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M Schreck

Publications and source records attributed to M Schreck.

10 recordsLinked to original sources
PubMed2006

Reentrant superconductivity in Nb/Cu1-xNix bilayers.

We report on the first observation of a pronounced reentrant superconductivity phenomenon in a superconductor/ferromagnet layered system. The results were obtained using a superconductor/ferromagnetic-alloy bilayer of Nb/Cu(1-x)Ni(x). The superconducting transition temperature T(c) drops sharply with increasing thickness dCuNi) of the ferromagnetic layer, until complete suppression of superconductivity is observed at d(CuNi) approximately equal to 4 nm. Increasing the Cu(1-x)Ni(x) layer thickness further, superconductivity reappears at d(CuNi) > or =13 nm. Our experiments give evidence for the pairing function oscillations associated with a realization of the quasi-one-dimensional Fulde-Ferrell-Larkin-Ovchinnikov-like state in the ferromagnetic layer.

Journal Article↗
PubMed2006

Performance of CVD diamond as an optically and thermally stimulated luminescence dosemeter.

Diamond is a material with extreme physical properties. Its radiation hardness, chemical inertness and tissue equivalence qualify it as an ideal material for radiation dosimetry. In the present work, the optically stimulated luminescence (OSL) and thermoluminescence (TL) characteristics of a 10 microm thick CVD diamond (polycrystalline diamond films prepared by chemical vapor deposition) film were studied in order to test its performance as a beta radiation dosemeter. The TL response is composed of four main TL glow peaks; two of these are in the range of 150-200 degrees C and two additional peaks in the 250-400 degrees C temperature range. The integrated TL as a function of radiation dose is linear up to 100 Gy and increases with increasing dose exposure. The dose dependence of the integrated OSL exhibits a similar behavior. The observed OSL/TL behavior for the CVD diamond film clearly demonstrate its capability for applications in radiation dosimetry with special relevance in medical dosimetry owing to the diamond's intrinsic material properties.

Diamond↗
PubMed2005

Extended defect related energy loss in CVD diamond revealed by spectrum imaging in a dedicated STEM.

This article aims at investigations of the low EEL region in the wide band gap system diamond. The advent of the UHV Enfina electron energy loss spectrometer combined with Digital Micrograph acquisition and processing software has made reliable detection of absorption losses below 10 eV possible. Incorporated into a dedicated STEM this instrumentation allows the acquisition of spectral information via spectrum maps (spectrum imaging) of sample areas hundreds of nanometers across, with nanometers pixel sizes, adequate spectrum statistics and 0.3 eV energy resolution, in direct correlation with microstructural features in the mapping area. We aim at discerning defect related losses at band gap energies, and discuss different routes to simultaneously process and analyse the spectra in a map. This involves extracting the zero loss peak from each spectrum and constructing ratio maps from the intensities in two energy windows, one defect related and one at a higher, crystal bandstructure dominated energy. This was applied to the residual spectrum maps and their first derivatives. Secondly, guided by theoretical EEL spectra calculations, the low loss spectra were fitted by a series of gaussian distributions. Pixel maps were constructed from amplitude ratios of gaussians, situated in the defect and the unaffected energy regime. The results demonstrate the existence of sp2-bonded carbon in the vicinity of stacking faults and partial dislocations in CVD diamond as well as additional states below conduction band, tailing deep into the band gap, at a node in a perfect dislocation. Calculated EEL spectra of shuffle dislocations give similar absorption features at 5-8 eV, and it is thought that this common feature is due to sp2-type bonding.

Journal Article↗
PubMed2005

Psychological risk factors of incidence of breast cancer: a prospective cohort study in Finland.

BACKGROUND: Belief that depression and other psychological factors predict breast cancer is common, but there have been few prospective epidemiological studies on this relationship. METHOD: The relationship between depression, personality traits, illness attitudes, life events and health history, and breast cancer risk was studied in a prospective, 6-9 year follow-up of a cohort study of 10892 Finnish women of 48-50 years of age at the baseline. Cancer cases were obtained from the Cancer Registry of Finland. Multivariate logistic regression analysis was performed controlling for socioeconomic factors, family history of cancer, parity, and health behaviours. RESULTS: Breast cancer incidence in the cohort was 1.15 times the average in age group 50-59. There was no evidence of depression, trait anxiety, cynical distrust, or coping being significant predictors of breast cancer incidence. CONCLUSION: In this cohort study with the 6-9 year follow-up, psychological factors such as depression, trait anxiety, cynical distrust, or coping did not increase breast cancer risk.

Adaptation, Psychological↗
PubMed2003

Epitaxy of cubic boron nitride on (001)-oriented diamond.

