High-throughput screening of high-capacity electrodes for hybrid Li-ion-Li-O2 cells.

Recent experiments have shown that lithium and oxygen can be electrochemically removed from Li5FeO4 (5Li2O·Fe2O3) and re-accommodated during discharge, creating the possibility of its use as a high-capacity electrode in a hybrid Li-ion/Li-O2 electrochemical cell. Taking this novel chemistry as a model, we use density functional theory (DFT) within a high-throughput framework to screen for analogous reactions in other materials. We search for candidate materials possessing high capacity, voltages compatible with existing electrolytes, and reasonable electrical conductivity. We identify several promising candidate materials that may operate by a similar reaction mechanism and are worthy of investigation, such as Li6MnO4, Li6CoO4, Li4MoO5 and Li8IrO6. This work paves the way for accelerated exploration of this intriguing new battery chemistry.

Low intensity conduction states in FeS2: implications for absorption, open-circuit voltage and surface recombination.

Pyrite (FeS2), being a promising material for future solar technologies, has so far exhibited in experiments an open-circuit voltage (OCV) of around 0.2 V, which is much lower than the frequently quoted 'accepted' value for the fundamental bandgap of ∼0.95 eV. Absorption experiments show large subgap absorption, commonly attributed to defects or structural disorder. However, computations using density functional theory with a semi-local functional predict that the bottom of the conduction band consists of a very low intensity sulfur p-band that may be easily overlooked in experiments because of the high intensity onset that appears 0.5 eV higher in energy. The intensity of absorption into the sulfur p-band is found to be of the same magnitude as contributions from defects and disorder. Our findings suggest the need to re-examine the value of the fundamental bandgap of pyrite presently in use in the literature. If the contribution from the p-band has so far been overlooked, the substantially lowered bandgap would partly explain the discrepancy with the OCV. Furthermore, we show that more states appear on the surface within the low energy sulfur p-band, which suggests a mechanism of thermalization into those states that would further prevent extracting electrons at higher energy levels through the surface. Finally, we speculate on whether misidentified states at the conduction band onset may be present in other materials.

Efficient band gap prediction for solids.

An efficient method for the prediction of fundamental band gaps in solids using density functional theory (DFT) is proposed. Generalizing the Delta self-consistent-field (ΔSCF) method to infinite solids, the Δ-sol method is based on total-energy differences and derived from dielectric screening properties of electrons. Using local and semilocal exchange-correlation functionals (local density and generalized gradient approximations), we demonstrate a 70% reduction of mean absolute errors compared to Kohn-Sham gaps on over 100 compounds with experimental gaps of 0.5-4 eV, at computational costs similar to typical DFT calculations.

Injectable silicone biomaterial (PTQ) is more effective than carbon-coated beads (Durasphere) in treating passive faecal incontinence--a randomized trial.

OBJECTIVE: Both injectable silicone biomaterial (PTQ) and pyrolytic carbon-coated beads (Durasphere) have been shown to be effective in treating passive faecal incontinence due to internal sphincter dysfunction. This is a randomized study to evaluate their relative safety and efficacy. METHOD: Forty patients (mean age 59.5 years vs 58.9 years) were randomized to have inter-sphincteric injection of PTQ or submucosal injection of Durasphere. Patients were assessed with anorectal physiology, endoanal ultrasound, a validated incontinence score and quality of life questionnaires. RESULTS: In the Durasphere group, complications included rectal pain (5%), erosion through rectal mucosa (10%), and type III hypersensitivity reaction (5%). No complications occurred in the PTQ group. Compared with PTQ, Durasphere group has a more rapid action, with improved continence at 2 weeks after injection. In both groups, faecal continence significantly improved 6 weeks after injection, and continued to improve significantly up to 6 months in both groups (P < 0.0001). At 6 weeks, 6 and 12 months after injection, significantly more PTQ patients achieved greater than 50% improvement in Wexner's continence score than Durasphere patients (respectively, P = 0.01; P < 0.0001; P = 0.001). There was a significant improvement in faecal incontinence quality of life scale and the 12-month physical health scale of Short Form-12 health survey in the PTQ group but not in the Durasphere group. CONCLUSION: In patients with internal sphincter dysfunction, injectable silicone biomaterial was safer and more effective than Durasphere.

Predictive factors for faecal incontinence after third or fourth degree obstetric tears: a clinico-physiologic study.

