Singularities on charged viscous droplets

We study the evolution of charged droplets of a conducting viscous liquid. The flow is driven by electrostatic repulsion and capillarity. These droplets are known to be linearly unstable when the electric charge is above the Rayleigh critical value. Here we investigate the nonlinear evolution that develops after the linear regime. Using a boundary elements method, we find that a perturbed sphere with critical charge evolves into a fusiform shape with conical tips at time $t_0$, and that the velocity at the tips blows up as $(t_0-t)^\alpha$, with $\alpha$ close to -1/2. In the neighborhood of the singularity, the shape of the surface is self-similar, and the asymptotic angle of the tips is smaller than the opening angle in Taylor cones.Comment: 9 pages, 6 figure

On the Photorefractive Gunn Effect

We present and numerically solve a model of the photorefractive Gunn effect. We find that high field domains can be triggered by phase-locked interference fringes, as it has been recently predicted on the basis of linear stability considerations. Since the Gunn effect is intrinsically nonlinear, we find that such considerations give at best order-of-magnitude estimations of the parameters critical to the photorefractive Gunn effect. The response of the system is much more complex including multiple wave shedding from the injecting contact, wave suppression and chaos with spatial structure.Comment: Revtex, 8 pag., 4 fig. (jpg), submit to Physical Review

Asymptotics of the trap-dominated Gunn effect in p-type Ge

We present an asymptotic analysis of the Gunn effect in a drift-diffusion model---including electric-field-dependent generation-recombination processes---for long samples of strongly compensated p-type Ge at low temperature and under dc voltage bias. During each Gunn oscillation, there are different stages corresponding to the generation, motion and annihilation of solitary waves. Each stage may be described by one evolution equation for only one degree of freedom (the current density), except for the generation of each new wave. The wave generation is a faster process that may be described by solving a semiinfinite canonical problem. As a result of our study we have found that (depending on the boundary condition) one or several solitary waves may be shed during each period of the oscillation. Examples of numerical simulations validating our analysis are included.Comment: Revtex, 25 pag., 5 fig., to appear Physica

Electrically tunable GHz oscillations in doped GaAs-AlAs superlattices

Tunable oscillatory modes of electric-field domains in doped semiconductor superlattices are reported. The experimental investigations demonstrate the realization of tunable, GHz frequencies in GaAs-AlAs superlattices covering the temperature region from 5 to 300 K. The orgin of the tunable oscillatory modes is determined using an analytical and a numerical modeling of the dynamics of domain formation. Three different oscillatory modes are found. Their presence depends on the actual shape of the drift velocity curve, the doping density, the boundary condition, and the length of the superlattice. For most bias regions, the self-sustained oscillations are due to the formation, motion, and recycling of the domain boundary inside the superlattice. For some biases, the strengths of the low and high field domain change periodically in time with the domain boundary being pinned within a few quantum wells. The dependency of the frequency on the coupling leads to the prediction of a new type of tunable GHz oscillator based on semiconductor superlattices.Comment: Tex file (20 pages) and 16 postscript figure

Current-voltage characteristic and stability in resonant-tunneling n-doped semiconductor superlattices

We review the occurrence of electric-field domains in doped superlattices within a discrete drift model. A complete analysis of the construction and stability of stationary field profiles having two domains is carried out. As a consequence, we can provide a simple analytical estimation for the doping density above which stable stable domains occur. This bound may be useful for the design of superlattices exhibiting self-sustained current oscillations. Furthermore we explain why stable domains occur in superlattices in contrast to the usual Gunn diode.Comment: Tex file and 3 postscript figure

Lung Transplantation for Primary Ciliary Dyskinesia and Kartagener Syndrome: A Multicenter Study.

Primary ciliary dyskinesia, with or without situs abnormalities, is a rare lung disease that can lead to an irreversible lung damage that may progress to respiratory failure. Lung transplant can be considered in end-stage disease. This study describes the outcomes of the largest lung transplant population for PCD and for PCD with situs abnormalities, also identified as Kartagener's syndrome. Retrospectively collected data of 36 patients who underwent lung transplantation for PCD from 1995 to 2020 with or without SA as part of the European Society of Thoracic Surgeons Lung Transplantation Working Group on rare diseases. Primary outcomes of interest included survival and freedom from chronic lung allograft dysfunction. Secondary outcomes included primary graft dysfunction within 72 h and the rate of rejection ≥A2 within the first year. Among PCD recipients with and without SA, the mean overall and CLAD-free survival were 5.9 and 5.2 years with no significant differences between groups in terms of time to CLAD (HR: 0.92, 95% CI: 0.27-3.14, p = 0.894) or mortality (HR: 0.45, 95% CI: 0.14-1.43, p = 0.178). Postoperative rates of PGD were comparable between groups; rejection grades ≥A2 on first biopsy or within the first year was more common in patients with SA. This study provides a valuable insight on international practices of lung transplantation in patients with PCD. Lung transplantation is an acceptable treatment option in this population

Exclusion of known gene for enamel development in two Brazilian families with amelogenesis imperfecta

Amelogenesis imperfecta (AI) is a genetically heterogeneous group of diseases that result in defective development of tooth enamel. Mutations in several enamel proteins and proteinases have been associated with AI. The object of this study was to evaluate evidence of etiology for the six major candidate gene loci in two Brazilian families with AI. Genomic DNA was obtained from family members and all exons and exon-intron boundaries of the ENAM, AMBN, AMELX, MMP20, KLK4 and Amelotin gene were amplified and sequenced. Each family was also evaluated for linkage to chromosome regions known to contain genes important in enamel development. The present study indicates that the AI in these two families is not caused by any of the known loci for AI or any of the major candidate genes proposed in the literature. These findings indicate extensive genetic heterogeneity for non-syndromic AI

Patients’ perceived health information needs in inflammatory arthritis: A systematic review

Objectives: To identify the breadth of the literature regarding patients’ perceived health information needs related to inflammatory arthritis care. Methods: A systematic scoping review of MEDLINE, EMBASE, CINAHL and PsycINFO was performed to identify relevant articles (1990 -2016) examining patients’ perceived needs relating to health information in inflammatory arthritis. Data and themes were identified and categorised and risk of bias assessed. Results: Twenty nine studies (11 quantitative, 14 qualitative and 4 mixed methods) from 4121 identified articles were relevant for inclusion. Most focussed on rheumatoid arthritis. Key findings included: (1) Reasons for seeking health information often focussed on gaining ownership over their condition and facilitating self-management. (2) Demographic differences in information needs were inconsistent, but women and younger patients generally reported more needs. (3) Desired information content was broad, and included targeted and practical information covering disease treatment and psychosocial wellbeing. (4) Preferred information delivery method was consultation with a Rheumatologist; however group sessions had advantages for psychosocial issues while written information provided useful supplementation. (5) Barriers to meeting health information needs were around timely access. Conclusions: Patients with inflammatory arthritis have high information needs, desiring practical and individualised information. When developing strategies to meet patients’ information needs, aligning patient expectations with delivery methods that are accessible, cost-effective and flexible may help to optimize patient outcomes