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https://www.readbyqxmd.com/read/29245032/atomic-force-microscopy-capable-of-vibration-isolation-with-low-stiffness-z-axis-actuation
#1
Shingo Ito, Georg Schitter
For high-resolution imaging without bulky external vibration isolation, this paper presents an atomic force microscope (AFM) capable of vibration isolation with its internal Z-axis (vertical) actuators moving the AFM probe. Lorentz actuators (voice coil actuators) are used for the Z-axis actuation, and flexures guiding the motion are designed to have a low stiffness between the mover and the base. The low stiffness enables a large Z-axis actuation of more than 700 µm and mechanically isolates the probe from floor vibrations at high frequencies...
December 5, 2017: Ultramicroscopy
https://www.readbyqxmd.com/read/29244498/labile-low-valent-tin-azides-syntheses-structural-characterization-and-thermal-properties
#2
Rory Campbell, Sumit Konar, Steven Hunter, Colin Pulham, Peter Portius
The first two examples of the class of tetracoordinate low-valent, mixed-ligand tin azido complexes, Sn(N3)2(L)2, are shown to form upon reaction of SnCl2 with NaN3 and SnF2 with Me3SiN3 in either pyridine or 4-picoline (2, L = py; 3, L = pic). These adducts of Sn(N3)2 are shock- and friction-insensitive and stable at r.t. under an atmosphere of pyridine or picoline, respectively. A new, fast, and efficient method for the preparation of Sn(N3)2 (1) directly from SnF2, and by the stepwise de-coordination of py from 2 at r...
December 15, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/29243918/frustrated-lewis-pairs-catalyzed-asymmetric-metal-free-hydrogenations-and-hydrosilylations
#3
Wei Meng, Xiangqing Feng, Haifeng Du
The use of frustrated Lewis pairs is an extremely important approach to metal-free hydrogenations. In contrast to the rapid growth of catalytic reactions, asymmetric hydrogenations are far less developed due to a severe shortage of readily available chiral frustrated Lewis pair catalysts with high catalytic activities and selectivities. Unlike the stable Lewis base component of frustrated Lewis pairs, the moisture-sensitive boron Lewis acid component is difficult to prepare. The development of convenient methods for the quick construction of chiral boron Lewis acids is therefore of great interest...
December 15, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/29242020/selective-inhibition-of-%C3%AE-n-acetylhexosaminidases-by-thioglycosyl-naphthalimide-hybrid-molecules
#4
Wei Chen, Shengqiang Shen, Lili Dong, Jianjun Zhang, Qing Yang
To develop selective inhibitors for β-N-acetylhexosaminidases which are involved in a myriad of physiological processes, a series of novel thioglycosyl-naphthalimide hybrid inhibitors were designed, synthesized and evaluated for inhibition activity against glycosyl hydrolase family 20 and 84 (GH20 and GH84) β-N-acetylhexosaminidases. These compounds which incorporate groups with varied sizes and lengths at the linker region between thioglycosyl moiety and naphthalimide moiety are designed to improve the selectivity and stacking interactions...
November 28, 2017: Bioorganic & Medicinal Chemistry
https://www.readbyqxmd.com/read/29240444/regio-and-diastereodivergent-4-2-cycloadditions-with-cyclic-2-4-dienones
#5
Wei Xiao, Qian-Qian Yang, Zhi Chen, Qin Ouyang, Wei Du, Ying-Chun Chen
By employing activated alkenes with bulky α-functional groups, such as α-cyano-α,β-unsaturated ketones and Meldrum's acid-based alkenes, a previously unreported cross-trienamine pathway of cyclic 2,4-dienones is adopted to deliver γ',δ-regioselective [4 + 2] cycloadducts catalyzed by cinchona-derived amines. In addition, a diastereodivergent [4 + 2] cycloaddition reaction is realized with Z-configured 4-alkylideneisoxazol-5(4H)-ones under similar catalytic conditions, even through a three- or four-component cascade process with simple starting materials...
December 14, 2017: Organic Letters
https://www.readbyqxmd.com/read/29239501/revisiting-the-ullman-s-radical-chemistry-for-phthalocyanine-derivatives
#6
Catherine Hirel, Ismail Fidan, Dominique Luneau, Vefa Ahsen
Phthalocyanines derivatives does not cease to aroused attention due to their numerous properties and applications (e.g.,sensor, PDT). This makes them unique scaffold for the design of new material. In this expectative, we were interested to develop the synthesis of an imino nitroxyde-substituted phthalocyanine via the Ullman's procedure; a challenge due to intrinsic low solubility of most phthalocyanine derivative in much solvents. To overcome this solubility problem we designed phthalocyanine with bulky neopentyl substituents in peripheral position as counterpart to the imino nitroxyde moieties...
