880 research outputs found
Humic acid protein complexation
Interactions of purified Aldrich humic acid (PAHA) with lysozyme (LSZ) are investigated. In solution LSZ is moderately positively and PAHA negatively charged at the investigated pH values. The proton binding of PAHA and of LSZ is determined by potentiometric proton titrations at various KCl concentrations. It is also measured for two mixtures of PAHAÂżLSZ and compared with theoretically calculated proton binding assuming no mutual interaction. The charge adaptation due to PAHAÂżLSZ interaction is relatively small and only significant at low and high pH. Next to the proton binding, the mass ratio PAHA/LSZ at the iso-electric point (IEP) of the complex at given solution conditions is measured together with the pH using the MĂŒtek particle charge detector. From the pH changes the charge adaptation due to the interaction can be found. Also these measurements show that the net charge adaptation is weak for PAHAÂżLSZ complexes at their IEP. PAHA/LSZ mass ratios in the complexes at the IEP are measured at pH 5 and 7. At pH 5 and 50 mmol/L KCl the charge of the complex is compensated for 30Âż40% by K+; at pH 7, where LSZ has a rather low positive charge, this is 45Âż55%. At pH 5 and 5 mmol/L KCl the PAHA/LSZ mass ratio at the IEP of the complex depends on the order of addition. When LSZ is added to PAHA about 25% K+ is included in the complex, but no K+ is incorporated when PAHA is added to LSZ. The flocculation behavior of the complexes is also different. After LSZ addition to PAHA slow precipitation occurs (6Âż24 h) in the IEP, but after addition of PAHA to LSZ no precipitation can be seen after 12 h. Clearly, PAHA/LSZ complexation and the colloidal stability of PAHAÂżLSZ aggregates depend on the order of addition. Some implications of the observed behavior are discussed
A back-propagation neural network for mineralogical mapping from AVIRIS data
Imaging spectrometers have the potential to identify surface mineralogy based on the unique absorption features in pixel spectra. A back-propagation neural network (BPN) is introduced to classify Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) of the Cuprite mining district (Nevada) data into mineral maps. The results are compared with the traditional acquired surface mineralogy maps from spectral angle mapping (SAM). There is no misclassification for the training set in the case of BPN; however 17 percent misclassification occurs in SAM. The validation accuracy of the SAM is 69 percent, whereas BPN results in 86 per cent accuracy. The calibration accuracy of the BPN is higher than that of the SAM, suggesting that the training process of BPN is better than that of the SAM. The high classification accuracy obtained with the BPN can be explained by: (1)its ability to deal with complex relationships (e.g., 40 dimensions) and (2) the nature of the dataset, the minerals are highly concentrated and they are mostly represented by pure pixels. This paper demonstrates that BPN has superior classification ability when applied to imaging spectrometer data.Remote SensingImaging Science & Photographic TechnologySCI(E)EI29ARTICLE197-1102
The quantitative soil pit method for measuring belowground carbon and nitrogen stocks
Many important questions in ecosystem science require estimates of stocks of soil C and nutrients. Quantitative soil pits provide direct measurements of total soil mass and elemental content in depth-based samples representative of large volumes, bypassing potential errors associated with independently measuring soil bulk density, rock volume, and elemental concentrations. The method also allows relatively unbiased sampling of other belowground C and nutrient stocks, including roots, coarse organic fragments, and rocks. We present a comprehensive methodology for sampling these pools with quantitative pits and assess their accuracy, precision, effort, and sampling intensity as compared to other methods. At 14 forested sites in New Hampshire, nonsoil belowground pools (which other methods may omit, double-count, or undercount) accounted for upward of 25% of total belowground C and N stocks: coarse material accounted for 4 and 1% of C and N in the O horizon; roots were 11 and 4% of C and N in the O horizon and 10 and 3% of C and N in the B horizon; and soil adhering to rocks represented 5% of total B-horizon C and N. The top 50 cm of the C horizon contained the equivalent of 17% of B-horizon carbon and N. Sampling procedures should be carefully designed to avoid treating these important pools inconsistently. Quantitative soil pits have fewer sources of systematic error than coring methods; the main disadvantage is that because they are time-consuming and create a larger zone of disturbance, fewer observations can be made than with cores
Effect of Mercerization and Acetylation on Properties of Coconut Fiber and its Influence on Modified Bitumen
Coconut fiber, one of many types of natural fibers, is an agricultural waste which is left unutilized after the coconut fruits and juice are extracted. In this research, the effect of the different chemical treatments on the morphological, chemical and physical properties of coconut fiber and its influence on the properties of the modified bitumen were studied. The mercerization effectively altered the surface morphology and reduced the diameter of the coconut fiber. The waxy layer present on the surface of
