Isotopic and Zoogeographic Paleotemperatures of Californian Pleistocene Mollusca     

Valentine JW  Meade RF 《Science (New York, N.Y.)》1960,132(3430):810-811

Pleistocene paleotemperatures inferred from zoogeographic evidence are based on temperatures at species' range limits at present. Paleotemperatures inferred from isotopic evidence are based on average former shell-growth temperatures which commonly, but not exclusively, lie between present range-limiting temperatures. With allowance for these differences, the two lines of evidence suggest similar thermal patterns.  相似文献   

High-Power Infrared (8-Micrometer Wavelength) Superlattice Lasers     

G Scamarcio  F Capasso  C Sirtori  J Faist  AL Hutchinson  DL Sivco  AY Cho 《Science (New York, N.Y.)》1997,276(5313):773-776

A quantum-cascade long-wavelength infrared laser based on superlattice active regions has been demonstrated. In this source, electrons injected by tunneling emit photons corresponding to the energy gap (minigap) between two superlattice conduction bands (minibands). A distinctive design feature is the high oscillator strength of the optical transition. Pulsed operation at a wavelength of about 8 micrometers with peak powers ranging from approximately 0.80 watt at 80 kelvin to 0.2 watt at 200 kelvin has been demonstrated in a superlattice with 1-nanometer-thick AlInAs barriers and 4.3-nanometer-thick GaInAs quantum wells grown by molecular beam epitaxy. These results demonstrate the potential of strongly coupled superlattices as infrared laser materials for high-power sources in which the wavelength can be tailored by design.  相似文献   

Radar detection of the nucleus and coma of comet hyakutake     

JK Harmon  SJ Ostro  LAM Benner  KD Rosema  RF Jurgens  R Winkler  DK Yeomans  D Choate  R Cormier  JD Giorgini  DL Mitchell  PW Chodas  R Rose  D Kelley  MA Slade  ML Thomas 《Science (New York, N.Y.)》1997,278(5345):1921-1924

Radar observations of comet Hyakutake (C/1996 B2) made at the Goldstone Deep Space Communications Complex in California have detected echoes from the nucleus and from large grains in the inner coma. The nucleus of this bright comet was estimated to be only 2 to 3 kilometers in diameter. Models of the coma echo indicate backscatter from porous, centimeter-size grains ejected anisotropically at velocities of tens of meters per second. The radar observations suggest that a comet's activity may be a poor indicator of its size and provide evidence that large grains constitute an important component of the mass loss from a typical active comet.  相似文献   

Marine fossils at rancho la brea     

Valentine JW  Lipps JH 《Science (New York, N.Y.)》1970,169(3942):277-278

Marine assemblages of foraminifera, ostracods, mollusks, and echinoids were recovered from deposits stratigraphically beneath the classic vertebrate assemblages from the tar pits at Rancho La Brea. The marine fossils indicate deposition in quiet, shallow water and suggest that accumulation of the type Rancholabrean material began during Wisconsin time.  相似文献   

Land-based evolution     

Valentine JW 《Science (New York, N.Y.)》1993,260(5105):244-245

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Molecular biology of osmoregulation     

Le Rudulier D  Strom AR  Dandekar AM  Smith LT  Valentine RC 《Science (New York, N.Y.)》1984,224(4653):1064-1068

The drought of 1983 resulted in some 10 billion dollars in agricultural losses and has focused attention on the vulnerability of our major crops to this devastating form of environmental stress. This article is concerned with the molecular biology of a new class of genes, called osm (osmotic tolerance) genes, that protect bacteria like Escherichia coli against osmotic stress and may work in a similar manner in plants and animals. Osm genes govern the production of a class of molecules, such as betaine and proline, that protect the cell and its constituents against dehydration. These osmoprotectant molecules have been known for many years to accumulate in plants but have only recently been shown to have potent antistress activity for bacteria.  相似文献   

Anatomic and volumetric characterization of the cisterna chyli using CT lymphangiography and computer‐assisted design software in dogs with idiopathic chylothorax     

Jose L. Carvajal  J. Brad Case  Federico Vilaplana Grosso  Elizabeth Huynh  Valentine Verpaalen  Alexander Fox‐Alvarez  Penny J. Regier 《Veterinary radiology & ultrasound》2020,61(3):312-321

