3,496 research outputs found
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Miocene stable isotopic stratigraphy and magnetostratigraphy of Buff Bay, Jamaica
Previously reported biostratigraphic relationships from middle-upper Miocene sections exposed near Buff Bay, Jamaica (18°N, tropical bioprovince), differ from the subtropical North Atlantic (Sites 563 and 558). Time scales for this interval rely on correlations established at these subtropical sites, and the differences with the tropical section have implications to global correlations. Planktonic foraminiferal Zones N13 and N15 are thick at Buff Bay but are virtually absent at Sites 563 and 558; nannofossil Zone NN9 is associated with Zone N15 and uppermost Zone N14 at Buff Bay but is associated with Zone N16 at the other sites. Magnetostratigraphic data presented here further complicate the interpretation: Zone NN9 is associated with a thick normal magnetozone at Sites 563 and 558; at Buff Bay, it is associated with a thick reversed magnetozone. Although a secondary magnetization at Buff Bay makes it difficult to identify confidently Miocene normal magnetozones, the thick reversed magnetozone most likely represents the paleomagnetic field and correlates with Chron C5r. The magnetobiostratigraphic relationships require either diachrony of taxa or two mutually exclusive hiatuses in Jamaica and the North Atlantic. We address this problem by analyzing benthic foraminiferal δ^18O and δ^13C from the Buff Bay section. These isotopic data allow us to evaluate three hypotheses that reconcile the magneto-, bio-, and isotopic stratigraphic data and conclude that the first and last occurrences of five taxa were diachronous by ~0.3-0.5 m.y. between tropical and subtropical locations. This requires revised age estimates for late middle to early late Miocene biostratigraphic datum levels. We suggest that the ranges of several taxa are useful for endemic tropical or subtropical zonations, but correlations between the low and midlatitudes were affected by an increase in latitudinal thermal gradients during the late middle Miocene. However, we admit that further studies are needed before this issue is resolved
Mass and Redshift Dependence of Star Formation in Relaxed Galaxy Clusters
We investigate the star-formation properties of dynamically relaxed galaxy
clusters as a function of cluster mass for 308 low-redshift clusters drawn from
the Sloan Digital Sky Survey (SDSS) C4 cluster catalog. It is important to
establish if cluster star-formation properties have a mass dependence before
comparing clusters at different epochs, and here we use cluster velocity
dispersion as a measure of cluster mass. We find that the total stellar mass,
the number of star-forming galaxies, and total star-formation rate scale
linearly with the number of member galaxies, with no residual dependence on
cluster velocity dispersion. With the mass-dependence of cluster star-formation
rates established, we compare the SDSS clusters with a sample of z = 0.75
clusters from the literature and find that on average the total H-alpha
luminosity of the high-redshift clusters is 10 times greater than that of the
low-redshift clusters. This can be explained by a decline in the H-alpha
luminosities of individual cluster galaxies by a factor of up to 10 since z =
0.75. The magnitude of this evolution is comparable to that of field galaxies
over a similar redshift interval, and thus the effect of the cluster
environment on the evolution of star-forming galaxies is at most modest. Our
results suggest that the physical mechanism driving the evolution of cluster
star-formation rates is independent of cluster mass, at least for clusters with
velocity dispersion greater than 450 km/s, and operates over a fairly long
timescale such that the star-formation rates of individual galaxies decline by
an order of magnitude over ~7 billion years. (Abridged)Comment: 15 pages; 13 figures; accepted for publication in the Astrophysical
Journa
Rising prevalence of non-B HIV-1 subtypes in North Carolina and evidence for local onward transmission.
HIV-1 diversity is increasing in North American and European cohorts which may have public health implications. However, little is known about non-B subtype diversity in the southern United States, despite the region being the epicenter of the nation's epidemic. We characterized HIV-1 diversity and transmission clusters to identify the extent to which non-B strains are transmitted locally. We conducted cross-sectional analyses of HIV-1 partial pol sequences collected from 1997 to 2014 from adults accessing routine clinical care in North Carolina (NC). Subtypes were evaluated using COMET and phylogenetic analysis. Putative transmission clusters were identified using maximum-likelihood trees. Clusters involving non-B strains were confirmed and their dates of origin were estimated using Bayesian phylogenetics. Data were combined with demographic information collected at the time of sample collection and country of origin for a subset of patients. Among 24,972 sequences from 15,246 persons, the non-B subtype prevalence increased from 0% to 3.46% over the study period. Of 325 persons with non-B subtypes, diversity was high with over 15 pure subtypes and recombinants; subtype C (28.9%) and CRF02_AG (24.0%) were most common. While identification of transmission clusters was lower for persons with non-B versus B subtypes, several local transmission clusters (≥3 persons) involving non-B subtypes were identified and all were presumably due to heterosexual transmission. Prevalence of non-B subtype diversity remains low in NC but a statistically significant rise was identified over time which likely reflects multiple importation. However, the combined phylogenetic clustering analysis reveals evidence for local onward transmission. Detection of these non-B clusters suggests heterosexual transmission and may guide diagnostic and prevention interventions
Hospice in the nursing home: perspectives of front line nursing home staff
OBJECTIVE: Use of hospice has been associated with improved outcomes for nursing home residents and attitudes of nursing home staff toward hospice influences hospice referral. The objective of this study is to describe attitudes of certified nursing assistants (CNAs), nurses, and social workers toward hospice care in nursing homes.
