IPM synchronous machine drive response to symmetrical and asymmetrical short circuit faults

Copyright © 2003 IEEEA closed-form solution is presented for the steady-state response of interior permanent magnet (IPM) synchronous machines to symmetrical short circuits including the effects of q-axis magnetic saturation. Machine response to single-phase asymmetrical short circuits is also investigated. Experimental data are presented to verify predicted behavior for both types of short circuits. It is shown that single-phase asymmetrical short circuit faults produce more severe fault responses with high pulsating torque and a significant threat of rotor demagnetization. A control strategy that purposely transitions such faults into symmetrical three-phase short circuits can minimize the fault severity and associated demagnetization risks. Implications for the design of IPM machines with improved fault tolerance are discussed.Brian A. Welchko, Thomas M. Jahns, Wen L. Soong and James M. Nagashima

Benchmarking of 3D space charge codes using direct phase space measurements from photoemission high voltage DC gun

We present a comparison between space charge calculations and direct measurements of the transverse phase space for space charge dominated electron bunches after a high voltage photoemission DC gun followed by an emittance compensation solenoid magnet. The measurements were performed using a double-slit setup for a set of parameters such as charge per bunch and the solenoid current. The data is compared with detailed simulations using 3D space charge codes GPT and Parmela3D with initial particle distributions created from the measured transverse and temporal laser profiles. Beam brightness as a function of beam fraction is calculated for the measured phase space maps and found to approach the theoretical maximum set by the thermal energy and accelerating field at the photocathode.Comment: 11 pages, 23 figures. submitted to Phys Rev ST-A

The Amplitude of Non-Equilibrium Quantum Interference in Metallic Mesoscopic Systems

We study the influence of a DC bias voltage V on quantum interference corrections to the measured differential conductance in metallic mesoscopic wires and rings. The amplitude of both universal conductance fluctuations (UCF) and Aharonov-Bohm effect (ABE) is enhanced several times for voltages larger than the Thouless energy. The enhancement persists even in the presence of inelastic electron-electron scattering up to V ~ 1 mV. For larger voltages electron-phonon collisions lead to the amplitude decaying as a power law for the UCF and exponentially for the ABE. We obtain good agreement of the experimental data with a model which takes into account the decrease of the electron phase-coherence length due to electron-electron and electron-phonon scattering.Comment: New title, refined analysis. 7 pages, 3 figures, to be published in Europhysics Letter

Macroscopic transport by synthetic molecular machines

Nature uses molecular motors and machines in virtually every significant biological process, but demonstrating that simpler artificial structures operating through the same gross mechanisms can be interfaced with—and perform physical tasks in—the macroscopic world represents a significant hurdle for molecular nanotechnology. Here we describe a wholly synthetic molecular system that converts an external energy source (light) into biased brownian motion to transport a macroscopic cargo and do measurable work. The millimetre-scale directional transport of a liquid on a surface is achieved by using the biased brownian motion of stimuli-responsive rotaxanes (‘molecular shuttles’) to expose or conceal fluoroalkane residues and thereby modify surface tension. The collective operation of a monolayer of the molecular shuttles is sufficient to power the movement of a microlitre droplet of diiodomethane up a twelve-degree incline.

Relativistic effects and two-body currents in 2H(e⃗,e′p)n^{2}H(\vec{e},e^{\prime}p)n using out-of-plane detection

Measurements of the ${^2}H(\vec{e},e^{\prime}p)n$ reaction were performed using an 800-MeV polarized electron beam at the MIT-Bates Linear Accelerator and with the out-of-plane magnetic spectrometers (OOPS). The longitudinal-transverse, $f_{LT}$ and $f_{LT}^{\prime}$, and the transverse-transverse, $f_{TT}$, interference responses at a missing momentum of 210 MeV/c were simultaneously extracted in the dip region at Q$^2$=0.15 (GeV/c)$^2$. On comparison to models of deuteron electrodisintegration, the data clearly reveal strong effects of relativity and final-state interactions, and the importance of the two-body meson-exchange currents and isobar configurations. We demonstrate that these effects can be disentangled and studied by extracting the interference response functions using the novel out-of-plane technique.Comment: 4 pages, 4 figures, and submitted to PRL for publicatio

Protocol for a scoping review on information needs and information-seeking behaviour of people with dementia and their non-professional caregivers

