Chassis Dynamometer Torque Control System Design by Direct Inverse Compensation

This paper presents a methodology for the design of a robust torque control system for a transient 1.2m (48in) dia, 120 kW, DC Chassis Dynamometer. The method includes system identification of the nonlinear dynamometer torque supply system, linearisation by direct inverse compensation, and linear identification of both the compensated and uncompensated plants. A combined feedforward-feedback control structure is proposed and robust feedback controllers are designed using a fixed-order parameter space method. Keywords: Chassis Dynamometer, Direct Inverse Control, Feedback,Feedforward, Identification, Parameter Space, Multiplicative Uncertainty, Nonlinear, Road-Load Simulation

Phase-slip induced dissipation in an atomic Bose-Hubbard system

Phase slips play a primary role in dissipation across a wide spectrum of bosonic systems, from determining the critical velocity of superfluid helium to generating resistance in thin superconducting wires. This subject has also inspired much technological interest, largely motivated by applications involving nanoscale superconducting circuit elements, e.g., standards based on quantum phase-slip junctions. While phase slips caused by thermal fluctuations at high temperatures are well understood, controversy remains over the role of phase slips in small-scale superconductors. In solids, problems such as uncontrolled noise sources and disorder complicate the study and application of phase slips. Here we show that phase slips can lead to dissipation for a clean and well-characterized Bose-Hubbard (BH) system by experimentally studying transport using ultra-cold atoms trapped in an optical lattice. In contrast to previous work, we explore a low velocity regime described by the 3D BH model which is not affected by instabilities, and we measure the effect of temperature on the dissipation strength. We show that the damping rate of atomic motion-the analogue of electrical resistance in a solid-in the confining parabolic potential fits well to a model that includes finite damping at zero temperature. The low-temperature behaviour is consistent with the theory of quantum tunnelling of phase slips, while at higher temperatures a cross-over consistent with the transition to thermal activation of phase slips is evident. Motion-induced features reminiscent of vortices and vortex rings associated with phase slips are also observed in time-of-flight imaging.Comment: published in Nature 453, 76 (2008

Multilevel Deconstruction of the In Vivo Behavior of Looped DNA-Protein Complexes

Protein-DNA complexes with loops play a fundamental role in a wide variety of cellular processes, ranging from the regulation of DNA transcription to telomere maintenance. As ubiquitous as they are, their precise in vivo properties and their integration into the cellular function still remain largely unexplored. Here, we present a multilevel approach that efficiently connects in both directions molecular properties with cell physiology and use it to characterize the molecular properties of the looped DNA-lac repressor complex while functioning in vivo. The properties we uncover include the presence of two representative conformations of the complex, the stabilization of one conformation by DNA architectural proteins, and precise values of the underlying twisting elastic constants and bending free energies. Incorporation of all this molecular information into gene-regulation models reveals an unprecedented versatility of looped DNA-protein complexes at shaping the properties of gene expression.Comment: Open Access article available at http://www.plosone.org/article/fetchArticle.action?articleURI=info%3Adoi%2F10.1371%2Fjournal.pone.000035

First-in-human technique translation of oxygen-enhanced MRI to an MR Linac system in patients with head and neck cancer

BACKGROUND AND PURPOSE: Tumour hypoxia is prognostic in head and neck cancer (HNC), associated with poor loco-regional control, poor survival and treatment resistance. The advent of hybrid MRI - radiotherapy linear accelerator or 'MR Linac' systems - could permit imaging for treatment adaptation based on hypoxic status. We sought to develop oxygen-enhanced MRI (OE-MRI) in HNC and translate the technique onto an MR Linac system. MATERIALS AND METHODS: MRI sequences were developed in phantoms and 15 healthy participants. Next, 14 HNC patients (with 21 primary or local nodal tumours) were evaluated. Baseline tissue longitudinal relaxation time (T1) was measured alongside the change in 1/T1 (termed ΔR1) between air and oxygen gas breathing phases. We compared results from 1.5 T diagnostic MR and MR Linac systems. RESULTS: Baseline T1 had excellent repeatability in phantoms, healthy participants and patients on both systems. Cohort nasal concha oxygen-induced ΔR1 significantly increased (p < 0.0001) in healthy participants demonstrating OE-MRI feasibility. ΔR1 repeatability coefficients (RC) were 0.023-0.040 s-1 across both MR systems. The tumour ΔR1 RC was 0.013 s-1 and the within-subject coefficient of variation (wCV) was 25% on the diagnostic MR. Tumour ΔR1 RC was 0.020 s-1 and wCV was 33% on the MR Linac. ΔR1 magnitude and time-course trends were similar on both systems. CONCLUSION: We demonstrate first-in-human translation of volumetric, dynamic OE-MRI onto an MR Linac system, yielding repeatable hypoxia biomarkers. Data were equivalent on the diagnostic MR and MR Linac systems. OE-MRI has potential to guide future clinical trials of biology guided adaptive radiotherapy

