Separation Transition Research Articles

Photoexcitation of brilliant cresyl blue dye in aqueous solution: TD-DFT study

The vibronic absorption spectra of brilliant cresyl blue (BCB) oxazine dye in an aqueous solution using 40 hybrid functionals, the 6-31++G(d,p) basis set, and the SMD solvent model were calculated. It turned out that the X3LYP functional provided the best agreement with the experiment in the positions of the main maximum and the short-wavelength shoulder. Our calculations showed that this shoulder is vibronic and is not caused by a separate electronic transition. At the same time, the shoulder intensity in the calculated spectrum turned out to be lower than in the experimental one. Various parameters of the BCB cation in the ground and excited states (IR spectra, atomic charges, dipole moments, and transition moment) were calculated. Maps of the distribution of electron density and electrostatic potential have been built. The influence of four strong hydrogen bonds of the dye with water molecules on the absorption spectrum was analyzed. It has been shown that these bonds are strengthened upon BCB excitation. It was found that explicit assignment of water molecules strongly bound to the dye leads to a redshift of the spectrum. Photoexcitation of the dye leads to a noticeable polarization of only one of the four considered water molecules.

Photoexcitation of methylene green dye in aqueous solution: TD-DFT study

The vibronic absorption spectra of methylene green (MG) thiazine dye in an aqueous solution using X3LYP hybrid functional, the 6-31++G(d,p) basis set, and the SMD solvent model were calculated. It turned out that this theory level the choice of which is based on previous theoretical studies of thiazine dyes provided excellent agreement with the experiment in the positions of the main maximum and the short-wavelength shoulder. Our calculations showed that this shoulder is vibronic and is not caused by a separate electronic transition. At the same time, the shoulder intensity in the calculated spectrum turned out to be lower than in the experimental one. Various parameters of the MG cation in the ground and excited states (IR spectra, atomic charges, dipole moments, and transition moment) were calculated. The dipole moment of the dye molecule in the ground state turned out to be the same as in the excited one, contrary to previous studies, where the dipole moment of a thiazine dyes without a nitro group increases upon excitation. This could be explained by the influence of the MG nitro group in position 6, due to which electron density increases on both diametrically opposite N10 and S5 atoms of the central ring. At the same time, in other thiazine dyes (without a nitro group), photoexcitation leads to a one-sided increase in the electron density at the N10 atom, and as a result, the projection of the dipole moment directed across the chromophore increases significantly. Maps of the distribution of electron density and electrostatic potential have been built. The influence of the strong hydrogen bonds of the dye with three water molecules on the absorption spectrum was analyzed. It has been shown that these bonds are strengthened upon MG excitation. It was found that explicit assignment of water molecules strongly bound to the dye leads to a redshift of the spectrum as a whole and worsened its shape.

Theoretical analysis of lactone and carboxylate forms of camptothecin in aqueous solution: Electronic states, absorption spectra, and hydration

The vibronic absorption spectra of the camptothecin drug in an aqueous solution have been calculated for the first time. The calculations were carried out by the TD-DFT method. It was shown that both for lactone and carboxylate forms an excellent agreement with the experimental spectrum gives the BMK/6-31++G(d,p)/IEFPCM theory level. It was demonstrated that absorption spectra of both forms in the 300–400 nm wavelength range are due to single HOMO → LUMO (S0 → S1) electronic transition, and the short-wavelength smaller peak and shoulder are of vibronic origin. This result is at odds with the previous conclusions of other authors that this peak has a dimeric nature or is caused by interaction with an aqueous medium, and the shoulder is due to a separate electronic transition. According to my calculations, strong hydrogen bonds of the lactone and carboxylate forms with water molecules do not affect their absorption spectra. This is because some of these H-bonds were enhanced by photoexcitation of alkaloid molecules, while others were weakened. The opening of the lactone ring does not affect the position of the vibronic absorption bands but only leads to their significant broadening. Therefore, two separate maxima of the lactone form of the alkaloid merge into one broad peak. The absence of the influence of the lactone E ring on the absorption of the alkaloid is since the frontier orbitals are localized on other rings of the chromophore. Calculations have shown that the dipole moment of both forms of the alkaloid decreases significantly upon excitation. In combination with the practically zero contribution of specific interactions with an aqueous environment, this result indicates the n → π* type of the considered electronic transition. It agrees with both the experimental and theoretical results of some authors. Various characteristics of excited states of both drug forms (IR spectra, atomic charges, electron density, and electrostatic potential distributions) were obtained.

