Wesentliche Frequenzbereiche bei der Filtereinstellung

Übersicht Fehler der Schaltelemente wirken sich längs des Frequenzbereiches verschieden auf den Dämpfungsverlauf aus. Eine geringe Abweichung kann einen unbrauchbaren Dämpfungsverlauf erzeugen. Diese Eigenschaft läßt sich nützen, da man an diesen Frequenzstellen den Dämpfungsverlauf leichter einstellen kann. Die Ableitung der charakteristischen Funktion nach der Frequenz, bezogen auf die charakteristische Funktion selbst, dient als Empfindlichkeit. An Empfindlichkeitspolstellen wird der Wert bei einem geringen Frequenzabstand definiert.

---

Essential frequency ranges for filter adjustment

Contents Faults of the circuit elements affect the attenuation characteristic differently. A small deviation may produce a useless characteristic. This property is useful as at these frequency ranges the characteristic is easier to be adjusted. The sensitivity is the differential of the characteristic function to the frequency referred to the characteristic function itself. At sensitiv poles the values are defined at very small frequency distances.

     

Characterization of grain boudaries in silicon solar cells

Contents Proceeding from the results for the barrier height of a grain boundary in solar cell material evaluated from the measurement of the zero bias conductance at a bicrystal test structure the density of grain boundary states and their distribution in energy have been determined. The method is a spectroscopic one and yields a steplike energy distribution. In accordance with theoretical calculations simulating typical energy distributions of the states we find, that the density of states in the middle of the gap is negligible and increases towards the conduction band edge to values of about 10¹² cm^–2 V^–1. The capture cross section ratio is found to range from 1C _p C _n 10. The method is proved to yield definite and unambiguous results by means of additional model calculations.

---

Charakterisierung von Korngrenzen in Silizium-Solarzellen

Übersicht Ausgangspunkt für die Bestimmung der Zustandsdichte und der Energieverteilung von Korngrenzen-Zuständen sind die Ergebnisse für die Höhe der Potentialbarriere an den Korngrenzen von Solarzellenmaterial. Die Barrierenhöhe ist dabei aus Messungen des Gleichstrom-Leitwertes am Spannungs-Nullpunkt von Bikristall-Teststrukturen gewonnen worden. Bei dieser Bestimmung der Energieverteilung der Zustandsdichte von Korngrenzen-Zuständen handelt es sich um eine spektroskopische Methode, die den Gesamtverlauf in diskontinuierlichen Stufen beschreibt. Dabei ergibt sich, daß die Zustandsdichte in der Mitte der Verbotenen Zone unter die Nachweisgrenze sinkt und in Richtung der Leitungsbandkante bis auf Werte von 10¹² cm^–2 eV^–1 ansteigt. Die hier erhaltene Energieverteilung von Korngrenzen-Zuständen wurde durch Modellrechnungen für vorgegebene Zustandsverteilungen bestätigt. Für das Verhältnis der Einfangquerschnitte findet man 1C _p C _n 10. Anhand zusätzlicher Modellrechnungen kann gezeigt werden, daß die Ergebnisse dieser Untersuchungsmethode numerisch abgesichert und eindeutig sind.

     

Validation of a Lab-on-Chip Assay for Measuring Sorafenib Effectiveness on HCC Cell Proliferation

Hepatocellular carcinoma (HCC) is a highly lethal cancer, and although a few drugs are available for treatment, therapeutic effectiveness is still unsatisfactory. New drugs are urgently needed for hepatocellular carcinoma (HCC) patients. In this context, reliable preclinical assays are of paramount importance to screen the effectiveness of new drugs and, in particular, measure their effects on HCC cell proliferation. However, cell proliferation measurement is a time-consuming and operator-dependent procedure. The aim of this study was to validate an engineered miniaturized on-chip platform for real-time, non-destructive cell proliferation assays and drug screening. The effectiveness of Sorafenib, the first-line drug mainly used for patients with advanced HCC, was tested in parallel, comparing the gold standard 96-well-plate assay and our new lab-on-chip platform. Results from the lab-on-chip are consistent in intra-assay replicates and comparable to the output of standard crystal violet proliferation assays for assessing Sorafenib effectiveness on HCC cell proliferation. The miniaturized platform presents several advantages in terms of lesser reagents consumption, operator time, and costs, as well as overcoming a number of technical and operator-dependent pitfalls. Moreover, the number of cells required is lower, a relevant issue when primary cell cultures are used. In conclusion, the availability of inexpensive on-chip assays can speed up drug development, especially by using patient-derived samples to take into account disease heterogeneity and patient-specific characteristics.     

