41 research outputs found
Observation of inter-edge magnetoplasmon mode in a degenerate two-dimensional electron gas
We study the propagation of edge magnetoplasmons by time-resolved current
measurements in a sample which allows for selective detection of edge states in
the quantum Hall regime. We observe two decoupled modes of edge and inter-edge
magnetoplasmons at filling factors close to 3. From the analysis of the
propagation velocities of each mode the internal spatial parameters of the edge
structure are derived.Comment: 4 pages, 4 figures, submitte
Alginate-hydroxyapatite Beads for Medical Application
The paper describes the synthesis and characterization of alginate-hydroxyapatite (Alg/HA) beads that potentially can be used for drug release due to the adsorptive properties of HA and transmission ability of the soluble compounds through the alginate membrane. Calcium Alg/HA beads were manufactured by dropping of the Alg/HA suspension into CaCl2 solution. Morphology and phase composition of obtained Alg/HA beads were investigated. It was shown that alginate macromolecules influence the hydroxyapatite size and morphology. Obtained HA with crystal size 15-30 nm inside alginate beads correspond a bioapatite size therefore are interesting for the tissue engineering. The main features of alginate-controlled crystallization are discussed in order to understand some aspects in composite material design. Insertion of HA into the alginate microcapsules allows use such materials for production of drug release microspheres
ZnO Coatings on Ti6Al4V Substrate: Structural and Antibacterial Properties in Literature Review and Research
ZnO, ZnO/Alginate coatings were obtained on the pre-anodized Ti6Al4V substrates by the thermal substrate deposition method (TSD). In the frame of this work, the TSD method was at first applied for obtaining ZnO coating from aqueous alginate-containing and alginate-free solutions on a metal surface. XRD, SEM analyses show that the biopolymer has a significant influence on the formation of the coating, their morphology, texture, structure of ZnO nanoparticles. The average rate of ZnO deposition from alginate containing solution is 30 μm/min, while from alginate-free solutions – 6 μm/min. In the presence of alginate, spherical particles with flower-shaped inclusions are formed, while from the polymer-free solution, single crystals in the form of tetrahedral were obtained. Zone of inhibition test against Gram-positive S. aureus ATCC 25923 and Gram-negative E. coli ATCC 25922 proves
the antibacterial activity of the ZnO/Alg coatings
Why Does Exercise “Triggerâ€? Adaptive Protective Responses in the Heart?
Numerous epidemiological studies suggest that individuals who exercise have decreased cardiac morbidity and mortality. Pre-clinical studies in animal models also find clear cardioprotective phenotypes in animals that exercise, specifically characterized by lower myocardial infarction and arrhythmia. Despite the clear benefits, the underlying cellular and molecular mechanisms that are responsible for exercise preconditioning are not fully understood. In particular, the adaptive signaling events that occur during exercise to “trigger� cardioprotection represent emerging paradigms. In this review, we discuss recent studies that have identified several different factors that appear to initiate exercise preconditioning. We summarize the evidence for and against specific cellular factors in triggering exercise adaptations and identify areas for future study
Low Concentrations of Methamphetamine Can Protect Dopaminergic Cells against a Larger Oxidative Stress Injury: Mechanistic Study
Mild stress can protect against a larger insult, a phenomenon termed preconditioning or tolerance. To determine if a low intensity stressor could also protect cells against intense oxidative stress in a model of dopamine deficiency associated with Parkinson disease, we used methamphetamine to provide a mild, preconditioning stress, 6-hydroxydopamine (6-OHDA) as a source of potentially toxic oxidative stress, and MN9D cells as a model of dopamine neurons. We observed that prior exposure to subtoxic concentrations of methamphetamine protected these cells against 6-OHDA toxicity, whereas higher concentrations of methamphetamine exacerbated it. The protection by methamphetamine was accompanied by decreased uptake of both [3H] dopamine and 6-OHDA into the cells, which may have accounted for some of the apparent protection. However, a number of other effects of methamphetamine exposure suggest that the drug also affected basic cellular survival mechanisms. First, although methamphetamine preconditioning decreased basal pERK1/2 and pAkt levels, it enhanced the 6-OHDA-induced increase in these phosphokinases. Second, the apparent increase in pERK1/2 activity was accompanied by increased pMEK1/2 levels and decreased activity of protein phosphatase 2. Third, methamphetamine upregulated the pro-survival protein Bcl-2. Our results suggest that exposure to low concentrations of methamphetamine cause a number of changes in dopamine cells, some of which result in a decrease in their vulnerability to subsequent oxidative stress. These observations may provide insights into the development of new therapies for prevention or treatment of PD
Chitosan–hydroxyapatite composite biomaterials made by a one step co-precipitation method: preparation, characterization and in vivo tests
A series of biocompatible chitosan/hydroxyapatite composites has been synthesized in an
aqueous medium from chitosan solution and soluble precursor salts by a one-step
coprecipitation method. The composite materials were produced in dense and porous
variants. XRD and IR studies have shown that the apatite crystals in the composites have
structural characteristics similar to those of crystals in biogenic apatite. A study of in vivo
behaviour of the materials was carried out. Cylindrical rods made of the chitosan/
hydroxyapatite composite material were implanted into the tibial bones of rats. After 5, 10, 15
and 24 days of implantation, histological and histo-morphometric analyses of decalcified
specimens were undertaken to evaluate their biocompatibility and the possibility to apply
them in bone tissue engineering. The calcified specimens were examined by scanning
electron microscopy combined with X-ray microanalysis to compare the elemental
composition and morphological characteristics of the implant and the bone during
integration. Porous specimens were osteoconducting and were replaced in vivo by newly
formed bone tissue
Lost in translation: The biogenesis of non-LTR retrotransposon proteins.
"Young" APE-type non-LTR retrotransposons (non-LTRs) typically encode two open reading frames (ORFs 1 and 2). The shorter ORF1 translation product (ORF1p) comprises an RNA binding activity, thought to bind to non-LTR transcript RNA, protect against nuclease degradation and specify nuclear import of the ribonuclear protein complex (RNP). ORF2 encodes a multifunctional protein (ORF2p) comprising apurinic/apyrimidinic endonuclease (APE) and reverse-transcriptase (RT) activities, responsible for genome replication and re-integration into chromosomal DNA. However, some clades of APE-type non-LTRs only encode a single ORF-corresponding to the multifunctional ORF2p outlined above (and for simplicity referred-to as ORF2 below). The absence of an ORF1 correlates with the acquisition of a 2A oligopeptide translational recoding element (some 18-30 amino acids) into the N-terminal region of ORF2p. In the case of non-LTRs encoding two ORFs, the presence of ORF1 would necessarily downregulate the translation of ORF2. We argue that in the absence of an ORF1, 2A could provide the corresponding translational downregulation of ORF2. While multiple molecules of ORF1p are required to decorate the non-LTR transcript RNA in the cytoplasm, conceivably only a single molecule of ORF2p is required for target-primed reverse transcription/integration in the nucleus. Why would the translation of ORF2 need to be controlled by such mechanisms? An "excess" of ORF2p could result in disadvantageous levels of genome instability by, for example, enhancing short, interspersed, element (SINE) retrotransposition and the generation of processed pseudogenes. If so, the acquisition of mechanisms-such as 2A-to control ORF2p biogenesis would be advantageous