Insight into sulfur reactions in Li-S batteries

Understanding and controlling the sulfur reduction species (Li2Sx, 1 ≤ x ≤ 8) under realistic battery conditions are essential for the development of advanced practical Li-S cells that can reach their full theoretical capacity. However, it has been a great challenge to probe the sulfur reduction intermediates and products because of the lack of methods. This work employed various ex situ and in situ methods to study the mechanism of the Li-S redox reactions and the properties of Li2Sx and Li2S. Synchrotron high-energy X-ray diffraction analysis used to characterize dry powder deposits from lithium polysulfide solution suggests that the new crystallite phase may be lithium polysulfides. The formation of Li2S crystallites with a polyhedral structure was observed in cells with both the conventional (LiTFSI) electrolyte and polysulfide-based electrolyte. In addition, an in situ transmission electron microscopy experiment observed that the lithium diffusion to sulfur during discharge preferentially occurred at the sulfur surface and formed a solid Li2S crust. This may be the reason for the capacity fade in Li-S cells (as also suggested by EIS experiment in Supporting Information ). The results can be a guide for future studies and control of the sulfur species and meanwhile a baseline for approaching the theoretical capacity of the Li-S battery.

Paving the way for using Li₂S batteries

In this work, a novel lithium-sulfur battery was developed comprising Li2S as the cathode, lithium metal as the anode and polysulfide-based solution as the electrolyte. The electrochemical performances of these Li2S-based cells strongly depended upon the nature of the electrolytes. In the presence of the conventional electrolyte that consisted of lithium bis(trifluoromethanesulfonyl)-imide (LiTFSI) salt dissolved in a solvent combination of dimethoxyethane (DME)/1,3-dioxolane (DOL), the Li/Li2S cells showed sluggish kinetics, which translated into poor cycling and capacity retention. However, when using small amounts of polysulfides in the electrolyte along with a shuttle inhibitor the Li2S cathode was efficiently activated in the cell with the generation of over 1000 mAh g(-1) capacity and good cycle life.

Electroacupuncture for ileus after laparoscopic colorectal surgery: a randomised sham-controlled study

1. Electroacupuncture at acupoints of Zusanli, Sanyinjiao, Hegu, and Zhigou is more effective than no acupuncture and sham acupuncture in stimulating early return of bowel function and reducing analgesic requirement after laparoscopic colorectal surgery. 2. Electroacupuncture is more effective than no acupuncture in reducing the duration of hospital stay. 3. Receipt of electroacupuncture is an independent predictor of shorter duration of ileus and hospital stay after laparoscopic colorectal surgery.

Platinum nanowires produced by electrospinning

A method of making long (cm) Pt nanowires of a few nanometers diameter from electrospinning is described. A major problem of avoiding bead formation along the nanofibers is analyzed, and the conditions under which the bead formation is minimized are investigated. Our ultimate purpose is to make free-standing fuel cell electrodes from these nanowires.

Laparoscopic total colectomy for colorectal cancers: a comparative study

BACKGROUND

No previous report could be found in the literature comparing laparoscopic and open total colectomy for colorectal cancers, especially synchronous colorectal cancers. This study aimed to compare the short-term clinical outcomes and oncologic results of laparoscopic and open total colectomy or proctocolectomy for colorectal cancers.

METHODS

Between July 1997 and January 2005, six patients with colorectal cancers underwent elective laparoscopic total colectomy or proctocolectomy at the authors' institution. Clinical data for 12 patients who underwent elective open total colectomy or proctocolectomy for colorectal cancers during the same period were prospectively collected and compared.

RESULTS

The median follow-up periods were 43.9 months for the laparoscopic group and 48.2 months for the open group. Conversion to open procedure was required for one patient (16.7%) in the laparoscopic group because of bleeding. The median operative time was significantly longer in the laparoscopic group (427.5 min; range, 280-480 min vs 172.5 min; range, 90-260 min; p = 0.001). The patients in the laparoscopic group required a significantly shorter duration of parenteral analgesia (3 vs 5 days; p = 0.01), but there were no differences in time to first bowel motion, time to resumption of diet, time to full ambulation, and duration of hospital stay between the two groups. Perioperative morbidity rates were comparable between the two groups, and there was no operative mortality. The oncologic results, including number of lymph nodes removed, recurrence rates, and survival rates, were similar in the two groups.

CONCLUSIONS

Laparoscopic total colectomy has short-term clinical outcomes (postoperative recovery and perioperative morbidity and mortality rates) and oncologic results similar to those of open surgery for treating patients with colorectal cancers. Our study has shown that the only advantage of laparoscopic over open surgery is a shorter duration of analgesic requirement, but at the expense of a longer operative time.

Mechanical grain growth in nanocrystalline copper

Nanograined materials have some unusual properties. To maintain the small size of the grains, grain growth should be avoided. But recently grain growth has been observed under an indenter at liquid-nitrogen temperatures. Such grain growth has never been reported before. How can this happen and how can it be prevented? These questions are answered here using a simple tilt boundary. It is found that high purity and nonequilibrium structure are necessary conditions for mechanical grain growth. The material must be pure enough so that free dislocations are available to move out of the boundary. But the boundary should not be in the lowest-energy state so that extra dislocations are available to be emitted by stress. Based on these conditions, methods can be devised to avoid low temperature grain growth.

Percutaneous cholecystostomy for the treatment of acute cholecystitis in the critically ill and elderly

OBJECTIVE

To evaluate the clinical efficacy and outcomes of percutaneous cholecystostomy as an alternative treatment option for elderly and critically ill patients who have acute cholecystitis.

PATIENTS AND METHODS

The medical records of patients who underwent emergency percutaneous cholecystostomy at the North District Hospital, Hong Kong from September 1999 to July 2002 were reviewed. Indications for the procedure, patient demographics, and other clinical details were recorded.

RESULTS

A total of 25 patients (10 male, 15 female) with a median age of 81 years (range, 39-97 years) presented with acute cholecystitis and underwent percutaneous cholecystostomy with ultrasound guidance. Two patients required emergency cholecystectomy on day 1 after the procedures because of deteriorating conditions. The rest of the patients clinically improved after drainage. There was no major periprocedural complication, and four patients had their catheter accidentally dislodged but did not require re-insertion. There were five in-patient mortalities, although the majority of these deaths were from unrelated illness. Subsequently, only six patients underwent elective cholecystectomy, one open and five laparoscopic. Two patients were offered percutaneous endoscopic cholecystolithotripsy, one defaulted and the other could not tolerate the procedure. Eleven patients declined further intervention due to the high surgical risks, three of these patients developed biliary symptoms, one had acute cholecystitis, and the other two had cholangitis. The rest of patients had no symptoms related to the gallstones. The median follow-up period was 81 weeks (range, 27-162 weeks).

CONCLUSION

Percutaneous cholecystostomy is a viable treatment option for elderly and critically ill patients presenting with acute cholecystitis. It has a high success rate with minimal procedure-related complications. Elective cholecystostomy is the treatment of choice for low-risk patients after the initial acute cholecystitis.