Geography of the asteroid belt

The CSM classification serves as the starting point on the geography of the asteroid belt. Raw data on asteroid types are corrected for observational biases (against dark objects, for instance) to derive the distribution of types throughout the belt. Recent work on family members indicates that dynamical families have a true physical relationship, presumably indicating common origin in the breakup of a parent asteroid

The role of earth-based observations of asteroids during the next decade

Present reconnaissance studies of asteroids shift ground based programs to more specialized, intensive studies of selected individual bodies and special classes. Two powerful techniques--radar and mid-IR spectroscopy--have yet to be widely applied to asteroids; high priority should be given to: (1) search programs with a large Schmidt telescope (especially for Mars- and Earth-approaching bodies); (2) a moderate resolution visible and near-IR spectrophotometric survey of at least half the asteroids; (3) high resolution spectrophotometry and radiometry of unusual objects; (4) radar studies of representative main belt asteroids; and (5) application of the full complement of astrophysical techniques to objects of high scientific interest and to potential space mission targets. The infrared astronomical satellite also has high potential for contributing to asteroid science

Reducing Disparities by way of a Cancer Disparities Research Training Program

Background: For minority populations, there is a continuing disparity in the burden of death and illness from cancer. Research to address this disparity should be conducted by investigators who can best understand and address the needs of culturally diverse communities. However, minorities are under-represented in health-related research. The goal of this project was to develop and evaluate an approach to motivating and preparing master’s degree students for careers dedicated to cancer disparities research. Method: A Cancer Disparities Research Training Program (CDRTP) was initiated in 2010. The program consists of coursework, practicum experiences, and research opportunities. Assessment of the curriculum is based on monitoring achievement of evaluation indicators and includes a quantitative assessment and qualitative approach. Results: In its first three years, the program graduated 20 trainees, all of whom were minorities (18 African Americans and two Asians). When asked about career goals, two-thirds of the trainees indicated interest in pursuing careers in research on cancer prevention and control. The trainees expressed high satisfaction with the courses, instructor, materials, and curriculum. Although trainees had suggestions about course details, evaluations overall were positive. Across focus groups, three recurrent themes emerged regarding activities to enhance the student experience: having a wider variety of topics, more guest speakers, and field trips. Conclusion: The CDRTP was intended to recruit students – primarily African Americans – into research on prevention and control of cancer disparities. Although final evaluation of the program’s overall outcome will not be available for several years, a preliminary evaluation indicates the program is being successful

An Update and Report Failure of Surgical Syndactyly Repair in Harlequin Ichthyosis.

Harlequin ichthyosis (HI) is a rare congenital skin disorder caused by irregular epidermal differentiation. Syndactyly in HI is associated with thick hyperkeratotic skin flexion and angulation deformity of the hand and fingers resulting in limited function of the upper extremity. Traditional syndactyly release is limited as full-thickness skin grafts typically used in reconstruction are composed of diseased skin and require donor sites in a patient predisposed for adverse wound healing. This case report is a follow-up to a previous viewpoint written about digital escharotomies in a newborn with HI and outlines a second and fourth webspace syndactyly release with a dermal substitute. Despite early evidence of adequate release and improved hand function, recurrence of syndactyly was observed within 4 months of surgical release. Our experience described within this case report may suggest the limitations and possible alternatives of surgical release of syndactyly in the HI population

Use of Flexible Sensor to Characterize Biomechanics of Canine Skin

Background Suture materials and techniques are frequently evaluated in ex vivo studies by comparing tensile strengths. However, the direct measurement techniques to obtain the tensile forces in canine skin are not available, and, therefore, the conditions suture lines undergo is unknown. A soft elastomeric capacitor is used to monitor deformation in the skin over time by sensing strain. This sensor was applied to a sample of canine skin to evaluate its capacity to sense strain in the sample while loaded in a dynamic material testing machine. The measured strain of the sensor was compared with the strain measured by the dynamic testing machine. The sample of skin was evaluated with and without the sensor adhered. Results In this study, the soft elastomeric capacitor was able to measure strain and a correlation was made to stress using a modified Kelvin-Voigt model for the canine skin sample. The sensor significantly increases the stiffness of canine skin when applied which required the derivation of mechanical models for interpretation of the results. Conclusions Flexible sensors can be applied to canine skin to investigate the inherent biomechanical properties. These sensors need to be lightweight and highly elastic to avoid interference with the stress across a suture line. The sensor studied here serves as a prototype for future sensor development and has demonstrated that a lightweight highly elastic sensor is needed to decrease the effect on the sensor/skin construct. Further studies are required for biomechanical characterization of canine skin

