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1.
Org Lett ; 22(3): 1139-1143, 2020 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-31977229

RESUMO

Herein, we report on the unprecedented dimerization of 1,6-enynes using a commercially available ruthenium complex RuCl2(PPh3)3, which results in a series of bicyclo[3.1.0]hexyl allene derivatives in moderate to excellent yields. Mechanistic investigation indicates that the in-situ-generated ruthenium vinylidene undergoes a site-selective metathesis process to provide allenyl ruthenium carbene, which can be intramolecularly trapped by the pendent C=C bond of enyne through a [2 + 2] cycloaddition/metal elimination process.

2.
J Synchrotron Radiat ; 26(Pt 1): 1-10, 2019 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-30655462

RESUMO

X-ray free-electron lasers (XFELs) have been widely used for applications such as X-ray crystallography and magnetic spin probes because of their unprecedented performance. Recently, time-resolved X-ray magnetic circular dichroism (XMCD) with ultrafast XFEL pulses have made it possible to achieve an instantaneous view of atomic de-excitation. However, owing to the narrow bandwidth and coherence of XFELs, X-ray absorption spectroscopy (XAS) and XMCD are time- and effort-consuming for both machine scientists and users of XFELs. In this work, an efficient scheme using a broadband XFEL pulse and single-shot X-ray spectrometer is proposed, in which the XAS and XMCD measurements can be accomplished with the same machine conditions. An evolutionary multi-objective optimization algorithm is used to maximize the XFEL bandwidth offered by the Shanghai Soft X-ray FEL user facility without additional hardware. A numerical example using MnO is demonstrated, showing that, by using approximately 1000 consecutive XFEL shots with a central photon energy of 650 eV and full bandwidth of 4.4%, precise spectral measurements for XAS and XMCD can be achieved. Additional considerations related to single-shot XAS and XMCD are discussed.

3.
Sci Rep ; 8(1): 13363, 2018 Sep 06.
Artigo em Inglês | MEDLINE | ID: mdl-30190525

RESUMO

Recoil-proton track imaging (RPTI) is an attractive technique to optically record the tracks of recoil protons in scintillation gas by using realtime imaging devices. For the first time, its use as an online nuclear track detector for neutron spectrometry measurements (NSM) is explored. Based on the RPTI methodology for NSM, a very basic detector system is designed, consisting of the neutron-to-proton recoil system and proton track imaging system. Satisfactory performance of the RPTI neutron spectrometer has been examined with a series of Monte Carlo simulations. Moreover, using well-defined line-proton sources from a tandem accelerator, the capability of the detector for imaging proton tracks at the single-particle level in real time has been validated in preliminary experiments. From the clear single proton tracks in the images, the proton ranges were easily distinguished, and precise proton energy spectra were unfolded, laying a solid experimental foundation for the future implementation of NSM.

4.
Appl Radiat Isot ; 131: 67-70, 2018 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-29173810

RESUMO

This paper presents a Monte Carlo method to obtain the full energy peak efficiency (FEPE) curve for a High Purity Germanium (HPGe) detector, as it is difficult and time-consuming to measure the FEPE curve experimentally. The Geant4 simulation toolkit was adopted to establish a detector model since detector specifications provided by the nominal manufacturer are usually insufficient to calculate the accurate efficiency of a detector. Several detector parameters were optimized. FEPE curves for a given HPGe detectors over the energy range of 59.50-1836keV were obtained and showed good agreements with those measured experimentally. FEPE dependences on detector parameters and source-detector distances were investigated. A best agreement with experimental result was achieved for a certain detector geometry and source-detector distance.

