Month: August 2024

Abstract

In this paper, we incorporate spatial analysis to estimate industry-level productivity in the presence of inter-sectoral linkages. Since each industry plays a role in providing intermediate goods to other sectors, the interdependence of economic activities across industries is inevitable. We exploit the linkage patterns from the input-output relationship to define cross-industry dependencies in economic space. We propose a spatial stochastic frontier model, which extends the stochastic frontier model to a spatially dependent specification. The models are estimated using quasi-maximum likelihood methods. Applying the approach to U.S. industry-level data from 1947 to 2010, we find that sectoral dependencies are the consequences of indirect effects via the supply chain network of industries resulting in larger output elasticities as well as scale effects for the networked production processes. However, productivity growth is estimated comparably across different spatial and non-spatial model specifications.

Abstract

The Red Sea had inimitable geological ancient times and is considered a new ocean basin model. It has many islands of numerous sizes in the southern sector and a widespread group of shoals, such as Farasan (Saudi Arabia) and Dahlak (Eretria), due to its geological setting differences. In this work, a group of applications was used to provide a wider vision of the potential field, as well as to image the thermal and subsurface structures of the study area (Farasan and Dahlak Islands) using available marine potential field datasets (marine gravity and magnetic) and topographic and bathymetric datasets. These datasets were downloaded from the GEOSOFT server (Data sources: http://dap.geosoft.com/). We applied different filters of the marine potential field datasets data (e.g., horizontal gradient filter) to create a subsurface structure image. The horizontal gradient technique was used to locate density edges/boundaries from gravity data. The basement depth was displayed, as it was required during the Curie depth estimation by means of mathematical formulas. The profile ~ 500 km in length was selected to cross the study area and its surroundings so as to perform the joint 2D inversion modeling process. The results showed that the Farasan Islands have a shallower Curie point depth and basement relief than Dahlak Islands, indicating that both island groups were not isolated from each other but molded and formed independently. The results revealed that the islands’ different thermal systems were based on heat flow values calculated for each group.

Graphical abstract

Abstract

The main goal of this work is summed up in a univariate chaotic analysis of the runoff series using a topological approach. As such, nineteen series of daily runoff from eight large watersheds in northern Algeria were analyzed. Firstly, preliminary analyses of two traditional dynamic and metric approaches have been tested. In the dynamic approach, three algorithms have shown that the largest Lyapunov exponent for the series is positive, which supports the hypothesis of the existence of chaos. In the metric approach, the Grassberger and Procaccia algorithm clearly shows the saturation of the correlation dimension, which indicates the existence of deterministic dynamics for all studied stations. Secondly, the application of the topological approach in this study constitutes in itself a new contribution to the demonstration of chaos in hydrology by using the recurrence plot (RP) and the recurrence quantification analysis (RQA). As such, the RP structures of the runoff series seem to be more comparable to chaotic systems. In addition, RQA parameters give high values of determinism and laminarity, which supports the hypothesis of the existence of deterministic chaos. The presence of chaos in the runoff series can be identified by the existence of a strong probability of recurrence, indicating a fairly low level of complexity and fairly high predictability. Ultimately, the comparison of these approaches together made it possible to confirm the hypothesis according to which the process generating the runoff series is deterministic and suggests low-dimensional chaotic dynamics.

Abstract

Anthropogenic land use has caused a major crisis to the biodiversity of stream fishes in recent decades, especially with regard to biotic homogenisation. Understanding the response of stream fishes to anthropogenic land use will help to promptly implement effective conservation measures. In this study, we investigated the effects of agriculture on fish diversity in streams in the Wannan Mountains, China. We predicted that agriculture would influence fish diversity by affecting local habitat conditions. The results showed that habitat conditions (e.g. water temperature, water width, water depth) differed significantly between disturbed and reference sites. The disturbed sites had high species richness due to the addition of translocated species outpacing the loss of endemic species. Moreover, fish assemblages showed taxonomic differentiation accompanied by functional homogenisation, which mainly resulted from the addition of translocated species with redundant functional traits. However, the emergence of homogenisation shows a time delay. The biotic differentiation of fish assemblages in agroecosystems is temporary in the Wannan Mountains, and homogenisation may eventually develop as stress intensifies. Thus, it is urgent and necessary to take effective conservation measures to delay or prevent fish assemblages from worsening in agroecosystems before homogenisation develops.