Electronic phase diagram of La1.875_{1.875}Ba0.125−x_{0.125-x}Srx_xCuO4_4

We performed systematic measurements of magnetic susceptibility on single crystals of La$_{1.875}$Ba$_{0.125-x}$Sr$_x$CuO$_4$. The dependence of the superconducting transition temperature on Sr-concentration demonstrates a step-like pattern upon doping at {\it x}$\sim$0.08 as the crystal structure changes from low-temperature tetragonal (LTT) to low-temperature orthorhombic (LTO) phase at low temperature. Upon cooling, an anomalous upturn in the susceptibility was observed at the structural phase transition between the LTT-LTO phases under the magnetic field parallel to {\it c}-axis.Comment: 6 pages, 4 figures, Proceeding paper of the Stripes2000 conference in Roma, Ital

Measurement by FIB on the ISS: Two Emissions of Solar Neutrons Detected?

A new type of solar neutron detector (FIB) was launched onboard the Space Shuttle Endeavour on July 16, 2009, and it began collecting data at the International Space Station (ISS) on August 25, 2009. This paper summarizes the three years of observations obtained by the solar neutron detector FIB until the end of July 2012. The solar neutron detector FIB can determine both the energy and arrival direction of neutrons. We measured the energy spectra of background neutrons over the SAA region and elsewhere, and found the typical trigger rates to be 20 counts/sec and 0.22 counts/sec, respectively. It is possible to identify solar neutrons to within a level of 0.028 counts/sec, provided that directional information is applied. Solar neutrons were observed in association with the M-class solar flares that occurred on March 7 (M3.7) and June 7 (M2.5) of 2011. This marked the first time that neutrons were observed in M-class solar flares. A possible interpretaion of the prodcution process is provided.Comment: 36 pages, 16 figures, and 3 Tables; Advanced in Astronmy, 2012, Special issue on Cosmic Ray Variablity:Century of Its Obseravtion

Structural effect on the static spin and charge correlations in La1.875_{1.875}Ba0.125−x_{0.125-x}Srx_{x}CuO4_{4}

We report the results of elastic neutron scattering measurements performed on 1/8-hole doped La$_{1.875}$Ba$_{0.125-x}$Sr$_{x}$CuO$_{4}$ single crystals with {\it x}=0.05, 0.06, 0.075 and 0.085. In the low-temperature less-orthorhombic (LTLO, {\it Pccn} symmetry) phase, the charge-density-wave (CDW) and spin-density-wave (SDW) wavevectors were found to tilt in a low-symmetric direction with one-dimensional anisotropy in the CuO$_{2}$ plane, while they were aligned along the high-symmetry axis in the low-temperature tetragonal (LTT, {\it P}4$_2$/{\it ncm} symmetry) phase. The coincident direction of two wavevectors suggests a close relation between CDW and SDW orders. The SDW wavevector systematically deviates from the Cu-O bond direction in the LTLO phase upon Sr substitution and the tilt angle in the LTLO phase is smaller than that in the low-temperature orthorhombic phase (LTO, {\it B}{\it mab} symmetry) with comparable in-plane orthorhombic distortion. These results demonstrate a correlation between the corrugated pattern of CuO$_{2}$ plane and the deviations.Comment: 6 pages, 7figure

Solar wind dependence of the electron flux variation at geostationary orbit observed by ETS-V

In this study we have examined the relationship between the energetic electron flux at geostationary orbit and the solar wind speed. We have compared the electron flux ( >0.4MeV) observed by the Engineering Test Satellite V (ETS-V) with solar wind speed measurements in the OMNI data set obtained from the National Space Science Data Center (NSSDC). The tendency has been observed for the logarithm of the electron flux to be proportional to the solar wind speed at solar minimum, but scattered at solar maximum. We have found that during the main and recovery phases of magnetic storms occurring at solar minimum, the logarithm of the electron flux is roughly proportional to the solar wind speed. At solar maximum, however, there is no apparent correlation between both these parameters. Moreover, in quiet periods there is also no observable correlation at both solar minimum and maximum. The dependence of the electron flux at geostationary orbit on the solar wind speed is related to recurrent storms caused by high-speed solar wind streams

Competition between charge/spin-density-wave orders and superconductivity in La1.875_{1.875}Ba0.125−x_{0.125-x}Srx_{x}CuO4_{4}

We have performed a series of elastic neutron scattering measurements on 1/8-hole doped La$_{1.875}$Ba$_{0.125-x}$Sr$_{x}$CuO$_{4}$ single crystals with {\it x} = 0.05, 0.06, 0.075 and 0.085. % Both charge-density-wave (CDW) and spin-density-wave (SDW) orders are found to develop simultaneously below the structural transition temperature between the low-temperature orthorhombic (LTO) and low-temperature tetragonal (LTT) or low-temperature less-orthorhombic (LTLO) phases. % In the ground state the CDW order is observed only in the LTT/LTLO phase and drastically degrades towards the LTO boundary. The {\it x}-dependence of {\it T}$_{c}$ strongly suggests a direct effect of the CDW order on the suppression of superconductivity. % Results are discussed in comparison with those from the La$_{1.6-x}$Nd$_{0.4}$Sr$_{x}$CuO$_{4}$ system within the framework of the stripe model.Comment: 4 pages, 5figure

Diagnosis and management of extrahepatic oesophageal variceal bleed in children in a low resourced setting

Extrahepatic portal vein obstruction (EHPVO) is a major cause of portal hypertension (PH) in children. Portal vein thrombosis (PVT) is the most common cause accounting for up to 75% of cases in developing countries. Upper gastrointestinal bleeding is the most dreaded and commonest presentation of portal hypertension. Successful treatment of paediatric PH, though challenging is performed in resource constraint countries. Cases: Five children presented over three years to a tertiary hospital in Ghana, with massive upper gastrointestinal bleeding. They had anaemia, thrombocytopaenia and four had splenomegaly. Liver function tests, INR, haemoglobin electrophoresis as well as HIV serology, hepatitis B and C screening were all normal. Abdominal doppler ultrasound scan confirmed portal vein thromboses. They were resuscitated and managed with octreotide, propranolol, antibiotics and sclerotherapy or oesophageal variceal banding in the acute setting and long term secondary prophylaxis with propranolol. Subsequently, an algorithm was developed to assist with the management of bleeding from oesophageal varices and the diagnosis of EHPVO. Conclusion: Portal hypertension due to EHPVO is an important cause of upper gastrointestinal (GI) bleeding in children. This can be successfully managed even in a resource constraint setting once the appropriate measures are taken