Application of Graphene within Optoelectronic Devices and Transistors

Scientists are always yearning for new and exciting ways to unlock graphene's true potential. However, recent reports suggest this two-dimensional material may harbor some unique properties, making it a viable candidate for use in optoelectronic and semiconducting devices. Whereas on one hand, graphene is highly transparent due to its atomic thickness, the material does exhibit a strong interaction with photons. This has clear advantages over existing materials used in photonic devices such as Indium-based compounds. Moreover, the material can be used to 'trap' light and alter the incident wavelength, forming the basis of the plasmonic devices. We also highlight upon graphene's nonlinear optical response to an applied electric field, and the phenomenon of saturable absorption. Within the context of logical devices, graphene has no discernible band-gap. Therefore, generating one will be of utmost importance. Amongst many others, some existing methods to open this band-gap include chemical doping, deformation of the honeycomb structure, or the use of carbon nanotubes (CNTs). We shall also discuss various designs of transistors, including those which incorporate CNTs, and others which exploit the idea of quantum tunneling. A key advantage of the CNT transistor is that ballistic transport occurs throughout the CNT channel, with short channel effects being minimized. We shall also discuss recent developments of the graphene tunneling transistor, with emphasis being placed upon its operational mechanism. Finally, we provide perspective for incorporating graphene within high frequency devices, which do not require a pre-defined band-gap.Comment: Due to be published in "Current Topics in Applied Spectroscopy and the Science of Nanomaterials" - Springer (Fall 2014). (17 pages, 19 figures

Transition between Two Regimes Describing Internal Fluctuation of DNA in a Nanochannel

We measure the thermal fluctuation of the internal segments of a piece of DNA confined in a nanochannel about 50100 nm wide. This local thermodynamic property is key to accurate measurement of distances in genomic analysis. For DNA in 100 nm channels, we observe a critical length scale 10 m for the mean extension of internal segments, below which the de Gennes' theory describes the fluctuations with no fitting parameters, and above which the fluctuation data falls into Odijk's deflection theory regime. By analyzing the probability distributions of the extensions of the internal segments, we infer that folded structures of length 150250 nm, separated by 10 m exist in the confined DNA during the transition between the two regimes. For 50 nm channels we find that the fluctuation is significantly reduced since the Odijk regime appears earlier. This is critical for genomic analysis. We further propose a more detailed theory based on small fluctuations and incorporating the effects of confinement to explicitly calculate the statistical properties of the internal fluctuations. Our theory is applicable to polymers with heterogeneous mechanical properties confined in non-uniform channels. We show that existing theories for the end-to-end extension/fluctuation of polymers can be used to study the internal fluctuations only when the contour length of the polymer is many times larger than its persistence length. Finally, our results suggest that introducing nicks in the DNA will not change its fluctuation behavior when the nick density is below 1 nick per kbp DNA

Thermal Properties of Graphene, Carbon Nanotubes and Nanostructured Carbon Materials

Recent years witnessed a rapid growth of interest of scientific and engineering communities to thermal properties of materials. Carbon allotropes and derivatives occupy a unique place in terms of their ability to conduct heat. The room-temperature thermal conductivity of carbon materials span an extraordinary large range - of over five orders of magnitude - from the lowest in amorphous carbons to the highest in graphene and carbon nanotubes. I review thermal and thermoelectric properties of carbon materials focusing on recent results for graphene, carbon nanotubes and nanostructured carbon materials with different degrees of disorder. A special attention is given to the unusual size dependence of heat conduction in two-dimensional crystals and, specifically, in graphene. I also describe prospects of applications of graphene and carbon materials for thermal management of electronics.Comment: Review Paper; 37 manuscript pages; 4 figures and 2 boxe

Prognostic value of gross tumor volume delineated by FDG-PET-CT based radiotherapy treatment planning in patients with locally advanced pancreatic cancer treated with chemoradiotherapy

