Computation of sharp bounds on the distribution of a function of dependent risks

We propose a new algorithm to compute numerically sharp lower and upper bounds on the distribution of a function of d dependent random variables having fixed marginal distributions. Compared to the existing literature, the bounds are widely applicable, more accurate and more easily obtained.     

Weak association of random variables

The dependence concept of weak association is introduced and is shown to be equivalent to positive quadrant dependence. Furthermore, a characterization of independence in the class of positive quadrant dependent random variables by means of moment conditions is proved. Both results generalize some theorems proved by Lehmann and Jogdeo for the two- and three-dimensional case.     

13C n.m.r. spectroscopy of diethyl alkyl- and benzyl-phosphonates. A study of phosphorus–carbon spin–spin coupling constants over one to seven bonds

¹³C chemical shifts and ³¹P? ¹³C spin–spin coupling constants are reported for 10 alkyl-, 20 benzyl- and 3 (naphthylmethyl)-phosphonates. While in saturated aliphatic chains P–C couplings over more than four bonds cannot be resolved, couplings over up to seven bonds are observed in the benzyl type systems. Conformational and substituent effects on J(PC) are studied and discussed. ⁿJ(PF) (n = 4, 5, 6) are reported for the isomeric (fluorobenzyl)phosphonates and ⁿJ(PP) (n = 5, 6, 7) were obtained from the ¹³C satellites in the ³¹P n.m.r. spectra of the isomeric diphosphonates, C₆H₄[CH₂P(O)(OEt)₂]₂. Comparison of those ¹³C absorptions of the latter, which represent the X parts of ABX or AA′X spin systems, with the spectra of the corresponding (methylbenzyl)phosphonates, CH₃C₆H₄CH₂P(O)(OEt)₂, yielded the relative signs of ⁿJ(PC) (n = 2–6).     

A New Versatile Synthesis of Ring-Substituted 2-Cyclopropylglycines and Related Amino Acids

Alkyl 2-chloro-2-cyclopropylideneacetates 2 serve as universal starting materials for a new general synthesis of cyclopro-pylglycines by a simple three- to four-step methodology. 1,4-Addition of nucleophiles, substitution with azide ion, and mild catalytic deprotection lead to a variety of salt-free cyclopropyl-substituted amino acids in good yields, including the natural products 2-(1-methylcyclopropyl)glycine ( 4 ) and cleonin ( 5 ).     

Light Effects on Cyclic Nucleotide Levels and Phase Shifting of the Circadian Clock in Neurospora crassa

Abstract— Mycelia of Neurospora crassa (band [bd] mutant) were exposed to white light (blue light intensity 3.5 μ.mol s^?1 m^?2) of different durations during constant darkness. The concentrations of different second messenger molecules and the phase shifting of the circadian rhythm were determined during light exposures at circadian time (ct) 12 and thereafter. These light exposures elicited 8-12 ct units delay phase shifts but did not change the amount of inositol 1,4,5-triphosphate (InsP₃). In contrast, significant effects of light were observed on cyclic adenosine 3′,5′-monophosphate (cAMP) levels, which increased transiently about 30-90 s after the onset of light. The same kinetics was observed under continued exposure to light as well as after 10 s and 2 s of light followed by darkness. The relative amount of the cAMP-dependent protein kinase A (PKA) in the form of its catalytic sub-units was determined in isolated nuclei of the bd strain in relation to total nuclear proteins by means of western blot analysis, using a heterologous antibody. The nuclear PKA content changed parallel to the cAMP changes. The transient increase of cAMP did not occur in the “blind”white collar mutant (wc-2). Long-term kinetics of cAMP changes after different light pulses in bd showed the initial increase and a return to control levels about 10 min after the onset of the light pulse and a subsequent longer lasting decrease. Light-induced cAMP changes and light-induced phase shifts showed different duration dependencies, thus indicating that cAMP may not play a role in the signal transduction pathway to the clock. Light exposures, furthermore, led to a significant decrease of the cyclic guanosine 3′,5′-monophosphate (cGMP) level. Long-term kinetics of the cGMP content again showed the immediate decrease after 2 min and a slow recovery to (or above) control values after several hours. Various calcium channel blockers (nickel, cobalt, nifedipine, dantrolene, lanthanum) and the calcium calmodulin inhibitor chlorpromazine did not affect the phase shifting by light nor did they significantly phase shift the circadian rhythm in the dark themselves (again determined at ct 12). The data showed that InsP₃ did not change after exposure to light, whereas cAMP increased and cGMP decreased. There was no evidence, however, that these changes play a role in light signal transmission to the clock.     

CP non-violation in neutral K-meson decay: A non-standard explanation

A recently presented concept, where, in the framework of parametrized relativistic quantum field theory, antiparticles are described consistently with negative frequencies, but positive energy density, is used to analyse the decay of neutralK-mesons, where the experimental results usually are interpreted as an evidence forCP-violation. In the theory presented the charge conjugation is antilinear, as in original Dirac theory, and theCPT-transformation is unitary. The Hamiltonian is indefinite, and changes sign under theCPT-transformation, since positive and negative eigenvalues are interchanged. As a result the eigenstates of the Hamiltonian are notCPT-eigenstates. The interference of positive and negative frequencies leads to a mixing ofCPT-eigenstates, as is observed in experiment. The study of a simple model system shows that the proposed mechanism of dynamical mixing offers an explanation for the experiments on theK ⁰– ⁰-meson system, with respect to both the observed mixing of eigenstates and the observed difference in the number of CP-violating events in the decays of the longer and shorter living neutralK-mesonsK _L andK _S . No symmetry violation of the theory needs be assumed.     

Building the “Phosphoindigo” Backbone by Oxidative Coupling of Phosphindolin‐3‐ones with Selenium Dioxide

Oxidative coupling of racemic 1‐ethoxy‐1‐oxophosphindolin‐3‐one ( 1 ) and its 5‐CF₃‐derivative 6 with SeO₂ furnishes 1,1′‐diphosphaindigo derivatives 5 and 7 as bis‐phosphinic esters, i. e. as P^V‐compounds. Like indigo and thioindigo, 5 and 7 exist in the E‐configuration; the crude products of 5 and 7 are mixtures of isomers that are trans‐ and cis‐configurated with respect to the relative orientation of the ester groups oat phosphorus. The structure of the centrosymmetric E‐P(R)P′(S) isomer [(E)‐trans‐isomer] of 5 was determined by X‐ray crystallography. Ester cleavage of 5 , followed by addition of triethylamine to bis‐phosphinic acid 9 (the 1,1,1′,1′‐tetroxide of “phosphoindigo”), furnishes the related bis‐triethylammonium salt 10 as a crystalline hydrate that exhibits an extended hydrogen bonding network.     

ADHD candidate gene (DRD4 exon III) affects inhibitory control in a healthy sample

Background  

Dopamine is believed to be a key neurotransmitter in the development of attention-deficit/hyperactivity disorder (ADHD). Several recent studies point to an association of the dopamine D4 receptor (DRD4) gene and this condition. More specifically, the 7 repeat variant of a variable number of tandem repeats (VNTR) polymorphism in exon III of this gene is suggested to bear a higher risk for ADHD. In the present study, we investigated the role of this polymorphism in the modulation of neurophysiological correlates of response inhibition (Go/Nogo task) in a healthy, high-functioning sample.