Multi-segments kinematic model of the human spine during gait

The complex biomechanical structure of the human spine requires a deep investigation to properly describe its physiological function and its kinematic contribution during motion. The computational approach allows the segmentation of the human spine into several rigid bodies connected by 3D joints. Despite the numerous solutions proposed by previous literature studies based on both inertial and stereophotogrammetric systems, the modelling of the human spine is characterized by some limitations such as the lack of standardization. Accordingly, the present preliminary study focused on the development of a multi-segments kinematic model of the human spine and its validation during gait trials. Three-dimensional spinal angular patterns and ranges of motion of one healthy young subject were considered as outcomes of interest. They were obtained by applying the YXZ Euler angles convention to the custom model. First, results were compared with those of the standard Plug-in-Gait full-body model, which segments the human spine into pelvis and trunk segments. Then, outcomes of the multi-segments model were compared with those obtained using the Tilt-Twist method. Overall, results stressed the importance of the spine segmentation, the major angular contributions of spinal regions during gait (Medium-Lumbar segments for lateral bending and flexion-extension, Thoracic-Medium segments for axial rotation), and the reliability of the proposed custom model (differences between Euler angles method and Tilt-Twist method lower than 0.5° in most cases). Future analysis on a larger healthy population and in the clinical context might be implemented to optimize, standardize and validate the proposed human spine model

Oxygenation response to NO in newborns with severe pulmonary hypertension

Oxygenation Response to NO in Newborns With Severe Pulmonary Hypertensio

Vacuum Solutions of Einstein's Equations in Parabolic Coordinates

We present a simple method to obtain vacuum solutions of Einstein's equations in parabolic coordinates starting from ones with cylindrical symmetries. Furthermore, a generalization of the method to a more general situation is given together with a discussion of the possible relations between our method and the Belinsky-Zakharov soliton-generating solutions.Comment: 15 pages, version published in Class. Quantum Gra

Supermassive Black Holes and Galaxy Formation

The formation of supermassive black holes (SMBH) is intimately related to galaxy formation, although precisely how remains a mystery. I speculate that formation of, and feedback from, SMBH may alleviate problems that have arisen in our understanding of the cores of dark halos of galaxies.Comment: Talk at conference on Matter in the Universe, March 2001, ISSI Ber

Deep Extragalactic X-ray Surveys

Deep surveys of the cosmic X-ray background are reviewed in the context of observational progress enabled by the Chandra X-ray Observatory and the X-ray Multi-Mirror Mission-Newton. The sources found by deep surveys are described along with their redshift and luminosity distributions, and the effectiveness of such surveys at selecting active galactic nuclei (AGN) is assessed. Some key results from deep surveys are highlighted including (1) measurements of AGN evolution and the growth of supermassive black holes, (2) constraints on the demography and physics of high-redshift AGN, (3) the X-ray AGN content of infrared and submillimeter galaxies, and (4) X-ray emission from distant starburst and normal galaxies. We also describe some outstanding problems and future prospects for deep extragalactic X-ray surveys.Comment: 32 pages; Annu. Rev. Astron. Astrophys., Volume 43 (2005); updated to match accepted versio

Difficult abdominal access in laparoscopic cholecystectomy in elderly patients: our experience and literature review.

AbstractLaparoscopic cholecystectomy (LC) is currently the gold standard treatment for symptomatic cholelithiasis. LC is actually condidered a medium complexity surgical operation. LC could be technically hard, especially if patient underwent previous surgical operation. These difficulties increase in outcome of previous operation in right upper quadrant (RUQ): in this case laparoscopic access is defined as an “hard access”. We present two cases in which an unconventional access was performed: laparoscopic cholecistectomy is a safe and feasible procedure, although a careful assessment preoperative is indispensable. In particular, caution is required in both the triangulation of the trocar, which in pneumoperitoneum induction