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

Retinoic acid inhibits the fixation of initial transformational damage in X-irradiated Balb/3T3 mouse fibroblasts in vitro

We have examined the effects of all-trans retinoic acid (RA) on confluent holding recovery (cell survival) and on the fixation of initial transformational damage expressed as the ultimate yield of transformed foci following X-irradiation of density-inhibited cultures of Balb/3T3 cells. Non-cytotoxic concentrations of RA suppressed both recovery of potentially lethal damage and neoplastic transformation in a dosedependent manner when added for 24 h during postirradiation confluent holding after a dose of 5 Gy. At 100 μM, RA inhibited the fixation of initial transformational damage by 80%. These findings are discussed in terms of the hypothesis that retinoids may allow a selective enhancement of the inactivation of certain irradiated tumor cells in vivo while reducing the risk of secondary malignancies in successfully treated patient

Accurate Inversion of High-Resolution Snow Penetrometer Signals for Microstructural and Micromechanical Properties

Measurements of snow using a high-resolution micropenetrometer can be used to discriminate between different snow types; in lower-density snow the signal is sensitive to microstructure, and micromechanical properties can be estimated. Although a physics-based snow penetration theory was first developed almost a decade ago, since that time the majority of studies using snow micropenetrometers have focused on using direct hardness measurements in statistical relationships. We use Monte-Carlo simulations to rigorously test the existing physics-based snow micropenetration theories over a wide range of parameters. These tests revealed four major sources of error in the inversion, which are corrected in this analysis. It is shown that this improved inversion algorithm can recover micromechanical parameters in synthetic data with much greater accuracy over the entire range of micromechanical properties observed in natural snow. Detailed examples of the inversion results are shown for eight different snow types, collected in both Alaskan and alpine snowpacks. The resulting micromechanical properties are distinctly different, indicating that a snow characterization from snow micropenetrometer estimates of micromechanical properties is likely possible. Estimates of the microscale elastic modulus, microscale strength, and structural element length make sense physically when compared to the qualitative descriptions of the different snow types. Microscale strength estimates are used to estimate macroscale strength values, and results from 33 different snow samples, covering a wide range of densities and snow types, are consistent with previously reported values from macroscale tests

Coupling a single electron to a Bose-Einstein condensate

The coupling of electrons to matter is at the heart of our understanding of material properties such as electrical conductivity. One of the most intriguing effects is that electron-phonon coupling can lead to the formation of a Cooper pair out of two repelling electrons, the basis for BCS superconductivity. Here we study the interaction of a single localized electron with a Bose-Einstein condensate (BEC) and show that it can excite phonons and eventually set the whole condensate into a collective oscillation. We find that the coupling is surprisingly strong as compared to ionic impurities due to the more favorable mass ratio. The electron is held in place by a single charged ionic core forming a Rydberg bound state. This Rydberg electron is described by a wavefunction extending to a size comparable to the dimensions of the BEC, namely up to 8 micrometers. In such a state, corresponding to a principal quantum number of n=202, the Rydberg electron is interacting with several tens of thousands of condensed atoms contained within its orbit. We observe surprisingly long lifetimes and finite size effects due to the electron exploring the wings of the BEC. Based on our results we anticipate future experiments on electron wavefunction imaging, investigation of phonon mediated coupling of single electrons, and applications in quantum optics.Comment: 4 pages, 3 figures and supplementary informatio

Electrocortical and Autonomic Alteration by Administration of a Pleasant and an Unpleasant Odor

The present study was designed to investigate whether there is a consistent response in ongoing EEG due to repetitive olfactory stimulation. Two odors of different hedonic quality were presented bilaterally to five male subjects at suprathreshold levels. A room-air blank served as the control stimulus. Each odor was presented six times to each subject in each of three sessions. Electrocortical activity, heart rate, skin conductance and breathing cycle were recorded continuously. EEG variables assessed were difference scores of absolute power in the frequency bands theta, alpha1, alpha2 and beta1 at eight locations. Phenylethyl alcohol was rated pleasant, while valeric acid was judged unpleasant. Within 8 s after stimulus release, valeric acid increased alpha2 power, whereas phenylethyl alcohol did not. No further frequency bands were affected by olfactory stimulation. These findings suggest that smelling an unpleasant odor leads to a cortical deactivation. Chem. Senses 20: 505-515, 199

An experimental and theoretical guide to strongly interacting Rydberg gases

We review experimental and theoretical tools to excite, study and understand strongly interacting Rydberg gases. The focus lies on the excitation of dense ultracold atomic samples close to, or within quantum degeneracy, to high lying Rydberg states. The major part is dedicated to highly excited S-states of Rubidium, which feature an isotropic van-der-Waals potential. Nevertheless, the setup and the methods presented are also applicable to other atomic species used in the field of laser cooling and atom trapping.Comment: 23 pages, 22 figures, tutoria

Persistent currents through a quantum impurity: Protection through integrability

We consider an integrable model of a one-dimensional mesoscopic ring with the conduction electrons coupled by a spin exchange to a magnetic impurity. A symmetry analysis based on a Bethe Ansatz solution of the model reveals that the current is insensitive to the presence of the impurity. We argue that this is true for any integrable impurity-electron interaction, independent of choice of physical parameters or couplings. We propose a simple physical picture of how the persistent current gets protected by integrability.Comment: 5 pages, minor update

The novel missense mutation Met48Lys in FKBP22 changes its structure and functions.

Mutations in the FKBP14 gene encoding FKBP22 (FK506 Binding Protein 22 kDa) cause kyphoscoliotic Ehlers-Danlos Syndrome (kEDS). The first clinical report showed that a lack of FKBP22 protein due to mutations causing nonsense-mediated decay of the mRNA leads to a wide spectrum of clinical phenotypes including progressive kyphoscoliosis, joint hypermobility, hypotonia, hyperelastic skin, hearing loss and aortic rupture. Our previous work showed that these phenotypic features could be correlated with the functions of FKBP22, which preferentially binds to type III, VI and X collagens, but not to type I, II or V collagens. We also showed that FKBP22 catalyzed the folding of type III collagen through its prolyl isomerase activity and acted as a molecular chaperone for type III collagen. Recently, a novel missense mutation Met48Lys in FKBP22 was identified in a patient with kEDS. In this report, we expand the list of substrates of FKBP22 and also demonstrate that the Met48Lys mutation diminishes the activities of FKBP22, indicating that pathology can arise from absence of FKBP22, or partial loss of its function