Band Formation during Gaseous Diffusion in Aerogels

We study experimentally how gaseous HCl and NH_3 diffuse from opposite sides of and react in silica aerogel rods with porosity of 92 % and average pore size of about 50 nm. The reaction leads to solid NH_4Cl, which is deposited in thin sheet-like structures. We present a numerical study of the phenomenon. Due to the difference in boundary conditions between this system and those usually studied, we find the sheet-like structures in the aerogel to differ significantly from older studies. The influence of random nucleation centers and inhomogeneities in the aerogel is studied numerically.Comment: 7 pages RevTex and 8 figures. Figs. 4-8 in Postscript, Figs. 1-3 on request from author

A Single Sex Pheromone Receptor Determines Chemical Response Specificity of Sexual Behavior in the Silkmoth Bombyx mori

In insects and other animals, intraspecific communication between individuals of the opposite sex is mediated in part by chemical signals called sex pheromones. In most moth species, male moths rely heavily on species-specific sex pheromones emitted by female moths to identify and orient towards an appropriate mating partner among a large number of sympatric insect species. The silkmoth, Bombyx mori, utilizes the simplest possible pheromone system, in which a single pheromone component, (E, Z)-10,12-hexadecadienol (bombykol), is sufficient to elicit full sexual behavior. We have previously shown that the sex pheromone receptor BmOR1 mediates specific detection of bombykol in the antennae of male silkmoths. However, it is unclear whether the sex pheromone receptor is the minimally sufficient determination factor that triggers initiation of orientation behavior towards a potential mate. Using transgenic silkmoths expressing the sex pheromone receptor PxOR1 of the diamondback moth Plutella xylostella in BmOR1-expressing neurons, we show that the selectivity of the sex pheromone receptor determines the chemical response specificity of sexual behavior in the silkmoth. Bombykol receptor neurons expressing PxOR1 responded to its specific ligand, (Z)-11-hexadecenal (Z11-16:Ald), in a dose-dependent manner. Male moths expressing PxOR1 exhibited typical pheromone orientation behavior and copulation attempts in response to Z11-16:Ald and to females of P. xylostella. Transformation of the bombykol receptor neurons had no effect on their projections in the antennal lobe. These results indicate that activation of bombykol receptor neurons alone is sufficient to trigger full sexual behavior. Thus, a single gene defines behavioral selectivity in sex pheromone communication in the silkmoth. Our findings show that a single molecular determinant can not only function as a modulator of behavior but also as an all-or-nothing initiator of a complex species-specific behavioral sequence

Rheologische Untersuchung zur Messung und Standardisierung von Probenahrung sowie zur Bestimmung von Nahrungsrezepturen für die Ernährung der Dysphagie-Patienten

Aufgrund von rheologischer Messung (Viskosität, mPa.s) wurden diätetische Standards erarbeitet, die die Aspirationsgefahr mindern und das Bestimmen von Kalorien- und Flüssigkeitsgehalt der Nahrung ermöglichen.Es wurde zunächst eine Viskositätsreihe mit zunehmender Viskosität der Probenahrung bestimmt, indem Wasser mit im Handel erhältlichen Eindickungsmitteln zu zähflüssigem Wasser, zu Gelee, zu Pudding und zu Brei stufenweise eingedickt wurde. Zu der so erhaltenen Viskositätskurve wurden im zweiten Schritt Speisen des täglichen Bedarfs mit bekannter Rezeptur zugeordnet. Nun konnte bestimmt werden, welche Konsistenz/Viskosität der erfolgreich geschluckte Bolus hatte und welche Speise genau dieser Viskosität entspricht. Die Methode ermöglicht die Standardisierung des Probebolus sowie einiger Speisen, die in den Krankenhäusern oder zuhause dem Patienten ohne Gefahr angeboten werden können. Da der Flüssigkeitsgehalt und der Kaloriengehalt dieser Speisen bekannt sind, ist es möglich, zu beurteilen, ob die orale Ernährung ausreicht oder eine Ergänzung via Sonde notwendig ist

Assessment of degradability in whole effluent toxicity testing using bioluminescent bacteria

In whole effluent toxicity (WET) testing the aggregate toxicity of an effluent is measured, using different test organisms. Although these predicted deleterious effects will occur in natural (real-world) ecosystems, the tests are performed in the laboratory, under strictly controlled conditions. However, there are many reasons why these test results cannot be directly applied for real-world ecosystems. One basic problem is that exposure changes with space and time. Several physical, chemical and biological processes can result in significant decreases in exposure concentrations of a test substance over time. For many industrial effluents biodegradation is perhaps the most important process which affects the environmental concentration of the test substance. Biodegradation is a specific process as not only appropriate abiotic conditions are necessary but also a competent bacterial population, both anaerob and aerob should be established. Our main goal was to assess how toxicity of a selected industrial effluent changes over time, caused by degradation. In order to measure the aggregate toxicity of the effluent the ToxAlert ®100 luminometer was used, developed by Merck. This test is in compliance with ISO/EN/DIN 11348. The use of the bioluminescent bacterium Vibrio fischeri (or other bacteria) has several advantages comparing to conventional toxicity testing. The test is rapid and causes no ethical problems. Our results has shown that toxicity changes caused by degradation can be appropriately followed by bioluminescent bacteria

The Alarm Pheromone and Alarm Response of the Clonal Raider Ant.

Ants communicate via an arsenal of different pheromones produced in a variety of exocrine glands. For example, ants release alarm pheromones in response to danger to alert their nestmates and to trigger behavioral alarm responses. Here we characterize the alarm pheromone and the alarm response of the clonal raider ant Ooceraea biroi, a species that is amenable to laboratory studies but for which no pheromones have been identified. During an alarm response, ants quickly become unsettled, leave their nest pile, and are sometimes initially attracted to the source of alarm, but ultimately move away from it. We find that the alarm pheromone is released from the head of the ant and identify the putative alarm pheromone as a blend of two compounds found in the head, 4-methyl-3-heptanone and 4-methyl-3-heptanol. These compounds are sufficient to induce alarm behavior alone and in combination. They elicit similar, though slightly different behavioral features of the alarm response, with 4-methyl-3-heptanone being immediately repulsive and 4-methyl-3-heptanol being initially attractive before causing ants to move away. The behavioral response to these compounds in combination is dose-dependent, with ants becoming unsettled and attracted to the source of alarm pheromone at low concentrations and repulsed at high concentrations. While 4-methyl-3-heptanone and 4-methyl-3-heptanol are known alarm pheromones in other more distantly related ant species, this is the first report of the chemical identity of a pheromone in O. biroi, and the first alarm pheromone identified in the genus Ooceraea. Identification of a pheromone that triggers a robust, consistent, and conserved behavior, like the alarm pheromone, provides an avenue to dissect the behavioral and neuronal mechanisms underpinning chemical communication