Minimum Message Length Inference of the Exponential Distribution with Type I Censoring

Data with censoring is common in many areas of science and the associated statistical models are generally estimated with the method of maximum likelihood combined with a model selection criterion such as Akaike’s information criterion. This manuscript demonstrates how the information theoretic minimum message length principle can be used to estimate statistical models in the presence of type I random and fixed censoring data. The exponential distribution with fixed and random censoring is used as an example to demonstrate the process where we observe that the minimum message length estimate of mean survival time has some advantages over the standard maximum likelihood estimate.

THE IMPACT OF REGIONAL SOIL CHARACTERISTICS ON THE SEISMIC ACTIVITY OF TERRITORIES

Постановка задачи. Необходимо осуществить оценку влияния региональной компоненты на величины магнитуд землетрясений. Результаты. Представлены результаты исследований соотношения между параметрами сейсмогенных разрывов (протяженность, площадь) и магнитудой поверхностных волн M. Предложены эмпирические зависимости, позволяющие оценить магнитуду поверхностных сейсмических волн на основе параметров очаговых зон инструментальных записей землетрясений, зарегистрированных в различных регионах мира. Определено, что на величину M влияют тип сейсмогенные подвижки, а также региональные тектонические особенности территорий. При этом для одних районов региональная составляющая имеет существенное значение, для других решающими факторами являются размеры разрыва и тип подвижки. Выводы. Сравнение результатов расчетов с использованием длины разрыва и площади показали, что зависимости, определенные с применением протяженности разрыва, с большей достоверностью оценивают возможную магнитуду землетрясения. Statement of the problem. The influence of the regional component on earthquake magnitudes must be assessed. Results. The results of studies of the relationship between the parameters of seismogenic discontinuities (length, area) and the magnitude of surface waves M are presented. Empirical dependences are proposed that allow one to estimate the magnitude of surface seismic waves based on the parameters of focal zones of instrumental records of earthquakes recorded in various regions of the world. It is established that M is influenced by the type of seismogenic movement, as well as regional tectonic features of territories, while for some areas the regional component is of significant importance, for others the size of the gap and the type of movement are critical. Conclusions. The comparison of the results of calculations using the gap length and area showed that the dependences determined using the gap length estimate the possible magnitude of the earthquake more accurately.

Estimating the diffusion length in the deepest section of ice cores; A case study for MIS19 in Dome-C

<p>To recover very old climate information from ice core records, one needs to interpret the deepest part of an ice core. As the oldest record, the Dome-C ice core can serve as an analogue for the Beyond EPICA Oldest Ice Core that is currently being drilled.<br><br>Pol et al., EPSL 2010 analyzed high resolution water isotope data from the Dome-C ice core and found evidence for a limited preservation of climate variability in the deep section of the core due to mixing and diffusion. For instance, for Marine Isotope Stage 19, the study estimated a mixing/diffusion length between 40 and 60 cm, a value more than double than what is predicted by current firn and ice diffusion models. Knowing the diffusion length is important to interpret the isotope signal and is the basis to deconvolve climate records. As a result, it is key to bridge the gap in the estimation of the diffusion length between potentially biased statistical methods and firn and ice diffusion models.<br>We review this diffusion length estimate for MIS19, and also outline a new general method how to estimate the diffusion length in highly thinned deep ice.  This approach presents an important tool for better characterizing the preservation of the climate signal in old ice and thus for designing optimal sampling and recovery strategies.</p><p> </p>

Bayesian hierarchical models suggest oldest known plant-visiting bat was omnivorous

The earliest record of plant visiting in bats dates to the Middle Miocene of La Venta, the world's most diverse tropical palaeocommunity. Palynephyllum antimaster is known from molars that indicate nectarivory. Skull length, an important indicator of key traits such as body size, bite force and trophic specialization, remains unknown. We developed Bayesian models to infer skull length based on dental measurements. These models account for variation within and between species, variation between clades, and phylogenetic error structure. Models relating skull length to trophic level for nectarivorous bats were then used to infer the diet of the fossil. The skull length estimate for Palynephyllum places it among the larger lonchophylline bats. The inferred diet suggests Palynephyllum fed on nectar and insects, similar to its living relatives. Omnivory has persisted since the mid-Miocene. This is the first study to corroborate with fossil data that highly specialized nectarivory in bats requires an omnivorous transition.

A revised target strength–length estimate for blue whiting (Micromesistius poutassou): implications for biomass estimates

Pedersen, G., Godø, O. R., Ona, E., and Macaulay, G. J. 2011. A revised target strength–length estimate for blue whiting (Micromesistius poutassou): implications for biomass estimates. – ICES Journal of Marine Science, 68: 2222–2228. Acoustic abundance estimates of blue whiting have generally been higher than estimates based on catch data. One explanation has been that the relationship between acoustic target strength (TS) and length is too low and hence overestimates the number of fish. Measurements of TS were conducted during surveys of blue whiting in March/April 2003–2007 to the west of the British Isles from several different measurement platforms, and also during August 2005 in the Norwegian Sea. Results from these experiments confirm the view that the existing TS–length relationship is too low. A new TS–length relationship is proposed that is ∼5 dB higher. Blue whiting TS is considerably higher than observed and modelled for a similar species, southern blue whiting (Micromesistius australis).