Synthesis Of Carbon Nitride Films At Low Temperatures

Carbon nitride films (CN x) have been deposited by sputtering a graphite target with nitrogen ions. Films were grown both with and without the presence of an assisting focused N 2 ion beam. The sputter beam voltage was varied between 150 and 1500 V and the applied assisting beam voltage from 80 to 500 V. The substrate was held at fixed temperatures between 80 and 673 K. The coatings were characterized with respect to their electrical, optical, and structural properties. The nitrogen content was measured by x-ray photoelectron spectroscopy (XPS) and a maximum nitrogen concentration of 44 at. % was obtained for a nonassisted sample deposited at 140 K. The chemical structure was investigated by XPS and Fourier transform infrared spectroscopy. Reduction of the substrate temperature in conjunction with low sputter beam voltages (<200 V) caused the optical band gap to increase up to 2.2 eV, the sheet conductivity to decrease to less th an 10 -9 (Ω cm) -1 and the density to be reduced to 1.6 g/cm 3. The increasing transparency is accompanied by structural changes indicating a transition from a predominantly sp 2 bonded amorphous sp 2/sp 3 C-N network to a more linear polymerlike structure consisting predominantly of doubly and triply bonded C and N atoms. No evidence for the formation of the β-C 3N 4 phase was found. © 1997 American Vacuum Society.151107112Hammer, P., Gissler, W., (1996) Diam. Relat. Mater., 5, p. 1152Hammer, P., Baker, M.A., Lenardi, C., Gissler, W., Thin Solid Films, , to be publishedTodorov, S.S., Marton, D., Boyd, K.J., Al-Bayati, A.H., Rabalais, J.W., (1994) J. Vac. Sci. Technol. A, 12, p. 3192Liu, A.Y., Cohen, M.L., (1990) Phys. Rev. B, 41, p. 10727Baker, M.A., Hammer, P., Surf. Interface Anal., , submittedKaufman, J.H., Metin, S., Saperstein, D.D., (1989) Phys. Rev. B, 39, p. 13053Dolphin, D., Wick, A., (1977) Tabulation of Infrared Spectral Data, , Wiley, New YorkSocrates, G., (1980) Infrared Characteristic Group Frequencies, , Wiley, Chichester, U.KSjöström, H., Stafström, S., Boman, M., Sundgren, J.E., (1995) Phys. Rev. Lett., 75, p. 1336Marton, D., Al-Bayati, A.H., Todorov, S.S., Boyd, K.J., Rabalais, J.W., (1994) Nucl. Instrum. Methods Phys. Res. B, 90, p. 277Sjöström, H., Hultman, L., Sundgren, J.-E., Hainsworth, S.V., Page, T.F., Theunissen, G.S.A.M., (1996) J. Vac. Sci. Technol. A, 14, p. 56Briggs, D., Clark, D.T., Keable, H.R., Kilner, M., (1973) J. Chem. Soc. Dalton Trans., p. 2143Barber, M., Conner, J.A., Guest, M.F., Hillier, I.H., Schwartz, M., Stacey, M., (1973) J. Chem. Soc. Faraday Trans. II, 69, p. 551Bircumshaw, L.L., Tayler, F.M., Whiffen, D.H., (1954) J. Chem. Soc., p. 93

Degradation of Image Quality Induced by Thermal Loads and Slope Errors in a XUV High Resolution Synchrotron Radiation Monochromator

The limiting effects to the performances of an optical device, such as an XUV monochromator inserted in a synchrotron radiation facility, are mainly manufacturing slope errors and thermal loads induced by the optical beam itself. We have performed numerical simulations on such effects in the low energy section of a high resolution, wide spectral range monochromator for the storage ring ELETTRA in Trieste. The instrument will be used in the dedicated surface physics beamline ALOISA (advanced line for overlayer interface and surface analysis). Thermal effects have been evaluated by using finite element analysis. Thermal induced deformations and slope errors have been included in a ray tracing program. The resulting aberrations at the output of the instrument have been evaluated for the extreme conditions of maximum power density and asymmetrical illumination of the second mirror. The results stress the relevance of manufacturing slope errors in limiting spatial and spectral resolution

