388 research outputs found
Cross-sectional examination of the damage zone in impacted specimens of carbon/epoxy and carbon/PEEK composites
Drop weight impact testing was utilized to inflict damage on eight-ply bidirectional and unidirectional samples of carbon/epoxy and carbon/PEEK (polyetheretherketone) test specimens with impact energies ranging from 0.80 J to 1.76 J. The impacting tip was of a smaller diameter (4.2-mm) than those used in most previous studies, and the specimens were placed with a diamond wheel wafering saw through the impacted area perpendicular to the outer fibers. Photographs at 12 x magnification were taken of these cross-sections and examined. The results on the bidirectional samples show little damage until 1.13 J, at which point delaminations were seen in the epoxy specimens. The PEEK specimens showed less delamination than the epoxy specimens for a given impact energy level. The unidirectional specimens displayed more damage than the bidirectional samples for a given impact energy, with the PEEK specimens showing much less damage than the epoxy material
Morphology and Distribution of Volcanic Vents in the Orientale Basin from Chandrayaan-1 Moon Mineralogy Mapper (M3) Data
One of the most fundamental questions in the geological and thermal evolution of the Moon is the nature and history of mantle melting and its relationship to the formation and evolution of lunar multi-ringed basins. Mare volcanic deposits provide evidence for the nature, magnitude and composition of mantle melting as a function of space and time [1]. Many argue that mantle partial melts are derived from depths well below the influence of multiringed basin impact events [1], while others postulate that the formation of these basins can cause mantle perturbations that are more directly linked to the generation ascent and eruption of mare basalts [2,3]. In any case, longer-term basin evolution will considerably influence the state and orientation of stress in the lithosphere, and the location of mare volcanic vents in basins as a function of time [4]. Thus, the location, nature and ages of volcanic vents and deposits in relation to multi-ringed impact basins provides evidence for the role that these basins played in the generation of volcanism or in the influence of the basins on surface volcanic eruption and deposit concentration. Unfortunately, most lunar multi-ringed impact basins have been eroded by impacts or filled with lunar mare deposits [5-8], with estimates of the thickness of mare fill extending up to more than six km in the central part of some basins [9-11]. The interior of most basins (e.g., Crisium, Serenitatis, Imbrium, Humorum) are almost completely covered and obscured. Although much is known about the lava filling of multi-ringed basins, and particularly the most recent deposits [5-8], little is known about initial stages of mare volcanism and its relationship to the impact event. One multi-ringed basin, Orientale, offers substantial clues to the relationships of basin interiors and mare basalt volcanism
The role of BMI in allostatic load and risk of cancer death
INTRODUCTION: Obesity and proinflammatory conditions are associated with increased risks of cancer. The associations of baseline allostatic load with cancer mortality and whether this association is modified by body mass index (BMI) were examined.
METHODS: A retrospective analysis was performed in March-September 2022 using National Health and Nutrition Examination Survey years 1988 through 2010 linked with the National Death Index through December 31, 2019. Fine and Gray Cox proportional hazard models were stratified by BMI status to estimate subdistribution hazard ratios of cancer death between high and low allostatic load status (adjusted for age, sociodemographics, and health factors).
RESULTS: In fully adjusted models, high allostatic load was associated with a 23% increased risk of cancer death (adjusted subdistribution hazard ratio=1.23; 95% CI=1.06, 1.43) among all participants, a 3% increased risk of cancer death (adjusted subdistribution hazard ratio=1.03; 95% CI=0.78, 1.34) among underweight/healthy weight adults, a 31% increased risk of cancer death (adjusted subdistribution hazard ratio=1.31; 95% CI=1.02, 1.67) among overweight adults, and a 39% increased risk of death (adjusted subdistribution hazard ratio=1.39; 95% CI=1.04, 1.88) among obese adults, when compared to those with low allostatic load.
CONCLUSIONS: The risk of cancer death is highest among those with high allostatic load and obese BMI, but this effect was attenuated among those with high allostatic load and underweight/healthy or overweight BMI
IGEC2: A 17-month search for gravitational wave bursts in 2005-2007
We present here the results of a 515 days long run of the IGEC2 observatory,
consisting of the four resonant mass detectors ALLEGRO, AURIGA, EXPLORER and
NAUTILUS. The reported results are related to the fourfold observation time
from Nov. 6 2005 until Apr. 14 2007, when Allegro ceased its operation. This
period overlapped with the first long term observations performed by the LIGO
interferometric detectors. The IGEC observations aim at the identification of
gravitational wave candidates with high confidence, keeping the false alarm
rate at the level of 1 per century, and high duty cycle, namely 57% with all
four sites and 94% with at least three sites in simultaneous observation. The
network data analysis is based on time coincidence searches over at least three
detectors: the four 3-fold searches and the 4-fold one are combined in a
logical OR. We exchanged data with the usual blind procedure, by applying a
unique confidential time offset to the events in each set of data. The
accidental background was investigated by performing sets of 10^8 coincidence
analyses per each detector configuration on off-source data, obtained by
shifting the time series of each detector. The thresholds of the five searches
were tuned so as to control the overall false alarm rate to 1/century. When the
confidential time shifts was disclosed, no gravitational wave candidate was
found in the on-source data. As an additional output of this search, we make
available to other observatories the list of triple coincidence found below
search thresholds, corresponding to a false alarm rate of 1/month.Comment: 10 pages, 8 figures Accepted for publication on Phys. Rev.