The objectives of this retrospective, observational study were to characterize the anatomical features of the cisterna chyli (CC) in a cohort of dogs diagnosed with idiopathic chylothorax that underwent CT lymphangiography (CTLa), and to evaluate the feasibility of computer‐assisted design (CAD) software to quantify volumetric measurements of the CC. Twenty‐three client‐owned dogs with idiopathic chylothorax were included. Additionally, CTLa was performed in three canine cadavers to assess the ability of CAD software to accurately acquire volumetric measurements. Injection sites, attenuation values, anatomic location, dimensions, and aortic diameter to CC ratio (Ao:CC) were recorded. Video records of video‐assisted thoracic surgery (VATS) thoracic duct ligation (TDL) were reviewed in eight out of 23 dogs to compare operative and CTLa findings. The CC was dorsal and right‐sided in 18 out of 23 dogs, located between L1 and L4 in 21 dogs, and extended as far cranially as T11 in two dogs. The median measurements for length, height, and width were 150.0, 5.5, and 13.3 mm, respectively. Median total volume was 1.82 mL. Median volumes to the right and left of the aorta were 1.46 and 0.49 mL, respectively (P = .014). Median total CC volume to body weight ratio (CC:bw) was 0.07 mL/kg. The presence of an intrathoracic CC was observed intraoperatively in six out of eight cases that underwent VATS TDL. Findings supported the use of CTLa and CAD as feasible methods for characterizing the CC in dogs diagnosed with chylothorax. These methods may facilitate interventional planning involving the CC such as embolization.  相似文献   

Effects of disease control by fungicides on greenhouse gas emissions by UK arable crop production     

David J Hughes  Jonathan S West  Simon D Atkins  Peter Gladders  Michael J Jeger  Bruce DL Fitt 《Pest management science》2011,67(9):1082-1092

BACKGROUND: The UK government has published plans to reduce UK agriculture's greenhouse gas (GHG) emissions. At the same time, the goal of global food security requires an increase in arable crop yields. Foliar disease control measures such as fungicides have an important role in meeting both objectives. RESULTS: It is estimated that UK winter barley production is associated with GHG emissions of 2770 kg CO₂ eq. ha^?1 of crop and 355 kg CO₂ eq. t^?1 of grain. Foliar disease control by fungicides is associated with decreases in GHG emissions of 42–60 kg CO₂ eq. t^?1 in UK winter barley and 29–39 kg CO₂ eq. t^?1 in UK spring barley. The sensitivity of these results to the impact of disease control on yield and to variant GHG emissions assumptions is presented. Fungicide treatment of the major UK arable crops is estimated to have directly decreased UK GHG emissions by over 1.5 Mt CO₂ eq. in 2009. CONCLUSION: Crop disease control measures such as fungicide treatment reduce the GHG emissions associated with producing a tonne of grain. As national demand for food increases, greater yields as a result of disease control also decrease the need to convert land from non‐arable to arable use, which further mitigates GHG emissions. Copyright © 2011 Society of Chemical Industry  相似文献   

A cost comparison of more and less nutritious food choices in US supermarkets     

Katz DL  Doughty K  Njike V  Treu JA  Reynolds J  Walker J  Smith E  Katz C 《Public health nutrition》2011,14(9):1693-1699

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Equine motor neuron disease; a preliminary report   总被引：3，自引：0，他引：3  

J F Cummings  A de Lahunta  C George  L Fuhrer  B A Valentine  B J Cooper  B A Summers  C R Huxtable  H O Mohammed 《The Cornell veterinarian》1990,80(4):357-379

A spontaneous motor neuron disease or neuronopathy was identified in 10 horses from the northeastern United States. Signs of generalized weakness, muscle fasciculations, muscle atrophy and weight loss progressed over 1 to several months in young and old horses of various breeds. Pathologic studies revealed that degeneration and loss of motor neurons in the spinal cord and brain stem resulted in axonal degeneration in the ventral roots and peripheral and cranial nerves and denervation atrophy of skeletal muscle. Many spinal neurons were swollen, chromatolytic and contained neurofilamentous accumulations. Other cell bodies were shrunken and undergoing neuronophagia and some were lost and replaced by glia. This fatal equine motor neuron disease has not been reported previously and its cause has not been determined. The progressive weakness and wasting and the neuronal degenerative changes in these horses were similar to those described in people with sporadic amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease.  相似文献