Mechanotransduction in human and mouse beta cell lines: reliable models to characterize novel signaling pathways controlling beta cell fate

Background and aims: Attempts to influence \u3b2-cell differentiation by engineering substrates that mimic appropriate extracellular matrix (ECM) topographies are hampered by the fact that profound details of mechanosensing/transduction complexity remain elusive. We recently demonstrated that human islets of Langerhans sense the ECM nanotopography and activate a mechanotransductive pathway, which is essential for preserving long-term \u3b2-cell differentiation and function in vitro. However, human islets of Langerhans are extremely heterogeneous and their availability for research purpose is limited. Therefore, aim of the proposed research was to investigate whether mouse and human \u3b2-cell lines might sense changes innthe ECM topography and might be used as a simplified model to dissect the molecular pathways involved in mechanotransduction. Materials and methods: We used supersonic cluster beam deposition to fabricate nanostructured substrates characterized by a quantitatively controllable ECM-like nanoroughness. Mouse \u3b2TC3 and human 1.1B4 cells were seeded on these substrates and after five days in culture, the activation of the mechanotransductive pathway was verified by means of morphological (super-resolution fluorescence microscopy), functional and proteomic techniques. Results: Quantitative immunofluorescence studies demonstrated that the cell-nanotopography interaction affects the focal adhesion structures (smaller vinculin clusters), the organization of the actin cytoskeleton (shorter actin fiber) and the nuclear architecture. Functional studies revealed that nanostructured surfaces improve the \u3b2-cell mitochondrial activity and increase the glucose-stimulated Ca2+currents and insulin release. Label-free shotgun proteomics broadly confirmed the morphological and functional studies and showed the upregulation of a number of mechanosensors and transcription factors involved in \u3b2-cell differentiation in cells grown on nanostructured substrates compared to those grown on flat standard control surfaces. Conclusion: Our data reveal that mouse and human \u3b2-cell lines sense changes in extracellular mechanical forces and activate a mechanotransductive pathway. The findings from this study will be useful to clarify the link between mechanotransduction and cell fate and to successfully engineer scaffolds in order to have functional beta cells

Cellular response to cyclic compression of tissue engineered intervertebral disk constructs composed of electrospun polycaprolactone

There is lack of investigation capturing the complex mechanical interaction of tissue engineered IVD (intervertebral disc) constructs in physiologically-relevant environmental conditions. In this study, mechanical characterisation of anisotropic eletrospinning (ES) substrates made of polycaprolactone (PCL) was carried out in wet and dry conditions and viability of human bone marrow derived mesenchymal stem cells (hMSCs) seeded within double layers of ES PCL was also studied. Cyclic compression of IVD-like constructs composed of an agarose core confined by ES PCL double-layers was implemented using a bioreactor and the cellular response to the mechanical stimulation was evaluated. Tensile tests showed decrease of elastic modulus of ES PCL as the angle of stretching increased and at 60° stretching angle in wet, maximum ultimate tensile strength was observed. Based on the configuration of IVD-like constructs, the calculated circumferential stress experienced by the ES PCL double layers was 40 times of the vertical compressive stress. Confined compression of IVD-like constructs at 5% and 10% displacement dramatically reduced cell viability, particularly at 10%, although cell presence in small and isolated area can still be observed after mechanical conditioning. Hence, material mechanical properties of tissue-engineered scaffolds, composed of fibril structure of polymer with low melting point, are affected by the testing condition. Circumferential stress induced by axial compressive stimulation, conveyed to the ES PCL double-layer wrapped around an agarose core, can affect the viability of cells seeded at the interface, depending on the mechanical configuration and magnitude of the load

Nickel Phosphides Fabricated through a Codeposition–Annealing Technique as Low-Cost Electrocatalytic Layers for Efficient Hydrogen Evolution Reaction

Water splitting will be one of the most strategic techniques in the upcoming hydrogen-based economy. In this context, the development of efficient and low-cost Pt-free electrocatalysts is crucial t..

