Thermal neutron radiative capture on cadmium as a counting technique at the INES beam line at ISIS: A preliminary investigation of detector cross-talk.

Experimental tests are presented that assess the cross-talk level among three scintillation detectors used as neutron counters exploiting the thermal neutron radiative capture on Cd. The measurements were done at the INES diffractometer operating at the ISIS spallation neutron source (Rutherford Appleton Laboratory, UK). These tests follow a preliminary set of measurements performed on the same instrument to study the effectiveness of this thermal neutron counting strategy in neutron diffraction measurements, typically performed on INES using squashed 3He filled gas tubes. The experimental data were collected in two different geometrical configurations of the detectors and compared to results of Monte Carlo simulations, performed using the MCNP code.

Energy-selective neutron imaging for morphological and phase analysis of iron-nickel meteorites.

We propose energy-selective neutron imaging as a new and non-destructive method to investigate rare metallic meteorites. It is based on attenuation of a neutron beam of limited spectral distribution in a sample depending on the elemental composition and crystalline structure. Radiography and tomography allow obtaining the presence, morphology and orientation information in the bulk of mineral inclusions, oxide crust and crystalline structure. Its usage in classification and meteor formation studies would be of great value.

Ancient and historic steel in Japan, India and Europe, a non-invasive comparative study using thermal neutron diffraction.

The production and refinement of steel has followed very different paths in different parts of the Eurasian continent. In aiming to characterize the similarities and differences between various smelting and smithing methods, we have analysed steel samples from four different areas and historic periods: the Koto Age in Japan (twelfth-sixteenth century), the Moghul Empire in India (seventeenth-nineteenth century), the Ottoman Turkish Empire (seventeenth century) and the late Middle Ages (fifteenth century) in Italy. The best quality steel was employed for forging arms and armour of high quality, so that we have selected samples from Japan, India, the Middle East and Italy belonging to such a category. Traditional methods, such as metallography, used to characterize different steels in terms of their carbon contents, microconstituents and slag inclusions, entailed an invasive approach. Since many of the selected artefacts are in a very good state of conservation, a different and non-invasive approach was desirable. To this aim, we have used time of flight neutron diffraction on the Italian Neutron Experimental Station diffractometer, located at the pulsed neutron source ISIS in the United Kingdom. By this technique, we were able to quantify the phase distribution of the metal phases, the slag inclusion content, and the oxidation state of the samples, both as average concentration on the whole artefact and in selected gauge volumes. The results of the present investigation offer an interesting picture of the steel metallurgy in different areas of the world.

Characterization of copper alloys of archaeometallurgical interest using neutron diffraction: a systematic calibration study.

Neutron diffraction experiments have been performed on laboratory-prepared samples of copper alloys to determine their microscopic phase characteristics. The aim of this experiment is to set up a database that can be used in future neutron diffraction measurements on metal samples mainly of archaeological interest.

NIMROD: The Near and InterMediate Range Order Diffractometer of the ISIS second target station.

NIMROD is the Near and InterMediate Range Order Diffractometer of the ISIS second target station. Its design is optimized for structural studies of disordered materials and liquids on a continuous length scale that extends from the atomic, upward of 30 nm, while maintaining subatomic distance resolution. This capability is achieved by matching a low and wider angle array of high efficiency neutron scintillation detectors to the broad band-pass radiation delivered by a hybrid liquid water and liquid hydrogen neutron moderator assembly. The capabilities of the instrument bridge the gap between conventional small angle neutron scattering and wide angle diffraction through the use of a common calibration procedure for the entire length scale. This allows the instrument to obtain information on nanoscale systems and processes that are quantitatively linked to the local atomic and molecular order of the materials under investigation.

A neutron imaging device for sample alignment in a pulsed neutron scattering instrument.

A neutron-imaging device for alignment purposes has been tested on the INES beamline at ISIS, the pulsed neutron source of Rutherford Appleton Laboratory (U.K.). Its use, in conjunction with a set of movable jaws, turns out extremely useful for scattering application to complex samples where a precise and well-defined determination of the scattering volume is needed.

