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2.
Microsc Microanal ; 21(2): 290-7, 2015 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-25740406

RESUMEN

The oxidation of nickel powder under a controlled gas and temperature environment was studied using synchrotron-based full-field transmission X-ray microscopy. The use of this technique allowed for the reaction to be imaged in situ at 55 nm resolution. The setup was designed to fit in the limited working distance of the microscope and to provide the gas and temperature environments analogous to solid oxide fuel cell operating conditions. Chemical conversion from nickel to nickel oxide was confirmed using X-ray absorption near-edge structure. Using an unreacted core model, the reaction rate as a function of temperature and activation energy were calculated. This method can be applied to study many other chemical reactions requiring similar environmental conditions.

3.
J Physiol ; 591(24): 6209-20, 2013 Dec 15.
Artículo en Inglés | MEDLINE | ID: mdl-24167225

RESUMEN

While glucocorticoids (GCs) are known to be present in the zebrafish embryo, little is known about their physiological roles at this stage. We hypothesised that GCs play key roles in stress response, hatching and swim activity during early development. To test this, whole embryo cortisol (WEC) and corticosteroid-related genes were measured in embryos from 6 to 120 h post fertilisation (hpf) by enzyme linked immunosorbent assay (ELISA) and quantitative real-time polymerase chain reaction (qRT-PCR). Stress response was assessed by change in WEC following stirring, hypoxia or brief electrical impulses applied to the bathing water. The impact of pharmacological and molecular GC manipulation on the stress response, spontaneous hatching and swim activity at different stages of development was also assessed. WEC levels demonstrated a biphasic pattern during development with a decrease from 0 to 36 hpf followed by a progressive increase towards 120 hpf. This was accompanied by a significant and sustained increase in the expression of genes encoding cyp11b1 (GC biosynthesis), hsd11b2 (GC metabolism) and gr (GC receptor) from 48 to 120 hpf. Metyrapone (Met), an inhibitor of 11ß-hydroxylase (encoded by cyp11b1), and cyp11b1 morpholino (Mo) knockdown significantly reduced basal and stress-induced WEC levels at 72 and 120 hpf but not at 24 hpf. Spontaneous hatching and swim activity were significantly affected by manipulation of GC action from approximately 48 hpf onwards. We have identified a number of key roles of GCs in zebrafish embryos contributing to adaptive physiological responses under adverse conditions. The ability to alter GC action in the zebrafish embryo also highlights its potential value for GC research.


Asunto(s)
Embrión no Mamífero/metabolismo , Hidrocortisona/metabolismo , Estrés Fisiológico , 11-beta-Hidroxiesteroide Deshidrogenasa de Tipo 2/genética , 11-beta-Hidroxiesteroide Deshidrogenasa de Tipo 2/metabolismo , Animales , Embrión no Mamífero/fisiología , Locomoción , Receptores de Glucocorticoides/genética , Receptores de Glucocorticoides/metabolismo , Esteroide 11-beta-Hidroxilasa/genética , Esteroide 11-beta-Hidroxilasa/metabolismo , Pez Cebra , Proteínas de Pez Cebra/genética , Proteínas de Pez Cebra/metabolismo
4.
Phys Chem Chem Phys ; 15(39): 16377-407, 2013 Oct 21.
Artículo en Inglés | MEDLINE | ID: mdl-23897122

RESUMEN

Advances in the design of materials for energy storage and conversion (i.e., "energy materials") increasingly rely on understanding the dependence of a material's performance and longevity on three-dimensional characteristics of its microstructure. Three-dimensional imaging techniques permit the direct measurement of microstructural properties that significantly influence material function and durability, such as interface area, tortuosity, triple phase boundary length and local curvature. Furthermore, digital representations of imaged microstructures offer realistic domains for modeling. This article reviews state-of-the-art methods, across a spectrum of length scales ranging from atomic to micron, for three-dimensional microstructural imaging of energy materials. The review concludes with an assessment of the continuing role of three-dimensional imaging in the development of novel materials for energy applications.

