518 research outputs found
Design Procedures for a Fully Differential Telescopic Cascode Two-Stage CMOS Operational Amplifier
AbstractIn this paper, a fully differential telescopic operational amplifier design is presented which achieve both high dc gain and high unity-gain frequency. Trade-offs among such factors as bandwidth, gain, phase, margin, bias current, signal swing, slew rate, and power are made evidently. The characteristic of this kind of two-stage operational amplifier is investigated theoretically, in this paper. The results indicate that proposed two-stage operational amplifier achieves broader unity bandwidth, increases the DC gain. Simulation results show that, at 5V power supply, the output swing is ±4.3V, settling time is 167.4ns. Based on the two-stage operational amplifier structure, the operational amplifier with 2.5V output common voltage shows a DC gain greater than 87dB, Gain Bandwidth over 39MHz (5pF load) and a phase margin larger than 84° with power dissipation of 3mW. These good results could be used in Σ-△ modulation and A/D conversion etc
Collisional Radiative Model for Xe10+ Ions and the Contribution of Satellite Lines on EUV Spectra
The Analysis of SKP1 Gene Expression in Physiological Male Sterility Induced by Chemical Hybridizing Agent SQ-1 in Wheat (Triticum aestivum L.)
Physiological male sterility induced by the chemical hybridizing agent (CHA) overcomes problems of maintenance of sterile lines and restorers. However, the mechanism of sterility is unclear. The process of tapetum of CHA-treated ‘Xi’nong 2611’ at uninucleate, binucleate and trinucleate were compared with control to determine if tapetum varying differently during developmental stages. Tapetal degradation in CHA-treated ‘Xi’nong 2611’ began at late uninucleate stage, somewhat earlier than control plants. Cytological observations indicated that the gradual degradation of the tapetum in CHA-treated ‘Xi’nong 2611’ was initiated and terminated earlier than in the control. These findings implied that CHA-induced male sterility was related to abnormally early tapetal degradation. In order to indicate the role of the SKP1 gene in fertility/sterility in wheat, its expression was assessed in anthers at uninucleate, binucleate and trinucleate stages. SKP1 expression was reduced in the later developmental stages, and there was an obvious decrease from the uninucleate to trinucleate stages. Higher expression of the SKP1 gene occurred in ‘Xi’nong 2611’ compared to CHA-treated ‘Xi’nong 2611’. This implied that SKP1 gene expression was inhibited during the fertility transformation process and was related to transformation from fertility to sterility. Moreover, the results from this study suggest that SKP1 plays an essential role of conducting fertility in physiological male sterility
Dephasing and Metal-Insulator Transition
The metal-insulator transition (MIT) observed in two-dimensional (2D) systems
is apparently contradictory to the well known scaling theory of localization.
By investigating the conductance of disordered one-dimensional systems with a
finite phase coherence length, we show that by changing the phase coherence
length or the localization length, it is possible to observe the transition
from insulator-like behavior to metal-like behavior, and the transition is a
crossover between the quantum and classical regimes. The resemblance between
our calculated results and the experimental findings of 2D MIT suggests that
the observed metallic phase could be the result of a finite dephasing rate.Comment: 10 figures, to be published in Phys. Rev. B63, Jan. 15, (2000
Modeling Progressive Failure of Bonded Joints Using a Single Joint Finite Element
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90634/1/AIAA-55313-740.pd
Possible Role of Protein CPG15 in Hippocampal Mossy Fiber Sprouting Under Conditions of Pentylenetetrazole Kindling
We examined changes in expression of the candidate plasticity-related gene 15 (CPG15) in
the dentate gyrus (DG) and hippocampal CA3 region in the pentylenetetrazole (PTZ) kindling
model and investigated the role of this gene in the phenomenon of mossy fiber sprouting
(MFS). Experimental rats were divided into the control and PTZ groups. The epileptic model
was created by intraperitoneal PTZ injection, while control rats were injected with saline.
At days 3, 7, 14, 28, and 42 after the first PTZ injection, Timm staining was scored in the
CA3 hippocampal area, and a product of CPG15 (protein CPG15) was labeled in the DG
stratum granulosum and in the CA3 area using immunohistochemistry. The Timm scores in
the CA3 region increased gradually from day 3 and were significantly higher than those in
the control within the subsequent period. The level of CPG15 protein in the DG and CA3
area decreased gradually until day 14 and returned to the normal level at day 28. The results
obtained indicate, for the first time, that CPG15 may be involved in the process of MFS.
