1,459 research outputs found
Together We Are Better : Professional Learning Networks for Teachers
In recent years, many educators have turned to professional learning networks (PLNs) to grow in their craft with peers who are more accessible online because of reduced temporal and spatial constraints. While educators have cultivated PLNs, there is a dearth of research about the effects of PLNs. This manuscript reports the findings of a qualitative study that investigated PLN experiences through the analysis of survey data from 732 P-12 teachers. Data analysis suggests that the anytime, anywhere availability of expansive PLNs, and their capacity to respond to educators\u27 diverse interests and needs, appear to offer possibilities for supporting the professional growth of whole teachers. These findings have implications for defining the present and future of teacher learning in a digital age
Multiphoton Transitions in a Spin System Driven by Strong Bichromatic Field
EPR transient nutation spectroscopy is used to measure the effective field
(Rabi frequency) for multiphoton transitions in a two-level spin system
bichromatically driven by a transverse microwave (MW) field and a longitudinal
radio-frequency (RF) field. The behavior of the effective field amplitude is
examined in the case of a relatively strong MW field, when the derivation of
the effective Hamiltonian cannot be reduced to first-order perturbation theory
in w_{1} / w_{rf} (w_{1} is the microwave Rabi frequency, w_{rf} is the RF
frequency). Experimental results are consistently interpreted by taking into
account the contributions of second and third order in w_{1} / w_{rf} evaluated
by Krylov-Bogolyubov-Mitropolsky averaging. In the case of inhomogeneously
broadened EPR line, the third-order correction modifies the nutation frequency,
while the second-order correction gives rise to a change in the nutation
amplitude due to a Bloch-Siegert shift.Comment: 7 pages, 6 figure
Influence of Sample Mixing Techniques on Engine Oil Contamination Analysis by Infrared Spectroscopy
For the most reliable and reproducible results for calibration or general testing purposes of two immiscible liquids, such as water in engine oil, good emulsification is vital. This study explores the impact of emulsion quality on the Fourier transform infrared (FT-IR) spectroscopy calibration standards for measuring water contamination in used or in-service engine oil, in an attempt to strengthen the specific guidelines of ASTM International standards for sample preparation. By using different emulsification techniques and readily available laboratory equipment, this work is an attempt to establish the ideal sample preparation technique for reliability, repeatability, and reproducibility for FT-IR analysis while still considering the ease and efficiency of the technique. This study demonstrates that a stable emulsion within a sample, which depends heavily upon the method, provides a reliably consistent homogenous sample for quantification purposes with FT-IR analysis. Analysis of variance (ANOVA) modeling and limit of detection calculations demonstrate the stability of the emulsion. The results reveal that setting a mixing time for a calibration standard depends on the emulsification process. Inserting a probe directly into a sample (direct sonication) allows for a rapid, stable emulsion with high reproducibility. Indirect sonication produces relatively non-miscible liquids of different densities. The pan-shaker produces a reasonably stable emulsion, but without the long-term stability or quick production time of direct sonication. Reaction time plays a critical role in the rotary mixing method, which leads to a slow development of emulsification
Absorption Wavebands for Discriminating Oxidation Time of Engine Oil as Detected by FT-IR Spectroscopy
Fourier Transform-Infrared (FT-IR) spectroscopy was used to analyze gasoline engine oil (SAE 5W20) samples that were exposed to seven different oxidation times (0 h, 24 h, 48 h, 72 h, 96 h, 120 h, and 144 h) to determine the best wavenumbers and wavenumber ranges for the discrimination of the oxidation times. The thermal oxidation process generated oil samples with varying total base number (TBN) levels. Each wavenumber (400–3900 cm1) and wavenumber ranges identified from the literature and this study were statistically analyzed to determine which wavenumbers and wavenumber ranges could discriminate among all oxidation times. Linear regression was used with the best wavenumbers and wavenumber ranges to predict oxidation time
Coherent manipulation of charge qubits in double quantum dots
The coherent time evolution of electrons in double quantum dots induced by
fast bias-voltage switches is studied theoretically. As it was shown
experimentally, such driven double quantum dots are potential devices for
controlled manipulation of charge qubits. By numerically solving a quantum
master equation we obtain the energy- and time-resolved electron transfer
through the device which resembles the measured data. The observed oscillations
are found to depend on the level offset of the two dots during the manipulation
and, most surprisingly, also the on initialization stage. By means of an
analytical expression, obtained from a large-bias model, we can understand the
prominent features of these oscillations seen in both the experimental data and
the numerical results. These findings strengthen the common interpretation in
terms of a coherent transfer of electrons between the dots.Comment: 18 pages, 4 figure
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