1,116 research outputs found
Eine einfache Synthese von Tetramethyloxamid
Es wird eine neue, einfache Synthese von Tetramethyloxamid aus Dimethylformamid, Eisen(II)-sulfat-heptahydrat und tert-Butylhydroperoxid (Ausb. 43%) oder 30proz. Wasserstoffperoxid (Ausb. 77%) beschrieben
Nuclear expansion with excitation
The expansion of an isolated hot spherical nucleus with excitation energy and
its caloric curve are studied in a thermodynamic model with the SkM* force as
the nuclear effective two-body interaction. The calculated results are shown to
compare well with the recent experimental data from energetic nuclear
collisions. The fluctuations in temperature and density are also studied. They
are seen to build up very rapidly beyond an excitation energy of 9 MeV/u.
Volume-conserving quadrupole deformation in addition to expansion indicates,
however, nuclear disassembly above an excitation energy of 4 MeV/uComment: 17 pages, 5 figures, revtex4; calculations with deformation adde
Evidence for silicate dissolution on Mars from the Nakhla meteorite
Veins containing carbonates, hydrous silicates and sulphates that occur within and between grains of augite and olivine in the Nakhla meteorite are good evidence for the former presence of liquid water in the Martian crust. Aqueous solutions gained access to grain interiors via narrow fractures, and those fractures within olivine whose walls were oriented close to (001) were preferentially widened by etching along [001]. This orientation selective dissolution may have been due to the presence within olivine of shock-formed [001](100) and [001]{110} screw dislocations. The duration of etching is likely to have been brief, possibly less than a year, and the solutions responsible were sufficiently cool and reducing that laihunite is absent and Fe liberated from the olivine was not immediately oxidised. The pores within olivine were mineralised in sequence by siderite, nanocrystalline smectite, a Fe-Mg phyllosilicate, and then gypsum, whereas only the smectite occurs within augite. The nanocrystalline smectite was deposited as sub-micrometre thick layers on etched vein walls, and solution compositions varied substantially between and sometimes during precipitation of each layer. Together with microcrystalline gypsum the Fe-Mg phyllosilicate crystallised as water briefly returned to some of the veins following desiccation fracturing of the smectite. These results show that etching of olivine enhanced the porosity and permeability of the nakhlite parent rock and that dissolution and secondary mineralization took place within the same near-static aqueous system
A Unified Account of the Moral Standing to Blame
Recently, philosophers have turned their attention to the question, not when a given agent is blameworthy for what she does, but when a further agent has the moral standing to blame her for what she does. Philosophers have proposed at least four conditions on having âmoral standingâ:
1. Oneâs blame would not be âhypocriticalâ.
2. One is not oneself âinvolved inâ the target agentâs wrongdoing.
3. One must be warranted in believing that the target is indeed blameworthy for the wrongdoing.
4. The targetâs wrongdoing must some of âoneâs businessâ.
These conditions are often proposed as both conditions on one and the same thing, and as marking fundamentally different ways of âlosing standing.â Here I call these claims into question. First, I claim that conditions (3) and (4) are simply conditions on different things than are conditions (1) and (2). Second, I argue that condition (2) reduces to condition (1): when âinvolvementâ removes someoneâs standing to blame, it does so only by indicating something further about that agent, viz., that he or she lacks commitment to the values that condemn the wrongdoerâs action. The result: after we clarify the nature of the non-hypocrisy condition, we will have a unified account of moral standing to blame. Issues also discussed: whether standing can ever be regained, the relationship between standing and our "moral fragility", the difference between mere inconsistency and hypocrisy, and whether a condition of standing might be derived from deeper facts about the "equality of persons"
Thermally-induced expansion in the 8 GeV/c + Au reaction
Fragment kinetic energy spectra for reactions induced by 8.0 GeV/c
beams incident on a Au target have been analyzed in
order to deduce the possible existence and influence of thermal expansion. The
average fragment kinetic energies are observed to increase systematically with
fragment charge but are nearly independent of excitation energy. Comparison of
the data with statistical multifragmentation models indicates the onset of
extra collective thermal expansion near an excitation energy of E*/A
5 MeV. However, this effect is weak relative to the radial
expansion observed in heavy-ion-induced reactions, consistent with the
interpretation that the latter expansion may be driven primarily by dynamical
