Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 53
Filtrar
Mais filtros

Base de dados
País/Região como assunto
Tipo de documento
Intervalo de ano de publicação
1.
Nature ; 617(7961): 488-492, 2023 May.
Artigo em Inglês | MEDLINE | ID: mdl-37100906

RESUMO

The newly discovered kagome superconductors represent a promising platform for investigating the interplay between band topology, electronic order and lattice geometry1-9. Despite extensive research efforts on this system, the nature of the superconducting ground state remains elusive10-17. In particular, consensus on the electron pairing symmetry has not been achieved so far18-20, in part owing to the lack of a momentum-resolved measurement of the superconducting gap structure. Here we report the direct observation of a nodeless, nearly isotropic and orbital-independent superconducting gap in the momentum space of two exemplary CsV3Sb5-derived kagome superconductors-Cs(V0.93Nb0.07)3Sb5 and Cs(V0.86Ta0.14)3Sb5-using ultrahigh-resolution and low-temperature angle-resolved photoemission spectroscopy. Remarkably, such a gap structure is robust to the appearance or absence of charge order in the normal state, tuned by isovalent Nb/Ta substitutions of V. Our comprehensive characterizations of the superconducting gap provide indispensable information on the electron pairing symmetry of kagome superconductors, and advance our understanding of the superconductivity and intertwined electronic orders in quantum materials.

2.
Chemistry ; 29(65): e202302051, 2023 Nov 21.
Artigo em Inglês | MEDLINE | ID: mdl-37641954

RESUMO

A new organic-inorganic hybrid open-framework molybdovanadate with mixed-valences of vanadium (V4+ /V5+ =4/3) and molybdenum (Mo5+ /Mo6+ =8/2) cations has been synthesized. The complex possesses the unique V/Mo ratio (7/10), fascinating 8-C topological network and 1D 4-MR channels (7.793 Å×6.699 Å). Importantly, its catalytic activities for the selective oxidation of benzyl alcohol to benzaldehyde (oxidant: H2 O2 , 30 wt %) have been well evaluated. The results indicated that it exhibited improved catalytic activities (conv.: 96.8 %) compared with the catalyst (Cpyr)5 PV2 Mo5 W5 O40 [conv.: 88.51 %, Cpyr=(C16 H32 C5 H4 N)+ )], high recyclability and structural stability. Moreover, the conversions and selectivities (conv.: 82.4-92.5 %; sele.: 91.5-95.7 %) of the substrates containing electron donating groups (-OH, -CH3 , -OCH3 and -Cl) were significantly higher than those of the substrate containing electron withdrawing group (-NO2 ) (conv. 67.4 %; sele.: 80.8 %). This is due to the fact that the -NO2 with a large Hammett substituent constant is not conducive to the generation of transition state products. The studies revealed the complex could act as a highly efficient heterogeneous catalyst in selective oxidation of benzyl alcohols.

3.
J Fluoresc ; 33(6): 2119-2129, 2023 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-37040002

RESUMO

Two new 3D metal-organic frameworks (MOFs) ZZUT1 and ZZUT2 were prepared through the reaction of tris-(4-carboxylphenyl) phosphineoxide (H3TPO) ligand with nitrate of neodymium and praseodymium by solvothermal method. The structure, fluorescence and photocatalytic properties of ZZUT1 and ZZUT2 were studied. The crystalline structure of two 3D Ln(III)-MOFs both exhibit triclinic system and P-1 space group. The results of fluorescence analysis showed that two 3D Ln(III)-MOFs could selectively recognize acetone molecule through the fluorescence quenching mechanism. Meanwhile, ZZUT1 and ZZUT2 showed good adsorption and degradation ability on organic dye methylene blue (MB) in photocatalytic condition, and the degradation efficiency can reach to more than 90%.