DESIGN, SETTING, AND PARTICIPANTS: We conducted a survey of 1859 staff from 52 Indiana nursing homes.
MEASUREMENTS: Study data include responses to 6 scaled questions and 3 open-ended qualitative prompts. In addition, respondents who cared for a resident on hospice in the nursing home were asked how often hospice: (1) makes their job easier; (2) is responsive when a patient has symptoms or is actively dying; (3) makes care coordination smooth; (4) is needed; (5) taught them something; and (6) is appreciated by patients/families. Responses were dichotomized as always/often or sometimes/never.
RESULTS: A total of 1229 surveys met criteria for inclusion. Of the respondents, 48% were CNAs, 49% were nurses, and 3% were social workers; 83% reported caring for a nursing home patient on hospice. The statement with the highest proportion of always/often rating was 'patient/family appreciate added care' (84%); the lowest was 'hospice makes my job easier' (54%). More social workers responded favorably regarding hospice responsiveness and coordination of care compared with CNAs (P = .03 and P = .05, respectively).
CONCLUSIONS: A majority of staff responded favorably regarding hospice care in nursing homes. About one-third of nursing home staff rated coordination of care lower than other aspects, and many qualitative comments highlighted examples of when hospice was not responsive to patient needs, representing important opportunities for improvement
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Pass-through core measurements of magnetic susceptibility and natural gamma ray, New Jersey Coastal Plain
We measured magnetic susceptibility (MS) and core gamma radiation (CGR) on 3162 ft (963.9 m) of core recovered by the New Jersey Coastal Plain Drilling Project (Ocean Drilling Program Leg 150X) at Island Beach, Atlantic City, and Cape May, New Jersey. Integration of core lithology, core/log (MS and CGR), and downhole gamma-ray (DGR) log studies have (1) documented the core/log expression of previously determined unconformities; (2) shown that MS is a proxy for glauconite percent in the New Jersey Coastal Plain; (3) illustrated a major change in sedimentation from shelfal glauconite evidenced by very high MS values to deltaic deposition with low MS values in the earliest Miocene (ca. 22 Ma); (4) shown that comparison of MS and CGR with DGR can be used to resolve discrepancies in depth between downhole logs and cores; and (5) shown that the CGR detects some zones noted in the lithology (e.g., phosphate rich zones) that are not resolved in the DGR
Nitrous oxide emissions from a commercial cornfield (Zea mays) measured using the eddy covariance technique
Increases in observed atmospheric concentrations of the long-lived greenhouse gas nitrous oxide (N2O) have been well documented. However, information on event-related instantaneous emissions during fertilizer applications is lacking. With the development of fast-response N2O analyzers, the eddy covariance (EC) technique can be used to gather instantaneous measurements of N2O concentrations to quantify the exchange of nitrogen between the soil and atmosphere. The objectives of this study were to evaluate the performance of a new EC system, to measure the N2O flux with the system, and finally to examine relationships of the N2O flux with soil temperature, soil moisture, precipitation, and fertilization events. An EC system was assembled with a sonic anemometer and a fast-response N2O analyzer (quantum cascade laser spectrometer) and applied in a cornfield in Nolensville, Tennessee during the 2012 corn growing season (4 April–8 August). Fertilizer amounts totaling 217 kg N ha−1 were applied to the experimental site. Results showed that this N2O EC system provided reliable N2O flux measurements. The cumulative emitted N2O amount for the entire growing season was 6.87 kg N2O-N ha−1. Seasonal fluxes were highly dependent on soil moisture rather than soil temperature. This study was one of the few experiments that continuously measured instantaneous, high-frequency N2O emissions in crop fields over a growing season of more than 100 days
Feasibility of a Networked Air Traffic Infrastructure Validation Environment for Advanced NextGen Concepts
Abstract-Next Generation Air Transportation System (NextGen) applications reliant upon aircraft data links such as Automatic Dependent Surveillance-Broadcast (ADS-B) offer a sweeping modernization of the National Airspace System (NAS), but the aviation stakeholder community has not yet established a positive business case for equipage and message content standards remain in flux. It is necessary to transition promising Air Traffic Management (ATM) Concepts of Operations (ConOps) from simulation environments to full-scale flight tests in order to validate user benefits and solidify message standards. However, flight tests are prohibitively expensive and message standards for Commercial-off-the-Shelf (COTS) systems cannot support many advanced ConOps. It is therefore proposed to simulate future aircraft surveillance and communications equipage and employ an existing commercial data link to exchange data during dedicated flight tests. This capability, referred to as the Networked Air Traffic Infrastructure Validation Environment (NATIVE), would emulate aircraft data links such as ADS-B using in-flight Internet and easily-installed test equipment. By utilizing low-cost equipment that is easy to install and certify for testing, advanced ATM ConOps can be validated, message content standards can be solidified, and new standards can be established through full-scale flight trials without necessary or expensive equipage or extensive flight test preparation. This paper presents results of a feasibility study of the NATIVE concept. To determine requirements, six NATIVE design configurations were developed for two NASA ConOps that rely on ADS-B. The performance characteristics of three existing in-flight Internet services were investigated to determine whether performance is adequate to support the concept. Next, a study of requisite hardware and software was conducted to examine whether and how the NATIVE concept might be realized. Finally, to determine a business case, economic factors were evaluated and a preliminary cost-benefit analysis was performed
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