Preparation, structural characterisation and antibacterial properties of Ga-doped sol–gel phosphate-based glass

A sol–gel preparation of Ga-doped phosphate-based glass with potential application in antimicrobial devices has been developed. Samples of composition (CaO)_0.30(Na₂O)_0.20−x (Ga₂O₃) _x (P₂O₅)_0.50 where x = 0 and 0.03 were prepared, and the structure and properties of the gallium-doped sample compared with those of the sample containing no gallium. Analysis of the ³¹P MAS NMR data demonstrated that addition of gallium to the sol–gel reaction increases the connectivity of the phosphate network at the expense of hydroxyl groups. This premise is supported by the results of the elemental analysis, which showed that the gallium-free sample contains significantly more hydrogen and by FTIR spectroscopy, which revealed a higher concentration of –OH groups in that sample. Ga K-edge extended X-ray absorption fine structure and X-ray absorption near-edge structure data revealed that the gallium ions are coordinated by six oxygen atoms. In agreement with the X-ray absorption data, the high-energy XRD results also suggest that the Ga³⁺ ions are octahedrally coordinated with respect to oxygen. Antimicrobial studies demonstrated that the sample containing Ga³⁺ ions had significant activity against Staphylococcus aureus compared to the control.     

发挥咨询业作用,推进工程项目管理

承包商对工程的具体掌控力要远高于业主方,业主方面对工程实施中的各种问题往往鞭长莫及。为了帮助业主方从源头上实现项目的成功管理,就要发挥工程咨询机构的作用。本文论述了工程咨询机构在招标阶段项目管理的核心内容,指明了其在招标阶段的关键工作,在一定程度上实现了项目资源的优化配置,为业主节约了成本和效益最大化。同时,也分析了我国目前项目管理发展中存在的问题,并参照国内外先进管理思想和管理模式提出了我国工程咨询机构的发展方向及相应对策,对我国工程咨询业的发展有一定的参考价值。     

Hierarchically Structured Poly(alkyl‐p‐xylylene) Nonwovens with Superhydrophobic Properties

Hierarchically structured poly(alkyl‐p‐xylylene) (alkyl‐PPX) nonwovens are prepared by specific parameter variation during the electrospinning process. The investigated parameters are changes in solutions properties and ambient humidity level, which lead to the formation of different fiber architectures and surface morphologies. The characterization of the nonwovens by scanning electron microscopy confirms the formation of hierarchically structured fibers, comprising bead‐on‐string architecture if spun from tetra­hydrofuran (THF) solutions, and porous surfaces at relative humidity (RH) levels > 30% for both chloroform and THF solutions. The wetting properties of nonwovens spun from THF and chloroform solutions are analyzed by water contact angle (CA) measurements, roll‐angle determination, and high speed imaging. PPX‐heptyl and PPX‐butyl fiber mats spun from 2.5 wt% THF and PPX‐heptyl spun from 3 wt% chloroform solutions at RH > 75% show superhydrophobic and self‐cleaning properties with CA > 153° and roll‐off angles of 10–15°. The nonwovens maintain their fiber morphology and water‐repellent properties after thermal and mechanical stress.

     

Monitoring Insulin Aggregation via Capillary Electrophoresis

Early stages of insulin aggregation, which involve the transient formation of oligomeric aggregates, are an important aspect in the progression of Type II diabetes and in the quality control of pharmaceutical insulin production. This study is the first to utilize capillary electrophoresis (CE) with ultraviolet (UV) detection to monitor insulin oligomer formation at pH 8.0 and physiological ionic strength. The lag time to formation of the first detected species in the aggregation process was evaluated by UV-CE and thioflavin T (ThT) binding for salt concentrations from 100 mM to 250 mM. UV-CE had a significantly shorter (5-8 h) lag time than ThT binding (15-19 h). In addition, the lag time to detection of the first aggregated species via UV-CE was unaffected by salt concentration, while a trend toward an increased lag time with increased salt concentration was observed with ThT binding. This result indicates that solution ionic strength impacts early stages of aggregation and β-sheet aggregate formation differently. To observe whether CE may be applied for the analysis of biological samples containing low insulin concentrations, the limit of detection using UV and laser induced fluorescence (LIF) detection modes was determined. The limit of detection using LIF-CE, 48.4 pM, was lower than the physiological insulin concentration, verifying the utility of this technique for monitoring biological samples. LIF-CE was subsequently used to analyze the time course for fluorescein isothiocyanate (FITC)-labeled insulin oligomer formation. This study is the first to report that the FITC label prevented incorporation of insulin into oligomers, cautioning against the use of this fluorescent label as a tag for following early stages of insulin aggregation.     

