A semi-automatic computerized analysis of tracks of ciliates

Summary The behavior of Protozoa can be studied by using the ethogram as a conceptual tool capable of giving an almost complete picture of the motor biology of these microorganisms. A new semi-automatic, computerized method for drawing ethograms is described here: it allows a time-saving of about 70%, in comparison with the similar manual procedure. Microorganism movements are photographed by a Pentax LX camera from the screen of a TV monitor, connected to the stereomicroscope by a TV camera, and resolved into single images using a stroboscopic apparatus. The pictorial data are introduced into the computer by means of a digitizing tablet, and the track analysis is performed semi-automatically. The measurements recorded are then processed using a commercial statistics package in order to obtain a general view of the quantitative parameters of each ethogram.     

刨煤机平面振动的数学建模与仿真

为了降低刨头的振动,提高刨煤机的工作性能,通过简化和假设,应用牛顿定律建立了刨煤机在垂直煤壁方向振动和在水平面扭转振动的数学模型,通过对刨煤机的实体模型进行简化并导入Adams软件,得到了刨头沿垂直煤壁方向和平面扭转振动的仿真曲线,为研究刨煤机的振动、改进设计、合理确定刨煤机的参数提供了理论依据。     

Outline of a dynamical inferential conception of the application of mathematics

We outline a framework for analyzing episodes from the history of science in which the application of mathematics plays a constitutive role in the conceptual development of empirical sciences. Our starting point is the inferential conception of the application of mathematics, recently advanced by Bueno and Colyvan (2011). We identify and discuss some systematic problems of this approach. We propose refinements of the inferential conception based on theoretical considerations and on the basis of a historical case study. We demonstrate the usefulness of the refined, dynamical inferential conception using the well-researched example of the genesis of general relativity. Specifically, we look at the collaboration of the physicist Einstein and the mathematician Grossmann in the years 1912–1913, which resulted in the jointly published “Outline of a Generalized Theory of Relativity and a Theory of Gravitation,” a precursor theory of the final theory of general relativity. In this episode, independently developed mathematical theories, the theory of differential invariants and the absolute differential calculus, were applied in the process of finding a relativistic theory of gravitation. The dynamical inferential conception not only provides a natural framework to describe and analyze this episode, but it also generates new questions and insights. We comment on the mathematical tradition on which Grossmann drew, and on his own contributions to mathematical theorizing. The dynamical inferential conception allows us to identify both the role of heuristics and of mathematical resources as well as the systematic role of problems and mistakes in the reconstruction of episodes of conceptual innovation and theory change.     

Effect of daily parenteral injection of betamethasone on histamine concentration of gastric tissue in albino rats

Summary Gastric tissue histamine concentration was determined in albino rats following daily parenteral injection of betamethasone over a period of 12 days. The result shows a highly significant fall in gastric tissue histamine concentration in comparison with that in saline-treated albino rats over a similar period.This investigation was carried out as a part of a project supported by a research grant from Medical Research Centre, Bombay Hospital Trust, Bombay, India.     

Decomposition of almost Poisson structure of non-self-adjoint dynamical systems

Non-self-adjoint dynamical systems,e.g.,nonholonomic systems,can admit an almost Poisson structure,which is formulated by a kind of Poisson bracket satisfying the usual properties except for the Jacobi identity.A general theory of the almost Poisson structure is investigated based on a decomposition of the bracket into a sum of a Poisson one and an almost Poisson one.The corresponding relation between Poisson structure and symplectic structure is proved,making use of Jacobiizer and symplecticizer.Based on a...     

Suppressive effects of graft versus host reaction on humoral immunity: consequences of homograft of chicken spleen on differentiation of the bursa of Fabricius

By engrafting the chorio-allanto?s of Chick embryos with spleen fragments from homologous adult donors, one elicits a graft-versus-host disease. When the graft is performed before the bursa of Fabricius has reached the lymphoid differentiation state, the final follicular organization is greatly reduced. It seems that this suppression effect cannot be related to a diminution of the stem cell compartment available in the anlage but is a result of a direct impact on the mesenchyme and/or the epithelium of the bursa.     

