Teaching Physical Science Through Technology: Middle School VCU PHY 591

Teaching Physical Science through Technology is a new 3-credit laboratory-and-lecture based course designed to serve as an introduction to the teaching of physical science concepts at the middle school level. Physical science phenomena are presented through investigations of commonly known applications of technology and focus on the Virginia Science Standards of Learning for 6th Grade Science and the Physical Science courses. Topics include matter, gravity, mechanics, heat, optics, electricity and magnetism, and computers as seen in their roles in common devices. The development of the course includes assessment from six semesters, collaboration with other institutions including the Science Museum of Virginia, and an 800 page text written by Adam Niculescu

Optical and electrochemical studies of passive film formation in amorphous Ni‐Cr‐P‐C alloys

The investigation of passivation of an amorphous Ni‐l4Cr‐17P‐0.5C alloy in lN H2 SO4 through anodic polarization and near‐normal optical reflectance is reported. It was found that the alloy passivates with a current density of 10− 1 A/m2 extending to 1.0 V with current density dependent upon surface morphology. In the transpassive region under constant current density conditions the reflectance of the film exhibits strong interference phenomena and overall exponential decay in intensity. The behavior of the system in this region is described with a single thin‐film optical model consistent with the formation of a chromium phosphate deposit layer which increases in thickness at a rate of 7 nm/s at a 1.67 mV/s sweep rate

The Grasscutter: An Untapped Resource of Africa’s Grasslands

The grasscutter (or Greater cane rat – Thryonomys swinderianus) is a common rodent in Africa, south of the Sahara. Its distribution ranges from The Gambia to southern Sudan, across the continent down to south Namibia and South Africa (Fritzinger 1995). The grasscutter grows to \u3e 0.5 m in length and weighs ~8 kg. It has characteristic rounded ears, a short nose, coarse bristly hair, and forefeet smaller than its hind feet. Grasscutters are herbivores and their natural diet is mainly grasses and cane, but they also eat bark, fallen fruits, nuts and many different kinds of cultivated crops. Grasscutters get their name from the way they cut the grasses and other foods with their incisors, producing a chattering sound that is relatively loud and very distinguishable (Mills 1997). The meat is highly preferred by a wide range of West Africans and is gaining some acceptance in Central and Southern Africa (Van Zyl et. al. 1999a, Adu et. al 2005). The meat commands a premium price compared to other meat sources, with its sale being a major industry in both urban and rural centres (Adu et al. 2005). Grasscutter farming is therefore being promoted in most countries in West Africa as a model for poverty reduction (Baptist and Mensah 1986). Though various aspects of captive grasscutter production have been studied, it has a low uptake rate as a new farming venture (Anang et. al. 211). This paper therefore attempts to create a broader and clearer picture of the potential of grasscutter farming in parts of Africa where the animal occurs

Inhibitory effects of archetypical nucleic acid ligands on the interactions of HIV-1 nucleocapsid protein with elements of Ψ-RNA

Disrupting the interactions between human immunodeficiency virus type 1 (HIV-1) nucleocapsid (NC) protein and structural elements of the packaging signal (Ψ-RNA) could constitute an ideal strategy to inhibit the functions of this region of the genome leader in the virus life cycle. We have employed electrospray ionization (ESI) Fourier transform mass spectrometry (FTMS) to assess the ability of a series of nucleic acid ligands to bind selected structures of Ψ-RNA and inhibit their specific interactions with NC in vitro. We found that the majority of the ligands included in the study were able to form stable non-covalent complexes with stem–loop 2, 3 and 4 (SL2–4), consistent with their characteristic nucleic acid binding modes. However, only aminoglycosidic antibiotics were capable of dissociating preformed NC•SL3 and NC•SL4 complexes, but not NC•SL2. The apparent specificity of these inhibitory effects is closely dependent on distinctive structural features of the different NC•RNA complexes. The trends observed for the IC(50) values correlate very well with those provided by the ligand binding affinities and the dissociation constants of target NC•RNA complexes. This systematic investigation of archetypical nucleic acid ligands provides a valid framework to support the design of novel ligand inhibitors for HIV-1 treatment

