289 research outputs found
ZigBee/ZigBee PRO security assessment based on compromised cryptographic keys
Sensor networks have many applications in monitoring and controlling of environmental properties such as sound, acceleration, vibration and temperature. Due to limited
resources in computation capability, memory and energy, they are vulnerable to many kinds of attacks. The ZigBee specification based on the 802.15.4 standard, defines a set of layers specifically suited to sensor networks. These layers support secure messaging using symmetric cryptographic. This paper presents two different ways for grabbing the cryptographic key in ZigBee: remote attack and physical attack. It also surveys and categorizes some additional attacks which can be performed on ZigBee networks: eavesdropping, spoofing, replay and DoS attacks at different layers. From this analysis, it is shown that some vulnerabilities still in the existing security schema in ZigBee technology.Les xarxes de sensors tenen moltes aplicacions en el control i la monitoritzaciĂł de les propietats del medi ambient, com ara el so, lÂżacceleraciĂł, la vibraciĂł i la temperatura. A causa dels limitats recursos en la capacitat de cĂ lcul, la memòria i l'energia sĂłn vulnerables a molts tipus d'atacs. L'especificaciĂł ZigBee basada en l'estĂ ndard 802.15.4, defineix un conjunt de capes, adaptada especĂficament per a xarxes de sensors. Aquestes capes suporten missatgeria segura mitjançant criptografia simètrica. Aquest article presenta dues formes diferents per agafar la clau de xifrat en ZigBee: atac a distĂ ncia i atacs fĂsics. TambĂŠ les enquesta i classifica alguns atacs addicionals que es poden realitzar en les xarxes ZigBee: espionatge, falsificaciĂł, reproducciĂł i atacs DoS en les diferents capes. A partir d'aquesta anĂ lisi, es demostren algunes vulnerabilitats existents en l'esquema de seguretat en tecnologia ZigBee.Las redes de sensores tienen muchas aplicaciones en el control y la monitorizaciĂłn de las propiedades del medio ambiente, como el sonido, la aceleraciĂłn, la vibraciĂłn y la temperatura. Debido a los limitados recursos en la capacidad de cĂĄlculo, la memoria y la energĂa son vulnerables a muchos tipos de ataques. La especificaciĂłn ZigBee basada en el estĂĄndar 802.15.4, define un conjunto de capas, adaptada especĂficamente para redes de sensores. Estas capas soportan mensajerĂa segura mediante criptografĂa simĂŠtrica. Este artĂculo presenta dos formas diferentes para coger la clave de cifrado en ZigBee: ataque a distancia y ataques fĂsicos. TambiĂŠn las encuesta y clasifica algunos ataques adicionales que se pueden realizar en las redes ZigBee: espionaje, falsificaciĂłn, reproducciĂłn y ataques DoS en las diferentes capas. A partir de este anĂĄlisis, se demuestran algunas vulnerabilidades existentes en el esquema de seguridad en tecnologĂa ZigBee
Microbial production of next-generation stevia sweeteners
BACKGROUND: The glucosyltransferase UGT76G1 from Stevia rebaudiana is a chameleon enzyme in the targeted biosynthesis of the next-generation premium stevia sweeteners, rebaudioside D (Reb D) and rebaudioside M (Reb M). These steviol glucosides carry five and six glucose units, respectively, and have low sweetness thresholds, high maximum sweet intensities and exhibit a greatly reduced lingering bitter taste compared to stevioside and rebaudioside A, the most abundant steviol glucosides in the leaves of Stevia rebaudiana. RESULTS: In the metabolic glycosylation grid leading to production of Reb D and Reb M, UGT76G1 was found to catalyze eight different reactions all involving 1,3-glucosylation of steviol C (13)- and C (19)-bound glucoses. Four of these reactions lead to Reb D and Reb M while the other four result in formation of side-products unwanted for production. In this work, side-product formation was reduced by targeted optimization of UGT76G1 towards 1,3 glucosylation of steviol glucosides that are already 1,2-diglucosylated. The optimization of UGT76G1 was based on homology modelling, which enabled identification of key target amino acids present in the substrate-binding pocket. These residues were then subjected to site-saturation mutagenesis and a mutant library containing a total of 1748 UGT76G1 variants was screened for increased accumulation of Reb D or M, as well as for decreased accumulation of side-products. This screen was performed in a Saccharomyces cerevisiae strain expressing all enzymes in the rebaudioside biosynthesis pathway except for UGT76G1. CONCLUSIONS: Screening of the mutant library identified mutations with positive impact on the accumulation of Reb D and Reb M. The effect of the introduced mutations on other reactions in the metabolic grid was characterized. This screen made it possible to identify variants, such as UGT76G1(Thr146Gly) and UGT76G1(His155Leu), which diminished accumulation of unwanted side-products and gave increased specific accumulation of the desired Reb D or Reb M sweeteners. This improvement in a key enzyme of the Stevia sweetener biosynthesis pathway represents a significant step towards the commercial production of next-generation stevia sweeteners. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12934-016-0609-1) contains supplementary material, which is available to authorized users
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Impacts of climate change on global food trade networks
