Foxp3+ regulatory T cells and related cytokines differentially expressed in plaque vs. guttate psoriasis vulgaris

BACKGROUND

Differences in the number of Foxp3+ regulatory T cells (Tregs) in lesional skin and peripheral blood and their functioning in plaque vs. guttate psoriasis have not been reported.

OBJECTIVES

To investigate whether there is a differential expression of Foxp3+ Tregs and a differential regulation of inflammatory cytokines in plaque vs. guttate psoriasis vulgaris.

METHODS

The number and the percentage of Foxp3+ cells in different phases of skin lesions of patients with plaque and guttate psoriasis vulgaris were assessed by immunohistochemical staining. The expression of Foxp3 and interleukin (IL)-17 protein in CD4 populations was measured by flow cytometry. Inflammatory cytokine production by transforming growth factor-beta1-induced Foxp3+ Tregs was assessed in an in vitro study. The cytokines in supernatant and serum were determined by enzyme-linked immunosorbent assay.

RESULTS

The percentage of Foxp3+ CD3+ cells in the papillary layer was higher than in the reticular layer of dermis and in epidermis (P < 0.05). The numbers of Foxp3+ Tregs in skin lesions and peripheral blood were higher in plaque than in guttate psoriasis, whereas the percentage of IL-17+ CD4+ cells was higher in guttate than in plaque psoriasis (P < 0.05). The numbers of Foxp3+ cells were positively correlated with the Psoriasis Severity Index score of skin lesions (P < 0.0001), and the percentages of Foxp3+ CD4+ cells in peripheral blood were positively correlated with the Psoriasis Area and Severity Index score of patients (P < 0.05). The inhibitory functions of Tregs to IL-17 and IL-6 in guttate psoriasis and to tumour necrosis factor-alpha in plaque psoriasis were deficient.

CONCLUSIONS

Differential expression and regulatory functioning for inflammatory cytokine production by Foxp3+ Tregs may imply a different immunopathogenesis for plaque and guttate psoriasis.

First Report of Xylella fastidiosa Associated with Oleander Leaf Scorch in Louisiana

Oleander (Nerium oleander L.) is an evergreen shrub native to the Mediterranean Region and Southeast Asia. Despite being poisonous, it is a popular ornamental plant for use in landscapes, gardens, parks, roadsides, and highway medians. During the fall of 2008, several oleander plants with leaf scorch symptoms were observed at Arsenal Park in Baton Rouge, LA. Symptomatic oleander samples were also received from a commercial nursery in Baton Rouge, LA and a homeowner in Thibodeaux, LA. Symptoms resembled leaf scorch caused by Xylella fastidiosa Wells et al. and included chlorotic mottling of the leaves that started from the tips and margins and progressed toward the midribs. As disease developed, leaf tips and margins became necrotic. Severely infected plants defoliated and died. Leaf petioles from 13 samples (8 from Arsenal Park, 3 from the commercial nursery, and 2 from the homeowner) from symptomatic plants gave positive reactions for X. fastidiosa by ELISA (Agdia, Inc., Elkhart, IN). Leaf petioles from six healthy oleander plants gave a negative reaction for X. fastidiosa by ELISA. Isolation of X. fastidiosa was attempted from eight ELISA-positive and six ELISA-negative oleander samples. Leaf petioles weighing 0.05 g from each sample were used for isolation. The petioles were surface sterilized in 70% ethanol for 1.5 min and then in 2% sodium hypochlorite for 1.5 min, followed by three 1-min washes in sterile water. The petioles were chopped into small pieces under aseptic conditions and soaked in 500 μl sterile water for 30 min. One hundred microliters of the suspension were spread onto periwinkle wilt (PW) plates and incubated in the dark at 28°C. After incubation for 7 days, bacterial colonies typical of X. fastidiosa appeared on five of eight ELISA-positive sample plates. No colonies were observed on six ELISA-negative sample plates. Single colonies were transferred to fresh PW plates to obtain pure cultures. Bacterial colonies from five pure cultures were suspended in nuclease-free water and boiled for 10 min to obtain DNA. DNA from eight symptomatic and six healthy oleander plants was extracted with a DNeasy Plant Mini kit (Qiagen Inc., Valencia, CA) according to the manufacturer's guidelines. Primers (QHOLS-08 and QHOLS-05) (1) specific to the oleander strain of X. fastidiosa amplified a 274-bp portion of DNA from both symptomatic oleander tissues and pure culture of X. fastidiosa isolated from symptomatic tissue. No such amplification was observed in healthy tissue. These primers amplify a portion of DNA encoding a hypothetical protein of unknown function that has been shown to be unique to oleander strains of X. fastidiosa. The PCR product was sequenced and compared with the whole genome shotgun sequence of the oleander strain Ann-1 of X. fastidiosa (GenBank Accession No. AAAM03000099), which resulted in 100% identity with nucleotides 11343 to 11616 in contig 228. X. fastidiosa has been previously reported to cause oleander leaf scorch in California (3), Florida (4), and Texas (2). To our knowledge, this is the first report of X. fastidiosa associated with oleander leaf scorch in Louisiana, extending the geographic range of this important bacterial disease. References: (1) Q. Huang. Curr. Microbiol. 58:393, 2009. (2) Q. Huang et al. Plant Dis. 88:1049, 2004. (3) A. H. Purcell et al. Phytopathology 89:53, 1999. (4) R. L. Wichman et al. Plant Dis. 84:198, 2000.

