Bimodal fission in binary and ternary spontaneous fission of 252Cf

The hot bimodal fission of ²⁵²Cf is reexamined with new high-statistics data. We constructed a γ-γ-γ coincidence cube for binary fission and LCP-gated γ-γ matrix for ternary fission. By identifying the secondary fission fragments from their γ-ray transitions, we measured the yields for various fission splits. The normal neutron yield distribution is found to be Gaussian for Xe-Ru. However, the binary fission split of Ba-Mo is found to exhibit a bimodal neutron distribution with the “hot mode” corresponding to ≈3.1% of the total yield. In α ternary fission, the first measurements of yields for specific fission splits are presented. The Te-α-Ru and Xe-α-Mo neutron yields fit well with a single mode, but the Ba-α-Zr split shows evidence for an enhanced hot mode with an intensity of ≈13.8% of the normal mode. The text was submitted by the authors in English.     

Measurement of in vivo multi-component T2 relaxation times for brain tissue using multi-slice T2 prep at 1.5 and 3 T

The objective of this study was to implement a clinically relevant multi-slice multi-echo imaging sequence in order to quantify multi-component T2 relaxation times for normal volunteers at both 1.5 and 3 T. Multi-echo data were fitted using a nonnegative least square algorithm. Twelve echo data with nonlinear echo sampling were acquired using a receive-only eight-channel phased array coil and volume head coil for phantoms and normal volunteers, and compared to 32-echo data with linear echo sampling. It was observed that the performance of the 180 degrees refocusing trains was more spatially uniform for the receive-only eight-channel phased array coil than for the head coil, particularly at 3 T. The phantom study showed that the estimated T2 relaxation times were accurate and reproducible for both single- and multi-slice acquisition from a commercial phantom with known T2 relaxation times. Short T2 components (T2 <50 ms) were mainly observed within the white matter for normal volunteers, and the fraction of short T2 water components (i.e., myelin water) was 7-12% of total water. It was observed that the calculated myelin water fraction map from the nonlinearly sampled 12-echo data was comparable with that from the linearly sampled 32-echo data. Quantification of T2 relaxation times from multi-slice images was accomplished with a clinically acceptable scan times (16 min) for normal volunteers by using a nonselective T2 prep imaging sequence. The use of the eight-channel head coil involved more accurate quantification of T2 relaxation times particularly when the number of echoes was limited.     

A power-law distribution for tenure lengths of sports managers

We show that the tenure lengths for managers of sport teams follow a power law distribution with an exponent between 2 and 3. We develop a simple theoretical model which replicates this result. The model demonstrates that the empirical phenomenon can be understood as the macroscopic outcome of pairwise interactions among managers in a league, threshold effects in managerial performance evaluation, competitive market forces, and luck at the microscopic level.     

Broadly tunable dual-wavelength light source for coherent anti-Stokes Raman scattering microscopy

The signal and idler beams from a picosecond, synchronously pumped optical parametric oscillator (OPO) provide the two colors necessary for coherent anti-Stokes Raman scattering (CARS) microscopy. The OPO provides a continuously tunable frequency difference between the two beams over a broad range of Raman shifts (100-3700 cm(-1)) by varying the temperature of a single nonlinear crystal. The near-infrared output (900-1300 nm) allows for deep penetration into thick samples and reduced nonlinear photodamage. Applications of this light source to in vivo cell and ex vivo tissue imaging are demonstrated.     

Illuminating the BOLD signal: combined fMRI-fNIRS studies

Functional magnetic resonance imaging (fMRI) is currently combined with electrophysiological methods to identify the relationship between neuronal activity and the blood oxygenation level-dependent (BOLD) signal. Several processes like neuronal activity, synaptic activity, vascular dilation, blood volume and oxygenation changes underlie both response modalities, that is, the electrophysiological signal and the vascular response. However, accessing single process relationships is absolutely mandatory when aiming at a deeper understanding of neurovascular coupling and necessitates studies on the individual building blocks of the vascular response. Combined fMRI and functional near-infrared spectroscopy studies have been performed to validate the correlation of the BOLD signal to the hemodynamic changes in the brain. Here we review the current status of the integration of both technologies and judge these studies in the light of recent findings on neurovascular coupling.     

