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Reduction of conductivity and ferromagnetism induced by Ag doping in ZnO:Co
Bieber, H.,Colis, S.,Schmerber, G.,Pierron-Bohnes, V.,Boukhvalov, D.W.,Kurmaev, E.Z.,Finkelstein, L.D.,Bazylewski, P.,Moewes, A.,Chang, G.S.,Dinia, A. Elsevier 2013 THIN SOLID FILMS - Vol.545 No.-
<P><B>Abstract</B></P> <P>Cobalt and silver co-doping has been undertaken in ZnO thin films grown by pulsed laser deposition in order to investigate the ferromagnetic properties in ZnO-based diluted magnetic materials and to understand the eventual relation between ferromagnetism and charge carriers. Hall transport measurements reveal that Ag doping up to 5% leads to a progressive compensation of the native <I>n</I>-type carriers. The magnetization curves show ferromagnetic contributions for all samples at both 5K and room temperature, decreasing with increasing the Ag concentration. First principles modeling of the possible configurations of Co–Ag defects suggests the formation of nano-clusters around interstitial Co impurity as the origin of the ferromagnetism. The Ag co-doping results in a decrease of the total spin of these clusters and of the Curie temperature.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We fabricate ZnO:Co films co-doped by Ag. </LI> <LI> Reduction of the number of charge carriers in co-doped samples is observed. </LI> <LI> Decrease of magnetic moment per Co in Ag-rich samples is observed. </LI> <LI> Theoretical calculations support suppression of ferromagnetism in Ag-doped ZnO:Co. </LI> </UL> </P>
Bieber,Loran L.,Chang,Choong-Duk 濟州大學校 基礎科學硏究所 1993 基礎科學硏究 Vol.6 No.1
Carnitine octanoyltransferase (COT) purified from rat liver microsomes has ??? values between 1.0 and 4.0㎛ for saturated 6-carbon to 16-carbon length acyl-Co As, with little differences in ??? values. The reaction rate is linear with time in the forward direction (acyl-CoA→acylcarnitine), but it increases with time whin assayed in the reverse direction (acylcarnitine→acyl-CoA). The ??? for decanoylcarnitine and CoASH are 0.3 mM for CoASH and between 1.0 and 4.0 mM for decanoylcarnitine. The kinetic data indicate that the enzyme functions in the direction of acylcarnitine formation. It is moderately inhibited by aminocarnitine, and D-carnitine and etomoxiryl-CoA are weak inhibitors; malonyl-CoA does not inhibit the enzyme. The enzyme has little, if any, capacity to use valproylcarnitine, 3-methylglutarylcarnitine, or pivaloylcarnitine as a substrate. Polyclonal antibodies prepared against COT give a positive Western blot against the purified enzyme and against a protein in microsomes having the molecular mass of COT (53 kDA). Antimitochondrial CPT and antiperoxisomal CAT did not show appreciable cross-reactivity with purified microsomal COT. The inhibitor data, the kinetic data, the molecular masses, and the Western blotting profiles all show that the enzyme purified from rat liver microsomes is a different carnitine acyltransferase than those previously purified from other organelles.
Invited Review Article : Atopic Dermatitis
( Thomas Bieber ) 대한피부과학회 2010 Annals of Dermatology Vol.22 No.2
Atopic dermatitis (AD) is a chronic and relapsing disease affecting an increasing number of patients. Usually starting in early childhood, AD can be the initial step of the so-called atopic march, i.e. followed by allergic rhinitis and allergic asthma. AD is a paradigmatic genetically complex disease involving gene-gene and gene-environment interactions. Genetic linkage analysis as well as association studies have identified several candidate genes linked to either the epidermal barrier function or to the immune system. Stress, bacterial or viral infections, the exposure to aero- or food-allergens as well as hygienic factors are discussed to aggravate symptoms of AD. Athough generalized Th2-deviated immune response is closely linked to the condition of AD, the skin disease itself is a biphasic inflammation with an initial Th2 phase and while chronic lesions harbour Th0/Th1 cells. Regulatory T cells have been shown to be altered in AD as well as the innate immune system in the skin. The main treatment-goals include the elimination of inflammation and infection, preserving and restoring the barrier function and controlling exacerbating factors. The overall future strategy in AD will be aimed to control skin inflammation by a more proactive management in order to potentially prevent the emergence of sensitization as well as to design customized management based on genetic and pathophysiologic information. (Ann Dermatol 22(2) 125~137, 2010)
Chung, Choong-Duk,Loran L. Bieber 제주대학교 1992 논문집 Vol.35 No.-
쥐 간의 마이크로소옴에서 분리한 medium-chain/long-chain carnitine acyltransferase의 몇가지 특성과 kinetic parameter들을 결정하였다. 이 효소는 carnitine octanoyltransferase라고 하며 탄소수가 6개에서 16개의 탄소사슬을 가지는 포화 지방산의 acyl-CoA류에 대한 반응에서 Ko??는 1.0에서 4.0μM의 값을 가졌으며, Vmax값은 이들에 대하여 조금 씩의 차이를 보였다. 이 효소는 정반응에서 반응 시간에 따라 일정비의 증가를 보였으나 역반응에서는 반응시간이 경과하면 증가비율이 더 커지는 경향을 나타내었다. 이러한 양상이 역반응을 조사하는데 대하여 어려움을 주었으나 Ko??는 decanoylcarnitine과 CoASH의 반응에서 보면, CoASH에 대하여는 0.3mM, decanoylcarnitine에 대하여는 1.0과 4.0mM사이에 있었다. 이 효소에 대한 kinetic data는 acylcarnitine을 합성하는 반응에 대한 효소의 기능을 말해준다. 그리고 이 효소는 aminocarnitine에 의하여 어느 정도 저해가 되며 D-carnitine의 저해작용은 약했다. 이 효소를 기질의 없는 상태에서 4.4'dipyridildisulfide(-SH modifier 일종)과 항온처리반응을 시킨 후에는 활성이 저해되었다. 이러한 억제 작용은 여러가지 acyl-CoA들과 carnitine이 존재하에서는 일어나지 않았다. 다른 실험 결과들이 보여주는 것처럼 valproylcarnitine, 3-methylglutarylcanrnitine 또는 pivaloylcarnitine을 기질로 한 경우에는 조금 사용하거나 사용하지 못하였다. 막에 존재하는 다른 효소들의 연구결과와 비교하면 이 효소는 malonyl-CoA에 의해서 저해 받지 않았으나 etomoxiryl-CoA는 약간 저해시키는 효과를 나타내었다. COT에 대한 polyclonal antibody를 얻어서 순수 분리된 효소에 대한 Western blot을 한 결과 마이크로소옴의 단백질에 대한 COT의 M.W.는 53,000dalton이었다. anti-microsomal COT antibody는 순수 분리된 쥐 심장의 미토콘드리아의 carnitine palmitoyltransferase와 peroxisome의 COT에 대하여 약한 cross 반응을 보였으나 carnitine acetyltransferase와는 cross 반응을 하지 않았다. anti-mitochondrial CPT와 anti-peroxsomal CAT에 대한 microsomal COT는 cross반응을 보이지 않았다. 억제제에 대한 실험 data와 분자량 Western blot분석결과는 쥐 간의 마이크로소옴에서 정제된 효소에 대한 결과이나 다른 세포 소기관에서 분리한 carnitine acyltransferase는 이전에 정제된 효소를 사용하였다.