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Many long-term childhood cancer survivors suffer from treatment-related late effects, which may occur in any organ and include a wide spectrum of conditions. Long-term follow up (LTFU) is recommended to facilitate early diagnosis and to ensure better health outcomes. Due to the heterogeneity of these sequelae, different specialists work together in diagnosis and treatment of these conditions. Experts from both pediatric and internal medicine are involved in age-appropriate care by providing a transition process. Hence, LTFU of childhood cancer survivors is a prototypic example for multidisciplinary care of patients with complex needs treated in a specialized setting. International collaborations of health care professionals and scientists involved in LTFU of childhood cancer survivors, such as the International Guideline Harmonization Group, compile surveillance recommendations that can be clinically adopted all over the world. These global networks of clinicians and researchers make a joint effort to address gaps in knowledge, increase visibility and awareness of cancer survivorship and provide an excellent example of how progress in clinical care and scientific research may be achieved by international and multidisciplinary collaboration., + ID der Publikation: unilu_59783 + Sprache: Englisch + Letzte Aktualisierung: 2022-09-26 16:50:48

Hellmut J. Gebauer: Christian Jacob Zahn. Jurist, Verleger, Komponist, Unternehmer und Politiker (1765-1830). Markstein Verlag Filderstadt 2004. 415 Seiten. € 24,80. ISBN 3-935129-17-3

Background: Ototoxicity (hearing loss, tinnitus and/or vertigo) is a serious adverse event of cisplatin treatment in children with cancer. The heterogeneity in ototoxicity occurrence after similar treatment suggests a role for genetic susceptibility. This study investigated the association between carriership of novel single nucleotide polymorphisms (SNPs) and cisplatin-induced hearing loss (CIHL) in childhood cancer patients.Material and methods: The discovery cohort included cisplatin treated, non-cranial irradiated pediatric cancer patients within the European PanCareLIFE (PCL) study (N=390). CIHL at end of cancer treatment was defined as Muenster grade >=2b, assessed by pure tone audiometry. DNA was genotyped using the Infinium© Global Screening Array. Logistic regression models were applied including age at diagnosis, sex, cisplatin total cumulative dose and principal components 1-4, assuming an additive effect of the minor allele. Replication of the findings was performed in two independent, similarly treated cohorts (N=192 and N=188). Functional validation experiments in cultured human HeLa cell lines were performed to determine the effect of knockdown of the SNPs nearest identified gene on cisplatin-induced toxicity.Results: In the PCL discovery cohort, 8 SNPs reached a suggestive significance of P

Die Mühle in der Sächsischen Schweiz mit großer Geschichte und einer neuen Herausforderung für die Zukunft – Technikgeschichte von Gestern – Heute und in Zukunft erleben?

Methodology and results are presented for the “safety ranking” of legacy radioactive material storage sites that are situated in populated areas adjacent to the Chernobyl Exclusion Zone and contain wastes from clean-up and decontamination operations carried out in 1986 - 1989. Based on this safety ranking, recommendations regarding the order of remediation and management strategy for these sites are provided. The results suggest that remedial works for radioactive legacy sites can be optimized, and waste volumes that may require retrieval and further disposal in engineered facilities can be considerably minimized. It is recommended that the managing organization (Kyiv Inter-Regional Special Combine of UkrSC “Radon”) should focus their characterization, monitoring and maintenance works on the relatively few higher risk legacy sites identified in this study, while low-risk sites can be eventually released from regulatory control.

An approach is described for assessment of the end state radiological criteria for remediation of radioactively contaminated sites. The target criteria are set in a form of prospective effective doses for members of the population who are subject to the higher exposures (representative persons). Brief review of international best practice in setting risk based remedial criteria is presented. The site-specific release criteria for activity concentrations in released material (e.g., Bq/g of soil) are derived using tabulated values of radionuclide activity from IAEA Safety Guide RS-G-1.7 (corresponding to the effective dose of 10 μSv/a). These tabulated values are scaled with the relevant target dose criteria for remediation of the specific site. Applicability and limitations (e.g., with regard to volume of released material) of proposed approach are discussed. The procedure for incorporating complimentary site-specific scenarios is described. The article further illustrates the approach by application of the methodology to the specific radioactively contaminated site (i.e., radioactive waste storage site with clean-up wastes of Chernobyl origin situated in Kiev Region). The proposed approach is generally applicable to a wide range of similar problems.

