947 resultados para hyperpolarized gases, He-3, MRI, lung, administration unit
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The aim of Library Administration course led by Professor Gilda Chacon is that in addition to understanding the theory to be developed objectives for good management, learn to apply to a library or a department. Our group through this study sought to determine in what way the principles and purposes of the administration are applied in the Reference Department of the Central Library of the National University. Importantly, we believe that the Department of reference is the union between the user and bibliographic, and that its aim is to keep the user the right information. The theoretical part of the paper is prepared based on guided reading and class discussion of the basic literature presented in the course syllabus, information corresponding to the reference unit was obtained through collaboration that the staff gave us the same through interviews, written data, reports and so on.
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Background The benefits associated with some cancer treatments do not come without risk. A serious side effect of some common cancer treatments is cardiotoxicity. Increased recognition of the public health implications of cancer treatment-induced cardiotoxicity has resulted in a proliferation of systematic reviews in this field to guide practice. Quality appraisal of these reviews is likely to limit the influence of biased conclusions from systematic reviews that have used poor methodology related to clinical decision-making. The aim of this meta-review is to appraise and synthesise evidence from only high quality systematic reviews focused on the prevention, detection or management of cancer treatment-induced cardiotoxicity. Methods Using Cochrane methodology, we searched databases, citations and hand-searched bibliographies. Two reviewers independently appraised reviews and extracted findings. A total of 18 high quality systematic reviews were subsequently analysed, 67 % (n = 12) of these comprised meta-analyses. Results One systematic review concluded that there is insufficient evidence regarding the utility of cardiac biomarkers for the detection of cardiotoxicity. The following strategies might reduce the risk of cardiotoxicity: 1) The concomitant administration of dexrazoxane with anthracylines; 2) The avoidance of anthracyclines where possible; 3) The continuous administration of anthracyclines (>6 h) rather than bolus dosing; and 4) The administration of anthracycline derivatives such as epirubicin or liposomal-encapsulated doxorubicin instead of doxorubicin. In terms of management, one review focused on medical interventions for treating anthracycline-induced cardiotoxicity during or after treatment of childhood cancer. Neither intervention (enalapril and phosphocreatine) was associated with statistically significant improvement in ejection fraction or mortality. Conclusion This review highlights the lack of high level evidence to guide clinical decision-making with respect to the detection and management of cancer treatment-associated cardiotoxicity. There is more evidence with respect to the prevention of this adverse effect of cancer treatment. This evidence, however, only applies to anthracycline-based chemotherapy in a predominantly adult population. There is no high-level evidence to guide clinical decision-making regarding the prevention, detection or management of radiation-induced cardiotoxicity.
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Virotherapy, the use of oncolytic properties of viruses for eradication of tumor cells, is an attractive strategy for treating cancers resistant to traditional modalities. Adenoviruses can be genetically modified to selectively replicate in and destroy tumor cells through exploitation of molecular differences between normal and cancer cells. The lytic life cycle of adenoviruses results in oncolysis of infected cells and spreading of virus progeny to surrounding cells. In this study, we evaluated different strategies for improving safety and efficacy of oncolytic virotherapy against human ovarian adenocarcinoma. We examined the antitumor efficacy of Ad5/3-Δ24, a serotype 3 receptor-targeted pRb-p16 pathway-selective oncolytic adenovirus, in combination with conventional chemotherapeutic agents. We observed synergistic activity in ovarian cancer cells when Ad5/3-Δ24 was given with either gemcitabine or epirubicin, common second-line treatment options for ovarian cancer. Our results also indicate that gemcitabine reduces the initial rate of Ad5/3-Δ24 replication without affecting the total amount of virus produced. In an orthotopic murine model of peritoneally disseminated ovarian cancer, combining Ad5/3-Δ24 with either gemcitabine or epirubicin resulted in greater therapeutic benefit than either agent alone. Another useful approach for increasing the efficacy of oncolytic agents is to arm viruses with therapeutic transgenes such as genes encoding prodrug-converting enzymes. We