钢筋混凝土结构抗火性能试验研究现状及存在的问题

在大量调研的基础上,从材料、结构和构件三个层次分析了目前混凝土结构抗火性能试验现状、存在的问题及解决方法。这些问题有的是关于试验标准和方法认识上存在一定争议的,有些是实验室和真实情况的不一致造成的,有些是目前技术水平限制所产生的,有些是目前试验领域缺乏研究或还没有认识到需要研究的问题,讨论了一些有价值的建议和研究方向,对今后混凝土结构抗火性能试验有借鉴意义。     

超临界水氧化法处理竹子溶解浆生产废水的实验研究

介绍了利用目前国内最大超临界水氧化中试反应器(2.2L+1.7L)对竹子溶解浆生产废水进行处理的试验,其反应装置处理水量可以达到900~1100L/d。分析了超临界水氧化过程中不同反应温度、时间、压力及其氧气浓度对该废水COD处理效率的影响。实验结果表明:在温度为500℃、压力为24MPa,氧化反应时间为60s时,其COD去除率达到99.2%;氧化反应时间为90s时,其COD去除率达到99.95%。处理后的排水能够达到国家规定的排放标准。同时对超临界水氧化反应过程中出现的反应机理及放热现象进行了探讨。     

Nitrate reduction during ground-water recharge, Southern High Plains, Texas

In arid and semi-arid environments, artificial recharge or reuse of wastewater may be desirable for water conservation, but NO₃⁻ contamination of underlying aquifers can result. On the semi-arid Southern High Plains (USA), industrial wastewater, sewage, and feedlot runoff have been retained in dozens of playas, depressions that focus recharge to the regionally important High Plains (Ogallala) aquifer. Analyses of ground water, playa-basin core extracts, and soil gas in an 860-km² area of Texas suggest that reduction during recharge limits NO₃⁻ loading to ground water. Tritium and Cl⁻ concentrations in ground water corroborate prior findings of focused recharge through playas and ditches. Typical δ¹⁵N values in ground water (>12.5‰) and correlations between δ¹⁵N and ln C_NO⁻3–N suggest denitrification, but O₂ concentrations ≥3.24 mg l⁻¹ indicate that NO₃⁻ reduction in ground water is unlikely. The presence of denitrifying and NO₃⁻-respiring bacteria in cores, typical soil–gas δ¹⁵N values <0‰, and decreases in NO₃⁻–N/Cl⁻ and SO₄²⁻/Cl⁻ ratios with depth in cores suggest that reduction occurs in the upper vadose zone beneath playas. Reduction may occur beneath flooded playas or within anaerobic microsites beneath dry playas. However, NO₃⁻–N concentrations in ground water can still exceed drinking-water standards, as observed in the vicinity of one playa that received wastewater. Therefore, continued ground-water monitoring in the vicinity of other such basins is warranted.     

A simple and reliable method of chromosome banding for prenatal cytogenetics using a bromodeoxyuridine pulse

An extremely simple, fully defined and reliable technique for banding chromosomes in situ is described. The method uses a pulse of bromodeoxyuridine to produce replication pattern banding complete with G- and C-type banding in the same karyotype. This enables immediate resolution of problems otherwise requiring extra subculturing and the application of conventional banding techniques. The value of routine chromosome banding in prenatal cytogenetics using such an economical technique is discussed.     

A case of ring chromosome 22 with deletion of the 22q13.3 region associated with agenesis of the corpus callosum,fornix and septum pellucidum

We report a 16-week-gestation foetus obtained by voluntary abortion after prenatal diagnosis, in which a ring chromosome 22 was observed with deletion of the 22q13.3 region. A prenatal study of the amniotic fluid by standard chromosome technique with G bands and FISH (fluorescence in situ hybridisation) was performed. After the abortion, the anatomopathological study of the obtained foetus was carried out. Morphological and histological analysis of the foetus did not reveal severe physical abnormalities, although alterations of the nervous system were observed consisting of corpus callosum, fornix and septum pellucidum agenesia. It could be that the genes in this region that were involved in the development of the central nervous system were responsible for the alterations found in the morphological study. The wide range of manifestations observed in patients with this cytogenetic alteration is probably due to size differences in the deleted region. Copyright © 2004 John Wiley & Sons, Ltd.     

