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Lawrence E. Gilbert - One of the best experts on this subject based on the ideXlab platform.

  • biogeography and macroecology of phorid flies that attack fire ants in south eastern brazil and argentina
    Journal of Biogeography, 2005
    Co-Authors: Patricia Julia Folgarait, M A Pesquero, Sanford D. Porter, Octavio A Bruzzone, Lawrence E. Gilbert
    Abstract:

    Aim  Saevissima group fire ants, Solenopsis richteri and S. invicta, have become serious pests when introduced from Argentina and Brazil to other continents. In South America, Solenopsis are distributed across a great variety of habitats and climates. In North America, S. invicta, introduced free of phorids, now ranges from coast to coast in the south. Success in introducing particular Pseudacteon as agents for the biological control of fire ants has varied across climatic zones. We aimed at assembling all the information about fire ant phorids from Argentina and Brazil, to estimate their richness and geographical ranges, to perform a climatic analysis for these distributions, to define groups and climate-based communities, and to test and elucidate Rapoport's biogeographical rule. Location  Argentina and Brazil (South America). Methods  From field and museum collections and historical records, we developed a Database of fire ant-specific phorids throughout their known geographical range. A total of 123 sites with values for 15 climatic variables were mapped between 10° and 38° SL and between 35° and 65° C WL for the presence/absence of phorids. We calculated species richness across all sites combined, and for each phytogeographical region, using rarefaction curves, and ICE and Mmean estimators. We calculated mid-latitudinal points, geographical ranges and areas for each species. The correlation between mid-latitudinal point and ranges/areas was tested against a null model generated from the randomization of the raw distributional Data. We used several types of multivariate analyses to distinguish groups of phorids by phytogeographical regions, Hosts and climate, to find gradients of climate throughout the studied area, to define phorid communities in terms of their relationships with gradients of climate, and to test a mechanism for Rapoport's rule. Results  Richness estimations using ICE and Mmean estimators were similar or higher than the observed values depending on the phytogeographical region. Cluster multivariate analyses based on climatic, phytogeographic and Host Data revealed distinct groupings of Pseudacton. The ‘cerrado’ group was confined to tropical savanna areas. A more ‘widespread’ group included ‘Chaco’ and ‘Maritime’ subgroups defined by their respective association with extreme temperatures or precipitation. Ordination multivariate analyses showed (1) two climatic gradients throughout the study area: one of temperature and the other of precipitation, and (2) that climatic variables significantly explained the observed assemblages of phorids. Positive and negative signs of the eigenvalues from the main axes of a canonical correspondence analysis allowed us to define eight communities whose geographical distribution resembled that of phytogeographical regions. We found a significant and positive correlation between geographical areas and mid latitudinal points, and furthermore, the Mantel test based on climatic variables suggested a mechanism for Rapoport's rule applying in the case of Pseudacteon. Main conclusions Pseudacteon species with greater mid-latitudinal points occupy broader geographical areas and confront more stressful environmental conditions. Because the composition of Pseudacteon communities is largely determined by climatic variables, the correspondence between climates at sites of origin vs. sites of release should be an important consideration in choosing specific phorids for biocontrol efforts. Resumen Metas Solenopsis