环木菠萝烯醇阿魏酸酯分子结构性质的密度泛函理论研究

该文基于密度泛函理论对环木菠萝烯醇阿魏酸酯分子结构、反应活性位点(分子表面静电势、原子电荷、前线分子轨道、概念密度泛函活性指数)、分子内弱作用力、芳香性以及红外光谱进行分析.结果表明,环木菠萝烯醇阿魏酸酯酚羟基氢原子(H99)附近具有分子表面静电势极大点(53.580 kcal/mol),且H99带有较高正电荷(0.3...     

Characterization and density functional theory study of the antioxidant activity of quercetin and its sugar-containing analogues

Inhibition of free radicals using quercetin, hyperin and rutin is examined to determine their antioxidant effects and the structure–activity relationships of flavonoids. Two species of the free radicals are used, including hydroxyl radical (·OH) and superoxide anion radical (O₂ ^?·). Density functional theory calculations under the level of B3LYP/6-311G (d) have been utilized to explore the structure, molecular properties and antioxidant abilities of the three flavonoids. Bond dissociation enthalpy (BDE) and frontier molecular orbital energy gap are investigated. They are compared with the experiment results assayed by the spectrophotometric. All of the flavonoids show a high activity on inhibiting ·OH and O₂ ^?· radicals. Scavenging activity determined by half maximal inhibitory concentration (IC₅₀) values of the three flavonoids decreases in the order: quercetin > hyperin > rutin. The calculations show that quercetin owns the lowest BDE values, which agree well with the experimental results of antioxidant activity determined by IC₅₀ values.     

UV/Visible spectra of natural polyphenols: A time-dependent density functional theory study

In addition to their numerous biological activities, natural and hemisynthetic polyphenols contribute to the large variety of colours (from red to violet) in nature (e.g., fruit, vegetables, leaves and petals). In order to understand the colour variation attributed to the multitude of chemical structures of this wide class of compounds, time-dependent density functional quantum-chemical calculations at the B3P86/6-311+G(d,p) level of theory appears as a relevant and efficient tool. The UV/Vis properties of 33 polyphenols were systematically investigated, including mainly flavonoids, isoflavonoids and flavonolignans. On the basis of molecular orbital analysis we established the structure-property relationship, inter alia showing the role of π orbital (de-)localisation, mesomeric (+M) effects of hydroxyl groups and structural modification of the molecular backbone. The results might help in the future, for example, for the prediction of novel hemisynthetic compounds.     

Growth rate as a predictor of density and mechanical quality of sawn timber from fast growing species

Mechanical quality of structural timber (50×150×3200 mm) is assessed by means of growth rates in different softwoods (Pinus radiata, P. pinaster, P. sylvestris), most of them fast grown species, and hardwoods (Populus sp. andEucalyptus globulus) grown in Spain. The utility of using average density instead of average growth rate is also assessed. Growth rate did not appreciably influence the density and bending properties of timber, and so its utility as predictor of the mechanical quality of timber is very low.     

Sociometric status as a predictor of onset and progression in adolescent cigarette smoking.

The relation between sociometric status and adolescent cigarette smoking was examined in a 1-year longitudinal study. Students in 6th, 7th, and 8th grades (N=1,630) were asked to nominate peers in their grade at school whom they liked and peers whom they disliked. These nominations were used to classify participants into one of five sociometric categories (popular, rejected, controversial, neglected, and average). Participants also reported their lifetime cigarette use at two measurements in consecutive school years. The results indicated that rejected and controversial adolescents were more likely than average adolescents to (a) report lifetime smoking at time 1 (T1) and (b) report onset of smoking at time 2 (T2). However, among adolescents who had already tried cigarettes at T1, rejected and controversial youth were not at increased risk for progression in total lifetime cigarette smoking (i.e., higher levels of total lifetime cigarette use at T2). Thus the results confirm that controversial youth are similar to rejected youth in their risk for onset of cigarette smoking during adolescence.     

一类具有Beddington-DeAngelis功能反应捕食系统收获模型的稳定性

研究一类具有双线性密度制约及Beddington-DeAngelis功能反应的捕食系统收获模型.运用微分方程定性稳定性理论讨论系统正平衡点的性态,得到其局部渐近稳定及全局渐近稳定的充分条件,利用Pontryagin最大值原理得到系统的最优收获策略.     

