scholarly journals Blazar monitoring with LOFAR

2014 ◽  
Vol 10 (S313) ◽  
pp. 95-96 ◽  
Author(s):  
Sara Turriziani ◽  
Martin Hardcastle ◽  
James Miller-Jones ◽  
Jess Broderick ◽  
Sera Markoff ◽  
...  
Keyword(s):  
Low Frequencies ◽  
Available Bandwidth ◽  
Preliminary Results ◽  
Flux Variability ◽  
High Band ◽  
Proof Of Principle

AbstractWe have been monitoring some well-known bright blazars with short LOFAR observations since February 2013 with fortnightly cadence using the full available bandwidth of the High Band Antennas (i.e., 48 MHz centred at 226 MHz). The sources were chosen to be bright at low frequencies and to exhibit strong GHz-frequency radio variability on timescales of weeks to years. None of the five objects selected have been monitored previously in the MHz band. Here we report some preliminary results on flux variability obtained so far with LOFAR. These observations are scientifically valuable in their own right and also act as a proof of principle for broader, higher-cadence monitoring of the extragalactic sky with LOFAR and possibly SKA.

Enantioselective Multi-Component Cyclopropane Synthesis Enabled by Cu-Catalyzed Cyclopropene Carbometallation with Organoboron Reagent

2018 ◽  
Author(s):  
Zhanyu Li ◽  
Mengru Zhang ◽  
Yu Zhang ◽  
Shuang Liu ◽  
Jinbo Zhao ◽  
...  
Keyword(s):  
Carbon Source ◽  
Stereoselective Synthesis ◽  
Organometallic Reagents ◽  
Preliminary Results ◽  
Quaternary Center ◽  
Chiral Centers ◽  
Substituted Cyclopropanes ◽  
Proof Of Principle

Deployment of organoboron in lieu of the strongly basic <br>organometallic reagents as carbon source in Cu-catalyzed <br>cyclopropene carbometallation opens unprecedented three-<br>component reactivity for stereoselective synthesis of poly-substituted cyclopropanes. A proof-of-principle demonstration of this novel carbometallation strategy is presented herein for a highly convergent access to poly-substituted aminocyclopropane framework via <br>carboamination. Preliminary results on asymmetric desymmetrization with commercial bisphosphine ligands attained high levels of enantioselection, offering a straightforward access to enantioenriched aminocyclopropanes bearing all-three chiral centers, including an all-carbon quaternary center. This strategy may underpin a host of novel synthetic protocols for poly-substituted cyclopropanes. <br>

scholarly journals The eclipses of the black widow pulsar J1810+1744 at low radio frequencies

2017 ◽  
Vol 13 (S337) ◽  
pp. 396-397
Author(s):  
Elliott J. Polzin ◽  
Rene P. Breton ◽  
Ben W. Stappers ◽  
Keyword(s):  
Orbital Period ◽  
Line Of Sight ◽  
Dispersion Measure ◽  
Interferometric Imaging ◽  
Black Widow ◽  
Low Frequencies ◽  
Small Deviations ◽  
Imaging Mode ◽  
High Band ◽  
Observing Techniques

AbstractHere we present a study of the radio frequency eclipses of the black widow pulsar J1810+1744 at low frequencies, where we are most sensitive to small deviations in the effects of material along the line of sight. Utilising the simultaneous dual beamforming and interferometric (imaging) mode of LOFAR High Band Antenna, pulsar flux variations throughout the orbit are compared for the two observing techniques to test for the presence of scattering and absorption at eclipse orbital phases. Dispersion measure and scattering variations are used as a sensitive probe into outermost edges of the eclipsing material surrounding the companion star. We find the eclipsing medium to be variable on timescales shorter than the 3.6 hr orbital period, and propose cyclotron-synchrotron absorption as the most likely primary eclipse mechanism.

scholarly journals Reference-Electrode Free pH Sensing Using Impedance Spectroscopy

Proceedings ◽  
2018 ◽  
Vol 2 (13) ◽  
pp. 742 ◽  
Author(s):  
Laura Folkertsma ◽  
Lennart Gehrenkemper ◽  
Jan Eijkel ◽  
Karin Gerritsen ◽  
Mathieu Odijk
Keyword(s):  
Impedance Spectroscopy ◽  
Double Layer ◽  
Tin Oxide ◽  
Indium Tin Oxide ◽  
Reference Electrode ◽  
Ph Sensing ◽  
Low Frequencies ◽  
High Frequencies ◽  
Double Layer Capacity ◽  
Proof Of Principle

We present a reference-electrode free sensor able to measure both pH and conductivitybased on impedance spectroscopy. The electrode is made of a layer of indium-tin-oxide (ITO). Theimpedance of this electrode at low frequencies depends on its double layer capacity, which varieswith pH due to modification of oxide groups at the ITO surface. At high frequencies, the impedanceis determined by the resistance in the system, which corresponds to the inverse conductivity of thesolution. Because no reference electrode is needed for this technique, miniaturization of the pHsensor is simple. We demonstrate a proof-of-principle experiment of the sensor for human plasmapH measurements.

