Rôle of the Jahn-Teller Coupling in the Luminescence Spectra of Fe²⁺ in Zinc-Blende Compounds

The luminescence spectra of Fe2+ in zinc-blende-type II—VI and III—V compounds do not show an equally spaced set of emission lines as predicted by spin orbit interaction in a plain crystalline field. The unequal separation between these lines is a signature of the Jahn-Teller effect in these systems. Attention is focused here on the general trend of the 5 E-derived energy levels providing the end states for the emission transitions. The intervall between the second and third energy levels (γ4 and γ3) is employed as a sensitive test based on the two following characteristics: First, this is the spacing that varies the most; second, the emissions to these levels are usually quite sharp as they involve energies not overlapping with phonon-assisted transitions. This property is studied in the plane [hω,EJT] (energy of the coupling phonon and the Jahn-Teller energy which is directly related to the coupling strength). The general behaviour is then studied under different theoretical conditions, in particular those that maximize the effect. Application of this theory to each real compound is thus possible by choosing the right combination of the two variables. To this end, the examples of luminescent substitutional Fe2+ ions in ZnS, ZnTe, and CdTe are discussed based on published spectra. The main emphasis is placed on new precise measurements of the ZnSe : Fe2+ emission. With crystals containing different iron concentrations, changing line shapes, including self-inversion of several emission lines, have been obtained in the 2600 to 2800 cm-1 spectral range. The properties of the four host/impurity systems are satisfactorily explained while an overall description emerges for the whole family of these compounds from a compilation of the derived coupling parameters

Infrared luminescence and application of a vibronic-coupling Hamiltonian to the level structure of CdTe:Fe²⁺

Samples of crystalline CdTe doped with two different concentrations of iron were prepared by the vertical high-pressure Bridgman method. Absorption and emission spectra were recorded at liquid-helium temperature in the region of the 5T2(D)? 5E(D) infrared transitions of substitutional Fe2+(d6) ions. Especially in the range between 2200 and 2300 cm−1, a rich structure is resolved comprising more lines than predicted from plain crystal-field theory. The explanation of all the important lines is found after introducing a vibronic Jahn-Teller term to the Hamiltonian. A linear coupling between the double-degenerate vibrational mode ε (or γ3) to the electronic orbitals of the atomic multiplet of symmetry 5D leads to the diagonalization of the total Hamiltonian in a set of vibronic functions. Just one free parameter is used in the adjustment: the so-called Jahn-Teller energy representing the strength of the coupling. The corresponding value that we report here is 3 cm−1. The energies thus found are in good agreement with the positions of the observed lines in the spectra. With the final wave functions we can calculate the relative intensities of the most important transitions and approximate theoretical line shape. This is also in good agreement with the experiment. Using these same energies and wave functions a calculation was performed to explain data existing in the literature about far-infrared absorption for the system CdTe:Fe2+. Again, good agreement between experiment and theory is found

Ultrafast imaging Raman spectroscopy of large-area samples without stepwise scanning

Step-by-step, time-consuming scanning of the sample is still the state-of-the-art in imaging Raman spectroscopy. Even for a few 100 image points the measurement time may add up to minutes or hours. A radical decrease in measurement time can be achieved by applying multiplex spectrographs coupled to imaging fiber bundles that are successfully used in astronomy. For optimal use of the scarce and expensive observation time at astronomical observatories, special high-performance spectrograph systems were developed. They are designed for recording thousands of spatially resolved spectra of a two-dimensional image field within one single exposure. Transferring this technology to imaging Raman spectroscopy allows a considerably faster acquisition of chemical maps. Currently, an imaging field of up to 1 cm2 can be investigated. For porcine skin the required measurement time is less than 1 min. For this reason, this technique is of particular interest for medical diagnostics, e.g., the identification of potentially cancerous abnormalities of skin tissue

A guide to environmental monitoring data, 1945--1972: Hanford Environmental Dose Reconstruction Project