Birth weight as a predictor of calving ease and perinatal mortality in Holstein cattle

The objective of this research was to determine the effect of birth weight on perinatal mortality (PM) (alive or dead at 48 h of age) and dystocia (unassisted or assisted). Data were 4528 records of births between 1968 and 1999 from the Iowa State University research dairy farm in Ankeny. The incidence of PM was 7.1%; dystocia was 23.7%. A logistic regression model was used to predict both PM and dystocia. The PM model included effects of year of birth, season (summer or winter), dystocia, parity (first or later), birth weight (kg), ratio of calfs birth weight to dam's weight (%), and gestation length (d). Odds of PM increased by 2.1%/yr. Calves born in the winter have a 36% higher risk of PM than calves born in the summer. Difficult births tend to result in PM 2.7 times more often than unassisted births. First-parity cows have a 2.4 times higher risk of PM than cows in later parities. Probabilities of PM for birth weights of 29, 35, 40, 46, and 52 kg were 2.1, 2.5, 3.4, 5.1, and 9.6%, respectively, when other factors were set at their average value. Similarly, ratios of calf to cow weight of 4.5, 5.7, 6.9, 8.1, and 9.3% yield probabilities of PM at 8.2, 4.2, 3.1, 3.5, and 5.7%, respectively. Finally, gestation lengths of 268, 273, 279, 284, and 290 d yield probabilities of PM of 5.5, 3.9, 3.1, 3.1, and 3.6%, respectively. The dystocia model included effects of year of birth, season, sex of calf, PM, parity, birth weight, and pelvic area (externally measured). Odds for dystocia decreased by 4.7%/yr. Calves born in the winter have a 15% higher risk of dystocia than calves born in the summer. Odds of male calves needing assistance were 25% greater than female calves. If a calf died in the first 48 h, then it is 2.7 times more likely that the calf needed assistance. First-parity cows have a 4.7 times higher risk of dystocia than cows in later parities. Odds of dystocia increase by 13%/kg increase in birth weight. An 11% decrease in odds for dystocia is associated with a one square decimeter (dm2) increase in pelvic area.     

Electronic Nose as a Tool for Monitoring the Authenticity of Food. A Review

Counterfeiting of food is recently one of the risks relevant for producers, distributors, retailers, consumers, and national governments from economic (price), health (allergens), and religious reasons. Flavour of several food products is one of the key attributes of their quality and authenticity. In the case of some foods, the aroma of a product is specific enough to discriminate an original product from its fraud or adulterated counterpart. Electronic nose (e-nose) is a rapid and powerful technique, which requires no special sample preparation to determine the aroma of a product. In the present review, the applications of different e-noses and chemometrics for determination of food authenticity including adulteration and confirmation of origin are discussed. E-noses of various configurations are a very promising tool for testing the authenticity of food products.     

Mid-infrared spectrometry of milk as a predictor of energy intake and efficiency in lactating dairy cows

Interest is increasing in the feed intake complex of individual dairy cows, both for management and animal breeding. However, energy intake data on an individual-cow basis are not routinely available. The objective of the present study was to quantify the ability of routinely undertaken mid-infrared (MIR) spectroscopy analysis of individual cow milk samples to predict individual cow energy intake and efficiency. Feed efficiency in the present study was described by residual feed intake (RFI), which is the difference between actual energy intake and energy used (e.g., milk production, maintenance, and body tissue anabolism) or supplied from body tissue mobilization. A total of 1,535 records for energy intake, RFI, and milk MIR spectral data were available from an Irish research herd across 36 different test days from 535 lactations on 378 cows. Partial least squares regression analyses were used to relate the milk MIR spectral data to either energy intake or efficiency. The coefficient of correlation (R_EX) of models to predict RFI across lactation ranged from 0.48 to 0.60 in an external validation data set; the predictive ability was, however, strongest (R_EX = 0.65) in early lactation (<60 d in milk). The inclusion of milk yield as a predictor variable improved the accuracy of predicting energy intake across lactation (R_EX = 0.70). The correlation between measured RFI and measured energy balance across lactation was 0.85, whereas the correlation between RFI and energy balance, both predicted from the MIR spectrum, was 0.65. Milk MIR spectral data are routinely generated for individual cows throughout lactation and, therefore, the prediction equations developed in the present study can be immediately (and retrospectively where MIR spectral data have been stored) applied to predict energy intake and efficiency to aid in management and breeding decisions.     

Spirometry as a motivational tool to improve smoking cessation rates: a systematic review of the literature.

