Dark solitons under higher-order dispersion.

We show theoretically that stable dark solitons can exist in the presence of pure quartic dispersion, and also in the presence of both quadratic and quartic dispersive effects, displaying a much greater variety of possible solutions and dynamics than for pure quadratic dispersion. The interplay of the two dispersion orders may lead to oscillatory non-vanishing tails, which enables the possibility of bound, potentially stable, multi-soliton states. Dark soliton-like states that connect to low-amplitude oscillations are also shown to be possible. Dynamical evolution results corroborate the stability picture obtained, and possible avenues for dark soliton generation are explored.

Kink-Kink and Kink-Antikink Interactions with Long-Range Tails.

In this Letter, we address the long-range interaction between kinks and antikinks, as well as kinks and kinks, in φ^{2n+4} field theories for n>1. The kink-antikink interaction is generically attractive, while the kink-kink interaction is generically repulsive. We find that the force of interaction decays with the 2n/(n-1)th power of their separation, and we identify the general prefactor for arbitrary n. Importantly, we test the resulting mathematical prediction with detailed numerical simulations of the dynamic field equation, and obtain good agreement between theory and numerics for the cases of n=2 (φ^{8} model), n=3 (φ^{10} model), and n=4 (φ^{12} model).

Effects of parity-time symmetry in nonlinear Klein-Gordon models and their stationary kinks.

In this work, we introduce some basic principles of PT-symmetric Klein-Gordon nonlinear field theories. By formulating a particular antisymmetric gain and loss profile, we illustrate that the stationary states of the model do not change. However, the stability critically depends on the gain and loss profile. For a symmetrically placed solitary wave (in either the continuum model or a discrete analog of the nonlinear Klein-Gordon type), there is no effect on the steady state spectrum. However, for asymmetrically placed solutions, there exists a measurable effect of which a perturbative mathematical characterization is offered. It is generally found that asymmetry towards the lossy side leads towards stability, while towards the gain side produces instability. Furthermore, a host of finite size effects, which disappear in the infinite domain limit, are illustrated in connection to the continuous spectrum of the problem.

Growth indicators in orthodontic patients. Part 1: comparison of cervical vertebral maturation and hand-wrist skeletal maturation.

AIM: The purpose of this study was to predict the skeletal maturation status based on the assessment of cervical vertebrae from lateral cephalometric radiographs and to compare these findings with the skeletal maturity of the same individuals judged from the hand-wrist radiographs. MATERIALS AND METHODS: Lateral cephalometric and left hand-wrist radiographs of 393 Caucasian children from 8 to 18 years old were evaluated. On the hand-wrist radiographs the classification of Bjork [1972] and Grave and Brown [1976] was used to assess skeletal maturity (HWSS). Cervical vertebral maturation was also evaluated on lateral cephalometric radiographs using the improved CVMS method described by Baccetti, Franchi, and McNamara [2002]. These methods were correlated using the chi-square test. RESULTS: The chi-square test showed that skeletal maturational values obtained by the CVMS method were significantly correlated with the skeletal values obtained from the hand-wrist analysis for both genders (p<0.05). However, gender differentiation exists in CVMS method regarding the peak of growth spurt. CONCLUSION: The results of this study show that the CVMS method was compatible with a commonly used hand-wrist analysis method. The lateral cephalometric radiograph belonging to the standard set of records would be sufficient to evaluate skeletal maturity.

Growth indicators in orthodontic patients. Part 2: comparison of cervical bone age to hand-wrist skeletal age. Relationship with chronological age.

