Observation of chiral surface excitons in a topological insulator Bi2Se3.

The protected electron states at the boundaries or on the surfaces of topological insulators (TIs) have been the subject of intense theoretical and experimental investigations. Such states are enforced by very strong spin-orbit interaction in solids composed of heavy elements. Here, we study the composite particles-chiral excitons-formed by the Coulomb attraction between electrons and holes residing on the surface of an archetypical 3D TI, [Formula: see text] Photoluminescence (PL) emission arising due to recombination of excitons in conventional semiconductors is usually unpolarized because of scattering by phonons and other degrees of freedom during exciton thermalization. On the contrary, we observe almost perfectly polarization-preserving PL emission from chiral excitons. We demonstrate that the chiral excitons can be optically oriented with circularly polarized light in a broad range of excitation energies, even when the latter deviate from the (apparent) optical band gap by hundreds of millielectronvolts, and that the orientation remains preserved even at room temperature. Based on the dependences of the PL spectra on the energy and polarization of incident photons, we propose that chiral excitons are made from massive holes and massless (Dirac) electrons, both with chiral spin textures enforced by strong spin-orbit coupling. A theoretical model based on this proposal describes quantitatively the experimental observations. The optical orientation of composite particles, the chiral excitons, emerges as a general result of strong spin-orbit coupling in a 2D electron system. Our findings can potentially expand applications of TIs in photonics and optoelectronics.

Vascular control by infrarenal aortic cross-clamping in placenta accreta spectrum disorders: description of technique.

We describe a novel surgical technique in 31 women with histopathologically confirmed placenta accreta spectrum (PAS) disorders managed by a multidisciplinary team using a prophylactic infrarenal abdominal aortic cross-clamping technique during caesarean hysterectomy. We conclude that this new surgical procedure is a relatively safe technique to potentially control operative blood loss. Our work may stimulate others to develop protocols assessing this innovative technique to improve the surgical outcome of PAS disorders.

Epidemiology and clinical characteristics of invasive mould infections: A multicenter, retrospective analysis in five Asian countries.

Formal, large-scale, multicenter studies of invasive mould infection (IMI) in Asia are rare. This 1-year, retrospective study was designed to assess the incidence and clinical determinants of IMI in centers in five countries (Thailand, Taiwan, Singapore, China, India). Patients treated in a single year (2012) were identified through discharge diagnoses, microbiology, and histopathology logs, and entered based on published definitions of IMI. A total of 155 cases were included (median age 54 years; 47.7% male). Of these, 47.7% had proven disease; the remainder had probable IMI. The most frequent host factors were prolonged steroid use (39.4%) and recent neutropenia (38.7%). Common underlying conditions included diabetes mellitus (DM; 30.9%), acute myeloid leukemia (19.4%), and rheumatologic conditions (11.6%). DM was more common in patients with no recent history of neutropenia or prolonged steroid use (P = .006). The lung was the most frequently involved site (78.7%), demonstrating a range of features on computed tomography (CT). Aspergillus was the most common mould cultured (71.6%), primarily A. fumigatus and A. flavus, although proportions varied in different centers. The most often used antifungal for empiric therapy was conventional amphotericin. Ninety-day mortality was 32.9%. This is the first multicenter Asian study of IMI not limited to specific patient groups or diagnostic methods. It suggests that DM and rheumatologic conditions be considered as risk factors for IMI and demonstrates that IMI should not be ruled out in patients whose chest features on CT do not fit the conventional criteria.

Chiral Spin Mode on the Surface of a Topological Insulator.

Using polarization-resolved resonant Raman spectroscopy, we explore collective spin excitations of the chiral surface states in a three dimensional topological insulator, Bi_{2}Se_{3}. We observe a sharp peak at 150 meV in the pseudovector A_{2} symmetry channel of the Raman spectra. By comparing the data with calculations, we identify this peak as the transverse collective spin mode of surface Dirac fermions. This mode, unlike a Dirac plasmon or a surface plasmon in the charge sector of excitations, is analogous to a spin wave in a partially polarized Fermi liquid, with spin-orbit coupling playing the role of an effective magnetic field.

