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The interaction energy of three neutral molecules that form a nanocluster is studied. It is assumed that one molecule (M0) has a dipole moment, while the other two (M1 and M2) are nonpolar. The molecule interaction energy in such a nanocluster is determined by the sum of dispersion interaction energies of each pair of molecules and the sum of inductive energies of the molecules. Analytical expressions for these energies as functions of the distance between the centers of mass of the molecules have been obtained. A method for the determination of damping functions which takes the contribution of repulsive forces into account has been developed. Analytical expressions for the molecule interaction energies for a two-molecule cluster in an external field of the third molecule have been obtained. A nanocluster consisting of a molecule of polar isomer pentene C5H10 and a nonpolar molecule of polycyclic aromatic hydrocarbon pyrene C16H10 in the external electrostatic field of another pyrene molecule is considered. The calculation showed that the interaction energy of the two-molecule nanocluster increases by a factor of 1.5 if this cluster is in the field of the induced dipole moment of an external pyrene molecule.

The paper considers a donor-acceptor nanocluster fluorescing in a microwave infrared radiation field. It is assumed that the nanocluster consists of two dipole-dipole interacting organic molecules. It is shown that the fluorescence process of the nanocluster occurs if the donor molecule contains a substructure of identical diatomic pairwise interacting bonds of dipoles (an IR antenna). This antenna is capable of accumulating vibrational energy as a sum of collective vibrational quanta (excimols). The acceptor molecule has no permanent dipole moment and cannot be excited by microwave IR radiation. This molecule is polarized in the dipole moment field of the donor IR antenna and can receive energy accumulated in the IR antenna of the donor molecule. If the acceptor molecule has an electronically excited state in the long-wavelength visible region of its absorption spectrum, then after receiving energy equal to the energy of this state from the donor antenna, the electronic excitation of the acceptor molecule and its fluorescence is possible. As an example, the fluorescence of a nanocluster is considered whose donor molecule has a C n H2n IR antenna. The acceptor molecule is aromatic and the external infrared frequency, 1.1 × 1014 s−1, is equal to the frequency of the excimol in the donor infrared antenna.

The corrosion behavior of fullerene coated iron samples was investigated by using electrochemical techniques. Fullerene was deposited on iron substrates via thermal evaporation under high vacuum conditions. Subsequent sample preparation included heat treatment as well as Ar+ ion irradiation under various conditions, which were carried out to modify the fullerene coatings. Changes in the structure of the films due to the treatment were analyzed by Raman spectroscopy. To reveal the samples’ corrosion behavior, cyclovoltammetric measurements were performed in a weakly acidic aqueous medium particularly with regard to possible corrosion protective properties. As the results show, Ar-ion treatment of the fullerene films leads to considerably increased corrosion resistance, which is due to formation of a dense amorphous carbon network. In contrast, heat treatment of the fullerene films increases the corrosion rates, presumably due to formation of iron carbide, which leads to galvanic corrosion.

For developing a dihydropyridine/pyridinium salt redox delivery system that could be useful for SPECT investigations by 99m Tc compounds the synthesis of a mixed-ligand complex of the long-lived isotope 99 Tc is described. The new compound bearing a pyridinium salt moiety was characterised by NMR-spectrometry and X-ray structure analysis. By reduction with sodium dithionite the corresponding 1,4-dihydropyridine complex was prepared and the stability in buffer, tissue homogenates, blood plasma and cerebrospinal fluid was investigated by UV-VIS spectrometry.

