236 research outputs found
Rich polymorphism of a rod-like liquid crystal (8CB) confined in two types of unidirectional nanopores
We present a neutron and X-rays scattering study of the phase transitions of
4-n-octyl-4'-cyanobiphenyl (8CB) confined in unidirectional nanopores of porous
alumina and porous silicon (PSi) membranes with an average diameter of 30 nm.
Spatial confinement reveals a rich polymorphism, with at least four different
low temperature phases in addition to the smectic A phase. The structural study
as a function of thermal treatments and conditions of spatial confinement
allows us to get insights into the formation of these phases and their relative
stability. It gives the first description of the complete phase behavior of 8CB
confined in PSi and provides a direct comparison with results obtained in bulk
conditions and in similar geometric conditions of confinement but with reduced
quenched disorder effects using alumina anopore membranesComment: Accepted in EPJ E - Soft Matte
Tunability of the elastocaloric response in main-chain liquid crystalline elastomers
Materials exhibiting a large caloric effect could lead to the development of a new generation of heat-management technologies that will have better energy efficiency and be potentially more environmentally friendly. The focus of caloric materials investigations has shifted recently from solid-state materials towards soft materials, such as liquid crystals and liquid crystalline elastomers. It has been shown recently that a large electrocaloric effect exceeding 6 K can be observed in smectic liquid crystals. Here, we report on a significant elastocaloric response observed by direct elastocaloric measurements in main-chain liquid crystal elastomers. It is demonstrated that the character of the nematic to paranematic/isotropic transition can be tuned from the supercritical regime towards the first-order regime, by decreasing the density of crosslinkers. In the latter case, the latent heat additionally enhances the elastocaloric response. Our results indicate that a significant elastocaloric response is present in main-chain liquid crystalline elastomers, driven by stress fields much smaller than in solid elastocaloric materials. Therefore, elastocaloric soft materials can potentially play a significant role as active cooling/heating elements in the development of new heat-management devices
Orthogonal techniques to study the effect of pH, sucrose and arginine salts on monoclonal antibody physical stability and aggregation during long-term storage
Understanding the effects of additives on therapeutic protein stability is of paramount importance for obtaining stable formulations. In this work, we apply several high- and medium-throughput methods to study the physical stability of a model monoclonal antibody at pH 5.0 and 6.5 in the presence of sucrose, arginine hydrochloride and arginine glutamate. In low ionic strength buffer, the addition of salts reduces the antibody colloidal and thermal stability, attributed to screening of electrostatic interactions. The presence of glutamate ion in the arginine salt partially reduces the damaging effect of ionic strength increase. The addition of 280 mM sucrose shifts the thermal protein unfolding to a higher temperature. Arginine salts in the used concentration reduce the relative monomer yield after refolding from urea, while sucrose has a favorable effect on antibody refolding. In addition, we show 12-month long-term stability data and observe correlations between thermal protein stability, relative monomer yield after refolding and monomer loss during storage. The monomer loss during storage is related to protein aggregation and formation of subvisible particles in some of the formulations. This study shows that the effect of commonly used additives on the long-term antibody physical stability can be predicted using orthogonal biophysical measurements
HMG-CoA reductase is regulated by environmental salinity and its activity is essential for halotolerance in halophilic fungi
The activity and level of HMG-CoA reductase (HMGR) were addressed in
halophilic fungi isolated from solar saltpans. Representative fungi belonging
to the orders Dothideales, Eurotiales and Wallemiales have a
specific pattern of HMGR regulation, which differs from salt-sensitive and
moderately salt-tolerant yeasts. In all of the halophilic fungi studied, HMGR
amounts and activities were the lowest at optimal growth salinity and
increased under hyposaline and hypersaline conditions. This profile paralleled
isoprenylation of cellular proteins in H. werneckii. Inhibition of
HMGR in vivo by lovastatin impaired the halotolerant character. HMGR
may thus serve as an important molecular marker of halotolerance
A new picture of the Lifshitz critical behavior
New field theoretic renormalization group methods are developed to describe
in a unified fashion the critical exponents of an m-fold Lifshitz point at the
two-loop order in the anisotropic (m not equal to d) and isotropic (m=d close
to 8) situations. The general theory is illustrated for the N-vector phi^4
model describing a d-dimensional system. A new regularization and
renormalization procedure is presented for both types of Lifshitz behavior. The
anisotropic cases are formulated with two independent renormalization group
transformations. The description of the isotropic behavior requires only one
type of renormalization group transformation. We point out the conceptual
advantages implicit in this picture and show how this framework is related to
other previous renormalization group treatments for the Lifshitz problem. The
Feynman diagrams of arbitrary loop-order can be performed analytically provided
these integrals are considered to be homogeneous functions of the external
momenta scales. The anisotropic universality class (N,d,m) reduces easily to
the Ising-like (N,d) when m=0. We show that the isotropic universality class
(N,m) when m is close to 8 cannot be obtained from the anisotropic one in the
limit d --> m near 8. The exponents for the uniaxial case d=3, N=m=1 are in
good agreement with recent Monte Carlo simulations for the ANNNI model.Comment: 48 pages, no figures, two typos fixe
Biodiversity in the Cladosporium herbarum complex (Davidiellaceae, Capnodiales), with standardisation of methods for Cladosporium taxonomy and diagnostics
The Cladosporium herbarum complex comprises five species for which
Davidiella teleomorphs are known. Cladosporium herbarum s.
