3,591 research outputs found
The Effects of Variables on the Penetration and Pickup of Starch Applied at the Size Press
A literature research is presented concerning the pickup and penetration of starch at the size press. The literature research indicates there is very little quantitative results in this area. The objective of the experimental work is to determine the effect of starch temperature, sheet moisture, and machine speed on the penetration of starch into the sheet. The depth and quantity of penetration was obtained by using a spectrophotometer to determine the concentration of starch in microtomed samples.
The experimental results indicated that increased temperature of starch solutions and increased machine speeds increases penetration. Penetration also increases with increasing moisture content of the paper but only to an optimum moisture content. The effects of penetration and pickup on physical and optical test results are also discussed in the discussion section
Palaeoproterozoic adakite- and TTG-like magmatism in the Svecofennian orogen, SW Finland
The Palaeoproterozoic Svecofennian orogen in the Fennoscandian shield is an arc accretionary orogen that was formed at c. 1.92-1.86Ga. Arc accretion, magmatism and the subsequent continent-continent collision thickened the crust up to c. 70km, forming one of the thickest Palaeoproterozic orogens. At the end stage of accretionary tectonics, voluminous synorogenic magmatism occurred in southwestern Finland leading to the intrusion of intermediate to felsic plutonic rocks. Ion microprobe single zircon dating of one diorite sample yielded an age of 1872±3Ma (ΔNd=+2.2) and the trondhjemite sample an age of 1867±4Ma (ΔNd=+2.6). Inherited 2667-1965Ma cores and 1842±5Ma metamorphic rims were also found in zircons from the trondhjemite. The dioritic magmatism is mantle-derived and is slightly enriched by subduction-related processes. The felsic magmatism shows elevated Sr/Y and La/Yb ratios, which are typical for adakite- and TTG-like magmas. Their low Mg#, Ni and Cr contents argue against slab-melting and mantle-wedge contamination. We infer that the felsic magmatism was generated through crustal melting of the lower part of the previously generated volcanic-arc type crust. Based on published melting experiments and the Sr and Y contents of the felsic rocks we suggest that the melts were generated at a minimum pressure of 10kbar, with evidence of a 15kbar pressure for the highest Sr/Y trondhjemites. It is proposed that arc accretion combined with magmatic intrusions thickened the crust so that melting of the lower crust yielded adakite- and TTG-like compositions. The mafic magmatism is considered to be the heat source
Reversible Fluorination of Graphene: towards a Two-Dimensional Wide Bandgap Semiconductor
We report the synthesis and evidence of graphene fluoride, a two-dimensional
wide bandgap semiconductor derived from graphene. Graphene fluoride exhibits
hexagonal crystalline order and strongly insulating behavior with resistance
exceeding 10 G at room temperature. Electron transport in graphene
fluoride is well described by variable-range hopping in two dimensions due to
the presence of localized states in the band gap. Graphene obtained through the
reduction of graphene fluoride is highly conductive, exhibiting a resistivity
of less than 100 k at room temperature. Our approach provides a new
path to reversibly engineer the band structure and conductivity of graphene for
electronic and optical applications.Comment: 7 pages, 5 figures, revtex, to appear in PR
1.90-1.88Ga arc magmatism of central Fennoscandia: geochemistry, U-Pb geochronology, Sm-Nd and Lu-Hf isotope systematics of plutonic-volcanic rocks from southern Finland
The earliest Svecofennian magmatism in southern Finland has been dated at 1.90-1.88Ga. As an example of this, the OrijĂ€rvi (ca. 1.89Ga) and Enklinge (ca. 1.88Ga) volcanic centres comprise bimodal plutonic batholiths surrounded by volcanic rocks of comparable ages and chemical compositions. Here, we report geochemical and Sm-Nd isotope data from intrusive and extrusive samples, combined with zircon U-Pb and Lu-Hf isotopes for granodiorites from both study areas. The samples range from gabbros to granites and indicate a subduction-related continental margin setting. The zircons from the OrijĂ€rvi granodiorite define an age of 1892±4Ma whereas the Enklinge granodiorite yields an age of 1882±6Ma. Several inherited ages of 2.25-1.95Ga as well as younger ages of 1.86-1.80Ga were found in the Enklinge granodiorite. The initial ΔNd values from the mafic rocks from both locations fall in the range +1.1 to +2.9 whereas the felsic rocks exhibit initial ΔNd values of -0.4 to +1.2. The magmatic zircons from the OrijĂ€rvi and Enklinge granodiorites show average initial ΔHf values of -1.1 (at 1892Ma) and zero (at 1882Ma), respectively, each with a spread of about 7 Δ-units. The initial ΔHf values for the inherited zircons from Enklinge range from +3.5 to +7.6 with increasing age. The Sm-Nd data indicate that the mafic rocks were derived from a âmildly depletedâ mantle source while the felsic rocks show larger crustal contribution. Also, the variation in ΔHf values indicates minor mixing between mildly depleted mantle derived magmas and crustal sources. U-Pb ages and Hf isotopes for inherited zircons in the Enklinge granodiorite suggest the presence of juvenile Svecofennian âproto-crustâ at depth
