Experimental study of the formation of the bulboventricular loop in the chick

Development ◽  
1972 ◽  
Vol 27 (3) ◽  
pp. 623-637
Author(s):  
Alfredo Castro-Quezada ◽  
Bernardo Nadal-Ginard ◽  
María V. de la Cruz
Keyword(s):  
Electron Microscope ◽  
Time Lapse ◽  
Mirror Image ◽  
Heart Tube ◽  
Removal Experiments ◽  
Atrioventricular Groove ◽  
The Right ◽  
Time Lapse Photography ◽  
Made In

The formation of the normal bulboventricular loop (convex to the right) and the inverted loop (convex to the left) produced by the Lepori technique in chick embryos was studied. The development of the loops was recorded by means of diagrams, photographs and microscopic time-lapse photography. Electron-microscope studies were also made. The normal loop was studied by means of labelling and removal experiments on the heart tube. The results demonstrated that the fusion of both cardiac primordia is made in stage 9 — in the mid-line of the embryo and that the first asymmetry of the heart tube appears in stage 10. The truncus region developed in situ directed towards the right after the fusion of both cardiac primordia, and in this region the electron-microscope study demonstrated a gradient of caudo-cephalic differentiation. In stage 10 the left caudal groove is the prospective interventricular groove, but the right caudal groove is not the right atrioventricular groove as had been stated by others. The asymmetric incorporation of both primordia begins in stage 11 —, when the curvature of the loop is already developing. In the removal experiments it was evident that the different portions of the cardiac tube in situ are orientated in space independently of the whole of the loop. The formation of the experimentally inverted loop is a mirror-image of the normal loop and appears to be originated through mechanic traction of the cardiac tube by the left splachnopleure and not by a faster displacement of the right cardiac primordia.

In Situ Observations of Voiding in Metal Lines Under Passivation

1994 ◽  
Vol 338 ◽  
Author(s):  
T. Marieb ◽  
J.C. Bravman ◽  
P. Flinn ◽  
M. Madden
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Time Lapse ◽  
Still Images ◽  
In Situ Observations ◽  
Voltage Scanning ◽  
Morphology Changes ◽  
Passivated Metal ◽  
Scanning Electron

ABSTRACTMovies showing high voltage scanning electron microscope (HVSEM) in situ observations of void motion in passivated metal lines were produced. By taking pictures of the line when the void morphology changes and combining these images digitally with a technique called morphing, a time-lapse movie is constructed with the minimum amount of stored images. The sequence of still images from which a movie is constructed are shown in this paper. This sequence demonstrates that wedge voids do not cause failure in near-bamboo pure Al lines; rather the void will move until it encounters a grain which it can grow across in a slit-like manner.

Dynamic transduction properties of in situ baroreceptors of rabbit aortic depressor nerve

1998 ◽  
Vol 274 (1) ◽  
pp. H358-H365 ◽  
Author(s):  
Takayuki Sato ◽  
Toru Kawada ◽  
Toshiaki Shishido ◽  
Hiroshi Miyano ◽  
Masashi Inagaki ◽  
...  
Keyword(s):  
Transfer Function ◽  
White Noise ◽  
Innominate Artery ◽  
Operating Pressure ◽  
Frequency Range ◽  
Aortic Depressor Nerve ◽  
The Right ◽  
Common Carotid Arteries ◽  
Made In

We developed a new method for isolating in situ baroreceptor regions of the rabbit aortic depressor nerve (ADN) and estimated the transfer function from pressure to afferent nerve activity in the frequency range of 0.01–5 Hz by a white noise technique. Complete isolation of the baroreceptor area of the right ADN was made in situ by ligation of the innominate artery and the right subclavian and common carotid arteries. We altered the pressure in the isolated baroreceptor area according to a binary quasi-white noise between 80 and 100 mmHg in 12 urethan-anesthetized rabbits. The gain increased two to three times as the frequency of pressure perturbation increased from 0.01 to 2 Hz and then decreased at higher frequencies. The phase slightly led below 0.2 Hz. The squared coherence value was >0.8 in the frequency range of 0.01–4 Hz. The step responses estimated from the transfer function were indistinguishable from those actually observed. We conclude that the baroreceptor transduction of the ADN is governed by linear dynamics under the physiological operating pressure range.

Design of tunnel lining in rock for long term time effects

1981 ◽  
Vol 18 (1) ◽  
pp. 24-39 ◽  
Author(s):  
K. Y. Lo ◽  
Clement M. K. Yuen
Keyword(s):  
Time Lapse ◽  
Time Dependent ◽  
Initial Stresses ◽  
Time Interaction ◽  
Underground Openings ◽  
Rock Structure ◽  
Rock Movement ◽  
Made In

