Electrochemical and X-ray Examinations of Erosion Products during Dressing of Superhard Grinding Wheels Using Alternating Current and Ecological Electrolytes of Low Concentration of Chemical Compounds

This article introduces significant cognitive and usable values in the field of abrasive technology especially in the development of new methods of the electrochemical dressing of superhard grinding wheels with metal bonds. Cognitive values mainly concern the elaboration of the theoretical backgrounds of the electrochemical digestion of compounds of grinding wheel metal bond and gumming up products of the cutting surface of grinding wheel (CSGW). Cognitive values also deal with determining the mathematical relationships describing the influence of technological conditions of dressing on shaping of cutting abilities of superhard grinding wheels. On the other hand, the useful values refer to the industry implementation of the elaborated method and equipment for the electrochemical dressing of suparhard grinding wheels using alternating current (ECDGW-AC). The cost of the device for the realization of this process is low and can be applied in the production conditions. The novel achievements presented in the article are: the elaboration of a new method and equipment for electrochemical dressing of superhard grinding wheels (ECDGW-AC), the selection of electrolytes of low concentration of chemical compounds, tests concerning the digestion of grinding wheel metal bond compounds and gumming up products of CSGW using X-ray analysis, as well as the determination of chemical reactions taking place during elaborated new dressing process, the elaboration of mathematical relationships describing influence of technological conditions of this process on dressing speed and shaping of cutting abilities of superhard grinding wheels, and the performance of technological tests of dressing of superhard grinding wheels using ECDGW-AC method. The elaborated method can be used in ambient temperature and does not cause thermal damages of abrasive grains of cutting surface of grinding wheel and is useful not only for dressing super hard grinding wheels but also for correcting their geometrical deviations.     

Mother–child emotion dialogues: the disrupting effect of maternal history of communal sleeping

The study examined associations between mothers’ upbringing background (kibbutz vs. home) and maternal-sensitive guidance of emotional conversations with their preschool children; children’s cooperation and exploration; and the coherence of their conversations. Using a quasi-experimental design, 112 children and their mothers (72 kibbutz raised, 40 home) completed the Autobiographical Emotional Event Dialogue. We hypothesized that maternal kibbutz upbringing would be associated to lower levels of mothers’ sensitive guidance of the conversations, children’s lower cooperation and exploration, and lower overall coherence. Results showed no upbringing-related differences for the mothers, but significant differences were found for the children, with children of kibbutz-raised mothers showing less cooperation and exploration, and lower levels of coherence for these dyads. The role of maternal background in shaping the interaction with their child is discussed.     

The Momentary Relationship Between Stress and Headaches in Adolescent Girls

Objective.— The objective of this study was to compare the relationship between repeated momentary reports of stress and headaches in female adolescents with varying degrees of headache frequency. Background.— Headaches are the most common form of pain reported by adolescents affecting more than a third of all adolescents. High levels of stress during adolescence may predispose an adolescent to experience headaches in adulthood. Randomized, momentary data collection of stress and headaches provides the most accurate data regarding the adolescent experience of these variables. Methods.— The research methodology, ecological momentary assessment, is a valid approach to better understand the relationship between stress and headaches in adolescence. Data were obtained by each participant's use of an electronic diary (ED), which captured repeated momentary reports of perceived stress, head pain, and stress‐related symptoms in female adolescents with varying degrees of recurrent headache. Seven times per day for the 21‐day study period, teen girls responded to ED questions about their current stress levels, head pain, and stress‐related symptoms. Based on participants' momentary reports of headaches, Low Headache, Moderate Headache, and Chronic Headache groups were created. General estimating equation models were used to analyze the relationship between momentary variables as well as the lag effect between stress and head pain. Results.— Thirty‐one participants, aged 14‐18 years, completed 2841 randomized ED reports and reported 674 occurrences of headache. The Chronic Headache and Moderate Headache groups reported significantly increased levels of stress, head pain, and headaches. The relationship between momentary stress and head pain was significantly strong both within and across participants. The strength of this relationship increased with increased headache activity. A significant lag effect was found between stress and headaches; however, the effect of depression as a moderator of the stress and headache relationship remains unclear. Conclusion.— Perceived stress and head pain was highly correlated in these female adolescents. Given the large population of teens affected by headaches, a plausible next step would be to validate these results in other samples and to determine methods with which to identify teens who may be at risk for a pattern of increasing stress and headaches.     

