Direct vapor phase growth process and robust photoluminescence properties of large area MoS2 layers

There has been growing research interest in the use of molybdenum disulfide in the fields of optoelectronics and energy harvesting devices, by virtue of its indirect-to-direct band gap tunability. However, obtaining large area thin films of MoS2 for future device applications still remains a challenge. In the present study, the amounts of the precursors （S and MOO3） were varied systematically in order to optimize the growth of highly crystalline and large area MoS2 layers by the chemical vapor deposition method. Careful control of the amounts of precursors was found to the key factor in the synthesis of large area highly crystalline flakes. The thickness of the layers was confirmed by Raman spectroscopy and atomic force microscopy. The optical properties and chemical composition were studied by photoluminescence （PL） and X-ray photoelectron spectroscopy. The emergence of strong direct excitonic emissions at 1.82 eV （A-exciton, with a normalized PL intensity of -55 × 10^3） and 1.98 eV （B-exciton, with a normalized PL intensity of -5 × 10^3） of the sample at room temperature clearly indicates the high luminescence quantum efficiency. The mobility of the films was found to be 0.09 cm^2/（V.s） at room temperature. This study provides a method for the controlled synthesis of high-quality two-dimensional （2D） transition metal dichalcogenide materials, useful for applications in nanodevices, optoelectronics and solar energv conversion.     

A uniplanar printed antenna with an inverted L‐shaped coupling feed for LTE/GSM/DCS/PCS/UMTS operations

A novel uniplanar printed antenna with a total size of 115 × 40 mm² is proposed for mobile device application. By using an inverted L‐shaped feeding mechanism and a meandered shorting strip, a dual‐band operation with wideband characteristic can be achieved. Here, the lower operating band is able to cover the LTE 700 and GSM 850/900 operations, while the higher operating band allows DCS 1800, PCS 1900, UMTS, and LTE 2300 operations. Furthermore, in order to increase the bandwidth of the higher operating band so that LTE 2500 operation can also be covered, an additional parasitic stub is attached to the feed line to excite a resonant frequency at around 2.72 GHz. Parametric studies via simulation are carried out, and prototype of the proposed antenna is also experimentally investigated to validate the simulated results. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2012.     

Development of a Real Time PCR system for detection of ochratoxin A-producing strains of the Aspergillus niger aggregate

Members of Aspergillus section Nigri are distributed worldwide, being considered as common food spoilage fungi. Some species of this section produce ochratoxin A (OTA), mainly Aspergillus carbonarius and several members of the Aspergillus niger aggregate. Detection of ochratoxigenic A. niger aggregate strains is important to prevent OTA contamination in foodstuffs. A new Real Time PCR procedure has been developed for the rapid and specific detection and quantification of ochratoxin A-producing strains of the A. niger aggregate. Two specific primers delimiting a 120 bp fragment and a probe were designed and directed to a polyketide synthase (PKS) from A. niger CBS 513.88 genome. This PKS has a strong similarity to PKS of A. ochraceus fragment involved in ochratoxin biosynthesis. Specificity was confirmed by testing primers towards purified DNA from 91 fungal strains, including reference and food isolates. The SYBR-Green and the TaqMan approaches developed allowed the specific detection only of ochratoxigenic strains of the A. niger aggregate. All other analyzed food related fungi gave negative results. This is the first report on a Real Time PCR system for the detection of OTA-producing strains of the A. niger aggregate.     

Contrast enhancement dynamic histogram equalization for medical image processing application

Image processing requires an excellent image contrast‐enhancement technique to extract useful information invisible to the human or machine vision. Because of the histogram flattening, the widely used conventional histogram equalization image‐enhancing technique suffers from severe brightness changes, rendering it undesirable. Hence, we introduce a contrast‐enhancement dynamic histogram‐equalization algorithm method that generates better output image by preserving the input mean brightness without introducing the unfavorable side effects of checkerboard effect, artefacts, and washed‐out appearance. The first procedure of this technique is; normalizing input histogram and followed by smoothing process. Then, the break point detection process is done to divide the histogram into subhistograms before we can remap the gray level allocation. Lastly, the transformation function of each subhistogram is constructed independently. © 2011 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 21, 280‐289, 2011;     

Investigation of organic n-type field-effect transistor performance on the polymeric gate dielectrics

We report a copper hexadecafluorophthalocyanine (F₁₆CuPc) based n-type organic field-effect transistor (OFET) with polymeric gate dielectrics with different physical/electrical properties. The gate dielectrics are four types of cross-linked poly(4-vinylphenol) and newly prepared poly(4-phenoxy methyl styrene) and those are characterized based on surface tension, leakage current and capacitance. The performance of F₁₆CuPc OFETs with those gate dielectrics was compared. We found that the composition of the gate dielectrics and the interfacial interaction of F₁₆CuPc with the gate dielectric play a decisive role in the performance of OFETs. The effect of physical/electrical properties, composition and processing condition of the gate dielectrics on the device performance was investigated.     

Principle and application of ball SAW devices

A thin beam of waves usually diverges due to diffraction, which is a limitation of any device using such waves. However, a surface acoustic wave (SAW) on a sphere with an appropriate aperture does not diverge but is collimated, realizing ultra‐multiple roundtrips along an equator of the sphere. This effect is caused by the balance between diffraction and focusing on a spherical surface, and it enables realization of high‐performance ball SAW sensors. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 168(1): 41–51, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20817     

Nonsmooth stabilizability and feedback linearization of discrete-time nonlinear systems

We consider the problem of stabilizing a discrete-time nonlinear system using a feedback which is not necessarily smooth. A sufficient condition for global dynamical stabilizability of single-input triangular systems is given. We obtain conditions expressed in terms of distributions for the nonsmooth feedback triangularization and linearization of discrete-time systems. Relations between stabilization and linearization of discrete-time systems are given.     

Short-Term Immune Responses of Gilthead Seabream (Sparus aurata) Juveniles against Photobacterium damselae subsp. piscicida

Photobacteriosis is a septicaemic bacterial disease affecting several marine species around the globe, resulting in significant economic losses. Although many studies have been performed related to the pathogen virulence and resistance factors, information regarding the host defence mechanisms activated once an infection takes place is still scarce. The present study was designed to understand innate immune responses of farmed juvenile gilthead seabream (Sparus aurata) after Photobacterium damselae subsp. piscicida (Phdp) infection. Therefore, two groups of seabream juveniles were intraperitoneally injected with 100 µL of PBS (placebo) or 100 µL of exponentially growing Phdp (1 × 10⁶ CFU/mL; infected). The blood, plasma, liver, and head kidney of six fish from each treatment were sampled immediately before infection and 3, 6, 9, 24 and 48 h after infection for the broad screening of fish immune and oxidative stress responses. Infected animals presented marked anaemia, neutrophilia and monocytosis, conditions that are correlated with an increased expression of genes related to inflammation and phagocytic activity. Similar studies with different fish species and bacteria can be useful for the definition of health biomarkers that might help fish farmers to prevent the occurrence of such diseases.     

Composites based on high-density polyethylene,polylactide and calcium carbonate: effect of calcium carbonate nanoparticles as co-compatibilizers

Polymer Bulletin - Investigating the compatibility mechanism of hybrid composites based on two polymers and one mineral nanofiller is a challenge that needs to be better understood. This study...