4.
J Clin Lab Anal ; 35(2): e23640, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-33146916

RESUMO

BACKGROUND: With the initially defined thresholds, the most widely used serum biomarkers for staging liver fibrosis (ie, APRI and FIB-4 scores) proved to be ineffective among patients with chronic hepatitis B virus infection (CHB). Whether optimizing the FIB-4 and APRI thresholds could improve their diagnostic accuracy requires further research. METHODS: Using data of treat-naïve CHB patients from three tertiary hospitals, we explored the optimal FIB-4 and APRI thresholds to rule in liver fibrosis accurately. Subsequently, we validated the applicability of the newly defined thresholds to the CHB patients from another two tertiary hospitals. RESULTS: The fibrosis stages between discovery cohort (n = 433) and the external validation cohort (n = 568) were statistically different (P < .001). When ruling in significant fibrosis and advanced fibrosis by the newly defined FIB-4 thresholds (2.25 and 3.00, respectively), 24.0% and 14.3% of patients, respectively, could be classified with excellent accuracy (PPVs of 91.3% and 80.6%, respectively; misdiagnosis rates of 6.0% and 5.4%, respectively), supported by the internal and external validation tests. Regrettably, the more accurate and robust thresholds of APRI score for ruling in significant fibrosis and advanced fibrosis could not be found. Besides, the FIB-4 and APRI scores should not be recommended for ruling in cirrhosis because of poor clinical diagnostic performance. CONCLUSION: The newly defined FIB-4 thresholds for ruling in significant fibrosis and advanced fibrosis showed superior and reproducible clinical diagnostic accuracy. The well-validated threshold (≥2.25) of FIB-4 score could aid in antiviral treatment decisions for treat-naïve adult CHB patients by accurately ruling in significant fibrosis in tertiary care settings.


Assuntos
Hepatite B Crônica/complicações , Cirrose Hepática/diagnóstico , Adulto , Alanina Transaminase/sangue , Feminino , Humanos , Cirrose Hepática/sangue , Cirrose Hepática/etiologia , Cirrose Hepática/patologia , Masculino , Pessoa de Meia-Idade , Contagem de Plaquetas , Reprodutibilidade dos Testes , Atenção Terciária à Saúde , Transaminases/sangue
5.
Health Info Libr J ; 37(1): 48-59, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31090185

RESUMO

BACKGROUND: Online health communities (OHCs) experience difficulties in utilising patient reported posts to fulfil the information needs of online patients concerning health related issues. OBJECTIVES: We aim to propose a comprehensive method that leverages medical domain knowledge to extract useful information from posts to fulfil information needs of online patients. METHODS: A knowledge representation framework based on authoritative knowledge sources in the medical field for the OHC is proposed. On the basis of the framework, a health related information extraction process for analysing the posts in the OHC is proposed. Then, knowledge support rate (KSR) and effective information rate (EIR) are introduced as metrics to evaluate changes in knowledge extracted from the knowledge sources in terms of fulfilling the information needs of patients in the OHC. RESULTS: On the basis of a data set with 372 343 posts in an OHC, experimental results indicate that our method effectively extracts relevant knowledge for online patients. Moreover, KSR and EIR are feasible metrics of changes in knowledge in terms of fulfilling the information needs. CONCLUSIONS: The OHCs effectively fulfil the information needs of patients by utilising authoritative domain knowledge in the medical field. Knowledge based services for online patients facilitate an intelligent OHC in the future.


Assuntos
Comportamento de Busca de Informação , Avaliação das Necessidades/tendências , Saúde Pública/instrumentação , Mídias Sociais/normas , Humanos , Internet , Saúde Pública/métodos , Mídias Sociais/instrumentação , Mídias Sociais/tendências , Apoio Social
6.
Radiology ; 292(2): 429-437, 2019 08.
Artigo em Inglês | MEDLINE | ID: mdl-31210615