The hypothesis of the genetic transmission (autosomal recessive) of subtypes of HBs Ag. The example of Kel Kummer]

In a study of asymtomatic carriers of hepatitis B surface antigen (HBs Ag) in a closed population, the Twareg Kel Kummer, 18% of the population (79 individuals out of 439 tested) were found to be carriers of one of the 3 sub types: HBs Ag/a2 1 dw, HBs Ag/a2 1 yw and HBs Ag/a3 yw. Evidence from genealogies and the distribution of carriers in the pyramid of ages strongly supports the hypothesis of genetic transmission of the gene sub type as an autosomal recessive.     

Demonstration of intracellular release of calcium induced by sodium ions in the auricular trabeculae of the frog

In a Ca-free, Mg-free medium containing EGTA (10-3M) auricular trabecles develop a slow inward current which is a pure sodium current. After 12 min in this medium, it is still possible to obtain a phasic mechanical activity which shows a perfect correlation with the current. This kind of behavior indicates that a mechanism of sodium-induced calcium release is present at the level of some internal sites.     

Oxygen consumption of hibernating worker ants Dolichoderus quadripunctatus as a function of temperature and level of population]

The oxygen consumption of "hibernating" ants shows a grouping effect translated by a significant decrease in the level of oxygen consumption as a function of grouping effect. The general relation between oxygen consumption and the living body mass is the same, if the living material belongs to a single animal, or a social community of ants.     

Maimon's criticism of Kant's doctrine of mathematical cognition and the possibility of metaphysics as a science

The aim of this paper is to discuss Maimon's criticism of Kant's doctrine of mathematical cognition. In particular, we will focus on the consequences of this criticism for the problem of the possibility of metaphysics as a science. Maimon criticizes Kant's explanation of the synthetic a priori character of mathematics and develops a philosophical interpretation of differential calculus according to which mathematics and metaphysics become deeply interwoven. Maimon establishes a parallelism between two relationships: on the one hand, the mathematical relationship between the integral and the differential and on the other, the metaphysical relationship between the sensible and the supersensible. Such a parallelism will be the clue to the Maimonian solution to the Kantian problem of the possibility of metaphysics as a science.     

Implication of GABA in the spatial organization of the receptive fields of retinal ganglia cells of frogs]

An histoautoradiographic study of the Chicken and Frog retinae was made following an intravitreal injection if tritiated GABA. This amino acid was especially fixed at the amacrine and horizontal cell level. It has been suggested (Werblin, 1974) that horizontal cells might be responsible for the spatial organization of the receptive fields of retinal ganglion cells. GABA could thus be involved in bringing about of the centre-surround arrangement of the latter receptive fields. We have shown that picrotoxin, a specific GABA-antagonist, does indeed provoke marked changes in the activity of retinal ganglion cells. It provokes a decrease in the response threshold, a facilitation of spontaneous activities, and a marked increase in the receptive field area of the ON-OFF ganglion cells: from 12 at the start, it reaches 24 under the effect of picrotoxin.     

The stoichiometry of peptide-heparan sulfate binding as a determinant of uptake efficiency of cell-penetrating peptides

Binding to negatively charged heparan sulfates (HS) at the cell surface is considered the first step in the internalization of cationic cell-penetrating peptides (CPPs). However, little is known about the relation of the characteristics of the HS-CPP interaction such as affinity, stoichiometry, and clustering with uptake. In this study, we investigated a collection of mutants of a cyclic CPP derived from human lactoferrin with respect to HS binding and uptake. The thermodynamic parameters of HS binding were determined by isothermal titration calorimetry, clustering of HS was investigated by dynamic light scattering, and cellular uptake by flow cytometry and confocal microscopy. Whereas mutations of non-arginine amino acids that are conserved across lactoferrins of different mammalia only had a minor effect on uptake efficiency, changes in the number of arginine residues influenced the uptake significantly. In general, introduction of arginine residues and cyclization improved the HS affinity and the ability to cluster HS. In particular, there was a strong negative correlation between stoichiometry and uptake, indicating that crosslinking of HS is the driving force for the uptake of arginine-rich CPPs. Using glycan microarrays presenting a collection of synthetic HS, we show that a minimal chain length of HS is required for peptide binding.     