Combining high and low frequencies in rTMS antidepressive treatment: preliminary results

2002 ◽  
Vol 17 (7) ◽  
pp. 353-356 ◽  
Author(s):  
Andreas Conca ◽  
Jan Di Pauli ◽  
Wolfgang Beraus ◽  
Armand Hausmann ◽  
William Peschina ◽  
...  
Keyword(s):  
Low Frequencies ◽  
Preliminary Results ◽  
Antidepressive Treatment

scholarly journals The Lockman Hole Project: A Multi-frequency Study of the Faint Radio Population down to LOFAR bands

2013 ◽  
Vol 9 (S304) ◽  
pp. 108-109
Author(s):  
G. Guglielmino ◽  
I. Prandoni ◽  
R. Morganti ◽  
G. Heald ◽  
E. Mahony ◽  
...  
Keyword(s):  
Source Population ◽  
Low Frequencies ◽  
Radio Data ◽  
Preliminary Results ◽  
First Time ◽  
Lockman Hole

AbstractWe are performing a multi-frequency radio analysis of a well-known deep field: the Lockman Hole, which is one of the best studied sky regions in different wavebands. This will provide us with important complementary data (for example redshifts) to the radio data, allowing us to characterize the physical and evolutionary properties of the various classes of sources composing the faint radio population. LOFAR imaging of the Lockman Hole can play an important role in this project, allowing, for the very first time, to observe the sub-mJy source population at very low frequencies (30-200 MHz), where self-absorption phenomena are expected to be very important. Here we present some preliminary results.

scholarly journals A LOFAR census of non-recycled pulsars: extending to frequencies below 80 MHz

2020 ◽  
Vol 635 ◽  
pp. A75 ◽  
Author(s):  
A. V. Bilous ◽  
L. Bondonneau ◽  
V. I. Kondratiev ◽  
J.-M. Grießmeier ◽  
G. Theureau ◽  
...  
Keyword(s):  
Flux Density ◽  
Low Frequency ◽  
Spectral Indices ◽  
Low Frequencies ◽  
Density Measurements ◽  
High Band

We present the results from the low-frequency (40–78 MHz) extension of the first pulsar census of non-recycled pulsars carried out with the LOw-Frequency ARray (LOFAR). We used the low-band antennas of the LOFAR core stations to observe 87 pulsars out of 158 that had been previously detected using high-band antennas. We present flux densities and flux-calibrated profiles for the 43 pulsars we detected. Of this sample, 17 have not, to our knowledge, previously been detected at such low frequencies. Here we recalculate the spectral indices using the new low-frequency flux density measurements from the LOFAR census and discuss the prospects of studying pulsars at very low frequencies using current and upcoming facilities, such as the New Extension in Nançay Upgrading LOFAR (NenuFAR).

Enantioselective Multi-Component Cyclopropane Synthesis Enabled by Cu-Catalyzed Cyclopropene Carbometallation with Organoboron Reagent

2018 ◽  
Author(s):  
Zhanyu Li ◽  
Mengru Zhang ◽  
Yu Zhang ◽  
Shuang Liu ◽  
Jinbo Zhao ◽  
...  
Keyword(s):  
Carbon Source ◽  
Stereoselective Synthesis ◽  
Organometallic Reagents ◽  
Preliminary Results ◽  
Quaternary Center ◽  
Chiral Centers ◽  
Substituted Cyclopropanes ◽  
Proof Of Principle

Deployment of organoboron in lieu of the strongly basic <br>organometallic reagents as carbon source in Cu-catalyzed <br>cyclopropene carbometallation opens unprecedented three-<br>component reactivity for stereoselective synthesis of poly-substituted cyclopropanes. A proof-of-principle demonstration of this novel carbometallation strategy is presented herein for a highly convergent access to poly-substituted aminocyclopropane framework via <br>carboamination. Preliminary results on asymmetric desymmetrization with commercial bisphosphine ligands attained high levels of enantioselection, offering a straightforward access to enantioenriched aminocyclopropanes bearing all-three chiral centers, including an all-carbon quaternary center. This strategy may underpin a host of novel synthetic protocols for poly-substituted cyclopropanes. <br>

Using real-time fMRI neurofeedback to restore right occipital cortex activity in patients with left visuo-spatial neglect: proof-of-principle and preliminary results

2017 ◽  
Vol 29 (3) ◽  
pp. 339-360 ◽  
Author(s):  
Fabien Robineau ◽  
Arnaud Saj ◽  
Rémi Neveu ◽  
Dimitri Van De Ville ◽  
Frank Scharnowski ◽  
...  
Keyword(s):  
Real Time ◽  
Occipital Cortex ◽  
Spatial Neglect ◽  
Preliminary Results ◽  
Proof Of Principle
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