High-speed low-resolution ADCs are widely used for various applications, such as 60GHz receivers, serial links, and high-density disk drive systems. Flash architectures have the highest conversion rate without employing time interleaving. Moreover, flash architectures have the lowest latency, which is often required in feedback-loop systems. However, the area and power consumption are exponentially increased by increasing the resolution since the number of comparators must be 2 N . A folding architecture is a well-known technique to reduce the number of comparators in an ADC while maintaining high sampling rate and low latency [1,2]. Folding architectures were previously realized by generating a number of zero crossings with folding amplifiers. However, the conventional folding amplifiers consume a large amount of power to realize a fast response. In contrast, a folding ADC with only dynamic power consumption and without using amplifiers is reported in [3]. However, only a folding factor of 2 is realized, and therefore the number of comparators is reduced by half.
We report on a photoluminescence study of the X-electron resonance in a GaAs (3.4 nm)/AlAs (5.1 nm) type-II superlattice embedded in an $n\ensuremath{-}i\ensuremath{-}n$ structure. We have measured the photoluminescence spectra of the type-II exciton consisting of the first ${X}_{z} {(X}_{z}1)$ electron and the $\ensuremath{\Gamma}1$ heavy hole, which are confined in the AlAs and GaAs layers, respectively, as a function of an applied bias (electric field). We find that the electric-field dependence of the type-II photoluminescence intensity reflects various X-electron resonances such as ${X}_{z}1\ensuremath{-}{X}_{\mathrm{xy}}1,$ ${X}_{z}1\ensuremath{-}{X}_{z}2,$ and optical-phonon-assisted ${X}_{z}1\ensuremath{-}{X}_{\mathrm{xy}}1.$ The resonance conditions are discussed from the X-electron energies calculated in the framework of an effective-mass approximation taking account of lattice-mismatch strain and electric-field effects. In addition, it is demonstrated from the photocurrent--bias-voltage characteristics that the X-electron resonance improves the carrier sweep-out through the superlattice.
We report on the time-resolved study of the coherent coupled oscillation of excitonic quantum beats and GaAs-like longitudinal optical (LO) phonons in GaAs∕AlAs multiple quantum wells. The time-domain signals in GaAs∕AlAs multiple quantum wells observed by using a reflection-type pump-probe technique show the coherent coupled oscillation with fast dephasing time and the long-lived coherent GaAs-like LO phonon oscillation. Under the condition that the splitting energy of the heavy-hole and light-hole excitons is close to the energy of the GaAs-like LO phonon, the dependence of the coupled oscillation frequency on the splitting energy exhibits an anticrossing behavior. We discuss the dispersion relation of the coupled oscillation from the viewpoint of the linear coupling of the excitonic quantum beat and the GaAs-like LO phonon through the longitudinal polarization.
We present the strain-induced effects of the InxAl1−xAs-GaAs strained-layer superlattices grown by molecular beam epitaxy. The evaluation of the effects of biaxial strain in the planes perpendicular to the [001] superlattice direction was made by conventional photoluminescence measurements. The observed optical transition energies were evaluated by a Kronig-Penny model involving strain-induced band structure. Comparison between the observed transition energies and the calculated energies suggests that the optical transition of strained-layer superlattices is explained by the band-gap shift and the valence-band splitting, which are induced by the biaxial strain.
Vectors based on human adenovirus serotype 5 (HAdV-5) continue to show promise as delivery vehicles for cancer gene therapy. Nevertheless, it has become clear that therapeutic benefit is directly linked to tumor-specific vector localization, highlighting the need for tumor-targeted gene delivery. Aberrant glycosylation of cell surface glycoproteins and glycolipids is a central feature of malignant transformation, and tumor-associated glycoforms are recognized as cancer biomarkers. On this basis, we hypothesized that cancer-specific cell-surface glycans could be the basis of a novel paradigm in HAdV-5-based vector targeting.As a first step toward this goal, we constructed a novel HAdV-5 vector encoding a unique chimeric fiber protein that contains the tandem carbohydrate binding domains of the fiber protein of the NADC-1 strain of porcine adenovirus type 4 (PAdV-4). This glycan-targeted vector displays augmented CAR-independent gene transfer in cells with low CAR expression. Further, we show that gene transfer is markedly decreased in cells with genetic glycosylation defects and by inhibitors of glycosylation in normal cells.These data provide the initial proof-of-concept for HAdV-5 vector-mediated gene delivery based on the presence of cell-surface carbohydrates. Further development of this new targeting paradigm could provide targeted gene delivery based on vector recognition of disease-specific glycan biomarkers.
We have investigated the characteristics of multi-photon absorption (MPA) in a β-Ga2O3 single crystal at room temperature using the photoluminescence (PL) of the self-trapped exciton (STE) as a probe. From analysis of the excitation fluence dependence of the integrated STE-PL intensities at various excitation photon energies, we clearly confirmed the occurrence of two-, three-, four-, and five-photon absorption processes. The optical transition energies in the four- and five-photon absorption processes are almost consistent with the transition energies between lower-lying valence bands and the conduction-band bottom at the Γ point and those at critical points away from the Γ point, which are taken from previously reported first-principles calculations, respectively.
A 20-year-old woman with IgA nephropathy was admitted to Jikei University Hospital for the treatment of rapid deterioration of renal function after receiving 131I-therapy against hyperthyroidism on October 23, 1999, and hemodialysis was started. On admission, she was diagnosed as having Evans' syndrome in addition to known Graves' disease. Renal biopsy revealed end-stage renal damage, then, hemodialysis was maintained. Treatment for Evans' syndrome was also started and her general condition gradually improved. The present case implied that "Graves' disease" and "Evans' syndrome" could represent some of the manifestations of an underlying immunological disorder in the patient.(Internal Medicine 40: 1004-1010, 2001)
