Construction of Non-Perturbative, Unitary Particle-Antiparticle Amplitudes for Finite Particle Number Scattering Formalisms

Starting from a unitary, Lorentz invariant two-particle scattering amplitude , we show how to use an identification and replacement process to construct a unique, unitary particle-antiparticle amplitude. This process differs from conventional on-shell Mandelstam s,t,u crossing in that the input and constructed amplitudes can be off-diagonal and off-energy shell. Further, amplitudes are constructed using the invariant parameters which are appropriate to use as driving terms in the multi-particle, multichannel non-perturbative, cluster decomposable, relativistic scattering equations of the Faddeev-type integral equations recently presented by Alfred, Kwizera, Lindesay and Noyes. It is therefore anticipated that when so employed, the resulting multi-channel solutions will also be unitary. The process preserves the usual particle-antiparticle symmetries. To illustrate this process, we construct a J=0 scattering length model chosen for simplicity. We also exhibit a class of physical models which contain a finite quantum mass parameter and are Lorentz invariant. These are constructed to reduce in the appropriate limits, and with the proper choice of value and sign of the interaction parameter, to the asymptotic solution of the non-relativistic Coulomb problem, including the forward scattering singularity, the essential singularity in the phase, and the Bohr bound-state spectrum

Termination Reaction in the Anionic Polymerization of Methacrylonitrile

The anionic polymerization of methacrylonitrile initiated by triethylphosphine in dimethylformamide was studied. Experimental evidence for two mechanisms of termination reaction was obtained. By addition of water or alcohol in polymerizing system the rate of polymerization and molecular weight of polymethacrylon1itrile decrease, which proves the termination reaction to be bimolecular and proceed by interaction of the active carbanion with water or alcohol. The rate constant for termination of free anions with water was determined, k~,0 = 2.2 x 102 dm3 moP s-1• The termination reaction could not be excluded by purification and prolonged drying of all components of the system, which indicates that the second mechanism of termination is operative as well. Conductivity measurements gave evidence for a monomolecular spontaneous reaction leading to deactivation of the anion

What have we already learned from the CMB?

The COBE satellite, and the DMR experiment in particular, was extraordinarily successful. However, the DMR results were announced about 7 years ago, during which time a great deal more has been learned about anisotropies in the Cosmic Microwave Background (CMB). The CMB experiments currently being designed and built, including long-duration balloons, interferometers, and two space missions, promise to address several fundamental cosmological issues. We present our evaluation of what we already know, what we are beginning to learn now, and what the future may bring.Comment: 20 pages, 3 figures. Changes to match version accepted by PAS

Automatic Measurement in Metallography

Quantitative analysis of the structure of metals and alloys is an important part of modern metal science. To obtain quantitative data and build dependencies, metallographic image processing programs are used, oriented both for scientific research and for use in industry. Programs capable of automatically performing metallographic analysis are of great interest to consumers. When advertising such programs, it is often claimed that they allow quantitative analysis of the structure with virtually no time. The purpose of this work was to determine the time spent on quantitative metallographic analysis in some image processing programs presented on the Belarusian market. Connected and unconnected metallographic objects were considered. It is shown that automatic quantitative analysis is possible for unconnected objects (powders, cast iron graphite). The time required is within a minute. For connected objects (structures of metals and alloys after metallographic etching), the time required to detect objects and obtain digital data is 10–40 min or more, depending on the complexity of the object, which is unacceptable for factory laboratories that analyze a large number of samples per shift. Therefore, it is recommended that potential users of metallographic image processing software always require a substantive demonstration of the automatic measurement capabilities of the proposed software

Evolution of vacancy-related defects upon annealing of ion-implanted germanium

Positron annihilation spectroscopy was used to study defects created during the ion implantation and annealing of Ge. Ge and Si ions with energies from 600 keV to 2 MeV were implanted at fluences between 1×10 exp 12 cm exp−2 and 4×10 exp 14 cm exp−2. Ion channeling measurements on as-implanted samples show considerable lattice damage at a fluence of 1×10 exp 13 cm exp −2 and a fluence of 1×10 exp 14 cm exp -2 was enough to amorphize the samples. Positron experiments reveal that the average free volume in as-irradiated samples is of divacancy size. Larger vacancy clusters are formed during regrowth of the damaged layers when the samples are annealed in the temperature range 200–400 °C. Evolution of the vacancy-related defects upon annealing depends noticeably on fluence of ion implantation and for the highest fluences also on ion species.Peer reviewe