str. (D. tassiana), C. macrocarpum (D.
macrocarpa) and C. bruhnei (D. allicina) are
distinguishable by having conidia of different width, and by teleomorph
characters. Davidiella variabile is introduced as teleomorph of
C. variabile, a homothallic species occurring on Spinacia,
and D. macrospora is known to be the teleomorph of C. iridis
on Iris spp. The C. herbarum complex combines low molecular
distance with a high degree of clonal or inbreeding diversity. Entities differ
from each other by multilocus sequence data and by phenetic differences, and
thus can be interpreted to represent individual taxa. Isolates of the C.
herbarum complex that were formerly associated with opportunistic human
infections, cluster with C. bruhnei. Several species are newly
described from hypersaline water, namely C. ramotenellum, C.
tenellum, C. subinflatum, and C. herbaroides.
Cladosporium pseudiridis collected from Iris sp. in New
Zealand, is also a member of this species complex and shown to be distinct
from C. iridis that occurs on this host elsewhere in the world. A
further new species from New Zealand is C. sinuosum on Fuchsia
excorticata. Cladosporium antarcticum is newly described from a
lichen, Caloplaca regalis, collected in Antarctica, and C.
subtilissimum from grape berries in the U.S.A., while the new combination
C. ossifragi, the oldest valid name of the Cladosporium
known from Narthecium in Europe, is proposed. Standard protocols and
media are herewith proposed to facilitate future morphological examination of
Cladosporium spp. in culture, and neotypes or epitypes are proposed
for all species treated
Age-related changes in global motion coherence: conflicting haemodynamic and perceptual responses
Our aim was to use both behavioural and neuroimaging data to identify indicators of perceptual decline in motion processing. We employed a global motion coherence task and functional Near Infrared Spectroscopy (fNIRS). Healthy adults (n = 72, 18-85) were recruited into the following groups: young (n = 28, mean age = 28), middle-aged (n = 22, mean age = 50), and older adults (n = 23, mean age = 70). Participants were assessed on their motion coherence thresholds at 3 different speeds using a psychophysical design. As expected, we report age group differences in motion processing as demonstrated by higher motion coherence thresholds in older adults. Crucially, we add correlational data showing that global motion perception declines linearly as a function of age. The associated fNIRS recordings provide a clear physiological correlate of global motion perception. The crux of this study lies in the robust linear correlation between age and haemodynamic response for both measures of oxygenation. We hypothesise that there is an increase in neural recruitment, necessitating an increase in metabolic need and blood flow, which presents as a higher oxygenated haemoglobin response. We report age-related changes in motion perception with poorer behavioural performance (high motion coherence thresholds) associated with an increased haemodynamic response
Fruit fracture biomechanics and the release of Lepidium didymum pericarp-imposed mechanical dormancy by fungi
Mechanical dormancy imposed by a hard fruit pericarp prevents premature seed germination. Here, the authors show that the pericarp of Lepidium didymum prevents germination by limiting water uptake and that dormancy can be released by fungal activity that weakens predetermined breaking zones in the fruit coat
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