Order by static disorder in the Ising chain magnet Ca3Co2-xMnxO6

Ising chain compound Ca3Co2-xMnxO6 exhibits up-up-down-down long-range magnetic order (LRO) in a broad range of 0.75<x<1. The LRO is abruptly lost in the narrow vicinity of x=1, and the magnetic state becomes incommensurate. The commensurate state (but not the LRO) is recovered for larger x. This is surprising because the stoichiometric x=1 state exhibits the best Co/Mn ionic order, and the magnetic LRO appears only in the samples with reduced ionic order. We argue that this "order-by-static-disorder" phenomenon may be related to the disruption of the long-range magnetic interactions by the magnetic-site disorder, reducing magnetic frustration.

Neck injury is critical to elastase-induced aneurysm model

We modified the elastase-induced aneurysm model by use of a simple surgical technique in rabbits. A temporary arcuated aneurysm clip was placed at the origin of the right common carotid artery (RCCA), ascertaining the inner edge of the clip blade on the juncture of the RCCA and right subclavian artery (RSCA), and the elastase-induced aneurysm procedure was undertaken. We found elastase and location of the temporary arcuated aneurysm clip are critical to the success of this aneurysm model.

Cluster-glass behavior of a highly oxygen deficient perovskite, BaBi(0.28)Co(0.72)O(2.2)

A highly oxygen deficient perovskite, BaBi(0.28)Co(0.72)O(2.2), was synthesized by solid state reaction. The crystal structure was determined by means of neutron and x-ray powder diffraction. The material exhibits semiconducting behavior with an energy gap of 1.8 eV. The electron diffraction study does not reveal long range Bi:Co ordering; instead it shows the existence of short range ordering in this phase. The AC and DC magnetic susceptibility studies reveal cluster-glass behavior, which has its origin in the interacting ferromagnetic clusters present.

Neutron-diffraction measurements of magnetic order and a structural transition in the parent BaFe2As2 compound of FeAs-based high-temperature superconductors

The recent discovery of superconductivity in (Ba,K)Fe2As2, which crystallizes in the ThCr2Si2 (122) structure as compared with the LnFeAsO (Ln is lanthanide) systems that possess the ZrCuSiAs (1111) structure, demonstrates the exciting potential of the FeAs-based materials for high-T{C} superconductivity. Here we report neutron diffraction studies that show a tetragonal-to-orthorhombic distortion associated with the onset of q=(101) antiferromagnetic order in BaFe2As2, with a saturation moment 0.87(3)micro {B} per Fe that is orientated along the longer a axis of the ab planes. The simultaneous first-order structural and magnetic transition is in contrast with the separated transitions previously reported in the 1111-type materials. The orientational relation between magnetic alignment and lattice distortion supports a multiorbital nature for the magnetic order.

Crystal structure and antiferromagnetic order in NdFeAsO1-xFx (x=0.0 and 0.2) superconducting compounds from neutron diffraction measurements

The transition temperature T{C} approximately 26 K of the recently discovered superconductor LaFeAsO1-xFx is extremely sensitive to the lanthanide ion, reaching 55 K for the Sm containing oxypnictides. Therefore, it is important to determine how the moment on the lanthanide affects the overall magnetism in these systems. Here we report a neutron diffraction study of the Nd oxypnictides. Long-ranged antiferromagnetic order is apparent in NdFeAsO below 1.96 K. Rietveld refinement shows that both Fe and Nd magnetic ordering are required to describe the observed data with the staggered moment 1.55(4)micro{B}/Nd and 0.9(1)micro{B}/Fe at 0.3 K. The other structural properties such as the tetragonal-orthorhombic distortion are found to be very similar to those in LaFeAsO. Neither the magnetic ordering nor the structural distortion occur in the superconducting sample NdFeAsO0.80F0.20 at any temperatures down to 1.5 K.

Structural and magnetic phase diagram of CeFeAsO(1- x)F(x) and its relation to high-temperature superconductivity

Recently, high-transition-temperature (high-Tc) superconductivity was discovered in the iron pnictide RFeAsO(1-x)F(x) (R, rare-earth metal) family of materials. We use neutron scattering to study the structural and magnetic phase transitions in CeFeAsO(1-x)F(x) as the system is tuned from a semimetal to a high-Tc superconductor through fluorine (F) doping, x. In the undoped state, CeFeAsO develops a structural lattice distortion followed by a collinear antiferromagnetic order with decreasing temperature. With increasing fluorine doping, the structural phase transition decreases gradually and vanishes within the superconductivity dome near x=0.10, whereas the antiferromagnetic order is suppressed before the appearance of superconductivity for x>0.06, resulting in an electronic phase diagram remarkably similar to that of the high-Tc copper oxides. Comparison of the structural evolution of CeFeAsO(1-x)F(x) with other Fe-based superconductors suggests that the structural perfection of the Fe-As tetrahedron is important for the high-Tc superconductivity in these Fe pnictides.