December 14, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/29238096/assembly-of-a-mononuclear-ferrous-site-using-a-bulky-aldehyde-imidazole-ligand
#7
Jia Li, Monika A Molenda, Shannon M Biros, Richard J Staples, Ferman A Chavez
A new iron(II) complex has been prepared and characterized. [Fe(TrImA)2(OTf)2] (1, TrImA = 1-Tritylimidazole-4-carboxaldehyde). The solid state structure of 1 has been determined by X-ray crystallography. Compound 1 crystallizes in monoclinic space group P21/c, with a = 10.8323(18) Å, b = 8.1606(13) Å and c = 24.818(4) Å. The iron center is coordinated to two imidazole groups, two pendant aldehyde-derived carbonyl oxygens and two triflate oxygens. The complex is high spin between 300 and 20 K as indicated by variable field variable temperature magnetic measurements...
August 1, 2017: Inorganica Chimica Acta
https://www.readbyqxmd.com/read/29235730/smart-design-of-a-bulk-capped-supramolecular-segment-for-the-assembly-into-organic-interdigital-lipid-bilayer-like-ilb-nanosheets
#8
Yin-Xiang Li, Sha-Sha Wang, Yang Yu, He Zhang, Wu-You Wang, Ru-Qian Yang, Ling-Hai Xie, Feng Liu, Zong-Qiong Lin, Nai-En Shi, Li-Tao Sun, Wei Huang
Rational molecular design for the organic nanocrystal morphology still remains a challenge due to the structural diversity and complicated weak intermolecular interactions. In this work, a typical attractor-repulsor molecule N,N-diphenyl-4-(9-phenyl-fluoren-9-yl) phenylamine (TPA-PF) is designed to explore a general assembly strategy for 2D nanocrystals. Via an interdigital lipid bilayer-like (ILB) molecular packing mode, large-sized lamellar 2D nanosheets are obtained with a length:width:thickness ratio as ≈2500:1000:1...
December 13, 2017: Small
https://www.readbyqxmd.com/read/29235697/remote-sampling-mass-spectrometry-for-dry-samples-sheath-flow-probe-electrospray-ionization-pesi-using-a-gel-loading-tip-inserted-with-an-acupuncture-needle
#9
Dilshadbek T Usmanov, Khatam B Ashurov, Satoshi Ninomiya, Kenzo Hiraoka, Hiroshi Wada, Hiroshi Nakano, Masaya Matsumura, Sachiyo Sanada-Morimura, Hiroshi Nonami
RATIONALE: Probe electrospray ionization (PESI) is only applicable to liquid or wet samples. In this study, a sheath-flow PESI method for remote sampling mass spectrometry that can be applied to dry samples was developed. METHODS: An acupuncture needle (0.12 mm outer diameter, 700 nm tip diameter) was inserted into a gel-loading tip with a 0.1 mm protrusion out of the tip. Analytes were extracted by filling the latter tip with solvent and softly touching the sample surface for a short time (<1 s)...
December 13, 2017: Rapid Communications in Mass Spectrometry: RCM
https://www.readbyqxmd.com/read/29235203/selective-c-h-halogenations-with-a-highly-fluorinated-manganese-porphyrin
#10
Gang Li, Andrew Dilger, Peter Cheng, William Ewing, John T Groves
Selective C-H functionalizations of aliphatic molecules remain a challenge in organic synthesis. While radical chain halogenations provide an efficient way to access many halogenated molecules, application of typical protocols to selectively halogenate electron-deficient and strained aliphatic molecules are rare. Herein, we report selective C-H chlorinations and fluorinations that use an electron-deficient manganese pentafluorophenyl porphyrin catalyst, Mn(TPFPP)Cl. This catalyst displays superior properties for aliphatic halogenations of recalcitrant, electron-deficient and strained substrates with unique regio- and stereoselectivity...
