A choice of the semirigid bender model of the water molecule

In order to minimize momentum coupling between small- and large-amplitude internal motions special intrinsic semirigid models should be used. The intrinsic model for the water molecule is constructed as a Taylor series in the bending angle. Using sets of ab initio force constants up to quartic, expansions can be found up to and including cubic terms. A polynomial fit to the ab initio value of the bond length of the linear saddle configuration is used to find the quartic term in the expansion.     

Photodynamic inactivation of isolated crayfish mechanoreceptor neuron: different death modes under different photosensitizer concentrations

To study the mechanism of photodynamic nerve cell killing, isolated crayfish mechanoreceptor neurons were photosensitized by the sulfonated aluminum ophthalocyanine Photosens. Neuron activity was continuously recorded until irreversible abolition. Intense (10(-5) M Photosens) or weak (10(-7) M Photosens) photosensitization induced different bioelectric neuron responses: firing activation followed by irreversible depolarization block or gradual inhibition until firing abolition, respectively. These bioelectric responses were accompanied by different biochemical and morphological changes. In the case of intense photosensitization, neuron nuclei swelled and then shrank. Succinate dehydrogenase (SDH) was inhibited, and the plasma membrane was compromised just after firing cessation. Weak photosensitization did not induce these changes but caused swelling of the endoplasmic reticulum and destruction of the matrix, cristae and membranes in some of the mitochondria. Other mitochondria, however, retained the normal structure. Plasma membrane damage, SDH inhibition, nucleus shrinkage and impairment of the nuclear border occurred after 2-4 h. It is concluded that intense photosensitization induced necrotic processes during irradiation, whereas weaker impact caused delayed necrosis 2-4 h later. The observed electrophysiological neuron responses to photodynamic therapy may be considered as early hallmarks of different modes of forthcoming cell death.     

Disproportionation reaction of NO2/N2O4 with a Ru(II) porphyrin

A Ru(II) porphyrin rapidly reacts with NO2/N2O4 with the formation of a stable Ru(II) nitrosyl nitrato complex.     

Encapsulated reagents for nitrosation

[reaction: see text] A novel class of stable, mild, and size-shape-selective nitrosating agents for secondary amides is introduced. These are based on reversible entrapment and release of reactive nitrosonium species by calix[4]arenes. The NO(+) encapsulation controls the reaction selectivity.     

Zinc(II) and copper(II) complexes of edampda2−: octahedral,trigonal bipyramidal and in between [edampda2−=N,N′-bis-(pyridylmethyl)ethylenediamine-N,N′-diacetate]

ZnII and CuII complexes of the ligand edampda2– [N,N-bis(pyridylmethyl)-ethylenediamine-N,N-diacetate] have been studied in solution by 1H n.m.r. and e.p.r. spectroscopies, respectively. [ZnII(edampda)] exists in solution in a major octahedral isomer (ca. 83%) in which the two carboxylate donors and two pyridylmethyl donors remain stereochemically rigid up to 333K at pD=6.0. The major octahedral complex has equivalent glycinato and pyridyl donors as shown by equivalent AB quartets for each type of chelate. By contrast, the [ZnII(edta)]2– analogue complex is known to have processes which rapidly equilibrate the coordinated carboxylates leading to coalesced, broad singlets instead of AB quartets down to 273K (freezing point of the sample). The minor [ZnII(edampda)] species has one pendant pyridylmethyl arm. The complex does not increase in abundance up to 333K via dissociation of the major species, suggesting that it possesses a different five-coordinate geometry (approximate trigonal bipyramid). The [CuII(edampda)] complex exhibits an e.p.r. spectrum that is intermediate between rhombic or tetragonal CuII complexes (near D4h) and the reversed-e.p.r. type of trigonal bipyramidal CuII complexes (ca. D3h). The single g value of 2.079 for gg>2.03 identifies the [CuII(edampda)] complex as distorted toward trigonal bipyramidal whereas its [CuII(edtaH2)(H2O)] analogue is known to be distorted toward square pyramidal. A binuclear CuI complex of edampda2– is formed only as a transient, and it rapidly disproportionates into [CuII(edampda)] and Cu metal. A mononuclear [CuI(edampda)]– complex persists for up to 8 h, but is oxidized within 3 min by O2 to the CuII complex. [CuII(edampda)] oxidizes to CuIII with a highly irreversible wave on glassy-carbon at +1.09V compared to the [NiII/III(edampda)] wave at +1.32V.     

Bistability of rotational modes in a system of coupled pendulums

The main goal of this research is to examine any peculiarities and special modes observed in the dynamics of a system of two nonlinearly coupled pendulums. In addition to steady states, an in-phase rotation limit cycle is proved to exist in the system with both damping and constant external force. This rotation mode is numerically shown to become unstable for certain values of the coupling strength. We also present an asymptotic theory developed for an infinitely small dissipation, which explains why the in-phase rotation limit cycle loses its stability. Boundaries of the instability domain mentioned above are found analytically. As a result of numerical studies, a whole range of the coupling parameter values is found for the case where the system has more than one rotation limit cycle. There exist not only a stable in-phase cycle, but also two out-of phase ones: a stable rotation limit cycle and an unstable one. Bistability of the limit periodic mode is, therefore, established for the system of two nonlinearly coupled pendulums. Bifurcations that lead to the appearance and disappearance of the out-ofphase limit regimes are discussed as well.     

Rational design of a minimal size sensor array for metal ion detection

The focus of this study was to demonstrate that, in the luminescent sensors, the signal transduction may possibly be the most important part in the sensing process. Rational design of fluorescent sensor arrays for cations utilizing extended conjugated chromophores attached to 8-hydroxyquinoline is reported. All of the optical sensors utilized in the arrays comprise the same 8-hydroxyquinoline (8-HQ) receptor and various conjugated chromophores to yield a different response to various metal cations. This is because the conjugated chromophores attached to the receptor are partially quenched in their resting state, and upon the cation coordination by the 8-HQ, the resulting metalloquinolinolate complex displays a change in fluorescence. A delicate balance of conjugation, fluorescence enhancement, energy transfer, and a heavy metal quenching effect results in a fingerprint-like pattern of responses for each sensor-cation complex. Principal component analysis (PCA) and linear discriminant analysis (LDA) are used to demonstrate the contribution of individual sensors within the array, information that may be used to design sensor arrays with the smallest number of sensor elements. This approach allows discriminating between 10 cations by as few as two or even one sensor element. Examples of arrays comprising various numbers of sensor elements and their utility in qualitative identification of Ca(2+), Mg(2+), Cd(2+), Hg(2+), Co(2+), Zn(2+), Cu(2+), Ni(2+), Al(3+), and Ga(3+) ions are presented. A two-member array was found to identify 11 analytes with 100% accuracy. Also the best two of the sensors were tested alone and both were found to be able to discriminate among the samples with 99% and 96% accuracy, respectively. To illustrate the utility of this approach to a real-world application, identification of enhanced soft drinks based on their Ca(2+), Mg(2+), and Zn(2+) cation content was performed. The same approach to reducing array elements was used to construct three- and two-member arrays capable of identifying these complex analytes with 100% accuracy.     

Classifying Serre subcategories of finitely presented modules

Given a commutative coherent ring , a bijective correspondence between the thick subcategories of perfect complexes and the Serre subcategories of finitely presented modules is established. To construct this correspondence, properties of the Ziegler and Zariski topologies on the set of isomorphism classes of indecomposable injective modules are used in an essential way.