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Liver microphysiological systems (MPSs) are promising models for predicting hepatic drug effects. Yet, after a decade since their introduction, MPSs are not routinely used in drug development due to lack of criteria for ensuring reproducibility of results. We characterized the feasibility of a liver MPS to yield reproducible outcomes of experiments assaying drug toxicity, metabolism, and intracellular accumulation. The ability of the liver MPS to reproduce hepatotoxic effects was assessed using trovafloxacin, which increased lactate dehydrogenase (LDH) release and reduced cytochrome P450 3A4 (CYP3A4) activity. These observations were made in two test sites and with different batches of Kupffer cells. Upon culturing equivalent hepatocytes in the MPS, spheroids, and sandwich cultures, differences between culture formats were detected in CYP3A4 activity and albumin production. Cells in all culture formats exhibited different sensitivities to hepatotoxicant exposure. Hepatocytes in the MPS were more functionally stable than those of other culture platforms, as CYP3A4 activity and albumin secretion remained prominent for greater than 18 days in culture, whereas functional decline occurred earlier in spheroids (12 days) and sandwich cultures (7 days). The MPS was also demonstrated to be suitable for metabolism studies, where CYP3A4 activity, troglitazone metabolites, diclofenac clearance, and intracellular accumulation of chloroquine were quantified. To ensure reproducibility between studies with the MPS, the combined use of LDH and CYP3A4 assays were implemented as quality control metrics. Overall results indicated that the liver MPS can be used reproducibly in general drug evaluation applications. Study outcomes led to general considerations and recommendations for using liver MPSs. Study Highlights WHAT IS THE CURRENT KNOWLEDGE ON THE TOPIC? Microphysiological systems (MPSs) have been designed to recreate organ‐ or tissue‐specific characteristics of extracellular microenvironments that enhance the physiological relevance of cells in culture. Liver MPSs enable long‐lasting and stable culture of hepatic cells by culturing them in three‐dimensions and exposing them to fluid flow. WHAT QUESTION DID THIS STUDY ADDRESS? What is the functional performance relative to other cell culture platforms and the reproducibility of a liver MPS for assessing drug development and evaluation questions, such as toxicity, metabolism, and pharmacokinetics? WHAT DOES THIS STUDY ADD TO OUR KNOWLEDGE? The liver MPS systematically detected the toxicity of trovafloxacin. When compared with spheroids and sandwich cultures, this system had a more stable function and different sensitivity to troglitazone, tamoxifen, and digoxin. Quantifying phase II metabolism of troglitazone and intracellular accumulation of chloroquine demonstrated the potential use of the liver MPS for studying drug metabolism and pharmacokinetics. Quality control criteria for assessing chip function were key for reliably using the liver MPS. HOW MIGHT THIS CHANGE CLINICAL PHARMACOLOGY OR TRANSLATIONAL SCIENCE? Due to its functional robustness and physiological relevance (3D culture, cells expose to fluid flow and co‐culture of different cell types), the liver MPS can, in a reproducible manner: (i) detect inflammatory‐induced drug toxicity, as demonstrated with trovafloxacin, (ii) detect the toxicity of other drugs, such as troglitazone, tamoxifen, and digoxin, with different effects than those detected in spheroids and sandwich cultures, (iii) enable studies of hepatic function that rely on prolonged cellular activity, and (iv) detect phase II metabolites and drug accumulation to potentially support the interpretation of clinical data. The integration of MPSs in drug development will be facilitated by careful evaluation of performance and reproducibility as performed in this study.

New strategies allowing the transfer of molecules, especially peptides, through the blood-brain barriers are a major pharmacological challenge for the treatment of brain diseases. The present study aims at evaluating in vivo the cerebral bioavailability of carrier systems, based on small and functionalizable 2,5-diketopiperazine (DKP) motifs. We studied 2 different cyclo(Lys-Lys) DKP scaffolds alone and a cyclo(Lys-Gly) DKP carrier bearing as peptide model, the tau protein hexapeptide VQIVYK sequence. The different carrier systems were synthesized and radiolabeled using one of the free domains. The stability, biodistribution, and ability to cross blood-brain barrier were investigated in vivo in mice for 99mTc-DKP scaffolds, 99mTc-HVQIVYK peptide alone, and 99mTc-DKP-VQIVYK. 125I-labelled bovine serum albumin was used as negative control for brain uptake. Both radiolabeled DKPs scaffolds and 99mTc-DKP-VQIVYK showed a high stability, while peptide 99mTc-HVQIVYK alone was quickly degraded in vivo. The presence of 99mTc-DKPs scaffolds and 99mTc-DKP-VQIVYK was observed in the ventricular and subarachnoid spaces and to a lower extent in the brain parenchyma up to 45 minutes post-injection in mice. This work highlights the potentiality of DKP scaffolds as vectors to transport peptides into the brain by limiting proteolysis and favoring cerebral bioavailability.