A Fluorimetric Readout Reporting the Kinetics of Nucleotide‐Induced Human Ribonucleotide Reductase Oligomerization

Human ribonucleotide reductase (hRNR) is a target of nucleotide chemotherapeutics in clinical use. The nucleotide‐induced oligomeric regulation of hRNR subunit α is increasingly being recognized as an innate and drug‐relevant mechanism for enzyme activity modulation. In the presence of negative feedback inhibitor dATP and leukemia drug clofarabine nucleotides, hRNR‐α assembles into catalytically inert hexameric complexes, whereas nucleotide effectors that govern substrate specificity typically trigger α‐dimerization. Currently, both knowledge of and tools to interrogate the oligomeric assembly pathway of RNR in any species in real time are lacking. We therefore developed a fluorimetric assay that reliably reports on oligomeric state changes of α with high sensitivity. The oligomerization‐directed fluorescence quenching of hRNR‐α, covalently labeled with two fluorophores, allows for direct readout of hRNR dimeric and hexameric states. We applied the newly developed platform to reveal the timescales of α self‐assembly, driven by the feedback regulator dATP. This information is currently unavailable, despite the pharmaceutical relevance of hRNR oligomeric regulation.     

Modellrechnungen zur Beanspruchung heterogener elastischer Körper durch allseitigen Druck

Hydraulic comminution is especially suitable if the elastic properties of the components differ significantly. Here, the basic equations of the elasticity theory were drafted for two model shapes. In cylindrical as well as in Cartesian coordinates, the solution to the equation system is obtained through the solution of the bipotential equation via the introduction of a stress function. However, certain boundary conditions have to be fulfilled. In the case of all‐round constant compression, this can be achieved through an approach in integral form for both model shapes.     

Anticancer Ruthenium(III) Complex KP1019 Interferes with ATP‐Dependent Ca2+ Translocation by Sarco‐Endoplasmic Reticulum Ca2+‐ATPase (SERCA)

Sarco‐endoplasmic reticulum Ca²⁺‐ATPase (SERCA), a P‐type ATPase that sustains Ca²⁺ transport and plays a major role in intracellular Ca²⁺ homeostasis, represents a therapeutic target for cancer therapy. Here, we investigated whether ruthenium‐based anticancer drugs, namely KP1019 (indazolium [trans‐tetrachlorobis(1H‐indazole)ruthenate(III)]), NAMI‐A (imidazolium [trans‐tetrachloro(1H‐imidazole)(S‐dimethylsulfoxide)ruthenate(III)]) and RAPTA‐C ([Ru(η⁶‐p‐cymene)dichloro(1,3,5‐triaza‐7‐phosphaadamantane)]), and cisplatin (cis‐diammineplatinum(II) dichloride) might act as inhibitors of SERCA. Charge displacement by SERCA adsorbed on a solid‐supported membrane was measured after ATP or Ca²⁺ concentration jumps. Our results show that KP1019, in contrast to the other metal compounds, is able to interfere with ATP‐dependent translocation of Ca²⁺ ions. An IC₅₀ value of 1 μM was determined for inhibition of calcium translocation by KP1019. Conversely, it appears that KP1019 does not significantly affect Ca²⁺ binding to the ATPase from the cytoplasmic side. Inhibition of SERCA at pharmacologically relevant concentrations may represent a crucial aspect in the overall pharmacological and toxicological profile of KP1019.     

Evaluation of the Interaction between Phosphohistidine Analogues and Phosphotyrosine Binding Domains

We have investigated the interaction of peptides containing phosphohistidine analogues and their homologues with the prototypical phosphotyrosine binding SH2 domain from the eukaryotic cell signalling protein Grb2 by using a combination of isothermal titration calorimetry and a fluorescence anisotropy competition assay. These investigations demonstrated that the triazole class of phosphohistidine analogues are capable of binding too, suggesting that phosphohistidine could potentially be detected by this class of proteins in vivo.