Synthesis and characterization of citric acid-based pH-sensitive biopolymeric hydrogels

Biocompatible hydrogels based on citric acid (CA) with varying glycol unit, viz., ethylene glycol (EG), diethylene glycol and triethylene glycol were prepared along with acrylic acid. The formations of various hydrogels were confirmed using spectral techniques such as FT-IR and ¹H NMR. Thermal stability (thermogravimetric analysis, DTA and differential scanning calorimetry) and morphology (SEM) of the synthesized hydrogels were investigated. Swelling studies of hydrogels at various pH values ranging from 4.0 to 10.0 were also investigated. The results of swelling studies show that the percentage of swelling is comparatively higher at higher pH than lower pH. Swelling equilibrium for various hydrogels was also found. Increased composition of CA in hydrogels at different pH values of 4.0, 6.0, 7.4, 8.0 and 10.0 enhanced the swelling equilibrium.     

Mixed‐cation LiCa‐LSX zeolite with minimum lithium for air separation

The aim of this work was to reduce/minimize Li in Li‐LSX by replacing the 70% Li⁺ cations in Li‐LSX that are bonded to the interior or inaccessible sites which are not used for adsorption. Thus, mixed‐cation LiCa‐LSX containing minimum lithium were prepared by exchanging small fractions of Li⁺ into Ca‐LSX, followed by dehydration under mild conditions to avoid migration/equilibration of Li cations. Comparisons of adsorption isotherms of N₂/O₂ and heats of adsorption for the LiCa‐LSX samples with that for pure‐cation Li‐LSX and Ca‐LSX provided strong evidence that significant amounts of these Li cations indeed remained on the exposed sites (SIII). The mixed‐cation LiCa‐LSX samples were compared against the pure‐cation Ca‐LSX and Li‐LSX based on their performance for oxygen production by PSA, via model simulation. The results showed that the mixed‐cation LiCa‐LSX samples yielded significantly higher O₂ product productivities at the same product purity and recovery than their pure‐cation precursor (Ca‐LSX). © 2017 American Institute of Chemical Engineers AIChE J, 64: 406–415, 2018     

[Carboxyl‐11C]Labelling of Four High‐Affinity cPLA2α Inhibitors and Their Evaluation as Radioligands in Mice by Positron Emission Tomography

Cytosolic phospholipase A2α (cPLA2α) may play a critical role in neuropsychiatric and neurodegenerative disorders associated with oxidative stress and neuroinflammation. An effective PET radioligand for imaging cPLA2α in living brain might prove useful for biomedical research, especially on neuroinflammation. We selected four high‐affinity (IC₅₀ 2.1–12 nm ) indole‐5‐carboxylic acid‐based inhibitors of cPLA2α, namely 3‐isobutyryl‐1‐(2‐oxo‐3‐(4‐phenoxyphenoxy)propyl)‐1H‐indole‐5‐carboxylic acid ( 1 ); 3‐acetyl‐1‐(2‐oxo‐3‐(4‐(4‐(trifluoromethyl)phenoxy)phenoxy)propyl)‐1H‐indole‐5‐carboxylic acid ( 2 ); 3‐(3‐methyl‐1,2,4‐oxadiazol‐5‐yl)‐1‐(2‐oxo‐3‐(4‐phenoxyphenoxy)propyl)‐1H‐indole‐5‐carboxylic acid ( 3 ); and 3‐(3‐methyl‐1,2,4‐oxadiazol‐5‐yl)‐1‐(3‐(4‐octylphenoxy)‐2‐oxopropyl)‐1H‐indole‐5‐carboxylic acid ( 4 ), for labelling in carboxyl position with carbon‐11 (t_1/2=20.4 min) to provide candidate PET radioligands for imaging brain cPLA2α. Compounds [¹¹C] 1 – 4 were obtained for intravenous injection in adequate overall yields (1.1–5.5 %) from cyclotron‐produced [¹¹C]carbon dioxide and with moderate molar activities (70–141 GBq μmol^?1) through the use of Pd⁰‐mediated [¹¹C]carbon monoxide insertion on iodo precursors. Measured logD_7.4 values were within a narrow moderate range (1.9–2.4). After intravenous injection of [¹¹C] 1 – 4 in mice, radioactivity uptakes in brain peaked at low values (≤0.8 SUV) and decreased by about 90 % over 15 min. Pretreatments of the mice with high doses of the corresponding non‐radioactive ligands did not alter brain time–activity curves. Brain uptakes of radioactivity after administration of [¹¹C] 1 to wild‐type and P‐gp/BCRP dual knock‐out mice were similar (peak 0.4 vs. 0.5 SUV), indicating that [¹¹C] 1 and others in this structural class, are not substrates for efflux transporters.     

