Distribution of hydrogen in the near surface of Mars: evidence for subsurface ice deposits   总被引：1，自引：0，他引：1  

Boynton WV  Feldman WC  Squyres SW  Prettyman TH  Bruckner J  Evans LG  Reedy RC  Starr R  Arnold JR  Drake DM  Englert PA  Metzger AE  Mitrofanov I  Trombka JI  D'Uston C  Wanke H  Gasnault O  Hamara DK  Janes DM  Marcialis RL  Maurice S  Mikheeva I  Taylor GJ  Tokar R  Shinohara C 《Science (New York, N.Y.)》2002,297(5578):81-85

Using the Gamma-Ray Spectrometer on the Mars Odyssey, we have identified two regions near the poles that are enriched in hydrogen. The data indicate the presence of a subsurface layer enriched in hydrogen overlain by a hydrogen-poor layer. The thickness of the upper layer decreases with decreasing distance to the pole, ranging from a column density of about 150 grams per square centimeter at -42 degrees latitude to about 40 grams per square centimeter at -77 degrees. The hydrogen-rich regions correlate with regions of predicted ice stability. We suggest that the host of the hydrogen in the subsurface layer is ice, which constitutes 35 +/- 15% of the layer by weight.  相似文献   

Aventriculi associated with holoprosencephaly in a dog     

Laura Barnard  Alexane Durand  Lauren Blume  Laura Lee  Starr Cameron 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2020,34(6):2682-2686

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Relationships between native tree species and soil properties in the indigenous forest fragments of the Eastern Arc Mountains of the Taita Hills,Kenya     

Loice Mildred Akinyi OMORO  Raija LAIHO  Michael STARR  Petri K.E.PELLIKKA 《中国林学(英文版)》2011,13(3):198-210

The relationship between soil properties and spatial distribution of native woody species was studied in three Taita Hills forest fragments which, although degraded, are ranked among 34 biodiversity hotspots of the world due to their high biodiversity of both plant and animal species. This relationship was assessed by using Spearman correlation and principal component analyses (PCA). The results of these analyses should be useful in instituting forest restoration programs that are crucial for the forests. Both the soil and vegetation studied were sampled from 17 subplots in the natural forest fragments of Ngangao (120 ha), Chawia (86 ha) and Mbololo (185 ha). The soil variables measured were: pH, texture, soil nutrients of C, N, Ca, P, K, Mg and Na. In total 36 native tree species from 13 families were identified from the three forest fragments. Ordination results show that axis 1 accounted for 35% and axis 2 for 25% of the total variation in species composition, indicating that the structure of vegetation is related to two major environmental gradients. The correlation analyses of species and soil properties showed that Na and clay particles were the most important determinants of species distribution; pH and soil variables such as C, N, Ca and P also played minor roles. Unexpectedly, some species (e.g. Psychotria petitii) showed positive relationships with Na attributed to possible substitution for K. Relationships with P were both positive (e.g. Craibia zimmermannii) and negative (e.g. Albizia gummifera) with some species, attributable to pH levels. An ANOVA for soil variables showed that there were differences in the Ca content in Mbololo (due to the parent material) and P in Ngangao where a special relationship was observed between some of the species. The presence of gaps accounted for the distribution of seedlings but not for the saplings, whose distribution responded more to factors similar to those to which mature trees respond. Soil-species relationships that were established may be utilized along with soil analyses when choosing native species for restoration.  相似文献   

Serum biochemical reference intervals for wild dwarf ornate wobbegong sharks (Orectolobus ornatus)     

Otway NM  Ellis MT  Starr R 《Veterinary clinical pathology / American Society for Veterinary Clinical Pathology》2011,40(3):361-367

Background: Sharks are important to sport and commercial fishing, public aquaria, and research institutions. However, serum biochemical reference values have been established for few species. Objective: The aim of this study was to establish serum biochemical reference intervals for wild‐caught dwarf ornate wobbegong sharks (Orectolobus ornatus). Methods: Fifty wobbegongs were caught, and their health status, sex, length, and weight were evaluated and recorded. Following collection of blood, serum biochemical analytes were measured and analyzed using standard analytical and statistical methods. Combined samples generated means, medians, and reference intervals. Results: For the measured analytes, means (reference intervals) were as follows: sodium 287 (284–289) mmol/L, chloride 277 (274–280) mmol/L, potassium 5.2 (5.0–5.3) mmol/L, total calcium 4.6 (4.5–4.7) mmol/L, magnesium 1.9 (1.7–2.0) mmol/L, inorganic phosphate 1.8 (1.7–1.9) mmol/L, glucose 2.6 (2.4–2.8) mmol/L, total protein 46 (45–47) g/L, urea 396 (392–401) mmol/L, creatinine ≤0.02 mmol/L, total bilirubin 2.0 (1.9–2.1) μmol/L, cholesterol 1.3 (1.2–1.4) mmol/L, triglyceride 0.5 (0.4–0.6) mmol/L, alkaline phosphatase 24 (21–28) U/L, alanine aminotransferase 3 U/L, aspartate aminotransferase 28 (25–31) U/L, creatine kinase 49 (38–59) U/L, and osmolarity 1104 (1094–1114) mmol/L. Serum values were not affected by sex, length, or weight. Conclusions: Established reference values will assist with clinical evaluation and treatment of dwarf ornate wobbegongs in aquaria, research institutions, and the wild.  相似文献   

