Landscapes of Smolensk Oblast as a Consequence of Ancient Anthropogenic Activity: Paleoecological Study of Radomsky Mokh Swamp

The results of a paleoecological study of a peat deposit in Radomsky Mokh area (Smolensk Oblast, Krasninsky District) made it possible to reconstruct the history of the region's landscapes over the last 4 thousand years and identify its 4 contrasting periods. The reservoir was a lake at first, after which the pollen spectrum is dominated by pollen from native tree species. After a series of fires on the boundary of the Bronze and Early Iron Ages (3173–2969 14C calendar years ago) (2σ, 99.7%)) a forested mesotrophic swamp formed at the site of the lake, and pollen from pioneer trees with an admixture of alder started to dominate the pollen spectrum. At the third stage, the swamp became mesotrophic, and the landscapes around it become open, which is evidenced by an increase in the proportion of grasses and anthropogenic indicators in the pollen spectrum. The same period is marked with the appearance of pollen of cultivated grasses (2992–2912 simulated years ago), which coincides with the distribution of the monuments of the Dnieper-Dvinian culture in the study area. At the last stage, the swamp became oligotrophic, and a stable curve of cultivated grasses appeared (mid-1st Millennium AD), indicating the spread of agriculture in the study area. The absence of known archaeological sites in an 8-kilometer radius around Radomsky Mokh most likely indicates an insufficient archaeological study level of the area, whereas the economic development of the vicinity of the tract started at the boundary of the Bronze and Early Iron Ages.

COVID-19 Follows a Flattened Growth Curve Subsequent to Prolonged Intervention in A Population; Its Implication on Rate Of Doubling Time & Plausible Suppression of SARS-CoV-2 Infection

COVID-19 is fast spreading around the globe in a highly contagious manner. In this article we have described that after prolonged interventions the percentage growth curve for COVID-19 cases showed a flattened nature, after prolonged volatility in number of COVID-19 cases. The stability in the growth curve was continuously maintained from 18 April, 2020 to 29 April, 2020. The significance of this sustained stable curve on survival & doubling time has been discussed. One significant part of the study reflected that the doubling time of COVID-19 cases showed a negative correlation with the percent increase in COVID-19 cases (R=0.301). It is plausible that if such negative correlation is maintained with further flattening of the growth curve at a lower level, it may influence the infective ability of nCoV-19 & ultimately have a positive evolutionary implication on the spread of COVID-19 among the population.

Sebaran Peluang Acak Kontinu, Distribusi Normal, Distribusi Normal Baku, Distribusi T, Distribusi Chi Square, dan Distribusi F

In statistics, there are various terms that may feel unfamiliar to researcher who is not accustomed to discussing it. However, despite all of many functions and benefits that we can get as researchers to process data, it will later be interpreted into a conclusion. And then researcher can digest and understand the research findings. The distribution of continuous random opportunities illustrates obtaining opportunities with some detection of time, weather, and other data obtained from the field. The standard normal distribution represents a stable curve with zero mean and standard deviation 1, while the t distribution is used as a statistical test in the hypothesis test. Chi square deals with the comparative test on two variables with a nominal data scale, while the f distribution is often used in the ANOVA test and regression analysis.

General Variational Formulas for Abelian Differentials

We use the jump problem technique developed in a recent paper [9] to compute the variational formula of any stable differential and its periods to arbitrary precision in plumbing coordinates. In particular, we give the explicit variational formula for the degeneration of the period matrix, easily reproving the results of Yamada [21] for nodal curves with one node and extending them to an arbitrary stable curve. Concrete examples are included. We also apply the same technique to give an alternative proof of the sufficiency part of the theorem in [1] on the closures of strata of differentials with prescribed multiplicities of zeroes and poles.

Reversible Passive Bandgap Reconfiguration Using an Excitation Dependent On-Site Restoring Force

By applying an excitation dependent, on-site restoring force to oscillators in a uniform one-dimensional chain with nearest neighbor coupling, this paper demonstrates the feasibility of reversible passive bandgap reconfiguration. Waveguide devices are most commonly tuned using active controls, component replacement, or by manually varying design parameters. Recent studies on wave propagation have pursued passive controls, where high amplitude environmental excitation triggers a potential well escape in an asymmetric, bi-stable system, automatically changing its linear spectra without user interaction. Current designs, however, do not return to their initial state upon later excitation amplitude reduction, instead requiring manual reset for continued operation. In order to allow fully autonomous function, a passively reconfigurable system must also be designed to return to its low amplitude state after environmental excitation amplitude decreases. This paper proposes a system in which reversible bifurcations are observed by introducing an excitation dependent on-site stiffness. Instead of a fixed, bi-stable potential energy curve, the oscillators have a single mono-stable curve at low energy levels and a different mono-stable curve with its own distinct linear spectrum at high energy levels. Numerical simulations are provided to demonstrate system transitions from propagation zone to attenuation zone behavior, and back, when subjected to increasing and decreasing excitation amplitudes.

The Stability of a Two-dimensional Wall Jet

SummaryThe stability of a two-dimensional wall jet was studied theoretically and experimentally. As a result of the linear stability calculation, it was found that one eigenmode is separated into two modes when the Reynolds number is large, and inside a neutral stable curve in the α, R-plane there exists another neutral curve enclosing a stable region. Experimental results of small disturbances were compared with calculated results; agreement between them was satisfactory. It was found, further, that subharmonics of a predominant disturbance velocity component appear in the non-linear region.