The thermal conductivity of pure nitrogen and of mixtures of nitrogen and carbon dioxide at elevated temperatures and pressures

The thermal conductivities of nitrogen at 470 K and six mixtures of nitrogen and carbon dioxide at various temperatures have been measured as a function of pressure up to 25 MPa. The mixtures were measured at the following temperatures: one at 302 K, three at 380 K, one at 430 K, and one at 470 K. The data were used to test three prediction methods for the thermal conductivity of gas mixtures under pressure. Surprisingly good agreement was found with predictions using the corresponding-states method of Ely and Hanley. The predictions of the more theoretically based method of Mason et al. were low throughout, due partly to its use of the Hirschfelder-Eucken equation as the low-density limit, but also because the predicted density dependence rises too slowly. The simplified version of this method proposed by Svojskij gave slightly worse predictions, particularly at higher densities. The zero- density results for nitrogen are examined by comparing the zero-and first-density coefficients with the trends shown at lower temperatures.     

显卡散热系统改造

最近支持DirectX 9的游戏作品频频发布,让每位酷爱游戏的发烧级玩家为之兴奋。但是笔者所使用的升技Ti 4200 OTES,因为仅支持DirectX 8.1而显得越来越力不从心,在游戏中频频发生画面定格、拖影现象。为超到更高的核心/显存频率,笔者决定对Ti 4200的散热系统加以改造。     

Operation of PWM voltage source-inverters in the overmodulationregion

Pulse width modulated (PWM) inverters experience a reduction in gain when overmodulation occurs. The pulse dropping or transition region is examined for continuous and discontinuous modulation strategies. Transition region characteristics for a number of modulation strategies are introduced. The effect of the transition region on field oriented control (FOC) is presented. The adverse effects of bus disturbances on current regulated AC inverters, while in the transition region, are demonstrated by experimental results. The problems encountered are the consequence of the reduced gain of the PWM inverter regardless of the PWM strategy. A compensated modulation technique (CMT) adaptable to continuous and discontinuous modulators eliminates the voltage error and transitions to six-step operation without inducing a voltage transient. The CMT applies to voltage and current regulated PWM inverters employing most of the modern switching strategies. Experimental results presented in the paper demonstrate the CMT's smooth transition to six-step and the improved performance a CMT-PWM algorithm provides     

Metabotropic glutamate receptor-induced homosynaptic long-term depression and depotentiation in the dentate gyrus of the rat hippocampus in vitro

We have investigated the role of metabotropic glutamate receptors (mGluR) in the induction of homosynaptic long-term depression (LTD) and depotentiation (DP) in the dentate gyrus of the adult rat. Perfusion of the mGluR agonist (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid (1S,3R-ACPD) for a prolonged period (20 min) induced long-term depression (LTD) of field excitatory postsynaptic field potentials (epsps) from the baseline level and also depotentiation (DP) from the long-term potentiated level. Both the ACPD-and the low frequency stimulation (LFS)-induced LTD and DP were inhibited in the presence of the mGluR antagonist (+)-alpha-methyl-4-carboxyphenylglycine (MCPG), demonstrating the necessity for the activation of metabotropic glutamate receptors in the induction of LTD/DP. The LFS and ACPD-induced LTD were independent of the activation of N-methyl-D-aspartate (NMDA) receptors, as they were not blocked by the NMDA receptor antagonist D-2-amino-5-phophonopentanoate (AP5).     

Three hypotheses concerning young children's imitations of lexical items.

Examined 2 hypotheses concerning possible facilitative effects of imitation on lexical acquisition, using comprehension as well as production as metrics for lexical emergence. Three experiments, with 33 children aged 1 yr 4 mo to 2 yrs, provided evidence that imitation may facilitate children's ability to acquire words in production and that imitation of such words may decline only after a period in which the words are used both imitatively and spontaneously. Preliminary support was also found for a 3rd hypothesis: In some cases imitation of novel words may enable the child to respond to others when he/she is unable to contribute original information to the topic. (8 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An enriched model for the integrated berth allocation and quay crane assignment problem

