Why inhaling salt water changes what we exhale

We find that inhaling salt water diminishes subsequently exhaled biomaterial in man and animals due to reversible stabilization of the airway lining fluid (ALF)/air interface as a novel potential means for control of the spread of airborne infectious disease. The mechanism of this phenomenon relates to charge shielding of mucin or mucin-like macromolecules that consequently undergo gelation; this gelation alters the physical properties of the ALF surface and reduces its breakup. Cations in the nebulized solution and apparent surface viscoelasticity of the ALF (more than any other ALF intrinsic physical property) appear to be responsible for the reduced tendency of the ALF to disintegrate into very small droplets. We confirm these effects in vivo and show their reversibility through nebulization of saline solutions to anesthetized bull calves.     

Particle bridging between oil and water interfaces

Particle bridging between a water drop and a flat oil-water interface has been observed when the drop is brought into contact with the interface, leading to the formation of a dense particle monolayer of disc shape (namely, particle disc) that prevents the drop from coalescing into the bulk water phase. Unlike previous observations where particles from opposite interfaces appear to register with each other before bridging, the present experiment demonstrates that the particle registry is not a necessity for bridging. In many cases, the particles from one of the interfaces were repelled away from the contact region, leaving behind the particles from the other interface to bridge the two interfaces. This is confirmed by particle bridging experiments between two interfaces covered with different sized particles, and between a particle-covered interface and a clean interface. The dynamics associated with the growth of the particle disc due to particle bridging follows a power law relationship between the radius of the disc and time: r proportional, variant t0.32+/-0.03. A scaling analysis assuming capillary attraction as the driving force and a hydrodynamic resistance leads to the power law r proportional, variant t1/3, in good agreement with the experiment. In addition, we found that binary mixtures of two different sized particles can undergo phase segregation driven by the particle bridging process.     

Tris(pyrazolyl)borate amidoborane complexes of the group 4 metals

Treatment of the tris(pyrazolyl)borate metal triamides Tp'M(NMe(2))(3), where Tp' = (C(3)H(3)N(2))(3)BH (Tp) or (3,5-Me(2)C(3)HN(2))(3)BH (Tp*) and M = Ti, Zr and Hf, with the Br?nsted acidic Lewis adduct (C(6)F(5))(3)B·NH(3) in toluene solution leads to the formation of Tp'M(NMe(2))(2){NH(2)B(C(6)F(5))(3)} complexes. The exception to this was the attempted preparation of Tp*Ti(NMe(2))(2){NH(2)B(C(6)F(5))(3)} which was unsuccessful. Where Tp' = Tp and M = Ti and Zr and where Tp' = Tp* and M = Zr the complexes have been characterized by single crystal X-ray diffraction methods, revealing the first examples of octahedral amidoborane complexes of the group 4 metals. Attempts to drive the reactions to completion resulted in competing preferential hydrolysis of the amidoborane group, regenerating (C(6)F(5))(3)B·NH(3).     

Quasi-symmetric functions and up–down compositions

Carlitz (1973) [5] and Rawlings (2000) [13] studied two different analogues of up–down permutations for compositions with parts in {1,…,n}. Cristea and Prodinger (2008/2009) [7] studied additional analogues for compositions with unbounded parts. We show that the results of Carlitz, Rawlings, and Cristea and Prodinger on up–down compositions are special cases of four different analogues of generalized Euler numbers for compositions. That is, for any s≥2, we consider classes of compositions that can be divided into an initial set of blocks of size s followed by a block of size j where 0≤j≤s−1. We then consider the classes of such compositions where all the blocks are strictly increasing (weakly increasing) and there are strict (weak) decreases between blocks. We show that the weight generating functions of such compositions w=w₁?w_m, where the weight of w is , are always the quotients of sums of quasi-symmetric functions. Moreover, we give a direct combinatorial proof of our results via simple involutions.     

