Catheter-mounted pressure transducer using a fiber loop

A catheter-mounted fiber optic pressure sensor is described. The sensor consists of a looped fiber; light is coupled into one leg and detected at the other. When the loop bends, microbending in the neck of the loop couples light out of the fiber, resulting in a detectable signal. The catheter was placed in a closed-circuit pumping station in parallel with a strain gauge pressure transducer; the fiber sensor simulated the transducer's output with good fidelity. Aging tests indicate remarkably good reproducibility and stability.     

Reversible Photoinduced Switching of Permeability in a Cast Non‐Porous Film Comprising Azobenzene Liquid Crystalline Polymer

Permeation characteristics of an azobenzene‐containing liquid crystalline (LC) non‐porous film are investigated using a metallic corrosion method. Thin films (300 nm) are fabricated by the solution casting of an azobenzene side‐chain LC polymer on freshly polished carbon steel coupons. Coated coupons are treated under the following conditions: a) gradual annealing at a cooling rate lower than 1 °C · min⁻¹ from 150 °C (above its T_g) to room temperature, and b) irradiation at 465 nm (20 mW · cm⁻²) with either circularly polarized light (CPL) or non‐polarized light (NPL). The morphology of these films is characterized using X‐ray diffraction, polarized optical microscopy, and transmission measurements. The results suggest that the annealing treatment resulted in the formation of a polydomain structure consisting of locally ordered small smectic domains that lack mutual orientation. Ordered micro domains are surrounded by disordered phases. CPL and NPL irradiation generates a monodomain orientated structure and an isotropic liquid crystal glass, respectively. The permeability of these non‐porous films treated by CPL, NPL, and annealing are found to be 6.14 × 10⁻⁴, 1.92 × 10⁻², and 1.56 × 10⁻³ cm³ · m⁻² · d⁻¹. An orientation‐dependent structure model is constructed to explain the permeation phenomenon, considering the ordered phase is impermeable, only the disordered phase is accessible to penetrating molecules. Fast switching of gas permeation is demonstrated by alternative irradiation of the film with CPL and NPL, which results in an approximately 30‐fold difference in the permeability of the non‐porous film.

     

Non‐oxidized graphene/elastomer composite films for wearable strain and pressure sensors with ultra‐high flexibility and sensitivity

It remains challenging to prepare wearable strain and pressure sensors with excellent mechanical properties, ultra‐high flexibility and sensitivity. Electrically conductive graphene platelets (GnPs) with high structural integrity are used in making a composite film fabricated using robust fabrication techniques. The gauge factor for the strain is up to 100 at 0%‐5% strain and 50 at 5%‐30% strain, and the sensitivity to pressure is 2.7×10^‐2 kPa^‐1 between 0 and 10 kPa and 1.5×10^‐4 kPa^‐1 between 300 and 1000 kPa. In addition, the flexible sensor demonstrates good repeatability and durability after 1000 cycles of tensile and compression tests. The flexible sensor has fast response ability and a wide operating temperature range, suggesting the excellent response to temperature. The flexible sensor is applied in monitoring several human motions as a wearable device with high accuracy. The ability to detect strain, pressure and temperature of the flexible sensor extends its applications to multifunctional wearable devices.     

On the viscosity of two 1-butyl-1-methylpyrrolidinium ionic liquids: Effect of the temperature and pressure

A new calibration procedure was used and four new temperature probes have been placed on a falling-body viscometer to improve its accuracy. The new configuration and calibration procedure allow measuring viscosities with an uncertainty of 3.5% at pressures up to 150 MPa. This device was employed to measure viscosities as a function of temperature and pressure for two ionic liquids (ILs): 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate and 1-butyl-1-methylpyrrolidinium trifluoromethanesulfonate. Besides, we have measured the flow curves at pressures up to 75 MPa and shear rates up to 1000 s⁻¹ in a Couette rheometer. Dynamic viscosities were correlated as function of temperature and pressure with four different equations with average absolute deviation lower than 1%. The pressure-viscosity and temperature-viscosity derived properties were analyzed and compared with those of other ionic liquids. Furthermore, experimental data were used to check the application of the thermodynamic scaling approach as well as the hard-sphere scheme. Both models represent the viscosity values with average relative deviations lower than 2%.     

