scholarly journals Meissner Effect: History of Development and Novel Aspects

Author(s):  
Vladimir Kozhevnikov

Abstract The discovery of the Meissner (Meissner–Ochsenfeld) effect in 1933 was an incontestable turning point in the history of superconductivity. First, it demonstrated that superconductivity is an unknown before equilibrium state of matter, thus allowing to use the power of thermodynamics for its study. This provided a justification for the two-fluid model of Gorter and Casimir, a seminal thermodynamic theory founded on a postulate of zero entropy of the superconducting (S) component of conduction electrons. Second, the Meissner effect demonstrated that, apart from zero electric resistivity, the S phase is also characterized by zero magnetic induction. The latter property is used as a basic postulate in the theory of F. and H. London, which underlies the understanding of electromagnetic properties of superconductors. Here the experimental and theoretical aspects of the Meissner effect are reviewed. The reader will see that, in spite of almost nine decades age, the London theory still contains questions, the answers to which can lead to a revision of the standard picture of the Meissner state (MS) and, if so, of other equilibrium superconducting states. An attempt is made to take a fresh look at electrodynamics of the MS and try to work out with the issues associated with this the most important state of all superconductors. It is shown that the concept of Cooper's pairing along with the Bohr–Sommerfeld quantization condition allows one to construct a semi-classical theoretical model consistently addressing properties of the MS and beyond, including non-equilibrium properties of superconductors caused by the total current. As follows from the model, the three “big zeros” of superconductivity (zero resistance, zero induction and zero entropy) have equal weight and grow from a single root: quantization of the angular momentum of paired electrons. The model predicts some yet unknown effects. If confirmed, they can help in studies of microscopic properties of all superconductors. Preliminary experimental results suggesting the need to revise the standard picture of the MS are presented.

Forests ◽  
2019 ◽  
Vol 10 (6) ◽  
pp. 520 ◽  
Author(s):  
Kyle G. Dexter ◽  
Ricardo A. Segovia ◽  
Andy R. Griffiths

Lineage diversity can refer to the number of genetic lineages within species or to the number of deeper evolutionary lineages, such as genera or families, within a community or assemblage of species. Here, we study the latter, which we refer to as assemblage lineage diversity (ALD), focusing in particular on its richness dimension. ALD is of interest to ecologists, evolutionary biologists, biogeographers, and those setting conservation priorities, but despite its relevance, it is not clear how to best quantify it. With North American tree assemblages as an example, we explore and compare different metrics that can quantify ALD. We show that both taxonomic measures (e.g., family richness) and Faith’s phylogenetic diversity (PD) are strongly correlated with the number of lineages in recent evolutionary time, but have weaker correlations with the number of lineages deeper in the evolutionary history of an assemblage. We develop a new metric, time integrated lineage diversity (TILD), which serves as a useful complement to PD, by giving equal weight to old and recent lineage diversity. In mapping different ALD metrics across the contiguous United States, both PD and TILD reveal high ALD across large areas of the eastern United States, but TILD gives greater value to the southeast Coastal Plain, southern Rocky Mountains and Pacific Northwest, while PD gives relatively greater value to the southern Appalachians and Midwest. Our results demonstrate the value of using multiple metrics to quantify ALD, in order to highlight areas of both recent and older evolutionary diversity.


1959 ◽  
Vol 115 (1) ◽  
pp. 75-78 ◽  
Author(s):  
K. K. Gupta ◽  
V. S. Mathur

Author(s):  
Ирина Михайловна Ганжина

Статья посвящена исследованию этимологической истории некоторых лексических диалектизмов с затемненной внутренней формой в говорах Тверской области. Сделана попытка выявить мотивационные характеристики слов, связанных с польско-литовским влиянием, путем проникновения во внутреннюю форму слов, проследить их семантические связи с однокоренными лексемами в других славянских и индоевропейских языках. Анализируются историко-семантические преобразования, которые имели место при возникновении производных значений, в результате которых возникли новые слова, конкретизирующие в диалектах признаки, явления, действия и предметы. The article deals with the etymological history of some lexical dialecticisms with an implicit inner form in the dialects of the Tver region. An attempt is made to identify the motivational characteristics of the words, related to the Polish-Lithuanian influence, by penetrating into their inner forms, to trace their semantic connections with the single-root lexemes in other Slavic and Indo-European languages. The author analyzes the historical and semantic transformations that took place in the process of emergence of derived meanings, which resulted in the appearance of new words that concretize different features, phenomena, actions and objects in dialects.


