Observation of unusual topological surface states in half-Heusler compounds LnPtBi (Ln=Lu, Y)

Topological quantum materials represent a new class of matter with both exotic physical phenomena and novel application potentials. Many Heusler compounds, which exhibit rich emergent properties such as unusual magnetism, superconductivity and heavy fermion behaviour, have been predicted to host non-trivial topological electronic structures. The coexistence of topological order and other unusual properties makes Heusler materials ideal platform to search for new topological quantum phases (such as quantum anomalous Hall insulator and topological superconductor). By carrying out angle-resolved photoemission spectroscopy and ab initio calculations on rare-earth half-Heusler compounds LnPtBi (Ln=Lu, Y), we directly observe the unusual topological surface states on these materials, establishing them as first members with non-trivial topological electronic structure in this class of materials. Moreover, as LnPtBi compounds are non-centrosymmetric superconductors, our discovery further highlights them as promising candidates of topological superconductors.

Heusler compounds have been predicted to host topological order with other emergent properties, which yet awaits for experimental evidence. Here, Liu et al. report a direct observation of topological surface states on half-Heusler compounds LnPtBi.

[The application of full thicknes skin graft inpartial laryngectomy for glottic carcinoma]

Objective:The aim of this study is to explore the experience and advantages of the application of full thicknes skin graft in glottic carcinoma.partial laryngectomy for glottic carcinoma.Method:One hundred and forty-three patients with glottic cancer were treated with partial laryngectomy.Among those,78 cases were repaired with full-thickness skin graft and 65 cases were repaired with sternohyoid muscular fasciae.Compared the time of extubation and the formation of granulation in laryngeal cavity after operation between the two groups.Result:In the group of full-thickness skin graft,the mean time of decannulation was 6.8 days,5 cases with growth of granulation after operation.In other group,the mean time of decannulation was 10.7 days,16 cases with growth of granulation after operation.The mean time of decannulation(t=-4.739,P<0.01) and the growth of granulation(χ²=9.379,P<0.01) are significantly different between the two groups.No laryngostenosis was found in all patients.Conclusion:The application of full-thicknes skin graft in partial laryngectomy for glottic carcinoma.can shortthe time of extubation and reduce the formation of granulation.

Comprehensive studies of interfacial strain and oxygen vacancy on metal-insulator transition of VO2 film

As a typical strong correlation material, vanadium dioxide (VO2) has attracted wide interest due to its particular metal-insulator transition (MIT) property. However, the relatively high critical temperature (T c) of ~68 °C seriously hinders its practical applications. Thus modulating the phase transition process and decreasing the T c close to room temperature have been hot topics for VO2 study. In the current work, we conducted a multi-approach strategy to control the phase transition of VO2 films, including the interfacial tensile/compressive strain and oxygen vacancies. A synchrotron radiation reciprocal space mapping technique was used to directly record the interfacial strain evolution and variations of lattice parameters. The effects of interfacial strain and oxygen vacancies in the MIT process were systematically investigated based on band structure and d-orbital electron occupation. It was suggested that the MIT behavior can be modulated through the combined effects of the interfacial strain and oxygen vacancies, achieving the distinct phase transition close to room temperature. The current findings not only provide better understanding for strain engineering and oxygen vacancies controlling phase transition behavior, but also supply a combined way to control the phase transition of VO2 film, which is essential for VO2 film based device applications in the future.

[Effects of intubating laryngeal mask airway in prevention of extubation responses in patients with hypertensive cerebral hemorrhage during general anesthesia recovery period]

OBJECTIVE

To evaluate the effects of intubating laryngeal mask airway (ILMA) in prediction of extubation responses in patients with hypertensive cerebral hemorrhage during general anesthesia recovery period.

METHODS

A total of 120 patients with hypertensive cerebral hemorrhage aged 47-71 years, with Glasgow Coma Scale (GCS)11-15 scores and American Society of Anesthesiologists (ASA) physical status Ⅰ or Ⅱ, undergoing craniotomy surgery from December 2012 to December 2014 in the Affiliated First Municipal Hospital of Fujian Medical University were randomly divided into 2 groups (n=60): tracheal intubation (Group T) and intubating laryngeal mask airway (Group I), by using a random number table. Variations of invasive arterial blood pressure and responses of endotracheal extubation were compared between two groups before and after extubation.