effects such as compression/decompression.Comment: 12 pages including 4 postscript figure
The weekend matters: Relationships between stress recovery and affective experiences
Non-work experiences during the weekend provide opportunities to recover from work demands and to replenish lost resources. This longitudinal study examined how specific recovery experiences during the weekend (relaxation, mastery, control, and detachment), as well as non-work hassles, were associated with specific positive and negative affective states during the following workweek. Participants (N 1â4 229) completed surveys before the week- end, during the weekend, and during the following workweek. Hierarchical regression analyses revealed that after controlling for affective states the previous week, recovery experiences during the weekend significantly explained variance in affective states at the end of the weekend and during the following workweek. Suggestions for future research include a closer examination of the role of individual differences, self-regulation, and specific work demands in employee stress recovery
Correlations and Characterization of Emitting Sources
Dynamical and thermal characterizations of excited nuclear systems produced
during the collisions between two heavy ions at intermediate incident energies
are presented by means of a review of experimental and theoretical work
performed in the last two decades. Intensity interferometry, applied to both
charged particles (light particles and intermediate mass fragments) and to
uncharged radiation (gamma rays and neutrons) has provided relevant information
about the space-time properties of nuclear reactions. The volume, lifetime,
density and relative chronology of particle emission from decaying nuclear
sources has been extensively explored and has provided valuable information
about the dynamics of heavy-ion collisions. Similar correlation techniques
applied to coincidences between light particles and complex fragments are also
presented as a tool to determine the internal excitation energy of excited
primary fragments as it appears in secondary-decay phenomena.Comment: To appear on Euorpean Physics Journal A as part of the Topical Volume
"Dynamics and Thermodynamics with Nuclear Degrees of Freedom
Breakup Temperature of Target Spectators in Au + Au Collisions at E/A = 1000 MeV
Breakup temperatures were deduced from double ratios of isotope yields for
target spectators produced in the reaction Au + Au at 1000 MeV per nucleon.
Pairs of He and Li isotopes and pairs of He and H
isotopes (p, d and d, t) yield consistent temperatures after feeding
corrections, based on the quantum statistical model, are applied. The
temperatures rise with decreasing impact parameter from 4 MeV for peripheral to
about 10 MeV for the most central collisions.
The good agreement with the breakup temperatures measured previously for
projectile spectators at an incident energy of 600 MeV per nucleon confirms the
observed universality of the spectator decay at relativistic bombarding
energies. The measured temperatures also agree with the breakup temperatures
predicted by the statistical multifragmentation model. For these calculations a
relation between the initial excitation energy and mass was derived which gives
good simultaneous agreement for the fragment charge correlations.
The energy spectra of light charged particles, measured at =
150, exhibit Maxwellian shapes with inverse slope parameters much
higher than the breakup temperatures. The statistical multifragmentation model,
because Coulomb repulsion and sequential decay processes are included, yields
light-particle spectra with inverse slope parameters higher than the breakup
temperatures but considerably below the measured values. The systematic
behavior of the differences suggests that they are caused by
light-charged-particle emission prior to the final breakup stage.
PACS numbers: 25.70.Mn, 25.70.Pq, 25.75.-qComment: 29 pages, TeX with 11 included figures; Revised version accepted for
publication in Z. Phys. A Two additional figure
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A Search for MeV to TeV Neutrinos from Fast Radio Bursts with IceCube
We present two searches for IceCube neutrino events coincident with 28 fast radio bursts (FRBs) and 1 repeating FRB. The first improves on a previous IceCube analysis - searching for spatial and temporal correlation of events with FRBs at energies greater than roughly 50 GeV - by increasing the effective area by an order of magnitude. The second is a search for temporal correlation of MeV neutrino events with FRBs. No significant correlation is found in either search; therefore, we set upper limits on the time-integrated neutrino flux emitted by FRBs for a range of emission timescales less than one day. These are the first limits on FRB neutrino emission at the MeV scale, and the limits set at higher energies are an order-of-magnitude improvement over those set by any neutrino telescope
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