The Dynamic Impact Experiments Under Active Confining Pressure and the Constitutive Equation of PP/PA Blends at Multi-Axial Compressive Stress State

Summary : A special active hydraulic confining pressure installation matched with Φ14.5 mm SHPB apparatus was developed. A series of active confining pressure impact experiments for PP/PA blends are performed in this special SHPB system under two kinds of axial strain rate: 8.0*10², 1.4*10³ s⁻¹ and the active confining pressure of 0 MPa, 4 MPa, 8 MPa, 12 MPa, 15 MPa, 20 MPa. The axial strain-time profile, the axial stress-time profile and the hoop strain-time profile of the specimen are recorded online respectively. According to the equilibrium equation, the complete state of principal stress and principal strain of PP/PA blends under multi-axial stress state is analyzed. The experimental results reveal that the axial stress-strain curves all are related to the confining pressure and the strain rate. It can also be seen that under a constant effective strain rate the effective stress- effective strain curves at different confining pressures are coincident basically. This manifests that under a certain effective strain rate there is only one unique effective stress- effective strain curve. The multi-axial constitutive equation for PP/PA blends is suggested finally as: where σ_conf is the confining pressure value. For 113 PP/PA blends, E = 2.98 GPa, α = −31.15 GPa, β = 93.31 GPa, θ₂ = 8.54 µS, E₂ = 0.82 GPa.     

Viscoplasticité dynamique du polycarbonate: Influence de la vitesse de sollicitation et des traitements de recuit

The present paper deals with the study of engineering polycarbonates, investigated at high compressive strain rates (1100–3200 sec⁻¹), by means of Hopkinson pressure bar apparatus. Special attention was devoted to the influence of thermal pre-treatment and the viscoelastic behaviour in the glassy state. The results are compared to those obtained at low strain rates (10⁻²−1 sec⁻¹).     

Effect of pressure on the dimerization of benzoic acid in n-heptane

Ultraviolet absorption spectra of benzoic acid in n-heptane were measured at 25°C and up to 640 MPa. The reaction volume for the cyclic dimerization of benzoic acid was estimated as 0.4 ±0.9 cm³ mol⁻¹ from the pressure dependence of the dimerization constant. This is much more positive than those for noncylic hydrogen-bond formations which are from −3 to −6 cm³ mol⁻¹. It is ascribed to a compensation between a reduction in the volume accompanying the hydrogen-bond formation and an increase accompanying the cyclization. These two contributions to the reaction volume are estimated quantitatively.     

Lamellar thickening of polyethylene under high pressure

Single crystal mat (SCM) samples of polyethylene (PE) were prepared from dilute solution of p-xylen, then they were annealed at pressures of 200 and 500 MPa. Lamellar thickness of the original and annealed SCM samples was measured by small-angle X-ray scattering method. Orientation of the molecular chain in those SCM samples was investigated by wide-angle X-ray diffraction pattern. From these X-ray measurements, annealing temperature dependence of the lamellar thickness, i.e., lamellar thickening, under high pressure was obtained. Melting process of the SCM samples was also investigated at 200 and 500 MPa by high pressure differential thermal analysis. Then correspondence between the lamellar thickening and the melting process was studied. The lamellar thickness increases markedly with approaching to the melting temperature of the orthorhombic crystal even in the high pressure region where the high pressure phase (hexagonal phase) appears. The annealing temperature dependence curve of the lamellar thickness at 200 MPa can be superimposed on the curve at 500 MPa by shifting the curve along the temperature scale by 47 K. Large scale lamellar thickening occurs in the orthorhombic crystal phase in the high pressure region. The formation process of extended-chain crystal is discussed. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys, 35: 535–543, 1997     

Ionization gauge sensitivities of N2, O2, N2O,NO, NO2, NH3, CClF3 and CH3OH

A Bayard-Alpert (BA) gauge was used to determine apparent relative sensitivites S_rel,X for O₂, N₂O, NO, NO₂, NH₃, CClF₃ and CH₃OH from gauge calibration measurements in the range 1.3×10^?1 Pa≤p≤1.3·10^?3Pa. Nitrogen was used as a calibration standard.     