5.
Oncol Lett ; 12(2): 1101-1106, 2016 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-27446401

RESUMO

Immunotherapy with tumor lysate-pulsed dendritic cells (DCs) is one of the breakthrough strategies used in the treatment of cancer. However, DC-based immunotherapies for osteosarcoma are limited. In the present study, preclinical studies of a C3H osteosarcoma mouse model (produced by subcutaneous injection of LM8 murine osteosarcoma cells) validated the concept that LM8 cell lysate-pulsed bone marrow-derived DCs may evoke a more potent immune response compared with DCs that have been matured using polyinosinic:polycytidylic acid (poly I:C). A cytotoxic T lymphocyte (CTL) response was established using two groups of C3H mice (n=9) with osteosarcoma; the treatment group consisted of LM8 cell lysate-pulsed DCs and the control group consisted of DCs matured using poly I:C. Each group was immunized with doses of 1×106 cells twice per week for 3 weeks. No difference in the expression of cluster of differentiation markers was identified in the two groups. DCs pulsed with LM8 cell lysate were associated with the increased induction of CTL activity. Serum interferon-γ levels were increased in mice that received DCs pulsed with LM8 cell lysate compared with that in the poly I:C-matured DC group (P<0.041). Serum interleukin-4 was decreased in the treatment group vs. the control group (P<0.033). A mixed lymphocyte reaction assay confirmed that LM8-DC immunotherapy may evoke a significant antigen-specific immune response in a mouse model. The present study reveals promising data on efficacy of a DC-based immunotherapy in the treatment of osteosarcoma; however, further clinical studies are warranted.

6.
Rev Sci Instrum ; 86(7): 073310, 2015 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-26233375

RESUMO

Rayleigh scattering poses an intrinsic limit for the transparency of organic liquid scintillators. This work focuses on the Rayleigh scattering length of linear alkylbenzene (LAB), which will be used as the solvent of the liquid scintillator in the central detector of the Jiangmen Underground Neutrino Observatory. We investigate the anisotropy of the Rayleigh scattering in LAB, showing that the resulting Rayleigh scattering length will be significantly shorter than reported before. Given the same overall light attenuation, this will result in a more efficient transmission of photons through the scintillator, increasing the amount of light collected by the photosensors and thereby the energy resolution of the detector.

7.
Guang Pu Xue Yu Guang Pu Fen Xi ; 34(3): 777-81, 2014 Mar.
Artigo em Chinês | MEDLINE | ID: mdl-25208411

RESUMO

This paper made use of three-dimensional fluorescence and ultraviolet-absorption spectrum to analyze the spectral characteristics of etroleum ether extract from Guizhou flue-cured tobacco and the overall characteristic spectral information of tobacco chemical substances were obtained. The three dimensional fluorescence and ultraviolet-visible absorption spectrum of each petroleum ether extract of flue-cured tobacco from different areas are generally similar, but their intensity is different. There have three characteristic peaks in three dimensional fluorescence spectra: I: Ex/Em = 297/326 nm, II: Ex/Em = 250/330 nm, III: Ex/Em = 225/336 nm respectively and meanwhile the order of these peaks intensity is I > III > II. The ultraviolet-visible absorption spectrum in 300-300 nm range presents four characteristic absorption peaks, whose maximum absorption wavelength are 329, 419, 445 and 419 nm respectively. Meanwhile, in accord with the relative intensity of characteristic peaks, it is known that there exist differences in the relative contents of the total chemical substances obtained from different flavor styles of the flue-cured tobacco. The clustering analysis results of three-dimensional fluorescence intensity score (D) and intensity ratio (R) show that in a certain range of distance coefficient, the flue-cured tobacco from different regions in Guizhou can be clearly divided into two classes "mildly sweet "and "alcohol sweet ". The classification can be well achieved in the smaller distance coefficient according to the ratio cluster of fluorescence intensity instead of the score cluster of fluorescence intensity. The method of three-dimensional fluorescence was better than that of ultraviolet-visible spectrometry in the matter of the clustering characteristic.


