La responsabilidad de los Prácticos del Canal de Panamá a partir del año 2000

El fin de este estudio es determinar cuál sería el mejor sistema de practicaje en el Canal de Panamá y en los puertos de Balboa y Cristóbal, a partir del año 2000. Hay dos sistemas de practicaje que se diferencian por el rol de sus dos figuras principales: el capitán del buque y el práctico. En el sistema de practicaje internacional, el capitán tiene la responsabilidad de la navegación de su buque, pero en el sistema de practicaje actual del Canal de Panamá, la tiene el práctico. Es importante anotar que quien lleva la responsabilidad de la navegación del buque también la tiene en caso de que ocurra un accidente. Para solucionar el dilema, el investigador entrevistó a los 33 expertos marítimos locales más calificados en la materia; en los que se incluyen a empleados de la Comisión del Canal, abogados marítimos, agentes navieros y a ejecutivos de la Autoridad Portuaria Nacional. En el caso del Canal de Panamá, el 79% de los expertos en asuntos marítimos y la mayoría de cada uno de los cuatro grupos, concluyeron que es preferible mantener el sistema de practicaje actual. No obstante, en los puertos de Balboa y Cristóbal, el 67% de los expertos y la mayoría de cada uno de los cuatro grupos, se decidieron por el sistema de practicaje internacional. En este estudio se recomienda mantener el sistema de practicaje actual en el Canal de Panamá, en el cual es el práctico el responsable de la navegación del buque, y cambiar en los Puertos de Balboa y Cristóbal, al sistema de practicaje internacional, donde el capitán es el responsable de la navegación de su buque

Efficacy of angler catch data as a population and conservation monitoring tool for the flagship mahseer fishes (Tor spp.) of Southern India

Mahseer (Tor spp.) are flagship fishes in South Asian rivers. Their populations are threatened through poaching and habitat disturbance, yet they are highly prized game fishes due to their large size, appearance and sporting qualities. The international recreational angling community has frequently been cited as playing a vital role in conserving these fishes while also providing economic benefit to poor rural communities. Owing to a lack of scientific data and the considerable challenges associated with monitoring fish populations in large monsoonal rivers, efforts to determine the long-term trends in their populations has focused on sport-fishing catch records. Here, catch data collected between 1998 and 2012 from Galibore, a former fishing camp on the River Cauvery, Karnataka, India, were analysed to determine the catch per unit effort (CPUE – by number and weight) as an indicator of relative fish abundance, along with the size structure of catches. This fishery operated a mandatory catch-and-release (C&R) policy, and provided the fish community with protection from illegal fishing. Between 1998 and 2012, 23 620 hours fishing effort were applied to catch and release 6161 mahseer, ranging in size from 1 to 104 lbs (0.45–46.8 kg) in weight. Across the period, CPUE in number increased significantly over time with a concomitant decrease in CPUE by weight, revealing strong recruitment in the population and a shift in population size structure. This suggests a strong response to the C&R policy and the reduction in illegal fishing, indicating that conservation strategies focusing on the beneficial and negative aspects of exploitation can be successful in achieving positive outcomes. These outputs from angler catch data provide insights into the mahseer population that were impossible to collect by any alternative method. They provide the most comprehensive analysis of a long-term dataset specific to any of the mahseer species across their entire geographical range and demonstrate the value of organised angling as a conservation monitoring tool to enhance biological data, and inform conservation and fishery management actions

The use of fractal dimension for texture-based enhancement of aeromagnetic data.

