The natural course of the paravertebral muscles after the onset of osteoporotic vertebral fracture.

This study revealed the change in the paravertebral muscles in patients with osteoporotic vertebral fracture. Increased pain is likely to be the driver for reduced activity, reduced activities of daily living, and consequent increase in fat infiltration of the paravertebral muscles, assumed to be secondary to reduced activity level or, conversely, partial immobilization. INTRODUCTION: To reveal the time courses and impact of the paravertebral muscles (PVMs) on the healing process of osteoporotic vertebral fractures and risk factors for PVM decrease. METHODS: Consecutive patients with symptomatic osteoporotic vertebral fractures were enrolled in 11 hospitals. At enrollment and 3- and 6-month follow-up, PVMs, including the multifidus and erector spinae, were examined using magnetic resonance imaging (MRI). The PVM cross-sectional area (CSA) and fat signal fraction (FSF) were measured at L3. Low back pain (LBP), activities of daily living (ADLs), and risk factors for PVM decrease at the 6-month follow-up were investigated. PVM decrease was defined as > 1 standard deviation decrease of the CSA or > 1 standard deviation increase of the FSF. RESULTS: Among 153 patients who completed the 6-month follow-up, 117 (92 women, 79%) had MRI of L3 at enrollment and 3- and 6-month follow-up (mean age at enrollment, 78.5 years). The CSA did not change 6 months from onset (p for trend = 0.634), whereas the FSF significantly increased (p for trend = 0.033). PVM decrease was observed in 30 patients (26%). LBP was more severe, and delayed union was more frequent in patients with PVM decrease (p = 0.021 mixed-effect model and p = 0.029 chi-square test, respectively). The risk factors for PVM decrease were ADL decline at the 3-month follow-up (adjusted odds ratio = 5.35, p = 0.026). CONCLUSION: PVM decrease was significantly related to LBP and delayed union after osteoporotic vertebral fracture onset. ADL decline at the 3-month follow-up was a risk factor for PVM decrease. Therefore, restoring ADLs within 3 months after onset is important.

Observational Evidence for Stochastic Shock Drift Acceleration of Electrons at the Earth's Bow Shock.

The first-order Fermi acceleration of electrons requires an injection of electrons into a mildly relativistic energy range. However, the mechanism of injection has remained a puzzle both in theory and observation. We present direct evidence for a novel stochastic shock drift acceleration theory for the injection obtained with Magnetospheric Multiscale observations at the Earth's bow shock. The theoretical model can explain electron acceleration to mildly relativistic energies at high-speed astrophysical shocks, which may provide a solution to the long-standing issue of electron injection.

Large Variation of Dirac Semimetal State in Perovskite CaIrO_{3} with Pressure-Tuning of Electron Correlation.

The impact of electron correlation on the Dirac semimetal state is investigated for perovskite CaIrO_{3} in terms of the magnetotransport properties under varying pressures. The reduction of electron correlation with a pressure of 1 GPa enhances the Fermi velocity as much as 40%, but it reduces the mobility by an order of magnitude by detuning the Dirac node from the Fermi energy. Moreover, the giant magnetoresistance at the quantum limit due to the one-dimensional confinement of Dirac electrons is critically suppressed under pressure. These results indicate that the electron correlation is a crucial knob for controlling the transport of a correlated Dirac semimetal.

Revisiting the photoabsorption spectrum of NH3 in the 5.4-10.8 eV energy region.