RESUMO

Background Only sparse literature investigates the reproducibility and repeatability of relaxometry methods in MRI. However, statistical data on reproducibility and repeatability of any quantitative method is essential for clinical application. Purpose To evaluate the reproducibility and repeatability of two-dimensional fast imaging with steady-state free precession MR fingerprinting in vivo in human brains. Materials and Methods Two-dimensional section-selective MR fingerprinting based on a steady-state free precession sequence with an external radiofrequency transmit field, or B1+, correction was used to generate T1 and T2 maps. This prospective study was conducted between July 2017 and January 2018 with 10 scanners from a single manufacturer, including different models, at four different sites. T1 and T2 relaxation times and their variation across scanners (reproducibility) as well as across repetitions on a scanner (repeatability) were analyzed. The relative deviations of T1 and T2 to the average (95% confidence interval) were calculated for several brain compartments. Results Ten healthy volunteers (mean age ± standard deviation, 28.5 years ± 6.9; eight men, two women) participated in this study. Reproducibility and repeatability of T1 and T2 measures in the human brain varied across brain compartments (1.8%-20.9%) and were higher in solid tissues than in the cerebrospinal fluid. T1 measures in solid tissue brain compartments were more stable compared with T2 measures. The half-widths of the confidence intervals for relative deviations were 3.4% for mean T1 and 8.0% for mean T2 values across scanners. Intrascanner repeatability half-widths of the confidence intervals for relative deviations were in the range of 2.0%-3.1% for T1 and 3.1%-7.9% for T2. Conclusion This study provides values on reproducibility and repeatability of T1 and T2 relaxometry measured with fast imaging with steady-state free precession MR fingerprinting in brain tissues of healthy volunteers. Reproducibility and repeatability are considerably higher in solid brain compartments than in cerebrospinal fluid and are higher for T1 than for T2. © RSNA, 2019 Online supplemental material is available for this article. See also the editorial by Barkhof and Parker in this issue.


Assuntos
Encéfalo/anatomia & histologia , Processamento de Imagem Assistida por Computador/métodos , Imageamento por Ressonância Magnética/métodos , Adulto , Encéfalo/fisiologia , Feminino , Humanos , Masculino , Estudos Prospectivos , Valores de Referência , Reprodutibilidade dos Testes
7.
Nature ; 495(7440): 187-92, 2013 Mar 14.
Artigo em Inglês | MEDLINE | ID: mdl-23486058

RESUMO

Magnetic resonance is an exceptionally powerful and versatile measurement technique. The basic structure of a magnetic resonance experiment has remained largely unchanged for almost 50 years, being mainly restricted to the qualitative probing of only a limited set of the properties that can in principle be accessed by this technique. Here we introduce an approach to data acquisition, post-processing and visualization--which we term 'magnetic resonance fingerprinting' (MRF)--that permits the simultaneous non-invasive quantification of multiple important properties of a material or tissue. MRF thus provides an alternative way to quantitatively detect and analyse complex changes that can represent physical alterations of a substance or early indicators of disease. MRF can also be used to identify the presence of a specific target material or tissue, which will increase the sensitivity, specificity and speed of a magnetic resonance study, and potentially lead to new diagnostic testing methodologies. When paired with an appropriate pattern-recognition algorithm, MRF inherently suppresses measurement errors and can thus improve measurement accuracy.


Assuntos
Testes Diagnósticos de Rotina/métodos , Espectroscopia de Ressonância Magnética/métodos , Algoritmos , Humanos , Movimento (Física) , Reconhecimento Automatizado de Padrão , Imagens de Fantasmas , Reprodutibilidade dos Testes , Projetos de Pesquisa , Sensibilidade e Especificidade
8.
Mikrochim Acta ; 186(12): 803, 2019 11 19.
Artigo em Inglês | MEDLINE | ID: mdl-31741092