Discovery of an Unconventional Charge Density Wave at the Surface of K_{0.9}Mo_{6}O_{17}.

We use angle resolved photoemission spectroscopy, Raman spectroscopy, low energy electron diffraction, and x-ray scattering to reveal an unusual electronically mediated charge density wave (CDW) in K_{0.9}Mo_{6}O_{17}. Not only does K_{0.9}Mo_{6}O_{17} lack signatures of electron-phonon coupling, but it also hosts an extraordinary surface CDW, with T_{S_CDW}=220 K nearly twice that of the bulk CDW, T_{B_CDW}=115 K. While the bulk CDW has a BCS-like gap of 12 meV, the surface gap is 10 times larger and well in the strong coupling regime. Strong coupling behavior combined with the absence of signatures of strong electron-phonon coupling indicates that the CDW is likely mediated by electronic interactions enhanced by low dimensionality.

Analogy Between the "Hidden Order" and the Orbital Antiferromagnetism in URu_{2-x}Fe_{x}Si_{2}.

We study URu_{2-x}Fe_{x}Si_{2}, in which two types of staggered phases compete at low temperature as the iron concentration x is varied: the nonmagnetic "hidden order" (HO) phase below the critical concentration x_{c}, and unconventional antiferromagnetic (AFM) phase above x_{c}. By using polarization resolved Raman spectroscopy, we detect a collective mode of pseudovectorlike A_{2g} symmetry whose energy continuously evolves with increasing x; it monotonically decreases in the HO phase until it vanishes at x=x_{c}, and then reappears with increasing energy in the AFM phase. The mode's evolution provides direct evidence for a unified order parameter for both nonmagnetic and magnetic phases arising from the orbital degrees-of-freedom of the uranium-5f electrons.

Decreased expression of H3K27me3 in human ovarian carcinomas correlates with more aggressive tumor behavior and poor patient survival.

It has been confirmed that trimethylation of lysine 27 on histone H3 (H3K27me3) plays an important role in epigenetic process of tumorigenesis. However, the status of H3K27me3 in ovarian cancer and its impact on patients' clinicopathologic characteristics and prognosis are unclear. In the present study, the immunohistochemistry (IHC) was utilized to detect protein expression of H3K27me3 in 12 normal ovaries, 26 ovarian cystadenomas, 31 borderline ovarian tumors and 168 ovarian carcinomas by tissue microarray. The association between H3K27me3 expression with clinicopathologic features and patient prognosis were also evaluated using various statistical models. The expression of H3K27me3 was decreased in 2 of 12 (16.7%) cases of the normal ovaries, 8 of 26 (30.8%) cases of cystadenomas, 12 of 31 (38.7%) cases of borderline ovarian tumors, and 93 of 168 (55.4%) cases of primary ovarian carcinomas, respectively (P<0.05). Further correlation analysis suggested that decreased expression of H3K27me3 in ovarian carcinomas was significantly correlated with more advanced pM and FIGO stages (P<0.05). In addition, a significant association between decreased expression of H3K27me3 and shortened patient survival (mean 66 months versus 101 months, p=0.019) was demonstrated by univariate survival analysis of the ovarian carcinoma cohorts. Importantly, H3K27me3 expression provided a significant independent prognostic factor in multivariate analysis (p=0.028). These findings confirmed that decreased expression of H3K27me3 in primary ovarian cancer might be correlated with the acquisition of an invasive and/or aggressive phenotype of tumor, and might serve as an independent biomarker for poor prognosis in patients with ovarian carcinoma.

MiR-29c mediates epithelial-to-mesenchymal transition in human colorectal carcinoma metastasis via PTP4A and GNA13 regulation of ß-catenin signaling.

