The use of the platinum electrode coated with ultrathin poly(allylamine hydrochloride)/Nafion films for selective detection of hydrogen peroxide

In this paper, a novel polyelectrolyte multilayer (PEM) film-coated platinum electrode for the selective detection of H₂O₂ was presented. The PEM film was formed by the layer-by-layer assembly technique. The quartz crystal microbalance experiments showed that the thickness of the prepared Nafion layer was about 8 nm and depended on the pH of poly(allylamine hydrochloride) solution. The combination of different polyanions and polycations layers was investigated, and it is found that ploy(allylamine hydrochloride) (PAH) and Nafion composited film functioned best as a diffusion barrier toward uric acid (UA) and ascorbic acid (AA) while allowed H₂O₂ to pass through smoothly. When the platinum electrode coated with two-bilayer film, (PAH/Nafion)₂, the amperometric responses of 0.1 mM UA and 0.1 mM AA were respectively 0.008 and 0.006 μA, which were only 0.2% or less of the response of 0.1 mM H₂O₂ (4.0 μA). The linear response range of the electrode toward H₂O₂ was from 1.0 μM to 1.0 mM, and the detection limit was 0.3 μM. The electrode also displayed high operational stability and long-term storage stability.     

Glutamatergic alterations in the cortex of genetic absence epilepsy rats

Background  

In absence epilepsy, the neuronal hyper-excitation and hyper-synchronization, which induce spike and wave discharges in a cortico-thalamic loop are suspected to be due to an imbalance between GABA and glutamate (GLU) neurotransmission. In order to elucidate the role played by GLU in disease outcome, we measured cortical and thalamic extracellular levels of GLU and GABA. We used an in vivo quantitative microdialysis approach (no-net-flux method) in an animal model of absence epilepsy (GAERS). In addition, by infusing labelled glutamate through the microdialysis probe, we studied in vivo glutamate uptake in the cortex and thalamus in GAERS and non-epileptic control (NEC) rats. Expression of the vesicular glutamate transporters VGLUT1 and VGLUT2 and a synaptic component, synaptophysin, was also measured.     

The organizational effects of oxytocin on the central expression of estrogen receptor α and oxytocin in adulthood

Background  

Previous studies have demonstrated that neonatal manipulation of oxytocin (OT) has effects on the expression of estrogen receptor α (ERα) and the central production of oxytocin observed in juveniles (at weaning, 21 days of age). The goal of this study was to determine whether the effects of neonatal manipulation of OT last into adulthood, and if the effects differ from those observed during the early postnatal period. On the first day of life, prairie voles (Microtus ochrogaster) received one of three doses of OT (High, 3 μg; Med, 0.3 μg; Low, 0.03 μg), an OT antagonist, or isotonic saline. Another group was handled, but not injected. Then as adults, brains were collected, sectioned, and stained for ERα or OT using immunocytochemistry.     

Quantitative measurement of dynamic flow induced by <Emphasis Type="Italic">Tetrahymena pyriformis</Emphasis> (<Emphasis Type="Italic">T. pyriformis</Emphasis>) using micro-particle image velocimetry

Abstract  

In-depth quantitative visualization studies are required to understand the flow induced by swimming micro-organisms and find potential applications. The present study visualized the flow induced by Tetrahymena pyriformis of size 45–50 μm, which swam freely and via stimulation by galvanotaxis in a PDMS micro-chamber using a micro-particle image velocimetry system. The results showed that the maximum velocity of the induced flow was around 430 μm/s for free swimming and 700 μm/s for galvanotactic-controlled swimming. Due to the applied electric field, the electro-osmosis flow led to increased velocity of roughly 135 μm/s at 3 V/mm. The increased velocity stems from the increased motility of the cell under the electric field. Therefore, it was demonstrated that galvanotaxis can control the swimming direction and increase the induced velocity.     

Use of a silver ion selective electrode to assess mechanisms responsible for biological effects of silver nanoparticles

For a detailed analysis of the biological effects of silver nanoparticles, discrimination between effects related to the nano-scale size of the particles and effects of released silver ions is required. Silver ions are either present in the initial particle dispersion or released by the nanoparticles over time. The aim of this study is to monitor the free silver ion activity {Ag⁺} in the presence of silver nanoparticles using a silver ion selective electrode. Therefore, silver in the form of silver nanoparticles, 4.2 ± 1.4 nm and 2–30 nm in size, or silver nitrate was added to cell culture media in the absence or presence of A549 cells as a model for human type II alveolar epithelial cells. The free silver ion activity measured after the addition of silver nanoparticles was determined by the initial ionic silver content. The p {Ag⁺} values indicated that the cell culture media decrease the free silver ion activity due to binding of silver ions by constituents of the media. In the presence of A549 cells, the free silver ion activity was further reduced. The morphology of A549 cells, cultivated in DME medium containing 9.1% (v/v) FBS, was affected by adding AgNO₃ at concentrations of ≥30 μM after 24 h. In comparison, silver nanoparticles up to a concentration of 200 μM Ag did not affect cellular morphology. Our experiments indicate that the effect of silver nanoparticles is mainly mediated by silver ions. An effect of silver on cellular morphology was observed at p {Ag⁺} ≤ 9.2.     

