Diving behaviour of whale sharks in relation to a predictable food pulse

We present diving data for four whale sharks in relation to a predictable food pulse (reef fish spawn) and an analysis of the longest continuous fine-resolution diving record for a planktivorous shark. Fine-resolution pressure data from a recovered pop-up archival satellite tag deployed for 206 days on a whale shark were analysed using the fast Fourier Transform method for frequency domain analysis of time-series. The results demonstrated that a free-ranging whale shark displays ultradian, diel and circa-lunar rhythmicity of diving behaviour. Whale sharks dive to over 979.5 m and can tolerate a temperature range of 26.4 degrees C. The whale sharks made primarily diurnal deep dives and remained in relatively shallow waters at night. Whale shark diving patterns are influenced by a seasonally predictable food source, with shallower dives made during fish spawning periods

Silicide formation with bilayers of Pd-Pt, Pd-Ni, and Pt-Ni

Evaporated two-layered thin films of Pd-Ni, Pt-Ni, and Pt-Pd on single-crystal Si have been vacuum annealed in the temperature range 200–900°C. The sequence of films as well as substrate orientation have been varied. The silicide formation has been studied by MeV He + backscattering spectrometry and glancing angle x-ray diffraction. The silicide layers are highly inhomogeneous in the elemental depth distribution for annealing below 600°C. Above 700°C, the distributions become homogeneous. The silicide-substrate interface shows varying sharpness depending upon substrate orientation and evaporation sequence. We suggest the existence of ternary monosilicides of the type Pt1–xPdxSi, Pt1–xNixSi, and Pd1–xNixSi. The Pt1–xPdxSi ternary silicide is stable up to 900°C; the others are not

Growth of Ge Nanoparticles on SiO2/Si interfaces during Annealing of Plasma Enhanced Chemical Vapor Deposited Thin Films

Cataloged from PDF version of article.Multilayer germanosilicate (Ge:SiO2) films have been grown by plasma enhanced chemical vapor deposition. Each Ge:SiO2 layer is separated by a pure SiO2 layer. The samples were heat treated at 900 degrees C for 15 and 45 min. Transmission electron microscopy investigations show precipitation of particles in the layers of highest Ge concentration. Furthermore there is evidence of diffusion between the layers. This paper focuses mainly on observed growth of Ge particles close to the interface, caused by Ge diffusion from the Ge:SiO2 layer closest to the interface through a pure SiO2 layer and to the interface. The particles grow as spheres in a direction away from the interface. Particles observed after 15 min anneal time are 4 nm in size and are amorphous, while after 45 min anneal time they are 7 nm in size and have a crystalline diamond type Ge structure. (C) 2006 Elsevier B.V. All rights reserved

Water quality limits for Atlantic salmon (<i>Salmo salar</i> L.) exposed to short term reductions in pH and increased aluminum simulating episodes

International audienceAcidification has caused the loss or reduction of numerous Atlantic salmon (Salmo salar L.) populations on both sides of the North Atlantic. Acid deposition peaked in the 1980's and resulted in both chronically and episodically acidified rivers. At present, water quality is improving in all affected rivers due to reduced acid deposition. However, spring snow melt, heavy rainfall and sea salt episodes can still cause short term drops in pH and elevated concentrations of bioavailable aluminum. Technical malfunction in lime dozers will cause short termed episodic spates in the limed rivers. The current situation has prompted a need for dose-response relationships based on short term exposures of Atlantic salmon to assess the potential population effects of episodic acidification. Water quality guidelines for salmon have been lacking, despite a large number of experiments, all demonstrating dose-response relationships between water chemistry and fish health. We have summarized results from 347 short-term (+ and Al) and as Carlin-tagged smolt releases after preexposure to moderately acidic waters. The results from the various bioassays are compared to water quality limits proposed on basis of the relationship between water quality and population status/health in Norwegian rivers. The focus of this article is placed on chemical-biological interactions that can be drawn across experiments and exposure protocols. We propose dose-response relationships for acid neutralizing capacity (ANC), pH, cationic Al and gill accumulated Al, versus mortality in freshwater, effects on hypo-osmoregulatory capacity in seawater challenge tests and on smolt to adult survival in release experiments. The "no effect" dose depends on the life history stage tested and on the sensitivity of the biomarkers. Parr are more tolerant than smolt. Concentrations of Al that have no significant impact on freshwater life history stages can still have major population effects if they occur prior to smolt migration. While smolt can survive in freshwater for a prolonged period of time (>10 days) at an Al dose resulting in a gill Al concentration of up to 300 µg Alg?1 dw, a 3 day exposure resulting in a gill Al accumulation in the range of 25 to 60 µg Alg?1 dw reduces smolt to adult survival in a dose related manner by 20 to 50%. For smolt to adult survival, the biological significant response is delayed relative to the dose and occurs first after the fish enters the marine environment. In addition to exposure intensity and timing, exposure duration is important for the setting of critical limits

