scholarly journals The Maintenance of Sex and David Lack's Principle

2016 ◽  
Author(s):  
Joachim Dagg
Keyword(s):  
Reproductive Output ◽  
Reproductive Effort ◽  
Experimental Studies ◽  
Optimal Number ◽  
Evolutionary Constraints ◽  
Immune Functions ◽  
Maintenance Of Sex ◽  
Mutant Female ◽  
The Cost ◽  
David Lack

Combining George C. Williams' idea that evolutionary constraints prevent asexual mutants from arising more frequently in low fecundity organisms, like mammals and birds, with an earlier one by David Lack that the brood size of these organisms has an optimum, and producing larger broods reduces their fitness, leads to a novel hypothesis about the maintenance of sex in them. All else equal, the eggs of an asexual mutant female should simply start developing without fertilisation, and there is no reason to assume that they would stop doing so after the optimal number of offspring has been produced. Without a way to control their reproductive output, asexual mutants should over-reproduce and suffer a cost of doing so. Experimental studies suggest that the cost of enlarged broods could limit the advantage of asexual mutants considerably. Moreover, research discovered that increased reproductive effort reduces immune functions of low fecundity organisms. This offers a surprising synthesis between Williams' constraint and Hamilton's parasite hypothesis on maintaining sex in low fecundity organisms: Compromised immune functions of asexual hosts may render them susceptible rather than adaptation on the side of parasites to overcome host resistance.

The system of indicators of the quality of the carbon-carbon composite materials and technologies of their production

2018 ◽  
pp. 127-132
Author(s):  
T. N. Antipova ◽  
D. S. Shiroyan
Keyword(s):  
Composite Material ◽  
Low Cost ◽  
Experimental Studies ◽  
Carbon Matrix ◽  
Carbon Composite ◽  
Optimal Number ◽  
Laboratory Equipment ◽  
Carbon Composite Material ◽  
Carbon Composite Materials

The system of indicators of quality of carbon-carbon composite material and technological operations of its production is proved in the work. As a result of the experimental studies, with respect to the existing laboratory equipment, the optimal number of cycles of saturation of the reinforcing frame with a carbon matrix is determined. It was found that to obtain a carbon-carbon composite material with a low cost and the required quality indicators, it is necessary to introduce additional parameters of the pitch melt at the impregnation stage.

Influence of Temperature Fields on the Quality of Dried Wood Products

2021 ◽  
Vol 1038 ◽  
pp. 336-344
Author(s):  
Olena Pinchevska ◽  
Andriy Spirochkin ◽  
Denys Zavialov ◽  
Rostislav Oliynyk
Keyword(s):  
Experimental Studies ◽  
Wood Products ◽  
Temperature Fields ◽  
Drying Process ◽  
Wood Moisture ◽  
Adequate Model ◽  
Heating And Cooling ◽  
White Spots ◽  
The Cost ◽  
Wood Heating

The reasons of white spots appearance in the middle of oak timber are determined. These white spots reduce the cost of the lamina made of oak timbers - the front covering of floorboards. It is proposed to intensify the drying process by using oscillating drying schedules to avoid this defect. A method for calculating the duration of such drying is proposed. This method includes the peculiarities of heating and cooling periods kinetics of oak timbers with 25 mm and 30 mm thickness. The inexpediency of using the oscillation of the drying agent parameters in the range of wood moisture content below 20% has been established. An adequate model for calculating wood temperature and air humidity during wood heating and cooling periods has been developed using heat and mass transfer criteria and experimentally determined oak wood moisture conductivity coefficient. Based on the results of theoretical and experimental studies oscillating drying schedules of different thickness oak timbers are offered. Tests of the proposed schedules in industrial conditions showed no discoloration of the central layers of European oak (Quercus robur) timbers. The drying process duration was reduced by 1.5–2.4 times and energy consumption were reduced by 1.53 times.

