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All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Efficient and dynamic nuclear localization of green fluorescent protein via RNA binding

Classical nuclear localization signal (NLS) sequences have been used for artificial localization of green fluorescent protein (GFP) in the nucleus as a positioning marker or for measurement of the nuclear-cytoplasmic shuttling rate in living cells. However, the detailed mechanism of nuclear retention of GFP-NLS remains unclear. Here, we show that a candidate mechanism for the strong nuclear retention of GFP-NLS is via the RNA-binding ability of the NLS sequence. GFP tagged with a classical NLS derived from Simian virus 40 (GFP-NLS{sup SV40}) localized not only in the nucleoplasm, but also to the nucleolus, the nuclear subdomain in which ribosome biogenesis takes place. GFP-NLS{sup SV40} in the nucleolus was mobile, and intriguingly, the diffusion coefficient, which indicates the speed of diffusing molecules, was 1.5-fold slower than in the nucleoplasm. Fluorescence correlation spectroscopy (FCS) analysis showed that GFP-NLS{sup SV40} formed oligomers via RNA binding, the estimated molecular weight of which was larger than the limit for passive nuclear export into the cytoplasm. These findings suggest that the nuclear localization of GFP-NLS{sup SV40} likely results from oligomerization mediated via RNA binding. The analytical technique used here can be applied for elucidating the details of other nuclear localization mechanisms, including those of several types of nuclear proteins. In addition, GFP-NLS{sup SV40} can be used as an excellent marker for studying both the nucleoplasm and nucleolus in living cells. - Highlights: • Nuclear localization signal-tagged GFP (GFP-NLS) showed clear nuclear localization. • The GFP-NLS dynamically localized not only in the nucleoplasm, but also to the nucleolus. • The nuclear localization of GFP-NLS results from transient oligomerization mediated via RNA binding. • Our NLS-tagging procedure is ideal for use in artificial sequestration of proteins in the nucleus.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2012

Local Failure in Resected N1 Lung Cancer: Implications for Adjuvant Therapy

Purpose: To evaluate actuarial rates of local failure in patients with pathologic N1 non-small-cell lung cancer and to identify clinical and pathologic factors associated with an increased risk of local failure after resection. Methods and Materials: All patients who underwent surgery for non-small-cell lung cancer with pathologically confirmed N1 disease at Duke University Medical Center from 1995-2008 were identified. Patients receiving any preoperative therapy or postoperative radiotherapy or with positive surgical margins were excluded. Local failure was defined as disease recurrence within the ipsilateral hilum, mediastinum, or bronchial stump/staple line. Actuarial rates of local failure were calculated with the Kaplan-Meier method. A Cox multivariate analysis was used to identify factors independently associated with a higher risk of local recurrence. Results: Among 1,559 patients who underwent surgery during the time interval, 198 met the inclusion criteria. Of these patients, 50 (25%) received adjuvant chemotherapy. Actuarial (5-year) rates of local failure, distant failure, and overall survival were 40%, 55%, and 33%, respectively. On multivariate analysis, factors associated with an increased risk of local failure included a video-assisted thoracoscopic surgery approach (hazard ratio [HR], 2.5; p = 0.01), visceral pleural invasion (HR, 2.1; p = 0.04), and increasing number of positive N1 lymph nodes (HR, 1.3 per involved lymph node; p = 0.02). Chemotherapy was associated with a trend toward decreased risk of local failure that was not statistically significant (HR, 0.61; p = 0.2). Conclusions: Actuarial rates of local failure in pN1 disease are high. Further investigation of conformal postoperative radiotherapy may be warranted.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2013

Localization Accuracy and Immobilization Effectiveness of a Stereotactic Body Frame for a Variety of Treatment Sites

