77,984 research outputs found
Dialogical Skirmishes
No full textTan was guest editor for 'And Now China?', a special print edition of the Ctrl+P journal, which critically responded to the celebratory rhetoric’s of ‘China Now’ and other celebratory markers of China's global ascent in 2008. As well as the introductory article 'Dialogical Skirmishes', Tan also interviewed Hans Ulrich Obrist
Evidence for erbium-erbium energy migration in erbium(III) bis(perfluoro-p-tolyl)phosphinate
No full textCopyright 2008 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. This article appeared in Applied Physics Letters 92, 103303 (2008) and may be found at
Cesasundana lorniensis Tan 2014
No full textCesasundana lorniensis Tan, 2014 Fig. 11 H Material examined. 3 females: 1 female (paratype, ZRC.ORT. 1047), BTNR, coll. D. H. Murphy, 20 August 1970; 1 female (paratype, ZRC.ORT. 1046), BTNR, coll. D. H. Murphy 23 / 24 November 1971; 1 female (holotype, ZRC.ORT. 166), CCNR, MacRitchie forest, along Lornie Trail, primary/ old secondary forest, coll. M. K. Tan, 2 November 2010. Taxonomy. A key to currently known species is available in Tan (2014). Remarks. More images available in Tan (2014).Published as part of Tan, Ming Kai, 2014, An annotated checklist of the bush katydids (Orthoptera: Phaneropteridae: Phaneropterinae) from Singapore, including an illustrated key to species, pp. 573-593 in Zootaxa 3884 (6) on page 581, DOI: 10.11646/zootaxa.3884.6.6, http://zenodo.org/record/24981
Total Synthesis of the Anti Methicillin-Resistant <i>Staphylococcus aureus</i> Peptide Antibiotics TAN-1057A-D
No full textTAN-1057A−D, dipeptides isolated from bacteria
Flexibacter sp. PK-74 and PK-176, are new
antibiotics
with potent antibacterial activity against methicillin-resistant
Staphylococcus aureus. We describe, in detail,
the
total synthesis of TAN-1057A−D by a convergent route featuring a new
method to construct the cyclic amidinourea
functional group
Toward the Synthesis of the Fungal Metabolite (-)-TAN-2483B
No full textIn the search of chemical species with potential therapeutic biological activity, synthetic chemists have looked to nature for inspiration. Molecules built by biological machinery often have structures predisposed for biological interaction. (-)-TAN-2483B and the related compounds (-)-TAN-2483A, and waol A are fungal metabolites that display biological activity in kinase inhibition and parathyroid-induced bone resorption. Though total syntheses of (-)-TAN-2483A and waol A have been achieved, the established methodology does not afford access to (-)-TAN-2483B owing to the unique relative configuration about the ring system. Derivatives of D-galactal have been synthesised, and functionalised at the C-1 and C-2 positions, laying the groundwork for a route to (-)-TAN-2483B and analogues. Using D-galactal derivatives is advantageous as it circumvents some difficult transformations in the existing method for analogue synthesis. The functionalities installed were halide and formyl groups at the C-2 position, and acetylenes at the C-1 position. The synthesis of 2-haloglycals from tri-O-acetyl-D-galactal using N-halosuccinimides was achieved in 32% and <37% for the bromo- and iodo- variants respectively. Vilsmeier-Haack formylation was explored using per-benzylated and per-acetylated galactals as substrates. Formylation of the per-benzylated species was achieved in 78% yield in accordance with literature values. Vilsmeier-Haack formylation on the per-acetylated galactal has not been reported and the glycal was found to be a poor substrate for the formylation. Theories regarding the incompatibility of the per-acetylated species with Vilsmeier-Haack conditions were developed. Ferrier-type alkynylation of the 2-halo/formylglycals was explored, with yields up to 17% and 13% for the bromo- and iodo- species (unoptimised), and 7% for 2-formylglycal (after optimisation studies). The resulting 1-ethynyl-2-formyl/halo-2,3-unsaturated pyrans could be potential intermediates en route to the furanone ring of the target compound.</p
Free thinking - running
No full textWe've been running for two million years give or take. Shahidha Bari and Laurence Scott explore contemporary running as solitary inspiration and communal activity with the Geographer and 1999 Scottish Hill Running Champion, Hayden Lorimer, the artists Kai Syng Tan and Angus Farquhar, and the literary scholar and bare-foot artiste, Vybarr Cregan-Reid. Conversation ranges from feeling empowered on city streets to teaming up with the wind to the horrid history of the treadmill and explore whether Running deserves better representation in the arts. Guests: Vybarr Cregan-Reid - author of Footnotes How Running Makes Us Human Angus Farquhar, Creative Director of NVA Public Art, author of a blog 'The Grim Runner' Hayden Lorimer Running Geographer Kai Syng Tan, Artist and curator of a biennial festival Run Run Run Producer: Jacqueline Smith
