Excess Observed in CDF Bs0→μ+μ−B^0_s \to \mu^{+} \mu^{-} and SUSY at the LHC

The recent excess observed by CDF in $B^0_s \to \mu^{+} \mu^{-}$ is interpreted in terms of a possible supersymmetric origin. An analysis is given of the parameter space of mSUGRA and non-universal SUGRA models under the combined constraints from LHC-7 with 165 pb$^{-1}$ of integrated luminosity, under the new XENON-100 limits on the neutralino-proton spin independent cross section and under the CDF $B^0_s \to \mu^{+} \mu^{-}$ 90% C.L. limit reported to arise from an excess number of dimuon events. It is found that the predicted value of the branching ratio $B^0_s \to \mu^{+} \mu^{-}$ consistent with all the constraints contains the following set of NLSPs: chargino, stau, stop or CP odd (even) Higgs. The lower bounds of sparticles, including those from the LHC, XENON and CDF $B^0_s\to \mu^+\mu^-$ constraint, are exhibited and the shift in the allowed range of sparticle masses arising solely due to the extra constraint from the CDF result is given. It is pointed out that the two sided CDF 90% C.L. limit puts upper bounds on sparticle masses. An analysis of possible signatures for early discovery at the LHC is carried out corresponding to the signal region in $B^0_s \to \mu^{+} \mu^{-}$. Implications of GUT-scale non-universalities in the gaugino and Higgs sectors are discussed. If the excess seen by the CDF Collaboration is supported by further data from LHCb or D0, this new result could be a harbinger for the discovery of supersymmetry.Comment: References added, text update

Facile Protocol for Water-Tolerant “Frustrated Lewis Pair”-Catalyzed Hydrogenation

Despite rapid advances in the field of metal-free, “frustrated Lewis pair” (FLP)-catalyzed hydrogenation, the need for strictly anhydrous reaction conditions has hampered wide-scale uptake of this methodology. Herein, we report that, despite the generally perceived moisture sensitivity of FLPs, 1,4-dioxane solutions of B(C6F5)3 actually show appreciable moisture tolerance and can catalyze hydrogenation of a range of weakly basic substrates without the need for rigorously inert conditions. In particular, reactions can be performed directly in commercially available nonanhydrous solvents without subsequent drying or use of internal desiccants

Is strong CP invariance due to a massless up quark?

A standing mystery in the Standard Model is the unnatural smallness of the strong CP violating phase. A massless up quark has long been proposed as one potential solution. A lattice calculation of the constants of the chiral Lagrangian essential for the determination of the up quark mass, 2 alpha_8 - alpha_5, is presented. We find 2 alpha_8 - alpha_5 = 0.29 +/- 0.18, which corresponds to m_u / m_d = 0.410 +/- 0.036. This is the first such calculation using a physical number of dynamical light quarks, N_f = 3.Comment: 4 pages, 5 figures, submitted to Phys. Rev. Lett., corrected small normalization error in f_pi (conclusions were unaffected), improved lattice spacing analysis, improved finite volume analysi

Wide-Field Chandra X-Ray Observations of AGN in Abell 85 & Abell 754

To better understand the mechanism or mechanisms that lead to AGN activity today, we measure the X-ray AGN fraction in a new sample of nearby clusters and examine how it varies with galaxy properties, projected cluster-centric radius, and cluster velocity dispersion. We present new wide-field Chandra X-ray Observatory observations of Abell 85, Abell 754 and the background cluster Abell 89B out to their virial radii. Out of seventeen X-ray sources associated with galaxies in these clusters, we classify seven as X-ray AGN with L_{X,B} > 10^{41} erg/s. Only two of these would be classified as AGN based on their optical spectra. We combine these observations with archival data to create a sample of X-ray AGN from six z < 0.08 clusters and find that 3.4+1.1/-0.8% of M_R 10^{41} erg/s. We find that more X-ray AGN are detected in more luminous galaxies and attribute this to larger spheriods in more luminous galaxies and increased sensitivity to lower Eddington-rate accretion from black holes in those spheroids. At a given X-ray luminosity limit, more massive black holes can be accreting less efficiently, yet still be detected. If interactions between galaxies are the principal drivers of AGN activity, then the AGN fraction should be higher in lower velocity dispersion clusters and the outskirts of clusters. However, the tendency of the most massive and early-type galaxies to lie in the centers of the richest clusters could dilute such trends. While we find no variation in the AGN fraction with projected cluster-centric radius, we do find that the AGN fraction increases significantly from 2.6+1.0/-0.8% in rich clusters to 10.0+6.2/-4.3% in those with lower velocity dispersions.Comment: Accepted by Astrophysical Journal, 17 pages using emulateapj.cls, 10 B & W Figures (degraded): Full resolution paper available at http://www.astronomy.ohio-state.edu/~sivakoff/AGN/XAGN_A85_A754.pd