We present a comprehensive revisited experimental high-resolution vacuum ultraviolet (VUV) photoabsorption spectrum of ammonia, NH3, covering for the first time the full 5.4-10.8 eV energy-range, with absolute cross sections determined. The calculations on the vertical excitation energies and oscillator strengths were performed using the equation-of-motion coupled cluster method restricted to single and double excitation levels and used to help reanalyze the observed Rydberg structures in the photoabsorption spectrum. The VUV spectrum reveals several new features that are not previously reported in the literature, with particular reference to the vibrational progressions of the (D̃1E'←X̃1A1 '), the (F̃1E'←X̃1A1 '), and the (G̃1A2 ″←X̃1A1 ') absorption bands. In addition, new Rydberg members have been identified in nda1 '←1a2 ″D̃''1A2 ″←X̃1A1 ', where n > 3 has not been reported before as well as in nde″←1a2 ″F̃1E'←X̃1A1 ' and in nsa1 '←1a2 ″G̃1A2 ″←X̃1A1 '. The measured absolute photoabsorption cross sections have been used to calculate the photolysis lifetime of ammonia in the Earth's atmosphere (0-50 km).

8-Nitro-cGMP is a promoter of osteoclast differentiation induced by RANKL.

Osteoclasts are multinucleated giant cells differentiated from monocyte-macrophage-lineage cells under stimulation of receptor activator of nuclear factor κ-B (RANK) ligand (RANKL) produced by osteoblasts and osteocytes. Although it has been reported that nitric oxide (NO) and reactive oxygen species (ROS) are involved in this process, the mechanism by which these labile molecules promote osteoclast differentiation are not fully understood. In this study, we investigated the formation and function of 8-nitro-cGMP, a downstream molecule of NO and ROS, in the process of osteoclast differentiation in vitro. 8-Nitro-cGMP was detected in mouse bone marrow macrophages and osteoclasts differentiated from macrophages in the presence of RANKL. Inhibition of NO synthase suppressed the formation of 8-nitro-cGMP as well as RANKL-induced osteoclast differentiation from macrophages. On the other hand, RANKL-induced osteoclast differentiation was promoted by addition of 8-nitro-cGMP to the cultures. In addition, 8-nitro-cGMP enhanced the mRNA expression of RANK, the receptor for RANKL. However, 8-bromo-cGMP, a membrane-permeable derivative of cGMP, did not have an effect on either RANKL-induced osteoclast differentiation or expression of the RANK gene. These results suggest that 8-nitro-cGMP is a novel positive regulator of osteoclast differentiation, which might help to explain the roles of NO and ROS in osteoclast differentiation.

Absolute cross section measurements for the scattering of low- and intermediate-energy electrons from PF3. II. Inelastic scattering of vibrational and electronic excitations.

As a sequel paper to our study of the elastic scattering for electron collisions with phosphorus trifluoride, PF3 molecules, we report absolute inelastic differential and integral cross sections (DCS and ICS) of vibrational excitations for the compound fundamental vibrational modes v13 (v1 + v3), v24 (v2 + v4), and their sum in the impact energy range of 2.0-10 eV and over a scattering angle range of 20°-130°. The measured angular distributions of scattered electron intensities for the present inelastic scattering are normalized to the elastic peak intensity corresponding to the DCSs of He. These vibrational excitation measurements demonstrate the presence of resonances around 2 eV and also around 6-10 eV. In addition, a generalized oscillator strength analysis is applied to derive oscillator strength f0-values and (unscaled Born) ICSs from the corresponding DCSs measured for the low-lying optically allowed 8a1-1 → 7e (σ*) excitation band, which is assigned as the Jahn-Teller splitting and 8a1-1 → 4s Rydberg transition at impact energies of 100, 200, and 300 eV, over a scattering angle range of 1.0°-15°. The f0-values obtained in the present study are compared with the results of previous photoabsorption and pseudo-optical measurements. The unscaled Born ICSs are compared with the binary-encounter f-scaled Born ICSs estimated over a wide impact energy region from the excitation thresholds.

Time course of osteoporotic vertebral fractures by magnetic resonance imaging using a simple classification: a multicenter prospective cohort study.