Assuntos
Odorantes/análise , Espectrometria de Fluorescência , Tabaco/classificação , Espectrofotometria Ultravioleta
8.
Zhongguo Dang Dai Er Ke Za Zhi ; 15(6): 431-4, 2013 Jun.
Artigo em Chinês | MEDLINE | ID: mdl-23791056

RESUMO

For the children who suffer trauma in earthquake, rehabilitation care aims to promote functional recovery, shorten hospital stay, and reduce the incidence of complications or disability by evidence-based, multidisciplinary, and comprehensive early rehabilitation intervention on the basis of first aid and clinical treatment. Children are likely to suffer traumatic brain injury, spinal cord injury, peripheral nerve injury, limb fracture, and amputation in the earthquake disaster, so the clinical rehabilitation care designed considering the characteristics of children should be provided immediately after acute phase of trauma to promote functional recovery.


Assuntos
Desastres , Terremotos , Ferimentos e Lesões/reabilitação , Amputação Traumática/reabilitação , Lesões Encefálicas/reabilitação , Criança , Humanos , Traumatismos dos Nervos Periféricos/reabilitação , Traumatismos da Medula Espinal/reabilitação
9.
Bull Environ Contam Toxicol ; 86(3): 263-7, 2011 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-21290099

RESUMO

Over the last two centuries, anthropogenic activities have increased the nitrogen amount in aquatic ecosystems, which has resulted in increased occurrences of blooms of cyanobacteria. This study investigated the effects of nitrite and the cyanobacterium Microcystis aeruginosa on population growth in the rotifer Brachionus calyciflorus. The rotifer was treated for 12 days with nitrite alone (medium containing 0, 3, 6, 10 mg NO (2)(-) -N L(-1)), M. aeruginosa alone (medium containing 0 mg NO(2)(-)-N L(-1) + 5.0 × 10(5) cell ml(-1) M. aeruginosa precultured at 0, 3, 6, 10 mg NO(2)(-)-N L(-1)), and nitrite in combination with M. aeruginosa (medium containing 3, 10 mg NO(2)(-)-N L(-1) + 5.0 × 10(5) cell ml(-1) M. aeruginosa precultured at corresponding nitrite concentrations). We observed that a nitrite concentration of 10 mg NO(2)(-)-N L(-1) markedly inhibited the growth of B. calyciflorus; however, rotifer growth declined slightly in the presence of M. aeruginosa precultured at 6 mg NO(2)(-)-N L(-1). Furthermore, reduced population growth of B. calyciflorus was observed when it was treated with both nitrite and M. aeruginosa compared to nitrite alone or M. aeruginosa alone. These results suggested that a high tolerance of B. calyciflorus to nitrite levels may be attributed to the absence of specific respiratory structures and pigments; and that the increased toxicity of nitrite in combination with M. aeruginosa may have been due to increased production of microcystin. It is also possible that nitrite and microcystin could act in a synergistic way in causing toxicity.


Assuntos
Microcistinas/toxicidade , Microcystis , Nitritos/toxicidade , Rotíferos/efeitos dos fármacos , Poluentes Químicos da Água/toxicidade , Animais , Sinergismo Farmacológico , Microcistinas/análise , Nitritos/análise , Densidade Demográfica , Rotíferos/crescimento & desenvolvimento , Poluentes Químicos da Água/análise
10.
Chemosphere ; 77(6): 733-8, 2009 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-19751947

RESUMO

The degradation of three polycyclic aromatic hydrocarbons (PAHs), phenanthrene, pyrene and benzo[a]pyrene in soils by Phanerochaete chrysosporium, and the enzyme activities of lignin peroxidase (LiP) and manganese peroxidase (MnP) produced during degradation, were analyzed. The results showed that the 19-d percentage degradation ranged from 72.77+/-1.39% to 25.50+/-3.41% for the three compounds, and the maximum LiP and MnP activities ranged from 0.16+/-0.005 to 0.05+/-0.002 U g(-1) and from 1.92+/-0.03 to 0.54+/-0.03 U g(-1), respectively. Degradation percentage and enzyme activities both exhibited inverse relationships with the octanol/water partition coefficient (K(ow)) of the compounds, indicating that LiP and MnP from P. chrysosporium may be the primary enzymes responsible for PAH degradation in soil. As the soil organic matter (SOM) content increased from 0.3% for Soil 1 to 19% for Soil 4, the 19-d degradation percentage of pyrene decreased from 66.20+/-2.72% to 32.42+/-1.05%, and correspondingly, the maximum of LiP and MnP activities increased from 0.05+/-0.002 to 1.78+/-0.15 U g(-1) and from 0.34+/-0.03 to 1.78+/-0.15 U g(-1), respectively. Hence, it is plausible to conclude that the P. chrysosporium appeared to degrade not only the PAHs with small molecular size but also the macromolecular SOM. When SOM differences are large, as in this study, SOM has greater influence on enzyme activity than low-level exotic pollutants.


