Physiological behavior and quality of fresh ginseng stored in modified atmospheres generated by several package films

Physiological behaviors and quality attributes of fresh ginseng (Panax Ginseng) stored in modified atmospheres generated by several package films were investigated. The chemical compositions were also measured before and after storage. The respiration rates of fresh ginseng were inhibited effectively by film package, especially in package with lower gas permeability coefficient film. The polyphenol oxidase (PPO) activity reduced markedly and high Hunter L (*) value was maintained. Significant differences (p < 0.05) in firmness, weight loss, decay rate and pectin content were found between 0.10 mm packages and 0.05, 0.07 mm packages after 5 months of storage. The best quality parameters of fresh ginseng were obtained from the combination of 0 °C-0.10 mm. Significant difference (p < 0.05) in total saponin content was not found, and the highest total saponin content was also obtained from the combination of 0 °C-0.10 mm. The content of total sugar and reducing sugar increased significantly (p < 0.05), especially for package film with higher gas permeability coefficient. The storage life of fresh ginseng was extended significantly by film packages to 5 months with good quality and lower decay rate, especially for package film with low gas permeability coefficient.

Hydrogen sulfide alleviates lead-induced photosynthetic and ultrastructural changes in oilseed rape

The role of hydrogen sulfide (H2S) in alleviating lead (Pb) induced stress in oilseed rape (Brassica napus L.) was studied under laboratory conditions. Plants were grown hydroponically in greenhouse conditions under three levels (0, 100, and 400 µM) of Pb and three levels (0, 100 and 200 µM) of H2S donor, sodium hydrosulfide (NaHS). Application of H2S significantly improved the plant growth, root morphology, chlorophyll contents and photosynthetic activity in leaves of B. napus under Pb stress. Moreover, exogenously applied H2S significantly lowered the Pb concentration in shoots and roots of plants under Pb stress. The microscopic examination indicated that application of exogenous H2S enabled a clean mesophyll cell having a well developed chloroplast with thylakoid membranes and starch grains. A number of modifications could be observed in root tip cell i.e. mature mitochondria, long endoplasmic reticulum and golgibodies under combined application of H2S and Pb. On the basis of these findings, it can be concluded that application of exogenous H2S has a protective role on plant growth, net photosynthesis rate and ultrastructural changes in B. napus plants under high Pb exposures.

High energy pseudogap and its evolution with doping in Fe-based superconductors as revealed by optical spectroscopy

We report optical spectroscopic measurements on electron- and hole-doped BaFe2As2. We show that the compounds in the normal state are not simple metals. The optical conductivity spectra contain, in addition to the free carrier response at low frequency, a temperature-dependent gap-like suppression at fairly high energy scale near 0.6 eV. This suppression evolves with the As–Fe–As bond angle induced by electron or hole doping. Furthermore, the feature becomes much weaker in the Fe-chalcogenide compounds. We elaborate that the feature is mainly caused by the strong Hund's rule coupling effect between the itinerant electrons and localized electron moment arising from the multiple Fe 3d orbitals. The coupling strength changes with the environment of the Fe atom. Our experiments demonstrate the coexistence of itinerant and localized electrons in iron-based compounds, which would then lead to a more comprehensive picture of the metallic magnetism in the materials.

Measurement of the c-axis optical reflectance of AFe2As2 (A=Ba, Sr) single crystals: evidence of different mechanisms for the formation of two energy gaps

We present the c-axis optical reflectance measurement on single crystals of BaFe2As2 and SrFe2As2, the parent compounds of FeAs based superconductors. Different from the ab-plane optical response where two distinct energy gaps were observed in the spin-density-wave (SDW) state, only the smaller energy gap could be seen clearly for E∥c axis. The very pronounced energy gap structure seen at a higher energy scale for E∥ab plane is almost invisible. We propose a novel picture for the band structure evolution across the SDW transition and suggest different driving mechanisms for the formation of the two energy gaps.

