The Fertility Pattern of Twins and the General Population Compared: Evidence from Danish Cohorts 1945-64

Twin studies provide an important possibility for demographers to analyze patterns of heritability and to estimate structural models with controls for endowments. These possibilities are increasingly used in the context of fertility and related behaviors. A close congruence between the fertility patterns of twins and that of the general population, however, is an essential pre-condition in order to generalize the results of twin-based investigations of fertility and related behaviors to the general population. In this paper we therefore compare the fertility of Danish twins born 1945--64 to the fertility pattern of the general population born during the same period. Our analyses find a very close correspondence between the fertility pattern of twins and of the general population. There exist only few statistically significant differences, and the primary difference pertains to the fact that female twins have a slightly later onset of childbearing than non-twins. There are virtually no relevant differences between the fertility patterns of dizygotic and monozygotic twins.cohort fertility, Denmark, fertility, twin studies

Bacterial β-peptidyl aminopeptidases: on the hydrolytic degradation of β-peptides

The special chemical and biological features of β-peptides have been investigated intensively during recent years. Many studies emphasize the restricted biodegradability and the high metabolic stability of this class of compounds. β-Peptidyl aminopeptidases form the first family of enzymes that hydrolyze a variety of short β-peptides and β-amino-acid-containing peptides. All representatives of this family were isolated from Gram-negative bacteria. The substrate specificities of the peptidases vary greatly, but the enzymes have common structural properties, and a similar reaction mechanism can be expected. This review gives an overview on the β-peptidyl aminopeptidases with emphasis on their biochemical and structural properties. Their possible physiological function is discussed. Functionally and structurally related enzymes are compared to the β-peptidyl aminopeptidase

Vibrational effects in laser driven molecular wires

The influence of an electron-vibrational coupling on the laser control of electron transport through a molecular wire that is attached to several electronic leads is investigated. These molecular vibrational modes induce an effective electron-electron interaction. In the regime where the wire electrons couple weakly to both the external leads and the vibrational modes, we derive within a Hartree-Fock approximation a nonlinear set of quantum kinetic equations. The quantum kinetic theory is then used to evaluate the laser driven, time-averaged electron current through the wire-leads contacts. This novel formalism is applied to two archetypical situations in the presence of electron-vibrational effects, namely, (i) the generation of a ratchet or pump current in a symmetrical molecule by a harmonic mixing field and (ii) the laser switching of the current through the molecule.Comment: 12 pages, 7 figures, RevTeX4 require

Parametric correlations versus fidelity decay: the symmetry breaking case

We derive fidelity decay and parametric energy correlations for random matrix ensembles where time--reversal invariance of the original Hamiltonian is broken by the perturbation. Like in the case of a symmetry conserving perturbation a simple relation between both quantities can be established.Comment: 8 pages, 8 figure

Molecular wires acting as quantum heat ratchets

We explore heat transfer in molecular junctions between two leads in the absence of a finite net thermal bias. The application of an unbiased, time-periodic temperature modulation of the leads entails a dynamical breaking of reflection symmetry, such that a directed heat current may emerge (ratchet effect). In particular, we consider two cases of adiabatically slow driving, namely (i) periodic temperature modulation of only one lead and (ii) temperature modulation of both leads with an ac driving that contains a second harmonic, thus generating harmonic mixing. Both scenarios yield sizeable directed heat currents which should be detectable with present techniques. Adding a static thermal bias, allows one to compute the heat current-thermal load characteristics which includes the ratchet effect of negative thermal bias with positive-valued heat flow against the thermal bias, up to the thermal stop-load. The ratchet heat flow in turn generates also an electric current. An applied electric stop-voltage, yielding effective zero electric current flow, then mimics a solely heat-ratchet-induced thermopower (``ratchet Seebeck effect''), although no net thermal bias is acting. Moreover, we find that the relative phase between the two harmonics in scenario (ii) enables steering the net heat current into a direction of choice.Comment: 9 pages, 8 figure

Aquaculture Performance Comparison of Sunshine Bass, Palmetto Bass, and White Bass

