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Modern design of common adhesives, composites and polymeric parts makes use of polymer glasses that are stiff enough to maintain their shape under a high stress while still having a ductile behavior after the yield point. Typically, material compositions are tuned with co-monomers, polymer blends, plasticizers, or other additives to arrive at a tradeoff between the elastic modulus and toughness. In contrast, strong changes to the mechanics of a glass are possible by changing only the molecular packing during vitrification or even deep in the glassy state. For example, physical aging or processing techniques such as physical vapor deposition increase the density, embrittle the material, and increase elastic modulus. Here, we use molecular simulations, validated by positron annihilation lifetime spectroscopy (PALS) and quasi-elastic neutron scattering, to understand the free volume distribution and the resulting dynamics of glassy co-polymers where the composition is systemically varied between polar 5-norbornene-2-methanol (NBOH) and non-polar ethylidene norbornene (ENB) monomers. In these polymer glasses, we analyze the structural features of the unoccupied volume using clustering analysis, where the clustering is parameterized to reproduce experimental measurements of the same features from PALS. Further, we analyze the dynamics, quantified by the Debye-Waller factor, and compare the results with softer, lower density states. Our findings indicate that faster structural relaxations and potentially improved ductility are possible through changes to the geometric structure and fraction of the free volume, and that the resulting changes to the glass dynamics are comparable to large changes in the monomer composition.

This manuscript explores the connection between the fast relaxation processes in an undeformed polymer glass and essential trends in the mechanical toughness, a nonlinear mechanical property that i...

This article explores the relationship between the nano- to picosecond dynamics, as quantified by elastic incoherent neutron scattering, in polycarbonate (PC) glasses with their mechanical toughnes...

Polymeric membranes are ubiquitous in transport applications including gas separation, water desalination, solid-state batteries, and fuel cells. The transport mechanism in certain classes of membr...

Bioenergy has been promoted in Japan with ambitious targets. However, the incentive schemes excluded renewable heat and overlooked synergies with local forest management, leading to the development of large-scale biomass plants that heavily rely on overseas biomass supplies. This case report discussed an alternative scenario of decentralised bioenergy systems supported with local biomass through five important questions. The currently available knowledge indicates that such a scenario is feasible with integrative forest management that considers both ecosystem services and multiple uses of wood. In addition to various environmental benefits, replacing imported fossil fuels with local biomass can also enhance energy security. Realising this scenario requires careful consideration of local context, empowerment of local governments and encouragement of both public and private initiatives.

The single particle dynamics of water confined within two ordered mesoporous carbon matrices was investigated in the temperature range from 290 K to 170 K by quasielastic neutron scattering using three high resolution neutron spectrometers. Thus, it was possible to investigate the mobility of water confined in model hydrophobic cavities at the nanoscale. Models developed for the nanoscale dynamics of supercooled water and water confined within hydrophilic matrices were able to describe the collected data but remarkable differences with analogous silica confined matrices were observed in these carbon samples. A significant fraction of the water molecules was immobile on the nanosecond timescale, even at room temperature. As the temperature was lowered, the mobility of the water molecules slowed down, but the strongly non-Arrhenius behavior observed in bulk water and for fully hydrated hydrophilic confinement was absent, which indicates frustration of the hydrogen bond network formation. The obtained results were relevant for applications of mesoporous carbon materials.

We performed H2O and D2O double-contrast neutron reflectivity measurements on ∼25 nm thick Nafion thin films on hydrophilic and hydrophobic carbon in water and 80% relative humidity vapor to investigate the depth profile of the water and Nafion distribution. We found a dense Nafion layer at the air or water interface regardless of the carbon hydrophilicity. On the other hand, a water-rich Nafion dense layer was observed at the carbon interface only for hydrophilic carbon. The double-contrast measurements provided quantitative information about the depth profile but simultaneously indicated that the sum of the volume occupancies of water and Nafion in the film was less than unity. We assessed the problem based on two possibilities: voids in the film or "residual water", which cannot be exchanged or is difficult to exchange with water outside.

We combine the recently proposed spherical harmonic expansion (SHE) method [Phys. Rev. X 2017, 7, 031003] with a modified network model to analyze the small-angle neutron scattering (SANS) spectra ...

