168 research outputs found
Self-Managed Groups: Fitting Self-Management Approaches Into Classroom Systems
Examines the factors limiting the use of classroom self-management interventions. Self-management approaches that contribute to its inappropriateness and impracticality; Review peer tutoring as a strategy with self-management features in classroom use; Combination of student choice and student management with interdependent group reward contingencies; Reciprocal peer teaching
A joint estimation approach for monotonic regression functions in general dimensions
Regression analysis under the assumption of monotonicity is a well-studied
statistical problem and has been used in a wide range of applications. However,
there remains a lack of a broadly applicable methodology that permits
information borrowing, for efficiency gains, when jointly estimating multiple
monotonic regression functions. We introduce such a methodology by extending
the isotonic regression problem presented in the article "The isotonic
regression problem and its dual" (Barlow and Brunk, 1972). The presented
approach can be applied to both fixed and random designs and any number of
explanatory variables (regressors). Our framework penalizes pairwise
differences in the values (levels) of the monotonic function estimates, with
the weight of penalty being determined based on a statistical test, which
results in information being shared across data sets if similarities in the
regression functions exist. Function estimates are subsequently derived using
an iterative optimization routine that uses existing solution algorithms for
the isotonic regression problem. Simulation studies for normally and binomially
distributed response data illustrate that function estimates are consistently
improved if similarities between functions exist, and are not oversmoothed
otherwise. We further apply our methodology to analyse two public health data
sets: neonatal mortality data for Porto Alegre, Brazil, and stroke patient data
for North West England
Search for Light Gauge Bosons of the Dark Sector at the Mainz Microtron
A new exclusion limit for the electromagnetic production of a light U(1)
gauge boson {\gamma}' decaying to e^+e^- was determined by the A1 Collaboration
at the Mainz Microtron. Such light gauge bosons appear in several extensions of
the standard model and are also discussed as candidates for the interaction of
dark matter with standard model matter. In electron scattering from a heavy
nucleus, the existing limits for a narrow state coupling to e^+e^- were reduced
by nearly an order of magnitude in the range of the lepton pair mass of 210
MeV/c^2 < m_e^+e^- < 300 MeV/c^2. This experiment demonstrates the potential of
high current and high resolution fixed target experiments for the search for
physics beyond the standard model.Comment: 4 pages, 7 figure
Modeling congestion and service time in hub location problems
The final publication is available at Elsevier via http://dx.doi.org/10.1016/j.apm.2017.10.033 © 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/In this paper, we present a modeling framework for hub location problems with a service time limit considering congestion at hubs. Service time is modeled taking the traveling time on the hub network as well as the handling time and the delay caused by congestion at hubs into account. We develop mixed-integer linear programming formulations for the single and multiple allocation versions of this problem. We further extend the multiple allocation model with a possibility of direct shipments. We test our models on the well-known AP data set and analyze the effects of congestion and service time on costs and hub network design. We introduce a measure for the value of modeling congestion and show that not considering the effects of congestion may result in increased costs as well as in building infeasible hub networks
Search for light massive gauge bosons as an explanation of the anomaly at MAMI
A massive, but light abelian U(1) gauge boson is a well motivated possible
signature of physics beyond the Standard Model of particle physics. In this
paper, the search for the signal of such a U(1) gauge boson in
electron-positron pair-production at the spectrometer setup of the A1
Collaboration at the Mainz Microtron (MAMI) is described. Exclusion limits in
the mass range of 40 MeV up to 300 MeV with a sensitivity in the mixing
parameter of down to are presented. A large
fraction of the parameter space has been excluded where the discrepancy of the
measured anomalous magnetic moment of the muon with theory might be explained
by an additional U(1) gauge boson.Comment: 4 pages, 3 figure
Gender and Acute Myocardial Infarction: Is There a Different Response to Thrombolysis?
