Mag netic properties of $$\hbox{Ni}_{13- n}\hbox{Al}_ n$$ clusters with n = 0–13

We report the magnetic properties of small Ni_13-nAl_n\hbox{Ni}_{13-n}\hbox{Al}_n clusters with n = 0–13 calculated in the framework of density functional theory. The cluster magnetic moment decreases with the sequential substitution of Ni by Al atoms, which can be attributed to a greater degree of hybridization that forces the pairing of the electrons in the molecular orbitals of Ni and Al. For Ni₇Al₆, the complete quenching of the cluster magnetic moment appears to be due to the antiferromagnetic alignment of atomic spins as revealed by the spin density plots.     

Simultaneous Determination of Enalapril and Losartan in Pharmaceutical Preparations by UV Spectrophotometry and LC

The simultaneous determination of enalapril (Ena) and losartan (Los) in solid dosage forms were done by two methods. The first method involves spectrophotometric determination using the simultaneous equation method at 222 and 250 nm for Ena and Los, respectively. The second method involved an RP-LC method of analysis using methanol:water:acetonitrile (45:35:20% v/v) as the mobile phase. Both methods were satisfactorily validated as per ICH guidelines.     

Carbon multi-walled nanotubes grown by HWCVD on a pyroelectric detector

Carbon multi-wall nanotubes (MWNTs) were grown on a lithium niobate (LiNbO₃) pyroelectric detector with a nickel film as the catalyst by hot-wire chemical vapor deposition (HWCVD). Two detectors are documented, each with slightly different deposition conditions. The absolute spectral responsivity of each device was measured from 600 nm to 1800 nm and indicates that the MWNT-coating absorptance is spectrally uniform, with variations of only a few percent. We also discuss growth of MWNTs on LiTaO₃ by CVD and the limitations presented by the Curie temperature of the pyroelectric material.     

Long range forces and limits on unparticle interactions

Couplings between standard model particles and unparticles from a nontrivial scale invariant sector can lead to long range forces. If the forces couple to quantities such as baryon or lepton (electron) number, stringent limits result from tests of the gravitational inverse square law. These limits are much stronger than from collider phenomenology and astrophysics.     

Cast Polyurethanes: Effect of Chain Extenders on Thermal Mechanical and Dynamic Mechanical Properties

Effects of various diol chain extenders on thermal, mechanical, and viscoelastic properties of polyurethanes are discussed. Elastomers were prepared by using polyester (polyethylene-co-propylene adipate), toluene-2,4-diisocyanate, and α,ω-aliphatic diols. The properties imparted by the extenders are explained on the basis of the number of methylene carbons in the extenders. Butanediol-extended polymer showed superior properties, which are ascribed to regularity in the backbone chain of the polymer and ease of formation of hydrogen bonds.     

Synthesis of (±)-4-Demtthoxy-7 11-Dideoxydaungmy-Cinone

Our continued interest in the total synthesis of natural and unnatural antitumor anthracyclines¹ especially the aglycones such as daunomycinone (1)² and 4-demethoxydaunomycinone (2),³ 11-deoxydaunomycinone(3)⁴ and 4-demethoxy-11-deoxydau-nomycinone (4)⁵ led us to investigate various methods for obtaining these products. Recently we have reported the synthesis of 4-demethoxy-7, 11-dideoxydaunomycinone (5) from 5-methoxy-1-tetralone. Now we wish to report the synthesis of 5 starting from 5-methoxy-1-tetralone (9) which was prepared from 1,6-dimethoxy-naphthalene(8). Umezawa⁷ et al. have reported the total synthesis of 4-demethoxy-ll-deoxydaunomycin(6) and 4-demethoxy-11-deoxy-adriamycin (7) from 5-methoxy-2-tetralone.     

Efficient Microwave‐assisted One‐pot Synthesis of Novel Spironaphthopyrano‐one Derivatives

Rapid and efficient one‐pot three‐component synthesis of new spironaphthopyrano‐one derivatives by cyclocondensation reaction in aqueous media is achieved under microwave irradiation conditions. This protocol has the advantages of higher yield, lower cost, reduced time, environmental impact, and convenient procedure.