Position vector of spacelike biharmonic curves in the Lorentzian Heisenberg group Heis 3
In this paper, we study spacelike biharmonic curves in the Lorentzian Heisenberg group Heis 3 . We show that spacelike biharmonic curves are general helices. We characterize position vector of spacelike biharmonic general helices in terms of their curvature and torsion.
New Electromagnetic Fluids Inextensible Flows of Spacelike Particles and some Wave Solutions in Minkowski Space-time
In this paper, we construct a new method for inextensible flows of spacelike curves in Minkowski space-time. Using the Frenet frame of the given curve, we present partial differential equations and we obtain solitions some of this equations. We give some characterizations for curvatures of a spacelike curve in Minkowski space-time.
Work, Status, and Income: Men in the American Occupational Structure since the Late Nineteenth Century
The historical record rarely presents researchers with precisely the evidence they desire. This is particularly true for social historians and like-minded scholars, whose subjects left precious few signs of their passing. Consequently, certain data have borne a disproportionate evidentiary load in social-historical research. The occupation a person pursued is one key piece of information on which scholars have come to depend. Our understanding of the historical social structure and where people fit into it is bound up with the interpretation of occupations. But this reliance on occupation as the primary social locator in historical research depends on some largely unexamined premises. Whether scholars group occupations or convert them into numerical status measures, they make assumptions about the nature of the occupational structure. When researchers incorporate change over time into their analyses, they suggest that the meaning of occupations remained stable for the purpose of measuring social mobility, class position, or group status-attainment. This assumption has been the subject of little discussion and even less research. For all the use to which historians have put occupation, there has been little effort to assess systematically its stability as a social or economic indicator.