This study revealed the time course of osteoporotic vertebral fracture by magnetic resonance imaging using a simple classification. Signal changes were associated with the compression degree and mobility of the fractured vertebral body. This classification showed sufficient reliability in categorizing magnetic resonance imaging findings of osteoporotic vertebral fractures. INTRODUCTION: Magnetic resonance imaging (MRI) is useful in diagnosing osteoporotic vertebral fractures (OVFs). This study investigated the time course of OVFs by MRI using a simple classification. METHODS: This multicenter cohort study was performed from 2012 to 2015. Consecutive patients with ≤2-week-old OVFs were enrolled in 11 institutions. MRI was performed at enrollment and at 1-, 3-, 6-, and 12-month follow-up. Signal changes on T1-weighted imaging (T1WI), T2WI, and short τ inversion recovery (STIR) were classified according to signal intensity. Height and angular motion of vertebral bodies were also measured. RESULTS: The 6-month follow-up was completed by 153 patients. At enrollment, fractured vertebrae signal changes were 43 % diffuse and 57 % confined low on T1WI; on T2WI, 56, 24, and 5 % were confined low, high, and diffuse low, respectively; on STIR, 100 % were high. On T1WI, diffuse low remained most common (90 % at 1 month and 60 % at 3 months) until 6 and 12 months, when most were confined low (54 and 52 %, respectively). On T2WI, confined low remained most common (decreasing to 41 % at 12 months). On STIR, high signal change was shown in 98, 87, and 64 % at 3, 6, and 12 months, respectively. At 3, 6, and 12 months, diffuse low signal change was associated with significantly lower vertebral height, and high signal change was associated with significantly greater angular motion. CONCLUSIONS: MRI signal changes were associated with the compression degree and angular motion of fractured vertebrae. This classification showed sufficient reliability in categorizing MRI findings of OVFs.

Experimental scaling of plane-Born cross sections and ab initio assignments for electron-impact excitation and dissociation of XF4 (X = C, Si, and Ge) molecules.

Electron energy loss spectra of carbon tetrafluoride, silicon tetrafluoride, and germanium tetrafluoride molecules (CF4, SiF4, and GeF4) have been measured for incident electron energies of 50-360 eV at 1.5°-15.5° and for 30 eV and 30° scattering angle, while sweeping the energy loss over the range 9.0-20.0 eV. Low-lying valence excited triplet and singlet states are investigated by quantum chemical ab initio calculations. The Rydberg series converging to the (lowest) ionisation energy limits of XF4 (X = C, Si, Ge) are also identified and classified using the systematic behaviour according to the magnitude of the quantum defects. A generalized oscillator strength analysis is employed to derive oscillator strength f0 value and the apparent Born integral cross sections from the corresponding differential cross sections by using the Vriens formula for the optically allowed transitions. The f0 value is compared with the optical oscillator strength of the photoabsorption, pseudo-photon measurements, and theoretical values. The binary-encounter and f-scaled Born cross sections of the most intense optically allowed transitions have been also derived from the excitation threshold to the high energy region where the Born approximation is valid. Potential energy curves were obtained along the XF3 + F coordinate with two different basis sets to lend support on electron impact dissociation processes yielding radical formation. We found that in CF4, the lowest-lying dissociative character is due to intramolecular conversion from Rydberg 3s to valence character (σ*(C-F)), whereas in SiF4 and GeF4, an antibonding behaviour prevails.

Absolute cross section measurements for the scattering of low- and intermediate-energy electrons from PF3. I. Elastic scattering.

