The Impact of COVID-19 on the Dynamic Topology and Network Flow of World Stock Markets

Studies examining the impact of COVID-19 using network dynamics are scant and tend to evaluate a specific local stock market. We present a thorough investigation of 58 world stock market networks using a complex network approach spanning across the uncertain times that have resulted from the coronavirus outbreak. First, we use the daily closing prices of the world stock market indices to construct dynamic complex networks and sixteen minimum spanning tree (MST) maps for the period from December 2019 to March 2021. Second, we present the topological evolution properties of time-varying MSTs by applying normalized tree length, diameter, average path length, and centrality measures. Moreover, the empirical results suggest that (1) the highest correlation among the world stock markets is observed during the first wave of the COVID-19 pandemic in the months of February–March 2020; (2) most of the MSTs appear lower in hierarchy, and many chain-like structures are formed due to the sheer impact of pandemic-related crises; (3) Germany remained a hub node in many of the MSTs; and (4) the tree severely contracted during the first wave of the COVID-19 outbreak (during the months of February and March 2020) and expanded slightly afterwards. Moreover, the results obtained from this study can be used for the development of financial stability policies and stock market regulations worldwide.

Prodrssive soil succession after thinning in northern taiga bilberry spruce forest

Damage to the top soil layers during logging operations can be of various forms (compaction, mixing, pressing, etc.) and of a long-term character. The recovery of the morphological characters and the structure of the soil profile of the native soil can take decades or have irreversible effect. We have studied the soil damage during two-stage (1973 and 2002) conversion thinning operations in the spruce forest with blueberry cover in the northern taiga (tree-length log skidding, TDT-55 tractor). The types of damage that stay during the progressive succession for 50 years and have signs of disturbances due to the logging operations were identified. The mosaic structure of the mixed bedrocks still continues to exist. The forest litter pressed by the heavy machines is replaced by the newly formed one. And at the same time, the organic bedrock of the medium degree of decomposition, which is untypical for the native podzolic soil, is preserved. Mixing by tractor tracks and the formation of mixed bedrock is the most common disturbance of the upper bedrock during logging operations due to insufficient coverage of the skid roads by felling residues. The amount of such damage to the soil is 77 % and 79 % in the skid roads of 1973 and 2002, respectively. But the depth of damage is small, which is 10 cm on average, with fluctuations up to 22 cm. In nano- and micro-depressions, the processes of peat formation and gleying develop. The number of locations with the genesis of bog soils is gradually increasing. On the skid roads of 1973 the proportion of wetlands is 2,5 times higher than in the skid roads of 2002 (86,9 % and 37,3 %, respectively). The long-term soil disturbance in the structure of the soil profile makes it necessary to develop classification approaches to improve the analysis of anthropogenic disturbed soils in cutting areas. The classification units are suggested

Trial performance of the zero waste harvesting method in three forest concession companies, Central Kalimantan Province, Indonesia

Currently, natural forest management companies (concession permit of timber forest products utilization-natural forest/IUPHHK-HA) have implemented Reduced Impact Logging (RIL) technology but timber harvesting is still carried out using the conventional method. Tree length logging is an alternative method of harvesting wood in an effort to reduced waste and increases the efficiency of the utilization of timber forest products and the preservation of natural production forests. The potential for wood harvesting waste is estimated at 2.21 million m3year−1 and has remained left in the cutting compartment for decades. The purpose of this paper is to obtain technical and financial information about forest harvesting on a zero waste basis. Data collection was carried out by experimental methods. Productivity, efficiency, cost, and stand damage data were collected. The results of the research in three IUPHHK-HA in Central Kalimantan show that the zero waste logging method can reduced harvesting waste by 5.1% and increase the efficiency of wood utilization from 87.7-92.8%. Another advantage of the zero waste logging method is that the additional waste from the trunk above the first branch is about 5.8%. The productivity of the conventional method averaged 26.333 m3hour−1 at a cost of IDR 33,941 m−3 while the tree length logging method was 27.320 m3hour−1 at a cost of IDR 35,251 m−3. It is suggested that the tree length logging method be implemented in natural production forest harvesting.

