Private multiparty sampling and approximation of vector combinations

We consider the problem of private efficient data mining of vertically-partitioned databases. Each of several parties holds a column of a data matrix (a vector) and the parties want to investigate the componentwise combination of their vectors. The parties want to minimize communication and local computation while guaranteeing privacy in the sense that no party learns more than necessary. Sublinear-communication private protocols have primarily been studied only in the two-party case. In contrast, this work focuses on multi-party settings.     

Climate change and trace gases

Palaeoclimate data show that the Earth's climate is remarkably sensitive to global forcings. Positive feedbacks predominate. This allows the entire planet to be whipsawed between climate states. One feedback, the 'albedo flip' property of ice/water, provides a powerful trigger mechanism. A climate forcing that 'flips' the albedo of a sufficient portion of an ice sheet can spark a cataclysm. Inertia of ice sheet and ocean provides only moderate delay to ice sheet disintegration and a burst of added global warming. Recent greenhouse gas (GHG) emissions place the Earth perilously close to dramatic climate change that could run out of our control, with great dangers for humans and other creatures. Carbon dioxide (CO2) is the largest human-made climate forcing, but other trace constituents are also important. Only intense simultaneous efforts to slow CO2 emissions and reduce non-CO2 forcings can keep climate within or near the range of the past million years. The most important of the non-CO2 forcings is methane (CH4), as it causes the second largest human-made GHG climate forcing and is the principal cause of increased tropospheric ozone (O3), which is the third largest GHG forcing. Nitrous oxide (N2O) should also be a focus of climate mitigation efforts. Black carbon ('black soot') has a high global warming potential (approx. 2000, 500 and 200 for 20, 100 and 500 years, respectively) and deserves greater attention. Some forcings are especially effective at high latitudes, so concerted efforts to reduce their emissions could preserve Arctic ice, while also having major benefits for human health, agricultural productivity and the global environment.     

The effect of using a home computer on students' educational use of IT

With many students' access to computers at home out-weighing their use of Information Technology (IT) in school, the importance of home computing has grown immensely over the last decade. This paper therefore seeks to examine the nature and extent of students' domestic use of computers and the subsequent relationship with their use of IT in schools and colleges. Using a sample of 16–19-year-old students, quantitative and qualitative data were gathered to explore students' experiences of home computing. The results suggest that students using computers at home have significantly more positive attitudes toward using computers yet do not necessarily make more use of school or college-based IT; compensating for the inadequacies of educational IT with their use of computers at home. Nevertheless access to, and benefits gained from, home computers were found to differ significantly according to students' gender.     

Factors influencing the use of computer mediated communication by teachers in secondary schools

In this article, a survey on the factors influencing the use of computer mediated communication (CMC) by teachers in secondary schools in Brussels is described. The survey compared a group of CMC users with non-CMC users. It is demonstrated that language teaching was the best predictor for the use of CMC. The main reason for this is that education policy within the area under investigation has developed a specific CMC project that is primarily oriented towards a target group of language teachers. A second predictor of CMC use was the degree of technological innovativeness. This instrument is a measure of the willingness of the teacher to adopt technological innovation in his own teaching practice. A third predictor was perceived CMC attributes. This instrument indicates the degree to which users observe any congruence between the characteristics of CMC as a medium and their own teaching practice.     

Zircon mineral solids concentrated from Athabasca oil sands froth treatment tailings: Surface chemistry and flotation properties

Zircon mineral solids concentrated from Athabasca oil sands froth treatment tailings were compared by X-ray photoelectron spectroscopy, infrared spectroscopy, and collector-assisted froth flotation before and after surface cleaning in a low temperature, radio-frequency oxygen plasma. Plasma cleaning was effective at removing a surface bound layer of organic matter having chemical markers consistent with bituminous fractions. Specifically, the observation of long-chain aliphatics, ester and ether linkages, aromatic indicators, and hydroxyls in the absence of carboxylic acid groups, suggested the surface organic layer was representative of asphaltene or resin. Supporting this interpretation was the identification of pyrrolic and thiophenic chemical states. Plasma degradation of the hydrocarbon component transformed the zircon particles from hydrophobic to hydrophilic as evidenced by their recovery in water/ethanol froth flotation tests. The cleaned zircon particles were subsequently collected in the froth using dodecylamine. This work explains the surface conditions responsible for the reporting of zircon to the froth treatment tailings and demonstrates the efficacy of plasma cleaning as a means to condition zircon for coupling with collector agents. A physical model of surface adsorption is discussed and process implications are considered.     

Cognitive deficits, psychopathology, and psychosocial functioning in bipolar mood disorder

BACKGROUND: The nutrition management of patients with malabsorption syndromes due to acquired immunodeficiency syndrome (AIDS) is problematic. The aim of this study was to compare the effects of total parenteral nutrition (TPN) and an oral, semielemental diet (SED) on body weight, body composition, quality of life, survival, and medical costs in AIDS patients with malabsorption. METHODS: This was a prospective, randomized, open-label study performed in outpatients. Twenty-three AIDS subjects (TPN group, 12; SED group, 11) with cryptosporidiosis, microsporidiosis, or malabsorption of unknown cause were randomized and followed. Subjects were prescribed equivalent amounts of formulas of similar composition for 3 months. Monthly estimations of caloric intake, body weight, body composition by bioimpedance analysis, and quality of life were recorded. Nutritional variables were analyzed by repeated-measures analysis of covariance, with the baseline measure as the covariate. Nutrition-related medical costs, survival, and indices of absorptive and immune function were compared, RESULTS: Subjects had lost an average of 1.5 and 1.0 kg body wt/mo for TPN and SED during the 6 months before study entry (p < not significant). The TPN group consumed more total calories than the SED group (p < .05). Weight change during therapy was significantly different from pretreatment in both groups (p < .01 for TPN, p = .023 for SED). The TPN group gained more weight than the SED group (p = .057) and significantly more fat (p = .02), but the changes in body cell mass were similar in the two groups. Changes in weight and body composition correlated with caloric intake but not the mode of feeding. The SED group scored significantly better than the TPN group on a physical functioning subscale of quality of life (p < .01). Survival was similar in the two groups. TPN therapy cost almost four times more than SED. Peripheral blood CD4+ lymphocyte numbers were unaffected by either therapy. Intestinal function was not affected by either therapy. CONCLUSIONS: An oral SED may reverse weight loss and wasting in AIDS patients with malabsorption.     

Large-scale surface to surface transport for photons and electrons via Monte Carlo

A brief history of Monte Carlo methods is presented, with a differentiation between uses in engineering versus physics, indicating different computational approaches in each field. Particle tracing is presented for photons and then electrons in the presence of a uniform magnetic field. Next, a comprehensive formulation is presented for particle-material interactions, including absorptance, transmittance, and three models of reflectance: diffuse, specular, and semi-specular. Then, a discussion of event steps is presented, indicating that algorithms may be effectively vectorized. Vectorization results are analyzed using a modified version of Amdahl's Law, indicating that over 99% of the “work” of an algorithm may be vectorized.