1,221 research outputs found
Bacterial Colonisation of the Nasal and Nasopharyngeal Cavities in Children: The Generation R Study
Humans are surrounded by microorganisms: viruses, bacteria, fungi and parasites. We can
divide these organisms into the following four categories: innocent, beneficial, harmful and
dangerous. Most of the times, microorganisms are not harmful and are therefore referred to
as non-pathogenic. Innocent microorganisms cause no harm nor do they provide benefits.
Benefi cial microorganisms even provide a significant advantage for humans by aiding digestion
or preventing pathogenic microorganisms to cause infection via colonisation resistance.
By colonising the respiratory and/or gastro-intestinal tract, these organisms prevent pathogenic
microorganisms to settle and cause harm. Pathogens causing harm in certain cases, but
not per definition, are grouped into the harmful category. However, microbes that fall into
the dangerous category comprise organisms that cause morbidity and mortality in humans
even in those with an intact immune system
Nonequilibrium entropy production for open quantum systems
We consider open quantum systems weakly coupled to a heat reservoir and
driven by arbitrary time-dependent parameters. We derive exact microscopic
expressions for the nonequilibrium entropy production and entropy production
rate, valid arbitrarily far from equilibrium. By using the two-point energy
measurement statistics for system and reservoir, we further obtain a quantum
generalization of the integrated fluctuation theorem put forward by Seifert
[PRL 95, 040602 (2005)].Comment: 4 pages, 1 figur
Towards agent-based crowd simulation in airports using games technology
We adapt popular video games technology for an agent-based crowd simulation in an airport terminal. To achieve this, we investigate the unique traits of airports and implement a virtual crowd by exploiting a scalable layered intelligence technique in combination with physics middleware and a socialforces approach. Our experiments show that the framework runs at interactive frame-rate and evaluate the scalability with increasing number of agents demonstrating
navigation behaviour
Magnetoresistance Effects in SrFeO(3-x): Dependence on Phase Composition and Relation to Magnetic and Charge Order
Single crystals of iron(IV) rich oxides SrFeO(3-x) with controlled oxygen
content have been studied by Moessbauer spectroscopy, magnetometry,
magnetotransport measurements, Raman spectroscopy, and infrared ellipsometry in
order to relate the large magnetoresistance (MR) effects in this system to
phase composition, magnetic and charge order. It is shown that three different
types of MR effects occur. In cubic SrFeO3 (x = 0) a large negative MR of 25%
at 9 T is associated with a hitherto unknown 60 K magnetic transition and a
subsequent drop in resistivity. The 60 K transition appears in addition to the
onset of helical ordering at ~130 K. In crystals with vacancy-ordered
tetragonal SrFeO(3-x) as majority phase (x ~0.15) a coincident
charge/antiferromagnetic ordering transition near 70 K gives rise to a negative
giant MR effect of 90% at 9 T. A positive MR effect is observed in tetragonal
and orthorhombic materials with increased oxygen deficiency (x = 0.19, 0.23)
which are insulating at low temperatures. Phase mixtures can result in a
complex superposition of these different MR phenomena. The MR effects in
SrFeO(3-x) differ from those in manganites as no ferromagnetic states are
involved
Li-decorated BC3 nanopores: Promising materials for hydrogen storage
In the quest of new absorbent for hydrogen storage, we investigate the
capacities of slit pores formed by two BC3 sheets decorated with Li atoms.
Their hydrogen storage capacities are determined using density-functional
theory in conjunction with a quantum-thermodynamic model that allows to
simulate real operating conditions, i.e., finite temperatures and different
loading and depletion pressures applied to the adsorbent in the charge-delivery
cycles. We show that the capacities of the adsorbed hydrogen phase of
Li-decorated BC3 slit pores are larger than those reported recently for
graphene and Li-decorated borophene slit pores. On the other hand, the usable
volumetric and gravimetric capacities of Li-decorated BC3 slit pores can meet
the targets stipulated by the U.S. Department of Energy (DOE) for onboard
hydrogen storage at moderate temperatures and loading pressures well below
those used in the tanks employed in current technology. In particular, the
usable volumetric capacity for pore widths of about 10 {\AA} meets the DOE
target at a loading pressure of 6.6 MPa when depleting at ambient pressure. Our
results highlight the important role played by the rotational degree of freedom
of the H2 molecule in determining the confining potential within the slip pores
and their hydrogen storage capacities.Comment: Article itself: 26 pages, 12 figures, 13 equations, 1 table, 78 cited
articles; Supporting information: 8 pages, 6 figures, 6 equation
Chiral Polyalkylthiophenes for Organic Light Emitting Diodes
Chiral polyalkylthiophenes are noncentrosymmetric organic materials which can be used
both in second harmonic-generation devices and in polarized light emitting diodes. In this work
we present the synthesis and the characterization of a polyalkylthiophene with a chiral center
very close to the conjugated backbone: poly(3-[(S)-2-methylbutyl]thiophene) (PMBT). Circular
dichroism (CD) measurements have been carried out to ascertain the chirality of these materials.
