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The free radical nitric oxide (NO*) is involved in a variety of diverse biological processes from acting as a vasodilator in the cardiovascular system to being the rate-limiting component in the production of peroxynitrite (ONOO-), a contributor to neurodegenerative disorders such as multiple sclerosis (MS). Uric acid (UA), the end product of purine metabolism in humans and a selective inhibitor of toxic reactions attributed to radicals formed by the interaction of ONOO- and CO2, is generally low in MS patients. We investigated the relationship between serum ONOO-, CO2, and UA in MS patients and normal controls by comparing the circadian characteristics of the NO* metabolites nitrite/ nitrate (NO), CO2, and UA. In this preliminary study, we found the functional relationship ascribed to the circadian timing of the peak and trough levels of NO, CO2, and UA in healthy subjects to be clearly altered in MS patients. These findings suggest that alterations in the temporal relationship between the 24h pattern in serum ONOO- formation and UA may either contribute to or reflect the disease processes in MS.

Pediatric delirium (PD) is an acute state of brain dysfunction and is often seen in the pediatric intensive care unit (PICU). There is a growing awareness of its clinical interdisciplinary importance. The aim of this article was to describe the three clinical presentations, to evaluate the differential diagnosis and to give a concise and practical update for the pharmacological and non-pharmacological treatment of PD at the PICU, based on recent literature and expert opinions. We discuss an interdisciplinary flow chart which helps the reader dealing with the diagnosis and management of any acute emotional and or behavioral disturbance, of which PD is a special case.

We report a study on the magnetic nature of the two hyperfine fields observed in α-Mn by PAC. Both of the field sites behave completely differently under the influence of an external field ranging from zero to 4 Tesla. The so-called high field originates from the local moment antiferromagnetism of the matrix, while the low field should be associated with an itinerant magnetism.

PAC-experiments were performed on111Cd in Mn1−xSix (x=8.8at%) alloys. The high-field site (h) due to the local moments existing at site II positions is almost unaffected by the Si-impurities. For the second field site (1), supposed to be due to SDW, the ordering temperature is shifted to 77(2)K, although the field value is very similar to the pure α-Mn value. This observation supports our earlier interpretation of the magnetism in pure α-Mn.

We evaluated intragastric food distribution and antral motor activity in patients with functional dyspepsia.A standard gastric emptying test and dynamic imaging of the antrum were used to characterize gastric antral motility disturbances and to correlate them with total and compartmental gastric emptying in 25 dyspeptic patients.We found a 40% prevalence of gastroparesis in functional dyspepsia. Solid gastric emptying delay is indicated by a prolonged lag phase and an increase in frequency and amplitude of gastric contractions, resulting in nonexpulsive antral contractions and/or antropyloric dyscoordination. Food retention in the distal stomach and antral distention appears to account for patients' dyspeptic symptoms.This study demonstrates that scintigraphy not only detects abnormalities of food distribution in the stomach but also provides information on antral motor activity noninvasively. Dynamic antral scintigraphy and compartmental gastric emptying are useful tools to define the pathophysiology of dyspeptic patients with or without gastroparesis.

In this study, food distribution in the stomach and gastric antral motor activity in patients with longstanding diabetes have been evaluated. With use of a standard gastric emptying test with an acquisition protocol and a refined Fourier algorithm to analyze the data, antral contractions have been characterized and gastric motility parameters were correlated to gastric retention in 20 diabetic patients with or without gastroparesis and in 10 healthy subjects. The results of this study show that, in longstanding diabetes, gastric emptying retardation is accounted for by a retention of food in the proximal stomach, which is reflected by a prolonged lag phase as well as by a reduction in antral motor activity that is determined by a decrease in the amplitude of the antral contractions. This study demonstrates that scintigraphy can noninvasively characterize abnormalities of food distribution in the stomach and provides information similar to that obtained from manometry.

