Low Consumption Rate Research Articles

Nutritional Status of Pregnant Women in Relation to Anthropometric Measurements of Mothers and Their Newborns

Due to lack of awareness of food and incorrect food habits of pregnant women during pregnancy, the objective of this study is an assessment of the diets of pregnant women; that can affect anthropometric measurements of mothers and their newborns; in the third trimester of pregnancy (36- 40week).Information of pregnant women (20) was collected. The obtained results showed lower rates of food intake and consumption than allowable dietary recommendations with the exception of animal protein and fat, despite the lack of iron in the diet, and lack of hemoglobin in the blood. The intake of vegetable protein and fiber was very poor. The quantity of sodium consumed was higher than the recommended dietary allowances (RDA) while, the intakes of other micronutrients were lower than the respective RDA with the exception of phosphorus, copper and zinc which were not statistically different from the RDA. When, pregnant women were divided into two groups according to birth weights (Group one 2 kg and Group two< 2 kg), The data showed a significant increase in plant protein intake, total protein and calories for the second group compared to the first group also, the second group was characterized by higher amounts of sugar, fat and yogurt and cooked vegetables. Likewise significant increases in some anthropometric measurements of the second group compared to the first group, especially in weight and thickness of skin layer were found. Furthermore, the relationship between anthropometric measurements of infants and intake of nutrients of the mother revealed that there was a significant positive relationship between birth weight and total calories, and there was a significant positive relationship between protein intake and the length of birth and body mass index of births that was directly proportional to both total protein and total calorie intake during the last third of pregnancy. In conclusion, this study provides indications that pregnancy could indeed be a life event leading to increased general nutrition awareness that might influence pregnant women’s future nutrition-related behaviors.

Enhanced expression of genes involved in initial xylose metabolism and the oxidative pentose phosphate pathway in the improved xylose-utilizing Saccharomyces cerevisiae through evolutionary engineering

Fermentation of xylose in lignocellulosic hydrolysates by Saccharomycescerevisiae has been achieved through heterologous expression of the xylose reductase (XR)-xylitol dehydrogenase (XDH) pathway. However, the fermentation efficiency is far from the requirement for industrial application due to high yield of the byproduct xylitol, low ethanol yield, and low xylose consumption rate. Through evolutionary engineering, an improved xylose-utilizing strain SyBE005 was obtained with 78.3% lower xylitol production and a 2.6-fold higher specific ethanol production rate than those of the parent strain SyBE004, which expressed an engineered NADP(+)-preferring XDH. The transcriptional differences between SyBE005 and SyBE004 were investigated by quantitative RT-PCR. Genes including XYL1, XYL2, and XKS1 in the initial xylose metabolic pathway showed the highest up-regulation in SyBE005. The increased expression of XYL1 and XYL2 correlated with enhanced enzymatic activities of XR and XDH. In addition, the expression level of ZWF1 in the oxidative pentose phosphate pathway increased significantly in SyBE005, indicating an elevated demand for NADPH from XR. Genes involved in the TCA cycle (LAT1, CIT1, CIT2, KGD1, KGD, SDH2) and gluconeogenesis (ICL1, PYC1) were also up-regulated in SyBE005. Genomic analysis revealed that point mutations in transcriptional regulators CYC8 and PHD1 might be responsible for the altered expression. In addition, a mutation (Y89S) in ZWF1 was identified which might improve NADPH production in SyBE005. Our results suggest that increasing the expression of XYL1, XYL2, XKS1, and enhancing NADPH supply are promising strategies to improve xylose fermentation in recombinant S. cerevisiae.

New Vegetal Biopolymeric Flocculant: A Degradation and Flocculation Study

Polyacrylamide (PAM) is known to pose a hazard to human health. A newly explored plant-based flocculant, malva nut gum (MNG) is hypothesized to treat water and as a green material. This study investigates the biodegradation, thermal degradation and photodegradation of MNG and its flocculation capability. The results show MNG has a high biodegradation rate and low oxygen consumption rate. MNG biodegraded at Day-17, whilst, PAM did not show completion of biodegradation by the end of the experiment. Thermal degradation analysis shows MNG has a few decomposition stages and ash content. The photodegradation analysis shows photochemical changes in the structure of MNG and PAM. Factorial experiments show pH, concentration of cation and the concentration of MNG were the influential factors in coagulation-flocculation process. Optimization study observed 97% turbidity reduction at pH 5.77, the concentration of cation at 0.05 mM and the concentration of MNG at 0.42 mg/L. Conclusively, MNG operates effectively at near neutral pH and at low concentration. Such results strongly suggest that MNG is a suitable candidate, which could be used to replace PAM, as flocculant in water treatment.

