Antibacterial characteristics of magnesium oxide powder

The antibacterial activity of magnesium oxide (MgO) was studied. Inhibitory zones appeared around the MgO powder slurry put directly on nutrient agar plates seeded with Escherichia coli or Staphylococcus aureus. However, no zone was observed using a penicillin cup to avoid contact between the bacteria and the MgO powder. Moreover, the supernatant solution of the MgO powder slurry and a MgCl₂ solution containing Mg²⁺ at a concentration of the solubility of MgO did not affect the growth of E. coli and S. aureus. Moreover, elevated shaking speed increased the death of E. coli in the slurry, indicating that the contact frequency between bacterial cells and MgO powders affected the antibacterial activity. It was considered that the contact between MgO powder and bacteria was important for the occurrence of its antibacterial activity. Since the generation of active oxygen, such as O₂ ^–, from the MgO powder slurry was detected by chemiluminescence analysis, an investigation was carried out to determine whether active oxygen generated from MgO powder slurry was related to its antibacterial activity. The changes in the antibiotic sensitivity in E. coli treated by MgO powder agreed with those by active oxygen treatment. These results suggested that the active oxygen generated from the MgO powder slurry was one of the primary factors in its antibacterial activity.     

The cost of egg production: increased egg production reduces future fitness in gulls

Measurements of costs of reproduction are essential for our understanding of the evolution of reproductive effort. While in birds the effects of increased chick-rearing effort on subsequent survival and fecundity have been relatively well studied experimentally, costs associated with increased egg-production effort have received relatively little attention. We experimentally increased the egg-production effort of individually marked Lesser Black-backed Gulls Larus fuscus and followed their breeding performance in the next year. In the season following increased egg production, females, but not males, were less likely to be resighted in the study plot and those that did return were less likely to produce a clutch compared to control birds. It is unclear whether the observed effect on local return rate represents differential survival, differences in breeding propensity or differences in dispersal between experimental and control females. In any event, all of these would adversely affect the fitness of experimental females. In addition, those experimental females that did breed invested less in egg production the following season, which again is likely to affect breeding performance. Thus, this study provides evidence that there is an inter-brood trade-off between current egg-production effort and future fitness in birds.     

Correlates of Research Effort in Carnivores: Body Size,Range Size and Diet Matter

Given the budgetary restrictions on scientific research and the increasing need to better inform conservation actions, it is important to identify the patterns and causes of biases in research effort. We combine bibliometric information from a literature review of almost 16,500 peer-reviewed publications on a well-known group of 286 species, the Order Carnivora, with global datasets on species'' life history and ecological traits to explore patterns in research effort. Our study explores how species'' characteristics influenced the degree to which they were studied (measured as the number of publications). We identified a wide variation in intensity of research effort at both Family and Species levels, with some of the least studied being those which may need protection in future. Our findings hint at the complex role of human perspectives in setting research agendas. We found that better-studied species tended to be large-bodied and have a large geographic range whilst omnivory had a negative relationship with research effort. IUCN threat status did not exhibit a strong relationship with research effort which suggests that the conservation needs of individual species are not major drivers of research interest. This work is the first to use a combination of bibliometric analysis and biological data to quantify and interpret gaps in research knowledge across an entire Order. Our results could be combined with other resources, such as Biodiversity Action Plans, to prioritise and co-ordinate future research effort, whilst our methods can be applied across many scientific disciplines to describe knowledge gaps.     

Effects of Excess Dietary Fluoride on Serum Biochemical Indices,Egg Quality,and Concentrations of Fluoride in Soft Organs,Eggs, and Serum of Laying Hens

According to undiscovered toxicity and safety of magnesium oxide nanoparticles (MgO NPs) in isolated pancreatic islet cells, this study was designed to examine the effects of its various concentrations on a time-course basis on the oxidative stress, viability, and function of isolated islets of rat’s pancreas. Pancreatic islets were isolated and exposed to different MgO NP (<100 nm) concentrations within three different time points. After that, oxidative stress biomarkers were investigated and the best exposure time was selected. Then, safety of MgO NPs was investigated by flow cytometry and fluorescent staining, and levels of insulin secretion and caspase activity were measured. The results illustrated a considerable decrease in oxidative stress markers such as reactive oxygen species (ROS) and lipid peroxidation (LPO) levels of pancreatic islets which were treated by MgO NPs for 24 h. Also, in that time of exposure, cell apoptosis investigation by flow cytometry and insulin test showed that MgO NPs, in a concentration of 100 μg/ml, decreased the rate of apoptotic cells via inhibiting caspase-9 activity and made a significant increase in the level of insulin secretion. Data of function and apoptosis biomarkers correlated with each other. It is concluded that the use of MgO NPs in concentration of as low as 100 μg/ml can induce antiapoptotic, antioxidative, and antidiabetic effects in rat pancreatic islets, which support its possible benefit in islet transplantation procedures.     

