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Functional interaction between upper airway (UA) dilator muscles and the diaphragm is crucial in the maintenance of UA patency. This interaction could be altered by increasing respiratory drive. The aim of our study was to compare the effects of hypercapnic stimulation on diaphragm and genioglossus corticomotor responses to transcranial magnetic stimulation (TMS).10 self-reported healthy men (32 ± 9 yr; body mass index = 24 ± 3 kg/m(-2)) breathed, in random order, room air or 5% and then 7% Fi(CO(2)), both balanced with pure O(2). Assessments included ventilatory variables, isoflow UA resistance (at 300 ml/s), measurement of lower chest wall/diaphragm (LCW/diaphragm), and genioglossus motor threshold (MT) and motor-evoked potential (MEP) characteristics. TMS twitches were applied during early inspiration and end expiration at stimulation intensity 30% above LCW/diaphragm and genioglossus MT.Compared with room air, CO(2) inhalation significantly augmented minute ventilation, maximal inspiratory flow, tidal volume, and tidal volume/respiratory time ratio. UA resistance was unchanged with CO(2) inhalation. During 7% CO(2) breathing, LCW/diaphragm MT decreased by 9.6 ± 10.1% whereas genioglossus MT increased by 7.2 ± 9%. CO(2)-induced ventilatory stimulation led to elevation of LCW/diaphragm MEP amplitudes during inspiration but not during expiration. LCW/diaphragm MEP latencies remained unaltered both during inspiration and expiration. Genioglossus MEP latencies and amplitudes were unchanged with CO(2).In awake, healthy subjects, CO(2)-induced hyperventilation is associated with heightened LCW/diaphragm corticomotor activation without modulating genioglossus MEP responses. This imbalance may promote UA instability during increased respiratory drive.

Background Negative airway pressure loading such as seen during obstructive apnea/hypopnea may influence upper airway (UA) mechanical properties. We measured the effects of such loading on UA mechanical properties during wakefulness and assessed the potential link with night-time apnea worsening. Methods Twitch stimulations of the phrenic nerve were applied before and after a step-by-step increase in UA suction flow in 10 sleep apnea and 10 control males. Results Inspiratory closing pressure was lower in control than in apneic subjects. No consistent changes were observed in UA mechanical properties before and after the trial. In apneic patients, changes in the apnea index from the beginning to the end of the night correlated with changes in inspiratory closing pressure following suction flow. Conclusion (1) Apnea phenotype does not influence the impact of negative airway pressure on UA dynamic properties during wakefulness and (2) worsening of sleep apnea frequency during the night may relate to the exposure to recurrent UA negative pressure.

To assess upper airway (UA) dynamic properties, magnetic stimulation of the phrenic nerves (MSPN) is usually performed at cervical level or anterior-laterally at the neck base. We hypothesized that UA dynamic properties could be effectively assessed by MSPN performed at the sternal level. Instantaneous flow, pharyngeal and mask pressures were recorded in 12 healthy awake subjects. End-expiratory MSPN were applied in random order with a non-focal coil placed behind the 7th cervical vertebrae (C7-MS) and at the sternal level (a-MS). The percentage of flow-limited twitches was greater with a-MS (a-MS: 33% and C7-MS: 2%; P < 0.0001). For the non flow-limited twitches, maximal inspiratory flow was 36% greater (P < 0.001) and isoflow UA resistance was lower with a-MS (0.6 ± 0.1 and 0.9 ± 0.1 cm H2O l−1 s; P = 0.02). Maximal inspiratory flow of flow-limited twitches was 78% greater (P = 0.05) and isoflow UA resistance tended to be lesser with a-MS (0.9 ± 0.3 and 1.8 ± 0.7 cm H2O l−1 s; P = 0.09). a-MS could be a practical approach for assessing UA dynamic properties in awake subjects.

