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Research Interests:
Research Interests:
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After animals are euthanized, their tissues begin to die. Turtles offer an advantage because of a longer survival time of their tissues, especially when compared to warm-blooded vertebrates. Because of this, in vitro experiments in... more
After animals are euthanized, their tissues begin to die. Turtles offer an advantage because of a longer survival time of their tissues, especially when compared to warm-blooded vertebrates. Because of this, in vitro experiments in turtles can be performed for extended periods of time to investigate the neural signals and control of their target actions. Using an isolated head preparation, we measured the kinematics of eye movements in turtles, and their modulation by electrical signals carried by cranial nerves. After the brain was removed from the skull, leaving the cranial nerves intact, the dissected head was placed in a gimbal to calibrate eye movements. Glass electrodes were attached to cranial nerves (oculomotor, trochlear, and abducens) and stimulated with currents to evoke eye movements. We monitored eye movements with an infrared video tracking system and quantified rotations of the eyes. Current pulses with a range of amplitudes, frequencies, and train durations were used...
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Novel catalysis involving phosphonomethylation of N-methylaniline and asymmetric cyclopropylphosphonation reactions of N,N-diethylaniline derivatives with diazomethylphosphonates are reported. Optically active cyclopropylphosphonate... more
Novel catalysis involving phosphonomethylation of N-methylaniline and asymmetric cyclopropylphosphonation reactions of N,N-diethylaniline derivatives with diazomethylphosphonates are reported. Optically active cyclopropylphosphonate derivatives were directly synthesized from diazomethylphosphonates and N,N-diethylaniline derivatives catalyzed by a Ru(II)-Pheox complex in one step in good yields and high diastereoselectivities (up to trans/ cis = > 99:1<) and enantioselectivities (up to 99% ee). D-labeling mechanistic studies of phosphonomethylation and cyclopropylphosphonation suggested that an enamine or iminium intermediate was generated in the reaction process.
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Coadaptation between mistletoes and birds captured the attention of Charles Darwin over 150 years ago, stimulating considerable scientific research. Here we used Loranthaceae, a speciose and ecologically important mistletoe family, to... more
Coadaptation between mistletoes and birds captured the attention of Charles Darwin over 150 years ago, stimulating considerable scientific research. Here we used Loranthaceae, a speciose and ecologically important mistletoe family, to obtain new insights into the interrelationships among its hosts and dispersers. Phylogenetic analyses of Loranthaceae were based on a dataset of nuclear and chloroplast DNA sequences. Divergence time estimation, ancestral area reconstruction, and diversification rate analyses were employed to examine historical biogeography. The crown group of Loranthaceae was estimated to originate in Australasian Gondwana during the Paleocene to early Eocene (59 Ma, 95% HPD: 53-66 Ma), and rapidly diversified, converting from root parasitic to aerial parasitic trophic mode ca. 50 Ma during the Eocene climatic optimum. Subsequently, Loranthaceae were inferred to be widespread in Australasia and South America but absent in Africa. The African and European members were ...
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Research Interests:
Low-frequency electromagnetic casting (LFEC) processing could improve not only the metallurgical quality of magnesium billet including refining grain size, reducing regional microstructural difference and lightening segregation, but also... more
Low-frequency electromagnetic casting (LFEC) processing could improve not only the metallurgical quality of magnesium billet including refining grain size, reducing regional microstructural difference and lightening segregation, but also its surface quality due to the effect of applied electromagnetic field according to the results by microstructure observation and the numerical simulation. In this research in-situ temperature measurement was carried out in LFEC processing in order to investigate heat transfer behavior of billet during solidification. The effects of the electromagnetic conditions (frequency and the intensity) together with the casting temperature on the sump and the mushy zone were investigated in detail. The results indicate that all the casting conditions affect the temperature field of magnesium billet markedly during solidification. Electromagnetic field could decrease not only the sump depth but also the difference of regional temperature field along the solidi...
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Effects of low frequency electromagnetic field on surface quality, microstructure and hot-tearing tendency of direct chill casting of Φ500mm ZK60 magnesium alloy billets were investigated. The results show that with the application of the... more
Effects of low frequency electromagnetic field on surface quality, microstructure and hot-tearing tendency of direct chill casting of Φ500mm ZK60 magnesium alloy billets were investigated. The results show that with the application of the low frequency electromagnetic field, the surface quality of Φ500mm ZK60 magnesium alloy billets has been markedly improved, and the depth of cold fold is decreased. In the conventional direct chill casting, the microstructures of the billet, especially at the center, are coarse. The distribution of the grain size is non-uniform throughout the billet. From the edge to the center, the microstructure gradually changes from fine to coarse in all billets. However, under the low frequency electromagnetic casting, the microstructures of the billet is significantly refined, the distribution of the grains size is relatively uniform from the billets edge to the billets center. And it also shows that the hot-tearing tendency of direct chill casting Φ500mm ZK6...
