Polytechnic University of Valencia

About: Polytechnic University of Valencia is a education organization based out in Valencia, Spain. It is known for research contribution in the topics: Catalysis & Population. The organization has 16282 authors who have published 40162 publications receiving 850234 citations.

Overexpression of ADC2 in Arabidopsis induces dwarfism and late-flowering through GA deficiency.

Abstract: We have obtained Arabidopsis thaliana transgenic plants constitutively overexpressing ADC2, one of the two genes encoding arginine decarboxylase (ADC) in Arabidopsis. These plants contained very high levels of putrescine (Put) but no changes were observed in spermidine and spermine contents. The results obtained from quantification of free and conjugated polyamines suggest that conjugation may be a limiting step for control of Put homeostasis within a non-toxic range for plant survival. Transgenic plants with increased levels of ADC2 transcript and elevated Put content showed dwarfism and late-flowering, and the phenotype was rescued by gibberellin A3 (GA3) application. The contents of bioactive GA4 and GA1, and of GA9 (a precursor of GA4), as well as the levels of AtGA20ox1, AtGA3ox1 and AtGA3ox3 transcripts (quantified by real-time PCR) were lower in the ADC2 overexpressor plants than in the wild type. No change in the expression of genes encoding earlier enzymes in the GA biosynthesis pathway was detected by microarray analysis. These results suggest that Put accumulation affects GA metabolism through the repression of biosynthetic steps catalyzed by GA 20-oxidase and GA 3-oxidase.

Variation revealed by SNP genotyping and morphology provides insight into the origin of the tomato.

Abstract: Tomato, Solanum lycopersicum, is divided into two widely distributed varieties: the cultivated S. lycopersicum var. lycopersicum, and the weedy S. lycopersicum var. cerasiforme. Solanum pimpinellifolium is the most closely related wild species of tomato. The roles of S. pimpinellifolium and S. l. cerasiforme during the domestication of tomato are still under debate. Some authors consider S. l. cerasiforme to be the ancestor, whereas others think that S. l. cerasiforme is an admixture of S. pimpinellifolium and the cultivated S. l. lycopersicum. It is also not clear whether the domestication occurred in the Andean region or in Mesoamerica. We characterized 272 accessions (63 S. pimpinellifolium, 106 S. l. cerasiforme, 95 S. l. lycopersicum and 8 derived from hybridization processes) were morphologically and genetically using the SolCap platform (7,414 SNPs). The two species were distinguished in a PCA analysis and displayed a rich geographic structure. Solanum lycopersicum var. cerasiforme and S. l. lycopersicum were also differentiated in the PCA and Structure analyses, which supports maintaining them as different varieties. Solanum pimpinellifolium and the Andean S. l. cerasiforme were more diverse than the non-Andean S. lycopersicum. Solanum lycopersicum var. cerasiforme was morphologically and molecularly intermediate between S. pimpinellifolium and tomato. Solanum lycopersicum var. cerasiforme, with the exception of several Ecuadorian and Mexican accessions, is composed of the products of admixture processes according to the Structure analysis. The non-admixtured S. l. cerasiforme might be similar to the ancestral cultivars from which the cultivated tomato originated, and presents remarkable morphological diversity, including fruits of up to 6 cm in diameter. The data obtained would fit a model in which a pre-domestication took place in the Andean region, with the domestication being completed in Mesoamerica. Subsequently, the Spaniards took plants from Mesoamerica to Spain and from there they were exported to the rest of the world.

The Synthesis of an Extra‐Large‐Pore Zeolite with Double Three‐Ring Building Units and a Low Framework Density

