446 research outputs found
Generalized gravity model for human migration
The gravity model (GM) analogous to Newton's law of universal gravitation has
successfully described the flow between different spatial regions, such as
human migration, traffic flows, international economic trades, etc. This simple
but powerful approach relies only on the 'mass' factor represented by the scale
of the regions and the 'geometrical' factor represented by the geographical
distance. However, when the population has a subpopulation structure
distinguished by different attributes, the estimation of the flow solely from
the coarse-grained geographical factors in the GM causes the loss of
differential geographical information for each attribute. To exploit the full
information contained in the geographical information of subpopulation
structure, we generalize the GM for population flow by explicitly harnessing
the subpopulation properties characterized by both attributes and geography. As
a concrete example, we examine the marriage patterns between the bride and the
groom clans of Korea in the past. By exploiting more refined geographical and
clan information, our generalized GM properly describes the real data, a part
of which could not be explained by the conventional GM. Therefore, we would
like to emphasize the necessity of using our generalized version of the GM,
when the information on such nongeographical subpopulation structures is
available.Comment: 14 pages, 6 figures, 2 table
Matchmaker, Matchmaker, Make Me a Match: Migration of Populations via Marriages in the Past
The study of human mobility is both of fundamental importance and of great
potential value. For example, it can be leveraged to facilitate efficient city
planning and improve prevention strategies when faced with epidemics. The
newfound wealth of rich sources of data---including banknote flows, mobile
phone records, and transportation data---has led to an explosion of attempts to
characterize modern human mobility. Unfortunately, the dearth of comparable
historical data makes it much more difficult to study human mobility patterns
from the past. In this paper, we present an analysis of long-term human
migration, which is important for processes such as urbanization and the spread
of ideas. We demonstrate that the data record from Korean family books (called
"jokbo") can be used to estimate migration patterns via marriages from the past
750 years. We apply two generative models of long-term human mobility to
quantify the relevance of geographical information to human marriage records in
the data, and we find that the wide variety in the geographical distributions
of the clans poses interesting challenges for the direct application of these
models. Using the different geographical distributions of clans, we quantify
the "ergodicity" of clans in terms of how widely and uniformly they have spread
across Korea, and we compare these results to those obtained using surname data
from the Czech Republic. To examine population flow in more detail, we also
construct and examine a population-flow network between regions. Based on the
correlation between ergodicity and migration in Korea, we identify two
different types of migration patterns: diffusive and convective. We expect the
analysis of diffusive versus convective effects in population flows to be
widely applicable to the study of mobility and migration patterns across
different cultures.Comment: 24 pages, 23 figures, 5 table
Spatiotemporal Stochastic Resonance in Fully Frustrated Josephson Ladders
We consider a Josephson-junction ladder in an external magnetic field with
half flux quantum per plaquette. When driven by external currents, periodic in
time and staggered in space, such a fully frustrated system is found to display
spatiotemporal stochastic resonance under the influence of thermal noise. Such
resonance behavior is investigated both numerically and analytically, which
reveals significant effects of anisotropy and yields rich physics.Comment: 8 pages in two columns, 8 figures, to appear in Phys. Rev.
Vibrodissociation of Neurons from Rodent Brain Slices to Study Synaptic Transmission and Image Presynaptic Terminals
Mechanical dissociation of neurons from the central nervous system has the advantage that presynaptic boutons remain attached to the isolated neuron of interest. This allows for examination of synaptic transmission under conditions where the extracellular and postsynaptic intracellular environments can be well controlled. A vibration-based technique without the use of proteases, known as vibrodissociation, is the most popular technique for mechanical isolation. A micropipette, with the tip fire-polished to the shape of a small ball, is placed into a brain slice made from a P1-P21 rodent. The micropipette is vibrated parallel to the slice surface and lowered through the slice thickness resulting in the liberation of isolated neurons. The isolated neurons are ready for study within a few minutes of vibrodissociation. This technique has advantages over the use of primary neuronal cultures, brain slices and enzymatically isolated neurons including: rapid production of viable, relatively mature neurons suitable for electrophysiological and imaging studies; superior control of the extracellular environment free from the influence of neighboring cells; suitability for well-controlled pharmacological experiments using rapid drug application and total cell superfusion; and improved space-clamp in whole-cell recordings relative to neurons in slice or cell culture preparations. This preparation can be used to examine synaptic physiology, pharmacology, modulation and plasticity. Real-time imaging of both pre- and postsynaptic elements in the living cells and boutons is also possible using vibrodissociated neurons. Characterization of the molecular constituents of pre- and postsynaptic elements can also be achieved with immunological and imaging-based approaches
REMOTE SENSING OF WAVE DIRECTIONALITY BY TWO-DIMENSIONAL DIRECTIONAL WAVELETS : PART 2. APPLICATIONS TO THE NUMERICAL AND FIELD DATA
This paper presents the results of a study investigating methods of interpretation of wave directionality based on wavelet transform. In part 1 of this paper, the tools to be used in detection of wave directionality, i. e., the Morlet and Cauchy wavelets, were described. This paper presents the application results of the directional wavelet to numerically generated images and video images taken in laboratory wave flume, river, and sea. The results showed that directional wavelet transform can be an efficient tool in detecting wave directionality with extremely low effort and cost when it is compared to traditional practices in use
A STUDY ON THE TWO-ROW EFFECT IN THE SLOSHING PHENOMENON
In this study, changes in fluid impact loads inside a tank were examined according to a two-row tank arrangement in an LNG-FPSO (Liquefied Natural Gas-Floating Production Storage Offloading) vessel. The motion RAO (Response Amplitude Operator) of the LNG-FPSO, coupled with the sloshing phenomenon inside the tank, was calculated by using HydroStar by Bureau Veritas. The motion simulation in the tank was conducted under filling ratios of 30%H, 60%H, and 80%H. The RAO in each condition was calculated according to the one-row and the two-row tank arrangement. The motion response spectrum using the calculated RAO and the JONSWAP (Joint North Sea Wave Analysis Project) spectrum were computed by implementing irregular motion according to each filling ratio and tank arrangement. The sloshing phenomenon inside the tank was implemented by using a 6-DOF (Degree Of Freedom) sloshing motion platform; impact pressure on the walls of the tank was measured with pressure sensors installed inside the tank. The sloshing experiment was conducted under the three filling ratios in the one-row and the two-row tank arrangement and impact loads were compared under each filling ratio according to the one-row and the two-row tank arrangement
Traumatic Tricuspid Regurgitation Following Cardiac Massage
We report a 66-yr-old male patient who developed tricuspid regurgitation secondary to internal cardiac massage. After uneventful off-pump coronary artery bypass surgery, the subject experienced cardiac arrest in the intensive care unit. External cardiac massage was initiated and internal cardiac massage was performed eventually. A transesophageal echocardiography revealed avulsion of the anterior papillary muscle and chordae to the anterior leaflet after successful cardiopulmonary resuscitation. Emergency repair of the papillary muscle was performed under cardiopulmonary bypass
- ā¦