Microwave-assisted rapid synthesis of Ag nanoparticles/graphene nanosheet composites and their application for hydrogen peroxide detection

Abstract  

Ag nanoparticles/graphene nanosheet (AgNPs/GN) composites have been rapidly prepared by a one-pot microwave-assisted reduction method, carried out by microwave irradiation of a N,N-dimethylformamide (DMF) solution of graphene oxide (GO) and AgNO₃. Several analytical techniques including UV–vis spectroscopy, FT-IR spectroscopy, Raman spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) have been used to characterize the resulting AgNPs/GN composites. It suggests that such composites exhibit good catalytic activity toward reduction of hydrogen peroxide (H₂O₂), leading to a H₂O₂ sensor with a fast amperometric response time of less than 2 s. The linear detection range is estimated to be from 0.1 to 100 mM (r = 0.999), and the detection limit is estimated to be 0.5 μM at a signal-to-noise ratio of 3.     

An electrochemical sensing platform based on a new Cd(II)-containing ionic liquid for the determination of trichloroacetic acid and bromate

The present work reports on the synthesis, characterization and performance of a new metal-containing ionic liquid [(C₃H₇)₂-bim]₂[CdCl₄] (bim = benzimidazole) as an electrocatalyst for trichloroacetic acid (TCA) and bromate reduction. The structure of Cd(II)-containing ionic liquid (Cd-IL) was characterized by X-ray crystallography, IR spectroscopy, and elemental analysis. The molecular structure contains two independent cations of 1,3-dipropyl-benzimidazolium and one anion of CdCl₄²⁻. The cadmium atom has a tetrahedral geometry by coordinating to four chlorine atoms. The melting point of Cd-IL is 73 °C. Electrochemical properties of the Cd-IL have been investigated by preparing bulk-modified carbon paste electrode, and Cd-IL is used as a binder and an electrocatalyst. This modified electrode has good electrocatalytic activity toward reduction of TCA and bromate. The detection limit and the sensitivity are 0.01 μM and 102.72 μA μM⁻¹ for trichloroacetic acid detection and 0.003 μM and 496.15 μA μM⁻¹ for bromate detection. This work demonstrates that the Cd-IL may become a new kind of functional material in constructing chemicals and biosensors.     

A bouncing droplet on an inclined hydrophobic surface

Abstract  

A trajectory of a water droplet of volume 0.4 μL impacting and bouncing on the hydrophobic surface (143°) inclined with 12° is presented. The photograph was taken with a 35 mm format digital SLR camera in a long-time exposure of 2.5 s illuminated with a couple of continuous point lighting. Also, a selected comparison is shown for snapshots of a bouncing millimetric droplet, having volume of 10 μL, inclined angle of 15° and contact angle of 147°, during the first impact between the experimental results which were recorded with a high-speed camera at 1,222 frames/s and the 3D computation (using a Volume-of-Fluid method on 330 × 70 × 35 computational grids with dt = 1.0 × 10⁻⁴ s) which was carried out with FLUENT software. At the impact the droplet is found to deform and then dissipate the energy due to the surface tension.     

Dimerization of the transmembrane domain of amyloid precursor proteins and familial Alzheimer's disease mutants

Background  

Amyloid precursor protein (APP) is enzymatically cleaved by γ-secretase to form two peptide products, either Aβ40 or the more neurotoxic Aβ42. The Aβ42/40 ratio is increased in many cases of familial Alzheimer's disease (FAD). The transmembrane domain (TM) of APP contains the known dimerization motif GXXXA. We have investigated the dimerization of both wild type and FAD mutant APP transmembrane domains.     

Soy isoflavone glycitein protects against beta amyloid-induced toxicity and oxidative stress in transgenic <Emphasis Type="Italic">Caenorhabditis elegans</Emphasis>

Background  

Epidemiological studies have associated estrogen replacement therapy with a lower risk of developing Alzheimer's disease, but a higher risk of developing breast cancer and certain cardiovascular disorders. The neuroprotective effect of estrogen prompted us to determine potential therapeutic impact of soy-derived estrogenic compounds. Transgenic C. elegans, that express human beta amyloid (Aβ), were fed with soy derived isoflavones genistein, daidzein and glycitein (100 μg/ml) and then examined for Aβ-induced paralysis and the levels of reactive oxygen species.     

