Bounce cosmology in generalized modified gravities

We investigate the bounce realization in the framework of generalized modified gravities arising from Finsler and Finsler-like geometries. In particular, the richer intrinsic geometrical structure is reflected in the appearance of extra degrees of freedom in the Friedmann equations that can drive the bounce. We examine various Finsler and Finsler-like constructions. In the cases of general very special relativity as well as of Finsler-like gravity on the tangent bundle we show that a bounce cannot be easily obtained. However, in the Finsler-Randers space the induced scalar anisotropy can fulfill the bounce conditions and bouncing solutions are easily obtained. Finally, for the general class of theories that include a nonlinear connection a new scalar field is induced, leading to a scalar-tensor structure that can easily drive a bounce. These features reveal the capabilities of Finsler and Finsler-like geometries.Comment: 10 pages, 3 figures, to appear in Univers

Characterization of laboratory and real driving emissions of individual Euro 6 light-duty vehicles – Fresh particles and secondary aerosol formation

Emissions from passenger cars are one of major sources that deteriorate urban air quality. This study presents characterization of real-drive emissions from three Euro 6 emission level passenger cars (two gasoline and one diesel) in terms of fresh particles and secondary aerosol formation. The gasoline vehicles were also characterized by chassis dynamometer studies. In the real-drive study, the particle number emissions during regular driving were 1.1–12.7 times greater than observed in the laboratory tests (4.8 times greater on average), which may be caused by more effective nucleation process when diluted by real polluted and humid ambient air. However, the emission factors measured in laboratory were still much higher than the regulatory value of 6 × 10^(11) particles km^(−1). The higher emission factors measured here result probably from the fact that the regulatory limit considers only non-volatile particles larger than 23 nm, whereas here, all particles (also volatile) larger than 3 nm were measured. Secondary aerosol formation potential was the highest after a vehicle cold start when most of the secondary mass was organics. After the cold start, the relative contributions of ammonium, sulfate and nitrate increased. Using a novel approach to study secondary aerosol formation under real-drive conditions with the chase method resulted mostly in emission factors below detection limit, which was not in disagreement with the laboratory findings

Advantages of the Ilizarov external fixation in the management of intra-articular fractures of the distal tibia

<p>Abstract</p> <p>Background</p> <p>Treatment of distal tibial intra-articular fractures is challenging due to the difficulties in achieving anatomical reduction of the articular surface and the instability which may occur due to ligamentous and soft tissue injury. The purpose of this study is to present an algorithm in the application of external fixation in the management of intra-articular fractures of the distal tibia either from axial compression or from torsional forces.</p> <p>Materials and methods</p> <p>Thirty two patients with intra-articular fractures of the distal tibia have been studied. Based on the mechanism of injury they were divided into two groups. Group I includes 17 fractures due to axial compression and group II 15 fractures due to torsional force. An Ilizarov external fixation was used in 15 patients (11 of group I and 4 of group II). In 17 cases (6 of group I and 11 of group II) a unilateral hinged external fixator was used. In 7 out of 17 fractures of group I an additional fixation of the fibula was performed.</p> <p>Results</p> <p>All fractures were healed. The mean time of removal of the external fixator was 11 weeks for group I and 10 weeks for group II. In group I, 5 patients had radiological osteoarthritic lesions (grade III and IV) but only 2 were symptomatic. Delayed union occurred in 3 patients of group I with fixed fibula. Other complications included one patient of group II with subluxation of the ankle joint after removal of the hinged external fixator, in 2 patients reduction found to be insufficient during the postoperative follow up and were revised and 6 patients had a residual pain. The range of ankle joint motion was larger in group II.</p> <p>Conclusion</p> <p>Intra-articular fractures of the distal tibia due to axial compression are usually complicated with cartilaginous problems and are requiring anatomical reduction of the articular surface. Fractures due to torsional forces are complicated with ankle instability and reduction should be augmented with ligament repair, in order to restore normal movement of talus against the mortise. Both Ilizarov and hinged external fixators are unable to restore ligamentous stability. External fixation is recommended only for fractures of the ankle joint caused by axial compression because it is biomechanically superior and has a lower complication rate.</p

