Effects of thermal annealing on the structural and optical properties of carbon-implanted SiO2.

Amorphous carbon (a-C) nanoclusters were synthesized by the implantation of carbon ions (C-) into thermally grown silicon dioxide film (-500 nm thick) on a Si (100) wafer and processed by high temperature thermal annealing. The carbon ions were implanted with an energy of 70 keV at a fluence of 5 x 10(17) atoms/cm2. The implanted samples were annealed at 1100 degrees C for different time periods in a gas mixture of 96% Ar+4% H2. Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and High Resolution Transmission Electron Microscopy (HRTEM) were used to study the structural properties of both the as-implanted and annealed samples. HRTEM reveals the formation of nanostructures in the annealed samples. The Raman spectroscopy also confirms the formation of carbon nano-clusters in the samples annealed for 10 min, 30 min, 60 min and 90 min. No Raman features originating from the carbon-clusters are observed for the sample annealed further to 120 min, indicating a complete loss of implanted carbon from the SiO2 layer. The loss of the implanted carbon in the 120 min annealed sample from the SiO2 layer was also observed in the XPS depth profile measurements. Room temperature photoluminescence (PL) spectroscopy revealed visible emissions from the samples pointing to carbon ion induced defects as the origin of a broad 2.0-2.4 eV band, and the intrinsic defects in SiO2 as the possible origin of the -2.9 eV bands. In low temperature photoluminescence spectra, two sharp and intense photoluminescence lines at -3.31 eV and -3.34 eV appear for the samples annealed for 90 min and 120 min, whereas no such bands are observed in the samples annealed for 10 min, 30 min, and 60 min. The Si nano-clusters forming at the Si-SiO2 interface could be the origin of these intense peaks.

Anomalous formation of the circulus arteriosus and its clinico-anatomical significance.

Circulus arteriosus (Circle of Willis) is an anastomotic ring which unites the internal carotid and vertebrobasilar systems. It slows down the blood before it reaches the brain and helps in collateral circulation. Anatomic study reveals the variation in the pattern and calibre of vessels which make up the circulus arteriosus. The greatest variation in calibre occurs in the posterior communicating artery. The posterior cerebral artery is divided into three portions by the posterior communicating artery; these are- P1, P2, and P3. Three basic configurations of the posterior communicating artery has been described; foetal, transitional and adult. In foetal configuration: the diameter of the P1 segment of posterior cerebral artery is less than the diameter of posterior communicating artery so that the blood supply to the occipital lobes is mainly via the internal carotid arteries. Thirty five circulus arteriosus of the formalin embalmed brains were studied during the period of three years. Posterior cerebral and posterior communicating arteries were traced from their origins to terminations. It is revealed that in 8.6% of cases the formation of the circulus arteriosus was anomalous. The calibre of the pre communicating (P1) segment of posterior cerebral artery was smaller than the posterior communicating artery. It appeared that the posterior cerebral artery is the continuation of posterior communicating artery, thus the branch of the internal carotid artery. Anomalies of the formation of circulus arteriosus leads to stroke. The neurosurgical importance of this study lies during the exposure of the region for different purposes. Knowledge of the vascular variations will increase the success of the procedure.

Study on the variation of branching pattern of arch of aorta in Nepalese.

The variations of vessels arising from the aortic arch are numerous. The purpose of this study is the description of the variations on the branching pattern of arch of aorta, in order to offer useful data to anatomists, radiologists, vascular surgeons, neck and thorax surgeons in Nepalese subjects, and relating it with embryological basis. In this investigation, branching patterns of arch of aorta were studied in 85 cases of Nepali origin. Variations in the anatomical arrangements of the branches of arch of aorta in the Nepali population were as par with other populations of the world. Variations on the branching pattern of the arch of aorta were found in 17 cadavers (20.0%) of elderly Nepalese. The accurate information on this is vital for vascular surgery in the thorax, head and neck regions. Although, the variations are usually asymptomatic, they may cause dyspnea, dysphagia, intermittent claudication, misinterpretation ofradiological examinations and complications during neck and thorax surgery. These observations are precious while invading the arch of aorta and its branches by instruments, as all areas are susceptible to surgical attack.

Study on the supernumerary heads of biceps brachii muscle in Nepalese.

Biceps brachii is a double headed muscle. In terms of number and morphology of its head, it is one of the most variable muscles in the human body. Most common variation is third head, but four, five or even seven heads have been reported. In this study, 32 arms from 16 Nepalese cadavers were studied; supernumerary heads of biceps brachii were observed in 12.5% of 32 arms. Among these three headed biceps brachii was presented on 6.2% and the four headed was also on the same percentage. All the variations were in the right sided arms of males. Third heads of all cases originated from the medial border and adjoining anteromedial surface of humerus distal to the insertion of coracobrachialis thus have been classified as inferomedial humeral head. Fourth head of the four headed biceps brachii originated from the anterior border of humerus nearby the insertion of deltoid muscle. These supernumerary heads might be significant in producing the strong flexion as well as supination of forearm. They may cause compression of neurovascular structures because of their close relationship to brachial artery and median nerve. Variant biceps brachii may confuse a surgeon who performs procedures on the arm and may lead to iatrogenic injuries. The surgeons and traumatologists have to keep such muscular variations in mind.

Congenital anomaly of left renal vein.

Double left renal vein is a rare venous anomaly. In 6.5% of cases double left renal vein, one in front (preaortic) and another behind the abdominal aorta (retroaortic) has been reported. The development of renal vessels is very complicated. There are extensive changes which occur in subcardinal, supracardinal and sacrocardinal veins during development that may lead to congenital venous anomalies. Here, we report a case of congenital venous anomaly of persisting retroaortic left renal vein.

Unusual variation in musculocutaneous nerves in Nepalese.

BACKGROUND: Variations in origin, course, branching pattern, termination and connections of the musculocutaneous nerve in the arm are not as uncommon as was once thought. Variational study of nerve in Nepalese is very less and can be of surgical-clinical importance. This opinion led us to performing this study. OBJECTIVES: The aim of this study was to a study in Nepalese which could be important for clinical investigation and the surgical treatment of peripheral nerve injury. MATERIALS AND METHODS: This study was carried out in Manipal College of medical sciences (MCOMS). Dissection of formalised 16 cadavers (n=32 upper limbs) were carried out using normal dissection kit with the help of standard dissection manual in two and half years. RESULTS: The study revealed the variation in course, branching pattern and termination of musculocutaneous nerve in 6.25% of cases unilaterally on the right side. No statistically significant differences by gender and side were observed. CONCLUSION: This present study provides the evidence of variation of musculocutaneous nerve in Nepalese. The knowledge of the anatomical variations of the peripheral nerve system can help explain an incomprehensible clinical sign.