Toward high-performance nanostructured thermoelectric materials: The progress of bottom-up solution chemistry approaches

Significant research effort has recently gone into the synthesis of thermoelectric nanomaterials through different chemical approaches since nanomaterials chemistry became a promising strategy for improving thermoelectric performance. Different thermoelectric nanocrystals, especially PbTe, Bi2Te3 and CoSb3, with various compositions and morphologies have been successfully prepared by solvo/hydrothermal, electrochemical, and ligand-based synthesis methods. Such nanoscale materials show not only substantial reduction in thermal conductivity due to increased phonon scattering at nanoscale grain boundaries and lower densities of phonon states but possibly also an enhancement in thermopower due to electronic quantum size effects. More recently, the notoriously low power factors of thermoelectric nanomaterials prepared by wet chemistry have been significantly improved by using an increasingly cross-disciplinary approach towards the bottom-up synthesis that combines expertise from chemistry, physics, and materials engineering. In this review, we discuss the recent progress and current challenges of preparing thermoelectric nanomaterials with solution-based chemistry approaches

Optimization and evaluation of T7 based RNA linear amplification protocols for cDNA microarray analysis

BACKGROUND: T7 based linear amplification of RNA is used to obtain sufficient antisense RNA for microarray expression profiling. We optimized and systematically evaluated the fidelity and reproducibility of different amplification protocols using total RNA obtained from primary human breast carcinomas and high-density cDNA microarrays. RESULTS: Using an optimized protocol, the average correlation coefficient of gene expression of 11,123 cDNA clones between amplified and unamplified samples is 0.82 (0.85 when a virtual array was created using repeatedly amplified samples to minimize experimental variation). Less than 4% of genes show changes in expression level by 2-fold or greater after amplification compared to unamplified samples. Most changes due to amplification are not systematic both within one tumor sample and between different tumors. Amplification appears to dampen the variation of gene expression for some genes when compared to unamplified poly(A)(+) RNA. The reproducibility between repeatedly amplified samples is 0.97 when performed on the same day, but drops to 0.90 when performed weeks apart. The fidelity and reproducibility of amplification is not affected by decreasing the amount of input total RNA in the 0.3–3 micrograms range. Adding template-switching primer, DNA ligase, or column purification of double-stranded cDNA does not improve the fidelity of amplification. The correlation coefficient between amplified and unamplified samples is higher when total RNA is used as template for both experimental and reference RNA amplification. CONCLUSION: T7 based linear amplification reproducibly generates amplified RNA that closely approximates original sample for gene expression profiling using cDNA microarrays

Cardiovascular outcomes among elderly patients with heart failure and coronary artery disease and without atrial fibrillation: a retrospective cohort study

Background Coronary artery disease accelerates heart failure progression, leading to poor prognosis and a substantial increase in morbidity and mortality. This study was aimed to assess the impact of coronary artery disease on all-cause mortality, myocardial infarction (MI), and ischemic stroke (IS) among hospitalized newly-diagnosed heart failure (HF) patients with left ventricular systolic dysfunction (LVSD). Methods This retrospective cohort study included Medicare patients (aged ≥65 years) with ≥1 inpatient heart failure claim (index date = discharge date) during 01JAN2007-31DEC2013. Patients were required to have continuous enrollment for ≥1-year pre-index date (baseline: 1-year pre-index period) without a prior heart failure claim (in the 1 year pre-index prior to the index hospital admission); follow-up ran from the index date to death, disenrollment from the health plan, or the end of the study period, whichever occurred first. HF with LVSD patients, identified with diagnosis codes of systolic dysfunction (excluding baseline atrial fibrillation), were stratified based on prevalent coronary artery disease at baseline into coronary artery disease and non-coronary artery disease cohorts. Main outcomes were occurrence of major adverse cardiovascular events including all-cause mortality, myocardial infarction, and ischemic stroke. Propensity score matching (PSM) was used to balance patient characteristics. Kaplan-Meier curves of ACM and cumulative incidence distribution of MI/IS were presented. Results Of 22,230 HF with LVSD patients, 15,827 (71.2%) had coronary artery disease and were overall more likely to be younger (79.8 vs 80.9 years), male (49.6% vs. 35.6%), white (86.2% vs 81.4%), with more prevalent comorbidities including hypertension (80.7% vs 74.3%), hyperlipidemia (67.7% vs 46.7%), and diabetes (46.3% vs 35.8%) (all p < 0.0001). After propensity score matching, cohorts included 5792 patients each. The coronary artery disease cohort had significantly higher cumulative incidence of myocardial infarction and ischemic stroke at the end of 7-year follow-up vs non-coronary artery disease (myocardial infarction = 50.0% vs 18.0%; ischemic stroke = 23.3% vs 18.7%; all p < 0.0001). Follow-up all-cause mortality rates were similar between the two cohorts. Conclusions HF with LVSD patients with coronary artery disease had significantly higher incidence of ischemic stroke and myocardial infarction, but similar all-cause mortality compared to those without coronary artery disease