Study of trunk asymmetry in normal children and adolescents

The scoliometer readings in both standing and sitting position of 2071 children and adolescents (1099 boys and 972 girls) aged from 5 to 18 years old were studied. The angle of trunk rotation (ATR) was measured, in order to quantify the existing trunk asymmetry. Children and adolescents were divided in two groups according to the severity of trunk asymmetry. In the first group asymmetry was 1 to 6 degrees and in the second group was 7 or more degrees. Radiographic and leg length inequality evaluation were also performed in a number of children. The mean frequency of symmetric (ATR = 0 degrees) boys and girls was 67.06% and 65.01% for the standing screening position and 76.5% and 75.1% for the sitting position, respectively. The mean difference of frequency of asymmetry (ATR > 0 degrees) at standing minus sitting forward bending position for boys and girls was 10.22% and 9.37%, respectively. The mean frequency of asymmetry of 7 or more degrees was 3.23% for boys and 3.92% for girls at the standing forward bending position and 1.62% and 2.21% at the sitting, respectively. Girls are found to express higher frequency of asymmetry than boys. Right trunk asymmetry was more common than left. The sitting position is the preferred screening position for examining the rib or loin hump during school screening as it demonstrates the best correlation with the spinal deformity exposing the real trunk asymmetry

Relatively lower body mass index is associated with an excess of severe truncal asymmetry in healthy adolescents: Do white adipose tissue, leptin, hypothalamus and sympathetic nervous system influence truncal growth asymmetry?

<p>Abstract</p> <p>Background</p> <p>In healthy adolescents normal back shape asymmetry, here termed truncal asymmetry (TA), is evaluated by higher and lower subsets of BMI. The study was initiated after research on girls with adolescent idiopathic scoliosis (AIS) showed that higher and lower BMI subsets discriminated patterns of skeletal maturation and asymmetry unexplained by existing theories of pathogenesis leading to a new interpretation which has therapeutic implications <it>(double neuro-osseous theory)</it>.</p> <p>Methods</p> <p>5953 adolescents age 11–17 years (boys 2939, girls 3014) were examined in a school screening program in two standard positions, standing forward bending (FB) and sitting FB. The sitting FB position is thought to reveal intrinsic TA free from back humps induced by any leg-length inequality. TA was measured in both positions using a Pruijs scoliometer as angle of trunk inclinations (ATIs) across the back at each of three spinal regions, thoracic, thoracolumbar and lumbar. Abnormality of ATIs was defined as being outside 2 standard deviations for each age group, gender, position and spinal region, and termed <it>severe </it>TA.</p> <p>Results</p> <p>In the sitting FB position after correcting for age,<it>relatively lower BMIs </it>are statistically associated with a greater number of severe TAs than with relatively higher BMIs in both girls (thoracolumbar region) and boys (thoracolumbar and lumbar regions).</p> <p>The relative frequency of severe TAs is significantly higher in girls than boys for each of the right thoracic (56.76%) and thoracolumbar (58.82%) regions (p = 0.006, 0.006, respectively). After correcting for age, smaller BMIs are associated with more <it>severe TAs </it>in boys and girls.</p> <p>Discussion</p> <p>BMI is a surrogate measure for body fat and circulating leptin levels. The finding that girls with relatively lower BMI have significantly later menarche, and a significant excess of TAs, suggests a relation to energy homeostasis through the hypothalamus. The hypothesis we suggest for the pathogenesis of severe TA in girls and boys has the same mechanism as that proposed recently for AIS girls, namely: severe TAs are initiated by a <it>genetically-determined selectively </it>increased hypothalamic sensitivity (up-regulation, i.e. increased sensitivity) to leptin with asymmetry as an adverse response to stress (hormesis), mediated bilaterally mainly to the growing trunk via the sympathetic nervous system <it>(leptin-hypothalamic-sympathetic nervous system (LHS) concept)</it>. The putative autonomic dysfunction is thought to be increased by any lower circulating leptin levels associated with relatively lower BMIs. Sympathetic nervous system activation with asymmetry leads to asymmetries in ribs and/or vertebrae producing severe TA when beyond the capacity of postural mechanisms of the somatic nervous system to control the shape distortion of the trunk. A test of this hypothesis testing skin sympathetic responses, as in the Rett syndrome, is suggested.</p

Διερεύνηση τεχνολογιών μείωσης της κατανάλωσης και των εκπομπών ρύπων από σύγχρονα επιβατηγά οχήματα σε πραγματικές συνθήκες οδήγησης

