Traceable radiometric calibration of semiconductor detectors and their application for thermodynamic temperature measurement

The non-contact measurement of temperature by using the emitted thermal radiation has been an innovative field of measurement science and fundamental physics for more than a hundred years. It saw the first highlight in Gustav Kirchhoff’s principle of a blackbody with ideal emission characteristics and culminated in Max Planck’s formulation of the law of thermal radiation, the so-called Planck’s law, forming the foundation of quantum physics. A boost in accuracy was the development of semiconductor detectors and the cryogenic electrical substitution radiometer in the late 1970s. Semiconductor detectors, namely photodiodes, deliver an electrical current proportional to the absorbed optical radiation. Due to the measurements of thermal radiation over a wide range of temperature and wavelength, thermodynamic temperature measurements with radiometric methods have set benchmarks to all, the electrical, dimensional and optical metrology. The paper describes the measurement of the spectral responsivity of semiconductor detectors traceable to the SI units and their application for thermodynamic temperature measurement by the absolute measurement of thermal radiation using filter radiometers with calibrated spectral irradiance responsivity.     

Classical analog of electromagnetically induced absorption in plasmonics

The ability to manipulate the phase shift between two resonantly coupled plasmonic oscillators in a controlled fashion has been unavailable up to now. Here we present a strategy to overcome this limitation by employing the benefits of near-field coupling on the one hand and retardation effects due to far-field coupling on the other hand. We theoretically and experimentally demonstrate that in the intermediate regime the coupling of a broad dipolar to a narrow dark quadrupolar plasmon resonance is possible while simultaneously allowing for a retardation-induced phase shift. This leads to constructive interference and enhanced absorption. The observed phenomenon can thus be termed a classical analog of electromagnetically induced absorption.     

Contraction and resting stiffness of isolated cardiac muscle: effects of inotropic agents

The purpose of this study was to test the hypothesis that either hypoxia and its combined effects with extracellular calcium (Ca), digoxin, and ouabain, or these positive inotropic agents acting alone or in combination, influence contraction and resting stiffness of isolated papillary muscle. Stiffness was measured utilizing the sinusoidal forcing function technique. Neither an increase in extracellular calcium concentration (from 2.5 to 4.0 mM) nor digoxin or ouabain in either Ca concentration altered contraction or resting stiffness in the well-oxygenated environment. Resting stiffness for any given resting tension was increased at the end of hypoxia only in the presence of digoxin, and this occurred in both 2.5 mM Ca (P less than 0.02) and in 4.0 mM Ca (P = 0.05). Contraction stiffness for any given tension was increased in 2.5 mM Ca by hypoxia alone (P less than 0.05) and by hypoxia in the presence of digoxin (P less than 0.005) and ouabain (P less than 0.02), but was not increased in any experiments conducted in 4.0 mM Ca. The conclusions from these data are that certain experimental conditions of the study evoked different directional changes in stiffness and contractility. Further, changes in contraction stiffness are not always paralleled by changes in resting stiffness.     

Insights about the Absence of Rb Cation from the 3D Perovskite Lattice: Effect on the Structural,Morphological, and Photophysical Properties and Photovoltaic Performance

Efficiencies >20% are obtained from the perovskite solar cells (PSCs) employing Cs⁺ and Rb⁺ based perovskite compositions; therefore, it is important to understand the effect of these inorganic cations specifically Rb⁺ on the properties of perovskite structures. Here the influence of Cs⁺ and Rb⁺ is elucidated on the structural, morphological, and photophysical properties of perovskite structures and the photovoltaic performances of resulting PSCs. Structural, photoluminescence (PL), and external quantum efficiency studies establish the incorporation of Cs⁺ (x < 10%) but amply rule out the possibility of Rb‐incorporation into the MAPbI₃ (MA = CH₃NH₃ ⁺) lattice. Moreover, morphological studies and time‐resolved PL show that both Cs⁺ and Rb⁺ detrimentally affect the surface coverage of MAPbI₃ layers and charge‐carrier dynamics, respectively, by influencing nucleation density and by inducing nonradiative recombination. In addition, differential scanning calorimetry shows that the transition from orthorhombic to tetragonal phase occurring around 160 K requires more thermal energy for the Cs‐containing MAPbI₃ systems compared to the pristine MAPbI₃. Investigation including mixed halide (I/Br) and mixed cation A‐cation based compositions further confirms the absence of Rb⁺ from the 3D‐perovskite lattice. The fundamental insights gained through this work will be of great significance to further understand highly promising perovskite compositions.     

