High via resistance induced by ionized metal plasma vapor deposition of titanium liner film

For via structures landed on aluminum lines, a significant increase of via resistance has been observed if the titanium (Ti) via liner is introduced by the ionized metal plasma (IMP) vapor deposition method instead of the standard physical vapor deposition method. To understand the underlying mechanism of this phenomenon, the reaction between the IMP deposited Ti and the aluminum under-layer has been studied. The experimental results indicate that during IMP-Ti deposition, energetic titanium ions react with the aluminum under-layer, forming a resistive titanium aluminide (TiAl_x) layer. This reaction can be further enhanced by accelerating the titanium ions with a more negative substrate bias. The existence of this TiAl_x layer at the via interface contributes to the elevated via resistance that has been observed at subsequent electrical parametric testing.     

Stereospecific formation of a ternary complex of (S)-α,β-fluoromethylene-dATP with DNA pol β

The influence of water: crystallization of (R/S)-α,β-CHF-dATP with the preorganized pol β-DNA complex shows that (S)-α,β-CHF-dATP is preferentially bound to the active site with the C=F fluorine proximal to a structural water bound to Asp276.     

Time-resolved interventional cardiac C-arm cone-beam CT: an application of the PICCS algorithm

Time-resolved cardiac imaging is particularly interesting in the interventional setting since it would provide both image guidance for accurate procedural planning and cardiac functional evaluations directly in the operating room. Imaging the heart in vivo using a slowly rotating C-arm system is extremely challenging due to the limitations of the data acquisition system and the high temporal resolution required to avoid motion artifacts. In this paper, a data acquisition scheme and an image reconstruction method are proposed to achieve time-resolved cardiac cone-beam computed tomography imaging with isotropic spatial resolution and high temporal resolution using a slowly rotating C-arm system. The data are acquired within 14 s using a single gantry rotation with a short scan angular range. The enabling image reconstruction method is the prior image constrained compressed sensing (PICCS) algorithm. The prior image is reconstructed from data acquired over all cardiac phases. Each cardiac phase is then reconstructed from the retrospectively gated cardiac data using the PICCS algorithm. To validate the method, several studies were performed. Both numerical simulations using a hybrid motion phantom with static background anatomy as well as physical phantom studies have been used to demonstrate that the proposed method enables accurate reconstruction of image objects with a high isotropic spatial resolution. A canine animal model scanned in vivo was used to further validate the method.     

Thermal stability of SiC Schottky diode anode and cathode metalisations after 1000 h at 350 °C

The thermal stability of two commercially available silicon carbide Schottky diode types has been evaluated following a 1000 h non-biased storage test under vacuum at 350 °C. The Ti-based Schottky (Anode) contact shows excellent stability over the duration of the test with less than 5% change in either extracted Schottky barrier height or ideality values. The Al die attach metalisation on the anode also shows no evidence of degradation after the test. However, a considerable change in series resistance was observed for both diode types, with up to a factor of 100 measured for one of the diodes. The primary early failure mode is related to degradation of the NiAg Ohmic (cathode) die attach metalisation. Demixing of the NiAg alloy, leading to Ag agglomeration is proposed to be the underlying degradation mechanism involved resulting in delamination of the die attach metalisation and the corresponding series resistance increase.     

A review of membrane selection for the dehydration of aqueous ethanol by pervaporation

Four broad types of membranes are categorised: organic polymers generally, crosslinked poly(vinyl alcohol), organic-inorganic hybrids and charged polymers. The best performers in terms of flux, which reaches a maximum of 5 kg/m²h, are anionic or cationic polymers, including polysalts. Polyanion and polysalt membranes are superior. Two examples are thin layers of the active polysalt membrane on a supporting membrane. The best combination for flux and selectivity is a polyethyleneimine/poly (acrylic acid) polysalt deposited on a reverse osmosis membrane, at 4 kg/m²h and 1075 respectively. It is noticeable that hybrid poly(vinyl alcohol)/inorganic membranes do not show enhanced fluxes. Very high separation factors were observed, covering a range of polymers, of neutral, anionic or cationic character. The top results (>10,000) were for charged membranes, either cationic or anionic, but not polysalts. The fluxes encountered here were miniscule, the best being caesium alginate at about 1 kg/m²h. The ideal structure for high fluxes would appear to be one containing discrete domains of oppositely charged species of optimal size. Fresh approaches are being actively studied, such as layer-by-layer deposition of oppositely charged polyelectrolytes, with due attention to appropriate separation of the sites of opposite character.     

