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Objective The study aimed to analyze the risk factors and clinical features of metabolic bone disease of prematurity (MBDP) in premature infants compared with infants of similar gestational age and birth weight without MBDP. Study Design This retrospective case–control study was performed by comparing 81 cases of MBDP with 63 controls to identify potential risk factors. Premature infants with a gestational age ≤33 weeks and birth weight Results Bone fractures and invasive ventilator dependence were the most common clinical features of MBDP. Duration of invasive ventilation and total mechanical ventilation days, necrotizing enterocolitis, corticosteroid use, anticonvulsive drug use, duration of dexamethasone and caffeine use, total parenteral nutrition, and length of hospitalization were significantly higher in neonates with MBDP (p Conclusion Our results show that anticonvulsive drug use is a significant risk factor for the development of MBDP. If long-term use is not required, anticonvulsive drugs should be stopped as soon as possible. Further studies involving patients with MBDP are required to determine the risk factors and clinical features. Key Points

NEW FINDINGS What is the central question of this study? The aim was to compare the cost of transport and mechanical work between obese and non-obese children at different walking speeds. What is the main finding and its importance? Our data show that the cost of transport, mechanical efficiency and work are similar and directly mass dependent in obese and non-obese children. The optimal walking speed (most economical walking speed) is reduced in obese children. ABSTRACT Although studies have shown the influence of gait biomechanics on the metabolic economy in obese adults and adolescents, little is known regarding obese children. We compared the metabolic cost of transport, apparent mechanical efficiency and gait biomechanics (assessed by mechanical energy fluctuations) in obese children (n = 12; mean ± SD: 8.6 ± 0.51 years of age, 1.38 ± 0.04 m, 44.6 ± 6.65 kg, 24.1 ± 3.50 kg m-2 ) and age- and sex-matched non-obese children (n = 12, 7.8 ± 0.90 years of age, 1.31 ± 0.08 m, 26.8 ± 2.24 kg, 16.4 ± 1.40 kg m-2 ) while walking at different speeds (from 1 to 5 km h-1 ) on a treadmill. We found that the mechanical efficiency was higher at 3 km h-1 compared with the remaining speeds for both groups (P

Objectie: Calculate the mechanical work (W), applying the total mechanical work (Wtot) and segmental work (Wseg) as a new complementary evaluation resource of the postural control mechanisms in subjects undergoing motor and visual disturbance. Methods: Ten healthy adult male volunteers were selected with ages 25.6 (±2.26) years, whose height was 1.69 (± 0.25) m and body weight was 68.22 (± 0.25) kg. Kinematic data of trunk extension with eyes open and blindfolded were captured with a frequency of 200 Hz. This way the post perturbation interval has been selected and the Wseg (i.e. trunk, head, etc) and the total mechanical work (Wtot) calculated, which were obtained by means of total integral mechanical energy. Results: The statistical analyzing of information was done by paired-data Student's t test. There has been no significant difference (p

To quantify the mechanical work of breathing (Wb) during an indoor rowing test in men and women. Additionally, to compare sex-based differences in the Wb and its components through a rowing test. Fifteen collegiate rowers were recruited (8 women/7 men) and performed a 2000 m rowing test on a rowing ergometer. Esophageal pressure was measured during exercise via balloon catheterization, after which pressure–volume curves were used to calculate total, inspiratory resistive and elastic, and total expiratory Wb. Men had significantly higher values of instantaneous and cumulative total Wb at and beyond 37.5% (430.4 ± 42.5 vs. 282.1 ± 45.1 J min−1, P

Research Question Does complete mechanical removal of the zona pellucida modify the outcome of transfer of vitrified–warmed human blastocysts? Design In a prospective randomized controlled study, 419 couples were allocated to either zona pellucida-free (n = 209) or zona intact (n = 210) vitrified–warmed embryo transfer. Main outcome measures included clinical pregnancy, implantation and ongoing pregnancy rates. Results Transfer of zona pellucida-free blastocysts resulted in clinical pregnancy, implantation and ongoing pregnancy rates (35,9%, 33,9% and 32,1%, respectively), similar to those achieved with zona intact control embryos (39%, 36,4% and 33,1%, respectively). Conclusion Total mechanical removal of the zona pellucida did not affect the tested parameters of clinical outcomes.

In healthy adults, Nordic walking (NW) is known to increase the external mechanical energy fluctuations, though the external work is unaltered due to an improved pendulum-like recovery in comparison to free walking (FW). We aimed to compare mechanical, pendulum-like, and spatiotemporal parameters of gait at different speeds with and without NW poles in people with Parkinson's disease and healthy controls. The study included 11 people (aged 65.6±7.0 years) with idiopathic Parkinson's disease, scoring between 1 and 1.5 on the Hoehn and Yahr scale (H&Y), and nine healthy controls (aged 70.0±5.6 years). All the people were experienced Nordic walkers. Walking tests were performed at 1.8 km.h-1 and 4.7 km.h-1 , on eight 3D force platforms on a walkway. We found greater pendulum-like energy recovery (p 0.05). People with Parkinson's disease showed a major increase in vertical and forward energy fluctuations using poles than in healthy controls. In addition, the Parkinson group showed increased stride frequency and reduced stride length compared to controls in the NW and FW conditions. Our findings partly justify the lower walking economy in Parkinson's disease due to reduced pendulum-like mechanism at commonly used speeds. NW alters gait mechanics similarly in Parkinson group and healthy control, increasing the total mechanical work. Therefore, NW can be a compelling strategy for rehabilitation because of its potential for improving functional mobility, increasing pendulum-like mechanism in Parkinson's disease.

