Sth1p, a Saccharomyces cerevisiae Snf2p/Swi2p homolog, is an essential ATPase in RSC and differs from Snf/Swi in its interactions with histones and chromatin-associated proteins

The essential Sth1p is the protein most closely related to the conserved Snf2p/Swi2p in Saccharomyces cerevisiae. Sth1p purified from yeast has a DNA-stimulated ATPase activity required for its function in vivo. The finding that Sth1p is a component of a multiprotein complex capable of ATP-dependent remodeling of the structure of chromatin (RSC) in vitro, suggests that it provides RSC with ATP hydrolysis activity. Three sth1 temperature-sensitive mutations map to the highly conserved ATPase/helicase domain and have cell cycle and non-cell cycle phenotypes, suggesting multiple essential roles for Sth1p. The Sth1p bromodomain is required for wild-type function; deletion mutants lacking portions of this region are thermosensitive and arrest with highly elongated buds and 2C DNA content, indicating perturbation of a unique function. The pleiotropic growth defects of sth1-ts mutants imply a requirement for Sth1p in a general cellular process that affects several metabolic pathways. Significantly, an sth1-ts allele is synthetically sick or lethal with previously identified mutations in histones and chromatin assembly genes that suppress snf/swi, suggesting that RSC interacts differently with chromatin than Snf/Swi. These results provide a framework for understanding the ATP-dependent RSC function in modeling chromatin and its connection to the cell cycle.     

Anorectal reconstruction by coloperineal anastomosis and dynamic double graciloplasty after abdomino-perineal resection

The aim of this study was to assess the technical and functional results of total anorectal reconstruction with double dynamic graciloplasty after abdominoperineal resection (APR). PATIENTS AND METHODS: From May 1995 to December 1996. 10 patients (6 males and 4 females), with a mean age of 54 years (range 39-74), underwent anorectal reconstruction for low rectal adenocarcinoma. All patients had preoperative radiotherapy and six had postoperative chemotherapy. The surgical procedure was performed in three stages: 1) APR, coloperineal anastomosis, double graciloplasty and ileostomy; 2) three months later, implantation of stimulator and leads; 3) after a two-months training period, the stoma was closed. RESULTS: There was no postoperative mortality. Early and late morbidity occurred in 5 patients: 2 colonic fistulas, 1 necrosis of colon, 1 ileostomy prolapse, 1 neosphincter stenosis, 1 sepsis of stimulator. No patient had recurrence of the disease (mean follow-up 16 months), but two patients died at 3 and 8 months, respectively from anorexia and pulmonary embolism. Seven patients were available for evaluation (2 fistula, 1 death). Before training, the resting pressure and the squeeze pressure were 30 and 175 cm H2O respectively. At the time of evaluation, the electrical stimulated pressure was 95 cm H2O. Six of these 7 patients were continent (5 with spontaneous defecation, 1 with enemas) and 1 was incontinent. CONCLUSIONS: Anorectal reconstruction with dynamic graciloplasty can be an alternative to permanent colostomy for selected patients after APR. However, there is a high morbidity and the quality of life of the patients must be evaluated.     

Characteristics of aluminum-implanted 6H-SiC samples after different thermal treatments

Multiple energy aluminum (Al) implantations were performed at room temperature in n-type epitaxial 6H-SiC layers, aiming at amorphizing the material from the surface up to a depth inferior to 0.5 μm. Annealings were then carried out in an induction furnace. The goal of this paper is to optimize the furnace geometrical configuration, in order to reduce the surface degradation and improve the crystal reordering. This optimization was established for one-side amorphized wafers, which need restricting annealing parameters, and is therefore supposed to be valid for less crystal damaging implantations. Two types of geometrical parameters were essentially studied: the internal configuration, which tends to increase the silicon partial pressure inside the reactor, and the position of the sample, which has a direct influence on the recrystallization and on the dopant electrical activation. The annealings are compared for the same thermal parameters: the plateau temperature (1700 °C), the annealing duration (30 min), and the heating rate (60 °C s⁻¹). The surface roughness was evaluated by using atomic force microscopy. Two final configurations were retained, leading to satisfactory results with respect to the as-implanted material: (i) Rutherford backscattering spectrometry in channeling geometry revealed a very good recrystallization in both cases, giving a signal level similar to the virgin crystal one; (ii) secondary ion mass spectrometry showed two distinct results depending on the sample position: one position led to some material etching, especially the SiC part which was amorphized by the implantation, and the second position gave rise to the deposition of a crudely monocrystalline SiC layer on the surface of the sample implanted side. This coating was found to prevent from any dopant loss by exodiffusion or material etching. Electrical measurements (four-point probe at 300 K) proved an Al substitutional ratio of 97 and 78% depending on the configuration, giving room temperature sheet resistances of about 2×10⁴ and 4×10⁴ Ω sq.⁻¹, respectively, for 4×10¹⁹ cm⁻³ Al implanted samples.     

Curing of unsaturated polyester resins: Viscosity studies and simulations in pre-gel state

The curing of styrene-unsaturated polyester (UP) resins was studied until gelation. The viscosity and gel points were measured during curing and were correlated with curing temperature, initiator concentration, and accelerator concentration. A gelation model concerning the formation of intra-crosslinked polymer coils, called microgels, was proposed. The model describes the gelation mechanism in four stages: induction, microgel formation, transition, and macro-gelation. The kinetic and gelation parameters of the model were experimentally obtained. The gel points and viscosities in the pre-gel state were simulated by the gelation model for isothermal and nonisothermal curings. Comparisons of the simulation results with experimental data showed good agreement.     

