Showing papers by "California Institute of Technology published in 1998"
TL;DR: In this article, a visual attention system inspired by the behavior and the neuronal architecture of the early primate visual system is presented, where multiscale image features are combined into a single topographical saliency map.
Abstract: A visual attention system, inspired by the behavior and the neuronal architecture of the early primate visual system, is presented. Multiscale image features are combined into a single topographical saliency map. A dynamical neural network then selects attended locations in order of decreasing saliency. The system breaks down the complex problem of scene understanding by rapidly selecting, in a computationally efficient manner, conspicuous locations to be analyzed in detail.
10,525 citations
TL;DR: In this article, the authors adopt a multidisciplinary view of trust within and between firms, in an effort to synthesize and give insight into a fundamental construct of organizational science, while recognizing that the differing meanings scholars bring to the study of trust also can add value.
Abstract: Our task is to adopt a multidisciplinary view
of trust within and between firms, in an effort to
synthesize and give insight into a fundamental
construct of organizational science. We seek to
identify the shared understandings of trust
across disciplines, while recognizing that the
divergent meanings scholars bring to the study
of trust also can add value.
8,886 citations
TL;DR: The design and observation of two-dimensional crystalline forms of DNA that self-assemble from synthetic DNA double-crossover molecules that create specific periodic patterns on the nanometre scale are reported.
Abstract: Molecular self-assembly presents a `bottom-up' approach to the fabrication of objects specified with nanometre precision. DNA
molecular structures and intermolecular interactions are particularly
amenable to the design and synthesis of complex molecular objects. We
report the design and observation of two-dimensional crystalline forms
of DNA that self-assemble from synthetic DNA double-crossover
molecules. Intermolecular interactions between the structural units are
programmed by the design of `sticky ends' that associate according to
Watson-Crick complementarity, enabling us to create specific periodic
patterns on the nanometre scale. The patterned crystals have been
visualized by atomic force microscopy.
2,713 citations
TL;DR: The first realization of unconditional quantum teleportation where every state entering the device is actually teleported is realized, using squeezed-state entanglement.
Abstract: Quantum teleportation of optical coherent states was demonstrated experimentally using squeezed-state entanglement. The quantum nature of the achieved teleportation was verified by the experimentally determined fidelity Fexp = 0.58 +/- 0.02, which describes the match between input and output states. A fidelity greater than 0.5 is not possible for coherent states without the use of entanglement. This is the first realization of unconditional quantum teleportation where every state entering the device is actually teleported.
2,345 citations
TL;DR: The combination of large delta and high fluorescence quantum yield or triplet yield exhibited by molecules developed here offers potential for unprecedented brightness in two-photon fluorescent imaging or enhanced photosensitivity in two -photon sensitization, respectively.
Abstract: A strategy for the design of molecules with large two-photon absorption cross sections, δ, was developed, on the basis of the concept that symmetric charge transfer, from the ends of a conjugated system to the middle, or vice versa, upon excitation is correlated to enhanced values of δ. Synthesized bis(styryl)benzene derivatives with donor-π-donor, donor-acceptor-donor, and acceptor-donor-acceptor structural motifs exhibit exceptionally large values of δ, up to about 400 times that of trans-stilbene. Quantum chemical calculations performed on these molecules indicate that substantial symmetric charge redistribution occurs upon excitation and provide δ values in good agreement with experimental values. The combination of large δ and high fluorescence quantum yield or triplet yield exhibited by molecules developed here offers potential for unprecedented brightness in two-photon fluorescent imaging or enhanced photosensitivity in two-photon sensitization, respectively.
2,127 citations
TL;DR: A computer-accessible catalog of submillimeter, millimeter, and microwave spectral lines in the frequency range between 0 and 10 000 GHz (i.e. wavelengths longer than 30 μm) that has been constructed by using theoretical least-squares fits of published spectral lines to accepted molecular models.
