Depth-averaged relations for granular-liquid uniform flows over mobile bed in a wide range of slope values

The behavior of liquid-granular flows, driven by gravity, is experimentally analyzed. Two types of free-surface uniform flow can take place, having different boundary conditions at the bottom. The first one runs over a fixed surface behaving as a solid (non-deformable) impermeable wall; the second one runs over a mobile-bed at rest, formed by the same loose grains and liquid of the flowing mixture. In the paper we will mark the differences between the two, but focus on the latter one. The experiments span over, and characterize, the possible flow regimes. In mobile-bed uniform flows it has been found that the Froude number reduces as the slope increases. Accordingly, there is an increment of the solid-concentration. These results are meaning that as slope increases a progressive dominance and thickening of frictional layers over collisional ones is taking place through the flow depth. Same behaviours have been observed by changing the type of grains in the flowing mixture. These findings contrast with the case of flows over a solid wall, where different trends are observed. Application of force balances by means of Coulomb law provides interesting confirmation of what observed and allows to take into account the surface-tension effects, which come into play when the particles on top are going to desaturate. Experimental data have also been employed to assess the applicability of kinetic theories to wet granular flows. Energy and momentum balances, under the hypothesis of no contribution in the liquid phase (except for the added mass concept) to shear stress and to the energy processes, are applied throughout the flow depth of the solid phase. Although depth-averaged quantities come out to have a trend similar to the experimental one, deficiencies in the theoretical approach, mainly due to its inability to represent frictional contacts, are clearly detected. Same conclusions may be drawn by applying the quite simple Bagnold theory. Altogether, a more appropriate theory able to deal with both collisional and frictional mechanisms, including the transition between, is demanded.     

Beyond Intercalation‐Based Li‐Ion Batteries: The State of the Art and Challenges of Electrode Materials Reacting Through Conversion Reactions (Adv. Mater. 35/2010)

Despite the imminent commercial introduction of Li‐ion batteries in electric drive vehicles and their proposed use as enablers of smart grids based on renewable energy technologies, an intensive quest for new electrode materials that bring about improvements in energy density, cycle life, cost, and safety is still underway. This Progress Report highlights the recent developments and the future prospects of the use of phases that react through conversion reactions as both positive and negative electrode materials in Li‐ion batteries. By moving beyond classical intercalation reactions, a variety of low cost compounds with gravimetric specific capacities that are two‐to‐five times larger than those attained with currently used materials, such as graphite and LiCoO₂, can be achieved. Nonetheless, several factors currently handicap the applicability of electrode materials entailing conversion reactions. These factors, together with the scientific breakthroughs that are necessary to fully assess the practicality of this concept, are reviewed in this report.     

Impact of the guanidinium group on hybridization and cellular uptake of cationic oligonucleotides

The grafting of cationic groups to synthetic oligonucleotides (ONs) in order to reduce the charge repulsion between the negatively charged strands of a duplex or triplex, and consequently to increase a complex's stability, has been extensively studied. Guanidinium groups, which are highly basic and positively charged over a wide pH range, could be an efficient ON modification to enhance their affinity for nucleic acid targets and to improve cellular uptake. A straightforward post-synthesis method to convert amino functions attached to ONs (on sugar, nucleobase or backbone) into guanidinium tethers has been perfected. In comparison to amino groups, such cationic groups anchored to alpha-oligonucleotide phosphoramidate backbones play important roles in duplex stability, particularly with RNA targets. This high affinity could be explained by dual recognition resulting from Watson-Crick or Hoogsteen base pairing combined with cationic/anionic backbone recognition between strands involving H-bond formation and salt bridging. Molecular-dynamics simulations corroborate interactions between the cationic backbones of the alpha-ONs and the anionic backbones of the nucleic acid targets. Moreover, ONs with guanidinium modification increased cellular uptake relative to negatively charged ONs. The cellular localization of these new cationic phosphoramidate ONs is mainly cytoplasmic. The uptake of these ON analogues might occur through endocytosis.     

Rational Criterion for Designing Opening of Slit-Check Dam

This paper presents a theoretical approach to the problem of designing the opening in a slit-check dam. The approach is based on the conservation of the mass of water and sediments and on the energy balance under steady conditions. It leads to a relationship among opening width, sediment characteristics, mountain river geometry, and water and sediment discharge. The final relationship can be simplified to make it suitable for practical applications. Also, the problem of unsteadiness of both water and sediment is considered, as well as the possibility of treating the unsteady flow as a sequence of steady states. The results of the theory were checked in a laboratory investigation using a scale model. Different opening widths were tested under conditions of steady and unsteady supplies of water and sediment. The mean grain size of the sediment, as well as the rates of sediment and water discharge, were changed in the experiments. The results of the experiments confirm the theory quite well.     

