281 research outputs found
Resilience to DDoS attacks
Tese de mestrado, Segurança Informática, 2022, Universidade de Lisboa, Faculdade de CiênciasDistributed Denial-of-Service (DDoS) is one of the most common cyberattack used by malicious
actors. It has been evolving over the years, using more complex techniques to increase its attack power
and surpass the current defense mechanisms.
Due to the existent number of different DDoS attacks and their constant evolution, companies need
to be constantly aware of developments in DDoS solutions
Additionally, the existence of multiple solutions, also makes it hard for companies to decide which
solution best suits the company needs and must be implemented.
In order to help these companies, our work focuses in analyzing the existing DDoS solutions, for
companies to implement solutions that can lead to the prevention, detection, mitigation, and tolerance
of DDoS attacks, with the objective of improving the robustness and resilience of the companies against
DDoS attacks.
In our work, it is presented and described different DDoS solutions, some need to be purchased and
other are open-source or freeware, however these last solutions require more technical expertise by
cybersecurity agents.
To understand how cybersecurity agents protect their companies against DDoS attacks, nowadays, it
was built a questionnaire and sent to multiple cybersecurity agents from different countries and
industries.
As a result of the study performed about the different DDoS solutions and the information gathered
from the questionnaire, it was possible to create a DDoS framework to guide companies in the decisionmaking process of which DDoS solutions best suits their resources and needs, in order to ensure that
companies can develop their robustness and resilience to fight DDoS attacks.
The proposed framework it is divided in three phases, in which the first and second phase is to
understand the company context and the asset that need to be protected. The last phase is where we
choose the DDoS solution based on the information gathered in the previous phases. We analyzed and
presented for each DDoS solutions, which DDoS attack types they can prevent, detect and/or mitigate
Complete metrics with constant fractional higher order -curvature on the punctured sphere
This manuscript is devoted to constructing complete metrics with constant
higher fractional curvature on punctured spheres with finitely many isolated
singularities. Analytically, this problem is reduced to constructing singular
solutions for a conformally invariant integro-differential equation that
generalizes the critical GJMS problem. Our proof follows the earlier
construction in Ao {\it et al.} \cite{MR3694645}, based on a gluing method,
which we briefly describe. Our main contribution is to provide a unified
approach for fractional and higher order cases. This method relies on proving
Fredholm properties for the linearized operator around a suitably chosen
approximate solution. The main challenge in our approach is that the solutions
to the related blow-up limit problem near isolated singularities need to be
fully classified; hence we are not allowed to use a simplified ODE method. To
overcome this issue, we approximate solutions near each isolated singularity by
a family of half-bubble tower solutions. Then, we reduce our problem to solving
an (infinite-dimensional) Toda-type system arising from the interaction between
the bubble towers at each isolated singularity. Finally, we prove that this
system's solvability is equivalent to the existence of a balanced
configuration.Comment: 58 page
MUFIN: Improving Neural Repair Models with Back-Translation
Automated program repair is the task of automatically repairing software
bugs. A promising direction in this field is self-supervised learning, a
learning paradigm in which repair models are trained without commits
representing pairs of bug/fix. In self-supervised neural program repair, those
bug/fix pairs are generated in some ways. The main problem is to generate
interesting and diverse pairs that maximize the effectiveness of training. As a
contribution to this problem, we propose to use back-translation, a technique
coming from neural machine translation. We devise and implement MUFIN, a
back-translation training technique for program repair, with specifically
designed code critics to select high-quality training samples. Our results show
that MUFIN's back-translation loop generates valuable training samples in a
fully automated, self-supervised manner, generating more than half-a-million
pairs of bug/fix. The code critic design is key because of a fundamental
trade-off between how restrictive a critic is and how many samples are
available for optimization during back-translation
LRRK2 secretion in exosomes is regulated by 14-3-3
Mutations in the leucine-rich repeat kinase 2 (LRRK2) gene cause late-onset Parkinson's disease (PD). Emerging evidence suggests a role for LRRK2 in the endocytic pathway. Here, we show that LRRK2 is released in extracellular microvesicles (i.e. exosomes) from cells that natively express LRRK2. LRRK2 localizes to collecting duct epithelial cells in the kidney that actively secrete exosomes into urine. Purified urinary exosomes contain LRRK2 protein that is both dimerized and phosphorylated. We provide a quantitative proteomic profile of 1673 proteins in urinary exosomes and find that known LRRK2 interactors including 14-3-3 are some of the most abundant exosome proteins. Disruption of the 14-3-3 LRRK2 interaction with a 14-3-3 inhibitor or through acute LRRK2 kinase inhibition potently blocks LRRK2 release in exosomes, but familial mutations in LRRK2 had no effect on secretion. LRRK2 levels were overall comparable but highly variable in urinary exosomes derived from PD cases and age-matched controls, although very high LRRK2 levels were detected in some PD affected cases. We further characterized LRRK2 exosome release in neurons and macrophages in culture, and found that LRRK2-positive exosomes circulate in cerebral spinal fluid (CSF). Together, these results define a pathway for LRRK2 extracellular release, clarify one function of the LRRK2 14-3-3 interaction and provide a foundation for utilization of LRRK2 as a biomarker in clinical trial