RESUMO

A general approach is presented for synthesis of multicolored gold nanoparticles (GNPs) by Au(I)-mediated generation of interlocking rings in proteins and antibiotics. The Au(I) ions are shuttled from proteins to antibiotics, and this causes the formation of interlocking rings. The multicolored GNPs of different sizes were synthesized in the rings by using the rapid nucleation method. To take the unique colors of GNPs, a functional array was designed for the colorimetric determination and discrimination of antibiotics, specifically of amoxicillin, chlortetracycline, erythromycin, spiramycin, neomycin, thiamphenicol, gentamycin and lincomycin. The method is based on the "three color" (RGB) principle. The color response patterns are characteristic for each antibiotic and can be quantitatively differentiated by statistical techniques. The limits of detection (LOD, at S/N = 3) for spiramycin (Sp) have been calculated to be 0.18 µM and 0.10 µM in water and milk, respectively. The good linear range (from 0.3 to 3.5 µM) has been used for the quantitative assay of Sp in a certified reference material. Graphical abstractSchematic presentation of gold nanoparticles (GNPs) synthesis via formation of interlocking rings in protein and antibiotics. The Au(I) ions mediate protein and antibiotics to be interlocking rings, which are quickly fixed via microwave reaction. The GNPs are synthesized and assembled in the rings.


Assuntos
Antibacterianos/análise , Nanopartículas Metálicas/química , Animais , Colorimetria/métodos , Contaminação de Alimentos/análise , Ouro/química , Limite de Detecção , Leite/química , Tamanho da Partícula , Água/análise , Poluentes Químicos da Água/análise
9.
Rural Remote Health ; 18(3): 4483, 2018 09.
Artigo em Inglês | MEDLINE | ID: mdl-30176733

RESUMO

CONTEXT: Medical care in rural China has long suffered because of a concentration of medical resources in major hospitals in cities. The patients in rural areas thus do not have affordable access to quality medical services. To tackle such issues, a tiered medical scheme (TMS) was promoted by the Chinese State Council in 2015. It divides hospitals into three tiers and encourages collaborations among different tiers within a region in order to provide better accessibility to medical care for patients in rural areas. ISSUES: The implementation of the TMS policy has not been successful, because the previous funding model, which allocated funding to each hospital according to the number of patients treated, did not facilitate close collaborations between different hospitals. In this report, the medical service unity (MSU) approach, which has been piloted in Funan county, is reported. The MSU organises the tiered hospitals as a unity in terms of medical capabilities and financial abilities. With the radical reform of financial decentralisation, three flows are thereby enabled: the funding flow binds together the hospitals into a unity, the patient flow shares the load across the providers and eases barriers to access, and the resource flow ensures accessibility and affordability for patients. LESSONS LEARNED: The MSU approach has been shown by the pilot project in Funan to be effective for the realisation of the TMS policy, benefiting hospitals, doctors and patients. The successful experience of the Funan MSU could be introduced to other regions across China and other countries. In particular, future finance reform policies for the health system would largely benefit the health reforms and especially the decentralisation of medical resources to rural areas.


Assuntos
Serviços de Saúde Rural/organização & administração , China , Acessibilidade aos Serviços de Saúde/organização & administração , Hospitais Rurais/organização & administração , Humanos , Projetos Piloto , Política , Encaminhamento e Consulta/organização & administração , Alocação de Recursos/organização & administração , Serviços de Saúde Rural/estatística & dados numéricos
10.
Environ Toxicol ; 31(9): 1080-90, 2016 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-25846368