December 12, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/29234940/st-gallen-consensus-on-safe-implementation-of-transanal-total-mesorectal-excision
#11
Michel Adamina, Nicolas C Buchs, Marta Penna, Roel Hompes
BACKGROUND: The management of rectal cancer has evolved over the years, including the recent rise of Transanal Total Mesorectal Excision (TaTME). TaTME addresses the limitations created by the bony confines of the pelvis, bulky tumours, and fatty mesorectum, particularly for low rectal cancers. However, guidance is required to ensure safe implementation and to avoid the pitfalls and potential major morbidity encountered by the early adopters of TaTME. We report a broad international consensus statement, which provides a basis for optimal clinical practice...
December 12, 2017: Surgical Endoscopy
https://www.readbyqxmd.com/read/29234107/bulky-lesion-bypass-requires-dpo4-binding-in-distinct-conformations
#12
Pramodha S Liyanage, Alice R Walker, Alfonso Brenlla, G Andrés Cisneros, Louis J Romano, David Rueda
Translesion DNA synthesis is an essential process that helps resume DNA replication at forks stalled near bulky adducts on the DNA. Benzo[a]pyrene (B[a]P) is a polycyclic aromatic hydrocarbon (PAH) that can be metabolically activated to benzo[a]pyrene diol epoxide (BPDE), which then can react with DNA to form carcinogenic DNA adducts. Here, we have used single-molecule florescence resonance energy transfer (smFRET) experiments, classical molecular dynamics simulations, and nucleotide incorporation assays to investigate the mechanism by which the model Y-family polymerase, Dpo4, bypasses a (+)-cis-B[a]P-N 2-dG adduct in DNA...
December 12, 2017: Scientific Reports
https://www.readbyqxmd.com/read/29231728/protective-effect-of-mulberry-morus-alba-l-extract-against-benzo-a-pyrene-induced-skin-damage-through-inhibition-of-aryl-hydrocarbon-receptor-signaling
#13
Hyunju Woo, JungA Lee, Deokhoon Park, Eunsun Jung
Benzo[a]pyrene (B[a]P), a type of polycyclic aromatic hydrocarbon, is present in the atmosphere surrounding our environment. Although B[a]P is a procarcinogen, enzymatically metabolized benzo[a]pyrene-7,8-dihydrodiol-9,10-epoxide (BPDE) could intercalate into DNA to form bulky BPDE-DNA adducts as an ultimate carcinogenic product in human keratinocytes. The aim of this study was to evaluate the protective effect of mulberry extract, purified from the fruit of Morus Alba L., on B[a]P-induced cytotoxicity in human keratinocytes and its mechanisms of action...
December 12, 2017: Journal of Agricultural and Food Chemistry
https://www.readbyqxmd.com/read/29230134/guiding-elastic-rods-with-a-robot-manipulated-magnet-for-medical-applications
#14
Louis B Kratchman, Trevor L Bruns, Jake J Abbott, Robert J Webster
Magnet-tipped, elastic rods can be steered by an external magnetic field to perform surgical tasks. Such rods could be useful for a range of new medical applications because they do not require either pull wires or other bulky mechanisms that are problematic in small anatomical regions. However, current magnetic rod steering systems are large and expensive. Here, we describe a method to guide a rod using a robot-manipulated magnet located near a patient. We solve for rod deflections by combining permanent-magnet models with a Kirchhoff elastic rod model and use a resolved-rate approach to compute trajectories...
February 2017: IEEE Transactions on Robotics: a Publication of the IEEE Robotics and Automation Society
https://www.readbyqxmd.com/read/29229762/multiple-substitutions-lead-to-increased-loop-flexibility-and-expanded-specificity-in-acinetobacter-baumannii-carbapenemase-oxa-239
#15
Thomas M Harper, Cynthia M June, Magdalena A Taracila, Robert A Bonomo, Rachel A Powers, David A Leonard
OXA-239 is a class D carbapenemase isolated from an Acinetobacter baumannii strain found in Mexico.  This enzyme is a variant of OXA-23 with three amino acid substitutions in or near the active site.  These substitutions cause OXA-239 to hydrolyze late-generation cephalosporins and the monobactam aztreonam with greater efficiency than OXA-23.  OXA-239 activity against the carbapenems doripenem and imipenem is reduced approximately 3-fold and 20-fold respectively.  Further analysis demonstrated that two of the substitutions (P225S and D222N) are largely responsible for the observed alteration of kinetic parameters, while the third (S109L) may serve to stabilize the protein...