Concentration- and temperature dependent measurements were made on NiMn-alloys with the perturbed angular correlation technique (PAC). At room-temperature, samples of 1.3; 2.4; 3.6; 5.6; 6.9 and 8.3 at%Mn were examined. Field values on both sides of the Ni-value were observed with a pronounced concentration dependence above 3 at%Mn. The 3.6 at%Mn-sample was examined as function of temperature between 284 K and 573 K. Each of the fields has the same temperature-behaviour, resulting in the same Curie-temperature, which is however smaller than the Curie-temperature for pure Ni.

The hyperfine interaction is studied in two different crystal lografic forms of Mn. In the β-Mn no magnetic, but a distinct electric quadrupole interaction is found. Effects of heat treatment are discussed. For the α-Mn two magnetic field sites are found. Their temperature dependence and dependence on the In concentration are discussed.

Mesure, par la technique de correlation angulaire perturbee, des distributions de champ hyperfin dans Mn-α. Interpretation des resultats par une coexistence du moment local et de l'antiferromagnetisme itinerant

A perturbed angular correlation study on Au85Fe15 in different metallurgical states and over a wide temperature range is reported. The hyperfine field and its temperature variation reflect a cluster glass behaviour due to chemical clusters of different sizes rather than a magnetic double transition.

Etude de Au 85 Fe 15 par correlation angulaire perturbee dans differents etats metallurgiques et sur un vaste domaine de temperatures. Le champ hyperfin et sa variation thermique refletent un comportement de verre d'amas du aux amas de spin de differentes tailles plutot qu'une double transition magnetique

The temperature and concentration dependence of the transferred hyperfine field in Au 1− x Fe x with 0.15 x 111 Cd probe shows a slope change at T / T c =0.25 for all concentrations below 20 at% Fe, but an almost continuous behaviour for higher concentrations. These results manifest a percolation-like magnetic behaviour but no magnetic double transition.

Barium fluoride and cesium fluoride inorganic scintillators offer excellent timing, reasonable energy resolution and good gamma ray detection efficiencies. These characteristics are very desirable for accurate time differential perturbed angular correlation/distribution (TDPAC/D) experiments and enables one to extend the TDPAC/D techniques for the study of many interesting solid state aspects such as near neighbour interactions, conduction electron polarization, short and long range ordering etc. The performance of these detectors is compared with the commonly used ones and their potential for new solid state applications is demonstrated by means of some illustrative examples.

We report on PAC measurements revealing very different magnetic behaviour in two nearby alloys. The Ni79Mn21 alloy orders at TC=280(5) K, but a two field sites interpretation is needed. Both hyperfine fields (hff) are in the ratio 1∶2 and their distributions have the same absolute width, the relative abundance of the high field site is 30%. A slope change in the hff (T) curve at low temperature may indicate the transition into the mixed state. In the Ni76Mn24 alloy we observe magnetic ordering at T=95(3) K followed by a smooth increase of the effective hff upon cooling but with an anomalous minimum around T=20 K.

We report on the lattice location of indium in and the magnetic ordering of manganese in its α- and β-phases, as seen by perturbed angular correlation. Quadrupole interaction spectra show that indium prefers to replace Mn atoms of type I in α-Mn, but replaces type II atoms in the β-Mn structure. The interaction strength equalseQVzz/h=3.6 (6) MHz in α-Mn and 172.3 (3) MHz with ν=0.13 (1) in β-Mn. No magnetic ordering down to 4.2 K was observed in β-Mn, while belowTN=95 K in the α-Mn phase, a magnetic hyperfine interaction appears indicating two distinct magnetic probe environments. The hyperfine field, when measured atT=4.2 K, equals for 70% of the probes 6.33 (1) T, while the remaining fraction senses a 3.10 (4) T field. The magnitudes of the hyperfine fields are essentially unaffected by a variety of conditions in the sample preparation. The ordering temperature, on the contrary, turns out to be rather sensitive to residual impurities especially any oxygen contamination.

The annealing behaviour of indium implanted silicon (doses 1011−1013 atoms/cm2) was studied by time differential perturbed angular correlation spectroscopy. Besides the substitutional site two types of defect configurations were observed. In the as-implanted condition the substitutional In fraction remains below 20% even at the lowest dose. This result is in accordance with the prediction of the track amorphization model.