Abstract: This paper describes a computer-accessible catalog of submillimeter, millimeter, and microwave spectral lines in the frequency range between 0 and 10 000 GHz (i.e. wavelengths longer than 30 μm). The catalog can be used as a planning guide or as an aid in the identification and analysis of observed spectral lines in the interstellar medium, the Earth’s atmosphere, and the atmospheres of other planets. The information listed for each spectral line includes the frequency and its estimated error, the intensity, the lower state energy, and the quantum number assignment. The catalog is continuously updated and at present has information on 331 atomic and molecular species and includes a total of 1 845 866 lines. The catalog has been constructed by using theoretical least-squares fits of published spectral lines to accepted molecular models. The associated predictions and their estimated errors are based upon the resultant fitted parameters and their covariance. Future versions of this catalog will add more atoms and molecules and update the present listings as new data appear. The catalog is available on-line via anonymous FTP at spec.jpl.nasa.gov and on the world wide web at http: //spec.jpl.nasa.gov.
2,098 citations
TL;DR: An approach has been developed that involves the fit of a combination of three simple scattering mechanisms to polarimetric SAR observations, which is justified as a simplification of more complicated scattering models, which require many inputs to solve the forward scattering problem.
Abstract: An approach has been developed that involves the fit of a combination of three simple scattering mechanisms to polarimetric SAR observations. The mechanisms are canopy scatter from a cloud of randomly oriented dipoles, evenor double-bounce scatter from a pair of orthogonal surfaces with different dielectric constants and Bragg scatter from a moderately rough surface. This composite scattering model is used to describe the polarimetric backscatter from naturally occurring scatterers. The model is shown to describe the behavior of polarimetric backscatter from tropical rain forests quite well by applying it to data from NASA/Jet Propulsion Laboratory's (JPLs) airborne polarimetric synthetic aperture radar (AIRSAR) system. The model fit allows clear discrimination between flooded and nonflooded forest and between forested and deforested areas, for example. The model is also shown to be usable as a predictive tool to estimate the effects of forest inundation and disturbance on the fully polarimetric radar signature. An advantage of this model fit approach is that the scattering contributions from the three basic scattering mechanisms can be estimated for clusters of pixels in polarimetric SAR images. Furthermore, it is shown that the contributions of the three scattering mechanisms to the HH, HV, and VV backscatter can be calculated from the model fit. Finally, this model fit approach is justified as a simplification of more complicated scattering models, which require many inputs to solve the forward scattering problem.
2,079 citations
TL;DR: In this paper, a review of recent advances in olefin metathesis focusing on the areas of ring-closing olefi cation (RCM) and cross-metathesis is presented.
1,877 citations
TL;DR: The Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) was the first imaging sensor to measure the solar reflected spectrum from 400 nm to 2500 nm at 10 nm intervals as mentioned in this paper.
1,729 citations
TL;DR: In this paper, a new adaptive filtering algorithm was proposed to dramatically lower phase noise, improving both measurement accuracy and phase unwrapping, while demonstrating graceful degradation in regions of pure noise.
Abstract: The use of SAR interferometry is often impeded by decorrelation from thermal noise, temporal change, and baseline geometry. Power spectra of interferograms are typically the sum of a narrow-band component combined with broad-band noise. We describe a new adaptive filtering algorithm that dramatically lowers phase noise, improving both measurement accuracy and phase unwrapping, while demonstrating graceful degradation in regions of pure noise. The performance of the filter is demonstrated with SAR data from the ERS satellites over the Jakobshavns glacier of Greenland.
1,635 citations
TL;DR: In this paper, it was shown that ephrin-B2, an Eph family transmembrane ligand, marks arterial but not venous endothelial cells from the onset of angiogenesis.
TL;DR: This paper presents a method for robot motion planning in dynamic environments that consists of selecting avoidance maneuvers to avoid static and moving obstacles in the velocity space, based on the rental positions and velocities of the robot and obstacles.