Equinatoxin II (EqtII), a eukaryotic pore-forming toxin, lyses cell membranes through a mechanism involving the insertion of its N-terminal α-helix into the membrane. EqtII pore formation is dependent on sphingomyelin (SM), although cholesterol (Chol) and membrane microdomains have also been suggested to enhance its activity. We have investigated the mechanism of EqtII binding and insertion by using neutron reflection to determine the structures of EqtII–membrane assemblies in situ. EqtII has several different modes of binding to membranes depending on the lipid composition. In pure dimyristoyl-phosphatidylcholine (DMPC) membranes, EqtII interacts weakly and reversibly with the lipid head groups in an orientation approximately parallel to the membrane surface. The presence of sphingomyelin (SM) gives rise to a more upright orientation of EqtII, but Chol is required for insertion into the core of the membrane. Cooling the EqtII–lipid assembly below the lipid phase transition temperature leads to deep water penetration and a significant reduction in the extension of the protein outside the membrane, indicating that phase-separation plays a role in EqtII pore-formation. An inactive double-cysteine mutant of EqtII in which the α-helix is covalently tethered to the rest of the protein, interacts only reversibly with all the membranes. Releasing the α-helix in situ by reduction of the disulphide bridge, however, causes the mutant protein to penetrate in DMPC–SM–Chol membranes in a manner identical to that of the wild-type protein. Our results help clarify the early steps in pore formation by EqtII and highlight the valuable information on protein–membrane interactions available from neutron reflection measurements.

We have employed neutron Brillouin spectroscopy to study coherent collective density fluctuations in the biological macromolecular components of living Escherichia coli cells. To highlight the contribution of the macromolecular material alone, a suitably prepared mixture of light and heavy water was exploited to cancel the scattering length of intracellular water. The present results indicate that the cellular biomaterial sustains THz coherent density fluctuations, characterised by a propagating mode travelling at about 3600 m/s and by a localised mode at energies between 4 and 7 meV. A comparison with both hydration water and simpler biomolecules, such as proteins or DNA, brings further support to the idea that the dynamical coupling between biomolecular structures and biological water provides the delicate dynamical adaptation needed to achieve a full biological functionality. Finally, the behaviour of the damping factors of the observed collective modes strengthens the dynamical similarity of biological systems with glass-forming materials.

Crystal diffraction data of heart fatty acid binding protein (H-FABP) in complex with oleic acid were measured at room temperature with high-resolution X-ray and neutron protein crystallography (0.98 and 1.90 Å resolution, respectively). These data provided very detailed information about the cluster of water molecules and the bound oleic acid in the H-FABP large internal cavity. The jointly refined X-ray/neutron structure of H-FABP was complemented by a transferred multipolar electron-density distribution using the parameters of the ELMAMII library. The resulting electron density allowed a precise determination of the electrostatic potential in the fatty acid (FA) binding pocket. Bader's quantum theory of atoms in molecules was then used to study interactions involving the internal water molecules, the FA and the protein. This approach showed H···H contacts of the FA with highly conserved hydrophobic residues known to play a role in the stabilization of long-chain FAs in the binding cavity. The determination of water hydrogen (deuterium) positions allowed the analysis of the orientation and electrostatic properties of the water molecules in the very ordered cluster. As a result, a significant alignment of the permanent dipoles of the water molecules with the protein electrostatic field was observed. This can be related to the dielectric properties of hydration layers around proteins, where the shielding of electrostatic interactions depends directly on the rotational degrees of freedom of the water molecules in the interface., Facultad de Ciencias Exactas, Instituto de Física de Líquidos y Sistemas Biológicos