Copper‐based Metal‐organic Framework Applied in the Development of an Electrochemical Biomimetic Sensor for Catechol Determination

In this study, the synthesis and characterization of a Cu‐based metal‐organic framework (MOF) [Cu₃(BTC)₂(H₂O)₃]_n (where BTC=benzene‐1,3,5‐tricarboxylate), known as HKUST‐1, were performed. The Cu‐MOF was applied in the modification of a carbon paste to obtain a biomimetic sensor for the electrochemical determination of catechol. Kinetic assays confirmed that the Cu‐MOF acts as a catalyst for the oxidation of catechol and it can be considered as a catechol oxidase mimetic. Under optimized conditions, the calibration curve for catechol presented a linear range of 8.0×10⁻⁷ to 3.2×10⁻⁵ mol L⁻¹, with detection limit of=1.0×10⁻⁷ mol L⁻¹. The sensor demonstrated good intra‐day repeatability and inter‐electrode reproducibility (relative standard deviations of 3.8 % (n=10) and 4.3 % (n=6), respectively). In the selectivity study, an adequate peak‐to‐peak separation was observed for hydroquinone and uric acid in relation to catechol, demonstrating that this sensor has the potential for use in the simultaneous determination of these compounds. This sensor was successfully applied in the determination of catechol in water samples.     

Determination of chloride by stripping chronopotentiometry with silver-film electrode

The experimental parameters of cathodic stripping chronopotentiometry of chloride at a silver-film electrode are investigated and optimized. The chloride preconcentration is achieved in the form of silver chloride by a controlled potential oxidation of the working electrode under vigorous stirring. Cathodic stripping of the deposit is obtained by the constant current, under the condition of diffusive mass transfer. Deaeration of the solution is not necessary. A detection limit of 35 μ dm⁻³ (10⁻⁶ mol dm⁻³) is obtained at a deposition time of 180 s, with a reproducibility of 6.7 % (expressed as relative standard deviation, RSD).     

Effect of pressure on the luminescence of 9,10-dichloroanthracene crystals

Luminescence spectra of β-9,10-dichloroanthracene have been studied at room temperature in the pressure range ≈ 0–10 GPa. The initial shift to lower energies of the excimer emission is linear (≈500 cm⁻¹/GPa) up to ≈3 GPa. Above this pressure a sharper emission grows at the high-energy side at the expense of the excimer luminescence. The suppression of the excimer state at pressures above ≈ 7 GPa is attributed to the strong repulsive interactions between the molecular pair. The new emission is thought to arise from a more loosely bound configuration in the excited state which could originate from a crystal phase change around 3 GPa.     

MDMA Electrochemical Determination and Behavior at Carbon Screen-printed Electrodes: Cheap Tools for Forensic Applications

This article describes a method that uses Carbon Screen-printed Electrodes (C-SPEs) to detect 3,4 – methylenedioxyamphetamine (MDMA) by Linear Sweep Voltammetry in aqueous medium. Major parameters of this technique were evaluated aiming improve the method sensibility. Amines interference were conducted in order to verify disturbs at the MDMA response. The method obtained a linear response from 1×10⁻⁵ mol L⁻¹ to 1×10⁻⁴ mol L⁻¹ with linear correlation coefficient of 0.996, Amperometric Sensitivity (AS) of 0.025 A×mol⁻¹ L, Limit of Detection (LOD) of 1,83×10⁻⁶ mol L⁻¹, and Limit of Quantification (LOQ) of 6,11×10⁻⁶ mol L⁻¹. The method applicability, reproducibility and reproducibility were carried over inter/intra days tests and its application on seized samples.     

