212 research outputs found
Controlling for fixed effects in studies of income underreporting
The expenditure method of Pissarides and Weber (1989) [Journal of Public Economics, 39 (1), 17-
32) shows how one backs out measure of income underreporting by the self-employed by using
food consumption as trace of true income. In this paper we make a case for using panel data
and fixed effects estimation in such analysis, instead of OLS estimation. The main argument is
that fixed effects estimation addresses the problem of omitted variable bias in the
identification. We demonstrate the use of panel data and fixed effects estimation by using large
scale administrative register data on charitable donations, exploiting that the data can be
turned into a panel dataset. The results suggest that the estimation technique matters – fixed
effects estimates are smaller than OLS estimates
The LOTTE system of tax microsimulation models
Microsimulation models of the LOTTE system are key tools for tax policy-making in Norway and are
extensively used in the budget process. The aim of this paper is to give an overview of the different
modules in the LOTTE family – a non-behavioral tax-benefit model for personal income tax (LOTTESkatt), a labor supply model (LOTTE-Arbeid), and a model for distributional effects of commodity
taxation (LOTTE-Konsum). In addition to providing descriptions of the designs of the three
microsimulation models, we give examples of how the models are used in practical and academic
work.The development and maintenance of the models in the LOTTE family are supported by the Ministry of Finance
Effect of Folic Acid Supplementation on Levels of Circulating Monocyte Chemoattractant Protein-1 and the Presence of Intravascular Ultrasound Derived Virtual Histology Thin-Cap Fibroatheromas in Patients with Stable Angina Pectoris
Background:Virtual Histology Intravascular Ultrasound (VH-IVUS) may be used to detect early signs of unstable coronary artery disease. Monocyte Chemoattractant Protein-1 (MCP-1) is linked with coronary atherosclerosis and plaque instability and could potentially be modified by folic acid treatment.Methods:In a randomized, prospective study, 102 patients with stable angina pectoris (SAP) received percutaneous coronary intervention and established medical treatment as well as either homocysteine-lowering folic acid/vitamin B12 (±B6) or placebo (±B6) for 1 year before VH-IVUS was performed. The presence of VH-Thin-Cap Fibroatheroma (VH-TCFA) in non-intervened coronary vessels was registered and serum levels of MCP-1 were measured. The patients were subsequently followed for incident myocardial infarction (MI).Results:Patients treated with folic acid/vitamin B12 had a geometric mean (SD) MCP-1 level of 79.95 (1.49) versus 86.00 (1.43) pg/mL for patients receiving placebo (p-value 0.34). VH-TCFA lesions were present in 7.8% of patients and did not differ between intervention arms (p-value 0.47). Serum levels of MCP-1 were 1.46 (95% CI 1.12 to 1.92) times higher in patients with VH-TCFA lesions than in those without (p-value 0.005). Afterwards, patients were followed for median 2.1 years and 3.8% experienced a myocardial infarction (MI), which in post-hoc Cox regression analyses was independently predicted by both MCP-1 (P-value 0.006) and VH-TCFA (p-value 0.01).Conclusions:In patients with SAP receiving established medical treatment, folic acid supplementation is not associated with either presence of VH-TCFA or levels of MCP-1. MCP-1 is however associated with VH-TCFA, a finding corroborated by increased risk for future MI.ClinicalTrials.gov Identifier: NCT00354081
Intrinsic thermal vibrations of suspended doubly clamped single-wall carbon nanotubes
We report the observation of thermally driven mechanical vibrations of
suspended doubly clamped carbon nanotubes, grown by chemical vapor deposition
(CVD). Several experimental procedures are used to suspend carbon nanotubes.
