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极化中子衍射及在电子自旋密度研究中的应用

中国科学（B辑） 2009年第12期39卷 1569-1582页

作者： brenda A. Dougan 薛子陵 Department of Chemistry The University of TennesseeKnoxville Tennessee 37996-1600 USA

极化中子衍射方法常用于研究含未配对电子化合物中电子自旋密度的分布.分子中电子自旋密度分布从一个独特的角度反映化合物的磁性质.本文介绍极化中子衍射方法的背景知识和基本原理.包括中子源、中子和X射线衍射、极化中子衍射,以及一... 详细信息

极化中子衍射方法常用于研究含未配对电子化合物中电子自旋密度的分布.分子中电子自旋密度分布从一个独特的角度反映化合物的磁性质.本文介绍极化中子衍射方法的背景知识和基本原理.包括中子源、中子和X射线衍射、极化中子衍射,以及一些常用的实验数据处理方法.选用几个实例总结了用极化中子衍射方法得到的电子自旋密度分布在无机和有机化学中的应用.通过单分子磁体[Fe8O2(OH)12(tacn)6]8+和氰基桥联化合物K2[Mn(H2O)2]3[Mo(CN)7]2·6H2O,说明如何用该方法研究金属原子间的磁相互作用;并通过Ru(acac)3这个只含一个未配对电子的化合物来说明如何获得化合物中金属和配体上小的自旋密度;最后介绍了该方法在nitronyl nitroxide自由基研究中的应用.

关键词：极化中子衍射电子自旋(或未配对电子)密度顺磁反铁磁磁结构因子

钨卡宾化合物与水的不寻常反应——含氧配体三聚体的合成、表征和晶体结构(英文)

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中国科学：化学 2012年第1期42卷 93-94页

作者： DOUGAN brenda A 薛子陵美国田纳西大学化学系

烷基卡宾化合物W(CH2CMe3)3(/CSiMe3)(1)与水在四氢呋喃(THF)中,或者与重水在苯-d6中的反应分别生成两个新的含氧配体的三聚物W3O3(μ=O)3(CH2CMe3)6(THF)3(2)和[W3O3(μ=O)3(CH2CMe3)6(D2-O)3]·2benzene-d6(3·2benzene-d6).这两个产物中每个钨原子均含两个烷基配体,与以前报道过的从类似的烷基卡宾化合物W(CH2CMe3)3(/CCMe3)与水反应所生成的二聚物W2O2(μ-O)(CH2CMe3)6有很大不同.化合物1与重水在四氢呋喃的反应中,观测到一个不稳定的中间体W2O2(μ-O)(CD2SiMe3)2(CH2CMe3)4(4-d4).对1与水或者与重水在THF-d8中的反应生成4及4-d4进行了动力学研究,在298(1)K,动力学同位素效应(KIE)为3.46(3),显示1的消失是一个速率决定步骤.

关键词：烷基卡宾化合物水含氧配合物动力学同位素效应

Soluble CD40 ligand in prediction of acute severe pancreatitis

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World Journal of Gastroenterology 2006年第10期12卷 1613-1616页

作者： Jean Louis Frossard Philippe Morel brenda Kwak Catherine Pastor Thierry Berney Léo Buhler Alain Von Laufen Sandrine Demulder Francois Mach Division of Gastroenterology Geneva University HospitalGenève Switzerland Clinic of Digestive Surgery Geneva University Hospital Genève Switzerland Division of Cardiology Geneva University Hospital Genève Switzerland

AIM： TO assess the early predictability of the soluble CD40L （sCD40L） in pancreatitis severity. METHODS： Between February 2000 and February 2003, 279 consecutive patients with acute pancreatitis were prospectively enrolled in our study. In this report, 40 patients with mild and 40 patients with severe pancreatitis were randomly studied, sCD40L concentrations were measured 48 hours after admission. RESULTS： sCD40L levels were significantly higher 48 hours after admission in severe pancreatitis than in mild pancreatitis. Using a cutoff of 1000 pg/L, the sensitivity and specificity of sCD40L to detect a severe course of the disease were 78% and 62% respectively compared to 72% and 81% for CRP. Logistic regression analysis found that CRP was the only statistically significant marker able to detect a severe course of the disease. CONCLUSION： These findings indicate that CRP remains a valuable marker to determine the severity and prognosis of acute pancreatitis whereas sCD40L levels should be assessed in further studies.