constructed Ad5/3-Δ24-TK-GFP, an oncolytic adenovirus encoding the thymidine kinase (TK) green fluorescent protein (GFP) fusion protein. This novel virus replicated efficiently on ovarian cancer cells, which correlated with increased GFP expression. Delivery of prodrug ganciclovir (GCV) immediately after infection abrogated viral replication, which might have utility as a safety switch mechanism. Oncolytic potency in vitro was enhanced by GCV in one cell line, and the interaction was not dependent on scheduling of the treatments. However, in murine models of metastatic ovarian cancer, administration of GCV did not add therapeutic benefit to this highly potent oncolytic agent. Detection of tumor progression and virus replication with bioluminescence and fluorescence imaging provided insight into the in vivo kinetics of oncolysis in living mice. For optimizing protocols for upcoming clinical trials, we utilized orthotopic murine models of ovarian cancer to analyze the effect of dose and scheduling of intraperitoneally delivered Ad5/3-Δ24. Weekly administration of Ad5/3-Δ24 did not significantly enhance antitumor efficacy over a single treatment. Our results also demonstrate that even a single intraperitoneal injection of only 100 viral particles significantly increased the survival of mice compared with untreated animals. Improved knowledge of adenovirus biology has resulted in creation of more effective oncolytic agents. However, with more potent therapy regimens an increase in unwanted side-effects is also possible. Therefore, inhibiting viral replication when necessary would be beneficial. We evaluated the antiviral activity of chlorpromazine and apigenin on adenovirus replication and associated toxicity in fresh human liver samples, normal cells, and ovarian cancer cells. Further, human xenografts in mice were utilized to evaluate antitumor efficacy, viral replication, and liver toxicity. Our data suggest that these agents can reduce replication of adenoviruses, which could provide a safety switch in case of replication-associated side-effects. In conclusion, we demonstrate that Ad5/3-Δ24 is a useful oncolytic agent for treatment of ovarian cancer either alone or in combination with conventional chemotherapeutic drugs. Insertion of genes encoding prodrug-converting enzymes into the genome of Ad5/3-Δ24 might not lead to enhanced antitumor efficacy with this highly potent oncolytic virus. As a safety feature, viral activity can be inhibited with pharmacological substances. Clinical trials are however needed to confirm if these preclinical results can be translated into efficacy in humans. Promising safety data seen here, and in previous publications suggest that clinical evaluation of the agent is feasible.
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We study the bound states of two spin-1/2 fermions interacting via a contact attraction (characterized by a scattering length) in the singlet channel in three-dimensional space in presence of a uniform non-Abelian gauge field. The configuration of the gauge field that generates a Rashba-type spin-orbit interaction is described by three coupling parameters (lambda(x),lambda(y),lambda(z)). For a generic gauge field configuration, the critical scattering length required for the formation of a bound state is negative, i.e., shifts to the ``BCS side'' of the resonance. Interestingly, we find that there are special high-symmetry configurations (e.g., lambda(x) = lambda(y) = lambda(z)) for which there is a two-body bound state for any scattering length however small and negative. Remarkably, the bound-state wave functions obtained for such configurations have nematic spin structure similar to those found in liquid He-3. Our results show that the BCS-BEC (Bose-Einstein condensation) crossover is drastically affected by the presence of a non-Abelian gauge field. We discuss possible experimental signatures of our findings both at high and low temperatures.
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The crystal structure of the saccharide-free form of the basic form of winged-bean agglutinin (WBAI) has been solved by the molecular-replacement method and refined at 2.3 Angstrom resolution The final R factor is 19.74b for all data in the resolution range 8.0-2.3 Angstrom. The asymmetric unit contains two half-dimers, each located on a crystallographic twofold axis. The structure of the saccharide-free form is compared with that of the complex of WBAI wi th methyl-alpha-D-galactoside. The complex is composed of two dimers in the asymmetric unit. The intersubunit interactions in the dimer are nearly identical in the two structures The binding site of the saccharide-free structure contains three ordered water molecules at positions similar to those of the hydroxyl groups of the carbohydrate which an hydrogen bonded to the protein. Superposition of the saccharide-binding sites of the two structures shows that the major changes involve expulsion of these ordered water molecules and a shift of about 0.6 Angstrom of the main-chain atoms of the variable loop.