Goiter is still common in Uganda, despite the present iodized salt coverage of at least 95%. Where there is endemic goiter after adequate iodine supplementation, selenium deficiency could be a factor for the continued occurrence of goiter. The objectives of the present study, therefore, were to determine the serum selenium levels among goitrous patients and nongoitrous controls and to determine the association between goiter and selenium levels among these patients. The investigation was designed as a case control study in which 92 subjects were enrolled, 46 cases and 46 controls of similar age and sex distribution. Subjects were interviewed and examined. Blood samples were taken and selenium concentrations were determined by electrothermal atomic absorption spectrometry. The overall mean serum selenium levels were 77.25 μg/l (SD 16.78) for the goiter patients and 95.50 μg/l (24.47) for the nongoiter controls. The difference between goitrous and nongoitrous populations was statistically significant (p = 0.0001). Selenium levels above 102.8 μg/l had a statistically significant protective effect against goiter with adjusted odds ratio 0.3 (0.13–0.69); p = 0.005. Other factors, such as age, main food constituent, and use of iodized salt, had no association with goiter. There were significant differences between selenium levels among goitrous patients and nongoitrous controls. High selenium levels seem to have a protective effect against goiter. Selenium supplementation as a preventive strategy is worth further exploration

One of the failure modes in tube hydroforming (THF) is bursting. To predict the burst pressure in the THF process, Brozzo's decoupled ductile fracture criterion was used in conjunction with a dynamic nonlinear commercial finite element software, Ls-Dyna, and the criterion was evaluated using the data obtained from the free expansion (tube bulging) tests performed on 0.9 mm and 1.2 mm thick stainless steel (SS) 321 tubes. The predicted burst pressures were compared with the experimental results for both thicknesses. The predicted burst failure of the tube bulging, based on the Brozzo's criterion, demonstrated a good agreement with the experimental data, indicating that the present approach for predicting the burst failure for the tube bulging can be extended to predict formability limits in THF applications. © 2011 American Institute of Physics., THE 14TH INTERNATIONAL ESAFORM CONFERENCE ON MATERIAL FORMING: ESAFORM 2011, 27–29 April 2011, Belfast, United Kingdom, Series: AIP Conference Proceedings; no. 1353

Aircraft bird-strike events are very common and dangerous. Hailstone impacts represent another threat for aircraft structures. As part of the certification process, an aircraft must demonstrate the ability to land safely after impact with a foreign object at normal flight operating speeds. Since experimental studies can be cost prohibitive, validated numerical impact simulation seems to be a viable alternative. Modelling of these soft body impacts still represents a challenge, involving modelling of both the target and the projectile. Here the smooth particle hydrodynamics method (SPH), which has been used successfully in ballistic applications involving bird strike scenarios, is extended to hail impact. The paper thus presents the meshless SPH numerical method as a novel modeling approach. The method is applied to model bird and hail impacts which are problems that traditional FEM based modeling methods typically struggle to solve because of involved mesh distortion problems. The numerical results are then evaluated by comparing with the data collected during recent experimental tests. The data acquisition methods are also described and evaluated for applications where the short duration of the impact presents a challenge. The accuracy of the numerical results allows us to conclude that the models developed can be used in the certification and/or design process of moving (aircraft) and stationary (wind turbines) composite structures subject to bird and hail impact. ©2010 Society for Experimental Mechanics Inc., 28th IMAC, A Conference on Structural Dynamics, 2010, 1 February 2010 through 4 February 2010, Jacksonville, FL, Series: Conference Proceedings of the Society for Experimental Mechanics Series

International audience; A mechanical computer aided design and engineering system can be used to reduce the design-to-manufacture cycle time in metal forming process. Such a system could be built upon a solid modeling geometry engine and an efficient finite element (FE) solver. The maintenance of a high-quality mesh throughout the analysis is an essential feature of an efficient finite element simulation of large strain metal forming problems. In this paper, a mesh adaptation technique employing the Arbitrary Lagrangian-Eulerian formulation (ALE) is applied to some industrial metal forming problems. An ACIS boundary representation of the solid model is employed. This type of representation provides the necessary data for adaptive meshing techniques. To take care of large deformations, the Lagrangian types of mesh adaptation zones are used. The new mesh, which is updated at a given frequency, is found by iterating on the adaptation zones. During this process, mesh nodes are moved to new positions in order to have a more regular mesh size distribution. There are, however, cases where the ALE method needs an initial spatial mesh pattern to be able to complete the analysis. The required initial mesh depends on the plastic flow pattern of material. Examples of large strain metal forming problems illustrate the effectiveness of the method in industrial environment.

