276 research outputs found
Een geïndividualiseerd instruktiesysteem, gebaseerd op de "drill-and-practice"-methode, in de technische mechanika
Vergelijking van methoden voor de oplossing van elasto-plastische problemen, op basis van de eindige elementen methode
Novel thiophenes and method for polymerization of said thiophenes
The invention relates to novel thiophenes of formula (I) wherein R and R' are independently - hydrogen, alkyl or alkoxy or together a -O-(CH2)n-O bridge wherein n = 1 to 5. Said thiophenes are suitable for the production of polythiophenes which can be used as organic conductors
Coplanarity by hydrogen bonding in well-defined oligoheterocycles
(Hetero)aryl-aryl coupling for covalent bonding and intramol. hydrogen bond formation for establishing the secondary structure have been united to design and construct well-defined, functionalized macromols. The suitability of azaheterocyclic units to realize this concept is exemplified by star shaped discotic liq. cryst. compds. and ladder-type conjugated copolymers. A review with >40 ref
A scanning tunneling microscope capable of electron spin resonance and pump-probe spectroscopy at mK temperature and in vector magnetic field
In the last decade, detecting spin dynamics at the atomic scale has been
enabled by combining techniques like electron spin resonance (ESR) or
pump-probe spectroscopy with scanning tunneling microscopy (STM). Here, we
demonstrate an ultra-high vacuum (UHV) STM operational at milliKelvin (mK) and
in a vector magnetic field capable of both ESR and pump-probe spectroscopy. By
implementing GHz compatible cabling, we achieve appreciable RF amplitudes at
the junction while maintaining mK base temperature. We demonstrate the
successful operation of our setup by utilizing two experimental ESR modes
(frequency sweep and magnetic field sweep) on an individual TiH molecule on
MgO/Ag(100) and extract the effective g-factor. We trace the ESR transitions
down to MHz into an unprecedented low frequency band enabled by the mK base
temperature. We also implement an all-electrical pump-probe scheme based on
waveform sequencing suited for studying dynamics down to the nanoseconds range.
We benchmark our system by detecting the spin relaxation time T1 of individual
Fe atoms on MgO/Ag(100) and note a field strength and orientation dependent
relaxation time
Threefold enhancement of superconductivity and the role of field-induced odd-frequency pairing in epitaxial aluminum films near the 2D limit
BCS theory has been widely successful at describing elemental bulk
superconductors. Yet, as the length scales of such superconductors approach the
atomic limit, dimensionality as well as the environment of the superconductor
can lead to drastically different and unpredictable superconducting behavior.
Here, we report a threefold enhancement of the superconducting critical
temperature and gap size in ultrathin epitaxial Al films on Si(111), when
approaching the 2D limit, based on high-resolution scanning tunneling
microscopy/spectroscopy (STM/STS) measurements. In magnetic field, the Al films
show type II behavior and the Meservey-Tedrow-Fulde (MTF) effect for in-plane
magnetic fields. Using spatially resolved spectroscopy, we characterize the
vortex structure in the MTF regime and find strong deviations from the typical
Abrikosov vortex. We corroborate these findings with calculations that unveil
the role of odd-frequency pairing and a paramagnetic Meissner effect. These
results illustrate two striking influences of reduced dimensionality on a BCS
superconductor and present a new platform to study BCS superconductivity in
large magnetic fields
Synthesis of new fluorescent 2-(2’, 2’’-bithienyl)-1,3-benzothiazoles
Bithienyl-1,3-benzothiazole derivatives were synthesised by reacting various 5-formyl-5’-alkoxy- or 5-formyl-5’-N,N-dialkylamino-2,2’-bithiophenes with ortho-aminobenzenethiol in good to excellent yields. Evaluation of the fluorescence properties of these compounds was carried out. They show strong fluorescence in the 450-600 nm region, as well as high quantum yields and large Stokes’ shifts.Fundação para a Ciência e Tecnologia
- …