Purpose: The purpose of this study was to analyze the pretreatment setup errors and intrafraction motion using cone beam computed tomography (CBCT) for stereotactic body radiation therapy patients immobilized and localized with a stereotactic body frame for a variety of treatment sites. Methods and Materials: Localization errors were recorded for patients receiving SBRT for 141 lung, 29 liver, 48 prostate, and 45 spine tumors representing 1005 total localization sessions. All patients were treated in a stereotactic body frame with a large custom-molded vacuum pillow. Patients were first localized to the frame using tattoos placed during simulation. Subsequently, the frame was aligned to the room lasers according to the stereotactic coordinates determined from the treatment plan. Every patient received a pretreatment and an intrafraction CBCT. Abdominal compression was used for all liver patients and for approximately 40% of the lung patients to reduce tumor motion due to respiration. Results: The mean ± standard deviation pretreatment setup errors from all localizations were −2.44 ± 3.85, 1.31 ± 5.84, and 0.11 ± 3.76 mm in the anteroposterior, superoinferior, and lateral directions, respectively. The mean pretreatment localization results among all treatment sites were not significantly different (F test, P<.05). For all treatment sites, the mean ± standard deviation intrafraction shifts were 0.33 ± 1.34, 0.15 ± 1.45, and −0.02 ± 1.17 mm in the anteroposterior, superoinferior, and lateral directions, respectively. The mean unidimensional intrafraction shifts were statistically different for several of the comparisons (P<.05) as assessed by the Tukey-Kramer test. Conclusions: Despite the varied tumor locations, the pretreatment mean localization errors for all sites were found to be consistent among the treatment sites and not significantly different, indicating that the body frame is a suitable immobilization and localization device for a variety of tumor sites. Our pretreatment localization errors and intrafraction shifts compare favorably with those reported in other studies using different types of immobilization devices.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2015

Local Control for Intermediate-Risk Rhabdomyosarcoma: Results From D9803 According to Histology, Group, Site, and Size: A Report From the Children's Oncology Group

Purpose: To determine local control according to clinical variables for patients with intermediate-risk rhabdomyosarcoma (RMS) treated on Children's Oncology Group protocol D9803. Patients and Methods: Of 702 patients enrolled, we analyzed 423 patients with central pathology–confirmed group III embryonal (n=280) or alveolar (group III, n=102; group I-II, n=41) RMS. Median age was 5 years. Patients received 42 weeks of VAC (vincristine, dactinomycin, cyclophosphamide) or VAC alternating with VTC (T = topotecan). Local therapy with 50.4 Gy radiation therapy with or without delayed primary excision began at week 12 for group III patients. Patients with group I/II alveolar RMS received 36-41.4 Gy. Local failure (LF) was defined as local progression as a first event with or without concurrent regional or distant failure. Results: At a median follow-up of 6.6 years, patients with clinical group I/II alveolar RMS had a 5-year event-free survival rate of 69% and LF of 10%. Among patients with group III RMS, 5-year event-free survival and LF rates were 70% and 19%, respectively. Local failure rates did not differ by histology, nodal status, or primary site, though there was a trend for increased LF for retroperitoneal (RP) tumors (P=.12). Tumors ≥5 cm were more likely to fail locally than tumors <5 cm (25% vs 10%, P=.0004). Almost all (98%) RP tumors were ≥5 cm, with no difference in LF by site when the analysis was restricted to tumors ≥5 cm (P=.86). Conclusion: Local control was excellent for clinical group I/II alveolar RMS. Local failure constituted 63% of initial events in clinical group III patients and did not vary by histology or nodal status. The trend for higher LF in RP tumors was related to tumor size. There has been no clear change in local control over RMS studies, including IRS-III and IRS-IV. Novel approaches are warranted for larger tumors (≥5 cm).

