Precision measurements of thermoacoustics in a single pore

Abstract: Continuing experiments designed to look at therrnoacoustic effects in a single pore will be described. A volume-modulation technique is employed to measure the complex compressibility of a gas in the pore directly. When a temperature gradient is imposed on the pore, the complex compressibility is sensitive to thermoacoustic effects which can be measured to high precision. These effects depend on both thermal and viscous properties of the gas. Measurements for a wide range of gradients are presented and compared to predictions of the theory. Generally good qualitative agreement is found. The technique can easily be extended to study novel stack geometries such as those with varying cross section or with tailored temperature gradients

Carnivore impact on cave bear bones and the analysis of their dispersion. Case study: UrŞilor cave (NW Romania)

In taphonomy, the study of carnivore modification of fossil bones and the analysis of their dispersion represent the best approach to assessing the extent of bone modification and displacement for a given bone assemblage. Here we analyze the excavated bone deposit from Urşilor Cave, a well-documented and fossil-rich Upper Pleistocene cave bear site from the Romanian Carpathian Mountains. More than 1400 limb bones or bone remains were analyzed (NISPleft and right = 1424) and 69 measurable puncture marks were identified, measured and morphologically analyzed. Moreover, for assessing the degree of bone scattering, almost 540 cave bear limb bones and mandibles were refitted and the Index of Skeletal Disjunction (ISD) was calculated for the entire bone assemblage. More than 30 % of the analyzed cave bear limb bones were affected by carnivores: the ulnae were the most affected (39.3 %) while the humeri and femora were less modified (24.7 % and 25.5 %, respectively). The range of variation in size of the puncture marks, the morphological features of various tooth marks and the faunal composition of the studied bone assemblage indicate that at least two carnivore taxa are responsible for the bone modifications. The results obtained for the ISD index indicate higher displacement for femora when compared to other bones (e.g. tibiae, mandibles, humeri). Our analyses of bone modifications caused by carnivores indicate a low level of the scattering of intensely modified (by in situ consumption) bones, and notable carnivore impact on the configuration of the bone assemblage.Key words: Ursus spelaeus, taphonomy, ISD, tooth marks, Urşilor Cave, Romanian Carpathians.Vpliv zveri na kosti jamskih medvedov iz jame UrŞilor (SZ Romunija) in analiza njihove razkropljenostiProučevanje sledov zveri na fosilnih kosteh in razkropljenosti kosti v prostoru je najboljše tafonomsko orodje za pridobivanje podatkov o obsegu takšnih pojavov znotraj posameznega paleontološkega zbira. V raziskavi obravnavamo kosti jamskega medveda iz jame Urşilor, dobro raziskanega mlajšepleistocenskega najdišča v Romunskih Karpatih. Analizirali smo več kot 1424 dolgih cevastih kosti okončin ali njihovih odlomkov in pri tem prepoznali, izmerili in morfološko analizirali 69 odtiskov zob. Poleg tega smo izračunali indeks razkropljenosti okostja (Index of Skeletal Disjunction, ISD) za celotni paleontološki zbir, zaradi česar smo sestavili skoraj 540 dolgih cevastih kosti okončin in spodnjih čeljustnic jamskega medveda. Sledove zveri smo prepoznali na več kot 30 % kosti okončin, najpogosteje na komolčnicah (39.3 %), nekoliko redkeje pa na nadlahtnicah in stegnenicah (24.7 % oz. 25.5 %). Variabilnost v velikosti odtiskov zob, njihovih morfoloških značilnostih in favnistični sestavi proučevanega paleontološkega zbira pričajo o tem, da sta ugotovljene spremembe medvedjih kosti povzročili vsaj dve različni zveri. Vrednosti indeksa razkropljenosti okostja kažejo na izrazitejšo razkropljenost stegnenic v primerjavi z drugimi kostmi (npr. golenicami, nadlahtnicami, spodnjimi čeljustnicami). Naša analiza kaže na skromno razkropljenost intenzivno obgrizenih kosti (zaradi hranjenja v sami jami) in znaten vpliv zveri na konfiguracijo paleontološkega zbira.Ključne besede: Ursus spelaeus, tafonomija, ISD, ugrizi, jama Urşilor, Romunski Karpati

Silence on Shangri-La: attenuation of Huygens acoustic signals suggests surface volatiles

Objective: Characterize and understand acoustic instrument performance on the surface of Titan. Methods: The Huygens probe measured the speed of sound in Titan's atmosphere with a 1 MHz pulse time-of-flight transducer pair near the bottom of the vehicle. We examine the fraction of pulses correctly received as af unction of time. Results: This system returned good data from about 11 km altitude, where the atmosphere became thick enough to effectively transmit the sound, down to the surface just before landing: these data have been analyzed previously. After an initial transient at landing, the instrument operated nominally for about 10 min, recording pulses much as during descent. The fraction of pulses detected then declined and the transmitted sound ceased to be detected altogether, despite no indication of instrument or probe configuration changes. Conclusions: The most likely explanation appears to be absorption of the signal by polyatomic gases with relaxation losses at the instrument frequency, such as ethane, acetylene and carbon dioxide. These vapors, detected independently by the GCMS instrument, were evolved from the surface material by the warmth leaking from the probe, and confirm the nature of the surface materials as ‘damp’ with a cocktail of volatile compounds. Some suggestions for future missions are considered. Practice implications: None

Magnetostriction and elasticity of body centered cubic Fe100−xBex alloys

Magnetostriction measurements from 77 K to room temperature on oriented (100) and (110) disk samples of Fe93.9Be6.1 and Fe88.7Be11.3 reveal substantial increases in λ100compared to iron. For the 11.3% alloy, λ100=110 ppm, a sixfold increase above that of α-Fe. For the 6.1% alloy, λ100=81 ppm, ∼40% and ∼170% greater than λ100 of comparable Fe–Ga and Fe–Al alloys, respectively, for H=15 kOe. Large differences exist between the values of λ100 and λ111 (λ100\u3e0, λ111\u3c0) and their temperature dependencies. Elastic constants, c11, c12, and c44, from 4 to 300 K were obtained on the same Fe–Be alloys. From these measurements, the magnetoelastic energy coefficients b1 and b2 were calculated. While the magnitudes of the magnetostrictions λ100 and λ111 are widely different, the magnitudes of b1 and b2 are within a factor of 2. The Fe–Be alloys are highly anisotropic magnetostrictively, elastically, and magnetoelastically. For Fe88.7Be11.3 at room temperature λ100/λ111, 2c44/(c11−c12), and b1/b2 are −6.6, 3.55, and −1.86, respectively

Xylanase - the enzyme which makes the difference in nutrition

Nutrition plays a critical role in health status both for humans and animals, comprising very complex processes starting with the ingestion of food or feed and ending with the excretion. But in this whole chain of processes, one of the main elements is the enzyme system without which digestion could not be possible. Xylanase is one of the enzymes that can make the difference in the digestion and absorption of some carbohydrates, like the digestion and absorption of fibers, used in various fields - food processing, feed additives, biofuel production, paper and pulp industry, textile industry, as well as waste management. Biochemically, xylanase is an enzyme that breaks down xylan, a complex polysaccharide found in plant cell walls. This paper presents some characteristics of xylanase, the important role in biotechnology, and also some applications of this enzyme