This thesis investigates the potential of fractal dimension (FD) as a tool for enhancing airborne magnetic data. More specifically, this thesis investigates the potential of FD-based texture transform images as tools for aiding in the interpretation of airborne magnetic data. A series of different methods of estimating FD are investigated, specifically: • geometric methods (1D and 2D variation methods and 1D line divider method); • stochastic methods (1D and 2D Hurst methods and 1D and 2D semi-variogram methods), and; • spectral methods (1D and 2D wavelet methods and 1D and 2D Gabor methods). All of these methods are able to differentiate between varying theoretical FD in synthetic profiles. Moreover, these methods are able to differentiate between theoretical FDs when applied to entire profiles or in a moving window along the profile. Generally, the accuracy of the estimated FD improves when window size is increased. Similarly, the standard deviation of estimated FD decreases as window size increases. This result implied that the use of moving window FD estimates will require a trade off between the quality of the FD estimates and the need to use small windows to allow better spatial resolution. Application of the FD estimation methods to synthetic datasets containing simple ramps, ridges and point anomalies demonstrates that all of the 2D methods and most of the 1D methods are able to detect and enhance these features in the presence of up to 20% Gaussian noise. In contrast, the 1D Hurst and line divider methods can not clearly detect these features in as little as 10% Gaussian noise. Consequently, it is concluded that the 1D Hurst and line divider methods are inappropriate for enhancing airborne magnetic data. The application of these methods to simple synthetic airborne magnetic datasets highlights the methods’ sensitivity to very small variations in the data. All of the methods responded strongly to field lines some distance from the causative magnetic bodies. This effect was eliminated through the use of a variety of tolerances that essentially required a minimum level of difference between data points in order for FD to be calculated. Whilst this use of tolerances was required for synthetic datasets, its use was not required for noise corrupted versions of the synthetic magnetic data. The results from applying the FD estimation techniques to the synthetic airborne magnetic data suggested that these methods are more effective when applied to data from the pole. Whilst all of the methods were able to enhance the magnetic anomalies both at the pole and in the Southern hemisphere, the responses of the FD estimation techniques were notably simpler for the polar data. With the exception of the 1D Hurst and line divider methods, all of the methods were also able to enhance the synthetic magnetic data in the presence of 10% Gaussian noise. Application of the FD estimation methods to an airborne magnetic dataset from the Merlinleigh Sub-basin in Western Australia demonstrated their ability to enhance subtle structural features in relatively smooth airborne magnetic data. Moreover, the FD-based enhancements were able to enhance some features of this dataset better than any of the conventional enhancements considered (i.e. an analytic signal, vertical and total horizontal derivatives, and automatic gain control). Most of the FD estimation techniques enhanced similar features to each other. However, the 2D methods generally produced clearer results than their associated 1D methods. In contrast to this result, application of the FD-based enhancements to more variable airborne magnetic data from the Tanami region in the Northern Territory demonstrated that these methods are not as well suited to this style of data. The main conclusion from this work is that FD-based enhancement of relatively smooth airborne magnetic data can provide valuable input into an interpretation process. This suggests that these methods are particularly useful for aiding in the interpretation of airborne magnetic data from regions such as sedimentary basins where the distribution of magnetic sources is relatively smooth and simple.Thesis (Ph.D.) - University of Adelaide, Australian School of Petroleum, 200

The Brain, Memory, and Oral Tradition in Music

Recent studies of the brain in various subfields have shown that memory is really a type of re-creation—piecing together many elements stored separately. Memory, creativity and their connections have been focal points in cognitive studies of music, but seldom have they been approached from the vantage point of music in oral tradition, which is the primary mode of transmitting music in the world. This paper argues that the oral transmission of music provides a fertile ground for learning about memory and creativity and their connections. Traditional musicians often know hundreds of tunes and are ready to perform them at a moment’s notice—but seldom in exactly the same way. Depending upon the particular oral tradition studied, greater or lesser emphasis is laid upon the ‘accuracy’ and the unchanging nature of a rendition vs. creative variation. After recounting some of these remarkable feats of memory and creativity, drawn from my own fieldwork, I suggest a number of ways in which this “re-creative” feature of oral transmission illuminates cognitive research

Numerical and laboratory investigations of electrical resistance tomography for environmental monitoring

© ASEG 2004Numerical and laboratory studies have been conducted to test the ability of Electrical Resistance Tomography ? a technique used to map the electrical resistivity of the subsurface ? to delineate contaminant plumes. Two-dimensional numerical models were created to investigate survey design and resolution. Optimal survey design consisted of both downhole and surface electrode sites. Resolution models revealed that while the bulk fluid flow could be outlined, small-scale fingering effects could not be delineated. Laboratory experiments were conducted in a narrow glass tank to validate theoretical models. A visual comparison of fluid flow with ERT images also showed that, while the bulk fluid flow could be seen in most instances, fine-scale effects were indeterminate.T. Dhu and G. Heinsonhttp://www.publish.csiro.au/nid/224/paper/EG04033.ht