This report is a guide to the work accomplished by the Environmental Monitoring Data Task, which is one of the tasks in the Hanford Environmental Dose Reconstruction (HEDR) Project. The objective of the Environmental Monitoring Data Task was to recover, evaluate, process, and/or reconstruct the environmental monitoring data for the period 1945--1972. The period of time for which environmental monitoring data were sought was determined by the start-up and shut-down dates of the Hanford facilities that emitted the majority of radionuclides to the two major pathways: air and the Columbia River. Radionuclide emissions to the air were mainly the result of the operation of the chemical separations plants from 1944--1972 (Heeb 1994). Radionuclide emissions to the Columbia River were mainly the result of the operation of the single-pass production reactors from 1944--1971 (Heeb and Bates 1994). Therefore, the historical environmental monitoring data sought were for the period 1945--1972. Within the period of 1945--1972, specific periods of interest to the HEDR Project vary depending on the pathway. For example, 1945--1951 was the peak period for radionuclide emissions to the air and hence vegetation uptake of radionuclides, while 1956--1965 was the peak period for radionuclide emissions to the Columbia River and hence fish uptake of radionuclides. However, adequate historical data were not always available for the periods of interest. In the case of vegetation measurements, conversion and correction factors had to be developed to convert the historical measurements to modern standard measurements. Table S.1 lists the reports that explain these conversion and correction factors. In the case of Columbia River fish and waterfowl, bioconcentration factors were developed for use in any year where the river pathway data are insufficient

Primacy of effective communication and its influence on adherence to artemether-lumefantrine treatment for children under five years of age: a qualitative study.

BACKGROUND\ud \ud Prompt access to artemesinin-combination therapy (ACT) is not adequate unless the drug is taken according to treatment guidelines. Adherence to the treatment schedule is important to preserve efficacy of the drug. Although some community based studies have reported fairly high levels of adherence, data on factors influencing adherence to artemether-lumefantrine (AL) treatment schedule remain inadequate. This study was carried-out to explore the provider's instructions to caretakers, caretakers' understanding of the instructions and how that understanding was likely to influence their practice with regard to adhering to AL treatment schedule.\ud \ud METHODS\ud \ud A qualitative study was conducted in five villages in Kilosa district, Tanzania. In-depth interviews were held with providers that included prescribers and dispensers; and caretakers whose children had just received AL treatment. Information was collected on providers' instructions to caretakers regarding dose timing and how to administer AL; and caretakers' understanding of providers' instructions.\ud \ud RESULTS\ud \ud Mismatch was found on providers' instructions as regards to dose timing. Some providers' (dogmatists) instructions were based on strict hourly schedule (conventional) which was likely to lead to administering some doses in awkward hours and completing treatment several hours before the scheduled time. Other providers (pragmatists) based their instruction on the existing circumstances (contextual) which was likely to lead to delays in administering the initial dose with serious treatment outcomes. Findings suggest that, the national treatment guidelines do not provide explicit information on how to address the various scenarios found in the field. A communication gap was also noted in which some important instructions on how to administer the doses were sometimes not provided or were given with false reasons.\ud \ud CONCLUSIONS\ud \ud There is need for a review of the national malaria treatment guidelines to address local context. In the review, emphasis should be put on on-the-job training to address practical problems faced by providers in the course of their work. Further research is needed to determine the implication of completing AL treatment prior to scheduled time

Machine learning assisted real-time deformability cytometry of CD34+ cells allows to identify patients with myelodysplastic syndromes

