Enhanced electronic transport properties of Te roll-like nanostructures.

In this work, the electronic transport properties of Te roll-like nanostructures were investigated in a broad temperature range by fabricating single-nanostructure back-gated field-effect-transistors via photolithography. These one-dimensional nanostructures, with a unique roll-like morphology, were produced by a facile synthesis and extensively studied by scanning and transmission electron microscopy. The nanostructures are made of pure and crystalline Tellurium with trigonal structure (t-Te), and exhibit p-type conductivity with enhanced field-effect hole mobility between 273 cm2/Vs at 320 K and 881 cm2/Vs at 5 K. The thermal ionization of shallow acceptors, with small ionization energy between 2 and 4 meV, leads to free-hole conduction at high temperatures. The free-hole mobility follows a negative power-law temperature behavior, with an exponent between -1.28 and -1.42, indicating strong phonon scattering in this temperature range. At lower temperatures, the electronic conduction is dominated by nearest-neighbor hopping (NNH) conduction in the acceptor band, with a small activation energy E NNH ≈ 0.6 meV and an acceptor concentration of N A ≈ 1 × 1016 cm-3. These results demonstrate the enhanced electrical properties of these nanostructures, with a small disorder, and superior quality for nanodevice applications.

Photodegradation of Si-doped GaAs nanowire.

Researching optical effects in nanowires may require a high pump intensity which under ambient conditions can degrade nanowires due to thermal oxidation. In this work we investigated the photodegradation of a single Si-doped GaAs nanowire by laser heating in air. To understand the changes that occurred on the nanowire we carried out Raman spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, and photoluminescence spectroscopy in laser damaged regions as well as in non-affected ones. From Raman Stokes and anti-Stokes measurements we estimated the local temperature that the oxidation process of the nanowire (NW) surface starts at as 661 K, resulting in two new Raman modes at 200 cm-1 and 259 cm-1. Scanning electron microscopy and energy dispersive X-ray spectroscopy measurements showed a significant loss of arsenic in the oxidized regions, but no erosion of the nanowire. Micro-photoluminescence measurements showed the near-band-edge emission of GaAs along the nanowire, as well as a new emission band at 755 nm corresponding to polycrystalline ß-Ga2O3 formation. Our results also indicate that neither amorphous As nor crystalline As were deposited on the surface of the nanowire. Combining different experimental techniques, this study showed the formation of polycrystalline ß-Ga2O3 by oxidation of the nanowire surface and the limits for performing spectroscopic investigations on individual GaAs NWs under ambient air conditions.

[Adverse effects of cotrimoxazole in Spanish patients with AIDS and pneumonia caused by Pneumocystis carinii]. / Efectos indeseables del cotrimoxazol en pacientes españoles con SIDA y neumonía por Pneumocystis carinii.

We retrospectively analyze the untoward effects due to cotrimoxazole (CMX) when this drug was used as initial therapy in 37 Spanish AIDS patients with Pneumocystis carinii pneumonia (PCP). A total of 46% of patients developed an adverse reaction, that was considered severe in 24.3% of cases, and prompted to stop CMX therapy in 10.8% of patients. The most frequent untoward effects were low white blood cells count (29.7%), skin rash (16.2%) and low platelet count (13.5%). The overall compliance and absence of undesirable effects to CMX seen in our patients, together with the well established clinical efficacy of this drug, allow us to recommend the use of CMX as initial therapy for Spanish AIDS patients with PCP.

Metastases from carcinoma of mammary gland: an autopsy study.

Information on metastases from carcinoma of the mammary gland in an autopsy study of 707 cases occurring in white women over a 15-year period are presented and tabulated. Multiple primary cancers occurred in 19% of the cases. Of the 137 cases that exhibit more than one neoplastic malignancy, 31 (23%) were present in the contralateral mammary gland. Seventy patients had no metastasis from the mammary cancer at the time of death, and 55 of these patients had another cancer. Additional information has been added concerning the frequency of metastasis in parathyroid and thymus. When a parathyroid contains a metastasis, extensive metastases were noted in many organs and thus represents a late stage of the cancer.