Intersession reliability of a posturo-stabilometric test, using a force platform

To evaluate the intersession reliability of a posturo-stabilometric examination. METHODS: Single blind clinical trial conducted in two sessions over two weeks. 44 healthy volunteers free from postural and temporomandibular disorders. All the subjects complied with the criteria for completing the study. All the subjects underwent two sessions of posturo-stabilometric examinations in different visual and mandibular conditions. Sway area, sway length and the coordinates of the center of pressure were evaluated and statistically analyzed using the Intraclass correlation coefficient (ICC). RESULTS: All the posturo-stabilometric parameters seemed to have an excellent reproducibility with overall ICCs higher than 70% and good confidence intervals except for the sway area (ICC 0.422 with CI 0.283-0.560 with open eyes and ICC 0.554 with CI 0.424-0.683 with closed eyes). CONCLUSIONS: The posturo-stabilometric examination carried out using a force platform has a good intrasession and intersession reliability, especially considering sway velocity, COP X and COP Y parameters. The force platform usefulness in analyzing static posture is confirmed in any medical field

The association between Occlusion Time and Temporomandibular Disorders

Introduction: Recently, some published studies show there is a multifactorial origin for Temporomandibular Disorders, but the dental occlusion's contribution to the development of Temporomandibular Disorders, and how it may influence the adaptive capacity of the Stomatognathic system, it's still unclear. The aim of this study is to evaluate the correlation between the Occlusion Time and Temporomandibular Disorders. Methods: A total of 54 patients were enrolled in the study (24 males and 30 females, mean age 27.94±8.21years). The TMD group (8 males and 10 females) consisted of subjects who presented with at least 1 of the following signs of Temporomandibular Disorders: Temporomandibular Joint sounds (clicking or crepitation), Temporomandibular Joint locking episodes, limited mandibular opening, painful limitation of mandibular movements, pain to palpation of the Temporomandibular Joint or of the masticatory muscles. The control group (16 males and 20 females) presented as free from Temporomandibular Disorders. The T-Scan III computerized occlusal analysis system was to record the subjects' Occlusion. Times during eight mandibular opening-closing movements. Results: The two-ways ANOVA test analyzed the variations for group and sex, showing that the TMD group mean Occlusion Time (0.64±0.21s) was statistically significantly longer than the control group mean Occlusion Time (0.45±0.17s) (p<0.001). Significant differences were also found for gender where the mean OT of female subjects was longer than males one with statistical significance (p-value<0.01). Conclusions: The computerized analysis of the Occlusion Time in patients affected by TMJ problems has to be carefully considered as adjunctive instrumental device

Mean age gradient and asymmetry in the star formation history of the Small Magellanic Cloud

We derive the star formation history in four regions of the Small Magellanic Cloud (SMC) using the deepest VI color-magnitude diagrams (CMDs) ever obtained for this galaxy. The images were obtained with the Advanced Camera for Surveys onboard the Hubble Space Telescope and are located at projected distances of 0.5-2 degrees from the SMC center, probing the main body and the wing of the galaxy. We derived the star-formation histories (SFH) of the four fields using two independent procedures to fit synthetic CMDs to the data. We compare the SFHs derived here with our earlier results for the SMC bar to create a deep pencil-beam survey of the global history of the central SMC. We find in all the six fields observed with HST a slow star formation pace from 13 to 5-7 Gyr ago, followed by a ~ 2-3 times higher activity. This is remarkable because dynamical models do not predict a strong influence of either the LMC or the Milky Way (MW) at that time. The level of the intermediate-age SFR enhancement systematically increases towards the center, resulting in a gradient in the mean age of the population, with the bar fields being systematically younger than the outer ones. Star formation over the most recent 500 Myr is strongly concentrated in the bar, the only exception being the area of the SMC wing. The strong current activity of the latter is likely driven by interaction with the LMC. At a given age, there is no significant difference in metallicity between the inner and outer fields, implying that metals are well mixed throughout the SMC. The age-metallicity relations we infer from our best fitting models are monotonically increasing with time, with no evidence of dips. This may argue against the major merger scenario proposed by Tsujimoto and Bekki 2009, although a minor merger cannot be ruled out.Comment: 30 pages, 16 figures, accepted for publication in Ap

History and modes of star formation in the most active region of the Small Magellanic Cloud, NGC 346

