Bulk and surface electronic structure of 1T-TiS2 and 1T-TiSe2

Ab initio band-structure calculations were performed for bulk, single slab, and thin films of TiX2 (X=S, Se) using the localized spherical wave method. According to these calculations, bulk TiS2 and TiSe2 are semimetallic. The calculations show that TiS2 thin films are semiconductors, but thin films of TiSe2 are semimetallic. The indirect gap for single slab TiS2 is about 1.0 eV, and the gap becomes smaller with increasing number of layers. When the number of layers increases to 11, the TiS2 thin films are semimetallic. All but the surface layers are found to be electrically neutral. The density of states as a function of the energy for the surface layer is different from that of the bulk. The Madelung energy of the Ti atoms on the surface is about 0.35 eV lower than that for the Ti atoms in the bulk. The calculations are compared with photoemission spectra, reported in the literature

The electronic structure of the metastable layer compound 1T-CrSe2

The electronic structure of the metastable compound 1T-CrSe2 (a = 3.399 Å, c = 5.911 Å, space group P_3m1) was calculated with and without spin polarization using the LSW method. The energy is 0.29 eV/mol CrSe2 lower for the spin-polarized calculation. The total magnetic moment of +2.44 μB on Cr consists of 3.28 μB in spin-up and 0.84 μB in spin-down states; the total number of 3d electrons on Cr is 4.12, much greater than expected for Cr(IV) 3d2. The Cr 3d-based bands overlap the selenium 4p-based valence band which implies strong covalency of the Cr–Se bonding. At the Fermi level there are electrons and holes with Cr 3d character, and holes with Se 4p character. The results clearly indicate the reduction of the cations and the presence of holes in the Se 4p valence band. CrSe2 is a magnetic metal. Similar calculations for VSe2 showed a very small energy difference between the magnetic and non-magnetic states, indicating that VSe2 is a non-magnetic metal

Pressure and linear heat capacity in the superconducting state of thoriated UBe13

Even well below Tc, the heavy-fermion superconductor (U,Th)Be13 has a large linear term in its specific heat. We show that under uniaxial pressure, the linear heat capacity increases in magnitude by more than a factor of two. The change is reversible and suggests that the linear term is an intrinsic property of the material. In addition, we find no evidence of hysteresis or of latent heat in the low-temperature and low-pressure portion of the phase diagram, showing that all transitions in this region are second order.Comment: 5 pages, 4 figure

Asymptomatic Pulmonary Hypertension in Systemic Lupus Erythematosus

Introduction Pulmonary arterial hypertension (PAH) is a serious and often fatal complication of systemic lupus erythematosus (SLE). Because the diagnosis of PAH often is made years after symptom onset, early diagnostic strategies are essential. Doppler echocardiography currently is considered the noninvasive screening test of choice for evaluating pulmonary hypertension. Aim Screening for asymptomatic pulmonary hypertension in systemic lupus erythematosus patients using Doppler echocardiography, and correlating it with inflammatory parameters of the disease. Patients and Methods Doppler echocardiography was performed in 74 patients with systemic lupus erythematosus over one year (66 adult and 8 juvenile), adult SLE included 57 patients with adult-onset and 9 patients with childhood-onset. Pulmonary hypertension was diagnosed if the peak systolic pressure gradient at the tricuspid valve was more than 30 mmHg. All patients were subjected to full history taking, rheumatological examination, laboratory studies and chest x-ray. Results In seventy four SLE patients, the pulmonary hypertension was detected in 8 patients (10.8%), 7 adult-onset SLE patients (aged from 19 to 30 years) and 1 juvenile SLE (aged 12 years). The range of pulmonary artery systolic pressure was 34–61.2 mmHg (43.19 ± 9.28). No significant differences between patients with and those without pulmonary hypertension as regard clinical features. Significantly higher frequencies of rheumatoid factor and anti-cardiolipin antibodies were found in patients with pulmonary hypertension versus those without ( P = 0.02, P = 0.008 respectively). Positive rheumatoid factor and ACL were significantly associated with occurrence of PAH in SLE ( P = 0.007, P = 0.006 respectively). No significant correlations were found between pulmonary artery pressure, disease duration, SLE Disease Activity Index (SLEDAI), ESR, and anti-ds DNA. Conclusion Patients with SLE have an increased risk of pulmonary arterial hypertension. Echocardiography should be used as a screening tool in patients at high risk for development of pulmonary hypertension. Positive anti-cardiolipin antibodies and rheumatoid factor were significant predictors of pulmonary hypertension in our study

Electronic structure of the half-metallic ferromagnet KCrSe2

The electronic structure of the layered compound KCrSe2 in the ferromagnetic spin arrangement is calculated using the augmented-spherical-wave method. For the minority-spin direction the Fermi level lies in a 1.34-eV-wide gap between the bottom of the Cr 3d ↓ band and the Se 4p ↓ band, while for the majority-spin direction the Fermi level crosses the Cr 3d ↑ bands. This means that KCrSe2 is a half-metallic ferromagnet

Laser irradiation of parylene disks with a 1.06 mumum laser

Parylene disks supported on glass stalks were irradiated with 1.06 $mu$m wavelength laser light pulses focused to flux intensities in the range from 10$sup 15$ to 10$sup 17$ W/cm$sup 2$. According to photodiode measurements the fraction of laser light absorbed, 25 to 50 percent, increased slightly as the laser intensity was increased. However, box calorimeter measurements implied that the fraction absorbed was approximately 30 percent and insensitive to irradiation intensity. Some x-ray spectra are discussed. (MOW