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To report an outbreak of measles with epidemiological link between Hong Kong International Airport (HKIA) and a hospital.
Epidemiological investigations, patients’ measles serology, and phylogenetic analysis of the hemagglutinin (H) and nucleoprotein (N) genes of measles virus isolates were conducted.
In total, 29 HKIA staff of diverse ranks and working locations were infected with measles within 1 month. Significantly fewer affected staff had history of travel than non–HKIA-related measles patients [10 of 29 (34.5%) vs 28 of 35 (80%); P < .01]. Of 9 airport staff who could recall detailed exposure history, 6 (66.7%) had visited self-service food premises at HKIA during the incubation period, where food trays, as observed during the epidemiological field investigation, were not washed after use. Furthermore, 1 airport baggage handler who was admitted to hospital A before rash onset infected 2 healthcare workers (HCWs) known to have 2 doses of MMR vaccination with positive measles IgG and lower viral loads in respiratory specimens. Infections in these 2 HCWs warranted contact tracing of another 168 persons (97 patients and 71 HCWs). Phylogenetic comparison of H and N gene sequences confirmed the clonality of outbreak strains.
Despite good herd immunity with overall seroprevalence of >95% against measles, major outbreaks of measles occurred among HKIA staff having daily contact with many international pssengers. Lessons from severe acute respiratory syndrome (SARS) and measles outbreaks suggested that an airport can be a strategic epidemic center. Pre-exanthem transmission of measles from airport staff to HCWs with secondary vaccine failure poses a grave challenge to hospital infection control.
Prominent gas disks and dust lanes are found in a number of elliptical galaxies. It is widely believed that these disks are the result of the tidal capture of material from a nearby galaxy or the accretion of a gas rich companion into a larger galaxy. While a captured gas disk will ultimately settle into a steady-state orientation (“preferred plane”), the disk will initially be time varying due to precessional and viscous forces. We have developed methods for modeling the evolution of such inclined dissipative galactic gas disks (Steiman-Cameron 1984, Ph.D. dissertation, Indiana U.; Steiman-Cameron and Durisen 1986, Ap.J., in press, hereafter SCD), and we here present some of the results of this work.
The possible existence of strong electromagnetic fields in pulsars has motivated extensive interest in investigation of various quantum electrodynamics processes. In particular, the process of converting high energy photons into electron-positron pairs is of great significance in pulsar theory.
Segregation has long been recognized as a source of ignorance which breeds negative feelings and hostility. This view maintains that interactions between members of different groups can foster social bonds and promote positive group relationship. Employing recently collected survey data, this study examines the effect of cross-Strait contacts on Taiwan citizens’ negative views toward Chinese citizens and the Beijing government. The empirical results show that casual encounters have no effect on the island residents’ general perception of China. Serious interactions in the form of friendship moderate their unfavorable feelings of Chinese citizens but have no effects on the perception of a hostile Beijing. Unless contacts can invoke true social bonds, frequent interactions do not have transformative effects on individuals’ political views. The moderating effect of contacts at the personal level is not transferable to a political entity when the latter is perceived as a suppressing agent.
The Miyun Synthesis Radio Telescope (MSRT), Beijing Astronomical Observatory, has been used in observation of the Sun as an one dimension heliograph. Daily observation with MSRT and other two single dishes for total power measurement have been performed since May,1998.(Zhang, X.Z., 1999)
The different procedures of the transforation from FK4 to FK5 are reviewed. With these procedures some numerical examples for selected FK4 stars are given. Basing on the original work of Fricke (1985), we prefer to select the procedure developed by Standisti (1982). One of the main reasons for the procedure of Aoki et al. (1983) is to consist with the new definition of UT. Since the corrections “FK5 - FK4” for many stars are significant, even if adopting this procedure, it is still impossible to avoid the effect of the right ascension discontinuities on UT.
