Teeth characterization using ion beam analysis

Summary A collaboration project between the School of Dentistry and the Institute of Physics of the University of S?o Paulo has been established to measure elemental concentrations in teeth by proton induced X-ray emission (PIXE) and heavy ion elastic recoil detection analysis (HI-ERDA) techniques. Data on trace elements in human, bovine and swine teeth, analyzed by PIXE with a 2.4 MeV proton beam, were compared and concentrations for several elements were obtained with tens of mg/g sensitivity. HI-ERDA measurements employing a 52 MeV Cl beam were done to evaluate changes in elementary concentration in dental enamel after bleaching treatment with different products in 25 bovine incisors teeth. This non-destructive technique allowed the measurements of Ca, P, O and C concentrations above the limit of 100 mg/g.     

Asymmetric autocorrelation function to resolve directional ambiguity in PIV images

 Autocorrelation of a double-exposed image, unlike cross-correlation between two images, produces a correlation function that is symmetric about the origin. Thus, while it is possible to calculate the speed and direction of tracer particles in a particle image velocimetry (PIV) image using autocorrelation, it is impossible to tell whether the velocity is in the positive or negative direction. This ambiguity can be resolved by spatially shifting one exposure relative to the next or labeling exposures with color or polarization, but the complexity and limitations of these methods can be prohibitive. It is, however, possible to resolve the sign of the velocity from a triple-exposed image using unequal time intervals between exposures. Triple-exposed images, like double-exposed images, correlate symmetrically about zero. The directional ambiguity, however, can be resolved by calculating the probability that the three exposures occur in a specific temporal order; that is, by assuming that the correlation has a specific sign and testing to see if the assumption is correct. Traditional spectral and statistical correlation techniques are unable to accomplish this. Presented herein is a computationally efficient asymmetric correlation function that is able to differentiate the temporal order of triple exposed images. Included is a discussion of the limitations of this function and of difficulties in experimental implementation. Received: 28 July 1997/Accepted: 18 February 1998     

Spin dynamics in exchange-biased F/AF bilayers

The spin dynamics of the ferromagnetic pinned layer of ferro-antiferromagnetic coupled NiFe/MnNi bilayers is investigated in a broad frequency range (30 MHz–6 GHz). A phenomenological model based on the Landau-Lifshitz equation for the complex permeability of the F/AF bilayer is proposed. The experimental results are compared to theoretical predictions.     

Dodecanoyl thiosemicarbazide derivatives as useful synthons in the synthesis of 1,2,4-triazole, 1,3,4-thiadiazole,and 1,3-benzothiazole derivatives

A convenient synthesis of the dodecanoyl thiosemicarbazide derivatives 3a, b has been achieved from the reaction of 2-benzamido-3-arylacryloylhydrazides 1a, b and lauroyl isothiocyanate (2). The thiosemicarbazide derivative 3a is used as precursor for synthesis of 1,2,4-triazole, 1,3,4-thiadiazole, and 1,3-benzothiazole derivatives. The antimicrobial activity of some of the synthesized compounds was tested.     

Efficient purification and complete NMR characterization of galactinol,sucrose, raffinose,and stachyose isolated from Pinus halepensis (Aleppo pine) seeds using acetylation procedure

The use of precipitation followed by acetylation procedures and preparative TLC purification allowed a facile isolation of four carbohydrates from the methanol extract of Pinus halepensis seeds. The isolated oligosaccharides exhibited high degree of purity. They were identified as α-D-galactosyl-(1→1)-myo-inositol nonaacetate (1), α-D-glucosyl-(1→2)-β-D-fructosyl octaacetate (2), α-D-galactosyl-(1→6)-α-D-glucosyl-(1→2)-β-D-frutosyl undecaacetate (3), and α-D-galactosyl-(1→6)-α-D-galactosyl-(1→6)-α-D-glucosyl-(1→2)-β-D-frutosyl tetradecaacetate (4) and were isolated for the first time from this plant. The ¹H and ¹³C NMR assignments for compounds 2, 3, and 4 were detailed herein for the first time.     

A new lanostane-type triterpene and sesquiterpene lactones from Vernonia leopoldii and their in vitro cytotoxicity

Investigation of the aerial parts of Vernonia leopoldii (Sch. Bip.) Vatke afforded a new lanostane-type triterpene along with known hirsutinolide-type sesquiterpene lactones and flavonoid glycosides, all are identified for the first time in this species. The new compound was identified as lanost-3β, 23S-dihydroxy-22(31)-ene. The structures of the isolated compounds were elucidated based on spectroscopic evidence. The hirsutinolides and the triterpene were evaluated for their cytotoxicity against four human cancer cell lines using MTT assay.     

Problem of generalized thermoelastic infinite medium with cylindrical cavity subjected to a ramp-type heating and loading

This paper presents the problem of thermoelastic interactions in an elastic infinite medium with cylindrical cavity at an elevated temperature field arising out of a ramp-type heating and loading bounding surface of the cavity, and the surface is assumed initially quiescent. The governing equations are taken in a unified system from which the field equations for coupled thermoelasticity as well as for generalized thermoelasticity can be easily obtained as particular cases. Due attention has been paid to the finite time of rise of temperature, stress, displacement, and strain. The problem has been solved analytically using a direct approach. The derived analytical expressions have been computed for a specific situation. Numerical results for the temperature distribution, thermal stress, displacement, and strain are represented graphically. A comparison is made with the results predicted by the three theories.     

Novel Synthesis of Some Imidazolyl‐, Benzoxazinyl‐, and Quinazolinyl‐2,4‐dioxothiazolidine Derivatives

2‐(2,4‐Dioxothiazolidin‐5‐yl)acetic acid 1 and its chloride derivative 2 were allowed to react with different aromatic amines such as o‐phenylenediamine, o‐aminothiophenol, p‐aminoacetophenone, and anthranilic acid to give the biologically active nuclei such as imidazoles, thiazoles, benzoxazines, and quinazolines incorporated with the thiazolidindione nucleus. The antimicrobial activity of five of the synthesized compounds was examined against one gram positive bacteria (Staphylococcus aureus), one gram negative bacteria (Escherichia coli), and two fungi (Aspergillus flavus and Candida albicans). Four compounds showed moderate antibacterial and antifungal activities.