pH sensor based on boron nitride nanotubes

A submicrometer-sized pH sensor based on biotin-fluorescein-functionalized multiwalled BN nanotubes with anchored Ag nanoparticles is designed. Intrinsic pH-dependent photoluminescence and Raman signals in attached fluorescein molecules enhanced by Ag nanoparticles allow this novel nanohybrid to perform as a practical pH sensor. It is able to work in a submicrometer-sized space. For example, the sensor may determine the environmental pH of sub-units in living cells where a traditional optical fiber sensor fails because of spatial limitations.

Three-dimensional optical coherence tomography of Barrett's esophagus and buried glands beneath neosquamous epithelium following radiofrequency ablation

We report three-dimensional (3D) endoscopic microscopy findings in Barrett's esophagus, using an endoscopic optical coherence tomography (OCT) system in one patient before and in one patient after radiofrequency ablation (RFA). Findings were compared with those in a normal patient without Barrett's esophagus. In the normal patient,findings were of regular flat squamous mucosa with small subepithelial vessels and glands. In the Barrett's esophagus patient, findings were of large, densely packed glands with distortion of mucosal architecture. In the post-RFA case, findings were of a small number of isolated glands buried beneath 300-500 microm of neosquamous epithelium and lamina propria. Neosquamous epithelium is a marker of successful ablative therapy, while buried glands may have potential for dysplastic progression and are difficult to detect using conventional methods. These results indicate a potential role of 3D-OCT endoscopic microscopy for follow-up, including subsurface assessment, of ablative treatments for Barrett's esophagus.

A simple method for fixation and microdissection of frozen fresh tissue sections for molecular cytogenetic analysis of cancers

Microdissection has been widely used for procuring DNA from specific microscopic regions of formalin fixed, paraffin embedded tissue sections. We have developed a method for fixation and microdissection of frozen fresh biopsy tissue sections. Five micrometer frozen fresh tissue sections were fixed with ethanol and stored at room temperature. Well defined regions from hematoxylin and eosin (H & E) stained or unstained sections were briefly steamed and microdissected using a needle. The dissected tissue was digested with proteinase K and DNA was isolated. Whole genome amplifications were obtained by degenerate oligonucleotide primed polymerase chain reaction (DOP-PCR) from these samples. The reliability of this technique was demonstrated by comparing conventional comparative genomic hybridization (CGH) with DOP-PCR-CGH. The advantages of this method are that frozen fresh sections can be fixed easily and stored for more than 4 years, it is easy to microdissect and pick-up very minute regions (0.1 mm(2)), and it is rapid; microdissection and purification can be accomplished within 3 h. Using DNA from microdissected sections, DOP-PCR-CGH revealed genetic abnormalities more accurately than conventional CGH. Although this novel method was demonstrated using DOP-PCR-CGH, we believe that it will be useful for other genetic analyses of specific small regions and cell populations. We also observed whether storage time, H & E staining and crude DNA extracts affected the quality of amplified DNA. DNA integrity was maintained for at least 49 months in ethanol fixed sections that were stored at room temperature, but DNA was gradually degraded after one month if the ethanol fixed sections had been H & E stained and stored. When crude DNA extracts from H & E stained sections were used, the size of the DOP-PCR product was reduced. Our study suggests that ethanol fixed tissue sections may be stored at room temperature for at least 4 years without DNA degradation, the H & E stains may not affect the quality of amplified DNA, but H & E or other components in the staining process may reduce the size of DOP-PCR product, which is critical for the quality of CGH hybridization.

First Report of Botryosphaeria dothidea Causing Canker and Shoot Blight of Eucalyptus in China

