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Unstart/restart phenomena induced by backpressure in a general inlet with a freestream of M = 2.7 are investigated in an in-draft supersonic quiet wind tunnel. The boundary layers are turbulent on the forebody while are laminar on the lip wall, which could mimick real flight conditions. The high-speed Schlieren imaging system and the nanoparticle-based planar laser scattering (NPLS) method are used to visualize the inlet flowfield. The inlet wall pressure is measured by high-frequency pressure transducers. The backpressure is reproduced by downstream transverse jets other than mechanical throttlers, which is more suitable to mimic backpressure caused by combustion. The high spatio-temporal resolution full-view images of inlet flow features during the complete unstart/restart process are captured, which are seldom seen before. The formation and disappearance process of massive boundary layer separation at the entrance of the unstarted inlet is observed. The backpressure transmits upstream through the shock wave/boundary layer interaction (SWBLI) regions. The shock structures change the angles and merge upstream to balance the pressure rise. The Mach shock reflection configuration is observed in both unstart/restart process, accompanied by the boundary layer separation extending to the leading edge. The experiment also revealed notable hysteresis in the unstart/restart process.

High-strength high-entropy alloys (HEAs) reinforced by hard intermetallics generally show a propensity for embrittlement, significantly undercutting their applications. Here we report a strategy to intrinsically toughen strong-yet-brittle HEAs via altering the valence electron concentration (VEC) of precipitates. It was found that a decrease of the VEC of precipitates by Co substitution for Ni atoms effectively destabilizes the brittle hexagonal-ordered precipitate and promotes the formation of ductile cubic-ordered nano-precipitates in Ni–Co–Fe–Cr–Ti system. Benefiting from such a transformation, a fivefold enhancement of tensile elongation (from 7% to 35%) was successfully achieved together with a simultaneously improved strength up to ∼1.35 GPa.

Metallic oxide SrNbO3has been identified as an efficient hydrogen evolution photocatalyst. Here, Venkatesan and co-workers show that its visible light absorption stems from plasmon resonance, thanks to its large carrier density (despite a large 4.1 eV bandgap), as opposed to from an interband transition.

Los trilobites oryctocefálidos del tránsito ‘Cámbrico inferior-medio’ representan herramientas clave para la correlación internacional. Las zonas de trilobites en China meridional a través del tránsito Serie cámbrica 2-Miaolingiense se basan en este grupo fósil. La base de una de estas zonas de trilobites se sitúa con la aparición de Protoryctocephalus arcticus. El género Protoryctocephalus, procedente del área de Balang en China meridional, fue descrito originalmente como Protoryctocephalus wuxunensis, también de la serie cámbrica 2 de China meridional. Sin embargo, en Balang Protoryctocephalus muestra diferentes caracteres morfológicos, tales como la forma glabelar, la presencia de un surco transglabelar S1 y más segmentos en el tronco (tórax + pigidio). Estos caracteres cuadran mejor con Protoryctocephalus arcticus de la Serie cámbrica 2 of Groenlandia.

To characterize aerosol pollution in Beijing, size-resolved aerosols were collected by MOUDIs during CAREBEIJING-2006 field campaign at Peking University (urban site) and Yufa (upwind rural site). Fine particle concentrations (PM1.8 by MOUDI) were 99.8±77.4 μg/m3 and 78.2±58.4 μg/m3, with PM1.8/PM10 ratios of 0.64±0.08 and 0.76±0.08 at PKU and Yufa, respectively, and secondary compounds accounted for more than 50% in fine particles. PMF model analysis was used to resolve the particle modes. Three modes were resolved at Yufa, representing condensation, droplet and coarse mode. However, one more droplet mode with bigger size was resolved, which was considered probably from regional transport. Condensation mode accounted for 10%–60% of the total mass at both sites, indicating that the gas-to-particle condensation process was important in summer. The formation of sulfate was mainly attributed to in-cloud or aerosol droplet process (PKU 80%, Yufa 70%) and gas condensation process (PKU 14%, Yufa 22%). According to the thermodynamic instability of NH4NO3, size distributions of nitrate were classified as three categories by RH. The existence of Ca(NO3)2 in droplet mode indicated the reaction of HNO3 with crustal particles was also important in fine particles. A rough estimation was given that 69% of the PM10 and 87% of the PM1.8 in Beijing urban were regional contributions. Sulfate, ammonium and oxalate were formed regionally, with the regional contributions of 90%, 87% and 95% to PM1.8. Nitrate formation was local dominant. In summary regional secondary formation led to aerosol pollution in the summer of Beijing.

