XMCD study of the Ruddlesden-Popper Phase La1.2Nd0.2Sr1.6Mn2O7.

X-ray Magnetic Circular Dichroism (XMCD) measurements of the Ruddlesden-Popper Phase La1,2Nd0,2Sr1.6Mn2O7 are reported. The Mn K. La and Nd L2,L3 edges have been measured on a powder sample at two different magnetic fields at low temperature. The analysis of the spectra at B = 1T indicates a large orbital moment of the Nd 5d-states and a significant spin-polarization of the La 5d-band. Furthermore at the Mn K-edge a XMCD-signal is observed, showing a polarization of the Mn 4p-band. At lower field (0.2T) all XMCD-signals are about two times smaller corresponding to the lower total magnetization. The signal at the Nd L2 edge vanishes completely at 0.2T.

Characterization and mapping of sequence-tagged microsatellite sites in the chickpea (Cicer arietinum L.) genome.

A size-selected genomic library comprising 280,000 colonies and representing approximately 18% of the chickpea genome, was screened for (GA)n, (GAA)n and (TAA)n microsatellite-containing clones, of which 389 were sequenced. The majority (approximately 75%) contained perfect repeats; interrupted, interrupted compound and compound repeats were only present in 6%-9% of cases. (TAA)-microsatellites contained the longest repeats, with unit numbers from 9 to 131. For 218 loci primers could be designed and used for the detection of microsatellite length polymorphisms in six chickpea breeding cultivars, as well as in C. reticulatum and C. echinospermum, wild, intercrossable relatives of chickpea. A total of 174 primer pairs gave interpretable banding patterns, 137 (79%) of which revealed at least two alleles on native polyacrylamide gels. A total of 120 sequence-tagged microsatellite site (STMS) markers were genetically mapped in 90 recombinant inbred lines from an inter-species cross between C. reticulatum and the chickpea cultivar ICC 4958. Markers could be arranged in 11 linkage groups (at a LOD score of 4) covering 613 cM. Clustering as well as random distribution of loci was observed. Segregation of 46 markers (39%) deviated significantly (P > or = 0.05) from the expected 1:1 ratio. The majority of these loci (73%) were located in three distinct regions of the genome. The present STMS marker map represents the most advanced co-dominant DNA marker map of the chickpea genome.

Sequence-tagged microsatellite site markers for chickpea (Cicer arietinum L.).

Two small-insert genomic libraries of chickpea (Cicer arietinum L.) were screened with a set of microsatellite-specific oligonucleotide probes. A total of 121 positive clones were identified among 13,000 plated colonies. Thirty-nine clones were recognized by (TAA)5, 26 by (GA)8, 18 by (GT)8, 27 by a pool of AT-rich trinucleotide repeats [(CAA)5, (CAT)5, and (GAA)5], and 11 by a pool of GC-rich trinucleotides [(TCC)5, (CAC)5, (CAG)5, and (CGA)5]. Of 53 clones selected for sequencing, 43 carried a microsatellite. Flanking primer pairs were designed for 28 loci, and used on a small test-set comprising one C. reticulatum and four C. arietinum accessions. Separation of the PCR products on agarose or polyacrylamide gels revealed single bands of the expected size with 22 of the primer pairs. Sixteen of these "Cicer arietinum sequence-tagged microsatellite site" (CaSTMS) markers were polymorphic at an intraspecific level, detecting 2-4 alleles within the four accessions examined. Primer pairs CaSTMS10 and CaSTMS15 revealed 25 and 16 alleles among 63 C. arietinum accessions from different geographic locations, reflecting gene diversity values of 0.937 and 0.922, respectively. Mendelian inheritance of CaSTMS markers was demonstrated using a set of recombinant inbred lines and their parents.

Allelic variation at (TAA)n microsatellite loci in a world collection of chickpea (Cicer arietinum L.) germplasm.

