Correction: Character angle effects on dissociated dislocation core energy in aluminum.

Correction for 'Character angle effects on dissociated dislocation core energy in aluminum' by X. W. Zhou et al., Phys. Chem. Chem. Phys., 2021, 23, 3290-3299, DOI: https://doi.org/10.1039/D0CP05333C.

Character angle effects on dissociated dislocation core energy in aluminum.

Dislocation core energy is an important property in materials mechanics but can only be obtained from atomistic simulations. Periodic boundary conditions are ideally suited for atomistic calculations of dislocation energies but have faced two major challenges. First, viable methods to extract core energies from atomistic data of total energies have been developed only for non-dissociated dislocations whereas realistic dislocations are often dissociated into partials. Second, core energy is a function of dislocation character angle. This functional dependence can only be revealed through calculations at a variety of character angles. This requires both additional computational resources and a robust method to implement arbitrary character angles. Here a new procedure has been developed to overcome both challenges. By applying this approach, we have calculated 22 core energies of dissociated dislocations in aluminium over the entire character angle range between 0° and 90°. In addition to the discrete core energy data for dissociated dislocations, we found that core energy can be approximated by a continuous function of character angle. Specifically, our dissociated dislocation core energies have been well fitted to a polynomial Sinoidal function of character angle. We have also discovered that there exists a critical system dimension below which dislocation core energies cannot be calculated due to dislocation transformation.

Molecular dynamics discovery of an extraordinary ionic migration mechanism in dislocation-containing TlBr crystals.

TlBr can surpass CZT as the leading semiconductor for γ- and X-radiation detection. Unfortunately, the optimum properties of TlBr quickly decay when an operating electrical field is applied. Quantum mechanical studies indicated that if this property degradation comes from the conventional mechanism of ionic migration of vacancies, then an unrealistically high vacancy concentration is required to account for the rapid aging of TlBr seen in experiments. In this work, we have applied large scale molecular dynamics simulations to study the effects of dislocations on ionic migration of TlBr crystals under electrical fields. We found that electrical fields can drive the motion of edge dislocations in both slip and climb directions. These combined motions eject enormous vacancies in the dislocation trail. Both dislocation motion and a high vacancy concentration can account for the rapid aging of the TlBr detectors. These findings suggest that strengthening methods to pin dislocations should be explored to increase the lifetimes of TlBr crystals.

An analytical bond-order potential for carbon.

Carbon is the most widely studied material today because it exhibits special properties not seen in any other materials when in nano dimensions such as nanotube and graphene. Reduction of material defects created during synthesis has become critical to realize the full potential of carbon structures. Molecular dynamics (MD) simulations, in principle, allow defect formation mechanisms to be studied with high fidelity, and can, therefore, help guide experiments for defect reduction. Such MD simulations must satisfy a set of stringent requirements. First, they must employ an interatomic potential formalism that is transferable to a variety of carbon structures. Second, the potential needs to be appropriately parameterized to capture the property trends of important carbon structures, in particular, diamond, graphite, graphene, and nanotubes. Most importantly, the potential must predict the crystalline growth of the correct phases during direct MD simulations of synthesis to achieve a predictive simulation of defect formation. Because an unlimited number of structures not included in the potential parameterization are encountered, the literature carbon potentials are often not sufficient for growth simulations. We have developed an analytical bond order potential for carbon, and have made it available through the public MD simulation package LAMMPS. We demonstrate that our potential reasonably captures the property trends of important carbon phases. Stringent MD simulations convincingly show that our potential accounts not only for the crystalline growth of graphene, graphite, and carbon nanotubes but also for the transformation of graphite to diamond at high pressure.

Complications and mortality following stoma formation.

