Importance of the irradiation timing within a chemoradiotherapy sequence including cisplatin and 5-FU-folinic acid. Experimental results

The objective of the present in vitro study was to determine an optimal timing of the irradiation in the combination cisplatin (CDDP) and 5-fluorouracil-folinic-acid (5-FU-FA) allowing a maximal cytotoxic effect on a human cell line derived from a head and neck carcinoma (CAL 27 cells). The various tested chemoradiotherapy sequences were applied in parallel to human keratinocytes in culture (SVK 14 cells). This was done in order to define the best sequence allowing the achievement of an optimal selectivity of the cytotoxic effects. The drug sequence was: CDDP over 2 h then fresh medium was added including the tandem 5-FU-d,I FA applied 6 h after CDDP, for 5 days. Irradiation was applied only once and at various times within the drug sequence. The cytotoxicity effects of the different chemoradiotherapy combinations were assessed by the MTT semi-automated test. The part taken by the 5-FU-FA combinations in the overall cytotoxicity was examined; an effect was apparent on CAL 27 cells only. The evolution of the radiation effect (RE = cell survival after drugs/cell survival after drugs plus irradiation) was analysed as a function of the different times of irradiation within the given drug sequence. Clearly, the RE values were dependent upon time at which the radiation dose in the chemoradiotherapy regimen was administered. For CAL 27 cells, irradiation effects were maximal at the first irradiation time tested after the end of the CDDP exposure (i.e. t = 3.5 h). In contrast, this optimal chemoradiotherapy timing for better cytotoxicity on CAL 27 cells did not correspond to that of SVK 14 cells. Consequently, it was possible to establish that the best time for the selectivity index was located shortly after the CDDP exposure.     

Towards a continuous microfluidic rheometer

In a previous paper we presented a way to measure the rheological properties of complex fluids on a microfluidic chip (Guillot et al., Langmuir 22:6438, 2006). The principle of our method is to use parallel flows between two immiscible fluids as a pressure sensor. In fact, in a such flow, both fluids flow side by side and the size occupied by each fluid stream depends only on both flow rates and on both viscosities. We use this property to measure the viscosity of one fluid knowing the viscosity of the other one, both flow rates and the relative size of both streams in a cross-section. We showed that using a less viscous fluid as a reference fluid allows to define a mean shear rate with a low standard deviation in the other fluid. This method allows us to measure the flow curve of a fluid with less than 250 μL of fluid. In this paper we implement this principle in a fully automated set up which controls the flow rate, analyzes the picture and calculates the mean shear rate and the viscosity of the studied fluid. We present results obtained for Newtonian fluids and complex fluids using this set up and we compare our data with cone and plate rheometer measurements. By adding a mixing stage in the fluidic network we show how this set up can be used to characterize in a continuous way the evolution of the rheological properties as a function of the formulation composition. We illustrate this by measuring the rheological curve of four formulations of polyethylene oxide solution with only 1.3 mL of concentrated polyethylene oxide solution. This method could be very useful in screening processes where the viscosity range and the behavior of the fluid to an applied stress must be evaluated.     

Traps centers and deep defects contribution in current instabilities for AlGaN/GaN HEMT's on silicon and sapphire substrates

AlGaN/GaN high electron mobility transistors (HEMTs) with Si and Al₂O₃ substrates reveals anomalies on I_ds-V_ds-T and I_gs-V_gs-T characteristics (degradation in drain current, kink effect, barrier height fluctuations, etc.). Stress and random telegraph signal (RTS) measurements prove the presence of trap centers responsible for drain current degradation. An explanation of the trapping mechanism responsible for current instabilities is proposed. Deep defects analysis performed by capacitance transient spectroscopy (C-DLTS), frequency dispersion of the output conductance (G_ds(f)), respectively, on gate/source and drain/source contacts and RTS prove the presence of deep defects localized, respectively, in the gate and in the channel regions. Defects detected by C-DLTS and G_ds(f) are strongly correlated, respectively, to barrier height inhomogeneities and kink anomalies. Gate current analysis confirms the presence of (G-R) centers acting like traps at the interface GaN/AlGaN. Finally, the localization of these traps defects is proposed.     

Deep levels and nonlinear characterization of AlGaN/GaN HEMTs on silicon carbide substrate

Deep levels in AlGaN/GaN high electron mobility transistors (HEMTs) on SiC substrate are known to be responsible for trapping processes like: threshold voltage shift, leakage current, degradation current, kink effect and hysteresis effect. The related deep levels are directly characterized by conductance deep level transient spectroscopy (CDLTS) method. Hereby, we have detected five carrier traps with activation energy ranging from 0.84 to 0.07 eV. In this study, we have revealed the presence of two hole-like traps (HL1 and HL2) observed for the first time by CDLTS with activations energy of 0.40 and 0.84 eV. The localisation and the identification of these traps are presented. Finally, the correlation between the anomalies observed on output and defects is discussed.     

