Machine learned interatomic potential for dispersion strengthened plasma facing components.

Tungsten (W) is a material of choice for the divertor material due to its high melting temperature, thermal conductivity, and sputtering threshold. However, W has a very high brittle-to-ductile transition temperature, and at fusion reactor temperatures (≥1000 K), it may undergo recrystallization and grain growth. Dispersion-strengthening W with zirconium carbide (ZrC) can improve ductility and limit grain growth, but much of the effects of the dispersoids on microstructural evolution and thermomechanical properties at high temperatures are still unknown. We present a machine learned Spectral Neighbor Analysis Potential for W-ZrC that can now be used to study these materials. In order to construct a potential suitable for large-scale atomistic simulations at fusion reactor temperatures, it is necessary to train on ab initio data generated for a diverse set of structures, chemical environments, and temperatures. Further accuracy and stability tests of the potential were achieved using objective functions for both material properties and high temperature stability. Validation of lattice parameters, surface energies, bulk moduli, and thermal expansion is confirmed on the optimized potential. Tensile tests of W/ZrC bicrystals show that although the W(110)-ZrC(111) C-terminated bicrystal has the highest ultimate tensile strength (UTS) at room temperature, observed strength decreases with increasing temperature. At 2500 K, the terminating C layer diffuses into the W, resulting in a weaker W-Zr interface. Meanwhile, the W(110)-ZrC(111) Zr-terminated bicrystal has the highest UTS at 2500 K.

Tree water-use strategies to improve stormwater retention performance of biofiltration systems.

Biofiltration systems are highly valued in urban landscapes as they remove pollutants from stormwater runoff whilst contributing to a reduction in runoff volumes. Integrating trees in biofilters may improve their runoff retention performance, as trees have greater transpiration than commonly used sedge or herb species. High transpiration rates will rapidly deplete retained water, creating storage capacity prior to the next runoff event. However, a tree with high transpiration rates in a biofilter system will likely be frequently exposed to drought stress. Selecting appropriate tree species therefore requires an understanding of how different trees use water and how they respond to substrate drying. We selected 20 tree species and quantified evapotranspiration (ET) and drought stress (leaf water potential; Ψ) in relation to substrate water content. To compare species, we developed metrics which describe: (i) maximum rates of ET under well-watered conditions, (ii) the sensitivity of ET and (iii) the response of Ψ to declining substrate water content. Using these three metrics, we classified species into three groups: risky, balanced or conservative. Risky and balanced species showed high maximum ET, whereas conservative species always had low ET. As substrates dried, the balanced species down-regulated ET to delay the onset of drought stress; whereas risky species did not. Therefore, balanced species with high ET are more likely to improve the retention performance of biofiltration systems without introducing significant drought risk. This classification of tree water use strategies can be easily integrated into water balance models and improve tree species selection for biofiltration systems.

A process for energy-efficient high-solids fed-batch enzymatic liquefaction of cellulosic biomass.

The enzymatic hydrolysis of cellulosic biomass is a key step in the biochemical production of fuels and chemicals. Economically feasible large-scale implementation of the process requires operation at high solids loadings, i.e., biomass concentrations >15% (w/w). At increasing solids loadings, however, biomass forms a high viscosity slurry that becomes increasingly challenging to mix and severely mass transfer limited, which limits further addition of solids. To overcome these limitations, we developed a fed-batch process controlled by the yield stress and its changes during liquefaction of the reaction mixture. The process control relies on an in-line, non-invasive magnetic resonance imaging (MRI) rheometer to monitor real-time evolution of yield stress during liquefaction. Additionally, we demonstrate that timing of enzyme addition relative to biomass addition influences process efficiency, and the upper limit of solids loading is ultimately limited by end-product inhibition as soluble glucose and cellobiose accumulate in the liquid phase.

YouTube™ as a source of patient information for lumbar discectomy.