关键词： Acute pancreatitis Prognostic factor sCD40

Analogs of Antifungal Indoles Isolated from Aporpium Caryae with Activity Against Sudden-Death Syndrome of Soybean

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American Journal of Plant Sciences 2011年第2期2卷 245-254页

作者： brenda Bertinetti Mercedes Scandiani Gabriela Cabrera 不详

Based on the precedent discovery of a weak antifungal indole isolated from Aporpium caryae, which increased its activity when changing the N-alkyl chain, nineteen N-alkyl indoles, with alkyl chains from one to ten carbons and one or two hydroxyls, one amine or bromine functional groups, were prepared and fully characterized by spectroscopic methods. The aim of this study is the search for new synthetic agrochemical leads derived from natural products. The antifungal activity of the synthesized compounds against three fungal strains was measured in vitro. Six compounds presented good activity against Fusarium virguliforme, the causal agent of sudden-death syndrome (SDS) in soybean, in a bioautography assay. Four of them were tested in a germination test and in a greenhouse experiment. All tested compounds, applied as seed treatment, showed antifungal properties being effective to control SDS when there was low level of fungal contamination. Results indicate that some of the tested compounds are acting as growth inhibitors and represent new leads for the treatment of SDS for which no specific treatment has been previously reported.

关键词： N-Alkyl Indole Soybean Phytopathogen Fusarium Virguliforme Sudden-Death Syndrome

Diagnosing Drug-Resistant Tuberculosis with the Xpert<sup>®</sup>MTB/RIF. The Risk for Rifampin Susceptible Cases

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Journal of Tuberculosis Research 2017年第3期5卷 155-160页

作者： brenda Zaragoza Rafael Laniado-Laborín Clínica y Laboratorio de Tuberculosis Hospital General de Tijuana Tijuana Mexico Facultad de Medicina Universidad Autónoma de Sinaloa Culiacán Mexico Facultad de Medicina y Psicología Universidad Autónoma de Baja California Mexico Regional Green Light Committee for the Americas World Health Organization Geneva Switzerland

Setting: Tuberculosis clinic in México. Objective: Since the Xpert®MTB/RIF does not detect resistance to isoniazid, our objective was to emphasize the need for additional drug susceptibility testing. Design: A prospective study. All patients with an Xpert®MTB/RIF and a positive tuberculosis culture with drug susceptibility testing were included. Results: 70 patients were included. Forty-two (60%) had a history of previous treatment for TB. Fourteen patients (20%) had a strain resistant to isoniazid (H), twelve of them (85.7%) with a history of TB treatment in the past vs. 2 (7.1%) among new cases (p = 0.028). Four patients (5.7%) had resistance to rifampin (R);three of them were previously treated cases. Additionally, six patients with a negative Xpert test (8.6%) had a positive MGIT culture;three of them were resistant to H (the 3 were poly-resistant). Two patients with a positive Xpert®MTB/RIF test without R resistance were phenotypically multidrug-resistant. Conclusion: Isoniazid resistance is associated with overall increased treatment failure, relapse, and acquired multidrug resistance in patients treated with regimens containing only first-line tuberculosis drugs. It is urgent that national TB programs implement the necessary infrastructure to complement the Xpert®MTB/RIF results with DST either by phenotypic or genotypic methods.