Since blood transfusion is linked to the magnitude of the surgical procedure, comparing transfused patients to untransfused patients will always be confounded by infection risks due to factors related to the procedure. To control for these factors one must compare patients transfused with red cells from different sources or prepared in a manner which minimize infection risk. Patients transfused with homologous blood have infection rates several fold higher than recipients of equal values of autologous blood undergoing the same operative procedure (20-23). Homologous blood recipients have significantly longer hospital stays attributed to treating infections. The cost of a blood transfusion exceeds the cost of collection, storage and administration because of transfusion's association with length of stay. In this era of cost-containment the association with prolonged stay may ultimately curtail the use of blood. Homologous blood can be filtered to remove donor leukocytes which may be contributing to immune suppression and infection risk. A prospective randomized trial comparing the infection rates among colorectal cancer patients receiving filtered and unfiltered blood has been conducted (9). There were 17 infectious complications among the 56 recipients of whole blood and one infectious complication among the 48 recipients of filtered blood. Infections were prevented by the seemingly simplistic addition of a $25/filter to every bag of blood transfused. These clinical studies are very convincing: homologous blood transfusion is associated with increased risk of infection in every clinical situation examined. In multivariate analyses transfusion was a significant predictor of infection after consideration of other variables measured and in the majority of those studies transfusion was the single most significant factor. Patients receiving homologous blood exhibited an incidence of infectious complications that was approximately four times higher than patients receiving autologous blood. The association of transfusion with infection is found among patients undergoing surgery for cardiac, orthopedic and gastrointestinal disorders and for trauma as well as among unoperated patients transfused for bums and gastrointestinal bleeding. The observation that nosocomial infections are increased in these studies argues strongly that the association of transfusion with infection is not simply a reflection of transfusion as a marker of tissue destruction and contamination. Infections that develop in transfused patients away from the site of trauma or in the absence of trauma, cannot be attributed to the quantity of tissue destroyed or to the degree of bacterial contamination. Filtered blood can remove leukocytes and prevent postoperative infections. Since filtering blood can significantly reduce the incidence of infection among transfused patients, all transfused blood will be passing through filters in the very near future. EXPERIMENTAL STUDIES RELATING BLOOD TRANSFUSION TO INCREASED RISK OF INFECTION Patients are extremely heterogeneous and even in prospective randomized trials, factors which influence patients' participation affect the outcome despite double-blinding and randomization. In animal studies using syngeneic strains with identical housing, lighting, access to food and water, control over the extent of injury, use of antibiotics and exposure to other variables the influence of a single variable such as blood transfusion can be measured. Dr. Waymack's laboratory has intensively studied parameters which interact with transfusion in

1995 ◽  
pp. 296-296
Keyword(s):  
Blood Transfusion ◽  
Autologous Blood ◽  
Experimental Studies ◽  
Infection Risk ◽  
Infectious Complications ◽  
Risk Of Infection ◽  
Infection Rates ◽  
Homologous Blood ◽  
Increased Risk ◽  
The Cost

scholarly journals ESTIMATION OF THE EFFICIENCY OF THE LUBRICATION OF THE WORKING SURFACES OF THE SADDLE-COUPLING DEVICE OF THE FOREST TRUCK

2021 ◽  
Author(s):  
Valeriy Posmetev ◽  
Vadim Nikonov ◽  
Viktor Posmetev
Keyword(s):  
Computer Experiments ◽  
Base Plate ◽  
Optimal Number ◽  
Actual Problem ◽  
Premature Failure ◽  
Coupling Device ◽  
Excessive Consumption ◽  
Operational Factors ◽  
Friction Surfaces ◽  
The Cost