Abstract: This paper presents a method for robot motion planning in dynamic environments. It consists of selecting avoidance maneuvers to avoid static and moving obstacles in the velocity space, based on the cur rent positions and velocities of the robot and obstacles. It is a first- order method, since it does not integrate velocities to yield positions as functions of time.The avoidance maneuvers are generated by selecting robot ve locities outside of the velocity obstacles, which represent the set of robot velocities that would result in a collision with a given obstacle that moves at a given velocity, at some future time. To ensure that the avoidance maneuver is dynamically feasible, the set of avoidance velocities is intersected with the set of admissible velocities, defined by the robot's acceleration constraints. Computing new avoidance maneuvers at regular time intervals accounts for general obstacle trajectories.The trajectory from start to goal is computed by searching a tree of feasible avoidance maneuve...
TL;DR: In this paper, a protocol for teleportation of a single mode of the electromagnetic field with high fidelity using squeezed-state entanglement and current experimental capability is presented, including the roles of finite quantum correlation and nonideal detection efficiency.
Abstract: Quantum teleportation is analyzed for states of dynamical variables with continuous spectra, in contrast to previous work with discrete (spin) variables. The entanglement fidelity of the scheme is computed, including the roles of finite quantum correlation and nonideal detection efficiency. A protocol is presented for teleporting the wave function of a single mode of the electromagnetic field with high fidelity using squeezed-state entanglement and current experimental capability.
TL;DR: The micromachining technology that emerged in the late 1980s can provide micron-sized sensors and actuators that can be integrated with signal conditioning and processing circuitry to form micro-electromechanical-systems (MEMS) that can perform real-time distributed control.
Abstract: The micromachining technology that emerged in the late 1980s can provide micron-sized sensors and actuators. These micro transducers are able to be integrated with signal conditioning and processing circuitry to form micro-electromechanical-systems (MEMS) that can perform real-time distributed control. This capability opens up a new territory for flow control research. On the other hand, surface effects dominate the fluid flowing through these miniature mechanical devices because of the large surface-to-volume ratio in micron-scale configurations. We need to reexamine the surface forces in the momentum equation. Owing to their smallness, gas flows experience large Knudsen numbers, and therefore boundary conditions need to be modified. Besides being an enabling technology, MEMS also provide many challenges for fundamental flow-science research.
TL;DR: Validation using airborne simulator images taken over playas and ponds in central Nevada demonstrates that, with proper atmospheric compensation, it is possible to meet the theoretical expectations of temperature/emissivity separation (TES), and ASTER's TES algorithm hybridizes three established algorithms.
Abstract: The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) scanner on NASA's Earth Observing System (EOS)-AM1 satellite (launch scheduled for 1998) will collect five bands of thermal infrared (TIR) data with a noise equivalent temperature difference (NE/spl Delta/T) of /spl les/0.3 K to estimate surface temperatures and emissivity spectra, especially over land, where emissivities are not known in advance. Temperature/emissivity separation (TES) is difficult because there are five measurements but six unknowns. Various approaches have been used to constrain the extra degree of freedom. ASTER's TES algorithm hybridizes three established algorithms, first estimating the normalized emissivities and then calculating emissivity band ratios. An empirical relationship predicts the minimum emissivity from the spectral contrast of the ratioed values, permitting recovery of the emissivity spectrum. TES uses an iterative approach to remove reflected sky irradiance. Based on numerical simulation, TES should be able to recover temperatures within about /spl plusmn/1.5 K and emissivities within about /spl plusmn/0.015. Validation using airborne simulator images taken over playas and ponds in central Nevada demonstrates that, with proper atmospheric compensation, it is possible to meet the theoretical expectations. The main sources of uncertainty in the output temperature and emissivity images are the empirical relationship between emissivity values and spectral contrast, compensation for reflected sky irradiance, and ASTER's precision, calibration, and atmospheric compensation.
TL;DR: In this article, the Lagrangian analogue of Lie-Poisson Hamiltonian systems is defined on semidirect product Lie algebras, and an abstract Kelvin-Noether theorem for these equations is derived.
TL;DR: In this paper, the authors present an introduction to ionic polymer-metal composites and some mathematical modeling pertaining to them and discuss a number of recent findings in connection with ion-exchange polymer metal composites (IPMCS) as biomimetic sensors and actuators.