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Research Interests:
Photocatalysis for organic synthesis has experienced an exponential growth in the past 10 years. However, the variety of experimental procedures that have been reported to perform photon-based catalyst excitation has hampered the... more
Photocatalysis for organic synthesis has experienced an exponential growth in the past 10 years. However, the variety of experimental procedures that have been reported to perform photon-based catalyst excitation has hampered the establishment of general protocols to convert visible light into chemical energy. To address this issue, we have designed an integrated photoreactor for enhanced photon capture and catalyst excitation. Moreover, the evaluation of this new reactor in eight photocatalytic transformations that are widely employed in medicinal chemistry settings has confirmed significant performance advantages of this optimized design while enabling a standardized protocol.
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A new strategy for ross-electrophile coupling has been developed via the merger of photoredox and transition metal catalysis. In this report, we demonstrate the use of commercially available tris(trimethylsilyl)silane in conjunction with... more
A new strategy for ross-electrophile coupling has been developed via the merger of photoredox and transition metal catalysis. In this report, we demonstrate the use of commercially available tris(trimethylsilyl)silane in conjunction with metallaphotoredox catalysis to efficiently couple alkyl bromides with aryl or heteroaryl bromides in excellent yields. We hypothesize that a photocatalytically generated silyl radical species can perform halogen-atom abstraction to activate alkyl halides as nucleophilic cross-coupling partners. This strategy facilitates the use of mild yet robust conditions to construct Csp3-Csp2-synthons generically via a unique cross-coupling pathway.
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The effects of high intensity ultrasonic melt treatment on the microstructure of magnesium alloys were investigated in this paper. Magnesium melts were treated with power ultrasonic wave and then cooled to a predetermined temperature.... more
The effects of high intensity ultrasonic melt treatment on the microstructure of magnesium alloys were investigated in this paper. Magnesium melts were treated with power ultrasonic wave and then cooled to a predetermined temperature. With the increase in ultrasonic power, the structure exhibited refined and spheroidzed crystal grains. After further increasing the ultrasonic power, the grains tended to somewhat coarsened. And increasing the ultrasonic processing time led to a grain refinement of magnesium alloy.
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Application of magnesium alloy is restricted by its bad formability and low corrosion resistance. In order to resolve these problems, rolling-bonding has been tried as a new method. Pre-heating, rolling and annealing were used in the... more
Application of magnesium alloy is restricted by its bad formability and low corrosion resistance. In order to resolve these problems, rolling-bonding has been tried as a new method. Pre-heating, rolling and annealing were used in the process of bonding, and aluminum cladding magnesium alloys obtained. The effects of many parameters in the processes of pre-heating, rolling and heat-treatment on bonding strength have been analyzed, and the mechanism of rolling-bonding been studied. It was found that intermediate phase played an important role in the bonding. Good bonding of aluminum cladding magnesium alloys achieved after annealing at 200oC for 1 hour.
Effect of different melt temperatures, holding time, cooling rate and C2Cl6 degasser treatment on the density of Mg-6Zn-0.5Y alloy was studied. The experimental results indicated that the density of RPT samples decreased with increasing... more
Effect of different melt temperatures, holding time, cooling rate and C2Cl6 degasser treatment on the density of Mg-6Zn-0.5Y alloy was studied. The experimental results indicated that the density of RPT samples decreased with increasing of melt temperature, which indicating that the hydrogen content increased with the increment of temperature. And the results also showed that the density of RPT samples rapidly decreased at first and then decreased slowly with increasing of holding time, suggesting that the hydrogen content rapidly increased at first and then reached a saturated state with increasing of holding time. When cooling rate increased, the density of ingots gradually increased at the same melt temperature. When the melt was treated by 1%, 3% and 5% C2Cl6 degasser at 720°C, the density of ingots gradually increased compared with the ingot without treatment by C2Cl6 degasser. The density of ingot reached the maximum value when C2Cl6 degasser content was 3%, i.e, the ingot density value increased from 1.8649g.cm-3 of the untreated sample to 1.8774g.cm-3 of the sample treated by 3% C2Cl6 degasser, indicating that 3% C2Cl6 degasser treatment has an optimum degassing effect.