The importance of the need for further constructive improvement of fifth-wheel couplings of timber tractors with semi-trailers has been substantiated. The main operational factors arising during the movement of a timber tractor with a semitrailer in the process of hauling timber and affecting the premature failure of the main parts of the fifth wheel coupling are considered. The influence on the resource of the fifth wheel coupling device of strict fulfillment of the mandatory operations of periodic lubrication of the saddle and the base plate of the semitrailer in the process of connecting and disconnecting it with a timber tractor is given. Described is the actual problem associated with excessive consumption of lubricant in the process of applying it to the friction surfaces of the saddle and the base plate of the semitrailer by the traditional method of extrusion. A possible method of dosed supply of the required volume of lubricant through the optimal number of lubrication holes to the friction surfaces is considered, which makes it possible to significantly reduce the cost of maintaining the operable state of the fifth wheel coupling. In order to preliminary evaluate the application of this lubrication method, which ensures the effective functioning of the fifth wheel coupling of a timber tractor with a semitrailer, several series of computer experiments were performed to determine the optimal number of lubrication holes in the saddle that evenly and dosed distribute the lubricant between the saddle and the base plate of the semitrailer.

scholarly journals INVESTIGATION OF THE METHOD OF PROCESSING HOLES WITH A ROTARY CUP CUTTER WITH SURFACING

2021 ◽  
pp. 1-6
Author(s):  
Bakytzhan Donenbayev ◽  
Karibek Sherov ◽  
Assylkhan Mazdubay ◽  
Aybek Sherov ◽  
Medgat Mussayev ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Cutting Tool ◽  
Large Diameter ◽  
Cutting Tools ◽  
Experimental Studies ◽  
Surface Hardness ◽  
Hard Metal ◽  
Metal Plates ◽  
Study Results ◽  
The Cost

This article presents the experimental study results of the process of rotational friction holes boring using a cup cutter surfaced by STOODY M7-G material. As a result of experimental studies, the following quality indicators were achieved: surface roughness within Ra=10÷1,25 micrometer; surface hardness within HB 212-248. Using a cup cutter surfaced by STOODY M7-G material in case of rotational friction boring of large-diameter holes for large-sized parts can improve processing performance in comparison with cutting tools equipped with hard metal plates and provided the required surface roughness. Preliminary calculations showed that the manufacture of cup cutters from non-instrumental materials reduces the cost of the cutting tool by 5-7 times and the cost of the operation by 1.5-2 times.

scholarly journals PLANNING OF EXPERIMENTAL STUDIES WITH THE PURPOSE OF DEVELOPING THE MODE OF FACING DSTP WITH A THIN SLED VENEER OF WOOD MAHAGONI

2021 ◽  
Author(s):  
Tatyana Efimova ◽  
Tatyana Ishchenko ◽  
S. Dunaev
Keyword(s):  
Wood Species ◽  
Experimental Studies ◽  
Second Order ◽  
Synthetic Materials ◽  
Natural Wood ◽  
Cost Of Production ◽  
Wood Furniture ◽  
The Cost ◽  
Huge Variety

The modern market offers mainly furniture made from traditional materials: chipboard and fiberboard, faced with synthetic materials (films, plastics). However, despite the huge variety of synthetic materials, they cannot convey the original texture, color of natural wood. Furniture made of natural wood and furniture made of panel materials, faced with sliced veneer, are classified as premium furniture due to the high cost and shortage of valuable wood species. To reduce the cost of production, it is proposed to use thin sliced and peeled veneer with a thickness of 0.4 mm. The problem is that the most common veneering defect is glue leakage, which depends on many factors, as well as the lack of clear recommendations for the choice of veneering modes. In this regard, the problem of developing a mode for veneering chipboards with thin sliced veneer of mahogany wood is relevant and requires research. The paper identifies variable factors and factors that remained constant during research. The conditions for conducting experimental studies are also given. To develop a methodology for conducting experimental studies, the method of uniform- rotatable planning of a second-order experiment was used.

scholarly journals An Experimental Study to Evaluate the Impact of the Programming Paradigm in the Testing Activity

2012 ◽  
Vol 15 (1) ◽  
Author(s):  
Simone de Rocio Senger de Souza ◽  
Marllos Paiva Prado ◽  
Ellen Francine Barbosa ◽  
José Carlos Maldonado
Keyword(s):  
Experimental Study ◽  
Experimental Studies ◽  
Programming Paradigm ◽  
Time Restrictions ◽  
Activity Cost ◽  
The Cost ◽  
Programming Paradigms ◽  
The Impact ◽  
Initial Results ◽  
Testing Criteria