We report absolute elastic differential cross sections (DCSs) for electron collisions with phosphorus trifluoride, PF3, molecules (e- + PF3) in the impact energy range of 2.0-200 eV and over a scattering angle range of 10°-150°. Measured angular distributions of scattered electron intensities were normalized by reference to the elastic DCSs of He. Corresponding integral and momentum-transfer cross sections were derived by extrapolating the angular range from 0° to 180° with the help of a modified phase-shift analysis. In addition, due to the large dipole moment of the considered molecule, the dipole-Born correction for the forward scattering angles has also been applied. As a part of this study, independent atom model calculations in combination with screening corrected additivity rule were also performed for elastic and inelastic (electronic excitation plus ionization) scattering using a complex optical potential method. Rotational excitation cross sections have been estimated with a dipole-Born approximation procedure. Vibrational excitations are not considered in this calculation. Theoretical data, at the differential and integral levels, were found to reasonably agree with the present experimental results. Furthermore, we explore the systematics of the elastic DCSs for the four-atomic trifluoride molecules of XF3 (X = B, N, and P) and central P-atom in PF3, showing that, owing to the comparatively small effect of the F-atoms, the present angular distributions of elastic DCSs are essentially dominated by the characteristic of the central P-atom at lower impact energies. Finally, these quantitative results for e- - PF3 collisions were compiled together with the previous data available in the literature in order to obtain a cross section dataset for modeling purposes. To comprehensively describe such a considerable amount of data, we proceed by first discussing, in this paper, the vibrationally elastic scattering processes whereas vibrational and electronic excitation shall be the subject of our following paper devoted to inelastic collisions.

Predicting delayed union in osteoporotic vertebral fractures with consecutive magnetic resonance imaging in the acute phase: a multicenter cohort study.

This study demonstrated the predictive values of radiological findings for delayed union after osteoporotic vertebral fractures (OVFs). High-signal changes on T2WI were useful findings. INTRODUCTION: The purpose of the present study is to determine predictive radiological findings for delayed union by magnetic resonance imaging (MRI) and plain X-rays at two time points in the acute phase of OVFs. METHODS: This multicenter cohort study was performed from 2012 to 2015. A total of 218 consecutive patients with OVFs ≤2 weeks old were enrolled. MRIs and plain X-rays were performed at the time of enrollment and at 1- and 6-month follow-ups. Signal changes on T1-weighted imaging (T1WI) were classified as diffuse low-, confined low-, or no-signal change; those on T2WI were classified as high (similar to the intensity of cerebrospinal fluid), confined low-, diffuse low-, or no-signal change. The angular motion of the fractured vertebral body was measured with X-rays. RESULTS: A total of 153 patients completed the 6-month follow-up. A high-signal change on T2WI was most useful in predicting delayed union. Sensitivity, specificity, and positive predictive values were 53.3, 87.8, and 51.6 % at enrollment and 65.5, 84.8, and 51.4 % at the 1-month follow-up, respectively. The positive predictive value increased to 62.5 % with observation of high- or diffuse low-signal changes at both enrollment and the 1-month follow-up. The cutoff value of vertebral motion was 5 degrees. Sensitivity and specificity at enrollment were 52.4 and 74.1 %, respectively. CONCLUSIONS: This study demonstrated the radiological factors predicting delayed union after an OVF. T2 high-signal changes showed the strongest association with delayed union. Consecutive MRIs were particularly useful as a differential tool to predict delayed union following OVFs.

In utero gene therapy rescues microcephaly caused by Pqbp1-hypofunction in neural stem progenitor cells.

Human mutations in PQBP1, a molecule involved in transcription and splicing, result in a reduced but architecturally normal brain. Examination of a conditional Pqbp1-knockout (cKO) mouse with microcephaly failed to reveal either abnormal centrosomes or mitotic spindles, increased neurogenesis from the neural stem progenitor cell (NSPC) pool or increased cell death in vivo. Instead, we observed an increase in the length of the cell cycle, particularly for the M phase in NSPCs. Corresponding to the developmental expression of Pqbp1, the stem cell pool in vivo was decreased at E10 and remained at a low level during neurogenesis (E15) in Pqbp1-cKO mice. The expression profiles of NSPCs derived from the cKO mouse revealed significant changes in gene groups that control the M phase, including anaphase-promoting complex genes, via aberrant transcription and RNA splicing. Exogenous Apc4, a hub protein in the network of affected genes, recovered the cell cycle, proliferation, and cell phenotypes of NSPCs caused by Pqbp1-cKO. These data reveal a mechanism of brain size control based on the simple reduction of the NSPC pool by cell cycle time elongation. Finally, we demonstrated that in utero gene therapy for Pqbp1-cKO mice by intraperitoneal injection of the PQBP1-AAV vector at E10 successfully rescued microcephaly with preserved cortical structures and improved behavioral abnormalities in Pqbp1-cKO mice, opening a new strategy for treating this intractable developmental disorder.

