993 research outputs found
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
Distance and Percent Distance from Median BMI as Alternatives to BMI z-score
Body mass index z-score (BMIz) based on the CDC growth charts is widely used, but it is inaccurate above the 97th percentile. We explored the performance of alternative metrics based on the absolute distance or % distance of a child's BMI from the median BMI for sex and age.We used longitudinal data from 5628 children who were first examined < 12 y to compare the tracking of three BMI metrics: distance from median, % distance from median, and % distance from median on a log scale. We also explored the effects of adjusting these metrics for age differences in the distribution of BMI. The intra-class correlation coefficient (ICC) was used to compare tracking of the metrics
Paediatrician workforce in Nigeria and impact on child health
Objective: To determine the number and distribution of paediatricians in Nigeria. It also aims to determine the association between paediatrician workforce and under five mortality (U5MR) and immunization coverageacross the six geopolitical zones of the country.Methods: The part II fellowship examination pass list of the West African College of Physicians and the National Postgraduate Medical College and the register and financial records of the Paediatric Association of Nigeria were searched for the purpose of the study. Using a structured questionnaire, personal and professional data was obtained frommembers at the 2011 Annual Paediatric Association of Nigeria Conference or via the Association’s website, email network and phone calls to Departments of Paediatrics in institutions (private and public) across the Country. Data on the paediatricians residing within Nigeria was then extracted from the comprehensive database and subsequently analyzed.Population data, mortality and immunization rates were obtained from the National Population Commission census and their most recent National Demographic health survey in Nigeria. Correlations were drawn betweennumber of paediatricians and U5MR and diphtheria-pertussistetanus(DPT) vaccine coverage.Results: There were 492 practicing paediatricians in Nigeria at theend of year 2011, comprising 282 (57.3%) males and 210 (42.7%)females; 476 (96.7%). Majority (84.7%) worked for the governmentwith 97% of them in hospital settings, mostly tertiary centres (344=88%). Lagos State had the highest number (85; 17.9%) of practicing paediatricians followed by the Federal Capital Territory with 37 (7.8%) paediatricians. More than two thirds of the paediatricians (336; 70.6%) were practicing in the southern part of the country. The average child:p a e d i a t r i c i a n r a t i o wa s 157,878:1for the country. TheNorth East zone had the highest chi ld- to-pa ediat r ician rat io (718,412:1) while South West had the lowest ratio (95,682:1).Higher absolute numbers of paediatricians in each zone were associatedwi th lower U5MR (Spearman ñ=-0.94, p=0.0048), accounting for 84% of the variability among zones. Higher ratios of child-to-paediatrician were significantly associated with higher U5MR (Spearman ñ=0.82, p=0.04,linear R2=0.73) and marginally with lower DPT coverage by geopoliticalzone (Spearman ñ=-0.77, p=0.07, linear R2=0.59).Conclusion: The study reveals that the number of paediatricians inNigeria is grossly inadequate with a huge child-to-paediatrician ratio.There is also an uneven distribution of the paediatricians with higher numbers in the southern states. Zones of the country with lower child-to-paediatrician ratios also experienced lower U5MR. There is a need to train more paediatricians in Nigeria and promote an even distribution of the paediatrician workforceKey words: Paediatrician, workforce, child-to-paediatrician ratio, under-5 mortality, immunization, childhealth, Nigeri
Genome sequencing as a first-line genetic test in familial dilated cardiomyopathy
Purpose: We evaluated genome sequencing (GS) as an alternative to multigene panel sequencing (PS) for genetic testing in dilated cardiomyopathy (DCM). Methods: Forty-two patients with familial DCM underwent PS and GS, and detection rates of rare single-nucleotide variants and small insertions/deletions in panel genes were compared. Loss-of-function variants in 406 cardiac-enriched genes were evaluated, and an assessment of structural variation was performed. Results: GS provided broader and more uniform coverage than PS, with high concordance for rare variant detection in panel genes. GS identified all PS-identified pathogenic or likely pathogenic variants as well as two additional likely pathogenic variants: one was missed by PS due to low coverage, the other was a known disease-causing variant in a gene not included on the panel. No loss-of-function variants in the extended gene set met clinical criteria for pathogenicity. One BAG3 structural variant was classified as pathogenic. Conclusion: Our data support the use of GS for genetic testing in DCM, with high variant detection accuracy and a capacity to identify structural variants. GS provides an opportunity to go beyond suites of established disease genes, but the incremental yield of clinically actionable variants is limited by a paucity of genetic and functional evidence for DCM association