TiO2 thin films are of importance in oxide electronics, e.g., Pt/TiO2/Pt for memristors and Co-TiO2/TiO2/Co-TiO2 for spin tunneling devices. When such structures are deposited at a variety of oxygen pressures, how does TiO2 behave as an insulator? We report the discovery of an anomalous resistivity minimum in a TiO2 film at low pressure (not strongly dependent on deposition temperature). Hall measurements rule out band transport and in most of the pressure range the transport is variable range hopping (VRH) though below 20 K it was difficult to differentiate between Mott and Efros-Shklovskii's (ES) mechanism. Magnetoresistance (MR) of the sample with lowest resistivity was positive at low temperature (for VRH) but negative above 10 K indicating quantum interference effects.

Electrochemical impedance spectroscopy measurements of pulsed laser deposited single crystal anatase TiO2 thin films with various concentrations of Ta substituting for Ti were carried out. The qualities of the films were characterized by X-ray diffraction and Rutherford back scattering-channeling measurements. UV-visible measurements show a systematic increase of the bandgap with Ta incorporation. Corresponding Mott-Schottky plot was applied to obtain a continuous shift of the flat band potential with increasing free charge carrier (provided by Ta) concentration. This was verified theoretically by ab initio calculation which shows that extra Ta d-electrons occupy Ti t2g orbital with increasing Ta concentration, thereby pushing up the Fermi level. The Mott-Schottky results were consistent when compared with Hall effect and temperature dependent resistivity measurements. From the measured deviation of carrier densities from Hall and Mott-Schottky measurements we have estimated the static dielectric constant of the TiO2 as a function of Ta incorporation, not possible from capacitive measurements.

A pot experiment was conducted to examine the effects of Glomus mosseae on some growth and physiological parameters, and cadmium (Cd) amounts in ryegrass (Lolium perenne L.) plants under the toxic levels of Cd. The experiment was carried out with two treatments (G. mosseae inoculation and non-inoculation), each having four Cd concentrations (0, 30, 90 and 180 mg Cd kg-1 soil). The results showed that mycorrhizal infection rate of G. mosseae was still as high as 43% under 180 mg kg-1 Cd concentration, indicating that G. mosseae colonized plants were tolerant to Cd stress. In non-inoculated and inoculated plants, by increasing Cd concentration in the soil, growth parameters, root activity, growth index, biomass, N and P content in plant and photosynthetic characteristic were reduced. Root activity, growth index, biomass, N and P content, photosynthetic physiology, superoxide dismutase (SOD) and catalase (CAT) contents of G. mosseae inoculated plants were increased compared to non-inoculated plants, whereas malondialdehyde (MDA) content decreased to a certain extent. In conclusion, inoculation of G. mosseae enhanced the resistance and tolerance of ryegrass to Cd stress, reduced the damage of harmful substances to cells, and promoted its growth. [ABSTRACT FROM AUTHOR]

Several modular studies of the hybrid zones are conducted to explain the significance of the sex-based hybrid heterogametic and homogametic incompatibilities. These incompatibilities are found to be extremely helpful in maintaining the differential barrier strength and allele frequencies in the hybrid zones.

Although the magnetoelectric effects - the mutual control of electric polarization by magnetic fields and magnetism by electric fields, have been intensively studied in a large number of inorganic compounds and heterostructures, they have been rarely observed in organic materials. Here we demonstrate magnetoelectric coupling in a metal-organic framework [(CH3)2NH2]Mn(HCOO)3 which exhibits an order-disorder type of ferroelectricity below 185 K. The magnetic susceptibility starts to deviate from the Curie-Weiss law at the paraelectric-ferroelectric transition temperature, suggesting an enhancement of short-range magnetic correlation in the ferroelectric state. Electron spin resonance study further confirms that the magnetic state indeed changes following the ferroelectric phase transition. Inversely, the ferroelectric polarization can be improved by applying high magnetic fields. We interpret the magnetoelectric coupling in the paramagnetic state in the metal-organic framework as a consequence of the magnetoelastic effect that modifies both the superexchange interaction and the hydrogen bonding. [ABSTRACT FROM AUTHOR]

Previous high-level theoretical calculations of aluminum clusters mostly relied on density functional theory (DFT) or theories less sophisticated than it. Here, we point out that a second-order Møller−Plesset perturbation (MP2) method is more appropriate and is the minimum level of theory in the predictions of property such as geometries, electronic structures, and IR and Raman spectra of Al4, Al4, and Al4-clusters. The theoretical electron affinities and ionization potentials predicted with MP2 geometries are closer to experimental ones than those by DFT. The p-electron characters and single valence state of aluminum atoms and IR and Raman spectra of the aluminum clusters were also reliably predicted by MP2 and could be based on for further experimental and theoretical studies. [ABSTRACT FROM AUTHOR]