International audience; This study compared changes in the energy-time profiles in pole vaulting using several body models. Two-dimensional kinematics were collected from 20 successful vaults (5.20-6.01 m) performed by 10 athletes during a national meet. The linear and angular kinetic, potential, and total mechanical energy-time profiles were obtained from three pole vaulter models composed of 12, 5, and 3 segments (M12, M5, and M3, respectively), as well as calculated and approximated centre of mass models. One-dimensional statistical parametric mapping was used to compare these energy-time profiles from the models, while agreements of discrete energy parameters were assessed. For all the studied energy-time profiles, there was a main effect (0.05 < p < 0.001) of the models, but pairwise comparisons showed that M5 presented the lowest differences with M12 in comparison with the other models (M3 and approximated centre of mass models). In addition, M5 showed better agreement (lower bias and small effect size) with M12 for the studied energy parameters compared to the other models. Therefore, M5 may be a reliable option to simplify the body model and speed up the computation of the energy-time profiles of the pole vaulter.

Stress-strain analyses are studied under the bottom of the pavementlayer, and pavement life values are calculated depending on the cross-sectionvariation because of the superelevation in horizontal curves. For this purpose,1st principal total mechanical strain values are analyzed with thesuperelevation values changing between 0-8 (%) and the different positions ofwheel contact pressure. Finite element method is used for analysis. Accordingto results of the study, it is obtained that pavement life decreases with theincreasing superelevation, in the case of 8% superelevation and decreasing thedistance to pavement edge, pavement life decreasing gets to 34%., Bu çalışmada dever uygulaması yapılmış bir yatay kurbanın kaplama tabakasıaltındaki gerilme-birim şekil değiştirme ve kaplama ömrü değerleri dever sebebiyledeğişen kesitlere bağlı olarak analiz edilmiştir. Bu amaçla deverin 0-8 (%)değerleri arasında değişimine bağlı olarak ve ayrıca tekerlek temas gerilmesininpozisyonu değiştirilerek birim şekil değiştirme değerleri sonlu elemanlar yöntemiile analiz edilmiştir. Çalışmadan elde edilen sonuçlara göre dever değerinin artmasınabağlı olarak kaplama ömrü azalmıştır. Bu azalma değeri deverin 8% olması ve yüklemenoktasının kaplama kenarına olan mesafesinin azalması ile 34% seviyesinde hesaplanmıştır.

We develop a theory that leads to the explanation of the atom manipulations due to active quadrupole interaction of twisted light with atoms at near-resonance frequencies. We demonstrate that the total mechanical effects of active quadrupole interaction on atoms just gives a rotational motion in the case of the configuration of a two counter-propagating beams. Typical parameters are assumed to determine both dissipative and quadrupole forces to obtain the trajectories for an atom.

Understanding the mechanisms involved in the higher energy cost of walking (NC w : the energy expenditure above resting per unit distance) in adults with obesity is pivotal to optimizing the use of walking in weight management programmes. Therefore, this study aimed to investigate the mechanics, energetics and mechanical efficiency of walking after a large body mass loss induced by bariatric surgery in individuals with obesity. Nine adults (39.5 ± 8.6 year; BMI: 42.7 ± 4.6 kg m -2 ) walked at five fixed speeds before (baseline) and after the bariatric surgery (post 1 and post 2). Gas exchanges were measured to obtain NC w . A motion analysis system and instrumented treadmill were combined to assess total mechanical work (W tot ). Mechanical efficiency (W tot NC w -1 ) was also calculated. Participants lost 25.7 ± 3.4% of their body mass at post 1 (6.6 months; P < 0.001) and 6.1 ± 4.9% more at post 2 (12 months; P = 0.014). Mass-normalized NC w was similar between baseline and post 1 and decreased at post 2 compared to that at baseline (-6.2 ± 2.7%) and post 1 (-8.1 ± 1.9%; P ≤ 0.007). No difference was found in mass-normalized W tot during follow-up (P = 0.36). Mechanical efficiency was similar at post 1 and post 2 when compared to that at baseline (P ≥ 0.19), but it was higher (+14.1 ± 4.6%) at post 2 than at post 1 (P = 0.013). These findings showed that after a very large body mass loss, individuals with obesity may reorganize their walking pattern into a gait more similar to that of lean adults, thus decreasing their NC w by making their muscles work more efficiently. KEY POINTS: A higher net (above resting) energy cost of walking (lower gait economy) is observed in adults with obesity compared to lean individuals. Understanding the mechanisms (i.e. mass driven, gait pattern and behavioural changes) involved in this extra cost of walking in adults with obesity is pivotal to optimizing the use of walking to promote daily physical activity and improve health in these individuals. We found that very large weight loss induced by bariatric surgery significantly decreased the energy cost of walking per kg of body mass after 1 year with similar total mechanical work per kg of body mass, resulting in an increased mechanical efficiency of walking. Individuals with obesity may reorganize their walking pattern into a gait more similar to that of adults of normal body mass, thus decreasing their energy cost of walking by making their muscles work more efficiently.

Barefoot weightlifting has become a popular training modality in recent years due to anecdotal suggestions of improved performance. However, research to support these anecdotal claims is limited. Therefore, the purpose of this study was to assess the differences between the conventional deadlift (CD) and the sumo deadlift (SD) in barefoot and shod conditions. On day one, one-repetition maximums (1 RM) were assessed for thirty subjects in both the CD and SD styles. At least 72 h later, subjects returned to perform five repetitions in four different conditions (barefoot and shod for both CD and SD) at 70% 1 RM. A 2 × 2 (footwear × lifting style) MANOVA was used to assess differences between peak vertical ground reaction force (VGRF), total mechanical work (WORK), barbell vertical displacement (DISP), peak vertical velocity (PV) and lift time (TIME) during the concentric phase. The CD displayed significant increases in VGRF, DISP, WORK, and TIME over the SD. The shod condition displayed increased WORK, DISP, and TIME compared to the barefoot condition. This study suggests that lifting barefoot does not improve performance as no differences in VGRF or PV were evident. The presence of a shoe does appear to increase the DISP and WORK required to complete the lift, suggesting an increased work load is present while wearing shoes.

