Effect of Heat Treatment Time and Temperature on the Microstructure and Shape Memory Properties of Nitinol Wires.

In this study, the effect of heat treatment parameters on the optimized performance of Ni-rich nickel-titanium wires (NiTi/Nitinol) were investigated that were intended for application as actuators across various industries. In this instance, the maximum recovery strain and actuation angle achievable by a nitinol wire were employed as indicators of optimal performance. Nitinol wires were heat treated at different temperatures, 400-500 °C, and times, 30-120 min, to study the effects of these heat treatment parameters on the actuation performance and properties of the nitinol wires. Assessment covered changes in density, hardness, phase transition temperatures, microstructure, and alloy composition resulting from these heat treatments. DSC analysis revealed a decrease in the austenite transformation temperature, which transitioned from 42.8 °C to 24.39 °C with an increase in heat treatment temperature from 400 °C to 500 °C and was attributed to the formation of Ni4Ti3 precipitates. Increasing the heat treatment time led to an increase in the austenite transformation temperature. A negative correlation between the hardness of the heat-treated samples and the heat treatment temperature was found. This trend can be attributed to the formation and growth of Ni4Ti3 precipitates, which in turn affect the matrix properties. A novel approach involving image analysis was utilized as a simple yet robust analysis method for measurement of recovery strain for the wires as they underwent actuation. It was found that increasing heat treatment temperature from 400 °C to 500 °C above 30 min raised recovery strain from 0.001 to 0.01, thereby maximizing the shape memory effect.

Total Center Percutaneous Coronary Intervention Volume and 30-Day Mortality: A Contemporary National Cohort Study of 427 467 Elective, Urgent, and Emergency Cases.

BACKGROUND: The relationship between procedural volume and prognosis after percutaneous coronary intervention (PCI) remains uncertain, with some studies finding in favor of an inverse association and some against. This UK study provides a contemporary reassessment in one of the few countries in the world with a nationally representative PCI registry. METHODS AND RESULTS: A nationwide cohort study was performed using the national British Cardiovascular Intervention Society registry. All adult patients undergoing PCI in 93 English and Welsh NHS hospitals between 2007 and 2013 were analyzed using hierarchical modeling with adjustment for patient risk. Of 427 467 procedures (22.0% primary PCI) in 93 hospitals, 30-day mortality was 1.9% (4.8% primary PCI). 87.1% of centers undertook between 200 and 2000 procedures annually. Case mix varied with center volume. In centers with 200 to 399 PCI cases per year, a smaller proportion were PCI for ST-segment-elevation myocardial infarction (8.4%) than in centers with 1500 to 1999 PCI cases per year (24.2%), but proportionally more were for ST-segment-elevation myocardial infarction with cardiogenic shock (8.4% versus 4.3%). For the overall PCI cohort, after risk adjustment, there was no significant evidence of worse, or better, outcomes in lower volume centers from our own study, or in combination with results from other studies. For primary PCI, there was also no evidence for increased or decreased mortality in lower volume centers. CONCLUSIONS: After adjustment for differences in case mix and clinical presentation, this study supports the conclusion of no trend for increased mortality in lower volume centers for PCI in the UK healthcare system. CLINICAL TRIAL REGISTRATION: https://www.clinicaltrials.gov. Unique identifier: NCT02184949.

Twenty-Five-Year Alcohol Consumption Trajectories and Their Association With Arterial Aging: A Prospective Cohort Study.