Quasi-elastic neutron scattering (QENS) measuring the energy transfer (E) and momentum exchange (Q) between a neutron and a sample target is often used to study hydration water in cement. A global model introducing a Q-independent elastic component, a Q-dependent elastic component, and a quasi-elastic component with explicit translational and rotational intermediate scattering functions has been developed to analyze the quasi-elastic neutron scattering (QENS) spectra from water confined in cement pastes. To demonstrate the advantage of this model, it has been used to analyze four sets of cement data: calcium–silicate–hydrate (CSH), pure magnesium–silicate–hydrate (MSH), MSH with aluminum–silicate nanotubes (ASN), and MSH with carboxyl-functionalized ASN (ASN-COOH), previously studied with a much simpler model. It is shown that, with this new model, several important parameters that describe the structure of the cementitious materials can be extracted from the QENS data. Particularly, the structural water ...

Hypothesis The mechanical properties of cement pastes depend strongly on their porosities. In a saturated paste, the porosity links to the free water volume after hydration. Structural water, constrained water, and free water have different dynamical behavior. Hence, it should be possible to extract information on pore system by exploiting the water dynamics. Experiments We investigated the slow dynamics of hydration water confined in calcium- and magnesium-silicate-hydrate (C-S-H and M-S-H) gels using high-resolution quasi-elastic neutron scattering (QENS) technique. C-S-H and M-S-H are the chemical binders present in calcium rich and magnesium rich cements. We measured three M-S-H samples: pure M-S-H, M-S-H with aluminum-silicate nanotubes (ASN), and M-S-H with carboxyl group functionalized ASN (ASN-COOH). A C-S-H sample with the same water content (i.e. 0.3) is also studied for comparison. Findings Structural water in the gels contributes to the elastic component of the QENS spectrum, while constrained water and free water contribute the quasi-elastic component. The quantitative analysis suggests that the three components vary for different samples and indicate the variance in the system porosity, which controls the mechanical properties of cement pastes.

The dynamic properties of water confined in Sephadex G15 gel were investigated over the temperature range of 275–320 K at a hydration level h (= mass of water/mass of dry G15 gel) of 0.38, where bo...

Differential scanning calorimetry (DSC), X-ray diffraction (XRD), and quasi-elastic neutron scattering (QENS) measurements have been made at 200~330 K for capillary-condensed water confined in periodic mesoporous organosilica (PMO) materials with the phenyl groups embedded in silica matrix (Ph-PMO; pore diameter 30 Å). The DSC data showed that the capillary-condensed water in Ph-PMO freezes at 228 K. X-ray radial distribution functions (RDFs) showed that the tetrahedral-like hydrogen-bonded structure of water is distorted in Ph-PMO pores, compared with bulk water; however, with lowering temperature the tetrahedral moiety of water is gradually recovered in the pores. Below the freezing point, cubic ice I c was formed in the Ph-PMO pores. The QENS data showed that the translational diffusion constant and the residence time and the rotational relaxation time of water molecule in Ph-PMO are comparable with those in bulk. The corresponding activation energies suggested that the more hydrophobic the nature of the wall is, the smaller the activation energy of diffusion and rotation of a water molecule; this implies that water molecules confined in the hydrophobic pores are present in the core of the pores, whereas those in the hydrophilic pores strongly interact with the silanol groups.

The boson peak in deeply cooled water confined in nanopores is studied to examine the liquid-liquid transition (LLT). Below ∼180 K, the boson peaks at pressures P higher than ∼3.5 kbar are evidently distinct from those at low pressures by higher mean frequencies and lower heights. Moreover, the higher-P boson peaks can be rescaled to a master curve while the lower-P boson peaks can be rescaled to a different one. These phenomena agree with the existence of two liquid phases with different densities and local structures and the associated LLT in the measured (P, T) region. In addition, the P dependence of the librational band also agrees with the above conclusion.

In situ X-ray diffraction measurements have been made on monolayer and capillary condensed acetonitrile in mesoporous MCM-41 C18 (pore diameter 37 A) in a temperature range of 298–200 K. FTIR spectra of acetonitrile in C18 were also measured at 298 K as a function of the vapor pressure of acetonitrile to confirm the monolayer and capillary-condensed acetonitrile in C18 used for the X-ray experiments. The radial distribution functions of the monolayer acetonitrile have shown that an acetonitrile molecule is hydrogen bonded via N atom to the silanol O atom with an N–O distance of ~ 2.6 A. The structure of the monolayer acetonitrile is almost independent of temperature, suggesting the strong hydrogen N O hydrogen bonds. On the other hand, the radial distribution functions of the capillary-condensed acetonitrile have shown that the structure of acetonitrile in the central region of the pores is gradually enhanced with lowering temperature, practically similar to that in the bulk. The present static structure of confined acetonitrile at low temperatures is compared with those predicted from molecular simulations and discussed with the dynamical properties previously obtained from quasi-elastic neutron scattering measurements.

