Oxygen Dependence in a Dual‐Phase Electrochemical Biosensing System

Oxygen dependence of a tyrosinase‐based electrochemical biosensor for determination of phenol in aqueous and organic media was systematically investigated. The result demonstrated that the enzymatic coupling reaction rate of tyrosinase (deoxy form) and O₂ to regenerate tyrosinase (oxy form) is a kinetically fast reaction, and the significant change of O₂ concentration in aqueous solution did not affect the coupling reaction. The further increase of O₂ concentration did not increase the overall oxidation reaction rate of the substrate at low substrate concentration (e.g.,<10 μM phenol) when O₂ concentration was greater than 8.9 ppm. The oxygen dependence was observed in the case of high substrate concentration due to insufficient amount of O₂ available for the regeneration of tyrosinase. In other words, the upper linear range is oxygen dependent for tyrosinase biosensors. The phenol biosensors employing microelectrodes had wider upper linear ranges than macroelectrodes in both aqueous and organic phase, which can be explained by the oxygen dependence.     

ESR study of free radicals formed upon UV irradiation of nitropentafluoroacetone in various solvents

The formation of CF₃C(O)CF₂N(O^.)O₂CF₂C(O)CF₃ free radicals upon the UV irradiation of nitropentafluoroacetone (1) in toluene and mesitylene is established by ESR. The most likely cause of their formation is the one-electron oxidation of the solvents by photoexcited1 followed by decay of the radical anion formed from1 with the expulsion of an NO₂ anion and attachment of the radical to a molecule of original1. The irradiation of 1 in triethylsilane results in the elimination of a fluoride ion and fixation of a CF₃COCFN(O^–)O' radical. UV irradiation of ketone1 in pentane results in the abstraction of a hydrogen atom from the solvent and the formation of a CF₃COCF₂N(OH)O ' radical.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 512–514, March, 1993.     

Aqueous partial molar heat capacities and volumes for NaTcO4 and NaReO4

A flow microcalorimeter/densimeter system has been commissioned to measure heat capacities and densities of solutions containing radioactive species as a function of temperature. Measurements were made for NaTcO₄(aq) at six temperatures (189.15 K to 373.15 K for the heat capacities, 287.43 K to 396.67 K for the densities) over the molality range 0.01 to 0.29 mol-kg^–1. Measurements for NaReO₄(aq) (NaReO₄ is a common nonradioactive analogue for NaTcO₄) were made under similar conditions, but for eight temperatures and a more extensive range of molalities, 0.05 to 0.65 mol-kg^–1. Heat capacities of NaCl(aq) reference solutions were also measured from 293.15 K to 398.15 K.The heat capacity and density data are analysed using Pitzer's ioninteraction model. Equations for the apparent molar heat capacities and volumes are reported. Values of the NaReO₄(aq) partial molar heat capacities are compared to literature values based on integral heats of solution. The agreement between the two sets of NaReO₄ results is good below 330 K, but only fair at the higher temperatures. Values of the partial molar volumes have also been derived. Using literature values and the results of our experiments, it is calculated that the disproportionation of hydrated TcO₂(s) to form TcO ₄ ^– (aq) and Tc(cr) occurs more readily at high temperatures. The uncertainties introduced by using thermodynamic values for ReO ₄ ^– (aq), in the absence of values for TcO ₄ ^– (aq), are discussed.     

Frequency and voltage-dependent electrical and dielectric properties of Al/Co-doped PVA/p-Si structures at room temperature

In order to investigate of cobalt-doped interracial polyvinyl alcohol （PVA） layer and interface trap （Dit） effects, A1/p- Si Schottky barrier diodes （SBDs） are fabricated, and their electrical and dielectric properties are investigated at room temperature. The forward and reverse admittance measurements are carded out in the frequency and voltage ranges of 30 kHz-300 kHz and -5 V-6 V, respectively. C-V or er-V plots exhibit two distinct peaks corresponding to inversion and accumulation regions. The first peak is attributed to the existence of Dit, the other to the series resistance （Rs）, and interfacial layer. Both the real and imaginary parts of dielectric constant （er and err） and electric modulus （Mr and Mrr）, loss tangent （tan~）, and AC electrical conductivity （aac） are investigated, each as a function of frequency and applied bias voltage. Each of the M~ versus V and Mrr versus V plots shows a peak and the magnitude of peak increases with the increasing of frequency. Especially due to the Dit and interfacial PVA layer, both capacitance （C） and conductance （G/w） values are strongly affected, which consequently contributes to deviation from both the electrical and dielectric properties of A1/Co-doped PVA/p-Si （MPS） type SBD. In addition, the voltage-dependent profile of Dit is obtained from the low-high frequency capacitance （CLF-CHF） method.     

