2,165 research outputs found
Work statistics, irreversible heat and correlations build-up in joining two spin chains
We investigate the influences of quantum many-body effects, such as
criticality and the existence of factorisation fields, in the thermodynamic
cost of establishing a bonding link between two independent quantum spin
chains. We provide a physical interpretation of the behavior of irreversible
work spent in such process by linking the phenomenology of such quantities to
the properties of the spectrum of the systemComment: 9 pages, 8 figures. Contribution to the FQMT13 special volum
Chronic Inflammation (Inflammaging) and Its Potential Contribution to Age-Associated Diseases
Human aging is characterized by a chronic, low-grade inflammation, and this phenomenon has been termed as "inflam maging." Inflammaging is a highly significant risk factor for both morbidity and mortality in the elderly people, as most if not all age-related diseases share an inflammatory pathogenesis. Nevertheless, the precise etiology of inflammaging and its potential causal role in contributing to adverse health outcomes remain largely unknown. The identification of pathways that control age-related inflammation across multiple systems is therefore important in order to understand whether treatments that modulate inflammaging may be beneficial in old people. The session on inflammation of the Advances in Gerosciences meeting held at the National Institutes of Health/National Institute on Aging in Bethesda on October 30 and 31, 2013 was aimed at defining these important unanswered questions about inflammaging. This article reports the main outcomes of this session
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Oncogenic senescence: a multi-functional perspective.
Cellular senescence is defined as an irreversible growth arrest with the acquisition of a distinctive secretome. The growth arrest is a potent anticancer mechanism whereas the secretome facilitates wound healing, tissue repair, and development. The senescence response has also become increasingly recognized as an important contributor to aging and age-related diseases, including cancer. Although oncogenic mutations are capable of inducing a beneficial senescence response that prevents the growth of premalignant cells and promotes cancer immune-surveillance, the secretome of senescent cells also includes factors with pro-tumorigenic properties. On June 23rd and 24th, 2016, the Division of Cancer Biology of the National Cancer Institute sponsored a workshop to discuss the complex role of cellular senescence in tumorigenesis with the goal to define the major challenges and opportunities within this important field of cancer research. Additionally, it was noted how the development of novel tools and technologies are required to accelerate research into a mechanistic understanding of senescent cells in carcinogenesis in order to overcome the current limitations in this exciting, yet ill-defined area
Eigenstate Thermalization Hypothesis and Quantum Jarzynski Relation for Pure Initial States
Since the first suggestion of the Jarzynski equality many derivations of this
equality have been presented in both, the classical and the quantum context.
While the approaches and settings greatly differ from one to another, they all
appear to rely on the initial state being a thermal Gibbs state. Here, we
present an investigation of work distributions in driven isolated quantum
systems, starting off from pure states that are close to energy eigenstates of
the initial Hamiltonian. We find that, for the nonintegrable system in quest,
the Jarzynski equality is fulfilled to good accuracy.Comment: 9 pages, 7 figure
Analysing Magnetism Using Scanning SQUID Microscopy
Scanning superconducting quantum interference device microscopy (SSM) is a
scanning probe technique that images local magnetic flux, which allows for
mapping of magnetic fields with high field and spatial accuracy. Many studies
involving SSM have been published in the last decades, using SSM to make
qualitative statements about magnetism. However, quantitative analysis using
SSM has received less attention. In this work, we discuss several aspects of
interpreting SSM images and methods to improve quantitative analysis. First, we
analyse the spatial resolution and how it depends on several factors. Second,
we discuss the analysis of SSM scans and the information obtained from the SSM
data. Using simulations, we show how signals evolve as a function of changing
scan height, SQUID loop size, magnetization strength and orientation. We also
investigated 2-dimensional autocorrelation analysis to extract information
about the size, shape and symmetry of magnetic features. Finally, we provide an
outlook on possible future applications and improvements.Comment: 16 pages, 10 figure
Transient fluctuation theorem in closed quantum systems
Our point of departure are the unitary dynamics of closed quantum systems as
generated from the Schr\"odinger equation. We focus on a class of quantum
models that typically exhibit roughly exponential relaxation of some observable
within this framework. Furthermore, we focus on pure state evolutions. An
entropy in accord with Jaynes principle is defined on the basis of the quantum
expectation value of the above observable. It is demonstrated that the
resulting deterministic entropy dynamics are in a sense in accord with a
transient fluctuation theorem. Moreover, we demonstrate that the dynamics of
the expectation value are describable in terms of an Ornstein-Uhlenbeck
process. These findings are demonstrated numerically and supported by
analytical considerations based on quantum typicality.Comment: 5 pages, 6 figure
SNS Experience with a High-Energy Superconducting Proton Linac
The Spallation Neutron Source (SNS) requires a high power (> 1 MW) 1 GeV proton beam to produce an intense source of neutrons. The proton beam acceleration is primarily provided by a Superconducting Cavity Linac (SCL). This SCL is the first use of superconducting cavities to accelerate protons to energies this high and is also the first application of pulsed SRF with proton beams. The SCL has been in operation for over two years now. The experience in commissioning and operating the linac are discussed in this paper
Efficient solar cells by space processing
Thin films of electron beam evaporated silicon were deposited on molybdenum, tantalum, tungsten and molybdenum disilicide under ultrahigh vacuum conditions. Mass spectra from a quadrapole residual gas analyzer were used to determine the partial pressure of 13 residual gases during each processing step. Surface contamination and interdiffusion were monitored by in situ Auger electron spectrometry. The presence of phosphorus in the silicon was responsible for attaining elevated temperatures with silicide formations. Heteroepitaxial silicon growth was sensitive to the presence of oxygen during deposition, the rate and length of deposition as well as the substrate orientation
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