Enhanced nonperturbative effects in jet distributions

We consider the triple differential distribution d\Gamma/(dE_J)(dm_J^2)(d\Omega_J) for two-jet events at center of mass energy M, smeared over the endpoint region m_J^2 << M^2, |2 E_J -M| ~ \Delta, \lqcd << \Delta << M. The leading nonperturbative correction, suppressed by \lqcd/\Delta, is given by the matrix element of a single operator. A similar analysis is performed for three jet events, and the generalization to any number of jets is discussed. At order \lqcd/\Delta, non-perturbative effects in four or more jet events are completely determined in terms of two matrix elements which can be measured in two and three jet events.Comment: Significant changes made. The first moment does not vanish--the paper has been modified to reflect this. Relations between different numbers of jets still hol

Comment on Ds∗→Dsπ0D_s^* \to D_s \pi^0 Decay

We calculate the rate for $D_s^* \rightarrow D_s \pi^0$ decay using Chiral Perturbation Theory. This isospin violating process results from $\pi^0$ - $\eta$ mixing, and its amplitude is proportional to $(m_d - m_u)/\bigl(m_s-(m_u+m_d)/2 \bigr)$. Experimental information on the branching ratio for $D_s^* \rightarrow D_s \pi^0$ can provide insight into the pattern of $SU(3)$ violation in radiative $D^*$ decays.Comment: 7 pages with 2 figures not included but available upon request, CALT-68-191

Crew Resource Management and Its Possible Role in Nursing Risk Management

Crew Resource Management (CRM) was introduced within the aviation industry in the late 1970s after an aircraft ran out of fuel whilst the pilots were trying to solve an undercarriage problem. To reduce such errors and ultimately lower the probability of failure and the severity of risks that occur, training in CRM was rolled out across the whole industry. It has been successful over the last few years in major reductions in the number of crashes and fatalities in the commercial aviation sector. Nursing has similar concerns in that errors can ultimately result in fatalities. There are parallels in the needs and expectations of pilots and nurses to assess risk, reduce risk and deliver reliable and dependable professional services. In this paper the parallels of pilots and nurses demands are compared to assess if the lessons learned in aviation can assist nurses deliver procedures with lower risks. The analysis will draw on the demands and expectations and how they both deal with risk, challenging errors and ensuring that identified risks are not overlooked or ignored. Finally, suggestions of adopting, sharing and benchmarking between these two industries can adopt best practices so that both industries can learn from each other

Shape control and whole-life energy assessment of an 'infinitely stiff' prototype adaptive structure

A previously developed design methodology produces optimum adaptive structures that minimise the whole-life energy which is made of an embodied part in the material and an operational part for structural adaptation. Planar and complex spatial reticular structures designed with this method and simulations showed that the adaptive solution achieves savings as high as 70% in the whole-life energy compared to optimised passive solutions. This paper describes a large-scale prototype adaptive structure built to validate the numerical findings and investigate the practicality of the design method. Experimental results show that (1) shape control can be used to achieve 'infinite stiffness' (i.e. to reduce displacements completely) in real-time without predetermined knowledge regarding position, direction and magnitude (within limits) of the external load; (2) the whole-life energy of the structure is in good agreement with that predicted by numerical simulations. This result confirms the proposed design method is reliable and that adaptive structures can achieve substantive total energy savings compared to passive structures

Infinite stiffness structures via active control

Active control has been used in civil engineering structures for a variety of purposes. Although the potential for using deflection-control adaptation to save material has been investigated by a few other authors, little attention has been given to assessing whether these material savings outweigh the energy consumed through control and actuation. Our paper seeks to address this gap, presenting experimental work on a truss with effective infinite stiffness which builds on earlier theoretical studies. Senatore previously developed a design method that produces an optimum adaptive structure that minimises the total energy spent throughout the whole life of the structure (embodied in the materials + operational for the control) (Senatore, et al., 2013). The method was used to design a range of structures from trusses to space frames, both determinate and indeterminate, and it was shown that it allows energy saving up to 70% compared to state of the art optimisation methods. A large scale prototype structure has now been built to validate the numerical findings and investigate the practicality of the method. This paper discusses recent experimental findings and the making of the prototype. Using the insight acquired after the making and testing of the prototype the authors will discuss potential applications of adaptive structures in selection of different scenarios, ranging from cantilever seating tiers in sports stands to lightweight roofs to slender beams with 80:1 span/depth ratio

Designing adaptive structures for whole life energy savings

Designing structures with minimal environmental impact is emerging as a seriou concern in the construction sector. Conventional structural design practice involves designing first for strength, followed by secondary checks on deflections and other serviceability limits states. If these limits are exceeded, the con-ventional solution has been to add material to increase stiffness. When the design is governed by unpredicta-ble events such as fluctuating loads, strong wind storms or earthquakes, the structure is effectively overde-signed for most of its working life. This paper presents a methodology to design adaptive structures that minimize the whole life energy consumption. The methodology is illustrated on plane pin-jointed trusses, both determinate and indeterminate. Strategically placing actuators allow the internal flow of forces to be ho-mogenized and displacements to be controlled. The actuators only start working when the loads reach a cer-tain threshold. Below this threshold, the structure resists loads mainly passively thereby limiting significantly the operational energy used. It was found that both indeterminate and determinate topologies bring substantial energy savings up to 70% of the total energy

Chiral Perturbation Theory for τ→ρπντ\tau \to \rho \pi\nu_\tau, τ→K∗πντ\tau \to K^* \pi \nu_\tau, and τ→ωπντ\tau \to \omega \pi \nu_\tau

We use heavy vector meson $SU(2)_L \times SU(2)_R$ chiral perturbation theory to predict differential decay distributions for $\tau \rightarrow \rho \pi \nu_\tau$ and $\tau \rightarrow K^* \pi \nu_\tau$ in the kinematic region where $p_V \cdot p_\pi/m_V$ (here $V = \rho$ or $K^*$) is much smaller than the chiral symmetry breaking scale. Using the large number of colors limit we also predict the rate for $\tau \rightarrow \omega \pi \nu_\tau$ in this region (now $V = \omega$). Comparing our prediction with experimental data, we determine one of the coupling constants in the heavy vector meson chiral Lagrangian.Comment: 14 pages, latex 2e. We include the decay of the tau into the omega, pi minus and the tau neutrino, and extract a value for the coupling constant g2, using experimental dat

Criteria for the experimental observation of multi-dimensional optical solitons in saturable media

Criteria for experimental observation of multi-dimensional optical solitons in media with saturable refractive nonlinearities are developed. The criteria are applied to actual material parameters (characterizing the cubic self-focusing and quintic self-defocusing nonlinearities, two-photon loss, and optical-damage threshold) for various glasses. This way, we identify operation windows for soliton formation in these glasses. It is found that two-photon absorption sets stringent limits on the windows. We conclude that, while a well-defined window of parameters exists for two-dimensional solitons (spatial or spatiotemporal), for their three-dimensional spatiotemporal counterparts such a window \emph{does not} exist, due to the nonlinear loss in glasses.Comment: 8 pages, to appear in Phys. Rev.