Construction of a complete genomic library of Saccharomyces cerevisiae and physical mapping of chromosome XI at 3·7 kb resolution

A consortium of European laboratories has been organized to systematically sequence the genome of Saccharomyces cerevisiae. As part of the BIOTECH program aimed at sequencing chromosomes XI and II, we have constructed a total genomic library of yeast strain FY1679 (a direct S288C derivative) into cosmid vectors pWE15 and pOU61cos. Primary clones from four independent libraries totalling 190 genome equivalents have been stored at ?80°C. A subset of 1939 independent clones (six genome equivalents) was hybridized using purified chromosomes XI and X as probes. A total of 147 chromosome XI-specific cosmid clones was used to construct the physical map of that chromosome. Mapping methods included a combination of classical bottom-up strategies (fingerprinting, hybridizations) and a novel top-down strategy using I-SceI chromosome fragmentation. The 147 cosmid clones form a unique contig covering the entire chromosome XI (666 kb) with the sole exceptions of the (C_1?3A)_n repeats of the telomeres. Colinearity of cosmid inserts with yeast DNA was directly verified. A complete EcoRI map of chromosome XI was deduced from partial overlaps of cosmids and used for the sequencing program. Comparison of this map with the genetic map shows unexpected divergences that have been solved by subsequent genetic analysis, yet underline the necessity of independent physical mapping in genome projects.     

Towards a Realization of a Wavelet Galerkin Method on Non-Trivial Domains

In this paper we describe a realization of a Wavelet–Galerkin method for numerically solving second order elliptic PDEs on general domains using the Wavelet Element Method (WEM) [4, 5]. Suitable C++ data structures allowing an efficient implementation of this method are described and numerical results also indicating the flexibility of our realization are presented.     

Semantic and pragmatic processing in FIDO: A flexible interface for data-base operations

This article deals with a flexible natural language interface to access data stored in a relational data base. This interface may prove of great value to the less sophisticated user.The FIDO system (Flexible Interface for Database Operations) is presented; it accepts queries issued in natural language (Italian) and translates them into relational algebra operations. FIDO is composed of a parser (not described in the paper), a two-level semantic network, which (among other things) expresses the correspondence between the natural language terms and the conceptual database objects, and a translator/optimizer, which translates the conceptual query into its logical equivalent (i.e. into a query expressed in terms of stored relations and their attributes). The article describes the main characteristics of the semantic network and addresses, in greater detail, the problem of query translation and optimization.The flexibility of FIDO is due to the complete independence of the semantic knowledge source from the logical schema of the data base. In fact, the logical schema can be designed on the basis of considerations not related to the overall structure of FIDO (e.g. the presence of particular types of applications that have to be implemented in a particularly efficient way). In principle, the (relational) data base could be preexistent with respect to the adoption of FIDO, in that the data structures used by the translator/optimizer and described in this paper are able to describe the correspondence between the conceptual model of the domain and different logical schemas.     

KINETIC AND STRUCTURAL STUDIES OF CALCIUM-BASED SORBENTS FOR HIGH-TEMPERATURE COAL-GAS DESULFURIZATION

The absorption of H₂S by large particles of limestone, dolomitic limestone and dolomite (average mass-radius of 0·40 mm) was tested under simulated coal gases. Below the calcination temperature of CaCO₃ (about 900^°C under 1 bar of CO₂), complete conversion of the calcium carbonate to calcium sulfide can only be achieved with dolomite. Above the calcination temperature of CaCO₃, the conversion to CaS is complete for all three sorbents in about one hour when 10,000 ppm H₂S is present in the gas phase. Large particles of limestone thus appear to be a suitable sorbent for high-temperature coal-gas desulfurization (above about 900 ^°C). A mathematical model based on the kinetic information collected in this work predicts the desulfurization performance of a packed or moving bed of limestone particles. Finally, a low-temperature regeneration scheme for the spent sorbent (CaS) in which sulfur can be subsequently recovered as the element is suggested.     

Improvement of weldability of TRIP steels by use of in‐situ pre‐ and post‐heat treatments

Low alloy TRIP‐aided steels are very interesting for the automotive industry as they combine both a high strength and an excellent formability. Though the actually developed TRIP steels can be considered as low alloyed when compared to the first generations of steels exhibiting TRIP effect, due to their chemical composition, they still exhibit a quite high carbon equivalent. This is particularly detrimental for the weldability of those materials. After solidification, welds are very hard and can show a brittle behaviour. The hardness of the heat affected zone of the welds can even exceed 500HV and cold cracking phenomena is prone to occur. In the automotive industry, spot welding is the main joining process. During spot welding of TRIP steels, the interface between the plates can act like a notch and promote fracture of the weld. This is particularly dangerous when brittle welds are submitted to peel stresses. The aim of the paper is to demonstrate that a careful choice of the process parameters can significantly improve the resistance of the welds. The selection of the welding cycle parameters is far from being an easy task as many different parameters are involved. Therefore, a design of experiment methodology (DOE) was chosen to optimise the welding cycle for a cold‐rolled TRIP steel with a tensile strength above 700 MPa. Mechanical properties of the welds were significantly improved by use of pre‐ and post‐heat treatments. Those improved welding cycles were realised without excessive extension of the total weld cycle on a conventional spot welding machine. This means that the optimised welds can be obtained in the existing production lines without any additional investment or significant decrease in productivity.