5.
Respirology ; 23(1): 111-112, 2018 01.
Artículo en Inglés | MEDLINE | ID: mdl-29053200
6.
Nat Genet ; 21(1): 115-8, 1999 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-9916803

RESUMEN

The ectopic expression of telomerase in normal human cells results in an extended lifespan, indicating that telomere shortening regulates the timing of cellular senescence. As telomerase expression is a hallmark of cancer, we investigated the long-term effects of forced expression of human telomerase catalytic component (hTERT) in normal human fibroblasts. In vitro growth requirements, cell-cycle checkpoints and karyotypic stability in telomerase-expressing cells are similar to those of untransfected controls. In addition, co-expression of telomerase, the viral oncoproteins HPV16 E6/E7 (which inactivate p53 and pRB) and oncogenic HRAS does not result in growth in soft agar. Thus, although ectopic expression of telomerase in human fibroblasts is sufficient for immortalization, it does not result in changes typically associated with malignant transformation.


Asunto(s)
Dominio Catalítico , Senescencia Celular , Fibroblastos/citología , Proteínas/metabolismo , ARN , Proteínas Represoras , Telomerasa/metabolismo , Dominio Catalítico/genética , División Celular , Línea Celular , Inhibidor p21 de las Quinasas Dependientes de la Ciclina , Ciclinas/metabolismo , Proteínas de Unión al ADN , Galactosidasas/biosíntesis , Humanos , Proteínas Oncogénicas Virales/genética , Proteínas E7 de Papillomavirus , Fosforilación , Proteínas/genética , Proteínas Proto-Oncogénicas p21(ras)/genética , Proteína de Retinoblastoma/metabolismo , Telomerasa/genética , Proteína p53 Supresora de Tumor/metabolismo
7.
Curr Oncol ; 20(2): e165-9, 2013 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-23559884

RESUMEN

New antitumour immunotherapy strategies for stage iv metastatic melanoma include ipilimumab, a monoclonal antibody against ctla-4. Patterns of response with cancer immunotherapy differ from those with cytotoxic chemotherapy. We present two cases of long-duration immune-related responses with ipilimumab in a phase ii trial. A 66-year-old woman with multiple lung metastases from a scalp primary melanoma received 4 doses of ipilimumab with mixed clinical response. However, after the first maintenance dose, she developed severe ileitis and colitis that responded to steroid therapy. Four months later, she had surgery and radiotherapy for a single brain metastasis. Radiologically, stable disease continued for 36 months after the last ipilimumab dose, and partial response for 5 years after ipilimumab start. A 54-year-old man with cervical lymph node and pulmonary metastases from a scalp primary melanoma received three induction doses of ipilimumab. He developed alopecia universalis and widespread vitiligo, and he discontinued treatment because of hypophysitis. Maintenance ipilimumab was started after a 6-month drug-free interval, with no further adverse events over 15 cycles. At week 12, computed tomography imaging showed no lung metastases and partial response in a supraclavicular lymph node, which was positive on positron-emission tomography. Five years after starting ipilimumab, the supraclavicular lymph node was calcified, and the patient was off steroid therapy and asymptomatic. The foregoing patients demonstrate long responses with ipilimumab (in association with delayed severe colitis in one case, and a constellation of immune events, including alopecia universalis in another). Re-treatment with ipilimumab may be possible even after significant immune adverse events.

