G eant 4 is a toolkit for simulating the passage of particles through matter. It includes a complete range of functionality including tracking, geometry, physics models and hits. The physics processes offered cover a comprehensive range, including electromagnetic, hadronic and optical processes, a large set of long-lived particles, materials and elements, over a wide energy range starting, in some cases, from 250 eV and extending in others to the TeV energy range. It has been designed and constructed to expose the physics models utilised, to handle complex geometries, and to enable its easy adaptation for optimal use in different sets of applications. The toolkit is the result of a worldwide collaboration of physicists and software engineers. It has been created exploiting software engineering and object-oriented technology and implemented in the C++ programming language. It has been used in applications in particle physics, nuclear physics, accelerator design, space engineering and medical physics.

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Geant4—a simulation toolkit

Geant4 - A Simulation Toolkit

* Caring for children * The origins of attachment theory * Psychoanalysis as art and science * Psychoanalysis as a natural science * Violence in the family * On knowing what you are not supposed to know and feeling what you are not supposed to feel * The role of attachment in personality development * Attachment, communication, and the therapeutic process * Developmental psychiatry comes of age

A Secure Base. Parent-Child Attachment and Healthy Human Development. New York (Basic Books) 1988.

More is different.

Feshbach resonances are the essential tool to control the interaction between atoms in ultracold quantum gases. They have found numerous experimental applications, opening up the way to important breakthroughs. This review broadly covers the phenomenon of Feshbach resonances in ultracold gases and their main applications. This includes the theoretical background and models for the description of Feshbach resonances, the experimental methods to find and characterize the resonances, a discussion of the main properties of resonances in various atomic species and mixed atomic species systems, and an overview of key experiments with atomic Bose-Einstein condensates, degenerate Fermi gases, and ultracold molecules.

Feshbach resonances in ultracold gases

. disintegration electrons are observed only for positive mesotrons. This was indeed to be expected' because negative mesotrons after being slowed down can approach the nuclei and disappear by nuclear interactions. If, on the other hand, graphite is used for stopping the mesotrons, delayed disintegration electrons are observed to be about equally abundant for positive and negative mesotrons. This is in sharp disagreement with current expectations and seems to indicate that the interaction of mesotrons with nucleons according to the conventional schemes is many orders of magnitude weaker than usually assumed. The disappearance of a negative mesotron can be analyzed into a process of approach of the mesotron to the nucleus and the process of capture by short range interaction of the mesotron and the nucleons. The slowing down of mesotrons to an energy of about 2000 ev takes place according to the coriventional theory. In estimating the energy loss for lower energies we have considered energy exchange with electrons and radiation. We consider the electrons as a degenerate gas with a maximum velocity vo and assume that the velocity U of the mesotron is small compared to vo. Then the energy loss to the electrons per unit time is of the order of magnitude e'm'T/(5'p). Here m and p are the masses of the electrons and the mesotrons, respectively, and T is the kinetic energy of the mesotron. This formula allows losses of energy even when the total energy is negative (mesotron bound to an atom), and is P+p =N+hv X+p, =N+ Y. (&)

Victor F. Weisskopf

Papers

The Decay of Negative Mesotrons in Matter

Night Thoughts of a Classical Physicist

The problem of an effective mass in nuclear matter

Theoretical Nuclear Physics

The formation of a compound nucleus in neutron reactions