Role of positive ions in determining the deposition rate and film chemistry of continuous wave hexamethyl disiloxane plasmas

New data shed light on the mechanisms of film growth from low power, low pressure plasmas of organic compounds. These data rebalance the widely held view that plasma polymer formation is due to radical/neutral reactions only and that ions play no direct role in contributing mass at the surface. Ion reactions are shown to play an important role in both the plasma phase and at the surface. The mass deposition rate and ion flux in continuous wave hexamethyl disiloxane (HMDSO) plasmas have been studied as a function of pressure and applied RF power. Both the deposition rate and ion flux were shown to increase with applied power; however, the deposition rate increased with pressure while the ion flux decreased. Positive ion mass spectrometry of the plasma phase demonstrates that the dominant ionic species is the (HMDSO-CH(3))(+) ion at m/z 147, but significant fragmentation and subsequent oligomerization was also observed. Chemical analysis of the deposits by X-ray photoelectron spectroscopy and secondary ion mass spectrometry show that the deposits were consistent with deposits reported by previous workers grown from plasma and hyperthermal (HMDSO-CH(3))(+) ions. Increasing coordination of silicon with oxygen in the plasma deposits reveals the role of ions in the growth of plasma polymers. Comparing the calculated film thicknesses after a fixed total fluence of 1.5 × 10(19) ions/m(2) to results for hyperthermal ions shows that ions can contribute significantly to the total absorbed mass in the deposits.     

Experimental estimates of compression heating and decompression cooling in ethylene glycol

The chemical shift difference, Δσ, between the methylene and hydroxyl protons in the high resolution ¹H nuclear magnetic resonance spectrum of ethylene glycol is shown to be pressure dependent. The equilibrium Δσ values for ethylene glycol are reported as a function of temperature and pressure between ambient conditions, 323 K and 2 kbar, respectively. This surface is used along with Δσ values measured in response to a rapid pressure increase to calculate a temperature rise that is used to infer a temperature change for water that is consistent with theoretical estimates. This work implies that compression heating and decompression cooling are not significant enough to interfere with pressure induced protein folding studies.     

Simulation of molecular orientational dynamics in a model polar fluid

A molecular dynamics simulation of a Stockmayer fluid with μ* = 1·0, ρ* = 0·7 and T* = 1·13 (±0·03) is reported. In addition to evaluations of a number of static properties, orientational time correlation functions C_l (t) = <P(cos δθ(t))> were calculated for l = 1 through 4 ; P_l is a Legendre polynomial and δθ(t) is the angle of reorientation of the dipole in time t. These time correlation functions are characteristic of nearly free rotation and agree well with curves calculated from a perturbation theory for the memory functions that utilizes the simulated value of the mean square torque. The angular velocity autocorrelation function for this fluid was also simulated and compared with perturbation theory. Agreement is not good, primarily because of the presence of a pronounced long time tail in the simulated function. The relationship between these results and those of other simulations and theories is discussed.     

Crosslinked Polyvinylnorbornene‐Based Membranes as a New Class of Solvent‐Resistant Nanofiltration Membranes

Solvent resistant nanofiltration (SRNF) has received increasing attention since the turn of the century within energy‐ and waste‐efficient unit processes. This work explores the synthesis and characterization of crosslinked polynorbornenes for SRNF. A series of polyvinylnorbornene thin‐film composite membranes with increasing degree of crosslinking were prepared and tested for their SRNF performance in heptane, chloroform, and toluene. Sudan Black B (457 g mol^?1) was used as the solute. Then, 99% retention was achieved in heptane, 86% in chloroform, and 75% in toluene. It was further shown that the permeance and retention can be fine‐tuned in these solvents by controlling the extent of crosslinking. This work thus introduces the crosslinking of polynorbornenes as a promising material route for SRNF. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1593–1600     

Mixed tetrahedral anionic framework in the K3Ga2(PO4)3 crystal structure

The crystal structure of a new synthetic potassium gallophosphate K₃Ga₂(PO₄)₃ grown from a solution in the melt of a mixture of GaPO₄ and K₂MoO₄ is determined using X-ray diffraction (Bruker Smart diffractometer, 2θ_max= 56.6°, R = 0.044 for 2931 reflections, T = 100 K). The main crystal data are as follows: a = 8.661(2) Å, b = 17.002(4) Å, c = 8.386(2) Å, space group Pna2₁, Z= 4, and ρ_calcd = 2.91 g/cm³. The synthesized crystals represent the third phase in the structure type previously established for the K₃Al₂[(As,P)O₄]₃ compound. It is shown that the structure consists of a three-dimensional anionic microporous tetrahedral framework of the mixed type, which is formed by PO₄ and GaO₄ tetrahedra shared by vertices. Large-sized cations K⁺ occupy channels of the zeolite-like framework. The crystal chemical features of the formation of structure types of compounds with mixed frameworks described by the general formula A ₃ ⁺ M ₂ ³⁺ (TO₄)₃ (where A = K, Rb, (NH₄), Tl; M = Al, Ga, Fe, Sc, Yb; T = P, As) are analyzed.     