Assuntos
Phanerochaete/enzimologia , Hidrocarbonetos Policíclicos Aromáticos/metabolismo , Poluentes do Solo/metabolismo , Solo , Benzopirenos/química , Benzopirenos/metabolismo , Biodegradação Ambiental , Peroxidases/metabolismo , Fenantrenos/química , Fenantrenos/metabolismo , Hidrocarbonetos Policíclicos Aromáticos/química , Pirenos/química , Pirenos/metabolismo , Microbiologia do Solo , Poluentes do Solo/química
11.
J Hazard Mater ; 167(1-3): 1170-7, 2009 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-19272704

RESUMO

Immobilization of cadmium (10 mg Cd per kilogram soil) in soil by bioaugmentation of a UV-mutated microorganism, Bacillus subtilis 38 accompanied with amendment of a bio-fertilizer, NovoGro was investigated using extractable cadmium (E-Cd) by DTPA. B. subtilis 38, the mutant with the strongest resistance against Cd, could bioaccumulate Cd four times greater than the original wild type. Single bioaugmentation of B. subtilis 38 (SB treatment) to soil however did not reduce E-Cd significantly, while the amendment of NovoGro (SN treatment) reduced E-Cd remarkably. Simultaneous application of B. subtilis 38 and NovoGro (SNB treatment) exhibited a synergetic effect compared to the single SB and SN treatment. The immobilization effect was significantly affected by temperature, soil moisture, and pH. It seems that the immobilization on Cd reached the maximum when environmental conditions favored the activity of microorganisms. Under the optimum conditions, after 90 days incubation, E-Cd was 3.34, 3.39, 2.25 and 0.87 mg kg(-1) in the control soil, SB, SN and SNB soils, respectively. NovoGro not only showed a great capacity for Cd adsorption, but also promoted the growth of B. subtilis 38. This study provides a potential cost-effective technique for in situ remediation of Cd contaminated soils with bioaugmentation.


Assuntos
Bacillus subtilis/crescimento & desenvolvimento , Bacillus subtilis/metabolismo , Cádmio/metabolismo , Poluentes do Solo/metabolismo , Bacillus subtilis/genética , Cádmio/isolamento & purificação , Concentração de Íons de Hidrogênio , Mutação/efeitos da radiação , Microbiologia do Solo , Poluentes do Solo/isolamento & purificação , Temperatura Ambiente , Raios Ultravioleta
12.
Chemistry ; 13(6): 1731-6, 2007.
Artigo em Inglês | MEDLINE | ID: mdl-17136780

RESUMO

A mesostructured silica/organic composite 1-MS, constructed from a rodlike micelle of amino acid amphiphile 1 that has a condensable head group and that can be used as a template, was found to be able to catalyze the acetalization of cyclohexanone, in ethanol at 25 degrees C (50% in 12 h), whereas no reaction took place with unfunctionalized mesoporous silica. In sharp contrast, hydrolytic removal of the C16 alkyl tail of immobilized 1 resulted in the complete disappearance of the catalytic activity, which suggests the importance of a hydrophobic inner domain for the admission of cyclohexanone. Unsupported peptide amphiphile 2, under identical conditions to those above, was inefficient for acetalization regardless of the absence (2% in 24 h) or presence of mesoporous silica (7% in 24 h). Reference composite 2-MS, which is a noncovalently immobilized peptidic micelle, was virtually inactive (1% in 24 h). These observations indicate the importance of covalent immobilization of the peptidic rod micelle for catalysis. Mesostructured silicate 3-MS hybridized with a nonpeptidic, ammonium ion amphiphile (3) showed a certain catalytic activity, but the yield (12% in 24 h) of the acetal was much lower than that achieved by using 1-MS as the catalyst. Amorphous silica with immobilized 1 on its surface was much less active than 1-MS for acetalization (5% in 24 h).