Converging multistep methods for initial value problems involving multivalued maps

Every consistent and strongly stable multistep method of stepnumberk yields a solution, of the setvalued initial value problem \(\dot y \in F(t,y),y(t_0 ) = y_0 \) . The setF(t, z) is assumed to be nonvoid, convex and closed. Upper semicontinuity of F with respect to both variables is not required everywhere. If the initial value problem is uniquely solvable, the solutions of the multistep method will converge to the solution of the continuous problem. These results carry over to functional differential equations \(\dot y \in F(t,M_t y)\) of Volterra type and to discontinuous problems \(\dot y(t) = f(t,M_t y)\) in the sense of A.F. Filippov. A difference method is applied to the discontinuous delay equation \(\ddot x(t) + 2D\dot x(t) + \omega ^2 x(t) = = - \operatorname{sgn} (x(t - \tau ) + \dot x(t - \tau ))\) . In the limit τ→0 we obtain results for the problem \(\ddot x + 2D\dot x + \omega ^2 x = = - \operatorname{sgn} (x + \dot x)\) which cannot be solved classically everywhere.     

Surface Modification of Nickel/Titanium Alloy and Titanium Surfaces via a Polyelectrolyte Multilayer/Calcium Phosphate Hybrid Coating

The report shows that simple LbL deposition of positively charged chitosan and negatively charged heparin can be used to efficiently modify the native surface of both NiTi and Ti without any previous treatments. Moreover, mineralization of the polymer multilayers with calcium phosphate leads to surfaces with low contact angles around 70 and 20° for NiTi and Ti, respectively. This suggests that a polymer multilayer/calcium phosphate hybrid coating could be useful for making NiTi or Ti implants that are at the same time antibacterial (via the chitosan), suppress blood clot formation (via the heparin), and favor fast endothelialization (via the improved surface hydrophilicity compared to the respective neat material).

     

Betulinic Acid Derivatives NVX-207 and B10 for Treatment of Glioblastoma—An in Vitro Study of Cytotoxicity and Radiosensitization

Betulinic acid (BA), a pentacyclic triterpene, represents a new therapeutic substance that has potential benefits for treating glioblastoma. Recently, new strategies for producing BA derivatives with improved properties have evolved. However, few studies have examined the combination of BA or BA derivatives using radiotherapy. The effects of two BA derivatives, NVX-207 and B10, on cellular and radiobiological behavior were analyzed using glioblastoma cell lines (U251MG, U343MG and LN229). Based on IC₅₀ values under normoxic conditions, we detected a 1.3–2.9-fold higher cytotoxicity of the BA derivatives B10 and NVX-207, respectively, compared to BA. Incubation using both BA derivatives led to decreased cell migration, cleavage of PARP and decreased protein expression levels of Survivin. Weak radiation sensitivity enhancement was observed in U251MG cells after treatment with both BA derivatives. The enhancement factors at an irradiation dose of 6 Gy after treatment with 5 µM NVX-207 and 5 µM B10 were 1.32 (p = 0.029) and 1.55 (p = 0.002), respectively. In contrast to BA, neither NVX-207 nor B10 had additional effects under hypoxic conditions. Our results suggest that the BA derivatives NVX-207 and B10 improve the effects of radiotherapy on human malignant glioma cells, particularly under normoxic conditions.