Reconstruction of an 8,000-year record of typhoons in the Pearl River estuary, China

An 8,000-year record of typhoons in the Pearl River Estuary is reconstructed through the study of offshore boreholes, beach-dune barriers, historical record and instrumental documentation. In 5 offshore boreholes, a maximum of 17 siliciclastic-dominated storm beds and/or shell-dominated storm beds was identified since about 8,000 calendar years BP. Holocene beach-dune barriers in the vicinity of the estuary were used to study the distribution of landfalling typhoons assisted by radiocarbon and archaeological ages. The pattern found is consistent with multiple typhoons making landfall. Historical record for the period AD 700-1883 has revealed 161 typhoons with reported damage out of which the typhoons of AD 957, 1245, 1862 and 1874 were the most disastrous. During the Little Ice Age, the frequency of typhoons was found to decrease. Only three typhoons in the instrumental documentation period from AD 1884-2000 exceeded the Saffir-Simpson hurricane intensity scale of 3. The frequency of typhoons with paths falling within the South China Sea was found to decrease and increase during El Niňo years and La Niňa years respectively. Since the mid-1970s, the frequency of typhoons in the South China Sea was found to show a decline probably due to a northerly shift of typhoon paths during El Niňo years. However, whether this shift is the result of climate change or natural multidecadal oscillations will require further investigation. Instrumental documentation is concluded to provide the best record of typhoons followed by historical record, beach-dune barriers and offshore boreholes. This is attributed to the inadequate sensitivity of radiocarbon and archaeological ages in distinguishing typhoons and the discontinuous sedimentary record provided by beach-dune barriers and offshore borehole. The degree of damage by typhoons in the historical record is influenced by subjective interpretation.postprin

Direct Visualization of Soliton CO Overlayers on Supported Pd Nanoparticles

The interaction of carbon monoxide (CO) molecules with the facets of noble metal nanoparticles forms the basis of many important catalytic reactions. Using scanning tunneling microscopy (STM), we have studied the adsorption of CO molecules on the (111) facets of Pd nanocrystals supported on a rutile TiO2(110) substrate. We observed four compact CO overlayers with coverages ranging between 0.5 and 0.6 monolayers. Examination of the positions of the CO molecules in each of the unit cells reveals that one of the overlayers has a rhombic (√7 × √7) R19.1°-4CO structure. The other three form rectangular structures, namely, (7 × √3) rect-8CO, c(5 × √3) rect-3CO, and c(9 × √3) rect-5CO. These are closely related via a soliton model previously proposed on the basis of infrared absorption spectroscopy and low-energy electron diffraction. By imaging the CO molecules, we provide direct evidence for the soliton model

Probing the local electronic structure of the cross-linked (1×2) reconstruction of rutile TiO2(110)

The electronic structure of cross-linked TiO2(110)-(1×2) has been investigated using scanning tunneling spectroscopy (STS) and by monitoring changes in ultraviolet photoelectron spectroscopy (UPS) following exposure of the surface to O2. STS reveals two states located in the bandgap, at 0.7 and 1.5 eV below the Fermi level. The population of these two states varies over different parts of the (1×2)- reconstructed surface. An addition state at 1.1 eV above the Fermi level is observed at the double link part of the structure. All of the bandgap states are attenuated following exposure to O2, while the workfunction is increased. We attribute this to an electron transfer from the surface to the adsorbed oxygen

Simulation of Near Edge X-ray Absorption Fine Structure (NEXAFS) Measurements of CO on Supported Pd Nanoparticles

Near edge X-ray absorption fine structure (NEXAFS) measurements of CO on Pd nanoparticles have been simulated. This was achieved by calculating the CO π* resonance signal of CO on a nanoparticle both as a function of the angle of incidence (I vs θ) and the direction of the electric field vector E of the incident photon beam (I vs β), with the nanoparticle defined as a (111) top facet with {111} and {100} side facets. The dependence of the π* resonance intensity signal of CO covered nanoparticles on the particle geometry and orientation as well as the bond orientation of CO is examined. In addition, we compare our simulations to a set of C K-edge NEXAFS experimental data obtained from a single Pd nanoparticle decorated with CO. Our simulation predicts that the nanoparticle has a high lateral aspect ratio of 37.7 ± 4.1

