Analysis of sprint cross-country skiing using a differential global navigation satellite system

The purpose was to examine skiing velocities, gear choice (G2–7) and cycle rates during a skating sprint time trial (STT) and their relationships to performance, as well as to examine relationships between aerobic power, body composition and maximal skiing velocity versus STT performance. Nine male elite cross-country skiers performed three tests on snow: (1) Maximum velocity test (V _max) performed using G3 skating, (2) V _max test performed using double poling (DP) technique and (3) a STT over 1,425 m. Additional measurements of VO_2max during roller skiing and body composition using iDXA were made. Differential global navigation satellite system data were used for position and velocity and synchronized with video during STT. The STT encompassed a large velocity range (2.9–12.9 m s⁻¹) and multiple transitions (21–34) between skiing gears. Skiing velocity in the uphill sections was related to gear selection between G2 and G3. STT performance was most strongly correlated to uphill time (r = 0.92, P < 0.05), the percentage use of G2 (r = −0.72, P < 0.05), and DP V _max (r = −0.71, P < 0.05). The velocity decrease in the uphills from lap 1 to lap 2 was correlated with VO_2max (r = −0.78, P < 0.05). V _max in DP and G3 were related to percent of racing time using G3. In conclusion, the sprint skiing performance was mainly related to uphill performance, greater use of the G3 technique, and higher DP and G3 maximum velocities. Additionally, VO_2max was related to the ability to maintain racing velocity in the uphills and lean body mass was related to starting velocity and DP maximal speed.     

H wave and spinal root potentials in neuromonitoring of S1 root function during evacuation of herniated disc: preliminary results

Aim

To determine the changes in the tibial H reflex and spinal nerve root potentials (SRPs) of the S1 root during posterior discectomy and the effects of surgical manipulation.

Methods

Tibial H reflex responses (M and H waves) were intermittently recorded from the soleus muscle by surface electrodes during different stages of surgery in 5 patients with S₁ radiculopathy. All patients had Achilles reflex preserved bilateraly and no paresis on manual strength testing preoperatively. SRPs were additionally obtained by direct epidural recordings from the surgically exposed S₁ root in 2 of them.

Results

The variations in the amplitude of H wave were minor and reversible upon the cessation of surgical manipulation of the root, but the H reflex was not lost either temporarily or permanently in any of the patients. Prolongation of H wave latency by up to 18% at the end of surgery in comparison with preoperative value was noticed in 4 patients. However, there was increased degree of desynchronization of the SRP in some phases of the spinal root manipulation, such as root mobilization before the disc incision and retraction during the disc evacuation. H waves and SRPs were continuously present during the surgery. Ankle jerks were preserved postoperatively in all 5 patients.

Conclusion

Unremarkable variations in H wave latency may be followed by increased SRP desynchronization. Monitoring of the epidurally recorded SRPs seems to be more sensitive to surgical manipulations of the spinal nerve root than the tibial H reflex recordings from the soleus muscle.Surgical manipulation of the lumbosacral nerve root is an inevitable step in posterior discectomy. Monosynaptic H reflex can be used in neuromonitoring of the S1 root function during evacuation of the herniated disc at the level L5-S1 to assess the extent of surgical manipulation. A subpopulation of patients with S1-root compression by herniated disc has a preserved ankle jerk at the time of surgery. The effect of surgical manipulations on the H wave amplitude and latency can be monitored during the surgery for herniated disc removal in such patients.The H reflex plays an important role in the electrodiagnostic work-up of compressive lumbosacral radiculopathies, but it does not always give specific information even in clinical S₁-radiculopathy. Needle recording electrodes may be placed percutaneously under a fluoroscopic view as close as possible to each of the L₄-S₁ roots to identify exactly the abnormal spinal nerve root potential (SRP) of the compressed root upon tibial H reflex (1,2).The H reflex has already been used intraoperatively as a neurophysiological test for the identification of certain roots or rootlets to increase the selectivity of partial dorsal rhyzotomy in spastic patients (3-5). However, continuous assessment of the S₁ spinal nerve root function by H reflex during discectomy has not yet been studied. In the present study, the H reflex and spinal root potentials (SRP) were during posterior discectomy to assess the effects of surgical manipulation.     

