scholarly journals THE PHOTIC SENSITIVITY OF CIONA INTESTINALIS

1918 ◽  
Vol 1 (2) ◽  
pp. 147-166 ◽  
Author(s):  
Selig Hecht
Keyword(s):  
Reaction Time ◽  
Latent Period ◽  
Dark Adaptation ◽  
Local Reaction ◽  
The Body ◽  
Chemical System ◽  
Intensity Analysis ◽  
Constant Ratio ◽  
Neural Mass ◽  
Photosensitive Substance

1. Ciona possesses two means of responding to an increase in the intensity of illumination. One is by means of a local reaction; the other is by a retraction reflex of the body as a whole. 2. The "ocelli" are not photoreceptors. The photosensitive area is in the intersiphonal region containing the neural mass. This area contains no pigment. 3. The reaction time to light is composed of a sensitization period during which Ciona must be exposed to the light, and of a latent period during which it need not be illuminated in order to react to the stimulus received during the sensitization period. 4. The duration of the reaction time varies inversely as the intensity. Analysis shows the latent period to be constant. The relation between the sensitization period and the intensity follows the Bunsen-Roscoe rule. 5. During dark adaptation the reaction time is at first large, then it decreases until a constant minimum is reached. 6. A photochemical system consisting of a reversible reaction is suggested in order to account for the phenomena observed. This system includes a photosensitive substance and its precursor, the dynamics of the reaction following closely the peculiarities of the photosensitivity of Ciona. 7. It is shown that in order to produce a reaction, a constant ratio must be reached between the amount of sensitive substance broken down by the stimulus and the amount previously broken down. 8. From the chemical system suggested certain experimental predictions were made. The actual experiments verified these predictions exactly. 9. The results obtained with regularly repeated stimulation not only fail to show any basis for a learning process or for the presence of a "higher behavior," but follow the requirements of the photochemical system suggested before.

scholarly journals SENSORY EQUILIBRIUM AND DARK ADAPTATION IN MYA ARENARIA

1919 ◽  
Vol 1 (5) ◽  
pp. 545-558 ◽  
Author(s):  
Selig Hecht
Keyword(s):  
Reaction Time ◽  
Latent Period ◽  
Dark Adaptation ◽  
Photochemical Reaction ◽  
Short Interval ◽  
Bimolecular Reaction ◽  
Mya Arenaria ◽  
Rational Explanation ◽  
Order Of Magnitude ◽  
Photosensitive Substance

1. The reaction time of Mya to light is composed of two parts. The first, a sensitization period, is an exceedingly short interval of the order of magnitude associated with photographic processes. The second is a latent period of about 1.3 seconds, during which Mya need not remain exposed to the stimulating light. 2. The process of dark adaptation in Mya is orderly. Its progress may be represented by the formation of a photosensitive substance according to the dynamics of a bimolecular reaction. See PDF for Structure 3. Photosensory equilibrium as represented by the light- and dark-adapted conditions finds a rational explanation in terms of the "stationary state" of a reversible photochemical reaction involving a photosensitive substance and its two precursors. 4. There are two corollaries to this hypothesis. The first requires that the reaction time at sensory equilibrium for a given intensity should vary inversely with the temperature; the second, that the rate of dark adaptation should vary directly with the temperature. Experiments verified both of these requirements.

Enhanced surface hydrophilicity of polylactic acid sutures treated by lipase and chitosan

2018 ◽  
Vol 89 (16) ◽  
pp. 3291-3302 ◽  
Author(s):  
Shuqiang Liu ◽  
Mingfang Liu ◽  
Gaihong Wu ◽  
Xiaofang Zhang ◽  
Juanjuan Yu ◽  
...  
Keyword(s):  
Reaction Time ◽  
Friction Coefficient ◽  
Surface Area ◽  
Polylactic Acid ◽  
The Body ◽  
Optimal Conditions ◽  
Absorbable Sutures ◽  
Surgical Sutures ◽  
New Type ◽  
Enhanced Surface

