Does inter-vertebral range of motion increase after spinal manipulation? A prospective cohort study.

Background: Spinal manipulation for nonspecific neck pain is thought to work in part by improving inter-vertebral range of motion (IV-RoM), but it is difficult to measure this or determine whether it is related to clinical outcomes. Objectives: This study undertook to determine whether cervical spine flexion and extension IV-RoM increases after a course of spinal manipulation, to explore relationships between any IV-RoM increases and clinical outcomes and to compare palpation with objective measurement in the detection of hypo-mobile segments. Method: Thirty patients with nonspecific neck pain and 30 healthy controls matched for age and gender received quantitative fluoroscopy (QF) screenings to measure flexion and extension IV-RoM (C1-C6) at baseline and 4-week follow-up between September 2012-13. Patients received up to 12 neck manipulations and completed NRS, NDI and Euroqol 5D-5L at baseline, plus PGIC and satisfaction questionnaires at follow-up. IV-RoM accuracy, repeatability and hypo-mobility cut-offs were determined. Minimal detectable changes (MDC) over 4 weeks were calculated from controls. Patients and control IV-RoMs were compared at baseline as well as changes in patients over 4 weeks. Correlations between outcomes and the number of manipulations received and the agreement (Kappa) between palpated and QF-detected of hypo-mobile segments were calculated. Results: QF had high accuracy (worst RMS error 0.5o) and repeatability (highest SEM 1.1o, lowest ICC 0.90) for IV-RoM measurement. Hypo-mobility cut offs ranged from 0.8o to 3.5o. No outcome was significantly correlated with increased IV-RoM above MDC and there was no significant difference between the number of hypo-mobile segments in patients and controls at baseline or significant increases in IV-RoMs in patients. However, there was a modest and significant correlation between the number of manipulations received and the number of levels and directions whose IV-RoM increased beyond MDC (Rho=0.39, p=0.043). There was also no agreement between palpation and QF in identifying hypo-mobile segments (Kappa 0.04-0.06). Conclusions: This study found no differences in cervical sagittal IV-RoM between patients with non-specific neck pain and matched controls. There was a modest dose-response relationship between the number of manipulations given and number of levels increasing IV-RoM - providing evidence that neck manipulation has a mechanical effect at segmental levels. However, patient-reported outcomes were not related to this

Classical Simulation of Relativistic Quantum Mechanics in Periodic Optical Structures

Spatial and/or temporal propagation of light waves in periodic optical structures offers a rather unique possibility to realize in a purely classical setting the optical analogues of a wide variety of quantum phenomena rooted in relativistic wave equations. In this work a brief overview of a few optical analogues of relativistic quantum phenomena, based on either spatial light transport in engineered photonic lattices or on temporal pulse propagation in Bragg grating structures, is presented. Examples include spatial and temporal photonic analogues of the Zitterbewegung of a relativistic electron, Klein tunneling, vacuum decay and pair-production, the Dirac oscillator, the relativistic Kronig-Penney model, and optical realizations of non-Hermitian extensions of relativistic wave equations.Comment: review article (invited), 14 pages, 7 figures, 105 reference

U-Pb baddeleyite ages and geochemistry of dolerite dykes in the Bas Draa Inlier of the Anti-Atlas of Morocco: Newly identified 1380 Ma event in the West African Craton

In the Bas-Draa Inlier (Anti-Atlas, Morocco), the Paleoproterozoic basement which is cut by the Ediacaran Taourgha granite is also crosscut by numerous dykes of a variety of trends, mostly of uncertain age. Two doleritic dykes are dated by the ID-TIMS U-Pb method on baddeleyite and yield emplacement ages of 1381 +/- 8 Ma (MSWD = 0.84) and 1384 +/- 6 Ma (MSWD = 1.4) determined for a N135 degrees E and a N40 degrees E trending dyke, respectively. These dates represent the first geochronological evidence of a Mesoproterozoic magmatic event in the Anti-Atlas. This magmatic event falls in the previously considered ca 1.7-1.0 Ga (Mesoproterozoic) gap in geological activity in the Anti-Atlas. The poorly dated Taghdout and Taarotihate sequences could represent remnants of the ca. 1380 Ma magmatism and rift-related sedimentation. The Mesoproterozoic sedimentary succession of the Atar Group in the Taoudeni basin (Mauritania) could also represent a good candidate for rift-related sedimentation but it postdates the 1380 Ma magmatic event by 270 Ma. The dated 1380 Ma dykes are transitional to mildly alkaline basalts, not unlike some Hawaiian lavas. However, these dykes have a distinct negative Nb anomaly (a common features in many Large Igneous Provinces, LIPs), and this requires interaction with the lithosphere. This interaction may have occurred at the level of the lithospheric mantle or the crust. These newly dated 1380 Ma dykes may converge to the north, speculatively suggesting a magmatic center (associated with a 1380 Ma mantle plume?) along the northern margin, and possibly linked to rifting and possible breakup on that margin, and also to a regional uplift that largely removed the evidence of a 1380 Ma cover sequence. Contemporaneous 1380-1390 Ma magmatism is reported elsewhere on other crustal blocks, and that in northeastern Laurentia (northern Greenland), northern Siberia (Anabar shield), and Baltica (southern Urals) can be reconstructed with that of the Bas Draa Inlier (Anti Atlas region of the West African Craton, WAC) into a single Large Igneous Province (LIP) extending over an area of >1 million km(2), and associated with the final fragmentation of the Columbia (Nuna) supercontinent. (C) 2012 Elsevier B.V. All rights reserved