Krebskranke Kinder und Jugendliche werden heutzutage in etwa 80 % der Falle geheilt. Allerdings haben diese Patienten, abhangig von der Art der Krebserkrankung sowie der Behandlung, ein erhohtes Risiko, chronische Erkrankungen zu entwickeln. Wenn sich diese Spatfolgen erst nach Jahrzehnten manifestieren, sind die Patienten bereits erwachsen und nicht mehr in padiatrisch-onkologischer Betreuung. Die haufigsten Spatfolgen einer onkologischen Therapie im Kindesalter werden in dieser Ubersicht beschrieben. Daruber hinaus werden die Schwierigkeiten in der Transition dieser Patienten sowie multidisziplinare Versorgungsstrukturen in Deutschland diskutiert. Untersuchungen an Langzeituberlebenden zeigen, dass Spatfolgen nach einer onkologischen Behandlung im Kindesalter eine zunehmende Anzahl von Patienten betreffen. Diese Spatfolgen konnen sich an verschiedenen Organen manifestieren und, wenn sie rechtzeitig entdeckt werden, oft gut behandelt werden. Daher werden lebenslang Nachsorge‑/Vorsorgeuntersuchungen empfohlen, die nach Abschluss der onkologischen Krebsnachsorge fortgefuhrt werden mussen. Eine erfolgreiche Transition der Langzeituberlebenden einer Kinderkrebserkrankung stellt eine besondere Herausforderung dar, da sie den Ubergang von der padiatrischen in die internistische Versorgung sowie die Anderung des Versorgungsschwerpunkts, von einer rezidivbasierten Nachsorge hin zu einer spatfolgenorientierten Nach- bzw. Vorsorge, gewahrleisten muss. In spezialisierten Nachsorgezentren konnen die empfohlenen Untersuchungen stattfinden, um eine fruhe Diagnose und Behandlung von Spatfolgen zu ermoglichen.

The term neuroendocrine neoplasms (NEN) encompasses a molecularly and biologically very heterogeneous group of tumors, which have in common their origin in neuroendocrine cells. The also very heterogeneous subgroup of gastroenteropancreatic neuroendocrine neoplasms (GEP-NEN) is the best classified and investigated group. This article provides a systematic review of the current classification, diagnostics and treatment options of GEP-NEN. In order to achieve a better overview, it was consciously decided not to use an approach based on the primary localization. Instead, a thematic organization according to classification, clinical phenotype, diagnostics and treatment was chosen.

Fibre-reinforced thermoplastic materials enable an automated and economical manufacturing of lightweight structures in series-production. By combining different material-configurations, highly stressable components can be designed. Previous studies have shown that the combination of continuous fibre-reinforced hollow profiles and injection moulding compounds is suitable even for crash-relevant automotive parts. During the overmoulding process, the pre-consolidated hollow profile must remain cold in order to withstand high injection pressures. However, this leads to a poor adhesion between the profile and the overmoulding material. To increase the bonding strength, the interface can be pre-treated using laser and plasma technology. In this work, fibre-laser and atmospheric pressure plasma treatment are applied to glass fibre reinforced polyamide 6 composite (PA6/GF) sheets. The resulting surface properties are investigated by wettability and microscopy analysis. Afterwards, single-lap-shear specimens and special rib specimens are manufactured by overmoulding the sheets with PA6-66/GF bulk material. The resulting bonding strengths are characterised in tensile shear tests as well as pull-off tests of the ribs. The effects of different pre-treatment parameters on the bonding strength are analysed. Additionally, the effect of sheet temperature on the bonding strength is investigated, also including specimens without pre-treatment. Finally, the results are discussed with regard to the surface treatment of composite hollow profiles, considering bonding strength, manufacturing environment and processing times.