Lattice distortion and magnetic quantum phase transition in CeFeAs(1-x)P(x)O

We use neutron diffraction to study the structural and magnetic phase diagram of CeFeAs(1-x)P(x)O. We find that replacing the larger arsenic with smaller phosphorus in CeFeAs(1-x)P(x)O simultaneously suppresses the AFM order and orthorhombic distortion near x=0.4, thus suggesting the presence of a magnetic quantum critical point. Our detailed structural analysis reveals that the pnictogen height is an important controlling parameter for their electronic and magnetic properties, and may play an important role in electron pairing and superconductivity of these materials.

Multiple phase transitions in single-crystalline Na_{1-delta}FeAs

Specific heat, resistivity, susceptibility, and Hall coefficient measurements were performed on high-quality single-crystalline Na_{1-delta}FeAs. This compound is found to undergo three successive phase transitions at around 52, 41, and 23 K, which correspond to structural, magnetic, and superconducting transitions, respectively. The Hall effect result indicates the development of energy gap at low temperature due to the occurrence of spin-density-wave instability. Our results provide direct experimental evidence of the magnetic ordering in the nearly stoichiometric NaFeAs.

Static magnetic order and superfluid density of RFeAs(O,F) (R=La,Nd,Ce) and LaFePO studied by muon spin relaxation: unusual similarities with the behavior of cuprate superconductors

Muon spin relaxation measurements in iron-oxypnictide systems have revealed: (1) commensurate long-range order in undoped LaFeAsO; (2) a Bessel function line shape in LaFeAs(O0.97F0.03) which indicates possible incommensurate or stripe magnetism; (3) anomalous weak magnetism existing in superconducting LaFePO, CeFeAs(O0.084F0.16), and NdFeAs(O0.88F0.12) but absent in superconducting LaFeAs(O0.92F0.08); and (4) scaling of the superfluid density with T_{c} in the Ce-, La-, and Nd-FeAs superconductors following a nearly linear relationship found in cuprates.

Origin of the spin density wave instability in AFe2As2 (A=Ba,Sr) as revealed by optical spectroscopy

We performed optical spectroscopy measurement on single crystals of BaFe2As2 and SrFe2As2, the parent compounds of FeAs-based superconductors. Both are found to be quite metallic with fairly large plasma frequencies at high temperature. Upon entering the spin-density-wave state, the formation of partial energy gaps was clearly observed with the surprising presence of two different energy scales. A large part of the Drude component was removed by the gapping of Fermi surfaces. Meanwhile, the carrier scattering rate was even more dramatically reduced. We elaborate that the spin-density-wave instability is more likely to be driven by the Fermi surface nesting of itinerant electrons than a local-exchange mechanism.

Origin of the spin density wave instability in AFe2As2 (A=Ba,Sr) as revealed by optical spectroscopy

We performed optical spectroscopy measurement on single crystals of BaFe2As2 and SrFe2As2, the parent compounds of FeAs-based superconductors. Both are found to be quite metallic with fairly large plasma frequencies at high temperature. Upon entering the spin-density-wave state, the formation of partial energy gaps was clearly observed with the surprising presence of two different energy scales. A large part of the Drude component was removed by the gapping of Fermi surfaces. Meanwhile, the carrier scattering rate was even more dramatically reduced. We elaborate that the spin-density-wave instability is more likely to be driven by the Fermi surface nesting of itinerant electrons than a local-exchange mechanism.

Probing the superconducting energy gap from infrared spectroscopy on a Ba0.6K0.4Fe2As2 single crystal with Tc=37 K

We performed optical spectroscopy measurement on a superconducting Ba0.6K0.4Fe2As2 single crystal with T{c}=37 K. Formation of the superconducting energy gaps in the far-infrared reflectance spectra below T{c} is clearly observed. A flat and close to unity reflectance is observed roughly below 150 cm;{-1} for T<<T{c}, following an s-wave pairing line shape. A more rapid decrease occurs near 200 cm;{-1}, leading to a peak in the ratio of the reflectance at T<<T{c} over that for T>or=T{c}. We determined the absolute value of the penetration depth at 10 K as lambda approximately 2000+/-80 A. A spectral weight analysis shows that the Ferrell-Glover-Tinkham sum rule is satisfied at low energy scale, less than 6Delta.