RESULTS

There were no significant differences in ages, sex ratio, preoperative GCS, operation time and the time from the end of operation to Train of Four stimulation (TOF) becoming to 4 between the two groups. The mean arterial pressure (MAP) at the time point of extubation (T3), 1 min (T4), 3 min (T5), 5 min (T6) after extubation were (136±20), (130±16), (128±12), (125±10) mmHg in Group T, and heart rate(HR) at these four time points were (105±11), (96±8), (92±7), (86±6) bpm, respectively. While in group I, MAP were (108±10), (106±8), (105±9), (106±7) mmHg, and HR were (75±8), (76±7), (68±5), (67±6) bpm, respectively. MAP and HR of the two groups at these four time points had significant differences (T3: t=10.91, 17.20; T4: t=13.72, 14.69; T5: t=12.54, 13.35; T6: t=13.39, 11.27; all P<0.01). During recovery, the incidences of extubation responses of group T and group I were 92% and 2%, respectively, and the difference had statistically significant (χ(2)=94.05, P<0.01). The incidences of coughing of group T and group I were 97% and 0, respectively, and the difference had statistically significant (χ(2)=148.69, P<0.01).

CONCLUSION

Compared with tracheal intubation, ILMA can decrease the incidence of extubation responses and coughing in patients with hypertensive cerebral hemorrhage during general anesthesia recovery period, and avoid cere-brovascular accidents.

Smart conjugated polymer nanocarrier for healthy weight loss by negative feedback regulation of lipase activity

Healthy weight loss represents a real challenge when obesity is increasing in prevalence. Herein, we report a conjugated polymer nanocarrier for smart deactivation of lipase and thus balancing calorie intake. After oral administration, the nanocarrier is sensitive to lipase in the digestive tract and releases orlistat, which deactivates the enzyme and inhibits fat digestion. It also creates negative feedback to control the release of itself. The nanocarrier smartly regulates activity of the lipase cyclically varied between high and low levels. In spite of high fat diet intervention, obese mice receiving a single dose of the nanocarrier lose weight over eight days, whereas a control group continues the tendency to gain weight. Daily intragastric administration of the nanocarrier leads to lower weight of livers or fat pads, smaller adipocyte size, and lower total cholesterol level than that of the control group. Near-infrared fluorescence of the nanocarrier reveals its biodistribution.

Evolution of the Fermi surface of Weyl semimetals in the transition metal pnictide family

Topological Weyl semimetals (TWSs) represent a novel state of topological quantum matter which not only possesses Weyl fermions (massless chiral particles that can be viewed as magnetic monopoles in momentum space) in the bulk and unique Fermi arcs generated by topological surface states, but also exhibits appealing physical properties such as extremely large magnetoresistance and ultra-high carrier mobility. Here, by performing angle-resolved photoemission spectroscopy (ARPES) on NbP and TaP, we directly observed their band structures with characteristic Fermi arcs of TWSs. Furthermore, by systematically investigating NbP, TaP and TaAs from the same transition metal monopnictide family, we discovered their Fermiology evolution with spin-orbit coupling (SOC) strength. Our experimental findings not only reveal the mechanism to realize and fine-tune the electronic structures of TWSs, but also provide a rich material base for exploring many exotic physical phenomena (for example, chiral magnetic effects, negative magnetoresistance, and the quantum anomalous Hall effect) and novel future applications.

Changes in astrocyte functional markers and β-amyloid metabolism-related proteins in the early stages of hypercholesterolemia

Cholesterol is an essential substance for maintaining normal structure and function of the brain. But unfortunately, a long-term high-cholesterol diet can lead to a variety of pathological changes of the brain such as β-amyloid (Aβ) accumulation, Tau hyperphosphorylation, reactive gliosis, neuroinflammation, neuronal death and synaptic degeneration. These pathological changes have complex internal relations with one other, causing memory impairment and participating in the pathogenesis of Alzheimer's disease (AD). However, early hypercholesterolemia-induced events that lead to brain deterioration are not clear. To address this, 6-month-old female mice were fed a 3% cholesterol diet for 8weeks, followed by behavioral, biochemical and neuropathological analyses. The high-cholesterol-fed mice did not show neuronal and synaptic impairment or cognitive deficits compared with mice given a normal diet, but astrocytes were mildly activated with increased expression of functional markers including apolipoprotein E and aquaporin 4 in the hippocampus. Hippocampal interleukin-1β expression slightly increased, but interleukin-6 (IL-6) and tumor necrosis factor-α did not change significantly compared with those in the control group. Levels of Aβ, and its precursor protein, were unaffected, but levels of presenilin 1 and insulin-degrading enzyme (IDE), that initiate Aβ generation and degradation, respectively, increased in the hippocampus of the model mice. In addition, Tau phosphorylation levels were not different between the control and model groups. These results suggest that changes in astrocyte functional markers and Aβ metabolism proteins, which contribute to maintaining brain cholesterol and Aβ homeostasis, are early events in the process of hypercholesterolemia-related neuropathological changes.

