Raman scattering in a two-dimensional electron gas: Boltzmann equation approach

The inelastic light scattering in a 2-d electron gas is studied theoretically using the Boltzmann equation techniques. Electron-hole excitations produce the Raman spectrum essentially different from the one predicted for the 3-d case. In the clean limit it has the form of a strong non-symmetric resonance due to the square root singularity at the electron-hole frequency $\omega = vk$ while in the opposite dirty limit the usual Lorentzian shape of the cross section is reestablished. The effects of electromagnetic field are considered self-consistently and the contribution from collective plasmon modes is found. It is shown that unlike 3-d metals where plasmon excitations are unobservable (because of very large required transfered frequencies), the two-dimensional electron system gives rise to a low-frequency ($\omega \propto k^{1/2}$) plasmon peak. A measurement of the width of this peak can provide data on the magnitude of the electron scattering rate.Comment: 4 pages, 3 figures. to appear in Phys. Rev. B 59 (1999

Inelastic light scattering and the excited states of many-electron quantum dots

A consistent calculation of resonant inelastic (Raman) scattering amplitudes for relatively large quantum dots, which takes account of valence-band mixing, discrete character of the spectrum in intermediate and final states, and interference effects, is presented. Raman peaks in charge and spin channels are compared with multipole strengths and with the density of energy levels in final states. A qualitative comparison with the available experimental results is given.Comment: 5 pages, accepted in J. Phys.: Condens. Matte

First Principles Calculation of Anomalous Hall Conductivity in Ferromagnetic bcc Fe

We perform a first principles calculation of the anomalous Hall effect in ferromagnetic bcc Fe. Our theory identifies an intrinsic contribution to the anomalous Hall conductivity and relates it to the k-space Berry phase of occupied Bloch states. The theory is able to account for both dc and magneto-optical Hall conductivities with no adjustable parameters.Comment: 4 pages, 6 figures, author list correcte

Smart subtitles for vocabulary learning

Language learners often use subtitled videos to help them learn. However, standard subtitles are geared more towards comprehension than vocabulary learning, as translations are nonliteral and are provided only for phrases, not vocabulary. This paper presents Smart Subtitles, which are interactive subtitles tailored towards vocabulary learning. Smart Subtitles can be automatically generated from common video sources such as subtitled DVDs. They provide features such as vocabulary definitions on hover, and dialog-based video navigation. In our pilot study with intermediate learners studying Chinese, participants correctly defined over twice as many new words in a post-viewing vocabulary test when they used Smart Subtitles, compared to dual Chinese-English subtitles. Learners spent the same amount of time watching clips with each tool, and enjoyed viewing videos with Smart Subtitles as much as with dual subtitles. Learners understood videos equally well using either tool, as indicated by self-assessments and independent evaluations of their summaries

Semiquantitative theory of electronic Raman scattering from medium-size quantum dots

A consistent semiquantitative theoretical analysis of electronic Raman scattering from many-electron quantum dots under resonance excitation conditions has been performed. The theory is based on random-phase-approximation-like wave functions, with the Coulomb interactions treated exactly, and hole valence-band mixing accounted for within the Kohn-Luttinger Hamiltonian framework. The widths of intermediate and final states in the scattering process, although treated phenomenologically, play a significant role in the calculations, particularly for well above band gap excitation. The calculated polarized and unpolarized Raman spectra reveal a great complexity of features and details when the incident light energy is swept from below, through, and above the quantum dot band gap. Incoming and outgoing resonances dramatically modify the Raman intensities of the single particle, charge density, and spin density excitations. The theoretical results are presented in detail and discussed with regard to experimental observations.Comment: Submitted to Phys. Rev.

Cholestatic hepatitis as a possible new side-effect of oxycodone: a case report

<p>Abstract</p> <p>Introduction</p> <p>Oxycodone is a widely-used semisynthetic opioid analgesic that has been used for over eighty years. Oxycodone is known to cause side effects such as nausea, pruritus, dizziness, constipation and somnolence. As far as we are aware cholestatic hepatitis as a result of oxycodone use has not been reported so far in the world literature.</p> <p>Case presentation</p> <p>A 34-year-old male presented with cholestatic jaundice and severe pruritus after receiving oxycodone for analgesia post-T11 vertebrectomy. Extensive laboratory investigations and imaging studies did not reveal any other obvious cause for his jaundice and a liver biopsy confirmed canalicular cholestatis suggestive of drug-induced hepatotoxicity. The patient's symptoms and transaminases normalised on withdrawal of oxycodone confirming that oxycodone was the probable cause of the patient's hepatotoxicity.</p> <p>Conclusion</p> <p>We conclude that cholestatic hepatitis is possibly a rare side effect of oxycodone use. Physicians should be aware of the possibility of this potentially serious picture of drug-induced hepatotoxicity.</p

Submucosal Tunnel Endoscopic Resection of Gastric Lesion Before Obesity Surgery: a Case Series

Background: Submucosal tumors (SMTs) of the gastrointestinal tract are a rare pathological entity comprising a wide variety of neoplastic and non-neoplastic lesions. Even if most SMTs are benign tumors (e.g., leiomyomas), a smaller portion may have a malignant potential (e.g., gastrointestinal stromal tumor (GIST)). Preoperative diagnosis of SMT in bariatric patients may arise challenging clinical dilemmas. Long-term surveillance may be difficult after bariatric surgery. Moreover, according to SMT location, its presence may interfere with planned surgery. Submucosal tunneling endoscopic resection (STER) has emerged as an effective approach for minimally invasive en bloc excision of SMTs. This is the first case series of STER for SMTs before bariatric surgery. Methods: Seven female patients underwent STER for removal of SMTs before bariatric surgery. All lesions were incidentally diagnosed at preoperative endoscopy. STER procedural steps comprised mucosal incision, submucosal tunneling, lesion enucleation, and closure of mucosal defect. Results: En bloc removal of SMT was achieved in all cases. Mean procedural time was of 45 min (SD 18.6). No adverse event occurred. Mean size of the lesions was 20.6 mm (SD 5.8). Histological diagnoses were 5 leyomiomas, 1 lipoma, and 1 low grade GIST. Bariatric procedure was performed after a mean period of 4.1 months (SD 1.6) from endoscopic resection. Conclusion: STER is a safe and effective treatment for the management of SMT even in bariatric patients awaiting surgery. Preoperative endoscopic resection of SMTs has the advantages of reducing the need for surveillance and removing lesions that could interfere with planned surgery. STER did not altered accomplishment of bariatric procedures