Different Strengths Of Interaction Research Articles

Tensile failure mechanisms investigation of mesophase pitch-based carbon fibers based on continuous defective graphene nanoribbon model

Mesophase pitch (MPP)-based carbon fibers exhibit outstanding mechanical properties, notably an exceptionally high Young’s modulus. Despite extensive investigations into the microstructure of MPP-based carbon fibers, the influence of these factors on deformation mechanisms under tension remains unclear. This study employs the continuous defective graphene nanoribbons (dGNR) atomistic structure model for molecular dynamics simulations to explore the tensile failure mechanisms of MPP-based carbon fibers. In the simulation model, the structure of the defective region was generated through high-temperature annealing, and a transition region was introduced to prevent distortion and damage to the active graphene edges. The simulation reveals the evolutionary process of the microstructure of MPP-based carbon fibers under tension and achieves Young’s modulus predictions with greater accuracy than theoretical models. Additionally, the study shows that different strengths of interactions between adjacent graphene nanoribbons can lead to two distinct failure modes. Models with larger crystallite dimensions along the fiber axis and lower average defective concentrations exhibit geometric deformation coordination between adjacent nanoribbons, potentially elucidating the increasing strength trend in MPP-based carbon fibers with rising graphitization levels. Our simulations provide insights into the tensile failure mechanisms of MPP-based carbon fibers, offering valuable guidance for regulating their microstructure to enhance mechanical performance.

Mixtures of discotic and spherical soft particles: de-mixing, liquid crystal behaviour and relative solubility

Liquid crystals (LC) mixtures are ubiquitous in all real-life applications of LCs. This is due to the need of modulating the macroscopic properties of the LC phase used in specific devices. However, mixing particles of different shapes, not to mention different strength of interaction, often results in de-mixing (phase separation) with the formation of one phase rich in one type of particles separated from the other phase. In this work we investigate the phase behaviour of mixtures of discotic Gay-Berne (GB) particles with spherical Lennard-Jones (LJ) particles using molecular dynamics (MD) simulations. We have considered compositions ranging from the pure GB system up to a GB mole fraction of 0.1 and we have studied the systems at constant volume as a function of the temperature keeping all systems at the same packing fraction. We observe an interesting behaviour where GB-rich systems undergo a nematic-to-isotropic transition, with decreasing transition temperature as the fraction of LJ solutes is increased, keeping a single phase with a relatively large amount of LJ particles dissolved. Lowering the temperature eventually results in a phase separated hexagonal columnar in coexistence with an isotropic phase. In contrast, for LJ-rich systems the de-mixing occurs together with the transition to the nematic phase and the transition point raises again close to the values observed for the pure GB. A clear correlation is also observed between the orientational order parameter of the LC phase and the solubility of LJ particles within the LC phase itself.

6-Methoxylated Flavonoids: Jacein, and 3-demethyljacein from Centaurea schmidii with Their Endoplasmic Reticulum Stress and Apoptotic Cell Death in Breast Cancer Cells Along with In-silico Analysis.

In phytochemical analysis, Jacein derivatives: 5,7,4’-trihydroxy-3,6,3’-trimethoxyflavone-7(β)-D-glucopyranoside (1), and 3-demethyljacein: 3,5,7,4’-tetrahydroxy-6,3’-dimethoxyflavone-7(β)-D-glucopyranoside (2) were isolated from Campylopus schmidii (C. schmidii) for the first time. The structures were determined by interpretation of NMR, UV, and Mass spectra. To check the roles of ER stress and consequent apoptosis in MCF-7 cell by these compounds, UPR signaling pathway was further examined by analysis of expression of ER stress-related genes. In MTT assay, compounds 1-2 showed cytotoxicity activity against MCF-7 (A) and MDA-MB cells (B) with IC50 values (μM) of 1) 60.04 ± 7.98 (A), and > 200 (B); 2) 42.89 ± 1.91 (A), and 85.31 ± 2.68 (B). The Annexin/PI flow cytometry apoptosis of tested compounds 1-2 was increased significantly in a dose-dependent manner. For example, MCF-7 treatment at the concentration of 100 μM of compounds 1, 2 resulted in total apoptosis (early + late) of 42.04 (18.1 + 24.0), and 66.49 (2.7 + 63.8)%, respectively. Fluorescence microscopy analysis detected an increased protein aggregation, indicating induced ER stress with a marked increase in XBP-1, sXBP-1, ATF-4, and CHoP compared to untreated cells. In-silico characterization, suggested that Adenosine diphosphate site (A-site) and quercetin site (Q-Site) in IRE1a enzyme are both available interacting sites of a target for the investigated ligands but with different strengths of interactions. The results indicated that the ligand∼A-Site complexes are stronger than the ligand∼Q-Site complexes, but the already available ADP ligand in cells does not allow other ligands to interact with the A-Site and cause them to bond in Q-Site.