The LOSS OF APOMEIOSIS (LOA) locus is one of two dominant loci known to control apomixis in the eudicot Hieracium praealtum. LOA stimulates the differentiation of somatic aposporous initial cells after the initiation of meiosis in ovules. Aposporous initial cells undergo nuclear proliferation close to sexual megaspores, forming unreduced aposporous embryo sacs, and the sexual program ceases. LOA-linked genetic markers were used to isolate 1.2 Mb of LOA-associated DNAs from H. praealtum. Physical mapping defined the genomic region essential for LOA function between two markers, flanking 400 kb of identified sequence and central unknown sequences. Cytogenetic and sequence analyses revealed that the LOA locus is located on a single chromosome near the tip of the long arm and surrounded by extensive, abundant complex repeat and transposon sequences. Chromosomal features and LOA-linked markers are conserved in aposporous Hieracium caespitosum and Hieracium piloselloides but absent in sexual Hieracium pilosella. Their absence in apomictic Hieracium aurantiacum suggests that meiotic avoidance may have evolved independently in aposporous subgenus Pilosella species. The structure of the hemizygous chromosomal region containing the LOA locus in the three Hieracium subgenus Pilosella species resembles that of the hemizygous apospory-specific genomic regions in monocot Pennisetum squamulatum and Cenchrus ciliaris. Analyses of partial DNA sequences at these loci show no obvious conservation, indicating that they are unlikely to share a common ancestral origin. This suggests convergent evolution of repeat-rich hemizygous chromosomal regions containing apospory loci in these monocot and eudicot species, which may be required for the function and maintenance of the trait.

Asexual seed formation, or apomixis, in the Hieracium subgenus Pilosella is controlled by two dominant independent genetic loci, LOSS OF APOMEIOSIS (LOA) and LOSS OF PARTHENOGENESIS (LOP). We examined apomixis mutants that had lost function in one or both loci to establish their developmental roles during seed formation. In apomicts, sexual reproduction is initiated first. Somatic aposporous initial (AI) cells differentiate near meiotic cells, and the sexual pathway is terminated as AI cells undergo mitotic embryo sac formation. Seed initiation is fertilization-independent. Using a partially penetrant cytotoxic reporter to inhibit meioisis, we showed that developmental events leading to the completion of meiotic tetrad formation are required for AI cell formation. Sexual initiation may therefore stimulate activity of the LOA locus, which was found to be required for AI cell formation and subsequent suppression of the sexual pathway. AI cells undergo nuclear division to form embryo sacs, in which LOP functions gametophytically to stimulate fertilization-independent embryo and endosperm formation. Loss of function in either locus results in partial reversion to sexual reproduction, and loss of function in both loci results in total reversion to sexual reproduction. Therefore, in these apomicts, sexual reproduction is the default reproductive mode upon which apomixis is superimposed. These loci are unlikely to encode genes essential for sexual reproduction, but may function to recruit the sexual machinery at specific time points to enable apomixis.

