A new anisotropic soft-core model for the simulation of liquid crystal mesophases

A new anisotropic soft-core model is presented, which is suitable for the rapid simulation of liquid crystal mesophases. The potential is based on a soft spherocylinder, which can be easily tuned to favor different liquid crystal mesophases. The soft-core nature of the potential makes it suitable for long-time step molecular dynamics or dissipative particle dynamics simulations, particularly as a reference model for mesogens or as an anisotropic solvent for use in combination with atomistic models. Results are presented for two variants of the new potential, which show different mesophase behaviors. Variants of the potential can also be linked together to produce more complicated molecular structures. Here, as an example, results are provided for a model multipedal liquid crystal, which has eight liquid crystalline groups linked to a central core via semiflexible chains. Here, despite the complexity of molecular structure, the model succeeds in showing the spontaneous formation of a liquid crystal phase. The results also demonstrate that there is a very strong coupling between the internal structure of the multipedal mesogen and the molecular order of the phase, with the mesogen spontaneously undergoing major structural rearrangement at the transition to the liquid crystal phase.     

Photoinduced Charge Transfer in a Conformational Switching Chlorin Dimer–Azafulleroid in Polar and Nonpolar Media

In the present study, a biomimetic reaction center model, that is, a molecular triad consisting of a chlorin dimer and an azafulleroid, is synthesized and its photophysical properties are studied in comparison with the corresponding molecular dyad, which consists only of a chlorin monomer and an azafulleroid. As evidenced by ¹H NMR, UV/Vis, and fluorescence spectroscopy, the chlorin dimer–azafulleroid folds in nonpolar media into a C₂‐symmetric geometry through hydrogen bonding, resulting in appreciable electronic interactions between the chlorins, whereas in polar media the two chlorins diverge from contact. Femtosecond transient absorption spectroscopy studies reveal longer charge‐separated states for the chlorin dimer–azafulleroid; ≈1.6 ns in toluene, compared with the lifetime of ≈0.9 ns for the corresponding chlorin monomer–azafulleroid in toluene. In polar media, for example, benzonitrile, similar charge‐separated states are observed, but the lifetimes are inevitably shorter: 65 and 73 ps for the dimeric and monomeric chlorin–azafulleroids, respectively. Nanosecond transient absorption and singlet oxygen phosphorescence studies corroborate that in toluene, the charge‐separated state decays indirectly via the triplet excited state to the ground state, whereas in benzonitrile, direct recombination to the ground state is observed. Complementary DFT studies suggest two energy‐minima conformations, that is, a folded chlorin dimer–azafulleroid, which is present in nonpolar media, and another conformation in polar media, in which the two hydrophobic chlorins wrap the azafulleroid. Inspection of the frontier molecular orbitals shows that in the folded conformation, the HOMO on each chlorin is equivalent and is shared owing to partial π–π overlap, resulting in delocalization of the conjugated π electrons, whereas the wrapped conformation lacks this stabilization. As such, the longer charge‐separated lifetime for the dimer is rationalized by both the electron donor–acceptor separation distance and the stabilization of the radical cation through delocalization. The chlorin folding seems to change the photophysical properties in a manner similar to that observed in the chlorophyll dimer in natural photosynthetic reaction centers.     

Cationic wood cellulose films with high strength and bacterial anti-adhesive properties

In this work, periodate oxidized birch wood pulp and microfibrillated cellulose (MFC) were cationized using Girard’s reagent T or aminoguanidine. Cationic celluloses were used to obtain films via solvent-casting method, and the effects of the cationization route and the cellulose fiber source on the properties of the films were studied. Thermal and optical properties of the films were measured using differential scanning calorimetry and UV–Vis spectrometry, and the morphology of the films was examined using an optical microscope and a field emission scanning electron microscope. Bacterial anti-adhesive properties of the films were also studied using a modified leaf print method and against Staphylococcus aureus and Escherichia coli. Both cationizing agents exhibited similar reactivity with periodate oxidized celluloses, however, MFC had significantly higher reactivity compared to birch pulp. The films with high tensile strength (39.1–45.3 MPa) and modulus (3.5–7.3 GPa) were obtained from cationized birch pulp, aminoguanidine modification producing a film with slightly better mechanical properties. Modulus of the films was significantly increased (up to 14.0 GPa) when MFC was used as a cellulose fiber source. Compared to the unmodified MFC films, the cationic MFC films were less porous and significantly more transparent; however, they had slightly lower tensile strength values. It was found that aminoguanidine modified celluloses had no culturable bacteria on its surface and also exhibited resistance to microbial degradation, whereas there were culturable bacteria on the surface of Girard’s reagent modified films and they were partially degraded by the bacteria.     

