Measurements of water-film thickness on cave walls and speleothems

A four-wavelength near-infrared (NIR) tunable diode laser sensor has been developed for the simultaneous measurement of liquid water film thickness, liquid-phase temperature and vapor-phase temperature above the film. This work is an important improvement of a three-wavelength concept previously introduced by Yang et al. (Appl. Phys. B 99:385, 2010), which measured the film thickness in environments with known temperature only. In the new sensor, an optimized combination of four wavelengths is chosen based on a sensitivity analysis with regard to the temperature dependence of the liquid water absorption cross section around 1.4 μm. The temperature of liquid water and the film thickness are calculated from absorbance ratios taken at three wavelength positions assessing the broad-band spectral signature of liquid water. The vapor-phase temperature is determined from the absorbance ratio of two lasers rapidly tuned across two narrow-band gas-phase water absorption transitions. The performance of the sensor was demonstrated in a calibration cell providing liquid layers of variable thickness and temperature with uncertainties smaller than 5% for thickness measurements and 1.5% for liquid-phase temperatures, respectively. Experiments are also presented for time-resolved thickness and temperature measurements of evaporating water films on a quartz plate.

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A dual-wavelength diode laser-based absorption sensor for standoff point measurements of water film thickness on an opaque surface is presented. The sensor consists of a diode laser source, a foil as backscattering target, and off-axis paraboloids for collecting the fraction of the laser radiation transmitted through the liquid layer via retro-reflection. Laser wavelengths in the near infrared at 1412 and 1353 nm are used where the temperature dependence of the liquid water absorption cross section is known. The lasers are fiber coupled and the detection of the retro-reflected light was accomplished through a multimode fiber and a single photodiode using time-division multiplexing. The water film thickness at a given temperature was determined from measured transmittance ratios at the two laser wavelengths. The sensor concept was first validated with measurement using a temperature-controlled calibration cell providing liquid layers of variable and known thickness between 100 and 1000 µm. Subsequently, the sensor was demonstrated successfully during recording the time-varying thickness of evaporating water films at fixed temperatures. The film thickness was recorded as a function of time at three temperatures down to 50 µm.

A dual-wavelength diode laser absorption spectroscopy (DLAS)-based sensor makes use of a retro-reflective foil as scattering target and time-division multiplexing (TDM) to enable remote measurements of the water film thickness in the 50-1000 μm range.

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Cave Rituals and the Brain's Theatre Mark Pizzato (bio) The term "theatre" comes from the ancient Greek theatron, the "seeing place" for the audience. But theatre in its most basic sense, as the space and activity of a spectator and a performer with reflective awareness between them, extends much further back into prehistory. Such reflective awareness of Self and Other in performance also relates to the theatres of imagination, memories, dreams, and reality representations within the brains of each actor and spectator. This inner theatre extends back to prehistory, too, with brain structures that we have inherited along with evolving rituals of transcendence and reflective performance spaces. A primal form of theatrical performance and awareness of Self and Other emerged in certain caves thirty-t wo thousand to eleven thousand years ago during the Ice Age (or Upper Paleolithic Period), as evidenced by the art on the cave walls and other artifacts. One of the earliest, with some of the finest art, is shown in Werner Herzog's 2010 3-D documentary film Cave of Forgotten Dreams. It explores prehistoric art in the Chauvet Cave in France, which was discovered in 1994 and has since been off-limits to the public. This essay considers that film and cave, plus details from lesser-known caves in France and Spain, which I visited in June 2011.1 Such caves offer evidence of a primal form of reflective performance: the evolution of human subjectivity based in, yet moving beyond, primate playfulness through shared emotions, neural filters, and simulations of the Other. How did the selection of specific cave spaces for paintings and engravings on the walls, along with the types of images made, express not only the performances in them but also the birth [End Page 116] of a distinct sense of Self, of human character being like and unlike observed animals, using the cave wall as a map and mirror? Theories of Cave Theatre In his recent book, Palaeoperformance, and in earlier essays, Yann-Pierre Montelle explores the evidence for many aspects of theatricality in the prehistoric caves of France: not only the paintings, etchings, and carvings on the rock walls but also the various sizes and shapes of caverns; the bone flutes, scrapers, and bullroarers found in them; and the resonant tones produced today by tapping stalactites of different lengths.2 Prior to Montelle, Jean Clottes and David Lewis-Williams developed a theory, based on such evidence along with neuroscience research and anthropological comparisons with recent African traditions, that prehistoric cave art shows the recording, display, and ritual use of hallucinatory trance experiences involving animal-spirit guides.3 Ice Age peoples may have produced cave art through visions that occurred spontaneously in the extreme darkness with its echoing sounds, evoked by the flickering fires of torches and animal-fat lamps, painful treks deep into the earth, loss of oxygen and increase of other gases, and the rock's natural shapes and crevices.4 Shamanic drugs might also have been involved. The mysterious geometric lines and dots in prehistoric cave art, along with realistic animal figures and hybrid human-animal creatures, correspond to the types and stages of hallucinatory visions that can be evoked today in the laboratory through sensory deprivation or flashing lights. Such hallucinations, though now involving objects in our own cultural context, are also experienced by people with migraines and other disorders. Thus, cave art may reveal two possible manifestations of prehistoric theatre: (1) visionary experiences of geometric, abstract, and supernatural figures from within a human brain projected onto or through the rock surface and (2) shared performances in the cave using the rock art as scenic background, mythic illustrations, or moving characters in the firelight and its shadows. The types of cave-art spaces also demonstrate various aspects of prehistoric theatre. Some are easily accessible in huge chambers. Others are hundreds of meters inside the earth, requiring crouched walking or crawling through narrow passages. In more accessible chambers, processions and large ritual gatherings may have occurred. But for those with tight corridors deep into the darkness, with slippery surfaces, low ceilings, and sudden cliffs, and with bears, hyenas, and lions potentially present, great courage and painful ordeals...

