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Energy Values (energy + value)
Kinds of Energy Values Selected AbstractsDiscontinuous deformation in an elastic material.POLYMER ENGINEERING & SCIENCE, Issue 10 2007Part 1. The concept of energy or work dissipation from a perfectly elastic material, due to a discontinuous deformation mechanism, is developed in this study. Dissipation occurs even from a perfectly elastic material, preferably an elastomer, when subjected to a discontinuous "jump" stretch or "jump" contraction. Stretching an elastomeric member through free extension requires a large amount of work. Such a sudden jump stretch of an elastic material is difficult to accomplish and is equivalent to thermodynamic free compression of a gas. The amount of work required can greatly exceed the strain energy stored in the material if the extension were applied without the jump or "shock" process. Interestingly, only part of the stored energy is recovered on unloading the elastomer the same way (through contraction). Excess work lost in contraction dissipates as heat but is not due to the common viscoelastic/plastic losses associated with internal friction in solids. Dissipation is possible even from a perfectly elastic material. Energy values associated in this jump deformation process are independent of the stress,strain curve path, and depend only on initial and final states for the material. Heat dissipation from an elastic rubber belt is examined and some applications extended from the developed principle are enunciated. POLYM. ENG. SCI., 47:1511,1520, 2007. © 2007 Society of Plastics Engineers [source] Short-term scheduling of a wind generation and hydrogen storage in the electricity marketEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 5 2010G. Tina Abstract Intermittent renewable energy sources (RES) are promising to be the future of electricity generation. In particular wind generation, owing to its stochastic behaviour, has to be carefully managed. Its lack of sufficient predictability decreases the energy value in the current framework of electrical markets, therefore, beyond a certain threshold; this kind of generation into the electrical system represents a problem for the transmission system operator (TSO) during its despatching service. The coupling of wind energy conversion system (WECS) with a storage medium (i.e. hydrogen) could improve the programmability of such generation plants in electrical markets. In this paper, an economical optimization tool has been developed in order to find the short-term scheduling so as to maximize the economic revenues in the day-ahead electricity market of a storage plant coupled with a wind farm. This tool needs as input the forecasts of both wind generation power and market prices, obtained with the adoption of pre-processing input data algorithm based on different methods that involve both statistical and probabilistic approaches. Copyright © 2009 John Wiley & Sons, Ltd. [source] Incorporating Penalty Function to Reduce Spill in Stochastic Dynamic Programming Based Reservoir Operation of Hydropower PlantsIEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 5 2010Deependra Kumar Jha Non-member Abstract This paper proposes a framework that includes a penalty function incorporated stochastic dynamic programming (SDP) model in order to derive the operation policy of the reservoir of a hydropower plant, with an aim to reduce the amount of spill during operation of the reservoir. SDP models with various inflow process assumptions (independent and Markov-I) are developed and executed in order to derive the reservoir operation policies for the case study of a storage type hydropower plant located in Japan. The policy thus determined consists of target storage levels (end-of-period storage levels) for each combination of the beginning-of-period storage levels and the inflow states of the current period. A penalty function is incorporated in the classical SDP model with objective function that maximizes annual energy generation through operation of the reservoir. Due to the inclusion of the penalty function, operation policy of the reservoir changes in a way that ensures reduced spill. Simulations are carried out to identify reservoir storage guide curves based on the derived operation policies. Reservoir storage guide curves for different values of the coefficient of penalty function , are plotted for a study horizon of 64 years, and the corresponding average annual spill values are compared. It is observed that, with increasing values of ,, the average annual spill decreases; however, the simulated average annual energy value is marginally reduced. The average annual energy generation can be checked vis-à-vis the average annual spill reduction, and the optimal value of , can be identified based on the cost functions associated with energy and spill. © 2010 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source] The effect of roasting on the nutritional and antioxidant properties of yellow and white maize varietiesINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 6 2010Ganiyu Oboh Summary Maize varieties (yellow and white) were roasted for 17 min; and allowed to cool, and later milled into powder. The nutritional evaluation (proximate composition, mineral and antinutrient content determination) and antioxidant properties investigation (reducing power, free radicals scavenging ability and Fe2+ chelating ability) of the product was subsequently carried out. The result of the study revealed that roasting caused a significant increase (P < 0.05) in the crude fat, carbohydrate, Ca, Na, Mg and Zn content. Conversely, a significant decrease (P < 0.05) was observed in crude protein, crude fibre, Fe and K content. A significant decrease in the phytate content was also observed. However, the reduced phytate content did not have sparing effect on Zn bioavailability. Roasting significantly (P < 0.05) reduced the extractible phenol and flavonoid content of the maize varieties. The antioxidant properties (1,1-diphenyl-2-picrylhydracyl free radical scavenging ability and Fe2+ chelating ability) followed the phenolic content pattern. However, roasting caused a significant increase in the ferric reducing antioxidant power of the maize varieties. Thus, roasting reduced the protein content of maize but also increased the energy value and antioxidant capacity as exemplified by high reducing power. [source] Convective hot air drying of blanched yam slicesINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 7 2008Olajide Philip Sobukola Summary In this study, a laboratory convective hot air dryer was used for the thin layer drying of blanched yam slices and experimental moisture ratio was compared with Newton, Logarithmic, Henderson and Pabis, modified Henderson and Pabis, approximation of diffusion, modified page 1, two-term exponential, Verma et al. and Wang and Singh models. Among all the models, the approximation of diffusion model was found to satisfactorily describe the kinetics of air-drying of blanched yam slices. The increase in air temperature significantly reduced the drying time with no constant rate period but drying occurs in falling rate period. The effective diffusivity values varied between 7.62 × 10,8 to 9.06 × 10,8 m2 s,1 and increased with increase in temperature. An Arrhenius relation with an activation energy value of 8.831 kJ mol,1 showed the effect of temperature on moisture diffusivity. [source] Comparison of some properties on the different types of pestil: a traditional product in TurkeyINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 8 2005Ozlem Cagindi Summary Pestil is a traditional dried fruit snack, which is consumed in Turkey. Wheat starch is mixed with different clarified fruit juices such as grape, mulberry, apricot or plum and cooked using traditional techniques. In this work the proximate chemical composition (moisture, ash, fat, crude protein and total carbohydrate), energy value and thickness of grape, apricot and mulberry pestils were investigated. The colour properties (Hunter L, a and b) were determined by a Minolta Chroma-Meter and the mineral content (Ca, Fe, K, Mg, Na, Cu, Zn, Mn) of each product was determined by inductively coupled plasma atomic emission spectrometry (ICP-AES). The carbohydrate value of pestil samples ranged between 73.7 and 82.4% and energy value was between 321.5 and 356.4 kcal 100 g,1. Mulberry pestil was a better source of energy than grape and apricot pestils. Apricot pestils were rich in calcium, sodium and zinc, and mulberry pestil samples were rich in magnesium. [source] The use of hybrid anaerobic solid,liquid (HASL) system for the treatment of lipid-containing food wasteJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 4 2005Olena Stabnikova Abstract The hybrid anaerobic solid,liquid (HASL) system was a modified two-phase anaerobic digester developed for bioconversion of food waste. The aim of this study was to estimate the feasibility of the HASL system for the treatment of food waste with a high content of lipids. The presence of lipids in food waste increased the energy value of nutrients but could inhibit growth of methanogens. The positive effect of lipids on the performance of anaerobic digestion dominated when the contents of lipids were in the range from 20 to 30% of total solids of food waste. Lipid contents of 40% diminished the production of volatile fatty acids in the acidogenic reactor as well as biogas production and the concentration of total bacteria and methanogens in the methanogenic reactor. Therefore, the HASL system can be used for the treatment of lipid-containing food wastes if the lipid content is below 40% of total solids. Copyright © 2005 Society of Chemical Industry [source] PROCESSING AND ACCEPTABILITY OF FRIED CASSAVA BALLS ("AKARA-AKPU") SUPPLEMENTED WITH MELON AND SOYBEAN FLOURSJOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 2 2007CHIEMELA ENYINNAYA CHINMA ABSTRACT The processing and acceptability of fried cassava balls ("Akara-akpu") supplemented with melon and soybean flours were studied. Cassava flour, defatted soybean flour and cassava mash were produced. Some functional and chemical properties of the flours were determined. Akara-akpu prepared from 100% cassava mash served as control; 100% cassava flour, 80% cassava flour + 20% defatted soybean and 70% cassava flour + 30% defatted melon flour were prepared. Akara-akpu balls were subjected to chemical and physical analyses. Akara-akpu prepared from composite flour blends had higher protein, fat, ash and energy value than Akara-akpu from 100% cassava mash. The cyanide content and degree of starch gelatinization of Akara-akpu prepared from 100% cassava mash (control) were higher than Akara-akpu prepared from cassava mash plus composite flour blends. There was a significant difference (P , 0.05) in weight and yield between Akara-akpu prepared from 100% cassava mash (control) and cassava mash plus composite flour blends. There was no significant difference (P , 0.05) in volume between Akara-akpu made from control sample and those cassava plus composite flour blends. [source] Docking study and free energy simulation of the complex between p53 DNA-binding domain and azurinJOURNAL OF MOLECULAR RECOGNITION, Issue 4 2007Valentina De Grandis Abstract Molecular interaction between p53 tumor suppressor and the copper protein azurin (AZ) has been demonstrated to enhance p53 stability and hence antitumoral function, opening new perspectives in cancer treatment. While some experimental work has provided evidence for AZ binding to p53, no crystal structure for the p53,AZ complex was solved thus far. In this work the association between AZ and the p53 DNA-binding domain (DBD) was investigated by computational methods. Using a combination of rigid-body protein docking, experimental mutagenesis information, and cluster analysis 10 main p53 DBD,AZ binding modes were generated. The resulting structures were further characterized by molecular dynamics (MD) simulations and free energy calculations. We found that the