6,230 research outputs found
Radiocarbon Dioxide detection based on Cavity Ring-Down Spectroscopy and a Quantum Cascade Laser
Monitoring of radiocarbon (C) in carbon dioxide is demonstrated using
mid-infrared spectroscopy and a quantum cascade laser. The measurement is based
on cavity ring-down spectroscopy, and a high sensitivity is achieved with a
simple setup. The instrument was tested using a standardised sample containing
elevated levels of radiocarbon. Radiocarbon dioxide could be detected from
samples with an isotopic ratio C/C as low as 50 parts-per-trillion,
corresponding to an activity of 5 kBq/m in pure CO, or 2 Bq/m in
air after extraction of the CO from an air sample. The instrument is
simple, compact and robust, making it the ideal tool for on-site measurements.
It is aimed for monitoring of radioactive gaseous emissions in nuclear power
environment, during the operation and decommissioning of nuclear power plants.
Its high sensitivity also makes it the ideal tool for the detection of leaks in
radioactive waste repositories.Comment: 5 pages, 4 figure
Evidence from the Patent Record on the Development of Cash Dispensing Technology
There are but a handful of systematic studies on the history of automated teller machines (ATMs) yet all fail to address the issue of paternity while perpetrating âcommon wisdomâ beliefs. This article looks at the birth of currency dispensing equipment, the immediate predecessor to the ATM. At the simplest level, at least four separate instance of innovation can reasonably claim to be the origin of the concept. However, the question as to who invented it is less illuminating than an understanding of the process of innovation itself and how these competing families developed into the modern conception of an ATM. Our research supports the view of user-driven innovation as surviving business records and oral histories tell of close involvement of bank staff in establishing requirements and choosing amongst alternative solutions in the implementation of first generation technology. This case thus shows greater understanding in the userâs role in shaping and directing technological development.Cash dispensers (ATMs), History, Financial data processing, Patents, Research and development, User interfaces
Surface spin magnetism controls the polarized exciton emission from CdSe nanoplatelets
The surface of nominally diamagnetic colloidal CdSe nanoplatelets can
demonstrate paramagnetism owing to the uncompensated spins of dangling bonds
(DBSs). We reveal that by optical spectroscopy in high magnetic fields up to 15
Tesla using the exciton spin as probe of the surface magnetism. The strongly
nonlinear magnetic field dependence of the circular polarization of the exciton
emission is determined by the DBS and exciton spin polarization as well as by
the spin-dependent recombination of dark excitons. The sign of the exciton-DBS
exchange interaction can be adjusted by the nanoplatelet growth conditions
Electron and hole g-factors and spin dynamics of negatively charged excitons in CdSe/CdS colloidal nanoplatelets with thick shells
We address spin properties and spin dynamics of carriers and charged excitons
in CdSe/CdS colloidal nanoplatelets with thick shells. Magneto-optical studies
are performed by time-resolved and polarization-resolved photoluminescence,
spin-flip Raman scattering and picosecond pump-probe Faraday rotation in
magnetic fields up to 30 T. We show that at low temperatures the nanoplatelets
are negatively charged so that their photoluminescence is dominated by
radiative recombination of negatively charged excitons (trions). Electron
g-factor of 1.68 is measured and heavy-hole g-factor varying with increasing
magnetic field from -0.4 to -0.7 is evaluated. Hole g-factors for
two-dimensional structures are calculated for various hole confining potentials
for cubic- and wurtzite lattice in CdSe core. These calculations are extended
for various quantum dots and nanoplatelets based on II-VI semiconductors. We
developed a magneto-optical technique for the quantitative evaluation of the
nanoplatelets orientation in ensemble
- âŠ