Summary Background The increasing prevalence of atopic eczema has been linked to the alteration of the Western diet, namely the reduced consumption of omega-3 (n-3) polyunsaturated fatty acids (PUFA) and an increased omega-6 (n-6) PUFA intake. Objectives The aim of the pilot study was to determine the efficacy of dietary n-3 PUFA docosahexaenoic acid (DHA) in patients with atopic eczema. Methods Fifty-three patients suffering from atopic eczema aged 18–40 years were recruited into this randomized, double-blind, controlled trial and received either DHA 5·4 g daily (n = 21) or an isoenergetic control of saturated fatty acids (n = 23) for 8 weeks. At weeks 0, 4, 8 and 20 the clinical outcome was assessed by the SCORAD (severity scoring of atopic dermatitis) index. IgE production and activation of peripheral blood mononuclear cells (PBMC) were analysed. Plasma fatty acids were measured by gas chromatography. Results DHA, but not the control treatment, resulted in a significant clinical improvement of atopic eczema in terms of a decreased SCORAD [DHA: baseline 37·0 (17·9–48·0), week 8 28·5 (17·6–51·0); control: baseline 35·4 (17·2–63·0), week 8 33·4 (10·7–56·2)]. A significant reduction of anti-CD40/interleukin 4-mediated IgE synthesis of PBMC was detected in the DHA group only. Supplementation led to a modulated activation status of PBMC in both groups. The DHA group showed an increase of plasma n-3 PUFA and a decrease in the n-6/n-3 PUFA ratio. Conclusions Our data suggest that dietary DHA could be bioactive and might have a beneficial impact on the outcome of atopic eczema, but our results need to be confirmed in a larger study.

Currently the significance of the sentinel node (SN) biopsy also for head and neck cancer is discussed intensively. Based on the complex anatomic structures of this region with a low distance between primary and sentinel node as well as approximately 300 lymph nodes an intensive discussion of the methodical basis of sentinel node detection seems to be essential. Thus it was the aim of the present study to examine the detection spectrum of a gamma probe for identification of cervical lymph nodes using an in vitro model to describe and objectify the particularities of measurement existing in the head and neck region.In an in vitro model the detection spectrum of a gamma probe is examined in 29 different series of measurements (variation of the specimen filled with 99m pertechnetat regarding activity, position, collimator distance, tissue sheath).The presented in vitro model reflects the clinical problem of narrow intranodal activity of neighbouring lymph nodes and reveals a direct relation between the number of radiation sources and their isolated evidence. Using muscle tissue with a thickness of 0.4 cm, two two-rowed radiation sources, the more powerful is placed 1.5 cm behind the other specimen, with a lateral difference of 3 cm, can be resolved only with a maximal detector distance of 1 cm. Not the difference of the tissue but the thickness of the tissue is decisive for detection.Especially for pharyngeal and laryngeal lymph nodes a transcutaneous measurement reflecting the exact localisation of hot nodes in the area of the deep jugular lymph nodes is not possible with increasing tissue thickness. The described results require a critical discussion of the different detection techniques varying among the different working groups of this field.

The sentinel node (SN) biopsy in an actually discussed topic. The use of a well-type NaI detector for gamma ray spectroscopy (WTD) beside the use of a handheld gamma probe (HGP), is investigated. In 18 patients suffering from a head and neck squamous cell carcinoma (HNSCC) with different lymph node status an intraoperative SN biopsy was accomplished with a HGP. 64 separately taken lymph nodes were supplied to an additional measurement in a WTD. A tumor-free SN represented the tumor-free lymph node status in 9 patients. In 5 cases an isolated tumor metastasis could be proven in the SN. SN biopsy has no meaningfullness in cases of advanced metastatic spread ipsilaterally, but possibly in contralateral N0-neck. In 64 separately investigated lymph nodes an activity enrichment could be proven in the WTD. With this procedure small count rates could be determined in contrast to the HGP. The distinction of weakly enriching lymph nodes was less favourable with the HGP but successful with the WTD. The additional use of a WTD offers a more exact distinction of intranodal disintegration rates of the draining lymph nodes. The WTD may increase the security of intraoperative SN biopsy.

The grazing incidence surface-induced dissociation (GI-SID) of various protonated peptides with typical kinetic energies of 350 eV was investigated. Peptide ions were generated by matrix-assisted laser desorption/ionization (MALDI) using delayed extraction. The collision target surfaces used were aluminum and a liquid film of perfluorinated hydrocarbons. All peptides studied in these experiments showed enhanced fragment ion yields at grazing incidence (GI-SID effect) as observed in our former experiments with other precursor ion types. In general the GI-SID spectra exhibit N-terminal a(1)-type fragment ions, immonium ions and side-chain fragment ions in the low mass-to-charge region. Fragment ion series of the peptide backbone were not observed, which are typical and abundant in the spectra of established fragmentation techniques like collision-induced dissociation, MALDI post-source decay or surface-induced dissociation at steeper angles. The potential of the GI-SID process to yield useful information for primary structure determination of peptides is indicated by the observed differences in the GI-SID spectra of the isomeric dipeptides LR and IR.