RESUMO

Hexavalent chromium [Cr (VI)] is prevalent in ground water in some areas, but evidence on the toxic effects of Cr (VI) via ingestion through drinking water remains insufficient. The aims of our study were to investigate the toxic effects of Cr (VI) through oral water ingestion on oxidative stress and DNA methylation. Thirty-two Sprague-Dawley rats were randomly divided into four groups, and exposed to porassium dichromate (K2 Cr2 O7 ; 0, 30, 100, and 300 mg/L) in drinking water for 4 weeks. Mean body weight gain, mean water consumption, clinical chemistry determinations, and oxidative stress levels in plasma were measured. Global DNA methylation changes and DNA methylation status at the promoter of p16 gene were also detected. After 4 weeks, mild anemic effects and increased plasma malondialdehyde (MDA) levels occurred in rats exposed to 100 mg/L or 300 mg/L of Cr (VI). Plasma glutathione peroxidase (GSH-Px) activity decreased in all exposed groups. Global DNA methylation levels were reduced in 100 mg/L and 300 mg/L exposure groups. However, DNA methylation status at the promoter of P16 gene remained unchanged in all K2 Cr2 O7- treated groups. The correlation analysis indicated that increased MDA levels were closely correlated to global DNA hypomethylation. Our results indicated that oral ingestion of Cr (VI) through drinking water caused not only oxidative stress in plasma, but also global DNA hypomethylation in blood cells from male rats, and a good correlation was found between increased MDA levels and reduced global DNA methylation. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1080-1090, 2016.


Assuntos
Metilação de DNA/efeitos dos fármacos , Água Potável/química , Dicromato de Potássio/toxicidade , 8-Hidroxi-2'-Desoxiguanosina , Administração Oral , Animais , Inibidor p16 de Quinase Dependente de Ciclina/genética , Inibidor p16 de Quinase Dependente de Ciclina/metabolismo , DNA/sangue , Desoxiguanosina/análogos & derivados , Desoxiguanosina/análise , Feminino , Glutationa Peroxidase/sangue , Rim/química , Rim/patologia , Fígado/química , Fígado/patologia , Masculino , Malondialdeído/sangue , Estresse Oxidativo/efeitos dos fármacos , Regiões Promotoras Genéticas , Ratos , Ratos Endogâmicos F344 , Ratos Sprague-Dawley
13.
Inorg Chem ; 54(17): 8264-70, 2015 Sep 08.
Artigo em Inglês | MEDLINE | ID: mdl-26270128

RESUMO

A cyclometalated platinum chloride [(L)PtCl] {L = 4-[p-(diphenylamino)phenyl]-6-phenyl-2,2'-bipyridine} was successfully synthesized and characterized by (1)H NMR, (13)C NMR, MALDI-TOF MS, elemental analysis, and X-ray crystallography. Its oxidative electropolymerization proceeds smoothly on the working Pt and ITO electrodes by cyclic voltammetry. The film thickness can be easily tuned by controlling the CV scan number. The orange hybrid polymer film shows the nondiffusion-controlled redox processes and a unusually inverse dependence of ac impedance on its thickness. As a result of switching of the MLCT/ICT and dication absorption transitions, the adherent metallopolymer film exhibits the low-voltage-controlled anodic coloration near-IR electrochromism with significant optical contrast ratio (ΔT% = 88.8% at 820 nm), fast response time (1.9 s for the coloration step and 2.3 s for the bleaching step), and high coloration efficiency (CE = 363.3 C(-1)·cm(2)).

14.
Phys Chem Chem Phys ; 17(36): 23489-95, 2015 Sep 28.
Artigo em Inglês | MEDLINE | ID: mdl-26293350

RESUMO

In this paper, BiOI@(BiO)2CO3 facet coupling heterostructures were synthesized via exfoliation and ion exchange, and characterized by X-ray diffraction (XRD) patterns, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), UV-vis diffuse reflectance spectra (DRS), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) spectra and valence-band XPS spectra. With the reaction time increasing, more BiOI can be transformed to (BiO)2CO3, and BiOI@(BiO)2CO3 facet coupling heterostructures were obtained. The photocatalytic results showed that BiOI@(BiO)2CO3 displays much higher photocatalytic activity than BiOI and (BiO)2CO3 under visible-light. The photocatalytic mechanism study revealed that BiOI@(BiO)2CO3 has strong adsorption for RhB molecules due to the ultrathin nanosheets and higher BET, and displays better separation efficiency of photoinduced charge carriers and higher photocurrent due to the {001}/{001} facet coupling.

