Drexel University

About: Drexel University is a education organization based out in Philadelphia, Pennsylvania, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 26770 authors who have published 51438 publications receiving 1949443 citations. The organization is also known as: Drexel & Drexel Institute.

The Eighth Data Release of the Sloan Digital Sky Survey: First Data from SDSS-III

Abstract: The Sloan Digital Sky Survey (SDSS) started a new phase in 2008 August, with new instrumentation and new surveys focused on Galactic structure and chemical evolution, measurements of the baryon oscillation feature in the clustering of galaxies and the quasar Lyα forest, and a radial velocity search for planets around ~8000 stars. This paper describes the first data release of SDSS-III (and the eighth counting from the beginning of the SDSS). The release includes five-band imaging of roughly 5200 deg2 in the southern Galactic cap, bringing the total footprint of the SDSS imaging to 14,555 deg2, or over a third of the Celestial Sphere. All the imaging data have been reprocessed with an improved sky-subtraction algorithm and a final, self-consistent photometric recalibration and flat-field determination. This release also includes all data from the second phase of the Sloan Extension for Galactic Understanding and Exploration (SEGUE-2), consisting of spectroscopy of approximately 118,000 stars at both high and low Galactic latitudes. All the more than half a million stellar spectra obtained with the SDSS spectrograph have been reprocessed through an improved stellar parameter pipeline, which has better determination of metallicity for high-metallicity stars.

Flexible and conductive MXene films and nanocomposites with high capacitance

Abstract: MXenes, a new family of 2D materials, combine hydrophilic surfaces with metallic conductivity Delamination of MXene produces single-layer nanosheets with thickness of about a nanometer and lateral size of the order of micrometers The high aspect ratio of delaminated MXene renders it promising nanofiller in multifunctional polymer nanocomposites Herein, Ti 3 C 2 T x MXene was mixed with either a charged polydiallyldimethylammonium chloride (PDDA) or an electrically neutral polyvinyl alcohol (PVA) to produce Ti 3 C 2 T x /polymer composites The as-fabricated composites are flexible and have electrical conductivities as high as 22 × 10 4 S/m in the case of the Ti 3 C 2 T x /PVA composite film and 24 × 10 5 S/m for pure Ti 3 C 2 T x films The tensile strength of the Ti 3 C 2 T x /PVA composites was significantly enhanced compared with pure Ti 3 C 2 T x or PVA films The intercalation and confinement of the polymer between the MXene flakes not only increased flexibility but also enhanced cationic intercalation, offering an impressive volumetric capacitance of ∼530 F/cm 3 for MXene/PVA-KOH composite film at 2 mV/s To our knowledge, this study is a first, but crucial, step in exploring the potential of using MXenes in polymer-based multifunctional nanocomposites for a host of applications, such as structural components, energy storage devices, wearable electronics, electrochemical actuators, and radiofrequency shielding, to name a few

Freshwater Ecoregions of the World: A New Map of Biogeographic Units for Freshwater Biodiversity Conservation

Abstract: We present a new map depicting the first global biogeographic regionalization of Earth's freshwater systems. This map of freshwater ecoregions is based on the distributions and compositions of freshwater fish species and incorporates major ecological and evolutionary patterns. Covering virtually all freshwater habitats on Earth, this ecoregion map, together with associated species data, is a useful tool for underpinning global and regional conservation planning efforts (particularly to identify outstanding and imperiled freshwater systems); for serving as a logical framework for large-scale conservation strategies; and for providing a global-scale knowledge base for increasing freshwater biogeographic literacy. Preliminary data for fish species compiled by ecoregion reveal some previously unrecognized areas of high biodiversity, highlighting the benefit of looking at the world's freshwaters through a new framework.

Synthesis and Characterization of a Remarkable Ceramic: Ti3SiC2

Abstract: Polycrystalline bulk samples of Ti{sub 3}SiC{sub 2} were fabricated by reactively hot-pressing Ti, graphite, and SiC powders at 40 MPa and 1,600 C for 4 h. This compound has remarkable properties. Its compressive strength, measured at room temperature, was 600 MPa, and dropped to 260 MPa at 1,300 C in air. Although the room-temperature failure was brittle, the high-temperature load-displacement curve shows significant plastic behavior. The oxidation is parabolic and at 1,000 and 1,400 C the parabolic rate constants were, respectively, 2 {times} 10{sup {minus}8} and 2 {times} 10{sup {minus}5} kg{sup 2}{center_dot}m{sup {minus}4}{center_dot}s{sup {minus}1}. The activation energy for oxidation is thus {approx}300 kJ/mol. The room-temperature electrical conductivity is 4.5 {times} 10{sup 6} {Omega}{sup {minus}1}{center_dot}m{sup {minus}1}, roughly twice that of pure Ti. The thermal expansion coefficient in the temperature range 25 to 1,000 C, the room-temperature thermal conductivity, and the heat capacity are respectively, 10 {times} 10{sup {minus}6} C{sup {minus}1}, 43 W/(m{center_dot}K), and 588 J/(kg{center_dot}K). With a hardness of 4 GPa and a Young`s modulus of 320 GPa, it is relatively soft, but reasonably stiff. Furthermore, Ti{sub 3}SiC{sub 2} does not appear to be susceptible to thermal shock; quenching from 1,400 C into water does not affect the postquench bend strength.more » As significantly, this compound is as readily machinable as graphite. Scanning electron microscopy of polished and fractured surfaces leaves little doubt as to its layered nature.« less

Opportunities and obstacles for deep learning in biology and medicine.

Abstract: Deep learning describes a class of machine learning algorithms that are capable of combining raw inputs into layers of intermediate features. These algorithms have recently shown impressive results across a variety of domains. Biology and medicine are data-rich disciplines, but the data are complex and often ill-understood. Hence, deep learning techniques may be particularly well suited to solve problems of these fields. We examine applications of deep learning to a variety of biomedical problems-patient classification, fundamental biological processes and treatment of patients-and discuss whether deep learning will be able to transform these tasks or if the biomedical sphere poses unique challenges. Following from an extensive literature review, we find that deep learning has yet to revolutionize biomedicine or definitively resolve any of the most pressing challenges in the field, but promising advances have been made on the prior state of the art. Even though improvements over previous baselines have been modest in general, the recent progress indicates that deep learning methods will provide valuable means for speeding up or aiding human investigation. Though progress has been made linking a specific neural network's prediction to input features, understanding how users should interpret these models to make testable hypotheses about the system under study remains an open challenge. Furthermore, the limited amount of labelled data for training presents problems in some domains, as do legal and privacy constraints on work with sensitive health records. Nonetheless, we foresee deep learning enabling changes at both bench and bedside with the potential to transform several areas of biology and medicine.