Alkali metals in beryl and their role in the formation of derivative structural motifs: Comparative crystal chemistry of vorobyevite and pezzottaite

The crystal structures of high-alkali beryl, i.e., vorobyevite Cs_0.08Na_0.42(H₂O)_{0.18 + y} × [Al₂(Be_2.35Li_0.65)Si₆O₁₈], (a = 9.2102(14) Å, c = 9.2179(14) Å, space group P6/mcc, Z = 2, ρ_calcd= 2.74 g/cm³) and pezzottaite Cs_0.75Na_0.23(H₂O)_0.24[Al₂Be₂Li(Si₆O₁₈)] (a = 15.955(3) Å, c = 27.810(8) Å, space group, R $ \bar 3 The crystal structures of high-alkali beryl, i.e., vorobyevite Cs_0.08Na_0.42(H₂O)_{0.18 + y} × [Al₂(Be_2.35Li_0.65)Si₆O₁₈], (a = 9.2102(14) ?, c = 9.2179(14) ?, space group P6/mcc, Z = 2, ρ_calcd= 2.74 g/cm³) and pezzottaite Cs_0.75Na_0.23(H₂O)_0.24[Al₂Be₂Li(Si₆O₁₈)] (a = 15.955(3) ?, c = 27.810(8) ?, space group, R c, Z = 18, ρ_calcd= 3.13 g/cm³), are determined at a temperature of 100 K. It is confirmed that, at a high lithium content in minerals of the beryl group, lithium is selectively incorporated into Be tetrahedra. The positive charge deficit due to the replacement of Be²⁺ cations by Li⁺ cations is compensated by incorporating large alkali cations into the “zeolite” channel. It is shown that, when the lithium content becomes close to unity per the corresponding formula, the Li and Be atoms are ordered and the rhombohedral structure of pezzottaite is formed. It is proposed to retain the historical name vorobyevite for the lithium- and cesium-containing variety of beryl with a disordered distribution of Be and Li atoms. Original Russian Text ? O.V. Yakubovich, I.V. Pekov, I.M. Steele, W. Massa, N.V. Chukanov, 2009, published in Kristallografiya, 2009, Vol. 54, No. 3, pp. 432–445.     

Electrokinetic model of cochlear hair cell motility

Recent experiments have shown that isolated outer hair cells of the cochlea can vibrate under the influence of a transcellular oscillating electric field. Since high voltages have been measured in the cochlea, this result might suggest a basis for electromechanical feedback. A mechanical model of the hair cell has been developed and adapted to test the electrokinetic theory of motility, a postulate of which is that cochlear voltage gradients act on charged proteins embedded in the cell membrane to deform the cell. From the model it was deduced that the amount of charge density required is within the physiologic range. The significant result is that the amplitude of cell elongation for a fixed voltage amplitude is virtually constant for frequency less than a certain cutoff. The value of this frequency depends on the various physical parameters of the system and especially on the spacing between cells. Power transfer to the basilar membrane appears to peak near the cutoff frequency, and the amount is not very dependent on cell length, but is highly dependent on cell spacing.     

Chromatographic separation and determination of noble metals in matte-leach residues

The practical application of various chromatographic methods to the analysis of residues obtained from the leaching of copper-nickel mattes is described. The procedure involves the separation of gold on a TBP-treated Porasil column, the separation of base metals by cation-exchange, the separation of tellurium from platinum-group metals, and the separation of the non-volatile platinum-group metals on one cellulose column.     

A survey of the (3He, 7Be) reaction at 70 MeV

A study of the (³He, ⁷Be) reaction has been undertaken using a 70 MeV ³He beam. By surveying a wide range of target nuclides, namely ^{12, 13}C, ¹⁶O, ^{24, 26}Mg, ^{40, 42, 44}Ca, ^{58, 60, 62, 64}Ni, ⁹⁰Zr, ^{120, 124}Sn, ¹⁴⁴Sm and ²⁰⁶Pb, systematics of the α-clustering phenomenon were investigated. In addition, masses and energy levels of ⁶⁰Fe and ¹²⁰Cd were measured. The ⁷Be particles were detected in a single wire proportional counter backed by a plastic scintillator in the focal plane of an Enge spectrometer to ensure adequate particle identification. Total energy resolution as small as 140 keV full width at half maximum was obtained, although in most cases the target thickness limited the energy resolution to larger values. Differential cross sections as low as 20 nb/sr were measured. The finite range programs LOLA and LOLITA were used to calculate differential cross sections for comparison to data, assuming the reaction to proceed by a direct α-transfer. The spectroscopic factors which were extracted show a marked decrease with increasing atomic mass number, implying a decrease in surface α-clustering for heavier nuclei.