The Mechanism of Statocyst Operation in the Mysid Shrimp Praunus Flexuosus

1975 ◽  
Vol 62 (3) ◽  
pp. 685-700
Author(s):  
D. M. NEIL
Keyword(s):  
Body Tilt ◽  
Structural Constraints ◽  
Decapod Crustaceans ◽  
Before And After ◽  
Adequate Stimulus ◽  
Gravity Receptors ◽  
Mysid Shrimp

Analysis of the compensatory eyestalk responses of mysid shrimps before and after the removal of one statocyst has revealed, in the light of statocyst anatomy, that the two statocysts co-operate in their action at all angles of body tilt. Many features of statocyst operation in mysids are shared by decapod crustaceans, but an important difference exists between the geometries of the two statocyst systems. The consequences of this difference highlight the structural constraints on systems of statolithic gravity receptors for which shear magnitude is the adequate stimulus.

The Control of Eyestalk Movements in the Mysid Shrimp Praunus Flexuosus

1975 ◽  
Vol 62 (2) ◽  
pp. 487-504
Author(s):  
D. M. NEIL
Keyword(s):  
Light Beam ◽  
Visual Cues ◽  
Light Conditions ◽  
Free Swimming ◽  
Light Reaction ◽  
Gravity Receptors ◽  
Light Stimuli ◽  
Necessary And Sufficient ◽  
Tracking Response ◽  
Mysid Shrimp

The compensatory eyestalk movements of intact and statocystless mysid shrimps Praunus flexuosus have been measured under a variety of light conditions. The results indicate that the statocyst organs in the urppods are the major gravity receptors, and that they are both necessary and sufficient to produce sinusoidal compensatory eyestalk movements. The addition of visual cues (vertical light beam, optokinetic stimuli) modifies the eyestalk response to some extent, but does not alter its general form. When the statocysts are removed, however, light stimuli become important orientational cues, and the eyestalks perform a tracking response which is considered to be the experimental counterpart of the dorsal light reaction of the free-swimming animal.

Light Organ and Eyestalk Compensation to Body Tilt in the Luminescent Midwater Shrimp, Sergestes Similis

1982 ◽  
Vol 98 (1) ◽  
pp. 83-104
Author(s):  
MICHAEL I. LATZ ◽  
JAMES F. CASE
Keyword(s):  
Angular Distribution ◽  
Light Source ◽  
The Body ◽  
Body Tilt ◽  
Light Organ ◽  
Total Compensation ◽  
Angular Movement ◽  
Counter Rotation ◽  
Light Organs ◽  
Before And After

The posterior light organ and eyestalk of the midwater shrimp, Sergestes similis Hansen, are capable of 140° of angular movement within the body during pitch body tilt, maintaining the organs at near horizontal orientations. Counter-rotations compensate for 74–80% of body inclination. These responses are statocyst mediated. Unilateral statolith ablation reduces compensation by 50%. There is no evidence for either homolateral or contralateral control by the single functioning statocyst. Bilateral lith ablation abolishes counter-rotation. Light organ and eyestalk orientations are unaffected by the direction of imposed body tilt. Bioluminescence is emitted downward from horizontal animals with an angular distribution similar to the distribution of oceanic light. The amount of downward directed luminescence in tilted animals decreases at large angles of body inclination due to less than total compensation by the light organs. Eye turning towards a light source is induced by upward-directed illumination. The resulting change in eyestalk orientations never amounts to more than 25°. The turning is abolished by bilateral statolith ablation. Downward directed illumination, comparable in intensity to oceanic light, generally does not generate significant eye turning. Light organ orientations remain unaffected by directional illumination, both before and after bilateral statolith ablation. The compensatory counter-rotations by the posterior light organ and eyestalk suggest that counter-illumination by S. similis remains effective in inclined animals.

scholarly journals IN WHAT WAYS DOES INTIMATE PARTNER VIOLENCE (IPV) AGAINST IRANIAN WOMEN CHANGE AFTER THEY HAVE EXPERIENCED FORCED IMMIGRATION?

2021 ◽  
Author(s):  
Sima Farid Kian
Keyword(s):  
Partner Violence ◽  
Narrative Approach ◽  
Sampling Techniques ◽  
Structural Constraints ◽  
Psychological Violence ◽  
Snowball Sampling ◽  
Structured Interviews ◽  
Different Types ◽  
Before And After ◽  
Financial Dependency

In this research, I explored different forms of IPV before and after immigration. Feminism and theories developed by Foucault guided the study to further understand IPV by addressing issues related to power inequities, structural constraints, and oppressions within society. Applying a narrative approach, I recruited three Iranian refugee women who were survivors of IPV and have experienced IPV before and after immigration. Snowball sampling techniques were used for recruitment and semi-structured interviews were utilized to collect relevant data. Through thematic analysis, seven main themes were defined, which shape different forms of IPV pre- and post-immigration. These themes are defined as different types of physical, sexual and psychological violence as well as economic abuse, internalizing men’s power by women, immigration statues, financial dependency, cultural and patriarchal sets of beliefs, social supports, and living in Iranian communities before and after immigration.

