Titanium alloy is well known for its difficulty to machine, owing to the important “tool wear” phenomenon. Machining assistance is an interesting solution to lengthen the tool lifetime. In this study, we focused on the effect of cryogenic assistance—during machining of Ti17—on the tool wear and cutting forces for different combinations of cutting speed, feed rate and depth of cut. Compared to conventional lubrication, cryogenic support lengthens the tool life for all tested conditions and has no significant influence on cutting force. A comparison of the cryogenic effect and high-pressure water jet assistance is also presented.

L’amelioration de la productivite et de la qualite des pieces necessite le developpement de nouvelles techniques d’usinage. L’assistance cryogenique est l’une de ces techniques. Les differents principes de l’assistance cryogenique ainsi que les gains constates sont presentes dans cet article.

The origin of this article is the quantification of productivity gains and the improvement in surface integrity seen for a recent titanium alloy that is seeing increasing use in the aeronautical industry. The Ti555-3 titanium alloy, which is starting to find greater application in the aeronautical field, exhibits certain difficulties in terms of machining. High Pressure Coolant (HPC) assisted turning consists of projecting a high pressure coolant jet between the chip and the tool. Comparisons are made between assisted turning using variable jet pressure and conventional turning (dry and classical lubrication). It is shown that it is possible to improve productivity by using HPC-assisted machining. The results highlight good chip fragmentation and a great improvement of tool life with HPC assistance. Surface integrity is also shown to be improved, through surface roughness parameters that decrease, and surface residual stresses that become more compressive. These effects have been attributed to the thermo-mechanical action of the coolant jet resulting in lower cutting forces, lower coefficient of friction and lower temperature in the cutting zone.

L'amelioration des techniques d'usinage est en constante evolution. De nombreuses voies sont etudiees pour ameliorer la qualite des pieces fabriquees ou gagner en productivite. Cet article presente des procedes d'assistance en usinage qui consistent a fournir une «energie» supplementaire au niveau de la zone de coupe. Cinq assistances sont presentees pour le procede de tournage les trois assistances les plus avancees sont detaillees: l'assistance haute pression, l'assistance laser et l'assistance cryogenique.

The objective of this work is to propose an anisotropic fatigue criterion for the sizing of industrial forged components. The results from different experimental campaigns using three different rolled steels are first presented. The effect of inclusions and the microstructure on the fatigue behaviour are investigated. For the two ferrite-pearlitic steels tested, the presence of a microstructure consisting of elongated grains has no observable effects on the fatigue behaviour. For two of the three steels studied the presence of non-metallic inclusions, elongated in the rolling direction, form the origin of the anisotropic fatigue behaviour.The proposed probabilistic model is based on the competition between two possible fatigue crack initiation mechanisms. The anisotropic character of the fatigue resistance of forged components is taken into account by the definition of the geometry and the orientation of the non-metallic inclusion. This criterion results in the establishment of a probabilistic Kitagawa type diagram. (C) 2012 Elsevier Ltd. All rights reserved.

