ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Lunar and Planetary Science and Exploration  (65)
  • General Chemistry  (61)
  • Organic Chemistry  (50)
  • 2000-2004  (82)
  • 1975-1979  (94)
  • 1
    Publication Date: 2019-08-15
    Description: The Mars Climate Orbiter failed to achieve Mars orbit on September 23, 1999. On December 3, 1999, Mars Polar Lander and two Deep Space 2 microprobes failed. As a result, the NASA Administrator established the Mars Program Independent Assessment Team (MPIAT) with the following charter: 1) Review and analyze successes and failures of recent Mars and Deep Space Missions which include: a) Mars Global Surveyor, b) Mars Climate Orbiter, c) Pathfinder, d) Mars Polar Lander, e) Deep Space 1, and f) Deep Space 2; 2) Examine the relationship between and among, NASA Jet Propulsion Laboratory (JPL), California Institute of Technology (Caltech), NASA Headquarters, and industry partners; 3) Assess effectiveness of involvement of scientists; 4) Identify lessons learned from successes and failures; 5) Review revised Mars Surveyor Program to assure lessons learned are utilized; 6) Oversee Mars Polar Lander and Deep Space 2 failure reviews; and 7) Complete by March 15, 2000. In-depth reviews were conducted at NASA Headquarters, JPL, and Lockheed Martin Astronautics (LMA). Structured reviews, informal sessions with numerous Mars Program participants, and extensive debate and discussion within the MPIAT establish the basis for this report. The review process began on January 7, 2000, and concluded with a briefing to the NASA Administrator on March 14, 2000. This report represents the integrated views of the members of the MPIAT who are identified in the appendix. In total, three related reports have been produced: a summary report, this report entitled "Mars Program Independent Assessment Team Report," and the "Report on the Loss of the Mars Polar Lander and Deep Space 2 Missions".
    Keywords: Lunar and Planetary Science and Exploration
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Activated quinones: O- versus C-addition of phenols. New regiospecific syntheses of xanthones, thioxanthones and N-methyl-9-acridonesThe acid catalyzed reaction of phenols with activated quinones, e.g. 2-methoxycarbonyl-1, 4-benzoquinone or 2-acetyl-1, 4-benzoquinone, leads to substituted biphenylderivatives (C, C-addition) as has been previously described [1]. O, C-Addition of phenols has now been achieved by using 2-methoxypyridin or 4-dimethyl-aminopyridin [4] as basic catalysts. The resulting substituted diphenylethers can serve as convenient starting materials for regiospecific syntheses of substituted xanthones, especially for 1, 4-dimethoxyxanthones.Arylthiols and N-methyl-N-arylamines also react readily with activated quinones to give substituted di-aryl-thioethers and N-methyl-N, N-diarylamines respectively; both types of compounds are convenient materials for regiospecific syntheses of substituted thioxanthones and N-methyl-9-acridones.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The potentiometric study of the complexation of Cu2+ with 1,4,7-triazacyclononane (1), 1,4,8-triazacyclodecane (2) 1,5,9-triazacyclododecane (3) has shown that CuL, CuL2 and (CuLOH)2 are the main species present in solution. Their stabilities (Table 1) and their absorption spectra (Table 2) indicate facial coordination of the cyclic triamines in a distorted octahedral geometry.The formation and dissociation kinetics have been measured by stopped-flow techniques. The formation in acetate buffer can be described by the reaction of Cu2+ and CuAcO+ with the monoprotonated species of the ligand. The bimolecular rate constants for these complexations (Table 3) decrease when the ring size increases. In contrast the dissociation induced by acid is only little affected by the ring size. Thus for these complexes the rate of formation and not that of the dissociation determines the overall stability.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 62 (1979), S. 2833-2840 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Activated Quinones: Regiospecific Syntheses of Substituted Dibenzo [b, d]pyran-6-ones and Benzo[b]naphtho [d]pyran-6-onesThe reaction of 2-methoxycarbonyl-1, 4-benzoquinone (1) with substituted phenols leads in an acid-catalyzed, regiospecific way to substituted dibenzo [b, d]-pyran-6-ones (compounds 3 and 6). The cycloaddition of 1,3-butadiene to the latter yields compounds 7. Tautomerisation of 7 and oxidation gives the benzo[b]-naphtho[d]pyran-6-ones 8 and 10, respectively.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 5
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The enthalpy of formation of tris(methylidene)-cyclopropane (“[3]radialene”, 1) has been determined as ΔHfO = 396 ± 12 kJ mol-1 from three fragmentation reactions of its molecular ion 1+ formed from 1 by photoionisation using synchrotron radiation. Comparative electron impact measurements using conventional mass spectrometry were also performed. A treatment of the latter data is described which leads to satisfactory agreement with the photoionization data. The experimental value of ΔHfO(1) is compared with various theoretical estimates. The strain energy of 1 is calculated to be 226.3 kJ mol-1. Linear extrapolation of this quantity from the increase of strain in passing from cyclopropane to methylidenecyclopropane yields 282.4 kJ mol-1. The discrepancy between these values, already predicted by Dewar and Baird ten years ago from theoretical calculations, is discussed on the basis of maximum overlap considerations. The enthalpy of formation of bis(methylidene)cyclopropane is predicted to be ΔHfO= 309 kJ mol-1.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 6