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The structural, magnetic and dielectric properties of nano zinc ferrite prepared by the propellant chemistry technique are studied. The PXRD measurement at room temperature reveal that the compound is in cubic spinel phase, belong to the space group Fd (3) over barm. The unit cell parameters have been estimated from Rietveld refinement. The calculated force constants from FTIR spectrum corresponding to octahedral and tetrahedral sites at 375 and 542 cm(-1) are 6.61 x 10(2) and 3.77 x 10(2) N m(-1) respectively; these values are slightly higher compared to the other ferrite systems. Magnetic hysteresis and EPR spectra show superparamagnetic property nearly to room temperature due to comparison values between magnetic anisotropy energy and the thermal energy. The calculated values of saturation magnetization, remenant magnetization, coercive field and magnetic moment supports for the existence of multi domain particles in the sample. The temperature dependent magnetic field shows the spin freezing state at 30 K and the blocking temperature at above room temperature. The frequency dependent dielectric interactions show the variation of dielectric constant, dielectric loss and impedance as similar to other ferrite systems. The AC conductivity in the prepared sample is due to the presence of electrons, holes and polarons. The synthesized material is suitable for nano-electronics and biomedical applications. (C) 2014 Elsevier B.V. All rights reserved.
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In 1990 JET operated with a number of technical improvements which led to advances in performance and permitted the carrying out of experiments specifically aimed at improving physics understanding of selected topics relevant to the "NEXT STEP". The new facilities include beryllium antenna screens, a prototype lower hybrid current drive system, and modification of the NI system to enable the injection of He-3 and He-4. Continued investigation of the hot-ion H-mode produced a value of n(D)(0)tau-E(T)(i)(0) = 9 x 10(20)m-3s keV, which is near conditions required for Q(DT) = 1, while a new peaked density profile H-mode was developed with only slightly lower performance. Progress towards steady state operation has been made by achieving ELMy H-modes under certain operating conditions, while maintaining good tau-E values. Experimental simulation of He ash transport indicates effective removal of alpha-particles from the plasma core for both L and H mode plasmas. Detailed analyses of particle and energy transport have helped establish a firmer link between particle and energy transport, and have suggested a connection between reduced energy transport and reversed shear. Numerical and analytic studies of divertor physics carried out for the pumped divertor phase of JET have helped clarify the key parameters governing impurity retention, and an intensive model validation effort has begun. Experimental simulation of alpha-particle effects with beta-fast up to 8% have shown that the slowing down processes are classical, and have given no evidence of deleterious collective effects.
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During its 1990 operation, 2 large RF systems were available on JET. The Ion Cyclotron Resonance Heating (ICRH) system was equipped with new beryllium screens and with feedback matching systems. Specific impurities generated by ICRH were reduced to negligible levels even in the most stringent H-mode conditions. A maximum power of 22 MW was coupled to L-mode plasmas. High quality H-modes (tau-E greater-than-or-equal-to 2.5 tau-EG) were achieved using dipole phasing. A new high confinement mode was discovered. It combines the properties of the H-mode regime to the low central diffusivities obtained by pellet injection. A value of n(d) tau-E T(i) = 7.8 x 10(20) m-3 s keV was obtained in this mode with T(e) approximately T(i) approximately 11 keV. In the L-mode regime, a regime, a record (140 kW) D-He-3 fusion power was generated with 10 - 14 MW of ICRH at the He-3 cyclotron frequency. Experiments were performed with the prototype launcher of the Lower Hybrid Current Drive (LHCD) systems with coupled power up to 1.6 MW with current drive efficiencies up to < n(e) > R I(CD)/P = 0.4 x 10(20) m-2 A/W. Fast electrons are driven by LHCD to tail temperatures of 100 keV with a hollow radial profile. Paradoxically, LHCD induces central heating particularly in combination with ICRH. Finally we present the first observations of the synergistic acceleration of fast electrons by Transit Time Magnetic Pumping (TTMP) (from ICRH) and Electron Landau Damping (ELD) (from LHCD). The synergism generates TTMP current drive even without phasing the ICRH antennae.
