Microscale Patterning of Mesoscopic PZN-PT Single Crystal Films by Crystal ion Slicing and Laser-Induced Etching

Advances in the fabrication of solid-solution single crystal relaxor ferroelectrics have made it possible to produce highly efficient piezoelectric crystals, and have attracted renewed interest in the use of these crystals for a new generation of piezoelectric transducers, actuators and sensors. Of particular interest is their incorporation into micro-electromechanical systems (MEMS). In this paper we report on the laser-induced wet chemical etching of lead zinc niobate-lead titanate (PZN-PT) in hydrochloric acid (HCl). Argon-ion laser radiation at power levels up to 4 W is focused to a spot diameter of about 15μm and results in the chemical etching of grooves at patterning speeds up to 5μm/sec. Crystal ion slicing, an ion-implant-based film separation technique, is used in combination with laser etching to form 5 to 10μm-thick patterned and freestanding films for incorporation into micro-electromechanical devices.     

SiC半导体技术--即将腾飞的新一代半导体技术

电源设计者们仿佛正在目睹一个新的半导体技术的诞生。随之而来的新一代功率半导体器件远远优于现有的硅技术。SiC 材料可以让器件具有迄今为止设计工程师们梦寐以求却不能得到的出色特性。其最重要的优点包括以下几个方面：:工作结温高达225 ℃，而相应的漏电流只有适度的增加。由于本质上不会出现热偏移thermal run－away)，故可以在 很高的结温下可靠的工作。 没有正向或反向恢复，故即使在高温 下以高频工作时，也没有开关损耗。 甚至可以实现开关损耗极小、频率 高达1 M H z 的深度切换(h a rd 正向电阻具有…     

A set expression based inheritance system

This paper describes a new formalism for inheritance systems, based on the formal semantics of set expressions. Using the formalism, it is possible to define new semantic classes by arbitrary set expressions operating on previously defined classes. Thus generalizing bothIS-A links andIS-NOT-A links and adding the set intersection operation. We present an efficient algorithm which follows these definitions to deduce the properties implied by the inheritance network, i.e., the properties of the classes containing a given element. The application which motivated the development of the formalism, namely semantic disambiguation of natural language, is also described.     

Forensic implications of the difficulties of defining delusions

Delusions are evasive to define: (1) Within the process of defining, one uses part of the final conclusion, which should derive from the basic definition (in other words, Circular reasoning); (2) Many, if not most, of so-called normal persons, hold delusion-like ideas; (3) Delusion becomes, usually, more understandable and less bizarre when investigated; (4) Delusions are not unique by remaining resistible to reason; (5) For every delusional content, as bizarre and remote as it may be, there is at least one cultural niche, in which the same content is considered legitimate and reasonable, (if no important and dignified). The forensic implications of these difficulties (to define delusions), will be discussed and elaborated.     

Detection of cytomegalovirus in semen from a population of men seeking infertility evaluation

This paper presents the results of in vivo measurements on a worker from a fuel reprocessing plant who was involved in an actinide intake. The results revealed that false indications of an actinide lung burden could arise from a contaminant present elsewhere in the chest region. Consequently, it is important that lung monitoring programs for occupational workers handling actinides are conducted with this caution in mind and that due consideration is given even in cases of minor cuts/wounds in order to rule out substantial overestimation of internal radiation doses.     

The entry of antiviral and antiretroviral drugs into the central nervous system

The ability of antiviral and antiretroviral drugs to enter the brain is a critical issue in the treatment of many viral brain diseases, including HIV-related neurologic disease. Much of the literature concerning nucleoside analog entry into the nervous system focuses on drug levels in the cerebrospinal fluid (CSF), equating these with drug levels in the brain extracellular fluid (ECF) as though the two compartments intermix freely. We review the anatomic and physiologic aspects of drug entry into CSF and into brain ECF, as well as the exchange processes between these two compartments. In most instances drug concentrations in the CSF and ECF compartments bear little relationship to one another and using CSF concentrations to extrapolate brain ECF concentrations may significantly overestimate the latter. Accepted terminology and methodology for making measurements of blood-brain barrier function are discussed. Studies of brain uptake that express results as brain:plasma ratios, or that have used microdialysis, may overestimate the amount of drug reaching the brain. Using published data, we present an estimate of the time course of Zidovudine (AZT) concentrations in brain ECF and show that brain concentrations of AZT will likely be below that necessary to inhibit HIV-1 replication when AZT is administered systemically. Antiviral nucleosides and oligonucleotides appear to have limited entry into the brain when given systemically, which may hinder therapy of viral brain diseases, while some of the protease inhibitors may enter the brain more readily. Alternative methods for increasing antiviral and antiretroviral drug delivery to brain are discussed.     

The making of a spam zombie army. Dissecting the Sobig worms

On 25 June 2003, a new mass-mailing worm, Sobig.E, emerged. The worm was highly successful at infecting computer systems. It is the fifth revision of a worm that first raised its ugly head in January 2003. There is strong evidence that spammers use infected computers to relay unsolicited commercial e-mail.     

Consumer knowledge of foodborne microbial hazards and food-handling practices.

A national telephone survey was conducted of 1,620 randomly selected U.S. residents who spoke English, were at least 18 years old, and resided in households with kitchen facilities. Respondents were interviewed about their recognition of foodborne pathogens, foods at risk for transmitting infection, knowledge of safe food handling, and food-handling practices. One-third of the respondents who prepared meals reported unsafe food hygiene practices: e.g., they did not wash hands or take precautions to prevent cross-contamination from raw meat. Unsafe practices were reported more often by men, adults 18 to 29 years of age, and occasional food preparers than by women, persons 30 years old or older, and frequent food preparers. Respondents who identified a food vehicle for Salmonella spp. were more likely to report washing their hands and cleaning cutting boards after preparing raw meat and poultry. The results raise concerns about consumer food-handling practices. The influence of food safety training, food-handling experience, and age on food-handling practices should be studied further. Awareness of a food vehicle for Salmonella spp., for example, may indicate knowledge of the etiology of foodborne disease that promotes safe food handling. Understanding the factors associated with safe food handling will assist in development of effective safe-food instruction programs.     

Fractional composition of partly hydrolysed polyvinyl acetate and its compatibility with hydroxypropyl methylcellulose in aqueous solutions

Fractionation of partly hydrolysed polyvinyl acetate (PVA) was performed by warming of its aqueous solutions. The following properties of the obtained fractions were determined: viscosity, molecular weight and molecular weight distribution, surface tension, and absorbance in the IR range. The blockiness of the polymer molecules, characterized by their behaviour towards iodine-containing systems such as I₂,-H₃BO₃ and I₂,-KI, was estimated. Fractionation of the aqueous solutions of PVA by warming is based mainly on the different internal molecular structure of the separated products, i.e. on the length of the vinyl acetate blocks in the PVA molecules and, to a lesser extent, on the degree of hydrolysis and the degree of polymerization. The more blocklike are the PVA molecules, the less compatible are the polymers in the PVA-hydroxypropyl methylcellulose (HPMC)-water system. At phase separation in this sytem the PVA molecules which are not compatible with HPMC are, in the first place, those of the highest blockiness.