Photoexcitation of oxazine 170 dye in aqueous solution: TD-DFT study.

The vibronic absorption spectra of OX170 dye in an aqueous solution using 40 hybrid functionals, the 6-31 + + G(d,p) basis set, and the SMD solvent model were calculated. It turned out that the long-range corrected ωB97XD functional provided the best agreement with the experiment in the positions of the main maximum and the short-wavelength shoulder. Calculations showed that this shoulder is vibronic and is not caused by a separate electronic transition. At the same time, the shoulder intensity in the calculated spectrum turned out to be lower than in the experimental one. Various parameters of the OX170 cation in the ground and excited states (IR spectra, atomic charges, dipole moments, and transition moment) were calculated. Maps of the distribution of electron density and electrostatic potential have been built. The influence of four strong hydrogen bonds of the dye with water molecules on the absorption spectrum was analyzed. It was shown that these bonds are strengthened upon OX170 excitation. It was found that explicit assignment of water molecules strongly bound to the dye leads to a redshift of the calculated spectrum by ≈15nm as a whole, and worsened its shape. Photoexcitation of the dye leads to a noticeable polarization of only one of the four considered water molecules (associated with the endocyclic nitrogen atom in the central ring of the chromophore, the electron density on which increases the most).

Wall cooling effect on separated flow transition over a highly loaded compressor blade

Large eddy simulations (LESs) were conducted to investigate the effects of wall cooling on the separated flow transition over a highly loaded compressor blade at two Reynolds numbers of 2.0 × 105 and 1.0 × 105. The locations of transition onset and completion were identified by linear stability theory (LST). As the transition was triggered, the streamwise gradient of the near-wall temperature increased to a higher level. Therefore, the transitional region can be roughly diagnosed through the distribution of temperature. Results showed that wall cooling weakened the relative role of turbulent dissipation in suppressing rapid amplification of disturbances, which promoted the transition process and reduced the length of the transitional region. Compared with the case of the adiabatic wall, the scale of three-dimensional vortex structures on the cooled wall was reduced, and the vortex rolling-up and breakdown were weakened. For such conditions, the region of high-level Reynolds shear stresses shrunk and the loss generation rate declined. By comparison, the effect of wall cooling on controlling the transition process was more pronounced at a lower Reynolds number, and the profile loss was reduced by 18.23% and 25.05% at Reynolds numbers of 2.0 × 105 and 1.0 × 105, respectively.

Study of Segregation in Non-Dilute Solutions of Linear Diblock Copolymers and Symmetric Miktoarm (or Janus Star) Polymers Using Monte Carlo Simulations with the Bond Fluctuation Model

The bond fluctuation model was employed to characterize the approach to the mesophase separation transition of pure linear AB copolymers and symmetric miktoarms, also called Janus, star polymers, Af/2Bf/2, where f = 6 or 12 is the total number of arms, in a common good solvent. We consider a concentration sufficiently high to mimic the melting behavior and also a lower concentration. The segregation between A and B units is represented by a repulsive interaction parameter, ε. Different total numbers of units are also considered. Results for different properties, such as the molecular size, the asphericity and orientational correlation of blocks, or arms, of different compositions are obtained as a function of the segregation parameter. We also calculate scattering structure factors. The initial effect of segregation on the scattering with opposite contrast factors between the A and B blocks can be explained with a common description based on the random phase approximation for both the linear copolymers and the f = 6 miktoarms, once the numerical form factors of the different molecules in their particular systems are considered. However, the results for f = 12 clearly deviate from this description probably due to some degree of ordering in the position of highly armed molecules.

Effect of softness on glass melting and re-entrant solidification in mixtures of soft and hard colloids.

