Race and employment dislocation in California’s aerospace industry

This article finds that African American and Latino workers have borne a disproportionate share of employment costs associated with defense cuts in California’s aerospace industry. The data for this analysis come from administrative files, which contain demographic and employment-related information for everyone who collects unemployment-insurance benefits. The analysis shows that African Americans suffered higher displacement rates, longer unemployment spells, and poorer outcomes in new jobs than whites. Latinos were disadvantaged in several ways, but not consistently in all categories. Asian Americans, on the other hand, generally fared better than whites. These results show that economic dislocation, in the form of defense cuts, reinforces racial inequality in the labor market.     

In-situ characterization of microbial community in an A/O submerged membrane bioreactor with nitrogen removal.

The bacterial community involved in removing nitrogen from sewage and their preferred DO environment within an anoxic/oxic membrane bioreactor (A/O MBR) was investigated. A continuously operated laboratory-scale A/O MBR was maintained for 360 d. At a sludge age of 150 d and a C/N ratio of 3.5, the system was capable of removing 88% of the influent nitrogen from raw wastewater through typical nitrogen removal transformations (i.e. aerobic ammonia oxidation and anoxic nitrate reduction). Characterization of the A/O MBR bacterial community was carried out using fluorescence in situ hybridization (FISH) techniques. FISH results further showed that Nitrosospira spp. and Nitrospira spp. were the predominant groups of ammonia and nitrite oxidizing group, respectively. They constituted up to 11% and 6% of eubacteria at DO below 0.05 mg/l (low DO), respectively, and about 14% and 9% of eubacteria at DO between 2-5 mg/l (sufficient DO), respectively, indicating preference of nitrifiers for a higher DO environment. Generally low counts of the genus Paracoccus were detected while negative results were observed for Paracoccus denitrificans, Alcaligenes spp, and Pseudomonas stutzeri under the low and sufficient DO environments. The overall results indicate that Nitrosospira spp., Nitrospira spp. and members of Paracoccus spp. can be metabolically functional in nitrogen removal in the laboratory-scale A/O MBR system.     

The idiosyncratic risks of a Shariah compliant REIT investor

This paper investigates the impact of Shariah compliant investment principles on the idiosyncratic risks of a Shariah compliant REIT investor. The importance of idiosyncratic risks in explaining cross-sectional returns of a constructed Shariah compliant REIT investor’s portfolio is further examined in this paper. In all constructed portfolios examined, there is a positive and significant relationship between expected idiosyncratic volatility and expected REIT returns of the constructed Shariah compliant portfolio (GCC Shariah compliance standards). This result is consistent and persistent after robustness tests are carried out. As such, idiosyncratic risks are an important factor to consider in the pricing of Shariah compliant REIT stock returns. On further examination, the significant relationship as seen in the constructed Shariah compliant portfolio can be explained from the firm-specific risks of the residential REIT sector which is the most dominant sector during the period of investigation. The implications of these results also point to the importance of Shariah compliance standards and screening methods which is a significant feature associated with the understanding of the relationship of idiosyncratic risks on expected REIT returns of Shariah portfolios. Results show contrasting results between a less-restrictive and restrictive Shariah compliant portfolio. We find a significant relationship between expected returns and the idiosyncratic risks specifically in the restrictive Shariah compliant portfolio.     

On a class of discrete distributions arising from the birth-death-with-immigration process

This paper considers a class of distributions which may be regarded as the convolution of a negative binomial and a stopped-sum generalized hypergeometric factorial-moment random variables. Some properties are derived and it is shown that this class of distributions is a subset of distributions for the birth-and-death process with immigration (also reversible counter system). Formulations by mixing, limiting distributions and maximum likelihood equations are also discussed.     

Two-stage SBR for treatment of oil refinery wastewater.

A two-stage sequencing batch reactor (SBR) system was used for treatment of oily wastewater with COD and oil and grease (O&G) concentrations ranging from 1,722-7,826 mg/L and 5,365-13,350 mg/L, respectively. A suitable start-up protocol was developed using gradual increase in oily wastewater composition with methanol as the co-substrate. This strategy enabled a short acclimation period of 12 days for the sludge in the two-stage SBR to adapt to the oily wastewater. After acclimation, the 1st stage and 2nd stage SBRs were able to achieve COD removals of 47.0+/-2.4% and 95.3+/-0.5%, respectively. The 1st stage SBR was able to achieve 99.8+/-0.1% of O&G removal and effluent O&G from the 1st stage SBR was only 6+/-2 mg/L. The 2nd stage SBR was used to further remove COD in the effluent from the 1st stage SBR. The final effluent from the 2nd stage SBR had a COD concentration of 97+/-16 mg/L with no detectable O&G content. Thus, a two-stage SBR system was shown to be feasible for treating high strength oily wastewater to meet the local discharge standards.     

Some notes on the non-central negative binomial distribution

Summary In this paper we shall record some facts and further examine certain properties of the non-central negative binomial (NNB) distribution (Laguerre series distribution of Gurland, Chen and Hernandez 1983). We consider, among others, a stochastic formulation (birth-and-death process), the series expansion of the probability distribution and the corresponding series expansion of a generalized exponential distribution (Ong/Lee 1986), and the connection of the NNB distribution with the non-central beta, gamma and non-central gamma distributions. A four-parameter version of the NNB distribution is also presented.     

Industrial Relations Climate in the Manufacturing Sector in Singapore

The objective of this study is to assess the state of workplace industrial relations climate in the manufacturing sector in Singapore. Based on a survey of 73 manufacturing companies in Singapore and subsequent intensive study of eight of them, it was found that the overall labor-management relations in the industry were good and had improved over the past few years. Union membership was reported to have increased and this was accompanied by a perceived increase in union role and influence on labor-management relations. The findings also highlighted the need to strengthen the communication processes among the three parties—workers, unionists and management.     

The bivariate non-central negative binomial distributions

Summary Four bivariate generalisations (Type I–IV) of the non-central negative binomial distribution (Ong/Lee) are considered. The Type I generalisation is constructed using the latent structure model scheme (Goodman) while the Type II generalisation arises from a variation of this scheme. The Type III generalisation is formed by using the method of random elements in common (Mardia). The Type IV is an extension of the Type I generalisation. Properties of these bivariate distributions including joint central and factorial moments are discussed; several recurrence formulae of the probabilities are given. An application to the childhood accident data of Mellinger et al. is considered with the precision of the Type I maximum likelihood estimates computed.