Using pulse-shape information for reconstructing cosmic-ray air showers and validating antenna responses with LOFAR and SKA

The Low Frequency Array (LOFAR) is capable of measuring extensive air showers through their radio emission in the frequency range of 30–80 MHz, while the Square Kilometer Array (SKA) will be able to expand this range to 50–350 MHz. A very important characteristic of cosmic rays is the mass of the primary particle, which is associated with the atmospheric depth of the shower maximum (max). The standard max reconstruction procedure with LOFAR involves the use of a library of CORSIKA/CoREAS simulations for a specific measured event and uses the energy deposited to the ground in terms of radio fluence. In this study, to extract information about shower development, not only the energy fluence is considered but the possibility of using information from the pulse shape is investigated in both frequency ranges (30–80 MHz and 50–350 MHz). The study of the pulse shape through the pulse agreement of measured data and simulations also provides a way to diagnose the proper functioning of individual LOFAR dipoles

Radio Emission Reveals Inner Meter-Scale Structure of Negative Lightning Leader Steps

We use the Low Frequency Array (LOFAR) to probe the dynamics of the stepping process of negatively charged plasma channels (negative leaders) in a lightning discharge. We observe that at each step of a leader, multiple pulses of vhf (30-80 MHz) radiation are emitted in short-duration bursts (&lt;10 mu s). This is evidence for streamer formation during corona flashes that occur with each leader step, which has not been observed before in natural lightning and it could help explain x-ray emission from lightning leaders, as x rays from laboratory leaders tend to be associated with corona flashes. Surprisingly, we find that the stepping length is very similar to what was observed near the ground, however with a stepping time that is considerably larger, which as yet is not understood. These results will help to improve lightning propagation models, and eventually lightning protection models.</p

Radio emission from negative lightning leader steps reveals inner meter-scale structure

We use the Low Frequency ARray (LOFAR) to probe the dynamics of the stepping process of negatively-charged plasma channels (negative leaders) in a lightning discharge. We observe that at each step of a leader, multiple pulses of VHF (30~--~80 MHz) radiation are emitted in short-duration bursts (<10 μs). This is evidence for streamer formation during corona flashes that occur with each leader step, which has not been observed before in natural lightning and it could help explain X-ray emission from lightning leaders, as X-rays from laboratory leaders tend to be associated with corona flashes. Surprisingly we find that the stepping length is very similar to what was observed near the ground, however with a stepping time that is considerably larger, which as yet is not understood. These results will help to improve lightning propagation models, and eventually lightning protection models

Plasma clearance of 5-FU and IrC™ administered as single agents or co-administered.

<p>Mice were injected i.v. with radio-labeled 5-FU (40 mg/kg) or IrC™ (40 mg IRI/kg), or both agents simultaneously. At various time points post-injection, the plasma concentrations of 5-FU and IRI (lactone) were determined. A) Mean plasma concentration of 5-FU +/− standard deviation (n = 4) after administration alone (solid gray line) or after co-administration with IrC™ (solid black line). B) Mean plasma concentration of IRI lactone +/− standard deviation (n = 4) after administration of IrC™ alone (dashed gray line) or after co-administration of IrC™ with 5-FU (solid black line).</p

Exposure time dependency of IRI and/or 5-FU cytotoxicity <i>in vitro</i>.

<p>A–D) Single agent exposure time dependency. LS174T (A and B) and HT-29 (C and D) cells were exposed to IRI (A and C) or 5-FU (B and D) for 1 (•, dotted line), 4 (<b>□</b>, solid line), 8 (▾, dotted line) 24 (<b>⋄</b>, solid line), 48 (<b>X</b>, dotted line), or 72 h (○, solid line). E) Combination exposure time dependency. HT-29 cells were exposed to IRI/5-FU (1∶1 molar ratio) for 1 h (•), 8 h (▾), or 48 h (<b>X</b>). F) Calculated CI values at FA = 0.9 for HT-29 cells exposed to IRI/5-FU (1∶1 molar ratio) for 1–72 h. A–D) Each point represents the mean +/− standard deviation (n = 3–9) from 2–3 experiments, each completed in triplicate. E, F) Each point or bar represents a combination index value calculated from cytotoxicity data compiled from 2–4 separate experiments, each completed in triplicate. CI of 0.8 to 1.2 suggests additive interactions; CI <0.8 suggests synergistic interactions; and CI >1.2 suggests antagonistic interactions.</p

Efficacy of IRI/5-FU and IrC™/5-FU treatment in the HT-29 s.c. model of CRC.

