Large linear magnetoresistance in heavily-doped Nb:SrTiO3 epitaxial thin films.

Interaction between electrons has long been a focused topic in condensed-matter physics since it has led to the discoveries of astonishing phenomena, for example, high-Tc superconductivity and colossal magnetoresistance (CMR) in strongly-correlated materials. In the study of strongly-correlated perovskite oxides, Nb-doped SrTiO3 (Nb:SrTiO3) has been a workhorse not only as a conducting substrate, but also as a host possessing high carrier mobility. In this work, we report the observations of large linear magnetoresistance (LMR) and the metal-to-insulator transition (MIT) induced by magnetic field in heavily-doped Nb:STO (SrNb0.2Ti0.8O3) epitaxial thin films. These phenomena are associated with the interplay between the large classical MR due to high carrier mobility and the electronic localization effect due to strong spin-orbit coupling, implying that heavily Nb-doped Sr(Nb0.2Ti0.8)O3 is promising for the application in spintronic devices.

Investigations of metastable Ca2IrO4 epitaxial thin-films: systematic comparison with Sr2IrO4 and Ba2IrO4.

We have synthesized thermodynamically metastable Ca2IrO4 thin-films on YAlO3 (110) substrates by pulsed laser deposition. The epitaxial Ca2IrO4 thin-films are of K2NiF4-type tetragonal structure. Transport and optical spectroscopy measurements indicate that the electronic structure of the Ca2IrO4 thin-films is similar to that of Jeff = 1/2 spin-orbit-coupled Mott insulator Sr2IrO4 and Ba2IrO4, with the exception of an increased gap energy. The gap increase is to be expected in Ca2IrO4 due to its increased octahedral rotation and tilting, which results in enhanced electron-correlation, U/W. Our results suggest that the epitaxial stabilization growth of metastable-phase thin-films can be used effectively for investigating layered iridates and various complex-oxide systems.

Conducting LaAlO3/SrTiO3 heterointerfaces on atomically-flat substrates prepared by deionized-water.

We have investigated how the recently-developed water-leaching method for atomically-flat SrTiO3 (STO) substrates affects the transport properties of LaAlO3 (LAO) and STO heterointerfaces. Using pulsed laser deposition at identical growth conditions, we have synthesized epitaxial LAO thin-films on two different STO substrates, which are prepared by water-leaching and buffered hydrofluoric acid (BHF) etching methods. The structural, transport, and optical properties of LAO/STO heterostructures grown on water-leached substrates show the same high-quality as the samples grown on BHF-etched substrates. These results indicate that the water-leaching method can be used to grow complex oxide heterostructures with atomically well-defined heterointerfaces without safety concerns.

Domain wall conductivity in semiconducting hexagonal ferroelectric TbMnO3 thin films.

Although enhanced conductivity of ferroelectric domain boundaries has been found in BiFeO3 and Pb(Zr,Ti)O3 films as well as hexagonal rare-earth manganite single crystals, the mechanism of the domain wall conductivity is still under debate. Using conductive atomic force microscopy, we observe enhanced conductance at the electrically-neutral domain walls in semiconducting hexagonal ferroelectric TbMnO3 thin films where the structure and polarization direction are strongly constrained along the c-axis. This result indicates that domain wall conductivity in ferroelectric rare-earth manganites is not limited to charged domain walls. We show that the observed conductivity in the TbMnO3 films is governed by a single conduction mechanism, namely, the back-to-back Schottky diodes tuned by the segregation of defects.

The association of uterine cervical microbiota with an increased risk for cervical intraepithelial neoplasia in Korea.