The term ocular rigidity is widely used in clinical ophthalmology. Generally it is assumed as a resistance of the whole eyeball to mechanical deformation and relates to biomechanical properties of the eye and its tissues. Basic principles and formulas for clinical tonometry, tonography and pulsatile ocular blood flow measurements are based on the concept of ocular rigidity. There is evidence for altered ocular rigidity in aging, in several eye diseases and after eye surgery. Unfortunately, there is no consensual view on ocular rigidity: it used to make a quite different sense for different people but still the same name. Foremost there is no clear consent between biomechanical engineers and ophthalmologists on the concept. Moreover ocular rigidity is occasionally characterized using various parameters with their different physical dimensions. In contrast to engineering approach, clinical approach to ocular rigidity claims to characterize the total mechanical response of the eyeball to its deformation without any detailed considerations on eye morphology or material properties of its tissues. Further to the previous chapter this section aims to describe clinical approach to ocular rigidity from the perspective of an engineer in an attempt to straighten out this concept, to show its advantages, disadvantages and various applications.

In the design of reinforced concrete structures several limit states are usually verified using simplified methods instead of using complex direct calculation. Span-to-depth ratio limits are applied for deflection control. In the same way, a redistribution factor and the relative depth of the compression zone are applied for the required ductility, but this is not enough. In fact, specific span-to-depth ratio limits, which are developed in this paper, should also complement the conditions referred to here. A numerical study is developed to compute the deflection ductility index of a wide range of continuous beams (or one-way slabs) considering as ultimate point when the rotation capacity (given by MC2010 and EC2) is achieved. From the boundary between fragile and ductile failures, the new span-to-depth ratio limits for the required ductility are defined and compared with the existing similar limits for deflection control. The results indicate that: (i) for normal strength concrete (up to 50 MPa), the ductility limit is more restrictive than the deflection limit when the redistribution factor delta is lower than 0.9, being always more restrictive for high strength concrete; (ii) for the current building beams, the slenderness used (10 < 1/d < 20) allows ductile failures, while for typical building slabs (low reinforcement ratio, but high redistribution), the slenderness should be 1/d

An energy-based approach to quantifying the mechanical demands of overground, constant velocity and/or intermittent running patterns is presented. Total mechanical work done (Wtotal ) is determined...

Although mechanical ventilation is a life-saving therapy in the treatment of acute respiratory failure, weaning should be performed as soon as possible to prevent complications of invasive ventilation. Weaning time is known to constitute half of the total mechanical ventilation time [1].

Although mechanical ventilation is a life-saving therapy in the treatment of acute respiratory failure, weaning should be performed as soon as possible to prevent complications of invasive ventilation. Weaning time is known to constitute half of the total mechanical ventilation time [1].

Biofilms are important in medicine, industry and the natural environment, however their structure is largely unexplored across multiple spatial scales. We have studied the architecture of matureEscherichia colimacro-colony biofilms by means of the Mesolens, an optical system which uniquely allows simultaneous imaging of individual bacteria and over one hundred cubic millimetres of its biofilm milieu. Our chief finding is the presence of intra-colony channels on the order of 10 μm in diameter inE. colibiofilms. These channels have a characteristic structure and reform after total mechanical disaggregation of the colony. We present evidence that the channels transport particles and function to assist the absorption of nutrients. These channels potentially offer a new route for the delivery of dispersal agents or antimicrobial drugs to biofilms, ultimately lowering their impact on public health and industry.

Background The impacts of Leg Length Discrepancy (LLD) on the kinematic and dynamic parameters of walking have been widely discussed. But little is known on total mechanical work and energy cost. These two variables are more representative of the functional impairment undergone by the LLD patients. Aim To assess the changes of the mechanical work and energy cost of walking in subjects with real LLD and to compare their results with healthy subjects in whom the LLD has been simulated. Method The mechanical work and energy cost data of 60 healthy subjects (speed: 4 km/h) with artificial LLD induced by soles (2 and 4 cm), 20 patients (speed: 3.75 ± 0.5 km/h) with real LLD and 20 matched subjects (speed: 3.75 ± 0.5 km/h) were collected. Statistical comparisons between the groups were performed using a t-paired test and ANOVA. Results Patients with a real LLD showed a significant decrease in mechanical work and energy cost when compared to norms. Patients with real LLD provide a better recovery when compared to subjects with artificial LLD of 2 cm, and a decrease of energy cost and higher muscular efficiency (mechanical work/energy cost) when compared to subjects with artificial LLD of 4 cm. Conclusions Our results showed that patients with a real LLD develop compensatory strategies during gait, probably to minimize the displacement of the body center of mass and consequently reduce the amount of energy expenditure useful for their displacement. Moreover, they adopt a better gait strategy compared to the subjects in whom LLD was simulated.

This work was carried out to study some physical and mechanical properties of orange Navel variety, develop, construct and test of small grading machine for horticultural crops suitable for the small Egyptian farms. To evaluate the performance of the modified grading machine, some engineering factors were studied. These factors were feeding conveyor speeds (0.20, 0.25, 0.30 and 0.35 m/s), grading belts speeds (0.30, 0.40, 0.50 and 0.60 m/s) and grading belts at slope angle (zero deg.). Efficiency indicators such as grading efficiency, machine capacity, power and energy requirements and total mechanical damage were measured and calculated. The obtained results can be summarized as follows: Physical properties of Navel orange were 61.5 - 85.6 mm (length), 61.6 - 85.9 mm (width), 114 - 295 g (weight), 130 - 320 mm3 (volume) and 1.01 (sphericity). The firmness was42.2 N, the rolling angle was 13.12 deg. and the friction angle values were 15 and 11.55 deg. for rubber and metal, respectively. The minimum and maximum grading capacity values were 2.721 t/h and 3.817 t/h at 0.20, 0.30 and 0.35, 0.60 m/s of feeding conveyor and grading belts speeds, respectively for Navel variety. The total mechanical damage values were 0.115% and 0.304% as min. and max., respectively. The minimum machine grading efficiency values were 81.4% and 95.8% as min. and max., respectively. The energy requirements were 7.5 kW.h/t and 0.153kW.h/t for manual and mechanical grading, respectively. The results indicated that fruit feeding conveyor speed (0.20m/s), grading belts speed (0.30 m/s) and zero deg. of grading belts slope angle during grading of orange produced maximum grading efficiency (95.8%) and permissible mechanical damage (0.115%).

