Sensitivity enhancement of a flexible MEMS strain sensor by a field effect transistor in an all organic approach

We report a low-cost piezoresistive nanocomposite based organic micro electro mechanical system (MEMS) strain sensor that has been combined to an organic field effect transistor (OFET) with the objective of amplifying the sensitivity of the sensor. When the MEMS cantilever is strained by a mechanical deflection, the resulting variation of resistivity influences the gate voltage (V_GS) of the OFET and, hence, changes the drain current (I_DS) of the transistor. The present combination allows an enhancement of sensitivity to strain by a factor 3.7, compared to the direct detection of resistance changes of the nanocomposite. As a consequence, a low limit of detection of 24 ppm has been estimated in terms of strain transduction efficiency. Furthermore, the organic microsystem exhibits a short response time and operates reversibly with an excellent robustness.     

Hysteresis‐Free 1D Network Mixed Halide‐Perovskite Semitransparent Solar Cells

The morphology of hybrid organic–inorganic perovskite films is known to strongly affect the performance of perovskite‐based solar cells. CH₃NH₃PbI_3‐xCl_x (MAPbI_3‐xCl_x) films have been previously fabricated with 100% surface coverage in glove boxes. In ambient air, fabrication generally relies on solvent engineering to obtain compact films. In contrast, this work explores the potential of altering the perovskites microstructure for solar cell engineering. This work starts with CH₃NH₃PbI_3‐xCl_x, films with grain morphology carefully controlled by varying the deposition speed during the spin‐coating process to fabricate efficient and partially transparent solar cells. Devices produced with a CH₃NH₃PbI_3‐xCl_x film and a compact thick top gold electrode reach a maximum efficiency of 10.2% but display a large photocurrent hysteresis. As it is demonstrated, the introduction of different concentrations of bromide in the precursor solution addresses the hysteresis issues and turns the film morphology into a partially transparent interconnected network of 1D microstructures. This approach leads to semitransparent solar cells with negligible hysteresis and efficiencies up to 7.2%, while allowing average transmission of 17% across the visible spectrum. This work demonstrates that the optimization of the perovskites composition can mitigate the hysteresis effects commonly attributed to the charge trapping within the perovskite film.     

Some theoretical results about second-order work, uniqueness, existence and controllability independent of the constitutive equation

When they are studied as continuum media, granular materials and other soils and rocks exhibit a complex behavior. Contrary to metals, their isotropic and deviatoric behavior are coupled. This implies some mathematical difficulties concerning boundary-value problems solved with constitutive equations modelling the salient features of such geomaterials. One of the well-known consequences is that the so-called second-order work can be negative long before theoretical failure occurs. Keeping this in mind, the starting point of this work is the pioneering and illuminating work of Nova (1994), who proved that using an isotropic hardening elasto-plastic model not obeying the normality rule, it is possible to exhibit either loss of uniqueness or loss of existence of the solution of a boundary-value problem as soon as the second-order work is negative. Because the geomaterial behavior is quite difficult to model, in practice many different constitutive equations are used. It is then important to study the point raised by Nova for other constitutive equations. In this paper, his result is generalized for any inelastic rate-independent constitutive equation. Similarly the link between localization and controllability proved by Nova (1989) is extended to some extent to a general inelastic model.     

INTERACTIVE SEMANTIC ANALYSIS OF TECHNICAL TEXTS

Sentence syntax is the basis for organizing semantic relations in TANKA, a project that aims to acquire knowledge from technical text. Other hallmarks include an absence of precoded domain-specific knowledge; significant use of public-domain generic linguistic information sources; involvement of the user as a judge and source of expertise; and learning from the meaning representations produced during processing. These elements shape the realization of the TANKA project: implementing a trainable text processing system to propose correct semantic interpretations to the user. A three-level model of sentence semantics, including a comprehensive Case system, provides the framework for TANKA's representations. Text is first processed by the DIPETT parser, which can handle a wide variety of unedited sentences. The semantic analysis module HAIKU then semi-automatically extracts semantic patterns from the parse trees and composes them into domain knowledge representations. HAIKU's dictionaries and main algorithm are described with the aid of examples and traces of user interaction. Encouraging experimental results are described and evaluated.     

