The positive-acting sulfur regulatory protein CYS3 of Neurospora crassa: nuclear localization, autogenous control, and regions required for transcriptional activation

The positive-acting global sulfur regulatory protein, CYS3, of Neurospora crassa turns on the expression of a family of unlinked structural genes that encode enzymes of sulfur catabolism. CYS3 contains a leucine zipper and an adjacent basic region (b-zip), which together constitute a bipartite sequence-specific DNA-binding domain. Specific anti-CYS3 antibodies detected a protein of the expected size in nuclear extracts of wild-type Neurospora under conditions in which the sulfur circuit is activated. The CYS3 protein was not observed in cys-3 mutants. Nuclear extracts of wild type, but not cys-3 mutants, also showed specific DNA-binding activity identical to that obtained with a CYS3 protein expressed in Escherichia coli. A truncated CYS3 protein that contains primarily the b-zip domain binds to DNA with high specificity and affinity in vitro, yet fails to activate gene expression in vivo, and instead inhibits the function of the wild-type CYS3 protein. Amino-terminal, carboxyterminal, and internal deletions as well as alanine scanning mutagenesis were employed to identify regions of the CYS3 protein that are required for its trans-activation function. Regions of CYS3 carboxy terminal to the b-zip motif are not completely essential for function although loss of an alanine-rich region results in decreased activity. All deletions amino terminal to the b-zip motif led to a complete loss of CYS3 function. Alanine scanning mutagenesis demonstrated that an unusual prolinerich domain of CYS3 appears to be very important for function and is presumed to constitute an activation domain. It is concluded that CYS3 displays nuclear localization and positive autogenous control in Neurospora and functions as a trans-acting DNA-binding protein.     

Degradation of retinyl acetate in simple solvent systems

The degradation of vitamin A acetate was studied by u.v. spectrophotometry in three solvent systems: absolute ethanol, ethanol: water (95:5) and hexanes. Three potential degradative factors were investigated: exposure to light, presence of air and temperature. In all systems studied, exposure to light was the major factor. In the ethanol systems, the rate constants calculated for the degradation in the presence or in the absence of oxygen are not significantly different. Analysis of the data by first order kinetic models yielded the best fit in all cases. The activation energy for the degradation reaction in absolute ethanol was found to be 56 ± 8 kJ/mol. The presence of water in ethanol did accelerate the reaction, but the dependence of the rate on the water content is not a simple one.     

Singularity Analysis of Lower Mobility Parallel Manipulators Using Grassmann–Cayley Algebra

This paper introduces a methodology to analyze geometrically the singularities of manipulators, of which legs apply both actuation forces and constraint moments to their moving platform. Lower mobility parallel manipulators and parallel manipulators, of which some legs have no spherical joint, are such manipulators. The geometric conditions associated with the dependency of six PlUumlcker vectors of finite lines or lines at infinity constituting the rows of the inverse Jacobian matrix are formulated using Grassmann-Cayley algebra (GCA). Accordingly, the singularity conditions are obtained in vector form. This study is illustrated with the singularity analysis of four manipulators.     

Base Flip in DNA Studied by Molecular Dynamics Simulations of Differently-Oxidized Forms of Methyl-Cytosine

Distortions in the DNA sequence, such as damage or mispairs, are specifically recognized and processed by DNA repair enzymes. Many repair proteins and, in particular, glycosylases flip the target base out of the DNA helix into the enzyme’s active site. Our molecular dynamics simulations of DNA with intact and damaged (oxidized) methyl-cytosine show that the probability of being flipped is similar for damaged and intact methyl-cytosine. However, the accessibility of the different 5-methyl groups allows direct discrimination of the oxidized forms. Hydrogen-bonded patterns that vary between methyl-cytosine forms carrying a carbonyl oxygen atom are likely to be detected by the repair enzymes and may thus help target site recognition.     

Degradation Kinetics of Anthocyanin of Traditional and Low-Sugar Blackberry Jam

The objective of this study was to monitor the stability of anthocyanin and phenolic compounds contained in two formulations of blackberry jam (traditional and low-sugar) during storage. For that purpose, jams were prepared with varying amounts of hydrocolloids and investigated as to pH, total soluble solids, water activity, total acidity, total anthocyanins and total polyphenols. In order to accompany and assess the levels of phenolic compounds and colour (L*, a* and b*) changes, the samples were stored for 180 days at two different temperatures (10 and 25 °C). The Arrhenius model was used to determine the relationship between the reaction rate (k) at the different storage temperatures, yielding activation energy values of 19 and 12 kcal/mol and Q ₁₀ values of 3.0 and 2.0 for traditional and low-sugar jams, respectively. The results show that by the end of the storage time investigated, the anthocyanin compounds had been partially degraded, with the greatest loss being observed in traditional jam stored at 25 °C. Colour stability was also lower in traditional jam as compared to the low-sugar product.     

