The effect of biphasic waveform tilt in transvenous atrial defibrillation

Atrial defibrillation can be accomplished using low energy shocks and transvenous catheters. The biphasic waveform tilt required to achieve optimal atrial defibrillation thresholds (ADFTs) is, however, not known. The effect of single capacitor biphasic waveform tilt modification on ADFT was assessed in 20 patients. Following AF induction the defibrillation pulses were delivered between the catheters positioned in the coronary sinus and the right atrium. The single capacitor biphasic waveform shocks, delivered over the same pathways, consisted of 65% tilt (65/65 biphasic waveform) to produce an overall tilt of 88%, or 50% tilt (50/50 biphasic waveform) to produce an overall tilt of 75%. Although 65/65 biphasic waveform delivers more energy, the shorter duration 50/50 biphasic waveform reduced stored energy ADFT 21%, from 1.34 +/- 0.82 J with 65/65 biphasic to 1.06 +/- 0.81 J. These differences were not statistically significant. Nine patients had lower ADFT with 50/50 biphasic waveform while five patients had lower ADFT with 65/65 biphasic waveform. Equivalent reduction in ADFT was seen in the remaining six patients. The ADFT was 0.83 +/- 0.65 J when both tilts were considered. In conclusion, biphasic waveform tilt modification may affect the ADFT in an individual patient. The optimal biphasic waveform for ADFT is not known.     

Determining the Castability of Simple Polyhedra

A polyhedron P is castable if its boundary can be partitioned by a plane into two polyhedral terrains. Castable polyhedra can be manufactured easily using two cast parts, where each cast part can be removed from the object without breaking the cast part or the object. If we assume that the cast parts are each removed by a single translation, it is shown that for a simple polyhedron with n vertices, castability can be decided in time and linear space using a simple algorithm. A more complicated algorithm solves the problem in time and space, for any fixed ε > 0. In the case where the cast parts are to be removed in opposite directions, a simple O(n ² )-time algorithm is presented. Finally, if the object is a convex polyhedron and the cast parts are to be removed in opposite directions, a simple algorithm is presented. Received June 1, 1994; revised May 25, 1995.     

The effects of stress on memory and the hippocampus throughout the life cycle: implications for childhood development and aging

Studies in animals showing hippocampal atrophy and associated memory deficits in stress and aging have implications for stress and aging in humans. Clinical studies in traumatized human populations with posttraumatic stress disorder (PTSD) have replicated studies in animals, showing reduction in volume of the hippocampus measured with magnetic resonance imaging and associated memory deficits. Trauma at different stages of development (early childhood abuse versus trauma in later life due to combat) may influence the nature of memory deficits and hippocampal atrophy. Studies in aging human subjects are consistent with animal studies, although future research is needed in this area. The similarities between biological findings related to cortisol and the hippocampus in stress and aging in both animal and human studies raises the question of whether PTSD can be seen as a form of accelerated aging. Evidence that stress affects the hippocampus and the capacity for learning has broad implications for public health policy, underlying the need for additional resources in this important area and a reexamination of our understanding of factors influencing academic achievement.     

Duodenoesophageal reflux induces esophageal adenocarcinoma without exogenous carcinogen

Central nervous system (CNS) disease is a major feature of simian immunodeficiency virus (SIV) infection of macaques. To define the spectrum of CNS lesions in SIV-infected macaques and the potential associations with viral strain and disease course, we performed a retrospective analysis of necropsies on 124 macaques with SIV-induced AIDS. Histologic evidence of CNS disease was observed in 71 (57.3%) of the 124 animals. SIV encephalitis was the most common CNS lesion occurring in 43.7% (31/71) of the animals with CNS disease and 25% of all animals. The incidence of SIVE correlated significantly with shortened survival (P=0.0207). In addition, SIVE was seen in 42.9% (15/35) of rapid progressors (animals that died within 200 days) compared to only 18% (16/89) of normal progressors (animals that lived longer than 200 days) (P=0.011). Animals with SIVE had higher viral loads in peripheral blood than those that did not, but this difference did not reach statistical significance. Similarly, while animals infected with uncloned SIVmac251 had a higher incidence of SIVE (27.5%; 14/51) than animals infected with molecularly cloned SIVmac239 and its T-cell tropic derivatives (18.5%; 10/54) this difference was not statistically significant. In this study rapid disease progression and SIVE were highly correlated making separation of viral determinants of virulence from those of neurovirulence difficult.     

Solutions of the general equations for the radiation dose dependence of the molecular weights of irradiated polymers with an initial Schulz-Zimm distribution

Summary The general equations for the radiation dose dependence of irradiated polymer molecular weights have been solved exactly. For an initial most probable molecular weight distribution (=1), the solutions are analytical and exact. For the general case (1) the solutions are numerical and exact. The present approach has resulted in the solutions for both =1 and 1 being incorporated into a group of FORTRAN computer programs which will solve experimental data for scission and crosslinking yields by both minimization and exact treatments. Simulated data treated using these FORTRAN programs are give. The FORTRAN programs are available from the authors.     

