Modeling with graded interfaces: Tool for understanding and designing record-high power and efficiency mid-infrared quantum cascade lasers.

By employing a graded-interfaces model based on a generalized formalism for interface-roughness (IFR) scattering that was modified for mid-infrared emitting quantum cascade lasers (QCLs), we have accurately reproduced the electro-optical characteristics of published record-performance 4.9 µm- and 8.3 µm-emitting QCLs.

Terahertz difference-frequency-generation quantum cascade lasers on silicon with wire grid current injectors.

We propose the concept and experimentally verify the operation of terahertz quantum cascade laser sources based on intra-cavity Cherenkov difference-frequency generation on a silicon substrate with the current injection layer configured as a metal wire grid. Such a current injector configuration enables high transmission of TM-polarized terahertz radiation into the silicon substrate while simultaneously providing a low-resistivity metal contact for current injection.

Model-based robustness and bistability analysis for methylation-based, epigenetic memory systems.

In recent years, epigenetic memory systems have been developed based on DNA methylation and positive feedback systems. Achieving a robust design for these systems is generally a challenging and multifactorial task. We developed and validated a novel mathematical model to describe methylation-based epigenetic memory systems that capture switching dynamics of methylation levels and methyltransferase amounts induced by different inputs.

Beam stability of buried-heterostructure quantum cascade lasers employing HVPE regrowth.

Measurements of beam stability for mid-infrared (IR)-emitting quantum cascade lasers (QCLs) are important for applications that require the beam to travel through air to remote targets, such as free-space communication links. We report beam-quality measurement results of narrow-ridge, 4.6 µm-emitting buried-heterostructure (BH) QCLs fabricated using ICP etching and HVPE regrowth.

Measurements of the Thermal Resistivity of InAlAs, InGaAs, and InAlAs/InGaAs Superlattices.

Thermal management efforts in nanoscale devices must consider both the thermal properties of the constituent materials and the interfaces connecting them. It is currently unclear whether alloy/alloy semiconductor superlattices such as InAlAs/InGaAs have lower thermal conductivities than their constituent alloys. We report measurements of the crossplane thermal resistivity of InAlAs/InGaAs superlattices at room temperature, showing that the superlattice resistivities are larger by a factor of 1.

86% internal differential efficiency from 8 to 9 µm-emitting, step-taper active-region quantum cascade lasers.

8.4 μm-emitting quantum cascade lasers (QCLs) have been designed to have, right from threshold, both carrier-leakage suppression and miniband-like carrier extraction. The slope-efficiency characteristic temperature T, the signature of carrier-leakage suppression, is found to be 665 K.

Pulmonary drug delivery: from generating aerosols to overcoming biological barriers-therapeutic possibilities and technological challenges.

Research in pulmonary drug delivery has focused mainly on new particle or device technologies to improve the aerosol generation and pulmonary deposition of inhaled drugs. Although substantial progress has been made in this respect, no significant advances have been made that would lead pulmonary drug delivery beyond the treatment of some respiratory diseases. One main reason for this stagnation is the still very scarce knowledge about the fate of inhaled drug or carrier particles after deposition in the lungs.

Mucus as a barrier to lipophilic drugs.

Mucus is a complex hydrogel, comprising glycoproteins, lipids, salts, DNA, enzymes and cellular debris, covering many epithelial surfaces in the human body. Once secreted, mucin forms a barrier to protect the underlying tissues against the extracellular environment. Mucus can therefore adversely affect the absorption or action of drugs administered by the oral, pulmonary, vaginal, nasal or other routes.

Optical tweezers reveal relationship between microstructure and nanoparticle penetration of pulmonary mucus.

In this study, the mobility of nanoparticles in mucus and similar hydrogels as model systems was assessed to elucidate the link between microscopic diffusion behavior and macroscopic penetration of such gels. Differences in particle adhesion to mucus components were strongly dependent on particle coating. Particles coated with 2 kDa PEG exhibited a decreased adhesion to mucus components, whereas chitosan strongly increased the adhesion.

The interplay of lung surfactant proteins and lipids assimilates the macrophage clearance of nanoparticles.

The peripheral lungs are a potential entrance portal for nanoparticles into the human body due to their large surface area. The fact that nanoparticles can be deposited in the alveolar region of the lungs is of interest for pulmonary drug delivery strategies and is of equal importance for toxicological considerations. Therefore, a detailed understanding of nanoparticle interaction with the structures of this largest and most sensitive part of the lungs is important for both nanomedicine and nanotoxicology.