We present a systematic investigation of the structure and dynamic properties of model soft-hard colloidal mixtures. Results of a coarse-grained theoretical model are contrasted with rheological data, where the soft and hard colloids are mimicked by large star polymers with high functionality as the soft component and smaller stars with ultrahigh functionality as the hard one. Previous work by us revealed the recovery of the ergodicity of glassy soft star solutions and subsequent arrested phase separation and re-entrant solid transition upon progressive addition of small hard depletants. Here, we use different components to show that a small variation in softness has a significant impact on the state diagram of such mixtures. In particular, we establish that rendering the soft component more penetrable and modifying the size ratio bring about a remarkable shift in both the phase separation region and the glass-melting line so that the region of restored ergodicity can be notably enhanced and extended to much higher star polymer concentrations than for pure systems. We further rationalize our findings by analyzing the features of the depletion interaction induced by the smaller component that result from the interplay between the size ratio and the softness of the large component. These results demonstrate the great sensitivity of the phase behavior of entropic mixtures to small changes in the molecular architecture of the soft stars and point to the importance of accounting for details of the internal microstructure of soft colloidal particles for tailoring the flow properties of soft composites.

The Aligned Orbit of the Eccentric Warm Jupiter K2-232b

Abstract Measuring the obliquity distribution of stars hosting warm Jupiters may help us to understand the formation of close-orbiting gas giants. Few such measurements have been performed due to practical difficulties in scheduling observations of the relatively infrequent and long-duration transits of warm Jupiters. Here, we report a measurement of the Rossiter–McLaughlin effect for K2-232 b, a warm Jupiter on an 11.17 day orbit with an eccentricity of 0.26. The data were obtained with the Automated Planet Finder during two separate transits. The planet’s orbit appears to be well aligned with the spin axis of the host star, with a projected spin–orbit angle of λ = −11.°1 ± 6.°6. Combined with the other available data, we find that high obliquities are almost exclusively associated with planets that either have an orbital separation greater than 10 stellar radii or orbit stars with effective temperatures hotter than 6000 K. This pattern suggests that the obliquities of the closest-orbiting giant planets around cooler stars have been damped by tidal effects.

Phylogeny and evolution of large body size in the rove beetle genus Phlaeopterus Motschulsky, 1853 (Coleoptera: Staphylinidae: Omaliinae: Anthophagini)

Abstract The omaliine rove beetle genus Phlaeopterus Motschulsky, 1853 contains 22 species. The genus is distributed across northwestern North America and eastern Asia. These beetles occur primarily along the edges of alpine snowfields and streams, habitats that are particularly sensitive to the impacts of climate change. Two species have not been collected since 1979 and 1984, one of which, Phlaeopterus bakerensis Mullen and Campbell, 2018, is a contender for the largest-bodied species among the over 1,600 species of the subfamily Omaliinae. Here, we present the first phylogeny of the genus, using Bayesian and maximum likelihood analyses based on DNA sequences from the mitochondrial gene COI and morphological data. We tested previous taxonomic hypotheses and most were rejected by all three analyses. Phlaeopterus castaneus Casey, 1893 is non-monophyletic based on COI sequences and may have hybridized with P. loganensis Hatch, 1957. We found support for the monophyly of the genus Phlaeopterus. Our analyses suggest the common ancestor of the genus had small-bodied adults (maximum body size under 5 mm) with ocelli. Within this small-bodied radiation of species, ocelli were lost once and there were two separate evolutionary transitions to large-bodied adults. Although all the large-bodied species are snowfield-associated and only 25% of the small-bodied species are, we did not find statistical support for a relationship between large body size and use of snowfield habitats. These findings represent the first modern phylogenetic reconstruction of species-level relationships within the rove beetle subfamily Omaliinae using both morphological and molecular data.

Prior On-Off Relationship Instability and Distress in the Separation and Divorce Transition.

Divorce is considered distressing for many individuals (Sbarra etal., Current Directions in Psychological Science, 2015, 24, 109); however, individuals in poor-quality relationships may experience certain benefits of leaving an unstable union (Amato & Hohmann-Marriott, Journal of Marriage and Family, 2007, 69, 621). On-off relationship cycling, or the breakup and reconciliation of a relationship, is a salient indicator of poor relationship quality and a common form of relationship instability (Dailey etal., Personal Relationships, 2009, 16, 23) that is associated with distress (Monk etal., Family Relations, 2018, 67, 523). In line with divorce-stress-adjustment and relational turbulence theory perspectives, we hypothesized that those whose relationships were characterized by on-off instability would experience less distress during the separation and divorce process. Given gender inequality in marriage (e.g., Dempsey, Journal of Sociology, 2002, 38, 91; Monin & Clark, Sex Roles, 2011, 65, 320), we also hypothesized that this association would be more pronounced for women. Using data from 98 divorced or separating couples, we found that relationship cycling prior to the separation and divorce process was associated with fewer distress symptoms for women. Conversely, a history of relationship cycling was associated with more distress symptoms for men. Our study provides support and extends prior investigations illustrating that, for some, those in unions characterized by more turmoil, may experience relief following a termination.