<p>Abstract</p> <p>Background</p> <p>We aimed to assess whether gross tumor volume (GTV) determined by fusion of contrast-enhanced computerized tomography (CT) and 18F-fluoro-deoxy-D-glucose positron emission tomography-CT (FDG-PET-CT) based radiotherapy planning could predict outcomes, namely overall survival (OS), local-regional progression-free survival (LRPFS), and progression-free survival (PFS) in cases with locally advanced pancreas cancer (LAPC) treated with definitive concurrent chemoradiotherapy.</p> <p>Methods</p> <p>A total of 30 patients with histological proof of LAPC underwent 50.4 Gy (1.8 Gy/28 fractions) of radiotherapy concurrent with continuously infused 5-FU followed by 4 to 6 courses of maintenance gemcitabine. Target volume delineations were performed on FDG-PET-CT-based RTP. Patients were stratified into 2 groups: GTV lesser (GTV_L) versus greater (GTV_G) than cut off value determined by receiver operating characteristic (ROC) analysis, and compared in terms of OS, LRPFS and PFS.</p> <p>Results</p> <p>Median GTV delineated according to the FDG-PET-CT data was 100.0 cm³. Cut off GTV value determined from ROC curves was 91.1 cm³. At a median follow up of 11.2 months, median OS, LRPFS and PFS for the entire population were 10.3, 7.8 and 5.7 months, respectively. Median OS, LRPFS and PFS for GTV_Land GTV_Gcohorts were 16.3 vs. 9.5 (<it>p </it>= 0.005), 11.0 vs. 6.0 (<it>p </it>= 0.013), and 9.0 vs. 4.8 months (<it>p </it>= 0.008), respectively.</p> <p>Conclusions</p> <p>The superior OS, LRPFS and PFS observed in GTV_Lpatients over GTV_Gones suggests a potential for FDG-PET-CT-defined GTV size in predicting outcomes of LAPC patients treated with definitive C-CRT, which needs to be validated by further studies with larger cohorts.</p

Can FDG PET predict radiation treatment outcome in head and neck cancer? Results of a prospective study

Contains fulltext : 96692.pdf (publisher's version ) (Closed access)PURPOSE: In head and neck cancer (HNC) various treatment strategies have been developed to improve outcome, but selecting patients for these intensified treatments remains difficult. Therefore, identification of novel pretreatment assays to predict outcome is of interest. In HNC there are indications that pretreatment tumour (18)F-fluorodeoxyglucose (FDG) uptake may be an independent prognostic factor. The aim of this study was to assess the prognostic value of FDG uptake and CT-based and FDG PET-based primary tumour volume measurements in patients with HNC treated with (chemo)radiotherapy. METHODS: A total of 77 patients with stage II-IV HNC who were eligible for definitive (chemo)radiotherapy underwent coregistered pretreatment CT and FDG PET. The gross tumour volume of the primary tumour was determined on the CT (GTV(CT)) and FDG PET scans. Five PET segmentation methods were applied: interpreting FDG PET visually (PET(VIS)), applying an isocontour at a standardized uptake value (SUV) of 2.5 (PET(2.5)), using fixed thresholds of 40% and 50% (PET(40%), PET(50%)) of the maximum intratumoral FDG activity (SUV(MAX)) and applying an adaptive threshold based on the signal-to-background (PET(SBR)). Mean FDG uptake for each PET-based volume was recorded (SUV(mean)). Subsequently, to determine the metabolic volume, the integrated SUV was calculated as the product of PET-based volume and SUV(mean). All these variables were analysed as potential predictors of local control (LC), regional recurrence-free survival (RRFS), distant metastasis-free survival (DMFS), disease-free survival (DFS) and overall survival (OS). RESULTS: In oral cavity/oropharynx tumours PET(VIS) was the only volume-based method able to predict LC. Both PET(VIS) and GTV(CT) were able to predict DMFS, DFS and OS in these subsites. Integrated SUVs were associated with LC, DMFS, DFS and OS, while SUV(mean) and SUV(MAX) were not. In hypopharyngeal/laryngeal tumours none of the variables was associated with outcome. CONCLUSION: There is no role yet for pretreatment FDG PET as a predictor of (chemo)radiotherapy outcome in HNC in daily routine. However, this potential application needs further exploration, focusing both on FDG PET-based primary tumour volume, integrated SUV and SUV(MAX) of the primary tumour

Protective coating of lithium metal electrode for interfacial enhancement with gel polymer electrolyte

