Role of water current and related variables in determining buoyancy in the sticklebacks Culaea inconstans and Pungitius pungitius

1988 ◽  
Vol 66 (9) ◽  
pp. 2006-2014 ◽  
Author(s):  
Barbara J. Beaver ◽  
John H. Gee
Keyword(s):  
Inverse Relationship ◽  
Water Velocity ◽  
Water Current ◽  
Swim Bladder ◽  
Pungitius Pungitius ◽  
Weak Current ◽  
Low Velocity ◽  
Culaea Inconstans ◽  
Time Required

The sticklebacks Culaea inconstans and Pungitius pungitius alter buoyancy (lift from the swim bladder) in the field primarily in response to changes in water velocity. Potential adjustment is extensive and is only realized when fish are exposed to current for several days. Buoyancy measured on fish from the field showed an inverse relationship with water velocity and temperature. Buoyancy was also highest in fish living among vegetation. However, vegetation was restricted to still water or areas of very low velocity. In the laboratory, water temperature affected buoyancy of C. inconstans in current only; there, at 6 °C, buoyancy was greater than at higher temperatures. In the field an unknown factor(s), dependent on temperature, affects buoyancy. An inverse relationship was found between buoyancy and water velocity in the laboratory, and adjustment of buoyancy was slow. The time required for buoyancy to decrease from maximum to minimum levels was 4 and 7 d for P. pungitius and C. inconstans, respectively. In the field, minimum buoyancy levels were not reached because fish were exposed to weak current velocities for short intervals. The ability to reduce swim bladder lift (volume) in strong velocities and replace it with hydrodynamic lift and vice versa is seen as an adaptation to environments where water velocity varies in time and space permitting fishes to use the most effective source of lift.

Buoyancy regulation by the sticklebacks Culaea inconstans and Pungitius pungitius in response to different salinities and water densities

1992 ◽  
Vol 70 (8) ◽  
pp. 1590-1594 ◽  
Author(s):  
John H. Gee ◽  
Heidi M. Holst
Keyword(s):  
Fresh Water ◽  
Brackish Water ◽  
Laboratory Experiments ◽  
Hydrodynamic Forces ◽  
Bladder Volume ◽  
Swim Bladder ◽  
Water Density ◽  
Pungitius Pungitius ◽  
Culaea Inconstans

The sticklebacks Culaea inconstans and Pungitius pungitius maintain buoyancy equilibrium in laboratory experiments by altering swim-bladder volume when held in a range of salinities (0–22.5 ppt). By holding C. inconstans in a Percoll solution in which water density is increased but tonicity remains similar to that of fresh water, we show that this species adjusts its buoyancy in response to a change in water density. When C. inconstans is transferred abruptly from fresh water to brackish water (10 ppt) buoyancy equilibrium is not regained until 96 h later. During this period of swim-bladder adjustment, hydrodynamic forces are used to provide the appropriate lift. Both species encounter variation in salinity in nature and the ability to respond to such changes could be highly adaptive.

Buoyancy Response to Changes in Water Velocity and Its Function in Creek Chub (Semotilus atromaculatus)

1978 ◽  
Vol 35 (3) ◽  
pp. 295-299 ◽  
Author(s):  
Gordon Berezay ◽  
John H. Gee
Keyword(s):  
Angle Of Attack ◽  
Water Velocity ◽  
The Body ◽  
Bladder Volume ◽  
Water Current ◽  
Acclimation Temperature ◽  
Small Fish ◽  
Swim Bladder ◽  
Semotilus Atromaculatus ◽  
Creek Chub

