Abstract
Constrained by the Nielsen-Ninomiya no-go theorem, in all so-far experimentally determined Weyl semimetals (WSMs) the Weyl points (WPs) always appear in pairs in the momentum space with no ...exception. As a consequence, Fermi arcs occur on surfaces which connect the projections of the WPs with opposite chiral charges. However, this situation can be circumvented in the case of unpaired WP, without relevant surface Fermi arc connecting its surface projection, appearing singularly, while its Berry curvature field is absorbed by nontrivial charged nodal walls. Here, combining angle-resolved photoemission spectroscopy with density functional theory calculations, we show experimentally that a singular Weyl point emerges in PtGa at the center of the Brillouin zone (BZ), which is surrounded by closed Weyl nodal walls located at the BZ boundaries and there is no Fermi arc connecting its surface projection. Our results reveal that nontrivial band crossings of different dimensionalities can emerge concomitantly in condensed matter, while their coexistence ensures the net topological charge of different dimensional topological objects to be zero. Our observation extends the applicable range of the original Nielsen-Ninomiya no-go theorem which was derived from zero dimensional paired WPs with opposite chirality.
Discovery of magnetic Weyl fermions: Dirac fermions split into pairs of Weyl fermions by slow magnetic fluctuations.
Weyl fermions as emergent quasiparticles can arise in Weyl semimetals (WSMs) in ...which the energy bands are nondegenerate, resulting from inversion or time-reversal symmetry breaking. Nevertheless, experimental evidence for magnetically induced WSMs is scarce. Here, using photoemission spectroscopy, we observe that the degeneracy of Bloch bands is already lifted in the paramagnetic phase of EuCd
2
As
2
. We attribute this effect to the itinerant electrons experiencing quasi-static and quasi–long-range ferromagnetic fluctuations. Moreover, the spin-nondegenerate band structure harbors a pair of ideal Weyl nodes near the Fermi level. Hence, we show that long-range magnetic order and the spontaneous breaking of time-reversal symmetry are not essential requirements for WSM states in centrosymmetric systems and that WSM states can emerge in a wider range of condensed matter systems than previously thought.
We report a new measurement of electron antineutrino disappearance using the fully constructed Daya Bay Reactor Neutrino Experiment. The final two of eight antineutrino detectors were installed in ...the summer of 2012. Including the 404 days of data collected from October 2012 to November 2013 resulted in a total exposure of 6.9×10^{5} GW_{th} ton days, a 3.6 times increase over our previous results. Improvements in energy calibration limited variations between detectors to 0.2%. Removal of six ^{241}Am-^{13}C radioactive calibration sources reduced the background by a factor of 2 for the detectors in the experimental hall furthest from the reactors. Direct prediction of the antineutrino signal in the far detectors based on the measurements in the near detectors explicitly minimized the dependence of the measurement on models of reactor antineutrino emission. The uncertainties in our estimates of sin^{2}2θ_{13} and |Δm_{ee}^{2}| were halved as a result of these improvements. An analysis of the relative antineutrino rates and energy spectra between detectors gave sin^{2}2θ_{13}=0.084±0.005 and |Δm_{ee}^{2}|=(2.42±0.11)×10^{-3} eV^{2} in the three-neutrino framework.
This Letter reports an improved search for light sterile neutrino mixing in the electron antineutrino disappearance channel with the full configuration of the Daya Bay Reactor Neutrino Experiment. ...With an additional 404 days of data collected in eight antineutrino detectors, this search benefits from 3.6 times the statistics available to the previous publication, as well as from improvements in energy calibration and background reduction. A relative comparison of the rate and energy spectrum of reactor antineutrinos in the three experimental halls yields no evidence of sterile neutrino mixing in the 2×10^{-4}≲|Δm_{41}^{2}|≲0.3 eV^{2} mass range. The resulting limits on sin^{2}2θ_{14} are improved by approx imately a factor of 2 over previous results and constitute the most stringent constraints to date in the |Δm_{41}^{2}|≲0.2 eV^{2} region.
