Immersion In Fresh Water Research Articles

Adhesive bonding of grp

A number of two-part acrylic adhesives have been evaluated on a comparative basis when used to bond grp. The influence of open time, of glue-line thickness and of shear strain rate on joint strength were all investigated. The effects of various environmental conditions on joint durability were also examined. This latter work involved both unstressed and stressed ageing of grp/grp bonded joints. The investigation of unstressed joints involved immersion in fresh water at 40°C, dry heat at 70°C and 70°C coupled with 90% relative humidity. Stressed joints were aged both in the atmosphere and under seawater.

Prognostic factors in fresh water immersion

The records of 63 consecutive fresh water immersion patients seen from 1969 to 1978 were examined retrospectively to evaluate those factors most relevant to the patients' eventual outcome. Nineteen patients had hematuria on admission, all 19 had complicated courses or died as a result of their immersion. Nine of the 63 patients had plasma hemoglobin concentrations of 30 mg/dl or above. Five of the nine died as a result of their immersion. The remaining four developed Adult Respiratory Distress Syndrome but survived. All other parameters measured seemed to have little effect on the prognosis. An elevation of PCO2 on admission seemed difficult to evaluate but might in certain circumstances suggest an ominous prognosis.

Secondary drowning in children.

Secondary drowning (and near-drowning) is one of the post-immersion respiratory syndromes. It is defined as deterioration of pulmonary function that follows deficient gas exchange due to loss or inactivation of surfactant. A review of 94 consecutive cases of near-drowning in childhood showed that this syndrome occurred in five (5%) cases. Its onset was usually rapid and characterised by a latent period of one to 48 hours of relative respiratory well-being. It occurred more rapidly after immersion in fresh water. The two children immersed in salt water died of secondary drowning, while the three immersed in fresh water recovered completely. If it is anticipated, recognised, and treated vigorously prognosis of secondary drowning is good in fresh water cases but bad after salt water immersion.

SPERM PENETRATION AND THE FORMATION OF A FERTILIZATION CONE IN THE COMMON CARP EGG.

Sperm penetration and the formation of a fertilization cone in the micropylar canal of the egg of the common carp were examined by electron microscopy. The overwhelming majority of inseminated eggs fixed without immersion in fresh water showed that the first spermatozoon had penetrated into the ooplasm before the cortical reaction had occurred, and in many cases had formed a fertilization cone to plug the micropylar canal. At this stage the sperm head was usually located at the base of the cone, and the tail part did not participate in the formation of the cone. Inseminated eggs fixed soon after immersion in fresh water showed that the elevation of the fertilization membrane and the simultaneous recession of the fertilization cone often permitted the penetration of a few supernumerary spermatozoa into the perivitelline space near the micropylar canal, but polyspermic fertilization was never observed. The mechanism of the block to polyspermy in the egg of the common carp is discussed in connection with the fertilization cone.

Salinity Tolerance in Some Selected Aquatic Oligochaetes

AbstractSalt tolerance of the freshwater tubificid Limnodrilus hoffmeisteri varied from an LD 50 of 10 ppt to 10.5 ppt for mature and immature worms without sediment, 9.4 to 10.5 in sand, and 14.3 for immatures acclimated to 5 ppt. Ilyodrilus templetoni was similarly intolerant to higher salinities. The estuarine Tubificoides gabriellae tolerated salt water, but was susceptible to freshwater, with LD 50's of 2 and 3.5 when acclimated to 5 and 10 ppt sea water. It survived immersion in freshwater for 3 hours. The estuarine naidids Paranais litoralis and frici experienced mortalities at both high and low salinities but showed a wide tolerance range. The coastal tubificid Monopylephorus irroratus showed almost complete tolerance to the salinity range employed. The findings reflected field distributions especially when interstitial salinities were measured, but worms did not occupy the full range of habitats possible in terms of salinity alone.

An analysis of the causes of freshwater immersion accidents involving children

An analysis is presented of the aetiological factors responsible for 111 consecutive childhood freshwater immersion accidents. The study comprises data from 56 survivors and 55 fatal cases in the Brisbane Drowning Study, being a total population five year analysis. A total of 16 separate aetiological factors have been identified. Quantitative scores for the relative importance of each of these have been calculated. Lack of parental supervision (78%), absent or inadequate safety barriers surrounding water hazards (63%) and an identifiable parental “vulnerable period” (44%) were the three most common factors. Most drowning accidents were due to multiple coincident causes; in only 16 cases (14%) could the accident be attributed to a single cause. Swimming pool accidents had a median of four separate but coincident causal factors compared with a median of two for those occurring in bathtubs, rivers and creeks. Causes have been classified according to three groups—environmental factors, parental factors, and factors relating to the child himself; quantitative scores for each of these causal groups, by immersion site, are presented. The significance of this work in the context of preventive strategems is discussed.

Survival rates after serious immersion accidents in childhood

A study of childhood survival rates, after loss of consciousness in fresh water, has been undertaken. Age-specific, sex-specific and site-specific survival rates for childhood fresh water immersion accidents are reported for the first time. The overall survival rate, after loss of consciousness in the water was 0.49; swimming pool and domestic bath tub serious immersion accidents have a survival rate of 0.60 compared with a rate of 0.05 for similar immersion accidents in creeks and rivers. Young male schoolboys have the lowest potential survival (0.20 or less) of any group. Survival rates were significantly higher during the winter (0.86) than during the warmer months (survival rate of 0.49). This gives a quantitative expression to the protection from cerebral anoxia afforded by body chilling which is not extreme. Survival rates have increased significantly over the 5 year period 1971–1975; it is considered that this is due to public education campaigns of the potential danger of water to children. The use of survival rates to measure factors which modify the pathophysiology of human drowning and near-drowning is discussed.

