In quantum field theory, Lorentz invariance leads to three types of fermion-Dirac, Weyl and Majorana. Although the existence of Weyl and Majorana fermions as elementary particles in high-energy ...physics is debated, all three types of fermion have been proposed to exist as low-energy, long-wavelength quasiparticle excitations in condensed-matter systems. The existence of Dirac and Weyl fermions in condensed-matter systems has been confirmed experimentally, and that of Majorana fermions is supported by various experiments. However, in condensed-matter systems, fermions in crystals are constrained by the symmetries of the 230 crystal space groups rather than by Lorentz invariance, giving rise to the possibility of finding other types of fermionic excitation that have no counterparts in high-energy physics. Here we use angle-resolved photoemission spectroscopy to demonstrate the existence of a triply degenerate point in the electronic structure of crystalline molybdenum phosphide. Quasiparticle excitations near a triply degenerate point are three-component fermions, beyond the conventional Dirac-Weyl-Majorana classification, which attributes Dirac and Weyl fermions to four- and two-fold degenerate points, respectively. We also observe pairs of Weyl points in the bulk electronic structure of the crystal that coexist with the three-component fermions. This material thus represents a platform for studying the interplay between different types of fermions. Our experimental discovery opens up a way of exploring the new physics of unconventional fermions in condensed-matter systems.
This study investigated the effects of different acute high ambient temperatures on dysfunction of hepatic mitochondrial respiration, the antioxidative enzyme system, and oxidative injury in broiler ...chickens. One hundred twenty-eight 6-wk-old broiler chickens were assigned randomly to 4 groups and subsequently exposed to 25 (control), 32, 35, and 38°C (RH, 70 ± 5%) for 3 h, respectively. The rectal temperatures, activity of antioxidative enzymes (superoxide dismutase, catalase, and glutathione peroxidase), content of malondialdehyde and protein carbonyl, and the activity of mitochondrial respiratory enzymes were determined. The results showed that exposure to high ambient temperature induced a significant elevation of rectal temperature, antioxidative enzyme activity, and formation of malondialdehyde and protein carbonyl, as well as dysfunction of the mitochondrial respiratory chain in comparison with control (P < 0.05). Almost all of the indicators changed in a temperature-dependent manner with the gradual increase of ambient temperature from 32 to 38°C; differences in each parameter (except catalase) among the groups exposed to different high ambient temperatures were also statistically significant (P < 0.05). The results of the present study suggest that, in the broiler chicken model used here, acute exposure to high temperatures may depress the activity of the mitochondrial respiratory chain. This inactivation results subsequently in overproduction of reactive oxygen species, which ultimately results in oxidative injury. However, this hypothesis needs to be evaluated more rigorously in future studies. It has also been shown that, with the gradual increase in temperature, the oxidative injury induced by heat stress in broiler chickens becomes increasingly severe, and this stress response presents in a temperature-dependent manner in the temperature range of 32 to 38°C.
Abstract
A quantum thermal machine is an open quantum system coupled to hot and cold thermal baths. Thus, its dynamics can be well understood using the concepts and tools from non-Hermitian quantum ...systems. A hallmark of non-Hermiticity is the existence of exceptional points where the eigenvalues of a non-Hermitian Hamiltonian or a Liouvillian superoperator and their associated eigenvectors coalesce. Here, we report the experimental realization of a single-ion heat engine and demonstrate the effect of Liouvillian exceptional points on the dynamics and the performance of a quantum heat engine. Our experiments have revealed that operating the engine in the exact- and broken-phases, separated by a Liouvillian exceptional point, respectively during the isochoric heating and cooling strokes of an Otto cycle produces more work and output power and achieves higher efficiency than executing the Otto cycle completely in the exact phase where the system has an oscillatory dynamics and higher coherence. This result opens interesting possibilities for the control of quantum heat engines and will be of interest to other research areas that are concerned with the role of coherence and exceptional points in quantum processes and in work extraction by thermal machines.