highest scored docking conformation for the p53 DBD,AZ complex also yielded the most favorable free energy value. This best three-dimensional model for the complex was validated by using a computational mutagenesis strategy. In this structure AZ binds to the flexible L1 and s7,s8 loops of the p53 DBD and stabilizes them through protein,protein tight packing interactions, resulting in high degree of both surface matching and electrostatic complementarity. Copyright © 2007 John Wiley & Sons, Ltd. [source] A review of the effectiveness of aspartame in helping with weight controlNUTRITION BULLETIN, Issue 2 2006A. De La Hunty Summary, Strategies to reverse the upward trend in obesity rates need to focus on both reducing energy intake and increasing energy expenditure. The provision of low- or reduced-energy-dense foods is one way of helping people to reduce their energy intake and so enable weight maintenance or weight loss to occur. The use of intense sweeteners as a substitute for sucrose potentially offers one way of helping people to reduce the energy density of their diet without any loss of palatability. This report reviews the evidence for the effect of aspartame on weight loss, weight maintenance and energy intakes in adults and addresses the question of how much energy is compensated for and whether the use of aspartame-sweetened foods and drinks is an effective way to lose weight. All studies which examined the effect of substituting sugar with either aspartame alone or aspartame in combination with other intense sweeteners on energy intake or bodyweight were identified. Studies which were not randomised controlled trials in healthy adults and which did not measure energy intakes for at least 24 h (for those with energy intakes as an outcome measure) were excluded from the analysis. A minimum of 24-h energy intake data was set as the cut-off to ensure that the full extent of any compensatory effects was seen. A total of 16 studies were included in the analysis. Of these 16 studies, 15 had energy intake as an outcome measure. The studies which used soft drinks as the vehicle for aspartame used between 500 and about 2000 ml which is equivalent to about two to six cans or bottles of soft drinks every day. A significant reduction in energy intakes was seen with aspartame compared with all types of control except when aspartame was compared with non-sucrose controls such as water. The most relevant comparisons are the parallel design studies which compare the effects of aspartame with sucrose. These had an overall effect size of 0.4 standardised difference (SD). This corresponds to a mean reduction of about 10% of energy intake. At an average energy intake of 9.3 MJ/day (average of adult men and women aged 19,50 years) this is a deficit of 0.93 MJ/day (222 kcal/day or 1560 kcal/week), which would be predicted (using an energy value for obese tissue of 7500 kcal/kg) to result in a weight loss of around 0.2 kg/week with a confidence interval 50% either side of this estimate. Information on the extent of compensation was available for 12 of the 15 studies. The weighted average of these figures was 32%. Compensation is likely to vary with a number of factors such as the size of the caloric deficit, the type of food or drink manipulated, and timescale. An estimate of the amount of compensation with soft drinks was calculated from the four studies which used soft drinks only as the vehicle. A weighted average of these figures was 15.5%. A significant reduction in weight was seen. The combined effect figure of 0.2 SD is a conservative figure as it excludes comparisons where the controls gained weight because of their high-sucrose diet and the long-term follow-up data in which the aspartame groups regained less weight than the control group. An effect of 0.2 SD corresponds to about a 3% reduction in bodyweight (2.3 kg for an adult weighing 75 kg). Given the weighted average study length was 12 weeks, this gives an estimated rate of weight loss of around 0.2 kg/week for a 75-kg adult. The meta-analyses demonstrate that using foods and drinks sweetened with aspartame instead of sucrose results in a significant reduction in both energy intakes and bodyweight. Meta-analyses both of energy intake and of weight loss produced an estimated rate of weight loss of about 0.2 kg/week. This close agreement between the figure calculated from reductions in energy intake and actual measures of weight loss gives confidence that this is a true effect. The two meta-analyses used different sets of studies with widely differing designs and controls. Although this makes comparisons between them difficult, it suggests that the final figure of around 0.2 kg/week is robust and is applicable to the variety of ways aspartame-containing foods are used by consumers. This review has shown that using foods and drinks sweetened with aspartame instead of those sweetened with sucrose is an effective way to maintain and lose weight without reducing the palatability of the diet. The decrease in energy intakes and the rate of weight loss that can reasonably be achieved is low but meaningful and, on a population basis, more than sufficient to counteract the current average rate of weight gain of around 0.007 kg/week. On an individual basis, it provides a useful adjunct to other weight loss regimes. Some compensation for the substituted energy does occur but this is only about one-third of the energy replaced and is probably less when using soft drinks sweetened with aspartame. Nevertheless, these compensation values are derived from short-term studies. More data are needed over the longer term to determine whether a tolerance to the effects is acquired. To achieve the average rate of weight loss seen in these studies of 0.2 kg/week will require around a 220-kcal (0.93 MJ) deficit per day based on an energy value for obese tissue of 7500 kcal/kg. Assuming the higher rate of compensation (32%), this would require the substitution of around 330 kcal/day (1.4 MJ/day) from sucrose with aspartame (which is equivalent