Fabrication of high permeability SiC ceramic membrane with gradient pore structure by one-step freeze-casting process

A highly permeable porous SiC ceramic membrane with multilayered unidirectional gradient pore microstructure was prepared by one-step freeze-casting process. The multilayer microstructures, mechanical properties and filtering performances of freeze-casting SiC ceramic membranes were controlled by optimizing the preparation process. It was found that with the increase of solid content from 30 vol% to 40 vol%, the directional pore channels gradually narrowed by about 50% and the mechanical properties increased from 0.47 MPa to 5.44 MPa. In addition, the increase of coarse particle content not only thickened the separation layer and the transition layer, but also widened the directional pore channel, which is beneficial to improve the permeability efficiency. When the coarse particle content of SiC ceramic membranes was 90%, the average pore size of separation layer, transition layer and lamellar structure was 5.52 μm, 7.63 μm and 36.09 μm, respectively. The maximum water permeability of S35C90 ceramic membrane reached up to 5.67 × 105 L/m2 h bar, and the rejection rate for ground calcium carbonate was 96.1%, confirming the superior perviousness and separation efficiency of freeze-casting ceramic membranes in the field of filtration.

Numerical simulation of transitional flows using a blended IDDES and correlation-based transition model

In the present study, a hybrid RANS/LES model and a correlation-based transition model were coupled for simulating flow involving massive flow separation and laminar-turbulent transition including crossflow direction. For this purpose, blending of IDDES model and the γ−Reθt−CF+ transition model was accomplished in a tightly coupled manner. For validations, numerical simulations around a circular cylinder involving laminar flow separation without turbulent reattachment were conducted. Numerical simulations were also conducted for flows around an Aerospatiale A-airfoil at a larger Reynolds number accompanying turbulent flow reattachment. As an application of the present blended model for flows involving crossflow transition, calculations were performed for flows around a 6:1 prolate spheroid, and the results were compared with experiment and those without considering flow transition induced by the crossflow instability. Additional application was also made for flows around an ONERA M6 wing at a relatively high angle of attack, and the results were compared with those of the baseline models and experiment. It was founded that the results by the present blended model are in good agreements with experiment, and show improvements over other models by considering flow transition and unsteady flow feature simultaneously. It was concluded that the present blended model is useful for predicting flows involving massive flow separation and crossflow transition.

First Principles Study on Electronic and Optical Properties of Quinary Copper-based Sulfides and Selenides Cu2HgGe(S1-xSex)4

Electronic and optical properties of Cu2HgGe(S1-xSex)4 compounds (x = 0, 0.25, 0.5, 0.75, and 1) were revealed by density functional theory (DFT), in which the Heyd-Scuseria-Ernzerhof hybrid functional was used. Dependence of band gap on the Se constituent in Cu2HgGe(S1-xSex)4 was reported. The substitution of Se element basically cause a slightly lattice expansion and minor change of the band gap. Meanwhile, the overlap of Cu and S/Se states becomes more dense leading to better electron/hole pair separation and inter-band transition of photo-excited electrons. The Cu2HgGe(S0.75Se0.25)4 compound was predicted to be very promising absorber due to the low band gap, high absorption rate, and low reflectivity in the incoming light energy range from 0 eV to 2 eV.
 

How do Ligands Tune the Assembly and Dissolution of Biomolecular Condensates?

Biomolecular condensates are thought to assemble via spontaneous or driven phase transitions of condensate-specific scaffold molecules. Scaffolds are multivalent protein or RNA molecules that enable concentration dependent phase separation and percolation transitions. Condensates also encompass non-scaffold molecules and the diversity of these molecules determines the compositional complexity of condensates. Non-scaffold molecules known as ligands can tune the phase behavior of scaffold molecules by preferentially binding to scaffolds in condensates or the coexisting dilute phase. Accordingly, cells can control condensate formation / dissolution by tuning the expression levels of ligands. Here, we show phase separation is destabilized when multivalent ligands bind to stickers, which are scaffold regions that drive phase separation. Phase separation is also destabilized by monovalent ligands, irrespective of whether they bind to sticker or spacer regions on scaffolds. In contrast, multivalent ligands that bind to spacer regions can promote scaffold phase separation. In this scenario, the binding of ligands adds valence to the scaffold molecules by enabling additional physical crosslinking of molecules within condensates. This suggests that the driving forces for condensate formation can be enhanced or diminished by controlling the expression levels of distinct categories of ligands - monovalent and/or multivalent ligands that bind to stickers vs. spacers. We show that modulatory effects of ligands cannot be discerned by measurements of partition coefficients of ligands. While these measurements are useful for compositional profiling of condensates, they have to be augmented by measuring the effects of ligands on the scaffold concentrations in coexisting dilute and dense phases. Overall, our studies provide a rigorous framework for modeling the effects of networks of ligands on the phase behavior of condensates, thereby enabling a deeper understanding of the compositional biases of condensates and ligand-mediated regulation of condensates in cells.

