Polymer nanocomposite‐based shielding against diagnostic X‐rays

Lead is commonly used in medical radiology departments as a shielding material. Lead‐based protective materials are also used by clinical personnel during X‐ray image‐guided interventional radiology (IVR) procedures. However, lead is extremely toxic and prolonged exposure to it can result in serious health concerns. Polymer composites, on the other hand, can be designed to be lead‐free in addition to being lightweight, conformable, cost effective, and potentially capable of significantly attenuating X‐rays. Nanomaterials have unique material properties that can be exploited to develop novel lead‐free radiation‐protection materials. In this study, polydimethylsiloxane (PDMS) nanocomposites were fabricated using different weight percentages (wt %) of bismuth oxide (BO) nanopowder. The attenuation properties of the nanocomposites were characterized using diagnostic X‐ray energies from 40 to 150 kV tube potential and were compared to the attenuation characteristics of 0.25‐mm‐thick pure lead sheet. The PDMS/BO nanocomposite (44.44 wt% of BO and 3.73‐mm thick) was capable of attenuating all the scattered X‐rays generated at a tube potential of 60 kV, which is the beam energy commonly employed in IVR. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2013     

Impact of pixel size on mapping surface water in subsolar imagery

We observed surface water in a wetland, imaging in the subsolar or specular direction the exceptionally bright specular reflection of sunlight at a ground resolution of 0.3 m. We then simulated ground resolutions between 1.7 m and 1.2 km through aggregation of the 0.3 m pixels. Contrary to the expectations of some of our colleagues in the wetlands community, for these data, the accuracy of spectral mixture analysis (SMA) estimates of surface water increases as pixel ground footprint size increases. Our results suggest that regional to global scale assessments of flooded landscapes and wetlands that do not involve issues requiring 1 m resolution per se may be addressed with acceptable accuracy by applying SMA techniques to low resolution imagery. Our results indicate within-pixel estimates of surface water area derived from data measured by subsolar viewing sensors with large ground pixel footprints, such as satellite POLarization and Directionality of Earth Radiance (POLDER) data, may be highly accurate under strong surface wind conditions.     

Designing a Fault-tolerant Fully-Chained Combining Switches Multi-stage Interconnection Network with Disjoint Paths

Multi-stage Interconnection Networks (MINs) are designed to achieve fault-tolerance and collision solving by providing a set of disjoint paths. Ching-Wen Chen and Chung-Ping Chung had proposed a fault-tolerant network called Combining Switches Multi-stage Interconnection Network (CSMIN) and an inaccurate algorithm that provided two correct disjoint paths only for some source-destination pairs. This paper provides a more comprehensive and accurate algorithm that always generate correct routing-tags for two disjoint paths for every source-destination pair in the CSMIN. The 1-fault tolerant CSMIN causes the two disjoint paths to have regular distances at each stage. Moreover, our algorithm backtracks a packet to the previous stage and takes the other disjoint path in the event of a fault or a collision in the network. Furthermore, to eliminate the backtracking penalties of CSMIN, we propose a new design called Fault-tolerant Fully-Chained Combining Switches Multi-stage Interconnection Network (FCSMIN). It has similar characteristics of 1-fault tolerance and two disjoint paths between any source-destination pair, but it can tolerate only one link or switch fault at each stage without backtracking. Our simulation and comparative analysis result shows that FCSMIN has added advantages of destination-tag routing, lower hardware costs, strong reroutability, lower preprocessing overhead, and higher fault-tolerance power in comparison to CSMIN.     

Insights into the folding pathway of the Engrailed Homeodomain protein using replica exchange molecular dynamics simulations

Protein folding studies were carried out by performing microsecond time scale simulations on the ultrafast/fast folding protein Engrailed Homeodomain (EnHD) from Drosophila melanogaster. It is a three-helix bundle protein consisting of 54 residues (PDB ID: 1ENH). The positions of the helices are 8-20 (Helix I), 26-36 (Helix II) and 40-53 (Helix III). The second and third helices together form a Helix-Turn-Helix (HTH) motif which belongs to the family of DNA binding proteins. The molecular dynamics (MD) simulations were performed using replica exchange molecular dynamics (REMD). REMD is a method that involves simulating a protein at different temperatures and performing exchanges at regular time intervals. These exchanges were accepted or rejected based on the Metropolis criterion. REMD was performed using the AMBER FF03 force field with the generalised Born solvation model for the temperature range 286-373 K involving 30 replicas. The extended conformation of the protein was used as the starting structure. A simulation of 600 ns per replica was performed resulting in an overall simulation time of 18 μs. The protein was seen to fold close to the native state with backbone root mean square deviation (RMSD) of 3.16 ?. In this low RMSD structure, the Helix I was partially formed with a backbone RMSD of 3.37 ? while HTH motif had an RMSD of 1.81 ?. Analysis suggests that EnHD folds to its native structure via an intermediate in which the HTH motif is formed. The secondary structure development occurs first followed by tertiary packing. The results were in good agreement with the experimental findings.     

Number‐Resolved Single‐Photon Detection with Ultralow Noise van der Waals Hybrid

Van der Waals hybrids of graphene and transition metal dichalcogenides exhibit an extremely large response to optical excitation, yet counting of photons with single‐photon resolution is not achieved. Here, a dual‐gated bilayer graphene (BLG) and molybdenum disulphide (MoS₂) hybrid are demonstrated, where opening a band gap in the BLG allows extremely low channel (receiver) noise and large optical gain (≈10¹⁰) simultaneously. The resulting device is capable of unambiguous determination of the Poissonian emission statistics of an optical source with single‐photon resolution at an operating temperature of 80 K, dark count rate 0.07 Hz, and linear dynamic range of ≈40 dB. Single‐shot number‐resolved single‐photon detection with van der Waals heterostructures may impact multiple technologies, including the linear optical quantum computation.     

