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2. Cage-Walking: Vertex Differentiation by Palladium-Catalyzed Isomerization of B(9)-Bromo-meta-Carborane.

Author

Dziedzic, Rafal M, Martin, Joshua L, Axtell, Jonathan C, Saleh, Liban MA, Ong, Ta-Chung, Yang, Yun-Fang, Messina, Marco S, Rheingold, Arnold L, Houk, KN, and Spokoyny, Alexander M

Subjects
Chemical Sciences, General Chemistry
Abstract

We report the first observed Pd-catalyzed isomerization ("cage-walking") of B(9)-bromo-meta-carborane during Pd-catalyzed cross-coupling, which enables the formation of B-O and B-N bonds at all boron vertices (B(2), B(4), B(5), and B(9)) of meta-carborane. Experimental and theoretical studies suggest this isomerization mechanism is strongly influenced by the steric crowding at the Pd catalyst by either a biaryl phosphine ligand and/or substrate. Ultimately, this "cage-walking" process provides a unique pathway to preferentially introduce functional groups at the B(2) vertex using B(9)-bromo-meta-carborane as the sole starting material through substrate control.

Published
2017

7. Controversy and Consensus on Indications for Sperm DNA Fragmentation Testing in Male Infertility: A Global Survey, Current Guidelines, and Expert Recommendations

