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https://www.readbyqxmd.com/read/29028394/active-sampling-system-for-gas-phase-analyzers
#1
Artem E Akmalov, Alexander A Chistyakov, Olga I Dubkova, Gennadii E Kotkovskii, Alexei V Sychev
The approaches for increasing a contact-free sampling distance up to 40 cm for a field asymmetric ion mobility spectrometer were investigated and implemented by use both the vortex flow made by a rotating impeller and the laser desorption of traces of low volatile explosives. The sampling device for a laser-based field asymmetric ion mobility spectrometer including a high-speed rotating impeller was designed and built with help of computer simulation of vortex and analytical flows. The dependence of a signal of trinitrotoluene vapors on a rotational speed of an impeller was obtained...
August 2017: European Journal of Mass Spectrometry
https://www.readbyqxmd.com/read/29024395/deep-eutectic-solvent-based-magnetic-nanofluid-in-the-development-of-stir-bar-sorptive-dispersive-microextraction-an-efficient-hyphenated-sample-preparation-for-ultra-trace-nitroaromatic-explosives-extraction-in-wastewater
#2
Ali Reza Zarei, Maryam Nedaei, Sohrab Ali Ghorbanian
A deep eutectic solvent based magnetic nanofluid was coupled with stir bar sorptive dispersive microextraction as a hyphenated sample preparation technique. The neodymium core magnetic stir bar was coated physically with nanofluid of magnetic carbon nanotube nanocomposites and deep eutectic solvents. The prepared nanofluid has magnetic and strong sorbing properties and is compatible with gas chromatography. In this nanofluid, the deep eutectic solvent acts simultaneously as both carrier and stabilizer for magnetic nanotubes...
October 12, 2017: Journal of Separation Science
https://www.readbyqxmd.com/read/29020612/covering-the-stem-cell-explosion-at-the-2017-isscr-conference-in-boston
#3
Thomas Graf
The meeting covered a plethora of rapidly evolving approaches and areas, such as organoid cultures modeling tissues and organs; stem cell-specific metabolites revealing new signaling pathways; single-cell technologies discovering new cell types and exploring stem cell niche interactions; novel methods studying stem cells in aging and cancer; lineage-tracing experiments exploring cell plasticity of tissues before and after injury; epigenetic studies illuminating cell reprogramming; new protocols improving cells for regenerative purposes; and several other timely and exciting topics...
October 10, 2017: Stem Cell Reports
https://www.readbyqxmd.com/read/28967704/reappraising-the-early-evidence-of-durophagy-and-drilling-predation-in-the-fossil-record-implications-for-escalation-and-the-cambrian-explosion
#4
Russell D C Bicknell, John R Paterson
The Cambrian Explosion is arguably the most extreme example of a biological radiation preserved in the fossil record, and studies of Cambrian Lagerstätten have facilitated the exploration of many facets of this key evolutionary event. As predation was a major ecological driver behind the Explosion - particularly the radiation of biomineralising metazoans - the evidence for shell crushing (durophagy), drilling and puncturing predation in the Cambrian (and possibly the Ediacaran) is considered. Examples of durophagous predation on biomineralised taxa other than trilobites are apparently rare, reflecting predator preference, taphonomic and sampling biases, or simply lack of documentation...
October 2, 2017: Biological Reviews of the Cambridge Philosophical Society
https://www.readbyqxmd.com/read/28945089/uv-resonance-raman-investigation-of-pentaerythritol-tetranitrate-solution-photochemistry-and-photoproduct-hydrolysis
#5
Katie L Gares, Sergei V Bykov, Sanford A Asher
Ultraviolet resonance Raman spectroscopy (UVRR) is being developed for standoff trace explosives detection. To accomplish this, it is important to develop a deep understanding of the accompanying UV excited photochemistry of explosives, as well as the impact of reactions on the resulting photoproducts. In the work here we used 229 nm excited UVRR spectroscopy to monitor the photochemistry of pentaerythritol tetranitrate (PETN) in acetonitrile. We find that solutions of PETN in CD3CN photodegrade with a quantum yield of 0...
October 9, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28846394/two-dimensional-titanium-nitride-ti2n-mxene-synthesis-characterization-and-potential-application-as-surface-enhanced-raman-scattering-substrate
#6
Bhuvaneswari Soundiraraju, Benny Kattikkanal George
We report on the synthesis, characterization, and application of Ti2N (MXene), a two-dimensional transition metal nitride of M2X type. Synthesis of nitride-based MXenes (Mn+1Nn) is difficult due to their higher formation energy from Mn+1ANn and poor stability of Mn+1Nn layers in the etchant employed, typically HF. Herein, the selective etching of Al from ternary layered transition metal nitride Ti2AlN (MAX) and intercalation were achieved by immersing the powder in a mixture of potassium fluoride and hydrochloric acid...