INTRODUCTION: As stoma formation is thought to be declining, we performed a study to evaluate the rate of stoma formation and the impact on stoma complication rates, together with risk factors for complications. PATIENTS AND METHODS: Stoma incidence, individual complications and mortality rates were retrieved from a stoma nurse database of 345 stomas created over an 8-year period. RESULTS: Stoma formation increased over the study period, although the incidence of complications declined. Stoma complications were more frequently seen in emergency surgery. A significant association between stoma complications and mortality was identified. CONCLUSIONS: Age of patient, urgency of surgery and diagnosis were associated with high levels of morbidity and mortality. Stomas are often formed in frail patients unsuitable for anastomosis formation, which may explain the high mortality in ostomy patients.

Laparoscopic colorectal surgery in Great Britain and Ireland--where are we now?

OBJECTIVE: We aimed to gather information from the members of the Association of Coloproctology of Great Britain and Ireland (ACPGBI) to assess trends in the current practice of laparoscopic colorectal surgery. METHODS: A postal questionnaire survey of the members of ACPGBI. RESULTS: The response rate was 37% (200/540). Only 45 surgeons currently perform laparoscopic colorectal work in Great Britain and Ireland mainly right hemicolectomy and laparoscopic stoma formation, of these about one third practiced laparoscopy for benign colorectal conditions only. The majority (68%) of surgeons had enough resources at their place of work, but further training seemed to be a major issue. Nearly 22% of surgeons had not had any formal training. Only 50% of surgeons trained their specialist registrars. The incidence of conversion rate was not different for benign or malignant conditions and also did not appear to be related to the duration of experience. Only four surgeons had noted port a site recurrence during the past 10 years. Seventy-five percent (150/200) felt that laparoscopic colorectal work could be carried out safely in a District General Hospital. CONCLUSION: Laparoscopic colorectal surgery was being performed by a small minority of members of the ACPGBI although more surgeons had started to work in this field in recent years. The main areas of concern appeared to be a wide variation in the range of experience as indicated by the number of operations performed and limited formal training for consultants.

Registrar operating experience over a 15-year period: more, less or more or less the same?

BACKGROUND: Concerns have been raised on the effects that recent changes in junior doctor work patterns may have on the breadth and depth of operative exposure achieved during specialist registrar training. This study aimed to determine whether there was any justification for these concerns by assessing whether there have been significant changes in either the number of cases or the case mix operated upon by registrars over the course of the past fifteen years. METHODS: A retrospective review of theatre records was undertaken, looking at the caseload of the registrars working for the same two consultant surgeons at one district general hospital in four one-year periods (1986-7; 1991-2; 1998-9; 2001-2). The number, subspecialty, and time of each operation were recorded. RESULTS: Whilst operating experience for the first three periods of the study was static, the most recent assessment point has demonstrated a significant reduction in trainee routine operative experience and also a small reduction in the emergency workload performed by both firms. There was also a significant change in the elective case mixes corresponding to consultant sub-specialisation during this period. In addition, there were notable changes in the nature of the emergency workload and a reduction in the number of cases performed after midnight. CONCLUSION: SpRs trained during the Calman era appear to be gaining less operative experience than their predecessors in both the elective and emergency settings. With further changes in working patterns currently being implemented, major changes to SpR programmes are required if surgeons are to be adequately trained.

Assessment of basic surgical trainees: can we do more?