In the Everest valley of Nepal, because of the rugged mountain terrain, roads are nothing more than dirt paths and all material must be conveyed on foot. The Nepalese porters routinely carry head-supported loads, which often exceed their body mass, over long distances up and down the steep mountain footpaths. In Africa, women transport their loads economically thanks to an energy-saving gait adaptation. We hypothesized that the Nepalese porters may have developed a corresponding mechanism. To investigate this proposition, we measured the mechanical work done during level walking in Nepalese porters while carrying different loads at several speeds. Our results show that the Nepalese porters do not use an equivalent mechanism as the African women to reduce work. In contrast, the Nepalese porters develop an equal amount of total mechanical work as Western control subjects while carrying loads of 0 to 120% of their body mass at all speeds measured (0.5–1.7 m s−1), making even more impressive their ability to carry loads without any apparent mechanically determined tricks. Nevertheless, our results show that the Nepalese porters have a higher efficiency, at least at slow speeds and high loads.

Ventilation is needed in air-conditioned residential buildings, particularly the bedrooms in nighttime sleeping periods, to maintain an acceptable indoor air quality. Our previous on-site measurements evaluating various ventilation strategies suggest that short-term mechanical ventilation is overall the most appropriate ventilation strategy for air-conditioned residential buildings. However, there is still no a general design framework of short-term mechanical ventilation strategy, which can determine appropriate design parameters, including ventilation period, ventilation frequency, and start concentration of ventilation, based on various combinations of indoor CO 2 generation rate, net room volume, infiltration rate, and mechanical ventilation rate. This study for the first time develops such a design framework and then provides the detailed design guidelines. A whole sleeping period of 8 h is divided into many repeated single V -shape ventilation periods; each single ventilation period is comprised of a short-term mechanical ventilation period and a follow-up CO 2 build-up period. The single V -shape ventilation process is particularly investigated based on a criterion that the average indoor CO 2 concentration is less than but close to 1000 ppm. A high efficient ventilation strategy, namely requiring a minimum total mechanical ventilation period, is a short single ventilation period and a high ventilation frequency. The outcomes of this study are presented in the form of figures and tables, with most parameters normalized, which are useful to assist a rapid ventilation design.

A high work of breathing can compromise limb oxygen delivery during sustained high-intensity exercise. However, it is unclear if the same is true for intermittent sprint exercise. This project examined the addition of an inspiratory load on locomotor muscle tissue reoxygenation during repeated-sprint exercise. Ten healthy males completed three experimental sessions of ten 10 s sprints, separated by 30 s of passive rest on a cycle ergometer. The first two sessions were "all-out efforts performed without (CTRL) or with inspiratory loading (INSP) in a randomised and counterbalanced order. The third experimental session (MATCH) consisted of ten 10 s work-matched intervals. Tissue saturation index (TSI) and deoxy-haemoglobin (HHb) of the vastus lateralis and sixth intercostal space was monitored with near-infrared spectroscopy. Vastus lateralis reoxygenation ({Delta}Reoxy) was calculated as the difference from peak HHb (sprint) to nadir HHb (recovery). Total mechanical work completed was similar between INSP and CTRL (effect size: -0.18, 90% confidence limit {+/-}0.43), and differences in vastus lateralis TSI during the sprint (-0.01, {+/-}0.33) and recovery (-0.08, {+/-}0.50) phases were unclear. There was also no meaningful difference in {Delta}Reoxy (0.21, {+/-}0.37). Intercostal HHb was higher in the INSP session compared to CTRL (0.42, {+/-}0.34), whilst the difference was unclear for TSI (-0.01, {+/-}0.33). During MATCH exercise, differences in vastus lateralis TSI were unclear compared to INSP for both sprint (0.10, {+/-}0.30) and recovery (-0.09, {+/-}0.48) phases, and there was no meaningful difference in {Delta}Reoxy (-0.25, {+/-}0.55). Intercostal TSI was higher during MATCH compared to INSP (0.95, {+/-}0.53), whereas HHb was lower (-1.09, {+/-}0.33). The lack of difference in {Delta}Reoxy between INSP and CTRL suggests that for intermittent sprint exercise, the metabolic O2 demands of both the respiratory and locomotor muscles can be met. Additionally, the similarity of the MATCH suggests that {Delta}Reoxy was maximal in all exercise conditions.

Sprint running is a common feature of many sport activities. The ability of an athlete to cover a distance in the shortest time relies on his/her power production. The aim of this study was to provide an exhaustive description of the mechanical determinants of power output in sprint running acceleration and to check whether a predictive equation for internal power designed for steady locomotion is applicable to sprint running acceleration. Eighteen subjects performed two 20 m sprints in a gym. A 35-camera motion capture system recorded the 3D motion of the body segments and the body center of mass (BCoM) trajectory was computed. The mechanical power to accelerate and rise BCoM (external power, Pext ) and to accelerate the segments with respect to BCoM (internal power, Pint ) was calculated. In a 20 m sprint, the power to accelerate the body forward accounts for 50% of total power; Pint accounts for 41% and the power to rise BCoM accounts for 9% of total power. All the components of total mechanical power increase linearly with mean sprint velocity. A published equation for Pint prediction in steady locomotion has been adapted (the compound factor q accounting for the limbs' inertia decreases as a function of the distance within the sprint, differently from steady locomotion) and is still able to predict experimental Pint in a 20 m sprint with a bias of 0.70 ± 0.93 W kg-1 . This equation can be used to include Pint also in other methods that estimate external horizontal power only.

