Real-time observation of non-equilibrium phonon-electron energy and angular momentum flow in laser-heated nickel

Identifying the microscopic nature of non-equilibrium energy transfer mechanisms among electronic, spin, and lattice degrees of freedom is central to understanding ultrafast phenomena such as manipulating magnetism on the femtosecond timescale. Here, we use time- and angle-resolved photoemission spectroscopy to go beyond the often-used ensemble-averaged view of non-equilibrium dynamics in terms of quasiparticle temperature evolutions. We show for ferromagnetic Ni that the non-equilibrium electron and spin dynamics display pronounced variations with electron momentum, whereas the magnetic exchange interaction remains isotropic. This highlights the influence of lattice-mediated scattering processes and opens a pathway toward unraveling the still elusive microscopic mechanism of spin-lattice angular momentum transfer.

Robust Surface States and Coherence Phenomena in Magnetically Alloyed SmB_{6}

Samarium hexaboride is a candidate for the topological Kondo insulator state, in which Kondo coherence is predicted to give rise to an insulating gap spanned by topological surface states. Here we investigate the surface and bulk electronic properties of magnetically alloyed Sm_{1-x}M_{x}B_{6} (M=Ce, Eu), using angle-resolved photoemission spectroscopy and complementary characterization techniques. Remarkably, topologically nontrivial bulk and surface band structures are found to persist in highly modified samples with up to 30% Sm substitution and with an antiferromagnetic ground state in the case of Eu doping. The results are interpreted in terms of a hierarchy of energy scales, in which surface state emergence is linked to the formation of a direct Kondo gap, while low-temperature transport trends depend on the indirect gap.

Orbital Fingerprint of Topological Fermi Arcs in the Weyl Semimetal TaP

The monopnictides TaAs and TaP are well-established Weyl semimetals. Yet, a precise assignment of Fermi arcs, accommodating the predicted chiral charge of the bulk Weyl points, has been difficult in these systems, and the topological character of different surface features in the Fermi surface is not fully understood. Here, employing a joint analysis from linear dichroism in angle-resolved photoemission and first-principles calculations, we unveil the orbital texture on the full Fermi surface of TaP(001). We observe pronounced switches in the orbital texture at the projected Weyl nodes, and show how they facilitate a topological classification of the surface band structure. Our findings establish a critical role of the orbital degrees of freedom in mediating the surface-bulk connectivity in Weyl semimetals.

Geant4-DNA example applications for track structure simulations in liquid water: A report from the Geant4-DNA Project

This Special Report presents a description of Geant4-DNA user applications dedicated to the simulation of track structures (TS) in liquid water and associated physical quantities (e.g., range, stopping power, mean free path…). These example applications are included in the Geant4 Monte Carlo toolkit and are available in open access. Each application is described and comparisons to recent international recommendations are shown (e.g., ICRU, MIRD), when available. The influence of physics models available in Geant4-DNA for the simulation of electron interactions in liquid water is discussed. Thanks to these applications, the authors show that the most recent sets of physics models available in Geant4-DNA (the so-called "option4" and "option 6" sets) enable more accurate simulation of stopping powers, dose point kernels, and W-values in liquid water, than the default set of models ("option 2") initially provided in Geant4-DNA. They also serve as reference applications for Geant4-DNA users interested in TS simulations.

Matching DMFT calculations with photoemission spectra of heavy fermion insulators: universal properties of the near-gap spectra of SmB6

Paramagnetic heavy fermion insulators consist of fully occupied quasiparticle bands inherent to Fermi liquid theory. The gap emergence below a characteristic temperature is the ultimate sign of coherence for a many-body system, which in addition can induce a non-trivial band topology. Here, we demonstrate a simple and efficient method to compare a model study and an experimental result for heavy fermion insulators. The temperature dependence of the gap formation in both local moment and mixed valence regimes is captured within the dynamical mean field (DMFT) approximation to the periodic Anderson model (PAM). Using the topological coherence temperature as the scaling factor and choosing the input parameter set within the mixed valence regime, we can unambiguously link the theoretical energy scales to the experimental ones. As a particularly important result, we find improved consistency between the scaled DMFT density of states and the photoemission near-gap spectra of samarium hexaboride (SmB₆).

