853 research outputs found
Self-assembling behaviour of Pt nanoparticles onto surface of TiO2 and their resulting photocatalytic activity
In the present study, self-assembling behaviour of guest nanoparticles (platinum) onto the surface of host support (titanium dioxide) during photodeposition process as a function of solution pH has been explored in detail by means of transmission electron microscope (TEM). The photocatalytic activity of the resulting bimetallic nanoassembly (Pt/TiO2) was evaluated by studying the degradation of two organic pollutants viz. triclopyr and methyl orange. Microscopic studies revealed that the deposition and/or distribution of Pt nanoparticles onto the surface of TiO2 were strongly guided by the ionization state of support which in turn was regulated by the solution pH of photodeposition process. A direct relationship between the solution pH of deposition process and the photocatalytic activity of resulting bimetallic catalyst has been observed. A mechanism based on the interparticle interaction between TiO2 and hydrolytic products of metal ions has been proposed for the differences in the photocatalytic activity of the resulting nanocomposite
Two-Dimensional General Rate Model of Liquid Chromatography Incorporating Finite Rates of Adsorption−Desorption Kinetics and Core−Shell Particles
A two-dimensional general rate model
of liquid chromatography incorporating
slow rates of adsorption–desorption kinetics, axial and radial
dispersions, and core–shell particles is formulated. Radial
concentration gradients are generated inside the column by considering
different regions of injection at the inlet. Analytical solutions
are obtained for a single-component linear model by simultaneously
utilizing the Laplace and Hankel transformations for the considered
two sets of boundary conditions. These linear solutions are useful
for simulating liquid-chromatographic columns with diluted or small-volume
samples and those in which radial concentration gradients are significant.
To gain further insight into the process, analytical moments are also
deduced from the Laplace–Hankel-domain solutions. For situations
of concentrated and large-volume samples, which are not solvable analytically,
formulation of nonlinear models is necessary. In this study, a semidiscrete,
high-resolution, finite-volume scheme is extended to approximate the
resulting nonlinear-model equations for multicomponent mixtures. The
performance of the column is analyzed by implementing a specified
criterion of performance. A few numerical case studies are conducted
to inspect the effects of the model parameters on the elution profiles
Remote Sensing Satellites Planning System
A Remote Sensing Satellites Planning system (RSSP) for satellite constellations is responsible for managing these satellites by assigning the imaging tasks to each satellite in the constellation such that the loads are balanced and the resources are well used. The proposed system can be used with heterogeneous constellations that consist of satellites whose different specifications, different orbits' types and/or different payload types. This problem is a combinatorial optimization NP-hard problem modeled in this paper as a Constraint Satisfaction Problem using the Constraint Programming Technique. The output plan is obtained using one of three objective functions (gain maximization, area maximization, and image quality maximization) using four search algorithms (simulated annealing, hill climbing, tabu search and late acceptance) and different planning horizons (one track, one day and one month)
Nano strain-amplifier: making ultra-sensitive piezoresistance in nanowires possible without the need of quantum and surface charge effects
This paper presents an innovative nano strain-amplifier employed to
significantly enhance the sensitivity of piezoresistive strain sensors.
Inspired from the dogbone structure, the nano strain-amplifier consists of a
nano thin frame released from the substrate, where nanowires were formed at the
centre of the frame. Analytical and numerical results indicated that a nano
strain-amplifier significantly increases the strain induced into a free
standing nanowire, resulting in a large change in their electrical conductance.
The proposed structure was demonstrated in p-type cubic silicon carbide
nanowires fabricated using a top down process. The experimental data showed
that the nano strain-amplifier can enhance the sensitivity of SiC strain
sensors at least 5.4 times larger than that of the conventional structures.
This result indicates the potential of the proposed strain-amplifier for
ultra-sensitive mechanical sensing applications.Comment: 4 pages, 5 figure
Antimicrobial activity of bBanana (Musa paradisiaca L.) peels against food borne pathogenic microbes
Banana (Musa paradisiaca L.) peels are usually considered as wastes and are
discarded during the processing, which eventually contribute to polluting the
environment. Hence, this study was aimed to evaluate the antimicrobial activity of two
different varieties of M. paradisiaca peels, i.e., Nangka (M. paradisiaca variety Nangka)
and Tanduk (M. paradisiaca variety Tanduk) with regard to generate safe and cheap
antimicrobials as well as address pollution related issues due to such wastes.
Antimicrobial study was carried out on the extracts using disc diffusion and broth
micro-dilution methods. The best activity through disc diffusion method for bacteria
and fungi was demonstrated by Tanduk peel’s ethanol and dichloromethane extracts
against S. aureus (30 mm) and C. krusei (10 mm), respectively. However, the least active
bacteria and fungi were found to be V. parahaemolyticus and C. albicans, respectively.
