Controlling Exciton-Phonon Interactions via Electromagnetically Induced Transparency.

Highly excited Rydberg states of excitons in Cu_{2}O semiconductors provide a promising approach to explore and control strong particle interactions in a solid-state environment. A major obstacle has been the substantial absorption background that stems from exciton-phonon coupling and lies under the Rydberg excitation spectrum, weakening the effects of exciton interactions. Here, we demonstrate that two-photon excitation of Rydberg excitons under conditions of electromagnetically induced transparency (EIT) can be used to control this background. Based on a microscopic theory that describes the known single-photon absorption spectrum, we analyze the conditions under which two-photon EIT permits separating the optical Rydberg excitation from the phonon-induced absorption background, and even suppressing it entir7ely. Our findings thereby pave the way for the exploitation of Rydberg blockade with Cu_{2}O excitons in nonlinear optics and other applications.

Rydberg Excitons in the Presence of an Ultralow-Density Electron-Hole Plasma.

We study the Rydberg exciton absorption of Cu_{2}O in the presence of free carriers injected by above-band-gap illumination. Already at plasma densities ρ_{EH} below one hundredth electron-hole pair per µm^{3}, exciton lines are bleached, starting from the highest observed principal quantum number, while their energies remain constant. Simultaneously, the band gap decreases by correlation effects with the plasma. An exciton line loses oscillator strength when the band gap approaches its energy, vanishing completely at the crossing point. Adapting a plasma-physics description, we describe the observations by an effective Bohr radius that increases with rising plasma density, reflecting the Coulomb interaction screening by the plasma.

Signatures of Quantum Coherences in Rydberg Excitons.

Coherent optical control of individual particles has been demonstrated both for atoms and semiconductor quantum dots. Here we demonstrate the emergence of quantum coherent effects in semiconductor Rydberg excitons in bulk Cu_{2}O. Because of the spectral proximity between two adjacent Rydberg exciton states, a single-frequency laser may pump both resonances with little dissipation from the detuning. As a consequence, additional resonances appear in the absorption spectrum that correspond to dressed states consisting of two Rydberg exciton levels coupled to the excitonic vacuum, forming a V-type three-level system, but driven only by one laser light source. We show that the level of pure dephasing in this system is extremely low. These observations are a crucial step towards coherently controlled quantum technologies in a bulk semiconductor.

Optimal squeezing in resonance fluorescence via atomic-state purification.

Squeezing of atomic resonance fluorescence is shown to be optimized by a properly designed environment, which can be realized by a quasiresonant cavity. Optimal squeezing is achieved if the atomic coherence is maximized, corresponding to a pure atomic quantum state. The atomic-state purification is achieved by the backaction of the cavity field on the atom, which increases the atomic coherence and decreases the atomic excitation. For realistic cavities, the coupling of the atom to the cavity field yields a purity of the atomic state of more than 99%. The fragility of squeezing against dephasing is substantially reduced in this scenario, which may be important for various applications.

Entanglement in atomic resonance fluorescence.

The resonance fluorescence from regular atomic systems is shown to represent a continuous source of non-gaussian entangled radiation propagating in two different directions. For a single atom entanglement occurs under the same conditions as squeezing. For more atoms, the entanglement can be more robust against dephasing than squeezing, hence providing a useful continuous source for various applications of entangled radiation.

Comparison of caloric intake and weight outcomes of an ad lib feeding regimen for preterm infants in two nurseries.