Turning back from the brink: Detecting an impending regime shift in time to avert it

Ecological regime shifts are large, abrupt, long-lasting changes in ecosystems that often have considerable impacts on human economies and societies. Avoiding unintentional regime shifts is widely regarded as desirable, but prediction of ecological regime shifts is notoriously difficult. Recent research indicates that changes in ecological time series (e.g., increased variability and autocorrelation) could potentially serve as early warning indicators of impending shifts. A critical question, however, is whether such indicators provide sufficient warning to adapt management to avert regime shifts. We examine this question using a fisheries model, with regime shifts driven by angling (amenable to rapid reduction) or shoreline development (only gradual restoration is possible). The model represents key features of a broad class of ecological regime shifts. We find that if drivers can only be manipulated gradually management action is needed substantially before a regime shift to avert it; if drivers can be rapidly altered aversive action may be delayed until a shift is underway. Large increases in the indicators only occur once a regime shift is initiated, often too late for management to avert a shift. To improve usefulness in averting regime shifts, we suggest that research focus on defining critical indicator levels rather than detecting change in the indicators. Ideally, critical indicator levels should be related to switches in ecosystem attractors; we present a new spectral density ratio indicator to this end. Averting ecological regime shifts is also dependent on developing policy processes that enable society to respond more rapidly to information about impending regime shifts.     

Urbanisation effects on groundwater chemical quality: findings focusing on the nitrate problem from 2 African cities reliant on on-site sanitation

By 2010 Africa's urban population will have grown to over 420 million with on-site sanitation the predominant excreta disposal option. The use of on-site sanitation has important public health benefits but can result in large faecally derived loadings of nitrogen and chloride to groundwater resources. Nitrate is of particular concern, with elevated concentrations linked to potentially serious health problems. N and Cl can derive from natural sources so it is important to quantify the additional impact of human activities. Several authors have used empirical relationships between nitrate and chloride concentrations to assess the extent to which excreta influences groundwater quality. However, these relationships have assumed fixed loadings from excreta. Relationships between N and Cl have been extended here by adding country-specific estimates of average annual per capita nitrogen and chloride content of, and loading from, excreta. The results are compared with groundwater monitoring results from two very different mid-sized African cities (Timbuktu, Mali and Lichinga, Mozambique) where the vast majority of residents use on-site sanitation and are dependent on the subsurface water for drinking purposes. The results illustrate the impact of urbanisation on groundwater quality. They are compared with data from other African cities to allow the calculation of a general nitrate and chloride relationship for unsewered African urban areas. Potential interventions to help arrest rising nitrate levels and so provide a public health benefit are also examined.     

Are Ecological and Social Models Influencing Prevention Practices? An Overview of the State of Affairs in Quebec for Child, Youth and Family Intervention

This paper presents the findings of a study designed to increase empirical knowledge of prevention and promotion practices targeted directly or indirectly at children, youth, and their families in the province of Quebec. A profile of these practices emerged from our analysis of the problems and concerns addressed by projects and programs in Quebec, targets for action, activities, strategies, links between organizations, and types of funding. These prevention and promotion practices are discussed in light of recent analyses and critiques in this field. It is hoped that this examination will encourage a healthy criticism of preventive efforts in Quebec, broaden of the scope of our interventions, and stimulate the creation of links between the actors involved in the welfare of children, youth, and families.     

密闭系统中四种共培养植物光合作用效率研究

目的 探讨大型密闭系统中几种共培养植物的光合效率等特性,为开展人与植物的物质交换实验提供基础数据.方法 利用受控生态生保系统集成实验平台植物舱开展常压下生菜等4种共培养色拉型蔬菜的光合效率研究.植物共培养面积为36.0 m2;采用Hoagland营养液培养;光源为90％红+10％蓝LED组合光源,光照强度为450μmol·m-2·s-1PPF,光照周期为24 h;根据植物不同生长阶段调节CO2浓度,控制范围为0.2％ ～0.8％.结果 系统运行平稳,环境参数控制状态良好,植物生长状态基本正常;共培养植物产O2量和CO2吸收量平均分别为0.915 kg·d-1和1.204 kg·d-1,植物平均每天能产生约1.1人呼吸所需的O2,同时吸收其排出的CO2.结论 通过该实验,基本掌握植物共培养技术及系统放O2和吸收CO2的能力,可为开展多人多天的受控生态生保系统集成试验研究提供技术支持.     

Molecular Link between Vitamin D and Cancer Prevention

The metabolite of vitamin D, 1α,25-dihydroxyvitamin D₃ (also known as calcitriol), is a biologically active molecule required to maintain the physiological functions of several target tissues in the human body from conception to adulthood. Its molecular mode of action ranges from immediate nongenomic responses to longer term mechanisms that exert persistent genomic effects. The genomic mechanisms of vitamin D action rely on cross talk between 1α,25-dihydroxyvitamin D₃ signaling pathways and that of other growth factors or hormones that collectively regulate cell proliferation, differentiation and cell survival. In vitro and in vivo studies demonstrate a role for vitamin D (calcitriol) in modulating cellular growth and development. Vitamin D (calcitriol) acts as an antiproliferative agent in many tissues and significantly slows malignant cellular growth. Moreover, epidemiological studies have suggested that ultraviolet-B exposure can help reduce cancer risk and prevalence, indicating a potential role for vitamin D as a feasible agent to prevent cancer incidence and recurrence. With the preventive potential of this biologically active agent, we suggest that countries where cancer is on the rise—yet where sunlight and, hence, vitamin D may be easily acquired—adopt awareness, education and implementation strategies to increase supplementation with vitamin D in all age groups as a preventive measure to reduce cancer risk and prevalence.