고성능 히트펌프 해석모델 개발 연구

히트 펌프는 지열이나 태양열 등의 신재생 에너지를 이용하거나 기타 폐열을 재활용하여 기존의 전기 히팅 난방 시스템들보다 에너지 소비율을 낮출 수 있다는 장점으로 인해 그린 에너지 시스템으로써 주목을 받아 왔다. 고효율 히트펌프 시스템 설계를 위한 연구는 오랫동안 지속되어 왔지만, 각각의 구성요소가 유기적이며, 변화에 유연한 해석모델은 존재하지 않는다. 따라서 본 연구에서는 공기 열 원식 히트 펌프를 AMESim Software를 이용해 구성하였다. 독자적으로 개발한 스크롤 압축기 해석 모델을 히트펌프 시스템에 조합함으로써 효율 향상 방안을 모색하였으며, 실험 데이터를 이용하여 개발한 해석모델을 검증하였다. 실험 데이터와 개발한 해석 모델을 이용하여 예측된 데이터를 비교한 결과 최대 오차가 10% 이내로 두 데이터가 잘 일치하였다. 본 연구에서 개발한 히트펌프 해석모델은 향후 시제품을 개발하고 효율 향상을 위한 연구 등에 유용하게 사용될 것으로 사료된다. Heat pumps have attracted considerable attention as a green energy system because they use renewable energy, such as geothermal, solar energy and waste heat, and can have a low electricity consumption rate compared to other conventional electric heating system. Many studies of high efficient heat pump system design was performed previously,but it is not easy to find any an analytical model that consists of components (e.g. compressor, heat exchangers, and expansion valve), not only having an interrelation and interconnection each other but also being flexible to any change in geometry and operating parameters. In this study, a computational model was developed for a heat pump with warm air as a heat source using the one-dimensional modeling software, AMESim. In combination with an independently-developed analytical model for a scroll compressor, the heat pump model can simulate the physical characteristics and actual behavior of the heat pump precisely. In addition, the reliability of the model was improved by verifying the simulation results using experimental data. The simulation data fell into the 10% error range compared with the experimental data. The heat pump model can be used for system optimization studies of product development and applied to other applications in a range of industrial field.

A reactive-transport model for examining tectonic and climatic controls on chemical weathering and atmospheric CO2 consumption in granitic regolith

We developed a 1D reactive-transport model for examining how tectonic and climatic parameters, namely uplift rate, water seepage velocity, and temperature, control chemical weathering and atmospheric CO2 consumption rates during regolith development. The model consists of mass-conservation equations describing how mineral and solute concentrations change temporally and spatially (vertically) during weathering of granite containing 30% plagioclase (An20) and up to 3% accessory calcite. The equations are coupled by volumetric weathering rates, which depend on mineral abundances, intrinsic dissolution rate constants, and surface areas as well as the departure of pore water from thermodynamic equilibrium. We numerically solve a non-steady-state, non-dimensional version of the model. By eliminating the need to prescribe regolith thickness, non-dimensionalization introduces two key scaling parameters that drive variations in the model results: the rock residence time (τr, the time for rock to travel upward through the model domain) and the water residence time (τw, the time for water to travel downward through the model domain). We use the model to examine fundamental properties of chemical weathering, especially reaction front propagation, with the primary aim of characterizing weathering regimes and identifying factors that maximize the dissolution of plagioclase because only silicate weathering regulates atmospheric CO2 levels over geological timescales.Weathering regimes are commonly classified as transport (or supply)-limited versus weathering (or kinetically)-limited, but as outgrowths of geomorphology, these terms primarily refer to the role of τr in regulating regolith thickness. Our findings suggest that the paradigm should be expanded to include kinetic controls determined by τw. Both regimes can experience far-from- and near-equilibrium mineral dissolution. However, transport-limited regimes generally have lower τw/τr ratios compared to kinetically-limited regimes. Under transport limitation, thick to thin reaction fronts propagate downward indefinitely yielding extensive mineral depletion, deeply weathered regolith, and high ratios of silicate-to-carbonate weathering. Under kinetic limitation, thin to non-existent reaction fronts evolve to steady-state yielding minimal mineral depletion, no regolith development, and low ratios of silicate-to-carbonate weathering. Kinetically-limited regimes typifying tectonically active mountain ranges have low long-term atmospheric CO2 consumption rates. Transport-limited regimes typifying tectonically stable cratons also have low long-term atmospheric CO2 consumption rates, but because much of the Earth's surface is transport-limited, we infer that such environments have the greatest impact on the global atmospheric CO2 consumption flux. The model output leads us to hypothesize that the maximum contribution should occur for extensive regions of silicate bedrock consolidated in warm, wet climates because the combination of tectonic stability, high temperatures, and rapid seepage velocities accelerates reaction front propagation, facilitates calcite depletion, and sustains deep regolith development over long timescales. Our findings point to the importance of internal climate feedbacks for stabilizing long-term atmospheric CO2 levels.

