Effect of defocused infrared diode laser on salivary flow rate and some salivary parameters of rats

This study aims to investigate whether infrared diode low-level laser therapy (LLLT) increased salivary flow rate and altered pH value, protein concentration, and peroxidase and amylase activities in saliva of rats. Wistar rats were used and divided into three groups. Experimental groups (A and 13) had their parotid, submandibular and sublingual glands submitted to diode laser, 808-nm wavelength, on two consecutive days. The dose results were 4 and 8 J/cm(2), respectively. A red guide light was used to visualize the irradiated area. Group C was irradiated only with red pilot beam and served as control. The saliva samples were collected after each irradiation step (first and second collection days) and 1 week after the first irradiation (seventh day). Statistical analysis was performed, and differences were observed according to different days of salivary collection. The results showed that salivary flow rate for groups A and B was higher on the seventh day if it is compared to data obtained for the first day (p<0.05). LLLT applications on salivary glands are a therapy procedure that requires further studies.

Copolymerization of methyl methacrylate and allyl acetate Part I. Rate of reaction

Free radical bulk copolymerization of methyl methacrylate (MMA) and allyl acetate (AAc) has been investigated using electron spin resonance (ESR) and FT-near infrared (FTNIR) spectroscopy. Data are used to evaluate the rate constants. The mole fraction of AAc plays an important role in the copolymerization of these two monomers. AAc not only delays the Trommsdorff effect but also increases the onset of percentage total conversion at which the Trommsdorff region begins. With AAc fraction 0.5 and higher, no Trommsdorff effect was observed. Inclusion of AAc into copolymer structure mainly occurs in the Trommsdorf region or when the AAc fraction in the comonomer feed is dominant. This is associated with a drop in the concentration of propagating radicals. However, ESR spectra indicate that the MMA propagating radical is predominant during the reaction. In the comonomer mixtures where a Trommsdorff region can be observed, the addition of AAc does not produce any significant change in k(p) and k(t) in the steady state region. Major changes in k(p) and k(t) are observed after the gel point and glassy state, respectively. (C) 2001 Society of Chemical Industry.

Free-radical bulk polymerization of styrene: ESR and near-infrared spectroscopic study of the entire conversion range

The free radical polymerization of styrene in bulk was monitored by ESR and FT near-infrared spectroscopy at 70°C for a series of concentrations of the initiator, dimethyl 2,2′-azobis(isobutyrate). In order to obtain detailed kinetic information over the intire conversion range, and the gel effect range in particular, conversion and free radical concentration data points were accumulated with exceptionally short time intervals. The polystyrene radical concentration ([St•]) went through a sharp maximum at the gel effect, a feature that has hitherto escaped observation due to the rapid concentration changes in the gel effect range relative to the data point time intervals of previous studies. Temperature measurements throughout the polymerization were employed to calculate that a temperature increase was not the cause of the [St•] maximum, which thus appeares to be a genuine feature of the gel effect of this system under isothermal conditions. The propagation rate constant (kp) as a function of monomer conversion exhibited a marked dependence on initiator concentration at high monomer conversion; the sharp decrease in kp with increasing conversion was shifted to higher conversions with increasing initiator concentration.

Fluorescence spectrum of a two-level atom driven by a multiple modulated field

We investigate the fluorescence spectrum of a two-level atom driven by a multiple amplitude-modulated field. The driving held is modeled as a polychromatic field composed of a strong central (resonant) component and a large number of symmetrically detuned sideband fields displaced from the central component by integer multiples of a constant detuning. Spectra obtained here differ qualitatively from those observed for a single pair of modulating fields [B. Blind, P.R. Fontana, and P. Thomann, J. Phys. B 13, 2717 (1980)]. In the case of a small number of the modulating fields, a multipeaked spectrum is obtained with the spectral features located at fixed frequencies that are independent of the number of modulating fields and their Rabi frequencies. As the number of the modulating fields increases, the spectrum ultimately evolves to the well-known Mellow triplet with the sidebands shifted from the central component by an effective Rabi frequency whose magnitude depends on the initial relative phases of the components of the driving held. For equal relative phases, the effective Rabi frequency of the driving field can be reduced to zero resulting in the disappearance of fluorescence spectrum, i.e., the atom can stop interacting with the field. When the central component and the modulating fields are 180 degrees out of phase, the spectrum retains its triplet structure with the sidebands located at frequencies equal to the sum of the Rabi frequencies of the component of the driving field. Moreover, we shaw that the frequency of spontaneous emission can be controlled and switched from one frequency to another when the Rabi frequency or initial phase of the modulating fields are varied.

