Prolonging charge separation in P3HT-SWNT composites using highly enriched semiconducting nanotubes

Single-walled carbon nanotubes (SWNTs) have potential as electron acceptors in organic photovoltaics (OPVs), but the currently low-power conversion efficiencies of devices remain largely unexplained. We demonstrate effective redispersion of isolated, highly enriched semiconducting and metallic SWNTs into poly(3-hexylthiophene) (P3HT). We use these enriched blends to provide the first experimental evidence of the negative impact of metallic nanotubes. Time-resolved microwave conductivity reveals that the long-lived carrier population can be significantly increased by incorporating highly enriched semiconducting SWNTs into semiconducting polymer composites.     

Understanding the Role of Ferroelastic Domains on the Pyroelectric and Electrocaloric Effects in Ferroelectric Thin Films

Temperature‐ and electric‐field‐induced structural transitions in a polydomain ferroelectric can have profound effects on its electrothermal susceptibilities. Here, the role of such ferroelastic domains on the pyroelectric and electrocaloric response is experimentally investigated in thin films of the tetragonal ferroelectric PbZr_0.2Ti_0.8O₃. By utilizing epitaxial strain, a rich set of ferroelastic polydomain states spanning a broad thermodynamic phase space are stabilized. Using temperature‐dependent scanning‐probe microscopy, X‐ray diffraction, and high‐frequency phase‐sensitive pyroelectric measurements, the propensity of domains to reconfigure under a temperature perturbation is quantitatively studied. In turn, the “extrinsic” contributions to pyroelectricity exclusively due to changes between the ferroelastic domain population is elucidated as a function of epitaxial strain. Further, using highly sensitive thin‐film resistive thermometry, direct electrocaloric temperature changes are measured on these polydomain thin films for the first time. The results demonstrate that temperature‐ and electric‐field‐driven domain interconversion under compressive strain diminish both the pyroelectric and the electrocaloric effects, while both these susceptibilities are enhanced due to the exact‐opposite effect from the extrinsic contributions under tensile strain.     

How long do Chinese Americans stay in psychotherapy?

A sample of 145 Chinese-American outpatient clients was analyzed to determine how long they would stay in psychotherapy when ethnic- and language-matched therapists were provided. Results indicate that the median duration of psychotherapy for this sample was 8 sessions. The mean duration was 12.00 sessions, and the dropout rate was 12.38%. The Chinese-American clients' length of psychotherapy was comparable to that of the general American public. The results also showed that a small percentage of clients made the majority of psychotherapy visits. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Descriptive characteristics and length of psychotherapy of Chinese American clients seen in private practice.

Professional psychologists often have a need for information on the patterns of service accessing and service use by ethnic groups. Demographic characteristics and psychotherapy use of 229 Chinese American clients, seen in a Southern California private practice between 1989 and 1996, are described. Diagnostic evaluations of 27 assessment requests, 77 consultations, and 125 psychotherapy cases indicated that depressive disorders, adjustment disorders, anxiety disorders, and relational problems were the most frequently presented problems. For the 125 treated cases, length of treatment ranged from 1–38 sessions with a median of 4 and mean of 5.98 sessions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Governing Decentralized Production: Institutions, Public Policy, and the Prospects for Inter-firm Collaboration in US Manufacturing

Much of the literature on the changing face of US manufacturing acknowledges that successful governance of decentralized production is vital to its future but questions whether in practice firms will engage in the collaborative relationships envisaged by optimistic theorists of a "new production paradigm". Our interview-based field research on large and small metalworking firms in the US upper Midwest shows that although large manufacturers are actively seeking to improve collaboration by sharing strategic information and engaging in joint design, pervasive organizational dysfunctions create systemic barriers to the fuller development of cooperative relations with suppliers. But these barriers do not appear insurmountable. The example of a Wisconsin policy experiment is used to demonstrate the viability of institutional solutions that can help resolve inter- and intra-organizational blockages, while encouraging manufacturing firms to follow through on the collaborative strategies they officially espouse.     

Electric field sensing with a hybrid polymer/glass fiber

We demonstrate the operation of an in-fiber electric field sensor. The sensor is fabricated with selective chemical etching of the core of a D-shaped optical fiber followed by the deposition of an electro-optic polymer (PMMA/DR1), which forms a hybrid core. The device demonstrates electromagnetic field sensitivity less than 100 V/m at a frequency of 2.9 GHz. Epi is estimated to be 60 MV/m with an insertion loss of 14.4 dB.     

Catalytic performance of Pt-promoted cobalt-based catalysts for the steam reforming of ethanol

In this study, Pt-promoted Co_x/ZrO₂ catalysts (including 1.5 wt% Pt and Co loading of 0.75, 1.5, 3.0, 6.0, 9.0, 12, 24 and 48 wt%, respectively) were prepared by the incipient wet impregnation method for hydrogen production by steam reforming of ethanol (SRE). Evaluation of catalytic activities and products distribution toward the SRE reaction were carried out in a fixed-bed reactor with 100 mg of catalyst under an H₂O/EtOH molar ratio of 13.0 and gas hourly space velocity (GHSV) of 22,000 h⁻¹. The results revealed that the optimal loading of cobalt could enhance the capacities of catalytic performance and C–C scission, further raised the yield of hydrogen (YH₂)$\left({\text{Y}}_{{\text{H}}_2}\right)$ and lowered the deposited carbon, CH₄ and CO side-products due to the combination effect of cobalt and platinum. The Pt_1.5Co₁₂/ZrO₂ catalyst exhibited superiority in the SRE reaction, where complete conversion of ethanol was achieved at 275 °C. The (YH₂)$\left({\text{Y}}_{{\text{H}}_2}\right)$ approached 4.95, and only minor CO (<2%), CH₄ (<4%), and carbon deposition (<0.5%) were detected at 500 °C. In addition, the ethanol conversion still remained complete, and the selectivity of hydrogen exceeded 70% during a 116 h time-on-stream test under the same condition.     

电信时钟设计的新趋势

当网络和通信解决方案提供的传输速率超过1Gbps、甚至10Gbps时,精确的系统定时就成为优先考虑的设计关键.随着性能要求的提高,各种元件必须工作的速率也随之提高.更快的系统工作速度意味着分布式时钟信号中的细小相差,会因为ASIC、FPGA、CPU不能在预定时间处理预定信息,可较大机会引起灾害性故障.