15.
Hum Reprod ; 29(11): 2512-21, 2014 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-25187598

RESUMO

STUDY QUESTION: What are the epigenetic mechanisms underlying the transgenerational effect of p,p'-DDE on male fertility? SUMMARY ANSWER: Impaired male fertility with an Igf2 epigenetic defect is transgenerationally inherited upon exposure of p,p'-DDE. WHAT IS KNOWN ALREADY: p,p'-Dichlorodiphenoxydichloroethylene (p,p'-DDE) is one of the primary metabolite products of the ancestral organochlorine pesticide dichlorodiphenoxytrichloroethane. As it is a known anti-androgen endocrine disruptor, it could cause harmful effects on the male reproductive system. STUDY DESIGN, SIZE, DURATION: Pregnant rats (F0) were administered with p,p'-DDE or corn oil at the critical time of testis development, i.e. from gestation days 8 to 15. Male and female rats of the F1 generation were mated with each other to produce F2 progeny. To reveal whether the transgenerational phenotype is produced by the maternal or paternal line, F3 progeny were generated by intercrossing control (C) and treated (DDE) males and females of the F2 generation according to the following groups: (i) C♂-C♀, (ii) DDE♂-DDE♀, (iii) DDE♂-C♀ and (iv) C♂-DDE♀. PARTICIPANTS/MATERIALS, SETTING, METHODS: Mature sperm and testes were collected from male offspring of the F1-F3 generations for the examination of male fertility parameters, i.e. sperm count and motility, testis histology and apoptosis. Expression of the imprinted genes, H19 and Igf2, was detected by real-time PCR. Igf2 DMR2 methylation was analyzed by bisulfite genomic sequencing. MAIN RESULTS AND THE ROLE OF CHANCE: Upon exposure of p,p'-DDE, the male F1 generation showed impaired male fertility and altered imprinted gene expression caused by Igf2 DMR2 hypomethylation. These defects were transferred to the F3 generation through the male germline. LIMITATIONS, REASONS FOR CAUTION: This study has examined the effect of p,p'-DDE only on the sperm number and motility and the possible mechanism of Igf2 DMR2 methylation in vivo and thus has some limitations. Further investigation is necessary to focus on the epigenetic effects of p,p'-DDE at the genome level and to include a more detailed semen quality analysis including sperm morphology assessment. WIDER IMPLICATIONS OF THE FINDINGS: Impaired male fertility with epigenetic alterations is transgenerationally inherited after environmental exposure of p,p'-DDE, posing significant implications in the etiology of male infertility. STUDY FUNDING/COMPETING INTERESTS: The present research was supported by National Natural Science Fund for Young Scholar (81102161), the Natural Science Fund of Zhejiang Province (LY14H260004) and funding from the Health Department of Zhejiang Province (201475777). No competing interests are declared.


Assuntos
Diclorodifenil Dicloroetileno/farmacologia , Epigênese Genética/efeitos dos fármacos , Infertilidade Masculina/genética , Inseticidas/farmacologia , Fator de Crescimento Insulin-Like II/genética , Animais , Feminino , Masculino , Gravidez , Efeitos Tardios da Exposição Pré-Natal/genética , Ratos , Contagem de Espermatozoides , Motilidade dos Espermatozoides/efeitos dos fármacos , Espermatozoides/efeitos dos fármacos , Testículo/efeitos dos fármacos
16.
NMR Biomed ; 27(5): 519-28, 2014 May.
Artigo em Inglês | MEDLINE | ID: mdl-24610770

