Structural,optical and electrical properties of sulfur-incorporated amorphous carbon films

Amorphous carbon–sulfur (a-C:S) composite films were prepared by vapor phase pyrolysis technique. The structural changes in the a-C:S films were investigated by electron microscopy. A powder X-ray diffraction (XRD) study depicts the two-phase nature of a sulfur-incorporated a-C system. The optical bandgap energy shows a decreasing trend with an increase in the sulfur content and preparation temperature. This infers a sulfur incorporation and pyrolysis temperature induced reduction in structural disorder or increase in sp ² or π-sites. The presence of sulfur (S 2p) in the a-C:S sample is analyzed by the X-ray photoelectron spectroscopy (XPS). The sp ³/sp ² hybridization ratio is determined by using the XPS C 1s peak fitting, and the results confirm an increase in sp ² hybrids with sulfur addition to a-C. The electrical resistivity variation in the films depends on both the sulfur concentration and the pyrolysis temperature.     

High-speed camera study of Stage III crack propagation in chemically strengthened glass

Thermally or chemically strengthened glass is more resistant to damage and breakage compared to non-strengthened glass. Both strengthening mechanisms are based on incorporation of a compressive stress profile in the surface of the glass, which must be balanced by an equivalent amount of integrated tensile stress in the interior of the glass. This tensile stress is believed to affect the kinetics of Stage III crack propagation upon fracture of the sample. In this study, we use a high-speed camera to perform direct measurement of the kinetics of Stage III fracture in a strengthened glass sample. Data including crack propagation speed, crack bifurcation distance, and bifurcation angles are collected at a rate of 500,000 frames per second and then characterized. The authors believe that these data will provide a foundation for understanding the physics of Stage III fracture in strengthened glass samples.     

Protein and nanoparticle adsorption on orthogonal, charge-density-versus-net-charge surface-chemical gradients

An orthogonal, charge-density-versus-net-charge, surface-chemical gradient, composed of ternary mixed self-assembled monolayers, has been prepared from three hydrophilic components: positively chargeable amine-terminated, negatively chargeable carboxylic-acid-terminated, and hydroxyl-terminated alkanethiols, with the latter bearing a slight negative charge in electrolytes. The chemical composition and its distribution have been monitored by X-ray photoelectron spectroscopy. The adsorption behavior of negatively charged SiO(2) nanoparticles and positively charged amine-modified SiO(2) nanoparticles has been studied. Additionally, negatively charged proteins (bovine serum albumin and fibrinogen) and positively charged proteins (lysozyme) were adsorbed on the gradients. Negatively charged nanoparticles and proteins adsorb mainly in the positively charged region and vice versa, illustrating that the adsorption behavior is mainly influenced by electrostatic interactions, and showing the potential of the gradient for sorting applications. Despite literature reports to the contrary, no area was found that was completely resistant to protein adsorption.     

Morphology and bilayer integrity of small liposomes during aerosol generation by air-jet nebulisation

Small liposome suspensions (hydrodynamic diameter, 80–130 nm) were nebulised, and the resulting changes in morphology and bilayer integrity were found to be related to surface properties controlled by bilayer composition. Four separate liposome compositions (or liposome types) were investigated using three different phospholipids with unique properties. Morphological changes were studied using light scattering and imaging of liposomes before and after nebulisation, and structural integrity was investigated on the basis of the retention of an encapsulated dye (probe molecule). Nebulisation generated droplets contained liposomes. The liposome particles generated on droplet evaporation had a hollow structure as evidenced by electron imaging, indicating that the lipid bilayer does not collapse on evaporation. The particles of all compositions had mobility diameters between 50 and 90 nm, 1.4–1.6 times smaller than their diameters (hydrodynamic) measured before nebulisation, implying considerable volume shrinkage. Liposomes that had polymer-conjugated lipids covering their external surface underwent aggregation during nebulisation, evidenced by increased diameter after nebulisation. Incorporation of charged lipids reduced nebulisation-induced aggregation, but induced greater membrane rupture during aerosol generation, causing leakage of encapsulated probe molecules. Incorporation of both cholesterol and charged lipids prevented aggregation, but also preserved bilayer integrity, evidenced by the maximum retention of encapsulated dye observed in these conditions (>85%). The findings suggest that liposome bilayer composition can be manipulated to improve the efficiency of liposome aerosol delivery.     

Investigation of antibacterial phytochemicals in the bark and leaves of Ficus coronata by high-performance liquid chromatography-electrospray ionization-ion trap mass spectrometry (HPLC-ESI-MS(n) ) and ESI-MS(n)

The ethyl acetate extracts of the bark and leaves of Ficus coronata were separated by column chromatography and the resulting fractions tested for their bioactivity toward methicillin-resistant-Staphylococcus aureus (MRSA) and M. luteus. The bioactive column chromatography fractions were further separated by preparative thin layer chromatography (TLC) and the resulting bands investigated by high-performance liquid chromatography-electrospray ionization-ion trap mass spectrometry (HPLC-ESI-MS(n) ) and ESI-MS(n) . The resulting retention times, molecular masses, their fragmentation patterns, and the chemnet database (www.chemnetbase.com) were then used in the dereplication process by structural elucidation of some of the compounds when compared with known structures of natural origin. Some molecular masses and the corresponding fragmentations were found that did not correlate with any known compounds thus revealing potentially novel natural products that could be investigated on a larger scale and could ultimately find application as new drugs against MRSA and other multidrug-resistant microorganisms. Structures are also proposed for known compounds that have not been previously reported for F. coronata.     