Assuntos
Cicloexanonas/química , Nanotecnologia/métodos , Peptídeos/química , Dióxido de Silício/química , Acetais/química , Catálise , Cátions , Interações Hidrofóbicas e Hidrofílicas , Micelas , Modelos Químicos , Tamanho da Partícula , Porosidade , Compostos de Amônio Quaternário/química , Fatores de Tempo
13.
J Am Chem Soc ; 128(29): 9387-93, 2006 Jul 26.
Artigo em Inglês | MEDLINE | ID: mdl-16848474

RESUMO

An important polysaccharide, amylose crystallizes as a regular single left-handed helix from a propanol, butanol, or iodine solution. However, its solution structure remains elusive because amylose does not form molecular solutions in these solvents, and standard spectroscopic techniques cannot be exploited to determine its structure. Using AFM, we forced individual amylose chains adsorbed to a surface to enter these poor solvents and carried out stretch-release measurements on them in solution. In this manner, we directly captured the formation of individual amylose helices induced by butanol and iodine. With an accuracy approaching that of X-ray diffraction on amylose crystals, we determined that the pitch of the helix in solution is 1.3 angstroms/ring. We also directly measured the force driving the formation of the helix in solution to be 50 pN. SMD simulations in explicit butanol reproduced the AFM-measured force-extension curves and revealed that the long plateau feature is caused by the rupture of O(2)n-O(6)(n+6) and O(3)n-O(6)(n+6) hydrogen bonds and by the unwinding of the helix. We also found that amylose helices formed in iodine solution are more compliant and hysteretic as compared to helices in butanol, which extend/relax reversibly. In iodine solution, the formation of the helix is inhibited by force and limited by the slow kinetics of the amylose-iodine complex. By forcing individual molecules into poor solvents and performing force spectroscopy measurements in solution, our AFM approach uniquely supplements X-ray diffraction and NMR methods for investigating solution conformations of insoluble biopolymers.


Assuntos
Amilose/química , Análise Espectral/métodos , Amilose/análogos & derivados , Butanóis/química , Configuração de Carboidratos , Iodo/química , Estrutura Molecular , Soluções , Solventes/química , Água/química
14.
J Am Chem Soc ; 128(17): 5596-7, 2006 May 03.
Artigo em Inglês | MEDLINE | ID: mdl-16637601

RESUMO

The nanomechanical properties of beta-galactan, a 1 --> 4 linked beta-d-galactose polysaccharide, were investigated with AFM-based single-molecule force spectroscopy. AFM captured a unique plateau at 640 pN in the force spectrogram of beta-galactan, which is significantly different than the plateau at 280 pN in the force spectrogram of amylose. Thus, our results demonstrate that force spectroscopy is able to discriminate between sugar isomers in which axial and equatorial bonds at C1 and C4 are swapped.


Assuntos
Carboidratos/química , Análise Espectral/métodos , Sequência de Carboidratos , Isomerismo
16.
Biophys J ; 87(3): 1456-65, 2004 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-15345528

