245 research outputs found
Stigma and the in(visible) perspectives and expectations of home oxygen therapy among people with chronic breathlessness syndrome: A qualitative study
© The Author(s) 2018. Background: Chronic breathlessness syndrome in the context of advancing disease is distressing for all concerned. Oxygen is commonly prescribed in this setting; however, little is known about the perspectives of breathless people who either are on oxygen or are yet to have it prescribed. Aim: To understand and describe the perspectives and experiences of breathless people towards oxygen use at home. Design: This qualitative study utilised an interpretive description approach using semi-structured interviews and thematic analysis. Setting/participants: A total of 19 people with chronic breathlessness syndrome living in South Australia participated in semi-structured interviews. Participants were divided into sub-groups according to whether they were chronically breathless and (1) not using home oxygen (n = 6), (2) using funded home oxygen for severe hypoxaemia (n = 7) and (3) using home oxygen for palliation outside of funding guidelines (n = 6). Results: Three main themes were identified: (1) managing distress and living with chronic breathlessness syndrome, with or without oxygen, requires a range of self-management strategies; (2) expectations of oxygen use: ‘Not as good as I thought it would be’; and (3) the stigma of using oxygen: the visible and invisible. Conclusion: People living with chronic breathlessness struggle daily with both the progression of the underlying disease and the distressing nature of the syndrome. While oxygen does provide benefit for some people, its use and the perceptions of its use are often associated with both the visible and invisible manifestations of stigma. Clinicians need to promote self-management strategies and give careful thought to the prescribing of home oxygen, especially outside the current funding guidelines
Impact of Endogenous Bile Salts on the Thermodynamics of Supersaturated Active Pharmaceutical Ingredient Solutions
A variety of formulation strategies have been developed to mitigate the inadequate aqueous solubility of certain therapeutic agents. Among these, achieving supersaturation in vivo is a promising approach to improve the extent of oral absorption. Because of the thermodynamic instability of supersaturated solutions, inhibitors are needed to kinetically hinder crystallization. In addition to commonly used polymeric additives, bile salts, naturally present in the gastrointestinal tract, have been shown to exhibit crystallization inhibition properties. However, the impact of bile salts on solution thermodynamics is not well understood, although this knowledge is essential in order to explore the mechanism of crystallization inhibition. To better describe solution thermodynamics in the presence of bile salts, a side-by-side diffusion cell was used to evaluate solute flux for solutions of telaprevir in the absence and presence of the six most abundant bile salts in human intestinal fluid at various solute concentrations; flux measurements provide information about the solute thermodynamic activity and hence can provide an improved measurement of supersaturation in complex solutions. Trihydroxy bile salts had minimal impact on solution phase boundaries as well as solute flux, while micellar dihydroxy bile salts solubilized telaprevir leading to reduced solute flux across the membrane. An inconsistency between the concentration-based supersaturation ratio and that based on solute thermodynamic activity (the fundamental driving force for crystallization) was noted, suggesting that the activity-based supersaturation should be determined to better interpret any modification in crystallization kinetics in the presence of these additives. These findings indicate that bile salts are not interchangeable from a thermodynamic perspective and provide a foundation for further studies evaluating the mechanism of crystallization inhibition
First order isotropic - smectic-A transition in liquid crystal-aerosil gels
The short-range order which remains when the isotropic to smectic-A
transition is perturbed by a gel of silica nanoparticles (aerosils) has been
studied using high-resolution synchrotron x-ray diffraction. The gels have been
created \textit{in situ} in decylcyanobiphenyl (10CB), which has a strongly
first-order isotropic to smectic-A transition. The effects are determined by
detailed analysis of the temperature and gel density dependence of the smectic
structure factor. In previous studies of the continuous nematic to smectic-A
transition in a variety of thermotropic liquid crystals the aerosil gel
appeared to pin, at random, the phase of the smectic density modulation. For
the isotropic to smectic-A transition the same gel perturbation yields
different results. The smectic correlation length decreases more slowly with
increasing random field variance in good quantitative agreement with the effect
of a random pinning field at a transition from a uniform phase directly to a
phase with one-dimensional translational order. We thus compare the influence
of random fields on a \textit{freezing} transition with and without an
intervening orientationally ordered phase.Comment: 8 pages, 8 figure
Harmonic crossover exponents in O(n) models with the pseudo-epsilon expansion approach
We determine the crossover exponents associated with the traceless tensorial
quadratic field, the third- and fourth-harmonic operators for O(n) vector
models by re-analyzing the existing six-loop fixed dimension series with
pseudo-epsilon expansion. Within this approach we obtain the most accurate
theoretical estimates that are in optimum agreement with other theoretical and
experimental results.Comment: 12 pages, 1 figure. Final version accepted for publicatio
Dynamics of Weak First Order Phase Transitions
The dynamics of weak vs. strong first order phase transitions is investigated
numerically for 2+1 dimensional scalar field models. It is argued that the
change from a weak to a strong transition is itself a (second order) phase
transition, with the order parameter being the equilibrium fractional
population difference between the two phases at the critical temperature, and
the control parameter being the coefficient of the cubic coupling in the