Studies on GeF4 Valence and Rydberg States by Electron Impact Spectroscopy and Ab Initio Calculations.

Electron energy loss (EEL) spectra of GeF4 have been measured with incident electrons at 100 eV for 5° scattering angle and at 30 eV for 30° scattering angle, while sweeping the energy loss over the range 7.0-18.0 eV. Low-lying excited triplet, singlet, valence, and Rydberg states are investigated and the assignments supported by quantum chemical ab initio calculations. This provides the first comprehensive investigation of all singlet and triplet excited electronic states of germanium tetrafluoride up to the first ionization energy. The Rydberg series converging to the (lowest) ionization energy limits of GeF4 are also identified according to the magnitude of the quantum defects (δ).

High-resolution manometry findings in symptomatic post-Nissen fundoplication patients with normal endoscopic configuration.

The aim of this study was to investigate high-resolution manometry (HRM) findings in symptomatic post-fundoplication patients with normal endoscopic configuration. A retrospective review of a prospectively maintained database was conducted to identify patients who underwent evaluation with HRM and endoscopy for symptom evaluation after previous fundoplication. Study period extends from September 2008 to December 2012. Only patients with complete 360° fundoplication (Nissen) were included, and patients with partial fundoplication were excluded. Patients with endoscopic abnormality or patients who underwent Collis procedure were also excluded. Additionally, contrast study and 24-hour pH study if done were reviewed. Symptoms were graded using a standard questionnaire with symptoms graded on a scale of 0-3. Symptom grade 2 or 3 was considered a significant symptom. One hundred seventy-nine symptomatic patients with previous Nissen fundoplication underwent HRM and endoscopy during the study period. Of these, 136 patients were excluded (51 had recurrent hiatal hernia, 2 had disrupted fundoplication, 68 had slipped fundoplication, 10 had twisted fundoplication, 2 had esophageal stricture, and 3 had Collis procedure). Remaining forty-three patients met inclusion criteria (mean age of 56.0 ± 14.8, 32 females).The most common symptom was dysphagia (67%). Patients with dysphagia had a significantly longer length of distal esophageal high pressure zone (HPZ) and a higher integrated relaxation pressure (IRP) than patients without dysphagia (P = 0.020, 0.049). Especially, patients who had shorter HPZ (≤2 cm) were less likely to have significant dysphagia. Twenty-three patients (53%) had heartburn. There was no significant difference in HRM findings between patients with and without heartburn. Only 4 of 28 patients with concomitant pH study showed abnormal DeMeester score (>14.7), and there was no correlation between results of pH study and lower esophageal sphincter pressure/length and IRP. Longer HPZ complex length and higher IRP as measured with HRM is associated with post-Nissen fundoplication dysphagia in patients with normal endoscopic configuration. No HRM parameters are associated with reported heartburn or a positive pH score.

Effects of Cold Stimulation on Mitochondrial Activity and VEGF Expression in vitro.

We aimed to clarify the effects of cold stimulation at various temperatures on mitochondrial activity and vascular endothelial growth factor (VEGF) expression in vitro. Human fibroblast, human mesenchymal stem cell, and rat skeletal muscle myoblast cell lines were used. For each cell type, cells were divided into 4 groups and stimulated in various cold temperatures (0, 4, 17 and 25°C) 3 times for 15 min each by placement on crushed ice or floating on cold water set at each temperature. Control cells were subjected to warm water at 37°C. Factors related to mitochondrial activity, mitochondrial DNA copy numbers, and VEGF expression were analyzed 24 h after the last cold stimulation. In all cell types, significant increases of factors related to mitochondrial activity and mitochondrial DNA copy numbers were seen in the 4°C and 17°C-stimulated cells compared with control cells. In rat skeletal muscle cells stimulated at 4°C, VEGF expression significantly increased compared to the control cells. Our data suggest that cold stimulation at certain temperatures promotes mitochondrial activity, biogenesis and VEGF expression.

