The wetting behavior of alkanes on water

This paper presents recent experimental and theoretical results concerning the wetting behavior of n-alkanes on water as a function of thermodynamic conditions (i.e., temperature, pressure, etc.). The transition from lenses to a macroscopically thick film, that takes place when the temperature is increased, occurs for n-alkanes on water in a manner very different from that encountered in other fluid systems. For n-pentane on water, ellipsometric measurements reveal that the growth of the pentane layer to a macroscopically thick film occurs in a continuous manner, for a temperature (≈53°C) corresponding to a change in the sign of the Hamaker constant. A theoretical approach based on the Cahn–Landau theory, which takes into account long-range (van der Waals) forces, enables us to explain the mechanism of this continuous wetting transition. This transition is preceded (at a lower temperature) by a discontinuous transition from a thin film (of adsorbed molecules) to a thick (but not macroscopically thick) film. The latter transition was not visible for pentane on water (it should occur below the freezing temperature for water), but we expect to observe it for longer alkanes (e.g., hexane) on water. Work is underway to examine the wetting behavior of oil/brine systems more representative of reservoir conditions.     

Monolithic porous polymer layer for the separation of peptides and proteins using thin-layer chromatography coupled with MALDI-TOF-MS

Plates for thin-layer chromatography (TLC) with an attached layer of porous polymer monolith have been prepared and used for the separation of small molecules, peptides, and proteins. The 50-200-mum. thin poly(butyl methacrylate-co-ethylene dimethacrylate) layers were prepared in situ using UV-initiated polymerization. Precise control of the reaction conditions enables the preparation of monolithic layers with a well-defined porous structure that determines the chromatographic performance. Compared to conventional TLC and high-performance TLC using precoated layers based on silica, the small layer thickness and absence of any binder is expected to improve both retention characteristics and separation efficiency of the polymer-based monolithic thin-layer chromatographic plates. Spots of the separated compounds were first detected using typical UV imaging. Since the monolithic thin layers can be also prepared directly on the stainless steel MALDI carrier plate, the separation in TLC format can be coupled with MALDI-TOF-MS. Application of a conventional MALDI matrix facilitated desorption and ionization of peptides and proteins for molecular weight determination of the separated compounds.     

Upconversion Nanocarriers Encapsulated with Photoactivatable Ru Complexes for Near‐Infrared Light‐Regulated Enzyme Activity

Enzyme activity is important for metabolism, cell functions, and treating diseases. However, remote control of enzyme activity in deep tissue remains a challenge. This study demonstrates near‐infrared (NIR) light‐regulated enzyme activity in living cells based on upconverting nanoparticles (UCNPs) and a photoactivatable Ru complex. The Ru complex is a caged enzyme inhibitor that can be activated by blue light. To prepare a nanocarrier for NIR photoinhibition of enzyme activity, a UCNP and the caged enzyme inhibitors are encapsulated in a hollow mesoporous silica nanoparticle. In such a nanocarrier, the UCNP can harvest NIR light and convert it into blue light, which can activate the caged enzyme inhibitors. This photoactivation process is feasible in deep tissue because of the tissue penetration ability of NIR light. The nanocarrier is compatible to LNCaP, PC3, and SAOS‐2 cells, which show high enzyme expression. NIR irradiation induces release of the inhibitors and inhibition of enzyme activity in living cells. NIR light provides high spatiotemporal resolution to regulate enzyme activity in deep tissue.     

Centroid virtual coordinates – A novel near-shortest path routing paradigm

Geographic routing has received increasing attention in the context of Wireless Sensor Networks since it frees the network from the energy-demanding task of building and maintaining a structure. It requires however each node to know its position, which may be a prohibitive assumption for many applications. To this end, some prior work has focused on inferring a node’s location from a set of location-aware anchor nodes.In this work, we free ourselves from positioning techniques and anchor nodes altogether, and introduce and analyze the concept of virtual coordinates. These coordinates are chosen randomly when a node is switched on, and are updated each time the node relays a packet. As this process goes on, the virtual coordinates of the nodes converge to a near-optimal state. When using a greedy geographic approach on top of these coordinates, we show that the number of hops to reach the destination exceeds the shortest path by a few percent only. Moreover, our approach guarantees delivery even when nodes appear/disappear in the network, and under realistic transmission models.We analytically prove the correctness of our protocol. Moreover, extensive simulations are used to show that our position-free solution outperforms existing geographic protocols – such as Greedy-Face-Greedy (GFG) or Greedy Perimeter Stateless Routing (GPSR) – in terms of energy-efficiency, path length and robustness.     

