707 research outputs found
Characteristics of biochemical markers and quality parameters using whole wheat flours in Korean wheat cultivars and lines
Characteristics of biochemical markers and quality parameters using whole wheat flours in Korean wheat cultivars and lines
Tese de doutoramento em Ciências e Tecnologias da Informação, apresentada ao Departamento de Engenharia Informática da Faculdade de Ciências e Tecnologia da Universidade de CoimbraO espectro rádio tem vindo a ser regulado de um modo estático. Ou seja, este encontra-se essencialmente dividido em bandas de frequência licenciadas, com utilização restringida a um número limitado de utilizadores autorizados, e em algumas bandas de frequência não licenciadas para utilização livre. Devido à falta de flexibilidade resultante desta abordagem, partes significativas do espectro rádio encontram-se subutilizadas. Em simultâneo, outras bandas de frequência estão a ficar cada vez mais saturadas, nomeadamente as não licenciadas em áreas densamente povoadas.
O Rádio Cognitivo é um paradigma recente cujo objetivo é melhorar o nível de eficiência na utilização do espectro rádio. Os seus princípios gerais consistem em permitir que dispositivos sem fios não licenciados (os denominados Utilizadores Secundários) possam aceder às bandas de frequência licenciadas desde que estes não interferiram de forma prejudicial com os utilizadores licenciados (os denominados Utilizadores Primários). A abordagem preponderante na área de Rádio Cognitivo consiste em ter utilizadores secundários com capacidade para, de um modo dinâmico, detetar e aceder a oportunidades espectrais, ou seja, bandas de frequência que não estão a ser acedidas pelos respetivos utilizadores primários num determinado momento numa determinada localização. Neste contexto, os utilizadores secundários devem ser capazes de analisar o espectro rádio com precisão e, de preferência, possuírem mecanismos de aprendizagem baseados em observação local e experiência passada. Apesar da área de Rádio Cognitivo ter implicações na totalidade das camadas das pilhas protocolares de comunicação, os seus problemas fundamentais localizam-se nos níveis físico (PHY) e de controlo de acesso ao meio (MAC). Em particular, os protocolos de controlo de acesso ao meio desempenham um papel fundamental no âmbito de operações de controlo de acesso ao espectro rádio e de suporte à cooperação entre utilizadores secundários. Os utilizadores primários, quanto a eles, devem manter-se abstraídos das operações de Rádio Cognitivo e, em consequência, não estarem sujeitos a qualquer tipo de alteração em cenários de Rádio Cognitivo.
Esta tese apresenta cinco contribuições, essencialmente relacionadas com o nível do controlo de acesso ao meio, com o objetivo de incrementar os níveis de proteção dos utilizadores primários e de desempenho dos utilizadores secundários em redes de Rádio Cognitivo distribuídas, especialmente quando os utilizadores secundários não têm antecipadamente acesso a qualquer tipo de informação, tal como a localização de utilizadores primários. Neste tipo de cenário, não existe qualquer entidade central responsável por recolher e processar dados de origem diversa ou tomar decisões de acesso ao espectro rádio. Ou seja, as soluções propostas adequam-se a utilizadores secundários que operam de um modo autónomo e cooperativo. Estes tomam as suas decisões baseando-se, essencialmente, em observações locais, em eventuais resultados de aprendizagem e em dados trocados entre si.
A primeira contribuição desta tese consiste numa descrição da área de Rádio Cognitivo através de um estado da arte detalhado.
A segunda contribuição resulta na definição de um protocolo de controlo de acesso ao meio apoiado num mecanismo inovador, designado COSBET (Cooperative Sense-Before-Transmit), que oferece um nível superior de proteção dos utilizadores primários em cenários de Rádio Cognitivo distribuídos sujeitos ao problema do utilizador primário oculto. Este tipo de anomalia ocorre quando um utilizador secundário é incapaz de detetar as atividades de um determinado utilizador primário apesar de poder provocar interferências na respetiva área de abrangência.
Tal como já foi referido, na área de Rádio Cognitivo, é considerado desejável os utilizadores secundários terem capacidades de aprendizagem baseadas em observação local e experiência passada. No entanto, em cenários distribuídos, o problema do utilizador primário oculto afeta negativamente a qualidade dos resultados de aprendizagem obtidos e, em consequência, o nível efetivamente alcançado em termos de proteção dos utilizadores primários. Sendo assim, esta tese também analisa esta questão e propõe uma solução destinada a tratá-la, estando esta terceira contribuição baseada num conceito chave designado FIBASC (Filtering Based on Suspicious Channels).