NEUROLOGICAL AND PSYCHOMETRIC STUDIES IN CHILDREN SURVIVING FRESHWATER IMMERSION ACCIDENTS

A study of the neurological and intellectual sequelæ of childhood near-drowning is reported. Results are from a total population study, without selection, of all freshwater immersion accidents in which consciousness was lost in the water. Such accidents affected 56 children in the city of Brisbane and environs over the period 1971-75. 54 of these children have been re-examined medically and psychometrically. Over 95% of children who survived such accidents were neurologically normal. The median I.Q. of survivors was 110 (range 90 to 137), which is higher than that of the general population. There is a suggestion that visual-motor (performance) skills are particularly vulnerable to freshwater immersion hypoxia. In 20% of survivors subscale disparities between verbal and performance skills exceeded 15 I.Q. points. No correlation between the post-immersion I.Q. and either estimated immersion-time or water temperature was demonstrated in this study. No long-term emotional or personality disorders were encountered. Uncommon gross clinical sequelæ of prolonged immersion in fresh water included spastic quadriplegia and gross mental retardation. All children in this study were apparently dead at the moment of rescue; despite this, the prognosis of near-drowning in childhood is excellent.

Freshwater drowning and near-drowning accidents involving children: a five-year total population study.

A large total population study of childhood fresh water immersion accidents is reported. The study was undertaken in the City of Brisbane over the five-year period 1971 to 1975 inclusive, and 111 fresh water immersion accidents involving children were studied and analysed. The childhood fresh water immersion accident rate, including drowning and near-drownings, of 10-43 per year per 100,000 at risk (fatality rate of 5-17) is the highest reported. If an unsupervised child gets into difficulties in fresh water and loses consciousness he has a 50% chance of dying. The immersion accident rate has doubled over the last six years. Age-specific immersion accident rates have been calculated, and have revealed that, in the toddler group (12 months to 23 months), the fresh water immersion accident rate is 50-01 per 100,000 (fatality rate of 22-55). Rates for drowning and near-drowning accidents after a fresh water immersion, by site, age and outcome (survival versus fatality), are also presented for the first time. Swimming pools produce 6-20 immersion accidents per year per 100,000 children at risk, and the domestic family bath tub produces 1-78. Possible factors explaining the high incidence are discussed, and comparisons of drowning rates from other centres are made.

PHYSIOLOGICAL ECOLOGY AND INTERTIDAL ZONATION IN LIMPETS (ACMAEA): A CRITICAL LOOK AT "LIMITING FACTORS"

1. This study tests the hypothesis that physical factors limit the ranges of five species of limpets (Acmaea) inhabiting the splash zone (Zone I) and upper midtidal (Zone II) of the Central California rocky shore. Two criteria are considered necessary to establish the hypothesis. First, interspecific differences in adaptation to physical factors must permit exploitation of different portions of the intertidal gradient. Secondly, physical conditions, by occasionally causing mortality, must set the limits of ranges at different levels depending upon the interspecific differences in physiological tolerances.2. Dilution by winter rainwater runoff probably presents no osmotic threat to Acmaea. No pronounced differences are evident in either resistance to or tolerance of dilution. All five species tolerate immersion in fresh water for periods in excess of the maximum exposure expected in nature. Under exceptional circumstances some Zone I limpets may experience entrapment and lethal dilution in fresh water seep...

Salinity tolerance in three Scandinavian populations ofLittorina littorea(L.) (Gastropoda)

Abstract Specimens of Littorina littorea collected at Helsingør in Denmark throve in salinities between 11.5 and 30‰, and in 10‰ S they were rather active. The animals could not survive in salinities of 8‰ or lower for extended periods. The critical diminished salinities for a population collected at Bornö in the Gullmarfjord (western Sweden) were around 11.5 and 13.5‰. In salinities lower than 11.5‰ the animals were idle or died. About 50% of the specimens from Bornö survived 14 days of immersion in fresh water. The gastropods collected at Kristineberg at the mouth of the Gullmarfjord showed a considerably decreased activity in salinities lower than 13.5‰. The adaptability of the three populations to different salinities is discussed.

Susceptibility of Epoxy Coatings To Damage by Fresh Water Immersion

Abstract Data are given on tests of epoxy coatings, resistance to submersion in fresh water with a variety of curing agents as the variable. Examples are given showing where formulations cured by amines failed. Naval Research Laboratory tests showed epoxy coatings blistered consistently. A hypothesis is offered on the mechanism by which the coatings fail and the mechanism of blistering. 5.4.5,4.6.7

Effects of corticosteroids on electrolyte metablism during osmoregulation in teleosts.

The effects of injections of hydrocortisone, 9 α fluorohydrocortisone and d, l aldosterone on rates of loss of Na and K and on serum and muscle electrolyte concentrations were studied in euryhaline and stenohaline marine teleosts during immersion in fresh water for periods of 1–16 hours. Survival time was not affected by administration of adrenal steroids. Survival in fresh water was inversely correlated to the rates of Na loss. Administration of corticosteroids had no consistent effect on either Na or K loss or on the changes in plasma or muscle electrolyte content during immersion in fresh water. It is inferred from the data that euryhalinity depends on the ability to conserve Na, K and Cl in hypotonic water and that NaCl depletion, extracellular fluid contraction and hypovolemia are major factors in the failure of marine teleosts to survive in fresh water.

Thermal and Osmotic Countermeasures Against Some Typical Marine Fouling Organisms

Abstract Tests were conducted to determine the tolerance of mussels of the genus Mytilus to immersion in fresh water at ambient temperatures and in sea water at elevated temperatures. It was found ...