Recent studies have suggested potential roles of the microbiome in cervicovaginal diseases. However, there has been no report on the cervical microbiome in cervical intraepithelial neoplasia (CIN). We aimed to identify the cervical microbiota of Korean women and assess the association between the cervical microbiota and CIN, and to determine the combined effect of the microbiota and human papillomavirus (HPV) on the risk of CIN. The cervical microbiota of 70 women with CIN and 50 control women was analysed using pyrosequencing based on the 16S rRNA gene. The associations between specific microbial patterns or abundance of specific microbiota and CIN risk were assessed using multivariate logistic regression, and the relative excess risk due to interaction (RERI) and the synergy index (S) were calculated. The phyla Firmicutes, Actinobacteria, Bacteroidetes, Proteobacteria, Tenericutes, Fusobacteria and TM7 were predominant in the microbiota and four distinct community types were observed in all women. A high score of the pattern characterized by predominance of Atopobium vaginae, Gardnerella vaginalis and Lactobacillus iners with a minority of Lactobacillus crispatus had a higher CIN risk (OR 5.80, 95% CI 1.73-19.4) and abundance of A. vaginae had a higher CIN risk (OR 6.63, 95% CI 1.61-27.2). The synergistic effect of a high score of this microbial pattern and oncogenic HPV was observed (OR 34.1, 95% CI 4.95-284.5; RERI/S, 15.9/1.93). A predominance of A. vaginae, G. vaginalis and L. iners with a concomitant paucity of L. crispatus in the cervical microbiota was associated with CIN risk, suggesting that bacterial dysbiosis and its combination with oncogenic HPV may be a risk factor for cervical neoplasia.

The anteroposterior axis of the tibia in Korean patients undergoing total knee replacement.

The aim of this study was to find anatomical landmarks for rotational alignment of the tibial component in total knee replacement (TKR) in a CT-based study. Pre-operative CT scanning was performed on 94 South Korean patients (nine men, 85 women, 188 knees) with osteoarthritis of the knee joint prior to TKR. The tibial anteroposterior (AP) axis was defined as a line perpendicular to the femoral surgical transepicondylar axis and passing through the centre of the posterior cruciate ligament (PCL). The angles between the defined tibial AP axis and anatomical landmarks at various levels of the tibia were measured. The mean values of the angles between the defined tibial AP axis and the line connecting the anterior border of the proximal third of the tibia to the centre of the PCL was -0.2° (-17 to 14.1, sd 4.1). This was very close to the defined tibial axis, and remained so regardless of lower limb alignment and the degree of tibial bowing. Therefore, AP axis defined as described, is a reliable anatomical landmark for rotational alignment of tibial components.

Room-temperature ferroelectricity in hexagonal TbMnO3 thin films.

Piezoresponse force microscopy imaging in conjunction with first-principles calculations provide strong evidence for room-temperature ferroelectricity in epitaxially stabilized hexagonal TbMnO3 thin films, which in the bulk form are with orthorhombic structure. The obtained results demonstrate that new phases and functional properties of complex oxide materials can be strain-engineered using epitaxial growth.

Tuning magnetic coupling in Sr2IrO4 thin films with epitaxial strain.

We report x-ray resonant magnetic scattering and resonant inelastic x-ray scattering studies of epitaxially strained Sr2IrO4 thin films. The films were grown on SrTiO3 and (LaAlO3)0.3(Sr2AlTaO6)0.7 substrates, under slight tensile and compressive strains, respectively. Although the films develop a magnetic structure reminiscent of bulk Sr2IrO4, the magnetic correlations are extremely anisotropic, with in-plane correlation lengths significantly longer than the out-of-plane correlation lengths. In addition, the compressive (tensile) strain serves to suppress (enhance) the magnetic ordering temperature TN, while raising (lowering) the energy of the zone-boundary magnon. Quantum chemical calculations show that the tuning of magnetic energy scales can be understood in terms of strain-induced changes in bond lengths.

Reversal of the lattice structure in SrCoO(x) epitaxial thin films studied by real-time optical spectroscopy and first-principles calculations.

Using real-time spectroscopic ellipsometry, we directly observed a reversible lattice and electronic structure evolution in SrCoO(x) (x=2.5-3) epitaxial thin films. Drastically different electronic ground states, which are extremely susceptible to the oxygen content x, are found in the two topotactic phases: i.e., the brownmillerite SrCoO2.5 and the perovskite SrCoO3. First-principles calculations confirmed substantial differences in the electronic structure, including a metal-insulator transition, which originate from the modification in the Co valence states and crystallographic structures. More interestingly, the two phases can be reversibly controlled by changing the ambient pressure at greatly reduced temperatures. Our finding provides an important pathway to understanding the novel oxygen-content-dependent phase transition uniquely found in multivalent transition metal oxides.

