Leveraging Insulator's Tacticity in Semiconducting Polymer Blends.

Blending conjugated polymers with insulating matrices is often utilized for engineering extrinsic properties in organic electronics. Semiconductor/insulator blends are typically processed to form a uniformly distributed network of conductive domains within the insulating matrix, marrying electronic and physical properties from individual components. Understanding of polymer-polymer interactions in such systems is thus crucial for property co-optimization. One of the commonly overlooked parameters is the structural configuration of the insulator on the resulting properties, especially the electronic properties. This study investigated how the tacticity of the matrix polymer, among other relevant parameters in play, impacts solid state crystallization in semiconductor/matrix blends and hence the resulting charge transport properties. We found an intricate dependence of the film morphology, aggregation behavior, electronic charge transport, and mixed ionic-electronic coupling properties on the insulator's tacticity. Our experimentally iterative approach shows that for a given application, when selecting semiconductor/insulator combinations, the tacticity of the matrix can be leveraged to optimize performance and vary solid-state structure.

Storylines of family medicine III: core principles-primary care, systems and family.

Storylines of Family Medicine is a 12-part series of thematically linked mini-essays with accompanying illustrations that explore the many dimensions of family medicine, as interpreted by individual family physicians and medical educators in the USA and elsewhere around the world. In 'III: core principles-primary care, systems, and family', authors address the following themes: 'Continuity of care-building therapeutic relationships over time', 'Comprehensiveness-combining breadth and depth of scope', 'Coordination of care-managing multiple realities', 'Access to care-intersectional, systemic, and personal', 'Systems theory-a core value in patient-centered care', 'Family-oriented practice-supporting patients' health and well-being', 'Family physician as family member' and 'Family in the exam room'. May readers develop new understandings from these essays.

First demonstration of an all-solid-state optical cryocooler.

Solid-state optical refrigeration uses anti-Stokes fluorescence to cool macroscopic objects to cryogenic temperatures without vibrations. Crystals such as Yb3+-doped YLiF4 (YLF:Yb) have previously been laser-cooled to 91 K. In this study, we show for the first time laser cooling of a payload connected to a cooling crystal. A YLF:Yb crystal was placed inside a Herriott cell and pumped with a 1020-nm laser (47 W) to cool a HgCdTe sensor that is part of a working Fourier Transform Infrared (FTIR) spectrometer to 135 K. This first demonstration of an all-solid-state optical cryocooler was enabled by careful control of the various desired and undesired heat flows. Fluorescence heating of the payload was minimized by using a single-kink YLF thermal link between the YLF:Yb cooling crystal and the copper coldfinger that held the HgCdTe sensor. The adhesive-free bond between YLF and YLF:Yb showed excellent thermal reliability. This laser-cooled assembly was then supported by silica aerogel cylinders inside a vacuum clamshell to minimize undesired conductive and radiative heat loads from the warm surroundings. Our structure can serve as a baseline for future optical cryocooler devices.

Prostaglandin H synthase 2 variant (Val511Ala) in African Americans may reduce the risk for colorectal neoplasia.

Prostaglandin H synthase 2 (also known as cyclooxygenase-2) is thought to play a role in the prevention of colon cancer by aspirin, an inhibitor of the enzyme. We used DNA heteroduplex analysis to screen the prostaglandin H synthase 2 gene, to search for naturally occurring enzyme variants that may simulate the effects of aspirin. We found among African-Americans a single-nucleotide polymorphism that changes valine to alanine at residue 511 (V511A; GTT>GCT; g.5939T>C; allele frequency 0.045). The polymorphism was also seen among Asian-Indians (allele frequency, 0.03) but not among Chinese, Filipinos, Hispanics, Japanese, Koreans, Samoans, and Caucasians. The amino acid change is predicted to open a 53 cubic angstrom cavity near the active site of the enzyme, but no change in V(max), K(m), or thermal stability was observed for the variant enzyme in COS-1 cell transfection assays. Case-control analysis of African-Americans from two different study populations showed a 0.56 odds ratio for colorectal adenomas among polymorphism carriers (95% confidence interval, 0.25-1.27; 161 cases and 219 controls). A similar analysis of African-Americans nested in the Multiethnic Cohort Study showed a 0.67 odds ratio for colorectal cancer (95% confidence interval, 0.28-1.56; 138 cases and 258 controls). Consistency of the results across all three of the studies is potentially compatible with a protective effect of the polymorphism, mimicking aspirin.

Search for fractional-charge particles in meteoritic material.

We have used an automated Millikan oil drop method to search for free fractional-charge particles in a sample containing in total 3.9 mg of pulverized Allende meteorite suspended in 259 mg of mineral oil. The average diameter of the drops was 26.5 microm with the charge on about 42 500 000 drops being measured. This search was motivated by the speculation that isolatable, fractional-charge particles produced in the early Universe and present in our Solar System are more likely to be accumulated in asteroids than on Earth's surface. No evidence for fractional-charge particles was found. With 95% confidence, the concentration of particles with fractional-charge more than 0.25 e (e being the magnitude of the electron charge) from the nearest integer charge is less than 1.3 x 10(-21) particles per nucleon in the meteoritic material and less than 1.9 x 10(-23) particles per nucleon in the mineral oil.