INTRODUCTION: Changes to surgical training and reduction of junior doctors' working hours has resulted in trainees spending less time in surgical specialties before becoming eligible to apply for specialist registrar posts. A high quality basic surgical training programme is needed to improve the competence of trainees during their shortened period, an essential part of which is to conduct a formal assessment at the end of each training post and regular appraisals during their period of training. AIMS: To analyse the existing practice with regard to conducting assessment and appraisals for basic surgical trainees in the South East Wales region. METHODS: A questionnaire was sent to all the basic surgical trainees in the South East Wales region. RESULTS: A total of 52 questionnaires were sent out and 44 (84%) were returned. Four candidates were in the first post of their rotation, and were therefore excluded from the study. Nine of the 40 trainees (23%) did not have an assessment in one or more of their posts. There are 17 senior house officer posts available in general surgery in the rotation. Of the 31 "six month" episodes spent in these 17 posts, 27 (87%) underwent an assessment, 12 of the 17 (70%) episodes in trauma and orthopaedics (12 available posts) were assessed, and 31 of the 35 (88%) episodes in accident and emergency (eight available posts) underwent an assessment. Twenty eight of the 40 trainees (70%) did not undergo regular appraisals during the majority of their posts. Only 30%-50% of episodes spent in general surgery, orthopaedics, and accident and emergency underwent appraisals. The majority of the episodes spent in the other surgical specialties (12 posts available in total) had formal assessment and regular appraisals except for urology in which two of seven episodes underwent assessment and one underwent an appraisal. Twelve candidates (30%) expressed the view that operative experience and technical skills must form part of their assessment. Eight trainees (20%) felt that they needed more help from tutors with regard to career advice, preparation of curriculum vitae, and interview techniques for specialist registrar posts. Eight trainees mentioned that they had discussed unsatisfactory posts with their tutors but were not aware of any changes made to these posts. CONCLUSIONS: This study has shown that the formal assessment of basic surgical trainees at the end of each training post has to improve further. The existing practice of conducting regular appraisals for the trainees is grossly inadequate. There appears to be a need for formulating guidelines for conducting such appraisals, which would help to improve practice in the future.

Costs of waiting for gall bladder surgery.

Laparoscopic cholecystectomy is one of the most commonly awaited general surgical procedures in the UK. However, many patients awaiting a cholecystectomy are admitted with recurrent gallstone related symptoms while on the waiting list, resulting in significant morbidity. The aim of this study was to quantify this problem, and also to analyse the cost implications of these admissions for the NHS. A retrospective study was performed of all patients who underwent an elective cholecystectomy by three consultants in a district general hospital between January 1999 and January 2000. The demographic details, indications for surgery, details of the emergency admissions while on the waiting list, and the treatment given during these episodes were recorded. One hundred and fifty six patients were included in the study, of which 122 (78%) were females. The mean (SD) age of the patients was 54 (5) years. The mean waiting time for surgery in these patients was 12 (3) months. Thirty seven patients (23.7%) were admitted as an emergency due to gallstone related symptoms and complications while awaiting surgery. There were 47 episodes of admissions in total, of which 32 were for biliary colic, 13 were for acute cholecystitis, and two were for acute pancreatitis. In addition to routine blood tests, 20 abdominal radiographs, 10 chest radiographs, three endoscopic retrograde cholangiopancreatography tests, five ultrasonograms, and one computed tomogram were carried out in these patients. The mean duration of each episode of admission was three days. The cost of treatment per episode was pound 946 and the total cost of treating the 37 patients was calculated to be pound 44 462. Performing early laparoscopic cholecystectomy for acute cholecystitis may help to reduce costs by preventing recurrent emergency admissions in these patients. Further studies to identify risk factors associated with recurrent symptoms and complications in patients with gallstone disease may help to prioritize them for early surgery.

Tuberculous parotitis.

Tuberculosis, though rare, should be considered in the differential diagnosis of a diffuse swelling of the parotid with enlarged cervical glands, particularly in young, feverish adults.

The implications of subspecialisation on the management and outcome of surgery for rectal carcinoma.

BACKGROUND: The management of rectal carcinoma has changed significantly over the last decade. We studied the changing trends in the management of rectal carcinoma over a 7-year period in a district general hospital. METHODS: A retrospective analysis of all patients with histologically proven rectal adenocarcinoma who underwent operative treatment between January 1991 and December 1997 was performed. The type of operative procedure, local recurrence rate and completeness of pathology reporting was documented. RESULTS: There were 200 operative procedures: 102 anterior resections (AR), and 98 abdominoperineal resections (APR). This included 17 palliative resections because of metastatic disease (n = 8) or extensive local invasion (n = 7) or both (n = 2). The APR rate steadily declined from 72% in 1991 to 19% in 1997 (p < 0.005). Subspecialist 'colorectal' surgeons performed only 24% of the operations in 1991 but the figure for 1997 was 85% (p < 0.01). No circumferential resection margin was reported in 1991 but was reported in 85% of the cases in 1997 (p < 0.001). There was a steady increase in stapled anastomoses from 43% in 1991 to 93% in 1997 (p < 0.03). There were 15 local recurrences following 'curative' resection; 7 following APR and 8 following AR (n.s.). CONCLUSION: There was a significant increase in the rate of restorative resection of rectal cancer with a concomitant reduction in permanent stoma formation; this may be attributed to an increase in subspecialisation. Despite this, a low rate of local recurrence was maintained throughout the study period.

