Salicylaldiminato chromium complex supported on chemically modified silica as highly active catalysts for the oxidation of cyclohexene

Immobilization of chromium complexes on modified silica support was achieved via two different synthetic routes using 3-aminopropyl triethoxysilane (APTS) as a linking group. The FTIR spectra, elemental and solid-state NMR analyses demonstrated incorporation of amine functional groups on the surface of the APTS-functionalized silica support, which was further confirmed by 29 Si solid-state CP MAS NMR spectroscopy. Oxidation of cyclohexene was carried out over the chromium complex supported on organically modified silica using H2 O2 as an oxidant under various conditions and different atmospheres viz. oxygen, nitrogen and air. The supported catalysts exhibited excellent activity (>94%) after 6 h reaction time under O2 atmosphere using THF as solvent. The catalysts showed high chemoselectivity towards formation 2-cyclohexen-1-ol and 2-cyclohexen-1-one. Activity of the immobilized catalysts remains nearly the same after three consecutive cycles, suggesting the true heterogeneous nature of the catalyst.Web of Scienc

New National Gallery of Art Project, San Jose, Costa Rica

Thesis (M. Arch.)--Massachusetts Institute of Technology, Dept. of Architecture, 1992.Includes bibliographical references (p. 293-297).The primary focus of this investigation is the insertion of a new piece in an environment where the natural elements of site and the man-made elements of city can begin to inform the ordering systems used in the design process. The existing footprint of the ruins of La Antigua Penitenciaria, in the center of the Costa Rican capital, San Jose, is transformed in meaning and character to become a cultural center for the city. The problem presented is a contextual one of making a place in the world through a reading, cataloguing and reinterpretation of /lature, city, and culture. The .goal of the process is a building that reveals the meaning of its present time and place, set in a landscape that tells stories of its past.by Mayer S. Abbo.M.Arch

The Chickpea, Summer Cropping, and a New Model for Pulse Domestication in the Ancient Near East

The widely accepted models describing the emergence of domesticated grain crops from their wild type ancestors are mostly based upon selection (conscious or unconscious) of major features related either to seed dispersal (nonbrittle ear, indehiscent pod) or free germination (nondormant seeds, soft seed coat). Based on the breeding systems (self-pollination) and dominance relations between the allelomorphs of seed dispersal mode and seed dormancy, it was postulated that establishment of the domesticated forms and replacement of the wild ancestral populations occurred in the Near East within a relatively short time. Chickpea (Cicer arietinum L.), however, appears as an exception among all other “founder crops” of Old World agriculture because of its ancient conversion into a summer crop. The chickpea is also exceptional because its major domestication trait appears to be vernalization insensitivity rather than pod indehiscence or free germination. Moreover, the genetic basis of vernalization response in wild chickpea (Cicer reticulatum Ladiz.) is polygenic, suggesting that a long domestication process was imperative due to the elusive phenotype of vernalization nonresponsiveness. There is also a gap in chickpea remains in the archaeological record between the Late Prepottery Neolithic and the Early Bronze Age. Contrary to the common view that Levantine summer cropping was introduced relatively late (Early Bronze Age), we argue for an earlier (Neolithic) Levantine origin of summer cropping because chickpea, when grown as a common winter crop, was vulnerable to the devastating pathogen Didymella rabiei, the causal agent of Ascochyta blight. The ancient (Neolithic) conversion of chickpea into a summer crop required seasonal differentiation of agronomic operation from the early phases of the Neolithic revolution. This topic is difficult to deal with, as direct data on seasonality in prehistoric Old World field crop husbandry are practically nonexistent. Consequently, this issue was hardly dealt with in the literature. Information on the seasonality of ancient (Neolithic, Chalcolithic, and Early Bronze Age, calibrated 11,500 to 4,500 years before present) Near Eastern agriculture may improve our understanding of the proficiency of early farmers. This in turn may provide a better insight into Neolithic agrotechniques and scheduling. It is difficult to fully understand chickpea domestication without a Neolithic seasonal differentiation of agronomic practice because the rapid establishment of the successful Near Eastern crop package which included wheats, barley, pea, lentil, vetches, and flax, would have preempted the later domestication of this rare wild legume

Genetics of flowering time in chickpea and its bearing On productivity in semiarid environments

Chickpea (Cicer arietinum L.),a grain legume of Near-East origin has a unique natural history. The crop cycle in most of its traditional growing areas is completely different from the autumn germination, spring flowering, and summer maturation of its wild progenitor Cicer reticulatum Ladiz., in eastern Turkey. Millennia of summer cropping in the Near-East and later dissemination into the lower latitude growing areas of eastern Africa and the Indian subcontinent ,as a postrainy season crop, had profound effects on allelic variation in major adaptive loci of chickpea. In this chapter we discuss the consequences of the traditional cropping practices on the flowering time genes of chickpea. The recently identified genes for flowering time are described with special reference to their effect on chickpea adaptation, seed weight, seed yield, and stability under semiarid Near-East and Indian subcontinental growing environments. It is suggested that the genetic research on flowering time of this species and its wild relatives needs much attention, as only two genes affecting this trait are identified so far. Genes allowing a reduced crop cycle will provide pathways for new cropping systems and increased population density. Reduced crop duration may also help chickpea escape damage by the major biotic and abiotic stresses that mostly affect the crop at flowering and podding stages. It is concluded that the relatively simple inheritance of flowering time opens up new possibilities for breeding high yielding and stable chickpea cultivars for the semiarid and arid regions globally