A set of 12 randomly selected (TAA)n microsatellite loci of the cultivated chickpea (Cicer arietinum L.) were screened in a worldwide sample comprising 72 landraces, four improved cultivars and two wild species of the primary gene pool (C. reticulatum and C. echinosperum) to determine the level and pattern of polymorphism in these populations. A single fragment was amplified from all the accessions with each of 12 sequence-tagged microsatellite site markers, except for one locus where no fragment was obtained from either of the two wild species. There was a high degree of intraspecific polymorphism at these microsatellite loci, although isozymes, conventional RFLPs and RAPDs show very little or no polymorphism. Overall, the repeat number at a locus (excluding null alleles) ranged from 7 to 42. The average number of alleles per locus was 14.1 and the average genetic diversity was 0.86. Based on the estimates obtained, 11 out of the 12 frequency distributions of alleles at the loci tested can be considered to be non-normal. A significant positive correlation between the average number of repeats (size of the locus) and the amount of variation was observed, indicating that replication slippage may be the molecular mechanism involved in generation of variability at the loci. A comparison between the infinite allele and stepwise mutation models revealed that for 11 out of the 12 loci the number of alleles observed fell in between the values predicted by the two models. Phylogenetic analysis of microsatellite polymorphism in C. arietinum showed no relationship between accession and geographic origin, which is compatible with the recent expansion of this crop throughout the world.

A phoneme effect in visual word recognition.

In alphabetic writing systems like English or French, many words are composed of more letters than phonemes (e.g. BEACH is composed of five letters and three phonemes, i.e./biJ/). This is due to the presence of higher order graphemes, that is, groups of letters that map into a single phoneme (e.g. EA and CH in BEACH map into the single phonemes /i/ and /J/, respectively). The present study investigated the potential role of these subsyllabic components for the visual recognition of words in a perceptual identification task. In Experiment 1, we manipulated the number of phonemes in monosyllabic, low frequency, five-letter, English words, and found that identification times were longer for words with a small number of phonemes than for words with a large number of phonemes. In Experiment 2, this 'phoneme effect' was replicated in French for low frequency, but not for high frequency, monosyllabic words. These results suggest that subsyllabic components, also referred to as functional orthographic units, play a crucial role as elementary building blocks of visual word recognition.

Spectral parameters for quantitative mobility contrast in NMR imaging of solid polymers.

Different procedures based on parameters of the wideline NMR absorption spectrum are presented to obtain localized molecular mobility contrast for imaging of solid polymers. For this purpose a 1H-NMR imaging technique with magic sandwich echoes is used for acquiring localized wideline spectra. With samples composed of polystyrene and high impact strength polystyrene, and polycarbonate and low density polyethylene a spatial difference in NMR absorption spectrum lineshape and linewidth is displayed. Furthermore, the spatial distribution of rigid and mobile domains in a heterogeneous polymer can be derived from the NMR spectral components. It is demonstrated that a van Vleck moment analysis can be performed from spatially resolved magic echo decays. The second (M2) and fourth (M4) moments of the rigid components show considerable variation with the spatial composition of the investigated samples.

Should antibiotic prophylaxis be used routinely in clean surgical procedures: a tentative yes.

BACKGROUND: The incidence of surgical site infection (SSI) after clean surgical procedure has traditionally been regarded as too low for routine antibiotic prophylaxis. But we now know that host factors may increase the risk of SSI to as high as 20%. We assessed the value of prophylactic cefotaxime in patients stratified for risk of SSI in a randomized double-blind trial. METHODS: Patients admitted for clean elective operations were enrolled, stratified for risk by National Nosocomial Infection Survey criteria, and randomized to receive intravenous cefotaxime 2 gm or placebo on call for operation. They were followed for 4 to 6 weeks for SSI diagnosed by Centers for Disease Control and Prevention criteria. RESULTS: Analysis of 775 patients showed that the 378 evaluable patients who received cefotaxime had 70% fewer SSI than those who did not--Mantel-Haenszel risk ratio (MH-RR) 0.31; 95% confidence intervals (CI) 0.11 to 0.83. Benefit was clear in the 616 low risk patients--0.97% versus 3.9% SSI (MH-RR 0.25, CI 0.07 to 0.87, p = 0.018), but only a trend was seen in 136 high risk patients--2.8% versus 6.1% SSI (MH-RR 0.48, CI 0.09 to 2.5). CONCLUSIONS: The results indicate clear benefit for routine antibiotic prophylaxis in clean surgical procedures. High risk patients need more study.

