7,992 research outputs found
Village economies and the structure of extended family networks
This paper documents how the structure of extended family networks in rural Mexico relates to the poverty and inequality of the village of residence. Using the Hispanic naming convention, we construct within-village extended family networks in 504 poor rural villages. Family networks are larger (both in the number of members and as a share of the village population) and out-migration is lower the poorer and the less unequal the village of residence. Our results are consistent with the extended family being a source of informal insurance to its members
Family networks and school enrolment: evidence from a randomized social experiment
We present evidence on whether and how a householdâs behavior is influenced by the
presence and characteristics of its extended family. Using data from the PROGRESA
program in Mexico, we exploit information on the paternal and maternal surnames of
heads and spouses in conjunction with the Spanish naming convention to identify the inter
and intra generational family links of each household to others in the same village. We
then exploit the randomized research design of the PROGRESA evaluation data to identify
whether the treatment effects of PROGRESA transfers on secondary school enrolment
vary according to the characteristics of extended family. We find PROGRESA only raises
secondary enrolment among households that are embedded in a family network. Eligible
but isolated households do not respond. The mechanism through which the extended
family influences household schooling choices is the redistribution of resources within
the family network from eligibles that receive de facto unconditional cash transfers from
PROGRESA, towards eligibles on the margin of enrolling children into secondary school
The nearby Galaxy structure toward the Vela Gum nebula
We report on photometry and spectroscopy for MK classification
purposes carried out in the fields of five open clusters projected against the
Vela Gum in the Third Galactic Quadrant of the Galaxy. They are Ruprecht 20,
Ruprecht 47, Ruprecht 60, NGC 2660 and NGC 2910. We could improve/confirm the
parameters of these objects derived before. The spectroscopic parallax method
has been applied to several stars located in the fields of four out of the five
clusters to get their distances and reddenings. With this method we found two
blue stars in the field of NGC 2910 at distances that make them likely members
of Vela OB1 too. Also, projected against the fields of Ruprecht 20 and Ruprecht
47 we have detected other young stars favoring not only the existence of Puppis
OB1 and OB2 but conforming a young stellar group at kpc from the Sun
and extending for more than 6 kpc outward the Galaxy. If this is the case,
there is a thickening of the thin Galactic disk of more than 300 pc at just 2-3
kpc from the Sun. Ruprecht 60 and NGC 2660 are too old objects that have no
physical relation with the associations under discussion. An astonishing result
has been the detection in the background of Ruprecht 47 of a young star at the
impressive distance of 9.5 kpc from the Sun that could be a member of the
innermost part of the Outer Arm. Another far young star in the field of NGC
2660, at near 6.0 kpc, may become a probable member of the Perseus Arm or of
the inner part of the Local Arm. The distribution of young clusters and stars
onto the Third Galactic Quadrant agrees with recent findings concerning the
extension of the Local Arm as revealed by parallaxes of regions of star
formation. We show evidences too that added to previous ones found by our group
explain the thickening of the thin disk as a combination of flare and warp.Comment: Accepted for publication in New Astronom
Effective Hamiltonian for a half-filled asymmetric ionic Hubbard chain with alternating on-site interaction
We derive an effective spin Hamiltonian for the one-dimensional half-filled asymmetric ionic Hubbard model (IHM) with alternating on-site interaction in the limit of strong repulsion. It is shown that the effective Hamiltonian is that of a spin S = 1/2 anisotropic XXZ Heisenberg chain with alternating next-nearest-neighbor (NNN) and three-spin couplings in the presence of a uniform and a staggered magnetic field
Radiative emission of solar features in Ca II K
We investigated the radiative emission of different types of solar features
in the spectral range of the Ca II K line.
We analyzed full-disk 2k x 2k observations from the PSPT Precision Solar
Photometric Telescope. The data were obtained by using three narrow-band
interference filters that sample the Ca II K line with different pass bands.
Two filters are centered in the line core, the other in the red wing of the
line. We measured the intensity and contrast of various solar features,
specifically quiet Sun (inter-network), network, enhanced network, plage, and
bright plage (facula) regions. Moreover, we compared the results obtained with
those derived from the numerical synthesis performed for the three PSPT filters
with a widely used radiative code on a set of reference semi-empirical
atmosphere models.Comment: In Proceedings of the 25th NSO Workshop: Chromospheric Structure and
Dynamic
Graphdiyne based membranes: exceptional performances for helium separation applications
Graphdiyne is a novel two-dimensional material deriving from graphene that
has been recently synthesized and featuring uniformly distributed sub-nanometer
pores. We report accurate calculations showing that graphdiyne pores permit an
almost unimpeded helium transport which can be used for its chemical and
isotopic separation. Exceptionally high He/CH_4 selectivities are found which
largely exceed the performance of the best membranes used to date for
extraction from natural gas. Moreover, by exploiting slight differences in the
tunneling probabilities of ^3He and ^4He, we also find promising results for
the separation of the Fermionic isotope at low temperature
Steady states analysis and exponential stability of an extensible thermoelastic system
In this work we consider a nonlinear model for the vibrations of a thermoelastic beam with fixed ends resting on an elastic foundation. The behavior of the related dissipative system accounts for both the midplane stretching of the beam and the Fourier heat conduction. The nonlinear term enters the motion equation, only, while the dissipation is entirely contributed by the heat equation. Under stationary axial load and uniform external temperature the problem uncouples and the bending equilibria of the beam satisfy a semilinear equation. For a general axial load , the existence of a finite/infinite set of steady states is proved and buckling occurrence is discussed. Finally, long-term dynamics of solutions and exponential stability of the straight position are scrutinized
On some nonlinear models for suspension bridges
In this paper we discuss some mathematical models describing the nonlinear vibrations of different kinds of single-span simply supported suspension bridges and we summarize some results about the longtime behavior of solutions to the related evolution problems. Finally, in connection with the static counterpart of a general string-beam nonlinear model, we present some original results concerning the existence of multiple buckled solutions
Plasma flows and magnetic field interplay during the formation of a pore
We studied the formation of a pore in AR NOAA 11462. We analysed data
obtained with the IBIS at the DST on April 17, 2012, consisting of full Stokes
measurements of the Fe I 617.3 nm lines. Furthermore, we analysed SDO/HMI
observations in the continuum and vector magnetograms derived from the Fe I
617.3 nm line data taken from April 15 to 19, 2012. We estimated the magnetic
field strength and vector components and the LOS and horizontal motions in the
photospheric region hosting the pore formation. We discuss our results in light
of other observational studies and recent advances of numerical simulations.
The pore formation occurs in less than 1 hour in the leading region of the AR.
The evolution of the flux patch in the leading part of the AR is faster (< 12
hour) than the evolution (20-30 hour) of the more diffuse and smaller scale
flux patches in the trailing region. During the pore formation, the ratio
between magnetic and dark area decreases from 5 to 2. We observe strong
downflows at the forming pore boundary and diverging proper motions of plasma
in the vicinity of the evolving feature that are directed towards the forming
pore. The average values and trends of the various quantities estimated in the
AR are in agreement with results of former observational studies of steady
pores and with their modelled counterparts, as seen in recent numerical
simulations of a rising-tube process. The agreement with the outcomes of the
numerical studies holds for both the signatures of the flux emergence process
(e.g. appearance of small-scale mixed polarity patterns and elongated granules)
and the evolution of the region. The processes driving the formation of the
pore are identified with the emergence of a magnetic flux concentration and the
subsequent reorganization of the emerged flux, by the combined effect of
velocity and magnetic field, in and around the evolving structure.Comment: Accepted for publication in Astronomy and Astrophysic
- âŠ