Abstract: This paper presents an introduction to ionic polymer-metal composites and some mathematical modeling pertaining to them. It further discusses a number of recent findings in connection with ion-exchange polymer-metal composites (IPMCS) as biomimetic sensors and actuators. Strips of these composites can undergo large bending and flapping displacement if an electric field is imposed across their thickness. Thus, in this sense they are large motion actuators. Conversely by bending the composite strip, either quasi-statically or dynamically, a voltage is produced across the thickness of the strip. Thus, they are also large motion sensors. The output voltage can be calibrated for a standard size sensor and correlated to the applied loads or stresses. They can be manufactured and cut in any size and shape. In this paper first the sensing capability of these materials is reported. The preliminary results show the existence of a linear relationship between the output voltage and the imposed displacement for almost all cases. Furthermore, the ability of these IPMCs as large motion actuators and robotic manipulators is presented. Several muscle configurations are constructed to demonstrate the capabilities of these IPMC actuators. This paper further identifies key parameters involving the vibrational and resonance characteristics of sensors and actuators made with IPMCS. When the applied signal frequency varies, so does the displacement up to a critical frequency called the resonant frequency where maximum deformation is observed, beyond which the actuator response is diminished. A data acquisition system was used to measure the parameters involved and record the results in real time basis. Also the load characterizations of the IPMCs were measured and it was shown that these actuators exhibit good force to weight characteristics in the presence of low applied voltages. Finally reported are the cryogenic properties of these muscles for potential utilization in an outer space environment of a few Torrs and temperatures of the order of - 140 degrees Celsius. These muscles are shown to work quite well in such harsh cryogenic environments and thus present a great potential as sensors and actuators that can operate at cryogenic temperatures.
TL;DR: The formation of vortex rings generated through impulsively started jets is studied experimentally in this paper, where the velocity and vorticity field of the leading vortex ring formed is disconnected from that of the trailing jet.
Abstract: The formation of vortex rings generated through impulsively started jets is studied experimentally. Utilizing a piston/cylinder arrangement in a water tank, the velocity and vorticity fields of vortex rings are obtained using digital particle image velocimetry (DPIV) for a wide range of piston stroke to diameter (L/D) ratios. The results indicate that the flow field generated by large L/D consists of a leading vortex ring followed by a trailing jet. The vorticity field of the leading vortex ring formed is disconnected from that of the trailing jet. On the other hand, flow fields generated by small stroke ratios show only a single vortex ring. The transition between these two distinct states is observed to occur at a stroke ratio of approximately 4, which, in this paper, is referred to as the ‘formation number’. In all cases, the maximum circulation that a vortex ring can attain during its formation is reached at this non-dimensional time or formation number. The universality of this number was tested by generating vortex rings with different jet exit diameters and boundaries, as well as with various non-impulsive piston velocities. It is shown that the ‘formation number’ lies in the range of 3.6–4.5 for a broad range of flow conditions. An explanation is provided for the existence of the formation number based on the Kelvin–Benjamin variational principle for steady axis-touching vortex rings. It is shown that based on the measured impulse, circulation and energy of the observed vortex rings, the Kelvin–Benjamin principle correctly predicts the range of observed formation numbers.
TL;DR: It is found that CTLs inefficiently lysed primary cells infected with HIV-1 if the viral nef gene product was expressed and Nef protected infected cells by reducing the epitope density on their surface.
Abstract: Cytotoxic T lymphocytes (CTLs) lyse virally infected cells that display viral peptide epitopes in association with major histocompatibility complex (MHC) class I molecules on the cell surface. However, despite a strong CTL response directed against viral epitopes, untreated people infected with the human immunodeficiency virus (HIV-1) develop AIDS. To resolve this enigma, we have examined the ability of CTLs to recognize and kill infected primary T lymphocytes. We found that CTLs inefficiently lysed primary cells infected with HIV-1 if the viral nef gene product was expressed. Resistance of infected cells to CTL killing correlated with nef-mediated downregulation of MHC class I (ref. 1) and could be overcome by adding an excess of the relevant HIV-1 epitope as soluble peptide. Thus, Nef protected infected cells by reducing the epitope density on their surface. This effect of nef may allow evasion of CTL lysis by HIV-1-infected cells.
