50,983 research outputs found
An experimental study on the pressure dependence of viscosity in silicate melts
No full textThe effect of pressure on melt viscosity was investigated for five compositions along the join An(CaAl2Si2O8)–Di(CaMgSi2O6) and four alkali silicates containing lithium, sodium, and potassium in constant ratio of ∼ 1:1:1, but alkali-silica ratios are varying. The experiments were performed in an internally heated gas pressure vessel at pressures from 50 to 400 MPa in the viscosity range from 108 to 1011.5 Pa⋅s using parallel plate viscometry. The polymerized An composition shows a negative pressure dependence of viscosity while the other, more depolymerized compositions of the join An–Di have neutral to positive pressure coefficients. The alkali silicates display neutral to slightly positive pressure coefficients for melt viscosity. These findings in the high viscosity range of 108–1011 Pa⋅s, where pressure appears to be more efficient than in low viscous melts at high temperature, are consistent with previous results on the viscosity of polymerized to depolymerized melts in the system NaAlSi3O8–CaMgSi2O6 by Behrens and Schulze [ H. Behrens and F. Schulze, Am. Mineral. 88, 1351 (2003) ]. Thus we confirm that the sign of the pressure coefficient for viscosity is mainly related to the degree of melt polymerization in silicate and aluminosilicate melts.DFG Grant n.°BE1720/9Published044504-142.3. TTC - Laboratori di chimica e fisica delle rocceJCR Journalope
On the Behrens radical of matrix rings and polynomial rings
No full textAbstractIt is shown that the Behrens radical of a polynomial ring, in either commuting or non-commuting indeterminates, has the form of “polynomials over an ideal”. Moreover, in the case of non-commuting indeterminates, for a given coefficient ring, the ideal does not depend on the cardinality of the set of indeterminates. However, in contrast to the Brown–McCoy radical, it can happen that the polynomial ring R[X] in an infinite set X of commuting indeterminates over a ring R is Behrens radical while the polynomial ring R〈X〉 in an infinite set Y of non-commuting indeterminates over R is not Behrens radical. This is connected with the fact that the matrix rings over Behrens radical rings need not be Behrens radical. The class of Behrens radical rings, which is closed under taking matrix rings, is described
Viscosity and glass transition temperature of hydrous float glass
No full textViscosity of water-bearing float glass (0.03–4.87 wt% H2O) was measured in the temperature range of 573–1523 K and pressure range
of 50–500 MPa using a parallel plate viscometer in the high viscosity range and the falling sphere method in the low viscosity range. Melt
viscosity depends strongly on temperature and water content, but pressure up to 500 MPa has only minor influence. Consistent with
previous studies on aluminosilicate compositions we found that the effect of dissolved water is most pronounced at low water content,
but it is still noticeable at high water content. A new model for the calculation of the viscosities as a function of temperature and water
content is proposed which describes the experimental data with a standard deviation of 0.22 log units. The depression of the glass tran-
sition temperature Tg by dissolved water agrees reasonably well with the prediction by the model of Deubener [J. Deubener, R. Mu¨ ller,
H. Behrens, G. Heide, J. Non-Cryst. Solids 330 (2003) 268]. Using water speciation measured by near-infrared spectroscopy we infer that
although the effect of OH groups in reducing Tg is larger than that of H2O molecules, the difference in the contribution of both species is
smaller than predicted by Deubener et al. (2003). Compared to alkalis and alkaline earth elements the effect of protons on glass fragility is
small, mainly because of the relatively low concentration of OH groups (max. 1.5 wt% water dissolved as OH) in the glasses.PublishedJCR Journalope
Cultural and Chemical Weed Control in Field Crops (Revised 1968)
No full textThis archival publication may not reflect current scientific knowledge or recommendations. Current information available from the University of Minnesota Extension: https://www.extension.umn.edu.Miller, G. R.; Behrens, R.; Otto, H. J.; Robinson, R. G.; Strand, O. E.; Andersen, R. N.. (1968). Cultural and Chemical Weed Control in Field Crops (Revised 1968). Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/204945
A 2 h periodic variation in the low-mass X-ray binary Ser X-1
No full textSpectroscopy of the low-mass X-ray binary Ser X-1 using the Gran Telescopio Canarias have revealed a ?2 h periodic variability that is present in the three strongest emission lines. We tentatively interpret this variability as due to orbital motion, making it the first indication of the orbital period of Ser X-1. Together with the fact that the emission lines are remarkably narrow, but still resolved, we show that a main-sequence K dwarf together with a canonical 1.4 M? neutron star gives a good description of the system. In this scenario, the most likely place for the emission lines to arise is the accretion disc, instead of a localized region in the binary (such as the irradiated surface or the stream-impact point), and their narrowness is due instead to the low inclination (?10°) of Ser X-1
Tips for profitable corn production
No full text1 online resource (PDF, 4 pages)This archival publication may not reflect current scientific knowledge or recommendations. Current information available from the University of Minnesota Extension: https://www.extension.umn.edu.Hicks, D. R.; Rehm, G. W.; Behrens, R.; Stienstra, W. C.; Ostlie, K. R.; Cloud, H. A.; Fuller, E. I.. (1986). Tips for profitable corn production. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/207464
Review of the book Unbegrenzte moglichkeiten: Amerikanisierung in Deutschland und Frankreich (1900-1933) by Egbert Klautke
No full textDr. Jeff R. Schutts (Douglas College) reviews the book Unbegrenzte Moglichkeiten: Amerikanisierung in Deutschland und Frankreich (1900-1933) by Egbert Klautke (2005).Final article published
Sprachgebrauch und Sprachbewusstsein: Implikationen der empirischen Linguistik für die Sprachtheorie
No full textMalaria clusters among illegal Chinese immigrants to Europe through Africa.
No full textBetween November 2002 and March 2003, 17 cases of malaria (1 fatal) were observed in illegal Chinese immigrants who traveled to Italy through Africa. A further cluster of 12 was reported in August, 2002. Several immigrants traveled by air, making the risk of introducing sudden acute respiratory syndrome a possibility should such illegal immigrations continue
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