关键词： Diagnosis Tuberculosis Isoniazid Failure Relapse

A murine model of tuberculosis/type 2 diabetes comorbidity for investigating the microbiome,metabolome and associated immune parameters

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Animal Models and Experimental Medicine 2021年第2期4卷 181-188页

作者： Harindra D.Sathkumara Janet L.Eaton Matt A.Field brenda L.Govan Natkunam Ketheesan Andreas Kupz Centre for Molecular Therapeutics Australian Institute of Tropical Health and MedicineJames Cook UniversityCairns&TownsvilleQLDAustralia College of Public Health Medical and Veterinary SciencesJames Cook UniversityTownsvilleQLDAustralia Centre for Tropical Bioinformatics and Molecular Biology James Cook UniversityCairnsQLDAustralia John Curtin School of Medical Research Australian National UniversityCanberraACTAustralia Science and Technology University of New EnglandArmidaleNSWAustralia

Tuberculosis(TB)is one of the deadliest infectious diseases in the *** meta-bolic disease type 2 diabetes(T2D)significantly increases the risk of developing ac-tive *** new TB vaccine candidates and novel therapeutic interventions are required to meet the challenges of global TB *** evidence suggests that the microbiota plays a significant role in how the host responds to infection,in-jury and neoplastic *** models that closely reflect human physiology are crucial in assessing new treatments and to decipher the underlying immunological defects responsible for increased TB susceptibility in comorbid *** this study,using a diet-induced murine T2D model that reflects the etiopathogenesis of clinical T2D and increased TB susceptibility,we investigated how the intestinal microbiota may impact the development of T2D,and how the gut microbial composition changes following a very low-dose aerosol infection with Mycobacterium tuberculosis(Mtb).Our data revealed a substantial intestinal microbiota dysbiosis in T2D mice compared to non-diabetic *** observed differences were comparable to previous clini-cal reports in TB patients,in which it was shown that Mtb infection causes rapid loss of microbial ***,diversity index and principle component analyses demonstrated distinct clustering of Mtb-infected non-diabetic mice ***-infected T2D *** findings support a broad applicability of T2D mice as a tractable small animal model for studying distinct immune parameters,microbiota and the immune-metabolome of TB/T2D *** model may also enable answers to be found to critical outstanding questions about targeted interventions of the gut mi-crobiota and the gut-lung axis.

关键词： gut microbiota host microbe interaction infectious diseases tuberculosis type 2 diabetes

Alternative Nitrogenases in Anabaena variabilis: The Role of Molybdate and Vanadate in Nitrogenase Gene

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Advances in Microbiology 2013年第6期3卷 87-95页

作者： Teresa Thiel brenda S. Pratte Department of Biology University of Missouri-St. Louis St. Louis USA

Anabaena variabilis ATCC 29413 has two distinct nitrogenases that function in heterocysts, a conventional Mo-nitrogenase and an alternative V-nitrogenase. Synthesis of these two enzymes was repressed in cells growing with a source of fixed nitrogen, such as ammonium;however, the V-nitrogenase was also repressed by Mo. Expression of the V-nitrogenase which was not affected by V and expression of the Mo-nitrogenase was not affected by the presence or absence of either Mo or V. In the absence of both Mo and V in an environment lacking fixed nitrogen, cells became starved for both metals;however, low levels of nitrogen fixation and slow growth persisted. A mutant lacking the V-nitrogenase was still able to grow very slowly in Mo-and V-free medium;however, loss of the Mo-nitrogenase in a nifDK1 mutant abolished the residual growth, suggesting that only the Mo-nitrogenase functioned under these conditions to support slow growth. The addition of vanadate, molybdate, or tungstate, which is transported by the molybdate transporter, to cells starved for these metals resulted in an increase in nitrogenase activity within two hours after the addition of the metal and this increase required new protein synthesis. While tungstate functioned about as well as vanadate in supporting acetylene reduction, the cells were not able to grow any better with tungstate than with no added metal. A mutant lacking the V-nitrogenase showed no increase in nitrogenase activity upon addition of tungstate, suggesting that the V-nitrogenase was able to incorporate tungstate. Tungstate was able to substitute for molybdate in repressing transcription of a Mo-transport gene, but it did not repress transcription of the vnfH gene, which was repressed by Mo. The availability of Mo and V plays an important role in controlling whether the Mo-or the V-nitrogenase is used for nitrogen fixation.

