3,528 research outputs found
Demonstration of a Benchmarking Technique to Compare Graduate Education Level of Air Force Project Managers and Selected Benchmarking Partners
This thesis demonstrated a benchmarking technique to support determining graduate education requirements for officers in the Acquisition Program Management utilization field. The technique is also applicable to other Air Force career fields. The USAF currently uses the Graduate Education Management System GEMS to quantify officer graduate education requirements. Weaknesses in the GEMS-based process include the inability to address future technologies, vulnerability to inconsistency and change, and confusion of training with education. AFIT developed and recommended an alternative requirements determination approach that relies on benchmarking. This thesis reviewed literature on benchmarking principles. The research methodology developed and implemented benchmarking procedures to include identifying attributes to benchmark, determining measures, identifying suitable benchmark subjects, collecting benchmark data, and analyzing the data. Primary benchmark partners were project managers from the Project Management Institute PMI, a non-profit professional organization. Percentages of Air Force, PMI, and PMI defense/Aerospace sector project managers holding relevant graduate degrees were 53.21%, 12.41% and 18.67% respectively. Six limitations identified in the thesis prevented the determination of firm education requirements based solely on these results. Securing senior USAF support, developing rigorous best practices criteria, using trend data and developing numerical bridging factors were recommended to improve the benchmarking technique
Spitzer Observations of Comet 67P/Churyumov-Gerasimenko at 5.5-4.3 AU From the Sun
We report Spitzer Space Telescope observations of comet
67P/Churyumov-Gerasimenko at 5.5 and 4.3 AU from the Sun, post-aphelion. Comet
67P is the primary target of the European Space Agency's Rosetta mission. The
Rosetta spacecraft will rendezvous with the nucleus at heliocentric distances
similar to our observations. Rotationally resolved observations at 8 and 24
microns (at a heliocentric distance, rh, of 4.8 AU) that sample the size and
color-temperature of the nucleus are combined with aphelion R-band light curves
observed at the Very Large Telescope (VLT) and yield a mean effective radius of
2.04 +/- 0.11 km, and an R-band geometric albedo of 0.054 +/- 0.006. The
amplitudes of the R-band and mid-infrared light curves agree, which suggests
that the variability is dominated by the shape of the nucleus. We also detect
the dust trail of the comet at 4.8 and 5.5 AU, constrain the grain sizes to be
less than or similar to 6 mm, and estimate the impact hazard to Rosetta. We
find no evidence for recently ejected dust in our images. If the activity of
67P is consistent from orbit to orbit, then we may expect the Rosetta
spacecraft will return images of an inactive or weakly active nucleus as it
rendezvous with the comet at rh = 4 AU in 2014.Comment: 19 pages, 2 tables, 10 figures. Accepted for publication in the
Astronomical Journa
RECONOCIMIENTOS ARQUEOLÓGICOS EN LA COSTA NORTE DEL PERÚ
La numeración de campo de yacimientos y los nombres tentativos para cultura dados en este informe están sujetos a cambios. Se espera que un sistema más regular de numeración de campo permanente sea dado, pero los nombres de culturas serán mayormente retenidos. Sólo se ha hecho un análisis muy preliminar de los materiales. Al presente, la evidencia de seriaciones y comparaciones con otros yacimientos peruanos situados al Sur no han dado resultados comparables y tampoco han sido suficientemente aclarados como para ser definitivos. Muy poca evidencia estratigráfica ha sido obtenible hasta ahora y este poco todavía no ha sido analizado. Sin embargo, un número de culturas arqueológicamente distintas han sido encontradas, muchas del ellas presentan, en más de un yacimiento sobre una distancia considerable, una diferencia mayormente cronológica que geográfica, aparentemente. Sobre esta base, varios periodos han sido distinguidos a pesar que su secuencia no ha sido todavía determinada
Absorption Efficiencies of Forsterite. I: DDA Explorations in Grain Shape and Size
We compute the absorption efficiency (Qabs) of forsterite using the discrete
dipole approximation (DDA) in order to identify and describe what
characteristics of crystal grain shape and size are important to the shape,
peak location, and relative strength of spectral features in the 8-40 {\mu}m
wavelength range. Using the DDSCAT code, we compute Qabs for non-spherical
polyhedral grain shapes with a_eff = 0.1 {\mu}m. The shape characteristics
identified are: 1) elongation/reduction along one of three crystallographic
axes; 2) asymmetry, such that all three crystallographic axes are of different
lengths; and 3) the presence of crystalline faces that are not parallel to a
specific crystallographic axis, e.g., non-rectangular prisms and (di)pyramids.