Insertion mechanism of a poly(ethylene oxide)-poly(butylene oxide) block copolymer into a DPPC monolayer

Interactions between amphiphilic block copolymers and lipids are of medical interest for applications such as drug delivery and the restoration of damaged cell membranes. A series of monodisperse poly(ethylene oxide)-poly(butylene oxide) (EOBO) block copolymers were obtained with two ratios of hydrophilic/hydrophobic block lengths. We have explored the surface activity of EOBO at a clean interface and under 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) monolayers as a simple cell membrane model. At the same subphase concentration, EOBO achieved higher equilibrium surface pressures under DPPC compared to a bare interface, and the surface activity was improved with longer poly(butylene oxide) blocks. Further investigation of the DPPC/EOBO monolayers showed that combined films exhibited similar surface rheology compared to pure DPPC at the same surface pressures. DPPC/EOBO phase separation was observed in fluorescently doped monolayers, and within the liquid-expanded liquid-condensed coexistence region for DPPC, EOBO did not drastically alter the liquid-condensed domain shapes. Grazing incidence X-ray diffraction (GIXD) and X-ray reflectivity (XRR) quantitatively confirmed that the lattice spacings and tilt of DPPC in lipid-rich regions of the monolayer were nearly equivalent to those of a pure DPPC monolayer at the same surface pressures.     

Highly Active,Thermally Stable,Ethylene‐Polymerisation Pre‐Catalysts Based on Niobium/Tantalum?Imine Systems

The reactions of MCl₅ or MOCl₃ with imidazole‐based pro‐ligand L¹H, 3,5‐tBu₂‐2‐OH‐C₆H₂‐(4,5‐Ph₂‐1H‐)imidazole, or oxazole‐based ligand L²H, 3,5‐tBu₂‐2‐OH‐C₆H₂(1H‐phenanthro[9,10‐d])oxazole, following work‐up, afforded octahedral complexes [MX(L^{1, 2})], where MX=NbCl₄ (L¹, 1 a ; L², 2 a ), [NbOCl₂(NCMe)] (L¹, 1 b ; L², 2 b ), TaCl₄ (L¹, 1 c ; L², 2 c ), or [TaOCl₂(NCMe)] (L¹, 1 d ). The treatment of α‐diimine ligand L³, (2,6‐iPr₂C₆H₃N?CH)₂, with [MCl₄(thf)₂] (M=Nb, Ta) afforded [MCl₄(L³)] (M=Nb, 3 a ; Ta, 3 b ). The reaction of [MCl₃(dme)] (dme=1,2‐dimethoxyethane; M=Nb, Ta) with bis(imino)pyridine ligand L⁴, 2,6‐[2,6‐iPr₂C₆H₃N?(Me)C]₂C₅H₃N, afforded known complexes of the type [MCl₃(L⁴)] (M=Nb, 4 a ; Ta, 4 b ), whereas the reaction of 2‐acetyl‐6‐iminopyridine ligand L⁵, 2‐[2,6‐iPr₂C₆H₃N?(Me)C]‐6‐Ac‐C₅H₃N, with the niobium precursor afforded the coupled product [({2‐Ac‐6‐(2,6‐iPr₂C₆H₃N?(Me)C)C₅H₃N}NbOCl₂)₂] ( 5 ). The reaction of MCl₅ with Schiff‐base pro‐ligands L⁶H–L¹⁰H, 3,5‐(R¹)₂‐2‐OH‐C₆H₂CH?N(2‐OR²‐C₆H₄), (L⁶H: R¹=tBu, R²=Ph; L⁷H: R¹=tBu, R²=Me; L⁸H: R¹=Cl, R²=Ph; L⁹H: R¹=Cl, R²=Me; L¹⁰H: R¹=Cl, R²=CF₃) afforded [MCl₄(L^6–10)] complexes (M=Nb, 6 a – 10 a ; M=Ta, 6 b – 9 b ). In the case of compound 8 b , the corresponding zwitterion was also synthesised, namely [Ta^?Cl₅(L⁸H)⁺] ? MeCN ( 8 c ). Unexpectedly, the reaction of L⁷H with TaCl₅ at reflux in toluene led to the removal of the methyl group and the formation of trichloride 7 c [TaCl₃(L^7‐Me)]; conducting the reaction at room temperature led to the formation of the expected methoxy compound ( 7 b ). Upon activation with methylaluminoxane (MAO), these complexes displayed poor activities for the homogeneous polymerisation of ethylene. However, the use of chloroalkylaluminium reagents, such as dimethylaluminium chloride (DMAC) and methylaluminium dichloride (MADC), as co‐catalysts in the presence of the reactivator ethyl trichloroacetate (ETA) generated thermally stable catalysts with, in the case of niobium, catalytic activities that were two orders of magnitude higher than those previously observed. The effects of steric hindrance and electronic configuration on the polymerisation activity of these tantalum and niobium pre‐catalysts were investigated. Spectroscopic studies (¹H NMR, ¹³C NMR and ¹H? ¹H and ¹H? ¹³C correlations) on the reactions of compounds 4 a / 4 b with either MAO(50) or AlMe₃/[CPh₃]⁺[B(C₆F₅)₄]^? were consistent with the formation of a diamagnetic cation of the form [L⁴AlMe₂]⁺ (MAO(50) is the product of the vacuum distillation of commercial MAO at +50 °C and contains only 1 mol % of Al in the form of free AlMe₃). In the presence of MAO, this cationic aluminium complex was not capable of initiating the ROMP (ring opening metathesis polymerisation) of norbornene, whereas the 4 a / 4 b systems with MAO(50) were active. A parallel pressure reactor (PPR)‐based homogeneous polymerisation screening by using pre‐catalysts 1 b , 1 c , 2 a , 3 a and 6 a , in combination with MAO, revealed only moderate‐to‐good activities for the homo‐polymerisation of ethylene and the co‐polymerisation of ethylene/1‐hexene. The molecular structures are reported for complexes 1 a – 1 c , 2 b , 5 , 6 a , 6 b, 7 a, 8 a and 8 c .     