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This thesis examines several examples of systems in which non-Abelian magnetic flux and non-Abelian forms of the Aharonov-Bohm effect play a role. We consider the dynamical consequences in these systems of some of the exotic phenomena associated with non-Abelian flux, such as Cheshire charge holonomy interactions and non-Abelian braid statistics. First, we use a mean-field approximation to study a model of U(2) non-Abelian anyons near its free-fermion limit. Some self-consistent states are constructed which show a small SU(2)-breaking charge density that vanishes in the fermionic limit. This is contrasted with the bosonic limit where the SU(2) asymmetry of the ground state can be maximal. Second, a global analogue of Chesire charge is described, raising the possibility of observing Cheshire charge in condensedmatter systems. A potential realization in superfluid He-3 is discussed. Finally, we describe in some detail a method for numerically simulating the evolution of a network of non-Abelian (S3) cosmic strings, keeping careful track of all magnetic fluxes and taking full account of their non-commutative nature. I present some preliminary results from this simulation, which is still in progress. The early results are suggestive of a qualitatively new, non-scaling behavior.
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A asma é um distúrbio crônico pulmonar caracterizado por inflamação, obstrução e remodelamento brônquico, levando a sintomas como sibilo, tosse e falta de ar. A terapia antiasmática consiste em corticosteroides inalados e agonistas β2 de curta ou longa duração. O tratamento é limitado por efeitos colaterais e refratariedade de alguns pacientes, justificando a necessidade de novas terapias. Estudos demonstram que a 15-deoxy-delta- 12,14-prostaglandina J2 (15d-PGJ2), um ligante endógeno de receptores ativados por proliferadores de peroxissomos do tipo gama (PPAR-γ), é capaz de reduzir a expressão de citocinas pró-inflamatórias, o que pode resultar em benefícios no tratamento de doenças com esse perfil. O objetivo deste estudo foi avaliar o potencial anti-inflamatório e antiasmático da 15d-PGJ2 em modelos experimentais de asma. Camundongos A/J machos foram sensibilizados nos dias 0 e 7 através de injeção subcutânea (s.c.), contendo ovoalbumina (OVA) e Al(OH)3, e desafiados com 4 instilações intranasais (i.n.) de OVA em intervalos semanais. O tratamento com 15d-PGJ2 (30 e 100 g/Kg, s.c.) foi realizado 30 min antes dos desafios a partir da terceira provocação antigênica. Em outro modelo, camundongos A/J foram desafiados intranasalmente com extrato de ácaro 3 vezes por semana durante 3 semanas. As administrações de 15d-PGJ2 (30, 70 e 100 g/Kg, s.c. e 0,65; 1,5 e 2,3 g/animal, i.n.) foram realizadas a partir da 3 semana, 30 min antes dos desafios. As análises ocorreram 24 h após o último desafio. Nossos resultados mostraram que, em camundongos previamente sensibilizados e desafiados com OVA, a administração de 15d-PGJ2 limitou significativamente o influxo peribrônquico de eosinófilos e neutrófilos, bem como a produção de muco por células caliciformes e fibrose sub-epitelial, além da hiperreatividade das vias aéreas e produção de IL-5. A redução do epitélio brônquico e das citocinas IL-13 e TNF-α foram observadas somente na maior dose administrada. No modelo HDM a inflamação e o remodelamento foram atenuados em todas as doses administradas do composto, enquanto que a hiperresponssividade brônquica foi inibida apenas nas doses de 70 e 100 μg/Kg (via sistêmica) e na dose intermediária dada topicamente (1,5 μg/animal, i.n.). Os níveis de citocinas foram atenuados pelo tratamento subcutâneo, porém somente os níveis de IL-17, eotaxina-1 e TNF-α foram inibidos com a dose intranasal de 0,65 g/animal. O aumento da expressão de NF-κB, induzido por provocação com HDM também foi reduzido significativamente pela administração de 15d-PGJ2. Em conjunto, nossos dados indicam que o tratamento com 15d-PGJ2 inibe alterações cruciais associadas à patogênese da asma, em modelos experimentais distintos da doença, demonstrando possuir grande potencial para controlar e reverter inflamação, hiperreatividade e remodelamento pulmonar desencadeados por provocação alérgica.
