Carbon nanotube-Si diode as a detector of mid-infrared illumination

We report a room temperature mid-infrared photodetector based on a carbon nanotube-silicon heterojunction nanostructure. The observed mid-infrared band (8–12 μm) role= presentation \u3e(8–12μm) in the photocurrent spectrum is consistent with the estimated band gap energy of semiconducting multiwall nanotubes (15 to 30 nm diameter). The fast response time (16 ms) and small temperature change (∼10−8 K) role= presentation \u3e(∼10−8K) upon infrared light suggest that the photocurrent response is not due to bolometric effect. We determined that the primary mechanism of the photocurrent in this spectral range is associated with photon absorption of semiconducting multiwalled carbon nanotubes followed by charge separation at the interface, their transport, and collection at the external electrodes

Fatma Aliye and Defense of Islamic Values

The article concerns an analysis of the recently published text by Fatma Aliye debating with European ideas and prejudices about Islam that has not been a subject of interest in the South Slavonic intellectual and academic circles. Fatma Aliye (1862–1936) was the first Turkish woman novelist, the first Turkish woman philosopher, and the author of the book Tezâhür-i Hakikat (Appearance of Truth) that was published for the first time in January 2016 on the occasion of the 80th anniversary of her death. Like some writers of the Tanzimat era, especially Namik Kemal, Fatma Aliye entered the debate with the European writers wishing to oppose the prevailing Orientalist approach in Europe that had been blaming Islam for the stagnation of sciences and culture. She demonstrated enviable erudition and devotion to the Islamic culture. Her views show the permanent duality of the Ottoman intellectuals between their desire for Westernization and their need to stay in the Islamic tradition. In many aspects, the approaches to Islam and the defence of Islamic values of Fatma Aliye are still current

Effective transcription factor binding site prediction using a combination of optimization, a genetic algorithm and discriminant analysis to capture distant interactions

<p>Abstract</p> <p>Background</p> <p>Reliable transcription factor binding site (TFBS) prediction methods are essential for computer annotation of large amount of genome sequence data. However, current methods to predict TFBSs are hampered by the high false-positive rates that occur when only sequence conservation at the core binding-sites is considered.</p> <p>Results</p> <p>To improve this situation, we have quantified the performance of several Position Weight Matrix (PWM) algorithms, using exhaustive approaches to find their optimal length and position. We applied these approaches to bio-medically important TFBSs involved in the regulation of cell growth and proliferation as well as in inflammatory, immune, and antiviral responses (NF-κB, ISGF3, IRF1, STAT1), obesity and lipid metabolism (PPAR, SREBP, HNF4), regulation of the steroidogenic (SF-1) and cell cycle (E2F) genes expression. We have also gained extra specificity using a method, entitled SiteGA, which takes into account structural interactions within TFBS core and flanking regions, using a genetic algorithm (GA) with a discriminant function of locally positioned dinucleotide (LPD) frequencies.</p> <p>To ensure a higher confidence in our approach, we applied resampling-jackknife and bootstrap tests for the comparison, it appears that, optimized PWM and SiteGA have shown similar recognition performances. Then we applied SiteGA and optimized PWMs (both separately and together) to sequences in the Eukaryotic Promoter Database (EPD). The resulting SiteGA recognition models can now be used to search sequences for BSs using the web tool, SiteGA.</p> <p>Analysis of dependencies between close and distant LPDs revealed by SiteGA models has shown that the most significant correlations are between close LPDs, and are generally located in the core (footprint) region. A greater number of less significant correlations are mainly between distant LPDs, which spanned both core and flanking regions. When SiteGA and optimized PWM models were applied together, this substantially reduced false positives at least at higher stringencies.</p> <p>Conclusion</p> <p>Based on this analysis, SiteGA adds substantial specificity even to optimized PWMs and may be considered for large-scale genome analysis. It adds to the range of techniques available for TFBS prediction, and EPD analysis has led to a list of genes which appear to be regulated by the above TFs.</p

Porous Silicon Structures as Optical Gas Sensors

We present a short review of recent progress in the field of optical gas sensors based on porous silicon (PSi) and PSi composites, which are separate from PSi optochemical and biological sensors for a liquid medium. Different periodical and nonperiodical PSi photonic structures (bares, modified by functional groups or infiltrated with sensory polymers) are described for gas sensing with an emphasis on the device specificity, sensitivity and stability to the environment. Special attention is paid to multiparametric sensing and sensor array platforms as effective trends for the improvement of analyte classification and quantification. Mechanisms of gas physical and chemical sorption inside PSi mesopores and pores of PSi functional composites are discussed

Electromechanical actuation of composite material from carbon nanotubes and ionomeric polymer

An actuating system composed of nafion ionomeric polymer coated with single-walled carbon nanotubes electrodes was studied as an electromechanical actuator. The actuator gives a sizable mechanical response to low voltages (turn-on voltage of ∼2.5 V) under open-air conditions, i.e., in the absence of a surrounding supporting electrolyte. The actuator is active under both dc and ac bias and has a strong resonance at low frequencies which is dependent upon the size of the actuator. The actuator was studied using Fourier transform infrared and vis-NIR spectroscopies, cyclic voltammetry, and by the current-time response under an applied step voltage. An analytical model is proposed to understand the electrical behavior, which is consistent with the spectroscopic results

Fluorescent polymer-porous silicon microcavity devices for explosive detection

Conjugated polymers entrapped in porous silicon microcavity have been studied as optical sensors for low volatility explosives such as trinitrotoluene. The fluorescence spectra of entrapped polymers were modulated by the microcavity via a spectral “hole” that matches the resonance peak of the microcavity reflectance. Exposure of the porous silicon microcavity containing entrapped polymer to explosives vapor results in a red shift of the resonance peak and the spectral hole, accompanied by the quenching of the fluorescence. This multiplexed response provides multiple monitoring parameters, enabling the development of an optical sensor array for the detection of target explosive vapor

Organic / IV, III-V Semiconductor Hybrid Solar Cells

We present a review of the emerging class of hybrid solar cells based on organic-semiconductor (Group IV, III-V), nanocomposites, which states separately from dye synthesized, polymer-metal oxides and organic-inorganic (Group II-VI) nanocomposite photovoltaics. The structure of such hybrid cell comprises of an organic active material (p-type) deposited by coating, printing or spraying technique on the surface of bulk or nanostructured semiconductor (n-type) forming a heterojunction between the two materials. Organic components include various photosensitive monomers (e.g., phtalocyanines or porphyrines), conjugated polymers, and carbon nanotubes. Mechanisms of the charge separation at the interface and their transport are discussed. Also, perspectives on the future development of such hybrid cells and comparative analysis with other classes of photovoltaics of third generation are presented

Field effect of carbon nanotubes with an ionomeric polymer

Flexible field effect transistors based on a single walled carbon nanotube (SWNT) network and an ionomeric polymer (nafion) were obtained by spraying nanotubes onto the polymer film, The threshold gate voltage was extremely low, ~1 V, which was surprising since the nafion layer was so thick, ∼ 180 μm. This was attributed to the electrolytic nature of nafion, which results in the existence of a screening layer at the polymer-nanotube interface. FET hysteresis can be rationalized in terms of charge redistribution induced by mobile protons inside nafion clusters in proximity to the nanotube surface. © 2007 WILEY-VCH Verlag GmbH & Co. KGaA

Organic / IV, III-V Semiconductor Hybrid Solar Cells

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