Internal Migration and Regional Population Dynamics in Europe: Sweden Case Study

This paper describes the structure of internal migration and population change in Sweden in recent decades, focussing on the years 1988 and 1998 to capture change in the last decade. Up to the 1970s and again in the early 1990s natural increase play an important role in regional population dynamics. In the late 1990s growing international migration, decreasing fertility and strong net internal migration into large cities increased the importance of migration at both national and local levels. In 1988 migration flows contributed to a pattern of relatively even deconcentration of population. Urban centres and surrounding communities experienced mixed patterns of growth. The pattern observed in 1998 was entirely different. It showed a strong movement up the urban hierarchy. Rural and remote areas, especially those in Norrland, depopulated. In 1998 migrants moved from low-density areas to high-density. High density areas had much higher population gains than low density over the 1988–1998 period. There is a difference in migration pattern between the north of the country, which mostly loses population and the central and southern parts, which mostly gain people. The pattern of migration of the Swedish population is, to large extent, related to the level of unemployment. Low unemployment areas attract migrants; high unemployment areas lose them. However, the level of unemployment cannot be considered in isolation, because the level of unemployment is correlated with the level of urbanisation and with type of regional economy. Areas with an educated population have a very strong attraction for migrants. A high level of education is indispensable for high level services, including tertiary education, and for high technology enterprises, which attract migrants. Young people migrate to metropolitan areas and university towns out of the other types of municipality. Medium sized municipalities attract families. Outflows from industrial regions and Inner Norrland municipalities are visible in all age groups. Metropolitan areas are gaining popularity among families. The elderly population migrates to university and medium size municipalities

Model-based investigation on the effects of spatial evenness, and size selection in thinning of Picea abies stands

Size and spatial distribution of trees are important for forest stand growth, but the extent to which it matters in thinning operations, in terms of wood production and stand economy, has rarely been documented. Here we investigate how the choice of spatial evenness and tree-size distribution of residual trees impacts wood production and stand economy. A spatially explicit individual-based growth model was used, in conjunction with empirical cost functions for harvesting and forwarding, to calculate net production and net present value for different thinning operations in Norway spruce stands in Northern Sweden. The in silico thinning operations were defined by three variables: (1) spatial evenness after thinning, (2) tree size preference for harvesting, and (3) basal area reduction. We found that thinning that increases spatial evenness increases net production and net present value by around 2.0%, compared to the worst case. When changing the spatial evenness in conjunction with size preference we could observe an improvement of the net production and net present value up to 8.0%. The magnitude of impact differed greatly between the stands (from 1.7% to 8.0%) and was highest in the stand with the lowest stem density

Low frequency radio and X-ray properties of core-collapse supernovae

Radio and X-ray studies of young supernovae probe the interaction between the supernova shock waves and the surrounding medium and give clues to the nature and past of the progenitor star. Here we discuss the early emission from type Ic SN 2002ap and argue that repeated Compton boosting of optical photons by hot electrons presents the most natural explanation of the prompt X-ray emission. We describe the radio spectrum of another type Ic SN 2003dh (GRB030329) obtained with combined GMRT and VLA data. We report on the low frequency radio monitoring of SN 1995N and our objectives of distinguishing between competing models of X-ray emission from this SN and the nature of its progenitor by X-ray spectroscopy. Radio studies on SN 2001gd, SN 2001ig and SN 2002hh are mentioned.Comment: 5 pages, 4 figures. Uses svmult.cls. To appear in proceedings of IAU Colloquium 192 "Supernovae (10 years of SN 1993J)", April 2003, Valencia, Spain, eds. J. M. Marcaide and K. W. Weile

Use of pepper spray in policing : retrospective study of situational characteristics and implications for violent situations

Pepper spray (OC) is a policing tool aimed to prevent or stop aggressive behavior by quickly and temporarily incapacitate without injuring. To date, few studies have investigated OC’s operational usefulness and limitations. OC reduced violent behavior in 93% of the 936 incidents investigated. However, the operative range was often <2 m and it took between 3 and 5 s of spraying before obtaining effect, partly owing to the difficulties of hitting a small, sometimes erratically moving target. Collateral hits were noted in 24% of the incidents, whereof 90% were other officers. Noteworthy, in 21% of incidents officers put themselves at large personal risk by using OC at close range against people armed with lethal weapons. Hence, OC emerges as a suitable tool for handling low threat situations but lacks key traits to ensure safe and efficient policing of high threat situations, e.g., handling armed assailants