Successive orbital ordering transitions in NaVO2

Physical property measurements on samples of triangular-lattice NaVO2 reveal two successive orbital ordering transitions. At 300 K, the structure is rhombohedral. At 98 K, the system undergoes a second-order transition to a monoclinic phase in which the in-plane V-V distances separate into four short and two long bonds, corresponding to orbital ordering of one electron per V3+. Below 93 K, there is a first-order transition to a second monoclinic phase with four long and two short V-V bonds, consistent with orbital ordering of two electrons per V3+. Long range magnetic ordering of 0.98(2)mu_(B) per V3+ (3d(2)) sets in at the 93 K structural transition. The orbital ordering relieves the geometric frustration and leads to a magnetically ordered ground state.

Plasma membrane damage to Candida albicans caused by chlorine dioxide (ClO2)

AIM

To investigate the plasma membrane damage of chlorine dioxide (ClO(2)) to Candida albicans ATCC10231 at or below the minimal fungicidal concentration (MFC).

METHODS AND RESULTS

ClO(2) at MFC or below was adopted to treat the cell suspensions of C. albicans ATCC10231. Using transmission electron microscopy, no visible physiological alteration of cell shape and plasma membrane occurred. Potassium (K(+)) leakages were significant; likewise, it showed time- and dose-dependent increases. However, adenosine triphosphate (ATP) leakages were very slight. Research shows that when 99% of the cells were inactivated, the leakage was measured at 0.04% of total ATP. Compared with the mortality-specific fluorescent dye of DiBAC(4)(3), majority of the inactivated cells were poorly stained by propidium iodide, another mortality-specific fluorescent dye which can be traced by flow cytometry.

CONCLUSION

At or below MFC, ClO(2) damages the plasma membranes of C. albicans mainly by permeabilization, rather than by the disruption of their integrity. K(+) leakage and the concomitant depolarization of the cell membrane are some of the critical events.

SIGNIFICANCE AND IMPACT OF THE STUDY

These insights into membrane damages are helpful in understanding the action mode of ClO(2).

Frustrated ferroelectricity in niobate pyrochlores

The crystal structures of the A(2)B(2)O(7-x) niobium based pyrochlores Y(2)(Nb(0.86)Y(0.14))(2)O(6.91), CaYNb(2)O(7), and Y(2)NbTiO(7) are reported, determined by means of powder neutron diffraction. These compounds represent the first observation of B-site displacements in the pyrochlore structure: the B-site ions are found to be displaced from the ideal pyrochlore positions, creating electric dipoles. The orientations of these dipoles are fully analogous to orientations of the magnetic moments in Ising spin based magnetically frustrated pyrochlores. Diffuse scattering in electron diffraction patterns shows that the displacements are only short range ordered, indicative of geometric frustration of the collective dielectric state of the materials. Comparison to the crystal structure of the Nb(5+) (d(0)) pyrochlore La(2)ScNbO(7) supports the prediction that charge singlets, driven by the tendency of Nb to form metal-metal bonds, are present in these pyrochlores. The observed lack of long range order to these singlets suggests that Nb(4+) based pyrochlores represent the dielectric analogy to the geometric frustration of magnetic moments observed in rare earth pyrochlores.

SCF and IL-31 rather than IL-17 and BAFF are potential indicators in patients with allergic asthma

BACKGROUND

Although the prevalence of allergic asthma increased quickly in the past decade, the diagnostic criteria have not been well established. The aim of the present study was to explore whether stem cell factor (SCF), B cell-activating factor (BAFF), and cytokines interleukin (IL)-17 and IL-31 are usable parameters for the diagnosis of allergic asthmatics.

METHODS

Blood samples were collected from patients with allergic asthma, control patients, and healthy control subjects. The serum concentrations of SCF, BAFF, IL-17, and IL-31 were measured by enzyme-linked immunosorbent assay. The corresponding mRNA levels in peripheral blood mononuclear cells (PBMCs) were determined by real-time reverse-transcription polymerase chain reaction.

