Repeated elicitation of the acoustic startle reflex leads to sensitisation in subsequent avoidance behaviour and induces fear conditioning

Background  

Autonomous reflexes enable animals to respond quickly to potential threats, prevent injury and mediate fight or flight responses. Intense acoustic stimuli with sudden onsets elicit a startle reflex while stimuli of similar intensity but with longer rise times only cause a cardiac defence response. In laboratory settings, habituation appears to affect all of these reflexes so that the response amplitude generally decreases with repeated exposure to the stimulus. The startle reflex has become a model system for the study of the neural basis of simple learning processes and emotional processing and is often used as a diagnostic tool in medical applications. However, previous studies did not allow animals to avoid the stimulus and the evolutionary function and long-term behavioural consequences of repeated startling remain speculative. In this study we investigate the follow-up behaviour associated with the startle reflex in wild-captured animals using an experimental setup that allows individuals to exhibit avoidance behaviour.     

Indications of field-directing and self-templating effects on the formation of organic lines on silicon

It has previously been shown that multimolecular organic nanostructures form on H-Si(100)-2×1 via a radical mediated growth process. In this mechanism, growth begins through the addition of a molecule to a silicon surface dangling bond, followed by the abstraction of a neighboring H atom and generation of a new dangling bond on the neighboring site. Nanostructures formed by this mechanism grow along one edge of a dimer row. Here, we explored the possibility of using lithographically prepared, biased metal contacts on the silicon surface to generate an electric field that orients molecules during the growth process to achieve growth in the perpendicular-to-row direction. The formation of some nanostructures in a direction that was nearly perpendicular to the dimer rows was achieved, whereas such features were not formed in the absence of the field. Analysis of the scanning tunneling microscopy images suggests that the formation of these nanostructures may involve self-templating effects in addition to dangling bond diffusion rather than a straightforward addition∕abstraction mechanism. These initial results offer some indication that a molecular pattern writer can be achieved.     

1. Allgemeine Analytische Chemie

Ohne Zusammenfassung     

Tritium monitoring with a scintillation chamber

A tritium monitor based on plastic scintillation sheets is described. The sensitive volume of the scintillation chamber is 0.95 l. The chamber with coincidence electronics has a discrimination capability and permits to detect tritium in the presence of other radionuclides and external gamma-radiation. The monitor characteristics obtained with tritiated air are presented. The monitor sensitivity for tritium in air is 5.6 cpm for each kBq·m⁻³. The monitoring of tritium in air and water is possible using the instrument described.     

Neutron Scattering by a Liquid Crystal Substance with a “Cubic” Phase

The applicability of the rotational diffusion model around the long molecular axes in liquid crystalline phases is being questioned.     

Synthesis and crystal structure of [{CpFe(CO)}2(μ-CO)-(μ-CHPMe3)+][PF 6 − ]

The title compound crystallizes in the non-centrosymmetric space groupP2₁ withZ=2. Two CpFe(CO) fragments are held together by an iron-iron bond (Fe(1)?Fe(2)=2.539(3)Å), a bridging carbonyl ligand (Fe(1)?C(2)=1.910(16)Å, Fe(2)?C(2)=1.978(14)Å) and a bridging phosphonium ylid ligand Fe(1)?C(1)=1.978(12)Å, Fe(2)?C(1)=1.967(15)Å).     

Effect of temperature variation on the visible and near infrared spectra of wine and the consequences on the partial least square calibrations developed to measure chemical composition

Many studies have reported the use of near infrared (NIR) spectroscopy to characterize wines or to predict wine chemical composition. However, little is known about the effect of variation in temperature on the NIR spectrum of wine and the subsequent effect on the performance of calibrations used to measure chemical composition. Several parameters influence the spectra of organic molecules in the NIR region, with temperature being one of the most important factors affecting the vibration intensity and frequency of molecular bonds. Wine is a complex mixture of chemical components (e.g. water, sugars, organic acids, and ethanol), and a simple ethanol and water model solution cannot be used to study the possible effects of temperature variations in the NIR spectrum of wine. Ten red and 10 white wines were scanned in triplicate at six different temperatures (25 °C, 30 °C, 35 °C, 40 °C, 45 °C and 50 °C) in the visible (vis) and NIR regions (400-2500 nm) in a monochromator instrument in transmission mode (1 mm path length). Principal component analysis (PCA) and partial least squares (PLS) regression models were developed using full cross validation (leave-one-out). These models were used to interpret the spectra and to develop calibrations for alcohol, sugars (glucose + fructose) and pH at different temperatures. The results showed that differences in the spectra around 970 nm and 1400 nm, related to OH bonding were observed for both varieties. Additionally an effect of temperature on the vis region of red wine spectra was observed. The standard error of cross validation (SECV) achieved for the PLS calibration models tended to inverse as the temperature increased. The practical implication of this study it is recommended that the temperature of scanning for wine analysis using a 1 mm path length cuvette should be between 30 °C and 35 °C.     

One-nucleon removal cross-sections for 17, 19C and 8, 10B

One-neutron removal cross-sections ( ) of ^{17, 19}C in various targets at about 900 MeV/nucleon, and one-proton removal cross-sections ( ) of ^{8, 10}B at about 1400 MeV/nucleon were measured using the fragment separator FRS at GSI. A significant increase of for ¹⁹C compared to its neighbors was observed. The same behavior was found for for the neutron-deficient nucleus ⁸B compared to the stable isotope ¹⁰B. These results support a one-neutron halo structure in ¹⁹C and a one-proton halo in ⁸B. Received: 26 July 2000 / Accepted: 11 January 2001     

Molecular reorientation in the nematic and rotatory phases of 4,4'-di-n-pentyloxyazoxybenzene

Abstract

Results of dielectric relaxation, quasielastic neutron scattering, calorimetric D.S.C. and preliminary X-ray measurements on the fifth member, POAOB, of the 4,4'-di-n-alkoxyazoxybenzene homologous series are presented. It has been found that POAOB exhibits two mesophases: a nematic (N) and an intermediate crystalline phase (CI) just below it. From comparison of the dielectric relaxation and quasielastic neutron scattering studies we can conclude that in the nematic phase the molecule as a whole performs rotational diffusion around the long axis (ω ~ 150ps) and at the same time the two moieties perform faster independent reorientations around the N-δ bonds (ω denotes a benzene ring) with δ ~ 5 ps. The intermediate crystal phase is identified as a solid uniaxial rotational phase in which fast molecular reorientations exist. It seems that the fast reorientations observed in the nematic phase to some extent survive to the crystal I phase. A model of molecular arrangements in the crystal I phase is proposed, and it explains the reduction of the dielectric increment observed on passing from the nematic phase to this phase.