Silver oxalate-based solders: New materials for high thermal conductivity microjoining

Micrometric oxalate powders can be decomposed starting from temperatures as low as 90°C, leading to the formation of temporary nanometric grains of metallic silver with a high propensity for sintering. The decomposition being highly exothermic, this additional energy favours the sintering, i.e. the soldering, process. Solders processed at 300°C and very low pressure (<0.5 MPa) displayed a thermal conductivity close to 100 W m-1 K-1, making silver oxalate very promising for safe, moderate temperature and very low pressure bonding

Developing new joining materials for low-temperature electronics assembly

International audienceThe present work focuses on a new kind of lead-free joining method for surface-mount technology based on precursor chemistry. The interest of metal oxalates as new soldering materials for die attachment (1st level packaging) was previously demonstrated with silver oxalate. The thermal decomposition of metal oxalates under controlled atmosphere can be used to produce small metal particles below their melting point. These particles are found to be in a highly active particulate form. First experimental studies are focusing on several metal oxalates (tin oxalate and bismuth oxalate) to assess their suitability for low-temperature metal particle production. The main work is dealing with controlled chemical precipitation synthesis and characterization of the compounds as well as study of the properties of decomposition solid products (powder X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy and thermal analyses under different atmospheres)

Arthroscopic Bristow-Latarjet Combined With Bankart Repair Restores Shoulder Stability in Patients With Glenoid Bone Loss

BACKGROUND: Arthroscopic Bankart repair alone cannot restore shoulder stability in patients with glenoid bone loss involving more than 20% of the glenoid surface. Coracoid transposition to prevent recurrent shoulder dislocation according to Bristow-Latarjet is an efficient but controversial procedure. QUESTIONS/PURPOSES: We determined whether an arthroscopic Bristow-Latarjet procedure with concomitant Bankart repair (1) restored shoulder stability in this selected subgroup of patients, (2) without decreasing mobility, and (3) allowed patients to return to sports at preinjury level. We also evaluated (4) bone block positioning, healing, and arthritis and (5) risk factors for nonunion and coracoid screw pullout. METHODS: Between July 2007 and August 2010, 79 patients with recurrent anterior instability and bone loss of more than 20% of the glenoid underwent arthroscopic Bristow-Latarjet-Bankart repair; nine patients (11%) were either lost before 2-year followup or had incomplete data, leaving 70 patients available at a mean of 35 months. Postoperative radiographs and CT scans were evaluated for bone block positioning, healing, and arthritis. Any postoperative dislocation or any subjective complaint of occasional to frequent subluxation was considered a failure. Physical examination included ROM in both shoulders to enable comparison and instability signs (apprehension and relocation tests). Rowe and Walch-Duplay scores were obtained at each review. Patients were asked whether they were able to return to sports at the same level and practice forced overhead sports. Potential risk factors for nonhealing were assessed. RESULTS: At latest followup, 69 of 70 (98%) patients had a stable shoulder, external rotation with arm at the side was 9° less than the nonoperated side, and 58 (83%) returned to sports at preinjury level. On latest radiographs, 64 (91%) had no osteoarthritis, and bone block positioning was accurate, with 63 (90%) being below the equator and 65 (93%) flush to the glenoid surface. The coracoid graft healed in 51 (73%), it failed to unite in 14 (20%), and graft osteolysis was seen in five (7%). Bone block nonunion/migration did not compromise shoulder stability but was associated with persistent apprehension and less return to sports. Use of screws that were too short or overangulated, smoking, and age higher than 35 years were risk factors for nonunion. CONCLUSIONS: The arthroscopic Bristow-Latarjet procedure combined with Bankart repair for anterior instability with severe glenoid bone loss restored shoulder stability, maintained ROM, allowed return to sports at preinjury level, and had a low likelihood of arthritis. Adequate healing of the transferred coracoid process to the glenoid neck is an important factor for avoiding persistent anterior apprehension. LEVEL OF EVIDENCE: Level IV, therapeutic study. See Instructions for Authors for a complete description of levels of evidence

Conscious Brain-to-Brain Communication in Humans Using Non-Invasive Technologies

Human sensory and motor systems provide the natural means for the exchange of information between individuals, and, hence, the basis for human civilization. The recent development of brain-computer interfaces (BCI) has provided an important element for the creation of brain-to-brain communication systems, and precise brain stimulation techniques are now available for the realization of non-invasive computer-brain interfaces (CBI). These technologies, BCI and CBI, can be combined to realize the vision of non-invasive, computer-mediated brain-to-brain (B2B) communication between subjects (hyperinteraction). Here we demonstrate the conscious transmission of information between human brains through the intact scalp and without intervention of motor or peripheral sensory systems. Pseudo-random binary streams encoding words were transmitted between the minds of emitter and receiver subjects separated by great distances, representing the realization of the first human brain-to-brain interface. In a series of experiments, we established internet-mediated B2B communication by combining a BCI based on voluntary motor imagery-controlled electroencephalographic (EEG) changes with a CBI inducing the conscious perception of phosphenes (light flashes) through neuronavigated, robotized transcranial magnetic stimulation (TMS), with special care taken to block sensory (tactile, visual or auditory) cues. Our results provide a critical proof-of-principle demonstration for the development of conscious B2B communication technologies. More fully developed, related implementations will open new research venues in cognitive, social and clinical neuroscience and the scientific study of consciousness. We envision that hyperinteraction technologies will eventually have a profound impact on the social structure of our civilization and raise important ethical issues