The harpacticoid copepod, Nitokra affinis Gurney, 1927 was recorded from Vellar estuary (south-east India) for the first time. This species was consistently found in plankton samples collected during June and July, 2010. The samples were collected by the horizontal towing of a plankton net for 20 min. In this paper, we provide drawings and descriptions of Nitokra affinis and discuss the possible mechanisms of its introduction. We also compare a 769 bp sequence of its 18S ribosomal (r) DNA with already publicly available sequences, which is characterized as a meaningful barcode for the subspecies identification of Nitokra affinis in the future.
The present study examined sequence variability in two mitochondrial DNA (mtDNA) regions, namely cytochrome c oxidase subunit 1 (cox1) and NADH dehydrogenase subunit 1 (nad1), and internal transcribed spacer (ITS) of nuclear ribosomal DNA (rDNA) among Oesophagostomum asperum isolates from goats in Hunan Province, China. A portion of the cox1 (pcox1), nad1 (pnad1) genes and the ITS (ITS1+5.8S rDNA+ITS2) rDNA were amplified by polymerase chain reaction (PCR) separately from adult O. asperum individuals and the representative amplicons were subjected to sequencing from both directions. The lengths of pcox1, pnad1 and ITS rDNA were 366 bp, 681 bp and 785 bp, respectively. The A+T contents of gene sequences were 71.5–72% for pcox1, 73.7–74.2% for pnad1 and 58–58.8% for ITS rDNA. Intra-specific sequence variations within O. asperum were 0–1.6% for pcox1, 0–1.9% for pnad1 and 0–1.7% for ITS rDNA, while inter-specific sequence differences among members of the genus Oesophagostomum were significantly higher, being 11.1–12.5%, 13.3–17.7% and 8.5–18.6% for pcox1, pnad1 and ITS rDNA, respectively. Phylogenetic analyses using combined sequences of pcox1 and pnad1, with three different computational algorithms (Bayesian inference, maximum likelihood and maximum parsimony), revealed distinct groups with high statistical support. These findings demonstrated the existence of intra-specific variation in mtDNA and rDNA sequences among O. asperum isolates from goats in Hunan Province, China, and have implications for studying molecular epidemiology and population genetics of O. asperum.
We report x-ray scattering studies of polarons and tilt ordering in the high-temperature, paramagnetic insulating phase of La0.7Ca0.3MnO3. The temperature dependence of scattering due to individual and correlated polarons was measured, and the latter was found to disappear at ∼400 K. The scattering due to tilt ordering, which was observed by tuning the incident photon energy near the La L1 edge, was also measured as a function of temperature. The destruction of tilt ordering at ∼690 K is believed to be associated with the orthorhombic-rhombohedral structural transition.
Electrical performance of in-situ steam generated (ISSG) oxide nitrided using remote plasma nitridation (RPN) has been evaluated. An equivalent oxide thickness (EOT) of 1.6 nm with gate leakage current around 5×10−3 A/cm2 (at −1.5V) has been achieved. The leakage current of remote plasma nitrided ISSG oxide is lower than that of ISSG only, where more than one order of magnitude leakage current reduction (at the same EOT) has been achieved for some RPN conditions. Moreover, it is observed that the extent to which the RPN process conditions modify device parameters such as EOT, flatband voltage (VFB), and time-to-breakdown (tbd) increases with decreasing ISSG thickness. The thinner ISSG oxides appear to be more susceptible to plasma damage and accumulation of positively charged nitrogen atoms at the oxide/Si interface. Therefore, RPN processes that use lower temperature and shorter time are preferred for very thin oxides. The nitrogen content and profile in the samples evaluated using SIMS analysis, indicate that RPN offers higher nitrogen content and better nitrogen profile compared to conventional nitrogen incorporation methods such as NO annealing .
Gallium arsenide films grown on (211)Si by molecular-beam epitaxy have been investigated using transmission electron microscopy. The main defects observed in the alloy were of misfit dislocations, stacking faults, and microtwin lamellas. Silicon surface preparation was found to play an important role on the density of defects formed at the Si/GaAs interface.
