Sort vs. hash revisited

Efficient algorithms for processing large volumes of data are very important both for relational and new object-oriented database systems. Many query-processing operations can be implemented using sort- or hash-based algorithms, e.g. intersections, joins, and duplicate elimination. In the early relational database systems, only sort-based algorithms were employed. In the last decade, hash-based algorithms have gained acceptance and popularity, and are often considered generally superior to sort-based algorithms such as merge-join. In this article, we compare the concepts behind sort- and hash-based query-processing algorithms and conclude that (1) many dualities exist between the two types of algorithms, (2) their costs differ mostly by percentages rather than by factors, (3) several special cases exist that favor one or the other choice, and (4) there is a strong reason why both hash- and sort-based algorithms should be available in a query-processing system. Our conclusions are supported by experiments performed using the Volcano query execution engine     

An investigation of phase transformation behavior in sputter-deposited PtMn thin films

Sputter-deposited, equiatomic PtMn thin films have application in giant magnetoresistive spin valves, tunneling magnetoresistive spin valves, and magnetic random access memory. However, the as-deposited films are found to be a disordered A1 phase in a paramagnetic state rather than an antiferromagnetic phase with L1₀ structure, which is needed for device operation. Therefore, a postannealing step is required to induce the phase transformation from the asdeposited A1 face-centered-cubic phase to the antiferromagnetic L1₀ phase. The A1 to L1₀ metastable transformation was studied by x-ray diffraction and differential-scanning calorimetry. An exothermic transformation enthalpy of −12.1 kJ/mol of atoms was determined. The transformation kinetics were simulated using the Johnson-Mehl-Avrami analysis.     

The effectiveness of a tobacco prevention program with adolescents living in a tobacco-producing region

OBJECTIVES: This study investigated the efficacy of a social-influences tobacco prevention program conducted with adolescents living in a high tobacco production area. METHODS: Students in 10 experimental schools completed the tobacco prevention program and a booster intervention. Control students received health education as usual. RESULTS: After 2 years of treatment, smoking rates in the treatment group (vs the control group) were lower for 30-day, 7-day, and 24-hour smoking. The intervention had more of an impact on those who were involved in raising tobacco than it did on those not involved in raising tobacco. CONCLUSIONS: Although modest, effects were achieved with minimal intervention time in a high-risk group, indicating that social-influences prevention programs may be effective in such groups.     

Improving the performance of college freshmen with attributional techniques.

Reports 2 replications of the authors' (see record 1982-26799-001) study in which college freshmen were given information suggesting that the causes of low grades are unstable. Compared with a control group, these Ss did better on both short-term and long-term performance measures. The long-term results, however, tended to be weak or open to alternative explanations. In the 1st replication, 39 2nd-semester freshmen with low GPAs who worried about their academic performance were assigned to control or treatment conditions. Ss in the treatment conditions received information that grades are low in the freshman year; some Ss were also told that grades improve thereafter. In the 2nd replication, 41 1st-semester freshmen who worried about their low GPAs received grade information, completed questionnaires, and completed some items from the Graduate Record Examination (GRE). Considered together, these 3 studies found that attributional interventions improved the performance of Ss on both short-term and long-term measures. Presenting Ss with information indicating that the causes of low grades in the 1st yr are temporary led to (a) improvement on sample items from the GRE and (b) increases in actual grades in the semester after the studies were conducted. Results were stronger for males than for females. This may have been due to the fact that females were more likely to find out on their own that the causes of poor grades are unstable. (11 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Investigation of Scents on Cheeks and Foreheads of Large Felines in Connection to the Facial Marking Behavior

