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  • 1990-1994  (224)
  • 1985-1989  (195)
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  • 1
    Call number: ZSP-201-94/12
    In: CRREL Report, 94-12
    Description / Table of Contents: Subsurface radar was used to profile ice and snow conditions on the Ross Ice Shelf at McMurdo Station, Antarctica, during mid-January 1993. Deconvolution and migration were often used to improve vertical resolution and spatial imaging. Profiles at a pulse center frequency of 400 MHz along the 3.2-km-long Pegasus ice runway show many low-density horizons above 9 m depth that are up to 30 m long. They are associated with air bubbles included during refreezing of meltwater and are interpreted as layers between a few and tens of centimeters thick. There is a strong reflecting horizon at about 9 m depth that is probably from brine intrusion as it is continuous with the intrusion into the snow to the east. Diffraction asymptotes give a dielectric constant near 3.2 for material above the brine level, a value that implies near-solid ice. Profiles at 100 MHz along the road between Pegasus runway and Williams Field in the accumulation zone show snow features such as layer deformation and intrusive brine layers that both abruptly and gradually change in depth. A single profile at a relic solid waste dump at Williams Field detected buried debris and ice within the upper 7 m. A survey of a suspected fuel spill shows some local disturbances near the center, but no excavation was done to verify the findings. Profiles traversing the sewage sumps at Williams Field outline the extent of the sewage deposition, and give depths to contaminated snow that closely agree with observation. Despite variability in dielectric properties, single-layer migration effectively improves the resolution of subsurface conditions. Recommendations are made for future surveys.
    Type of Medium: Series available for loan
    Pages: iv, 29 Seiten , Illustrationen
    Series Statement: CRREL Report 94-12
    Language: English
    Note: CONTENTS Preface Introduction Radar equipment General operation Antennas Waveforms and phase polarity Antenna directivity Field procedures and data processing Field procedures Data recording Data processing Site location Results Pegasus runway Access road from Williams Field to Pegasus runway Williams Field Summary and conclusions Literature cited Appendix A: Airborne profile of a portion of the access road Abstract
    Location: AWI Archive
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  • 2
    Call number: ZSP-201-86/11
    In: CRREL Report, 86-11
    Description / Table of Contents: This initial study of the ice-covered Tanana River, near Fairbanks, Alaska, attempted to 1) establish field methods for systematic and repetitive quantitative analyses of an ice-covered river's regime, 2) evaluate the instruments and equipment for sampling, and 3) obtain the initial data of a long-term study of ice cover effects on the morphology, hydraulics and sediment transport of a braided river. A methodology was established, and detailed measurements and samplings, including profiling by geophysical techniques, were conducted along cross sections of the river. A small, portable rotary drill rig equipped with a 356-mm (14-in.) ice auger was used to cut large diameter holes in the ice cover for through-the-ice measurements. Portable heat sources and a heated shelter were required to continuously thaw and dry equipment for the repetitive measurements. Measurements included ice cover thickness, water level, water depth, temperature, flow velocity, suspended load and bed load, frazil ice distribution and bed material composition. Remotely gathered data included apparent resistivity and subsurface radar profiling. The various techniques, sampling gear and problems encountered during use in the subfreezing cold are described in detail in this report.