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In this study we demonstrate that molecular fragments, which can be readily coupled via a simple, in situ RO-C═OR bond-forming reaction, can subsequently undergo metal insertion-decarboxylation-recombination to generate Csp(2)-Csp(3)... more
In this study we demonstrate that molecular fragments, which can be readily coupled via a simple, in situ RO-C═OR bond-forming reaction, can subsequently undergo metal insertion-decarboxylation-recombination to generate Csp(2)-Csp(3) bonds when subjected to metallaphotoredox catalysis. In this embodiment the conversion of a wide variety of mixed anhydrides (formed in situ from carboxylic acids and acyl chlorides) to fragment-coupled ketones is accomplished in good to high yield. A three-step synthesis of the medicinal agent edivoxetine is also described using this new decarboxylation-recombination protocol.
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Few laboratory exercises have been developed using the crayfish as a model for teaching how neural processing is done by sensory organs that detect light stimuli. This article describes the dissection procedures and methods for conducting... more
Few laboratory exercises have been developed using the crayfish as a model for teaching how neural processing is done by sensory organs that detect light stimuli. This article describes the dissection procedures and methods for conducting extracellular recording from light responses of both the optic nerve fibers found in the animal's eyestalk and from the caudal photoreceptor located in the ventral nerve cord. Instruction for ADInstruments' data acquisition system is also featured for the data collection and analysis of responses. The comparison provides students a unique view on how spike activities measured from neurons code image-forming and non-image-forming processes. Results from the exercise show longer latency and lower frequency of firing by the caudal photoreceptor compared to optic nerve fibers to demonstrate evidence of different functions. After students learn the dissection, recording procedure, and the functional anatomy, they can develop their own experiment...
Direct chill (DC) casting is a dominant way of producing aluminum and copper alloy billets. In the past we developed a new technique, namely Low Frequency Electromagnetic Casting (LFEC), in which low-frequency electromagnetic field (LFEF)... more
Direct chill (DC) casting is a dominant way of producing aluminum and copper alloy billets. In the past we developed a new technique, namely Low Frequency Electromagnetic Casting (LFEC), in which low-frequency electromagnetic field (LFEF) is incorporated to DC casting processing. In this work, LFEF was introduced to the magnesium DC casting processing. Experimental investigations and numerical simulation indicate that application of LFEF to DC casting magnesium alloy can significantly improve the surface quality of the AZ91 billets, refine microstructure and reduce both macro and micro segregations. It was also found that high casting velocity become possible for magnesium alloys through LFEC processing.
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... An introduction to law and legal reasoning. Post a Comment. CONTRIBUTORS: Author: Burton, Steven J. PUBLISHER: Little, Brown (Boston). SERIES TITLE: YEAR: 1995. PUB TYPE: Book (ISBN 0316114898 ). VOLUME/EDITION: 2nd edition. PAGES... more
... An introduction to law and legal reasoning. Post a Comment. CONTRIBUTORS: Author: Burton, Steven J. PUBLISHER: Little, Brown (Boston). SERIES TITLE: YEAR: 1995. PUB TYPE: Book (ISBN 0316114898 ). VOLUME/EDITION: 2nd edition. PAGES (INTRO/BODY): xii, 178 p. ...
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As CPT penetration tends to show a similar behavior to that of pile driving, a number of methods for estimating the toe bearing capacity of piles based on CPT data have been proposed. To evaluate the applicability of the methods in this... more
As CPT penetration tends to show a similar behavior to that of pile driving, a number of methods for estimating the toe bearing capacity of piles based on CPT data have been proposed. To evaluate the applicability of the methods in this country, a total of 172 dynamic load tests data on PHC piles and 82 CPT data at a site in the Nakdong River estuary were collected. A specific four-step procedure was adopted for the selection of the reliable data, and statistical techniques were then applied to the analysis of the applicability. The results indicated that among a total of 10 CPT-based methods applied, the best one is the Aoki method (1975), followed by the LCPC (1982), ICP (2005) methods and others.
The structures for two cross-reactive capsular polysaccharides isolated from Streptococci pneumoniae types 19 and 57 are proposed based on the analytical data obtained from methylation, enzymatic degradation, and periodate oxidation... more
The structures for two cross-reactive capsular polysaccharides isolated from Streptococci pneumoniae types 19 and 57 are proposed based on the analytical data obtained from methylation, enzymatic degradation, and periodate oxidation experiments performed on both intact polysaccharides and oligosaccharides isolated from hydrofluoric acid hydrolysates. Both polysaccharides exhibit an identical structure of 4)-beta-2-acetamido-2-deoxymannose-(1 leads to 4)-alpha-D-glucose-(1 leads to 2)-alpha-L-rhamnose-1-phosphate. This trisaccharide is considered the only repeating unit in the type 19 polysaccharide. The type 57 polysaccharide contains this same repeating unit and side chains composed of a beta-D-2-acetamido-2-deoxyglucose-(1 leads to 3)-beta-D-galactose-1-phosphate side chain attached to C-2 of the glucose and an alpha-L-fucose-1-phosphate attached to C-3 of the rhamnose.
