3,928 research outputs found
Doppler Effects from Bending of Light Rays in Curved Space-Times
We study Doppler effects in curved space-time, i.e. the frequency shifts
induced on electromagnetic signals propagating in the gravitational field. In
particular, we focus on the frequency shift due to the bending of light rays in
weak gravitational fields. We consider, using the PPN formalism, the
gravitational field of an axially symmetric distribution of mass. The zeroth
order, i.e. the sphere, is studied then passing to the contribution of the
quadrupole moment, and finally to the case of a rotating source. We give
numerical estimates for situations of physical interest, and by a very
preliminary analysis, we argue that analyzing the Doppler effect could lead, in
principle, in the foreseeable future, to the measurement of the quadrupole
moment of the giant planets of the Solar System.Comment: 16 pages, 2 EPS figures; to appear in the International Journal of
Modern Physics
SoK: A Unified Data Model for Smart Contract Vulnerability Taxonomies
Modern blockchains support the execution of application-level code in the form of smart contracts, allowing developers to devise complex Distributed Applications (DApps). Smart contracts are typically written in high-level languages, such as Solidity, and after deployment on the blockchain, their code is executed in a distributed way in response to transactions or calls from other smart contracts. As a common piece of software, smart contracts are susceptible to vulnerabilities, posing security threats to DApps and their users.
The community has already made many different proposals involving taxonomies related to smart contract vulnerabilities. In this paper, we try to systematize such proposals, evaluating their common traits and main discrepancies. A major limitation emerging from our analysis is the lack of a proper formalization of such taxonomies, making hard their adoption within, e.g., tools and disfavoring their improvement over time as a community-driven effort. We thus introduce a novel data model that clearly defines the key entities and relationships relevant to smart contract vulnerabilities. We then show how our data model and its preliminary instantiation can effectively support several valuable use cases, such as interactive exploration of the taxonomy, integration with security frameworks for effective tool orchestration, and statistical analysis for performing longitudinal studies
Two-color holography concept (T-CHI)
The Material Processing in the Space Program of NASA-MSFC was active in developing numerous optical techniques for the characterization of fluids in the vicinity of various materials during crystallization and/or solidification. Two-color holographic interferometry demonstrates that temperature and concentration separation in transparent (T-CHI) model systems is possible. The experiments were performed for particular (succinonitrile) systems. Several solutions are possible in Microgravity Sciences and Applications (MSA) experiments on future Shuttle missions. The theory of the T-CHI concept is evaluated. Although particular cases are used for explanations, the concepts developed will be universal. A breadboard system design is also presented for ultimate fabrication and testing of theoretical findings. New developments in holography involving optical fibers and diode lasers are also incorporated
Topology-Induced Critical Current Enhancement in Josephson Networks
We investigate the properties of Josephson junction networks with
inhomogeneous architecture. The networks are shaped as "quare comb" planar
lattices on which Josephson junctions link superconducting islands arranged in
the plane to generate the pertinent topology. Compared to the behavior of
reference linear arrays, the temperature dependencies of the Josephson currents
of the branches of the network exhibit relevant differences. The observed
phenomena evidence new and surprising behavior of superconducting Josephson
arrays as well as remarkable similarities with bosonic junction arrays.Comment: improved figures (added magnetic pattern and single junction
switching) some changes in the text and in the titl
Precision Medicine in Targeted Therapies for Severe Asthma: Is There Any Place for "omics" Technology?
According to the current guidelines, severe asthma still represents a controversial topic in terms of definition and management. The introduction of novel biological therapies as a treatment option for severe asthmatic patients paved the way to a personalized approach, which aims at matching the appropriate therapy with the different asthma phenotypes. Traditional asthma phenotypes have been decomposing by an increasing number of asthma subclasses based on functional and physiopathological mechanisms. This is possible thanks to the development and application of different omics technologies. The new asthma classification patterns, particularly concerning severe asthma, include an increasing number of endotypes that have been identified using new omics technologies. The identification of endotypes provides new opportunities for the management of asthma symptoms, but this implies that biological therapies which target inflammatory mediators in the frame of specific patterns of inflammation should be developed. However, the pathway leading to a precision approach in asthma treatment is still at its beginning. The aim of this review is providing a synthetic overview of the current asthma management, with a particular focus on severe asthma, in the light of phenotype and endotype approach, and summarizing the current knowledge about "omics" science and their therapeutic relevance in the field of bronchial asthma
Towards precision medicine: The application of omics technologies in asthma management
Asthma is a chronic obstructive respiratory disease characterised by bronchial inflammation. Its biological and clinical features have been widely explored and a number of pharmacological treatments are currently available. Currently several aspects of asthma pathophysiological background remain unclear, and this is represent a limitation for the traditional asthma phenotype approach. In this scenario, the identification of new molecular and clinical biomarkers may be helpful in order to better understand the disease, define specific diagnostic tools and highlight relevant novel targets for pharmacological treatments. Omics technologies offer innovative research tools for addressing the above mentioned goals. However, there is still a lot to do both in the fields of basic research and in the clinical application. Recently, genome-wide association studies, microRNAs and proteomics are contributing to enrich the available data for the identification of new asthma biomarkers. A precise approach to the patient with asthma, particularly with severe uncontrolled asthma, requires new and specific therapeutic targets, but also proper tools able to drive the clinician in tailoring the treatment. On the other hand, there is a need of predictors to treatment's response, particularly in the field of biological drugs, whose sustainability implies a correct and precise selection of the patients. Translating acquired omics knowledge in clinical practice may address the unmet needs described above, but large-scale studies are required in order to confirm their relevance and effectiveness in daily practice. Thus in our opinion the application of omics is still lagging in the real-life setting
An Interoperable Electronic Health Record System for Clinical Cardiology
Currently in hospitals, there are several separate information systems that manage, very often autonomously, the patient’s personal, clinical and diagnostic data. An electronic health record system has been specifically developed for a cardiology ward and it has been designed “ab initio” to be fully integrated into the hospital information system and to exchange data with the regional health information infrastructure. All documents have been given as Health Level 7 (HL7) clinical document architecture and messages are sent as HL7-Version 2 (V2) and/or HL7 Fast Healthcare Interoperability Resources (FHIR). Specific decision support sections for specific aspects have also been included. The system has been used for more than three years with a good level of satisfaction by the users. In the future, the system can be the basis for secondary use for clinical studies, further decision support systems and clinical trials
Caracterização de linhagens comerciais de café através de marcadores moleculares.
