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Context: Clinical reasoning is an essential skill to be learned by medical students, and thus requires to be assessed. Although written exams are widely used as one of the tools to assess clinical reasoning, there are no specific guidelines to help an exam writer to develop good clinical reasoning assessment questions. Therefore, we conducted a modified Delphi study to identify guidelines for writing questions that assess clinical reasoning. Methods: Participants were identified from: 1) the literature on clinical reasoning (i.e., people who wrote about clinical reasoning and assessment), 2) the people responsible for assessment in Canadian medical faculties, and 3) a snowball sampling strategy. Thirty-two question-writing guidelines were drawn from the literature and adapted by the team members. Participants were asked to indicate on a ten-point Likert scale their perceived importance of each guideline, and, starting in the second round, the relevance of each guideline in five assessment contexts. A total of three rounds were conducted. Results: Response rates were 24%, 57%, and 62% for each round, respectively. Consensus about the importance of the guidelines (interquartile range < 2.5) was reached for all but four guidelines. Four guidelines were identified as important (median ≥ 9 on ten-point scale): the question should be based on a clinical case, the question represents a challenge achievable for the student, the correction scale (i.e., scoring grid) is explicit, and a panel of experts revises the questions. Conclusion: A large number of guidelines seem relevant for written-exam clinical reasoning assessment questions. We are considering grouping those guidelines into categories to create a simple tool for use by medical educators in the design of written-exam clinical reasoning assessment questions. The next step will then be to collect evidence of validity about this tool: Does it really help to build questions that assess clinical reasoning? Keywords: Clinical reasoning, Assessment, Written-exam questions, Guidelines, UGME

Background Lumbar stabilization exercise programs (LSEPs) act positively on clinical outcome measures in patients with low back pain (LBP), but the underlying mechanisms are not well understood. Among the various neuromuscular mechanisms, a good candidate is better activation of the abdominal wall, as measured with rehabilitative ultrasound imaging (RUSI). Objectives To determine whether RUSI measures are (1) sensitive to LBP status and treatment (LSEP) and (2) correlate with clinical outcomes following the LSEP. Design An exploratory one-arm clinical trial with healthy participants as a control group. Setting LSEP was delivered in a clinical setting; outcomes were measured in a laboratory setting. Participants Thirty-one patients with nonacute LBP and 30 healthy controls. Methods Outcome measures were performed before and after an 8-week LSEP in patients with LBP, and with the same time interval for control participants to compare with patients at baseline. Main outcome measurements Pain, disability, as well as static (at rest) and dynamic (percent thickness change) RUSI measures for abdominal muscles (transversus abdominis, internal oblique [IO], and external oblique [EO]). Results Patients did not produce systematic changes in RUSI measures relative to controls, even if patients had significant improvement in pain and disability. However, the correlational analyses between the absolute change (pre- to post-LSEP) (1) of EO and IO thickness (in mm) at rest (bilaterally), and (2) in pain following the LSEP were significant and consistent (range: .36-.45) in patients. Conclusions Although positive clinical improvements were observed following LSEP, there were minimal systematic changes in RUSI measures, likely because patients were not different from controls at baseline. Correlational analyses, however, indicated that greater reductions in pain were associated with reduced thickness of the EO and IO following the LSEP, suggesting the presence of some heterogeneity (or clinical subgroups) among the patients. Level of evidence II.

INTRODUCTION: Cervicogenic headache (CGH) may originate from the C1-C2 zygapophyseal joints. CGH is often associated with loss of range of motion (ROM), specific to this segment, and measurable by the cervical flexion-rotation test (CFRT). The main purposes of the study were: 1) to investigate the immediate effect of C1-C2 rotation SNAG mobilizations plus C1-C2 self-SNAG rotation exercise for patients with CGH and 2) to explore the link between the CFRT results and treatment response. METHODS: A prospective quasi-experimental single-arm design was used where patients with CGH received eight physical therapy treatments using a C1-C2 rotational SNAG technique combined with a C1-C2 self-SNAG rotation exercise over a four-week period. Outcome measures were pain intensity/frequency and duration, active cervical ROM, CFRT, neck-related and headache-related self-perceived physical function, fear-avoidance beliefs, pain catastrophizing and kinesiophobia. RESULTS: The intervention produced strong effects on pain intensity, CFRT, physical function and pain catastrophizing. Moderate improvement was noted on active cervical ROM and on fear-avoidance beliefs and kinesiophobia. No link was found between pre-intervention CFRT ROM and treatment response. CONCLUSION: SNAG mobilization combined with a self-SNAG exercise resulted in favorable outcomes for the treatment of CGH on patient-important and biomechanical outcomes, as well as pain-related cognitive-affective factors.