8.
J Phys Chem B ; 127(27): 6091-6101, 2023 Jul 13.
Artículo en Inglés | MEDLINE | ID: mdl-37399503

RESUMEN

Complementary X-ray absorption fine structure (XAFS) spectroscopy and Raman spectroscopy studies were conducted on several UCl3 concentrations in several chloride salt compositions. The samples were 5% UCl3 in LiCl (S1), 5% UCl3 in KCl (S2), 5% UCl3 in LiCl-KCl eutectic (S3), 5% UCl3 in LiCl-KCl eutectic (S4), 50% UCl3 in KCl (S5), and 20% UCl3 in KCl (S6) molar concentrations. Sample S3 had UCl3 sourced from Idaho National Laboratory (INL), and all other samples were UCl3 sourced from TerraPower. The initial compositions were prepared in an inert and oxygen-free atmosphere. XAFS measurements were performed in the atmosphere at a beamline, and Raman spectroscopy was conducted inside a glovebox. Raman spectra were able to confirm initial UCl3. XAFS and later Raman spectra measured, however, did not correctly match the literature and computational spectra for the prepared UCl3 salt. Rather, the data shows some complex uranium oxychloride phases at room temperature that transition into uranium oxides upon heating. Oxygen pollution due to failure of the sealing mechanism can result in oxidation of the UCl3 salts. The oxychlorides present may be both a function of the unknown O2 exposure concentration, depending on the source of the leak and the salt composition. Evidence of this oxychloride claim and its subsequent decomposition is justified in this work.

9.
J Synchrotron Radiat ; 19(Pt 5): 789-96, 2012 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-22898959

RESUMEN

The preparation of hard material samples with the necessary size and shape is critical to successful material analysis. X-ray nanotomography requires that samples are sufficiently thin for X-rays to pass through the sample during rotation for tomography. One method for producing samples that fit the criteria for X-ray nanotomography is focused ion beam/scanning electron microscopy (FIB/SEM) which uses a focused beam of ions to selectively mill around a region of interest and then utilizes a micromanipulator to remove the milled-out sample from the bulk material and mount it on a sample holder. In this article the process for preparing X-ray nanotomography samples in multiple shapes and sizes is discussed. Additionally, solid-oxide fuel cell anode samples prepared through the FIB/SEM technique underwent volume-independence studies for multiple properties such as volume fraction, average particle size, tortuosity and contiguity to observe the characteristics of FIB/SEM samples in X-ray nanotomography.


Asunto(s)
Manejo de Especímenes/métodos , Tomografía por Rayos X/métodos , Iones , Microscopía Electrónica de Rastreo/métodos , Tamaño de la Partícula , Rayos X
10.
J Synchrotron Radiat ; 19(Pt 5): 705-9, 2012 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-22898949

RESUMEN

Full-field transmission X-ray microscopy is a unique non-destructive technique for three-dimensional imaging of specimens at the nanometer scale. Here, the use of zone-doubled Fresnel zone plates to achieve a spatial resolution better than 20 nm in the hard X-ray regime (8-10 keV) is reported. By obtaining a tomographic reconstruction of a Ni/YSZ solid-oxide fuel cell, the feasibility of performing three-dimensional imaging of scientifically relevant samples using such high-spatial-resolution Fresnel zone plates is demonstrated.

11.
Materials (Basel) ; 15(3)2022 Jan 27.
Artículo en Inglés | MEDLINE | ID: mdl-35160914

RESUMEN

Graded foam-filled channels are a very promising solution for improving the thermal performance of heat sinks because of their customized structures that leave large amounts of room for heat transfer enhancement. Accordingly, this paper proposes a comprehensive optimization framework to address the design of such components, which are subjected to a uniform heat flux boundary condition. The graded foam is achieved by parameterizing the spatial distributions of porosity and/or Pores Per Inch (PPI). Mono- and multi-objective optimizations are implemented to find the best combination of the foam's fluid-dynamic, geometrical and morphological design variables. The mono-objective approach addresses the Performance Evaluation Criterion (PEC) as an objective function to maximize the thermal efficiency of graded foams. The multi-objective approach addresses different objective functions by means of Pareto optimization to identify the optimal tradeoff solutions between heat transfer enhancement and pressure drop reduction. Optimizations are performed by assuming a local thermal non-equilibrium in the foam. They allowed us to achieve a 1.51 PEC value with H* = 0.50, ReH = 15000, iε = iPPI = 0.50, ε(0) = 0.85, ε(1) = 0.97, PPI(0) = 5, PPI(1) = 40, and ks→f = 104 as the design variables. For the three multi-objective functions investigated, one can extrapolate the optimum from the Pareto front via the utopia criterion, obtaining h¯ = 502 W/m2 K and Δp = 80 Pa, NuH,unif¯ = 2790 and f = 42, ⟨Ts*⟩s¯= 0.011, and Δp* = 91. The optimal solutions provide original insights and guidelines for the thermal design of graded foam-filled channels.