Patent•
01 Oct 1998TL;DR: In this paper, a system which uses redundant storage and redundant communication to provide a robust distributed server system is described, which is a system that uses redundancy in both storage and communication.
Abstract: A system which uses redundant storage and redundant communication to provide a robust distributed server system.
TL;DR: It is revealed that ETR1, ETR2, EIN4, and ERS2 negatively regulate ethylene responses and that the induction of ethylene response in Arabidopsis is through inactivation rather than activation of these proteins.
TL;DR: It is shown that Pearl's algorithm can be used to routinely derive previously known iterative, but suboptimal, decoding algorithms for a number of other error-control systems, including Gallager's low-density parity-check codes, serially concatenated codes, and product codes.
Abstract: We describe the close connection between the now celebrated iterative turbo decoding algorithm of Berrou et al. (1993) and an algorithm that has been well known in the artificial intelligence community for a decade, but which is relatively unknown to information theorists: Pearl's (1982) belief propagation algorithm. We see that if Pearl's algorithm is applied to the "belief network" of a parallel concatenation of two or more codes, the turbo decoding algorithm immediately results. Unfortunately, however, this belief diagram has loops, and Pearl only proved that his algorithm works when there are no loops, so an explanation of the experimental performance of turbo decoding is still lacking. However, we also show that Pearl's algorithm can be used to routinely derive previously known iterative, but suboptimal, decoding algorithms for a number of other error-control systems, including Gallager's (1962) low-density parity-check codes, serially concatenated codes, and product codes. Thus, belief propagation provides a very attractive general methodology for devising low-complexity iterative decoding algorithms for hybrid coded systems.
TL;DR: Photopolymerized crosslinked networks of poly(ethylene glycol; PEG) diacrylate (MW 8000) were derivitized throughout their bulk with Arg-Gly-Asp (RGD)-containing peptide sequences to promote spreading of human foreskin fibroblasts over 24 h.
Abstract: Photopolymerized crosslinked networks of poly(ethylene glycol; PEG) diacrylate (MW 8000) were derivitized throughout their bulk with Arg-Gly-Asp (RGD)-containing peptide sequences. Incorporation was achieved by functionalizing the amine terminus of the peptide with an acrylate moiety, thereby enabling the adhesion peptide to copolymerize rapidly with the PEG diacrylate upon photoinitiation. PEG diacrylate hydrogels derivitized with RGD peptide at surface concentrations ranging from 0.001 to 1 pmol/cm2 were studied in vitro for their ability to promote spreading of human foreskin fibroblasts over 24 h. Hydrogels not derivitized with peptides were poor substrates for adhesion, permitting spreading of only 5% of the seeded cells. When immobilized with no spacer arm, both RGD and RDG (inactive control) supported spreading of approximately 50% and approximately 15% of cells at 1 and 0.1 pmol/cm2 surface concentrations respectively; lower concentrations did not promote spreading. When a MW 3400 PEG spacer arm was incorporated between the hydrogel and the peptide linkage, incorporation of 1 pmol/cm2 RGD promoted 70% spreading whereas RDG at the same concentration did not promote spreading. In addition, when cells were seeded in serum-free medium, only RGD peptides incorporated with a spacer arm were able to promote spreading. Thus peptide incorporated into PEG 8000 diacrylate hydrogels without a spacer arm nonspecifically mediated cell spreading whereas incorporation via a MW 3400 PEG spacer arm was required to permit cell spreading to be specifically mediated.
TL;DR: The structure of the MscL homolog from Mycobacterium tuberculosis was determined by x-ray crystallography to 3.5 angstroms resolution and may serve as a model for other mechanosensitive channels, as well as the broader class of pentameric ligand-gated ion channels exemplified by the nicotinic acetylcholine receptor.
