Search results for " format"

5-Carbonyl-1,3-oxazine-2,4-diones from N-Cyanosulfoximines and Meldrum’s Acid Derivatives

2020

At elevated temperatures, N-cyanosulfoximines react with Meldrum's acid derivatives to give sulfoximines with N-bound 5-carbonyl-1,3-oxazine-2,4-dione groups. A representative product was characterized by single-crystal X-ray structure analysis. The product formation involves an unexpected molecular reorientation requiring several sequential bond-forming and -cleaving processes.

Decisive influence of substitution positions in molecular self-assembly

2014

Molecular self-assembly provides a versatile tool for creating functional molecular structures at surfaces. A rational design of molecular structure formation requires not only an in-depth understanding of the subtle balance between intermolecular and molecule-surface interactions, but might also involve considering chemical changes of the molecules, such as deprotonation. Here, we present a systematic investigation of a comparatively simple class of molecules, namely dihydroxybenzoic acid, which, nevertheless, enables creating a rich variety of structures when deposited onto calcite (10.4) held at room temperature. Based on non-contact atomic force microscopy measurements in ultra-high vac…

Cosmological origin of anomalous radio background

2012

The ARCADE 2 collaboration has reported a significant excess in the isotropic radio background, whose homogeneity cannot be reconciled with clustered sources. This suggests a cosmological origin prior to structure formation. We investigate several potential mechanisms and show that injection of relativistic electrons through late decays of a metastable particle can give rise to the observed excess radio spectrum through synchrotron emission. However, constraints from the cosmic microwave background (CMB) anisotropy, on injection of charged particles and on the primordial magnetic field, present a challenge. The simplest scenario is with a greater than or similar to 9 GeV particle decaying i…

Structure finding in cosmological simulations: the state of affairs

2013

The ever increasing size and complexity of data coming from simulations of cosmic structure formation demands equally sophisticated tools for their analysis. During the past decade, the art of object finding in these simulations has hence developed into an important discipline itself. A multitude of codes based upon a huge variety of methods and techniques have been spawned yet the question remained as to whether or not they will provide the same (physical) information about the structures of interest. Here we summarize and extent previous work of the "halo finder comparison project": we investigate in detail the (possible) origin of any deviations across finders. To this extent we decipher…

Late decaying 2-component dark matter scenario as an explanation of the AMS-02 positron excess

2016

The long standing anomaly in the positron flux as measured by the PAMELA and AMS-02 experiments could potentially be explained by dark matter (DM) annihilations. This scenario typically requires a large "boost factor" to be consistent with a thermal relic dark matter candidate produced via freeze-out. However, such an explanation is disfavored by constraints from CMB observations on energy deposition during the epoch of recombination. We discuss a scenario called late-decaying two-component dark matter (LD2DM), where the entire DM consists of two semi-degenerate species. Within this framework, the heavier species is produced as a thermal relic in the early universe and decays to the lighter…

Structure and dynamics of amphiphilic Janus spheres and spherocylinders under shear.

2019

We study the structure formation and flow properties of colloidal dispersions comprised of Janus spheres, Janus spherocylinders, and their mixtures, using hybrid molecular dynamics simulations that take into account hydrodynamic interactions. We systematically vary the Janus balance and the shape anisotropy of the particles, and explore a range of colloid volume fractions in the liquid regime of the phase diagram. At rest, Janus spheres with small hydrophobic patches form spherical micelles for all investigated colloid concentrations. In contrast, Janus spheres with an entirely hydrophobic hemisphere aggregate to larger worm-like micelles and network-like structures. Janus spherocylinders e…

Structural and morphological rearrangements in quenched poly(ethylene) by simultaneous SAXS/WAXS

2000

Structure formation by crystallization from the melt in a wide range of cooling rates (0.08-1 000°C/s) in low-density polyethylene has been studied by simultaneous small- and wide-angle X-ray scattering at the synchroton radiation source of DESY. The occurrence of two periodicities, characterized by different angular position of Bragg's maxima, was observed, pointing to the existence of two types of lamellar stacks, associated with two different long period values L 1 and L 2 (L 1 > L 2 ). L 1 depends on the cooling rate, whereas L 2 is almost constant. A comparison with isotactic polypropylene is performed, where a similar phenomenon takes place. While in the case of i-PP a definite correl…

Recent Changes in Student Life and Study ProcessesABSTRACT

1995

This research on university and university students was carried out during the 1980s at the University of Jyvaskyla in Finland. It is argued that the student years no longer constitute a ‘classically’ academic life stage; instead, the modem student's life is divided between study and part‐time employment. The uncertain economic situation and social immaturity of today's students hampers their identity formation. Student culture has lost its independence and vitality, and the basic structures of students’ life‐world have fragmented so that their lives no longer revolve around the university. Moreover, curricularization in universities has instrumentalized the study process and the relation o…

A trace element perspective on Archean crust formation and on the presence or absence of Archean subduction

2008

Favorire la riuscita a scuola degli alunni stranieri: potenziare il problem solving in matematica

2015

Nel presente capitolo ci si sofferma sulla riuscita scolastica in matematica, e in modo particolare sul potenziamento del problem solving, tenendo conto della diversità culturale e linguistica.