scholarly journals The Biomechanics of the Locust Ovipositor Valves: a Unique Digging Apparatus

2021 ◽  
Author(s):  
Rakesh Das ◽  
Shmuel Gershon ◽  
Benny Bar-On ◽  
Maryam Tadayon ◽  
Amir Ayali ◽  
...  
Keyword(s):  
Sexual Maturation ◽  
Environmental Conditions ◽  
Granular Matter ◽  
Propagation Direction ◽  
Optimal Conditions ◽  
Hydration Level ◽  
3D Printed ◽  
Maturation State ◽  
Force Range ◽  
Unique Mechanism

The female locust has a unique mechanism for digging in order to deposit its eggs deep in the ground. It utilizes two pairs of sclerotized valves to displace the granular matter, while extending its abdomen as it propagates underground. This ensures optimal conditions for the eggs to incubate, and provides them with protection from predators. Here, two major axes of operation of the digging valves are identified, one in parallel to the propagation direction of the ovipositor, and one perpendicular to it. The direction-dependent biomechanics of the locust major, dorsal digging valves are quantified and analyzed, under forces in the physiological range and beyond, considering hydration level, as well as the females age, or sexual maturation state. Our findings reveal that the responses of the valves to compression forces in the specific directions change upon sexual maturation to follow their function, and depend on environmental conditions. Namely, in the physiological force range, the valves are resistant to mechanical failure. In addition, mature females, which lay eggs, have stiffer valves, up to roughly nineteen times the stiffness of the pre-mature locusts. The valves are stiffer in the major working direction, corresponding to soil shuffling and compression, compared to the direction of propagation. Hydration of the valves reduces their stiffness but increases their resilience against failure. These findings provide mechanical and materials guidelines for the design of novel non-drilling excavating tools, including 3D-printed anisotropic materials based on composites.

Structural performance of 3D-printed composites under various loads and environmental conditions

2020 ◽  
Vol 91 ◽  
pp. 106770 ◽  
Author(s):  
Mohammad Reza Khosravani ◽  
Ali Zolfagharian ◽  
Matt Jennings ◽  
Tamara Reinicke
Keyword(s):  
Environmental Conditions ◽  
Structural Performance ◽  
3D Printed

Hygroscopic Swelling Behavior of 3D Printed Parts due to Changes in Environmental Conditions

2016 ◽  
Author(s):  
Ju-young Park ◽  
Sangho Ha ◽  
Eunju Park ◽  
Daeil Kwon ◽  
Namhun Kim
Keyword(s):  
Relative Humidity ◽  
Environmental Conditions ◽  
Room Temperature ◽  
Selective Laser Sintering ◽  
Swelling Behavior ◽  
Hygroscopic Swelling ◽  
Dimension Change ◽  
Nylon 12 ◽  
3D Printed ◽  
Local Weather

Selective laser sintering (SLS) printers have been used for rapid prototyping, and the prototypes of part assemblies have been reported to expand or shrink over time. This paper examines the hygroscopic swelling behavior of 3D printed parts from SLS printers. A total of 10 hexahedron samples were produced using nylon-12, which is a common material used for prototyping. Half of the samples were exposed to a high temperature to reduce the moisture content, and the rest were left at a room temperature. In the meantime, 13 dimensions of each sample were measured periodically along with the local weather records including relative humidity in order to track the hygroscopic swelling behavior of the samples. The results showed that the deformation was mostly occurred to the dimensions parallel to the sintering layers. Also, changes in these dimensions were found to have a high correlation with the relative humidity regardless of temperature conditions. These results imply that changes in environmental conditions such as relative humidity result in the deformation of 3D printed parts after production. The high correlation between dimension change and relative humidity also indicates the layup orientation is a decisive factor to predict the deformation of 3D printed parts. Thus, unexpected deformation of 3D printed parts can be avoided by optimizing the parts design considering the layup orientation and by controlling the environmental conditions.

