On the micromechanics of void growth by prismatic-dislocation loop emission

Experimental evidence and recent molecular dynamics simulations of void growth indicate that prismatic dislocation loop emission by externally applied stresses is a viable mechanism of void growth under shock loading conditions when diffusive processes are given no time to operate. In this paper, the process of growth by loop emission is studied in a model system comprised of a void in an infinite linearly elastic and isotropic solid loaded axisymmetrically by remote applied stresses. First, the interaction between applied stresses, the stress field of a single dislocation loop or a pile-up of loops next to the void, the surface energy expenditure on void surface change, and the lattice resistance to the motion of loops is reviewed. The necessary condition for interstitial loop emission is used to determine the equilibrium positions of the loops as well as the maximum number of loops in a pile-up under given applied stresses. For the parameters of the model-material with purely hydrostatic loading, the numerical results yield a volume change for the void, which when normalized by the initial undeformed volume, exhibits a strong dependence on the size of the void for radii less than ∼400 times the lattice Burgers vector. For larger voids, the normalized volume change was found to be independent of the void radius.     

Mode identification of a rotating disk

A modal testing method permitting identification of the natural frequencies, the number of nodal diameters and wave motions in a rotating disk is presented in this paper. This method is applicable at arbitrary rotation speed without requiring a priori information about the vibration modes of the stationary disk. The influence of disk rotation speed on the prediction of mode shapes with this method is shown, and experimental predictions of modal parameters are presented for both axisymmetric and asymmetric disks.     

Obviously Enhanced Fluorescent Signal of Core-Shell Nanostructures through Simultaneous Regulation of Spectral Overlap and Shell Thickness for Imaging and Photothermal Therapy of Ovarian Cancer Cells

In this research, by simultaneously regulating the two major factors affecting the plasmonic enhanced fluorescence (PEF), spectral overlap and the distance between the fluororophores and the noble metal nanoparticles, a significantly enhanced fluorescent signal is achieved. Core-shell nanostructures composed of aspect ratio (AR) adjustable gold nanorods (GNRs) and various thickness of SiO₂ are prepared and the decorated fluorophores are realized optimized PEF. A typical stimuli-responsive conjugated polymer, polydiacetylene (PDA), and a near-infrared (NIR) dye Cy5.5 are selected as fluorophores and their fluorescent signal are enhanced 7.26 and 4.41 times, respectively. Based on the optimized optical properties, a multifunctional antibody modified Mab-Cy5.5-GNRs@SiO₂ is successfully demonstrated the targeting, imaging, and photothermal therapy (PTT) effects on SKOV-3 ovarian cancer cells.     

Quantitative analysis of low-abundance serological proteins with peptide affinity-based enrichment and pseudo-multiple reaction monitoring by hybrid quadrupole time-of-flight mass spectrometry

Multiple reaction monitoring (MRM) is commonly used for the quantitative analysis of proteins during mass pectrometry (MS), and has excellent specificity and sensitivity for an analyte in a complex sample. In this study, a pseudo-MRM method for the quantitative analysis of low-abundance serological proteins was developed using hybrid quadrupole time-of-flight (hybrid Q-TOF) MS and peptide affinity-based enrichment. First, a pseudo-MRM-based analysis using hybrid Q-TOF MS was performed for synthetic peptides selected as targets and spiked into tryptic digests of human serum. By integrating multiple transition signals corresponding to fragment ions in the full scan MS/MS spectrum of a precursor ion of the target peptide, a pseudo-MRM MS analysis of the target peptide showed an increased signal-to-noise (S/N) ratio and sensitivity, as well as an improved reproducibility. The pseudo-MRM method was then used for the quantitative analysis of the tryptic peptides of two low-abundance serological proteins, tissue inhibitor of metalloproteinase 1 (TIMP1) and tissue-type protein tyrosine phosphatase kappa (PTPκ), which were prepared with peptide affinity-based enrichment from human serum. Finally, this method was used to detect femtomolar amounts of target peptides derived from TIMP1 and PTPκ, with good coefficients of variation (CV 2.7% and 9.8%, respectively), using a few microliters of human serum from colorectal cancer patients. The results suggest that pseudo-MRM using hybrid Q-TOF MS, combined with peptide affinity-based enrichment, could become a promising alternative for the quantitative analysis of low-abundance target proteins of interest in complex serum samples that avoids protein depletion.     

