559 research outputs found
Tuning Nanocrystal Surface Depletion by Controlling Dopant Distribution as a Route Toward Enhanced Film Conductivity
Electron conduction through bare metal oxide nanocrystal (NC) films is
hindered by surface depletion regions resulting from the presence of surface
states. We control the radial dopant distribution in tin-doped indium oxide
(ITO) NCs as a means to manipulate the NC depletion width. We find in films of
ITO NCs of equal overall dopant concentration that those with dopant-enriched
surfaces show decreased depletion width and increased conductivity. Variable
temperature conductivity data shows electron localization length increases and
associated depletion width decreases monotonically with increased density of
dopants near the NC surface. We calculate band profiles for NCs of differing
radial dopant distributions and, in agreement with variable temperature
conductivity fits, find NCs with dopant-enriched surfaces have narrower
depletion widths and longer localization lengths than those with
dopant-enriched cores. Following amelioration of NC surface depletion by atomic
layer deposition of alumina, all films of equal overall dopant concentration
have similar conductivity. Variable temperature conductivity measurements on
alumina-capped films indicate all films behave as granular metals. Herein, we
conclude that dopant-enriched surfaces decrease the near-surface depletion
region, which directly increases the electron localization length and
conductivity of NC films
Effect of Temperature on Gamete Production and Biochemical Composition of Gonads in the Sea Urchin Lytechinus variegatus
Temperature is one of the most important proximate factors affecting the biology of ectothermal organisms. In the sea urchin, Lytechimus variegatus, the reproductive cycle in wild populations is correlated with changing water temperature, suggesting that reproduction may be dependent, in part, on temperature. Adult L. variegatus (ca. 35.63 ± 1.24 g wet weight, 40-mm diameter) were collected in October 2001 from St. Joseph Bay, FL (30°N, 85.5°W) and transported to the University of Alabama at Birmingham. Sea urchins were placed into nine 80-liter aquaria (n = eight sea urchins per aquarium) maintained in enclosed incubators (n = three aquaria per incubator) at a specific constant temperature of 16, 22, or 28°C and 32 ppt salinity synthetic seawater (Instant Ocean). Within each aquarium, individuals were maintained in 1-liter containers with recirculation and were fed daily a formulated feed ad libitum for 8 wk. At the end of week 8, final measurements of each individual were recorded, individuals were dissected, gonads were measured, and gonad histology and biochemistry were analyzed. Gonad weights were highest for individuals held at the 22°C treatment, but did not vary between individuals held at 16 or 28°C. The acinus volume in the gonad was occupied primarily by nutritive phagocytes at all temperature treatments. In females, gamete volumes were highest for females held at 22°C, whereas gamete volumes were not different for females held at 16 or 28°C. In males, gamete volumes were significantly lower at 28°C, and gamete volumes were not different between males held at 16 or 22°C. Gamete volumes were small in all temperature treatments, suggesting that gamete production had not substantially advanced within the 8-wk study period. The cellular ultrastructure of the nutritive phagocytes varied with temperature. Vacuolated nutritive phagocytes were common in the acini of individuals held at 16°C, and globulated nutritive phagocytes were common in the acini of individuals held at 28°C, Females held at 22°C had the highest protein content in the gonad, and protein content was not different between females held at 16 or 28°C. The amount of lipid was highest for males held at 16°C and did not differ between males held at 22 or 28°C. These data lead us to suggest that L. variegatus utilize different nutrient allocation strategies in the gonad in response to temperature, which could affect the reproductive success of the species if subjected to long-term changes in seawater temperature