Residual Stress Measurement on a MEMS Structure With High-Spatial Resolution

A new approach to the local measurement of residual stress in microstructures is described in this paper. The presented technique takes advantage of the combined milling-imaging features of a focused ion beam (FIB) equipment to scale down the widely known hole drilling method. This method consists of drilling a small hole in a solid with inherent residual stresses and measuring the strains/displacements caused by the local stress release, that takes place around the hole. In the presented case, the displacements caused by the milling are determined by applying digital image correlation (DIC) techniques to high resolution micrographs taken before and after the milling process. The residual stress value is then obtained by fitting the measured displacements to the analytical solution of the displacement fields. The feasibility of this approach has been demonstrated on a micromachined silicon nitride membrane showing that this method has high potential for applications in the field of mechanical characterization of micro/nanoelectromechanical systems

Interaction between GRIP and Liprin-α/SYD2 Is Required for AMPA Receptor Targeting

Interaction with the multi-PDZ protein GRIP is required for the synaptic targeting of AMPA receptors, but the underlying mechanism is unknown. We show that GRIP binds to the liprin-α/SYD2 family of proteins that interact with LAR receptor protein tyrosine phosphatases (LAR-RPTPs) and that are implicated in presynaptic development. In neurons, liprin-α and LAR-RPTP are enriched at synapses and coimmunoprecipitate with GRIP and AMPA receptors. Dominant-negative constructs that interfere with the GRIP-liprin interaction disrupt the surface expression and dendritic clustering of AMPA receptors in cultured neurons. Thus, by mediating the targeting of liprin/GRIP-associated proteins, liprin-α is important for postsynaptic as well as presynaptic maturation

Early release of high mobility group box nuclear protein 1 after severe trauma in humans: role of injury severity and tissue hypoperfusion

IntroductionHigh mobility group box nuclear protein 1 (HMGB1) is a DNA nuclear binding protein that has recently been shown to be an early trigger of sterile inflammation in animal models of trauma-hemorrhage via the activation of the Toll-like-receptor 4 (TLR4) and the receptor for the advanced glycation endproducts (RAGE). However, whether HMGB1 is released early after trauma hemorrhage in humans and is associated with the development of an inflammatory response and coagulopathy is not known and therefore constitutes the aim of the present study.MethodsOne hundred sixty eight patients were studied as part of a prospective cohort study of severe trauma patients admitted to a single Level 1 Trauma center. Blood was drawn within 10 minutes of arrival to the emergency room before the administration of any fluid resuscitation. HMGB1, tumor necrosis factor (TNF)-alpha, interleukin (IL)-6, von Willebrand Factor (vWF), angiopoietin-2 (Ang-2), Prothrombin time (PT), prothrombin fragments 1+2 (PF1+2), soluble thrombomodulin (sTM), protein C (PC), plasminogen activator inhibitor-1 (PAI-1), tissue plasminogen activator (tPA) and D-Dimers were measured using standard techniques. Base deficit was used as a measure of tissue hypoperfusion. Measurements were compared to outcome measures obtained from the electronic medical record and trauma registry.ResultsPlasma levels of HMGB1 were increased within 30 minutes after severe trauma in humans and correlated with the severity of injury, tissue hypoperfusion, early posttraumatic coagulopathy and hyperfibrinolysis as well with a systemic inflammatory response and activation of complement. Non-survivors had significantly higher plasma levels of HMGB1 than survivors. Finally, patients who later developed organ injury, (acute lung injury and acute renal failure) had also significantly higher plasma levels of HMGB1 early after trauma.ConclusionsThe results of this study demonstrate for the first time that HMGB1 is released into the bloodstream early after severe trauma in humans. The release of HMGB1 requires severe injury and tissue hypoperfusion, and is associated with posttraumatic coagulation abnormalities, activation of complement and severe systemic inflammatory response

Matériaux innovants sans plomb pour l'assemblage de composants électroniques à basse température

Dans le cadre du développement de nouveaux matériaux d’assemblage sans plomb, les premiers résultats de synthèse et de caractérisations physicochimiques d’oxalate de bismuth sont présentés. Par une méthode de décomposition thermique de précurseurs métal-organiques, la possibilité de produire des particules métalliques en dessous de la température de fusion du bismuth massif (271°C) est discutée ici. L’étude du comportement en température de l’oxalate de bismuth montre l’influence de l’atmosphère (air ou azote) sur la nature des produits de décomposition (oxyde ou métal). Sous une atmosphère inerte contrôlée, les échantillons d’oxalate préparés se décomposent en bismuth métallique entre 210 et 250°C

Bi2(C2O4)3·7H2O and Bi(C2O4)OH Oxalates Thermal Decomposition Revisited. Formation of Nanoparticles with a Lower Melting Point than Bulk Bismuth

Two bismuth oxalates, namely, Bi2(C2O4)3·7H2O and Bi(C2O4)OH, were studied in terms of synthesis, structural characterization, particle morphology, and thermal behavior under several atmospheres. The oxalate powders were produced by chemical precipitation from bismuth nitrate and oxalic acid solutions under controlled pH, then characterized by X-ray diffraction (XRD), temperature-dependent XRD, IR spectroscopy, scanning electron microscopy, and thermogravimetric differential thermal analyses. New results on the thermal decomposition of bismuth oxalates under inert or reducing atmospheres are provided. On heating in nitrogen, both studied compounds decompose into small bismuth particles. Thermal properties of the metallic products were investigated. The Bi(C2O4)OH decomposition leads to a Bi−Bi2O3 metal−oxide composite product in which bismuth is confined in a nanometric size, due to surface oxidation. The melting point of such bismuth particles is strongly related to their crystallite size. The nanometric bismuth melting has thus been evidenced ∼40 °C lower than for bulk bismuth. These results should contribute to the development of the oxalate precursor route for low-temperature soldering applications