Two different types of strained-layer superlattices, InGaAs/InGaP and InGaAs/GaAs, were applied either directly to the Si substrate, to a graded layer (GaP-InGaP), or to a GaAs buffer layer to stop the defect propagation into the GaAs films. Applying InGaAs/GaAs instead of InGaAs/InGaP was found to be more effective in blocking defect propagation. In all cases of strained-layer superlattices investigated, dislocation propagation was stopped primarily at the top interface between the superlattice package and GaAs. Graded layers and unstrained AlGaAs/GaAs superlattices did not significantly block dislocations propagating from the interface with Si. Growing of a 50 nm GaAs buffer layer at 505°C followed by 10 strained-layer superlattices of InGaAs/GaAs (5 nm each) resulted in the lowest dislocation density in the GaAs layer (∼;5×l07/cm2) among the structures investigated. This value is comparable to the recently reported density of dislocations in the GaAs layers grown on (100)Si substrates . Applying three sets of the same strained layersdecreased the density of dislocations an additional ∼2/3 times.
An understanding of the mechanisms of self-diffusion and of interdiffusion in the compound materials GaAs and AlAs may be arrived at byt noting the effects of (i) charge, (ii) As pressure, and (iii) point defect supersaturation, on the doping enhanced superlattice disordering phenomena. The Ga self-diffusion (and hence Ga-Al interdiffusion) is dominated by the triply-negatively-charged Ga (or Al) vacancy, , under intrinsic and n-doping conditions. Under p-doping, a positively charged Ga self-interstitial , with m not known, contributes to the Ga(AI) diffusion process. Less is known for the group V element diffusion, but the As vacancy (VAs) should be contributing under intrinsic and n-doping conditions while the As selfinterstitial (LAs) may be contributing under p-doping. The contribution of a defect pair may also be involved under p-doping.
We report the study of high-dose Si-implanted GaAs containing doses ranging from 1×1014 to 1×1015 cm-2 and with subsequent anneals at 850°C for 1 hour. At doses ≥ 3×1014 cm-2, a severe reduction of carrier concentration and anomalous Si diffusion are observed in the near-surface region. In the same region, small, near-spherical voids are found by transmission electron microscopy. In contrast, for samples implanted with doses ≤ 1×1014 cm-2, voids are not found, and both normal carrier activation and Si diffusion profiles are observed. The concurrent onset of these three phenomena in the same region in high-dose samples leads us to conclude that the severe reduction of carrier concentration and anomalous Si diffusion are attributable to the formation of voids.
Vacancy behaviors during ageing of Cu-26Zn-4A1 and Cu-14Al-4Ni alloys have been investigated and compared by means of positron annihilation (PA) and electrical resistivity measurement. For ageing in martensitic state after direct quenching, it is observed that the S parameter values of Cu-Zn- Al specimens, measured in liquid nitrogen, increase at first and then decrease, while those of Cu-Al-Ni remain unchanged. The activation energies calculated from the S parameter for increasing and decreasing stages are o.4lev and o.63ev respectively, and the former can be corresponding to the formation energy of vacancy clustering, while the latter may be regarded as the migration energy of effective vacancies. A mechanism is put forward that the clustering of quenched-in vacancies results in a decreasing of the ordering degree and a reduction of the stored energy in martensite, which is responsible for the early stage of the stabilization of martensite in Cu-Zn-Al alloys. However, the fact that Cu-Al-Ni alloy is not subject to the stabilization is assumed to be owing to the immobility of supersaturated vacancies in its martensitic state which may be associated with the strong binding force between Ni and Al atoms.
As known to all,shape memory behaviour has been observed in a variety of metallic alloys. This phenomenon, however, is not only observed in that field but also in other materials recently, such as in polymers,intermetallic compounds and ceramics, especially in zirconia ceramics.
Swain  observed the shape recovery of a bent magnesia-partiallystabilized zirconia (Mg-PSZ) bar upon heating above a certain temperature. The maximum deflection which was nearly completely recovered on heating is about 300 μm.
Chen et al  investigated the pseudoelasticity and shape memory effect (SME) in ceria-stabilized tetragonal zirconia polycrystals (Ce- TZP) containing 12 mol% CeO2.Wang et al  also observed the SME in Ce-TZP containing 10 mol% CeO2,.Here we would like to introduce some of results conducted recently in our group on SHE in Ce-TZP ceramics.