Über die Beschleunigung und Verzögerung von elektrischen Ladungsträgern im Vakuum bei explizit vorgegebenen elektrischen und kinetischen Randwerten

Übersicht Die Theorie der Ionenraketen basiert darauf, daß die elektrische Feldstärke und die Geschwindigkeit am Beginn der Beschleunigungsstrecke vernachlässigbar sind. Will man Ionen-Durchström-Triebwerke oder Ionen-Vielfachbeschleuniger konzipieren, so kann die elektrische Feldstärke und die Geschwindigkeit am Beginn der Umwandlungstrecke wesentlich von Null abweichen. Es wird deshalb hier eine Theorie der Ionenbeschleunigung entwickelt, bei der die elektrischen und kinetischen Randwerte innerhalb der physikalischen Grenzen frei wählbar sind und explizit vorgegeben werden können. Mit der gleichen Zielsetzung wird die Ionenverzögerung behandelt, welche die Grundlage für die Konzipierung von Ionenstrahl-Generatoren ist. Mit dieser Arbeit wird also ein Beitrag zur Theorie der elektrokinetischen Energiewandlungsprozesse geleistet.

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On the acceleration and deceleration of electric charge carriers in vacuum with explicitely given electrical and kinetic boundary values

Contents The theory of ion rocket engines is based upon the neglection of the electric field strength and the velocity at the beginning of the acceleration path. In the design of ion-flow accelerators or multi-stage ion accelerators the strength of the electric field and the velocity at the beginning of the transfer path may differ significantly from zero. A theory of the ion acceleration is therefore developed, where the electrical and kinetic boundary values can be chosen freely within the limits of physics and where these boundary values can be given explicitely. With the same intent the deceleration of ions is treated: the basic design of ion-jet power generators. This paper may therefore be a contribution to the theory of processes of electro-kinetic energy transfer.

     

Predicting 1-year outcome following acute myocardial infarction: physicians versus computers

Whether decision rules derived statistically from patient data can produce better decisions than an expert clinician or a model of the expert clinician (expert system) is controversial. We examined this issue in the context of predicting cardiac death by 1 year for patients discharged from the hospital following acute myocardial infarction. Decision rules were derived from a base sample of 781 patients. These decision rules and three experienced cardiologists then estimated probability of death by 1 year for each patient in a separate test sample (n = 400). In our evaluation of the performance of the decision rules and physicians, we detected no differences, although the decision rules and physicians tended to classify the patients somewhat differently. Further multivariate analyses on the physicians' predictions showed that two of the physicians paid attention to somewhat different variables than the third physician. Lack of agreement among expert cardiologists would complicate modeling of a consensual decision-making process within the framework of an expert system.     

Plasma and nanoparticle shielding during pulsed laser ablation in liquids cause ablation efficiency decrease

Understanding shielding cross-effects is a prerequisite for maximal power-specific nanosecond laser ablation in liquids(LAL).However,discrimination between cavitation bubble(CB),nanoparticle(NP),and shielding,e.g.,by the plasma or a transient vapor layer,is challenging.Therefore,CB imaging by shadowgraphy is performed to better understand the plasma and laser beam-NP interaction during LAL.By comparing the fluence-dependent CB volume for ablations performed with 1 ns pulses with reports from the literature,we find larger energy-specific CB volumes for 7 ns-ablation.The increased CB for laser ablation with higher ns pulse durations could be a first explanation of the efficiency decrease reported for these laser systems having higher pulse durations.Consequently,1 ns-LAL shows superior ablation efficiency.Moreover,a CB cascade occurs when the focal plane is shifted into the liquid.This effect is enhanced when NPs are present in the fluid.Even minute amounts of NPs trapped in a stationary layer decrease the laser energy significantly,even under liquid flow.However,this local concentration in the sticking film has so far not been considered.It presents an essential obstacle in high-yield LAL,shielding already the second laser pulse that arrives and presenting a source of satellite bubbles.Hence,measures to lower the NP concentration on the target must be investigated in the future.     