BACKGROUND: Distant metastasis is the major cause of cancer-related death, and epithelial-to-mesenchymal transition (EMT) has a critical role in this process. Accumulating evidence indicates that EMT can be regulated by microRNAs (miRNAs). miR-29c has been implicated as a tumor suppressor in several human cancers. However, the role of miR-29c in the progression of colorectal cancer (CRC) metastasis remains largely unknown. PATIENTS AND METHODS: The expression of miR-29c was examined by qRT-PCR in a cohort of primary CRC (PC) and distant liver metastasis (LM) tissues. A series of in vivo and in vitro assays were carried out in order to elucidate the functions of miR-29c and the molecular mechanisms underlying the pathogenesis of metastatic CRC. RESULTS: miR-29c was markedly downregulated in PCs with distant metastasis and determined to be an independent predictor of shortened patient survival. But LM tissues showed higher levels of miR-29c than that in PC tissues. In CRC cells, miR-29c dramatically suppressed cell migration and invasion abilities in vitro and cancer metastasis in vivo. In addition, miR-29c inhibited EMT and negatively regulated Wnt/ß-catenin signaling pathway. Guanine nucleotide binding protein alpha13 (GNA13) and protein tyrosine phosphatase type IVA (PTP4A) were identified as direct targets of miR-29c, which acted through ERK/GSK3ß/ß-catenin and AKT/GSK3ß/ß-catenin pathways, respectively, to regulate EMT. Furthermore, significant associations between miR-29c, its target genes (GNA13 and PTP4A) and EMT markers were validated in both PC and LM tissues. CONCLUSION: Our findings highlight the important role of miR-29c in regulating CRC EMT via GSK-3ß/ß-catenin signaling by targeting GNA13 and PTP4A and provide new insights into the metastatic basis of CRC.

Trends in the susceptibility of methicillin-resistant Staphylococcus aureus to nine antimicrobial agents, including ceftobiprole, nemonoxacin, and tyrothricin: results from the Tigecycline In Vitro Surveillance in Taiwan (TIST) study, 2006-2010.

This study investigated the in vitro susceptibilities of methicillin-resistant Staphylococcus aureus (MRSA) to nine antimicrobial agents in Taiwan. A total of 1,725 isolates were obtained from 20 hospitals throughout Taiwan from 2006 to 2010. The minimum inhibitory concentrations (MICs) of the nine agents were determined by the agar dilution method. The MICs of mupirocin and tyrothricin were determined for 223 MRSA isolates collected from 2009 to 2010. For vancomycin, 99.7 % were susceptible; however, 30.0 % (n = 517) exhibited MICs of 2 µg/ml and 0.3 % (n = 6) demonstrated intermediate susceptibility (MICs of 4 µg/ml). Nearly all isolates (≥ 99.9 %) were susceptible to teicoplanin, linezolid, and daptomycin. The MIC90 values were 2 µg/ml for ceftobiprole and 1 µg/ml for nemonoxacin. The MIC90 values of mupirocin and tyrothricin were 0.12 and 4 µg/ml, respectively. MIC creep was noted for daptomycin during this period, but not for vancomycin, teicoplanin, linezolid, or tigecycline. For isolates with vancomycin MICs of 2 µg/ml, the MIC90 values were 2 µg/ml for teicoplanin, 0.5 µg/ml for daptomycin, and 0.5 µg/ml for tigecycline. Those values were four- to eight-fold higher than those among isolates with vancomycin MICs of 0.5 µg/ml (2, 0.06, and 0.12 µg/ml, respectively). Of the nine MRSA isolates exhibiting non-susceptibility to vancomycin (n = 6), teicoplanin (n = 1), daptomycin (n = 2), or tigecycline (n = 1), all had different pulsotypes, indicating the absence of intra-hospital or inter-hospital spread. The presence of a high proportion of MRSA isolates with elevated MICs (2 µg/ml) and MIC creep of daptomycin might alert clinicians on the therapy for serious MRSA infections in Taiwan.

Optical manipulation of Rashba-split 2-dimensional electron gas.

