US housing problems,politics and policies in the 1990s

Housing policy in the US reflects its general approach to economic and social problems. Among all western democracies, the US relies most on private market forces to provide housing for its population. American housing policy emphasises bolstering market forces and minimising assistance for the poor. Despite its significant achievements (for example, two out of every three American households now owns its dwelling), the US is now facing a severe housing crisis, not only for the poor, but for a sizeable portion of the troubled middle class. To guarantee every American an opportunity to live in decent, safe and affordable housing, the US has to change national priorities and spend more on housing. But it also must spend better: reduce development costs, eliminate bureaucratic waste, and target assistance more efficiently. Following a review of past and current housing programmes, we outline a progressive housing policy agenda and then discuss the political obstacles and opportunities that confront such an ambitious plan.     

先进的钻机为亚泥保驾护航

水泥是经济建设与城镇发展的基础材料,水泥业是工商繁荣的指标.随着中国经济的崛起,特别是基础设施建设的蓬勃发展,水泥行业正处于产量和价格同步增长的上升通道.作为台湾排名前五位的巨头企业之一-台湾远东集团于1957年设立的亚洲水泥历经半个世纪的风雨,目前已是台湾第二大水泥制造商,其经营业绩、产品品质、获利能力在同行业中遥遥领先,它同时也致力于环保事业并提升产品的附加值.     

A 1320 nm experimental optical phase-locked loop

An experimental balanced optical second-order phase-locked loop constructed using 1320 nm diode laser pumped miniature Nd:YAG lasers is discussed. The loop is stable and has a phase error of less than 1.8° when the received signal power is -65 dBm or more. The phase error appears to be dominated by the lasers' frequency noise as long as the signal power is more than -60 dBm     

Recurrent neural networks and robust time series prediction

We propose a robust learning algorithm and apply it to recurrent neural networks. This algorithm is based on filtering outliers from the data and then estimating parameters from the filtered data. The filtering removes outliers from both the target function and the inputs of the neural network. The filtering is soft in that some outliers are neither completely rejected nor accepted. To show the need for robust recurrent networks, we compare the predictive ability of least squares estimated recurrent networks on synthetic data and on the Puget Power Electric Demand time series. These investigations result in a class of recurrent neural networks, NARMA(p,q), which show advantages over feedforward neural networks for time series with a moving average component. Conventional least squares methods of fitting NARMA(p,q) neural network models are shown to suffer a lack of robustness towards outliers. This sensitivity to outliers is demonstrated on both the synthetic and real data sets. Filtering the Puget Power Electric Demand time series is shown to automatically remove the outliers due to holidays. Neural networks trained on filtered data are then shown to give better predictions than neural networks trained on unfiltered time series.     

Biocatalytic sulfur removal from fuels: applicability for producing low sulfur gasoline

Environmental regulations are driving R&D efforts to produce low sulfur fuels, including diesel fuel and gasoline for motor vehicles. Biocatalytic sulfur removal from fuels has potential applicability for producing low sulfur gasoline. Microbial biocatalysts have been identified that can biotransform sulfur compounds found in fuels, including ones that selectively remove sulfur from dibenzothiophene heterocyclic compounds. Most attention is give to the 4S pathway of Rhodococcus, which can remove sulfur from substituted and unsubstituted dibenzothiophenes, including sulfur compounds that hinder chemical catalysis and that resist removal by mild hydrotreatment. Various bioreactor and bioprocess designs are being tested for use with biocatalysts, including recombinant biocatalysts, for use in removing sulfur from fuels and feedstocks within the petroleum refinery stream. With bioprocess improvements that enhance biocatalyst stability, achieve faster kinetics, improve mass transfer limitations, temperature and solvent tolerance, as well as broaden substrate specificity to attack a greater range of heterocyclic compounds, biocatalysis may be a cost-effective approach to achieve the production of low sulfur gasoline. The challenge will be to accomplish these improvements by the time the regulations for low sulfur gasoline and other vehicle fuels go into effect in order to be competitive with emerging nonbiological desulfurization technologies.     

The effect of the putative endogenous imidazoline receptor ligand, clonidine-displacing substance, on insulin secretion from rat and human islets of Langerhans

1. The effects of a rat brain extract containing clonidine-displacing substance (CDS), a putative endogenous imidazoline receptor ligand, on insulin release from rat and human isolated islets of Langerhans were investigated. 2. CDS was able to potentiate the insulin secretory response of rat islets incubated at 6 mM glucose, in a dose-dependent manner. The magnitude of this effect was similar to that in response to the well-characterized imidazoline secretagogue, efaroxan. 3. CDS, like other imidazoline secretagogues, was also able to reverse the inhibitory action of diazoxide on glucose-induced insulin release, in both rat and human islets. 4. These effects of CDS on secretion were reversed by the imidazoline secretagogue antagonists, RX801080 and the newly defined KU14R, providing the first evidence that imidazoline-mediated actions of CDS can be blocked by specific imidazoline antagonists. 5. The effects of CDS on insulin secretion were unaffected when the method of preparation involved centri-filtration through a 3,000 Da cut-off membrane or when the extract was treated with protease. These results confirm that the active principle is of low molecular weight and is not a peptide. 6. Overall, the data suggest that CDS behaves as a potent endogenous insulin secretagogue acting at the islet imidazoline receptor.     

The corrosion of copper by chlorinated drinking waters

The study demonstrates that free chlorine is the agent chiefly responsible for the corrosion of copper in chlorinated domestic water supplies, and that dissolved oxygen plays a comparatively minor role. The impact of chlorine is enhanced at low pH values by the pH dependence of the HOCl electrode reactions, and because of the greater oxidizing strength of hypochlorous acid over that of hypochlorite ion.Adjustment of the water pH to about 7 or 8, after chlorination, markedly reduces the rate and extent of copper corrosion. If, in addition, free chlorine can be maintained no higher than about 2 mg l⁻¹ only minor corrosion of copper will occur, and the service life of copper plumbing greatly extended.