Understanding the molecular mechanisms underlying this phenomenon may lead to successful
therapeutic interventions that limit epileptogenesis.Ми досліджували зміни експресії продукту гена CPG15
у зубчастій звивині (ЗЗ) та зоні CA3 гіпокампа в моделі
пентилентетразолового (ПТЗ-) кіндлінгу та можливу роль цього гена у феномені спрутингу моховитих волокон
(СМВ). Піддослідні щури були поділені на групи контролю та ПТЗ-кіндлінгу. Модель епілепсії створювали за допомогою внутрішньоочеревинних ін’єкцій пентилентетразолу
(ПТЗ); контрольним щурам ін’єкували фізіологічний
розчин. На третю, сьому, 14-ту, 28-му та 42-гу добу після
першої ін’єкції ПТЗ оцінювали забарвлення, за Тіммом, у
зоні CA3. Локалізацію протеїну CPG15 у stratum granulosum ЗЗ та зоні CA3 гіпокампа визначали з використанням
імуногістохімічної методики. Інтенсивність забарвлення, за
Тіммом, у зоні CA3 поступово збільшувалася починаючи з
третьої доби та була вірогідно вищою, ніж така в контролі,
протягом усього наступного періоду. Рівень протеїну CPG15
у ЗЗ та полі CA3 поступово зменшувався до 14-ї доби та
повертався до нормальних значень на 28-му добу. Отримані
результати вперше вказують на те, що CPG15 може бути
залученим у процес СМВ. Зрозуміння молекулярних механізмів, на яких базується цей феномен, може призвести до розробки успішних терапевтичних заходів, котрі обмежували б епілептогенез
Ground state properties of the 2D disordered Hubbard model
We study the ground state of the two-dimensional (2D) disordered Hubbard
model by means of the projector quantum Monte Carlo (PQMC) method. This
approach allows us to investigate the ground state properties of this model for
lattice sizes up to , at quarter filling, for a broad range of
interaction and disorder strengths. Our results show that the ground state of
this system of spin-1/2 fermions remains localised in the presence of the
short-ranged Hubbard interaction.Comment: 7 pages, 9 figure
Formation of ethane and propane via abiotic reductive conversion of acetic acid in hydrothermal sediments
A mechanistic understanding of formation pathways of lowmolecular- weight hydrocarbons is relevant for disciplines such as atmospheric chemistry, geology, and astrobiology. The patterns of stable carbon isotopic compositions (δ13C) of hydrocarbons are commonly used to distinguish biological, thermogenic, and abiotic sources. Here, we report unusual isotope patterns of nonmethane hydrocarbons in hydrothermally heated sediments of the Guaymas Basin; these nonmethane hydrocarbons are notably 13Cenriched relative to sedimentary organic matter and display an isotope pattern that is reversed relative to thermogenic hydrocarbons (i.e., δ13C ethane > δ13C propane > δ13C n-butane > δ13C n-pentane). We hypothesized that this pattern results from abiotic reductive conversion of volatile fatty acids, which were isotopically enriched due to prior equilibration of their carboxyl carbon with dissolved inorganic carbon. This hypothesis was tested by hydrous pyrolysis experiments with isotopically labeled substrates at 350°C and 400 bar that demonstrated 1) the exchange of carboxyl carbon of C2 to C5 volatile fatty acids with 13C-bicarbonate and 2) the incorporation of 13C from 13C-2-acetic acid into ethane and propane. Collectively, our results reveal an abiotic formation pathway for nonmethane hydrocarbons, which may be sufficiently active in organic-rich, geothermally heated sediments and petroleum systems to affect isotopic compositions of nonmethane hydrocarbons
Two-species percolation and Scaling theory of the metal-insulator transition in two dimensions
Recently, a simple non-interacting-electron model, combining local quantum
tunneling via quantum point contacts and global classical percolation, has been
introduced in order to describe the observed ``metal-insulator transition'' in
two dimensions [1]. Here, based upon that model, a two-species-percolation
scaling theory is introduced and compared to the experimental data. The two
species in this model are, on one hand, the ``metallic'' point contacts, whose
critical energy lies below the Fermi energy, and on the other hand, the
insulating quantum point contacts. It is shown that many features of the
experiments, such as the exponential dependence of the resistance on
temperature on the metallic side, the linear dependence of the exponent on
density, the scale of the critical resistance, the quenching of the
metallic phase by a parallel magnetic field and the non-monotonic dependence of
the critical density on a perpendicular magnetic field, can be naturally
explained by the model.
Moreover, details such as the nonmonotonic dependence of the resistance on
temperature or the inflection point of the resistance vs. parallel magnetic are
also a natural consequence of the theory. The calculated parallel field
dependence of the critical density agrees excellently with experiments, and is
used to deduce an experimental value of the confining energy in the vertical
direction. It is also shown that the resistance on the ``metallic'' side can
decrease with decreasing temperature by an arbitrary factor in the degenerate
regime ().Comment: 8 pages, 8 figure
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