Deformation of Delone dynamical systems and pure point diffraction

This paper deals with certain dynamical systems built from point sets and, more generally, measures on locally compact Abelian groups. These systems arise in the study of quasicrystals and aperiodic order, and important subclasses of them exhibit pure point diffraction spectra. We discuss the relevant framework and recall fundamental results and examples. In particular, we show that pure point diffraction is stable under ``equivariant'' local perturbations and discuss various examples,including deformed model sets. A key step in the proof of stability consists in transforming the problem into a question on factors of dynamical systems.Comment: 25 pages; revised version with minor corrections, an extended summary of the topic, and further reference

Decompactification of space or time in large N QCD_2

QCD_2 with fundamental quarks on a cylinder is solved to leading order in the 1/N expansion, including the zero mode gluons. As a result of the non-perturbative dynamics of these gauge degrees of freedom, the compact space-time direction gets effectively decompactified. In a thermodynamic interpretation, this implies that there is no pressure of order N and that the chiral condensate of order N is temperature independent. These findings are consistent with confinement of quarks, rule out both chiral and deconfining phase transitions in the finite temperature 't Hooft model, and help to resolve some controversial issues in the literatureComment: Latex2e, 8 pages, no figur

Dynamical versus diffraction spectrum for structures with finite local complexity

It is well-known that the dynamical spectrum of an ergodic measure dynamical system is related to the diffraction measure of a typical element of the system. This situation includes ergodic subshifts from symbolic dynamics as well as ergodic Delone dynamical systems, both via suitable embeddings. The connection is rather well understood when the spectrum is pure point, where the two spectral notions are essentially equivalent. In general, however, the dynamical spectrum is richer. Here, we consider (uniquely) ergodic systems of finite local complexity and establish the equivalence of the dynamical spectrum with a collection of diffraction spectra of the system and certain factors. This equivalence gives access to the dynamical spectrum via these diffraction spectra. It is particularly useful as the diffraction spectra are often simpler to determine and, in many cases, only very few of them need to be calculated.Comment: 27 pages; some minor revisions and improvement

Characterizations of model sets by dynamical systems

It is shown how regular model sets can be characterized in terms of regularity properties of their associated dynamical systems. The proof proceeds in two steps. First, we characterize regular model sets in terms of a certain map $\beta$ and then relate the properties of $\beta$ to ones of the underlying dynamical system. As a by-product, we can show that regular model sets are, in a suitable sense, as close to periodic sets as possible among repetitive aperiodic sets.Comment: 41 pages, revised versio

Comparison of Immediate vs. Delayed Recall of Orthodontic Information Following an Electronic Reminder

Patients and parents in dentistry often do not remember important information disclosed during the informed consent process, so improvement in the delivery of information is needed. This study explored the effect of an emailed narrated instructional PowerPoint on the immediate vs. delayed recall and comprehension of informed consent information in orthodontics. Thirty-two subjects were recruited from a university and private practice orthodontic clinic. At the initial visit, subjects were alternately assigned to one of two groups and were presented with a mock orthodontic treatment plan and informed consent presentation for a pretend patient. Immediately following the presentation, the subjects’ verbal recall and comprehension of information required for informed consent was assessed. Within 24 hours, subjects in the treatment group were emailed an informational PowerPoint video reinforcing information about the treatment plan and risks and benefits of treatment, while the remaining participants did not receive additional information. A week after the initial meeting, all subjects were contacted by phone and the assessment they received at the initial visit was readministered. A statistically significant interaction was found between the effects of the PowerPoint and the time of patient recall. Those subjects who received the PowerPoint video were more likely to recall and comprehend the treatment plan and informed consent information seven days following the initial visit than did participants who had not received the adjunct material. Additionally, for the subjects who received the PowerPoint, there was a statistically significant improvement in recall and comprehension of the factors that would increase orthodontic treatment time beyond the original estimate. All subjects within the study recalled and comprehended that orthodontic treatment results are not guaranteed for life. Few studies have examined the retention of informed consent material in orthodontics beyond the initial visit, and the present results are consistent with the need for improvement of this process. With the use of an emailed home informational video reviewing treatment plan and informed consent information, delayed recall and comprehension in orthodontics can be improved. By improving the parent’s recall and comprehension, a higher quality of care can be delivered in orthodontics

Characterization of spectral response of a quantum dots-in-a-well infrared focal plane array

Spectral characterization of a novel single bump, two-color InAs/InGaAs quantum dots-in-a-well (DWELL) infrared focal plane array (FPA) was undertaken and reported here. The hypothesis of the study is that the FPA will exhibit bias-tunable spectral response. Broadband and two-color performance measures of the DWELL FPA are discussed and presented. The DWELL structure is a hybrid of a quantum dot (QD) photodetector consisting of an active region composed of InAs quantum dots embedded in InGaAs quantum wells. The DWELL FPA demonstrates mid-wave infrared (MWIR) and long-wave infrared (LWIR) performance believed to be attributed to transitions from bound states in the dot to higher and lower lying energy states in the quantum well, respectively. The DWELL samples were grown by molecular beam epitaxy (MBE) and fabricated into 320 x 256 focal plane arrays with indium bumps via standard lithography at the University of New Mexico (UNM). The samples were hybridized to Indigo Systems Corporation ISC9705 read out integrated circuits and investigated with a SE-IR Corporation CamIRa\u2122 test system. The DWELL FPA exhibited temporal noise equivalent difference in temperature (NEDT) values of 43mK and 63mK (MWIR and LWIR respectively) at 77K