An algorithm for computing compatibly Frobenius split subvarieties

This paper describes an algorithm which produces all ideals compatible with a given surjective Frobenius near-splitting.     

Homogenization and crystallization of histidine ammonia-lyase by exchange of a surface cysteine residue

Histidase (histidine ammonia-lyase, EC 4.3.1.3) from Pseudomonasputida was expressed in Escherichia coli and purified. In theabsence of thiols the tetrameric enzyme gave rise to undefinedaggregates and suitable crystals could not be obtained. Thesolvent accessibility along the chain was predicted from theamino acid sequence. Among the seven cysteines, only one waslabeled as `solvent-exposed'. The exchange of this cysteineto alanine abolished all undefined aggregations and yieldedreadily crystals diffracting to 1.8 Å resolution.     

Cyclic diamides with (CH2) x segments: Phase transitions in the solid state

Summary Cyclic diamides with various CH₂ segment lengths were synthesized. Cyclo-(octamethylene sebacamide) I, x=8, was investigated as a model system by means of calorimetry, X-ray diffraction and Raman spectroscopy with special emphasis on its phase behaviour. In the low temperature phase the molecules exist as collapsed rings where the amide groups are located in the folds and the straight stems consist of nondisordered CH₂ segments. During the solid phase transition at about 84°C a strong increase of conformational disorder (4 additional gauche defects per molecule) occurs which does not change significantly during subsequent melting. It is shown that the conformation of the molecules in the high temperature phase is similar to that in the melt (liquid-like). In spite of conformational disorder the linewidth of the X-ray reflection peaks is smaller in the high temperature phase compared to that in the solution crystallized phase.     

Increased Reactor Performance versus Reactor Safety Aspects in Acrylate Copolymerization

The aim of reducing cycle times of semibatch‐polymerization processes requires systematic investigations of the kinetics, careful adjustment of the desired polymer properties, proper thermal reactor design and reliable reactor safety assessment [1]. As a concrete example, a semibatch‐copolymerization was carefully examined with respect to four different aspects. Thermo‐kinetics of the reaction were investigated with isoperibolic reaction calorimetry and GC. In order to obtain reliable values for the overall heat transfer coefficient of the production scale reactor, cooling experiments were carried out with solvent and final copolymer solution as reactor content. For consistent reactor safety assessment additional investigations are necessary including case studies of breakdown incidences. These simulations were performed with a mathematical model based on the GC data and experimental vapor pressure curves. As a result of these calculations, a reduction of reaction time from 10 to 6 hours was possible. To convert into practice, it must be ensured that even in this shortened time a product of the same quality is produced.     

Enhanced cGMP Interactor Rap Guanine Exchange Factor 4 (EPAC2) Expression and Activity in Degenerating Photoreceptors: A Neuroprotective Response?

The disease retinitis pigmentosa (RP) leads to photoreceptor degeneration by a yet undefined mechanism(s). In several RP mouse models (i.e., rd mice), a high cyclic GMP (cGMP) level within photoreceptors is detected, suggesting that cGMP plays a role in degeneration. The rap guanine exchange factor 4 (EPAC2) is activated by cyclic AMP (cAMP) and is an accepted cGMP-interacting protein. It is unclear whether and how cGMP interacts with EPAC2 in degenerating photoreceptors; we therefore investigated EPAC2 expression and interactions with cGMP and cAMP in retinas of the rd1 and rd10 models for retinal degeneration. EPAC2 expression in the photoreceptor layer increased significantly during rd1 and rd10 degeneration, and an increase in EPAC2 interactions with cGMP but not cAMP in the rd1 was also seen via a proximity ligation assay on histological sections. Retinal explant cultures revealed that pharmacological inhibition of the EPAC2 activity reduced the photoreceptor layer thickness in the rd10 retina, suggesting that EPAC2 inhibition promotes degeneration. Taken together, our results support the hypothesis that high degeneration-related cGMP leads to increased EPAC2 and cGMP interactions, inhibiting EPAC2. By inference, EPAC2 could have neuroprotective capacities that may be exploited in the future.     

Pepsinogen synthesis during long-term culture of porcine chief cells

This article describes suicide-related penal legislation in contemporary Europe, and analyzes and relates the results to cultural attitudes towards suicide and to national suicide rates. Data were obtained from 42 legal entities. Of these, 34 have penal regulations which--according to definition--chiefly and directly deal with suicide. There are three main types of act: aiding suicide, abetting suicide, and driving to suicide. The laws vary considerably with regard to which acts are sanctioned, how severely they are punished, and whether any special circumstances such as the motive, the result, or the object can make the crime more serious. Various ideologies have inspired legislation: religions, the euthanasia movement, and suicide prevention have all left their mark. There are some cases in which neighboring legal systems have clearly influenced laws on the topic. However, the process seems mostly to have been a national affair, resulting in surprisingly large discrepancies between European legal systems. The laws seem to reflect public opinions: countries which punish the crimes harder have significantly less permissive cultural attitudes towards suicide. Likewise, suicide rates were significantly higher in countries with a narrow scope of criminalization and milder punishments for suicide-related crimes. The cultural and normative elements of society are connected with its suicide mortality.     

Life cycle assessment of bio-methane and biogas-based electricity production from organic waste for utilization as a vehicle fuel

Clean Technologies and Environmental Policy - The concerns about climate change, energy security and price fluctuation of fossil fuels are driving the growing interest in the development and...     

Highly diastereoselective synthesis of 11β,17β-diaryl-18a-homo-19-nor steroids

In a highly diastereoselective fashion novel 11β, 17β-diaryl steroids 17 and 18 were synthesized via Birch-type reduction [1] of styrylic precursors 11 and 15 . Both precursors were readily available by Suzuki-type coupling reactions [2] of aromatic boronic acids [3] and the corresoponding enol triflates 6, 10 , and 14 . Regioselective 17-enol triflate formation in presence of a 11-keto function could be demonstrated in case of steroid 5 . The remarkably high degree of stereo-selectivity observed parallels results from the natural series [4] and demonstrated a broader applicability of such single electron transfer reductions in stereoselective transformations on the steroid skeleton.