Collective modes of Weyl fermions with repulsive S-wave interaction* *Project supported by the National Natural Science Foundation of China (Grant No. 2016YFA0301500).

We calculate the spin and density susceptibility of Weyl fermions with repulsive S-wave interaction in ultracold gases. Weyl fermions have a linear dispersion, which is qualitatively different from the parabolic dispersion of conventional materials. We find that there are different collective modes for the different strengths of repulsive interaction by solving the poles equations of the susceptibility in the random-phase approximation. In the long-wavelength limit, the sound velocity and the energy gaps vary with the different strengths of the interaction in the zero sound mode and the gapped modes, respectively. The particle–hole continuum is obtained as well, where the imaginary part of the susceptibility is nonzero.

The importance of dynamic effects in chemical reactions in condensed phase

Energy transfer and spatial diffusion are two significant sub-processes in chemical reaction. Traditional rate theory is based on two assumptions: (1) energy transfer is faster than chemical reaction so that specific energy transfer channel is not important. (2) The solvents can respond to the change of solute quickly resulting in equilibrium solvation. Then once system cross the barrier, it will enter the product basin. But when energy transfer is fast enough to distribute the energy into all degrees of freedom according to certain ratio, the specific energy transfer pathways should be considered. Our previous studies have found that the polar functional groups play the major role in the intermolecular energy transfer process. And the energy accumulation and dissipation are completed by the motion with specific frequency. Furthermore, the major energy transfer channel is different in different solutions. Moreover, the length of transition path is very short, leading to the existence of different transient solvation configurations with distinctly different strengths of interaction between solutes and solvents. Consequently, the motion of solvents modulates the reaction dynamics and results in heterogeneous reaction paths. Therefore, the dynamic effects are vital for understanding and controlling the chemical reaction.

Microgel in a Pore: Intraparticle Segregation or Snail-like Behavior Caused by Collapse and Swelling

We demonstrate that a microgel can enter and exit a narrow cylindrical pore under external stimuli leading to collapse and swelling of the microgel. Attractive interactions between the microgel and the pore surface stimulate the microgel entering upon its collapse. The entering is driven by a gain in the surface energy: the area of the microgel–pore contacts is maximized within the pore. Swelling of the microgel within the pore of a finite size is thermodynamically favorable if the pore thickness exceeds a certain threshold value. Otherwise, the swelling leads to the microgel exit. The physical reason for this is a gain in the elastic free energy of the subchains which are less stretched outside the pore. We systematically study swelling and collapse of the microgel within the pore. Both longitudinal size and radial concentration profiles are calculated for different strength of interactions of the beads with each other and the pore surface. We predict an intramicrogel “phase” coexistence leading to the f...

