The salt, [F3S(triple bond)NXeF][AsF6], has been synthesized by the reaction of [XeF][AsF6] with liquid N(triple bond)SF3 at -20 degrees C. The Xe-N bonded cation provides a rare example of xenon bound to an inorganic nitrogen base in which nitrogen is formally sp-hybridized. The F3S(triple bond)NXeF+ cation was characterized by Raman spectroscopy at -150 degrees C and by 129Xe, 19F, and 14N NMR spectroscopy in HF solution at -20 degrees C and in BrF5 solution at -60 degrees C. Colorless [F3S(triple bond)NXeF][AsF6] was crystallized from HF solvent at -45 degrees C, and its low-temperature X-ray crystal structure was determined. The Xe-N bond is among the longest Xe-N bonds known (2.236(4) A), whereas the Xe-F bond length (1.938(3) A) is significantly shorter than that of XeF2 but longer than in XeF+ salts. The Xe-F and Xe-N bond lengths are similar to those of HC(triple bond)NXeF+, placing it among the most ionic Xe-N bonds known. The nonlinear Xe-N-S angle (142.6(3)o) contrasts with the linear angle predicted by electronic structure calculations and is attributed to close N...F contacts within the crystallographic unit cell. Electronic structure calculations at the MP2 and DFT levels of theory were used to calculate the gas-phase geometries, charges, bond orders, and valencies of F3S(triple bond)NXeF+ and to assign vibrational frequencies. The calculated small energy difference (7.9 kJ mol-1) between bent and linear Xe-N-S angles also indicates that the bent geometry is likely the result of crystal packing. The structural studies, natural bond orbital analyses, and calculated gas-phase dissociation enthalpies reveal that F3S(triple bond)NXeF+ is among the weakest donor-acceptor adducts of XeF+ with an Xe-N donor-acceptor interaction that is very similar to that of HC(triple bond)NXeF+, but considerably stronger than that of F3S(triple bond)NAsF5. Despite the low dissociation enthalpy of the donor-acceptor bond in F3S(triple bond)NXeF+, 129Xe, 19F, and 14N NMR studies reveal that the F3S(triple bond)NXeF+ cation is nonlabile at low temperatures in HF and BrF5 solvents.
The widespread adoption of electronic health records (EHRs) and the growing wealth of digitized information sources about patients is ushering in an era of 'Big Data' that may revolutionize clinical research in oncology. Research will likely be more efficient and potentially more accurate than the current gold standard of manual chart review studies. However, EHRs as they exist today have significant limitations: important data elements are missing or are only captured in free text or PDF documents. Using two case studies, we illustrate the challenges of leveraging the data that are routinely collected by the healthcare system in EHRs (e.g., real-world data), specific challenges encountered in the cancer domain and opportunities that can be achieved when these are overcome.
Luminal epithelial projections formed during bronchoconstriction define interstices in which liquid can collect. Liquid in these interstices could amplify the degree of luminal compromise due to muscular contraction in at least two distinct ways. First, the luminal cross-sectional area is reduced by simple filling of the interstices. Second, if the surface tension (gamma) of the air-liquid interface is positive, the pressure drop across the interface produces an additional inward force that can further constrict the airway. We present a theoretical treatment of these two mechanisms together with data which suggest that both may significantly amplify the luminal narrowing due to airway smooth muscle contraction, particularly in small airways when gamma is high. To qualitatively assess the effects of altered gamma, guinea pig lungs with normal and altered airway liquid lining layers were frozen and studied while fully hydrated by low-temperature scanning electron microscopy. Airway gamma was altered in these animals by intratracheal instillation of 0.5 mg lysoplatelet-activating factor (lyso-PAF). The interstices of normal airways were dry, whereas the interstices of airways with altered surface lining layers were liquid filled. In addition, the surfactant inhibitory properties of lyso-PAF, 2-arachidonyl-PAF, and dipalmitoyl phosphatidylcholine (DPPC) were measured with a pulsating bubble surfactometer, using surfactant TA as the model surfactant. Minimal gamma (gamma min) of surfactant TA alone was 4.0 +/- 0.2 dyn/cm; a 5% mixture of lyso-PAF with surfactant TA resulted in a significantly (P less than 0.02) greater gamma min of 8.8 +/- 1.8 dyn/cm. In contrast, 2-arachidonyl-PAF and DPPC had minimal effects on gamma min of surfactant TA.