Multiphoton Transitions in a Spin System Driven by Strong Bichromatic Field

EPR transient nutation spectroscopy is used to measure the effective field (Rabi frequency) for multiphoton transitions in a two-level spin system bichromatically driven by a transverse microwave (MW) field and a longitudinal radio-frequency (RF) field. The behavior of the effective field amplitude is examined in the case of a relatively strong MW field, when the derivation of the effective Hamiltonian cannot be reduced to first-order perturbation theory in w_{1} / w_{rf} (w_{1} is the microwave Rabi frequency, w_{rf} is the RF frequency). Experimental results are consistently interpreted by taking into account the contributions of second and third order in w_{1} / w_{rf} evaluated by Krylov-Bogolyubov-Mitropolsky averaging. In the case of inhomogeneously broadened EPR line, the third-order correction modifies the nutation frequency, while the second-order correction gives rise to a change in the nutation amplitude due to a Bloch-Siegert shift.Comment: 7 pages, 6 figure

Автоматические измерения в металлографии

Quantitative analysis of the structure of metals and alloys is an important part of modern metal science. To obtain quantitative data and build dependencies, metallographic image processing programs are used, oriented both for scientific research and for use in industry. Programs capable of automatically performing metallographic analysis are of great interest to consumers. When advertising such programs, it is often claimed that they allow quantitative analysis of the structure with virtually no time. The purpose of this work was to determine the time spent on quantitative metallographic analysis in some image processing programs presented on the Belarusian market. Connected and unconnected metallographic objects were considered. It is shown that automatic quantitative analysis is possible for unconnected objects (powders, cast iron graphite). The time required is within a minute. For connected objects (structures of metals and alloys after metallographic etching), the time required to detect objects and obtain digital data is 10–40 min or more, depending on the complexity of the object, which is unacceptable for factory laboratories that analyze a large number of samples per shift. Therefore, it is recommended that potential users of metallographic image processing software always require a substantive demonstration of the automatic measurement capabilities of the proposed software.Количественный анализ структуры металлов и сплавов является важной частью современного металловедения. Для получения количественных данных и построения зависимостей используются металлографические программы обработки изображений, ориентированные как на научные исследования, так и для использования в промышленности. Большой интерес у потребителя вызывают программы, способные автоматически проводить металлографический анализ. При рекламе таких программ зачастую утверждается, что они позволяют провести количественный анализ структуры практически без затрат времени. Целью данной работы являлось определение затрат времени на количественный металлографический анализ в некоторых программах обработки изображений, представленных на белорусском рынке. Рассматривались связанные и несвязанные металлографические объекты. Показано, что для несвязанных объектов (порошки, графит чугуна) возможен автоматический количественный анализ; затраты времени при этом составляют в пределах минуты. Для связанных объектов (структуры металлов и сплавов после металлографического травления) затраты времени на обнаружение объектов и получение цифровых данных составляют 10–40 мин и более в зависимости от сложности объекта, что неприемлемо для заводских лабораторий, которые анализируют большое количество образцов за смену. Поэтому потенциальным потребителям программ обработки металлографических изображений рекомендуется всегда требовать предметной демонстрации возможности автоматических измерений предлагаемого программного обеспечения

Структурные превращения в тонких металлических пленках при импульсном лазерном воздействии

Processes occurring in metal films by laser irradiation are reviewed. Driving force of recrystallization, grain growth issues, education grooves of thermal etching, the formation of pores are considered. The preparation of nanoparticles in liquids by laser ablation is also addressed.Рассмотрены особенности структурных превращений, происходящих в металлических пленках при импульсном лазерном воздействии, и получение наночастиц в жидкостях методом лазерной абляции. Рассмотрены движущие силы рекристаллизации, вопросы роста зерен, образования канавок термического травления, формирования пор. Отмечена перспективность таких исследований в области сверхкоротких импульсов воздействия

Gettering of interstitial iron in silicon by plasma enhanced chemical vapour deposited silicon nitride films

It is known that the interstitial iron concentration in silicon is reduced after annealing silicon wafers coated with plasma-enhanced chemical vapour deposited (PECVD) silicon nitride films. The underlying mechanism for the significant iron reduction has remained unclear and is investigated in this work. Secondary ion mass spectrometry (SIMS) depth profiling of iron is performed on annealed iron- contaminated single-crystalline silicon wafers passivated with PECVD silicon nitride films. SIMS measurements reveal a high concentration of iron uniformly distributed in the annealed silicon nitride films. This accumulation of iron in the silicon nitride film matches the interstitial iron loss in the silicon bulk. This finding conclusively shows that the interstitial iron is gettered by the silicon nitride films during annealing over a wide temperature range from 250o C to 900o C, via a segregation gettering effect. Further experimental evidence is presented to support this finding. Deep-level transient spectroscopy (DLTS) analysis shows that no new electrically active defects are formed in the silicon bulk after annealing iron-containing silicon with silicon nitride films, confirming that the interstitial iron loss is not due to a change of the chemical structure of iron related defects in the silicon bulk. In addition, once the annealed silicon nitride films are removed, subsequent high temperature processes do not result in any reappearance of iron. Finally, the experimentally measured iron decay kinetics are shown to agree with a model of iron diffusion to the surface gettering sites, indicating a diffusion-limited iron gettering process for temperatures below 700o C. The gettering process is found to become reaction-limited at higher temperatures