Crystalline thiophene - Calorimetric evidence for a glassy crystalline state in both phase sequences

Both phase sequences of crystalline thiophene have been investigated during a new calorimetric study from 14 to 300 K. The phase transition temperatures are reported Around 40 K, each phase sequence exhibits a glass transition which seems to arise from the freezing of the reorientational motion of the molecules at the low temperature stage of the ordering process. Kinetic data that characterize the enthalpy relaxation in both glassy crystalline states have been determined : this leads to activation enthalpies which are close to those associated with the in-plane reorientational motions of thiophene molecules in the corresponding phase sequences. This supports the hypothesis that both processes are related. Some speculations are made about the influence of the molecular quasi-five-fold symmetry.Les deux séquences de phases du thiophène cristallin ont été étudiées au cours d'une nouvelle étude calorimétrique de ce composé, de 14 à 300 K. On donne ici les températures de transitions de phase. Aux alentours de 40 K, chacune des deux séquences de phases présente une transition vitreuse qui pourrait être liée au gel des réorientations moléculaires lors du processus d'ordonnancement à très basse température. Les grandeurs cinétiques qui caractérisent les relaxations enthalpiques dans chacune des deux phases cristal vitreux ont été déterminées : on obtient ainsi des enthalpies d'activation pour la relaxation voisines de celles qui régissent les mouvements de réorientation des molécules de thiophène autour d'un axe perpendiculaire au plan moléculaire dans les deux séquences de phases. Cela vient à l'appui de l'hypothèse selon laquelle relaxation enthalpique et réorientations moléculaires sont liées. Le rôle éventuel de la symétrie pseudo-pentagonale de la molécule de thiophène est évoqué

An acoustic technique for investigating the sol–gel transition

International audienc

Managing PMT/vPvM substances in consumer products through the concepts of essential-use and functional substitution: a case-study for cosmetics

Measures are needed to protect water sources from substances that are mobile, persistent and toxic (PMT) or very persistent and very mobile (vPvM). PMT/vPvM substances are used in a diverse range of applications, including consumer products. The combined application of the essential-use and functional substitution concepts has been proposed to phase out substances of concern and support the transition to safer and more sustainable chemicals, a key goal of the European Commission's Chemicals Strategy for Sustainability. Here, we first identified the market share of PMT/vPvM containing cosmetic products. We found that 6.4% of cosmetic products available on the European market contain PMT or vPvM substances. PMT/vPvM substances were most often found in hair care products. Based on their high occurrence, the substances Allura red (CAS 25956-17-6), benzophenone-4 (CAS 4065-45-6) and climbazole (CAS 38083-17-9) were selected as case-studies for assessment of their functionality, availability of safer alternatives and essentiality. Following the functional substitution framework, we found that the technical function of Allura red was not necessary for the performance of some cosmetic products, making the use non-essential. For other applications of Allura red, as well as all applications of benzophenone-4 and climbazole, the technical function of the chemical was considered necessary for the performance. Via the alternative's assessment procedure, which used experimental and in silico data and three different multicriteria decision analysis (MCDA) strategies, safer alternatives were identified for all case-study chemicals. All assessed uses of PMT/vPvM substances were thus deemed non-essential and should consequently be phased out

Adductomics: How DNA adducts can be useful tools from toxicology to exposome determination

National audienc

miR-491-5p-induced apoptosis in ovarian carcinoma depends on the direct inhibition of both BCL-XL and EGFR leading to BIM activation

