Modern environmental and sustainability issues as well as the growing demand for applications in the life sciences and medicine put special requirements to the chemical composition of many functional ...materials. To achieve desired performance within these requirements, innovative approaches are needed. In this work, we experimentally demonstrate that thermal strain can effectively tune the crystal structure and versatile properties of relatively thick films of environmentally friendly, biocompatible, and low-cost perovskite ferroelectric barium titanate. The strain arises during post-deposition cooling due to a mismatch between the thermal expansion coefficients of the films and the substrate materials. The strain-induced in-plane polarization enables excellent performance of bottom-to-top barium titanate capacitors akin to that of exemplary lead-containing relaxor ferroelectrics. Our work shows that controlling thermal strain can help tailor response functions in a straightforward manner.
Diamond-like carbon (DLC) is a biocompatible material that has many potential biomedical applications, including in orthopaedics. DLC layers doped with Cr at atomic percent (at.%) of 0, 0.9, 1.8, ...7.3, and 7.7 at.% were evaluated with reference to their osteoinductivity with human bone marrow mesenchymal stromal cells (hMSCs), immune activation potential with RAW 264.7 macrophage-like cells, and their effect on apoptosis in Saos-2 human osteoblast-like cells and neonatal human dermal fibroblasts (NHDFs). At mRNA level, hMSCs on DLC doped with 0.9 and 7.7 at.% of Cr reached higher maximum values of both RUNX2 and alkaline phosphatase. An earlier onset of mRNA production of type I collagen and osteocalcin was also observed on these samples; they also supported the production of both type I collagen and osteocalcin. RAW 264.7 macrophages were screened using a RayBio™ Human Cytokine Array for cytokine production. 10 cytokines were at a concentration more than 2 × as high as the concentration of a positive control, but the values for the DLC samples were only moderately higher than the values on glass. NHDF cells, but not Saos-2 cells, had a higher expression of pro-apoptotic markers Bax and Bim and a lower expression of anti-apoptotic factor BCL-XL in proportion to the Cr content. Increased apoptosis was also proven by annexin V staining. These results show that a Cr-doped DLC layer with a lower Cr content can act as an osteoinductive material with relatively low immunogenicity, but that a higher Cr content can induce cell apoptosis.
Hydrogen free Ti-doped amorphous carbon layers were prepared by dual beam pulsed laser deposition using two excimer lasers. The air-exposed surfaces were analyzed by high-energy resolved and ...angular-resolved core-level photoelectron spectroscopy, and were then step-by-step sputtered with an argon gas cluster ion beam (ArGCIB), which is known to be a very gentle technique with respect to changes in surface chemistry. The results show that the top surface of the sample and its sub-surface region differ in composition and in bonding. The top surface is enriched by oxygen-bearing species. Carbon-bearing species located on the surface are mostly in sp3 hybridization. Titanium carbide clusters, TiC, are not directly exposed at the surface. They are embedded in a carbon network with dominating C sp2 hybridization. Their interface is formed by a distinct carbon-rich titanium carbide with stoichiometry close to TiC3. The surface damage induced by ArGCIB was found to be minimal, verifiably affecting carbon atoms in the carbon network.
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•The virgin surface of DLC:Ti films is enriched by C sp3, while C sp2 is dominant in the sub-surface region.•TiC clusters are embedded in a carbon network.•The interface between TiC clusters and the carbon network is formed by TiCx, x~3.•Sputtering DLC:Ti films with ArGCIB caused a structural damage in the carbon network.•The results of an in-depth analysis by ArGCIB are in qualitative agreement with the ARXPS analysis.
We have gathered optical photometry data from the literature on a large sample of Swift-era gamma-ray burst (GRB) afterglows including GRBs up to 2009 September, for a total of 76 GRBs, and present ...an additional three pre-Swift GRBs not included in an earlier sample. Furthermore, we publish 840 additional new photometry data points on a total of 42 GRB afterglows, including large data sets for GRBs 050319, 050408, 050802, 050820A, 050922C, 060418, 080413A, and 080810. We analyzed the light curves of all GRBs in the sample and derived spectral energy distributions for the sample with the best data quality, allowing us to estimate the host-galaxy extinction. We transformed the afterglow light curves into an extinction-corrected z = 1 system and compared their luminosities with a sample of pre-Swift afterglows. The results of a former study, which showed that GRB afterglows clustered and exhibited a bimodal distribution in luminosity space, are weakened by the larger sample. We found that the luminosity distribution of the two afterglow samples (Swift-era and pre-Swift) is very similar, and that a subsample for which we were not able to estimate the extinction, which is fainter than the main sample, can be explained by assuming a moderate amount of line-of-sight host extinction. We derived bolometric isotropic energies for all GRBs in our sample, and found only a tentative correlation between the prompt energy release and the optical afterglow luminosity at 1 day after the GRB in the z = 1 system. A comparative study of the optical luminosities of GRB afterglows with echelle spectra (which show a high number of foreground absorbing systems) and those without, reveals no indication that the former are statistically significantly more luminous. Furthermore, we propose the existence of an upper ceiling on afterglow luminosities and study the luminosity distribution at early times, which was not accessible before the advent of the Swift satellite. Most GRBs feature afterglows that are dominated by the forward shock from early times on. Finally, we present the first indications of a class of long GRBs, which form a bridge between the typical high-luminosity, high-redshift events and nearby low-luminosity events (which are also associated with spectroscopic supernovae) in terms of energetics and observed redshift distribution, indicating a continuous distribution overall.
