3,028 research outputs found
Formation of stationary and transient spots on thermionic cathodes and its prevention
Spots on cathodes of high-pressure arc discharges induced by a rapid increase in the arc
current are studied numerically and experimentally. Appearance of stationary and transient
spots is analysed in the context of the general pattern of steady-state modes of current transfer
to thermionic cathodes and their stability. Transient spots are studied in experiments with
COST-529 standard lamps. Modelling and experimental results are in reasonable agreement.
A method to prevent formation of transient spots on cathodes of high-pressure arc discharges
by means of short negative rectangular current pulses is proposed and validated both
numerically and experimentally. Experimental indications are found that the main mechanism
of blackening of burners of HID lamps that accompanies appearance of transient cathode spots
is evaporation of the cathode material and not sputtering.info:eu-repo/semantics/publishedVersio
Computing Different Modes on Cathodes of DC Glow and High-Pressure Arc Discharges: Time-Dependent Versus Stationary Solvers
Complex behavior can appear in the modeling of gas discharges even in apparently simple
steady-state situations. Time-dependent solvers may fail to deliver essential information in
such cases. One of such cases considered in this work is
the 1D DC discharge. The other case is represented by
multiple multidimensional solutions existing in the
theory of DC discharges and describing modes of
current transfer with different patterns of spots on the
cathodes. It is shown that, although some of the
solutions, including those describing beautiful self organized patterns, can be computed by means of a
time-dependent solver, in most examples results of
time-dependent modeling are at best incomplete. In
most examples, numerical stability of the time dependent solver was not equivalent to physical
stability.info:eu-repo/semantics/publishedVersio
A simple model of distribution of current over cathodes of vacuum circuit breakers
There are several hundreds of spots operating
simultaneously on cathodes of vacuum arcs in high-power vac uum circuit breakers. In this work, the spot distribution along
the contact surface is simulated by means of an approach
that is based on the concept of surface density of spots and
represents a natural alternative to tracing individual spots.
An equation governing the evolution of the surface density
of the spots or, equivalently, the distribution of macroscopic
(averaged over individual spots) current density over the cathode
is obtained by generalizing the concept of random walk of a
single cathode spot in low-current vacuum arcs. The model
relies on empirical parameters characterizing individual spots
(the diffusion coefficient of the random motion of cathode spots
and the velocity of drift superimposed over the random motion),
which may be taken from experiments with low-current arcs,
and does not involve adjustable parameters. The model is simple
and physically transparent and correctly reproduces the trends
observed in the experiments under conditions where the cathode
arc attachment is diffuse. The distribution of the macroscopic
current density on the cathode, given by the model, represents
the boundary condition that is required for existing numerical
models of vacuum arcs in high-power vacuum circuit breakers.info:eu-repo/semantics/publishedVersio
Ionic-liquid-based approaches to improve biopharmaceuticals downstream processing and formulation
The emergence of biopharmaceuticals, including proteins, nucleic acids, peptides,
and vaccines, revolutionized the medical field, contributing to significant advances in
the prophylaxis and treatment of chronic and life-threatening diseases. However,
biopharmaceuticals manufacturing involves a set of complex upstream and
downstream processes, which considerably impact their cost. In particular,
despite the efforts made in the last decades to improve the existing technologies,
downstream processing still accounts for more than 80% of the total
biopharmaceutical production cost. On the other hand, the formulation of
biological products must ensure they maintain their therapeutic performance and
long-term stability, while preserving their physical and chemical structure. Ionicliquid (IL)-based approaches arose as a promise alternative, showing the potential to
be used in downstream processing to provide increased purity and recovery yield, as
well as excipients for the development of stable biopharmaceutical formulations.
This manuscript reviews the most important progress achieved in both fields. The
work developed is critically discussed and complemented with a SWOT analysis.publishe
Computational and experimental study of time-averaged characteristics of positive and negative DC corona discharges in point-plane gaps in atmospheric air
The use of stationary solvers instead of approximate
solution methods or time-dependent solvers, which are standard
tools in gas discharge modeling, allows one to develop a very
fast and robust numerical model for studying the time-averaged
characteristics of dc corona discharges. Such an approach is
applied to dc corona discharges in point-plane gaps in ambi ent air. A wide range of currents of both voltage polarities
and various gap lengths are investigated, and the simulation
results are validated by comparing the computed current–voltage
characteristics and spatial distributions of the radiation intensity
with experimental results. Specific features of the numerical and
experimental results at both polarities are discussed.info:eu-repo/semantics/publishedVersio
Boosting antibiotics performance by new formulations with deep eutectic solvents
The critical scenario of antimicrobial resistance to antibiotics highlights the need for improved therapeutics and/or formulations. Herein, we demonstrate that deep eutectic solvents (DES) formulations are very promising to remarkably improve the solubility, stability and therapeutic efficacy of antibiotics, such as ciprofloxacin. DES aqueous solutions enhance the solubility of ciprofloxacin up to 430-fold while extending the antibiotic stability. The developed formulations can improve, by 2 to 4-fold, the susceptibility of Gram-negative (Escherichia coli and Pseudomonas aeruginosa) and Gram-positive (Staphylococcus aureus) bacteria to the antibiotic. They also improve the therapeutic efficacy at concentrations where bacteria present resistance, without promoting tolerance development to ciprofloxacin. Furthermore, the incorporation of DES decreases the toxicity of ciprofloxacin towards immortalized human epidermal keratinocytes (HaCat cells). The results herein reveal the pioneering use of DES in fluoroquinolone-based formulations and their impact on the antibiotic's characteristics and on its therapeutic action.publishe
Sequence-aware multimodal page classification of Brazilian legal documents
The Brazilian Supreme Court receives tens of thousands of cases each
semester. Court employees spend thousands of hours to execute the initial
analysis and classification of those cases -- which takes effort away from
posterior, more complex stages of the case management workflow. In this paper,
we explore multimodal classification of documents from Brazil's Supreme Court.
