Search Results - (Author, Cooperation:R. Jahn)

2012-06-02

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

Animals ; Lipid Bilayers/chemistry/*metabolism ; *Liposomes/chemistry/metabolism ; *Membrane Fusion ; Protein Binding ; Protein Conformation ; Rats ; SNARE Proteins/chemistry/*metabolism ; Vesicle-Associated Membrane Protein 2/metabolism

2011-10-25

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

Animals ; Cholesterol ; Membrane Microdomains/*chemistry/metabolism ; Microscopy, Confocal ; Molecular Dynamics Simulation ; Nerve Tissue Proteins/metabolism ; PC12 Cells ; Phosphatidylinositol 4,5-Diphosphate/*chemistry/*metabolism ; Phosphoric Monoester Hydrolases/metabolism ; *Protein Binding ; Rats ; *Static Electricity ; Syntaxin 1/*chemistry/*metabolism ; Unilamellar Liposomes/chemistry/metabolism

2016-02-26

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

2015-03-31

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

Adenosine Triphosphate/*metabolism ; Animals ; Cattle ; Cricetinae ; Fluorescence Resonance Energy Transfer ; Hydrolysis ; N-Ethylmaleimide-Sensitive Proteins/*metabolism ; Rats ; SNARE Proteins/*metabolism ; Soluble N-Ethylmaleimide-Sensitive Factor Attachment Proteins/*metabolism ; Spectrometry, Fluorescence

2012-10-13

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

Animals ; Calcium/metabolism ; Exocytosis/*physiology ; Humans ; Lipid Metabolism ; Models, Biological ; SNARE Proteins/chemistry/metabolism ; Synaptic Vesicles/*physiology

1089-7623

AIP Digital Archive

Physics

Electrical Engineering, Measurement and Control Technology

An optical interferometric proximeter system (IPS) for measuring thrust and impulse bit of pulsed electric thrusters was developed. Unlike existing thrust stands, the IPS-based thrust stand offers the advantage of a single system that can yield electromagnetic interference-free, high accuracy (〈2% error) thrust measurements within a very wide range of impulses (100 μN s to above 10 N s) covering the impulse range of all known pulsed plasma thrusters. In addition to pulsed thrusters, the IPS is theoretically shown to be capable of measuring steady-state thrust values as low as 20 μN for microthrusters such as the field emission electric propulsion thruster. The IPS-based thrust stand relies on measuring the dynamic response of a swinging arm using a two-sensor laser interferometer with 10 nm position accuracy. The wide application of the thrust stand is demonstrated with thrust measurements of an ablative pulsed plasma thruster and a quasi-steady magnetoplasmadynamic thruster. © 1997 American Institute of Physics.

Electronic Resource

1089-7623

AIP Digital Archive

Physics

Electrical Engineering, Measurement and Control Technology

The cylindrical triple probe method is an attractive technique for measuring electron temperatures (Te) and electron number densities (ne) in a variety of plasmas sources. In practice, however, the cylindrical triple probe can be sensitive to sources of error that affect all Langmuir probe techniques. In particular, the presence of an ion drift velocity component that is perpendicular to the probe axis has been known to result in erroneous measurements of ne. Less obvious, however, is that ion flow perpendicular to the probe has a significant effect on the indicated Te. The purpose of this note is to make researchers aware of such an effect and to demonstrate a technique which can mitigate it. The approach taken to investigate this phenomenon was to make Te measurements in the plume of a 20 kW magnetoplasmadynamic thruster with the probe oriented at several angles with respect to the local ion flow.

