Efficient passivation of n-type and p-type silicon surface defects by hydrogen sulfide gas reaction

An efficient surface defect passivation is observed by reacting clean Si in a dilute hydrogen sulfide-argon gas mixture (<5% H₂S in Ar) for both n-type and p-type Si wafers with planar and textured surfaces. Surface recombination velocities of 1.5 and 8 cm s^-1are achieved on n-type and p-type Si wafers, respectively, at an optimum reaction temperature of 550 °C that are comparable to the best surface passivation quality used in high efficiency Si solar cells. Surface chemical analysis using x-ray photoelectron spectroscopy shows that sulfur is primarily bonded in a sulfide environment, and synchrotron-based soft x-ray emission spectroscopy of the adsorbed sulfur atoms suggests the formation of S-Si bonds. The sulfur surface passivation layer is unstable in air, attributed to surface oxide formation and a simultaneous decrease of sulfide bonds. However, the passivation can be stabilized by a low-temperature (300 °C) deposited amorphous silicon nitride (a-Si:N_X:H) capping layer.

Refractory hypercalcaemia secondary to localised gastrointestinal stromal tumour

Gastrointestinal stromal tumours are a rare form of intra-abdominal neoplasm derived from mesenchymal tissue, typically presenting with abdominal pain, anaemia or bleeding into the bowel or abdominal cavity. Hypercalcaemia is an unusual complication, having been documented in only seven previous patients, all of whom had advanced metastatic disease. We present a case of treatment-resistant hypercalcaemia in a patient with non-metastatic gastrointestinal stromal tumour, which resolved following excision of the tumour.

Optimization Of Porous Silicon Reflectance For Solar Cell Applications

The potential use of porous silicon as an antireflective coating on solar cells has recently been recognized. This study investigates the effect of current density, anodization time, and surface conditions on the reflectance of porous silicon which was fabricated by anodizing (100) float zone single crystal Si wafers. The wafers were coated on one side with Al prior to anodization, and a HFbased solution was used as the electrolyte. Current densities of 5 – 100 mA/cm2 were used to anodize both polished and unpolished wafers over time intervals ranging from 2sec - 30 minutes. Reflectance properties were tested over the 400 - 1100 nm range, and minimum reflectances of 3 – 5% were achieved. The reflectance of the best porous Si sample normalized with respect to the sun's spectrum compares favorably with the reflectance of a double layer ZnS/ MgF2 with prior texturing.

Acute superior vena cava obstruction following Ivor-Lewis oesophagectomy

A 53 year old man developed upper body swelling, hypotension, anuria and a metabolic acidosis within 24 h following an Ivor-Lewis oesophagectomy. His co-morbidities included hypertension, hypercholesterolaemia, ischaemic heart disease and he was a smoker. He did not have radiotherapy but had received neo-adjuvant chemotherapy through an in-dwelling right subclavian central venous catheter. Azygous vein ligation during oesophagectomy resulted in acute upper body venous hypertension and signs of hypovolaemic shock which were attributed to undiagnosed thrombotic occlusion of the superior vena cava. The patient was anticoagulated and made a full recovery after a period of stay in intensive care.

Effect of understaging of early oesophageal tumors on treatment

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Background: Early and node negative oesophageal cancers do not undergo chemotherapy as it is felt that as the risk of lymph node metastasis is small, early operative intervention is considered the best option. We analysed a prospective database in a tertiary referral centre to see, with current preoperative staging modalities, if a significant number of patients were under staged and hence under treated preoperatively. Methods: Four hundred and fifteen patients underwent esophagectomies for cancer in our unit between March 2000 and December 2006. 117 were preoperatively staged as either T1/T2 N0. Pre-operative staging was by gastroscopy, endoscopic ultrasound (EUS), CT scan and PET-CT. These were discussed in a multi-disciplinary meeting and as per current evidence did not undergo preoperative chemotherapy. Results: 115 patients were analysed as two were excluded. Preoperatively there were 35 T0N0, 30 T1N0, and 50 T2N0. There were 42 (36.5%) patients who were under staged utilising the standard preoperative staging protocol. These were preoperatively staged as T0N0 –2, T1N0 –6, T2N0 –34. 6 did not have EUS, only 4 had a PET- CT and 1 had a staging laparoscopy. Gastroscopy, CT scan and EUS was the staging protocol in 87%. Post op staging was T1N1–7, T2N1–12, T2N2–1, T3N0–10, T3N1–11, T3N2–1. Conclusions: Utilising current preoperative staging methods one third of patients were under staged. Looking specifically at T2N0 68% were under staged. We feel that early oesophageal cancer especially T2N0 disease may benefit from neoadjuvant chemotherapy based on the current staging protocols.

