scholarly journals The theory of metallic corrosion in the light of quantitative measurements

The principal object of the present research is the discovery of a satisfactory way of measuring the corrosion of metals in water and dilute salt solutions, and the use of it to test the adequacy of the newer electrochemical theory of corrosion as applied to such media. The theory suggests that a large number of factors can influence the rate of corrosion, but does not indicate quantita­tively their relative importance in given conditions, in fact, the theory is based at present upon qualitative or only roughly quantitative measurements. It is desirable, therefore, that a determined attempt should be made to place it upon a sounder basis, on account, both of the inherent interest of the theory and of its importance in technical problems of steadily increasing insistence. The present communication is the first portion of an extensive research; it is divided into three sections, the first gives an outline of the theory as understood by the authors; the second, a brief review of the kind of measurement upon which it rests; the third an improved method of measuring corrosion as applied to the metal zinc, together with an interpretation of the results so far obtained.

1960 ◽  
Vol XXXIII (III) ◽  
pp. 417-427 ◽  
Author(s):  
John Kristoffersen

ABSTRACT By means of chromatographic and spectrophotometric methods progesterone and a substance closely similar to 20β-hydroxy-pregn-4-ene-3-one has been detected in luteal tissue from non-pregnant and pregnant cows. In 21 animals quantitative measurements based on a method giving an average net recovery of 56 per cent showed that in pregnancy the average progesterone content in the corpus luteum reached a maximum in the third to fifth month, with low values before and after this period. For 6 nonpregnant cows, the average value was 20.2 μg/g tissue, which is considerably higher than previous values reported in the literature. The relation between these findings and the bovine dependence on a functional corpus luteum in pregnancy is discussed, and it is pointed out that more information about the metabolism of progesterone in cattle is highly desirable.


2021 ◽  
pp. 5-10
Author(s):  
A.M. Hohol ◽  
A.I. Pankevych ◽  
I.A. Kolisnyk ◽  
D.S. Machulenko ◽  
Ya.A. Hohol

Topic relevance. The dental surgeon often is left alone with the dilemma: to save or remove the third lower molars. The justification of indications for tooth extraction must have objective criteria. It should be noted that a patient with this problem does not always have the opportunity to receive comprehensive advice from an orthodontist. In view of this, the solution to this problem requires the search for radiological data, which are the most available today and would help to justify treatment tactics for preservation or removal of the tooth. The conditions of tooth preservation in the dentition are most favorable with a slight medio-distal inclination and a vertical position of the third lower molars. However, this does not exclude the possibility of tooth impaction, which is often accompanied by periodic inflammatory phenomena in the tissues adjacent to the tooth and motivates both the patient and the dental surgeon to solve this problem. The aim of our study was to research of radiographic indicators of orthopantomography of the mandible to predict the vertical retention of the third lower molars. Material and methods of research. The platforms of Google Scholar, Research Gate and PubMed are used for research and analysis of the scientific literature on the application of objective criteria of mandibular orthopantomography data in the prediction of vertical impaction of the third lower molars. Impaction of mandibular molars is the result of a number of factors, including heredity, racial characteristics, muscle function, the nature of the food consumed, insufficient growth of the mandible, the size of the retromolar space. The accurately determination the positions of the molars and the size of the retromolar space of the mandible by available methods of X-ray diagnosis (the most common of which is the method of orthopantomography of the jaws) are necessary to prediction of tooth retention. The accuracy of imaging and measurements on orthopantomograms of the jaws was studied by both domestic and foreign authors. The angle of inclination of lower wisdom tooth, the size of the retromolar space of the mandible and the mesiodistal size of the teeth are determined on OPTG of jaws in the vast majority of publications. The age aspect of patients is also important for prediction of tooth impaction. In particular, most researchers state the fact that up to 20 years of life there is a significant probability of changing the position of the teeth during their eruption and therefore it is quite appropriate to wait. To predict the nature of the impaction of the third lower molars, the authors provide indicators of the angle of the tooth, the structure of their roots, the degree of impact and age of the patient. The publication of Maria Mersedes Gallas-Torreira and co-authors, which compared two methods of linear measurements on OPTG – Olive-Basford’s and Olmos ’methods have greatest interest. Both methods can be used to predict of impaction of lower wisdom tooth. However, if the prognostic estimate is based on orthopantomogram data rather than cone-beam computed tomography, the Olmos` method demonstrates a lower error rate and a more plausible prediction. To substantiate the algorithm for predicting the vertical retention of third lower molar in order to improve treatment tactics for the preservation or removal of the tooth which based on the obtained search data and the results of our own clinical observations and it is planned in the future.