We discuss the star formation history of the SMC region NGC 346 based on Hubble Space Telescope images. The region contains both field stars and cluster members. Using a classical synthetic CMD procedure applied to the field around NGC 346 we find that there the star formation pace has been rising from a quite low rate 13 Gyr ago to \approx 1.4 \times 10^{-8} Mo yr^{-1}pc^{-2} in the last 100 Myr. This value is significantly higher than in other star forming regions of the SMC. For NGC 346 itself, we compare theoretical and observed Color-Magnitude Diagrams (CMDs) of several stellar sub-clusters identified in the region, and we derive their basic evolution parameters. We find that NGC 346 experienced different star formation regimes, including a dominant and focused "high density mode", with the sub-clusters hosting both pre-main sequence (PMS) and upper main sequence (UMS) stars, and a diffuse "low density mode", as indicated by the presence of low-mass PMS sub-clusters. Quantitatively, the star formation in the oldest sub-clusters started about 6 Myr ago with remarkable synchronization, it continued at high rate (up to 2 \times 10^{-5} Mo yr^{-1} pc^{-2}) for about 3 Myr and is now progressing at a lower rate. Interestingly, sub-clusters mainly composed by low mass PMS stars seem to experience now the first episode of star formation, following multi-seeded spatial patterns instead of resulting from a coherent trigger. Two speculative scenarios are put forth to explain the deficiency of UMS stars: the first invokes under-threshold conditions of the parent gas; the second speculates that the initial mass function (IMF) is a function of time, with the youngest sub-clusters not having had sufficient time to form more massive stars.Comment: 17 pages. Accepted for publication in A

Study of the luminous blue variable star candidate G26.47+0.02 and its environment

The luminous blue variable (LBV) stars are peculiar very massive stars. The study of these stellar objects and their surroundings is important for understanding the evolution of massive stars and its effects on the interstellar medium. We study the LBV star candidate G26.47+0.02. Using several large-scale surveys in different frequencies we performed a multiwavelength study of G26.47+0.02 and its surroundings. We found a molecular shell (seen in the 13CO J=1-0 line) that partially surrounds the mid-infrared nebula of G26.47+0.02, which suggests an interaction between the strong stellar winds and the molecular gas. From the HI absorption and the molecular gas study we conclude that G26.47+0.02 is located at a distance of ~4.8 kpc. The radio continuum analysis shows a both thermal and non-thermal emission toward this LBV candidate, pointing to wind-wind collision shocks from a binary system. This hypothesis is supported by a search of near-IR sources and the Chandra X-ray analysis. Additional multiwavelength and long-term observations are needed to detect some possible variable behavior, and if that is found, to confirm the binary nature of the system.Comment: accepted in A&A 01/05/201

Star formation history in the SMC: the case of NGC602

Deep HST/ACS photometry of the young cluster NGC 602, located in the remote low density "wing" of the Small Magellanic Cloud, reveals numerous pre-main sequence stars as well as young stars on the main sequence. The resolved stellar content thus provides a basis for studying the star formation history into recent times and constraining several stellar population properties, such as the present day mass function, the initial mass function and the binary fraction. To better characterize the pre-main sequence population, we present a new set of model stellar evolutionary tracks for this evolutionary phase with metallicity appropriate for the Small Magellanic Cloud (Z = 0.004). We use a stellar population synthesis code, which takes into account a full range of stellar evolution phases to derive our best estimate for the star formation history in the region by comparing observed and synthetic color-magnitude diagrams. The derived present day mass function for NGC 602 is consistent with that resulting from the synthetic diagrams. The star formation rate in the region has increased with time on a scale of tens of Myr, reaching $0.3-0.7 \times 10^{-3} M_\odot yr^{-1}$ in the last 2.5 Myr, comparable to what is found in Galactic OB associations. Star formation is most complete in the main cluster but continues at moderate levels in the gas-rich periphery of the nebula.Comment: 24 pages. Accepted for publication in A

Star Formation History in two fields of the Small Magellanic Cloud Bar

The Bar is the most productive region of the Small Magellanic Cloud in terms of star formation but also the least studied one. In this paper we investigate the star formation history of two fields located in the SW and in the NE portion of the Bar using two independent and well tested procedures applied to the color-magnitude diagrams of their stellar populations resolved by means of deep HST photometry. We find that the Bar experienced a negligible star formation activity in the first few Gyr, followed by a dramatic enhancement from 6 to 4 Gyr ago and a nearly constant activity since then. The two examined fields differ both in the rate of star formation and in the ratio of recent over past activity, but share the very low level of initial activity and its sudden increase around 5 Gyr ago. The striking similarity between the timing of the enhancement and the timing of the major episode in the Large Magellanic Cloud is suggestive of a close encounter triggering star formation.Comment: 30 pages, 22 figures, accepted for publication in Ap

Influence of activation protocol on perceived pain during rapid maxillary expansion

To investigate the influence of two different activation protocols on the timing and intensity of pain during rapid maxillary expansion (RME)