ICOS is an inducible T-cell co-stimulator structurally and functionally related to CD28

The T-cell-specific cell-surface receptors CD28 and CTLA-4 are important regulators of the immune system. CD28 potently enhances those T-cell functions that are essential for an effective antigen-specific immune response, and the homologous CTLA-4 counterbalances the CD28-mediated signals and thus prevents an otherwise fatal overstimulation of the lymphoid system. Here we report the identification of a third member of this family of molecules, inducible co-stimulator (ICOS), which is a homodimeric protein of relative molecular mass 55,000-60,000 (M(r) 55K-60K). Matching CD28 in potency, ICOS enhances all basic T-cell responses to a foreign antigen, namely proliferation, secretion of lymphokines, upregulation of molecules that mediate cell-cell interaction, and effective help for antibody secretion by B cells. Unlike the constitutively expressed CD28, ICOS has to be de novo induced on the T-cell surface, does not upregulate the production of interleukin-2, but superinduces the synthesis of interleukin-10, a B-cell-differentiation factor. In vivo, ICOS is highly expressed on tonsillar T cells, which are closely associated with B cells in the apical light zone of germinal centres, the site of terminal B-cell maturation. Our results indicate that ICOS is another major regulator of the adaptive immune system.     

Datenbankunterstützung für den ingenieurwissenschaftlichen Entwurf

Zusammenfassung Datenbanksysteme zeichnen sich durch Charakteristika aus, die über den klassischen administrativ-betriebswirtschaftlichen Bereich hinaus zunehmend auch für Ingenieuranwendungen als vorteilhaft erkannt werden. Die Schwierigkeiten für einen sofortigen Einsatz in diesem Sektor liegen darin, daß existierende Systeme hinsichtlich Datenstrukturierung, Konsistenz, Mehrbenutzerbetrieb und Datensicherung keine den neuen Anforderungen entsprechenden Konzepte anbieten. Der Bericht nennt beispielhaft für den Bereich des Entwurfs technischer Objekte die wichtigsten Unterschiede zu traditionellen Anwendungen und stellt Lösungsvorschläge für die genannten Problemkreise vor.     

Production and secretion of recombinant proteins in Dictyostelium discoideum

We have expressed useful amounts of three recombinant proteins in a new eukaryotic host/vector system. The cellular slime mold Dictyostelium discoideum efficiently secreted two recombinant products, a soluble form of the normally cell surface associated D. discoideum glycoprotein (PsA) and the heterologous protein glutathione-S-transferase (GST) from Schistosoma japonicum, while the enzyme beta-glucuronidase (GUS) from Escherichia coli was cell associated. Up to 20mg/l of recombinant PsA and 1mg/l of GST were obtained after purification from a standard, peptone based growth medium. The secretion signal peptide was correctly cleaved from the recombinant GST- and PsA-proteins and the expression of recombinant PsA was shown to be stable for at least one hundred generations in the absence of selection.     

Acute and chronic toxicity effects of silver nanoparticles (NPs) on Drosophila melanogaster

The use of nanoscaled materials is rapidly increasing, however, their possible ecotoxicological effects are still not precisely known. This work constitutes the first complex study focused on in vivo evaluation of the acute and chronic toxic effects and toxic limits of silver nanoparticles (NPs) on the eukaryotic organism Drosophila melanogaster. For the purpose of this study, silver NPs were prepared in the form of solid dispersion using microencapsulation method, where mannitol was used as an encapsulation agent. This newly prepared solid dispersion with a high concentration of silver NPs was exploited to prepare the standard Drosophila culture medium at a silver concentration range from 10 mg·L(-1) to 100 mg·L(-1) of Ag in the case of the acute toxicity testing and at a concentration equal to 5 mg·L(-1) in the case of the chronic toxicity testing. The acute toxic effect of silver NPs on Drosophila melanogaster was observed for the silver concentration equal to 20 mg·L(-1). At this silver concentration, 50% of the tested flies were unable to leave the pupae, and they did not finish their developmental cycle. Chronic toxicity of silver NPs was assessed by a long-term exposure of overall eight filial generations of Drosophila melanogaster to silver NPs. The long-term exposure to silver NPs influenced the fertility of Drosophila during the first three filial generations, nevertheless the fecundity of flies in subsequent generations consequently increased up to the level of the flies from the control sample due to the adaptability of flies to the silver NPs exposure.