September 26, 2017: ACS Nano
https://www.readbyqxmd.com/read/28797796/low-134-cs-137-cs-ratio-anomaly-in-the-north-northwest-direction-from-the-fukushima-dai-ichi-nuclear-power-station
#7
Shingo Kobayashi, Takayuki Shinomiya, Takahiro Ishikawa, Hitoshi Imaseki, Kazuki Iwaoka, Hisashi Kitamura, Satoshi Kodaira, Keisuke Kobayashi, Masakazu Oikawa, Norihiro Miyaushiro, Yoshio Takashima, Yukio Uchihori
A low (134)Cs/(137)Cs ratio anomaly in the north-northwest (NNW) direction from the Fukushima Dai-ichi Nuclear Power Station (FDNPS) is identified by a new analysis of the (134)Cs/(137)Cs ratio dataset which we had obtained in 2011-2015 by a series of car-borne surveys that employed a germanium gamma-ray spectrometer. We found that the (134)Cs/(137)Cs ratio is slightly lower (0.95, decay-corrected to March 11, 2011) in an area with a length of about 15 km and a width of about 3 km in the NNW direction from the FDNPS than in other directions from the station...
August 7, 2017: Journal of Environmental Radioactivity
https://www.readbyqxmd.com/read/28782932/visualization-of-colloidal-nanocrystal-formation-and-electrode-electrolyte-interfaces-in-liquids-using-tem
#8
Zhiyuan Zeng, Wenjing Zheng, Haimei Zheng
Transmission electron microscopy (TEM) has become a powerful analytical tool for addressing unique scientific problems in chemical sciences as well as in materials sciences and other disciplines. There has been a lot of recent interest in the development and applications of liquid phase environmental TEM. In this Account, we review the development and applications of liquid cell TEM for the study of dynamic phenomena at liquid-solid interfaces, focusing on two areas: (1) nucleation, growth, and self-assembly of colloidal nanocrystals and (2) electrode-electrolyte interfaces during charge and discharge processes...
August 7, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28744547/broad-spectrum-infrared-thermal-desorption-of-wipe-based-explosive-and-narcotic-samples-for-trace-mass-spectrometric-detection
#9
Thomas P Forbes, Matthew Staymates, Edward Sisco
Wipe collected analytes were thermally desorbed using broad spectrum near infrared heating for mass spectrometric detection. Employing a twin tube filament-based infrared emitter, rapid and efficiently powered thermal desorption and detection of nanogram levels of explosives and narcotics was demonstrated. The infrared thermal desorption (IRTD) platform developed here used multi-mode heating (direct radiation and secondary conduction from substrate and subsequent convection from air) and a temperature ramp to efficiently desorb analytes with vapor pressures across eight orders of magnitude...
August 7, 2017: Analyst
https://www.readbyqxmd.com/read/28738664/bomb-swab-can-trace-explosive-particle-sampling-and-detection-be-improved
#10
Danny Fisher, Raya Zach, Yossef Matana, Paz Elia, Shiran Shustack, Yarden Sharon, Yehuda Zeiri
The marked increase in international terror in recent years requires the development of highly efficient methods to detect trace amounts of explosives at airports, border crossings and check points. The preferred analytical method worldwide is the ion mobility spectrometry (IMS) that is capable of detecting most explosives at the nano-gram level. Sample collection for the IMS analysis is based on swabbing of a passenger's belongings to collect possible explosive residues. The present study examines a wide range of issues related to swab-based particle collection and analysis, in the hope of gaining deeper understanding into this technique that will serve to improve the detection process...
November 1, 2017: Talanta
https://www.readbyqxmd.com/read/28731098/a-reaction-model-on-the-self-assembly-process-of-octahedron-shaped-coordination-capsules
#11
Yoshihiro Matsumura, Shuichi Hiraoka, Hirofumi Sato
Herein, the self-assembly process of an octahedron-shaped coordination capsule was analyzed based on a master equation approach using a reaction network model. This model was found to adequately reproduce the overall experimentally observed time evolutions and enabled us to trace the real-time evolution of transient intermediates, ranging from milli-second to hours. The time evolution of the distribution of individual intermediates species was obtained; a few linear-oligomers located near the reactant were produced at first, followed by an explosive increase in several types of intermediates...