BACKGROUND: Emerging evidence suggests that arterial stiffness, an important marker of cardiovascular health, is associated with alcohol consumption. However, the role of longer-term consumption patterns in the progression of arterial stiffness over time remains unclear. A longitudinal cohort design was used to evaluate the association between alcohol consumption over 25 years and subsequent changes in arterial stiffness. METHODS AND RESULTS: Data (N=3869; 73% male) were drawn from the Whitehall II cohort study of British civil servants, in which participants completed repeat pulse wave velocity assessments of arterial stiffness across a 4- to 5-year interval. Repeated alcohol intake measurements were used to categorize participants into alcohol consumer types, accounting for longitudinal variability in consumption. Sex-stratified linear mixed-effects modeling was used to investigate whether drinker types differed in their relationship to pulse wave velocity and its progression over time. Males with consistent long-term heavy intake >112 g of ethanol/week had significantly higher baseline pulse wave velocity (b=0.26 m/s; P=0.045) than those who drank consistently moderately (1-112 g of ethanol/week). Male former drinkers showed significantly greater increases in arterial stiffness longitudinally compared to consistently moderate drinkers (b=0.11 m/s; P=0.009). All associations were nonsignificant for females after adjustment for body mass index, heart rate, mean arterial pressure, diabetes mellitus, high-density lipoprotein, and triglycerides. CONCLUSIONS: This work demonstrates that consistently heavy alcohol consumption is associated with higher cardiovascular risk, especially among males, and also provides new insights into the potential impact of changes in drinking levels over time. It discusses the additional insights possible when capturing longitudinal consumption patterns in lieu of reliance on recent intake alone. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT02663791.

Underestimating the Alcohol Content of a Glass of Wine: The Implications for Estimates of Mortality Risk.

AIMS: Increases in glass sizes and wine strength over the last 25 years in the UK are likely to have led to an underestimation of alcohol intake in population studies. We explore whether this probable misclassification affects the association between average alcohol intake and risk of mortality from all causes, cardiovascular disease and cancer. METHODS: Self-reported alcohol consumption in 1997-1999 among 7010 men and women in the Whitehall II cohort of British civil servants was linked to the risk of mortality until mid-2015. A conversion factor of 8 g of alcohol per wine glass (1 unit) was compared with a conversion of 16 g per wine glass (2 units). RESULTS: When applying a higher alcohol content conversion for wine consumption, the proportion of heavy/very heavy drinkers increased from 28% to 41% for men and 15% to 28% for women. There was a significantly increased risk of very heavy drinking compared with moderate drinking for deaths from all causes and cancer before and after change in wine conversion; however, the hazard ratios were reduced when a higher wine conversion was used. CONCLUSIONS: In this population-based study, assuming higher alcohol content in wine glasses changed the estimates of mortality risk. We propose that investigator-led cohorts need to revisit conversion factors based on more accurate estimates of alcohol content in wine glasses. Prospectively, researchers need to collect more detailed information on alcohol including serving sizes and strength. SHORT SUMMARY: The alcohol content in a wine glass is likely to be underestimated in population surveys as wine strength and serving size have increased in recent years. We demonstrate that in a large cohort study, this underestimation affects estimates of mortality risk. Investigator-led cohorts need to revisit conversion factors based on more accurate estimates of alcohol content in wine glasses.

Impact of operator volume for percutaneous coronary intervention on clinical outcomes: what do the numbers say?

The impact of operator and centre volume on clinical outcomes and quality of care has been of considerable debate in recent years in a number of surgical- and procedural-based specialities. A relationship between higher volumes at both the institutional and operator levels and better clinical outcomes would at first appear intuitive, based on the premise that performing a procedure very infrequently would be likely to lead to unfamiliarity, complications, and poorer outcomes. In the current review, we study the relationship between operator volume and outcomes in the setting of percutaneous coronary intervention (PCI), and examine the evidence for current clinical competency guidelines that advocate that a minimum number of PCI procedures be undertaken annually. Whilst both high institutional and operator volumes have been shown to be associated with better outcomes by reducing death and in-hospital mortality, these data are often derived from the pre-stent era, or when high-volume operators undertook far smaller numbers of procedures than is currently recommended to maintain clinical competency. The emphasis of specific volume requirements for optimal outcomes needs to be interpreted with caution, as volume is not a surrogate for quality and merely one of the variables associated with outcome. Healthcare providers should focus on other measures of quality such as robust clinical care pathways, evidence-based treatments, periodic case review, using validated risk assessment scores, and ascertainment of outcome to improve care and reduce adverse events.

