UNUSUALLY STRONG ATTRACTION IN THE PRESENCE OF CONTINUUM BOUND-STATE

The result of few-particle ground-state calculation employing a two-particle nonlocal potential supporting a continuum bound state in addition to a negative-energy bound state has occasionally revealed unusually strong attraction in producing a very strongly bound ground state. In the presence of the continuum bound state the difference of phase shift between zero and infinite energies has an extra jump of pi as in the presence of an additional bound state. The wave function of the continuum bound state is identical with that of a strongly bound negative-energy state, which leads us to postulate a pseudo bound state in the two-particle system in order to explain the unexpected attraction. The role of the Pauli forbidden states is expected to be similar to these pseudo states.

XPS investigation of plasma-deposited polysiloxane films irradiated with helium ions

This work describes an XPS investigation of plasma-deposited polysiloxane films irradiated with 170 keV He+ ions at fluences, Phi, ranging from 1 x 10(14) to 1 x 10(16) cm(-2). Modifications in the atomic concentrations of the surface atoms with (D were revealed by changes in the [O]/[Si], [O]/[C] and [C]/[Si] atomic ratios. Surface chemical structure modifications were evidenced by the increasing C1s peak width and asymmetry as Phi was increased, due to the formation of ether and carboxyl functionalities. Moreover, structural transformations were indicated by the positive binding energy shift of the Si2p peaks, due to the increasing Si oxidation. Correlations of the XPS data with other results from previous work on polysiloxanes illustrate the role of ion beam-induced bond breaking on the structural modifications.

How do cold water biota arrive in a tropical bay near Rio de Janeiro, Brazil?

Previous ecological studies on foraminifera and ostracoda from the tropical Sepetiba Bay, located in the southern part of the State of Rio de Janeiro, Brazil, have noted the presence in this area of some cool water taxons typical of the Argentine continental platform. These studies have proposed that parcels of these temperate waters with their associated biological indicators are advected northward along the platform, penetrating into some tropical entrances of the southeast coast of Brazil. In the present study, ecological data (foraminifera, ostracoda and microbivalves), are used together with information obtained by satellite tracked drifting buoys and digital thermal imagery obtained from NOAA satellites to indicate the path taken by these high latitude species along the southern Brazilian coast to arrive in the Sepetiba Bay, near the city of Rio de Janeiro. Our general conclusion is that biotic elements native to the colder, less saline marine waters seen to the south of Brazil have been and are being advected northward along the inner part of the continental platform to about 22 degrees S. Water parcels containing this biota may, in a sporadic fashion, enter into the tropical Sepetiba Bay. The passage of meteorological fronts through the region is considered to be an important if not the principal mechanism for the sporadic entry of the cool water into the Southern Coastal Entrance of the State of Rio de Janeiro. (C) 1998 Elsevier B.V.s Ltd. All rights reserved.

Neural networks in chemosystematic studies of asteraceae: A classification based on a dichotomic approach

This paper describes the application of artificial neural nets as an alternative and efficient method for the classification of botanical taxa based on chemical data (chemosystematics). A total of 28,000 botanical occurrences of chemical compounds isolated from the Asteraceae family were chosen from the literature, and grouped by chemical class for each species. Four tests were carried out to differentiate and classify different botanical taxa. The qualifying capacity of the artificial neural nets was dichotomically tested at different hierarchical levels of the family, such as subfamilies and groups of Heliantheae subtribes. Furthermore, two specific subtribes of the Heliantheae and two genera of one of these subtribes were also tested. In general, the artificial neural net gave rise to good results, with multiple-correlation values R > 0.90. Hence, it was possible to differentiate the dichotomic character of the botanical taxa studied.