The influence of obesity on the outcome of treatment of lumbar disc herniation: analysis of the Spine Patient Outcomes Research Trial (SPORT).

BACKGROUND: Questions remain as to the effect that obesity has on patients managed for symptomatic lumbar disc herniation. The purpose of this study was to determine if obesity affects outcomes following the treatment of symptomatic lumbar disc herniation. METHODS: An as-treated analysis was performed on patients enrolled in the Spine Patient Outcomes Research Trial for the treatment of lumbar disc herniation. A comparison was made between patients with a body mass index of/m² (nonobese) (n = 854) and those with a body mass index of ≥30 kg/m² (obese) (n = 336). Baseline patient demographic and clinical characteristics were documented. Primary and secondary outcomes were measured at baseline and at regular follow-up time intervals up to four years. The difference in improvement from baseline between operative and nonoperative treatment was determined at each follow-up period for both groups. RESULTS: At the time of the four-year follow-up evaluation, improvements over baseline in primary outcome measures were significantly less for obese patients as compared with nonobese patients in both the operative treatment group (Short Form-36 physical function, 37.3 compared with 47.7 points [p \u3c 0.001], Short Form-36 bodily pain, 44.2 compared with 50.0 points [p = 0.005], and Oswestry Disability Index, -33.7 compared with -40.1 points [p \u3c 0.001]) and the nonoperative treatment group (Short Form-36 physical function, 23.1 compared with 32.0 points [p \u3c 0.001] and Oswestry Disability Index, -21.4 compared with -26.1 points [p \u3c 0.001]). The one exception was that the change from baseline in terms of the Short Form-36 bodily pain score was statistically similar for obese and nonobese patients in the nonoperative treatment group (30.9 compared with 33.4 points [p = 0.39]). At the time of the four-year follow-up evaluation, when compared with nonobese patients who had been managed operatively, obese patients who had been managed operatively had significantly less improvement in the Sciatica Bothersomeness Index and the Low Back Pain Bothersomeness Index, but had no significant difference in patient satisfaction or self-rated improvement. In the present study, 77.5% of obese patients and 86.9% of nonobese patients who had been managed operatively were working a full or part-time job. No significant differences were observed in the secondary outcome measures between obese and nonobese patients who had been managed nonoperatively. The benefit of surgery over nonoperative treatment was not affected by body mass index. CONCLUSIONS: Obese patients realized less clinical benefit from both operative and nonoperative treatment of lumbar disc herniation. Surgery provided similar benefit over nonoperative treatment in obese and nonobese patients

Effectiveness of Surgery for Lumbar Stenosis and Degenerative Spondylolisthesis in the Octogenarian Population: Analysis of the Spine Patient Outcomes Research Trial (SPORT) Data.