Polylactic acid (PLA) surgical sutures are a new type of absorbable sutures that can be degraded and absorbed in the body. However, there is high hydrophobicity for the surface of PLA sutures, which leads to poor biocompatibility and cellular affinity. In order to increase the hydrophilicity, the PLA sutures were etched by lipase firstly, and then grafted with chitosan. The results indicate that the optimal conditions of treating PLA sutures by lipase were as follows: 45℃ reaction temperature, 4.5 g/L concentration of lipase and 8 h reaction time. The sutures were etched by lipase and then formed some grooves and a number of hydroxyl (-OH) bonds, which led to increased surface area and hydrophilicity, but a drop in mass and strength. The optimal conditions of grafting chitosan onto PLA sutures were as follows: 4 h reaction time and 3 g/L concentration of chitosan. The chitosan grafted and loaded on the surface of PLA sutures, and in some areas of the sutures the chitosan reunited, which led to a rough surface and large friction coefficient. Finally, the hydrophilicity of the PLA sutures, treated by lipase and then grafted with chitosan, was greatly improved.

The effect of size on the fast-start performance of rainbow trout Salmo gairdneri, and a consideration of piscivorous predator-prey interactions

1976 ◽  
Vol 65 (1) ◽  
pp. 157-177 ◽  
Author(s):  
P. W. Webb
Keyword(s):  
Rainbow Trout ◽  
Reaction Time ◽  
Reaction Times ◽  
The Body ◽  
Salmo Gairdneri ◽  
Escape Behaviour ◽  
Predator Prey ◽  
Average Value ◽  
Fast Start ◽  
Prey Escape

The fast-start (acceleration) performance of seven groups of rainbow trout from 9-6 to 38-7 cm total length was measured in response to d.c. electric shock stimuli. Two fast-start kinematic patterns, L- and S-start were observed. In L-starts the body was bent into an L or U shape and a recoil turn normally accompanied acceleration. Free manoeuvre was not possible in L-starts without loss of speed. In S-starts the body was bent into an S-shape and fish accelerated without a recoil turn. The frequency of S-starts increased with size from 0 for the smallest fish to 60–65% for the largest fish. Acceleration turns were common. The radius of smallest turn for both fast-start patterns was proportional to length (L) with an overall radius of 0–17 L. The duration of the primary acceleration stages increased with size from 0–07 s for the group of smallest fish to 0–10 s for the group of largest fish. Acceleration rates were independent of size. The overall mean maximum rate was 3438 cm/s2 and the average value to the end of the primary acceleration movements was 1562 cm/s2. The distance covered and velocity attained after a given time for fish accelerating from rest were independent of size. The results are discussed in the context of interactions between a predator and prey fish following initial approach by the predator. It is concluded that the outcome of an interaction is likely to depend on reaction times of interacting fish responding to manoeuvres initiated by the predator or prey. The prey reaction time results in the performance of the predator exceeding that of the prey at any instant. The predator reaction time and predator error in responses to unpredictable prey manoeuvre are required for prey escape. It is predicted that a predator should strike the prey within 0-1 s if the fish are initially 5–15 cm apart as reported in the literature for predator-prey interactions. These distances would be increased for non-optimal prey escape behaviour and when the prey body was more compressed or depressed than the predator.

scholarly journals DARK ADAPTATION AND THE LIGHT-GROWTH RESPONSE OF PHYCOMYCES

1929 ◽  
Vol 12 (3) ◽  
pp. 391-400 ◽  
Author(s):  
E. S. Castle
Keyword(s):  
Latent Period ◽  
Dark Adaptation ◽  
Growth Response ◽  
Light Adaptation ◽  
Exposure Period ◽  
Bimolecular Reaction ◽  
Dark Reaction ◽  
Action Time ◽  
Kinetics Of ◽  
Photochemical Action