Optical studies of SN 2009jf: A type Ib supernova with an extremely slow decline and aspherical signature

Optical $UBVRI$ photometry and medium resolution spectroscopy of the type Ib supernova SN 2009jf, during the period $\sim -15$ to +250days with respect to the $B$ maximum are reported. The light curves are broad, with an extremely slow decline. The early post-maximum decline rate in the $V$ band is similar to SN 2008D, however, the late phase decline rate is slower than other studied type Ib supernovae. With an absolute magnitude of $M_{V} = -17.96\pm0.19$ magnitude at peak, SN 2009jf is a normally bright supernova. The peak bolometric luminosity and the energy deposition rate via $^{56}$Ni $\rightarrow$ $^{56}$Co chain indicate that $\sim {0.17}^{+0.03}_{-0.03}$ M$_{\odot}$ of $^{56}$Ni was ejected during the explosion. He\,I 5876 \AA\ line is clearly identified in the first spectrum of day $\sim -15$, at a velocity of $\sim 16000$ km sec$^{-1}$. The [O\,I] 6300-6364 \AA\ line seen in the nebular spectrum has a multi-peaked and asymmetric emission profile, with the blue peak being stronger. The estimated flux in this line implies \ga 1.34 M$_\odot$ oxygen was ejected. The slow evolution of the light curves of SN 2009jf indicates the presence of a massive ejecta. The high expansion velocity in the early phase and broader emission lines during the nebular phase suggest it to be an explosion with a large kinetic energy. A simple qualitative estimate leads to the ejecta mass of M$_{\rm ej} = 4-9$ M$_\odot$, and kinetic energy E$_{\rm K} = 3-8 \times 10^{51}$ erg. The ejected mass estimate is indicative of an initial main-sequence mass of \ga 20- 25 M$_\odot$.Comment: 14 pages, 13 figures; accepted for publication in MNRA

Starburst-driven Mass Loss from Dwarf Galaxies: Efficiency and Metal Ejection

We model the effects of repeated supernova explosions from starbursts in dwarf galaxies on the interstellar medium of these galaxies, taking into account the gravitational potential of their dominant dark matter haloes. We explore supernova rates from one every 30,000 yr to one every 3 million yr, equivalent to steady mechanical luminosities of L=0.1-10 x 10^38 ergs/s, occurring in dwarf galaxies with gas masses M_g=10^6 - 10^9 solar masses. We address in detail, both analytically and numerically, the following three questions: 1. When do the supernova ejecta blow out of the disk of the galaxy? 2. When blowout occurs, what fraction of the interstellar gas is blown away, escaping the potential of the galactic halo? 3. What happens to the metals ejected from the massive stars of the starburst? Are they retained or blown away? We give quantitative results for when blowout will or will not occur in galaxies with 10^6 \leq M_g \leq 10^9 solar masses. Surprisingly, we find that the mass ejection efficiency is very low for galaxies with mass M_g \geq 10^7 solar masses. Only galaxies with M_g \leq 10^6 solar masses have their interstellar gas blown away, and then virtually independently of L. On the other hand, metals from the supernova ejecta are accelerated to velocities larger than the escape speed from the galaxy far more easily than the gas. We find that for L_38=1, only about 30% of the metals are retained by a 10^9 solar mass galaxy, and virtually none by smaller galaxies. We discuss the implications of our results for the evolution, metallicity and observational properties of dwarf galaxies.Comment: 24 pages, 9 figures, uses AASTeX v4.0, full-resolution figures available from http://www.mpia-hd.mpg.de/theory/preprints.html#maclow Revised version includes minor changes to reply to referee (including explanation of why multiple clusters are less efficient at blowing away gas than single cluster) and to correct a minor error in computation. No new conclusions, but tables and figures have changed quantitativel

