Enzymatic control of lipid homeostasis in the cell is a vital element in the complex organization of life. Phosphatidylserine (PS) is an essential anionic phospholipid of cell membranes, and conducts ...numerous roles for their structural and functional integrity. In mammalian cells, two distinct enzymes phosphatidylserine synthases‐1 (PSS1) and ‐2 (PSS2) in the mitochondria‐associated membrane (MAM) in the ER perform de novo synthesis of PS. It is based on base‐exchange reactions of the preexisting dominant phospholipids phosphatidylcholine (PC) and phosphatidylethanolamine (PE). While PSS2 specifically catalyzes the reaction “PE → PS,” whether or not PSS1 is responsible for the same reaction along with the reaction “PC → PS” remains unsettled despite its fundamental impact on the major stoichiometry. We propose here that a key but the only report that appeared to have put scientists on hold for decades in answering to this issue may be viewed consistently with other available research reports; PSS1 utilizes the two dominant phospholipid classes at a similar intrinsic rate. In this review, we discuss the issue in view of the current information for the enzyme machineries, membrane structure and dynamics, intracellular network of lipid transport, and PS synthesis in health and disease. Resolution of the pending issue is thus critical in advancing our understanding of roles of the essential anionic lipid in biology, health, and disease.
Abstract
Ferroaxial materials that exhibit spontaneous ordering of a rotational structural distortion with an axial vector symmetry have gained growing interest, motivated by recent extensive studies ...on ferroic materials. As in conventional ferroics (e.g., ferroelectrics and ferromagnetics), domain states will be present in the ferroaxial materials. However, the observation of ferroaxial domains is non-trivial due to the nature of the order parameter, which is invariant under both time-reversal and space-inversion operations. Here we propose that NiTiO
3
is an order-disorder type ferroaxial material, and spatially resolve its ferroaxial domains by using linear electrogyration effect: optical rotation in proportion to an applied electric field. To detect small signals of electrogyration (order of 10
−5
deg V
−1
), we adopt a recently developed difference image-sensing technique. Furthermore, the ferroaxial domains are confirmed on nano-scale spatial resolution with a combined use of scanning transmission electron microscopy and convergent-beam electron diffraction. Our success of the domain visualization will promote the study of ferroaxial materials as a new ferroic state of matter.
We investigated the effects of silica(SiO2) and clay nanoparticles on the tensile properties of poly(vinyl alcohol) (PVA) hydrogels containing borax. Clay/PVA/borax hydrogels possessed comparatively ...high tensile strength even at low concentrations of clay, but the mechanical performance drastically became worse at high concentrations. On the contrary, the tensile strength of SiO2/PVA/borax hydrogels increased with increasing SiO2 concentrations under high elongation. In these hydrogels, multiple crosslinking such as physical interactions between clay and PVA, complexations between PVA (or SiO2) and borate, microcrystals of PVA produced a tough polymer network. Besides, the synergistic effects of clay and SiO2 nanoparticles on the mechanical performance of the PVA/borax hydrogels were confirmed, i.e., both extensibility and modulus were largely improved compared to clay/PVA/borax or SiO2/PVA/borax hydrogels. Synchrotron small-angle X-ray scattering analysis revealed that the addition of both clay and SiO2 nanoparticles suppressed inhomogeneities in the composite gel.
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•Clay/PVA/borax gels possessed high tensile strength at low clay concentrations.•SiO2/PVA/borax gels possessed high elongation even at high SiO2 concentrations.•The addition of SiO2 and clay to PVA/borax gels caused high elongation and strength.•Combined use of nanoparticles and borax was effective for production of tough polymer gels.
Long-term creep deformation property of modified 9Cr–1Mo steel Kimura, K.; Kushima, H.; Sawada, K.
Materials science & engineering. A, Structural materials : properties, microstructure and processing,
06/2009, Letnik:
510
Journal Article, Conference Proceeding
Recenzirano
The first volume of “Atlas of Creep Deformation Properties” was published on modified 9Cr–1Mo steels in March 2007, as a part of the NIMS (National Institute for Materials Science) Creep Data Sheet ...series. Creep deformation properties up to about 70,000
h have been investigated. No clear steady-state creep stage has been observed, and creep deformation of the steel consists of transient and accelerating creep stages. Good linear relationships between creep strain vs. time and creep rate vs. time were observed within a transient stage in a log–log plot. It was appropriately expressed by a power law rather than an exponential law, logarithmic law and Blackburn's equation. With decrease in stress, the magnitude of creep strain at the onset of accelerating creep stage decreased from about 2% in the short-term to less than 1% in the long-term region. Life fraction of the time to specific strain of 1% creep strain and 1% total strain, to time to rupture tended to increase with decrease in stress. The time to 1% total strain, that is an important parameter for design of high temperature components, was observed to lie in the transient creep stage in the short-term regime, however, it shifted to the accelerating creep stage in the long-term regime. For evaluation of long-term creep strength properties, an experimental creep test data should be extrapolated in consideration of the stress dependence of creep deformation properties.
Mission Design of LiteBIRD Matsumura, T.; Akiba, Y.; Borrill, J. ...