A measurement of the energy dependence of antineutrino disappearance at the Daya Bay reactor neutrino experiment is reported. Electron antineutrinos (ν¯(e)) from six 2.9 GW(th) reactors were ...detected with six detectors deployed in two near (effective baselines 512 and 561 m) and one far (1579 m) underground experimental halls. Using 217 days of data, 41 589 (203 809 and 92 912) antineutrino candidates were detected in the far hall (near halls). An improved measurement of the oscillation amplitude sin(2)2θ(13)=0.090(-0.009)(+0.008) and the first direct measurement of the ν¯(e) mass-squared difference |Δm(ee)2|=(2.59(-0.20)(+0.19))×10(-3) eV2 is obtained using the observed ν¯(e) rates and energy spectra in a three-neutrino framework. This value of |Δm(ee)2| is consistent with |Δm(μμ)2| measured by muon neutrino disappearance, supporting the three-flavor oscillation model.
Repeated stress relaxation tests and strain rate jump tests have been carried out over a range of deformation temperatures (77–373
K) on electrodeposited nanocrystalline Ni with an average grain size ...of ∼30
nm. The strain rate sensitivity, the apparent and physical activation volume, and the activation energy have been determined. The magnitude observed for these characteristic deformation parameters, as well as their temperature-dependent behavior, is very different from those of coarse-grained Ni. This suggests that the thermally activated process in nanocrystalline Ni is different from the conventional forest dislocation cutting mechanism. It is concluded that grain boundary diffusion-controlled processes such as Coble creep and grain boundary sliding can be ruled out as dominant mechanisms for the grain sizes and temperature range studied. Instead, our experimental findings and analysis suggest that the deformation kinetics are controlled by the activities of dislocations. The dominant thermally activated mechanism is suggested to originate from three possible processes, all involving interactions of mobile dislocations with grain boundaries.
Purpose
To compare febrile neutropenia (FN) incidence and hospitalization among breast cancer patients on docetaxel with no granulocyte colony-stimulating factors (GCSF) primary prophylaxis (PP), ...4/5-day PP, or 7-day PP.
Methods
We identified 3916 breast cancer patients using docetaxel-cyclophosphamide (TC), doxorubicin-cyclophosphamide then docetaxel (AC-T), fluorouracil-epirubicin-cyclophosphamide then docetaxel (FEC-T), docetaxel-carboplatin-trastuzumab (TJH), or docetaxel-doxorubicin-cyclophosphamide (TAC) from a hospital pharmacy dispensing database in Hong Kong between 2014 and 2016. Patients were offered GCSF within 5 days since administering docetaxel. Outcomes included FN incidence, time to first hospitalization, hospitalization rate, and duration.
Results
In TC regimen, FN incidence (with odds ratio, OR) of patients with no PP, 4/5-day PP, and 7-day PP was 21.69%, 7.95% (OR 0.31,
p
< 0.001), and 5.33% (OR 0.20,
p
< 0.001), respectively. In TJH regimen, FN incidence of patients with no PP, 4/5-day PP, and 7-day PP was 38.26%, 8.33% (OR 0.15,
p
< 0.001), and 8.57% (OR 0.15,
p
< 0.001), respectively. FN incidence of patients on AC-T regimen with no PP and 4/5-day PP was 20.93% and 6.84%, respectively (OR 0.28,
p
= 0.005); with FEC-T regimen, the incidence was 9.91% and 4.77%, respectively (OR 0.46,
p
= 0.035). Only 3.27% FN cases were not hospitalized. Mean (±standard deviation, SD) time to first hospitalization was 8.21 ± 2.44 days. Mean (±SD) duration of hospitalization for patients with no PP, 4/5-day PP, and 7-day PP was 4.66 ± 2.60, 4.37 ± 2.85, and 5.12 ± 2.97 days, respectively.
Conclusion
GCSF prophylaxis in breast cancer patients on docetaxel could reduce FN incidence and hospitalization. 4/5-day PP demonstrated similar efficacy to 7-day PP with superior saving benefits on healthcare expenditure.