Pulsed laser deposition with simultaneous in situ real-time monitoring of optical spectroscopic ellipsometry and reflection high-energy electron diffraction.

We present a pulsed laser deposition system that can monitor growth by simultaneously using in situ optical spectroscopic ellipsometry (SE) and reflection high-energy electron diffraction (RHEED). The RHEED precisely monitors the number of thin-film layers and surface structure during the deposition, and the SE measures the optical spectra of the samples simultaneously. The thin-film thickness information obtained from RHEED facilitates the SE modeling process, which allows extracting the in situ optical spectra, i.e., the dielectric functions of thin-films during growth. The in situ dielectric functions contain indispensable information about the electronic structure of thin-films. We demonstrate the performance of this system by growing LaMnO(3+δ) (LMO) thin-films on SrTiO3 (001) substrates. By using in situ SE and RHEED simultaneously, we show that real-time thickness and dielectric functions of the LMO thin-films can be effectively extracted. The simultaneous monitoring of both optical SE and RHEED offers important clues to understand the growth mechanism of atomic-scale thin-films.

Oxygen-vacancy-induced orbital reconstruction of Ti ions at the interface of LaAlO3/SrTiO3 heterostructures: a resonant soft-X-ray scattering study.

Resonant soft-x-ray scattering measurements have been performed to investigate interface electronic structures of (LaAlO(3)/SrTiO(3)) superlattices. Resonant scattering intensities at superlattice reflections show clear evidence of degeneracy lifting in t(2g) states of interface Ti ions. Polarization dependence of intensities indicates the energy of d(xy) states is lower by ~1 eV than two other t(2g) states. The energy splitting is insensitive to epitaxial strain. The orbital reconstruction is induced by oxygen vacancies and confined to the interface within two unit cells, indicating charge compensation at the polar interfaces.

High control rate for lymph nodes in cervical cancer treated with high-dose radiotherapy using helical tomotherapy.

The purpose of this study was to evaluate whether bulky lymphadenopathy located in the abdominopelvic cavity in cervical cancer can be controlled without severe toxicity by increasing radiation dose using helical tomotherapy. From January 2007 to December 2010, 26 patients with cervical cancer with metastatic lymph nodes (LNs) having at least one short diameter > 1.5 cm were treated with helical tomotherapy. A total of 58 LN sites were treated and the largest LN of each site was evaluated for response. Median follow-up time was 28 months (4-50 months). Median short diameter of the LNs was 1.7 cm (0.7-4.2 cm) with median radiation dose of 62.6 Gy(10) in 2 Gy equivalent dose (53.3-77.9 Gy(10)). Initial LN response was evaluated on imaging obtained within 4 months after radiotherapy. Initial complete response (CR), partial response (PR), and stable disease (SD) were observed in 54, 2 and 2 lesions, respectively. Recurrence occurred in two with CR and progression in one with PR. Therefore, final CR, PR, SD, and progression of disease were observed in 52, 1, 2, and 3, respectively. Actuarial 3-year LN progression-free survival and overall survival (OS) were 63% and 65%, respectively. Multivariate analysis revealed final LN response (CR vs. non-CR) as a strong prognostic factor for OS (p = 0.016). Radiation Therapy Oncology Group grade 2 or more acute and late toxicity was observed in 8 and 1 patients, respectively. The treatment of bulky lymphadenopathy using helical tomotherapy in advanced cervical cancer is highly effective and has acceptable toxicity.

Two-dimensional confinement of 3d{1} electrons in LaTiO_{3}/LaAlO{3} multilayers.

We report spectroscopic ellipsometry measurements of the anisotropy of the interband transitions parallel and perpendicular to the planes of (LaTiO3)n(LaAlO3)5 multilayers with n=1-3. These provide direct information about the electronic structure of the two-dimensional (2D) 3d{1} state of the Ti ions. In combination with local density approximation, including a Hubbard U calculation, we suggest that 2D confinement in the TiO2 slabs lifts the degeneracy of the t{2g} states leaving only the planar d{xy} orbitals occupied. We outline that these multilayers can serve as a model system for the study of the t{2g} 2D Hubbard model.

