Solid-state Graft Copolymer Electrolytes for Lithium Battery Applications

Battery safety has been a very important research area over the past decade. Commercially available lithium ion batteries employ low flash point (<80 °C), flammable, and volatile organic electrolytes. These organic based electrolyte systems are viable at ambient temperatures, but require a cooling system to ensure that temperatures do not exceed 80 °C. These cooling systems tend to increase battery costs and can malfunction which can lead to battery malfunction and explosions, thus endangering human life. Increases in petroleum prices lead to a huge demand for safe, electric hybrid vehicles that are more economically viable to operate as oil prices continue to rise. Existing organic based electrolytes used in lithium ion batteries are not applicable to high temperature automotive applications. A safer alternative to organic electrolytes is solid polymer electrolytes. This work will highlight the synthesis for a graft copolymer electrolyte (GCE) poly(oxyethylene) methacrylate (POEM) to a block with a lower glass transition temperature (T_g) poly(oxyethylene) acrylate (POEA). The conduction mechanism has been discussed and it has been demonstrated the relationship between polymer segmental motion and ionic conductivity indeed has a Vogel-Tammann-Fulcher (VTF) dependence. Batteries containing commercially available LP30 organic (LiPF₆ in ethylene carbonate (EC):dimethyl carbonate (DMC) at a 1:1 ratio) and GCE were cycled at ambient temperature. It was found that at ambient temperature, the batteries containing GCE showed a greater overpotential when compared to LP30 electrolyte. However at temperatures greater than 60 °C, the GCE cell exhibited much lower overpotential due to fast polymer electrolyte conductivity and nearly the full theoretical specific capacity of 170 mAh/g was accessed.     

Concurrent Quantification of Cellular and Extracellular Components of Biofilms

Confocal laser scanning microscopy (CLSM) is a powerful tool for investigation of biofilms. Very few investigations have successfully quantified concurrent distribution of more than two components within biofilms because: 1) selection of fluorescent dyes having minimal spectral overlap is complicated, and 2) quantification of multiple fluorochromes poses a multifactorial problem. Objectives: Report a methodology to quantify and compare concurrent 3-dimensional distributions of three cellular/extracellular components of biofilms grown on relevant substrates. Methods: The method consists of distinct, interconnected steps involving biofilm growth, staining, CLSM imaging, biofilm structural analysis and visualization, and statistical analysis of structural parameters. Biofilms of Streptococcus mutans (strain UA159) were grown for 48 hr on sterile specimens of Point 4 and TPH³ resin composites. Specimens were subsequently immersed for 60 sec in either Biotène PBF (BIO) or Listerine Total Care (LTO) mouthwashes, or water (control group; n=5/group). Biofilms were stained with fluorochromes for extracellular polymeric substances, proteins and nucleic acids before imaging with CLSM. Biofilm structural parameters calculated using ISA3D image analysis software were biovolume and mean biofilm thickness. Mixed models statistical analyses compared structural parameters between mouthwash and control groups (SAS software; α=0.05). Volocity software permitted visualization of 3D distributions of overlaid biofilm components (fluorochromes). Results: Mouthwash BIO produced biofilm structures that differed significantly from the control (p<0.05) on both resin composites, whereas LTO did not produce differences (p>0.05) on either product. Conclusions: This methodology efficiently and successfully quantified and compared concurrent 3D distributions of three major components within S. mutans biofilms on relevant substrates, thus overcoming two challenges to simultaneous assessment of biofilm components. This method can also be used to determine the efficacy of antibacterial/antifouling agents against multiple biofilm components, as shown using mouthwashes. Furthermore, this method has broad application because it facilitates comparison of 3D structures/architecture of biofilms in a variety of disciplines.     

Modelling Gas Adsorption in Slit-Pores Using Monte Carlo Simulation

Abstract

We discuss the use of Monte Carlo simulation to model the equilibrium adsorption of gases in slit pores. Databases of adsorption isotherms have been calculated for nitrogen, carbon-monoxide, methane and carbon-dioxide for a range of pressures, pore widths and temperatures. We discuss the implications of these results for materials characterisation procedures based on gas adsorption data.     

Alterations in trunk bending stiffness following changes in stability and equilibrium demands of a load holding task

The contribution of the trunk neuromuscular system (TNS) to spine stability has been shown in earlier studies by characterizing changes in antagonistic activity of trunk muscles following alterations in stability demands of a task. Whether and/or how much such changes in the response of TNS to alteration in stability demand of the task alter spinal stiffness remains unclear. To address this research gap, a repeated measure study was conducted on twenty gender-balanced asymptomatic individuals to evaluate changes in trunk bending stiffness throughout the lumbar spine’s range of flexion following alterations in both stability and equilibrium demands of a load holding task. Trunk bending stiffness was determined using trunk stiffness tests in upright posture on a rigid metal frame under different equilibrium and stability demands on the lower back. Increasing the stability demand by increasing the height of lifted load ∼30 cm only increased trunk bending stiffness (∼39%) over the lower range of lumbar flexion and under the low equilibrium demand condition. Similarly, increasing the equilibrium demand of the task by increasing the weight of lifted load by 3.5 kg only increased trunk bending stiffness (55%) over the low range of lumbar flexion and under the low stability demand condition. Our results suggest a non-linear relationship between changes in stability and equilibrium demands of a task and the contribution of TNS to trunk bending stiffness. Specifically, alterations in TNS response to changes in stability and equilibrium demand of a given task will increase stiffness of the trunk only if the background stiffness is low.     