Nuclear detection of cellular retinoic acid binding proteins I and II with new antibodies

Apart from the retinoic acid nuclear receptor family, there are two low molecular weight (15 kD) cellular retinoic acid binding proteins, named CRABPI and II. Mouse monoclonal and rabbit polyclonal antibodies were raised against these proteins by using as antigens either synthetic peptides corresponding to amino acid sequences unique to CRABPI or CRABPII, or purified CRABP proteins expressed in E. coli. Antibodies specific for mouse and/or human CRABPI and CRABPII were obtained and characterized by immunocytochemistry and immunoblotting. They allowed the detection not only of CRABPI but also of CRABPII in both nuclear and cytosolic extracts from transfected COS-1 cells, mouse embryos, and various cell lines.     

Phosphorylation of activation functions AF-1 and AF-2 of RAR alpha and RAR gamma is indispensable for differentiation of F9 cells upon retinoic acid and cAMP treatment

The role of RAR alpha 1 and RAR gamma 2 AF-1 and AF-2 activation functions and of their phosphorylation was investigated during RA-induced primitive and parietal differentiation of F9 cells. We found that: (i) primitive endodermal differentiation requires RAR gamma 2, whereas parietal endodermal differentiation requires both RAR gamma 2 and RAR alpha 1, and in all cases AF-1 and AF-2 must synergize; (ii) primitive endodermal differentiation requires the proline-directed kinase site of RAR gamma 2-AF-1, whereas parietal endodermal differentiation additionally requires that of RAR alpha 1-AF-1; (iii) the cAMP-induced parietal endodermal differentiation also requires the protein kinase A site of RAR alpha-AF-2, but not that of RAR gamma; and (iv) the AF-1-AF-2 synergism and AF-1 phosphorylation site requirements for RA-responsive gene induction are promoter context-dependent. Thus, AF-1 and AF-2 of distinct RARs exert specific cellular and molecular functions in a cell-autonomous system mimicking physiological situations, and their phosphorylation by kinases belonging to two main signalling pathways is required to enable RARs to transduce the RA signal during F9 cell differentiation.     

Contribution of retinoic acid receptor beta isoforms to the formation of the conotruncal septum of the embryonic heart

To investigate the relative contribution of retinoic acid receptor (RAR)beta isoforms in conotruncal septation, RAR beta 1 and beta 3 were inactivated in the mouse. Mice lacking RAR beta 1 and beta 3 appear normal. Disruption of these isoforms in RAR alpha or RAR gamma null genetic backgrounds results in a high postpartum lethality. However, except for ocular defects found in RAR beta 1-3/RAR gamma compound mutants, the double null mutants display only abnormalities seen in single null mutants. This probably reflects a functional redundancy with other RARs, most notably with RAR beta 2 which is five- to sixfold more abundant than RAR beta 1 and beta 3 and whose domain of expression is largely overlapping. The conotruncal ridges form normally in retinoid X receptor (RXR)alpha/RAR beta compound mutants but fail to fuse, apparently as a result of excessive apoptosis of mesenchymal cells. Additionally, many cardiomyocytes in the conotruncal wall of these mutants appear necrotic. Although RAR beta 1 and beta 3 are expressed specifically in the conotruncal ridges, failure of fusion of these structures is not more frequent in RXR alpha/RAR beta 1-3 double null mutants than in RXR alpha single null mutants. Similarly, the disruption of the sole RAR beta 2 isoform in a RXR alpha null genetic background does not result in an increase of the frequency of conotruncal septum agenesis. However, this agenesis is fully penetrant in RXR alpha/RAR beta +/- mutants, which reflects distinct role of RXR alpha:RAR beta 1 (and beta 3) and RXR alpha:RAR beta 2 heterodimers in promoting the survival of conotruncal mesenchymal cells. Unexpectedly, we discovered that, in wild-type embryos, the conotruncal mesenchyme is a major site of morphogenetic cell death and that conotruncal myocytes are occasionally necrotic. Thus, excessive cell death in the conotruncus is a potential cause of ventricular septal defects in humans.     

Comparative study of the dialysability of iobitridol and iohexol in the rat with impaired renal function

PURPOSE: To assess the dialysability of iobitridol, a comparative study with iohexol was conducted in the rat over 4 hours. MATERIAL AND METHODS: After ligature of the renal veins and arteries, a group of animals was submitted to continuous peritoneal dialysis, while the remainder were not. RESULTS: In the event of total renal failure, biliary excretion rose from 0.4 to 9% for iobitridol and from 2 to 16% for iohexol. In the rats submitted to peritoneal dialysis, biliary excretion decreased to 5% in the iobitridol group and to 13% in the iohexol group. Further, 18% of the test substances were eliminated in the dialysis liquid. CONCLUSIONS: As their physicochemical characteristics are very similar, the differences between the biliary excretion levels of these 2 media may be caused by a factor related to their respective molecular conformations.