We study the transformation from molecular to crystalline of (non-)graphitic carbons synthesized from organic precursors by heat-treatment. Easy assessment of structural properties resulting from ...heat-treatment protocols is mandatory for industrial process monitoring. We demonstrate that Raman spectroscopy, in particular, the Raman lineshape analysis of G and D mode, offers quick assessment of the average sheet size of such carbons. We validate this method by performing Raman, WAXS and EPR measurements of series of resin and pitch-based carbons synthesized. The crystallite sizes of the WAXS analysis for the individual samples are related to corresponding positions and linewidths of G and D Raman modes and show excellent agreement between experiment and modelling from large sizes down to 4 nm. The theoretical master curves are independent of the precursor used in the synthesis, in contrast to models for the intensity ratio of D and G band versus size. We show that the latter are not universally valid and differ for each class of precursors. For sizes below 4 nm, our lineshape model fails as it is based on the bandstructure and phonon dispersions of ideal graphene. Thus, 4 nm corresponds to the fundamental transition from molecular to crystalline character for non-graphitic carbons.
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This paper reviews progress that has been made in the use of Raman spectroscopy to study graphene and carbon nanotubes. These are two nanostructured forms of sp
2
carbon materials that are of major ...current interest. These nanostructured materials have attracted particular attention because of their simplicity, small physical size and the exciting new science they have introduced. This review focuses on each of these materials systems individually and comparatively as prototype examples of nanostructured materials. In particular, this paper discusses the power of Raman spectroscopy as a probe and a characterization tool for sp
2
carbon materials, with particular emphasis given to the field of photophysics. Some coverage is also given to the close relatives of these sp
2
carbon materials, namely graphite, a three-dimensional (3D) material based on the AB stacking of individual graphene layers, and carbon nanoribbons, which are one-dimensional (1D) planar structures, where the width of the ribbon is on the nanometer length scale. Carbon nanoribbons differ from carbon nanotubes is that nanoribbons have edges, whereas nanotubes have terminations only at their two ends.
Women and men, female and male animals and cells are biologically different, and acknowledgement of this fact is critical to advancing medicine. However, incorporating concepts of sex-specific ...analysis in basic research is largely neglected, introducing bias into translational findings, clinical concepts and drug development. Research funding agencies recently approached these issues but implementation of policy changes in the scientific community is still limited, probably due to deficits in concepts, knowledge and proper methodology. This expert review is based on the EUGenMed project (www.eugenmed.eu) developing a roadmap for implementing sex and gender in biomedical and health research. For sake of clarity and conciseness, examples are mainly taken from the cardiovascular field that may serve as a paradigm for others, since a significant amount of knowledge how sex and oestrogen determine the manifestation of many cardiovascular diseases (CVD) has been accumulated. As main concepts for implementation of sex in basic research, the study of primary cell and animals of both sexes, the study of the influence of genetic vs. hormonal factors and the analysis of sex chromosomes and sex specific statistics in genome wide association studies (GWAS) are discussed. The review also discusses methodological issues, and analyses strength, weaknesses, opportunities and threats in implementing sex-sensitive aspects into basic research.
Magnetic particle imaging is a quantitative functional imaging technique that allows imaging of the spatial distribution of super-paramagnetic iron oxide particles at high temporal resolution. The ...raw data acquisition can be performed at frame rates of more than 40 volumes s−1. However, to date image reconstruction is performed in an offline step and thus no direct feedback is available during the experiment. Considering potential interventional applications such direct feedback would be mandatory. In this work, an online reconstruction framework is implemented that allows direct visualization of the particle distribution on the screen of the acquisition computer with a latency of about 2 s. The reconstruction process is adaptive and performs block-averaging in order to optimize the signal quality for a given amount of reconstruction time.
The neural correlates of most cognitive functions in fish are unknown. This project aimed to identify brain regions involved in visual learning in the cichlid fish
Pseudotropheus zebra
. The ...expression of the protein pS6 was measured in 19 brain areas and compared between groups of individuals subjected to four different behavioral contexts (control, avoidance, trained, and novelty groups). Control group individuals were sacrificed with minimal interactions. Fish in the avoidance group were chased with a net for an hour, after which they were sacrificed. Individuals in the trained group received daily training sessions to associate a visual object with a food reward. They were sacrificed the day they reached learning criterion. Fish in the novelty group were habituated to one set of visual stimuli, then faced a change in stimulus type (novelty stimulus) before they were sacrificed. Fish in the three treatment groups showed the largest activation of pS6 in the inferior lobes and the tectum opticum compared to the control group. The avoidance group showed additional activation in the preoptic area, several telencephalic regions, the torus semicircularis, and the reticular formation. The trained group that received a food reward, showed additional activation of the torus lateralis, a tertiary gustatory center. The only area that showed strong activation in all three treatment groups was the nucleus diffusus situated within the inferior lobe. The inferior lobe receives prominent visual input from the tectum via the nucleus glomerulosus but so far, nothing is known about the functional details of this pathway. Our study showed for the first time that the inferior lobes play an important role in visual learning and object recognition.