The CD spectra show intense signals both in mixed solvents and in the solid state. The strong
Cotton effect can be associated to a highly ordered aggregated phase whose nature is still under
investigation. We also present the photo and electroluminescence characterization of single layer
light emitting diode (LED) with the following configuration: ITO (Tin Indium Oxide)/PMBT/Al
Structural phase transition and dielectric relaxation in Pb(Zn1/3Nb2/3)O3 single crystals
The structure and the dielectric properties of Pb(Zn1/3Nb2/3)O3 (PZN) crystal
have been investigated by means of high-resolution synchrotron x-ray
diffraction (with an x-ray energy of 32 keV) and dielectric spectroscopy (in
the frequency range of 100 Hz - 1 MHz). At high temperatures, the PZN crystal
exhibits a cubic symmetry and polar nanoregions inherent to relaxor
ferroelectrics are present, as evidenced by the single (222) Bragg peak and by
the noticeable tails at the basis of the peak. At low temperatures, in addition
to the well-known rhombohedral phase, another low-symmetry, probably
ferroelectric, phase is found. The two phases coexist in the form of mesoscopic
domains. The para- to ferroelectric phase transition is diffused and observed
between 325 and 390 K, where the concentration of the low-temperature phases
gradually increases and the cubic phase disappears upon cooling. However, no
dielectric anomalies can be detected in the temperature range of diffuse phase
transition. The temperature dependence of the dielectric constant show the
maximum at higher temperature (Tm = 417 - 429 K, depending on frequency) with
the typical relaxor dispersion at T < Tm and the frequency dependence of Tm
fitted to the Vogel-Fulcher relation. Application of an electric field upon
cooling from the cubic phase or poling the crystal in the ferroelectric phase
gives rise to a sharp anomaly of the dielectric constant at T 390 K and
diminishes greatly the dispersion at lower temperatures, but the dielectric
relaxation process around Tm remains qualitatively unchanged. The results are
discussed in the framework of the present models of relaxors and in comparison
with the prototypical relaxor ferroelectric Pb(Mg1/3Nb2/3)O3.Comment: PDF file, 13 pages, 6 figures collected on pp.12-1
On the use of an appropriate TdT-mediated dUTP-biotin nick end labeling assay to identify apoptotic cells.
Apoptosis is an essential cellular mechanism involved in many processes such as embryogenesis, metamorphosis, and tissue homeostasis. DNA fragmentation is one of the key markers of this form of cell death. DNA fragmentation is executed by endogenous endonucleases such as caspase-activated DNase (CAD) in caspase-dependent apoptosis. The TUNEL (TdT-mediated dUTP-biotin nick end labeling) technique is the most widely used method to identify apoptotic cells in a tissue or culture and to assess drug toxicity. It is based on the detection of 3'-OH termini that are labeled with dUTP by the terminal deoxynucleotidyl transferase. Although the test is very reliable and sensitive in caspase-dependent apoptosis, it is completely useless when cell death is mediated by pathways involving DNA degradation that generates 3'-P ends as in the LEI/L-DNase II pathway. Here, we propose a modification in the TUNEL protocol consisting of a dephosphorylation step prior to the TUNEL labeling. This allows the detection of both types of DNA breaks induced during apoptosis caspase-dependent and independent pathways, avoiding underestimating the cell death induced by the treatment of interest
Dynamic Ligand Discrimination in the Notch Signaling Pathway
The Notch signaling pathway comprises multiple ligands that are used in distinct biological contexts. In principle, different ligands could activate distinct target programs in signal-receiving cells, but it is unclear how such ligand discrimination could occur. Here, we show that cells use dynamics to discriminate signaling by the ligands Dll1 and Dll4 through the Notch1 receptor. Quantitative single-cell imaging revealed that Dll1 activates Notch1 in discrete, frequency-modulated pulses that specifically upregulate the Notch target gene Hes1. By contrast, Dll4 activates Notch1 in a sustained, amplitude-modulated manner that predominantly upregulates Hey1 and HeyL. Ectopic expression of Dll1 or Dll4 in chick neural crest produced opposite effects on myogenic differentiation, showing that ligand discrimination can occur in vivo. Finally, analysis of chimeric ligands suggests that ligand-receptor clustering underlies dynamic encoding of ligand identity. The ability of the pathway to utilize ligands as distinct communication channels has implications for diverse Notch-dependent processes
General Non-equilibrium Theory of Colloid Dynamics
A non-equilibrium extension of Onsager's canonical theory of thermal
fluctuations is employed to derive a self-consistent theory for the description
of the statistical properties of the instantaneous local concentration profile
n(r,t) of a colloidal liquid in terms of the coupled time evolution equations
of its mean value n(r,t) and of the covariance {\sigma}(r,r';t) \equiv
of its fluctuations {\delta}n(r, t) = n(r, t) -
n(r, t). These two coarse-grained equations involve a local mobility function
b(r, t) which, in its turn, is written in terms of the memory function of the
two-time correlation function C(r, r' ; t, t') \equiv <{\delta}n(r,
t){\delta}n(r',t')>. For given effective interactions between colloidal
particles and applied external fields, the resulting self-consistent theory is
aimed at describing the evolution of a strongly correlated colloidal liquid
from an initial state with arbitrary mean and covariance n^0(r) and
{\sigma}^0(r,r') towards its equilibrium state characterized by the equilibrium
local concentration profile n^(eq)(r) and equilibrium covariance
{\sigma}^(eq)(r,r').
This theory also provides a general theoretical framework to describe
irreversible processes associated with dynamic arrest transitions, such as
aging, and the effects of spatial heterogeneities
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