International audienceWe sought to identify miRNAs that can efficiently induce apoptosis in ovarian cancer cells by overcoming BCL-X(L) and MCL1 anti-apoptotic activity, using combined computational and experimental approaches. We found that miR-491-5p efficiently induces apoptosis in IGROV1-R10 cells by directly inhibiting BCL-X(L) expression and by inducing BIM accumulation in its dephosphorylated form. This latter effect is due to direct targeting of epidermal growth factor receptor (EGFR) by miR-491-5p and consequent inhibition of downstream AKT and MAPK signalling pathways. Induction of apoptosis by miR-491-5p in this cell line is mimicked by a combination of EGFR inhibition together with a BH3-mimetic molecule. In contrast, SKOV3 cells treated with miR-491-5p maintain AKT and MAPK activity, do not induce BIM and do not undergo cell death despite BCL-XL and EGFR downregulation. In this cell line, sensitivity to miR-491-5p is restored by inhibition of both AKT and MAPK signalling pathways. Altogether, this work highlights the potential of miRNA functional studies to decipher cell signalling pathways or major regulatory hubs involved in cell survival to finally propose the rationale design of new strategies on the basis of pharmacological combinations

Experimental Evidence of the Tonic Vibration Reflex during Whole-Body Vibration of the Loaded and Unloaded Leg

Increased muscle activation during whole-body vibration (WBV) is mainly ascribed to a complex spinal and supraspinal neurophysiological mechanism termed the tonic vibration reflex (TVR). However, TVR has not been experimentally demonstrated during low-frequency WBV, therefore this investigation aimed to determine the expression of TVR during WBV.  Whilst seated, eight healthy males were exposed to either vertical WBV applied to the leg via the plantar-surface of the foot, or Achilles tendon vibration (ATV) at 25Hz and 50Hzfor 70s. Ankle plantar-flexion force, tri-axial accelerations at the shank and vibration source, and surface EMG activity of m. soleus (SOL) and m. tibialis anterior (TA) were recorded from the unloaded and passively loaded leg to simulate body mass supported during standing.  Plantar flexion force was similarly augmented by WBV and ATV and increased over time in a load- and frequency dependent fashion. SOL and TA EMG amplitudes increased over time in all conditions independently of vibration mode. 50Hz WBV and ATV resulted in greater muscle activation than 25Hz in SOL when the shank was loaded and in TA when the shank was unloaded despite the greater transmission of vertical acceleration from source to shank with 25Hz and WBV, especially during loading. Low-amplitude WBV of the unloaded and passively loaded leg produced slow tonic muscle contraction and plantar-flexion force increase of similar magnitudes to those induced by Achilles tendon vibration at the same frequencies. This study provides the first experimental evidence supporting the TVR as a plausible mechanism underlying the neuromuscular response to whole-body vibration

Effect of slow, small movement on the vibration-evoked kinesthetic illusion

The study reported in this paper investigated how vibration-evoked illusions of joint rotation are influenced by slow (0.3°/s), small (2–4°) passive rotation of the joint. Normal human adults (n=15) matched the perceived position of the left (“reference”) arm with the right (“matching”) arm while vibration (50 pps, 0.5 mm) was applied for 30 s to the relaxed triceps brachii of the reference arm. Both arms were constrained to rotate horizontally at the elbow. Three experimental conditions were investigated: (1) vibration of the stationary reference arm, (2) slow, small passive extension or flexion of the reference arm during vibration, and (3) slow, small passive extension or flexion of the reference arm without vibration. Triceps brachii vibration at 50 pps induced an illusion of elbow flexion. The movement illusion began after several seconds, relatively fast to begin with and gradually slowing down to a stop. On average, triceps vibration produced illusory motion at an average latency of 6.3 s, amplitude of 9.7°, velocity of 0.6°/s, and duration of 16.4 s. During vibration, slow, small (≈0.3°/s, 1.3°) passive rotations of the joint dramatically enhanced, stopped, or reversed the direction of illusory movement, depending on the direction of the passive joint rotation. However, the subjects’ perceptions of these passive elbow rotations were exaggerated: 2–3 times the size of the actual movement. In the absence of vibration, the subjects accurately reproduced these passive joint rotations. We discuss whether the exaggerated perception of slow, small movement during vibration is better explained by contributions of non muscle spindle Ia afferents or by changes in the mechanical transmission of vibration to the receptor