Outcomes of transient evoked otoacoustic emission testing in 6-year-old school children: A comparison with pure tone screening and tympanometry

Objectives: (1) To establish test performance measures for Transient Evoked Otoacoustic Emission testing of 6-year-old children in a school setting; (2) To investigate whether Transient Evoked Otoacoustic Emission testing provides a more accurate and effective alternative to a pure tone screening plus tympanometry protocol. Methods: Pure tone screening, tympanometry and transient evoked otoacoustic emission data were collected from 940 subjects (1880 ears), with a mean age of 6.2 years. Subjects were tested in non-sound-treated rooms within 22 schools. Receiver operating characteristics curves along with specificity, sensitivity, accuracy and efficiency values were determined for a variety of transient evoked otoacoustic emission/pure tone screening/tympanometry comparisons. Results: The Transient Evoked Otoacoustic Emission failure rate for the group was 20.3%. The failure rate for pure tone screening was found to be 8.9%, whilst 18.6% of subjects failed a protocol consisting of combined pure tone screening and tympanometry results. In essence, findings from the comparison of overall Transient Evoked Otoacoustic Emission pass/fail with overall pure tone screening pass/fail suggested that use of a modified Rhode Island Hearing Assessment Project criterion would result in a very high probability that a child with a pass result has normal hearing (true negative). However, the hit rate was only moderate. Selection of a signal-to-noise ratio (SNR) criterion set at greater than or equal to 1 dB appeared to provide the best test performance measures for the range of SNR values investigated. Test performance measures generally declined when tympanometry results were included, with the exception of lower false alarm rates and higher positive predictive values. The exclusion of low frequency data from the Transient Evoked Otoacoustic Emission SNR versus pure tone screening analysis resulted in improved performance measures. Conclusions: The present study poses several implications for the clinical implementation of Transient Evoked Otoacoustic Emission screening for entry level school children. Transient Evoked Otoacoustic Emission pass/fail criteria will require revision. The findings of the current investigation offer support to the possible replacement of pure tone screening with Transient Evoked Otoacoustic Emission testing for 6-year-old children. However, they do not suggest the replacement of the pure tone screening plus tympanometry battery. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.

Olfaction in the Queensland fruit fly, Bactrocera tryoni. II: Response spectra and temporal encoding characteristics of the carbon dioxide receptors

Single-unit electrophysiology was used to record the nerve impulses from the carbon dioxide receptors of female Queensland fruit flies, Bactrocera tryoni. The receptors responded to stimulation in a phasic-tonic manner and also had a period of inhibition of the nerve impulses after the end of stimulation, at high stimulus intensities. The cell responding to carbon dioxide was presented with a range of environmental odorants and found to respond to methyl butyrate and 2-butanone. The coding characteristics of the carbon dioxide cell and the ability to detect other odorants are discussed, with particular reference to the known behavior of the fly.

The damped and coherently-driven Jaynes-Cummings model

We investigate the influence of a single-mode cavity on the Autler-Townes doublet that arises when a three-level atom is strongly driven by a laser field tuned to one of the atomic transitions and probed by a tunable, weak field coupled to the other transition. We assume that the cavity mode is coupled to the driven transition and the cavity and laser frequencies are equal to the atomic transition frequency. We find that the Autler-Townes spectrum can have one, two or three peaks depending on the relative magnitudes of the Rabi frequencies of the cavity and driving fields. We show that, in order to understand the three-peaked spectrum, it is necessary to go beyond the secular approximation, leading to interesting quantum interference effects. We find that the positions and relative intensities of the three spectral components are affected strongly by the atom-cavity coupling strength g and the cavity damping K. For an increasing g and/or decreasing K the triplet evolves into a single peak. This results in 'undressing' of the system such that the atom collapses into its ground state. We interpret the spectral features in terms of the semiclassical dressed-atom model, and also provide complementary views of the cavity effects in terms of quantum Langevin equations and the fully quantized, 'double -dressing' model.

Carbene and nitrene rearrangements: A theoretical study of cyclic allenes and carbenes, carbodiimides, and azirines

B3LYP/6-31G(d) calculations of structures, energies, and infrared spectra of several rearrangement products of (hetero)aromatic nitrenes and carbenes are reported. 3-Isoquinolylnitrene 36 ring closes to the azirine 37 prior to ring expansion to the potentially stable but unobserved seven-membered-ring carbodiimide 38 and diazacycloheptatrienylidene C-s-39S. A new, stable cycloheptatrienylidene, C-s-19S, is located on the naphthylcarbene energy surface. 4-Quinolylnitrene undergoes reaction via the azirine 50 in solution, but ring expansion to the stable seven-membered-ring ketenimine 47 under Ar matrix photolysis conditions. There is excellent agreement between calculated infrared spectra of 1,5-diazacyclohepta-1,2,4,6-tetraene 54 (obtained by photolysis of 4-pyridyl azide), 1-azacyclohepta-1,2,4,6-tetraene 5, 1-azacyclohepta-1,3,5,6-tetraene 55, and 1-azacyclohepta-1,3,4,6-tetraene 56 and the available experimental data.