August 9, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28723138/hand-held-femtogram-detection-of-hazardous-picric-acid-with-hydrophobic-ag-nanopillar-sers-substrates-and-mechanism-of-elasto-capillarity
#12
Aron Hakonen, FengChao Wang, Per Ola Andersson, Håkan Wingfors, Tomas Rindzevicius, Michael Stenbæk Schmidt, Venugopal Rao Soma, Shicai Xu, YingQi Li, Anja Boisen, HengAn Wu
Picric acid (PA) is a severe environmental and security risk due to its unstable, toxic, and explosive properties. It is also challenging to detect in trace amounts and in situ because of its highly acidic and anionic character. Here, we assess sensing of PA under nonlaboratory conditions using surface-enhanced Raman scattering (SERS) silver nanopillar substrates and hand-held Raman spectroscopy equipment. The advancing elasto-capillarity effects are explained by molecular dynamics simulations. We obtain a SERS PA detection limit on the order of 20 ppt, corresponding attomole amounts, which together with the simple analysis methodology demonstrates that the presented approach is highly competitive for ultrasensitive analysis in the field...
February 24, 2017: ACS Sensors
https://www.readbyqxmd.com/read/28688450/alignment-orientation-and-coulomb-explosion-of-difluoroiodobenzene-studied-with-the-pixel-imaging-mass-spectrometry-pimms-camera
#13
Kasra Amini, Rebecca Boll, Alexandra Lauer, Michael Burt, Jason W L Lee, Lauge Christensen, Felix Brauβe, Terence Mullins, Evgeny Savelyev, Utuq Ablikim, Nora Berrah, Cédric Bomme, Stefan Düsterer, Benjamin Erk, Hauke Höppner, Per Johnsson, Thomas Kierspel, Faruk Krecinic, Jochen Küpper, Maria Müller, Erland Müller, Harald Redlin, Arnaud Rouzée, Nora Schirmel, Jan Thøgersen, Simone Techert, Sven Toleikis, Rolf Treusch, Sebastian Trippel, Anatoli Ulmer, Joss Wiese, Claire Vallance, Artem Rudenko, Henrik Stapelfeldt, Mark Brouard, Daniel Rolles
Laser-induced adiabatic alignment and mixed-field orientation of 2,6-difluoroiodobenzene (C6H3F2I) molecules are probed by Coulomb explosion imaging following either near-infrared strong-field ionization or extreme-ultraviolet multi-photon inner-shell ionization using free-electron laser pulses. The resulting photoelectrons and fragment ions are captured by a double-sided velocity map imaging spectrometer and projected onto two position-sensitive detectors. The ion side of the spectrometer is equipped with a pixel imaging mass spectrometry camera, a time-stamping pixelated detector that can record the hit positions and arrival times of up to four ions per pixel per acquisition cycle...
July 7, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28662404/novel-laser-induced-photoacoustic-spectroscopy-for-instantaneous-trace-detection-of-explosive-materials
#14
Yasser H El-Sharkawy, Sherif Elbasuney
Laser photoacoustic spectroscopy (LPAS) is an attractive technology in terms of simplicity, ruggedness, and overall sensitivity; it detects the time dependent heat generated (thermo-elastic effect) in the target via interaction with pulsed optical radiation. This study reports on novel LPAS technique that offers instant and standoff detection capabilities of trace explosives. Over the current study, light is generated using pulsed Q-switched Nd:YAG laser; the generated photoacoustic response in stimulated explosive material offers signature values that depend on the optical, thermal, and acoustical properties...
June 15, 2017: Forensic Science International
https://www.readbyqxmd.com/read/28648260/broadening-the-perspective-on-gun-violence-an-examination-of-the-firearms-industry-1990-2015
#15
Victoria M Smith, Michael Siegel, Ziming Xuan, Craig S Ross, Sandro Galea, Bindu Kalesan, Eric Fleegler, Kristin A Goss
INTRODUCTION: Firearm violence injures or kills 100,000 Americans each year. This paper applies the Host-Agent-Vector-Environment model to this issue. Research on firearm violence tends to focus on two elements-the host (i.e., victims of firearm violence) and the environment (i.e., gun policies)-but little attention has been paid to the agent (the gun and ammunition) or the vector (firearm manufacturers, dealers, and the industry lobby). METHODS: Using Bureau of Alcohol, Tobacco, Firearms and Explosives data, trends in firearm manufacturing were investigated from 1990 to 2015...
