n-type conversion of SnS by isovalent ion substitution: Geometrical doping as a new doping route

Tin monosulfide (SnS) is a naturally p-type semiconductor with a layered crystal structure, but no reliable n-type SnS has been obtained by conventional aliovalent ion substitution. In this work, carrier polarity conversion to n-type was achieved by isovalent ion substitution for polycrystalline SnS thin films on glass substrates. Substituting Pb²⁺ for Sn²⁺ converted the majority carrier from hole to electron, and the free electron density ranged from 10¹² to 10¹⁵ cm⁻³ with the largest electron mobility of 7.0 cm²/(Vs). The n-type conduction was confirmed further by the position of the Fermi level (E_F) based on photoemission spectroscopy and electrical characteristics of pn heterojunctions. Density functional theory calculations reveal that the Pb substitution invokes a geometrical size effect that enlarges the interlayer distance and subsequently reduces the formation energies of Sn and Pb interstitials, which results in the electron doping.

In vitro expansion of CD34(+)CD38(-) cells under stimulation with hematopoietic growth factors on AGM-S3 cells in juvenile myelomonocytic leukemia

Using serum-containing culture, we examined whether AGM-S3 stromal cells, alone or in combination with hematopoietic growth factor(s), stimulated the proliferation of CD34(+) cells from patients with juvenile myelomonocytic leukemia (JMML). AGM-S3 cells in concert with stem cell factor plus thrombopoietin increased the numbers of peripheral blood CD34(+) cells to approximately 20-fold of the input value after 2 weeks in nine JMML patients with either PTPN11 mutations or RAS mutations, who received allogeneic hematopoietic transplantation. Granulocyte-macrophage colony-stimulating factor (GM-CSF) also augmented the proliferation of JMML CD34(+) cells on AGM-S3 cells. The expansion potential of CD34(+) cells was markedly low in four patients who achieved spontaneous hematological improvement. A large proportion of day-14-cultured CD34(+) cells were negative for CD38 and cryopreservable. Cultured JMML CD34(+)CD38(-) cells expressed CD117, CD116, c-mpl, CD123, CD90, but not CXCR4, and formed GM and erythroid colonies. Day-7-cultured CD34(+) cells from two of three JMML patients injected intrafemorally into immunodeficient mice stimulated with human GM-CSF after transplantation displayed significant hematopoietic reconstitution. The abilities of OP9 cells and MS-5 cells were one-third and one-tenth, respectively, of the value obtained with AGM-S3 cells. Our culture system may provide a useful tool for elucidating leukemogenesis and for therapeutic approaches in JMML.

Narrow bandgap in β-BaZn₂As₂ and its chemical origins

β-BaZn2As2 is known to be a p-type semiconductor with the layered crystal structure similar to that of LaZnAsO, leading to the expectation that β-BaZn2As2 and LaZnAsO have similar bandgaps; however, the bandgap of β-BaZn2As2 (previously reported value ~0.2 eV) is 1 order of magnitude smaller than that of LaZnAsO (1.5 eV). In this paper, the reliable bandgap value of β-BaZn2As2 is determined to be 0.23 eV from the intrinsic region of the temperature dependence of electrical conductivity. The origins of this narrow bandgap are discussed based on the chemical bonding nature probed by 6 keV hard X-ray photoemission spectroscopy, hybrid density functional calculations, and the ligand theory. One origin is the direct As-As hybridization between adjacent [ZnAs] layers, which leads to a secondary splitting of As 4p levels and raises the valence band maximum. The other is that the nonbonding Ba 5d(x(2)-y(2)) orbitals form an unexpectedly deep conduction band minimum (CBM) in β-BaZn2As2 although the CBM of LaZnAsO is formed mainly of Zn 4s. These two origins provide a quantitative explanation for the bandgap difference between β-BaZn2As2 and LaZnAsO.

Growth of c-axis-oriented superconducting KFe₂As₂ thin films

KFe2As2, an iron-based superconductor, is expected to exhibit large spin Hall conductivity, and fabrication of high-quality thin films is requisite for evaluation of this effect and application to spintronics devices. Thin-film growth of KFe2As2 is difficult because of two intrinsic properties; its extremely hygroscopic nature and the high vapor pressure of potassium. We solved these issues by combining room-temperature pulsed laser deposition using K-rich KFe2As2 targets with thermal crystallization in KFe2As2 powder after encapsulation in an evacuated silica-glass tube with all of the processes conducted in a vacuum chamber and a dry Ar atmosphere in a glovebox. The optimized KFe2As2 films on (La,Sr)(Al,Ta)O3 single-crystal substrates were obtained by crystallization at 700 °C, and they were strongly c-axis oriented. The electrical measurements were performed with thin films protected by grease passivation to block reaction with the atmosphere. The KFe2As2 films exhibited a superconductivity transition at 3.7 K.