The minimum inhibitory concentration (MIC) values ranged from 6.25 to 100 mg/mL.
Tanduk peel’s ethanol extract exhibited the lowest MIC and minimum bactericidal
concentration (MBC) values against B. cepacia (6.25 mg/mL) whereas for fungi, Tanduk
peel’s dichloromethane extract exhibited lowest MIC and minimum fungicidal
concentration (MFC) values against C. albicans (25 mg/mL). The results of MBC or MFC
showed that some extracts were bactericidal or fungicidal while others were bacteriostatic
or fungistatic against certain microbes. Banana peel waste’s extracts could be potential
antimicrobial alternatives and may be effective to utilize as a natural source of
antimicrobial agent in pharmaceutical industries.
Key words: Musa paradisiaca L., Nangka, Tanduk, Antimicrobial activity, MIC, MBC, MFC
Magnetic and photocatalytic properties of nanocrystalline ZnMn<SUB>2</SUB>O<SUB>4</SUB>
The present study describes the synthesis of ZnMn2O4 nanoparticles with the spinel structure. These oxide nanoparticles are obtained from the decomposition of metal oxalate precursors synthesized by (a) the reverse micellar and (b) the coprecipitation methods. Our studies reveal that the shape, size and morphology of precursors and oxides vary significantly with the method of synthesis. The oxalate precursors prepared from the reverse micellar synthesis method were in the form of rods (micron size), whereas the coprecipitation method led to spherical nanoparticles of size, 40-50 nm. Decomposition of oxalate precursors at low temperature (~ 450°C) yielded phase pure ZnMn2O4 nanoparticles. The size of the nanoparticles of ZnMn2O4 obtained from reverse micellar method is relatively much smaller (20-30 nm) as compared to those made by the co-precipitation (40-50 nm) method. Magnetic studies of nanocrystalline ZnMn2O4 confirm antiferro-magnetic ordering in the broad range of ~ 150 K. The photocatalytic activity of ZnMn2O4 nanoparticles was evaluated using photo-oxidation of methyl orange dye under UV illumination and compared with nanocrystalline TiO2
Essential but partially redundant roles for POU4F1/Brn-3a and POU4F2/Brn-3b transcription factors in the developing heart
Congenital heart defects contribute to embryonic or neonatal lethality but due to the complexity of cardiac development, the molecular changes associated with such defects are not fully understood. Here, we report that transcription factors (TFs) Brn-3a (POU4F1) and Brn-3b (POU4F2) are important for normal cardiac development. Brn-3a directly represses Brn-3b promoter in cardiomyocytes and consequently Brn-3a knockout (KO) mutant hearts express increased Brn-3b mRNA during mid-gestation, which is linked to hyperplastic growth associated with elevated cyclin D1, a known Brn-3b target gene. However, during late gestation, Brn-3b can cooperate with p53 to enhance transcription of pro-apoptotic genes e.g. Bax, thereby increasing apoptosis and contribute to morphological defects such as non-compaction, ventricular wall/septal thinning and increased crypts/fissures, which may cause lethality of Brn-3a KO mutants soon after birth. Despite this, early embryonic lethality in e9.5 double KO (Brn-3a(-/-) : Brn-3b(-/-)) mutants indicate essential functions with partial redundancy during early embryogenesis. High conservation between mammals and zebrafish (ZF) Brn-3b (87%) or Brn-3a (76%) facilitated use of ZF embryos to study potential roles in developing heart. Double morphant embryos targeted with morpholino oligonucleotides to both TFs develop significant cardiac defects (looping abnormalities and valve defects) suggesting essential roles for Brn-3a and Brn-3b in developing hearts
A high-resolution structure of the EF-hand domain of human polycystin-2.
Autosomal dominant polycystic kidney disease (ADPKD) affects over 1:1000 of the worldwide population and is caused by mutations in two genes, PKD1 and PKD2. PKD2 encodes a 968-amino acid membrane spanning protein, Polycystin-2 (PC-2), which is a member of the TRP ion channel family. The C-terminal cytoplasmic tail contains an EF-hand motif followed by a short coiled-coil domain. We have determined the structure of the EF-hand region of PC-2 using NMR spectroscopy. The use of different boundaries, compared with those used in previous studies, have enabled us to determine a high resolution structure and show that the EF hand motif forms a standard calcium-binding pocket. The affinity of this pocket for calcium has been measured and mutants that both decrease and increase its affinity for the metal ion have been created
Nanoparticles in the environment: assessment using the causal diagram approach
Nanoparticles (NPs) cause concern for health and safety as their impact on the environment and humans is not known. Relatively few studies have investigated the toxicological and environmental effects of exposure to naturally occurring NPs (NNPs) and man-made or engineered NPs (ENPs) that are known to have a wide variety of effects once taken up into an organism
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