Acoustic control of the strengthening of building ceramics obtained by extrusion through an ultrasonic die

Extrusion through a die, vibrating with an ultrasonic frequency is a promising method for hardening ceramic materials (bricks, tiles, pipes, etc.). We present the results of studying low-frequency acoustic spectra of cylindrical samples of face brick ceramics reinforced by extrusion and addition of fiberglass waste. Correlations between structure changes in the obtained ceramics, parameters of the acoustic spectrum of the samples, and the destructive forces upon their compression (bending) in a press were analyzed. It is shown that ultrasonic extrusion increases the destruction force of the cylinders by 1 – 7 kN (~30 %) and thus shifts the frequency of the fundamental tones of transverse and longitudinal oscillations (6 and 17 kHz) with a coefficient of ~0.1 kHz/kN. The fiberglass particles strengthen the ceramics due to the formation of a needle-like crystalline bond during firing. At the same time, an increased addition of the fiberglass particles reduces the plasticity of the batch thus resulting in formation of the microcracks, cavities and internal stresses in the samples. The occurrence of internal defects shifts the frequency of longitudinal and transverse vibrations to a different extend, which can be used as an indicator of the defects present in the samples and provide the possible of their objective sorting and rejection. The vibration relaxation time (about 0.1 sec) does not change significantly under the described strengthening effects and being characterized by a wide scatter in each series of the samples cannot be considered an informative parameter. Thus, the effectiveness of the presented combined method of ceramics hardening can be accurately tested by the shift in the frequencies of longitudinal and transverse free vibrations of cylindrical specimens. The presented approach facilitates the process of developing new ceramic compositions and extrusion technology in conditions of depletion of sources of high-quality clay raw materials.

Statistical Distributions of Lightning Parameters with Emphasis on their Extremely High Values

The paper is devoted to the review of the data on the lightning parameters necessary for development and perfection of lightning protection systems. It is shown, that down to present time national and international lightning protection standards are based on the Berger’s data on distribution of lightning amplitudes currents. Experimental data on amplitude of the return-stroke current the received recently in Brazil, Japan, USA (Florida) and Austria are resulted. It is emphasized, that the given data on currents of a lightning are characterized by a wide scatter that specifies necessity of realization of the further researches. The detailed description of parameters of the return-stroke peak current, including duration of front time, duration of a pulse, a steepness of a current at the front is given. It is emphasized, that median value of amplitude of a current of the first making the return-stroke in 3-4 times is higher than a current of the subsequent components. The analysis measured median (50%) and severe (1%) values of lighting parameters which are necessary for construction of a curve of distribution in the assumption of its submission lognormal law is carried out. Results of theoretical researches are given according to extreme values of currents of a lightning. It is shown, that, depending on length of the lightning channel (from 4 up to 6 kms), the maximal current can vary from 300 kA up to 500 кА. The minimal value of lightning current is appreciated in 2 кА. The analysis of results of new direct measurements has shown, that for a lightning of positive polarity the maximal current can reach 340 кА, that appreciably is higher than a settlement maximum for a lightning of negative polarity (200 кА). Recent theoretical researches have allowed to prove experimentally received lognormal distribution of currents for lightning of negative polarity.

NEW RESULTS OF DIRECT RADIOCARBON AMS DATING OF THE POTTERY FROM THE BUH-DNISTER SUB-NEOLITHIC СULTURE

Traditional ideas about the origin of the Buh-Dnister Culture (BDC) and its synchronisation with the Neolithic cultures of the Danube-Carpathian region were questioned by series of radiocarbon dates measured on bones at the Kyiv laboratory in the 1998—2004. To start addressing this problem, 11 AMS dates on organic inclusions in the ceramic paste and charred residues on the surface of vessels were obtained at the Tokyo University laboratory. The set of new dates has given a wide scatter of their values within the entire period outlined by the previous BDC dates. Moreover, the two results of the second quarter of the 7th millennium BC for the Hlynske 1 and Bazkiv Ostriv site are beyond it and may potentially be the oldest dates of the culture. However, analysis of the samples in terms of carbon content, their susceptibility to the influence of the freshwater reservoir effect, correspondence to the stratigraphy of the sites and typology of materials detected only six more credible dates. Their order on the timeline coincides with generally accepted ideas about the sequence of existence of the different BDC pottery types. The youngest is the vessel of the Savran type from Shumyliv-Cherniatka has yielded two dates falling into the range of 4723—4491 cal BC, when the Trypillia culture bearers already populat the region. Two vessels of the Samchyntsi type from Bazkiv Ostriv yield three dates within the range of 5288—4847 cal BC, which corresponds to their finding next to fragments of fine «music-note» bowls of the Linear Band Pottery Culture. The Skybyntsi type vessel from Bazkiv Ostriv yield the oldest plausible date of 5621—5514 cal BC, which corresponds to the age of the Criş monuments in Moldova. Unfortunately, the new dates did not shed light on the issues of the time and direction of the first pottery spreading in the region. Thus, this needs further research including reliably direct radiocarbon dating on pottery.

