749 research outputs found
Multiphase thermo-hydro-mechanical coupled soil drying model with phase-exchange based on mixture coupling theory
The drying phenomenon in soils involves complex interactions between thermal, hydrological, and mechanical effects within a multiphase system. While several researches (both mechanics and mixture theory approach) has been applied to study various thermo-hydro-mechanical (THM) coupled processes in porous media, incorporating both multiphase flow and phase change in soil drying remains limited. This work addresses this research gap by deriving new governing equations for a two-phase flow model suitable for soil drying by extending the mixture coupling approach. The derived model is implemented in COMSOL Multiphysics and validated against experimental data, demonstrating good agreement between the model predictions and the ob- served results. A sensitivity analysis is performed to investigate the impact of critical parameters on the drying process. The findings reveal that volumetric strain is most sensitive to Youngβs modulus, while the saturation of liquid water is most affected by intrinsic permeability. Additionally, preliminary results for a kaolinite clay sample during the drying process are presented, extending the applicability of the derived model to specific soil types. This research provides a comprehensive framework for fully THM coupled modelling of soil drying, which can serve as a basis for future investigations
Development and Application of an Indirect Competitive Enzyme-Linked Immunoassay for Aflatoxin M1 in Milk and Milk-Based Confectionery
High-titer rabbit polyclonal antibodies to aflatoxin M1 (AFM1) were produced by utilizing AFM1-
bovine serum albumin (BSA) conjugate as an immunogen. An indirect competitive enzyme-linked
immunosorbent assay was standardized for estimating AFM1 in milk and milk products. To avoid the
influence of interfering substances present in the milk samples, it was necessary to prepare AFM1
standards in methanol extracts of certified reference material (CRM) not containing detectable AFM1
(<0.05 ng/g). The reliability of the procedure was assessed by using CRM with AFM1 concentrations
of <0.5 and 0.76 ng/g. Also, assays of milk samples mixed with AFM1 ranging in concentration
between 0.5 and 50 ng/L gave recoveries of >93%. The relative cross-reactivity with aflatoxins (AF)
and ochratoxin A, assessed as the amount of AFM1 necessary to cause 50% inhibition of binding,
was 5% for AFB1 and much less for AFB2, AFG1, and AFG2; there was no reaction with ochratoxin
A. AFM1 contamination was measured in retail milk and milk products collected from rural and
periurban areas in Andhra Pradesh, India. Of 280 milk samples tested, 146 were found to contain
<0.5 ng/mL of AFM1; in 80 samples it varied from 0.6 to 15 ng/mL, in 42 samples from 16 to 30
ng/mL, and in 12 samples from 31 to 48 ng/mL. Most of the milk samples that contained high AFM1
concentrations were obtained from periurban locations. The results revealed a significant exposure
of humans to AFM1 levels in India and thus highlight the need for awareness of risk among milk
producers and consumers
On the relevance of earnings components in valuation and forecasting
Pre-print also submitted to SSRN Archive. The final publication is available at Springer via http://dx.doi.org/ 10.1007/s11156-013-0347-yThis paper articulates the links between relevance of an earnings component in forecasting (abnormal) earnings and its relevance in valuation in a nonlinear framework. The analysis shows that forecasting relevance does not imply valuation relevance even though valuation irrelevance is implied by forecasting irrelevance. Firstly, I consider an accounting information system where earnings components "add up" to a fully informative earnings number. Secondly, I analyze two accounting systems where a "core" earnings component is the relevant earnings construct for valuation and the second earnings component is irrelevant but may be predictable and relevant in forecasting other accounting items. I find that dividend displacement effect on earnings and the dynamics of individual earnings components are critical in this analysis
Alteration of Proteins and Pigments Influence the Function of Photosystem I under Iron Deficiency from Chlamydomonas reinhardtii
BACKGROUND: Iron is an essential micronutrient for all organisms because it is a component of enzyme cofactors that catalyze redox reactions in fundamental metabolic processes. Even though iron is abundant on earth, it is often present in the insoluble ferric [Fe (III)] state, leaving many surface environments Fe-limited. The haploid green alga Chlamydomonas reinhardtii is used as a model organism for studying eukaryotic photosynthesis. This study explores structural and functional changes in PSI-LHCI supercomplexes under Fe deficiency as the eukaryotic photosynthetic apparatus adapts to Fe deficiency. RESULTS: 77K emission spectra and sucrose density gradient data show that PSI and LHCI subunits are affected under iron deficiency conditions. The visible circular dichroism (CD) spectra associated with strongly-coupled chlorophyll dimers increases in intensity. The change in CD signals of pigments originates from the modification of interactions between pigment molecules. Evidence from sucrose gradients and non-denaturing (green) gels indicates that PSI-LHCI levels were reduced after cells were grown for 72 h in Fe-deficient medium. Ultrafast fluorescence spectroscopy suggests that red-shifted pigments in the PSI-LHCI antenna were lost during Fe stress. Further, denaturing gel electrophoresis and immunoblot analysis reveals that levels of the PSI subunits PsaC and PsaD decreased, while PsaE was completely absent after Fe stress. The light harvesting complexes were also susceptible to iron deficiency, with Lhca1 and Lhca9 showing the most dramatic decreases. These changes in the number and composition of PSI-LHCI supercomplexes may be caused by reactive oxygen species, which increase under Fe deficiency conditions. CONCLUSIONS: Fe deficiency induces rapid reduction of the levels of photosynthetic pigments due to a decrease in chlorophyll synthesis. Chlorophyll is important not only as a light-harvesting pigment, but also has a structural role, particularly in the pigment-rich LHCI subunits. The reduced level of chlorophyll molecules inhibits the formation of large PSI-LHCI supercomplexes, further decreasing the photosynthetic efficiency
Low-Resolution Molecular Models Reveal the Oligomeric State of the PPAR and the Conformational Organization of Its Domains in Solution
