Dielectrophoresis of Lossy Dielectrics

Dielectrophoresis of a solid particle in a liquid medium is usually studied under the assumption that the dielectrics are ideal. Real dielectrics, however, exhibit nonzero conductivities, and the results are sometimes unpredictable. The particular case of a lossy dielectric sphere in a lossy dielectric liquid is considered. The dielectrophoretic motion following the application of a dc field is studied, and it is shown that the motion is strongly affected by conductivities. From the results it can be deduced, for instance, that the separation of solid particles in liquid media can be based on differences of conductivities rather than differences of permitivities of the two media.     

WPHACT 2.0: A fully massive Monte Carlo generator for four fermion physics at ee colliders

WPHACT 2.0 is the new fully massive version of a MC program and unweighted event generator which computes all Standard Model processes with four fermions in the final state at e⁺e⁻ colliders. The program can now generate unweighted events for any subset of all four fermion final states in a single run, by making use of dedicated pre-samples which can cover the entire phase space. Improvements with respect to WPHACT 1.0 include the Imaginary Fermion Loop gauge restoring scheme, new phase space mappings, a new input system, the possibility to compute subsets of Feynman diagrams and options for including ISR via QEDPS, running α_QED, CKM mixing, resonances in channels.     

Optimisation of the throttling system in a CO2 refrigerating machine

This paper is an answer to the need of finding the optimal solution for the throttling system in refrigerating machines using CO₂ as working fluid; such a solution must combine reliability, low installation cost and high energy efficiency. To this purpose, different expansion systems are compared by means of a simulation programme, including a new one, operating with a differential valve, a liquid receiver and a thermostatic valve. The typical compression refrigerating cycle performed by CO₂ involves transcritical operations and therefore the upper pressure needs to be adjusted to the optimal value, that, unlike the traditional cycle, is not determined by heat transfer. The innovative system here proposed shows an intrinsic self-adjusting capability that leads to COP values quite close to the maximum ones when a fixed suitable value of the differential pressure is chosen, even if the temperature of the secondary fluid varies to a large extent.     

Driver exposure: The indirect approach for obtaining relative measures

The induced exposure procedure is used to obtain three indices: relative exposure index, liability index and hazard index. Values of these indices are computed for the following categories: rural/urban, male/female, age (7), day/night, time of day, weekend/weekday for 1.7 million qccidents in 25 states. The liability index comparing males under 20 with males 21–24 agrees quite well with established weighting factors for an insurance group.     

New processes in the environmental chemistry of nitrite. 2. The role of hydrogen peroxide

The oxidation of nitrite and nitrous acid to *NO2 upon irradiation of dissolved Fe(III), ferric (hydr)oxides, and nitrate has previously been shown to enhance phenol nitration. This allowed the proposal of a new role for nitrite and nitrous acid in natural waters and atmospheric aerosols. This paper deals with the interaction between hydrogen peroxide, a key environmental factor in atmospheric oxidative chemistry, and nitrite/nitrous acid. The reaction between nitrous acid and hydrogen peroxide yields peroxynitrous acid, a powerful nitrating agent and an important intermediate in atmospheric chemistry. The kinetics of this reaction is compatible with a rate-determining step involving either H3O2+ and HNO2 or H2O2 and protonated nitrous acid. In the former case the rate constant between the two species would be 179.6 +/- 1.4 M(-1) s(-1), in the latter case it would be as high as (1.68 +/- 0.01) x 10(10) M(-1) s(-1) (diffusion-controlled reaction). Due to the more reasonable value of the rate constant, the reaction between H3O2+ and HNO2 seems more likely. In the presence of HNO2 + H2O2 the nitration of phenol is strongly enhanced when compared with HNO2 alone. The nitration rate of phenol in the presence of peroxynitrous acid decreases as pH increases, thus HOONO is a potential source of atmospheric nitroaromatic compounds in acidic water droplets. The mixture Fe(II) + H2O2 (Fenton reagent) can oxidize nitrite and nitrous acid to nitrogen dioxide, which results in phenol nitration. The nitration in the presence of Fe(II) + H2O2 + NO2-/HNO2 occurs more rapidly than the one with H2O2 + NO2-/HNO2 at pH 5, where little HNO2 is available to directly react with hydrogen peroxide. Both systems, however, are more effective than NO2-/HNO2 alone in producing nitrophenols from phenol. Another process leading to the oxidation of nitrite to nitrogen dioxide is the photo-Fenton one. It can be relevant at pH > or = 6, as nitrite does not react with H2O2 at room temperature. Under such conditions the source of Fe(II) is the photolysis of ferric (hydr)oxides (heterogeneous photo-Fenton reaction). In the presence of nitrite this reaction induces very effective nitrophenol formation from phenol.     

