The Vintage Effect in TPF-Growth: An Analysis of the Age Structure of Capital

The age structure of capital plays an important role in the measurement of productivity.It has been argued that the slowdown in the 1970 s can be ascribed to the aging of the stock of capital.In this paper we incorporate the age structure in productivity measurement.One proposition proves that Nelson s (1964) formula is only an approximation.Our final proposition shows that inclusion of the vintage effect prompts an upward correction of measured productivity growth in times of an aging stock of capital.Here capital ages if the investment/capital ratio falls short of the inverse of the capital age, as a first proposition shows.The analysis rests on a rigorous accounting for vintages.We translate the Bureau of Economic Analysis age of capital data into a measure of rates of obsolescence.Empirically, the correction of productivity growth for the vintage effect requires an estimate of the obsolescence and depreciation parameters on the basis of age data.The results indicate that the use of capital stock in efficiency units does cause some smoothing of Total Factor Productivity growth over time.In the 1950s, when investment accelerated, the vintage-adjusted capital growth rate well exceeded the BEA growth rate, and vintageadjusted TFP growth is significantly lower than unadjusted TFP growth.The measured productivity slowdown of the 1970s is somewhat ameliorated.capital;productivity;growth;expenditure;tfp

Spectral Formation in X-Ray Pulsar Accretion Columns

We present the first self-consistent model for the dynamics and the radiative transfer occurring in bright X-ray pulsar accretion columns, with a special focus on the role of the shock in energizing the emerging X-rays. The pressure inside the accretion column of a luminous X-ray pulsar is dominated by the photons, and consequently the equations describing the coupled radiative-dynamical structure must be solved simultaneously. Spectral formation in these sources is therefore a complex, nonlinear phenomenon. We obtain the analytical solution for the Green's function describing the upscattering of monochromatic radiation injected into the column from the thermal mound located near the base of the flow. The Green's function is convolved with a Planck distribution to model the X-ray spectrum resulting from the reprocessing of blackbody photons produced in the thermal mound. These photons diffuse through the infalling gas and eventually escape out the walls of the column, forming the observed X-ray spectrum. We show that the resulting column-integrated, phase-averaged spectrum has a power-law shape at high energies and a blackbody shape at low energies, in agreement with the observational data for many X-ray pulsars.Comment: Accepted for publication in ApJ Letters. Several typos noticed during the proof review were correcte

Single and Double Photoionization and Photodissociation of Toluene by Soft X-rays in Circumstellar Environment

The formation of polycyclic aromatic hydrocarbons (PAHs) and their methyl derivatives occurs mainly in the dust shells of asymptotic giant branch (AGB) stars. The bands at 3.3 and 3.4 $\mu$m, observed in infrared emission spectra of several objects, are attributed C-H vibrational modes in aromatic and aliphatic structures, respectively. In general, the feature at 3.3 $\mu$m is more intense than the 3.4 $\mu$m. Photoionization and photodissociation processes of toluene, the precursor of methylated PAHs, were studied using synchrotron radiation at soft X-ray energies around the carbon K edge with time-of-flight mass spectrometry. Partial ion yields of a large number of ionic fragments were extracted from single and 2D-spectra, where electron-ion coincidences have revealed the doubly charged parent-molecule and several doubly charged fragments containing seven carbon atoms with considerable abundance. \textit{Ab initio} calculations based on density functional theory were performed to elucidate the chemical structure of these stable dicationic species. The survival of the dications subjected to hard inner shell ionization suggests that they could be observed in the interstellar medium, especially in regions where PAHs are detected. The ionization and destruction of toluene induced by X-rays were examined in the T Dra conditions, a carbon-rich AGB star. In this context, a minimum photodissociation radius and the half-life of toluene subjected to the incidence of the soft X-ray flux emitted from a companion white dwarf star were determined.Comment: 11 pages, 4 figures, accept for publication in Ap