free-energy density. The critical point is identified, and a power law
controlling the relaxation dynamics at this point is obtained. Possible
applications are briefly discussed.Comment: 11 pages, 4 figures in uuencoded compressed file (see instructions in
main text), RevTeX, DART-HEP-94/0
A lattice model for the kinetics of rupture of fluid bilayer membranes
We have constructed a model for the kinetics of rupture of membranes under
tension, applying physical principles relevant to lipid bilayers held together
by hydrophobic interactions. The membrane is characterized by the bulk
compressibility (for expansion), the thickness of the hydrophobic part of the
bilayer, the hydrophobicity and a parameter characterizing the tail rigidity of
the lipids. The model is a lattice model which incorporates strain relaxation,
and considers the nucleation of pores at constant area, constant temperature,
and constant particle number. The particle number is conserved by allowing
multiple occupancy of the sites. An equilibrium ``phase diagram'' is
constructed as a function of temperature and strain with the total pore surface
and distribution as the order parameters. A first order rupture line is found
with increasing tension, and a continuous increase in proto-pore concentration
with rising temperature till instability. The model explains current results on
saturated and unsaturated PC lipid bilayers and thicker artificial bilayers
made of diblock copolymers. Pore size distributions are presented for various
values of area expansion and temperature, and the fractal dimension of the pore
edge is evaluated.Comment: 15 pages, 8 figure
Critical structure factors of bilinear fields in O(N)-vector models
We compute the two-point correlation functions of general quadratic operators
in the high-temperature phase of the three-dimensional O(N) vector model by
using field-theoretical methods. In particular, we study the small- and
large-momentum behavior of the corresponding scaling functions, and give
general interpolation formulae based on a dispersive approach. Moreover, we
determine the crossover exponent associated with the traceless
tensorial quadratic field, by computing and analyzing its six-loop perturbative
expansion in fixed dimension. We find: ,
, and for respectively.Comment: 27 page
Shear induced instabilities in layered liquids
Motivated by the experimentally observed shear-induced destabilization and
reorientation of smectic A like systems, we consider an extended formulation of
smectic A hydrodynamics. We include both, the smectic layering (via the layer
displacement u and the layer normal p) and the director n of the underlying
nematic order in our macroscopic hydrodynamic description and allow both
directions to differ in non equilibrium situations. In an homeotropically
aligned sample the nematic director does couple to an applied simple shear,
whereas the smectic layering stays unchanged. This difference leads to a finite
(but usually small) angle between n and p, which we find to be equivalent to an
effective dilatation of the layers. This effective dilatation leads, above a
certain threshold, to an undulation instability of the layers. We generalize
our earlier approach [Rheol. Acta, vol.39(3), 15] and include the cross
couplings with the velocity field and the order parameters for orientational
and positional order and show how the order parameters interact with the
undulation instability. We explore the influence of various material parameters
on the instability. Comparing our results to recent experiments and molecular
dynamic simulations, we find a good qualitative agreement.Comment: 15 pages, 12 figures, accepted for publication in PR
Morphology of supported polymer electrolyte ultra-thin films: a numerical study
Morphology of polymer electrolytes membranes (PEM), e.g., Nafion, inside PEM
fuel cell catalyst layers has significant impact on the electrochemical
activity and transport phenomena that determine cell performance. In those
regions, Nafion can be found as an ultra-thin film, coating the catalyst and
the catalyst support surfaces. The impact of the hydrophilic/hydrophobic
character of these surfaces on the structural formation of the films has not
been sufficiently explored yet. Here, we report about Molecular Dynamics
simulation investigation of the substrate effects on the ionomer ultra-thin
film morphology at different hydration levels. We use a mean-field-like model
we introduced in previous publications for the interaction of the hydrated
Nafion ionomer with a substrate, characterized by a tunable degree of
hydrophilicity. We show that the affinity of the substrate with water plays a
crucial role in the molecular rearrangement of the ionomer film, resulting in
completely different morphologies. Detailed structural description in different
regions of the film shows evidences of strongly heterogeneous behavior. A
qualitative discussion of the implications of our observations on the PEMFC
catalyst layer performance is finally proposed
Model driven design for integrated twin screw granulator and fluid bed dryer via flowsheet modelling
This paper presents a flowsheet modelling of an integrated twin screw granulation (TSG) and fluid bed dryer (FBD) process using a Model Driven Design (MDD) approach. The MDD approach is featured by appropriate process models and efficient model calibration workflow to ensure the product quality. The design space exploration is driven by the physics of the process instead of extensive experimental trials. By means of MDD, the mechanistic-based process kernels are first defined for the TSG and FBD processes. With the awareness of the underlying physics, the complementary experiments are carried out with relevance to the kinetic parameters in the defined models. As a result, the experiments are specifically purposeful for model calibration and validation. The L/S ratio (liquid to solid ratio) and inlet air temperature are selected as the Critical Process Parameters (CPPs) in TSG and FBD for model validation, respectively. Global System Analysis (GSA) is further performed to assess the uncertainty of CPPs imposed on the Critical Quality Attributes (CQAs), which provides significant insights to the exploration of the design space considering both TSG and FBD process parameters
- …