Self-incompatibility in the Brassicaceae is controlled by multiple haplotypes encoding the pollen ligand (S-locus protein 11, SP11, also known as S-locus cysteine-rich protein, SCR) and its stigmatic receptor (S-receptor kinase, SRK). A haplotype-specific interaction between SP11/SCR and SRK triggers the self-incompatibility response that leads to self-pollen rejection, but the signalling pathway remains largely unknown. Here we show that Ca2+ influx into stigma papilla cells mediates self-incompatibility signalling. Using self-incompatible Arabidopsis thaliana expressing SP11/SCR and SRK, we found that self-pollination specifically induced an increase in cytoplasmic Ca2+ ([Ca2+]cyt) in papilla cells. Direct application of SP11/SCR to the papilla cell protoplasts induced Ca2+ increase, which was inhibited by D-(?)-2-amino-5-phosphonopentanoic acid (AP-5), a glutamate receptor channel blocker. An artificial increase in [Ca2+]cyt in papilla cells arrested wild-type (WT) pollen hydration. Treatment of papilla cells with AP-5 interfered with self-incompatibility, and Ca2+ increase on the self-incompatibility response was reduced in the glutamate receptor-like channel (GLR) gene mutants. These results suggest that Ca2+ influx mediated by GLR is the essential self-incompatibility response leading to self-pollen rejection.Flowering plants have developed self-incompatibility as a genetic system to prevent inbreeding and thus promote outcrossing. In many species, self-incompatibility is controlled by an S locus with multiple haplotypes1. Each S-haplotype encodes both male- and female-specificity determinants (S-determinants), and self/non-self-discrimination is accomplished by the S-haplotype-specific interaction between these S-determinants., In the Brassicaceae, the male and female S-determinants have been identified as SP11/SCR and SRK, respectively1. SP11/SCR is a polymorphic small peptide secreted from the anther tapetum that localizes to the pollen surface, whereas SRK is a polymorphic Ser/Thr receptor kinase that localizes to the plasma membrane of stigma papilla cells. SP11/SCR and SRK from each S-haplotype function respectively as a ligand and its cognate receptor. Upon self-pollination, the S-haplotype-specific interaction between SP11/SCR and SRK induces autophosphorylation of SRK, which is thought to trigger a signalling cascade in the papilla cells, resulting in the rejection of self-pollen2. Although self-pollination is known to evoke multiple physiological changes in the papilla cells, including disruption of actin bundles, fragmentation of vacuolar structure and modification of microtubules3,4, the signalling pathway downstream of SRK that leads to these processes remains largely unknown.Thus far, two candidate molecules, M-locus protein kinase (MLPK) and Arm-repeat containing 1 (ARC1), have been identified as the direct downstream effectors of SRK. MLPK was identified as a gene responsible for a self-compatibility mutation in Brassica rapa5, and encodes a membrane-anchored cytoplasmic protein kinase that interacts with SRK on the papilla cell membrane6. Recent studies have suggested that MLPK is also involved in intraspecies unilateral incompatibility of B. rapa7, but it remains unclear whether MLPK is required for self-incompatibility throughout the Brassicaceae., ARC1 is known to interact with, and is phosphorylated by, the kinase domain of SRK in Brassica napus9,10. ARC1 is a U-box protein with E3 ubiquitin ligase activity11, and interacts with Exo70A112, a putative component of the exocyst complex, which generally functions in polarized secretion13. These results suggested a model in which activated SRK phosphorylates ARC1, leading to the preclusion of as-yet unknown ‘compatibility factors’ secretion to the stigmatic surface and inhibiting pollen entrance14. However, the suppression of ARC1 expression results in incomplete breakdown of self-incompatibility in both B. napus and Arabidopsis lyrata10,14, and self-compatible Arabidopsis thaliana that lacks ARC1 acquires the self-incompatibility phenotype by introducing SRK and SP11/SCR genes15. Therefore, the extent ARC1 to which is involved in the signalling pathway downstream of SRK remains unclear8,16,17.In this study, we focused on investigating the cytoplasmic Ca2+ dynamics in stigma papilla cells during the self-incompatibility response. A previous study injected dyes to monitor Ca2+ dynamics in the self-incompatibility response18. By combining the in vivo imaging using genetically encoded [Ca2+]cyt probes and pharmacological approaches, we found that cytoplasmic Ca2+ drastically increases in the papilla cells after self-pollination, which can be efficiently blocked by the inhibitors of glutamate receptor channels that mediate the influx of extracellular Ca2+. Pretreatment of papilla cells with glutamate receptor channel inhibitor compromised the self-incompatibility response in vivo, whereas an artificial increase in [Ca2+]cyt in papilla cells induced arrest of pollen hydration to compatible pollen. The [Ca2+]cyt increase in papilla cells during the self-incompatibility response of GLR mutants was significantly reduced. Our results overall strongly suggest that the Ca2+ influx in papilla cells mediated by GLR is the key self-incompatibility response that leads to self-pollen rejection.

Using neutron diffraction technique, we measure the average density of the heavy water confined in a nanoporous silica matrix, MCM-41, over the pressure-temperature plane. The result suggests the existence of a line of liquid-liquid phase transition with its end point at 1.29 ± 0.34 kbar and 213 ± 3 K in a fully hydrated sample. This point would be the liquid-liquid critical point (LLCP) according to the "liquid-liquid critical point" scenario. The phase diagram of the deeply cooled confined heavy water is then discussed. Moreover, in a partially hydrated sample, the phase transition completely disappears. This result shows that it is the free water part, rather than the bound water part, of the confined water that undergoes a liquid-liquid transition.