richteri y S. invicta, dos miembros de las hormigas de fuego del grupo Saevissima, se han tornado serias plagas despues de ser introducidas desde Argentina/Brasil a otros continentes. En Sud America, estas especies, asi como otras Solenopsis, se encuentran distribuidas a lo largo de una gran variedad de habitats y zonas climaticas. En Norte America, S. invicta, que fue introducida sin su fauna parasitoide, ahora se distribuye de costa a costa en el Sur de ese pais. El exito de la introduccion de los foridos Pseudacteon como una estrategia de control biologico ha variado dependiendo de las zonas climaticas. Nuestro objetivo fue juntar toda la informacion sobre los foridos parasitoides de las hormigas de fuego de Argentina y Brasil, para estimar su riqueza y rangos geograficos, para realizar analisis climaticos de sus distribuciones, para definir grupos y comunidades climaticas, y para poner a prueba la regla de Rapoport y un mecanismo que la explique. Ubicacion  Argentina y Brasil (America del Sur). Metodos  Construimos una base de datos de los parasitoides especificos de las hormigas de fuego a lo largo del rango geografico conocido, a partir de datos de colectas de campo, de colecciones de museos, y de registros historicos. Ubicamos en un mapa entre los 10° y 38° LS y entre los 35° y 65° LO, los 123 sitios donde se registraron los parasitoides; en ellos ademas asignamos los valores correspondientes de 15 variables ambientales. Calculamos la riqueza para toda la region asi como para cada provincia fitogeografica, usando curvas de rarefaccion con los estimadores ICE y Mmean. Calculamos los puntos latitudinales medios, los rangos geograficos, y las areas de cada especie. La correlacion entre el punto latitudinal medio y los rangos/areas fue puesta a prueba con la generacion de un modelo nulo producto de la aleatorizacion de las especies. Usamos distintos tipos de analisis multivariados para distinguir grupos de foridos por regiones fitogeograficas, huesped y clima, para encontrar gradientes de clima a lo largo del area estudiada, para definir comunidades de foridos en relacion al clima, y para poner a prueba un mecanismo para la regla de Rapoport. Resultados  Las estimaciones de riqueza, usando ambos estimadores, fue similar o mas alta a la observada dependiendo de las provincias fitogeograficas. Los analisis de clasificacion multivariados basados en provincias fitogeograficas, huespedes y clima, revelaron distintos agrupamientos de Pseudacteon. El grupo del ‘Cerrado’ estuvo confinado a ambientes de savanas. El grupo de ‘Amplia Distribucion’ incluyo al sub-grupo del ‘Chaco’ y al ‘Maritimo’ debido a su respectiva asociacion con la temperatura y precipitacion. Los analisis multivariados de ordenamiento mostraron (1) dos gradientes climaticos en el area de estudio, uno de temperatura y otro de precipitacion, (2) que las variables climaticas explicaron significativamente el ensamble de foridos observado. Los signos, positivos y negativos, de los autovalores de los tres ejes principales del analisis de correspondencia canonica nos permitio definir ocho comunidades cuya distribucion geografica se parecia a la de las provincias fitogeograficas. Encontramos una correlacion positiva y significativa entre las areas geograficas y los puntos latitudinales medios, es mas, el Test de Mantel basado en las variables climaticas permitio identificar un mecanismo para este ensamble de Pseudacteon. Conclusiones principales  Las especies de Pseudacteon con puntos latitudinales medios mayores ocupan areas geograficas mas grandes y confrontan condiciones de stress climatico mayores. Dado que la composicion de las comunidades de Pseudacteon esta en su mayor parte determinada por variables climaticas, la correspondencia climatica entre el sitio de origen y el sitio de liberacion de los parasitoides deberia ser una consideracion importante para la seleccion de especies de foridos para el control biologico.

