cluster approach

  • 文章类型: Journal Article
    问题陈述:逐步城市化减少了人类与自然的互动,引起人们对其对心理健康影响的担忧。以前的研究通常集中在自然接触的特定方面,忽视了它的多方面及其对心理健康的影响,特别是在发展中国家。研究差距:探索自然接触的综合维度的研究很少,比如频率,持续时间,强度,和空间自然性,以及它们与发展中国家城市环境中心理健康的相关性。目的:本研究旨在使用探索性聚类分析来确定与巴西大都市地区心理健康相关的自然接触模式。弥合现有的知识差距,并告知有针对性的干预措施,以通过自然接触来增强心理健康。方法:一项在线调查收集了巴西大都市地区2136名参与者的数据,使用抑郁焦虑和压力量表(DASS-21)关注他们的自然互动模式和心理健康状况,通过多尺度引导重采样对p值进行分层聚类,和方差分析。结果和结论:确定了三个不同的组,显示不同的自然接触模式和人口统计学特征。更大和更频繁的自然接触与更低的抑郁水平相关,焦虑,和压力。这些发现表明,自然接触与心理健康之间存在有益的关系。实际影响:结果强调了促进进入自然空间的城市规划和公共卫生政策的重要性,强调社会经济因素是这种获取的重大障碍。未来方向:进一步的研究应该探索因果关系,并考虑发展中国家居民面临的具体现实和挑战。
    Statement of Problem: Progressive urbanization has reduced human interactions with nature, raising concerns about its impact on mental well-being. Previous research has often focused on specific aspects of nature contact, neglecting its multifaceted dimensions and their effects on mental health, particularly in developing countries. Research Gap: There is a scarcity of studies exploring the comprehensive dimensions of nature contact, such as frequency, duration, intensity, and space naturalness, and their correlation with mental well-being in developing countries\' urban settings. Purpose: This study aims to identify patterns of nature contact related to mental well-being in metropolitan areas of Brazil using exploratory cluster analysis, bridging the existing knowledge gap and informing targeted interventions to enhance mental health through nature contact. Method: An online survey collected data from 2136 participants in Brazil\'s metropolitan areas, focusing on their nature interaction patterns and mental health status using the Depression Anxiety and Stress Scale (DASS-21), hierarchical clustering with p-values via multiscale bootstrap resampling, and analysis of variance. Results and Conclusions: Three distinct groups were identified, showing varied patterns of nature contact and demographic profiles. Greater and more frequent nature contact was associated with lower levels of depression, anxiety, and stress. These findings suggest a beneficial relationship between nature contact and mental well-being. Practical Implications: The results underline the importance of urban planning and public health policies that facilitate access to natural spaces, highlighting socioeconomic factors as significant barriers to this access. Future Directions: Further research should explore causal relationships and consider the specific realities and challenges faced by residents of developing nations.
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  • 文章类型: Journal Article
    来自假单胞菌蛋白原的酰基转移酶(PpATase)在自然界中催化单乙酰间苯三酚向二乙酰间苯三酚和间苯三酚的可逆转化。有趣的是,该酶已被证明可以催化乙酸3-羟基苯酯向2'的混杂转化,4\'-二羟基苯乙酮,代表Fries重排的生物学版本。在本研究中,我们报告了使用量子化学计算对PpATase的这种活性进行的机理研究。提出了一种详细的机制,并给出了反应的能量分布。计算表明,酶的酰化是高度放热的,而转移回底物的乙酰基只是轻微放热。底物C6-H的去质子化是限速的,和远程天冬氨酸残基(Asp137)被建议作为该步骤中的一般碱基基团。对各种乙酰受体的结合能的分析表明,PpATase可以促进分子内和分子间Fries向多种化合物的重排。
    The acyltransferase from Pseudomonas protegens (PpATase) catalyzes in nature the reversible transformation of monoacetylphloroglucinol to diacetylphloroglucinol and phloroglucinol. Interestingly, this enzyme has been shown to catalyze the promiscuous transformation of 3-hydroxyphenyl acetate to 2\',4\'-dihydroxyacetophenone, representing a biological version of the Fries rearrangement. In the present study, we report a mechanistic investigation of this activity of PpATase using quantum chemical calculations. A detailed mechanism is proposed, and the energy profile for the reaction is presented. The calculations show that the acylation of the enzyme is highly exothermic, while the acetyl transfer back to the substrate is only slightly exothermic. The deprotonation of the C6-H of the substrate is rate-limiting, and a remote aspartate residue (Asp137) is proposed to be the general base group in this step. Analysis of the binding energies of various acetyl acceptors shows that PpATase can promote both intramolecular and intermolecular Fries rearrangement towards diverse compounds.