BACKGROUND: Effects on caloric intake and weight gain of an ad libitum (ad lib) feeding regimen for preterm infants may be specific to a special care nursery. OBJECTIVE: To explore across two nurseries the similarity of effect on caloric intake and weight gain of an ad lib feeding regimen compared with a prescribed regimen and the similarity of effect of caloric intake on weight gain. METHODS: All infants participating in the multi-site randomized clinical trial (RCT) of the ad lib feeding regimen were <35 weeks gestational age at birth and had birth weight appropriate for gestational age. Data on caloric intake and weight gain were collected at two nurseries (A, n=22; B, n=78) with the same feeding regimen protocols. Two strategies were used to explore similarity of regimen effect on caloric intake and weight gain. Repeated measures analysis of variance (ANOVA) was used to examine the effect on caloric intake and weight gain of time, feeding regimen, and time-by-regimen interaction for each nursery. RESULTS: In both nurseries, regimen effects were reasonably consistent for caloric intake and weight gain. Caloric intake was lower across nurseries for infants fed ad lib. After accounting for caloric intake, the ad lib regimen did not affect weight gain. The time-by-regimen interaction effect on caloric intake was significant in both nurseries. Caloric intake for infants fed ad lib increased significantly over 5 days. CONCLUSIONS: Despite differences between nurseries in infant characteristics and in protocol implementation, the feeding regimen effect was consistent for caloric intake and weight gain. Further support was found for the development of infant self-regulatory capacity.

Model Selection Based on Minimum Description Length.

We introduce the minimum description length (MDL) principle, a general principle for inductive inference based on the idea that regularities (laws) underlying data can always be used to compress data. We introduce the fundamental concept of MDL, called the stochastic complexity, and we show how it can be used for model selection. We briefly compare MDL-based model selection to other approaches and we informally explain why we may expect MDL to give good results in practical applications. Copyright 2000 Academic Press.

Experimental treatment of the laws of heterogeneous catalysis with immobilized yeast cells (Saccharomyces cerevisiae).

A series of simple, low-cost experiments is described in this paper that allows students to be introduced to some basic kinetic laws relating to heterogeneous catalysis. Immobilized yeast cells are used as the example and therefore simultaneously offer the opportunity to acquaint the students with the theoretical and practical background of an important branch of biotechnology.

Contextual dynamics of ethical decision making in the NICU.

The manner in which the contextual dynamics of the neonatal intensive care unit (NICU) culture influence decisions around withholding and withdrawing treatment for very low birth weight infants is examined based on sociological studies of the NICU culture. The influence of these dynamics on nurse and parent participation in treatment decisions is discussed. Steps toward increasing nurses' role in decision making and ability to empower the participation of parents include (a) using an understanding of the dynamics of the individual NICU to establish a collaborative team culture, and (b) demonstrating that data obtained through relationship with the infant make an important and valid contribution to ethical decision making.

Motor organization in very low birth weight infants during caregiving: effects of a developmental intervention.

The purpose of this study was to determine whether an individualized approach to handling very low birth weight (VLBW) infants designed to support development would result in less motor disorganization than the task-oriented approach in traditional use. Using a quasi-experimental crossover design, motor responses were investigated in 38 infants (< or = 1700 g, 53% male, 89% white) observed at 28, 32, and 36 weeks post-conceptional age. Subjects served as their own controls. Motor responses were coded from direct observation and videotapes. Results demonstrated that during developmental handling, (1) the overall amount of movement was less, the number of organized movements was greater, and the number of disorganized movements was less than during traditional handling; and (2) the amount of movement increased over time, but in the traditional condition, it peaked at 32 weeks. Results support positive effects of developmental handling and suggest the potential for reducing the prevalence of minor motor impairments in VLBW infants.

[Postoperative results of stapes revision]. / Postoperative Ergebnisse nach Stapesrevision.

BACKGROUND: In this retrospective study indications, intraoperative findings, reconstruction techniques and postoperative hearing results in revision stapes surgery were evaluated. PATIENTS: Between March 1988 and January 1996, 150 patients underwent stapes revision. Indications for surgery were the presence of conductive hearing loss (132), dizziness (12), sensorineural hearing loss (3), deafness (2), and tinnitus (1). RESULTS: Intraoperative findings were lateral migration of the implant, regrowth of bone in the oval window niche, erosion of incus, cholesteatoma, and others. In most cases a new prosthesis (gold piston) was inserted between incus and vestibulum. In cases with incus erosion, a malleovestibulopexy was performed. Seventy-three percent of patients who underwent revision stapes surgery because of conductive hearing loss showed a hearing improvement of 20 dB or more. All patients who underwent revision stapes surgery because of dizziness reported an improvement of their symptoms postoperatively. CONCLUSIONS: Revision stapes surgery should be approached by experienced surgeons, because the risk of severe sensorineural hearing loss is higher than at the time of primary stapedectomy. Informed consent is mandatory.