Massive Dirac Fermion Observed in Lanthanide-Doped Topological Insulator Thin Films

The breaking of time reversal symmetry (TRS) in three-dimensional (3D) topological insulators (TIs), and thus the opening of a ‘Dirac-mass gap’ in the linearly dispersed Dirac surface state, is a prerequisite for unlocking exotic physical states. Introducing ferromagnetic long-range order by transition metal doping has been shown to break TRS. Here, we present the study of lanthanide (Ln) doped Bi₂Te₃, where the magnetic doping with high-moment lanthanides promises large energy gaps. Using molecular beam epitaxy, single-crystalline, rhombohedral thin films with Ln concentrations of up to ~35%, substituting on Bi sites, were achieved for Dy, Gd, and Ho doping. Angle-resolved photoemission spectroscopy shows the characteristic Dirac cone for Gd and Ho doping. In contrast, for Dy doping above a critical doping concentration, a gap opening is observed via the decreased spectral intensity at the Dirac point, indicating a topological quantum phase transition persisting up to room-temperature.

Conjugated Polymer Nanoparticles for Fluorescence Imaging and Sensing of Neurotransmitter Dopamine in Living Cells and the Brains of Zebrafish Larvae

Nanoscale materials are now attracting a great deal of attention for biomedical applications. Conjugated polymer nanoparticles have remarkable photophysical properties that make them highly advantageous for biological fluorescence imaging. We report on conjugated polymer nanoparticles with phenylboronic acid tags on the surface for fluorescence detection of neurotransmitter dopamine in both living PC12 cells and brain of zebrafish larvae. The selective enrichment of dopamine and fluorescence signal amplification characteristics of the nanoparticles show rapid and high-sensitive probing such neurotransmitter with the detection limit of 38.8 nM, and minimum interference from other endogenous molecules. It demonstrates the potential of nanomaterials as a multifunctional nanoplatform for targeting, diagnosis, and therapy of dopamine-relative disease.

pH-Responsive and near-infrared-emissive polymer nanoparticles for simultaneous delivery, release, and fluorescence tracking of doxorubicin in vivo

Dextran modified with pendant acetals is used to load doxorubicin (DOX) and a near-infrared-emissive conjugated polymer (BTTPF), and this aims to provide selective drug release at therapeutic targets including tumors. The BTTPF is applicable to tracking the anticancer drug release through the change of Förster resonance energy transfer efficiency between doxorubicin and BTTPF during degradation of the nanoparticles in vivo.

Control of the metal-insulator transition in VO₂ epitaxial film by modifying carrier density

External controlling the phase transition behavior of vanadium dioxide is important to realize its practical applications as energy-efficient electronic devices. Because of its relatively high phase transition temperature of 68 °C, the central challenge for VO2-based electronics, lies in finding an energy efficient way, to modulate the phase transition in a reversible and reproducible manner. In this work, we report an experimental realization of p-n heterojunctions by growing VO2 film on p-type GaN substrate. By adding the bias voltage on the p-n junction, the metal-insulator transition behavior of VO2 film can be changed continuously. It is demonstrated that the phase transition of VO2 film is closely associated with the carrier distribution within the space charge region, which can be directly controlled by the bias voltage. Our findings offer novel opportunities for modulating the phase transition of VO2 film in a reversible way as well as extending the concept of electric-field modulation on other phase transition materials.