New Cu(TiIrNx) Alloy Films for Solder Bump Flip-Chip Application

A new copper alloy that shows fine thermal stability and adhesion to the substrate is developed in this study by cosputtering Cu, Ti, and Ir on a barrierless Si substrate within an Ar/N2 gas atmosphere to form a Cu(TiIrNx) film. To reduce manufacture cost, we can replace both the wetting and diffusion layers underneath flip-chip solder joints in conventional under bump metallurgy with this thermally stable film, which exhibits weak, if any, interactions between the film and the substrate after annealing at 700 °C for 1 h. The alloy film's dissolution rate is lower than that of pure Cu by at least one order of magnitude, with a fine solderability similar to that of pure Cu. The film developed in this study seems to be a good candidate material for barrierless Si metallization and/or flip-chip solder bump application, with a low consumption rate comparable to that of Ni.

Residual feed intake: a nutritional tool for genetic improvement

The goal of this bibliographical study was to provide information about residual feed intake (RFI), a new criterion used in the selection of beef cattle for growth rate, food ingestion, and feed efficiency. RFI is calculated as the difference between real consumption and the quantity of food an animal is expected to eat based on its mean live weight and rate of weight gain. In studies of RFI, many speculations are made among researchers about the reliability of this criterion. However, there is a high genetic correlation with characteristics related to post-weaning consumption and maturity, indicating that the biological processes that regulate consumption and efficiency in young animals are similar to the processes that regulate consumption and efficiency in animals of greater age. In contrast to feed conversion, selection based on RFI seems to select for lower rates of consumption and lower animal maintenance requirements without changing adult weight or weight gain. Therefore, we conclude that the data indicate that there are extraordinary benefits to be gained from changing the goals of selection from increased weight gain to improved nutritional efficiency. Given the importance of animal production for economic development in Brazil choosing the best selection goals for livestock improvement is essential. To include an index of feed efficiency in future goals would be desirable, and RFI may play a part in this if economic methods of implementation can be developed.

Flexibility in feeding periodicity of a grazing mayfly in response to different concentrations of benthivorous fish

Abstract Flexibility is an important adaptive attribute of the feeding periodicity of grazing mayfly larvae because most natural environments offer a wide variation in local predation risk in terms of space, time or predator species. In this study any changes of diel feeding periodicity and consumption rates of Baetis rhodani (Ephemeroptera) were analysed in response to different densities of benthivorous fish ( Barbatula barbatula , Gobio gobio ) by quantifying gut fullness using the fluorescence of algal pigments. Laboratory experiments with the grazer species B. rhodani were conducted by using different concentrations of chemical fish cues. In order to assess the transferability of the results to a larger scale, the experimental results were compared with field observations in two second order streams using different densities of freely foraging benthivorous fish. During the presence of chemical fish cues in the laboratory experiments the feeding periodicity of the B. rhodani larvae were mostly diurnal while in the absence of fish chemicals nocturnal feeding was observed. The same patterns could be detected in the field during the experiments with the different fish densities. These findings indicate that the larvae were able to assess variations in the predation risk and to alter their feeding habits by making flexible behavioural adjustments. The results from the laboratory experiments further suggested that the behavioural response is controlled by fish density. Behavioural changes were observed for medium and high concentrations of the fish cues but not for a very low concentration. In the field however, the mere presence of fish seemed to be sufficient to induce the observed behavioural shifts. Although the presence of benthivorous fish seemed to cause a lower consumption rate of the B. rhodani larvae in the field, such a reduction could not be found in the laboratory experiments. A conclusion from this study is that the identification of behavioural modifications is an essential component needed for a better understanding of complex trophic interactions in benthic communities. Accurate evaluation and detailed observation of direct and indirect effects cannot be made without the consideration of such behavioural mechanisms.