Capillary electrophoresis and contactless conductivity detection of ions in narrow inner diameter capillaries

Capillary electrophoresis and conductometry represent a combination of a high-resolution separation method with a sensitive detection principle for the analysis of ionic species. In this paper, results are reported that are obtained with a contactless conductivity detector. This device works without a galvanic contact of the electrolyte and the electrodes. The conductivity sensor is based on two metal tubes that act as cylindrical capacitors. These electrodes are both placed around a fused-silica capillary with a detection gap of 1 mm left in between. When a high audio or low ultrasonic oscillation frequency between 40 and 100 kHz is applied to one of the electrodes, a signal is produced as soon as an analyte zone with a different conductivity compared to the background electrolyte passes the detection gap. An amplifier and rectifier is connected to the other electrode where the signal is further processed. Limits of detection for lithium and fluoride are 4 and 13 ppb, respectively, with a linear range over 4 orders of magnitude from 90 ppb up to more than 1000 ppm for both anions and cations. Furthermore, it is demonstrated that for species with lower equivalent conductivities, such as organic ions, indirect conductivity detection is a sensitive alternative to indirect optical detection methods. Limits of detection of 50 ppb and below are obtained for organic acids.     

Land degradation and erosion risk mapping by fusion of spectrally-based information and digital geomorphometric attributes

The Guadalentin basin, located in the SE of Spain, has a semiarid climate and presents typical characteristics of Mediterranean landscapes vulnerable to land degradation processes and desertification risks. In such an environment, when the vegetation cover is low, the signal received by satellites is dominated by the spectral properties of soils. Changes in these properties can be interpreted in terms of varying soil surface conditions. These optical changes underline the major modifications affecting soil surface under land degradation processes. The present research uses remote sensing techniques to characterise land degradation based on two approaches: spectral mixture analysis and a set of indices describing the spectrum shape. It also presents an integrated approach for evaluating ecosystem vulnerability to land degradation, through the combined analysis of spectrally-derived land units and geomorphometric units. Specific objectives consist of evaluating the potential of extending the indices describing the spectrum shape to the short-wave infrared region, and of identifying landscape units according to their sensitivity to land degradation. Our results demonstrate that the spatial distribution of regional patterns of land degradation can be reliably mapped by using both indices describing the spectrum shape and spectral unmixing. The latter holds great potential for operational mapping of soil conditions and erosion features from optical images. Moreover, landscape-unit analysis shows that DEM (Digital Elevation Model) variables combined with spectral information are very useful for land degradation assessment. This approach allowed us to segment the landscape into different units according to their lithology and vegetation characteristics, as well as their susceptibility to water erosion.     

Semi-empirical calibration of the IEM backscattering model using radar images and moisture and roughness field measurements

Estimating surface parameters by radar-image inversion requires the use of well-calibrated backscattering models. None of the existing models is capable of correctly simulating scatterometer or satellite radar data. We propose a semi-empirical calibration of the Integral Equation Model (IEM) backscattering model in order to better reproduce the radar backscattering coefficient over bare agricultural soils. As correlation length is not only the least accurate but also the most difficult to measure of the parameters required in the models, we propose that it be replaced by a calibration parameter that would be estimated empirically from experimental databases of radar images and field measurements. This calibration was carried out using a number of radar configurations with different incidence angles, polarization configurations, and radar frequencies. Using several databases, the relationship between the calibration parameter and the surface roughness was determined for each radar configuration. In addition, the effect of the correlation function shape on IEM performance was studied using the three correlation functions (exponential, fractal, and Gaussian). The calibrated version of the IEM was then validated using another independent set of experimental data. The results show good agreement between the backscattering coefficient provided by the radar systems and that simulated by the calibrated version of the IEM. This calibrated version of the IEM can be used in inversion procedures to retrieve surface roughness and/or moisture values from radar images.     