Linear magnetoresistance caused by mobility fluctuations in n-doped Cd(3)As(2)

Cd(3)As(2) is a candidate three-dimensional Dirac semimetal which has exceedingly high mobility and nonsaturating linear magnetoresistance that may be relevant for future practical applications. We report magnetotransport and tunnel diode oscillation measurements on Cd(3)As(2), in magnetic fields up to 65 T and temperatures between 1.5 and 300 K. We find that the nonsaturating linear magnetoresistance persists up to 65 T and it is likely caused by disorder effects, as it scales with the high mobility rather than directly linked to Fermi surface changes even when approaching the quantum limit. From the observed quantum oscillations, we determine the bulk three-dimensional Fermi surface having signatures of Dirac behavior with a nontrivial Berry phase shift, very light effective quasiparticle masses, and clear deviations from the band-structure predictions. In very high fields we also detect signatures of large Zeeman spin splitting (g∼16).

A stable three-dimensional topological Dirac semimetal Cd3As2

Three-dimensional (3D) topological Dirac semimetals (TDSs) are a recently proposed state of quantum matter that have attracted increasing attention in physics and materials science. A 3D TDS is not only a bulk analogue of graphene; it also exhibits non-trivial topology in its electronic structure that shares similarities with topological insulators. Moreover, a TDS can potentially be driven into other exotic phases (such as Weyl semimetals, axion insulators and topological superconductors), making it a unique parent compound for the study of these states and the phase transitions between them. Here, by performing angle-resolved photoemission spectroscopy, we directly observe a pair of 3D Dirac fermions in Cd3As2, proving that it is a model 3D TDS. Compared with other 3D TDSs, for example, β-cristobalite BiO2 (ref. 3) and Na3Bi (refs 4, 5), Cd3As2 is stable and has much higher Fermi velocities. Furthermore, by in situ doping we have been able to tune its Fermi energy, making it a flexible platform for exploring exotic physical phenomena.

Discovery of a three-dimensional topological Dirac semimetal, Na3Bi

Three-dimensional (3D) topological Dirac semimetals (TDSs) represent an unusual state of quantum matter that can be viewed as "3D graphene." In contrast to 2D Dirac fermions in graphene or on the surface of 3D topological insulators, TDSs possess 3D Dirac fermions in the bulk. By investigating the electronic structure of Na3Bi with angle-resolved photoemission spectroscopy, we detected 3D Dirac fermions with linear dispersions along all momentum directions. Furthermore, we demonstrated the robustness of 3D Dirac fermions in Na3Bi against in situ surface doping. Our results establish Na3Bi as a model system for 3D TDSs, which can serve as an ideal platform for the systematic study of quantum phase transitions between rich topological quantum states.

A fluorescence-Raman dual-imaging platform based on complexes of conjugated polymers and carbon nanotubes

The present study describes a flexible nanoplatform based on electrostatic assembly of conjugated polyelectrolytes (CPEs) and carboxylated multi-walled carbon nanotubes (cMWNTs). It is demonstrated that the obtained nanocomposites inherit intrinsic optical properties of CPEs and characteristic Raman vibration modes of MWNTs, providing a fluorescence-Raman dual-imaging method for intracellular tracking and locating of MWNTs. We suggest that the cellular internalization of the CPE-cMWNT nanocomposites is a surface charge-dependent process. The strengths of this nanoplatform include satisfying biocompatibility, enhanced protein-repellent property, and ease of implementation, making it available for both in vitro and in vivo applications.

Measurement of coherent polarons in the strongly coupled antiferromagnetically ordered iron-chalcogenide Fe1.02Te using angle-resolved photoemission spectroscopy

The nature of metallicity and the level of electronic correlations in the antiferromagnetically ordered parent compounds are two important open issues for the iron-based superconductivity. We perform a temperature-dependent angle-resolved photoemission spectroscopy study of Fe(1.02)Te, the parent compound for iron chalcogenide superconductors. Deep in the antiferromagnetic state, the spectra exhibit a "peak-dip-hump" line shape associated with two clearly separate branches of dispersion, characteristics of polarons seen in manganites and lightly doped cuprates. As temperature increases towards the Néel temperature (T(N)), we observe a decreasing renormalization of the peak dispersion and a counterintuitive sharpening of the hump linewidth, suggestive of an intimate connection between the weakening electron-phonon (e-ph) coupling and antiferromagnetism. Our finding points to the highly correlated nature of the Fe(1.02)Te ground state featured by strong interactions among the charge, spin, and lattice and a good metallicity plausibly contributed by the coherent polaron motion.

