XPS and XAES study of the interaction of palladium and copper overlayers with fullerene films

X-ray photoelectron and Auger spectroscopies were used to examine surface bonding and overlayer growth during palladium and copper deposition onto films of fullerene, C₆₀ The results were consistent with metal cluster formation on C₆₀. The observed positive core electron binding energy shifts in small metallic clusters supported on C₆₀ were shown to originate in metal-fullerene interaction accompanied by charge transfer. Palladium-fullerene intermixing at temperatures as low as ss 50°C was observed for small Pd coverages.     

Fluorimetric determination of the levels of urinary neopterin and serum thiobarbituric acid reactive substances in the nonagenarians

Twelve self-sustaining nonagenarians, 10 women and two men, aged 94+/-3 years, and eight institutionalised nonagenarians, eight women, aged 91+/-1 year as well as 11 control subjects, seven women and four men, aged 84+/-5 years entered the study. Urinary neopterin, an indicator of systemic immune activation, and serum thiobarbituric acid reactive substances (TBARS), a marker of lipoperoxidation, were determined initially, and collection of the blood and urine samples was repeated at 3-month interval. Neopterin was measured in the urine specimens by reversed-phase high performance liquid chromatography. A C(18) reversed-phase column 3.3x150 mm, 5 mum-diameter packing Separon SGX was used. Potassium phosphate buffer (15 mmol l(-1), pH 6.4) at flow rate of 0.8 ml min(-1) was used as mobile phase. After centrifugation (5 min, 1300xg) and diluting 100 mul of urine specimens with 1.0 ml of mobile phase containing 2 g of disodium-EDTA per litre, a 20 mul sample was injected on a column. Neopterin was identified by its native fluorescence (353 nm excitation, 438 nm emission). Creatinine was determined by Jaffé kinetic reaction after dilution of sample 1:50 (v/v). The concentration of neopterin in urine was expressed as neopterin/creatinine ratio (mumol mol(-1) creatinine). TBARS were determined spectrofluorometrically using LS-5 spectrofluorimeter (excitation wavelength 528 nm, emission wavelength 558 nm) after extraction with n-butanol treatment with thiobarbituric acid. The significance of differences between nonagenarians and control group was examined by ANOVA-Kruskal-Wallis tests, using statistical software NCSS 6.0.21 (Kaysville, UT, 1996). The decision on significance was based on P=0.05. Urinary neopterin was significantly higher in institutionalised compared to self-sustaining subjects and controls (625+/-565 vs. 203+/-63 mumol mol(-1) creatinine, and 198+/-128 mumol mol(-1) creatinine, respectively, P=0.006). The serum TBARS were higher in both groups of nonagenarians (3.23+/-1.16 mumol l(-1) and 2.69+/-0.39 vs. 2.12+/-0.83 mumol l(-1) for the self-sustaining, institutionalised and controls, respectively, P=0.023). We conclude that the fluorimetric determinations of urinary neopterin and serum TBARS can be useful for the monitoring health status in the elderly patients.     

Temperature Development of Homo- and Hetero-Clustering in Saturated Vapors

Computational findings of temperature increase of clustering degree in saturated vapors are analyzed. A thermodynamic proof is presented and a simple criterion derived. Illustrations are based on saturated steam, magnesium and carbon vapor. The results are applicable to synthesis of fullerenes, metallofullerenes, and heterofullerenes, chemical vapor deposition technique, or atmospheric chemistry.     

Effect of support on the synergy in HDS of thiophene and HDN of pyridine over Mo sulfide catalysts promoted by Rh

The effect of support (SiO₂-Al₂O₃, Al₂O₃,MgO) of the Rh-Mo(S) sulfide catalysts on the synergy in hydrodesulfurization (HDS) of thiophene and hydrodenitrogenation (HDN) of pyridine was studied. The synergy in HDS was between 7–10 regardless of the kind of support used. The synergy in HDN varied from none over the MgO supported sample to about 3 over SiO₂-Al₂O₃ supported catalyst, in accord with the positive effect of increasing support acidities. This revised version was published online in June 2006 with corrections to the Cover Date.     

Flow-injection determination of creatine in animal tissues

After deproteination of samples with trichloroacetic acid, creatine is determined by reaction with 1-naphthol and biacetyl, based on a stopped-flow method. The calibration graph is linear over the range 0–250 mg l^?1, and recoveries from muscle samples are quantitative.     