Glucagon Regulation of Energy Expenditure Kleinert, Maximilian; Sachs, Stephan; Habegger, Kirk M ...
International journal of molecular sciences,
10/2019, Letnik:
20, Številka:
21
Journal Article
Recenzirano
Odprti dostop
Glucagon's ability to increase energy expenditure has been known for more than 60 years, yet the mechanisms underlining glucagon's thermogenic effect still remain largely elusive. Over the last ...years, significant efforts were directed to unravel the physiological and cellular underpinnings of how glucagon regulates energy expenditure. In this review, we summarize the current knowledge on how glucagon regulates systems metabolism with a special emphasis on its acute and chronic thermogenic effects.
Summary
It has been one and a half centuries since Enrico Sertoli published the seminal discovery of the testicular ‘nurse cell’, not only a key cell in the testis, but indeed one of the most amazing ...cells in the vertebrate body. In this review, we begin by examining the three phases of morphological research that have occurred in the study of Sertoli cells, because microscopic anatomy was essentially the only scientific discipline available for about the first 75 years after the discovery. Biochemistry and molecular biology then changed all of biological sciences, including our understanding of the functions of Sertoli cells. Immunology and stem cell biology were not even topics of science in 1865, but they have now become major issues in our appreciation of Sertoli cell's role in spermatogenesis. We end with the universal importance and plasticity of function by comparing Sertoli cells in fish, amphibians, and mammals. In these various classes of vertebrates, Sertoli cells have quite different modes of proliferation and epithelial maintenance, cystic vs. tubular formation, yet accomplish essentially the same function but in strikingly different ways.
Aims: Human epidermal growth factor receptor 2 (HER2) overexpression/amplification is implicated in the development of various solid tumour types. Validated methods and scoring systems for ...evaluating HER2 status exist in breast cancer, but not in gastric cancer. The aim was to establish a HER2 scoring system for gastric cancer to identify suitable patients for enrolment in a trial of trastuzumab (Herceptin®) in advanced metastatic gastric cancer.
Methods and results: Formalin‐fixed paraffin‐embedded gastric cancer samples were tested for HER2 status using the fluorescence in situ hybridization (FISH) pharmDx™ kit (Dako Denmark A/S). Immunohistochemistry (IHC) was performed using the HercepTest™ (Dako). Concordance between FISH and IHC was 93.5% in 168 evaluable samples. Eleven samples were scored as FISH+ but IHC− or equivocal.
Conclusions: IHC/FISH discrepancies were attributed to basolateral membranous immunoreactivity of glandular cells resulting in incomplete membranous reactivity and/or a higher rate of tumour heterogeneity in gastric cancer compared with breast cancer. With modifications to the IHC scoring system, the HercepTest™ is considered valid for the identification of HER2+ gastric tumours for this clinical trial. Correlation of HER2 scores with clinical outcomes will be needed to determine which patients might benefit from trastuzumab therapy.
Photonic structures can be designed to tailor luminescence properties of materials, which becomes particularly interesting for non-linear phenomena, such as photon upconversion. However, there is no ...adequate theoretical framework to optimize photonic structure designs for upconversion enhancement. Here, we present a comprehensive theoretical model describing photonic effects on upconversion and confirm the model's predictions by experimental realization of 1D-photonic upconverter devices with large statistics and parameter scans. The measured upconversion photoluminescence enhancement reaches 82 ± 24% of the simulated enhancement, in the mean of 2480 separate measurements, scanning the irradiance and the excitation wavelength on 40 different sample designs. Additionally, the trends expected from the modeled interaction of photonic energy density enhancement, local density of optical states and internal upconversion dynamics, are clearly validated in all experimentally performed parameter scans. Our simulation tool now opens the possibility of precisely designing photonic structure designs for various upconverting materials and applications.
Because of its relevance for the global climate the Atlantic meridional overturning circulation (AMOC) has been a major research focus for many years. Yet the question of which physical mechanisms ...ultimately drive the AMOC, in the sense of providing its energy supply, remains a matter of controversy. Here we review both observational data and model results concerning the two main candidates: vertical mixing processes in the ocean's interior and wind‐induced Ekman upwelling in the Southern Ocean. In distinction to the energy source we also discuss the role of surface heat and freshwater fluxes, which influence the volume transport of the meridional overturning circulation and shape its spatial circulation pattern without actually supplying energy to the overturning itself in steady state. We conclude that both wind‐driven upwelling and vertical mixing are likely contributing to driving the observed circulation. To quantify their respective contributions, future research needs to address some open questions, which we outline.
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