Methanogenic fermentation of scots pine (Pinus sylvestris) sawdust: Enhancement by physicochemical pretreatment

The three major polymeric components of Scots Pine sawdust–lignin, hemicellulose and cellulose–represent potential substrates for methanogenic fermentation although, in the absence of physicochemical pretreatment, low digestibility was demonstrated even after protracted incubation (18 months). Acid (H₂SO₄) and alkali (NaOH) pretreatments mediated different effects although, in general, the rates and percent solubilisations increased with concentration, temperature, pressure and time, either singly or in combination. Individual methanogenic fermentations with the hydrolysates and residual solids showed that although 3.3% more methane resulted from the H₂SO₄ hydrolysate than the corresponding NaOH hydrolysate, in total, 7% more methane was generated from the two alkali fractions than from the corresponding acid fractions. The results thus exemplified that choice of a specific physicochemical strategy must be made in conjunction with the expected yield from the selected fraction(s).     

Implementation of a New Linear Control Technique Based on Experimentally Validated Small-Signal Model of Three-Phase Three-Level Boost-Type Vienna Rectifier

In this paper, the design and implementation of a new multiple-input-multiple-output linear control technique based on a theoretically established and experimentally validated small- signal model for the three-phase three-level boost-type ac/dc Vienna converter are presented. Averaging and local linearization techniques are used to derive the dynamic model expressed in the dqo reference frame. The resulted transfer functions are discretized for the sake of a digital controller design. Multiple-loop control strategy is adopted and consists of inner current feedback loops, which are based on the straightforward looping technique that neglects interactions between the dq components of control inputs and currents, respectively, and of an outer voltage loop, which is designed to ensure dc voltage regulation by adjusting the magnitude of the references for the inner current loops. The output dc voltage unbalance is also controlled in the inner loops. The proposed modeling and control approaches are first simulated and then validated on a 1.5-kW laboratory prototype supported by the DS 1104 digital real-time controller board of dSPACE. The obtained results prove the accuracy of the proposed new small-signal model and, therefore, its reliability for dynamic analysis and control design purposes. It is also proved that a judicious choice of controller parameters, as well as an adequate rating of boost inductors, allows one to meet the IEEE standard requirements in terms of ac line-current total harmonic distortion and power factor. The efficiency of the proposed control technique is maintained in case of disturbances occurring on both source and load sides.     

Thin‐film encapsulated white organic light top‐emitting diodes using a WO3/Ag/WO3 cathode to enhance light out‐coupling

An alternative design of a semitransparent cathode for top‐emission white‐fluorescent organic light‐emitting diodes (OLEDs) has been investigated. The scope of this study was to improve the luminance of OLEDs used for displays while keeping the current density versus voltage characteristic unchanged for addressing purposes. The use of an optical simulation tool allowed the optimization of the tri‐layer cathode WO₃/Ag/WO₃ to increase the light out‐coupling coefficient of the device leading to an increased white emission compared with a reference device with a Ca/Ag cathode. An increase of ~40% in luminance has been calculated by simulation and experimentally confirmed. The p‐i‐n OLED structure underneath the tri‐layer cathode allowed an efficient injection of electrons independently from the work function of WO₃. The WO₃/Ag/WO₃ cathode has been also confirmed to be compatible with the atomic layer deposition technique for thin film encapsulation. Finally, lifetime measurements up to 600 h have been carried out to quantify the enhancements induced by the new cathode compared with the control device. It has been found that lifetimes of both cathode architectures are similar on this time scale, while the WO₃/Ag/WO₃ cathode shows a lower voltage drift versus aging.     

Craniocervical junction tuberculosis: a rare but dangerous disease

BACKGROUND: Mycobacterium tuberculosis of the cervical spine is a rare but dangerous manifestation of extra-pulmonary tuberculosis. The clinical picture ranges from early, nonspecific, insidious symptoms to severe neurological complications and death, attributed to craniocervical junction instability and cervicomedullary compression. The different lines of management include antituberculous medication with traction and external fixation or adjunctive surgery (debridement and stabilization) in patients with severe or persistent neurological complications and/or vertebral instability. METHODS: We describe two patients with advanced craniocervical junction tuberculosis. The early clinical picture was nonspecific in Case 1 and obscured by psychiatric illness in Case 2. The detailed clinical and radiological findings, and the management, will be described. Involvement of the occipital condyles and foramen magnum, which has not been reported previously, will be demonstrated. RESULTS: Both cases underwent transoral biopsy, aspiration, and debridement of retropharyngeal abscess (granuloma). Histological and tissue culture studies proved the abscesses were tuberculous and anti-tuberculous medications were started. Case 1 showed complete resolution of the clinical and radiological findings. Case 2 developed cardiorespiratory arrest while in a halo jacket. He was resuscitated but remained quadriplegic and semiconscious; he developed nosocomial gram negative pneumonia. He was referred back to his local hospital where he died 1 year later. CONCLUSIONS: Tuberculosis is an infrequent but notable cause of cervicomedullary compression. It should be suspected in patients with infective spondylitis who are immunocompromised or reside in an area highly endemic for tuberculosis. Management strategies include antituberculosis medication, transoral biopsy and drainage of the abscess, traction and external fixation, posterior decompression, and internal fixation, according to the clinical and radiological findings.