Abundance and polymorphism of di-, tri-and tetra-nucleotide tandem repeats in chickpea (Cicer arietinum L.).

The abundance and polymorphism of 38 different simple-sequence repeat motifs was studied in four accessions of cultivated chickpea (Cicer arietinum L.) by in-gel hybridization of synthetic oligonucleotides to genomic DNA digested with 14 different restriction enzymes. Among 38 probes tested, 35 yielded detectable hybridization signals. The abundance and level of polymorphism of the target sequences varied considerably. The probes fell into three broad categories: (1) probes yielding distinct, polymorphic banding patterns; (2) probes yielding distinct, monomorphic banding patterns, and (3) probes yielding blurred patterns, or diffused bands superimposed on a high in lane background. No obvious correlation existed between abundance, fingerprint quality, and the sequence characteristics of a particular motif. Digestion with methyl-sensitive enzymes revealed that simple-sequence motifs are enriched in highly methylated genomic regions. The high level of intraspecific polymorphism detected by oligonucleotide fingerprinting suggests the suitability of simple-sequence repeat probes as molecular markers for genome mapping.

Application of nuclear magnetic resonance magic sandwich echo imaging to solid polymers.

A solid-state 1H nuclear magnetic resonance (NMR) imaging technique based on magic sandwich echoes (MSE) is described for obtaining spatial projections of solid polymer samples. The modification of MSE multiple echo detection is combined with short gradient pulses applied during the sandwich windows. This allows proton homonuclear decoupling in solids with dipolar couplings up to 50 kHz. For a rapid gating of the gradients a fast gradient pulse driver was constructed with switching times between 550 and 910 ns giving a maximum gradient strength of 330 mT/m. With our detection technique the spectral width can be doubled. One-dimensional projections and spatially resolved spectra of rigid polymer phantoms are presented. For contrast enhancement the use of the T1 relaxation time and the number of the magic sandwiches functioning as an adjustable magnetization filter discriminating between different strengths of the dipolar coupling is demonstrated.

Spatially resolved NMR of rigid polymers and elastomers.

NMR imaging with protons is becoming a more and more versatile tool for material research. Two different approaches are presented to obtain spatial resolution in elastomers and solids. The first, magic-sandwich-echo-imaging, belongs to the group of multiple-pulse techniques which are applied to overcome the strong dipolar couplings in solids. A driver for fast gradient pulses was constructed, and the technique was used to measure one-dimensional projections and spatially resolved spectra of rigid polymers. The second approach uses surface coils. In this way large objects can be investigated from the surface at optimum signal to noise. The drawback of the inhomogeneous B1 field resulting in signal attenuation across the image can be overcome by imaging an NMR parameter like the relaxation time T2. This was applied to image a phantom of different polyurethane foams. Furthermore spin-echo images of signal intensity maps around conducting wires are presented for the analysis of current distributions.

Oligonucleotide fingerprinting of plant and fungal genomes: a comparison of radioactive, colorigenic and chemiluminescent detection methods.

Digoxigenated oligonucleotide probes complementary to simple repetitive DNA sequences were introduced into nonradioactive fingerprint analysis of plant and fungal DNA. The fragment patterns, obtained by blot hybridization of TaqI-restricted DNA from chickpea (Cicer arietinum) and its fungal pathogen Ascochyta rabiei with digoxigenated probes and either a colorigenic or a chemiluminescent detection method, were compared to those obtained with 32P-labeled probes. In combination with alkaline phosphatase and its chemiluminescent substrate 3-(2'-spiroadamantane)-4-methoxy-4-(3"-phosphoryloxy)phenyl- 1,2-dioxetane (AMPPD) digoxigenated oligonucleotides yielded clear-cut fingerprints with high signal-to-background ratios within several minutes of exposure to X-ray films. The chemiluminescence reaction remained stable for at least two weeks. A comparison of banding patterns obtained by radioactive versus digoxigenin-based hybridization and detection techniques revealed substantial differences in the relative signal intensities of bands. Both nonradioactive techniques show a tendency to "equalize" band intensity differences. Whereas 32P-labeled oligonucleotides are also applicable to in situ hybridization with DNA immobilized in dried agarose gels, gel hybridization did not work efficiently with digoxigenated probes and either substrate.