AIM: The purpose of this study was to investigate the relationship between hand-wrist skeletal age, chronological age and cervical skeletal age as assessed by lateral cephalometric radiograph. MATERIALS AND METHODS: Lateral cephalometric and left hand-wrist radiographs of 393 Caucasian children from 8 to 18 years old were evaluated. On the hand-wrist radiographs average values of the children's skeletal age as described by Schopf (1978), based on the classification of Bjork (1972), Grave and Brown (1976) were used. Cervical vertebral bone age also was depicted, using the method described by Mito, Sato, and Mitani. Pearson correlation coefficients (r) and regression analysis were calculated to assess the linear relationship between chronological, cervical bone and hand-wrist skeletal age. RESULTS: The cervical skeletal age correlated significantly with both the chronological and the hand-wrist skeletal age for each gender. However, the correlation coefficient between cervical skeletal age and hand-wrist skeletal age for both females (r 0.81) and males (0.76) is higher than that between cervical skeletal age and chronological age (females r 0.73; males r 0.72). In addition, regression analysis indicates that the relationship between cervical skeletal age and hand-wrist skeletal age is stronger than the relationship between cervical skeletal age and chronological age for both sexes. CONCLUSION: Cervical skeletal age reflects skeletal status because it can approximate hand-wrist skeletal age, which is considered to be the most reliable method for measuring the degree of maturity.

Comparison of increased overjet cases and controls: normative data for condylar positions.

The aim was to compare normal overjet versus large overjet cases with clinically healthy temporomandibular joints (TMJ); to establish normative data regarding the difference between condylar positions in centric occlusion (CO) and maximum intercuspation (MI) and deflective CO contacts. Two study groups of normal overjet and large overjet cases consisted each of 33 subjects with no detectable clinical signs of temporomandibular disorder (TMD). CO-MI differences were recorded using the SAM Mandibular Position Indicator. Deflective contacts were examined on models mounted in CO. There was a significant difference between groups in the vertical (P = 0.030) and transverse (P = 0.008) range of movement from CO to MI, but not in the antero-posterior direction. There were no differences in the location of deflective contacts. Results of this study showed that patients with increased overjet show some differences compared with normal overjet patients, even in the non-patients. Further research on TMD patients is needed to find out about the role these features play in the aetiology and treatment of temporomandibular disorder (TMD). This study indicates that the clinician should be paying special attention to the TMJ status of patients with a large overjet.

Compatibility of mechanical and computerized axiographs: a pilot study.

STATEMENT OF PROBLEM: There is little known information comparing axiographic data obtained with a mechanical device and data obtained with a computerized device. However, long-term follow-up of patients may necessitate comparison of previously made mechanical axiographic data with records obtained through computer-aided axiography. PURPOSE: The purpose of this study was to compare measurements between mechanical and computerized axiographs in recording the rotational and translation movements of the mandible. MATERIAL AND METHODS: The study enrolled 31 subjects with no detectable clinical signs of temporomandibular disorders. A single operator obtained 3 separate axiographic tracings of right and left condylar paths for each subject, using repeated opening, closing, protrusive, and retrusive movements. Data were collected for both the mechanical (SAM Axiograph Axo 200), and the computerized axiographs (SAM Axiotron and Axo 500). Angular (degrees) and linear measurements (mm) for the mechanical axiograph were made from the tracings obtained on grid paper using a compass, ruler, and protractor. The computer performed the measurements for the computerized axiograph tracings. All parameters were compared statistically with a Wilcoxon signed rank test (alpha = .05). The same operator remeasured all mechanical axiographic tracings for 20 subjects 1 week later to evaluate measurement error. Chronbach's alpha was used as a measure of consistency between the 2 measurements. RESULTS: Mean opening and closing angles varied between 52.4 and 54.2 degrees, and mean protrusive, and retrusive angles varied between 50.1 and 54.9 degrees. Mean opening and closing distances varied between 11.4 and 12.3 mm, and mean protrusive and retrusive distances varied between 8.2 and 8.7 mm. Comparison with the Wilcoxon signed rank test showed no significant differences for any parameter tested. There were high and medium inter-item correlations between repeated measurements of the manual device when Chronbach's alpha was applied, but these results were not sufficient to prove consistency between 2 consecutive measurements. CONCLUSION: The results showed nonsignificant differences between the recordings of the mechanical and computerized axiographs tested. The authors hypothesize that minor differences may be attributed to hand-measuring errors for the tracings generated by the mechanical axiograph. This study is limited due to the impact of poor precision of the manual device on the study results when these recordings are compared to another instrument. Therefore, it is not possible to conclude that data from the manual and the computerized axiographs are compatible with each other.