Aims
This study investigated the role of L‐3‐n‐Butylphthalide (NBP) in cardiac protection.
Methods
The left anterior descending coronary arteries (LAD) of the rats were occluded for 30 min following ...by 2‐h reperfusion to make the ischaemia/reperfusion models. Neonatal cardiomyocytes were cultured and subjected to hypoxia. L‐3‐n‐Butylphthalide was administered intraperitoneally 2 h before the surgery and right after the reperfusion in the in vivo experiments or added to the culture medium in vitro. Haemodynamic parameters were recorded to evaluate the cardiac functions, triphenyltetrazolium chloride (TTC) and Evens blue staining were used to determine the area of risk and infarct area, apoptotic cell numbers were counted with terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL) staining. Western blotting was used to determine the apoptotic protein levels and immune staining to determine the translocation of Glyceraldehyde‐3‐phosphate dehydrogenase (GAPDH) protein.
Results
Our research showed for the first time that L‐3‐n‐Butylphthalide had great effects in improving cardiac hemodynamic function and decreasing cardiac infarct areas and apoptotic cell numbers in the peri‐infarct areas. The apoptotic signals investigation showed that L‐3‐n‐Butylphthalide affected the mitochondrial pathway including Bcl‐2 protein expression, inhibition of caspase 3 activation and cytochrome C releasing. Besides, Glyceraldehyde‐3‐phosphate dehydrogenase protein translocation was inhibited by L‐3‐n‐Butylphthalide treatment, and this effect was mediated by endogenous reactive oxygen species (ROS).
Conclusion
L‐3‐n‐Butylphthalide protects cardiomyocytes from ischaemia/reperfusion‐induced apoptosis by antioxidant effect and affecting mitochondrial apoptotic pathway.
Icotinib has been previously shown to be non-inferior to gefitinib in non-selected advanced non-small-cell lung cancer patients when given as second- or further-line treatment. In this open-label, ...randomized, phase 3 CONVINCE trial, we assessed the efficacy and safety of first-line icotinib versus cisplatin/pemetrexed plus pemetrexed maintenance in lung adenocarcinoma patients with epidermal growth factor receptor (EGFR) mutation.
Eligible participants were adults with stage IIIB/IV lung adenocarcinoma and exon 19/21 EGFR mutations. Participants were randomly allocated (1 : 1) to receive oral icotinib or 3-week cycle of cisplatin plus pemetrexed for up to four cycles; non-progressive patients after four cycles were maintained with pemetrexed until disease progression or intolerable toxicity. The primary end point was progression-free survival (PFS) assessed by independent response evaluation committee. Other end points included overall survival (OS) and safety.
Between January 2013 and August 2014, 296 patients were randomized, and 285 patients were treated (148 to icotinib, 137 to chemotherapy). Independent response evaluation committee-assessed PFS was significantly longer in the icotinib group (11.2 versus 7.9 months; hazard ratio, 0.61, 95% confidence interval 0.43-0.87; P = 0.006). No significant difference for OS was observed between treatments in the overall population or in EGFR-mutated subgroups (exon 19 Del/21 L858R). The most common grade 3 or 4 adverse events (AEs) in the icotinib group were rash (14.8%) and diarrhea (7.4%), compared with nausea (45.9%), vomiting (29.2%), and neutropenia (10.9%) in the chemotherapy group. AEs (79.1% versus 94.2%; P < 0.001) and treatment-related AEs (54.1% versus 90.5%; P < 0.001) were significantly fewer in the icotinib group than in the chemotherapy group.
First-line icotinib significantly improves PFS of advanced lung adenocarcinoma patients with EGFR mutation with a tolerable and manageable safety profile. Icotinib should be considered as a first-line treatment for this patient population.