to around 88 g of sucrose). Using the lower estimated rate of compensation for soft drinks alone (15.5%) would require the substitution of about 260 kcal/day (1.1 MJ/day) from sucrose with aspartame. This is equivalent to 70 g of sucrose or about two cans of soft drinks every day. [source] Imperfection Sensitivity and Limit Loads of Spherical Shells under Radial PressurePROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2005Jens Pontow The evaluation of the imperfection sensitivity of shell structures and the estimation of their limit loads are widely discussed phenomena. The perturbation energy concept according to Dinkler et al. [1], [2] enables to assess the imperfection sensitivity of shell structures by means of an energy value, the perturbation energy. A buckling criterion may be developed from the comparison between the perturbation energy and experimental data. This paper focuses on the imperfection sensitivity and limit loads of spherical shells of revolution under radial pressure. The investigations include the influence of the meridional angle and different types of boundary conditions. By comparing the numerical results with the German design rule DIN 18800, critical values for the perturbation energy are derived to predict the limit loads. These critical values for the perturbation energy allow to judge whether the German design rule DIN18800 predicts the limit loads of spherical shells under external pressure with varying meridional angles and different boundary conditions with the same reliability in respect of the perturbation energy. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Chemical characterization, energy values, protein and carbohydrate fractions, degradation kinetics of frost damaged wheat (with severely overall weight loss) in ruminantsANIMAL SCIENCE JOURNAL, Issue 2 2009Peiqiang YU ABSTRACT In Canada, frost damage can result in millions of tonnes of wheat that is not suitable for human consumption (such wheat is referred to as ,frozen') each year. There is a need to systematically evaluate the nutritive value of frozen wheat for ruminants. So far, little research has been conducted to determine the magnitude of the differences in nutritive value between frozen and normal wheat. The objectives of this study were to compare frozen wheat and normal wheat (AC Barrie) in terms of (i) chemical characteristics; (ii) protein and carbohydrate fractions; (iii) energy value; and (iv) rumen degradation kinetics. The results showed that the overall yield losses of the frozen wheat were around 24%. The frozen wheat was significantly lower (P < 0.05) in starch (47 vs. 62%DM), non-structural carbohydrates (60 vs. 70%DM), and non-protein N (63 vs. 93%SCP); and higher (P < 0.05) in crude fat (3 vs. 2%DM), acid (6 vs. 2%DM), neutral detergent fiber (22 vs. 10%DM), lignin (2 vs. 1%DM), acid (3 vs. 1%CP) and neutral detergent insoluble CP (19 vs. 14%CP). The frozen wheat was also lower in (P < 0.05) energy (TDN, DE3X, ME3X, NEL3X, DE4X, ME4X, NEL4X for dairy; ME, NEm, and NEg beef cattle). After partitioning of protein and carbohydrate (CHO) subfractions, the results showed that the frozen wheat was lower (P < 0.05) in the intermediately degradable CP (PB2: 47 vs. 59%CP); and higher in rapidly degradable CP (PB1: 12 vs. 2%CP) and unavailable CP (PC: 3 vs. 1%CP). The frozen wheat was also lower (P < 0.05) in intermediately degradable CHO (CB1: 60 vs. 77%CHO); and higher (P < 0.05) in slowly degradable CHO (CB2: 20 vs. 8%CHO) and unavailable CHO (CC: 5 vs. 2%CHO). The in situ results showed that the frozen wheat had different patterns in rumen degradation kinetics of protein and starch. The extent of the changes varied according to the specific nutrient examined. In conclusion, the frozen wheat differed in chemical characteristics, TDN and energy values, protein and carbohydrate fractions and in situ degradation behavior from normal wheat. The chemical and nutritional characterization of wheat was highly associated with climate condition (frost damage). The frost damage to the wheat reduced nutrient content and availability and thus reduced nutrient supply to ruminants. [source] Comparison of Perfusion Quality in Hollow-Fiber Membrane Oxygenators for Neonatal Extracorporeal Life SupportARTIFICIAL ORGANS, Issue 4 2010Jonathan Talor Abstract Perfusion quality is an important issue in extracorporeal life support (ECLS); without adequate perfusion of the brain and other vital organs, multiorgan dysfunction and other deficits can result. The authors tested three different pediatric oxygenators (Medos Hilite 800 LT, Medtronic Minimax Plus, and Capiox Baby RX) to determine which gives the highest quality of perfusion at flow rates of 400, 600, and 800 mL/min using human blood (36°C, 40% hematocrit) under both nonpulsatile and pulsatile flow conditions. Clinically identical equipment and a pseudo-patient were used to mimic operating conditions during neonatal ECLS. Traditionally, the postoxygenator surplus hemodynamic energy value (SHEpost, extra energy obtained through pulsatile flow) is the one relied upon to give a qualitative determination of the amount of perfusion in the patient; the authors also examined SHE retention through the membrane, as well as the contribution of SHEpost to the postoxygenator total hemodynamic energy (THEpost). At each experimental condition, pulsatile flow outperformed nonpulsatile flow for all factors contributing to perfusion quality: the SHEpost values for pulsatile flow were 4.6,7.6 times greater than for nonpulsatile flow, while the THEpost remained nearly constant for pulsatile versus nonpulsatile flow. For both pulsatile and nonpulsatile flow, the Capiox Baby RX oxygenator was found to deliver the highest quality of perfusion, while the Minimax Plus oxygenator delivered the least perfusion. It is the authors' recommendation that the Baby RX oxygenator running under pulsatile flow conditions be used for pediatric ECLS, but further studies need to be done in order to establish its effectiveness beyond the FDA-approved time