Epidemiological determinants of spread of causal agent of severe acute respiratory syndrome in Hong Kong.

BACKGROUND: Health authorities worldwide, especially in the Asia Pacific region, are seeking effective public-health interventions in the continuing epidemic of severe acute respiratory syndrome (SARS). We assessed the epidemiology of SARS in Hong Kong. METHODS: We included 1425 cases reported up to April 28, 2003. An integrated database was constructed from several sources containing information on epidemiological, demographic, and clinical variables. We estimated the key epidemiological distributions: infection to onset, onset to admission, admission to death, and admission to discharge. We measured associations between the estimated case fatality rate and patients' age and the time from onset to admission. FINDINGS: After the initial phase of exponential growth, the rate of confirmed cases fell to less than 20 per day by April 28. Public-health interventions included encouragement to report to hospital rapidly after the onset of clinical symptoms, contact tracing for confirmed and suspected cases, and quarantining, monitoring, and restricting the travel of contacts. The mean incubation period of the disease is estimated to be 6.4 days (95% CI 5.2-7.7). The mean time from onset of clinical symptoms to admission to hospital varied between 3 and 5 days, with longer times earlier in the epidemic. The estimated case fatality rate was 13.2% (9.8-16.8) for patients younger than 60 years and 43.3% (35.2-52.4) for patients aged 60 years or older assuming a parametric gamma distribution. A non-parametric method yielded estimates of 6.8% (4.0-9.6) and 55.0% (45.3-64.7), respectively. Case clusters have played an important part in the course of the epidemic. INTERPRETATION: Patients' age was strongly associated with outcome. The time between onset of symptoms and admission to hospital did not alter outcome, but shorter intervals will be important to the wider population by restricting the infectious period before patients are placed in quarantine

Tissue culture and protoplasts of two rare Araceae (Aroid) plants

University of Technology, Sydney. Faculty of Science.As a major family of tropical rainforest plants, ‘Araceae’ or Aroids are not only of horticultural importance, but also have some agricultural significance in the eastern tropics and subtropics. On the other hand, many species are rare and endangered, and the need for conserving them from extinction is urgent. However, details of their propagation in general is hampered by the slow rate of vegetative multiplication. This project therefore describes studies on the in vitro micropropagation of ‘Alocasia lauterbachiana’ Engler and ‘Homalomena davidiana’ A. Hay, as a beginning to more detailed studies on the propagation of Aroid in general. Protoplasts were successfully isolated. The best digestion enzyme combination was 2% cellulysin (from ‘Trichoderma viride’), plus 1% cellulase (from ‘Aspergillus niger’) and 1% cellulase (from ‘Penicillium funiculosum’). A period of 4-5 hours of incubation time produced a maximum number of isolated protoplasts at 25°C. A successful protocol for the rapid micropropagation of both Aroid species was developed, which combined callus induction and a high rate of shoot multiplication, followed by root development. Plantlets could then be directly transferred to green house acclimatization conditions, with high survival rates. The effects of different explant sources, various auxins and cytokinins, and basal media on callus and shoot initiation were determined. Half strength Murashige and Skoog media was superior to full strength and quarter strength media. The best plant growth regulator and concentration was 5.0 μM thidiazuron for continued callus induction, and 2.5 μM thidiazuron for continued callus growth. Root development was best achieved by 0.25 μM naphthalene acetic acid. The present study therefore introduced a tissue culture method aimed at preserving cell lines and tissues derived from differentiated callus and shoots, which should aid in the preservation of these two rare Aroid species; of which one (‘Alocasia lauterbachiana’) is also endangered

Regulation of stream water dissolved organic carbon (DOC) concentrations during snowmelt; the role of discharge, winter climate and memory effects

Using a 15 year stream record from a northern boreal catchment, we demonstrate that the inter-annual variation in dissolved organic carbon (DOC) concentrations during snowmelt was related to discharge, winter climate and previous DOC export. A short and intense snowmelt gave higher stream water DOC concentrations, as did long winters, while a high previous DOC export during the antecedent summer and autumn resulted in lower concentrations during the following spring. By removing the effect of discharge we could detect that the length of winter affected the modeled soil water DOC concentrations during the following snowmelt period, which in turn affected the concentrations in the stream. Winter climate explained more of the stream water DOC variations than previous DOC export during the antecedent summer and autumn

Regulation of stream water dissolved organic carbon (DOC) concentrations during snowmelt; the role of discharge, winter climate and memory effects

Using a 15 year stream record from a northern boreal catchment, we demonstrate that the inter-annual variation in dissolved organic carbon (DOC) concentrations during snowmelt was related to discharge, winter climate and previous DOC export. A short and intense snowmelt gave higher stream water DOC concentrations, as did long winters, while a high previous DOC export during the antecedent summer and autumn resulted in lower concentrations during the following spring. By removing the effect of discharge we could detect that the length of winter affected the modeled soil water DOC concentrations during the following snowmelt period, which in turn affected the concentrations in the stream. Winter climate explained more of the stream water DOC variations than previous DOC export during the antecedent summer and autumn