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2016

Trends in Local Therapy Utilization and Cost for Early-Stage Breast Cancer in Older Women: Implications for Payment and Policy Reform

Purpose: Older women with early-stage disease constitute the most rapidly growing breast cancer demographic, yet it is not known which local therapy strategies are most favored by this population in the current era. Understanding utilization trends and cost of local therapy is important for informing the design of bundled payment models as payers migrate away from fee-for-service models. We therefore used the Surveillance, Epidemiology, and End Results Medicare database to determine patterns of care and costs for local therapy among older women with breast cancer. Methods and Materials: Treatment strategy and covariables were determined in 55,327 women age ≥66 with Tis-T2N0-1M0 breast cancer who underwent local therapy between 2000 and 2008. Trends in local therapy were characterized using Joinpoint. Polychotomous logistic regression determined predictors of local therapy. The median aggregate cost over the first 24 months after diagnosis was determined from Medicare claims through 2010 and reported in 2014 dollars. Results: The median age was 75. Local therapy distribution was as follows: 27,896 (50.3%) lumpectomy with external beam radiation, 18,356 (33.1%) mastectomy alone, 6159 (11.1%) lumpectomy alone, 1488 (2.7%) mastectomy with reconstruction, and 1455 (2.6%) lumpectomy with brachytherapy. Mastectomy alone declined from 39.0% in 2000 to 28.2% in 2008, and the use of breast conserving local therapies rose from 58.7% to 68.2%. Mastectomy with reconstruction was more common among the youngest, healthiest patients, whereas mastectomy alone was more common among patients living in rural low-income regions. By 2008, the costs were $36,749 for lumpectomy with brachytherapy, $35,030 for mastectomy with reconstruction, $31,388 for lumpectomy with external beam radiation, $21,993 for mastectomy alone, and $19,287 for lumpectomy alone. Conclusions: The use of mastectomy alone in older women declined in favor of breast conserving strategies between 2000 and 2008. Using these cost estimates, price points for local therapy bundles can be constructed to incentivize the treatment strategies that confer the highest value.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2017

{sup 18}F-Fluorodeoxyglucose/Positron Emission Tomography Predicts Patterns of Failure After Definitive Chemoradiation Therapy for Locally Advanced Non-Small Cell Lung Cancer

Background: We previously reported that pretreatment positron emission tomography (PET) identifies lesions at high risk for progression after concurrent chemoradiation therapy (CRT) for locally advanced non-small cell lung cancer (NSCLC). Here we validate those findings and generate tumor control probability (TCP) models. Methods: We identified patients treated with definitive, concurrent CRT for locally advanced NSCLC who underwent staging {sup 18}F-fluorodeoxyglucose/PET/computed tomography. Visible hypermetabolic lesions (primary tumors and lymph nodes) were delineated on each patient's pretreatment PET scan. Posttreatment imaging was reviewed to identify locations of disease progression. Competing risks analyses were performed to examine metabolic tumor volume (MTV) and radiation therapy dose as predictors of local disease progression. TCP modeling was performed to describe the likelihood of local disease control as a function of lesion size. Results: Eighty-nine patients with 259 hypermetabolic lesions (83 primary tumors and 176 regional lymph nodes) met the inclusion criteria. Twenty-eight patients were included in our previous report, and the remaining 61 constituted our validation cohort. The median follow-up time was 22.7 months for living patients. In 20 patients, the first site of progression was a primary tumor or lymph node treated with radiation therapy. The median time to progression for those patients was 11.5 months. Data from our validation cohort confirmed that lesion MTV predicts local progression, with a 30-month cumulative incidence rate of 23% for lesions above 25 cc compared with 4% for lesions below 25 cc (P=.008). We found no evidence that radiation therapy dose was associated with local progression risk. TCP modeling yielded predicted 30-month local control rates of 98% for a 1-cc lesion, 94% for a 10-cc lesion, and 74% for a 50-cc lesion. Conclusion: Pretreatment FDG-PET identifies lesions at risk for progression after CRT for locally advanced NSCLC. Strategies to improve local control should be tested on high-risk lesions, and treatment deintensification for low-risk lesions should be explored.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2014