  • Biogeography and macroecology of phorid flies that attack fire ants in south‐eastern Brazil and Argentina
    Journal of Biogeography, 2005
    Co-Authors: Patricia Julia Folgarait, M A Pesquero, Sanford D. Porter, Octavio A Bruzzone, Lawrence E. Gilbert
    Abstract:

    Aim  Saevissima group fire ants, Solenopsis richteri and S. invicta, have become serious pests when introduced from Argentina and Brazil to other continents. In South America, Solenopsis are distributed across a great variety of habitats and climates. In North America, S. invicta, introduced free of phorids, now ranges from coast to coast in the south. Success in introducing particular Pseudacteon as agents for the biological control of fire ants has varied across climatic zones. We aimed at assembling all the information about fire ant phorids from Argentina and Brazil, to estimate their richness and geographical ranges, to perform a climatic analysis for these distributions, to define groups and climate-based communities, and to test and elucidate Rapoport's biogeographical rule. Location  Argentina and Brazil (South America). Methods  From field and museum collections and historical records, we developed a Database of fire ant-specific phorids throughout their known geographical range. A total of 123 sites with values for 15 climatic variables were mapped between 10° and 38° SL and between 35° and 65° C WL for the presence/absence of phorids. We calculated species richness across all sites combined, and for each phytogeographical region, using rarefaction curves, and ICE and Mmean estimators. We calculated mid-latitudinal points, geographical ranges and areas for each species. The correlation between mid-latitudinal point and ranges/areas was tested against a null model generated from the randomization of the raw distributional Data. We used several types of multivariate analyses to distinguish groups of phorids by phytogeographical regions, Hosts and climate, to find gradients of climate throughout the studied area, to define phorid communities in terms of their relationships with gradients of climate, and to test a mechanism for Rapoport's rule. Results  Richness estimations using ICE and Mmean estimators were similar or higher than the observed values depending on the phytogeographical region. Cluster multivariate analyses based on climatic, phytogeographic and Host Data revealed distinct groupings of Pseudacton. The ‘cerrado’ group was confined to tropical savanna areas. A more ‘widespread’ group included ‘Chaco’ and ‘Maritime’ subgroups defined by their respective association with extreme temperatures or precipitation. Ordination multivariate analyses showed (1) two climatic gradients throughout the study area: one of temperature and the other of precipitation, and (2) that climatic variables significantly explained the observed assemblages of phorids. Positive and negative signs of the eigenvalues from the main axes of a canonical correspondence analysis allowed us to define eight communities whose geographical distribution resembled that of phytogeographical regions. We found a significant and positive correlation between geographical areas and mid latitudinal points, and furthermore, the Mantel test based on climatic variables suggested a mechanism for Rapoport's rule applying in the case of Pseudacteon. Main conclusions Pseudacteon species with greater mid-latitudinal points occupy broader geographical areas and confront more stressful environmental conditions. Because the composition of Pseudacteon communities is largely determined by climatic variables, the correspondence between climates at sites of origin vs. sites of release should be an important consideration in choosing specific phorids for biocontrol efforts. Resumen Metas Solenopsis richteri y S. invicta, dos miembros de las hormigas de fuego del grupo Saevissima, se han tornado serias plagas despues de ser introducidas desde Argentina/Brasil a otros continentes. En Sud America, estas especies, asi como otras Solenopsis, se encuentran distribuidas a lo largo de una gran variedad de habitats y zonas climaticas. En Norte America, S. invicta, que fue introducida sin su fauna parasitoide, ahora se distribuye de costa a costa en el Sur de ese pais. El exito de la introduccion de los foridos Pseudacteon como una estrategia de control biologico ha variado dependiendo de las zonas climaticas. Nuestro objetivo fue juntar toda la informacion sobre los foridos parasitoides de las hormigas de fuego de Argentina y Brasil, para estimar su riqueza y rangos geograficos, para realizar analisis climaticos de sus distribuciones, para definir grupos y comunidades climaticas, y para poner a prueba la regla de Rapoport y un mecanismo que la explique. Ubicacion  Argentina y Brasil (America del Sur). Metodos  Construimos una base de datos de los parasitoides especificos de las hormigas de fuego a lo largo del rango geografico conocido, a partir de datos de colectas de campo, de colecciones de museos, y de registros historicos. Ubicamos en un mapa entre los 10° y 38° LS y entre los 35° y 65° LO, los 123 sitios donde se registraron los parasitoides; en ellos ademas asignamos los valores correspondientes de 15 variables ambientales. Calculamos la riqueza para toda la region asi como para cada provincia fitogeografica, usando curvas de rarefaccion con los estimadores ICE y Mmean. Calculamos los puntos latitudinales medios, los rangos geograficos, y las areas de cada especie. La correlacion entre el punto latitudinal medio y los rangos/areas fue puesta a prueba con la generacion de un modelo nulo producto de la aleatorizacion de las especies. Usamos distintos tipos de analisis multivariados para distinguir grupos de foridos por regiones fitogeograficas, huesped y clima, para encontrar gradientes de clima a lo largo del area estudiada, para definir comunidades de foridos en relacion al clima, y para poner a prueba un mecanismo para la regla de Rapoport. Resultados  Las estimaciones de riqueza, usando ambos estimadores, fue similar o mas alta a la observada dependiendo de las provincias fitogeograficas. Los analisis de clasificacion multivariados basados en provincias fitogeograficas, huespedes y clima, revelaron distintos agrupamientos de Pseudacteon. El grupo del ‘Cerrado’ estuvo confinado a ambientes de savanas. El grupo de ‘Amplia Distribucion’ incluyo al sub-grupo del ‘Chaco’ y al ‘Maritimo’ debido a su respectiva asociacion con la temperatura y precipitacion. Los analisis multivariados de ordenamiento mostraron (1) dos gradientes climaticos en el area de estudio, uno de temperatura y otro de precipitacion, (2) que las variables climaticas explicaron significativamente el ensamble de foridos observado. Los signos, positivos y negativos, de los autovalores de los tres ejes principales del analisis de correspondencia canonica nos permitio definir ocho comunidades cuya distribucion geografica se parecia a la de las provincias fitogeograficas. Encontramos una correlacion positiva y significativa entre las areas geograficas y los puntos latitudinales medios, es mas, el Test de Mantel basado en las variables climaticas permitio identificar un mecanismo para este ensamble de Pseudacteon. Conclusiones principales  Las especies de Pseudacteon con puntos latitudinales medios mayores ocupan areas geograficas mas grandes y confrontan condiciones de stress climatico mayores. Dado que la composicion de las comunidades de Pseudacteon esta en su mayor parte determinada por variables climaticas, la correspondencia climatica entre el sitio de origen y el sitio de liberacion de los parasitoides deberia ser una consideracion importante para la seleccion de especies de foridos para el control biologico.

