3,536 research outputs found
Advanced Silicon Avalanche Photodiodes on NASA's Global Ecosystem Dynamics Investigation (GEDI) Mission
Silicon Avalanche Photodiodes (APDs) are used in NASAs Global Ecosystem Dynamics Investigation (GEDI) which was launched in December 2018 and is currently measuring the Earths vegetation vertical structure from the International Space Station. The APDs were specially made for space lidar with a much lower hole-to-electron ionization coefficient ratio (k-factor ~0.008) than that of commercially available silicon APDs in order to reduce the APD excess noise from the randomness of the avalanche gain. A silicon heater resistor was used under the APD chip to heat the device up to 70C and improve its quantum efficiency at 1064 nm laser wavelength while maintaining a low dark current such that the overall signal to noise ratio is improved. Special APD protection circuits were used to raise the overload damage threshold to prevent device damage from strong laser return by specular surfaces, such as still water bodies, and space radiation events. The APD and a hybrid transimpedance amplifier circuit were hermetically sealed in a package with a sufficiently low leak rate to ensure multi-year operation lifetime in space. The detector assemblies underwent a series of pre-launch tests per NASA Goddard Environmental Verification Standard for space qualification. They have performed exactly as expected with GEDI in orbit. A detailed description of the GEDI detector design, signal and noise model, and test results are presented in this paper
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Temozolomide and Pazopanib Combined with FOLFOX Regressed a Primary Colorectal Cancer in a Patient-derived Orthotopic Xenograft Mouse Model.
PurposeThe goal of the present study was to determine the efficacy of temozolomide (TEM) and pazopanib (PAZ) combined with FOLFOX (oxaliplatin, leucovorin and 5-fluorouracil) on a colorectal cancer patient-derived orthotopic xenograft (PDOX) mouse model.Materials and methodsA colorectal cancer tumor from a patient previously established in non-transgenic nude mice was implanted subcutaneously in transgenic green fluorescence protein (GFP)-expressing nude mice in order to label the tumor stromal cells with GFP. Then labeled tumors were orthotopically implanted into the cecum of nude mice. Mice were randomized into four groups: Group 1, untreated control; group 2, TEM + PAZ; group 3, FOLFOX; group 4, TEM + PAZ plus FOLFOX. Tumor width, length, and mouse body weight were measured weekly. The Fluor Vivo imaging System was used to image the GFP-lableled tumor stromal cells in vivo. H&E staining and immunohistochemical staining were used for histological analysis.ResultsAll three treatments inhibited tumor growth as compared to the untreated control group. The combination of TEM + PAZ + FOLFOX regressed tumor growth significantly more effectively than TEM + PAZ or FOLFOX. Only the combination of TEM + PAZ + FOLFOX group caused a decrease in body weight. PAZ suppressed lymph vessels density in the colorectal cancer PDOX mouse model suggesting inhibition of lymphangiogenesis.ConclusionOur results suggest that the combination of TEM + PAZ + FOLFOX has clinical potential for colorectal cancer patient
Functional Requirements-Based Automated Testing for Avionics
We propose and demonstrate a method for the reduction of testing effort in
safety-critical software development using DO-178 guidance. We achieve this
through the application of Bounded Model Checking (BMC) to formal low-level
requirements, in order to generate tests automatically that are good enough to
replace existing labor-intensive test writing procedures while maintaining
independence from implementation artefacts. Given that existing manual
processes are often empirical and subjective, we begin by formally defining a
metric, which extends recognized best practice from code coverage analysis
strategies to generate tests that adequately cover the requirements. We then
formulate the automated test generation procedure and apply its prototype in
case studies with industrial partners. In review, the method developed here is
demonstrated to significantly reduce the human effort for the qualification of
software products under DO-178 guidance
DRG-LLaMA : Tuning LLaMA Model to Predict Diagnosis-related Group for Hospitalized Patients
In the U.S. inpatient payment system, the Diagnosis-Related Group (DRG) is
pivotal, but its assignment process is inefficient. The study introduces
DRG-LLaMA, an advanced large language model (LLM) fine-tuned on clinical notes
to enhance DRGs assignment. Utilizing LLaMA as the foundational model and
optimizing it through Low-Rank Adaptation (LoRA) on 236,192 MIMIC-IV discharge
summaries, our DRG-LLaMA-7B model exhibited a noteworthy macro-averaged F1
score of 0.327, a top-1 prediction accuracy of 52.0%, and a macro-averaged Area
Under the Curve (AUC) of 0.986, with a maximum input token length of 512. This
model surpassed the performance of prior leading models in DRG prediction,
showing a relative improvement of 40.3% and 35.7% in macro-averaged F1 score
compared to ClinicalBERT and CAML, respectively. Applied to base DRG and
complication or comorbidity (CC)/major complication or comorbidity (MCC)
prediction, DRG-LLaMA achieved a top-1 prediction accuracy of 67.8% and 67.5%,
respectively. Additionally, our findings indicate that DRG-LLaMA's performance
correlates with increased model parameters and input context lengths
Dispersal of Galactic Magnetic Fields into Intracluster Space
Little is known about the origin and basic properties of magnetic fields in
clusters of galaxies. High conductivity in magnetized interstellar plasma
suggests that galactic magnetic fields are (at least partly) ejected into
intracluster (IC) space by the same processes that enrich IC gas with metals.
We explore the dispersal of galactic fields by hydrodynamical simulations with
our new {\em Enzo-Galcon} code, which is capable of tracking a large number
galaxies during cluster assembly, and modeling the processes that disperse
their interstellar media. Doing so we are able to describe the evolution of the
mean strength of the field and its profile across the cluster. With the known
density profile of dispersed gas and an estimated range of coherence scales, we
predict the spatial distribution of Faraday rotation measure and find it to be
consistent with observational data
Search for dark matter annihilation in the Wolf-Lundmark-Melotte dwarf irregular galaxy with H.E.S.S.
Simulations of AGN feedback in galaxy clusters and groups: impact on gas fractions and the Lx-T scaling relation
Recently, rapid observational and theoretical progress has established that
black holes (BHs) play a decisive role in the formation and evolution of
individual galaxies as well as galaxy groups and clusters. In particular, there
is compelling evidence that BHs vigorously interact with their surroundings in
the central regions of galaxy clusters, indicating that any realistic model of
cluster formation needs to account for these processes. This is also suggested
by the failure of previous generations of hydrodynamical simulations without BH
physics to simultaneously account for the paucity of strong cooling flows in
clusters, the slope and amplitude of the observed cluster scaling relations,
and the high-luminosity cut-off of central cluster galaxies. Here we use
high-resolution cosmological simulations of a large cluster and group sample to
study how BHs affect their host systems. We focus on two specific properties,
the halo gas fraction and the X-ray luminosity-temperature scaling relation,
both of which are notoriously difficult to reproduce in self-consistent
hydrodynamical simulations. We show that BH feedback can solve both of these
issues, bringing them in excellent agreement with observations, without
alluding to the `cooling only' solution that produces unphysically bright
central galaxies. By comparing a large sample of simulated AGN-heated clusters
with observations, our new simulation technique should make it possible to
reliably calibrate observational biases in cluster surveys, thereby enabling
various high-precision cosmological studies of the dark matter and dark energy
content of the universe.Comment: 4 pages, 2 figures, minor revisions, ApJL in pres
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