The structure of dense poly(N-isopropylacrylamide) (PNIPAM) brushes and oligo(ethylene glycol) (OEG) monolayers has been probed using neutron reflectometry and ellipsometry. The PNIPAM brush is swollen below the Lower Critical Solution Temperature (LCST) of 32 ∘C and is collapsed at 37 ∘C. Neutron reflectivity shows that below the LCST, the brush is described by a two-layer model: an inner dense layer and a hydrated outer layer. Above the LCST the collapsed brush forms a homogenous layer. With a fully deuterated myoglobin protein to increase the neutron scattering length density contrast, the reflectivity data show no detectable primary adsorption on the grafted OEG surface. A bound on the ternary adsorption onto PNIPAM chains forming dense brushes below and above the LCST is obtained.

Microfabricated cantilever sensors were used to measure the surface stress induced by protein adsorption onto a gold surface. Two proteins, immoglobulin G (IgG) and albumin (BSA), were studied. The change of surface stress upon adsorption of IgG was found to be compressive, whereas that of BSA was tensile. This difference is elucidated in terms of protein deformation and packing. Most stress change occurs not on adsorption but over very long time scales, up to 12 h, as protein conformational changes occur. The ability to monitor slow protein changes (e.g., from protein denaturing) is a particular strength of the technique.

A total of 588 blood specimens collected in an emergency unit were screened for benzodiazepines (BZDs) using enzyme-multiplied immunoassay and gas chromatography. Two-hundred eighty-five samples were positive for BZDs, and 303 samples that were negative by EMIT included 20 samples with BZDs detectable by gas-liquid chromatography. A total of 15 BZDs were identified, and the most frequently occurring were nordiazepam, bromazepam, diazepam, and alprazolam. Individual BZDs were found in 74% of cases, but some samples contained two, three, or even four BZDs. There is a risk of missing intoxication by BZDs with low therapeutic range and/or low cross-reactivity (alprazolam, bromazepam, flunitrazepam). There is a risk of misinterpreting a positive result for some BZDs with high therapeutic range and/or high cross-reactivity (nordiazepam), which may reflect a pharmacologically ineffective concentration. A semiquantitative analysis is inappropriate even when the identity of BZD is known. Immunoassays are the only methods presently available for use in emergencies, but physicians must be clearly informed of their limitations and interpret results with caution.

Water dynamics plays a fundamental role for the fulfillment of biological functions in living organisms. Decades of hydrated protein powder studies have revealed the peculiar dynamical properties of hydration water with respect to pure water, due to close coupling interactions with the macromolecule. In such a framework, we have studied coherent collective dynamics in protein and DNA hydration water. State-of-the-art neutron instrumentation has allowed us to observe the propagation of coherent density fluctuations within the hydration shell of the biomolecules. The corresponding dispersion curves resulted to be only slightly affected by the coupling with the macromolecules. Nevertheless, the effects of the interaction appeared as a marked increase of the mode damping factors, which suggested a destructuring of the water hydrogen-bond network. Such results were interpreted as the signature of a glassy dynamical character of macromolecule hydration water, in agreement with indications from measurements of the density of vibrational states. Extending the investigations to living organisms at physiological conditions, we present here an in-vivo study of collective dynamics of intracellular water in Escherichia coli cells. The cells and water were fully deuterated to minimise the incoherent neutron scattering background. The water dynamics observed in the living cells is discussed in terms of the dynamics of pure bulk water and that of hydration water measured in powder samples.

