Beta spectrometry with metallic magnetic calorimeters in the framework of the European EMPIR project MetroBeta

The aim of the European Metrology Research Project MetroBeta is to improve the knowledge of the shapes of beta spectra, both in terms of theoretical calculation and measurement. The precise knowledge of beta spectra is required for the activity standardisation of pure beta emitters. Metallic magnetic calorimeters (MMCs), a type of cryogenic detectors, with the beta emitter embedded in the absorber have proven to be among the best beta spectrometers, in particular for low-energy beta transitions. Within this project, new designs of MMCs optimized for five different beta energy ranges were developed and a new detector module was constructed. The beta spectra of ¹⁵¹Sm, ¹⁴C and ⁹⁹Tc have been measured so far; additional measurements with ³⁶Cl are under preparation. Improved theoretical calculation methods and complementary measurement techniques complete the project.

Measurement of the electron capture probabilities of 55Fe with a metallic magnetic calorimeter

The ratios of the electron capture probabilities P_K, P_L and P_M of ⁵⁵Fe have been measured with a metallic magnetic calorimeter, a specific type of cryogenic detector. The ⁵⁵Fe source was enclosed in the detector absorber, whose dimensions were chosen such that the detection efficiency for Mn K X-rays was larger than 99.99%. Since all electrons and photons emitted by the source are absorbed in the detector, the detection efficiency is virtually 100% for K, L and M captures. The energy threshold was low enough to allow for clear separation of the M captures (~ 80eV) from noise. The capture probability ratios were translated to capture probabilities using the recommended value for the probability of the undetected N captures. The resulting values are in agreement both with the recommended values of P_K, P_L and P_M and with the experimental data of Pengra and coworkers.

Development of 100 Mo -containing scintillating bolometers for a high-sensitivity neutrinoless double-beta decay search

This paper reports on the development of a technology involving 100 Mo -enriched scintillating bolometers, compatible with the goals of CUPID, a proposed next-generation bolometric experiment to search for neutrinoless double-beta decay. Large mass ( ∼ 1 kg ), high optical quality, radiopure 100 Mo -containing zinc and lithium molybdate crystals have been produced and used to develop high performance single detector modules based on 0.2-0.4 kg scintillating bolometers. In particular, the energy resolution of the lithium molybdate detectors near the Q-value of the double-beta transition of 100 Mo (3034 keV) is 4-6 keV FWHM. The rejection of the α -induced dominant background above 2.6 MeV is better than 8 σ . Less than 10 μ Bq/kg activity of 232 Th ( 228 Th ) and 226 Ra in the crystals is ensured by boule recrystallization. The potential of 100 Mo -enriched scintillating bolometers to perform high sensitivity double-beta decay searches has been demonstrated with only 10 kg × d exposure: the two neutrino double-beta decay half-life of 100 Mo has been measured with the up-to-date highest accuracy as T 1 / 2 = [6.90 ± 0.15(stat.) ± 0.37(syst.)] × 10 18 years . Both crystallization and detector technologies favor lithium molybdate, which has been selected for the ongoing construction of the CUPID-0/Mo demonstrator, containing several kg of 100 Mo .

Beta spectrometry with metallic magnetic calorimeters

Metallic magnetic calorimeters are a specific type of cryogenic detectors that have been shown to enable precise measurement of the shape of low energy beta spectra. The aim of their use at LNHB is the determination of the shape factors of beta spectra. The beta source is enclosed in the detector absorber, allowing for very high detection efficiency. It has turned out that the type of source is of crucial importance for the correctness of the measured spectrum. Spectra of (63)Ni measured with several sources prepared by drying a NiCl2 solution differ from one another and from theory, whereas spectra measured with electroplated sources are reproducible and agree with theory. With these latter measurements we could confirm the atomic exchange effect down to very low energy (200 eV).

Validation study of a new technique for absolute activity measurement with 4pi solid angle metallic magnetic calorimeters

In this paper we present a prototype of a new class of detectors, metallic magnetic calorimeters operating at cryogenic temperatures, which we are developing for absolute activity measurement of low-energy-emitting radionuclides. We explain the detection principle and give a detailed description of the realisation of the prototype, containing an (55)Fe source inside the detector absorber. The analysis of first data taken with this detector is presented and the result of activity measurement compared with liquid scintillation counting. Some ways for reducing the uncertainty that can be achieved with this new technique are proposed.

High-energy resolution X-ray, gamma and electron spectroscopy with cryogenic detectors

Cryogenic detectors offer remarkably better energy resolutions than those achievable with conventional semiconductor or scintillation detectors. With the additional asset of a detection efficiency close to unity for low-energy X-ray photons and electrons, these detectors have the potential to perform X-ray, gamma and electron spectroscopy of a hitherto unknown quality, in particular at low energies. Two types of cryogenic detectors are described and the results of prototype detectors are presented.

A new absolute method for the standardization of radionuclides emitting low-energy radiation

Microcalorimeters (or bolometers) operated at temperatures below 100 mK allow individual counting of photons and electrons with a very low energy detection threshold. The physics is based on the pulse temperature increase of the target (or absorber) of the detector due to the complete absorption of both electrons and photons. Since this target can be constructed with a perfect 4-pi geometry, a bolometer offers potentially a new method for absolute activity measurements of radionuclides emitting low-energy radiation. In this paper we present our first results of a feasibility study of activity standardization of a 55Fe solution with a prototype 4-pi bolometer.

