Binding energies of hydrogen-like impurities in a semiconductor in intense terahertz laser fields

A detailed theoretical study is presented for the influence of linearly polarised intense terahertz (THz) laser radiation on energy states of hydrogen-like impurities in semiconductors. The dependence of the binding energy for 1s and 2p states on intensity and frequency of the THz radiation has been examined.Comment: 14 pages, 4 figure

Project Lead the Way: Analysis of Statewide Student Outcomes

poster abstractProject Lead the Way (PLTW) is a STEM education programming provider implementing hands-on, project-based engineering or biomedical science curricula in U.S. secondary schools. The goal of PLTW is to increase student interest and knowledge in these and other STEM majors/careers. A large, longitudinal dataset of students who graduated from an Indiana high school in 2010 was created. Preliminary analysis of the dataset found that students who took PLTW engineering courses were significantly more likely to select a STEM major, select an engineering major in college, and persist from the first to the second year of college. Additionally, taking three or more PLTW classes increased the likelihood of selecting a STEM major, selecting an engineering major in college, and persisting from the first to the second year of college. We also examined factors of PLTW students that made them more likely to major in a STEM field, enroll in a 4-year institution, and persist from their first to their second year of college. We found that being male, having a higher math ISTEP+ score, and receiving an honors diploma increased a PLTW students’ likelihood of majoring in STEM. PLTW students who were not eligible for free and reduced lunch, who were part of an underrepresented minority, who received an honors diploma, and who had higher ELA ISTEP+ scores were more likely to attend a 4-year institution. PLTW students who received an honors diploma and were not eligible for free and reduced lunch are more likely to persist from freshman to sophomore year. These findings elucidate interesting and important patterns in the data, highlighting a need for “scale-up research” to further determine the potential factors influencing student access and success. As such, the broad objective of our future research is to produce a multi-scalar representation of PLTW outcomes in Indiana, which can then be used as a modality for understanding the outcomes, impacts, and factors influencing PLTW success nationwide. More specifically, the project will identify PLTW outcomes in rural, suburban, and urban schools and their effects on the everyday experience of students in STEM programs at IUPUI. This multi-scalar approach will explore the broader sociocultural configuration of Indiana high schools, the extent to which those schools evidence PLTW implementation fidelity, and the longitudinal impact of PLTW curriculum on current STEM majors at IUPUI

Efficient frequency doubler for the soft X-ray SASE FEL at the TESLA Test Facility

This paper describes an effective frequency doubler scheme for SASE free electron lasers. It consists of an undulator tuned to the first harmonic, a dispersion section, and a tapered undulator tuned to the second harmonic. The first stage is a conventional soft X-ray SASE FEL. Its gain is controlled in such a way that the maximum energy modulation of the electron beam at the exit is about equal to the local energy spread, but still far away from saturation. When the electron bunch passes through the dispersion section this energy modulation leads to effective compression of the particles. Then the bunched electron beam enters the tapered undulator and produces strong radiation in the process of coherent deceleration. We demonstrate that a frequency doubler scheme can be integrated into the SASE FEL at the TESLA Test Facility at DESY, and will allow to reach 3 nm wavelength with GW-level of output peak power. This would extend the operating range of the FEL into the so-called water window and significantly expand the capabilities of the TTF FEL user facility.Comment: 17 pages, 13 figure

Core Hole Double-Excitation and Atomiclike Auger Decay in N₂

Core hole decay spectra of the free N2 molecule show evidence for hitherto unobserved molecular resonances both below and above the K-shell photoionization threshold. Based on earlier calculations they are assigned to doubly excited neutral states which could not be seen below threshold in recent high resolution absorption spectra because of the more intense core-to-Rydberg excitations. By calculating the Auger spectrum of core-excited nitrogen atoms, we show that the features are atomiclike

Examining decentralization and managerial decision making for child immunization program performance in India

Despite widespread adoption of decentralization reforms, the impact of decentralization on health system attributes, such as access to health services, responsiveness to population health needs, and effectiveness in affecting health outcomes, remains unclear. This study examines how decision space, institutional capacities, and accountability mechanisms of the Intensified Mission Indradhanush (IMI) in India relate to measurable performance of the immunization program. Data on decision space and its related dimensions of institutional capacity and accountability were collected by conducting structured interviews with managers based in 24 districts, 61 blocks, and 279 subcenters. Two measures by which to assess performance were selected: (1) proportion reduction in the DTP3 coverage gap (i.e., effectiveness), and (2) total IMI doses delivered per incremental USD spent on program implementation (i.e., efficiency). Descriptive statistics on decision space, institutional capacity, and accountability for IMI managers were generated. Structural equation models (SEM) were specified to detect any potential associations between decision space dimensions and performance measures. The majority of districts and blocks indicated low levels of decision space. Institutional capacity and accountability were similar across areas. Increases in decision space were associated with less progress towards closing the immunization coverage gap in the IMI context. Initiatives to support health workers and managers based on their specific contextual challenges could further improve outcomes of the program. Similar to previous studies, results revealed strong associations between each of the three decentralization dimensions. Health systems should consider the impact that management structures have on the efficiency and effectiveness of health services delivery. Future research could provide greater evidence for directionality of direct and indirect effects, interaction effects, and/or mediators of relationships