Defect-mediated turbulence in systems with local deterministic chaos

We show that defect-mediated turbulence can exist in media where the underlying local dynamics is deterministically chaotic. While many of the characteristics of defect-mediated turbulence, such as the exponential decay of correlations and a squared Poissonian distribution for the number of defects, are identical to those seen in oscillatory media, the fluctuations in the number of defects differ significantly. The power spectra suggest the existence of underlying correlations that lead to a different and non-universal scaling structure in chaotic media.Comment: 4 pages, 5 figure

Modeling the diurnal tide with dissipation derived from UARS/HRDI measurements

International audienceThis paper uses dissipation values derived from UARS/HRDI observations in a recently published diurnal-tide model. These model structures compare quite well with the UARS/HRDI observations with respect to the annual variation of the diurnal tidal amplitudes and the size of the amplitudes themselves. It is suggested that the annual variation of atmospheric dissipation in the mesosphere-lower thermosphere is a major controlling factor in determining the annual variation of the diurnal tide

Spatially Resolved Mapping of Local Polarization Dynamics in an Ergodic Phase of Ferroelectric Relaxor

Spatial variability of polarization relaxation kinetics in relaxor ferroelectric 0.9Pb(Mg1/3Nb2/3)O3-0.1PbTiO3 is studied using time-resolved Piezoresponse Force Microscopy. Local relaxation attributed to the reorientation of polar nanoregions is shown to follow stretched exponential dependence, exp(-(t/tau)^beta), with beta~~0.4, much larger than the macroscopic value determined from dielectric spectra (beta~~0.09). The spatial inhomogeneity of relaxation time distributions with the presence of 100-200 nm "fast" and "slow" regions is observed. The results are analyzed to map the Vogel-Fulcher temperatures on the nanoscale.Comment: 23 pages, 4 figures, supplementary materials attached; to be submitted to Phys. Rev. Let

Hierarchical Gaussian process mixtures for regression

As a result of their good performance in practice and their desirable analytical properties, Gaussian process regression models are becoming increasingly of interest in statistics, engineering and other fields. However, two major problems arise when the model is applied to a large data-set with repeated measurements. One stems from the systematic heterogeneity among the different replications, and the other is the requirement to invert a covariance matrix which is involved in the implementation of the model. The dimension of this matrix equals the sample size of the training data-set. In this paper, a Gaussian process mixture model for regression is proposed for dealing with the above two problems, and a hybrid Markov chain Monte Carlo (MCMC) algorithm is used for its implementation. Application to a real data-set is reported

Artificial Neural Network-based error compensation procedure for low-cost encoders

An Artificial Neural Network-based error compensation method is proposed for improving the accuracy of resolver-based 16-bit encoders by compensating for their respective systematic error profiles. The error compensation procedure, for a particular encoder, involves obtaining its error profile by calibrating it on a precision rotary table, training the neural network by using a part of this data and then determining the corrected encoder angle by subtracting the ANN-predicted error from the measured value of the encoder angle. Since it is not guaranteed that all the resolvers will have exactly similar error profiles because of the inherent differences in their construction on a micro scale, the ANN has been trained on one error profile at a time and the corresponding weight file is then used only for compensating the systematic error of this particular encoder. The systematic nature of the error profile for each of the encoders has also been validated by repeated calibration of the encoders over a period of time and it was found that the error profiles of a particular encoder recorded at different epochs show near reproducible behavior. The ANN-based error compensation procedure has been implemented for 4 encoders by training the ANN with their respective error profiles and the results indicate that the accuracy of encoders can be improved by nearly an order of magnitude from quoted values of ~6 arc-min to ~0.65 arc-min when their corresponding ANN-generated weight files are used for determining the corrected encoder angle.Comment: 16 pages, 4 figures. Accepted for Publication in Measurement Science and Technology (MST