Ultrasensitive Serum Estradiol Measurement by Liquid Chromatography-Mass Spectrometry in Postmenopausal Women and Mice

Accurate measurement of very low circulating estradiol (E2) (<5 pg/ml) in postmenopausal women and in mice is essential to investigating sex steroid action in target tissues. However, direct immunoassays are too inaccurate and conventional mass spectrometry-based measurement too insensitive at these serum E2 levels. We report application of an ultrasensitive method using a novel estrogen-selective derivatization in liquid chromatography-mass spectrometry to measure serum E2, with a detection limit of 0.25 pg/ml in small (0.2 ml) serum volumes that can quantify serum E2 in 98% and serum E1 in 100% of healthy postmenopausal women. Aromatase inhibitor (AI) treatment of postmenopausal women with breast cancer further reduces serum E2 by 85% and serum estrone (E1) by 80%. The wide scatter of circulating E2 in AI-treated women suggests that the degree of sustained E2 depletion, now quantifiable, may be an efficacy or safety biomarker of adjuvant AI treatment. This ultrasensitive method can also measure serum E2 in most (65%) female but not in any male mice. Further studies are warranted using this and comparable ultrasensitive liquid chromatography-mass spectrometry estrogen measurements to investigate the relationship of circulating E2 (and E1) in male, postmenopausal female, and childhood health where accurate quantification of serum estrogens was not previously feasible. This will focus on the direct impact of estrogens as well as the indirect effects of androgen aromatization on reproductive, bone, and brain tissues and, notably, the efficacy and safety of AIs in adjuvant breast cancer treatment.

Rapid evolution and transformation into quiescence?: ALMA view on z > 6 low-luminosity quasars

We present ALMA [CII] line and far-infrared (FIR) continuum observations of seven z > 6 low-luminosity quasars (M1450 > −25 mag) discovered by our on-going Subaru Hyper Suprime-Cam survey. The [CII] line was detected in all targets with luminosities of ∼(2−10) × 108 L⊙, about one order of magnitude smaller than optically luminous quasars. Also found was a wide scatter of FIR continuum luminosity, ranging from LFIR < 1011L⊙ to ∼2 × 1012L⊙. With the [CII]-based dynamical mass, we suggest that a significant fraction of low-luminosity quasars are located on or even below the local Magorrian relation, particularly at the massive end of the galaxy mass distribution. This is a clear contrast to the previous finding that luminous quasars tend to have overmassive black holes relative to the relation. Our result is expected to show a less-biased nature of the early co-evolution of black holes and their host galaxies.

Effective Mechanical Properties and Thickness Determination of Boron Nitride Nanosheets Using Molecular Dynamics Simulation

Research in boron nitride nanosheets (BNNS) has evoked significant interest in the field of nano-electronics, nanoelectromechanical (NEMS) devices, and nanocomposites due to its excellent physical and chemical properties. Despite this, there has been no reliable data on the effective mechanical properties of BNNS, with the literature reporting a wide scatter of strength data for the same material. To address this challenge, this article presents a comprehensive analysis on the effect of vital factors which can result in variations of the effective mechanical properties of BNNS. Additionally, the article also presents the computation of the correct wall thickness of BNNS from elastic theory equations, which is an important descriptor for any research to determine the mechanical properties of BNNS. It was predicted that the correct thickness of BNNS should be 0.106 nm and the effective Young’s modulus to be 2.75 TPa. It is anticipated that the findings from this study could provide valuable insights on the true mechanical properties of BNNS that could assist in the design and development of efficient BN-based NEMS devices, nanosensors, and nanocomposites.

Metameric Light Sources: A Recent Paradigm for Functional Lighting

Recent progress in tuneable solid-state light sources opens new opportunities in a niche and high added value lighting applications. The standard colorimetric technique of composing an identical colour coordinate metameric light spectra are facing the challenges due to the colour discrepancy noticed by the observers. A side-by-side colour matching experiment was performed with two tuneable tetrachromatic RAGB lamps (638 nm red, 598 nm pc amber, 518 nm green, 451 nm blue LEDs) to compare the colour of the metameres in a 10-deg viewing angle. The metameric light matching was investigated using a 2-deg (CIE 1931) and 10-deg (CIE 1964) XYZ colour matching function. Both colour matching functions of standard colorimetric observers were shown to be inaccurate for aligning of metameric spectral power distributions without a noticeable difference in a perceived colour. On the other hand, a wide scatter of individual results revealed that the standard colour matching functions are inherently limited and in some cases, especially in professional lighting applications, the individually adjustable metameric lighting approach is to be considered.

Simultaneity and Flux Bias between 43 and 86 GHz SiO Masers

Using quasi-simultaneous observations of 86 stars with known SiO maser emission, we searched for systematic differences between the strengths of the 43 and 86 GHz v=1 maser lines. Although for individual stars there is wide scatter between the line strengths spanning nearly an order of magnitude, there is no evidence of a systematic difference between these line strengths for the entire sample.

Design procedures for footbridges subjected to walking loads: comparison and remarks

This paper aims at pointing out some misconceptions concerning the evaluation of the walking-induced dynamic response of footbridges, and their impact on design procedures. First, a review of the existing Code provisions is briefly presented. In particular single-walker models and multiple-walker models are addressed; in doing so, models originally presented in different forms are made homogeneous for the purpose of comparison; their limits of applicability and advantages are pointed out. Then, the response of six steel box girder footbridges with different spans is evaluated following the provisions of existing Standards and Guidelines, and compared with allowable comfort levels. The comparison showed a wide scatter of the results, revealing some inconsistencies of the procedures, and underlining a clear need for their critical revision.