The possible impact of an alcohol welfare surcharge on consumption of alcoholic beverages in Taiwan.

BackgroundThe abuse of alcoholic beverages leads to numerous negative consequences in Taiwan, as around the world. Alcohol abuse not only contributes to cardiovascular disease, hypertension, diabetes and cancer, but it is also an underlying cause of many other serious problems, such as traffic accidents, lost productivity, and domestic violence. International leaders in health policy are increasingly using taxation as an effective tool with which to lower alcohol consumption. In this study, we assessed how consumption patterns in Taiwan would be affected by levying a welfare surcharge on alcoholic beverages of 20%, 40% or 60% in accordance with the current excise tax. We also assessed the medical savings Taiwan would experience if consumption of alcoholic beverages were to decrease and how much additional revenue a welfare surcharge would generate.MethodsWe estimated the elasticity of four types of alcoholic beverages (beer, wine, whisky and brandy) using the Central Bureau of Statistics (CBS) Demand Model. Specifically, we estimated alcohol’s price elasticity by analyzing the sales prices and time statistics of these products from 1974 to 2009.ResultsAlcoholic beverages in Taiwan have the following price elasticities: beer (−0.820), wine (−0.955), whisky (−0.587), brandy (−0.958). A welfare surcharge tax of 40% in accordance with the excise tax would decrease overall consumption of beer, wine, whisky and brandy between 16.24% and 16.42%. It would also generate New Taiwan Dollar (NT$) revenues of 5.782 billion to 5.993 billion. Savings in medical costs would range from NT$871.07 million to NT$897.46 million annually.ConclusionsA social and welfare surcharge of 40% on alcoholic beverages in Taiwan would successfully lower consumption rates, decrease medical costs, and generate revenue that could be used to educate consumers and further decrease consumption rates. Consequently, we strongly recommend that such a tax be imposed in Taiwan.

Metabolism of an Antarctic solitary coral, Flabellum impensum

Few physiological or behavioral studies have been undertaken on the genus Flabellum, particularly on Antarctic species. The present study characterizes the metabolism of the endemic Antarctic coral F. impensum, one of the world's largest solitary corals, with measurements of oxygen consumption rate and metabolic enzyme activity. F. impensum had a low rate of oxygen consumption at 0°C, ranging from 0.06 to 0.64μmolO2g−1h−1 and averaging 0.31μmolO2g−1h−1, calculated using tissue wet mass. Ammonium excretion averaged 4.21nmolNH4+gwm−1h−1 (range: 0.54–13.99nmolNH4+gwm−1h−1). The activity values of the metabolic enzymes citrate synthase (CS), malate dehydrogenase (MDH), and lactate dehydrogenase (LDH) fell within the normal range expected for a cnidarian, averaging 0.13 (range: 0.04–0.32), 1.01(range: 0–3.51), and 0.42 (range: 0.18–0.99) activity units (U) gwm−1, respectively. Skeletal density averaged 22% more than the density of pure aragonite and a count of the growth bands on the calyx suggests that this species has a linear extension rate of approximately 1mm per year. F. impensum is a long-lived, slow-growing coral, with a low metabolic rate.

Feed Efficiency Versus Feed Conversion Ratio -- Demonstrated on Feeding Experiments with Juvenile Cod (Gadus Morhua)

Feed conversion ratio (FCR), which is used as a description of growth as a function of feed intake, depends mainly on the feeding rate but also on temperature. The estimation of the FCR is simple; however, the practical application of this ratio is limited to cases in which fish are fed beyond maintenance rate. In addition, FCRs are not comparable if they are measured at different temperatures. Ivlev (1939) proposed the more universal temperature independent metric K3 -- also known as feed efficiency. Even if the feed efficiency is a measure of the usable percentage of the food it has not been in common use in research and practice. This is most likely due to difficulties in determining this parameter in conjunction with temperature dependency of the maintenance rate and its temperature constant in practice. In this work we present an estimation method, which allows the determination of these parameters indirectly by the “system response” of fish. The parameter estimation is performed by least square fitting, comparing the food intake of the model with the food intake observed in feeding experiments with juvenile cod (Gadus morhua), carried out by Soofiani (1983) and Hawkins et al. (1985) over a wide range of feeding rates and temperatures. For individual fish, the model works not very accurately, while a comparison of the computed model results with the de facto consumed amounts (mean feed intake per fish and size group) demonstrates a high level of agreement. The relative estimation error is generally highest at the lowest consumption rates. The developed model is particularly suitable for the optimization of the feed ration at different temperatures in aquaculture systems.