The drug MDL 72222, a selective 5-HT3 receptor antagonist, was labelled with 11C and evaluated for distribution kinetics in brain and in vivo binding to 5-HT3 receptors using cold MDL 72222 challenge and positron emission tomography (PET), in three anaesthetized baboons. After tracer doses of [11C]MDL 72222 (i.v. bolus), 11C radioactivity was equally partitioned between plasma and blood cells and readily crossed the blood-brain barrier; it was distributed heterogeneously into 17 different structures of the brain. The kinetic curves for 11C in tissue showed a rapid initial uptake, followed by a slower ascending phase, up to about the twentieth minute and by a plateau, until the end of experiment (90 min). The plateau values indicated marked uptake in brain which, however, varied according to the region considered. In inhibition studies with cold MDL 72222 (1 mg·kg−1) as pretreatment, co-injection or displacement, no clear-cut effects on the kinetics of [11C]MDL 72222 in brain were detected in any region, including those known to be rich in 5-HT3 receptors. These observations suggest that specific binding to 5-HT3 receptors was not detectable in brain in vivo, because of the high lipophilicity (thus a great capacity for non-specific binding) of MDL 72222. These negative findings may also result from both the possible suboptimal affinity of MDL 72222 for 5-HT3 receptors in vivo and the relatively low density of 5-HT3 receptors present only in selected areas of the mammalian brain. This study is a step in the search of selective 5-HT3 receptor radioligands, adequate for in vivo applications. Slow clearance of[11C]MDL 72222 from brain tissue in baboons, should be accounted for in clinical pharmacokinetic investigations for optimal posology considerations.

MDL 72222, an antagonist of 5HT3 receptors, was labeled with a specific radioactivity of 340-400 mCi/mumol by alkylation of the nor-precursor with [11C]CH3I. The yield of the synthesis, starting from [11C]methyliodide to the purified product and corrected for decay, was good approximately 70-75%. After i.v. injection, [11C]MDL 72222 diffuses readily in the central nervous system but is not detected as metabolites in brain and blood, during 1 h study carried out in rats. The time course and distribution of [11C]MDL 72222 was assessed in various organs (liver, lung, kidney, heart, whole brain) and in blood; the organ uptake was rapid and large; the highest accumulation was found in the lung. The regional brain distribution shows initial uptake and subsequent retention of tracer in favor of the cerebral cortex. The level of brain radioactivity was not reduced by pretreatment with a 1000-fold excess of unlabeled MDL 72222. These results suggest that [11]MDL 72222 is of limited interest for 5HT3 receptor binding studies in brain in vivo, presumably mainly because of large non-specific binding.

Flumazenil is a specific antagonist of the central benzodiazepine receptor (CBZR). Labelled with 11C, this compound is the reference radioligand for positron emission tomography (PET) study of the CBZR in humans and primates. The time-course of [11C]-flumazenil radioactivity and its main acid metabolite [11C] Ro 15-3890 were reconstructed from the time-course of total radioactivity in plasma after administration with high or low SRA in primates and humans, applying an extraction procedure validated by TLC. The measured pharmacokinetics of [11C]-flumazenil (T1/2 beta = 45.1 +/- 12.3 min, T1/2 alpha = 1.5 +/- 1.5 min; K = 0.14 +/- 0.14 min-1; Vd area = 44.0 +/- 17.0 l; Clp = 40.0 +/- 8.5 l/h) exhibited a very rapid distribution phase followed by fast elimination, with a large volume of distribution; these results were confirmed by HPLC determinations and agree with previously published data on unlabelled flumazenil. Pharmacokinetics of [11C] Ro 15-3890 acid metabolite show that high drug concentrations in the blood are promptly achieved (kf = 0.13 +/- 0.004 min-1), with a very rapid elimination half-life (T1/2m = 4.47 +/- 1.31 min) comparable to that of [11C]-flumazenil. The percentage metabolization of parent compound to the acid [11C] Ro 15-3890 was constant from the 15th minute and was significantly higher in man compared to the monkey. This percentage was increased by prior eating. The other putative metabolites, i.e. labelled [11C] Ro 15-4965 and unlabelled Ro 15-5528, were never observed at detectable concentrations with TLC and HPLC in rabbit, baboon and human blood samples. This pharmacokinetic study of plasma flumazenil may be useful to implement a dynamic method of CBZR quantification using PET and for analysis of pharmacokinetics in brain tissue.

A gas chromatographic method using a short, high-resolution capillary column connected to a specific thermoionic detector and requiring a simple and short extraction step without evaporation was developed for the rapid and precise determination of two new hypnotics, zolpidem and zopiclone, in serum at concentrations greater than 5 ng/mL. The assay was linear between 5 and 200 ng/mL, with coefficients of intra- and interassay variation less than 5% for both. The method was validated and then used to analyze zolpidem serum concentrations in nine rabbits after oral administration of 0.5 mg/kg and zopiclone serum concentrations in six patients treated orally with a 7.5-g dose.