Comparison of ICD code-based diagnosis of obesity with measured obesity in children and the implications for health care cost estimates
<p>Abstract</p> <p>Background</p> <p>Administrative health databases are a valuable research tool to assess health care utilization at the population level. However, their use in obesity research limited due to the lack of data on body weight. A potential workaround is to use the ICD code of obesity to identify obese individuals. The objective of the current study was to investigate the sensitivity and specificity of an ICD code-based diagnosis of obesity from administrative health data relative to the gold standard measured BMI.</p> <p>Methods</p> <p>Linkage of a population-based survey with anthropometric measures in elementary school children in 2003 with longitudinal administrative health data (physician visits and hospital discharges 1992-2006) from the Canadian province of Nova Scotia. Measured obesity was defined based on the CDC cut-offs applied to the measured BMI. An ICD code-based diagnosis obesity was defined as one or more ICD-9 (278) or ICD-10 code (E66-E68) of obesity from a physician visit or a hospital stay. Sensitivity and specificity were calculated and health care cost estimates based on measured obesity and ICD-based obesity were compared.</p> <p>Results</p> <p>The sensitivity of an ICD code-based obesity diagnosis was 7.4% using ICD codes between 2002 and 2004. Those correctly identified had a higher BMI and had higher health care utilization and costs.</p> <p>Conclusions</p> <p>An ICD diagnosis of obesity in Canadian administrative health data grossly underestimates the true prevalence of childhood obesity and overestimates the health care cost differential between obese and non-obese children.</p
Long-term burden of increased body mass index from childhood on adult dyslipidemia: the i3C Consortium study
Background: Data are limited regarding the association of cumulative burden and trajectory of body mass index (BMI) from early life with adult lipid disorders. Methods: The study cohort consisted of 5195 adults who had BMI repeatedly measured 4 to 21 times from childhood and had blood lipid measurements of low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), and triglycerides (TG) and information on lipid-lowering medications in the last adult survey. The area under the curve (AUC) was calculated as a measure of long-term burden (total AUC) and trends (incremental AUC) of BMI. Results: Participants with dyslipidemia, high LDL-C, low HDL-C and high TG had consistently and significantly higher BMI levels from childhood to adulthood compared to those with normal lipid levels. After adjusting for age, race, sex, and cohort, increased risk of adult dyslipidemia was significantly associated with higher values of childhood BMI, adulthood BMI, total AUC and incremental AUC, with odds ratio (95% confidence interval) = 1.22 (1.15-1.29), 1.85 (1.74-1.97), 1.61 (1.52-1.71), and 1.59 (1.50-1.69), respectively, and p Conclusions: Adults with dyslipidemia versus normal lipid levels have consistently higher levels and distinct life-course trajectories of BMI, suggesting that the impact of excessive body weight on dyslipidemia originates in early life
Childhood/adolescent smoking and adult smoking and cessation: The International Childhood Cardiovascular Cohort (i3C) Consortium
Background: Despite declining US adolescent smoking prevalence from 40% among 12th graders in 1995 to around 10% in 2018, adolescent smoking is still a significant problem. Using the International Childhood Cardiovascular Cohort (i3C) Consortium, which includes 7 international cohorts recruited in childhood and followed into adulthood, the present study was designed to confirm the important relation between adolescent smoking and daily adult smoking and present new data on adult smoking into the forties and comparison of smoking in the United States, Finland, and Australia. Methods and Results: Childhood smoking experience during ages 6 to 19 in the 1970s and 1980s was classifiable in 6687 i3C participants who also provided smoking status in their twenties and forties through 2011-2018. Prevalence of daily smoking in their twenties was directly related to degree of smoking during adolescence and inversely related to the age at which that smoking experience occurred (P trend, P trend, Conclusions: These long-term follow-up data show that smoking intensity increased throughout adolescence. Prevalence of adult smoking and cessation by the forties were both correlated with levels of childhood smoking intensity. These data lend support to preventive strategies designed to reduce, delay, or eliminate any youth access to cigarettes
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