12.
J Phys Chem B ; 126(7): 1539-1550, 2022 Feb 24.
Artículo en Inglés | MEDLINE | ID: mdl-35138853

RESUMEN

Understanding the local environment of the metal atoms in salt melts is important for modeling the properties of melts and predicting their behavior and thus helping enable the development of technologies such as molten salt reactors and solar-thermal power systems and new approaches to recycling rare-earth metals. Toward that end, we have developed an in situ approach for measuring the coordination of metals in molten salt coupling X-ray absorption spectroscopy (XAS) and Raman spectroscopy. Our approach was demonstrated for two salt mixtures (1.9 and 5 mol % SrCl2 in NaCl, 0.8 and 5 mol % ZrF4 in LiF) at up to 1100 °C. Near-edge (X-ray absorption near-edge structure, XANES) and extended X-ray absorption fine structure (EXAFS) spectra were measured. The EXAFS response was modeled using ab initio FEFF calculations. Strontium's first shell is observed to be coordinated with chlorine (Sr2+-Cl-) and zirconium's first shell is coordinated by fluorine (Zr4+-F-), both having coordination numbers that decrease with increasing temperature. Multiple zirconium complexes are believed to be present in the melt, which may interfere and distort the EXAFS spectra and result in an anomalously low zirconium first shell coordination number. The use of boron nitride (BN) powder as a salt diluent for XAFS measurements was found to not interfere with measurements and thus can be used for investigations of such systems.

13.
Acta Crystallogr D Biol Crystallogr ; 67(Pt 4): 386-94, 2011 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-21460457

RESUMEN

CCP4mg is a molecular-graphics program that is designed to give rapid access to both straightforward and complex static and dynamic representations of macromolecular structures. It has recently been updated with a new interface that provides more sophisticated atom-selection options and a wizard to facilitate the generation of complex scenes. These scenes may contain a mixture of coordinate-derived and abstract graphical objects, including text objects, arbitrary vectors, geometric objects and imported images, which can enhance a picture and eliminate the need for subsequent editing. Scene descriptions can be saved to file and transferred to other molecules. Here, the substantially enhanced version 2 of the program, with a new underlying GUI toolkit, is described. A built-in rendering module produces publication-quality images.


Asunto(s)
Cristalografía por Rayos X/métodos , Proteínas/análisis , Diseño de Software , Secuencia de Aminoácidos , Gráficos por Computador , Bases de Datos de Proteínas , Modelos Moleculares , Datos de Secuencia Molecular , Estructura Cuaternaria de Proteína , Estructura Terciaria de Proteína , Alineación de Secuencia , Propiedades de Superficie
14.
Nanotechnology ; 20(11): 115605, 2009 Mar 18.
Artículo en Inglés | MEDLINE | ID: mdl-19420445

RESUMEN

Chemical vapor deposition (CVD) of carbon nanotubes (CNTs) has been investigated using a coupled gas phase and surface chemistry model. This model successfully bridged the gap between the reactor and molecular length scales and allowed individual surface kinetic processes to be identified as growth limiting directly from reactor scale parameters. Carbon nanotube growth rate is a function of the reactor wall temperature such that deposition would occur in the transition region between the hydrogen abstraction and hydrocarbon adsorption limited regimes. Deposition was limited under low reactor temperatures or rich methane conditions by hydrogen abstraction from surface bound hydrocarbons due to the availability of gaseous H(1). At high reactor temperatures and rich hydrogen conditions, the deposition reaction was shown to be limited by hydrocarbon adsorption onto the nanoparticle surface. Optimal process conditions for efficient CNT production are discussed, as well as identifying the limiting reaction steps for the surface chemistry.