Ubiquitous Internet in an integrated satellite-terrestrial environment: The SUITED solution

yesThe current Internet architecture appears to not be particularly suited to addressing the emerging needs of new classes of users who wish to gain access to multimedia services made available by ISPs, regardless of their location, while in motion and with a guaranteed level of quality. One of the main objectives of so-called nextgeneration systems is to overcome the limitations of today¿s available Internet by adopting an approach based on the integration of different mobile and fixed networks. The SUITED project moves in this direction since it aims at contributing to the design and deployment of the global mobile broadband system (GMBS), a unique satellite/terrestrial infrastructure ensuring nomadic users access to Internet services with a negotiated QoS. A description of the main features of the GMBS architecture, characterized by the integration of a multisegment access network with a federated ISP network is given in this article. The GMBS multimode terminal is schematically described, and an overview of the so-called QoS-aware mobility management scheme, devised for such a heterogeneous scenario,is provided

Discussion on Quaternary sea-level change on the continental shelf of Hong Kong

Yim et al comment on Fyfe et al's sequence stratigraphical interpretation of the Quaternary inner shelf sediments of Hong Kong. Fyfe et al respond to the comments.published_or_final_versio

Temporal Stability and Precision of Ventricular Defibrillation Threshold Data

Over two-hundred measurements of the minimum damped sinusoidal current and energy for transchest electrical ventricular defibrillation (ventricular defibrillation threshold) were made to determine the stability and precision of threshold data in 15 pentobarbital-anesthetized dogs. Threshold was determined by repeated trials of fibrillation and defibrillation with successive shocks of diminishing current, each 19% less than that of the preceeding shock. The lowest shock intensity that defibrillated was defined as threshold. In three groups of five dogs each, threshold was measured at intervals of 60, 15, and 5 min. over periods of 8, 5, and 1 hr. respectively. Similar results were obtained for all groups. There was no significant change in mean threshold current with time. Due to a decrease in transchest impedance, threshold delivered energy decreased by 10% during the first hour of testing. The standard deviations for threshold peak current and delivered energy in a given animal were 11 and 22 percent of their respective mean values. Arterial blood pH, pc02, and p02 averaged 7.38, 34 mmHg, and 72 mmHg respectively. The rates of change of pH, pCO2 and p02 were not significantly different from zero. The data demonstrate that ventricular defibrillation threshold is a stable physiologic parameter which may be measured with reasonable precision

Structure of a model TiO2 photocatalytic interface

The interaction of water with TiO2 is crucial to many of its practical applications, including photocatalytic water splitting. Following the first demonstration of this phenomenon 40 years ago there have been numerous studies of the rutile single-crystal TiO2(110) interface with water. This has provided an atomic-level understanding of the water-TiO2 interaction. However, nearly all of the previous studies of water/TiO2 interfaces involve water in the vapour phase. Here, we explore the interfacial structure between liquid water and a rutile TiO2(110) surface pre-characterized at the atomic level. Scanning tunnelling microscopy and surface X-ray diffraction are used to determine the structure, which is comprised of an ordered array of hydroxyl molecules with molecular water in the second layer. Static and dynamic density functional theory calculations suggest that a possible mechanism for formation of the hydroxyl overlayer involves the mixed adsorption of O2 and H2O on a partially defected surface. The quantitative structural properties derived here provide a basis with which to explore the atomistic properties and hence mechanisms involved in TiO2 photocatalysis

Dependence of Defibrillation Threshold Upon Extracellular/Intracellular K+ Concentrations

The effect of increasing extracellular potassium concentration (Ko) upon electrical ventricular defibrillation threshold was investigated in pentobarbital anesthetized dogs treated with intravenous potassium chloride. Defibrillation threshold fell during potassium intoxication. The percent decrease in defibrillation threshold was linearly related to the logarithm of Ko and to the potassium equilibrium potential, EK, calculated from measured extracellular and intracellular potassium concentrations of ventricular muscle. In dogs supported by left ventricular bypass in order to maintain the circulation during potassium intoxication, the values of Ko and EK required for spontaneous, K+ induced defibrillation (electrical defibrillation threshold = zero) were 16.6 mEq/L and -46 mV compared to the normal values of 3.9 mEq/L and -84 mV. Changes in defibrillation threshold related to changes in EK may be significant events in digitalis intoxication and in myocardial anoxia during prolonged fibrillation. Defibrillation of the heart is often discussed as a large scale analog of cardiac pacing. Termination of atrial or ventricular fibrillation by a strong electric shock, applied with paddle electrodes across the chest or directly to the heart, is assumed to be the result of stimulation of a diffuse mass of potentially excitable cells (1, 2). The mechanism of defibrillation is usually stated to be the consequent production of a simultaneously refractory state in the entirety of a critical mass of the fibrillating myocardium (3, 4)