Cu(In,Ga)Se2 based ultrathin solar cells: the pathway from lab rigid to large scale flexible technology
For the first time, the incorporation of interface passivation structures in ultrathin Cu(In,Ga)Se2 (CIGS) based solar cells is shown in a flexible lightweight stainless-steel substrate. The fabrication was based on an industry scalable lithography technique - nanoimprint lithography (NIL) - for a 15x15 cm2 dielectric layer patterning, needed to reduce optoelectronic losses at the rear interface. The nanopatterning schemes are usually developed by lithographic techniques or by processes with limited scalability and reproducibility (nanoparticle lift-off, spin-coating, etc). However, in this work the dielectric layer is patterned using NIL, a low cost, large area, high resolution, and high throughput technique. To assess the NIL performance, devices with a NIL nanopatterned dielectric layer are benchmarked against electron-beam lithography (EBL) patterning, using rigid substrates. Up to now, EBL is considered the most reliable technique for patterning laboratory samples. The device patterned by NIL shows similar light to power conversion efficiency average values compared to the EBL patterned device - 12.6 % vs 12.3 %, respectively - highlighting the NIL potential for application in the solar cell sector. Moreover, the impact of the lithographic processes, such as different etch by-products, in the rigid solar cells’ figures of merit were evaluated from an elemental point of view via X-ray Photoelectron Spectroscopy and electrically through a Solar Cell Capacitance Simulator (SCAPS) fitting procedure. After an optimised NIL process, the device on stainless-steel achieved an average power conversion efficiency value of 11.7 % - a slightly lower value than the one obtained for the rigid approach, due to additional challenges raised by processing and handling steel substrates, even though scanning transmission electron microscopy did not show any clear evidence of impurity diffusion towards the absorber. Notwithstanding, time-resolved photoluminescence results strongly suggested the presence of additional non-radiative recombination mechanisms in the stainless-steel absorber, which were not detected in the rigid solar cells, and are compatible with elemental diffusion from the substrate. Nevertheless, bending tests on the stainless-steel device demonstrated the mechanical stability of the CIGS-based device up to 500 bending cycles.This work was funded in part by the Fundação para a Ciência e a Tecnologia (FCT) under Grants 2020.04564.BD, IF/00133/2015, PD/BD/142780/2018, SFRH/BD/146776/2019, UIDB/04564/2020 and UIDP/04564/2020, 2020.07073.BD, as well as through the projects NovaCell (PTDC/CTMCTM/28075/2017), CASOLEM (028917) “Correlated Analysis of Inorganic Solar Cells in and outside an Electron Microscope”, and InovSolarCells (PTDC/FISMAC/29696/2017) co-funded by FCT and the ERDF through COMPETE2020. And by the European Union's Horizon 2020 research and innovation 15 programme under the grants agreements N°. 720887 (ARCIGS-M project) and grand agreement N°.715027 (Uniting PV). The Special Research Fund (BOF) of Hasselt University is also acknowledged. P. Salomé and P. A. Fernandes would like to acknowledge FCT for the support of the project FCT UIDB/04730/2020. This work was developed within the scope of the project i3N, UIDB/50025/2020 & UIDP/50025/2020, financed by national funds through the FCT/MEC. The authors also acknowledge the support of Carlos Calaza in the fabrication for the 200 mm Si point contact stamp.info:eu-repo/semantics/publishedVersio
Precision measurement of cardiac structure and function in cardiovascular magnetic resonance using machine learning
BACKGROUND: Measurement of cardiac structure and function from images (e.g. volumes, mass and derived parameters such as left ventricular (LV) ejection fraction [LVEF]) guides care for millions. This is best assessed using cardiovascular magnetic resonance (CMR), but image analysis is currently performed by individual clinicians, which introduces error. We sought to develop a machine learning algorithm for volumetric analysis of CMR images with demonstrably better precision than human analysis. METHODS: A fully automated machine learning algorithm was trained on 1923 scans (10 scanner models, 13 institutions, 9 clinical conditions, 60,000 contours) and used to segment the LV blood volume and myocardium. Performance was quantified by measuring precision on an independent multi-site validation dataset with multiple pathologies with n = 109 patients, scanned twice. This dataset was augmented with a further 1277 patients scanned as part of routine clinical care to allow qualitative assessment of generalization ability by identifying mis-segmentations. Machine learning algorithm ('machine') performance was compared to three clinicians ('human') and a commercial tool (cvi42, Circle Cardiovascular Imaging). FINDINGS: Machine analysis was quicker (20 s per patient) than human (13 min). Overall machine mis-segmentation rate was 1 in 479 images for the combined dataset, occurring mostly in rare pathologies not encountered in training. Without correcting these mis-segmentations, machine analysis had superior precision to three clinicians (e.g. scan-rescan coefficients of variation of human vs machine: LVEF 6.0% vs 4.2%, LV mass 4.8% vs. 3.6%; both P < 0.05), translating to a 46% reduction in required trial sample size using an LVEF endpoint. CONCLUSION: We present a fully automated algorithm for measuring LV structure and global systolic function that betters human performance for speed and precision
Processing and characterization of chitosan microspheres to be used as templates for layer-by-layer assembly
Chitosan (Ch) microspheres have been developed
by precipitation method, cross-linked with glutaraldehyde
and used as a template for layer-by-layer (LBL)
deposition of two natural polyelectrolytes. Using a LBL
methodology, Ch microspheres were alternately coated with
hyaluronic acid (HA) and Ch under mild conditions. The
roughness of the Ch-based crosslinked microspheres was
characterized by atomic force microscopy (AFM). Morphological
characterization was performed by environmental
scanning electron microscopy (ESEM), scanning
electron microscopy (SEM) and stereolight microscopy.
