FAST

We propose Frontier Allocation Synchronized by Token passing (FAST), a distributed algorithm for online terrain coverage using multiple mobile robots, ensuring mutually exclusive selection of frontier cells. Many existing approaches cover the terrain in an irregular fashion, without considering the usability of the already covered region. For instance, in the task of floor cleaning in an office building, these approaches do not guarantee the cleanliness of large unbroken areas until a majority of the task is complete. FAST on the other hand, incrementally traverses the terrain generating structured trajectories for each robot. Following a structured trajectory for coverage path planning is proven to be a very powerful approach in literature. This renders large portions of the terrain usable even before the completion of the coverage task. The novel map representation techniques used in FAST render it scalable to large terrains, without affecting the volume of communication among robots. Moreover, the distributed nature of FAST allows incorporation of fault-tolerance mechanisms. Empirical investigations on maps of varied complexities and sizes both in simulation and on an experimental test-bed demonstrate that the proposed algorithm performs better than some of the benchmark approaches in terms of coverage completion time and less redundant coverage.     

Magnetic and dielectric studies of barium hexaferrite (BaFe 12 O 19 ) ceramic synthesized by chemical route

Barium hexaferrite BaFe12O19 (BHF) ceramic was synthesized by chemical route on sintering at 1050 °C for 12 h. The synthesized material was characterized by XRD, SEM, AFM and TEM analysis. Metal oxide stretching frequencies corresponding to Fe-O, Ba-O, and Fe-O-Fe bands are confirmed by FTIR studies. The hexagonal nature of the BHF ceramic was confirmed by TEM analysis and Rietveld refinement with space group P63/mmc. The particle size observed by TEM is 175 nm. The root means square and average roughness were found to be 61.048 nm and 44.025 nm respectively. The M-T and M-H hysteresis loop indicates temperature dependent ferromagnetic behavior of BHF ceramic. The temperature and frequency dependent dielectric properties were explained by Maxwell-Wagner theory. The value of dielectric constant (ε′) for BHF ceramic was found to be 22× 103 at 100 Hz and 483 K.     

Peptide‐Based Fluorescent Probes for Deacetylase and Decrotonylase Activity: Toward a General Platform for Real‐Time Detection of Lysine Deacylation

Histone deacetylases regulate the acetylation levels of numerous proteins and play key roles in physiological processes and disease states. In addition to acetyl groups, deacetylases can remove other acyl modifications on lysines, the roles and regulation of which are far less understood. A peptide‐based fluorescent probe for single‐reagent, real‐time detection of deacetylase activity that can be readily adapted for probing broader lysine deacylation, including decrotonylation, is reported. Following cleavage of the lysine modification, the probe undergoes rapid intramolecular imine formation that results in marked optical changes, thus enabling convenient detection of deacylase activity with good statistical Z′ factors for both absorption and fluorescence modalities. The peptide‐based design offers broader isozyme scope than that of small‐molecule analogues, and is suitable for probing both metal‐ and nicotinamide adenine dinucleotide (NAD⁺)‐dependent deacetylases. With an effective sirtuin activity assay in hand, it is demonstrated that iron chelation by Sirtinol, a commonly employed sirtuin inhibitor, results in an enhancement in the inhibitory activity of the compound that may affect its performance in vivo.     

The Impact of Sequential Fluorination of π‐Conjugated Polymers on Charge Generation in All‐Polymer Solar Cells

The performance of all‐polymer solar cells (all‐PSCs) is often limited by the poor exciton dissociation process. Here, the design of a series of polymer donors ( P1 – P3 ) with different numbers of fluorine atoms on their backbone is presented and the influence of fluorination on charge generation in all‐PSCs is investigated. Sequential fluorination of the polymer backbones increases the dipole moment difference between the ground and excited states (Δµ_ge) from P1 (18.40 D) to P2 (25.11 D) and to P3 (28.47 D). The large Δµ_ge of P3 leads to efficient exciton dissociation with greatly suppressed charge recombination in P3 ‐based all‐PSCs. Additionally, the fluorination lowers the highest occupied molecular orbital energy level of P3 and P2 , leading to higher open‐circuit voltage (V_OC). The power conversion efficiency of the P3 ‐based all‐PSCs (6.42%) outperforms those of the P2 and P1 (5.00% and 2.65%)‐based devices. The reduced charge recombination and the enhanced polymer exciton lifetime in P3 ‐based all‐PSCs are confirmed by the measurements of light‐intensity dependent short‐circuit current density (J_SC) and V_OC, and time‐resolved photoluminescence. The results provide reciprocal understanding of the charge generation process associated with Δµ_ge in all‐PSCs and suggest an effective strategy for designing π‐conjugated polymers for high performance all‐PSCs.     

Online model-based diagnosis to support autonomous operation of an advanced life support system

This article describes methods for online model-based diagnosis of subsystems of the advanced life support system (ALS). The diagnosis methodology is tailored to detect, isolate, and identify faults in components of the system quickly so that fault-adaptive control techniques can be applied to maintain system operation without interruption. We describe the components of our hybrid modeling scheme and the diagnosis methodology, and then demonstrate the effectiveness of this methodology by building a detailed model of the reverse osmosis (RO) system of the water recovery system (WRS) of the ALS. This model is validated with real data collected from an experimental testbed at NASA JSC. A number of diagnosis experiments run on simulated faulty data are presented and the results are discussed.     