A troca de informação de controlo em redes de Rádio Cognitivo distribuídas é frequentemente suportada por um canal partilhado e acessível à globalidade dos utilizadores secundários. Este é o designado canal de controlo comum (CCC), sendo igualmente esta a abordagem seguida pelo protocolo COSBET-MAC proposto. No entanto, os CCC estão sujeitos a problemas de saturação. A ocorrência deste tipo de problema impede os utilizadores secundários de tirarem pleno proveito das potencialidades oferecidas pelo Rádio Cognitivo, acabando por limitar os níveis de desempenho de comunicação alcançáveis. Sendo assim, nesta tese também analisamos esta questão e propomos uma solução destinada a abordá-la, correspondendo esta à nossa quarta contribuição. A solução proposta, designada CORHYS (Cognitive Radio Hybrid Signalling), baseia-se num esquema de sinalização híbrido que recorre simultaneamente a um CCC e aos canais de dados que vão sendo alocados de forma dinâmica.
A quinta e última contribuição desta tese consiste na definição de uma estratégia adicional, igualmente localizada no nível do controlo de acesso ao meio, destinada a melhorar o desempenho dos utilizadores secundários em cenários de Rádio Cognitivo distribuídos em que se recorre a um CCC. Fazem parte das suas linhas orientadoras a otimização da reutilização espacial do espectro rádio e a redução do tráfego de controlo gerado entre utilizadores secundários.
As soluções de Rádio Cognitivo propostas no âmbito desta tese foram avaliadas em ambiente de simulação, sendo esta uma prática comum, nomeadamente devido a limitações de tempo e de outros tipos de recursos. Para o efeito, recorreu-se ao OMNET++ (Objective Modular Network Testbed in C++), um simulador baseado em eventos discretos e de código aberto.
A totalidade das contribuições da presente tese podem ser aplicadas em conjunto. A integração destas deu origem a uma solução única e otimizada de controlo de acesso ao meio destinada a cenários de Rádio Cognitivo distribuídos. Esta aborda as duas principais preocupações existentes em cenários de Rádio Cognitivo: proteger os utilizadores primários de qualquer tipo de interferência prejudicial; e melhorar o desempenho de comunicação dos utilizadores secundários. Tanto quanto sabemos, as várias soluções propostas e o nível de completude que a utilização conjunta destas permite não são oferecidos por qualquer outra proposta de controlo de acesso ao meio existente para cenários de Rádio Cognitivo distribuídos. As contribuições desta tese também apontam direções que podem ser seguidas no âmbito de outros protocolos de controlo de acesso ao meio, especialmente aqueles que se destinam a redes de Rádio Cognitivo distribuídas.The radio spectrum has been statically regulated, i.e., essentially partitioned into licensed
frequency bands, which are accessed exclusively by authorized users, and unlicensed frequency
bands that can be freely accessed. Due to this inflexible policy, large portions of the entire radio
spectrum remain unused independently of time and location in the world, while some frequency
bands suffer from increasing levels of saturation, particularly the unlicensed ones in densely
populated areas. Cognitive Radio (CR) is a recent paradigm that aims at improving efficiency
regarding spectrum utilization. Its principles consist in allowing unlicensed wireless devices (i.e.,
secondary users) to access licensed frequency bands provided that the respective incumbent users
(i.e., primary users) do not suffer any harmful interference. The most preponderant CR approach
consists in having a secondary user (SU) dynamically locating and accessing spectrum
opportunities, i.e., frequency bands that are not being accessed by any primary user (PU) at a
given time and location. Consequently, sensing the spectrum and learning through local
observation and past experience, which enables proactive spectrum decision, are key CR issues.
Despite CR has implications in all the layers of the communication protocol stack, its
fundamentals are mainly related to the physical (PHY) and medium access control (MAC) levels.
In fact, CR MAC protocols are at the heart of spectrum access control and cooperation between
SUs. PUs are expected to be unware of CR operations and, consequently, should not suffer any
modification under CR scenarios.
This thesis provides five contributions, essentially related to the MAC level, with the aim of
improving the protection of PUs and the communication performance of SUs in cooperative
distributed CR networks, particularly when there is no access to any a priori known information,
such as the locations of primary transmitters. In this type of scenario, there are no central entities
that collect and fuse data, or take spectrum decisions. That is, the proposed solutions fit into
totally autonomous and cooperating SUs, i.e., SUs that take their own decisions based on local
observation, on learning outcomes if any is available, and on data they exchange with each other.