Countriesâ reliance on global food trade networks implies that regionally different climate change impacts on crop yields will be transmitted across borders. This redistribution constitutes a significant challenge for climate adaptation planning and may affect how countries engage in cooperative action. This paper investigates the long-term (2070-2099) potential impacts of climate change on global food trade networks of three key crops: wheat, rice and maize. We propose a simple network model to project how climate change impacts on crop yields may be translated into changes in trade. Combining trade and climate impact data, our analysis proceeds in three steps. First, we use network community detection to analyse how the concentration of global production in present-day trade communities may become disrupted with climate change impacts. Second, we study how countries may change their network position following climate change impacts. Third, we study the total climate-induced change in production plus import within trade communities. Results indicate that the stability of food trade network structures compared to today differs between crops, and that countriesâ maize trade is least stable under climate change impacts. Results also project that threats to global food security may depend on production change in a few major global producers, and whether trade communities can balance production and import loss in some vulnerable countries. Overall, our model contributes a baseline analysis of cross-border climate impacts on food trade networks
Using qualitative research to develop an elaboration of the TIDieR checklist for interventions to enhance vaccination communication: short report
BACKGROUND: The COVID-19 pandemic has led to an increased interest in communication with the public regarding vaccination. Our recent Cochrane qualitative evidence synthesis points to several factors that could influence the implementation and success of healthcare worker communication with older adults about vaccination. However, it is often difficult to assess whether factors identified as potentially important in qualitative studies have been considered in randomized trials because of poor trial reporting. We therefore decided to use our qualitative evidence synthesis findings to encourage better reporting of vaccination communication interventions in trials by developing an elaboration of the TIDieR (Template for Intervention Description and Replication) checklist for intervention reporting. METHODS: We examined the findings from our Cochrane qualitative evidence synthesis on healthcare workersâ perceptions of and experiences with communicating about vaccination with adults over the age of 50Â years. We identified factors that could influence the implementation and uptake, and thereby the effectiveness, of vaccination communication interventions. We then drafted a list of the information elements we would need from trial reports to assess whether these factors had been considered in the development of the interventions evaluated in these trials. Finally, we compared our list of information elements to the TIDieR checklist items. We were able to align all of our information elements with the TIDieR items. However, for several of the TIDieR items, we developed a more detailed description to ensure that relevant information would be captured sufficiently in trial reports. RESULTS: We developed elaborations for the following TIDieR items: âWhyâ (item 2), âWhatâmaterialsâ (item 3), âWho providedâ (item 5), âHowâ (item 6), âWhereâ (item 7) and âTailoringâ (item 9). CONCLUSIONS: Both qualitative research and trials of intervention effectiveness are critical to furthering our understanding of what works, where, for whom and through which mechanisms. However, a key ingredient for developing this understanding is adequate reporting of intervention design, content and implementation in randomized trials. We hope that this elaboration of the TIDier checklist will improve reporting of interventions in trials focused on vaccine communication with older adults, and thereby enhance the usability of this research for developing future communication strategies
Bayesian sample sizes for exploratory clinical trials comparing multiple experimental treatments with a control
In this paper, a Bayesian approach is developed for simultaneously comparing
multiple experimental treatments with a common control treatment in an
exploratory clinical trial. The sample size is set to ensure that, at the end
of the study, there will be at least one treatment for which the investigators
have a strong belief that it is better than control, or else they have a strong
belief that none of the experimental treatments are substantially better than
control. This criterion bears a direct relationship with conventional
frequentist power requirements, while allowing prior opinion to feature in the
analysis with a consequent reduction in sample size. If it is concluded that at
least one of the experimental treatments shows promise, then it is envisaged
that one or more of these promising treatments will be developed further in a
definitive phase III trial. The approach is developed in the context of
normally distributed responses sharing a common standard deviation regardless
of treatment. To begin with, the standard deviation will be assumed known when
the sample size is calculated. The final analysis will not rely upon this
assumption, although the intended properties of the design may not be achieved
if the anticipated standard deviation turns out to be inappropriate. Methods
that formally allow for uncertainty about the standard deviation, expressed in
the form of a Bayesian prior, are then explored. Illustrations of the sample
sizes computed from the new method are presented, and comparisons are made with
frequentist methods devised for the same situation.Comment: 28 pages, 3 tables, 2 figure
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