537 research outputs found
Identification and Quantification of Protein Carbonylation by Mass Spectrometry
Accumulated evidence indicates oxidative stress plays important roles in disease and aging. Under oxidative stress, lipid peroxidation (LPO) leads to reactive carbonyl species (RCS) that can modify a wide range of biomolecules including protein, DNA and carbohydrate. In this dissertation, we investigate the modification of two model proteins, human serum albumin (HSA) and aconitase (ACO), by the LPO-relevant a, b-unsaturated aldehydes, acrolein (ACR) and 4-hydroxy-2-nonenal (HNE). The investigation is focused on the characterization and quantification ACR and HNE addition to the model proteins. A correlation between HNE modification and ACO activity is also determined. These results provide insights into the impact of oxidative stress at the molecular level and are relevant to aging and disease states. We finally investigate protein carbonylation in ischemic mouse heart mitochondria, and develop a quantitative method for detecting carbonylated protein in this system. The research is based on liquid chromatography/mass spectrometry (LC/MS), Western Blots, and enzymatic assay
Design of autonomous robot device for accurate pacing of track athletes
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2008.Includes bibliographical references (leaf 42).Given the health and weight gain concerns plaguing the country, there is currently a great need for products that encourage athletic activity. A robotic pacing device that facilitates running along a track was developed to help fulfill this requirement. The need for this device, determined from interviews and a survey of experienced running athletes and coaches, was found to be substantial for a number of age groups and experience levels of runners. An experimental robot prototype was designed and manufactured to aid in pacing runners around a track. The robot was designed to accurately follow the lines of the track using IR sensors that detect reflectivity of the track's surface. The prototype was tested and optimized to determine a successful control logic that reduced error and the amount of overshoot the robot experiences as it adjusts to follow the lines at high speeds. Large overshoots lead to robot malfunction and breakdown in the logic as the robot reaches curves in the track. The optimized prototype currently has the capability of running full lengths around various shaped tracks that incorporate white lines dividing dark colored lanes at speeds of up to eight miles per hour. In this form, the robot might be useful for beginner runners, runners that are doing distance training, and physical education classes that have access to running tracks. Future versions of the robot pacing device will need to incorporate additional features in order to be useful for the full range of people that want to use this product, including a flexible user interface that allows users to program the robot to their needs, a more sophisticated robot control system that allows for accurate control based on the dynamics of the robot, and a more durable cover that is easily spotted by runners looking straight ahead.by Qinyuan (Chen) Liu and Albert Hernandez.S.B
Using gyro stabilizer for active anti-rollover control of articulated wheeled loader vehicles
Articulated wheeled loader vehicles have frequent rollover accidents as they operate in the complex outdoor environments. This article proposes an active anti-rollover control method based on a set of single-frame control moment gyro stabilizer installed on the rear body of the vehicle. The rollover dynamic model is first established for articulated wheeled loader vehicle with gyro stabilizer. The proposed control strategy is then applied in simulation to verify the rollover control effect on the vehicle under steady-state circumferential conditions. Finally, a home-built articulated wheel loader vehicle with gyro stabilizer is used to further verify the proposed control strategy. The results show that the vehicle can quickly return to the stable driving state and effectively avoid the vehicle rollover when a suitable anti-roll control moment can be provided by the gyro stabilizer. As a result, the articulated wheeled loader vehicle is able to operate safely in a complex outdoor environment
Processing of novel grammatical features during real-time second language production and comprehension
Second language (L2) learners often have difficulties acquiring grammatical
features which do not exist in their first language (e.g. inflectional morphology,
number agreement etc.), and exhibit real-time production and comprehension errors
when these features are involved. What are the causes behind such errors? Moreover,
what do they tell us about second language processing in general?
The primary aim of this thesis was to examine the nature of second language
production errors and to scrutinise them with reference to each stage of accepted
models of language production, specifically, whether there are consistent error
patterns which reveal the source(s) of erroneous production in L2 learners. The
second aim of this thesis was to examine the comprehension of novel grammatical
features in the second language, more specifically, whether L2 learners could acquire
the ability to consistently apply L2 grammatical knowledge relating to newly
acquired grammatical features in real-time. The third aim of this thesis was to
examine whether L2 learners have fundamental perceptual deficiencies or biases
concerning selective L2 phonological features as a result of first language
experience, and whether this would affect the perception of specific grammatical
features in the L2.