2018 ◽  
Vol 8 (9) ◽  
pp. 1558 ◽  
Author(s):  
Giuseppe Cirella ◽  
Felix Iyalomhe

Nigeria’s 196 million people is the third fastest growing population in the world; the interactions of this build up has left an indelible mark on the landscape and environment. Urbanization, deforestation, flooding, desertification, over population and all levels of pollution are resultant effects of this interaction with the environment. These changes directly relate to a seemingly endless desire for food, shelter, recreation and infrastructural facilities and urbanization in general. This has placed enormous pressure on ecosystem stability and environmentally sound living conditions. Flooding has become an annual event for Nigerian cities—where it consistently causes economic problems in the rainy season. Effort made by the government and residents to forestall this problem has produced sub-optimal results. There is a need to adopt more proactive, standard and reliable procedures that can offer sustainable outcomes and restore the socioeconomic growth of urban areas. Frequency of flooding is due to a number of factors relating to differing climatological patterns of precipitation, urban growth and increase in paved surfaces. The aim of this review is to utilize a conceptual framework to assess and identify areas within Nigeria prone to flooding and examine possible means of alleviating damage and harm.


The recent work of Carpenter and Elam on the growth of single crystals of large dimensions has rendered possible the study of the physical constants of single crystals of the commoner metals, and the present communication describes the determination of the thermal and electrical conductivity of aluminium in the form of an isolated crystal. The form of the crystal investigated is shown in fig. 1. This crystal had been prepared at the National Physical Laboratory employing the technique described by Carpenter in “Nature,” p. 266, August 21, 1926, which briefly is as follows:— The test specimen is machined and subjected to three treatments, thermal, mechanical, and thermal. The first treatment is necessary to soften the metal completely and produce new equiaxed crystals of so far as possible uniform size, the average diameter being 1/150 inch. The second consists in straining these crystals to the required amount, and the third in heating the strained crystals to the requisite temperature, so that the potentiality of growth conferred by strain could be brought fully into operation.


The present paper includes some experiments suggested by criticisms of Part III of the research, and describes work upon the effect of depth of im­mersion on the corrosion of zinc in potassium chloride solutions. Some of the factors which influence the distribution of corrosion over the metallic surface are discussed with particular reference to the effect of differential aeration. Curves are given showing the effect of concentration of potassium chloride and potassium sulphate on the initial corrosion rate of zinc in tranquil conditions. The experimental methods used are those described in previous papers, supple­mented by micrographic work and a few potential measurements. The criticism has been made that the tranquil conditions in which the present series of experiments is being conducted cause abnormally slow rates of oxygen supply which dictate the corrosion rates; these, therefore, are not considered characteristic of the metal under test, but merely of the rate of penetration of oxygen through the liquid and any corrosion products which cover the metal. It has also been suggested that much faster rates of oxygen supply would be required to bring out the true corrosion characteristics of a metal or even to differentiate between two fairly reactive metals.


1989 ◽  
Vol 35 (4) ◽  
pp. 512-521 ◽  
Author(s):  
A. C. Perriman

1 Cor 15.50–57 is frequently cited as evidence that Paul expected to be alive at the parousia, chiefly on the basis of the distinction in v. 52 between ‘the dead’ who ‘will be raised imperishable’ and ‘we’ who ‘will be changed’. Paul ‘expects that at the parusia he himself will not be among the dead (of whom he speaks in the third person), but among the living (of whom he speaks in the first person)’. There are, however, a number of factors that persuade us to question this conclusion.


