Comment on "On an identity for the volume integral of the square of a vector field"

Stewart has provided a position-space derivation of an identity for the volume integral of the square of a vector field that was quoted by Gubarev, Stodolsky and Zakharov. In this comment, I provide a momentum-space derivation of this result, generalized to the scalar product of two complex vector fields. This approach demonstrates the effective use of the Fourier transform technique in the context of vector analysis at a level suitable for undergraduate instruction.Comment: 5 page

The investigation of flow instabilities on a rotating disk with curvature in the radial direction

The major objective is to explore any visible differences of the flow field with wall curvature of the test body, including possible interaction between Taylor-Gortler instabilities present along concave walls and the inflexional instabilities investigated here. An experimental study was conducted with emphasis placed on making visual observations and recording photographically the flow instabilities present under three different rotating bodies: a flat disk, a concave paraboloid, and a convex paraboloid. The data collected for the three test bodies lead to the conclusion that the wall curvature of the concave and convex paraboloids did not alter the observed flow field significantly from that observed on the flat disk

Escalera: stairway to better education, evidence from rural Mexico

As a basic input to human capital development, access to quality education remains a significant barrier to growth in most developing countries. Today’s blog looks at evidence of an innovative NGO approach that has been tested in Chiapas, Mexico’s poorest state

Інтерпретації художньої мови мінімалізму у творчості японського дизайнера Н.Фукасави

Мета роботи полягає в аналізі художньо-проектної діяльності відомого японського дизайнера-мінімаліста Н.Фукасави на прикладі окремих промислових об’єктів, а також популяризації поданої інформації

Subsonic high-angle-of-attack aerodynamic characteristics of a cone and cylinder with triangular cross sections and a cone with a square cross section

Experiments were conducted in the 12-Foot Pressure Wind Tunnel at Ames Research Center on three models with noncircular cross sections: a cone having a square cross section with rounded corners and a cone and cylinder with triangular cross sections and rounded vertices. The cones were tested with both sharp and blunt noses. Surface pressures and force and moment measurements were obtained over an angle of attack range from 30 deg to 90 deg and selected oil-flow experiments were conducted to visualize surface flow patterns. Unit Reynolds numbers ranged from 0.8x1,000,000/m to 13.0x1,000,000/m at a Mach number of 0.25, except for a few low-Reynolds-number runs at a Mach number of 0.17. Pressure data, as well as force data and oil-flow photographs, reveal that the three dimensional flow structure at angles of attack up to 75 deg is very complex and is highly dependent on nose bluntness and Reynolds number. For angles of attack from 75 deg to 90 deg the sectional aerodynamic characteristics are similar to those of a two dimensional cylinder with the same cross section

Orbital electron capture by the nucleus

The theory of nuclear electron capture is reviewed in the light of current understanding of weak interactions. Experimental methods and results regarding capture probabilities, capture ratios, and EC/Beta(+) ratios are summarized. Radiative electron capture is discussed, including both theory and experiment. Atomic wave function overlap and electron exchange effects are covered, as are atomic transitions that accompany nuclear electron capture. Tables are provided to assist the reader in determining quantities of interest for specific cases

Search for Oscillation of the Electron-Capture Decay Probability of 142^{142}Pm

We have searched for time modulation of the electron capture decay probability of $^{142}$Pm in an attempt to confirm a recent claim from a group at the Gesellschaft f\"{u}r Schwerionenforschung (GSI). We produced $^{142}$Pm via the $^{124}$Sn($^{23}$Na, 5n)$^{142}$Pm reaction at the Berkeley 88-Inch Cyclotron with a bombardment time short compared to the reported modulation period. Isotope selection by the Berkeley Gas-filled Separator is followed by implantation and a long period of monitoring the $^{142}$Nd K$_{\alpha}$ x-rays from the daughter. The decay time spectrum of the x-rays is well-described by a simple exponential and the measured half-life of 40.68(53) seconds is consistent with the accepted value. We observed no oscillatory modulation at the proposed frequency at a level 31 times smaller than that reported by Litvinov {\it et al.} (Phys. Lett. B 664 (2008) 162; arXiv:0801.2079 [nucl-ex]). A literature search for previous experiments that might have been sensitive to the reported modulation uncovered another example in $^{142}$Eu electron-capture decay. A reanalysis of the published data shows no oscillatory behavior.Comment: 12 pages (double-spaced), 6 figure

Migration and Children\u27s School and Labor: Evidence from El Salvador

This paper examines the impact of parental migration on schooling outcomes for children left behind in El Salvador. Using cross sectional data collected in 2012, outcomes for children are observed for children with migrant parents. The outcomes are also analyzed by gender of the migrant parent who left his or her child behind. Results are observed using instrumental variable estimations, as well as a seemingly unrelated regression to estimate the impact of migration on a child’s time allocation. Outcomes are also analyzed measuring the impact of remittances. Results show that children with at least one migrant parent will complete more years of school. The gender of that migrant parent has no significant impact. Also, parental migration has no significant influence on time allocation, but the presence of remittances in the child’s household does. This paper studies the impact of both migration and remittances on a child’s schooling behavior. Results suggest that the same factors that affect schooling may have a strong correlation with the propensity to migrate as well

The New Particles in High-Energy Physics: What Do They Mean?

Since the earliest of times man has searched for an underlying unity to the rich diversity observed in nature. That search has taken him from the world of atoms and molecules to the domain of sub-nuclear particles and quarks as powerful accelerators have enabled physicists to probe smaller and smaller distances with higher and higher energies. The last six years have been especially significant in high-energy physics. During this brief period there have been unexpected discoveries of matter described by such whimsical names as \u27\u27charm\u27\u27 and \u27\u27beauty.\u27\u27 These recent developments are reviewed for the purpose of explaining the role which these new particles may play in attempts to identify the fundamental building blocks of matter