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排序方式: 共有259条查询结果,搜索用时 31 毫秒
251.
Using the precision feeding technique, an experiment was conducted to evaluate the influence of tannic acid (TA) and polyethylene glycol (PEG) on the excretion of amino acids and the apparent and true digestibilities of casein protein in broilers. Seventy‐two 9‐week‐old broiler cockerels grouped in nine treatments of eight replicates were fed warm water (50 mL, control birds), casein alone (12 or 18 g) or casein (12 or 18 g) with TA solution (4.5 g per 10 mL) or/and PEG solution (2 g per 10 mL). Total excreta were collected for 48 h and freeze‐dried. The amino acid content of casein and excreta was determined by reverse phase high‐performance liquid chromatography. In the absence of TA the digestibility of casein was almost complete. TA increased the excretion of amino acids to a varying extent (P < 0.01). Although the digestibility of all essential and non‐essential amino acids was adversely affected by the presence of TA, raising the amount of casein from 12 to 18 g improved significantly (P < 0.05) the apparent and true digestibilities of all amino acids. PEG reduced significantly (P < 0.01) the excretion of amino acids and improved significantly (P < 0.01) the amino acid digestibility of casein in TA‐dosed birds. However, the improvement was greater when the lower level of casein (12 g) was fed. Thus PEG might play an important role in inactivating dietary tannins in the gastrointestinal tract of birds and improving protein digestibility and utilisation, particularly when the diet is low or intermediate in protein. Copyright © 2007 Society of Chemical Industry  相似文献   
252.
Problem, research strategy, and findings: Local jurisdictions in 36 states have implemented transfer of development rights (TDR) programs to provide a market-based approach to preserving farmlands and open space while redirecting future development to targeted areas. Participation in TDR programs involves transaction costs over and above paying for TDR credits. Planners know little about the magnitude of transaction costs; who, if anyone, incurs a disproportionate share of these costs; or how transaction costs affect TDR participation. In this study we estimate the magnitude and distribution of transaction costs incurred by participants in 4 countywide TDR programs in Maryland, a TDR pioneer, by interviewing multiple participants in these programs. We fi nd that total transaction costs were high and borne largely by private sector participants, although we exclude the initial public sector costs of establishing the programs. Total transaction costs range from 13% to 21% of total TDR costs per transaction. Our findings are based on data reported by participants and may not be scalable; transaction costs, however, might deter landowners from participating in TDR programs, thus thwarting the land use goals of planners.

Takeaway for practice: Planners should work to reduce transaction costs by better constructing TDR programs and providing greater information on TDR sale prices and potential buyers and sellers. Lowering and more fairly distributing transaction costs will make the TDR program a more successful approach to achieving land use goals and addressing the externalities arising from land use markets.  相似文献   

253.
The location of superconducting tokamak magnets decides the position and shape of plasma, it is significant to acquire the real-time location of tokamak magnets to stably operate the tokamak. Using an improved monocular laser triangle measuring method, it can effectively reduce the distractions, the new measurement system has been installed inside the experimental hall of EAST in 2010 and was tested in the entire process of EAST experiment in 2011. After the annual experiment, we got roughly trend of the torodial field coil displacement. The measurement system was upgraded and reformed in 2012, the measurement system stably and reliably obtained large amount of experimental data, the real-time three-dimensional magnet displacement from room temperature to around 4 K and combined with excitation situation during the whole experiment have been obtained.  相似文献   
254.
The presence of allicin in green garlic plant extracts was investigated. Allicin in aqueous extracts from green garlic leaf, shoot and young bulbs were determined by HPLC. Allicin was present at highest level in extracts from whole green garlic plant at 0.48 ± 0.01 mg/mL, followed by that in shoot and leaf extracts at 0.44 ± 0.00 and 0.26 ± 0.01 mg/mL, respectively. The results obtained in this study offer green garlic as a new source of allicin, as green garlic plant is used as a favourite vegetable in many countries.  相似文献   
255.
Zheng J  Shamsi SA 《Analytical chemistry》2006,78(19):6921-6927
Benzo[a]pyrene, one of the most carcinogenic PAHs, has 12 monomethylated positional isomers (MBAPs). A strong correlation between the carcinogenicity of these isomers and methyl substitution has been reported. In this study, on-line coupling of capillary electrochromatography (CEC) and atmospheric pressure photoionization mass spectrometry (APPI-MS) provides a unique solution to highly selective separation and sensitive detection of MBAP isomers. The studies indicated that APPI provides significantly better sensitivity compared to electrospray ionization and atmospheric pressure chemical ionization modes of MS. A systematic investigation of APPI-MS detection parameters and CEC separation is established. First, several sheath liquid parameters (including type and concentration of volatile buffers, type and content of organic modifiers, use of dopants and inorganic/organic additives, and sheath liquid flow rate) and APPI-MS spray chamber parameters (capillary voltage, vaporizer temperature, nebulizer pressure) were found to have effects on detection sensitivity as well as the profile of mass spectrum. For example, when ammonium acetate was replaced with acetic acid in the sheath liquid, the MS signal was enhanced as much as 90% and the formation of ammonia adduct was effectively suppressed. Next, the separation of MBAP isomers was conducted on internal tapered columns packed with polymeric C18 stationary phase. With the use of a mobile phase consisting of slightly higher acetonitrile content (90%,v/v) and a small amount of tropylium ion, the analysis times were significantly shortened by 20 min without compromising the resolutions between the isomers. Finally, quantitative aspects of the CEC-APPI-MS method were demonstrated using 7-MBAP as the internal standard. The calibration curves of three of the most carcinogenic isomers, namely, 1-MBAP, 3-MBAP, and 11-MBAP, showed good linearity in the range of 2.5-50 microg/mL with a limit of detection at 400 ng/mL.  相似文献   
256.
257.
Cloud computing is one of the most attractive and cost-saving models, which provides online services to end-users. Cloud computing allows the user to access data directly from any node. But nowadays, cloud security is one of the biggest issues that arise. Different types of malware are wreaking havoc on the clouds. Attacks on the cloud server are happening from both internal and external sides. This paper has developed a tool to prevent the cloud server from spamming attacks. When an attacker attempts to use different spamming techniques on a cloud server, the attacker will be intercepted through two effective techniques: Cloudflare and K-nearest neighbors (KNN) classification. Cloudflare will block those IP addresses that the attacker will use and prevent spamming attacks. However, the KNN classifiers will determine which area the spammer belongs to. At the end of the article, various prevention techniques for securing cloud servers will be discussed, a comparison will be made with different papers, a conclusion will be drawn based on different results.  相似文献   
258.
Many organizations have insisted on protecting the cloud server from the outside, although the risks of attacking the cloud server are mostly from the inside. There are many algorithms designed to protect the cloud server from attacks that have been able to protect the cloud server attacks. Still, the attackers have designed even better mechanisms to break these security algorithms. Cloud cryptography is the best data protection algorithm that exchanges data between authentic users. In this article, one symmetric cryptography algorithm will be designed to secure cloud server data, used to send and receive cloud server data securely. A double encryption algorithm will be implemented to send data in a secure format. First, the XOR function will be applied to plain text, and then salt technique will be used. Finally, a reversing mechanism will be implemented on that data to provide more data security. To decrypt data, the cipher text will be reversed, salt will be removed, and XOR will be implemented. At the end of the paper, the proposed algorithm will be compared with other algorithms, and it will conclude how much better the existing algorithm is than other algorithms.  相似文献   
259.
Clean Technologies and Environmental Policy - Experts are increasingly interested in incorporating environmental and climate action into all projects. Mining projects face a broader range of...  相似文献   
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