1977 ◽  
Author(s):  
R.-M. Moeller ◽  
I. Mahn ◽  
G. Müller-Berqhaus

During gestation increased concentrations of fibrin (ogen)derivatives are observed indicative of intravascular action of thrombin. The aim of this study was to elucidate the kinetics of fibrinogen during gestation. The elimination of homologous 1-125-fibrinogen was studied in 14 pregnant rabbits during the first as well as during the third trimesters of gestation. Control studies were performed with 10 non-pregnant rabbits.The mean distribution volume of labeled fibrinogen did not significantly differ between pregnant and non-pregnant rabbits. During the third trimester pregnant rabbits demonstrated a pronounced shortening of T 1/2 of labeled fibrinogen from a mean of 55.3 hr during the first to a mean of 29.7 hr during the third trimester. The experiments showed a significant increase in the fractional catabolic rate from 45.0 to 69.9% per day in the course of gestation. The shortening of T 1/2 of labeled fibrinogen correlated to the number of fetusses per litter.This study indicates an average acceleration of the fibrinogen turnover during gestation of about 50%. These direct quantitative measurements demonstrate that fibrinogen catabolism is pronouncedly accelerated during pregnancy.


In a previous paper it was shown that if dilute solutions of potassium chloride were allowed to act upon metallic zinc in the presence of oxygen, the corrosion-time curves obtained by means of the observed absorption of oxygen gas were exponential for part of their course. The reason why this particular form of curve was obtained was considered to be the gradual falling off in the concentration of chlorine ions in the experimental conditions of limited volume of solution. For N/10000 and N/5000 solutions the agreement between the experimental and calculated curves was satisfactory up to about 25 days except for a short initial period of two or three days. After about 25 days the experimental curves fell notably below the calculated values, and the suggestion that the reason for this discrepancy was mainly the barring out of chlorine ions from the anodic areas by means of accumulations of corrosion products received some support from the fact that chlorine ions were actually found in solution even after long periods of experiment with the N/5000 solution, in which this discrepancy was most pronounced, but since none were found in the more dilute solutions it seemed probable that some other factor was also operative.


1977 ◽  
Vol 55 (12) ◽  
pp. 2011-2017 ◽  
Author(s):  
B. Mondet ◽  
G. O. Poinar Jr. ◽  
J. Bernadou

The present communication describes a new species of mermithid nematode, Isomermis lairdi, found parasitizing blackflies in the Ivory Coast, West Africa. This nematode is the most common mermithid parasite of Simulium damnosum Theobald and occurs in the larval, pupal, and adult stages of this blackfly in streams of various sizes. The diagnostic characters of the adults of I. lairdi are (1) terminal mouth. (2) strongly S-shaped vagina, (3) ratio of spicule length to anal body width (1.7–2.8), and (4) circular amphids and amphidial openings.The postparasitic juveniles of I. lairdi differ from those of I. tansaniensis Rubtsov, 1972, in having three or four rows of cells in the lateral cords and a longer tail appendage in the male.This is the third species of mermithid nematode described from blackflies (including Simulium damnosum) in West Africa, and the first of the genus.


1934 ◽  
Vol 11 (3) ◽  
pp. 254-263 ◽  
Author(s):  
Geo. S. Field

A consideration of recently published results on the transmission of longitudinal waves in cylinders of liquid, in hollow tubes and in solid rods shows that the first two cases give velocity-frequency curves which are quite similar to each other but different from that obtained with the third case. The reason for these results is discussed and is shown to be most probably the relative importance of shear forces in each case. The effect of viscosity on the phase velocity of longitudinal waves is considered, and it is shown that the classical method of introducing viscosity leads to erroneous results.


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