Ultra-thin graphene edges at the nanowire tips: a cascade cold cathode with two-stage field amplification

A multistage field emitter based on graphene-linked ZnO nanowire array is realized by means of spin-coating a graphene dispersion (reduced graphene oxide) over a nanostructured platform followed by plasma modification. Spin-coating leads to interlinking of graphene sheets between the neighboring nanowires whereas plasma etching in the subsequent step generates numerous ultra-sharp graphene edges at the nanowire tips. The inherent tendency of graphene to lay flat over a plane substrate can easily be bypassed through the currently presented nanostructure platform based technique. The turn-on and threshold field significantly downshifted compared to the individual components in the cascade emitter. Through the facile electron transfer from nanowires to graphene due to band bending at the ZnO-graphene interface together with multistage geometrical field enhancement at both the nanowire and graphene edges remain behind this enriched field emission from the composite cold cathode. This strategy will open up a new direction to integrate the functionalities of both the graphene array and several other inorganic nanostructure array for practical electronic devices.     

Effect of copper additions in directly quenched titanium–boron steels

The present study concerns the effect of copper additions on the microstructural evolution and mechanical properties of directly quenched Ti–B steels. Ti and B are added as microalloying elements with an aim of achieving adequate austenite hardenability and Cu is added to retard the austenite (γ) → ferrite (α) transformation. Therefore, the microalloying and Cu additions together allow the transformation of austenite to occur at a lower temperature, resulting in a finer microstructure containing martensitic constituents. The direct-quenching route is adopted with an aim of facilitating the nucleation of the constituent phases from the deformed austenite. In order to circumvent the hot-shortness due to the Cu addition, 0.79 wt% Ni has been added to one of the 1.5 wt% Cu microalloyed steels. The present study has demonstrated that the Ni-containing 1.5Cu–Ti–B steel is capable of providing an attractive combination of strength and ductility comparable to the high strength varieties of HSLA steels in directly quenched condition.     

Elastic–plastic J and COD estimation schemes for 90° elbow with throughwall circumferential crack at intrados under in-plane opening moment

Leak-before-break (LBB) assessment of primary heat transport piping of nuclear reactors involves detailed fracture assessment of pipes and elbows with postulated throughwall cracks. Fracture assessment requires the calculation of elastic–plastic J-integral and crack opening displacement (COD)¹ for these piping components. Analytical estimation schemes to evaluate elastic–plastic J-integral and COD simplify the calculations. These types of estimation schemes are available for pipes with various crack configurations subjected to different types of loading. However, such schemes for elbow (or pipe bend), which is one of the important components for LBB analyses, is very meager. Recently, elastic–plastic J and COD estimation scheme has been developed for throughwall circumferentially cracked elbow subjected to closing bending moment. However, it is well known that the elbow deformation characteristics are distinctly different for closing and opening bending modes because the ovalisation patterns of elbow cross section are different under these two modes. Development of elastic–plastic J and COD estimation scheme for an elbow with throughwall circumferential crack at intrados subjected to opening bending moment forms the objective of the present paper. Experimental validation of proposed J-estimation scheme has been provided by comparing the crack initiation, unstable ductile tearing loads and crack extension at instability with the test data. The COD estimation scheme has been validated by comparing the COD of test data with the predictions of the proposed scheme.     

Influence of adjacent channel interference on thefrequency-modulated WDM optical communication system

The effect of adjacent channel interference on the frequency modulated wavelength division multiplexing (FM-WDM) optical communication system is analyzed in this paper. This system uses injection-locked optical discriminator at the output for the demodulation of FM channels. Adjacent channel interference results in crosstalk in the FM-WDM communication system which has been calculated. Dependence of crosstalk on the channel spacing, received signal power in a particular channel, and linewidth enhancement factor of the slave laser incorporated in the optical discriminator has been numerically investigated. The injection-locked discriminator has a typical output crosstalk level of -50 dB for a channel spacing of 100 GHz with optical injection level of -30 dB into the slave laser and is a suitable subsystem to be used in FM-WDM communication system     

The effect of ternary addition of silicon on the structure and microstructure of rapidly solidified equiatomic TiNi alloys

The influence of a small amount of silicon (up to 6 at %) on the structure and microstructure of rapidly solidified equiatomic TiNi alloys is reported. It is shown that a small amount of silicon suppresses the B2 TiNi formation and promotes a competitive nucleation of Ti2Ni phase. Further additions of silicon promote the formation of glass. The behaviour of the ternary replacement of both titanium and nickel by silicon has been studied. It is shown that replacement of titanium increases the tendency for the formation of silicide phases while the latter is absent when silicon replaces the nickel atoms. This revised version was published online in November 2006 with corrections to the Cover Date.     