The growth of mathematical knowledge—Introduction of convex bodies

The article addresses the topic of the growth of mathematical knowledge with a special focus on the question: How are mathematical objects introduced to mathematical practice? It takes as starting point a proposal made in a previous paper which is based on a case study on the introduction of Riemann surfaces. The claim is that (i) a new object first refers to previously accepted objects, and that (ii) reasoning is possible via a correspondence to the objects with reference to which it is introduced. In addition Riemann surfaces are geometrical objects, i.e., they are placed in a geometrical context, which makes new definitions possible. This proposal is tested on a case study on Minkowski’s introduction of convex bodies. The conclusion is that the proposal holds also for this example. In both cases we notice that in a first stage is a close connection between the new object and the objects it is introduced with reference to, and that in a later stage, the new object is given an independent definition. Even though the two cases display similarity in these respects, we also point to certain differences between the cases in the process of the first stage. Overall we notice the fruitfulness of representing problems in different contexts.     

Reconstruction of a Greek table of chords

Summary R. R. Newton has shown that Ptolemy's table of solar declinations (Almagest I, 15) was not computed from Ptolemy's own table of chords. Newton explains this by assuming that Ptolemy copied his table of declinations from an earlier source, and that originally the table has been computed by means of a less accurate table of chords.In the present paper I shall venture a tentative reconstruction of the method of computation of this ancient table of chords. The clue to this reconstruction is a recursion formula which allows a rapid calculation of the chords belonging to arcs of 1°, 2°, ... in a circle. This recursion formula, which was suggested to me by a verse in the ryabhtya of ryabhata, can be deduced from a theorem of Archimedes concerning a certain sum of chords in a circle. I suppose that this recursion formula was used by Apollonius of Perga in order to obtain a table of chords, and that this table of chords was used by a Greek author (possibly Apollonios himself or Hipparchos) to calculate the table of solar declinations used by Ptolemy. If this hypothesis is adopted, the errors in Ptolemy's table can be explained.     

Tracings of the north of Europe: Robert Chambers in search of the Ice Age

Scottish publisher and naturalist Robert Chambers pursued an amateur interest in geology through much of his life. His early measurements of raised beaches in Scotland earned him membership in the Geological Society of London in 1844, a recognition much appreciated by the anonymous author of the ‘scandalous’ Vestiges published the same year. Although familiar with emerging ice age theories, Chambers remained with most British geologists a sceptic through the 1840s, even after a trip to the glaciers of the Alps in 1848, which nevertheless prepared him for the turning point, which came in 1849 during an extensive field trip in Norway and Sweden. Here a wealth of observations left him in no doubt that vast glaciers had formerly covered Scandinavia, polishing cliffs, scouring striations, depositing old moraines and erratic boulders. This also led him to a new glacial reading of the British landscape, and with the ardent conviction of a fresh convert he became one of the most vocal supporters of glacial theory in Britain in the 1850s at a time when the iceberg drift theory for boulder transport was still favoured by most prominent British geologists. While Chambers through his popular Chambers’s Edinburgh Journal communicated his travels and ice age vision to a wide audience, and also pointed out ice age evidence on guided excursions around Edinburgh, he did not enter this new vision into subsequent editions of Vestiges, probably in order not to reveal its author. This paper explores Chambers’s contributions to the ice age debate, his field trips and the genesis of his convictions, and evaluates his impact on the scientific debate.     

