208 research outputs found
Micropaleontological Zones in Iowa
Micropaleontological studies in the Iowa geologic section have been gaining impetus in the past few years, but no previous attempt has been made to assemble the accumulated information. The value of microfossils in defining and correlating stratigraphic units is generally accepted. This paper is a compilation of existing information in an attempt to establish preliminary fauna zones. Where diagnostic fossils for the various zones were not indicated by the original author we have chosen them according to relative abundance and unique occurrence, if possible. In some instances inadequate data limit the application of this method, and require listing of a larger part of the assemblage than would otherwise be necessary. Available data permit zoning of the Ordovician, Devonian, and Pennsylvanian, as shown on the following charts
Evidence Acquisition and Evaluation for Evidence Summit on Enhancing Provision and Use of Maternal Health Services through Financial Incentives
Recognizing the need for evidence to inform US Government and
governments of the low- and middleincome countries on efficient,
effective maternal health policies, strategies, and programmes, the US
Government convened the Evidence Summit on Enhancing Provision and Use
of Maternal Health Services through Financial Incentives in April 2012
in Washington, DC, USA. This paper summarizes the background and
methods for the acquisition and evaluation of the evidence used for
achieving the goals of the Summit. The goal of the Summit was to obtain
multidisciplinary expert review of literature to inform both US
Government and governments of the low- and middle-income countries on
evidence-informed practice, policies, and strategies for financial
incentives. Several steps were undertaken to define the tasks for the
Summit and identify the appropriate evidence for review. The process
began by identifying focal questions intended to inform governments of
the low-and middle-income countries and the US Government about the
efficacy of supply- and demand-side financial incentives for enhanced
provision and use of quality maternal health services. Experts were
selected representing the research and programme communities, academia,
relevant non-governmental organizations, and government agencies and
were assembled into Evidence Review Teams. This was followed by a
systematic process to gather relevant peer-reviewed literature that
would inform the focal questions. Members of the Evidence Review Teams
were invited to add relevant papers not identified in the initial
literature review to complete the bibliography. The Evidence Review
Teams were asked to comply with a specific evaluation framework for
recommendations on practice and policy based on both expert opinion and
the quality of the data. Details of the search processes and methods
used for screening and quality reviews are described
Rapid Suppression of the Spin Gap in Zn-doped CuGeO_3 and SrCu_2O_3
The influence of non-magnetic impurities on the spectrum and dynamical spin
structure factor of a model for CuGeO is studied. A simple extension to
Zn-doped is also discussed. Using Exact Diagonalization
techniques and intuitive arguments we show that Zn-doping introduces states in
the Spin-Peierls gap of CuGeO. This effect can beunderstood easily in the
large dimerization limit where doping by Zn creates ``loose'' S=1/2 spins,
which interact with each other through very weak effective antiferromagnetic
couplings. When the dimerization is small, a similar effect is observed but now
with the free S=1/2 spins being the resulting S=1/2 ground state of severed
chains with an odd number of sites. Experimental consequences of these results
are discussed. It is interesting to observe that the spin correlations along
the chains are enhanced by Zn-doping according to the numerical data presented
here. As recent numerical calculations have shown, similar arguments apply to
ladders with non-magnetic impurities simply replacing the tendency to
dimerization in CuGeO by the tendency to form spin-singlets along the rungs
in SrCuO.Comment: 7 pages, 8 postscript figures, revtex, addition of figure 8 and a
section with experimental predictions, submmited to Phys. Rev. B in May 199
Enhancement of Antiferromagnetic Correlations Induced by Nonmagnetic Impurities: Origin and Predictions for NMR Experiments
Spin models that have been proposed to describe dimerized chains, ladders,
two dimensional antiferromagnets, and other compounds are here studied when
some spins are replaced by spinless vacancies, such as it occurs by
doping. A small percentage of vacancies rapidly destroys the spin gap, and
their presence induces enhanced antiferromagnetic correlations near those
vacancies. The study is performed with computational techniques which includes
Lanczos, world-line Monte Carlo, and the Density Matrix Renormalization Group
methods. Since the phenomenon of enhanced antiferromagnetism is found to occur
in several models and cluster geometries, a common simple explanation for its
presence may exist. It is argued that the resonating-valence-bond character of
the spin correlations at short distances of a large variety of models is
responsible for the presence of robust staggered spin correlations near
vacancies and lattice edges. The phenomenon takes place regardless of the long
distance properties of the ground state, and it is caused by a ``pruning'' of
the available spin singlets in the vicinity of the vacancies. The effect
produces a broadening of the low temperature NMR signal for the compounds
analyzed here. This broadening should be experimentally observable in the
structurally dimerized chain systems
, , , and
, in ladder materials such as , in the
spin-Peierls systems and , and in several others since it
is a universal effect common to a wide variety of models and compounds.Comment: 18 pages revtex with 26 figures include
Financial Incentives and Maternal Health: Where Do We Go from Here?
Health financing strategies that incorporate financial incentives are
being applied in many low- and middle-income countries, and improving
maternal and neonatal health is often a central goal. As yet, there
have been few reviews of such programmes and their impact on maternal
health. The US Government Evidence Summit on Enhancing Provision and
use of Maternal Health Services through Financial Incentives was
convened on 24-25 April 2012 to address this gap. This article, the
final in a series assessing the effects of financial
incentives\u2014performance-based incentives (PBIs), insurance, user
fee exemption programmes, conditional cash transfers, and
vouchers\u2014summarizes the evidence and discusses issues of context,
programme design and implementation, cost-effectiveness, and
sustainability. We suggest key areas to consider when designing and
implementing financial incentive programmes for enhancing maternal
health and highlight gaps in evidence that could benefit from
additional research. Although the methodological rigor of studies
varies, the evidence, overall, suggests that financial incentives can
enhance demand for and improve the supply of maternal health services.
