Numerische Simulation dichtebeeinflusster und reaktiver Stofftransportprozesse im Grundwasser

Für die Prognose der Gef?hrdung der Schutzgüter Grundwasser und Boden gewinnen numerische Programmsysteme zur Simulation von Str?mungs- und Stofftransportprozessen immer mehr an Bedeutung. Im Mittelpunkt des Interesses stehen dabei komplexe geochemische Reaktionsvorg?nge, dichtebeeinflusste Str?mungs- und Stofftransportvorg?nge, komplizierte hydraulische Gegebenheiten und die Parameterbelegung gro?er Modelle. Das hier beschriebene Programmsystem MODCALIF erlaubt die dreidimensionale Simulation der dichtebeeinflussten Str?mung und des Stofftransportes. Die Verwendung neu integrierter L?sungalgorithmen erm?glicht eine grobe r?umliche Diskretisierung und damit eine deutliche Verringerung des Rechenaufwandes. Die Berücksichtigung unterschiedlicher Ans?tze zur Beschreibung der Wechselwirkungen zwischen gel?stem Stoff und Feststoff sowie die Kopplung mit dem geochemischen Gleichgewichtsprogramm PHREEQC erlauben die Simulation des Stofftransportes für vielf?ltige Problemstellungen. Aufbauend auf einer kurzen Darstellung der theoretischen Grundlagen des Programmsystems MODCALIF wird das Programm verifiziert und seine Anwendbarkeit an zwei ausgew?hlten Fallbeispielen praktisch demonstriert.     

Experiential learning of clinical skills by beginning nursing students: "coaching" project by fourth-year student interns

Cutaneous larva migrans is the result of infestation of human skin by helminth larvae, which burrow through the epidermis. This route of infestation makes the foot a typical site for origination of this infection. Children, who frequently play barefoot in locations where the most common of the helminth larvae, the dog and cat hookworms, are endemic, are at particular risk for this disorder. This article reviews the differential diagnosis of cutaneous larva migrans and current concepts in management. Two cases of related children who presented to their pediatricians with this condition are reported.     

Elastographic dynamic range expansion using variable applied strains

In elastography, we want to image the entire range of stiffnesses of the elastic components found in inhomogeneous tissues. In order to achieve this, the elastographic dynamic range should equal the entire stiffness dynamic range in the target. Various sources of noise limit the dynamic range of elastography. The recently-defined strain filter concept offers an analytical and graphical way of observing these limitations. In this paper, we describe a method that achieves the expansion of the elastographic dynamic range. It involves the application of variable strains in combination with selective storage of strain data that have optimal elastographic signal-to-noise ratios. This expands the current dynamic range of elastography by orders of magnitude when compared to single compression elastography. The process is explained theoretically using the strain filter framework, and 1 D as well as 2D tissue simulations are used to corroborate the theory.     

Optimization of speed-of-sound estimation from noisy ultrasonic signals

The effects of prefiltering and the choice of time-delay estimators and statistical data reduction techniques on the precision of speed-of-sound estimation were investigated using the beam-tracking technique. It was found that prefiltering the data with an ideal 50-kHz low-pass filter improved the precision of the estimation in all cases. Echo cross-correlation had an advantage over peak detection for low signal-to-noise ratio (SNR) levels, but its advantage diminished as the signal-to-noise level improved due to filtering. The linear regression method was superior to the paired-point analysis technique under all conditions. Using the optimal set of parameters, precision on the order of 0.1% was achieved in a tissue-mimicking phantom when one beam was tracking along 75 mm in 1-mm increments.     

Functionalized Cellulose for Water Purification,Antimicrobial Applications,and Sensors

As the most abundant natural polymer, cellulose presents a unique advantage for large‐scale applications. To fully unlock its potential, the introduction of desired functional groups onto the cellulose backbone is required, which can be realized by either chemical bonding or physical surface interactions. This review gives an overview of the chemistry behind the state‐of‐the‐art functionalization methods (e.g., oxidation, esterification, grafting) for cellulose in its various forms, from nanocrystals to bacterial cellulose. The existing and foreseeable applications of the obtained products are presented in detail, spanning from water purification and antibacterial action, to sensing, energy harvesting, and catalysis. A special emphasis is put on the interactions of functionalized cellulose with heavy metals, focusing on copper as a prime example. For the latter, its toxicity can either have a harmful influence on aquatic life, or it can be conveniently employed for microbial disinfection. The reader is further introduced to recent sensing technologies based on functionalized cellulose, which are becoming crucial for the near future especially with the emergence of the internet of things. By revealing the potential of water filters and conductive clothing for mass implementation, the near future of cellulose‐based technologies is also discussed.     

应用酶放大电极的免疫测定

该文评述了应用酶放大电极的免疫测定法的进展,从原理和应用两方面进行了探讨.着重介绍了作者所在实验室在90年代以来的相关工作.     

A theoretical framework for performance characterization of elastography: the strain filter

This paper presents a theoretical framework for performance characterization in strain estimation, which includes the effect of signal decorrelation, quantization errors due to the finite temporal sampling rate, and electronic noise. An upper bound on the performance of the strain estimator in elastography is obtained from a strain filter constructed using these limits. The strain filter is a term used to describe the nonlinear filtering process in the strain domain (due to the ultrasound system and signal processing parameters) that allows the elastographic depiction of a limited range of strains from the compressed tissue. The strain filter predicts the elastogram quality by specifying the elastographic signal-to-noise ratio (SNR(e)), sensitivity, and the strain dynamic range at a given resolution. The dynamic range is limited by decorrelation errors for large tissue strain values, and electronic noise for low strain values. Tradeoffs between different techniques used to enhance elastogram image quality may also be analyzed using the strain filter.     

Biased random mutagenesis of peptides: determination of mutation frequency by computer simulation

Cassette mutagenesis is a method of protein engineering whichgenerates a wide diversity of genetic variants that can be subjectedto either selection or screening. As long as the target sequenceto be modified is kept short (corresponding to four to six aminoacids), complete combinatorial libraries can be produced. Amajor problem arises when longer peptides are to be engineeredfor desired functions. In such situations the production ofa limited collection of variants can be helpful; thus, biasedrandom mutagenesis and ‘doping schemes’ have beenreported previously. Here we describe a computer algorithm thatenables the determination of the degree of phosphoramidite contaminationof nucleotide precursor reservoirs. Through simulation of biologicaltranslation, the algorithm allows the prediction of the effectof contamination levels on the number of mutations to occurfor any given peptide sequence. In this study the cholinergicbinding site was used as a model sequence (22 amino acids).Considerations, based on the computer program, are discussedregarding the efficient design of phage-display combinatoriallibraries.     

Injection molding of thermotropic liquid crystal polymers

Thermotropic liquid crystal polymers consist of rod-like molecules and are often called “self reinforcing thermoplastics.” Their rheological behaviors as well as orientation development during processing are often very similar to those of short fiber-filled composites. Without reinforcement, the polymer shows superior mechanical properties to conventional glass fiber-reinforced engineering resins. The orientation distribution in the crosssection as well as flow patterns in the molded thermotropic polymers are clearly visible to the naked eye due to color differences. This makes it particularly convenient to study the orientation distribution as well as the flow patterns of packing, back flow, jetting, flow instabilities, and weld line formation in injection molding. This paper discusses physical properties of a typical ther motropic polymer and their relationship to mold filling process in the injection molding.