Prenatal diagnosis of partial tetrasomy 14: a case study

Prenatal specimens were received from a fetus with abnormalities noted on ultrasound. A supernumerary marker chromosome (SMC) was detected: 47,XY,+mar. Fluorescence in situ hybridisation (FISH) further classified this to be partial tetrasomy for chromosome 14. We compare this finding with other cases of SMC (14) and further classify phenotype with karyotype. Copyright © 2002 John Wiley & Sons, Ltd.     

Solving the United States National Park overflight controversy

By mid-1990 the National Park Service (NPS) must present to Congress recommendations for managing overflights of at least ten national parks. The authors examine the potential role of formal negotiation in setting overflight policy in these parks by reviewing the overflight controversy at Grand Canyon National Park (GCNP). Regulations controlling overflights of the GCNP are only now being implemented after a 17-year conflict that culminated in a congressionally mandated solution. The authors review this controversy and find that, contrary to common perception, the number of park visitors bothered by overflights is not small but roughly equals the number of airborne visitors (up to 450,000 per year). On the basis of this investigation, the authors determine that formal negotiation would have been an appropriate policy-making process because of the clearly defined and limited number of parties and issues involved. Considering the number of park visitors that will continue to be affected by this issue, the authors conclude that formal negotiations should be considered for overflight problems involving other parks. Such negotiations should be park-specific. Differences in park size, extent of the problem, and parties involved would prohibit park-wide negotiations.This article has been adapted from Tourist Flights over the Grand Canyon: The Potential for Negotiated Solutions to Similar Problems, Analysis and Management, October 30, 1987. The opinions expressed in this article are those of the authors; they are not meant to represent the views of the organizations with which the authors are associated.     

VARIABILITY IN ADJUSTMENT PREFERENCES TO GROUNDWATER DEPLETION IN THE AMERICAN HIGH PLAINS1

ABSTRACT: This paper explores the adjustments and institutions that residents of the American High Plains prefer in coping with the depletion of the High Plains (Ogallaia) aquifer. The authors identify 48 possible adjustments and report on public preferences for them as determined from a mail survey of 956 respondents in 14 counties. For purposes of analysis, the adjustments are categorized into five groups: user practices, management policies, financial incentives and disincentives, technological fixes, and other. Preferences were also determined among five levels of government to enforce each of the adjustments. Adjustments associated with user conservation practices were generally most preferred while financial incentives and disincentives were least favored. Local groundwater management agencies were the most favored level of institution to administer conservation adjustments followed by the state, county, and federal levels. The most preferred option for 20 adjustments was that no agency should be involved. Respondents in agriculturally related occupations showed less support for water conservation laws and gave greater acceptance to the continuance of existing methods. Irrigators viewed the increasing cost of lifting water as a more serious problem than the depletion of groundwater.     

THE CENTRAL ARIZONA WATER CONTROL STUDY: A CASE FOR MULTIOBJECTIVE PLANNING AND PUBLIC INVOLVEMENT1

This paper describes the successful application of a multiobjective planning framework, incorporating substantial public involvement, to a major water resources decision involving intense confilcts. The study was initiated to help resolve more than a decade of controversy over a project proposed to control flooding and provide regulatory storage in the Phoenix, Arizona, area. The public was actively involved in the development of study goals and the specification of acceptable tradeoffs between multiple objectives. A wide range of structural and nonstructural alternatives was formulated and evaluated in relation to these objectives, and broad-based support was developed for a new plan. Reasons for the successful outcome are discussed, as well as implications for water resources planning under the new Federal Principles and Guidelines.