The Bose-Einstein correlation function C2(Q)C_2(Q) from a Quantum Field Theory point of view

We show that a recently proposed derivation of Bose-Einstein correlations (BEC) by means of a specific version of thermal Quantum Field Theory (QFT), supplemented by operator-field evolution of the Langevin type, allows for a deeper understanding of the possible coherent behaviour of the emitting source and a clear identification of the origin of the observed shape of the BEC function $C_2(Q)$. Previous conjectures in this matter obtained by other approaches are confirmed and have received complementary explanation.Comment: Some misprints corrected. To be publishe in Phys. Rev.

Experimental Determination of the Key Heat Transfer Mechanisms in Pharmaceutical Freeze Drying

Freeze-drying is often used in manufacture of pharmaceuticals to remove a solvent in such a way that the sensitive molecular structure of the active substance of a drug is least disturbed, and to provide a sterile powder that can be quickly and completely rehydrated. In this work heat transfer rates in a laboratory-scale freeze-dryer have been measured to investigate the contribution of different heat transfer modes. Pure water was partially dried under low-pressure conditions and sublimation rates were determined gravimetrically. The heat transfer rates were observed to be independent of the separation distance between a product vial and a dryer shelf and linearly dependent on the pressure in the free molecular limit. However, under higher pressures the heat transfer rates were independent of pressure and inversely proportional to the separation distance. Previous heat transfer studies in conventional freeze-drying cycles have attributed a dominant portion of the total heat transfer to radiation, the rest to conduction, whereas the convection has been found insignificant. While the measurements revealed the significance of the radiative and gas conduction components, the convective component was found to be comparable to the gas conduction contribution at pressures greater than 100mTorr. The current investigation suggests that the convective component of the heat transfer cannot be ignored at typical laboratory-scale freeze-drying conditions

Magnetic trapping of ultracold neutrons

Three-dimensional magnetic confinement of neutrons is reported. Neutrons are loaded into an Ioffe-type superconducting magnetic trap through inelastic scattering of cold neutrons with 4He. Scattered neutrons with sufficiently low energy and in the appropriate spin state are confined by the magnetic field until they decay. The electron resulting from neutron decay produces scintillations in the liquid helium bath that results in a pulse of extreme ultraviolet light. This light is frequency downconverted to the visible and detected. Results are presented in which 500 +/- 155 neutrons are magnetically trapped in each loading cycle, consistent with theoretical predictions. The lifetime of the observed signal, 660 s +290/-170 s, is consistent with the neutron beta-decay lifetime.Comment: 17 pages, 18 figures, accepted for publication in Physical Review

Mass Measurements in Protoplanetary Disks from Hydrogen Deuteride

Stars and planetary system

Grain Surface Models and Data for Astrochemistry

AbstractThe cross-disciplinary field of astrochemistry exists to understand the formation, destruction, and survival of molecules in astrophysical environments. Molecules in space are synthesized via a large variety of gas-phase reactions, and reactions on dust-grain surfaces, where the surface acts as a catalyst. A broad consensus has been reached in the astrochemistry community on how to suitably treat gas-phase processes in models, and also on how to present the necessary reaction data in databases; however, no such consensus has yet been reached for grain-surface processes. A team of ∼25 experts covering observational, laboratory and theoretical (astro)chemistry met in summer of 2014 at the Lorentz Center in Leiden with the aim to provide solutions for this problem and to review the current state-of-the-art of grain surface models, both in terms of technical implementation into models as well as the most up-to-date information available from experiments and chemical computations. This review builds on the results of this workshop and gives an outlook for future directions