Photon Splitting in a Strong Magnetic Field: Recalculation and Comparison With Previous Calculations

We recalculate the amplitude for photon splitting in a strong magnetic field below the pair production threshold, using the worldline path integral variant of the Bern--Kosower formalism. Numerical comparison (using programs that we have made available for public access on the Internet) shows that the results of the recalculation are identical to the earlier calculations of Adler and later of Stoneham, and to the recent recalculation by Baier, Milstein, and Shaisultanov.Comment: Revtex, 9 pages, no figure

Bistable states of quantum dot array junctions for high-density memory

We demonstrate that two-dimensional (2D) arrays of coupled quantum dots (QDs) with six-fold degenerate p orbitals can display bistable states, suitable for application in high-density memory device with low power consumption. Due to the inter-dot coupling of $p_x$ and $p_y$ orbitals in these QD arrays, two dimensional conduction bands can be formed in the x-y plane, while the $p_z$ orbitals remain localized in the x-y plane such that the inter-dot coupling between them can be neglected. We model such systems by taking into account the on-site repulsive interactions between electrons in $p_z$ orbitals and the coupling of the localized $p_z$ orbitals with the 2D conduction bands formed by $p_x$ and $p_y$ orbitals. The Green's function method within an extended Anderson model is used to calculate the tunneling current through the QDs. We find that bistable tunneling current can exist for such systems due to the interplay of the on-site Coulomb interactions (U) between the $p_z$ orbitals and the delocalized nature of conduction band states derived from the hybridization of $p_x$ / $p_y$ orbitals. This bistable current is not sensitive to the detailed band structure of the two dimensional band, but depends critically on the strength of $U$ and the ratio of the left and right tunneling rates. The behavior of the electrical bistability can be sustained when the 2D QD array reduces to a one-dimensional QD array, indicating the feasibility for high-density packing of these bistable nanoscale structures

Measuring Charge Transport in an Amorphous Semiconductor Using Charge Sensing

We measure charge transport in hydrogenated amorphous silicon (a-Si:H) using a nanometer scale silicon MOSFET as a charge sensor. This charge detection technique makes possible the measurement of extremely large resistances. At high temperatures, where the a-Si:H resistance is not too large, the charge detection measurement agrees with a direct measurement of current. The device geometry allows us to probe both the field effect and dispersive transport in the a-Si:H using charge sensing and to extract the density of states near the Fermi energy.Comment: 4 pages, 4 figure

A rare case of low-grade myofibroblastic sarcoma of the femur in a 38-year-old woman: a case report

<p>Abstract</p> <p>Introduction</p> <p>Primary myofibroblastic sarcoma of the bone is a rare spindle cell tumour with, to the best of our knowledge, only eight cases reported in the available English language literature. The disease's rarity and its low-grade features make an accurate diagnosis difficult in most cases. The differential diagnoses of this unusual tumour include various benign entities as well as other sarcomas. Due to the difference in prognosis, a precise pathologic diagnosis is essential, which requires a combination of thorough morphologic examination, immunohistochemistry and electron microscopy wherever available.</p> <p>Case presentation</p> <p>We report the case of a 38-year-old Indian woman with a lytic lesion in her left femur. The tumour was associated with cortical destruction and soft tissue extension. A biopsy from the soft tissue component showed features suggestive of a low-grade malignant mesenchymal tumour. Excision of the tumour was performed and histopathological examination showed a low-grade spindle cell sarcoma with collagenous stroma. Expressions of vimentin and smooth muscle actin were also noted. Ultrastructural examination confirmed its myofibroblastic nature. A final diagnosis of low-grade myofibroblastic sarcoma of the left femur was thus rendered.</p> <p>Conclusion</p> <p>Low-grade myofibroblastic sarcoma is one of the rarer osseous spindle cell sarcomas depicting a favourable prognosis in the cases reported so far. Its diagnosis requires ancillary techniques like immunohistochemistry and electron microscopy. To the best of our knowledge, we report the ninth case in the literature and the first case from our subcontinent.</p

Photon Splitting in a Very Strong Magnetic Field

Photon splitting in a very strong magnetic field is analyzed for energy $\omega < 2m$. The amplitude obtained on the base of operator-diagram technique is used. It is shown that in a magnetic field much higher than critical one the splitting amplitude is independent on the field. Our calculation is in a good agreement with previous results of Adler and in a strong contradiction with recent paper of Mentzel et al.Comment: 5 pages,Revtex , 4 figure