AbstractObjectives. This study sought to 1) determine the effect of gender on early and late infarct-related artery patency and reocclusion after thrombolytic therapy for acute myocardial infarction; 2) examine the effect of gender on left ventricular function in response to injury/reperfusion; and 3) assess the independent contribution of gender to early (30-day) mortality after acute myocardial infarction.Background. Women have a higher mortality rate than men after myocardial infarction. However, the effect of gender on infarct-related coronary artery patency and left ventricular response to injury/reperfusion have not been fully defined in the thrombolytic era.Methods. Patency rates and global and regional left ventricular function were determined in patients at 90 min and 5 to 7 days after thrombolytic therapy for acute myocardial infarction. The effect of gender on infarct-related artery patency and left ventricular function was determined. Thirty-day mortality differences between women and men were compared.Results. Women were significantly older and had more hypertension, diabetes, hypercholesterolemia, heart failure and shock. They were less likely to have had a previous myocardial infarction, history of smoking or previous bypass surgery. Ninety-minute patency rates (Thrombolysis in Myocardial Infarction [TIMI] flow grade 3) in women and men were 39% and 38%, respectively (p = 0.5). Reocclusion rates were 8.7% in women versus 5.1% in men (p = 0.14). Women had more recurrent ischemia than men (21.4% vs. 17.0%, respectively, p = 0.01). Ninety-minute ejection fraction and regional ventricular function were clinically similar in women and men with TIMI 2 or 3 flow (ejection fraction [mean ± SD]: 63.4 ± 6% vs. 59.4 ± 0.7%, p = 0.02; number of chords: 21.4 ± 0.9 vs. 21.0 ± 1.9, p = 0.7; SD/chord: −2.4 ± 08 vs. −2.4 ± 0.2, p = 0.9, respectively). No clinically significant differences in left ventricular function were noted at 5- to 7-day follow-up. Women had a greater hyperkinetic response than men in the noninfarct zone (SD/chord: 2.4 ± 0.2 vs. 1.7 ± 0.1, p = 0.005). The 30-day mortality rate was 13.1% in women versus 4.8% in men (p ≤ 0.0001). After adjustment for other clinical and angiographic variables, gender remained an independent determinant of 30-day mortality.Conclusions. Women do not differ significantly from men with regard to either early infarct-related artery patency rates or reocclusion after thrombolytic therapy or ventricular functional response to injury/reperfusion. Gender was an independent determinant of 30-day mortality after acute myocardial infarction.(J Am Coll Cardiol 1997;29:35–42)
Two birds with one stone: dual grain-boundary and interface passivation enables >22% efficient inverted methylammonium-free perovskite solar cells
Advancing inverted (p–i–n) perovskite solar cells (PSCs) is key to further enhance the power conversion efficiency (PCE) and stability of flexible and perovskite-based tandem photovoltaics. Yet, the presence of defects at grain boundaries and in particular interfacial recombination at the perovskite/electron transporting layer interface induce severe non-radiative recombination losses, limiting the open-circuit voltage (VOC) and fill factor (FF) of PSCs in this architecture. In this work, we introduce a dual passivation strategy using the long chain alkylammonium salt phenethylammonium chloride (PEACl) both as an additive and for surface treatment to simultaneously passivate the grain boundaries and the perovskite/C60 interface. Using [2-(9H-carbazol-9-yl)ethyl]phosphonic acid (2PACz) as a hole transporting layer and a methylammonium (MA)-free Cs0.18FA0.82PbI3 perovskite absorber with a bandgap of ∼1.57 eV, prolonged charge carrier lifetime and an on average 63 meV enhanced internal quasi-Fermi level splitting are achieved upon dual passivation compared to reference p–i–n PSCs. Thereby, we achieve one of the highest PCEs for p–i–n PSCs of 22.7% (stabilized at 22.3%) by advancing simultaneously the VOC and FF up to 1.162 V and 83.2%, respectively. Using a variety of experimental techniques, we attribute the positive effects to the formation of a heterogeneous 2D Ruddlesden–Popper (PEA)2(Cs1−xFAx)n−1Pbn(I1−yCly)3n+1 phase at the grain boundaries and surface of the perovskite films. At the same time, the activation energy for ion migration is significantly increased, resulting in enhanced stability of the PSCs under light, humidity, and thermal stress. The presented dual passivation strategy highlights the importance of defect management both in the grain boundaries and the surface of the perovskite absorber layer using a proper passivation material to achieve both highly efficient and stable inverted p–i–n PSCs
Regulators of floral fragrance production and their target genes in petunia are not exclusively active in the epidermal cells of petals
In which cells of the flower volatile biosynthesis takes place is unclear. In rose and snapdragon, some enzymes of the volatile phenylpropanoid/benzenoid pathway have been shown to be present in the epidermal cells of petals. It is therefore generally believed that the production of these compounds occurs in these cells. However, whether the entire pathway is active in these cells and whether it is exclusively active in these cells remains to be proven. Cell-specific transcription factors activating these genes will determine in which cells they are expressed. In petunia, the transcription factor EMISSION OF BENZENOIDS II (EOBII) activates the ODORANT1 (ODO1) promoter and the promoter of the biosynthetic gene isoeugenol synthase (IGS). The regulator ODO1 in turn activates the promoter of the shikimate gene 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS). Here the identification of a new target gene of ODO1, encoding an ABC transporter localized on the plasma membrane, PhABCG1, which is co-expressed with ODO1, is described. PhABCG1 expression is up-regulated in petals overexpressing ODO1 through activation of the PhABCG1 promoter. Interestingly, the ODO1, PhABCG1, and IGS promoters were active in petunia protoplasts originating from both epidermal and mesophyll cell layers of the petal, suggesting that the volatile phenylpropanoid/benzenoid pathway in petunia is active in these different cell types. Since volatile release occurs from epidermal cells, trafficking of (volatile) compounds between cell layers must be involved, but the exact function of PhABCG1 remains to be resolved
Metagenes Associated with Survival in Non-Small Cell Lung Cancer
NSCLC (non-small cell lung cancer) comprises about 80% of all lung cancer cases worldwide. Surgery is most effective treatment for patients with early-stage disease. However, 30%–55% of these patients develop recurrence within 5 years. Therefore, markers that can be used to accurately classify early-stage NSCLC patients into different prognostic groups may be helpful in selecting patients who should receive specific therapies
- …