Isolation and continuous growth of Chlamydia pneumoniae from arterectomy specimens

For the purpose of collecting Chlamydia pneumoniae strains of vascular origin that could be grown continuously in vitro, a cell culture system has been established. Using different types of vascular specimens obtained from 38 patients, Chlamydia pneumoniae could be isolated in three (7.9%) cases. The strains were obtained from specimens of the carotid artery, the femoral artery and an infrarenal aneurysm of the abdominal aorta of three male atherosclerosis patients. Thus, viable Chlamydia pneumoniae strains are also present in vascular regions other than those hitherto described.

Pseudomonas acidovorans: a bacterium capable of mineralizing 2-chloroaniline

Prolonged adaptation of Ca-alginate immobilized cells of Pseudomonas acidovorans CA28 to a mixture of 3-chloroaniline (3-CA)1) and 2-CA and subsequently to 2-CA as sole substrate led to the isolation of another strain, termed CA50 with the additional capability of utilizing 2-CA as sole source of carbon, nitrogen, and energy. Batch-degradation of 190 mg/l of 2-CA at pH 6.1 by this newly isolated strain was achieved within 3 days, at higher concentrations up to 0.6 g/l increasing lag-phases and degradation periods were observed. Except chloride and ammonium no further metabolites were detectable in the medium. Mineralization of 2-CA proceeds via the modified ortho-cleavage pathway as demonstrated by the presence of catechol 1,2-dioxygenase (C120) activity, which is characterized by its substrate specificity and elution behaviour on DEAE-cellulose.

Characterization of isofunctional ring-cleaving enzymes in aniline and 3-chloroaniline degradation by Pseudomonas acidovorans CA28

During degradation of aniline and 3-chloroaniline, respectively, by Pseudomonas acidovorans CA28, selective induction of two catechol 1,2-dioxygenases (C12O) was observed. C12O I activity was the sole ring-cleaving enzyme detectable in cell-free extracts after growth on aniline, while C12O II was exclusively found after growth on 3-chloroaniline. Both enzymes were clearly differentiated by their elution behaviour on DEAE-cellulose and their substrate specificities. For C12O I high activity was demonstrable only with unsubstituted catechol, while C12O II showed preference for and high affinity towards chlorinated catechols. Therefore, evidence of different ortho-cleavage enzymes in Pseudomonas acidovorans CA28 involved in aniline and 3-chloroaniline metabolism, respectively, is indicated.

Degradation of phenol and phenolic compounds by Pseudomonas putida EKII

The phenol-degrading strain Pseudomonas putida EKII was isolated from a soil enrichment culture and utilized phenol up to 10.6 mM (1.0 g.l-1) as the sole source of carbon and energy. Furthermore, cresols, chlorophenols, 3,4-dimethylphenol, and 4-chloro-m-cresol were metabolized as sole substrates by phenol-grown resting cells of strain EKII. Under conditions of cell growth, degradation of these xenobiotics was achieved only in co-metabolism with phenol. Phenol hydroxylase activity was detectable in whole cells but not in cell-free extracts. The specificity of the hydroxylating enzyme was found during transformation of cresols and chlorophenols: ortho- and meta-substituted phenols were degraded via 3-substituted catechols, while degradation of para-substituted phenols proceeded via 4-substituted catechols. In cell-free extracts of phenol-grown cells a high level of catechol 2,3-dioxygenase as well as smaller amounts of 2-hydroxymuconic semialdehyde hydrolyase and catechol 1,2-dioxygenase were detected. The ring-cleaving enzymes were characterized after partial purification by DEAE-cellulose chromatography.

Isolation and characterization of a 2-(2,4-dichlorophenoxy) propionic acid-degrading soil bacterium

The 2-(2,4-dichlorphenoxy)propionic acid (2,4-DP)-degrading bacterial strain MH was isolated after numerous subcultivations of a mixed culture obtained by soil-column enrichment and finally identified as Flavobacterium sp. Growth of this strain was supported by 2,4-DP (maximum specific growth rate 0.2 h-1) as well as by 2,4-dichlorophenoxyacetic acid (2,4-D), 4-(2,4-dichlorophenoxy)butyric acid (2,4-DB), and 2-(4-chloro-2-methylphenoxy)propionic acid (MCPP) as sole sources of carbon and energy under aerobic conditions. 2,4-DP-Grown cells (10(8] of strain MH degraded 2,4-dichlorophenoxyalkanoic acids, 2,4-dichlorophenol (2,4-DCP), and 4-chlorophenol at rates in the range of 30 nmol/h. Preliminary investigations indicate that cleavage of 2,4-DP results in 2,4-DCP, which is further mineralized via ortho-hydroxylation and ortho-cleavage of the resulting 3,5-dichlorocatechol.

Efficacy and safety of moclobemide compared with imipramine in the treatment of major depressive disorder. Double-blind multicenter study, Austria

In a double-blind, 4-week, prospective, randomized multicenter (17 centers) study we checked on the efficacy, tolerability and safety of moclobemide (300-600 mg/d) compared to imipramine (100-200 mg/d) in parallel groups of patients with a Major Depressive Episode (DSM III). The mean % reduction of the HAMD at the end of treatment was 51.7 in the moclobemide group and 52.1 in the imipramine group. The percentage of patients in whom efficacy was globally judged as "good" or "very good" was 62% in the moclobemide group and 60% in the imipramine group. There was no statistically significant difference in the efficacy in both groups but in some factors there was a trend for a better amelioration favoring moclobemide. The final overall physician's judgement of tolerability was "good" or "very good" in 83% of moclobemide patients and in 74% of imipramine patients. Adverse events were reported or observed in 56% of moclobemide patients and in 69% of imipramine patients. The number of mild, moderate and severe adverse events was higher in the imipramine group with a total of 286 versus 189. There was a statistically high significant difference considering the tolerability favoring moclobemide again. In this project the basic goal to find a substance with at least the same efficacy but a much better tolerability for sure got fulfilled.