Elongation/reduction dominates the locations and shapes of spectral features
near 10, 11, 16, 23.5, 27, and 33.5 {\mu}m, while asymmetry and tips are
secondary shape effects. Increasing grain sizes (0.1-1.0 {\mu}m) shifts the 10,
11 {\mu}m features systematically towards longer wavelengths and relative to
the 11 {\mu}m feature increases the strengths and slightly broadens the longer
wavelength features. Seven spectral shape classes are established for
crystallographic a-, b-, and c-axes and include columnar and platelet shapes
plus non-elongated or equant grain shapes. The spectral shape classes and the
effects of grain size have practical application in identifying or excluding
columnar, platelet or equant forsterite grain shapes in astrophysical environs.
Identification of the shape characteristics of forsterite from 8-40 {\mu}m
spectra provides a potential means to probe the temperatures at which
forsterite formed.Comment: 55 pages, 15 figure
Planning Activity Report for NDE of Adhesive Bonded Structures
Following a workshop held at the Rockwell International Science Center, Thousand Oaks, California in January, 1979, an ad hoc planning activity was undertaken to set forth a program plan to address the needs in NDE for adhesive bonded structures. The objectives of the planning activity were to develop a program rationale and strategy, determine the existence of reasonable approaches, and to propose a detailed plan of action for review at the annual DARPA/AF meeting in September, 1979. The plan encompasses the basic elements of an accept/reject methodology based on fracture mechanics, expected developments of valid flaw growth models, stress analysis, and non-destructive measurement techniques. A central issue is the prospect for determining a valid non-destructive measure of strength for the bonded joint as might be reflected in the tendency for preexistent flaws to propagate under environmental loads
Low endemism, continued deep-shallow interchanges, and evidence for cosmopolitan distributions in free-living marine nematodes (order Enoplida)
Background: Nematodes represent the most abundant benthic metazoa in one of the largest habitats on earth, the deep sea. Characterizing major patterns of biodiversity within this dominant group is a critical step towards understanding evolutionary patterns across this vast ecosystem. The present study has aimed to place deep-sea nematode species into a phylogenetic framework, investigate relationships between shallow water and deep-sea taxa, and elucidate phylogeographic patterns amongst the deep-sea fauna. Results: Molecular data (18 S and 28 S rRNA) confirms a high diversity amongst deep-sea Enoplids. There is no evidence for endemic deep-sea lineages in Maximum Likelihood or Bayesian phylogenies, and Enoplids do not cluster according to depth or geographic location. Tree topologies suggest frequent interchanges between deep-sea and shallow water habitats, as well as a mixture of early radiations and more recently derived lineages amongst deep-sea taxa. This study also provides convincing evidence of cosmopolitan marine species, recovering a subset of Oncholaimid nematodes with identical gene sequences (18 S, 28 S and cox1) at trans-Atlantic sample sites. Conclusions: The complex clade structures recovered within the Enoplida support a high global species richness for marine nematodes, with phylogeographic patterns suggesting the existence of closely related, globally distributed species complexes in the deep sea. True cosmopolitan species may additionally exist within this group, potentially driven by specific life history traits of Enoplids. Although this investigation aimed to intensively sample nematodes from the order Enoplida, specimens were only identified down to genus (at best) and our sampling regime focused on an infinitesimal small fraction of the deep-sea floor. Future nematode studies should incorporate an extended sample set covering a wide depth range (shelf, bathyal, and abyssal sites), utilize additional genetic loci (e.g. mtDNA) that are informative at the species level, and apply high-throughput sequencing methods to fully assay community diversity. Finally, further Molecular studies are needed to determine whether phylogeographic patterns observed in Enoplids are common across other ubiquitous marine groups (e. g. Chromadorida, Monhysterida)