Excavation of underground openings in rock relieves the in situ state of stresses, providing an initiating mechanism for time-dependent deformation in shaly rocks to occur. The construction of a permanent lining restrains the rock movement, resulting in an increase with time of pressure acting on the lining.Closed form solutions for this problem of rock structure – time interaction of circular tunnels have been developed, taking into account (a) the state of initial stresses, (b) the time-dependent properties of the lining as well as the rock, and (c) the time lapsed between excavation and lining. Expressions for lining pressures, stresses, thrusts, and moments are given for both "no slip" and "full slip" interface conditions.The effects of material parameters, lining flexibilities, and time lapse on quantities of engineering interest are studied and their implications on design illustrated.The results of analysis are compared with the field observations made in three tunnels. It is shown that the theoretical results are consistent with the observed extent and location of cracking in these tunnels.It is suggested that the methods proposed may be used for design considerations of permanent linings of tunnels in rock exhibiting significant time-dependent deformation.

scholarly journals Subglacial hydrology at Rink Isbræ, West Greenland inferred from sediment plume appearance

2016 ◽  
Vol 57 (72) ◽  
pp. 118-127 ◽  
Author(s):  
Kristin M. Schild ◽  
Robert L. Hawley ◽  
Blaine F. Morriss
Keyword(s):  
Time Lapse ◽  
Short Term ◽  
Velocity Change ◽  
Tidewater Glaciers ◽  
West Greenland ◽  
Meltwater Runoff ◽  
Subglacial Meltwater ◽  
Time Lapse Photography ◽  
Frontal Ablation

ABSTRACTMarine-terminating outlet glaciers discharge most of the Greenland ice sheet's mass through frontal ablation and meltwater runoff. While calving can be estimated by in situ and remote sensing observations, submarine melting and subglacial meltwater transport are more challenging to quantify. Here we investigate the subglacial hydrology of Rink Isbræ, a fast-flowing West Greenland tidewater glacier, using time-lapse photography, modeled runoff estimates and daily satellite imagery from 2007 to 2011. We find that sediment plumes appear episodically at four distinct locations across the terminus, and last between 2 h and 17 d. This suggests short-term variability in discharge and the existence of persistent pathways. The seasonal onset of sediment plumes occurs before supraglacial lake drainages, shortly after the onset of runoff, and only after the wintertime ice mélange has begun disintegrating. Plumes were also visible after the cessation of runoff (23 ± 5 d), which is indicative of subglacial storage. The lack of either a seasonal velocity change or a correspondence between meltwater availability and plume occurrence suggests that the subglacial system persists in a state of inefficient drainage. Subglacial hydrology at tidewater glaciers is of critical importance in understanding dynamics at the ice front.

scholarly journals Effects of dead conspecifics, hunger states, and seasons on the foraging behavior of the purple urchin Heliocidaris crassispina

2020 ◽  
Author(s):  
Dominic Franco C. Belleza ◽  
Yuuki Kawabata ◽  
Tatsuki Toda ◽  
Gregory N. Nishihara
Keyword(s):  
Foraging Behavior ◽  
Field Experiments ◽  
Prey Species ◽  
Sea Urchins ◽  
Time Lapse ◽  
Aquatic Environments ◽  
Feeding Rates ◽  
Avoidance Behaviors ◽  
Time Lapse Photography

ABSTRACTTrophic cascades exerts a powerful effect between predator and prey relationships in an ecosystem. In aquatic environments, the signals associated with predators and predation are used by prey as a cue to avoid encountering predators when foraging for food. These cues are powerful enough to control prey populations and indirectly protect primary producers. We evaluated the effects of cues associated with predation on the purple urchin, Heliocidaris crassispina and examined effects of hunger state and season using time-lapse photography, we conducted a series of manipulative and in situ behavior experiments to determine foraging behavior patterns which demonstrate behavior modification. The results suggest that starved urchins were less sensitive to predation cues when compared to normally fed urchins. Field experiments indicated that 70% of fed urchins fled when exposed to a predation cue (presence of a dead urchin), whereas all starved urchins remained regardless of the cue, supporting the results from the laboratory using the dead urchin and algae treatment cues. Sea urchin activity and feeding rates were lower in winter-spring than in summer-autumn. We suggest that hunger state has a large influence over the behavioral-response of sea urchins, while also being affected by season due to metabolic control. In general, starvation overrides predator avoidance behaviors and exposes prey species to higher risks of predation.

In Situ SEM Observations of Sintering of Gold Compacts

1976 ◽  
Vol 34 ◽  
pp. 440-441
Author(s):  
E. R. Levin ◽  
G. R. Auth ◽  
K. R. Bube
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Video Tape ◽  
High Magnification ◽  
Ceramic Substrates ◽  
Direct Observations ◽  
Ceramic Surfaces ◽  
Scanning Electron ◽  
Made In

As part of a study of metallization of preglazed ceramic surfaces for hybrid microcircuits, direct observations of the sintering of gold powders at temperatures in the 800-900°C range have been made in the scanning electron microscope. The changes occurring in the layers at the high temperatures were followed in detail at high magnification. Video tape recordings were made showing the sintering of the gold and the accompanying flow of the glass bonding medium.The specimens were specially prepared for the SEM studies on thin rectangular ceramic substrates 0.13mmx2mmx8mm. The unsintered gold powder, dispersed in an organic vehicle, was screen-printed in 1 mm-wide stripes along the length of substrate. Prior to sintering, the organic binder was removed by prefiring in air, typically at 400 °C for two minutes (Fig. 1). An intermediate layer of lead-borosilicate glass was used between the substrate and the metal compact to promote adhesion on sintering.

