Variation in blubber cortisol levels in a recovering humpback whale population inhabiting a rapidly changing environment.

Glucocorticoids are regularly used as biomarkers of relative health for individuals and populations. Around the Western Antarctic Peninsula (WAP), baleen whales have and continue to experience threats, including commercial harvest, prey limitations and habitat change driven by rapid warming, and increased human presence via ecotourism. Here, we measured demographic variation and differences across the foraging season in blubber cortisol levels of humpback whales (Megaptera novaeangliae) over two years around the WAP. Cortisol concentrations were determined from 305 biopsy samples of unique individuals. We found no significant difference in the cortisol concentration between male and female whales. However, we observed significant differences across demographic groups of females and a significant decrease in the population across the feeding season. We also assessed whether COVID-19-related reductions in tourism in 2021 along the WAP correlated with lower cortisol levels across the population. The decline in vessel presence in 2021 was associated with a significant decrease in humpback whale blubber cortisol concentrations at the population level. Our findings provide critical contextual data on how these hormones vary naturally in a population over time, show direct associations between cortisol levels and human presence, and will enable comparisons among species experiencing different levels of human disturbance.

Energy requirements for osteotomy of femora and tibiae with a moving CW CO2 laser.

This paper describes the laser cutting and the amount of laser energy needed to remove a unit mass of compact or cancellous human cadaveric bones ("heat-of-removal") by using a CO2 laser. Data are collected under different operating conditions, such as laser power, scanning speed, and lens focusing for fresh and fixed human bones from male and female femora and tibiae samples with ages varying between 28 and 73 years old. The aim of the present experiments was to demonstrate the feasibility of laser osteotomy, to find the energy requirements for given groove depths or bone removal rates, and to shed some light on optimum conditions for laser osteotomy. Only cadaveric bones were used in this study, since the present aim did not include the investigation of heating rates and the extent and effect of thermal necrosis adjacent to the cut. In vivo properties may be somewhat different from those of cadaveric material. While blood circulation within the living bone may contribute to the laser cutting characteristics, it cannot be addressed here. Experiments showed that very deep cuts are difficult to achieve with a CO2 laser, as at high-power/low-scan-speed the groove becomes rather wide, with unacceptable thermal damage adjacent to the cut, while multiple passes do not easily attain large depths. There was no significant difference for the laser heat-of-removal for different age groups and for male and female samples. The laser heat-of-removal was found to be higher for compact bone than for cancellous bone samples. Comparison of cross-sections of the cuts with an existing model gave good agreement.

Measurements of thermal properties for human femora.

In this study, density, specific heat, thermal conductivity, and thermal diffusivity were measured experimentally along the lengths of human cadaveric femora. Fresh and dry bone samples were selected from both male and female specimens, and for different age groups varying between 44 and 73 years old. Measured values for specific heat vary between 1.14 and 2.37 J/gm degrees C; for thermal conductivities the range is from 0.16 to 0.34 W/m degrees C; and for thermal diffusivities the range is from 0.10 to 0.23 cm2/sec, depending on whether the bone samples were fresh or dry, cancellous or cortical. The experimental results are presented in non-dimensional coordinates and are compared with the few other data available in the literature.

Measurement of spectral, directional reflectivities of solids at high temperatures between 9 and µm.

A new apparatus to measure spectral,