New constraints on the geochronology and Sm-Nd isotopic characteristics of Bas-Drâa mafic dykes, Anti-Atlas of Morocco

The Precambrian inliers of the Anti-Atlas belt across the southern part of Morocco contain numerous mafic dyke and sill swarms, which are thought to represent the erosional remnants of Proterozoic Large Igneous Provinces (LIPs). As part of an extended research campaign to date and characterize these LIPs, two amphiboles from one dyke within the Bas-Drâa inlier (western Anti-Atlas) yielded consistent 40Ar-39Ar ages of 611 Ma ± 1.3; i.e., evidence of magmatic activity during the Ediacaran (635-542 Ma). Furthermore, Nd isotope ratios and model ages identifies four groups of dykes within the Bas-Drâa inlier, all of which were derived from a previously enriched mantle reservoir with very low 143Nd/144Nd ratios (0.51065–0.51170) and corresponding εNd(t) values (−16.44 to −2.45). Such low Nd-ratios arguably reflect either a contribution of crustal components, such as the Paleoproterozoïc schisto-granitic basement, or metasomatic modification of the sub-continental lithospheric mantle

Reply to Comment on "U-Pb baddeleyite ages and geochemistry of dolerite dykes in the Bas-Draa inlier of the Anti-Atlas of Morocco: Newly identified 1380 Ma event in the West African Craton" by Andre Michard and Dominique Gasquet

Baddeleyite (ZrO2) is today recognized as the key mineral for dating the emplacement of mantle-derived igneous rocks, primarily gabbro and dolerite dykes and sills. The comment by Michard and Gasquet calls for a discussion on the significance of baddeleyite U-Pb TIMS dates of two dykes in the Bas-Draa inlier, dated at 1381 +/- 8 and 1384 +/- 6 Ma, presented in El Bahat et al. (2013-in this issue). They suggest that the U-Pb systematics were "seriously perturbed in the Bas-Draa region" with the main argument being a lack of age matches between the ca. 1385 Ma dykes in Bas-Draa and the 2040, 1650 and 885 Ma dykes in adjacent inliers to the east. To infer an older age for these dykes, as suggested by Michard and Gasquet, and explain the ca. 1385 Ma TIMS results would require two separate events of perturbation, in the Mesoproterozoic and a subsequent Variscan event. However, such an alternative is improbable from basic theoretical reasoning using U-Pb isotopic systematics and our current understanding of the behaviour of baddeleyite in metamorphic systems. In addition, we present new LA-ICPMS U-Pb age data of baddeleyite from one of the dated dykes from Bas-Draa. The new LA-ICPMS U-Pb age of 1416 +/- 7 Ma is slightly but significantly older than our TIMS 1384 +/- 6 Ma upper intercept age, nevertheless confirming this dyke could not correspond to any of the other mafic intrusions dated in the inliers to the east. The IA-ICPMS result also contributes to a deeper understanding on the effects of secondary processes in baddeleyite in general, and suggests a modified methodological approach for samples with complex geological histories. (C) 2013 Elsevier B.V. All rights reserved

The 1750 Ma Magmatic Event of the West African Craton (Anti-Atlas, Morocco)

The Precambrian inliers of the Anti Atlas belt located at the southern part of Morocco contain numerous mafic dyke and sill swarms thought to represent the erosional remnants of Proterozoic Large Igneous Provinces (LIPS). As part of a continuing research campaign to date and characterize these LIPs, four dykes have been dated by the U-Pb TIMS (Thermal Ionization Mass Spectrometry) method on baddeleyite and zircon: ca. 1758 Ma in the Tagragra of Akka inlier, 1741 +/- 10 Ma in the Tafeltast-Kerdous inlier, 1746.8 +/- 3.7 Ma in the Iguerda-Tanst and 1734 +/- 5 Ma in the Zenaga inlier. The age matches (and chemical features akin to continental flood basalts) confirm a widespread intraplate magmatic event at 1750 Ma, herein termed the Tagragra of Akka LIP, that represents an important new magmatic tarcode' line for the West African Craton (WAC). Contemporaneous 1750 Ma LIP magmatism is reported in other crustal blocks including northwestern Laurentia and Siberia; together with the newly defined Tagragra of Akka event of the Anti Atlas region of the WAC this widespread 1750 Ma magmatism is postulated to collectively constitute a single huge LIP associated with a breakup attempt of Nuns (Columbia) shortly after its final assembly at ca. 1.8 Ga. (C) 2013 Elsevier B.V. All rights reserved