We investigated head- and cheek-rubbing behavior in four species of large felines, lions (Leo panther), leopards (Panthera pardus), tigers (Panthera tigris), and cougars (Puma concolor), in captivity. Preliminary behavioral observations found that lions and tigers, but not leopards and cougars, showed behavioral responses to cardboard rubbing samples from head and cheek areas from conspecific felines, compared to the blank cardboard controls. In this context, surface samples on the facial areas of each species were collected to analyze volatile organic compounds that could be involved in the facial marking of felines. Previously developed stir bar surface sampling methodology was used. From all cheek and forehead samples, 100 volatile organic compounds were identified or tentatively identified. Among these, 41 have been previously reported to be present in feline urine and marking secretions. Several new compounds were identified on facial surfaces. Some of the compounds showed substantial quantitative differences among the species. One compound, that has not been reported previously in mammals, 3-acetamidofuran, was found in all investigated species. It was synthesized and tested for behavioral responses. No responses were elicited in a preliminary test. Future research will test other potential signaling compounds and their mixtures for ability to elicit behavioral responses.     

Self-complexity as a cognitive buffer against stress-related illness and depression.

This prospective study tested the self-complexity buffering hypothesis that greater self-complexity moderates the adverse impact of stress on depression and illness. This hypothesis follows from a model that assumes self-knowledge is represented in terms of multiple self-aspects. As defined in this model, greater self-complexity involves representing the self in terms of a greater number of cognitive self-aspects and maintaining greater distinctions among self-aspects. Subjects completed measures of stressful events, self-complexity, depression, and illness in two sessions separated by 2 weeks. A multiple regression analysis used depression and illness at Time 2 as outcomes, stressful life events and self-complexity at Time 1 as predictors, and drepression and illness at Time 1 as control variables. The Stress?×?Self-Complexity interaction provided strong support for the buffering hypothesis. Subjects higher in self-complexity were less prone to depression, perceived stress, physical symptoms, and occurrence of the flu and other illnesses following high levels of stressful events. These results suggest that vulnerability to stress-related depression and illness is due, in part, to differences in cognitive representations of the self. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perceived covariation among the features of ingroup and outgroup members: The outgroup covariation effect.

The authors show a new outgroup homogeneity bias—outgroup covariation. They investigated perceived covariation among the features describing group subtypes. Results support a familiarity covariation effect. Those more familiar with a group perceive lower covariation among features of group members. Results also support an outgroup covariation effect. In cases in which people are less familiar with the outgroup, they perceive greater covariation among features of outgroup members. For age, in which young and old people were less familiar with the outgroup, both perceived greater covariation among features of outgroup subtypes. For occupation, in which undergraduates had less work experience than masters of business students, undergraduates perceived greater covariation among features of business subtypes. For gender, in which students were equally familiar with men and women, no covariation effect occurred. Familiarity mediated outgroup covariation effects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perceived distributions of the characteristics of in-group and out-group members: Empirical evidence and a computer simulation.

This research studied 2 properties of perceived distributions of the characteristics of social category members: the probability of differentiating (making distinctions) among category members and the perceived variability (variance) of category members. The results of 4 experiments supported the hypothesis that greater familiarity with a social group leads to greater perceived differentiation and variability regarding that group. In-group members formed more differentiated and variable distributions for groups defined by age and more differentiated distributions for groups defined by nationality. Also, students perceived greater differentiation and variability among classmates over the course of a semester. To explain these results, we developed PDIST, a multiple exemplar model that assumes that people form perceived distributions by activating a set of category exemplars and then judging the relative likelihoods of different feature values on the basis of the relative activation strengths of these feature values. The results of a computer simulation experiment indicated that PDIST is sufficient to explain the results of our 4 experiments. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Changes in glottal configuration in women after loud talking

The purpose of this investigation was to examine changes in glottal configuration in women under a variety of pitch and loudness conditions after an interval of loud reading. Twelve young adult women with normal laryngeal structures were photographed under stroboscopic light and sustained the vowel/i/for a minimum of 3 s, at three pitch levels and three loudness levels, before and after a 15-min interval of loud reading. Results indicate that female speakers tend to alter glottic configurations across phonatory conditions after loud reading, particularly during high-pitch phonation. Specifically, five subjects tended to increase glottal closure, one tended to increase glottal opening, two tended to maintain the identical configuration, and four demonstrated no consistent pattern of response.