The relative effects of transection of the gustatory branches of the seventh and ninth cranial nerves on NaCl taste detection in rats.

Chorda tympani nerve (CT) transection in rats severely impairs NaCl taste detection. These rats can detect higher concentrations of NaCl, however, suggesting that remaining oral nerves maintain some salt sensibility. Rats were tested in a gustometer with a 2-response operant taste-detection task before and after sham surgery (n = 5), combined transection of the CT and the greater superficial petrosal nerves (GSP; 7x, n = 6), or transection of the glossopharyngeal nerve (GL; 9x, n = 4). Thresholds did not significantly change after sham surgery. Although the GL responds to NaCl and innervates nearly 60% of total taste buds, 9x surgery had no effect. However, 7x surgery increased NaCl detection threshold by ～2.5 log?? units, greater than that reported for CT transection alone. These results suggest that the GSP contributes to NaCl sensitivity in rats and also demonstrate that the GL and perhaps the superior laryngeal and lingual nerve proper can maintain some NaCl detectability at high concentrations. These findings confirm the primacy of the 7th nerve relative to the 9th nerve in sensibility of NaCl in the rat model. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An integrated multiple criteria preference ranking approach to the Canadian west coast port congestion conflict

An integrative conflict analysis approach, incorporating an Analytic Hierarchy Process (AHP) based preference ranking method into the Graph Model for Conflict Resolution (GMCR), is employed to investigate the Canadian west coast port congestion dispute. The Canadian west coast has historically been an important gateway connecting North America to Asia thanks to its specific geographical and strategic location. Despite successful operations and maintenance of the port facilities to handle international trade during the past few decades, the west coast is now facing increasing congestion problems, resulting in significant delays in transporting goods from the west coast to other parts of Canada and the USA. The strategic analyses carried out in this research suggest potential resolutions in which Canada would expand port facilities at various locations, encouraging traders to continue choosing the Canadian west coast as one of their trade gateways to North America.     

An absolute interval scale of order for point patterns

Human observers readily make judgements about the degree of order in planar arrangements of points (point patterns). Here, based on pairwise ranking of 20 point patterns by degree of order, we have been able to show that judgements of order are highly consistent across individuals and the dimension of order has an interval scale structure spanning roughly 10 just-notable-differences (jnd) between disorder and order. We describe a geometric algorithm that estimates order to an accuracy of half a jnd by quantifying the variability of the size and shape of spaces between points. The algorithm is 70% more accurate than the best available measures. By anchoring the output of the algorithm so that Poisson point processes score on average 0, perfect lattices score 10 and unit steps correspond closely to jnds, we construct an absolute interval scale of order. We demonstrate its utility in biology by using this scale to quantify order during the development of the pattern of bristles on the dorsal thorax of the fruit fly.     

Preparation of Photodegradable Oligomers Containing Metal–Metal Bonds Using ADMET

ADMET was evaluated as a method for preparing organometallic polymers with metal–metal bonds in the main chain. The Cp₂Mo₂CO₄(Ph₂P(CH₂)₆CH=CH₂)₂ complex was synthesized, and the X-ray crystal structure is reported. The molecule did not undergo ADMET polymerization with Grubbs’ or Schrock’s catalysts. In a control experiment to test if the Ph₂P(CH₂)₆CH=CH₂ ligand was interfering with the ADMET reaction, the phosphine was reacted with Grubbs’ 2nd generation catalyst. The dimerized metathesis product Ph₂P(CH₂)₆CH=CH(CH₂)₆PPh₂ was obtained with no observed degradation or deactivation of the catalyst. To test the inherent ADMET reactivity of the Ph₂P(CH₂)₆CH=CH₂ ligand when it is bonded to a metal center, the mononuclear cis-Mo(CO)₄(Ph₂P(CH₂)₆CH=CH₂)₂ complex was synthesized and polymerized using Grubbs’ 2nd generation catalyst. These control experiments suggest that the inability of Cp₂Mo₂CO₄(Ph₂P(CH₂)₆CH=CH₂)₂ to polymerize is not due to electronic effects pertaining to the C=C unit of the Ph₂P(CH₂)₆CH=CH₂ ligand. Accordingly, steric effects are implicated in the inability of the Cp₂Mo₂CO₄(Ph₂P(CH₂)₆CH=CH₂)₂ to polymerize by ADMET.     

Position Around A Tree: Consequences For Pheromone Detection

The air flow pattern expected around a cylindrical object such as a tree in slow wind, is predicted from fluid mechanics to have areas of faster flow (upwind) and slower recirculating flow with eddies (downwind). An organism located on the surface of a tree would experience different flow depending on its circumferential position. If that organism was searching for a chemical signal, such as a pheromone plume, it might maximize its probability of chemodetection by placing itself in areas of greatest flow speed (the upwind surface of the cylinder, i.e., in front of the separation points). We tested whether wood cockroaches in the genus Parcoblatta exhibit such upwind positioning; they live in forests, and males actively fly from tree to tree, while searching for females releasing sex pheromone. In contrast to an expectation of upwind preference, male cockroaches were evenly distributed around trees relative to upwind (measured with a novel “feather boa” flow visualization technique), even though the wind direction was relatively steady. We investigated whether sex pheromone could be detected at any location around a cylindrical surface in a laboratory flow chamber by using Bombyx mori wing fanning as a bioassay. Although upwind moths arrayed on the surface detected pheromone more rapidly, pheromone detection occurred at least a third of the time at any position, which could explain the even distribution of Parcoblatta males around trees.     

Amplified Spontaneous Emission in Close‐Packed Films of Semiconductor Nanocrystals Using Picosecond Excitation

We present experimental observations of line‐narrowing of the photoluminescence in close‐packed thin films of CdSe nanocrystals with epitaxial ZnS shells, under excitation from a pulsed source of 100 ps duration, both at 77 K and at room temperature (RT). Atomic force microscopy (AFM) of these films reveals them to be optically flat to less than 1 % of the emission wavelength and we propose that waveguiding and amplified spontaneous emission is the principal mechanism for line‐narrowing. We observe that line‐narrowing is assisted by the use of films with a bimodal distribution of nanocrystal sizes, where the excited state population is concentrated on the larger nanocrystals due to energy transfer.     

Time-resolved electrostatic force microscopy of polymer solar cells

Blends of conjugated polymers with fullerenes, polymers, or nanocrystals make promising materials for low-cost photovoltaic applications. Different processing conditions affect the efficiencies of these solar cells by creating a variety of nanostructured morphologies, however, the relationship between film structure and device efficiency is not fully understood. We introduce time-resolved electrostatic force microscopy (EFM) as a means to measure photoexcited charge in polymer films with a resolution of 100 nm and 100 micros. These EFM measurements correlate well with the external quantum efficiencies measured for a series of polymer photodiodes, providing a direct link between local morphology, local optoelectronic properties and device performance. The data show that the domain centres account for the majority of the photoinduced charge collected in polyfluorene blend devices. These results underscore the importance of controlling not only the length scale of phase separation, but also the composition of the domains when optimizing nanostructured solar cells.