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1.
Phys Rev Lett ; 102(19): 196102, 2009 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-19518977

RESUMO

We use scanning tunneling spectroscopy to explore the quantum well states in the Pb islands grown on a Cu(111) surface. Our observation demonstrates that the empty quantum well states, whose energy levels lie beyond 1.2 eV above the Fermi level, are significantly affected by the image potential. As the quantum number increases, the energy separation between adjacent states is shrinking rather than widening, contrary to the prediction for a square potential well. By simply introducing a phase factor to reckon the effect of the image potential, the shrinking behavior of the energy separation can be reasonably explained with the phase accumulation model. The model also reveals that there exists a quantum regime above the Pb surface in which the image potential is vanished. Moreover, the quasi-image-potential state in the tunneling gap is quenched because of the existence of the quantum well states.

2.
Eur J Nucl Med Mol Imaging ; 34(8): 1291-301, 2007 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-17334765

RESUMO

PURPOSE: Currently available diagnostic techniques can be unreliable in the diagnosis of delayed fracture healing in certain clinical situations, which can lead to increased complication rates and costs to the health care system. This study sought to determine the utility of positron emission tomography (PET) scanning with (18)F-fluoride ion, which localizes in regions of high osteoblastic activity, and (18)F-fluorodeoxyglucose (FDG), an indicator of cellular glucose metabolism, in assessing bone healing in a rat femur fracture model. METHODS: Fractures were created in the femurs of immunocompetent rats. Animals in group I had a fracture produced via a manual three-point bending technique. Group II animals underwent a femoral osteotomy with placement of a 2-mm silastic spacer at the fracture site. Fracture healing was assessed with plain radiographs, (18)F-fluoride, and (18)F-FDG PET scans at 1, 2, 3, and 4-week time points after surgery. Femoral specimens were harvested for histologic analysis and manual testing of torsional and bending strength 4 weeks after surgery. RESULTS: All fractures in group I revealed abundant callus formation and bone healing, while none of the nonunion femurs were healed via assessment with manual palpation, radiographic, and histologic evaluation at the 4-week time point. (18)F-fluoride PET images of group I femurs at successive 1-week intervals revealed progressively increased signal uptake at the union site during fracture repair. In contrast, minimal tracer uptake was seen at the fracture sites in group II at all time points after surgery. Data analysis revealed statistically significant differences in mean signal intensity between groups I and II at each weekly interval. No significant differences between the two groups were seen using (18)F-FDG PET imaging at any time point. CONCLUSION: This study suggests that (18)F-fluoride PET imaging, which is an indicator of osteoblastic activity in vivo, can identify fracture nonunions at an early time point and may have a role in the assessment of longitudinal fracture healing. PET scans using (18)F-FDG were not helpful in differentiating metabolic activity between successful and delayed bone healing.


Assuntos
Fraturas do Fêmur/diagnóstico por imagem , Fraturas do Fêmur/patologia , Fêmur/diagnóstico por imagem , Fêmur/patologia , Fluoretos , Radioisótopos de Flúor , Fluordesoxiglucose F18 , Tomografia por Emissão de Pósitrons/métodos , Animais , Calibragem , Fluoretos/química , Consolidação da Fratura , Processamento de Imagem Assistida por Computador/métodos , Tomografia por Emissão de Pósitrons/instrumentação , Ratos , Fatores de Tempo
3.
Bone ; 40(4): 931-8, 2007 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-17236835

RESUMO

The objective of the present study was to assess the ability of bone marrow cells expressing BMP-2 created via lentiviral gene transfer to heal a critical sized femoral defect in a rat model. Femoral defects in Lewis rats were implanted with 5x10(6) rat bone marrow stromal cells (RBMSC) transduced with a lentiviral vector containing either the BMP-2 gene (Group I), the enhanced green fluorescent protein (LV-GFP) gene (Group IV), or RBMSC alone (Group V). We also included femoral defects that were treated with BMP-2-producing RBMSC transduced with lentivirus, 8 weeks after infection (Group III), and a group with 1x10(6) RBMSC transduced with a lentiviral vector with the BMP-2 gene (Group II). All defects (10/10) treated in Group I healed at 8 weeks compared with none of the femora in the control groups (Groups IV and V). In Group II, only one out of 10 femora healed. In Group III, 5 out of 10 femora healed. Significantly higher amounts of in vitro BMP-2 protein production were detected in Groups I, II, and III when compared to that of the control groups (p<0.05). Histomorphometric analysis revealed significantly greater total bone volume in defects in Group I and III when compared to control specimens (p<0.003). Biomechanical testing revealed no significant differences in the healed defects in Groups I and III when compared to intact, nonoperated femora with respect to peak torque and torque to failure. Our results indicate that BMP-2-producing RBMSC created through lentiviral gene transfer have the capability of inducing long-term protein production in vitro and producing substantial new bone formation in vivo.