Thermodynamics of H2O and CO2 Absorption and Guest-Induced Phase Transitions in Zeolite RHO

Gas absorption calorimetry at low pressures has been employed to probe the interaction of water and carbon dioxide with several ion-exchanged zeolite RHO samples. It reveals that guest-induced framework flexibility transitions from a less hydrated (initially anhydrous) acentric form to the more hydrated centric phase during water absorption. The differential enthalpy of absorption as a function of water loading directly identifies the strengths of different interactions along with possible water binding mechanisms. Interactions with CO2 are weaker, and no phase transition is seen except in Li,H-RHO. The most negative initial enthalpies have been obtained in both water and CO2 absorption for Cd and Cs-RHO. However, Li,H-RHO shows the strongest capture ability for CO2 despite a less exothermic initial enthalpy of absorption. The derived differential enthalpy, chemical potential, and entropy elucidate the thermodynamic behavior of multiple interactions of small guest molecules (H2O and CO2) and ion-exchanged...

Molecular Dynamics Study on Proton Transport in Supported Nafion Ionomer Thin Films on Lennard-Jones Walls

The catalyst layer, one of the components of membrane electrode assembly in polymer electrolyte fuel cells, was modeled by molecular dynamics methods, and proton transport in ionomer thin films was simulated to elucidate the effect of surface wetting interaction on the ionomer thin film morphology and proton transport property. Ionomer thin film properties are considered to be affected by the surface property of supported carbon due to their nano-scale thickness (4-10 nm thick). One of the surface properties is surface wetting interaction basically attributed to the physical or chemical property of surfaces.In this study, modeled Nafion thin films with 4 nm and 10 nm thick were generated on the two ideal LJ smooth surfaces which have different strength of interactions to focus on the effect of the surface wetting interaction on the ionomer thin film morphology and proton transport. Protons exist as hydronium ions in ionomer thin films for chemical stability and are transported by the two transport mechanisms which are the vehicle mechanism (just move as hydronium ions) and the Grotthuss mechanism called proton hopping. It is common that proton transport model is restricted to only the vehicle mechanism when using classical molecular dynamics method, however, our proton transport model includes the Grotthuss mechanism by using aTS-EVB method (anharmonic two-state empirical valence bond method) in order to make proton transport model more reproducible.From the analysis in the ionomer thin films with 4 nm thick, surface wetting interaction was found to affect the orientation of sulfonic group near the surface. The orientation is well-ordered on the higher hydrophobic surface, and the sulfonic groups point to the gas phase direction, while it is randomly distributed on the lower hydrophobic surface, which make differences in the water cluster connectivity and size in ionomer thin films between the two surfaces. Proton transport property was evaluated by the self-diffusion coefficient. The proton self-diffusion coefficient in ionomer thin films was indicated to be improved on higher hydrophobic surface probably because higher hydrophobic surface makes ideal water cluster structures for proton transport in ionomer thin films.As compared to the ionomers with the different film thickness, the proton self-diffusion coefficient in ionomer thin films on higher hydrophobic surface was indicated to decrease in the increase of the film thickness, while that on lower hydrophobic surface was indicated to increase slightly. This result is expected to come from the confinement and interface effects which can be remarkable when the thickness decrease. The ionomer morphology on higher hydrophobic surface has advantages for proton transport probably thanks to the effects as observed in the ionomer with 4 nm thick, while that on lower hydrophobic surfaces has disadvantage. Since the effects can be weaker with the increase in the film thickness, the proton self-diffusion coefficient in ionomer thin films on higher hydrophobic surface was found to decrease with the increase in the film thickness, while that on lower hydrophobic surface was found to increase slightly.

Proteomic Interaction Patterns between Human Cyclins, the Cyclin-Dependent Kinase Ortholog pUL97 and Additional Cytomegalovirus Proteins.