The falsifiability of the models for the origin of eukaryotes

One group of hypotheses suggests archaeal and/or bacterial ancestry of eukaryotes, while the second group suggests that the ancestor of eukaryotes was different. Especially, the followers of the first group of hypotheses should ask the following: is the replacement of archaeal lipids by bacterial (or vice versa) possible? Do the phylogenies support the origin of one domain from another (or the others)? Can we consider the nutritional mode to resolve the problems of cell origin(s)? Is there any evidence that the ancestor of eukaryotes was intron-free? Would the symbiosis of α-proteobacterial ancestors of mitochondria be successful in an asexual host? Is there evidence that the last universal common ancestor (LUCA) or the last eukaryotic common ancestor was bounded by one membrane only? With respect to the current knowledge about cells and their molecular components, the answer to most of these questions is: No! A model for the origins of domains is briefly presented which cannot be assigned as false through the current scientific data, and is rather consistent with the assumption that eukaryotes are direct descendants of neither archaea nor bacteria. It is proposed that the domain Bacteria arose the first, and that the last common ancestor of Archaea and Eukarya was a pre-cell or a progenote similar to LUCA. The pre-karyote (the host entity for α-proteobacterial ancestors of mitochondria) was probably bounded by two membranes, possessed spliceosomal introns and spliceosomes, was sexual, and α-proteobacterial ancestors of mitochondria were most likely parasites of the pre-karyote periplasm (intermembrane space).     

Shear stress in epiphyseal growth plate is a risk factor for slipped capital femoral epiphysis

BACKGROUND: Slipping of the capital femoral epiphysis is an important orthopaedic problem of early adolescence. Many hypotheses about its etiology have been examined, yet the underlying mechanisms have not yet been fully elucidated. We examined elevated shear stress in the epiphyseal growth plate and elevated contact hip stress exerted on the femoral head as risk factors for slipping of the capital femoral epiphysis. METHODS: Two groups of hips were compared: a group of 100 hips contralateral to the slipped ones and a group of 70 age- and gender-matched healthy hips. The characteristics of individual hips were incorporated by means of geometrical parameters determined from standard anteroposterior radiographs. Shear stress was calculated by using a mathematical model where the femoral neck was considered to function as an elastic rod. Contact hip stress was calculated by the HIPSTRESS method. RESULTS: Hips contralateral to the slipped ones had higher average shear stress (0.81 vs 0.51 MPa; P < 0.001) and more vertically inclined physeal angle (55.4 vs 63.2 degrees.; P < 0.001) in comparison to healthy hips. Shear stress in the contralateral hips to the slipped ones remained significantly higher even when normalized to the body weight (1400 vs 1060 Pa/N; P < 0.001). There was no significant difference in the average contact hip stress (1.86 vs 1.74 MPa; P = 0.145). CONCLUSIONS: Elevated shear stress, but not elevated contact stress, is a risk factor for slipping of the capital femoral epiphysis. LEVEL OF EVIDENCE: III (prognostic study, case-control study).     

Long-term outcome and quality of life of patients treated in surgical intensive care: a comparison between sepsis and trauma

Introduction  

Our aim was to determine long-term survival and quality of life of patients admitted to a surgical intensive care unit (ICU) because of sepsis or trauma.     

Metabolomic approaches to phenotype characterization and applications to complex diseases

Metabolites are the key regulators of systems homeostasis. As such, concentration changes of specific groups of metabolites may reflect systemic responses to environmental, therapeutic or genetic interventions. Thus, the study of metabolites is a powerful tool for the characterization of complex phenotypes as well as for the development of biomarkers for specific physiological responses. Therefore, metabolomics is a valuable platform for studies of complex diseases and the development of new therapies, both in nonclinical disease model characterization and clinical settings.     