Creek chub (Semotilus atromaculatus) reduce buoyancy by decreasing swim-bladder volume when exposed to water current. Fish were near neutral buoyancy (0.956–0.997 mL∙g−1) in still water but in current small fish (< 73 mm) were more buoyant (0.668 mL∙g−1) than larger fish (0.540 mL∙g−1). Extent of buoyancy alteration was influenced by acclimation temperature, water velocity, and an interaction of both these factors. Reduction of buoyancy on exposure to water current required 3–6 h and the rate of decrease (0.035–0.068 mL∙g−1∙h−1) was independent of acclimation temperature and water velocity. The hypothesis that creek chub reduce buoyancy when exposed to water current to compensate for the lift created due to deflection of water over the dorsal surface of the body was supported by the following findings. When initially exposed to current, fish lowered the head assuming an angle of attack of 9–12° from horizontal. A horizontal (< 1°) angle of attack was gradually assumed during buoyancy adjustment. Fish acclimated to moderate current for 12 or 24 h tired less readily in strong current (80% took 43 and 44 min, respectively) than those not acclimated or acclimated for 6 h (80% took 33 and 25 min, respectively). Fish induced to swim in still water reduced buoyancy to a similar extent as those in current. Key words: swim-bladder volume change, temperature, hydrodynamic lift, swimming angle of attack, time to fatigue

scholarly journals Towards 6G IoT: Tracing Mobile Sensor Nodes with Deep Learning Clustering in UAV Networks

Sensors ◽  
2021 ◽  
Vol 21 (11) ◽  
pp. 3936
Author(s):  
Yannis Spyridis ◽  
Thomas Lagkas ◽  
Panagiotis Sarigiannidis ◽  
Vasileios Argyriou ◽  
Antonios Sarigiannidis ◽  
...  
Keyword(s):  
Deep Learning ◽  
Heuristic Method ◽  
Sensor Nodes ◽  
Convolutional Network ◽  
Received Signal Strength Indicator ◽  
Anchor Nodes ◽  
Time Required ◽  
Rf Signal ◽  
Deep Learning Model

Unmanned aerial vehicles (UAVs) in the role of flying anchor nodes have been proposed to assist the localisation of terrestrial Internet of Things (IoT) sensors and provide relay services in the context of the upcoming 6G networks. This paper considered the objective of tracing a mobile IoT device of unknown location, using a group of UAVs that were equipped with received signal strength indicator (RSSI) sensors. The UAVs employed measurements of the target’s radio frequency (RF) signal power to approach the target as quickly as possible. A deep learning model performed clustering in the UAV network at regular intervals, based on a graph convolutional network (GCN) architecture, which utilised information about the RSSI and the UAV positions. The number of clusters was determined dynamically at each instant using a heuristic method, and the partitions were determined by optimising an RSSI loss function. The proposed algorithm retained the clusters that approached the RF source more effectively, removing the rest of the UAVs, which returned to the base. Simulation experiments demonstrated the improvement of this method compared to a previous deterministic approach, in terms of the time required to reach the target and the total distance covered by the UAVs.

scholarly journals Revisiting the Role of Worries in Explaining the Link Between Test Anxiety and Test Performance

2021 ◽  
Author(s):  
Frieder L. Schillinger ◽  
Jochen A. Mosbacher ◽  
Clemens Brunner ◽  
Stephan E. Vogel ◽  
Roland H. Grabner
Keyword(s):  
University Students ◽  
Standardized Tests ◽  
Test Anxiety ◽  
Test Performance ◽  
Inverse Relationship ◽  
Curvilinear Relationship ◽  
General Intelligence ◽  
Mathematical Competencies ◽  
And Performance

AbstractThe inverse relationship between test anxiety and test performance is commonly explained by test-anxious students’ tendency to worry about a test and the consequences of failing. However, other cognitive facets of test anxiety have been identified that could account for this link, including interference by test-irrelevant thoughts and lack of confidence. In this study, we compare different facets of test anxiety in predicting test performance. Seven hundred thirty university students filled out the German Test Anxiety Inventory after completing a battery of standardized tests assessing general intelligence and mathematical competencies. Multiple regressions revealed that interference and lack of confidence but not worry or arousal explained unique variance in students’ test performance. No evidence was found for a curvilinear relationship between arousal and performance. The present results call for revisiting the role of worries in explaining the test anxiety-performance link and can help educators to identify students who are especially at risk of underperforming on tests.