Electronic Resource

1365-2389

Blackwell Publishing Journal Backfiles 1879-2005

Geosciences

Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Preservation of organic matter in soils depends on the chemical structure of organic compounds and on the surface properties of the mineral matrix. We tested the effect of mineral surface reactivity on organic matter decomposition by (i) investigating changes of organic matter composition in clay subfractions of an illitic Haplic Chernozem along a time series of fertilizer deprivation and (ii) simultaneously characterizing the reactivity of mineral surfaces. The soil was subjected to fertilizer deprivation for 18, 44 and 98 years, respectively. Mineral surface properties were characterized by selective dissolution of pedogenic oxides. The number of hydroxyls released after exposure to sodium fluoride was taken as an index for mineral surface reactivity. Organic soil constituents were determined by 13C cross-polarization magic-angle spinning nuclear magnetic resonance (13C CPMAS NMR).Clay subfractions had different mineral surface properties. The coarse fractions have more reactive surfaces and contain more organic carbon than the fine clay fractions. Mineral surface properties are constant over time and are not affected by fertilizer deprivation. Surface reactivity is a function of iron oxide density and controls carbon concentrations in the clay subfractions. Within the time frame of our investigation, alkyl C and aromatic C responded to the duration of fertilizer deprivation, but were indifferent to mineral surface reactivity. O–alkyl C seems to be protected by interactions with pedogenic oxides.

Electronic Resource

1365-2389

Blackwell Publishing Journal Backfiles 1879-2005

Geosciences

Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Soil minerals are known to influence the biological stability of soil organic matter (SOM). Our study aimed to relate properties of the mineral matrix to its ability to protect organic C against decomposition in acid soils. We used the amount of hydroxyl ions released after exposure to NaF solution to establish a reactivity gradient spanning 12 subsoil horizons collected from 10 different locations. The subsoil horizons represent six soil orders and diverse geological parent materials. Phyllosilicates were characterized by X-ray diffraction and pedogenic oxides by selective dissolution procedures. The organic carbon (C) remaining after chemical removal of an oxidizable fraction of SOM with NaOCl solution was taken to represent a stable organic carbon pool. Stable organic carbon was confirmed as older than bulk organic carbon by a smaller radiocarbon (14C) content after oxidation in all 12 soils. The amount of stable organic C did not depend on clay content or the content of dithionite–citrate-extractable Fe. The combination of oxalate-extractable Fe and Al explained the greatest amount of variation in stable organic C (R2 = 0.78). Our results suggest that in acid soils, organic matter is preferentially protected by interaction with poorly crystalline minerals represented by the oxalate-soluble Fe and Al fraction. This evidence suggests that ligand exchange between mineral surface hydroxyl groups and negatively charged organic functional groups is a quantitatively important mechanism in the stabilization of SOM in acid soils. The results imply a finite stabilization capacity of soil minerals for organic matter, limited by the area density of reactive surface sites.

Electronic Resource

1365-2389

Blackwell Publishing Journal Backfiles 1879-2005

Geosciences

Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Oxidative treatment can isolate a stable organic matter pool in soils for process studies of organic matter stabilization. Wet oxidation methods using hydrogen peroxide are widely used for that purpose, but are said to modify poorly crystalline soil constituents. We investigated the effect of a modified NaOCl oxidation (pH 8) on the mineral composition of 12 subsoils (4.9–38.2 g organic C kg−1) containing varying amounts of poorly crystalline mineral phases, i.e. 1.1–20.5 g oxalate-extractable Fe kg−1, and of different phyllosilicate mineralogy. Post-oxidative changes in mineral composition were estimated by (i) the determination of elements released into the NaOCl solution, (ii) the difference in dithionite- and oxalate-extractable Si, Al and Fe, and (iii) the specific surface areas (SSAs) of the soils. The NaOCl procedure reduced the organic C concentrations by 12–72%. The amounts of elements released into the NaOCl extracts were small (≤ 0.14 g kg−1 for Si, ≤ 0.13 g kg−1 for Al, and ≤ 0.03 g kg−1 for Fe). The SSA data and the amounts of dithionite- and oxalate-extractable elements suggest that the NaOCl oxidation at pH 8 does not attack pedogenic oxides and hydroxides and only slightly dissolves Al from the poorly crystalline minerals. Therefore, we recommend NaOCl oxidation at pH 8 for the purpose of isolating a stable organic matter pool in soils for process studies of organic matter stabilization.

