Determination of the miscibility of phosphorus additives in polymer matrices by high resolution solid state NMR

Summary The measurement of high resolution solid state NMR proton T_1p values (relaxation time in the rotating frame) provides a method for the study of the compatibility of phosphorus additives with polymer matrices. Results are compared for two commercial phosphorus stabilizers, bis (2,4 di-t-butylphenyl) pentaerythritol diphosphite (Phosphite 1) and tris (2,4 di-t-butylphenyl) phosphite (Phosphite 2), in 5% masterbatches in linear low density polyethylene (LLDPE). Phosphite 1 shows compatibility even when poorly mixed while the Phosphite 2 shows separation into two domains with different relaxation rates and different chemical shifts in the solid state.     

Low-threshold, high-power, 1.3-μm wavelength, InGaAsP-InPetched-facet folded-cavity surface-emitting lasers

A 1.3-μm wavelength, InGaAsP-InP folded-cavity, surface-emitting laser with CH₄-H₂ reactive ion-etched vertical and 45° angled facets was demonstrated for the first time. Continuous-wave threshold currents of 32 mA have been achieved, with >15 mW CW power for the surface-emitted light. These surface-emitting lasers with two dry-etched facets are suitable for wafer-level testing and for monolithic integration with other InP-based photonic devices     

Channel response to grade-control structures on Muddy Creek,Mississippi

Grade-control structures are commonly employed to prevent bed degradation and concomitant bank instability of channelized reaches of rivers. A study of a 20 km reach of a coastal plains stream was conducted in 1985 to determine the effects of 12 rock-lined grade-control structures that were installed between 1977 and 1983 prior to channel excavation. An Allowable Tractive Stress Method (TR.25) was used to determine the placement of grade-control structures, and the gradients between them, for a trapezoidal-shaped channel designed to convey the 1 year recurrence interval peak flow. The design was successful in preventing bed degradation and bank erosion over the period of observation. However, unpredicted channel responses have occurred. Aggradation is apparent between control structures, and a two-stage compound channel has formed as a consequence of berm development, especially in the lower, older subreach. In the lower subreach, the vegetated berms have constricted the cross-sectional area at the design discharge (99 m³ s^?1), and as a result, water-surface slope, shear stress, and unit-stream power have incresed. Bed material has become coarser and better sorted, which has increased shear intensity values. These unexpected changes are attributed to the lack of adequate consideration of the requirement for balance between sediment supply and transport in the TR.25 procedure; seven tributaries contribute sediment to the main channel of the study reach. It appears that the increased energy is utilized in bedload transport rather than channel erosion. This study demonstrates that the TR.25 method is too conservative if significant amounts of sediment are being supplied to the design channel. In such cases, adjustments in channel morphology will increase the energy to accommodate bedload transport.     

Children's concepts of volume and flotation.

Conducted a pilot study in which children (aged 7–9 yrs and 11–13 yrs) were asked to judge which 1 out of 3 wooden blocks would float (or sink), given weight and volume information for each block relative to a block that was known to float (or sink). Analysis of explanations indicated that judgments may have been based on the size–weight illusion. An experiment exploring the basis of flotation judgments was conducted with 14 children aged 7 yrs 1 mo to 9 yrs 6 mo and 16 children aged 11 yrs 4 mo to 14 yrs 11 mo that involved a test for judgment of volume based on information integration theory. Results show that Ss aged 7–24 yrs accurately judged volume by integrating 3 dimensions—width, depth, and height—according to the multiplicative rule. A rule assessment of their flotation judgments showed no age differences in initial rule, with weight rules being most popular. However, after feedback there were marked age effects; the 7–9 yr olds abandoned their initial rule without finding an alternative, and the 11–24 yr olds were generally able to find the correct flotation rule. It is concluded that children aged 7–24 yrs can judge volume but 7–9 yr olds have difficulty with the concept of flotation, possibly because it requires mental comparison of 2 ratios, a task known to be difficult for 7–9 yr olds. (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mice deficient in both p53 and Rb develop tumors primarily of endocrine origin

To examine whether a cooperative role exists between inherited Rb and p53 deficiency in tumorigenesis, crosses were made between p53- and Rb-deficient mice and were monitored for subsequent tumor incidence and spectrum. Parental mice containing either Rb or p53 mutant alleles showed a predisposition for pituitary adenomas or lymphomas and sarcomas, respectively. Mice heterozygous for both Rb and p53 mutant alleles developed tumors of endocrine origin (medullary thyroid carcinomas, pancreatic islet cell carcinomas, and pituitary adenomas) in addition to lymphomas and sarcomas. Except for pituitary adenomas, these endocrine tumors were rarely seen in the parental p53 or Rb mutant mice. Mice deficient for both Rb and p53 showed a faster rate of tumor development than mice deficient only in Rb or p53. These results indicate that p53 and Rb do cooperate in the acceleration of tumorigenesis and in the development of endocrine tumor types.     