The human cytomegalovirus (HCMV)-encoded cyclin-dependent kinase (CDK) ortholog pUL97 associates with human cyclin B1 and other types of cyclins. Here, the question was addressed whether cyclin interaction of pUL97 and additional viral proteins is detectable by mass spectrometry-based approaches. Proteomic data were validated by coimmunoprecipitation (CoIP), Western blot, in vitro kinase and bioinformatic analyses. Our findings suggest that: (i) pUL97 shows differential affinities to human cyclins; (ii) pUL97 inhibitor maribavir (MBV) disrupts the interaction with cyclin B1, but not with other cyclin types; (iii) cyclin H is identified as a new high-affinity interactor of pUL97 in HCMV-infected cells; (iv) even more viral phosphoproteins, including all known substrates of pUL97, are detectable in the cyclin-associated complexes; and (v) a first functional validation of pUL97-cyclin B1 interaction, analyzed by in vitro kinase assay, points to a cyclin-mediated modulation of pUL97 substrate preference. In addition, our bioinformatic analyses suggest individual, cyclin-specific binding interfaces for pUL97-cyclin interaction, which could explain the different strengths of interactions and the selective inhibitory effect of MBV on pUL97-cyclin B1 interaction. Combined, the detection of cyclin-associated proteins in HCMV-infected cells suggests a complex pattern of substrate phosphorylation and a role of cyclins in the fine-modulation of pUL97 activities.

Chelating Surfaces for Native State Proteins Patterning: The Human Serum Albumin Case.

The paper reports a new "soft" surface functionalization strategy, based on a highly selective ion metal chelation process. The proposed stepwise methodology implies at first the construction of a monolayer of terpyridine-based thiol (Tpy), whose highly packed structuring has been followed in situ by using quartz crystal microbalance (QCM-D) measurements, showing that the monolayers consist of about 2.7 × 10(14) Tpy/cm(2). Then, the tridentate sites of the each Tpy moiety are employed to partially chelate divalent metal ions, providing an effective platform to anchoring proteins by completing the metal ion coordination with an available site on the protein of interest. We report the case study of the application of the process to the HSA immobilization onto various surfaces, including Tpy-Fe(II) and Tpy-Cu(II) complexes, as well as hydrophilic bare gold substrates and hydrophobic self-assembled Tpy-based monolayers. It is shown that the chelation interaction between Tpy-Cu(II) complexes and HSA produces the highest and most robust HSA immobilization, with an adsorbed mass at the steady state of ∼800 ng/cm(2), with respect to an average adsorption of ∼350 ng/cm(2) for the other surfaces. Furthermore, Cu(II)-chelated surfaces seem to promote a sort of protein "soft" landing, preventing the ubiquitous surface-induced major unfolding and transmitting an orientation information to the protein, owing to the highly specific symmetry coordination of the Tpy-Cu(II)-protein complex. Indeed, the interaction with a specific monoclonal antiboby (anti-HSA) indicated the lack of a significant protein denaturation, while a massive reorientation/denaturation process was found for all the remaining surfaces, including the Tpy-Fe(II) complex. Finally, the metal-ion-dependent HSA immobilization selectivity has been exploited to obtain micropatterned surfaces, based on the strikingly different strength of interaction and stability observed for Fe(II) and Cu(II) complexes.

Copper-manganese-zinc spinels in zeolites: study of EMR spectra

Abstract The aim of this study is the application of electron magnetic resonance (EMR) spectroscopy to determine the interactions between NaY and HY zeolites and Cu-Mn-Zn spinels loaded onto the zeolite surfaces. The materials were characterized using XRD and IR spectroscopies. Four types of EMR lines were observed for Cu-Mn-Zn/NaY, Cu-Mn-Zn/HY samples. The difference between the EMR spectra recorded at 77 and 293 K has been shown. The spectra recorded at 77 K allowed us to distinguish between the species formed on NaY and HY zeolites. The EMR spectrum of Cu-Mn-Zn/NaY recorded at 77 K showed only one line attributed to antiferromagnetic spinels Cu1.4Mn1.6O4 and ZnMn2O4 or/and Cu0.5Zn0.5Mn2O4. The spinels appeared to be more stable (more strongly attached) on HY zeolite than on NaY one. It was proved that different strength of interactions between the zeolites and Cu-Mn-Zn spinels was caused by differences in the acidity of NaY and HY zeolites.