the coconut fiber was significantly reduced after mercerization. Acetylation reported minor reduction on the waxy layer and did not cause any significant changes on the diameter of the coconut fiber. The chemical characterization reported that the hemicelluloses were present only on the surface of the natural coconut fiber whereas the peak of Fourier Transform Infrared spectra associated with the presence of waxes was observed for natural and chemically treated coconut fibers. The bitumen modified with chemically treated coconut fibers exhibited lower penetration values and higher softening point. From the analyses of
penetration value, softening point and penetration index, the bitumen modified with 10% NaOH and 50% CH3COOH treated
coconut fibers resulted in enhanced properties for paving binders to be used in warmer region
Diffusion Resonances in Action Space for an Atom Optics Kicked Rotor with Decoherence
We numerically investigate momentum diffusion rates for the pulse kicked
rotor across the quantum to classical transition as the dynamics are made more
macroscopic by increasing the total system action. For initial and late time
rates we observe an enhanced diffusion peak which shifts and scales with
changing kick strength, and we also observe distinctive peaks around quantum
resonances. Our investigations take place in the context of a system of
ultracold atoms which is coupled to its environment via spontaneous emission
decoherence, and the effects should be realisable in ongoing experiments.Comment: 4 Pages, RevTeX 4, 5 Figures. Updated Figures, Minor Changes to text,
Corrected Reference
Determination of oxygen stoichiometry in the mixed-valent manganites
The possible redox (oxidation reduction) chemical methods for precisely
determining the oxygen content in the perovskite manganites including
hole-doped La1-xCaxMnOy and electron-doped La1-xTexMnOy compounds are
described. For manganites annealed at different temperatures, the oxygen
content of the samples was determined by a redox back titration in which the
powder samples taken in a quartz crucible were dissolved in (1+1) sulfuric acid
containing an excess of sodium oxalate, and the excess sodium oxalate was
titrated with permanganate standard solution. The results indicate that the
method is effective and highly reproducible. Moreover, the variation of oxygen
content is also reflected in significantly affecting the electrical transport
property of the samples, which is mainly considered to be closely related to
introduce oxygen vacancies in the Mn-O-Mn network.Comment: 13 pages, 1 figure. J. Magn. Magn .Mater (accepted
The effect of grain size on electrical transport and magnetic properties of La0.9Te0.1MnO3
The effect of grain size on structural, magnetic and transport properties in
electron-doped manganites La0.9Te0.1MnO3 has been investigated. All samples
show a rhombohedral structure with the space group at room temperature. It
shows that the Mn-O-Mn bond angle decreases and the Mn-O bond length increases
with the increase of grain size. All samples undergo paramagnetic
(PM)-ferromagnetic (FM) phase transition and an interesting phenomenon that
both magnetization and the Curie temperature decrease with increasing grain
size is observed, which is suggested to mainly originate from the increase of
the Mn-O bond length . Additionally, obviously increases with decreasing grain
size due to the increase of both the height and width of tunneling barriers
with decreasing the grain size. The results indicate that both the intrinsic
colossal magnetoresistance (CMR) and the extrinsic the extrinsic interfacial
magnetoresistance (IMR) can be effectively tuned in La0.9Te0.1MnO3 by changing
grain size.Comment: 15 pages,4 figures. Solid state communications 132(2004)83-8
Dynamic contrast-enhanced magnetic resonance imaging of radiation therapy-induced microcirculation changes in rectal cancer
Impact of n-methyl-2-pyrrolidone in monoethanolamine solution to the co2 absorption in packed column: analysis via mathematical modeling
This work investigates the reason behind the change of CO2
absorption behaviour exhibited by monoethanolamine
(MEA) solution via mathematical modeling analysis when physical absorbent, i.e. n-methyl-2-pyrrolidone (NMP), was
added into the solution. The mathematical modeling included the heat model using time resolved numerical method.
Based on the results, it was found that lower CO2
removal performance with the addition of NMP into MEA solution at
pressure of 0.1 MPa was mainly due to the lower temperature rise along the column, which resulted in lower reaction
rate. However, at 3 and 5 MPa pressure conditions, the high physical absorption capability contributed by the presence
of NMP in MEA hybrid solution enhanced the CO2
absorption performance of MEA hybrid solution significantly.
As such, temperature rise of solution was identified as the dominating factor affecting the performance of the hybrid
solvent. The reaction rate of MEA was not affected by the addition of physical solvent. This finding shed crucial insight
on the behaviour MEA-NMP hybrid solution which can be applied during scale-up of the process
Melanocytoma of the optic nerve head: a diagnostic dilemma
The clinical features, autofluorescence, Bscan ultrasonography, optical coherence tomography and fluorescein angiography of the lesion were described. Multiple investigation modalities are needed to confirm the benign nature of the lesion. Careful evaluation and follow-up is crucial to avoid misdiagnosis and erroneous management
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