Author

Agarwal, A, Farkouh, A, Saleh, R, Abdel-Meguid Hamoda, TA-A, Harraz, AM, Kavoussi, P, Arafa, M, Salvio, G, Rambhatla, A, Toprak, T, Gül, M, Phuoc, NHV, Boitrelle, F, Birowo, P, Ghayda, RA, Cannarella, R, Kuroda, S, Durairajanayagam, D, Zini, A, Wyns, C, Sarikaya, S, Tremellen, K, Mostafa, T, Sokolakis, I, Evenson, DP, Henkel, R, Zohdy, W, Chung, E, Ziouziou, I, Falcone, M, Russo, GI, Al-Hashimi, M, Calogero, AE, Ko, E, Colpi, G, Lewis, S, Serefoglu, EC, Bahar, F, Martinez, M, Nguyen, Q, Ambar, RF, Bakircioglu, ME, Kandil, H, Mogharabian, N, Sabbaghian, M, Taniguchi, H, Tsujimura, A, Sajadi, H, Ibrahim, W, Atmoko, W, Vogiatzi, P, Gunes, S, Gilani, MAS, Roychoudhury, S, Güngör, ND, Hakim, L, Adriansjah, R, Kothari, P, Jindal, S, Amar, E, Park, HJ, Long, TQT, Homa, S, Karthikeyan, VS, Zilaitiene, B, Rosas, IM, Marino, A, Pescatori, E, Ozer, C, Akhavizadegan, H, Garrido, N, Busetto, GM, Adamyan, A, Al-Marhoon, M, Elbardisi, H, Dolati, P, Darbandi, M, Darbandi, S, Balercia, G, Pinggera, G-M, Micic, S, Ho, CCK, Moussa, M, Preto, M, Zenoaga-Barbăroșie, C, Smith, RP, Kosgi, R, Rosette, JDL, El-Sakka, AI, Abumelha, SM, Mierzwa, TC, Ong, TA, Banihani, SA, Bowa, K, Fukuhara, S, Boeri, L, Danacıoğlu, YO, Gokalp, F, Selim, OM, Cho, C-L, Tadros, NN, Ugur, MR, Ozkent, MS, Chiu, P, Kalkanli, A, Khalafalla, K, Vishwakarma, RB, Finocchi, F, Andreadakis, S, Giulioni, C, Çeker, G, Ceyhan, E, Malhotra, V, Yilmaz, M, Timpano, M, Barrett, TL, Kim, SHK, Ahn, S-T, Giacone, F, Palani, A, Duarsa, GWK, Kadioglu, A, Gadda, F, Zylbersztejn, DS, Aydos, K, Kulaksız, D, Gupte, D, Calik, G, Karna, KK, Drakopoulos, P, Baser, A, Kumar, V, Molina, JMC, Rajmil, O, Ferreira, RH, Leonardi, S, Avoyan, A, Sogutdelen, E, Franco, G, Ramsay, J, Ramirez, L, Shah, R, Global Andrology Forum, Agarwal, Ashok, Farkouh, Ala'A, Saleh, Ramadan, Abdel-Meguid Hamoda, Taha Abo-Almagd, Harraz, Ahmed M, Kavoussi, Parviz, Arafa, Mohamed, Salvio, Gianmaria, Rambhatla, Amarnath, Toprak, Tuncay, Gül, Murat, Phuoc, Nguyen Ho Vinh, Boitrelle, Florence, Birowo, Ponco, Ghayda, Ramy Abou, Cannarella, Rossella, Kuroda, Shinnosuke, Durairajanayagam, Damayanthi, Zini, Armand, Wyns, Christine, Sarikaya, Selcuk, Tremellen, Kelton, Mostafa, Taymour, Sokolakis, Ioanni, Evenson, Donald P, Henkel, Ralf, Zohdy, Wael, Chung, Eric, Ziouziou, Imad, Falcone, Marco, Russo, Giorgio I, Al-Hashimi, Manaf, Calogero, Aldo E, Ko, Edmund, Colpi, Giovanni, Lewis, Sheena, Serefoglu, Ege Can, Bahar, Fahmi, Martinez, Marlon, Nguyen, Quang, Ambar, Rafael F, Bakircioglu, Mustafa Emre, Kandil, Hussein, Mogharabian, Nasser, Sabbaghian, Marjan, Taniguchi, Hisanori, Tsujimura, Akira, Sajadi, Hesamoddin, Ibrahim, Wael, Atmoko, Widi, Vogiatzi, Paraskevi, Gunes, Sezgin, Gilani, Mohammad Ali Sadighi, Roychoudhury, Shubhadeep, Güngör, Nur Dokuzeylül, Hakim, Lukman, Adriansjah, Ricky, Kothari, Priyank, Jindal, Sunil, Amar, Edouard, Park, Hyun Jun, Long, Tran Quang Tien, Homa, Sheryl, Karthikeyan, Vilvapathy Senguttuvan, Zilaitiene, Birute, Rosas, Israel Maldonado, Marino, Angelo, Pescatori, Edoardo, Ozer, Cevahir, Akhavizadegan, Hamed, Garrido, Nicola, Busetto, Gian Maria, Adamyan, Aram, Al-Marhoon, Mohamed, Elbardisi, Haitham, Dolati, Parisa, Darbandi, Mahsa, Darbandi, Sara, Balercia, Giancarlo, Pinggera, Germar-Michael, Micic, Sava, Ho, Christopher Chee Kong, Moussa, Mohamad, Preto, Mirko, Zenoaga-Barbăroșie, Cătălina, Smith, Ryan P, Kosgi, Raghavender, Rosette, Jean de la, El-Sakka, Ahmed I, Abumelha, Saad Mohammed, Mierzwa, Tiago Cesar, Ong, Teng Aik, Banihani, Saleem A, Bowa, Kasonde, Fukuhara, Shinichiro, Boeri, Luca, Danacıoğlu, Yavuz Onur, Gokalp, Fatih, Selim, Osama Mohamed, Cho, Chak-Lam, Tadros, Nicholas N, Ugur, Muhammet Rasit, Ozkent, Mehmet Serkan, Chiu, Peter, Kalkanli, Arif, Khalafalla, Kareim, Vishwakarma, Ranjit B, Finocchi, Federica, Andreadakis, Sotiri, Giulioni, Carlo, Çeker, Gökhan, Ceyhan, Erman, Malhotra, Vineet, Yilmaz, Mehmet, Timpano, Massimiliano, Barrett, Trenton L, Kim, Shannon Hee Kyung, Ahn, Sun-Tae, Giacone, Filippo, Palani, Ayad, Duarsa, Gede Wirya Kusuma, Kadioglu, Ate, Gadda, Franco, Zylbersztejn, Daniel Suslik, Aydos, Kaan, Kulaksız, Deniz, Gupte, Deepak, Calik, Gokhan, Karna, Keshab Kumar, Drakopoulos, Panagioti, Baser, Aykut, Kumar, Vijay, Molina, Juan Manuel Corral, Rajmil, Osvaldo, Ferreira, Raphael H, Leonardi, Sofia, Avoyan, Armen, Sogutdelen, Emrullah, Franco, Giorgio, Ramsay, Jonathan, Ramirez, Liliana, Shah, Rupin, and Rocco, Lucia