Signatures of electronic correlations in optical properties of LaFeAsO1-xFx.

Spectroscopic ellipsometry is used to determine the dielectric function of superconducting LaFeAsO0.9F0.1 (T_{c}=27 K) and undoped LaFeAsO polycrystalline samples in the wide range 0.01-6.5 eV at temperatures 10< or =T< or =350 K. The charge carrier response in both samples is heavily damped. The spectral weight transfer in LaFeAsO associated with an opening of the pseudogap at about 0.65 eV is restricted to energies below 2 eV. The spectra of superconducting LaFeAsO0.9F0.1 reveal a significant transfer of spectral weight to a broad optical band above 4 eV with increasing temperature. Our data may imply that the electronic states near the Fermi surface are strongly renormalized due to electron-phonon and/or electron-electron interactions.

Laparoscopic and laparotomic staging in stage I epithelial ovarian cancer: a comparison of feasibility and safety.

The aim of this study was to compare laparoscopic and laparotomic surgical staging in patients with stage I epithelial ovarian cancer in terms of feasibility and safety. A retrospective chart review was undertaken of all patients with apparent stage I epithelial ovarian cancer who underwent laparoscopic (laparoscopy group) or laparotomic (laparotomy group) surgical staging at the Center for Uterine Cancer, National Cancer Center, Korea, between January 2001 and August 2006. During the study period, 19 patients underwent laparotomic surgical staging and 17 patients underwent laparoscopic surgical staging. No cases were converted from laparoscopy to laparotomy. The two groups were similar in terms of age, body mass index, procedures performed, number of lymph nodes retrieved, and operating time. The laparoscopy group had less estimated blood loss (P = 0.001), faster return of bowel movement (P < 0.001), and a shorter postoperative hospital stay (P = 0.002) compared to the laparotomy group. Transfusions were required only in two laparotomy patients, and postoperative complications occurred only in four laparotomy patients. However, two patients with stage IA grade 1 and 2 disease in laparoscopy group had recurrence with one patient dying of disease. The accuracy and adequacy of laparoscopic surgical staging were comparable to laparotomic approach, and the surgical outcomes were more favorable than laparotomic approach. However, the oncologic safety of laparoscopic staging was not certain. This is the first report on the possible hazards of laparoscopic staging in early-stage ovarian cancer. In the absence of a large prospective trial, this technique should be performed cautiously.

Does the use of a uterine manipulator with an intrauterine balloon in total laparoscopic hysterectomy facilitate tumor cell spillage into the peritoneal cavity in patients with endometrial cancer?

The objective of this study was to determine if total laparoscopic hysterectomy using a uterine manipulator with an intrauterine balloon increases the risk of positive peritoneal washings in patients with endometrial cancer. Three sets of peritoneal washings were obtained during surgery from 46 women with endometrial cancer at the Center for Uterine Cancer, National Cancer Center, Korea, between May 2004 and July 2006: the first before the insertion of the uterine manipulator (premanipulator), the second after clipping the fallopian tubes and inserting the uterine manipulator (postmanipulator), and the third after the removal of the uterus through the vagina (posthysterectomy). The cytology samples were examined by the same cytopathologist for the presence of malignant cells. Two of 46 (4.3%) patients were upstaged to IIIA disease due to positive cytology conversion after the insertion of the uterine manipulator, one after the insertion of the uterine manipulator, and the other after the hysterectomy. However, during the follow-up for 3-28 months (median 18), neither of the 2 patients experienced a tumor recurrence. In conclusion, using a uterine manipulator with an intrauterine balloon during the laparoscopic surgery for endometrial cancer might be associated with positive cytologic conversion. Possible explanations are retrograde seeding of tumor cells into the peritoneal cavity, the pressure effect of the inflatable manipulator tip, and spillage of preexited tumor cells between the isthmus and the fimbriae. More effective preventive methods such as distal tubal clipping or coagulation of the fimbriae may be necessary in treating women with endometrial cancer.

Mutual exclusiveness between PIK3CA and KRAS mutations in endometrial carcinoma.

