Healing substrates with mobile, particle-filled microcapsules: designing a ‘repair and go’ system

We model the rolling motion of a fluid-driven, particle-filled microcapsule along a heterogeneous, adhesive substrate to determine how the release of the encapsulated nanoparticles can be harnessed to repair damage on the underlying surface. We integrate the lattice Boltzmann model for hydrodynamics and the lattice spring model for the micromechanics of elastic solids to capture the interactions between the elastic shell of the microcapsule and the surrounding fluids. A Brownian dynamics model is used to simulate the release of nanoparticles from the capsule and their diffusion into the surrounding solution. We focus on a substrate that contains a damaged region (e.g. a crack or eroded surface coating), which prevents the otherwise mobile capsule from rolling along the surface. We isolate conditions where nanoparticles released from the arrested capsule can repair the damage and thereby enable the capsules to again move along the substrate. Through these studies, we establish guidelines for designing particle-filled microcapsules that perform a ‘repair and go’ function and thus, can be utilized to repair damage in microchannels and microfluidic devices.     

Three closely related herpesviruses are associated with fibropapillomatosis in marine turtles

Green turtle fibropapillomatosis is a neoplastic disease of increasingly significant threat to the survivability of this species. Degenerate PCR primers that target highly conserved regions of genes encoding herpesvirus DNA polymerases were used to amplify a DNA sequence from fibropapillomas and fibromas from Hawaiian and Florida green turtles. All of the tumors tested (n = 23) were found to harbor viral DNA, whereas no viral DNA was detected in skin biopsies from tumor-negative turtles. The tissue distribution of the green turtle herpesvirus appears to be generally limited to tumors where viral DNA was found to accumulate at approximately two to five copies per cell and is occasionally detected, only by PCR, in some tissues normally associated with tumor development. In addition, herpesviral DNA was detected in fibropapillomas from two loggerhead and four olive ridley turtles. Nucleotide sequencing of a 483-bp fragment of the turtle herpesvirus DNA polymerase gene determined that the Florida green turtle and loggerhead turtle sequences are identical and differ from the Hawaiian green turtle sequence by five nucleotide changes, which results in two amino acid substitutions. The olive ridley sequence differs from the Florida and Hawaiian green turtle sequences by 15 and 16 nucleotide changes, respectively, resulting in four amino acid substitutions, three of which are unique to the olive ridley sequence. Our data suggest that these closely related turtle herpesviruses are intimately involved in the genesis of fibropapillomatosis.     

Visualization of fuzzy clusters by fuzzy Sammon mapping projection: application to the analysis of phase space trajectories

Since in practical data mining problems high-dimensional data are clustered, the resulting clusters are high-dimensional geometrical objects, which are difficult to analyze and interpret. Cluster validity measures try to solve this problem by providing a single numerical value. As a low dimensional graphical representation of the clusters could be much more informative than such a single value, this paper proposes a new tool for the visualization of fuzzy clustering results. By using the basic properties of fuzzy clustering algorithms, this new tool maps the cluster centers and the data such that the distances between the clusters and the data-points are preserved. During the iterative mapping process, the algorithm uses the membership values of the data and minimizes an objective function similar to the original clustering algorithm. Comparing to the original Sammon mapping not only reliable cluster shapes are obtained but the numerical complexity of the algorithm is also drastically reduced. The developed tool has been applied for visualization of reconstructed phase space trajectories of chaotic systems. The case study demonstrates that proposed FUZZSAMM algorithm is a useful tool in user-guided clustering.     

Experiences with Open Source Software Engineering Tools

For software engineering (SE) and computer science (CS) programs to deliver on their promises, they must go beyond teaching students about principles, processes, models, and strategies and offer them realistic, practical experience as well. Although industry has been pressing to increase the emphasis on practical aspects, many CS programs continue to give students relatively simple problems focused on selected computing and software concepts and theories. Open source software offers CS and SE educators an opportunity to give their students practical, hands-on software engineering experience     

Temperature regulation and salivation following preoptic lesions in the rat.

Investigated whether the preoptic's thermoregulatory deficit might be a reflection of a general salivary deficit. 3 experiments were conducted with adult female Sherman albino rats. Results show that Ss with preoptic lesions quickly become hyperthermic under extreme heat stress. They do not salivate in response to heat as intact Ss do and thus cannot employ this animal's most effective means of evaporative heat loss, saliva spreading. However, if salivation is pharmacologically stimulated, lesioned Ss are able to resist hyperthermia by spreading the saliva. Further, given access to a lever which they can press in order to obtain exogenous coolant from a shower bath, Ss with lesions press more frequently with the higher, more stressful, ambient temperatures than with the more moderate ones, hence maintaining normothermia. Data suggest that rats with preoptic lesions do not lack the capacity for thermoregulation, but only an essential physiological tool, saliva. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On the elastic and thermodynamic properties of transition metal carbides

Values of the Debye temperature,θ _E, for a number of refractory carbides were calculated from elastic constant data and then compared with those of the Debye temperature,θ _D, as derived from low-temperatureC _P data. It is found that an apparent discrepancy existed in the literature between the values ofθ _E andθ _D for these carbides. However, when the same units are used, agreement of 10 pct or better between the values ofθ _E andθ _D is found for all the carbides with the exception of MoC_1/2. A discrepancy of 10 pct is reasonable based on an analysis of both the experimental and theoretical difficulties associated with the evaluation ofθ _E and θ_D for this class of materials. All the elastic constant data used were taken from the literature. Values ofC _P for TiC, HfC, and WC were measured in the present study from 1.5° to 15°K. These values in addition to the literature data were used in derivingθ _D values. A correlation of the bulk modulus with interatomic spacing is presented for these refractory carbides. Based on this correlation, the bonding forces responsible for the cohesion of this class of materials are discussed.     