Contexte : Développer le raisonnement est une nécessité dans la formation des professionnels de la santé. La formation par concordance (FpC) est une approche pédagogique qui place les apprenants dans des situations authentiques. Les questions posées sont celles que se posent les professionnels dans leur pratique et les réponses sont comparées à celles qu’ont données les membres d’un panel de référence. But : Décrire les variables dont il est nécessaire de tenir compte pour concevoir une FpC. Méthodes : Ces variables sont au nombre de six : 1) les buts de l’activité pédagogique ; 2) la nature de la tâche ; 3) le contenu et le niveau de complexité ; 4) le panel de référence ; 5) les rétroactions ; 6) l’environnement numérique d’apprentissage. Résultats : Les exemples illustrés dans cet article permettent de constater la versatilité de cette approche pour mettre l’accent sur les divers éléments critiques au raisonnement de diverses professions. Conclusion : Les exemples présentés illustrent comment il est possible de mettre au point des outils de FpC qui se prêtent à l’amélioration à chaque itération. Il est désormais possible d’imaginer qu’un jour cette approche à la formation fera partie importante de toute formation professionnelle.

International audience; In the building field, the topic of thermal storage is generally studied with assistance from dedicated software programs. To generate transient thermal simulations, these software programs use enthalpy functions h (T) to describe the thermal behaviour of the different parts of a modelled structure. Unfortunately, the mathematical form of these functions is often extremely unrealistic due to an erroneous interpretation of the calorimetric experiments that were performed to determine these functions. The purpose of this study was to evaluate the energy-related errors that occur if a misinterpreted enthalpy function is used and to thereby assess the impact that these inaccurate functions generate with respect to thermal simulations of buildings.

Background Lumbar stabilization exercise programs (LSEP) produce positive effects on clinical outcomes, but the underlying mechanisms remain relatively unexplored. Psychological and neuromuscular mechanisms can be involved, such as a better activation of the lumbar multifidus, which represents one possibility. Objectives To determine the following: (1) the effect of an LSEP on lumbar multifidus muscle thickness and activation, as measured with rehabilitative ultrasound imaging (RUSI), in patients with low back pain (LBP); (2) the correlation between RUSI measures and any change in clinical outcomes following the LSEP; and (3) the reliability of RUSI measures in control subjects over 8 weeks. Design One-arm clinical trial with healthy subjects as a control group; reliability study. Setting LSEP delivered in a clinical setting; outcomes measured in a laboratory setting. Participants A total of 34 patients with nonacute LBP and 28 healthy control subjects. Methods Outcomes were measured before and after an 8-week LSEP in patients with LBP, and at the same time interval (without treatment, to assess reliability) in control subjects. Main Outcome Measurements Pain numeric rating scale, Oswestry Disability Index (function), as well as RUSI measures for the lumbar multifidus (LM) muscles at 3 vertebral levels (L5-S1, L4-5, and L3-4) during rest (static) and dynamic contractions (percent thickness change). Results Patients did not show systematic changes in RUSI measures relative to controls, even though RUSI impairments were observed at baseline (dynamic measure at L5-S1) and even though patients had significant improvements in pain and disability. Correlational analyses with these clinical outcomes suggested that patients had reduced muscle thickness at baseline that was associated with a greater reduction in disability following LSEP; however, LM activation measured at baseline showed the opposite. Static RUSI measures showed excellent reliability at the L4-5 and L3-4 levels, whereas dynamic measures were not reliable. Conclusions Patients showed less muscle activation than controls at baseline (L5-S1 level), but the LSEP did not normalize this impairment. The links between RUSI measures and the change in clinical outcomes during LSEP should be further explored. This clinical trial has been recorded in the International Standard Registered Clinical/soCial sTudy Number (ISRCTN) registry (ID: ISRCTN94152969). Level of Evidence II

Performances of spherical macrocapsules (nodules) currently used in latent heat-based thermal energy storage (TES) industrial units have been enhanced by the addition of graphite particles to the phase change material (PCM). Two different graphite types, namely graphite flakes (GF) and expanded natural graphite (ENG), have been tested at constant PCM content in the nodule. Using water as PCM, both graphite types have been proven to lead to significant reduction in storage/discharge durations (up to 35% and 58% for a graphite load of only 13%wt) without reduction in storage capacity. Therefore, enhancement using ENG greatly enhances efficiency, but it is also more expensive. GF maybe preferred, considering both its ease of use and economical issues. At the highest experimented graphite load (13%wt) the overall thermal behavior of the nodule is advantageously improved, with simultaneously no apparent supercooling,a very stable phase change plateau, and very sharp and straight sensible heat exchange periods. The graphites induce both extensive thermal power enhancement and improvement in thermal behaviors. These experimental results have been simulated using numerical Comsol®-based models with success. The simulated charge/discharge steps have shown that the air gap present in the nodules induces modifications in the phase change front profile only at the beginning of the periods.

