Surface-Modified Graphene for Mid-Infrared Detection

In this chapter, morphology variation and electronic structure in a surface-modified graphene are demonstrated by both calculation and experimental results. The results indicate that the band structure and morphology of modified graphene sheets are altered because of changing in the type of hybridization of carbon atoms in the graphene sheet. Accordingly, the band gap of graphene can be tuned by surface modification using organic molecules. Then, modified graphene is used for fabrication of infrared detectors. The properties of unmodified graphene photodetectors were also measured so as to compare with modified graphene photodetectors. The results demonstrate that modification of graphene using organic ligands improved the detection parameters such as fast response time, electrical stability and low dark current. Moreover, the sensitivity of photodetectors based on modified graphene was significantly improved

Security challenges in mobile assisted language learning in the millennium for education

Distance learning technologies enrich learning opportunities due to many advantages like ubiquity and flexibility. Although the usefulness of such technologies in teaching and learning is clear, their testing part is remained to be discussed due to the security issue. Administrators and teachers need to use more authentic and secure distant testing software in which the scores are guaranteed and the testees keep away from cheating. Static and online authentication systems like “username” and “password” and face detection have empowered educational parties to have more reliable testing outcomes. Mobile devices as the necessity of the new millennium need to use authentication software in their testing. Mobile devices with their multimedia course materials provide learners with many optimistic learning opportunities through collaboration, cooperation, interaction and testing. The unique chances of ubiquity, individualization, informality, and spontaneity make the mobile learning of particular importance not only for digital natives but also for teachers, administrators, developers, instructors, and policy makers. Yielding an economical learning opportunity along with providing authentic contexts for collaborative learning is beneficial for the economy of the country in general an d for the meaningful and deep learning of the learners. This paper will discuss how authentication techniques have applied to electronic devices like mobile phones

Frequency of Beijing family of Mycobacterium tuberculosis in Mashhad, Northeast of Iran

Background: Beijing family of Mycobacterium tuberculosis (M. tuberculosis) is widespread in Asia and has been involved in outbreaks of multidrug-resistant tuberculosis in various parts of the world. The aim of the current study was to evaluate the frequency of Beijing family of M. tuberculosis in patients with tuberculosis in Mashhad, Iran.Materials and Methods: Totally, 72 specimens of M. tuberculosis were collected from pulmonary samples of patients at Ghaem hospital in Mashhad (Iran) between April 2011 and May 2012. The authors used IS6110-based polymerase chain reaction (IS6110-based PCR) method to identify Beijing family of M. tuberculosis. Based on PCR results, strains belonging to Beijing and non-Beijing families were detected. Also, among members of Beijing family, ancient and modern subfamilies were distinguished.Results: Beijing genotype was observed in five (6.9%) of 72 culture positive samples. In the present study, no cases of modern subfamilies were detected. M. tuberculosis had a higher frequency in men (61.1%) compared to that of women (38.9%). Our data demonstrated that IS6110-based PCR can be used to distinguish Beijing family from non-Beijing family, with high specificity and sensitivity.Conclusion: The improvement of convenient and quick methods to detect and control Beijing family of M. tuberculosis in clinical samples is an interesting subject in areas where M. tuberculosis is prevalent. This method has the advantages of being quick, cost-effective, and requires comparatively less clinical laboratory equipment

Partial Purification and Characterization of a Thermoalkalophilic Lipase Originated from Bacillus atrophaeus FSHM2 and its Application for Ester Synthesis

A thermoalkalophilic lipase producing bacterial strain, identified as Bacillus atrophaeus FSHM2 using 16S rDNA sequencing analysis was isolated from salty soil and its lipase was partially purified and characterized. The obtained results revealed that glucose, hazelnut oil, urea and calcium ion positively affected the lipase production by increasing the lipolytic activity to 13582.5, 6270, 4442 and 5505 U LG1, respectively compared to that of basal medium (4150 U LG1). The partially purified lipase acted optimally at pH 9 and retained 88.2% of its initial activity after 1 h of incubation at 100°C. A two fold increase in the relative activity of the partially purified lipase was obtained in the presence of 4 M of NaCl. Application of the partially purified lipase for the synthesis of ethyl and methyl valerate in the organic solvent medium (xylene) resulted in 81.6 and 62.4% esterification, respectively, after 24 h of incubation

Surface Coating of Polyurethane Films with Gelatin, Aspirin and Heparin to Increase the Hemocompatibility of Artificial Vascular Grafts

Purpose: A hemocompatible substrate can offer a wonderful facility for nitric oxide (NO) production by vascular endothelial cells in reaction to the inflammation following injuries. NO inhibits platelet aggregation this is especially critical in small-diameter vessels. Methods: The substrate films were made of polyurethane (PU) in a casting process and after plasma treatments, their surface was chemically decorated with polyethylene glycol (PEG) 2000, gelatin, gelatin-aspirin, gelatin-heparin and gelatin-aspirin-heparin. The concentrations of these ingredients were optimized in order to achieve the biocompatible values and the resulting modifications were characterized by water contact angle and Fourier transform infra-red (FTIR) assays. The values of NO production and platelet adhesion were then examined. Results: The water contact angle of the modified surface was reduced to 26±4⸰ and the newly developed hydrophilic chemical groups were confirmed by FTIR. The respective concentrations of 0.05 mg/ml and 100 mg/mL were found to be the IC50 values for aspirin and heparin. However, after the surface modification with aspirin, the bioactivity of the substrate increased in compared to the other experimental groups. In addition, there was a synergistic effect between these reagents for NO synthesis. While, heparin inhibited platelet adhesion more than aspirin. Conclusion: Because of the highly hydrophilic nature of heparin, this reagent was hydrolyzed faster than aspirin and therefore its influence on platelet aggregation and cell growth was greater. Taken together, the results give the biocompatible concentrations of both biomolecules that are required for endothelial cell proliferation, NO synthesis and platelet adhesion

