Particle characterization using THz spectroscopy

THz extinction spectroscopy extends UV-Vis and NIR-spectroscopy to characterize particles from fine powders and dust to sand, grains and granulated materials. We extract particle sizes from the spectral position of the first peak of the interference structure and size distributions from the visibility of the fine ripple structure in the measured extinction spectra. As such, we can demonstrate a route for a quick determination of these parameters from single measurements.Comment: 6 pages, 6 figure

Granular Structure Determined by Terahertz Scattering

Light-scattering in the terahertz region is demonstrated for granular matter. A quantum-cascade laser is used in a benchtop setup to determine the angle-dependent scattering of spherical grains as well as coffee powder and sugar grains. For the interpretation of the form factors for the scattering from single particles one has to go beyond the usual Rayleigh-Gans-Debye theory and apply calculations within Mie theory. In addition to single scattering also collective correlations can be identified and extracted as a static structure factor.Comment: 7 pages, 12 figure

Dense fluidized granular media in microgravity

Handling and transport of granular media are inevitably governed by the settling of particles. Settling into a dense state is one of the defining characteristics of granular media, among dissipation and absence of thermal agitation. Hence, settling complicates the adaptation of microscopic theories from atomic, molecular, or colloidal media to granular media. It is desirable to provide experiments in which selectively one of the granular characteristics is tuned to test suitable adaptation of a theory. Here we show that gas fluidization of granular media in microgravity is a suitable approach to achieve steady states closer to thermally agitated systems free of settling. We use diffusing-wave spectroscopy to compare the spatial homogeneity and the microscopic dynamics of gas-fluidized granular media on the ground and in drop tower flights with increasing packing densities up to full arrest. The gas fluidization on the ground leads to inhomogeneous states as known from fluidized beds, and partial arrest occurs at packing fractions lower than the full arrested packing. The granular medium in microgravity in contrast attains a homogeneous state with complete mobilization even close to full arrest. Fluidized granular media thus can be studied in microgravity with dynamics and packing fractions not achievable on the ground

Enhanced granular medium-based tube press hardening

Active and passive control strategies of internal pressure for hot forming of tubes and profiles with granular media are described. Force transmission and plastic deformation of granular medium is experimentally investigated. Friction between tube, granular medium and die as also the external stress field are shown to be essential for the process understanding. Wrinkling, thinning and insufficient forming of the tube establishes the process window for the active pressure process. By improving the punch geometry and controlling tribological conditions, the process limits are extended. Examples for the passive pressure process reveal new opportunities for hot forming of tubes and profiles.Comment: 4 pages, 11 figure

Hypoxic modulation of exogenous nitrite-induced vasodilation in humans

Peer reviewedPublisher PD

Развитие чирлидинга в городе Таганроге

Современное общество, высочайшие темпы его развития предъявляют все новые, более высокие требования к человеку и его здоровью. В последние годы наблюдается значительное ухудшение здоровья молодежи. В молодежном обществе пока еще медленно вырабатывается «мода» на здоровье, культура здорового поведения. Физическое воспитание студентов проводится на протяжении всего обучения в вузе и осуществляется в многообразных формах, которые взаимосвязаны, дополняют друг друга и представляют собой единый процесс учебно-воспитательной работы

Self-assembly of gold nanoparticles at the oil-vapor interface: from mono- to multilayers

Alkylthiol-coated gold nanoparticles spontaneously segregate from dispersion in toluene to the toluene-vapor interface. We show that surface tension drops during segregation with a rate that depends on particle concentration. Mono- and multilayers of particles form depending on particle concentration, time, and temperature. X-ray reflectometry indicates fast monolayer formation and slow multilayer formation. A model that combines diffusion-limited segregation driven by surface energy and heterogeneous agglomeration driven by dispersive van der Waals particle interactions is proposed to describe film formation

Analysis of Granular Packing Structure by Scattering of THz Radiation

Scattering methods are widespread used to characterize the structure and constituents of matter on small length scales. This motivates this introductory text on identifying prospective approaches to scattering-based methods for granular media. A survey to light scattering by particles and particle ensembles is given. It is elaborated why the established scattering methods using X-rays and visible light cannot in general be transferred to granular media. Spectroscopic measurements using Terahertz radiation are highlighted as they to probe the scattering properties of granular media, which are sensitive to the packing structure. Experimental details to optimize spectrometer for measurements on granular media are discussed. We perform transmission measurements on static and agitated granular media using Fourier-transform spectroscopy at the THz beamline of the BessyII storage ring. The measurements demonstrate the potential to evaluate degrees of order in the media and to track transient structural states in agitated bulk granular media.Comment: 12 Pages, 9 Figures, 56 Reference

A PBMC-Based System to Assess Human T Cell Responses to Influenza Vaccine Candidates In Vitro

Vaccine development is an expensive and time-consuming process that heavily relies on animal models. Yet, vaccine candidates that have previously succeeded in animal experiments often fail in clinical trials questioning the predictive value of animal models. Alternative assay systems that can add to the screening and evaluation of functional characteristics of vaccines in a human context before embarking on costly clinical trials are therefore urgently needed. In this study, we have established an in vitro system consisting of long-term cultures of unfractionated peripheral blood mononuclear cells (PBMCs) from healthy volunteers to assess (recall) T cell responses to vaccine candidates. We observed that different types of influenza vaccines (whole inactivated virus (WIV), split, and peptide vaccines) were all able to stimulate CD4 and CD8 T cell responses but to different extents in line with their reported in vivo properties. In-depth analyses of different T cell subsets revealed that the tested vaccines evoked mainly recall responses as indicated by the fact that the vast majority of the responding T cells had a memory phenotype. Furthermore, we observed vaccine-induced activation of T follicular helper cells, which are associated with the induction of humoral immune responses. Our results demonstrate the suitability of the established PBMC-based system for the in vitro evaluation of memory T cell responses to vaccines and the comparison of vaccine candidates in a human immune cell context. As such, it can help to bridge the gap between animal experiments and clinical trials and assist in the selection of promising vaccine candidates, at least for recall antigens