Recent studies concerning phase change material (PCM) characterization show that important errors occur if differential scanning calorimetry (DSC) experiments are misinterpreted. Therefore, it is important to know the influence of such misinterpretation on system modeling. The present work deals with phase change materials integrated in building structure to reduce overheating. The objective is to evaluate the discrepancies consequences (temperatures, heat fluxes), due to the use of the misinterpreted DSC experiments at different heating rates to determine the enthalpy, in comparison with those determined with the actual value of the enthalpy of the PCM determined by a proven inverse method. A numerical model of a single-family house with a phase change material mortar is developed to evaluate the thermal comfort in the building. The results show that for free-running temperature, none of the enthalpy curve deduced directly from DSC can predict correctly the thermal behavior of the house and the thermal comfort. Moreover, the more the DSC heating rate and the more the discrepancy with the results from the reference inverse method.

Thermal energy storage is now a key parameter to overcome the delay between energy supply and demand in many applications. To address this issue, the use of phase change materials (PCM) tends to be more and more common. Given the attempted objectives of such applications, performances of the PCM are a cornerstone of the whole system. Therefore, a correct determination of their intrinsic properties is crucial. To perform this step, one may use a calorimetry experiment. Unfortunately, the interpretation of the thermogram is not straightforward and consequently, when not feasible at all, estimations may be wrong. As an example, pure substance as sometimes said to melt at a non-uniform temperature (their enthalpy being smeared over several degrees), and binary solutions are associated with liquidus temperature and latent heat that do not match the correct form of their enthalpy. The present work proposes a new method to avoid such issues. To summarize the novelty of our approach, the main idea is to use an inverse method to identify the thermodynamical parameters of the sample through a matching step between the experimental curves and theoretical ones. It means that contrary to many others methods, we do not directly extrapolate the thermodynamical properties ( e.g. the enthalpy) from the thermogram. Instead, we suppose an a priori formulation of the enthalpy, based on thermodynamical principles. Thus the thermodynamical parameters are inputs of which only values are computed from the experiments. Capabilities of the method are shown on pure substances and binary solutions examples.

The consideration of environmental constraints in production, transport and distribution of cold energy resulted in reconsidering the practices of installations dimensioning in particular. Their containment led to the development of secondary refrigerants such as ice slurries to store, transport and distribute the cold energy. These heat transfer fluids should have good thermophysical properties, giving high transport capability, high heat transfer ability as well as low pressure drops. The use of ice slurries can lead to lower flow rates and smaller pumping power compared to single phase fluid. The purpose of the presented work is to study the distribution network of indirect cold systems thanks to a model allowing the evaluation of the influence of various parameters on the operating behaviour of the installation. The available domain for the use of secondary heat transfer fluid (whether in their single phase or two phase form) is determined considering the best design from an energetic point of view. Because of the essential role of the fluid distribution between the production site and consumers, we focus our study on pressure drops and pumping power due to the fluid flow in cooling loops. For each investigated case, the minimum consumption power is obtained with the two phases (solid-liquid) heat transfer fluid (ice slurry).