Peripapillary choroidal thickness in childhood

Hand print/stencil is one object that is common found at prehistoric caves. Many aspects can be studied using hand stencils as sources, and one of them is the study of gender identity of the maker of the hand stencils, whose hands were printed on cave walls. It is John T. Manning who introduced the idea about “ratio 2-digit/4-digit (2D/4D)” to differ male palm/hand and female. It is said that the length of forefinger and ring finger can differ whether they belong to male or female. Manning’s idea is tested and applied on the hand stencils from prehistoric cave Petta Kere in Maros District, South Sulawesi, particularly from the panel where hand stencils are in a context with big belly wild boar.

We present two non-intrusive, laser-based imaging techniques for the quantitative measurement of water fluid film thickness. The diagnostics methods are based on laser-induced fluorescence (LIF) of the organic tracer ethyl acetoacetate added to the liquid in sub-percent (by mass) concentration levels, and on spontaneous Raman scattering of liquid water, respectively, both with excitation at 266 nm. Signal intensities were calibrated with measurements on liquid layers of known thickness in a range between 0 and 500 μm. Detection via an image doubler and appropriate filtering in both light paths enabled the simultaneous detection of two-dimensional liquid film thickness information from both methods. The thickness of water films on transparent quartz glass plates was determined with an accuracy of 9% for the tracer LIF and 15% for the Raman scattering technique, respectively. The combined LIF/Raman measurements also revealed a preferential evaporation of the current tracer during the time-resolved recording of film evaporation.

Mabedda Bola is a ritual which has been handed down from the ancestors of the Bugis – Makassarese people in South Sulawesi. At the ceremony which is called menre bola baru, held as part of the ritual inauguration of a new house, the Mabedda Bola, handprints are made on the poles and walls of the new house. In the region in which this custom is still honoured, hand stencils on the walls of the prehistoric caves have also been found. This article examines the significance of handprints in the Mabedda Bola ritual which might possibly be related to the hand stencils on the walls of the prehistoric caves. Using the perspective of analogy, one of the methods of ethnoarchaeology, it has been discovered that handprints and hand stencils take more or less the same form. The similarities between them hint at the same behavioural patterns between the present day and the prehistoric period. The print of the hand palm is meant to mark the ownership of the family or group who dwell in a traditional house or it is thought in a particular cave. Moreover, it is and was to avert danger or the intrusion of bad influences from outside.