Microstructural Characterization of Deformation Localization at Small Strains in a Neutron Irradiated 304 Stainless Steel

Deformation localization and structure evolution were investigated in an AISI 304 austenitic stainless steel deformed to 0.8% strain. Using SEM-EBSD, it was shown local plastic deformation may reach significant levels even when the bulk averaged strain level remains below 1%. Local misorientation values up to 24 were observed in these regions of high local plastic deformation. EBSD analysis of FIB lift-out specimens demonstrated that local misorientation level was highest near the free surface and diminished with increasing depth. (S)TEM observations on the same specimen indicated the local density of dislocation channels may vary up to an order of magnitude depending on local grain configuration, distance to the surface and/or local grain boundary structure. It was found that in the case of RT deformation, dislocation defect-free channels may contain twin or may be twin-free with twinning occurring inside channels. Formation of BCC-phase colonies (martensite) was observed in near-surface layer whereas no transformation in the volume of the specimen was detected at this strain level. Martensite formation was associated with channel-grain boundary intersection points where high local misorientation was observed using EBSD.

Deformation↗
DOE OSTI2017

Correspondence: Reply to ‘Phantom phonon localization in relaxors’

The Correspondence by Gehring et al. mistakes Anderson phonon localization for the concept of an atomic-scale local mode. An atomic-scale local mode refers to a single atom vibrating on its own within a crystal. Such a local mode will have an almost flat intensity profile, but this is not the same as phonon localization. Anderson localization is a wave interference effect in a disordered system that results in waves becoming spatially localized. The length scale of the localized waves is set by the wavelength, which is approximately 2 nm in this case. This larger length scale in real space means narrower intensity profiles in reciprocal space. Here, we conclude that the claims in the Correspondence by Gehring et al. are incorrect because they mistakenly assume that the length scale for Anderson localization is atomic, and because the experimental observations rule out multiple scattering as the origin.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Towards improved local hybrid functionals by calibration of exchange-energy densities

A new approach for the calibration of (semi-)local and exact exchange-energy densities in the context of local hybrid functionals is reported. The calibration functions are derived from only the electron density and its spatial derivatives, avoiding spatial derivatives of the exact-exchange energy density or other computationally unfavorable contributions. The calibration functions fulfill the seven more important out of nine known exact constraints. It is shown that calibration improves substantially the definition of a non-dynamical correlation energy term for generalized gradient approximation (GGA)-based local hybrids. Moreover, gauge artifacts in the potential-energy curves of noble-gas dimers may be corrected by calibration. The developed calibration functions are then evaluated for a large range of energy-related properties (atomization energies, reaction barriers, ionization potentials, electron affinities, and total atomic energies) of three sets of local hybrids, using a simple one-parameter local-mixing. The functionals are based on (a) local spin-density approximation (LSDA) or (b) Perdew-Burke-Ernzerhof (PBE) exchange and correlation, and on (c) Becke-88 (B88) exchange and Lee-Yang-Parr (LYP) correlation. While the uncalibrated GGA-based functionals usually provide very poor thermochemical data, calibration allows a dramatic improvement, accompanied by only a small deterioration of reaction barriers. In particular, an optimized BLYP-based local-hybrid functional has been found that is a substantial improvement over the underlying global hybrids, as well as over previously reported LSDA-based local hybrids. It is expected that the present calibration approach will pave the way towards new generations of more accurate hyper-GGA functionals based on a local mixing of exchange-energy densities.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Local entropy of a nonequilibrium fermion system

The local entropy of a nonequilibrium system of independent fermions is investigated and analyzed in the context of the laws of thermodynamics. It is shown that the local temperature and chemical potential can only be expressed in terms of derivatives of the local entropy for linear deviations from local equilibrium. The first law of thermodynamics is shown to lead to an inequality, not equality, for the change in the local entropy as the nonequilibrium state of the system is changed. The maximum entropy principle (second law of thermodynamics) is proven: a nonequilibrium distribution has a local entropy less than or equal to a local equilibrium distribution satisfying the same constraints. It is shown that the local entropy of the system tends to zero when the local temperature tends to zero, consistent with the third law of thermodynamics