Complex regional pain syndrome: An optimistic perspective.

Complex regional pain syndrome (CRPS) presents with clinical symptoms that can no longer be explained by the initial trauma, including pain, sensory, motor, and trophic symptoms, and impairment of autonomic control of the limb. These symptoms spread distally and go beyond single nerve innervation territories. Typically, the symptoms change through the course of CRPS as a result of the varying pathophysiology. Diagnosis is made clinically after the rigorous elimination of other possible causes, and 3-phase bone scintigraphy can be a useful tool for confirming CRPS. In acute stages, inflammatory symptoms prevail and should be treated with anti-inflammatory agents (steroids), bisphosphonates, or topical application of dimethyl sulfoxide. In chronic stages, many symptoms are related to so-called central neuroplasticity; these include hyperalgesia, sensory loss, motor symptoms, body perception disturbance, autonomic symptoms, and learned incorrect behavior such as nonuse. At this stage, the only medical treatment that is effective against pain without improving the function is ketamine infusions, but this has side effects. Physical therapy, graded motor imagery, and pain exposure/graded exposure in vivo therapy can help to overcome central reorganization. If a relevant mental comorbidity is present, the patient should be referred for psychotherapeutic treatment. Invasive treatment should be restricted to special cases and only offered after psychosomatic assessment. If these recommendations are followed, CRPS prognosis is not as poor as commonly assumed. Whether the patients can return to their previous life depends on particular individual factors.

CI Therapy is Beneficial to Patients with Chronic Low-Functioning Hemiparesis after Stroke.

CI therapy is effective in patients with relatively good levels of residual arm function but its applicability to patients with low-functioning hemiparesis is not entirely clear. In the present study, we examined the feasibility and efficacy of the CI therapy concept in patients with very limited upper arm function prior to treatment, and further tested how the length of daily shaping training and constraining the good arm affects treatment outcome. In a baseline-controlled design, 65 chronic patients were treated with 2 weeks of modified CI therapy. Patients were randomly allocated to four treatment groups receiving 90 or 180 min of daily shaping training applied with or without constraint, respectively. Outcome was measured through the Reliable Change Index, which was calculated for parameters of motor function, health, and psychological wellbeing. Follow-up data were collected at 6 and 12 months. Two analyses were conducted, a whole-group analysis across all 65 participants and a sub-group analysis contrasting the four treatment variants. The whole-group analysis showed a significant treatment effect, which was largely sustained after 1 year. The sub-group analysis revealed a mixed picture; while improvements against the baseline period were observed in all four subgroups, 180 min of daily shaping training coupled with the constraint yielded better outcome on the MAL but not the WMFT, while for 90 min of training the level of improvement was similar for those who wore the constraint and those who did not. Together these results suggest that, at least in those patients available for follow-up measures, modified CI therapy induces sustained improvements in motor function in patients with chronic low-functioning hemiparesis. The absence of clear differences between the four treatment variants points to a complex relationship between the length of daily shaping training and the constraint in this patient group, which is likely to be mediated by fatigue and/or compliance with the constraint.

Post-concussion syndrome: prevalence after mild traumatic brain injury in comparison with a sample without head injury.

