Scrutiny on Physical Properties of Sawdust From Tropical Commercial Wood Species: Effects of Different Mills and Sawdust's Particle Size

Physical properties of sawdust (i.e. particle size distribution, particle density, porosity, and water retention) from five tropical commercial wood species (Shorealeprosula, Dryobalanops lanceolata, Dipterocarpus cornutus, Shorea laevis, and Eusideroxylon zwageri) as prepared in various mill types (i.e. handsaw, sawmill, and milling ) were analyzed. This study aims to look into the relationship and interconnected between the use of different mill types, density of wood species origin and physical properties of the resulting sawdust. Generally, different mill types produced sawdust with different particle size distributions. The use of a handsaw produced a higher proportion of oversized particles (OS) and coarser particle size (CPS) than that of sawmill and milling , while also commonly producing the lowest proportion of fine particle size (FPS). For each wood species, the proportion of OS was lower than that of CPS and FPS. In addition, particle density and water retention produced by handsaw in CPS as well as FPS was the smallest, followed in an increasing order sawmill and milling. Porosity of CPS and FPS was the highest in handsaw-cut sawdust, followed in a decreasing order sawmill and milling cut sawdust. This study showed that the different mill types and particle size influenced the physical properties of sawdust. Further, analysis of influential factors on porosity and water retention using General Linear Model revealed that particle density inflicted a strong influence on porosity, as did particle size on water retention

Picosecond time-resolved fluorescence spectra of photosystem I and II in Chlorella pyrenoidosa

AbstractPicosecond time-resolved fluorescence spectra emitted from intact cells of the green alga Chlorella pyrenoidosa have been measured by means of a new detection technique using a microchannel-plate photomultiplier. A fluorescence band (F700) was observed at 690–730 nm in the initial time region (0–180 ps), in addition to the well-known spectrum (F685) of photosystem II (PS II)-chlorophyll a (Chla) with a peak at 685 nm. F700 decays rapidly with lifetime of 104 ps, while F685 decays much more slowly in bi-exponential form with lifetimes of 0.64 and 1.7 ns. Appearance of F700 is independent of closure of the reaction center II (RC II). F700 is thus assigned to the fluorescence from PS I-Chl a, whose decay is governed by a fast energy transfer process from the antenna Chl aof PS I to P700 of RC I

Quasiparticle dynamics and spin-orbital texture of the SrTiO3 two-dimensional electron gas

Two-dimensional electron gases (2DEGs) in SrTiO$_3$ have become model systems for engineering emergent behaviour in complex transition metal oxides. Understanding the collective interactions that enable this, however, has thus far proved elusive. Here we demonstrate that angle-resolved photoemission can directly image the quasiparticle dynamics of the $d$-electron subband ladder of this complex-oxide 2DEG. Combined with realistic tight-binding supercell calculations, we uncover how quantum confinement and inversion symmetry breaking collectively tune the delicate interplay of charge, spin, orbital, and lattice degrees of freedom in this system. We reveal how they lead to pronounced orbital ordering, mediate an orbitally-enhanced Rashba splitting with complex subband-dependent spin-orbital textures and markedly change the character of electron-phonon coupling, co-operatively shaping the low-energy electronic structure of the 2DEG. Our results allow for a unified understanding of spectroscopic and transport measurements across different classes of SrTiO$_3$-based 2DEGs, and yield new microscopic insights on their functional properties.Comment: 10 pages including supplementary information, 4+4 figure

Control of a two-dimensional electron gas on SrTiO3(111) by atomic oxygen

We report on the formation of a two-dimensional electron gas (2DEG) at the bare surface of (111) oriented SrTiO3. Angle resolved photoemission experiments reveal highly itinerant carriers with a 6-fold symmetric Fermi surface and strongly anisotropic effective masses. The electronic structure of the 2DEG is in good agreement with self-consistent tight-binding supercell calculations that incorporate a confinement potential due to surface band bending. We further demonstrate that alternate exposure of the surface to ultraviolet light and atomic oxygen allows tuning of the carrier density and the complete suppression of the 2DEG.Comment: 5 pages, 4 figure

Model for the hydration of non-polar compounds and polymers

We introduce an exactly solvable statistical-mechanical model of the hydration of non-polar compounds, based on grouping water molecules in clusters where hydrogen bonds and isotropic interactions occur; interactions between clusters are neglected. Analytical results show that an effective strengthening of hydrogen bonds in the presence of the solute, together with a geometric reorganization of water molecules, are enough to yield hydrophobic behavior. We extend our model to describe a non-polar homopolymer in aqueous solution, obtaining a clear evidence of both ``cold'' and ``warm'' swelling transitions. This suggests that our model could be relevant to describe some features of protein folding.Comment: REVTeX, 6 pages, 3 figure

Collapse of the Mott gap and emergence of a nodal liquid in lightly doped Sr2_2IrO4_4

Superconductivity in underdoped cuprates emerges from an unusual electronic state characterised by nodal quasiparticles and an antinodal pseudogap. The relation between this state and superconductivity is intensely studied but remains controversial. The discrimination between competing theoretical models is hindered by a lack of electronic structure data from related doped Mott insulators. Here we report the doping evolution of the Heisenberg antiferromagnet Sr$_2$IrO$_4$, a close analogue to underdoped cuprates. We demonstrate that metallicity emerges from a rapid collapse of the Mott gap with doping, resulting in lens-like Fermi contours rather than disconnected Fermi arcs as observed in cuprates. Intriguingly though, the emerging electron liquid shows nodal quasiparticles with an antinodal pseudogap and thus bares strong similarities with underdoped cuprates. We conclude that anisotropic pseudogaps are a generic property of two-dimensional doped Mott insulators rather than a unique hallmark of cuprate high-temperature superconductivity