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稻属(Oryza L.)隶属于禾本科(Gramineae)Ehrhartoideae亚科的稻族(Oryzeae),包括两个栽培种(亚洲栽培稻O. sativa和非洲栽培稻O. glaberrima)和大约20多个野生种,广布于热带亚洲、非洲、大洋洲、中美洲和南美洲。药用野生稻复合体(O. officinalis complex)是稻属中最大、也是最复杂的一个复合体,共包括9个种,含有5种染色体组类型(B、C、BC、CD 和E)。作为栽培稻品质改良的重要基因库,药用野生稻复合体在稻属中具有重要的地位。但是,相似的形态和重叠的地理分布使部分物种的分类和鉴定一直较为困难;种内染色体组构成和倍性的不同更增加了分类鉴定的复杂性。这种情况阻碍了对这些野生稻遗传优势的有效利用。另外,由于物种间断分布和缺乏明确的二倍体亲本等原因,药用野生稻复合体内的异源多倍体起源一直存在争议。本文通过细胞核乙醇脱氢酶基因(Adh)和nrDNA的内转录间隔区(ITS)限制性片段长度多态性(RFLP)分析;叶绿体matK 基因、trnL 内含子和trnL-trnF 基因间隔区、核基因Adh和GPA1以及核糖体DNA ITS片段等序列比较的方法,对药用野生稻复合体中染色体组和物种的鉴定、种间系统发育关系,以及异源多倍体CCDD物种的起源和多倍体ITS的分子进化等进行了研究。主要研究结果如下: 1. 利用核Adh 基因限制性片段长度多态性,检测了来自国际水稻研究所基因库的64份药用野生稻复合体的样品。结果证明,所有O. rhizomatis样品都是含C染色体组的二倍体,所有O. minuta样品都是含BC 染色体组的四倍体。但是,种子库中鉴定为O. officinalis、O. punctata和O. eichingeri的样品中,同时都发现了含C染色体组的二倍体和含BC染色体组的四倍体。四倍体的O. officinalis只在印度分布,而且曾被描述为另一个种O. malampuzhaensis。 四倍体的O. punctata,也被一些学者称为O. schweinfurthiana,被发现和其二倍体一样分布广泛。值得注意的是,有两个曾被作为O. officinalis 四倍体的样品实际上是含有CD染色体组的物种O. latifolia。我们的结果增进了对国际水稻研究所种子库中部分野生稻样品染色体组构成的理解, 纠正了以往对药用野生稻复合体样品的错误鉴定,为今后进一步研究和利用这部分资源提供了种质编目的重要基础。 2. 对稻属中代表不同地理分布区的、含CD染色体组的11个样品(包括77个克隆)的ITS片段进行了测序。基于这些ITS序列的限制性片段长度多态性,提出一个快速而可靠的区分稻属CD 染色体组物种的方法。这个方法的具体步骤是:(1)利用通用引物扩增ITS 片段;(2)利用限制性内切酶FokI和/或DraⅢ消化PCR扩增产物;(3)用1%的琼脂糖胶电泳并根据消化产物的片段长度多态性来区分不同物种。 3. 利用包括两个叶绿体片段(matK和 trnL-trnF)、nrDNA内转录间隔区(ITS)和三个核基因(Adh1、Adh2和GPA1)的同源序列分析,探讨了药用野生稻复合体中二倍体物种和它们所代表的染色体组之间的系统发育关系。独立和合并的基因系统发育树都显示了一致的结果,即C染色体组和B染色体组的亲缘关系要比它们和E染色体组的近。三个含C染色体组的二倍体中,O. officinalis 和O. rhizomatis表现出较近的亲缘关系。值得注意的是,在O. eichingeri种内,尽管基于多基因的数据支持来自斯里兰卡的样品和来自非洲的样品聚成一个分支,但是较低的支持率表明, 两个地区的样品之间存在着较高的遗传分化。 4. 稻属中含CD染色体组的物种特产于拉丁美洲,包括O. alta、 O. grandiglumis 和O. latifolia。由于具有相同的染色体组类型、相似的形态特征和重叠的地理分布,这3个物种间的系统发育关系一直存在争论。另外,因为美洲大陆上没有含C和D染色体组的二倍体物种存在,对这些含CD染色体组物种的可能起源也有不同的假设被提出。使这个问题更具挑战性的是,尽管开展了世界范围的收集,至今仍没有找到含D 染色体组的二倍体物种。在本研究中,代表含C、CD和E染色体组以及含G染色体组的外类群共7个物种,共15份样品的2个叶绿体片段(matK和trnL-trnF)和3个核基因(Adh1,Adh2 和 GPA1)部分片段被测序。基于简约法、距离法和最大似然法的系统发育分析都充分支持含CD染色体组的物种起源于一次杂交事件的推论,并且显示,在物种形成时,含C染色体组的物种(O. officinalis 或O. rhizomatis 而非O. eichingeri)可能承担了母本,而含E染色体组的物种(O. australiensis)则可能承担了父本。另外,CCDD物种间非常一致的系统发育关系表明,非常大的分歧存在于 O. latifolia 和其它两个种(O. alta和O. grandiglumis)之间,这个结果倾向于将后两个种处理为同种或同种下不同分类群。 5. 基于178个克隆序列比较,探讨了ITS在稻属多倍体中的致同进化及其系统学意义。