Some Geographical Implications of the Revolution in Education in China     

C. K. Leung  T. N. Chiu 《Asia Pacific viewpoint》1974,15(1):51-60

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Solute redistribution during normal freezing     

Wei Keung  Solomon Leung  Gregory R. Carmichael 《Water, air, and soil pollution》1984,21(1-4):141-150

Mathematical models used in metallurgy to describe solute partitioning are applied to solute distribution in ice crystals. Results demonstrate that the model developed under the assumption of ideal directional freezing can be used to estimate distribution coefficients from experimental data. The deviation of experimental results from normal freezing theory is consistent with the Burton-Slichter film theory model.  相似文献   

Pro-bone and antifat effects of green tea and its polyphenol, epigallocatechin, in rat mesenchymal stem cells in vitro     

Ko CH  Siu WS  Wong HL  Shum WT  Fung KP  San Lau CB  Leung PC 《Journal of agricultural and food chemistry》2011,59(18):9870-9876

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Chemical and genetic assessment of variability in commercial Radix Astragali (Astragalus spp.) by ion trap LC-MS and nuclear ribosomal DNA barcoding sequence analyses     

Xiao WL  Motley TJ  Unachukwu UJ  Lau CB  Jiang B  Hong F  Leung PC  Wang QF  Livingston PO  Cassileth BR  Kennelly EJ 《Journal of agricultural and food chemistry》2011,59(5):1548-1556

Radix Astragali (Huangqi) has been demonstrated to have a wide range of immunopotentiating effects and has been used as an adjuvant medicine during cancer therapy. Identity issues in the collection of Radix Astragali exist because many sympatric species of Astragalus occur in the northern regions of China. In order to assess the quality, purity, and uniformity of commercial Radix Astragali, 44 samples were purchased from herbal stores in Hong Kong and New York City. The main constituents, including four isoflavonoids and three saponins, were quantitatively determined by liquid chromatography mass spectrometry (LC-MS). There was significant sample-to-sample variability in the amounts of the saponins and isoflavonoids measured. Furthermore, DNA barcoding utilizing the variable nuclear ITS spacer regions of the 44 purchased Radix Astragali samples were sequenced, aligned and compared. Eight polymorphic point mutations were identified which separated the Radix Astragali samples into three groups. These results indicate that the chemical and genetic variability that exists among Radix Astragali medicinal products is still a consistency and quality issue for this herbal. Two-way ANOVA analysis showed significant effects on the contents of the seven tested compounds when both phylogenetic and geographic (i.e., point of purchase) factors were considered. Therefore, chemical profiles determined by LC-MS and DNA profiles in ITS spacer domains could serve as barcode markers for quality control of Radix Astragali.  相似文献   

A Review on Ozone Evolution and Its Relationship with Boundary Layer Characteristics in Urban Environments   总被引：1，自引：0，他引：1  

Nelson Y. O. Tong  Dennis Y. C. Leung  Chun-Ho Liu 《Water, air, and soil pollution》2011,214(1-4):13-36

This paper reviews the interrelationship among boundary layer, urbanization, and evolution of ozone, with particular emphasis on how boundary layer dynamics and urbanization affects the evolution of ozone under different meteorological and climatological conditions. The aim of this work is not only to provide an exhaustive investigation of individual ozone episodes but to look at the underlying issues and hypotheses that are available for understanding the evolution of ozone. The review concludes with a summary of the current state of knowledge and outlines some of the remaining questions. It is the intention of this paper to serve as an ecumenical reference to the community for reappraising the relation of boundary layer climate to the evolution of ozone in an urban setting, especially on a peculiar feature of ozone dynamic, nocturnal ozone maxima. To date, there is still no overarching consensus on the mechanisms that lead to its formation. The importance of levels of urbanization and advantage of ascertaining the substantial weights of the respective mixing height and emission structure in exploring the relationship between ozone evolutions should not be overlooked.  相似文献   

The rice genome. The most precious things are not jade and pearls     

Ronald P  Leung H 《Science (New York, N.Y.)》2002,296(5565):58-59

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Vascular endothelial growth factor is a secreted angiogenic mitogen   总被引：324，自引：0，他引：324  

D W Leung  G Cachianes  W J Kuang  D V Goeddel  N Ferrara 《Science (New York, N.Y.)》1989,246(4935):1306-1309

Vascular endothelial growth factor (VEGF) was purified from media conditioned by bovine pituitary folliculostellate cells (FC). VEGF is a heparin-binding growth factor specific for vascular endothelial cells that is able to induce angiogenesis in vivo. Complementary DNA clones for bovine and human VEGF were isolated from cDNA libraries prepared from FC and HL60 leukemia cells, respectively. These cDNAs encode hydrophilic proteins with sequences related to those of the A and B chains of platelet-derived growth factor. DNA sequencing suggests the existence of several molecular species of VEGF. VEGFs are secreted proteins, in contrast to other endothelial cell mitogens such as acidic or basic fibroblast growth factors and platelet-derived endothelial cell growth factor. Human 293 cells transfected with an expression vector containing a bovine or human VEGF cDNA insert secrete an endothelial cell mitogen that behaves like native VEGF.  相似文献   

水稻抗稻瘟病鉴定中的几个相关问题的探讨   总被引：6，自引：0，他引：6  

何月秋  唐文华 《云南农业大学学报(自然科学版)》2003,18(3):234-238

 利用CO39近等基因系及其累加系和4个稻瘟病菌的原始菌株及其突变体,研究稻瘟病抗性鉴定中经常考虑的几个因子。结果表明,接种孢子量与植株的病级、病斑数和发病叶面积呈正相关,品种对混合菌株接种的抗病性主要取决于致病性强的菌株,弱菌株的诱导抗性有限,过量施用氮肥可使部分抗病品种感病,被克服的主效基因没有明显的残效抗性。  相似文献   

Analytical challenges: determination of tetrodotoxin in human urine and plasma by LC-MS/MS     

Leung KS  Fong BM  Tsoi YK 《Marine drugs》2011,9(11):2291-2303

Tetrodotoxin (TTX) is a powerful sodium channel blocker found in puffer fish and some marine animals. Cases of TTX poisoning most often result from puffer fish ingestion. Diagnosis is mainly from patient's signs and symptoms or the detection of TTX in the leftover food. If leftover food is unavailable, the determination of TTX in the patient's urine and/or plasma is essential to confirm the diagnosis. Although various methods for the determination of TTX have been published, most of them are for food tissue samples. Dealing with human urine and blood samples is much more challenging. Unlike in food, the amount of toxin in the urine and blood of a patient is generally extremely low; therefore a very sensitive method is required to detect it. In this regard, mass spectrometry (MS) methods are the best choice. Since TTX is a very polar compound, there will be lack of retention on conventional reverse-phase columns; use of ion pair reagent or hydrophilic interaction liquid chromatography (HILIC) can help solve this problem. The problem of ion suppression is another challenge in analyzing polar compound in biological samples. This review will discuss different MS methods and their pros and cons.  相似文献   

AN EXPLORATORY PERFORMANCE ASSESSMENT OF SHRIMP EXPORTERS FOR THE U.S. MARKET     

Run Yu  Junning Cai  PingSun Leung 《Aquaculture Economics & Management (Blackwell Science)》2013,17(4):225-251

This paper develops a systematic approach for the assessment of export performance and applies it to evaluate the major shrimp exporters for the U.S. market during the period from 1991 to 2007. Export performance is evaluated from two perspectives: (1) an individual exporter's competitiveness in a specific shrimp product in terms of comparative advantage, and (2) an individual exporter's overall competitiveness in the U.S. market in terms of specialization.  相似文献