Superheavy elements (SHE) might be formed via a reaction mechanism called “fusion after instantaneous fission”, which is supposed to occur during the collision of a deformed very heavy nucleus with a spherical one. We bombarded natural uranium targets with lead ions and searched for alpha-emitting and spontaneously fissioning reaction products. Different techniques were used: a rotating wheel, a gas jet system and a radiochemical procedure. No SHE have been found. The upper cross section limits are between 10−33 cm2 and 10−34 cm2 within the half-life range from 1 ms to 1 year. In addition, the production cross sections of some Cm and Cf isotopes and of Am fission isomers were determined.

A gas-jet transport system is greatly improved by loading the sweep gas with aerosols of a specific size. In the thermalization chamber of such a gas-jet system the radioactive atoms are attached to these aerosols. The aerosols then are transported with negligible losses to some collector foil. Optimizing all parameters of the system a stable overall transport efficiency of approximately 80% can be achieved for up to several days, with variations of only ±1.5%.

Level energies of low-spin yrast states up to spin 8+ are firmly established on the basis ofα-γ-spectroscopy. Six newα-lines associated with the decay from212Po suggest additional levels populated in theβ-decay of212Bi.

The multiplicity of neutron emission in /sup 12/C-induced nuclear reactions with /sup 197/Au, /sup 209/Bi, /sup 232/Th, and /sup 238/U was measured directly on-line using a Gd-loaded scintillation neutron multiplicity counter with 1 m diameter recording single neutrons with a registration efficiency of about 80%. Using a well-focused carbon beam one could measure up to about 30 neutrons per nuclear interaction directly, when the neutron multiplicity counter was triggered with a prompt fission fragment. For /sup 197/Au and /sup 209/Bi targets, fission was observed to follow compound-nucleus formation, whereas in the cases of /sup 232/Th and /sup 238/U, fission following incomplete fusion was seen to contribute also. An average multiplicity of nu-bar = (4 +- 1) neutrons was measured for incomplete fusion, while for complete fusion, nu-bar varied between 8 and 12, depending on target and bombarding energy. The results complement measurements of Viola et al. on fragment-angular correlations and agree with them.

At the heavy ion accelerator UNILAC a gas jet transport system has been installed for the investigation of short-lived reaction products. The actual working conditions of the system were tested, for instance, by means of the compound reaction 84 Kr+ 75 As. The existence of 157 Tm was confirmed by alpha-decay measurements. In the reaction 136 Xe+ 209 Bi no indication for the formation of superheavy elements has been found with a cross section limit of 10 nb.

We are searching for superheavy elements in the carbonaceous chondrite Allende, a recently fallen meteorite. We separated from the bulk material those elements (Pb, Cd, etc.), which can be dissolved in strong acids and precipitated at PH ⋍ 1.5 with H2S. In a precipitate isolated from 2.3 kg Allende no spontaneous fission activities were found: zero decays during one year. The present results yield an upper concentration limit of 2·10−15 g/g for superheavy elements in this meteorite.

Haloes were investigated in cordierite from Brazil, some of the haloes being rather large or “giant”. Their sizes seem to be too large to be explained on the basis of known natural alpha emitters. We propose a rather trivial geometric explanation of the very large haloes observed by us: random cuts through “normal” haloes around large inclusions can lead to the apparent observation of “giant” haloes. This interpretation is supported by an observed correlation between halo radii and inclusion diameters. Furthermore, no spontaneous fission activity or unusual alpha-activity could be measured by counting techniques in these inclusions.

A He-jet system has been developed for the transport of 252Cf fission fragments and 228Th decay products. The essential cluster formation occurs in a cluster breeder separated from the radioactive source. This cluster breeding is accomplished by adding liquids such as H2O or CCl4 to the transport gas and then blowing the mixture past an UV lamp. The efficiency of the transport from the radioactive source to the end of the capillary ranges between 50 and 80%. The efficiency of the skimming process alone is about 50%. K X-ray spectroscopy indicates that the transport of activity is largely independent of the particular element.

