Extended early childhood intervention and school achievement: Age 13 findings from the Chicago longitudinal study

We evaluated the effects of participation in an extended program of compensatory education for a large sample of inner-city black children up to the seventh grade. The intervention is the Chicago Child-Parent Center and Expansion Program. Groups included 426 children who participated in the program from preschool to grades 2 or 3 and 133 school-stable children whose participation ceased in kindergarten. After taking into account initial differences in both the level and the growth rate of achievement, frequency of school mobility after the program, and sample selection bias, program participation for two or three years after preschool and kindergarten is positively associated with reading and math achievement in grade 7 and negatively associated with cumulative grade retention four years after the end of the program. Study findings provide rare longitudinal evidence from an established program concerning the effects of extending compensatory education into the primary grades.

Grade Retention and School Performance: An Extended Investigation

This study extends Reynolds’ (1992) investigation of the social- psychological influences on grade retention and school adjustment in early childhood by tracing the predictors and consequences of grade retention for school achievement, perceived competence, and delinquency in early adolescence (age 14). The study sample included 1,164 (93 percent of the sample from the original study) low-income, mostly black children in the Chicago Longitudinal Study. Twenty-eight percent of the study sample were retained-in-grade by age 14 (first grade to eighth grade). The strongest predictors of retention were early school performance (test scores and grades), sex (boys were more likely to be retained), parent participation in school, and school mobility. Overall, grade retention was significantly associated with lower reading and math achievement at age 14 above and beyond a comprehensive set of explanatory variables. Results based on same-age comparison groups yielded larger effects of retention on school achievement than those based on same-grade comparisons, but both approaches indicated that grade retention was associated with significantly lower reading achievement. In the full model, grade retention was unrelated to perceived school competence at age 12 and to delinquency infractions at age 14. With the exception of reading achievement, retention during the primary grades and retention during grades 4 to 7 yielded a similar pattern of effects. Findings were largely consistent with the earlier study and suggest that intervention approaches other than grade retention are needed to better promote school achievement and adjustment.

Chemical application of diffusion quantum Monte Carlo

The diffusion quantum Monte Carlo (QMC) method gives a stochastic solution to the Schroedinger equation. This approach is receiving increasing attention in chemical applications as a result of its high accuracy. However, reducing statistical uncertainty remains a priority because chemical effects are often obtained as small differences of large numbers. As an example, the single-triplet splitting of the energy of the methylene molecule CH sub 2 is given. The QMC algorithm was implemented on the CYBER 205, first as a direct transcription of the algorithm running on the VAX 11/780, and second by explicitly writing vector code for all loops longer than a crossover length C. The speed of the codes relative to one another as a function of C, and relative to the VAX, are discussed. The computational time dependence obtained versus the number of basis functions is discussed and this is compared with that obtained from traditional quantum chemistry codes and that obtained from traditional computer architectures

An integrated development facility for the calibration of low-energy charged particle flight instrumentation

A system was developed for the calibration and development of thermal ion instrumentation. The system provides an extended beam with usable current rates, approx. 1 pA/sq cm, at beam energies as low as 1 eV, with much higher values available with increasing energy. A tandem electrostatic and variable geometry magnetic mirror configuration within the ion source optimizes the use of the ionizing electrons. The system is integrated under microcomputer control to allow automatic control and monitoring of the beam energy and composition and the mass and angle-dependent response of the instrument under test. The system is pumped by a combination of carbon vane and cryogenic sorption roughing pumps and ion and liquid helium operating pumps

Searching for additional heating - [OII] emission in the diffuse ionized gas of NGC891, NGC4631 and NGC3079

We present spectroscopic data of ionized gas in the disk--halo regions of three edge-on galaxies, NGC 891, NGC 4631 and NGC 3079, covering a wavelength range from [\ion{O}{2}] $\lambda$3727\AA to [\ion{S}{2}] $\lambda$6716.4\AA. The inclusion of the [\ion{O}{2}] emission provides new constraints on the properties of the diffuse ionized gas (DIG), in particular, the origin of the observed spatial variations in the line intensity ratios. We used three different methods to derive electron temperatures, abundances and ionization fractions along the slit. The increase in the [\ion{O}{2}]/H$\alpha$ line ratio towards the halo in all three galaxies requires an increase either in electron temperature or in oxygen abundance. Keeping the oxygen abundance constant yields the most reasonable results for temperature, abundances, and ionization fractions. Since a constant oxygen abundance seems to require an increase in temperature towards the halo, we conclude that gradients in the electron temperature play a significant role in the observed variations in the optical line ratios from extraplanar DIG in these three spiral galaxies.Comment: 43 pages, 29 figure