Histopathological and immunohistochemical detection of protective effects of University of Wisconsin solution supplemented with iloprost on donor lung damage.

OBJECTIVE: Histopathological evaluation and immunohistochemical markers of surfactant B and CD34 were used to detect alveolar type II cell and pulmonary endothelial cell damage in order to assess the efficacy on donor lung protection of University of Wisconsin (UW) solution supplementation with iloprost. METHODS: Twelve rats were divided into two groups: UW solution was used alone in group I, and UW iloprost solution in group II. Lung samples were taken at regular intervals for pathological examination to evaluate alveolar cell integrity with hematoxylin and eosin staining. Preservation, of alveolar type II cell and pulmonary endothelial cells was assessed using surfactant B and CD34 immunomarkers, respectively. RESULTS: In both groups, alveolar integrity, surfactant, and CD34 revealed time-dependent, progressive damage, although this deterioration was less apparent among the iloprost-supplemented group. Alveolar integrity was better preserved at 4, 6, 8, 12, and 48 hours among group II rate. Surfactant staining showed significantly more deterioration at 12 and 24 hours in group I. Similarly, CD34 demonstrated significantly more injury at 6, 12, 24, and 48 hours in group I. CONCLUSION: Although progressive lung tissue damage assessed by histopathological and immunohistochemical methods was observed in both groups, our findings suggest less deterioration in the iloprost-supplemented group.

Comparison of deep bite and open bite cases: normative data for condylar positions, paths and radiographic appearances.

To compare normal overbite, deep bite and open bite cases with clinically healthy temporomandibular joints (TMJ) regarding the difference between condylar positions in centric relation (CR) and habitual or centric occlusion (CO), condylar paths and radiographic findings of condylar appearance in order to establish normative data. Three study groups of normal overbite, deep bite and open bite cases consisted each of 30 subjects with no detectable clinical signs of temporomandibular disorder. The CR-CO differences and axiographic tracings were recorded using the School Artikulator of Mack (SAM) diagnostic system. Condylar shape was evaluated on panoramic radiographs. The CR-CO differences were greater in the vertical plane in open bite cases, and direction of movements from CR to CO showed great variability. Open bite cases had significantly shorter condylar paths. Radiographic findings exhibited that 23% of the total sample showed evidence of erosion and 83% evidence of flattening of condyles. The erosion rates were higher in the open bite group, but flattening was seen more often in the deep bite group. Results of this study showed that open bite cases show larger vertical CR-CO slides and, shorter protrusion paths than normal and deep overbite cases. The radiographic appearance of condyles in non-patients may also differ significantly according to vertical incisor guidance type. Deep bite cases demonstrated a higher incidence of condylar flattening. This study indicates that the clinician should be paying special attention to the TMJ status of open bite patients.

Cephalometric evaluation of open bite treatment with NiTi arch wires and anterior elastics.

The aim of this study was to evaluate cephalometrically the effects of open bite treatment with NiTi arch wires and anterior elastics. The study group comprised of 17 patients who displayed a high angle skeletal pattern, along with an anterior open bite. After initial leveling, 0.016 x 0.022 inch upper accentuated-curve and lower reverse-curve arch wires were placed, with anterior elastics applied in the canine regions. Cephalometric assessment was carried out on lateral head films taken at the beginning of treatment and on average 2.8 months after open bite closure was obtained. The results of this study indicated that open bite closure had been achieved mainly by extrusion of the lower incisors and uprighting of the upper incisors. The functional occlusal plane was leveled by extrusion of lower premolars and uprighting of lower molars. Lateral cephalograms obtained from 10 patients who had been available after 1 year postretention were used to evaluate relapse changes. During the follow-up period, position of the upper and lower incisors and the inclination of the occlusal plane were maintained. However, extrusion of upper and lower molar teeth resulted in a reduction in overbite.