Electrical and magnetic properties of Polystyrene doped with Iron nanoparticles

Summary Polymer composites have recently received a considerable amount of scientific and technological interest, because their properties can be properly controlled, choosing the adequate doped particles, their size and concentrations, and the synthesis conditions. In this work we report the synthesis and characterization of a polystyrene (PS) matrix doped with different concentrations of iron nanoparticles. X-ray diffraction and transmission electron microscopy were used to characterize the structure of the samples. The behaviour of the d.c. electrical conductivity (σ_dc) and the complex permittivity (ε*=ε^′-iε^′′) as a function of frequency (100 Hz–10 MHz) reflects the important effect of the iron nanoparticles concentration in the sample properties. A percolation threshold in the conductivity was observed at a critical concentration of iron nanoparticles. A noticeable increase in the saturation magnetization and coercivity is observed with the rise of the iron nanoparticles concentration, being thisbehaviour also noticed in the remanent magnetization. A rise of the initial a.c. susceptibility with the iron concentration is also observed.     

Product and by-product formation in laboratory studies on disinfection electrolysis of water using boron-doped diamond anodes

Boron-doped diamond (BDD) electrodes were studied with respect to the formation of inorganic by-products in water electrolysis. Experiments in non-divided cells were performed with systems containing sulphate, chloride, chlorite, chlorate and nitrate ions. Discontinuous experiments in thermostated cells with rotating disk diamond anodes and expanded mesh IrO₂ cathodes were carried out at 20 °C. Current density was varied between 50 and 300 A m⁻². Ion chromatography was mainly used for species detection.

It was not possible to demonstrate the decomposition of sulphate although a slight tendency seems to exist in some experiments. Hydrogen peroxide is one of the anodic and cathodic by-products. Active chlorine is detectable at higher chloride concentrations compared with the use of mixed oxide anodes (MIO). One reason for this is the reaction of formed chlorine with ozone or hydrogen peroxide. Chlorate can be formed electrolysing chloride, hypochlorite and chlorite solutions. Perchlorate formation was detected. Cathodic processes are responsible for the formation of nitrite ions and ammonia. If chlorine is present, the formation of monochloramine is one possible side reaction. Results show that the processes are very complex. Reaction spectra may vary from case to case. Perchlorate formation is a high risk in drinking water treatment.     

The residential therapeutic caring community.

The residential therapeutic caring community (RTCC) for adolescents combines psychotherapeutic principles of the professional model and self-help concept of the therapeutic community by using the collective resources of members to mobilize peer pressure. The RTCC is a safe, structured, supportive treatment environment that employs a confrontation, teaching, interpretative, and reasoning approach and uses the psychotherapeutic principles of reality therapy and existential thought. In the RTCC, the staff serve as mentors and role models, and they demonstrate their concern by maintaining high expectations for immediate improved behavior. The personal qualities necessary for a psychotherapist working in an RTCC are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An electrocoaters guide to selecting and maintaining rectifiers

Considering the critical contribution of your rectifier to the safe, effective, and reliable operation of your electrocoating process, the selection and maintenance of the optimum unit for your operation is time well spent.     

Optimal control of nonlinear systems to given orbits

Using optimal control techniques we derive and demonstrate the use of an explicit single-step control method for directing a nonlinear system to a target orbit and keeping it there. We require that control values remain near the uncontrolled settings. The full nonlinearity of the problem in state space variables is retained. The “one-step” of the control is typically a composition of known or learned maps over (a) the time required to learn the state, (b) the time to compute the control and (c) the time to apply the control. No special targeting is required, yet the time to control is quite rapid. Working with the dynamics of a well-studied nonlinear electrical circuit, we show how this method works efficiently and accurately in two situations: when the known circuit equations are used, and when control is performed only on a Poincaré section of the reconstructed phase space. In each case, because the control rule is known analytically, the control strategy is computationally efficient while retaining high accuracy. The target locations on the selected target trajectory at each control stage are determined dynamically by the initial conditions and the system dynamics, and the target trajectory is an approximation to an unstable periodic orbit of the uncontrolled system. A linear stability analysis shows that dissipation in the dynamical system is essential for reaching a controllable state.     