Self-incompatibility (SI) in angiosperms prevents inbreeding and promotes outcrossing to generate genetic diversity. SI in the Brassicaceae is controlled by the S-haplotype-specific interaction between pollen ligand (S-locus protein 11, SP11 or SCR) and its stigmatic receptor (S-receptor kinase, SRK). SP11/SCR binding to cognate SRK induces autophosphorylation of SRK, which triggers a signaling cascade leading to the rejection of self-pollen. However, the mechanism of self-pollen rejection downstream of this ligand–receptor interaction is unknown. Here, we generated self-incompatible Arabidopsis thaliana accession C24 for the forward-genetic approach and live-cell imaging of SI in the Brassicaceae. Furthermore, for reverse-genetic analysis, we extended the Arabidopsis Targeting Induced Local Lesions IN Genomes (TILLING) resources by developing a new population of ethyl methanesulfonate (EMS)-induced mutant lines in A. thaliana accession C24. We believe that the reverse-genetic approach is a useful tool for identifying genes that function in the SI signaling pathway of the Brassicaceae.

The thermal behavior and structure of water confined in Sephadex G15 gel were investigated over a temperature range of 298-173 K at hydration levels, h (= mass of water/mass of dry G15 gel), of 0.24-1.38 by differential scanning calorimetry (DSC) and an X-ray diffraction (XRD) method, respectively. The ice-melting peaks on the DSC curves were deconvoluted to estimate the amounts of three states of water in G15 with h: free water, freezable bound water, and unfrozen water. The X-ray radial distribution functions of unfrozen water at h = 0.24 revealed that the hydrogen-bonded structure of water is largely distorted, due to hydrogen bonding with the surface hydroxyl groups of gel substrates, compared with those of freezable bound water at h = 0.47 and bulk water. A plausible separation mechanism of solutes in gel chromatography was considered from a structural point of view of confined water.

The behavior of hydrated Ag+ ions in a 1.5 mol dm(-3) AgNO3 aqueous solution confined in mesoporous silica MCM-41 with different pore sizes was characterized by synchrotron X-ray absorption spectroscopy. The hydrated Ag+ ions are stabilized in 4-fold coordination down to 195 K in the pores (21 A in diameter), whereas in the larger pores (28 A) the hydrated Ag+ ions are reduced to Ag0 to form nano clusters with the Ag-Ag interactions of 2.80 A.

Asexual seed formation, or apomixis, in the Hieracium subgenus Pilosella is controlled by two dominant independent genetic loci, LOSS OF APOMEIOSIS (LOA) and LOSS OF PARTHENOGENESIS (LOP). We examined apomixis mutants that had lost function in one or both loci to establish their developmental roles during seed formation. In apomicts, sexual reproduction is initiated first. Somatic aposporous initial (AI) cells differentiate near meiotic cells, and the sexual pathway is terminated as AI cells undergo mitotic embryo sac formation. Seed initiation is fertilization-independent. Using a partially penetrant cytotoxic reporter to inhibit meioisis, we showed that developmental events leading to the completion of meiotic tetrad formation are required for AI cell formation. Sexual initiation may therefore stimulate activity of the LOA locus, which was found to be required for AI cell formation and subsequent suppression of the sexual pathway. AI cells undergo nuclear division to form embryo sacs, in which LOP functions gametophytically to stimulate fertilization-independent embryo and endosperm formation. Loss of function in either locus results in partial reversion to sexual reproduction, and loss of function in both loci results in total reversion to sexual reproduction. Therefore, in these apomicts, sexual reproduction is the default reproductive mode upon which apomixis is superimposed. These loci are unlikely to encode genes essential for sexual reproduction, but may function to recruit the sexual machinery at specific time points to enable apomixis.

With quasi-elastic neutron scattering, we study the single-particle dynamics of the water confined in a hydrophilic silica material, MCM-41, at 4 kbar. A dynamic crossover phenomenon is observed at 219 K. We compare this dynamic crossover with the one observed at ambient pressure and find that (a) above the crossover temperature, the temperature dependence of the characteristic relaxation time at ambient pressure exhibits a more evident super-Arrhenius behavior than that at 4 kbar. Especially, at temperatures below about 230 K, the relaxation time at 4 kbar is even smaller than that at ambient pressure. This feature is different from many other liquids. (b) Below the crossover temperature, the Arrhenius behavior found at ambient pressure has a larger activation energy compared to the one found at 4 kbar. We ascribe the former to the difference between the local structure of the low-density liquid (LDL) phase and that of the high-density liquid (HDL) phase, and the latter to the difference between the strength of the hydrogen bond of the LDL and that of the HDL. Therefore, we conclude that the phenomena observed in this paper are consistent with the LDL-to-HDL liquid-liquid transition hypothesis.