Characterization of DNA adducts formed by anti-benzo[g]chrysene 11,12-dihydrodiol 13,14-epoxide

The anti-11,12-dihydrodiol 13,14-epoxide of benzo[g]chrysene, a fjord-region-containing hydrocarbon, was found to react with DNA in vitro to yield, as the major product, an adduct in which the epoxide of the 11R, 12S, 13S, 14R enantiomer was opened trans by the amino group of deoxyadenosine. The structures of this adduct and other deoxyadenosine and deoxyguanosine adducts were established by spectroscopic methods. In reactions with deoxyguanylic acid, a product tentatively identified as a 7-substituted guanine was also detected. The mutagenic properties of this dihydrodiol epoxide in shuttle vector pSP189 showed that mutation at AT pairs accounted for 39% of base change mutations whereas chemical findings indicated that about 60% of adducts formed in calf thymus DNA involved adenines. Since calf thymus DNA is 56% AT and the target supF gene is 41% AT, the findings represent a fairly close relationship between adduct formation and mutagenic response. Overall, the chemical and mutagenic selectivities for the two purine bases in DNA were similar, though not identical, to those for the only other fjord-region-containing hydrocarbon studied in depth, i.e., benzo[c]phenanthrene. A major difference for these two hydrocarbon derivatives, however, is that benzo[c]phenanthrene dihydrodiol epoxides react to much higher extents (approximately 4-fold) with DNA than did the benzo[g]chrysene derivative.     

Surface organometallic chemistry on metals. Application to chemicals and fine chemicals

Some applications of surface organometallic chemistry on metals to catalysis are presented, showing the great importance of the modification of a metallic surface by organometallic compounds on its catalytic properties. The selective hydrogenation of α–β unsaturated aldehydes such as citral (Z and E) can be achieved on rhodium–tin catalysts. While rhodium alone is relatively unselective, geraniol (and nerol) can be obtained selectively (> 98%) without a significant loss of activity by use of a rhodium–tin catalyst showing a typical ligand effect of the organotin fragment on the surface. Similarly, in the isomerization of (+) 3-carene into (+) 2-carene or the dehydrogenation of butan–2–ol into methyl ethyl ketone, the selectivity into the desired product is increased by introduction of small amounts of tin which will form adatoms poisoning unselective sites. An alloying effect of tin is also presented in the dehydrogenation reaction of isobutane in isobutene. This revised version was published online in June 2006 with corrections to the Cover Date.     

Partially glucose-capped oligosaccharides are found on the hemoglobins of the deep-sea tube worm Riftia pachyptila

We report here the structural determination of N-linked oligosaccharides found on extracellular hemoglobins of the hydrothermal vent tube worm Riftia pachyptila. Structures were elucidated by a combination of electrospray ionization tandem mass spectrometry, matrix-assisted laser desorption/ionization mass spectrometry, normal-phase high performance liquid chromatography, and exoglycosidase digestion. The sugar chains were found to consist mainly of high-mannose-type glycans with some structures partially capped by one or two terminal glucose residues. The present study represents the first report of the occurrence of glucose capping of N-linked carbohydrates in a secreted glycoprotein of a metazoan. Previously, glucose capping has only been described for a membrane-bound surface glycoprotein from the unicellular parasite Leishmania mexicana amazonensis.     

Spatial behavior in gerbils (Meriones unguiculatus).

Investigated whether adult gerbils could use an allocentric frame of reference to efficiently solve a spatial memory task. 38 male Ss were allowed to explore an arena containing an object. The external reference frame was reduced to a single visual landmark. After habituation, Ss entered the arena from a new direction. A 2nd object, identical to the 1st object, was placed symmetrically with regard to the landmark. The 2nd object was explored more than the 1st object, a result showing that the 2nd object was differentiated on the basis of location. This result suggests that, during the course of exploration, Ss had learned about the spatial features of the experimental situation. It is suggested that Ss' final discrimination performance (preference for the novel stimulus location) reflected an allocentric rather than egocentric frame of reference. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)