An algorithm for solving the parametric linear complementary problem (PLCP) deduced from the boundary element (BE) frictional contact approach is presented. This numerical procedure is based on the decoupling of normal pressure and tangential traction. In the beginning of each load increment, the node pairs corning into real contact are determined. The principal pivoting algorithm is applied to the normal contact variables of the LCP system to find normal contact pressures, P N , for contact node pairs and normal gaps, D N , for node pairs not in contact. The values of P N are then used as known data for the calculation of tangential tractions, P T , as well as tangential displacements, W T . Because in both these two main steps we use some types of direct method, the CPU time is predictable and convergence of the algorithm can be guaranteed. This is one of the advantages of the present method over the standard principal pivot method or iteration method in dealing with a non-symmetric BE matrix. Some numerical examples are also given.

A general solution method for three-dimensional quasistatic frictional contact problems is presented. It is based on the direct boundary element formulation with substructuring and a particular mathematical programming technique identified as the parametric linear complementarity problem (PLCP) with mixed complementary conditions. A solution algorithm that deals with the special form of PLCP is presented and allows one to define and check a criterion assessing the algorithm convergence. The frictional law is represented by a piecewise linear approximation of the Coulomb's friction cone which, when combined with the spatial discretization, yields a solution process that is linear in ‘time’ and thus not requiring an explicit time discretization of the original problem.

This paper presents a three dimensional boundary element formulation for numerical treatment of lubricated contact between two deformable thermoelastic solids. A unified approach based on continuum thermodynamics is used to derive the equations governing the thermomechanical behavior of the contacting bodies and their interfacial fluid layer. For the thermoviscous fluid layer (lubricant), we use the full Navier-Stokes and energy equations instead of the usual lubrication equations based on a reduced momentum-continuity equation (Reynold's Equation). This approach is shown to be amenable to standard boundary element formulation of the thermohydrodynamic problem that is easily coupled to the thermoelastic boundary element problem of the contacting bodies. An iterative solution procedure for this solid-fluid interaction problem is then presented.

Recent bird impact tests were conducted using gelatine as a bird substitute. A recipe for the gelatine is suggested in order to use as a reference in further bird test certification procedures. Results from the tests are also given so that they can be used to validate numerical models and promote the use of numerical tools in aircraft design and certification process., available, unclassified, unlimited

Based on the Mindlin-Deresiewicz displacement field solution, a simple method is presented to obtain the force-displacement relationship for a contact between two elastically similar bodies. The bodies are initially pressed together along the normal to their mutual tangential plane and subsequently loaded by a monotonically increasing tangential force acting at an angle to the axes of the contact ellipse. The results are derived based on both no-slip and microslip assumptions, and compared with the available solutions.

Summary Background Missed injuries (MIs) have been noted worldwide in all trauma centres that have studied them, and they are a significant cause of patient morbidity and mortality. Objective To establish the prevalence, contributing factors and short-term outcome of missed injuries in cases of multiple and major trauma. Method Longitudinal prospective study involving 403 patients over 5 months. Results Missed injuries were discovered in 78 cases (prevalence 19.4%). Contributing factors included incomplete assessment (52.5%), radiological errors, surgical failures and patient's arrival time. The most affected body regions were the head and neck, extremities and pelvic girdle and contents; in the abdomen, 49.1% of injuries were missed. Among the 28 deaths in the study, 21 occurred in cases with missed injuries, and 13 (62%) of these deaths were directly attributable to missed injuries ( R 2 = 12.5, p = 0.0001, 95% CI 5.5–28.35). Conclusion There is need for improvement in patient assessment and monitoring, in efficiency of the trauma team, and for staff redistribution to address the increase in night arrivals.