Sorption of Pb(II), Cd(II), and Ni(II) From Single- and Multimetal Solutions by Recycled Waste Porous Glass

Selective sorption of lead, cadmium, and nickel ions on recycled waste porous glass beads was investigated. Single-metal equilibrations were carried out in demineralized water and ternary metal equilibrations were carried out in demi- and tap water. Freundlich isotherm gave a good correlation of the experimental data. Maximum metal retention (q_max) in single-ion solutions were 18.66 mg/g_RPWG (0.090 mmol/g_RPWG), 4.83 mg/g_RPWG (0.043 mmol/g_RPWG), 4.00 mg/g_RPWG (0.068 mmol/g_RPWG), respectively, for Pb⁺², Cd⁺², and Ni⁺², and lower figures were in the case of ternary systems: 13.50 mg/g_RPWG(0.065 mmol/g_RPWG), 2.23 (0.020 mmol/g_RPWG), 2.05 mg/g_RPWG(0.034 mmol/g_RPWG), respectively, for Pb⁺², Cd⁺², and Ni⁺², with further drastic reduction in tap water. Metal exhausted beads were used as thermal insulators in cement mortars, minimizing their potential impact in the environment.     

Biguanide-, imine-, and guanidine-based networks as catalysts for transesterification of vegetable oil

Polycationic systems based on poly(hexamethylene biguanide) (PHMBG), branched polyethyleneimine (PEI) and poly(N-vinylguanidine) (PVG) have been evaluated as heterogeneous catalysts for the transesterification of sunflower oil by methanol. Insoluble networks are synthesized via cross-linking of PHMBG by either 4,4′-methylenebis(N,N-diglycidylaniline) or polyisocyanate prepolymer, PEI with sebacoyl chloride, and PVG with 1,4-butanediol diglycidyl ether. PHMBG and its cross-linked networks appeared to be remarkably efficient catalysts, enabling 80–100% triglyceride conversion within 0.5 h at 70 °C. PEI-based networks catalyzed triglyceride transesterification with rates 8- to 12-fold slower than their PHMBG-based counterparts. The PVG-based networks, which were devoid of hydrophobic moieties, appeared to be inefficient catalysts due to limited accessibility of the basic guanidine groups to reactants. The PHMBG networks were shown to be recyclable by a simple centrifugal filtration. After 15 cycles of recovery and reuse, only 10–15% decline in performance was observed.     

Conditioning of and contextual sensitization to apomorphine-induced climbing in mice: Evidence against the habituation hypothesis.

Several predictions of the habituation hypothesis of conditioned drug effects were tested by looking at contextual sensitization to apomorphine-induced climbing in mice (Mus musculus). Mice were first sensitized to that effect after 9 daily injections of 0.4 mg/kg apomorphine in the test context. Other mice received the same treatment outside the test context. On Day 10, all mice were challenged with either saline (conditioned drug effects test) or apomorphine (contextual sensitization test). On both tests, the levels of climbing of mice that received apomorphine paired with the test context during the intermittent treatment were significantly higher than those of mice that were experiencing the test context for the first time (unexposed mice). Also, the rate of extinction in conditioned mice did not parallel the rate of habituation in the unexposed mice. Results contradict the habituation hypothesis of conditioned drug effects and contextual sensitization. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Structure-activity relationship study of 16 a-thiocamptothecins: an integrated in vitro and in silico approach

The instability of the hydroxylactone E ring represents a critical drawback of camptothecins, because the lactone ring is recognized to be essential for stabilization of topoisomerase I‐mediated DNA cleavage. In an attempt to investigate the effect of the thiopyridone pharmacophofore on the molecular and pharmacological features of the drug, we prepared a series of novel 16 a‐thiocamptothecin analogues. Due to the sulfur atom, a destabilization of the hydrogen bond between the hydroxy group in position 17 of the opened E ring and the carbonyl of the pyridone moiety is predicted, thus shifting the equilibrium toward the closed lactone form and increasing the lipophilic properties of the compounds. This feature was associated with superior antiproliferative potency, with reduced interaction with the human serum albumin and with substantial increase of the persistence of the topoisomerase I–DNA cleavable complex. These effects were prominent for thio‐SN38, the most active compound of the series. The favorable interactions at the molecular and cellular level of the reported thiocamptothecins confer promising features, and these compounds warrant preclinical development.     

Co-Channel Interference in Cellular Mobile Radio Systems with Coded PSK and Diversity

In this paper, the performance of coding and diversity in narrowband wireless cellular systems affected by fading, shadowing and co-channel interference is analyzed. We consider low-order diversity, that can be practically realized for both coherent and differential phase shift keying. We assume that the shadowing random processes affecting all transmitted signals do not vary appreciably over the transmission duration. Fading, on the contrary, is assumed to vary more rapidly. Our main focus here is on outage probability. After choosing a performance indicator, its expectation is taken with respect to fading and co-channel interference, conditionally on shadowing. Hence, the resulting average performance indicator is a random variable. The probability that this random variable exceeds a specified threshold defines the outage probability. We consider as performance indicators (i) the channel cut-off rate R₀ and (ii) the bit error rate P_b of an actual coded scheme. As we are interested in interference-limited, rather than power-limited systems, we evaluate both R₀ and P_b for very high signal-to-noise ratios. Results are parameterized by the frequency reuse factor and the diversity order.