<p>Mice bearing s.c. HT-29 tumors were treated with saline+D5W (grey solid square), 5-FU (16 mg/kg; black solid upright triangle), IRI (60 mg/kg; grey solid diamond), IrC™ (40 or 60 mg IRI/kg; black solid inverted triangle or black solid circle, respectively), IRI +5-FU (60 mg/kg +16 mg/kg; black open circle), or IrC™ +5-FU (40 mg IRI/kg +16 mg/kg; grey solid star). Beginning on day 14, D5W and 5-FU were administered QD×5 (x 3 weeks) via i.p. injection (arrowheads); all other treatments were administered Q7D×3 via i.v. injection (full arrows). Data are presented as mean fold tumor volume increase +/− standard error of the mean (n = 6).</p

Radio emission from negative lightning leader steps reveals inner meter-scale structure

We use the Low Frequency ARray (LOFAR) to probe the dynamics of the stepping process of negatively-charged plasma channels (negative leaders) in a lightning discharge. We observe that at each step of a leader, multiple pulses of VHF (30~--~80 MHz) radiation are emitted in short-duration bursts (<10 μs). This is evidence for streamer formation during corona flashes that occur with each leader step, which has not been observed before in natural lightning and it could help explain X-ray emission from lightning leaders, as X-rays from laboratory leaders tend to be associated with corona flashes. Surprisingly we find that the stepping length is very similar to what was observed near the ground, however with a stepping time that is considerably larger, which as yet is not understood. These results will help to improve lightning propagation models, and eventually lightning protection models

Radio Emission Reveals Inner Meter-Scale Structure of Negative Lightning Leader Steps

We use the Low Frequency Array (LOFAR) to probe the dynamics of the stepping process of negatively charged plasma channels (negative leaders) in a lightning discharge. We observe that at each step of a leader, multiple pulses of vhf (30–80 MHz) radiation are emitted in short-duration bursts (<10  μs). This is evidence for streamer formation during corona flashes that occur with each leader step, which has not been observed before in natural lightning and it could help explain x-ray emission from lightning leaders, as x rays from laboratory leaders tend to be associated with corona flashes. Surprisingly, we find that the stepping length is very similar to what was observed near the ground, however with a stepping time that is considerably larger, which as yet is not understood. These results will help to improve lightning propagation models, and eventually lightning protection models

Decay of oriented Rydberg wave-packets excited with far-infrared radiation.

Transitions from bound atomic Rydberg Stark states in a static electric field to autoionizing Rydberg states above the electric-field-induced ionization threshold are studied using a broadband, tunable free-electron laser (photon energy 160-1400 cm(-1), pulse duration similar to 1 ps) and compared with multichannel quantum defect theory calculations. An atomic streak camera is used to record the time-resolved electron emission transients of the autoionizing atoms. For Stark states located on the downfield side of the potential, the far-infrared ionization spectrum is found to be smooth and the electron emission prompt (<2 ps), whereas for Stark states located on the upfield side, the far-infrared spectrum has sharp resonances, and the lifetime of the quasicontinuum states is considerably longer. The electron-emission transients from optical ionization of ground-state atoms are compared to transients from far-infrared ionization of Rydberg atoms, showing that the angular motion of the wave packet is responsible for the ionization dynamics for both cases, but different coherent superpositions of angular momentum states are excited depending on the initial state. Finally, we discuss the feasability of using Rydberg atoms as an ultrafast far-infrared detector, starting from a downfield state, or as a wavelength-selective detector, starting from an upheld state