Synergetic Evolution of Diketopyrrolopyrrole‐Based Polymeric Semiconductor for High Reproducibility and Performance: Random Copolymerization of Similarly Shaped Building Blocks

A new random copolymer consisting of similarly shaped donor–acceptor building blocks of diketopyrrolopyrrole‐selenophene‐vinylene‐selenophene (DPP‐SVS) and DPP‐thiophene‐vinylene‐thiophene (DPP‐TVT) is designed and synthesized. The resulting P‐DPP‐SVS(5)‐TVT(5) with an equal molecular ratio of the two building blocks produced significantly enhanced solubility when compared to that of the two homopolymers, PDPP‐SVS and PDPP‐TVT. More importantly, despite the maximum segmental randomness of the PDPP‐SVS(5)‐TVT(5) copolymer, its crystalline perfectness and preferential orientation are outstanding, even similar to those of the homopolymers thanks to the similarity of the two building blocks. This unique property produces a high charge carrier mobility of 1.23 cm² V⁻¹ s⁻¹ of PDPP‐SVS(5)‐TVT(5), as determined from polymer field‐effect transistor (PFET) measurements. The high solubility of PDPP‐SVS(5)‐TVT(5) promotes formulation of high‐viscosity solutions which could be successfully processed to fabricate large‐areal PFETs onto hydrophobically treated 4 in. wafers. A total of 269 individual PFETs are fabricated. These devices exhibit extremely narrow device‐to‐device deviations without a single failure and demonstrate an average charge carrier mobility of 0.66 cm² V⁻¹ s⁻¹ with a standard deviation of 0.064. This is the first study to report on successfully realizing large‐areal reproducibility of high‐mobility polymeric semiconductors.

     

Single‐Nanoparticle Collision Events: Tunneling Electron Transfer on a Titanium Dioxide Passivated n‐Silicon Electrode

Single‐nanoparticle collisions were observed on an n‐type silicon electrode (600 μm diameter) passivated by a thin layer of amorphous TiO₂, where the current steps occurred by tunneling electron transfer. The observed collision frequency was in reasonable agreement with that predicted from theory. The isolated electrode, after a collision experiment, with a Pt/TiO₂/n‐Si architecture was shown to retain the photoelectrochemical properties of n‐Si without photocorrosion or current decay. The Pt/TiO₂/n‐Si electrode produced 19 mA cm^?2 of photocurrent density under 100 mW cm^?2 irradiation from a xenon lamp during oxygen evolution without current fading for over 12 h.     

Search for third-generation scalar leptoquarks in pp at square root s=1.96 TeV

We report on a search for charge-1/3 third-generation leptoquarks (LQ) produced in pp collisions at square root s =1.96 TeV using the D0 detector at Fermilab. Third-generation leptoquarks are assumed to be produced in pairs and to decay to a tau neutrino and a b quark with branching fraction B. We place upper limits on sigma(pp --> LQLQ)B2 as a function of the leptoquark mass M(LQ). Assuming B=1, we exclude at the 95% confidence level third-generation scalar leptoquarks with M(LQ)<229 GeV.     

In vivo three-dimensional spectral domain endoscopic optical coherence tomography using a microelectromechanical system mirror

A biopsy is a well-known medical test used to evaluate tissue abnormality. Biopsy specimens are invasively taken from part of a lesion and visualized by microscope after chemical treatment. However, diagnosis by means of biopsy is not only variable due to depth and location of specimen but may also damage the specimen. In addition, only a limited number of specimens can be obtained, thus, the entire tissue morphology cannot be observed. We introduce a three-dimensional (3-D) endoscopic optical biopsy via optical coherence tomography employing a dual-axis microelectromechanical system scanning mirror. Since this technique provides high-resolution, noninvasive, direct, and multiple visualization of tissue, it could function as a clinical biopsy with advanced performance. The device was integrated with a conventional endoscope and utilized to generate in vivo 3-D clinical images in humans and animals.     

Direct time-response measurement of high-speed optical modulators based on stretched-pulse interferometry

A simple technique for the direct measurement of the complex temporal response of a high-speed electro-optic (EO) modulator is proposed. This technique recovers the amplitude and phase temporal profiles of an instantaneous modulation over the duration of a chirped pulse (obtained by linear dispersion) using Fourier-transform interferometry, and it exploits the time-to-frequency mapping induced by the pulse dispersion process. The method can be implemented by using either time- or frequency-domain interferometric detection, allowing the characterization of modulation bandwidths in the tens-of-gigahertz range. The concept is demonstrated by accurately measuring the complex temporal response of a 2.5 Gbps intensity EO modulator.     

Quantification of a three-dimensional velocity vector using spectral-domain Doppler optical coherence tomography

Multiangle, fiber-based, spectral-domain Doppler optical coherence tomography with a phase-resolved algorithm is presented to measure three components of an arbitrary velocity vector. A beam divider that divides a probe beam to have five independent viewpoints and path length delays was designed. The divider was inserted into the sampling arm of a Doppler optical coherence tomography system between the collimator and the first galvo mirror of a two-axis galvo scanner. The divider produced five independent D k's (the average difference between the wave vectors of incoming and outgoing beams) after passing through the focusing lens while keeping two-axis scanning capability. After calibration, an unknown velocity vector field inside a microtube was quantified by solving a three-dimensional minimization problem.