Thin film growth of Fe-based superconductors: from fundamental properties to functional devices. A comparative review

Fe-based superconductors bridge a gap between MgB2 and the cuprate high temperature superconductors as they exhibit multiband character and transition temperatures up to around 55 K. Investigating Fe-based superconductors thus promises answers to fundamental questions concerning the Cooper pairing mechanism, competition between magnetic and superconducting phases, and a wide variety of electronic correlation effects. The question addressed in this review is, however, is this new class of superconductors also a promising candidate for technical applications? Superconducting film-based technologies range from high-current and high-field applications for energy production and storage to sensor development for communication and security issues and have to meet relevant needs of today’s society and that of the future. In this review we will highlight and discuss selected key issues for Fe-based superconducting thin film applications. We initially focus our discussion on the understanding of physical properties and actual problems in film fabrication based on a comparison of different observations made in the last few years. Subsequently we address the potential for technological applications according to the current situation.

Arterial spin-labeled perfusion imaging reflects vascular density in nonfunctioning pituitary macroadenomas

BACKGROUND AND PURPOSE

Angiogenesis is very important in clinical features of pituitary adenomas. We investigated the relationship between the blood flow of nonfunctioning pituitary macroadenomas measured by arterial spin-labeled perfusion imaging and the microvessel attenuation of the tissue.

MATERIALS AND METHODS

Conventional MR imaging with contrast-enhanced T1WI and arterial spin-labeled perfusion imaging were performed before surgery in 11 consecutive patients with nonfunctioning pituitary macroadenomas. ROIs were drawn on the tumors, and the degrees of enhancement were calculated by dividing the signal intensity on the contrast-enhanced T1WI by that on the nonenhanced TIWI. As an index of tumor perfusion, a quantitative analysis was performed by using normalized tumor blood flow values calculated by dividing the mean value of the tumor region of interest by the mean region of interest values in the 2 cerebellar hemispheres. The relative microvessel attenuation was determined as the total microvessel wall area divided by the entire tissue area on CD-31-stained specimens. The degree of enhancement and the normalized tumor blood flow values were compared with relative microvessel attenuation. Additionally, intra- and postoperative tumor hemorrhages were visually graded.

RESULTS

The degree of enhancement was not correlated with relative microvessel attenuation. Statistically significant correlations were observed between normalized tumor blood flow values and relative microvessel attenuation (P < .05). At surgery, 3 cases were visually determined to be hypervascular tumors, and 1 of these cases had symptomatic postoperative hemorrhage. A statistically significant difference in normalized tumor blood flow values was observed visually between the intraoperative hypovascular and hypervascular groups (P < .05).

CONCLUSIONS

Arterial spin-labeled perfusion imaging reflects the vascular density of nonfunctioning pituitary macroadenomas, which may be useful in the preoperative prediction of intra- and postoperative tumor hemorrhage.

Solid-state source of atomic oxygen for low-temperature oxidation processes: application to pulsed laser deposition of TiO2:N films

An atomic oxygen (AO) source has been redesigned to coordinate with a pulsed laser deposition system and used to grow nitrogen-doped TiO(2) films by deposition of TiN and simultaneous irradiation of the substrate with AO. The AO source uses an incandescently heated thin tube of zirconia as an oxygen permeation media to generate pure AO of low kinetic energy. The emission flux is calibrated using a silver-coated quartz crystal microbalance. The thin shape of the probe and transverse emission geometry of this emission device allow the emission area to be positioned close to the substrate surface, enhancing the irradiation flux at the substrate. AO irradiation is crucial for formation of TiO(2) phases via oxidation of the deposited TiN laser plume, and is effective for decrease of the substrate temperature for crystallization of anatase phase to as low as around 200 °C.

Advantageous grain boundaries in iron pnictide superconductors

High critical temperature superconductors have zero power consumption and could be used to produce ideal electric power lines. The principal obstacle in fabricating superconducting wires and tapes is grain boundaries-the misalignment of crystalline orientations at grain boundaries, which is unavoidable for polycrystals, largely deteriorates critical current density. Here we report that high critical temperature iron pnictide superconductors have advantages over cuprates with respect to these grain boundary issues. The transport properties through well-defined bicrystal grain boundary junctions with various misorientation angles (θ(GB)) were systematically investigated for cobalt-doped BaFe(2)As(2) (BaFe(2)As(2):Co) epitaxial films fabricated on bicrystal substrates. The critical current density through bicrystal grain boundary (J(c)(BGB)) remained high (>1 MA cm(-2)) and nearly constant up to a critical angle θ(c) of ∼9°, which is substantially larger than the θ(c) of ∼5° for YBa(2)Cu(3)O(7-δ). Even at θ(GB)>θ(c), the decay of J(c)(BGB) was much slower than that of YBa(2)Cu(3)O(7-δ).

Pseudoisotropic upper critical field in cobalt-doped SrFe2As2 epitaxial films

We present resistivity measurements of the complete superconducting upper critical field (H{c2}) phase diagram as a function of angle (theta) and temperature (T) for cobalt-doped SrFe2As2 epitaxial films to 0.5 K and 50 T. Although H{c2}(theta) at 10 K is indistinguishable from that derived from a single-band anisotropy model, the apparent anisotropy H{c2}{ perpendicularc}/H{c2};{ parallelc} linearly decreases to 1 at low T, with H{c2}(0)=47 T. The data are well described by a two-band model with small, opposing anisotropies for the bands. This unusual relationship is confirmed by the observation of a local maximum for H{c2};{ parallelc} at low T.