scholarly journals Youth migration and life course transitions: Comparing the impact of women’s mobility across generations in Bulgaria

Sociologija ◽  
2019 ◽  
Vol 61 (2) ◽  
pp. 210-226 ◽  
Author(s):  
Siyka Kovacheva ◽  
Darena Hristozova
Keyword(s):  
Qualitative Interviews ◽  
Life Transitions ◽  
National Identities ◽  
Structural Constraints ◽  
Life Trajectories ◽  
The Social ◽  
Depth Analysis ◽  
Before And After ◽  
Two Generations ◽  
The Impact

Migration abroad has become a significant part of the life experiences of a growing number of Bulgarian youths, since the regime change in 1989. In this paper we explore the effect of migration on the life transitions of two generations of young Bulgarians - the ?Transition? generation o f those who had their formative years in the 1990s during the country?s transition from state socialism to a market economy and the ?Accession? generation of those who grew up after the country joined the EU in 2007 in a somewhat better economic situation. Taking into consideration the impact of the social context in the sending country in two different historical periods (before and after 2007) a nd in the receiving countries we focus on the differences of the transition paths of lower and higher skilled female migrants within the two migrant generations. The paper draws on a data base of 42 qualitative interviews with Bulgarian migrants living in EU countries that were conducted in 2017 and an in -depth analysis of the life trajectories of four women belonging to the two migrant generations. Our findings suggest that facing different structural constraints in their countries of departure and reception, young people employ diverse strategies of settling down, achieving success and attaining happiness. In the process they transform their social ties and national identities.

scholarly journals IN WHAT WAYS DOES INTIMATE PARTNER VIOLENCE (IPV) AGAINST IRANIAN WOMEN CHANGE AFTER THEY HAVE EXPERIENCED FORCED IMMIGRATION?

2021 ◽  
Author(s):  
Sima Farid Kian
Keyword(s):  
Partner Violence ◽  
Narrative Approach ◽  
Sampling Techniques ◽  
Structural Constraints ◽  
Psychological Violence ◽  
Snowball Sampling ◽  
Structured Interviews ◽  
Different Types ◽  
Before And After ◽  
Financial Dependency

In this research, I explored different forms of IPV before and after immigration. Feminism and theories developed by Foucault guided the study to further understand IPV by addressing issues related to power inequities, structural constraints, and oppressions within society. Applying a narrative approach, I recruited three Iranian refugee women who were survivors of IPV and have experienced IPV before and after immigration. Snowball sampling techniques were used for recruitment and semi-structured interviews were utilized to collect relevant data. Through thematic analysis, seven main themes were defined, which shape different forms of IPV pre- and post-immigration. These themes are defined as different types of physical, sexual and psychological violence as well as economic abuse, internalizing men’s power by women, immigration statues, financial dependency, cultural and patriarchal sets of beliefs, social supports, and living in Iranian communities before and after immigration.

Deformation Replication

1970 ◽  
Vol 28 ◽  
pp. 280-281
Author(s):  
J. Temple Black
Keyword(s):  
Cutting Speed ◽  
Machining Process ◽  
Depth Of Cut ◽  
Rake Face ◽  
Orthogonal Machining ◽  
Aluminum Chips ◽  
Before And After ◽  
Materials Used ◽  
Glass Knife ◽  
Very High

Tool materials used in ultramicrotomy are glass, developed by Latta and Hartmann (1) and diamond, introduced by Fernandez-Moran (2). While diamonds produce more good sections per knife edge than glass, they are expensive; require careful mounting and handling; and are time consuming to clean before and after usage, purchase from vendors (3-6 months waiting time), and regrind. Glass offers an easily accessible, inexpensive material ($0.04 per knife) with very high compressive strength (3) that can be employed in microtomy of metals (4) as well as biological materials. When the orthogonal machining process is being studied, glass offers additional advantages. Sections of metal or plastic can be dried down on the rake face, coated with Au-Pd, and examined directly in the SEM with no additional handling (5). Figure 1 shows aluminum chips microtomed with a 75° glass knife at a cutting speed of 1 mm/sec with a depth of cut of 1000 Å lying on the rake face of the knife.