Cytology and mating systems in the climbing cacti Hylocereus and Selenicereus

Chromosome numbers and meiotic behavior are reported for the climbing cacti species Hylocereus undatus, Hylocereus polyrhizus, and Selenicereus megalanthus. The Hylocereus spp. are diploid (2n 5 22), while S. megalanthus is a tetraploid (2n 5 44). Irregular chromosome disjunction at anaphase I in pollen mother cells of S. megalanthus is probably the major cause of its reduced pollen viability and may contribute to low seed set, low number of viable seeds and, consequently, low fruit mass. A pollination study confirmed self-incompatibility in H. polyrhizus and a weakened incompatibility reaction in H. undatus and S. megalanthus. Major crossability barriers do not exist between the Hylocereus spp. investigated. Reciprocal intergeneric crosses were successful between Hylocereus spp. and S. megalanthus, suggesting that an Hylocereus sp. Might be one of the diploid progenitors of the tetraploid S. megalanthus. The implications of the results on cacti nomenclature and systematics are briefly discussed

MCTK: a Multi-modal Conversational Troubleshooting Kit for supporting users in web applications

Conversational Interfaces for user assistance are becoming persuasive. Today, though, most chatbots are not integrated into the application in which they are placed, but only superimposed, with no communication between the conversational and the graphical interface. We propose Multi-modal Conversational Troubleshooting Kit (MCTK), a Python package to easily integrate a conversational agent for troubleshooting in web applications. MCTK is multi-modal: once the system recognizes the problem the user is encountering, the textual solution in the chat is coupled with visual hints in the GUI. On top of that, MCTK is easy to configure and offers separation of concerns: dialogue designers can work on the conversation without the necessity of modifying the code, and vice versa

Morphology, dynamics and plasma parameters of plumes and inter-plume regions in solar coronal holes

Coronal plumes, which extend from solar coronal holes (CH) into the high corona and - possibly - into the solar wind (SW), can now continuously be studied with modern telescopes and spectrometers on spacecraft, in addition to investigations from the ground, in particular, during total eclipses. Despite the large amount of data available on these prominent features and related phenomena, many questions remained unanswered as to their generation and relative contributions to the high-speed streams emanating from CHs. An understanding of the processes of plume formation and evolution requires a better knowledge of the physical conditions at the base of CHs, in plumes and in the surrounding inter-plume regions (IPR). More specifically, information is needed on the magnetic field configuration, the electron densities and temperatures, effective ion temperatures, non-thermal motions, plume cross-sections relative to the size of a CH, the plasma bulk speeds, as well as any plume signatures in the SW. In spring 2007, the authors proposed a study on "Structure and dynamics of coronal plumes and inter-plume regions in solar coronal holes" to the International Space Science Institute (ISSI) in Bern to clarify some of these aspects by considering relevant observations and the extensive literature. This review summarizes the results and conclusions of the study. Stereoscopic observations allowed us to include three-dimensional reconstructions of plumes. Multi-instrument investigations carried out during several campaigns led to progress in some areas, such as plasma densities, temperatures, plume structure and the relation to other solar phenomena, but not all questions could be answered concerning the details of plume generation process(es) and interaction with the SW.Comment: To appear on: The Astronomy and Astrophysics Review. 72 pages, 30 figure

Observed and simulated coronal UV lines at solar minimum activity: The impact of the 3D tilted coronal streamer belt

The aim of this study is to improve the knowledge of the slow solar wind origin. In particular, we compute the emissivities and the intensities of UV spectral lines starting from the physical parameters of a time-dependent 3D three-fluid MHD model of the tilted coronal streamer belt. The results obtained from the model are compared in the extended corona (at 1.5 and 1.9 R�) to the UV spectroscopic data from the Ultraviolet Coronagraph Spectrometer (UVCS) onboard SOHO in the streamer belt during the minimum of solar activity (1996). The discussion is focused on the importance of the projection effects due to the integration along the line of sight in the coronal ultraviolet observations of streamer core dimming

Xetal-Pro : an ultra-low energy and high throughput SIMD processor

This paper presents Xetal-Pro SIMD processor, which is based on Xetal-II, one of the most computational-efficient (in terms of GOPS/Watt) processors available today. Xetal-Pro supports ultra wide VDD scaling from nominal supply to the sub-threshold region. Although aggressive VDD scaling causes severe throughput degradation, this can be compensated by the nature of massive parallelism in the Xetal family. The predecessor of Xetal-Pro, Xetal-II, includes a large on-chip frame memory (FM), which cannot operate reliably at ultra low voltage. Therefore we investigate both different FM realizations and memory organization alternatives. We propose a hybrid memory architecture which reduces the non-local memory traffic and enables further VDD scaling. Compared to Xetal-II operating at nominal voltage, we could gain more than 10× energy reduction while still delivering a sufficiently high throughput of 0.69 GOPS (counting multiply and add operations only). This work gives a new insight to the design of ultra-low energy SIMD processors, which are suitable for portable streaming applications