June 17, 2017: American Journal of Preventive Medicine
https://www.readbyqxmd.com/read/28604118/practical-tips-for-working-as-an-expedition-doctor-on-high-altitude-expeditions
#16
Anne Brants, Tracee Metcalfe
Brants, Anne, and Tracee Metcalfe. Practical tips for working as an expedition doctor on high-altitude expeditions. High Alt Med Biol. 18:193-198, 2017.-With the explosion of adventure travel over the past decade, there has been a concurrent increase in mountaineering expeditions to extreme elevations, including many of the 8000-m peaks. This trend has created an increased demand for qualified expedition doctors to provide specialized medical advice and care to climbers and expedition staff. This review is intended to help physicians prepare for work on such expeditions...
September 2017: High Altitude Medicine & Biology
https://www.readbyqxmd.com/read/28581557/a-porous-two-dimensional-zn-ii-coordination-polymer-exhibiting-sc-sc-transmetalation-with-cu-ii-efficient-heterogeneous-catalysis-for-the-henry-reaction-and-detection-of-nitro-explosives
#17
Mayank Gupta, Dinesh De, Sanchari Pal, Tapan K Pal, Kapil Tomar
The linker 5-(benzylamino)isophthalic acid (H2L) forms a robust 2D Zn(ii)-coordination polymer, {[Zn8(L)6(μ3-OH)4(H2O)6]·(DMF)·(H2O)2.5}n(1Zn) consisting of [Zn4(μ3-OH)2](6+) SBUs. It further shows strong ππ interactions between the layers to form an overall 3D structure with well-defined channels. Metal bound water molecules are directed towards these channels. Upon heating, these metal bound water molecules are lost along with lattice solvent molecules to afford coordinatively unsaturated metal centers that can be utilized as an efficient heterogeneous catalyst for the C-C bond forming nitroaldol or Henry reaction...
June 13, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28547850/detection-of-contact-traces-of-powdery-substances
#18
Wojciech Pawłowski, Łukasz Matyjasek, Monika Karpińska
The current practice in securing the contact traces of chemical substances taken from clothes belonging to a person suspected of manual handling explosives is focused on pockets and cuffs. The outerwear worn by people who had contact with fluorescent powders that simulate explosives and drugs was the subject of this study. Clothes were first exposed to the test substance for a period of time and then analyzed by fluorescence methods to determine the location of the highest quantity of traces. The results obtained from the study confirm that the areas with the highest concentration of powdery traces are different from those suggested by current forensic practice...
May 26, 2017: Journal of Forensic Sciences
https://www.readbyqxmd.com/read/28469009/heroes-of-the-engram
#19
REVIEW
Sheena A Josselyn, Stefan Köhler, Paul W Frankland
In 1904, Richard Semon introduced the term "engram" to describe the neural substrate responsible for (or at least important in) storing and recalling memories (i.e., a memory trace). The recent introduction of a vast array of powerful new tools to probe and manipulate memory function at the cell and neuronal circuit level has spurred an explosion of interest in studying the engram. However, the present "engram renaissance" was not borne in isolation but rather builds on a long tradition of memory research. We believe it is important to acknowledge the debts our current generation of scientists owes to those scientists who have offered key ideas, persevered through failed experiments and made important discoveries before us...
May 3, 2017: Journal of Neuroscience: the Official Journal of the Society for Neuroscience
https://www.readbyqxmd.com/read/28451678/a-novel-luminescent-pb-ii-organic-framework-exhibiting-a-rapid-and-selective-detection-of-trace-amounts-of-nacs-and-fe-3-with-excellent-recyclability
#20
Xuan Luo, Xiao Zhang, Yuanling Duan, Xiaolin Wang, Jiaming Zhao
A novel three-dimensional metal organic framework, Pb3O2L (1) (H2L = 4-(1H-tetrazol-5-yl)phenol), with a unique 3D network structure exhibits excellent luminescence and good stability in water and other organic solvents. 1 can act as a promising dual functional sensor for the detection and recognition of nitroaromatic explosives (NACs) and Fe(3+) ions via fluorescence quenching with high selectivity and sensitivity in an aqueous phase. Importantly, 1 as a fluorescent sensor of Fe(3+) can be simply and quickly regenerated, which represents a rare example of a reported luminescent sensor of Fe(3+) ions...
May 16, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
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