Degree growth of meromorphic surface maps

We study the degree growth of iterates of meromorphic selfmaps of compact Kahler surfaces. Using cohomology classes on the Riemann-Zariski space we show that the degrees grow similarly to those of mappings that are algebraically stable on some birational model.Comment: 17 pages, final version, to appear in Duke Math Journa

Recent observed changes in severe storms over the United Kingdom and Iceland

Severe storms defined as 3-hourly pressure changes exceeding an extreme magnitude, were carefully manually quality-controlled and analyzed at stations in the UK and Iceland which had at least 45 years of digitized data. Iceland showed significant distribution differences between the periods before and after 1980 with a tendency towards less extreme severe events in latter decades. In contrast, the UK regions have tended towards larger magnitude events in recent decades, particularly in the more southerly regions. There has been a significant increase in the number of severe storms over the UK as a whole since the 1950s, however, this may not be unusual in longer-term variability. For both the UK and Iceland in winter these changes in severe storms appear to be related to changes in the North Atlantic Oscillation (NAO) but UK changes during October to December do not appear to be related to changes in the NAO

Singular semipositive metrics in non-Archimedean geometry

Let X be a smooth projective Berkovich space over a complete discrete valuation field K of residue characteristic zero, endowed with an ample line bundle L. We introduce a general notion of (possibly singular) semipositive (or plurisubharmonic) metrics on L, and prove the analogue of the following two basic results in the complex case: the set of semipositive metrics is compact modulo constants, and each semipositive metric is a decreasing limit of smooth semipositive ones. In particular, for continuous metrics our definition agrees with the one by S.-W. Zhang. The proofs use multiplier ideals and the construction of suitable models of X over the valuation ring of K, using toroidal techniques.Comment: 49 pages, 1 figure. Accepted in the Journal of Algebraic Geometr

Long time motion of NLS solitary waves in a confining potential

We study the motion of solitary-wave solutions of a family of focusing generalized nonlinear Schroedinger equations with a confining, slowly varying external potential, $V(x)$. A Lyapunov-Schmidt decomposition of the solution combined with energy estimates allows us to control the motion of the solitary wave over a long, but finite, time interval. We show that the center of mass of the solitary wave follows a trajectory close to that of a Newtonian point particle in the external potential $V(x)$ over a long time interval.Comment: 42 pages, 2 figure

Effects of surface forces and phonon dissipation in a three-terminal nano relay

We have performed a theoretical analysis of the operational characteristics of a carbon-nanotube-based three-terminal nanorelay. We show that short range and van der Waals forces have a significant impact on the characteristics of the relay and introduce design constraints. We also investigate the effects of dissipation due to phonon excitation in the drain contact, which changes the switching time scales of the system, decreasing the longest time scale by two orders of magnitude. We show that the nanorelay can be used as a memory element and investigate the dynamics and properties of such a device

Reconstructing past atmospheric circulation changes using oxygen isotopes in lake sediments from Sweden

Here we use lake sediment studies from Sweden to illustrate how Holocene-aged oxygen isotope records from lakes located in different hydrological settings, can provide information about climate change. In particular changes in precipitation, atmospheric circulation and water balance. We highlight the importance of understanding the present lake hydrology, and the relationship between climate variables and the oxygen isotopic composition of precipitation (18Op) and lake waters (18Olakewater) for interpretation of the oxygen isotopic record from the sediments (18O). Both precipitation reconstructions from northern Sweden and water balance reconstructions from south and central Sweden show that the atmospheric circulation changed from zonal to a more meridional airflow over the Holocene. Superimposed on this Holocene trend are δ18Op minima resembling intervals of the negative phase of the North Atlantic Oscillation (NAO), thus suggesting that the climate of Northern Europe is strongly influenced by atmospheric and oceanic circulation changes over the North Atlantic

Negotiating across difference: gendered exclusions and cooperation in the shea value chain

