Catalytic performance of carbonaceous materials in the esterification of succinic acid

Mesoporous carbonaceous materials have outstanding potential in many different applications such as adsorption, medicine and catalysis. We have recently reported the synthesis of a new form of mesoporous carbon, named Starbon((R)), obtained after low temperature carbonization of expanded starch. Such starch-derived mesoporous materials have several tunable properties including surface energies (ranging from hydrophilic to hydrophobic surfaces), which can be easily controlled by the degree of carbonization (from 200 to 700 degrees C). Due to the diversity of surface functional groups, Starbons((R)) can be easily chemically modified. Treatment of Starbon((R)) materials with sulfuric acid gave a solid acid that has promising properties as heterogeneous catalyst. Comparative catalytic studies with some other similar commercial carbonaceous materials such as DARCO((R)) and NORIT (R), as well as phosphorous-containing microporous carbons, are reported. (c) 2008 Elsevier B.V. All rights reserved

P-cymenesulphonyl chloride : A bio-based activating group and protecting group for greener organic synthesis

A bio-derived protecting/activating group has been synthesized by introducing a sulphonyl chloride group to the aromatic ring of p-cymene derived from citrus peel waste. The resulting p-cymenesulphonyl chloride was evaluated as an activating group by reacting with 1-octanol, 2-octanol, phenol and piperidine, and further reactions of the activated alcohols. The comparison to tosyl chloride demonstrates that the bio-based alternative can be effectively utilized as a direct replacement for the current fossil derived equivalent

Safety of guselkumab in hepatitis B virus infection

Reactivation of hepatitis B virus (HBV) following the use of TNF antagonists has been reported and is a contraindication to use of these medications. Although the risk of reactivation of HBV during use of ustekinumab and secukinumab is low in patients with only HBV core antibody positivity, the risk is substantial in patients with chronic HBV infection. Less information is available regarding the use of pure IL-23 antagonists. Herein we discuss the successful treatment with guselkumab of a patient with HBV core antibody positivity, without evidence of HBV reactivation or other liver complications

Using lidar remote sensing and support vector machines to classify fire disturbance legacies in a Florida oak scrub landscape

Background/Question/Methods

Ecologists have long emphasized the reciprocal interactions between spatial pattern and ecological processes in the creation of landscape mosaics. While an enormous amount of recent research has focused on the quantification of spatial patterns, efforts to infer process from pattern have been hindered by the presence of multi-scale, often confounding, drivers of pattern in many landscapes. At the mesoscale, Holling’s extended keystone hypothesis posits that spatially contagious disturbances such as fire are the dominant pattern-generating processes. To test this hypothesis, we used fire history data and discrete, small-footprint lidar remote sensing acquired over a 22 sq. km landscape of oak scrub in the Kennedy Space Center/Merritt Island National Wildlife Refuge area on the east-central coast of Florida. We binned the lidar return data into 1 m vertical height intervals for each 5 m x 5 m horizontal cell. Since community structure tends to recover by 7 years post-fire, we tested for significant differences between recently-burned (< 7 years) and unburned (≥ 7 years) patches with multivariate analysis of variance. To predict the burn status of each cell, we then used distribution-free, nonlinear support vector machine (SVM) classifiers, which have proven to be highly accurate for complex pattern recognition problems.

Results/Conclusions 

We detected statistically significant differences in vegetation structure between burned and unburned patches for all of the dominant land cover types (upland non-forested, upland forested, wetland hardwood forest, and non-forested wetlands) in the study area. Initially, we obtained a predicted error rate of approximately 34% from the SVM classifier; by averaging the binned lidar data over a moving window of increasing size, however, we achieved substantial reductions in the predicted error rate for the SVM classifier. The optimal window size of 100 m x 100 m yielded a predicted misclassification rate of approximately 3%, an order of magnitude lower than the error rate obtained on the same data using a logistic regression classifier. These results suggest that, as predicted by the extended keystone hypothesis, fire disturbance is a dominant pattern-generating process at the patch scale in this oak scrub landscape. Furthermore, these results indicate that it is possible to use vertical vegetation structure, as represented by the binned lidar data, to predict burn status with a high level of accuracy. While our study employed a simple binary classification scheme, future research will focus on using SVM regression techniques to predict burn status with finer-grained classes of time since fire

Modeling and performance of a 100-element pHEMT grid amplifier

A 100-element hybrid grid amplifier has been fabricated, The active devices in the grid are custom-made pseudomorphic high electron mobility transistor (pHEMT) differential-pair chips. We present a model for gain analysis and compare measurements with theory. The grid includes stabilizing resistors in the gate. Measurements show the grid has a peak gain of 10 db when tuned for 10 GHz and a gain of 12 dB when tuned for 9 GHz. The maximum 3-dB bandwidth is 15% at 9 GHz. The minimum noise figure is 3 dB. The maximum saturated output power is 3.7 W, with a peak power-added efficiency of 12%. These results area significant improvement over previous grid amplifiers based on heterojunction bipolar transistors (HBT's)

Accelerometer-based physical activity levels differ between week and weekend ways in British preschool children

Participation in physical activity (PA) is fundamental to children’s future health. Studies examining the temporal pattern of PA between weekdays and weekends in British preschool children are lacking. Therefore, the aim of this study was to compare PA levels between week and weekend days for UK preschool children, using objective measurements. One hundred and eighty-five preschool children (99 boys, 86 girls, aged 4–5 years), from central England wore a triaxial accelerometer (GENEActiv) for 4 days to determine PA. The time (min) and percentage (%) of time spent in light, moderate and vigorous PA (MVPA) was determined using specific cut-points for counts per minute related to 3–5 year olds. Of the sample, none of the children met the UK recommended 180 min or more of PA per day. A significant difference (P < 0.05) was observed between the amount of time that preschool children spent in sedentary behaviours on weekdays (91.9%) compared to weekend days (96.9%). During weekdays and weekend days, 6.3% and 2.0% of time was spent in MVPA, respectively. Therefore, a substantial proportion of British preschool children’s day is spent in sedentary behaviours, with less MVPA accrued during the weekend. Regular engagement during the weekdays provides opportunities to accrue PA, which may not be present on weekend days.N/

The Size of the Radio-Emitting Region in Low-luminosity Active Galactic Nuclei

We have used the VLA to study radio variability among a sample of 18 low luminosity active galactic nuclei (LLAGNs), on time scales of a few hours to 10 days. The goal was to measure or limit the sizes of the LLAGN radio-emitting regions, in order to use the size measurements as input to models of the radio emission mechanisms in LLAGNs. We detect variability on typical time scales of a few days, at a confidence level of 99%, in half of the target galaxies. Either variability that is intrinsic to the radio emitting regions, or that is caused by scintillation in the Galactic interstellar medium, is consistent with the data. For either interpretation, the brightness temperature of the emission is below the inverse-Compton limit for all of our LLAGNs, and has a mean value of about 1E10 K. The variability measurements plus VLBI upper limits imply that the typical angular size of the LLAGN radio cores at 8.5 GHz is 0.2 milliarcseconds, plus or minus a factor of two. The ~ 1E10 K brightness temperature strongly suggests that a population of high-energy nonthermal electrons must be present, in addition to a hypothesized thermal population in an accretion flow, in order to produce the observed radio emission.Comment: 61 pages, 17 figures, 10 tables. Accepted for publication in the Astrophysical Journa