Identification of genes preferentially expressed in goat hair follicle anagen-catagen transition using suppression subtractive hybridization

Suppressive subtraction hybridization (SSH) was used to identify differentially expressed genes in goat (Capra hircus) hair follicle anagen-catagen transition. The cDNA fragments, derived from SSH positive subtractive library (tester: anagen-catagen transition, driver: later anagen), were cloned into pEGM-T vector. Two hundred cDNA fragments screened from this library were subjected to identify forty-five unregulated isolates. Sequence analysis revealed that these fragments represented twenty-three genes. Blasting analysis with database in GenBank showed that twenty genes were previously clearly annotated, two were homologous to un-annotated expressed sequence tag (ESTs), and one might be novel. To identify characters of gene expression, seven genes in later anagen and anagen-catagen transition skin tissues were chosen for quantitative real-time PCR. Results indicated that expression of these seven genes varied much, reaching threefold among them, furthering indicating that expression of those genes was up-regulation in the anagen-catagen transition. We characterized expression levels of this potential novel gene and the goat ectodysplasin A during differential stages of hair cycle. These profiles suggested that these two genes might play a role in the goat secondary hair follicle cycle.

Ultrafast optical excitation of a persistent surface-state population in the topological insulator Bi2Se3

Using femtosecond time- and angle-resolved photoemission spectroscopy, we investigated the nonequilibrium dynamics of the topological insulator Bi2Se3. We studied p-type Bi2Se3, in which the metallic Dirac surface state and bulk conduction bands are unoccupied. Optical excitation leads to a metastable population at the bulk conduction band edge, which feeds a nonequilibrium population of the surface state persisting for >10 ps. This unusually long-lived population of a metallic Dirac surface state with spin texture may present a channel in which to drive transient spin-polarized currents.

The effect of overweight and obesity on psoriasis patients in Chinese Han population: a hospital-based study

BACKGROUND

Accumulating evidence indicates that psoriasis is associated with increased risk of overweight and obesity. However, few studies have investigated this relationship in Chinese Han population.

OBJECTIVE

The aim of this study was to explore the relationship between overweight/obesity and psoriasis and to evaluate the overweight/obesity effect on the clinical features of psoriasis in Chinese Han population.

METHODS

A hospital-based study was conducted, which involved in 4452 patients and 1166 controls of Chinese Han through epidemiological investigation. Controls used in the study were individuals without psoriasis from health examination centre, and other skin disease patients from outpatient department.

RESULTS

Compared with the control group, a significantly greater prevalence of overweight and obesity was observed in psoriasis patients. The estimated ORs were 1.301 (95% CI, 1.105-1.531) and 1.680 (95% CI, 1.134-2.491) respectively. The disease severity of psoriasis measured by psoriasis area and severity index (PASI) was statistically correlated with body mass index (BMI) (r = 0.184, P < 0.01). Moreover, a high proportion of overweight patients had affected hands or/and feet, buttocks, trunk, legs, arms and arthritis (P < 0.01).

CONCLUSIONS

Our study suggested that psoriatic patients have a higher prevalence of overweight and obesity compared with non-psoriatic patients in Chinese Han population. Overweight and obesity has different risk effect on severity and manifestations of psoriasis and might be useful for better evaluating psoriasis clinically.

Quantum Hall effect from the topological surface states of strained bulk HgTe

We report transport studies on a three-dimensional, 70-nm-thick HgTe layer, which is strained by epitaxial growth on a CdTe substrate. The strain induces a band gap in the otherwise semimetallic HgTe, which thus becomes a three-dimensional topological insulator. Contributions from residual bulk carriers to the transport properties of the gapped HgTe layer are negligible at mK temperatures. As a result, the sample exhibits a quantized Hall effect that results from the 2D single cone Dirac-like topological surface states.

