Conductance of Graphene Nanoribbon Junctions and the Tight Binding Model.

Planar carbon-based electronic devices, including metal/semiconductor junctions, transistors and interconnects, can now be formed from patterned sheets of graphene. Most simulations of charge transport within graphene-based electronic devices assume an energy band structure based on a nearest-neighbour tight binding analysis. In this paper, the energy band structure and conductance of graphene nanoribbons and metal/semiconductor junctions are obtained using a third nearest-neighbour tight binding analysis in conjunction with an efficient nonequilibrium Green's function formalism. We find significant differences in both the energy band structure and conductance obtained with the two approximations.

Multiplexing of polarization-maintaining photonic crystal fiber based Sagnac interferometric sensors.

Three multiplexing schemes are presented for polarization-maintaining photonic crystal fiber based Sagnac interferometric sensors. The first technique is wavelength division multiplexing using coarse wavelength division multiplexers (CWDMs) to distinguish signals from each multiplexed sensor in different wavelength channels. The other two schemes are to multiplex sensors in series along a single fiber link and in parallel by using fiber-optic couplers. While for the CWDM scheme, the multiplexed sensing signal can be obtained by direct measurement; for the other two multiplexing techniques, the sensing signal is more complex and cannot be easily demultiplexed. Thus, some signal processing methods are required. In this regard, two mathematical transformations, namely the discrete wavelet transform and Fourier transform, have been independently and successfully implemented into these two schemes. The operating principles, experimental setup, and overall performance are discussed.

A systematic review of stapled hemorrhoidectomy.

HYPOTHESIS: Use of circular stapled hemorrhoidectomy will result in the same or improved safety and efficacy outcomes as those of the conventional methods for hemorrhoidectomy in patients with hemorrhoids. DATA SOURCES: Studies on stapled hemorrhoidectomy were identified using PREMEDLINE and MEDLINE (June 1966-June 2001), EMBASE (January 1980-June 2001), Current Contents (June 1993-June 2001), Ovid HEALTHSTAR (January 1975-June 2001), the National Institutes of Health Clinical Trials database (searched June 13, 2001), and The National Coordinating Centre for Health Technology Assessment database (searched June 14, 2001). The search terms were as follows: haemorrhoid* and (stapl* or convent*) or hemorrhoid* and (stapl* or convent*). The Cochrane Library (2001, issue 2) was searched using the search terms haemorrhoid* or hemorrhoid*. STUDY SELECTION: Articles detailing randomized controlled trials were included if they compared circular stapled with conventional hemorrhoidectomy and provided relevant safety and efficacy outcome information. DATA EXTRACTION: Data from all included studies were extracted using standardized data extraction tables that were developed a priori. In addition, the randomized controlled trials were examined with respect to the adequacy of allocation concealment, handling of those unavailable for follow-up, and any other aspect of the study design or execution that may have introduced bias. DATA SYNTHESIS: Seven randomized controlled trials met the inclusion criteria. A meta-analysis was conducted when the studies had comparable outcomes, inclusion criteria, and follow-up. There was reasonably clear evidence in favor of the stapled procedure for bleeding at 2 weeks (relative risk, 0.55; 95% confidence interval, 0.37-0.82) and length of hospital stay (weighted mean difference, -0.89 days; 95% confidence interval, -1.42 to -0.36). Other less robust results in favor of the stapled hemorrhoidectomy related to pain, bleeding, anal discharge, wound healing, tenderness to per rectal examination, incontinence scores, earlier return of bowel function, analgesic requirement, and resumption of normal activities. One trial showed that prolapse occurred at significantly higher rates in the stapled hemorrhoidectomy group. However, the outcomes were poorly reported and generally showed statistically significant heterogeneity. CONCLUSIONS: Stapled hemorrhoidectomy may be at least as safe as conventional hemorrhoidal surgical techniques. However, the efficacy of the stapled procedure compared with the conventional techniques could not be determined. More rigorous studies with longer follow-up periods and larger sample sizes need to be conducted.

Effects of morning phototherapy on circadian markers in seasonal affective disorder.

BACKGROUND: The suppression of melatonin by light at 00.30 hours has been shown to be greater in winter than in summer on patients with seasonal affective disorder (SAD) but not in matched normal controls. METHOD: In this study 12 patients with SAD and 12 matched normal controls were exposed to morning light therapy in the winter. Melatonin profiles and sensitivity to light were measured before and after treatment. RESULTS: The SAD but not the normal group showed a phase advance of melatonin rhythms in response to phototherapy. There was an association between phase position and phase shift in the SAD but not in the normal group. CONCLUSIONS: There may be instability of circadian rhythms in SAD mediated by a high-amplitude phase response curve, rather than a fixed phase abnormality as had been previously suggested. This instability may be secondary to impaired serotoninergic function in the afferent pathways to the suprachiasmatic nuclei.

Surgical management of cutaneous infection caused by atypical mycobacteria after penetrating injury: the hidden dangers of horticulture.

We identified two patients in a 12-month period who presented with cutaneous infection and secondary lymph node involvement from atypical mycobacterial infection after minor gardening injuries. One patient had a coinfection with Nocardia asteroides. Both patients required multiple surgical interventions, despite appropriate antibiotic therapy, before resolution of the disease. The course of the infection was characterized by chronic relapses with complete healing at 12 to 18 months after the original injury. The identification and management of this clinical problem are reviewed.

Case report: giant choledochal cyst.

We report an adult female with a rare giant choledochal cyst. The patient presented following a normal pregnancy with the classical triad of an abdominal mass associated with jaundice and right upper quadrant abdominal pain. The cyst was excised using an intramural technique and biliary reconstruction achieved with a Roux-en-Y hepaticojejunostomy. Our patient has remained well with no evidence of malignancy over a 12 year review period. The aetiology and current management of this condition are discussed.

Effect of fluoxetine on melatonin in patients with seasonal affective disorder and matched controls.

BACKGROUND: The aim was to investigate the secretion profile of melatonin and seasonal affective disorder before and after treatment with fluoxetine. METHOD: A six-week case-controlled study with repeated overnight blood sampling was conducted. Ten patients fulfilling the criteria for major depressive disorder, seasonal type, with a 29-item Hamilton Depression Rating Scale (HDRS) score of at least 20 were compared with ten age- and sex-matched healthy controls in a clinical laboratory. The effects of fluoxetine (20 mg/day) on the HDRS and melatonin concentration were measured. RESULTS: Fluoxetine significantly reduced melatonin levels in both groups. There was no significant difference in melatonin secretion between the groups. CONCLUSIONS: The effect of fluoxetine differs from tricyclics and fluvoxamine, both of which increase melatonin.

Closure of double-barrel colostomy with stapling instruments.

A technique for closure of double-barrel colostomies using the GIA and TA 90 stapling instruments is described. The method is straight forward and time saving, and represents a further application of automatic staplers to gastro-intestinal surgery.