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The photoelectron spectrum of tris (methylidene)-cyclopropane 1 (“[3]radialene”) is reported and the electronic states of 1+ assigned. Jahn-teller activity in the degenerate states of 1+is discussed. Differences in the Franck-Condon profile of the first PE band and the Rydberg series in the Vacuum-UV./UV. absorption spectrum indicate for the Rydberg series (n=3) a 1A″2-species, which supports earlier tentative proposals. The high intensity absorption in the 5.5 eV-6 eV energy range of the latter spectrum recorded earlier are definitely due to impurities. The vibrational fine structure of a weak band system around 5.5 eV in our spectrum suggests for this transition S0→S2(1A′1), which is dipole forbidden but borrows intensity from S1(1E′) trough vibronic coupling via an e′-mode. From vapor pressure measurements ε(λmax=289 nm) = 9390± 1170 for gaseous 1 was found.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 7
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Comparative investigation of reactivities and ion structures upon electron impact induced degradations of the isomeric hydroxy cinnamic acid methyl estersBy analysis of energy release data in metastable peaks it is shown that m- and p-hydroxy cinnamic acid methylesters retain specific structural features upon degradation under electron impact, although their spectra are very similar and the shapes of the metastable peaks due to the initial methoxy cleavage are identical. A pronounced charge radical localization in the molecular ion is indicated. The o-isomer is found to yield a coumarin type structure by elimination of methanol, whose further degradation by decarbonylation involves at least three different mechanisms. The resulting ion structures are different from benzofuran.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 8
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the presence of Ni2+ the template reaction between 2,6-diacetylpyridine and 4-(2-dimethylaminoethyl)- or 4-(2-hydroxyethyl)-1, 7-diamino-4-azaheptane yields the complexes of either the open-chain ligand (3 and 11) or of the macrocycle (4 and 12). Reduction of the imino group in 4 and 12 with PtO2/H2 gives 5 and 13, respectively. In the case of the dimethylamino derivative 5 a mixture of at least four isomers was obtained. These were partially separated by chromatography on Sephadex SP-25 cation exchanger. Through demetalation of the Ni2+ complexes by cyanide the new macrocycles 7 and 14 were isolated, from which the corresponding Zn2+ and Cu2+ complexes were prepared.The macrocyclic Ni2+-complexes 4, 12, 5 and 13 can exist in two forms depending on the pH of the solution. At low pH protonation of the dimethylamino or hydroxy group in the side chain occurs. The metal ion is then bound to the four nitrogen atoms of the macrocycle in a square planar ligand field. At higher pH, however, the dimethylamino or hydroxy group (the last one also in its deprotonated form) can coordinate to one of the axial positions, whereby pseudooctahedral coordination geometry is induced. This reaction can be quantitatively described by a reversible acid-base equilibrium, the pKH of which greatly depends on the nature of the functional group, the degree of unsaturation of the macrocycle and the metal ion.The acid-base reaction and the concomitant structural change are a direct consequence of the unique combination of the rigid and kinetically stable structure of the macrocycle and of the flexible and kinetically labile functional group of the side chain.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 62 (1979), S. 577-582 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Electrocyclic reactions connecting radical cations are compared with those of the parent neutrals. Principles governing over-all reactivity and stereoselectivity of the open-shell processes are discussed.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 10
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The previously discussed principles involved in electrocyclic reactions of openshell ions are exemplified for a type C system, the radical cation couple quadricyclane+ (Q+)/norbornadiene+ (NBD+). Exhaustive calculations (MINDO/3) for the various states of the ions support the general predictions for such types of systems. The barrier of interconversion Q+ → NBD+ is estimated to be significantly lower than that for the corresponding neutrals. Experimental support to this prediction is obtained by γ-irradiation of Q or NBD in an electron scavenging matrix. In both cases only NBD+ is observed, indicating that Q+ is not stable at 77 K. Previous observations and propositions referring to the system Q+/NBD+ are discussed in view of the present findings.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...