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31.
In biomechanics, the calculation of individual muscle forces during movements is based on a model of the musculoskeletal system and a method for extracting a unique set of muscle forces. To obtain a unique set of muscle forces, non-linear, static optimisation is commonly used. However, the optimal solution is dependent on the musculoskeletal geometry, and single joints may be represented using one, two or three degrees-of-freedom. Frequently, a system with multiple degrees-of-freedom is replaced with a system that contains a subset of all the possible degrees-of-freedom. For example, the cat ankle joint is typically modelled as a planar joint with its primary degree-of-freedom (plantar-dorsiflexion), whereas, the actual joint has three rotational degrees-of-freedom. Typically, such simplifications are justified by the idea that the reduced case is contained as a specific solution of the more general case. However, here we demonstrate that the force-sharing solution space of a general, three degrees-of-freedom musculoskeletal system does not necessarily contain the solutions from the corresponding one or two degrees-of-freedom systems. Therefore, solutions of a reduced system, in general, are not sub-set solutions of the actual three degrees-of-freedom system, but are independent solutions that are often incompatible with solutions of the actual system. This result shows that representing a three degrees-of-freedom system as a one or two degrees-of-freedom system gives force-sharing solutions that cannot be extrapolated to the actual system, and vice-versa. These results imply that general solutions cannot be extracted from models with fewer degrees-of-freedom than the actual system. They further emphasise the need for precise geometric representation of the musculoskeletal system, if general force-sharing rules are to be derived. 相似文献
32.
Two new myrmecophilous species of the genus Scutacarus (Acari: Prostigmata: Scutacaridae) with world keys to related species groups 下载免费PDF全文
In a survey on heterostigmatic mites (Acari: Prostigmata: Heterostigmata) associated with insects including ants in northwestern Iran, two new species of myrmecophilous mites of the genus Scutacarus (Acari: Scutacaridae) were found. They are S. shajariani sp. nov. phoretic on Tetramorium sp. (Hymenoptera: Formicidae) and S. ebermanni sp. nov. phoretic on Messor sp. The mentioned new species belong to groups of species with reduced setae e and h2, and no setae 4b, respectively. These two new species are described and illustrated, and world keys are provided for respective species groups. 相似文献
33.
Azim Parandakh Mohammad Tafazzoli-Shadpour Mohammad-Mehdi Khani 《In vitro cellular & developmental biology. Animal》2017,53(6):547-553
This study aimed to investigate stepwise remodeling of human mesenchymal stem cells (hMSCs) in response to cyclic stretch through rearrangement and alignment of cells and cytoskeleton regulation toward smooth muscle cell (SMC) fate in different time spans. Image analysis techniques were utilized to calculate morphological parameters. Cytoskeletal reorganization was observed by investigating F-actin filaments using immunofluorescence staining, and expression level of contractile SMC markers was followed by a quantitative polymerase chain reaction method. Applying cyclic uniaxial stretch on cultured hMSCs, utilizing a costume-made device, led to alteration in fractal dimension (FD) and cytoskeleton structure toward continuous alignment and elongation of cells by elevation of strain duration. Actin filaments became more aligned perpendicular to the axis of mechanical stretch by increasing uniaxial loading duration. At first, FD met a significant decrease in 4 h loading duration then increased significantly by further loading up to 16 h, followed by another decrease up to 1 d of uniaxial stretching. HMSCs subjected to 24 h cyclic uniaxial stretching significantly expressed early and intermediate contractile SM markers. It was hypothesized that the increase in FD after 4 h while cells continuously became more aligned and elongated was due to initiation of change in phenotype that influenced arrangement of cells. At this point, change in cell phenotype started leading to change in morphology while mechanical loading still caused cell alignment and rearrangement. Results can be helpful when optimized engineered cells are needed based on mechanical condition for functional engineered tissue and cell therapy. 相似文献
34.
Growth and nutrient removal of three macrophytes in response to concentrations and ratios of N and P
JianXiong Liao DeNan Zhang Azim Mallik ChengXin He GuangPing Xu 《International journal of phytoremediation》2017,19(7):651-657
Wastewater from different sources shows great differences in concentrations and ratios of N and P. In order to choose suitable plant species to remove excess N and/or P from polluted waters, it is important to know the performances of these plants under different N and P concentrations. In this study, we investigated the growth and N and P removal rate of three macrophytes, Coix lacryma-jobi, Iris wilsonii, and Arundo donax under six N and P combination treatments. C. lacryma-jobi preferred higher N and P concentrations (16 mg N L?1 and 3.2 mg P L?1), and increasing N supply could increase its P removal rate. I. wilsonii exhibited a growth preference at a combination of moderate N and P concentrations (8 mg N L?1 and 0.8 mg P L?1). A. donax could grow well at all combinations of N and P and had significantly higher relative growth rate and N and P removal rates than the other two species. These results showed A. donax is a promising species to treat various polluted waters and the other two species can be used specifically to treat certain types of wastewater. 相似文献
35.