Bayesian Analysis of Instrumental Variable Models: Acceptance-Rejection within Direct Monte Carlo

We discuss Bayesian inferential procedures within the family of instrumental variables regression models and focus on two issues: existence conditions for posterior moments of the parameters of interest under a flat prior and the potential of Direct Monte Carlo (DMC) approaches for efficient evaluation of such possibly highly non-elliptical posteriors. We show that, for the general case of m endogenous variables under a flat prior, posterior moments of order r exist for the coefficients reflecting the endogenous regressors' effect on the dependent variable, if the number of instruments is greater than m +r, even though there is an issue of local non-identification that causes non-elliptical shapes of the posterior. This stresses the need for efficient Monte Carlo integration methods. We introduce an extension of DMC that incorporates an acceptance-rejection sampling step within DMC. This Acceptance-Rejection within Direct Monte Carlo (ARDMC) method has the attractive property that the generated random drawings are independent, which greatly helps the fast convergence of simulation results, and which facilitates the evaluation of the numerical accuracy. The speed of ARDMC can be easily further improved by making use of parallelized computation using multiple core machines or computer clusters. We note that ARDMC is an analogue to the well-known "Metropolis-Hastings within Gibbs" sampling in the sense that one 'more difficult' step is used within an 'easier' simulation method. We compare the ARDMC approach with the Gibbs sampler using simulated data and two empirical data sets, involving the settler mortality instrument of Acemoglu et al. (2001) and father's education's instrument used by Hoogerheide et al. (2012a). Even without making use of parallelized computation, an efficiency gain is observed both under strong and weak instruments, where the gain can be enormous in the latter case

Differential expression analysis with global network adjustment

<p>Background: Large-scale chromosomal deletions or other non-specific perturbations of the transcriptome can alter the expression of hundreds or thousands of genes, and it is of biological interest to understand which genes are most profoundly affected. We present a method for predicting a gene’s expression as a function of other genes thereby accounting for the effect of transcriptional regulation that confounds the identification of genes differentially expressed relative to a regulatory network. The challenge in constructing such models is that the number of possible regulator transcripts within a global network is on the order of thousands, and the number of biological samples is typically on the order of 10. Nevertheless, there are large gene expression databases that can be used to construct networks that could be helpful in modeling transcriptional regulation in smaller experiments.</p> <p>Results: We demonstrate a type of penalized regression model that can be estimated from large gene expression databases, and then applied to smaller experiments. The ridge parameter is selected by minimizing the cross-validation error of the predictions in the independent out-sample. This tends to increase the model stability and leads to a much greater degree of parameter shrinkage, but the resulting biased estimation is mitigated by a second round of regression. Nevertheless, the proposed computationally efficient “over-shrinkage” method outperforms previously used LASSO-based techniques. In two independent datasets, we find that the median proportion of explained variability in expression is approximately 25%, and this results in a substantial increase in the signal-to-noise ratio allowing more powerful inferences on differential gene expression leading to biologically intuitive findings. We also show that a large proportion of gene dependencies are conditional on the biological state, which would be impossible with standard differential expression methods.</p> <p>Conclusions: By adjusting for the effects of the global network on individual genes, both the sensitivity and reliability of differential expression measures are greatly improved.</p&gt

The triaxial ellipsoid dimensions, rotational pole, and bulk density of ESA Rosetta target asteroid (21) Lutetia

