A major problem in developing an effective gene therapy for the nervous system lies in understanding the principles that maintain or turn off the expression of genes following their transfer into the CNS.

SummaryDiffraction gratings have contributed enormously to modern science. Although some historians have written about them, there is much more to be brought to light. This paper discusses their development and use in the period up to about 1880 before Rowland began to produce them. Rittenhouse described the action of a diffraction grating in 1786, but no explanation was possible until the wave theory of light was developed. Fraunhofer discovered the dark lines in the solar spectrum in 1814, and then investigated (...) diffraction, producing the first ruled gratings, making detailed measurements and calculating the wavelengths of prominent spectral lines. After Bunsen and Kirchhoff showed the association between spectral lines and chemical elements there was an upsurge of interest in measuring wavelengths. The gratings used in this work almost all came from one source, a relatively unknown instrument maker called Nobert, who made them by an extremely laborious process using a machine he had built himself. The most significant wavelength measurements were made by Ångström, but Mascart, Van der Willigen, Stefan, Ditscheiner and Cornu also did important work. Nobert gratings were investigated by Quincke, copied photographically by Rayleigh, and were known and discussed in the USA. Nobert's work helped to advance spectroscopy much more than has been acknowledged. (shrink)

The principle of relativity, that there is no preferred state of uniform motion, has recently come into conflict with certain cosmological observations. In an attempt to overcome this difficulty, an alternative formulation is explored in which this principle is replaced by the principle of universal time, while retaining the invariance of the speed of light. These two postulates lead to a well-defined world model in which one inertial frame has a preferred status. But the invariance properties of the laws of (...) physics are unaffected, and the model may be regarded as a modified form of special relativity which is in accordance with the new cosmological evidence. (shrink)

Transsexualism, a condition in which from earliest recollection the individual is unshakeably convinced he or she has been endowed with the wrong physical sexual body presents one of the most difficult problems as regards management and treatment in clinical medicine. The aetiology and treatment is discussed and the problems with which the medical practitioner may be faced in advising his transsexual patient which include change in social role and marriage and the difference between sex and gender.

We consider Berezin's algebraic considerations regarding the quantization of phase space polynomials. After making a connection with Prugovečki's stochastic quantization approach, we give a particular construction of Berezin's L-Kernel in terms of Prugovečki's ξ-functions.

The prelims comprise: Introduction The Mother of All Cells Embryonic Stem (ES) Cells Specialized Stem Cells Therapeutic Implications of Stem Cell Biology Cellular Philosophy and the Mind Problem The New Alchemists Stem Cell Biology: God in a Test Tube?

The present paper is an extract from a thesis concerning the debate between bradley and russell on the nature of relations. it concerns only the most general points of interaction - the positive influence of bradley upon russell with respect to psychologism, logic, and constructions; the negative influence: russell's work seen as a reaction to bradley. the intention is to show that bradley was an extremely strong influence in russell's development hardly worthy of the disregard which russell showed him.

The objective of this work is to categorize the available fly ashes in different parts of the world into distinct groups based on its compositional attributes. Kohonen's self-organizing feature map and radial basis function networks are applied in a cascading fashion for the classification of fly ashes in terms of its chemical parameters. The basic procedure of the methodology consists of three stages: apply self-organizing neural net to ascertain possible number of groups, delineate them and identify the group sensitive attributes; (...) find mean values of sensitive attributes of the elicited groups and augment them as start-up prototypes in k-means algorithm and find the refined centroids of these groups; incorporate the centroids in a two layer radial basis function network and fine-tune the delineated groups and develop an indexing equation using the weights of the stabilized network. Further, to demonstrate the utility of this classification scheme, the so formed groups were correlated with their performance in High Volume Fly Ash Concrete System [HVFAC]. The categorization was found to be excellent and compares well with Canadian Standard Association's [CSA A 3000] classification scheme. (shrink)

ABSTRACTDiffraction gratings are famously associated with Henry Rowland of Johns Hopkins University but there were precursors. Although gratings were first made and used in Europe, reliable machines for ruling gratings were developed in the USA, and two men, Lewis Rutherfurd and William Rogers, tackled the problem before Rowland. Rutherfurd, a wealthy independent astronomer, designed and built the first screw-operated engine for ruling diffraction gratings, the fore-runner of almost all subsequent ruling engines. With it he and his assistant D. C. Chapman (...) ruled many gratings which he generously distributed to practising scientists, thereby materially advancing the science of spectroscopy. Rogers was a Harvard astronomer who developed an interest in the ruling of fine lines on glass that led him to construct a ruling engine with which he investigated the causes of the errors in the rulings he had examined. He continued to seek improvements with a second engine designed for ruling diffraction gratings. He ceased developing this engine when Rowland’s excellent gratings began to be available, concentrating instead on related problems to which he could apply the knowledge and skills he had gained, but his investigations assisted Rowland and other later ruling engine builders. This paper brings together what is known about the ruling engines of Rutherfurd and Rogers, their development, the gratings they produced, their quality and the work that was done with them, and assesses and compares their achievements and the impacts of the work of these two men. (shrink)

A new edition containing slight revisions and new appendices extending the debates opened in the original book. Drawing on a comprehensive knowledge of ancient texts and recent research, Merlan argues for a tighter connection between Platonism and Neoplatonism. Heracleides, Hermodorus, Iamblichus, Posidonius, Speusippus, and Xenocrates are all carefully treated.--R. C. N.

In “Two Concepts of Liberty” Berlin notes the protean nature of the word “freedom” and then systematically proceeds to narrow its range of meanings. In the process, Berlin eliminates much of what most people, in everyday communication, regard as freedom, believing that this is in the best interest of intellectual clarity. As he puts it: [N]othing is gained by a confusion of terms. To avoid glaring inequality or widespread misery I am ready to sacrifice some, or all, of my freedom: (...) I may do so willingly and freely: but it is freedom that I am giving up for the sake of justice or equality or the love of my fellow men. I should be guilt‐stricken, and rightly so, if I were not, in some circumstances, ready to make this sacrifice. But a sacrifice is not an increase in what is being sacrificed, namely freedom, however great the moral need or the compensation for it. Everything is what it is: liberty is liberty, not equality or fairness or justice or culture, or human happiness or a quiet conscience. (Emphasis added). Berlin's other, perhaps overarching, aim is to show how inattention to the specificity of the meanings of concepts might have potentially dangerous political repercussions. He implicitly argues that the intellectuals who promoted the idea of positive freedom as opposed to that of negative freedom contributed to the emergence of totalitarianism and fascism in Europe. (shrink)

Feed-forward Pavlovian conditioning can serve as a proximate mechanism for the evolution of social behavior. Feed-forward can provide the impetus for animals to associate other individuals' presence, and cooperation with them, with the acquisition of resources, whether or not the animals are genetically related. Other social behaviors such as play and grooming may develop as conditioned stimuli in feed-forward social systems.