Comparing the effect of homogenization and heat processing on the properties and in vitro digestion of milk from organic and conventional dairy herds

We compared the effects of homogenization and heat processing on the chemical and in vitro digestion traits of milk from organic and conventional herds. Raw milk from organic (>50% of dry matter intake from pasture) and conventional (no access to pasture) farms were adjusted to commercial whole and nonfat milk fat standards, and processed with or without homogenization, and with high-temperature-short-time or UHT pasteurization. The milk then underwent in vitro gastrointestinal digestion. Comparison of milk from organic and conventional herds showed that the milks responded to processing in similar ways. General composition was the same among the whole milk samples and among the nonfat milk samples. Protein profiles were similar, with intact caseins and whey proteins predominant and only minor amounts of peptides. Whole milk samples from grazing cows contained higher levels of α-linolenic (C18:3), vaccenic (C18:1 trans), and conjugated linoleic acids, and lower levels of palmitic (C16:0) and stearic (C18:0) acids than samples from nongrazing cows. Processing had no effect on conjugated linoleic acid and linolenic acid levels in milk, although homogenization resulted in higher levels of C8 to C14 saturated fatty acids. Of the 9 volatile compounds evaluated, milk from grazing cows contained lower levels of 2-butanone than milk from nongrazing cows, and milk from both farms showed spikes for heptanal in UHT samples and spikes for butanoic, octanoic, nonanoic, and N-decanoic acids in homogenized samples. At the start of in vitro digestion, nonfat raw and pasteurized milk samples formed the largest acid clots, and organic milk clots were larger than conventional milk clots; UHT whole milk formed the smallest clots. Milk digests from grazing cows had lower levels of free fatty acids than digests from nongrazing cows. In vitro proteolysis was similar in milk from both farms and resulted in 85 to 95% digestibility. Overall, milk from organic/grass-fed and conventional herds responded in similar ways to typical homogenization and heat processing used in United States dairy plants and showed only minor differences in chemical traits and in vitro digestion. Findings from this research enhance our knowledge of the effect of processing on the quality traits and digestibility of milk from organic/pasture-fed and confined conventional herds and will help health-conscious consumers make informed decisions about dairy selections.     

Synthesis of Carbon-Encapsulated Metal Nanoparticles by a Detonation Method

Carbon-encapsulated metal nanoparticles are synthesized by a detonation method using a home-made water-soluble composite explosive. The results of the study show that detonation products contain face-centered cubic cobalt/nickel nanocrystals approximately 10–25 nm in size, which are encapsulated by thin (3–5 nm) carbon layers. These spherical and ellipsoidal nanoparticles exhibit a good superparamagnetism state at 300 K.     

国际油价2008年一季度走势回顾与二季度预测

分析了2008年第一季度国际油价的走势及要因。根据影响2008年二季度国际油价上升和下降的主要因素,分析并预测了二季度国际油价的可能变化趋势。     

逆作法施工中钢格构柱施工技术研究

作为永久结构的钢格构柱施工精度要求高,如何既满足设计要求的格构柱的安装精度,又能降低成本、提高施工速度是研究重点.结合天津和黄地铁广场基础桩工程,从格构柱定位到格构柱施工进行了较为深入的研究,为今后类似工程提供了宝贵的经验.     

Tribological properties of MoS<Subscript>2</Subscript> and carbon fiber reinforced polyimide composites

The tribological properties of carbon fiber reinforced polyimide (PI) composites with different MoS₂ containing sliding against GCr15 steel were comparatively evaluated on an M-2000 model ring-on-block test rig. The wear mechanisms were also comparatively discussed, based on scanning electron microscopic examination of the worn surface of the PI composites and the transfer film formed on the counterpart. It was found that small incorporation of MoS₂ was harmful to the improvement of friction and wear behaviors of carbon fiber reinforced PI composites. However, it was found that the increasing filler of MoS₂ significantly improved the wear resistance and decreased the friction coefficient of carbon fiber reinforced PI composites. It was also found that the tribological properties of MoS₂ and short carbon fiber reinforced PI composites were closely related with the sliding condition such as sliding rate and applied load.     

Air pollution and meteorological processes in the growing dryland city of Urumqi (Xinjiang, China)

Seven years (2000-2006) of monthly PM₁₀ (particulate matter, d ≤ 10 μm), SO₂, and NO₂ concentrations are reported for Urumqi, the capital of Xinjiang in NW China. Considerably high mean annual concentrations have been observed, which ranged between 150 and 240 μg m^− 3 (PM₁₀), 31 and 50 μg m^− 3 (NO₂), and 49 and 160 μg m^− 3 (SO₂). The shapes of seasonal variation of all pollutants were remarkably similar; however, winter/summer ratios of concentrations were quite different for PM₁₀ (2-3) and NO₂ (≈ 4) compared to SO₂ (up to 30). Very high consumption rates of fossil fuels for energy generation and domestic heating are mainly responsible for high annual pollution levels, as well as the (very) high winter/summer ratios. Detailed analysis of the 2000-2006 records of Urumqi's meteorological data resulted in inter-annual and seasonal frequency distributions of (a) (surface) inversion events, (b) heights of surface inversions, (c) stability classes of Urumqi's boundary layer, and (d) the “Air Stagnation Index (ASI)”. Urumqi's boundary layer is shown to be characterized by high mean annual and seasonal frequencies of (surface) inversions and by the dominance of stable dispersion classes. A further outcome of the meteorological analysis is the proof of Urumqi's strong diurnal wind system, which might have particularly contributed to the stabilization of the nocturnal boundary layer. Annual and seasonal variations of pollutant's concentrations are discussed in the context of occurrences of inversions, boundary layer, stability classes, and ASI. The trend of Urumqi's air pollution indicates a strong increase of mean annual concentrations 2000-2003, followed by a slight increase during 2003-2006. These are in strong contrast to (a) the growth of Urumqi's fleet of motor vehicles and (b) to the growing number of stable regimes of Urumqi's boundary layer climate during same period. It is concluded that the (regional and) local administrative technical countermeasures have efficiently lowered Urumqi's air pollution levels.     

Determination of Fracture Toughness of Underfill/Chip Interface With Digital Image Speckle Correlation Technique

The layered packages are prone to multimode damages and failures when they are subjected to complicated and coupling environmental loading. As a result, fracture toughness is usually used as a fracture criterion to evaluate the reliability of polymer/inorganic interface. In this study, an in-situ/real-time micro-digital image speckle correlation (mu-DiSC) system was established and employed to determine the fracture toughness of underfill/chip interface involved in flip chip assembly. The tests were carried out over a wide range of temperatures and at various loading angles. In order to verify the finding of the mu-DiSC technique, an interface fracture mechanics based finite element model is implemented into ANSYS to calculate the values of crack-tip opening displacement of underfill/chip joint under different loading configurations. The results obtained from the simulation are found to be in good agreement with those measured by the mu-DiSC system, indicating that the system can be used as an accurate and effective experimental tool for the electronic packages. The fractographs, with respect to different temperatures and loading angles, are further discussed