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  • 文章类型: Journal Article
    二氧化钛(TiO2)已被广泛研究为适用于包括催化和传感在内的广泛领域的材料。例如,基于TiO2的纳米颗粒在将葡萄糖催化转化为增值化学品方面具有活性,而二氧化钛的良好生物相容性允许其应用于葡萄糖检测的创新生物传感装置。高效和选择性生物传感器和催化剂的关键过程是分析物和传感器/催化剂表面之间的相互作用和结合模式。相关特征涉及分子识别事件及其对纳米粒子电子结构的影响。在这项工作中,我们通过结合基于周期性边界条件和聚类方法(CA)的两种第一原理方法来解决这两个特征。虽然前者允许研究延伸的材料和表面,CA仅关注表面的局部区域,但允许使用具有低计算成本的混合泛函。导致对电子特性的高度精确描述。此外,CA适用于反应机理和带电系统的研究,这对PBC来说可能很麻烦。这里,对两种计算方法进行了直接和详细的比较,以研究TiO2(100)锐钛矿表面上的d-葡萄糖。作为常用的PBC计算的替代方法,CA被成功地用于表征表面和地下氧空位的形成,并确定它们在d-葡萄糖吸附中的决定性作用。这种直接比较的结果允许选择有效的,有限尺寸的结构模型,适用于生物传感器电催化过程和生物质转化催化的未来研究。
    Titanium dioxide (TiO2) has been extensively studied as a suitable material for a wide range of fields including catalysis and sensing. For example, TiO2-based nanoparticles are active in the catalytic conversion of glucose into value-added chemicals, while the good biocompatibility of titania allows for its application in innovative biosensing devices for glucose detection. A key process for efficient and selective biosensors and catalysts is the interaction and binding mode between the analyte and the sensor/catalyst surface. The relevant features regard both the molecular recognition event and its effects on the nanoparticle electronic structure. In this work, we address both these features by combining two first-principles methods based on periodic boundary conditions and cluster approaches (CAs). While the former allows for the investigation of extended materials and surfaces, CAs focus only on a local region of the surface but allow for using hybrid functionals with low computational cost, leading to a highly accurate description of electronic properties. Moreover, the CA is suitable for the study of reaction mechanisms and charged systems, which can be cumbersome with PBC. Here, a direct and detailed comparison of the two computational methodologies is applied for the investigation of d-glucose on the TiO2 (100) anatase surface. As an alternative to the commonly used PBC calculations, the CA is successfully exploited to characterize the formation of surface and subsurface oxygen vacancies and to determine their decisive role in d-glucose adsorption. The results of such direct comparison allow for the selection of an efficient, finite-size structural model that is suitable for future investigations of biosensor electrocatalytic processes and biomass conversion catalysis.
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  • 文章类型: Journal Article
    该研究证实了俄罗斯医疗保健系统发展集群方法的可能性。通过对国外医疗集群运作经验的分析,可以确定有助于其成功发展的因素。根据对国内医疗行业创建集群实践的评估,他们的典型是通过确定生物医学技术和创新的高科技集群来进行的,药品供应和专用设备的医疗集群,医疗服务集群,实习和医学创新的转移。根据拟议的类型对俄罗斯联邦医疗保健部门的集群进行分组表明,实际上没有医疗服务集群能够将该国人口的医疗质量提高到更高的水平。本文确定了阻止在该地区领土上形成医疗服务集群的问题。为了解决这些问题,提出了一种在公私伙伴关系的基础上创建医疗科技园的方法,它将作为医疗服务集群的基础,并建立其结构和功能模型。
    The study substantiates the possibility of the cluster approach for the development of the healthcare system in Russia. The analysis of foreign experience in the functioning of medical clusters made it possible to identify factors that contribute to their successful development. Based on the assessment of the domestic practice of creating clusters in the healthcare sector, their typification was carried out with the identification of groups of high-tech clusters of biomedical technologies and innovations, medical clusters of drug provision and specialized equipment, clusters of medical services, internships and transfer of medical innovations. The grouping of clusters in the healthcare sector operating in the Russian Federation according to the proposed types showed that there are practically no clusters of medical services that are able to bring the quality of medical care to the population to a higher level in the country. The article identifies the problems that prevent the formation of clusters of medical services on the territory of the regions. To solve these problems, an approach was proposed to create a medical technology park on the basis of public-private partnership, which will serve as the basis for a cluster of medical services and built its structural and functional model.