The peroxisome proliferator-activated receptors (PPARs) regulate genes involved in lipid and carbohydrate metabolism, and are targets of drugs approved for human use. Whereas the crystallographic structure of the complex of full length PPARΞ³ and RXRΞ± is known, structural alterations induced by heterodimer formation and DNA contacts are not well understood. Herein, we report a small-angle X-ray scattering analysis of the oligomeric state of hPPARΞ³ alone and in the presence of retinoid X receptor (RXR). The results reveal that, in contrast with other studied nuclear receptors, which predominantly form dimers in solution, hPPARΞ³ remains in the monomeric form by itself but forms heterodimers with hRXRΞ±. The low-resolution models of hPPARΞ³/RXRΞ± complexes predict significant changes in opening angle between heterodimerization partners (LBD) and extended and asymmetric shape of the dimer (LBD-DBD) as compared with X-ray structure of the full-length receptor bound to DNA. These differences between our SAXS models and the high-resolution crystallographic structure might suggest that there are different conformations of functional heterodimer complex in solution. Accordingly, hydrogen/deuterium exchange experiments reveal that the heterodimer binding to DNA promotes more compact and less solvent-accessible conformation of the receptor complex
Socioeconomic Inequalities in Childhood Undernutrition in India: Analyzing Trends between 1992 and 2005
India experienced a rapid economic boom between 1991 and 2007. However, this economic growth has not translated into improved nutritional status among young Indian children. Additionally, no study has assessed the trends in social disparities in childhood undernutrition in the Indian context. We examined the trends in social disparities in underweight and stunting among Indian children aged less than three years using nationally representative data.We analyzed data from the three cross-sectional rounds of National Family Health Survey of India from 1992, 1998 and 2005. The social factors of interest were: household wealth, maternal education, caste, and urban residence. Using multilevel modeling to account for the nested structure and clustering of data, we fit multivariable logistic regression models to quantify the association between the social factors and the binary outcome variables. The final models additionally included age, gender, birth order of child, religion, and age of mother. We analyzed the trend by testing for interaction of the social factor and survey year in a dataset pooled from all three surveys.While the overall prevalence rates of undernutrition among Indian children less than three decreased over the 1992-2005 period, social disparities in undernutrition over these 14 years either widened or stayed the same. The absolute rates of undernutrition decreased for everyone regardless of their social status. The disparities by household wealth were greater than the disparities by maternal education. There were no disparities in undernutrition by caste, gender or rural residence.There was a steady decrease in the rates of stunting in the 1992-2005 period, while the decline in underweight was greater between 1992 and 1998 than between 1998 and 2005. Social disparities in childhood undernutrition in India either widened or stayed the same during a time of major economic growth. While the advantages of economic growth might be reaching everyone, children from better-off households, with better educated mothers appear to have benefited to a greater extent than less privileged children. The high rates of undernutrition (even among the socially advantaged groups) and the persistent social disparities need to be addressed in an urgent and comprehensive manner
Generation of Induced Pluripotent Stem Cells from the Prairie Vole
The vast majority of animals mate more or less promiscuously. A few mammals, including humans, utilize more restrained mating strategies that entail a longer term affiliation with a single mating partner. Such pair bonding mating strategies have been resistant to genetic analysis because of a lack of suitable model organisms. Prairie voles are small mouse-like rodents that form enduring pair bonds in the wild as well as in the laboratory, and consequently they have been used widely to study social bonding behavior. The lack of targeted genetic approaches in this species however has restricted the study of the molecular and neural circuit basis of pair bonds. As a first step in rendering the prairie vole amenable to reverse genetics, we have generated induced pluripotent stem cell (IPSC) lines from prairie vole fibroblasts using retroviral transduction of reprogramming factors. These IPSC lines display the cellular and molecular hallmarks of IPSC cells from other organisms, including mice and humans. Moreover, the prairie vole IPSC lines have pluripotent differentiation potential since they can give rise to all three germ layers in tissue culture and in vivo. These IPSC lines can now be used to develop conditions that facilitate homologous recombination and eventually the generation of prairie voles bearing targeted genetic modifications to study the molecular and neural basis of pair bond formation
Locating the Binding Sites of Pb(II) Ion with Human and Bovine Serum Albumins
Lead is a potent environmental toxin that has accumulated above its natural level as a result of human activity. Pb cation shows major affinity towards protein complexation and it has been used as modulator of protein-membrane interactions. We located the binding sites of Pb(II) with human serum (HSA) and bovine serum albumins (BSA) at physiological conditions, using constant protein concentration and various Pb contents. FTIR, UV-visible, CD, fluorescence and X-ray photoelectron spectroscopic (XPS) methods were used to analyse Pb binding sites, the binding constant and the effect of metal ion complexation on HSA and BSA stability and conformations. Structural analysis showed that Pb binds strongly to HSA and BSA via hydrophilic contacts with overall binding constants of KPb-HSAβ=β8.2 (Β±0.8)Γ104 Mβ1 and KPb-BSAβ=β7.5 (Β±0.7)Γ104 Mβ1. The number of bound Pb cation per protein is 0.7 per HSA and BSA complexes. XPS located the binding sites of Pb cation with protein N and O atoms. Pb complexation alters protein conformation by a major reduction of Ξ±-helix from 57% (free HSA) to 48% (metal-complex) and 63% (free BSA) to 52% (metal-complex) inducing a partial protein destabilization
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