Choosing between Cox proportional hazards and logistic models for interval-censored data via bootstrap

This work develops a new methodology in order to discriminate models for interval-censored data based on bootstrap residual simulation by observing the deviance difference from one model in relation to another, according to Hinde (1992). Generally, this sort of data can generate a large number of tied observations and, in this case, survival time can be regarded as discrete. Therefore, the Cox proportional hazards model for grouped data (Prentice & Gloeckler, 1978) and the logistic model (Lawless, 1982) can befitted by means of generalized linear models. Whitehead (1989) considered censoring to be an indicative variable with a binomial distribution and fitted the Cox proportional hazards model using complementary log-log as a link function. In addition, a logistic model can be fitted using logit as a link function. The proposed methodology arises as an alternative to the score tests developed by Colosimo et al. (2000), where such models can be obtained for discrete binary data as particular cases from the Aranda-Ordaz distribution asymmetric family. These tests are thus developed with a basis on link functions to generate such a fit. The example that motivates this study was the dataset from an experiment carried out on a flax cultivar planted on four substrata susceptible to the pathogen Fusarium oxysoprum. The response variable, which is the time until blighting, was observed in intervals during 52 days. The results were compared with the model fit and the AIC values.

A relação entre o social e o natural nas abordagens de hazards e de desastres

O artigo aborda as teorias dos Hazards e dos Desastres. Nos últimos anos estas duas tradições teóricas têm recebido novos impulsos pela renovação de seus marcos de referência conceitual. Construídas em torno de uma longa tradição de pesquisa empírica, estas teorias explicam os impactos provocados por fenômenos como enchentes, terremotos, tornados e epidemias mediante a integração analítica das dimensões natural e social. Neste sentido, seu estudo pode fornecer subsídios para a interpretação destes problemas no Brasil.

Los recursos hídricos de América Latina y del Caribe: planificación, desastres naturales y contaminación = The water resources of Latin America and the Caribbean: planning, hazards and pollution

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Los desastres naturales relacionados con el agua = Water-related natural hazards

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Los recursos hídricos de América Latina y el Caribe: riesgos naturales relacionados con el agua = The water resources of Latin America and the Caribbean: water-related natural hazards

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Tobacco in adolescence: importance to knowledge the health hazards and preventive measures

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Thermal Imagery Applied to Reducing Bird Hazards to Aircraft at Airports

Airports worldwide are at a disadvantage when it comes to being able to spot birds and warn aircrews about the location of flocks either on the ground or close to the airfield. Birds simply cannot be easily seen during the day and are nearly invisible targets for planes at night or during low visibility. Thermal imaging (infrared) devices can be used to allow ground and tower personnel to pinpoint bird locations day or night, thus giving the airport operators the ability to launch countermeasures or simply warn the aircrews. This technology is available now, though it has been predominately isolated to medical and military system modifications. The cost of these devices has dropped significantly in recent years as technology, capability, and availability have continued to increase. Davison Army Airfield (DAAF), which is located about 20 miles south of Ronald Reagan National Airport in Washington, DC, is the transient home to many bird species including an abundance of ducks, seagulls, pigeons, and migrating Canadian geese. Over the past few years, DAAF implemented a variety of measures in an attempt to control the bird hazards on the airfield. Unfortunately, when it came to controlling these birds on or near our runways and aircraft movement areas we were more reactive than proactive. We would do airfield checks several times an hour to detect and deter any birds in these areas. The deterrents used included vehicle/human presence, pyrotechnics, and the periodic use of a trained border collie. At the time, we felt like we were doing all we could to reduce the threat to aircraft and human life. It was not until a near fatal accident in October 1998, when we truly realized how dangerous our operating environment really was to aircraft at or near the airfield. It was at this time, we had a C-12 (twin-engine passenger plane) land on our primary runway at night. The tower cleared the aircraft to land, and upon touchdown to the runway the aircraft collided with a flock of geese. Neither the tower nor the crew of the aircraft saw the geese because they were obscured in the darkness. The end result was 12 dead geese and $374,000 damage to the C-12. Fortunately, there were no human fatalities, but it was painfully clear we needed to improve our method of clearing the runway at night and during low visibility conditions. It was through this realization that we ventured to the U.S. Army Communications and Electronics Command for ideas on ways to deal with our threat. It was through a sub-organization within this command, Night Vision Labs, that we realized the possibilities of modifying thermal imagery and infrared technology to detecting wildlife on airports.

BIRD HAZARDS TO AIRCRAFT

When I spoke to the third Bird Control Seminar in 1966 on "Ecological Control of Bird Hazards to Aircraft", I reviewed what we had accomplished up to that time. I spoke about the extent of the problem, the bird species involved and the methods we used to make the airports less attractive to birds that created hazards to aircraft. I wish to discuss today our accomplishments since 1966. I have presented a number of papers on the topic including one with Dr. W. W. H. Gunn, in 1967 at a meeting in the United Kingdom, and others in the United States (1968 and 1970) and at the World Conference on Bird Hazards to Aircraft in Canada in 1969. There is no longer any question about the consequences of collision between birds and aircraft. Aircraft have not become less vulnerable either. Engines on the Boeing 747 have been changed as a result of damage caused by ingested birds. Figures crossing my desk daily show that while we are reducing the number of serious incidents and cutting down repair costs, we will continue to have bird strikes. Modification of the airport environment (Solman, 1966) has gone on continuously since 1963. The Department of Transport of Canada has spent more than 10 million dollars modifying major Canadian airports to reduce their attractiveness to birds. Modifications are still going on and will continue until bird attraction has been reduced to a minimum.

EFFECTS OF A BIRD HAZARD REDUCTION FORCE ON REDUCING BIRD/AIRCRAFT STRIKE HAZARDS AT THE ATLANTIC CITY INTERNATIONAL AIRPORT, NJ

Bird-aircraft strikes at the Atlantic City International Airport (ACY) increased from 18 in 1989 to 37 in 1990. The number of bird-aircraft strikes involving gulls (Larus spp.) during this time rose from 6 to 27, a 350% increase. The predominant species involved in bird strikes was the laughing gull (L. atricilla). Pursuant to an interagency agreement between the U.S. Department of Transportation (USDOT), Federal Aviation Administration (FAA) and the U.S. Department of Agriculture (USDA)l Animal and Plant Health Inspection Service (APHIS)/Animal Damage Control (ADC), ADC established a Emergency/Experimental Bird Hazard Reduction Force (BHFF) at ACY in 1991. An Environmental Assessment (EA) and Finding of No Significant Impact (FONSI) for the 1991 Emergency/Experimental BHRF was executed and signed by the FAA on 19 May 1991. The BHRF was adopted at this time by the FAA Technical Center as an annual program to reduce bird strikes at ACY. The BHRF goals are to minimize or eliminate the incidence of bird-aircraft strikes and runway closures due to increased bird activities. A BHRF team consisting of ADC personnel patrolled ACY for 95 days from 26 May until 28 August 1992, for a total of 2,949 person-hours. The BHRF used a combination of pyrotechnics, amplified gull distress tapes and live ammunition to harass gulls away from the airport from dawn to dusk. Gullaircraft strikes were reduced during BHRF operations in 1992 by 86% compared to gull strikes during summer months of 1990 when there was not a BHRF team. Runway closures due to bird activity decreased 100% compared to 1990 and 1991 closures. The BHRF should continue at ACY as long as birds are a threat to human safety and aircraft operations.