The spontaneous ionization of a hydrogen atom in an electric field, 1

Numerical integration of spontaneous ionization of hydrogen atom in electric field using Schroedinger equatio

Optical excitations in organic molecules, clusters and defects studied by first-principles Green's function methods

Spectroscopic and optical properties of nanosystems and point defects are discussed within the framework of Green's function methods. We use an approach based on evaluating the self-energy in the so-called GW approximation and solving the Bethe-Salpeter equation in the space of single-particle transitions. Plasmon-pole models or numerical energy integration, which have been used in most of the previous GW calculations, are not used. Fourier transforms of the dielectric function are also avoided. This approach is applied to benzene, naphthalene, passivated silicon clusters (containing more than one hundred atoms), and the F center in LiCl. In the latter, excitonic effects and the $1s \to 2p$ defect line are identified in the energy-resolved dielectric function. We also compare optical spectra obtained by solving the Bethe-Salpeter equation and by using time-dependent density functional theory in the local, adiabatic approximation. From this comparison, we conclude that both methods give similar predictions for optical excitations in benzene and naphthalene, but they differ in the spectra of small silicon clusters. As cluster size increases, both methods predict very low cross section for photoabsorption in the optical and near ultra-violet ranges. For the larger clusters, the computed cross section shows a slow increase as function of photon frequency. Ionization potentials and electron affinities of molecules and clusters are also calculated.Comment: 9 figures, 5 tables, to appear in Phys. Rev. B, 200

Understanding shared family meals on the autism spectrum

There is ample evidence on the positive effects of the family meal for children and families, but few of these studies have examined families where a child has autism. In order to better understand (1) the nature of shared family meals when a child has autism, (2) how families establish useful mealtime routines and meaningful mealtime rituals, (3) what are the barriers to achieving the family meal, and (4) the role mealtime rituals and routines play in family life I analyzed recorded observations of family dinners in the home and interviews with mothers of 16 Midwestern families. Each family had at least one child between the ages of 5 and 14 with autism. The families in this study shared many of the universal features of mealtimes such as using the time to share and problem solve, but they also had features salient to their identities as autistic families. For example, having to anticipate throughout the meal their children’s capacities and limitations. The creation of useful routines was enmeshed with the creation of meaningful rituals. Logistical considerations, the ideal family meal, and the family-of-origin-family-meal placed constraints on what the mealtime routine could be. The repetition of routine created symbolic meaning which, in turn, both reinforced and reflected family functioning. Thus, family meals were a symbol unto themselves and the enactment of them had the potential to create connection and communicate closeness; however this was predicated upon the families ability to negotiate a dialectic of acceptance and control

The Crayfishes of West Virginia

Author Institution: University of Illinoi

Effects of Solute-Solute Interactions on Protein Stability Studied Using Various Counterions and Dendrimers

Much work has been performed on understanding the effects of additives on protein thermodynamics and degradation kinetics, in particular addressing the Hofmeister series and other broad empirical phenomena. Little attention, however, has been paid to the effect of additive-additive interactions on proteins. Our group and others have recently shown that such interactions can actually govern protein events, such as aggregation. Here we use dendrimers, which have the advantage that both size and surface chemical groups can be changed and therein studied independently. Dendrimers are a relatively new and broad class of materials which have been demonstrated useful in biological and therapeutic applications, such as drug delivery, perturbing amyloid formation, etc. Guanidinium modified dendrimers pose an interesting case given that guanidinium can form multiple attractive hydrogen bonds with either a protein surface or other components in solution, such as hydrogen bond accepting counterions. Here we present a study which shows that the behavior of such macromolecule species (modified PAMAM dendrimers) is governed by intra-solvent interactions. Attractive guanidinium-anion interactions seem to cause clustering in solution, which inhibits cooperative binding to the protein surface but at the same time, significantly suppresses nonnative aggregation.Singapore-MIT Allianc

