Comparison of Horace and Photos Algorithms for Multi-Photon Emission in the Context of the W Boson Mass Measurement

The W boson mass measurement is sensitive to QED radiative corrections due to virtual photon loops and real photon emission. The largest shift in the measured mass, which depends on the transverse momentum spectrum of the charged lepton from the boson decay, is caused by the emission of real photons from the final-state lepton. There are a number of calculations and codes available to model the final-state photon emission. We perform a detailed study, comparing the results from the Horace and Photos implementations of the final-state multi-photon emission in the context of a direct measurement of the W boson mass at the Tevatron. Mass fits are performed using a simulation of the CDF II detector

Two-channel Kondo physics in tunnel-coupled double quantum dots

We investigate theoretically the possibility of observing two-channel Kondo (2CK) physics in tunnel-coupled double quantum dots (TCDQDs), at both zero and finite magnetic fields; taking the two-impurity Anderson model (2AIM) as the basic TCDQD model, together with effective low-energy models arising from it by Schrieffer-Wolff transformations to second and third order in the tunnel couplings. The models are studied primarily using Wilson's numerical renormalization group. At zero-field our basic conclusion is that while 2CK physics arises in principle provided the system is sufficiently strongly-correlated, the temperature window over which it could be observed is much lower than is experimentally feasible. This finding disagrees with recent work on the problem, and we explain why. At finite field, we show that the quantum phase transition known to arise at zero-field in the two-impurity Kondo model (2IKM), with an essentially 2CK quantum critical point, persists at finite fields. This raises the prospect of access to 2CK physics by tuning a magnetic field, although preliminary investigation suggests this to be even less feasible than at zero field.Comment: 10 pages, 8 figures. Version as published in PR

Structural Investigation of MscL Gating Using Experimental Data and Coarse Grained MD Simulations

The mechanosensitive channel of large conductance (MscL) has become a model system in which to understand mechanosensation, a process involved in osmoregulation and many other physiological functions. While a high resolution closed state structure is available, details of the open structure and the gating mechanism remain unknown. In this study we combine coarse grained simulations with restraints from EPR and FRET experiments to study the structural changes involved in gating with much greater level of conformational sampling than has previously been possible. We generated a set of plausible open pore structures that agree well with existing open pore structures and gating models. Most interestingly, we found that membrane thinning induces a kink in the upper part of TM1 that causes an outward motion of the periplasmic loop away from the pore centre. This previously unobserved structural change might present a new mechanism of tension sensing and might be related to a functional role in osmoregulation.The study was supported by a grant from the Australian Research Council. The simulations were carried out using computer time from iVEC and a Merit Allocation Scheme on the NCI National Facility at the Australian National University. ED was supported by a Jean Rogerson Postgraduate scholarship and the Beryl Henderson Memorial Grant by the Australian Federation of University Women ACT. Websites of funding agencies: http://nci.org.au/access/merit-allocationscheme/, http://www.ivec.org/ http://www.arc.gov.au/ncgp/default.htm, http://spe.publishing.uwa.edu.au/latest/scholarships/postgraduate/rogerson, http://www. afgw.org.au/what-we-do/scholarships-2/ The authors hereby confirm that the funding agencies had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

Precision measurement of the W boson mass at CDF

A measurement of the mass of the W boson, MW, is presented using 2.2 fb−1 of the data from pp collisions at √s = 1.96TeV collected with the CDF II detector at the Fermilab Tevatron. The mass is determined by fitting simulated signal and background distributions to 470126 W candidates decaying to eνe and 624708 decaying to μνμ. The result is MW = 80387±19MeV and is the most precise determination of the mass to date

Interplay between Kondo physics and spin-orbit coupling in carbon nanotube quantum dots

We investigate the influence of spin-orbit coupling on the Kondo effects in carbon nanotube quantum dots, using the numerical renormalization group technique. A sufficiently large spin-orbit coupling is shown to destroy the SU(4) Kondo effects at zero magnetic field, leaving only two SU(2) Kondo effects in the one- and three-electron Coulomb blockade valleys. On applying a finite magnetic field, two additional, spin-orbit induced SU(2) Kondo effects arise in the three- and two-electron valleys. Using physically realistic model parameters, we calculate the differential conductance over a range of gate voltages, temperatures and fields. The results agree well with measurements from two different experimental devices in the literature, and explain a number of observations that are not described within the standard framework of the SU(4) Anderson impurity model.Comment: 15 pages, 11 figure