Clinical measurement, validity and intrarater reliability study.(1) To confirm the validity and assess between-day test-retest reliability of cervical spine motion measurements made with the cervical range of motion (CROM) device in flexion, extension, bilateral rotation, and bilateral side flexion; (2) to provide meaningful information to clinicians about the standard error of measurement and the minimal detectable change for the CROM device.Range of motion is a common outcome measure used in the assessment of the cervical spine. The CROM device is one of the tools used to measure cervical range of motion in the clinical setting. However, its psychometric properties are not well established, especially for measurements taken on separate days.Quasi-experimental design with 1 group comparison. Twenty healthy adults (9 men and 11 women) participated in this study. Cervical range of motion was simultaneously recorded with the CROM device and the Fastrak motion analysis system for all 6 cervical movements mentioned above. The CROM device was placed on the participant's head consistent with standard clinical procedures. Two Fastrak sensors were positioned with 1 on the forehead and 1 over the spinous process of the T6 vertebra. Test-retest reliability of measurements made with the CROM device was assessed, as well as its standard error of measurement and minimal detectable change, with measures taken on 2 separate days spaced 48 hours apart.Values obtained by the 2 measuring devices yielded Pearson correlation coefficients ranging between 0.93 and 0.98. Test-retest reliability of measurements of cervical range of motion using the CROM was found to be good, with ICCs ranging between 0.89 and 0.98. The standard errors of measurement across the 6 movements ranged from 1.6 degrees to 2.8 degrees and the minimal detectable changes across the 6 movements ranged from 3.6 degrees to 6.5 degrees .The measurements made with the CROM were shown to be reliable in all movement directions. J Orthop Sports Phys Ther 2010;40(5):318-323, Epub 12 March 2010. doi:10.2519/jospt.2010.3180.

The mechanisms underlying sensory hypersensitivity (SH) in acute whiplash associated disorders (WAD) are not well understood. We examined the extent of the relationships between the sensory measures of pressure pain threshold (PPT) and cold pain threshold (CPT), catastrophizing, pain and disability levels and gender in acute WAD. Thirty-seven subjects reporting neck pain following a motor vehicle accident were examined within five weeks post-injury. Measures of neck pain and disability (Neck Disability Index, NDI) and catastrophizing (Pain Catastrophizing Scale, PCS) were taken. CPT was assessed in the cervical spine and PPTs were assessed in the cervical spine (PPTcx) and at a remote site (PPTdistal). CPT and PCS were moderately correlated (r = 0.46; p < 0.01); however there were no significant relationships between PPT (cervical and distal) and PCS. Both CPT (r = 0.55, p < 0.01) and PPTcx (r = -0.42, p < 0.01) were significantly correlated with NDI but PPTdistal was not (r = -0.08, p = 0.65). Finally, gender modulated the relationships between sensory measures, catastrophizing, and pain and disability levels. In conclusion, subjects with higher levels of catastrophizing presented with sensory hypersensitivity to cold stimuli in the acute phase of whiplash. Differences between genders are in accordance with the growing body of evidence suggesting that the relationships between some psychological factors and injury-related symptoms are modulated by gender.

Controlled laboratory study using a cross-sectional, repeated-measures design.To quantify maximal voluntary isometric neck forces in healthy subjects and individuals with whiplash-associated disorder (WAD), using an objective measurement system to evaluate the test-retest properties of these strength measurements and to assess the links between neck strength, pain, kinesiophobia, and catastrophizing in patients with WAD.The prognosis of WAD is difficult to predict due to a lack of objective measurement methods and to our limited understanding of the role of psychological factors in the development of chronic WAD symptoms.Fourteen subjects with chronic WAD grade I or II and an age-matched, healthy group (n = 28) participated in this study. Cervical strength was measured with the Multi-Cervical Unit (MCU) in 6 directions, and pain was measured with a visual analog scale. Individuals in the WAD group completed the Neck Disability Index (NDI), the Tampa Scale for Kinesiophobia (TSK), and the Pain Catastrophizing Scale (PCS).Significant deficits in strength were observed for the individuals in the WAD group compared to the healthy group, particularly in extension, retraction, and left lateral flexion (P.05). The MCU demonstrated good intratester reliability for the healthy group (ICC = 0.80-0.92) and the WAD group (ICC = 0.85-0.98), and small standard errors of measurement for both groups. No significant association was found between neck strength and NDI, TSK, and PCS.The MCU demonstrated good test-retest properties for healthy subjects and individuals with WAD. Cervical strength was lower in individuals with WAD; however, the strength deficits were not clearly linked with psychological factors.

Resume Dans la poursuite d'une efficacite energetique accrue, le stockage d'energie thermique a haute temperature peut jouer un role significatif dans les secteurs industriel et de production d'electricite. Les materiaux a changement de phase, en particulier les sels, seraient de bons candidats pour se faire. Neanmoins, pour des applications exigeantes en termes de puissance, la faible conductivite thermique des sels est souvent redhibitoire. Afin de remedier a cette difficulte, la capacite de stockage des sels est associee aux proprietes conductrices du graphite. Toutefois, il est necessaire de verifier que l'amelioration des proprietes de transfert des composites graphite/sel ne se fait pas au detriment des proprietes de stockage souhaitees. C'est l'objet de cette Note ou l'analyse calorimetrique des composites permet d'observer les effets du graphite et de la microstructure des composites sur les proprietes de changement de phase des sels. Pour citer cet article : J. Lopez et al., C. R. Mecanique 336 (2008).