Low-frequency modes in the Raman spectrum of sp-sp2 nanostructured carbon

A novel form of amorphous carbon with sp-sp2 hybridization has been recently produced by supersonic cluster beam deposition showing the presence in the film of both polyynic and cumulenic species [L. Ravagnan et al. Phys. Rev. Lett. 98, 216103 (2007)]. Here we present a in situ Raman characterization of the low frequency vibrational region (400-800 cm-1) of sp-sp2 films at different temperatures. We report the presence of two peaks at 450 cm-1 and 720 cm-1. The lower frequency peak shows an evolution with the variation of the sp content and it can be attributed, with the support of density functional theory (DFT) simulations, to bending modes of sp linear structures. The peak at 720 cm-1 does not vary with the sp content and it can be attributed to a feature in the vibrational density of states activated by the disorder of the sp2 phase.Comment: 15 pages, 5 figures, 1 tabl

RSVconf: Node Autoconfiguration for MANETs

Abstract — A Mobile Ad-hoc NETwork (MANET) is a self-configuring network of mobile nodes connected by wireless links, which can form an arbitrary topology. We have worked on a new protocol, RSVconf, to ensure the IP address self-configuration of MANETs, with a special focus on the ITS (Intelligent Transportation System) context which is indeed the most mobile scenario. The RSVconf protocol manages the creation, merger and re-merger (merger after part of the network temporarily separated) of networks at IP layer. It is stateful, distributed and routing independent. The simulation results show its capability to react fast and correctly to the rapid topology changes of mobile networks without a waste of bandwidth. In this paper we present the current status of our research, open aspects and future directions

The Effect of Mn Depleted Surface Layer on the Corrosion Resistance of Shape Memory Fe-Mn-Si-Cr Alloys

In this work, we have examined Fe-Mn-Si-Cr alloys possessing a good shape memory effect due to a high Mn content (28 wt pct). The addition of Cr (5 wt pct) was made in order to give fairly good corrosion resistance to the alloy. But we have verified that even in moderately corrosive environ-ments, the presence of chromium does not bear any passivation. On the other hand, we have found that the alloy can acquire corrosion resistance by means of the formation of a Mn-depleted surface layer obtained by heating the alloy at high temperature (.10507C) in air. This modified layer forms since manganese is selectively oxidized with respect to the other components. The adhesion of this layer is maintained even under severe stress if the thickness of the modified region does not exceed 20mm. Under this limit, the shape memory characteristics of the alloy are not affected, and at the same time, the specimen acquires properties of passivity comparable with one of the most common austenitic stainless steels at the presence of the same environmental conditions

Knowledge, Perception, and Attitude of Universitas Indonesia Medical Students toward Complementary and Alternative Medicine

Introduction. Rate of Complementary and Alternative Medicine (CAM) use, including the Indonesian jamu, has increased in the last decade. This paper aims to identify the factors contributing to jamu development and to measure medical students’ knowledge, perception, and attitude toward CAM and jamu. Method. This is a cross-sectional study using questionnaire administered to Year 1-3 students of Faculty of Medicine, Universitas Indonesia. Results. Students generally show positive attitude towards CAM and jamu, but their knowledge is not complete. The majority (68,4%) of respondents had known about CAM and 90,4% believe CAM can be integrated into conventional medicine; 91,6% wants materials on CAM in the curricula. Almost half (48,4%) of the respondents are also users of CAM.  Conclusion. Students are open to the development of CAM and the government has issued policies supporting jamu, including Jamu Scientification Program. However, more evidence is needed, including clinical trials, before jamu can integrate into mainstream medicine

Effects of the 3D Geometry Reconstruction on the Estimation of 3D Porous Scaffold Permeability

3D scaffolds for tissue engineering typically need to adopt a dynamic culture to foster cell distribution and survival throughout the scaffold. It is, therefore, crucial to know fluids' behavior inside the scaffold architecture, especially for complex porous ones. Here we report a comparison between simulated and measured permeability of a porous 3D scaffold, focusing on different modeling parameters. The scaffold features were extracted by microcomputed tomography (μCT) and representative volume elements were used for the computational fluid-dynamic analyses. The objective was to investigate the sensitivity of the model to the degree of detail of the μCT image and the elements of the mesh. These findings highlight the pros and cons of the modeling strategy adopted and the importance of such parameters in analyzing fluid behavior in 3D scaffolds