X-ray Tomographic Study of Chemical Vapor Infiltration Processing of Ceramic Composites     

Kinney JH  Breunig TM  Starr TL  Haupt D  Nichols MC  Stock SR  Butts MD  Saroyan RA 《Science (New York, N.Y.)》1993,260(5109):789-792

The fabrication of improved ceramic-matrix composites will require a better understanding of processing variables and how they control the development of the composite microstructure. Noninvasive, high-resolution methods of x-ray tomography have been used to measure the growth of silicon carbide in a woven Nicalon-fiber composite during chemical vapor infiltration. The high spatial resolution allows one to measure the densification within individual fiber tows and to follow the closure of macroscopic pores in situ. The experiments provide a direct test of a recently proposed model that describes how the surface area available for matrix deposition changes during infiltration. The measurements indicate that this surface area is independent of the fiber architecture and location within the preform and is dominated by large-scale macroporosity during the final stages of composite consolidation. The measured surface areas are in good agreement with the theoretical model.  相似文献   

Role of ANC-1 in tethering nuclei to the actin cytoskeleton     

Starr DA  Han M 《Science (New York, N.Y.)》2002,298(5592):406-409

Mutations in anc-1 (nuclear anchorage defective) disrupt the positioning of nuclei and mitochondria in Caenorhabditis elegans. ANC-1 is shown to consist of mostly coiled regions with a nuclear envelope localization domain (called the KASH domain) and an actin-binding domain; this structure was conserved with the Drosophila protein Msp-300 and the mammalian Syne proteins. Antibodies against ANC-1 localized cytoplasmically and were enriched at the nuclear periphery in an UNC-84-dependent manner. Overexpression of the KASH domain or the actin-binding domain caused a dominant negative anchorage defect. Thus, ANC-1 may connect nuclei to the cytoskeleton by interacting with UNC-84 at the nuclear envelope and with actin in the cytoplasm.  相似文献   

Letters to the editor     

Starr C  Häfele W 《Science (New York, N.Y.)》1975,187(4173):216-216

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The major-element composition of Mercury's surface from MESSENGER X-ray spectrometry     

Nittler LR  Starr RD  Weider SZ  McCoy TJ  Boynton WV  Ebel DS  Ernst CM  Evans LG  Goldsten JO  Hamara DK  Lawrence DJ  McNutt RL  Schlemm CE  Solomon SC  Sprague AL 《Science (New York, N.Y.)》2011,333(6051):1847-1850

X-ray fluorescence spectra obtained by the MESSENGER spacecraft orbiting Mercury indicate that the planet's surface differs in composition from those of other terrestrial planets. Relatively high Mg/Si and low Al/Si and Ca/Si ratios rule out a lunarlike feldspar-rich crust. The sulfur abundance is at least 10 times higher than that of the silicate portion of Earth or the Moon, and this observation, together with a low surface Fe abundance, supports the view that Mercury formed from highly reduced precursor materials, perhaps akin to enstatite chondrite meteorites or anhydrous cometary dust particles. Low Fe and Ti abundances do not support the proposal that opaque oxides of these elements contribute substantially to Mercury's low and variable surface reflectance.  相似文献   

Farmers' perceptions and approaches to detection,treatment and prevention of lameness in pasture-based dairy herds in New South Wales,Australia     

S Ranjbar  AR Rabiee  L Ingenhoff  JK House 《Australian veterinary journal》2020,98(6):264-269

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Tail docking in dogs: A sample of attitudes of veterinarians and dog breeders in Queensland     

GJ NOONAN  JS RAND  JK BLACKSHAW †  J. PRIEST ‡ 《Australian veterinary journal》1996,73(3):86-88

One hundred veterinarians and 100 breeders of traditionally docked dogs from Queensland were surveyed by telephone to determine their attitudes towards tail docking. Eighty-four percent of the breeders surveyed were in favour of docking, whereas 83% of veterinarians were opposed to the practice. Most pups were docked between 1 and 3 days of age. All veterinarians surgically amputated the tail, whereas 16% of breeders applied rubber bands to the tail. Seventy-six percent of the veterinarians, but only 18% of the breeders believed that docking caused significant to severe pain. No veterinarians, but 25% of the dog breeders believed that docking was painless. Although recent changes to the Queensland Canine Control Council's rulings allow dogs with intact tails to be shown in traditionally docked classes, the requirement of breed standard was cited as the major reason for tail docking by both breeders and veterinarians.  相似文献