Opacity measurements of a hot iron plasma using an x-ray laser

The temporal evolution of the opacity of an iron plasma at high temperature (30-350 eV) and high density (0.001-0.2 g cm-3) has been measured using a nickel-like silver x-ray laser at 13.9 nm. The hot dense iron plasma was created in a thin (50 nm) iron layer buried 80 nm below the surface in a plastic target that was heated using a separate 80 ps pulse of 6-9 J, focused to a 100 microm diameter spot. The experimental opacities are compared with opacities evaluated from plasma conditions predicted using a fluid and atomic physics code.     

π‐Aryl/heteroaryl conjugated coumarin‐thiazoles: Synthesis,optical spectral and nonlinear optic properties

A series of π‐aryl/heteroaryl conjugated coumarin‐thiazole systems 8a‐f has been synthesized by using Hantzsch thiazole protocol and Wittig olefination as the keys. In the UV‐Visible spectra of 8a‐f , a main absorption band associated with a dominant π‐π* transition is observed in the region of 338 to 390 nm. Qualitatively, the values of λ_max have been found to correlate satisfactory with the donor/acceptor characteristics of the π‐attached chromophores. Marked changes observed in the absorption maxima of 8a under acidic conditions are rationalized on the basis of mono‐or bis‐protonation and modification of the donor/acceptor properties of chromophores undergoing protonation. The emission spectra of 8a‐f , obtained by exciting the molecules at their main absorption bands showed emission maxima in the region of 429 nm to 537 nm, with relatively high Stokes shifts of 145 and 171 nm being observed for 8a and 8e , carrying a π‐donor, dimethylaminophenyl and a π‐acceptor, p‐nitrophenyl chromophore, respectively. Although, the first hyperpolarisability β, measured by the hyper‐Reileigh scattering (HRS) technique are modest (12 to 23 × 10^?30 esu), all the compounds exhibited complete transparency in the frequency doubling region at 532 nm and showed high thermal stability (T_d from 330 to 365 °C).     

Diastereoselective synthesis of functionalized 2-methyltetrahydropyran-4-ones

A simple procedure for the synthesis of functionalized 2-methyl-2,3-dihydropyran-4-ones, based on the Maitland-Japp reaction, and their diastereoselective conversion into functionalized 2-methyltetrahydropyran-4-ones has been developed. This allows access to a structural unit present in a large number of biologically active natural products, and has been successfully applied to the synthesis of the molecule found in Civet cat secretion.     

Syntheses,Structures, and Magnetic Behavior of New Azide Linked Compounds with One‐ and Two‐Dimensional Structures

Three azide based compounds were synthesized employing aliphatic amines as site blocking agents: [Ni(N₃)(C₆H₁₆N₂)₂]ClO₄ ( I ) [C₆H₁₆N₂ = N,N′‐diethylethylenediamine (DEDA)], [Cu₈(N₃)₁₆(C₆H₁₈N₄)₂] ( II ) [C₆H₁₈N₄ = tris(2‐aminoethyl) amine (TREN)], and [Cu₇(N₃)₁₄(C₇H₁₉N₃)₂] · 2H₂O ( III ) [C₇H₁₉N₃ = 3,3′‐diamino‐N‐methyldipropylamine (DMDA)]. The compounds I and II have one‐dimensional structure and III has a two‐dimensional structure. Compound I is a simple linear cationic Ni–azide chain and compound II has Cu₆ azide units forming a column terminated by the copper‐metalloligand generated in‐situ during the course of the reaction. The charge compensation perchlorate anions occupy spaces in between the chains in I . Compound II packs in a herringbone arrangement, which is not commonly observed in low‐dimensional structures. Compound III has one‐dimensional copper‐azide chains connected through copper‐metalloligand forming the two‐dimensional structure. All the three compounds exhibit anti‐ferromagnetic behavior.     

DC and transient characterization of a compact Schottky bodycontact technology for SOI transistors

A self-aligned Schottky diode method for body contacting partially depleted silicon-on-insulator (SOI) transistors applicable to technologies that incorporate silicide cladded junctions is presented. The Schottky body contacted transistor requires no extra manufacturing steps, uses the same or less area than a transistor using other body contacting schemes and allows bi-directional operation. Extensive dc and transient characterization of the Schottky body contact illustrates its utility     

Estimation of tungsten in complex matrices using toluene 3,4-dithiol and thiocyanate

 A rapid less labour-intensive procedure for complete decomposition of tungsten bearing complex matrices by potassium pyrosulphate and its determination using toluene 3,4-dithiol and thiocyanate is reported. The analytical results of various standard reference materials are presented (Jasperoid GXR-1, Deposit GXR-3, copper mill head GXR-4, tin-tungsten ore IGS-26, Mo-W ore IGS-27, tungsten concentrate SRM-277, scheelite ore SRM-2430, reference tungsten ore TLG-1, CT-1, BH-1 and Mo-W ore MP-2) along with two manganese nodules (GSPN-2 and GSPN-3) recently introduced by the Chinese Academy of Geological Sciences and one Polish soil sample (SRM-2710). For most of the samples the agreement between the observed value and the published data have been found to be extremely good. Derivations have been noted in some samples where published concentrations are indicative values only, indicating that more data are still required to upgrade the status from proposed/unspecified to the certified level. Results of various statistical analyses (intermethod comparison, F-test and regression analysis) reveal that the methods are matrix dependent. Separation of tungsten from molybdenum is straightforward, hence can be used for a quality control programme and in the evaluation of reference materials. Received: 30 December 1996 / Revised: 12 March 1997 / Accepted: 15 March 1997     

Parasitic bipolar gain reduction and the optimization of 0.25-μmpartially depleted SOI MOSFETs

An in-depth analysis of the role of parasitic bipolar gain reduction in 0.25-μm partially depleted SOI MOSFETs is presented, considering both dc characteristics as well as circuit operation. The effect of channel doping, silicide proximity, and germanium implantation on the lateral bipolar gain are characterized for optimal performance and manufacturability. Channel doping has the expected impact on bipolar gain. Silicide proximity is shown also to have a large impact. Germanium implantation into the source/drain regions reduces the lateral bipolar gain due to the introduction of defects that act as recombination centers in the source, reducing emitter efficiency. Further, germanium implantation serves to finely control the silicidation process, leading to good manufacturing control of the lateral silicide encroachment. Analysis of MOSFET dc I-V characteristics shows that threshold voltages for SOI have to be set only 30-50 mV higher for comparable dc off current to bulk CMOS. Finally, the impact of bipolar gain on floating-body-induced hysteretic effects and on alpha-particle-induced SRAM soft error rates are described