The natural history diverticular disease: is there a role for elective colectomy?

BACKGROUND: The natural history of colonic diverticular disease is unclear leading to a debate on the value of elective colectomy in preventing complications of the disease. AIM: To assess whether the complications of diverticular disease requiring emergency surgery are related to previous episodes of diverticulitis and whether elective colectomy might prevent such complications. MATERIALS AND METHODS: A retrospective study was done on all patients admitted with complicated diverticular disease in two adjacent district general hospitals between 1995 and 2000. Information was collected on the details of management of the complications and past history of the investigations and treatment for diverticular disease in these patients. RESULTS: A total of 108 patients were admitted with complicated diverticular disease. Ninety eight (91%) patients were admitted as an emergency for perforated diverticular disease and rectal bleeding. Ten patients were urgent admissions for fistulae and diverticular phlegmons. Ninety eight patients underwent a Hartmann's operation, two had a subtotal colectomy and 4 patients had a sigmoid colectomy. Thirty four (31.4%) patients died in hospital post-operatively. Of the 108 patients, only 28 (26%) patients were known to have diverticular disease previously. Only three (2.7%) patients had had an episode of acute diverticulitis before they presented with further complications. CONCLUSIONS: Complications of diverticular disease occur de novo in the majority of patients who have no previous history of the disease. Further studies are needed to identify risk factors for complicated diverticular disease before adopting a policy of elective interval colectomy.

Nurse-led direct access endoscopy clinics: the future?

BACKGROUND: Many studies have shown that rectal bleeding is a good indicator of underlying colorectal pathology, and that ost of the lesions in patients presenting with rectal bleeding lie in the left side of the colon [1, 5, 9, 12, 23, 26]. The recent acceptance of the nurse-practitioner by the National Health Service may allow the use of nurse-endoscopists to develop throughout the United Kingdom. This study aimed to audit a unique nurse-led direct-access nurse-endoscopy service with regard to its efficacy and cost effectiveness, and to monitor patient satisfaction and direct referrals from the primary health sector. METHODS: A nurse-led open-access flexible sigmoidoscopy (OAFS) service for patients reporting fresh rectal bleeding was established at our center in February 1996. A prospective audit of sigmoidoscopic findings and a retrospective analysis of referral patterns from local general practitioners were conducted. A questionnaire survey of both patient and general practitioner satisfaction also was conducted at the same time. RESULTS: Since February 1996, 706 patients have been referred to our service. Rectal bleeding was by far the most common cause for referral, representing the dominant symptom in 92% of the referrals received. Although 99% of the patients underwent a complete sigmoidoscopic examination, 16% of these examinations were limited because of several factors combined. A cause for bleeding was identified in 91% of the patients, with 24% of them experiencing subsequent significant pathology. Of the patients surveyed, 99% were satisfied with the service provided. The results also show nurse-led OAFS to be a more effective use of financial resources, costing $90 less per patient than general practitioner referrals sent to a consultant for further action. CONCLUSIONS: Rectal bleeding is a good indicator of underlying colorectal disease. Most of the significant lesions presenting with this symptom are found in the left side of the colon. A nurse-led OAFS is safe, effective, and acceptable to patients. It also is more cost effective than a consultant-led service.

Prevention of venous thromboembolism in Wales: results of a survey among general surgeons.