OBJECT:Recent technological developments open the field of therapeutic application of focused ultrasound to the brain through the intact cranium. The goal of this study was to apply the new transcranial magnetic resonance imaging-guided focused ultrasound (tcMRgFUS) technology to perform noninvasive central lateral thalamotomies (CLTs) as a treatment for chronic neuropathic pain.METHODS:In 12 patients suffering from chronic therapy-resistant neuropathic pain, tcMRgFUS CLT was proposed. In 11 patients, precisely localized thermal ablations of 3-4 mm in diameter were produced in the posterior part of the central lateral thalamic nucleus at peak temperatures between 51 ° C and 64 ° C with the aid of real-time patient monitoring and MR imaging and MR thermometry guidance. The treated neuropathic pain syndromes had peripheral (5 patients) or central (6 patients) origins and covered all body parts (face, arm, leg, trunk, and hemibody).RESULTS:Patients experienced mean pain relief of 49% at the 3-month follow-up (9 patients) and 57% at the 1-year follow-up (8 patients). Mean improvement according to the visual analog scale amounted to 42% at 3 months and 41% at 1 year. Six patients experienced immediate and persisting somatosensory improvements. Somatosensory and vestibular clinical manifestations were always observed during sonication time because of ultrasound-based neuronal activation and/or initial therapeutic effects. Quantitative electroencephalography (EEG) showed a significant reduction in EEG spectral overactivities. Thermal ablation sites showed sharply delineated ellipsoidal thermolesions surrounded by short-lived vasogenic edema. Lesion reconstructions (18 lesions in 9 patients) demonstrated targeting precision within a millimeter for all 3 coordinates. There was 1 complication, a bleed in the target with ischemia in the motor thalamus, which led to the introduction of 2 safety measures, that is, the detection of a potential cavitation by a cavitation detector and the maintenance of sonication temperatures below 60 ° C.CONCLUSIONS:The authors assert that tcMRgFUS represents a noninvasive, precise, and radiation-free neurosurgical technique for the treatment of neuropathic pain. The procedure avoids mechanical brain tissue shift and eliminates the risk of infection. The possibility of applying sonication thermal spots free from trajectory restrictions should allow one to optimize target coverage. The real-time continuous MR imaging and MR thermometry monitoring of targeting accuracy and thermal effects are major factors in optimizing precision, safety, and efficacy in an outpatient context.

PurposeMagnetic resonance-guided high-intensity focused ultrasound surgery (MRgFUS) has been applied to non-invasively perform thalamic ablations in a group of patients with neuropathic pain. The current standard for targeting subcortical structures relies on transferring stereotactic 3D coordinates from an anatomical atlas onto the patient's MR brain images. However, additional information such as patient-specific functional maps would greatly improve atlas-to-patient "in vivo" coregistration and targeting. Our objectives are twofold: 1) demonstrate the consistency between histology- and connectivity-based mappings by using in vivo diffusion imaging (DTI), and 2) utilize connectivity information for target map individualization.Material & MethodsStructural mapping of the thalamus was achieved by transferring a three-dimensional representation of the Morel atlas of the human thalamus onto MRI images of a group of 40 control subjects. Cortical regions were defined by using the Harvard-Oxford atlas. DTI and tractography were employed to calculate parametric maps depicting the probability of interconnections between cortical regions and histology-based thalamic nuclei.ResultsOverlaps between atlas- and connectivity-based delineations were qualitatively observed and good agreement was found between the locations of lateral thalamic nuclei (in particular VPL, VL and VA) on the connectivity and atlas-based maps.ConclusionOur preliminary results suggest that augmentation of histology-based targeting with diffusion-based structural connectivity information might be beneficial. However, this method is currently limited to subcortical targets that have specific connections with the cortex. PurposeMagnetic resonance-guided high-intensity focused ultrasound surgery (MRgFUS) has been applied to non-invasively perform thalamic ablations in a group of patients with neuropathic pain. The current standard for targeting subcortical structures relies on transferring stereotactic 3D coordinates from an anatomical atlas onto the patient's MR brain images. However, additional information such as patient-specific functional maps would greatly improve atlas-to-patient "in vivo" coregistration and targeting. Our objectives are twofold: 1) demonstrate the consistency between histology- and connectivity-based mappings by using in vivo diffusion imaging (DTI), and 2) utilize connectivity information for target map individualization. Magnetic resonance-guided high-intensity focused ultrasound surgery (MRgFUS) has been applied to non-invasively perform thalamic ablations in a group of patients with neuropathic pain. The current standard for targeting subcortical structures relies on transferring stereotactic 3D coordinates from an anatomical atlas onto the patient's MR brain images. However, additional information such as patient-specific functional maps would greatly improve atlas-to-patient "in vivo" coregistration and targeting. Our objectives are twofold: 1) demonstrate the consistency between histology- and connectivity-based mappings by using in vivo diffusion imaging (DTI), and 2) utilize connectivity information for target map individualization. Material & MethodsStructural mapping of the thalamus was achieved by transferring a three-dimensional representation of the Morel atlas of the human thalamus onto MRI images of a group of 40 control subjects. Cortical regions were defined by using the Harvard-Oxford atlas. DTI and tractography were employed to calculate parametric maps depicting the probability of interconnections between cortical regions and histology-based thalamic nuclei. Structural mapping of the thalamus was achieved by transferring a three-dimensional representation of the Morel atlas of the human thalamus onto MRI images of a group of 40 control subjects. Cortical regions were defined by using the Harvard-Oxford atlas. DTI and tractography were employed to calculate parametric maps depicting the probability of interconnections between cortical regions and histology-based thalamic nuclei. ResultsOverlaps between atlas- and connectivity-based delineations were qualitatively observed and good agreement was found between the locations of lateral thalamic nuclei (in particular VPL, VL and VA) on the connectivity and atlas-based maps. Overlaps between atlas- and connectivity-based delineations were qualitatively observed and good agreement was found between the locations of lateral thalamic nuclei (in particular VPL, VL and VA) on the connectivity and atlas-based maps. ConclusionOur preliminary results suggest that augmentation of histology-based targeting with diffusion-based structural connectivity information might be beneficial. However, this method is currently limited to subcortical targets that have specific connections with the cortex. Our preliminary results suggest that augmentation of histology-based targeting with diffusion-based structural connectivity information might be beneficial. However, this method is currently limited to subcortical targets that have specific connections with the cortex.