Protein Interactions with Corroding Metal Surfaces

Low-corrosion resistant metals, such as Mg or Fe based alloys, have been in the focus of intensive research activities in recent years to be used in biodegradable implants. A general challenge is to tailor the materials and surfaces to achieve the desired and controlled corrosion rate for the targeted applications. A further challenge is to elucidate the influence of the complex biological environment on the corrosion mechanisms of these materials. A vast majority of the studies in this field have been carried out on Mg based materials; far less attention has been given to Fe. A comparison of the behavior of Fe and Mg based alloys in simulated biological environments is on one hand side of practical interest in view of possible biomedical applications of these materials. Moreover, from mechanistic point of view, a direct comparison may aid in elucidating mechanisms of interactions between the constituents of the biological environment and the corroding metal surfaces in more detail. In the present study, we are investigating the influence of proteins on the corrosion behavior of Mg and Fe by electrochemical and surface analytical techniques. Proteins in solution can have multiple effects on corrosion reactions: on one hand side, protein adsorption layers can block electrochemically active surface sites and therefore slow down corrosion. Protein adsorption will be influenced by the surface chemistry of the metals (e.g., wettability, type of oxides/hydroxides formed on the surface, and the resulting surface charges) - therefore different interactions may be expected for Mg and Fe. On the other side, complexation of metal cations can take place by proteins (and amino acids), thereby reducing the free cation concentration and possibly accelerating corrosion. Also this effect depends on the nature of the metal cations; for Fe and Mg dissolution products different strength of interactions can be expected. Electrochemical studies indeed indicate very different interactions of proteins (bovine serum albumin, BSA) on Mg as compared with Fe. For Mg, inhibition of corrosion in presence of albumin in solution can be observed for short-term experiments. For Fe, a slight increase of corrosion by addition of albumin in solution takes place. In general, the influence of BSA on the corrosion behaviour of Mg is much stronger than that observed for Fe. Surface analytical studies (XPS and ToF-SIMS) demonstrate stronger adsorption of albumin on Mg than on Fe. Moreover, protein adsorption on Mg and Fe varies for different proteins (for instance: albumin vs. lysozyme). Possible mechanisms and critical factors of protein interactions with corroding Fe and Mg surfaces will be discussed.

Proteomic analysis of interaction between P7-1 of Southern rice black-streaked dwarf virus and the insect vector reveals diverse insect proteins involved in successful transmission

Southern rice black-streaked dwarf virus (SRBSDV), transmitted by the white-backed planthopper (Sogatella furcifera) in a persistent-propagative manner, has caused serious yield losses in Asia. Here in a yeast two-hybrid system, protein interactions between SRBSDV P7-1 as a bait protein and a cDNA library of S. furcifera as prey protein were assessed. Of 153 proteins identified as putative interactors, 24 were selected for further analysis. Of the 24 proteins, 18 were further confirmed in a chemiluminescent coimmunoprecipitation (Co-IP) assay as true positive interactors with different strengths of interactions. Six potential candidate proteins (neuroglian, myosin light chain 2 [MLC2], polyubiquitin, E3 ubiquitin ligase, ribophorin ii, and profilin) were analyzed for gene expression in five organs by qRT-PCR; mRNA levels were highest in the gut for neuroglian, MLC2, polyubiquitin and profilin, in the salivary glands for ribophorin ii, and in the haemolymph for E3 ubiquitin ligase. A virus-host protein interaction network was constructed using SRBSDV P7-1 and 18 prey positive protein homologs of Drosophila melanogaster. Our findings suggest that these proteins are involved in the complex host reaction to infection by SRBSDV and provide new insights into the molecular basis of transmission. Southern rice black-streaked dwarf virus (SRBSDV), transmitted by S. furcifera in a persistent-propagative manner, is a new found virus and a tentative member of the genus Fijivirus in the family Reoviridae. It was widely noted by plant virologist, government officials and the farmers in Asia in recent years because of its epidemic outbreak and causing serious yield losses after 2009. However, the molecular mechanism by which SRBSDV successfully infects and replicates in both plant and insect hosts remains unclear, and much less is known about how the virus spreads from initially infected cells to adjacent cells in the insect vector. In the present study, we examined protein interactions between SRBSDV P7-1 as the bait and cDNA library of WBPH as the prey by using yeast two-hybrid system, 153 proteins were identified as putative interactors and 24 putative proteins were selected for chemiluminescent coimmunoprecipitation (Co-IP) assay, and then constructed a viral protein-host protein interaction network with homologs of D. melanogaster. Six WBPH proteins were confirmed as potential P7-1 partners that take part in a pivotal role for viral movement in insect vector. These findings will greatly facilitate the understanding of the transmission mechanisms of SRBSDV by its insect vector. This is the first to study the molecular interaction between SRBSDV and its insect vector.