Diagnosis of myelodysplastic syndrome (MDS) mainly relies on a manual assessment of the peripheral blood and bone marrow cell morphology. The WHO guidelines suggest a visual screening of 200 to 500 cells which inevitably turns the assessor blind to rare cell populations and leads to low reproducibility. Moreover, the human eye is not suited to detect shifts of cellular properties of entire populations. Hence, quantitative image analysis could improve the accuracy and reproducibility of MDS diagnosis. We used real-time deformability cytometry (RT-DC) to measure bone marrow biopsy samples of MDS patients and age-matched healthy individuals. RT-DC is a high-throughput (1000 cells/s) imaging flow cytometer capable of recording morphological and mechanical properties of single cells. Properties of single cells were quantified using automated image analysis, and machine learning was employed to discover morpho-mechanical patterns in thousands of individual cells that allow to distinguish healthy vs. MDS samples. We found that distribution properties of cell sizes differ between healthy and MDS, with MDS showing a narrower distribution of cell sizes. Furthermore, we found a strong correlation between the mechanical properties of cells and the number of disease-determining mutations, inaccessible with current diagnostic approaches. Hence, machine-learning assisted RT-DC could be a promising tool to automate sample analysis to assist experts during diagnosis or provide a scalable solution for MDS diagnosis to regions lacking sufficient medical experts

Azacitidine for treatment of imminent relapse in MDS or AML patients after allogeneic HSCT: results of the RELAZA trial

This study evaluated azacitidine as treatment of minimal residual disease (MRD) determined by a sensitive donor chimerism analysis of CD34+ blood cells to pre-empt relapse in patients with CD34+ myelodysplastic syndromes (MDS) or acute myeloid leukemia (AML) after allogeneic hematopoietic stem cell transplantation (HSCT). At a median of 169 days after HSCT, 20/59 prospectively screened patients experienced a decrease of CD34+ donor chimerism to <80% and received four azacitidine cycles (75 mg/m2/day for 7 days) while in complete hematologic remission. A total of 16 patients (80%) responded with either increasing CD34+ donor chimerism to ⩾80% (n=10; 50%) or stabilization (n=6; 30%) in the absence of relapse. Stabilized patients and those with a later drop of CD34+ donor chimerism to <80% after initial response were eligible for subsequent azacitidine cycles. A total of 11 patients (55%) received a median of 4 (range, 1–11) additional cycles. Eventually, hematologic relapse occurred in 13 patients (65%), but was delayed until a median of 231 days (range, 56–558) after initial decrease of CD34+ donor chimerism to <80%. In conclusion, pre-emptive azacitidine treatment has an acceptable safety profile and can substantially prevent or delay hematologic relapse in patients with MDS or AML and MRD after allogeneic HSCT

Comprehensive Analysis of the 16p11.2 Deletion and Null Cntnap2 Mouse Models of Autism Spectrum Disorder

Autism spectrum disorder comprises several neurodevelopmental conditions presenting symptoms in social communication and restricted, repetitive behaviors. A major roadblock for drug development for autism is the lack of robust behavioral signatures predictive of clinical efficacy. To address this issue, we further characterized, in a uniform and rigorous way, mouse models of autism that are of interest because of their construct validity and wide availability to the scientific community. We implemented a broad behavioral battery that included but was not restricted to core autism domains, with the goal of identifying robust, reliable phenotypes amenable for further testing. Here we describe comprehensive findings from two known mouse models of autism, obtained at different developmental stages, using a systematic behavioral test battery combining standard tests as well as novel, quantitative, computer-vision based systems. The first mouse model recapitulates a deletion in human chromosome 16p11.2, found in 1% of individuals with autism. The second mouse model harbors homozygous null mutations in Cntnap2, associated with autism and Pitt-Hopkins-like syndrome. Consistent with previous results, 16p11.2 heterozygous null mice, also known as Del(7Slx1b-Sept1)4Aam weighed less than wild type littermates displayed hyperactivity and no social deficits. Cntnap2 homozygous null mice were also hyperactive, froze less during testing, showed a mild gait phenotype and deficits in the three-chamber social preference test, although less robust than previously published. In the open field test with exposure to urine of an estrous female, however, the Cntnap2 null mice showed reduced vocalizations. In addition, Cntnap2 null mice performed slightly better in a cognitive procedural learning test. Although finding and replicating robust behavioral phenotypes in animal models is a challenging task, such functional readouts remain important in the development of therapeutics and we anticipate both our positive and negative findings will be utilized as a resource for the broader scientific community

Constraining Deformation in the North Pamir and the Westernmost Tarim Basin

Abstract HKT-ISTP 2013 A