In the context of this dissertation, the fuel consumption and emissions of many vehicles were measured under various driving conditions and emission and consumption reduction technologies were investigated. The impact of conventional fuel consumption reduction technologies was simulated by modeling a gasoline and diesel vehicle under NEDC, WLTP and CADC driving cycles, using the AVL Cruise platform. The technologies tested include brake energy recuperation, start-stop, vehicle mass reduction, aerodynamic resistance reduction, rolling resistance reduction, gearbox changes and engine efficiency improvements. Each technology has a different impact on each driving cycle, while the overall reduction in fuel consumption and CO2 emissions achieved by combining all technologies was in the range of 12-14%. Concerning pollutant reduction technologies, the possibility of reducing NOx emissions of a Euro 6b diesel vehicle was studied. Initially, the vehicle was tested on the road following the RDE regulation where it emitted 5 times more NOx than the 80 mg/km limit. The vehicle’s engine operation was simulated on a laboratory dyno, where an identical engine was installed. Modifications were made to the exhaust aftertreatment system, including the replacement of the LNT system with an SCR system. The modifications reduced NOx emissions by 90%, achieving compliance with the Euro 6 limits without requiring any additional fuel consumption. The effect of driving conditions on emissions and fuel consumption was then addressed. In particular, three Euro 6 diesel vehicles were tested in the NEDC, WLTP, CADC driving cycles and on the road, on normal RDE-compliant routes and other more dynamic ones. The emissions reduction strategy of the three vehicles seems to be exclusively targeting the NEDC cycle, as at non-NEDC operating conditions the use of anti-pollution systems is minimized. WLTP emissions were closer to the emissions measured under real conditions; however, the engine operating range during the road tests was greater than the range during laboratory tests. In addition, NOx emission levels increase dramatically when driving the vehicle in a more dynamic manner outside the boundaries of the RDE regulation. Finally, on-road emissions measurements were carried out on a fleet of eight vehicles, two diesel, one gasoline, one LPG vehicle, one CNG, one hybrid and two older gasoline vehicles which had been converted to gasoline-LPG dual fuels. No fuel/engine type had low CO2, CO and NOx emissions over the full range of real world driving conditions. However, it is worth mentioning that the older gasoline-LPG vehicles had the worst emission performance, the CNG vehicle had the lowest CO2 emissions and the hybrid had the lowest CO and NOx emissions combined. With regard to conventional vehicle types, diesel vehicles had very high NOx emissions, while gasoline vehicles had extremely high CO emissions under dynamic driving conditions, reaching 35 times the regulatory limits.Στα πλαίσια της παρούσας διατριβής αποτυπώθηκαν οι εκπομπές και η κατανάλωση καυσίμου πολλών οχημάτων σε διάφορες συνθήκες οδήγησης και διερευνήθηκαν οι τεχνολογίες μείωσής τους. Η επίπτωση συμβατικών τεχνολογιών μείωσης κατανάλωσης εξετάστηκε με μοντελοποιήσεις κύκλων οδήγησης NEDC, WLTP, CADC σε ένα βενζινοκίνητο και ένα πετρελαιοκίνητο όχημα χρησιμοποιώντας την πλατφόρμα AVL Cruise. Οι τεχνολογίες που εξετάστηκαν περιλαμβάνουν ανάκτηση ενέργειας φρεναρίσματος, σύστημα start-stop, μείωση μάζας οχήματος, μείωση αεροδυναμικών αντιστάσεων, μείωση αντιστάσεων κύλισης, αλλαγές στο κιβώτιο ταχυτήτων και βελτιώσεις στην απόδοση του κινητήρα. Κάθε τεχνολογία έχει διαφορετική επίδραση σε κάθε κύκλο οδήγησης, ενώ η συνολική μείωση κατανάλωσης καυσίμου και εκπομπών CO2 που επιτεύχθηκε συνδυάζοντας όλες τις τεχνολογίες ήταν της τάξης του 12-14%. Όσον αφορά τις τεχνολογίες μείωσης ρύπων, εξετάστηκε η δυνατότητα μείωσης των εκπομπών NOx ενός Euro 6b ντίζελ οχήματος. Αρχικά μετρήθηκαν κατά RDE οι εκπομπές NOx και βρέθηκαν 5 φορές περισσότερες από το όριο των 80mg/km. H λειτουργία του κινητήρα του οχήματος προσομοιώθηκε σε εργαστηριακή πέδη, όπου εγκαταστάθηκε ένας πανομοιότυπος κινητήρας. Σε αυτόν έγιναν τροποποιήσεις στο σύστημα μετεπεξεργασίας καυσαερίων, με κύρια αλλαγή την αντικατάσταση του συστήματος LNT με σύστημα SCR. Οι τροποποιήσεις μείωσαν στις εκπομπές NOx κατά 90%, επιτυγχάνοντας συμμόρφωση με τα Euro 6 όρια, χωρίς να επιβαρύνουν την κατανάλωση καυσίμου. Στη συνέχεια εξετάστηκε η επίδραση των συνθηκών οδήγησης στις εκπομπές και την κατανάλωση καυσίμου. Συγκεκριμένα διερευνήθηκε η λειτουργία τριών Euro 6 ντίζελ σε κύκλους οδήγησης NEDC, WLTP, CADC και στο δρόμο σε κανονικά δρομολόγια εντός RDE νομοθεσίας και σε άλλα πιο δυναμικά. Η στρατηγική μείωσης των εκπομπών και των τριών οχημάτων φαίνεται να στοχεύει αποκλειστικά τον κύκλο NEDC, καθώς στα σημεία λειτουργίας εκτός του NEDC η χρήση αντιρρυπαντικών συστημάτων ελαχιστοποιείται. Οι εκπομπές κατά τον WLTP ήταν πιο κοντά στις εκπομπές που μετρήθηκαν σε πραγματικές συνθήκες, ωστόσο, το εύρος λειτουργίας του κινητήρα κατά τη μέτρηση στον δρόμο ήταν μεγαλύτερο από το εύρος κατά τις εργαστηριακές συνθήκες. Επιπλέον, τα επίπεδα εκπομπών NOx αυξάνονται δραματικά κατά την οδήγηση του οχήματος με πιο δυναμικό τρόπο, εκτός των προδιαγραφών του RDE κανονισμού. Τέλος, πραγματοποιήθηκαν μετρήσεις εκπομπών στο δρόμο σε ένα στόλο οχτώ οχημάτων, δύο ντίζελ, ένα βενζινοκίνητο, ένα όχημα φυσικού αερίου, ένα υγραεριοκίνητο, ένα υβριδικό και δύο παλαιότερα βενζινοκίνητα που έχουν μετατραπεί σε υγραεριοκίνητα. Κανένας τύπος καυσίμου/κινητήρα δεν είχε χαμηλές εκπομπές CO2, CO και NOx σε όλο το φάσμα των πραγματικών συνθηκών λειτουργίας. Ωστόσο αξίζει να σημειωθεί ότι τα παλαιότερα οχήματα υγραερίου-βενζίνης είχαν τις χειρότερες επιδόσεις εκπομπών, το όχημα με φυσικό αέριο είχε τις χαμηλότερες εκπομπές CO2 και ότι το υβριδικό είχε τις χαμηλότερες εκπομπές ρύπων CO και NOx συνδυαστικά. Όσον αφορά τους συμβατικούς τύπους οχημάτων, τα ντίζελ είχαν πολύ υψηλές εκπομπές NOx, ενώ τα βενζινοκίνητα σε δυναμικές συνθήκες οδήγησης, είχαν εξαιρετικά υψηλές εκπομπές CO φτάνοντας τις 35 φορές πάνω από τα νομοθετημένα όρια