研究发现稻属异源四倍体的ITS存在不同形式的进化方式:首先,非洲BBCC四倍体O. eichingeri和O. punctata 的ITS片段同时保留了双亲拷贝,而且系统发育研究表明,二倍体的O. eichingeri和O. punctata 可能是这两个四倍体的直接祖先;其次,亚洲四倍体O. malampuzhaensis和O. minuta 的ITS仅定向保留母本ITS拷贝;另外,美洲CCDD四倍体的ITS序列发生了双向致同进化,即O. alta和O. grandiglumis的ITS位点一致化成C染色体组类型,而O. latifolia一致化成 D/E 染色体组类型。我们的研究进一步表明在利用ITS片段进行系统发育分析时,特别是涉及异源多倍体时必须慎重。 6. 利用栽培稻的微卫星引物,对含B/C染色体组的6个物种,157个体的SSR位点进行扩增。结果在这些亲缘关系稍远的野生稻中得到7个SSR位点,其中5个位点表现出多态性。比较BB、CC和BBCC物种SSR位点的每位点平均等位基因数A、多态位点百分率P和期望杂合度He ,3项指标发现,四倍体物种的遗传多样性,总体上要高于二倍体物种;二倍体物种内部,O. officnalis的遗传变异最大。另外,以遗传相关性为标准,讨论了B/C染色体组物种间的系统发育关系,同时推测了现存二倍体物种和4个BBCC四倍体物种的遗传关系。
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磁共振成像(magnetic resonance imaging, MRI)以其分辨率高、对人体无电离辐射损伤、多参数成像等优点而得到迅速发展和广泛应用。目前,MRI已从单一形态学向分子影像学的深度发展,对医学临床和医学研究产生了巨大影响。为了提高病变部位与正常组织间信号的对比度,约30%~40%的诊断需要使用磁共振成像造影剂。它是一类能缩短成像时间、提高成像对比度和清晰度、显示组织器官功能状态的诊断用药。下一代磁共振成像造影剂的设计目标将集中在对特定组织或器官具有选择性或靶向性、高弛豫性能和减少用药剂量等方面。本论文在此领域的研究内容可归纳如下: (1) 以多糖为载体的MRI造影剂 设计合成了阿拉伯半乳聚糖修饰的Gd-DTPA配合物(Gd-DTPA-CMAG-An)和葡聚糖修饰的Gd-DTPA配合物(Gd-DTPA-CMDn-Cyst)。通过体外弛豫时间测试和体内磁共振成像实验研究了Gd-DTPA-CMAG-An弛豫性能、器官选择性、体内滞留时间和代谢情况,结合体外稳定性综合评价了其应用于临床的可能性。研究结果表明,Gd-DTPA-CMAG-An配合物在水溶液中弛豫性能为Gd-DTPA的1.4倍左右,Gd-DTPA-CMAG-A2对肝脏信号的增强效果是Gd-DTPA的2.0倍左右,并且能在较长时间内产生良好稳定的增强效果。这与肝脏表面的去唾液酸糖蛋白受体的专一性识别有关。Gd-DTPA-CMAG-A2良好的肝脏选择性和肾脏代谢能力,有望成为有前景的肝脏选择性造影剂。通过小鼠MRI实验初步评价了Gd-DTPA-CMDn-Cyst配合物造影剂对血管信号的增强作用。Gd-DTPA-CMD4-Cyst对血管产生了良好的增强效果,并且能在较长时间内对血管产生良好稳定的增强,从而有充分的时间优化成像窗口获得理想的成像效果。但造影剂在体内的分布和代谢是一个非常复杂的过程,Gd-DTPA-CMD4-Cyst在血液中的滞留情况及能否用于血管造影仍需进一步的实验证实。 (2) MnNaY 型分子筛作为胃肠道MRI造影剂 离子交换法制备了Mn2+交换的NaY分子筛MnNaY,从对造影剂的一般要求出发,对其酸性水溶液中的稳定性和离子交换选择性、体外弛豫性能和体内成像等方面进行研究,并对器官的选择性及体内滞留时间和代谢情况进行了分析,从而对其应用于临床的可能性进行了探讨。研究结果表明,MnNaY悬浮液能长时间在较低的酸性条件下保持良好的稳定性,其弛豫效率高于目前临床所用造影剂Gd-DTPA,随Mn2+的含量在NaY分子筛中的增加(3.2%~5.2%),弛豫效率反而降低。MnNaY (3.2% Mn)对胃部具有良好的增强效果,并且能在较长时间内产生良好稳定的增强效果,有利于获得理想的成像效果。它是一种比较好的潜在口服胃肠道造影剂。 (3) 甘草酸为载体的MRI造影剂 合成了甘草酸为载体的配合物GL-(A-Gd-DTPA)3,对其体外弛豫性能和体内成像等方面进行了研究,结果表明,其在水中的弛豫效率约为目前临床所用造影剂Gd-DTPA的1.4倍,体内成像表明它能在较长时间内对大鼠肝脏产生良好稳定的增强效果,这是由于肝(实质)细胞膜表面存在GL和GA受体,Gd-DTPA 以GL为载体后具有良好的趋肝性与肝细胞靶向性。 (4) 中性的Gd-DTPA双酰胺衍生物 合成了两种中性的Gd-DTPA双酰胺衍生物Gd-DTPA-BBA和Gd-DTPA-BtBA,其弛豫效率与Gd-DTPA相近,对肝脏和肾脏具有较好的增强效果,由于这两种配合物均为电中性化合物,这样配合物溶液的渗透压值与血液的渗透压值较接近,可能更易为生物体所接受。
