The Graphitizing Behavior of Iron Carbide in Pure Iron Carbon Alloys for the Temperature Interval 700 to 1100 C

The following reaction represents a possible mechanism for the graphitization of pure iron carbon alloys below the critical range. (1) 2CO=C+CO2 (2) Fe3C + CO2 = 3Fe(alpha) + 2CO. Adding (1) and (2) gives (3) Fe3C =3Fe(alpha) +

The influence of carbon dioxide on the catalytic oxidative coupling of methane over A-La2O3 and II-La2O2CO3

Previous work conducted in our laboratory suggested a strong correlation between the presence of oxycarbonate and the ability of lanthanum oxide-based materials to selectively promote the oxidative coupling of methane (OCM). Since A-La[subscript]2O[subscript]3 and II-La[subscript]2O[subscript]2CO[subscript]3 may be prepared from each other by the loss and gain, respectively, of CO[subscript]2 at temperatures ranging from 415 to 970°C (depending on the gas phase environment), the influence of CO[subscript]2 on the OCM process is of great interest;This work found that co-feeding CO[subscript]2 over pure A-La[subscript]2O[subscript]3 and II-La[subscript]2O[subscript]2CO[subscript]3 starting materials depresses catalytic performance by both decreasing the catalysts\u27 ability to activate methane and inhibiting the homogeneous reaction pathway by which ethane dehydrogenates to ethene. Superior catalytic performance was found to depend upon the presence of both A-La[subscript]2O[subscript]3 and II-La[subscript]2O[subscript]2CO[subscript]3;Both A-La[subscript]2O[subscript]3 and II-La[subscript]2O[subscript]2CO[subscript]3 starting materials were found to uptake CO[subscript]2 at typical OCM reaction temperatures via incorporation between their (LaO)[subscript]2[superscript]2+ layers. CO[subscript]2 uptake by II-La[subscript]2O[subscript]2CO[subscript]3 was greater due to its more open structure long the c axis of the unit cell (i.e., perpendicular to the (LaO)[subscript]2[superscript]2+ planes);Isotopic labeling studies revealed that the CO[subscript]2 used in preparing II-La[subscript]2O[subscript]2CO[subscript]3 from A-La[subscript]2O[subscript]3 inserts directly into the oxide layers of A-La[subscript]2O[subscript]3 to give layers of (CO[subscript]3)[superscript]2- anions (all C-O bonds being equivalent). Carbon dioxide evolved during the thermal decomposition of II-La[subscript]2O[subscript]2CO[subscript]3 originates from the same (CO[subscript]3)[superscript]2- layers of the oxycarbonate;During OCM, C atoms originating in II-La[subscript]2O[subscript]2CO[subscript]3 were detected in products CO and CO[subscript]2, but not in the coupling products. Therefore, C[subscript]2H[subscript]6 and C[subscript]2H[subscript]4 are produced only via methane coupling. The O atoms originating in the (CO[subscript]3)[superscript]2- layers of the catalyst were also detected in products CO and CO[subscript]2 during OCM. Furthermore, CO[subscript]2 was concluded to be produced on the catalyst rather than in the gas phase;Oxygen present in II-La[subscript]2O[subscript]2CO[subscript]3 was found to be capable of activating methane. The amounts of coupling products detected following a He/CH[subscript]4 pulse were equivalent to approximately 2% of those observed following a He/CH[subscript]4/O[subscript]2 feed pulse;Finally, a scheme was proposed which explains the catalytic performance of A-La[subscript]2O[subscript]3 and II-La[subscript]2O[subscript]2CO[subscript]3 in terms of their relative basicity

Stable and Metastable Structures of Cobalt on Cu(001): An ab initio Study

We report results of density-functional theory calculations on the structural, magnetic, and electronic properties of (1x1)-structures of Co on Cu(001) for coverages up to two monolayers. In particular we discuss the tendency towards phase separation in Co islands and the possibility of segregation of Cu on top of the Co-film. A sandwich structure consisting of a bilayer Co-film covered by 1ML of Cu is found to be the lowest-energy configuration. We also discuss a bilayer c(2x2)-alloy which may form due to kinetic reasons, or be stabilized at strained surface regions. Furthermore, we study the influence of magnetism on the various structures and, e.g., find that Co adlayers induce a weak spin-density wave in the copper substrate.Comment: 11 pages including 4 figures. Related publications can be found at http://www.fhi-berlin.mpg.de/th/paper.htm

Apteniols A-F, oxyneolignans from the leaves of Aptenia cordifolia.