Given the increasing pressure to improve the efficiency of container terminals, a lot of research efforts have been devoted to optimizing container terminal operations. Most papers deal with either the berth allocation problem (BAP) or the (quay) crane assignment problem (CAP). In the literature on the BAP, handling times are often simplified to be berth dependent or proportional to vessel size, so the CAP can be ignored when scheduling vessels. This is unsatisfactory for real-life applications because the handling time primarily depends on the number of containers to be handled and the number of cranes deployed. Only a limited number of papers deals with the combination of berth allocation and crane assignment. In these papers however, authors often have resorted to algorithmic simplifications that limit the practical use of the models. This paper presents a MILP model for the integrated BAP–CAP taking into account vessel priorities, preferred berthing locations and handling time considerations. The model is used in a hybrid heuristic solution procedure that is validated on real-life data illustrating the potential to support operational and tactical decision-making.     

Investigation of Biosynthetic Pathways to Hydroxycoumarins During Post‐Harvest Physiological Deterioration in Cassava Roots by Using Stable Isotope Labelling

Cassava (Manihot esculenta Crantz) is an important starch‐rich crop, but the storage roots only have a short shelf‐life due to post‐harvest physiological deterioration (PPD), which includes the over‐production and polymerisation of hydroxycoumarins. Key aspects of coumarin secondary‐metabolite biosynthesis remain unresolved. Here we exploit the accumulation of hydroxycoumarins to test alternative pathways for their biosynthesis. Using isotopically labelled intermediates (p‐coumarate‐2‐¹³C, caffeate‐2‐¹³C, ferulate‐2‐¹³C, umbelliferone‐2‐¹⁸O and esculetin‐2‐¹⁸O), we show that the major biosynthetic pathway to scopoletin and its glucoside, scopolin, in cassava roots during PPD is through p‐coumaric, caffeic and then ferulic acids. An alternate pathway through 2′,4′‐dihydroxycinnamate and umbelliferone leads to esculetin and esculin. We have used C¹⁸O₂‐carboxylate‐labelled cinnamic and ferulic acids, and feeding experiments under an atmosphere of ¹⁸O₂, to investigate the o‐hydroxylation and cyclisation steps. We demonstrate that the major pathway is through o‐hydroxylation and not via a proposed spirolactone‐dienone intermediate.     

Developing regional calibration coefficients for estimation of hourly global solar radiation in Ireland

This study proposed regional coefficients for estimating hourly global solar radiation through the adaptation of some empirical models that relate radiation to climatological and geographical variables. A total of 10 models were adapted over 7 stations in Ireland. The performance of the models was evaluated using some selected error indicators including the global performance index which combines all other error indices. The results indicated that the sunshine based regional calibration coefficients generated through a polynomial approach was most superior over other models with the lowest RMSE (0.2–0.3?MJm^?2?hr^?1), MAE (0.1–0.2?MJm^?2?hr^?1) and Pbias (0–7.0%) and highest R² and KGE (>0.85). The study found no local effect such as instrumental siting, observational uncertainty and climate on the variations of these coefficients. This outcome will therefore facilitate the design of various local and/or regional solar energy applications at microscale in a temperate region.     

Tuning Hydrogel Mechanics Using the Hofmeister Effect

The mechanical properties of hydrogels are commonly modified by changing the concentration of the molecular components. This approach, however, does not only change hydrogel mechanics, but also the microstructure, which in turn alters the macroscopic properties of the gel. Here, the Hofmeister effect is used to change the thermoresponsiveness of polyisocyanide hydrogels. In contrast to previous Hofmeister studies, the effect is used to change the phase transition temperatures and to tailor the mechanics of the thermoresponsive (semiflexible) polymer gels. It is demonstrated that the gel stiffness can be manipulated over more than two orders of magnitude by the addition of salts. Surprisingly, the microstructure of the gels does not change upon salt addition, demonstrating that the Hofmeister effect provides an excellent route to change the mechanical properties without distorting other influential parameters of the gel.     

Metabolomics for measuring phytochemicals, and assessing human and animal responses to phytochemicals, in food science

Metabolomics, comprehensive metabolite analysis, is finding increasing application as a tool to measure and enable the manipulation of the phytochemical content of foods, to identify the measures of dietary intake, and to understand human and animal responses to phytochemicals in the diet. Recent applications of metabolomics directed toward understanding the role of phytochemicals in food and nutrition are reviewed.