Quantitative Analysis of DoS Attacks and Client Puzzles in IoT Systems

Denial of Service (DoS) attacks constitute a major security threat to today's Internet. This challenge is especially pertinent to the Internet of Things (IoT) as devices have less computing power, memory and security mechanisms to mitigate DoS attacks. This paper presents a model that mimics the unique characteristics of a network of IoT devices, including components of the system implementing `Crypto Puzzles' - a DoS mitigation technique. We created an imitation of a DoS attack on the system, and conducted a quantitative analysis to simulate the impact such an attack may potentially exert upon the system, assessing the trade off between security and throughput in the IoT system. We model this through stochastic model checking in PRISM and provide evidence that supports this as a valuable method to compare the efficiency of different implementations of IoT systems, exemplified by a case study

Key exchange with the help of a public ledger

Blockchains and other public ledger structures promise a new way to create globally consistent event logs and other records. We make use of this consistency property to detect and prevent man-in-the-middle attacks in a key exchange such as Diffie-Hellman or ECDH. Essentially, the MitM attack creates an inconsistency in the world views of the two honest parties, and they can detect it with the help of the ledger. Thus, there is no need for prior knowledge or trusted third parties apart from the distributed ledger. To prevent impersonation attacks, we require user interaction. It appears that, in some applications, the required user interaction is reduced in comparison to other user-assisted key-exchange protocols

Coverage of the 2011 Q fever vaccination campaign in the Netherlands, using retrospective population-based prevalence estimation of cardiovascular risk-conditions for chronic Q fever

Background: In 2011, a unique Q fever vaccination campaign targeted people at risk for chronic Q fever in the southeast of the Netherlands. General practitioners referred patients with defined cardiovascular risk-conditions (age >15 years). Prevalence rates of those risk-conditions were lacking, standing in the way of adequate planning and coverage estimation. We aimed to obtain prevalence rates retrospectively in order to estimate coverage of the Q fever vaccination campaign. Methods: With broad search terms for these predefined risk-conditions, we extracted patient-records from a large longitudinal general-practice research-database in the Netherlands (IPCI-database). Afte

Coverage of the 2011 Q fever vaccination campaign in the Netherlands, using retrospective population-based prevalence estimation of cardiovascular risk-conditions for chronic Q fever

Background: In 2011, a unique Q fever vaccination campaign targeted people at risk for chronic Q fever in the southeast of the Netherlands. General practitioners referred patients with defined cardiovascular risk-conditions (age >15 years). Prevalence rates of those risk-conditions were lacking, standing in the way of adequate planning and coverage estimation. We aimed to obtain prevalence rates retrospectively in order to estimate coverage of the Q fever vaccination campaign. Methods: With broad search terms for these predefined risk-conditions, we extracted patient-records from a large longitudinal general-practice research-database in the Netherlands (IPCI-database). Afte

Reference Ranges of Left Ventricular Strain Measures by Two-Dimensional Speckle-Tracking Echocardiography in Children: A Systematic Review and Meta-Analysis