The first contribution of this thesis consists in a description of the CR area through an indepth
state of the art.
The second contribution lies in the definition of a CR MAC protocol that follows a novel
approach, named Cooperative Sense-Before-Transmit (COSBET), which provides a higher
protection of PUs in distributed CR scenarios that suffer from the hidden PU problem. This issue
occurs when a SU cannot sense the activities of a given PU despite it can cause harmful
interference to its coverage area. As already mentioned, CR considers that the SUs might have learning capabilities based on
local observation and past experience. However, in distributed scenarios, the hidden PU problem
affects the accuracy of learning and, therefore, the effectiveness of PU protection. For that reason,
in this thesis we also discuss this issue and propose a novel solution that addresses it. This
solution is based on a key concept named FIBASC (Filtering Based on Suspicious Channels).
Utilizing a common control channel (CCC), i.e., a channel that is available to all the SUs in
a CR network, for signalling purposes is a frequent practice concerning existing distributed CR
MAC solutions. It is also the solution adopted by COSBET-MAC. However, a CCC is susceptible
to saturation and can, therefore, become a performance bottleneck that inhibits the SUs from
taking full advantage of CR potentialities. Consequently, the fourth contribution of this thesis
consists in analysing this issue and addressing it through a novel solution, which we named
CORHYS (Cognitive Radio Hybrid Signalling). CORHYS is based on a hybrid signalling
approach that performs signalling over the CCC and over the allocated data channels
simultaneously.
The fifth and last contribution of this thesis consists in a MAC-level strategy that aims at
further improving the performance of SUs in distributed CR scenarios that are based on a CCC.
The key guidelines for this strategy are optimizing the spatial reuse of the radio spectrum and
reducing control traffic.
The CR solutions that resulted from this thesis were evaluated through simulation, which is
a common practice, particularly due to time and other resource restrictions. For this purpose, we
used OMNET++ (Objective Modular Network Testbed in C++), an open source discrete event
simulator.
The contributions of this thesis can be applied jointly and were successfully integrated with
each other, which resulted in an optimized CR MAC solution that addresses the two main
concerns in distributed CR scenarios: protecting the PUs from harmful interference; and
improving the communication performance of the SUs. To the best of our knowledge, the
proposed solutions and the level of completeness that they jointly achieve are not found in any
other existing distributed CR MAC proposal. We also note that they define directions that can be
followed by other CR MAC protocols, particularly those that target distributed CR networks
Measurement of the inclusive and dijet cross-sections of b-jets in pp collisions at sqrt(s) = 7 TeV with the ATLAS detector
The inclusive and dijet production cross-sections have been measured for jets
containing b-hadrons (b-jets) in proton-proton collisions at a centre-of-mass
energy of sqrt(s) = 7 TeV, using the ATLAS detector at the LHC. The
measurements use data corresponding to an integrated luminosity of 34 pb^-1.
The b-jets are identified using either a lifetime-based method, where secondary
decay vertices of b-hadrons in jets are reconstructed using information from
the tracking detectors, or a muon-based method where the presence of a muon is
used to identify semileptonic decays of b-hadrons inside jets. The inclusive
b-jet cross-section is measured as a function of transverse momentum in the
range 20 < pT < 400 GeV and rapidity in the range |y| < 2.1. The bbbar-dijet
cross-section is measured as a function of the dijet invariant mass in the
range 110 < m_jj < 760 GeV, the azimuthal angle difference between the two jets
and the angular variable chi in two dijet mass regions. The results are
compared with next-to-leading-order QCD predictions. Good agreement is observed
between the measured cross-sections and the predictions obtained using POWHEG +
Pythia. MC@NLO + Herwig shows good agreement with the measured bbbar-dijet
cross-section. However, it does not reproduce the measured inclusive
cross-section well, particularly for central b-jets with large transverse
momenta.Comment: 10 pages plus author list (21 pages total), 8 figures, 1 table, final
version published in European Physical Journal
Rising caesarean section rates and factors affecting women's decision-making about mode of birth in Indonesia: a longitudinal qualitative study.