Many macromolecules in the cell function by forming multi-component assemblies. We have applied the technique of small angle neutron scattering to study a nucleic acid–protein complex and a multi-protein complex. The results illustrate the versatility and applicability of the method to study macromolecular assemblies. The neutron scattering experiments, complementing X-ray solution scattering data, reveal that the conserved catalytic domain of RNase E, an essential ribonuclease in Escherichia coli (E. coli), undergoes a marked conformational change upon binding a 5′monophosphate–RNA substrate analogue. This provides the first evidence in support of an allosteric mechanism that brings about RNA substrate cleavage. Neutron contrast variation of the multi-protein TIM10 complex, a mitochondrial chaperone assembly comprising the subunits Tim9 and Tim10, has been used to determine a low-resolution shape reconstruction of the complex, highlighting the integral subunit organization. It shows characteristic features involving protrusions that could be assigned to the six subunits forming the complex.

The solution NMR structure of a 22-residue Zn(2+)-binding domain (ZBD) from Esherichia coli preprotein translocase subunit SecA is presented. In conjunction with X-ray absorption analysis, the NMR structure shows that three cysteines and a histidine in the sequence CXCXSGX(8)CH assume a tetrahedral arrangement around the Zn(2+) atom, with an average Zn(2+)-S bond distance of 2.30 A and a Zn(2+)-N bond distance of 2.03 A. The NMR structure shows that ND1 of His20 binds to the Zn(2+) atom. The ND1-Zn(2+) bond is somewhat strained: it makes an angle of approximately 17 degrees with the plane of the ring, and it also shows a significant "in-plane" distortion of 13 degrees. A comprehensive sequence alignment of the SecA-ZBD from many different organisms shows that, along with the four Zn(2+) ligands, there is a serine residue (Ser12) that is completely conserved. The NMR structure indicates that the side chain of this serine residue forms a strong hydrogen bond with the thiolate of the third cysteine residue (Cys19); therefore, the conserved serine appears to have a critical role in the structure. SecB, an export-specific chaperone, is the only known binding partner for the SecA-ZBD. A phylogenetic analysis using 86 microbial genomes shows that 59 of the organisms carry SecA with a ZBD, but only 31 of these organisms also possess a gene for SecB, indicating that there may be uncharacterized binding partners for the SecA-ZBD.

The use of surface stress-based sensors as bio-chemical sensors was investigated. In principle, adsorption of bio-chemical species on a functionalised surface of a microfabricated cantilever will cause surface stress and consequently the cantilever bends. Two applications are presented: first lipoproteins and their oxidised form which are responsible for cholesterol accumulation in arteries were differentiated by measuring the surface stress involved in their adsorption on a sugar (heparin); secondly, the surface stress resulting from surface induced conformational changes in protein was monitored. That provided experimental evidence of long time-scale surface processes.

Nine patients with supraventricular rhythm disorders were treated during 5-day periods with different oral doses (300, 450, 600, and 900 mg daily) of propafenone concomitantly to long-term digoxin treatment. A poor correlation (r = .398; P less than .05) was obtained when the difference between the mean digoxin serum level (calculated with the Cmin data determined each of the 5 days) observed during a given propafenone dose and the mean digoxin serum level observed before propafenone treatment, was correlated with the dose of propafenone; but an evident correlation (r = .778; P less than .01) was found when the difference in digoxin level was correlated with the plasma propafenone concentration. The propafenone effect of increasing digoxin blood levels was thus concluded to be poorly dose dependent but strongly concentration dependent. The association of propafenone to a long-term digoxin treatment can be considered with a low risk of toxicity when plasma propafenone concentration does not exceed about 1000 ng/mL. Propafenone plasma levels are unpredictable in view of their wide interindividual variation for a given dose, so their measurement is advised to detect high levels and consequently to prevent a rise in digoxin serum concentrations with the possibility of toxicity. In clinical practice, when propafenone concentration determinations are not readily available, digoxin serum levels at least have to be carefully monitored.