Exogenous Sonic hedgehog modulates the pool of GABAergic interneurons during cerebellar development.

All cerebellar GABAergic interneurons were derived from a common pool of precursor cells residing in the embryonic ventricular zone (VZ) and migrating in the prospective white matter (PWM) after birth, where both intrinsic and extrinsic factors contribute to regulate their amplification. Among the environmental factors, we focused on Sonic hedgehog (Shh), a morphogen well known to regulate neural progenitor cell proliferation. We asked if and how exogenous Shh treatment affects the lineage of cerebellar GABAergic interneurons. To address these issues, exogenous Shh was administered to embryonic and postnatal organotypic slices. We found that Shh is able to expand the pool of interneuron progenitors residing in the embryonic epithelium and in the postnatal PWM. In particular, Shh signalling pathway was highly mitogenic at early developmental stages of interneuron production, whereas its effect decreased after the first postnatal week. Gene expression analysis of sorted cells and in situ hybridization further showed that immature interneurons express both the Shh receptor patched and the Shh target gene Gli1. Thus, within the interneuron lineage, Shh might exert regulatory functions also in postmitotic cells. On the whole, our data enlighten the role of Shh during cerebellar maturation and further broaden our knowledge on the amplification mechanisms of the interneuron progenitor pool.

Crossed-beam experiment for the scattering of low- and intermediate-energy electrons from BF3: A comparative study with XF3 (X = C, N, and CH) molecules.

Absolute differential cross sections (DCSs) for electron interaction with BF3 molecules have been measured in the impact energy range of 1.5-200 eV and recorded over a scattering angle range of 15°-150°. These angular distributions have been normalized by reference to the elastic DCSs of the He atom and integrated by employing a modified phase shift analysis procedure to generate integral cross sections (ICSs) and momentum transfer cross sections (MTCSs). The calculations of DCSs and ICSs have been carried out using an independent atom model under the screening corrected additivity rule (IAM-SCAR). The present elastic DCSs have been found to agree well with the results of IAM-SCAR calculation above 20 eV, and also with a recent Schwinger multichannel calculation below 30 eV. Furthermore, in the comparison with the XF3 (X = B, C, N, and CH) molecules, the elastic DCSs reveal a similar angular distribution which are approximately equal in magnitude from 30 to 200 eV. This feature suggests that the elastic scattering is dominated virtually by the 3-outer fluorine atoms surrounding the XF3 molecules. The vibrational DCSs have also been obtained in the energy range of 1.5-15 eV and vibrational analysis based on the angular correlation theory has been carried out to explain the nature of the shape resonances. Limited experiments on vibrational inelastic scattering confirmed the existence of a shape resonance with a peak at 3.8 eV, which is also observed in the vibrational ICS. Finally, the estimated elastic ICSs, MTCSs, as well as total cross sections are compared with the previous cross section data available.

Electronic excitation of carbonyl sulphide (COS) by high-resolution vacuum ultraviolet photoabsorption and electron-impact spectroscopy in the energy region from 4 to 11 eV.