Electronic Resource

1365-2389

Blackwell Publishing Journal Backfiles 1879-2005

Geosciences

Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

A prerequisite to investigate the importance of osmotic potential (Ψo) in relation to matric potential (Ψm) in the soil for water uptake is the existence of a method that measures the temporal and spatial dynamics of Ψo in the vicinity of roots. One method for measuring Ψoin situ is the collection of soil solution with micro suction cups, the spatial resolution of which is suitable for rhizosphere studies. A major drawback of soil solution sampling is the disturbance of soil solution equilibrium, which makes frequent measurements impossible, so another method is required to provide information on the temporal dynamics of Ψo. The time-domain reflectometry (TDR) technique might be suitable as the signal attenuation (σ) shows a close linear correlation with the salt concentration for a known soil water content. The temporal resolution of the TDR technique is high and the measurement has no impact on soil solution equilibrium. However, the spatial resolution of the TDR technique is too coarse to be used on its own in rhizosphere studies.We used a combination of TDR (fine temporal resolution) and micro suction cups (fine spatial resolution) to measure Ψo in a model system with Zea mays grown in quartz substrates. Osmotic potential changed continuously with time, and a steep gradient between bulk soil and the root compartment developed during the 39-day growing period. The steepest gradient measured over a distance of 6 mm across the nylon net, separating the bulk soil from the root compartment, was −365 kPa. The combination of both methods made it possible to extend the time interval between micro suction cup samplings and thus minimize the impact of sampling on soil solution equilibrium. Problems of separate calibration were avoided by calibrating the TDR measurements against the results obtained with the micro suction cups within the same experiment.

Electronic Resource

1365-2389

Blackwell Publishing Journal Backfiles 1879-2005

Geosciences

Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

We used the specific surface area (SSA), the cation exchange capacity (CEC) and the content of dithionite-extractable iron (Fed) to predict the content of organic carbon in illitic clay fractions of topsoils from loess. We determined SSA (BET-N2 method) and CEC of clay fractions after removing organic C or reducing oxides or both. The CEC and the SSA of the carbon- and oxide-free clay fraction explained 56% and 54% of the variation in C content, respectively. The Fed content of the clay fractions was strongly and negatively related to the C content, and with the SSA of the carbon-free clay fraction it predicted C content almost completely (R2 = 0.96). The results indicate that the amount of cations adhering to the silicate clay minerals and the size of the silicate mineral surface area are important properties of the mineral phase for the storage potential of C. The reason for the negative relation between iron oxides and C content remains unclear.

Electronic Resource

0006-291X

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Biology

Chemistry and Pharmacology

Physics

Electronic Resource

0890-8508

chromogranin A ; electron microscopy ; immunohistochemistry ; neuroendocrine cells ; neuroendocrine tumours ; protein p38 ; synaptophysin

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Biology

Medicine

Electronic Resource

0003-2697

CMP-N-acetylsialic acids ; N-acetylsialic acids

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Biology

Chemistry and Pharmacology

Electronic Resource

0003-2697

neurochemistry ; nitrocellulose ; protein blotting ; protein kinases ; protein phosphorylation ; synapsin I

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Biology

Chemistry and Pharmacology

Electronic Resource

0928-4257

SNAP-25 ; clostridial toxins ; glutamate release ; membrane fusion complex ; synaptobrevin ; synaptosomes ; syntaxin

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Biology

Medicine

Electronic Resource

0962-8924

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Biology

Medicine

Electronic Resource

0014-5793

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Biology

Chemistry and Pharmacology

Physics

Electronic Resource

0014-5793

Calcium ; Endoplasmic reticulum ; Parotid gland ; Protein phosphorylation ; cAMP

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Biology

Chemistry and Pharmacology

Physics

Electronic Resource