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We present a method for synchronization of chaos generators based on transmission of an analog chaotic waveform in a digital form. Experimental comparisons between digital and analog transmission of chaos from a delayed differential feedback system are performed. Synchronization is demonstrated to be between 18 and 39 dB (or equivalently 63 to 7943 times) better for digital transmission than analog. Coherent chaotic modulation and demodulation is demonstrated in a situation where there is no effective synchronization using analog transmission. [ABSTRACT FROM AUTHOR]

The aims of this study were to test the hypothesis that flossing after brushing with a fluoridated toothpaste may lower salivary fluoride (F), and to evaluate the consequence of subsequent F mouthwash use. Twenty adults used 3 oral hygiene regimes in a randomised order: A, brushing with an NaF toothpaste; B, as A but followed by professional flossing; C, as B followed by rinsing with an NaF mouthwash. Saliva samples were collected up to 120 min after each regime and analysed for F. The mean area under the clearance curve value for regime C was statistically significantly greater than the corresponding values for A and B (p < 0.0001), which differed little. The regime that included the mouthwash may provide better anticaries protection. Copyright © 2009 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

We present a methodology for designing wideband, shot noise limited photodetectors using commercially available components and microwave engineering techniques. We use this methodology to design and construct a photodetector using wideband microwave amplifiers and a 3.5 GHz bandwidth photodiode. Consistent with our analytic models, the photodetector exhibits linear behavior up to a level of 6.5 dB clearance between shot noise and dark noise from 2.0 to 3.5 GHz at 10 mA of photocurrent, reducing to 3.5 dB of clearance at 6.4 GHz. [ABSTRACT FROM AUTHOR]

Abstract Background and Aim: The experimental gingivitis model is a well-established method in comparing the chemical antiplaque activity of agents and products. The aim of the present study was to use time in order to achieve an exit level of bleeding on probing (BOP) as the primary outcome variable. Methods: The study was a single blind, randomised four treatment parallel group design employing 76 healthy volunteers. The cohort was accepted into the study proper if they achieved a level of ≤ 25% BOP after a 5-week pre-study oral hygiene phase. At baseline, 1, 2, 3, 4, 5 weeks BOP, modified gingival index (MGI) and plaque index scores were obtained from each subject. After baseline, oral hygiene was suspended and subjects rinsed twice daily with one of the test rinses, namely: 1 0.05% cetylpyridinium chloride 2 Control fluoride 3 0.2% chlorhexidine 4 0.3% triclosan Subjects were removed from the study when they achieved ≥ 50% BOP. Using the baseline and exit BOP, MGI and plaque, a deterioration rate for each parameter was derived and used as the unit of analysis. Results: There were highly significant treatment differences for all three parameters. Paired analyses revealed chlorhexidine was highly significantly more effective than the other rinses for all three parameters. CPC and triclosan were not different from the control for BOP, but CPC was significantly different from the control for MGI and plaque, and triclosan was different from the control for plaque. There were no differences between the CPC and triclosan rinses. Conclusions: The method achieved the expected result of differentiating between the chlorhexidine and the other rinses. Some modification of the method, primarily to group sizes, should improve specificity. The method has the considerable volunteer appeal of early exit, particularly when allocated to control or low activity treatments for plaque. [ABSTRACT FROM AUTHOR]

It is possible to estimate the time-domain Green’s function of a channel based on measurements of ambient noise by sensors at either end of the channel. This paper presents theoretical results for the impact of filtering on this problem. These results lead to the development of two experimental rules-of-thumb. It is shown that there exists a relationship between system bandwidth and sensor separation, which determines the resolvability of the measurements. The relationship between high-pass filtering and differentiation is discussed, contributing to the debate about whether or not differentiation is required to estimate the time-domain Green’s function. [ABSTRACT FROM AUTHOR]

It is possible to estimate the time-domain Green’s function of a channel based on measurements of ambient noise by sensors at either end of the channel. This paper presents theoretical results for the impact of filtering on this problem. These results lead to the development of two experimental rules-of-thumb. It is shown that there exists a relationship between system bandwidth and sensor separation, which determines the resolvability of the measurements. The relationship between high-pass filtering and differentiation is discussed, contributing to the debate about whether or not differentiation is required to estimate the time-domain Green’s function. [ABSTRACT FROM AUTHOR]