15.
Hong Kong Med J ; 15(6): 427-33, 2009 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-19966346

RESUMEN

OBJECTIVE: To examine the management practice of pneumothorax in hospitalised patients in Hong Kong, especially the choice of drainage options and their success rates, as well as the factors associated with procedural failures. DESIGN: Retrospective study. SETTING: Multi-centre study involving 12 public hospitals in Hong Kong. PATIENTS: All adult patients admitted as an emergency in the year 2004 with a discharge diagnosis of 'pneumothorax' were included. Data on the management and outcomes of the various types of pneumothoraces were collected from their case records. RESULTS: Altogether these patients had 1091 episodes (476 primary spontaneous pneumothoraces, 483 secondary spontaneous pneumothoraces, 87 iatrogenic pneumothoraces, and 45 traumatic pneumothoraces). Conservative treatment was offered in 182 (17%) episodes, which were more common among patients with small primary spontaneous pneumothoraces (71%). Simple aspiration was performed to treat 122 (11%) of such episodes, and had a success rate of 15%. Aspiration failure was associated with having a pneumothorax of size 2 cm or larger (odds ratio=3.7; 95% confidence interval, 1.2-11.5; P=0.03) and a smoking history (4.1; 1.2-14.3; P=0.03). Intercostal tube drainage was employed in 890 (82%) episodes, with a success rate of 77%. Failure of intercostal tube drainage was associated with application of suction (odds ratio=4.1; 95% confidence interval, 2.8-5.9; P<0.001) and presence of any tube complications (1.55; 1.0-2.3; P=0.03). Small-bore catheters (<14 French) were used in 12 (1%) of the episodes only. Tube complications were encountered in 214 (24%) episodes. CONCLUSION: Notwithstanding recommendations from international guidelines, simple aspiration and intercostal tube drainage with small-bore catheters were not commonly employed in the management of hospitalised patients with the various types of pneumothoraces in Hong Kong.


Asunto(s)
Neumotórax/cirugía , Adolescente , Adulto , Anciano , Femenino , Hong Kong , Humanos , Masculino , Persona de Mediana Edad , Estudios Retrospectivos , Succión , Resultado del Tratamiento , Adulto Joven
16.
Curr Oncol ; 16(4): 67-70, 2009 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-19672427

RESUMEN

BACKGROUND: Cancer patients frequently use alternative therapies. Two follicular lymphoma patients who had objective tumour regression after taking Devil's Claw without cytotoxic therapy are reported here. METHODS AND RESULTS: Patient 1 presented with coexistent immunoglobulin G plasma cell dyscrasia and stage iiia lymphoma (nodes 5 cm in diameter). Computed tomography scan 10 months later showed partial regression. On enquiry, it was learned that the patient was taking Devil's Claw and Essiac (Essiac Products Services, Pompano Beach, FL, U.S.A.). This patient later developed overt myeloma, at which time he stopped the herbal supplements and underwent high-dose chemotherapy and stem cell transplantation, since which no lymphoma progression has occurred. Patient 2 presented with stage IIIA lymphoma (nodes 2.5 cm in diameter). He learned of patient 1 through our lymphoma patient support group and started Devil's Claw. Computed tomography scan 11 months later showed decreased adenopathy and splenomegaly, which has been sustained for 4 years. DISCUSSION AND CONCLUSIONS: Devil's Claw tuberous root has anti-inflammatory properties, probably through suppression of cyclooxygenase 2 (COX-2) and inducible nitric oxide synthase expression. There are no prior reports of anticancer activity. Inhibition of COX-2 has a role in colon cancer prevention, has been implicated in lymphomagenesis, and is associated both with lymphoma stage and with response to treatment. However, spontaneous regression in lymphoma has been reported in 16% of patients in one series, of whom none were on herbal medications or COX-2 inhibitors. The key issue in both these patients is whether disease regression was "spontaneous" or causally related to therapy with Devil's Claw. The timing of the response suggests a positive effect. Further investigation is warranted, preferably with a COX-2 inhibitor of known purity.