Comparison and validation of drug loading parameters of PEGylated nanoparticles purified by a diafiltration centrifugal device and tangential flow filtration

This article describes drug loading validation of nanoparticles. Ultracentrifugation was avoided because of problems arising from small-sized particles. Ultrafiltration was adopted in two different modes followed by monitoring of polyvinyl alcohol (PVA), dextran sulfate (DS), and loperamide HCl contents. Diafiltration centrifugation removed all PVA at the fourth cycle and provided significantly (p = .000, .017) higher drug loading values compared with tangential flow filtration (TFF). This was due to residual PVA associated with the nanoparticles. TFF enabled satisfactory dry weight recovery (101.66 +/- 4.45%, n = 3) of nanoparticles during extended purification. Indirect drug loading (from the purification curve) was not significantly different (p = .450, .487) to the direct drug loading values. Encapsulation parameters were obtained from the purification curve once quantitative estimation of the all formulation components was established.     

Stiffness Matrices of Isoparametric Four-Node Finite Elements by Exact Analytical Integration

Explicit algebraic expressions needed to compute element stiffness matrices using procedural (FORTRAN) and object oriented (C++) computer programs are presented. Numerical illustrations for a convex quadrilateral and a triangle with a side node are included. The wide controversy due to conventional element level approximate numerical quadrature within the computational square domain in η and ξ coordinates is completely resolved here by the closed form analytical integration within the physical element, in x and y coordinates.     

Studies on dechlorination of DDT (1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane) using magnesium/palladium bimetallic system

The aim of our investigation was to compare the rates of dechlorination of DDT using Mg0/Pd4+ system in two different reaction phases, namely, water-acetone and 0.05% biosurfactant in water. Since palladium is expensive and its toxicity effects are not well known we also examined the reuse efficiency of Pd0 immobilized on alumina for dechlorinating DDT. Studies on the dechlorination of DDT in water-acetone (1:1, v/v) and 0.05% biosurfactant phases revealed that the reaction followed second order kinetics and rate of reaction is dependent upon both initial concentrations of the target compound and Mg0/Pd4+. The presence of acid enhanced the rate of reaction by providing protons and preventing passivation of metal that occurs due to deposition of magnesium hydroxide. GC-MS analyses revealed the formation of completely dechlorinated hydrocarbon skeleton of DDT namely, diphenylethane (DPE), as the end product in both reaction phases (water-acetone and 0.05% biosurfactant in water) thereby implying the removal of all five chlorine atoms (three alkyl and two aryl) of DDT. The optimum ratio of water and acetone to facilitate successful dechlorination reaction was found to be 9:1. Results suggested that salt form (K2PdCl6) of palladium had higher potential to dechlorinate DDT as compared to pellet (Pd0-alumina) form (efficiencies of 95 and 36%, respectively, for 100 ppm initial concentration of DDT). We noted that Pd0-alumina pellets could be reused at least four times for successful dechlorination of DDT provided Mg0 granules are present in sufficient quantity. Technical grade DDT (50 ppm) containing significant amounts of DDD was dechlorinated almost completely by the Mg0/Pd4+ (10mg/0.2mg/ml) within 1h in water-biosurfactant phase. Our studies reveal that Mg/Pd system is a promising option due to its high reactivity and its ability to achieve complete dechlorination of DDT. This bimetallic system may be useful for designing indigenous permeable barriers or reactors for the treatment of DDT contaminated water.     

Ultra-thin crystalline films of CdSe and CuSe formed at the organic-aqueous interface

Two-dimensional nanostructures in the form of ultra-thin crystalline films of CdSe and CuSe have been prepared at the organic-aqueous interface by reacting toluene solutions of metal cupferronates with an aqueous solution of N,N-dimethyl selenourea. The films have been examined using electron microscopy and optical spectroscopy. At lower concentrations of the reacting species, the CdSe films formed at the toluene-water interface at approximately 30 degrees C consisted mostly of nanocrystals. With increase in concentration as well as temperature, the interface reaction yielded thicker films which are mostly single-crystalline. We have studied the time-dependent growth of the CdSe film at the interface using UV-visible absorption spectroscopy. Ultra-thin films of CuSe formed at the toluene-water interface are generally single-crystalline.     

Development of Apparels from Silk Waste and Pineapple Leaf Fiber

The degummed mulberry silk waste and eri silk waste were blended with degummed and bleached pineapple leaf fibers (PALF) at fiber stage in different proportions, and spun into yarn in a jute spinning system. The 90-tex blended yarn thus developed was analyzed for different physico-mechanical properties. Properties of fabric developed in a traditional handloom using 2/40-s cotton as warp and blended yarn as weft were also analyzed. The quality parameters, viz., tensile property, crease recovery, fabric cover, stiffness, drape, and thickness of the developed fabric, met essential apparel requirements. A comparative subjective evaluation of the fabric quality, viz., aesthetic appearance, luster, and texture, was made with the help of a group of people from different age, educational, and occupational background to examine its marketability; all respondents felt that appearance of PALF with silk waste was excellent. Texture and luster were found to be from medium to moderate. About 95% of respondents felt that fabric was crispy.