THE EFFECTS OF NEIGHBORHOOD DEMOCRACY ON COOPERATION: A LABORATORY STUDY

What effect does participation in neighborhood governments have on residents’ willingness to contribute to the provision of public goods? This is an important question to ask given the growth of homeowners associations (HOAs) in the United States. HOAs provide a medium through which citizens can practice democratic skills. The social capital and efficacy built through this participation may increase an individual's willingness to use his or her own resources to help provide for a community public good. In this article the author hypothesizes that such participation increases the probability that individuals donate to public goods provision. Using an experimental design where subjects in treatment groups participate in a mock HOA meeting and then play an iterated public goods game, the study finds evidence that participation in HOA meetings improves cooperative behavior. This finding suggests that HOA participation has some effect on an individual's propensity to contribute to the provision of a public good.     

钻井液用流型调节剂的研究进展

流型调节剂是用来改善钻井液流变性的处理剂,通过增黏提切使钻井液具有较高的动塑比和较好的剪切稀释性。但随着大位移井、大斜度定向井及深水、超深水井等技术的发展,复杂地层中钻井液的流变性还是易出现黏度、切力不足,性能衰减过快,甚至失去悬浮与携带能力的问题,尤其是大位移井和复杂井经常出现井眼清洁能力不足的问题。该文主要按钻井液类型:典型钻井液用流型调节剂、恒流变钻井液用流型调节剂和其他钻井液用流型调节剂,综述了现有钻井液用流型调节剂的研究进展和应用情况。对不同钻井液用流型调节剂的增黏提切能力、耐温性、环保性和价格优势进行比较和评价,随后对流型调节剂未来的发展方向提出了建议,以期为相关研究提供参考。     

SUPERCRITICAL FLUID EXTRACTION of QUERCETIN FROM ONION SKINS

Supercritical fluid extraction, with ethanol‐modified carbon dioxide, of free quercetin from onion skins (red and yellow varieties) was studied. Static mode was investigated as an extraction method, which generated a total of 0.024 g of free quercetin per kg of onion skin for the red variety, and 0.020 g per kg for the yellow variety, at 5700 psi, 40C, an average of 7.6% (molar concentration) of ethanol, and in an extraction period of 2.5 h. The modifier was found to have an important influence on free quercetin recovery. the greater the amount of ethanol collected in the trap, the greater the amount of free quercetin recovered. Identification and quantification analysis were conducted in a High Performance Liquid Chromatography system.     

CORPORATELY SPONSORED REDEVELOPMENT CAMPAIGNS AND THE DEMOGRAPHIC STABILITY OF URBAN NEIGHBORHOODS: ST. LOUIS RE‐REVISITED

ABSTRACT: Much popular speculation and scientific thinking continues to hold that inner‐city neighborhoods cannot be redeveloped in a manner that is congenial to a broad array of interests and people. Lower income and minority citizens are not supposed to find a permanent place in redeveloped neighborhoods, especially, perhaps, when the rebuilding process is influenced strongly by corporations with a stake in the area being rehabilitated. This reassessment of five redevelopment campaigns in Saint Louis affirms that rebuilding sponsored by businesses and nonprofit institutions and aided by government agencies can attract and hold persons from different backgrounds, stages of life, and social classes. Maintaining a racial mix of people that is proportionate to their representation in the general population much less skewed toward becoming whiter is difficult, however.     

Brief communication: Simple and high precision frequency meter for use in power systems

A new instrument for measuring the frequency of power networks (50 Hz or 60 Hz) is proposed. It achieves 0· 01Hz of resolution in 20 ms of measuring time. This meter has a simple and low cost electronic circuit.     

The choice and use of normal approximations to transfer-function matrices of multivariable control systems

Approximating the transfer-function matrix of a multivariable system by a normal matrix provides a reliable way for assessing the stability of feedback systems in the presence of uncertainty or non-linearities. The appropriate stability results, however, must take into account the error in the approximation, and if this is large the stability assessment becomes conservative. The present paper proposes techniques for obtaining improved normal approximations and presents results which, for the 2 × 2 case, minimize the error of approximation. The approach is amenable to a numerically robust implementation on a digital computer and has obvious application in the analysis of feedback stability.     

ROTERM: A MICROPROCESSOR BASED CIPHER TERMINAL SYSTEM

Microprocessors are playing an increasingly important role in cryptographic systems. ROTERM is an implementation of a cipher terminal using an inexpensive microcomputer system. ROTERM behaves like a mechanical rotor system of eight rotors with 96 elements each. Control features have been implemented in ROTERM which permit keyboard and/or remote control of the encipherment and decipherment of ASCII character strings. Examples are given demonstrating the use of ROTERM in user-user communications as well as user-electronic mail system posting and reading of messages.     

Convergence of least squares identification algorithms applied to unstable stochastic processes

In this paper we prove the convergence of least squares identification algorithms when applied to unstable signal models. The proof is in terms of the properties of infinite sequences of matrices and of their norms to show that the convergence of least squares identification algorithms applies to unstable deterministic and stochatics processes.     

MODELING OF THE GERMINATION OF SPORES FROM CLOSTRIDIUM PERFRINGENS FOOD POISONING ISOLATES

Clostridium perfringens type A isolates carrying a chromosomal gene for enterotoxin production (chromosomal c. perfringens enterotoxin [ C- cpe] strains) are frequent causative agents of food poisoning. Predictive models for their growth in meat products have been published; however, the development of germination models needs further research. In this study, the Weibull function was used to describe the germination of C- cpe food poisoning strains in phosphate and Tris–HCl buffer as affected by pH (5.8–8.5), germinant concentration (1–100 mM KCl) and germination temperature (23–60C). As indicated by estimators of model accuracy and bias, an empirical model for spore germination as a function of germination temperature only, predicted accurately the germination potential of 4 C- cpe food poisoning strains in buffer and in laboratory media in the 23–50C range.

PRACTICAL APPLICATIONS

Thermal processing models based on the inactivation of a heat-resistant spore ignore the potential germination and outgrowth of spore survivors as recommended by new food safety guidelines. Germination models for spore survivors to be used in conjunction with outgrowth models should be developed using as samples the product of interest because the bioavailability and concentration of germinants such as ions and free amino acids vary with the product and its manufacturing process. Another germination model application is in conjunction with new processing technologies such as high pressure processing (HPP). The inactivation of bacterial spores has been a major challenge to HPP process developers. Since germinated spores are sensitive to pressure, germination models would be useful to design combined strategies of food thermal treatment and HPP.     

Dielectric strength and interface-state behaviour of oxygen plasma-grown SiO2 films annealed at high temperature†

The behaviour of the interface-state density in plasma oxidized silicon dioxide on silicon MOS structures has been investigated as a function of annealing temperature and time for anneals in an ambient of dry nitrogen. It was found that the interface-state density decreases with increasing annealing time and temperature, saturating at a temperature of approximately 950^°C and a time of approximately one hour.

In situ r.f. sputter-cleaning prior to oxidation produces dielectric films of uniformly high and reproducible dielectric strength of up to 10⁷ volts/em, in contrast to most chemical cleaning processes which typically yield lower dielectric strengths and greater variability.