The Role of Developer and User Knowledge Domains and Learning in Systems Development

Research on Information Systems development has been central to the Information Systems field and the focus had been to improve the interactions between the users and developers during the process. Further examination of the change process reveals the necessity for research on user and developer knowledge domains and on approaches to change them resulting in better systems. IS development outsourcing intensifies the necessity to understand the user developer relations from a knowledge perspective. A framework is developed to explain the user-developer knowledge domains and a case research is performed, spanning insourcing and outsourcing environments, to further explore and explain the learning processes that could occur

X-Irradiation of DNA Components in the Solid State: Experimental and Computational Studies of Stabilized Radicals in Guanine Derivatives

Single crystals of sodium salt of guanosine dihydrate and 9 Ethyl Guanine were X-irradiated with the objective of identifying the radical products. Study with K-band EPR, ENDOR, and ENDOR-Induced EPR techniques indicated at least four radical species to appear in both crystals in the temperature range of 6K to room temperature. Three of these radicals (Radicals R1, R2, and R3) were present immediately after irradiation at 6K. Computational chemistry and EPR spectrum simulation methods were also used to assist in radical identifications. Radical R1, the product of net hydrogen addition to N7, and Radical R2, the product of electron loss from the parent molecule, were observed in both systems. Radical R3, in Na+.Guanosine-.2H2O, is the product of net hydrogen abstraction from C1\u27 of ribose group and radical R3 in 9EtG was left unassigned due to insufficient experimental data. Radical R4, the C8-H addition radical, was also detected in both systems. For Na+.Guanosine-.2H2O, R4 was observed after warming the irradiated crystals to the room temperature. But for the 9EtG crystals the corresponding radical form was detected after irradiation at room temperature. Density functional theory (DFT) based computational studies was conducted to investigate the radical formation mechanisms and their stability. Here possibilities of proton transfers from the neighboring molecules were considered. The first approach was to consider the proton affinities of the acceptor sites and deprotonation enthalpies of the donor sites. This approach supported the formation of radicals observed in both systems. The second approach, applied only to the 9EtG system, was based on proton transfers between 9EtG base-pair anion and cation radicals. Even though the charge and spins were localized as expected, the computed thermodynamic data predicted that the proton transfer processes are unfavorable for both anionic and cationic base-pairs. This indicates the need for additional work to draw final conclusions. In addition, DFT methods were used to compute the geometries and hyperfine coupling constants of 9EtG derived radicals in both single molecule and cluster models. The calculated results agreed well with the experimental results

An investigation of family literacy practices of eight families with preprimary children and a family literacy program conducted in a low socio-economic area

Study of the research literature showed that literacy skills are socialised in young children along with their learning of oral language. This socialisation process occurs within a child\u27s home environment long before they enter formal schooling. Family literacy has been shown to have the potential to impact powerfully on children\u27s perceptions about literacy use through role models and support provided by various family and community members. Literacy activity is often deeply embedded in daily family practices. For some children, differences between home and school literacy practices can occur. Where this mismatch occurs for children in low socio economic homes the problems associated can be compounded. In the present study a formative experimental design was used to investigate and describe some of the literacy practices of eight families living in a low socio-economic environment as identified by the parents of children attending a preprimary centre. Some family literacy programs designed to reduce the effect of the literacy mismatch between home and school have been found, in research literature, to be unsuitable for certain communities because of their inability to address the needs of individual families. The present study reports on the results of a family literacy program jointly planned by the teacher/researcher and parents of eight families from a low socio-economic community. It describes the nature of the family literacy program and the perceptions of the program held by the eight participants. Issues arising from this family literacy program design are highlighted and some implications for educational practice and further research are presented

Where there is no information: IDP vulnerability assessments in Sri Lanka’s borderlands

A third of the estimated 600,000 IDPs in Sri Lanka live in areas controlled by the Liberation Tigers of Tamil Elam (LTTE). Displaced people within these so-called ‘un-cleared’ or ‘liberated areas’ (termsused by the Sri Lankan government and the LTTE respectively) are at especial risk. Their situation highlights the difficulties of assessing protection and assistance in the context of conflict