Ionization, Kinematics, and Extent of the Diffuse Ionized Gas Halo of NGC 5775

We present key results from deep spectra of the Diffuse Ionized Gas (DIG) halo of the edge-on galaxy NGC 5775. [NII]6583 has been detected up to about z=13 kpc above the plane in one of two vertically oriented long slits -- making this the spiral galaxy with the greatest spectroscopically detected halo extent in emission. Key diagnostic line ratios have been measured up to about z=8 kpc, allowing the source of ionization and physical state to be probed. Ionization by a dilute radiation field from massive stars in the disk can explain some of the line ratio behavior, but departures from this picture are clearly indicated, most strongly by the rise of [OIII]/Halpha with z. Velocities of the gas in both slits approach the systemic velocity of the galaxy at several kpc above the plane. We interpret this trend as a decrease in rotation velocity with z, with essentially no rotation at heights of several kpc. Such a trend was observed in the edge-on galaxy NGC 891, but here much more dramatically. This falloff is presumably due to the gravitational potential changing with z, but will also depend on the hydrodynamic nature of the disk-halo cycling of gas and projection effects. More detailed modeling of the ionization and kinematics of this and other edge-ons will be presented in future papers.Comment: figures 1, 2a-d and 3 included. ApJ Letters, in pres

The matter content of the jet in M87: evidence for an electron-positron jet

Recent observations have allowed the geometry and kinematics of the M87 jet to be tightly constrained. We combine these constraints with historical Very Long Baseline Interferometry (VLBI) results and the theory of synchrotron self-absorbed radio cores in order to investigate the physical properties of the jet. Our results strongly suggest the jet to be dominated by an electron-positron (pair) plasma. Although our conservative constraints cannot conclusively dismiss an electron-proton plasma, the viability of this solution is extremely vulnerable to further tightening of VLBI surface brightness limits. The arguments presented, coupled with future high-resolution multi-frequency VLBI studies of the jet core, will be able to firmly distinguish these two possibilities.Comment: 8 pages, 1 ps figure. Revised and accepted for publication in MNRA

An outburst scenario for the X-ray spectral variability in 3C 111

We present a combined Suzaku and Swift BAT broad-band E=0.6-200keV spectral analysis of three 3C 111 observations obtained in 2010. The data are well described with an absorbed power-law continuum and a weak (R~0.2) cold reflection component from distant material. We constrain the continuum cutoff at E_c~150-200keV, which is in accordance with X-ray Comptonization corona models and supports claims that the jet emission is only dominant at much higher energies. Fe XXVI Ly\alpha emission and absorption lines are also present in the first and second observations, respectively. The modelling and interpretation of the emission line is complex and we explore three possibilities. If originating from ionized disc reflection, this should be emitted at r_in> 50r_g or, in the lamp-post configuration, the illuminating source should be at a height of h> 30r_g over the black hole. Alternatively, the line could be modeled with a hot collisionally ionized plasma with temperature kT = 22.0^{+6.1}_{-3.2} keV or a photo-ionized plasma with log\xi=4.52^{+0.10}_{-0.16} erg s^{-1} cm and column density N_H > 3x10^23 cm^{-2}. However, the first and second scenarios are less favored on statistical and physical grounds, respectively. The blue-shifted absorption line in the second observation can be modelled as an ultra-fast outflow (UFO) with ionization parameter log\xi=4.47^{+0.76}_{-0.04} erg s^{-1} cm, column density N_H=(5.3^{+1.8}_{-1.3})x 10^{22} cm^{-2} and outflow velocity v_out = 0.104+/-0.006 c. Interestingly, the parameters of the photo-ionized emission model remarkably match those of the absorbing UFO. We suggest an outburst scenario in which an accretion disc wind, initially lying out of the line of sight and observed in emission, then crosses our view to the source and it is observed in absorption as a mildly-relativistic UFO.Comment: Accepted for publication in MNARS on July 1st 201

The theoretical reflectance of X-rays from optical surfaces

The theoretical reflectance of X-rays from various materials and evaporated films is presented. A computer program was written that computes the reflected intensity as a function of the angle of the incident radiation. The quantities necessary to generate the efficiency and their effect on the data are demonstrated. Five materials were chosen for evaluation: (1) fused silica, (2) chromium, (3) beryllium, (4) gold, and (5) a thin layer contaminant. Fused silica is a versatile and common material; chromium has high reflection efficiency at X-ray wavelengths and is in the middle of the atomic number range; beryllium contains a single atomic shell and has a low range atomic number; gold contains multiple atomic shells and has a high atomic number; the contaminant is treated as a thin film in the calculations and results are given as a function of thickness for selected wavelengths. The theoretical results are compared to experimental data at lambda = 8.34 A