We seek the best size estimates of the asteroid (21) Lutetia, the direction of its spin axis, and its bulk density, assuming its shape is well described by a smooth featureless triaxial ellipsoid, and to evaluate the deviations from this assumption. Methods. We derive these quantities from the outlines of the asteroid in 307 images of its resolved apparent disk obtained with adaptive optics (AO) at Keck II and VLT, and combine these with recent mass determinations to estimate a bulk density. Our best triaxial ellipsoid diameters for Lutetia, based on our AO images alone, are a x b x c = 132 x 101 x 93 km, with uncertainties of 4 x 3 x 13 km including estimated systematics, with a rotational pole within 5 deg. of ECJ2000 [long,lat] = [45, -7], or EQJ2000 [RA, DEC] = [44, +9]. The AO model fit itself has internal precisions of 1 x 1 x 8 km, but it is evident, both from this model derived from limited viewing aspects and the radius vector model given in a companion paper, that Lutetia has significant departures from an idealized ellipsoid. In particular, the long axis may be overestimated from the AO images alone by about 10 km. Therefore, we combine the best aspects of the radius vector and ellipsoid model into a hybrid ellipsoid model, as our final result, of 124 +/- 5 x 101 +/- 4 x 93 +/- 13 km that can be used to estimate volumes, sizes, and projected areas. The adopted pole position is within 5 deg. of [long, lat] = [52, -6] or[RA DEC] = [52, +12]. Using two separately determined masses and the volume of our hybrid model, we estimate a density of 3.5 +/- 1.1 or 4.3 +/- 0.8 g cm-3 . From the density evidence alone, we argue that this favors an enstatite-chondrite composition, although other compositions are formally allowed at the extremes (low-porosity CV/CO carbonaceous chondrite or high-porosity metallic). We discuss this in the context of other evidence.Comment: 9 pages, 8 figures, 5 tables, submitted to Astronomy and Astrophysic

Ultraviolet and visible photometry of asteroid (21) Lutetia using the Hubble Space Telescope

The asteroid (21) Lutetia is the target of a planned close encounter by the Rosetta spacecraft in July 2010. To prepare for that flyby, Lutetia has been extensively observed by a variety of astronomical facilities. We used the Hubble Space Telescope (HST) to determine the albedo of Lutetia over a wide wavelength range, extending from ~150 nm to ~700 nm. Using data from a variety of HST filters and a ground-based visible light spectrum, we employed synthetic photometry techniques to derive absolute fluxes for Lutetia. New results from ground-based measurements of Lutetia's size and shape were used to convert the absolute fluxes into albedos. We present our best model for the spectral energy distribution of Lutetia over the wavelength range 120-800 nm. There appears to be a steep drop in the albedo (by a factor of ~2) for wavelengths shorter than ~300 nm. Nevertheless, the far ultraviolet albedo of Lutetia (~10%) is considerably larger than that of typical C-chondrite material (~4%). The geometric albedo at 550 nm is 16.5 +/- 1%. Lutetia's reflectivity is not consistent with a metal-dominated surface at infrared or radar wavelengths, and its albedo at all wavelengths (UV-visibile-IR-radar) is larger than observed for typical primitive, chondritic material. We derive a relatively high FUV albedo of ~10%, a result that will be tested by observations with the Alice spectrograph during the Rosetta flyby of Lutetia in July 2010.Comment: 14 pages, 2 tables, 8 figure

Expression of an Arc-Immunoreactive Protein in the Adult Zebrafish Brain Increases in Response to a Novel Environment

Zebrafish are a powerful research tool in the field of neuroscience, offering several logistical and physiological advantages over rodents as a research model. However, the molecular dynamics of this model organism, especially with regards to learning and memory, are scarcely known. The current study explored the zebrafish brain for the presence of a protein bearing a similar function to the activity-regulated, cytoskeleton-associated protein (Arc), a critical player in synaptic plasticity. The adult zebrafish brain was found to express a protein with immunoreactivity against the anti-Arc antibody H-300. Immunoreactivity was detected ubiquitously, especially in areas known as adult progenitor cell zones. The protein, termed Arc-immunoreactive protein (AIP), increased in the telencephalon but not the optic tectum 60 min after exposure to a novel environment. Epileptiform brain activity, however, did not induce AIP expression. Evidence presented herein suggests AIP may be the neuropeptide Y receptor rather than a zebrafish homolog of Arc