The geometric distance and proper motion of the Triangulum Galaxy (M33)     

Brunthaler A  Reid MJ  Falcke H  Greenhill LJ  Henkel C 《Science (New York, N.Y.)》2005,307(5714):1440-1443

We measured the angular rotation and proper motion of the Triangulum Galaxy (M33) with the Very Long Baseline Array by observing two H2O masers on opposite sides of the galaxy. By comparing the angular rotation rate with the inclination and rotation speed, we obtained a distance of 730 +/- 168 kiloparsecs. This distance is consistent with the most recent Cepheid distance measurement. M33 is moving with a velocity of 190 +/- 59 kilometers per second relative to the Milky Way. These measurements promise a method to determine dynamical models for the Local Group and the mass and dark-matter halos of M31, M33, and the Milky Way.  相似文献   

Temporal variability in plant and soil nitrogen pools in a high-Arctic ecosystem     

Richard D. Bardgett  Rene van der Wal  Helen Quirk 《Soil biology & biochemistry》2007,39(8):2129-2137

This study determined temporal variability in N pools, both aboveground and belowground, across two contrasting plant communities in high-Arctic Spitsbergen, Svalbard (78°N). We measured N pools in plant material, soil microbial biomass and soil organic matter in moist (Alopecurus borealis dominated) and dry (Dryas octopetala dominated) meadow communities at four times during the growing season. We found that plant, microbial and dissolved inorganic and organic N pools were subject to significant, but surprisingly low, temporal variation that was controlled primarily by changes in temperature and moisture availability over the short growing season. This temporal variability is much less than that experienced in other seasonally cold ecosystems such as alpine tundra where strong seasonal partitioning of N occurs between plant and soil microbial pools. While only a small proportion of the total ecosystem N, the microbial biomass represented the single largest of the dynamic N pools in both moist and dry meadow communities (3.4% and 4.6% of the total ecosystem N pool, respectively). This points to the importance of soil microbial community dynamics for N cycling in high-Arctic ecosystems. Microbial N was strongly and positively related to soil temperature in the dry meadow, but this relationship did not hold true in the wet meadow where other factors such as wetter soil conditions might constrain biological activity. Vascular live belowground plant parts represented the single largest plant N pool in both dry and moist meadow, constituting an average of 1.6% of the total N pool in both systems; this value did not vary across the growing season or between plant communities. Overall, our data illustrate a surprisingly low growing season variability in labile N pools in high-Arctic ecosystems, which we propose is controlled primarily by temperature and moisture.  相似文献   

Biomass and nutrient accumulation in young Prosopis juliflora at Mombasa,Kenya     

Jumanne A. Maghembe  Esther M. Kariuki  Rene D. Haller 《Agroforestry Systems》1983,1(4):313-321

The biomass of a six-year-old plantation of Prosopis juliflora was determined using simple linear regressions of (y) the tree components: stem (over bark), large branches, small branches and leaves on (x), diameter at the base of the trees. Similar regressions were used to estimate height and volume produced by both stem and large branches. Macronutrient concentrations in the different tree components were determined and multiplied by the appropriate total dry weights to obtain total contents per hectare. The total stem volume (at age 6) was 209 m³/ha and large branch volume was 75 m³/ha. Total biomass was 216 tons/ha. Over 77% of the total biomass was accounted for by stem and large branches. Nevertheless, the leaves plus small branches (making 22.6% of the biomass) contained over 50% of the total pool of the individual nutrients N, P, K and Mg. The implications of this finding on site depletion due to total tree use as fuelwood and folder is discussed.  相似文献   

DIAGNOSIS OF CEREBRAL VENTRICULOMEGALY IN NORMAL ADULT BEAGLES USING QUANTITATIVE MRI   总被引：1，自引：0，他引：1  

Thomas  Vullo  PHD  Eric  Korenman  MD  Rene P.  Manzo  MD  Daniel G.  Gomez  PHD  Michael D.F.  Deck  MD  Patrick T.  Cahill  PHD 《Veterinary radiology & ultrasound》1997,38(4):277-281

The brain of 17 asymptomatic normal adult beagles was evaluated with magnetic resonance imaging. Lateral ventricular size was quantified using computer algorithms. In beagles with large ventricles, contrast medium was introduced into the cerebellomedullary cistern to determine whether obstructive hydrocephalus was present. Total lateral ventricular volume ranged from 73^mm3. to 11, 726 ^mm3. Based on Gd-DTPA diffusion, the csf flow pattern was considered normal neural morphology was seen using electron microscopy. Results Suggest a high incidence of clinically asymptomatic vetriculomegaly in normal adult beagles.  相似文献   

Squamous cell carcinoma of the paranasal sinuses in two horses     

L. Kowalczyk  A. Boehler  R. Brunthaler  M. Rathmanner  A. B. M. Rijkenhuizen 《Equine Veterinary Education》2011,23(9):435-440

This case report describes the history, clinical findings, diagnostic imaging (including computed tomography), gross pathology and histopathology of 2 cases of squamous cell carcinoma in the paranasal sinuses. Radiography of the skull is a useful tool to detect a mass in the paranasal sinuses, but the position, extent and character of the lesion can be better visualised with computed tomography.  相似文献   

Computerized ultrasonographic tissue characterization of equine superficial digital flexor tendons by means of stability quantification of echo patterns in contiguous transverse ultrasonographic images     

van Schie HT  Bakker EM  Jonker AM  van Weeren PR 《American journal of veterinary research》2003,64(3):366-375

