117 research outputs found
Role of active layer in the performance of aromatic and semi-aromatic nanofiltration membranes for water purification
Nanofiltration (NF) membranes that differ in molecular weight cut off (MWCO), active layer chemistry, porosity and pore size distribution are available for different applications. These membranes are typically made of three layers: the active layer, polysulfone support layer and a fabric for mechanical strength. It has been proven that the performance of an NF membrane is almost entirely dependent on the active layer, which can be made of polyamide, polypiperazine amide, cellulose acetate or polyethersulfone. Polyamide, which is considered fully aromatic (FA) and polypiperazine, which is considered semi-aromatic (SA), are the most commonly used active layers in NF membranes for water treatment. Several studies evaluated commercially available NF membranes for ion rejection, effect of pH, temperature, pressure but very few have attempted to explain their performance based on the membrane active layer chemistry.
This study is focused on understanding the difference in performance between fully aromatic (FA) and semi-aromatic (SA) membranes for the removal of typical ions of concern in water purification. Four commercially available membranes, two each of FA and SA types were selected for this study. Fourier Transform Infrared (FTIR) spectroscopy was used to substantiate that the selected membranes are truly representative of FA and SA membrane type without any coating or other surface modifications. Membrane performance was analyzed in terms of ion rejection and permeate flux. Membrane volume charge densities as a function of electrolyte concentration were analyzed by measuring their zeta potential as function of pH and electrolyte composition and concentration. The membrane mean pore size was determined using the membrane potential technique [1]. Membrane potential data were analyzed using the steric, electric and dielectric exclusion (SEDE) model [2]. Also, SEDE model was used to calculate the dielectric constants for different electrolyte composition and compare them for FA and SA membranes.
The ion rejection and permeate flux for all four membranes was studied for different feed composition using a SEPA cross flow NF cell at a fixed transmembrane pressure and temperature. The feed composition was selected such that it is representative of the acid mine drainage (AMD) typically found in Pennsylvania, which is characterized by high sulfate concentration and low pH. The resulting ion rejection and permeate flux were compared for the four membranes with goal of understanding the difference in the performance of FA and SA membranes as a function of the active layer chemistry.
The experimental results indicate that the rejection of sulfate was in all cases above 98% but the rejection of the counterions was significantly better for the fully aromatic membranes. Major disparity was observed in the rejection of sodium and chloride ions between FA and SA membranes even when they had the same MWCO’s. This disparity was studied in terms of the electronegativity of the four membranes and the results will be presented at the conference.
1. Escoda, A., et al., Determining the Dielectric Constant inside Pores of Nanofiltration Membranes from Membrane Potential Measurements. Langmuir, 2010. 26(18): p. 14628-14635.
2. Szymczyk, A. and P. Fievet, Investigating transport properties of nanofiltration membranes by means of a steric, electric and dielectric exclusion model. Journal of Membrane Science, 2005. 252(1–2): p. 77-88
Peyer's Patches Are Precocious to the Appendix in Human Development
PP are first visible at ∼15.5 wk gestation after which there is a rapid spurt in the development
and maturation of lymphoid follicles so that at any given point of time new foci of PP development
are continuously formed at a rapid rate. Addition of rows of follicles results in the
formation of a PP. Immature PP of younger fetuses have a spongy structure in contrast with
the compact lymphoid follicles of mature PP of older fetuses. Immunocytochemical studies
reveal that there is a subtle gradation in the expression of lymphocyte surface markers with
increasing fetal age. Expression of antigenic markers occurs in an ordered sequence viz. HLA – DR, CD19 (B cell population), CD9 (pre-B cells), CD3 T lymphocytes, CD4 helper / inducer lymphocytes, the CD8 suppressor / cytotoxic cells and lastly, the CD57 Natural Killer cells. The antigens are expressed first on lymphocytes of PP and thereafter in those of the appendix. Our findings clearly demonstrate that the
∼5 wk fetal period from 17.5 wk to 22 wk
