Regular subalgebras and nilpotent orbits of real graded Lie algebras

For a semisimple Lie algebra over the complex numbers, Dynkin (1952) developed an algorithm to classify the regular semisimple subalgebras, up to conjugacy by the inner automorphism group. For a graded semisimple Lie algebra over the complex numbers, Vinberg (1979) showed that a classification of a certain type of regular subalgebras (called carrier algebras) yields a classification of the nilpotent orbits in a homogeneous component of that Lie algebra. Here we consider these problems for (graded) semisimple Lie algebras over the real numbers. First, we describe an algorithm to classify the regular semisimple subalgebras of a real semisimple Lie algebra. This also yields an algorithm for listing, up to conjugacy, the carrier algebras in a real graded semisimple real algebra. We then discuss what needs to be done to obtain a classification of the nilpotent orbits from that; such classifications have applications in differential geometry and theoretical physics. Our algorithms are implemented in the language of the computer algebra system GAP, using our package CoReLG; we report on example computations

Ab initio correlation approach to a ferric wheel-like molecular cluster

We present an ab initio study of electronic correlation effects in a molecular cluster derived from the hexanuclear ferric wheel [LiFe6(OCH3)12-(dbm)6]PF6. The electronic and magnetic properties of this cluster have been studied with all-electron Hartree-Fock, full-potential density functional calculations and multi-reference second-order perturbation theory. For different levels of correlation, a detailed study of the impact of the electronic correlation on the exchange parameter was feasible. As the main result, we found that the influence of the bridge oxygen atoms on the exchange parameter is less intense than the influence of the apical ligand groups, which is due to the geometry of the cluster. With respect to the cluster model approach, the experimental value of the exchange parameter was affirmed.Comment: to be published in EPJ

Quasimodes of a chaotic elastic cavity with increasing local losses

We report non-invasive measurements of the complex field of elastic quasimodes of a silicon wafer with chaotic shape. The amplitude and phase spatial distribution of the flexural modes are directly obtained by Fourier transform of time measurements. We investigate the crossover from real mode to complex-valued quasimode, when absorption is progressively increased on one edge of the wafer. The complexness parameter, which characterizes the degree to which a resonance state is complex-valued, is measured for non-overlapping resonances and is found to be proportional to the non-homogeneous contribution to the line broadening of the resonance. A simple two-level model based on the effective Hamiltonian formalism supports our experimental results

Development of a small-scale protope of the GOSSIPO-2 chip in 0.13 um CMOS technology

The GOSSIP (Gas On Slimmed Silicon Pixel) detector is a proposed alternative for silicon based pixel detectors. The Gossip Prototype (GOSSIPO) chip is being developed to serve as a prototype read-out chip for such a gas-filled detector. Thanks to the very low capacitance at the preamplifier input, the front-end of the chip demonstrates low-noise performance in combination with a fast peaking time and low analog power dissipation. Measurement of the drift time of every primary electron in the gas volume enables 3D reconstruction of the particle tracks. For this purpose a Time-to- Digital converter must be placed in each pixel. A small-scale prototype of the GOSSIP chip has been developed in the 0.13 μm CMOS technology. The prototype includes a 16 by 16 pixel array where each pixel is equipped with a front-end circuit, threshold DAC, and a 4-bit TDC. The chip is available for testing in May 2007 and after initial tests it will be postprocessed to build a prototype detector. This paper describes the detector design goals, the design of the chip and the first experimental results

Single-chip CMOS optical microspectrometer

Numerous applications, e.g., systems for chemical analysis by optical absorption and emission line characterization, will benefit from the availability of low-cost single-chip spectrometers. A single-chip CMOS optical microspectrometer containing an array of 16 addressable Fabry–Perot etalons (each one with different resonance cavity length), photodetectors and circuits for read-out, multiplexing and driving a serial bus interface has been fabricated. The result is a chip that can operate using only four external connections (including Vdd and Vss). covering the visible spectral range of the spectrum with FWHM = 18 nm. Frequency output and serial bus interface allow easy multi-sensor, multi-chip interfacing using a microcontroller or a personal computer. Power consumption is 1250 µW for a clock frequency of 1 MHzFundação para a Ciência e a Tecnologia (FCT