Sudden incapacitation: USAF experience, 1970-80

During the period 1970-80, there were reported 146 cases of in-flight sudden incapacitation in the USAF. Of these, 62 involved pilots, 14 were navigators, and 70 were student pilots. The etiologies of sudden incapacitation included illness without loss of consciousness, loss of consciousness, spatial disorientation, and improper M-1 maneuver. Each of these categories is analyzed with emphasis upon prevention, for example, not flying with symptomatic preexisting disease, continued emphasis upon spatial disorientation training, and correct performance of the M-1 maneuver. Based upon the data, conclusions and recommendations are suggested to minimize the risk of episodes of in-flight sudden incapacitation.     

Comparison of data gap-filling methods for Landsat ETM+ SLC-off imagery for monitoring forest degradation in a semi-deciduous tropical forest in Mexico

A number of methods to overcome the 2003 failure of the Landsat 7 Enhanced Thematic Mapper (ETM+) scan-line corrector (SLC) are compared in this article in a forest-monitoring application in the Yucatan Peninsula, Mexico. The objective of this comparison is to determine the best approach to accomplish SLC-off image gap-filling for the particular landscape in this region, and thereby provide continuity in the Landsat data sensor archive for forest-monitoring purposes. Four methods were tested: (1) local linear histogram matching (LLHM); (2) neighbourhood similar pixel interpolator (NSPI); (3) geostatistical neighbourhood similar pixel interpolator (GNSPI); and (4) weighted linear regression (WLR). All methods generated reasonable SLC-off gap-filling data that were visually consistent and could be employed in subsequent digital image analysis. Overall accuracy, kappa coefficients (κ), and quantity and allocation disagreement indices were used to evaluate unsupervised Iterative Self-Organizing Data Analysis (ISODATA) land-cover classification maps. In addition, Pearson correlation coefficients (r) and root mean squares of the error (RMSEs) were employed for estimates agreement with fractional land cover. The best results visually (overall accuracy > 85%, κ < 9%, quantity disagreement index < 5.5%, and allocation disagreement index < 12.5%) and statistically (r > 0.84 and RMSE < 7%) were obtained from the GNSPI method. These results suggest that the GNSPI method is suitable for routine use in reconstructing the imagery stack of Landsat ETM+ SLC-off gap-filled data for use in forest-monitoring applications in this type of heterogeneous landscape.     

Classification of soil‐ and bedrock‐dominated landslides in British Columbia using segmentation of satellite imagery and DEM data

Landsat Enhanced Thematic Mapper Plus (ETM+) and digital elevation model (DEM) data were used in a segmentation and classification procedure to classify slide scars in the northern Cascade Mountains of British Columbia, Canada. The area was stratified into features that were likely candidates for landsliding and those that were not; shape criteria were applied that were used to identify objects as slides; and finally, rules based on shape, texture and neighbouring features were used to separate soil‐dominated slides from bedrock‐dominated slides, an important distinction in mass movement inventories and for applied and theoretical studies. Approximately 65% classification accuracy was obtained. Slopes experiencing multiple failures, which can create less distinct features on the ground, may have contributed to some of the error in classification.     

Performance models for network processor design

To provide a variety of new and advanced communications services, computer networks are required to perform increasingly complex packet processing. This processing typically takes place on network routers and their associated components. An increasingly central component in router design is a chip-multiprocessor (CMP) referred to as "network processor" or NP. In addition to multiple processors, NPs have multiple forms of on-chip memory, various network and off-chip memory interfaces, and other specialized logic components such as CAMs (content addressable memories). The design space for NPs (e.g., number of processors, caches, cache sizes, etc.) is large due to the diverse workload, application requirements, and system characteristics. System design constraints relate to the maximum chip area and the power consumption that are permissible while achieving defined line rates and executing required packet functions. In this paper, an analytic performance model that captures the processing performance, chip area, and power consumption for a prototypical NP is developed and used to provide quantitative insights into system design trade offs. The model, parameterized with a networking application benchmark, provides the basis for the design of a scalable, high-performance network processor and presents insights into how best to configure the numerous design elements associated with NPs.     

Improving fairness in IEEE 802.11 networks using MAC layer opportunistic retransmission

This paper introduces DAFMAC (Decode And Forward MAC), a scalable opportunistic cooperative retransmission enhancement for the IEEE 802.11 MAC protocol which operates without the need for additional explicit control signalling. Distributed opportunistic retransmission algorithms rely on selecting a single suitable relay without direct arbitration between nodes. Simulations show that DAFMAC offers a significant improvement in fairness for both throughput and jitter, giving multiple parallel data flows a more equal opportunity to utilise the channel. DAFMAC cooperative retransmissions are shown to reduce node energy consumption for a given throughput. Further, the DAFMAC relay selection algorithm is shown to scale very well in terms of complexity and memory requirements in comparison to other cooperative retransmission schemes.