1. A single-celled, elongating sporangiophore of Phycomyces responds to a sufficient increase in intensity of illumination by a brief increase in growth rate. This is the "light-growth response" of Blaauw. 2. The reaction time is compound, consisting of an exposure period and a latent period (this comprising both the true latent period resulting from photochemical action and any "action time" necessary for the response). During the latter period the plant may be in darkness, responding nevertheless at the end of the latent period. 3. Both light adaptation and dark adaptation occur in the sporangiophore. The kinetics of dark adaptation can be accounted for on the basis of a bimolecular reaction, perhaps modified by autocatalysis. Attention is called to the bimolecular nature of the "dark" reaction in all other photosensory systems that have been studied, in spite of the diversity of the photosensitive substances themselves and of the different forms of the responses to light.

scholarly journals PEMBUATAN BENANG OPERASI DARI ECENG GONDOK

2018 ◽  
Vol 7 (2) ◽  
pp. 172
Author(s):  
Sari Purnavita ◽  
Lucia Hermawati Rahayu ◽  
Sri Sutanti
Keyword(s):  
Lactic Acid ◽  
Reaction Time ◽  
Water Hyacinth ◽  
Tensile Elongation ◽  
The Body ◽  
Polymerization Reaction ◽  
Poly Lactic Acid ◽  
Absorbable Suture ◽  
Yarn Production ◽  
Effect On Yield

Operating thread needs in Indonesia to increase, but until now to supply the needs of operating threads absorbed (can be integrated with the body) still depends on imported products that are expensive. To reduce Indonesia's dependence on biomaterials imports in the field of biomedicine, it can be done through the engineering of operating yarn production absorbed from Indonesia's natural resources. Poly Lactic Acid (PLA) is a polymer that is widely applied as a biomaterial in biomedical fields such as operating threads. In this research, absorbable suture was made from poly lactic acid poly polymer blend from water hyacinth with natural glucomannan polymer of iles-iles. The aim of the study was to study: 1) the effect of polymerization reaction time on PLA yields and 2) the effect of poly lactic acid-glucomannan composition on the mechanical properties of operating threads. Making PLA using the ring opening polymerization method and making yarn using the wet spinning method. The independent variables at the manufacturing stage of the PLA polymer are reaction time = 60, 90, 120, and 150 minutes, while for the variable at the stage of operation yarn making is the ratio between the PLA period: glucomannan = (1: 3); (1: 2); ( 1: 1); (2: 1); (3: 1). The results showed that: 1) reaction time had a very significant effect on yield PLA and 2) different composition of poly lactic acid - glucomannan gave different tensile strength and tensile elongation values. Keywords: water hyacinth, poly lactic acid, glucomannan, operating thread

scholarly journals Effects of maintaining different body positions on attentional allocation of obese and non-obese women

Kinesiology ◽  
2019 ◽  
Vol 51 (2) ◽  
pp. 271-275
Author(s):  
Fernando Garbeloto dos Santos ◽  
Umberto Cesar Côrrea ◽  
Ricardo Drews ◽  
Go Tani ◽  
Flavio Henrique Bastos
Keyword(s):  
Reaction Time ◽  
Postural Control ◽  
The Body ◽  
Obese Women ◽  
Visual Reaction Time ◽  
Attentional Allocation ◽  
Body Postures ◽  
Attentional Resources ◽  
Visual Reaction ◽  
Different Levels

Studies have shown that obese individuals may require more attentional resources to perform postural control compared to non-obese individuals. However, it is unclear if this difference in the allocation of attention can only be observed in body positions that lead to a higher level of instability. The objective of this study was to investigate if obesity affects the allocation of attention for maintaining body postures with different levels of balance demand. Ten obese women (BMI=41.7±8.5) and ten non-obese women (BMI=21.8±1.3) volunteers were assigned into two groups (M age=39.7±7.6): obese and eutrophic. The visual reaction time simultaneous with the maintenance of the body positions with different levels of balance demand (sitting, standing and unipedal stance) was used to infer the allocation of attentional resources. A longer reaction time was observed in the unipedal stance, compared to the other positions, for both groups. However, no difference was observed between the obese and eutrophic groups, for any of the body positions. The results diverge from the existing literature, showing that obesity does not affect the allocation of attention for postural control.