span. [source] Enthalpy relaxation of bovine serum albumin and implications for its storage in the glassy state,BIOPOLYMERS, Issue 2 2005Asgar Farahnaky Abstract Two endothermic peaks could be observed for five commercial samples of bovine serum albumin (BSA). The smaller peak observed by differential scanning calorimetry (DSC) corresponded to enthalpy relaxation. This peak was followed on storage of BSA, in its glassy state, after it had been heated above its denaturation temperature. Enthalpy and peak temperature increased with duration of storage. On storage for one week at 60°C, a sample at 8.3% moisture showed a peak at 100°C with an energy value of approximately 2 J per g protein. BSA samples were heated within the DSC sufficiently to eliminate the lower enthalpy peak but without altering the denaturation enthotherm. The amount of physical aging shown by these BSA samples was similar to that of the heat-denatured samples. It was concluded that the heating endotherms of dry BSA reflect both the storage and thermal history of the sample. Possible implications of the enthalpy relaxation of BSA on the behavior of this important protein are considered. © 2005 Wiley Periodicals, Inc. Biopolymers 78: 69,77, 2005 [source] Thermal, phase transition and spectral studies in erythromycin pseudopolymorphs: dihydrate and acetone solvateCRYSTAL RESEARCH AND TECHNOLOGY, Issue 12 2006Zhanzhong Wang Abstract The thermal, phase transition and spectral studies of erythromycin A dihydrate and acetone solvate were performed by Differential Scanning calorimetry (DSC), Thermo Gravimetry (TG-DTA), X-Ray Powder Diffraction (XRPD) and Fourier Transform Infra-Red (FTIR) spectrum. The non-thermal kinetic analysis of erythromycin A dihydrate was carried out by DSC at different heating rates in dynamic nitrogen atmosphere. The result showed that heating rate has substantial influence on the thermal behavior of erythromycin dihydrate. The Arrhenius parameters were estimated according to the Kissinger method. Corresponding to dehydration of dihydrate, melting of dehydrated dihydrate, phase transition from dehydrated dihydrate to anhydrate, and melting of anhydrate, the calculated activation energy were 39.60, 269.85, 261.23, and 582.16 kJmol,1, the pre-exponential factors were 3.46 × 103, 8.06 × 1032, 9.23 × 1030, and 7.29 × 1063 s,1, respectively. Ozawa method was used to compare activation energy values calculated by Kissinger method. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Two variable semi-empirical and artificial neural-network-based modeling of peptide mobilities in CZE: The effect of temperature and organic modifier concentrationELECTROPHORESIS, Issue 5 2009Stefan Mittermayr Abstract This work was focused on investigating the effects of two separation influencing parameters in CZE, namely temperature and organic additive concentration upon the electrophoretic migration properties of model tripeptides. Two variable semi-empirical (TVSE) models and back-propagation artificial neural networks (ANN) were applied to predict the electrophoretic mobilities of the tripeptides with non-polar, polar, positively charged, negatively charged and aromatic R group characteristics. Previously published work on the subject did not account for the effect of temperature and buffer organic modifier concentration on peptide mobility, in spite of the fact that both were considered to be influential factors in peptide analysis. In this work, a substantial data set was generated consisting of actual electrophoretic mobilities of the model tripeptides in 30,mM phosphate buffer at pH 7.5, at 20, 25, 30, 35 and 40°C and at four different organic additive containing running buffers (0, 5, 10 and 15% MeOH) applying two electric field strengths (12 and 16,kV) to assess our mobility predicting models. Based on the Arrhenius plots of natural logarithm of mobility versus reciprocal absolute temperature of the various experimental setups, the corresponding activation energy values were derived and evaluated. Calculated mobilities by TVSE and back-propagation ANN models were compared with each other and to the experimental data, respectively. Neural network approaches were able to model the complex impact of both temperature and organic additive concentrations and resulted in considerably higher predictive power over the TVSE models, justifying that the effect of these two factors should not be neglected. [source] Cone calorimeter analysis of UL-94 V-rated plastics,FIRE AND MATERIALS, Issue 4 2007Alexander B. Morgan Abstract Cone calorimeter analysis was conducted on 18 thermoplastics with different UL-94 vertical burn test (V) ratings. Ratings varied from V-0 to no rating (NR), and the types of thermoplastics included were polycarbonate (PC), acrylonitrile,butadiene,styrene (ABS), PC/ABS blends, high-impact polystyrene (HIPS), polypropylene (PP), and poly(vinyl chloride) (PVC). Our analysis of the cone calorimeter data found that there were correlations between UL-94 V rating and some cone calorimeter measurements (peak heat release rate (HRR) average and HRR at 60 s) and no relationship for other measurements (time to ignition and total heat release). However, no precise correlation was found due to significant differences in flame retardant mechanism and polymer fuel energy values. In this paper, we seek to explain further why a broad quantitative relationship between UL-94 V and cone calorimeter remains elusive, and also to show how the cone calorimeter can be used to understand why a material passes or fails a particular UL-94 V rating. Copyright © 2006 John Wiley & Sons, Ltd. [source] Comparative theoretical study of small Rhn nanoparticles (2 , n , 8) using DFT methodsINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 6 2010V. Bertin Abstract This work is aimed at identifying some key characteristics (energy, geometry, and spin) concerning Rhn particles (2 = n , 8) to perform further studies on adsorption and coadsorption sites of pollutants (CO and NO). The DFT methods of the Gaussian 03 