Secure Beamforming with Artificial Noise for Two-way Relay Networks

This paper studies the problem of secure information exchange between two sources via multiple relays in the presence of an eavesdropper. To this end, we propose a relay beamforming scheme, i.e., relay beamforming with artificial noise (RBwA), where the relay beamforming vector and the artificial noise vector are jointly designed to maintain the received signal-to-interference-ratio (SINR) at the two sources over a predefined Quality of Service (QoS) threshold while limiting the received SINR at the eavesdropper under a predefined secure threshold. For comparsion, the relay beamforming without artificial noise (RBoA) is also considered. We formulate two optimization problems for the two schemes, where our goal is to seek the optimal beamforming vector to minimize the total power consumed by relay nodes such that the secrecy of the information exchange between the two sources can be protected. Since both optimization problems are nonconvex, we solve them by semidefinite program (SDP) relaxation theory. Simulation results show that, via beamforming design, physical layer secrecy of two-way relay networks can be greatly improved and our proposed RBwA outperforms the RBoA in terms of both low power consumption and low infeasibility rate.

High prevalence of ESBL-producing Enterobacteriaceae carriage in Dutch community patients with gastrointestinal complaints

The aim of this study was to determine the rate of carriage of ESBL-producing Enterobacteriaceae (ESBL-E) in the community in the Netherlands and to gain understanding of the epidemiology of these resistant strains. Faecal samples from 720 consecutive patients presenting to their general practitioner, obtained in May 2010, and between December 2010 and January 2011, were analysed for presence of ESBL-E. Species identification and antibiotic susceptibility testing were performed according to the Dutch national guidelines. PCR, sequencing and microarray were used to characterize the genes encoding for ESBL. Strain typing was performed with amplified fragment length polymorphism (AFLP) and multilocus sequence typing (MLST). Seventy-three of 720 (10.1%) samples yielded ESBL-producing organisms, predominantly E. coli. No carbapenemases were detected. The most frequent ESBL was CTX-M-15 (34/73, 47%). Co-resistance to gentamicin, ciprofloxacin and cotrimoxazole was found in (9/73) 12% of the ESBL-E strains. AFLP did not show any clusters, and MLST revealed that CTX-M-15-producing E. coli belonged to various clonal complexes. Clonal complex ST10 was predominant. This study showed a high prevalence of ESBL-producing Enterobacteriaceae in Dutch primary care patients with presumed gastrointestinal discomfort. Hence, also in the Netherlands, a country with a low rate of consumption of antibiotics in humans, resistance due to the expansion of CTX-M ESBLs, in particular CTX-M-15, is emerging. The majority of ESBL-producing strains do not appear to be related to the international clonal complex ST131.

Mathematical modeling of nanofiltration for concentrated electrolyte solutions

As one of the most newly developed liquid-phase membrane separation processes, nanofiltration (NF) is used in several industrial and environmental applications due to low energy consumption and elevated flux rates. In spite of several attempts for modeling NF separation ranging from rigorous space-charge approaches to simpler irreversible thermodynamics, neither have been totally sufficient either due to extensive computational requirements limiting their application in multi-component systems or oversimplifying assumptions leading to loss of generality. A promising model as a compromise between simplicity and accuracy can then be very helpful in this regard.This paper is an effort for modeling the nanofiltration separation process based on the modified extended Nernst–Planck equation (MENP) for solute transport through membrane active layer which is improved for concentrated electrolyte solutions. Based on simulation results, the effect of high ionic concentrations on the rejection of chloride ion is investigated, in case of pure NaCl solutions. The modified version of ENP, takes into account the variations of activity coefficient and the resulting influence on the retention behavior by increasing the ionic strength. The results show significant reduction of the predicted rejection by increasing the ionic strength.

