The Definition of Fatherhood: In the Words of Never-Married African American Custodial Mothers and the Noncustodial Fathers of Their Children

This qualitative study explores the meaning of fatherhood from the perspective of never-married parents. Specifically, the study describes: how African American custodial mothers perceive the roles and responsibilities of their children\u27s fathers; the extent to which these mothers\u27 perceptions and definitions of noncustodial fatherhood are consistent with those of noncustodial fathers and the dominant cultural ideal ; and what mothers do to enhance men\u27s paternal participation. A convenience sample of 25 never-married,f ormer couples was drawn from the predominantlyA frican American population of a mid-sized Midwestern city. Data was collected via in-depth interviews with each individual respondent. The findings suggest that African American custodial mothers\u27 expressed definition of ideal fatherhood tends to reflect traditional Western standards, which emphasize the paternal economic role. However, in practice, mothers, like fathers, emphasize the social and emotional aspects of paternal responsibilities. Overall, it appears that while these mothers really want financial support, they are willing to forego economic support in lieu of the social and emotional support fathers provide

Cold gas in group-dominant elliptical galaxies

We present IRAM 30m telescope observations of the CO(1-0) and (2-1) lines in a sample of 11 group-dominant elliptical galaxies selected from the CLoGS nearby groups sample. Our observations confirm the presence of molecular gas in 4 of the 11 galaxies at >4 sigma significance, and combining these with data from the literature we find a detection rate of 43+-14%, comparable to the detection rate for nearby radio galaxies, suggesting that group-dominant ellipticals may be more likely to contain molecular gas than their non-central counterparts. Those group-dominant galaxies which are detected typically contain ~2x10^8 Msol of molecular gas, and although most have low star formation rates (<1 Msol/yr) they have short depletion times, indicating that the gas must be replenished on timescales ~100 Myr. Almost all of the galaxies contain active nuclei, and we note while the data suggest that CO may be more common in the most radio-loud galaxies, the mass of molecular gas required to power the active nuclei through accretion is small compared to the masses observed. We consider possible origin mechanisms for the gas, through cooling of stellar ejecta within the galaxies, group-scale cooling flows, and gas-rich mergers, and find probable examples of each type within our sample, confirming that a variety of processes act to drive the build up of molecular gas in group-dominant ellipticals.Comment: 9 pages, 5 postscript figures, 4 tables, accepted by A&A. Revised throughout in response to referee's comments, including updates to Table 1 and Figure 4, and addition of Figure

Critical and off-critical studies of the Baxter-Wu model with general toroidal boundary conditions

The operator content of the Baxter-Wu model with general toroidal boundary conditions is calculated analytically and numerically. These calculations were done by relating the partition function of the model with the generating function of a site-colouring problem in a hexagonal lattice. Extending the original Bethe-ansatz solution of the related colouring problem we are able to calculate the eigenspectra of both models by solving the associated Bethe-ansatz equations. We have also calculated, by exploring the conformal invariance at the critical point, the mass ratios of the underlying massive theory governing the Baxter-Wu model in the vicinity of its critical point.Comment: 32 pages latex, to appear in J. Phys. A: Math. Ge

Path Integral Monte Carlo Approach to the U(1) Lattice Gauge Theory in (2+1) Dimensions

Path Integral Monte Carlo simulations have been performed for U(1) lattice gauge theory in (2+1) dimensions on anisotropic lattices. We extractthe static quark potential, the string tension and the low-lying "glueball" spectrum.The Euclidean string tension and mass gap decrease exponentially at weakcoupling in excellent agreement with the predictions of Polyakov and G{\" o}pfert and Mack, but their magnitudes are five times bigger than predicted. Extrapolations are made to the extreme anisotropic or Hamiltonian limit, and comparisons are made with previous estimates obtained in the Hamiltonian formulation.Comment: 12 pages, 16 figure

A closer look at symmetry breaking in the collinear phase of the J1−J2J_1-J_2 Heisenberg Model

The large $J_2$ limit of the square-lattice $J_1-J_2$ Heisenberg antiferromagnet is a classic example of order by disorder where quantum fluctuations select a collinear ground state. Here, we use series expansion methods and a meanfield spin-wave theory to study the excitation spectra in this phase and look for a finite temperature Ising-like transition, corresponding to a broken symmetry of the square-lattice, as first proposed by Chandra et al. (Phys. Rev. Lett. 64, 88 (1990)). We find that the spectra reveal the symmetries of the ordered phase. However, we do not find any evidence for a finite temperature phase transition. Based on an effective field theory we argue that the Ising-like transition occurs only at zero temperature.Comment: 4 pages and 5 figure