Abstract: Zeolites are crystalline inorganic solids formed by TO4 tetrahedra (T=Si, P, Al, Ge, etc.) with a well-defined system of regular pores having diameters up to about 2 nm. The possibility of tuning pore dimensions and framework compositions have made zeolites the most successful materials for applications in gas adsorption and separation and for catalysis. Their uses have been further expanded to microelectronics for preparing materials with low values of the high-frequency dielectric constant or manufacturing encapsulated light-emitting devices (LEDs), to medicine for diagnostic treatments and controlled drug delivery, or for release of semiotics for controlling insect populations in agricultural uses. Those applications often require structures with low framework densities, large internal volumes, and preferentially, extra-large pores. However, up to now, the number of known zeolites with a low framework density (FD 12) is almost negligible, and the number with extra-large pores ( 18-R) is also extremely small. Computational methods can predict a large number of thermodynamically feasible new structures, and they can stimulate and inspire the discovery of new structures. For example, Foster and Treacy have used a symmetry-constrained intersite bond searching method and have generated more than two million structures. With that methodology, the authors predicted a series of thermodynamically feasible extra-large-pore zeolites. Deem et al. have also modeled relatively large number of low density zeolites and were able to show that the low-energy and low-density materials also tend to have desirably large rings. Among the zeolite structures with extra large pores predicted by Foster and Treacy, there is one with 18 10 10-R pore topology that could be of particular interest for catalysis, as it combines an extra-large pore (18-R) for molecular accessibility with connected 10-R pores that can introduce shape-selectivity effects. Recently, the predicted zeolite was synthesized and named ITQ-33. This zeolite has 3-R and D4R units in the structure, and was at the time the silicate-based zeolite with the lowest framework density (12.3.T/1000 ). The pore topology of this extra-large-pore zeolite presented quite unique and interesting catalytic properties: The pore accessibility to large molecules through the 18-R was combined with shape selectivity in the 10-R pores for the primary products formed. In the same data base, Foster and Treacy also predicted an extra-large-pore zeolite that was closely related to ITQ-33 (Zeolite reference 191_4_1985). In that new structure, the 10-R pores of ITQ-33 were expanded to 12-R pores connecting the larger perpendicular 18-R channels. The result was a zeolite with 18 12 12 pore topology instead of the 18 10 10 for ITQ-33. In particular, along with D4R units, the new zeolite contains D3R units that have never been seen in synthesized zeolites, which could be related to geometric strains introduced in the framework owing to the formation of D3R based on silicon. In any case, the pore expansion with the 18 12 12-R pore system in the new zeolite should result in a decrease of the framework density from 12.3 in the case of ITQ-33 to 10.9 T atoms/1000 . Herein, we show that the zeolite containing D3R that was predicted above can be successfully synthesized (ITQ-44) as a silicogermanate by combining a relatively inexpensive, rigid and bulky organic structure-directing agent (SDA) with the directing effect of germanium. Furthermore, we show that in ITQ-44, germanium locates preferentially in D3R (with 50% Ge occupancy), followed by D4R (with 37% Ge occupancy). ITQ-44 was synthesized using (2’-(R),6’-(S))-2’,6’-dimethylspiro[isoindole-2,1’-piperidin-1’-ium] as the SDA (Supporting Information, Figure S1). The synthesis of ITQ-44 was carried out in fluoride media using high-throughput (HT) synthesis techniques, which involve the use of a 15-well multiautoclave. The XRD pattern of a calcined ITQ-44 sample (Figure 1) was collected (as described in the Supporting Information), and the crystal structure was solved using the program FOCUS. The agreement between the observed and calculated XRD patterns are shown in Figure 1; it certainly confirms that this structure corresponds to that of the pure silica polymorph of this material predicted by Foster and Treacy (reference number 191_4_19854). The structure of ITQ-44 is closely related to the previously described zeolite ITQ-33 (Figure 2). It also comprises a building unit formed by a [346] cage with two additional [*] J. Jiang, Dr. J. L. Jorda, Dr. M. J. Diaz-Cabanas, Prof. A. Corma Instituto de Tecnologia Quimica (UPV-CSIC) Universidad Politecnica de Valencia Consejo Superior de Investigaciones Cientificas Av. de los Naranjos s/n, 46022 Valencia (Spain) Fax: (+34)96-387-7809 E-mail: acorma@itq.upv.es

A vocabulary of program slicing-based techniques

Abstract: This article surveys previous work on program slicing-based techniques. For each technique, we describe its features, its main applications, and a common example of slicing using such a technique. After discussing each technique separately, all of them are compared in order to clarify and establish the relations between them. This comparison gives rise to a classification of techniques which can help to guide future research directions in this field.