The determination of the percentage of unchanged [11C]Ro 15-1788 with respect to total radioactivity, essential for the pharmacokinetic exploitation of data of blood radioactivity decrease obtained in PET studies, may be carried out with equal results using either an extraction procedure or a TLC method. The analysis of blood samples of various sources (rabbits, baboons, healthy volunteers and anxious patients) and the use of an automatic linear scanner to quantify the radioactive distribution on the TLC plates lead to the conclusion that only [11C]Ro 15-1788 and its acid metabolite [11C]Ro 15-3890 and no other radioactive compound are present in blood at detectable concentration.

Water constitutes the intracellular matrix in which biological molecules interact. Understanding its dynamic state is a main scientific challenge, which continues to provoke controversy after more than 50 years of study. We measured water dynamics in vivo in the cytoplasm of Escherichia coli by using neutron scattering and isotope labelling. Experimental timescales covered motions from pure water to interfacial water, on an atomic length scale. In contrast to the widespread opinion that water is ‘tamed’ by macromolecular confinement, the measurements established that water diffusion within the bacteria is similar to that of pure water at physiological temperature.

In this paper, we discuss different modes of coupling photovoltaic detectors to a readout silicon CCD in infrared hybrid arrays, and we analyze, for different types of application, the critical parameters and the related structures. We also give experimental results for the readout of Pb 0.80 Sn 0.20 Te detectors (sensitive in the 8-12-µm range) operated at 77 K, direct-injection coupled to a linear multiplexing silicon CCD. The measured injection efficiency (65 percent), the dispersion in detector biasing (15 to 25 mV), amplitude modulation (±15 percent), and the measured equivalent detectivity (>2.1010cm/W . Hz1/2) are in good agreement with values that were calculated from the characteristics of the detectors and the multiplexing CCD. At present, the equivalent detectivity is limited by the coupling noise current in the MOSFET channel of each CCD input. An equivalent detectivity of better than 5.1010is anticipated for 8-12-µm photovoltaic detectors that are operated at 60 K. We also give results for an area hybrid array of 8-12-µm photovoltaic detectors on a silicon CCD. A specific detectivity of 2.1010W-1. cm . Hz1/2has been obtained with direct detector readout. A silicon CCD multiplexer has proved to be effective for reading out 8-12-µm infrared photovoltaic detectors (HgCdTe, PbSnTe). It should also be well suited to the readout of 3-5-µm infrared photovoltaic detectors (HgCdTe, InSb, InAsSb).

The liquid-solid phase diagram of the quaternary system GaInAsP has been calculated in order to grow Ga x In 1− x As 1− y P y layers on indium phosphide substrates by liquid phase epitaxy. Mixed compounds with an energy gap of 1.17 eV at 300 K and lattice-matched with the substrates have been obtained. The lattice parameter a was determined by X-ray diffraction. The energy gap E g was determined by photoluminescence or electro-reflectance at 300 K and studied as a function the thickness of the epilayer. variations of a have been observed by measuring the lattice parameter by X-ray diffraction for different hkl reflections. The measurements were shown to be depth dependent. The use of a double-reflection X-ray diffractometer with copper radiation confirms this dependence. Also, E g varied with thickness. The thickness dependence of the composition can be interpreted as an effect of diffusion-limited growth and phosphorus evaporation from the melts.

An indirect encapsulation technique for growing GaAs by pulling using a rotating liquid seal of B 2 O 3 is presented together with experimental results on the assessment of the pulled crystals. The use of a special silica crucible and an after heater furnace minimizes the need for pressure regulation in the growth chamber and provides a crystal surface free of defects during the complete run. No contamination of the melt and the crystal by B 2 O 3 is observed in this procedure. Large ingots of 20 to 30 mm in diameter and 7 cm long have been pulled along the [111] direction from undoped and oxygen doped melts, with typical etch pit densities (EPD) concentration of 10 4 cm -2 . Undoped crystals are n-type having 1 × 10 15 carriers cm -3 with Hall mobilities between 5000 and 6000 cm 2 /V sec at room temperature or semi-insulating having a resistivity of 10 6 –10 7 ohm cm. A high life time of τ n ∼ 3 × 10 -7 sec and τ p ∼ 4 × 10 -8 sec has been measured on compensated and oxygen doped materials by photo-magneto-electric methods.