No significant financial relationships to disclose.

Transhiatal oesophagectomy: techniques, tips and outcomes

AIM

To demonstrate our technique and valuable tips for transhiatal oesophagectomies.

METHOD

215 patients underwent transhiatal oesophagectomies in our unit between 2000 and 2006.

RESULTS

In-hospital mortality was 0.9%. Anastomotic leak in 12 patients (5.6%). Chyle leak was seen in five patients and recurrent nerve neuropraxia in six patients. Iatrogenic splenectomy rate was 6%. The median operative time was 151 minutes (range 93-276 minutes). Overall median length of hospital stay was 15 days (range 8-95 days). The median survival for all patients undergoing transhiatal oesophagectomy for invasive malignancy was 42.9 months and the one-year and five-year survival were 81% and 48% respectively.

CONCLUSION

This is a safe and oncologically sound procedure. We feel that the tips can be helpful for anyone performing this procedure.

Anastomotic strictures and delayed gastric emptying after esophagectomy: incidence, risk factors and management

The aim of this study was to report the incidence, risk factors, and management of gastric conduit dysfunction after esophagectomy in 177 patients over a 3-year period in a single center. Patients with anastomotic strictures or delayed gastric emptying (DGE) were identified from a prospective database. Anastomotic strictures occurred in 48 patients (27%). Eighty-three percent of early anastomotic strictures (<1 year) were benign, and all late strictures (>1 year) were malignant. Dilatation was effective in 98% of benign and 64% of malignant strictures. DGE occurred in 21 patients (12%), and was associated with both anastomotic leak (P = 0.001) and anastomotic stricture (P = 0.001). 4/8 patients with late DGE (>3 months postesophagectomy) were tumor-related. Pyloric dilatation was effective in 92% of early and 63% of late DGE. Pyloric stents were inserted in 3 patients with tumor-related DGE. After esophagectomy, early anastomotic strictures (within 1 year) and early delayed gastric emptying (within 3 months) are usually benign and respond to dilatation. However, patients presenting later with tumor-related obstruction are unlikely to respond to anastomotic or pyloric dilatation and should be stented.

Training in oesophageal surgery--the gold standard: a prospective study

INTRODUCTION

Competency in complex oesophagogastric surgery, within the current climate of changes to medical training and reduced hours, requires repeated, focused, hands-on training. We describe the training methods for oesophagectomy in our institution.

METHODS

All oesophageal resections under the care of one consultant surgeon are regarded as training cases. When trainees start they are shown the first resection; subsequently, the trainees then perform every case with the consultant scrubbed. Consultant input consists of retraction and tips in difficult situations. All data were collected on a prospective database.

RESULTS

Two hundred and seventy patients (215 males, median age=64 years) underwent primary oesophagectomy under the consultant, between January 2000 and May 2007. Fifteen resections (6%) were performed solely by the consultant. ASA grading was: I=15, II=154, III=95, IV=5, and unrecorded=1. In-hospital mortality and clinically apparent leak rate was 1.9% (5 deaths) and 6.2% (n=17), respectively. Reoperation was required in 15 patients (5.5%). The median length of hospital stay was 14 days (range=8-95 days). Median lymph node yield was 13 (range=0-64).

CONCLUSIONS

Trainees under supervision can competently perform an oesophagectomy without compromising patient care. An early hands-on approach leads to a rapid ascent of the learning curve and is essential in today's climate of limited training opportunity.

Laparoscopic gastrectomy for gastric cancer: early experience among the elderly

BACKGROUND

The data are scarce on the outcome for elderly patients presenting with resectable gastric cancer in the West who have been treated with minimally invasive surgery. This report presents the authors' early experience with totally laparoscopic gastric resections for cancer in elderly patients.

METHODS

A total of 20 patients underwent laparoscopic gastrectomy procedures: 14 distal, 5 subtotal, and 1 total gastrectomy. The male-to-female ratio was 15 to 5. The ages ranged from 75 to 88 years (mean, 80 years).

RESULTS

All cases were managed laparoscopically with R0 resection. Four patients needed high-dependency unit care postoperatively. There were no perioperative deaths. The median time required for the procedure was 212 min, and time to diet was 4 days. The hospital stay was 8 days. Four patients experienced significant complications, with two patients requiring reoperation. The pathology was adenocarcinoma for 17 patients and high-grade dysplasia for 3 patients.

