H2 activation using the first 1:1:1 hetero-tri(aryl)borane

The novel 1:1:1 hetero-tri(aryl)borane (pentafluorophenyl){3,5-bis(trifluoromethyl)phenyl}(pentachlorophenyl)borane has been synthesised and structurally characterised. This has been show to act as the Lewis acidic component in FLPs for the heterolytic cleavage of H2 with three Lewis bases

Understanding the subtleties of frustrated Lewis pair activation of carbonyl compounds by N-Heterocyclic carbene/alkyl gallium pairings

This study reports the use of the trisalkylgallium GaR3 (R=CH2 SiMe3 ), containing sterically demanding monosilyl groups, as an effective Lewis-acid component for frustrated Lewis pair activation of carbonyl compounds, when combined with the bulky N-heterocyclic carbene 1,3-bis(tert-butyl)imidazol-2-ylidene (ItBu) or 1,3-bis(tert-butyl)imidazolin-2-ylidene (SItBu). The reduction of aldehydes can be achieved by insertion into the C=O functionality at the C2 (so-called normal) position of the carbene affording zwitterionic products [ItBuCH2 OGaR3 ] (1) or [ItBuCH(p-Br-C6 H4 )OGaR3 ] (2), or alternatively, at its abnormal (C4) site yielding [aItBuCH(p-Br-C6 H4 )OGaR3 ] (3). As evidence of the cooperative behaviour of both components, ItBu and GaR3 , neither of them alone are able to activate any of the carbonyl-containing substrates included in this study NMR spectroscopic studies of the new compounds point to complex equilibria involving the formation of kinetic and thermodynamic species as implicated through DFT calculations. Extension to ketones proved successful for electrophilic α,α,α-trifluoroacetophenone, yielding [aItBuC(Ph)(CF3 )OGaR3 ] (7). However, in the case of ketones and nitriles bearing acidic hydrogen atoms, C-H bond activation takes place preferentially, affording novel imidazolium gallate salts such as [{ItBuH}(+) {(p-I-C6 H4 )C(CH2 )OGaR3 }(-) ] (8) or [{ItBuH}(+) {Ph2 C=C=NGaR3 }(-) ] (12)

Novel B(Ar')2(Ar'') hetero-tri(aryl)boranes: a systematic study of Lewis acidity

A series of homo- and hetero-tri(aryl)boranes incorporating pentafluorophenyl, 3,5-bis(trifluoromethyl)phenyl, and pentachlorophenyl groups, four of which are novel species, have been studied as the acidic component of frustrated Lewis pairs for the heterolytic cleavage of H2. Under mild conditions eight of these will cleave H2; the rate of cleavage depending on both the electrophilicity of the borane and the steric bulk around the boron atom. Electrochemical studies allow comparisons of the electrophilicity with spectroscopic measurements of Lewis acidity for different series of boranes. Discrepancies in the correlation between these two types of measurements, combined with structural characterisation of each borane, reveal that the twist of the aryl rings with respect to the boron-centred trigonal plane is significant from both a steric and electronic perspective, and is an important consideration in the design of tri(aryl)boranes as Lewis acids

Benchmarking of Rapid Prototyping Systems - Beginning to Set Standards

Many rapid prototyping (RP) technologies are available today and more are being developed around the world. The absence of benchmarking standards in the RP industry has led manufacturers to use their own standards and make claims about superior performance. The need for testing standards is already felt; standardization will become imperative in the near future. The present work aims to lay the groundwork for the development of standards to measure various performance factors. Issues such as appearance and finish are studied qualitatively; the test part and some findings are presented. Issues such as repeatability, warpage, curl, creep, shrinkage and tensile strength are proposed to be studied quantitatively; test parts designed for studying these are described. Benchmarking standards will help users choose proper systems for their applications and help operators in monitoring machine performance, enabling better control over part building.Mechanical Engineerin

Tanggapan Pelajar UiTM Sarawak Kampus Samarahan terhadap Etika Sahsiah Rupadiri / Aida Montong