scholarly journals CULTURE OF RED OAK VORONEZH UPLAND OAK

2020 ◽  
Vol 8 (1) ◽  
pp. 176-180
Author(s):  
Aleksey Chernodubov
Keyword(s):  
Mixed Culture ◽  
Environmental Conditions ◽  
Arable Land ◽  
Red Oak ◽  
Optimal Conditions ◽  
Optimal Density ◽  
Pure Cultures ◽  
Soil Preparation ◽  
Growing Conditions ◽  
Intensive Growth

The influence of some agrotechnical methods of planting 29-35-year-old artificial plantations of red oak on growth and productivity in the type of growing conditions – fresh substrate Was studied. Soils-gray forest loamy. It was found that the best indicators of preservation (55%) were revealed during continuous soil preparation in contrast to furrow cutting (19-32%). This is due to the optimal conditions for survival and adaptation to new environmental conditions. The optimal density of 5.6 thousand pieces per ha, which is achieved when placing 2, 5x0, 7 m. the scheme of mixing rocks is Important. In pure cultures of red oak on furrows the stock makes 132-163 m3/ha. At creation of the mixed culture of 5dkr5dch on an arable land it is respectively equal – 435 and 205 m3/ha. At the scheme of mixing of 3dkr2yao2lp2klo the stock decreases to 147 m3/ha. According to schemes of mixing the highest productivity (487-488 m3 / ha) is revealed at structure of 7dkr3b or 6dkr2yao2klo. At these compositions the most intensive growth on height and stocks of wood is noted. This is due to the fact that the red oak needs fitting breed because of its biological characteristics.

Evaluation of Paravalvular Leakage in Novel Mechanical Heart Valve

2017 ◽  
Author(s):  
Ankit Saxena ◽  
Rohan Shad ◽  
Mrudang Mathur ◽  
Anwesha Chattoraj ◽  
Sujay Shad
Keyword(s):  
Heart Valve ◽  
Heart Valves ◽  
Cardiac Tissue ◽  
Mechanical Heart Valve ◽  
Prosthetic Heart Valve ◽  
3D Printed ◽  
Novel Method ◽  
Novel Devices ◽  
Careful Assessment ◽  
Unique Mechanism

We developed a new mechanical heart valve prototype with a unique mechanism for attachment to cardiac tissue. The development of novel prosthetic heart valve systems requires careful assessment of paravalvular leaks — leakage of fluid that takes place between the valve and the cardiac tissue it is attached to. Traditional methods of testing paravalvular leaks in flow chambers are not ideal for novel devices and may underestimate its true extent. In this paper we developed a novel method of quantifying paravalvular leaks involving the use of 3D printed prototype heart valves and cadaveric bovine hearts, and compared the results with those from commercially available Medtronic ATS mechanical bileaflet valves. The average leak in our final prototype heart valves were found to be 0.13 ml/sec, compared to 0.33 ml/sec in the ATS valve.

Microbial Modification Of Crude Oil In The Sea

1969 ◽  
Vol 1969 (1) ◽  
pp. 317-326 ◽  
Author(s):  
C.E. ZoBell
Keyword(s):  
Microbial Biomass ◽  
Environmental Conditions ◽  
Coastal Waters ◽  
Bacterial Population ◽  
Oil Pollution ◽  
Crude Oils ◽  
Oil Oxidation ◽  
Optimal Conditions ◽  
Microbial Oxidation ◽  
Open Sea