CONCLUSION

Among elderly patients for whom conventional gastric surgery carries a high morbidity and mortality risk, minimal access surgery may offer equivalent oncologic integrity but with superior safety and economy. The primary aim is to remove the tumor with at least a D1 lymphadenectomy.

Does rectus sheath infusion of bupivacaine reduce postoperative opioid requirement?

INTRODUCTION

The aim of this work was to assess the effect of intermittent bupivacaine infusion into rectus sheath space on postoperative opioid requirement, postoperative pain score and peak expiratory flow rate.

PATIENTS AND METHODS

A prospective, randomised study involving patients undergoing midline laparotomy. Patients were randomised to receive either intermittent infusion of bupivacaine 0.25% or normal saline via catheters placed in the rectus sheath for 48 h after operation. All patients received intravenous morphine infusion on demand with a patient-controlled analgesic device (PCAD).

RESULTS

Forty ASA I-III patients were studied. Nineteen were randomised to receive bupivacaine and 21 patients received normal saline. Patient characteristics and surgical variables were comparable in the two groups. The mean wound lengths were similar. There was no statistically significant difference in postoperative opioid requirement, postoperative pain score and peak expiratory flow rate between the two groups.

CONCLUSIONS

Intermittent bupivacaine infusion into the rectus sheath space after midline laparotomy does not reduce postoperative opioid requirement nor does it affect postoperative pain score or peak expiratory flow rate.

Use of porcine dermal collagen graft and topical negative pressure on infected open abdominal wounds

This article reports on two cases in which porcine dermal collagen grafts were used successfully alongside topical negative pressure therapy in order to close open abdominal wounds in which severe infection was present.

Laparoscopic management of a torted appendix

Torted appendices are a rare occurrence but should be considered when encountering a haemorrhagic congested appendix on laparoscopy. As adhesions are rarely present, laparoscopic excision is usually a feasible option.

Mirizzi syndrome: laparoscopic management by subtotal cholecystectomy

BACKGROUND

The authors present their experience with laparoscopic subtotal cholecystectomy for the management of Mirizzi's syndrome and their review of the literature.

METHODS

Over a period of 24 months, five cases of Mirizzi's syndrome were encountered, representing 1.5% of all the laparoscopic cholecystectomies performed in the authors' unit. The sex ratio was 4 females to 1 male, and the mean age of the patients was 66 years. All underwent a subtotal cholecystectomy.

RESULTS

All procedures were completed laparoscopically. Morbidities involved one case of biliary peritonitis and a one case of biliary leak requiring endoscopic stenting.

CONCLUSION

Mirizzi's syndrome cannot always be anticipated on the basis of preoperative staging, and often is encountered during the procedure. The "anatomic scenario" of this condition should be suspected for patients presenting with conditions such as empyema or mucocoele when there is a likelihood of stone impaction in the infundibulum of the gallbladder. Subtotal cholecystectomy with secure intraperitoneal biliary drainage appears to be a safe option for these patients.

An audit of cystic duct closure in laparoscopic cholecystectomies

BACKGROUND

Cystic duct leak is an infrequent but potentially serious complication of laparoscopic cholecystectomy. The aims of this audit were to assess the efficacy of locking absorbable clips for closing the cystic duct and to compare the results with those for simple clips used previously.

METHODS

The records for all laparoscopic cholecystectomies performed in one hospital over a 5-year period were reviewed. The results were compared using Fisher's exact test.

RESULTS

Of 518 laparoscopic cholecystectomies attempted, 24 were excluded. There was no difference in age or sex ratio between the two groups. Cystic duct leaks were identified either on endoscopic retrograde choloangio pancreatography or at laparotomy. No cystic duct leak occurred in any of the 344 locking clip cases, as compared with 3 leaks in the 146 (2%) simple clip cases (p < 0.03).

CONCLUSION

Locking clips are a safe and effective method for cystic duct closure. They are associated with a reduced cystic duct leak rate, as compared with that for simple clips.

Left subcostal closed (Veress needle) approach is a safe method for creating a pneumoperitoneum

BACKGROUND

The left subcostal closed approach utilizing the Veress needle has been the preferred method at one surgical practice for the past 5 years. The aims of this study were to determine whether this was a safe method for creating a pneumoperitoneum and its success rate.

METHODS

The medical records for all laparoscopic procedures performed at one practice from 1996 through 2001 were reviewed.

RESULTS

A total of 352 laparoscopic cases were reviewed. The median age of the patients was 55 years (range, 14-72), with a sex ratio of 1 male to 3.5 females. The left subcostal closed approach was not attempted in 8 patients (2%) due to left subcostal surgical scars. The left subcostal approach was successful in 342 of 344 attempts (99%). In 2 patients the method failed because the Veress needle hole could not be placed in the peritoneal cavity. An omental hematoma in one patient was the only complication.