Variation in the group velocity of Lamb waves as a tool for the detection of delamination in GLARE aluminium plate-like structures

With the development of new technology and use of lightweight material such as composite laminates, new methods must be developed for in situ structural health monitoring of these materials. This paper introduces an approach for the detection of delamination present in GLARE aluminium specimens. The approach is based on the change in group velocity of Lamb waves with frequency–thickness product as the determinant parameter for the detection of delamination. Two methods are applied: a surface contact method, which utilises a wedge probe tuned to excite a single Lamb mode, and the embedded PZT method, which involves incorporating lead zirconate titanate (PZT) elements in the glass fibre reinforced resin matrix during the manufacture of the GLARE aluminium specimens. It was found that both methods enabled the detection of delaminations in the GLARE aluminium specimens, within certain limits, which are stated.     

Moisture distribution in drying ordinary and high performance concrete cured in a simulated hot dry climate

Adequate moisture is very important during early age of portland cement concrete. The Single Point Magnetic Resonance Imaging technique was used to study the effects of various lengths of moist curing, and the use of curing compound, on the amount and distribution of evaporable water during drying of ordinary and high performance concrete. The specimens subjected to six different curing regimes, were cast in triplicate for a total of 72. After moist curing at 38°C, the specimens were subjected to uniaxial drying in an environmental chamber at 38°C and 40% relative humidity that simulated hot dry climate conditions. As the specimens were drying, Magnetic Resonance Imaging was used to study the evaporable water distribution, non-destructively and with millimetric resolution. The Magnetic Resonance Imaging profiles indicated a reduced moisture loss with increasing length of moist curing. Extended moist curing was especially beneficial for the two self-compacting concrete mixtures, particularly for the cover concrete. In all mixtures the use of curing compound was only marginally better than one day moist curing, but was significantly better than air curing, particularly for the cover concrete. The moisture diffusivity was evaluated from the transient moisture distribution profiles using the Boltzmann transformation method. The results indicated a strong dependence of the moisture diffusivity on the moisture content when above 80% saturation, whereas below this value it remains almost constant. The moisture diffusivity is significantly reduced with increased moist curing period.     

Machine learning in vehicular networking: An overview

As vehicle complexity and road congestion increase, combined with the emergence of electric vehicles, the need for intelligent transportation systems to improve on-road safety and transportation efficiency using vehicular networks has become essential. The evolution of high mobility wireless networks will provide improved support for connected vehicles through highly dynamic heterogeneous networks. Particularly, 5G deployment introduces new features and technologies that enable operators to capitalize on emerging infrastructure capabilities. Machine Learning (ML), a powerful methodology for adaptive and predictive system development, has emerged in both vehicular and conventional wireless networks. Adopting data-centric methods enables ML to address highly dynamic vehicular network issues faced by conventional solutions, such as traditional control loop design and optimization techniques. This article provides a short survey of ML applications in vehicular networks from the networking aspect. Research topics covered in this article include network control containing handover management and routing decision making, resource management, and energy efficiency in vehicular networks. The findings of this paper suggest more attention should be paid to network forming/deforming decision making. ML applications in vehicular networks should focus on researching multi-agent cooperated oriented methods and overall complexity reduction while utilizing enabling technologies, such as mobile edge computing for real-world deployment. Research datasets, simulation environment standardization, and method interpretability also require more research attention.     

Resonant Tunneling through Monolayer Si Colloidal Quantum Dots and Ge Nanocrystals

Resonant tunneling through a 4 nm nanocrystal Ge (nc‐Ge) layer and a 2.4 nm monolayer of Si colloidal quantum dots (QD) is achieved with 0.7 nm amorphous Al₂O₃ (a‐Al₂O₃) barriers. The nc‐Ge resonant tunneling diode (RTD) demonstrates a peak‐to‐valley current ratio (PVCR) of 8 and a full width at half maximum (FWHM) of 30 mV at 300 K, the best performance among RTDs based on annealed nanocrystals. The Si QD RTD is first achieved with PVCRs up to 47 and FWHMs as small as 10 mV at room temperature, confirming theoretically expected excellences of 3D carrier confinements. The high performances are partially due to the smooth profile of nc‐Ge layer and the uniform distribution of Si QDs, which reduce the adverse influences of many‐body effects. More importantly, carrier decoherence is avoided in the 0.7 nm a‐Al₂O₃ barriers thinner than the phase coherence length (≈1.5 nm). Ultrathin a‐Al₂O₃ also passivates well materials and suppresses leakage currents. Additionally, the interfacial bandgap of ultrathin a‐Al₂O₃ is found to be similar to the bulk, forming deep potential wells to sharpen transmission curves. This work can be easily extended to other materials, which may enable resonant tunneling in various nanosystems for diverse purposes.     

The Political Life of Rising Acid Mine Water

The discovery of gold on the Witwatersrand in 1886 that gave rise to the exploitation of the world’s largest gold reserves inaugurated new associations of air and earth, science and politics, humans and nonhumans. Very rapidly, these were organised into two apparently distinct realms—an aboveground world of capital, commerce, culture and politics and a belowground world of labour, minerals, rocks and science. Yet the two realms were deeply interconnected, and the threshold between them was always, literally and figuratively, in danger of collapsing. In this paper, I explore the use of legislation and cartography to stabilise this section and keep the two realms apart, and the aesthetic practices that portrayed their interrelatedness. I then chronicle the incursion of acid mine water, a geological by-product of mining operations, from the mining voids into the above-ground world of human affairs. This not only made the invisible processes of its commodification visible but also became a proposition around which new forms of political life have been assembled.