Improving the beam quality of solid-state systems using both outside and inside cavity devices with variable optical characteristics along the cross section

This paper presents the results of application to different laser installations of soft or apodized apertures (AA) [1–3] with smooth transmission profiles decreasing from center to edges. Two types of AA, which were made of CaF₂:Pr crystals, have been used: induced absorption (IA) AA and photooxidation (PhO) AA. The 3–45-mm-diameter IA and PhO AA with smooth monotonic flat-top profiles have been used in 1.06-m laser amplifier systems to suppress hard-edge Fresnel diffraction rings in beam cross section and to increase the second harmonic conversion efficiency. The 3–4-mm-diameter PhO AA with bell-like transmission profiles were placed inside the 2.94-m and 1.06-m resonators of master oscillators. The tendency of the output energy to increase by 1.3–1.8 times and the decrease in beam divergence in single-mode lasing as compared with a hard-edge aperture have been observed in the experiments described below.Institute of Radioengineering and Electronics, Academy of Sciences of the USSR. Institute of General Physics, Academy of Sciences of the USSR. Translated from Preprint No. 17 of the Institute of General Physics, Moscow, 1991.     

Overcoming antigen masking of anti-amyloidbeta antibodies reveals breaking of B cell tolerance by virus-like particles in amyloidbeta immunized amyloid precursor protein transgenic mice

Background  

In prior work we detected reduced anti-Aβ antibody titers in Aβ-vaccinated transgenic mice expressing the human amyloid precursor protein (APP) compared to nontransgenic littermates. We investigated this observation further by vaccinating APP and nontransgenic mice with either the wild-type human Aβ peptide, an Aβ peptide containing the "Dutch Mutation", E22Q, or a wild-type Aβ peptide conjugated to papillomavirus virus-like particles (VLPs).     

Dynamics of laser-induced bubble collapse visualized by time-resolved optical shadowgraph

Abstract  

Following the first shock wave generation and the successive single bubble expansion after the breakdown by the Nd:YAG laser pulse with 35 mJ and 10 ns in distilled water, the strong secondary shock wave is generated at the instant of the bubble collapse. The single bubble expands up to 0.59 mm in radius, and then closes up by the pressure difference between the ambient liquid pressure at 10² kPa and the vapor pressure inside the bubble at 2 kPa. The maximum pressure up to 3 GPa is attained without the strong rebounding surface motion at about 93 μs after the laser shedding. We present time-resolved velocity measurements for estimating the extreme peak pressures of the first and second shock waves with the Rankine–Hugoniot analysis.     

Optimization of field emission properties from multi-walled carbon nanotubes using ceramic fillers

The field emission properties of multi-walled carbon nanotubes were examined using a screen-printed thick film with a diode-type configuration in a vacuum. The effects of various concentrations of two different ceramic fillers, indium tin oxide (ITO) powder and a glass frit, on the emission current density and turn-on field were evaluated. The emission properties of both pastes were dependent on the amount of filler. Considerably enhanced emission properties were obtained with the paste containing 5–10 wt.% of either ITO or the glass frit compared with those without a filler. The paste containing the ceramic filler showed enhanced emission properties compared with that containing the 5 wt.% Ag conventionally used, which confirmed the importance of the filler. The paste containing 10 wt.% ITO represented an emission current density of 176.4 μA/cm² at 5 V/μA, a turn-on field of 1.87 V/μA for an emission current density of 1 μA/cm² and a field enhancement factor of 7580. The paste formulation was also found to be suitable for fine patterning using UV-lithography techniques. A long-term stability test for 110 h of a paste containing 10 wt.% ITO revealed a half-life of approximately 30000 h, which is appropriate for commercial applications.     

Micro-PIV measurements of capillary underfill flows and effect of bump pitch on filling process

Abstract  

This study is devoted to investigate the effects of the bump pitch on the capillary underfill flow. A micro particle image velocimetry (μPIV) system was used to visualize the flows and the shape of meniscus. Transparent flip chip specimens with quadrilateral bump arrangements were fabricated by etching silicon on glass wafer. Six bump pitches from 60 to 160 μm were tested and glycerin was dispensed to fill into the flip chip specimens. From the present experiments, it is shown that the overall filling speed becomes faster at larger bump pitch and changes abruptly when the bump pitch is twice the bump diameter. The detailed meniscus movement also has different behavior if the bump pitch gets smaller and larger than twice the bump diameter. The variation of dynamic contact angle is synchronized with that of the meniscus velocity throughout the whole process. During the interaction with the flip chip bumps, the contact line of the meniscus becomes concave or convex. The curvature of the concave and convex lines is larger at the smaller bump pitch.     