Obtaining spirometric testing and providing those results to individuals who smoke has been advocated as a motivational tool to improve smoking cessation. However, its effectiveness is not known. We conducted a systematic review to determine if this approach improves rates of smoking cessation. Data sources included MEDLINE (1966 to October 2005), the Cochrane Library, and experts in the field. Eligible randomized controlled trials (RCTs) enrolled at least 25 smokers per arm, evaluated spirometry with associated counseling or in combination with other treatments, followed subjects at least 6 months, and provided smoking abstinence rates. Results from nonrandomized studies also were summarized. The primary outcome was patient-reported long-term (at least 6 months) sustained abstinence with biological validation. Additional outcomes included self-reported abstinence and point-prevalence abstinence. Seven RCTs (N = 6,052 subjects) met eligibility criteria. Follow-up duration ranged from 9 to 36 months. In six trials, the intervention group received concomitant treatments previously demonstrated to increase cessation independently. The range of abstinence was 3%-14% for control subjects and 7%-39% among intervention groups, statistically significantly in favor of intervention in four studies. The only RCT that assessed the independent contribution of spirometry in combination with counseling demonstrated a nonsignificant 1% improvement in patient-reported point-prevalence abstinence at 12 months in the group that received spirometry plus counseling versus counseling alone (6.5% versus 5.5%). Findings from observational studies were mixed, and the lack of controls makes interpretation problematic. Available evidence is insufficient to determine whether obtaining spirometric values and providing that information to patients improves smoking cessation compared with other smoking cessation methods. Spirometric values are of limited benefit as a predictor of smoking cessation or as a tool to "customize" smoking cessation strategies.     

Isolation and study of the functional properties of pea proteins.

Proteins of pea seeds were isolated after defatting with hexane using alkaline (0.1 M sodium hydroxide) extraction and acid (HCl) precipitation. Concentrates were also prepared by hexane extraction and ethanolic extraction (pH = 5). Gross chemical composition amino acid content and functional properties (solubility profile, emulsifying--and foaming properties, water--and oil absorption) were studied. The results were compared with the same parameters of soy and lupin protein products. Although the majority of functional characteristics of isolates were lower in comparison to soy isolates, pea protein concentrate and isolate could be successfully used in bakery products for enrichment in protein and improvement of biological value. Their utilization as meat protein substitute in some Frankfurter type sausages is also possibly.     

The Prestige oil spill. 2. Enhanced biodegradation of a heavy fuel oil under field conditions by the use of an oleophilic fertilizer

A field bioremediation assay using the oleophilic fertilizer S200 was carried out 10 months after the Prestige heavy fuel-oil spill on a beach of the Cantabrian coast (North Spain). The field survey showed that S200 significantly enhanced the biodegradation rate, particularly of high molecular weight n-alkanes, alkylcyclohexanes, and benzenes, and alkylated PAHs, paralleling the results previously found in vitro. The most significant molecular bioremediation indicators were the depletion of diasteranes and C-27 sterane components. Enhanced isomeric selectivity was also observed within the C1-phenanthrenes and dibenzothiophenes. Through the analysis of some target aliphatic and aromatic hydrocarbons a number of chemical indicators for assessing the efficiency of field bioremediation as well as identifying the source of highly weathered samples collected in the area after the spill are defined.     

CO2-filling capacity and selectivity of carbon nanopores: synthesis, texture, and pore-size distribution from quenched-solid density functional theory (QSDFT)

Porous carbons synthesized by KOH activation of petroleum coke can have high surface areas, over 3000 m(2)/g, and high CO(2) sorption capacity, over 15 wt % at 1 bar. This makes them attractive sorbents for carbon capture from combustion flue gas. Quenched solid density functional theory (QSDFT) analysis of high-resolution nitrogen-sorption data for such materials leads to the conclusion that it is the pores smaller than 1 nm in diameter that fill with high-density CO(2) at atmospheric pressure. Upon increasing pressure, larger and larger pores are filled, up to about 4 nm at 10 bar. An ideal CO(2)/N(2) selectivity of such carbon materials tends to decrease substantially upon increasing pressure, for example, from about 8-10 at 1 bar to about 4-5 at 10 bar. All in all, this work confirms the robust CO(2)-filling properties of porous carbon sorbents, their low-pressure selectivity advantages, and points to the critical role of <1 nm pores that can be controlled with activation conditions.     

Oil biodegradation and bioremediation: a tale of the two worst spills in U.S. history

The devastating environmental impacts of the Exxon Valdez spill in 1989 and its media notoriety made it a frequent comparison to the BP Deepwater Horizon spill in the popular press in 2010, even though the nature of the two spills and the environments impacted were vastly different. Fortunately, unlike higher organisms that are adversely impacted by oil spills, microorganisms are able to consume petroleum hydrocarbons. These oil degrading indigenous microorganisms played a significant role in reducing the overall environmental impact of both the Exxon Valdez and BP Deepwater Horizon oil spills.     

pH treatment as an effective tool to select the functional and structural properties of yak milk caseins