The energy-irrigation nexus and its impact on groundwater markets in eastern Indo-Gangetic basin: Evidence from West Bengal, India

South Asia in general and India in particular is heavily dependent on groundwater for supporting its largely agrarian population. Informal pump irrigation services markets have played an important role in providing access to irrigation to millions of small and marginal farmers and had positive equity, efficiency and sustainable impacts in water-abundant regions such as West Bengal. Quite predictably, in such pump lift-based economy, fortunes of energy and irrigation sectors are closely entwined. This has often been called the ‘energy-irrigation’ nexus. There are two major sources of energy for pumping groundwater, viz. electricity and diesel. Most of the current discourse in the field has looked only at the ‘electricity-irrigation’ nexus to the exclusion of the ‘diesel-irrigation nexus’. This paper looks at both these aspects. In doing so, it makes two propositions. First, high flat-rate electricity tariff encourages development of water markets whereby the water buyers—who are mostly small and marginal farmers—benefit through access to irrigation. Second, low rate of rural electrification has forced majority of farmers to depend on diesel for groundwater pumping and the steep increase in diesel prices over the last few years has resulted in economic scarcity of groundwater. This in turn has had serious negative impacts on crop production and farm incomes. Using primary field data from West Bengal, India, this paper makes a case for rapid rural electrification and continuation of high flat-rate tariff, which would in turn support developed groundwater markets and provide access to irrigation to the poor and marginal farmers.     

The effects of reverse micelles on the reaction mechanism of alpha-chymotrypsin

Reverse micelles were employed to test the accuracy of the widely accepted mechanism for alpha-chymotrypsin in a highly structured aqueous system similar to intracellular conditions. Results yielded from spectrophotometrical assays of the alpha-chymotrypsin catalyzed hydrolysis of both p-nitrophenyl acetate (p-NPA) and p-nitrophenyl trimethylacetate (p-NPTA) were kinetically analyzed to determine constants typical of the proposed mechanistic model. This was accomplished through the establishment of a control, i.e. the well studied buffer system, for comparison between the reverse micellular environment and a bulk aqueous solution. Control group results yielded kinetic constants in favor of the proposed mechanism (Km = 1.55 x 10(-5) +/- 1.40 x 10(-6) M for p-NPA and a Km = 4.97 x 10(-6) +/- 2.29 x 10(-7) M, Km(app) = 4.92 x 10(-6) +/- 2.33 x 10(-8) M, k2 = 4.34 x 10(-3) +/- 1.31 x 10(-3), k(cat) = 1.96 x 10(-3) +/- 2.47 x 10(-4), and Ks = 1.60 x 10(-5) +/- 4.61 x 10(-6) M for p-NPTA). In contrast, similar reactions of the enzyme in a reverse micellular system produced kinetic constants atypical to that representative of the textbook mechanism. (Km = 1.59 x 10(-4) +/- 2.70 x 10(-5) M, Ks = -8.67 x 10(-5) +/- 4.46 x 10(-5) M and Km(app) = -4.80 x 10(-5) +/- 7.05 x 10(-5) M for p-NPA and Km = 1.95 x 10(-4) +/- 9.28 x 10(-5) M, Km(app) = -1.79 x 10(-4) +/- 2.36 x 10(-5) M, and Ks = -3.95 x 10(-4) +/- 1.18 x 10(-4) M for p-NPTA). In addition to negative kinetic constants, alpha-chymotrypsin seemed to display characteristics indicative of super-activity and a hysteretic response. Overall, the widely accepted mechanism for alpha-chymotrypsin appeared to fail within the confines of reverse micelles, due to the direct influence of the system's highly structured form.     

Local oscillator chain for 1.55 to 1.75THz with 100-/spl mu/W peak power

We report on the design and performance of a fix-tuned /spl times/2/spl times/3/spl times/3 frequency multiplier chain that covers 1.55-1.75THz. The chain is nominally pumped with 100mW at W-band. At 120K the measured output power is larger than 4/spl mu/W across the band with a peak power of 100/spl mu/W at 1.665THz. A similar chain operated at room temperature produced a peak power of 21/spl mu/W. These power levels now make it possible to deploy multipixel heterodyne imaging arrays in this frequency range.     

Interaction of relativistic electrons with ultrashort laser pulses:generation of femtosecond X-rays and microprobing of electron beams

The interaction of relativistic electrons with terawatt femtosecond laser pulses is reviewed with emphasis on how the scattering process can be used as a source of ultrashort X-ray pulses and as a time-resolved diagnostic for measuring transverse and longitudinal phase space distributions of an electron beam with microns spatial and subpicosecond temporal resolution. Recent experimental results are presented in which 90° Thomson scattering was utilized to generate 300 fs duration pulses of X-rays with peak energy of 30 keV. It is shown that, through analysis of the scattered X-ray beam properties, transverse and longitudinal distributions of the electron beam can be obtained     

Optical Measurements of SuperSpec: A Millimeter-Wave On-Chip Spectrometer

SuperSpec is a novel on-chip spectrometer we are developing for (sub)millimeter wavelength astronomy. Our approach utilizes a filterbank of moderate resolution ( \(R \sim 500{)}\) channels, coupled to lumped element kinetic inductance detectors (KIDs), all integrated onto a single silicon chip. The channels are half-wave resonators formed by lithographically depositing segments of superconducting transmission line, and the KIDs are titanium nitride resonators. Here we present optical measurements of a first generation prototype, operating in the 180–280 GHz frequency range. We have used a coherent source to measure the spectral profiles of 17 channels, which achieve linewidths corresponding to quality factors as high as \(Q_\mathrm {filt} = 700{,}\) consistent with the designed values plus additional dissipation characterized by \(Q_i \approx 1440{.}\) We have also used a Fourier Transform Spectrometer to characterize the spectral purity of all 72 channels on the chip, and measure typical out of band responses \({\sim }30\) dB below the peak response.