Electronic Structure of YbB_{6}: Is it a Topological Insulator or Not?

To finally resolve the controversial issue of whether or not the electronic structure of YbB_{6} is nontrivially topological, we have made a combined study using angle-resolved photoemission spectroscopy (ARPES) of the nonpolar (110) surface and density functional theory (DFT). The flat-band conditions of the (110) ARPES avoid the strong band bending effects of the polar (001) surface and definitively show that YbB_{6} has a topologically trivial B 2p-Yb 5d semiconductor band gap of ∼0.3  eV. Accurate determination of the low energy band topology in DFT requires the use of a modified Becke-Johnson exchange potential incorporating spin-orbit coupling and an on-site Yb 4f Coulomb interaction U as large as 7 eV. The DFT result, confirmed by a more precise GW band calculation, is similar to that of a small gap non-Kondo nontopological semiconductor. Additionally, the pressure-dependent electronic structure of YbB_{6} is investigated theoretically and found to transform into a p-d overlap semimetal with small Yb mixed valency.

Automation and uncertainty analysis of a method for in-vivo range verification in particle therapy

We introduce the automation of the range difference calculation deduced from particle-irradiation induced β(+)-activity distributions with the so-called most-likely-shift approach, and evaluate its reliability via the monitoring of algorithm- and patient-specific uncertainty factors. The calculation of the range deviation is based on the minimization of the absolute profile differences in the distal part of two activity depth profiles shifted against each other. Depending on the workflow of positron emission tomography (PET)-based range verification, the two profiles under evaluation can correspond to measured and simulated distributions, or only measured data from different treatment sessions. In comparison to previous work, the proposed approach includes an automated identification of the distal region of interest for each pair of PET depth profiles and under consideration of the planned dose distribution, resulting in the optimal shift distance. Moreover, it introduces an estimate of uncertainty associated to the identified shift, which is then used as weighting factor to 'red flag' problematic large range differences. Furthermore, additional patient-specific uncertainty factors are calculated using available computed tomography (CT) data to support the range analysis. The performance of the new method for in-vivo treatment verification in the clinical routine is investigated with in-room PET images for proton therapy as well as with offline PET images for proton and carbon ion therapy. The comparison between measured PET activity distributions and predictions obtained by Monte Carlo simulations or measurements from previous treatment fractions is performed. For this purpose, a total of 15 patient datasets were analyzed, which were acquired at Massachusetts General Hospital and Heidelberg Ion-Beam Therapy Center with in-room PET and offline PET/CT scanners, respectively. Calculated range differences between the compared activity distributions are reported in a 2D map in beam-eye-view. In comparison to previously proposed approaches, the new most-likely-shift method shows more robust results for assessing in-vivo the range from strongly varying PET distributions caused by differing patient geometry, ion beam species, beam delivery techniques, PET imaging concepts and counting statistics. The additional visualization of the uncertainties and the dedicated weighting strategy contribute to the understanding of the reliability of observed range differences and the complexity in the prediction of activity distributions. The proposed method promises to offer a feasible technique for clinical routine of PET-based range verification.

Site-specific range uncertainties caused by dose calculation algorithms for proton therapy