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2012

A UNIVERSAL, LOCAL STAR FORMATION LAW IN GALACTIC CLOUDS, NEARBY GALAXIES, HIGH-REDSHIFT DISKS, AND STARBURSTS

Star formation laws are rules that relate the rate of star formation in a particular region, either an entire galaxy or some portion of it, to the properties of the gas, or other galactic properties, in that region. While observations of Local Group galaxies show a very simple, local star formation law in which the star formation rate per unit area in each patch of a galaxy scales linearly with the molecular gas surface density in that patch, recent observations of both Milky Way molecular clouds and high-redshift galaxies apparently show a more complicated relationship in which regions of equal molecular gas surface density can form stars at quite different rates. These data have been interpreted as implying either that different star formation laws may apply in different circumstances, that the star formation law is sensitive to large-scale galaxy properties rather than local properties, or that there are high-density thresholds for star formation. Here we collate observations of the relationship between gas and star formation rate from resolved observations of Milky Way molecular clouds, from kpc-scale observations of Local Group galaxies, and from unresolved observations of both disk and starburst galaxies in the local universe and at high redshift. We show that all of these data are in fact consistent with a simple, local, volumetric star formation law. The apparent variations stem from the fact that the observed objects have a wide variety of three-dimensional size scales and degrees of internal clumping, so even at fixed gas column density the regions being observed can have wildly varying volume densities. We provide a simple theoretical framework to remove this projection effect, and we use it to show that all the data, from small solar neighborhood clouds with masses {approx}10{sup 3} M{sub Sun} to submillimeter galaxies with masses {approx}10{sup 11} M{sub Sun }, fall on a single star formation law in which the star formation rate is simply {approx}1% of the molecular gas mass per local free-fall time. In contrast, proposed star formation laws in which the star formation timescale is set by the galactic rotation period are inconsistent with the data from the Milky Way and the Local Group, while those in which the star formation rate is linearly proportional to the gas mass above some density threshold fail both in the Local Group and for starburst galaxies.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Alignments of the galaxies in and around the Virgo cluster with the local velocity shear

Observational evidence is presented for the alignment between the cosmic sheet and the principal axis of the velocity shear field at the position of the Virgo cluster. The galaxies in and around the Virgo cluster from the Extended Virgo Cluster Catalog that was recently constructed by Kim et al. are used to determine the direction of the local sheet. The peculiar velocity field reconstructed from the Sloan Digital Sky Survey Data Release 7 is analyzed to estimate the local velocity shear tensor at the Virgo center. Showing first that the minor principal axis of the local velocity shear tensor is almost parallel to the direction of the line of sight, we detect a clear signal of alignment between the positions of the Virgo satellites and the intermediate principal axis of the local velocity shear projected onto the plane of the sky. Furthermore, the dwarf satellites are found to appear more strongly aligned than their normal counterparts, which is interpreted as an indication of the following. (1) The normal satellites and the dwarf satellites fall in the Virgo cluster preferentially along the local filament and the local sheet, respectively. (2) The local filament is aligned with the minor principal axis of the local velocity shear while the local sheet is parallel to the plane spanned by the minor and intermediate principal axes. Our result is consistent with the recent numerical claim that the velocity shear is a good tracer of the cosmic web.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

The metallicity’s fundamental dependence on both local and global galactic quantities