Angle‐resolved photoelectron spectroscopy of the core levels of N₂O

We have measured photoionization cross sections and photoelectron asymmetry parameters for each of the core levels of N2O. We have also carried out frozen‐ and relaxed‐core Hartree–Fock studies of these cross sections so as to better understand the underlying shape resonant structure and the role of electronic relaxation in these processes. A broad shape resonance is observed in each of the core‐hole cross sections at 10‐20 eV kinetic energy and there is some evidence of a second shape resonance near the thresholds, an energy region which is not accessible experimentally. The cross sections also exhibit site‐specific behavior with maxima at widely separated photoelectron kinetic energies. These differences probably arise from the fact that photoelectron matrix elements for different core orbitals probe different regions of the shape resonant orbital which extends over the entire molecule. Although the higher energy shape resonances appear quite similar, Hartree–Fock studies show that the central nitrogen resonance is more sensitive to effects of electronic relaxation than the terminal nitrogen or oxygen resonances. Large differences are also seen between the photoelectron asymmetry parameters for the central and terminal atoms

Angle-resolved photoelectron spectroscopy of the core levels of N_2O

We have measured photoionization cross sections and photoelectron asymmetry parameters for each of the core levels of N_2O. We have also carried out frozen‐ and relaxed‐core Hartree–Fock studies of these cross sections so as to better understand the underlying shape resonant structure and the role of electronic relaxation in these processes. A broad shape resonance is observed in each of the core‐hole cross sections at 10‐20 eV kinetic energy and there is some evidence of a second shape resonance near the thresholds, an energy region which is not accessible experimentally. The cross sections also exhibit site‐specific behavior with maxima at widely separated photoelectron kinetic energies. These differences probably arise from the fact that photoelectron matrix elements for different core orbitals probe different regions of the shape resonant orbital which extends over the entire molecule. Although the higher energy shape resonances appear quite similar, Hartree–Fock studies show that the central nitrogen resonance is more sensitive to effects of electronic relaxation than the terminal nitrogen or oxygen resonances. Large differences are also seen between the photoelectron asymmetry parameters for the central and terminal atoms

High-resolution C 1s photoelectron spectra of methane

The C 1s partial photoionization cross section and photoelectron angular distribution of methane (CH4) have been measured with high-energy resolution between threshold and 385 eV photon energy. From the analysis of the vibrational fine structure on the C 1s−1 photoelectron line a vibrational energy of 396±2 meV and an equilibrium bond length of 1.039(±0.001) Å for the CH+4 ion have been determined. The lifetime broadening was found to be 83(±10) meV. The weak feature in the photoabsorption cross section just above threshold does not influence the vibrational fine structure in a way typical for a shape resonance. We therefore suggest that it is due to doubly excited states of the type C (1s)−1(Val)−1(Ryd)1a(Ryd)1b, an assignment which is supported by recent Auger decay studies. Measurements of the shakeup structure revealed six satellite lines, one of which increases strongly in intensity at threshold, thus pointing to the existence of a conjugate shakeup process

Understanding and Assessing Demographic (In)Equity Resulting From Extreme Heat Exposure Due to Lack of Tree Canopies in Norfolk, VA Using Agent-Based Modeling

Prolonged exposure to extreme heat can result in illness and death. In urban areas of dense concentrations of pavement, buildings, and other surfaces that absorb and retain heat, extreme heat conditions can arise regularly and create harmful environmental exposures for residents daily during certain parts of the year. Tree canopies provide shade and help to cool the environment, making mature trees with large canopies a simple and effective way to reduce urban heat. We develop a demographically representative 1 (agent): 1 (person) agent-based model to understand the extent to which different demographics of residents in Norfolk, VA are equitably shaded from extreme heat conditions during a walk on a clear summer day. We use the model to assess the extent to which the city\u27s Tree Planting Plan will be effective in remediating any existing inequities. Our results show that inequitable conditions exist for residents (1) at different education levels, (2) at different income levels and, (3) living in different census tracts. Norfolk\u27s Tree Planting Program effectively reduces the distance residents of all demographics walk in extreme heat. However, residents of the city at lower income levels still experience statistically significantly more extreme heat exposure due to a lack of tree canopies in summer months than those at higher income levels