INTRODUCTION: YouTube™ contains more than 60% of all videos on the internet. Its popularity has increased, and it has now become a source of patient education and information. It is unregulated for the quality of its videos. This project was designed to assess the quality of videos on YouTube™ on lumbar discectomy. METHODS: A systematic search of YouTube™ was performed. The search terms used were 'lumbar' and 'discectomy'. The first ten pages were reviewed. Information was recorded relating to the date of publishing, the publisher and the number of viewings. The content was reviewed using criteria based on recommendations from the British Association of Spine Surgeons website. Content was assessed and points were awarded for information relating to management options, description of the procedure (including anaesthetic, likely recovery and outcome) and complications as well as information relating to the author and his or her institute. An overall rating of 'inadequate', 'poor', 'average' or 'good' was given. RESULTS: Overall, 81 videos were identified. The total number of viewings was 2,722,964 (range: 139-111,891), with an average number of 34,037 viewings per video. There were 16 with a rating of 'good', 25 with a rating of 'average' and 40 with a rating of 'poor' or 'inadequate'. The most common missing information related to anaesthesia or complications. Most videos (69/81) were broadcast by surgeons or surgical institutes. CONCLUSIONS: The quality of YouTube™ videos is variable and we believe this represents the unregulated nature of broadcasts on YouTube™. Thought should be given to information in videos prior to placement.

Is there any purpose in classifying subtrochanteric fractures? The reproducibility of four classification systems.

INTRODUCTION: Classification systems are used for communication, planning treatment options, predicting outcomes and research purposes. The majority of subtrochanteric fractures are now treated with intramedullary nails and therefore questioning the need for classification. OBJECTIVES: To assess the intra- and inter-observer reproducibility of the Seinsheimer, AO and Russell-Taylor (RT) classification systems and to assess a new simple system (MCG). MATERIALS AND METHODS: The MCG system was developed to alert the surgeon to potential hazards: type 1-subtrochanteric fracture (ST#) with intact trochanters, type 2-ST# involving greater trochanter (entry point for nailing difficult), and type 3-ST# involving lesser trochanter (most unstable). Thirty-two anteroposterior and lateral radiographs of subtrochanteric fractures were classified independently for each of the 4 classification systems by 4 observers on 2 separate occasions. RESULTS: The intra- and inter-observer variation was poor in all systems (highest Kappa 0.35). MCG had the best reproducibility followed by RT, then AO and Seinsheimer. The data were re-analysed to determine whether the findings were due to the presence of too many subgroups and whether the observers could more accurately identify important individual subclassifications: Seinsheimer 3a, AO31-A3.1, RT 1 or 2, RT a or b, and MCG3. The MCG3 had the narrowest ranges for intra- and inter-observer reproducibility. CONCLUSIONS: The classification systems analysed in this study have poor reproducibility and seem to be of little value in predicting the outcome of intramedullary nailing as all of the fractures achieved union. The MCG system may be of some use in alerting the surgeon to potential problems.

Procedural risk following carotid endarterectomy in the hyperacute period after onset of symptoms.

OBJECTIVES: There have been concerns that performing carotid endarterectomy (CEA) in the hyperacute period after onset of a transient ischaemic attack (TIA) or stroke may be associated with a significant increase in the procedural risk that could offset any long-term benefit to the patient. The aim of this audit was to determine the 30-day risk of stroke/death after CEA in symptomatic patients, stratified for delay from the most recent neurological event, mode of presentation, and age. METHODS: Retrospective audit in 475 recently symptomatic patients between October 1, 2008, and April 24, 2013. RESULTS: Forty-one patients (9%) underwent surgery <48 hours of their most recent event, with a 30-day death/stroke rate of 2.4% (1/41). The procedural risk was 1.8% in 167 patients who underwent surgery within 3-7 days (3/167), falling to 0.8% in 133 patients who underwent surgery between 8 and 14 days (1/133) and 0.8% in 134 patients whose surgery took place after >14 days had elapsed (1/134). Overall, 208 (44%) underwent surgery within 7 days of their most recent neurological event (30-day risk = 1.9%), while 341 (72%) underwent CEA within 14 days (30 day risk = 1.5%). There was no evidence of any systematic differences in procedural risk by operating in the hyperacute period relating to mode of presentation (TIA, stroke, amaurosis) or age (<80 years; >80 years). CONCLUSIONS: This audit found no evidence that the procedural risk was increased when CEA was performed in the hyperacute period whether this time period was defined as <48 hours, <7 days, or <14 days.

Genetic and clinical factors predict lithium's effects on PER2 gene expression rhythms in cells from bipolar disorder patients.