Aquaculture performance of phase II and phase III sunshine bass (a female white bass Morone chrysops × male striped bass M. saxatilis), palmetto bass (a female striped bass × male white bass), and white bass were evaluated in separate 12-week yield trials conducted in indoor recirculating-water systems. Phase II sunshine bass, palmetto bass, and white bass had mean initial weights of 40.0 g, 39.7 g, and 41.0 g, respectively. A diet containing 40.2% crude protein (CP) was fed to fish twice daily at a rate of 3% body weight/d. At the end of the trial, sunshine bass and white bass had mean weights of 124.2 g and 126.0 g, respectively and were significantly larger than palmetto bass (93.5 g mean weight). Phase II sunshine bass and white bass outperformed palmetto bass by having higher relative growth (h), mean daily growth, and relative weight, as well as better feed conversion ratios (weight of food fed/weight gained). Survival was 100% for all three taxonomic groups. In the phase III study, mean initial weights for sunshine bass (177.5 g) and palmetto bass (185.9 g) were similar but significantly greater than the mean initial weight of white bass (153.8 g). In this trial, fish were fed a floating trout chow (44.1% CP) to satiation twice per day. At the termination of the study, sunshine bass (611.1 g) and palmetto bass (517.8 g) had significantly greater mean weights than white bass (254.4 g). Significant differences among all three taxonomic groups were found for h and for mean daily growth rate. Both crosses of hybrid striped bass had lower feed conversion ratios when compared with white bass. Relative weight values (ratio of a fish\u27s weight to the weight of a standard fish of the same length) for sunshine bass were significantly greater than values for palmetto bass and white bass. Survival rates ranged from 98% to 100% for the three taxonomic groups. Differences were not detected between sunshine bass and palmetto bass for eviscerated percentage, headed and eviscerated percentage, or dressout percentage. Sunshine bass outperformed palmetto bass at phase II and phase III sizes under the conditions of this study

Adherence to Nutrition and Physical Activity Cancer Prevention Guidelines and Development of Colorectal Adenoma.

Adherence to the American Cancer Society's (ACS) Nutrition and Physical Activity Cancer Prevention Guidelines is associated with reductions in overall cancer incidence and mortality, including site-specific cancers such as colorectal cancer. We examined the relationship between baseline adherence to the ACS guidelines and (1) baseline adenoma characteristics and (2) odds of recurrent colorectal adenomas over 3 years of follow-up. Cross-sectional and prospective analyses with a pooled sample of participants from the Wheat Bran Fiber (n = 503) and Ursodeoxycholic Acid (n = 854) trials were performed. A cumulative adherence score was constructed using baseline self-reported data regarding body size, diet, physical activity and alcohol consumption. Multivariable logistic regression demonstrated significantly reduced odds of having three or more adenomas at baseline for moderately adherent (odds ratio [OR] = 0.67, 95% confidence intervals [CI]: 0.46⁻0.99) and highly adherent (OR = 0.50, 95% CI: 0.31⁻0.81) participants compared to low adherers (p-trend = 0.005). Conversely, guideline adherence was not associated with development of recurrent colorectal adenoma (moderate adherence OR = 1.16, 95% CI: 0.85⁻1.59, high adherence OR = 1.23, 95% CI: 0.85⁻1.79)

Dust-Impregnated Ear Tags for Horn Fly Control of Pasure Cattle

Fly control is a problem to all cattlemen during the summer months. The irritation of flies has been shown to cause decreased weight gains and loss in milk production. Cattlemen are continually looking for economical and effective means of controlling flies under various management systems. Among the more recently developed fly control possibilities has been an insecticide dust-impregnated ear tag. The idea was developed for control of ear ticks in Texas. The tags are white, about 2 by 2 1/2 inches in size and about the same weight as a standard, plastic tag commonly used for identifying cattle. They are applied with a standard Allflex pliers. Rabon (2-chloro-1-(2, 4, 5,-trichlorophenyl)) vinyl dimethyl phosphate (13.7 w/w) is impregnated in the plastic ear tag in such a way the tag continually dusts the animal as it moves its head. Marking paint on the tags lasted up to 5 months in these studies