The electronic state spectroscopy of carbonyl sulphide, COS, has been investigated using high resolution vacuum ultraviolet photoabsorption spectroscopy and electron energy loss spectroscopy in the energy range of 4.0-10.8 eV. The spectrum reveals several new features not previously reported in the literature. Vibronic structure has been observed, notably in the low energy absorption dipole forbidden band assigned to the (4π←3π) ((1)Δ←(1)Σ(+)) transition, with a new weak transition assigned to ((1)Σ(-)←(1)Σ(+)) reported here for the first time. The absolute optical oscillator strengths are determined for ground state to (1)Σ(+) and (1)Π transitions. Based on our recent measurements of differential cross sections for the optically allowed ((1)Σ(+) and (1)Π) transitions of COS by electron impact, the optical oscillator strength f0 value and integral cross sections (ICSs) are derived by applying a generalized oscillator strength analysis. Subsequently, ICSs predicted by the scaling are confirmed down to 60 eV in the intermediate energy region. The measured absolute photoabsorption cross sections have been used to calculate the photolysis lifetime of carbonyl sulphide in the upper stratosphere (20-50 km).

BF3 valence and Rydberg states as probed by electron energy loss spectroscopy and ab initio calculations.

In this contribution we probe BF3 low-lying excited singlet states measured at 100 eV, 2.8° scattering angle and triplet states at 40 eV, 40° scattering angle, while sweeping the energy loss over the range 10.0-20.0 eV. The electronic state spectroscopy has been investigated and the assignments supported by quantum chemical calculations. This provides the first comprehensive investigation of all singlet and triplet excited electronic states of boron trifluoride up to the first ionization potential. A generalized oscillator strength analysis is employed to derive oscillator strength f0 value and integral cross sections (ICSs) from the corresponding differential cross sections (DCSs). The f0 value is compared with the optical oscillator strength (OOS) from photoabsorption, and the unscaled Born ICSs are then compared with relevant energy and binary-encounter and f-scaled Born cross section (BEf-scaling) results determined as a part of this investigation. The lowest n members of the Rydberg series have been assigned as converging to the lowest ionization energy limits of boron trifluoride and classified according to the magnitude of the quantum defects (δ).

Elastic differential cross sections for C4F6 isomers in the 1.5-200 eV energy electron impact: similarities with six fluorine containing molecules and evidence of F-atom like scattering.

We report absolute elastic differential cross sections for electron interactions with the C4F6 isomers, hexafluoro-1,3-butadiene (1,3-C4F6), hexafluoro-2-butyne (2-C4F6), and hexafluorocyclobutene (c-C4F6). The incident electron energy range is 1.5-200 eV, and the scattered electron angular range for the differential measurements varies from 15° to 150°. In all cases the absolute scale of the differential cross section was set using the relative flow technique, with helium as the reference species. Atomic-like behaviour in these scattering systems is shown here for the first time, and is further investigated by comparing the elastic cross sections for the C4F6 isomers with other fluorinated molecules, such as SF6 and CnF6 (n = 2, 3, and 6). We note that for all the six-F containing molecules, the scattering process for electron energies above 30 eV is indistinguishable. Finally, we report results for calculations of elastic differential cross sections for electron scattering from each of these isomers, within an optical potential method and assuming a screened corrected independent atom representation. The level of agreement between these calculations and our measurements is found to be quite remarkable in all cases.

Electron acceleration in a nonrelativistic shock with very high Alfvén Mach number.

Electron acceleration associated with various plasma kinetic instabilities in a nonrelativistic shock with very high Alfvén Mach number (M(A)~45) is revealed by means of a two-dimensional fully kinetic particle-in-cell simulation. Electromagnetic (ion Weibel) and electrostatic (ion-acoustic and Buneman) instabilities are strongly activated at the same time in different regions of the two-dimensional shock structure. Relativistic electrons are quickly produced predominantly by the shock surfing mechanism with the Buneman instability at the leading edge of the foot. The energy spectrum has a high-energy tail exceeding the upstream ion kinetic energy accompanying the main thermal population. This gives a favorable condition for the ion-acoustic instability at the shock front, which in turn results in additional energization. The large-amplitude ion Weibel instability generates current sheets in the foot, implying another dissipation mechanism via magnetic reconnection in a three-dimensional shock structure in the very-high-M(A) regime.