Element Replacement Approach by Reaction with Lewis Acidic Molten Salts to Synthesize Nanolaminated MAX Phases and MXenes
Nanolaminated materials are important because of their exceptional properties
and wide range of applications. Here, we demonstrate a general approach to
synthesize a series of Zn-based MAX phases and Cl-terminated MXenes originating
from the replacement reaction between the MAX phase and the late transition
metal halides. The approach is a top-down route that enables the late
transitional element atom (Zn in the present case) to occupy the A site in the
pre-existing MAX phase structure. Using this replacement reaction between Zn
element from molten ZnCl2 and Al element in MAX phase precursors (Ti3AlC2,
Ti2AlC, Ti2AlN, and V2AlC), novel MAX phases Ti3ZnC2, Ti2ZnC, Ti2ZnN, and V2ZnC
were synthesized. When employing excess ZnCl2, Cl terminated MXenes (such as
Ti3C2Cl2 and Ti2CCl2) were derived by a subsequent exfoliation of Ti3ZnC2 and
Ti2ZnC due to the strong Lewis acidity of molten ZnCl2. These results indicate
that A-site element replacement in traditional MAX phases by late transition
metal halides opens the door to explore MAX phases that are not
thermodynamically stable at high temperature and would be difficult to
synthesize through the commonly employed powder metallurgy approach. In
addition, this is the first time that exclusively Cl-terminated MXenes were
obtained, and the etching effect of Lewis acid in molten salts provides a green
and viable route to prepare MXenes through an HF-free chemical approach.Comment: Title changed; experimental section and discussion revise
Generation of A-type granitic melts during the late Svecofennian metamorphism in southern Finland
Across southern Finland the Late Svecofennian Granite Migmatite zone contains large amounts of migmatites and S-type granites formed during the high temperature and low pressure metamorphism between 1.84 and 1.80 Ga. Within this zone, the Karjaa granite intrudes the surrounding migmatites. The granite is more fine-grained and darker than the surrounding anatectic S-type granites, which are associated with the migmatites. The Karjaa granite cuts the migmatites suggesting that it is coeval or younger than the migmatites. It is a two-feldspar biotite granite containing apatite and zircon as accessory minerals. The granite displays elevated TiO, PO and F contents and is characterized by high Ba, Zr, Nb, and Ga contents. The REE patterns indicate strong enrichment in LREEs and a pronounced europium minimum. The crystallization temperature of the granite is estimated to about 900°C using the PO and Zr-saturation methods. Cathodoluminescence images on zircons indicate core domains and overgrowth structures. SIMS dating of the zircon cores and rims yielded concordia ages of 1880±16 Ma and 1826±11 Ma, respectively. On the basis of these data, it seems that c. 1880 Ma old igneous rocks at deeper crustal levels partially melted during at c. 1825 Ma metamorphism and generated hot melts having a composition close to A-type granites.</p
Slim Epistemology with a Thick Skin
The distinction between âthickâ and âthinâ value concepts, and its importance to ethical theory, has been an active topic in recent meta-ethics. This paper defends three claims regarding the parallel issue about thick and thin epistemic concepts. (1) Analogy with ethics offers no straightforward way to establish a good, clear distinction between thick and thin epistemic concepts. (2) Assuming there is such a distinction, there are no semantic grounds for assigning thick epistemic concepts priority over the thin. (3) Nor does the structure of substantive epistemological theory establish that thick epistemic concepts enjoy systematic theoretical priority over the thin. In sum, a good case has yet to be made for any radical theoretical turn to thicker epistemology
Electronic structure investigation of Ti3AlC2, Ti3SiC2, and Ti3GeC2 by soft-X-ray emission spectroscopy
The electronic structures of epitaxially grown films of Ti3AlC2, Ti3SiC2 and
Ti3GeC2 have been investigated by bulk-sensitive soft X-ray emission
spectroscopy. The measured high-resolution Ti L, C K, Al L, Si L and Ge M
emission spectra are compared with ab initio density-functional theory
including core-to-valence dipole matrix elements. A qualitative agreement
between experiment and theory is obtained. A weak covalent Ti-Al bond is
manifested by a pronounced shoulder in the Ti L-emission of Ti3AlC2. As Al is
replaced with Si or Ge, the shoulder disappears. For the buried Al and
Si-layers, strongly hybridized spectral shapes are detected in Ti3AlC2 and
Ti3SiC2, respectively. As a result of relaxation of the crystal structure and
the increased charge-transfer from Ti to C, the Ti-C bonding is strengthened.
The differences between the electronic structures are discussed in relation to
the bonding in the nanolaminates and the corresponding change of materials
properties.Comment: 15 pages, 8 figure
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