In the ordinary quantum Maxwell theory of a free electromagnetic field, formulated on a curved 3-manifold, we observe that
magnetic and electric fluxes cannot be simultaneously measured. This uncertainty principle reflects torsion: fluxes modulo
torsion can be simultaneously measured. We also develop the Hamilton theory of self-dual fields, noting that they are quantized
by Pontrjagin self-dual cohomology theories and that the quantum Hilbert space is -graded, so typically contains both bosonic and fermionic states. Significantly, these ideas apply to the Ramond-Ramond field
in string theory, showing that its K-theory class cannot be measured. 相似文献
A theorem of Maranda [1, Section 30] states that if F is a finitegroup, p is a prime and pe exactly divides |F|, then a ZpF-latticeM is determined up to isomorphism by its finite quotient M/pe+1M.If M is a free Zp-module of rank d, this is equivalent to sayingthat representations of F in GLd(Zp) are determined up to equivalenceby their images modulo pe+1. 1991 Mathematics Subject Classification20E18, 22E20. 相似文献
The polynuclear coordination compounds LnCr(tartrate)3·nH2O where Ln(III)=La-Er, obtained through a precipitation method, were characterized on the basis of elemental analysis, their
electronic and vibrational spectra and magnetic susceptibility measurements. The possibility of obtaining chromites through
the transformations of the polynuclear coordination compounds in the solid state was considered. The thermal decompositions
of these compounds, studied by TG and DTA methods, were found to follow an almost uniform pattern. The decompositions occurred
in six-eight steps. The first two steps involved dehydration, and the third the transformation of tartrate anions to oxalate,
followed by conversion to carbonate and oxocarbonate intermediates. The final product in each case was LnCrO3. A non-isothermal kinetic analysis of the first decomposition steps was performed, the most probable decomposition mechanism
being selected and the kinetic parameters evaluated. The final products of the transformations were characterized.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
A critical analysis is presented of the use of an overall single rate reaction equation instead of the true rate equation
corresponding to a complex process consisting of two consecutive reactions. In accordance with this approximation, which is
often used in the kinetic analysis of systems in which several reactions take place, the overall process is described by apparent
activation parameters (the apparent activation energy Eap and the apparent pre-exponential factor Aap) and an apparent conversion function.
The theoretical isotherms (α=α(t), where α is the conversion degree and t is time) were simulated for a system in which two
consecutive reactions occur. In this case, the apparent activation parameters depend on (a) the considered range of temperature;
and (b) the temperature for a given conversion degree. It is shown that the apparent activation parameters are correlated
by the compensation effect relationship: ln Aap = α* + β*Eap where α* and β* are the linear regression parameters.
The possibility of using the apparent kinetic parameters to predict the isotherms α=α(t) for temperatures lower than those
for which these parameters were evaluated is discussed.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
Bonding, structure, and stability of solid A2MH2 with A = Li, Na; M = Pd, Pt were investigated with a relativistically corrected density-functional approach, which reliably describes the trends among these four compounds. In order to examine the influence of the ligands (A) and of the crystalline environment, calculations were also made for free A2MH2 molecules and MH22– ions. The free MH22– complex is held together by strong bonds between formally closed shell atomic units because of strong M-d,s hybridization. The M–H bonds are further stabilized by the alkali metal ion ligands and by the crystal surrounding. The crystal field expands the H–A distance and enhances the H–A polarity. Relativistic effects contribute to M–H bonding in the solid state. The experimentally determined bond lengths and their trends are in accordance with theory. Due to relativistic and lanthanide effects, the Pt–H bond length becomes nearly as short as the Pd–H one. The small Li ion causes a distortion of the Li2PtH2 crystal resulting in an even shorter Pt–H bond length. In the gas-phase, A2PtH2 is more stable against dissociation than A2PdH2. The stability of the solid compounds is strongly influenced by the cohesive energy of the metal M, and also by the nature of the alkali metal. The evaluated enthalpies of formation favor increasing stability of solid A2MH2 against disproportionation into M and AH from Pt to Pd and from Li to Na. This is in agreement with experimental findings. The assignment of the experimental vibrational excitations should be reconsidered. 相似文献
In the present study, a HPLC/DAD method was set up to allow for the determination and quantification of malondialdehyde (MDA) in the brain of rodents (rats). Chromatographic separation was achieved on Supelcosil LC-18 (3 μm) SUPELCO Column 3.3 cm × 4.6 mm and Supelco Column Saver 0.5 μm filter by using a mobile phase acetonitrile (A) and phosphate buffer (20 mM, pH = 6) (B). Isocratic elution was 14% for (A) and 86% for (B). The injection volume (loop mode) was 100 μL with an analysis time of 1.5 min. Flow rate was set at 1 mL/min. The eluted compound was detected at 532 nm by a DAD detector by keeping the column oven at room temperature. The results indicated that the method has good linearity in the range of 0.2–20 μg/g. Both intra- and inter-day precision, expressed as RSD, were ≤15% and the accuracies ranged between ±15%. The lower limit of quantification (LLOQ), stability, and robustness were evaluated and satisfied the validation criteria. The method was successfully applied in a study of chronic toxicology following different treatment regimens with haloperidol and metformin. 相似文献
We present the results of the interaction of iron oxide nanoparticles with some biologically active surfactants, namely, oleic acid and cytotoxic alkanolamine derivatives. Physico-chemical properties, as magnetization, magnetite concentration and particle diameter, of the prepared magnetic samples were studied. The nanoparticle size of 11 nm for toluene magnetic fluid determined by TEM is in good agreement with the data obtained by the method of magnetogranulometry. In vitro cytotoxic effect of water-soluble nanoparticles with different iron oxide:oleic acid molar ratio were revealed against human fibrosarcoma and mouse hepatoma cells. In vivo results using a sarcoma mouse model showed observable antitumor action. 相似文献
Just a drop of water : Esterification in water is possible by confining the reactants in small miniemulsion droplets protected by nonionic surfactants. A lipase located at the interface between the droplet and aqueous surroundings catalyzes the esterification and expels generated water from the reaction site (see picture). High yields of the ester can be obtained after short reaction times under ambient conditions.