The role of vitamin D in the development of type 2 diabetes

2021 ◽  
Vol 19 (1) ◽  
pp. 44-52
Author(s):  
A.P. Shumilov ◽  
◽  
M.Yu. Semchenkova ◽  
D.S. Mikhalik ◽  
T.G. Avdeeva ◽  
...  
Keyword(s):  
Insulin Resistance ◽  
Type 2 Diabetes ◽  
Vitamin D ◽  
Inverse Relationship ◽  
Biological Mechanisms ◽  
Β Cell ◽  
Cell Dysfunction ◽  
Vitamin D Levels

Vitamin D plays an important role in decreasing the risk of developing type 2 diabetes by influencing calcium metabolism, thereby reducing β-cell dysfunction and preventing insulin resistance. The findings of research works are contradictory enough, although some of them demonstrated an inverse relationship between vitamin D levels and the incidence of type 2 diabetes. The article describes the biological mechanisms of relationships between vitamin D levels and type 2 diabetes, reviews the results of the studies conducted and summarizes the available data. Key words: vitamin D, type 2 diabetes mellitus, insulin resistance

Health needs of Gypsy Travellers

2018 ◽  
Vol 11 (12) ◽  
pp. 681-688 ◽  
Author(s):  
Patrice Van Cleemput
Keyword(s):  
Ethnic Group ◽  
Health Inequality ◽  
Inverse Relationship ◽  
Healthcare Services ◽  
Access To Healthcare ◽  
Health Needs ◽  
Specific Health

Gypsy Travellers have the poorest health of any ethnic group in the population; they also have an inverse relationship between their health needs and access to healthcare services. This article aims to explain the reasons for such stark health inequality, to identify the specific health needs of Gypsy Travellers, and to describe the role of the GP in meeting those needs.

scholarly journals Role of Social Capital on Prospering Informal sector Enterprise (Case of Street Vendors in street market Dewi Sartika, Bogor)

2018 ◽  
Vol 2 (2) ◽  
pp. 207 ◽  
Author(s):  
Dedy Yahya Harahap ◽  
Ivanovich Agusta
Keyword(s):  
Social Capital ◽  
Informal Sector ◽  
Inverse Relationship ◽  
Qualitative Data ◽  
Positive Relationship ◽  
Survey Methods ◽  
Rank Test ◽  
Street Vendors ◽  
Spearman Rank

PERAN MODAL SOSIAL TERHADAP KESEJAHTERAAN PENGUSAHA SEKTOR INFORMAL (Kasus Pengusaha Sektor Informal di Pasar Jl. Dewi Sartika, Bogor)Goal of the study was to test contribution social capital on migration, of the informal sector, social capital education entrepreneurs to improve informal sector entrepreneurs. The research conducts quantitative approach by survey methods and supported by qualitative data. The results showed assosiation between social capital and informal entrepreneur’s welfare. Spearman rank test between social anf welfare showed -0.480. That indicated inverse relationship among them. Spearman rank test between social capital on imigration and welfare showed 0.723. That indicate positive relationship between them. Spearman rank test between social capital an education and welfare showed 1.000. That indicated fully positive relationship between them.Keywords : Welfare, Social Capital, Informal Sector.---------------------ABSTRAK Tujuan dalam penelitian ini adalah menguji kontribusi modal sosial pekerja pengusaha sektor informal, modal sosial migrasi sektor informal, modal sosial pendidikan pengusaha sektor informal dalam meningkatkan kesejahteraan pengusaha sektor informal. Penelitian ini menggunakan pendekatan kuantitatif dengan metode survey didukung dengan data kualitatif berupa wawancara mendalam, observasi. Hasil penelitian menunjukkan bahwa, peran modal sosial terhadap kesejahteraan berhubungan nyata. Uji kolerasi rank spearman menunjukkan bahwa hubungan pengusaha sektor informal dan kesejahteraan sebesar -0.480 dan nilai probabilitas sebesar 0.004. Hasil tersebut menunjukkan hubungan kuat namun berdifat negatif. Hubungan modal sosial migrasi pengusaha sektor informal dan kesejahteraan sebesar 0.723 dan nilai probabilitas sebesar 0.000. Hasil tersebut menunjukkan hubungan yang kuat dan bersifat positif antara kedua variabel. Hubungan modal sosial pendidikan pengusaha sektor informal dan kesejahteraan sebesar 1.000 dan nilai probabiliti sebesar 1.000. Hasil tersebut menunjukkan hubungan yang kuat, bersifat positif antara kedua variabel.Kata Kunci : Kesejahteraan, modal sosial, sektor informal.

