CRUSHING CHARACTER OF SAND-SODIUM-SILICATE MIXTURES STRUCTURED BY STEAM-MICROWAVE TREATMENT

At the present, from among the known methods of sand-sodium-silicate mixtures structuring, the least studied, but the most promising, is the method of steam-microwave solidification. Among unexplored elements of steam-microwave solidification method is nature of mixtures destruction. This is especially important for determining the ways to increase the sand-sodium-silicate casting molds and cores strength before pouring and lowering their strength by the time when casting should be knocked out the mold and the core from cast product. Knowledge about mixture destruction nature is also necessary for appropriate technical solutions elaboration concerning sand regeneration. In this regard, the purpose of the present work has to be nature of sand-sodium-silicate mixtures structured by steam-microwave solidification method destruction establishing. Quartz sand cladded with sodium-silicate solute has been used in the present investigation. Mixture (cladded sand) structuring has been carried out by microwave radiation at nominal magnetron power of 700 W and radiation frequency of 2.45 GHz in area of standing waves. To cladded sand structuring, 1 g water portion has been added, which has been placed in bottom of container in which mixture has been microwave treated. To make decision on mixture destruction nature, images of structured mixtures destruction places within one grain (sand grain), which are typical for adhesive and cohesive character of destruction, obtained with scanning electron microscope have been used. It has been found that with sodium-silicate solute for quartz sand cladding mass content from 0.5 to 6 % (by weight) increasing, as well as with mixture processing by the method of steam-microwave solidification duration increasing, mixture compression ultimate strength increases according to dependence closed to exponential. Character of structured mixture destruction, in this case, is not depend on sodium-silicate solute used for quartz sand cladding content, but depends on steam-microwave solidification duration. With its time increasing it changes from adhesive to mix or from adhesive to mixed and cohesive.

Statistics of Lifetimes for Transient Bursting States in Coupled Noisy Excitable Systems

In ensembles of oscillators, intrinsic fluctuations often enable nontrivial dynamics in seemingly simple situations. One of such effects occurs in coupled FitzHugh–Nagumo oscillators subjected to external noise. At the considered parameter values, the global deterministic attractor is the resting state. Additive noise invokes transient bursting: series of intermittent patches of spikes, followed by the abrupt decay to rest. Duration of this transient, small for weak noise, asymptotically diverges when the noise becomes stronger. Remarkably, in repeated trials at fixed parameters, the number of bursts until the ultimate decay strongly varies. Lifetime statistics for this transient in large ensembles of numerical realizations features the exponential distribution. Observations on transient bursting are confirmed by experiments with coupled analog electronic circuits, modeling the FitzHugh–Nagumo dynamics. We relate the exponential character of the distribution to the probability that the system, disturbed by noise, escapes the local attraction basin of the resting state.

Technological Revolutions and the Political Economy of Time

The paper investigates the role of time as one of the most precious politico-economic resources. It shows that the compression of time during every successive industrial revolution brings contradictions that change the logic of the politico-economic system. To prove this thesis historical and political-economic approaches are used. The historical approach shows the correlation between the development of technologies, time and society. The politico-economic approach emphasizes on the different dimensions of this change, trying to answer the question about the transformation of the role of time in contemporary economy and politics. One of the main contributions is that time is correlated with the different technological revolutions. Thus, I first examine the correlation between time and technological changes during different technological stages. Then the exponential character of the technologies of the Fourth Industrial Revolution is shown, as well as the transformation they bring to politics, economics, society, science, human beings and so on. I finish with the necessary transformation of the state as a result of the technological revolutions and particularly as a result of the ongoing Fourth Industrial Revolution, and in the conclusion I provide some possible answers to the contradictions brought about by exponential technological changes.

On Reliability of the COVID-19 Forecasts

In this expository article, we are aiming to show with an example that even short term forecasts regarding the COVID-19 spread pattern may sometimes not be very reliable. We have studied data published by Worldometers.info to get numerically an approximate formula of the spread pattern for a short period. We have observed that in the United States of America, there was a nearly exponential spread pattern for a very short period from May 3 to May 8, 2020. From May 9 to May 13, the nearly exponential character of the spread was found to be absent. Hence it can be concluded that the COVID-19 spread pattern, even after more than four months from the start of the outbreak, is not quite predictable. Therefore even short term forecasts regarding the spread may not be very reliable. We have found that forecasts using the assumption of an exponential pattern of spread may actually lead to overestimation.

