587 research outputs found
Cluster evolution in steady-state two-phase flow in porous media
We report numerical studies of the cluster development of two-phase flow in a
steady-state environment of porous media. This is done by including biperiodic
boundary conditions in a two-dimensional flow simulator. Initial transients of
wetting and non-wetting phases that evolve before steady-state has occurred,
undergo a cross-over where every initial patterns are broken up. For flow
dominated by capillary effects with capillary numbers in order of , we
find that around a critical saturation of non-wetting fluid the non-wetting
clusters of size have a power-law distribution with
the exponent for large clusters. This is a lower value
than the result for ordinary percolation. We also present scaling relation and
time evolution of the structure and global pressure.Comment: 12 pages, 11 figures. Minor corrections. Accepted for publication in
Phys. Rev.
How Black Lives Matter Has Influenced and Interacted with Global Social Movements
Black Lives Matter (BLM) is a chapter-based and member-led organization created out of grief by three queer black women. This thesis examines the international impact of BLM. I conducted telephone interviews with activists and advocacy organizations who have organized activist networks and/or won struggles against institutional racism outside of the United States. These activists are located in Kenya, South Africa, Brazil, Australia, India, Spain, The Netherlands, Sweden, and Paris. I conclude that BLM has inspired the creation and supported the continued development of organizations advocating for national and transnational social and racial justice on a global scale. BLM in spite of its imperfections, is the social justice yellow brick road helping to build a path toward, what political activist Angela Davis conceptualizes as, intersectionality of movements, or the joining of different struggles to strengthen each fight against oppression
Sickness Behaviors Across Vertebrate Taxa: Proximate and Ultimate Mechanisms
There is nothing like a pandemic to get the world thinking about how infectious diseases affect individual behavior. In this respect, sick animals can behave in ways that are dramatically different from healthy animals: altered social interactions and changes to patterns of eating and drinking are all hallmarks of sickness. As a result, behavioral changes associated with inflammatory responses (i.e. sickness behaviors) have important implications for disease spread by affecting contacts with others and with common resources, including water and/or sleeping sites. In this Review, we summarize the behavioral modifications, including changes to thermoregulatory behaviors, known to occur in vertebrates during infection, with an emphasis on non-mammalian taxa, which have historically received less attention. We then outline and discuss our current understanding of the changes in physiology associated with the production of these behaviors and highlight areas where more research is needed, including an exploration of individual and sex differences in the acute phase response and a greater understanding of the ecophysiological implications of sickness behaviors for disease at the population level
Electron scattering in atomic force microscopy experiments
It has been shown that electron transitions, as measured in a scanning
tunnelling microscope (STM), are related to chemical interactions in a
tunnelling barrier. Here, we show that the shape and apparent height of
subatomic features in an atomic force microscopy (AFM) experiment on Si(111)
depend directly on the available electron states of the silicon surface and the
silicon AFM tip. Simulations and experiments confirm that forces and currents
show similar subatomic variations for tip-sample distances approaching the bulk
bonding length.Comment: 5 pages and 4 figure
Use of a radiopaque localizer grid to reduce radiation exposure
Abstract Background Minimally invasive spine surgery requires placement of the skin incision at an ideal location in the patient's back by the surgeon. However, numerous fluoroscopic x-ray images are sometimes required to find the site of entry, thereby exposing patients and Operating Room personnel to additional radiation. To minimize this exposure, a radiopaque localizer grid was devised to increase planning efficiency and reduce radiation exposure. Results The radiopaque localizer grid was utilized to plan the point of entry for minimally invasive spine surgery. Use of the grid allowed the surgeon to accurately pinpoint the ideal entry point for the procedure with just one or two fluoroscopic X-ray images. Conclusions The reusable localizer grid is a simple and practical device that may be utilized to more efficiently plan an entry site on the skin, thus reducing radiation exposure. This device or a modified version may be utilized for any procedure involving the spine
Imaging and Dynamics of Light Atoms and Molecules on Graphene
Observing the individual building blocks of matter is one of the primary
goals of microscopy. The invention of the scanning tunneling microscope [1]
revolutionized experimental surface science in that atomic-scale features on a
solid-state surface could finally be readily imaged. However, scanning
tunneling microscopy has limited applicability due to restrictions, for
example, in sample conductivity, cleanliness, and data aquisition rate. An
older microscopy technique, that of transmission electron microscopy (TEM) [2,
3] has benefited tremendously in recent years from subtle instrumentation
advances, and individual heavy (high atomic number) atoms can now be detected
by TEM [4 - 7] even when embedded within a semiconductor material [8, 9].
However, detecting an individual low atomic number atom, for example carbon or
even hydrogen, is still extremely challenging, if not impossible, via
conventional TEM due to the very low contrast of light elements [2, 3, 10 -
12]. Here we demonstrate a means to observe, by conventional transmision
electron microscopy, even the smallest atoms and molecules: On a clean
single-layer graphene membrane, adsorbates such as atomic hydrogen and carbon
can be seen as if they were suspended in free space. We directly image such
individual adatoms, along with carbon chains and vacancies, and investigate
their dynamics in real time. These techniques open a way to reveal dynamics of
more complex chemical reactions or identify the atomic-scale structure of
unknown adsorbates. In addition, the study of atomic scale defects in graphene
may provide insights for nanoelectronic applications of this interesting
material.Comment: 9 pages manuscript and figures, 9 pages supplementary informatio
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