The Si−C bond breakings in tetramethylsilane (TMS) when interacting with H/H2and the successive H abstractions from SiH4/CH4in the gas mixture of H2/ CH4/TMS were studied at the CCSD(T)/6-311G//MP2/6-31G level of theory. Their rate constants between 1500 and 2500 K were estimated using a conventional transition state theory. The results indicate that (i) it is mainly the H radical that causes the Si−C bond breaking in TMS, and (ii) the successive H abstractions from SiH4are much easier and faster than those from CH4. At low temperatures the differences of rate constants among the four types of the reactions are large, but generally reduced at high temperatures. The reaction rates show no selectivity over the pressure as verified at P0.00025, 0.025, 1, and 100 atm, respectively. Our results could provide the following microscopic level understanding of reactions in the synthesis of diamond/-SiC nanocomposite films. Although the Si content is smaller than that of C in the precursor gases, the gas mixture activated by microwave plasma technique could provide Si sources with a higher rate. The produced Si sources with excellent rigidity in sp3hybridization competitively occupy the space on the substrate together with C sources, resulting in the deposition of diamond/-SiC nanocomposite films. [ABSTRACT FROM AUTHOR]

Abstract Zn-substituted Ni(OH)2 for alkaline rechargeable batteries was prepared by a chemical coprecipitation method. The structures were characterized by X-ray diffraction and scanning electron microscopy, and the electrochemical performance, including chargedischarge behavior, the proton diffusion coefficient (DH+), and the cycle life, was investigated in detail. The results showed that the chargedischarge potentials of Zn-substituted -Ni(OH)2 are much higher than those of Zn-substituted a-Ni(OH)2. For a single a (for 30.548.4% Zn content) or a single (from 0 to 9.3% Zn content) phase in the sample, the discharge potentials increase with the increase of Zn content. However, when there is an a and phase mixture in the sample, the discharge potential decreases with an increase of Zn content. The DH+ values of Zn0% and Zn38.1% samples measured by the current-pulse relaxation method are much lower than those of Zn9.3% and Zn19.6% samples. DH+ of all the samples decreases with an increase of the depth of discharge. The effects of different Zn contents on the chargedischarge potentials of the nickel electrodes can be attributed to the differences of the electrochemical and diffusion polarization. [ABSTRACT FROM AUTHOR]

A fossil arthropod similar to Fuxianhuia and displaying an exceptionally well-preserved alimentary canal with in situ gut contents is reported from the lower Middle Cambrian (ca. 510 Myr ago) of South China. Three-dimensionally preserved, paired phosphatic nodules, arranged in series along both sides of the gut and containing spherical bacteria, probably represent serial digestive glands. The gut is filled with fragments of the eodiscoid trilobite, Pagetia. The well-developed digestive glands and the fragmentary trilobite remains suggest (i) that the arthropod was a durophagous, possibly selective predator, and (ii) that small trilobites such as eodiscoids were a major food source in Cambrian marine ecosystems. This fossil association augments the small number of previously described associations providing more or less direct evidence of predator-prey relationships in Cambrian epibenthic communities. [ABSTRACT FROM AUTHOR]

Obesity is currently a worldwide pandemic. Leptin resistance is a main mechanism of obese human and rodents. The downregulation of the long form of the leptin receptor (Lrb) was involved in leptin resistance in diet-induced obese rats. In the studies, we investigated whether arcuate nucleus (ARC) silencing of Lrb would promote diet-induced obesity in rats. Lentiviral vectors expressing Lrb-shRNA were administered to 5-week-old male rats by ARC injection. Following viral delivery, the rats were provided with a high-fat diet (HFD) or a chow diet (CD). After 8 weeks of the diet, serum leptin, and insulin concentrations were measured by RIA, gene expression of Lrb in the ARC was detected by a real-time RT-PCR, and leptin signaling was examined by western blot. The Lrb-shRNA knocked down the expression of Lrb mRNA in infected regions by 54% for the HFD rats and 47% for the CD rats respectively. The Lrb knockdown reduced Stats3 activation and increased expression of Npy mRNA. The rats with reduced Lrb in the ARC showed a significant increase in energy intake and body weight (BW) againwhen fed with a HFD. By contrast, therewere no effects of Lrb reductiononenergy intake or BW when rats maintained on a low-fat chow. Our results provide evidence that Lrb knockdown selectively in the ARC promotes diet-induced obesity and associated metabolic complications in rats. [ABSTRACT FROM AUTHOR]