EVALUATION OF BARLEY AND MALT QUALITY USING NEAR-INFRARED REFLECTANCE TECHNIQUES

A scanning near-infrared reflectance spectrophotometer was calibrated for the prediction of barley aleurone colour and malt moisture. The malt moisture was predicted on malt ground for the determination of malt extract (coarse grind) making the method suitable for moisture correction in malt extract estimation. Calibrations for the prediction of malt extract and endosperm modification from barley and malt were also attempted. A correlation (r= 0.851 n = 135) was found between malt hot water extract and the percentage of the endosperm estimated as being modified by microscopy following staining with Calcofluor. Probably because of this influence of modification on malt extract, the use of near-infrared reflectance to predict malt extract was most successful at predicting the malt extract values obtained following micro-malting in the absence of the additives, gibberellic acid and potassium bromate.     

Performance and tissue zinc and metallothionein accumulation in chicks fed a high dietary level of zinc

Four experiments were conducted to identify several factors that might improve the accuracy and reproducibility of Zn bioavailability assays for chicks. Response of tissue Zn and metallothionein (MT) concentrations to various elevated levels and soluble sources of dietary Zn were measured, as well as the effect of delaying high Zn administration until 7 d posthatching to alleviate the detrimental effect of Zn sulfate on feed intake to 3 wk of age. Bone Zn increased (P < 0.01) in all experiments in response to increasing dietary Zn concentrations. Liver and pancreas MT were affected (P < 0.01) by a source by age interaction and variability that made this criterion unsuitable for bioavailability assays. Lastly, 1-d-old chicks were used to study the effect of delaying feeding of a high-Zn diet up to 7 d of age. The basal diet was fed continuously for 21 d as a control. A diet containing 1,000 ppm Zn was either fed continuously from Day 1, or started on Day 3, 5, or 7. Chicks given high Zn on Day 3, 5, or 7 decreased (P < 0.01) feed intake within 24 h of feeding. Delayed feeding of high dietary Zn might help to alleviate decreased feed intake observed in previous studies. Delaying the onset of high Zn feeding by several days may help alleviate feed intake problems observed with Zn sulfate. Use of either Zn gluconate or Zn acetate as a standard in assays or use of MT synthesis as a bioavailability criterion will probably not be useful to improve accuracy of the estimates.     

The controversy over recovered memories.

Comments on the article by J. L. Alpert et al (see record 2000-13581-002), which presented the report of the American Psychological Association Working Group on Investigation of Memories of Childhood Abuse. The authors discuss 4 issues in this commentary: (a) the assumptions and evidence used to support the case for dissociated and recovered memories (noting that the evidence is weak and the assumptions internally inconsistent as well as contradictory to a mass of experimental evidence about human memory); (b) the process by which dissociated memories are said to be recovered (events that were originally very poorly encoded as fragmentary, kinesthetic memories cannot be recovered with accuracy later); (c) 4 bodies of relevant, but neglected, research on human memory (reminiscence and hypermnesia, effectiveness of retrieval cues, priming in implicit memory tests, and intentional forgetting); and (d) the issue of appropriate research strategies to gain evidence on the thorny issues of long-delayed retrieval of information. Current evidence does not support the conclusion that memories of repeated abuse are dissociated and recovered with accuracy years later. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Induction of forward mutations at the thymidine kinase locus of mouse lymphoma cells: evidence for electrophilic and non-electrophilic mechanisms

A database of 209 chemicals tested for induction of forward mutations at the heterozygous thymidine kinase (TK +/-) locus in L5178Y mouse lymphoma cells was analyzed for structure-activity relationships using the MultiCASE expert system. Consistent with evidence of several contributing biological mechanisms, these studies suggest that such mutations may occur by more than one mechanism. As might be expected, there was evidence for a component involving direct electrophilic attack on the cellular DNA, in a manner previously established as causative in the induction of mutations in Salmonella. In addition, however, there was also strong evidence for another mechanism or mechanisms involving chromosome missegregation, cellular toxicity or an alternate site of action, such as the microtubules.