Author(s):  
Katrin Kello ◽  
Hesi Siimets-Gross

This paper analyses court cases, a hitherto little acknowledged source in Estonian history of early modern law. Specifically, we analyse six cases where a person’s status – that of a free man or of a serf – was at stake. We ask how different sources of law were used in the claims of the parties and the judgments of the courts, and which arguments and interpretations were drawn upon. The cases took place about two to three decades before the abolishment of serfdom in the province. They are of interest from the perspective of the history of early modern serfdom, modern reception of Roman law and the hierarchy of legal sources, as well as with regard to the history of the Enlightenment and human rights. The court cases illustrate how legal practice participates in discourses of its time. They shed light on the legal situation during the Regency Era, when Estland’s local system of justice was altered with the aim of harmonising the administrative system in the Russian Empire. The scarcity of such cases is explained by the fact that they affected only a small portion of the population of the province of Estland. Of the approximately 200,000 people living in the countryside, only 3.5 per cent were of free status – mainly people such as craftsmen, millers, sextons, innkeepers, and manor servants. It is not surprising that there were even fewer persons of borderline status who could go to court to claim their freedom. Peasant families of foreign origin, families descending from sextons, and a manor servant figure in the trials. The court cases were shaped by the scarcity of local law and the uncertainty of court practice under Regency. There was no provision in Estland’s written law concerning the two central questions in the trials – the expiry and the relinquishment of a person’s freedom. The most relevant stipulation was a 30-year limit, after which the affiliation of runaway peasants expired. Whether a court considered it possible to carry this limitation over to the expiry of a person’s freedom as well depended on the court’s interpretation of both local custom and the current legal situation. Local custom and earlier Russian ordinances permitted the enserfment of free persons, whereas more recent ordinances prohibited it. The question arose in the courts concerning the extent to which the more recent provisions should be implemented retroactively, and how to relate the ‘spirit of the age’ manifested in them to local custom. Moreover, if a court considered it appropriate to apply the provisions concerning Roman slaves or coloni to local serfs, it had to consider the prohibition in Roman law against enserfing free persons and negating the possibility of expiry of freedom. In fact, the judgments depended on the court’s understanding of the applicability of favor libertatis in Roman law – the principle that court judgments were to be pronounced in favour of freedom in cases where there was evidence of equal weight in favour of a person’s serfdom and freedom. Deriving from favor libertatis, the principle of praesumptio libertatis stated that what had to be proven was a person’s slave or serf status, not their freedom. Therefore, applying Roman slave law to local serfs was beneficial for claimants of freedom, whereas for landlords it was useful to state a difference between Roman slavery and local serfdom. Estate owners also claimed that in provinces like Estland, presumption of serfdom was to be applied in cases concerning peasants. The question of whether or not someone appeared like a ‘normal peasant’ hence became one of the issues discussed in court. We can see a certain consolidation of court practice over time. The courts applied Roman law in the event that they wished to take the ‘spirit of the age’ into account: when they needed to ground the position that a free man could not have been enserfed even prior to Catherine’s ordinances that prohibited enserfment. In the two earliest cases in the 1780s, the court of first instance applied Roman law almost exclusively in justifying its positions. In the three subsequent cases, living like a serf for 30 years, or having been registered among the serfs of an estate during land audits was seen either as evidence of the expiry of freedom, or as evidence of the acceptance of serf status, yet without referring to any specific legal provision. Thus, over time the courts’ emphasis shifted from applying “foreign law” towards local practice and Russian regulations. The sixth court case was exceptional in that the person in question was a manor servant rather than a peasant. In his case, the central questions were whether a soldier had the right to grant freedom to his servant, who was given to him by his parents to accompany him in war, and whether or not returning to the manor to serve as a valet entailed becoming a serf once again.


Author(s):  
Michael Jerryson

This postscript examines religious authority that is beyond strictly doctrine and practice. It traces the history of Western scholarship on religion and authority. Drawing from their own religious background, Western scholars first emphasized orthodoxy (doctrine) as an important religious authority in Buddhism. This was gradually expanded to include orthopraxy (the practice itself). Throughout this development, scholars acknowledged the importance of culture, but never as an equal authoritative axis to orthodoxy and orthopraxy. The postscript argues that the absence of an alternative religious authority, of equal weight, hinders the analysis of Buddhist roles in politics and violence, as well as the study of Buddhism in general.


