A Wick Rotation for Spinor Fields: the Canonical Approach

Recently we proposed a new Wick rotation for Dirac spinors which resulted in a hermitean action in Euclidean space. Our work was in a path integral context, however, in this note, we provide the canonical formulation of the new Wick rotation along the lines of the proposal of Osterwalder and Schrader.Comment: 14 pages, Late

Looking Out for the Future: An Orientation for Twenty-first Century Philanthropists

The final report of a four-year initiative, supported by the David and Lucile Packard Foundation and the W.K. Kellogg Foundation, shows how long-term trends (privatization, connectivity, acceleration, etc.) are combining to create a new reality for philanthropy. Anyone who wants to give has more choices than ever. The authors believe that if donors understand how philanthropy is evolving, they will make better decisions in support of the issues, institutions, and communities they care about. The authors explain the new context for philanthropy, which they call "the new ecology of social benefit." Then they offer examples how philanthropists (individual and institutional) are responding in imaginative ways. The new context and the emerging responses combine to create the future of philanthropy, which the authors illustrate by stories and scenarios of the year 2025, such as the development of mutualist societies, the decline of foundations, joint venture philanthropy, or googling giving

PP-Wave / CFT_2 Duality

We investigate the pp-wave limit of the AdS_3\times S^3\times K3 compactification of Type IIB string theory from the point of view of the dual Sym_N(K3) CFT. It is proposed that a fundamental string in this pp-wave geometry is dual to the c=6 effective string of the Sym_N(K3) CFT, with the string bits of the latter being composed of twist operators. The massive fundamental string oscillators correspond to certain twisted Virasoro generators in the effective string. It is shown that both the ground states and the genus expansion parameter (at least in the orbifold limit of the CFT) coincide. Surprisingly the latter scales like J^2/N rather than the J^4/N^2 which might have been expected. We demonstrate a leading-order agreement between the pp-wave and CFT particle spectra. For a degenerate special case (one NS 5-brane) an intriguing complete agreement is found.Comment: JHEP3 LaTeX, 20 pages; discussion of WZW levels clarified, reference adde

Ethnic buffer institutions: the immigrant press: New York City, 1820-1984

Die Verfasser untersuchen die Rolle der Einwanderer-Presse in der Stadt New York zwischen 1820 und 1984. Dabei unterscheiden sie zwischen den aus Europa stammenden alten Einwanderern und den neuen Einwanderern aus Süd-, Mittel- und Osteuropa. Geprüft werden verschiedene Hypothesen, die Bezug nehmen auf Einwanderungswellen, auf jeweilige Zahlen neuer Ankünfte, auf fremdstämmige Verschiedenheiten, auf Arbeitslosigkeit und auf Einwanderungsbeschränkungen. Als Schlussfolgerung ergibt sich: Zeitungen werden gegründet, wenn neue Einwanderer ankommen. Sie spielen deshalb in ersten Linie eine wichtige Rolle für die zu empfangenden Neuankömmlinge, nicht für das Establishment und die Aufrechterhaltung der ethnischen Gemeinschaften. Die Publikationen gehen jedoch zurück, wenn Einwanderungsbeschränkungen auferlegt werden und vermutlich Furcht diesen Prozess begleitet. Schließlich gestatten die Ergebnisse einige Vermutungen über die Zufälligkeit der ethnischen Identität und darüber, ob die Identität eher von der Herkunft der Einwanderer oder von den Bedingungen am Zielort abhängt. (prh)'Among the most important ethnic institutions is the immigrant press, but the role it plays is subject to some debate. Distinguishing between old (Northern European) and New (South, Central and Eastern European) immigrants to New York City and their newspapers, this research examines hypotheses that relate to immigration waves, actual numbers of new arrivals, foreign-born diversity, unemployment, and immigration restrictions. The conclusion is that newspapers are founded as new immigrants arrive and, therefore, they primarily play an important role in the reception of newcomers and not in the establishment and maintenance of ethnic communities. Fear also plays a role; newspaper publication declines when immigration restrictions are imposed. Finally, the results permit some speculation about the contingencies of ethnic identity, and whether identity depends more on the origins of immigrants or is contingent on conditions in the places of their destinations.' (author's abstract