This research aims to investigate the impact of fever on total mechanical ventilation time (TVT) in critically ill patients. Subgroup analysis was conducted using a previous prospective, multicenter observational study. We included mechanically ventilated patients for more than 24 hours from 10 Korean and 15 Japanese intensive care units (ICU), and recorded maximal body temperature under the support of mechanical ventilation (MAXMV). To assess the independent association of MAXMV with TVT, we used propensity-matched analysis in a total of 769 survived patients with medical or surgical admission, separately. Together with multiple linear regression analysis to evaluate the association between the severity of fever and TVT, the effect of MAXMV on ventilator-free days was also observed by quantile regression analysis in all subjects including non-survivors. After propensity score matching, a MAXMV ≥ 37.5°C was significantly associated with longer mean TVT by 5.4 days in medical admission, and by 1.2 days in surgical admission, compared to those with MAXMV of 36.5°C to 37.4°C. In multivariate linear regression analysis, patients with three categories of fever (MAXMV of 37.5°C to 38.4°C, 38.5°C to 39.4°C, and ≥ 39.5°C) sustained a significantly longer duration of TVT than those with normal range of MAXMV in both categories of ICU admission. A significant association between MAXMV and mechanical ventilator-free days was also observed in all enrolled subjects. Fever may be a detrimental factor to prolong TVT in mechanically ventilated patients. These findings suggest that fever in mechanically ventilated patients might be associated with worse mechanical ventilation outcome., Graphical Abstract

In internal combustion engines, friction losses caused by piston ring and cylinder liner pair account for approximately 20% of total mechanical friction losses as reported in literature. A reduction in friction between piston ring and cylinder liner pair would therefore result in higher efficiency, lower fuel consumption and reduced emissions. In this study, the effects of different types of fuel which is contaminated to cylinder oil have been tested for investigating the friction behavior between piston ring and cylinder liners pair by a reciprocating tester depending on the load, revolution and temperature. The results showed that lubricant type and revolution have been found significant on friction behavior.

A corrosive wear model is considered at the asperity-scale of a tribocorrosive wear system as well as the traditional Archard-type mechanical wear model. The geometry of the surface asperities is modified in a contact mechanics model with respect to both corrosive and mechanical wear calculations. This model was presented and validated for prediction of the electrochemistry in the first part of this work. The material used in the experimental part of this work was CoCrMo plate working electrode (WE) and Si3N4 ball as the counter body in a reciprocating configuration. Experiments were conducted at loads of 5, 7.5, and 10 N and the contributions of total mechanical wear and corrosion were measured. The model is then tuned to predict the chemical and mechanical components of the total wear of the system. The synergistic effect of corrosion on mechanical wear and mechanical wear on corrosion are modeled numerically in this work. The values are then used to explain different components of mechanistic tribocorrosive wear models present in the literature. This deterministic model, for the first time, calculates the corrosion-enhanced wear in a tribocorrosive wear environment and proposes that changes in the topography are responsible for this synergistic effect. The results show a linear dependence of the corrosion enhanced wear, wear-enhanced corrosion, and the pure mechanical wear on the applied load. Results also suggest that the wear enhanced corrosion has a significant contribution in the overall degradation of the material.

SUMMARY A study was conducted in South Georgia to assess the carbon footprint of poultry farms. The study included broiler grow-out farms, pullet farms, and breeder farms from one commercial broiler complex. Data collection included the fuel and electricity bills from each farm, house size and age, flock size and number of flocks per year, and manure management. Emissions were calculated using a greenhouse gas (GHG) calculation tool. The carbon dioxide, nitrous oxide,andmethane(CH4)emissionswerecomputedandacarbonfootprintdetermined.Carbon footprint comparisons were made based on house construction and age. Based on these results, an evaluation of the mechanical sources of emissions showed that approximately 96% of the emissions from the broiler and pullet farms were from propane use, while only 3.9% of the total mechanical emissions from breeder farms were from propane use. On breeder farms, 83% of mechanical GHG emissions were the result of electricity use, while the pullet and broiler grow-out farms accounted for 2.9 and 2.7%, respectively, of the total mechanical emissions from electricity use. The data collected from the farms and entered into the GHG calculation tool revealed that breeder houses had higher levels of CH4 emissions from manure management when compared to emissions from broiler and pullet houses. Even though the GHG emissions from poultry production farms were minimal compared to other animal production farms, the different sources of emissions were identified, thereby enabling the farmer to target specific areas for mitigation.

This paper deals with practical application of acceleration method for evaluation of induction machine torque-speed and current-speed characteristics. Influence of measuring time on the shape of evaluated torque-speed characteristics is presented based on the results of measurements. One of the aims of this paper is also calculation and measurement of mechanical losses from deceleration test. A method for determination of distribution of friction and windage mechanical losses from the measurement is described. The influence of a cooling fan on the total mechanical losses is also discussed.

The mechanical response of intact blood vessels to applied loads can be delineated into passive and active components using an isometric decomposition approach. Whereas the passive response is due predominantly to the extracellular matrix (ECM) proteins and amorphous ground substance, the active response depends on the presence of smooth muscle cells (SMCs) and the contractile machinery activated within those cells. To better understand determinants of active stress generation within the vascular wall, we subjected porcine common carotid arteries (CCAs) to biaxial inflation–extension testing under maximally contracted or passive SMC conditions and semiquantitatively measured two known markers of the contractile SMC phenotype: smoothelin and smooth muscle-myosin heavy chain (SM-MHC). Using isometric decomposition and established constitutive models, an intuitive but novel correlation between the magnitude of active stress generation and the relative abundance of smoothelin and SM-MHC emerged. Our results reiterate the importance of stretch-dependent active stress generation to the total mechanical response. Overall these findings can be used to decouple the mechanical contribution of SMCs from the ECM and is therefore a powerful tool in the analysis of disease states and potential therapies where both constituent are altered.

The purpose of this study was to explore the relationships between mechanical power, thrust power, propelling efficiency and sprint performance in elite swimmers. Mechanical power was measured in 12 elite sprint male swimmers: (1) in the laboratory, by using a whole-body swimming ergometer (W'TOT) and (2) in the pool, by measuring full tethered swimming force (FT) and maximal swimming velocity (Vmax): W'T = FT · Vmax. Propelling efficiency (ηP) was estimated based on the “paddle wheel model” at Vmax. Vmax was 2.17 ± 0.06 m · s−1, ηP was 0.39 ± 0.02, W'T was 374 ± 62 W and W'TOT was 941 ± 92 W. Vmax was better related to W'T (useful power output: R = 0.943, P < 0.001) than to W'TOT (total power output: R = 0.744, P < 0.01) and this confirms the use of the full tethered test as a valid test to assess power propulsion in sprinters and to estimate swimming performance. The ratio W'T/W'TOT (0.40 ± 0.04) represents the fraction of total mechanical power that can be utilised in water (e.g., ηP) and was indeed the same as that estimated based on the “paddle wheel model”; this supports the use of this model to estimate ηP in swimming. © 2017 Informa UK Limited, trading as Taylor & Francis Group.

