Loss factor and resonant frequency of viscoelastic shear-damped structural composites

Loss factor and resonant frequency of viscoelastic shear damped structural composite

Botulinum Toxin A for the Treatment of Keloids

Introduction: Keloids are the result of excessive scar tissue formation. Besides their poor aesthetic appearance, keloids can be associated with severe clinical symptoms such as pain, itching, and rigidity. Unfortunately, most therapeutic approaches remain clinically unsatisfactory. Recently, injections with botulinum toxin A (BTA) were proposed for the treatment of established keloids in a clinical trial. In this study, we aimed to verify the effects of intralesional BTA for the treatment of therapy-resistant keloids using objective measurements. In addition, the underlying molecular mechanisms were investigated using cultured keloid-derived fibroblasts. Materials and Methods: Four patients received BTA (doses varying from 70 to 140 Speywood units per session) injected directly into their keloids every 2 months for up to 6 months. Differences in height and volume were evaluated clinically and measured with a 3-D optical profiling system. Keloid-derived fibroblasts were treated with different concentrations of BTA, and expression of collagen (COL)1A1, COL1A2, COL3A1, TGF-beta 1, TGF-beta 2, TGF-beta 3, fibronectin-1, laminin-beta 2, and alpha-SMA was determined by real-time quantitative PCR. MTT and BrdU assays were used to analyze the effects of BTA on fibroblast proliferation and metabolism. Results: Intralesional administration of BTA did not result in regression of keloid tissue. No differences in expression of ECM markers, collagen synthesis, or TGF-beta could be observed after BTA treatment of keloid fibroblasts. In addition, cell proliferation and metabolism of keloid fibroblasts was not affected by BTA treatment. Conclusion: The suggested clinical efficiency of intralesional BTA for the therapy of existent keloids could not be confirmed in this study. Based on our data, the potential mechanisms of action of BTA on keloid-derived fibroblasts remain unclear. Copyright (C) 2012 S. Karger AG, Base

Charge-density wave formation in Sr_{14}Cu_{24}O_{41}

The electrodynamic response of the spin-ladder compound Sr$_{14-x}$Ca$_x$Cu$_{24}$O$_{41}$ ($x=0, 3, 9$) has been studied from radiofrequencies up to the infrared. At temperatures below 250 K a pronounced absorption peak appears around 12 cm$^{-1}$ in Sr$_{14}$Cu$_{24}$O$_{41}$ for the radiation polarized along the chains/ladders (${\bf E}\parallel {\bf c}$). In addition a strongly temperature dependent dielectric relaxation is observed in the kHz - MHz range. We explain this behavior by a charge density wave which develops in the ladders sub-system and produces a mode pinned at 12 cm$^{-1}$. With increasing Ca doping the mode shifts up in frequency and eventually disappears for $x=9$ because the dimensionality of the system crosses over from one to two dimensions, giving way to the superconducting ground state under pressure.Comment: One name added to author list 4 pages, 2 figures, email: [email protected]

Sex differences in deleterious mutational effects in Drosophila melanogaster: combining quantitative and population genetic insights

Fitness effects of deleterious mutations can differ between females and males due to: (i) sex differences in the strength of purifying selection; and (ii) sex differences in ploidy. Although sex differences in fitness effects have important broader implications (e.g., for the evolution of sex and lifespan), few studies have quantified their scope. Those that have belong to one of two distinct empirical traditions: (i) quantitative genetics, which focusses on multi-locus genetic variances in each sex, but is largely agnostic about their genetic basis; and (ii) molecular population genetics, which focusses on comparing autosomal and X-linked polymorphism, but is poorly suited for inferring contemporary sex differences. Here, we combine both traditions to present a comprehensive analysis of female and male adult reproductive fitness among 202 outbred, laboratory-adapted, hemiclonal genomes of Drosophila melanogaster. While we find no clear evidence for sex differences in the strength of purifying selection, sex differences in ploidy generate multiple signals of enhanced purifying selection for X-linked loci. These signals are present in quantitative genetic metrics—i.e., a disproportionate contribution of the X to male (but not female) fitness variation—and population genetic metrics—i.e., steeper regressions of an allele’s average fitness effect on its frequency, and proportionally less nonsynonymous polymorphism on the X than autosomes. Fitting our data to models for both sets of metrics, we infer that deleterious alleles are partially recessive. Given the often-large gap between quantitative and population genetic estimates of evolutionary parameters, our study showcases the benefits of combining genomic and fitness data when estimating such parameters

Anisotropic Charge Modulation in Ladder Planes of Sr_14-xCa_xCu_24O_41

The charge response of the ladders in Sr_14-xCa_xCu_24O_41 is characterized by dc resistivity, low frequency dielectric and optical spectroscopy in all three crystallographic directions. The collective charge-density wave screened mode is observed in the direction of the rungs for x=0, 3 and 6, in addition to the mode along the legs. For x=8 and 9, the charge-density-wave response along the rungs fully vanishes, while the one along the legs persists. The transport perpendicular to the planes is always dominated by hopping.Comment: 4 pages, 3 figures, submitted to PRB R