Optimal conservation effort for a population in a stochastic environment

We study the optimal conservation effort for a population in a fluctuating environment. The survivorship of a population is affected by unpredictable environmental fluctuation (noise) and can be improved by conservation effort accompanied by a cost. The optimal effort level is the one that minimizes the total cost, defined as the weighted sum of the population extinction risk and the economic cost of conservation effort. The optimal effort depends on the variance and the probability distribution of the noise, the relative importance of the population's survival vs. the economic cost, the effectiveness of conservation effort, and the time scope over which we optimize. The analysis of dynamic programming illustrates that the choice of extinction risk function greatly affects the optimal effort level. The conservation effort level that is the best solution of a multiple-year optimization may be higher than that for the corresponding single-year optimization, if the population is relatively safe. However, the conservation level for the multiple-year optimization becomes lower than for the single-year optimization if the population is endangered. In a similar manner, the optimal conservation effort level for the problem with a short time scope is either higher or lower than that for the problem with a long time scope, depending on the extinction risk of the population. Next, for each parameter of the model, we define five different sensitivities of extinction probability or of the total cost. We then study the mean increase in the total cost caused by the uncertainty of parameters. To achieve the best conservation result, we need to invest the limited research effort to the parameter with the largest effect to the optimal effort level, rather than to those with large impacts on the extinction probability or on the total cost. The recommended policy should depend critically on the choice of the criterion to optimize, which shows the importance of theoretical study of the relationship in performing proper decision making in conservation practice.     

Trust and Reciprocity: Are Effort and Money Equivalent?

Trust and reciprocity facilitate cooperation and are relevant to virtually all human interactions. They are typically studied using trust games: one subject gives (entrusts) money to another subject, which may return some of the proceeds (reciprocate). Currently, however, it is unclear whether trust and reciprocity in monetary transactions are similar in other settings, such as physical effort. Trust and reciprocity of physical effort are important as many everyday decisions imply an exchange of physical effort, and such exchange is central to labor relations. Here we studied a trust game based on physical effort and compared the results with those of a computationally equivalent monetary trust game. We found no significant difference between effort and money conditions in both the amount trusted and the quantity reciprocated. Moreover, there is a high positive correlation in subjects' behavior across conditions. This suggests that trust and reciprocity may be character traits: subjects that are trustful/trustworthy in monetary settings behave similarly during exchanges of physical effort. Our results validate the use of trust games to study exchanges in physical effort and to characterize inter-subject differences in trust and reciprocity, and also suggest a new behavioral paradigm to study these differences.     

Perceived Extrinsic Mortality Risk and Reported Effort in Looking after Health

Socioeconomic gradients in health behavior are pervasive and well documented. Yet, there is little consensus on their causes. Behavioral ecological theory predicts that, if people of lower socioeconomic position (SEP) perceive greater personal extrinsic mortality risk than those of higher SEP, they should disinvest in their future health. We surveyed North American adults for reported effort in looking after health, perceived extrinsic and intrinsic mortality risks, and measures of SEP. We examined the relationships between these variables and found that lower subjective SEP predicted lower reported health effort. Lower subjective SEP was also associated with higher perceived extrinsic mortality risk, which in turn predicted lower reported health effort. The effect of subjective SEP on reported health effort was completely mediated by perceived extrinsic mortality risk. Our findings indicate that perceived extrinsic mortality risk may be a key factor underlying SEP gradients in motivation to invest in future health.     