Assuntos
Proteínas Morfogenéticas Ósseas/genética , Consolidação da Fratura/genética , Técnicas de Transferência de Genes , Fator de Crescimento Transformador beta/genética , Animais , Fenômenos Biomecânicos , Células da Medula Óssea/metabolismo , Transplante de Medula Óssea , Proteína Morfogenética Óssea 2 , Proteínas Morfogenéticas Ósseas/biossíntese , Feminino , Fêmur/lesões , Fêmur/patologia , Fêmur/fisiologia , Expressão Gênica , Proteínas de Fluorescência Verde/biossíntese , Proteínas de Fluorescência Verde/genética , Técnicas In Vitro , Lentivirus/genética , Ratos , Ratos Endogâmicos Lew , Proteínas Recombinantes/biossíntese , Proteínas Recombinantes/genética , Células Estromais/metabolismo , Células Estromais/transplante , Fator de Crescimento Transformador beta/biossíntese
4.
Philos Trans A Math Phys Eng Sci ; 362(1823): 2127-42, 2004 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-15370474

RESUMO

Research has demonstrated that the structure and properties of a nanoscale system are inextricably linked. The advent of nanoscale research in 1991 relied upon nanoscale material production through random formation techniques, such as arc discharge, and the inherent properties and morphology of the system were therefore difficult to control. This article reviews some of the methods and ideas that have developed since the inception of nanotechnology, leading to fine control over the morphology of nanoscale systems and highlighting some interesting nanoscale architecture.


Assuntos
Materiais Revestidos Biocompatíveis/química , Cristalização/métodos , Instalação Elétrica , Eletroquímica/métodos , Nanotecnologia/métodos , Nanotubos de Carbono , Cristalização/tendências , Eletroquímica/instrumentação , Eletroquímica/tendências , Desenho de Equipamento , Substâncias Macromoleculares , Conformação Molecular , Nanotecnologia/instrumentação , Nanotecnologia/tendências , Nanotubos/química , Nanotubos/ultraestrutura
5.
Environ Pollut ; 112(2): 145-52, 2001.
Artigo em Inglês | MEDLINE | ID: mdl-11234530

RESUMO

The amounts of organotin compounds such as butyltins [sigma BTs: tributyl- (TBT), dibutyl- (DBT), monobutyl- (MBT)] and phenyltins [sigma PhTs: triphenyl- (TPhT), diphenyl- (DPhT) and monophenyl- (MPhT)] in rock shells, Thais clavigera, from the northern (Shiangsan), central (Lukang) and southern (Chiku) Taiwan oyster mariculture areas varied with season and location. High values of sigma BTs (mainly TBT) and low values of sigma PhTs (mainly TPhT) were found during winter (January 1999) at Shiangsan, while high amounts of sigma PhTs (mainly TPhT) and low sigma BTs (mainly TBT) were found during summer (August 1998) at Lukang. The snails were also affected by imposex. Imposex at Shiangsan, Lukang and Chiku increased from 67.1, 59.3 and 36.7% in summer to 100, 100 and 80% in winter, respectively. Relative penis size indices similar trend at Chiku site. No male displayed rock shells were found at Shiangsan and Lukang in winter. Linear correlations between pseudopenis length versus TBT (r = 0.7655, P < 0.001), DBT (r = 0.4253, P < 0.05), MBT (r = 0.5865, P < 0.01) and TPhT (r = -0.6160, P < 0.01) were obtained significant. Among 200 samples, significant positive correlations between length (pseudopenis/shell) ratio of female versus TBT (r = 0.6944, P < 0.005) and sigma BTs (r = 0.6413, r < 0.01) were also observed. The weak correlations between length (pseudopenis/shell) ratio of female versus DBT (r = 0.3085) and MBT (r = 0.4240, P < 0.1) and TPhT (-0.4917, P < 0.05; negative correlation) could indicate that DBT, MBT and TPhT have little or no effect on the development of imposex in rock shells.


Assuntos
Aquicultura , Genitália/anormalidades , Moluscos/fisiologia , Compostos Orgânicos de Estanho/efeitos adversos , Poluentes Químicos da Água/efeitos adversos , Animais , Genitália/efeitos dos fármacos , Estações do Ano
6.
Chem Commun (Camb) ; (21): 2184-5, 2001 Nov 07.
Artigo em Inglês | MEDLINE | ID: mdl-12240103

RESUMO

NbS2 nanotubes/rods have been generated successfully employing carbon nanotube template promoted growth; high resolution transmission electron microscopy, coupled with EDX analysis, confirm the template effect and existence of NbS2 tube structures.

7.
Chemphyschem ; 2(10): 620-3, 2001 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-23686882

RESUMO

An insulated nanotube wire is formed by the binary phase of layered tungsten disulphide and carbon nanotubes (shown in the HRTEM image) generated by the sulphidization of tungsten oxide coated multiwalled carbon nanotubes at 900 °C. Thermogravimetric analysis shows that the tungsten disulphide coat acts as an antioxidant.

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