A review of fracture mechanics life technology

Current lifetime prediction technology for structural components subjected to cyclic loads was reviewed. The central objectives of the project were to report the current state of and recommend future development of fracture mechanics-based analytical tools for modeling and forecasting subcritical fatigue crack growth in structures. Of special interest to NASA was the ability to apply these tools to practical engineering problems and the developmental steps necessary to bring vital technologies to this stage. A survey of published literature and numerous discussions with experts in the field of fracture mechanics life technology were conducted. One of the key points made is that fracture mechanics analyses of crack growth often involve consideration of fatigue and fracture under extreme conditions. Therefore, inaccuracies in predicting component lifetime will be dominated by inaccuracies in environment and fatigue crack growth relations, stress intensity factor solutions, and methods used to model given loads and stresses. Suggestions made for reducing these inaccuracies include: development of improved models of subcritical crack growth, research efforts aimed at better characterizing residual and assembly stresses that can be introduced during fabrication, and more widespread and uniform use of the best existing methods

Search for New Physics with Long-Lived Neutral Particles in ATLAS: The Hidden Valley Scenario

With the start of the Large Hadron Collider a new energy frontier will be accessible to experimental particle physics, and many new models and extensions to the Standard Model will be tested. A unique class of these new models are those in which long-lived particles can decay mid-detector, leaving atypical signatures that are often missed by standard LHC-detector triggers. Such models include the Hidden Valley models and some supersymmetric models. Prospects for triggering-on and detecting long-lived neutral particles in the ATLAS detector are presented

Search for new physics with Long-Lived particles in ATLAS: The Hidden Valley Scenario

With the start of the Large Hadron Collider a new energy frontier will be accessible to experimental particle physics, and many new models and extensions to the Standard Model will be tested. A unique class of these new models are those in which long-lived particles can decay mid-detector, leaving atypical signatures that are often missed by standard LHC-detector triggers. Such models include the Hidden Valley models and some supersymmetric models. Prospects for triggering-on and detecting long-lived particles in the ATLAS detector are presented

Layered Fabrication of Branched Networks Using Lindenmayer Systems

A current challenge impeding the growth of bone tissue engineering is the lack of functional scaffolds of geometric sizes greater than 10mm due to the inability of cells to survive deep within the scaffold. It is hypothesized that these scaffolds must have an inbuilt nutrient distribution network to sustain the uniform growth of cells. In this paper, we seek to enhance the design and layered fabrication of scaffold internal architecture through the development of Lindenmayer systems, a graphical language based theory to create nutrient delivery networks. The scaffolds are fabricated using the Texas Instruments DLP™ system through UV‐photopolymerization to produce polyethylene glycol hydrogels with internal branch structures. The paper will discuss the Lindenmayer system, process planning algorithms, layered fabrication of samples, challenges and future tasks.Mechanical Engineerin

Towards a historical ecology of intertidal foraging in the Mafia Archipelago: archaeomalacology and implications for marine resource management

Understanding the timing and nature of human influence on coastal and island ecosystems is becoming a central concern in archaeological research, particularly when investigated within a historical ecology framework. Unfortunately, the coast and islands of eastern Africa have not figured significantly within this growing body of literature, but are important given their historically contingent environmental, social, and political contexts, as well as the considerable threats now posed to marine ecosystems. Here, we begin developing a longer-term understanding of past marine resource use in the Mafia Archipelago (eastern Africa), an area of high ecological importance containing the Mafia Island Marine Park. Focusing on the comparatively less researched marine invertebrates provides a means for initiating discussion on potential past marine ecosystem structure, human foraging and environmental shifts, and the implications for contemporary marine resource management. The available evidence suggests that human-environment interactions over the last 2000 years were complex and dynamic; however, these data raise more questions than answers regarding the specific drivers of changes observed in the archaeomalacological record. This is encouraging as a baseline investigation and emphasizes the need for further engagement with historical ecology by a range of cognate disciplines to enhance our understanding of these complex issues

Interacting Dark Resonances: Interference Effects Induced by Coherently Altered Quantum Superpositions

We predict the possibility of sharp, high-contrast resonances in the optical response of a broad class of systems, wherein interference effects are generated by coherent perturbation or interaction of dark states. The properties of these resonances can be manipulated to design a desired atomic response.Comment: 4 pages, 3 figures, RevTeX, submitted to PRL; changed three numbers in Fig. 3 (caption

Tensions in relation: How peer support is experienced and received in a hepatitis C treatment intervention.