We train and evaluate our methods on a novel multimodal dataset of 6,510
lawsuits (339,478 pages) with manual annotation assigning each page to one of
six classes. Each lawsuit is an ordered sequence of pages, which are stored
both as an image and as a corresponding text extracted through optical
character recognition. We first train two unimodal classifiers: a ResNet
pre-trained on ImageNet is fine-tuned on the images, and a convolutional
network with filters of multiple kernel sizes is trained from scratch on
document texts. We use them as extractors of visual and textual features, which
are then combined through our proposed Fusion Module. Our Fusion Module can
handle missing textual or visual input by using learned embeddings for missing
data. Moreover, we experiment with bi-directional Long Short-Term Memory
(biLSTM) networks and linear-chain conditional random fields to model the
sequential nature of the pages. The multimodal approaches outperform both
textual and visual classifiers, especially when leveraging the sequential
nature of the pages.Comment: 11 pages, 6 figures. This preprint, which was originally written on 8
April 2021, has not undergone peer review or any post-submission improvements
or corrections. The Version of Record of this article is published in the
International Journal on Document Analysis and Recognition, and is available
online at https://doi.org/10.1007/s10032-022-00406-7 and
https://rdcu.be/cRvv
Multimedia geocoding: the RECOD 2014 approach
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)This work describes the approach proposed by the RECOD team for the Placing Task of MediaEval 2014. This task requires the definition of automatic schemes to assign geographical locations to images and videos. Our approach is based on the use of as much evidences as possible (textual, visual, and/or audio descriptors) to geocode a given image/video. We estimate the location of test items by clustering the geographic coordinates of top-ranked items in one or more ranked lists defined in terms of different criteria.This work describes the approach proposed by the RECOD team for the Placing Task of MediaEval 2014. This task requires the definition of automatic schemes to assign geographical locations to images and videos. Our approach is based on the use of as much e1263FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOCAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIORFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)2013/08645-0 ; 2013/11359-0306580/2012-8 ; 484254/2012-0sem informaçãoMediaEval 2014 Worksho
Moving towards personalized medicine - the broad use of aptamers for targeted theranostic
Aptamers are short, single-stranded oligonucleotides synthesized in vitro from a randomized oligonucleotide library against a specific target. These molecules are capable of binding to a wide range of biological targets with high specificity and affinity. They present great advantages over antibodies with potential applications in research, diagnosis, and therapeutics. Specifically for tumors with late-stage identification and poor prognosis, like pancreatic cancer, the study of novel aptamers holds tremendous potential for cancer diagnosis and treatment. Along with cancer treatment, aptamers have also shown high potential in regulating the immune response and modulating several critical steps of signaling cascades, such as in immune checkpoints. In the context of microbiota and infection, aptamers are being studied to identify microbes and their metabolites. This assessment has the potential to improve the detection and management of infectious diseases while assisting us in better understanding health risks and treatment outcomes by tracking changes in the microbiota. In this review, the potential of aptamers is explored regarding their applications in cancer, immune, and microbiota therapy.Pilar Baylina (P.B.) acknowledges on the behalf of the authors the support of Fundação para a Ciência e Tecnologia (FCT), Portuguese Government, under the Strategic Project Reference: UID/BIM/04293/2013. Pilar Baylina (P.B.) and R.F. was also supported by FEDER/02/SAICT/2020/072560. Ana Cláudia Pereira (A.C.P.) acknowledges the support of Fundação para a Ciência e
Tecnologia (FCT), Portuguese Government, under the Strategic Project Reference: 2022.09032.PTDC. André P. Sousa acknowledges FCT for the PhD grant 2022.12441.BD. Ana C. Rocha acknowledges FCT for the PhD grant 2021.06521.BD. Patrick P. Pais acknowledges FCT for the PhD grant 2021.09498.BD. Susana Ramalho acknowledges LaBMI for the PhD grant LABMI/BI/2021/01 (NEURO4COVID).info:eu-repo/semantics/publishedVersio
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