Hellmut J. Gebauer, Johann Georg Doertenbach. Unternehmer – Bankier – Politiker (1795 – 1870) (Kleine Reihe – Archiv der Stadt Calw 29), Calw 2013. 380 S. ISBN 978-3-939148-34-0. € 18,–

The recommended amount and quality of protein in diets of diabetic patients are highly controversial. In order to provide evidence-based information, the Diabetes Nutrition Study Group (DNSG) used a grading procedure used for quality of evidence and strength of recommendations (GRADE). A protein intake of 10% to 20% of energy intake (E%) or about 0.8 to 1.3 g/kg body weight in people below 65 years of age, and 15% to 20% of E% in people above 65 years of age appeared safe in weight-stable conditions. There were no intervention studies addressing metabolic effects, mortality, or cardiovascular events over prolonged periods. Body weight is closely linked to metabolic control and high protein diets are often recommended. Weight-loss diets that include 23% to 32% of E% as protein for up to one year reduced blood pressure and body weight slightly but significantly more than lower protein diets, whereas blood lipids, fasting blood glucose, and HbA1c improved similarly with higher or lower protein intakes in participants with a glomerular filtration rate (GFR) >60 mL/min/1.73 m2 . Patients with a GFR

Whitney, Cory W., Eike Luedeling, J. Gebauer, Nyamukuru A, John R. S. Tabuti, and K. Kehlenbeck. “Cluster Assignment Indicates Four Distinct Homegarden Types in Southwest Uganda,” 50. June 5-9: Society for Economic Botany, 2016.

Background & Aim Pericyte dropout is a significant contribution to the microvascular complications leading to diabetic retinopathy (DR). The similarities with pericytes render adipose stromal cells (ASC) candidates to prevent vessel destabilization and control neoangiogenesis. In models of DR, ASC not only generate a cytoprotective and reparative environment by secretion of trophic factors acting on endothelial, neuronal and glial cells, but also engraft and integrate into the retina in a pericyte-like fashion. Concerns, however, are that AC may not withstand the hyperglycemic stress and may worsen DR by secretion of proangiogenic factors. Thus, we compared the angiogenic features of human ASC and retinal pericytes. Methods, Results & Conclusion We compared growth curves and marker expression of both cells. As angiogeneic features, we first assessed adhesion to endothelial extracellular matrix, modified by high-glucose. Next, we tested pro-angiogeneic properties of both cell types and their conditioned media on human retinal endothelial cells by means of vascular network formation. Further, we used whole genome microarrays to compare gene expression profiles. Based on multiplex cytokine results, inhibitors of certain cytokines used to assess their role in the angiogenic support. Although cells were not to be distinguished based on their phenotype, the pro-angiogenic activity was solely featured by ASC, whereas pericytes suppressed vascular network formation. Pericytes, in contrast to ASC, adhered and proliferated at reduced rates on high-glucose modified endothelial extracellular matrix. Differentially expressed genes clustered to cell adhesion and cell migration. Pericytes expressed predominantly genes related to vessel stabilisation, whereas ASC showed higher expression of genes related to angiogenesis. This was linked to cytokine secretion. In fact, VEGFR-2 was required for ASC angiogenic supportive capacities, whereas Ang-1 appeared not to be required for pericytes inhibitory action. Our results clearly document that the pro-angiogeneic activity discriminates ASC from retinal pericytes. Pericytes are marked by endothelial stabilizing properties whereas ASC rather show angiogenic supportive characteristics. These striking pro-angiogenic discrepancies prompts to investigate the ASC angiogeneic and potential pericyte replacement properties in more detail.

Childhood cancer survivors are at risk of cancer- and treatment-related chronic health conditions. Since these sequelae may occur years after the end of treatment, many patients are already adults and have completed pediatric oncological care. Thus, successful transition is essential in order to ensure long-term surveillance.The present review outlines the most frequent late effects of childhood cancer treatment. Moreover, difficulties in transition of these patients are discussed and interdisciplinary models of care are presented.Late effects following childhood cancer treatment occur in over two thirds of patients 30 years after the end of the oncological treatment and can affect different organs. The most frequent sequelae are endocrine disturbances, cardiac conditions, and subsequent neoplasms. Many late effects are effectively manageable if detected early. This necessitates an interdisciplinary approach as well as life-long surveillance.Transition from pediatric to internal medicine care as well as a change in the focus of care, shifting from relapse centered follow-up to late-effects centered surveillance, constitute a special challenge for a successful transition of long-term childhood cancer survivors. Specialized late-effects survivorship clinics offering interdisciplinary care from pediatric oncologists, specialists of internal medicine, and further disciplines enable the early diagnosis and treatment of late-effects.