program with the LANL2DZ basis set and the LANL2 potential are used. With the purpose to obtain a better nanoparticles definition, five different functionals were tested: B3LYP, O3LYP, BPW91, BP86, and HCTH; and the corresponding results are used to determine which of them best describes distances, spin, and gives acceptable highest vibration frequency and binding energy values, by comparing these results with values measured or calculated by many other authors. For the structure optimization process of the particles, the initial geometric shape was taken mainly from the literature, using the Rh,Rh distance: 2.67 Å, known for the bulk; and doing a complete optimization. We also considered flat nanoparticles structures, which most of them display three-dimensional structures after the optimization process. The few flat shapes are mainly higher in energy than those of three-dimensional structure. For some Rhn particles for different n values, the spin of the ground state present degeneration. In some cases, the optimization process changes the initial geometry, but in most cases, there are only minor changes in bonds and geometry. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 [source] Theoretical study of the reaction of alkynes with furan catalyzed by AuCl3 and AuClINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 2 2007Hassan Rabaâ Abstract A general scheme for the endo- and exo-cyclization of furan reactivity with [L -AuIII, IClx] with (x = 3, 1 and L -acetylene and vinylidene) complexes is investigated using density functional theory (DFT) code. Two conceivable mechanisms via a [4 + 2] Diels,Alder process or carbene complex are analyzed. According to the activation energy values of the gold (III and I) catalyst, the first mechanism, which implies the Diels,Alder reaction of AuIII, is thermodynamically favored and gives more evidence of the intramolecular addition of the furan with the alkynes. The second mechanism, presumably assisted by the spontaneous formation of the exo-vinylidene complexes and intermediates of gold (III, I) by forming the carbene complex, is kinetically favored. Additionally, we compare our results with other structures with intramolecular additions that exhibit the quasi-similarity of gold analogue structures. Differences in activation energies are observed, according to the functional used. Finally, we probe the solvent effects, which decrease the energy barrier in the path. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 [source] Quantum chemical studies on molecular structural conformations and hydrated forms of salicylamide and O-hydroxybenzoyl cyanideINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 3 2005K. Anandan Abstract Ab initio and density functional theory (DFT) methods have been employed to study the molecular structural conformations and hydrated forms of both salicylamide (SAM) and O-hydroxybenzoyl cyanide (OHBC). Molecular geometries and energetics have been obtained in the gaseous phase by employing the Møller,Plesset type 2 MP2/6-311G(2d,2p) and B3LYP/6-311G(2d,2p) levels of theory. The presence of an electron-releasing group (SAM) leads to an increase in the energy of the molecular system, while the presence of an electron-withdrawing group (OHBC) drastically decreases the energy. Chemical reactivity parameters (, and ,) have been calculated using the energy values of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) obtained at the Hartree,Fock (HF)/6-311G(2d,2p) level of theory for all the conformers and the principle of maximum hardness (MHP) has been tested. The condensed Fukui functions have been calculated using the atomic charges obtained through the natural bond orbital (NBO) analysis scheme for all the optimized structures at the B3LYP/6-311G(2d,2p) level of theory, and the most reactive sites of the molecules have been identified. Nuclear magnetic resonance (NMR) studies have been carried out at the B3LYP/6-311G(2d,2p) level of theory for all the conformers in the gaseous phase on the basis of the method of Cheeseman and coworkers. The calculated chemical shift values have been used to discuss the delocalization activity of the electron clouds. The dimeric structures of the most stable conformers of both SAM and OHBC in the gaseous phase have been optimized at the B3LYP/6-311G(2d,2p) level of theory, and the interaction energies have been calculated. The most stable conformers of both compounds bear an intramolecular hydrogen bond, which gives rise to the formation of a pseudo-aromatic ring. These conformers have been allowed to interact with the water molecule. Special emphasis has been given to analysis of the intermolecular hydrogen bonds of the hydrated conformers. Self-consistent reaction field (SCRF) theory has been employed to optimize all the conformers in the aqueous phase (, = 78.39) at the B3LYP/6-311G(2d,2p) level of theory, and the solvent effect has been studied. Vibrational frequency analysis has been performed for all the optimized structures at MP2/6-311G(2d,2p) level of theory, and the stationary points corresponding to local minima without imaginary frequencies have been obtained for all the molecular structures. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005 [source] Impact of citrate therapy on the circadian rhythm of urinary magnesium ammonium phosphate saturation in normal individualsINTERNATIONAL JOURNAL OF UROLOGY, Issue 8 2000Yoshihide Ogawa Abstract Background: Alkaline citrate has been used widely in the prevention of stone formation. However, the risk of struvite stone during the alkalinizing therapy has not been adequately studied in terms of magnesium ammonium phosphate saturation. Methods: The circadian rhythm of the urinary saturation of magnesium ammonium phosphate was estimated by using the differential Gibbs' free energy values of magnesium ammonium phosphate before and during 5 days of treatment with sodium,potassium citrate (1 g t.i.d., 1 g q.i.d. or 3 g t.i.d.) in five healthy male volunteers. Results: The magnesium ammonium phosphate saturation varied during the day, peaking far below the solubility product between 08.00 and 10.30 h and between 13.00 and 18.00 h. The mean peak levels were increased by each treatment regimen in comparison with the control day. The mean increase on day 1 was significant between 10.30 and 23.00 h with the 3 g t.i.d. regimen, but the mean saturation still remained below the solubility product throughout the day. Conclusions: The urinary magnesium ammonium phosphate saturation appeared hard to exceed the solubility product with a high dose of alkaline citrate. [source] Effect of the Environmental Factors on the Caloric Content of Benthic and Phytophilous Invertebrates in Neotropical Reservoirs in the Paraná State, BrazilINTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 3 2010Yara Moretto Bagatini Abstract The complexity of the relations between the organisms and the environment are reflected through the energy content. So we tested the hypothesis on body energy content variation in invertebrates and its relation with some environmental factors (season, habitat type, trophic status and trophic guild). We expected higher energy values for phytophilous fauna, rainy season, in reservoirs with higher trophic levels and for herbivorous invertebrates. The results showed the influence of seasonality and trophic status of the reservoir on the energy content of invertebrates, which was higher in the rainy season and in the mesotrophic reservoirs, due to the input of allochthonous material during this season, confirming our initial prediction. A higher caloric content was recorded for carnivorous and detritivorous invertebrates. The differences between the trophic guilds were primarily related to the opportunistic feeding behavior, which may be considered as one of the main factors controlling the energy flow of benthic and phytophilous invertebrates. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Investigation of the postcure reaction and surface energy of epoxy resins using time-of-flight secondary ion mass spectrometry and contact-angle measurementsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2009Firas Awaja Abstract Time-of-flight secondary ion mass spectrometry (ToF-SIMS) was used to investigate correlations between the molecular changes and postcuring reaction on the surface of a diglycidyl ether of bisphenol A and diglycidyl ether of bisphenol F based epoxy resin cured with two different amine-based hardeners. The aim of this work was to present a proof of concept that ToF-SIMS has the ability to provide information regarding the reaction steps, path, and mechanism for organic reactions in general and for epoxy resin curing and postcuring reactions in particular. Contact-angle measurements were taken for the cured and postcured epoxy resins to correlate changes in the surface energy with the molecular structure of the surface. Principal components analysis (PCA) of the ToF-SIMS positive spectra explained the variance in the molecular information, which was related to the resin curing and postcuring reactions with different hardeners and to the surface energy values. The first principal component captured information related to the chemical phenomena of the curing reaction path, branching, and network density based on changes in the relative ion density of the aliphatic hydrocarbon and the C7H7O+ positive ions. The second principal component captured information related to the difference in the surface energy, which was correlated to the difference in the relative intensity of the CxHyNz+ ions of the samples. PCA of the negative spectra provided insight into the extent of consumption of the hardener molecules in the curing and postcuring reactions of both systems based on the relative ion intensity of the nitrogen-containing negative ions and showed molecular correlations with the sample surface energy. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Theoretical study of the interaction between sodium ion and a cyclopeptidic tubular structureJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 13 2007Francesco Ferrante Abstract DFT calculations have been carried out to describe the pathway of a sodium ion along the stacking direction of a tubular structure set up by five cyclopeptidic units, which can be considered a suitable model of a hollow tubular structure of indefinite length. A lattice of points inside the tubular structure is defined and the DFT interaction energy values with a sodium ion are obtained. The data allow predicting a zigzag path of the ion inside the hosting structure. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007 [source] A CSOV study of the difference between HF and DFT intermolecular interaction energy values: The importance of the charge transfer contributionJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 10 2005Jean-Philip Piquemal Abstract Intermolecular interaction energy decompositions using the Constrained Space Orbital Variation (CSOV) method are carried out at the Hartree,Fock level on the one hand and using DFT with usual GGA functionals on the other for a number of model complexes to analyze the role of electron correlation in the intermolecular stabilization energy. In addition to the overall stabilization, the results provide information on the variation, with respect to the computational level, of the different contributions to the interaction energy. The complexes studied are the water linear dimer, the N -methylformamide dimer, the nucleic acid base pairs, the benzene,methane and benzene-N2 van der Waals complexes, [Cu+ -(ImH)3]2, where "ImH" stands for the Imidazole ligand, and ImH-Zn++. The variation of the frozen core energy (the sum of the intermolecular electrostatic energy and the Pauli repulsion energy) calculated from the unperturbed orbitals of the interacting entities indicates that the intramolecular correlation contributions can be stabilizing as well as destabilizing, and that general trends can be derived from the results obtained using usual density functionals. The most important