Qula is made from yak milk after defatting, acidifying, and drying. Yak milk caseins are purified from Qula by dissolving in alkali solution. The effects of different pH treatments on the functional and structural properties of yak milk caseins were investigated. Over a broad range of pH (from 6.0 to 12.0), functional properties of yak milk caseins, including solubility, emulsifying activities, and thermal characteristics, and the structural properties, including 1-anilino-8-naphthalene-sulfonate fluorescence, turbidity and particle diameter, were evaluated. The results showed that the yak milk casein yield increased as the pH increased from 6.0 to 12.0. The solubility dramatically increased as the pH increased from 6.0 to 8.0, and decreased as the pH increased from 9.0 to 12.0. The changes in emulsifying activity were not significant. Caseins were remarkably heat stable at pH 9.0. The turbidity of the casein solution decreased rapidly as the pH increased from 6.0 to 12.0, and the results suggested that reassembled casein micelles were more compact at low pH than high pH. At pH values higher than 8.0, the yield of yak milk caseins reached more than 80%. The highest solubility was at pH 8.0, the best emulsification was at pH 10.0 and the greatest thermal stability was at pH 9.0. According to the functional characteristics of yak milk caseins, alkali conditions (pH 8.0–10.0) should be selected for optimum production. These results suggested that pH-dependent treatment could be used to modify the properties of yak milk caseins by appropriate selection of the pH level.     

Geometric dimensions,density, and specific heat of chilli as a function of moisture content

Abstract

The geometric dimensions, weight of 1000 fruits, bulk density and specific heat of chilli (variety balijuri, Mymensingh local) were determined experimentally at the moisture contents of 5.14, 13.94, 26.47, 40.69, 58.94 and 73.03% (wet basis). Length of chilli fruit was found to be linearly dependent on moisture content. Chillies pose flat shape from the moisture contents 5.14 to 40.69% (wet basis) and in this moisture range the width and thickness were linearly dependent on moisture content. Above the moisture content of 40.69%, chilli fruit remained round in shape and fruit diameter was also increased linearly with the increase of moisture content. The weight of 1000 fruits, bulk density and specific heat appeared to be linearly dependent on moisture contents and these properties increased with the increase of moisture contents from 5.14 to 73.03% (wet basis).     

Physicochemical and functional properties of soy protein isolate as a function of water activity and storage

The effect of storage temperature on the physicochemical characteristics, solubility and gelling properties of soy protein isolate (SPI) with different water activities (a_w) was investigated. SPI with a_w of 0.19 (SPI-0.19) was placed in environments with relative humidity (RH) of 33% and 74%. After reaching equilibrium, in 20 days, the samples were named SPI-0.33 and SPI-0.74. For SPI-0.74, modifications in the protein characteristics started during the equilibrium period, with a decrease in the solubility and alterations in both the electrophoretic profile of the soluble proteins and in the gelling characteristics. During the 180-day storage period, SPI-0.19 and SPI-0.33 showed similar behaviours: decrease in protein solubility and alteration in hardness, cohesiveness and microstructure of the gels. These alterations were more pronounced during storage at 45 °C than at 25 °C, and in SPI-0.33 more than in SPI-0.19. Results suggest that storage conditions – temperature and RH – affect the functional properties of the proteins and the use of the isolates as a functional ingredient.     

Bifurcaria bifurcata: a key macro‐alga as a source of bioactive compounds and functional ingredients

The aim of this work was to study the proximate composition and the bioactive profile of Bifurcaria bifurcata. It contains 73.31 ± 0.69% of moisture, 8.57 ± 0.11 g per 100 g dry weight (d.w.) of protein, 5.81 ± 0.14 g per 100 g d.w. of lipid content and 30.15 ± 0.00 g per 100 g d.w. of ash. The polyunsaturated fatty acids were the most abundant fatty acid (FA), accounting for 2426.56 mg per 100 g which represents 41.77% of the total FA. The methanolic fraction showed high quantity of polyphenols (220.01 ± 0.010 phloroglucinol equivalents g^?1 extract), DPPH radical reduction capacity (EC₅₀:58.82 μg mL^?1) and oxygen radical absorbent capacity (3151.35 ± 119.33 μmol Trolox equivalents g^?1 extract). The highest antimicrobial effect was observed against Pseudomonas aeruginosa (11.3 ± 1.5 mm) and Saccharomyces cerevisiae (IC₅₀:17.07 μg mL^?1) induced by methanolic and dichloromethane fractions, respectively. Dichloromethane fraction revealed the highest antitumor activity on Caco‐2 and HepG‐2 cells. Bifurcaria bifurcata can be a promising source of bioactive compounds and functional ingredients.