Community structure and distributions of two terrestrial salamanders : a pluralistic approach

A goal of evolutionary ecology is to understand the forces that generate ecological communities and maintain species boundaries. Although the effects of particular biotic and abiotic forces have been well studied, much less is known about how these forces interact to influence the evolution of community structure. Here, I report an example of compensatory abiotic and biotic factors limiting the distribution of two terrestrial salamanders and effectively maintaining community structure. The distribution of the wide-ranging Plethodon cinereus completely surrounds the range of P. hubrichti, thus it was believed that P. hubrichti was geographically restricted as a result of interspecific competition from P. cinereus. Using a combination of morphological analysis, resource use (food) data, climatic data, and ecological-niche modeling, I found no evidence to support the hypothesis that biotic interactions with P. cinereus have restricted the range of P. hubrichti. I found no partitioning of food resources in sympatry and no evidence of sympatric morphological divergence. Conversely, there was significant evidence supporting the hypothesis that abiotic forces affected the distribution of P. hubrichti. There was a significant association between local environmental variables and average population morphology, as well as significant morphological convergence of the two species in sympatry, both consistent with adaptation to the local environment. Additionally, ecological niche modeling accurately predicted the range of P. hubrichti, lending further support to this hypothesis. Most notably, even though ecological niche modeling predicted that the ecologically-viable range of P. cinereus included nearly 90% of the range of P. hubrichti, it is absent from nearly this entire region. Combined with the prior behavioral research (where P. hubrichti was the more aggressive of the two), these results strongly suggest that biotic interactions with P. hubrichti negatively impact and restrict the distribution of P. cinereus. This finding is the converse of what was predicted based upon the species distributions alone. This study provides a concrete example of how both biotic and abiotic forces interact to maintain joint species distributions and influence community structure. It also stresses the need for a pluralistic approach to community ecology as well as species\u27 distributions that integrate multiple data sets

Smart Grid Security: Threats, Challenges, and Solutions

The cyber-physical nature of the smart grid has rendered it vulnerable to a multitude of attacks that can occur at its communication, networking, and physical entry points. Such cyber-physical attacks can have detrimental effects on the operation of the grid as exemplified by the recent attack which caused a blackout of the Ukranian power grid. Thus, to properly secure the smart grid, it is of utmost importance to: a) understand its underlying vulnerabilities and associated threats, b) quantify their effects, and c) devise appropriate security solutions. In this paper, the key threats targeting the smart grid are first exposed while assessing their effects on the operation and stability of the grid. Then, the challenges involved in understanding these attacks and devising defense strategies against them are identified. Potential solution approaches that can help mitigate these threats are then discussed. Last, a number of mathematical tools that can help in analyzing and implementing security solutions are introduced. As such, this paper will provide the first comprehensive overview on smart grid security

The homogeneous q-difference operator and the related polynomials

We create the homogeneous q-difference operator Ee(a, b; θ) as an extension of the exponential operator E(bθ). A new polynomials hn(a, b, x|q−1) are defined as an extension of the q−1-Rogers-Szegö polynomial hn(a, b|q−1). We provide an operator proof of the generating function and its extension, Rogers formula and the invers linearization formula, and Mehler’s formula for the polynomials hn(a, b|q−1). The generating function and its extension, Rogers formula and the invers linearization formula, and Mehler’s formula for the polynomials hn(a, b|q−1) are deduced by giving special values to parameters of a new polynomial hn(a, b, x|q−1).Publisher's Versio

Dual strongly Rickart modules

In this paper we introduce and study the concept of dual strongly Rickart modules as a stronger than of dual Rickart modules [8] and a dual concept of strongly Rickart modules. A module M is said to be dual strongly Rickart if the image of each single element in S = EndR(M) is generated by a left semicentral idempotent in S. If M is a dual strongly Rickart module, then every direct summand of M is a dual strongly Rickart. We give a counter example to show that direct sum of dual strongly Rickart module not necessary dual strongly Rickart. A ring R is dual strongly Rickart if and only if R is a strongly regular ring. The endomorphism ring of d-strongly Rickart module is strongly Rickart. Every d-strongly Rickart ring is strongly Rickart. Properties, results, characterizations are studied

Strongly Rickart Modules

In this paper we introduce and study the concept of strongly Rickart modules and strongly CS-Rickart modules as a stronger than of  Rickart modules [8] and CS-Rickart modules[3] respectively. A module M is said to be strongly Rickart module if the right annihilators of each single element in S = EndR(M) is generated by a left semicentral idempotent in S. A module M is said to be strongly CS- Rickart if for any  ??S, rM(?) is an essential in fully invariant direct summand of M. Properties, results, characterizations and relation of these concepts with others known concepts of modules are studied