Ursula E Bauer - One of the best experts on this subject based on the ideXlab platform.

  • monitoring the tobacco use epidemic iii the Host Data sources and methodological challenges
    Preventive Medicine, 2009
    Co-Authors: Cristine D Delnevo, Ursula E Bauer
    Abstract:

    Abstract Objective This Host paper (III of V) reviews key surveillance and evaluation systems that monitor the characteristics, attitudes and behaviors of tobacco users that are crucial for tobacco control efforts. Methods We summarize and expand on the recommendations from the Host Working Group of the National Tobacco Monitoring, Research and Evaluation Workshop. We also discuss research challenges and make additional recommendations for improving tobacco control surveillance and evaluation. Results We reviewed 10 major US surveys that collect Data on tobacco use. A great deal of Data is collected but gaps exist. Data collection on cigars, smokeless tobacco, brand, menthols, and PREPs is sparse and infrequent. Also, a number of factors, including, but not limited to, changes in US population composition, declines in survey response rates, and increases in cell phone use present research challenges that may impact the ongoing utility of these systems. Conclusions Although the field of tobacco control research is an advanced area of public health, improvements in Data systems are necessary to accurately evaluate progress and continue tobacco control gains. A coordinated surveillance and evaluation network would increase efficiency and improve the overall utility, quality and timeliness of the current Data systems.

  • Monitoring the tobacco use epidemic III: The Host: Data sources and methodological challenges.
    Preventive medicine, 2008
    Co-Authors: Cristine D Delnevo, Ursula E Bauer
    Abstract:

    This Host paper (III of V) reviews key surveillance and evaluation systems that monitor the characteristics, attitudes and behaviors of tobacco users that are crucial for tobacco control efforts. We summarize and expand on the recommendations from the Host Working Group of the National Tobacco Monitoring, Research and Evaluation Workshop. We also discuss research challenges and make additional recommendations for improving tobacco control surveillance and evaluation. We reviewed 10 major US surveys that collect Data on tobacco use. A great deal of Data is collected but gaps exist. Data collection on cigars, smokeless tobacco, brand, menthols, and PREPs is sparse and infrequent. Also, a number of factors, including, but not limited to, changes in US population composition, declines in survey response rates, and increases in cell phone use present research challenges that may impact the ongoing utility of these systems. Although the field of tobacco control research is an advanced area of public health, improvements in Data systems are necessary to accurately evaluate progress and continue tobacco control gains. A coordinated surveillance and evaluation network would increase efficiency and improve the overall utility, quality and timeliness of the current Data systems.

Michael J Medley - One of the best experts on this subject based on the ideXlab platform.

  • optimal signature design for spread spectrum steganography
    IEEE Transactions on Image Processing, 2007
    Co-Authors: M Gkizeli, Dimitris A Pados, Michael J Medley
    Abstract:

    For any given Host image or group of Host images and any (block) transform domain of interest, we find the signature vector that when used for spread-spectrum (SS) message embedding maximizes the signal-to-interference-plus-noise ratio (SINR) at the output of the corresponding maximum-SINR linear filter. We establish that, under a (colored) Gaussian assumption on the transform domain Host Data, the same derived signature minimizes Host distortion for any target message recovery error rate and maximizes the Shannon capacity of the covert steganographic link. Then, we derive jointly optimal signature and linear processor designs for SS embedding in linearly modified transform domain Host Data and demonstrate orders of magnitude improvement over current SS steganographic practices. Optimized multisignature/multimessage embedding in the same Host Data is studied as well

  • ICIP - SINR, bit error rate, and Shannon capacity optimized spread-spectrum steganography
    2004 International Conference on Image Processing 2004. ICIP '04., 1
    Co-Authors: M Gkizeli, Dimitris A Pados, Michael J Medley
    Abstract:

    For any given Host image and (block) transform domain of interest, we derive the signature vector that when used for spread-spectrum (SS) message embedding that maximizes the signal-to-interference-plus-noise ratio (SINR) at the output of the maximum SINR linear filter receiver. Under a (colored) Gaussian assumption on the transform domain Host Data, we see that the same signature offers minimum probability of error message recovery at any Host distortion level or -conversely- minimizes the Host distortion for any probability of error target level. In addition, we show that the same signature maximizes the Shannon capacity of the covert link. All developments are then generalized to cover SS embedding in linearly processed block transform domain Host Data with orders of magnitude demonstrated improvement over current SS steganographic practices.

