tract lining fluid. Contrary to hypothesised contrasts in particulate OP between school site types, no robust size-fractionated differences in OP were identified due high temporal variability in concentrations of PM components over the one-week sampling campaigns. For OP assessed both by ascorbate (OPAA m−3) and glutathione (OPGSH m−3) depletion, the highest OP per cubic metre of air was in the largest size fraction, PM1.9–10.2. However, when expressed per unit mass of particles OPAA µg−1 showed no significant dependence upon particle size, while OPGSH µg−1 had a tendency to increase with increasing particle size, paralleling increased concentrations of Fe, Ba and Cu. The two OP metrics were not significantly correlated with one another, suggesting that the glutathione and ascorbate depletion assays respond to different components of the particles. Ascorbate depletion per unit mass did not show the same dependence as for GSH and it is possible that other trace metals (Zn, Ni, V) or organic components which are enriched in the finer particle fractions, or the greater surface area of smaller particles, counter-balance the redox activity of Fe, Ba and Cu in the coarse particles. Further work with longer-term sampling and a larger suite of analytes is advised in order to better elucidate the determinants of oxidative potential, and to fuller explore the contrasts between site types.\ud
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A framework for the successful implementation of food traceability systems in China
Implementation of food traceability systems in China faces many challenges due to the scale, diversity and complexity of China’s food supply chains. This study aims to identify critical success factors specific to the implementation of traceability systems in China. Twenty-seven critical success factors were identified in the literature. Interviews with managers at four food enterprises in a pre-study helped identify success criteria
and five additional critical success factors. These critical success factors were tested through a survey of managers in eighty-three food companies. This study identifies six dimensions for critical success factors: laws, regulations and standards; government support; consumer knowledge and support; effective management and communication; top management and vendor support; and information and system quality
Elaboraci?n e implementaci?n de un Cuadro de Mandos para el control y monitoreo de las nuevas sedes de Pardo?s Chicken
El presente trabajo presenta un plan de acci?n para la apertura de dos unidades de la red Pardos Chicken en provincias usando el Modelo OKR. Pardos Chicken es una importante cadena peruana de restaurantes con m?s de 36 a?os de experiencia en el sector. Pardos pertenece al Holding Wu Restaurantes y son embajadores de la gastronom?a peruana a trav?s del plato bandera de Pollo a la Brasa. En concordancia con los objetivos empresariales de Pardos, las ciudades a elecci?n para la apertura de sus nuevas unidades son Arequipa y Cusco, ciudades no solo importantes econ?micamente, sino con alto atractivo tur?stico, tanto nacional como internacional. El campo de acci?n del presente trabajo son las actividades de marketing necesarias y esenciales a la hora de realizar el desarrollo de nuevos mercados con un servicio, en este caso, una sucursal de una cadena de restaurantes
Avicenna and cancer study
Cancer is the main cause of mortality after COVID-19, reaching pandemicity and remains one of major public health concern. It is worthwhile to consider the perspectives of the renowned medical scholar, Avicenna and he is widely regarded as the prince of physicians. However not much recent paper discussed on his practice on treating cancer. The review's goal was to discuss the background of Avicenna's bibliography and history in cancer study. This review encompasses 25 literatures and begins with a description of his profile and attitude. It then explains his medical background and interests, with an emphasis on cancer research. His contribution and a major milestone in cancer research were described. It also explains in great depth his perspective on cancer research. His proposed and implemented cancer prevention and treatment are listed and advised in order to lessen the negative impacts of cancer. To conclude, early detection and preventative measures aid in the reduction of cancer progression. In addition, plant base and less irritant treatment as well as improving the diet help to reduce malignancy. This review might contribute to give an insight to improve the current cancer treatment by looking back into the perspective of great scholar in medical field
Deficiency and Also Transgenic Overexpression of Timp-3 Both Lead to Compromised Bone Mass and Architecture In Vivo
Tissue inhibitor of metalloproteinases-3 (TIMP-3) regulates extracellular matrix via its inhibition of matrix metalloproteinases and membrane-bound sheddases. Timp-3 is expressed at multiple sites of extensive tissue remodelling. This extends to bone where its role, however, remains largely unresolved. In this study, we have used Micro-CT to assess bone mass and architecture, histological and histochemical evaluation to characterise the skeletal phenotype of Timp-3 KO mice and have complemented this by also examining similar indices in mice harbouring a Timp-3 transgene driven via a Col-2a-driven promoter to specifically target overexpression to chondrocytes. Our data show that Timp-3 deficiency compromises tibial bone mass and structure in both cortical and trabecular compartments, with corresponding increases in osteoclasts. Transgenic overexpression also generates defects in tibial structure predominantly in the cortical bone along the entire shaft without significant increases in osteoclasts. These alterations in cortical mass significantly compromise predicted tibial load-bearing resistance to torsion in both genotypes. Neither Timp-3 KO nor transgenic mouse growth plates are significantly affected. The impact of Timp-3 deficiency and of transgenic overexpression extends to produce modification in craniofacial bones of both endochondral and intramembranous origins. These data indicate that the levels of Timp-3 are crucial in the attainment of functionally-appropriate bone mass and architecture and that this arises from chondrogenic and osteogenic lineages
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