520 research outputs found
Density-functional study of defects in two-dimensional circular nematic nanocavities
We use density--functional theory to study the structure of two-dimensional
defects inside a circular nematic nanocavity. The density, nematic order
parameter, and director fields, as well as the defect core energy and core
radius, are obtained in a thermodynamically consistent way for defects with
topological charge (with radial and tangential symmetries) and .
An independent calculation of the fluid elastic constants, within the same
theory, allows us to connect with the local free--energy density predicted by
elastic theory, which in turn provides a criterion to define a defect core
boundary and a defect core free energy for the two types of defects. The radial
and tangential defects turn out to have very different properties, a feature
that a previous Maier--Saupe theory could not account for due to the simplified
nature of the interactions --which caused all elastic constants to be equal. In
the case with two defects in the cavity, the elastic r\'egime cannot
be reached due to the small radii of the cavities considered, but some trends
can already be obtained.Comment: 9 figures. Accepted for publication in liquid crystal
Expert System Design for Sewage Treatment Plant
Peer ReviewedPostprint (published version
Capillary and anchoring effects in thin hybrid nematic films and connection with bulk behavior
By means of a molecular model, we examine hybrid nematic films with
antagonistic anchoring angles where one of the surfaces is in the strong
anchoring regime. If anchoring at the other surface is weak, and in the absence
of wetting by the isotropic phase, the anchoring transition may interact with
the capillary isotropic-nematic transition in interesting ways. For general
anchoring conditions on this surface we confirm the existence of the step-tilt,
biaxial phase and the associated transition to the linear,
constant-tilt-rotation, configuration. The step-like phase is connected with
the bulk isotropic phase for increasing film thickness so that the latter
transition is to be interpreted as the capillary isotropic-nematic transition.
Finally, we suggest possible global surface phase diagrams.Comment: 7 pages, 5 figure
Dissecting the functional behavior of the differentially phosphorylated prolyl isomerase, Pin1
Protein post‐translational modifications (PTMs) play an intricate role in a diverse range of cellular processes creating a complex PTM code that governs cell homeostasis. Understanding the molecular build‐up and the critical factors regulating this PTM code is essential for targeted therapeutic design whereby PTM mis‐regulation is prevalent. Here, we focus on Pin1, a peptidyl‐prolyl cis‐trans isomerase whose regulatory function is altered by a diverse range of PTMs. Through employing advanced mass spectrometry techniques in combination with fluorescence polarization and enzyme activity assays, we elucidate the impact of combinatorial phosphorylation on Pin1 function. Moreover, two phosphorylation sites were identified whereby Ser71 phosphorylation preceded Ser16 phosphorylation, leading to the deactivation of Pin1's prolyl isomerase activity before affecting substrate binding. Together, these findings shed light on the regulatory mechanisms underlying Pin1 function and emphasize the importance of understanding PTM landscapes in health and disease
Extreme-ultraviolet structured beams via high harmonic generation
Funding European Research Council (851201); Ministerio de Ciencia de Innovación y Universidades, Agencia Estatal de Investigaci ́on and European Social Fund (PID2019106910GB-I00, RYC-2017-22745); Junta de Castilla y León and FEDER Funds (SA287P18); Université ParisSaclay (2012-0333TOASIS, 50110000724-OPTX, PhOM REC-2019-074-MAOHAm); Conseil Régional, I ˆle-de-France (501100003990); Barcelona Supercomputing Center (FI2020-3-0013).Vigorous efforts to harness the topological properties of light have enabled a multitude of novel applications. Translating the applications of structured light to higher spatial and temporal resolutions mandates their controlled generation, manipulation, and thorough characterization in the short-wavelength regime. Here, we resort to high-order harmonic generation (HHG) in a noble gas to upconvert near-infrared (IR) vector, vortex, and vector-vortex driving beams that are tailored, respectively, in their spin angular momentum (SAM), orbital angular momentum (OAM), and simultaneously in their SAM and OAM. We show that HHG enables the controlled generation of extreme-ultraviolet (EUV) vector beams exhibiting various spatially dependent polarization distributions, or EUV vortex beams with a highly twisted phase. Moreover, we demonstrate the generation of EUV vector-vortex beams (VVB) bearing combined characteristics of vector and vortex beams. We rely on EUV wavefront sensing to unambiguously affirm the topological charge scaling of the HHG beams with the harmonic order. Interestingly, our work shows that HHG allows for a synchronous controlled manipulation of SAM and OAM. These EUV structured beams bring in the promising scenario of their applications at nanometric spatial and sub-femtosecond temporal resolutions using a table-top harmonic source
Service-oriented architecture of adaptive, intelligent data acquisition and processing systems for long-pulse fusion experiments
The data acquisition systems used in long-pulse fusion experiments need to implement data reduction and pattern recognition algorithms in real time. In order to accomplish these operations, it is essential to employ software tools that allow for hot swap capabilities throughout the temporal evolution of the experiments. This is very important because processing needs are not equal during different phases of the experiment. The intelligent test and measurement system (ITMS) developed by UPM and CIEMAT is an example of a technology for implementing scalable data acquisition and processing systems based on PXI and CompactPCI hardware. In the ITMS platform, a set of software tools allows the user to define the processing algorithms associated with the different experimental phases using state machines driven by software events. These state machines are specified using the State Chart XML (SCXML) language. The software tools are developed using JAVA, JINI, an SCXML engine and several LabVIEW applications. Within this schema, it is possible to execute data acquisition and processing applications in an adaptive way. The power of SCXML semantics and the ability to work with XML user-defined data types allow for very easy programming of the ITMS platform. With this approach, the ITMS platform is a suitable solution for implementing scalable data acquisition and processing systems based on a service-oriented model with the ability to easily implement remote participation applications
Attosecond vortex pulse trains
The landscape of ultrafast structured light pulses has recently evolved
driven by the capability of high-order harmonic generation (HHG) to up-convert
orbital angular momentum (OAM) from the infrared to the extreme-ultraviolet
(EUV) spectral regime. Accordingly, HHG has been proven to produce EUV vortex
pulses at the femtosecond timescale. Here we demonstrate the generation of
attosecond vortex pulse trains, i.e. a succession of attosecond pulses with a
helical wavefront, resulting from the synthesis of a comb of EUV high-order
harmonics with the same OAM. By driving HHG with a polarization tilt-angle fork
grating, two spatially separated circularly polarized high-order harmonic beams
with order-independent OAM are created. Our work opens the route towards
attosecond-resolved OAM light-matter interactions.Comment: Main text (1-14 pages) and supplemental material (14-16 pages
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