Isolation and Profiling of Circulating Tumor‐Associated Exosomes Using Extracellular Vesicular Lipid–Protein Binding Affinity Based Microfluidic Device

Extracellular vesicles (EVs) are emerging as a potential diagnostic test for cancer. Owing to the recent advances in microfluidics, on‐chip EV isolation is showing promise with respect to improved recovery rates, smaller necessary sample volumes, and shorter processing times than ultracentrifugation. Immunoaffinity‐based microfluidic EV isolation using anti‐CD63 is widely used; however, anti‐CD63 is not specific to cancer‐EVs, and some cancers secrete EVs with low expression of CD63. Alternatively, phosphatidylserine (PS), usually expressed in the inner leaflet of the lipid bilayer of the cells, is shown to be expressed on the outer surface of cancer‐associated EVs. A new exosome isolation microfluidic device (^newExoChip), conjugated with a PS‐specific protein, to isolate cancer‐associated exosomes from plasma, is presented. The device achieves 90% capture efficiency for cancer cell exosomes compared to 38% for healthy exosomes and isolates 35% more A549‐derived exosomes than an anti‐CD63‐conjugated device. Immobilized exosomes are then easily released using Ca²⁺ chelation. The recovered exosomes from clinical samples are characterized by electron microscopy and western‐blot analysis, revealing exosomal shapes and exosomal protein expressions. The ^newExoChip facilitates the isolation of a specific subset of exosomes, allowing the exploration of the undiscovered roles of exosomes in cancer progression and metastasis.     

Processing of Functionalized and Pristine Carbon Nanotube Epoxy Composites with Silane-Treated Glass Fiber

In this work, an attempt has been made to study the bonding between the silane coupling agents and the glass fiber (GF) surface. The mechanical properties of the composites so obtained have been specifically analyzed. It has been experimentally found that epoxy silane (ES)-treated GF mat in a neat epoxy matrix showed considerable improvement compared to amino silane (AS)-treated GF. The effect of heat treatment on GF has also been looked into. Moreover, a new processing technique has been explored, which involves the use of amino functionalized nanotube (ACNT) and pristine nanotube (PCNT), homogeneously and uniformly dispersed in an epoxy matrix. Additionally, the effect of ES- and AS-treated GF in the presence of PCNTs and ACNTs has been studied and it has been found that AS shows strong interfacial adhesion in the ACNT matrix, whereas ES shows improved mechanical behavior in the PCNT matrix. The findings from this study have certainly helped us design improved fiber reinforced nanocomposites with enhanced mechanical properties suitable for marine structures.     

Substrate integrated waveguide dual‐frequency dual‐sense circularly polarized cavity‐backed slot antenna

A novel design of dual‐frequency dual‐sense circularly polarized (CP) substrate integrated waveguide (SIW) cavity‐backed slot antenna is presented for dual‐band wireless communication systems. The proposed antenna consists of square SIW cavity, asymmetrical bow‐tie‐shaped cross slot and probe feed. Due to use of asymmetrical bow‐tie‐shaped cross slot, circularly polarized wave radiates at two different frequencies with opposite sense of polarizations. The RHCP radiation occurs at (10.45‐10.54) GHz (Lower band) and LHCP occurs at (11.26‐11.34) GHz (Upper band). Moreover, in each band, sense of polarization can be change by changing the feed position. The front to back radiation ratio (FTBRR) is more than 10.5 dB and cross polarization level is lower than ?20 dB in both the bands.     

Individual differences in valence modulation of face-selective m170 response.

Magnetoencephalography was used to examine the effect of individual differences on the temporal dynamics of emotional face processing by grouping subjects based on their ability to detect masked valence-laden stimuli. Receiver operating characteristic curves and a nonparametric sensitivity measure were used to categorize subjects into those that could and could not reliably detect briefly presented fearful faces that were backward-masked by neutral faces. Results showed that, in a cluster of face-responsive sensors, the strength of the M170 response was modulated by valence only when subjects could reliably detect the masked fearful faces. Source localization of the M170 peak using synthetic aperture magnetometry identified sources in face processing areas such as right middle occipital gyrus and left fusiform gyrus that showed the valence effect for those target durations at which subjects were sensitive to the fearful stimulus. Subjects who were better able to detect fearful faces also showed higher trait anxiety levels. These results suggest that individual differences between subjects, such as trait anxiety levels and sensitivity to fearful stimuli, may be an important factor to consider when studying emotion processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Studies of microstructural,dielectric, and impedance spectroscopic properties of Bi0.617Y0.05Cu3Ti4O12 ceramic synthesized through semi-wet route

Bi_0.617Y_0.05Cu₃Ti₄O₁₂(BYCTO) was successfully synthesized through an economically semi-wet route using metals nitrates, acetate, and TiO₂ precursor and sintered at 1173 K for 8 h. The single phase of ceramic was authorized by XRD analysis. The crystallite size of BYCTO ceramic was calculated to be 62.3 nm through XRD measurement. The particle size obtained by TEM analysis was to be in the range of 55?±?7 nm. The average grain size observed through the SEM technique was 0.783 μm. The route means square roughness, as well as average roughness, were determined to be 0.224 μm and 0.179 μm by atomic force microscope. The dielectric constant (?′) of BYCTO was measured to be 1481 at 307 K and 100 Hz. The tangent loss (tan δ) was observed to be in the range of 0.13–0.29 at all selected temperatures (307–487 K) and 10 kHz which is lower than that of Bi_2/3Cu₃Ti₄O₁₂. The oxidation state of all metal present in the ceramic material was verified by XPS analysis.