Thermochemistry of Sr2Ce(1-x)Pr(x)O4 (x = 0, 0.2, 0.5, 0.8, and 1): variable-temperature and -atmosphere in-situ and ex-situ powder X-ray diffraction studies and their physical properties

A novel family of metal oxides with a chemical formula of Sr(2)Ce(1-x)Pr(x)O(4) (x = 0, 0.2, 0.5, 0.8, and 1) was developed as mixed oxide ion and electronic conductors for solid oxide fuel cells (SOFCs). All of the investigated samples were synthesized by the ceramic method at 1000 °C in air and characterized by powder X-ray diffraction (PXRD), selected area electron diffraction (SAED), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and electrochemical impedance spectroscopy (EIS). Ex-situ PXRD reveals that the Sr(2)PbO(4)-type Sr(2)CeO(4) decomposes readily into a mixture of perovskite-type SrCeO(3) and rock-salt-type SrO at 1400 °C in air. Surprisingly, the decomposed products are converted back to the original Sr(2)PbO(4)-type Sr(2)CeO(4) phase at 800 °C in air, as confirmed by in-situ PXRD. Thermal decomposition is highly suppressed in Sr(2)Ce(1-x)Pr(x)O(4) compounds for Pr > 0, suggesting that Pr improves the thermal stability of the compounds. Rietveld analysis of PXRD and SAED supported that both Pr and Ce ions are located on the 2a site in Pbam (space group no. 55). The electrical transport mechanism could be correlated to the reduction of Pr and/or Ce ions and subsequent loss of oxide ions at elevated temperatures, as shown by TGA and in-situ PXRD. Conductivity increases with Pr content in Sr(2)Ce(1-x)Pr(x)O(4). The highest total conductivity of 1.24 × 10(-1) S cm(-1) was observed for Sr(2)Ce(0.2)Pr(0.8)O(4) at 663 °C in air.     

Mixed ionic-electronic conductivity in phases in the praseodymium oxide system

The praseodymium oxide system contains a series of related phases with very narrow compositional width and unique extended defect structures, rather than the more common isolated point defects. The electrical conductivity of three of these phases has been measured by the use of AC complex impedance and DC methods in the temperature range 75–400 °C. The beta phase, Pr₆O₁₁, exhibits a total conductivity of 6.77×10^–2 S/cm at 400 °C, with an activation energy of 0.52 eV/atom. The conductivity of the epsilon phase, Pr₅O₉, is slightly lower, with an activation energy of 0.51 eV/atom. The iota phase, Pr₇O₁₂, has a very low conductivity. The activation energies for electrical transport in the beta and epsilon phases are in the general range found in a number of mixed conductors based upon LSGM oxides. Electronic Publication     

Role of Intracellular Iron in Switching Apoptosis to Ferroptosis to Target Therapy-Resistant Cancer Stem Cells

Iron is a crucial element required for the proper functioning of the body. For instance, hemoglobin is the vital component in the blood that delivers oxygen to various parts of the body. The heme protein present in hemoglobin comprises iron in the form of a ferrous state which regulates oxygen delivery. Excess iron in the body is stored as ferritin and would be utilized under iron-deficient conditions. Surprisingly, cancer cells as well as cancer stem cells have elevated ferritin levels suggesting that iron plays a vital role in protecting these cells. However, apart from the cytoprotective role iron also has the potential to induce cell death via ferroptosis which is a non-apoptotic cell death dependent on iron reserves. Apoptosis a caspase-dependent cell death mechanism is effective on cancer cells however little is known about its impact on cancer stem cell death. This paper focuses on the molecular characteristics of apoptosis and ferroptosis and the importance of switching to ferroptosis to target cancer stem cells death thereby preventing cancer relapse. To the best of our knowledge, this is the first review to demonstrate the importance of intracellular iron in regulating the switching of tumor cells and therapy resistant CSCs from apoptosis to ferroptosis.     

Calcium-Dependent Translocation of S100B Is Facilitated by Neurocalcin Delta

S100B is a calcium-binding protein that governs calcium-mediated responses in a variety of cells—especially neuronal and glial cells. It is also extensively investigated as a potential biomarker for several disease conditions, especially neurodegenerative ones. In order to establish S100B as a viable pharmaceutical target, it is critical to understand its mechanistic role in signaling pathways and its interacting partners. In this report, we provide evidence to support a calcium-regulated interaction between S100B and the neuronal calcium sensor protein, neurocalcin delta both in vitro and in living cells. Membrane overlay assays were used to test the interaction between purified proteins in vitro and bimolecular fluorescence complementation assays, for interactions in living cells. Added calcium is essential for interaction in vitro; however, in living cells, calcium elevation causes translocation of the NCALD-S100B complex to the membrane-rich, perinuclear trans-Golgi network in COS7 cells, suggesting that the response is independent of specialized structures/molecules found in neuronal/glial cells. Similar results are also observed with hippocalcin, a closely related paralog; however, the interaction appears less robust in vitro. The N-terminal region of NCALD and HPCA appear to be critical for interaction with S100B based on in vitro experiments. The possible physiological significance of this interaction is discussed.     

Palladium catalyzed reaction in aqueous DMF: synthesis of 3-alkynyl substituted flavones in the presence of prolinol

(S)-Prolinol facilitated the coupling reaction of terminal alkynes with 3-iodoflavone under palladium-copper catalysis in aqueous DMF affording a mild and convenient method for the synthesis of 3-alkynyl substituted flavones of potential biological interest.