Oxidative stress and the differential expression of traits associated with mating effort in humans

Oxidative stress is a physiological condition in which reactive oxygen species created through cellular respiration can potentially damage DNA and tissue. Oxidative stress may partially mediate trade-offs between reproductive effort and survival efforts. On the one hand, traits associated with reproductive effort, particularly costly male-male competition, are expected to raise oxidative stress. On the other hand, behavioral strategies may be a critical mediating mechanism, such that those who can better resist the physiological costs of oxidative damage exhibit increased mating effort. In a sample of 248 college students (173 men), we examined the associations between traits linked to mating effort—including personality features, athleticism, and history of illness—with levels of 8-OHdG, a biomarker of oxidative stress. 8-OHdG was measured twice, one week apart, once during active hours and once at awakening. In men, surgency, social dominance, and athleticism were all negatively associated with 8-OHdG levels in awakening, but not lab samples collected during active hours. In women, these same traits were positively associated with 8-OHdG levels, particularly in morning samples. Differences in associations based on sex and time of collection introduce additional complexities to understanding links between oxidative stress and mating effort.     

The Influence of Chronic Ego Depletion on Goal Adherence: An Experience Sampling Study

Although ego depletion effects have been widely observed in experiments in which participants perform consecutive self-control tasks, the process of ego depletion remains poorly understood. Using the strength model of self-control, we hypothesized that chronic ego depletion adversely affects goal adherence and that mental effort and motivation are involved in the process of ego depletion. In this study, 203 students reported their daily performance, mental effort, and motivation with respect to goal directed behavior across a 3-week time period. People with high levels of chronic ego depletion were less successful in goal adherence than those with less chronic ego depletion. Although daily effort devoted to goal adherence increased with chronic ego depletion, motivation to adhere to goals was not affected. Participants with high levels of chronic ego depletion showed a stronger positive association between mental effort and performance, but chronic ego depletion did not play a regulatory role in the effect of motivation on performance. Chronic ego depletion increased the likelihood of behavior regulation failure, suggesting that it is difficult for people in an ego-depletion state to adhere to goals. We integrate our results with the findings of previous studies and discuss possible theoretical implications.     

Within-trial contrast: The effect of probability of reinforcement in training

There is evidence that pigeons prefer conditioned reinforcers that are preceded by greater effort over those that are preceded by less effort (an effect that has been attributed to within-trial contrast). In past research the probability of reinforcement for correct choice of the conditioned reinforcer has been 100%, however, the high level of reinforcement for both alternatives in training may result in a performance ceiling when choice between those alternatives is provided on test trials. In the present study we tested this hypothesis by including a group for which the probability of reinforcement in training was only 50%. Pigeons were trained on two simultaneous discriminations, one that was preceded by a 30 peck requirement the other by a single peck requirement. On test trials, we found a significant preference for the S+ that required the greater effort in training for pigeons trained with 100% and a small but nonsignificant effect for pigeons trained with 50% reinforcement. Although the hypothesis that the within-trial contrast effect was constrained by a performance ceiling was not confirmed, we did find a reliable within-trial contrast effect with 100% reinforcement.     

Carboxylic and Dicarboxylic Acids Extracted from Crushed Magnesium Oxide Single Crystals

Carboxylic and dicarboxylic acids (glycolic, oxalic, malonic and succinic) have been extracted with tetrahydrofuran (THF) and H₂O from large synthetic MgO crystals, crushed to a medium fine powder. The extracts were characterized by infrared spectroscopy and ¹H-NMR. The THF extracts were derivatized with tert-butyldimethylsilyl (t-BDMS) for GC-MS analysis. A single crystal separated from the extract was used for an x-ray structure analysis, giving the monoclinic unit cell, space group P2₁/c with a_o = 5.543 Å, b_o = 8.845 Å, c_o = 5.086 Å, and = 91.9°, consistent with -succinic acid, HOOC(CH₂)COOH. The amount of extracted acids is estimated to be of the order of 0.1 to 0.5 mg g^-1 MgO. The MgO crystals from which these organic acids were extracted grew from the 2860 °C hot melt, saturated with CO/CO₂ and H₂O, thereby incorporating small amounts of the gaseous components to form a solid solution (ss) with MgO. Upon cooling, the ss becomes supersaturated, causing solute carbon and other solute species to segregate not only to the surface but also internally, to dislocations and subgrain boundaries. The organic acids extracted from the MgO crystals after crushing appear to derive from these segregated solutes that formed C–C, C–H and C–O bonds along dislocations and other defects in the MgO structure, leading to entities that can generically be described as (H_xC_yO_z)^n-. The processes underlying the formation of these precursors are fundamental in nature and expected to be operational in any minerals, preferentially those with dense structures, that crystallized in H₂O–CO₂-laden environments. This opens the possibility that common magmatic and metamorphic rocks when weathering at the surface of a tectonically active planet like Earth may be an important source of abiogenically formed complex organic compounds.     