The production of K0, Λ and {Mathematical expression} particles is studied in the E665 muon-nucleon experiment at Fermilab. The average multiplicities and squared transverse momenta are measured as a function of xF and W2. Most features of the data can be well described by the Lund model. Within this model, the data on the K0/π± ratios and on the average K0 multiplicity in the forward region favor a strangeness suppression factor s/u in the fragmentation process near 0.20. Clear evidence for QCD effects is seen in the average squared transverse momentum of K0 and Λ particles. © 1994 Springer-Verlag.

Results on density integrals Fq(Q2) and correlation integrals Kq(Q2) are presented for the first time in muon-nucleon scattering at ∼ 490 GeV, using data from the E665 experiment at the Tevatron of Fermilab. A clear rise of the Fq integrals with decreasing size of the phase-space cells (“intermittency”) is observed for pairs and triplets of negative hadrons whereas the effect is much weaker for mixed charge combinations. From these findings it is concluded that the observed intermittency signal is mainly caused by Bose-Einstein interference. Furthermore, no energy (W) dependence of F2(Q2) is observed within the W range of the E665 experiment. Finally, the third-order correlation integrals K3(Q2) are found to be significantly different from zero which implies the presence of genuine three-particle correlations in muon-nucleon interactions.

In this paper the spectrometer constructed by the E665 Collaboration is described. The spectrometer was built during the period 1982–87 and the first data were taken during the 1987–88 Fixed Target run of the Fermi National Accelerator Laboratory (FNAL) Tevatron. This is the first of a series of runs in which a comprehensive program of high energy muon scattering experiments will be performed.

The diffractive production of ρ0(770 @#@) mesons in muon-proton interactions is studied in the kinematic region 0.15 GeV2 < Q2 < 20 GeV2 and 20 GeV < ? < 420 GeV. The data were obtained in the Fermilab fixed-target experiment E665 with primary muons of 470 GeV energy. Results are presented on the Q2, x and ? dependence of the cross section, on the shape of the ρ+ρt - mass spectrum, on the slope of the diffraction peak and on the production and decay angular distributions of the ρ0(770). The cross section for diffractive production of ρ0 by virtual photons on protons depends mainly on Q2. At fixed Q2, no significant dependence on x or ? is observed. The extrapolation to Q2 = 0 yields a photoproduction cross section of (10.30 ± 0.33) μb. The slope of the t′ distribution has a value of (7.0 ± 0.2) GeV−2, with a tendency to decrease as Q2 increases. The production and decay angular distributions of the ρ0 depend strongly on Q2 and are consistent with s-channel helicity conservation. The ratio R = σ l /σ t deduced from the decay angular distributions rises strongly with Q2, passing the value of 1 at Q2 ≈ 2 GeV2.

The production of charged hadrons is studied in μXe and μD interactions at 490 GeV beam energy. The data were taken at the Tevatron at Fermilab with the E665 spectrometer, equipped with a streamer chamber as vertex detector. Differences between the μXe and μD data are explained by cascading of hadrons in the Xe nucleus. The average multiplicity of charged hadrons in μXe scattering is compared to previously published pXe scattering data and is found to be strongly reduced. This is traced back to the low number of ‘projectile’ collisions in μXe interactions. From a study of thex Bj dependence of hadron production in μXe scattering, and by considering events with a large rapidity gap, evidence is found for a significant contribution of diffractive scattering, which is enhanced in the kinematic region where shadowing of the cross section is observed. This result supports recent models in which diffractive scattering and nuclear shadowing are closely related.

Repetitive nocturnal sympathetic activation during episodes of apnea and postapneic hyperventilation increases cardiovascular risk. The effects of hypopnea and non-apneic, non-hypopneic intervals before and after hypopnea/apnea on sympathico-vagal balance have not been assessed yet. Hypopnea and non-apneic, non-hypopneic intervals before and after hypopnea/apnea cause increased sympathetic activity when compared to normal respiration in nonREM stages 2–4. A total of 34 patients were studied using in-laboratory polysomnography including continuous ECG recording. Absolute spectral power of heart rate variability in the very low (VLF), low (LF), and high frequency (HF) bands and low frequency to high frequency power ratio (LF/HF ratio) were analyzed during apnea, hypopnea, and during the pre- and post-phases of such respiratory episodes and compared to spectral powers during normal respiration in nonREM sleep 2–4. Patients with hypopnea and/or obstructive apnea showed higher power of VLF and the LF/HF ratio in intervals of hypopnea/apnea and in non-apneic, non-hypopneic intervals before and after hypopnea/apnea compared to normal respiration in nonREM stages 2–4. The effect of sleep-disordered breathing on alteration of autonomic tone in patients with hypopnea and obstructive apnea is more severe than estimated by conventional polysomnographic assessment of apnea and hypopnea. Patients with sleep apnea show a sympathetic overdrive not only during phases of hypopnea and obstructive apnea but also in non-apnea, non-hypopnea intervals before and after hypopnea, and obstructive apnea.