CONCLUSION

The left subcostal closed approach is a safe and effective method for creating a pneumoperitoneum.

Spontaneous rupture of a left gastroepiploic artery aneurysm

Gastroepiploic aneurysms are extremely rare. They occur mainly in elderly men and in 90% of cases are ruptured at presentation. Visceral aneurysms though rare should be borne in mind in cases of unexplained haemorrhagic shock. We present a case of a 79-year-old man who presented with abdominal pain, hypotension and anaemia but no obvious source of bleeding. He had undergone a prior aorto-bifemoral graft. The patient refused an operation and died the following day.

A case of a destructive lesion of sphenoidal sinus

This interesting case deals with the possible origin of pituitary tumor from cell rests located outside the pituitary gland. In the present case we found an elderly lady presenting with a suspected mass lesion of the sphenoidal sinus, clinically suspected to be either an infective granuloma or a chordoma which finally turned out to be an adenoma of the pituitary gland.

Duodenal tamponade in the treatment of an intractable peptic ulcer bleed

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Japanese encephalitis with movement disorder and atypical magnetic resonance imaging

With the advent of magnetic resonance imaging, brain lesions associated with Japanese encephalitis are increasingly being recognized and correlated with movement disorder. Bilateral haemorrhagic thalamic infarcts on MRI, suggested as a characteristic finding in Japanese encephalitis were conspicuous by their absence in this case report of Japanese encephalitis.

Stimulation of nonspecific resistance by thymopentin and its analogs against Leishmania donovani infection in hamsters

Thymopentin and its analogs have been synthesized by the solution phase method of peptide synthesis and evaluated for their prophylactic efficacy against L. donovani infection in hamsters. Thymopentin and some of the analogs were found to stimulate nonspecific resistance of the host against Leishmania donovani infection in hamsters.

Characterization and optimization of absorbing plasma-enhanced chemical vapor deposited antireflection coatings for silicon photovoltaics

We have optimized plasma-enhanced chemical vapor deposition (PECVD) of SiN-based antireflection (AR) coatings with special consideration for the short-wavelength (<600 nm) parasitic absorption in SiN. Spectroscopic ellipsometry was used to measure the dispersion relation for both the refractive index n and the extinction coefficient k, allowing a precise analysis of the trade-off between reflection and absorption in SiN-based AR coatings. Although we focus on photovoltaic applications, this study may be useful for photodetectors, IR optics, and any device for which it is essential to maximize the transmission of light into silicon. We designed and optimized various AR coatings for minimal average (spectrally) weighted reflectance (? R(w) ?) and average weighted absorptance (? A (w) ?), using the air mass 1.5 global solar spectrum. In most situations ? R (w) ? decreased with higher n, but ? A (w) ? increased because k increased with n. For the practical case of a single-layer AR coating for silicon under glass, an optimum refractive index of ~2.23 (at 632.8 nm) was determined. Further simulations revealed that a double-layer SiN stack with an n = 2.42 film underneath an n = 2.03 film gives the minimum total photocurrent loss. Similar optimization of double-layer SiN/SiO(2) coatings for silicon in air revealed an optimum of n = 2.28 for SiN. To determine the allowable tolerance in index and film thickness, we generated isotransmittance plots, which revealed more leeway for n values below the optimum than above because absorption begins to reduce photocurrent for high n values.

Study of serum prealbumin and serum alpha fetoprotein in cases of fulminant hepatic failure

We studied serum prealbumin (SPA) and serum alpha fetoprotein (AFP) to assess liver cell injury and prognosis in patients with fulminant hepatic failure (FHF). We studied 21 patients of FHF of viral etiology, 10 acute viral hepatitis (AVH) and 10 healthy controls. Initial (on the day of admission) AFP levels were significantly elevated in FHF group (30.28 +/- 63.58 ng/ml, p < 0.01 compared to AVH and control group in whom it was undetectable. Serum AFP correlated well with deranged Liver Functions (LFT). In the Survivors (n = 4) of FHF, serial estimations (on Day 5 and Day 10 of admission) revealed declining AFP Levels, correlating with clinical recovery. SPA on admission was significantly reduced in FHF group (15.10 +/- 9 mg/dl p < 0.05) compared to AVH (37.0 +/- 9.34 mg/dl) and control group (40.25 +/- 5.92 mg/dl). Low SPA also correlated with deranged LFT. Serial estimations in the survivors (Day 5, Day 10) revealed rising SPA which correlated with clinical recovery.