Several techniques and criteria are available to help conducting testing activity. The choice for one of them depends on different aspects, such as the time restrictions, ef- fectiveness of the testing criteria or the features of the program under test. In this context, the programming paradigm might influence in the testing activity cost. This paper presents the results of an experimental study to characterize and evaluate the cost and strength of structural and functional testing criteria, comparing object-oriented and procedural programming paradigms. A set of 32 programs from the data structure do- main was considered in this study. The main goals in the execution of this research were: i) to obtain initial results about the investigated questions; ii) to generate artifacts which can be used as basis to define and conduct further experimental studies; iii) to support training and teaching of software testing activity.

Approximate Matching Between XML Documents and Schemas with Applications in XML Classification and Clustering

2011 ◽  
pp. 99-124 ◽  
Author(s):  
Guangming Xing
Keyword(s):  
Structural Information ◽  
Experimental Studies ◽  
Feature Representation ◽  
Document Management ◽  
Data Sets ◽  
Structural Classification ◽  
Approximate Matching ◽  
Xml Documents ◽  
Efficiency And Effectiveness ◽  
The Cost

Classification/clustering of XML documents based on their structural information is important for many tasks related with document management. In this chapter, we present a suite of algorithms to compute the cost for approximate matching between XML documents and schemas. A framework for classifying/clustering XML documents by structure is then presented based on the computation of distances between XML documents and schemas. The backbone of the framework is the feature representation using a vector of the distances. Experimental studies were conducted on various XML data sets, suggesting the efficiency and effectiveness of our approach as a solution for structural classification/clustering of XML documents.

The cost of reproduction in women: Reproductive effort and oxidative stress in premenopausal and postmenopausal American women

2017 ◽  
Vol 30 (1) ◽  
pp. e23069 ◽  
Author(s):  
Anna Ziomkiewicz ◽  
Amara Frumkin ◽  
Yawei Zhang ◽  
Amelia Sancilio ◽  
Richard G. Bribiescas
Keyword(s):  
Oxidative Stress ◽  
Reproductive Effort ◽  
Cost Of Reproduction ◽  
American Women ◽  
The Cost ◽  
And Oxidative Stress

scholarly journals Preparation and Characterization of Al/HTPB Composite for High Energetic Materials

Nanomaterials ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 2222
Author(s):  
Alexander Vorozhtsov ◽  
Marat Lerner ◽  
Nikolay Rodkevich ◽  
Sergei Sokolov ◽  
Elizaveta Perchatkina ◽  
...  
Keyword(s):  
Energetic Materials ◽  
Experimental Studies ◽  
High Energy ◽  
High Reactivity ◽  
Ease Of Use ◽  
Slow Heating ◽  
Energy Materials ◽  
Nanosized Powders ◽  
The Cost

Nanosized Al (nAl) powders offer increased reactivity than the conventional micron-sized counterpart, thanks to their reduced size and increased specific surface area. While desirable from the combustion viewpoint, this high reactivity comes at the cost of difficult handling and implementation of the nanosized powders in preparations. The coating with hydroxyl-terminated polybutadiene (HTPB) is proposed to improve powder handling and ease of use of nAl and to limit its sensitivity to aging. The nAl/HTPB composite can be an intermediate product for the subsequent manufacturing of mixed high-energy materials while maintaining the qualities and advantages of nAl. In this work, experimental studies of the high-energy mixture nAl/HTPB are carried out. The investigated materials include two composites: nAl (90 wt.%) + HTPB (10 wt.%) and nAl (80 wt.%) + HTPB (20 wt.%). Thermogravimetric analysis (TGA) is performed from 30 to 1000 °C at slow heating rate (10 °C/min) in inert (Ar) and oxidizing (air) environment. The combustion characteristics of propellant formulations loaded with conventional and HTPB-coated nAl are analyzed and discussed. Results show the increased burning rate performance of nAl/HTPB-loaded propellants over the counterpart loaded with micron-sized Al.

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