Application of very-high-frequency (VHF) method to ceramic insulators

A VHF method (30-300 MHz) is applied to identify faults and defects in ceramic insulators. Insulators which exhibit internal cracks and fractures are used as test samples. Different artificial conditions are introduced to the test samples according to the IEC 507 standard under wet and dry conditions. Using a cascading signal processing technique and analysis methods such as FFT and fractal analysis, VHF signals acquired by digital scope are processed and analyzed. This study indicates that the fractal dimension can be used as an effective tool to isolate the common faulty conditions found on the ceramic insulators. The results from this study strongly support the prospect of using a VHF method to monitor the physical condition of ceramic insulators.

High frequency dielectric response of the ionic liquid N-methyl-N-ethylpyrrolidinium dicyanamide

A study of the room-temperature ionic liquid N-methyl-N-ethylpyrrolidinium dicyanamide by dielectric relaxation spectroscopy over the frequency range 0.2 GHz ≤ ν ≤ 89 GHz has revealed that, in addition to the already known lower frequency processes, there is a broad featureless dielectric loss at higher frequencies. The latter is probably due to the translational (oscillatory) motions of the dipolar ions of the IL relative to each other, with additional contributions from their fast rotation.

The impact of continuous versus intermittent high frequency stimulation of the nucleus accumbens shell on ethanol preference and circadian locomotor activity in alcohol preferring rats

This study aimed to investigate the effect of different patterns of high-frequency stimulation at the nucleus accumbens shell on ethanol preference and circadian locomotor activity in adult male alcohol preferring (P) and nonpreferring (NP) rats.

Does the flicker frequency of fluorescent lighting affect the welfare of captive European starlings?

It is common practice for captive birds to be kept under fluorescent lighting, which typically flickers at either 100Hz (UK) or 120 Hz (USA). Such lighting was developed for human vision and it is thought that birds may be able to detect higher frequencies of flicker than humans. For humans, 100Hz fluorescent lighting has been linked to eyestrain, headaches and migraine, even though this rate of flicker is above the human perceptual flicker-fusion frequency of around 60 Hz. Keeping birds under 100 Hz lighting is therefore potentially detrimental to their welfare. We studied the preferences of wild-caught European starlings, Sturnus vulgaris, for high-frequency (HF, >30 kHz) fluorescent lighting versus conventional low-frequency (LF, 100 Hz) fluorescent lighting. The flicker frequency of the HF lighting would be undetectable to the nervous system of any animal. We also exposed starlings to either HF or LF light for 2 weeks, and investigated the degree of stress caused by each environment by monitoring their behaviour and plasma corticosterone levels. Groups of starlings showed a preference for HF lighting over LF lighting (P < 0.001), which indicates that they can detect a difference between the two lighting conditions and find the HF lighting preferable. However, there were no measurable differences in behaviour or plasma corticosterone levels when the birds were housed under either HF or LF for 2 weeks, thus providing initial evidence that housing starlings under 100Hz lighting may not be detrimental to the welfare of starlings during early captivity. (C) 2003 Elsevier B.V. All rights reserved.

Not so fast: swimming behavior of sailfish during predator-prey interactions using high-speed video and accelerometry

Billfishes are considered among the fastest swimmers in the oceans. Despite early estimates of extremely high speeds, more recent work showed that these predators (e.g., blue marlin) spend most of their time swimming slowly, rarely exceeding 2 m s(-1). Predator-prey interactions provide a context within which one may expect maximal speeds both by predators and prey. Beyond speed, however, an important component determining the outcome of predator-prey encounters is unsteady swimming (i.e., turning and accelerating). Although large predators are faster than their small prey, the latter show higher performance in unsteady swimming. To contrast the evading behaviors of their highly maneuverable prey, sailfish and other large aquatic predators possess morphological adaptations, such as elongated bills, which can be moved more rapidly than the whole body itself, facilitating capture of the prey. Therefore, it is an open question whether such supposedly very fast swimmers do use high-speed bursts when feeding on evasive prey, in addition to using their bill for slashing prey. Here, we measured the swimming behavior of sailfish by using high-frequency accelerometry and high-speed video observations during predator-prey interactions. These measurements allowed analyses of tail beat frequencies to estimate swimming speeds. Our results suggest that sailfish burst at speeds of about 7 m s(-1) and do not exceed swimming speeds of 10 m s(-1) during predator-prey interactions. These speeds are much lower than previous estimates. In addition, the oscillations of the bill during swimming with, and without, extension of the dorsal fin (i.e., the sail) were measured. We suggest that extension of the dorsal fin may allow sailfish to improve the control of the bill and minimize its yaw, hence preventing disturbance of the prey. Therefore, sailfish, like other large predators, may rely mainly on accuracy of movement and the use of the extensions of their bodies, rather than resorting to top speeds when hunting evasive prey.