Patient, Surgery, and Hospital Related Risk Factors for Surgical Site Infections following Total Hip Arthroplasty

Surgical site infections (SSI) following total hip arthroplasty (THA) have a significantly adverse impact on patient outcomes and pose a great challenge to the treating surgeon. Therefore, timely recognition of those patients at risk for this complication is very important, as it allows for adopting measures to reduce this risk. This review discusses literature reported risk factors for SSI after THA. These can be classified into patient-related factors (age, gender, obesity, comorbidities, history of infection, primary diagnosis, and socioeconomic profile), surgery-related factors (allogeneic blood transfusion, DVT prophylaxis and coagulopathy, duration of surgery, antibiotic prophylaxis, bearing surface and fixation, bilateral procedures, NNIS index score, and anesthesia type), and hospital-related factors (duration of hospitalization, institution and surgeon volume, and admission from a healthcare facility). All these factors are discussed with respect to potential measures that can be taken to reduce their effect and consequently the overall risk for infection

Giant cell tumor of the fifth lumbar vertebra with a three-year follow-up: case report and review of the literature

We report the case of a patient with giant cell tumor of the L5 vertebra. A 35-year-old female patient with giant cell tumor of the L5 vertebra was subjected to a combined treatment. Three years after treatment, there is no recurrence of the disease and no increase in the residual tumor’s size. Giant cell tumor of the L5 vertebra requires careful planning of treatment and close follow-up of the patient

Acute Infrarenal Aortic Thrombosis Presenting With Flaccid Paraplegia

Study Design. This study is a case report. Objective. To report a case of a patient with paraplegia and low back pain, who was diagnosed with acute infrarenal aortic thrombosis. Summary of Background Data. There have been few reports in the literature regarding acute aortic thrombosis presenting with paraplegia. Methods. A 56-year-old man was referred to our emergency department with flaccid paraplegia and low back pain. Clinical examination and imaging revealed acute infrarenal aortic thrombosis, with lower limb ischemia. The patient underwent transcutaneous embolectomy. Results. Despite successful revascularization, the patient finally died because of development of revascularization syndrome. Conclusion. Acute aortic occlusion is a catastrophic event and may present with paraplegia, because of acute spinal cord ischemia. This can mislead the clinician to a wrong diagnosis and delay initiation of definite treatment