Fertilisation and cell cycle in angiosperms

Fertilisation is the result of successful fusion of female and male gametes, forming a zygote that develops into the embryo. From the perspective of cell cycle control, fertilisation is a hat‐trick. Firstly, the generation of gametes depends on the generation of haploid spores by meiosis and a sequence of mitotic divisions. Mitosis is required to produce the cells of the gametophyte, closely associated with differential fate acquisition. Secondly, cell cycle progression in both male and female gametes has to be synchronised in order to avoid chromosomal imbalance at karyogamy, and last but not least, the cell cycle should only be relaunched after a successful fusion. Here, we seek to survey our current knowledge of these processes from a cell cycle perspective and explore possible mechanisms involved in cell cycle control and coordination

Caudal cervical vertebral morphological variation is not associated with clinical signs in Warmblood horses

Background Variation in equine caudal cervical spine morphology at C6 and C7 has high prevalence in Warmblood horses and is suspected to be associated with pain in a large mixed-breed group of horses. At present no data exist on the relationship between radiographic phenotype and clinical presentation in Warmblood horses in a case-control study. Objectives To establish the frequency of radiographically visible morphologic variation in a large group of Warmblood horses with clinical signs and compare this with a group without clinical signs. We hypothesised that occurrence of morphologic variation in the case group would not differ from the control group, indicating there is no association between clinical signs and morphologic variation. Study design Retrospective case-control. Methods Radiographic presence or absence of morphologic variation of cervical vertebrae C6 and C7 was recorded in case (n = 245) and control horses (n = 132). Case and control groups were compared by univariable Pearson's Chi-square and multivariable logistic regression for measurement variables age, sex, breed, degenerative joint disease and morphologic variation at C6 and C7. Odds ratio and confidence intervals were obtained. A P <= 0.05 was considered statistically significant. Results Morphologic variation at C6 and C7 (n = 108/377 = 28.6%; Cases 58/245 = 23.7%; Control 50/132 = 38%) was less frequent in horses with clinical signs in univariable testing (OR 0.48, 95% CI 0.3-0.8, P = 0.001). Age, sex, breed and degenerative joint disease were not retained in the final multivariable logistic regression step whereas morphologic variation remained significantly less present in horses with clinical signs. Main limitations Possible demographic differences between equine clinics. Conclusions Morphologic variation in the caudal cervical spine was detected more frequently in horses without clinical signs. Therefore, radiographic presence of such variation does not necessarily implicate the presence of clinical signs

Is the glass half full or half empty?: Perceptions of the scale and nature of corruption in the Netherlands

This paper summarises the empirical results of a study on the scale, nature and outcome of corruption cases in The Netherlands. It turns out that the number of convictions for corruption offences in The Netherlands has remained very stable in recent decades. Research into the nature of corruption leads to the conclusion that civil servants who are found to be susceptible to corruption tend not to be low-profile officials, but rather personalities with a reputation in the civil service organisation for being noticeable, colourful and astute 'fixers'. They frequently possess or demand the freedom to arrange matters on their own and are known as thorough and enterprising people. The research material further shows that the briber and the bribed usually know each other well before the violation of integrity occurs. This is not confined to business or instrumental relationships, because an element of friendship or affection is regularly involved. Something that plays a role in this setting is that trust is pivotal to prolonged corruption relationships. Research into the outcome of corruption cases leads to the conclusion that criminal prosecutions, once instituted, result, in nine out of ten instances, in a criminal conviction. Although suspects are sometimes acquitted on certain counts, complete acquittals are rare. The punishment most frequently handed down is a community service order. Combinations with other punishments occur regularly, with a custodial sentence or fine often being suspended. An average of five civil servants and three bribers actually end up behind bars each year