Nickel-Based Oxyphosphide Superconductor with a Layered Crystal Structure, LaNiOP

A layered oxyphosphide, LaNiOP, was synthesized by solid-state reactions. This crystal was confirmed to have a layered structure composed of an alternating stack of (La(3+)O(2-))(+) and (Ni(2+)P(3-))(-). We found that the resulting LaNiOP shows a superconducting transition at approximately 3 K. This material exhibited metallic conduction and Pauli paramagnetism in the temperature range of 4-300 K. The resistivity sharply dropped to zero and the magnetic susceptibility became negative at <4 K, indicating that a superconducting transition occurs. The volume fraction of the superconducting phase estimated from the diamagnetic susceptibility reached approximately 40 vol % at 1.8 K, substantiating that LaNiOP is a bulk superconductor.

Extracranial vertebral artery aneurysm associated with neurofibromatosis type 1. A case report

SUMMARY

Extracranial vertebral artery aneurysm associated with neurofibromatosis (NF1) is very rare. The aneurysm was successfully treated by endovascular trapping of the aneurysm and proximal vertebral artery with coils.

Iron-Based Layered Superconductor: LaOFeP

We report superconductivity in an iron-based layered oxy-pnictide LaOFeP. LaOFeP is composed of an alternate stack of lanthanum oxide (La3+O2-) and iron pnictide (Fe2+P3-) layers. Magnetic and electrical resistivity measurements verify the occurrence of the superconducting transition at approximately 4 K.

Quantum beat between two excitonic levels split by spin--orbit interactions in the oxychalcogenide LaCuOS

Degenerate four-wave mixing signals excited by femtosecond laser pulses were measured in LaCuOCh (Ch = S and Se) at 4 K. The signals for LaCuOS exhibit a beat structure with a period of 480 fs just at the exciton peak energy, indicating that the lowest exciton states are split by 9 meV, but no beat structure was observed in LaCuOSe, regardless of the laser's energy. The spin--orbit interaction of the Ch ion accompanied by the hybridization of Cu 3d orbitals causes splitting of the exciton levels. Furthermore, the contribution of Ch p orbitals in the valence band maximum is larger in LaCuOSe owing to increased covalency in the Cu--Ch bond when S is replaced with Se.

Cyclic thrombocytopenia and polycythemia vera

A periodic fall of platelet number characterizes an acquired pathological condition named cyclic thrombocytopenia. We describe an unusual case of polycythemia vera in which the episodes of thrombocytopenia were followed regularly by thrombocytosis. The period of platelet count fluctuation was about 50 days, with the counts ranging from 34 to 820 x 10(9)/l. Bone marrow megakaryocytes were decreased in number during platelet nadir. Circulating thrombopoietin levels fluctuated out of phase with the platelet count. We suggest that at least some cases of polycythemia vera may have an unstable hematopoietic stem cell pool in nature, which could contribute to the development of unprovoked cyclic thrombocytopenia.

A rare case of advanced ovarian carcinoma who developed difficulty walking 25 days after treatment with weekly paclitaxel

Although taxol has shown significant activity in advanced ovarian cancer, peripheral neuropathy is likely to become the major dose-limiting toxicity. We describe a case of advanced ovarian carcinoma who developed difficulty walking because of marked pain in the lower extremities and loss of proprioception 25 days after treatment with weekly taxol (80 mg/m(2)x3).

Sentinel lymph node biopsy using tin colloid RI and blue dye method

Axillary dissection has been considered essential for breast cancer staging because nodal metastasis is the most powerful predictive factor for recurrence. On the other hand, morbidity, such as lymphedema and shoulder dysfunction, may occur. Sentinel node biopsy is a good way to avoid unnecessary axillary dissection. We used tin colloid as a carrier of Tc99m tracer together with the blue dye method. The detection rate of the sentinel node was 27 cases out of 29 (90%) for the blue dye method, 10 cases out of 19 (53%) for the RI method, and 27 out of 33 (82%) for the combined method. The detection rate of the RI method was improved after adding the subcutaneous injection over the tumor from 45% before adding the subcutaneous injection to 82% after adding it. The false negative rate was 11% for the blue dye method, 0% for the RI method, and 10% for the combined method. This yields a sensitivity of 89% for the blue dye method, 100% for the RI method, and 90% for the combined method. Specificity was 100% for all three methods. Accuracy was 96% for the blue dye method, 100% for the RI method, and 96% for the combined method. There were two false negative cases. The average number of sentinel lymph nodes was 2.12 for the dye method, 1.66 for the RI method, and 1.95 for the combined method. There were three of 49 cases with identified parasternal lymph nodes by RI imaging. Lymphatic mapping using tin colloid may be useful for detecting sentinel nodes.