Does the bracket-ligature combination affect the amount of orthodontic space closure over three months? A randomized controlled trial

OBJECTIVE: To investigate the effect of bracket-ligature combination on the amount of orthodontic space closure over three months. DESIGN: Randomized clinical trial with three parallel groups. SETTING: A hospital orthodontic department (Chesterfield Royal Hospital, UK). PARTICIPANTS: Forty-five patients requiring upper first premolar extractions. METHODS: Informed consent was obtained and participants were randomly allocated into one of three groups: (1) conventional pre-adjusted edgewise brackets and elastomeric ligatures; (2) conventional pre-adjusted edgewise brackets and Super Slick((R)) low friction elastomeric ligatures; (3) Damon 3MX((R)) passive self-ligating brackets. Space closure was undertaken on 0.019x0.025-inch stainless steel archwires with nickel-titanium coil springs. Participants were recalled at four weekly intervals. Upper alginate impressions were taken at each visit (maximum three). The primary outcome measure was the mean amount of space closure in a 3-month period. RESULTS: A one-way ANOVA was undertaken [dependent variable: mean space closure (mm); independent variable: group allocation]. The amount of space closure was very similar between the three groups (1 mm per 28 days); however, there was a wide variation in the rate of space closure between individuals. The differences in the amount of space closure over three months between the three groups was very small and non-significant (P = 0.718). CONCLUSION: The hypothesis that reducing friction by modifying the bracket/ligature interface increases the rate of space closure was not supported. The major determinant of orthodontic tooth movement is probably the individual patient response

Explicit Solution of the Time Domain Volume Integral Equation Using a Stable Predictor-Corrector Scheme

An explicit marching-on-in-time (MOT) scheme for solving the time domain volume integral equation is presented. The proposed method achieves its stability by employing, at each time step, a corrector scheme, which updates/corrects fields computed by the explicit predictor scheme. The proposedmethod is computationally more efficient when compared to the existing filtering techniques used for the stabilization of explicit MOT schemes. Numerical results presented in this paper demonstrate that the proposed method maintains its stability even when applied to the analysis of electromagnetic wave interactions with electrically large structures meshed using approximately half a million discretization elements

Supplmentary Feeding and Management Strategies to Overcome Drought Situations on Three High Producing New Zealand Seasonal Dairy Farms

This paper investigates the outcomes of the management strategies to overcome dry summer conditions on three New Zealand seasonal supply dairy farms where the summer management philosophy is towards production rather than survival aimed at giving the farmer control rather than accepting the unreliable production outcomes often achieved. Actual data collected from the case farms as part of a large on-farm monitoring programme was used to model the dry 1998/99 season. This was compared with simulated models for an average season to estimate milksolids responses (g milksolids (MS)/kg DM) and net returns (cents/kg DM) to the additional feeds used. In response to a 30% reduction in summer pasture growth, farmers fed more additional feeds (542 kg DM/ha) and achieved fewer lactation days/ha resulting a reduction of 12.5% in per cow and 19.8% in per hectare milksolids production. The average response achieved to the addition feed was 104g MS/kg DM at a net return of 20.6cents/kg DM fed above the cost of additional feed. It was concluded that the management strategies achieved the target of having cows in good condition and at a satisfactory level of production at the end of summer to enable autumn milk production to be captured and that farmers should look at further increasing the level of supplement fed in dry summer conditions

On hemispheric differences in evoked potentials to speech stimuli

Confirmation is provided for the belief that evoked potentials may reflect differences in hemispheric functioning that are marginal at best. Subjects were right-handed and audiologically normal men and women, and responses were recorded using standard EEG techniques. Subjects were instructed to listen for the targets while laying in a darkened sound booth. Different stimuli, speech and tone signals, were used. Speech sounds were shown to evoke a response pattern that resembles that to tone or clicks. Analysis of variances on peak amplitude and latency measures showed no significant differences between hemispheres, however, a Wilcoxon test showed significant differences in hemispheres for certain target tasks

Topologically Alice Strings and Monopoles

Symmetry breaking can produce ``Alice'' strings, which alter scattered charges and carry monopole number and charge when twisted into loops. Alice behavior arises algebraically, when strings obstruct unbroken symmetries -- a fragile criterion. We give a topological criterion, compelling Alice behavior or deforming it away. Our criterion, that \pi_o(H) acts nontrivially on \pi_1(H), links topologically Alice strings to topological monopoles. We twist topologically Alice loops to form monopoles. We show that Alice strings of condensed matter systems (nematic liquid crystals, helium 3A, and related non-chiral Bose condensates and amorphous chiral superconductors) are topologically Alice, and support fundamental monopole charge when twisted into loops. Thus they might be observed indirectly, not as strings, but as loop-like point defects. We describe other models, showing Alice strings failing our topological criterion; and twisted Alice loops supporting deposited, but not fundamental, monopole number.Comment: 2 figures; this paper consolidates preprints hep-th/0304161 and hep-th/0304162, to appear in Phys. Rev.

On the generalized Davenport constant and the Noether number

Known results on the generalized Davenport constant related to zero-sum sequences over a finite abelian group are extended to the generalized Noether number related to the rings of polynomial invariants of an arbitrary finite group. An improved general upper bound is given on the degrees of polynomial invariants of a non-cyclic finite group which cut out the zero vector.Comment: 14 page

Building robust age models for speleothems – A case-study using coeval twin stalagmites

We use the uranium-series (U-Th) dating method to investigate the accuracy of a relative chronology based on laminae correlation between a pair of coeval twin stalagmites and compare their stable isotope and trace element records based on the two chronologies. U-Th dating shows that a relative chronology based on laminae correlation can be inaccurate: a hiatus in one of the stalagmites was not recognised, as well as more subtle changes in growth rates. Use of the stratigraphic correlation alone resulted in significant differences in the timing of stable isotopes and trace element peaks, with implications for their interpretation. Our results reveal the importance of a robust and direct chronology with which to interpret proxy data. Poor relative chronologies can lead to a misinterpretation of palaeoclimate data. The study reveals potential implications for speleothem records where proxy data and samples for dating were not taken in close proximity to each other and/or were correlated via laminae over distances of more than a few centimetres