Mucociliary clearance of micro- and nanoparticles is independent of size, shape and charge--an ex vivo and in silico approach.

The fate of inhaled particles after deposition onto the pulmonary mucosa is far from being solved, in particular with respect to mucociliary clearance and mucus penetration. Due to the fact that these phenomena govern pulmonary residence time and thus bioavailability, they are highly relevant for any kind of controlled release formulation delivered via that route. This study applies ex vivo and in silico approaches to investigate the dependency of muciliary clearance of micro-, submicrometer and nanoparticles on size, shape, charge and surface chemistry of such particles.

Uptake of nanoparticles by alveolar macrophages is triggered by surfactant protein A.

Unlabelled: Understanding the bio-nano interactions in the lungs upon the inhalation of nanoparticles is a major challenge in both pulmonary nanomedicine and nanotoxicology. To investigate the effect of pulmonary surfactant protein A (SP-A) on the interaction between nanoparticles and alveolar macrophages, we used magnetite nanoparticles (110-180 nm in diameter) coated with different polymers (starch, carboxymethyldextran, chitosan, poly-maleic-oleic acid, phosphatidylcholine). Cellular binding and uptake of nanoparticles by alveolar macrophages was increased for nanoparticles treated with SP-A, whereas albumin, the prevailing protein in plasma, led to a significant decrease.

Dry powder aerosols of polyethylenimine (PEI)-based gene vectors mediate efficient gene delivery to the lung.

Aerosol gene delivery holds great therapeutical potential for many inherited and acquired pulmonary diseases. The physical instability of aqueous suspensions of non-viral vector complexes is a major limitation for their successful application. In this study, we investigated dry powder aerosols as novel gene vector formulations for gene transfer in vitro and murine lungs in vivo.

Facet-embedded thin-film III-V edge-emitting lasers integrated with SU-8 waveguides on silicon.

A thin-film InGaAs/GaAs edge-emitting single-quantum-well laser has been integrated with a tapered multimode SU-8 waveguide onto an Si substrate. The SU-8 waveguide is passively aligned to the laser using mask-based photolithography, mimicking electrical interconnection in Si complementary metal-oxide semiconductor, and overlaps one facet of the thin-film laser for coupling power from the laser to the waveguide. Injected threshold current densities of 260A/cm(2) are measured with the reduced reflectivity of the embedded laser facet while improving single mode coupling efficiency, which is theoretically simulated to be 77%.

Low-threshold thin-film III-V lasers bonded to silicon with front and back side defined features.

A III-V thin-film single-quantum-well edge-emitting laser is patterned on both sides of the epitaxial layer and bonded to silicon. Injected threshold current densities of 420 A/cm(2) for gain-guided lasers with bottom p-stripes and top n-stripes and 244 A/cm(2) for index-guided bottom p-ridge and top n-stripe lasers are measured with a lasing wavelength of approximately 995 nm. These threshold current densities, among the lowest for thin-film edge-emitting lasers on silicon reported to date (to our knowledge), enable the implementation of integrated applications such as power-efficient portable chip-scale photonic sensing systems.

Decreased collagen type I/III ratio in patients with recurring hernia after implantation of alloplastic prostheses.

Background: Abnormal collagen metabolism is suspected to play an important role in the pathogenesis of recurring inguinal and incisional hernias. Whereas alloplastic prostheses are nowadays routinely used, the quantity and quality of collagen formation after repair in humans has not been analysed in a large cohort.

Method: Seventy-eight prostheses (Prolene, Atrium, Marlex, Vypro, Mersilene, Gore-Tex) implanted for inguinal and incisional hernia repair were explanted because of recurrence, chronic pain or infection.

Adenosine deaminase complexing protein (ADCP) expression and metastatic potential in prostatic adenocarcinomas.

The expression of the adenosine deaminase complexing protein (ADCP) was investigated by immunohistochemistry in the normal and hyperplastic human prostate, in 30 prostatic adenocarcinomas, and in seven human prostatic adenocarcinoma cell lines grown as xenografts in athymic nude mice. In the normal and hyperplastic prostate, ADCP was localized exclusively in the apical membrane and the apical cytoplasm of the glandular epithelial cells. In prostatic adenocarcinomas, four distinct ADCP expression patterns were observed: diffuse cytoplasmic, membranous, both cytoplasmic and membranous, and no ADCP expression.