2,258 research outputs found
Matching Estimators of Causal Effects in Clustered Observational Studies with Application to Quantifying the Impact of Marine Protected Areas on Biodiversity
Marine conservation preserves fish biodiversity, protects marine and coastal
ecosystems, and supports climate resilience and adaptation. Despite the
importance of establishing marine protected areas (MPAs), research on the
effectiveness of MPAs with different conservation policies is limited due to
the lack of quantitative MPA information. In this paper, leveraging a global
MPA database, we investigate the causal impact of MPA policies on fish
biodiversity. To address challenges posed by this clustered and confounded
observational study, we construct a matching estimator of the average treatment
effect and a cluster-weighted bootstrap method for variance estimation. We
establish the theoretical guarantees of the matching estimator and its variance
estimator. Under our proposed matching framework, we recommend matching on both
cluster-level and unit-level covariates to achieve efficiency. The simulation
results demonstrate that our matching strategy minimizes the bias and achieves
the nominal confidence interval coverage. Applying our proposed matching method
to compare different MPA policies reveals that the no-take policy is more
effective than the multi-use policy in preserving fish biodiversity.Comment: 25 pages, 4 figure
Using Active Learning Strategies in Calculus to Improve Student Learning and Influence Mathematics Department Cultural Change
An interdisciplinary team of physics, education, math and chemistry faculty developed MATH-GAINS (Growing as Adaptive INstructors) creating an ecosystem where mathematics faculty persistently and sustainably apply active learning strategies in their teaching of calculus courses. As a result of implementation, MATH-GAI NS proposed to positively affect the wide-spread adaptation of active learning strategies by department faculty as well as student learning, retention and graduation of over 900 students annually. The objective of this paper is to provide details on how the project was conceived and implemented; instruments, research methodologies and active learning strategies used; and examples of faculty projects and preliminary results of the study. Results of the study add to the growing body of knowledge of how research-based instructional strategies designed in other STEM disciplines work in math courses, as well as an understanding of the critical factors that influence math faculty’s teaching practices
High speed photometry of faint cataclysmic variables - VI. Car2, V1040 Cen, Ha 075648, IL Nor (Nova Nor 1893), HS Pup (Nova Pup 1963), SDSS J2048-06, CSS 081419-005022 and CSS 112634-100210
We have observed 8 faint cataclysmic variable stars photometrically. The
nova-like Car2 was extensively sampled but showed little variability. V1040 Cen
was observed near the end of a dwarf nova outburst and possessed dwarf nova and
quasi-periodic oscillations. Ha 075648 has strong large amplitude flickering
and a possible orbital modulation at 3.49 h. The correct identification for the
nova remnant IL Nor (Nova Nor 1893) has been established. HS Pup (Nova Pup
1963) has a possible orbital period of 3.244 h. SDSS J2048-06 is a low mass
transfer dwarf nova that in quiescence shows slow variations at 7.67 h (though
poorly sampled with our observations) and an orbital modulation at 87.26 min.
The dwarf nova CSS 081419-005022 has an orbital period of 1.796 h and the
eclipsing dwarf nova CSS 112634-100210 has an orbital period of 1.8581 h.Comment: 7 pages, 15 figures. Accepted for publication in MNRA
57 second oscillations in Nova Centauri 1986 (V842 Cen)
High speed photometry in 2008 shows that the light curve of V842 Cen
possesses a coherent modulation at 56.825 s, with sidebands at 56.598 s and
57.054 s. These have appeared since this nova remnant was observed in 2000 and
2002. We deduce that the dominant signal is the rotation period of the white
dwarf primary and the sidebands are caused by reprocessing from a surface
moving with an orbital period of 3.94 h. Thus V842 Cen is an intermediate polar
(IP) of the DQ Herculis subclass, is the fastest rotating white dwarf among the
IPs and is the third fastest known in a cataclysmic variable. As in other IPs
we see no dwarf nova oscillations, but there are often quasi-periodic
oscillations in the range 350 - 1500 s. There is a strong brightness modulation
with a period of 3.78 h, which we attribute to negative superhumps, and there
is an even stronger signal at 2.886 h which is of unknown origin but is
probably a further example of that seen in GW Lib and some other systems. We
used the Swift satellite to observe V842 Cen in the ultra-violet and in X-rays,
although no periodic modulation was detected in the short observations. The
X-ray luminosity of this object appears to be much lower than that of other IPs
in which the accretion region is directly visible.Comment: 6 pages, 10 figures, accepted for publication in MNRA
Anti-persister and Anti-biofilm Activity of Self-Assembled Antimicrobial Peptoid Ellipsoidal Micelles
[Image: see text] Although persister cells are the root cause of resistance development and relapse of chronic infections, more attention has been focused on developing antimicrobial agents against resistant bacterial strains than on developing anti-persister agents. Frustratingly, the global preclinical antibacterial pipeline does not include any anti-persister drug. Therefore, the central point of this work is to explore antimicrobial peptidomimetics called peptoids (sequence-specific oligo-N-substituted glycines) as a new class of anti-persister drugs. In this study, we demonstrate that one particular antimicrobial peptoid, the sequence-specific pentamer TM5, is active against planktonic persister cells and sterilizes biofilms formed by both Gram-negative and Gram-positive bacteria. Moreover, we demonstrate the potential of TM5 to inhibit cytokine production induced by lipopolysaccharides from Gram-negative bacteria. We anticipate that this work can pave the way to the development of new anti-persister agents based on antimicrobial peptoids of this class to simultaneously help address the crisis of bacterial resistance and reduce the occurrence of the relapse of chronic infections
Association of selenium, tocopherols, carotenoids, retinol, and 15-isoprostane F(2t) in serum or urine with prostate cancer risk: the multiethnic cohort.