Weed Science ◽  
2007 ◽  
Vol 55 (5) ◽  
pp. 528-535 ◽  
Author(s):  
Dale L. Shaner ◽  
W. Brien Henry ◽  
L. Jason Krutz ◽  
Brad Hanson

Atrazine is widely used to control broadleaf weeds and grasses in corn, sorghum, and sugarcane. Field persistence data published before 1995 showed that the average half-life of atrazine in soil was 66 d, and farmers expect to achieve weed control with a single application for the full season. However, reports of enhanced atrazine degradation in soil from fields that have a history of atrazine applications are increasing. A rapid laboratory assay was developed to screen soils for enhanced atrazine degradation. Soil (50 g) was placed in a 250 ml glass jar and treated with 7.5 ml of water containing atrazine (5 µg ai ml−1) and capped with a Teflon-lined lid. The assay was conducted at room temperature (25 C). Soil subsamples (1.5 to 3 g) were removed at 0, 1, 2, 4, 8, and 16 d after treatment and extracted with an equal weight of water (wt/vol). The atrazine in the water extract was assayed with high-pressure liquid chromatography (HPLC). The half-life of atrazine in soils with a history of use was ≤ 1.5 d, whereas the half-life in soils with no history of atrazine use was > 8 d. The advantages of this assay are (1) the ease of set up; (2) the rapidity of extraction, and (3) the simplicity of the quantification of the atrazine.


2021 ◽  
pp. 1-31
Author(s):  
Vladimir Z. Kresin ◽  
Sergei G. Ovchinnikov ◽  
Stuart A. Wolf

This chapter outlines the story of superconductivity, which started at the beginning of the twentieth century, and describes major breakthroughs, such as the discovery of the Meissner effect and the isotope effect. Several important developments preceded the microscopic theory formulated by Bardeen, Cooper, and Schrieffer: the two-fluid model, London equations, and the Ginzburg–Landau theory. Formulation of the theory brought further progress, such as quasiparticle tunnelling and the Josephson effect, and the search for new mechanisms of superconductivity and novel materials such as high-Tc oxides and hydrides. The main excitations in normal solids, including phonons, polaronic states, plasmons, and magnons, are described. A rigorous description of the adiabatic method, the foundation of the theory of solids, is provided, and the electron–phonon interaction, renormalisation phenomena, and the dynamic polaronic effect are introduced. The Heisenberg model, the key ingredient of the theory of magnetism, is also described.


2019 ◽  
Vol 2 (1) ◽  
Author(s):  
Abdullahi Suleiman Gwani ◽  
Eduitem Sunday Otong ◽  
Sani Abubakar Bello ◽  
Hamza Mustapha Ahmed ◽  
Dlama Zira Joseph ◽  
...  

Studies have shown that knee alignment parameters differ among races. However, to our knowledge, radiographic frontal plane knee alignment has not been studied in normal northern Nigerian adults. The objective of this study was therefore to determine the frontal plane knee alignment in normal northern Nigerian adults. This study recruited a total of 59 consented subjects (44 males, 15 females). The entire subjects are without any history of lower extremity deformity. Anteroposterior radiographs of both knees with the patella positioned straight ahead were obtained from each participant while standing in a relaxed bipedal stance and placing equal weight on each limb. Alignment was assessed by measuring the tibiofemoral angle (TFA), distal femoral angle (DFA) and proximal tibial angle (PTA). The angles were measured with the aid of a universal plastic goniometre and a plastic ruler. Descriptive statistics of the alignment parameters, independent and paired t-test were computed. In the male population, the mean (standard deviation) obtained were 179.06 (3.87)o for the TFA, 85.94 (3.03 o for the DFA and 89.27 (3.26)o for the PTA. In the female population, the values were 179.53 (3.38)o for the TFA, 86.40 (2.97)o for the DFA and 89.27 (2.15)o for the PTA. No significant mean difference was observed between genders in all the parameters. The TFA does not show any significant difference between the right and left angle regardless of gender. However, significant mean differences were observed in the DFA and PTA of males and combined population. No significant difference was observed in the DFA and PTA of females. Accordingly, northern Nigerian adults may have varus knee alignment compared to other races. Thus, this pre-existing varus alignment should be taken into consideration during clinical examination, preoperative planning and postoperative evaluations of knee deformities in this population.


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