Quantitative measurement of plasma Epstein–Barr virus (EBV) DNA by real-time PCR at the end of primary treatment is a robust prognostic marker for nasopharyngeal carcinoma (NPC) patients. However, up ...to 40% of patients who would later develop disease recurrence had undetectable post-treatment plasma EBV DNA. Targeted sequencing for the entire EBV genome potentially allows a more comprehensive and unbiased detection of plasma EBV DNA and enables the use of other parameters such as fragment size as biomarkers. Hence, we explored if plasma EBV DNA sequencing might allow more accurate prognostication of NPC patients.
Plasma samples collected from 769 patients with stage IIB-IVB NPC at 6-8 weeks after radiotherapy were analysed using targeted sequencing for EBV DNA.
The sensitivities of the PCR-based analysis, at a cut-off of any detectable levels of plasma EBV DNA, for prediction of local and distant recurrences were 42.3% and 85.3%, respectively. The sequencing-based analysis (involving quantitation and size profiling) achieved better performance for both local and distant recurrences than PCR. Using a cut-off of the proportion of plasma EBV DNA deduced by sequencing at 0.01%, the sensitivities of the sequencing-based analysis for local and distant recurrences were 88.5% and 97.1%, with the resultant negative predictive values of 99.1% and 99.4%, respectively. Among patients with undetectable EBV DNA on quantitative PCR, sequencing could further define a subgroup that enjoyed superior survival outcomes based on the proportion of plasma EBV DNA, with a 5-year progression-free survival (PFS) approaching 90%. On multivariate analysis, sequencing-based quantitative level of plasma EBV DNA was the independent prognostic factor with the highest hazard ratio for prediction of overall survival and PFS.
NPC prognostication using post-treatment plasma EBV DNA could be enhanced through sequencing.
•PCR-based analysis of plasma EBV DNA has limited sensitivity in predicting recurrences of NPC.•Sequencing analysis of post-treatment plasma EBV DNA improves the sensitivity for both local and distant relapses of NPC.•Sequencing analysis of post-treatment plasma EBV DNA could better stratify the mortality risk of NPC patients than PCR.
Objective
Incidental detection of thyroid cancers has been proposed as a cause of thyroid cancer increases over past decades, but few studies assess the impact of imaging utilization on thyroid ...cancer incidence. This study quantifies neck CT prevalence and its relationship with thyroid cancer incidence as a function of age, sex and race.
Design and Patients
Medical records of over 1 million patients at our institution were retrospectively analysed to quantify neck CT prevalence from 2004 to 2011 (study period). A national cancer database was used to compute thyroid cancer incidences over the study period and a reference period (1974‐81) and to calculate change in thyroid incidence between the two periods. Both populations were partitioned into demographic subgroups of varying age, sex and race. Linear correlation between neck imaging and thyroid cancer incidence changes among subgroups was assessed using Pearson's correlation.
Results
Neck CT imaging and change in thyroid cancer incidence varied across all examined demographic variables, particularly age. When stratifying by age, CT use correlated strongly with recent national thyroid cancer incidence (R = .97) and with 30‐year change in thyroid cancer incidence (R = .87). Across all demographic subgroups, CT prevalence correlated strongly and positively with change in thyroid cancer incidence (R = .60), greater for whites (R = .60) and blacks (R = .70) than other races (R = .28).
Conclusion
Differences in neck CT usage strongly and positively correlates with the variation in thyroid cancer trends based on age, gender and race.
EAS (extensive air shower) thermal neutron measurement gives advantages to study energy and mass composition of primary cosmic rays especially in the knee region. After the success of the PRISMA-YBJ ...experiment, we build a new EAS thermal neutron detection array at Tibet University, Lhasa, China (3700 m a.s.l.) in March, 2017. This prototype array so called "PRISMA-LHAASO-16" consists of 16 EAS EN-detectors ("EN" is abbreviation for electron and neutron) measuring two main EAS components: hadronic and electromagnetic ones. Different from PRISMA-YBJ, these detectors use a thin layer of a novel type of ZnS(Ag) scintillator alloyed with natural boron compound for thermal neutron capture. PRISMA-LHAASO-16 will be moved to the LHAASO site in the near future. In this paper, we introduce principle of the detection technique, deployment of the array, and the test results of the array.
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