Definitive evidence demonstrating a link between incentives and
improved health outcomes is lacking; however, the evidence suggests
that financial incentives can increase the quantity and quality of
maternal health services and address health systems and financial
barriers that prevent women from accessing and providers from
delivering quality, lifesaving maternal healthcare
Competitive and uncompetitive N -methyl- d -aspartate antagonist discriminations in pigeons: CGS 19755 and phencyclidine
The purpose of the present studies was to examine representative uncompetitive and competitive NMDA antagonists, as well as the glycine/NMDA antagonist, HA 966, in pigeons trained to discriminate either PCP or CGS 19755 from saline. Separate groups of pigeons were trained to discriminate either the uncompetitive, phencyclidine (PCP; 0.32 and 1.0 mg/kg, IM), or the competitive, CGS 19755 ( cis -4-phosphonomethyl-2-piperidine-carboxylic acid; 1.8 mg/kg, IM), NMDA antagonists from saline. Uncompetitive and competitive NMDA antagonists were examined in generalization studies, as were the racemate and the (+) and (â) stereoisomers of HA 966 (3-amino-1-hydroxypyrrolid-2-one). Dizocilpine (MK 801) was fully generalized to PCP but not to CGS 19755. All competitive NMDA antagonists tested were fully generalized to CGS 19755, but not to PCP. The competitive antagonists, however, produced >50% PCP-appropriate responding. The (+) isomer of HA 966 was fully generalized by three of four pigeons discriminating PCP (1.0 mg/kg) or CGS 19755, whereas the racemate and the (â) isomer produced 10% drug-appropriate responding in either discrimination group. The competitive antagonists tended to produce peak drug-appropriate responding at times greater than 60 min after administration, whereas uncompetitive antagonists produced peak drug-appropriate responding at earlier times. HA 966 also had a relatively slow onset of action as compared to PCP. These results suggest that antagonists acting at different modulatory sites of the NMDA receptor complex produce similar, but not identical, discriminative stimuli.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46346/1/213_2005_Article_BF02245248.pd
The Impact of a Science Education Game on Studentsâ Learning and Perception of Inhalants as Body Pollutants
Methylphenidate Attenuates Limbic Brain Inhibition after Cocaine-Cues Exposure in Cocaine Abusers
Dopamine (phasic release) is implicated in conditioned responses. Imaging studies in cocaine abusers show decreases in striatal dopamine levels, which we hypothesize may enhance conditioned responses since tonic dopamine levels modulate phasic dopamine release. To test this we assessed the effects of increasing tonic dopamine levels (using oral methylphenidate) on brain activation induced by cocaine-cues in cocaine abusers. Brain metabolism (marker of brain function) was measured with PET and 18FDG in 24 active cocaine abusers tested four times; twice watching a Neutral video (nature scenes) and twice watching a Cocaine-cues video; each video was preceded once by placebo and once by methylphenidate (20 mg). The Cocaine-cues video increased craving to the same extent with placebo (68%) and with methylphenidate (64%). In contrast, SPM analysis of metabolic images revealed that differences between Neutral versus Cocaine-cues conditions were greater with placebo than methylphenidate; whereas with placebo the Cocaine-cues decreased metabolism (p<0.005) in left limbic regions (insula, orbitofrontal, accumbens) and right parahippocampus, with methylphenidate it only decreased in auditory and visual regions, which also occurred with placebo. Decreases in metabolism in these regions were not associated with craving; in contrast the voxel-wise SPM analysis identified significant correlations with craving in anterior orbitofrontal cortex (p<0.005), amygdala, striatum and middle insula (p<0.05). This suggests that methylphenidate's attenuation of brain reactivity to Cocaine-cues is distinct from that involved in craving. Cocaine-cues decreased metabolism in limbic regions (reflects activity over 30 minutes), which contrasts with activations reported by fMRI studies (reflects activity over 2â5 minutes) that may reflect long-lasting limbic inhibition following activation. Studies to evaluate the clinical significance of methylphenidate's blunting of cue-induced limbic inhibition may help identify potential benefits of this medication in cocaine addiction
Reconstructing terrestrial nutrient cycling using stable nitrogen isotopes in wood
Although recent anthropogenic effects on the global nitrogen (N) cycle have been significant, the consequences of increased anthropogenic N on terrestrial ecosystems are unclear. Studies of the impact of increased reactive N on forest ecosystemsâimpacts on hydrologic and gaseous loss pathways, retention capacity, and even net primary productivityâ have been particularly limited by a lack of long-term baseline biogeochemical data. Stable nitrogen isotope analysis (ratio of Âčâ”N to ÂčâŽN, termed ÎŽÂčâ”N) of wood chronologies offers the potential to address changes in ecosystem N cycling on millennial timescales and across broad geographic regions. Currently, nearly 50 studies have been published utilizing wood ÎŽÂčâ”N records; however, there are significant differences in study design and data interpretation. Here, we identify four categories of wood ÎŽÂčâ”N studies, summarize the common themes and primary findings of each category, identify gaps in the spatial and temporal scope of current wood ÎŽÂčâ”N chronologies, and synthesize methodological frameworks for future research by presenting eight suggestions for common methodological approaches and enhanced integration across studies. Wood ÎŽÂčâ”N records have the potential to provide valuable information for interpreting modern biogeochemical cycling. This review serves to advance the utility of this technique for long-term biogeochemical reconstructions
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