OBJECTIVE: This is a prospective study to review the natural history of anorectal dysfunction after primary repair for third or fourth degree obstetric tear and to identify the predictive factors for significant faecal incontinence. METHOD: From January 2003 to December 2005, 121 consecutive women (mean age 29.9 +/- 4.7) who sustained third or fourth degree obstetric tears were assessed. All had primary repair by obstetricians. They were assessed using anorectal physiology testing and endoanal ultrasound. Short-term (3-month postpartum) and medium-term (mean 18.8 +/- 7.7 months) Wexner's continence scores were obtained. RESULTS: Among the 121 women, seven were excluded because of incomplete follow-up. At short-term assessment, 25 out of 114 women were incontinent. One of them underwent another sphincter repair for significant faecal incontinence. Twenty-one and three patients respectively, had mild (Wexner's score 1-4) and moderate (Wexner's score 5-8) symptoms. At medium-term assessment, 24 patients remained incontinent; of these, 20 had mild symptoms (Wexner's score 1-4) and four had moderate incontinence (Wexner's score 5-8). The parity (P = 0.04), degree of obstetric tear (P = 0.036) and short-term Wexner's scores at 3 months postpartum (P < 0.0001) were significantly related to the change in Wexner's scores at medium-term assessment. However, the short-term Wexner's score was the only identifiable predictive factor for significant faecal incontinence. CONCLUSION: Most women suffering from third or fourth degree obstetric tear were continent or mildly incontinent. Poor Wexner's score at short-term assessment at 3 months postpartum was predictive of faecal incontinence in the medium-term.

Prospective, case-matched study of heated and humidified carbon dioxide insufflation in laparoscopic colorectal surgery.

PURPOSE: Laparoscopic colorectal surgery is often prolonged and may cause hypothermia. It is uncertain if heated and humidified carbon dioxide (CO(2)) in laparoscopic colorectal surgery is beneficial. This is a prospective case-matched study on the use of heated and humidified CO(2) in patients undergoing laparoscopic colorectal surgery. METHOD: Twenty consecutive patients undergoing laparoscopic colorectal surgery with heated (36 degrees C) and humidified (95%) CO(2) were compared with 20 consecutive patients using standard CO(2) (30.2 degrees C). All procedures were performed by a single surgeon in an institution. The changes in core temperature during surgery, visual quality of images and the short-term clinical outcome were documented. RESULTS: The core temperature fell during surgery in both groups. Although the fall of core temperature was more in the control group, it was not statistically significant (P > 0.05). The passage of flatus was more delayed in heated and humidified group (P = 0.004), but it did not affect the hospital discharge. All the other parameters, including the quality of visual images and the postoperative pain, were similar in both groups. CONCLUSIONS: Despite better temperature maintenance (nonsignificant), pneumoperitoneum using heated and humidified CO(2) gas did not appear to have any clinical benefits in laparoscopic colorectal surgery.

Systematic review on the short-term outcome of laparoscopic resection for colon and rectosigmoid cancer.

OBJECTIVE: Several large randomized controlled trials on laparoscopic resection for colon and rectosigmoid cancer have recently been published. There is a need to provide an up-to-date systematic review in this subject. METHODS: A literature search of all published randomized trials in English between January 1991 and September 2005 was obtained, from Ovid MEDLINE, EMBASE, CINAHL, and All EBM Reviews (Cochrane Central Register of Controlled Trial, Cochrane Database of Systemic Review, and Database of Abstracts of Reviews of Effects), including e-links to the related articles. Two independent assessors reviewed the trials using a standardized protocol. Where means and standard deviations were available, meta-analysis was performed using the Forest plot review. Studies where medians and ranges were presented were separately analysed. RESULTS: A total of 17 randomized controlled trials with 4013 procedures were reviewed. The conversion rate varied widely between studies and was lowest in single-Centre trials. There were no significant differences in overall and surgical complication rate, anastomotic leak rate, re-operation rate and oncological clearance. However, laparoscopic resection has a significantly lower peri-operative mortality (odds ratio 0.33; P = 0.005), lower wound complications (odds ratio 0.65; P = 0.01), less blood loss (weighted mean difference 0.11 l; P < 0.00001) and reduced postoperative pain scores by 12.6% with reduction of requirements for narcotic analgesia by 30.7%. After laparoscopic surgery, patients passed flatus 38.8% earlier (weighted mean difference 27.6 h; P < 0.00001) and had bowel movement 21.0% earlier (weighted mean difference 23.9 h; P < 0.00001) and resumed oral diet 28.3% sooner than patients in the open group (weighted mean difference 27.3 h; P < 0.00001). Patients were discharged 19.1% earlier after laparoscopic surgery than open surgery (weighted mean difference 1.7 days; P < 0.00001). Laparoscopic resection took 28.7% longer (weighted mean difference 40.1 min; P < 0.00001) to perform. CONCLUSIONS: Laparoscopic resection for colon and rectosigmoid cancer is feasible, safe and has many short-term benefits.

Ruptured phaeochromocytoma--a lesson in acute abdomen.

Phaeochromocytoma may present as acute abdomen. This report is of a patient with spontaneous rupture of phaeochromocytoma who presented with abdominal pain and a tender abdominal mass. Ruptured phaeochromocytoma is a rare surgical emergency, with only 30 cases reported in the literature. The classical clinical triad of signs is intense vasoconstriction, tachycardia, and labile blood pressure. Computed tomography scanning of the abdomen is the investigation of choice, and a high index of suspicion is the key to diagnosis. Prompt recognition, appropriate supportive measures, and early surgical intervention can improve the likelihood of survival.