12,296 research outputs found
SWAS observations of comet 9P/Tempel 1 and Deep Impact
On 4 July 2005 at 1:52 UT the Deep Impact mission successfully completed its
goal to hit the nucleus of 9P/Tempel 1 with an impactor, forming a crater on
the nucleus and ejecting material into the coma of the comet. The 370 kg
impactor collided with the sunlit side of the nucleus with a relative velocity
of 10.2 km/s. NASA's Submillimeter Wave Astronomy Satellite (SWAS) observed the
1(10)-1(01) ortho-water ground-state rotational transition in comet 9P/Tempel 1
before, during, and after the impact. No excess emission from the impact was
detected by SWAS. However, the water production rate of the comet showed large
natural variations of more than a factor of three during the weeks before the
impact.Comment: to appear in the proceedings of the IAU Symposium No. 231:
"Astrochemistry - Recent Successes and Current Callenges". Typo corrected in
author affiliation lis
Asynchronous Changes in Vegetation, Runoff and Erosion in the Nile River Watershed during the Holocene
The termination of the African Humid Period in northeastern Africa during the early
Holocene was marked by the southward migration of the rain belt and the
disappearance of the Green Sahara. This interval of drastic environmental changes
was also marked by the initiation of food production by North African huntergatherer
populations and thus provides critical information on human-environment
relationships. However, existing records of regional climatic and environmental
changes exhibit large differences in timing and modes of the wet/dry transition at
the end of the African Humid Period. Here we present independent records of
changes in river runoff, vegetation and erosion in the Nile River watershed during
the Holocene obtained from a unique sedimentary sequence on the Nile River fan
using organic and inorganic proxy data. This high-resolution reconstruction allows
to examine the phase relationship between the changes of these three parameters
and provides a detailed picture of the environmental conditions during the
Paleolithic/Neolithic transition. The data show that river runoff decreased gradually
during the wet/arid transition at the end of the AHP whereas rapid shifts of
vegetation and erosion occurred earlier between 8.7 and ,6 ka BP. These
asynchronous changes are compared to other regional records and provide new
insights into the threshold responses of the environment to climatic changes. Our
record demonstrates that the degradation of the environment in northeastern Africa
was more abrupt and occurred earlier than previously thought and may have
accelerated the process of domestication in order to secure sustainable food
resources for the Neolithic African populations
Outflows From Evolved Stars: The Rapidly Changing Fingers Of CRL 618
Our ultimate goal is to probe the nature of the collimator of the outflows in the pre-planetary nebula CRL 618. CRL 618 is uniquely suited for this purpose owing to its multiple, bright, and carefully studied finger-shaped outflows east and west of its nucleus. We compare new Hubble Space Telescope images to images in the same filters observed as much as 11 yr ago to uncover large proper motions and surface brightness changes in its multiple finger-shaped outflows. The expansion age of the ensemble of fingers is close to 100 yr. We find strong brightness variations at the fingertips during the past decade. Deep IR images reveal a multiple ring-like structure of the surrounding medium into which the outflows propagate and interact. Tightly constrained three-dimensional hydrodynamic models link the properties of the fingers to their possible formation histories. We incorporate previously published complementary information to discern whether each of the fingers of CRL 618 are the results of steady, collimated outflows or a brief ejection event that launched a set of bullets about a century ago. Finally, we argue on various physical grounds that fingers of CRL 618 are likely to be the result of a spray of clumps ejected at the nucleus of CRL 618 since any mechanism that form a sustained set of unaligned jets is unprecedented.HST GO 11580NASA through Space Telescope Science Institute GO11580NASA NAS5-26555Boeing ScholarshipOffice of Undergraduate Academic Affairs at the University of WashingtonSpanish MICINN CSD2009-00038NASA Office of Space Science NAG5-7584Astronom
ATR-FTIR spectroscopy detects alterations induced by organotin(IV) carboxylates in MCF-7 cells at sub-cytotoxic/-genotoxic concentrations.
The environmental impact of metal complexes such as organotin(IV) compounds is of increasing concern. Genotoxic effects of organotin(IV) compounds (0.01 ΞΌg/ml, 0.1 ΞΌg/ml or 1.0 ΞΌg/ml) were measured using the alkaline single-cell gel electrophoresis (comet) assay to measure DNA single-strand breaks (SSBs) and the cytokinesis-block micronucleus (CBMN) assay to determine micronucleus formation. Biochemical-cell signatures were also ascertained using attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy. In the comet assay, organotin(IV) carboxylates induced significantly-elevated levels of DNA SSBs. Elevated micronucleus-forming activities were also observed. Following interrogation using ATR-FTIR spectroscopy, infrared spectra in the biomolecular range (900 cm-1 β 1800 cm-1) derived from organotin-treated MCF-7 cells exhibited clear alterations in their biochemical-cell fingerprint compared to control-cell populations following exposures as low as 0.0001 ΞΌg/ml. Mono-, di- or tri-organotin(IV) carboxylates (0.1 ΞΌg/ml, 1.0 ΞΌg/ml or 10.0 ΞΌg/ml) were markedly cytotoxic as determined by the clonogenic assay following treatment of MCF-7 cells with β₯ 1.0 ΞΌg/ml. Our results demonstrate that ATR-FTIR spectroscopy can be applied to detect molecular alterations induced by organotin(IV) compounds at sub-cytotoxic and sub-genotoxic concentrations. This biophysical approach points to a novel means of assessing risk associated with environmental contaminants
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A Novel Lumbar Motion Segment Classification to Predict Changes in Segmental Sagittal Alignment After Lateral Interbody Fixation.