The derepression of transposable elements in lung cells is associated with the inflammatory response and gene activation in idiopathic pulmonary fibrosis

Abstract Background Transposable elements (TEs) are repetitive sequences of viral origin that compose almost half of the human genome. These elements are tightly controlled within cells, and if activated, they can cause changes in both gene regulation and immune viral responses that have been associated with several chronic inflammatory diseases in humans. As oxidants are potent activators of TEs, and because oxidative injury is a major risk factor in relation to idiopathic pulmonary fibrosis (IPF), we hypothesized that TEs might be involved in the regulation of gene expression and so contribute to inflammation in cases of IPF. IPF is a fatal lung disease that involves the gradual replacement of the alveolar tissue with fibrotic scars as well as the accumulation of inflammatory cells in the lower respiratory tract. Although IPF is known to occur as a result of the complex interaction between age, environmental risk factors (i.e., oxidative stress) and genetics, the relative contributions of these factors to the disease remain unclear. To determine whether TEs are associated with IPF, we compared the transcriptional profiles of the genes and TEs of lung cells obtained from both healthy donors and IPF patients. Results We quantified TE and gene expression levels using a published bulk RNA-seq dataset containing 24 subjects (16 donors and eight IPF patients), including three lung-cell types per subject, as well as an scRNA-seq dataset concerning 16 subjects (eight donors and eight IPF patients). We found evidence of TE dysregulation in the alveolar type II lung cells and alveolar macrophages of the IPF patients. In addition, the activation of the LINE1 family of elements in IPF is associated with the increased expression of TE cellular regulators (MOV10, IFI16, SAMHD1, and APOBECG3), interferon-stimulating genes (ISG15, IFI6, IFI27, IFI44, and OAS1), chemokines (CX3CL1 and CXCL9), and interleukins (IL15RA). We also propose that TE derepression might be involved in the regulation of previously reported IPF candidate genes (MUC5B, CHL1, SPP1, and MMP7). Conclusion Based on our findings, we propose that TE derepression plays an important role in the regulation of gene expression and can also prompt both the recruitment of inflammatory processes and the disruption of the immunological balance, which can lead to chronic inflammation in IPF

High-Performance Solution Processed Inorganic Quantum-Dot LEDs

In this research paper, fabrication of novel CdSe\ZnS QD-LEDs with solution processing method is presented, and the impact of trap energy levels in the electron and hole transport levels on these QD-LEDs brightness is investigated. Two types of QD-LEDs are fabricated with ITO as the transparent anode electrode, NiO nanoparticles as the hole transport layer (HTL), CdSe\ZnS QDs as the luminescent layer, ZnO:Ga as the electron transport layer (ETL), and Al as the cathode electrode. The NiO nanoparticles are synthesized by the sol-gel or alternatively the electrochemical method. Formation of different trap levels is observed in the crystal structures of the NiO nanoparticles synthesized by each of these methods. Considering the electrochemically prepared NiO nanoparticles, it is found that the density of trap levels is higher in the crystal structure of the NiO nanoparticles synthesized by sol-gel method, and the device fabricated by the latter material shows higher performance. Calculation of the electronic structure of ZnO:Ga by DFT methods (GGA-PBE) indicates that doping of Ga in the structure of crystalline ZnO creates new energy levels in conduction band and intermediate bands at the bandgap of ZnO host. It facilitates electron injection from Al cathode to the ZnO:Ga ETL layer and from this layer to the QD-luminescent layer. The fabricated devices show turn-on lower voltages than 5 V in which a peak brightness of 500 and 340 cd.m(-2) is measured for the LEDs fabricated with sol-gel and electrochemically synthesized NiO nanoparticles, respectively

UV/IR Dual-Wavelength Photodetector Design Based on ZnO/PMMA/PbSe Nanocomposites

A UV/IR dual-wavelength photodetector based on a ZnO/PMMA/PbSe nanocomposite [PMMA = poly(methyl methacrylate)] for simultaneous detection of 365 nm UV and 4 mu m IR radiation is presented. For UV detection spherical nanoparticles of boron-doped ZnO were synthesized and stabilized using hexamethylenetetramine. The absorption intensity in the UV-vis range is increased upon B doping and discrete Fourier transform calculations confirm the results. Responsivity of the fabricated UV detector is 7.8 AW(-1) and the detector gain is 26.49 at a 365 nm input wavelength. For the synthesis of IR detecting PbSe a new method was worked out, including the stabilization of the particles with thioacetamide. The performance of the PbSe based IR detector turns out to be superior to previously reported PbSe based detectors synthesized by established methods. The responsivity and gain of the detector is 8 AW(-1) and 3.31, respectively for 4 mu m incident wavelength. The sensitivity is 30 for IR detection and overall this sensitivity is excellent for sensing in the mid-IR range. All three chemical factors, the B-doping, the synthesis conditions for nanoparticles, and the surface modification have contributed to the excellent optoelectronic performance of these new photodetector devices, while the polymethyl methacrylate layer turned out to be very effectively reducing the noise for IR detection