Bipolar disorder (BD) is associated with abnormal circadian rhythms. In treatment responsive BD patients, lithium (Li) stabilizes mood and reduces suicide risk. Li also affects circadian rhythms and expression of 'clock genes' that control them. However, the extent to which BD, Li and the circadian clock share common biological mechanisms is unknown, and there have been few direct measurements of clock gene function in samples from BD patients. Hence, the role of clock genes in BD and Li treatment remains unclear. Skin fibroblasts from BD patients (N=19) or healthy controls (N=19) were transduced with Per2::luc, a rhythmically expressed, bioluminescent circadian clock reporter gene, and rhythms were measured for 5 consecutive days. Rhythm amplitude and period were compared between BD cases and controls with and without Li. Baseline period was longer in BD cases than in controls. Li 1 mM increased amplitude in controls by 36%, but failed to do so in BD cases. Li 10 mM lengthened period in both BD cases and controls. Analysis of clock gene variants revealed that PER3 and RORA genotype predicted period lengthening by Li, whereas GSK3ß genotype predicted rhythm effects of Li, specifically among BD cases. Analysis of BD cases by clinical history revealed that cells from past suicide attempters were more likely to show period lengthening with Li 1 mM. Finally, Li enhanced the resynchronization of damped rhythms, suggesting a mechanism by which Li could act therapeutically in BD. Our work suggests that the circadian clock's response to Li may be relevant to molecular pathology of BD.

Closing the loop: a 21-year audit of strategies for preventing stroke and death following carotid endarterectomy.

The objective of this review was to identify causes of stroke/death after carotid endarterectomy (CEA) and to develop transferable strategies for preventing stroke/death after CEA, via an overview of a 21-year series of themed research and audit projects. Three preventive strategies were identified: (i) intra-operative transcranial Doppler (TCD) ultrasound and completion angioscopy which virtually abolished intra-operative stroke, primarily through the removal of residual luminal thrombus prior to restoration of flow; (ii) dual antiplatelet therapy with a single 75-mg dose of clopidogrel the night before surgery in addition to regular 75 mg aspirin which virtually abolished post-operative thromboembolic stroke and may also have contributed towards a decline in stroke/death following major cardiac events; and (iii) the provision of written guidance for managing post-CEA hypertension which was associated with virtual abolition of intracranial haemorrhage and stroke as a result of hyperperfusion syndrome. The pathophysiology of peri-operative stroke is multifactorial and no single monitoring or therapeutic strategy will reduce its prevalence. Two of the preventive strategies developed during this 21-year project (peri-operative dual antiplatelet therapy, published guidance for managing post-CEA hypertension) are easily transferable to practices elsewhere.

The war against error: a 15 year experience of completion angioscopy following carotid endarterectomy.

BACKGROUND: A policy of intra-operative transcranial Doppler (TCD) and completion angioscopy was previously associated with virtual abolition of intra-operative stroke (apparent upon recovery from anaesthesia) following carotid endarterectomy (CEA). The aims of this study were to determine whether the prevalence of technical error has diminished with experience and whether our monitoring/quality control policy was still associated with low rates of intra-operative stroke 20 years after its introduction. METHODS: Retrospective review of four consecutive cohorts of 400 patients undergoing CEA between October 1995 and March 2010 (1600 CEAS in total). RESULTS: One hundred four patients (7%) had thrombus removed following angioscopy and prior to flow restoration, while 31 (2.1%) underwent repair of a distal intimal flap. The prevalence of intimal flaps diminished from 4.9% in the first 400 patients to 0.8% in the last 400 patients (p = 0.006). By contrast, the prevalence of retained thrombus did not decline with experience (8.5%, 3.7%, 10.3% and 5.4% for the four consecutive periods). Intra-operative TCD and completion angioscopy was, however, associated with extremely low rates of intra-operative stroke (0.25%, 0.25%, 0.5% and 0.25% during the four study periods). CONCLUSION: Most intra-operative strokes probably follow embolisation of thrombus following restoration of flow. This can be prevented by angioscopy which has the advantage of being performed prior to flow restoration. Increasing experience was associated with a decline in the detection of intimal flaps, but not in the prevalence of retained thrombus. Even the most experienced of surgeons can still be responsible for inadvertent technical error.

A radiological comparison of anterior fusion rates in anterior lumbar interbody fusion.

Aim To compare anterior fusion in standalone anterior lumbar interbody fusion (ALIF) using cage and screw constructs and anterior cage-alone constructs with posterior pedicle screw supplementation but without posterior fusion. Methods Eighty-five patients underwent single- or two-level ALIF procedure for degenerative disk disease or lytic spondylolisthesis (SPL). Posterior instrumentation was performed without posterior fusion in all cases of lytic SPL and when the anterior cage used did not have anterior screw through cage fixation. Results Seventy (82%) patients had adequate radiological follow-up at a mean of 19 months. Forty patients had anterior surgery alone (24 single level and 16 two levels) and 30 had front-back surgery (15 single level and 15 two levels). Anterior locked pseudarthrosis was only seen in the anterior surgery-alone group when using the STALIF cage (Surgicraft, Worcestershire, UK) (37 patients). This occurred in five of the single-level surgeries (5/22) and nine of the two-level surgeries (9/15). Fusion was achieved in 100% of the front-back group and only 65% (26/40) of the anterior surgery-alone group. Conclusion Posterior pedicle screw supplementation without posterolateral fusion improves the fusion rate of ALIF when using anterior cage and screw constructs. We would recommend supplementary posterior fixation especially in cases where more than one level is being operated.