Kajian ini adalah mengenai tanggapan para pelajar Universiti Teknologi Mara (UiTM) terhadap etika sahsiah rupadiri dimana kajian kesnya bertempat di UiTM Cawangan Sarawak Kampus Samarahan. la dilihat dalam konteks untuk mengenalpasti tanggapan para pelajar disamping mengkajisambutan dan mendapatkan cadangan untuk diajukan kepada pihak pengurusan mengenai langkah-langkah yang pertu dititikberatkan serta sesuai dan boleh diterima oleh golongan pelajar untuk metnpraktikkan etika sahsiah rupadiri. Sampel kajian kami terdiri daripada 100 orang responden yang dipilih melalui kaedah pemerhatian, temuduga dan pengedaran borang soalselidik. Ujian untuk penganalisaan data adalah menggunakan programStatisticalPackageforSocialScience 7.5for window (SPSS). Basil kajian ini menunjukkan bahawa a) Pelajar yang sering melanggar peraturan universiti adalah diantara golongan yang banyak menolak etika sahsiah rupadiri. b) Pelajar yang kurang memahami kebaikan-kebaikan yang terdapat dalam etika sahhsiah rupadiriseringmempertikaikan keberkesanan etika ini dan c) Pelajar yang terpengaruh dengan peraturan -peraturan dan gaya hidup pelajar-pelajar dari universiti lain lebih cenderung mempcotes kecana mereka inginkan kebebasan dan mengikut perkembangan terkini. Kesimpulannya, masatah untuk mengaplikasikan etika sahsiah rupadiri yang di praktikkan di Universiti Teknologi Mara Cawangan Sarawak Kampus Samarahan (UiTMCSKS) adalah disebabkan oteh faktor-faktor dalaman dan luaran yang menjadi penentu kepada pemahaman mereka kepada konsep iniKuasa penentu ini merupakan jentera yang berfungsi untuk mempastikan samaada para petajar menerimadan seterusnyamengaplikasikannyaataupun sebaliknya

A Boronium Ion with Exceptional Electrophilicity

No AbstractPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/83171/1/2098_ftp.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/83171/2/anie_201005663_sm_miscellaneous_information.pd

Mobile Press-Register sleeve MP0084633

Bret Lankford, police officer at Naval Station Mobile / (Naval Station Mobile) / [Taken by Navy Homeport public affairs representative

Division asymétrique dans les embryons unicellulaires de nématodes hors du genre Caenorhabditis

Asymmetric cell division is an essential process of development. The process and its regulation have been studied extensively in the Caenorhabditis elegans embryo. Asymmetric division of the single-cell embryo is a conserved process in nematode species, however, the cellular features leading up to division are surprisingly variable. During my PhD, I aimed to study these differences by using two non-C. elegans embryos: Diploscapter pachys and Pristionchus pacificus. D. pachys is the closest parthenogenetic relative to C. elegans. Since the polarity cue in C. elegans is brought by the sperm, how polarity is triggered in D. pachys remains unknown. My results show that the nucleus inhabits principally the hemisphere of the D. pachys embryo that will become the posterior pole. Moreover, in embryos where the nucleus is forced to one pole by centrifugation, it returns to its preferred pole. Although the embryo is polarized, cortical ruffling and actin cytoskeleton at both poles appear identical. Interestingly, the location of the meiotic spindle also correlates with the future posterior cell. In some oocytes, a slight actin enrichment along with unusual microtubule structures emanating from the meiotic spindle are observed at the future posterior pole. Overall, my main PhD project shows that polarity of the D. pachys embryo is attained during meiosis wherein the meiotic spindle could potentially be playing a role by a mechanism that may be present but suppressed in C. elegans. For P. pacificus, biolistic transgenesis has been shown recently successful. However, due to a lack of a stringent selection marker, the continuation of this project was unfeasible during my PhD. Altogether, the results of my PhD add to the understanding of non-C. elegans early embryogenesis and emphasizes on the importance of using these species for comparative studies.La division cellulaire asymétrique est un processus essentiel du développement. Ce processus ainsi que sa régulation ont fait l’objet de nombreuses études chez l’embryon de Caenorhabditis elegans. La division asymétrique de l'embryon unicellulaire est un processus conservé à travers les espèces de nématodes, cependant les caractéristiques cellulaires menant à la division sont étonnamment variables. Au cours de mon doctorat, j'ai voulu étudier ces différences en utilisant deux embryons non-C. elegans : Diploscapter pachys et Pristionchus pacificus. D. pachys est le parent parthénogénétique le plus proche de C. elegans. La polarité étant induite par le sperme chez C. elegans, on ne peut expliquer ce qui brise la symétrie chez D. pachys. Mes résultats montrent que le noyau occupe le plus souvent l’hémisphère de D. pachys qui deviendra le pole postérieur. Dans les embryons où il est astreint à un pôle par centrifugation, le noyau fini par revenir à son pôle préférentiel. Même si l’embryon est polarisé, l’agitation corticale et le cytosquelette d’actine semblent identiques aux deux pôles. D’autre part, la position du fuseau méiotique est corrélée avec la future cellule postérieure. Dans certains ovocytes, on observe des structures de microtubules émanant du fuseau méiotique combiné à un faible enrichissement en actine au future pôle postérieur. Finalement, mon principal projet de thèse montre que la polarité de D. pachys est atteinte durant la méiose, au cours de laquelle le fuseau méiotique pourrait jouer un rôle par un mécanisme présent mais inhibé chez C. elegans. Chez P. pacificus, la transgénèse biolistique a été récemment utilisée avec succès. Toutefois, par manque d’un marqueur de sélection fiable, il était illusoire de poursuivre cette approche. En conclusion, les résultats de ma thèse contribuent à une meilleure compréhension de l’embryogénèse hors C. elegans. Ils soulignent l’importance de ces espèces dans l’optique d’études comparatives