Design of a Low-Cost Autoclave for Developing World Health Clinics

Incidence of surgical site infection is 2–5 times higher in developing nations as compared to developed nations. A low-cost, easy to use autoclave was designed to address the unique technical, behavioral, and market challenges present in rural, health posts of the developing world. A thorough stakeholder analysis was performed very early in the design process to address non-technical needs for sustained user adoption as well as manufacturability and scalability. Twelve partnering clinics in Nepal trialed these autoclaves from July until December 2012. Usage statistics and follow-up observations highlight important factors for successful adoption. These findings were used to improve the autoclave design. The goal of this paper is to detail a case study and methodology to incorporate multiple stakeholder needs into the early design process.MIT IDEAS Global ChallengeMassachusetts Institute of Technology. Priscilla King Gray Public Service CenterMIT International Development Initiativ

Lenient multi-agent deep reinforcement learning

Much of the success of single agent deep reinforcement learning (DRL) in recent years can be attributed to the use of experience replay memories (ERM), which allow Deep Q-Networks (DQNs) to be trained efficiently through sampling stored state transitions. However, care is required when using ERMs for multi-agent deep reinforcement learning (MA-DRL), as stored transitions can become outdated because agents update their policies in parallel [11]. In this work we apply leniency [23] to MA-DRL. Lenient agents map state-action pairs to decaying temperature values that control the amount of leniency applied towards negative policy updates that are sampled from the ERM. This introduces optimism in the value-function update, and has been shown to facilitate cooperation in tabular fully-cooperative multi-agent reinforcement learning problems. We evaluate our Lenient-DQN (LDQN) empirically against the related Hysteretic-DQN (HDQN) algorithm [22] as well as a modified version we call scheduled-HDQN, that uses average reward learning near terminal states. Evaluations take place in extended variations of the Coordinated Multi-Agent Object Transportation Problem (CMOTP) [8] which include fully-cooperative sub-tasks and stochastic rewards. We find that LDQN agents are more likely to converge to the optimal policy in a stochastic reward CMOTP compared to standard and scheduled-HDQN agents

Template-induced structuring and tunable polymorphism of three-dimensionally ordered mesoporous (3DOm) metal oxides

Convectively assembled colloidal crystal templates, composed of size-tunable (ca. 15–50 nm) silica (SiO2) nanoparticles, enable versatile sacrificial templating of three-dimensionally ordered mesoporous (3DOm) metal oxides (MOx) at both mesoscopic and microscopic size scales. Specifically, we show for titania (TiO2) and zirconia (ZrO2) how this approach not only enables the engineering of the mesopore size, pore volume, and surface area but can also be leveraged to tune the crystallite polymorphism of the resulting 3DOm metal oxides. Template-mediated volumetric (i.e., interstitial) effects and interfacial factors are shown to preserve the metastable crystalline polymorphs of each corresponding 3DOm oxide (i.e., anatase TiO2 (A-TiO2) and tetragonal ZrO2 (t-ZrO2)) during high-temperature calcination. Mechanistic investigations suggest that this polymorph stabilization is derived from the combined effects of the template–replica (MOx/SiO2) interface and simultaneous interstitial confinement that limit the degree of coarsening during high-temperature calcination of the template–replica composite. The result is the identification of a facile yet versatile templating strategy for realizing 3DOm oxides with (i) surface areas that are more than an order of magnitude larger than untemplated control samples, (ii) pore diameters and volumes that can be tuned across a continuum of size scales, and (iii) selectable polymorphism