Shea butter, derived from the African shea tree, has acquired a pivotal position in global agro-food and cosmetics industries. In Burkina Faso, public and private actors as well as civil society are converging upon the product to boost the incomes of rural female producers. As a result of these trends, the shea value chain is increasingly segmented; shea nuts are sold in a low-return, conventional market and simultaneously enter an alternative, high-value niche market. In the latter strand of the value chain, some producers are improving their prospects by forming an association. Tracing relationships across the two strands, we demonstrate how ‘horizontal’ relations based on gender, ethnicity, age and geography contribute to shaping participation and benefit capture in the shea value chain. We argue that processes of social inclusion and exclusion operate in parallel, as differentiated actors both cooperate and compete to secure their place within the chain. While collective organizing brings positive social and economic benefits, we show that producers’ associations need not be empowering for all women. The significance ofcollective enterprises, but also their drawbacks must be considered when valorising pathways to women’s empowerment. Our study reinforces calls for greater integration of horizontal elements in value chain analyses

High-temperature deep-level transient spectroscopy system for defect studies in wide-bandgap semiconductors

Full investigation of deep defect states and impurities in wide-bandgap materials by employing commercial transient capacitance spectroscopy is a challenge, demanding very high temperatures. Therefore, a high-temperature deep-level transient spectroscopy (HT-DLTS) system was developed for measurements up to 1100 K. The upper limit of the temperature range allows for the study of deep defects and trap centers in the bandgap, deeper than previously reported by DLTS characterization in any material. Performance of the system was tested by conducting measurements on the well-known intrinsic defects in n-type 4H-SiC in the temperature range 300-950 K. Experimental observations performed on 4H-SiC Schottky diodes were in good agreement with the literatures. However, the DLTS measurements were restricted by the operation and quality of the electrodes

Boundary Conditions for Singular Perturbations of Self-Adjoint Operators

Let A:D(A)\subseteq\H\to\H be an injective self-adjoint operator and let \tau:D(A)\to\X, X a Banach space, be a surjective linear map such that \|\tau\phi\|_\X\le c \|A\phi\|_\H. Supposing that \text{\rm Range} (\tau')\cap\H' =\{0\}, we define a family $A^\tau_\Theta$ of self-adjoint operators which are extensions of the symmetric operator $A_{|\{\tau=0\}.}$. Any $\phi$ in the operator domain $D(A^\tau_\Theta)$ is characterized by a sort of boundary conditions on its univocally defined regular component \phireg, which belongs to the completion of D(A) w.r.t. the norm \|A\phi\|_\H. These boundary conditions are written in terms of the map $\tau$, playing the role of a trace (restriction) operator, as \tau\phireg=\Theta Q_\phi, the extension parameter $\Theta$ being a self-adjoint operator from X' to X. The self-adjoint extension is then simply defined by A^\tau_\Theta\phi:=A \phireg. The case in which $A\phi=T*\phi$ is a convolution operator on LD, T a distribution with compact support, is studied in detail.Comment: Revised version. To appear in Operator Theory: Advances and Applications, vol. 13

Impact of changes to reimbursement of fixed combinations of inhaled corticosteroids and long-acting β₂ -agonists in obstructive lung diseases: a population-based, observational study.

To access publisher's full text version of this article, please click on the hyperlink in Additional Links field or click on the hyperlink at the top of the page marked Files. This article is open access.In 2010, the Icelandic government introduced a new cost-saving policy that limited reimbursement of fixed inhaled corticosteroid/long-acting β₂ -agonist (ICS/LABA) combinations.This population-based, retrospective, observational study assessed the effects of this policy change by linking specialist/primary care medical records with data from the Icelandic Pharmaceutical Database. The policy change took effect on 1 January 2010 (index date); data for the year preceding and following this date were analysed in 8241 patients with controlled/partly controlled asthma and/or chronic obstructive pulmonary disease (COPD) who had been dispensed an ICS/LABA during 2009. Oral corticosteroid (OCS) and short-acting β₂ -agonist (SABA) use, and healthcare visits, were assessed pre- and post-index.The ICS/LABA reimbursement policy change led to 47.8% fewer fixed ICS/LABA combinations being dispensed during the post-index period among patients whose asthma and/or COPD was controlled/partly controlled during the pre-index period. Fewer ICS monocomponents were also dispensed. A total of 48.6% of patients were no longer receiving any respiratory medications after the policy change. This was associated with reduced disease control, as demonstrated by more healthcare visits (44.0%), and more OCS (76.3%) and SABA (51.2%) dispensations.Overall, these findings demonstrate that changes in healthcare policy and medication reimbursement can directly impact medication use and, consequently, clinical outcomes and should, therefore, be made cautiously.AstraZenec