A Gd-Film Thermomagnetic Generator in Resonant Self-Actuation Mode

Thermomagnetic generation is a promising technology for conversion of low-grade waste heat into electricity. Key requirements for the development of efficient thermomagnetic generators (TMGs) are tailored thermomagnetic materials as well as innovative designs enabling fast heat transfer. Recently, film-based thermomagnetic generators are developed that operate in the mode of resonant self-actuation enabling high frequency and stroke of a movable cantilever and, thus, efficient conversion of thermal energy into electrical energy. Here, the performance of a Gadolinium (Gd)-film-based TMG that is optimized for resonant self-actuation near room temperature is reported. The Gd-film TMG exhibits large oscillation frequencies up to 106 Hz and large strokes up to 2 mm corresponding to 38% of the oscillating cantilever's length. This performance occurs in a sharply bound range of ambient temperatures with an upper limit near the film's ferromagnetic to paramagnetic transition temperature T_c of 20 °C and of heat source temperatures ranging between 40 and 75 °C. The maximum power per footprint is 23.8 µWcm⁻², at which the Gd film undergoes a temperature change of only 0.9 °C at ≈10 °C above T_c.     

Explaining the <Literal>cumulative</Literal> propagator

The global cumulative constraint was proposed for modelling cumulative resources in scheduling problems for finite domain (FD) propagation. Since that time a great deal of research has investigated new stronger and faster filtering techniques for cumulative, but still most of these techniques only pay off in limited cases or are not scalable. Recently, the “lazy clause generation” hybrid solving approach has been devised which allows a finite domain propagation engine possible to take advantage of advanced SAT technology, by “lazily” creating a SAT model of an FD problem as computation progresses. This allows the solver to make use of SAT explanation and autonomous search capabilities. In this article we show how, once we use lazy clause generation, modelling the cumulative constraint by decomposition creates a highly competitive version of cumulative. Using decomposition into component parts automatically makes the propagator incremental and able to explain itself. We then show how, using the insights from the behaviour of the decomposition, we can create global cumulative constraints that explain their propagation. We compare these approaches to explaining the cumulative constraint on resource constrained project scheduling problems. All our methods are able to close a substantial number of open problems from the well-established PSPlib benchmark library of resource-constrained project scheduling problems.     

Long-term results of intrarenal surgery for branched calculi: is such surgery still valid?

OBJECTIVE: To evaluate whether intrarenal surgery for branched calculi remains valid in the light of current new techniques, e.g. percutaneous nephrolithotomy and extracorporeal shockwave lithotripsy. PATIENTS AND METHODS: Between January 1978 and October 1984, 44 patients (24 male and 20 female, mean age 42.5 years, range 14-66) underwent complex surgery for large stones, requiring opening of the renal pelvis and a transparenchymal approach to the calices; 47 renal units were operated in 49 procedures. The evaluation before surgery included creatinine and blood nitrogen levels, blood pressure measurement, urine culture, abdominal plain X-ray (44 patients), intravenous urography (42) and isotopic renography with renal scintigraphy (five). Renal lithiasis was categorized and all patients underwent extended pyelolithotomy with a transparenchymal approach, achieved by partial nephrectomy (six patients), radial paravascular nephrotomy (10), posterior lower nephrolithotomy (29), resection of the posterior segment (two), and posterior segmentotomy and reconstruction (2); 16 operations were performed under ischaemia. In October 1996, the patients were clinically evaluated by serum creatinine levels (42), urine cultures (42), abdominal plain X-ray (42), IVU (34), isotopic renography (eight), renal ultrasonography (eight) and blood pressure measurement (44). The mean follow-up was 14.8 years. RESULTS: The major postoperative complications were; residual stones (six patients), fistula with ureteric stenosis (one, with a permanent nephrostomy), toxic temporary hepatic failure (one), femoral arterial embolism (one, resolved using a Fogarty catheter) and recurrent large stones (two, operated 1 and 5 years later). From 1984 to 1996, 19 patients had recurrent stones and two underwent dialysis. In October 1996, the renal function of 47 renal units was stable or normal in 36 (77%), reduced in seven (15%) and lost in four (8%); 24 patients were hypertensive (12 preoperatively), nine have urinary tract infection, three are positive for hepatitis B or C virus, and lithiasis has recurred in 15 renal units. CONCLUSIONS: Intrarenal surgery, conducted using modern anatomical guidelines, was an effective treatment for renal branched stones. The long-term results are satisfactory after appropriate correction of the urinary tract, with the consequent prevention of stasis and chronic infection. The definitive comparison between surgical and combined endoscopic/extracorporeal methods will only become clear when there is a comparable follow-up. Currently, surgery remains preferable in patients with giant calculi, a small pelvis and prevalent calyceal development.     

Statistical simulation of leakage currents in MOS and flash memory devices with a new multiphonon trap-assisted tunneling model

A new physics-based model of leakage current suitable for MOS and Flash memory gate oxide is presented in this paper. This model, which assumes the multiphonon trap-assisted tunneling as conduction mechanism, calculates the total leakage current summing the contributions of the percolation paths formed by one or more aligned traps. Spatial positions and energetic levels of traps have been randomly generated within the oxide by a random number generator which has been integrated into the model. Using this model, statistical simulations of leakage currents measured from both MOS and Flash EEPROM memory tunnel oxides have been carried out. In this way, experimental leakage current distributions can be directly reproduced, thus opening a wide range of useful applications in MOS and Flash EEPROM memory reliability prediction.