Surface area production during grinding

During grinding, in cascading mills, the mass distribution of the material moves continuously to finer sizes. Grinding models are usually designed to predict the size distribution of the mill products either as a function of effective breakage events and the time or the energy consumed by the mill. Mill products are always tested for their size analysis and their fineness is usually expressed as the size d through which a certain amount of material passes, i.e. d₈₀. However, particulate materials have some supplementary properties that a grinding model should predict as well. The specific surface area is such an important supplementary property. Initially, the present work examines the relationship between mass distribution and the surface area of ground materials and determines the conditions under which, mass distribution can be used to determine the surface area. Based on these findings the work further examines the operating conditions of a cascading mill under which the surface area of the material increases at the highest rate. The operating parameter examined is the mill load ratio expressed as the mass ratio of mill grinding media and the material present in the mill.     

Antimicrobial Activity of a Pullulan–Caraway Essential Oil Coating on Reduction of Food Microorganisms and Quality in Fresh Baby Carrot

This research evaluated the antimicrobial efficacy of pullulan films containing caraway essential oil (CEO). The films were prepared from a 10% of pullulan, containing from 0.12% to 10.0% of CEO. The composition of the CEO was analyzed with the use of gas chromatography. The antimicrobial activity of the CEO was evaluated with the method of serial microdilutions, and the films containing CEO—with the agar diffusion method against selected Gram‐negative, Gram‐positive bacteria, and fungi. The structure of the film surface and its cross‐section were analyzed using a scanning electron microscope (SEM). Analyses were also carried out to determine the efficacy of a pullulan coating with 10% CEO on baby carrots experimentally inoculated with Salmonella enteritidis, Staphylococcus aureus, Saccharomyces cerevisiae, or Aspergillus niger and stored at a room temperature for 7 d. At a concentration of 0.12%, CEO inhibited the growth of all the tested microorganisms. Pullulan films containing 8% to 10% of CEO were active against all tested microorganisms. Populations of S. aureus on carrot samples were reduced by approximately 3 log CFU/g, while those of A. niger and S. cerevisiae by, respectively, 5 and 4 log CFU/g, after 7 d of storage. S. enteritidis was the most resistant among the tested species, since it was not significantly reduced after 7 d of storage. At the end of storage, samples treated with pullulan–caraway oil coating maintained better visual acceptability than control samples. Results of this study suggest the feasibility of applying a pullulan film with incorporated CEO to extend the microbiological stability of minimally processed foods.     

Impaired timing precision produced by striatal D2 receptor overexpression is mediated by cognitive and motivational deficits.

Increased striatal dopamine D2 receptor activity is thought to contribute to the pathophysiology of schizophrenia. To model this condition in mice, Kellendonk et al. (2006) generated transgenic mice that selectively overexpress the D2 receptor in striatum (D2OE). Drew et al. (2007) reported that D2OE mice display deficits in interval timing and motivation. The present study further explored the impaired timing in D2OE mice. Experiment 1 assessed the role of motivation in producing timing deficits in the peak procedure and found that performance in D2OE mice was improved by increasing motivation. In addition, performance was impaired in control mice when motivation was decreased. In Experiment 2, we found that D2OE mice have no timing impairment when tested using the bisection task, a procedure in which the measure of timing performance is less influenced by motivation to respond. In Experiment 3, we also used the bisection task and found selective impairment in timing of long durations in D2OE mice. These results suggest that striatal D2 overexpression impairs timing by decreasing motivation and through its impact on working memory and/or sustained attention. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Economic effects of regulating the seismic strengthening of older buildings

The marked increase in the awareness of earthquake risk following the Canterbury earthquakes in New Zealand offered a unique opportunity to investigate the economic effect of disaster-mitigation regulations on the commercial building stock. A difference-in-differences (DD) framework was used to determine whether earthquake risk has been capitalized into the property prices of buildings constructed prior to 1976, as a response to the national policy requiring assessment and strengthening (or demolition) of the existing earthquake-prone building stock. A negative externality is found in the policy announcement on affected (pre-1970s) office and retail buildings which caused office buildings to suffer a 12.5% stigma discount. However, retail properties were less impacted suffering a 2.3% stigma loss. The value of the commercial building stock has been affected by the policy. These findings provide policy-makers with timely evidence as to the economic effects of New Zealand’s earthquake-prone buildings policy. Facing losses in property value and financial responsibility for retrofitting their assets, building owners will be looking for a workable set of regulatory and non-regulatory incentives to encourage disaster risk management and protect the built environment.     