Control of vertical phase separation in high performance non-fullerene organic solar cell by introducing oscillating stratification preprocessing

Non-fullerene organic solar cell (NFOSC) has attracted tremendous attention due to their great potential for commercial applications. To improve its power conversion efficiency (PCE), generally, sequential solution deposition (SSD) methods have been employed to construct the graded vertical phase separation (VPS) of the bulk-heterojunction (BHJ) active layer for efficient exciton separation and charge transition. However, a variety of orthogonal solvents used in the SSD may lead to the unpredicted change in the BHJ morphology and introduce additional defects inside the BHJ bulk thus complicate the fabrication process. Here, a simple oscillating stratification preprocessing (OSP) is developed to facilitate the formation of graded VPS among the BHJ layer. As a result, a significant improvement is obtained in PCE from 10.96% to 12.03%, which is the highest value reported among PBDB-T: ITIC based NFOSC.

New-phase retention in colloidal core/shell nanocrystals via pressure-modulated phase engineering.

Core/shell nanocrystals (NCs) integrate collaborative functionalization that would trigger advanced properties, such as high energy conversion efficiency, nonblinking emission, and spin–orbit coupling. Such prospects are highly correlated with the crystal structure of individual constituents. However, it is challenging to achieve novel phases in core/shell NCs, generally non-existing in bulk counterparts. Here, we present a fast and clean high-pressure approach to fabricate heterostructured core/shell MnSe/MnS NCs with a new phase that does not occur in their bulk counterparts. We determine the new phase as an orthorhombic MnP structure (B31 phase), with close-packed zigzagged arrangements within unit cells. Encapsulation of the solid MnSe nanorod with an MnS shell allows us to identify two separate phase transitions with recognizable diffraction patterns under high pressure, where the heterointerface effect regulates the wurtzite → rocksalt → B31 phase transitions of the core. First-principles calculations indicate that the B31 phase is thermodynamically stable under high pressure and can survive under ambient conditions owing to the synergistic effect of subtle enthalpy differences and large surface energy in nanomaterials. The ability to retain the new phase may open up the opportunity for future manipulation of electronic and magnetic properties in heterostructured nanostructures.

Short-Range Order and Macroscopic Lithium Transport in Cation-Disordered Rocksalt Cathodes