Fatigue phenomena, which appear generally below the yield stress, is the cause of more than 80% of in-service mechanical failures. However, the optimization of the weight and cost when designing mechanical components or structures, linked to improved performance, leads to increasingly stressed components. Therefore, a fatigue design approach must be done by the engineer. This paper shows the experience gained over five academic years of teaching fatigue, the assessment of automotive components using a reliability approach to predict probability of failure, in the engineering school, Arts et Métiers ParisTech, in France. The choice was made to present a comprehensive fatigue assessment approach using a method, initially developed in the automotive industry and since extended to the aeronautical and mechanical industries. This method is known as the “stress–strength interference analysis”. The “stress” represents the distribution of the driver severity, and the “strength” represents the distribution of the fatigue strength of all the components. A suspension arm is used to illustrate the approach. The Dang Van multi-axial fatigue criterion is implemented in a finite-element code and a danger coefficient is visualized on the meshed structure. The fatigue analysis is interpreted with respect to the target reliability sought by the car manufacturer.

Minimally invasive deep brain neurosurgical interventions require a profound knowledge of the morphology of the human brain. Generic brain atlases are based on histology including multiple preparation steps during the sectioning and staining. In order to correct the distortions induced in the anisotropic, inhomogeneous soft matter and therefore improve the accuracy of brain atlases, a non-destructive 3D imaging technique with the required spatial and density resolution is of great significance. Micro computed tomography provides true micrometer resolution. The application to post mortem human brain, however, is questionable because the differences of the components concerning X-ray absorption are weak. Therefore, magnetic resonance tomography has become the method of choice for three-dimensional imaging of human brain. Because the spatial resolution of this method is limited, an alternative has to be found for the three-dimensional imaging of cellular microstructures within the brain. Therefore, the present study relies on the synchrotron radiationbased micro computed tomography in the recently developed grating-based phase contrast mode. Using data acquired at the beamline ID 19 (ESRF, Grenoble, France) we demonstrate that grating-based tomography yields premium images of human thalamus, which can be used for the correction of histological distortions by 3D non-rigid registration.