Carbon atom coordination at diamond-like carbon (DLC) film surfaces and in sub-surface regions has been determined nondestructively from high-energy resolved C 1s photoelectron spectra, X-ray induced ...C KVV Auger electron spectra, and angular-resolved C 1s spectra (ARXPS) aided by maximum entropy method (MEM). The spectra were recorded from hydrogen-free DLC films prepared by a pulsed laser deposition under medium energy Ar ion beam assisted growth. The sp3 and sp2 fractions determined from C 1s and C KVV spectra recorded at the normal emission angle differ substantially. This indicates an inhomogeneous depth-resolved distribution of the fractions. The result is validated by the analysis of angular-resolved C 1s spectra using the MEM approach. In-depth reconstructions of the carbon bonding states show that sp2 coordination is dominant at the surfaces. We found that Ar ion beam assisted growth induces a C sp2 peak beneath the surface. The peak shifts towards the surface and is growing with Ar ion energy. C sp3 hybridization is dominant in deeper layers. The in-depth reconstruction is further supported by the depth-dependent mass density determined from the low-loss electron spectra excited at various primary electron energy. The results are discussed within the subplantation model.
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This review focuses on the problem of oxidative stress in early brain injury (EBI) after spontaneous subarachnoid hemorrhage (SAH). EBI involves complex pathophysiological mechanisms, including ...oxidative stress. In the first section, we describe the main sources of free radicals in EBI. There are several sources of excessive generation of free radicals from mitochondrial free radicals’ generation and endoplasmic reticulum stress, to hemoglobin and enzymatic free radicals’ generation. The second part focuses on the disruption of antioxidant mechanisms in EBI. The third section describes some newly found molecular mechanisms and pathway involved in oxidative stress after EBI. The last section is dedicated to the pathophysiological mechanisms through which free radicals mediate early brain injury.
A new effect of the pulse shortening of the parametrically generated radiation down to hundreds of picosecond via depletion of pumping of intracavity Raman conversion in the miniature passively ...Q-switched Nd:
SrMoO
4
parametric self-Raman laser with the increasing energy of the shortened pulse under pulsed pumping by a high-power laser diode bar is demonstrated. The theoretical estimation of the depletion stage duration of the convertible fundamental laser radiation via intracavity Raman conversion is in agreement with the experimentally demonstrated duration of the parametrically generated pulse. Using the mathematical modeling of the pulse shortening quality and quantity deterioration is disclosed, and the solution ways are found by the optimization of the laser parameters.
•UNCD and DLC films were modified by UV/O3 treatments, O2 or NH3-containing plasmas.•Surface composition, wettability and surface energy change upon modifications.•Higher efficiency of UNCD ...modifications was observed.•Cell attachment and growth were influenced by the surface termination and roughness.
Diamond and diamond-like carbon (DLC) films possess a set of excellent physical and chemical properties which together with a high biocompatibility make them attractive candidates for a number of medical and biotechnological applications. In the current work thin ultrananocrystalline diamond (UNCD) and DLC films were comparatively investigated with respect to cell attachment and proliferation after different surface modifications. The UNCD films were prepared by microwave plasma enhanced chemical vapor deposition, the DLC films by pulsed laser deposition (PLD). The films were comprehensively characterized with respect to their basic properties, e.g. crystallinity, morphology, chemical bonding nature, etc. Afterwards the UNCD and DLC films were modified applying O2 or NH3/N2 plasmas and UV/O3 treatments to alter their surface termination. The surface composition of as-grown and modified samples was studied by X-ray photoelectron spectroscopy (XPS). Furthermore the films were characterized by contact angle measurements with water, formamide, 1-decanol and diiodomethane; from the results obtained the surface energy with its dispersive and polar components was calculated. The adhesion and proliferation of MG63 osteosarcoma cells on the different UNCD and DLC samples were assessed by measurement of the cell attachment efficiency and MTT assays. The determined cell densities were compared and correlated with the surface properties of as-deposited and modified UNCD and DLC films.
The complex index of refraction in the spectral range of 0.74 to 4.5 eV is studied by variable-angle spectroscopic ellipsometry in ferroelectric K0.5Na0.5NbO3 films. The 20-nm-thick cube-on-cube-type ...epitaxial films are grown on SrTiO3(001) and DyScO3(011) single-crystal substrates. The films are transparent and exhibit a significant difference between refractive indices Δn = 0.5 at photon energies below 3 eV. The energies of optical transitions are in the range of 3.15-4.30 eV and differ by 0.2-0.3 eV in these films. The observed behavior is discussed in terms of lattice strain and strain-induced ferroelectric polarization in epitaxial perovskite oxide films.
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