The tremendous success and growth of Lithium(Li)-ion based energy storage in a broad range of applications is likely to strain our natural resources. Projected growth of Li-ion production towards 1 TWh/year will require more than a million tons of Co/Ni combined, which constitutes a very sizeable fraction of the annual production of these metals. The recent development of Li-excess cation-disordered rocksalt (DRX) cathodes, which require no separate Li layer and transition metal (TM) layer in the cation sublattice, is providing an avenue for the Li-ion battery field to develop high energy density cathodes with more abundant and less expensive metals, such as Mn, Fe and Ti. Unlike the traditional layered NCM cathodes in which Li ions transport within the well-defined Li layers, the Li ions diffuse through a “3-D” Li rich pathway (‘0-TM’ channel) in DRX cathodes, i.e., the feasible Li hops require that the intermediate tetrahedral sites along the Li diffusion path are coordinated only by Li (no transition metal). The complexity of this class of DRX cathodes mainly lies in the fact that lacking in long-range order though, DRX cathodes, in most cases, present various types of cation short-range order (SRO), which controls the frequency and connectivity of Li migration channels, thus, macroscopic Li transport.Here we demonstrate two general strategies to engineer the cation SRO in DRX cathodes through compositional design, combining computational investigations, electrochemical tests, and advanced characterizations. (1) Fluorine doping on anion sublattices.The strong Li-F interaction modifies the cation SRO in DRX materials by forming Li-rich domains around F ions. We will present a design map which shows that the macroscopic Li transport is strongly controlled by the Li-excess level and F content within a fixed DRX chemical space and can be correlated to the observed capacities of a DRX cathode, as corroborated by electrochemical tests. (2) TM doping on cation sublattices.With a fixed Li and F content, TM doping can frustrate the cation SRO in DRX cathodes by increasing configurational entropy, thus improve the Li transport, i.e. capacity and rate capability in a significant way. The compatibility between various TM ions in DRX compounds is also investigated to facilitate future experimental design. We show that this can lead to DRX materials that combine high rate capability and high capacity. Reference [1] Ji, H.et al.Hidden structural and chemical order controls lithium transport in cation-disordered oxides for rechargeable batteries. Nature Communications 10, 592, doi:10.1038/s41467-019-08490-w (2019).[2] Lun, Z.et al.Design Principles for High-Capacity Mn-Based Cation-Disordered Rocksalt Cathodes. Chem, doi:https://doi.org/10.1016/j.chempr.2019.10.001(2019).[3] Ouyang, B.et al.Effect of Fluorination on Lithium Transport and Short-Range Order in Disordered-Rocksalt-Type Lithium-Ion Battery Cathodes. Advanced Energy Materials 10, 1903240, doi:10.1002/aenm.201903240 (2020).[4] Clément, R. J., Lun, Z. & Ceder, G. Cation-disordered rocksalt transition metal oxides and oxyfluorides for high energy lithium-ion cathodes. Energy & Environmental Science 13, 345-373, doi:10.1039/C9EE02803J (2020).

(Keynote) Solar CO2 Conversion into Liquid Fuels Via Thermodynamic and Kinetic Control

In this report, photoelectrochemical (PEC) system for the reduction of CO2 into liquid fuels of formaldehyde and acetaldehyde with minor hydrogen gas bubbling has been described in the aspect of thermodynamics and kinetics of the CO2 reduction reaction to have efficient method by lowering activation energy of CO2 reduction on the electron transfer reaction and to do reduction potential tuning of CO2 reduction reaction for the selective reduction products. Ca/Fe doped TiO2 photoanode oxidizes water and generates the large amount of O2, electrons and protons. On the other side, rGO(reduced graphene oxide)/PVP(poly(4-vinyl)pyridine)/Nafion multi-layers have been coated and fabricated on the surface of Cu foil cathode to reduce CO2 into acetaldehyde and formaldehyde compounds with different combined functions of each layer in the cathode. When solar light was irradiated on the surface of photoanode, electrons get excited to the conduction band of Ca/Fe doped TiO2 and transported to the cathode via external wire with low external bias potential. rGO on Cu foil has been used for the dual functions of reduction potential tuning and multi-electron shuttling process of CO2 reduction reaction. The multi-electron shuttling function was illuminated by larger number and longer life-time of excited electrons and generating electron cloud, which have been confirmed by time-resolved photoluminescence (TR-PL) decay curves and 2D time-resolved photoluminescence (TR-PL) mapping images of Cu/rGO electrode. This allows the sequential multi-electron transport process from Cu/rGOcathode to CO2, which was studied with time-resolved chronoamperometry and identification of the charge transfer complex formation with UV-vis spectrophotometer. The reduction potential tuning was controlled by the combined function of bias potential given by external wire and reduction degree of rGO to add proper amount of potential energy to transfer multi-electrons to CO2 in the thermodynamic aspect. Those combined functions are given to supply the tuned amount of energy into the open circuit potential of the system for photoanode of Ca/Fe doped TiO2 and Cu/rGO cathode to transport excited electrons to produce CO2 reduction product selectively. N-heterocyclic poly(4-vinyl)pyridine (PVP) helps to capture and do chemical activation of reactant CO2 molecule by complexation as [PVP-CO2*] complex via charge separation and lowering transition state energy level of the electron transfer for the formation of anion radical of carbon dioxide complex with PVP as [e- + PVP-CO2*]≠ complex via electron delocalization, which is basically possible due to high basicity of lone pair electrons of nitrogen atoms of N-heterocyclic PVP compounds. These functions result in the lowered activation energy for the CO2 reduction reaction to have faster kinetics. The decreased amount of activation energy was determined with Tafel plots by measuring the slopes of it and semicircles of the electrochemical impedance spectroscopy (EIS) Nyquist plots at different temperatures. Nafion film coated on the surface of cathode assists the faster transport of H+ ions to CO2 reduction reaction sites for the simultaneous one-pot reaction of proton coupled electron transfer reactions. It was checked with comparing the current density of the I-V curves of cathodes with and without Nafion layer coating of Cu foil cathode. Obtained results of CO2 reduction into liquid fuels via photoelectrochemical process show formaldehyde as major product with 25% current efficiency in Cu/rGO cathode and acetaldehyde as a major product with 35% current efficiency in Cu/rGO/PVP/Nafion as cathode during 4 h of photoelectrochemical reaction at 0.68 V vs RHE as an external bias potential.

