Solid friction between soft filaments

Any macroscopic deformation of a filamentous bundle is necessarily accompanied by local sliding and/or stretching of the constituent filaments. Yet the nature of the sliding friction between two aligned filaments interacting through multiple contacts remains largely unexplored. Here, by directly measuring the sliding forces between two bundled F-actin filaments, we show that these frictional forces are unexpectedly large, scale logarithmically with sliding velocity as in solid-like friction, and exhibit complex dependence on the filaments' overlap length. We also show that a reduction of the frictional force by orders of magnitude, associated with a transition from solid-like friction to Stokes' drag, can be induced by coating F-actin with polymeric brushes. Furthermore, we observe similar transitions in filamentous microtubules and bacterial flagella. Our findings demonstrate how altering a filament's elasticity, structure and interactions can be used to engineer interfilament friction and thus tune the properties of fibrous composite materials

The Hopf algebra of Feynman graphs in QED

We report on the Hopf algebraic description of renormalization theory of quantum electrodynamics. The Ward-Takahashi identities are implemented as linear relations on the (commutative) Hopf algebra of Feynman graphs of QED. Compatibility of these relations with the Hopf algebra structure is the mathematical formulation of the physical fact that WT-identities are compatible with renormalization. As a result, the counterterms and the renormalized Feynman amplitudes automatically satisfy the WT-identities, which leads in particular to the well-known identity $Z_1=Z_2$.Comment: 13 pages. Latex, uses feynmp. Minor corrections; to appear in LM

Data model issues in the Cherenkov Telescope Array project

The planned Cherenkov Telescope Array (CTA), a future ground-based Very-High-Energy (VHE) gamma-ray observatory, will be the largest project of its kind. It aims to provide an order of magnitude increase in sensitivity compared to currently operating VHE experiments and open access to guest observers. These features, together with the thirty years lifetime planned for the installation, impose severe constraints on the data model currently being developed for the project. In this contribution we analyze the challenges faced by the CTA data model development and present the requirements imposed to face them. While the full data model is still not completed we show the organization of the work, status of the design, and an overview of the prototyping efforts carried out so far. We also show examples of specific aspects of the data model currently under development.Comment: In Proceedings of the 34th International Cosmic Ray Conference (ICRC2015), The Hague, The Netherlands. All CTA contributions at arXiv:1508.0589

Chemical and physical small-scale structure in a pre-stellar core

We present a comparative study of several molecular lines and of the dust contiunuum at 1.2mm in a pre-stellar core that is embedded in the Galactic cirrus cloud MCLD123.5+24.9. Previous studies found that the core is gravitationally stable and shows signs of inward motion. Using the Owens Valley (OVRO) and Plateau de Bure (PdB) interferometers we obtained high-angular resolution maps of the core in the carbon monosulfide CS 2-1 and the cyanoacetylene HC3N 10-9 transitions. Together with CS 5-4, C34S 3-2, and bolometer data obtained with the IRAM 30m telescope, we analyse the excitation conditions and the structural properties of the cloud. On the one hand, the new CS 2-1 observations reveal significant substructure on a scale of about 7", i.e., the beam size, corresponding to about 1050 AU at an adopted distance of 150pc. On the other hand, the interferometric observations in the HC3N 10-9 transition shows just one single well resolved clump in the inner part of the core. This core is well described by an intensity profile following from a centrally peaked volume density distribution. We find no evidence for depletion of CS onto dust grains. The inward motion seen in the CS 2-1 occurs one-sided from the middle of the filamentary cloud towards the HC3N core.Comment: 8 pages, 8 figures, accepted by A&

Cherenkov Telescope Array Data Management

Very High Energy gamma-ray astronomy with the Cherenkov Telescope Array (CTA) is evolving towards the model of a public observatory. Handling, processing and archiving the large amount of data generated by the CTA instruments and delivering scientific products are some of the challenges in designing the CTA Data Management. The participation of scientists from within CTA Consortium and from the greater worldwide scientific community necessitates a sophisticated scientific analysis system capable of providing unified and efficient user access to data, software and computing resources. Data Management is designed to respond to three main issues: (i) the treatment and flow of data from remote telescopes; (ii) "big-data" archiving and processing; (iii) and open data access. In this communication the overall technical design of the CTA Data Management, current major developments and prototypes are presented.Comment: 8 pages, 2 figures, In Proceedings of the 34th International Cosmic Ray Conference (ICRC2015), The Hague, The Netherlands. All CTA contributions at arXiv:1508.0589

What do general practitioners know about ADHD? Attitudes and knowledge among first-contact gatekeepers: systematic narrative review

Background: Attention Deficit Hyperactivity Disorder (ADHD) is a common childhood disorder with international prevalence estimates of 5 % in childhood, yet significant evidence exists that far fewer children receive ADHD services. In many countries, ADHD is assessed and diagnosed in specialist mental health or neuro-developmental paediatric clinics, to which referral by General (Family) Practitioners (GPs) is required. In such ‘gatekeeper’ settings, where GPs act as a filter to diagnosis and treatment, GPs may either not recognise potential ADHD cases, or may be reluctant to refer. This study systematically reviews the literature regarding GPs’ views of ADHD in such settings. Methods: A search of nine major databases was conducted, with wide search parameters; 3776 records were initially retrieved. Studies were included if they were from settings where GPs are typically gatekeepers to ADHD services; if they addressed GPs’ ADHD attitudes and knowledge; if methods were clearly described; and if results for GPs were reported separately from those of other health professionals. Results: Few studies specifically addressed GP attitudes to ADHD. Only 11 papers (10 studies), spanning 2000–2010, met inclusion criteria, predominantly from the UK, Europe and Australia. As studies varied methodologically, findings are reported as a thematic narrative, under the following themes: Recognition rate; ADHD controversy (medicalisation, stigma, labelling); Causes of ADHD; GPs and ADHD diagnosis; GPs and ADHD treatment; GP ADHD training and sources of information; and Age, sex differences in knowledge and attitudes. Conclusions: Across times and settings, GPs practising in first-contact gatekeeper settings had mixed and often unhelpful attitudes regarding the validity of ADHD as a construct, the role of medication and how parenting contributed to presentation. A paucity of training was identified, alongside a reluctance of GPs to become involved in shared care practice. If access to services is to be improved for possible ADHD cases, there needs to be a focused and collaborative approach to training

