O USO DO FEEDBACK AUTOMÁTICO NO APLICATIVO EDUCACIONAL BUSUU E SUA INFLUÊNCIA NA APRENDIZAGEM DE LÍNGUAS

A tecnologia permeia a aprendizagem de línguas há muitos anos e de várias formas. É o caso do aplicativo Busuu, que possibilita a aprendizagem de 12 idiomas, colaborativa e gratuitamente, contando com 4 milhões de usuários no Brasil. Percebendo esse alcance do Busuu, observamos como se constitui o seu feedback automático, pois essa é sua principal forma de interação com o usuário, sendo essencial no processo de aquisição de uma LE. A base para a análise são as categorias de feedback de Leffa (2003) para AVAs, que são: genérico, situado e estratégico. Realizamos todos os modelos de tarefas do aplicativo em busca das formas de feedback que ele disponibiliza e de como o usuário as recebe. Constatamos que o feedback mais utilizado é o genérico, que pouco proporciona estratégias de aprendizagem e, em menor proporção, o feedback situado, o qual oferece dicas ao usuário para ajudá-lo a chegar na resposta correta

Uso do Doppler vascular para detectar o efeito agudo do estradiol em mulheres na pós-menopausa

OBJECTIVES: To report on a simple practical test for assessing acute estradiol vascular effects on healthy and unhealthy postmenopausal women. INTRODUCTION: Estradiol acts in the endothelium to promote vasodilatation through genomic and non-genomic mechanisms, but its vascular action may be impaired in diabetes mellitus, hypertension, smoking and obesity. METHODS: Nineteen postmenopausal women (nine healthy and 10 with two or more of the above factors) of similar age and time since menopause were examined with vascular Doppler ultrasound. Resistance indexes and systolic and diastolic flow velocities were determined for the brachial and internal carotid arteries at baseline and 20 minutes after administration of a nasal estradiol formulation, available on the market, which reaches 1,200-1,500 pg/ml in the serum in 10-30 minutes. Estradiol blood levels were measured at 30 minutes. RESULTS: The carotid resistance index increased 14.2% (vasoconstriction) in the unhealthy group after estradiol, from a mean ± S.E. of 0.56 ± 0.016 at baseline to 0.64 ± 0.05 (p=0.033), and remained unchanged in healthy women. Brachial diastolic flow velocity increased 19.7% (vasodilatation) in healthy women, from 16.2 ± 1.93 to 19.4 ± 0.64 cm/s (p=0.046), and did not change in the unhealthy subjects. Estradiol levels were similar in both groups. DISCUSSION: Healthy postmenopausal women showed brachial vasodilatation while unhealthy postmenopausal women displayed vasoconstriction at the carotid artery. Vascular responses to estradiol were divergent between the groups. CONCLUSIONS: The acute estradiol test, coupled with Doppler ultrasound, seemed to be able to differentiate women with normal and abnormal endothelial function in a simple, non-invasive manner.OBJETIVO: Descrever um teste simples e prático para avaliar o efeito vascular agudo do estradiol em mulheres saudáveis e não-saudáveis na menopausa. INTRODUÇÃO: O estradiol atua no endotélio promovendo vasodilatação através de mecanismos genômicos e não-genômicos e esta ação pode estar prejudicada em morbidades como diabetes mellitus, hipertensão, tabagismo e obesidade. MÉTODOS: Dezenove mulheres na pós-menopausa (9 saudáveis e 10 com dois ou mais dos fatores acima), com idade e tempo de menopausa semelhantes foram examinadas por Doppler vascular. O índice de resistência e as velocidades de fluxo sistólico e diastólico foram medidos nas artérias braquial e carótida, em condições basais e 20 min após a administração de uma preparação nasal de estradiol, disponível comercialmente, que atinge 1200 a 1500 pg/ml no soro, entre 10 e 30 min após a aplicação. Os níveis séricos de estradiol foram determinados 30 min após a aplicação nasal. RESULTADOS: O índice de resistência da artéria carótida aumentou em 14,2% (vasoconstricção) após o estradiol no grupo não-saudável, partindo da média ± SE de 0,56 ± 0,016 para 0,64 ± 0,05 (p=0,033) e não se modificou nas mulheres saudáveis. A velocidade de fluxo diastólico da artéria braquial aumentou 19,7% (vasodilatação) nas mulheres saudáveis, partindo de 16,2 ± 1,93 para 19,4 ± 0,64 cm/s (p=0,046) e não apresentou alteração nas não saudáveis. Os níveis de estradiol foram semelhantes nos dois grupos. DISCUSSÃO: Nas mulheres saudáveis na menopausa houve vasodilatação da artéria braquial e nas não-saudáveis vasoconstricção na artéria carótida. A resposta vascular ao estradiol foi divergente entre os grupos estudados. CONCLUSÃO: O teste com estradiol agudo, associado ao Doppler vascular, parecem diferenciar, de forma simples e não-invasiva, mulheres com função endotelial normal e anormal