Lgr5, an intestinal stem cell marker, is abnormally expressed in Barrett's esophagus and esophageal adenocarcinoma

Lgr5 (leucine-rich-repeat-containing G-protein-coupled receptor 5), a recently discovered intestinal stem cell marker, is expressed in premalignant lesions including Barrett's esophagus (BE) and cancers including colon cancer, ovarian cancer, and hepatocellular carcinoma. It was also recently found to be expressed in tumor spheres prepared from colon cancer, suggesting that it will likely serve as a cancer stem cell marker. We sought to examine Lgr5 as a biomarker in BE-associated neoplasia. Using standard immunohistochemistry, we performed immunostaining on 81 esophageal specimens (53 biopsy specimens and 28 surgical resections) representing BE, BE-associated dysplasia, and esophageal adenocarcinoma (EAC). Each immunostain was scored based on intensity of immunostaining and percentage of positive cells. For 24 EAC cases, survival analysis was performed with expression scores and other clinicopathological variables. We found that Lgr5 expression was detected in 70% of BE cases and between 90 and 100% of advanced dysplastic lesions and EAC. The intensity of expression was significantly higher in high-grade dysplasia and EAC than BE. In EAC, high Lgr5 expression scores (> or = 5) were associated with worse survival, independent of stage, age, and neoadjuvant/adjuvant therapy (P = 0.03). Our findings suggest that Lgr5 has potential utility as a biomarker for BE-associated dysplasia and EAC.

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.

KCNJ11 Lys23Glu and TCF7L2 rs290487(C/T) polymorphisms affect therapeutic efficacy of repaglinide in Chinese patients with type 2 diabetes

This study showed that the polymorphisms KCNJ11 Lys23Glu and TCF7L2 rs290487(C/T) are associated with a heightened risk of developing type 2 diabetes mellitus (T2DM). We also explored the effects of these polymorphisms on the efficacy of repaglinide therapy in Chinese patients with T2DM. A total of 259 patients with T2DM and 188 healthy controls were genotyped. Forty patients with various genotypes were randomly selected to undergo an 8-week repaglinide treatment regimen. Patients with the G allele of the KCNJ11 Lys23Glu polymorphism showed higher levels of fasting plasma glucose (FPG) and postprandial plasma glucose (PPG) (P < 0.05). After repaglinide treatment, patients with the GA or AA genotype showed higher levels of FPG, PPG, and glycated hemoglobin (HbA(1c)) compared with patients with the GG genotype (P < 0.05). Patients with the C allele of TCF7L2 rs290487(C/T) had higher total cholesterol levels and lower body mass index (BMI) (P < 0.05). In patients with the TT genotype, the drug showed better efficacy with respect to levels of fasting insulin, triglycerides, and low-density lipoprotein cholesterol (LDL-c) than in patients with the CC or CT genotype (P < 0.05). The KCNJ11 and TCF7L2 polymorphisms were associated with repaglinide efficacy.

Endovascular treatment of wide-neck middle cerebral artery aneurysms with stents: a review of 16 cases

BACKGROUND AND PURPOSE

MCA aneurysms are common and often pose technical challenges to interventionalists. Intracranial stents are widely used in treating wide-neck aneurysms in other locations. To evaluate the feasibility, effectiveness, and safety of stent placement in MCA aneurysms, we performed this retrospective study.

MATERIALS AND METHODS

Between October 2003 and May 2009, 16 patients with 16 wide-neck MCA aneurysms were treated with stents at our institution. We retrospectively collected and analyzed the data for these patients, including demographics, morphologic features of the aneurysms, treatment results, and follow-up.

RESULTS

Seventeen stents, including 12 Neuroform, 4 LEO, and 1 Enterprise, were successfully deployed in this series. Of the 13 aneurysms treated with stent-assisted embolization, complete occlusion was achieved in 9 aneurysms; residual neck remained in 1, and residual aneurysm was present in 3. Contrast stasis in the aneurysm sac was observed in the other 3 aneurysms treated with stent alone. Procedure-related complication occurred in 1 patient, leading to no permanent effect. The mRS score at discharge was 0-2 in 14 patients and 3-6 in 2. The angiographic follow-up results of 9 patients (mean, 5.6 months) showed that all aneurysms remained stable or improved; there was no in-stent stenosis, recurrence, or retreatment. The clinical follow-up (mean, 20.1 months) demonstrated no neurologic deterioration or rebleeding.

CONCLUSIONS

Our preliminary experience demonstrates that stent placement for the treatment of selected wide-neck MCA aneurysms is feasible. However, its safety and efficacy should be further evaluated by larger case series and more adequate follow-up.