Study designRetrospective cohort study.ObjectivesLateral interbody fixation is being increasingly used for the correction of segmental sagittal parameters. One factor that affects postoperative correction is the resistance afforded by posterior hypertrophic facet joints in the degenerative lumbar spine. In this article, we describe a novel preoperative motion segment classification system to predict postoperative correction of segmental sagittal alignment after lateral lumbar interbody fusion.MethodsPreoperative computed tomography scans were analyzed for segmental facet osseous anatomy for all patients undergoing lateral lumbar interbody fusion at 3 institutions. Each facet was assigned a facet grade (min = 0, max = 2), and the sum of the bilateral facet grades was the final motion segment grade (MSG; min = 0, max = 4). Preoperative and postoperative segmental lordosis was measured on standing lateral radiographs. Postoperative segmental lordosis was also conveyed as a percentage of the implanted graft lordosis (%GL). Simple linear regression was conducted to predict the postoperative segmental %GL according to MSG.ResultsA total of 36 patients with 59 operated levels were identified. There were 19 levels with MSG 0, 14 levels with MSG 1, 13 levels with MSG 2, 8 levels with MSG 3, and 5 levels with MSG 4. Mean %GL was 115%, 90%, 77%, 43%, and 5% for MSG 0 to 4, respectively. MSG significantly predicted postoperative %GL (P < .01). Each increase in MSG was associated with a 28% decrease in %GL.ConclusionsWe propose a novel facet-based motion segment classification system that significantly predicted postoperative segmental lordosis after lateral lumbar interbody fusion
Can\u27t Find Your 404s?
PDF of a powerpoint presentation at the Santa Fe Complex, Santa Fe, New Mexico, March 13, 2009. Also available on Slideshare.https://digitalcommons.odu.edu/computerscience_presentations/1026/thumbnail.jp
Delivering the Goods: The Determinants of Norwegian Seafood Exports
Seafood is the worldβs most traded food product. In recent years, aquaculture has become an increasingly important part of seafood production, facilitating increased trade. However, despite evidence that fish farmers have better ability to target markets and ship their seafood through more efficient supply chains (due to the higher degree of control with the production process), little attention has been given to the fact that this is likely to influence trade patterns as well. This article investigates if trade margins for aquaculture products differ from trade in wild seafood products along three margins of trade, in addition to total export value on export data for Norway, the worldβs second largest seafood exporting country. The results indicate aquaculture products are different. In particular, aquaculture products are influenced by more factors than fisheries products (such as transportation costs and per-unit shipment costs), highlighting another dimension where the control of the production process can be used to improve competitiveness. Moreover, exports of aquaculture products increase with a countryβs wealth level, reflecting producersβ ability to target higher paying markets.acceptedVersio
Critical Temperature and Energy Gap for the BCS Equation
We derive upper and lower bounds on the critical temperature and the
energy gap (at zero temperature) for the BCS gap equation, describing
spin 1/2 fermions interacting via a local two-body interaction potential
. At weak coupling and under appropriate
assumptions on , our bounds show that and
for some explicit coefficients , and
depending on the interaction and the chemical potential . The ratio
turns out to be a universal constant, independent of both and
. Our analysis is valid for any ; for small , or low density,
our formulas reduce to well-known expressions involving the scattering length
of .Comment: RevTeX4, 23 pages. Revised version, to appear in Phys. Rev.
