Redesigning the Jefferson Lab Hall A beam line for high precision parity experiments

The Continuous Electron Beam Accelerator Facility (CEBAF) was built with a thermionic electron source and the three original experimental hall lines reflected this. A few years after beam delivery began a parity violation experiment was approved and two polarimeters were installed in the Hall A beam line. The beam raster system was placed after the new Compton polarimeter, before one accelerator quadrupole and four quadrupoles in the new Moller polarimeter. It was very difficult to meet experimental requirements on envelope functions and raster shape with this arrangement so a sixth quadrupole was installed downstream of the Moller polarimeter to provide an additional degree of freedome. All of the parity experiments in Hall A have been run with this still-unsatisfactory configuration. The MOLLER experiment is predicated on achieving a 2% error on a 32 ppb asymmetry. Beam line changes are required to meet the systematic error budget. This paper documents the existing beam line, an interim change which can be accomplished during a annual maintenance down, and the final configuration for MOLLER and subsequent experiments.

Долинно-орбитальное взаимодействие в германии, легированном донорами V группы: количественный анализ

In the framework of the envelope function approximation, the wave functions of electrons localized at shallow donors P, As, Sb in Ge are calculated taking into account the valley-orbit coupling caused by the donor short-range potential. It is proposed an approach that makes it possible to include inter-valley mixing in the equation for a multi-component envelope function. The calculation of the effects of the valley-orbit interaction was carried out according to the perturbation theory, while the "bare" single-valley functions were found using the Ritz method. The parameters of the short-range part of the potential and the coefficient of inter-valley mixing were found individually for each donor, making it possible to obtain the best agreement with the results of experimental measurements of the energies of the singlet and triplet states. The envelope functions of the 1s(A1) and 1s(T2) states are calculated. The parameters of the valley-orbit interaction are found for each donor. It is also shown how the functions of the excited 2s, 2p0, 2p±, 3p0 states should be modified in order to remain orthogonal to the singlet and triplet functions within the framework of a more rigorous multivalley model.

Электронные состояния доноров V группы в германии: вариационный расчет с учетом короткодействующего потенциала

In the framework of the envelope function approximation, the wave functions of low-lying 1s(A1), 2s, 2p0, 2p±, 3p0 states of shallow donor centers P, As, Sb in germanium are calculated considering the short-range part of the impurity potential. The latter is constructed individually for each impurity, taking into account the spatial dispersion of the dielectric function and the difference between the ionic cores of germanium and the impurity center. The envelope function equation was solved using the Ritz variational method, and selected trial wave functions of the orbitally non-degenerate s-states are characterized by two spatial scales: the first one is of the order of the donor effective Bohr radius and corresponds to the long-range part of the potential, and the second one, which is an order of magnitude less, simulates the electron response to the short-range part of the donor potential. The electron density in the donor ground state is shifted to the nucleus due to the attractive “central cell” correction. The envelope functions of p-states, in turn, are constructed in such a way they are orthogonal to the ground state envelope functions for each impurity center, and, unlike previous works, are different for various donors.

Mycobacterium tuberculosis Rv2700 Contributes to Cell Envelope Integrity and Virulence