The polymer electrolyte based on semi-interpenetrating polymer network (IPN) structure for protection was formed on lithium electrode surface by the ultraviolet (UV) radiation-curing method. A curable mixed solution consists of linear polymer (Kynar 2801), a crosslinking agent (1,6-Hexanediol diacrylate), liquid electrolyte (ethylene carbonate (EC)/propylene carbonate (PC)/1 M LiClO4), and a photoinitiator (methyl benzoylformate). The lithium morphology deposited on the protected lithium electrode was less dendritic and smoother than that on the nonprotected lithium electrode during the 1st charge at 0.25 mAcm(-2). The discharge capacity obtained from the unit cell applying the lithium anode protected with gel polymer electrolyte based on semi-IPN [Kynar 2801/1,6-Hexanediol diacrylate, 5/5 (w/w)] was 80% of the initial discharge capacity during 100 cycles at C/2 rate (1.25 mAcm(-2)).close282

Novel porous separator based on PVdF and PE non-woven matrix for rechargeable lithium batteries

The novel porous separator based on PVdF (poly(vinylidene fluoride)) and a PE (polyethylene) non-woven matrix is prepared by coating PVdF/NMP solution on the matrix (NMP: N-methyl-2-pyrrolidone). The pore structure is generated in the PVdF region by phase inversion of the polymer solution. The PE non-woven matrix imparts mechanical strength and a thermal shut-down property to the separator, while the PVdF component provides a hydrophilic ionic conducting phase. The physical properties of the separator, such as morphology, pore size and its distribution, porosity and mechanical strength, are measured. The ionic conductivity of the separator is 8.9 x 10(-4) S cm(-1) at 25 degreesC. The capacity at the C/2 rate is maintained at about 86% of the initial value on the 100th cycle at the room temperature. The electrolyte is stable up to 4.5 V in the presence of the novel separator.close818

Electrochemical effect of coating layer on the separator based on PVdF and PE non-woven matrix

The coated separator was prepared by coating poly(vinyl acetate) (PVAc) on the surface of the novel separator based on poly(vinylidene fluoride) (PVdF) and polyethylene (PE) non-woven matrix. The ionic conductivity of the coated separator was 1.1 ?? 10-3 S cm-1 at 25 ??C, a little higher than that of bare separator. The coated separator showed smoother surface morphology and better adhesion property toward electrodes, and thereby it resulted in lower total resistance than the bare separator. The discharge capacity of the unit cell with coated separator at C/2 rate was maintained at about 84% of the theoretical capacity, which is quite higher than that of the unit cell with the bare separator.close151

THE P-1 REACTIVE-SITE METHIONINE RESIDUE OF ECOTIN IS NOT CRUCIAL FOR ITS SPECIFICITY ON TARGET PROTEASES - A POTENT INHIBITOR OF PANCREATIC SERINE PROTEASES FROM ESCHERICHIA-COLI

The importance of the P-1 reactive site for the specificity of ecotin on target proteases was examined by site-directed mutagenesis. The replacement of Met at the P-1 site with Ile, Arg, Glu, or Tyr showed little or no effect on the ability of ecotin to inhibit trypsin. Similar results were obtained for chymotrypsin, except that its replacement with Glu caused about 40% reduction of the inhibitory activity of ecotin. On the other hand, the replacement of the Met residue with Arg, Tyr, or Glu dramatically reduced its ability to inhibit elastase, while that with lie showed little or no effect. Nevertheless, elastase could be completely inhibited upon incubation with excess amounts of the mutant ecotin containing Arg, Glu, or Tyr. Moreover, all the mutant forms of ecotin could be cleaved at the mutated P-1 site upon incubation with trypsin at pH 3.75. In addition, the re placement of a Cys residue in the disulfide bridge with Ser showed little or no effect on the ability of ecotin to inhibit trypsin, chymotrypsin, or elastase. However, the mutant ecotin containing Ser was more sensitive to inactivation by heating at 100 degrees C than the wild-type inhibitor. Furthermore, the wild-type ecotin whose disulfide bond had been reduced and alkylated was also more easily inactivated by heat treatment than the untreated control. These results strongly suggest that the P-1 site of ecotin is not crucial for its specificity on target proteases and that the disulfide bridge in ecotin appears to play an important role in maintenance of its structural stability.X1111sciescopu