Evidence of anomalous dispersion of the generalized sound velocity in glasses

The dynamic structure factor, S(Q,w), of vitreous silica, has been measured by inelastic X-ray scattering in the exchanged wavevector (Q) region Q=4-16.5 nm-1 and up to energies hw=115 meV in the Stokes side. The unprecedented statistical accuracy in such an extended energy range allows to accurately determine the longitudinal current spectra, and the energies of the vibrational excitations. The simultaneous observation of two excitations in the acoustic region, and the persistence of propagating sound waves up to Q values comparable with the (pseudo-)Brillouin zone edge, allow to observe a positive dispersion in the generalized sound velocity that, around Q=5 nm-1, varies from 6500 to 9000 m/s: this phenomenon was never experimentally observed in a glass.Comment: 5 pages, 3 figures. To appear in Phys. Rev.

High-Definition Optical Coherence Tomography for the in vivo Detection of Demodex Mites

Background: Demodex mites are involved in different skin diseases and are commonly detected by skin scrape tests or superficial biopsies. A new high-definition optical coherence tomography (HD-OCT) with high lateral and axial resolution in a horizontal (en-face) and vertical (slice) imaging mode might offer the possibility of noninvasive and fast in vivo examination of demodex mites. Methods: Twenty patients with demodex-related skin diseases and 20 age- and gender-matched healthy controls were examined by HD-OCT. Mites per follicle and follicles per field of view were counted and compared to skin scrape tests. Results: HD-OCT images depicted mites in the en-face mode as bright round dots in groups of 3-5 mites per hair follicle. In the patients with demodex-related disease, a mean number of 3.4 mites per follicle were detected with a mean number of 2.9 infested follicles per area of view compared to a mean of 0.6 mites in 0.4 infested follicles in the controls. The skin scrape tests were negative in 21% of the patients. Conclusion: The innovative HD-OCT enables fast and noninvasive in vivo recognition of demodex mites and might become a useful tool in the diagnosis and treatment monitoring of demodex-related skin diseases. Copyright (C) 2012 S. Karger AG, Base

Experimental modelling of evaporation and boiling processes in a two-phase thermosyphon

A model of a closed two-phase thermosyphon was developed to study thermo-physical processes in a thermosyphon thermal condition systems of energy-saturated equipment. This model differs from the known by reasoned choice of thermocouples installation providing sealing the device during operation. In addition, the program VI (Virtual Instrument) was created in graphical environment Labview for registration of the temperatures and pressure in the thermosyphon

Accretion of Warm Chondrules in Weakly Metamorphosed Ordinary Chondrites and Their Subsequent Reprocessing

To better understand chondrite accretion and subsequent processes, the textures, crystallography, deformation, and compositions of some chondrite constituents in ten lithologies of different cluster texture strength were studied in seven weakly metamorphosed (Type 3) and variably shocked ordinary chondrites (Ragland—LL3 S1, Tieschitz—H/L3 S1, NWA 5421—LL3 S2, NWA 5205—LL3 S2, NWA 11905—LL3-5 S3, NWA 5781—LL3 S3, NWA 11351—LL3-6 S4) using optical and electron microscopy and microtomography techniques. Results support a four-stage model for chondrite formation. This includes 1) limited annealing following collisions during chondrule crystallization and rapid cooling in space prior to accretion, as evidenced by olivine microstructures consistent with dislocation recovery and diffusion; 2) initial accretion of still-warm chondrules into aggregates at an effective chondrite accretion temperature of ∼900-950 °C with nearly in situ impingement deformation between adjacent chondrules in strongly clustered lithologies (NWA 5781, Tieschitz, NWA 5421, NWA 5205 Lithology A), as evidenced by intragranular lattice distortions in olivine consistent with high-temperature slip systems, and by evidence that some olivine-rich objects in Tieschitz accreted while partly molten; 3) syn- or post-accretion bleaching of chondrule mesostases, which transferred feldspathic chondrule mesostasis to an interchondrule glass deposit found in strongly clustered lithologies, as evidenced by chemical data and textures; and 4) post-bleaching weak or strong shocks that resulted in destruction of interchondrule glass and some combination of brecciation, foliation of metal and sulfide, and melting and shock-overprinting effects, as evidenced by poor cluster textures and presence of clastic texture, alignment of metal and sulfide grains caused by shock compression, presence of impact-generated glass, and changes in olivine slip systems. The data support the model of Metzler (2012), who suggested that chondrules in ordinary chondrites accreted while still warm to form cluster chondrite textures as a “primary accretionary rock” (our Stage 2), and that subsequent brecciation destroyed this texture to create chondrites with weak cluster texture (our Stage 4)