Subjects
Male infertility, Practice guideline, Delphi method, DNA fragmentation, Survey, Sperm
Abstract

PURPOSE: Sperm DNA fragmentation (SDF) testing was recently added to the sixth edition of the World Health Organization laboratory manual for the examination and processing of human semen. Many conditions and risk factors have been associated with elevated SDF; therefore, it is important to identify the population of infertile men who might benefit from this test. The purpose of this study was to investigate global practices related to indications for SDF testing, compare the relevant professional society guideline recommendations, and provide expert recommendations. MATERIALS AND METHODS: Clinicians managing male infertility were invited to take part in a global online survey on SDF clinical practices. This was conducted following the CHERRIES checklist criteria. The responses were compared to professional society guideline recommendations related to SDF and the appropriate available evidence. Expert recommendations on indications for SDF testing were then formulated, and the Delphi method was used to reach consensus. RESULTS: The survey was completed by 436 experts from 55 countries. Almost 75% of respondents test for SDF in all or some men with unexplained or idiopathic infertility, 39% order it routinely in the work-up of recurrent pregnancy loss (RPL), and 62.2% investigate SDF in smokers. While 47% of reproductive urologists test SDF to support the decision for varicocele repair surgery when conventional semen parameters are normal, significantly fewer general urologists (23%; p=0.008) do the same. Nearly 70% would assess SDF before assisted reproductive technologies (ART), either always or for certain conditions. Recurrent ART failure is a common indication for SDF testing. Very few society recommendations were found regarding SDF testing. CONCLUSIONS: This article presents the largest global survey on the indications for SDF testing in infertile men, and demonstrates diverse practices. Furthermore, it highlights the paucity of professional society guideline recommendations. Expert recommendations are proposed to help guide clinicians.

Published
2023

10. Biradical Polarizing Agents at High Fields

Author

Michaelis, Vladimir K., primary, Keeler, Eric G., additional, Bahri, Salima, additional, Ong, Ta-Chung, additional, Daviso, Eugenio, additional, Colvin, Michael T., additional, and Griffin, Robert G., additional

Published
2022
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13. STREET KETAMINE-ASSOCIATED BLADDER DYSFUNCTION: AN EMERGING HEALTH PROBLEM

Author

TEH GC, CCM Lei, CHUA CB, ONG TA, and LEE PY

Subjects
Ketamine, lower urinary tract symptoms, bladder dysfunction., Medicine
Abstract

Introduction: Ketamine is frequently abused nowadays as a recreational drug. Case reports are emerging since 2007 to describe a new clinical entity of severe bladder dysfunction associated with chronic abuse of street ketamine. Clinical presentation: Severe lower urinary tract symptoms of urinary frequency and urgency which are refractory to conventional treatment. Quality of life is adversely affected as a consequence. Chronic kidney disease will develop in advanced cases. Investigation findings: The urine is sterile on culture. Ultrasound will show reduced bladder capacity with thickened bladder wall. In advanced stage, hydronephrosis and renal impairment will develop. Treatment: Patients should be advised to stop street ketamine use immediately. Anticholinergic medication could be tried to alleviate the symptoms. Refractory cases with dilatation of the upper urinary tract might need urinary diversion. Conclusion: Awareness of this new condition is essential in diagnosis. Early intervention offers better treatment outcome.