Do policing honeybee (<Emphasis Type="Italic">Apis mellifera</Emphasis>) workers target eggs in drone comb?

Summary. Honey bee (Apis mellifera) workers police each other's reproduction by eating worker-laid eggs while preferentially leaving queen-laid eggs. Policing effort is presumably associated with biological costs, including those of search time and of errors of identification of eggs so that the wrong eggs are retained or eaten. Selection should act to minimise these costs. One way costs can be reduced is to focus policing effort on eggs that are most likely to be worker laid. We show here, in accordance with this prediction, that policing effort is focussed on drone cells where workers are more likely to lay eggs, rather than on worker cells which are more likely to contain queen-laid eggs.     

The quantitative single-neuron modeling competition

As large-scale, detailed network modeling projects are flourishing in the field of computational neuroscience, it is more and more important to design single neuron models that not only capture qualitative features of real neurons but are quantitatively accurate in silico representations of those. Recent years have seen substantial effort being put in the development of algorithms for the systematic evaluation and optimization of neuron models with respect to electrophysiological data. It is however difficult to compare these methods because of the lack of appropriate benchmark tests. Here, we describe one such effort of providing the community with a standardized set of tests to quantify the performances of single neuron models. Our effort takes the form of a yearly challenge similar to the ones which have been present in the machine learning community for some time. This paper gives an account of the first two challenges which took place in 2007 and 2008 and discusses future directions. The results of the competition suggest that best performance on data obtained from single or double electrode current or conductance injection is achieved by models that combine features of standard leaky integrate-and-fire models with a second variable reflecting adaptation, refractoriness, or a dynamic threshold.     

纳米氧化镁对柑橘炭疽菌的抗菌效应

纳米氧化镁(MgO NP)因其自身卓越的物理化学性质,尤其是较高的比表面积,使其在光学、电学、材料学和生物医学等各个领域都表现出重要的应用前景.MgO NP对细菌表现出良好的抗菌性,而对真菌的抗菌性研究较少.本文研究了MgO NP对柑橘炭疽病菌胶孢炭疽菌(Colletotrichum gloeosporioides)的抗菌作用,测定了其对胶孢炭疽菌的菌丝生长和菌丝形态的影响,以及对孢子萌发的抑制作用,并测定了MgO NP对柑橘炭疽病的防控效果.研究结果表明,100~800μg/mL的MgO NP都能较好抑制胶孢炭疽菌菌丝生长和孢子萌发,其中400μg/mL和800μg/mL剂量效果最明显;同时提前施用400μg/mL的MgO NP表现出较好的柑橘炭疽病防治效果,说明MgO NP具有作为植物保护剂的潜力.     

Natural variation in a testosterone-mediated trade-off between mating effort and parental effort

Male birds frequently face a trade-off between acquiring mates and caring for offspring. Hormone manipulation studies indicate that testosterone often mediates this trade-off, increasing mating effort while decreasing parental effort. Little is known, however, about individual covariation between testosterone and relevant behavior on which selection might act. Using wild, male dark-eyed juncos (Junco hyemalis), we measured individual variation in testosterone levels before and after standardized injections of gonadotropin-releasing hormone (GnRH). The GnRH challenges have been shown to produce short-term testosterone increases that are similar to those produced naturally in response to social stimuli, repeatable in magnitude, and greater in males with more attractive ornaments. We correlated these testosterone increases with behavioral measures of mating and parental effort (aggressive response to a simulated territorial intrusion and nestling feeding, respectively). Males that showed higher postchallenge testosterone displayed more territorial behavior, and males that produced higher testosterone increases above initial levels displayed reduced parental behavior. Initial testosterone levels were positively but nonsignificantly correlated with aggression but did not predict parental behavior. These relationships suggest that natural variation in testosterone, specifically the production of short-term increases, may underlie individual variation in the mating effort/parental effort trade-off. We discuss the implications of these results for the evolution of hormonally mediated trade-offs.     

The problem of the mentally defective child

Continued effort is necessary not only to prevent mental deficiency but to find methods of treating it. Meanwhile, physicians must have a keener appreciation of the feelings of the parents about their retarded children and must interpret the implications of the problems in a way the parents can understand. Further community effort is necessary to provide institutional and foster home care for those who need it. Educational and training programs should be extended and developed for all those who can benefit from such programs. The problem of mental deficiency is not that of the parents alone, nor of physicians, nor of the psychologists, nor of the social workers, nor of the educators. It is a problem which requires the cooperation of all these groups for solution.     