Eucalyptus spp. are grown on approximately 2 million ha in China and is the most important genus in forest plantations worldwide. An outbreak of cankers and shoot blight was observed for the first time on Eucalyptus grandis in China during May of 2008. Symptoms included dieback of shoots and branches, lesions and canker formation on the stems, and clear or yellow-to-red exudates on stems and branches. Isolations were made from affected trees in Shilin County from May to July of 2008. Diseased samples were plated on potato dextrose agar (PDA) and incubated at 26°C. Fungal isolates developed copious, white, aerial mycelium that became dark gray after 5 to 6 days and formed black pycnidia after 14 days. Conidia were hyaline, aseptate, thin walled, fusiform, and measured 19 to 28 × 4 to 6 μm. Ascospores were hyaline, aseptate, and widest from the middle to upper third (17 to 28 × 6 to 13 μm). Identity was confirmed by analysis of the rDNA internal transcribed spacer region (ITSI-5.8S-ITS2) with primers ITS1 and ITS4. BLAST searches showed 99 to 100% identity with Botryosphaeria dothidea isolates from GenBank (Accession Nos. FJ358703 and EU080916). Representative sequences of B. dothidea from eucalyptus from China were deposited into GenBank (Accession Nos. FJ517657 and FJ517658). On the basis of morphological and molecular results, the fungus isolated from diseased eucalyptus wood was confirmed to be B. dothidea. Pathogenicity tests were conducted by stem inoculation of 10-month-old E. grandis seedlings. Two experiments were conducted using two inoculation techniques. In the first experiment, 2-mm-diameter actively growing mycelium plugs of B. dothidea were applied to 2-mm-long bark wounds on the middle point of the stems, and control seedlings were inoculated with sterile PDA plugs in a similar fashion as above. Inoculated and control seedlings were inoculated in a greenhouse and watered as needed. In the second experiment, segments of branches (averaging 18 mm in diameter and 30 cm long) were inoculated with 5-mm-diameter plugs of actively growing mycelium. Control segments of branches were inoculated as previously described. The branches were incubated at 26°C in moist chambers. There were five replicate seedlings per inoculation technique. After 20 days, all E. grandis seedlings showed leaf wilting, Dark, vascular stem tissue was observed. Symptoms were more abundant on the segment of branches. After 6 days, vascular necroses that developed on the inoculated plants were 5.2 ± 1.2 cm. B. dothidea was reisolated from all inoculated symptomatic tissue; no symptoms were visible in the control seedlings and no fungus was isolated from them. These results confirm previous reports of B. dothidea causing canker and dieback symptoms of Eucalyptus species in Australia (2), the United States (1), and South Africa (3). To our knowledge, this is the first report of B. dothidea causing canker disease on eucalyptus in China. References: (1) E. L. Barnard et al. Plant Dis. 71:358, 1987. (2) E. M. Davison and C. S. Tay. Plant Dis. 67:1285, 1983. (3) H. Smith et al. Plant Pathol. 43:1031, 1994.

Tunable (deltapi, deltapi)-type antiferromagnetic order in alpha-Fe(Te,Se) superconductors

The new alpha-Fe(Te,Se) superconductors share the common iron building block and ferminology with the LaFeAsO and BaFe(2)As(2) families of superconductors. In contrast with the predicted commensurate spin-density-wave order at the nesting wave vector (pi, 0), a completely different magnetic order with a composition tunable propagation vector (deltapi, deltapi) was determined for the parent compound Fe_{1+y}Te in this powder and single-crystal neutron diffraction study. The new antiferromagnetic order survives as a short-range one even in the highest T_{C} sample. An alternative to the prevailing nesting Fermi surface mechanism is required to understand the latest family of ferrous superconductors.

Stent-assisted embolization of wide-neck anterior communicating artery aneurysms: review of 21 consecutive cases

BACKGROUND AND PURPOSE

Anterior communicating artery (AcomA) aneurysm is the most frequent form of aneurysm. Stent placement is particularly difficult and of limited use for AcomA aneurysms. We report our experience with stent-assisted embolization for wide-neck AcomA aneurysms in 21 patients. Particular attention is given to the morphologic characteristics and strategy of stent deployment.

MATERIALS AND METHODS

Between January 2005 and February 2008, stent-assisted coiling was performed in 21 patients with wide-neck AcomA aneurysms. Patient demographics, aneurysm morphology, procedures, and clinical and angiographic outcomes were retrospectively reviewed.

RESULTS

Successful deployment of the stent in the targeted artery was achieved in all patients. Nineteen Neuroform 2 or Neuroform 3 stents and 2 LEO stents were used. The distal segment of the stent was positioned in the ipsilateral A2 in 12 patients, in the contralateral A2 across the AcomA in 5 patients, and into the aneurysm sac in 4 patients. Complete occlusion was achieved in 18 patients; near-complete occlusion, in 2 patients; and partial occlusion, in 1 patient. Intraoperative perforation of the aneurysm developed in 1 patient, which was secured by subsequent coiling. Angiographic follow-up in 12 patients for 6.9 months showed 1 recanalization and no in-stent stenosis.

CONCLUSIONS

Our preliminary results suggest that stent-assisted embolization for wide-neck AcomA aneurysms is technically feasible and safe. Further follow-up is needed for long-term efficacy of stent placement.

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).