Nanosatellites for quantum science and technology

Bringing quantum science and technology to the space frontier offers exciting prospects for both fundamental physics and applications such as long-range secure communication and space-borne quantum probes for inertial sensing with enhanced accuracy and sensitivity. But despite important terrestrial pathfinding precursors on common microgravity platforms and promising proposals to exploit the significant advantages of space quantum missions, large-scale quantum test beds in space are yet to be realised due to the high costs and lead times of traditional ‘Big Space’ satellite development. But the ‘small space’ revolution, spearheaded by the rise of nanosatellites such as CubeSats, is an opportunity to greatly accelerate the progress of quantum space missions by providing easy and affordable access to space and encouraging agile development. We review space quantum science and technology, CubeSats and their rapidly developing capabilities and how they can be used to advance quantum satellite systems.     

SOLEIL shining on the solution‐state structure of biomacromolecules by synchrotron X‐ray footprinting at the Metrology beamline

Synchrotron X‐ray footprinting complements the techniques commonly used to define the structure of molecules such as crystallography, small‐angle X‐ray scattering and nuclear magnetic resonance. It is remarkably useful in probing the structure and interactions of proteins with lipids, nucleic acids or with other proteins in solution, often better reflecting the in vivo state dynamics. To date, most X‐ray footprinting studies have been carried out at the National Synchrotron Light Source, USA, and at the European Synchrotron Radiation Facility in Grenoble, France. This work presents X‐ray footprinting of biomolecules performed for the first time at the X‐ray Metrology beamline at the SOLEIL synchrotron radiation source. The installation at this beamline of a stopped‐flow apparatus for sample delivery, an irradiation capillary and an automatic sample collector enabled the X‐ray footprinting study of the structure of the soluble protein factor H (FH) from the human complement system as well as of the lipid‐associated hydrophobic protein S3 oleosin from plant seed. Mass spectrometry analysis showed that the structural integrity of both proteins was not affected by the short exposition to the oxygen radicals produced during the irradiation. Irradiated molecules were subsequently analysed using high‐resolution mass spectrometry to identify and locate oxidized amino acids. Moreover, the analyses of FH in its free state and in complex with complement C3b protein have allowed us to create a map of reactive solvent‐exposed residues on the surface of FH and to observe the changes in oxidation of FH residues upon C3b binding. Studies of the solvent accessibility of the S3 oleosin show that X‐ray footprinting offers also a unique approach to studying the structure of proteins embedded within membranes or lipid bodies. All the biomolecular applications reported herein demonstrate that the Metrology beamline at SOLEIL can be successfully used for synchrotron X‐ray footprinting of biomolecules.     

Canonical methods for Hamiltonian systems: numerical experiments

A Hamiltonian system possesses dynamics (e.g. preservation of volume in phase space and symplectic structure) that call for special numerical integrators, namely canonical methods. Recent research on this aspect have shown that canonical numerical integrators may be needed for Hamiltonian systems. In this paper, we focus on numerical experiments that compare canonical and non-canonical numerical integrators. Test problems are taken from different areas in physical sciences. These experiments help to buttress the claims that canonical numerical integrators give results that mimic the qualitative behavior of the original system and that canonical numerical integrators are suitable for long time integrations. Our experiments indicate that higher-order canonical methods allow for larger timestep than lower-order canonical methods.     

Collisional-radiative model for non-Maxwellian inductively coupled argon plasmas using detailed fine-structure relativistic distorted-wave cross sections

Our recently developed collisional-radiative model which included fine-structure cross sections calculated with a fully relativistic distorted-wave method [R.K. Gangwar, L. Sharma, R. Srivastava, A.D. Stauffer, J. Appl. Phys. 111, 053307 (2012)] has been extended to study non-Maxwellian inductively coupled argon plasmas. We have added more processes to our earlier collisional-radiative model by further incorporating relativistic distorted-wave electron impact cross sections from the 3p ⁵4sJ = 0, 2 metastable states, (1s ₃, 1s ₅ in Paschen’s notation) to the 3p ⁵5p (3p _i ) excited states. The population of various excited levels at different pressures in the range of 1–25 mTorr for an inductively coupled argon plasma have been calculated and compared with the recent optical absorption spectroscopy measurements as well as emission model results of Boffard et al. [Plasma Sources Sci. Technol. 19, 065001 (2010)]. We have also calculated the intensities of two emission lines, 420.1 nm (3p ₉ → 1s ₅) and 419.8 nm (3p ₅ → 1s ₄) and compared with measured intensities reported by Boffard et al. [J. Phys. D 45, 045201 (2012)]. Our results are in good agreement with the measurements.