Calculation of photogenerated carrier escape rates from GaAs/AlGa1-xAs quantum wells

We present a new theory for photogenerated carrier escape rates from single quantum wells, as a function of an applied electric field, that includes thermionic emission, direct tunneling, and tunneling via thermal occupation of upper subbands, and compare the results for GaAs/Al_xGa_1-xAs quantum wells with recent experiments. We account for the two dimensional (2D) density of states below the barrier, assume thermal equilibrium of carriers within the well, allow for the possibility of strain in the well and/or barrier, and include the contribution to electron thermionic emission from indirect conduction band minima. Our expressions for thermionic emission reduce, in the limit of large well width, to those derived by assuming a three-dimensional (3D) density of states. The results for electron emission from GaAs/Al_xGa_1-xAs quantum wells with x=0.2 and x=0.4 barriers at room temperature agree well with experiment. For wells with x=0.2 barriers, thermally assisted tunneling overtakes thermionic emission around 40 kV/cm, while for wells with x=0.4 barriers thermionic emission from the L valley conduction band minima dominates for fields less than 70 kV/cm. For holes we show that the escape rates are very sensitive to the in-plane effective masses, and results using simple expressions for the in-plane masses that do not include light/heavy-hole mixing agree poorly with experiment. The agreement with experiment is improved using in-plane masses that include light/heavy-hole mixing, particularly for wells with high barriers. We suggest that agreement with experiment would be improved by using more accurate in-plane hole masses for all of the subbands     

Indoor exposure to particulate matter and the incidence of acute lower respiratory infections among children: A birth cohort study in urban Bangladesh

Approximately half of all children under two years of age in Bangladesh suffer from an acute lower respiratory infection (ALRI) each year. Exposure to indoor biomass smoke has been consistently associated with an increased risk of ALRI in young children. Our aim was to estimate the effect of indoor exposure to particulate matter (PM_2.5) on the incidence of ALRI among children in a low‐income, urban community in Bangladesh. We followed 257 children through two years of age to determine their frequency of ALRI and measured the PM_2.5 concentrations in their sleeping space. Poisson regression was used to estimate the association between ALRI and the number of hours per day that PM_2.5 concentrations exceeded 100 μg/m³, adjusting for known confounders. Each hour that PM_2.5 concentrations exceeded 100 μg/m³ was associated with a 7% increase in incidence of ALRI among children aged 0–11 months (adjusted incidence rate ratio (IRR) 1.07, 95% CI 1.01–1.14), but not in children 12–23 months old (adjusted IRR 1.00, 95% CI 0.92–1.09). Results from this study suggest that reducing indoor PM_2.5 exposure could decrease the frequency of ALRI among infants, the children at highest risk of death from these infections.     

Effective learning in science: The use of personal response systems with a wide range of audiences

This paper describes the flexibility of Personal Response Systems (PRSs), (also known as ‘clickers’ or electronic voting systems (EVS)), as part of strategies to support students’ learning in science. Whilst variants of this technology began to appear 12 years ago, there is now a steadily increasing adoption of these systems within higher education, including science programmes, and this use has grown significantly in the last six years. They have previously been shown to offer a measurable learning benefit. Typically, someone at an institution buys these systems for learning support and they never make it out of their cases. Far less work has been done with these systems at school level. In this practitioner based paper, the broad range of practical uses for these systems is described in a variety of formal and informal learning situations – from testing the understanding of science concepts (from primary aged school children up to physics undergraduates), to undertaking evaluation of events as well as public participation in data collection for research on attitudes to careers. In addition, the data collected on such handsets can be mapped to demographic factors such as gender and age yielding further layers of analysis. Overall this is a highly flexible and transferable approach to the use of interactive technology for engaging learners of all ages as well as carrying out research.     