Estudos sobre a diversidade genética de espécies com finalidade de melhoramento genético representam importante preocupação dos melhoristas. Diversas técnicas moleculares têm permitido revelar uma diversidade genética presente no genoma que até então era desconhecida pelos cientistas. Muitas espécies de interesse agronômico têm sido alvo de estudos que abordam a diversidade genética em nível molecular. De uma maneira geral, os resultados obtidos a partir do uso dos marcadores têm sido bastante satisfatórios, principalmente para aquelas espécies que apresentam ampla base genética e insuficiente número de descritores botânicos para diferenciação de genótipos, como é o caso da mandioca. A base genética formada pelos cultivares de C. arabica, principal espécie cultivada, é considerada estreita. Em relação ao Brasil, principal produtor mundial desta cultura, a própria história explica em parte a ausência de variação genética nos materiais atualmente em cultivo. Historicamente, as primeiras plantações de café formaram-se há mais de dois séculos a partir de poucas plantas, constituindo material muito uniforme e de pouca variabilidade genética. De fato, estudos sobre a diversidade genética de cafeeiros em cultivo realizados no IAC utilizando descritores botânicos e agronômicos têm revelado baixo nível de variação genética entre as diferentes linhagens que compõem um cultivar. Entre diferentes cultivares esta variação é mais notória, mão não tão acentuada como se pensava, mesmo quando diferentes espécies participam da genealogia destes cultivares. Desta maneira, este trabalho teve como objetivo principal a avaliação das técnicas de RAPD e AFLP para a identificação e caracterização de diversas linhagens comerciais de C. arabica selecionadas pelo IAC. Os resultados obtidos com estes marcadores confirmam os dados obtidos anteriormente de que a variabilidade genética entre as linhagens é pequena. Além disso, os dados sugerem que a técnica de RAPD não é eficiente para a identificação e determinação da distância genética entre as linhagens avaliadas, apesar de representar uma ferramenta adequada para avaliação da variabilidade no cafeeiro. No entanto, embora o nível de variação observado através dos marcadores moleculares seja baixo, sabe-se que estas linhagens apresentam comportamento agronômico bastante diferenciado. Isso nos leva a pensar que poucos genes diferenciam os principais materiais genéticos de cafeeiro de importância agronômica e que o uso de marcadores moleculares para estudos de diversidade genética e localização de genes de interesse agronômico deve ser repensada
The Sagnac Effect in curved space-times from an analogy with the Aharonov-Bohm Effect
In the context of the natural splitting, the standard relative dynamics can
be expressed in terms of gravito-electromagnetic fields, which allow to
formally introduce a gravito-magnetic Aharonov-Bohm effect. We showed elsewhere
that this formal analogy can be used to derive the Sagnac effect in flat
space-time as a gravito-magnetic Aharonov-Bohm effect. Here, we generalize
those results to study the General Relativistic corrections to the Sagnac
effect in some stationary and axially symmetric geometries, such as the
space-time around a weakly gravitating and rotating source, Kerr space-time,
G\"{odel} universe and Schwarzschild space-time.Comment: 14 pages, 1 EPS figure, LaTeX, accepted for publication in General
Relativity and Gravitatio
NANO-SQUIDs based on niobium Dayem bridges for nanoscale applications
Abstract. We report on the design, the fabrication and the performance of an integrated
magnetic nano-sensor based on niobium dc-SQUID (Superconducting QUantum Interference
Device) for nanoscale applications is presented. The nano-sensors are based on nanometric
niobium constrictions (Dayem bridges) inserted in a square loop having a side length of 200
nm. Measurements of voltage-flux characteristic, flux to voltage transfer factor and noise
performances are reported. In small signal mode, the sensors have shown a magnetic flux noise
spectral density of 1.5 µΦ0/Hz1/2 corresponding to a spin sensitivity in unit of Bohr magneton
of 60 spin/Hz1/2. Supercurrent decay measurements of these devices are also reported. Such
measurements provide useful information for applications which employ the SQUID as a
trigger where the sensor works on the zero voltage state. The experimental data, have shown an
intrinsic current fluctuation less than 0.2% of the critical current at liquid helium temperature,
corresponding to an intrinsic sensor magnetic flux resolution of a few mΦ0. In view of the
nano-SQUID employments in the detection of small spin populations, the authors calculated
the spin sensitivity and the magnetic response relative to the single spin, as a function of its
position within the SQUID hole. The results show that the SQUID response depends strongly
on the spin position
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