1,327 research outputs found
Branching Transport Model of Alkali-Halide Scintillators
We measure the time dependence of the scintillator light-emission pulses in
NaI(Tl) crystals at different temperatures, after activation by gamma rays. We
confirm that there are two main nonexponential components to the time decay and
find that their amplitude ratio shows Arrhenius temperature dependence. We
explain these nonexponential components as arising from two competing
mechanisms of carrier transport to the Tl activation levels. The total light
output of the NaI(Tl) detectors shows a linear temperature dependence explained
by our model
Surface Adsorption Properties of Peptides Produced by Non-optimum pH Pepsinolysis of Proteins: A Combined Experimental and Self-Consistent-Field Calculation Study
Hypothesis
Partial hydrolysis of large molecular weight (Mw), highly aggregated plant proteins is frequently used to improve their solubility. However, if this hydrolysis is extensive, random or nonselective, it is unlikely to improve functional properties such as surface activity, emulsion, or foam-stabilising capacity.
Experiments and simulation
Soy protein isolate (SPI) was hydrolysed by pepsin under optimal (pH 2.1) and non-optimal (pH 4.7) conditions. The surface activity and emulsion stabilising capacity of the resultant peptides were measured and compared. The colloidal interactions between a pair of emulsion droplets were modelled via Self-Consistent-Field Calculations (SCFC).
Findings
Hydrolysis at pH 2.1 and 4.7 resulted in a considerable increase in measured surface activity compared to the native (non-hydrolysed) SPI, but the hydrolysate from pH 2.1 was not as good an emulsion stabiliser as the hydrolysate (particularly the fraction Mw > 10 kDa) at pH 4.7. Furthermore, peptide analysis of the latter suggested it was dominated by a fragment of one of the major soy proteins Ī²-conglycinin, with Mw ā 25 kDa. SCFC calculations confirmed that interactions mediated by adsorbed layers of this peptide point to it being an excellent emulsion stabiliser
The Effect of Radiation Pressure on the Equilibrium Points in the Generalised Photogravitational Restricted Three Body Problem
The existence of equilibrium points and the effect of radiation pressure have
been discussed numerically. The problem is generalized by considering bigger
primary as a source of radiation and small primary as an oblate spheroid. We
have also discussed the Poynting-Robertson(P-R) effect which is caused due to
radiation pressure. It is found that the collinear points deviate
from the axis joining the two primaries, while the triangular points
are not symmetrical due to radiation pressure. We have seen that
are linearly unstable while are conditionally stable in the sense of
Lyapunov when P-R effect is not considered. We have found that the effect of
radiation pressure reduces the linear stability zones while P-R effect induces
an instability in the sense of Lyapunov
Nonlinear Stability in the Generalised Photogravitational Restricted Three Body Problem with Poynting-Robertson Drag
The Nonlinear stability of triangular equilibrium points has been discussed
in the generalised photogravitational restricted three body problem with
Poynting-Robertson drag. The problem is generalised in the sense that smaller
primary is supposed to be an oblate spheroid. The bigger primary is considered
as radiating. We have performed first and second order normalization of the
Hamiltonian of the problem. We have applied KAM theorem to examine the
condition of non-linear stability. We have found three critical mass ratios.