RESULTS

A good correlation existed between protein levels of SCF and IL-31 and their mRNA levels (SCF: r = 0.6162; IL-31: r = 0.5463). The serum concentrations of SCF and IL-31 in allergic asthmatic patients, but not control patients, were significantly higher than those in normal control subjects (SCF: median 1.83 vs 0.85 ng/ml, P < 0.01; IL-31: 50.15 vs 10.01 pg/ml, P < 0.001). Consistently, the levels of SCF and IL-31 mRNAs in allergic asthmatic patients' PBMCs were also significantly higher than those in normal control subjects (P = 0.002 and P < 0.001, respectively).

CONCLUSIONS

These findings suggest that allergic asthma is characterized by an elevation of cytokines SCF and IL-31 and the measurement of their expression at either protein level in serum or mRNA level in PBMCs will be a valuable parameter for the diagnosis of allergic asthma.

Interventional treatment of hepatic artery stenosis after orthotopic liver transplantation with balloon-expandable coronary stent

OBJECTIVE

The aim of this study was to evaluate the efficacy of hepatic artery stenting with a balloon-expandable coronary stent for the treatment of hepatic artery stenosis (HAS) after orthotopic liver transplantation (OLT).

PATIENTS AND METHODS

We performed retrospective review of all 11 patients who underwent hepatic artery stenting after a diagnosis of HAS.

RESULTS

A total of 13 balloon-expandable coronary stents were placed into 11 patients. The technical and immediate success rate was 100%; all stents remained patent during follow-up. One patient required 2 stents due to the length of the stenotic artery. Another underwent a second stenting after developing restenosis proximal to the original stenotic site. No procedure-related complications occurred, and no surgical revascularization or retransplantation was required during follow-up.

CONCLUSIONS

A balloon-expandable coronary stent can play a role in the management of HAS. It can be used with great safety, with immediate as well as longer-term success.

Magnetic and orbital ordering in the spinel MnV2O4

Neutron inelastic scattering and diffraction techniques have been used to study the MnV2O4 spinel system. Our measurements show the existence of two transitions to long-range ordered ferrimagnetic states, the first collinear and the second noncollinear. The lower temperature transition, characterized by development of antiferromagnetic components in the basal plane, is accompanied by a tetragonal distortion and the appearance of a gap in the magnetic excitation spectrum. The low-temperature noncollinear magnetic structure has been definitively resolved. Taken together, the crystal and magnetic structures indicate a staggered ordering of the V d orbitals. The anisotropy gap is a consequence of unquenched V orbital angular momentum.

Ferroelectricity in an ising chain magnet

We report discovery of collinear-magnetism-driven ferroelectricity in the Ising chain magnet Ca3Co2-xMn(x)O6 (x approximately 0.96). Neutron diffraction shows that Co2+ and Mn4+ ions alternating along the chains exhibit an up-up-down-down ( upward arrow upward arrow downward arrow downward arrow) magnetic order. The ferroelectricity results from the inversion symmetry breaking in the upward arrow upward arrow downward arrow downward arrow spin chain with an alternating charge order. Unlike in spiral magnetoelectrics where antisymmetric exchange coupling is active, the symmetry breaking in Ca3(Co,Mn)2O6 occurs through exchange striction associated with symmetric superexchange.

The study of beta-lactoglobulin adsorption on polyethersulfone thin film surface using QCM-D and AFM

The adsorption process of beta-lactoglobulin on the polyethersulfone-coated surface has been investigated using a quartz crystal microbalance with dissipation monitoring (QCM-D), which allowed simultaneous measurements of frequency and energy dissipation changes caused by the formation of a beta-lactoglobulin layer during the protein adsorption process. The results showed that the protein adsorption on the spin-coated polyethersulfone surface consisted of reversible and irreversible adsorption processes, and the irreversible adsorption was the principal factor to cause the permanent protein adsorption onto the polymer surface. The amount of irreversible adsorption of beta-lactoglobulin increased significantly, from 380.5 +/- 23.2 to 745.5 +/- 29.7 ng/cm2, when the concentration of beta-lactoglobulin solution varied from 0.1% to 2.0% (w/v). The pH also played an important role in the protein adsorption. When the pH of the solution varied from 7.0 to 3.0, the amount of irreversible adsorption of beta-lactoglobulin increased from 427.1 +/- 80.7 to 741.2 +/- 135.1 ng/cm2.