77 research outputs found
In situ photoacoustic spectroscopy of phycobiliproteins in Gracilaria chilensis
peer reviewedPhycobiliproteins, the main polypeptidic components of the phycobilisomes (PBS), are biolog-
ical macromolecules arranged in complex interaction systems to perform light harvesting and conduction.
The optical properties of these systems can hardly be studied by conventional spectroscopic techniques.
Furthermore this techniques also involve laborious chemical extraction methods. Photoacoustic (PA) spec-
troscopy was successfully applied to an in situ study of the phycobiliproteins expression in the eukaryotic
red algae: Gracilaria chilensis
Spacelike Singularities and Hidden Symmetries of Gravity
We review the intimate connection between (super-)gravity close to a
spacelike singularity (the "BKL-limit") and the theory of Lorentzian Kac-Moody
algebras. We show that in this limit the gravitational theory can be
reformulated in terms of billiard motion in a region of hyperbolic space,
revealing that the dynamics is completely determined by a (possibly infinite)
sequence of reflections, which are elements of a Lorentzian Coxeter group. Such
Coxeter groups are the Weyl groups of infinite-dimensional Kac-Moody algebras,
suggesting that these algebras yield symmetries of gravitational theories. Our
presentation is aimed to be a self-contained and comprehensive treatment of the
subject, with all the relevant mathematical background material introduced and
explained in detail. We also review attempts at making the infinite-dimensional
symmetries manifest, through the construction of a geodesic sigma model based
on a Lorentzian Kac-Moody algebra. An explicit example is provided for the case
of the hyperbolic algebra E10, which is conjectured to be an underlying
symmetry of M-theory. Illustrations of this conjecture are also discussed in
the context of cosmological solutions to eleven-dimensional supergravity.Comment: 228 pages. Typos corrected. References added. Subject index added.
Published versio
Higher spin extension of cosmological spacetimes in 3D: asymptotically flat behaviour with chemical potentials and thermodynamics
A generalized set of asymptotic conditions for higher spin gravity without
cosmological constant in three spacetime dimensions is constructed. They
include the most general temporal components of the gauge fields that
manifestly preserve the original asymptotic higher spin extension of the
BMS algebra, with the same central charge. By virtue of a suitable
permissible gauge choice, it is shown that this set can be directly recovered
as a limit of the boundary conditions that have been recently constructed in
the case of negative cosmological constant, whose asymptotic symmetries are
spanned by two copies of the centrally-extended W algebra. Since the
generalized asymptotic conditions allow to incorporate chemical potentials
conjugated to the higher spin charges, a higher spin extension of locally flat
cosmological spacetimes becomes naturally included within the set. It is shown
that their thermodynamic properties can be successfully obtained exclusively in
terms of gauge fields and the topology of the Euclidean manifold, which is
shown to be the one of a solid torus, but with reversed orientation as compared
with one of the black holes. It is also worth highlighting that regularity of
the fields can be ensured through a procedure that does not require an explicit
matrix representation of the entire gauge group. In few words, we show that the
temporal components of generalized dreibeins can be consistently gauged away,
which partially fixes the chemical potentials, so that the remaining conditions
can just be obtained by requiring the holonomy of the generalized spin
connection along a thermal circle to be trivial. The extension of the
generalized asymptotically flat behaviour to the case of spins is also
discussed.Comment: 33 pages, one figure. Talk given at the "Meeting on the horizon",
Valparaiso, Chile, March 201
Improved functionalization of oleic acid-coated iron oxide nanoparticles for biomedical applications
Superparamagnetic iron oxide nanoparticles
can providemultiple benefits for biomedical applications
in aqueous environments such asmagnetic separation or
magnetic resonance imaging. To increase the colloidal
stability and allow subsequent reactions, the introduction
of hydrophilic functional groups onto the particles’
surface is essential. During this process, the original
coating is exchanged by preferably covalently bonded
ligands such as trialkoxysilanes. The duration of the
silane exchange reaction, which commonly takes more
than 24 h, is an important drawback for this approach. In
this paper, we present a novel method, which introduces
ultrasonication as an energy source to dramatically
accelerate this process, resulting in high-quality waterdispersible nanoparticles around 10 nmin size. To prove
the generic character, different functional groups were
introduced on the surface including polyethylene glycol
chains, carboxylic acid, amine, and thiol groups. Their
colloidal stability in various aqueous buffer solutions as
well as human plasma and serum was investigated to
allow implementation in biomedical and sensing
applications.status: publishe
Effect of sitagliptin on cardiovascular outcomes in type 2 diabetes
BACKGROUND: Data are lacking on the long-term effect on cardiovascular events of adding sitagliptin, a dipeptidyl peptidase 4 inhibitor, to usual care in patients with type 2 diabetes and cardiovascular disease. METHODS: In this randomized, double-blind study, we assigned 14,671 patients to add either sitagliptin or placebo to their existing therapy. Open-label use of antihyperglycemic therapy was encouraged as required, aimed at reaching individually appropriate glycemic targets in all patients. To determine whether sitagliptin was noninferior to placebo, we used a relative risk of 1.3 as the marginal upper boundary. The primary cardiovascular outcome was a composite of cardiovascular death, nonfatal myocardial infarction, nonfatal stroke, or hospitalization for unstable angina. RESULTS: During a median follow-up of 3.0 years, there was a small difference in glycated hemoglobin levels (least-squares mean difference for sitagliptin vs. placebo, -0.29 percentage points; 95% confidence interval [CI], -0.32 to -0.27). Overall, the primary outcome occurred in 839 patients in the sitagliptin group (11.4%; 4.06 per 100 person-years) and 851 patients in the placebo group (11.6%; 4.17 per 100 person-years). Sitagliptin was noninferior to placebo for the primary composite cardiovascular outcome (hazard ratio, 0.98; 95% CI, 0.88 to 1.09; P<0.001). Rates of hospitalization for heart failure did not differ between the two groups (hazard ratio, 1.00; 95% CI, 0.83 to 1.20; P = 0.98). There were no significant between-group differences in rates of acute pancreatitis (P = 0.07) or pancreatic cancer (P = 0.32). CONCLUSIONS: Among patients with type 2 diabetes and established cardiovascular disease, adding sitagliptin to usual care did not appear to increase the risk of major adverse cardiovascular events, hospitalization for heart failure, or other adverse events
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