    Type of Medium: Series available for loan
    Pages: v, 49 Seiten , Illustrationen
    Series Statement: CRREL Report 86-11
    Language: English
    Note: CONTENTS Abstract Preface Introduction Study objectives and field locale Study site Equipment Vehicles Drilling equipment Sampling equipment Geophysical equipment Shelter and icing control Surveying equipment Miscellaneous equipment Field techniques and methodology Logistics Drilling procedures Data collection Geophysical analyses Experiences summary Morphology, transport and hydraulic data Mid-winter physical characteristics Hydraulic characteristics Sediment transport Late winter physical characteristics Seasonal morphology Geophysical data interpretation Spatial morphology Frazil ice characteristics Discussion and conclusions Recommendations Equipment Research Literature cited
    Location: AWI Archive
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  • 3
    Call number: ZSP-201-86/6
    In: CRREL Report, 86-6
    Description / Table of Contents: Short-pulse radar profiles and waveform traces were recorded over natural, freshwater ice sheets and an artificially made, 1.6-m-diameter column of brash ice. The purpose was to study the feasibility of this type of radar to detect ice thickness, determine ice properties and distinguish ice forms. The radar utilized two antennas: one with a spectrum centered near 900 MHz and a second more powerful one near 700 MHz. Distinct top and bottom reflections from several ice sheets were produced by both antennas, but the value of dielectric permittivity calculated from the time of delay of the reflections varied between sheets as one ice sheet was ready to candle and contained free water. The brash ice distorted signals and allowed no discernible bottom return. The lower frequency antenna also gave returns from the lake bottom (separated from the ice bottom by about 1 m of water), which could allow ice thickness to be determined indirectly. The report concludes that these antennas can be used to determine sheet ice thickness and to supply information to help in the detection of brash ice. The water content of an ice sheet may also be estimated if independent studies show a correlation between dielectric permittivity and free water content.
    Type of Medium: Series available for loan
    Pages: iv, 15 Seiten , Illustrationen
    Series Statement: CRREL Report 86-6
    Language: English
    Note: CONTENTS Abstract Preface Introduction Materials and methods Sites and site preparation Results and discussion Lake Morey Post Pond Conclusions and recommendations Literature cited
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Entomologia experimentalis et applicata 44 (1987), S. 31-35 
    ISSN: 1570-7458
    Keywords: host quality ; nitrogen ; survival ; Leptinotarsa decemlineata ; Lycopersicon esculentum ; plant virus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Résumé Pour vérifier l'hypothèse selon laquelle une contamination par un virs végétal peut accroître la consommation de plantes délaissées ou partiellement résistantes, nous avons examiné les interactions entre Leptinotarsa decemlineata Say, Lycopersicon esculentum Mill., et le virus de la mosaïque du tabac (TMV). La survie des larves de L. decemlineata a augmenté avec la contamination par TMV; les teneurs en azote et en tomatine étaient toutes deux plus élevées dans les plantes contaminées par le virus. La survie a augmenté linéairement avec la teneur en azote, mais sans dépendre de la teneur en tomatine. L'influence positive pour L. decemlineata de la contamination par le virus peut être attribuée au moins en partie à la teneur en azote plus élevée. Nos résultats correspondent à l'hypothèse selon laquelle la consommation de plantes délaissées ou partiellement résistantes peut être augmentée par la contamination virale, et que cette contamination peut faciliter l'adaptation d'insectes phytophages sur des plantes marginalement consommables.
    Notes: Abstract Infection by tobacco mosaic virus improved the suitability of tomato, Lycopersicon esculentum Mill. for survival of Colorado potato beetle, Leptinotarsa decemlineata (Say), larvae. This improvement was due, at least in part, to the increase in total nitrogen content of virus-infected plants. The simultaneous increase in tomatine content had no discernable effect on L. decemlineata survival. Our results are consistent with the suggestions that virus infection may improve the suitability of partially resistant or non-preferred hosts, and that virus infection may facilitate the adaption of phytophagous insects to such ‘marginal’ host plant species.
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  • 5
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] A 60-kb region of DNA from the R. leguminosarum symbiotic plasmid pRLUI carries a cluster of nodulation genes which is flanked by two groups of genes involved in nitrogen fixation7. Downie et al4 found that two overlapping cosmid clones of pRLUI-pIJ1089 and pi J108 5-containing a 10-kb region in ...