Π‘ΠΎΠ·Π΄Π°Π½ΠΈΠ΅ Π½ΠΎΠ²ΡΡ ΠΊΠΎΠΌΠΏΠΎΠ·ΠΈΡΠΈΠΎΠ½Π½ΡΡ ΠΌΠ°ΡΠ΅ΡΠΈΠ°Π»ΠΎΠ² Π½Π° ΠΏΠΎΠ»ΠΈΠΌΠ΅ΡΠ½ΠΎΠΉ ΠΎΡΠ½ΠΎΠ²Π΅ Π΄Π»Ρ ΠΏΡΠΈΠΌΠ΅Π½Π΅Π½ΠΈΡ Π² Π°Π΄Π΄ΠΈΡΠΈΠ²Π½ΡΡ ΡΠ΅Ρ Π½ΠΎΠ»ΠΎΠ³ΠΈΡΡ
Π Π½Π°ΡΡΠΎΡΡΠ΅ΠΉ ΡΠ°Π±ΠΎΡΠ΅ ΠΏΡΠΈΠ²Π΅Π΄Π΅Π½ΠΎ ΠΈΡΡΠ»Π΅Π΄ΠΎΠ²Π°Π½ΠΈΠ΅ ΠΊΠΎΠΌΠΏΠΎΠ·ΠΈΡΠΈΠΎΠ½Π½ΡΡ
ΡΠΈΠ»Π°ΠΌΠ΅Π½ΡΠΎΠ² "ABS - ΡΠ³Π»Π΅Π²ΠΎΠ»ΠΎΠΊΠ½ΠΎ" Ρ ΡΠΎΠ΄Π΅ΡΠΆΠ°Π½ΠΈΠ΅ΠΌ ΡΠ³Π»Π΅Π²ΠΎΠ»ΠΎΠΊΠ½Π° Π΄ΠΎ 10 Π²Π΅Ρ.%. ΠΡΡΠ»Π΅Π΄ΠΎΠ²Π°Π½Π° ΠΌΠ°ΠΊΡΠΎΡΡΡΡΠΊΡΡΡΠ° ΠΏΠΎΠ»ΡΡΠ΅Π½Π½ΡΡ
ΡΠΈΠ»Π°ΠΌΠ΅Π½ΡΠΎΠ², Π² ΡΠ°ΡΡΠ½ΠΎΡΡΠΈ Π½Π°ΠΈΠ±ΠΎΠ»ΡΡΠ΅Π΅ Π²Π½ΠΈΠΌΠ°Π½ΠΈΠ΅ ΡΠ΄Π΅Π»Π΅Π½ΠΎ ΠΈΡΡΠ»Π΅Π΄ΠΎΠ²Π°Π½ΠΈΡ ΠΎΡΠΈΠ΅Π½ΡΠΈΡΠΎΠ²Π°Π½ΠΈΡ Π²ΠΎΠ»ΠΎΠΊΠΎΠ½ Π² ΠΎΠ±ΡΠ΅ΠΌΠ΅ ΡΠΈΠ»Π°ΠΌΠ΅Π½ΡΠ°. ΠΠΏΠΈΡΠ°Π½Ρ ΡΠ΅Ρ
Π½ΠΎΠ»ΠΎΠ³ΠΈΡΠ΅ΡΠΊΠΈΠ΅ ΠΎΡΠΎΠ±Π΅Π½Π½ΠΎΡΡΠΈ ΠΏΡΠΎΡΠ΅ΡΡΠ° ΠΏΠΎΠ»ΡΡΠ΅Π½ΠΈΡ ΠΊΠΎΠΌΠΏΠΎΠ·ΠΈΡΠΈΠΎΠ½Π½ΠΎΠ³ΠΎ ΡΠΈΠ»Π°ΠΌΠ΅Π½ΡΠ°, ΠΏΡΠΈΠ²Π΅Π΄Π΅Π½Π° Π½Π°ΠΈΠ±ΠΎΠ»Π΅Π΅ ΠΎΠΏΡΠΈΠΌΠ°Π»ΡΠ½Π°Ρ ΡΡ
Π΅ΠΌΠ° ΠΏΠΎΠ»ΡΡΠ΅Π½ΠΈΡ ΡΠΈΠ»Π°ΠΌΠ΅Π½ΡΠ°, Π² ΡΠΎΠΌ ΡΠΈΡΠ»Π΅ ΠΎΠΏΠΈΡΠ°Π½Π° ΠΎΠΏΡΠΈΠΌΠ°Π»ΡΠ½Π°Ρ ΡΠ΅Ρ
Π½ΠΎΠ»ΠΎΠ³ΠΈΡ ΠΏΠΎΠ΄Π³ΠΎΡΠΎΠ²ΠΊΠΈ ΡΠ³Π»Π΅Π²ΠΎΠ»ΠΎΠΊΠ½Π° Π΄Π»Ρ Π²Π²Π΅Π΄Π΅Π½ΠΈΡ Π² ΠΊΠΎΠΌΠΏΠΎΠ·ΠΈΡ.In the present work, a study of composite filaments "ABS-carbon fiber" with a carbon fiber content of up to 10% by weight is made. The macrostructure of the filaments is studied, in particular, the greatest attention is paid to the study of fiber orientation in the filament volume. Technological features of the process of composite filament preparation are described, the most optimal scheme of filament production is given, besides the optimal technology of carbon fiber preparation for introduction into the composite is described
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