Cubic boron nitride (c-BN), although offering a number of highly attractive properties comparable to diamond, like hardness, chemical inertness and a large electronic bandgap, up to now has not found the attention it deserves. This mostly has to do with preparational problems, with easy chemical routes not available and, instead, the necessity to apply ion-bombardment-assisted methods. Hence, most of the c-BN samples prepared as thin films have been nanocrystalline, making the prospect of using this material for high-temperature electronic applications an illusion. Although heteroepitaxial nucleation of c-BN on diamond substrates has been demonstrated using the high-pressure-high-temperature technique, none of the low-pressure methods ever succeeded in the epitaxial growth of c-BN on any substrate. Here, we demonstrate that heteroepitaxial c-BN films can be prepared at 900 degrees C on highly (001)-oriented diamond films, formed by chemical vapour deposition, using ion-beam-assisted deposition as a low-pressure technique. The orientation relationship was found to be c-BN(001)[100]||diamond(001)[100]. High-resolution transmission electron microscopy additionally proved that epitaxy can be achieved without an intermediate hexagonal BN layer that is commonly observed on various substrates.

Journal Article↗
PubMed2001

Two distinct groups of non-attenders in an organized mammography screening program.

OBJECTIVE: To find out reasons for non-attendance and to study subgroup differences of the non-attenders in an organized mammography screening program. DESIGN: Prospective for background and psychosocial factors, retrospective for reasons of non-attendance. SETTING: Finnish screening based on personal first round invitations, with 89% attendance rate. PARTICIPANTS: Four hundred thirty six women with both pre-screening response to socioeconomic and psychosocial measures, and post-screening response reporting reasons of non-attendance. MAIN RESULTS: Most common single reason for non-attendance was previous recent mammogram (53%), but also reasons related to practical obstacles, worry and fear, knowledge and attitudes, and organization of screening were mentioned. Two distinct groups of non-attenders were found based on the reasons for non-attendance. Those who did not attend because a mammogram taken elsewhere (ELSE, n = 233) were urban, well-to-do women, who took care of their health by own initiation and felt more susceptible to breast cancer, and also expected mammogram to be painful. Other (real) non-attenders (REAL, n = 155) were less compliant with health recommendations and services, more socially isolated, depressed and anxious than ELSE. Level of depression among REAL was clearly higher (10.80) than the mean value (7.91, SD = 7.28) of the age group, and was also slightly above the cut-off score of 10 indicating mild or moderate depression. Trait anxiety was also markedly higher (40.18) than that of the same age group (37.76, SD = 8.95). CONCLUSIONS: Further research should clarify determinants and consequences of depression and anxiety among real non-attenders. Knowledge gaps and attitudinal barriers among non-attenders require more targeted campaigns.

Breast Neoplasms↗
PubMed1999

Psychosocial predictors of first attendance for organised mammography screening.

OBJECTIVE: To study psychosocial predictors of attendance at an organised breast cancer screening programme. SETTING: Finnish screening programme based on personal first round invitations in 1992-94, and with 90% attendance rate. METHODS: Attenders (n = 946) belonged to a 10% random sample (n = 1680 women, age 50, response rate 64%) of the target population (n = 16,886), non-attenders (n = 641, 38%) came from the whole target population. Predictors were measured one month before the screening invitation. Measures included items for social and behavioural factors, Breast Cancer Susceptibility Scale, Illness Attitude Scale, Health Locus of Control Scale, Anxiety Inventory, and Depression Inventory. Univariate and multivariate logistic regression analyses were used to predict attendance. RESULTS: Those most likely to attend were working, middle income, and averagely educated women, who had not had a mass mammogram recently, but who regularly visited gynaecologists, attended for Pap smear screening, practised breast self examination, and who did not smoke. Low confidence in their own capabilities in breast cancer prevention, overoptimism about the sensitivity of mammography, and perception of breast cancer risk as moderate were also predictive of attendance. Expectation of pain at mammography was predictive of non-attendance. CONCLUSION: Mammography screening organised as a public health service was well accepted. A recent mammogram, high reliance on self control of breast cancer, and an expectation of pain at mammography deterred attendance at screening. Further information about these factors and health information on screening are needed.

Breast Neoplasms↗
PubMed1991

Experimental pain thresholds and plasma beta-endorphin levels during exercise.

Experimental pain thresholds (electrical intracutaneous finger and dental pulp stimulation) and plasma hormone levels (beta-endorphin, cortisol, and catecholamines) were measured in ten healthy sportive men before, during, and after progressively more strenuous physical exercise. In a double-blind study conducted on two different days, 20 mg of the opioid-antagonist naloxone or placebo was administered prior to exercise. A significant pain threshold elevation was found during exercise for finger (ANOVA, P less than 0.004) and dental pulp stimulation (P less than 0.01). Pain threshold elevation was most pronounced during maximal exertion, at which time the subjects reported the greatest subjective fatigue. Thresholds remained elevated 10-15 min after the end of exercise, and, 60 min after exercise, thresholds returned to baseline values. The subjective magnitude estimation of suprathreshold stimuli was significantly reduced (P less than 0.0001) 5-10 min after exercise. Plasma beta-endorphin, cortisol, and catecholamines increased significantly (P less than 0.0005, all values) during exercise. Plasma beta-endorphin levels did not correlate significantly with pain thresholds (r = -0.37, NS). Naloxone failed to affect pain thresholds, although beta-endorphin and cortisol increased significantly more (P less than 0.02) during exercise after naloxone. It is concluded that short-term, exhaustive physical exercise can evoke a transient elevation in pain thresholds. This exercise-induced elevation in pain threshold does not, however, appear to be directly related to plasma endorphin levels.

Adult↗