In this research, based on the work of Jamil et al. [A. Jamil, T. Kousksou, Y. Zeraouli, J.P. Dumas, E. Schall, Isothermal and non-isothermal melting of the binary solution inside an emulsion. Thermochim. Acta 460 (2007) 22–27], an experimental method and numerical simulations were developed to determine the liquidus temperatures of the dispersed binary solution. The method is based on the analysis of the DSC curves. The liquidus temperatures as functions of component composition are found to be in good agreement with some available literature data.

The measurements of solid–liquid phase diagrams for a binary mixture using a differential scanning calorimeter are revisited in this paper. A new method employing the DSC curves and a theoretical model to detect solid–liquid equilibrium temperature of the initial mixture before freezing is proposed. The liquidus temperatures for different compositions are found to be in good agreement with the available literature data.

The aim of the present paper is to study the melting process inside an emulsion using the non-equilibrium model of microscopic heat transfer between the emulsifying medium and the dispersed droplet of binary solution (DSC). DSC experiments are used to validate the numerical results. The effects of the heating rate, mass fraction of the dispersed saline binary solution, initial mass fraction of the solute and the sample mass on the kinetics of the melting process are examined.

International audience; The objective of this study is to evaluate three different phase change models used to predict the energy behaviour of a PCM cement mortar sample. Reference data are measured on large samples of composite material using a special experimental set-up. The phase change models tested are: the apparent specific capacity method, the enthalpy method assuming a pure body and the enthalpy method assuming a binary mixture. Numerical results are compared to the reference data of heat flux and energy stored/released. The main conclusions of the study are: (1) the thermodynamically inconsistent apparent specific capacity method is not suitable, (2) the enthalpy method gives better results than the specific capacity method and (3) the enthalpy method gives better results with an appropriate guess of the enthalpy curve.

The Grenoble High Magnetic Field Facility (GHMFL) is open to the international scientific community. It can produce steady magnetic fields on 3 magnet sites with a 24MW power supply and on 6 sites with 12 MW. One of the 24 MW sites is designed to reach 40T in a future hybrid arrangement. The two other sites give either 33T in a 34mm bore diameter or 29T in 50 mm. The GHMFL has developed the use of helix inserts made of copper alloy tubes cut by spark erosion. This technique allows making high field magnets with more stable mechanical and electrical behaviors than by the 'Bitter' technique. Based on this technique a 14 helix insert powered by 11 MW was developed. It was first tested in 2002 and is now in operation on one of our three 24 MW site giving access to 33 T. In parallel a 8 helix insert with enhanced homogeneity was developed taking advantage of the possibility offered by the helix technique to make a variable pitch along the main axis. It gives access to a field of 20 T in a 160 mm bore. In 2006, a new high field version of the 14 helix is under construction and expected to reach 34 T. This technology will also be used for the design of a magnet with homogeneity of the order of 10 ppm on a sphere of 1cm3 (with extra shimming). This magnet will be dedicated to high resolution NMR studies.

In order to understand the non-isothermal melting kinetics in the ice slurry, a differential scanning calorimetry (DSC) was used. Experimental results were compared to those obtained by a numerical simulation in which a general enthalpy method was applied. In this work the ice slurry studied consists of ice particles uniformly dispersed within a water–antifreeze liquid mixture. The effects of the heating rate and the initial antifreeze mass fraction are discussed. It has been found that the temperature gradients inside the sample of the solution become important if either heating rate increases or initial antifreeze mass fraction decreases.

International audience; This article deals with the study of a mixture of a cement mortar with a phase change material. We performed together an experimental analysis and a theoretical modeling of the sample associated with transient simulation of its behavior when a heating or a cooling is imposed to this later one. A non pure enthalpy profile is supposed, which permits to better describe the measurements. Furthermore, the drawbacks no to use such a method in order to prefer a more classical one are pointed out.

The objective of this work is the study of an industrial process of energy storage which consists in the use of a cylindrical tank filled with encapsulated phase change materials (PCM). A particularity is met in this kind of processes; it concerns the delay of the crystallization of the PCM, called supercooling phenomenon. A detailed analysis of the system permitted the development of the two-dimensional porous-medium model for cold storage with coolant flowing. First the numerical model has been compared with experimental results for the tank in vertical position. Then, the code was used to study the thermal behaviour of the tank in horizontal position. We found that the optimum running of the charge mode is obtained in the case of the vertical position where the motions due to the natural convection are in the same direction as the forced convection.

