Self-similar structure and experimental signatures of suprathermal ion distribution in inertial confinement fusion implosions

The distribution function of suprathermal ions is found to be self-similar under conditions relevant to inertial confinement fusion hot-spots. By utilizing this feature, interference between the hydro-instabilities and kinetic effects is for the first time assessed quantitatively to find that the instabilities substantially aggravate the fusion reactivity reduction. The ion tail depletion is also shown to lower the experimentally inferred ion temperature, a novel kinetic effect that may explain the discrepancy between the exploding pusher experiments and rad-hydro simulations and contribute to the observation that temperature inferred from DD reaction products is lower than from DT at National Ignition Facility.Comment: Revised version accepted for publication in PRL. "Copyright (2015) by the American Physical Society.

From chemotherapy to targeted treatment

Today, melanoma is considered as a spectrum of melanocytic malignancies that can be characterized by clinical and molecular features, including targetable mutations in several kinases. The successful development of therapies, targeting mutated BRaF (v-raf murine sarcoma viral oncogene homolog B1) or c-KIT (v-kit Hardy-Zuckerman 4 feline sarcoma viral oncogene homolog), has resulted in new treatment options including vemurafenib, imatinib and mitogen-activated protein kinase inhibitors. These molecules are selected if the respective mutation is present. after this first progress in the treatment of advanced melanoma, there is expectation that combinations of kinase inhibitor will additionally improve the overall survival rates and progression-free survival in advanced melanom

The structure of human lymphotoxin (tumor necrosis factor-β) at 1.9-Å resolution

The three-dimensional structure of recombinant human lymphotoxin (residues 24-171 of the mature protein) has been determined by x-ray crystallography at 1.9-Å resolution (Rcryst = 0.215 for I \u3e 3σ(I)). Phases were derived by molecular replacement using tumor necrosis factor (TNF-α) as a search model. Like TNF-α, lymphotoxin (LT) folds to form a jellyroll β-sheet sandwich. Three-fold related LT subunits form a trimer stabilized primarily by hydrophobic interactions. A cluster of 6 basic residues around the 3-fold axis may account for the acid lability of the trimer. Although the structural cores of TNF-α and LT are similar, insertions and deletions relative to TNF-α occur in loops at the top of the LT trimer and significantly alter the local structure and the overall shape of the molecule. The structure of the base of the trimer is highly conserved. The sites of two mutations (Asp-50 and Tyr-108) that abolish the cytotoxicity of LT are contained within poorly ordered loops of polypeptide chain that flank the cleft between neighboring subunits at the base of the molecule, suggesting that the receptor recognizes an intersubunit binding site

A fundamental investigation of the interaction and impact of controlled torque ripples on gear mesh dynamics

Gear trains are plagued by self-excited vibrations that are concentrated at the mesh frequency and its harmonics due to their varying mesh stiffness and deviations from the ideal involute profile. This is even more pronounced in spur gears due to their lower contact ratio in comparison to helical gears. For an electric vehicle, due to the absence of an internal combustion engine, noise and vibration signature of the gearbox becomes an important aspect of the vehicle's comfort. However, the presence of a traction motor offers the advantage of having a potential actuator for actively countering these vibrations without adding any additional weight or packaging constraints. This paper presents a fundamental insight into the effect of introducing controlled torque ripples at the mesh frequency and its harmonics, on the noise and vibration characteristics, and the efficiency of the gear mesh. The study utilises a dynamic model of a single stage gear train that accounts for the time varying mesh stiffness and sliding friction at the gear teeth contact. This model is used to provide an understanding of gear mesh dynamics and their resulting interaction with the imposed torque ripples. The study demonstrates the positive effects that controlled torque ripples can have on the noise and vibration behaviour of gear trains and the underlying mechanics that govern this improvement

Assessment of ion kinetic effects in shock-driven inertial confinement fusion implosions using fusion burn imaging

The significance and nature of ion kinetic effects in D3He-filled, shock-driven inertial confinement fusion implosions are assessed through measurements of fusion burn profiles. Over this series of experiments, the ratio of ion-ion mean free path to minimum shell radius (the Knudsen number, NK) was varied from 0.3 to 9 in order to probe hydrodynamic-like to strongly kinetic plasma conditions; as the Knudsen number increased, hydrodynamic models increasingly failed to match measured yields, while an empirically-tuned, first-step model of ion kinetic effects better captured the observed yield trends [Rosenberg et al., Phys. Rev. Lett. 112, 185001 (2014)]. Here, spatially resolved measurements of the fusion burn are used to examine kinetic ion transport effects in greater detail, adding an additional dimension of understanding that goes beyond zero-dimensional integrated quantities to one-dimensional profiles. In agreement with the previous findings, a comparison of measured and simulated burn profiles shows that models including ion transport effects are able to better match the experimental results. In implosions characterized by large Knudsen numbers (NK3), the fusion burn profiles predicted by hydrodynamics simulations that exclude ion mean free path effects are peaked far from the origin, in stark disagreement with the experimentally observed profiles, which are centrally peaked. In contrast, a hydrodynamics simulation that includes a model of ion diffusion is able to qualitatively match the measured profile shapes. Therefore, ion diffusion or diffusion-like processes are identified as a plausible explanation of the observed trends, though further refinement of the models is needed for a more complete and quantitative understanding of ion kinetic effects

Neutron time-of-flight measurements of charged-particle energy loss in inertial confinement fusion plasmas

Neutron spectra from secondary ^{3}H(d,n)α reactions produced by an implosion of a deuterium-gas capsule at the National Ignition Facility have been measured with order-of-magnitude improvements in statistics and resolution over past experiments. These new data and their sensitivity to the energy loss of fast tritons emitted from thermal ^{2}H(d,p)^{3}H reactions enable the first statistically significant investigation of charged-particle stopping via the emitted neutron spectrum. Radiation-hydrodynamic simulations, constrained to match a number of observables from the implosion, were used to predict the neutron spectra while employing two different energy loss models. This analysis represents the first test of stopping models under inertial confinement fusion conditions, covering plasma temperatures of k_{B}T≈1-4  keV and particle densities of n≈(12-2)×10^{24}  cm^{-3}. Under these conditions, we find significant deviations of our data from a theory employing classical collisions whereas the theory including quantum diffraction agrees with our data