The limit of detectability in X-ray electron-probe microanalysis

Summary The definitions given by various authors for the limit of detectability are compared and their relationship to the basic measurements (especially the background value) is explained. A new definition is derived on the assumption that the relative standard deviation must not exceed 33.3% if negative results are to be avoided. Negative results may still appear, but only very rarely. The properties of this limit of detectability are discussed, together with the effect of making multiple measurements of the background and peak.

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Zusammenfassung Die von verschiedenen Autoren angegebenen Definitionen der Nachweisgrenze wurden verglichen und deren Beziehung zu den Bezugsmessungen (besonders des Untergrundes) wurde erklärt. Eine neue Definition wurde von der Annahme abgeleitet, daß die relative Standardabweichung 33,3% nicht überschreiten darf, sollen negative Resultate vermieden werden. Solche können zwar auftreten, aber nur sehr selten. Die Eigenschaften dieser Nachweisgrenze wurden ebenso wie die Auswirkung mehrfacher Messungen des Untergrundes und der Peaks diskutiert.

     

The structural phase transitions of aminoguanidinium(1+) dihydrogen phosphate—study of crystal structures, vibrational spectra and thermal behavior

Aminoguanidinium(1+) dihydrogen phosphate was prepared by crystallization from aqueous solution. On the basis of the results of DSC measurements, X-ray structural analysis was carried out at temperatures of 160, 215 and 293 K for three aminoguanidinium(1+) dihydrogen phosphate phases ( |Z=2|non-ferroic |melting point 408 K; II |201-222 K|(2) |Z=2|non-ferroic|-; III |<201 K|(2)|Z=4|non-ferroic|-). The triclinic unit cell dimensions (a=6.8220(2), b=7.1000(2), c=7.4500(2) Å, α=86.925(2)°, β=80.731(2)°, γ=79.630(2)°, V=350.21(2) Å³—phase I) are similar for all three structural phases with the exception of phase III, where doubling of the c-axis length leads to an increase in the volume to 692.34(3) Å³. The crystal structure of all three modifications consists of parallel layers of dihydrogen phosphate anions that are interconnected by aminoguanidinium(1+) cations through hydrogen bonds of the N-H…O type. The planar aminoguanidinium(1+) cations are oriented almost parallel to each other and are perpendicular to the anion layers. The primary differences amongst phases I, II and III lie in the location of the H atom in the short O-H…O bonds connecting the dihydrogen phosphate anions in layers. The FTIR and FT Raman spectra of natural and deuterated compounds were recorded and interpreted. The FTIR spectra were studied down to a temperature of 90 K.     

Study of Pr1−xMn1+xO3 perovskites

The structural and magnetic properties of the Pr_1?xMn_1+xO₃ perovskites were studied. The increase of x (i.e., $\text{Pr}\text{Mn}\text{< 1}$) leads to the decrease of the orthorhombic deformation and of the Néel temperature and, simultaneously, to an increase of the ferromagnetic contribution. The latter effect is explained from the suggested distribution of the cations (Pr³⁺_1?xMn²⁺_x)_A(Mn³⁺_1?xMn⁴⁺_x)O^2?₃ by the double exchange of Mn³⁺Mn⁴⁺ pairs at the B—sublattice.     

Square-Planar Nickel(II) O,O′-Dialkyldithiophosphato Complexes with Triphenylphosphine of the Type [NiX(S2P{OR}2)(PPh3)] (X = Cl,Br, I and NCS)

A series of new [NiX(S₂P{O-c-Hex}₂)(PPh₃)](X = Cl^–, Br^–, I^– and NCS^–)(1)–(4) and [Ni(NCS)(S₂P{OR}₂)(PPh₃)][R =n-Pr (5), i-Pr (6)] complexes has been synthesized and characterized by elemental analyses, f.i.r., i.r., u.v.–vis., ¹H-, ¹³C{¹H}- and ³¹P{¹H}-n.m.r. spectra, magnetochemical and conductivity measurements. A single crystal X-ray analysis of [Ni(NCS)(S₂P{O-n-Pr}₂)(PPh₃)](5) reveals the molecular structure of the complex and confirms a square-planar geometry around the central atom of nickel with the NCS anion coordinated via the nitrogen atom.     

C36 fullerenes and quasi-fullerenes: computational search through 598 cages

C₃₆ is computed at the SAM1 level and partially also at the HF/4-31G and B3LYP/6-31G^* levels. Altogether 598 cages are generated by a topological Stone–Wales treatment. Three cages contribute by more than 10% to the high-temperature equilibrium isomeric mixture – two conventional fullerenes with D_2d and C_2v symmetries and a C_s quasi-fullerene containing one four-membered ring.