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  • 6
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 361 (1993), S. 179-182 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] TABLE 1 Structure solution and refinement Self-rotation Orientation of particle determined by direction of 2-, function11'12 3- and 5-fold axes Rigid-body Resolution: 5-15 A; result: ft ^0.48; (A〈/〉) = 83°; refinement36 of input: atomic model oriented according to self-STNV atomic ...
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Figure 1 shows an alignment of 10 sequences to illustrate the extensive homology between the various members of this family of bacterial proteins. The sequences are from nine independent proteins, as the RbsA protein has two distinct but homologous domains. Six of these proteins are transport ...
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  • 8
    ISSN: 1617-4623
    Keywords: Rhizobium ; DNA polymerase ; Plasmids ; Symbiosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A population of Tn5 mutagenised Rhizobium leguminosarum cells was screened for mutants affected in protein secretion by introducing a plasmid carrying the Erwinia chrysanthemi prtB gene and screening for mutants defective in secretion of the protease PrtB. One such mutant (A301) also appeared to be defective in secretion of the R. leguminosarum nodulation protein NodO. Genetic analysis showed that the defect in A301 was caused by the Tn5 insertion. However the DNA sequence adjacent to the site of Tn5 insertion had significant homology to the Escherichia coli polA gene, which encodes DNA polymerase I. The mutant A301 showed increased sensitivity to ultraviolet light, a characteristic of polA mutants of E. coli. The apparent defect in secretion by A301 was due to a large decrease in the copy number of the IncQ group replicon on which prtB and nodO were cloned and this decreased the total amounts of PrtB or NodO protein synthesised and secreted by the polA mutant. The polA mutant had a lower growth rate than the parent strain on both rich and minimal media, but there was no obvious effect of the polA mutation on the symbiosis of R. leguminosarum bv. viciae with pea.
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  • 9
    ISSN: 1573-6830
    Keywords: pontogeniculooccipital waves ; rapid eye movement (REM) sleep ; monoamines ; acetylcholine ; pontine reticular formation ; lateral geniculate bodies ; occipital cortex ; corollary discharge
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary 1. Pontogeniculooccipital (PGO) waves are recorded during rapid eye movement (REM) sleep from the pontine reticular formation, lateral geniculate bodies, and occipital cortex of many species. 2. PGO waves are associated with increased visual system excitability but arise spontaneously and not via stimulation of the primary visual afferents. Both auditory and somatosensory stimuli influence PGO wave activity. 3. Studies using a variety of techniques suggest that the pontine brain stem is the site of PGO wave generation. Immediately prior to the appearance of PGO waves, neurons located in the region of the brachium conjunctivum exhibit bursts of increased firing, while neurons in the dorsal raphe nuclei show a cessation of firing. 4. The administration of pharmacological agents antagonizing noradrenergic or serotonergic neurotransmission increases the occurrence of PGO waves independent of REM sleep. Cholinomimetic administration increases the occurrence of both PGO waves and other components of REM sleep. 5. Regarding function, the PGO wave-generating network has been postulated to inform the visual system about eye movements, to promote brain development, and to facilitate the response to novel environmental stimuli.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 8 (1988), S. 137-158 
    ISSN: 0741-0581
    Keywords: Kaposi's sarcoma ; Lymphoma ; Histology ; Ultrastructure ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Malignancies frequently arise in patients infected with human immunodeficiency virus (HIV), including those patients classified as having the acquired immunodeficiency syndrome (AIDS). Currently, Kaposi's sarcoma and certain types of lymphoma are considered to develop as a result of HIV infection, and other cancers have also been reported in these patients. For the most part, ultrastructural study of HIV-associated malignancies has been limited to Kaposi's sarcoma; the ultrastructural features of the epidemic form of this disease are generally the same as those of the classical form. The occurrence of these cancers in HIV-infected individuals appears to be related to the immunodeficiency caused by this virus, but the basic etiologic mechanisms remain unknown. In general, only palliative treatments are presently available for HIV-associated malignancies.
    Additional Material: 10 Ill.
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