Moir, GL, Munford, SN, Moroski, LL, Davis, SE. The effects of ballistic and nonballistic bench press on mechanical variables. J Strength Cond Res 32(12): 3333-3339, 2018-The purpose of this study was to investigate the effects of ballistic and nonballistic bench press performed with loads equivalent to 30 and 90% 1 repetition maximum (1RM) on mechanical variables. Eleven resistance-trained men (age: 23.0 ± 1.4 years; mass: 98.4 ± 14.4 kg) attended 4 testing sessions where they performed one of the following sessions: (a) 3 sets of 5 nonballistic repetitions performed with a load equivalent to 30% 1RM (30N-B), (b) 3 sets of 5 ballistic repetitions performed with a load equivalent to 30% 1RM (30B), (c) 3 sets of 4 nonballistic repetitions with a load equivalent to 90% 1RM (90N-B), or (d) 3 sets of 4 ballistic repetitions with a load equivalent to 90% 1RM (90B). Force plates and a 3-dimensional motion analysis system were used to determine the velocity, force, power output (PO), and work during each repetition. The heavier loads resulted in significantly greater forces applied to the barbell (mean differences: 472-783 N, p < 0.001), but lower barbell velocities (mean differences: 0.85-1.20 m·s, p < 0.001) and PO (mean differences: 118-492 W, p ≤ 0.022). The ballistic conditions enhanced the mechanical variables only at the lower load, with 30B producing significantly greater force (mean difference: 263 N, p < 0.001), velocity (mean difference: 0.33 m·s, p < 0.001), and PO (mean difference: 335 W, p < 0.001) compared with 30N-B. Furthermore, the increase in PO across the 3 sets in 30B was significantly different from all other conditions (p = 0.013). The total mechanical work performed was significantly greater for the conditions with the heavier loads compared with those with the lighter loads (mean differences: 362-5,600 J, p < 0.001) and that performed during the ballistic conditions was significantly greater than that performed during the nonballistic conditions with the same load (mean differences: 945-1,030 J, p < 0.001). Ballistic bench press may be an effective exercise for developing PO, and multiple sets may elicit postactivation potentiation that enhances force production. However, these benefits may be negated at heavier loads.

This research on "America's Cup" grinders investigated the effects of a specific eight-week long-arm cranking ergometer (ACE) training on upper body (UB) aerobic fitness (ventilatory threshold - Tvent, respiratory compensation point- RCP, -oxygen uptake peak - VO₂peak) and high intensity working capacity. The training consisted of sessions carried out for 20-30 mins, three times per week, at an intensity between the UB-Tvent and UB-RCP, and replaced part of a typical lower limb aerobic training whilst maintaining the usual weekly schedule of callisthenics, resistance training and sailing. Seven sailors, including four grinders and three mastmen (age 30 ± 5.5 years, height 1.9 ± 0.04 m, body mass 102 ± 3.6 kg), were evaluated through both an ACE cardiopulmonary maximal exercise test (CPET) and an ACE all-out up to exhaustion exercise test, before and after the ACE training. UB aerobic fitness improved significantly: UB-VO₂peak increased from 4.29 ± 0.442 to 4.52 ± 0.522 l·min(-1) (6.4 ± 3.66%), VO₂ at UB-Tvent from 2.42 ± 0.282 to 2.97 ± 0.328 l·min(-1) (22.8 ± 5.09%) and VO₂ at UB-RCP from 3.25 ± 0.402 to 3.75 ± 0.352 l·min(-1) (16.1 ± 10.83%). Peak power at the ACE CPET increased from 351 ± 27.5 to 387 ± 33.5 W (10.5 ± 6.93%). The all-out test total mechanical work increased from 28.9 ± 2.35 to 40.1 ± 3.76 kJ (72.1 ± 4.67%). In conclusion, a high intensity aerobic ACE training can be effective in improving grinding performance by increasing UB aerobic fitness and all-out working capacity.

Anastomotic leak from cervical esophagogastric anastomoses is a serious problem after esophagectomy. We explored the efficacy of partial or total mechanical anastomoses accomplished with the endoscopic linear cutting and stapling device as an alternative to hand-sewn anastomotic techniques. Along that we compared various clinical outcomes associated with the same.

tMW with 0 % hypohydra- tion, tMW was reduced by 15.5 and 23.3 % with 1 and 2 % hypohydration, respectively (p < 0.05 for both). At the start of the cycling performance test, Hr was 13 and 15 bpm higher, and T re was 0.3 °c higher (p < 0.05 for all) with 1 and 2 % hypohydration, respectively, compared with 0 % hypohydration. Conclusion Mild (~1 %) to moderate (~2 %) hypohydra- tion reduces high-intensity cycling performance of healthy young boys in the heat. Abstract Purpose to evaluate the effect of 1 and 2 % hypohy- dration on high-intensity cycling performance of 10- to 12-year-old boys in the heat. Methods In a counterbalanced order, nine boys attended three sessions in which they cycled intermittently (6 × 10-min bouts at 40-45 % u V O2max) in a climate cham- ber. During each session, environmental conditions and water intake were individually adjusted to achieve a tar - get hypohydration level of 0, 1 or 2 %, based on change in body weight (BW). Following 45 min of rest in thermon- eutral conditions when the target hypohydration was main- tained, each boy re-entered the climate chamber (35 °c and 50-55 % rH) to perform the cycling performance test at 90 % u V O2max until exhaustion. Heart rate (Hr) and rectal temperature (T re) were recorded continuously throughout each session. total mechanical work (tMW) was taken as a measure of cycling performance. Results Actual hypohydration level at the start of the cycling performance test in each session was: 0.1 ± 0.0 %, 1.1 ± 0.1 % and 2.0 ± 0.1 %. With 2 % hypohydration, tMW (35.5 ± 6.8 kJ) was significantly (p < 0.05) lower than with 0 % hypohydration (49.3 ± 9.8 kJ). When