High-Fluence Multi-Energy Ion Irradiation for Testing of Materials

Structural materials of the new generation of nuclear reactors, fission as well as fusion, must often cope with high production rates of transmutation helium. Their testing hence requires either a powerful source of fast neutrons or a high-fluence ion-irradiation facility providing sufficient amounts of high-energy helium to investigate its effect on the material. Most ion irradiation studies, however, concentrate on basic effects such as defect evolution or bubble swelling in narrow near-surface regions modified by ion bombardment. Studies on bulk samples with a relatively thick implanted region, which would enable, for instance, micromechanical testing, are underrepresented. This gap might be filled by high-fluence multi-energy ion irradiations modifying several tens of micrometres of the investigated substrate. High-energy ion accelerators providing reasonable currents with energies of tens of MeV are rarely employed in such studies due to their scarcity or considerable beamtime costs. To contribute to this field, this article reports a unique single-beam He implantation experiment aimed at obtaining quasi-uniform displacement damage across >60 μm with the He/dpa ratio roughly one order of magnitude above the typical spallation neutron target irradiation conditions. Some technical aspects of this irradiation experiment, along with recent developments and upgrades at the 6 MV Tandetron accelerator of the Slovak university of technology in Bratislava, are presented.     

Effect of Fast High-Irradiance Photo-Polymerization of Resin Composites on the Dentin Bond Strength

This study investigated the influence of conventional (10 s at 1160 mW/cm²) and fast high-irradiance (3 s at 2850 mW/cm²) light curing on the micro-tensile bond strength (μTBS) of bulk-fill resin composites bonded to human dentin. Sixty-four extracted human molars were ground to dentin and randomly assigned into eight groups (n = 8 per group). After application of a three-step adhesive system (Optibond FL), four different bulk-fill composites (two sculptable and two flowable composites) were placed. Of these, one sculptable (Tetric PowerFill) and one flowable (Tetric PowerFlow) composite were specifically developed for fast high-irradiance light curing. Each composite was polymerized with the conventional or the fast high-irradiance light-curing protocol. The specimens were cut into dentin-composite sticks, μTBS was determined and failure modes were analyzed. Statistical analysis was performed using t-test for independent observations and one-way ANOVA. A statistical difference between the curing protocols was only found for Tetric PowerFlow, where the conventional protocol (23.8 ± 4.2 MPa) led to significantly higher values than the fast high-irradiance light-curing protocol (18.7 ± 3.7 MPa). All other composite materials showed statistically similar values for both polymerization protocols. In conclusion, the use of fast high-irradiation light curing has no negative influence on the μTBS of the investigated high-viscosity bulk-fill composites. However, it may reduce the dentin bond strength of flowable bulk-fill composite.     

Effect of Varying Working Distances between Sandblasting Device and Composite Substrate Surface on the Repair Bond Strength

This study investigates the effect of defined working distances between the tip of a sandblasting device and a resin composite surface on the composite–composite repair bond strength. Resin composite specimens (Ceram.x Spectra ST (HV); Dentsply Sirona, Konstanz, Germany) were aged by thermal cycling (5000 cycles, 5–55 °C) and one week of water storage. Mechanical surface conditioning of the substrate surfaces was performed by sandblasting with aluminum oxide particles (50 µm, 3 bar, 10 s) from varying working distances of 1, 5, 10, and 15 mm. Specimens were then silanized and restored by application of an adhesive system and repair composite material (Ceram.x Spectra ST (HV)). In the negative control group, no mechanical surface pretreatment or silanization was performed. Directly applied inherent increments served as the positive control group (n = 8). After thermal cycling of all groups, microtensile repair bond strength was assessed, and surfaces were additionally characterized using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The negative control group reached the significantly lowest microtensile bond strength of all groups. No significant differences in repair bond strength were observed within the groups with varying sandblasting distances. Composite surfaces sandblasted from a distance of 1 mm or 5 mm showed no difference in repair bond strength compared to the positive control group, whereas distances of 10 or 15 mm revealed significantly higher repair bond strengths than the inherent incremental bond strength (positive control group). In conclusion, all sandblasted test groups achieved similar or higher repair bond strength than the inherent incremental bond strength, indicating that irrespective of the employed working distance between the sandblasting device and the composite substrate surface, repair restorations can be successfully performed.