Different methods for administering 17β-estradiol to ovariectomized rats result in opposite effects on ischemic brain damage

Background  

Numerous stroke studies have controversially shown estrogens to be either neuroprotective or neurodamaging. The discordant results observed in rat brain ischemia models may be a consequence of discrepancies in estrogen administration modes resulting in plasma concentration profiles far from those intended. To test this hypothesis we reproduced in detail and extended an earlier study from our lab using a different mode of 17β-estradiol administration; home-made silastic capsules instead of commercial slow-release 17β-estradiol pellets. Four groups of female rats (n = 12) were ovariectomized and administered 17β-estradiol or placebo via silastic capsules. All animals underwent MCAo fourteen days after ovariectomy and were sacrificed three days later.     

Jumping of a droplet on a superhydrophobic surface in AC electrowetting

Abstract  

Consistent droplet bouncing driven by AC electrowetting was achieved by introducing a superhydrophobic surface instead of conventional hydrophobic surfaces. A superhydrophobic surface is very effective to reduce interfacial energy barrier or adhesion, allowing complete detachment of a droplet from the substrate. While a fixed electric potential (100 V_rms) was applied, the shape deformation and the droplet bouncing were significantly influenced by the frequency of the AC electrowetting. Consistent droplet bouncing only occurred at very narrow frequency ranges (e.g., 30–31 Hz for 8 μL droplets), indicating that resonance dominates the droplet bouncing. Interestingly, the resonance was 1/2 sub-harmonics, where every other actuation was skipped, when the droplet was in the air. Theoretical evaluation of the resonant frequency based on the linear theory implies that the fundamental resonance between the AC electrowetting and the vertical vibration of the shape oscillation could be important to produce consistent droplet bouncing.     

GABAergic synaptic response and its opioidergic modulation in periaqueductal gray neurons of rats with neuropathic pain

Background  

Neuropathic pain is a chronic and intractable symptom associated with nerve injury. The periaqueductal gray (PAG) is important in the endogenous pain control system and is the main site of the opioidergic analgesia. To investigate whether neuropathic pain affects the endogenous pain control system, we examined the effect of neuropathic pain induced by sacral nerve transection on presynaptic GABA release, the kinetics of postsynaptic GABA-activated Cl^- currents, and the modulatory effect of μ-opioid receptor (MOR) activation in mechanically isolated PAG neurons with functioning synaptic boutons.     

Exposure to nanoscale particles and fibers during machining of hybrid advanced composites containing carbon nanotubes

This study investigated airborne exposures to nanoscale particles and fibers generated during dry and wet abrasive machining of two three-phase advanced composite systems containing carbon nanotubes (CNTs), micron-diameter continuous fibers (carbon or alumina), and thermoset polymer matrices. Exposures were evaluated with a suite of complementary instruments, including real-time particle number concentration and size distribution (0.005–20 μm), electron microscopy, and integrated sampling for fibers and respirable particulate at the source and breathing zone of the operator. Wet cutting, the usual procedure for such composites, did not produce exposures significantly different than background whereas dry cutting, without any emissions controls, provided a worst-case exposure and this article focuses here. Overall particle release levels, peaks in the size distribution of the particles, and surface area of released particles (including size distribution) were not significantly different for composites with and without CNTs. The majority of released particle surface area originated from the respirable (1–10 μm) fraction, whereas the nano fraction contributed ~10% of the surface area. CNTs, either individual or in bundles, were not observed in extensive electron microscopy of collected samples. The mean number concentration of peaks for dry cutting was composite dependent and varied over an order of magnitude with highest values for thicker laminates at the source being >1 × 10⁶ particles cm⁻³. Concentration of respirable fibers for dry cutting at the source ranged from 2 to 4 fibers cm⁻³ depending on the composite type. Further investigation is required and underway to determine the effects of various exposure determinants, such as specimen and tool geometry, on particle release and effectiveness of controls.

The ATLAS discovery potential for MSSM neutral Higgs bosons decaying to a μ<Superscript>+</Superscript>μ<Superscript>-</Superscript> pair in the mass range up to 130 GeV

Results are presented on the discovery potential for MSSM neutral Higgs bosons in the m_h-max scenario. The region of large cosβ, between 15 and 50, and mass between ≈95 and 130 GeV is considered in the framework of the ATLAS experiment at the large hadron collider (LHC), for a centre-of-mass energy = 14 TeV. This parameter region is not fully covered by the present data either from LEP or from Tevatron. The h/A bosons, supposed to be very close in mass in that region, are studied in the channel h/A→μ⁺μ^- accompanied by two b-jets. The study includes a method to control the most copious background, Z→μ⁺μ^- accompanied by two b-jets. A possible contribution of the H boson to the signal is also considered.