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We discuss the non-Abelian topological objects, in particular the non-Abrikosov vortex and the magnetic knot made of the twisted non-Abrikosov vortex, in two-gap superconductor. We show that there are two types of non-Abrikosov vortex in Ginzburg-Landau theory of two-gap superconductor, the D-type which has no concentration of the condensate at the core and the N-type which has a non-trivial profile of the condensate at the core, under a wide class of realistic interaction potential. We prove that these non-Abrikosov vortices can have either integral or fractional magnetic flux, depending on the interaction potential. We show that they are described by the non-Abelian topology pi(2)(S-2) and pi(1)(S-1), in addition to the well-known Abelian topology pi(1)(S-1). Furthermore, we discuss the possibility to construct a stable magnetic knot in two-gap superconductor by twisting the non-Abrikosov vortex and connecting two periodic ends together, whose knot topology pi(3)(S-2) is described by the Chern-Simon index of the electromagnetic potential. We argue that similar topological objects may exist in multi-gap or multi-layer superconductors and multi-component Bose-Einstein condensates and superfluids, and discuss how these topological objects can be constructed in MgB2, Sr2RuO4, He-3, and liquid metallic hydrogen.
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We present a numerical study of shear viscosity and thermal conductivity of symmetric nuclear matter, pure neutron matter, and beta-stable nuclear matter, in the framework of the Brueckner theory. The calculation of in-medium cross sections and nucleon effective masses is performed with a consistent two- and three-body interaction. The investigation covers a wide baryon density range as needed in the applications to neutron stars. The results for the transport coefficients in beta-stable nuclear matter are used to make preliminary predictions on the damping time scales of nonradial modes in neutron stars.
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We discuss experimental evidence for a nuclear phase transition driven by the different concentrations of neutrons to protons. Different ratios of the neutron to proton concentrations lead to different critical points for the phase transition. This is analogous to the phase transitions occurring in He-4-He-3 liquid mixtures. We present experimental results that reveal the N/A (or Z/A) dependence of the phase transition and discuss possible implications of these observations in terms of the Landau free energy description of critical phenomena.