Intrinsic Optical and Electronic Properties from Quantitative Analysis of Plasmonic Semiconductor Nanocrystal Ensemble Optical Extinction
The optical extinction spectra arising from localized surface plasmon
resonance in doped semiconductor nanocrystals (NCs) have intensities and
lineshapes determined by free charge carrier concentrations and the various
mechanisms for damping the oscillation of those free carriers. However, these
intrinsic properties are convoluted by heterogeneous broadening when measuring
spectra of ensembles. We reveal that the traditional Drude approximation is not
equipped to fit spectra from a heterogeneous ensemble of doped semiconductor
NCs and produces fit results that violate Mie scattering theory. The
heterogeneous ensemble Drude approximation (HEDA) model rectifies this issue by
accounting for ensemble heterogeneity and near-surface depletion. The HEDA
model is applied to tin-doped indium oxide NCs for a range of sizes and doping
levels but we expect it can be employed for any isotropic plasmonic particles
in the quasistatic regime. It captures individual NC optical properties and
their contributions to the ensemble spectra thereby enabling the analysis of
intrinsic NC properties from an ensemble measurement. Quality factors for the
average NC in each ensemble are quantified and found to be notably higher than
those of the ensemble. Carrier mobility and conductivity derived from HEDA fits
matches that measured in the bulk thin film literature
The Effect of Selection for Desiccation Resistance on Cold Tolerance of Drosophila Melanogaster
Low Temperature and Desiccation Stress Are Thought to Be Mechanistically Similar in Insects, and Several Studies Indicate that There is a Degree of Cross-Tolerance between Them, such that Increased Cold Tolerance Results in Greater Desiccation Tolerance and Vice Versa. This Assertion is Tested at an Evolutionary Scale by Examining Basal Cold Tolerance, Rapid Cold-Hardening (RCH) and Chill Coma Recovery in Replicate Populations of Drosophila Melanogaster Selected for Desiccation Resistance (With Controls for Both Selection and Concomitant Starvation) for over 50 Generations. All of the Populations Display a RCH Response, and There is No Effect of Selection Regime on RCH or Basal Cold Tolerance, Although There Are Differences in Basal Cold Tolerance between Sampling Dates, Apparently Related to Inter-Individual Variation in Development Time. Flies Selected for Desiccation Tolerance Recover from Chill Coma Slightly, But Significantly, Faster Than Control and Starvation-Control Flies. These Findings Provide Little Support for Cross-Tolerance between Survival of Near-Lethal Cold and Desiccation Stress in D. Melanogaster. © 2007 the Authors
Congenital heart disease protein 5 associates with CASZ1 to maintain myocardial tissue integrity
The identification and characterization of the cellular and molecular pathways involved in the differentiation and morphogenesis of specific cell types of the developing heart are crucial to understanding the process of cardiac development and the pathology associated with human congenital heart disease. Here, we show that the cardiac transcription factor CASTOR (CASZ1) directly interacts with congenital heart disease 5 protein (CHD5), which is also known as tryptophan-rich basic protein (WRB), a gene located on chromosome 21 in the proposed region responsible for congenital heart disease in individuals with Down's syndrome. We demonstrate that loss of CHD5 in Xenopus leads to compromised myocardial integrity, improper deposition of basement membrane, and a resultant failure of hearts to undergo cell movements associated with cardiac formation. We further report that CHD5 is essential for CASZ1 function and that the CHD5-CASZ1 interaction is necessary for cardiac morphogenesis. Collectively, these results establish a role for CHD5 and CASZ1 in the early stages of vertebrate cardiac development
The Chandra Source Catalog
The Chandra Source Catalog (CSC) is a general purpose virtual X-ray
astrophysics facility that provides access to a carefully selected set of
generally useful quantities for individual X-ray sources, and is designed to
satisfy the needs of a broad-based group of scientists, including those who may
be less familiar with astronomical data analysis in the X-ray regime. The first
release of the CSC includes information about 94,676 distinct X-ray sources
detected in a subset of public ACIS imaging observations from roughly the first
eight years of the Chandra mission. This release of the catalog includes point
and compact sources with observed spatial extents <~ 30''. The catalog (1)
provides access to the best estimates of the X-ray source properties for
detected sources, with good scientific fidelity, and directly supports
scientific analysis using the individual source data; (2) facilitates analysis
of a wide range of statistical properties for classes of X-ray sources; and (3)
provides efficient access to calibrated observational data and ancillary data
products for individual X-ray sources, so that users can perform detailed
further analysis using existing tools. The catalog includes real X-ray sources
detected with flux estimates that are at least 3 times their estimated 1 sigma
uncertainties in at least one energy band, while maintaining the number of
spurious sources at a level of <~ 1 false source per field for a 100 ks
observation. For each detected source, the CSC provides commonly tabulated
quantities, including source position, extent, multi-band fluxes, hardness
ratios, and variability statistics, derived from the observations in which the
source is detected. In addition to these traditional catalog elements, for each
X-ray source the CSC includes an extensive set of file-based data products that
can be manipulated interactively.Comment: To appear in The Astrophysical Journal Supplement Series, 53 pages,
27 figure
The Vehicle, 1966, Vol. 8
Vol. 8
Table of Contents
CommentaryBill Moser & Avis Eaglestonpage 3
The Vengeance of the DeadStephen W. Gibbspage 5
Ode To A MeadowKathleen McCormackpage 12
Row OnDavid Helmpage 13
Sonnet 63R.L. Hudsonpage 14
UntitledKathleen McCormackpage 14
The Pure GoldDavid Helmpage 15
CommunionDavid Helmpage 15
PreludeMichael Baldwinpage 15
The AlbatrossKaren Cooleypage 16
The Albatross (photo)DeWittpage 17
Ruff and the VaseDavid Helmpage 18
LaBelleKathleen McCormackpage 19
Not Quite SoR.L. Hudsonpage 20
Feeling (no number)David Reifpage 21
Song at DuskDavid Helmpage 21
Arcadia RuminationsR.L. Hudsonpage 22
The BarWayne Johnsonpage 25
HelloWilliam Framepage 26
The ProcessJerry DeWittpage 27
The KillingAdrian Beardpage 30
The Amusement Park GameStephen W. Gibbspage 38
DamnMel Tylerpage 40
PainWilliam Framepage 40
UntitledSusan Champlinpage 41
Portrait of A Scholar As A Young ManStephen W. Gibbspage 42
The TimesW.D.Mpage 46
ParadoxW.D.M.page 46
MankindDavid Helmpage 47https://thekeep.eiu.edu/vehicle/1014/thumbnail.jp
The Vehicle, 1966, Vol. 8
Vol. 8
Table of Contents
CommentaryBill Moser & Avis Eaglestonpage 3
The Vengeance of the DeadStephen W. Gibbspage 5
Ode To A MeadowKathleen McCormackpage 12
Row OnDavid Helmpage 13
Sonnet 63R.L. Hudsonpage 14
UntitledKathleen McCormackpage 14
The Pure GoldDavid Helmpage 15
CommunionDavid Helmpage 15
PreludeMichael Baldwinpage 15
The AlbatrossKaren Cooleypage 16
The Albatross (photo)DeWittpage 17
Ruff and the VaseDavid Helmpage 18
LaBelleKathleen McCormackpage 19
Not Quite SoR.L. Hudsonpage 20
Feeling (no number)David Reifpage 21
Song at DuskDavid Helmpage 21
Arcadia RuminationsR.L. Hudsonpage 22
The BarWayne Johnsonpage 25
HelloWilliam Framepage 26
The ProcessJerry DeWittpage 27
The KillingAdrian Beardpage 30
The Amusement Park GameStephen W. Gibbspage 38
DamnMel Tylerpage 40
PainWilliam Framepage 40
UntitledSusan Champlinpage 41
Portrait of A Scholar As A Young ManStephen W. Gibbspage 42
The TimesW.D.Mpage 46
ParadoxW.D.M.page 46
MankindDavid Helmpage 47https://thekeep.eiu.edu/vehicle/1014/thumbnail.jp
- …