Secular evolution versus hierarchical merging: galaxy evolution along the Hubble sequence, in the field and rich environments

In the current galaxy formation scenarios, two physical phenomena are invoked to build disk galaxies: hierarchical mergers and more quiescent external gas accretion, coming from intergalactic filaments. Although both are thought to play a role, their relative importance is not known precisely. Here we consider the constraints on these scenarios brought by the observation-deduced star formation history on the one hand, and observed dynamics of galaxies on the other hand: the high frequency of bars and spirals, the high frequency of perturbations such as lopsidedness, warps, or polar rings. All these observations are not easily reproduced in simulations without important gas accretion. N-body simulations taking into account the mass exchange between stars and gas through star formation and feedback, can reproduce the data, only if galaxies double their mass in about 10 Gyr through gas accretion. Warped and polar ring systems are good tracers of this accretion, which occurs from cold gas which has not been virialised in the system's potential. The relative importance of these phenomena are compared between the field and rich clusters. The respective role of mergers and gas accretion vary considerably with environment.Comment: 18 pages, 8 figures, review paper to "Penetrating Bars through Masks of Cosmic Dust: the Hubble Tuning Fork Strikes a New Note", Pilanesberg, ed. D. Block et al., Kluwe

Carbon stable isotope analysis of cereal remains as a way to reconstruct water availability: preliminary results

Reconstructing past water availability, both as rainfall and irrigation, is important to answer questions about the way society reacts to climate and its changes and the role of irrigation in the development of social complexity. Carbon stable isotope analysis of archaeobotanical remains is a potentially valuable method for reconstructing water availability. To further define the relationship between water availability and plant carbon isotope composition and to set up baseline values for the Southern Levant, grains of experimentally grown barley and sorghum were studied. The cereal crops were grown at three stations under five different irrigation regimes in Jordan. Results indicate that a positive but weak relationship exists between irrigation regime and total water input of barley grains, but no relationship was found for sorghum. The relationship for barley is site-specific and inter-annual variation was present at Deir ‘Alla, but not at Ramtha and Khirbet as-Samra

Therapeutic aims of drugs offering only progression-free survival are misunderstood by patients, and oncologists may be overly optimistic about likely benefits

PURPOSE: The use of novel and often expensive drugs offering limited survival benefit in advanced disease is controversial. Treatment recommendations are influenced by patient characteristics and trial data showing overall response rates (ORR), progression-free survival (PFS) and overall survival (OS). PFS is frequently the primary outcome in licencing studies. PATIENTS AND METHODS: As part of a longitudinal study Assessing the 'VALue' to patients of PROgression Free Survival (AVALPROFS), oncologists completed checklists at baseline following consultations with patients. Questions probed perceived clinical benefits of the drugs to populations in general. Patients completed study-specific interview schedules at baseline, 6 weeks into treatment, and at withdrawal due to toxicity or progression. Patients also completed tumour- and treatment-specific quality of life questionnaires monthly for their time in the study. Only baseline results are reported here. RESULTS: Thirty-two UK oncologists discussed management options with 90 patients with heterogeneous advanced cancers. Oncologists' estimates of medical benefit in general from treatment varied between 10 and 80 %. They expected 46/90 (51 %) of their patients to derive some clinical benefit from the prescribed treatment but were either unsure or expected none for 44/90 (49 %). Predictions of life expectancy were variable but 62 % (56/90) of patients were expected to survive longer with treatment. A majority of patients 51/90 (57 %) had 'no idea' or were 'unclear' what PFS meant and 45/90 (50 %) thought extension of life was the primary therapeutic aim of treatment. CONCLUSION: Discussions between doctors and patients with metastatic disease about future management plans and likely therapeutic gains are challenging. Factors influencing decisions about putative benefits of novel drugs are often applied inconsistently can be overly optimistic and may even contradict published data

“In the Beginning, It Was Little Whispers...Now, We’re Almost a Roar”: Conceptualizing a Model for Community and Self in LGBTQ+ Health Information Practices

Although LGBTQ+ populations experience significant health challenges, little research exists that investigates their health from an informational perspective. Our study addresses this gap by exploring the health information practices of LGBTQ+ communities in South Carolina, focusing on how sociocultural context shapes these practices. Thirty semi-structured interviews with South Carolina LGBTQ+ community leaders analyzed using open qualitative coding informed the development of a conceptual framework describing their information practices. Findings show that participants engaged in two broad types of practices – protective and defensive – as responses to risks and barriers experienced, which are in turn produced by social and structural factors. Findings advance information practices and marginalization approaches and offer ways for medical professionals to improve service to LGBTQ+ populations