Obwohl Kliniken und Praxen im Sinne des Marketing klassische Dienstleister sind, findet eine Auseinandersetzung mit marketingrelevanten Themen haufig nur unzureichend statt. Praxisbeispiele zeigen jedoch, wie wichtig und sinnvoll der Einsatz von Marketinginstrumenten fur medizinische Dienstleister sein kann. Dieser Artikel beschaftigt sich daher mit der Frage, wie die Leistung von Kliniken und Praxen mit Hilfe von Marketingmasnahmen verbessert werden kann. Dazu ist als erstes zu untersuchen, welchen besonderen Herausforderungen diese Dienstleister gegenuberstehen. Ein besonderer Fokus wird dann auf die Analyse der dienstleistungsspezifischen Qualitat gelegt. Dabei wird deutlich, dass die Unsicherheiten und Risiken der Patienten zu minimieren und die von ihnen wahrgenommene Leistungsqualitat zu maximieren ist.

Investigations on the lattice distortion caused by point defects in As-rich GaAs have been performed employing a self-consistent-charge density-functional-based tight-binding method. While both probable defects in As-rich material, the As antisite and the As interstitial, are causing significant lattice distortion, only the isolated As antisite leads to lattice strain in agreement with experiment. Agglomerations of As antisites always show a negative binding energy, which is growing with size of the precipitate. We show that already for the smallest agglomerates of two and three antisites the induced lattice strain is slightly relaxed.

We report on the progress of the development of a hybrid photomultiplier (PMT) with a high QE, red extended photocathode and a new, fast avalanche diode as electron bombarded anode with internal gain. The new PMT is intended to replace classical PMTs in the camera of the 17-m-diameter MAGIC telescope (The MAGIC telescope, the design study for the construction of a 17 m diameter Cherenkov telescope for γ-astronomy above 10 GeV , Max Planck Institute Report, March 1998, unpublished) for ground-based gamma-ray astronomy.

A simple method to enhance the sensitivity of photomultipliers (PMTs) will be described. The method is based on applying onto the cathode window a specially prepared lacquer containing a wavelength shifter (WLS). A rapidly evaporating lacquer solvent results in a milky surface that acts as a photon scatterer. Applying the method to the ET 9116A PMT (hemispherical borosilicate window and Rubidium-bialkali photocathode) resulted in a good sensitivity in the short-wave UV range as well as an \20% increase above 330 nm: Details of the study, the procedure and a simple model for the explanation of the enhancement are presented. r 2003 Published by Elsevier Science B.V.

Using data from the HEGRA air shower array, taken in the period from April 1998 to March 2000, upper limits on the ratio Iγ/ICR of the diffuse photon flux Iγ to the hadronic cosmic ray flux ICR are determined for the energy region 20–100 TeV. The analysis uses a gamma–hadron discrimination which is based on differences in the development of photon- and hadron-induced air showers after the shower maximum. A method which is sensitive only to the non-isotropic component of the diffuse photon flux yields an upper limit of Iγ/ICR (at 54 TeV)

A search for potential point sources of very high energy gamma rays has been carried out on the data taken simul- taneously by the HEGRA AIROBICC and Scintillator arrays from August 1994 to March 2000. The list of sought sources includes supernova remnants, pulsars, AGNs and binary systems. The energy threshold is around 15 TeV. For the Crab Nebula, a modest excess of 2.5 standard deviations above the cosmic ray background has been observed. Flux upper limits (at 90% c.l.) of around 1.3 times the flux of the Crab Nebula are obtained, in average, for the candidate sources. A dierent search procedure has been used for an all-sky search which yields absolute flux upper limits between 4 and 9crabs depending on declination, in the band from= 0t o= 60.