The general context of this work concerns the latent heat storage (cold storage) by encapsulated spherical nodules of 7.7 cm in diameter containing a Phase Change Material (PCM) and filling a cylindrical tank (about 2500 nodules per m3). During the storage process, a cold heat transfer liquid flows through the tank to crystallize the PCM inside the nodules. The stored energy is released when a hotter heat transfer liquid flows through the tank to induce the melting of the PCM. As the velocity in the tank is relatively small (a few mm·s−1), natural convection is expected on the coolant when the latent heat is released at the crystallization of the PCM. The present study concerns a single nodule surrounded by a flowing heat transfer liquid at a temperature TC lower than the melting temperature TF. This text presents an enthalpic modelling of the phase change inside the nodule coupled with a CFD simulation of the external flow to describe the mutual influence of the natural convection and the kinetics of crystallization. This study is afterwards extended to the case of two superposed nodules to investigate the influence of the crystallization of the lower nodule on the upper one.

A new method of determination of the nucleation probability of undercooled liquid dispersed within an emulsion is presented. The nucleation probability is a nonlinear function of the temperature depending on two parameters acting very differently. The aim of this paper is to present a method to determine these parameters by an inverse analysis of the heat transfer during the cooling of the emulsion. Information about the precision of the identification is also presented.

Resume Dans ce texte, nous presentons une modelisation concernant les transferts thermiques lors de la cristallisation des gouttes surfondues de solutions binaires salines aqueuses dispersees. Ce modele est different de celui deja presente concernant la fusion a cause du phenomene de surfusion. Il tient compte du caractere aleatoire de la cristallisation des liquides surfondus, en separant l'influence de la probabilite de cristallisation de l'eau d'une part, et de celle de la probabilite d'apparition du sel d'autre part. Le modele est base sur la resolution de l'equation de la chaleur par conduction avec un terme de source d'energie, du au degagement de la chaleur provoque essentiellement par la cristallisation de chaque goutte. Ce modele a ete applique a la calorimetrie a balayage dans le cas d'une solution aqueuse de chlorure de sodium dispersee dans une huile industrielle. Les echantillons etudies ont la forme cylindrique de quelques mm 3 de volume caracteristique de la cellule du calorimetre. La bonne concordance entre les resultats numeriques et experimentaux nous a permis de valider le modele, et par consequent de mieux decrire les transferts thermiques dans ces dispersions. Nous avons ainsi determine la repartition spatio-temporelle de la temperature dans la cellule, du pourcentage des gouttes cristallisees et des proportions transformees de chaque goutte. Une estimation des differents coefficients d'echanges intervenant dans le modele est egalement proposee.

In a recent meeting of IEA’s Annex 23, several members presented their conclusions on the modeling of phase change materials behavior in the context of building applications. These conclusions were in agreement with those of a vast review, involving the survey of more than 250 journal papers, undertaken earlier by the group of École de technologie supérieure. In brief, it can be stated that, at this point, the confidence in reviewed models is too low to use them to predict the future behavior of a building with confidence. Moreover, it was found that overall thermal behaviors of phase change material are poorly known, which by itself creates an intrinsic unknown in any model. Models themselves are most of time suspicious as they are often not tested in a very stringent or exhaustive way. In addition, it also appears that modeling parameters are somewhat too simplified to realistically describe the complete physics needed to predict the real life performance of PCMs added to a building. As a result, steps are now taken to create standard model benchmarks that will improve the confidence of the users. Hopefully, following these efforts, confidence will increase and usage of PCM in buildings should be eased. This work was supported by the t3e industrial research chair and its financial partners. The authors would like to acknowledge their invaluable contributions. The work was partially funded by the European Union (COST Action COST TU0802) and the Spanish Government (project ENE2008-06687-C02-01/CON). The authors would like to thank the Catalan Government for the quality accreditation given to their research group (2009 SGR 534).

Resume Dans cet article, nous proposons un modele decrivant les transferts thermiques lors de la fusion de gouttes cristallisees d'une solution binaire dispersees dans une huile. Ce modele tient compte de la conduction de chaleur dans la dispersion associee a un puits d'energie du a la transformation endothermique des gouttes lors de la fusion eutectique puis de la fusion progressive. Le modele a ete applique a la calorimetrie a balayage dans le cas de quelques solutions aqueuses de chlorure d'ammonium dispersees dans une huile de moteur. La cellule utilisee contenant les dispersions est un cylindre de quelques mm 3 de volume. Par simulation, nous avons pu reproduire la forme des thermogrammes experimentaux. La validation du modele permet de determiner des parametres inaccessibles par l'experience a cause de la petite taille de la cellule comme la repartition spatio-temporelle de la temperature dans la dispersion, de la concentration et de la proportion fondue dans chaque goutte.