ACPC: Efficient revocation of pseudonym certificates using activation codes

Vehicular communication (V2X) technologies allow vehicles to exchange information about the road conditions and their own status, and thereby enhance transportation safety and efficiency. For broader deployment, however, such technologies are expected to address security and privacy concerns, preventing abuse by users and by the system\u27s entities. In particular, the system is expected to enable the revocation of malicious vehicles, e.g., in case they send invalid information to their peers or to the roadside infrastructure; it should also prevent the system from being misused for tracking honest vehicles.Both features are enabled by Vehicular Public Key Infrastructure (VPKI) solutions such as Security Credential Management Systems (SCMS), one of the leading candidates for protecting V2X communication in the United States. Unfortunately, though, SCMS\u27s original revocation mechanism can lead to large Certification Revocation Lists (CRLs), which in turn impacts the bandwidth usage and processing overhead of the system. In this article, we propose a novel design called Activation Codes for Pseudonym Certificates (ACPC), which can be integrated into SCMS to address this issue. Our proposal is based on activation codes, short bitstrings without which certificates previously issued to a vehicle cannot be used by the latter, which are periodically distributed to non-revoked vehicles using an efficient broadcast mechanism. As a result, the identifiers of the corresponding certificates do no need to remain on the CRL for a long time, reducing the CRLs\u27 size and streamlining their distribution and verification of any vehicle\u27s revocation status. Besides describing ACPC in detail, we also compare it to similar-purpose solutions such as Issue First Activate Later (IFAL) and Binary Hash Tree based Certificate Access Management (BCAM).This analysis shows that our proposal not only brings security improvements (e.g., in terms of resilience against colluding system authorities), but also leads to processing and bandwidth overheads that are orders of magnitude smaller than those observed in the state of the art

Faster verification of V2X BSM messages via Message Chaining

Vehicular-to-Everything (V2X) communications enable vehicles to exchange messages with other entities, including nearby vehicles and pedestrians. V2X is, thus, essential for establishing an Intelligent Transportation System (ITS), where vehicles use information from their surroundings to reduce traffic congestion and improve safety. To avoid abuse, V2X messages should be digitally signed using valid digital certificates. Messages sent by unauthorized entities can then be discarded, while misbehavior can lead to the revocation of the corresponding certificates. One challenge in this scenario is that messages must be verified shortly after arrival (e.g., within centiseconds), whereas vehicles may receive thousands of them per second. To handle this issue, some solutions propose prioritization or delayed-verification mechanisms, while others involve signature schemes that support batch verification. In this manuscript, we discuss two mechanisms that complement such proposals, enabling the authentication of a sequence of messages from the same source with one single signature verification. Our analysis shows that the technique can reduce the number of verified signatures by around 90% for reliable communication channels, and by more than 65% for a maximum packet loss rate of 20%

The Unified Butterfly Effect: Efficient Security Credential Management System for Vehicular Communications