THE ROLE OF LIGHT IN THE FRUITING OF PANUS FRAGILIS

1967 ◽  
Vol 45 (11) ◽  
pp. 1939-1943 ◽  
Author(s):  
Orson K. Miller Jr.
Keyword(s):  
Temperature Cycle ◽  
Light Cycle ◽  
Fluctuating Temperature ◽  
Time Required ◽  
Role Of Light ◽  
Pink Pigment

The role of light in the fruiting of Panus fragilis was explored under controlled temperature and light cycles. No fruiting occurred in the absence of light. A daily light cycle of 1.5 h at 792 ft-c was sufficient to produce fruiting initials, but not mature sporophores. Only at the longest daily light cycle tested, 12 h at 792 ft-c, were mature sporophores produced. The time required was 22–31 days with a daily fluctuating temperature cycle of 22 °C for 12 h followed by 8 °C for 12 h. The development of a pink pigment associated with fruiting initials and young sporophores was strongest at the longer light cycles and almost absent in the short cycles.

Time- and age-dependent effects of serotonin on gasping and autoresuscitation in neonatal mice

2013 ◽  
Vol 114 (12) ◽  
pp. 1668-1676 ◽  
Author(s):  
Jianping Chen ◽  
Jennifer Magnusson ◽  
Gerard Karsenty ◽  
Kevin J. Cummings
Keyword(s):  
Heart Rate ◽  
Tryptophan Hydroxylase ◽  
Single Injection ◽  
Heart Rate Recovery ◽  
Wild Type ◽  
Tryptophan Hydroxylase 2 ◽  
Age Dependent ◽  
Long Time ◽  
Time Required

The role of brain stem serotonin (5-hydroxytryptamine, 5-HT) in autoresuscitation in neonatal life is unclear. We hypothesized that a specific loss of 5-HT would compromise gasping and autoresuscitation mainly in the second postnatal week and that acute restoration of 5-HT would reverse the defects. We exposed postnatal day (P)4–5, P8–9, and P11–12 tryptophan-hydroxylase-2 knockout ( TPH2−/−) and wild-type littermates (WT) to 10 episodes of anoxia (97% N2, 3% CO2), measuring survival, gasp latency, gasp frequency ( fB), and the time required to restore eupnea and heart rate. We also tested P8–9 TPH2−/− mice after restoring 5-HT with a single injection of 5-hydroxytryptophan (5-HTP) 1–2 h before testing or with multiple injections beginning 24 h before testing. At P4–5 and P8–9, but not at P11–12, gasp latency and the recovery of eupnea were delayed ∼2- to 3-fold in TPH2−/− pups compared with WT ( P < 0.001). At all ages, TPH2−/− pups displayed reduced gasp fB (∼20–30%; P < 0.001) and delayed heart rate recovery (∼60%; P = 0.002) compared with WT littermates. TPH2−/− survival was reduced compared with WT ( P < 0.001), especially at P8–9 and P11–12 ( P = 0.004). Whereas 1–2 h of 5-HTP treatment improved the gasp latency and fB of P8–9 TPH2−/− pups, improved cardiorespiratory recovery and survival required 24 h of treatment. Our data suggest that 5-HT operates over a long time span (∼24 h) to improve survival during episodic severe hypoxia. Early in development (P4–9), 5-HT is critical for both respiratory and cardiovascular components of autoresuscitation; later (P11–12), it is critical mainly for cardiovascular components. Nevertheless, the effect of 5-HT deficiency on survival is most striking from P8 to P12.

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