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The BioCD is a spinning biochip that uses quadrature laser interferometry to detect captured protein on the disc surface. We describe the detection limits of protein binding on this optical biosensor. The fundamental metrology limit is 1 picometer for a single 100-micron diameter spot. Under assay conditions for prostate specific antigen, we can detect 25 pg/ml at 10 assays per disc.
Molecular interferometric imaging (MI2) is a label-free optical biosensor that combines common-path interferometry with shot-noise limited characteristics of a CCD array detector to detect protein binding to surfaces. In the metrology limit, it has achieved roughness-limited surface height resolution of 15 pm per 0.4 micron pixel, corresponding to a scaling mass sensitivity of 7 fg/mm, and a molecular resolution of about 15 IgG molecules per pixel. We have applied MI2 to detect cytokine interleukin-5 at a concentration detection limit of 50 pg/mL with a sandwich immunoassay. Real-time binding assays with MI2 enable the study of reaction kinetics, with a scaling mass sensitivity of 2 pg/mm under 7x magnification. Real-time MI2 measurements of anti-rabbit IgG against rabbit IgG were compared with results from surface plasmon resonance, with identical association rate constants at 5x103 M-1sec-1.
The mean skin-friction drag in a wall-bounded turbulent flow can be decomposed into different physics-informed contributions based on the mean and statistical turbulence quantities across the wall layer. Following Renard & Deck’s study (J. Fluid Mech., vol. 790, 2016, pp. 339–367) on the skin-friction drag decomposition of incompressible wall-bounded turbulence, we extend their method to a compressible form and use it to investigate the effect of density and viscosity variations on skin-friction drag generation, using direct numerical simulation data of compressible turbulent channel flows. We use this novel decomposition to study the skin-friction contributions associated with the molecular viscous dissipation and the turbulent kinetic energy production and we investigate their dependence on Reynolds and Mach number. We show that, upon application of the compressibility transformation of Trettel & Larsson (Phys. Fluids, vol. 28, 2016, 026102), the skin-friction drag contributions can be only partially transformed into the equivalent incompressible ones, as additional terms appear representing deviations from the incompressible counterpart. Nevertheless, these additional contributions are found to be negligible at sufficiently large equivalent Reynolds number and low Mach number. Moreover, we derive an exact relationship between the wall heat flux coefficient and the skin-friction drag coefficient, which allows us to relate the wall heat flux to the skin-friction generation process.
In this work, we investigate misfit dislocations in PbTe/PbSe heteroepitaxial systems using the concurrent atomistic–continuum (CAC) method. A potential model containing the long-range Coulombic interaction and short-range Buckingham potential is developed for the system. By considering the minimum potential energy of relaxed interface structures for various initial conditions and PbTe layer thicknesses, the equilibrium structure of misfit dislocations and the dislocation spacings in PbTe/PbSe(001) heteroepitaxial thin films are obtained as a function of the PbTe layer thicknesses grown on a PbSe substrate. The critical layer thickness above which misfit dislocations inevitably form, the structure of the misfit dislocations at the interfaces, and the dependence of average dislocation spacing on PbTe layer thickness are obtained and discussed. The simulation results provide an explanation for the narrowing of the spread of the distribution of misfit dislocation spacing as layer thickness increases in PbTe/PbSe(001) heteroepitaxy.
Controlling microscopic morphology of energetic materials is of significant interest for the improvement of their performance and production consistency. As an important insensitive high explosive material, triaminotrinitrobenzene (TATB) has attracted tremendous research effort for military grade explosives and propellants. In this study, a new, rapid and inexpensive synthesis method for monodispersed TATB microparticles based on micelle-confined precipitation was developed. Surfactant with proper hydrophilic-lipophilic balance value was found to be critical to the success of this synthesis. The morphology of the TATB microparticles can be tuned between quasi-spherical and faceted by controlling the speed of recrystallization.
Morphological control of energetic materials (EM) is highly desired because ill-defined morphology arising from variations in processing method and supplier make it impossible to reproducibly engineer their physicochemical properties. As the most powerful, non nuclear energetic material to date, 2,4,6,8,10,12-hexanitro -2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) has been the subject of significant interest for improved applications in military grade explosives. Here we report a new method for recrystallization of CL-20 from irregular bulk EMs using a surfactant assisted self-assembly process to produce uniform spherical micron-sized particles. Detailed electron microscopy studies indicate that surfactant plays a critical role in controlling CL-20 morphology. Combined X-ray diffraction and Raman spectroscopy results reveal that the resultant spherical CL-20 particles exhibit an orthorhombic β-phase crystal structure. This material is expected to display enhanced functional reproducibility due to its monodisperse nature as well as decreased shock sensitivity due to their sub-micron particle size.
We recently developed a vacuum assisted micelle confinement synthesis for spherical microparticles of CL-20 with outstanding monodispersity. These microparticles are promising energetic material for explosive devices with enhanced and predictable performances. In this work, to facilitate further development and application of this synthesis, the particle growth process was monitored by in-situ dynamic light scattering measurements. The result was interpreted by a finite element model to obtain critical parameters. These parameters were then used to predict the behavior and product quality of batch synthesis under various operation conditions.