Abstract Virtually all kinds of hydrocarbons and crude oils from many fields are susceptible to microbial oxidation. More than a hundred species of bacteria, yeasts, and fungi are able to oxidize hydrocarbons. Each species is limited in the kinds of hydrocarbons it can attack. Each species is also limited by the temperature, salinity, surface tension, pH, oxygen tension, and other environmental conditions at which it is biochemically active. Environmental conditions also affect the rate of microbial reporduction and oil oxidation. Enrichment cultures, consisting of several different species growing under optimal conditions, tend to convert crude oils and refinery products mainly to carbon dioxide and microbial biomass. From 10 to 90 per cent of the carbon may be converted into microbial biomass. Oil-oxidizing bacteria are most abundant in coastal waters and mud where oil pollution is chronic. Such bacteria are extremely scarce in the open sea. In unpolluted waters the ratio of oil oxidizers to the total bacterial population in marine environments ranges from 1:100 to 1:10,000. In chronically oil-polluted coastal areas from 5 to 50 per cent of the bacteria may be able to oxidize one or more kinds of hydrocarbons. In such areas, bacteria in well-oxygenated waters might oxidize oil at rates ranging from 0.02 to 2 grams per square meter per day at 20° to 30° C.

scholarly journals The 3D printed models technology for the management of intracranial aneurysms

2020 ◽  
pp. 373-378
Author(s):  
A. Chiriac ◽  
Georgiana Ion ◽  
G. Stan ◽  
S. Munteanu ◽  
N. Dobrin ◽  
...  
Keyword(s):  
Intracranial Aneurysms ◽  
Professional Training ◽  
Three Dimensional ◽  
Simulation Models ◽  
Optimal Management ◽  
Optimal Conditions ◽  
Three Dimensional Printing ◽  
3D Printed ◽  
Intervention Planning ◽  
Dimensional Printing

Management of intracranial aneurysms is still a therapeutic challenge, especially in cases of complex lesions. Thus, the improvement of the study and intervention planning possibilities correlated with the access to continuous professional training based on simulation and clinical diversity represent optimal conditions for the efficient solution of this pathology. The development of three-dimensional printing technology offers a new opportunity in the modern treatment of intracranial aneurysms. The aim of this study is to present some aspects related to the materials and methods of manufacturing simulation models of individual 3D printed aneurysms and their influence in the optimal management of these lesions.

scholarly journals Tracking the Subtle Mutations Thriving Host Sensing by the Plant PathogenStreptomyces scabies

2017 ◽  
Author(s):  
Samuel Jourdan ◽  
Isolde M. Francis ◽  
Benoit Deflandre ◽  
Rosemary Loria ◽  
Sébastien Rigali
Keyword(s):  
Plant Pathogen ◽  
Environmental Conditions ◽  
Plant Tissue ◽  
Physiological Response ◽  
Virulence Genes ◽  
Common Scab ◽  
Genetic Material ◽  
Optimal Conditions ◽  
Nutrient Sources ◽  
Root Crops

AbstractThe acquisition of genetic material conferring the arsenal necessary for host virulence is a prerequisite on the path to become a plant pathogen. More subtle mutations are also required for perception of cues witnessing the presence of the target host and optimal conditions for colonization. The decision to activate the pathogenic lifestyle is not ‘taken lightly’ and involves efficient systems monitoring environmental conditions. But how can a pathogen timely trigger the expression of virulence genes if the main signal inducing its pathogenic behavior originates from cellulose, the most abundant polysaccharide on earth? This situation is encountered byStreptomyces scabiesresponsible for common scab disease on tuber and root crops. We here propose a series of hypotheses of howS. scabiescould optimally distinguish whether cello-oligosaccharides originate from decomposing lignocellulose (nutrient sources) or, instead, emanate from living and expanding plant tissue (virulence signals), and accordingly adapt its physiological response.

The special clothing for firefighters – the normative requirements and original research results

2018 ◽  
Vol 560 (5) ◽  
pp. 12-15
Author(s):  
Magdalena Młynarczyk
Keyword(s):  
Thermal Comfort ◽  
Natural Disasters ◽  
Environmental Conditions ◽  
Protective Clothing ◽  
Thermal Sensation ◽  
Original Research ◽  
Optimal Conditions ◽  
Normative Requirements ◽  
The Right ◽  
The Impact

The firefighters work in extreme environmental conditions and have to solve a wide variety of problems during their work. These can be rescuing and firefighting actions or removing effects of accidents or natural disasters. In order to protect, not only others but also themselves, they must be focused as much as possible in order to avoid mistakes. Optimal conditions for such work could create so-called thermal comfort, characterized by a thermoneutral state of a body. Lack of thermal comfort can also cause an increased number of mistakes. That is why it is so important to select the right protection and to know the impact of the protective clothing (special clothing) on the thermal sensation of firefighters. This article presents the requirements for special clothing for firefighters, the results of thermal insulation tests of the above-mentioned clothing and the analysis of thermal sensations of its users (by PMV index).