BACKGROUND: Establishment of the range of reference values and associated variations of two-dimensional speckle-tracking echocardiography (2DSTE)-derived left ventricular (LV) strain is a prerequisite for its routine clinical adoption in pediatrics. The aims of this study were to perform a meta-analysis of normal ranges of LV global longitudinal strain (GLS), global circumferential strain (GCS), and global radial strain (GRS) measurements derived by 2DSTE in children and to identify confounding factors that may contribute to variance in reported measures. METHODS: A systematic review was launched in MEDLINE, Embase, Scopus, the Cumulative Index to Nursing and Allied Health Literature, and the Cochrane Library. Search hedges were created to cover the concepts of pediatrics, STE, and left-heart ventricle. Two investigators independently identified and included studies if they reported 2DSTE-derived LV GLS, GCS, or GRS. The weighted mean was estimated by using random effects models with 95% CIs, heterogeneity was assessed using the Cochran Q statistic and the inconsistency index (I(2)), and publication bias was evaluated using the Egger test. Effects of demographic (age), clinical, and vendor variables were assessed in a metaregression. RESULTS: The search identified 2,325 children from 43 data sets. The reported normal mean values of GLS among the studies varied from -16.7% to -23.6% (mean, -20.2%; 95% CI, -19.5% to -20.8%), GCS varied from -12.9% to -31.4% (mean, -22.3%; 95% CI, -19.9% to -24.6%), and GRS varied from 33.9% to 54.5% (mean, 45.2%; 95% CI, 38.3% to 51.7%). Twenty-six studies reported longitudinal strain only from the apical four-chamber view, with a mean of -20.4% (95% CI, -19.8% to -21.7%). Twenty-three studies reported circumferential strain (mean, -20.3%; 95% CI, -19.4% to -21.2%) and radial strain (mean, 46.7%; 95% CI, 42.3% to 51.1%) from the short-axis view at the midventricular level. A significant apex-to-base segmental longitudinal strain gradient (P 94% and P < .001 for each strain measure), which was not explained by age, gender, body surface area, blood pressure, heart rate, frame rate, frame rate/heart rate ratio, tissue-tracking methodology, location of reported strain value along the strain curve, ultrasound equipment, or software. The metaregression showed that these effects were not significant determinants of variations among normal ranges of strain values. There was no evidence of publication bias (P = .40). CONCLUSIONS: This study defines reference values of 2DSTE-derived LV strain in children on the basis of a meta-analysis. In healthy children, mean LV GLS was -20.2% (95% CI, -19.5% to -20.8%), mean GCS was -22.3% (95% CI, -19.9% to -24.6%), and mean GRS was 45.2% (95% CI, 38.3% to 51.7%). LV segmental longitudinal strain has a stable apex-to-base gradient that is preserved throughout maturation. Although variations among different reference ranges in this meta-analysis were not dependent on differences in demographic, clinical, or vendor parameters, age- and vendor-specific referenced ranges were established as well

On the chronological structure of the solutrean in Southern Iberia

The Solutrean techno-complex has gained particular significance over time for representing a clear demographic and techno-typological deviation from the developments occurred during the course of the Upper Paleolithic in Western Europe. Some of Solutrean's most relevant features are the diversity and techno-typological characteristics of the lithic armatures. These have been recurrently used as pivotal elements in numerous Solutrean-related debates, including the chronological organization of the techno-complex across Iberia and Southwestern France. In Southern Iberia, patterns of presence and/or absence of specific point types in stratified sequences tend to validate the classical ordering of the techno-complex into Lower, Middle and Upper phases, although some evidence, namely radiocarbon determinations, have not always been corroborative. Here we present the first comprehensive analysis of the currently available radiocarbon data for the Solutrean in Southern Iberia. We use a Bayesian statistical approach from 13 stratified sequences to compare the duration, and the start and end moments of each classic Solutrean phase across sites. We conclude that, based on the current data, the traditional organization of the Solutrean cannot be unquestionably confirmed for Southern Iberia, calling into doubt the status of the classically defined type-fossils as precise temporal markers.Fundacao para a Ciencia e Tecnologia [PTDC/HAH/64184/2006, PTDC/HIS-ARQ/117540/2010, SFRH/BD/65527/2009, SFRH/BPD/96277/2013]; National Geographic Society [8045-06]; Wenner-Gren Foundation for Anthropological Research [8290

Precipitation mediates sap flux sensitivity to evaporative demand in the neotropics

Transpiration in humid tropical forests modulates the global water cycle and is a key driver of climate regulation. Yet, our understanding of how tropical trees regulate sap flux in response to climate variability remains elusive. With a progressively warming climate, atmospheric evaporative demand [i.e., vapor pressure deficit (VPD)] will be increasingly important for plant functioning, becoming the major control of plant water use in the twenty-first century. Using measurements in 34 tree species at seven sites across a precipitation gradient in the neotropics, we determined how the maximum sap flux velocity (vmax) and the VPD threshold at which vmax is reached (VPDmax) vary with precipitation regime [mean annual precipitation (MAP); seasonal drought intensity (PDRY)] and two functional traits related to foliar and wood economics spectra [leaf mass per area (LMA); wood specific gravity (WSG)]. We show that, even though vmax is highly variable within sites, it follows a negative trend in response to increasing MAP and PDRY across sites. LMA and WSG exerted little effect on vmax and VPDmax, suggesting that these widely used functional traits provide limited explanatory power of dynamic plant responses to environmental variation within hyper-diverse forests. This study demonstrates that long-term precipitation plays an important role in the sap flux response of humid tropical forests to VPD. Our findings suggest that under higher evaporative demand, trees growing in wetter environments in humid tropical regions may be subjected to reduced water exchange with the atmosphere relative to trees growing in drier climates