Investigation of the Au-Ge-Ni and Au-Ge-Pt system used for alloyed contacts to GaAs

Widely used metallization schemes for alloyed contacts to n‐type GaAs consist of a Au–Ge alloy with a cover layer of Ni or Pt. We have studied the interaction of these elements (Au–Ge and Ni, Au–Ge and Pt) upon heat treatment on an inert substrate. Our results show that Ni and Pt play an active role in contact formation. During heat treatment the Ge diffuses out of the Au into the Ni or Pt layer, respectively, where it forms stable compounds. Due to the fact that Ni and Pt act as a sink for Ge the composition and, as it is shown, the uniformity of the heat‐treated layers depend on the ratio of the amount of evaporated Ge to Ni or to Pt

Adult Height, Insulin Levels and 17β-Estradiol in Young Women

Background: Adult height and insulin levels have independently been associated with breast cancer risk. However, little is known about whether these factors influence estradiol levels. Thus, we hypothesize that adult height in combination with insulin levels may influence premenopausal 17β-estradiol throughout the entire menstrual cycle of possible importance of breast cancer risk. Methods: Among 204 healthy women, aged 25-35 years who participated in the Norwegian EBBA I study, birth weight and age at menarche were assessed by questionnaire, personal health record and interview. 17β-estradiol concentrations were estimated by daily saliva samples throughout one entire menstrual cycle using radioimmunoassay (RIA). Measures of height (cm) were taken as well as waist circumference (cm), body mass index (BMI kg/m2) and total fat percentage (DEXA % fat). Fasting blood samples were drawn, and serum concentrations of insulin were determined. Results: The women reported a mean height of 166.5 cm, birth weight of 3389 g and age at menarche 13.1 years. Mean BMI was 24.4 kg/m2, mean waist circumference 79.5 cm and mean total fat percentage 34.1%. Women with an adult height of more than 170 cm and insulin levels higher than 90 pmol/L experienced on average an 37.2 % increase in 17β- estradiol during an entire menstrual cycle compared to those with the same height, and insulin levels below 90 pmol/L. Moreover, this was also observed throughout the entire menstrual cycle. Conclusion: Our findings support that premenopausal levels of 17β-estradiol vary in response to adult height and insulin levels, suggesting that women who become taller are put at risk for higher estradiol levels when their insulin levels rise of possible importance for breast cancer risk.Anthropolog

Ovarian hormones and reproductive risk factors for breast cancer in premenopausal women: the Norwegian EBBA-I study

BACKGROUND: Ovarian hormones, parity and length of 'menarche-to-first birth' time interval are known risk factors for breast cancer, yet the associations between I 7$\beta$-estradiol, progesterone and these reproductive factors remain unclear. METHODS: A total of 204 women (25-35 years) who participated in the Norwegian EBBA-I study collected daily saliva samples for one complete menstrual cycle, and filled in a reproductive history questionnaire. Anthropometry was measured and saliva samples were analyzed for ovarian hormones. Associations between parity, the interval and ovarian hormones, and effects of hormone-related lifestyle factors were studied in linear regression models. RESULTS: Mean age was 30.7 years, and age of menarche 13.1 years. Parous women had on average 1.9 births, and age at first birth was 24.5 years. No association was observed between parity and ovarian steroids. In nulliparous women, higher waist circumference ($\ge$)77.75 cm) and longer oral contraceptive (OC) use ($\ge$)3 years) were associated with higher levels of I 7$\beta$-estradiol. Short (13.5 years) 'menarche-to-first birth' interval was associated with higher overall mean (P$_{trend}$ = 0.029), 47% higher maximum peak and 30% higher mid-cycle levels of I 7$\beta$-estradiol. We observed a 2.6% decrease in overall mean salivary I 7$\beta$-estradiol with each 1-year increase in the interval. CONCLUSIONS: Nulliparous women may be more susceptible to lifestyle factors, abdominal overweight and past OC use, influencing metabolic and hormonal profiles and thus breast cancer risk. Short time between 'menarche-to-first birth' is linked to higher ovarian hormone levels among regularly cycling women, suggesting that timing of first birth is related to fecundity.Human Evolutionary Biolog