Effects of a localized beam on the dynamics of excitable cavity solitons

We study the dynamical behavior of dissipative solitons in an optical cavity filled with a Kerr medium when a localized beam is applied on top of the homogeneous pumping. In particular, we report on the excitability regime that cavity solitons exhibits which is emergent property since the system is not locally excitable. The resulting scenario differs in an important way from the case of a purely homogeneous pump and now two different excitable regimes, both Class I, are shown. The whole scenario is presented and discussed, showing that it is organized by three codimension-2 points. Moreover, the localized beam can be used to control important features, such as the excitable threshold, improving the possibilities for the experimental observation of this phenomenon.Comment: 9 Pages, 12 figure

Evidence for Asphericity in the Type IIn Supernova 1998S

We present optical spectropolarimetry obtained at the Keck-II 10-m telescope on 1998 March 7 UT along with total flux spectra spanning the first 494 days after discovery (1998 March 2 UT) of the peculiar type IIn supernova (SN) 1998S. The SN is found to exhibit a high degree of linear polarization, implying significant asphericity for its continuum-scattering environment. Prior to removal of the interstellar polarization, the polarization spectrum is characterized by a flat continuum (at p ~ 2%) with distinct changes in polarization associated with both the broad (FWZI >= 20,000 km/s) and narrow (unresolved, FWHM < 300 km/s) line emission seen in the total flux spectrum. When analyzed in terms of a polarized continuum with unpolarized broad-line recombination emission, an intrinsic continuum polarization of p ~ 3% results (the highest yet found for a SN), suggesting a global asphericity of >= 45% from the oblate, electron-scattering dominated models of Hoflich (1991). The smooth, blue continuum evident at early times is shown to be inconsistent with a reddened, single-temperature blackbody, instead having a color temperature that increases with decreasing wavelength. Broad emission-line profiles with distinct blue and red peaks are seen in the total flux spectra at later times, perhaps suggesting a disk-like or ring-like morphology for the dense (n_e ~ 10^7 cm^{-3}) circumstellar medium. Implications of the circumstellar scattering environment for the spectropolarimetry are discussed, as are the effects of uncertain removal of interstellar polarization.Comment: 25 pages + 2 tables + 14 figures, Submitted to The Astrophysical Journa

A very low mass of Ni-56 in the ejecta of SN 1994W

We present spectroscopic and photometric observations of the luminous narrow- line Type IIP (plateau) supernova 1994W. After the plateau phase (t >120 days), the light curve dropped by 3.5 mag in V in only 12 days. Between 125 and 197 days after explosion the supernova faded substantially faster than the decay rate of Co-56, and by day 197 it was 3.6 magnitudes less luminous in R compared to SN 1987A. The low R-luminosity could indicate less than 0.0026 {+0.0017}/ {-0.0011} Msun of Ni-56 ejected at the explosion, but the emission between 125 and 197 days must then have been dominated by an additional power source, pre- sumably circumstellar interaction. Alternatively, the late light curve was dominated by Co-56 decay. In this case, the mass of the ejected Ni-56 was 0.015 {+0.012}/{-0.008} Msun, and the rapid fading between 125 and 197 days was most likely due to dust formation. Though this value of the mass is higher than in the case with the additional power source, it is still lower than estimated for any previous Type II supernova. Only progenitors with M(ZAMS) = 8-10 Msun and M(ZAMS) > 25 Msun are expected to eject such low masses of Ni-56. If M(ZAMS) = 8-10 Msun, the plateau phase indicates a low explosion energy, while for a progenitor with M(ZAMS) > 25 Msun the energy can be the canonical 1.0E{51} ergs. As SN 1994W was unusually luminous, the low-mass explosion may require an uncomfortably high efficiency in converting explosion energy into radiation. This favors a M(ZAMS) > 25 Msun progenitor. The supernova's narrow (roughly 1000 km s^{-1}) emission lines were excited by the hot supernova spectrum, rather than a circumstellar shock. The thin shell from which the lines origi- nated was most likely accelerated by the radiation from the supernova.Comment: 19 pages AASTeX v.4.0, including 5 Postscript figures; ApJ, in pres