Search

Epidemiologists recently have worked more closely with social scientists. Their objective was to better understand human behavior as a risk factor for disease spread, and to analyze barriers to the effective implementation of control measures. A number of socio-psychology and behavior sciences studies undoubtedly have provided new insights on farmer's behavior. These studies tend to focus on farmers as individuals, and on cognitive or psychologic factors that may bias their perceptions of risks. However, the next research challenge is to give more attention to the collective dimension of health risks. This encompasses professional, institutional, political and market issues that also structure the way risks are managed by different stakeholders. From a sociological point of view, animal diseases can be considered as collective risks, and their management can be analyzed through the concept of collective action: action taken together by groups of people, based on common rules and mutual trust, to achieve shared objectives or to defend shared values. This shift, from individual perceptions to collective action, raises new questions that sociologists can contribute to answer. These questions include the structuration and relationships within and between groups of stakeholders (farmers, veterinarians...) as well the strategies of organizations -sometimes with competing interests- involved in risk management (public authorities, industry...). Our communication exposes this perspective shift. Based on researches conducted by the authors (especially on avian flu management and antibiotic use in livestock) and a large literature review, it points out the role of factors such as social bonds, market chain organization, shared values, trust in vet services...in framing farmer's risk management strategies. It concludes on the potential of this shift to renew the collaboration between epidemiologists and social scientists and to explore new paths of health intervention.

We present a technique to significantly improve the accuracy of bremsstrahlung spectra reconstructed from central-axis depth-dose data using inverse methods. While typical approaches directly use the measured depth-dose data, we show the advantage of using the gradient of these data for reconstruction. The inverse problem in terms of gradients is shown to be markedly less ill-conditioned than the usual inverse problem. In each case, a regularization is introduced to alleviate the effects of noise due to measurement and computation. The error in taking derivatives of depth-dose data is demonstrated to be sufficiently controllable as not to overtake the improvements in the conditioning of the inverse problem in a pair of simulated examples.

The identification of tumor antigens has spurred the development of efficient adjuvants and novel delivery systems for cancer immunotherapy. To this end, a peptide-based vaccine consisting of the Antennapedia transduction sequence (ANTP) attached to an antigenic peptide was designed to enhance per-cutaneous delivery into cells of the epidermis and dermis. Here we show that the topical application of OVA(257-264) linked to ANTP in mice onto tape-stripped skin resulted in enhanced delivery of the antigen through the skin whereas OVA(257-264) alone remained distributed uniformly on the skin surface. This delivery correlated with an increase in the CTL response against OVA. When mixed with CpG oligodinucleotides (ODN), the recombinant antigen protected mice from tumor challenge. These data provide the first indication that in vivo use of a translocation sequence can enhance delivery of therapeutic peptides and increase anti-tumor immunity through a simple and safe mechanism involving enhanced penetration of the skin barrier.

The convolution/superposition algorithm for computing dose from photon beams in radiation therapy planning requires knowledge of the energy spectrum. The algorithm can compute the dose for a polyenergetic beam as the weighted sum of the individual dose contributions from monoenergetic beams. In this study we exploit interface effects apparent in the dose distributions to discriminate among spectra of high energyphoton beams. We have studied the sensitivity of the depth dose distribution to the energy components using a hypothetical beam for various field sizes and depths in water and water–lung–water media. Six theoretical spectra were simulated. We compared depth dose data from these spectra using three quantitative measures which are inherently free of normalization ambiguities: for homogeneous water, the ratio D 20 /D 10 and a logarithmic derivative in the buildup region LD build-up and for inhomogeneous lung/water, the lung correction factor (CF). It was found that the ability of both the CF and the LD build-up tests to discriminate between the various theoretical spectra were superior to that of the D 20 /D 10 test. This discriminating power of the CF test decreases with increasing field size due to restored electronic equilibrium. The CF test, though, has some advantages over the LD build-up test since it is less prone to electron contamination issues and numerical errors. A practical example with a 15 MV photon beam illustrates the process. Consequently, we suggest that as part of a beam-commissioning methodology, designated electronic disequilibrium test cases be implemented in unambiguously determining the correct energy spectrum to be used.