Abstract—Investigation of the organic extract of Aptenia cordifolia leaves revealed six new oxyneolignans named apteniols A–F. The structures were determined by means of spectroscopic methods. The C6C3 units are linked by an oxygen atom at C4–C40 or C4–C20 and they are dihydrophenylpropanoid acid units. Their effects on germination and growth of Lactuca sativa L. have been studied in the range concentration 10K4–10K7 M

Synthesis and Characterization of a Series of Co(II) NNN Pincer Complexes

Several new Co(II) complexes supported by NNN pincer ligands in various ligand-to-metal ratios are reported. The synthesis and characterization of CztBu(PyriPr)2Co (1) completes a series of analogous compounds (CztBu(PyriPr)2M, M = Fe(II), Co(II), Ni(II)), offering insights into chemical trends across late first-row transition metal complexes. Additionally, chemical oxidation of (CztBu(PyriPr)2)2Co (2) gave complex 5, in which unprecedented, cobalt-facilitated C-C coupling of pyrazole moieties has occurred

The hot core towards the intermediate mass protostar NGC7129 FIRS 2: Chemical similarities with Orion KL

NGC 7129 FIRS 2 (hereafter FIRS 2) is an intermediate-mass (2 to 8 Msun) protostar located at a distance of 1250 pc. High spatial resolution observations are required to resolve the hot core at its center. We present a molecular survey from 218200 MHz to 221800 MHz carried out with the IRAM Plateau de Bure Interferometer. These observations were complemented with a long integration single-dish spectrum taken with the IRAM 30m telescope. We used a Local Thermodynamic Equilibrium (LTE) single temperature code to model the whole dataset. The interferometric spectrum is crowded with a total of ~300 lines from which a few dozens remain unidentified yet. The spectrum has been modeled with a total of 20 species and their isomers, isotopologues and deuterated compounds. Complex molecules like methyl formate (CH3OCHO), ethanol (CH3CH2OH), glycolaldehyde (CH2OHCHO), acetone (CH3COCH3), dimethyl ether (CH3OCH3), ethyl cyanide (CH3CH2CN) and the aGg' conformer of ethylene glycol (aGg'-(CH2OH)_2) are among the detected species. The detection of vibrationally excited lines of CH3CN, CH3OCHO, CH3OH, OCS, HC3N and CH3CHO proves the existence of gas and dust at high temperatures. In fact, the gas kinetic temperature estimated from the vibrational lines of CH3CN, ~405 K, is similar to that measured in massive hot cores. Our data allow an extensive comparison of the chemistry in FIRS~2 and the Orion hot core. We find a quite similar chemistry in FIRS 2 and Orion. Most of the studied fractional molecular abundances agree within a factor of 5. Larger differences are only found for the deuterated compounds D2CO and CH2DOH and a few molecules (CH3CH2CN, SO2, HNCO and CH3CHO). Since the physical conditions are similar in both hot cores, only different initial conditions (warmer pre-collapse phase in the case of Orion) and/or different crossing time of the gas in the hot core can explain this behavior.Comment: 30 pages, 9 figure

Arcsecond resolution images of the chemical structure of the low-mass protostar IRAS 16293-2422

It remains a key challenge to establish the molecular content of different components of low-mass protostars, like their envelopes and disks, and how this depends on the evolutionary stage and/or environment of the young stars. Observations at submillimeter wavelengths provide a direct possibility to study the chemical composition of low-mass protostars through transitions probing temperatures up to a few hundred K in the gas surrounding these sources. This paper presents a large molecular line survey of the deeply embedded protostellar binary IRAS 16293-2422 from the Submillimeter Array (SMA) - including images of individual lines down to approximately 1.5-3" (190-380 AU) resolution. More than 500 individual transitions are identified related to 54 molecular species (including isotopologues) probing temperatures up to about 550 K. Strong chemical differences are found between the two components in the protostellar system with a separation between, in particular, the sulfur- and nitrogen-bearing species and oxygen-bearing complex organics. The action of protostellar outflow on the ambient envelope material is seen in images of CO and SiO and appear to influence a number of other species, including (deuterated) water, HDO. The effects of cold gas-phase chemistry is directly imaged through maps of CO, N2D+ and DCO+, showing enhancements of first DCO+ and subsequently N2D+ in the outer envelope where CO freezes-out on dust grains.Comment: Accepted for publication in A&A, 30 pages, 22 figure

β-diketonate versus β-ketoiminate:the importance of a ferrocenyl moiety on improving the anticancer potency

Herein we present a library of fully characterized beta-diketonate and beta-ketoiminate compounds that are functionalized with a ferrocenyl moiety. Their cytotoxic potential has been determined by screening against human breast adenocarcinomas (MCF-7 and MDA-MB-231), human colorectal carcinoma p53 wild type (HCT116 p53(+/+)) and normal human prostate (PNT2) cell lines. The ferrocenyl beta-diketonate compounds are more than 18 times more cytotoxic than the ferrocenyl beta-ketoiminate analogues. Against MCF-7, compounds functionalized at the meta position are up to nine times more cytotoxic than when functionalized at the para position. The ferrocenyl beta-diketonate compounds have increased selectivity towards MCF-7 and MDA-MB-231, with several complexes having selectivity index (SI) values that are more than nine times (MCF-7) and more than six times (MDA-MB-231) that of carboplatin. The stability of these compounds in dimethyl sulfoxide (DMSO) and dimethylformamide (DMF) has been assessed by NMR spectroscopy and mass spectrometry studies, and the compounds show no oxidation of the iron center from Fe-II to Fe-III. Cytotoxicity screening was performed in both DMSO and DMF, with no significant differences observedin their potency

Uniqueness and Lipschitz stability for the identification of Lam\'e parameters from boundary measurements

In this paper we consider the problem of determining an unknown pair $\lambda$, $\mu$ of piecewise constant Lam\'{e} parameters inside a three dimensional body from the Dirichlet to Neumann map. We prove uniqueness and Lipschitz continuous dependence of $\lambda$ and $\mu$ from the Dirichlet to Neumann map