Security and privacy are important requirements for the broad deployment of intelligent transportation systems (ITS). This motivated the development of many proposals aimed at creating a Vehicular Public Key Infrastructure (VPKI) for addressing such needs. Among them, schemes based on pseudonym certificates are considered particularly prominent: they provide data authentication in a privacy-preserving manner while allowing vehicles to be revoked in case of misbehavior. Indeed, this is the approach followed by the Security Credential Management System (SCMS), one of the leading candidate designs for protecting vehicular communications in the United States. Despite SCMS\u27s appealing design, in this article we show that it still can be further improved. Namely, one of the main benefits of SCMS is its so-called butterfly key expansion process, which allows batches of pseudonym certificates to be issued for authorized vehicles by means of a single request. Whereas this procedure requires the vehicle to provide two separate public/private key pairs for registration authorities, we present a modified protocol that uses a single key for the same purpose. As a result, the processing and bandwidth costs of the certificate provisioning protocol drop as far as 50%. Such performance gains come with no negative impact in terms of security, flexibility or scalability when compared to the original SCMS

Recurrent Pregnancy Loss: Investigations and Interventions

Recurrent pregnancy loss (RPL) affects 0.8–1.4% of couples, and this prevalence increases with aging. However, etiology is commonly unknown, and most therapies are not supported by strong evidence. There are many examinations that investigate causes of RPL: hormonal status, spermatozoa morphology and DNA fragmentation, immunologic status, uterine assessment, thrombophilia, and others. Recently different types of treatment have emerged, most lacking good evidence. As for example, we may mention the use of anticoagulants, aspirin, corticosteroids, progesterone, and antioxidants and psychological support. It is argued that some procedures such as preimplantation genetic testing for aneuploidy and intracytoplasmic morphologically selected sperm injection would impact on the outcomes and help RPL management. This chapter will discuss the current evidence concerning examinations and treatments that would improve the outcomes in patients with RPL, with recommended practice

A privacy-preserving method for temporarily linking/revoking pseudonym certificates in vehicular networks

Vehicular communication (V2X) technologies are expected to become increasingly common in the future. Although they enable improvements on transportation safety and efficiency, the large scale deployment of V2X requires addressing some challenges. In particular, to prevent abuse by drivers and by the system itself, V2X architectures must: (1) ensure the authenticity of messages, which is usually accomplished by means of digital certification; and (2) preserve the privacy of honest users, so owners of non-revoked certificates cannot be easily identified and tracked by eavesdroppers. A promising design to address these requirements is the Security Credential Management System (SCMS), which is currently among the main candidates for protecting V2X communications in the United States. Even though SCMS provides efficient, scalable and privacy-preserving mechanisms for managing V2X-oriented certificates, in this article we show that its certificate revocation process can be further enhanced. Namely, we present two birthday attacks against SCMS\u27s revocation process, both of which degrade the system\u27s security as time passes and more certificates are revoked. We then describe an alternative design to prevent such security degradation with minimal computational overhead. In complement to these security gains, we also describe a mechanism for improving the flexibility of the revocation procedure, allowing certificates (as well as their owner\u27s privacy) to be temporarily revoked in an efficient manner. This should be useful, for example, to implement suspension mechanisms or to aid in investigations by law-enforcement authorities

Use of vascular Doppler ultrasound to detect acute estradiol vascular effect in postmenopausal women