Cell membrane fatty acids influence fundamental properties of the plasma membrane, including membrane fluidity, protein functionality, and lipid raft signalling. Evidence suggests that dietary n-3 PUFA may target the plasma membrane of immune cells by altering plasma membrane lipid dynamics, thereby regulating the attenuation of immune cell activation and suppression of inflammation. As lipid-based immunotherapy might be a promising new clinical strategy for the treatment of inflammatory disorders, we conducted in vitro and in vivo experiments to examine the effects of n-3 PUFA on CD4+ T cell membrane order, mitochondrial bioenergetics and lymphoproliferation. n-3 PUFA were incorporated into human primary CD4+ T cells phospholipids in vitro in a dose-dependent manner, resulting in a reduction in whole cell membrane order, oxidative phosphorylation and proliferation. At higher doses, n-3 PUFA induced unique phase separation in T cell-derived giant plasma membrane vesicles. Similarly, in a short-term human pilot study, supplementation of fish oil (4 g n-3 PUFA/d) for 6 weeks in healthy subjects significantly elevated EPA (20 : 5n-3) levels in CD4+ T cell membrane phospholipids, and reduced membrane lipid order. These results demonstrate that the dynamic reshaping of human CD4+ T cell plasma membrane organisation by n-3 PUFA may modulate down-stream clonal expansion.
This paper uses the ideodynamic model to assess the impact of persuasive messages on candidate preference in the 1992 presidential election. The methodology is based on approaches common to the natural sciences. These approaches suggested that opinion predictions are most robust when they explicitly omit such factors as opinion poli values, incumbency, and economic performance. Instead, the only persuasive messages used to predict opinion came from 3,394 stories from the Major Paper library of the NEXIS electronic data base scored by computer for news favorable and unfavorable to George Bush, Bill Clinton, and Ross Perot. The scores were used in the equations of ideodynamics to compute media share time trends that predicted 55 public opinion polls with R2 of 0.84 and 0.79 for Clinton and Perot, respectively. These high R2 values together with the significance of the model's parameters suggested that the news media comprised the dominant influence on candidate preference. Campaign stories were also scored for coverage of different issues, and this coverage was related to good and bad news for the candidates.
The discovery of many cool brown dwarfs similar to Gliese 229B has led to the definition of a new spectral class, the T dwarfs, whose 1–2.5 μm spectra exhibit signatures of CH4 absorption. Two classification schemes have been proposed for these objects by Burgasser et al. and Geballe et al. We discuss and compare these schemes, and describe a joint classification scheme currently in development that closely follows the guidelines of the MK process. We also address future work toward establishing gravity classes, classifying at other wavelengths, and identifying those features that may signify the end of the T spectral class.
Phase identification of multi-phase materials provides essential information relating the material to its mechanical properties. In this study we selected DP980, a type of dual-phase steel, to investigate the content of martensite and ferrite grains. A combination of advanced techniques was used to provide detailed and precise information of the microstructure. Scanning and transmission electron microscopy were used to provide observations of the sample surface at different scales. Martensite and ferrite phases of DP980 were further identified and characterized using electron backscatter diffraction and scanning probe microscopy. Results obtained with nanoindentation tests confirmed that the differences in nanohardness values in single-phase grains are martensite and ferrite with different surface heights shown by scanning probe microscopy. The similarity shown in the image quality map and scanning probe microscopy proves that a large fraction of martensite can be distinguished in this undeformed material using image quality parameters obtained during electron backscatter diffraction imaging.
The existence of black holes with masses of about one billion solar masses in quasars at redshifts z > 6 presents significant challenges to theories of the formation and growth of black holes and the black hole/galaxy co-evolution in the early Universe. Here we report a recent discovery of an ultra-luminous quasar at redshift z = 6.30, which has an observed optical and near-infrared luminosity a few times greater than those of previously known z > 6 quasars. With near-infrared spectroscopy, we obtain a black hole mass of about 12 billion solar masses, which is well consistent with the mass derived by assuming an Eddington-limited accretion. This ultra-luminous quasar with at z > 6 provides a unique laboratory to the study of the mass assembly and galaxy formation around the most massive black holes at cosmic dawn. It raises further challenges to the black hole/galaxy co-evolution in the epoch of cosmic reionization because the black hole needs to grow much faster than the host galaxy.
Metastatic tumors can spread via release of circulating tumor cells (CTCs) into the bloodstream. Early detection of these CTCs could greatly improve cancer survival rates by enabling diagnosis, and therefore treatment, before secondary tumors arise. However, tumor cells are typically present in very low concentrations, making them difficult to detect in a fluid dominated by red blood cells (RBCs), leukocytes and serum proteins. Separation of CTCs from blood plasma, leukocytes and RBCs is predicted to improve cell capture via antibody-based methods and reduce interference in capture/detection assays. Previously, members of our team have demonstrated microfluidic, size-based separation of blood components, but have yet to integrate this sorting capability with an affinity-based detection technology. To this end, we have developed a microfluidic platform to separate CTCs from mouse blood and detect them using grating coupled surface plasmon resonance (GCSPR). We have implemented a size-based sorting array, which separates objects based upon their diameter, within a microfluidic channel. Separation of beads (2 μm, 6 μm, 10 μm) has been demonstrated, as well as separation of white blood cells and CTCs from blood. The resulting stream of large blood cells (including CTCs) is then directed onto an integrated SPR grating for affinity based capture and detection. Using GCSPR vs. conventional SPR enables detection of multiple cell types across the grating in an array-based format. We have demonstrated differential capture and detection of cells on GCSPR gratings following size-based separation of blood. Using capture antibodies specific to unique CTC surface proteins enables identification of cell types and may provide prognostic capability, beyond the diagnostic capacity of this system.