Journal of low temperature physics,
09/2014, Letnik:
176, Številka:
5-6
Journal Article
Recenzirano
Odprti dostop
LiteBIRD is a next-generation satellite mission to measure the polarization of the cosmic microwave background (CMB) radiation. On large angular scales the B-mode polarization of the CMB carries the ...imprint of primordial gravitational waves, and its precise measurement would provide a powerful probe of the epoch of inflation. The goal of LiteBIRD is to achieve a measurement of the characterizing tensor to scalar ratio
r
to an uncertainty of
δ
r
=
0.001
. In order to achieve this goal we will employ a kilo-pixel superconducting detector array on a cryogenically cooled sub-Kelvin focal plane with an optical system at a temperature of 4 K. We are currently considering two detector array options; transition edge sensor (TES) bolometers and microwave kinetic inductance detectors. In this paper we give an overview of LiteBIRD and describe a TES-based polarimeter designed to achieve the target sensitivity of 2
μ
K arcmin over the frequency range 50–320 GHz.
Abstract
In vortex-like spin arrangements, multiple spins can combine into emergent multipole moments. Such multipole moments have broken space-inversion and time-reversal symmetries, and can ...therefore exhibit linear magnetoelectric (ME) activity. Three types of such multipole moments are known: toroidal; monopole; and quadrupole moments. So far, however, the ME activity of these multipole moments has only been established experimentally for the toroidal moment. Here we propose a magnetic square cupola cluster, in which four corner-sharing square-coordinated metal-ligand fragments form a noncoplanar buckled structure, as a promising structural unit that carries an ME-active multipole moment. We substantiate this idea by observing clear magnetodielectric signals associated with an antiferroic ME-active magnetic quadrupole order in the real material Ba(TiO)Cu
4
(PO
4
)
4
. The present result serves as a useful guide for exploring and designing new ME-active materials based on vortex-like spin arrangements.
Spin ice is a magnetic analog of H2O ice that harbors dense static disorder. Dipolar interactions between classical spins yield a frozen frustrated state with residual configurational Pauling entropy ...and emergent magnetic monopolar quasiparticles. Introducing quantum fluctuations is of great interest as this could melt spin ice and allow coherent propagation of monopoles. Here, we report experimental evidence for quantum dynamics of magnetic monopolar quasiparticles in a new class of spin ice based on exchange interactions, Pr2Zr2O7. Narrow pinch point features in otherwise diffuse elastic neutron scattering reflects adherence to a divergence-free constraint for disordered spins on long time scales. Magnetic susceptibility and specific heat data correspondingly show exponentially activated behaviors. In sharp contrast to conventional ice, however, >90% of the neutron scattering is inelastic and devoid of pinch points furnishing evidence for magnetic monopolar quantum fluctuations.
Materials with the pyrochlore/fluorite structure have diverse technological applications, from magnetism to nuclear waste disposal. Here we report the observation of structural instability present in ...the pyrochlores A
Zr
O
O' (A = Pr, La) and Yb
Ti
O
O', that exists despite ideal stoichiometry, ideal cation-ordering, the absence of lone pair effects, and a lack of magnetic order. Though these materials appear to have good long-range order, local structure probes find displacements, of the order of 0.01 nm, within the pyrochlore framework. The pattern of displacements of the A
O' sublattice mimics the entropically-driven fluxional motions characteristic of and well-known in the silica mineral β-cristobalite. The universality of such displacements within the pyrochlore structure adds to the known structural diversity and explains the extreme sensitivity to composition found in quantum spin ices and the lack of ferroelectric behavior in pyrochlores.
Sludge filterability in membrane bioreactors (MBRs) fluctuates and affects membrane fouling. Therefore, understanding the reasons for the fluctuations of sludge filterability is important for the ...efficient operation of MBRs. In this study, a pilot-scale MBR treating municipal wastewater was operated for about 600 days and the variations in sludge filterability were continuously monitored by batch-filtration experiments using the same membranes as in the MBR. To investigate the reasons for the deterioration of sludge filterability, constituents in sludge supernatant were intensively monitored, and the correlations with sludge filterability were determined. The concentration of lipopolysaccharides (LPS) in sludge supernatant exhibited significantly higher correlation with sludge filterability than did conventional indexes (i.e. polysaccharides and proteins). Size fractions affecting MBR sludge filterability were also investigated, and it was suggested that colloidal LPS deteriorated MBR sludge filterability. Based on the long-term operation of the MBR, increase in colloidal LPS under low temperatures of the mixed liquor suspension was a key factor in the deterioration of sludge filterability. The impact of LPS increasing under low temperatures should be investigated by operating bench-scale MBRs fed with synthetic wastewater in controlled conditions.
► In Gr.91 steel, premature creep failure occurred in the long-term at 600
°C and 650
°C. ► Dislocation structure slightly recovered during creep up to later stage of tertiary creep. ► Number density ...of MX particles abruptly decreased in tertiary stage due to the Z-phase formation. ► The decrease in number density of MX particles causes decrease in creep resistance.
Microstructural changes during creep at 600
°C under 70
MPa were investigated in the case of interrupted Gr.91 steel samples by taking into account the dislocation structure and Z-phase formation. The creep life monotonically increased with a decrease in the applied stress at each temperature considered in the study. However, the long-term creep life was shorter than that determined from the short-term creep data at 600
°C and 650
°C, meaning premature failure. The subgrain size gradually increased during creep up to 70,000
h, after which rapid subgrain coarsening occurred. Preferential recovery of the subgrain structure occurred around the prior-austenite grain boundary (PAGB) after 50,000
h and 70,000
h. After creep rupture, subgrain recovery was observed over the entire area of each sample. Z-phase formation was clearly visible for 30,000
h after creep. The number density of the MX particles gradually decreased after 30,000
h because of Z-phase formation. After creep rupture, the number density of the MX particles was almost the same as that of the Z-phase particles. During creep, the V content of the Z-phase gradually increased but the Nb content decreased. Changes in the chemical composition of the Z-phase occurred after a longer time in Gr.91 steel than in 12Cr steel.
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