D2 Values Research Articles

Laser spectroscopy of hydrogen desorption from Pd(100)

The recombinative desorption flux of hydrogen molecules from a Pd{100} surface is investigated with rovibrational state selectivity by resonantly enhanced [vacuum ultraviolet (VUV)+ ultraviolet (UV)] two photon ionization. Using a permeation source for the hydrogen supply the surface temperature can be changed from 325 to 740 K. The population in the rotational states is significantly lower than expected for molecules in thermal equilibrium at the respective surface temperatures, whereas the vibrational population is much higher. This vibrational population increases exponentially with Ts. When interpreted as desorption rates into (v‘=1) and plotted versus T−1s, activation energies Ea for vibrational excitation can be derived. For the three isotopes D2, HD, and H2 values for Ea of 234, 282, and 428 meV, respectively, are obtained, being in all three cases lower than the corresponding gas phase energies. The rotational cooling and the vibrational excitation are discussed in the context of current theoretic...

Isoleucyl-tRNA synthetase from baker's yeast. Discrimination of 20 amino acids in aminoacylation of tRNA(Ile)-C-C-3'dA; role of terminal hydroxyl groups aminoacylation of tRNA(Ile)-C-C-A.

Specificity with regard to amino acids in aminoacylation of tRNA(Ile)-C-C-3'dA by isoleucyl-tRNA synthetase is characterized by discrimination factors (D2) which are calculated from kcat and Km values. The lowest values are observed for Cys, Val, His, and Trp (D2 = 180-1700), indicating that at same amino acid concentrations isoleucine is 180-1700 times more attached to tRNA(Ile)-C-C-3'dA. The highest values are observed for Gly, Ala, Ser, Pro, Gln, Leu, Glu, and Phe (D2 = 10,000-30,000). D2 values of the other amino acids are in the range of 2000-10,000. Recognition of most amino acids is achieved in a four-step process. Two initial discrimination steps are due to different hydrophobic interactions with the binding pockets; two proof-reading steps occur on the pre- and the post-transfer stage. For nine amino acids (Ser, Asp, Asn, Val, Leu, His, Phe, Lys, Trp) post-transfer proof-reading is negligible. As a special case in discrimination of valine, one initial discrimination step and the post-transfer proof-reading step are lacking. The role of the terminal hydroxyl groups of the tRNA for post-transfer proof-reading is assigned to a simple neighbouring group effect. No preference for the 2' or 3' position in proof-reading can be postulated.

Variation of dendrite arm spacing in Al-rich Zn-Al off-eutectic alloys

Primary and secondary arm spacings were measured in various unidirectionally solidified Al-rich Zn-Al off-eutectic alloys. In order to determine the influence of convective processes on dendrite arm spacings, freezing was carried out both vertically upwards and downwards, and over a wide range of growth rates. The primary arm spacing parameter (d1) has been correlated with the growth rate (R), the temperature gradient in the liquid immediately ahead of the solid/liquid interface (GL) and the bulk alloy composition (C0). Similar correlations were made for the secondary arm spacing (d2). In addition,d2 values were found to be related to the local solidification time (tf). It was observed that the relationshipRkGmd1 =K, the primary arm spacing, andRld2 =K′, secondary arm spacing, were obeyed (K andK′ are constants). In addition, the effects of solute gradient-induced convection on the extent of macrosegregation in these alloys have been determined as a function of composition and growth rate.

Some Effects of Viscoelastic Matrix on the Squeeze Films

The solution method in (6) is extended to include a viscoelastic, linear solid matrix. The film thickness and the bearing volume of the viscoelastic cases are obtained and show lower values than that of the elastic counterpart. The result is also compared with the Winkler solid case (7) and it shows a larger film thickness than Winkler obtained. The squeeze-suction phenomenon is again observed for low applied load, small period and large compliance parameter cases, and it becomes stronger for small D2 values. It clearly indicates that for the viscoelastic model a fluid film can be maintained under cyclic positive load conditions.