Peer support and involvement is recognised as a vital component of hepatitis C (HCV) treatment provision for marginalised populations, such as people who inject drugs (PWID). Developments in HCV treatments enable increased provision in community settings - expanding the possibilities for meaningful peer involvement in HCV treatment plans. To date, HCV peer support has generally been viewed as a positive intervention, with little critical reflection on the ways social structures, policies, health and drug services and social identity impact on how peer support is experienced and received. We report on the qualitative component of a UK-based intervention designed to increase HCV diagnosis and treatment in primary care and drug treatment settings. Data were collected between 2014 and 2016. Pre-intervention, a total of 35 PWID clients took part in nine in-depth interviews and four focus groups. In addition, 22 drug services and intervention providers took part in two focus groups and nine interviews. Post-intervention, one focus group and eight interviews were conducted with 13 PWID clients, and four focus groups and ten interviews were conducted with 26 drug services and intervention providers. Our data generation and thematic analysis focused on the peer education and buddy support component of the intervention. Participants had common expectations of the peer role (to 'just be there') and its occupants' attributes (empathy, trustworthy, etc.). However, in practice, peers faced constraints on realising these expectations. A 'recovery' dominated drug treatment ethos in the UK appeared to influence the selection of 'recovery champions' as peers for the intervention. This created tensions in relations with clients, particularly when risk-adverse discourses were internalised by the peers. Peers were poorly integrated and supported within the service, affecting opportunities to relate and build trust with clients. Thus, the scope for peer support to impact on the nature and extent of clients' testing and treatment for HCV was limited. The efficacy of peer involvement can be constrained by organisational structures and boundaries - especially regarding who is deemed to be 'a peer'. Peer programmes take time and care to implement and weave into wider recovery and harm reduction frameworks

A Bootstrapping Approach for Generating Maximally Path-Entangled Photon States

We propose a bootstrapping approach to generation of maximally path-entangled states of photons, so called ``NOON states''. Strong atom-light interaction of cavity QED can be employed to generate NOON states with about 100 photons; which can then be used to boost the existing experimental Kerr nonlinearities based on quantum coherence effects to facilitate NOON generation with arbitrarily large number of photons all within the current experimental state of the art technology. We also offer an alternative scheme that uses an atom-cavity dispersive interaction to obtain sufficiently high Kerr-nonlinearity necessary for arbitrary NOON generation

Exactly solvable model with two conductor-insulator transitions driven by impurities

We present an exact analysis of two conductor-insulator transitions in the random graph model. The average connectivity is related to the concentration of impurities. The adjacency matrix of a large random graph is used as a hopping Hamiltonian. Its spectrum has a delta peak at zero energy. Our analysis is based on an explicit expression for the height of this peak, and a detailed description of the localized eigenvectors and of their contribution to the peak. Starting from the low connectivity (high impurity density) regime, one encounters an insulator-conductor transition for average connectivity 1.421529... and a conductor-insulator transition for average connectivity 3.154985.... We explain the spectral singularity at average connectivity e=2.718281... and relate it to another enumerative problem in random graph theory, the minimal vertex cover problem.Comment: 4 pages revtex, 2 fig.eps [v2: new title, changed intro, reorganized text

Photonic band gap via quantum coherence in vortex lattices of Bose gases

We investigate the optical response of an atomic Bose-Einstein condensate with a vortex lattice. We find that it is possible for the vortex lattice to act as a photonic crystal and create photonic band gaps, by enhancing the refractive index of the condensate via a quantum coherent scheme. If high enough index contrast between the vortex core and the atomic sample is achieved, a photonic band gap arises depending on the healing length and the lattice spacing. A wide range of experimentally accessible parameters are examined and band gaps in the visible region of the electromagnetic spectrum are found. We also show how directional band gaps can be used to directly measure the rotation frequency of the condensate.Comment: 4 pages, 4 figures, Final version to appear in PR