Finally we conclude that triangular points are stable in the nonlinear sense
except three critical mass ratios at which KAM theorem fails.Comment: Including Poynting-Robertson Drag the triangular equilibrium points
are stable in the nonlinear sense except three critical mass ratios at which
KAM theorem fail
Fabrication and lubrication performance of sustainable Pickeringālike waterāināwater emulsions using plant protein microgels
Aqueous multiphasic systems have attracted a great deal of interest recently owing to the growing demands of sustainability for the development of stable āoil-freeā emulsions, often complicated by their limited stability against droplet coarsening. Although particles may provide ultrastability to water-in-water (W/W) emulsions formed in phase-separating polymer systems, the need for lubrication in such W/W emulsions presents an important challenge for their use in diverse applications. Herein, W/W Pickering emulsions were stabilized by sustainable plant protein (pea)-based microgels (PPM) using starch and xanthan gum as the biopolymers to generate the W/W phase separating droplet structures. The lubricity of these systems was compared with that of parallel systems stabilized by animal (whey) protein microgels (WPM). New results reveal that PPM are more soft and adhesive than WPM and outperform the latter in boundary lubrication performance, in striking contrast to the behavior of the non-microgelled pea or whey proteins. Furthermore, the PPM tend to stabilize a different, less spherical type of W/W droplet than the WPM that may explain the lower friction observed in PPM-stabilized systems. The novel approach of fabricating W/W emulsions stabilized by sustainable microgels opens up new solutions in designing aqueous lubricants for future nutritional and biomedical applications
Linear Stability of Triangular Equilibrium Points in the Generalized Photogravitational Restricted Three Body Problem with Poynting-Robertson Drag
In this paper we have examined the linear stability of triangular equilibrium
points in the generalised photogravitational restricted three body problem with
Poynting-Robertson drag. We have found the position of triangular equilibrium
points of our problem. The problem is generalised in the sense that smaller
primary is supposed to be an oblate spheroid. The bigger primary is considered
as radiating. The equations of motion are affected by radiation pressure force,
oblateness and P-R drag. All classical results involving photogravitational and
oblateness in restricted three body problem may be verified from this result.
With the help of characteristic equation, we discussed the stability. Finally
we conclude that triangular equilibrium points are unstable.Comment: accepted for publication in Journal of Dynamical Systems & Geometric
Theories Vol. 4, Number 1 (2006
Ī³-Cyclodextrin Metal-Organic Frameworks: Do Solvents Make a Difference?
Conventionally, methanol is the solvent of choice in the synthesis of gamma-cyclodextrin metal-organic frameworks (Ī³-CD-MOFs), but using ethanol as a replacement could allow for a more food-grade synthesis condition. Therefore, the aim of the study was to compare the Ī³-CD-MOFs synthesised with both methanol and ethanol. The Ī³-CD-MOFs were characterised by scanning electron microscopy (SEM), surface area and pore measurement, Fourier transform infrared spectroscopy (FTIR) and powder X-ray diffraction (PXRD). The encapsulation efficiency (EE) and loading capacity (LC) of the Ī³-CD-MOFs were also determined for curcumin, using methanol, ethanol and a mixture of the two as encapsulation solvent. It was found that Ī³-CD-MOFs synthesised by methanol and ethanol do not differ greatly, the most significant difference being the larger crystal size of Ī³-CD-MOFs crystallised from ethanol. However, the change in solvent significantly influenced the EE and LC of the crystals. The higher solubility of curcumin in ethanol reduced interactions with the Ī³-CD-MOFs and resulted in lowered EE and LC. This suggests that different solvents should be used to deliberately manipulate the EE and LC of target compounds for better use of Ī³-CD-MOFs as their encapsulating and delivery agents
Geochemical analysis of bulk marine sediment by Inductively Coupled PlasmaāAtomic Emission Spectroscopy on board the JOIDES Resolution
Geochemical analyses on board the JOIDES Resolution have been enhanced with the addition of a Jobin-Yvon Ultrace inductively coupled plasma-atomic emission spectrometer (ICP-AES) as an upgrade from the previous X-ray fluorescence facility. During Leg 199, we sought to both challenge and utilize the capabilities of the ICP-AES in order to provide an extensive bulk-sediment geochemical database during the cruise. These near real-time analyses were then used to help characterize the recovered sedimentary sequences, calculate mass accumulation rates of the different sedimentary components, and assist with cruise and postcruise sampling requests. The general procedures, sample preparation techniques, and basic protocol for ICP-AES analyses on board ship are outlined by Murray et al. (2000) in Ocean Drilling Program Tech Note, 29. We expand on those concepts and offer suggestions for ICP-AES methodology, calibration by standard reference materials, data reduction procedures, and challenges that are specific to the analysis of bulk-sediment samples. During Leg 199, we employed an extensive bulk-sediment analytical program of ~600 samples of varying lithologies, thereby providing several opportunities for refinement of techniques. We also discuss some difficulties and challenges that were faced and suggest how to alleviate such occurrences for sedimentary chemical analyses during future legs
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