In spintronics, the two main approaches to actively control the electrons' spin involve static magnetic or electric fields. An alternative avenue relies on the use of optical fields to generate spin currents, which can bolster spin-device performance, allowing for faster and more efficient logic. To date, research has mainly focused on the optical injection of spin currents through the photogalvanic effect, and little is known about the direct optical control of the intrinsic spin-splitting. To explore the optical manipulation of a material's spin properties, we consider the Rashba effect. Using time- and angle-resolved photoemission spectroscopy (TR-ARPES), we demonstrate that an optical excitation can tune the Rashba-induced spin splitting of a two-dimensional electron gas at the surface of Bi2Se3. We establish that light-induced photovoltage and charge carrier redistribution - which in concert modulate the Rashba spin-orbit coupling strength on a sub-picosecond timescale - can offer an unprecedented platform for achieving optically-driven spin logic devices.

Regulation of the PH-domain-containing tyrosine kinase Etk by focal adhesion kinase through the FERM domain.

Etk/BMX, a member of the Btk family of tyrosine kinases, is highly expressed in cells with great migratory potential, including endothelial cells and metastatic carcinoma cell lines. Here, we present evidence that Etk is involved in integrin signalling and promotes cell migration. The activation of Etk by extracellular matrix proteins is regulated by FAK through an interaction between the PH domain of Etk and the FERM domain of FAK. The lack of Etk activation by extracellular matrix in FAK-null cells could be restored by co-transfection with wild-type FAK. Disrupting the interaction between Etk and FAK diminished the cell migration promoted by either kinase. Furthermore, inhibiting Etk expression in metastatic carcinoma cell lines with an antisense oligonucleotide blocks integrin-mediated migration of these cells. Taken together, our data indicate the essential role of the interaction of the PH domain of Etk and the FERM domain of FAK in integrin signalling.

Negative regulation of human immune deficiency virus replication in monocytes. Distinctions between restricted and latent expression in THP-1 cells.

In THP-1 monocytoid cells infected with HIV, viral expression can be regulated in several ways: (a) latency (no viral expression); (b) restricted expression (chronic low-level viral expression with little or no detectable virus released); and (c) continuous production. In cells with restricted HIV expression, nuclear factor(s) were found that blocked tat-associated DNA binding complex formation, suggesting that initiation of transcription was negatively regulated. Also, viral particles were seen budding into and accumulating within intracytoplasmic vacuoles with little virus released, suggesting multiple levels of regulation. These cells with restricted expression had no detectable viral antigens on the cell surface and were not lysed by IL-2-activated large granular lymphocytes. However, they could cause viral-mediated T cell cytolysis in cell-cell assays, suggesting viral transmission through cell contact. In addition, cells with latent HIV were identified and could still produce infectious virus after 5-azacytidine exposure 10 mo later. LPS and other treatments could increase viral production in cells with restricted but not latent expression, suggesting they occur by distinct mechanisms. These infected cells provide a reservoir for viral transmission to uninfected T cells that itself is not detected by immune surveillance mechanisms.

Molecular cloning of a human monocyte-derived neutrophil chemotactic factor (MDNCF) and the induction of MDNCF mRNA by interleukin 1 and tumor necrosis factor.

The cDNA coding for human monocyte-derived neutrophil-specific chemotactic factor (MDNCF) was cloned from LPS-stimulated human monocyte mRNA. The cDNA sequence codes for a polypeptide consisting of 99 amino acids, including a putative signal sequence. Comparison of the deduced amino acid sequence with the NH2-terminal amino acid sequence of natural MDNCF shows that the mature functional protein comprises 72 amino acids, beginning with serine at residue 28. The deduced amino acid sequence shows striking similarity to several platelet-derived factors, a v-src-induced protein, a growth-regulated gene product (gro), and an IFN-gamma inducible protein. The availability of the MDNCF cDNA enabled us to use it as a probe to identify inducers of MDNCF mRNA expression in human PBMC. MDNCF mRNA was increased greater than 10-fold within 1 h after stimulation with LPS, IL-1, or TNF, but not by IFN-gamma, IFN-alpha, or IL-2. Furthermore, we also determined that LPS, IL-1, and TNF stimulated the mononuclear cells to produce biologically active MDNCF. This observation may account for the in vivo capacity of IL-1 and TNF to induce netrophil infiltrates.