传统城市水适应性空间格局研究——以济南为例

为研究古人在长期适应与改造自然过程中积累的水资源利用及水患治理的经验,选取泉城济南为例,通过古籍、舆图的收集及实地踏查的研究方法,基于区域尺度、城市尺度和城—水相互作用的不同层面,从区域水网格局约束、防洪需求、用水需求3个方面,探讨水环境影响下城市的起源与格局演变,以及基于不同需求的宏观尺度城乡水适应性空间格局特征。进而总结水适应性空间格局营建的生态智慧,分别是顺应自然与利用自然、水利设施层层叠加与协调运作、自然—人工水系网络的内外贯通、依水营建特色居住空间4方面,从而对济南古城水环境及水工设施保护、城市水环境规划提供一定参考     

Effects of three simultaneous demands on glucose transport, resting metabolism and morphology of laboratory mice

In nature, animals must successfully respond to many simultaneous demands from their environment in order to survive and reproduce. We examined physiological and morphological responses of mice given three demands: intestinal parasite infection with Heligmosomoides polygyrus followed by caloric restriction (70% of ad libitum food intake versus ad libitum for 10 days) and/or cold exposure (5°C vs. 23°C for 10 days). We found significant interactions between these demands as well as independent effects. Small intestine structure and function changed with demands in both independent and interactive ways. Body mass decreased during caloric restriction and this decrease was greater for cold-exposed than warm-exposed mice. In ad libitum fed mice, body mass did not change with either cold exposure or parasite infection but body composition (fat versus lean mass of whole body or organs) changed with both demands. Generally, organ masses decreased with caloric restriction (even after accounting for body mass effects) and increased with cold exposure and parasite infection whereas fat mass decreased with both caloric restriction and parasite infection. Mass adjusted resting metabolic rate (RMR) increased with cold exposure, decreased with caloric restriction but, unlike previous studies with laboratory mice, did not change with parasite infection. Our results demonstrate that the ability of mice to respond to a demand is influenced by other concurrent demands and that mice show phenotypic plasticity of morphological and physiological features ranging from the tissue level to the level of the whole organism when given three simultaneous demands.     

Recovery of V79 cell clones with different phenotypes in aminopterin- or azaserine-containing media used for the selection of HGPRT revertants

Three 6-thioguanine (6TG)-resistant mutants were mutagen-treated and selected for clones capable of growing in 2 selective media: HAT medium, containing aminopterin (AP) and HAS medium, containing L-azaserine (AS). Both 6TG-sensitive, wild-type clones and 6TG-resistant mutants were found among colonies growing in HAT medium, while only 6TG-sensitive clones grew in HAS medium. Time for expression was required by 6TG-resistant but not by 6TG-sensitive clones, that were fully expressed immediately after treatment. All HAT-resistant, 6TG-resistant clones which were analyzed proved to be resistant to AP. These data were interpreted as follows: in HAT medium, both HGPRT⁺ revertants and double mutants (HGPRT^?, AP-resistant) were selected, while only HGPRT⁺ revertants were selected in HAS medium. Not all 6TG-resistant mutants were able to produce both classes of HAT-resistant clones.     

Infectious poxvirus vectors have capacity for at least 25 000 base pairs of foreign DNA

To test the capacity of poxviruses for added foreign DNA, a recombinant was constructed that contains 24 700 bp of bacteriophage λ DNA inserted within the vaccinia virus thymidine kinase (TK) gene. The recombinant is stable, infectious and replicates in tissue culture at the same rate and to the same titer as standard vaccinia virus. This size flexibility of the poxvirus genome and the lack of stringent packaging requirements are useful features for an infectious eukaryotic cloning vector.     

Transcriptional mapping of two yeast genes coding for glyceraldehyde 3-phosphate dehydrogenase isolated by sequence homology with the chicken gene

Homology between the coding regions of the chicken and yeast glyceraldehyde 3-phosphate dehydrogenase (GAPDH) genes was directly demonstrated by the hybridization of a cDNA clone coding for GAPDH in the chicken with EcoRI-digested yeast DNA. A yeast EcoRI fragment library in bacteriophage lambda was screened using the chicken cDNA plasmid as probe, and two recombinant phages were isolated, each one containing a different GAPDH gene. The initiation and termination sites for the GAPDH mRNA were localized for the two different GAPDH genes and compared to those of other yeast genes. Measurements of the relative mRNA levels for the two genes show that both genes are transcribed at about the same level when yeasts are grown on glucose media.     

Simulation,Fabrication and Characterization of THz Metamaterial Absorbers

Metamaterials (MM), artificial materials engineered to have properties that may not be found in nature, have been widely explored since the first theoretical¹ and experimental demonstration² of their unique properties. MMs can provide a highly controllable electromagnetic response, and to date have been demonstrated in every technologically relevant spectral range including the optical³, near IR⁴, mid IR⁵ , THz⁶ , mm-wave⁷ , microwave⁸ and radio⁹ bands. Applications include perfect lenses¹⁰, sensors¹¹, telecommunications¹², invisibility cloaks¹³ and filters^14,15. We have recently developed single band¹⁶, dual band¹⁷ and broadband¹⁸ THz metamaterial absorber devices capable of greater than 80% absorption at the resonance peak. The concept of a MM absorber is especially important at THz frequencies where it is difficult to find strong frequency selective THz absorbers¹⁹. In our MM absorber the THz radiation is absorbed in a thickness of ~ λ/20, overcoming the thickness limitation of traditional quarter wavelength absorbers. MM absorbers naturally lend themselves to THz detection applications, such as thermal sensors, and if integrated with suitable THz sources (e.g. QCLs), could lead to compact, highly sensitive, low cost, real time THz imaging systems.