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showing 10 items of 1506 documents
Humusvielu izcelsmes – īpašību izpēte izmantojot to multiparametru raksturojumu
2019
Humusvielu izcelsmes-īpašību izpēte izmantojot to multiparametru raksturojumu. Upska K., zinātniskais vadītājs prof., Dr. habil. chem. Kļaviņš M. prof. Dr.chem. Vīksna A. un, Kursa darbs, 62 lappuses, 22 attēli, 11 tabulas, 37 literatūras avoti, 2 pielikumi. Latviešu valodā. Bakalaura darbā tika apkopota zinātniskā literatūra par humusvielām, to izcelsmi, funkcijām biosfērā, ražošanas, izdalīšanas un pētīšanas metodēm. Tika noteikts humusvielu organiskais un neorganiskais elementsastāvs, kas sniedz informāciju par rūpnieciski ražotu humusvielas produktu kvalitāti. Izmantojot UV-Vis un FTIR molekulārās absorbcijas metodi tika uzņemti un analizēti humusvielu absorbcijas spektri. Izmantojot fl…
Semi-Empirical Calculations of Hole Polarons in MgO and KNbO3 Crystals
1998
The semi-empirical quantum chemical INDO method has been used for cluster and large unit cell calculations of hole polarons bound to a cation vacancy in highly ionic MgO and partly covalent perovskite KNbO 3 . In both cases a hole is well localized on an oxygen atom displaced towards the vacancy. The calculated optical and thermal ionization energies for V - and V 0 centers are in excellent agreement with experimental data for MgO. In KNbO 3 we predict the existence of one-site and two-site (molecular) polarons with close absorption energies (1 e V). The relevant experimental data are discussed.
Modeling of defects and surfaces in perovskite ferroelectrics
2002
The results of electronic structure calculations for different terminations of SrTiO3 (100) and (110) perovskite thin films are discussed. These calculations are based on the ab initio Hartree-Fock (HF) method and Density Functional Theory (DFT). Results are compared with previous ab initio plane-wave LDA and classical Shell Model (SM) calculations. Calculated considerable increase of the Ti – O chemical bond covalency nearby the surface is confirmed by experimental data. Our quantum chemical calculations performed by means of the intermediate neglect of differential overlap (INDO) method confirm the existence of self-trapped electrons in KNbO3, KTaO3 and BaTiO3 crystals. The relevant latti…
Bacterial community response to changes in a tri-trophic cascade during a whole-lake fish manipulation
2015
Microbial communities play a key role in biogeochemical processes by degrading organic material and recycling nutrients, but can also be important food sources for upper trophic levels. Trophic cascades might modify microbial communities either directly via grazing or indirectly by inducing changes in other biotic or in abiotic factors (e.g., nutrients). We studied the effects of a tri-trophic cascade on microbial communities during a whole-lake manipulation in which European perch (Perca fluviatilis) were added to a naturally fishless lake divided experimentally into two basins. We measured environmental parameters (oxygen, temperature, and nutrients) and zooplankton biomass and studied th…
Depletion of naive T cells using clinical grade magnetic CD45RA beads: a new approach for GVHD prophylaxis
2013
Depletion of naive T cells from donor leukapheresis products (LPs) aims at the reduction of alloreactivity, while preserving memory T-cell reactivity (for example, to pathogens). This study established the immunomagnetic depletion procedure under clean room conditions using CD45RA beads and analyzed LPs of six donors for cell composition and functional immune responses. CD45RA depletion resulted in 3.4-4.7 log (median 4.4) reduction of CD45RA(+) T cells, thereby eliminating naive and late effector T cells. B cells were also completely removed, whereas significant proportions of NK cells, monocytes and granulocytes persisted. CD45RA-depleted LPs contained effector and central memory CD4(+) a…
Increase of CCR7- CD45RA+ CD8 T cells (TEMRA) in Chronic Graft-versus-host Disease
2006
Among the late effects of hematopoietic stem cell transplantation (HSCT), chronic graft-vs-host disease (cGVHD) still remains as the major determinant of long-term outcome and quality of life. The disease typically appears between 3 months to 1.5 years following an allogeneic transplantation and is characterized by symptoms similar to those of autoimmune disease.
Pharmacokinetics of Oral Posaconazole in Allogeneic Hematopoietic Stem Cell Transplant Recipients with Graft-versus-Host Disease
2007
Study Objective. To analyze the pharmacokinetics of posaconazole administered as prophylaxis for invasive fungal infections in recipients of hematopoietic stem cell transplants (HSCTs) who have graft-versus-host disease (GVHD). Design. Pharmacokinetic analysis in a subset of posaconazole-treated patients from a large, multicenter, phase III, randomized, double-blind, double-dummy, parallel-group trial that compared posaconazole with fluconazole. Setting. Ninety international medical centers. Patients. The subset of patients comprised 246 HSCT recipients for whom pharmacokinetic data were available. Intervention. All patients received posaconazole 200 mg oral suspension 3 times/day for a max…
Discrimination des expressions faciales et environnement olfactif – Corrélats cérébraux en électroencéphalographie (EEG) chez l’adulte et le très jeu…
2019
This thesis examines the mechanisms subtending the perception of emotional facial expressions and their early development using a Fast Periodic Visual Presentation (FPVS) approach coupled with electroencephalography (EEG). More specifically, we tried to characterize brain responses reflecting facial expression discrimination and to determine whether hedonic odor contexts influence these responses in adults (studies 1 and 2), and in infants at different developmental stages (studies 3 and 4).We showed specific responses to the discrimination of every facial expression in the adult brain, indicating rapid and automatic categorization of basic facial expressions (study 1). In addition, we reve…
Selective Depletion of Alloreactive T Lymphocytes Using Patient-Derived Nonhematopoietic Stimulator Cells in Allograft Engineering
2008
Background. Selective depletion of alloreactive T cells in vitro results in efficient graft-versus-host disease prophylaxis in allogeneic hematopoietic stem-cell transplantation, but it is accompanied by increased recurrence of leukemia. To spare donor T-cell-mediated graft-versus-leukemia immunity against hematopoiesis-restricted minor histocompatibility (minor-H) antigens, we explored the use of patient-derived nonhematopoietic antigen-presenting cells (APC) as allogeneic stimulators for selective allodepletion in leukemia-reactive donor T-cell lines. Methods. Primary keratinocytes, dermal fibroblasts, and bone marrow fibroblasts were generated from skin biopsies and diagnostic bone marro…
Adipose tissue-derived mesenchymal stromal cells as part of therapy for chronic graft-versus-host disease: A phase I/II study
2017
Abstract Background aims Despite the efficacy of allogeneic hematopoietic stem cell transplantation (allo-HSCT), the procedure is still associated with high toxicity in patients with refractory graft-versus-host disease (GvHD). Mesenchymal stromal cells (MSCs) are a new mode of therapy in the context of allo-HSCT. The objective of this study was to evaluate the safety and feasibility of the use of adipose tissue–derived MSCs (AT-MSCs) in patients with chronic GvHD. Methods Fourteen patients with moderate (n = 7) or severe (n = 7) chronic GvHD received 1 × 106/kg (group A, n = 9) or 3 × 106/kg (group B, n = 5) AT-MSCs with cyclosporine and prednisone as first-line therapy. Results Ten of the…