Functional genetic variation in the Rev-Erbα pathway and lithium response in the treatment of bipolar disorder.

Bipolar disorder (BD) is characterized by disruptions in circadian rhythms such as sleep and daily activity that often normalize after lithium treatment in responsive patients. As lithium is known to interact with the circadian clock, we hypothesized that variation in circadian 'clock genes' would be associated with lithium response in BD. We determined genotype for 16 variants in seven circadian clock genes and conducted a candidate gene association study of these in 282 Caucasian patients with BD who were previously treated with lithium. We found that a variant in the promoter of NR1D1 encoding Rev-Erbα (rs2071427) and a second variant in CRY1 (rs8192440) were nominally associated with good treatment response. Previous studies have shown that lithium regulates Rev-Erbα protein stability by inhibiting glycogen synthase kinase 3ß (GSK3ß). We found that GSK3ß genotype was also suggestive of a lithium response association, but not statistically significant. However, when GSK3ß and NR1D1 genotypes were considered together, they predicted lithium response robustly and additively in proportion to the number of response-associated alleles. Using lymphoblastoid cell lines from patients with BD, we found that both the NR1D1 and GSK3ß variants are associated with functional differences in gene expression. Our findings support a role for Rev-Erbα in the therapeutic mechanism of lithium and suggest that the interaction between Rev-Erbα and GSK3ß may warrant further study.

Fenestrated aortic endografts for juxtarenal aortic aneurysm: medium term outcomes.

AIMS: The utility of fenestrated-endovascular aneurysm repair (FEVAR) remains uncertain. This study examines the medium term outcomes of patients undergoing FEVAR for asymptomatic juxtarenal abdominal aortic aneurysm (AAA). METHODS: Consecutive patients undergoing elective FEVAR for juxtarenal AAA at a single tertiary centre were studied between October 2005 and March 2010. Patients were followed up for at least six-months within a protocol including clinical examination, laboratory studies, CT and duplex imaging, and abdominal radiographs. Outcomes were assessed in terms of survival, target vessel patency and graft related complications. RESULTS: Twenty-nine patients were analysed on an intention to treat basis. There were 27 men and two women of median (range) age 74 (54-86) years. Mean (SD) aneurysm diameter was 68 (7) mm. Median (range) ASA score was 3 (2-4). No procedures required conversion to an open procedure, but one procedure was abandoned. Seventy-nine visceral vessels were perfused through a fabric fenestration or scallop. All vessels remained patent at completion angiography. No patients died within 30-days of surgery. During follow up there were four (14%) deaths at a median (range) of 17 (8-21) months after aneurysm repair. None of these deaths were aneurysm related. Eighteen (62%) patients suffered one or more graft related complications, of whom 11 (38%) required one or more early or late reintervention. CONCLUSIONS: Fenestrated aortic endografts can be utilized safely in the management of juxtarenal AAA in patients at high-risk for open surgery. However, the rate of graft related complication and reintervention is high at medium term follow up.

Dual antiplatelet therapy prior to carotid endarterectomy reduces post-operative embolisation and thromboembolic events: post-operative transcranial Doppler monitoring is now unnecessary.