INTRODUCTION: Caesarean section (CS) rates in Indonesia are increasing rapidly. Understanding women's preferences about mode of birth is important to help contextualise these rising rates and can help develop interventions to optimise CS. This study aimed to explore Indonesian women's preferences and decision-making about mode of birth, and how their preferences may change throughout pregnancy and birth. METHODS: We conducted a longitudinal qualitative study using in-depth interviews with 28 women accessing private and public health facilities in Jakarta, the region with the highest CS rates. Interviews were conducted two times: during the woman's third trimester of pregnancy and in the postpartum period, between October 2022 and March 2023. We used a reflexive thematic approach for analysis. RESULTS: We generated three themes: (1) preferences about the mode of birth, (2) decision-making about the mode of birth and (3) regrets about the actual mode of birth. Most women preferred vaginal birth. However, they were influenced by advertisements promoting enhanced recovery after CS (ERACS) as an 'advanced technique' of CS, promising a comfortable, painless and faster recovery birth. This messaging influenced women to perceive CS as equivalent or even superior to vaginal birth. Where women's preferences for mode of birth shifted around the time of birth, this was primarily due to the obstetricians' discretion. Women felt they did not receive adequate information from obstetricians on the benefits and risks of CS and vaginal birth and felt disappointed when their actual mode of birth was not aligned with their preferences. CONCLUSION: Our study shows that despite rising CS rates, Indonesian women prefer vaginal birth. This highlights the need for better communication strategies and evidence-based information from healthcare providers. Given the rising popularity of ERACS, more work is urgently needed to standardise and regulate its use
Comparing generative and retrieval-based chatbots in answering patient questions regarding age-related macular degeneration and diabetic retinopathy
BACKGROUND/AIMS: To compare the performance of generative versus retrieval-based chatbots in answering patient inquiries regarding age-related macular degeneration (AMD) and diabetic retinopathy (DR). METHODS: We evaluated four chatbots: generative models (ChatGPT-4, ChatGPT-3.5 and Google Bard) and a retrieval-based model (OcularBERT) in a cross-sectional study. Their response accuracy to 45 questions (15 AMD, 15 DR and 15 others) was evaluated and compared. Three masked retinal specialists graded the responses using a three-point Likert scale: either 2 (good, error-free), 1 (borderline) or 0 (poor with significant inaccuracies). The scores were aggregated, ranging from 0 to 6. Based on majority consensus among the graders, the responses were also classified as ‘Good’, ‘Borderline’ or ‘Poor’ quality. RESULTS: Overall, ChatGPT-4 and ChatGPT-3.5 outperformed the other chatbots, both achieving median scores (IQR) of 6 (1), compared with 4.5 (2) in Google Bard, and 2 (1) in OcularBERT (all p ≤8.4×10−3). Based on the consensus approach, 83.3% of ChatGPT-4’s responses and 86.7% of ChatGPT-3.5’s were rated as ‘Good’, surpassing Google Bard (50%) and OcularBERT (10%) (all p ≤1.4×10−2). ChatGPT-4 and ChatGPT-3.5 had no ‘Poor’ rated responses. Google Bard produced 6.7% Poor responses, and OcularBERT produced 20%. Across question types, ChatGPT-4 outperformed Google Bard only for AMD, and ChatGPT-3.5 outperformed Google Bard for DR and others. CONCLUSION: ChatGPT-4 and ChatGPT-3.5 demonstrated superior performance, followed by Google Bard and OcularBERT. Generative chatbots are potentially capable of answering domain-specific questions outside their original training. Further validation studies are still required prior to real-world implementation
Integrated genomic characterization of oesophageal carcinoma
Oesophageal cancers are prominent worldwide; however, there are few targeted therapies and survival rates for these cancers remain dismal. Here we performed a comprehensive molecular analysis of 164 carcinomas of the oesophagus derived from Western and Eastern populations. Beyond known histopathological and epidemiologic distinctions, molecular features differentiated oesophageal squamous cell carcinomas from oesophageal adenocarcinomas. Oesophageal squamous cell carcinomas resembled squamous carcinomas of other organs more than they did oesophageal adenocarcinomas. Our analyses identified three molecular subclasses of oesophageal squamous cell carcinomas, but none showed evidence for an aetiological role of human papillomavirus. Squamous cell carcinomas showed frequent genomic amplifications of CCND1 and SOX2 and/or TP63, whereas ERBB2, VEGFA and GATA4 and GATA6 were more commonly amplified in adenocarcinomas. Oesophageal adenocarcinomas strongly resembled the chromosomally unstable variant of gastric adenocarcinoma, suggesting that these cancers could be considered a single disease entity. However, some molecular features, including DNA hypermethylation, occurred disproportionally in oesophageal adenocarcinomas. These data provide a framework to facilitate more rational categorization of these tumours and a foundation for new therapies.ope
Prophylactic antibiotics may not be necessary for transoral endoscopic thyroidectomy