Arterial lactate responses in dogs made apneic or breathing nitrogen

1977 ◽  
Vol 42 (1) ◽  
pp. 39-43 ◽  
Author(s):  
S. M. Cain
Keyword(s):  
Latent Period ◽  
Venous Blood ◽  
Tissue Hypoxia ◽  
The Body ◽  
Mixed Venous Blood ◽  
Arterial Lactate ◽  
Mean Values ◽  
The Mean ◽  
Curvilinear Relation ◽  
Mixed Venous

O2 stores are kept more intact in apnea than in N2 breathing which removes O2stores from the body. If lactate moves readily into the circulation, arterial lactate should rise sooner with N2 breathing than with apnea because tissue O2 is lowered faster. This was tested in 10 anesthetized, paralyzed dogs made hypoxic both ways. Arterial and mixed venous blood were sampledevery minute until circulation began to fail. Calculated changes in O2 stores would have supported control V O2 for 1.3 min with N2 and 2.7 min with apnea. The PVO2 at those times were 23.1 and 20.1 Torr. Although arterial lactate rose sooner with N2 than with apnea, the mean values for lactate increase for both N2 and apnea were fitted by a single curvilinear relation with PVO2. The PVO2 at which lactate first rosores were depleted. Latent period for lactate rise, therefore, was nearly the same as that for development of tissue hypoxia.

scholarly journals On the relative sizes of the organs of rats and mice bearing malignant new growths

1910 ◽  
Vol 82 (555) ◽  
pp. 286-292 ◽  
Keyword(s):  
Cancer Metabolism ◽  
Normal Growth ◽  
The Body ◽  
Constant Ratio ◽  
Reasonable Expectation ◽  
Fundamental Conception ◽  
Rats And Mice ◽  
Physical And Chemical ◽  
Detailed Work ◽  
Tumour Weight

The object of the present investigation has been to determine the effects of the growth of tumours on the weight of the principal organs of the body. The fundamental conception on which the work is based is that the weights of the different organs of normal animals bear a relatively constant ratio to the total weight of the body. Such investigations are capable of throwing light on many debatable points of cancer metabolism, and give important indications of promising directions for future more detailed work. The previous investigations of workers in the Imperial Cancer Research Fund (Cramer, Haaland, Murray), and recently by Moreschi, in Ehrlich's Institute, have dealt with this subject from the standpoint of the ratio of tumour-weight and the influence of the former on the latter and on the normal growth of the body. In the present investigation a closer analysis of the factors is attempted, in reasonable expectation that under the influence of the physical and chemical changes taking place in the bodies of animals bearing tumours, definite aberrations from the normal relations may be produced. From a consideration of these aberrations it may be possible to infer the nature of these changes.

scholarly journals GEOTROPIC EXCITATION IN HELIX

1931 ◽  
Vol 15 (1) ◽  
pp. 15-28 ◽  
Author(s):  
H. Hoagland ◽  
W. J. Crozier
Keyword(s):  
Gravitational Field ◽  
Standard Deviation ◽  
Reaction Time ◽  
Latent Period ◽  
Stable Equilibrium ◽  
Supporting Surface ◽  
The Mean ◽  
Inclined Surface ◽  
Relative Variability

Rotation of an inclined surface on which Helix is creeping straight upward, such that the axis of the animal is turned at a right angle to its previous position, but in the same plane, leads to negatively geotropic orientation after a measurable latent period or reaction time. The duration of the latent period is a function of the slope of the surface. The magnitude of the standard deviation of the mean latent period is directly proportional to the mean latent period itself, so that the relative variability of response is constant. The dependence of reaction time upon extent of displacement from symmetrical orientation in the gravitational field is found also by tilting the supporting surface, without rotation in the animal's own plane. On slopes up to 55°, the relation between latent period and the sine of the slope is hyperbolic; above this inclination, the latent period sharply declines. This change in the curve is not affected by the attachment of moderate loads to the snail's shell (up to 1/3 of its own mass), and is probably a consequence of loss of passive stable equilibrium when rotated. When added loads do not too greatly extend the snail's anterior musculature, the latent period for the geotropic reaction is decreased, and, proportionately, its σ. These facts are discussed from the standpoint that geotropic excitation in these gasteropods is due to impressed muscle-tensions.

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