Common micro- and macroscale principles of connectivity in the human brain

The brain requires efficient information transfer between neurons and between large-scale brain regions. Brain connectivity follows predictable organizational principles: at the cellular level, larger supragranular pyramidal neurons have larger dendritic trees, more synapses, more complex branching and perform more complex neuronal computations; at the macro-scale, region-to-region connections are suggested to display a diverse architecture with highly connected hub-areas facilitating complex information integration and computation. Here, we explore the hypothesis that the branching structure of large-scale region-to-region connectivity follows similar organizational principles as known for the neuronal scale. We examine microscale connectivity of basal dendritic trees of supragranular pyramidal neurons (300+) across ten cortical areas in five human donor brains (1M/4F). Dendritic complexity was quantified as the number of branch points, tree length, spine count, spine density and overall branching complexity. High-resolution diffusion-weighted MRI was used to construct ‘white matter trees’ of cortico-cortical wiring. Examining the complexity of the resulting white matter trees using the same measures as for dendritic trees shows multimodal association areas to have larger, more complexly branched white matter trees than primary areas (all p<0.0001) and regional macroscale complexity to run in parallel with microscale measures, in terms of number of inputs (r=0.677, p=0.032), branch points (r=0.790, p=0.006), total tree length (r=0.664, p=0.036) and branching complexity (r=0.724, p=0.018). Our findings support the integrative theory that brain connectivity is structured following similar ‘principles of connectivity’ at the neuronal and macroscale level, and provide a framework to study connectivity changes in brain conditions at multiple levels of brain organization.

Who Has the Last Word? Understanding How to Sample Online Discussions

In online debates, as in offline ones, individual utterances or arguments support or attack each other, leading to some subset of arguments (potentially from different sides of the debate) being considered more relevant than others. However, online conversations are much larger in scale than offline ones, with often hundreds of thousands of users weighing in, collaboratively forming large trees of comments by starting from an original post and replying to each other. In large discussions, readers are often forced to sample a subset of the arguments being put forth. Since such sampling is rarely done in a principled manner, users may not read all the relevant arguments to get a full picture of the debate from a sample. This article is interested in answering the question of how users should sample online conversations to selectively favour the currently justified or accepted positions in the debate. We apply techniques from argumentation theory and complex networks to build a model that predicts the probabilities of the normatively justified arguments given their location in idealised online discussions of comments and replies, which we represent as trees. Our model shows that the proportion of replies that are supportive, the distribution of the number of replies that comments receive, and the locations of comments that do not receive replies (i.e., the “leaves” of the reply tree) all determine the probability that a comment is a justified argument given its location. We show that when the distribution of the number of replies is homogeneous along the tree length, for acrimonious discussions (with more attacking comments than supportive ones), the distribution of justified arguments depends on the parity of the tree level, which is the distance from the root expressed as number of edges. In supportive discussions, which have more supportive comments than attacks, the probability of having justified comments increases as one moves away from the root. For discussion trees that have a non-homogeneous in-degree distribution, for supportive discussions we observe the same behaviour as before, while for acrimonious discussions we cannot observe the same parity-based distribution. This is verified with data obtained from the online debating platform Kialo. By predicting the locations of the justified arguments in reply trees, we can therefore suggest which arguments readers should sample, to grasp the currently accepted opinions in such discussions. Our models have important implications for the design of future online debating platforms.

Design Improvement of the Mechanism of Delimbing by Multi-Operational Forest Machines

The principles of increasing the use of modern multifunctional forest machines (harvesters and processors) for felling and delimbing in Russia and abroad are currently becoming more widespread and deserve increased attention from esearchers. The results of the studies performed made it possible to identify a wide range of constructive solutions of technological equipment interesting in the opinion of the authors of the publication and to develop a new technical solution. The idea of creating an additional shock load by the working body of multifunctional forest machines for delimbing during the processing of a tree trunk is one of the most effective options for the development of additional cutting force, allowing to facilitate the operation of the device. The proposed method involves delimbing the trunk by pulling rollers and is a combination of the operation of standard delimbing knives together with the gripping arms and a reciprocating delimbing knife that complements the design. The use of compressed air energy provides the reciprocating motion of the knife, creating a new principle of the cutting mechanism for this design. The article describes in detail the design of the device, its operation, as well as options for the interaction of individual technological elements. The implementation of the proposed idea will make it possible to introduce harvester and processor heads into the forestry sector, facilitating the operation of individual assemblies of forest machines with large average volume of the tree-length log. For citation: Rukomojnikov K.P., Kuptcova V.O. Design Improvement of the Mechanism of Delimbing by Multi-Operational Forest Machines. Lesnoy Zhurnal [Russian Forestry Journal], 2021, no. 3, pp. 117–124. DOI: 10.37482/0536-1036-2021-3-117-124