Published
2009

17. DO UNIVERSITY STUDENTS HAVE HIGH CARDIOVASCULAR RISK? A PILOT STUDY FROM UNIVERSITI MALAYSIA SARAWAK (UNIMAS)

Author

KAMARUDIN K, SYED ALWI SAR, MUNA S, ONG TA, and LEE PY

Subjects
Cardiovascular risk factors, university students, undergraduate., Medicine
Abstract

A health screening was done in UNIMAS in August 2008 for 237 undergraduate students. Body mass index (BMI), waist circumference (WC) and blood pressure (BP) were measured for all subjects. Total cholesterol and glucose levels were checked for those who fulfilled the screening criteria. The proportion of participants with cardiovascular (CVD) risk factors was high. The strategies for health promotion should not only be targeted to the older community but also to the younger community.

Published
2010

20. Dendritic polarizing agents for DNP SENS† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c6sc03139k Click here for additional data file

Author

Liao, Wei-Chih, Ong, Ta-Chung, Gajan, David, Bernada, Florian, Sauvée, Claire, Yulikov, Maxim, Pucino, Margherita, Schowner, Roman, Schwarzwälder, Martin, Buchmeiser, Michael R., Jeschke, Gunnar, Tordo, Paul, Ouari, Olivier, Lesage, Anne, Emsley, Lyndon, and Copéret, Christophe

Subjects
Chemistry
Abstract

Dendrimer-shielded polarizing agents for the application of DNP SENS to reactive surfaces., Dynamic Nuclear Polarization Surface Enhanced NMR Spectroscopy (DNP SENS) is an effective method to significantly improve solid-state NMR investigation of solid surfaces. The presence of unpaired electrons (polarizing agents) is crucial for DNP, but it has drawbacks such as leading to faster nuclear spin relaxation, or even reaction with the substrate under investigation. The latter can be a particular problem for heterogeneous catalysts. Here, we present a series of carbosilane-based dendritic polarizing agents, in which the bulky dendrimer can reduce the interaction between the solid surface and the free radical. We thereby preserve long nuclear T′2 of the surface species, and even successfully enhance a reactive heterogeneous metathesis catalyst.

Published
2016

21. Lipid Dynamics and Protein–Lipid Interactions in 2D Crystals Formed with the β-Barrel Integral Membrane Protein VDAC1

Author

Eddy, Matthew T., Ong, Ta-Chung, Clark, Lindsay, Teijido, Oscar, van der Wel, Patrick C. A., Garces, Robert, Wagner, Gerhard, Rostovtseva, Tatiana K., and Griffin, Robert G.

Abstract

We employ a combination of 13C/15N magic angle spinning (MAS) NMR and 2H NMR to study the structural and functional consequences of different membrane environments on VDAC1 and, conversely, the effect of VDAC1 on the structure of the lipid bilayer. MAS spectra reveal a well-structured VDAC1 in 2D crystals of dimyristoylphosphatidylcholine (DMPC) and diphytanoylphosphatidylcholine (DPhPC), and their temperature dependence suggests that the VDAC structure does not change conformation above and below the lipid phase transition temperature. The same data show that the N-terminus remains structured at both low and high temperatures. Importantly, functional studies based on electrophysiological measurements on these same samples show fully functional channels, even without the presence of Triton X-100 that has been found necessary for in vitro-refolded channels. 2H solid-state NMR and differential scanning calorimetry were used to investigate the dynamics and phase behavior of the lipids within the VDAC1 2D crystals. 2H NMR spectra indicate that the presence of protein in DMPC results in a broad lipid phase transition that is shifted from 19 to ∼27 °C and show the existence of different lipid populations, consistent with the presence of both annular and bulk lipids in the functionally and structurally homogeneous samples.

