Evaporation du sol nu en zone semi-aride et en conditions hivernales. Relations avec l'albédo et la température de la surface du sol

L'évaporation d'un sol nu dans le Sud Tunisien au mois de novembre, est mesurée après une pluie, ainsi que son albédo, sa température de surface et celle d'une parcelle maintenue humide par irrigation. Les mesures font apparaître une chute rapide de l'évaporation par rapport à l'évaporation potentielle, malgré l'existence d'une réhumectation nocturne. L'albédo, très sensible d'abord, évolue ensuite lentement et rend mal compte des derniers stades du dessèchement du sol. L'écart entre les températures de surface des deux parcelles suit par contre fidèlement la chute de l'évaporation et peut donc être considéré comme un bon témoin de ce phénomène. (Résumé d'auteur

Charge redistribution in electrochemically-actuated mechanical sensors

International audienceMany proofs of concept studies have established the mechanical sensitivity of functionalized microcantilevers to a large spectrum of target molecules. However, moving to real-life applications also requires the monitored mechanical effect to be highly specific. Moving towards more specificity in cantilever-based sensing, monitoring the mechanical response of electrochemically actuated microcantilevers is then thought to provide a fast, reliable and complementary experimental information to the long-time cantilever bending measurement for the detection of target molecules. Full-field measurements are therefore used to investigate the way the electro-elastic coupling is altered when a microcantilever undergoes decane-thiol adsorption. The proposed technique reveals that the latter results in a charge density redistribution along the cantilever in addition to the local surface passivation. Focusing on the cantilever tip displacement under electrochemical actuation, this redistribution partially compensates the electro-elastic coupling alteration due to the surface passivation, therefore possibly yielding an ambiguous detection result. This effect should be taken into account for the optimal design of specific electrochemically actuated mechanical sensors

Thickness-dependent thermal properties of amorphous insulating thin films measured by photoreflectance microscopy

In this work, we report on the measurement of the thermal conductivity of thin insulating films of SiO2 obtained by thermal oxidation, and Al2O3 grown by atomic layer deposition (ALD), both on Si wafers. We used photoreflectance microscopy to determine the thermal properties of the films as a function of thickness in the 2 nm to 1000 nm range. The effective thermal conductivity of the Al2O3 layer is shown to decrease with thickness down to 70% for the thinnest layers. The data were analyzed upon considering that the change in the effective thermal conductivity corresponds to an intrinsic thermal conductivity associated to an additional interfacial thermal resistance. The intrinsic conductivity and interfacial thermal resistance of SiO2 were found to be equal to 0.95 W/m·K and 5.1 × 10− 9 m2K/W respectively; those of Al2O3 were found to be 1.56 W/m·K and 4.3 × 10− 9 m2K/W

Lipid nanocapsules maintain full integrity after crossing a human intestinal epithelium model

Lipid nanocapsules (LNCs) have demonstrated great potential for the oral delivery of drugs having very limited oral bioavailability (BCS class II, III and IV molecules). It has been shown previously that orally-administered LNCs can permeate through mucus, increase drug absorption by the epithelial tissue, and finally, increase drug bioavailability. However, even if transport mechanisms through mucus and the intestinal barrier have already been clarified, the preservation of particle integrity is still not known. The aim of the present work is to study in vitro the fate of LNCs after their transportation across an intestinal epithelium model (Caco-2 cell model). For this, two complementary techniques were employed: Förster Resonance Energy Transfer (FRET) and Nanoparticle Tracking Analysis (NTA). Results showed, after 2 h, the presence of nanoparticles in the basolateral side of the cell layer and a measurable FRET signal. This provides very good evidence for the transcellular intact crossing of the nanocarriers

Multiple wavelengths reflectance microscopy to study the multi-physical behavior of MEMS

International audienceIn order to characterize surface chemomechanical driving micro-electro-mechanical systems (MEMS) behavior, we propose herein a method to simultaneously obtain a full kinematic field describing the surface displacement and a map of its chemical modification from optical measurements. Using a microscope, reflected intensity fields are recorded for two different illumination wavelengths. Decoupling the wavelength-independent and -dependent contributions to the measured relative intensity changes then yields the sought fields. This method is applied to the investigation of the electro-elastic coupling, providing images of both the local surface electrical charge density and the device deformation field

Formulation and evaluation of new oxazaphosphorine prodrugs-loaded lipid nanocapsules for cancer treatment

