孩子的天然学堂

在澳大利亚,伴随着妇女就业和单亲家庭的增长,多数家庭和儿童都非常依赖于儿童看护服务,比如,社区幼儿园、幼儿中心、临时家     

How do biologists respond to low-intensity armed conflicts? The case of Bangladesh (1961–2011)

Armed conflict affects the biological diversity and biological research regime of a country. This paper takes a low-intensity armed conflict in the biologically and ethnically diverse Chittagong Hill Tracts (CHT) of Bangladesh, as an example, and assesses the response of biologists to this conflict. The study spans the last 50 years dividing it into three periods: pre-conflict (1961?1974), conflict (1975–1997) and post-conflict (1998–2011). Interactions with selected researchers and a literature survey showed that sporadic, intermittent biological research was conducted in this region even during the conflict. The number of research initiatives substantially increased and became more diverse over the last decade. Research opportunity has increased mainly because of improved security and accessibility. Nevertheless, despite the research capacity and a positive attitude among the researchers, some fundamental issues still limit long-term research in this area. The continuing volatile situation due to slow implementation of the 1997 Peace Accord and the tension between rebel factions and indigenous and settler communities in some areas continue to be serious concerns for studying and conserving the biodiversity of this region. Innovative research approaches and the full implementation of the peace agreement are vital to improving the situation for biological research in the CHT. The paper underlines the importance of a biologist’s self-motivation to respond to low-intensity armed conflicts.     

England's Town Development Act: 1952: PART I: Background of the Act

The land use model recasts an unsuccessful urban form of the past. Concentric rings of declining land value begin at the intense, historic center and grade down through concentric rings to become the city plan. Little planning remains after such a model is accepted. The new freedom of the auto-age city is lost to the principle of a falling body. Further, the land use model plan restricts mobility of resident and employer by type, each to his ring Urban land value patterns are sustained by public action or inaction. A true city plan musters this power to form the best possible city.     

Developing eco-friendly methods for purification of compounds derived from hydrogenated cardanol

The present work made a comparative study between two purification methods, column chromatography and recrystallization, for compounds derived from cardanol, a by-product of the cashew industry (Anacardium occidentale L.). The compounds were successfully synthesized and characterized, focusing our attention to results obtained in terms of yield, purity, generation of solid waste and amount of solvent used in each purification process. For all the synthesized compounds, the amount of solvent used was greatly reduced in the recrystallization process, with purities above 80%, when compared to chromatographic column, which still demands high amounts of eluent.     

Mechanical property enhancement in short-fiber composites through the control of fiber orientation during fabrication

The mechanical properties of plastics and elastomers reinforced by short fibers are generally dictated by the selection of matrix and reinforcement. However, the high tensile properties attainable in these systems through laboratory processing techniques are frequently not obtained in conventional fabrication operations. To gain a wider latitude in meeting economic and performance constraints, the control of composite structure in the fabrication step should not be overlooked. Tool geometry and processing conditions can be manipulated specifically to control the fiber orientation distribution in the product. A study of fiber orientation in composite compounds during flow through runners, gates, and dies leads to recommendations for optimizing the directional strength and stiffness according to a kinematic model. Performance data on parts fabricated from various short-fiber composite materials bear out these projections.     

The extrusion and performance of plasticized poly(vinyl chloride) hose reinforced with short cellulose fibers

Short fibers of natural cellulose treated to provide dispersability and strong interfacial bonding are ideal reinforcements for plasticized vinyl compounds. The development of substantial strength and stiffness in unidirectional composites indicates the reinforcing potential of these high aspect-ratio fibers in soft compositions. Special extrusion dies developed to control fiber directionality in rubber extrudates are equally applicable to vinyl hose. The unusual expanding geometry of these tools aligns the fibers toward the circumferential direction to provide optimum reinforcement against contained pressure loading. Thus, reinforced poly(vinyl chloride) air and water hoses can be produced in a single extrusion step, since all of the necessary reinforcement is contained in the compound.     

Molecular Weight Patterns of Nägeli Amylodextrins

This research was designed to assess the utility of a four-column high performance size-exclusion chromatography (HPSEC) system to characterize starch-based carbohydrates of different sizes. Corn starches with varying amounts of amylose were treated with 16% sulfuric acid to create Nägeli amylodextrins. During treatment, sub-samples were taken at various intervals from 0–100 days. The washed, dried sub-samples were chromatographically analyzed using four Shodex lonpak columns linked in series. Chromatograms showed the progressive depolymerization of starch. Pullulan molecular weight standards were used to estimate amylodextrin molecular weights (MW). Number-average MWs of amylodextrins decreased as the original starches' amylopectin content decreased. A single HPSEC system can be effectively used to characterize carbohydrates ranging in size from starch to amylodextrins; and to monitor the acid (or enzyme) depolymerization of starches.     

Fractionation of Starch Amylopectin and Amylose by High Performance Gel Filtration Chromatography

A gel filtration chromatographic method has been developed which is capable of fractionating amylose and amylopectin in starch. Three GFC columns (2 × 4000 A and 1 × 300A PL Separation Sciences, Polymer Laboratories Ltd,) are used in series using sodium chloride solution as eluent. Minimal sample preparation is involved which includes a preliminary wetting of powder starch with ethanol followed by dissolution with sodium hydroxide. Since the solvent system is aqueous, cooked starch samples are analysed by direct dissolution with sodium hydroxide. The method shows promise as a rapid technique in elucidating starch structure.     

Flexible and Conductive 3D Printable Polyvinylidene Fluoride and Poly(N,N‐dimethylacrylamide) Based Gel Polymer Electrolytes

In this work, 3D printable gel polymer electrolytes (GPEs) based on N,N‐dimethylacrylamide (DMAAm) and polyvinylidene fluoride (PVDF) in lithium chloride containing ethylene glycol solution are synthesized and their physicochemical properties are investigated. 3D printing is carried out with a customized stereolithography type 3D gel printer named “Soft and Wet Intelligent Matter‐Easy Realizer” and free forming GPE samples having variable shapes and sizes are obtained. Printed PVDF/PDMAAm‐based GPEs exhibit tunable mechanical properties and favorable thermal stability. Electrochemical proprieties of the printed GPEs are carried out via impedance spectroscopy in the temperature range of 25–90 °C by varying PVDF content. Ionic conductivity as high as 6.5 × 10^?4 S cm^?1 is achieved at room temperature for GPE containing low PVDF content (5 wt%) and conductivity of the GPEs is increased as temperature rises.