Quantification of the D2-glycoprotein in amniotic fluid and serum from pregnancies with fetal neural tube defects.

D2 is a glycoprotein existing in both membrane-bound and soluble forms. Employing a specific rabbit antibody against purified human brain D2, we developed an enzyme-linked immunosorbent assay (ELISA) for the quantification of D2 and applied it to amniotic fluids from 87 normal and 36 pathological pregnancies. With a cut-off point of 150 ng D2/ml, no false positive D2 values were obtained in any of the amniotic fluids from normal fetuses, although the alpha-fetoprotein concentrations were slightly increased in 13 cases. No false negative D2 values were found in any of the 18 investigated amniotic fluids from fetuses with anencephaly. Of 8 amniotic fluids from fetuses with spina bifida, 2 false negative D2 values were found. No false negative alpha-fetoprotein values were found in any of the cases with neural tube defects in this study. In 10 amniotic fluids from fetuses with other malformations, 5 samples showed raised D2 concentrations. The D2 level in sera from 10 women carrying normal fetuses and 16 women carrying malformed fetuses was also determined, but no statistically significant difference in D2 level was found in the pathological sera when compared with normal sera. It was concluded that the determination of D2 concentrations in amniotic fluid by means of the D2-ELISA may be used as an additional test in the screening of fetal malformations in early pregnancy.

The negative gravity field over the 85°E ridge

An isopach map made from seismic reflection and refraction data in the Bay of Bengal shows two prominent N‐S trending features in the basement topography. One is the northernmost portion of the Ninetyeast Ridge which is totally buried by sediments north of 10°N. The other buried ridge trends roughly N‐S for 1400 km at 85°E to the latitude of Sri Lanka and then curves toward the west. It has basement relief up to 6 km. Two free‐air gravity anomaly profiles across the region show a strong gravity low (∼−60 mGal) over the 85°E Ridge, while the Ninetyeast Ridge shows a gravity high. To understand the negative free‐air gravity anomaly over the 85°E Ridge, we model the lithosphere as a thin elastic plate and calculate its flexural and gravitational response to an uneven sediment load. A plausible formation history for a buried ridge consists of at least two major episodes. The first is the formation of the ridge on a lithosphere with a flexural rigidity of D1. At some later time the ridge is buried by an influx of sediments, the lithosphere is cooler, and the flexural rigidity has increased to D2. The character of the gravity field depends primarily upon the initial and final values of flexural rigidity. These D1 and D2 values are varied to obtain good agreement between the model and observed gravity anomalies. Best fitting models have a 180 times increase in flexural rigidity between ridge formation and sediment burial. An approximate relationship between flexural rigidity and crustal age shows that the 85°E Ridge was formed on relatively young lithosphere, 5–15 m.y. old and that it was buried when the lithosphere was 40–80 m.y. old.

D-state effects in low-energy ([formula omitted]) and ([formula omitted]) reactions

Measurements of the tensor analyzing powers are presented for (d,t) reactions on 91Zr,119Sn and 208Pb and for the (d,3He) reaction on 63Cu. The measurements are sensitive to D-state components in the three-nucleon bound-state wave function and allow one to determine the value of the parameter D2. The D2 values are compared with recent theoretical predictions.

Mitotic analysis in thirteen varieties of Cajanus cajan (L.) Mill sp.

The somatic chromosomes studied in the root tips of thirteen varieties of C. cajan revealed that all the varieties had the same chromosome number (2n=22) but there is much variation in their chromosome morphology. The total chromatin length was maximum (51.2μ) in variety NP 41 and its minimum value was noted in variety Ranchi. When the individual chromosomes were taken into account the shortest (1.0μ) and the largest (3.0μ) chromosomes were recorded in var. Ranchi and var. PT 301 respectively. The TF percent was maximum in variety Mothihari (45.05) and minimum in variety PT 301. The SAT chromosomes were noted in varieties T1, No 148 and NP 80. On the basis of D2 values the varieties were classified into seven distinct groups. (A-varieties PT 301; ILRI and 7S; B-T1 and C11; C-NP 39 and NP 80; D-Ranchi; E-NP 41, Motihari and BR 60; F-No 148 and G-Assam). This indicates that the variety formation in C. cajan had taken place mainly due to the change in the chromosome morphology and nature of genes.