Furano-1,2-naphthoquinone inhibits EGFR signaling associated with G2/M cell cycle arrest and apoptosis in A549 cells

Furano-1,2-naphthoquinone (FNQ), prepared from 2-hydroxy-1,4-naphthoquinone and chloroacetaldehyde in an efficient one-pot reaction, exhibits an anti-carcinogenic effect. FNQ exerted anti-proliferative activity with the G(2)/M cell cycle arrest and apoptosis in A549 cells. FNQ-induced G(2)/M arrest was correlated with a marked decrease in the expression levels of cyclin A and cyclin B, and their activating partner cyclin-dependent kinases (Cdk) 1 and 2 with concomitant induction of p53, p21, and p27. FNQ-induced apoptosis was accompanied with Bax up-regulation and the down-regulation of Bcl-2, X-linked inhibitor of apoptosis (XIAP), and survivin, resulting in cytochrome c release and sequential activation of caspase-9 and caspase-3. Western blot analysis revealed that FNQ suppressed EGFR phosphorylation and JAK2, STAT3, and STAT5 activation, but increased in activation of p38 MAPK and c-Jun NH2-terminal kinase (JNK) stress signal. The combined treatment of FNQ with AG1478 (a specific EGFR inhibitor) significantly enhanced the G(2)/M arrest and apoptosis, and also led to up-regulation in Bax, p53, p21, p27, release of mitochondrial cytochrome c, and down-regulation of Bcl-2, XIAP, survivin, cyclin A, cyclin B, Cdk1, and Cdk2 in A549 cells. These findings suggest that FNQ-mediated cytotoxicity of A549 cell related with the G(2)/M cell cycle arrest and apoptosis via inactivation of EGFR-mediated signaling pathway.

Single Dirac cone topological surface state and unusual thermoelectric property of compounds from a new topological insulator family

Angle resolved photoemission spectroscopy study on TlBiTe2 and TlBiSe2 from a thallium-based ternary chalcogenides family revealed a single surface Dirac cone at the center of the Brillouin zone for both compounds. For TlBiSe2, the large bulk gap (∼200 meV) makes it a topological insulator with better mechanical properties than the previous binary 3D topological insualtor family. For TlBiTe2, the observed negative bulk gap indicates it as a semimetal, instead of a narrow-gap semiconductor as conventionally believed; this semimetality naturally explains its mysteriously small thermoelectric figure of merit comparing to other compounds in the family. Finally, the unique band structures of TlBiTe2 also suggest it as a candidate for topological superconductors.

Effect of the route of foot-and-mouth disease virus infection of piglets on the course of disease

Three different routes of Foot-and-mouth disease virus (FMDV) infection of piglets, namely intranasal (i.n.) through drops, intradermal (i.d.) into the foot, and intramuscular (i.m.) were compared regarding the onset and severity of the disease. The results showed that the i.d. injection of the virus resulted in the fastest onset of the disease. The i.m. injection led to a delayed onset, but the final effect was identical with i.d. injection. Moreover, the i.m. injection was simpler to perform and easier to evaluate. Therefore, the i.m. injection of piglets is recommended as the optimal infection route for evaluation of the FMDV vaccine potency.

Measurements of conformational changes during adhesion of lipid and protein (polylysine and S-layer) surfaces

The adhesion forces between various surfaces were measured using the "surface forces apparatus" technique. This technique allows for the thickness of surface layers and the adhesion force between them to be directly measured in controlled vapor or liquid environments. Three types of biological surfaces were prepared by depositing various lipid-protein monolayers (with thicknesses ranging from 1 to 4 nm) on the inert, molecularly smooth mica surface: (i) hydrophobic lipid monolayers; (ii) amphiphilic polyelectrolyte surfaces of adsorbed polylysine; and (iii) deposited bacterial S-layer proteins. The adhesion, swelling, and wetting properties of these surfaces was measured as a function of relative humidity and time. Initial adhesion is due mainly to the van der Waals forces arising from nonpolar (hydrophobic) contacts. Following adhesive contact, significant molecular rearrangements can occur which alter their hydrophobic-hydrophilic balance and increase their adhesion with time. Increased adhesion is generally enhanced by (i) increased relative humidity (or degree of hydration); (ii) increased contact time; and (iii) increased rates of separation. The results are likely to be applicable to the adhesion of many other biosurfaces, and show that the hydrophobicity of a lipid or protein surface is not an intrinsic property of that surface but depends on its environment (e.g., on whether it is in aqueous solution or exposed to the atmosphere), and on the relative humidity of the atmosphere. It also depends on whether the surface is in adhesive contact with another surface and-when considering dynamic (nonequilibrium) conditions-on the time and previous history of its interaction with that surface.