Published
2024
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23. Resolving the Core and the Surface of CdSe Quantum Dots and Nanoplatelets Using Dynamic Nuclear Polarization Enhanced PASS–PIETA NMR Spectroscopy

Author

Piveteau, Laura, primary, Ong, Ta-Chung, additional, Walder, Brennan J., additional, Dirin, Dmitry N., additional, Moscheni, Daniele, additional, Schneider, Barbara, additional, Bär, Janine, additional, Protesescu, Loredana, additional, Masciocchi, Norberto, additional, Guagliardi, Antonietta, additional, Emsley, Lyndon, additional, Copéret, Christophe, additional, and Kovalenko, Maksym V., additional

Published
2018
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27. DNP Enhanced Solid-State NMR Spectroscopy of Heterogeneous Catalysts

Author

Gajan, David, Berruyer, Pierrick, Ong, Ta-Chung, Liao, Wei-Chih, Mougel, Victor, Conley, Matthew P, Silverio, Daniel L, Widdifield, Cory, Lelli, Moreno, Thieuleux, Chloé, Lesage, Anne, Copéret, Christophe, Emsley, Lyndon, Solid-State NMR Methods for Materials - Méthodes de RMN à l'état solide pour les matériaux, Institut des Sciences Analytiques (ISA), Institut de Chimie du CNRS (INC)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS), Department of Chemistry and Applied Biosciences [ETH Zürich] (D-CHAB), Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich), Department of Chemistry, Durham University, Center for Magnetic Resonance, Università degli Studi di Firenze = University of Florence [Firenze] (UNIFI), Laboratoire de Chimie, Catalyse, Polymères et Procédés, R 5265 (C2P2), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-École supérieure de Chimie Physique Electronique de Lyon (CPE)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Institut des sciences et ingénierie chimiques (ISIC), Ecole Polytechnique Fédérale de Lausanne (EPFL), American Chemical Society - Colorado section, and Society for Applied Spectroscopy

Subjects
[CHIM.ANAL]Chemical Sciences/Analytical chemistry
Abstract

International audience; Heterogeneous catalysts are key to efficient processes in the chemical industry. However, they are difficult to improve because of the lack of access to their active-site structures. Although solid-state NMR is the method of choice to describe at atomic level the structure of catalysts, it is plagued by its intrinsic low sensitivity. This limitation is further exacerbated by the small fraction of active sites on the materials and by their often disordered and multi-site nature. Recently it has been demonstrated that this limit can be overcome by using dynamic nuclear polarization (DNP) which allows enhancement factors of up to 250 in solutions, at a magnetic field of 9.4 T and sample temperatures of ca. 100 K. Key to transposing the high enhancement factors observed for bulk frozen solutions to materials is the use of incipient wetness impregnation. In this approach, the materials are wetted by a minimal amount of radical solution. If the first proof of concepts was reported on model mesoporous silica materials, recent applications by our group and others concern a diverse range of chemical systems such as nanoparticles, mixed oxides, cementitious materials or microcrystalline solids. Here we will present new applications of DNP SENS in heterogeneous catalysis. We will show that DNP SENS allows to directly measure structural information of surface reaction intermediates in alkene metathesis catalysts, namely by obtaining C-C connectivities and bond distances. We will also show how the gain in sensitivity provided by DNP allows us to determine the full three-dimensional atomic-scale structure of a catalytically relevant organometallic complex anchored on a silica surface. This is done through a series of multi-dimensional and multi-nuclear NMR experiments producing several inter-nuclear distance constraints and the implementation of sophisticated NMR structure determination protocols.