How Low Can You Go?: Widespread Challenges in Measuring Low Stream Discharge and a Path Forward

Low flows pose unique challenges for accurately quantifying streamflow. Current field methods are not optimized to measure these conditions, which in turn, limits research and management. In this essay, we argue that the lack of methods for measuring low streamflow is a fundamental challenge that must be addressed to ensure sustainable water management now and into the future, particularly as climate change shifts more streams to increasingly frequent low flows. We demonstrate the pervasive challenge of measuring low flows, present a decision support tool (DST) for navigating best practices in measuring low flows, and highlight important method developmental needs

Observations of Arp 220 using Herschel-SPIRE: An Unprecedented View of the Molecular Gas in an Extreme Star Formation Environment

We present Herschel SPIRE-FTS observations of Arp~220, a nearby ULIRG. The FTS continuously covers 190 -- 670 microns, providing a good measurement of the continuum and detection of several molecular and atomic species. We detect luminous CO (J = 4-3 to 13-12) and water ladders with comparable total luminosity; very high-J HCN absorption; OH+, H2O+, and HF in absorption; and CI and NII. Modeling of the continuum yields warm dust, with T = 66 K, and an unusually large optical depth of ~5 at 100 microns. Non-LTE modeling of the CO shows two temperature components: cold molecular gas at T ~ 50 K and warm molecular gas at T ~1350 K. The mass of the warm gas is 10% of the cold gas, but dominates the luminosity of the CO ladder. The temperature of the warm gas is in excellent agreement with H2 rotational lines. At 1350 K, H2 dominates the cooling (~20 L_sun/M_sun) in the ISM compared to CO (~0.4 L_sun/M_sun). We found that only a non-ionizing source such as the mechanical energy from supernovae and stellar winds can excite the warm gas and satisfy the energy budget of ~20 L_sun/M_sun. We detect a massive molecular outflow in Arp 220 from the analysis of strong P-Cygni line profiles observed in OH+, H2O+, and H2O. The outflow has a mass > 10^{7} M_sun and is bound to the nuclei with velocity < 250 km/s. The large column densities observed for these molecular ions strongly favor the existence of an X-ray luminous AGN (10^{44} ergs/s) in Arp 220.Comment: Accepted in ApJ on September 1, 201

The impact of pre‐operative intravenous iron on quality of life after colorectal cancer surgery: outcomes from the intravenous iron in colorectal cancer‐associated anaemia (IVICA) trial

Anaemia is associated with a reduction in quality of life, and is common in patients with colorectal cancer . Werecently reported thefindings of the intravenous iron in colorectal cancer-associated anaemia (IVICA) trialcomparing haemoglobin levels and transfusion requirements following intravenous or oral iron replacement inanaemic colorectal cancer patients undergoing elective surgery. In this follow-up study, we compared theefficacy of intravenous and oral iron at improving quality of life in this patient group. We conducted amulticentre, open-label randomised controlled trial. Anaemic colorectal cancer patients were randomlyallocated at least two weeks pre-operatively, to receive either oral (ferrous sulphate) or intravenous (ferriccarboxymaltose) iron. We assessed haemoglobin and quality of life scores at recruitment, immediately beforesurgery and at outpatient review approximately three months postoperatively, using the Short Form 36,EuroQoL 5-dimension 5-level and Functional Assessment of Cancer Therapy–Anaemia questionnaires. Werecruited 116 anaemic patients across seven UK centres (oral iron n=61 (53%), and intravenous iron n=55(47%)). Eleven quality of life components increased by a clinically significant margin in the intravenous irongroup between recruitment and surgery compared with one component for oral iron. Median (IQR [range])visual analogue scores were significantly higher with intravenous iron at a three month outpatient review (oraliron 70, (60–85 [20–95]); intravenous iron 90 (80–90 [50–100]), p=0.001). The Functional Assessment ofCancer Therapy–Anaemia score comprises of subscales related to cancer, fatigue and non-fatigue itemsrelevant to anaemia. Median outpatient scores were higher, and hence favourable, for intravenous iron on theFunctional Assessment of Cancer Therapy–Anaemia subscale (oral iron 66 (55–72 [23–80]); intravenous iron 71(66–77 [46–80]); p=0.002), Functional Assessment of Cancer Therapy–Anaemia trial outcome index (oral iron108 (90–123 [35–135]); intravenous iron 121 (113–124 [81–135]); p=0.003) and Functional Assessment ofCancer Therapy–Anaemia total score (oral iron 151 (132–170 [69–183]); intravenous iron 168 (160–174 [125–186]); p=0.005). Thesefindings indicate that intravenous iron is more efficacious at improving quality of lifescores than oral iron in anaemic colorectal cancer patients