QWIP focal plane arrays on InP substrates for single and dual band thermal imagers

Alternative material systems on InP substrate provide certain advantages for mid-wavelength infrared (MWIR), long-wavelength infrared (LWIR) and dual band MWIR/LWIR quantum well infrared photodetector (QWIP) focal plane arrays (FPAs). While InP/InGaAs and InP/InGaAsP LWIR QWIPs provide much higher responsivity when compared to the AlGaAs/GaAs QWIPs, AlInAs/InGaAs system facilitates completely lattice matched single band MWIR and dual band MWIR/LWIR FPAs.We present an extensive review of the studies on InP based single and dual band QWIPs. While reviewing the characteristics of InP/InGaAs and InP/InGaAsP LWIR QWIPs at large format FPA level, we experimentally demonstrate that the cut-off wavelength of AlInAs/InGaAs QWIPs can be tuned in a sufficiently large range in the MWIR atmospheric window by only changing the quantum well (QW) width at the lattice matched composition. The cut-off wavelength can be shifted up to ～5.0 μm with a QW width of 22 Å in which case very broad spectral response (Δλ/λ_p = ～30%) and a reasonably high peak detectivity are achievable leading to a noise equivalent temperature difference as low as 14 mK (f/2) with 25 μm pitch in a 640 × 512 FPA. We also present the characteristics of InP based two-stack QWIPs with wavelengths properly tuned in the MWIR and LWIR bands for dual color detection. The results clearly demonstrate that InP based material systems display high potential for dual band MWIR/LWIR QWIP FPAs needed by third generation thermal imagers.     

Momentum evolution of ejected and entrained fluid during laminar vortex ring formation

The evolution of total circulation and entrainment of ambient fluid during laminar vortex ring formation has been addressed in a number of previous investigations. Motivated by applications involving propulsion and fluid transport, the present interest is in the momentum evolution of entrained and ejected fluid and momentum exchange among the ejected, entrained fluid and added mass during vortex ring formation. To this end, vortex rings are generated numerically by transient jet ejection for fluid slug length-to-diameter (L/D) ratios of 0.5–3.0 using three different velocity programs [trapezoidal, triangular negative slope (NS), and positive slope (PS)] at a jet Reynolds number of 1,000. Lagrangian coherent structures (LCS) were utilized to identify ejected and entrained fluid boundaries, and a Runge-Kutta fourth order scheme was used for advecting these boundaries with the numerical velocity data. By monitoring the center of mass of these fluid boundaries, momentum of each component was calculated and related to the total impulse provided by the vortex ring generator. The results demonstrate that ejected fluid exchanges its momentum mostly with added mass during jet ejection and that the momentum of the entrained fluid at jet termination was < 11% of the total ring impulse in all cases except for the triangular NS case. Following jet termination, momentum exchange was observed between ejected and entrained fluid yielding significant increase in entrained fluid’s momentum. A performance metric was defined relating the impulse from over-pressure developed at the nozzle exit plane during jet ejection to the flow evolution, which increased preferentially with L/D over the range considered. An additional benefit of this study was the identification of the initial (i.e., before jet initiation) location of the fluid to be entrained into the vortex ring.     

Determination and analysis of the dispersive optical constants of the 5,5′,6,6′-tetraphenyl-2,2′-bi([1,3]dithiolo[4,5-b][1,4]dithiinylidene)–DDQ complex thin film

The synthesis and optical properties of the 5,5′,6,6′-tetraphenyl-2,2′-bi([1,3]dithiolo [4,5-b] [1,4]dithiinylidene)–2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) complex thin film were investigated by the optical characterization. The optical constants such as refractive index, extinction coefficient and absorption coefficient were determined using the transmittance T(λ) and reflectance R(λ) spectra and the refractive index dispersion was analyzed using single oscillator of Wemple–Didomenico model. The single oscillator energy E₀ and the dispersion energy E_d were calculated. The effect of temperature on refractive dispersion and optical band gap E_g is also discussed. As a result, the annealing temperatures have an important effect on refractive index of thin film.     

Three-dimensional seismic array characterization study: experiment and modeling

In the summer of 2003, the Littoral Acoustic Demonstration Center conducted an acoustic characterization experiment for a 21-element marine seismic exploration airgun array of total volume of 0.0588 m(3) (3590 in.(3)). Two Environmental Acoustic Recording System buoys, one with a desensitized hydrophone, were deployed at a depth of 758 m in a water depth of 990 m, near Green's Canyon in the Gulf of Mexico. Shots over a grid were recorded and calibrated to produce absolute broadband (up to 25 kHz) pressure-time dependencies for a wide range of offsets and arrival angles in the water column. Experimental data are analyzed to obtain maximum received zero-to-peak pressure levels, maximum received sound exposure levels, and pressure levels in 13-octave frequency bands for each shot. Experimental data are quantitatively modeled by using an upgraded version of an underwater acoustic propagation model and seismic source modeling packages for a variety of ranges and arrival angles. Experimental and modeled data show good agreement in absolute pressure amplitudes and frequency interference patterns for frequencies up to 1000 Hz. The analysis is important for investigating the potential impact on marine mammals and fish and predicting the exposure levels for newly planned seismic surveys in other geographic areas.     