The Clinical, Roentgenological and Morphological Effects of an Acute Exposure of Phosgene on the Lungs of Dogs

1971 ◽  
Vol 29 ◽  
pp. 236-237
Author(s):  
R. F. Bils ◽  
W. F. Diller ◽  
F. Huth
Keyword(s):  
Latent Period ◽  
Chemical Industry ◽  
Toxic Substance ◽  
Lung Edema ◽  
X Rays ◽  
Beagle Dogs ◽  
Male And Female ◽  
Morphological Alterations ◽  
Before And After ◽  
Electron Microscopes

Phosgene still plays an important role as a toxic substance in the chemical industry. Thiess (1968) recently reported observations on numerous cases of phosgene poisoning. A serious difficulty in the clinical handling of phosgene poisoning cases is a relatively long latent period, up to 12 hours, with no obvious signs of severity. At about 12 hours heavy lung edema appears suddenly, however changes can be seen in routine X-rays taken after only a few hours' exposure (Diller et al., 1969). This study was undertaken to correlate these early changes seen by the roengenologist with morphological alterations in the lungs seen in the'light and electron microscopes.Forty-two adult male and female Beagle dogs were selected for these exposure experiments. Treated animals were exposed to 94.5-107-5 ppm phosgene for 10 min. in a 15 m3 chamber. Roentgenograms were made of the thorax of each animal before and after exposure, up to 24 hrs.

Ultrastructure of Melanin Formation in Curvularia sp., Alternaria sp., and Drechslera Sorokiniana

1977 ◽  
Vol 35 ◽  
pp. 398-399
Author(s):  
M. H. Wheeler ◽  
W. J. Tolmsoff ◽  
A. A. Bell
Keyword(s):  
Potassium Phosphate ◽  
Thielaviopsis Basicola ◽  
Wild Type ◽  
Potassium Phosphate Buffer ◽  
Transmission Microscopy ◽  
Electron Transmission ◽  
Melanin Formation ◽  
Before And After ◽  
Alternaria Sp ◽  
Electron Transmission Microscopy

(+)-Scytalone [3,4-dihydro-3,6,8-trihydroxy-l-(2Hj-naphthalenone] and 1,8-di- hydroxynaphthalene (DHN) have been proposed as intermediates of melanin synthesis in the fungi Verticillium dahliae (1, 2, 3, 4) and Thielaviopsis basicola (4, 5). Scytalone is enzymatically dehydrated by V. dahliae to 1,3,8-trihydroxynaphthalene which is then reduced to (-)-vermelone [(-)-3,4- dihydro-3,8-dihydroxy-1(2H)-naphthalenone]. Vermelone is subsequently dehydrated to DHN which is enzymatically polymerized to melanin.Melanin formation in Curvularia sp., Alternaria sp., and Drechslera soro- kiniana was examined by light and electron-transmission microscopy. Wild-type isolates of each fungus were compared with albino mutants before and after treatment with 1 mM scytalone or 0.1 mM DHN in 50 mM potassium phosphate buffer, pH 7.0. Both chemicals were converted to dark pigments in the walls of hyphae and conidia of the albino mutants. The darkened cells were similar in appearance to corresponding cells of the wild types under the light microscope.

Evaluation of Freezing Methods by Low Temperature X-Ray Diffraction

1977 ◽  
Vol 35 ◽  
pp. 330-333
Author(s):  
T. Gulik-Krzywicki ◽  
M.J. Costello
Keyword(s):  
Biological Materials ◽  
Molecular Organization ◽  
X Ray Diffraction ◽  
Glass Capillary ◽  
X Ray ◽  
Rate Dependent ◽  
Before And After ◽  
Freeze Etching ◽  
Diffraction Patterns ◽  
Set Up

Freeze-etching electron microscopy is currently one of the best methods for studying molecular organization of biological materials. Its application, however, is still limited by our imprecise knowledge about the perturbations of the original organization which may occur during quenching and fracturing of the samples and during the replication of fractured surfaces. Although it is well known that the preservation of the molecular organization of biological materials is critically dependent on the rate of freezing of the samples, little information is presently available concerning the nature and the extent of freezing-rate dependent perturbations of the original organizations. In order to obtain this information, we have developed a method based on the comparison of x-ray diffraction patterns of samples before and after freezing, prior to fracturing and replication.Our experimental set-up is shown in Fig. 1. The sample to be quenched is placed on its holder which is then mounted on a small metal holder (O) fixed on a glass capillary (p), whose position is controlled by a micromanipulator.

The Precipitation of Si in AlCuSi Thin Films

1973 ◽  
Vol 31 ◽  
pp. 34-35 ◽  
Author(s):  
R. M. Anderson
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Heat Treatment ◽  
Solid Solution ◽  
Integrated Circuit ◽  
Copper Film ◽  
Solution Concentration ◽  
X Ray ◽  
Silicon Thin Films ◽  
Before And After

Aluminum-copper-silicon thin films have been considered as an interconnection metallurgy for integrated circuit applications. Various schemes have been proposed to incorporate small percent-ages of silicon into films that typically contain two to five percent copper. We undertook a study of the total effect of silicon on the aluminum copper film as revealed by transmission electron microscopy, scanning electron microscopy, x-ray diffraction and ion microprobe techniques as a function of the various deposition methods.X-ray investigations noted a change in solid solution concentration as a function of Si content before and after heat-treatment. The amount of solid solution in the Al increased with heat-treatment for films with ≥2% silicon and decreased for films <2% silicon.

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