Heteroepitaxial growth of CdS on semi-insulating GaAs substrates has been studied, using the (H 2 -CdS) vapour growth technique. High mobility single crystal layers were prepared on (111) A GaAs surfaces, with 1 to 15 μm thickness and 710-550 °C deposition temperature range. An investigation was made of the electrical properties of the layers. Mobilities up to 200 cm 2 /V-sec and 10 18 cm -3 typical carrier concentration were obtained at 700 °C. For low temperature deposit (550 °C) carrier concentration is lowered at 3 × 10 16 cm -3 with carrier mobilities in the 40 to 100 cm 2 /V-sec range. Relations between growth conditions and electrical characteristics of the CdS layers are analysed in terms of contamination by the substrate. A redistribution model of gallium and arsenic by the vapour phase during the growth is proposed and based on correlatives results given by ionic analysis, resistivity, and Hall effect measurements. Gallium and arsenic profiles were recorded at the heteroepitaxial interface and in the CdS layer. The role of a chemical reaction including substrate reactivity and formation of the gallium sulfide is suggested to explain these results.

The ion microanalyzer permits a localized mass spectrometric analysis, i.e. the qualitative and quantitative analysis of the impurities contained in a small selected volume. This procedure makes possible the analysis of very thin epitaxial layers (for example silicon and gallium arsenide). As regards qualitative analysis, the apparatus is designed for the selection of ions. After the recording and analysis of the ion spectrum, a large number of the impurities present in the sample are determined qualitatively. Quantitative analysis can be performed with the equipment, but this requires the analysis of a homogeneous standard sample previously dosed by spark-source mass spectrometry. The quantitative analysis of bulk and epitaxial silicon and gallium arsenide is described and the limits of detection of the principal impurities are given. It is also shown how the possibility of localized analysis was exploited. A correlation was established between the existing impurities and the chemically revealed crystal imperfections. A comparative analysis of the distribution of the impurities in the epitaxial layers was also carried out. The periodic analysis of epitaxial layers makes it possible to follow the deterioration by contamination, if any, under the epitaxial conditions, and to improve the sample quality.

Using a very well defined material, a description is given of the electronic and optical schemes. A comparison of a Golay detector mounted at the focus of an ellipsoidal mirror with the germanium bolometer at the end of a cylindrical light pipe, corner mirror, and filters whose gross transmission is only 2%, shows that the germanium bolometer is still favoured by a factor greater than 18. Hence NEP(Ge + optics) ≈ 5 × 10−12 and NEP(Ge) ≈ ≈ 10−13 W Hz−1/2. The second value is the best one described up today. It could be still improved by a factor two. En preparant un materiau particulierement bien defini, l'electronique et l'optique sont decrites. La comparaison avec un recepteur de Golay, monte au foyer d'un miroir elliptique, et un bolometre au germanium place a l'extrěmite d'une optique comprenant un guide de lumiere cylindrique, un miroir de coin et des filtres, dont la transmission totale n'atteint guere que 2%, est encore en faveur du bolometre au germanium avec un facteur superieur a 18. On trouve un NEP(Ge+optique) ≈ 5 × 10−12 W Hz−1/2 et un NEP(Ge) ≈ 10−11 W Hz−1/2. Le second est un des meilleurs decrits a ce jour. II peut etre ameliore dans un rapport deux, et le premier dans un rapport voisin de dix, grǎce a une optique plus soignee.

Thermochemistry of oxidation and hydrolysis of YCl3 and FeCl2 have been studied. It has been shown that Y3Fe5O12 cannot be formed by hydrolysis. Conditions of synthesis have been established in oxidation, particularly it is pointed out that excess of HCl or Cl2 is not recommended for moderating reactions. It makes the synthesis difficult to control. Theoretical results are compared to experimental data.

We present direct quasielastic neutron scattering measurements, in vivo, of macromolecular dynamics in Escherichia coli. The experiments were performed on a wide range of timescales to cover the large panel of internal and self-diffusion motions. Three major internal processes were extracted at physiological temperature: a fast picosecond process that corresponded to restricted jump diffusion motions and two slower processes that resulted from reorientational motions occurring in approximately 40 ps and 90 ps, respectively. The analysis of the fast process revealed that the cellular environment leads to an appreciable increase in internal molecular flexibility and diffusive motion rates compared with those evaluated in fully hydrated powders. The result showed that the amount of cell water plays a decisive role in internal molecular dynamics. Macromolecular interactions and confinement, however, attenuate slightly the lubricating effect of water, as revealed by the decrease of the in vivo parameters compared with those measured in solution. The study demonstrated that standard sample preparations do not mimic accurately the physiological environment and suggested that intracellular complexity participates in functional dynamics necessary for biological activity. Furthermore, the method allowed the extraction of the self-diffusion of E. coli macromolecules, which presented similar parameters as those extracted for hemoglobin in red blood cells.