Metal–Organic Frameworks for Oxygen Storage

We present a systematic study of metal–organic frameworks (MOFs) for the storage of oxygen. The study starts with grand canonical Monte Carlo simulations on a suite of 10 000 MOFs for the adsorption of oxygen. From these data, the MOFs were down selected to the prime candidates of HKUST‐1 (Cu‐BTC) and NU‐125, both with coordinatively unsaturated Cu sites. Oxygen isotherms up to 30 bar were measured at multiple temperatures to determine the isosteric heat of adsorption for oxygen on each MOF by fitting to a Toth isotherm model. High pressure (up to 140 bar) oxygen isotherms were measured for HKUST‐1 and NU‐125 to determine the working capacity of each MOF. Compared to the zeolite NaX and Norit activated carbon, NU‐125 has an increased excess capacity for oxygen of 237 % and 98 %, respectively. These materials could ultimately prove useful for oxygen storage in medical, military, and aerospace applications.     

Molecular structure of interfacial human meibum films

Meibum is the primary component of the tear film lipid layer. Thought to play a role in tear film stabilization, understanding the physical properties of meibum and how they change with disease will be valuable in identifying dry eye treatment targets. Grazing incidence X-ray diffraction and X-ray reflectivity were applied to meibum films at an air-water interface to identify molecular organization. At room temperature, interfacial meibum films formed two coexisting scattering phases with rectangular lattices and next-nearest neighbor tilts, similar to the Ov phase previously identified in fatty acids. The intensity of the diffraction peaks increased with compression, although the lattice spacing and molecular tilt angle remained constant. Reflectivity measurements at surface pressures of 18 mN/m and above revealed multilayers with d-spacings of 50 ?, suggesting that vertical organization rather than lateral was predominantly affected by meibum-film compression.