Acceleration and deceleration phases characterise shuttle running (SR) compared to constant speed running (CR); mechanical work is thus expected to be larger in the former compared to the latter, at the same average speed (v mean). The aim of this study was to measure total mechanical work (W tot + , J kg−1 m−1) during SR as the sum of internal (W int + ) and external (W ext + ) work and to calculate the efficiency of SR. Twenty males were requested to perform shuttle runs over a distance of 5 + 5 m at different speeds (slow, moderate and fast) to record kinematic data. Metabolic data were also recorded (at fast speed only) to calculate energy cost (C, J kg−1 m−1) and mechanical efficiency (eff+ = W tot + C −1) of SR. Work parameters significantly increased with speed (P

Three computer models of varying complexity were developed in order to investigate the kinematics, kinetics, muscle operating ranges, and energetics of rock climbing. First, inverse dynamic models were used to investigate the joint angles and torques used in climbing and to quantify the total mechanical work required for typical rock climbing. Climbing experience was found to have a significant effect on the kinematics used in climbing; however, there were no significant differences in mechanical work. Second, a musculoskeletal model of the whole body was developed, this model combined with the kinematic data was used to analyze the operating ranges of the upper and lower limb muscles during climbing. In general, the experienced climbers employed kinematic motions that corresponded to muscle fibers used for climbing operating much closer to their optimum length than the kinematics of inexperienced climbers. Third, a forward dynamic model was developed to predict the metabolic goal of climbing. The results...

Purpose Athletes are trained to choose the pace which is perceived to be correct during a specific effort, such as the 1500-m speed skating competition. The purpose of the present study was to "override" self-paced (SP) performance by instructing athletes to execute a theoretically optimal pacing profile.Methods Seven national-level speed-skaters performed a SP 1500-m which was analysed by obtaining velocity (every 100 m) and body position (every 200 m) with video to calculate total mechanical power output. Together with gross efficiency and aerobic kinetics, obtained in separate trials, data were used to calculate aerobic and anaerobic power output profiles. An energy flow model was applied to SP, simulating a range of pacing strategies, and a theoretically optimal pacing profile was imposed in a second race (IM).Results Final time for IM was similar to 2 s slower than SP. Total power distribution per lap differed, with a higher power over the first 300 m for IM (637.0 (49.4) vs 612.5 (50.0) W). Anaerobic parameters did not differ. The faster first lap resulted in a higher aerodynamic drag coefficient and perhaps a less effective push-off.Conclusion Experienced athletes have a well-developed performance template, and changing pacing strategy towards a theoretically optimal fast start protocol had negative consequences on speed-skating technique and did not result in better performance.

Buoyancy has a substantial contribution to the total mechanical cost of diving in waterbirds. Most of the techniques currently employed to estimate buoyancy are based on measuring the volume of carcasses or forcibly submerged birds using the water displacement (Archimedes) principle. In such techniques, the voluntary control the bird might have over plumage and respiratory air volumes is neglected. Here, I propose an adjustment to the water displacement measurement that allows the measurement of buoyancy in real-time from unrestrained live birds diving voluntarily. The novelty and accuracy of the technique lie in using a pressure sensor to continuously measure the water level inside the dive tank while filtering out the interference from surface waves. The error of the volume measurement in the proposed technique was only ±2.4%. Feasibility of measurement is demonstrated on captive Great Cormorants (Phalacrocorax carbo sinensis). The measured volumes of Great Cormorants exceeded predictions made based on the volume of carcasses and on average resembled values measured from live restrained birds. However the technique highlighted the high variation in buoyancy of live birds (up to 30%) as a result of small changes in the air volumes taken with the bird underwater.

The kinesin motor converts the chemical energy from ATP turnover into mechanical work, which produces successive 8-nm steps in the forward and backward direction along a microtubule. A key problem for kinesin mechanochemistry is explaining how ATP turnover is coordinated with mechanical work. We investigated this by measuring the ATP dependent properties of kinesin forward and backward steps using optical trapping nanometry. The results showed that the rate for both forward and backward steps are ATP-dependent, indicating that ATP binding to kinesin triggers both forward and backward steps. This suggests that ATP turnover in kinesin is not rigidly coupled to total mechanical work at high load.

Methods were developed for dividing the total mechanical work of deformation and the deformation corresponding to it into elastic-reversible and viscoelastic-plastic components which suggests use in both calculation of the resistance of chemical fibres in the dynamic deformation regime and for assessing the ability of materials to resist a mechanical effect and recover the initial shape during use. Incorporation of a coefficient for the irreversibility of deformation allows separating the viscoelastic and plastic components of deformation after the total deformation of chemical fibres is broken down into the constituent components.

SUMMARY Walking humans prefer to use the stride rate that results in the lowest rate of metabolic energy expenditure. Mechanical power requirements have been suggested to underlie the metabolic response, but mechanical power is consistently reported to be minimal at stride rates 20–30% lower than preferred. This may be due to limitations in how total mechanical power has been computed, as well as a failure to account for the efficiency with which muscular work is done. We investigated how mechanical power and efficiency depend on stride rate in walking, with both quantities computed from the work done by the hip, knee and ankle joint moments. Our hypotheses were that mechanical power and efficiency are both optimized at the preferred stride rate, which would explain why metabolic energy expenditure is minimized at this rate. Contrary to our hypotheses, mechanical power curves exhibited plateaus that spanned stride rates lower than preferred (predicted optima:11–12% below preferred), while net mechanical efficiency exhibited a plateau that spanned stride rates higher than preferred (predicted optimum: 8%above preferred). As expected, preferred stride rate (54.3 strides min–1) was not different from the stride rate that minimized net metabolic energy expenditure (predicted optimum: 0.2% above preferred). Given that mechanical power and mechanical efficiency exhibited plateaus on opposite sides of the preferred stride rate, the preferred rate in walking likely represents a compromise between these two factors. This may also explain the relative flatness of the curve for metabolic rate in the vicinity of the preferred stride rate.