BACKGROUND: The purpose of this study was to determine whether surgery is an effective option for the treatment of stenosis of the lumbar spine and degenerative spondylolisthesis in the octogenarian population. METHODS: An as-treated analysis of patients with lumbar stenosis and degenerative spondylolisthesis enrolled in the Spine Patient Outcomes Research Trial (SPORT) was performed. Patients who were at least eighty years of age (n = 105) were compared with those younger than eighty years (n = 1130). Baseline patient and clinical characteristics were noted, and the difference in improvement from baseline between operative and nonoperative treatment was determined for each group at each follow-up time period up to four years. RESULTS: There were no significant baseline differences in the primary or secondary patient-reported clinical outcome measures between the two patient age groups. Patients at least eighty years of age had higher prevalences of multilevel stenosis, severe stenosis, and asymmetric motor weakness. Patients at least eighty years of age also had higher prevalences of hypertension, heart disease, osteoporosis, and joint problems at baseline, but they had a lower body mass index and lower prevalences of depression and smoking. Fifty-eight of the 105 patients at least eighty years of age and 749 of the 1130 younger patients underwent operative management. There were no differences in the rates of intraoperative or postoperative complications, reoperation, or postoperative mortality between the older and younger groups. Averaged over a four-year follow-up period, operatively treated patients at least eighty years of age had significantly greater improvement in all primary and secondary outcome measures compared with nonoperatively treated patients. The treatment effects in patients at least eighty years of age were similar to those in younger patients for all primary and secondary measures except the SF-36 (Short Form-36) bodily pain domain and the percentage who self-rated their progress as a major improvement, in both of which the treatment effect was significantly smaller. CONCLUSIONS: Operative treatment of lumbar stenosis and degenerative spondylolisthesis offered a significant benefit over nonoperative treatment in patients at least eighty years of age (p \u3c 0.05). There were no significant increases in the complication and mortality rates following surgery in this patient population compared with younger patients (p \u3e 0.05). LEVEL OF EVIDENCE: Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence

Prolonged Drying Trend Coincident with the Demise of Norse Settlement in Southern Greenland

Declining temperature has been thought to explain the abandonment of Norse settlements, southern Greenland, in the early 15th century, although limited paleoclimate evidence is available from the inner settlement region itself. Here, we reconstruct the temperature and hydroclimate history from lake sediments at a site adjacent to a former Norse farm. We find no substantial temperature changes during the settlement period but rather that the region experienced a persistent drying trend, which peaked in the 16th century. Drier climate would have notably reduced grass production, which was essential for livestock overwintering, and this drying trend is concurrent with a Norse diet shift. We conclude that increasingly dry conditions played a more important role in undermining the viability of the Eastern Settlement than minor temperature changes

Nonparametric Evaluation of Dynamic Disease Risk: A Spatio-Temporal Kernel Approach

Quantifying the distributions of disease risk in space and time jointly is a key element for understanding spatio-temporal phenomena while also having the potential to enhance our understanding of epidemiologic trajectories. However, most studies to date have neglected time dimension and focus instead on the “average” spatial pattern of disease risk, thereby masking time trajectories of disease risk. In this study we propose a new idea titled “spatio-temporal kernel density estimation (stKDE)” that employs hybrid kernel (i.e., weight) functions to evaluate the spatio-temporal disease risks. This approach not only can make full use of sample data but also “borrows” information in a particular manner from neighboring points both in space and time via appropriate choice of kernel functions. Monte Carlo simulations show that the proposed method performs substantially better than the traditional (i.e., frequency-based) kernel density estimation (trKDE) which has been used in applied settings while two illustrative examples demonstrate that the proposed approach can yield superior results compared to the popular trKDE approach. In addition, there exist various possibilities for improving and extending this method

Electrophysiological Guidance of Epidural Electrode Array Implantation over the Human Lumbosacral Spinal Cord to Enable Motor Function after Chronic Paralysis.

Epidural electrical stimulation (EES) of the spinal cord has been shown to restore function after spinal cord injury (SCI). Characterization of EES-evoked motor responses has provided a basic understanding of spinal sensorimotor network activity related to EES-enabled motor activity of the lower extremities. However, the use of EES-evoked motor responses to guide EES system implantation over the spinal cord and their relation to post-operative EES-enabled function in humans with chronic paralysis attributed to SCI has yet to be described. Herein, we describe the surgical and intraoperative electrophysiological approach used, followed by initial EES-enabled results observed in 2 human subjects with motor complete paralysis who were enrolled in a clinical trial investigating the use of EES to enable motor functions after SCI. The 16-contact electrode array was initially positioned under fluoroscopic guidance. Then, EES-evoked motor responses were recorded from select leg muscles and displayed in real time to determine electrode array proximity to spinal cord regions associated with motor activity of the lower extremities. Acceptable array positioning was determined based on achievement of selective proximal or distal leg muscle activity, as well as bilateral muscle activation. Motor response latencies were not significantly different between intraoperative recordings and post-operative recordings, indicating that array positioning remained stable. Additionally, EES enabled intentional control of step-like activity in both subjects within the first 5 days of testing. These results suggest that the use of EES-evoked motor responses may guide intraoperative positioning of epidural electrodes to target spinal cord circuitry to enable motor functions after SCI