ABSTRACT We study the scaling relations between gas-phase metallicity, stellar mass surface density (Σ*), star formation rate surface density (ΣSFR), and molecular gas surface density ($\Sigma _{{\rm H}_2}$) in local star-forming galaxies on scales of a kpc. We employ optical integral field spectroscopy from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey, and ALMA data for a subset of MaNGA galaxies. We use partial correlation coefficients and Random Forest regression to determine the relative importance of local and global galactic properties in setting the gas-phase metallicity. We find that the local metallicity depends primarily on Σ* (the resolved mass–metallicity relation, rMZR), and has a secondary anticorrelation with ΣSFR (i.e. a spatially resolved version of the ‘Fundamental Metallicity Relation’, rFMR). We find that $\Sigma _{{\rm H}_2}$ is less important than ΣSFR in determining the local metallicity. This result indicates that gas accretion, resulting in local metallicity dilution and local boosting of star formation, is unlikely to be the primary origin of the rFMR. The local metallicity depends also on the global properties of galaxies. We find a strong dependence on the total stellar mass (M*) and a weaker (inverse) dependence on the total SFR. The global metallicity scaling relations, therefore, do not simply stem out of their resolved counterparts; global properties and processes, such as the global gravitational potential well, galaxy-scale winds and global redistribution/mixing of metals, likely contribute to the local metallicity, in addition to local production and retention.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

Quantifying local rearrangements in three-dimensional granular materials: Rearrangement measures, correlations, and relationship to stresses

Quantifying the ways in which local particle rearrangements contribute to macroscopic plasticity is one of the fundamental pursuits of granular mechanics and soft matter physics. Here we examine local rearrangements that occur naturally during the deformation of three samples of 3D granular materials subjected to distinct boundary conditions by employing in situ x-ray measurements of particle-resolved structure and stress. We focus on five distinct rearrangement measures, their statistics, interrelationships, contributions to macroscopic deformation, repeatability, and dependence on local structure and stress. Our most significant findings are that local rearrangements (1) are correlated on a scale of three to four particle diameters, (2) exhibit volumetric strain-shear strain and nonaffine displacement-rotation coupling, (3) exhibit correlations that suggest either rearrangement repeatability or that rearrangements span multiple steps of incremental sample strain, and (4) show little dependence on local stress but correlate with quantities describing local structure, such as porosity. Our results are presented in the context of relevant plasticity theories and are consistent with recent findings suggesting that local structure may play at least as important of a role as local stress in determining the nature of local rearrangements.

58 GEOSCIENCES↗
DOE OSTI2019

Localization in Fractonic Random Circuits

We study the spreading of initially local operators under unitary time evolution in a one-dimensional random quantum circuit model that is constrained to conserve a U ( 1 ) charge and also the dipole moment of this charge. These constraints are motivated by the quantum dynamics of fracton phases. We discover that the charge remains localized at its initial position, providing a crisp example of a nonergodic dynamical phase of random circuit dynamics. This localization can be understood as a consequence of the return properties of low-dimensional random walks, through a mechanism reminiscent of weak localization, but insensitive to dephasing. The charge dynamics is well described by a system of coupled hydrodynamic equations, which makes several nontrivial predictions that are all in good agreement with numerics in one dimension. Importantly, these equations also predict localization in two-dimensional fractonic random circuits. We further find that the immobile fractonic charge emits nonconserved operators, whose spreading is governed by exponents that are distinct from those observed in nonfractonic circuits. These nonstandard exponents are also explained by our coupled hydrodynamic equations. Where entanglement properties are concerned, we find that fractonic operators exhibit a short time linear growth of observable entanglement with saturation to an area law, as well as a subthermal volume law for operator entanglement. The entanglement spectrum is found to follow semi-Poisson statistics, similar to eigenstates of many-body localized systems. The nonergodic phenomenology is found to persist to initial conditions containing nonzero density of dipolar or fractonic charge, including states near the sector of maximal charge. Our work implies that low-dimensional fracton systems should preserve forever a memory of their initial conditions in local observables under noisy quantum dynamics, thereby constituting ideal memories. It also implies that one- and two-dimensional fracton systems should realize true many-body localization (MBL) under Hamiltonian dynamics, even in the absence of disorder, with the obstructions to MBL in translation-invariant systems and in spatial dimensions greater than one being evaded by the nature of the mechanism responsible for localization. We also suggest a possible route to new nonergodic phases in high dimensions.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Local adaptation of both plant and pathogen: an arms‐race compromise in switchgrass rust