ABSTRACT The cell envelope of Mycobacterium tuberculosis is a key target for antibiotics, yet its assembly and maintenance remain incompletely understood. Here we report that Rv2700, a previously uncharacterized M. tuberculosis gene, contributes to envelope integrity. Specifically, an Rv2700 mutant strain had a decreased growth rate, increased sensitivity to antibiotics that target peptidoglycan crosslinking, and increased cell envelope permeability. We propose that Rv2700 be named a “cell envelope integrity” gene (cei). Importantly, a cei mutant had attenuated virulence in mice. Cei shares predicted structural homology with another M. tuberculosis protein, VirR (Rv0431), and we found that a virR mutant had growth rate, antibiotic sensitivity, and envelope permeability phenotypes similar to those of the cei mutant. Both Cei and VirR are predicted to consist of a transmembrane helix and an extracellular LytR_C domain. LytR_C domains have no known function, but they are also found in a family of proteins, the LytR-Cps2A-Psr (LCP) enzymes, that perform important cell envelope functions in a range of bacteria. In mycobacteria, LCP enzymes attach arabinogalactan to peptidoglycan, and mycobacterial LCP enzyme mutants have phenotypes similar to those of virR- and cei-deficient strains. Collectively, our results suggest that LytR_C domain proteins may contribute to the cell envelope functions performed by LCP proteins. This study provides a framework for further mechanistic investigations of LytR_C proteins and, more broadly, for advancing our understanding of the cell envelopes of mycobacteria and other medically and economically important genera. IMPORTANCE Mycobacterium tuberculosis causes about 1.5 million deaths per year. The unique composition of the Mycobacterium tuberculosis cell envelope is required for this bacterium to cause disease and is the target for several critical antibiotics. By better understanding the mechanisms by which mycobacteria assemble and maintain their cell envelope, we might uncover new therapeutic targets. In this work, we show that a previously uncharacterized protein, Rv2700, is important for cell envelope integrity in Mycobacterium tuberculosis and that loss of Rv2700 attenuates virulence in mice. This family of proteins is found in a broad group of bacterial species, so our work provides a first insight into their potential functions in many species important to the environment, industry, and human health.

Asymmetrically Dynamic Coupling Hysteresis in Piezoelectric Actuators: Modeling Identification and Experimental Assessments

An asymmetrically dynamic coupling hysteresis (ADCH) model is proposed as an extension of the Prandtl–Ishlinskii (PI) model to characterize the hysteretic nonlinearities in piezoelectric actuators (PEAs). When subject to two-input: dynamic excitation and external loads. In this model, the developed asymmetrically one-side play operator helps to represent the saturation, nonlinearity, and centrally asymmetric properties of PEAs employed inverse hyperbolic envelope functions. The dynamic threshold functions are put in place to characterize the width of rate-dependent hysteresis property. Introductions of continuously coupled density functions are beneficial to the cross-coupled hysteresis behaviors of external load/excitation voltage-to-expansion. Besides, the proposed ADCH model is verified to satisfy indeed the wiping-out property and equal vertical chords property, which means that it can be regarded as well-suited in modeling the complicated hysteresis nonlinearity of PEAs. Furthermore, this paper also tackles the identification issue of the proposed ADCH model by using a global research method, which possesses satisfactory accuracy without strict requirements for the initially iterative value.

Green envelope as an architectural strategy for energy efficiency in a library building

In the context of Malaysian tropical climate, green envelope functions to provide satisfying indoor environment and achieve the best performance with minimal energy consumption. Buildings that rely on air-conditioning to improve thermal comfort could benefit from green envelope potentials. Hence, the objective of this paper is to explore the impacts of various types of green envelope towards reducing the energy consumption of a two-storey library building. The methodology approach is quantitative and data are collected through building simulation using Revit Building Information Modelling (BIM). Parameters studied are building orientation, wall insulation, envelope materials, and façade treatment. Results showed that different types of green envelope posed different impact on energy consumption of the library and double glazed windows contribute the most significant reduction of energy consumption. The study establishes the contribution of green envelope and advocates the use of building simulation as research methodology, as it helps to improve envelope design, and to predict the possible outcomes of design alternatives.

Building envelope and energy demand in retrofitting office

Building envelopes have a significant role in the protection of interiors against weather conditions. While wind, rain barriers and barriers against excessive heat gains were constructed from insufficient elements in the past, the current requirements for envelope functions are different. New materials and technologies allow for more complex design and evaluation of parameters in regard to the needs of occupants and economical interior performance. This paper is focused on the daylighting solutions inside lit office space in which renovation of the lighting system is expected. Several retrofit scenarios based on window shading variations and lighting systems are investigated. Achieved results are evaluated from the point of view of energy demand. The integrative multi-platform tool, the Lighting Retrofit Adviser (LRA) is applied to calculate energy renovation preferences and to accept decision.