5,784 research outputs found
On Source Density Evolution of Gamma-ray Bursts
Recent optical afterglow observations of gamma-ray bursts indicate a setting
and distance scale that many relate to star-formation regions. In this paper,
we use and a set of artificial trigger thresholds to probe
several potential GRB source density evolutionary scenarios. In particular, we
compare a uniform subset of BATSE 4B data to cosmological scenarios where GRBs
evolve as the comoving density, the star formation rate, the QSO rate, and the
SN Type Ic rate. Standard candle bursts with power-law spectra and a universe
without vacuum energy were assumed. Our results significantly favor a comoving
density model, implying that GRB source density evolution is weaker than
expected in these evolutionary scenarios. GRB density might still follow
star-formation rates given proper concurrent GRB luminosity evolution,
significant beaming, significant error in standard candle assumptions, or were
a significant modification of star formation rate estimates to occur.Comment: 12 pages, 4 figures, accepted by Ap
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Willingness to Pay for Brand Reputation: Lessons from the Volkswagen Diesel Emissions Scandal
In this study, we use the announcement of the Volkswagen emissions scandalon September 18, 2015, as an exogenous shock to measure consumers’ willing-ness to pay (WTP) for brand reputation. Only Volkswagen diesel cars producedin2009-2015were announced as emissions violators. Using eBay car auction data,we estimate the impacts of the scandal on the prices of Volkswagen emissionsnon-violatingcars. Our difference-in-differences estimates show that final bid prices decreased by 14% and 9% in diesel and gasoline car markets, respectively, whichpurely reflected a decline in consumers’ WTP for Volkswagen’s brand reputation.Additionally, the difference in price-drops between the violating and non-violating diesel cars is statistically insignificant. This may be due to the fact that consumers rationally adjust their WTP by expecting compensation which will almost surely be provided by Volkswagen for violating models
Carbon nanomaterials as drug transporter for cancer therapy
There is a vigorous and growing research effort developing carbon nanotubes (CNTs) for medical applications. It is now known that nanocomposites of Single Wall Nanotubes (SWNTs) can be used to deliver anti-cancer drugs to cells. Also, SWNTs are efficient at converting near infrared (NIR) light to heat, and can do so in a cell, and so cancer cells can be targeted for destruction by NIR radiation, once the cells have taken up SWNTs. SWNTs are highly insoluble in water, but can be functionalized via physical or covalent attachment of solubilizing molecules and drugs of interest. Once this is done, they are readily taken up by cells. We found evidence that our CNT nanocomposites were found to enter cells via endocytosis (the mechanism cells use to take up nutrients); this agrees with earlier work by Dai and coworkers. Herein, we perform systematic study of the internalization, delivery and subcellular localization and possible adverse effects of SWNTs dispersed in culture media and SWNTs wrapped with different fluorescently labelled peptide (FLP-SWNTs) on Chinese hamster ovary (CHO) cells and SWNTs attached with anti-cancer drug on two common cancerous cell lines, human epithelial carcinoma cell line (HeLa) and colorectal cancer cell lines (WiDr)
Momentum anisotropies in the quark coalescence model
Based on the quark coalescence model, we derive relations among the momentum
anisotropies of mesons and baryons in relativistic heavy ion collisions from a
given, but arbitrary azimuthal distribution for the partons. Besides the
familiar even Fourier coefficients such as the elliptic flow, we also pay
attention to odd Fourier coefficients such as the directed flow, which has been
observed at finite rapidity even at RHIC energies.Comment: 5 page
Teacher Stress: Causes, Stages, and Effects
This article presents a discussion of teacher stress including a definition of stress, the symptoms of stress, and the cause of stress in the classroom, laboratory, and clinical experiences. The three stages of stress are identified as well as the effects stress has on teachers both at the secondary and postsecondary levels. Also discussed are the reactions to stress and suggestions for alleviation of stress. A recommendation is provided in regards to educating vocational educators, especially health occupations teachers, about stress
Determination of the stiffness of the nuclear symmetry energy from isospin diffusion
With an isospin- and momentum-dependent transport model, we find that the
degree of isospin diffusion in heavy ion collisions at intermediate energies is
affected by both the stiffness of the nuclear symmetry energy and the momentum
dependence of the nucleon potential. Using a momentum dependence derived from
the Gogny effective interaction, recent experimental data from NSCL/MSU on
isospin diffusion are shown to be consistent with a nuclear symmetry energy
given by at
subnormal densities. This leads to a significantly constrained value of about
-550 MeV for the isospin-dependent part of the isobaric incompressibility of
isospin asymmetric nuclear matter.Comment: 4 pages, 4 figures, 1 table, revised version, to appear in PR
Effects of nano-void density, size, and spatial population on thermal conductivity: a case study of GaN crystal
The thermal conductivity of a crystal is sensitive to the presence of
surfaces and nanoscale defects. While this opens tremendous opportunities to
tailor thermal conductivity, a true "phonon engineering" of nanocrystals for a
specific electronic or thermoelectric application can only be achieved when the
dependence of thermal conductivity on the defect density, size, and spatial
population is understood and quantified. Unfortunately, experimental studies of
effects of nanoscale defects are quite challenging. While molecular dynamics
simulations are effective in calculating thermal conductivity, the defect
density range that can be explored with feasible computing resources is
unrealistically high. As a result, previous work has not generated a fully
detailed understanding of the dependence of thermal conductivity on nanoscale
defects. Using GaN as an example, we have combined physically-motivated
analytical model and highly-converged large scale molecular dynamics
simulations to study effects of defects on thermal conductivity. An analytical
expression for thermal conductivity as a function of void density, size, and
population has been derived and corroborated with the model, simulations, and
experiments
Perancangan Buku Cerita Bertema Olahraga Bulu Tangkis Bagi Usia 5-7 Tahun
Bulu tangkis merupakan olahraga yang menjadi “khas” berprestasi bagi negara Indonesia. Namun,permasalahannya adalah bulu tangkis hanya diliput ketika ada kejuaraan atau lomba saja, selain itu sejak dinitidak dibiasakan dekat dengan olahraga bulu tangkis. Untuk menyikapi hal di atas, maka dibuat media buku yangdiharapkan media ini mampu menimbulkan kecintaan pada bulu tangkis. Media buku dipilih karena buku adalahmedia yang cocok untuk mengajarkan sesuatu bagi anak-anak untuk mengenal serta memahami, serta mediayang dekat dengan anak-anak. Melalui media buku, dapat diperoleh pengetahuan-pengetahuan, serta buku dapatmengimajinasi anak-anak tersebut ketika membacanya. Ditambahkannya interaksi harapannya akan lebih paham,tertarik, dan timbul minat akan olahraga bulu tangkis. khusus target audience yang dituju adalah anak-anakdengan usia 5-7 tahun. Perancangan ini merupakan stimulus awal bagi anak-anak usia 5-7 tahun, sebelum usiakeemasan di mana anak-anak bertemu dengan dunia olahraga bulu tangkis yang sesungguhnya
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