8 research outputs found
Electronic Structure of Carbon Nanotube Ropes
We present a tight binding theory to analyze the motion of electrons between
carbon nanotubes bundled into a carbon nanotube rope. The theory is developed
starting from a description of the propagating Bloch waves on ideal tubes, and
the effects of intertube motion are treated perturbatively in this basis.
Expressions for the interwall tunneling amplitudes between states on
neighboring tubes are derived which show the dependence on chiral angles and
intratube crystal momenta. We find that conservation of crystal momentum along
the tube direction suppresses interwall coherence in a carbon nanorope
containing tubes with random chiralities. Numerical calculations are presented
which indicate that electronic states in a rope are localized in the transverse
direction with a coherence length corresponding to a tube diameter.Comment: 15 pages, 10 eps figure
Efeito da Suplementação de Lipídios na Ração sobre a Produção de Ácido Linoléico Conjugado (CLA) e a Composição da Gordura do Leite de Vacas
Laparoscopic Intragastric Approach for Stromal Tumours Located at the Posterior Gastric Wall
Surgical resection is indicated for gastrointestinal stromal tumour (GIST). Laparoscopic resection with clear margins is effective in gastric GIST. However, GIST located in the posterior gastric wall with close proximity to the oesophagogastric junction poses special challenges. Laparoscopic intragastric resection offers a new approach to the management of these tumours. The surgical technique, our experience and a summary of the literature are presented
Non-attendance and effective equity of access at four public specialist outpatient centers in Hong Kong
This study tests whether socio-economic status (SES), at either the individual or ecologic levels, exerts a direct impact on non-attendance or an indirect impact on attendance through longer waiting time for appointments and/or doctor-shopping behavior at four public specialist outpatient centers in Hong Kong. We collected information through three main sources, namely patients' referral letters, telephone interviews with both open- and closed-ended questions (e.g. doctor-shopping data) and hospital administrative databases from a total of 6495 attenders and non-attenders enrolled from July 2000 through October 2001. Individual-level SES was measured by education, occupation and monthly household income. Tertiary planning unit (TPU)-level SES data consisted of proportion unemployed, proportion with tertiary education, median income and Gini coefficient. Direct effects of SES on non-attendance were examined by logistic regression. Indirect contributions mediated through waiting time and doctor-shopping were analyzed by structural equation modeling. We found that SES, at the individual or ecologic level, did not exert a direct effect on non-attendance. Instead, TPU-level SES contributed positively to waiting time ([beta]=0.06±0.03, p=0.048), i.e. worse-off neighborhoods (and those with greater income inequality) had a shorter waiting time. Individual-level SES was also directly associated with the likelihood of doctor-shopping ([beta]=0.16±0.02, pNon-attendance Horizontal equity Socio-economic status Hong Kong Access to care