Strongly Rickart Rings

Let R be a ring with identity. In this paper we introduce a strongly Rickart ring as a stronger concept of a Rickart ring. A ring R is said to be strongly Rickart ring if the right annihilators of each single element in R is generated by a left semicentral idempotent in R. This class of rings is proper class in right Rickart rings, p.q.-Baer rings, reduced rings and semiprime rings. The relation between strongly Rickart and strongly regular are studied. We discuss some types of extension of strongly Rickart ring such as the Dorroh extension and the idealization ring. Key words: strongly Rickart ring, Rickart ring, right annihilator element, semicentral idempotent element, Dorroh extension, idealization of a module

Single phase asymmetrical multilevel inverter topology with reduced device count

Multilevel Inverters (MLIs) are vital components for medium voltage and high-power applications. However, the number of components will increase with increased output voltage levels. It leads to high power losses. In this thesis, a new single-phase asymmetrical multilevel inverter topology used for medium and high voltage applications is proposed. The topology is capable of producing n-level output voltage with reduced device counts. It is achieved by arranging available switches and direct current (dc)-sources to obtain the maximum combinations of addition and subtraction of the input dc-sources. A comprehensive literature review has been carried out, and the proposed topology is compared with the topologies available in the literature. Comparison based on the number of switches utilized, the number of dc sources used, and the total number of devices is made. To verify the viability of the proposed topology, circuit models for 9-level, 25-level, and 67-level inverters are developed and simulated in Matlab-Simulink software first. Voltage and current waveforms and THD for resistive and inductive loads are obtained from the simulation model and validated with the experimental setup. Experimental results of the proposed inverter prototype for 9-level and 25-level output, developed in the laboratory, are presented. A low-frequency and high-frequency switching strategy for the proposed inverter topology are also presented in this work. Thermal modelling of the proposed topology is done in PLECS software, and detailed loss analysis for 9-level as well as 25-level topologies is carried out. The fundamental topology utilizes 9 switches with a total standing voltage (TSV) of 6.75 per unit while the 25-level topology structure has 12 switches with the TSV of 6.92 per unit only. Comparison with the other multilevel topologies shows that the proposed circuit requires fewer power switches and dc-sources to produce the same output levels. Due to the low switching frequency requirement, the proposed topology is applicable for high and medium voltage applications, resulting in lower switching losses

Bioclimatic modelling, morphology, and behaviour reveal alternative mechanisms regulating the distributions of two parapatric salamander species

Question: What ecological and evolutionary processes are important in maintaining parapatric distributions of sibling species? Hypotheses: Previous research has suggested that competition is a likely factor limiting species distributions and maintaining parapatric distributions. Alternatively, abiotic restrictions such as climatic factors and local adaptation can also limit species’ ranges. Organisms: Plethodon hubrichti, a mountaintop endemic salamander, has an extremely limited geographic range that is entirely surrounded by the widespread Plethodon cinereus. Previous studies have suggested that P. hubrichti may be geographically restricted as a result of interspecific competition with P. cinereus. Methods: We studied the relationship between trophic morphology and diet in allopatric and sympatric populations to examine the effect of exploitative competition on geographic distribution. Behavioural experiments were conducted in the laboratory to determine the effects of interference competition. We complemented these analyses with bioclimatic modelling of species’ ranges and climate–phenotype correlations to examine the abiotic impact. Results: Our results suggest that aggressive interactions with P. hubrichti restrict the distribution of P. cinereus and not the converse, whereas P. hubrichti appears to be limited by abiotic climatic factors

Novel expression of microRNAs in serum samples of Iraqi breast cancer women

Although a lot of hard work against cancer to reduces its spread but it still continues to kill with abandon. The need for a biomarker for cancer early detection becomes the most mind concentrated scientists. MicroRNAs the tiny non coding RNA molecules opened new path for the scientists to determine the cancer in its early stages. Expression of microRNAs profiles has been investigated to be involved in cancer development. Here we determined the expression of microRNAs in serum of Iraqi healthy volunteers and other women diagnosed with breast cancer. MicroRNAs expression has been determined by using real time qPCR and delta method has been used. Four of thirteen microRNAs were shown to be expressed in serum of Iraqi breast cancer women. Let-7a and miR-21 were shown to be significantly over expressed in serum of breast cancer compared with healthy serum volunteers (P= 0.022 and 0.026) respectively. While miR-26b and miR-429 found to be significantly down expressed in serum of breast cancer women (P= 0.0034 and 0.031) respectively. The result concluded that these expressed microRNAs in serum of breast cancer women could be used as a first indicator of breast cancer occurrence