Some Textile Applications of Finite-element Analysis Part II: Finite Elements for Yarn Mechanics

The concepts of modal decomposition developed in an earlier paper are used to produce a three-dimensional element for aligned fibre assemblies. The element degrees of freedom are introduced and the chosen mode shapes of the element demonstrated. The finite element is tested by using simple material-property assumptions, and the element is verified against a theoretical model of the twisting of a single fibre about a solid core. The element is then verified qualitatively by modelling realistic yarn situations, and the resultant deformation plots are presented.     

Preface: Volume 65, Issue 1

This volume contains the Proceedings of the Fifth Workshop on Coalgebraic Methods in Computer Science (CMCS'2002). The Workshop was held in Grenoble, France on April 6--7 2002, as satellite event to ETAPS'2002.Over the last few years it has become clear that a great variety of state-based dynamical systems, like transition systems, automata, process calculi and class-based systems can be captured uniformly as coalgebras. The aim of the CMCS workshops is to bring together researchers with a common interest in the theory and application of coalgebras. The five CMCS volumes demonstrate that coalgebra is developing into a field of its own, presenting a deep mathematical foundation and a growing field of applications and interactions with various other fields, such as modal logic, category theory, dynamical systems, control systems, object-oriented and concurrent programming, formal systems specifications, algebra, analysis, combinatorics, and set theory.The papers in this volume were reviewed by the program committee:

Jiri Adamek	(Department of Computer Science, Technical University of Braunschweig)
Alexandru Baltag	(Department of Computer Science, Oxford University)
H. Peter Gumm	(Department of Mathematics and Computer Science, University of Marburg)
Jesse Hughes	(Department of Computer Science, University of Nijmegen)
Bart Jacobs	(Department of Computer Science, University of Nijmegen)
Alexander Kurz	(Department of Software Technology, CWI)
Marina Lenisa	(Department of Mathematics and Computer Science, University of Udine)
Ugo Montanari	(Department of Computer Science, University of Pisa)
Larry Moss	(Department of Mathematics, Indiana University)
Ataru T. Nakagawa	(SRA Key Technology Laboratory, Tokyo)
John Power	(Department of Computer Science, The University of Edinburgh)
Horst Reichel	(Institute of Theoretical Computer Science, Dresden University of Technology)
Jan Rutten	(Department of Software Technology, CWI)

Full-size table

Several outside reviewers also assisted. CMCS received 20 submissions and accepted 15 of them. In addition, there were two invited speakers: Jose Meseguer and Luigi Santocanale. Their papers appear in this volume along with the 15 submitted contributions. We are grateful to everyone who sent us papers, and we regret that the length of the conference did not allow more papers to be presented.We thank the organizers of ETAPS'2002 for their help and encouragement. Special thanks to Rachid Echahed for his constant help with the organization of the workshop, and also to Mike Mislove for his work as a Managing Editor of the ENTCS series. Their efforts have been crucial for the success of CMCS'2002.September 1, 2002 Lawrence S. Moss     

Understanding the behavior of compiler optimizations

Compiler optimizations are difficult to implement and add complexity to a compiler. For this reason, compiler writers are selective about implementing them: they implement only the ones that they believe will be beneficial. To support compiler writers in this, we describe a method for measuring the cost and benefits of compiler optimizations, both individually and in synergy with other optimizations. We demonstrate our method by presenting results for the optimizations implemented in the Jikes Research Virtual Machine on the PowerPC and IA32 platforms. Copyright © 2006 John Wiley & Sons, Ltd.