Results concerning the crystallization of a hot melt adhesive are presented. This adhesive was a liquid at high temperature (160°C) and was deposited on a wood slab kept at ambient temperature. Cooling can be enhanced by circulating air above the adhesive. The temperature within the adhesive and the wood were measured versus time under three conditions: when the cooling of the upper external part of the adhesive was due to free convection; when it was due to forced convection (to simulate the moving of the assembly line), and in the case where a second wood slab was placed to simulate a joint. It was observed that for a sufficiently thick adhesive film the cooling was slowed down by heat transfer to the wood. A model combining the heat conduction and the kinetic law of crystallization is presented. This model permits the prediction of the evolution of temperature at each point in the adhesive or in the wood for different geometries. The beginning of the crystallization at each point in the adhesive is als...

In this paper, a model is developed in order to determine the melting thermogram of a binary mixture, presenting a solid solution. Considering the case of an ideal solution, whose enthalpy function is analytically derived, we highlight the large differences existing between the thermogram and the derivative of the enthalpy function. The influence of the heating rates and the mass of the sample are analyzed for different concentrations. Finally, in the case of a thermodynamical equilibrium, we describe how to construct the phase diagram of the solution (liquidus and solidus temperatures, total latent heat).

International audience; It is known that when studying the fusion of phase change materials (PCM) in differential scanning calorimetry (DSC) experiments, the geometry of the samples is not well known. Yet, some studies show that a numerical model, needing obviously to clearly define the shape of the sample, may reproduce the experimental DSC curve. In particular, such methods are currently applied to identification process based on inversion methods applied to the thermodynamical parameters governing the numerical model. Consequently, it means that if several numerical models are able to reproduce the thermal behavior of a PCM undergoing phase transition, the best one is the simplest one, that is to say the one which is the fastest to solve.Recently, we have thus shown that for pure substances PCM, a reduced model based on a spherical assumption for the shape of the sample leads to similar DSC curves that a more general model based on cylindrical shape.Clearly, if this result may be extended to other kinds of PCM, this will promote the capability of this method to be used in inversion process involved by identification process. The aim of the present paper is therefore to further study this method by considering non-pure materials, i.e. binary solution in the present case.

Air conditioning and refrigeration have an increasing technological importance and the use of storage process is economically a good solution. The presented cool thermal storage process consists in the use of the solid-liquid transformation of Phase Change Materials (PCM) encapsulated in spherical nodules. These nodules fill a tank placed in the refrigeration loop. Laboratory experiments allow to know exactly the crystallization process of one nodule or of a small number of nodules and to specify the nature and the importance of the undercooling phenomenon (delay of crystallization). The erratic character of the crystallizations is particularly in evidence. A model, based on a combination of the energy equation and nucleation theories, is validated by the experiments and gives information on the kinetics of phase transformations. Copyright © 1996 Elsevier Science Ltd.

The aim of this paper is the study of an industrial process of energy storage usable for air conditioning or refrigeration, investigating a test plant which is a tank with a reduced size, filled with randomly dispersed commercial nodules, placed in a refrigeration loop. The nodules are spherical capsules in which phase change materials (PCM) are encapsulated. This test plant permits the study at length of the behaviour of the tank with, in particular, the charge mode taking into account the undercooling and the discharge mode. A simulation program that considers aspects of both the surrounding heat transfer fluid and the phase-change material packed inside the nodules is developed here in the cases of the charge and the discharge processes. The simulation results are then compared with experimental observations.

The Grenoble High Magnetic Field Laboratory, (GHMFL) is a French German Research Institute funded by the CNRS (Centre National de la Recherche Scientifique, France) and the MPG (Max-Planck Gesellschaft, Germany) which provides high magnetic fields and scientific support to the scientific and technologic international community. It is now setting into operation a large superconducting magnet which delivers 8 T in a 800 mm warm bore diameter. This magnet has been constructed and the first tests were performed in August 2002. Two projects are based on the use of this superconducting magnetic field. The first one give researchers' access to 40 T in a 34 mm bore with the help of a resistive magnet that gives 32 T. The second version provides 23.5 T in a 160 mm room temperature bore with a homogeneity of 1 part per million on a sphere of 1 cubic centimeter. These fields should be available at the laboratory during the year 2004. This paper presents key points of the technical development that were achieved at the laboratory in order to fulfill the high level of specifications of these two projects.