The impact of secondary compounds and functional characteristics on lichen palatability and decomposition

Summary There has been much recent interest in understanding how functional traits of vascular plant species drive ecological processes such as herbivory and litter decomposition. In plants, these two processes are often driven by the same or similar suites of traits and therefore correlate across species. However, few studies have considered how traits of plant‐like life forms such as lichens determine species differences in their effects on ecological processes. This is despite the significant contribution of lichens to carbon and nutrient cycling in many environments. We collected 28 lichen species that differed in their growth form, substrate type and capacity to fix N, and determined key traits for each species. For each species, we performed a feeding bioassay using the generalist snail Cepaea hortensis and carried out a laboratory bioassay to assess decomposability. We did these tests both with intact lichen material containing natural concentrations of carbon‐based secondary compounds (CBSCs), and material that had been acetone rinsed to reduce concentrations of CBSCs, to evaluate the effect of CBSC on palatability and decomposability. We found that reducing CBSC concentrations greatly increased palatability for 17 species, and decomposability of 10 species. However, decomposability was correlated with several lichen traits while palatability was not, regardless of whether or not CBSCs were removed, and we therefore found no relationship between decomposability and palatability across species. Decomposability and palatability both varied, but in contrasting directions, among N‐fixing vs. non‐fixing lichens, lichens with different growth forms and those from contrasting substrate types. As such, N‐fixing lichens had higher decomposition rates but lower consumption rates than non‐fixing lichens, while foliose species had higher decomposition rates but lower consumption rates than fruticose species. Synthesis: We have shown that lichen CBSCs regulate key processes such as lichenivory and decomposition, that lichen decomposability but not palatability are related to traits, and that these two processes are unrelated across species. These results highlight the potential role of lichen species differences in influencing ecosystem processes relating to decomposition and nutrient cycling and the role that grazers may play in driving this.

A Comparative Study of Environmental Impacts of Two Delivery Systems in the Business‐to‐Customer Book Retail Sector

SummaryChina has the highest carbon dioxide (CO2) emissions in the world. In China, logistics accounts for a significant portion of the total energy use and CO2 emissions in business‐to‐customer (B2C) retailing. This study focuses on the environmental impacts of B2C delivery in China, focusing on the book retail industry. Mathematical models are proposed based on the practical operations of the “e‐commerce networked delivery” (END) system and the “sustainable networked delivery” (SND) system. The energy consumption and CO2 emissions per book are then determined and compared for the two systems. Furthermore, we contrast the findings with those of similar studies conducted for other countries and provide explanations for the differences. The results show that (1) in general, in China, the SND system is better than the END system in terms of environmental impacts; (2) the END system in China generates fewer environmental impacts than those in the United States and the United Kingdom, while the SND system in China has greater environmental impacts than that in the United States; and (3) the wide use of vehicles such as electric bicycles that have low energy consumption rates contributes to the reduction of environmental impacts per book in both the END and SND systems in China. The limitations of the study and suggestions for future research are also discussed.

Total and methyl-mercury in hair and milk of mothers living in the city of Porto Velho and in villages along the Rio Madeira, Amazon, Brazil

High fish consumption and extended breastfeeding are hallmarks of traditional lifestyle in Western Amazonia. We studied sources of mercury exposure, fish-methylmercury (meHg) and dental-amalgam filling, in 75 urban and 82 rural lactating mothers. Total mercury was determined in all samples while meHg concentrations were determined in subsamples of milk (45) and hair (27) of urban mothers living in Porto Velho (PV) and in hair (46) and milk (37) of mothers living in traditional communities (TC) of the Rio Madeira. The TC mothers showed significantly higher median hair-Hg concentrations (8.2μgg(-1)) than PV mothers (1.3μgg(-1)). Median total Hg in milk of PV mothers (0.36ngg(-1)) was significantly lower (p=0.0000) than that found in milk of TC mothers (2.30ngg(-1)). The median meHg concentrations in milk of TC mothers were also significantly higher (1.0ngg(-1)) than in milk of PV mothers (0.07ngg(-1)). For urban mothers with low fish consumption rates (and relatively higher dental amalgam fillings) the proportion of inorganic Hg in milk was higher (85%) than in TC (62%). In TC mothers 51% of breast milk Hg concentrations were above 2ngg(-1) (world median concentrations), contrasting with 8% in PV mothers. Despite this, there was no significant correlation between total Hg concentrations in milk and either amalgam filling or daily fish consumption. Socioeconomic changes occurring in Western Amazonia are causing changes in fish-eating habits of urban mothers. However, traditional lifestyle and attendant high fish consumption in riverine populations can still impact total Hg and methylmercury concentrations in mothers' milk and hair.

