656 research outputs found
Sediment processes monitoring data report for calendar year 1989
Pairs of particle interceptor traps were deployed at three depths - 3, 6, and 9 meters with deployment intervals typically lasting about two weeks. At times of deployment and retrieval, profiles of water temperature, salinity and dissolved oxygen content were made and water samples were collected at trap depths. Bottom sediments also were collected and a sub-sample of the surficial sediments taken. Water samples, bottom sediments, and the materials collected in the traps were returned to the Virginia Institute of Marine Sciences for analysis. The data collected during both 1988 and 1989 are presented in the appendices. Both 1988 and 1989 data sets have been archived in ASCII and IBM PC spreadsheet formats. Individuals desiring the data in ASCII or spreadsheet formats (Lotus or Quattro) should contact one of the authors
Effects of Retinoic Acid on Embryonic Chick Skin
The influence of vitamin A on differentiating epithelia was examined in explants of skin from 14-day chick embryos exposed to retinoic acid (RA) in low, moderate, and high doses. The changes observed in RA-treated cultures are both dose- and time-dependent and are reversible when explants are transferred to control medium. The periderm sloughs prematurely and horizontal stratification is lost. Keratinization is inhibited and fewer desmosomes and tonofilaments are seen. Surface epidermal cells develop microvilli, bulge upwards, and detach. Golgi elements, rough endoplasmic reticulum, and polyribosomes are unusually prominent. Mucin granules form and gland-like structures develop with intercellular canaliculi characterized by tight junctions, brush borders, and dense secretory contents. On the basis of present evidence there are several possible mechanisms by which RA could alter epidermal differentiation. RA-induced gaps in the basal lamina allow direct contact between epidermal basal cells and fibroblasts and collagen fibers which could result in inappropriate dermal signals reaching the epidermis. In younger embryos the entire epidermis, including the mitotically inactive surface cells, appears to respond to RA, and this could imply an epigenetic modulation of cell phenotype. Finally, after the formation of a stratum corneum in older embryos only the relatively undifferentiated basal layer shows a metaplastic response, indicating that RA could be acting directly on the genome
ULTRASTRUCTURAL LOCALIZATION OF ACID MUCOSUBSTANCES IN THE MOUSE COLON WITH IRON-CONTAINING STAINS
The Astropy Problem
The Astropy Project (http://astropy.org) is, in its own words, "a community
effort to develop a single core package for Astronomy in Python and foster
interoperability between Python astronomy packages." For five years this
project has been managed, written, and operated as a grassroots,
self-organized, almost entirely volunteer effort while the software is used by
the majority of the astronomical community. Despite this, the project has
always been and remains to this day effectively unfunded. Further, contributors
receive little or no formal recognition for creating and supporting what is now
critical software. This paper explores the problem in detail, outlines possible
solutions to correct this, and presents a few suggestions on how to address the
sustainability of general purpose astronomical software
N2O Temporal Variability from the Middle Troposphere to the Middle Stratosphere Based on Airborne and Balloon-Borne Observations during the Period 1987–2018
Nitrous oxide (N2O) is the fourth most important greenhouse gas in the atmosphere
and is considered the most important current source gas emission for global stratospheric ozone
depletion (O3
). It has natural and anthropogenic sources, mainly as an unintended by-product of
food production activities. This work examines the identification and quantification of trends in the
N2O concentration from the middle troposphere to the middle stratosphere (MTMS) by in situ and
remote sensing observations. The temporal variability of N2O is addressed using a comprehensive
dataset of in situ and remote sensing N2O concentrations based on aircraft and balloon measurements
in the MTMS from 1987 to 2018. We determine N2O trends in the MTMS, based on observations.
This consistent dataset was also used to study the N2O seasonal cycle to investigate the relationship between abundances and its emission sources through zonal means. The results show a longterm increase in global N2O concentration in the MTMS with an average of 0.89 ± 0.07 ppb/yr in
the troposphere and 0.96 ± 0.15 ppb/yr in the stratosphere, consistent with 0.80 ppb/yr derived
from ground-based measurements and 0.799 ± 0.024 ppb/yr ACE-FTS (Atmospheric Chemistry
Experiment Fourier Transform Spectrometer) satellite measurements
NO Temporal Variability from the Middle Troposphere to the Middle Stratosphere Based on Airborne and Balloon-Borne Observations during the Period 1987–2018
Nitrous oxide (NO) is the fourth most important greenhouse gas in the atmosphere and is considered the most important current source gas emission for global stratospheric ozone depletion (O). It has natural and anthropogenic sources, mainly as an unintended by-product of food production activities. This work examines the identification and quantification of trends in the NO concentration from the middle troposphere to the middle stratosphere (MTMS) by in situ and remote sensing observations. The temporal variability of NO is addressed using a comprehensive dataset of in situ and remote sensing NO concentrations based on aircraft and balloon measurements in the MTMS from 1987 to 2018. We determine NO trends in the MTMS, based on observations. This consistent dataset was also used to study the NO seasonal cycle to investigate the relationship between abundances and its emission sources through zonal means. The results show a long-term increase in global NO concentration in the MTMS with an average of 0.89 ± 0.07 ppb/yr in the troposphere and 0.96 ± 0.15 ppb/yr in the stratosphere, consistent with 0.80 ppb/yr derived from ground-based measurements and 0.799 ± 0.024 ppb/yr ACE-FTS (Atmospheric Chemistry Experiment Fourier Transform Spectrometer) satellite measurements
- …