A high-performance liquid chromatographic method is described which determines noxytiolin and 1-methyl-2-thiourea concentrations in serum. Valid determination requires immediate ultracentrifugation of blood samples, rapid serum freezing, and injection into the chromatograph within 6 h. A number of pharmacokinetic parameters were calculated from serum concentration data in rabbits and humans. An unknown metabolite was detected in both species but its structure was not identified.

An accurate, rapid, and sensitive GLC determination of alprenolol and oxprenolol in serum is described. This method combines an electron-capture detector with a wall-coated open tubular column. The lowest detectable amount of the halogenated (heptafluoroacyl) derivatives of alprenolol and oxprenolol is 2 pg. The high resolving power and the rapid elution time of the wall-coated open tubular column dramatically improve the performance (accuracy and sensitivity) of the conventional electron-capture detector and packed column system in these determinations. This method allows the use of small volumes of sample (100-200 microliter), does not require redistilled reagents, and has a simplified extraction procedure.

Presented are some experimental results on the readout of a Pb 0.80 Sn 0.20 Te six-detector array at 77 K, coupled in the direct injection mode to a silicon CCD multiplexer. A 65 % typical injection efficiency is measured, in good agreement with the theoretical value, estimated from the dynamic impedance of the detector, and the input MOS transistor's transconductance. The detectors are reverse-biased between 15 and 25 mV, which is consistent with the injection efficiency and the ± 9 mV threshold voltage dispersion of the electrical inputs. The modulation amplitude shows a ± 15 % dispersion. An equivalent detectivity in excess of 2 × 1010W-1cm Hz1/2is measured at a 10 micron wavelength, limited by the noise current in the input MOS transistors.

Fluconazole concentrations in biological fluids were determined by high-performance gas chromatography. A simple extraction procedure with chloroform, under basic conditions and after the addition of UK-47,265 as the internal standard and with no evaporation stage, was carried out prior to analysis. A solid injector and a 15-m capillary column, coated with a nonpolar phase and connected to a nitrogen-selective detector that afforded an excellent selectivity and sensitivity, constituted the gas chromatographic system. The duration of each analysis was less than 4 min and the minimum detectable serum concentration was 50 ng/mL. In five patients undergoing chronic peritoneal dialysis, the mean serum concentrations +/- SD at 1, 6, and 48 h after the intraperitoneal administration of a single dose of fluconazole were, respectively, 325 +/- 75, 928 +/- 159, and 607 +/- 80 ng/mL.

The symptoms of acute poisoning after accidental administration of ten times the usually prescribed dosage of caffeine in a premature infant included the following neurological signs: incessant tremors, hypertonia, continuous opisthotonos posture, whining and crying and digestive disturbances. The very high serum caffeine levels, 160 mg/l, determined 66 hours after the first administration was confirmed by the very high cerebrospinal fluid caffeine concentration 115 mg/l. Two exchange transfusions performed at an interval of 16 hours produced a large decrease in serum caffeine levels of approximately 40 mg/l each time, and a similar decrease in the cerebrospinal fluid concentration. The clinical status of the infant improved very rapidly and the child's psychomotor development was normal at 3 months of age.

This work proposes the use of (a) a commercially available homologous system AVP antibody-AVP (Arginine Vasopressin) standard and (b) new acquisitions for the improvement of sensitivity for AVP radioimmunoassay by separate or simultaneous use of two-phase sequential incubation and ϵ-aminocaproic acid (EACA). The antiserum used in the system described is very specific since none even cross-reacted with lysine vasopressin (LVP) and has an apparent affinity constant (K) of 0.909 ± 0.047 ∗ 10 12 l/mol . This is sufficiently high to detect 0.5 ± 0.2 pg/tube, which is theoretically expected of biological AVP. The total assay time is less than 48 h.