Ecological problems of the Amu Darya delta

Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 3, pp. 6–8, March, 1992.     

A comparison of several approximations to the power function of the likelihood ratio test in covariance structure analysis*

In this paper we compare alternative asymptotic approximations to the power of the likelihood ratio test used in covariance structure analysis for testing the fit of a model. Alternative expressions for the noncentrality parameter (ncp) lead to different approximations to the power function. It appears that for alternative covariance matrices close to the null hypothesis, the alternative ncp's lead to similar values, while for alternative covariance matrices far from H_o the different expressions for the ncp can conflict substantively. Monte Carlo evidence shows that the ncp proposed in Satorra and Saris (1985) gives the most accurate power approximations.     

AN EMPIRICAL INVESTIGATION INTO THE IMPACT OF PROFIT SHARING SCHEMES OF EXECUTIVIES ON THE CONTENT OF CORPORATE SUBMISSIONS ON PROPOSED ACCOUNTING STANDARDS

This paper examines the comments submitted by UK companies on 20 proposed accounting standards to test the hypotheses that executives favor standards that increase, or dampen the variance of, accounting profit numbers on which their incentive remuneration is based. Test results were generally as hypothesised but only the profit variance outcomes were statistically significant. Allowing for political environment changes affected only the profit variance results. There was no evidence that the relative monetary size of bonus payments was a significant lobbying factor. No significant differences were found between the lobbying preferences of companies with or without executive incentive schemes.     

Floc size distribution in a stirred suspension.

This paper focuses on the distribution of alumino-humic flocs found in a stirred suspension. Distributions were scaled using the transformation u = d/dL in which d is floc diameter and dL its arithmetic mean value and fitted by a gamma distribution. Flocs were treated as monofractal with solids mass concentration specified by C = A'rhos (d/do)D-3 in which A' is a packing coefficient, rhos the density of the floc solids, D the fractal dimension and do a reference size. It was shown that the overall solids concentration (M) complies with the dependence M proportional to NA'dDL-S(D) in which N is the number of flocs per unit volume and S(D) a distribution moment. Initial estimates of A' and D were obtained from analysis of floc sedimentation behaviour. From knowledge of the base parameters, the calculated value of M did not match the measured M and varied with shear. This was attributed to a kinematic influence on C over and beyond changes associated with the response of dL to shear. Issues of self-similarity were examined and it was concluded that distributions did not display strict self-similarity. Data are provided on the size distribution found in the flocculators of a treatment works at full scale.     

Biofilm adaptation to sulfate reduction in anaerobic immobilized biomass reactors sujected to different COD/sulfate ratios.

Various aspects of biofilm adaptation to sulfate reduction in horizontal-flow anaerobic immobilized biomass (HAIB) reactors subjected to increasing sulfate concentrations and different COD/sulfate ratios are presented and discussed. Four bench-scale HAIB reactors filled with vegetal carbon (R1 and R2) and polyurethane foam matrices (R3 and R4) were utilized. Influent sulfate concentrations ranging from 500 to 3000 mg/L were applied at COD/sulfate ratios ranging from 5.0 to 1.7. Reactors R1 and R4 were operated with higher sulfate loads than those applied to R2 and R3. For the same COD/sulfate ratio, the highest sulfate reduction efficiency (approximately 80%) was displayed by the vegetal carbon reactor (R2) subjected to low sulfate loads. According to the results of our molecular biology analyses, the different support materials provided different biomass colonization conditions. The lowest diversity of sulfate-reducing bacteria was found in the HAIB filled with polyurethane foam matrices operating with high sulfate loads.     

On the Statistical Significance of Event Effects on Unsystematic Volatility

We develop a method for determining the significance of the effect of a certain event (stock split, corporate restructuring, change in regulation, etc.) on unsystematic volatility of asset returns. Simulations show that the suggested tests reject the true null hypothesis of no effect on volatility at appropriate levels, whereas the rejection rates of a false null hypothesis increase with the magnitude of the effect. An application of the method to corporate spin‐offs reveals statistically significant and long‐lasting estimated increases in unsystematic volatility of parent companies' returns.     

The effect of the scale of horizontal subsurface flow constructed wetlands on flow and transport parameters.

Horizontal subsurface flow constructed wetlands have proven their efficiency in treating wastewater and removing the pollutants of concern. Treatment efficiency depends on the wastewater residence time, which is a function of the hydraulic loading and the physical conditions of the constructed filter system, which can be described with effective parameters such as: hydraulic conductivity, porosity, dispersivity etc. Because spatial variability is often scale dependent, these effective parameters may be affected by the scale of the system being studied. In this paper the results of tracer experiments in constructed filters using saturated horizontal flow at three scales (small and medium lab scales and full-scale system) using the same filter media is reported. Light-weight aggregate (filter media termed Filtralite-P) was used at all scales. Increasing the scale was associated with increasing dispersivity, meanwhile hydraulic conductivity experienced dramatic reduction and variation by increasing the examined scale. Observed changes in the hydraulic parameters indicate that heterogeneity at different scales should be taken into account when the performance of LWA filters are evaluated from small-scale experiments.     

Nonlinear dynamics and competing behavioral interpretations: Evidence from intra‐day FTSE‐100 index and futures data

Extant empirical research has reported nonlinear behavior within arbitrage relationships. In this article, the authors consider potential nonlinear dynamics within FTSE‐100 index and index‐futures. Such nonlinearity can be rationalized by the existence of transactions costs or through the interaction between informed and noise traders. They consider several empirical models designed to capture these alternative dynamics. Their empirical results provide evidence of a stationary basis term, and thus cointegration between index and index‐futures, and the presence of nonlinear dynamics within that relationship. The results further suggest that noise traders typically engage in momentum trading and are more prone to this behavior type when the underlying market is rising. Fundamental, or arbitrage, traders are characterized by heterogeneity, such that there is slow movement between regimes of behavior. In particular, fundamental traders act more quickly in response to small deviations from equilibrium, but are reluctant to act quickly in response to larger mispricings that are exposed to greater noise trader price risk. © 2006 Wiley Periodicals, Inc. Jrl Fut Mark 26:343–368, 2006     

Harmonizing the interests of a city and its region: Krasnoyarsk krai experience

The paper focuses on the emerging system of territorial strategic planning in the constituent entities of the Russian Federation and municipalities. Suggested for practical application are the best Russian research studies and practices of coordinating the interests of municipal and regional authorities. The analysis of scholarly approaches to the issue in focus allows one to infer that the best elaborated position is that of the staff of the North-Western Office of the Russian Research Center for Local Governance (RRCLG). As regards the express-analysis of practices adopted in the number of the Russian Federation constituent entities, the practices of the Krasnodar krai appear to be the most promising.     

Social Capital and the Terms of Trade for Farmland

Social capital is a person or group's sympathy for or sense of obligation to another person or group. This article introduces social capital into a neoclassical model of farmland exchange and shows how relationships alter the terms of trade. Empirical evidence from a survey of farmers shows that the type of relationship farmland sellers have with farmland buyers has a statistically significant and economically important effect on the minimum-sell price for farmland. Compared to the minimum-sell price when selling to a total stranger in an arm's-length transaction, farmland sellers discount prices to friendly neighbors and relatives and require a premium from unfriendly neighbors and influential people in the community.