Our research deals with the evolution of wall surfaces in prehistoric caves. The focus of this paper is dedicated to the structural and chemical characterization of a white concretion partially covering some walls in caves. In one of the caves, a non-ornate one which became a laboratory-cave (the Leye cave at Marquay, Dordogne, France) located in the Vézère valley, a set of physical methods has been proposed and tested on the first samples taken: SEM-EDXS, cathodoluminescence and laser-based techniques such as Raman spectroscopy and Laser Induced Breakdown Spectroscopy and LIBS. Thus two facies mainly composed of calcium carbonate crystals have been determined: moonmilk and coralloids. The identification of theses crystalline phases is the first step of an ambitious research project that plans to understand the development of unexpected layers on the cave walls of the famous ornate caves listed as part of the UNESCO cultural heritage sites. This first set of data provides good insight to the structure and the physico-chemical composition of the involved materials. Future works will be dedicated to bring knowledge about the facies chronology, the climatic conditions of environment (temperature, CO<sub>2 </sub>rate and air velocities) over a long period.

BackgroundRetinal diseases are common in dogs. Some hereditary retinal dystrophies in dogs are important not only because they lead to vision loss but also because they show strong similarities to the orthologous human conditions. Advances in in vivo non-invasive retinal imaging allow the capture of retinal cross-section images that parallel low power microscopic examination of histological sections. Spectral domain - optical coherence tomography (SD-OCT) allows the measurement of retinal layer thicknesses and gives the opportunity for repeat examination to investigate changes in thicknesses in health (such as changes with maturation and age) and disease (following the course of retinal degenerative conditions). The purpose of this study was to use SD-OCT to measure retinal layer thicknesses in the dog during retinal maturation and over the first year of life. SD-OCT was performed on normal beagle cross dogs from 4 weeks of age to 52 weeks of age. To assess changes in layer thickness with age, measurements were taken from fixed regions in each of the 4 quadrants and the area centralis (the region important for most detailed vision). Additionally, changes in retinal layer thickness along vertical and horizontal planes passing through the optic nerve head were assessed.ResultsIn the four quadrants an initial thinning of retinal layers occurred over the first 12 to 15 weeks of life after which there was little change in thickness. However, in the area centralis there was a thickening of the photoreceptor layer over this time period which was mostly due to a lengthening of the photoreceptor inner/outer segment layer. The retina thinned with greater distances from the optic nerve head in both vertical and horizontal planes with the dorsal retina being thicker than the ventral retina. Most of the change in thickness with distance from the optic nerve head was due to difference in thickness of the inner retinal layers. The outer retinal layers remained more constant in thickness, particularly in the horizontal plane and dorsal to the optic nerve head.ConclusionsThese measurements will provide normative data for future studies.

The distribution of water in the diffuser of a wet gas compressor is not well understood. Measurements of water film thickness across the diffuser surface would improve the understanding of two-phase flow phenomena in wet gas compressors. Electromagnetic probes were designed in order to measure water film thickness in the diffuser of a SwRI-designed wet gas compressor. The probes consisted of two electrode foils plated on a thin insulating substrate, allowing them to be bonded in place without drilling through the diffuser. An AC signal was passed between the electrodes, and the voltage across a resistor in series with the electrodes was recorded. As the water level covering the electrodes increased, the recorded voltage increased. A method of calibrating the probes was developed and used prior to installation in the diffuser. Testing showed the probes to be effective at detecting the presence of water in the diffuser and indicating the general water level. Improvements in probe design, calibration, and installation are needed to provide more precise water film thickness data.

Near InfraRed FILM thickness PROfile (NIR-FILMPRO) is an optical technique for non-intrusive measurement of water film thickness. The technique is based on absorption of NIR light. A passband filter centered at 1612 nm was selected to measure isothermal gravity-driven films flowing on a vertical wall with sand blasted surface. Non-intrusive 2D mapping of the film thickness was acquired at 200 fps, with an image size of 320×256 pixels and a spatial resolution of 0.677 mm. Theoretical developments were brought to consider multiple reflections of light in the liquid film providing a more accurate model to compute the film thickness. Further improvements were made regarding the calibration procedure and the image processing. The measurements were compared against cold neutron imaging, an established technique which provides images of the time averaged thickness. An excellent correspondence between the two methods was found. The root mean square of the deviation between the two techniques taken over a region covered by a wavy film was found to be 2.3% of the measurement with film thicknesses fluctuating between approximately 100 and 500 µm. The spatial comparison with cold neutron imaging complements the previous comparisons and validates the application of the technique.