Phototransistor noise model based on noise measurements on PNP PIN phototransistors

A noise model for phototransistors in open base configuration is presented. The model was developed from the noise measurements on four different phototransistor designs. The extracted current gains from the noise model were verified by measured current gains from Gummel measurements. Furthermore the current noise spectral density was modeled and compared with the noise measurements. A difference of less than 12 % in the current gain was achieved. In addition to the extracted current gains also the most dominant shot noise terms including their values of each phototransistor are extracted.     

Statistical properties of a modified standard map in quantum and classical regimes

Nonlinear Dynamics - We present a model—a modified standard map. This model has interesting properties that allow quantum–classical correspondences to be studied. For some range of...     

Multifunctional Cationic PeptoStars as siRNA Carrier: Influence of Architecture and Histidine Modification on Knockdown Potential

RNA interference provides enormous potential for the treatment of several diseases, including cancer. Nevertheless, successful therapies based on siRNA require overcoming various challenges, such as poor pharmacokinetic characteristics of the small RNA molecule and inefficient cytosolic accumulation. In this respect, the development of functional siRNA carrier systems is a major task in biomedical research. To provide such a desired system, the synthesis of 3‐arm and 6‐arm PeptoStars is aimed for. The different branched polypept(o)idic architectures share a stealth‐like polysarcosine corona for efficient shielding and a multifunctional polylysine core, which can be independently varied in size and functionality for siRNA complexation‐, transport and intra cellular release. The special feature of star‐like polypept(o)ides is in their uniform small size (<20 nm) and a core–shell structure, which implies a high stability and stealth‐like properties and thus, they may combine long circulation times and a deep penetration of cancerous tissue. Initial toxicity and complement studies demonstrate well tolerated cationic PeptoStars with high complexation capability toward siRNA (N/P ratio up to 3:1), which can lead to potent RNAi for optimized systems. Here, the synthetic development of 3‐arm and 6‐arm polypept(o)idic star polymers, their modification with endosomolytic moieties, and first in vitro insights on RNA interference are reported on.     

Ca12[Mn19N23] and Ca133[Mn216N260]: Structural Complexity by 2D Intergrowth

Two new calcium nitridomanganates, Ca₁₂[Mn₁₉N₂₃] (P3, a=11.81341(3) Å, c=5.58975(2) Å, Z=1) and Ca₁₃₃[Mn₂₁₆N₂₆₀] ( , a=39.477(1) Å, c=5.5974(2) Å, Z=1), were obtained by a gas–solid reaction of Ca₃N₂ and Mn with N₂ at 1273 K and 1223 K, respectively. The crystal structure of Ca₁₂[Mn₁₉N₂₃] was determined from high‐resolution X‐ray synchrotron powder diffraction data, whereas single‐crystal X‐ray diffraction was employed to establish the crystal structure of the Ca₁₃₃[Mn₂₁₆N₂₆₀] phase, which classifies as a complex metallic alloy (CMA). Both crystal structures have 2D nitridomanganate layers containing similar building blocks but of different levels of structural complexity. Bonding analysis as well as magnetic susceptibility and electron spin resonance measurements revealed that only a fraction of the Mn atoms in both structures carries a localized magnetic moment, while for most Mn species the magnetism is quenched as a result of metal–metal bond formation.     

Mechanistic Studies on the Organocatalytic α‐Chlorination of Aldehydes: The Role and Nature of Off‐Cycle Intermediates

Herein we report the isolation and characterization of aminal intermediates in the organocatalytic α‐chlorination of aldehydes. These species are stable covalent ternary adducts of the substrate, the catalyst and the chlorinating reagent. NMR‐assisted kinetic studies and isotopic labeling experiments with the isolated intermediate did not support its involvement in downstream stereoselective processes as proposed by Blackmond. By tuning the reactivity of the chlorinating reagent, we were able to suppress the accumulation of rate‐limiting off‐cycle intermediates. As a result, an efficient and highly enantioselective catalytic system with a broad functional group tolerance was developed.     

Utility Function Programs and Optimization over the Efficient Set in Multiple-Objective Decision Making

Natural basic concepts in multiple-objective optimization lead to difficult multiextremal global optimization problems. Examples include detection of efficient points when nonconvexities occur, and optimization of a linear function over the efficient set in the convex (even linear) case. Assuming that a utility function exists allows one to replace in general the multiple-objective program by a single, nonconvex optimization problem, which amounts to a minimization over the efficient set when the utility function is increasing. A new algorithm is discussed for this utility function program which, under natural mild conditions, converges to an -approximate global solution in a finite number of iterations. Applications include linear, convex, indefinite quadratic, Lipschitz, and d.c. objectives and constraints.     

Three-transition cascade erbium laser at 1.7, 2.7, and 1.6 microm

We report on an upconversion cascade laser in an erbium-doped ZBLAN fiber emitting simultaneously on the three transitions (4)S(3/2) ? (4)I(9/2) at 1.7 microm , (4)I(11/2) ? (4)I(13/2) at 2.7 microm , and (4)I(13/2) ? (4)I(15/2) at 1.6 microm . At moderate pump powers, the laser transition at 1.6 microm supports 2.7-microm lasing and permits a slope efficiency at 2.7 microm of 15% versus launched pump power. Above the threshold of upconversion lasing at 1.7 microm , the slope efficiency at 2.7 microm increases to 25.4%. Taking pump excited-state absorption into account, this value represents more than 90% of the theoretical slope efficiency. A transversely single-mode output power of 99mW is achieved at 2.7 microm.     

Pterin chemistry. 46. Identification of substituted tetrahydropterins through gas chromatography and mass spectrometry

When treated with cyanide ion, 1,2:5,6-di-O-isopropylidene-α-_D-ribo-hexofuranos-3-ulose yields one or the other of the two corresponding epimeric cyanhydrines, depending on the experimental conditions. One of these epimers, reacted with ammonium cyanide, yields the corresponding amino-nitrile, the other being unreactive. Several derivatives of these compounds are briefly described.