Published
2016

28. One-pot solvothermal synthesis of a well-ordered layered sodium aluminoalcoholate complex: a useful precursor for the preparation of porous Al[subscript 2]O[subscript 3] particles

Author

Li, Xiansen, Michaelis, Vladimir K., Ong, Ta-Chung, Smith, Stacey J., McKay, Ian, Griffin, Robert Guy, Wang, Evelyn, Mueller, Peter, Massachusetts Institute of Technology. Department of Chemistry, Massachusetts Institute of Technology. Department of Mechanical Engineering, Francis Bitter Magnet Laboratory (Massachusetts Institute of Technology), Li, Xiansen, Michaelis, Vladimir K., Ong, Ta-Chung, Smith, Stacey J., McKay, Ian, Muller, Peter, Griffin, Robert Guy, and Wang, Evelyn N.

Abstract

One-pot solvothermal synthesis of a robust tetranuclear sodium hexakis(glycolato)tris(methanolato)aluminate complex Na[subscript 3][Al[subscript 4](OCH[subscript 3])[subscript 3](OCH[subscript 2]CH[subscript 2]O)[subscript 6]] via a modified yet rigorous base-catalyzed transesterification mechanism is presented here. Single crystal X-ray diffraction (SCXRD) studies indicate that this unique Al complex contains three pentacoordinate Al[superscript 3+] ions, each bound to two bidentate ethylene glycolate chelators and one monodentate methanolate ligand. The remaining fourth Al[superscript 3+] ion is octahedrally coordinated to one oxygen atom from each of the six surrounding glycolate chelators, effectively stitching the three pentacoordinate Al moieties together into a novel tetranuclear Al complex. This aluminate complex is periodically self-assembled into well-ordered layers normal to the [110] axis with the intra-/inter-layer bonding involving extensive ionic bonds from the three charge-counterbalancing Na[superscript +] cations rather than the more typical hydrogen bonding interactions as a result of fewer free hydroxyl groups present in its structure. It can also serve as a valuable precursor toward the facile synthesis of high-surface-area alumina powders using a very efficient rapid pyrolysis technique., United States. Advanced Research Projects Agency-Energy (0471-1627), National Institutes of Health (U.S.) (Grant EB-001960), National Institutes of Health (U.S.) (Grant EB-002026), National Science Foundation (U.S.) (Grant CHE-0946721), Natural Sciences and Engineering Research Council of Canada (Postdoctoral Fellowship)

Published
2013

31. Tailored Polarizing Hybrid Solids with Nitroxide Radicals Localized in Mesostructured Silica Walls

Author

Silverio, Daniel L., primary, van Kalkeren, Henri A., additional, Ong, Ta-Chung, additional, Baudin, Mathieu, additional, Yulikov, Maxim, additional, Veyre, Laurent, additional, Berruyer, Pierrick, additional, Chaudhari, Sachin, additional, Gajan, David, additional, Baudouin, David, additional, Cavaillès, Matthieu, additional, Vuichoud, Basile, additional, Bornet, Aurélien, additional, Jeschke, Gunnar, additional, Bodenhausen, Geoffrey, additional, Lesage, Anne, additional, Emsley, Lyndon, additional, Jannin, Sami, additional, Thieuleux, Chloé, additional, and Copéret, Christophe, additional

Published
2017
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32. Dendritic polarizing agents for DNP SENS

Author

Liao, Wei-Chih, primary, Ong, Ta-Chung, additional, Gajan, David, additional, Bernada, Florian, additional, Sauvée, Claire, additional, Yulikov, Maxim, additional, Pucino, Margherita, additional, Schowner, Roman, additional, Schwarzwälder, Martin, additional, Buchmeiser, Michael R., additional, Jeschke, Gunnar, additional, Tordo, Paul, additional, Ouari, Olivier, additional, Lesage, Anne, additional, Emsley, Lyndon, additional, and Copéret, Christophe, additional

Published
2017
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34. Identifying Sn Site Heterogeneities Prevalent Among Sn-Beta Zeolites