On a class of dependent Sparre Andersen risk models and a bailout application

In this paper a one-dimensional surplus process is considered with a certain Sparre Andersen type dependence structure under general interclaim times distribution and correlated phase-type claim sizes. The Laplace transform of the time to ruin under such a model is obtained as the solution of a fixed-point problem, under both the zero-delayed and the delayed cases. An efficient algorithm for solving the fixed-point problem is derived together with bounds that illustrate the quality of the approximation. A two-dimensional risk model is analyzed under a bailout type strategy with both fixed and variable costs and a dependence structure of the proposed type. Numerical examples and ideas for future research are presented at the end of the paper.     

Temperature dependence of GaSb and AlGaSb solar cells

Sb-based alloys offer great potential for photovoltaic and thermophotovoltaic applications. In this paper, we study the performance of Al_xGa_1-xSb (x = 0, 0.15, and 0.50) single-junction solar cells over a temperature range of 25–250 °C. The dark current-voltage, one-sun current-voltage, and external quantum efficiency measurements were acquired at different temperatures. Correlations between experimental and numerical results are made to draw conclusions about the thermal behavior of the cells. It is shown that, while the bandgaps decrease linearly with temperature leading to the reduction of open-circuit voltages, the short-circuit current densities decrease with non-linear trends. The temperature-dependent dark current densities were extracted by fitting the dark current-voltage curves to single- and double-diode models to give an insight into the effect of intrinsic carrier concentration (n_i) on the cell performance. We find that the n_i has a significant impact on temperature-dependent cell performance. These findings could lay a groundwork for the future Sb-based photovoltaic systems that operate at high temperatures.     

Implications of accelerated self-healing as a key design knob for cross-layer resilience

In this paper we propose a cross-layer accelerated self-healing (CLASH) system which “repairs” its wearout issues in a physical sense through accelerated and active recovery, by which wearout can be reversed while actively applying several accelerated self-healing techniques, such as high temperature and negative voltages. Different from previous solutions of coping with wearout issues (e.g. BTI) by “tolerating”, “slowing down” or “compensating”, which still leave the irreversible (permanent) wearout component unchecked, the proposed solution is able to fully avoid the irreversible wearout through periodic rejuvenation, and this is inspired by the explored frequency dependent behaviors of wearout and (accelerated and active) recovery based on measurements on FPGAs. We demonstrate a case where the chip can always be brought back to the fresh status by employing a pattern of 31-h regular operation (under room temperature and nominal voltage) followed by a 1-h accelerated self-healing (under high temperature and negative voltage). The proposed system integrates the notions of accelerated self-healing across multiple layers of the system stack. At the circuit level, a negative voltage generator and heating elements are designed and implemented; at the architecture level, the core can be allocated in a way such that the dark silicon or redundant resources can be healed by active elements; at the system level, right balance of stress and accelerated/active recovery can be employed by the system scheduler to fully mitigate the wearout; various wearout sensors act as the media between different layers. Overall, these techniques work together to guarantee that the whole system performs for more of the time at higher levels of performance and power efficiency by fully taking advantage of the extra opportunities enabled by the accelerated self-healing.     

Viscosity dependence of electrochemical etching for gold tip fabrication

We suggest an electrochemical etching method with viscous etchant to enhance the sharpness of tip of scanning probe microscope. The viscosity of the etchant mixed with HCl solution and glycerol was used as a control parameter in addition to the voltage applied to the tip. In order to improve the sharpness of the tip, a nano-scale meniscus formed between the end of the tip and the liquid level was used. The shapes, aspect ratios, and radii of tips were measured depending on the concentration of the etchant. It was found that the tip etched with the mixed liquid with glycerol was sharper than the tip with the pure HCl solution. This can be explained by the fact that the meniscus formed by viscous liquid is maintained with a thinner diameter and causes final etching until the meniscus bridge is ruptured.     

Statistical inference for Vasicek-type model driven by Hermite processes

Let $Z$ denote a Hermite process of order $q\ge 1$ and self-similarity parameter $H\in (\frac{1}{2},1)$. This process is $H$-self-similar, has stationary increments and exhibits long-range dependence. When $q=1$, it corresponds to the fractional Brownian motion, whereas it is not Gaussian as soon as $q?2$. In this paper, we deal with a Vasicek-type model driven by $Z$, of the form $d{X}_t=a(b?X_t)dt+d{Z}_t$. Here, $a>0$ and $b\in \mathbb{R}$ are considered as unknown drift parameters. We provide estimators for $a$ and $b$ based on continuous-time observations. For all possible values of $H$ and $q$, we prove strong consistency and we analyze the asymptotic fluctuations.