In Ireland, the grey field slug (Deroceras reticulatum) is the predominant slug pest species in arable crops. It can cause enormous damage, but the knowledge about its feeding biology is limited. Adult species were reared under laboratory conditions, and the survival, feeding activity, and weight change of slugs when feed on maize, peas, or wheat seeds were investigated. An especially high mortality was experienced in the wheat treatment. It was hypothesised that the high mortality was due to a Fusarium species, however, a Fusarium infection of the wheat seeds was not confirmed. The weight change of the slugs was very variable due to a high egg production of some slugs. A second experiment examined the food choice and feeding activity of D. reticulatum when offered a choice of the three seed types. Most of the slugs preferred to feed on a mixture of seeds, but the highest feeding activity was recorded on the pea seeds.

Native point defects in non-stoichiometric GaAs layers doped with Be were observed. Ga vacancies were identified by positron annihilation. As Ga antisite defects were investigated by near infrared absorption and magnetic circular dichroism of absorption, respectively. We found the properties of the As Ga antisites very similar to that of As Ga in bulk GaAs, i.e. they exhibit the same MCDA spectra and quenching behavior. The concentration of native point defects was not influenced by the Be doping. Therefore, the thermal stability of non-stoichiometric GaAs : Be can not be explained with a different incorporation of native defects.

A strong gettering effect appears after high-energy Si self-implantation and subsequent annealing in two zones at the projected range of the silicon ions (Rp) and in a region at about Rp/2. The defects responsible for the impurity gettering at Rp/2 were studied by means of positron annihilation. It was found that diffusing Cu impurities were captured by small vacancy agglomerates. Monoenergetic positron beams with improved depth resolution were used to characterize the defects. Excellent depth resolution was obtained when samples were wedge-shaped polished and studied using the Munich Scanning Positron Microscope.

Non-stoichiometric GaAs is known to contain a high concentration of native point defects. The dominant defect in the epilayers is the arsenic antisite (As Ga ), a deep double donor, which is incorporated at low growth temperatures (commonly between 200°C and 300°C) in molecular beam epitaxy (MBE). Consequently, p-doping of non-stoichiometric GaAs is difficult because large concentrations of acceptors are compensated by the As Ga . Recently, we found that despite this compensation effect we can achieve p-conductive GaAs : Be with almost one order of magnitude higher Be-doping than previously obtained in MBE grown GaAs. The kinetics of dopant incorporation during MBE growth at these low growth temperatures seem to allow pushing the doping concentration further beyond thermal equilibrium. The epilayers, which are about 1 μm thick, are pseudomorphic with a lattice mismatch to the substrate of up to Δ c / c =–0.4%. They remain free of structural defects such as dislocations and stacking faults. After annealing at 600 o C only the highest doped epilayers show a reduction in the Be concentration although the layers remain ultrahigh p-conductive. The increased incorporation of Be as well as its unusual stability in non-stoichiometric GaAs is likely influenced by the native defects in these layers, double positively charged As Ga defects and probably neutral gallium vacancies ( V Ga ). This novel material which is solely achievable through low-temperature growth may significantly enhance III–V semiconductor applicability due to ultrahigh doping capability with increased thermal stability.

Semi-insulating GaAs was contaminated by Cu. For this purpose, a thin Cu layer (30 nm) was deposited by evaporation. The diffusion and the homogeneous distribution of the Cu was performed during an annealing step at 1100°C under defined As vapour pressures. The samples were quenched to room temperature. During a subsequent isochronal annealing experiment, vacancy clusters were found to be created, grown, and finally disappeared. The number, size, and distance depend on the annealing temperature and quenching speed. Positron lifetime measurements show that the clusters contain more than 10 vacancies. Moreover, Doppler-coincidence spectroscopy shows clearly that the clusters are surrounded by Cu atoms. The association of Cu-rich precipitates and voids with a diameter of up to 50 nm could be evidenced by analytical transmission electron microscopy. The smaller clusters have a crystallographic shape, while larger voids are spherical with a Cu-rich shell. The particles are frequently bound to dislocations. A possible model related to the out-diffusion of copper and the agglomeration of the formed vacancies is discussed.