Author

Wolf, Patrick, primary, Liao, Wei-Chih, additional, Ong, Ta-Chung, additional, Valla, Maxence, additional, Harris, James W., additional, Gounder, Rajamani, additional, van der Graaff, William N. P., additional, Pidko, Evgeny A., additional, Hensen, Emiel J. M., additional, Ferrini, Paola, additional, Dijkmans, Jan, additional, Sels, Bert, additional, Hermans, Ive, additional, and Copéret, Christophe, additional

Published
2016
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35. Rapid Quantitative Analysis of Multiple Explosive Compound Classes on a Single Instrument via Flow‐Injection Analysis Tandem Mass Spectrometry.

Author

Ostrinskaya, Alla, Kunz, Roderick R., Clark, Michelle, Kingsborough, Richard P., Ong, Ta‐Hsuan, and Deneault, Sandra

Subjects
TNT (Chemical), QUANTITATIVE research, FLOW injection analysis, TANDEM mass spectrometry, FORENSIC sciences, TETRYL
Abstract

A flow‐injection analysis tandem mass spectrometry (FIA MSMS) method was developed for rapid quantitative analysis of 10 different inorganic and organic explosives. Performance is optimized by tailoring the ionization method (APCI/ESI), de‐clustering potentials, and collision energies for each specific analyte. In doing so, a single instrument can be used to detect urea nitrate, potassium chlorate, 2,4,6‐trinitrotoluene, 2,4,6‐trinitrophenylmethylnitramine, triacetone triperoxide, hexamethylene triperoxide diamine, pentaerythritol tetranitrate, 1,3,5‐trinitroperhydro‐1,3,5‐triazine, nitroglycerin, and octohy‐dro‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocine with sensitivities all in the picogram per milliliter range. In conclusion, FIA APCI/ESI MSMS is a fast (<1 min/sample), sensitive (~pg/mL LOQ), and precise (intraday RSD < 10%) method for trace explosive detection that can play an important role in criminal and attributional forensics, counterterrorism, and environmental protection areas, and has the potential to augment or replace several of the existing explosive detection methods. [ABSTRACT FROM AUTHOR]

Published
2019
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39. The β‐Agostic Structure in (C5Me5)2Sc(CH2CH3): Solid‐State NMR Studies of (C5Me5)2Sc−R (R=Me, Ph, Et).

Author

Culver, Damien B., Huynh, Winn, Tafazolian, Hosein, Ong, Ta‐Chung, and Conley, Matthew P.

Subjects
NUCLEAR magnetic resonance, DENSITY functional theory, COUPLING constants, CHEMICAL shift (Nuclear magnetic resonance), PHENYL compounds
Abstract

Abstract: Multinuclear solid‐state NMR studies of Cp*2Sc−R (Cp*=pentamethylcyclopentadienyl; R=Me, Ph, Et) and DFT calculations show that the Sc−Et complex contains a β‐CH agostic interaction. The static central transition 45Sc NMR spectra show that the quadrupolar coupling constants (Cq) follow the trend of Ph≈Me>Et, indicating that the Sc−R bond is different in Cp*2Sc−Et compared to the methyl and phenyl complexes. Analysis of the chemical shift tensor (CST) shows that the deshielding experienced by Cβ in Sc−CH2CH3 is related to coupling between the filled σC‐C orbital and the vacant π S c ⋯ H C * orbital. [ABSTRACT FROM AUTHOR]

Published
2018
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46. Topical Developments in High-Field Dynamic Nuclear Polarization

Author

Michaelis, Vladimir K., primary, Ong, Ta-Chung, additional, Kiesewetter, Matthew K., additional, Frantz, Derik K., additional, Walish, Joseph J., additional, Ravera, Enrico, additional, Luchinat, Claudio, additional, Swager, Timothy M., additional, and Griffin, Robert G., additional

Published
2014
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