Small excitonic complexes in a disk-shaped quantum dot

Confined excitonic complexes in two dimensions, consisting of N_e electrons and N_h holes, are studied by means of Bethe-Goldstone equations. Systems with up to twelve pairs, and asymmetric configurations with N_e \ne N_h are considered. The weak confinement regime gives indication of weak binding or even unbinding in the triexciton and the four-exciton system, and binding in the higher complexes.Comment: 13 pages, 4 figures, submitted to Physica

Duty, Responsibility, and Pride

Case Vignette: Graduate Student Teaching Assignments. Sally Student, a doctoral candidate in experimental psychology, has spent much of the summer preparing to teach an undergraduate course in experimental psychology, scheduled for the upcoming fall semester. Approximately 1 week before the semester begins, she receives a call from the department chair, who asks whether Sally could teach another course instead. The chair explains that a new faculty member has elected to teach Experimental Psychology but that she may teach the other course that is available, Clinical Psychology, an area in which Sally has little experience or training. Sally explains to the chair that she has spent some time preparing for the experimental course and that the clinical course would require additional preparation, as it is not within her field of study. The chair responds that flexibility is a part of academic life and reminds Sally that she must teach at least one course per semester to retain her funding within the graduate department. Discussion Questions. What course of action should Sally take? What are her responsibilities in accepting a teaching assignment? How might graduate students\u27 multiple responsibilities conflict? What are the department chair\u27s considerations in assigning a course? How might the department chair\u27s duties to Sally, the new faculty member, and Sally\u27s students conflict? What are the new faculty member’s rights regarding course selection? Can this dilemma be resolved equitably for all

Radiation effect of fractal sierpinski square patch antenna

Biological tissue interaction with Electromagnetic fields became one of the interesting studies in the last years. Wide variety wireless electronic devices are emerged in day to day life each providing a wireless connection for a certain service such as Global Positioning System, broadcasting systems, mobile communication systems, and networking. In this research article, Fractal Sierpinski Square Patch Antenna is proposed and simulated to operate over L1 frequency range of 1.575 GHz for GPS applications using CST studio Suite where the proposed antenna has been investigated on Carpet shaped substrate made of Arlon 250 AD lossy. The dielectric constant equals to 2.5 and thickness of 1.6 mm. Thickness of patch is 0.6 mm. Also, the electromagnetic fields absorption on the human fingers is investigated where SAR levels are calculated for 0th, 1st, 2nd and 3rd iteration of the Fractal Sierpinski Square Patch Antenna. The results reported that the SAR limit of human finger tissue is enhanced with increasing the number of iteration

Time-resolved spectroscopy of multi-excitonic decay in an InAs quantum dot

The multi-excitonic decay process in a single InAs quantum dot is studied through high-resolution time-resolved spectroscopy. A cascaded emission sequence involving three spectral lines is seen that is described well over a wide range of pump powers by a simple model. The measured biexcitonic decay rate is about 1.5 times the single-exciton decay rate. This ratio suggests the presence of selection rules, as well as a significant effect of the Coulomb interaction on the biexcitonic wavefunction.Comment: one typo fixe

Coulomb matrix elements of bilayers of confined charge carriers with arbitrary spatial separation

We describe a practical procedure to calculate the Coulomb matrix elements of 2D spatially separated and confined charge carriers, which are needed for detailed theoretical descriptions of important condensed matter finite systems. We derive an analytical expression, for arbitrary separations, in terms of a single infinite series and apply a u-type Levin transform in order to accelerate the resulting infinite series. This procedure has proven to be efficient and accurate. Direct consequences concerning the functional dependence of the matrix elements on the separation distance, transition amplitudes and the diagonalization of a single electron-hole pair in vertically stacked parabolic quantum dots are presented.Comment: 8 page

Few-Particle Effects in Semiconductor Quantum Dots: Observation of Multi-Charged-Excitons

We investigate experimentally and theoretically few-particle effects in the optical spectra of single quantum dots (QDs). Photo-depletion of the QD together with the slow hopping transport of impurity-bound electrons back to the QD are employed to efficiently control the number of electrons present in the QD. By investigating structurally identical QDs, we show that the spectral evolutions observed can be attributed to intrinsic, multi-particle-related effects, as opposed to extrinsic QD-impurity environment-related interactions. From our theoretical calculations we identify the distinct transitions related to excitons and excitons charged with up to five additional electrons, as well as neutral and charged biexcitons.Comment: 4 pages, 4 figures, revtex. Accepted for publication in Physical Review Letter

Polarization-Correlated Photon Pairs from a Single Quantum Dot

Polarization correlation in a linear basis, but not entanglement, is observed between the biexciton and single-exciton photons emitted by a single InAs quantum dot in a two-photon cascade. The results are well described quantitatively by a probabilistic model that includes two decay paths for a biexciton through a non-degenerate pair of one-exciton states, with the polarization of the emitted photons depending on the decay path. The results show that spin non-degeneracy due to quantum-dot asymmetry is a significant obstacle to the realization of an entangled-photon generation device.Comment: 4 pages, 4 figures, revised discussio

Method Improving Reading Comprehension In Primary Education Program Students

Abstract This study aims to determine the influence of reading comprehension skills of English for PGSD students through the application of SQ3R learning method. The type of this research is Pre-Experimental research because it is not yet a real experiment, there are external variables that influence the formation of a dependent variable, this is because there is no control variable and the sample is not chosen randomly. The research design is used is onegroup pretest-post-test design involving one group that is an experimental group. In this design, the observation is done twice before and after the experiment. Observations made before the experiment (O1) are called pretests and the post-experimental observation (O2) is called posttest. The difference between O1 and O2 ie O2 - O1 is the effect of the treatment. The results showed that there was an improvement in reading comprehension skills of PGSD students in Class M.4.3 using SQ3R method, and better SQ3R enabling SQ3R to improve English comprehension skills. Keywords: reading comprehension skills, application of SQ3R metho

Braving difficult choices alone: children's and adolescents' medical decision making.

OBJECTIVE: What role should minors play in making medical decisions? The authors examined children's and adolescents' desire to be involved in serious medical decisions and the emotional consequences associated with them. METHODS: Sixty-three children and 76 adolescents were presented with a cover story about a difficult medical choice. Participants were tested in one of four conditions: (1) own informed choice; (2) informed parents' choice to amputate; (3) informed parents' choice to continue a treatment; and (4) uninformed parents' choice to amputate. In a questionnaire, participants were asked about their choices, preference for autonomy, confidence, and emotional reactions when faced with a difficult hypothetical medical choice. RESULTS: Children and adolescents made different choices and participants, especially adolescents, preferred to make the difficult choice themselves, rather than having a parent make it. Children expressed fewer negative emotions than adolescents. Providing information about the alternatives did not affect participants' responses. CONCLUSIONS: Minors, especially adolescents, want to be responsible for their own medical decisions, even when the choice is a difficult one. For the adolescents, results suggest that the decision to be made, instead of the agent making the decision, is the main element influencing their emotional responses and decision confidence. For children, results suggest that they might be less able than adolescents to project how they would feel. The results, overall, draw attention to the need to further investigate how we can better involve minors in the medical decision-making process