Studies on genetic divergence in potato

Sixty-seven potato varieties/hybrids were grouped in 15 clusters on the basis of D2 values. The clustering pattern was not influenced by the geographic diversity of the varieties. However, a segregation between varieties of the Tuberosum and Andigena type varieties was observed. The exotic potato varieties and also the Indian varieties bred from Tuberosums showed a poor divergence. In contrast, the divergence in the varieties developed from Tuberosum-Andigena crosses was much greater. The inter-cluster distance of such varieties, with respect to Tuberosum and Andigena clusters, appeared to be influenced by the cytoplasm they carried. The varieties with Tuberosum cytoplasm were closer to clusters having Tuberosum varieties and those with Andigena cytoplasm were closer to clusters having Andigena type varieties. The characters least influenced by the selection during the course of evolution of the present day varieties were found to be mainly responsible for adding divergence to the population. A breeding plan involving varieties from different clusters has been outlined.

Size and shape differences among six South American Indian tribes.

Measurements of height, face height, nose height, nose breadth, head length and head breadth from individuals living in 17 villages of six South American Indian tribes were compared using Mahalanobis's morphological distances and their partition into size and shape components. Total D2 values correlate well with estimates of linguistic differentiation, but not with geographic distances between tribes. Three of the six tribes were also studied for blood polymorphisms, and again measures of distances based on these haematological traits did not correlate well with the morphological ones. The shape component was about three times as important as size in contributing to the intertribal variation.

Comparison of Mahalanobis's method and metroglyph technique in the study of genetic divergence in Linum usitatissimum L. germ plasm collection

A group of fifty-seven varieties of Linum usitatissimum L. collected from different geographics sources was studied to understand the nature of genetic divergence using Mahalanobis's statistical distance (D2). Varieties having genetic similarity were grouped into fifteen clusters. Most of the clusters at individual level included varieties of different geographical regions. However, Argentine and Indian types formed separate and distinct constellations. The Indian group was situated at a maximum distance from Argentine and US groups, and was nearest to the Australian group. For improvement of Indian linseed, hybridization of indigenous types with Argentine and US types might result in superior recombinants. 84.64% of the total divergence was attributable to plant height and seed size, which are based characteristics used in classifying the species into oil and flax types. Since it is difficult to compute D2 values among large numbers of germplasm collections, another relatively simple and easy method, the metroglyph technique, was tried upon the same set of fifty-seven varieties. Comparisons between the results of the two analyses revealed the striking similarity as regards to group arrangement. It has been suggested that the metroglyph technique would be suitable for preliminary grouping prior to undertaking D2 analysis.

Bond energy terms in oxides and oxo-anions

Experimental ΔH φ f values are employed to calculate mean bond dissociation energies for homogeneous neutral gaseous oxides MO p, D 1 for dissociation into neutral atoms, and D 2 for dissociation into oxide ions and cations M +2p: similarly, sums of bond energy terms ∑B 1 and ∑B 2 are calculated for heterogeneous neutral oxides. By use of ΔH φ f values for simple salts, D 2 values are calculated for the oxo-anions, CO −2 3, NO − 3, NO − 2, SO −2 3, SO −2 4, SeO −2 4, SeO −2 3, TeO −2 3, ClO − 4,ClO − 3, ClO − 2, BrO − 4, BrO − 3, IO − 4, IO − 3, CrO −2 4, MnO − 4, MnO −2 4, TcO − 4 and ReO − 4.

Features of the kinetics of the adsorption of proteins by macroporous polyelectrolytes

1. Proteins are sorbed on the macroporous KU-23 polyelectrolyte over the internal surface of the ion exchanger at a relatively high rate. The diffusion rate is two orders of magnitude higher than the diffusion rate on gelatinous ion exchangers. 2. The adsorption of proteins is at first fast (D1 ∼ 10−9 cm2/sec) and then slow (D2 ∼ 10−10 cm2/sec). The D1 values decrease, and the D2 values increase with increasing molecular weight of the protein. 3. The size of the grains of the ion exchanger has practically no effect on. the values of the diffusion coefficients.