Determination of trace elements in marine plankton by inductively coupled plasma mass spectrometry (ICP-MS)

A method has been developed for the determination of 23 elements in marine plankton in which inductively coupled plasma (ICP) source mass spectrometry (MS) was used to quantify the elements in the solution after digestion in a mixture of hydrofluoric and nitric acids in sealed PTFE vessels in a microwave field. The procedure was validated by the analysis of a standard reference soil (SRM 2709 San Joaquin Soil) and a standard reference fresh water plankton (CRM 414). The method was applied to the analysis of several marine plankton samples grown under controlled conditions including several whose growth media had been enriched with selenium. Matrix induced signal suppressions and instrumental drift were corrected by internal standardization. The suitabilities of germanium, indium, rhodium, scandium and yttrium as internal standard elements were evaluated. Neither scandium nor yttrium could be used due to the presence of these elements in the samples, germanium was used for the determination of As, Co, Cu, Fe, Ni, Se, Si and Zn, indium was used for Al, Ba, Ca, Eu, Sr, and Tl, and rhodium was used for Cd, Cr, Hg, Mg, Pb, Sb, Sn, and V. For Al, Ca, Cr, Cu, Fe, Mg, Mn, Ni, Si, Sr, V, and Zn internal standardization did not completely compensate for the suppressive effect of the heavier elements and the solutions were diluted. However, for As, Ba, Cd, Co, Eu, Hg, Pb, Sb, Se, Sn and Tl, it was possible to obtain accurate results despite the 35–¶40% suppression in the signals. Isobaric overlap was only a problem in the cases of ⁴²Ca and ⁷⁸Se; ⁴⁴Ca and ⁷⁷Se, respectively, were used. Memory effects were only observed with Hg for which a nitric acid-sodium chloride solution was the most effective wash-out solution. The marine plankton samples were able to tolerate a higher concentration of Hg as the selenium concentration increased.     

Electrochemical preparation of a soluble conducting aniline-thiophene copolymer

A new of soluble sulfonated conductive copolymer has been synthesized by electrochemical oxidation in the presence of anhydrous FSO₃H. The sulphur-to-nitrogen ratios indicated that copolymers were formed in addition to the incorporation of groups into polymeric backbone. The sulfonated copolymer films have better solubility in DMSO and KOH. The conductivity of the copolymer films increases with the increase in the number of thiophene rings in the polymeric backbone. Copolymer films synthesized were investigated by cyclic voltammetry, UV-visible, FT-IR and ¹H-NMR spectroscopy, dry conductivity and intrinsic viscosity measurements, elemental analysis and SEM pictures.     

A Selective LC Method for the Determination of Reboxetine in Human Plasma with Fluorescence Detection

A rapid, simple, accurate, sensitive and reproducible high performance liquid chromatographic method for the quantitation of reboxetine (REB) in human plasma using fluvoxamine as an internal standard (IS) has been developed and validated. The method is based on derivatization with 7-chloro-4-nitrobenzofurazan (NBD-Cl). The NBD-derivatives in plasma were extracted by liquid–liquid extraction and chromatographed on a reversed phase C₁₈ column with isocratic elution using acetonitrile and aqueous nitric acid (pH 3) solution. Calibration curve was linear over the range 2.0–200.0 ng mL⁻¹ with inter- and intra-assay precision (RSD%) of less than 4%. The mean recovery was about 94% for REB. The applicability of the method to the plasma was also studied.

     

Determination of the Absolute Configuration of Dimethyl (2S,3S)-2-Allyl-3-hydroxyglutarate: A Chiral Building Block for Preparing Branched-Chain Nucleoside Analogues

A yeast-catalyzed reduction of dimethyl (2S,3S)-2-allyl-3-hydroxyglutarate is the key step in the preparation of bis-homo, branched-chain nucleoside analogues. To establish unambiguously the stereochemical course of the microbial reaction, the product has been converted to a derivative esterified with camphanoyl chloride, and a crystal structure of the derivative solved.     

Synthesis of Some N-Alkoxycarbonyl-N″-benzoyl-benzamidrazones（p-toluamidrazones） and 1,3,5-Trisubstituted 1,2,4-Triazole Derivatives from N-Benzoylimidates and their Antimicrobial and Anticancer Screening Studies

Some new N-alkoxycarbonyl-N″-benzoyl-benzamidrazones （p-toluamidrazones） 3a-3d, and 1,3,5-trisubstituted 1,2,4-triazole 4a-4h derivatives by starting from N-benzoylbenzimidates or N-benzoyl-p-toluimidates. The structures of compounds 3 and 4 were established on the basis of elemental analyses, IR, ^1H NMR, ^13C NMR and UV data. Antimicrobial experiments of the compounds performed by using agar-well diffusion and broth microdilution methods revealed that only compounds 3a-3d, 4a and 4b showed inhibitory effect only on Candida albicans ATCC 60193. However, compound 4b had also specific antibacterial activity against Staphylococcus aureus ATCC 25923. The other compounds showed neither antifungal nor antibacterial activities. Compounds 3a, 4a and 4b have been screened on three human tumor cell lines, breast cancer （MCF7）, non small cell lung cancer （NCI-H460）, and CNS cancer （SF-268） at the National Cancer Institute （NCI）, USA, which were found to exhibit low antiproliferative activity.     

Reactions of Enone Ethylene Ketals with Methyl Diazomalonate/Bis(acetylacetonato)copper(II)

Several cyclic and acyclic enones and their ethylene ketals/acetals were reacted with dimethyl diazomalonate under bis(acetylacetonato)copper(II) catalysis. Cyclohex-2-en-1-one ( 1 ) yielded only C–H insertion products 2 and 3 , whereas but-3-en-2-one gave a cyclopropane albeit in very low yield. The ethylene ketals 6 of cyclopent-2-en-1-one and cyclohex-2-en-1-one gave the corresponding cyclopropanes 7 , which were in turn cleaved to the ketones 8 . The acetals 9 and 10 of crotonaldehyde ((E)-but-2-enal) and cinnamaldehyde ((E)-3-phenylprop-2-enal), respectively, yielded C–O insertion and [2,3]-sigmatropic rearrangement products 11b, c and 12b, c , as well as cyclopropanes 11a and 11b , all of which are polyfunctional and synthetically useful compounds.