Gradual Certified Programming in Coq

Expressive static typing disciplines are a powerful way to achieve high-quality software. However, the adoption cost of such techniques should not be under-estimated. Just like gradual typing allows for a smooth transition from dynamically-typed to statically-typed programs, it seems desirable to support a gradual path to certified programming. We explore gradual certified programming in Coq, providing the possibility to postpone the proofs of selected properties, and to check "at runtime" whether the properties actually hold. Casts can be integrated with the implicit coercion mechanism of Coq to support implicit cast insertion a la gradual typing. Additionally, when extracting Coq functions to mainstream languages, our encoding of casts supports lifting assumed properties into runtime checks. Much to our surprise, it is not necessary to extend Coq in any way to support gradual certified programming. A simple mix of type classes and axioms makes it possible to bring gradual certified programming to Coq in a straightforward manner.Comment: DLS'15 final version, Proceedings of the ACM Dynamic Languages Symposium (DLS 2015

Spermiogramm und Seminalplasma: Der andrologische Faktor

Zusammenfassung: Das Spermiogramm liefert als wenig standardisierte Methode nur grobe Informationen zur Diagnostik männlicher Subfertilität. Daher sollte außer bei hoch pathologischen Werten das Spermiogramm nicht als alleinige Entscheidungsgrundlage für die Therapie dienen. Therapeutisch können neben der ICSI (intrazytoplasmatische Spermieninjektion) bei einer männlichen Infertilität auch mit intrauterinen Inseminationen gute Ergebnisse erzielt werden. In Fällen, bei denen selbst die ICSI-Methode versagt, scheint die IMSI-Technik (intrazytoplasmatische, morphologische selektierte Spermieninjektion) vielversprechend zu sein. Unabhängig von der Behandlungsmethode ist es von entscheidender Bedeutung, eine möglichst gute Samenprobe zu gewinnen. Dabei ist es möglich, mit einfachen Methoden wie einer Verkürzung der Abstinenzzeit oder einer Probengewinnung zu Hause die Samenqualität entscheidend zu verbessern. Neueste Erkenntnisse zeigen, dass die Anwendung von Seminalplasma in der Reproduktionsmedizin das Endometrium rezeptiver macht und somit die Implantation des Embryos unterstützen kann. Auch Geschlechtsverkehr um den Zeitpunkt des Embryotransfers scheint die Behandlung positiv zu beeinflusse

Tests of the continuum limit for the SO(4)SO(4) Principal Chiral Model and the prediction for \L_\MS

We investigate the continuum limit in $SO(N)$ Principal Chiral Models concentrating in detail on the $SO(4)$ model and its covering group SU(2)xSU(2). We compute the mass gap in terms of Lambda_MS and compare with the prediction of Hollowood of m/\L_\MS = 3.8716. We use the finite-size scaling method of L\"uscher et al. to deduce m/\L_\MS and find that for the $SO(4)$ model the computed result of m/\L_\MS \sim 14 is in strong disagreement with theory but that a similar analysis of the SU(2)xSU(2) yields excellent agreement with theory. We conjecture that for $SO(4)$ violations of the finite-size scaling assumption are severe forthe values of the correlation length, $\xi$, investigated and that our attempts to extrapolate the results to zero lattice spacing, although plausible, are erroneous. Conversely, the finite-size scaling violations in the SU(2)xSU(2) simulation are consistent with perturbation theory and the computed $beta-$function agrees well with the 3-loop approximation for couplings evaluated at scales $L/a \le \xi$, where $\xi$ is measured in units of the lattice spacing, $a$. We conjecture that lattice vortex artifacts in the $SO(4)$ model are responsible for delaying the onset of the continuum limit until much larger correlation lengths are achieved notwithstanding the apparent onset of scaling. Results for the mass spectrum for SO(N) m, N=8,10 are given whose comparison with theory gives plausible support to our ideas.Comment: 27 pages , 1 Postscript-file, uuencode