December 11, 2017: Biochemical Journal
https://www.readbyqxmd.com/read/29228283/interaction-of-neisseria-meningitidis-group-x-n-acetylglucosamine-1-phosphotransferase-with-its-donor-substrate
#16
Shonoi A Ming, Ebony Cottman-Thomas, Natalee C Black, Yi Chen, Vamsee Veeramachineni, Dwight C Peterson, Xi Chen, Lauren M Tedaldi, Gerd K Wagner, Chao Cai, Robert J Linhardt, Willie F Vann
Neisseria meningitidis Group X is an emerging cause of bacterial meningitis in the Sub-Saharan Africa. The capsular polysaccharide of Group X is a homopolymer of N-acetylglucosamine α(1-4) phosphate and is a vaccine target for prevention of disease associated with this meningococcal serogroup. We have demonstrated previously that the formation of the polymer is catalyzed by a phosphotransferase which transfers N- acetylglucosamine-1-phosphate from UDP-N-acetylglucosamine to the 4- hydroxyl of the N-acetylglucosamine on the non-reducing end of the growing chain...
December 8, 2017: Glycobiology
https://www.readbyqxmd.com/read/29227040/towards-sustainable-h2-production-rational-design-of-hydrophobic-triphenylamine-based-dyes-for-sensitized-ethanol-photoreforming
#17
Alessio Dessì, Matteo Monai, Matteo Bessi, Tiziano Montini, Massimo Calamante, Alessandro Mordini, Gianna Reginato, Cosimo Trono, Paolo Fornasiero, Lorenzo Zani
Donor-acceptor dyes are a well-established class of photosensitizers, used to enhance visible light harvesting in solar cells and in direct photocatalytic reactions, such as H2 production by photoreforming of sacrificial electron donors (SEDs). Amines - typically triethanolamine (TEOA) - are commonly employed as SEDs in such reactions. Dye-sensitized photoreforming of more sustainable, biomass-derived alcohols, on the other hand, was only recently reported using methanol as the electron donor. In this work, several rationally designed donor-acceptor dyes were used as sensitizers in H2 photocatalytic production, comparing the efficiency of TEOA and EtOH as SEDs...
December 11, 2017: ChemSusChem
https://www.readbyqxmd.com/read/29226605/selective-coassembly-of-aromatic-amino-acids-to-fabricate-hydrogels-with-light-irradiation-induced-emission-for-fluorescent-imprint
#18
Pengyao Xing, Hongzhong Chen, Huijing Xiang, Yanli Zhao
Controlling the structural parameters in coassembly is crucial for the fabrication of multicomponent functional materials. Here a proof-of-concept study is presented to reveal the α-substituent effect of aromatic amino acids on their selective coassembly with bipyridine binders. With the assistance of X-ray scattering technique, it is found that individual packing in the solid state as well as bulky effect brought by α-substitution determines the occurrence of coassembly. A well-performed hydrogels based on the complexation between certain aromatic amino acids and bipyridine units are successfully constructed, providing unprecedented smart materials with light irradiation-triggered luminescence...
December 11, 2017: Advanced Materials
https://www.readbyqxmd.com/read/29225869/spontaneous-tumor-lysis-syndrome-in-colon-cancer-a-case-report-and-literature-review
#19
David Sommerhalder, Amol M Takalkar, Rodney Shackelford, Prakash Peddi
Although tumor lysis syndrome is well described, it is rarely seen or suspected in solid malignancies. Early recognition of this entity is paramount in reducing morbidity and mortality. Treating physicians should be aware of this possibility in solid tumor patients with either bulky disease or extensive liver involvement.
December 2017: Clinical Case Reports
https://www.readbyqxmd.com/read/29223302/modeling-the-target-dose-fall-off-in-imrt-and-vmat-planning-techniques-for-cervical-sbrt
#20
A Brito Delgado, D Cohen, T Y Eng, D N Stanley, Z Shi, M Charlton, A N Gutiérrez
There has been growing interest in the use of stereotactic body radiotherapy (SBRT) technique for the treatment of cervical cancer. The purpose of this study was to characterize dose distributions as well as model the target dose fall-off for intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) delivery techniques using 6 and 10 MV photon beam energies. Fifteen (n = 15) patients with non-bulky cervical tumors were planned in Pinnacle3 with a Varian Novalis Tx (HD120 MLC) using 6 and 10 MV photons with the following techniques: (1) IMRT with 10 non-coplanar beams (2) dual, coplanar 358° VMAT arcs (4° spacing), and (3) triple, non-coplanar VMAT arcs...
December 6, 2017: Medical Dosimetry: Official Journal of the American Association of Medical Dosimetrists
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