Simultaneous electrothermal vaporization and nebulizer sample introduction system for inductively coupled plasma mass spectrometry

The novel analytical application of the combination of an inline electrothermal vaporization (ETV) and nebulization source for inductively coupled plasma mass spectrometry (ICP-MS) has been studied. Wet plasma conditions are sustained during ETV introduction by 200 mL/min gas flow through the nebulizer, which is merged with the ETV transport line at the torch. The use of a wet plasma with ETV introduction avoided the need to change power settings and torch positions that normally accompany a change from wet to dry plasma operating conditions. This inline-ETV source is shown to have good detection limits for a variety of elements in both HNO₃ and HCl matrices. Using the inline-ETV source, improved limits of detection (LOD) were obtained for elements typically suppressed by polyatomic interferences using a nebulizer. Specifically, improved LODs for ⁵¹V and ⁵³Cr suffering from Cl interferences (⁵¹ClO⁺ and ⁵³ClO⁺ respectively) in a 1% HCl matrix were obtained using the inline-ETV source. LODs were improved by factors of 65 and 22 for ⁵¹V and ⁵³Cr, respectively, using the inline-ETV source compared to a conventional concentric glass nebulizer. For elements without polyatomic interferences, LODs from the inline-ETV were comparable to conventional dry plasma ETV-ICP time-of-flight mass spectrometry results. Lastly, the inline-ETV source offers a simple means of changing from nebulizer introduction to inline-ETV introduction without extinguishing the plasma. This permits, for example, the use of the time-resolved ETV-ICP-MS signals to distinguish between an analyte ion and polyatomic isobar.     

In situ variable temperature X-ray diffraction studies on the transformations of nano-precursors to La-Ni-O phases

In situ variable temperature XRD (VT-XRD) measurements on the transformation of nano-precursors to LaNiO phases are presented. Experimental results showed that LaNiO₃ and La₂NiO₄ phases were formed at ca. 700 °C via the reaction of La₂O₃ and NiO (from the initial nano-precursors), where a relatively low temperature of 700 °C was found for the synthesis of La₂NiO₄. The formation of La₃Ni₂O₇ at higher temperature (up to 1150 °C) appeared to proceed through a further reaction of La₂NiO₄ with unreacted NiO, whilst the formation of La₄Ni₃O₁₀ (at 1075 °C) proceeded via a further decomposition of LaNiO₃. Although phase pure La₃Ni₂O₇ and La₄Ni₃O₁₀ were not directly obtained under the processing conditions herein, the results of this study allow for a better understanding of formation pathways, particularly for the higher order La-Ni-O phases.     

Inductivism and Parmenidean epistemology: Kyburg’s way

cording to Henry Kyburg, all extralogical and extramathematical propositions accepted as evidence and all propositions accepted inductively on the basis of such evidence are uncertain. There is a possibility of error. Consequently, neither the corpus of inductively accepted statements nor the corpus of statements accepted as evidence can serve as a standard for serious possibility in the sense I have deployed since the 1970s. The standard for serious possibility remains an unchanging Parmenidean standard. In contrast to other Parmenidean epistemologists that eschew inductive acceptances Kyburg insists that the corpus of evidence and of inductively accepted statements is subject to critical review and change; but the changes have no bearing on the standard for serious possibility.have always agreed with Henry’s emphasis on a distinction between acceptance as evidence and inductive acceptance. But I have insisted that the corpus of evidence or state of full belief is a standard for serious possibility and that the standard is subject to modification.burg does think of acceptance as evidence and inductive acceptance as modal notions and has recently used the expression “serious possibility” in this connection. But when Kyburg and Teng speak of “risky knowledge”, they are speaking of claims that might be false in the sense of serious possibility that they seem to be suggesting is immune to change and seems to correlate with serious possibility as I have used it since the 1970s. So acceptance (both inductive and evidential) are modal notions subject to change but are not to be confused with the notion of serious possibility of error or riskiness.     

[Ni(NHC)2] as a Scaffold for Structurally Characterized trans [H−Ni−PR2] and trans [R2P−Ni−PR2] Complexes

The addition of PPh₂H, PPhMeH, PPhH₂, P(para-Tol)H₂, PMesH₂ and PH₃ to the two-coordinate Ni⁰ N-heterocyclic carbene species [Ni(NHC)₂] (NHC=IiPr₂, IMe₄, IEt₂Me₂) affords a series of mononuclear, terminal phosphido nickel complexes. Structural characterisation of nine of these compounds shows that they have unusual trans [H−Ni−PR₂] or novel trans [R₂P−Ni−PR₂] geometries. The bis-phosphido complexes are more accessible when smaller NHCs (IMe₄>IEt₂Me₂>IiPr₂) and phosphines are employed. P−P activation of the diphosphines R₂P−PR₂ (R₂=Ph₂, PhMe) provides an alternative route to some of the [Ni(NHC)₂(PR₂)₂] complexes. DFT calculations capture these trends with P−H bond activation proceeding from unconventional phosphine adducts in which the H substituent bridges the Ni−P bond. P−P bond activation from [Ni(NHC)₂(Ph₂P−PPh₂)] adducts proceeds with computed barriers below 10 kcal mol⁻¹. The ability of the [Ni(NHC)₂] moiety to afford isolable terminal phosphido products reflects the stability of the Ni−NHC bond that prevents ligand dissociation and onward reaction.     

Euler's Problem Revisited: 222 Years Later

This paper furnishes several closed-form solutions for the buckling eigenvalue problem of the columns with variable flexural rigidity along the axis. The column is either under uniformly distributed axial load or under concentrated compressive load. Sommario. Questo lavoro fornisce diverse soluzioni in forma chiusa per il problema agli autovalori dell'instabilità di colonne con rigidezza flessionale variabile lungo l'asse. La colonna è soggetta ad un carico assiale unifor-memente distribuito oppure ad una forza di compressione concentrata.     

Relaxations in chitin: Evidence for a glass transition

Relaxations in chitin have been investigated in the temperature range 298–523 K using impedance spectroscopy in the frequency range 10⁻¹–10⁸ Hz. The objective was to detect a glass‐transition temperature for this naturally occurring, semicrystalline polysaccharide. The impedance study was complemented with X‐ray diffraction, thermogravimetric, and differential scanning calorimetry measurements. Preliminary impedance data treatment includes the subtraction of the dc conductivity contribution, the exclusion of contact and interfacial polarization effects, and obtaining a condition of minimum moisture content for further analysis. When all these aspects are taken into account, two relaxations are clearly revealed in the impedance data. For the first time, evidence is presented for a relaxation process, which exhibits a non‐Arrhenius temperature dependence, in dry α‐chitin (∼0.1% moisture content), and likely represents the primary α‐relaxation. This evidence suggests a glass transition temperature for chitin of 335 ± 10 K estimated on the basis of the temperature dependence of the conductivity and of the relaxation time. A second relaxation in dry α‐chitin, not previously reported in the literature, is observed from 353 K to the onset of thermal degradation (∼483 K) and is identified as the σ‐relaxation often associated with proton mobility. It exhibits a normal Arrhenius‐type temperature dependence with activation energy of 113 ± 3 kJ/mol. The latter has not been previously reported in the literature. A high frequency secondary β‐relaxation is also observed with Arrhenius activation energy of 45 ± 1 kJ/mol. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 932–943, 2009