The purpose of this study was to assess the possibility of introducing site-specific range margins to replace current generic margins in proton therapy. Further, the goal was to study the potential of reducing margins with current analytical dose calculations methods. For this purpose we investigate the impact of complex patient geometries on the capability of analytical dose calculation algorithms to accurately predict the range of proton fields. Dose distributions predicted by an analytical pencil-beam algorithm were compared with those obtained using Monte Carlo (MC) simulations (TOPAS). A total of 508 passively scattered treatment fields were analyzed for seven disease sites (liver, prostate, breast, medulloblastoma-spine, medulloblastoma-whole brain, lung and head and neck). Voxel-by-voxel comparisons were performed on two-dimensional distal dose surfaces calculated by pencil-beam and MC algorithms to obtain the average range differences and root mean square deviation for each field for the distal position of the 90% dose level (R90) and the 50% dose level (R50). The average dose degradation of the distal falloff region, defined as the distance between the distal position of the 80% and 20% dose levels (R80-R20), was also analyzed. All ranges were calculated in water-equivalent distances. Considering total range uncertainties and uncertainties from dose calculation alone, we were able to deduce site-specific estimations. For liver, prostate and whole brain fields our results demonstrate that a reduction of currently used uncertainty margins is feasible even without introducing MC dose calculations. We recommend range margins of 2.8% + 1.2 mm for liver and prostate treatments and 3.1% + 1.2 mm for whole brain treatments, respectively. On the other hand, current margins seem to be insufficient for some breast, lung and head and neck patients, at least if used generically. If no case specific adjustments are applied, a generic margin of 6.3% + 1.2 mm would be needed for breast, lung and head and neck treatments. We conclude that the currently used generic range uncertainty margins in proton therapy should be redefined site specific and that complex geometries may require a field specific adjustment. Routine verifications of treatment plans using MC simulations are recommended for patients with heterogeneous geometries.

Importance of charge fluctuations for the topological phase in SmB(6)

Typical Kondo insulators (KIs) can have a nontrivial Z_{2} topology because the energy gap opens at the Fermi energy (E_{F}) by a hybridization between odd- and even-parity bands. SmB_{6} deviates from such KI behavior, and it has been unclear how the insulating phase occurs. Here, we demonstrate that charge fluctuations are the origin of the topological insulating phase in SmB_{6}. Our angle-resolved photoemission spectroscopy results reveal that with decreasing temperature the bottom of the d-f hybridized band at the X[over ¯] point, which is predicted to have odd parity and is required for a topological phase, gradually shifts from below to above E_{F}. We conclude that SmB_{6} is a charge-fluctuating topological insulator.

Chemopreventive effect of a probiotic preparation on the development of preneoplastic and neoplastic colonic lesions: an experimental study

BACKGROUND/AIMS

A number of studies have suggested a key role played by certain resident gut bacteria in the development of large bowel cancer. The aim of the present study was to test the effect of a novel symbiotic preparation, which has been recently shown to beneficially modify gut ecosystem and systemic immunity, on either preneoplastic and neoplastic changes in a colon carcinogenesis model.

METHODOLOGY

Sprague-Dawley rats were fed a standard diet for 1 week and then were randomly assigned to three groups. The control diet was given to groups A and B, whereas in group C, the same diet plus 2 mL of a probiotic mixture was given throughout the experiment. Thirty rats (groups B, C) each received a weekly subcutaneous injection of azoxymethane at a dose of 15 mg/kg of body weight for 10 weeks. Group A served as a control group and received a subcutaneous injection of saline for 10 weeks. Forty-five rats were sacrificed at 3-week observation and 60 rats at 20-week observation for assessing metaphase index together with aberrant crypt foci and intestinal immune system markers from one hand and tumor occurrence from the other, respectively.

RESULTS

Group A showed a significantly increased metaphase index either in aberrant crypt foci or in "normal appearing" crypts when compared to group A (p < 0.01). Group B rats caused a significant decrease at both sites (p < 0.05). The numbers of lymphocytes derived from the mesenteric lymph nodes in group B rats were significantly decreased (p < 0.01) as compared to either control and to group C. The percentage of CD8 lymphocytes in group C was significantly higher than that in group B. Group C showed a significantly reduced ratio of aberrant crypt foci/colon and of aberrant crypt per colon and per each single focus (p < 0.05). A total of 18 (90%) group B and 10 (50%) group C rats had colon tumors, this difference was significant. The mean number of colon tumors per rat was 2.2 and 1.0 in group B and C, respectively.

CONCLUSIONS

Effective probiotics treatment, through mechanisms still to be fully elucidated (decreased fecal pH, specific reduction of carcinogenetic bacterial enzymes, modulation of gut-associated and systemic immune system etc.) has the potential to exert significant antimutagenic properties against colon cancer.