Copolymerization of Carbon Dioxide and Propylene Oxide by Binary Cobalt Salen Complexes with Various Anion Groups

A series of salen–Co (III )(X) complexes tethering quaternary ammonium salts are designed to investigate the influence of the axial group X in the complex and the anion Y of quaternary ammonium salt on the copolymerization of CO₂ and PO . By copolymerization, the complex 9 , where X and Y are both 2,4‐dinitrophenolate, has the highest catalytic efficiency. When X is OAc and Y is BF₄ ⁻/NO₃ ⁻, the complexes 11/12 have lower catalytic efficiency. For the complex 10 , where X and Y are both OAc , the catalytic efficiency is the lowest. At the same time, complex 9 can produce the copolymer with the highest carbonate fraction and M _n. And the best copolymerization conditions were as follows: reaction temperature 30°C, copolymerization time 24 h, and CO₂ pressure 2 MPa with complex 9 . The thermal properties of the copolymers are also studied by differential scanning calorimetry (DSC) and thermogravimetry (TG) .     

Thermochemistry and Kinetics of the Thermal Decomposition of 1‐Chlorohexane

A theoretical kinetic study of the thermal decomposition of 1‐chlorohexane in gas phase between 600 and 1000 K was performed. Transition‐state theory and unimolecular reaction rate theory were combined with molecular information provided by quantum chemical calculations. Particularly, the B3LYP, BMK, M05–2X, and M06–2X formulations of the density functional theory (DFT) and the high‐level ab initio methods G3B3 and G4 were employed. The possible reaction channels for the thermal decomposition of 1‐chlorohexane were investigated, and the reaction takes place through the elimination of HCl with the formation of 1‐hexene. The derived high‐pressure limit rate coefficients are k _∞(600–1000 K) = (8 ± 5) × 10¹³ exp[‐((56.7 ± 0.4) kcal mol⁻¹/RT )] s⁻¹. The pressure effect over the reaction was analyzed from the calculation of the low‐pressure limit rate coefficients and the falloff curves. In addition, the standard enthalpies of formation at 298 K of −46.9 ± 1.5 kcal mol⁻¹ for 1‐chlorohexane and 5.8 ± 1.5 kcal mol⁻¹ for C₆H₁₃ radical were derived from isodesmic and isogiric reactions at high levels of theory.     

Piezoresistive properties of polycrystalline and crystalline silicon films

The piezoresistive properties of thin polycrystalline and crystalline boron-doped silicon films on thermally oxidized silicon substrates are reported, based on their calculated and measured gauge factors. A simple theoretical model for calculating the longitudinal and transverse gauge factors, including grain size, crystallite orientation and doping dependence, is described. Boron doping concentrations in the range 5 × 10¹⁸ cm⁻³ to 1 × 10²⁰ cm⁻³ have been investigated. Predictions of gauge factors using our model give good agreement with experimental results. Maximum gauge factors of K₁ ≅ 37 and K_t ≅ −9 for polycrystalline silicon with grain sizes of about 120 nm were obtained at doping concentrations of about 1 × 10¹⁹ cm⁻³. In the case of completely crystalline silicon films, the advantages of SOI technology are combined with excellent piezoresistive properties comparable to those of usual piezoresistors in monocrystalline silicon devices.     

Trace measurements of tetracyclines using adsorptive stripping voltammetry

The surface-active properties of tetracycline antibiotics are exploited for developing a sensitive adsorptive stripping method for trace measurements of these compounds. Controlled interfacial accumulation at the h.m.d.e. permits convenient quantitation at the submicromolar and nanomolar concentration levels. With 210 s accumulation, the method provides 28, 27, 26 and 23 signal enhancements for tetracycline hydrochloride, oxytetracycline, chlortetracycline and doxycycline, respectively. The adsorptive stripping response is evaluated with respect to accumulation time and potential, stripping mode, concentration dependence, electrolyte and pH, and other variables. Detection limits are 6 × 10⁻¹⁰ M for doxycycline, 1 × 10⁻⁹ M for oxytetracycline and chlortetracycline, and 2 × 10⁻⁹ M for tetracycline hydrochloride with 300 s accumulation. The reproducibility of the determination (at the 1 × 10⁻⁷ M level) expressed in terms of relative standard deviation, ranges from 0.8 to 2.0%.     