Double-sided van der Waals epitaxy of topological insulators across an atomically thin membrane

Atomically thin van der Waals (vdW) films provide a novel material platform for epitaxial growth of quantum heterostructures. However, unlike the remote epitaxial growth of three-dimensional bulk crystals, the growth of two-dimensional (2D) material heterostructures across atomic layers has been limited due to the weak vdW interaction. Here, we report the double-sided epitaxy of vdW layered materials through atomic membranes. We grow vdW topological insulators (TIs) Sb$_2$Te$_3$ and Bi$_2$Se$_3$ by molecular beam epitaxy on both surfaces of atomically thin graphene or hBN, which serve as suspended 2D vdW "$\textit{substrate}$" layers. Both homo- and hetero- double-sided vdW TI tunnel junctions are fabricated, with the atomically thin hBN acting as a crystal-momentum-conserving tunnelling barrier with abrupt and epitaxial interface. By performing field-angle dependent magneto-tunnelling spectroscopy on these devices, we reveal the energy-momentum-spin resonant tunnelling of massless Dirac electrons between helical Landau levels developed in the topological surface states at the interface.Comment: 24 pages, 4 main figures, 7 extended data figure

School Closure and Mitigation of Pandemic (H1N1) 2009, Hong Kong

In Hong Kong, kindergartens and primary schools were closed when local transmission of pandemic (H1N1) 2009 was identified. Secondary schools closed for summer vacation shortly afterwards. By fitting a model of reporting and transmission to case data, we estimated that transmission was reduced ≈25% when secondary schools closed

Abiotic Parameters and Pedogenesis as Controlling Factors for Soil C and N Cycling Along an Elevational Gradient in a Subalpine Larch Forest (NW Italy)

Mountain regions are vulnerable to climate change but information about the climate sensitivity of seasonally snow-covered, subalpine ecosystems is still lacking. We investigated the impact of climatic conditions and pedogenesis on the C and N cycling along an elevation gradient under a Larch forest in the northwest (NW) Italian Alps. The environmental gradient that occurs over short distances makes elevation a good proxy for understanding the response of forest soils and nutrient cycling to different climatic conditions. Subalpine forests are located in a sensitive elevation range—the prospected changes in winter precipitation (i.e., shift of snowfalls to higher altitude, reduction of snow cover duration, etc.) could determine strong effects on soil nitrogen and carbon cycling. The work was performed in the western Italian Alps (Long-Term Ecological Research- LTER site Mont Mars, Fontainemore, Aosta Valley Region). Three sites, characterized by similar bedrock lithology and predominance of Larix decidua Mill., were selected along an elevation gradient (1550–1900 m above sea level-a.s.l.). To investigate the effects on soil properties and soil solution C and N forms of changing abiotic factors (e.g., snow cover duration, number of soil freeze/thaw cycles, intensity and duration of soil freezing, etc.) along the elevation gradient, soil profiles were opened in each site and topsoils and soil solutions were periodically collected from 2015 to 2016. The results indicated that the coldest and highest soil (well-developed Podzol) showed the highest content of extractable C and N forms (N-NH4+, DON, DOC, Cmicr) compared to lower-elevation Cambisols. The soil solution C and N forms (except N-NO3−) did not show significant differences among the sites. Independently from elevation, the duration of soil freezing, soil volumetric water content, and snow cover duration (in order of importance) were the main abiotic factors driving soil C and N forms, revealing how little changes in these parameters could considerably influence C and N cycling under this subalpine forest stand

Climate-Mediated Changes to Linked Terrestrial and Marine Ecosystems across the Northeast Pacific Coastal Temperate Rainforest Margin

Coastal margins are important areas of materials flux that link terrestrial and marine ecosystems. Consequently, climate-mediated changes to coastal terrestrial ecosystems and hydrologic regimes have high potential to influence nearshore ocean chemistry and food web dynamics. Research from tightly coupled, high-flux coastal ecosystems can advance understanding of terrestrial–marine links and climate sensitivities more generally. In the present article, we use the northeast Pacific coastal temperate rainforest as a model system to evaluate such links. We focus on key above- and belowground production and hydrological transport processes that control the land-to-ocean flow of materials and their influence on nearshore marine ecosystems. We evaluate how these connections may be altered by global climate change and we identify knowledge gaps in our understanding of the source, transport, and fate of terrestrial materials along this coastal margin. Finally, we propose five priority research themes in this region that are relevant for understanding coastal ecosystem links more broadly.Ye