BACKGROUND: Thrombotic stroke following carotid endarterectomy (CEA) is preceded by high-grade embolisation (detected using transcranial Doppler (TCD)) and can be prevented by incremental doses of Dextran. However, this strategy is labour intensive and Dextran manufacture has now ceased. A randomised trial has suggested that a single 75 mg dose of Clopidogrel (administered the night before surgery in addition to daily 75 mg Aspirin) significantly reduces post-CEA embolisation. We hypothesized that this model of dual antiplatelet therapy might significantly reduce the need for adjuvant Dextran therapy. METHODS: Retrospective audit of prospectively acquired data in 297 patients undergoing CEA between 01.08.2006 and 30.07.2009. All received routine Aspirin (75 mg daily) in addition to a single 75 mg dose of Clopidogrel the night before surgery. All underwent completion angioscopy and those with a temporal window (n = 270) underwent intra- and post-operative TCD monitoring. RESULTS: High rate embolisation requiring Dextran (>25 emboli in any 10 min period) occurred in only 1/270 patients (0.4%), significantly less than the 3.2% rate in historical controls where Clopidogrel was not administered. There were no peri-operative deaths, but 3/297 patients suffered non-disabling strokes (intra-operative extension of a pre-existing deficit, haemorrhage into lentiform nucleus after hypertensive crisis, contralateral embolic stroke). The overall 30-day death/stroke rate (1.0%) was not-significantly lower than the 2.6% rate observed in the preceding 821 patients. CONCLUSIONS: 75 mg Clopidogrel administered the night before surgery (in addition to daily 75 mg Aspirin) was associated with a significant reduction in post-operative embolisation and Dextran utilisation. No ipsilateral thromboembolic ischaemic events occurred in this series. As a consequence of this audit, one dose of 75 mg Clopidogrel will continue to be given pre-operatively (in addition to daily 75 mg Aspirin) and routine post-operative TCD monitoring has now ceased.

Management of limb ischaemia in the neonate and infant.

AIM: This article aims to provide the reader with an insight into the diagnosis and management of limb ischaemia presenting in neonates and infants by examining the published literature. MATERIALS AND METHODS: A Pubmed search and an Ovid Medline/Embase search were both performed. The keywords were: 'neonatal' or 'paediatric' or 'pediatric' and 'limb' and 'ischemia' or 'ischaemia' and relevant articles were retrieved and analysed. Articles pertaining to children over the age of 3 years and non-English literature articles were excluded.

Buttock claudication and erectile dysfunction after internal iliac artery embolization in patients prior to endovascular aortic aneurysm repair.

Coil embolization of the internal iliac artery (IIA) is used to extend the application of endovascular aneurysm repair (EVAR) in cases of challenging iliac anatomy. Pelvic ischemia is a complication of the technique, but reports vary as to the rate and severity. This study reports our experience with IIA embolization and compares the results to those of other published series. The vascular unit database of the Leicester Royal Infirmary was used to identify patients who had undergone IIA coil embolization prior to EVAR. Data were collected from hospital case notes and by telephone interviews. Thirty-eight patients were identified; 29 of these were contactable by telephone. A literature search was performed for other studies of IIA embolization and the results were pooled. In this series buttock claudication occurred in 55% (16 of 29 patients) overall: in 52% of unilateral embolizations (11 of 21) and 63% of bilateral embolizations (5 of 8). New erectile dysfunction occurred in 46% (6 of 13 patients) overall: in 38% of unilateral embolizations (3 of 8) and 60% of bilateral embolizations (3 of 5). The literature review identified 18 relevant studies. The results were pooled with our results, to give 634 patients in total. Buttock claudication occurred in 28% overall (178 of 634 patients): in 31% of unilateral embolizations (99 of 322) and 35% of bilateral embolizations (34 of 98) (p = 0.46, Fisher's exact test). New erectile dysfunction occurred in 17% overall (27 of 159 patients): in 17% of unilateral embolizations (16 of 97) and 24% of bilateral embolizations (9 of 38) (p = 0.33). We conclude that buttock claudication and erectile dysfunction are frequent complications of IIA embolization and patients should be counseled accordingly.

Oil migration in chocolate-peanut butter paste confectionery as a function of chocolate formulation.

Migration of oil from high oil content filling to the chocolate coating can result in undesirable quality changes in filled chocolate confectionery products. The objective of this study was to monitor and model peanut oil migration in a 2-layer chocolate-peanut butter paste model confectionery. Spatial and temporal oil content changes were evaluated using magnetic resonance imaging. Five formulations of chocolate, which varied in chocolate particle size, milk fat content, and emulsifier level, were assessed at 2 temperatures, 20 and 30 degrees C. The spatial and temporal experimental data were modeled using a Fickian-based diffusion model, fitting for the diffusion coefficient, D, over a time frame of 17 d. Values of the diffusion coefficient ranged from 1.82 to 3.23 x 10(-11) m2/s for the chocolate formulations stored at 30 degrees C. No significant mass transfer took place in the 20 degrees C samples over the experimental time frame. This study describes the dynamic nature of the interface between the chocolate and peanut butter paste layers, quantifies the mass transfer from the peanut butter paste to the chocolate, and reinforces the importance of temperature control.