Alessandro Neri - One of the best experts on this subject based on the ideXlab platform.

  • Blind quality assessment system for multimedia communications using tracing watermarking
    IEEE Transactions on Signal Processing, 2003
    Co-Authors: Patrizio Campisi, Marco Carli, Gaetano Giunta, Alessandro Neri
    Abstract:

    This paper presents a novel method to blindly estimate the quality of a multimedia communication link by means of an unconventional use of digital fragile watermarking. Data hiding by digital watermarking is usually employed for multimedia copyright protection, authenticity verification, or similar purposes. However, watermarking is here adopted as a technique to provide a blind measure of the quality of service in multimedia communications. Specifically, a fragile watermark is hidden in an MPEG-like Host Data video transport stream using a spread-spectrum approach. Like a tracing signal, the watermark tracks the Data, where it is embedded, since both the watermark and the Host Data follow the same communication link. The estimation of the tracing watermark allows dynamically evaluating the effective quality of the provided video services. This depends on the whole physical layer, including the employed video co/decoder. The performed method is based on the evaluation of the mean-square-error between the estimated and the actual watermarks. The proposed technique has been designed for application to wireless multimedia communication systems. According to the results obtained, the sensitivity of the detected tracing watermark on the quality of service (QoS) indices provides for some useful capabilities for analyzing future mobile Universal Mobile Telecommunications System (UMTS) services

Marco Carli - One of the best experts on this subject based on the ideXlab platform.

  • Difference expansion and prediction for high bit-rate reversible Data hiding
    Journal of Electronic Imaging, 2012
    Co-Authors: Giulia Boato, Marco Carli, Federica Battisti, Marco Azzoni, Karen Egiazarian
    Abstract:

    Reversible Data hiding deals with the insertion of auxiliary information into a Host Data without causing any permanent degradation to the original signal. In this contribution a high capacity reversible Data hiding scheme, based on the classical difference expansion insertion algorithm, is presented. The method exploits a prediction stage, followed by prediction errors modification, both in the spatial domain and in the S-transform domain. Such two step embedding allows us to achieve high embedding capacity while preserving a high image quality, as demonstrated in the experimental results

  • EUVIP - Reversible watermarking using prediction and Difference Expansion
    2010 2nd European Workshop on Visual Information Processing (EUVIP), 2010
    Co-Authors: Marco Azzoni, Marco Carli, Giulia Boato, Karen Egiazarian
    Abstract:

    Reversible Data hiding deals with the insertion of auxiliary information into a Host Data without causing any permanent degradation to the original signal. In this paper a novel reversible Data hiding scheme, based on the classical Difference Expansion insertion algorithm, is presented. A prediction stage is adopted in the transform domain and the embedding algorithm is applied to computed prediction errors. To increase the overall embedding capacity, a multi resolution extension has been proposed. Experimental test demonstrate the effectiveness of the proposed approach in achieving high embedding capacity while preserving a high image quality.

  • Blind quality assessment system for multimedia communications using tracing watermarking
    IEEE Transactions on Signal Processing, 2003
    Co-Authors: Patrizio Campisi, Marco Carli, Gaetano Giunta, Alessandro Neri
    Abstract:

    This paper presents a novel method to blindly estimate the quality of a multimedia communication link by means of an unconventional use of digital fragile watermarking. Data hiding by digital watermarking is usually employed for multimedia copyright protection, authenticity verification, or similar purposes. However, watermarking is here adopted as a technique to provide a blind measure of the quality of service in multimedia communications. Specifically, a fragile watermark is hidden in an MPEG-like Host Data video transport stream using a spread-spectrum approach. Like a tracing signal, the watermark tracks the Data, where it is embedded, since both the watermark and the Host Data follow the same communication link. The estimation of the tracing watermark allows dynamically evaluating the effective quality of the provided video services. This depends on the whole physical layer, including the employed video co/decoder. The performed method is based on the evaluation of the mean-square-error between the estimated and the actual watermarks. The proposed technique has been designed for application to wireless multimedia communication systems. According to the results obtained, the sensitivity of the detected tracing watermark on the quality of service (QoS) indices provides for some useful capabilities for analyzing future mobile Universal Mobile Telecommunications System (UMTS) services