Simultaneous Capture,Detection, and Inactivation of Bacteria as Enabled by a Surface‐Enhanced Raman Scattering Multifunctional Chip

Herein, we present a multifunctional chip based on surface‐enhanced Raman scattering (SERS) that effectively captures, discriminates, and inactivates pathogenic bacteria. The developed SERS chip is made of a silicon wafer decorated with silver nanoparticles and modified with 4‐mercaptophenylboronic acid (4‐MPBA). It was prepared in a straightforward manner by chemical reduction assisted by hydrogen fluoride etching, followed by the conjugation of 4‐MPBA through Ag S bonds. The dominant merits of the fabricated SERS chip include excellent reproducibility with a relative standard deviation (RSD) value smaller than 11.0 %, adaptable bacterial‐capture efficiency (ca. 60 %) at low concentrations (500–2000 CFU mL⁻¹), a low detection limit (down to a concentration of 1.0×10² cells mL⁻¹), and high antibacterial activity (an antibacterial rate of ca. 97 %). The SERS chip enabled sensitive and specific discrimination of Escherichia coli and Staphylococcus aureus from human blood.     

Simple Analytical Method for the Determination of Paclitaxel (Taxol ® ) Levels in Human Plasma

Paclitaxel has been widely used for tumor chemotherapy in recent years and it would be useful to assess occupational exposure to the drug, if only to confirm that the procedures and measures for prevention and protection applied in health care structures are effective against this kind of risk. This study is to establish a simple, robust analytical method for routine use in biological monitoring of health workers exposed to taxanes, and extendable to patients receiving these drugs. HPLC equipped with a diode array detector was used. The assay was validated. Intra- and inter-day accuracy and reproducibility were good. Recovery of paclitaxel spiked in drug-free plasma was higher than 87% with SPE using extract-clean normal phase cyanopropyl silica cartridges for plasma clean-up. The calibration curve was linear in the range 10–500 ng mL⁻¹. The method was applied to plasma samples of nurses occupationally exposed to paclitaxel. The experimental analytical method performed well, detecting paclitaxel in plasma at a concentrations down to 10 ng mL⁻¹. This straightforward method for analytical determination of paclitaxel in human plasma is rapid and can measure up to 36 plasma samples per day. It uses more economical equipment than other methods proposed in the literature and its validation parameters are highly satisfactory.

     

Selective Electroanalysis of Ascorbic Acid Using a Nickel Hexacyanoferrate and Poly(3,4‐ethylenedioxythiophene) Hybrid Film Modified Electrode

The mixed‐valent nickel hexacyanoferrate (NiHCF) and poly(3,4‐ethylenedioxythiophene) (PEDOT) hybrid film (NiHCF‐PEDOT) was prepared on a glassy carbon electrode (GCE) by multiple scan cyclic voltammetry. The films were characterized using atomic force microscopy, field emission scanning electron microscopy, energy dispersive spectroscopy, X‐ray diffraction, and electrochemical impedance spectroscopy (AC impedance). The advantages of these films were demonstrated for the detection of ascorbic acid (AA) using cyclic voltammetry and amperometric techniques. The electrocatalytic oxidation of AA at different electrode surfaces, such as the bare GCE, the NiHCF/GCE, and the NiHCF‐PEDOT/GCE modified electrodes, was determined in phosphate buffer solution (pH 7). The AA electrochemical sensor exhibited a linear response from 5×10⁻⁶ to 1.5×10⁻⁴ M (R²=0.9973) and from 1.55×10⁻⁴ to 3×10⁻⁴ M (R²=0.9983), detection limit=1×10⁻⁶ M, with a fast response time (3 s) for AA determination. In addition, the NiHCF‐PEDOT/GCE was advantageous in terms of its simple preparation, specificity, stability and reproducibility.