Superconducting properties of the Fe-based layered superconductor LaFeAsO0.9F0.1-delta

We have employed a new route to synthesize single phase F-doped LaOFeAs compound and confirmed the superconductivity above 20 K in this Fe-based system. We show that the new superconductor has a rather high upper critical field of over 50 T. A clear signature of superconducting gap opening below T(c) was observed in the far-infrared reflectance spectra, with 2Delta/kT(c) approximately 3.5-4.2. Furthermore, we show that the new superconductor has electron-type conducting carriers with a rather low-carrier density.

Superconductivity at 41 K and its competition with spin-density-wave instability in layered CeO1-xFxFeAs

A series of layered CeO1-xFxFeAs compounds with x=0 to 0.20 are synthesized by the solid state reaction method. Similar to the LaOFeAs, the pure CeOFeAs shows a strong resistivity anomaly near 145 K, which was ascribed to the spin-density-wave instability. F doping suppresses this instability and leads to the superconducting ground state. Most surprisingly, the superconducting transition temperature could reach as high as 41 K. Such a high T_{c} strongly challenges the classic BCS theory based on the electron-phonon interaction. The closeness of the superconducting phase to the spin-density-wave instability suggests that the magnetic fluctuation plays a key role in the superconducting pairing mechanism. The study also reveals that the Ce 4f electrons form local moments and are ordered antiferromagnetically below 4 K, which could coexist with superconductivity.

Anomalous Metallic State of Cu0.07TiSe2: an optical spectroscopy study

We report an optical spectroscopy study on the newly discovered superconductor Cu0.07TiSe2. Consistent with the development from a semimetal or semiconductor with a very small indirect energy gap upon doping TiSe2, it is found that the compound has a low carrier density. Most remarkably, the study reveals a substantial shift of the screened plasma edge in reflectance towards high energy with decreasing temperature. This phenomenon, rarely seen in metals, indicates either a sizable increase of the conducting carrier concentration or/and a decrease of the effective mass of carriers with reducing temperature. We attribute the shift primarily to the latter effect.

Semimetal-to-semimetal charge density wave transition in 1T-TiSe(2)

We report an infrared study on 1T-TiSe(2), the parent compound of the newly discovered superconductor Cu(x)TiSe(2). Previous studies of this compound have not conclusively resolved whether it is a semimetal or a semiconductor-information that is important in determining the origin of its unconventional charge density wave (CDW) transition. Here we present optical spectroscopy results that clearly reveal that the compound is metallic in both the high-temperature normal phase and the low-temperature CDW phase. The carrier scattering rate is dramatically different in the normal and CDW phases and the carrier density is found to change with temperature. We conclude that the observed properties can be explained within the scenario of an Overhauser-type CDW mechanism.

Sulbactam/cefoperazone versus cefotaxime for the treatment of moderate-to-severe bacterial infections: results of a randomized, controlled clinical trial

We conducted a randomized, open-label, controlled, multicenter study to compare sulbactam/cefoperazone with cefotaxime in terms of efficacy and safety for the treatment of hospitalized patients with moderate-to-severe bacterial infections. More than two-thirds of the pathogens recovered from these patients produced beta-lactamase. Two hundred-seven (88.1%) of the 235 patients enrolled completed the study and were included in the efficacy and safety evaluations. One hundred-three patients received sulbactam/cefoperazone (2-4 g/d) administered in evenly divided doses every 12 hours by a 30-minute intravenous drip; 104 patients received cefotaxime (6-12 g/d) administered in evenly divided doses every 6 or 8 hours by a 30-minute intravenous drip. The overall efficacy rates (i.e., cure or markedly improved) were 95% for the sulbactam/cefoperazone group and 90% for the cefotaxime group (P = .186), whereas the bacterial eradication rates were 85% for the sulbactam/cefoperazone group and 81% for the cefotaxime group (P = .467). Both drug regimens were well tolerated. Sulbactam/cefoperazone is effective and safe for the treatment of moderate-to-severe bacterial infections caused mainly by beta-lactamase-producing organisms.