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  • 文章类型: Journal Article
    绿锈(GR)由于其高Fe(II)含量,是地下环境中还原重金属和有机污染物的潜在重要化合物,但是缺乏实际反应机理的许多细节。GR中的还原容量分布是了解氧化还原反应发生的方式和位置的关键,计算化学可以提供有关绿锈电子特性的更多详细信息。我们构建了三种大小的单层GR聚类模型(即,没有层间分子或离子),并使用密度泛函理论计算了这些结构的电荷分布。我们发现Fe(II)和Fe(III)在单层GR中分布不均匀。Fe(II)/Fe(III)比值在一定范围内,外部铁原子的行为更像Fe(III),内部铁原子的行为更像Fe(II)。这些发现表明,GR的内部比外部更具还原性,并将为理解GR的氧化还原相互作用提供新的信息。
    Green rust (GR) is a potentially important compound for the reduction of heavy metal and organic pollutants in subsurface environment because of its high Fe(II) content, but many details of the actual reaction mechanism are lacking. The reductive capacity distribution within GR is a key to understand how and where the redox reaction occurs and computational chemistry can provide more details about the electronic properties of green rust. We constructed three sizes of cluster models of single layer GR (i.e., without interlayer molecules or ions) and calculated the charge distribution of these structures using density functional theory. We found that the Fe(II) and Fe(III) are distributed unevenly in the single layer GR. Within a certain range of Fe(II)/Fe(III) ratios, the outer iron atoms behave more like Fe(III) and the inner iron atoms behave more like Fe(II). These findings indicate that the interior of GR is more reductive than the outer parts and will provide new information to understand the GR redox interactions.
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  • 文章类型: Journal Article
    Hydrogen has been proposed as a long-term non-fossil fuel to be used in a future ideal carbon-neutral energetic economy. However, its low volumetric energy density hinders its storage and transportation. Metal-organic frameworks (MOFs) represent very promising materials for this purpose due to their very extended surface areas. Azolates, in particular tetrazolates, are - together with carboxylate functionalities - very common organic linkers connecting metallic secondary building units in MOFs. This study addresses, from a theoretical perspective, the H2 adsorptive properties of tetrazolate linkers at the molecular level, following a size-progressive approach. Specifically, we have investigated how the physisorption energies and geometries are affected when changing the environment of the linker by considering the azolates in the gas phase, immersed in a finite cluster, or being part of an infinite extended crystal material. Furthermore, we also study the H2 adsorptive capacity of these linkers within the cluster model.
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  • 文章类型: Journal Article
    We present a comparative study of metal-organic interface properties obtained from dispersion corrected density functional theory calculations based on two different approaches: the periodic slab-supercell technique and cluster models with 32-290 Ag atoms. Fermi smearing and fixing of cluster borders are required to make the cluster calculation feasible and realistic. The considered adsorption structure and energy of a PTCDA molecule on the Ag(110) surface is not well reproduced with clusters containing only two metallic layers. However, all clusters with four layers of silver atoms and sufficient lateral extension reproduce the adsorbate structure within 0.04 Å with respect to the slab-supercell structure and provide adsorption energies of ( -4.45± 0.08 eV) consistent with the slab result of -4.47 eV. Thus, metal-organic adsorbate systems can be realistically represented by properly defined cluster models. © 2018 Wiley Periodicals, Inc.
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