Redox-sensitivity of the dimerization of occludin

Occludin is a self-associating transmembrane tight junction protein affected in oxidative stress. However, its function is unknown. The cytosolic C-terminal tail contains a coiled coil-domain forming dimers contributing to the self-association. Studying the hypothesis that the self-association is redox-sensitive, we found that the dimerization of the domain depended on the sulfhydryl concentration of the environment in low-millimolar range. Under physiological conditions, monomers and dimers were detected. Masking the sulfhydryl residues in the domain prevented the dimerization but affected neither its helical structure nor cylindric shape. Incubation of cell extracts containing full-length occludin with sulfhydryl reagents prevented the dimerization; a cysteine/alanine exchange mutant also did not show dimer formation. This demonstrates, for the first time, that disulfide bridge formation of the domain is involved in the occludin dimerization. It is concluded that the redox-dependent dimerization of occludin may play a regulatory role in the tight junction assembly under physiological and pathological conditions.     

On the necessary truth of the laws of classical mechanics

The idealization of primitive mechanical experience is shown to lead to four mutually related formulations of classical mechanics based on connections, action at a distance, stresses, and collisions. For a given structure of spacetime and a given characterization of mechanical systems, fundamental laws (including Newton's law of acceleration and d’Alembert's principle) are derived from a few general principles regarding the comprehensibility of motion. Special emphasis is placed on the “secular principle,” according to which the evolution of a system at the relevant time scale should not depend on finer details of the applied forces.     

Karyotypes of shrews of the generaCryptotis andBlarina (mammalia: Soricidae)

Summary Cryptotis parva has a diploid number of 52 and a fundamental number of 50. Blarina brevicauda in Nebraska and Pennsylvania has a diploid number of 49 or 50 and a fundamental number of 48. Blarina carolinensis in Nebraska and Kansas has a diploid number of 52 and a fundamental number of 62. The X-chromosome in all 3 species is a large metacentric chromosome. The Y-chromosome is a small acrocentric in Blarina, whereas in Cryptotis it is a small subtelocentric.Funds for field work were provided by the American Philosophical Society from the Johnson Fund. We thank Dr Robert J. Baker, Texas Tech University, for use of his karyological equipment and laboratory facilities.     

Misuses of biology in the context of the paranormal

Public suspicion of science stems from science's challenging of perceptions and myths about reality, and a public fear of new technology. The result is a susceptibility to pseudoscience. In claiming that creation 'science' is as valid as evolution the creationists misquote scientists and seek to spread their own 'scientific' myths concerning a young age for the earth, an act of creation based on a particular literalist interpretation of the Christian Bible and a single worldwide flood. They use methods of debate and politics, rather than scientific research. A selection of their arguments is examined and the nature of the evidence for evolution is discussed. Problems with the creation 'science' model are noted. In the myth of the hundredth monkey phenomenon, original research is misquoted to denigrate scientific research and support sentimental ideas of paranormal events. The misuse of science is seen as damaging to society because it reduces the effective gathering and application of scientific information. However, pseudoscience provides a valuable guide to gaps in public scientific education.     

Reevaluation of hydropathy profiles of voltage-gated ionic channels

A reevaluation of the secondary structure of Na, Ca and K channel proteins led to the following results. Only three segments (S1, S5 and S6) of each repeat are sufficiently hydrophobic to be predicted as transmembrane helices, if a window of 19 amino acids is used. Some of the S2 and S3 segments show higher hydrophobic values when calculated with the window of 9 amino acids and can be predicted as short helices. S4 segments are strongly hydrophilic and cannot be predicted as transmembrane helices. Some of the S2, S3 and S4 segments have an amphipathic character; however, these helices do not span a membrane. A model is proposed where 12 hydrophobic transmembrane helices surround 12 shorter helices, forming a hydrophilic pore. In addition, a unique pattern for S4 segments of voltage-gated channel proteins is defined.