This thesis addressed these questions in seven experiments by examining the
acquisition of inflectional morphology among L1 Mandarin speakers of L2 English.
Experiments 1, 2 and 3 investigated spoken and written production of inflectional
morphology via an elicited production paradigm. The results argued against
representational accounts and supported activation processing accounts of erroneous
second language production. Information complexity and production modality were
also found to contribute to low production accuracy. Experiments 4 and 5
investigated L2 learners’ auditory and visual sensitivity to inflectional omissions
using self-paced listening and self-paced reading paradigms, where auditory cues
were found to facilitate the detection of inflectional omissions. Experiments 6 and 7
investigated perceptual sensitivity to phonologically variable inflectional morphemes
in an auditory discrimination paradigm. Second language learners exhibited no
perceptual deficiency to novel phonological features, and no consistent perceptual
biases favouring L1 phonological features relative to native speakers.
Taking these findings as whole, the results favoured a processing account of
errors in language production and comprehension, whilst recognising the role of
phonological constraints in both processes. Importantly, these conclusions are drawn
from a broad analysis of multiple aspects of language processing, recognising the
role of conceptual distinctions, grammatical representations, lexical forms, and
phonological factors in second language production and comprehension.
Additionally, this thesis recognises the value of both psycholinguistic models of
language processing and linguistic theories of second language processing
Very high cycle fatigue behavior of bridge steel welded joint
AbstractVery high cycle fatigue (VHCF) behaviors of bridge steel (Q345) welded joints were investigated using an ultrasonic fatigue test system at room temperature with a stress ratio R = −1. The results show that the fatigue strength of welded joints is dropped by an average of 60% comparing to the base metal and the fatigue failure still occurred beyond 107 cycles. The fatigue fracture of welded joints in the low cycle regime generally occurred at the solder while at the heat-affected zone (HAZ) in the very high cycle regime. The fatigue fracture surface was analyzed with scanning electron microscopy (SEM), showing welding defects such as pore, micro-crack and inclusion were the main factors on decreasing the fatigue properties of welded joints. The effect of welding defects on the fatigue behaviors of welded joints was discussed in terms of experimental results and finite element simulations
Decentralized Control for Discrete-time Mean-Field Systems with Multiple Controllers of Delayed Information
In this paper, the finite horizon asymmetric information linear quadratic
(LQ) control problem is investigated for a discrete-time mean field system.
Different from previous works, multiple controllers with different information
sets are involved in the mean field system dynamics. The coupling of different
controllers makes it quite difficult in finding the optimal control strategy.
Fortunately, by applying the Pontryagin's maximum principle, the corresponding
decentralized control problem of the finite horizon is investigated. The
contributions of this paper can be concluded as: For the first time, based on
the solution of a group of mean-field forward and backward stochastic
difference equations (MF-FBSDEs), the necessary and sufficient solvability
conditions are derived for the asymmetric information LQ control for the mean
field system with multiple controllers. Furthermore, by the use of an
innovative orthogonal decomposition approach, the optimal decentralized control
strategy is derived, which is based on the solution to a non-symmetric
Riccati-type equation
A statistical method to estimate low-energy hadronic cross sections
In this article we propose a model based on the Statistical Bootstrap
approach to estimate the cross sections of different hadronic reactions up to a
few GeV in c.m.s energy. The method is based on the idea, when two particles
collide a so called fireball is formed, which after a short time period decays
statistically into a specific final state. To calculate the probabilities we
use a phase space description extended with quark combinatorial factors and the
possibility of more than one fireball formation. In a few simple cases the
probability of a specific final state can be calculated analytically, where we
show that the model is able to reproduce the ratios of the considered cross
sections. We also show that the model is able to describe proton\,-\,antiproton
annihilation at rest. In the latter case we used a numerical method to
calculate the more complicated final state probabilities. Additionally, we
examined the formation of strange and charmed mesons as well, where we used
existing data to fit the relevant model parameters.Comment: 12 pages, 12 figures, submitted to EPJ
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