Oceanic Ambient Noise as a Background to Acoustic Neutrino Detection

Ambient noise measured in the deep ocean is studied in the context of a search for signals from ultra-high energy cosmic ray neutrinos. The spectral shape of the noise at the relevant high frequencies is found to be very stable for an extensive data set collected over several months from 49 hydrophones mounted near the bottom of the ocean at ~1600 m depth. The slopes of the ambient noise spectra above 15 kHz are found to roll-off faster than the -6 dB/octave seen in Knudsen spectra. A model attributing the source to an uniform distribution of surface noise that includes frequency-dependent absorption at large depth is found to fit the data well up to 25 kHz. This depth dependent model should therefore be used in analysis methods of acoustic neutrino pulse detection that require the expected noise spectra.Comment: Minor changes. Submitted to PRD. 5 pages, 7 figure

Theoretical study of transition radiation from hot electrons generated in the laser-solid interaction

Copyright 2003 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Physics of Plasmas, 10(7), 2994-3003, 2003 and may be found at http://dx.doi.org/10.1063/1.157638

An introduction to neonatal EEG

Electroencephalography (EEG) is used in neonatal care to assess encephalopathy, seizure recognition and classification, to make epilepsy syndrome diagnoses and to assess the maturity of neonatal brain activity. A basic understanding of the EEG is very helpful in ensuring that clinicians gain as much information as possible from this helpful, non-invasive investigation. The neonatal EEG is complex and accurate reporting requires detailed clinical information to be provided on request forms. Even when this is provided EEG reports are frequently returned to the neonatal unit loaded with technical details, making it difficult for neonatal staff to fully understand them. This article reviews the basics of EEG, the changes seen with increasing gestational age, and changes seen in common pathologies. We also provide a structured approach to the interpretation of the neonatal EEG report, and discuss its role in prognostication. Amplitude integrated EEG is reviewed in our companion paper

Effect of a magnetic field on the long-range magnetic order in insulating Nd2CuO4, nonsuperconducting and superconducting Nd1.85Ce0.15CuO4

We have measured the effect of a c-axis aligned magnetic field on the long-range magnetic order of insulating Nd2CuO4, as-grown nonsuperconducting and superconducting Nd1.85Ce0.15CuO4. On cooling from room temperature, Nd2CuO4 goes through a series of antiferromagnetic (AF) phase transitions with different noncollinear spin structures. In all phases of Nd2CuO4, we find that the applied c-axis field induces a canting of the AF order but does not alter the basic zero-field noncollinear spin structures. Similar behavior is also found in as-grown nonsuperconducting Nd1.85Ce0.15CuO4. These results contrast dramatically with those of superconducting Nd1.85Ce0.15CuO4, where a c-axis aligned magnetic field induces a static, anomalously conducting, long-range ordered AF state. We confirm that the annealing process necessary to make superconducting Nd1.85Ce0.15CuO4 also induces epitaxial, three-dimensional long-range ordered cubic (Nd,Ce)2O3 as an impurity phase. In addition, the annealing process makes a series of quasi two-dimensional superlattice reflections associated with lattice distortions of Nd1.85Ce0.15CuO4 in the CuO2 plane. While the application of a magnetic field will induce a net moment in the impurity phase, we determine its magnitude and eliminate this as a possibility for the observed magnetic field-induced effect in superconducting Nd1.85Ce0.15CuO4.Comment: 12 pages, 10 figures, to be published in Phys. Rev.

Femtosecond X-ray emission study of the spin cross-over dynamics in haem proteins

In haemoglobin (consisting of four globular myoglobin-like subunits), the change from the low-spin (LS) hexacoordinated haem to the high spin (HS) pentacoordinated domed form upon ligand detachment and the reverse process upon ligand binding, represent the transition states that ultimately drive the respiratory function. Visible-ultraviolet light has long been used to mimic the ligand release from the haem by photodissociation, while its recombination was monitored using time-resolved infrared to ultraviolet spectroscopic tools. However, these are neither element- nor spin-sensitive. Here we investigate the transition state in the case of Myoglobin-NO (MbNO) using femtosecond Fe Kalpha and Kbeta non-resonant X-ray emission spectroscopy (XES) at an X-ray free-electron laser upon photolysis of the Fe-NO bond. We find that the photoinduced change from the LS (S = 1/2) MbNO to the HS (S = 2) deoxy-myoglobin (deoxyMb) haem occurs in ca. 800 fs, and that it proceeds via an intermediate (S = 1) spin state. The XES observables also show that upon NO recombination to deoxyMb, the return to the planar MbNO ground state is an electronic relaxation from HS to LS taking place in ca. 30 ps. Thus, the entire ligand dissociation-recombination cycle in MbNO is a spin cross-over followed by a reverse spin cross-over process

Characterization of preplasma produced by an ultrahigh intensity laser system

Copyright 2004 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Physics of Plasmas, 11(8), 3721-3725, 2004 and may be found at http://dx.doi.org/10.1063/1.176077

Association of body mass index and height with risk of prostate cancer among middle-aged Japanese men

In a population-based prospective study of 49 850 Japanese men, body mass index and height were not significantly associated with risk of prostate cancer (311 cases), although small positive effects could not be ruled out in advanced cases (91 cases)

IceCube Sensitivity for Low-Energy Neutrinos from Nearby Supernovae

This paper describes the response of the IceCube neutrino telescope located at the geographic South Pole to outbursts of MeV neutrinos from the core collapse of nearby massive stars. IceCube was completed in December 2010 forming a lattice of 5160 photomultiplier tubes that monitor a volume of approx. 1 cu km in the deep Antarctic ice for particle induced photons. The telescope was designed to detect neutrinos with energies greater than 100 GeV. Owing to subfreezing ice temperatures, the photomultiplier dark noise rates are particularly low. Hence IceCube can also detect large numbers of MeV neutrinos by observing a collective rise in all photomultiplier rates on top of the dark noise. With 2 ms timing resolution, IceCube can detect subtle features in the temporal development of the supernova neutrino burst. For a supernova at the galactic center, its sensitivity matches that of a background-free megaton-scale supernova search experiment. The sensitivity decreases to 20 standard deviations at the galactic edge (30 kpc) and 6 standard deviations at the Large Magellanic Cloud (50 kpc). IceCube is sending triggers from potential supernovae to the Supernova Early Warning System. The sensitivity to neutrino properties such as the neutrino hierarchy is discussed, as well as the possibility to detect the neutronization burst, a short outbreak's released by electron capture on protons soon after collapse. Tantalizing signatures, such as the formation of a quark star or a black hole as well as the characteristics of shock waves, are investigated to illustrate IceCube's capability for supernova detection