Efficacy and safety of pegylated interferon alpha-2a therapy for chronic hepatitis C in HIV-infected patients with haemophilia

The objective of this study was to evaluate the efficacy and safety of pegylated interferon (PEG-IFN) alpha-2a monotherapy in a cohort of Chinese haemophilic patients co-infected with human immunodeficiency virus (HIV)/hepatitis C virus (HCV) and undergoing highly active antiretroviral drugs therapy. Twenty-two (n = 22) patients with CD4 lymphocyte counts over 200 cells microL(-1) were treated with 180 microg of PEG-IFN alpha-2a subcutaneously once in a week for 48 weeks. HCV load (HCV RNA), HIV load (HIV RNA) and CD4 lymphocyte counts were measured at baseline and 4, 12, 24, 48 and 72 weeks after initiation of anti-HCV therapy. Efficacy and safety were analysed according to baseline CD4 status (> or =350 cells microL(-1)). Significant HCV-RNA decreases (>1 log(10) copies mL(-1)) were observed through week 72 after PEG-INF alpha-2a monotherapy across both CD4 strata. CD4 status was not associated with treatment outcomes as evaluated using rapid viral response rate (P = 0.655), early viral response rate (P = 0.387), end-of-treatment viral response rate (P = 1.000) or sustained viral response rate (SVR, P = 0.674). A sustained virological response was achieved in nine patients (41%), five with genotype 2a (83%) and four with genotype 1b (25%, P = 0.023). SVR was HCV genotype dependent. Eleven patients required a dose reduction in PEG-IFN alpha-2a. PEG-IFN alpha-2a monotherapy could be considered as a safe and effective option for the treatment of HCV infection in HIV patients with haemophilia, particularly in resource-limited settings. While higher CD4 lymphocyte counts resulted in greater HCV-RNA reduction, HCV genotype was a predictor for sustained virological response.

Novel strategies to augment genetically delivered immunotoxin molecular therapy for cancer therapy

Immunotoxin therapy is a promising molecular cancer treatment strategy. Its main advantage is seletive cytotoxicity towards tumor cells and minimal toxicity in normal tissues. However, a short half-life and rapid clearance severely hampers its clinical application. We report here a novel genetic approach in which a recombinant adenovirus vector was used to deliver an immunotoxin gene e23(scFv)-PE40 targeted to the oncogene c-erbB-2 (also known as Her2/neu). This vector, when combined with a low dose of a conditionally replicative adenovirus vector (CRAd), has enhanced tumor-killing ability either alone or in combination with the chemotherapeutic agent etoposide. Our data show that low-dose CRAd facilitated the replication of replication-deficient Ad-e23(scFv)-PE40 up to 6-20 times and the transcription of e23(scFv)-PE40 gene up to 12 times. Moreover, etoposide increased the e23(scFv)-PE40 transcription up to 8.5 times. Furthermore, we show that systemic application of Ad-e23(scFv)-PE40 and enhanced expression of the immunotoxin gene was well tolerated as determined by serum biochemical markers and histological examination of most vital organs. Taken together, our data support a novel genetic immunotoxin delivery approach that may yield enhanced efficacy against a variety of Her2/neu-expressing tumors.

The anti-glioma effect of suicide gene therapy using BMSC expressing HSV/TK combined with overexpression of Cx43 in glioma cells

The disseminated neoplastic foci of malignant gliomas are essentially responsible for the limited efficacy of current available therapeutic modalities. Bone marrow-derived stem cells (BMSCs) have the ability to migrate into these tumors and even track infiltrating tumor cells, making them to be promising cellular vehicles for delivering therapeutic agents to glioma cells. The herpes simplex virus thymidine kinase (HSV-TK)/ganciclovir (GCV) suicide gene therapy with a potent bystander effect has been considered as one of the most promising therapeutic strategies for malignant gliomas. In this study, we evaluate the anti-glioma effect of suicide gene therapy using BMSCs expressing HSV-TK combined with overexpression of connexin 43 (Cx43), which can restore the gap junction of intercellular communication and may enhance the bystander effect of suicide gene therapy. To assess the potential of BMSCs to track glioma cells, a spheroid co-culture system in matrigel was used to show that some BMSCs migrated to C6 glioma cell microspheres. Transwell assay showed the tumor tropic property of BMSCs. In addition, BrdU-labeled BMSCs injected directly into the cerebral hemisphere opposite to the established C6 rat gliomas were capable of migrating into the xenograft gliomas. C6 cell growth was more intensively inhibited by HSV-TK/GCV treatment mediated by BMSCs, and could be further enhanced by combination with Cx43 transfection into glioma cells. The same result was observed in vivo by the growth of C6 gliomas and the survival analysis of rats bearing C6 glioma. In conclusion, Cx43 combined with HSV-TK/GCV gene therapy using BMSCs as vehicles was highly effective in a rat glioma model and therefore hold great potential as a novel approach for the gene therapy of human malignant gliomas.

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.