Abstract: Mechanosensitive ion channels play a critical role in transducing physical stresses at the cell membrane into an electrochemical response. The MscL family of large-conductance mechanosensitive channels is widely distributed among prokaryotes and may participate in the regulation of osmotic pressure changes within the cell. In an effort to better understand the structural basis for the function of these channels, the structure of the MscL homolog fromMycobacterium tuberculosis was determined by x-ray crystallography to 3.5 angstroms resolution. This channel is organized as a homopentamer, with each subunit containing two transmembrane α helices and a third cytoplasmic α helix. From the extracellular side, a water-filled opening approximately 18 angstroms in diameter leads into a pore lined with hydrophilic residues which narrows at the cytoplasmic side to an occluded hydrophobic apex that may act as the channel gate. This structure may serve as a model for other mechanosensitive channels, as well as the broader class of pentameric ligand-gated ion channels exemplified by the nicotinic acetylcholine receptor.
TL;DR: Trellis and lattice codes designed for additive white Gaussian noise channels can be superimposed on adaptive modulation for fading channels, with the same approximate coding gains, to obtain trellis-coded adaptive MQAM.
Abstract: We apply coset codes to adaptive modulation in fading channels. Adaptive modulation is a powerful technique to improve the energy efficiency and increase the data rate over a fading channel. Coset codes are a natural choice to use with adaptive modulation since the channel coding and modulation designs are separable. Therefore, trellis and lattice codes designed for additive white Gaussian noise (AWGN) channels can be superimposed on adaptive modulation for fading channels, with the same approximate coding gains. We first describe the methodology for combining coset codes with a general class of adaptive modulation techniques. We then apply this methodology to a spectrally efficient adaptive M-ary quadrature amplitude modulation (MQAM) to obtain trellis-coded adaptive MQAM. We present analytical and simulation results for this design which show an effective coding gain of 3 dB relative to uncoded adaptive MQAM for a simple four-state trellis code, and an effective 3.6-dB coding gain for an eight-state trellis code. More complex trellis codes are shown to achieve higher gains. We also compare the performance of trellis-coded adaptive MQAM to that of coded modulation with built-in time diversity and fixed-rate modulation. The adaptive method exhibits a power savings of up to 20 dB.
TL;DR: An overview of the as-built instrument characteristics and the application of MISR to remote sensing of the Earth is provided.
Abstract: The Multi-angle Imaging SpectroRadiometer (MISR) instrument is scheduled for launch aboard the first of the Earth Observing System (EOS) spacecraft, EOS-AM1. MISR will provide global, radiometrically calibrated, georectified, and spatially coregistered imagery at nine discrete viewing angles and four visible/near-infrared spectral bands. Algorithms specifically developed to capitalize on this measurement strategy will be used to retrieve geophysical products for studies of clouds, aerosols, and surface radiation. This paper provides an overview of the as-built instrument characteristics and the application of MISR to remote sensing of the Earth.
TL;DR: The staggered extension process (StEP) consists of priming the template sequence(s) followed by repeated cycles of denaturation and extremely abbreviated annealing/polymerase-catalyzed extension, which results in recombination of polynu-cleotide sequences.
Abstract: We have developed a simple and efficient method for in vitro mutagenesis and recombination of polynu-cleotide sequences. The staggered extension process (StEP) consists of priming the template sequence(s) followed by repeated cycles of denaturation and extremely abbreviated annealing/polymerase-catalyzed extension. In each cycle the growing fragments anneal to different templates based on sequence complementarity and extend further. This is repeated until full-length sequences form. Due to template switching, most of the polynucleotides contain sequence information from different parental sequences. The method is demonstrated by the recombination of two genes encoding thermostable subtilisins carrying two phenotypic markers separated by 113 base pairs and eight other point mutation markers. To demonstrate its utility for directed evolution, we have used StEP to recombine a set of five thermostabilized subtilisin E variants identified during a single round of error-prone PCR mutagenesis and screening. Screening the StEP-recombined library yielded an enzyme whose half-life at 65°C is 50 times that of wild-type subtilisin E.