Rate and course of sporulation of oocysts ofEimeria acervulinaunder different environmental conditions

Parasitology ◽  
1994 ◽  
Vol 108 (5) ◽  
pp. 497-502 ◽  
Author(s):  
E. A. M. Graat ◽  
A. M. Henken ◽  
H. W. Ploeger ◽  
J. P. T. M. Noordhuizen ◽  
M. H. Vertommen
Keyword(s):  
Relative Humidity ◽  
Significant Influence ◽  
Interaction Effect ◽  
Environmental Conditions ◽  
Optimal Conditions ◽  
Maximum Percentage ◽  
Eimeria Acervulina ◽  
Rate Of Increase

SummaryAn experiment was conducted to determine the rate and maximum percentage of sporulation ofEimeria acervulinaoocysts at various environmental conditions relating to temperature (21 versus 33 °C) and relative humidity (RH) (40 versus 80%). Measurements were made during 44 h after excretion of oocysts in 3 substrates: dry litter, clammy litter and pure faeces respectively. Maximum sporulation percentage in both dry (22·6%) and clammy litter (19·5%) was higher (P< 0·005) than in pure faeces (11·6%). Neither temperature nor RH had a significant influence on percentage of oocysts that sporulated. Under these simulated practical conditions approximately 25% of all oocysts sporulated, whereas sporulation under optimal conditions (29 °C, aeration, 2% K2Cr2O7) showed a higher (68%) sporulation ability of oocysts. At 33 °C sporulation proceeded at a faster pace than at 21 °C (P< 0·005). With respect to RH and substrate, once sporulation started, the rate of increase to maximum percentage was not different. Time of onset of sporulation was influenced by temperature (P< 0·0001) and RH (P< 0·001). Time of onset occurred 15 h later at 21 °C compared with 33 °C and 5 h later at 40% RH compared with 80%. Also, an interaction effect (P< 0·01) was found with effect of RH being stronger at 21 °C compared with 33 °C. It was concluded that the most important aspect in the epidemiology ofE. acervulinaduring a flock cycle is the time of onset of sporulation with temperature being the most important factor.

scholarly journals Role of the adipocyte-derived hormone leptin in reproductive control

2014 ◽  
Vol 19 (3) ◽  
Author(s):  
David Garcia-Galiano ◽  
Susan J. Allen ◽  
Carol F. Elias
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Sexual Maturation ◽  
Environmental Conditions ◽  
Fat Reserves ◽  
Reproductive Control ◽  
Reproductive Axis ◽  
The Central Nervous System ◽  
Neuroendocrine Axis

AbstractAchievement of sexual maturation and maintenance of fertility in adulthood are functions that are sensitive to the metabolic status of the organism, particularly the magnitude of fat reserves. In this sense, the adipocyte-derived hormone, leptin, plays a major role in linking metabolic cues and the control of multiple neuroendocrine axes. The hypothalamus is a key site mediating leptin actions, including those involved in the modulation of the hypothalamus-pituitary-gonads (HPG) axis at different stages of development and in different environmental conditions. In the present review, we provide an update of the role of leptin in reproduction and discuss its interactions with neurons, neurotransmitters and downstream targets of the reproductive axis, with a special emphasis on the actions of leptin in the central nervous system. We hope this review will contribute to the understanding of the mechanisms whereby metabolic signals, especially leptin, influence the reproductive neuroendocrine axis modulating its activity in different nutritional states. Special attention will be given to recent advances in the identification of key hypothalamic sites and signaling pathways relevant to leptin’s action in reproductive control.

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