International audience; The aim of this paper is to present an inverse identification method to determine specific enthalpy of PCM from calorimetry experiments. We will focus on the cases of pure substances and ideal binary solutions including the eutectic equilibrium. The corresponding direct model, based on energy balance, is first presented. A classical enthalpy method is then used, which presents the advantage of easily decoupling the thermal transfers from the specific energetic behavior of the material (i.e. thermodynamical phenomenon). In the second part of the paper, we will present the used inverse method (genetic algorithms). The sensibilities of the different parameters for the identification are analyzed. Finally, we will present the identification from DSC experiments (1) at different rates of heating for pure substances and (2) at different concentrations of aqueous solutions of N H 4 Cl. In each case, we identify the thermodynamical parameters of the model and compare the corresponding thermograms with the experimental ones. A good agreement is obtained for both cases

Objective To (1) assess the intra- and inter-rater reliability of different ultrasound (US) measures of the lumbar multifidus muscle in subjects with and without chronic low back pain and (2) test 3 different ways to enhance reliability, that is, by testing different tasks, using a template, and averaging trials within or between days. Design Cross-sectional repeated-measures design. Setting Laboratory setting. Patients Fifteen subjects with chronic low back pain and 15 control subjects. Methods Subjects (n = 30) performed contralateral arm lifting and contralateral leg lifting while in the prone position. Two 7-second videos of the lumbar multifidus (from rest to contraction) were collected with and without a template (transparency) to reposition the transducer on the skin. One of the two raters repeated the testing 7 to 14 days later to assess intrarater reliability in addition to inter-rater reliability. Reliability was assessed with the generalizability theory as a framework. Main outcome measurements US imaging measures of the lumbar multifidus thickness were obtained in patients at rest and during standardized contractions (hereafter called primary measures) at 2 vertebral levels and on both sides. These primary measures were used to calculate different, potentially useful US parameters (hereafter called derived measures). Results Intrarater reliability was better than inter-rater reliability, and primary measures were more reliable than derived measures. The tasks investigated showed comparable reliability results, and the use of the transducer position template was not effective to increase reliability. Averaging the measures of 3 images increased reliability substantially. Conclusions Optimal reliability requires the use of a single rater and the averaging of at least 3 images per visit. In these conditions, primary measures reach acceptable levels of reliability, which was more difficult to achieve for most derived measures. Arm or leg lifting tasks showed similar reliability, and thus the arm-lifting task is recommended for comparisons with previous studies. The use of a transducer position template is not recommended.

Objective To assess the reliability of ultrasound (US) measures of the transversus abdominis (TrA) muscle in a sample of subjects with and without specific chronic low back pain and to test whether reliability is enhanced by using different abdominal muscle activation tasks, with use of a foam cube for US transducer stabilization or by averaging 3 measures on the same image. Design Cross-sectional repeated-measures design. Setting Laboratory setting. Patients Fifteen subjects with chronic low back pain and 15 control subjects. Methods Subjects (n = 30) performed 3 tasks in the supine position: (1) contralateral straight leg raise (SLR), (2) bilateral hook-lying leg raising (HLR), and (3) abdominal drawing-in maneuver (ADIM) (control subjects only). Two 7-second videos of the right and left abdominal wall (from rest to contraction) were collected, with and without use of the foam cube. One of the 2 raters repeated the testing 7 to 14 days later to assess intrarater reliability. Main outcome measurements US imaging of abdominal muscles thickness. Results The TrA muscle was recruited preferentially in the ADIM task compared with the automatic tasks (SLR and HLR). The reliability was comparable among the 3 tasks, with intrarater reliability results being better than interrater reliability results. The use of the foam cube or averaging measures on the same image was generally not effective to increase reliability. Conclusions Although they are not as preferential in TrA recruitment as the ADIM, the SLR and HLR tasks showed comparable reliability results. The foam cube used to control transducer orientation and pressure and averaging measures on the same image had limited effect on reliability.

A model is presented to explain the shape of the thermogram obtained by differential scanning calorimetry of the melting of the crystallized droplets of an emulsion. This model is entirely different from the model presented in Part 1 of this study concerning the crystallization of undercooled liquid droplets. In spite of the purity of the dispersed substance, significant temperature gradients are found, in contrast to the classical assumption of a uniform melting temperature. The model also gives the kinetics of the melting of the droplets which depends on their location.