Abstract Background/Aims: The abrasivity of toothpastes is usually determined using in vitro methods; as such, the clinical significance of the findings is uncertain. The aim of the present study was to develop and evaluate a method in situ to study abrasion of dentine by two toothpastes of different Relative Dentine Abrasivity (RDA). Method: The study was a single blind, randomised, 2 way cross over design involving 10 healthy dentate volunteers. Subjects wore an maxillary removable acrylic appliance containing two flat human dentine specimens, taped to expose a window of tissue, from 9 am to 4 pm during the two 10 working day study periods. No food or drink was consumed when the appliance was in place. On five occasions each day, the appliances were removed and the dentine windows brushed ex vivo with the allocated paste for 60 s each. Dentine abrasion at days 5 and 10 was measured using a profilometer. Results: Both toothpastes produced measurable abrasion in all subjects and the depth increased in most subjects between 5 and 10 days. There was significant subject and specimen variation both within and between toothpastes. There was significantly increased abrasion by the toothpaste with the higher RDA value and in mean terms the ratio of abrasion between the two pastes was similar to the ratio of the RDA values. Conclusion: The method in situ , already used to study dental hard tissue erosion, appears ideally suitable to study dental abrasion alone and the interaction between aetiological factors involved in tooth wear. [ABSTRACT FROM AUTHOR]

AbstractObjectives: To evaluate a modified tooth stain index and determine the effect of dietary factors on stain formation. Methods: At baseline, 182 adult volunteers were given a full oral prophylaxis followed by stain assessment using a modification of the Lobene index. This involved assigning separate scores to the mesial (M) and distal (D) sites of each tooth, in addition to the standard gingival area (G) and tooth body (B). For each site, stain intensity and areas were scored. The sum of (intensity×area) scores was calculated for all sites (GBMD-value) and for the gingival and body sites only (GB-value). The subjects used a standard abrasive dentifrice and a soft toothbrush for 6 weeks. Results: Stain was reassessed and the average increase in GBMD-value was 20.9 (sd=9.9) (buccal aspect) and 29.9 (sd=18.0) (lingual aspect). The corresponding GB-values were 4.4 (sd=4.8) and 12.5 (sd=10.2). The coefficients of variation of the GBMD index values were consistently lower than those of the GB values. Smoking and tea-drinking were found to be the only significant (p<0.001) factors investigated for stain formation. Conclusions: It is concluded that the modified index may well be advantageous to its conventional counterpart because sites with most visible stain are assessed separately and because it may also offer higher discriminatory power due to a lower coefficient of variation. [ABSTRACT FROM AUTHOR]

A potassium citrate-SMFP containing dentifrice was tested in a double-blind 8-week clinical trial on subjects with a history of dentinal hypersensitivity. A dentifrice containing SMFP but no potassium salt was used as the control and a 2nd test dentifrice containing potassium nitrate-SMFP was assessed at the same time. The sensitivity of the subjects was evaluated at 0, 3 and 8 weeks using electrical and tactile methods plus a 1-s air blast. The sensitivity scores for each subject at each examination were summarised as a proportion of the examined teeth deemed sensitive. Assessment of any effects of the dentifrices was via an analysis of covariance of the logit transformation of these proportions with the baseline value as the covariate. The use of this novel method of analysis had the advantage of taking into account changes in sensitivity of all of the teeth, both sensitive and non-sensitive, since electrical measurements indicated effects on both. Of the original 120 subjects, III completed the trial and the 3 dentifrice groups remained well balanced for age, sex and sensitivity. All 3 dentifrice groups showed statistically significant reductions in sensitivity over the 8 weeks. However, the potassium citrate-SMFP dentifrice was significantly mere effective than either the control SMFP dentifrice, or the potassium nitrate- SMFP dentifrice, at reducing sensitivity after 3 weeks, and this difference plus further sensitivity reduction with all 3 dentifrices was observed after 8 weeks. [ABSTRACT FROM AUTHOR]