represents a major growth phase in the development of surface markers of lymphocytes in the
mucosal immune system of the gut
Low temperature deformation behaviour of ASTM A-203D nuclear structural steel
The steel A-203D in martensitic, tempered martensitic and ferritic-pearlitic microstructural conditions, was deformed in tension at temperatures between 77 to 300 K and at a strain rate of 6.67×10-5 sec-1. The thermal component of the flow stress and the activation parameters were measured as a function of temperature. It was observed that the microstructure did not affect either the thermal part of the flow stress (σ*) or the activation parameters (V* and ΔH) and that its effect was felt only on the athermal component (σμ) of the flow stress. Further the relations of the activation parameters with stress, strain and temperature were found to be consistent with Dorn-Rajnak theory of Peierls mechanism of plastic deformation. In addition measurements of slow-bend and impact transition were also carried out for ferritic-pearlitic structure. Based on these observations, it is shown that the impact transition temperature of this structure can be emperically correlated with the thermal activation parameters
Precipitation hardening in nickel-copper base alloy monel K 500
The occurrence of a significant amount of age hardening, due to the precipitation of the γ' phase, has been demonstrated in the nickel-copper base alloy MONEL K 500. The micro-structure of the precipitation-hardened and deformed alloy has been examined in peak-aged underaged and overaged conditions. An attempt has been made to compare the observed increments in strength in these three aged conditions to those predicted on the basis of relevant theoretical models
Gastroretentive drug delivery system of captopril and hydrochlorothiazide bilayer tablet: formulation, optimization and in vivo evaluation
The purpose of the present study was to develop and optimize floating-bioadhesive bilayer
gastroretentive drug delivery system (GRDDS) exhibiting a unique combination of floatation and bioadhesion
to prolong residence in the stomach using captopril (CP) and hydrochlorothiazide (HCTZ) as a model
drug. Captopril being unstable in intestinal pH and HCTZ has specific absorption from duodenum and
the first part of the jejunum and to a small extent in the stomach are suitable candidate for GRDDS. 32
factorial design was employed in formulating and optimizing the GRDDS for bilayer tablet of CP and
HCTZ matrix tablet. The main effect and interaction terms were quantitatively evaluated using a mathematical
model. The gastroretentive ability of the tablets was evaluated by X-radiographic studies in
healthy human volunteer. The tablet releases CP and HCTZ for extended period up to 24 h in controlled
manner. The predicted values agreed well with the experimental values and the results demonstrate the
feasibility of the optimization methodology in the development of GRDDS. The tablet was buoyant for up
to 16 h in human stomach. Development of once a day gastroretentive formulation of CP and HCTZ improves
the patience compliance and bioavailability of drugs.Colegio de Farmacéuticos de la Provincia de Buenos Aire
Gastroretentive drug delivery system of captopril and hydrochlorothiazide bilayer tablet: formulation, optimization and in vivo evaluation
The purpose of the present study was to develop and optimize floating-bioadhesive bilayer
gastroretentive drug delivery system (GRDDS) exhibiting a unique combination of floatation and bioadhesion
to prolong residence in the stomach using captopril (CP) and hydrochlorothiazide (HCTZ) as a model
drug. Captopril being unstable in intestinal pH and HCTZ has specific absorption from duodenum and
the first part of the jejunum and to a small extent in the stomach are suitable candidate for GRDDS. 32
factorial design was employed in formulating and optimizing the GRDDS for bilayer tablet of CP and
HCTZ matrix tablet. The main effect and interaction terms were quantitatively evaluated using a mathematical
model. The gastroretentive ability of the tablets was evaluated by X-radiographic studies in
healthy human volunteer. The tablet releases CP and HCTZ for extended period up to 24 h in controlled
manner. The predicted values agreed well with the experimental values and the results demonstrate the
feasibility of the optimization methodology in the development of GRDDS. The tablet was buoyant for up
to 16 h in human stomach. Development of once a day gastroretentive formulation of CP and HCTZ improves
the patience compliance and bioavailability of drugs.Colegio de Farmacéuticos de la Provincia de Buenos Aire
Growth and characterization of heteroepitaxial La-substituted BaSnO films on SrTiO (001) and SmScO (110) substrates