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ABSTRACT The effects of high intensity ultrasonic melt treatment on the microstructure of magnesium alloys were investigated in this paper. Magnesium melts were treated with power ultrasonic wave and then cooled to a predetermined... more
ABSTRACT The effects of high intensity ultrasonic melt treatment on the microstructure of magnesium alloys were investigated in this paper. Magnesium melts were treated with power ultrasonic wave and then cooled to a predetermined temperature. With the increase in ultrasonic power, the structure exhibited refined and spheroidzed crystal grains. After further increasing the ultrasonic power, the grains tended to somewhat coarsened. Increasing the ultrasonic processing time led to a grain refinement of magnesium alloy.
Research Interests:
Effect of different melt temperatures, holding time, cooling rate and C2Cl6 degasser treatment on the density of Mg-6Zn-0.5Y alloy was studied. The experimental results indicated that the density of RPT samples decreased with increasing... more
Effect of different melt temperatures, holding time, cooling rate and C2Cl6 degasser treatment on the density of Mg-6Zn-0.5Y alloy was studied. The experimental results indicated that the density of RPT samples decreased with increasing of melt temperature, which indicating that the hydrogen content increased with the increment of temperature. And the results also showed that the density of RPT samples rapidly decreased at first and then decreased slowly with increasing of holding time, suggesting that the hydrogen content rapidly increased at first and then reached a saturated state with increasing of holding time. When cooling rate increased, the density of ingots gradually increased at the same melt temperature. When the melt was treated by 1%, 3% and 5% C2Cl6 degasser at 720°C, the density of ingots gradually increased compared with the ingot without treatment by C2Cl6 degasser. The density of ingot reached the maximum value when C2Cl6 degasser content was 3%, i.e, the ingot den...
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Several Mg alloys were processed to achieve the thixotropic microstructure of non-dendritic, globular primary grains for semisolid forming using a novel method that does not require stirring. The alloys were poured at their liquidus... more
Several Mg alloys were processed to achieve the thixotropic microstructure of non-dendritic, globular primary grains for semisolid forming using a novel method that does not require stirring. The alloys were poured at their liquidus temperatures or about ten degrees below the liquidus temperatures using either batch or semi-continuous casting. Although the compositions of the alloys had considerable effects on details of the resulting microstructure, generally fine, equiaxed primary grains were obtained by controlling the resting time, casting speed and cooling rate. The lower casting temperatures and addition of calcium were effective in preventing burning of Mg without using a protective atmosphere. This new method has great potential for industry applications.
The JWST Observatory currently under development for NASA and it's international partners contains a 6.5 meter diameter cryogenic telescope and a suite of 4 highly sensitive instruments which will collect imagery and spectroscopic... more
The JWST Observatory currently under development for NASA and it's international partners contains a 6.5 meter diameter cryogenic telescope and a suite of 4 highly sensitive instruments which will collect imagery and spectroscopic data over the spectral range of 0.6 to 30 micrometers. The Observatory architecture contains a number of innovative and aggressive technologies including a light-weight primary mirror made up of 18 individually controllable segments, a large sunshield to permit stable low temperature operation, and a nested multi-loop pointing and tracking subsystem to establish milli-arc second line of sight stability. Detailed analytical models are being developed for each of the individual elements of the Observatory. The work described in this paper draws on these models so as to create a high level end-to-end model for the total Observatory. The principal thrust of this end-to-end model (OPTOOL) is to verify that the Observatory meets its overall image quality requirements. These requirements are codified in terms of Strehl ratio, encircled energy, and image anisotropy, and are applied at wavelengths of 1,2, and 5.6 micrometers. OPTOOL is implemented through Matlab (Version 7.0.1) with a Fourier optics based approach for PSF calculations, and uses a direct integration calculation to permit high spatial sampling of the PSF. Polychromatic PSFs are calculated using the Observatory band pass characteristic and an assumed constant Jansky level target. The focal plane arrays of each of the 4 instruments are also included in the model so that realistic signal with noise imagery can be simulated. Exit pupil optical path difference (OPD) maps can be generated using combinations of Zernike polynomials or shaped power spectral densities. Aberrations can be applied to the entire pupil or to the individual segments which make up the pupil. Global exit pupil OPD maps can also be imported and used to generate predicted Point Spread Functions (PSFs). Sample results are presented.