Thermal coatings for titanium-aluminum alloys

Titanium aluminides and titanium alloys are candidate materials for use in hot structure and heat-shield components of hypersonic vehicles because of their good strength-to-weight characteristics at elevated temperature. However, in order to utilize their maximum temperature capability, they must be coated to resist oxidation and to have a high total remittance. Also, surface catalysis for recombination of dissociated species in the aerodynamic boundary layer must be minimized. Very thin chemical vapor deposition (CVD) coatings are attractive candidates for this application because of durability and very light weight. To demonstrate this concept, coatings of boron-silicon and aluminum-boron-silicon compositions were applied to the titanium-aluminides alpha2 (Ti-14Al-21Nb), super-alpha2 (Ti-14Al-23-Nb-2V), and gamma (Ti-33Al-6Nb-1Ta) and to the titanium alloy beta-21S (Ti-15Mo-3Al-3Nb-0.2Si). Coated specimens of each alloy were subjected to a set of simulated hypersonic vehicle environmental tests to determine their properties of oxidation resistance, surface catalysis, radiative emittance, and thermal shock resistance. Surface catalysis results should be viewed as relative performance only of the several coating-alloy combinations tested under the specific environmental conditions of the LaRC Hypersonic Materials Environmental Test System (HYMETS) arc-plasma-heated hypersonic wind tunnel. Tests were also conducted to evaluate the hydrogen transport properties of the coatings and any effects of the coating processing itself on fatigue life of the base alloys. Results are presented for three types of coatings, which are as follows: (1) a single layer boron silicon coating, (2) a single layer aluminum-boron-silicon coating, and (3) a multilayer coating consisting of an aluminum-boron-silicon sublayer with a boron-silicon outer layer

A Review of the Proposed Michigan Rules of Evidence

On January 6, 1977, the Supreme Court of Michigan entered an order stating that it is considering adoption of the proposed Michigan Rules of Evidence which were submitted to the Court by the committee which it appointed in March 1975. The Court has solicited comments from interested persons regarding the proposed rules. A copy of the Supreme Court\u27s order is published in this issue of the Bar Journal. The proposed rules are published in the January 26, 1977, issue of North Western Reporter, Second Series (Michigan Edition). The purpose of this article is to review in general the background and substance of the proposed rules. More detailed information concerning the rules may be obtained by consulting the text of the rules and the committee notes thereto. It is beyond the scope of this article to discuss in detail the policy considerations supporting adoption of each proposed rule which conflicts with prior Michigan law. For the most part the proposed rules are identical with the Federal Rules of Evidence and the policy considerations favoring adoption of the rules are discussed in the Federal Advisory Committee Notes and the legislative history of the Federal Rules

A Review of the Proposed Michigan Rules of Evidence

On January 6, 1977, the Supreme Court of Michigan entered an order stating that it is considering adoption of the proposed Michigan Rules of Evidence which were submitted to the Court by the committee which it appointed in March 1975. The Court has solicited comments from interested persons regarding the proposed rules. A copy of the Supreme Court\u27s order is published in this issue of the Bar Journal. The proposed rules are published in the January 26, 1977, issue of North Western Reporter, Second Series (Michigan Edition). The purpose of this article is to review in general the background and substance of the proposed rules. More detailed information concerning the rules may be obtained by consulting the text of the rules and the committee notes thereto. It is beyond the scope of this article to discuss in detail the policy considerations supporting adoption of each proposed rule which conflicts with prior Michigan law. For the most part the proposed rules are identical with the Federal Rules of Evidence and the policy considerations favoring adoption of the rules are discussed in the Federal Advisory Committee Notes and the legislative history of the Federal Rules

Attempted DNA extraction from a Rancho La Brea Columbian mammoth (Mammuthus columbi): prospects for ancient DNA from asphalt deposits.

Fossil-bearing asphalt deposits are an understudied and potentially significant source of ancient DNA. Previous attempts to extract DNA from skeletons preserved at the Rancho La Brea tar pits in Los Angeles, California, have proven unsuccessful, but it is unclear whether this is due to a lack of endogenous DNA, or if the problem is caused by asphalt-mediated inhibition. In an attempt to test these hypotheses, a recently recovered Columbian mammoth (Mammuthus columbi) skeleton with an unusual pattern of asphalt impregnation was studied. Ultimately, none of the bone samples tested successfully amplified M. columbi DNA. Our work suggests that reagents typically used to remove asphalt from ancient samples also inhibit DNA extraction. Ultimately, we conclude that the probability of recovering ancient DNA from fossils in asphalt deposits is strongly (perhaps fatally) hindered by the organic compounds that permeate the bones and that at the Rancho La Brea tar pits, environmental conditions might not have been ideal for the general preservation of genetic material

Sinks as saviors: why flawed inference cannot assist tiger recovery

A recent study of tigers in Chitwan, Nepal (1) stirred controversy by challenging the “source-sink” approach that underlies current global tiger conservation strategies (2). The observed lack of difference in tiger density estimates inside the protected area compared with a multiple-use area outside is offered as evidence. Based on this result, the study questions the relevance of strictly protected tiger reserves involving regulation of extractive uses and relocation of human settlements. The study offers an alternate vision of sustainable, syntopic “coexistence” of tigers and humans as a solution to increasing human resource demands on tiger habitats

Longitudinal Cognitive Decline in a Novel Rodent Model of Cerebral Amyloid Angiopathy Type-1