THE PROBLEM OF THE MENTALLY DEFECTIVE CHILD

Continued effort is necessary not only to prevent mental deficiency but to find methods of treating it. Meanwhile, physicians must have a keener appreciation of the feelings of the parents about their retarded children and must interpret the implications of the problems in a way the parents can understand. Further community effort is necessary to provide institutional and foster home care for those who need it. Educational and training programs should be extended and developed for all those who can benefit from such programs.The problem of mental deficiency is not that of the parents alone, nor of physicians, nor of the psychologists, nor of the social workers, nor of the educators. It is a problem which requires the cooperation of all these groups for solution.     

Influence of supports on catalytic behavior of nickel catalysts in carbon dioxide reforming of toluene as a model compound of tar from biomass gasification

A series of supported Ni catalysts including Ni/MgO, Ni/γ-Al2O3, Ni/α-Al2O3, Ni/SiO2 and Ni/ZrO2 was tested in CO2 reforming of toluene as a model compound of tar from biomass gasification in a fluidized bed reactor, and characterized by the means of temperature programmed reduction with hydrogen (H2-TPR), XRD, TEM and temperature programmed oxidation (TPO). Combining the characterization results with the performance tests, the activity of catalyst greatly depended on Ni particles size, and the stability was affected by the coke composition. Both of them (Ni particle size and coke composition) were closely related to the interaction between nickel and support which would determine the chemical environment where Ni inhabited. The best catalytic performance was observed on Ni/MgO due to the strong interaction between NiO and MgO via the formation of Ni-Mg-O solid solution, and the highest dispersion of Ni particle in the basic environment.     

Locus coeruleus neurons encode the subjective difficulty of triggering and executing actions

The brain stem noradrenergic nucleus locus coeruleus (LC) is involved in various costly processes: arousal, stress, and attention. Recent work has pointed toward an implication in physical effort, and indirect evidence suggests that the LC could be also involved in cognitive effort. To assess the dynamic relation between LC activity, effort production, and difficulty, we recorded the activity of 193 LC single units in 5 monkeys performing 2 discounting tasks (a delay discounting task and a force discounting task), as well as a simpler target detection task where conditions were matched for difficulty and only differed in terms of sensory-motor processes. First, LC neurons displayed a transient activation both when monkeys initiated an action and when exerting force. Second, the magnitude of the activation scaled with the associated difficulty, and, potentially, the corresponding amount of effort produced, both for decision and force production. Indeed, at action initiation in both discounting tasks, LC activation increased in conditions associated with lower average engagement rate, i.e., those requiring more cognitive control to trigger the response. Decision-related activation also scaled with response time (RT), over and above task parameters, in line with the idea that it reflects the amount of resources (here time) spent on the decision process. During force production, LC activation only scaled with the amount of force produced in the force discounting task, but not in the control target detection task, where subjective difficulty was equivalent across conditions. Our data show that LC neurons dynamically track the amount of effort produced to face both cognitive and physical challenges with a subsecond precision. This works provides key insight into effort processing and the contribution of the noradrenergic system, which is affected in several pathologies where effort is impaired, including Parkinson disease and depression.

Compared to reward, the neural basis of effort remains poorly understood. This study uses neurophysiological recordings in behaving macaques to show that locus coeruleus noradrenergic neurons provide information about both cognitive and physical effort, a few hundred milliseconds after it had been exerted.     

Life-history strategies of optimal foragers

The optimal life histories are examined for models in which the average life-history strategy adopted by the population affects the costs and benefits of any individual's strategy. The situation modeled is one in which organisms can gain energy to be used in reproduction by foraging, but in doing so, they expose themselves to increased mortality; thus the proportion of time spent foraging can be used to measure reproductive effort. Simple models of a demographically homogeneous population are used to reexamine questions which have been studied previously using other models. The effects upon optimal reproductive effort of the following factors are examined: increased births per unit effort, increased mortality, and variability in population parameters. In addition, the questions of whether optimal reproductive effort maximizes population size and whether there can be multiple alternative life histories are examined. Results in most cases differ significantly from those of previous studies. No generalizations emerge regarding the effects of the three factors listed above. Optimal life histories in this model generally do not maximize population size. It is possible to have globally stable alternative life histories. It is concluded that frequency dependence will often be important in determining optimal life histories.