Anser C. Azim Joan H. M. Knoll Shirin M. Marfatia David J. Peel Peter J. Bryant Athar H. Chishti 《Genomics》1995,30(3)
The Drosophila discs large tumor suppressor protein, Dlg, is the prototype of a newly discovered family of proteins termed MAGUKs (membrane-associated guanylate kinase homologues). MAGUKs are localized at the membrane-cytoskeleton interface, usually at cell-cell junctions, where they appear to have both structural and signaling roles. They contain several distinct domains, including a modified guanylate kinase domain, an SH3 motif, and one or three copies of the DHR (GLGF/PDZ) domain. Recessive lethal mutations in the discs large tumor suppressor gene interfere with the formation of septate junctions (thought to be the arthropod equivalent of tight junctions) between epithelial cells, and they cause neoplastic overgrowth of imaginal discs, suggesting a role for cell junctions in proliferation control. A homologue of the Dlg protein, named Hdlg, has been isolated from human B lymphocytes. It shows 65-79% identity to Dlg in the different domains, and it binds to the cytoskeletal protein 4.1. Here, we report that the gene for lymphocyte Hdlg, named DLG1, is located at chromosome band 3q29. This finding identifies a novel site for a candidate tumor suppressor on chromosome 3. 相似文献
36.
Ana Milstein Mohammed Ekram Azim Mohammed Abdul Wahab Marc Charles Jean Verdegem 《Environmental Biology of Fishes》2003,68(3):247-260
The potential of periphyton-based aquaculture in South Asia is under investigation in an extensive research program. This paper is a further analysis of data from four experiments carried out in that framework, to explore periphyton, fish and fertilizer dose effects on water quality. Factor analysis and ANOVA models applied to a data matrix of water quality parameters in ponds with and without artificial substrates (bamboo poles and kanchi sticks), with and without fish (filter feeders catla and rohu, with and without bottom feeder kalbaush), and with a standard or 50% increased fertilizer dose, allowed us to identify the underlying ecological processes governing this novel periphyton-based pond system, and construct conceptual graphic models of the periphyton–environment relationships observed. We clearly established that the phosphorus flow is mainly linked to phytoplankton activity in the water column and decomposition on the pond bottom, while nitrogen flow is mainly linked to autotrophic (photosynthesis) and heterotrophic (decomposition and nitrification) processes that take place in the periphyton in addition to the water column and pond bottom. Consequently, disruption of the pond bottom by bottom feeding fish primarily promoted phosphate cycling and phytoplankton, while periphyton development on the supplied substrates and fertilization mainly improved oxygen balance and nitrogen related processes developing in the water column. The use of bamboo poles led to better results than kanchi sticks, related to the greater autotrophic periphyton development on bamboo and to the larger surface of bamboo poles that facilitate fish grazing and periphyton dislodgment that in turn have a renewal effect on periphyton. Stocking bottom feeding fish produces a fertilizing effect through the food web that benefits the filter-feeding fish and that makes it unnecessary to increase the dose of inorganic and organic fertilizers applied to the ponds. Thus, the output of this analysis will help the fish farmers in resource constrained countries to improve their production in periphyton-based ponds just by choosing bamboo substrates, stocking a bottom feeder fish together with the filter feeders, and saving money on fertilizers. 相似文献
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39.
Shekhar R. Biswas Azim U. Mallik Junaid K. Choudhury Ainun Nishat 《Wetlands Ecology and Management》2009,17(4):365-383
The effect of intensive human intervention, poor socio-economic conditions and little knowledge on mangrove ecology pose enormous
challenges for mangrove restoration in Southeast Asia. We present a framework for tropical mangrove restoration. Our proposed
restoration framework addresses the ecology, economy and social issues simultaneously by considering the causes of mangrove
degradation. We provide a step by step guideline for its restoration. We argue that although, ecological issues are of prime
importance, economic and social issues must be considered in the restoration plan in order for it to be successful. Since
mangrove ecology is not adequately studied in this region, local ecological knowledge can be used to fill the baseline information
gaps. Unwanted human disturbance can be minimized by encouraging community participation. This can be ensured and sustained
by facilitating the livelihood of the coastal community. We translated the restoration paradigm into a readily available practical
guideline for the executors of the plans. We provide an example of mangrove restoration project that is closely related to
our proposed framework. We are optimistic that this framework has the potential for universal application with necessary adjustments. 相似文献
40.
Mohammad Momen Gharibvand Mina Mounesi Arman Shahriari Asghar Sharif Najafi Azim Motamed far Atefeh Roumi 《生物学前沿》2018,13(6):458-463