Karyotype Analysis in Some Varieties of <i>Lens culinaris</i>

Karyotype analysis in fifteen varieties of Lens culinaris was carried out. The varieties differ from each other in chromosome morphology and in total chromatin length. For much detailed studies D2 statistics was applied. According to D2 values the varieties were placed at nine different clusters.From the analysis of chromosome morphology and D2 values, it was revealed that variety formation in Lens culinaris has taken place due to structural changes in the chromosomes. It has also been accompanied by change in total chromatin length in different varieties. The SAT-chromosomes appear to have undergone changes as regard the position of secondary constriction, (NP varieties). In Russian and EC varieties they have not been recorded at all.

Diversity analysis in Boro rice (<i>Oryza sativa</i> L.) accessions

An experiment was conducted with 36 accessions of traditional (local) Boro rice germplasm accessions of three different groups (20 accessions as Kaliboro, 12 as Jagliboro and 4 as Tepiboro) during Boro season 2004 at BRRI farm to identify the duplicates with the help of morph-agronomic characters. On the basis of D2 values, the 36 genotypes were grouped into six clusters with a range of intra (0.00 for cluster II to 1.78 for cluster I) and inter cluster (1.99 between cluster I and III to 21.20 between cluster II and III) distances. Cluster I comprised the highest number of genotypes (10) and cluster II the lowest (1), while cluster III, IV, V, and VI included 6, 7, 5, and 7 genotypes, respectively. Differences in cluster means existed for almost all the characters. The highest mean value for seedling height (21.68 cm), 1000-grain weight (20.97 g) and grain yield/hill (6.87 g) were observed in cluster I, II for days to 50% flowering (116), panicle length (22.80 cm), grains/panicle (74), and grain length (8.35 mm), cluster IV for tillers/hill (16.44) and panicles/hill (14.17), cluster V for harvest index (0.32) along with cluster I and VI, and cluster VI for plant height (117.17 cm) and flag leaf area (30.68 cm2). None of the 12 characters had the highest mean value under cluster III. The canonical variate analysis showed in general that the important characters for the differentiation in the descending order of importance were grain length, days to 50% flowering, grains/panicle, grain yield/hill, panicle length, flag leaf area, plant height, seedling height, 1000-grain weight, panicles/hill, harvest index, and tillers/hill, but the similar name group accessions are not duplicate mainly due to dissimilarity of grain length, days to 50% flowering, grains/panicle and grain yield/hill characters. It is apparent from the results that the same name group accessions were quite different from each other. Keywords: Duplicate sorting; rice (Oryza sativa L.); germplasm. DOI: 10.3329/bjar.v35i1.5864Bangladesh J. Agril. Res. 35(1) : 29-36, March 2010

Estimation of morphological and molecular genetic diversity in blackgram [Vigna mungo (L.) Hepper] under YMV hotspot regime

A phenotypic and molecular diversity study was conducted using seven traits and 19 SSR markers in a collection of 26 black gram genotypes. Phenotypic characterization was based on seven yield and yield related variable. The field experiment was laid out at Panboli village (YMV hotspot) of Tirunelveli District in Tamilnadu during summer 2017. Genetic divergence was estimated on the basis of D2 values and 26 genotypes under study were grouped into six clusters by Tocher’s method. Seed yield per plant followed by Plant height and number of pods per plant contributed to the genetic divergence. The genetic distance announced using DICE dissimilarity co-efficient indicated highest divergence of 1.0 between VBN 8 and AUBG 17 and between VBN 8 and AUBG 19. The dendogram constructed using the DICE dissimilarity co-efficient between genotypes showed four apparent clusters based on marker allele distribution. Divergence was noted between the dissimilarity matrices based on the molecular and phenotypic diversity based on agronomic data.