The swelling behaviour of the microspheres demonstrated
that the ones with more bilayers presented the highest water
uptake and the uncoated cross-linked Ch microspheres
showed the lowest uptake capability. Microspheres presented
spherical shape with sizes ranging from 510 to
840 lm. ESEM demonstrated that a rougher surface with
voids is formed in multilayered microspheres caused by the
irregular stacking of the layers. A short term mechanical
stability assay was also performed, showing that the LBL
procedure with more than five bilayers of HA/Ch over Ch
cross-linked microspheres provide higher mechanical
stability
The Long-Baseline Neutrino Experiment: Exploring Fundamental Symmetries of the Universe
The preponderance of matter over antimatter in the early Universe, the
dynamics of the supernova bursts that produced the heavy elements necessary for
life and whether protons eventually decay --- these mysteries at the forefront
of particle physics and astrophysics are key to understanding the early
evolution of our Universe, its current state and its eventual fate. The
Long-Baseline Neutrino Experiment (LBNE) represents an extensively developed
plan for a world-class experiment dedicated to addressing these questions. LBNE
is conceived around three central components: (1) a new, high-intensity
neutrino source generated from a megawatt-class proton accelerator at Fermi
National Accelerator Laboratory, (2) a near neutrino detector just downstream
of the source, and (3) a massive liquid argon time-projection chamber deployed
as a far detector deep underground at the Sanford Underground Research
Facility. This facility, located at the site of the former Homestake Mine in
Lead, South Dakota, is approximately 1,300 km from the neutrino source at
Fermilab -- a distance (baseline) that delivers optimal sensitivity to neutrino
charge-parity symmetry violation and mass ordering effects. This ambitious yet
cost-effective design incorporates scalability and flexibility and can
accommodate a variety of upgrades and contributions. With its exceptional
combination of experimental configuration, technical capabilities, and
potential for transformative discoveries, LBNE promises to be a vital facility
for the field of particle physics worldwide, providing physicists from around
the globe with opportunities to collaborate in a twenty to thirty year program
of exciting science. In this document we provide a comprehensive overview of
LBNE's scientific objectives, its place in the landscape of neutrino physics
worldwide, the technologies it will incorporate and the capabilities it will
possess.Comment: Major update of previous version. This is the reference document for
LBNE science program and current status. Chapters 1, 3, and 9 provide a
comprehensive overview of LBNE's scientific objectives, its place in the
landscape of neutrino physics worldwide, the technologies it will incorporate
and the capabilities it will possess. 288 pages, 116 figure
The structure of the KtrAB potassium transporter
In bacteria, archaea, fungi and plants the Trk, Ktr and HKT ion transporters are key components of osmotic regulation, pH homeostasis and resistance to drought and high salinity. These ion transporters are functionally diverse: they can function as Na+ or K+ channels and possibly as cation/K+ symporters. They are closely related to potassium channels both at the level of the membrane protein and at the level of the cytosolic regulatory domains. Here we describe the crystal structure of a Ktr K+ transporter, the KtrAB complex from Bacillus subtilis. The structure shows the dimeric membrane protein KtrB assembled with a cytosolic octameric KtrA ring bound to ATP, an activating ligand. A comparison between the structure of KtrAB-ATP and the structures of the isolated full-length KtrA protein with ATP or ADP reveals a ligand-dependent conformational change in the octameric ring, raising new ideas about the mechanism of activation in these transporters.We are grateful for access to ID14-1/ID14-4/ID-29 at ESRF (through the Portuguese BAG), PXII at SLS, XRD1 at ELETTRA and PROXIMA1 at SOLEIL and thank the respective support staff. A.S. was supported by FEBS (Long term fellowship). This work was funded by EMBO (Installation grant), by FEDER funds through the Operational Competitiveness Program-COMPETE and by National Funds through FCT-Fundacao para a Ciencia e a Tecnologia under the projects FCOMP-01-0124-FEDER-022718 (PEst-C/SAU/LA0002/2011), FCOMP-01-0124-FEDER-009028 (PTDC/BIA-PRO/099861/2008) and FCOMP-01-0124-FEDER-010781 (PTDC/QUI-BIQ/105342/2008). We also thank G. Gabant and M. Cadene at the 'Plateforme de Spectrometrie de Masse' at CBM, CNRS, Orleans for mass spectrometry analysis, and C. Harley for critical reading of the manuscript
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