The vibration is observed as a blurring in images taken with a scanning
electron microscope. The measured vibration amplitudes are compared with a
model based on linear continuum mechanics.Comment: pdf including figures, see:
http://www.unibas.ch/phys-meso/Research/Papers/2003/NT-Thermal-Vibrations.pd
Direct transport between superconducting subgap states in a double quantum dot
We demonstrate direct transport between two opposing sets of Yu-Shiba-Rusinov (YSR) subgap states realized in a double quantum dot. This bound-state-to-bound-state transport relies on intrinsic quasiparticle relaxation, and the tunable gating of this quantum dot device allows us to explore also an additional relaxation mechanism based on charge transferring Andreev reflections. The transition between these two relaxation regimes is identified in the experiment as a marked gate-induced stepwise change in conductance. We present a transport calculation, including YSR bound states and multiple Andreev reflections alongside quasiparticle relaxation, due to a weak tunnel coupling to a nearby normal metal, and obtain excellent agreement with the dat
Spectral function of the Kondo model in high magnetic fields
Using a recently developed perturbative renormalization group (RG) scheme, we
calculate analytically the spectral function of a Kondo impurity for either
large frequencies w or large magnetic field B and arbitrary frequencies. For
large w >> max[B,T_K] the spectral function decays as 1/ln^2[ w/T_K ] with
prefactors which depend on the magnetization. The spin-resolved spectral
function displays a pronounced peak at w=B with a characteristic asymmetry. In
a detailed comparison with results from numerical renormalization group (NRG)
and bare perturbation theory in next-to-leading logarithmic order, we show that
our perturbative RG scheme is controlled by the small parameter 1/ln[
max(w,B)/T_K]. Furthermore, we assess the ability of the NRG to resolve
structures at finite frequencies.Comment: 8 pages, version published in PRB, minor change
Biosynthesis of Macrolactam BE-14106 Involves Two Distinct PKS Systems and Amino Acid Processing Enzymes for Generation of the Aminoacyl Starter Unit
SummaryBE-14106 is a macrocyclic lactam with an acyl side chain previously identified in a marine-derived Streptomyces sp. The gene cluster for BE-14106 biosynthesis was cloned from a Streptomyces strain newly isolated from marine sediments collected in the Trondheimsfjord (Norway). Bioinformatics and experimental analyses of the genes in the cluster suggested an unusual mechanism for assembly of the molecule. Biosynthesis of the aminoacyl starter apparently involves the concerted action of a distinct polyketide synthase (PKS) system and several enzymes that activate and process an amino acid. The resulting starter unit is loaded onto a second PKS complex, which completes the synthesis of the macrolactam ring. Gene inactivation experiments, enzyme assays with heterologously expressed proteins, and feeding studies supported the proposed model for the biosynthesis and provided new insights into the assembly of macrolactams with acyl side chain
Resonance Kondo Tunneling through a Double Quantum Dot at Finite Bias
It is shown that the resonance Kondo tunneling through a double quantum dot
(DQD) with even occupation and singlet ground state may arise at a strong bias,
which compensates the energy of singlet/triplet excitation. Using the
renormalization group technique we derive scaling equations and calculate the
differential conductance as a function of an auxiliary dc-bias for parallel DQD
described by SO(4) symmetry. We analyze the decoherence effects associated with
the triplet/singlet relaxation in DQD and discuss the shape of differential
conductance line as a function of dc-bias and temperature.Comment: 11 pages, 6 eps figures include
Nonequilibrium Transport through a Kondo Dot in a Magnetic Field: Perturbation Theory
Using nonequilibrium perturbation theory, we investigate the nonlinear
transport through a quantum dot in the Kondo regime in the presence of a
magnetic field. We calculate the leading logarithmic corrections to the local
magnetization and the differential conductance, which are characteristic of the
Kondo effect out of equilibrium. By solving a quantum Boltzmann equation, we
determine the nonequilibrium magnetization on the dot and show that the
application of both a finite bias voltage and a magnetic field induces a novel
structure of logarithmic corrections not present in equilibrium. These
corrections lead to more pronounced features in the conductance, and their form
calls for a modification of the perturbative renormalization group.Comment: 16 pages, 7 figure
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