In endometrial carcinomas (ECs), previous report suggested that PIK3CA mutations do not coexist with KRAS mutations, but the significant mutual exclusiveness has not been demonstrated. In this study, we examined the mutation frequency of PIK3CA in EC and its mutual exclusiveness with KRAS mutation. We performed mutational analysis of PIK3CA through a polymerase chain reaction single-strand conformation polymorphism assay in 44 cases of endometrial cancer and analyzed the correlation with loss of PTEN, KRAS mutation, and RASSF1A hypermethylation. Somatic mutations of PIK3CA were detected in 14 of 44 (31.8%) of endometrial cancers. In exon 9, seven PIK3CA mutations were located, while seven mutations were located in exon 20. The most common mutation was E545A (35.7%), followed by H1047R (28.6%). Concomitant loss of PTEN expression and PIK3CA mutation was found in four cases of endometrial cancer. KRAS mutations were mutually exclusive with PIK3CA mutations, and those mutations were inversely correlated with statistical significance (P = 0.039). Also, we found that mutations in ERBB2 were mutually exclusive with PIK3CA mutations. RASSF1A and hMLH1 methylation were not correlated with the presence of PIK3CA mutations. PIK3CA was frequently mutated in endometrial cancers. KRAS and PIK3CA mutations are inversely correlated, suggesting that genetic alterations of KRAS and PIK3CA may play equivalent roles in endometrial carcinogenesis.

Port-site and liver metastases after laparoscopic pelvic and para-aortic lymph node dissection for surgical staging of locally advanced cervical cancer.

Recently, we experienced a case of port-site and liver metastases after 75 cases of laparoscopic transperitoneal pelvic lymph node dissection (PLND) and para-aortic lymph node dissection (PALND) for surgical staging of locally advanced cervical cancer. A 45-year-old-woman with stage IIB cervical adenocarcinoma underwent laparoscopic PLND and PALND for surgical staging. There was no intraperitoneal disease and cervical tumor was not manipulated at the time of laparoscopic surgery. Pathologic examination revealed only one micrometastasis in left internal iliac lymph node (LN), measuring 1 mm, of the 60 pelvic and para-aortic LNs removed. She received concurrent chemoradiation therapy and pelvic mass disappeared completely. One month after the completion of therapy, both lateral and umbilical port-site and liver metastases were detected. We conclude that although cases of port-site metastasis have mostly occurred after extensive disease, the possibility of such complication should be kept in mind at laparoscopy of early cancer and laparoscopy which does not manipulate primary tumor.

The clinical values of squamous cell carcinoma antigen and carcinoembryonic antigen in patients with cervical cancer treated with concurrent chemoradiotherapy.

The objective of this study was to determine the prognostic significance of the pre- and posttreatment serum levels of the squamous cell carcinoma antigen (SCC-Ag) and carcinoembryonic antigen (CEA). From 2001 to 2005, 211 patients were treated with concurrent chemoradiotherapy (CCRT). The SCC-Ag and CEA levels were measured before treatment, 1 month after treatment, and during the follow-up. The association between the pretreatment tumor marker levels and the clinical prognostic factors was evaluated. The frequency of complete remission (CR) and the normalization of the posttreatment tumor marker were also analyzed. The pretreatment serum levels of CEA and SCC-Ag were elevated in 68 (32.2%) and 148 (70.1%) patients, respectively. The number of patients with an elevated pretreatment SCC-Ag level was associated with the FIGO stage, tumor volume, and pelvic lymph node status. The pretreatment CEA was only significantly related to the tumor volume and pelvic lymph node involvement. One month after completing CCRT, the CEA and SCC-Ag levels were normalized in almost all patients with an incidence of 88.2% (60/68) and 93.2% (138/148), respectively. Among the patients who gained CR with a previously elevated pretreatment CEA and SCC-Ag, the values were normalized in 92.1% (58/63) and 96.4% (134/139) at 1 month, respectively. Combination assays of the pre- and posttreatment serum CEA and SCC-Ag levels appear to be useful for both predicting the prognosis and estimating the clinical response in cervical cancer. However, the routine combined measurement with SCC-Ag of CEA in all patients had limited additional effect in predicting the prognostic significance.