Increased efficiency of direct nanoimprinting on planar and curved bulk titanium through surface modification

In this work the direct transfer of nanopatterns into titanium is demonstrated. The nanofeatures are imprinted at room temperature using diamond stamps in a single step. We also show that the imprint properties of the titanium surface can be altered by anodisation yielding a significant reduction in the required imprint force for pattern transfer. The anodisation process is also utilised for curved titanium surfaces where a reduced imprint force is preferable to avoid sample deformation and damage. We finally demonstrate that our process can be applied directly to titanium rods

Deep Learning of ab initio Hessians for Transition State Optimization

Identifying transition states -- saddle points on the potential energy surface connecting reactant and product minima -- is central to predicting kinetic barriers and understanding chemical reaction mechanisms. In this work, we train an equivariant neural network potential, NewtonNet, on an ab initio dataset of thousands of organic reactions from which we derive the analytical Hessians from the fully differentiable machine learning (ML) model. By reducing the computational cost by several orders of magnitude relative to the Density Functional Theory (DFT) ab initio source, we can afford to use the learned Hessians at every step for the saddle point optimizations. We have implemented our ML Hessian algorithm in Sella, an open source software package designed to optimize atomic systems to find saddle point structures, in order to compare transition state optimization against quasi-Newton Hessian updates using DFT or the ML model. We show that the full ML Hessian robustly finds the transition states of 240 unseen organic reactions, even when the quality of the initial guess structures are degraded, while reducing the number of optimization steps to convergence by 2--3$\times$ compared to the quasi-Newton DFT and ML methods. All data generation, NewtonNet model, and ML transition state finding methods are available in an automated workflow

Application of Wear-Resistant, NanoComposite Coatings Produced from Iron-Based Glassy Powders

This report talks about Application of Wear-Resistant, NanoComposite Coatings Produced from Iron-Based Glassy Powders

The intergenerational transmission of education : new evidence from adoptions in the United States

This article examines the influence of parental education on children’s grade-for-age using a large sample of adoptees drawn from the American Community Survey between 2008 and 2014. The results show that mother’s education is not an important determinant of the education of adopted children, despite statistically significant effects for own-birth children. The results for fathers are different. Among adopted white children, the effect of father’s education is shown to be a statistically significant determinant of grade retention. However, among black children, adoptive father’s education does not appear to have any discernible effect on children’s education. A range of sensitivity tests are undertaken to check the validity of these results. The differences in these patterns between white and black students suggest the presence of racial differences in the intergenerational transmission of education

Organic electrode coatings for next-generation neural interfaces

Traditional neuronal interfaces utilize metallic electrodes which in recent years have reached a plateau in terms of the ability to provide safe stimulation at high resolution or rather with high densities of microelectrodes with improved spatial selectivity. To achieve higher resolution it has become clear that reducing the size of electrodes is required to enable higher electrode counts from the implant device. The limitations of interfacing electrodes including low charge injection limits, mechanical mismatch and foreign body response can be addressed through the use of organic electrode coatings which typically provide a softer, more roughened surface to enable both improved charge transfer and lower mechanical mismatch with neural tissue. Coating electrodes with conductive polymers or carbon nanotubes offers a substantial increase in charge transfer area compared to conventional platinum electrodes. These organic conductors provide safe electrical stimulation of tissue while avoiding undesirable chemical reactions and cell damage. However, the mechanical properties of conductive polymers are not ideal, as they are quite brittle. Hydrogel polymers present a versatile coating option for electrodes as they can be chemically modified to provide a soft and conductive scaffold. However, the in vivo chronic inflammatory response of these conductive hydrogels remains unknown. A more recent approach proposes tissue engineering the electrode interface through the use of encapsulated neurons within hydrogel coatings. This approach may provide a method for activating tissue at the cellular scale, however, several technological challenges must be addressed to demonstrate feasibility of this innovative idea. The review focuses on the various organic coatings which have been investigated to improve neural interface electrodes