The salt, [F(4)S=NXe][AsF(6)], has been synthesized by the solid-state rearrangement of [F(3)S[triple bond]NXeF][AsF(6)] and by HF-catalyzed rearrangement of [F(3)S[triple bond]NXeF][AsF(6)] in anhydrous HF (aHF) and HF/BrF(5) solvents. The F(4)S=NXe(+) cation undergoes HF solvolysis to form F(4)S=NH(2)(+), XeF(2), and the recently reported F(5)SN(H)Xe(+) cation. Both [F(4)S=NXe][AsF(6)] and [F(4)S=NH(2)][AsF(6)] have been characterized by (129)Xe and (19)F NMR spectroscopy in aHF and HF/BrF(5) solvents and by single-crystal X-ray diffraction. The [F(4)S=NXe][AsF(6)] salt was also characterized by Raman spectroscopy. The Xe-N bond of F(4)S=NXe(+) is among the shortest Xe-N bonds presently known (2.084(3) A), and the cation interacts with the AsF(6)(-) anion by means of a Xe---F-As bridge in which the Xe---F distance (2.618(2) A) is significantly less than the sum of the Xe and F van der Waals radii. Both F(4)S=NXe(+) and F(4)S=NH(2)(+) exhibit trigonal bipyramidal geometries about sulfur, with nitrogen in the equatorial plane and the nitrogen substituents coplanar with the axial fluorine ligands of sulfur. The F(4)S=NH(2)(+) cation is isoelectronic with F(4)S=CH(2) and, like F(4)S=CH(2), has a high barrier to rotation about the S=N double bond and to pseudorotation of the trigonal bipyramidal F(4)S=N- moiety. The solution and solid-state rearrangements of F(3)S[triple bond]NXeF(+) to F(4)S=NXe(+) are proposed to result from attack at sulfur by fluoride ion arising from HF in solution and from the AsF(6)(-) anion in the solid state. Quantum-chemical calculations were employed to calculate the gas-phase geometries, charges, bond orders, valencies, and vibrational frequencies of F(4)S=NXe(+) and F(4)S=NH(2)(+). The F(4)S=NXe(+) cation provides the first example of xenon bonded to an imido-nitrogen, and together with the F(4)S=NH(2)(+) cation are presently the only cations known to contain the F(4)S=N-group. Both cations are intermediates in the HF solvolysis pathways of F(3)S[triple bond]NXeF(+) which lead to F(5)SN(H)Xe(+) and F(5)SNH(3)(+), and significantly extend the chemistry of the F(4)S=N-group.
The salt [F5SN(H)Xe][AsF6] has been synthesized by the reaction of [F5SNH3][AsF6] with XeF2 in anhydrous HF (aHF) and BrF5 solvents and by solvolysis of [F3S triple bond NXeF][AsF6] in aHF. Both F5SN(H)Xe(+) and F5SNH3(+) have been characterized by (129)Xe, (19)F, and (1)H NMR spectroscopy in aHF (-20 degrees C) and BrF5 (supercooled to -70 degrees C). The yellow [F5SN(H)Xe][AsF6] salt was crystallized from aHF at -20 degrees C and characterized by Raman spectroscopy at -45 degrees C and by single-crystal X-ray diffraction at -173 degrees C. The Xe-N bond length (2.069(4) A) of the F5SN(H)Xe(+) cation is among the shortest Xe-N bonds presently known. The cation interacts with the AsF6(-) anion by means of a Xe---F-As bridge in which the Xe---F distance (2.634(3) A) is significantly less than the sum of the Xe and F van der Waals radii (3.63 A) and the AsF6(-) anion is significantly distorted from Oh symmetry. The (19)F and (129)Xe NMR spectra established that the [F5SN(H)Xe][AsF6] ion pair is dissociated in aHF and BrF5 solvents. The F5SN(H)Xe(+) cation decomposes by HF solvolysis to F5SNH3(+) and XeF2, followed by solvolysis of F5SNH3(+) to SF6 and NH4(+). A minor decomposition channel leads to small quantities of F5SNF2. The colorless salt, [F5SNH3][AsF6], was synthesized by the HF solvolysis of F3S triple bond NAsF5 and was crystallized from aHF at -35 degrees C. The salt was characterized by Raman spectroscopy at -160 degrees C, and its unit cell parameters were determined by low-temperature X-ray diffraction. Electronic structure calculations using MP2 and DFT methods were used to calculate the gas-phase geometries, charges, bond orders, and valencies as well as the vibrational frequencies of F 5SNH3(+) and F5SN(H)Xe(+) and to aid in the assignment of their experimental vibrational frequencies. In addition to F5TeN(H)Xe(+), the F5SN(H)Xe(+) cation provides the only other example of xenon bonded to an sp (3)-hybridized nitrogen center that has been synthesized and structurally characterized. These cations represent the strongest Xe-N bonds that are presently known.
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