Direct currect arc-plasma synthesis of tungsten carbides

Chemical reactions which occur in a thermal plasma between fine powders of tungsten and graphite and between powdered tungsten and methane have been studied. When using a commercial d.c. torch and a standard reactor design, the conversion to tungsten carbide is relatively poor. With a specially designed reactor operating in a transferred-arc mode, nearly complete conversion to carbide results when operating at the same power level and with methane as a reactant. Crystal structures and particle morphologies have been studied with electron microscopy and X-ray diffraction. Several initial stages of the particle-particle and particle-gas reactions have been determined. A number of interesting composite particles corresponding to intermediate reaction steps has been observed.     

Phosphorus concentration and solubility in dairy feces: variability and affecting factors

Recent data from phosphorus (P) feeding trials have demonstrated that P concentration in dairy feces is directly affected by P levels in diets and that farm P surpluses as well as potential environmental losses can be reduced through dietary manipulation. The current study was conducted to examine the variability of fecal P under farm conditions and to elucidate factors affecting the concentration and solubility of fecal P. Feed and fecal samples from >30 commercial dairies in the Northeast and Mid-Atlantic regions were analyzed. Dietary P concentrations ranged from 3.45 to 5.78 g/kg of feed DM (DM), and P determined in acid digests (TP) of feces from 5.84 to 12.84 g/kg of fecal DM. On average, 50% of fecal TP was water soluble; of the latter, 83% was inorganic (Pi). Across-farm variability (n=33) had CV averaging 18.9% for fecal TP and >20% for Pi and total P (Pt) in water extracts. Within-farm variability based on multiple samples per herd had the same magnitude as across-farm and was independent of sample numbers from individual farms (n=7 to 30). Of all fecal parameters determined, pH and DM had the lowest variability (CV <10%), water-soluble Pi, Pt, and Ca the highest (CV of 20 to 30%), and total P, Ca, and Mg determined by acid digests were intermediate (CV 10 to 20%). Water-soluble Pi concentrations determined in dried-ground fecal samples were lower than in wet samples. The drying-grinding process changes Pi solubility and the change is not linear. This study confirms that dietary P concentration is the dominating factor affecting fecal P excretion; however, Ca concentration, DIM, and fecal pH also made small, but statistically significant contributions, although some of the mechanisms remain to be thoroughly investigated.     

Removal of Dissolved Brown Algal Phlorotannins Using Insoluble Polyvinylpolypyrrolidone (PVPP)

Tannins, a large and diverse group of phenolic secondary metabolites, are common in terrestrial plants and marine brown algae. It is sometimes desirable to remove the tannins from plant or algal extracts, e.g., when isolating enzymes and nucleic acids, when using certain colorimetric methods to quantify the tannin content, or to create reliable controls when using tannins in experimental studies. Insoluble polyvinylpolypyrrolidone (PVPP) can be used to specifically remove tannins from solution. In the present study, we evaluated the effect of different factors (amount of PVPP, number of PVPP treatments, type of solvent, pH, and incubation time) on the PVPP removal of dissolved brown algal phlorotannins. Our results imply that there is a limited amount of phlorotannins that can bind to a given amount of PVPP, and that it is preferable to use low quantities of PVPP repeatedly, compared to using fewer treatments with a high amount of PVPP. Furthermore, we found no consistent effect on the removal of phlorotannins due to solvent type (acetone, methanol, distilled water or filtered seawater). There was a slight decrease in the amount of phlorotannins removed from extracts with increasing pH when repeatedly treated with PVPP. All phlorotannins were removed from extracts with pH 6.2, and 89% of the initial phlorotannin content was removed at pH 9.7. These results are compared with previous methodological studies on tannin removal with PVPP. Furthermore, the implications of phlorotannin removal in analytical and ecological investigations are discussed.     

Prenatally elevated physiological arousal interferes with perceptual learning in bobwhite quail (Colinus virginianus) embryos.

Neonatal studies suggest elevated arousal can negatively influence perceptual and cognitive processes during early development. The authors explored this issue during the prenatal period by pharmacologically elevating physiological arousal in bobwhite quail (Colinus virginianus) embryos during exposure to a maternal call, then assessing preference for the familiar call following hatching. Embryos receiving norepinephrine showed a prenatal elevation in heart rate and failed to demonstrate a preference for the familiar call following hatching. Embryos not receiving norepinephrine showed no elevation in heart rate and demonstrated a preference for the familiar call. These results indicate elevated arousal can interfere with perceptual learning during the prenatal period and provide additional evidence for an optimal window of arousal necessary to foster species-typical perceptual functioning during early development. (PsycINFO Database Record (c) 2010 APA, all rights reserved)