Critical Behaviour of Mixed Heisenberg Chains

The critical behaviour of anisotropic Heisenberg models with two kinds of antiferromagnetically exchange-coupled centers are studied numerically by using finite-size calculations and conformal invariance. These models exhibit the interesting property of ferrimagnetism instead of antiferromagnetism. Most of our results are centered in the mixed Heisenberg chain where we have at even (odd) sites a spin-S (S') SU(2) operator interacting with a XXZ like interaction (anisotropy $\Delta$). Our results indicate universal properties for all these chains. The whole phase, $1>\Delta>-1$, where the models change from ferromagnetic $( \Delta=1 )$ to ferrimagnetic $(\Delta=-1)$ behaviour is critical. Along this phase the critical fluctuations are ruled by a c=1 conformal field theory of Gaussian type. The conformal dimensions and critical exponents, along this phase, are calculated by studying these models with several boundary conditions.Comment: 21 pages, standard LaTex, to appear in J.Phys.A:Math.Ge

Eikonal Regge Model for Elastic Scattering Processes

The Frautschi-Margolis version of the Regge eikonal model is extended to include secondary Regge trajectories. Physical properties of the model are discussed. In particular, the "shrinkage" of dσ/dt observed at present energies (rapid shrinkage for pp and K+p, little or no shrinkage for π±p and K-p, antishrinkage for pp is related to the energy dependence of σtot pp and K+p nearly flat, π±p and K-p falling slowly, pp falling rapidly)

Conformal invariance studies of the Baxter-Wu model and a related site-colouring problem

The partition function of the Baxter-Wu model is exactly related to the generating function of a site-colouring problem on a hexagonal lattice. We extend the original Bethe ansatz solution of these models in order to obtain the eigenspectra of their transfer matrices in finite geometries and general toroidal boundary conditions. The operator content of these models are studied by solving numerically the Bethe-ansatz equations and by exploring conformal invariance. Since the eigenspectra are calculated for large lattices, the corrections to finite-size scaling are also calculated.Comment: 12 pages, latex, to appear in J. Phys. A: Gen. Mat

Hamiltonian Study of Improved U(1U(1 Lattice Gauge Theory in Three Dimensions

A comprehensive analysis of the Symanzik improved anisotropic three-dimensional U(1) lattice gauge theory in the Hamiltonian limit is made. Monte Carlo techniques are used to obtain numerical results for the static potential, ratio of the renormalized and bare anisotropies, the string tension, lowest glueball masses and the mass ratio. Evidence that rotational symmetry is established more accurately for the Symanzik improved anisotropic action is presented. The discretization errors in the static potential and the renormalization of the bare anisotropy are found to be only a few percent compared to errors of about 20-25% for the unimproved gauge action. Evidence of scaling in the string tension, antisymmetric mass gap and the mass ratio is observed in the weak coupling region and the behaviour is tested against analytic and numerical results obtained in various other Hamiltonian studies of the theory. We find that more accurate determination of the scaling coefficients of the string tension and the antisymmetric mass gap has been achieved, and the agreement with various other Hamiltonian studies of the theory is excellent. The improved action is found to give faster convergence to the continuum limit. Very clear evidence is obtained that in the continuum limit the glueball ratio $M_{S}/M_{A}$ approaches exactly 2, as expected in a theory of free, massive bosons.Comment: 13 pages, 15 figures, submitted to Phys. Rev.

Late-onset myoclonic epilepsy in Down’s syndrome (LOMEDS)

AbstractThe aim of this paper is to report a patient with late-onset myoclonic epilepsy in Down’s syndrome (LOMEDS) as a differential diagnosis of adult-onset progressive myoclonic epilepsies. A 55-year-old male with Down’s syndrome (DS) is described who developed progressively frequent myoclonus and generalized myoclonic–tonic seizures (GMTSs) at the age of 52. EEG recordings demonstrated background slowing and generalized polyspike-wave discharges occasionally associated with myoclonic jerks, leading to the classification of primary generalized epileptic myoclonus. Descriptions of late-onset epilepsy in DS patients are rare. However, a review of the pertinent literature revealed at least two other cases of elderly DS patients developing progressive myoclonic epilepsy after the onset of dementia. We suggest that late-onset myoclonic epilepsy in Down’s syndrome as characterized here should be considered in the differential diagnosis of adult-onset myoclonic epilepsies. LOMEDS apparently shares features with myoclonic epilepsy in Alzheimer’s disease (AD) and Unverricht–Lundborg disease (ULD) caused by a mutation on chromosome 21. Since life expectation of DS patients has markedly increased, LOMEDS may be more frequent than currently acknowledged