Native vacancies in n-type, Te-doped GaAs (n=5×1016–5×1018 cm−3) were studied by means of positron annihilation. We investigated the influence of doping, thermal treatment, and stoichiometry adjusted by changing the As pressure during annealing. Negatively charged monovacancies were found in all Te-doped samples under investigation. By using positron lifetime spectroscopy in conjunction with measurements of the annihilation momentum distribution and theoretical calculations, they can directly be identified to be VGa–TeAs complexes. After thermal treatment at 1100°C the density of the vacancies cv increases with the As pressure (pAs) like cv=0.1cdp1/4As where cd is the donor concentration. For such a treatment, cv depends only on pAs but not on the thermal history. The vacancy concentration was found to increase slightly with decreasing annealing temperature at a given pAs. This can be explained by the so-called Fermi level effect, i.e. the dependence of the equilibrium concentration of charged point defects on the position of the Fermi level.

Undoped and n-doped GaAs samples were studied after in-di!usion of copper by means of positron annihilation. During di!usion, small microvoids are formed which are decorated by copper atoms. The small clusters dissolve during annealing at „’850 K. ( 1999 Elsevier Science B.V. All rights reserved.

Thin (∼1 μm) CuIn(Ga)Se 2 layers were grown by the rapid thermal processing technique under In-rich conditions. The as-grown samples were slightly p-type but highly compensated. They showed strong positron trapping in vacancies, indicated by a large valence annihilation parameter S . In order to identify the vacancies, we applied a novel PAS-method. In that, we compare the element-specific high-momentum part of the annihilation momentum distribution f ( p ) in CuInSe 2 with f ( p ) from the pure elements constituting the material (i.e. with Cu, In and Se). The results provide direct evidence that the vacancies in our as-grown CuInSe 2 layers are related to Cu vacancies. Annealing under Ar atmosphere did not alter the annihilation characteristics, i.e. it did not affect the vacancies. However, after annealing in air the samples become more heavily p-type and less compensated, whereas S is drastically reduced. PAS measurements as a function of temperature revealed that this effect is not due to a reduction of the vacancy concentration but due to the additional presence of negatively charged ions introduced by the annealing process. According to recent results, these ions are attributed to oxygen acceptors O Se . These new acceptors account for the increase of p-type conductivity after air annealing.

Positron annihilation Doppler broadening spectroscopy using the two-detector coincidence method turned out to be an important tool for the study and identification of defects and their chemical surrounding due to a strong reduction of the background. The lowest background (∼10−5) is obtained by using two Ge-detectors measuring the energy of both annihilation γ-rays. We used the FAST-ComTec multiparameter system which may be considered as a standard for that purpose. A systematic study of measurement parameters influencing the results in such a system was done. The spectra were recorded in list mode (i.e., event by event) allowing off-line stabilization during a replay. The choice of optimum parameters for the stabilization is discussed. We found, however, stabilization in most cases not necessary for the observation of high momentum spectra. The use of 22 Na foil sources in this study implies a relatively high background due to 1.28 MeV γ-rays from the source. However, no significant influence of the source activity on the spectra was found. It is thus possible to use sources of high activity (up to 70 μCi) to obtain a sufficient count rate for coincidence measurements with high statistics.

Native vacancies in Te-doped ${(5\ifmmode\times\else\texttimes\fi{}10}^{16}{\char21{}5\ifmmode\times\else\texttimes\fi{}10}^{18}{\mathrm{}\mathrm{cm}}^{\mathrm{\ensuremath{-}}3})\mathrm{ }\mathrm{GaAs}$ were investigated by means of positron lifetime and Doppler-broadening coincidence spectroscopy. The experimental data were related to theoretical calculations of the positron lifetime and the annihilation momentum distribution. Monovacancies were observed in all Te-doped GaAs samples under study. It will be shown that they can directly be identified to be Ga-vacancy\char21{}${\mathrm{Te}}_{\mathrm{As}}$-donor complexes. These complexes are the dominating type of vacancy defects in the doping range under observation.

Vacancy defects in as-grown silicon were observed by positron annihilation. We found a low density of vacancies in float-zone (FZ) silicon, either undoped or lightly nitrogen doped. In contrast, vacancies were less numerous in differ- ent Czochralski-grown samples. To obtain a quantitative cal- ibration, electron irradiation with low doses was performed. A vacancy concentration of 1- 4 10 14 cm 3 in FZ-Si was obtained.