Likelihood Ratio Tests for Principal Components

A particular class of tests for the principal components of a scatter matrix Σ is proposed. In the simplest case one wants to test whether a given vector is an eigenvector of Σ corresponding to its largest eigenvalue. The test statistics are likelihood ratio statistics for the classical Wishart model, and critical values are obtained parametrically as well as nonparametrically without making any assumptions on the eigenvalues of Σ. Still, the tests have asymptotic properties similar to those of classical procedures and are asymptotically admissible and optimal in some sense.     

Synthesis of 1,3,4,6,7,11b-hexahydro[1,4]thiazino[3,4,-a]-isoquinolin-4-one,an analog of prasiquantel

Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 994–996, July, 1992.     

On the resolving power of high-contrast saturated absorption spectroscopy

Recently Svanberg et al. [Optics Lett. 11 (1986) 138; J. Opt. Soc. Am. B 4 (1987) 462] obtained saturated absorption resonances with subnatural linewidth by working in the regime of high pumping intensities and optically thick atomic samples. We analyze here this new spectroscopic regime, within the formalism of Maxwell-Bloch-type equations, in the case of a Doppler broadened medium having two nearly degenerate but uncoupled resonances. We show that even in this most favourable case it is not possible to resolve spectral features that lie within the natural linewidth.     

Identification of metabolites of halofantrine, a new candidate anti-malarial drug, by gas chromatography-mass spectrometry.

Two previously unknown metabolites of halofantrine, a candidate anti-malarial drug, have been isolated by thin-layer chromatography from the plasma of dogs administered a single oral dose of 60 mg/kg. Their identifies were investigated after trimethylsilylation by gas chromatography-mass spectrometry under electron-impact and negative-ion chemical ionization conditions. The structural assignment was further confirmed by using a combination of elemental composition analysis of all the isotope peaks at low mass resolution and isotope pattern matching. These two metabolites were formed by modification of the dibutylaminopropyl side-chain of the parent compound involving deamination and oxidation or reduction.     

Intraspinal endodermal cyst: ultrastructural study of abnormal cilia.

Abnormal cilia were demonstrated in the lining epithelial cells of three cases of intraspinal endodermal (bronchogenic) cyst. The changes comprised a wide spectrum of ultrastructural abnormalities, including (a). cilia with abnormal axonemal microtubules, (b). swollen cilia, (c). compound cilia with or without excessive ciliary matrix, (d). naked cilia without limiting membrane, and (e). intracytoplasmic cilia and aggregates of microtubules. Of these, compound cilia and swollen cilia were most common. Cilia with dynein arm deficiency were not observed. Ciliary abnormalities found in the present study were very similar to those described in the bronchial epithelium of various diseases. The present findings suggest that the lining epithelium of intraspinal endodermal cyst shares similar ciliogenesis and susceptibility to abnormal ciliary formation as that of the bronchial epithelium.     

Difference in micellar properties of sodium dodecyl sulfonate from sodium 4-decyl naphthalene sulfonate in D2O solution studied by 1H NMR relaxation and 2D NOESY

¹H chemical shift changes of sodium 4-decyl naphthalene sulfonate (SDNS) at 313 K show that its critical micellar concentration lies between 0.82 and 0.92 mmol/dm³, which is in the same range as that of the previous study at 298 K. The spin–lattice relaxation time, spin–spin relaxation time and two-dimensional nuclear Overhauser enhancement spectroscopy experiments give information about the structure of the SDNS micelle and the dynamics of the molecules in the micelle. The size of the SDNS micelle remains almost unchanged in the temperature range from 298 to 313 K as deduced by analyzing the self-diffusion coefficient. Special arrangement of the naphthyl rings of SDNS in the micelles affects the packing of these hydrophobic chains. The methylene groups of the alkyl chain nearest the naphthalene groups penetrate into the aromatic region, which results in a more tightly packed hydrophobic micellar core than that of sodium dodecyl sulfonate.     

Sticking of carbon nanotube Y junction branches

The coalescence of branches in the Y junctions of single-wall carbon nanotubes (10 nm long) is predicted to occur when the branches approach each other under the action of a load (～10 nN) applied to their ends. A transition to the new state with parallel branches bound by molecular interactions was simulated and the energy characteristics were calculated by the molecular dynamics method. The Y junctions with parallel branches are stable at temperatures up to 2000 K. It is established that there is a threshold distance between the branch ends, below which the branches exhibit spontaneous sticking under the action of molecular attraction forces. If the branches are unloaded before this threshold distance is reached, they oscillate (acting as a nanodimensional “tuning fork”) at a frequency of ～100 GHz.     

Succinic acid adsorption from fermentation broth and regeneration

More than 25 sorbents were tested for uptake of succinic acid from aqueous solutions. The best resins were then tested for successive loading and regeneration using hotwater. The key desired properties for an ideal sorbent are high capacity, complete stable regenerability, and specificity for the product. The best resins have a stable capacity of about 0.06 g of succinic acid/g of resin at moderate concentrations (1–5 g/L) of succinic acid. Several sorbents were tested more exhaustively for uptake of succinic acid and for successive loading and regeneration using hot water. One resin, XUS 40285, has a good stable isotherm capacity, prefers succinate over glucose, and has good capacities at both acidic and neutral pH. Succinic acid was removed from simulated media containing salts, succinic acid, acetic acid, and sugar using a packed column of sorbent resin, XUS 40285. The fermentation byproduct, acetate, was completely separated from succinate. A simple hot water regeneration successfully concentrated succinate from 10 g/L (inlet) to 40–110 g/L in the effluent. If successful, this would lower separation costs by reducing the need for chemicals for the initial purification step. Despie promising initial results of good capacity (0.06 g of succinic/g of sorbent), 70% recovery using hot water, and a recovered concentration of >100 g/L, this regeneration was not stable over 10 cycles in the column. Alternative regeneration schemes using acid and base were examined. Two (XUS 40285 and XFS-40422) showed both good stable capacities for succinic acid over 10 cycles and >95% recovery in a batch operation using a modified extraction procedure combining acid and hot water washes. These resins showed comparable results with actual broth.