Extending ion-track lithography to the low-energy ion regime

Ion tracking and ion-track lithography have been performed almost exclusively using ions with energies near or above the maximum in electronic stopping, which occurs at {approx}1 MeV/amu. In this paper, ion-track lithography using ions with energies well below this maximum is discussed. The results of etching ion tracks created in polycarbonate films by ions with energies just above the anticipated threshold for creating etchable latent tracks with cylindrical geometry have been examined. Low-energy neon and argon ions with 18-60 keV/amu and fluences of {approx}10{sup 8}/cm{sup 2} were used to examine the limits for producing useful, etchable tracks in polycarbonate films. By concentrating on the early stages of etching (i.e., {approx}20 nm < SEM hole diameter < {approx}100 nm), the energy deposition calculated for the incident ion was correlated with the creation of etchable tracks. The experimental results are discussed with regard to the energy losses of the ions in the polycarbonate films and to the formation of continuous latent tracks through the entire thickness of the films. The probability distributions for large-angle scattering events were calculated to assess their importance as a function of ion energy. All these results have significant implications with respect to the threshold for formation of etchable tracks and to the use of low-energy ions for lithographic applications of ion tracking

Identifying Lepidopteran resistance within hcf mutants

Abstract only availableSouthwestern corn borer (SWCB) and fall armyworm (FAW) feeding on maize causes extensive crop damage in the United States. Previous proteomic analysis comparing resistant and susceptible lines of maize indicates genes found in the photosystem II pathway are highly expressed in the resistant line. The high chlorophyll fluorescence (hcf) mutants have defects in photosystem I or photosystem II genes. A preference test was performed comparing hcf mutants to their wild-type siblings. Oy, pg, and g mutants were also compared to their wild-type siblings to ensure that color was not a factor in feeding differences. SWCB preferred the wild-type over hcf11-N1205A and hcf49-N1480 mutants, indicating these genes may be resistance factors. Oy1-Andrew and hcf13-N1097B mutants were preferred by SWCB compared to their wild-type siblings, indicating these genes increase susceptibility to feeding damage. hcf49-N1480, hcf7-N1029D, and pg15-N340B had reduced FAW damage compared to wild-type siblings, indicating they may increase resistance to feeding damage. hcf44-N1278B showed increased susceptibility to FAW feeding compared to its wild-type sibling. An antibiosis test was performed using hcf mutants. Photographs and larval weights were taken at the end of the four days. Tissue damage areas were analyzed using AlphaEaseFC software. From the data, hcf7-N1029D and hcf50-N1481 had reduced larval weights for both FAW and SWCB indicating these genes have antibiotic properties and can reduce larval feeding damage. The mutants evaluated for effects of pigmentation displayed varying results indicating color differences associated with some hcf mutants are unlikely to be responsible for the differences in feeding behavior observed. These genes identified here may be useful in increasing resistance to FAW and SWCB in commercial hybrids.MU Monsanto Undergraduate Research Fellowshi

Characterizing and modeling the apparent anomalous behavior of resistivity in Cr–Si–O thin films

The Cr-Si-O material system is of interest for use as a thin film resistor. The films are sputter deposited onto conducting substrates from metal oxide compacts using a reactive gas mixture. the cermet films composition range from 50 to 100 vol.% SiO{sub 2} as determined from elemental measurements of the Cr, Si and O content. In a wide range of resistivities from 10{sup 1} to 10 {sup 14} {omega}-cm measured through the film thickness, an apparent anomalous behavior is found with the Cr, Si and O composition. The anomaly can be deducted to a discontinuous variation of resistivity with film composition near 80 vol.% SiO{sub 2}. The film microstructure is characterized as a distribution of conducting metal-silicide particles within an insulating matrix. The effective medium theory is used to predict the variation of conductivity and successfully models the anomalous resistivity behavior

Natural genetic variation for root traits among diversity lines of maize (Zea Mays L.)

Maize (Z. mays L.) is the third most important food grain for humankind after rice and wheat. Maize is mostly grown under rain-fed conditions and among the cereals, it is the second most susceptible to drought next to rice. Constitutive variation for root traits is an important adaptation under drought prone conditions. The objective of this study is to screen the twenty five diverse parental lines used in the maize nested association mapping panel along with the common parental line, B73, for constitutive root traits (including rooting depth and root biomass) and shoot traits. All the lines were grown with five replications in 72 cm deep pots containing a turface:sand mixture (2:1 v/v) for 30 days under well-watered conditions in a temperature and humidity controlled green house. Significant variation existed among the diverse lines for root length, root biomass, shoot length, and leaf area. The average root length ranged from 17.5 to 106 cm. The genotypes with a deep root system also recorded greater root biomass and leaf area. The natural genetic variation exhibited by these lines could be exploited to identify potential quantitative trait loci controlling root architecture. Using the nested association mapping populations that were developed from these diverse lines, would allow for in-depth analysis and fine-mapping of prospective candidate genes for root architecture in maize