RESUMO

The purpose of this work was to carry out diffusion tensor imaging (DTI) at multiple diffusion times Td in skeletal muscle in normal subjects and chronic exertional compartment syndrome (CECS) patients and analyze the data with the random permeable barrier model (RPBM) for biophysical specificity. Using an institutional review board approved HIPAA-compliant protocol, seven patients with clinical suspicion of CECS and eight healthy volunteers underwent DTI of the calf muscle in a Siemens MAGNETOM Verio 3 T scanner at rest and after treadmill exertion at four different T(d) values. Radial diffusion values λ(rad) were computed for each of seven different muscle compartments and analyzed with RPBM to produce estimates of free diffusivity D(0), fiber diameter a, and permeability κ. Fiber diameter estimates were compared with measurements from literature autopsy reference for several compartments. Response factors (post/pre-exercise ratios) were computed and compared between normal controls and CECS patients using a mixed-model two-way analysis of variance. All subjects and muscle compartments showed nearly time-independent diffusion along and strongly time-dependent diffusion transverse to the muscle fibers. RPBM estimates of fiber diameter correlated well with corresponding autopsy reference. D(0) showed significant (p < 0.05) increases with exercise for volunteers, and a increased significantly (p < 0.05) in volunteers. At the group level, response factors of all three parameters showed trends differentiating controls from CECS patients, with patients showing smaller diameter changes (p = 0.07), and larger permeability increases (p = 0.07) than controls. Time-dependent diffusion measurements combined with appropriate tissue modeling can provide enhanced microstructural specificity for in vivo tissue characterization. In CECS patients, our results suggest that high-pressure interfiber edema elevates free diffusion and restricts exercise-induced fiber dilation. Such specificity may be useful in differentiating CECS from other disorders or in predicting its response to either physical therapy or fasciotomy.


Assuntos
Síndromes Compartimentais/patologia , Modelos Biológicos , Músculo Esquelético/patologia , Esforço Físico , Adolescente , Adulto , Estudos de Casos e Controles , Doença Crônica , Difusão , Feminino , Humanos , Masculino , Permeabilidade , Imagens de Fantasmas , Razão Sinal-Ruído , Fatores de Tempo , Adulto Jovem
17.
Rev Sci Instrum ; 95(7)2024 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-38953720

RESUMO

We describe a setup for time- and angle-resolved photoemission spectroscopy with wavelength-tunable excitation and an extreme ultraviolet probe. It is enabled by using the 10 kHz twin Ti:sapphire amplifiers seeded by the common Ti:sapphire oscillator. The typical probe energy is 21.7 eV, and the wavelength of the pump excitation is tuned between 2400 and 1200 nm by using the optical parametric amplifier. The spectral width of the extreme ultraviolet probe is 53 meV, and the time resolution is dependent on the wavelength for the pump, better than 60 fs for the pump energy >0.7 eV. This system enables the pump energy to be matched with a specific interband transition and to probe a wider energy-momentum space. We present the results for the prototypical materials of highly oriented pyrolytic graphite and Bi2Se3 to show the performance of our system.

18.
Neuroimage ; 80: 234-45, 2013 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-23711537

RESUMO

The engineering of a 3 T human MRI scanner equipped with 300 mT/m gradients - the strongest gradients ever built for an in vivo human MRI scanner - was a major component of the NIH Blueprint Human Connectome Project (HCP). This effort was motivated by the HCP's goal of mapping, as completely as possible, the macroscopic structural connections of the in vivo healthy, adult human brain using diffusion tractography. Yet, the 300 mT/m gradient system is well suited to many additional types of diffusion measurements. Here, we present three initial applications of the 300 mT/m gradients that fall outside the immediate scope of the HCP. These include: 1) diffusion tractography to study the anatomy of consciousness and the mechanisms of brain recovery following traumatic coma; 2) q-space measurements of axon diameter distributions in the in vivo human brain and 3) postmortem diffusion tractography as an adjunct to standard histopathological analysis. We show that the improved sensitivity and diffusion-resolution provided by the gradients are rapidly enabling human applications of techniques that were previously possible only for in vitro and animal models on small-bore scanners, thereby creating novel opportunities to map the microstructure of the human brain in health and disease.