Characterisation of SiCf/SiC Specimens Using an In-Situ Tensile Stage Within a Scanning Electron Microscope

2019 ◽  
Author(s):  
Steven P. Jordan ◽  
Martin R. Bache ◽  
Christopher D. Newton ◽  
Louise Gale
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Time Lapse ◽  
Image Correlation ◽  
Small Scale ◽  
Initiation And Propagation ◽  
Gauge Section ◽  
Time Lapse Imaging ◽  
Scanning Electron

Abstract The present paper will introduce the use of scanning electron microscope based, in-situ tensile testing as a method of detecting cracking in a SiCf/SiC CMC at room temperature. Small scale tensile specimens were prepared, but still sampling multiple longitudinal and transverse fibre tows. Monotonic loading was applied to initiate cracking, whilst contemporary time lapse imaging and retrospective digital image correlation recorded the development of these cracks at the specimen surface. Examples of strain localization, crack initiation and propagation will be presented for a plain gauge section specimen and single edge notched specimen. The critical combination of SEM imaging together with real time loading, in order to identify microscopic cracking in this CMC system, will be demonstrated.

The Etching of Silicon by Oxygen Observed by in situ Tem

1991 ◽  
Vol 222 ◽  
Author(s):  
Frances M. Ross ◽  
J. Murray Gibson
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
In Situ Tem ◽  
Step Motion ◽  
Etching Mechanism ◽  
Transmission Electron ◽  
Macroscopic Parameters ◽  
Made In ◽  
Oxygen Etching

ABSTRACTWe describe observations made in situ in a modified UHV transmission electron microscope of the process of etching of the Si (111) surface by oxygen. Etching occurs by the motion of individual bilayer steps across the surface and by analysing the step motion we discuss the etching mechanism in the context of macroscopic parameters.

scholarly journals Pitx controls amphioxus asymmetric morphogenesis by promoting left-side development and repressing right-side formation

BMC Biology ◽  
2021 ◽  
Vol 19 (1) ◽  
Author(s):  
Chaofan Xing ◽  
Rongrong Pan ◽  
Guangwei Hu ◽  
Xian Liu ◽  
Yiquan Wang ◽  
...  
Keyword(s):  
Binding Sites ◽  
Essential Feature ◽  
Loss Of Function ◽  
Partial Loss ◽  
Developmental Mechanism ◽  
Right Isomerism ◽  
The Right ◽  
Insight Into ◽  
Made In

Abstract Background Left-right (LR) asymmetry is an essential feature of bilateral animals. Studies in vertebrates show that LR asymmetry formation comprises three major steps: symmetry breaking, asymmetric gene expression, and LR morphogenesis. Although much progress has been made in the first two events, mechanisms underlying asymmetric morphogenesis remain largely unknown due to the complex developmental processes deployed by vertebrate organs. Results We here addressed this question by studying Pitx gene function in the basal chordate amphioxus whose asymmetric organogenesis, unlike that in vertebrates, occurs essentially in situ and does not rely on cell migration. Pitx null mutation in amphioxus causes loss of all left-sided organs and incomplete ectopic formation of all right-sided organs on the left side, whereas Pitx partial loss-of-function leads to milder phenotypes with only some LR organs lost or ectopically formed. At the N1 to N3 stages, Pitx expression is gradually expanded from the dorsal anterior domain to surrounding regions. This leads to activation of genes like Lhx3 and/or Prop1 and Pit, which are essential for left-side organs, and downregulation of genes like Hex and/or Nkx2.1 and FoxE4, which are required for right-side organs to form ectopically on the left side. In Pitx mutants, the left-side expressed genes are not activated, while the right-side genes fail to decrease expression on the left side. In contrast, in embryos overexpressing Pitx genes, the left-side genes are induced ectopically on the right side, and the right-side genes are inhibited. Several Pitx binding sites are identified in the upstream sequences of the left-side and right-side genes which are essential for activation of the former and repression of the latter by Pitx. Conclusions Our results demonstrate that (1) Pitx is a major (although not the only) determinant of asymmetric morphogenesis in amphioxus, (2) the development of different LR organs have distinct requirements for Pitx activity, and (3) Pitx controls amphioxus LR morphogenesis probably through inducing left-side organs and inhibiting right-side organs directly. These findings show much more dependence of LR organogenesis on Pitx in amphioxus than in vertebrates. They also provide insight into the molecular developmental mechanism of some vertebrate LR organs like the lungs and atria, since they show a right-isomerism phenotype in Pitx2 knockout mice like right-sided organs in Pitx mutant amphioxus. Our results also explain why some organs like the adenohypophysis are asymmetrically located in amphioxus but symmetrically positioned in vertebrates.

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