Expression of ICAM-1 on the Hantaan virus-infected human umbilical vein endothelial cells

OBJECTIVES

In HFRS, there is a varying degree of disseminated intravascular coagulation which was evident in the early phase of the illness. It is believed also that DIC would be the consequence, at least in part, of functional changes of endothelium resulting in kinin activation and clinical syndrome. This study investigated the role of adhesion molecule in the pathogenesis of Hantaan virus-related disease.

METHODS

The expression of ICAM-1 antigen on the cell membrane of human umbilical vein endothelial cells was assessed by immunohistochemistry, and ICAM-1 mRNA in the endothelial cells was assessed by in situ hybridization after Hantaan virus infection (2.6 x 10(4) PFU/mL) with the time course.

RESULTS

In immunohistochemistry, the number of ICAM-1 positive cells increased with time during the 12 or 24 hours after infection. 5 to 10% of HUVECs had been positive after 12-24 hours and the number of positive cells decreased abruptly after 24 hours. Hantaan antigen had been noticed after 12 hours focally on the HUVECs but continued to proliferate into day 7 post-infection when most of HUVECs were infected by Hantaan virus. In situ hybridization showed identical patterns of ICAM-1 mRNA expression after Hantaan virus infection.

CONCLUSION

It implies that the Hantaan virus infection on HUVECs would express more ICAM-1 on their surface and implicated in the pathogenesis of early clinical syndrome of HFRS.

Recanalization of obstructed Tenckhoff peritoneal dialysis catheter: wire/stylet manipulation combined with endoluminal electrocauterization

We report the results of fluoroscopically guided wire/stylet manipulation combined with endoluminal electrocauterization in seven patients with obstructed Tenckhoff peritoneal dialysis catheters. In preparation for clinical application, electrocauterization was performed using a stone basket to recanalize surgically removed Tenckhoff catheters obstructed with omental fat ingrowing through the side holes. All ingrowing omental fat was removed easily by electrocauterization with the rotating movement of a stone basket. The technique was then applied in vivo in seven cases with ingrowing omental fat and malpositioned catheter; six (86%) were successfully recanalized. Among those six cases with initial success, four maintained good catheter function with durable patency (mean 261.3 days). No significant complication was noted.

Prevalence of antibodies to hepatitis C virus in patients with various types of liver diseases

BACKGROUND

Hepatitis C virus (HCV) is known to be a major cause of non-A, non-B hepatitis (NANBH) and is thought to be an important causative agent of serious liver disease. Recently the role of HCV in the development of various liver disease is suggested.

METHODS

Sera from 222 patients with various liver diseases had been kept frozen at -20 degrees C until the test. Anti-HCV was detected using the ABBOTT HCV EIA Test System (ABBOTT Co., America) following the manufacturer's instructions. The assay uses a recombinant HCV antigen (C 100-3) synthesized in yeast.

RESULTS

HCV antibodies (anti-HCV) were detected in 35 (31.5%) of 111 HBsAg-negative patients. The prevalence rate of anti-HCV was 61.9% (13 out of 21 patients) in chronic hepatitis, 29.1% (14 out of 48) in liver cirrhosis, 26.3% (5 out of 19) in hepatocellular carcinoma and 13% (3 out of 23) in acute hepatitis was far less (3 out of 111 patients, 2. 7%) than that of HBsAg-negative patients (p < 0.01). In this group, anti-HCV was detected in 2 (5.1%) out of 39 liver cirrhosis, 1 (1.9%) out of 52 chronic hepatitis, among them 47 were biopsy-proven chronic active hepatitis, and none of 20 hepatocellular carcinoma.

CONCLUSIONS

These data suggest that, in Korea, 1) coinfection of HCV and HBV is infrequent, 2) HCV might be an important cause of HBsAg-negative chronic hepatitis, 3) HCV is seemed to be a less likely important factor associated with liver cirrhosis or hepatocellular carcinoma in HBsAg-negative patients, but further prospective study with a large population is necessary.