Functional neurosurgery relies on robust localization of the subcortical target structures, which cannot be visualized directly with current clinically available in-vivo imaging techniques. Therefore, one has still to rely on an indirect approach, by transferring detailed histological maps onto the patient's individual brain images. In contrast to macroscopic MRI atlases, which often represent the average of a population, each stack of sections, which a stereotactic atlas provides, is based on a single specimen. In addition to this bias, the anatomy is displayed with a highly anisotropic resolution, leading to topological ambiguities and limiting the accuracy of geometric reconstruction. In this work we construct an unbiased, high-resolution three-dimensional atlas of the thalamic structures, representing the average of several stereotactically oriented histological maps. We resolve the topological ambiguity by combining the information provided by histological data from different stereotactic directions. Since the stacks differ not only in geometrical detail provided, but also due to inter-individual variability, we adopt an iterative approach for reconstructing the mean model. Starting with a reconstruction from a single stack of sections, we iteratively register the current reference model onto the available data and reconstruct a refined mean three-dimensional model. The results show that integration of multiple stereotactic anatomical data to produce an unbiased, mean model of the thalamic nuclei and their subdivisions is feasible and that the integration reduces problems of atlas reconstruction inherent to histological stacks to a large extent.

This work deals with the anisotropic fatigue behaviour of the Bainitic Steel Metasco®MC and aims at improving the fatigue criteria used for the design of forged components (suspension arm). This material contains elongated manganese sulphide (MnS) inclusions oriented parallel to the rolling or forging direction. Specimens with different orientations relative to the rolling direction have been tested in fatigue under push-pull uniaxial loads. The influence of "inclusion clusters" is clearly demonstrated via the observation of the fracture surfaces. A fracture mechanics approach together with a statistical approach is proposed to account for the anisotropic fatigue behaviour.

Multisensory and sensorimotor integrations are usually considered to occur in superior colliculus and cerebral cortex, but few studies proposed the thalamus as being involved in these integrative processes. We investigated whether the organization of the thalamocortical (TC) systems for different modalities partly overlap, representing an anatomical support for multisensory and sensorimotor interplay in thalamus. In 2 macaque monkeys, 6 neuroanatomical tracers were injected in the rostral and caudal auditory cortex, posterior parietal cortex (PE/PEa in area 5), and dorsal and ventral premotor cortical areas (PMd, PMv), demonstrating the existence of overlapping territories of thalamic projections to areas of different modalities (sensory and motor). TC projections, distinct from the ones arising from specific unimodal sensory nuclei, were observed from motor thalamus to PE/PEa or auditory cortex and from sensory thalamus to PMd/PMv. The central lateral nucleus and the mediodorsal nucleus project to all injected areas, but the most significant overlap across modalities was found in the medial pulvinar nucleus. The present results demonstrate the presence of thalamic territories integrating different sensory modalities with motor attributes. Based on the divergent/convergent pattern of TC and corticothalamic projections, 4 distinct mechanisms of multisensory and sensorimotor interplay are proposed.

Transcranial magnetic resonance (MR)-guided high-intensity focused ultrasound (tcMRgHIFU) implies a novel, noninvasive treatment strategy for various brain diseases. Nine patients with chronic neuropathic pain were treated with selective medial thalamotomies. Precisely located thermal ablations of 4mm in diameter were produced at peak temperatures of 51 degrees C to 60 degrees C under continuous visual MR guidance and MR thermometry. The resulting lesions are clearly visible on follow-up MR imaging. All treatments were well tolerated, without side effects or neurological deficits. This is the first report on successful clinical application of tcMRgHIFU in functional brain disorders, portraying it as safe and reliable for noninvasive neurosurgical interventions.

Potential applications of Transcranial Magnetic Resonance guided Focused Ultrasound (TcMRgFUS) include treatment of functional brain disorders, such as Parkinson's disease, dystonia and tremor, neurogenic pain and tinnitus, neuropsychiatric disorders and epilepsy. In this study we demonstrate the feasibility of non-invasive TcMRgFUS ablation of clinically well established targets in the human thalamus that are currently accessed stereotactically by interventional strategies based on the concept of the thalamocortical dysrhythmia (TCD). Thermal hotspots, suitable for clinical intervention were created successfully in anatomical preparations of human ex-vivo heads under pseudo clinical conditions. The hotspots could be positioned at the target locations is needed and local energy deposition was sufficient to create tissue ablation, Numerical simulations based on these experimental data predict that the acoustic energy needed to create ablative lesions in-vivo will be within limits that can safety applied.