OBJECTIVE: To describe a method of computerized ultrasonographic tissue characterization that includes structures below the size limits of resolution in equine superficial digital flexor tendons. SAMPLE POPULATION: 2 damaged and 2 structurally normal superficial digital flexor tendons. PROCEDURE: Transverse ultrasonographic images were collected along the tendon long axis. Stability of echo pattern was quantified by means of variation in gray levels of each pixel in contiguous images and expressed as correlation, entropy, and waviness ratios. RESULTS: Normal young and normal old tissues were characterized by high correlation and low entropy and waviness ratios. In necrotic tissue, collapsed intratendinous septa resulted in high correlation, moderate entropy, and high waviness ratios. In early granulation tissue, complete lack of bundle formation resulted in values of zero for correlation and waviness ratios; loose connective tissue matrix resulted in a high entropy ratio. In late granulation tissue, formation of new bundles resulted in a high correlation ratio; swollen intratendinous septa and incomplete organization of connective tissue matrix were reflected in high entropy and waviness ratios. In early fibrotic tissue, rearrangement of tendon bundles resulted in a correlation ratio within reference range and a slight increase in the waviness ratio; an increase in cellularity and lack of fibrillar arrangement led to an increase in the entropy ratio. In late fibrotic and scar tissues, inferior quality of repair with almost complete lack of organization was reflected in low to moderate correlation, low waviness, and high entropy ratios. CONCLUSIONS AND CLINICAL RELEVANCE: Stability of echo patterns accurately reflects homogeneity of tendons in horses.  相似文献   

Retrospective evaluation of 155 adult equids and 21 foals with tetanus from Western,Northern, and Central Europe (2000–2014). Part 2: Prognostic assessment          下载免费PDF全文

Gaby van Galen DVM  PhD  DECEIM  Joke Rijckaert DVM  Tim Mair BVSc  PhD  DECEIM  Helene Amory DVM  PhD  DECEIM  Lara Armengou DVM  PhD  DECEIM  Barbora Bezdekova DVM  PhD  DECEIM  Inge Durie DVM  DECEIM  Rikke Findshøj Delany DVM  Nathalie Fouché DVM  Laura Haley MVB  Michael Hewetson BVSc  DECEIM  Rene van den Hoven DVM  PhD  DECEIM  Anna Kendall DVM  DECEIM  Fernando Malalana DVM  DECEIM  MRCVS  Jessika Muller Cavalleri DVM  DECEIM  PhD  Tresemiek Picavet DVM  DECEIM  Katja Roscher DVM  DECEIM  Denis Verwilghen DVM  PhD  DECVS  Cornélie Westermann DVM  PhD  DECEIM  Claude Saegerman DVM  PhD  DECVPH 《Journal of Veterinary Emergency and Critical Care》2017,27(6):697-706

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Composition,architecture and biomechanical properties of articular cartilage in differently loaded areas of the equine stifle     

Maria Fugazzola  Mikko T. Nissinen  Jiri Jäntti  Juuso Tuppurainen  Saskia Plomp  Nikae Te Moller  Janne T. A. Mäkelä  Rene van Weeren 《Equine veterinary journal》2024,56(3):573-585

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Diagnosis and characterization of insecticide-insensitive acetylcholinesterase in three populations of the sweetpotato whitefly Bemisia tabaci     

Nicola M. Anthony  Judith K. Brown  Rene Feyereisen  Richard H. Ffrench-Constant 《Pest management science》1998,52(1):39-46

A biochemical approach was used to characterize acetylcholinesterase (AChE) insecticide insensitivity in several sweetpotato whitefly (Bemisia tabaci; SPW) populations. Discriminating doses of insecticide were established to differentiate between sensitive and insensitive SPW strains and to genotype individual whitefly. This technique was then used to examine the frequency of insensitive AChE alleles in several SPW populations and to isolate a line homozygous for insensitive AChE from a heterogenous B-type population. Inheritance of putative altered AChE genotypes was consistent with the proposed haplo-diploid status of B. tabaci. This biochemical diagnostic was also employed to determine the role of insensitive AChE in the observed resistance profiles of several laboratory populations subjected to different selection regimes. In keeping with previous studies on insecticide resistance in SPW, resistance does not appear to be uniquely associated with the B-type but rather with SPW populations found in crop systems. © 1998 SCI.  相似文献   

Effect of pressure and pH in ammonium retention for nanofiltration and reverse osmosis membranes to be used in recirculation aquaculture systems (RAS)     

Beatriz Cancino-Madariaga  Carlos Felipe Hurtado  Rene Ruby 《Aquacultural Engineering》2011,45(3):103-108

Recirculation systems are becoming widely used in the aquaculture industry, where ammonium removal results are crucial for a proper performance considering its high toxicity on fish. The objective of this study was to assess the ammonium retention, when the transmembrane pressure (TMP) in nanofiltration (NF) and reverse osmosis (RO) membranes are changed. Two pH levels were tested: pH 5, where ammonium is as NH⁴⁺, and pH 7 which is an average of the most common range in aquaculture (pH 6-8). In this study a model solution of ammonium-water and commercial membranes of polyamide supplied by Alfa Laval (DSSHR98PP) and Dow (NF90, NF200 and NF270) were used, with a membrane area of 0.01018 m². A critical TMP was determined, where the repulsive electrochemical forces at the active layer were exceeded by the transmembrane pressure, causing an irreversible decrease of the retention values. The maximum TMP values for NF and RO membranes were 16 bar and 24.5 bar, respectively. Ammonium retention at pH 7 was higher than pH 5 for all assessed membranes before the critical TMP was reached, with average values of 100, 99.7, 98.4 and 87.5% for membranes NF90, DSSHR98PP, NF200 and NF270, respectively. It may be concluded the ammonium retention mechanism in the studied membranes basically corresponds to an electrochemical mechanism, where pH and critical TMP influence the retention values of ammonium.  相似文献