An improved method of xylose utilization by recombinant Saccharomyces cerevisiae

The aim of this study was to develop a method to optimize expression levels of xylose-metabolizing enzymes to improve xylose utilization capacity of Saccharomyces cerevisiae. A xylose-utilizing recombinant S. cerevisiae strain YY2KL, able to express nicotinamide adenine dinucleotide phosphate, reduced (NADPH)-dependent xylose reductase (XR), nicotinamide adenine dinucleotide (NAD(+))-dependent xylitol dehydrogenase (XDH), and xylulokinase (XK), showed a low ethanol yield and sugar consumption rate. To optimize xylose utilization by YY2KL, a recombinant expression plasmid containing the XR gene was transformed and integrated into the aur1 site of YY2KL. Two recombinant expression plasmids containing an nicotinamide adenine dinucleotide phosphate (NADP(+))-dependent XDH mutant and XK genes were dually transformed and integrated into the 5S ribosomal DNA (rDNA) sites of YY2KL. This procedure allowed systematic construction of an S. cerevisiae library with different ratios of genes for xylose-metabolizing enzymes, and well-grown colonies with different xylose fermentation capacities could be further selected in yeast protein extract (YPX) medium (1 % yeast extract, 2 % peptone, and 2 % xylose). We successfully isolated a recombinant strain with a superior xylose fermentation capacity and designated it as strain YY5A. The xylose consumption rate for strain YY5A was estimated to be 2.32 g/gDCW/h (g xylose/g dry cell weight/h), which was 2.34 times higher than that for the parent strain YY2KL (0.99 g/gDCW/h). The ethanol yield was also enhanced 1.83 times by this novel method. Optimal ratio and expression levels of xylose-metabolizing enzymes are important for efficient conversion of xylose to ethanol. This study provides a novel method that allows rapid and effective selection of ratio-optimized xylose-utilizing yeast strains. This method may be applicable to other multienzyme systems in yeast.

Silver nanoparticle-alginate composite beads for point-of-use drinking water disinfection

Silver nanoparticles (AgNPs)-alginate composite beads were synthesized using three different approaches as filler materials of packed columns for simultaneous filtration-disinfection as an alternative portable water treatment process. The prepared composite beads were packed into a column through which Escherichia coli containing water was filtered to evaluate the disinfection efficacy. Excellent disinfection performance (no detectable viable colony) was achieved with a hydraulic retention time (HRT) as short as 1 min (the shortest tested) with the SGR (Simultaneous-Gelation-Reduction) and AR (Adsorption–Reduction) beads that were prepared using in situ reduction of Ag+. Comparatively, the SGR beads released significantly less Ag+/AgNPs than the AR beads did within the same HRT. From the results of this study it was identified that SGR may be the best choice among all three different synthesis approaches in that the SGR beads can achieve satisfactory bactericidal performance with a relatively low material consumption rate.

Effects of plant availability and habitat size on the coexistence of two competing parasitoids in a tri-trophic food web of canola, diamondback moth and parasitic wasps

Using experiments and spatial modeling, we here show the conditions for two competing parasitoids to coexist under two levels of plant availability in a tri-trophic food web of canola, diamondback moth (Plutella xylostella) and two parasitic wasps (Diadegma semiclausum and Cotesia vestalis) that target the same life stage of the herbivore diamondback moth. Plant availability had a significant effect on both the abundances of parasitoids and the herbivore. However, parasitoid abundances were not different with or without the occurrence of other parasitoid species, suggesting no effect of parasitoid coexistence on their abundances. Using a three-species Lotka–Volterra model, we confirmed the competitive exclusion of species with low consumption rate (=initial population size×per capita consumption rate) in a well-mixed habitat patch. We further built a cellular automaton (CA) to explore the minimum habitat size that ensures the coexistence of these two parasitoids, assuming different searching efficiencies (i.e. different radiuses of searching area and movement abilities for locating the host). With the in-patch dynamics portrayed by the three-species Lotka–Volterra model, the CA model demonstrated the possibility for the two parasitoids to coexist when the number of habitat patches reached a certain number. This research thus highlights the importance of both plant availability and habitat size to the dynamics and stability of the tri-trophic food web.