RESUMO

Recent atomic force microscopy stretching measurements of single polysaccharide molecules suggest that their elasticity is governed by force-induced conformational transitions of the pyranose ring. However, the mechanism of these transitions and the mechanics of the pyranose ring are not fully understood. Here we use steered molecular dynamics simulations of the stretching process to unravel the mechanism of forced conformational transitions in 1,6 linked polysaccharides. In contrast to most sugars, 1,6 linked polysaccharides have an extra bond in their inter-residue linkage, C5-C6, around which restricted rotations occur and this additional degree of freedom increases the mechanical complexity of these polymers. By comparing the computational results with the atomic force microscopy data we determine that forced rotations around the C5-C6 bond have a significant and different impact on the elasticity of alpha- and beta-linked polysaccharides. Beta-linkages of a polysaccharide pustulan force the rotation around the C5-C6 bonds and produce a Hookean-like elasticity but do not affect the conformation of the pyranose rings. However, alpha-linkages of dextran induce compound conformational transitions that include simultaneous rotations around the C5-C6 bonds and chair-boat transitions of the pyranose rings. These previously not-recognized transitions are responsible for the characteristic plateau in the force-extension relationship of dextran.


Assuntos
Configuração de Carboidratos , Microscopia de Força Atômica/métodos , Polissacarídeos/química , Sequência de Carboidratos , Carboidratos/química , Carbono/química , Simulação por Computador , Dextranos/química , Glucose/química , Líquens/metabolismo , Dados de Sequência Molecular , Polissacarídeos/ultraestrutura , Fatores de Tempo
17.
J Am Chem Soc ; 126(20): 6218-9, 2004 May 26.
Artigo em Inglês | MEDLINE | ID: mdl-15149204

RESUMO

Single molecules of beta-1 --> 6-linked d-glucose polysaccharides, when stretched in an atomic force microscope, display a hookean-like elasticity unusual for polymers. High-level ab initio calculations and microsecond-scale molecular dynamics simulations reveal that this elasticity is governed by force-induced rotations of the exocyclic group on the glucopyranose rings from their short and less energetic gt and gg conformations to the extended and high-energy tg state. These observations indicate that a simple stretching of 1 --> 6-linked glucose polysaccharides provide a unique means to control glucopyranose rotamer populations.


Assuntos
Glucose/química , Nanotecnologia , Álcoois , Configuração de Carboidratos , Polissacarídeos/química
18.
J Am Chem Soc ; 126(4): 988-9, 2004 Feb 04.
Artigo em Inglês | MEDLINE | ID: mdl-14746444

RESUMO

Use of a dialkoxysilane-containing, condensable alanine amphiphile with a cleavable hexadecyl ester tail (1) as a "lizard" template for sol-gel synthesis results in the formation of a mesoporous silicate (2) whose channels are filled with an organic group of the template. Treatment of 2 with aqueous HCl allows selective cleavage of the ester moiety to leave nanochannels (3) whose surface is densely covered with alanine-CO2H. According to XRD and TEM, 2, on conversion into 3, can preserve its regular hexagonal structure. 3 displays a clear N2 adsorption/desorption isotherm with a BET surface area of 536 m2 g-1. 3 can also adsorb a basic guest such as NH3 up to 0.7 mmol g-1, which is 7 times greater than that observed for mesoporous silica obtained by calcination of 2.

19.
Ying Yong Sheng Tai Xue Bao ; 14(6): 982-4, 2003 Jun.
Artigo em Chinês | MEDLINE | ID: mdl-12974010

RESUMO

This paper deals with the impact of a complex pollution system composed of a very toxic carbamate pesticide, aldicarb and the widely used anionic surfactant, sodium dodecylbenzenesulfonate(SDBS), on DNA of zebrafish (Brachydanio rerio) embryo. The results indicated that DNA damage caused by aldicarb became more serious with its increasing concentration, but single-strand break caused by aldicarb in low concentration and short time could be repaired, and high concentration led to double-strand break which was difficult to repaire. SDBS in certain concentration (20 mg.L-1) could reduce the toxicity of aldicarb in the complex pollution system.


Assuntos
Aldicarb/toxicidade , Benzenossulfonatos/toxicidade , Dano ao DNA , Inseticidas/toxicidade , Tensoativos/toxicidade , Peixe-Zebra/embriologia , Animais , Relação Dose-Resposta a Droga , Embrião não Mamífero/efeitos dos fármacos
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