A silicon photomultiplier readout for time of flight neutron spectroscopy with gamma-ray detectors.

The silicon photomultiplier (SiPM) is a recently developed photosensor used in particle physics, e.g., for detection of minimum ionizing particles and/or Cherenkov radiation. Its performance is comparable to that of photomultiplier tubes, but with advantages in terms of reduced volume and magnetic field insensitivity. In the present study, the performance of a gamma ray detector made of an yttrium aluminum perovskite scintillation crystal and a SiPM-based readout is assessed for use in time of flight neutron spectroscopy. Measurements performed at the ISIS pulsed neutron source demonstrate the feasibility of gamma-detection based on the new device.

Neutron diffraction characterization of Japanese artworks of Tokugawa age.

Neutron time-of-flight diffraction technique has been used to characterize some Japanese historical artifacts. With this method, metal samples can be analyzed in their bulk properties without need of sampling. Results shown here were obtained at the Italian Neutron Experimental Station (INES@ISIS) located at the pulsed neutron source ISIS (UK). The parallel use of a scanning electron microscope equipped with an energy-dispersive X-ray fluorescence device (SEM-EDX) permitted a full quantitative characterization of the investigated samples, namely four hand-guards (Tsubas) of Japanese swords attributed to the Tokugawa age. In particular, we were able to obtain, in a totally non-invasive non-destructive way, a full quantitative phase characterization of the samples, a detailed Bragg peak broadening analysis, and a quantitative texture determination. These results, complemented with those obtained via the traditional analysis method of SEM-EDX, allowed a full characterization of both the bulk and the surface of the artifacts.

An apparatus for simultaneous thermodynamic and optical measurements, with large temperature excursions.

We report the design and realization of an integrated system for measuring, at the same time, the thermodynamic and spectroscopic features of nanoporous materials interesting for hydrogen storage purposes. The whole investigation cycle, from thermal activation to the actual investigation of uptake and release of hydrogen, is carried out in the same vacuum tight vessel, equipped with an optical window, whose temperature can range between 10 and 750 K, up to a maximum pressure of 50 bars. The system has been designed to investigate properties of carbon nanotubes but its use can be extended to any kind of nanoporous sample such as, for example, carbon nanofibers, zeolytes, metal organic frameworks, and similar materials.

Anisotropic interactions of hydrogen molecules from the pressure dependence of the rotational spectrum in the Ar(H2)(2) compound.

We report the pressure evolution, up to 70 GPa, of the fine structure of the S0(0) rotational excitation in the high-pressure Ar(H(2))(2) compound (with almost 100% para-H(2)) at about 30 K. A perturbative theoretical analysis is developed to calculate intensities and frequency shifts of the active Raman rotational components, on the basis of the intermolecular anisotropic interaction. The comparison between experimental results up to 35 GPa and calculation allows a reliable determination of the anisotropic intermolecular potential in the solid, both for H(2)-H(2) and H(2)-Ar at short range. Such results are important for the interpretation of the high-pressure orientational properties of solid hydrogen.

Different effects of ACTH fragments on hippocampal EEG and behavior.

The hippocampal electrical activity and behavior of rabbits have been studied in the presence of novel and emotional stimuli. The effects of these stimuli have been recorded in controls and in groups of animals treated with ACTH (4-10)(10 micrograms/100 g, i.m.) and ACTH (1-24) (10 micrograms/100 g, i.m.). Recordings were made immediately and 30 min after injection. ACTH (4-10) injection failed to evoke any significant behavioral or electrical response. Rabbits recorded 30 min after ACTH (1-24) injection showed a reduction of hippocampal RSA (rhythmic slow activity) frequency and behavioral activity. In particular, reduction of exploration, self-grooming, motor activity and approaches to the new object have been observed. Since ACTH is characterized by a corticotropic action these results can be due to corticosteroid stimulation.

Cholinergic and glutaminergic control of hippocampal RSA during behavior in rabbits.