Anatomical knowledge of the structures to be targeted and of the circuitry involved is crucial in stereotactic functional neurosurgery. The present study was undertaken in the context of surgical treatment of motor disorders such as essential tremor (ET) and Parkinson's disease (PD) to precisely determine the course and three-dimensional stereotactic localisation of the cerebellothalamic and pallidothalamic tracts in the human brain. The course of the fibre tracts to the thalamus was traced in the subthalamic region using multiple staining procedures and their entrance into the thalamus determined according to our atlas of the human thalamus and basal ganglia [Morel (2007) Stereotactic atlas of the human thalamus and basal ganglia. Informa Healthcare Inc., New York]. Stereotactic three-dimensional coordinates were determined by sectioning thalamic and basal ganglia blocks parallel to stereotactic planes and, in two cases, by correlation with magnetic resonance images (MRI) from the same brains prior to sectioning. The major contributions of this study are to provide: (1) evidence that the bulks of the cerebellothalamic and pallidothalamic tracts are clearly separated up to their thalamic entrance, (2) stereotactic maps of the two tracts in the subthalamic region, (3) the possibility to discriminate between different subthalamic fibre tracts on the basis of immunohistochemical stainings, (4) correlations of histologically identified fibre tracts with high-resolution MRI, and (5) evaluation of the interindividual variability of the fibre systems in the subthalamic region. This study should provide an important basis for accurate stereotactic neurosurgical targeting of the subthalamic region in motor disorders such as PD and ET.

Accurate knowledge of the morphology of the human brain is required for minimally or non-invasive surgical interventions. On the (sub-)cellular level, brain tissue is generally characterized using optical microscopy, which allows extracting morphological features with a wide spectrum of staining procedures. The preparation of the histological slices, however, often leads to artifacts resulting in imperfect morphological data. In addition, the generation of 3D data is time-consuming. Therefore, we propose synchrotron radiation-based micro computed tomography (SRμCT) avoiding preparation artifacts and giving rise to the 3D morphology of features such as gray and white matter on the micrometer level. One can differentiate between white and gray matter without any staining procedure because of different X-ray absorption values. At the photon energy of 10keV, the white matter exhibits the absorption of 5.08cm−1, whereby the value for the gray matter corresponds to 5.25cm−1. The tomography data allow quantifying the local strains in the histological images using registration algorithms. The deformation of histological slices compared to the SRμCT in a 2D–2D registration leads to values of up to 6.3%. Mean deformation values for the Nissl-stained slices are determined to about 1%, whereas the myelin-stained slices yield slightly higher values than 2%.

Data on behavioral changes after thalamic lesion are sparse and largely based on isolated reports of patients with thalamic strokes. However, recent findings suggest that behavioral patterns can be delineated on the basis of the four main arterial thalamic territories. The anterior pattern consists mainly of perseverations and superimposition of unrelated information, apathy, and amnesia. After paramedian infarct, the most frequent features are disinhibition syndromes, with personality changes, loss of self-activation, amnesia, and, in the case of extensive lesions, thalamic "dementia"; this pattern may often be difficult to distinguish from primary psychiatric disorders, especially when neurologic dysfunction is lacking. After inferolateral lesion, executive dysfunction may develop but is often overlooked, although it may occasionally lead to severe long-term disability. After posterior lesion, whereas cognitive dysfunction with neglect and aphasia are well known, no specific behavioral syndrome has been reported. In the future, perfusion CT, functional MRI, and tractography using diffusion imaging in stroke patients may provide a better understanding of the role of the corticothalamic relationship in behavioral changes associated with thalamic stroke.