Homogeneous matchbox manifolds

We prove that a homogeneous matchbox manifold of any finite dimension is homeomorphic to a McCord solenoid, thereby proving a strong version of a conjecture of Fokkink and Oversteegen. The proof uses techniques from the theory of foliations that involve making important connections between homogeneity and equicontinuity. The results provide a framework for the study of equicontinuous minimal sets of foliations that have the structure of a matchbox manifold.Comment: This is a major revision of the original article. Theorem 1.4 has been broadened, in that the assumption of no holonomy is no longer required, only that the holonomy action is equicontinuous. Appendices A and B have been removed, and the fundamental results from these Appendices are now contained in the preprint, arXiv:1107.1910v

Embedding solenoids in foliations

In this paper we find smooth embeddings of solenoids in smooth foliations. We show that if a smooth foliation F of a manifold M contains a compact leaf L with H^1(L;R)= 0 and if the foliation is a product foliation in some saturated open neighbourhood U of L, then there exists a foliation F' on M which is C^1-close to F, and F' has an uncountable set of solenoidal minimal sets contained in U that are pair wise non-homeomorphic. If H^1(L;R) is not 0, then it is known that any sufficiently small perturbation of F contains a saturated product neighbourhood. Thus, our result can be thought of as an instability result complementing the stability results of Reeb, Thurston and Langevin and Rosenberg

A high performance scanning force microscope head design

A stable and highly sensitive scanning force microscope head design is presented. The head provides an implementation of the optical lever detection method in which mechanical vibration noise has been minimized

Emigration and the Age Profile of Retirement Among Immigrants

This paper analyzes the relationship between immigrants' retirement status and the prevalence of return migration from the host country to their country of origin. We develop a simple theoretical model to illustrate that under reasonable conditions the probability of return migration is maximized at retirement. Reduced-form models of retirement status which control for the rate of return migration are then estimated using unique data on emigration rates matched to individual-level data for Australia. We find that immigrants, particularly immigrant women, are more likely to be retired than are native-born men and women with the same demographic, human capital, and family characteristics. Moreover, within the immigrant population, there is a negative relationship between the propensity to be retired and the return migration rate of one's fellow countrymen, particularly amongst men. This link is strongest for those individuals who are at (or near) retirement age and among those with the highest cost of return migration. These results suggest that the fiscal pressures associated with aging immigrant populations vary substantially across origin countries.retirement, immigrants, return migration, emigration, Australia

Emigration and the Age Profile of Retirement among Immigrants

This paper analyzes the relationship between immigrants' retirement status and the prevalence of return migration from the host country to their country of origin. We develop a simple theoretical model to illustrate that under reasonable conditions the probability of return migration is maximized at retirement. Reduced-form models of retirement status which control for the rate of return migration are then estimated using unique data on emigration rates matched to individual-level data for Australia. We find that immigrants, particularly immigrant women, are more likely to be retired than are native-born men and women with the same demographic, human capital, and family characteristics. Moreover, within the immigrant population, there is a negative relationship between the propensity to be retired and the return migration rate of one's fellow countrymen, particularly amongst men. This link is strongest for those individuals who are at (or near) retirement age and among those with the highest cost of return migration. These results suggest that the fiscal pressures associated with aging immigrant populations vary substantially across origin countries.retirement, immigrants, return migration, emigration, Australia

The CLAVATA and SHOOT MERISTEMLESS loci competitively regulate meristem activity in Arabidopsis

The CLAVATA (CLV1 and CLV3) and SHOOT MERISTEMLESS (STM) genes specifically regulate shoot meristem development in Arabidopsis. CLV and STH appear to have opposite functions: c1v1 and Clv3 mutants accumulate excess undifferentiated cells in the shoot and floral meristem, while stm mutants fail to form the undifferentiated cells of the shoot meristem during embryonic development. We have identified a weak allele of stm (stm-2) that reveals STM is not only required for the establish- ment of the shoot meristem, but is also required for the continued maintenance of undifferentiated cells in the shoot meristem and for proper proliferation of cells in the floral meristem. We have found evidence of genetic interactions between the CLV and STM loci. clv1 and c1v3 mutations partially suppressed the stm-1 and stm-2 phenotypes, and were capable of suppression in a dominant fashion. clv stm double mutants and plants homozygous for stm but heterozygous for clv, while still lacking an embryonic shoot meristem, exhibited greatly enhanced postembryonic shoot and floral meristem development. Although stm phenotypes are recessive, stm mutations dominantly suppressed clv homozygous and heterozygous phenotypes. These results indicate that the stm phenotype is sensitive to the levels of CLV activity, while the clv phenotype is sensitive to the level of STM activity. We propose that these genes play related but opposing roles in the regulation of cell division and/or cell differentiation in shoot and floral meristems

Pensions and Firm Performance

This paper examines how pension plans affect employee behavior and firm performance. Theoretically, the impact of pensions on firm performance cannot be predicted. Firms with pensions should have lower turnover rates and more efficient retirement decisions; their employees will be less likely to shirk. On the other hand, pension compensation is not very closely linked to worker performance and there is some risk that turnover may fall too much. The evidence indicates that although wages do not seem to fall with pension compensation, profit rates are not affected by pension coverage. This suggests that pension coverage is associated with higher productivity, a proposition that is supported by indirect evidence on pensions, turnover, and productivity but not by direct tests of how pension coverage and productivity are correlated.

Unions, Pension Wealth, and Age-Compensation Profiles

This paper examines the effect of unions on both the magnitude and distribution of pension benefits. Our empirical results show that beneficiaries in collectively bargained plans receive larger benefits when they retire, receive larger increases in their benefits after they retire, and retire at an earlier age than beneficiaries in other pension plans. As a result, the pension wealth of union beneficiaries is 50 to 109 percent greater than that of nonunion beneficiaries. Just as wage differentials within and across establishments are smaller among union workers, benefit differentials within and across cohorts of retirees are smaller among union beneficiaries. This results from the smaller weight given to salary average in determining initial benefits and the larger percentage increases given to those who have been retired the longest under post-retirement increases. The more compressed benefit structure under unionism causes the union-nonunion compensation (wages plus pension contributions) differential to decline more quickly than the union-nonunion wage differential over the life cycle.