An experimental model, with novel environmental stimuli, has been used in order to study the effects of cholinergic and glutaminergic modulation on hippocampal electrical activity and behavior. The test consisted in the introduction of a rabbit in an experimental cage in the absence of external stimuli (neutral environment) followed by the introduction into the cage of a novel object containing odorous vegetable branches, a stuffed sparrow-hawk and a live cat. The effects of drug treatments on hippocampal rhythmic slow activity (RSA) parameters (total amount, episode durations and frequency) were studied. Physostigmine (0.1 mg/kg) increased RSA amount both during immobility and movements and was effective only on the frequency of the immobility related RSA. Scopolamine (0.4 mg/kg) reduced the percentage of RSA occurring during immobility and movements and the frequency of the movement related RSA. Glutamic acid diethyl ester (GDEE) (400 micrograms), injected into the dorsal hippocampus, had qualitative effects similar to those obtained with scopolamine, but, quantitatively, they were less pronounced. The combination between GDEE and scopolamine potentiated the effects of the two drugs. Results support the assumption that cholinergic septal input is responsible for hippocampal RSA and the glutaminergic entorhinal input to the hippocampus modulates RSA, probably under cholinergic control.

Effect of piracetam plus choline treatment on hippocampal rhythmic slow activity (RSA) and behavior in rabbits.

The effects of chronic treatment with piracetam (100 mg/Kg) plus choline (100 mg/Kg) on rabbits' hippocampal electrical activity and behavior have been studied. Animals were exposed to a neutral environment, in the absence of any external stimulus, and then to an object and a stuffed sparrow-hawk. Results show a drug related reduction in the amount of the hippocampal rhythmic slow activity (RSA) and an increase in RSA high frequency values in the presence of the object and of the stuffed animal, but not in the neutral environment. This would suggest that piracetam plus choline treatment has an effect on RSA in situations in which selective attention is required.

Physiological characteristics of pressure immobility. Effects of morphine, naloxone and pain.

This study is an attempt to detect the most important modifications of physiological parameters occurring during pressure immobility in rabbits and to compare them with those recorded during animal hypnosis. Like the latter, pressure immobility is characterized by the development of high voltage slow waves in the EEG, reduction in frequency and amount of rhythmic slow activity in the hippocampus (RSA) and depression of spinal polysynaptic reflexes. Systolic and diastolic blood pressures are not modified. Duration of two types of immobility is positively correlated within individuals. Treatment by a single dose of morphine (1 mg/kg) potentiates the duration and this effect is antagonized by naloxone (1 mg/kg). Repeated morphine injection up to tolerance reduces duration. Pressure immobility may also be produced under persistent nociceptive stimulation and is characterized by the development of high voltage slow waves in the EEG, as is typical in the absence of pain. Naloxone, (5 mg/kg) injected in a condition of persistent noxious stimulation, reduces immobility duration. In contrast to animal hypnosis, the duration of pressure immobility is neither potentiated by pain nor reduced by naloxone (1,5 or 20 mg/kg). It is suggested that the two immobilities are controlled by several mechanisms, some similar, some different.

Hippocampal rhythmic slow activity (RSA) during animal hypnosis in the rabbit.

Hippocampal electrical activity has been studied in 12 unanaesthetized, unrestrained rabbits during hypnosis and spontaneous activity in the experimental cage, before and among hypnosis trials. Quantitative analyses showed that rhythmic slow activity (RSA) occurred during exploratory movements (mean frequency 7.2 Hz) and also during spontaneous immobility, but a lower percentage and frequency (6.5 Hz). RSA was always present during the induction of hypnosis, but its frequency decreased and disappeared at the beginning of immobility, when it was replaced by a large amplitude irregular activity (LIA). During hypnosis RSA occurred in short periods, at low frequency (5.7 Hz). During the initial part of hypnosis, the lowest percentage of RSA was recorded. In the sec ond and third part, RSA increased in number of episodes, total amount, duration of a single episode and mean frequency. RSA of higher frequency occurred at the end of hypnosis, preceding righting movements. The relationships between hippocampal RSA and animal hypnosis are discussed.