Antioxidant quinonemethide triterpenes from Salacia campestris

A new quinonemethide triterpene named as salacin, has been isolated from the root bark of Salacia campestris in addition to the known pristimerin, maytenin, 20 alpha-hydroxymaytenin, and netzahualcoyene. Salacin was identified on the basis of NMR-spectral and mass spectrometric analysis. The free-radical scavenging activities of the quinonemethide triterpenes salacin (1), pristimerin (2), maytenin (3), 20a-hydroxymaytenin (4), and netzahualcoyene (5) towards DPPH have been evaluated and showed absorbance variation (AA) of 19, 20, 39, 28, 55, and 10%, respectively, having rutin (74% at 50 pm) and BHT (7% at 50 mu M) as standard compounds.

Caries resistance of lased human enamel with Er : YAG laser - morphological and ratio Ca/P analysis

Objective: In vitro analysis of caries resistance of dental enamel under caries simulation after irradiation with Er:YAG laser. Background Data: More susceptible to caries development spots at adjacent hard tissues from cavity preparations of dental tissues using burrs or lasers are quite common. Methods: Thirteen caries-free third permanent human molars were distributed as follows: G1: sound control and caries control; G2: Er:YAG 100, 200, 300, or 400 mJ/ 10 Hz/ 3 sec.; G3: the same parameters of G2 followed by artificial caries simulation, through dynamic model of demineralization and remineralization (DE/RE). Caries resistance analysis was evaluated through scanning electron microscopy (SEM) and Ca/P rate (X-Rays spectroscopy - EDX). Results: Photomicrographs showed that the Er:YAG laser created craters with rough aspect which became more evident as the energy per pulse was increased, but without change of regular morphology of enamel prisms. Significant statistical changes among the irradiated and control groups was observed considering the Ca/P ratio. Conclusion: Irradiated groups showed higher caries resistance than control groups. However, it is not possible to affirm that the enamel surface accidental irradiation could be a benefit to caries resistance for other situations can be considered, as biofilm deposit, which could increase the caries susceptibility.

Structure determination of an organometallic 1-(diazenylaryl)ethanol: A novel toxin subclass from the web of the spider Nephila clavipes

A novel chemical subclass of toxin, [1-(3-diazenylphenyl) ethanol]iron, was identified among the compounds present in the web of the spider Nephila clavipes. This type of compound is not common among natural products, mainly in spider-venom toxins; it was shown to be a potent paralytic and/or lethal toxin applied by the spider over its web to ensure prey capture only by topical application. The structure was elucidated by means of ESI mass spectrometry, H-1-NMR spectroscopy, high-resolution (HR) mass spectrometry, and ICP spectrometry. The structure of [1-( 3-diazenylphenyl)ethanol] iron and the study of its insecticidal action may be used as a starting point for the development of new drugs for pest control in agriculture.

Study of the morphological alterations to enamel and dentin in human and bovine teeth after irradiation with Er : YAG laser

Objective: the purpose of this study is to make use of scanning electron microscopy in order to comparatively analyze the morphological alterations to human and bovine enamel and dentin. Earlier data: Many a morphological study involving Er:YAG laser can be found in the literature. Still, not a single study comparing the effects of this infrared laser in human and bovine teeth has been reported. Materials and Methods: Thirty-two slices of human and bovine enamel and dentin were evenly divided into four groups. With the exception of the control group, the samples were irradiated with Er:YAG laser, focused at a distance of 12 mm and a 10-Hz frequency, with 150, 250, and 350 mJ of output energy per pulse for 10 seconds. After irradiation all specimens were observed under a scanning electron microscope. Results: There was practically no morphological difference for those samples that underwent 150 mJ/pulse irradiation. The dentin exposed to 250 mJ had a few open dentinal tubules. These were seen in enamel after a 350 mJ irradiation, in which the energy was able to reach the dentin. Conclusions: the breadth of this study allows us to state that the pattern between the species grew more heterogenous as the energy density was increased and that irradiation with 150 mJ/pulse resulted in greater likeness in human and bovine enamel and dentin.