Mid-Infrared Spectrophotometric Observations of Fragments B and C of Comet 73P/Schwassmann-Wachmann 3
We present mid-infrared spectra and images from the GEMINI-N (+Michelle)
observations of fragments SW3-[B] and SW3-[C] of the ecliptic (Jupiter Family)
comet 73P/Schwassmann-Wachmann 3 pre-perihelion. We observed fragment B soon
after an outburst event (between 2006 April 16 - 26 UT) and detected
crystalline silicates. The mineralogy of both fragments was dominated by
amorphous carbon and amorphous pyroxene. The grain size distribution (assuming
a Hanner modified power-law) for fragment SW3-[B] has a peak grain radius of
a_p ~ 0.5 micron, and for fragment SW3-[C], a_p ~ 0.3 micron; both values
larger than the peak grain radius of the size distribution for the dust ejected
from ecliptic comet 9P/Tempel 1 during the Deep Impact event (a_p = 0.2 micron.
The silicate-to-carbon ratio and the silicate crystalline mass fraction for the
submicron to micron-size portion of the grain size distribution on the nucleus
of fragment SW3-[B] was 1.341 +0.250 -0.253 and 0.335 +0.089 -0.112,
respectively, while on the nucleus of fragment SW3-[C] was 0.671 +0.076 -0.076
and 0.257 +0.039 -0.043, respectively. The similarity in mineralogy and grain
properties between the two fragments implies that 73P/Schwassmann-Wachmann 3 is
homogeneous in composition. The slight differences in grain size distribution
and silicate-to-carbon ratio between the two fragments likely arises because
SW3-[B] was actively fragmenting throughout its passage while the activity in
SW3-[C] was primarily driven by jets. The lack of diverse mineralogy in the
fragments SW3-[B] and SW3-[C] of 73P/Schwassmann-Wachmann 3 along with the
relatively larger peak in the coma grain size distribution suggests the parent
body of this comet may have formed in a region of the solar nebula with
different environmental properties than the natal sites where comet C/1995 O1
(Hale-Bopp) and 9P/Tempel 1 nuclei aggregated.Comment: 31 pages, 5 figure, accepted for publication in A
Skeletal muscle triglyceride. An aspect of regional adiposity and insulin resistance
Najnowsze dane uzyskane z badań, w których stosowano cztery niezależne metody wskazują, że nadmierne spichrzanie triglicerydów w mięśniach szkieletowych wiąże się z insulinoopornością. Potencjalne mechanizmy tłumaczące ten związek obejmują zlokalizowane w mitochondriach zaburzenia metabolizmu kwasów tłuszczowych w przebiegu otyłości oraz cukrzycy typu 2. Szczególnie dominują zaburzenia ścieżki oksydacyjnej kwasów tłuszczowych w fazie poabsorbcyjnej, które prowadzą do zmniejszonego zużycia oraz nadmiernej estryfikacji oraz spichrzania lipidów w mięśniach szkieletowych. Te zaburzenia metabolizmu kwasów tłuszczowych na czczo mogą się wiązać z niedostosowaniem metabolizmu w insulinooporności, co nie ogranicza się do defektu metabolizmu glukozy w warunkach stymulacji insuliną. Dowody te więc wskazują, że zaburzenia metabolizmu kwasów tłuszczowych odgrywają rolę w procesie gromadzenia triglicerydów mięśni szkieletowych oraz w patogenezie insulinooporności. Zmniejszenie masy ciała poprzez ograniczenie podaży kalorii poprawia wrażliwość na insulinę, ale wpływ na metabolizm kwasów tłuszczowych jest mniej wyraźny. Niemniej jednak obniżenie masy ciała zmniejsza zawartość triglicerydów w mięśniach szkieletowych, być może przyczyniając się do poprawy działania insuliny obserwowanej w miarę odchudzania. Zmiany w metabolizmie substratów w mięśniu szkieletowym pozwalają wyjaśnić związek pomiędzy akumulacją triglicerydów w mięśniu szkieletowym a insulinoopornością, co może prowadzić do zastosowania odpowiedniejszej terapii, mającej na celu poprawę metabolizmu glukozy oraz kwasów tłuszczowych w otyłości oraz w cukrzycy typu 2.Recent evidence derived from four independent methods
indicates that an excess triglyceride storage
within skeletal muscle is linked to insulin resistance.