Solvent influence on the phase behavior and glass transition of Amorphous Solid Dispersions

Understanding the long-term stability of amorphous solid dispersions (ASDs) is important for their successful approval for market. ASD stability does not only depend on the interplay between the active pharmaceutical ingredient (API) and the polymer in the final formulation but may already be disadvantageously influenced by process steps during the production (e.g. selection of inappropriate solvent for spray drying). Residual solvent can affect the API solubility in the polymer, molecular mobility (by influencing the glass-transition temperature) and induce liquid-liquid phase separation. Enhanced mobility in the ASD due to residual solvent can promote recrystallization in ASDs.The removal of residual solvent can be expensive, time-consuming, and usually requires secondary drying procedures to fulfil the regulatory requirements. The aim of this work is to predict the API solubility in polymer-solvent mixtures, solvent influence on the glass transition, and the occurrence of liquid-liquid phase separation of solvent-loaded ASDs using the thermodynamic model PC-SAFT and to experimentally validate these predictions. ASDs containing the APIs ritonavir or naproxen and the polymers poly(vinylpyrrolidone), poly (vinylpyrrolidone-co-vinyl acetate), or hydroxypropyl methylcellulose acetate succinate were spray-dried using the solvents acetone, ethanol, and dichloromethane. API solubility, sorption behavior, liquid-liquid phase separation and glass transition in the ternary API/polymer/solvent mixtures were predicted based on the binary phase behavior between API/solvent, API/polymer, and polymer/solvent and successfully validated experimentally using dynamic vapor sorption (DVS), and Raman spectroscopy. Thus, the presented methodology allows for an in-silico selection of appropriate solvent systems for solvent-based ASD preparation based on a limited amount of experimental data for binary systems only.

Does morphology have real impact on local and distant recurrences in head and neck cutaneous melanoma?

Introduction. The term “local recurrence” is usually understood as regrowth of a tumor after surgical treatment. The regrowth appears within 3–5 cm from postoperative cicatrix. The causes for such prolonged tumor growth or recurrence of patients with cutaneous melanoma are nonradical surgical treatment as well as satellite or transit metastases that were not removed in-block with primary tumor. A great number of clinical researches, aimed at examination of melanoma, its patterns, anatomical criteria and features of clinical course, gave an opportunity to separate satellite or transit metastases into an independent group. Such metastases are realized inside or subdermally, up to 2 cm or more than 2 cm from the primary tumor, yet, not reaching the location of the first regional barrier.The aim of the study is to define influence of the main prognostic factors such as tumor thickness according to Breslow, the level of invasion according to Clark and the presence of ulceration on the frequency of local recurrence with cutaneous melanoma of head and neck.Materials and methods. The research involved 174 patients with cutaneous melanoma of head and neck (1995–2014). According to our index of contraction of a skin flap (median 30 %) the true borders of resection were clearly defined within all the patients. Thereby, 3 groups were identified with the following resection margin: 1.0 cm, where followed-up treatment results were analyzed.Results. Progression-free survival didn’t correlate with the size of surgical resection margins. The survival rates were the best with the lowest resection margin under 0.5 cm (77.3 %) and the worst with the highest resection margin more then 1.0 cm (38.7 %). That means that the treatment results don’t depend on the width increase of tumor resection margin.Conclusions. We consider that clear surgical margins for any thickness of cutaneous melanoma of head and neck should be as follows: 4 mm – 0.72 mm (p = 0.016). In our work, the influence of the main prognostic factors, such as tumor thickness according to Breslow, level of invasion according to Clark and ulceration on the frequency of head and neck cutaneous melanoma local recurrences had no impact.