In this work, we are interested in modeling and numerical simulation using the dynamic finite element method for the hyperelastic behaviour of a thin, transverse isotropic and incompressible thermoplastic membrane. The hyperelastic (Mooney ‐Rivlin) is considered. The thermoforming of the long fibre reinforced sheet is done under the action of a perfect gas. The load in pressure used in modelling is deduced from the law of perfect gases pressure. The lagrangian formulation together with the assumption of the membrane theory is used. The numerical analyze is performed by comparing the obtained results with measured experimental data for the polymeric ABS membrane inflation without long fibre. Moreover, the influence of the orientation of fibre on the thickness and on the stress distribution in the thermoforming sheet are analyzed.

This paper is aimed at presenting recent advances in modeling and simulation of vibrating structures in presence of external as well as of internal fluid flows using methods based on symmetric variational BEM formulation coupled with the FE. The structural weak form is coupled with a novel boundary element variational formulation of a compressible viscous fluid. The proposed formulation has distinct advantages: (i) over the classical FE, it avoids the discretisation of the fluid domain; (ii) over the collocation BEM formulation, it avoids the explicit calculation of the finite part of hypersingular integrals. Also, the discretisation, by the boundary finite element procedure, of the resulting mixed variational functional leads to a symmetric algebraic system. A computer code based on these concepts has been developed and applied to calculate 3D vibroacoustic behavior of various coupled mechanical systems.

The presence of a thick ice layer on a post insulator can change considerably the distribution of the electric field along this equipment, and that especially when a water film flows on the accumulated ice surface. The main objective of this paper is the modelling of electric field distribution along a post insulator covered with atmospheric ice with air gaps, using the boundary element method (BEM). Moreover, the influence of the presence of a highly conductive water film at the ice surface on the field distribution is also studied. The results contribute to the prediction of flashover on industrial ice-covered insulators.

Background Alcohol drinking is linked to the development of breast cancer. However, there is little knowledge about the impact of alcohol consumption on breast cancer risk among African women. Methods We conducted a case-control study among 2,138 women with invasive breast cancer and 2,589 controls in Nigeria, Cameroon, and Uganda from 1998 to 2013. A structured questionnaire was used to collect information on alcohol consumption, defined as consuming alcoholic beverages at least once a week for six months or more. Logistic regression was used to estimate adjusted odds ratio (aOR) and 95% confidence interval (CI). Results Among healthy controls, the overall alcohol consumption prevalence was 10.4%, and the prevalence in Nigeria, Cameroon, and Uganda were 5.0%, 34.6%, and 50.0%, respectively. Cases were more likely to have consumed alcohol (aOR = 1.62, 95% CI: 1.33–1.97). Both past (aOR = 1.54; 95% CI: 1.19–2.00) and current drinking (aOR = 1.71; 95% CI: 1.30–2.23) were associated with breast cancer risk. A dose-response relationship was observed for duration of alcohol drinking (P-trend

Modeling and simulation of the compaction process in Powder Metallurgy is considered. The features of the mechanical behavior of metal powders are reviewed and a multisurface elastoplastic material constitutive law of the cap type is presented. The experimental characterization of the material model is done through resonant frequency measurements, uniaxial compression, hydrostatic and triaxial tests. A sensitivity study gives the relative influence of various parameters. Finite element simulations are performed and simulated results are validated by using experimental Vickers macrohardness measures in the context of industrial applications. The main conclusion of the study is that further experimental work is still needed in order to accurately identify the elasticity and the shear failure mode parameters.

In this paper, we give an extension of the Grzegorczyk Hierarchy to the BSS theory of computability which is a generalization of the classical theory. We adapt some classical results ([3, 4]) related to the Grzegorczyk hierarchy in the new setting.