Probing Silica Aerogel Structure with Spin-Polarised Helium-3 Gas

We report on systematic low-field NMR measurements on room temperature ³ He gas imbibed into a 98% porous silica aerogel. Laser polarised helium is used to obtain large NMR signals at 0.1 T even for small amounts of gas. We use a multi-echo technique in a controlled magnetic field gradient to characterize spin diffusion. Measurements are carried out for pressures P ranging from 10 mbar to 1 bar (mean free path of free ³ He ranging from 19 to 0.19 m respectively). In a free gas, the damping rate 1/T ₂ of the amplitude of the echoes is checked to be proportional to the known diffusion coefficient (T ₂ P). Damping rates 2–5 times smaller than those in a free gas are measured within the aerogel. This reduction is quite significant at 1 bar, suggesting that ³ He- ³ He and ³ He-silica collisions occur with comparable frequencies at this density. However, a stong dependence of T ₂ on P is still observed at low pressure, revealing a significant reduction of diffusion due to binary atomic collisions even for the lowest gas density. Measurements over such a large range of gas densities indirectely probe collisional effects over a wide range of sizes up to tens of m. In our sample, results are not consistent with a single geometrical mean free path for ³ He-silica collisions.     

Acceptability of partially dealcoholized wines – Measuring the impact of sensory and information cues on overall liking in real-life settings

In this study, the effect of partial alcohol reduction in wine on consumer expectation and overall liking was investigated in real-life settings (by a Home-Use-Test). By varying the wine in the bottle and by manipulating the information on the label, it was possible to assess the relative impact of sensory properties and information cues on overall liking.Standard Chardonnay and Syrah wines were partially dealcoholized from about 13.5% to about 9.5%. After bottling, these dealcoholized wines were presented once with information about real alcohol content (9.5%) and once with false information about alcohol content (13.5%). A third bottle with standard wine inside was also presented with real information about alcohol content (13.5%). A group of 194 French wine consumers rated the three wines at home for liking before and after tasting on continuous hedonic scales. Another group of 90 French wine consumers evaluated the wines at the laboratory.The same order of preference was obtained in both laboratory and home conditions but wines generally attained significantly higher hedonic scores in Home-Use-Tests. A strong segmentation of consumers highlighted specific consumer behaviors regarding expectation and overall liking of wines. Results emphasized the importance of both sensory and information cues in the development of overall liking by consumers.     

Faraday rotation of terbium-yttrium ferrite garnet

The authors report Faraday rotation (FR) measurements performed on single crystals of terbium-yttrium iron garnets at 1.15-μm wavelength for three terbium contents (1.98, 1.02, and 0.35) in the temperature range 6-300 K, under magnetic field up to 20 kOe applied along the [111] and [100] directions. The spontaneous FR (associated with the spontaneous magnetization) is isotropic while the FR susceptibilities are anisotropic at low temperature; this anisotropy originates mainly from spin reorientation transitions. To analyze the terbium contribution to FR, the Fe contribution to the YIG data is evaluated. The terbium electric dipole transition coefficient is found to consist in a linear temperature dependence in the temperature range 100-300 K as previously observed in pure TbIG     

Fatty acid membrane composition and activation of glycine-betaine transport in Lactococcus lactis subjected to osmotic stress

Lactococcus lactis subsp. cremoris NCDO763 accumulates glycine-betaine (betaine) when submitted to an osmotic stress with NaCl. Betaine transport activity increases with the extent of the osmotic upshock but also with growth temperature, and supplementation of the medium by Tween-80. Fatty acid analysis of the lipid fraction of L. lactis NCDO763 reveals significant modifications of the fatty acid composition of the membrane when cells are submitted to osmotic stress, high temperature or Tween-80 medium supplementation. The main modification in L. lactis membrane fatty acid composition in response to high osmolality is the increase of Cyclopropane Fatty Acid (CFA) deltaC19:0, whereas Unsaturated/Saturated ratio remains unchanged.     

Toxicity assessment of 16 inorganic environmental pollutants by six bioassays

ATP and ADP are simultaneously released from activated platelets in equimolar concentrations. Micromolar concentrations of ATP inhibit platelet aggregation by both competitive and non-competitive mechanisms. The current studies addressed the question of how platelets respond to agonists in the presence of nanomolar and micromolar concentrations of ATP and ADP alone or in combination. This is a significant issue since the concentration of ATP +/- ADP may vary widely within a microenvironment depending upon the source and cause for the release of the nucleotides. ATP (1-10 nM) was found to significantly enhance the thromboxane A2 analog, U44619-, collagen- and thrombin-induced platelet aggregations. Conversely, ATP at 1-100 microM inhibited these same reactions. ADP, in general, behaved exactly opposite to ATP. When equal amounts of ATP and ADP were added together the ADP response appeared to predominate. The observed ATP-induced response was not due to a hydrolytic product as evidenced by an unaltered response to ATP in the presence of adenosine deaminase or the ATP generating system, creatine phosphate plus creatine phosphokinase. Adenosine (1-10 nM), like ADP, inhibited agonist-induced platelet aggregation. The stimulation of agonist-induced platelet aggregation by 1-10 nM extracellular ATP appears to depend upon the phosphorylation of platelet membrane ecto proteins. The ATP analog, beta gamma-methylene ATP, that is incapable of serving as a phosphate donor for protein kinases, inhibited rather than stimulated agonist-induced platelet aggregation. The dual response of platelets to low and high concentrations of extracellular ATP +/- ADP may play a physiological role in hemostasis and thrombosis under normal and pathological conditions.