Validation experiments have been conducted using 6 and 15 MV photons in inhomogeneous (water/lung/water) media to benchmark the accuracy of the DPM Monte Carlo code for photon beam dose calculations. Small field sizes (down to 2×2 cm 2 ) and low-density media were chosen for this investigation because the intent was to test the DPM code under conditions where lateral electronic disequilibrium effects are emphasized. The treatment head components of a Varian 21EX linear accelerator, including the jaws (defining field sizes of 2×2, 3×3 and 10×10 cm 2 ), were simulated using the BEAMnrc code. The phase space files were integrated within the DPM code system, and central axis depth dose and profile calculations were compared against diode measurements in a homogeneous water phantom in order to validate the phase space. Results of the homogeneous phantom study indicated that the relative differences between DPM calculations and measurements were within ±1% (based on the rms deviation) for the depth dose curves; relative profile dose differences were on average within ±1%/1 mm. Depth dose and profile measurements were carried out using an ion-chamber and film, within an inhomogeneous phantom consisting of a 6 cm slab of lung-equivalent material embedded within solid water. For the inhomogeneous phantom experiment, DPM depth dose calculations were within ±1% (based on the rms deviation) of measurements; relative profile differences at depths within and beyond the lung were, on average, within ±2% in the inner and outer beam regions, and within 1–2 mm distance-to-agreement within the penumbral region. Relative point differences on the order of 2–3% were within the estimated experimental uncertainties. This work demonstrates that the DPM Monte Carlo code is capable of accurate photon beam dose calculations in situations where lateral electron disequilibrium effects are pronounced.

In this study, a dosimetric evaluation of the new Kodak extended dose range (EDR) film versus ionization measurements has been conducted in homogeneous solid water and water‐lung equivalent layered heterogeneous phantoms for a relevant range of field sizes (up to a field size of 25×25 cm2 and a depth of 15 cm) for 6 and 15 MV photon beams from a linear accelerator. The optical density of EDR film was found to be linear up to about 350 cGy and over‐responded for larger fields and depths (5% for 25×25 cm2 at depth of 15 cm compared to a 10×10 cm2, 5 cm depth reference value). Central axis depth dose measurements in solid water with the film in a perpendicular orientation were within 2% of the Wellhöfer IC‐10 measurements for the smaller field sizes. A maximum discrepancy of 8.4% and 3.9% was found for the 25×25 cm2 field at 15 cm depth for 6 and 15 MV photons, respectively (with curve normalization at a depth of 5 cm). Compared to IC‐10 measurements, film measured central axis depth dose inside the lung slab showed a slight over‐response (at most 2%). At a depth of 15 cm in the lung phantom the over‐response was found to be 7.4% and 3.7% for the 25×25 cm2 field for 6 and 15 MV photons, respectively. When results were presented as correction factors, the discrepancy between the IC‐10 and the EDR was greatest for the lowest energy and the largest field size. The effect of the finite size of the ion chamber was most evident at smaller field sizes where profile differences versus film were observed in the penumbral region. These differences were reduced at larger field sizes and in situations where lateral electron transport resulted in a lateral spread of the beam, such as inside lung material. Film profiles across a lung tumor geometry phantom agreed with the IC‐10 chamber within the experimental uncertainties. From this investigation EDR film appears to be a useful medium for relative dosimetry in higher dose ranges in both water and lung equivalent material for moderate field sizes and depths. © 2003 American College of Medical Physics. PACS number(s): 87.53.Dq, 87.66.Cd, 87.66.Jj, 87.66.Xa