Carbon dioxide as a contrast agent to guide vascular interventional procedures

OBJECTIVE: The purpose of this study was to assess the value and limitations of carbon dioxide (CO2) as a contrast agent to guide vascular interventional procedures. SUBJECTS AND METHODS: Twenty-two adults underwent 26 vascular interventional procedures (21 arterial, five venous). We aimed to use only CO2 if possible because these patients had renal insufficiency (n = 21; mean creatinine level, 2.8 mg/dl) or were allergic to contrast material (n = 1). Arterial procedures performed included renal angioplasty or stent (n = 6), iliac angioplasty or stent (n = 5), infrainguinal angioplasty (n = 5), arterial bypass graft angioplasty (n = 3), and thrombolysis (n = 2). Venous procedures included transjugular intrahepatic portosystemic shunt recanalization (n = 3), angioplasty of the venous anastomosis of a thigh dialysis graft (n = 1), and angioplasty of the inferior vena cava (n = 1). RESULTS: Twenty-five of the 26 procedures were successfully performed. Of the 26 procedures, eight required no iodinated contrast material and 11 required less than or equal to 20 ml of contrast material. CO2 proved to be inadequate for the remaining seven procedures. Iliac artery angioplasty or stent placement required an average of 9 ml of iodinated contrast material; infrainguinal angioplasty required an average of 22 ml of iodinated contrast material. CONCLUSION: CO2 can be successfully used as a contrast agent in a variety of vascular interventional procedures. Such procedures can usually be performed in the iliac and infrainguinal arteries using minimal supplemental iodinated contrast material. However, CO2 failed to provide satisfactory guidance in half of the intraabdominal procedures in our study.     

Histidine77, glutamic acid81, glutamic acid123, threonine126, asparagine194, and tryptophan197 of the human emopamil binding protein are required for in vivo sterol delta 8-delta 7 isomerization

The human emopamil binding protein (hEBP) exhibits sterol Delta8-Delta7 isomerase activity (EC 5.3.3.5) upon heterologous expression in a sterol Delta8-Delta7 isomerization-deficient erg2-3 yeast strain. Ala scanning mutagenesis was used to identify residues in the four putative transmembrane alpha-helices of hEBP that are required for catalytic activity. Isomerization was assayed in vivo by spectrophotometric quantification of Delta5,7-sterols. Out of 64 Ala mutants of hEBP only H77A-, E81A-, E123A-, T126A-, N194A-, and W197A-expressing yeast strains contained 10% or less of wild-type (wt) Delta5,7-sterols. All substitutions of these six residues with functionally or structurally similar amino acid residues failed to fully restore catalytic activity. Mutants E81D, T126S, N194Q, and W197F, but not H77N and E123D, still bound the enzyme inhibitor 3H-ifenprodil. Changed equilibrium and kinetic binding properties of the mutant enzymes confirmed our previous suggestion that residues required for catalytic activity are also involved in inhibitor binding [Moebius et al. (1996) Biochemistry 35, 16871-16878]. His77, Glu81, Glu123, Thr126, Asn194, and Trp197 are localized in the cytoplasmic halves of the transmembrane segments 2-4 and are proposed to line the catalytic cleft. Ala mutants of Trp102, Tyr105, Asp109, Arg111, and Tyr112 in a conserved cytoplasmic domain (WKEYXKGDSRY) between transmembrane segments 2 and 3 contained less than 10% of wt Delta5,7-sterols, implying that this region also could be functionally important. The in vivo complementation of enzyme-deficient yeast strains with mutated cDNAs is a simple and sensitive method to rapidly analyze the functional consequences of mutations in sterol modifying enzymes.