Surface physicochemical properties at the micro and nano length scales: role on bacterial adhesion and Xylella fastidiosa biofilm development.

The phytopathogen Xylella fastidiosa grows as a biofilm causing vascular occlusion and consequently nutrient and water stress in different plant hosts by adhesion on xylem vessel surfaces composed of cellulose, hemicellulose, pectin and proteins. Understanding the factors which influence bacterial adhesion and biofilm development is a key issue in identifying mechanisms for preventing biofilm formation in infected plants. In this study, we show that X. fastidiosa biofilm development and architecture correlate well with physicochemical surface properties after interaction with the culture medium. Different biotic and abiotic substrates such as silicon (Si) and derivatized cellulose films were studied. Both biofilms and substrates were characterized at the micro- and nanoscale, which corresponds to the actual bacterial cell and membrane/ protein length scales, respectively. Our experimental results clearly indicate that the presence of surfaces with different chemical composition affect X. fastidiosa behavior from the point of view of gene expression and adhesion functionality. Bacterial adhesion is facilitated on more hydrophilic surfaces with higher surface potentials; XadA1 adhesin reveals different strengths of interaction on these surfaces. Nonetheless, despite different architectural biofilm geometries and rates of development, the colonization process occurs on all investigated surfaces. Our results univocally support the hypothesis that different adhesion mechanisms are active along the biofilm life cycle representing an adaptation mechanism for variations on the specific xylem vessel composition, which the bacterium encounters within the infected plant.

Absorption and Scattering of Light by Hybrid Metal/J-Aggregate Nanoparticles: Plasmon–Exciton Coupling and Size Effects

We report the results of our theoretical studies of the optical properties of hybrid nanoparticles consisting of the metal core covered with molecular J-aggregates. We evaluate the cross sections of absorption and scattering of light by such particles on the basis of the extended Mie theory for two concentric spheres with material dielectric functions that take into account the size effect associated with scattering of free electrons from the core/shell interface. We carry out our calculations in a wide range of light wavelengths and geometrical parameters of the composite system for silver and gold core and for a J-aggregate shell composed of different cyanine dyes. The results obtained demonstrate the quite different behavior of the extinction spectra of such particles caused by the different strengths of interaction between the Frenkel exciton and the dipolar or multipolar plasmons. We pay particular attention to the investigation of spectral peak positions associated with the eigenfrequencies of hybrid modes in the system and peak intensities as functions of reduced oscillator strength in the molecular J-band for various relationships between the core radius and shell thickness. This provides an efficient means for the explanation of the main features in the optical properties of metal/J-aggregate nanoparticles and can be used for an effective control of the plasmon–exciton coupling strength in such hybrid complexes.

A Modified Active Brownian Dynamics Model using Asymmetric Energy Conversion and its Application to Cargo Transport by Multi-Motors

We consider a modified active Brownian particle model for an application to the cargo transport by multi-motors. In our model each motor has its own energy depot to convert the internal energy into mechanical energy via a non-linear conversion mechanism and is interacting with the cargo harmonically. A different kind of motor is described by a different strength of interaction. By introducing stochastic energy supply to each motor independently and flashing ratchet potential synchronized to the stochastic energy supply, we perform an active Brownian dynamics simulation. Mean velocity, stall force, forward-backward step profiles are investigated for various interaction strengths of the motors with the cargo under the influences of external load, thermal noise, and ATP concentration.