This is the first assessment of the status of cheetahs, Acinonyx jubatus , in Tanzania since 1965. It completes a series of recent studies in Kenya, Uganda, and Malawi to provide an overall understanding of the species’ status in East Africa. Interviews with 370 informants yielded 1050 cheetah sightings. Eighty nine percent of all sightings were made in 1990–1994, and 39% of all sightings occurred in protected areas. All-adult groups contained 1.92±0.04 S.D. individuals; the average number of dependent cubs was 2.63±0.08 S.D.; and the cub-to-adult ratio was 0.34. Since the 1960s, the distribution has remained stable overall with possible reductions in central Tanzania. No definite population trends were detected. With an estimated 569–1007 cheetahs, Tanzania emerges as a sanctuary for the species worldwide. However rangelands, which may hold half of Tanzania’s cheetahs, are undergoing rapid degradation. This precarious situation calls for the establishment of a nationwide monitoring program. Distribution map and population sizes from this study could serve as a baseline for monitoring the species’ status.

In this paper we examine whether the occurrence of cheetahs (Acinonyx jubatus) in Uganda can be predicted from habitat characteristics extracted from a vegetation map. We first established the status of the cheetah in Uganda through field-interviews that Gros conducted in 1990. Cheetahs occurred almost exclusively in the Karamoja region where we estimated 53–310 individuals. Based on 216 sightings, the average number of adults in all-adults sightings was 1.65 + SD 0.95 and the average number of cubs in family groups 2.5 + SD 1.65. Compared to Graham and Parker's 1965 East African survey, average adult group size was slightly smaller in 1990 and large family groups were rarer. Comparison with Gros 1990 survey showed considerably lower cub-to-adult ratio and percent of observations with cubs in Uganda than in Kenya. A Geographic Information System (GIS) analysis of vegetation structure in areas where cheetahs were observed and in those where none were reported suggested that cheetahs might favor habitats with 25–50% woody cover and grasses of medium height (50–100 cm). A discriminant analysis correctly classified 72.1% of ‘used’ habitats and 70.4% of ‘no-report’ habitats. A logistic regression analysis improved the correct allocation of ‘used’ habitats by 2.2%. Either the discriminant function or the logistic regression, which require only four easily obtainable vegetation characteristics, may help to pinpoint suitable cheetah habitats for conservation purposes. Our approach could be adapted for analyzing habitat suitability for other species of carnivores.

A field-interview survey of the distribution and abundance of the cheetah Acinonyx jubatus was conducted in Kenya between May and September 1989, and June and August 1990. Two hundred and twenty respondents ranging from wildlife conservationists to traditional pastoralists gave precise descriptions of cheetah observations, including dates and locations of sightings, and number, age class, and sex of the cheetahs observed. The 369 detailed sightings collected consisted of 249 observations of all-adult groups and 120 observations of family groups. The average number of adults in all-adult sightings was 1·8 + SE 0·07, and the average litter size in family groups was 2·6 + SE 0·10. Density estimates across the country ranged from 0·009 to 0·102 cheetah km−2, and were generally higher than elsewhere in Africa. A total number of 793 cheetahs was estimated in Kenya protected areas, and Masailand and the dry northern Districts appear to offer the best prospects for cheetah conservation in Kenya based on relative prey availability. The proportion of family groups among all sightings was twice as high in protected areas as on rangelands, and protected areas also held larger groups of males. The results do not support the thesis that cheetahs fare better on rangelands than in protected areas. Comparison with earlier surveys in Kenya showed remarkable stability in cheetah distribution and social structure over time. No firm conclusion could be drawn on trends in cheetah numbers, although scattered evidence supported a scenario of stability rather than decline in the last decades. Despite their limitations, interview based surveys can produce valuable results for monitoring elusive high-profile carnivores.