Total replacement of solvent in polyurethane synthesis using carbon dioxide soluble 1,3‐dichlorodistannoxane catalysts

This work demonstrates catalytic synthesis of polyurethanes using 1,3‐dichlorodistannoxane catalysts ( 1 ) in carbon dioxide (CO₂) and carbon dioxide expanded liquids (CXL). Catalytic polyurethane synthesis was also performed in pure organic solvent (dimethylformamide) for comparison. In this study, mainly, 4, 4′‐methylene‐bis‐(phenyl isocyanate) (MDI) as the diisocyanate precursor and ethylene glycol (EG) as the diol precursor were used for polyurethane synthesis. In addition to MDI, hexamethylene diisocyanate (HDI), toluene diisocyanate (TDI), and p‐isocyanatobenzylisocyanate (PIBI) were also used for polyurethane synthesis with different diols or triol in CO₂. Polyurethanes with a molecular weight ranging from 3000 to 70,000 were synthesized depending upon the combination of diisocyanate and diol used. Comparable yields of polyurethanes were obtained using an all butyl group substituted ( 1a ) catalyst in CO₂ (55 bars, 50°C) and in DMF (50°C). Additionally, the yield and polydispersity index (PDI) of polymer formed in neat CO₂ was comparable with those synthesized in the largely used organic solvent DMF. Interestingly, catalyst 1a in CXL (55 bars, 50°C) gave higher yields, and polymers with lower PDI (1.19). Reactions carried out in scCO₂ at 145 bars using PIBI and EG were found to be about three times faster than the reaction carried out in DMF. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Transport and Entrapment of Particles in Steel Continuous Casting

A particle-capture model based on local force balances has been developed, implemented into computational models of turbulent fluid flow and particle transport, and applied to simulate the entrapment of slag inclusions and bubbles during the continuous casting of steel slabs. Turbulent flow of molten steel is computed in the nozzle and mold using transient computational fluid flow models, both with and without the effects of argon gas injection. Next, the transport and capture of many particles are simulated using a Lagrangian approach. Particles touching the dendritic interface may be pushed away, dragged away by the transverse flow, or captured into the solidifying shell according to the results of a local balance of ten different forces. This criterion was validated by reproducing experimental results in two different systems. The implications of this criterion are discussed quantitatively. Finally, the fluid flow/particle transport model results and capture criterion are applied together to predict the entrapment distributions of different sized particles in a typical slab caster. More large particles are safely removed than small ones, but the entrapment rate into the solidifying shell as defects is still very high.     

The Hydroxide‐Promoted Catalytic Hydrodefluorination of Fluorocarbons by Ruthenium in Aqueous Media

A ruthenium complex ligated by the non‐innocent protic ligand 2,6‐imidizoylpyridine (IPI) in aqueous potassium hydroxide media is shown to be a suitable catalyst for the C F bond activation and subsequent hydrodefluorination (and hydrogenolysis) of a model fluorocarbon. Furthermore, the conversion of C F bonds was enhanced upon increasing the concentration of potassium hydroxide [KOH]. A simple, non‐ligated heterogeneous analogue derived from ruthenium(III) trichloride trihydrate dissolved in aqueous potassium hydroxide is shown to be an even more active catalyst, capable of hydrodefluorination of aryl fluorocarbons at room temperature and alkyl fluorocarbons under more forcing conditions.     

UPCBLAS: a library for parallel matrix computations in Unified Parallel C

The popularity of Partitioned Global Address Space (PGAS) languages has increased during the last years thanks to their high programmability and performance through an efficient exploitation of data locality, especially on hierarchical architectures such as multicore clusters. This paper describes UPCBLAS, a parallel numerical library for dense matrix computations using the PGAS Unified Parallel C language. The routines developed in UPCBLAS are built on top of sequential basic linear algebra subprograms functions and exploit the particularities of the PGAS paradigm, taking into account data locality in order to achieve a good performance. Furthermore, the routines implement other optimization techniques, several of them by automatically taking into account the hardware characteristics of the underlying systems on which they are executed. The library has been experimentally evaluated on a multicore supercomputer and compared with a message‐passing‐based parallel numerical library, demonstrating good scalability and efficiency. Copyright © 2012 John Wiley & Sons, Ltd.