673 research outputs found
Rhodium-catalysed hydroformylation of N-(2-propenyl)-β-lactams as a key step in the synthesis of functionalised N-[4-(2-oxoazetidin-1-yl)but-1-enyl]acetamides
Biologically relevant functionalised N-[4-(2-oxoazetidin-1-yl)but-1-enyl]acetamides have been prepared in a two-step approach starting from N-(2-propenyl)-beta-lactams, involving initial rhodium-catalysed hydroformylation followed by subjection of the obtained aldehydes to Staudinger reaction conditions after initial imination
Coexistence of charge and ferromagnetic order in fcc Fe
Phase coexistence phenomena have been intensively studied in strongly
correlated materials where several ordered states simultaneously occur or
compete. Material properties critically depend on external parameters and
boundary conditions, where tiny changes result in qualitatively different
ground states. However, up to date, phase coexistence phenomena have
exclusively been reported for complex compounds composed of multiple elements.
Here we show that charge- and magnetically ordered states coexist in
double-layer Fe on Rh(001). Scanning tunneling microscopy and spectroscopy
measurements reveal periodic charge order stripes below a temperature of 130 K.
Close to liquid helium temperature, they are superimposed by ferromagnetic
domains as observed by spin-polarized scanning tunneling microscopy.
Temperature-dependent measurements reveal a pronounced cross-talk between
charge and spin order at the ferromagnetic ordering temperature about 70 K,
which is successfully modeled within an effective Landau theory including
sixth-order terms. Our results show that subtle balance between structural
modifications can lead to competing ordering phenomena
Investigating the Structure of Son Bias in Armenia With Novel Measures of Individual Preferences
Sex ratios at birth favoring boys are being documented in a growing number of countries, a pattern indicating that families selectively abort females. Son bias also explains why, in many countries, girls have more siblings and are born at relatively earlier parities compared with their brothers. In this study, we develop novel methods for measuring son bias using both questionnaire items and implicit association tests, and we collect data on fertility preferences and outcomes from 2,700 participants in Armenia. We document highly skewed sex ratios, suggesting that selective abortions of females are widespread among parents in our sample. We also provide evidence that sex-selective abortions are underreported, which highlights the problem of social desirability bias. We validate our methods and demonstrate that conducting implicit association tests can be a successful strategy for measuring the relative preference for sons and daughters when social desirability is a concern. We investigate the structure of son-biased fertility preferences within households, across families, and between regions in Armenia, using measures of son bias at the level of the individual decision-maker. We find that men are, on average, considerably more son-biased than women. We also show that regional differences in son bias exist and that they appear unrelated to the socioeconomic composition of the population. Finally, we estimate the degree of spousal correlation in son bias and discuss whether husbands are reliably more son-biased than their wives
Einsatz des Kaltwand-Induktions-Tiegelofens zum Schmelzen und Gießen von TiAl-Legierungen
[no abstract
Trapping colloids near chemical stripes via critical Casimir forces
We study theoretically and experimentally the solvent-mediated critical
Casimir force acting on colloidal particles immersed in a binary liquid mixture
of water and 2,6-lutidine and close to substrates which are chemically
patterned with periodically alternating stripes of antagonistic adsorption
preferences. These patterns are experimentally realized via microcontact
printing. Upon approaching the critical demixing point of the solvent, normal
and lateral critical Casimir forces generate laterally confining effective
potentials for the colloids. We analyze in detail the rich behavior of the
spherical colloids close to such substrates. For all patterned substrates we
investigated, our measurements of these effective potentials agree with the
corresponding theoretical predictions. Since both the directions and the
strengths of the critical Casimir forces can be tuned by minute temperature
changes, this provides a new mechanism for controlling colloids as model
systems, opening encouraging perspectives for applications.Comment: Invited contribution to Molecular Physics Special Issue on Bob Evans'
65th birthda
Methods for estimating air pollutant emissions. PART 1: Review and source of input data.
This report is part of the development of a National Modelling System for local air quality (the “Nasjonalt Beregningsverktøy” or NBV project). The work focussed on the methods to estimate emissions and identified the main information sources of the needed input data for emissions. This report presents the most common methods to determine emissions and includes recommendations for future improvement of the emission calculations. The main purpose of the report is to identify the most relevant sources of emission information and the emission input data requirements necessary for modelling air quality in Norwegian cities and agglomerations
Note on basic features of large time behaviour of heat kernels
Large time behaviour of heat semigroups (and more generally, of positive
selfadjoint semigroups) is studied. Convergence of the semigroup to the ground
state and of averaged logarithms of kernels to the ground state energy is shown
in the general framework of positivity improving selfadjoint semigroups. This
framework includes Laplacians on manifolds, metric graphs and discrete graphs.Comment: 24 page
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