Error Estimation for Indirect Measurements: Interval Computation Problem Is (Slightly) Harder Than a Similar Probabilistic Computational Problem

One of main applications of interval computations is estimating errors of indirect measurements. A quantity y is measured indirectly if we measure some quantities xi related to y and then estimate y from the results of these measurements as by using a known relation f. Interval computations are used "to find the range of f(x1,...,xn) when xi are known to belong to intervals ," where i are guaranteed accuracies of direct measurements. It is known that the corresponding problem is intractable (NP-hard) even for polynomial functions f.In some real-life situations, we know the probabilities of different value of xi; usually, the errors xi - are independent Gaussian random variables with 0 average and known standard deviations i. For such situations, we can formulate a similar probabilistic problem: "given i, compute the standard deviation of f(x1,...,xn) ." It is reasonably easy to show that this problem is feasible for polynomial functions f. So, for polynomial f, this probabilistic computation problem is easier than the interval computation problem.It is not too much easier: Indeed, polynomials can be described as functions obtained from xi by applying addition, subtraction, and multiplication. A natural expansion is to add division, thus getting rational functions. We prove that for rational functions, the probabilistic computational problem (described above) is NP-hard.     

Automatic generation of quadrilateral finite element meshes

This paper describes an efficient, accurate and simple implementation of an algorithm for generation of quadrilateral finite element meshes. An original algorithm by Talbert and Parkinson [J.A. Talbert, A. Parkinson, Development of an automatic two-dimensional finite element mesh generator using quadrilateral elements and Bezier curve boundary definition, Int. J. Numer. Meth. Eng., 29 (1990) 1551–1567], has been substantially redeveloped and modified and presented in greater detail. We cover several important issues omitted in publication mentioned and we will provide interested readers with fully documented source code of the program.     

Interactions of CO and NO with the perovskite-type oxide larho3

Some aspects of the interactions of CO and NO with LaRhO₃ have been studied. The reduction of this oxide with CO occurs where the contracting sphere model is of perovskite structure stable up to a concentration of anion vacancies of ca. 2e^? per molecule. By reduction of LaRhO₃ at 817 K, rhodium was obtained, highly dispersed on a matrix of La₂O_3. After a reduction-oxidation cycle at 871 K the particle size of the perovskite decreased drastically. The activation energy of the reduction (67 kJ mol^?1) was significantly lower than that of other LaMO₃ oxides of group-VIII metals. Coverages of CO(θ_CO) and NO(θ_NO) at room temperature were lower than 3%, θ_NO being substantially higher than θ_CO. The reversibly adsorbed fractions of CO and NO underwent a remarkable decrease after preadsorbing NO and CO, respectively. This competitive adsorption is assumed to be associated with the adsorption of CO and NO on metallic sites. NO preadsorption inhibited the total adsorption of CO more severely than the reverse, indicating that NO is bound more strongly than CO to the LaRhO₃ surface.     

Postgraduate occupations of psychology major students.

During the last ten or fifteen years we have seen an increase in enrollment in undergraduate psychology courses that is far out of proportion to the general increase in overall university attendance. Psychology departments are overwhelmed with undergraduate students, and the numbers continue to increase each year. Since we are allocating so much of our time, energy, and resources to undergraduate teaching, it is important to determine what these students are being educated for. This note reports the results of an inquiry into the postgraduate occupations of the members of the first three graduating classes of the psychology major programme at McGill University. (PsycINFO Database Record (c) 2010 APA, all rights reserved)