550 research outputs found
Computing elastic tensors of amorphous materials from first-principles
No full textThe resources and services used in this work were partly provided by the VSC (Flemish Supercomputer Center) , funded by the Research Foundation-Flanders (FWO) and the Flemish Government. The various members of our group for discussions and aid over the course of this research
On the elastic tensors of ultra-thin films: A study of ruthenium
No full textThe resources and services used in this work were partly provided by the VSC (Flemish Supercomputer Center) , funded by the Research Foundation-Flanders (FWO) , Belgium and the Flemish Government, Belgium. The various members of our group for discussions and aid over the course of this research
Tweetraps per-O-methylering: een methode voor de structuuropheldering van koolhydraten en geglycosyleerde verbindingen
No full textDit rapport beschrijft tweetraps per-O-methylering (2-spOMe), een methode voor de structuuropheldering van koolhydraten en geglycosyleerde verbindingen. 2-spOMe is een uitbreiding van conventioneel monomeriseren: het monomeriseren wordt vooraf gegaan door per-O-methylering en gevolgd door per-O-deuteromethylering. Op deze manier worden vrije hydroxylgroepen gederivatiseerd tot methylethers en hydroxylgroepen van bindingsposities tot deuteromethylethers. De zo gevormde monomeren kunnen worden geidentificeerd met behulp van gaschromatografie. Het oorspronkelijke aantal bindingen per monomeer kan worden afgeleid uit het molecuulgewicht, dat werd bepaald met behulp van positieve ionen ammoniak chemische ionisatie massaspectrometrie. De methode werd succesvol getest met stachyose als testverbinding.Two stage per-O-methylation (2-spOMe), a method for structure elucidation of carbohydrates and glycosylated compounds, was developed. 2-spOMe is an extension of conventional monomerization: monomerization is preceeded by per-O-methylation while it is followed by per-O-deuteromethylation. In this way free hydroxyl groups are converted into methyl groups, while linking hydroxyl groups are converted into deuteromethyl groups. The monomers thus formed were identified using gas chromatography. The number of linkages per monomer is related to its molecular weight, which is determined using positive ion ammonia chemical ionization mass spectrometry. The method was successfully tested with stachyose as a probe.RIV
Hornschuchia cauliflora Maas & Setten
No full textHornschuchia cauliflora Maas & Setten Fig. 3 Proceedings of the Koninklijke Nederlandse Akademie van Wetenschappen, Series C: Biological and Medical Sciences 91 (3): 259, figs 16–17 (Maas et al. 1988). Type: BRAZIL – Bahia • (Aurelino Leal *) “ Km 5 a 15 da BR-101, ao sul de Ubaitaba ”; [14°20′26.8″ S, 39°19′07.2″ W]; 18 Nov. 1971; T.S. Santos 2193; holotype: CEPEC [CEPEC00008090]!; isotype: NY [NY00008359]!. Material examined BRAZIL – Bahia • “ Camamu, Fazenda Exílio, entrada no km 10.7 da BA 650 Camamú-Travessão, ca 2 km L da sede da fazenda ”; 14°0′7″ S, 39°10′7″ W; 21 Feb. 2000; J.G. Jardim 2716; ALCB [ALCB004361]!, CEPEC [CEPEC00088387]!, HUEFS [HUEFS062877]!, SPF! • “ Dom Macedo Costa, Fazenda Limeira ”; 12°54′35″ S, 39°9′10″ W; 18 Oct. 2015; G. Costa 1515; ALCB [ALCB030994]! • “ Itacaré, Entre Taboquinhas e Itacaré. BA-654. Interior de mata à beira da estrada ”; [14°16′55.2″ S, 38°59′47.3″ W]; 1 Jan. 1988; M. Sobral 5749; CEPEC [CEPEC00044273]!, ECT [ECT0003694]!, ICN [ICN00027827]!, NY [NY00395774]!, SPF! • “ Ubaitaba, Trecho da BR 101 Ubaitaba ao Porto Santo Antonio ao Sul ”; 22 Jun. 1972; T.S. dos Santos 2336; CEPEC [CEPEC00008836]!; NY [NY00395775]! • “ Uruçuca, Rodovia Uruçuca- Ubaitaba ”; [14°34′46.5″ S, 39°17′59.0″ W]; 20 Apr. 1970; T.S. dos Santos 752; CEPEC [CEPEC00005734]!, NY [NY00395776]!. Description Shrubs or trees, 3–8 m tall. Leaves subcoriaceous, petiole 3–9 mm long, lamina 14.9–32 × 3.5–15 cm, narrowly elliptic to elliptic, narrowly oblong to oblanceolate or lorate, both surfaces glabrous, base asymmetric, decurrent, acute to obtuse, apex acuminate to acute, attenuate to obtuse or rarely emarginate, primary vein impressed adaxially and raised abaxially, 13–22 pairs of secondary veins, angles between primary and secondary veins 50–60°. Inflorescence 2–22-flowered, trunciflorous, bracts absent. Flowers with pedicel 2–7 mm long, flower buds 3–7 × 1–2 mm, conical, densely covered in trichomes at the base and glabrescent towards the apex. Sepals completely connate, calyx cupuliform, apex truncate, 1–2 × 1–3 mm, glabrescent. Petals linear, white, 7–10 mm long, covered in trichomes, stamens (3–)6, 1.5–3.0 × 0.5 mm, carpels 3, 2–5 × 0.5 mm. Monocarps 1–3, fusiform, 1–6.3 × 0.3–0.6 cm, glabrous, green in vivo, stipe 2–5 mm long, calyx persistent. Seeds 4–6, ellipsoid, 13–19 × 4–7 mm, brownish, rugose, with aril. Distribution and habitat Hornschuchia cauliflora is endemic to Bahia, occurring in a small area from the municipalities of Uruçuca southward to Camamu, a distance of only 100 km. Hornschuchia cauliflora inhabits lowland tropical moist forest, but it is also found along the border with seasonal semideciduous forest (Gouvêa et al. 1976; Thomas & Barbosa 2008; Fig. 3). Phenology Flowering from October to January and fruiting from February to June. Preliminary conservation status Endangered, EN B1ab(i,ii,iii)+2ab(i,ii,iii) (Amorim et al. 2020a). There are only six preserved specimens of H. cauliflora. Since the last revision, 27 years ago (Johnson & Murray 1995), the species has been collected only twice, with a hiatus of 15 years between each collection, and has not been recollected in the last seven years. Notes The updated description includes more information about plant size and leaf morphology and dimensions (Johnson & Murray 1995). Hornschuchia cauliflora presents trunciflory, which is also found in some individuals of H. bryotrophe. However, H. bryotrophe is the only species in the genus with an evident commissural vein.Published as part of Vilela, Lucas & Lopes, Jenifer De Carvalho, 2022, Hornschuchia (Annonaceae), an endemic and threatened genus from the Brazilian Atlantic Forest, pp. 75-108 in European Journal of Taxonomy 828 on pages 85-86, DOI: 10.5852/ejt.2022.828.1859, http://zenodo.org/record/682376
[Monomer mapping: Een PC-programma voor de bepaling van monomeersamenstellingen op grond van massaspectrometrisch verkregen molecuulgewichten.]
No full textAbstract niet beschikbaarA method to establish the monomer composition of (bio) macromolecules has been developed. The method, to be called monomer mapping, involves the mass spectrometric determination of the molecular weight and a computer program. The program generates monomer compositions corresponding to the measured molecular weight. If more than one monomer composition for the polymer is generated by monomer mapping, a further limitation can be obtained from the determination of the number of exchangeable hydrogens. Monomer mapping can be used to determine the monomer compositions of individual components in mixtures without applying (chromatographic) separation techniques. This is a clear advantage over methods involving monomerization and consecutive determination of the relative amount of monomers. As a limitation, monomer mapping requires the elemental compositions of all monomer types possibly present in the polymer. The largest molecular weight resulting into one monomer composition depends on the number of monomer types considered. The method can be used as a supplement to amino acid analysis, generally resulting into the actual amina acid composition of peptides consisting of up to 25 amino acids. Monomer mapping was successfully applied to determine glycosyl compositions of fifty saponins.RIV
Combination of ab initio descriptors and machine learning approach for the prediction of the plasticity mechanisms in β-metastable Ti alloys
No full textThis study proposes a machine-learning (ML) model combining ab initio calculations and an experimental dataset of 201 alloys (in addition to pure Ti) to predict the activated plasticity mechanisms in β-Ti alloys. This meth- odology is shown to be more efficient than the so-called Bo Md approach, achieving 82% prediction accuracy while the Bo-Md approach leads to 52% correct predictions on the same dataset. In addition, four new alloy compositions were produced to verify the model validity. Specific cases where the present model disagreed with the Bo-Md predictions were chosen to increase the benefits of the produced results. The plasticity mechanisms of the four alloys experimentally confirmed the validity of the ML model. This approach particularly helps the design of specific Ti alloys exhibiting a high work hardening rate owing to the simultaneous activations of the Transformation-Induced Plasticity (TRIP) and mechanical twinning (TWIP) effects. Indeed, the class corre- sponding to the combination of TRIP and TWIP effects reach a prediction accuracy of 88%
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