This paper investigates using nonlinear finite element analysis (FEA) to determine the failure pressure and failure location for pressure vessels. The method investigated by this paper is to predict the pressure-vessel failure point by identifying the pressure and location where the total mechanical strain exceeds the actual elongation limit of the material. A symmetrically shaped component and a nonsymmetric shaped component are analyzed to determine the failure pressure and location. Data were then gathered by testing each pressure vessel to determine its actual failure pressure. Comparing the FEA results with experimental data showed that the fea software predicted the failure pressure and location very well for the symmetric shaped pressure vessel, however, for the nonsymmetrical shaped pressure-vessel, the fea software predicted the failure pressure within a reasonable range, but the component failed at a weld instead of the predicted location. This difference in failure location was likely caused by varying material properties in both the weld and the location where the vessel was predicted to fail.

A total knee arthroplasty performed with navigation results in more accurate component positioning with fewer outliers. It is not known whether image-based or image-free-systems are preferable and if navigation for only one component leads to equal accuracy in leg alignment than navigation of both components. We evaluated the results of total knee arthroplasties performed with femoral navigation. We studied 90 knees in 88 patients who had conventional total knee arthroplasties, image-based total knee arthroplasties, or total knee arthroplasties with image-free navigation. We compared patients' perioperative times, component alignment accuracy, and short-term outcomes. The total surgical time was longer in the image-based total knee arthroplasty group (109 +/- 7 minutes) compared with the image-free (101 +/- 17 minutes) and conventional total knee arthroplasty groups (87 +/- 20 minutes). The mechanical axis of the leg was within 3 degrees of neutral alignment, although the conventional total knee arthroplasty group showed more (10.6 degrees ) variance than the navigated groups (5.8 degrees and 6.4 degrees , respectively). We found a positive correlation between femoral component malalignment and the total mechanical axis in the conventional group. Our results suggest image-based navigation is not necessary, and image-free femoral navigation may be sufficient for accurate component alignment.

Fiber fracture is one of the dominant failure phenomena to determine total mechanical performance inside composites. Fiber fracture locations were measured and compared via either conventional optical microscopic method or nondestructive acoustic emission (AE) by pencil-lead-break method as functions of epoxy matrix modulus and surface treatment by the electrodeposition (ED). Two AE sensors were attached on single carbon fiber reinforced various epoxy composites and consecutive fiber fracture signals were monitored with the elapsing time and strain. The interfacial shear strength (IFSS) was measured using tensile fragmentation test and AE method. In ED-treated case, the numbers of the fiber fracture measured by optical method and AE were more than those of the untreated case. The signal number of fiber fracture measured by AE method was smaller than the number of fragments measured by an optical method, since some fiber fracture signals were lost during AE monitoring. However, the correspondence between AE detected location and optically observed location was generally established well with small error range. Wave speed was relied on the impact direction and the existence of induced defects, i.e., surface and internal damages of epoxy specimen. The fiber break source location and wave analysis by AE can be a valuable method to measure IFSS and mechanical properties of matrix indirectly for non-, semi- and/or transparent polymer composites nondestructively.

SUMMARYThe effect of age and body size on the total mechanical work done during walking is studied in children of 3–12 years of age and in adults. The total mechanical work per stride (Wtot) is measured as the sum of the external work, Wext (i.e. the work required to move the centre of mass of the body relative to the surroundings), and the internal work, Wint (i.e. the work required to move the limbs relative to the centre of mass of the body, Wint,k,and the work done by one leg against the other during the double contact period, Wint,dc). Above 0.5 m s–1, both Wext and Wint,k, normalised to body mass and per unit distance (J kg–1 m–1), are greater in children than in adults; these differences are greater the higher the speed and the younger the subject. Both in children and in adults, the normalised Wint,dc shows an inverted U-shape curve as a function of speed, attaining a maximum value independent of age but occurring at higher speeds in older subjects. A higher metabolic energy input (J kg–1 m–1) is also observed in children,although in children younger than 6 years of age, the normalised mechanical work increases relatively less than the normalised energy cost of locomotion. This suggests that young children have a lower efficiency of positive muscular work production than adults during walking. Differences in normalised mechanical work, energy cost and efficiency between children and adults disappear after the age of 10.

In the paper are presented results of grain outer quality loss investigation during its post-harvest treatment. Objective was to determine the grain damage during its transport by bucket elevators of type "SANFON" at bucket peripheral velocity 2.0 m/s and 2.8 m/s of capacity 40 t/h and 80 t/h, respectively. The damage was investigated at counter-flow and parallel-flow bucket filling. From the measured results resulted the conclusion, that the bucket elevators tend rather to grain crushing, i.e. fraction creation than to smaller damage. On basis of partial knowledge chain elevators have no significant tendency to fraction generation, but incline considerably to the transported grain total mechanical damage at performance significantly lower than is the nominal one. In that case total mechanical damage ranged from 1.78 to 1.98%. Auger conveyers tend rather to total mechanical damage of transported grain than to the fraction creation. This is caused mainly by the friction between the transported grain and transporting "trough". Total mechanical damage is in range from 1.36 to 1.73%. Belt elevators are friendly to transported grain and therefore are evitable for grain horizontal transport in lines for reception, treatment and storage of food grain crops.

Peak torque during an isokinetic bilateral knee extension or flexion is usually lower than the summed peak torque of two unilateral contractions, and this phenomenon is designated as bilateral deficit (BD). The objectives of this study were to determine whether a BD also exists for more complex, alternating movements (e.g., short-term, high-intensity cycling), and to assess the possible effects of gender and maturity. Forty children and adolescents performed two unilateral (ULWAnT) and one bilateral Wingate anaerobic test (BLWAnT). The highest power reached in any 3-s interval (peak power; PP), and the total mechanical work (TMW) performed during the test was determined. Individual BD for PP (BDpp, %) was calculated by dividing the PP in the BLWAnT by the sum of the PP values of both ULWAnTs. The BD for TMW (BDTMw) was calculated in the same way. The sum of PP generated during the two ULWAnTs was larger than the PP measured in the BLWAnT (P