17.
Curr Opin Struct Biol ; 5(6): 784-90, 1995 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-8749366

RESUMEN

Experimental advances in data collection, including bright sources, cryogenic cooling and two-dimensional detectors, have made it tractable to record data to beyond 1.2 A for several proteins, yielding high-accuracy models and fine details of structure. For small metalloproteins, atomic-resolution data have enabled ab initio solution of the phase problem.


Asunto(s)
Cristalografía por Rayos X , Proteínas/química , Computadores , Enzimas/química , Congelación , Metaloproteínas/química , Programas Informáticos
18.
Curr Opin Struct Biol ; 5(6): 830-6, 1995 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-8749373

RESUMEN

All natural proteins are composed of L-amino acids and are inherently chiral. The properties of both L- and chemically synthesized D-amino acids are identical except in optically asymmetric interactions. Structural studies of D-I racemic mixtures of crystallographic interest are discussed. The review also gives some recent examples of stereospecificity: how L-proteins deal with L- or D-substrates and how enzymes can function as racemases. Two particular examples of stereoselectivity are then discussed.


Asunto(s)
Proteínas/química , Estereoisomerismo , Aminoácidos/química , Conformación de Carbohidratos , Glicósido Hidrolasas/metabolismo , Lipasa/metabolismo , Estructura Molecular , Oxidorreductasas/metabolismo , Péptidos/química , Proteínas/metabolismo , Racemasas y Epimerasas/metabolismo
19.
Curr Opin Struct Biol ; 7(5): 681-8, 1997 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-9345627

RESUMEN

After a long gestation, the elucidation of the crystal structures of proteins at atomic resolution is now maturing. The use of such data for both refinement and structure solution is advancing space. The necessary technology is generally available, in terms of data collection, computing hardware and software. The structures appearing in the literature mainly relate to demonstration projects on native proteins. The importance of these alone is already obvious. Biologically significant results, in terms of ligand complexes and prosthetic groups, are just starting to emerge.


Asunto(s)
Cristalografía por Rayos X , Conformación Proteica , Proteínas/química , Algoritmos , Celulasa/química , Modelos Moleculares , Ribonucleasas/química , Sincrotrones , Agua/química
20.
Artículo en Inglés | MEDLINE | ID: mdl-17329826

RESUMEN

1,3-Propanediol dehydrogenase (1,3-PD-DH), encoded by the dhaT gene, is a key enzyme in the dissimilation process for converting glycerol to 1,3-propanediol in the human pathogen Klebsiella pneumoniae. Single colourless crystals were obtained from a recombinant preparation of 1,3-propanediol dehydrogenase overexpressed in Escherichia coli. The crystals belong to space group P2(1), with unit-cell parameters a = 91.9, b = 226.6, c = 232.6 A, beta = 92.9 degrees. The crystals probably contain two decamers in the asymmetric unit, with a V(M) value of 3.07 A3 Da(-1) and an estimated solvent content of 59%. Diffraction data were collected to 2.7 A resolution using synchrotron radiation at the ID14-4 beamline of the European Synchrotron Radiation Facility.


Asunto(s)
Oxidorreductasas de Alcohol/química , Proteínas Bacterianas/química , Cristalografía por Rayos X/métodos , Klebsiella pneumoniae/enzimología , Alcohol Deshidrogenasa , Oxidorreductasas de Alcohol/aislamiento & purificación , Proteínas Bacterianas/aislamiento & purificación , Cristalización , Humanos , Klebsiella pneumoniae/patogenicidad
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