OBJECTIVES: To report on a simple practical test for assessing acute estradiol vascular effects on healthy and unhealthy postmenopausal women. INTRODUCTION: Estradiol acts in the endothelium to promote vasodilatation through genomic and non-genomic mechanisms, but its vascular action may be impaired in diabetes mellitus, hypertension, smoking and obesity. METHODS: Nineteen postmenopausal women (nine healthy and 10 with two or more of the above factors) of similar age and time since menopause were examined with vascular Doppler ultrasound. Resistance indexes and systolic and diastolic flow velocities were determined for the brachial and internal carotid arteries at baseline and 20 minutes after administration of a nasal estradiol formulation, available on the market, which reaches 1,200-1,500 pg/ml in the serum in 10-30 minutes. Estradiol blood levels were measured at 30 minutes. RESULTS: The carotid resistance index increased 14.2% (vasoconstriction) in the unhealthy group after estradiol, from a mean ± S.E. of 0.56 ± 0.016 at baseline to 0.64 ± 0.05 (p=0.033), and remained unchanged in healthy women. Brachial diastolic flow velocity increased 19.7% (vasodilatation) in healthy women, from 16.2 ± 1.93 to 19.4 ± 0.64 cm/s (p=0.046), and did not change in the unhealthy subjects. Estradiol levels were similar in both groups. DISCUSSION: Healthy postmenopausal women showed brachial vasodilatation while unhealthy postmenopausal women displayed vasoconstriction at the carotid artery. Vascular responses to estradiol were divergent between the groups. CONCLUSIONS: The acute estradiol test, coupled with Doppler ultrasound, seemed to be able to differentiate women with normal and abnormal endothelial function in a simple, non-invasive manner.OBJETIVO: Descrever um teste simples e prático para avaliar o efeito vascular agudo do estradiol em mulheres saudáveis e não-saudáveis na menopausa. INTRODUÇÃO: O estradiol atua no endotélio promovendo vasodilatação através de mecanismos genômicos e não-genômicos e esta ação pode estar prejudicada em morbidades como diabetes mellitus, hipertensão, tabagismo e obesidade. MÉTODOS: Dezenove mulheres na pós-menopausa (9 saudáveis e 10 com dois ou mais dos fatores acima), com idade e tempo de menopausa semelhantes foram examinadas por Doppler vascular. O índice de resistência e as velocidades de fluxo sistólico e diastólico foram medidos nas artérias braquial e carótida, em condições basais e 20 min após a administração de uma preparação nasal de estradiol, disponível comercialmente, que atinge 1200 a 1500 pg/ml no soro, entre 10 e 30 min após a aplicação. Os níveis séricos de estradiol foram determinados 30 min após a aplicação nasal. RESULTADOS: O índice de resistência da artéria carótida aumentou em 14,2% (vasoconstricção) após o estradiol no grupo não-saudável, partindo da média ± SE de 0,56 ± 0,016 para 0,64 ± 0,05 (p=0,033) e não se modificou nas mulheres saudáveis. A velocidade de fluxo diastólico da artéria braquial aumentou 19,7% (vasodilatação) nas mulheres saudáveis, partindo de 16,2 ± 1,93 para 19,4 ± 0,64 cm/s (p=0,046) e não apresentou alteração nas não saudáveis. Os níveis de estradiol foram semelhantes nos dois grupos. DISCUSSÃO: Nas mulheres saudáveis na menopausa houve vasodilatação da artéria braquial e nas não-saudáveis vasoconstricção na artéria carótida. A resposta vascular ao estradiol foi divergente entre os grupos estudados. CONCLUSÃO: O teste com estradiol agudo, associado ao Doppler vascular, parecem diferenciar, de forma simples e não-invasiva, mulheres com função endotelial normal e anormal

Palaeontological framework from Pirabas Formation (North Brazil) used as potential model for equatorial carbonate platform

The Pirabas Formation (early to middle Miocene) from the equatorial margin of North Brazil is characterized by a shallow-marine carbonate platform with high fossil diversity and abundant micro- and macrofossil remains. The Pirabas Formation represents a unique carbonate system along the Atlantic margin of South America that developed before the onset of the Amazon delta. We studied the palaeontology and lithofacies of outcrops of the uppermost Pirabas Formation and found that was deposited in a coastal marine environment with marginal lagoons under the influence of a tidal regime and tropical storms. The remains of calcareous algae, molluscs, crustaceans, echinoiderms, bryozoans, solitary corals, fish and marine mammals, together with foraminifera, ostracods and other marine microfossils, shaped a biogenic framework, that together with the post-depositional processes of dissolution of skeletal grains, is responsible for the mean packstone-floatstone porosity of 14.9%. The palaeontological framework and the petrophysical characterization of the carbonate rocks from the uppermost Pirabas Formation outcrop represent a baseline to interpret the entire Pirabas Formation in the subsurface stratigraphic sections (cores) of this important Neogene unit. Considering that carbonate rocks account for ~50% of oil and gas reservoirs around the world, this research provides a model for Neogene tropical carbonate deposits useful for carbonate petroliferous reservoirs in the Brazilian equatorial basins.publishe