Helium ion irradiation of polymer films deposited from TMS-Ar plasmas

Polymer films synthesized from plasmas of a tetramethylsilane - Ar mixture were modified by irradiation with 170 keV He ions at fluences ranging from 1 x 10(14) to 1 x 10(16) cm(-2). As revealed by infrared spectroscopy, the ion beam produced intense bond rearrangements, such as the depletion of bonding groups (C-H and Si-H), and induced the formation of new ones, such as O-H and Si-O. From the nanoindentation measurements, a remarkable increase in the surface hardness of the films was observed as the ion fluence was increased. The increases in hardness were accompanied by an increase in the film compaction as shown by using a combination of RBS and film thickness measurements. From both hardness and infrared measurements A was concluded that, under the He ion bombardment, the polymer structure is transformed into a silicon oxycarbide network.

Enamel caries resistance accidentally irradiated by the Nd : YAG laser

When the carious tissue is eliminated either by conventional methods (with burs) or with lasers, the risk of accidentally damage the surface of adjacent teeth may occur, which hypothetically could lead to a more susceptible surface for canes formation. This in vitro study aims to evaluate the caries resistance of the dental enamel surface irradiated by the Nd:YAG laser applied in conditions simulating accidental exposition. Thirteen third molars were used in this study. The experimental groups were: G1: sound control and control + carious; G2: contact Nd:YAG laser at 0.75, 1, 2, or 3 W; 10 Hz; 3 sec (27, 35, 71, and 106 J/cm(2)); G3: same parameters from G2 + caries artificial induction through the demineralization and demineralization (DES/RE) dynamic model. The caries resistance analysis was evaluated by the superficial morphological aspect through SEM images and also by Ca/P proportion through energy dispersive X-ray spectroscopy (EDX). The micrograph images showed that the Nd:YAG laser changed the normalmorphology of the enamel prisms resulting in a melted and re-solidified surface intensified with the power increase. Significant statistical differences were observed applying the Kruskal-Wallis statistical test (p <= 0.01) among the Nd:YAG laser irradiated groups and the control with caries regarding the Ca/P proportion. As an exception, this was not observed when 3 W; 10 Hz; 3 sec; 106 J/cm(2) was applied and posteriously submitted to a cariogenic challenge. The results indicate that the Nd:YAG laser accidental irradiation at low power settings did not represent risks to the enamel caries resistance.

Effect of Different Solvent Ratios (Water/Ethylene Glycol) on the Growth Process of CaMoO4 Crystals and Their Optical Properties

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Evaluation of dental pulp repair using low level laser therapy (688 nm and 785 nm) morphologic study in capuchin monkeys

The aim of this study was to evaluate the hypothesis that low-level laser therapy (LLLT) 688 nm and 785 nm accelerate dentin barrier formation and repair process after traumatic pulp exposure. The sample consisted of 45 premolars of capuchin monkeys (Cebus apella) with pulp exposure Class V cavities. All premolars were treated with calcium hydroxide (Ca(OH)(2)), divided in groups of 15 teeth each, and analyzed on 7(th), 25(th), and 60(th) day. Group GI - only Ca(OH)(2), GIF- laser 688 nm, and GIII - laser 785 nm. Laser beam was used in single and punctual dose with the parameters: continuous, 688 nm and 785 nm wavelength, tip's area of 0.00785 cm(2), power 50 mW, application time 20 s, dose 255 J/cm(2), energy 2 J. Teeth were capped with Ca(OH)(2), Ca(OH)(2) cement and restored with amalgam. All groups presented pulp repair. on 25(th) day the thickness of the formed dentin barrier was different between the groups GI and GII (p < 0.05) and between groups GI and GIII (p < 0.01). on 60(th) day there was difference between GI and GIII (p < 0.01). It may be concluded that, LLLT 688 nm and 785 nm accelerated dentin barrier formation and consequently pulp repair process, with best results using infrared laser 785 nm. (c) 2009 by Astro Ltd. Published exclusively by WLLEY-VCH Verlag GmbH & Co. KGaA