In current policies, targets for GHG (greenhouse gas) and more specifically CO2 emissions are set on the basis of annual emissions. However, warming effects associated with global average temperature rise depend on accumulation of GHG in the atmosphere. Due to the quantity and longevity of CO2 in the atmosphere there is increasing awareness that taking into account cumulative CO2 emissions in defining targets for restraining the growth of CO2 emissions would be particularly effective. The notion of effectiveness is linked to measuring the degree of achievement of the objectives. Considering CO2 emissions targets set over a few decades, the path of emissions reduction contains relevant information that cannot be captured by a classical measure like the distance to the target. The main contribution of this paper is the definition of an original measure of carbon dioxide reduction effectiveness, which allows comparison of specified CO2 reduction paths expressed in deterministic or probabilistic ways. Appropriate metrics are used to illustrate the proposed measure which in particular captures the importance of early action. The χ 0 measure is applied to simple what-if scenarios for the EU27 electricity and heat sector to 2050, evaluating the impact of each scenario with respect to a reference case.

This paper presents the results of a field interview survey and a literature review of the status of the cheetah (Acinonyx jubatus) in Tanzania. The survey was conducted between September 1993 and May 1994. The presence of cheetahs was documented in 30 areas (seven national parks, Ngorongoro Conservation Area, six game reserves, 13 game controlled areas, and 3 open areas), where a minimum of 366 cheetahs was estimated based on the sightings collected. In each of the 30 areas, cheetah status was evaluated in terms of distribution, frequency of observation, relative abundance, perceived trends in total numbers, and, where possible, minimum density estimates. The densities estimated, ranging from 1 cheetah per 40 km2 to 1/925 km2, were lower than the average density in Africa. Estimators of abundance, frequency of observations, and trends tended to indicate a better cheetah status in the northern acacia savannas than in the southern miombo savannas. Family groups and large groups of adults where common in the north, while sightings of lone adults predominated in the south. Recommendations for the conservation of cheetahs in Tanzania include: starting a nationwide monitoring of populations using this study as a blueprint and its results as a baseline; maintaining spatial connections between currently established cheetah populations; and favouring semi-nomadic pastoralism over farming and intensive ranching on rangelands. Journal of East African Natural History Vol. 89 (1&2) 2000: pp. 85-100

El incremento en el desarrollo de campus virtuales por parte de las universidades españolas hace que cada vez tomen más importancia los sistemas de formación a distancia, y la forma en que éstos son desarrollados con el fin de ofrecer a los alumnos un entorno de aprendizaje adaptado a sus necesidades. Es fundamental, dentro de estos sistemas de formación a distancia, la adaptación a las características cognitivas de los alumnos. Este artículo recoge una propuesta para la adaptación de los sistemas de e-learning a los estilos de aprendizaje de los alumnos, basada en el estándar de e-learning SCORM. SIN FINANCIACIÓN No data (2005)

The focus of this study is to validate whether the sensitivity of dose distribution following the interface of different media can be used to distinguish between small variations of photon energy spectra in the context of the convolution/superposition algorithm in the polyenergetic implementation (Philips Pinnacle3, ADAC Laboratories, Milpitas, CA). Calculations were performed in homogeneous water and heterogeneous lung/water phantoms. Spectra were generated, in which the weights of the low-, medium- and high-energy components were adjusted sequentially. The heterogeneity correction factor CFlung, the D20/D10 ratio for homogeneous water and logarithmic derivative in buildup region LDbuildup were assessed for their relative ability to discriminate between different spectra for various field sizes. In accordance with another study (Charland et al 2004), the superior discrimination ability of the CFlung and LDbuildup tests over the D20/D10 test was observed for changes in an energy component as small as 0.3% of the total weight in the energy spectrum. Furthermore, new tests utilizing transverse dose profile data for discriminating between spectra, Fringe Index (FI) and Penumbra Index (PI), were introduced. The discrimination ability of the PI and FI tests was superior when a medium containing interface effects was exploited to obtain the transverse profile data (water/lung phantom for PIhung and FIlung tests) as opposed to when a homogeneous water medium was used (PIwater and FIwater tests).