Potential mechanisms for this association include
apparent defects in fatty acid metabolism that are
centered at the mitochondria in obesity and in type
2 diabetes. Specifically, defects in the pathways for
fatty acid oxidation during postabsorptive conditions
are prominent, leading to diminished use of
fatty acids and increased esterification and storage
of lipid within skeletal muscle. These impairments
in fatty acid metabolism during fasting conditions
may be related to a metabolic inflexibility in insulin
resistance that is not limited to defects in glucose
metabolism during insulin-stimulated conditions.
Thus, there is substantial evidence implicating perturbations
in fatty acid metabolism during accumulation
of skeletal muscle triglyceride and in the pathogenesis
of insulin resistance. Weight loss by caloric
restriction improves insulin sensitivity, but the
effects on fatty acid metabolism are less conspicuous.
Nevertheless, weight loss decreases the content
of triglyceride within skeletal muscle, perhaps contributing to the improvement in insulin action
with weight loss. Alterations in skeletal muscle substrate
metabolism provide insight into the link between
skeletal muscle triglyceride accumulation and
insulin resistance, and they may lead to more appropriate
therapies to improve glucose and fatty acid
metabolism in obesity and in type 2 diabetes
A Spitzer Study of Comets 2P/Encke, 67P/Churyumov-Gerasimenko, and C/2001 HT50 (LINEAR-NEAT)
We present infrared images and spectra of comets 2P/Encke,
67P/Churyumov-Gerasimenko, and C/2001 HT50 (LINEAR-NEAT) as part of a larger
program to observe comets inside of 5 AU from the sun with the Spitzer Space
Telescope. The nucleus of comet 2P/Encke was observed at two vastly different
phase angles (20 degrees and 63 degrees). Model fits to the spectral energy
distributions of the nucleus suggest comet Encke's infrared beaming parameter
derived from the near-Earth asteroid thermal model may have a phase angle
dependence. The observed emission from comet Encke's dust coma is best-modeled
using predominately amorphous carbon grains with a grain size distribution that
peaks near 0.4 microns, and the silicate contribution by mass to the sub-micron
dust coma is constrained to 31%. Comet 67P/Churyumov-Gerasimenko was observed
with distinct coma emission in excess of a model nucleus at a heliocentric
distance of 5.0 AU. The coma detection suggests that sublimation processes are
still active or grains from recent activity remain near the nucleus. Comet
C/2001 HT50 (LINEAR-NEAT) showed evidence for crystalline silicates in the
spectrum obtained at 3.2 AU and we derive a silicate-to-carbon dust ratio of
0.6. The ratio is an order of magnitude lower than that derived for comets
9P/Tempel 1 during the Deep Impact encounter and C/1995 O1 (Hale-Bopp).Comment: Accepted for publication in the Astrophysical Journal 48 pages, 15
figures, 10 table
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