Mineralogy of the Lunar Crust in Spatial Context: First Results from the Moon Mineralogy Mapper (M3)
India's Chandrayaan-1 successfully launched October 22, 2008 and went into lunar orbit a few weeks later. Commissioning of instruments began in late November and was near complete by the end of the year. Initial data for NASA's Moon Mineralogy Mapper (M3) were acquired across the Orientale Basin and the science results are discussed here. M 3 image-cube data provide mineralogy of the surface in geologic context. A major new result is that the existence and distribution of massive amounts of anorthosite as a continuous stratigraphic crustal layer is now irrefutable
Identification of a New Spinel-Rich Lunar Rock Type by the Moon Mineralogy Mapper (M (sup 3))
The canonical characterization of the lunar crust is based principally on available Apollo, Luna, and meteorite samples. The crust is described as an anorthosite-rich cumulate produced by the lunar magma ocean that has been infused with a mix of Mgsuite components. These have been mixed and redistributed during the late heavy bombardment and basin forming events. We report a new rock-type detected on the farside of the Moon by the Moon Mineralogy Mapper (M3) on Chandrayaan-1 that does not easily fit with current crustal evolution models. The rock-type is dominated by Mg-spinel with no detectible pyroxene or olivine present (<5%). It occurs along the western inner ring of Moscoviense Basin as one of several discrete areas that exhibit unusual compositions relative to their surroundings but without morphological evidence for separate processes leading to exposure
Results of the IGEC-2 search for gravitational wave bursts during 2005
The network of resonant bar detectors of gravitational waves resumed
coordinated observations within the International Gravitational Event
Collaboration (IGEC-2). Four detectors are taking part in this collaboration:
ALLEGRO, AURIGA, EXPLORER and NAUTILUS. We present here the results of the
search for gravitational wave bursts over 6 months during 2005, when IGEC-2 was
the only gravitational wave observatory in operation. The network data analysis
implemented is based on a time coincidence search among AURIGA, EXPLORER and
NAUTILUS, keeping the data from ALLEGRO for follow-up studies. With respect to
the previous IGEC 1997-2000 observations, the amplitude sensitivity of the
detectors to bursts improved by a factor about 3 and the sensitivity bandwidths
are wider, so that the data analysis was tuned considering a larger class of
detectable waveforms. Thanks to the higher duty cycles of the single detectors,
we decided to focus the analysis on three-fold observation, so to ensure the
identification of any single candidate of gravitational waves (gw) with high
statistical confidence. The achieved false detection rate is as low as 1 per
century. No candidates were found.Comment: 10 pages, to be submitted to Phys. Rev.
Character and spatial distribution of OH/H<SUB>2</SUB>O on the surface of the moon seen by M<SUP>3</SUP> on Chandrayaan-1
The search for water on the surface of the anhydrous Moon had remained an unfulfilled quest for 40 years. However, the Moon Mineralogy Mapper (M3) on Chandrayaan-1 has recently detected absorption features near 2.8 to 3.0 micrometers on the surface of the Moon. For silicate bodies, such features are typically attributed to hydroxyl- and/or water-bearing materials. On the Moon, the feature is seen as a widely distributed absorption that appears strongest at cooler high latitudes and at several fresh feldspathic craters. The general lack of correlation of this feature in sunlit M3 data with neutron spectrometer hydrogen abundance data suggests that the formation and retention of hydroxyl and water are ongoing surficial processes. Hydroxyl/water production processes may feed polar cold traps and make the lunar regolith a candidate source of volatiles for human exploration
Reverse glacier motion during iceberg calving and the cause of glacial earthquakes
Nearly half of Greenland’s mass loss occurs through iceberg calving, but the physical mechanisms operating during calving are poorly known and in situ observations are sparse. We show that calving at Greenland’s Helheim Glacier causes a minutes-long reversal of the glacier’s horizontal flow and a downward deflection of its terminus. The reverse motion results from the horizontal force caused by iceberg capsize and acceleration away from the glacier front. The downward motion results from a hydrodynamic pressure drop behind the capsizing berg, which also causes an upward force on the solid Earth. These forces are the source of glacial earthquakes, globally detectable seismic events whose proper interpretation will allow remote sensing of calving processes occurring at increasing numbers of outlet glaciers in Greenland and Antarctica
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