Oxazaphosphorines (cyclophosphamide (CPA) and ifosfamide (IFO)) represent an important group of therapeutic molecules due to their substantial antitumor and immunomodulating activities. Unfortunately, despite the benefits brought by these molecules, their clinical use shows limitations, notably in chemotherapy, due to the development of resistance, interpatients variation and toxicities (urinary toxicity, neurotoxicity and nephrotoxicity). To circumvent these problems, new oxazaphosphorine analogs have been synthetized and present an interesting anti-tumor activity alone with reduced toxicity [1]. Pentanoxy moiety has been grafted on C4 position of ifosfamide (P-IFO). Nevertheless, these new analogs are lipophilic and unstable in aqueous medium. To administer it, this paper proposes to formulate this analog into nanocarriers. Lipid nanocapsules form a new generation of nanovector that can encapsulate a number of anticancer agents [2]. In the present research, P-IFO-loaded LNCs were formulated and characterized. A new formulation based on glycerol monooleate (Peceol®) was developed, optimized and then characterized. Batches of P-IFO-LNCs were obtained with a size of 47.2±0.7nm with a narrow size distribution and a drug payload of 8.42±1.05mg/g. The suspension remained stable at 4°C for 14 days in terms of mean particle size, polydispersity index and pH. The drug payload decreased after 7 days but a high rate was still found (5.88±1.01mg/g) up to 14 days. The stealth properties of these nanoparticles were examined in vitro using the complement activation (CH50) test. This test revealed a low consumption of plasma protein in the presence of such P-IFO-LNCs. In vitro cytotoxicity of P-IFO-LNCs was determined in two human cell lines; i.e. rhabdomyosarcoma (RMS-1) and Ewing sarcoma (A673) and showed a similar activity compared to the free form. Finally, in vivo activity testing of P-IFO-LNCs is in progress in a murine model bearing a RMS-1 xenograft after intravenous administration. References [1] Skarbek C, et al., Preactivated Oxazaphosphorines Designed for Isophosphoramide Mustard Delivery as Bulk Form or Nanoassemblies: Synthesis and Proof of Concept. Journal of Medicinal Chemistry. 22;58(2):105-17, 2015. [2] Huynh NT, et al., Lipid nanocapsules: A new platform for nanomedicine. International Journal of Pharmaceutics. 379(2):201–9, 2009. Acknowledgments: The authors are very grateful to the Ligue contre le Cancer, Comité du Maine et Loire and Comité d’Ille et Vilaine which founded this work

Correction of moisture effects on near infrared calibration for the analysis of phenol content in eucalyptus wood extracts

Les méthodes basées sur la spectroscopie proche infrarouge pour estimer les propriétés du bois sont sensibles aux variations des paramètres physiques (température, granulométrie. . . ). Le bois étant un matériau hygroscopique sensible, l'influence de l'humidité sur l'absorbance et l'étalonnage proche infrarouge a été étudiée afin de mieux considérer les possibilités d'applications dans des conditions réelles.Un étalonnage de référence de la quantité de polyphénols présents dans les extraits a été établi à partir de spectres d'une collection de bois d'hybrides d'Eucalyptus urophylla × E. grandis à humidité constante fixée. D'autres spectres ont été obtenus sur des échantillons de même provenance mais à 8 teneurs en eau couvrant une large plage de variation. L'influence de l'humidité sur l'absorbance proche infrarouge puis sur l'estimation par le modèle de référence a été analysée. / Methods based on near infrared spectroscopy used to assess wood properties are susceptible to variations in physical parameters (temperature, grain size, etc). As wood is a hygroscopically sensitive material, we studied the effects of moisure on near infrared absorbance and calibration to accurately determine the application potential of this technique under routine. A collection of Eucalyptus urophylla x E. grandis hybrid wood pieces were analysed to obtain reference calibration of polyphenol contents in wood extracts via NIR spectra acquired under constant moisture conditions.Others specimens from the same source were assessed to obtain spectra for eight moisture contents spanning a broad variation range. The effects of moisture on absorption and on estimates based on a reference model were analysed. An increase in moisture content prompteda rise in near infrared absorption over the entire spectrum and the water O-H absorption bands. The polyphenol content estimates obtained by assessing specimens against the reference calibration at variable moisture contents revealed prediction bias. Five correction methods were then tested on enhance the robustness relative to moisture. In-depth calibration and external parameter orthogonalization were found to be the most efficient methods for offsetting this factor