Influence of processing on stability,microstructure and thermoelectric properties of Ca3Co4 − xO9 + δ

Due to high figure of merit, Ca₃Co_4 ? xO_9 + δ (CCO) has potential as p-type material for high-temperature thermoelectrics. Here, the influence of processing including solid state sintering, spark plasma sintering and post-calcination on stability, microstructure and thermoelectric properties is reported. By a new post-calcination approach, single-phase materials were obtained from precursors to final dense ceramics in one step. The highest zT of 0.11 was recorded at 800 °C for CCO with 98 and 72% relative densities. In situ high-temperature X-ray diffraction in air and oxygen revealed a higher stability of CCO in oxygen (～970 °C) than in air (～930 °C), with formation of Ca₃Co₂O₆ which also showed high stability in oxygen, even at 1125 °C. Since achievement of phase pure high density CCO by post-calcination method in air is challenging, the phase stability of CCO in oxygen is important for understanding and further improvement of the method.     

Performance of a Thermoelectric Module Based on n-Type (La0.12Sr0.88)0.95TiO3−δ and p-Type Ca3Co4−xO9+δ

Here, we present the performance of a thermoelectric (TE) module consisting of n-type (La_0.12Sr_0.88)_0.95TiO₃ and p-type Ca₃Co_4?xO_9+δ materials. The main challenge in this investigation was operating the TE module in different atmospheric conditions, since n-type has optimum TE performance at reducing conditions, while p-type has optimum at oxidizing conditions. The TE module was exposed to two different atmospheres and demonstrated higher stability in N₂ atmosphere than in air. The maximum electrical power output decreased after 40 h when the hot side was exposed to N₂ at 600°C, while only 1 h at 400°C in ambient air was enough to oxidize (La_0.12Sr_0.88)_0.95TiO₃ followed by a reduced electrical power output. The module generated maximum electrical power of 0.9 mW (～?4.7 mW/cm²) at 600°C hot side and δT?～?570 K in N₂, and 0.15 mW (～?0.8 mW/cm²) at 400°C hot side and δT?～?370 K in air. A stability limit of Ca₃Co_3.93O_9+δ at ～?700°C in N₂ was determined by in situ high-temperature x-ray diffraction.

     

Subject''s perceptions of the crew interaction dynamics under prolonged isolation

BACKGROUND: Short-term variability of RR interval and blood pressure occurs predominantly at low frequency (LF; approximately 0.1 Hz) and high frequency (approximately 0.25 Hz). The arterial baroreflex is thought to be the predominant determinant of the LF component of RR variability. Patients with severe congestive heart failure (CHF) have an attenuated or absent LF oscillation in RR variability. The left ventricular assist device (LVAD) offers a unique possibility for analysis of spectral oscillations in RR interval independent of any effects of blood pressure that influence these oscillations via the baroreflex. METHODS AND RESULTS: We performed spectral analysis of RR, blood pressure, and respiration in 2 patients with CHF before and after LVAD implantation. LF components of the RR-interval and blood pressure variability were absent in both CHF patients before LVAD implantation. After LVAD implantation, spectral analysis of the RR interval showed restoration of a clear and predominant LF oscillation in the native hearts of both patients, with no such oscillation evident in the blood pressure profile. CONCLUSIONS: During total circulatory support with the LVAD, the LF oscillation in RR interval of the native heart, absent in CHF, is restored. This LF oscillation in RR interval occurs in the absence of LF oscillations in blood pressure and thus is unlikely to be explained by baroreflex mechanisms. Hence, the absence of LF oscillation in the RR interval in CHF is functional and is reversible by LVAD circulation. The presence of a predominant LF oscillation in RR interval independent of any oscillation in blood pressure suggests that the LF oscillation is a fundamental property of central autonomic outflow.     

The effectiveness of group psychotherapy during the first three weeks of hospitalization. A controlled study

Insight-oriented group psychotherapy is a common modality of treatment on inpatient psychiatric wards, yet is effectiveness for acutely hospitalized patients has not been adequately studied. A comparison was made of the effects of three experimental conditions (insight-oriented group psychotherapy, activity-oriented task group, and unstructured control condition) on 86 acutely hospitalized psychiatric patients at a United States Air Force teaching hospital. The group psychotherapy and task group patients did not show greater improvement after 20 days of hospitalization than control patients. In fact, significantly more psychotic patients scored worse in the group psychotherapy condition. It is suggested that insight-oriented group psychotherapy may not be an effective treatment modality during the first 3 weeks of psychiatric hospitalization, especially for psychotic patients.