Assuntos
Encéfalo/citologia , Encéfalo/fisiologia , Conectoma/métodos , Imagem de Tensor de Difusão/métodos , Aumento da Imagem/métodos , Modelos Neurológicos , Rede Nervosa/citologia , Adulto , Animais , Feminino , Humanos , Masculino , Modelos Anatômicos , Rede Nervosa/fisiologia , Projetos Piloto , Adulto Jovem
19.
J Magn Reson Imaging ; 38(5): 1073-82, 2013 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-23440764

RESUMO

PURPOSE: To evaluate the performance of diffusion tensor imaging (DTI) in the evaluation of chronic exertional compartment syndrome (CECS) as compared to T2 -weighted (T2w) imaging. MATERIALS AND METHODS: Using an Institutional Review Board (IRB)-approved, Health Insurance Portability and Accountability Act (HIPAA)-compliant protocol, spectral adiabatic inversion recovery (SPAIR) T2w imaging and stimulated echo DTI were applied to eight healthy volunteers and 14 suspected CECS patients before and after exertion. Longitudinal and transverse diffusion eigenvalues, mean diffusivity (MD), and fractional anisotropy (FA) were measured in seven calf muscle compartments, which in patients were classified by their response on T2w: normal (<20% change), and CECS (>20% change). Mixed model analysis of variance compared subject groups and compartments in terms of response factors (post/pre-exercise ratios) of DTI parameters. RESULTS: All diffusivities significantly increased (P < 0.0001) and FA decreased (P = 0.0014) with exercise. Longitudinal diffusion responses were significantly smaller than transversal diffusion responses (P < 0.0001). Nineteen of 98 patient compartments were classified as CECS on T2w. MD increased by 3.8 ± 3.4% (volunteer), 7.4 ± 4.2% (normal), and 9.1 ± 7.0% (CECS) with exercise. CONCLUSION: DTI shows promise as an ancillary imaging method in the diagnosis and understanding of the pathophysiology in CECS. Future studies may explore its utility in predicting response to treatment.


Assuntos
Algoritmos , Síndromes Compartimentais/patologia , Interpretação de Imagem Assistida por Computador/métodos , Músculo Esquelético/patologia , Esforço Físico , Adolescente , Adulto , Imagem de Difusão por Ressonância Magnética , Imagem Ecoplanar , Feminino , Humanos , Aumento da Imagem/métodos , Perna (Membro)/patologia , Masculino , Adulto Jovem
20.
Mutat Res ; 752(1-2): 21-7, 2013 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-23291345

RESUMO

Polychlorinated biphenyls (PCBs) are ubiquitous, persistent pollutants found in the environment and human tissues. Exposure to PCBs is of great concern to human health because they are known to cause neurological, reproductive, endocrinal, and other effects. The aim of the present study was to find some novel gene markers induced by PCBs through a combination of microarray screening followed by validating with quantitative real time PCR in vitro and in population investigation. In the present study, gene expression profiles of human B lymphoblastoid cells treated with different concentrations of non-coplanar 2,2',4,4',5,5'-hexachlorobiphenyl (PCB153) were analyzed using microarray. The differentially expressed genes were further confirmed by real-time PCR in vitro and in individuals from PCBs-contaminated sites. Our results indicated an overlap of 15 differentially expressed genes among samples treated with different concentrations of PCB153, and six of them were selected for validating with qRT-PCR. Two up-regulated genes (CCDC92 and TMEM175) and three down-regulated genes (CCL22, GZMK, and STK38L) were further confirmed by qRT-PCR in vitro. The expression levels of CCL22 in individuals from PCBs-contaminated sites were significantly (P<0.05) lower than those in controls. Therefore, CCL22 seems to be a sensitive gene marker induced by PCBs, although it needs to be confirmed by further studies with a larger number of subjects.


Assuntos
Linfócitos B/efeitos dos fármacos , Quimiocina CCL22/metabolismo , Poluentes Ambientais/farmacologia , Marcadores Genéticos , Bifenilos Policlorados/farmacologia , Linfócitos B/metabolismo , Linhagem Celular , Quimiocina CCL22/genética , Regulação para Baixo , Humanos , Análise Serial de Tecidos
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA