1,359 research outputs found
II. On the structure and biology of archotermopsis, together with descriptions of new species of intestinal protozoa, and general observations on the isoptera
The following paper is intended as a contribution towards a knowledge of the structure and biology of Archotermopsis wroughtoni, Desn., one of the most primitive of living Termites. Included herewith are also observations and deductions bearing upon some of the more important general biological problems which are associated with the Isoptera. Archotermopsis wroughtoni was described 12 years ago by Desneux from examples taken by Wroughton in June, 1903. They were discovered in old stumps of trees, chiefly Pinus excelsa, in the Kashmir Valley. Since its discovery, this species has remained a great rarity, and practically nothing had been ascertained concerning its biology. In June, 1910, I first came across this insect in a decaying fallen trunk of Pinus excelsa, in a forest area situated between the Kuari Pass and Ramni, at an altitude of about 8,500 feet, in the Himalayas of British Garwhal. In the same month during 1912 I had the good fortune to meet with it in great abundance in a dead fallen trunk of Pinus longifolia near Dharmoti, in the Ranikhet District. This locality is situated at an altitude of about 4,000 feet in the Kumaon Himalaya. Being aware of the biological and phylogenetic interest likely to be afforded by a study of this species, I made a prolonged search in many other likely localities in the North Western Himalayas during the years 1912-13. It was subsequently found plentifully at Bhowali, near Naini Tal, at an elevation of 5,800 feet, near Nadh in the Ohakrata District of Jaunsar, and I have also been able to procure examples from near Gulmerg in Kashmir. It seems probable, therefore, that it will eventually be found to be generally distributed in the lower-level coniferous forests of the North Western Himalayas, up to an elevation of about 9,000 feet
The HI Content of Compact Groups of Galaxies
The HI content of Hickson Compact Groups in the southern hemisphere is
measured using data from the HI Parkes All Sky Survey (HIPASS), and dedicated
observations using the narrowband filter on the Multibeam instrument on the
Parkes telescope. The expected HI mass of these groups was estimated using the
luminosity, diameter and morphological types of the member galaxies, calibrated
from published data. Taking careful account of non-detection limits, the
results show that the compact group population that has been detected by these
observations has an HI content similar to that of galaxies in the reference
field sample. The upper limits for the undetected groups lie within the normal
range; improvement of these limits will require a large increase in
sensitivity.Comment: 27 pages, 5 figures. Accepted for publication in PAS
Are you a researcher as well as a medical illustrator?
When we list the areas of practice for medical illustrators we always include research, but how involved in research are we? The aim of this activity is to encourage your professional development not just as a medical illustrator but your involvement with research whether that is undertaking your own research, undertaking evidence based practice (1) , working as part of a research team, advising researchers on the value of medical illustration or supporting a student undertaking a research project for their degree or post-graduate qualification
Provenance and Paleogeography of the 25-17 Ma Rainbow Gardens Formation: Evidence for Tectonic Activity at Ca. 19 Ma and Internal Drainage rather than Throughgoing Paleorivers on the Southwestern Colorado Plateau
The paleogeographic evolution of the Lake Mead region of southern Nevada and northwest Arizona is crucial to understanding the geologic history of the U.S. Southwest, including the evolution of the Colorado Plateau and formation of the Grand Canyon. The ca. 25–17 Ma Rainbow Gardens Formation in the Lake Mead region, the informally named, roughly coeval Jean Conglomerate, and the ca. 24–19 Ma Buck and Doe Conglomerate southeast of Lake Mead hold the only stratigraphic evidence for the Cenozoic pre-extensional geology and paleogeography of this area. Building on prior work, we present new sedimentologic and stratigraphic data, including sandstone provenance and detrital zircon data, to create a more detailed paleogeographic picture of the Lake Mead, Grand Wash Trough, and Hualapai Plateau region from 25 to 18 Ma. These data confirm that sediment was sourced primarily from Paleozoic strata exposed in surrounding Sevier and Laramide uplifts and active volcanic fields to the north. In addition, a distinctive signal of coarse sediment derived from Proterozoic crystalline basement first appeared in the southwestern corner of the basin ca. 25 Ma at the beginning of Rainbow Gardens Formation deposition and then prograded north and east ca. 19 Ma across the southern half of the basin. Regional thermochronologic data suggest that Cretaceous deposits likely blanketed the Lake Mead region by the end of Sevier thrusting. Post-Laramide northward cliff retreat off the Kingman/Mogollon uplifts left a stepped erosion surface with progressively younger strata preserved northward, on which Rainbow Gardens Formation strata were deposited. Deposition of the Rainbow Gardens Formation in general and the 19 Ma progradational pulse in particular may reflect tectonic uplift events just prior to onset of rapid extension at 17 Ma, as supported by both thermochronology and sedimentary data. Data presented here negate the California and Arizona River hypotheses for an “old” Grand Canyon and also negate models wherein the Rainbow Gardens Formation was the depocenter for a 25–18 Ma Little Colorado paleoriver flowing west through East Kaibab paleocanyons. Instead, provenance and paleocurrent data suggest local to regional sources for deposition of the Rainbow Gardens Formation atop a stripped low-relief western Colorado Plateau surface and preclude any significant input from a regional throughgoing paleoriver entering the basin from the east or northeast
Stephan's Quintet: The X-ray Anatomy of a Multiple Galaxy Collision
Chandra observations of the compact galaxy group known as Stephan's Quintet
(SQ) are presented. The major morphological features that were discovered with
the ROSAT HRI are now imaged with higher resolution and S/N. The large scale
shock (1.5', ~40kpc if at 85 Mpc) is resolved into a narrow NS feature embedded
in more extended diffuse emission (D>=3'). The NS structure is somewhat clumpy,
more sharply bounded on the W side and prominent only in the soft band
(energies below ~2 keV). Its observational properties are best explained as a
shock produced by a high velocity encounter between NGC7318b, a ``new
intruder'', and the intergalactic medium in SQ. The shock conditions near the
high speed intruder suggest that a bow shock is propagating into a pre-existing
HI cloud and heating the gas to a temperature of ~0.5 keV. The low temperature
in the shock is a problem unless we postulate an oblique shock. One member,
NGC7319, hosts a Seyfert 2 nucleus, with an intrinsic luminosity Lx=10^43
erg/s, embedded in a region of more diffuse emission with 10'' radius extent.
The nuclear spectrum can be modeled with a strongly absorbed power-law typical
of this class of sources. Several additional compact sources are detected
including three in foreground NGC7320. Some of these sources are very luminous
and could be related to the ultraluminous X-ray sources found in nearby
galaxies.Comment: Accepted for publication in Astronomy & Astrophysics Quality of
figures has been degraded to fit in the astroph requirements; fig12 could not
be inserted in the tex and is given as a jpe
Review of important reactions for the nitrogen chemistry in the interstellar medium
Predictions of astrochemical models depend strongly on the reaction rate
coefficients used in the simulations. We reviewed a number of key reactions for
the chemistry of nitrogen-bearing species in the dense interstellar medium and
proposed new reaction rate coefficients for those reactions. The details of the
reviews are given in the form of a datasheet associated with each reaction. The
new recommended rate coefficients are given with an uncertainty and a
temperature range of validity and will be included in KIDA
(http://kida.obs.u-bordeaux1.fr).Comment: 39 pages, not published in refereed journal, datasheets are given in
KID
The ALHAMBRA Project: A large area multi medium-band optical and NIR photometric survey
(ABRIDGED) We describe the first results of the ALHAMBRA survey which
provides cosmic tomography of the evolution of the contents of the Universe
over most of Cosmic history. Our approach employs 20 contiguous, equal-width,
medium-band filters covering from 3500 to 9700 A, plus the JHKs bands, to
observe an area of 4 sqdeg on the sky. The optical photometric system has been
designed to maximize the number of objects with accurate classification by SED
and redshift, and to be sensitive to relatively faint emission lines. The
observations are being carried out with the Calar Alto 3.5m telescope using the
cameras LAICA and O-2000. The first data confirm that we are reaching the
expected magnitude limits of AB<~25 mag in the optical filters from the blue to
8300 A, and from AB=24.7 to 23.4 for the redder ones. The limit in the NIR is
(Vega) K_s~20, H~21, J~22. We expect to obtain accurate redshift values, Delta
z/(1+z) <~ 0.03 for about 5x10^5 galaxies with I<~25 (60% complete), and
z_med=0.74. This accuracy, together with the homogeneity of the selection
function, will allow for the study of the redshift evolution of the large scale
structure, the galaxy population and its evolution with redshift, the
identification of clusters of galaxies, and many other studies, without the
need for any further follow-up. It will also provide targets for detailed
studies with 10m-class telescopes. Given its area, spectral coverage and its
depth, apart from those main goals, the ALHAMBRA-Survey will also produce
valuable data for galactic studies.Comment: Accepted to the Astronomical Journal. 43 pages, 18 figures. The
images have been reduced in resolution to adapt to standard file sizes.
Readers can find the full-resolution version of the paper at the ALHAMBRA web
site (http://www.iaa.es/alhambra) under the "Publications" lin
BLM and RMI1 alleviate RPA inhibition of topoIIIα decatenase activity
RPA is a single-stranded DNA binding protein that physically associates with the BLM complex. RPA stimulates BLM helicase activity as well as the double Holliday junction dissolution activity of the BLM-topoisomerase IIIα complex. We investigated the effect of RPA on the ssDNA decatenase activity of topoisomerase IIIα. We found that RPA and other ssDNA binding proteins inhibit decatenation by topoisomerase IIIα. Complex formation between BLM, TopoIIIα, and RMI1 ablates inhibition of decatenation by ssDNA binding proteins. Together, these data indicate that inhibition by RPA does not involve species-specific interactions between RPA and BLM-TopoIIIα-RMI1, which contrasts with RPA modulation of double Holliday junction dissolution. We propose that topoisomerase IIIα and RPA compete to bind to single-stranded regions of catenanes. Interactions with BLM and RMI1 enhance toposiomerase IIIα activity, promoting decatenation in the presence of RPA
Long-term exposure to ambient air pollution and renal function in African Americans: the Jackson Heart Study
Renal dysfunction is prevalent in the US among African Americans. Air pollution is associated with renal dysfunction in mostly white American populations, but has not been studied among African Americans. We evaluated cross-sectional associations between 1-year and 3-year fine particulate matter (PM2.5) and ozone (O3) concentrations, and renal function among 5090 African American participants in the Jackson Heart Study. We used mixed-effect linear regression to estimate associations between 1-year and 3-year PM2.5 and O3 and estimated glomerular filtration rate (eGFR), urine albumin/creatinine ratio (UACR), serum creatinine, and serum cystatin C, adjusting for: sociodemographic factors, health behaviors, and medical history and accounting for clustering by census tract. At baseline, JHS participants had mean age 55.4 years, and 63.8% were female; mean 1-year and 3-year PM2.5 concentrations were 12.2 and 12.4 µg/m3, and mean 1-year and 3-year O3 concentrations were 40.2 and 40.7 ppb, respectively. Approximately 6.5% of participants had reduced eGFR ( 30 mg/g), both indicating impaired renal function. Annual and 3-year O3 concentrations were inversely associated with eGFR and positively associated with serum creatinine; annual and 3-year PM2.5 concentrations were inversely associated with UACR. We observed impaired renal function associated with increased O3 but not PM2.5 exposure among African Americans
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