Heteroepitaxial growth of BaSnO (BSO) and BaLaSnO (x = 7
%) (LBSO) thin films on different perovskite single crystal (SrTiO (001)
and SmScO (110)) substrates has been achieved by Pulsed Laser Deposition
(PLD) under optimized deposition conditions. X-ray diffraction measurements
indicate that the films on either of these substrates are relaxed due to the
large mismatch and present a high degree of crystallinity with narrow rocking
curves and smooth surface morphology while analytical quantification by proton
induced x-ray emission (PIXE) confirms the stoichiometric La transfer from a
polyphasic target, producing films with La contents above the bulk solubility
limit. The films show degenerate semiconducting behavior on both substrates,
with the observed room temperature resistivities, Hall mobilities and carrier
concentrations of 4.4 , 10.11 , and 1.38
on SmScO and 7.8 , 5.8 , and 1.36 on SrTiO ruling out any extrinsic
contribution from the substrate. The superior electrical properties observed on
the SmScO3 substrate are attributed to reduction in dislocation density from
the lower lattice mismatch.Comment: 11 pages, 3 figures, supplementary informations 2 figure
Gastroretentive drug delivery system of captopril and hydrochlorothiazide bilayer tablet: formulation, optimization and in vivo evaluation
The purpose of the present study was to develop and optimize floating-bioadhesive bilayer
gastroretentive drug delivery system (GRDDS) exhibiting a unique combination of floatation and bioadhesion
to prolong residence in the stomach using captopril (CP) and hydrochlorothiazide (HCTZ) as a model
drug. Captopril being unstable in intestinal pH and HCTZ has specific absorption from duodenum and
the first part of the jejunum and to a small extent in the stomach are suitable candidate for GRDDS. 32
factorial design was employed in formulating and optimizing the GRDDS for bilayer tablet of CP and
HCTZ matrix tablet. The main effect and interaction terms were quantitatively evaluated using a mathematical
model. The gastroretentive ability of the tablets was evaluated by X-radiographic studies in
healthy human volunteer. The tablet releases CP and HCTZ for extended period up to 24 h in controlled
manner. The predicted values agreed well with the experimental values and the results demonstrate the
feasibility of the optimization methodology in the development of GRDDS. The tablet was buoyant for up
to 16 h in human stomach. Development of once a day gastroretentive formulation of CP and HCTZ improves
the patience compliance and bioavailability of drugs.Colegio de Farmacéuticos de la Provincia de Buenos Aire
The CAMELS project: Cosmology and Astrophysics with MachinE Learning Simulations
We present the Cosmology and Astrophysics with MachinE Learning Simulations
--CAMELS-- project. CAMELS is a suite of 4,233 cosmological simulations of
volume each: 2,184 state-of-the-art
(magneto-)hydrodynamic simulations run with the AREPO and GIZMO codes,
employing the same baryonic subgrid physics as the IllustrisTNG and SIMBA
simulations, and 2,049 N-body simulations. The goal of the CAMELS project is to
provide theory predictions for different observables as a function of cosmology
and astrophysics, and it is the largest suite of cosmological
(magneto-)hydrodynamic simulations designed to train machine learning
algorithms. CAMELS contains thousands of different cosmological and
astrophysical models by way of varying , , and four
parameters controlling stellar and AGN feedback, following the evolution of
more than 100 billion particles and fluid elements over a combined volume of
. We describe the simulations in detail and
characterize the large range of conditions represented in terms of the matter
power spectrum, cosmic star formation rate density, galaxy stellar mass
function, halo baryon fractions, and several galaxy scaling relations. We show
that the IllustrisTNG and SIMBA suites produce roughly similar distributions of
galaxy properties over the full parameter space but significantly different
halo baryon fractions and baryonic effects on the matter power spectrum. This
emphasizes the need for marginalizing over baryonic effects to extract the
maximum amount of information from cosmological surveys. We illustrate the
unique potential of CAMELS using several machine learning applications,
including non-linear interpolation, parameter estimation, symbolic regression,
data generation with Generative Adversarial Networks (GANs), dimensionality
reduction, and anomaly detection.Comment: 33 pages, 18 figures, CAMELS webpage at
https://www.camel-simulations.or
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