TL;DR: The Advanced Composition Explorer (ACE) as mentioned in this paper was launched in 1997 with six high-resolution spectrometers that measured the elemental, isotopic, and ionic charge-state composition of nuclei from H to Ni (1≤Z≤28) from solar wind energies (∼1 keV nucl−1) to galactic cosmic-ray energies ( ∼1.5 million km sunward of Earth).
Abstract: The Advanced Composition Explorer was launched August 25, 1997 carrying six high-resolution spectrometers that measure the elemental, isotopic, and ionic charge-state composition of nuclei from H to Ni (1≤Z≤28) from solar wind energies (∼1 keV nucl−1) to galactic cosmic-ray energies (∼500 MeV nucl−1). Data from these instruments is being used to measure and compare the elemental and isotopic composition of the solar corona, the nearby interstellar medium, and the Galaxy, and to study particle acceleration processes that occur in a wide range of environments. ACE also carries three instruments that provide the heliospheric context for ion composition studies by monitoring the state of the interplanetary medium. From its orbit about the Sun-Earth libration point ∼1.5 million km sunward of Earth, ACE also provides real-time solar wind measurements to NOAA for use in forecasting space weather. This paper provides an introduction to the ACE mission, including overviews of the scientific goals and objectives, the instrument payload, and the spacecraft and ground systems.
TL;DR: ASTER will, for the first time, provide high-spatial resolution multispectral thermal infrared data from orbit and the highest spatial resolution surface spectral reflectance temperature and emissivity data of all of the EOS-AM1 instruments.
Abstract: The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is a research facility instrument provided by the Ministry of International Trade and Industry (MITI), Tokyo, Japan to be launched on NASA's Earth Observing System morning (EOS-AM1) platform in 1998. ASTER has three spectral hands in the visible near-infrared (VNIR), six bands in the shortwave infrared (SWIR), and five bands in the thermal infrared (TIR) regions, with 15-, 30-, and 90-m ground resolution, respectively. The VNIR subsystem has one backward-viewing band for stereoscopic observation in the along-track direction. Because the data will have wide spectral coverage and relatively high spatial resolution, it will be possible to discriminate a variety of surface materials and reduce problems in some lower resolution data resulting from mixed pixels. ASTER will, for the first time, provide high-spatial resolution multispectral thermal infrared data from orbit and the highest spatial resolution surface spectral reflectance temperature and emissivity data of all of the EOS-AM1 instruments. The primary science objective of the ASTER mission is to improve understanding of the local- and regional-scale processes occurring on or near the Earth's surface and lower atmosphere, including surface-atmosphere interactions. Specific areas of the science investigation include the following: (1) land surface climatology; (2) vegetation and ecosystem dynamics; (3) volcano monitoring; (4) hazard monitoring; (5) aerosols and clouds; (6) carbon cycling in the marine ecosystem; (7) hydrology; (8) geology and soil; and (9) land surface and land cover change. There are three categories of ASTER data: a global map, regional monitoring data sets, and local data sets to be obtained for requests from individual investigators.
TL;DR: The molecular and biochemical characteristics of the AP2/EREBP transcription factors and their diverse functions are reviewed here, and this multigene family is analyzed within the context of the Arabidopsis thaliana genome sequence project.
Abstract: AP2 (APETALA2) and EREBPs (ethylene-responsive element binding proteins) are the prototypic members of a family of transcription factors unique to plants, whose distinguishing characteristic is that they contain the so-called AP2 DNA-binding domain. AP2/ EREBP genes form a large multigene family, and they play a variety of roles throughout the plant life cycle: from being key regulators of several developmental processes, like floral organ identity determination or control of leaf epidermal cell identity, to forming part of the mechanisms used by plants to respond to various types of biotic and environmental stress. The molecular and biochemical characteristics of the AP2/EREBP transcription factors and their diverse functions are reviewed here, and this multigene family is analyzed within the context of the Arabidopsis thaliana genome sequence project.