关键词： Cyanobacteria V-Nitrogenase Molybdate Vanadate Tungstate

Shifts in hydropower operation to balance wind and solar will modify effects on aquatic biota

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Water Biology and Security 2022年第3期1卷 88-98页

作者： Henriette I.Jager Thushara De Silva Rocio Uria-Martinez brenda M.Pracheil Jordan Macknick Oak Ridge National Laboratory Oak RidgeTN37831-6038USA National Renewable Energy Laboratory GoldenCOUSA

To avoid negative consequences to freshwater biota from climate change,society must complete the transition from fossil to renewable electricity ***,temporal patterns in hydropower generation(and flow releases that affect aquatic biota)may change with increased wind and solar *** used power cost modeling to characterize current and future within-day and seasonal patterns in hydropower generation across the Eastern Interconnection in a wet and a dry *** to the baseline,future hydropower generation across the grid decreased during the day and increased before dawn and after *** a project level,such a pattern would suggest‘double peaking’operation(up-and down-ramping before dawn and after dusk,with lower releases midday).Variation in generation was higher in wet years than dry years,foreshadowing possible flow constraints on hydropower *** the grid scale,projected ramping rates were higher in all seasons.A review of the ecological literature suggests that these changes would shift the timing of invertebrate drift and elevate the risk of nest scouring during up-ramping and the risk of stranding or dewatering during down *** conditions may be moderated by increased *** for adapting to future shifts in the renewable portfolio range from re-regulation in reservoir cascades to providing flow refuge(structures and vegetation)below individual *** basin-scale operation can distribute peaking operation to maintain grid support while restricting local ramping at critical ecological *** addition,research to design hybrid renewable systems that add battery storage is needed to understand how we can mitigate future risks to aquatic communities while promoting the use of renewable *** study,which is among the first to examine ecological side-effects of the shift to renewable energy in freshwater ecosystems,lays out a path toward understanding and navigating changes to flow regime

关键词： Wind Solar Hydropower Hydropeaking Temporal niche Double peaking Ramping Stranding Dewatering PLEXOS

Body temperature,activity patterns and hunting in free-living cheetah:biologging reveals new insights

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Integrative Zoology 2019年第1期14卷 30-47页

作者： Robyn S.HETEM Duncan MITCHELL brenda A.DE WITT Linda G.FICK Shane K.MALONEY Leith C.R.MEYER and Andrea FULLER School of Animal Plant and Environmental SciencesFaculty of SciencesUniversity of the WitwatersrandJohannesburgSouth Africa Brain Function Research Group School of PhysiologyFaculty of Health SciencesUniversity of the Witwatersrand Medical SchoolParktownJohannesburgSouth Africa School of Human Sciences University of Western AustraliaPerthAustralia Department of Paraclinical Science Faculty of Veterinary ScienceUniversity of PretoriaSouth Africa

As one of the few felids that is predominantly diurnal,cheetahs(Acinonyx jubatus)can be exposed to high heat loads in their natural *** is known about long-term patterns of body temperature and activity(including hunting)in cheetahs because long-term concurrent measurements of body temperature and activity have never been reported for cheetahs,or,indeed,for any free-living *** report here body temperature and locomo-tor activity measured with implanted data loggers over 7 months in 5 free-living cheetahs in *** tem-perature ranged from a maximum of 39°C in summer to−2°C in *** had higher(~0.4°C)max-imum 24-h body temperatures,later acrophase(~1 h),with larger fluctuations in the range of the 24-h body temperature rhythm(approximately 0.4°C)during a hot-dry period than during a cool-dry period,but main-tained homeothermy irrespective of the climatic *** ambient temperatures increased,the cheetahs shifted from a diurnal to a crepuscular activity pattern,with reduced activity between 900 and 1500 hours and increased nocturnal *** timing of hunts followed the general pattern of activity;the cheetahs hunted when they were on the *** hunted if an opportunity presented itself;on occasion they hunted in the midday heat or in total darkness(new moon).Biologging revealed insights into cheetah biology that are not ac-cessible by traditional observer-based techniques.

关键词： Acinonyx jubatus heat stress nocturnal intraguild predators moonlight