In coevolving species, parasites locally adapt to host populations as hosts locally adapt to resist parasites. Parasites often outpace host local adaptation since they have rapid life cycles, but host diversity, the strength of selection, and external environmental influence can result in complex outcomes. To better understand local adaptation in host–parasite systems, we examined locally adapted switchgrass (Panicum virgatum), and its leaf rust pathogen (Puccinia novopanici) across a latitudinal range in North America. We grew switchgrass genotypes in 10 replicated multiyear common gardens, measuring rust severity from natural infection in a ‘host reciprocal transplant’ framework for testing local adaptation. We conducted genome-wide association mapping to identify genetic loci associated with rust severity. Genetically differentiated rust populations were locally adapted to northern and southern switchgrass, despite host local adaptation to environmental conditions in the same regions. Rust resistance was polygenic, and distinct loci were associated with rust severity in the north and south. We narrowed a previously identified large-effect quantitative trait locus for rust severity to a candidate YELLOW STRIPE-LIKE gene and linked numerous other loci to defense-related genes. Overall, our results suggest that both hosts and parasites can be simultaneously locally adapted, especially when parasites impose less selection than other environmental factors.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1989

Detection of edges using local geometry

Researchers described a new representation, the local geometry, for early visual processing which is motivated by results from biological vision. This representation is richer than is often used in image processing. It extracts more of the local structure available at each pixel in the image by using receptive fields that can be continuously rotated and that go to third order spatial variation. Early visual processing algorithms such as edge detectors and ridge detectors can be written in terms of various local geometries and are computationally tractable. For example, Canny's edge detector has been implemented in terms of a local geometry of order two, and a ridge detector in terms of a local geometry of order three. The edge detector in local geometry was applied to synthetic and real images and it was shown using simple interpolation schemes that sufficient information is available to locate edges with sub-pixel accuracy (to a resolution increase of at least a factor of five). This is reasonable even for noisy images because the local geometry fits a smooth surface - the Taylor series - to the discrete image data. Only local processing was used in the implementation so it can readily be implemented on parallel mesh machines such as the MPP. Researchers expect that other early visual algorithms, such as region growing, inflection point detection, and segmentation can also be implemented in terms of the local geometry and will provide sufficiently rich and robust representations for subsequent visual processing.

Gualtieri, J. A.↗
NASA NTRS1990

Localization effects in radiationally disordered high-temperature superconductors: Theoretical interpretation

Theoretical interpretation of recent experiments on radiationally disordered high-temperature superconductors is presented, based on the concepts of mutual interplay of Anderson localization and superconductivity. Microscopic derivation of Ginzburg-Landau coefficients for the quasi-two-dimensional system in the vicinity of localization transition is given in the framework of the self-consistent theory of localization. The 'minimal metallic conductivity' for the quasi-two-dimensional case is enhanced due to a small overlap of electronic states on the nearest neighbor conducting planes. This leads to a stronger influence of localization effects than in ordinary (three-dimensional) superconductors. From this point of view even the initial samples of high-temperature superconductors are already very close to Anderson transition. Anomalies of H(c2) are also analyzed, explaining the upward curvature of H(c2)(T) and apparent independence of dH(c2)/dT (T = T(sub c)) on the degree of disorder as due to localization effects. Researchers discuss the possible reasons of fast T(sub c) degradation due to the enhanced Coulomb effects caused by the disorder induced decrease of localization length. The appearance and growth of localized magnetic moments is also discussed. The disorder dependence of localization length calculated from the experimental data on conductivity correlates reasonably with the theoretical criterion for suppression of superconductivity in the system with localized electronic states.

Goshchitskii, B. N.↗