We examine the association of antioxidants and 15-isoprostane F(2t) with risk of prostate cancer.We conducted a nested case-control study of serum antioxidant biomarkers (selenium, tocopherols, carotenoids, and retinol) and a urinary oxidation biomarker (15-isoprostane F(2t)) with risk of prostate cancer within the Multiethnic Cohort. Demographic, dietary, and other exposure information was collected by self-administered questionnaire in 1993-1996. We compared prediagnostic biomarker levels from 467 prostate cancer cases and 936 cancer free controls that were matched on several variables. Multivariate conditional logistic regression models were used to compute adjusted odds ratios (ORs) and 95% confidence intervals (CIs).We observed that there was no overall association of serum concentrations of antioxidants and urinary concentrations of 15-isoprostane F(2t) with risk of prostate cancer or risk of advanced prostate cancer. However, we did observe an inverse association for serum selenium only among African-American men (p trend = 0.02); men in the third tertile of selenium concentrations had a 41% lower risk (95% CI: 0.38-0.93) of prostate cancer when compared to men in the first tertile.Overall, our study found no association of serum antioxidants or 15-isoprostane F(2t) with the risk of prostate cancer. The observed inverse association of selenium with prostate cancer in African-Americans needs to be validated in other studies
An Analysis of Private School Closings
We add to the small literature on private school supply by exploring exits of K-12 private schools. We find that the closure of private schools is not an infrequent event, and use national survey data from the National Center for Education Statistics to study closures of private schools. We assume that the probability of an exit is a function of excess supply of private schools over the demand, as well as the school's characteristics such as age, size, and religious affiliation. Our empirical results generally support the implications of the model. Working Paper 07-0
Effects of bark beetle outbreaks on forest landscape pattern in the southern rocky mountains, U.S.A.
Since the late 1990s, extensive outbreaks of native bark beetles (Curculionidae: Scolytinae) have affected coniferous forests throughout Europe and North America, driving changes in carbon storage, wildlife habitat, nutrient cycling, and water resource provisioning. Remote sensing is a cru-cial tool for quantifying the effects of these disturbances across broad landscapes. In particular, Landsat time series (LTS) are increasingly used to characterize outbreak dynamics, including the presence and severity of bark beetle-caused tree mortality, though broad-scale LTS-based maps are rarely informed by detailed field validation. Here we used spatial and temporal information from LTS products, in combination with extensive field data and Random Forest (RF) models, to develop 30-m maps of the presence (i.e., any occurrence) and severity (i.e., cumulative percent basal area mortality) of beetle-caused tree mortality 1997–2019 in subalpine forests throughout the Southern Rocky Mountains, USA. Using resultant maps, we also quantified spatial patterns of cumulative tree mortality throughout the region, an important yet poorly understood concept in beetle-affected forests. RF models using LTS products to predict presence and severity performed well, with 80.3% correctly classified (Kappa = 0.61) and R2 = 0.68 (RMSE = 17.3), respectively. We found that ≥10,256 km2 of subalpine forest area (39.5% of the study area) was affected by bark beetles and 19.3% of the study area experienced ≥70% tree mortality over the twenty-three year period. Variograms indi-cated that severity was autocorrelated at scales \u3c 250 km. Interestingly, cumulative patch-size dis-tributions showed that areas with a near-total loss of the overstory canopy (i.e., ≥90% mortality) were relatively small (\u3c0.24 km2) and isolated throughout the study area. Our findings help to in-form an understanding of the variable effects of bark beetle outbreaks across complex forested regions and provide insight into patterns of disturbance legacies, landscape connectivity, and susceptibility to future disturbance
Chemical Plants Remain Vulnerable to Terrorists: A Call to Action
U.S. chemical plants currently have potentially catastrophic vulnerabilities as terrorist targets. The possible consequences of these vulnerabilities echo from the tragedies of the Bhopal incident in 1984 to the terrorist attacks on 11 September 2001 and, most recently, Hurricanes Katrina and Rita. Findings from a 2004 nationwide participatory research study of 125 local union leaders at sites with very large volumes of highly hazardous chemicals suggest that voluntary efforts to achieve chemical plant security are not succeeding. Study respondents reported that companies had only infrequently taken actions that are most effective in preventing or in preparing to respond to a terrorist threat. In addition, companies reportedly often failed to involve key stakeholders, including workers, local unions, and the surrounding communities, in these efforts. The environmental health community thus has an opportunity to play a key role in advocating for and supporting improvements in prevention of and preparation for terrorist attacks. Policy-level recommendations to redress chemical site vulnerabilities and the related ongoing threats to the nation’s security are as follows: a) specify detailed requirements for chemical site assessment and security; b) mandate audit inspections supported by significant penalties for cases of noncompliance; c) require progress toward achieving inherently safer processes, including the minimizing of storage of highly hazardous chemicals; d) examine and require additional effective actions in prevention, emergency preparedness, and response and remediation; e) mandate and fund the upgrading of emergency communication systems; and f) involve workers and community members in plan creation and equip and prepare them to prevent and respond effectively to an incident
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