Kinetics and thermodynamics of carbon segregation and graphene growth on Ru(0001)

We measure the concentration of carbon adatoms on the Ru(0001) surface that are in equilibrium with C atoms in the crystal's bulk by monitoring the electron reflectivity of the surface while imaging. During cooling from high temperature, C atoms segregate to the Ru surface, causing graphene islands to nucleate. Using low-energy electron microscopy (LEEM), we measure the growth rate of individual graphene islands and, simultaneously, the local concentration of C adatoms on the surface. We find that graphene growth is fed by the supersaturated, two-dimensional gas of C adatoms rather than by direct exchange between the bulk C and the graphene. At long times, the rate at which C diffuses from the bulk to the surface controls the graphene growth rate. The competition among C in three states - dissolved in Ru, as an adatom, and in graphene - is quantified and discussed. The adatom segregation enthalpy determined by applying the simple Langmuir-McLean model to the temperature-dependent equilibrium concentration seriously disagrees with the value calculated from first-principles. This discrepancy suggests that the assumption in the model of non-interacting C is not valid

A pilot investigation of emotional regulation difficulties and mindfulness-based strategies in manic and remitted bipolar I disorder and major depressive disorder

Background: Both bipolar disorder and major depressive disorder are characterized by difficulties in emotion regulation. Little is known about which specific emotion regulatory patterns may be transdiagnostic versus disorder specific, and how such patterns change as a function of current mood states. Methods: This preliminary investigation examined specific patterns of self-reported trait emotion regulation difficulties and mindfulness-based regulations strategies across four groups: remitted adults with bipolar I disorder (BD-remitted; n = 32), currently manic adults with bipolar I disorder (BD-manic; n = 19), remitted adults with major depressive disorder (MDD-remitted; n = 32), and healthy controls (CTL; n = 30). Results: All three clinical groups reported significantly greater difficulties with emotion regulation and decreased overall mindfulness-based strategies. Conclusions: These results suggest that increased emotion regulation difficulties, decreased mindfulness, and increased emotion-driven impulsivity may be transdiagnostic across mood disorders and states, and that impulsivity may be particularly impaired during periods of mania. Keywords: Bipolar disorder; Emotion regulation; Emotional awareness; Impulsivity; Major depressive disorder; Mindfulness.</p

A BAC pooling strategy combined with PCR-based screenings in a large, highly repetitive genome enables integration of the maize genetic and physical maps

BACKGROUND: Molecular markers serve three important functions in physical map assembly. First, they provide anchor points to genetic maps facilitating functional genomic studies. Second, they reduce the overlap required for BAC contig assembly from 80 to 50 percent. Finally, they validate assemblies based solely on BAC fingerprints. We employed a six-dimensional BAC pooling strategy in combination with a high-throughput PCR-based screening method to anchor the maize genetic and physical maps. RESULTS: A total of 110,592 maize BAC clones (~ 6x haploid genome equivalents) were pooled into six different matrices, each containing 48 pools of BAC DNA. The quality of the BAC DNA pools and their utility for identifying BACs containing target genomic sequences was tested using 254 PCR-based STS markers. Five types of PCR-based STS markers were screened to assess potential uses for the BAC pools. An average of 4.68 BAC clones were identified per marker analyzed. These results were integrated with BAC fingerprint data generated by the Arizona Genomics Institute (AGI) and the Arizona Genomics Computational Laboratory (AGCoL) to assemble the BAC contigs using the FingerPrinted Contigs (FPC) software and contribute to the construction and anchoring of the physical map. A total of 234 markers (92.5%) anchored BAC contigs to their genetic map positions. The results can be viewed on the integrated map of maize [1,2]. CONCLUSION: This BAC pooling strategy is a rapid, cost effective method for genome assembly and anchoring. The requirement for six replicate positive amplifications makes this a robust method for use in large genomes with high amounts of repetitive DNA such as maize. This strategy can be used to physically map duplicate loci, provide order information for loci in a small genetic interval or with no genetic recombination, and loci with conflicting hybridization-based information

Genetic variation among 481 diverse soybean accessions, inferred from genomic re-sequencing

We report characteristics of soybean genetic diversity and structure from the resequencing of 481 diverse soybean accessions, comprising 52 wild (Glycine soja) selections and 429 cultivated (Glycine max) varieties (landraces and elites). This data was used to identify 7.8 million SNPs, to predict SNP effects relative to genic regions, and to identify the genetic structure, relationships, and linkage disequilibrium. We found evidence of distinct, mostly independent selection of lineages by particular geographic location. Among cultivated varieties, we identified numerous highly conserved regions, suggesting selection during domestication. Comparisons of these accessions against the whole U.S. germplasm genotyped with the SoySNP50K iSelect BeadChip revealed that over 95% of the resequenced accessions have a high similarity to their SoySNP50K counterparts. Probable errors in seed source or genotype tracking were also identified in approximately 5% of the accessions