The deexcitation of the compound nucleus150Gd formed by156O+134Ba and40Ar+110Pd have been studied. Excitation functions were determined for various exit channels: (HI, × n) withx=3, 4, 5 (HI, pxn) withx=2, 3, 4 (HI, axn) withx=3 and 5. A systematic comparison has been made between these experimental data and the results of evaporation calculation using the ALI CE code. The very good agreement obtained for the total residue cross section disappears completely when a more detailed analysis of the different contributions is performed. Absolute and relative cross sections are not reproduced; excitation functions of each individual channel (HI, 3n), (HI, 4n) etc. ... are not found at the right place in energy. A very preliminary explanation for such a shift towards higher energies is suggested.

A time-of-flight mass identification system connected to the Alice He-jet has been tested on-line with α and β emitters produced through known heavy-ion reactions. It is shown that masses up to 150 are well resolved. Experimental results are given and further developments are briefly described. This system is actually used for the search for exotic nuclei.

Experiments are described to look for SHE using SSNTD. First results on the investigation of the hot brine Atlantis II are given.

At the Darmstadt UNILAC newα-emitting nuclei were produced in the bombardment of89Y and93Nb targets using84Kr ions with energies in the range of 5.1 to 5.5 MeV/u, and 5.8 to 6.4 MeV/u, and using86Kr ions with energies in the range of 5.6 to 6.0 MeV/u. Reaction recoils emitted from the targets were stopped and transported with argon to a collection site. Using three alpha detectors and spectrum multiscaling, energies and half-lives were measured. Ir and Re isotopes were identified by cross bombardments, excitation function data andα-systematics. The decay characteristics of the new species are as follows: Estimates onα-branching ratios have been obtained for169, 170Os and166, 167, 168Re.

Excitation functions have been drawn for evaporation residues issued from150Gd, a compound nucleus produced either by16O ions on134Ba, or by40Ar on110Pd. Absolute cross sections were measured for145–147Gd,145–147Eu,141mSm,143mSm,140mPm and139mNd. Complete fusion cross sections have been obtained and compared to calculated estimations based, at low energies, on the simple expressionσCF=πRFuss2 (1−VFus/E) whereRFus andVFus are respectively the distance and the potential for fusion atdV/dr=0. For high energies σCF=πRcr2 (1−Vcr/E) with the model of critical distanceRcr and critical potentialVcr. Thresholds energies have been determined with a particular care. The analysis of the shape and the width of excitation functions, particularly for the emission of 4 and 5 neutrons, has been carried out and compared to calculated values. The difference between argon and oxygen induced reactions has been attributed to the difference inl population in the entrance channel.

A mobile helium-jet system has been set up, capable of transporting short-range spallation products (range in ThF4 ⩽ 66 μg/ cm2) in a closed loop helium circuit. This system was used for the transport of spallation products produced by 600 MeV protons from a 232Th and a 241Am target in the extracted beam of the CERN Synchrocyclotron (SC). The activity was transported through a 61 m long capillary to a low-background area, where it was collected in a vacuum chamber on a moving tape system. Alpha- and gamma-ray singles spectra, alpha-gamma coincidence spectra, as well as fission spectra could be investigated.

No superheavy elements were observed among gas jet collected reaction products of (natU+136Xe) and (natU+238U) at the UNILAC accelerator. The upper limits for their production are ⋖ 3×10 −33 cm 2 in the half-live range 10 s ⩽T 1 2 ⩽ 1000 s .

Evaporation residue cross sections have been measured by the technique of the telescopeΔE ·E counter at very small angles. The angular distribution has been followed down to 2°15′, and rather precise values were obtained for that fraction of the compound nucleus decay after complete fusion for the systems63Cu+Ni,63Cu+Ag and52Cr+56Fe at two bombarding energies. A comparison has been done with evaporation calculations using the code ALICE, and the rotating liquid drop concept. It is shown that a large discrepancy occurs at low energy for these heavy projectiles. The origin of this difference is discussed.

The basic principles of high energy heavy-ion induced desorption are summarized elsewhere [1,2] and assumed to be known. Secondary ions are desorbed either by the impact of a fission fragment from a Cf-252 source [1] or of a heavy ion beam pulse, e.g. I-127 [3] and their time-of-flight is analyzed event by event.