BACKGROUND: With the recent advances in thyroid cancer surgery techniques and the increasing number of patients concerned about cosmetics, the use of transoral endoscopic thyroidectomy is increasing globally. The aim of this study was to determine whether transoral endoscopic thyroidectomy is truly a clean-contaminated surgery. METHODS: From September 2016 to April 2018, 20 patients with thyroid cancer underwent transoral endoscopic thyroidectomy performed by a single surgeon at Gangnam Severance Hospital. Before and after surgery, the oral cavity was swabbed to obtain culture samples, and antibiotics were administered before and after surgery each once. RESULTS: Of the total 20 patients, no bacteria were identified before or after surgery in eight (40%) patients. Bacteria were identified both before and after surgery in seven patients (35%). In four patients (20%), bacteria were not identified before surgery, but bacteria were identified after surgery. Bacteria were identified before surgery but not after surgery in one patient (5%). No surgical site infection was observed. All the bacteria identified were normal flora of the oral cavity and skin. CONCLUSIONS: There was no difference between the preoperative culture and postoperative culture of the oral cavity in patients undergoing TOET, and there were no postoperative surgical site infection with prophylactic pre & post-operative antibiotics use. Considering the patient's position and surgical extent in TOET, it appears to be difficult for non-indigenous bacteria to invade the surgical site in oral cavity
Gut microbiome predicts cognitive function and depressive symptoms in late life
Depression in older adults with cognitive impairment increases progression to dementia. Microbiota is associated with current mood and cognition, but the extent to which it predicts future symptoms is unknown. In this work, we identified microbial features that reflect current and predict future cognitive and depressive symptoms. Clinical assessments and stool samples were collected from 268 participants with varying cognitive and depressive symptoms. Seventy participants underwent 2-year follow-up. Microbial community diversity, structure, and composition were assessed using high-resolution 16 S rRNA marker gene sequencing. We implemented linear regression to characterize the relationship between microbiome composition, current cognitive impairment, and depressive symptoms. We leveraged elastic net regression to discover features that reflect current or future cognitive function and depressive symptoms. Greater microbial community diversity associated with lower current cognition in the whole sample, and greater depression in participants not on antidepressants. Poor current cognitive function associated with lower relative abundance of Bifidobacterium, while greater GABA degradation associated with greater current depression severity. Future cognitive decline associated with lower cognitive function, lower relative abundance of Intestinibacter, lower glutamate degradation, and higher baseline histamine synthesis. Future increase in depressive symptoms associated with higher baseline depression and anxiety, lower cognitive function, diabetes, lower relative abundance of Bacteroidota, and lower glutamate degradation. Our results suggest cognitive dysfunction and depression are unique states with an overall biological effect detectable through gut microbiota. The microbiome may present a noninvasive readout and prognostic tool for cognitive and psychiatric states
Phylodynamics of HIV-1 Subtype B among the Men-Having-Sex-with-Men (MSM) Population in Hong Kong
The men-having-sex-with-men (MSM) population has become one of the major risk groups for HIV-1 infection in the Asia Pacific countries. Hong Kong is located in the centre of Asia and the transmission history of HIV-1 subtype B transmission among MSM remained unclear. The aim of this study was to investigate the transmission dynamics of HIV-1 subtype B virus in the Hong Kong MSM population. Samples of 125 HIV-1 subtype B infected MSM patients were recruited in this study. Through this study, the subtype B epidemic in the Hong Kong MSM population was identified spreading mainly among local Chinese who caught infection locally. On the other hand, HIV-1 subtype B infected Caucasian MSM caught infection mainly outside Hong Kong. The Bayesian phylogenetic analysis also indicated that 3 separate subtype B epidemics with divergence dates in the 1990s had occurred. The first and latest epidemics were comparatively small-scaled; spreading among the local Chinese MSM while sauna-visiting was found to be the major sex partner sourcing reservoir for the first subtype B epidemic. However, the second epidemic was spread in a large-scale among local Chinese MSM with a number of them having sourced their sex partners through the internet. The epidemic virus was estimated to have a divergence date in 1987 and the infected population in Hong Kong had a logistic growth throughout the past 20 years. Our study elucidated the evolutionary and demographic history of HIV-1 subtype B virus in Hong Kong MSM population. The understanding of transmission and growth model of the subtype B epidemic provides more information on the HIV-1 transmission among MSM population in other Asia Pacific high-income countries
Potential anti-cancer effect of N-hydroxy-7-(2-naphthylthio) heptanomide (HNHA), a novel histone deacetylase inhibitor, for the treatment of thyroid cancer
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