Dynamical aspects of inextensible chains

In the present work the dynamics of a continuous inextensible chain is studied. The chain is regarded as a system of small particles subjected to constraints on their reciprocal distances. It is proposed a treatment of systems of this kind based on a set Langevin equations in which the noise is characterized by a non-gaussian probability distribution. The method is explained in the case of a freely hinged chain. In particular, the generating functional of the correlation functions of the relevant degrees of freedom which describe the conformations of this chain is derived. It is shown that in the continuous limit this generating functional coincides with a model of an inextensible chain previously discussed by one of the authors of this work. Next, the approach developed here is applied to a inextensible chain, called the freely jointed bar chain, in which the basic units are small extended objects. The generating functional of the freely jointed bar chain is constructed. It is shown that it differs profoundly from that of the freely hinged chain. Despite the differences, it is verified that in the continuous limit both generating functionals coincide as it is expected.Comment: 15 pages, LaTeX 2e + various packages, 3 figures. The title has been changed and three references have been added. A large part of the manuscript has been rewritten to improve readability. Chapter 4 has been added. It contains the construction of the generating functional without the shish-kebab approximation and a new derivation of the continuous limit of the freely jointed bar chai

A comparison of spectral mixture analysis an NDVI for ascertaining ecological variables

In this study, we compare the performance of spectral mixture analysis to the Normalized Difference Vegetation Index (NDVI) in detecting change in a grassland across topographically-induced nutrient gradients and different management schemes. The Konza Prairie Research Natural Area, Kansas, is a relatively homogeneous tallgrass prairie in which change in vegetation productivity occurs with respect to topographic positions in each watershed. The area is the site of long-term studies of the influence of fire and grazing on tallgrass production and was the site of the First ISLSCP (International Satellite Land Surface Climatology Project) Field Experiment (FIFE) from 1987 to 1989. Vegetation indices such as NDVI are commonly used with imagery collected in few (less than 10) spectral bands. However, the use of only two bands (e.g. NDVI) does not adequately account for the complex of signals making up most surface reflectance. Influences from background spectral variation and spatial heterogeneity may confound the direct relationship with biological or biophysical variables. High dimensional multispectral data allows for the application position of techniques such as derivative analysis and spectral curve fitting, thereby increasing the probability of successfully modeling the reflectance from mixed surfaces. The higher number of bands permits unmixing of a greater number of surface components, separating the vegetation signal for further analyses relevant to biological variables

Van der Waals forces in density functional theory: perturbational long-range electron interaction corrections

Long-range exchange and correlation effects, responsible for the failure of currently used approximate density functionals in describing van der Waals forces, are taken into account explicitly after a separation of the electron-electron interaction in the Hamiltonian into short- and long-range components. We propose a "range-separated hybrid" functional based on a local density approximation for the short-range exchange-correlation energy, combined with a long-range exact exchange energy. Long-range correlation effects are added by a second-order perturbational treatment. The resulting scheme is general and is particularly well-adapted to describe van der Waals complexes, like rare gas dimers.Comment: 8 pages, 1 figure, submitted to Phys. Rev.

Lithologic and Structural Interpretation of Gravity Data, Northeastern Iowa

A gravity survey was conducted over approximately 4600 square km of northeast Iowa. It was undertaken to provide detailed gravity coverage at approximately 1.6 km intervals and to model the source of several significant gravity and magnetic anomalies. 1,460 gravity stations were occupied in the survey area. Bouguer gravity and residual gravity anomaly maps were prepared, the latter using band-pass filter and trend-surface analysis techniques. The residual maps reveal that the large oval Bouguer gravity anomaly centered beneath Decorah can be traced to the southern border of the survey. Profiles crossing this feature were prepared from the Bouguer map and a total intensity magnetic anomaly map. These profiles, combined with drill hole information, support the interpretation of a mafic (troctolite) intrusive extending over 90 km from the northwest corner of Winneshiek County to near the southern boundary of Fayette County. The western portion is dominated by a shallow elastic basin while the eastern portion appears to be dominantly felsic in nature. The gravity interpretation did not provide conclusive evidence for faulting near Decorah although faulting cannot be ruled out

Monoclonal antibody detects Ag polymorphism of apolipoprotein B

AbstractA monoclonal antibody (MB-19) was used to investigate the polymorphism of apolipoprotein B in a large family and in unrelated subjects. Apolipoprotein B was shown to exhibit high-, intermediate- or low-affinitybinding to this antibody. Thus, MB-19 bound strongly to the Ag(c) epitope, an Ag antigenic domain previously characterized by human antisera, while it bound only weakly to the allelic epitope Ag(g). It proved therefore useful for the detection of the two corresponding allelic apoB species designated apoBc (high-affinity binding) and apoBg (low-affinity binding), and for confirming their co-dominant transmission. Intermediate binding resulted from the presence of a mixture of both apoB populations in heterozygous subjects