Structural attributes for the recognition of weak and anomalous regions in coiled-coils of myosins and other motor proteins

BackgroundCoiled-coils are found in different proteins like transcription factors, myosin tail domain, tropomyosin, leucine zippers and kinesins. Analysis of various structures containing coiled-coils has revealed the importance of electrostatic and hydrophobic interactions. In such domains, regions of different strength of interactions need to be identified since they could be biologically relevant.FindingsWe have updated our coiled-coil validation webserver, now called COILCHECK+, where new features were added to efficiently identify the strength of interaction at the interface region and measure the density of charged residues and hydrophobic residues. We have examined charged residues and hydrophobic ladders, using a new algorithm called CHAHO, which is incorporated within COILCHECK + server. CHAHO permits the identification of spatial charged residue patches and the continuity of hydrophobic ladder which stabilizes and destabilizes the coiled-coil structure.ConclusionsThe availability of such computational tools should be useful to understand the importance of spatial clustering of charged residues and the continuity of hydrophobic residues at the interface region of coiled-coil dimers. COILCHECK + is a structure based tool to validate coiled-coil stability; it can be accessed at http://caps.ncbs.res.in/coilcheckplus.

Correlation of surface-enhanced Raman spectroscopy and laser desorption-ionization mass spectrometry acquired from silver nanoparticle substrates

Applying complementary experiments, like laser desorption-ionization mass spectrometry (LDI-MS) and confocal surface-enhanced Raman microscopy, to the same physical sample location has the potential to elucidate the behavior of complex chemical and biochemical systems in ways that are not available to either method applied in isolation. In these experiments surface-enhanced Raman scattering (SERS) and LDI-MS are applied to the same sample spot using a common structure, deposited Ag colloids, both as ionization matrix and simultaneously as enhancing media for surface-enhanced Raman scattering of small organic molecules, dyes and lipids, and the behavior is compared. Three compounds-p-aminothiophenol (ATP), rhodamine 6G and cholesterol-which exhibit different strengths of interaction with Ag are examined in detail by correlated SERS and LDI-MS. The related mechanisms of nanoparticle-assisted desorption-ionization and Raman enhancement are explored by correlating mass and Raman spectra. The correlated spectra highlight the manner in which the different test compounds interact with plasmonic metal nanostructures. These coupled studies yield new insight into the transition of analyte from the metal-solution interface to gaseous ions, including, in the case of organothiols, a rich set of mixed clusters that provide chemical insight into the ion formation process.

Surface properties of the Ni-silica gel catalyst precursors for the vegetable oil hydrogenation process: N2 sorption and XPS studies

The effect of the type of the silica gel pore structure on the surface properties of the Ni-silica gel catalyst precursors for the vegetable oil hydrogenation process has been examined applying N2 sorption and X-ray photoelectron spectroscopy techniques. The nickel catalyst precursors with identical composition (SiO2/Ni = 1.0) has been synthesized by precipitation of Ni(NO3)2 · 6H2O solution with Na2CO3 solution on the three types of silica gel with different pore structures. It is shown that the usage of the silica gel supports with different texture as source of SiO2 causes different location of Ni-species into the support pores and on the external surface area. The XPS data confirm the formation of surface species with different strength of interaction and different dispersion. These surface characteristics of the precursors will predetermine the formation of the active nickel metallic phase as well as the mass transfer of the reactants and products to and from the catalytic sites.

Phase behavior of linear heterogeneous trimers on a square lattice

Monte Carlo simulations in the grand canonical ensemble, the multiple-histogram analysis and finite-size scaling techniques have been used to study a phase behavior of trimer BAB on a square lattice. The systems with the same energies u(AA) = u(BB) and different strengths of interactions between unlike segments are considered. The AB-contacts are energetically unprofitable. There are two phase transitions: the first-order vapor-liquid transition and the second-order structural transition in the supercritical fluid. The phase diagram topology depends on the energy u(AB). The crossover between the tricritical point phase diagram topology and the critical end phase diagram topology is found. It is demonstrated that the transition to the ordered strip-like phase is non-universal.