An expedient enyne metathesis approach to dysidiolide

A short and efficient enyne metathesis route is reported for the construction of a key intermediate required in the synthesis of dysidiolide thus completing its formal synthesis.     

Synthesis and properties of polyamides of p-phenylenedioxydiacetic acid

Several polyamides of p-phenylenedioxydiacetic acid (PDDA) were synthesized by the low-temperature solution polycondensation techniques. Six different diamines were condensed independently with p-phenylenedioxydiacetyl chloride (PDC) in a mixture of N-methyl pyrolidone (NMP) and hexamethyl phosphoramide (HMPA). The polymers were obtained in 80–95% yield and possessed inherent viscosities in the range 0.32–0.81 dL/g. The polymers were characterized by infrared (IR) and H¹-NMR spectra. The solubility, density, crystallinity, and thermal stability of the polyamides were also determined. A model diamide (MDA-1) was also synthesized from aniline and PDC to confirm the formation of polyamides from diamines.     

High precision density studies near the smectic A-nematic tricritical point

We have carried out very accurate density measurements (with a precision of ±5 × 10^-5g cm^-3) near the smectic A-nematic transition in binary mixtures of 4-n-nonyl-4'-cyanobiphenyl (9CB) and 4-n-decyl-4'-cyanobiphenyl (10CB). The transition crosses over from second to first order as the temperature range of the nematic phase decreases. For mixtures with the shortest nematic range the data deviate noticeably from a single power law behaviour. Such a deviation is an indication of the first order nature of the transition. Very good fits to a single power law have been obtained for pure 9CB and the x = 0·04 mixture where x is the mole fraction of 10CB in 9CB. The critical exponent obtained from the power law fitting has enabled us to locate the tricritical point to be very close to x=0·04, which is in agreement with the results obtained previously by high resolution calorimetric [1] and X-ray scattering studies [2].     

Synthesis,properties and structural characterization of 4-(2-ammonioethyl)piperazin-1-ium tetrasulfidotungstate hemihydrate and 1-ethylpiperazinediium tetrasulfidotungstate

The reaction of ammonium tetrasulfidotungstate with 2-piperazin-1-ylethanamine or 1-ethylpiperazine results in the formation of 4-(2-ammonioethyl)piperazin-1-ium tetrasulfidotungstate hemihydrate (C₆H₁₇N₃)[WS₄]·½H₂O 1 or 1-ethylpiperazinediium tetrasulfidotungstate (C₆H₁₆N₂)[WS₄] 2. The hemihydrate 1 can be dehydrated to the anhydrous compound (C₆H₁₇N₃)[WS₄] 1a, which can be rehydrated to 1. Both 1 and 2 decompose to amorphous carbon containing tungsten disulphide. Compound 1 crystallizes in the centrosymmetric monoclinic space group C2/c, while compound 2 crystallizes in the centrosymmetric orthorhombic space group Pbca. The structures of 1 and 2 consist of a slightly distorted tetrahedral [WS₄]^2? anion and 4-(2-ammonioethyl)piperazin-1-ium (1) or 1-ethylpiperazinediium dication (2) and additionally a lattice water in 1. In the crystal structure of 1 and 2 the organic cation and the [WS₄]^2? anion are linked to each other via several weak N–H?S and C–H?S bonding interactions. The lattice water serves as a link between pairs of cations and pairs of anions with the aid of O–H?S and N–H?O interactions in compound 1.     

Ultralow-frequency magnetoelectric effect in a multilayer ferrite-piezoelectric structure

The magnetoelectric effect is experimentally studied in a multilayer nickel zinc ferrite-lead zirconate titanate structure at frequencies of 10^?3–10 Hz that is placed in a harmonically modulated magnetic field of amplitude to 1 kOe. The nonlinearity of the ferrite magnetostriction and the conductivity of the films are shown to double the frequency and distort the shape of the magnetoelectric voltage. The magnetoelectric signal amplitude decreases linearly with decreasing field modulation frequency. The feasibility of using the magnetoelectric effect to detect ultralow-frequency magnetic fields is demonstrated.     

Painlevé test for integrability for a combination of Yang’s self-dual equations for <Emphasis Type="Italic">SU</Emphasis> (2) gauge fields and Charap’s equations for chiral invariant model of pion dynamics and a comparative discussion among the three

Painlevé test for integrability for the combined equations generated from Yang’s self-dual equations for SU (2) gauge fields and Charap’s equations for chiral invariant model of pion dynamics faces some peculiar situations that allow none of the stages (leading order analysis, resonance calculation and checking of the existence of the requisite number of arbitrary functions) to be conclusive. It is also revealed from a comparative study with the previous results that the existence of abnormal behaviour at any of the stated stages may have a correlation with the existence of chaotic property or some other properties that do not correspond to solitonic behaviour.      

Demonstration of 640 × 512 pixels long-wavelength infrared (LWIR) quantum dot infrared photodetector (QDIP) imaging focal plane array

We have exploited the artificial atom-like properties of epitaxially grown self-assembled quantum dots (QDs) for the development of high operating temperature long wavelength infrared (LWIR) focal plane arrays (FPAs). QD infrared photodetectors (QDIPs) are expected to outperform quantum well infrared detectors (QWIPs) and are expected to offer significant advantages over II–VI material based FPAs. We have used molecular beam epitaxy (MBE) technology to grow multi-layer LWIR dot-in-a-well (DWELL) structures based on the InAs/InGaAs/GaAs material system. This hybrid quantum dot/quantum well device offers additional control in wavelength tuning via control of dot-size and/or quantum well sizes. DWELL QDIPs were also experimentally shown to absorb both 45° and normally incident light. Thus we have employed a reflection grating structure to further enhance the quantum efficiency. The most recent devices exhibit peak responsivity out to 8.1 μm. Peak detectivity of the 8.1 μm devices has reached 1 × 10¹⁰ Jones at 77 K. Furthermore, we have fabricated the first long-wavelength 640 × 512 pixels QDIP imaging FPA. This QDIP FPA has produced excellent infrared imagery with noise equivalent temperature difference of 40 mK at 60 K operating temperature.     

Vanadametry

Summary A vanadametric procedure has now been developed for the accurate determination of thiocyanate. Unlike most other oxidimetric methods, the vanadametric method is free from the interference of oxygen of the air.See also: Z. analyt. Chem. 156, 181 (1957).