Correlation of aluminum doping and lithiation temperature with electrochemical performance of LiNi1-xAlxO2 cathode material

Journal of Solid State Electrochemistry - This article presents a process for producing LiNi1-xAlxO2 (0 <  ×  < 0.05) cathode material with...     

Mechanical fabrication of high-strength and redispersible wood nanofibers from unbleached groundwood pulp

In the past, the direct production of lignin-containing nanofibers from wood materials has been very limited, and nanoscale fibers (nanocelluloses) have been mainly isolated from chemically delignified, bleached cellulose pulp. In this study, we have introduced a newly adapted, heat-intensified disc nanogrinding process for the enhanced nanofibrillation of wood nanofibers (WNF) with a high lignin content (27.4 wt%). The WNF produced this way have many unique and intriguing properties in their naturally occurring form, for example, being able to be dispersed in ethanol and having ethanol solution viscosities higher than water solution viscosities. When WNF nanopapers were formed with ethanol, the properties of the nanofibers were recoverable without a notable decrease in the viscosity or mechanical strength after redispersing them in water. The preservation of lignin in the WNF was noticed as an increase in the water contact angles (89°), the rapid removal of water in the fabrication of the nanopapers, and the enhanced strength of the nanopapers when subjected to high pressure and heat. The nanopapers fabricated from the WNF were mechanically stable, having an elastic modulus of 6.2 GPa, a maximum stress of 103.4 MPa, and a maximum strain of 3.5%. Throughout the study, characteristics of the WNF were compared to those of the delignified and bleached reference cellulose nanofibers. We envision that the exciting characteristics of the WNF and their lower cost of production compared to that of bleached cellulose nanofibers may offer new opportunities for nanocellulose and biocomposite research.     

E-Ring extended estrone derivatives: introduction of 2-phenylcyclopentenone to the estrone D-ring via an intermolecular Pauson-Khand reaction

An expedient synthetic route to E-ring extended estrone derivatives is reported. Estrone-derived cyclopentenones were accessed by an intermolecular Pauson-Khand (PK) cycloaddition. It was found that electron donating and withdrawing substituents in the arylalkyne increased and decreased the yields of PK products, respectively. The stereochemistry of the products was elucidated by X-ray and NMR studies.     

Conversion electron spectroscopy at IGISOL

Conversion elecron spectroscopy has been an important part of the nuclear spectrocopy research at the Department of Physics of the University of Jyväskylä since the commissioning of the first cyclotron in the mid 1970s. At the IGISOL facility a specialiced conversion electron spectrometer ELLI was developed in the late 1980s. The first results with ELLI were obtained using the beams from the old MC-20 cyclotron to study newly discovered isotopes of refractory fission products. In the present K130 cyclotron laboratory ELLI has been utilized in many decay-spectroscopy experiments both neutron-deficient and neutron-rich side of the valley of stability. In the early 2000s the new JYFLTRAP ion trap system overthrew ELLI from its permanent place in the IGISOL beamline. Conversion electron spectroscopy has continued with the new Penning trap that has been used in in-trap electron spectroscopy tests and post-trap electron spectroscopy is foreseen.     

Preoperative localization of the sensorimotor area using independent component analysis of resting-state fMRI

Analysis of resting-state functional magnetic resonance imaging (fMRI) data is based on detecting low-frequency signal fluctuations in functionally connected brain areas. These synchronous fluctuations in resting-state networks have been observed in several studies with healthy subjects. In this study, we explored if independent component analysis (ICA) can be used to localize the sensorimotor area from resting-state fMRI data in patients with brain tumors. Finger-tapping activation task and resting-state blood-oxygenation-level-dependent fMRI data were acquired from 8 patients with brain tumors and 10 healthy volunteers. Sensorimotor task independent components (IC_task) were used to verify resting-state independent components (IC_rest) individually. In addition, sensorimotor IC_rests were compared between the groups and no significant differences were detected in volume, spatial correlation or temporal correlation. These results show that it is possible to localize a sensorimotor area from resting-state data using ICA in patients with brain tumors. This offers a complementary method for assessing the sensorimotor area in subjects with brain tumors who have difficulties in performing motor paradigms.