Supervivencia global en pacientes con cáncer gástrico avanzado o metastásico en los últimos 10 años en el Centro Médico Nacional «20 de noviembre del ISSSTE»

ResumenAntecedentesLa introducción de nuevos fármacos para el tratamiento de los pacientes con cáncer gástrico irresecable, recurrente o metastásico ha reportado un modesto incremento en la supervivencia libre de progresión (SLP) y la supervivencia global (SG).ObjetivoDeterminar el impacto de la aplicación de los nuevos esquemas de quimioterapia paliativa en la SG de los pacientes con cáncer gástrico del Centro Médico Nacional 20 de noviembre, ISSSTE.Material y métodosEstudio retrospectivo, descriptivo. Analizamos expedientes de pacientes con cáncer gástrico irresecable o metastásico, tratados con quimioterapia paliativa de enero de 2002 a diciembre de 2012 en el Centro Médico Nacional 20 de noviembre, ISSSTE. Se evaluó la SG, SLP y los esquemas de quimioterapia más frecuentemente utilizados. Se asignaron los casos a 2 cohortes de acuerdo a la fecha de inicio de la quimioterapia, conformando la cohorte A los pacientes tratados de enero de 2002 hasta diciembre de 2006 y la cohorte B de enero de 2007 a diciembre de 2012. Se estableció estos periodos dado que representaba el cambio en los esquemas de tratamiento utilizados; es decir; la introducción de esquemas que incluyen antraciclinas, oxaliplatino, capecitabina y docetaxel.ResultadosRevisamos los expedientes de 291 pacientes con cáncer gástrico; excluimos a 221 pacientes por estar en etapas tempranas (i, ii o iii) resecables, recibir tratamiento con quimioterapia fuera de la unidad o no ser candidatos a quimioterapia. Finalmente incluimos 70 casos con tratamiento de primera línea. La mediana de SG para pacientes de la cohorte A fue de 11.2 vs. 10.5 meses para los pacientes de la cohorte B. La mediana de SLP en primera línea de tratamiento fue 8.5 vs. 5.2 meses respectivamente. Ambos resultados sin diferencia estadísticamente significativa.ConclusiónEn nuestro centro, no hay impacto de los nuevos esquemas de tratamiento en SLP o SG. Un tamaño de muestra pequeño y el hecho de que pacientes con pobre estado funcional recibieran quimioterapia podrían ser factores que influyeron en los resultados del estudio, en el cual se observó una tendencia a favor de los nuevos esquemas de quimioterapia, pero sin demostrar significación estadística.AbstractBackgroundThe introduction of new drugs for the treatment of patients with advanced, recurrent or metastatic gastric cancer has resulted in a small benefit in overall survival (OS) and progression free survival (PFS).ObjectiveTo determine the impact of new chemotherapy schedules on the OS of patients with advanced or metastic gastric cancer treated at the Centro Medico Nacional 20 de noviembre, ISSSTE.Material and methodologyRetrolective, descriptive study, the clinical files of patients with advanced, recurrent or metastatic gastric cancer treated with chemotherapy at the Centro Medico Nacional 20 de noviembre, ISSSTE, from january 2002 to december 2012, were analyzed. Chemotherapy schedules, OS and PFS were evaluated. Patients were assigned to two cohorts: those treated from january 2002 to december 2006 were included in cohort A and those treated from january 2007 to december 2012 in cohort B. These time periods were determined based on the years when newer chemotherapy agents (anthracyclines, oxaliplatin, capecitabine and docetaxel) were introduced in our institution.Results291 clinical files were analyzed; 221 patients were excluded for they had clinical stage I, II or resectable III disease, started first line chemotherapy as outpatients of our institution or were not candidates for chemotherapy. 70 cases treated with first line chemotherapy were included. OS for patients in cohort A was 11.2 months vs 10.5 months for patients in cohort B. PFS was 8.5 months vs 5.2, respectively. There was no statistical difference in either comparison.ConclusionThere was no impact of the introduction of newer chemotherapy agents in OS or PFS in patients treated in our institution. A small sample size and the fact that patients with poor performance status received chemotherapy could have had influenced the results of our study, in which tendency towards a better outcome for patients treated with newer chemotherapy schemes was observed, although a statistically significant benefit was not proven