CHARACTER LEVELS AND CHARACTER BOUNDS

We develop the concept of character level for the complex irreducible characters of finite, general or special, linear and unitary groups. We give characterizations of the level of a character in terms of its Lusztig label and in terms of its degree. Then we prove explicit upper bounds for character values at elements with not-too-large centralizers and derive upper bounds on the covering number and mixing time of random walks corresponding to these conjugacy classes. We also characterize the level of the character in terms of certain dual pairs and prove explicit exponential character bounds for the character values, provided that the level is not too large. Several further applications are also provided. Related results for other finite classical groups are obtained in the sequel [Guralnick et al. ‘Character levels and character bounds for finite classical groups’, Preprint, 2019, arXiv:1904.08070] by different methods.

Ethylene Emission of Apples Treated with 1-Methylcyclopropene During Storage

The effect of post-harvest application of 1-methylcyclopropene (1-MCP) on ethylene emission in early-winter apple (cv. ‘Calville’), winter (‘Gloster’, ‘Golden Delicious’ and ‘Jonagold’), and late-winter cultivars (‘Granny Smith’, ‘Idared’ and ‘Reinette Simirenko’) w as investigated. The fruits were picked at a commercial harvest time and half of them were treated with 1-MCP (‘SmartFresh™’ 0.068 gm-3) for 24 h at 5 °C. Then both groups of apples were placed in a common storage at the temperature of 2 °C. The intensity of fruit ethylene emission (rate of ethylene production) was measured and 1 -MCP inhibition index was calculated. During storage, activity of ethylene emission by control apples of ‘Calville’ and ‘Golden Delicious’ showed typical climacteric pattern, while the intensity of ethylene emission of apples of other cultivars only increased gradually. The change of ethylene activity of early-winter apple cv. ‘Calville’ and winter cv. ‘Jonagold’, both treated with 1-MCP after harvest, had exponential character, especially actively increasing after 3 months of storage. At the same time ethylene emission of 1 -MCP treated fruits of other cultivars changed steadily to a low level and was effectively suppressed during the whole 6-month period of storage in normal atmosphere. The value of inhibition index of fruits treated by 1-MCP confirmed the consistent restoration of the ability to ethylene synthesis and thus to post-harvest ripening of some apples cultivars.

Ultraweak luminescence of the Characeae plants under the circumstances of cyclical changes in temperature

Ultraweak luminescence of theCharaceaeplants under the circumstances of cyclical changes in temperatureThe study sought to measure ultraweak chemiluminescence (UWL) ofNitellopsis Obtusaplants with regards to temperature changes within the range from 4°C to 38°C. The temperature changes were being executed in reversible cycles. The variations of UWL intensity with temperature had an exponential character. In case when temperature was changed rapidly by 5°C every 20 min or fluently with rate of 0.17 °C/min we observed a temperature hysteresis loop in the first cycles and the loop character disappeared in the second cycles. When the temperature was being changed fluently but faster (1.3 °C/min) after 3 cycles (about 2 hours) the curves no longer manifested the loop character. This phenomenon can point that the plants adapted themselves to the temperature changes. We also observed a stimulation of UWL made in successful cycles. Our spectral experiments showed that the UWL may consist mainly of emission of the singlet oxygen sigma (762 nm) and induced emission of chlorophyll.

Metal Plasticity Operation by the Low Electric Influences

The influence of the electrical potential on the plasticity of Cu is studied experimentally. The dependence of the copper plasticity parameter on the electric potential for the range of values of –3 V < < 3 V is established. For the values equal to 0.2, 0.6 and 3 V the plasticity parameter relaxation times are established when the sample was switched of from the electric potential, created by electric field source. It is discovered, that the Cu plasticity parameter depends on connected Zr mass and this dependence has an exponential character.

Survey of subterranean termites (Isoptera: Rhinotermitidae) in a managed silvicultural plantation in Portugal, using a line-intersection method (LIS)

Subterranean termites (Reticulitermes grassei) were surveyed over successive seasons in a managed eucalyptus plantation in southeastern Portugal for 26 months. Termite activity in seven diameter categories of lying dead wood was investigated by a modified line intersection method (LIS). Each item sampled was inspected and assessed for termite attack and for general (i.e. fungal) decay status using standard protocols. Line intersection is quantitative to the extent that it can link foraging and decay parameters to woody biovolume. It was found that termites selected items with larger diameter, the observed trend showing an exponential character with greater termite attack as diameter increased. Attack by termites was positively associated with prior decay by fungi. A clear positive relationship was shown between rainfall and total woody biovolume containing live termites, underlining the importance of moisture for termite activity. Subterranean termites appeared to be important wood decomposers in the woodland studied, with an average of 30% of lying dead wood branches showing signs of termite attack.