Effects of developmental care on behavioral organization in very-low-birth-weight infants.

The purpose of this study was to determine whether modifying care to reduce stressors in the neonatal intensive care unit and support infant development affected physiological, motor, and behavioral state organization. Twenty-one infants weighing less than 1501 g were studied prior to a nursing staff-training program (control) and 24 infants were studied posttraining (study). Nurses were taught to lower environmental stress, reduce procedural stress, and facilitate motor and sleep-wake organization. Oxygen saturation, motor activity, posture, and sleep-wake states were measured biweekly during routine care. Study infants showed higher oxygen saturation levels, fewer disorganized and jerky movements, more flexor movements, more flexed posture, and more alert-wakefulness than controls. Results suggest that this approach to care may have potential to improve behavioral organization during the preterm period.

Outcomes of developmentally supportive nursing care for very low birth weight infants.

Numerous aspects of the intensive care environment are stressful for low birth weight infants and may play a role in adverse developmental and behavioral outcome. The purpose of this study was to determine whether staff education in care protocols designed to make the environment less stressful and thereby support the infant's development would improve short-term outcomes. Twenty-one infants (less than 1,501 gms) were studied during the preeducation period and 24 infants were studied following staff education. The educational program successfully altered nursing care. Experimental infants had more optimal respiratory and feeding status, lower levels of morbidity, shorter hospitalization, and improved behavioral organization.

[ECG during rest as an indicator of vascular changes in diabetic patients]. / Das Ruhe-EKG als Indikator für Gefässveränderungen beim diabetiker.

EKG-findings of 186 non-selected diabetic outpatients and 52 control subjects of the age group of 50 to 79 years have been examined in relation to cardiovascular risk factors as well as to peripheral vascular disease (PVD) and carotid artery stenosis (CS). The Whitehall-Criteria of the Minnesota-Code were seen in diabetics (D) approximately twice as frequently as in non-diabetics (C): Minnesota-Code I: D 7% vs C 4%; IV 27% vs 13%; V 25% vs 15%; VII1 2% vs 0%. Beside higher levels of blood glucose and HbAI, diabetics differed from controls mainly by higher systolic blood pressure (p less than 0.001). Furthermore, they showed more signs of PVD and CS. Only in 27% of diabetics normal EKG-findings were seen. In comparison to age-adjusted diabetics with EKG-abnormalities, these patients showed signs of PVD and CS only to a minor degree and lower values were found for systolic (p less than 0,01) and diastolic (p less than 0.05) blood pressure, weight (p less than 0.05), serum triglycerides (p less than 0.02), and markedly higher values for HDL-cholesterol (p less than 0.01). These data show that in diabetics more frequently abnormal EKG-findings are seen and that a normal EKG in diabetics older than 50 years indicates low cardiovascular morbidity and a favorable risk factor profile.

[The influence of anodizing conditions on the activity of urease immobilized to anodized sheet aluminium (author's transl)]. / Zur Beeinflussung der Aktivität von adsorptiv auf eloxierten Aluminiumblechen immobilisierter Urease durch die Anodisier-Bedingungen.

The activity of urease immobilized by adsorption on anodized sheet aluminium strongly depends on the method chosen for preparation of these carriers. If oxalic acid is applied as electrolyte, only the anodizing temperature significantly influences the activity of the preparations. In case of the well-known GS process, however, the activity is not only affected by the temperature, but also by other conditions of anodizing, for example the current density and the electrolyte concentration. For both methods the correlation between the topography of the carrier surfaces and the activity of enzyme immobilized to the surface is described.