Though immensely successful, the standard model of particle physics does not offer any explanation as to why our Universe contains so much more matter than antimatter. A key to a dynamically ...generated matter-antimatter asymmetry is the existence of processes that violate the combined charge conjugation and parity (CP) symmetry
. As such, precision tests of CP symmetry may be used to search for physics beyond the standard model. However, hadrons decay through an interplay of strong and weak processes, quantified in terms of relative phases between the amplitudes. Although previous experiments constructed CP observables that depend on both strong and weak phases, we present an approach where sequential two-body decays of entangled multi-strange baryon-antibaryon pairs provide a separation between these phases. Our method, exploiting spin entanglement between the double-strange Ξ
baryon and its antiparticle
Formula: see text, has enabled a direct determination of the weak-phase difference, (ξ
- ξ
) = (1.2 ± 3.4 ± 0.8) × 10
rad. Furthermore, three independent CP observables can be constructed from our measured parameters. The precision in the estimated parameters for a given data sample size is several orders of magnitude greater than achieved with previous methods
. Finally, we provide an independent measurement of the recently debated Λ decay parameter α
(refs.
). The Formula: see text asymmetry is in agreement with and compatible in precision to the most precise previous measurement
.
Based on electron-positron collision data collected with the BESIII detector operating at the Beijing Electron-Positron Collider II storage rings, the value of ...R≡σ(e^{+}e^{-}→hadrons)/σ(e^{+}e^{-}→μ^{+}μ^{-}) is measured at 14 center-of-mass energies from 2.2324 to 3.6710 GeV. The resulting uncertainties are less than 3.0% and are dominated by systematic uncertainties.
Quantum heat engines are expected to outperform the classical counterparts due to quantum coherences involved. Here we experimentally execute a single-ion quantum heat engine and demonstrate, for the ...first time, the dynamics and the enhanced performance of the heat engine originating from the Liouvillian exceptional points (LEPs). In addition to the topological effects related to LEPs, we focus on thermodynamic effects, which can be understood by the Landau-Zener-Stückelberg process under decoherence. We witness a positive net work from the quantum heat engine if the heat engine cycle dynamically encircles a LEP. Further investigation reveals that a larger net work is done when the system is operated closer to the LEP. We attribute the enhanced performance of the quantum heat engine to the Landau-Zener-Stückelberg process, enabled by the eigenenergy landscape in the vicinity of the LEP, and the exceptional point-induced topological transition. Therefore, our results open new possibilities toward LEP-enabled control of quantum heat engines and of thermodynamic processes in open quantum systems.
Quantum gates induced by geometric phases are intrinsically robust against noise due to the global properties of their evolution paths. Compared to conventional nonadiabatic geometric quantum ...computation, the recently proposed nonadiabatic noncyclic geometric quantum computation (NNGQC) works in a faster fashion while still remaining the robust feature of the geometric operations. Here, we experimentally implement the NNGQC in a single trapped ultracold 40Ca+ ion to verify the noise-resilient and fast feature. By performing unitary operations under imperfect conditions, we witness the advantages of the NNGQC with measured fidelities by quantum process tomography in comparison to other two quantum gates by conventional nonadiabatic geometric quantum computation and by straightforward dynamical evolution. Our results provide the first evidence confirming the possibility of accelerated quantum information processing with limited systematic errors even in an imperfect situation.
Topological semimetals with different types of band crossings provide a rich platform to realize novel fermionic excitations, known as topological fermions. In particular, some fermionic excitations ...can be direct analogs of elementary particles in quantum field theory when both obey the same laws of physics in the low-energy limit. Examples include Dirac and Weyl fermions, whose solid-state realizations have provided new insights into long-sought phenomena in high-energy physics. Recently, theorists predicted new types of fermionic excitations in condensed-matter systems without any high-energy counterpart, and their existence is protected by crystalline symmetries. By studying the topology of the electronic structure in PdBiSe using density functional theory calculations and bulk-sensitive soft x-ray angle-resolved photoemission spectroscopy, we demonstrate a coexistence of four different types of topological fermions: Weyl, Rarita-Schwinger-Weyl, double class-II three-component, and charge-2 fourfold fermions. Our discovery provides a remarkable platform to realize multiple fermions in a single solid, charting the way forward to studies of their potentially exotic properties as well as their interplay.
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