difference between the values obtained from HF and DFT computations concerns the charge transfer contribution, which, in most cases, undergoes the largest increase. The physical meaning of these results is discussed. The present work gives reference calculations that might be used to parametrize new correlated molecular mechanics potentials. © 2005 Wiley Periodicals, Inc. J Comput Chem 26: 1052,1062, 2005 [source] VISCOELASTICITY OF A SIMULATED POLYMER AND COMPARISON WITH CHICKPEA FLOUR DOUGHSJOURNAL OF FOOD PROCESS ENGINEERING, Issue 3 2006NIDHI YADAV ABSTRACT An integrated approach consisting of compression and stress relaxation is performed with a simulated model system of poly dimethyl siloxane (PDMS), a viscoelastic polymer material when the compressive strain, height of sample and crosshead speed were varied. The parameters derived are the forces at the end of compression and relaxation, energy for compression and the extent of elasticity of the sample based on the ratios of forces as well as the proposed energy values. The results were verified with food doughs undergoing large deformations that show a nonlinear behavior. The proposed extent of elasticity based on the ratios of energy stored and compression can be used as an index for the characterization of viscoelasticity. A nonlinear three-parameter model had also been proposed to predict the stress decay characteristics as a function of time, which was found suitable for the PDMS system, and was better than the two-parameter Peleg model as judged by lower variance values (0.0006,0.018 and 0.002,0.048, respectively). Further, an actual system of food doughs in the form of chickpea (Cicer arietinum L.) flour dough was used to verify the proposed model and viscoelastic index at different moisture contents (27,39%) subjected to compressive strains of 25,75%. The nonlinear relaxation characteristics of the food dough are sensitive to moisture content as well as to strain level. [source] Internal energy distribution of peptides in electrospray ionization : ESI and collision-induced dissociation spectra calculationJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 4 2008Alireza Pak Abstract The internal energy of ions and the timescale play fundamental roles in mass spectrometry. The main objective of this study is to estimate and compare the internal energy distributions of different ions (different nature, degree of freedom ,DOF' and fragmentations) produced in an electrospray source (ESI) of a triple-quadrupole instrument (Quattro I Micromass). These measurements were performed using both the Survival Yield method (as proposed by De Pauw) and the MassKinetics software (kinetic model introduced by Vékey). The internal energy calibration is the preliminary step for ESI and collision-induced dissociation (CID) spectra calculation. meta -Methyl-benzylpyridinium ion and four protonated peptides (YGGFL, LDIFSDF, LDIFSDFR and RLDIFSDF) were produced using an electrospray source. These ions were used as thermometer probe compounds. Cone voltages (Vc) were linearly correlated with the mean internal energy values ( Liquid Rb micrometric droplets confined in paraffin wax: an X-ray absorption spectroscopy studyJOURNAL OF SYNCHROTRON RADIATION, Issue 2 2001Simone De Panfilis We have performed high-quality X-ray absorption measurements on crystalline (c -Rb) and liquid (l -Rb) Rubidium in the range from 15 K to 320 K. Performing a consistent analysis that takes into account the contribution of the medium range structure, we observe that the l -Rb spectrum is compatible with pair correlation function g(r) previously determined by neutron diffraction experiments. Due to the micrometric size of the liquid droplets we were able to observe a slight undercooling down to 290 K. We were also able to study the details of the very strong multielectron excitations channels in terms of resonances, edges and shake-off features at proper theoretical energy values. [source] RHEOLOGICAL BEHAVIOR OF POMEGRANATE (PUNICA GRANATUM L.) JUICE AND CONCENTRATEJOURNAL OF TEXTURE STUDIES, Issue 1 2005N ALTAN ABSTRACT The rheological behavior of pomegranate juice (Punica granatum L.), prepared from fresh pomegranates, was studied as a function of solids concentration in the range 17.5,75°Brix at 10,55C, using a controlled stress rheometer. Concentration methods did not influence flow behavior. There were no significant differences (P > 0.05) between viscosity and activation energy values for the pomegranate juices concentrated by different methods. The juices exhibited Newtonian behavior regardless of the concentration method. The effect of temperature was described by an Arrhenius-type equation with an activation energy in the range 5.34,32.2 kJ/mol depending on concentration. An exponential model described better the effect of the soluble solids on the viscosity and Eavalues. A simple equation was proposed for describing the combined effect of temperature and soluble solids content on the juice viscosity. [source] Superplastic Behavior of Fine-Grained ,-Silicon Nitride Material under CompressionJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2000Guo-Dong Zhan The deformation behavior of a hot-pressed, fine-grained ,-Si3N4 ceramic was investigated in the temperature range 1450°,1650°C, under compression, and the results for strain rate and temperature dependence of the flow stress are presented here. The present results show that the material is capable of high rates of deformation (,10,4,10,3 s,1) within a wide range of deformation temperatures and under a pressure of 5,100 MPa; no strain hardening occurs in the material, even at slow deformation rates, because of its stable microstructure; Newtonian flow occurs, with a stress exponent of approximately unity; and the material has activation energy values for flow in the range 344,410 kJ·mol,1. Grain-boundary sliding and grain rotation, accommodated by viscous flow, might be the mechanisms of superplasticity for the present material. 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