R&D Investment Decision and Optimal Subsidy
No full textThis article assumes that a firm facing technological uncertainty must decide whether to purchase R&D capital at each instant. R&D capital exhibits both irreversibility and externality through the learning‐by‐doing effect. The combination of irreversibility and uncertainty drives agents to be more prudent; the maxim `better safe than sorry' applies. This maxim is more important if uncertainty is greater, technology progresses at a lower pace, the externality is stronger, or a catastrophic event is less likely to occur. A firm ignoring the externality will both invest later and disinvest earlier than a social planner who internalizes the externality. An equal rate of investment tax credits should be given to both costlessly reversible investments and irreversible ones, and the same rate of taxation should be imposed on disinvestment
Editorial note - On the aims and scope and priority areas in Materials and Design
No full textAlexander M. Korsunsky, A. Geoffrey Gibson, Giang D. Nguyen, Marco Sebastiani, Xu Song, Tan Su
Ornebius tampines Tan & Robillard 2012
No full textOrnebius tampines Tan & Robillard, 2012 (Fig. 6) Ornebius tampines Tan & Robillard, 2012: 418. Type specimens examined. Holotype (male): Singapore, Pasir Ris Park, Sungei Tampines, along mangrove boardwalk, coll. M. K. Tan, 17 June 2011 (ZRC). Paratypes: 3 males, same locality as holotype, coll. M. K. Tan, 17 June 2011, 15 September 2011 (all ZRC). New material examined. Singapore, 1 female, same locality as holotype, coll. M. K. Tan, 20 October 2012 (all ZRC). Description. Female. Habitus as shown in Fig. 6 A. Ninth abdominal tergite with apical margin straight. Supraanal plate setose, with tenth abdominal tergite and epiproct completely fused; furrowed in middle; with apex subtruncated (Fig. 6 B). Paraprocts simple and short. Subgenital plate wider than long, with apical margin roundlyemarginated (Fig. 6 C). Ovipositor of medium length; apical valves with margins smooth; ventral margin of dorsal valves with 2–3 bristles (n = 1) (Fig. 6 D). Measurements. See Table 4. Discussion. Only males were previously known of this species (Tan & Robillard, 2012). New material allowed the description of the female. A re-examination of the type specimens revealed that in the original description the male phallic complex was imprecisely described. The medial valve, also referred to as internal sclerite of medial valve, is not bifurcate at apex. The ventral lobes are membranous. Instead, it is the internal sclerite of medial valve with base gently curved upwards. The lateral valves are weakly sclerotised, which was not previously mentioned.Published as part of Tan, Ming Kai & Ingrisch, Sigfrid, 2013, New taxa and notes of some described species of scaly crickets (Orthoptera: Mogoplistidae: Mogoplistinae) from Singapore, pp. 17-28 in Zootaxa 3637 (1) on page 26, DOI: 10.11646/zootaxa.3637.1.2, http://zenodo.org/record/28357
Synthesis of Highly Functionalised Furo[3,4-b]pyrans: Towards the Fungal Metabolite (−)-TAN-2483B
No full textCarbohydrate-derived cyclopropanes combine both the stereochemical wealth of carbohydrates and the reactivity of cyclopropanes. A diverse variety of reaction modes for these cyclopropyl carbohydrates can be harnessed for the synthesis of natural products and other targets.
The natural products (−)-TAN-2483A and (−)-TAN-2483B are fungal secondary metabolites displaying a variety of bioactivities such as inhibition of c-src kinase action and parathyroid hormone-induced bone resorption. This thesis described several synthetic approaches to the natural product (−)-TAN-2483B and analogues of (−)-TAN-2483B employing cyclopropane ring expansion.
The synthetic route to (−)-TAN-2483B began with the readily available substrate D-mannose. The pyran ring unsaturation of the natural product was established by a cyclopropanation-ring expansion sequence. A synthetic strategy via dichlorocyclopropane-based intermediates is described in chapter 2. This being unsuccessful, an alternative approach via 2-fomyl-glycal was developed in chapter 3. The chapter 2 and 3 provided a solid background for the achievement of the analogues synthesis illustrated in chapter 4 via dibromocyclopropane. Lewis acid-mediated alkynylation followed by Pdcatalysed carbonylative lactonisation was successfully utilised in the revelation of the furo[3,4-b]pyran ring skeleton. This route afforded analogues of TAN-2483B; the Z-and E-unsaturated ethyl esters 140 and 141 and hydroxy(−)-TAN-2483B 145. The total synthesis of (−)-TAN-2483B was not achieved due to unforeseen obstacles encountered in the deoxygenation of the side arm of 335 (Chapter 4) into the E-propenyl side arm of (−)-TAN-2483B
- …