Cerebral amyloid angiopathy (CAA) is a small vessel disease characterized by β-amyloid (Aβ) accumulation in and around the cerebral blood vessels and capillaries and is highly comorbid with Alzheimer’s disease (AD). Familial forms of CAA result from mutations within the Aβ domain of the amyloid β precursor protein (AβPP). Numerous transgenic mouse models have been generated around expression of human AβPP mutants and used to study cerebral amyloid pathologies. While behavioral deficits have been observed in many AβPP transgenic mouse lines, relative to rats, mice are limited in behavioral expression within specific cognitive domains. Recently, we generated a novel rat model, rTg-DI, which expresses Dutch/Iowa familial CAA Aβ in brain, develops progressive and robust accumulation of cerebral microvascular fibrillar Aβ beginning at 3 months, and mimics many pathological features of the human disease. The novel rTg-DI model provides a unique opportunity to evaluate the severity and forms of cognitive deficits that develop over the emergence and progression of CAA pathology. Here, we present an in-depth, longitudinal study aimed to complete a comprehensive assessment detailing phenotypic disease expression through extensive and sophisticated operant testing. Cohorts of rTg-DI and wild-type (WT) rats underwent operant testing from 6 to 12 months of age. Non-operant behavior was assessed prior to operant training at 4 months and after completion of training at 12 months. By 6 months, rTg-DI animals demonstrated speed–accuracy tradeoffs that later manifested across multiple operant tasks. rTg-DI animals also demonstrated delayed reaction times beginning at 7 months. Although non-operant assessments at 4 and 12 months indicated comparable mobility and balance, rTg-DI showed evidence of slowed environmental interaction. Overall, this suggests a form of sensorimotor slowing is the likely core functional impairment in rTg-DI rats and reflects similar deficits observed in human CAA

Downward shortwave surface irradiance from 17 sites for the FIRE/SRB Wisconsin experiment

A field experiment was conducted in Wisconsin during Oct. to Nov. 1986 for purposes of both intensive cirrus cloud measurments and SRB algorithm validation activities. The cirrus cloud measurements were part of the FIRE. Tables are presented which show data from 17 sites in the First ISCCP (International Satellite Cloud Climatology Project) Regional Experiment/Surface Radiation Budget (FIRE/SRB) Wisconsin experiment region. A discussion of intercomparison results and calibration inconsistencies is also included

Whole-genome sequence analysis shows that two endemic species of North American wolf are admixtures of the coyote and gray wolf.

Protection of populations comprising admixed genomes is a challenge under the Endangered Species Act (ESA), which is regarded as the most powerful species protection legislation ever passed in the United States but lacks specific provisions for hybrids. The eastern wolf is a newly recognized wolf-like species that is highly admixed and inhabits the Great Lakes and eastern United States, a region previously thought to be included in the geographic range of only the gray wolf. The U.S. Fish and Wildlife Service has argued that the presence of the eastern wolf, rather than the gray wolf, in this area is grounds for removing ESA protection (delisting) from the gray wolf across its geographic range. In contrast, the red wolf from the southeastern United States was one of the first species protected under the ESA and was protected despite admixture with coyotes. We use whole-genome sequence data to demonstrate a lack of unique ancestry in eastern and red wolves that would not be expected if they represented long divergent North American lineages. These results suggest that arguments for delisting the gray wolf are not valid. Our findings demonstrate how a strict designation of a species under the ESA that does not consider admixture can threaten the protection of endangered entities. We argue for a more balanced approach that focuses on the ecological context of admixture and allows for evolutionary processes to potentially restore historical patterns of genetic variation

Uropathogenic Escherichia coli wield enterobactin-derived catabolites as siderophores

Uropathogenic Escherichia coli (UPEC) secrete multiple siderophore types to scavenge extracellular iron(III) ions during clinical urinary tract infections, despite the metabolic costs of biosynthesis. Here, we find the siderophore enterobactin (Ent) and its related products to be prominent components of the iron-responsive extracellular metabolome of a model UPEC strain. Using defined Ent biosynthesis and import mutants, we identify lower molecular weight dimeric exometabolites as products of incomplete siderophore catabolism, rather than prematurely released biosynthetic intermediates. In E. coli, iron acquisition from iron(III)-Ent complexes requires intracellular esterases that hydrolyze the siderophore. Although UPEC are equipped to consume the products of completely hydrolyzed Ent, we find that Ent and its derivatives may be incompletely hydrolyzed to yield products with retained siderophore activity. These results are consistent with catabolic inefficiency as means to obtain more than one iron ion per siderophore molecule. This is compatible with an evolved UPEC strategy to maximize the nutritional returns from metabolic investments in siderophore biosynthesis

The preparation and characterisation of monomeric and linked metal carbonyl clusters containing the closo-Si2Co4 pseudo-octahedral core

PhSiH3 reacts with [Co₄(CO)₁₂] at 50 °C in hydrocarbon solvents to give [(µ₄-SiPh)₂Co₄(CO)₁₁], 2c, shown by an X-ray crystal structure determination to have a pseudo-octahedral Si₂Co₄ core. Substituted aryl-silanes behaved similarly. Mixtures of PhSiH₃, H₃SiC₆H₄SiH₃ and [Co₄(CO)₁₂] in a ca. 2 1 2 ratio gave the dimeric cluster [{Co₄(µ₄-SiPh)(CO)₁₁Si}₂C₆H₄], 3a, which has the two Si₂Co₄ cores linked by a C₆H₄ group to give a rigid molecule which an X-ray structure analysis shows to be over 23 Å long. Related dimers linked by –(CH₂)₈– groups were isolated from mixtures of PhSiH₃, α ,ω-(H₃Si)₂(CH₂)₈ and [Co₄(CO)₁₂]. Electrochemical studies show the two cluster units in 3a do not interact electronically