The predictive power of stock market’s expectations volatility: A financial synchronization phenomenon

We explore the use of implied volatility indices as a tool for estimate changes in the synchronization of stock markets. Specifically, we assess the implied stock market’s volatility indices’ predictive power on synchronizing global equity indices returns. We built the correlation network of 26 stock indices and implemented in-sample and out-of-sample tests to evaluate the predictive power of VIX, VSTOXX, and VXJ implied volatility indices. To measure markets’ synchronization, we use the Minimum Spanning Tree length and the length of the Planar Maximally Filtered Graph. Our results indicate a high predictive power of all the volatility indices, both individually and together, though the VIX predominates over the evaluated options. We find that an increase in the markets’ volatility expectations, captured by the implied volatility indices, is a good Granger predictor of an increase in the synchronization of returns in the following month. Estimating, monitoring, and predicting returns’ synchronization is essential for investment decision-making, especially for diversification strategies and regulating financial systems.

Annual Shoot Segmentation and Physiological Age Classification from TLS Data in Trees with Acrotonic Growth

The development of terrestrial laser scanning (TLS) has opened new avenues in the study of trees. Although TLS provides valuable information on structural elements, fine-scale analysis, e.g., at the annual shoots (AS) scale, is currently not possible. We present a new model to segment and classify AS from tree skeletons into a finite set of “physiological ages” (i.e., state of specialization and physiological age (PA)). When testing the model against perfect data, 90% of AS year and 99% of AS physiological ages were correctly extracted. AS length-estimated errors varied between 0.39 cm and 2.57 cm depending on the PA. When applying the model to tree reconstructions using real-life simulated TLS data, 50% of the AS and 77% of the total tree length are reconstructed. Using an architectural automaton to deal with non-reconstructed short axes, errors associated with AS number and length were reduced to 5% and 12%, respectively. Finally, the model was applied to real trees and was consistent with previous findings obtained from manual measurements in a similar context. This new method could be used for determining tree phenotype or for analyzing tree architecture.

Improving the Efficiency of Multifunctional Machines for Intensive Forestry

The method of intensification of forestry by means of integrated mechanization of forestry and logging operations is considered. It is proposed to use manipulator-type machines, such as harvesters, forwarders and excavators, as a technical basis. Improving the efficiency of manipulator-type machines can be achieved through using a set of optional interchangeable equipment. This will allow to create crops by planting seedlings with open and closed root systems, to carry out soil cultivation, seed sowing, thinning of young plants and to carry out pest control, mulching of skidding tracks after major work in the logging site, as well as earthworks during the construction of forest roads. The use of optional interchangeable equipment transforms a manipulator-type machine into a multifunctional machine. It has been shown that the purchase of optional equipment for forestry and logging is a cost-effective investment even for a small amount of works. Intensive forestry is primarily based on the measures of mature and overmature stands cutting, forest tending, and reforestation. Several technological schemes with the use of the multifunctional machine for felling both in the harvester and feller buncher modes are offered. In the latter option, tree length bucking and branch pruning ensure the concentration of all logging residues at the upper depot and create favorable conditions for their processing into raw material for biofuel production and reduce woodwaste in cutting areas. An option of using small size equipment for hauling trees into the area of operation of a multifunctional machine with an installed harvester head is offered when performing selective felling using wide-strip technology of harvesting. Preliminary preparation of the cutting area with small sized equipment (harvesting of small-sized, dead and fallen trees) is proposed. This will significantly reduce the damage to plantation components and provide a greater degree of preservation of the natural environment during the main work of the multifunctional machine. Its use in the most favorable terms due to the work execution on a quarter-block scheme, reducing the number of downtime due to naturalproduction conditions and the number of relocations and, accordingly, increasing the number of machine hours, will minimize total costs of the range of forestry and harvesting works.