Constraints on s−sˉs-\bar s asymmetry of the proton in chiral effective theory

We compute the $s-\bar s$ asymmetry in the proton in chiral effective theory, using phenomenological constraints based upon existing data. Unlike previous meson cloud model calculations, which accounted for kaon loop contributions with on-shell intermediate states alone, this work includes off-shell terms and contact interactions, which impact the shape of the $s-\bar s$ difference. We identify a valence-like component of $s(x)$ which is balanced by a $\delta$-function contribution to $\bar s(x)$ at $x=0$, so that the integrals of $s$ and $\bar s$ over the experimentally accessible region $x > 0$ are not equal. Using a regularization procedure that preserves chiral symmetry and Lorentz invariance, we find that existing data limit the integrated value of the second moment of the asymmetry to the range $-0.07 \times 10^{-3} \leq \langle x(s-\bar s) \rangle \leq 1.12 \times 10^{-3}$ at a scale of $Q^2=1$GeV$^2$. This is too small to account for the NuTeV anomaly and of the wrong sign to enhance it.Comment: 5 pages, 4 figure

Spin-lattice order in frustrated ZnCr2O4

Using synchrotron X-rays and neutron diffraction we disentangle spin-lattice order in highly frustrated ZnCr$_2$O$_4$ where magnetic chromium ions occupy the vertices of regular tetrahedra. Upon cooling below 12.5 K the quandary of anti-aligning spins surrounding the triangular faces of tetrahedra is resolved by establishing weak interactions on each triangle through an intricate lattice distortion. The resulting spin order is however, not simply a N\'{e}el state on strong bonds. A complex co-planar spin structure indicates that antisymmetric and/or further neighbor exchange interactions also play a role as ZnCr$_2$O$_4$ resolves conflicting magnetic interactions

Retrofit modelling of existing dwellings in the UK : the Salford Energy House case study

There is a clear consensus that improving energy efficiency of existing housing stock is necessary to meet the UK’s legally binding carbon emission targets by 2050. The aim of this research is to assess the energy saving potentials from building retrofit using an end terrace house, similar houses represent about 30% of the existing building stock in the UK. The Salford Energy House - a unique pre-1919 Victorian end terrace house built within an environmental chamber was used. Retrofit modelling analysis was carried out using IESVE - a dynamic thermal simulation tool. The retrofitted model was also evaluated using future projected climate data (CIBSE latest release) to examine energy demands and overheating. Findings show that improving building fabric thermal characteristics can reduce space heating demands substantially. Heating modes, set point preferences and infiltration level all have strong impact on heating demands. Space heating demand savings can be as much as 77% when the property facades were upgraded to the similar requirements of Passivhaus standards. The research implicates that, for dwelling retrofit practices, a whole house holistic approach should be the preferred option to improve energy efficiency. With future climate scenarios where temperatures are potentially elevated, the heating demands can be potentially reduced as much as 27%. The likelihood of overheating in dwellings after a deep retrofit due to future elevated temperatures becomes apparent. Therefore, mitigation of overheating risk becomes a necessity for future domestic housing stock retrofit planning and policy making. The research presented in this paper highlights the effectiveness of various retrofit measures individually as well as holistically, also the implications on energy demands and the likelihood of overheating in dwellings under future climate scenarios

Period halving of Persistent Currents in Mesoscopic Mobius ladders

We investigate the period halving of persistent currents(PCs) of non-interacting electrons in isolated mesoscopic M\"{o}bius ladders without disorder, pierced by Aharonov-Bhom flux. The mechanisms of the period halving effect depend on the parity of the number of electrons as well as on the interchain hopping. Although the data of PCs in mesoscopic systems are sample-specific, some simple rules are found in the canonical ensemble average, such as all the odd harmonics of the PCs disappear, and the signals of even harmonics are non-negative. {PACS number(s): 73.23.Ra, 73.23.-b, 68.65.-k}Comment: 6 Pages with 3 EPS figure

Dynamic Analysis of a Two Member Manipulator

Attenuating start-up and stopping vibrations when maneuvering large payloads attached to flexible manipulator systems is a great concern for many space missions. To address this concern, it was proposed that the use of smart materials, and their applications in smart structures, may provide an effective method of control for aerospace structures. In this paper, a modified finite element model has been developed to simulate the performance of piezoelectric ceramic actuators, and was applied to a flexible two-arm manipulator system. Connected to a control voltage, the piezoelectric actuators produce control moments based on the optimal control theory. The computer simulation modeled the end-effector vibration suppression of the NASA manipulator testbed for berthing operations of the Space Shuttle to the Space Station. The results of the simulation show that the bonded piezoelectric actuators can effectively suppress follow-up vibrations of the end-effector, stimulated by some external disturbance