Secondary ion yields produced by keV atomic and polyatomic ion impacts on a self-assembled monolayer surface

A suite of keV polyatomic or 'cluster' projectiles was used to bombard unoxidized and oxidized self-assembled monolayer surfaces. Negative secondary ion yields, collected at the limit of single ion impacts, were measured and compared for both molecular and fragment ions. In contrast to targets that are orders of magnitude thicker than the penetration range of the primary ions, secondary ion yields from polyatomic projectile impacts on self-assembled monolayers show little to no enhancement when compared with monatomic projectiles at the same velocity. This unusual trend is most likely due to the structural arrangement and bonding characteristics of the monolayer molecules with the Au(111). Copyright 1999 John Wiley & Sons, Ltd.     

The study of the changes in the thermal properties of <Emphasis Type="Italic">Labeo rohita</Emphasis> bones due to arsenic exposure

The paper presents the changes in the thermal properties of control, arsenic exposed and DMSA treated Labeo rohita bones by using thermo analytical techniques. The result shows that the mass loss due to the thermal decomposition occurs in three distinct steps due to loss of water, organic and inorganic materials. The arsenic exposed bones present a different thermal behaviour compared to the control bones. The residue masses are increased due to arsenic exposure, while the DMSA treatment reduces the residue mass level. These thermal characteristics can be used as a qualitative method to check the metal accumulation in samples.     

Best one-sided L1 approximation to the Heaviside and sign functions

We find the polynomials of the best one-sided approximation to the Heaviside and sign functions. The polynomials are obtained by Hermite interpolation at the zeros of some Jacobi polynomials. Also we give an estimate of the error of approximation and characterize the extremal points of the convex set of the best approximants.     

Ethyl 6‐amino‐2‐methoxypyridine‐3‐carboxyl­ate,interplay of molecular and supramolecular structure

The title compound, C₉H₁₂N₂O₃, crystallizes with two mol­ecules in the asymmetric unit. There is extensive hydrogen bonding which results in the formation of a two‐dimensional corrugated sheet. This supramolecular structure is determined by the formation of hydrogen‐bonded chains resulting from the presence of a 6‐amino group and an ethoxy­carbonyl group as substituents on a pyridine ring in relative para positions which constitute a π‐electron `push–pull' system.     

Spectral analysis of wind speed determined at different sites in Sardinia

Summary A first evaluation of the characteristics of periodic fluctuations of the horizontal wind speed component at the ground has been determined in six stations in Sardinia. The analysis takes into account only wind speed component without considering variations in wind direction. The spectral analysis shows large variations in magnitudes from site to site and from season to season concerning the fundamental harmonic (24 hour) and the harmonics of periodT/2,T/3 andT/4. The largest fluctuations are associated with regimes of great windiness andvice versa.

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Riassunto Una prima valutazione delle caratteristiche delle fluttuazioni periodiche della componente orizzontale del vento a terra è stata effettuata prendendo in esame sei stazioni anemometriche situate in Sardegna. L'analisi spettrale ha messo in evidenza variazioni non trascurabili nelle ampiezze dell'armonica fondamentale (24 ore) della velocità del vento che dipendono dalla localizzazione delle stagioni e dalla stagione. In generale si può mettere in evidenza una relazione empirica che associa le ampiezze delle fluttuazioni con i valori medi stagionali della velocità del vento.

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Резюме На шести анемометрических станциях в Сардинии проведена первая оденка параметров периодических флуктуадий горизонтальной составляющей скорости ветра на поверхности Земли. Анализ учитывает только компоненту скорости ветра, не рассматвивая изменения направления ветра. Спектральный анализ обнаруживает большие изменения по амплитуде в зависимости от местоположения и от сезона при исследовании основной гармоники (24 часа) и гармоник с периодамиT/2,T/3 иT/4. Наибольшие флуктуации связаны с режимами сильного ветра и наоборот.

     

On an extremal relation of Bernstein operators

In this note we present a new characterization of Bernstein operators by showing that they are the only solution of a certain extremal relation.     

Determination of 27 dansyl amino acid derivatives in biological fluids by reversed-phase high-performance liquid chromatography

The concentrations of free amino acids in plasma and in ascitic liquid of mice with Ehrlich ascitic tumours were determined by reversed-phase high-performance liquid chromatography using pre-column derivatization with Dns chloride and UV detection at 254 nm. Sample preparation is simple, and the Dns derivatives are stable. Complete separation of 27 amino acids, including proline and cysteine, was achieved in 70 min with detection limits of less than 25 pmol. There was no interference from Dns-Cl, Dns-OH and Dns-NH2. Retention time reproducibility was better than 1%. The described method enables a rapid, economical and reproducible quantification of free amino acids in biological fluids.     

A Characterization of Quasi-copulas

The notion of quasi-copula was introduced by C. Alsina, R. B. Nelsen, and B. Schweizer (Statist. Probab. Lett.(1993), 85–89) and was used by these authors and others to characterize operations on distribution functions that can or cannot be derived from operations on random variables. In this paper, the concept of quasi-copula is characterized in simpler operational terms and the result is used to show that absolutely continuous quasi-copulas are not necessarily copulas, thereby answering in the negative an open question of the above mentioned authors.