Overexpression of AIB1 negatively affects survival of surgically resected non-small-cell lung cancer patients.

BACKGROUND: The amplified in breast cancer 1 (AIB1) gene has been considered to play an oncogenic role in human cancers, but its clinical/prognostic significance in non-small-cell lung cancer (NSCLC) is still unclear. PATIENTS AND METHODS: The methods of immunohistochemistry and FISH were utilized to examine protein expression and amplification of AIB1 in 230 informative surgically resected NSCLCs and in 30 samples of normal lung tissues. RESULTS: Overexpression and amplification of AIB1 were found in 48.3% and 8.2% of NSCLCs, respectively. AIB1 overexpression was associated with AIB1 gene amplification and cell proliferation but not related to estrogen receptor (ER)-alpha, ER-beta, progesterone receptor or androgen receptor status. A positive correlation between AIB1 overexpression and an ascending pathologic node stage in lung adenocarcinoma (ADC) was observed (P = 0.043). Univariate survival analysis demonstrated a significant association of AIB1 overexpression with shortened patient survival, especially for those with stage III disease (P < 0.001). Importantly, AIB1 expression was evaluated as the most significant predictor for survival in multivariate analysis (hazards ratio = 2.069, P < 0.001). CONCLUSION: Overexpression of AIB1 might provide a selective advantage for lymph node metastasis of lung ADC and serve as a useful biomarker for poor prognosis for NSCLC patients.

Low expression of Mel-18 predicts poor prognosis in patients with breast cancer.

BACKGROUND: Our previous study suggested that melanoma nuclear protein 18 (Mel-18) acted as a tumor suppressor in human breast cancer. This study was designed to investigate the clinical and prognostic significance of Mel-18 in breast cancer patients. PATIENTS AND METHODS: Mel-18 was detected by immunohistochemistry in paraffin-embedded tissues from 287 breast cancer patients, of which 287 were from primary cancer sites, 63 from matched adjacent noncancerous sites, and 35 from metastatic lymph nodes. Differences in Mel-18 expression and clinical characteristics were compared by χ² test. Prognostic outcomes correlated with Mel-18 were examined using Kaplan-Meier analysis and Cox proportional hazards model. RESULTS: The decreased Mel-18 expression is incremental depending upon the magnitude of cancer progression (P < 0.001). Mel-18 was conversely correlated with the pathological classifications (P < 0.001 for T, N, and M classifications, respectively), clinical staging (P < 0.001), and progesterone receptor (P = 0.030). Furthermore, patients with higher level of Mel-18 showed prolonged overall survivals (P < 0.001). The diminished Mel-18 expression may be a risk factor for the patients' survival (P < 0.001). CONCLUSIONS: Lower Mel-18 expression is correlated with advanced clinicopathologic classifications and a poor overall survival in breast cancer patients. These findings suggest that Mel-18 may serve as a useful marker in prognostic evaluation for patients.

Genetic polymorphisms and haplotype structures of HSPA5 gene in the Han population of Southern China.

The heat shock 70 kDa protein 5 (HSPA5) gene is known to be involved in stress-associated diseases. In this study, the promoter, exons, 3' untranslated region (3'UTR), and subtotal introns of the HSPA5 gene were sequenced in a sub-population of 161 healthy Han Chinese. Nine single-nucleotide polymorphisms (SNPs) including a new one (-86bp T > A from the estimated translation start site) were found and 15 haplotypes (frequencies > 1%) were inferred. Polymorphisms rs391957 and rs11355458 were completely linked in our population (r (2) = 1.00). Using this information, fellow scientists may be able to decrease the number of SNPs to be genotyped in future disease case-control studies.