Using the phonon model of Nishiyama and Riegel for the electric field gradient we have investigated the possibility of an isotopic mass effect. We will show that there is an isotopic mass effect nearT=0 K. In this temperature region the electric field gradient depends on the probe atom mass only.

In the binary Ni98.5Al1.5 alloy we observed well resolved satellite hyperfine fields at111Cd nuclear probes. The hyperfine shifts derivated are −4.0(3); −8.5(3) and 14.0(3)% relative to the pure nickel value. From the relative intensity of the four components as well as from the quadrupole interaction data we identify the satellites as impurity-probe configurations containing zero, one, two or three Al impurities in the third neighbour shell only. The third neighbour contribution to the hyperfine field at Cd in nickel equals ΔH3= +4.5kG/μB-atom, allowing an estimate ΔH1≃ −17.8 kG/μB-atom for the first shell contribution, confirmed by a similar experiment on Ni98.5Pd1.5.

Perturbed angular correlation spectroscopy was used to determine the magnetic hyperfine field at Cd impurities in PdFe alloys of nominal concentration 0.5, 1.5 and 3.5 at.% Fe. The mean hyperfine field follows the bulk magnetisation and shows a broad distribution with a minimum at 1.5 at.% Fe.

The electric field gradient at temperatures below the Debye temperature θ D is investigated by the time differential perturbed angular correlation technique. A small, but distinct maximum was found near θ D 2 for the system 111 Cd Zn , but not for 111 Cd Cd . This maximum is ascribed to the combined effect of lattice expansion and thermal lattice vibrations on the electric field gradient and discussed in the light of existing models.

High resolution time differential angular correlation, now achievable at low cost by the fast and efficient BaF2 detectors, will be introduced from some examples recently worked out. The results obtained manifest a new impetus for this technique in its extended application to particular problems in nuclear solid state research.

We introduce perturbed angular correlation (PAC) on radioactive isotopes as a new and feasible technique to sense the hyperfine field distribution in randomly disordered alloys. This technique is similar to μSR in the sense that it is a nuclear spin precession measurement, but more widely applicable in view of the limited instrumentation. We present our first results obtained using 111Cd as a typical PAC probe in Au–Fe alloys of different magnetic impurity concentration. Our data clearly show the onset of the spin glass freezing and allows one to derive the mean field value as a function of temperature as well as magnetic impurity concentration.

Time differential perturbed angular correlation experiments were carried out using111Cd probe nuclei to measure the change in conduction electron polarization at different lattice sites due to scattering around an impurity atom.

We demonstrate an application of PAC to the study of magnetic ordering in random alloys. Using111Cd as a probe the spin-glass freezing inAuFe-alloys of different concentrations could be observed. In the Au82Fe18 alloy no indication of ferromagnetism above the freezing temperature was found, due to the fact that the111In probe nuclei are located in a Au rich environment.

The temperature and concentration dependence of the hyperfine field in AuFe alloys in the concentration range of 15 to 28 at%Fe was measured by perturbed angular correlation (PAC) spectroscopy. The temperature dependence of the hyperfine field shows a slope change at T/TC = 0.25 for concentration below 20 at%Fe, while for higher concentration a continuous behaviour is seen.

Perturbed angular correlation on the 111 Cd nucleus as a probe in the Au 82 Fe 18 alloy observes only the spin-glass freezing process but no ferromagnetic spin correlation. This result strongly supports the idea that no long range ferromagnetism and thus no double magnetic phase transition (paramagnet-ferromagnet-spinglass) exists in this alloy.

For the alloy ${\mathrm{Au}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Fe}}_{\mathrm{x}}$ with 0.15lxl0.28, the magnetic ordering as a function of temperature was monitored by the magnetic hyperfine field at $^{111}\mathrm{Cd}$ probe nuclei. Using perturbed angular-correlation spectroscopy, we find a magnetically homogeneous behavior and for xl0.20 two distinct temperature regions (above and below T/${T}_{c}$=0.25). In addition two concentration regions are found, abruptly separating ferromagnetic ordering above ${x}_{c}$=0.202 from the cluster-glass region below. Our results support the interpretation of magnetic order in terms of a random iron distribution with the Fe coordination number as the critical factor.