Disc filtration for separation of flocs from a moving bed bio-film reactor.

A Discfilter with 10 and 18 microm filter openings, respectively, was placed in parallel to a flotation plant for separation of biological flocs from a post-denitrifying Kaldnes Moving Bed Process, the last treatment step at the municipal wastewater treatment plant at Sj?unda, Malm?, Sweden. The effluent concentrations from the 10 and 18 microm filter were 2-5 and 2-8 mg SS L(-1), respectively, which is comparable to, or better than, the flotation plant. Comparison with experiences from activated sludge plants shows that the Discfilter works especially well after the Kaldnes process. Particle size distribution (PSD) studies show that particles larger than the filter openings of 10 and 18 microm are separated with approximately 90% efficiency, whereas most of the smaller particles pass the filter. This fact indicates that the major particle separation mechanism is physical blocking. These findings point to the possibility of improving the prediction of the separation efficiency by combining measurements of turbidity and suspended solids with particle size analysis.     

The appraisal of ordinary shares by Saudi investors

This paper reports on a questionnaire survey about share valuation practices among investors and their intermediaries in Saudi Arabia. The findings suggest that fundamental analysis is used most by investor respondents where a P/E multiple is applied to an earnings forecast to generate a prediction of future price. However, technical analysis is also used to a much greater extent than in developed markets. Finally, the results indicate that quarterly and annual reports as well as newspapers are widely consulted by investors when forming their expectations about share valuations.     

An analysis of option pricing under systematic consumption risk using GARCH

An issue in the pricing of contingent claims is whether to account for consumption risk. This is relevant for contingent claims on stock indices, such as the FTSE 100 share price index, as investor’s desire for smooth consumption is often used to explain risk premiums on stock market portfolios, but is not used to explain risk premiums on contingent claims themselves. This paper addresses this fundamental question by allowing for consumption in an economy to be correlated with returns. Daily data on the FTSE 100 share price index are used to compare three option pricing models: the Black–Scholes option pricing model, a GARCH (1, 1) model priced under a risk-neutral framework, and a GARCH (1, 1) model priced under systematic consumption risk. The findings are that accounting for systematic consumption risk only provides improved accuracy for in-the-money call options. When the correlation between consumption and returns increases, the model that accounts for consumption risk will produce lower call option prices than observed prices for in-the-money call options. These results combined imply that the potential consumption-related premium in the market for contingent claims is constant in the case of FTSE 100 index options.     

Dynamics of photosynthetic pigments in an Andean lake in Colombia

Guatavita Lake is a small, sheltered tropical high mountain lake located in the Colombian Andes, with a closed watershed and a maximum depth of 25 m. It is the freshwater source for human consumption in nearby small towns, as well as being a site of cultural value for the country, as it was a sacred place to indigenous peoples until about five centuries ago. As the structure and function of this aquatic ecosystem is poorly understood, this study provides initial knowledge on its phytoplankton biomass dynamics, which should be useful in designing efficient management plans with environmental baseline information for similar lakes elsewhere. Physical and chemical data, and photosynthetic pigment concentrations, were measured for the period November 1999–November 2000 at the central vertical axis of Guatavita Lake. The vertical profile of the chlorophyll‐a concentration was closely related to the dissolved inorganic nitrogen concentrations and the thermal stratification characteristics. The maximum chlorophyll‐a concentration in the metalimnion was recorded for the thermal stratification period (November 1999–June 2000). Deepening of the maximum chlorophyll‐a concentration began in February, continuing to June, when it reached its lowest value at the 15 m depth. The phytoplankton biomass values showed an increment within the entire water column at the beginning of the mixing period (July). The relation between the metalimnetic peak of chlorophyll‐a and the dissolved inorganic nitrogen concentration suggests the growth of the phytoplankton community is limited mainly by the availability of nitrogen.     

Replacement Investment: Optimal Economic Life Under Uncertainty

Replacement investment is essentially a regenerative optimal stopping problem; that is, the key decision concerns when to terminate the life of existing plant – and hence when to start over again. This paper examines this optimisation problem within a continuous time framework and studies the qualitative and quantitative impact of uncertainty on the timing of new investment (and the criteria that should be used for terminating the life of existing plant).     

Unemployment compensation and episodes of nonemployment

This paper examines the influence of unemployment insurance (UI) on the length of nonemployment spells experienced by young workers. The analysis introduces a flexible duration model to estimate the effects of the weekly benefit amount and weeks of eligibility on the amount of time spent between jobs by men, distinguishing between the experiences of UI and non-UI recipients. The empirical findings suggest three conclusions: (1) UI recipients experience longer spells of nonemployment than their non-UI recipient counterparts, at least up to the point of exhaustion of UI benefits; (2) the level of the weekly benefit amount does not significantly affect the length of nonemployment spells; and (3) increasing the number of weeks of eligibility offered by a UI program leads to longer episodes of nonemployment.     

The Distribution of Multifamily Mortgage Originations: What We Know and Why We Care

Three policy-relevant questions about multifamily mortgage originations (MFOs) are addressed. First, what is the annual volume of MFOs? This analysis highlights differences and problems among three publicly available multifamily lending surveys; the 1993 volume is estimated at $30 billion. Second, what is the size distribution of multifamily mortgages? Using kernel density estimation, variation in this distribution among central cities and suburbs, underserved areas, and lender type is examined. Third, what are the primary determinants of the variation in multifamily lending? A relatively simple regression model is estimated to shed light on the variables most highly correlated with multifamily lending. Tract income relative to MSA median income and minority concentrations are shown to be highly correlated with lending volume, but the largest source of variation is the number of multifamily rental units in the tract.     

INITIAL PUBLIC OFFERINGS: GOING BY THE BOOK

In the U.S., and increasingly in other countries as well, IPO securities are marketed to investors in a process known as "book-building"—one that amounts to polling institutional investors to establish a demand schedule for the issue and then allotting stock to individual investors according to the strength of their professed interest. Although book-building methods require use of discriminatory tactics that have attracted strong criticism from investors and regulators, this article defends such practices by demonstrating that book-building is more efficient than alternative methods. It effectively allows issuers to increase the net proceeds of their offerings by making better use of information about market demand conditions.
In the process of explaining the efficiency of the book-building method, this article also offers a plausible explanation for a phenomenon that has long puzzled economists: the systematic underpricing of IPOs. The key to the success of a book-building effort lies in the use of a strategic pricing and allocation policy designed to offset the investor's incentive to understate his or her interest in an IPO. By committing to favor investors who provide strong indications of interest with relatively large allocations of underpriced shares, the investment bank can limit the distortion of investor's incentives in bidding and so increase the level of proceeds the issuing firm can expect to generate from its IPO.