Background: Dementia is a debilitating disease that can lead to major changes in a patient’s behaviour and function. It is important to educate both dementia patients and their non-professional caregivers about the disease. Yet, currently available sources do not seem to be effective for patients and caregivers, who report a need for more information and guidance. A systematic identification of the patients’ and caregivers’ needs for information and information seeking behaviour is needed to create information resources that are relevant and beneficial to the target population. Objective: This is a protocol for a scoping review aimed at gathering knowledge on the information needs and information seeking behaviour of dementia patients and their non- professional caregivers. Our aim is also to provide recommendations for development of future dementia information resources. Methods: The study will commence in November 2018. Both quantitative and qualitative studies on the information needs of dementia patients or caregivers will be examined using Arksey and O’Malley’s methodological framework for scoping studies. A comprehensive literature search will be conducted in electronic databases and grey literature sources. We will also screen reference lists of included studies and related systematic reviews for additional eligible studies. Two authors will perform screening of citations for eligibility, and independently extract data from the included studies in parallel. Any discrepancies will be resolved through discussion. The findings will be presented through a narrative synthesis and reported in line with PRISMA reporting guidelines. Ethics and dissemination: In this review, all included data will originate from published literature. Ethics approval is therefore not a requirement. We will present our findings at relevant conferences and will submit them for publication in peer-reviewed journals. Strengths and limitations of this study • In this scoping review, we will perform a comprehensive search of electronic databases and grey literature sources to identify up-to-date evidence on information needs and information seeking behaviour of dementia patients and their informal caregivers. • We will seek to identify evidence on information needs and information seeking behaviour of both dementia patients and their caregivers. • As this is a scoping review, a formal quality and risk of bias assessment of the included literature will not be performed. • This review will only include studies published in English

Caveolin-1 protects B6129 mice against Helicobacter pylori gastritis.

Caveolin-1 (Cav1) is a scaffold protein and pathogen receptor in the mucosa of the gastrointestinal tract. Chronic infection of gastric epithelial cells by Helicobacter pylori (H. pylori) is a major risk factor for human gastric cancer (GC) where Cav1 is frequently down-regulated. However, the function of Cav1 in H. pylori infection and pathogenesis of GC remained unknown. We show here that Cav1-deficient mice, infected for 11 months with the CagA-delivery deficient H. pylori strain SS1, developed more severe gastritis and tissue damage, including loss of parietal cells and foveolar hyperplasia, and displayed lower colonisation of the gastric mucosa than wild-type B6129 littermates. Cav1-null mice showed enhanced infiltration of macrophages and B-cells and secretion of chemokines (RANTES) but had reduced levels of CD25+ regulatory T-cells. Cav1-deficient human GC cells (AGS), infected with the CagA-delivery proficient H. pylori strain G27, were more sensitive to CagA-related cytoskeletal stress morphologies ("humming bird") compared to AGS cells stably transfected with Cav1 (AGS/Cav1). Infection of AGS/Cav1 cells triggered the recruitment of p120 RhoGTPase-activating protein/deleted in liver cancer-1 (p120RhoGAP/DLC1) to Cav1 and counteracted CagA-induced cytoskeletal rearrangements. In human GC cell lines (MKN45, N87) and mouse stomach tissue, H. pylori down-regulated endogenous expression of Cav1 independently of CagA. Mechanistically, H. pylori activated sterol-responsive element-binding protein-1 (SREBP1) to repress transcription of the human Cav1 gene from sterol-responsive elements (SREs) in the proximal Cav1 promoter. These data suggested a protective role of Cav1 against H. pylori-induced inflammation and tissue damage. We propose that H. pylori exploits down-regulation of Cav1 to subvert the host's immune response and to promote signalling of its virulence factors in host cells

DNA methylation subgroups and the CpG island methylator phenotype in gastric cancer: A comprehensive profiling approach

10.1186/1471-230X-14-55BMC Gastroenterology141-BGMA

Single-molecule experiments in biological physics: methods and applications

I review single-molecule experiments (SME) in biological physics. Recent technological developments have provided the tools to design and build scientific instruments of high enough sensitivity and precision to manipulate and visualize individual molecules and measure microscopic forces. Using SME it is possible to: manipulate molecules one at a time and measure distributions describing molecular properties; characterize the kinetics of biomolecular reactions and; detect molecular intermediates. SME provide the additional information about thermodynamics and kinetics of biomolecular processes. This complements information obtained in traditional bulk assays. In SME it is also possible to measure small energies and detect large Brownian deviations in biomolecular reactions, thereby offering new methods and systems to scrutinize the basic foundations of statistical mechanics. This review is written at a very introductory level emphasizing the importance of SME to scientists interested in knowing the common playground of ideas and the interdisciplinary topics accessible by these techniques. The review discusses SME from an experimental perspective, first exposing the most common experimental methodologies and later presenting various molecular systems where such techniques have been applied. I briefly discuss experimental techniques such as atomic-force microscopy (AFM), laser optical tweezers (LOT), magnetic tweezers (MT), biomembrane force probe (BFP) and single-molecule fluorescence (SMF). I then present several applications of SME to the study of nucleic acids (DNA, RNA and DNA condensation), proteins (protein-protein interactions, protein folding and molecular motors). Finally, I discuss applications of SME to the study of the nonequilibrium thermodynamics of small systems and the experimental verification of fluctuation theorems. I conclude with a discussion of open questions and future perspectives.Comment: Latex, 60 pages, 12 figures, Topical Review for J. Phys. C (Cond. Matt