OBJECTIVE: To examine the current attitudes towards the prevention of venous thromboembolism among a cohort of surgeons. DESIGN: A postal survey, comprising a questionnaire covering various aspects of venous thromboembolism prophylaxis was sent to all (n=84) consultant general surgeons in Wales. RESULTS: Replies were received from 57 surgeons (68%), all of whom routinely used prophylaxis, the most frequent modalities used being heparin (100%) and graded compression stockings (79%). A combination of physical and pharmacological methods was used by over 89% of surgeons, with 60% starting prophylaxis more than two hours before operation. All surgeons continued prophylaxis after surgery, 53% until patients were mobile, 45% until they were discharged, and one surgeon continued prophylaxis for seven days after discharge. The thrombosis risk factors considered most important by surgeons when deciding about prophylaxis were (i) a previous history of venous thromboembolism, (ii) hypercoagulability, and (iii) malignancy. CONCLUSIONS: This study confirms that Welsh surgeons conform to standard methods, but also highlights some uncertainties that are present in current surgical practice. Those who responded all routinely used prophylaxis, the timing of which was variable. The main risk factors identified when considering prophylaxis were previous history of deep vein thrombosis/pulmonary embolism, hypercoagulability, and the presence of malignancy. Suggestions for future practice are made.

Splenogonadal fusion: report of a rare variety.

We report an unusual case of splenogonal fusion in a 10-year-old boy with an undescended left testis. He suffered from congenital limb defects, a known association with splenogonadal fusion, and had originally been admitted for orchidopexy.

Management of the impalpable testis: a six year review together with a national experience.

The management of undescended testes remains variable, and the use of laparoscopy for localisation is controversial. This study reviews the need for laparoscopy and also assesses the current practice among a cohort of surgeons.A retrospective review of all patients undergoing orchidopexy was performed, together with a postal survey of all members of the Welsh Surgical Society. Of the 139 orchidopexies performed, the testis was deemed impalpable in 39 (28%) cases. All patients were treated with groin exploration, and only in two (5%) patients was the testis not located. From the survey, replies were received from 90 (81%) surgeons, of whom 65 (72%) were still performing orchidopexy. Forty eight (74%) surgeons performed orchidopexy between the age of 2 and 3, and only 32 (36%) performed preoperative investigations. The follow up period was variable with the majority of patients seen at six weeks. Laparoscopy for the impalpable testis is not initially warranted. An inguinal exploration is regarded as the definitive investigation. This has the advantage of providing the diagnosis and treatment in the majority of cases.

One-year survey of carcinoma of the oesophagus and stomach in Wales.

BACKGROUND: The aim of the study was to identify all patients who presented with oesophagogastric malignancy within a single National Health Service region (Wales) over 1 year, and to follow the cohort for 5 years. Management and outcome were analysed to identify current practice and draft guidelines for Wales. METHODS: Patients were identified from hospital records. Details were recorded in structured format for analysis. RESULTS: Analysable data were obtained for 910 of 916 patients. The overall incidence was 31.4 per 100 000 population. Treatment was by resection 298 (33 per cent), palliation 397 (44 per cent) or no treatment 215 (24 per cent). The 30-day mortality rate was 12 per cent and the in-hospital mortality rate was 13 per cent. Some 226 patients (25 per cent) were alive at 2 years. Resection conferred a significant survival advantage over palliation (P < 0.001) and no treatment. Anastomotic leakage occurred in 16 patients (5 per cent), of whom eight died in hospital. 'Open and close' operations were common (23 per cent), laparoscopy was infrequent (16 per cent), and many surgeons undertook small caseloads. Operating on fewer than six patients per year increased the mortality rate after partial gastrectomy (P < 0.05) and was associated with a trend to a higher mortality rate after mediastinal and cardia surgery. Operating on more than 70 per cent of patients seen resulted in a significantly higher mortality rate (P < 0.01) irrespective of case volume. CONCLUSION: Tumour resection conferred a survival advantage. Wider use of laparoscopy is advocated. Improved selection for surgery should result in a lower mortality rate.