Interrogating the place of Iks embodied in proverbs as a guide in love and family life counseling in contemporary Zimbabwe

The present paper sought to establish the extent to which the Indigenous Knowledge Systems ‘IKS’, preserved in Shona proverbs, as opposed to other knowledge systems, are relevant in counseling contemporary Zimbabwean youths on issues relating to love courtship and marriage and family life conflicts. Through desktop research, the questionnaires and focused group discussions methods, the researchers compiled an inventory of proverbs that embody IKS or traditional wisdom. An interrogation of these proverbs clarifies the distinction between IKS and other knowledge systems. The role of proverbs as a repository of IKS relevant in the counseling of youths today at strategic stages is asserted and the writers dispel the myth that IKS are static and backward. Proverbs are proved to be a relevant guide in ‘matters of the heart. The writers conclude that with appropriate adjustments, IKS based counseling will remain as relevant today and tomorrow as it was in the past. Furthermore, the writers conclude that IKS can help uphold values that promote the sanctity of marriage and the family unit in Zimbabwe

Small Molecule Activation with Main Group Complexes

The synthesis of monodentate biphenyl-amido proligands is reported as well as a series of complexes of lithium with these ligand systems. The solid-state molecular structure of these lithium amides are described as well as their use as synthons in the preparation of amido-arene aluminum complexes. Structural and spectroscopic data suggest that these species exhibit weak arene to metal donation. Attempts to generate aluminum cations from these species are detailed. A new synthetic route to titanium “constrained geometry” precatalysts was utilized to prepare a series of titanium complexes with similar pendant arene groups. The homopolymerization activity of these catalyst systems with ethylene and styrene is detailed. Combination of a sterically encumbered phosphine and large, electrophilic borane was used to effect heterolytic cleavage of disulfides to afford novel thiophosphoniumthioborate salts. A series of exchange reactions demonstrated the facile reversal of this reaction. Similar phosphine-borane systems are found to exhibit divergent reactivity with terminal alkynes, affording either phosphonium-alkynylborate salts from deprotonation or phosphonium-vinyl-borate zwitterions from addition. The scope of Lewis acid, Lewis base and alkyne combinations used to effect similar reactivity is detailed. It was found that the reaction of pyrroles, boranes, and alkynes formed similar addition products that were found to undergo further reactivity to afford C-vinyl pyrroles and nitrogen-boron bicyclic compounds. The synthesis of N-alkyl-bis(pentafluorophenyl)boryl amidinates is presented. The reactivity of these compounds with a variety of small molecules is reported. Reaction with CO2, CO, di-iso-propylcarbodiimide, tert-butyl isocyanide, and benzaldehyde as well as thermally-induced intramolecular rearrangement of these compounds affords a variety of novel nitrogen-boron heterocycles.Ph