PRIMARY OBJECTIVE: To compare the prevalence of persistent post-concussion syndrome (PCS; >1 year post-injury) in participants with mild traumatic brain injury (mTBI) and those without head injury. RESEARCH DESIGN: A cross-sectional sample of 119 participants with mTBI and 246 without previous head injury. METHODS: Online questionnaires collected data about post-concussion symptoms, cognitive failures, anxiety, depression, sleep behaviour and post-traumatic stress disorder. Variability within the sample was addressed by splitting by PCS diagnosis to create four groups: mTBI + PCS, mTBI-PCS, Control + PCS and Control-PCS. PCS was diagnosed using ICD-10 criteria in all groups, with controls not requiring previous head injury. MAIN OUTCOMES AND RESULTS: PCS was present to a similar extent in participants with no head injury (34%) compared to those with mTBI (31%). Only report of headaches, which could be caused by expectation bias, distinguished between mTBI + PCS and Control + PCS groups. In addition, significantly higher cognitive problems were observed in participants with mTBI compared with the control group. CONCLUSIONS: Persistent PCS, as currently defined, is not specific to mTBI. These data suggest that somatic and cognitive symptoms are most likely to be able to distinguish PCS after mTBI from that present in the general population. Further research is necessary into these factors in order to create more specific PCS diagnostic criteria.

Calculation of frequency-dependent hyperpolarizabilities using general coupled-cluster models.

By exploiting the similarities between response theory and analytic derivative theory, we present a scheme for calculating frequency-dependent hyperpolarizabilities at the coupled-cluster level within the framework for analytic third derivatives. This has been implemented for arbitrary levels of coupled-cluster theory up to the full-configuration-interaction limit. An investigation of some small molecules shows that the inclusion of triple excitations is essential for an accurate description of hyperpolarizabilities.

Advances in methods and algorithms in a modern quantum chemistry program package.

Advances in theory and algorithms for electronic structure calculations must be incorporated into program packages to enable them to become routinely used by the broader chemical community. This work reviews advances made over the past five years or so that constitute the major improvements contained in a new release of the Q-Chem quantum chemistry package, together with illustrative timings and applications. Specific developments discussed include fast methods for density functional theory calculations, linear scaling evaluation of energies, NMR chemical shifts and electric properties, fast auxiliary basis function methods for correlated energies and gradients, equation-of-motion coupled cluster methods for ground and excited states, geminal wavefunctions, embedding methods and techniques for exploring potential energy surfaces.

A family of intracules, a conjecture and the electron correlation problem.

We present a radical approach to the calculation of electron correlation energies. Unlike conventional methods based on Hartree-Fock or density functional theory, it is based on the two-electron phase-space information in the Omega intracule, a three-dimensional function derived from the Wigner distribution. Our formula for the correlation energy is isomorphic to the Hartree-Fock energy expression but requires a new type of four-index integral. Preliminary results, obtained using a model that is based on the known correlation energies of small atoms, are encouraging.

Stereoselective association of binuclear metallacycles in coordination polymers.

A series of structurally related binuclear metallacycles [Cd(NO(3))(2)L](2), where L is an angular exo-bidentate ligand, have been synthesized. Each metallacycle contains two coordinatively unsaturated, chiral metal centers within a single molecule, and the assembly of these metallacycles into polymeric framework structures has been studied systematically for the first time. Stereoselective homochiral association of [Cd(NO(3))(2)L](2) leads to the formation of helical coordination polymers, whereas meso type association results in nonhelical chain structures. The type of stereoselective aggregation depends on the conditions of self-assembly as well as on ligand functionality. Both helical and nonhelical polymeric complexes have been isolated for the metallacycle [Cd(NO(3))(2)(2,4'-pyacph)](2) (2,4'-pyacph = 2,4'-(4-ethynylphenyl)bipyridyl). Homochiral association results in the formation of helical [Cd(NO(3))]( infinity ) chains which link the binuclear [Cd(NO(3))(2)(2,4'-pyacph)](2) metallacycles into racemic two-dimensional sheets which contain both P and M [Cd(NO(3))]( infinity ) helices. In contrast, meso-association leads to the formation of nonhelical one-dimensional chains. It is shown that the product of homochiral association is predominately formed at room temperature and that of meso-association is generated at elevated temperatures. Thus, it may be concluded that the homochiral association appears to be energetically less favorable than the meso-association, a conclusion that has been confirmed by theoretical calculations of the crystal lattice energy. Several high-yield syntheses of bipyridyl-type ligands used for metallacyclic assembly are also reported.