Treatment of mixed (fresh and salt) wastewater

Hong Kong has the geographical advantage of being situated on the coast and therefore it is possible to use dual water supply systems (fresh + sea water systems in two separate distribution networks) for potable and non-potable uses. From the sea water supply system, about three quarters of the population in Hong Kong is supplied with salt water for toilet flushing. The seawater is extracted from the sea directly and pumped by pumping stations located near the shore and supplied to the households. The used toilet flushing water (saline wastewater) is discharged into the sewerage system which conducts the mixed (fresh + salt) wastewater into the STW (sewage treatment works). The salt concentration of the mixed wastewater is between 5,000 mg/l to 6,000 mg/l, about one-fifth of seawater salt concentration, in Hong Kong

Transport spectroscopy in a time-modulated open quantum dot

We have investigated the time-modulated coherent quantum transport phenomena in a ballistic open quantum dot. The conductance $G$ and the electron dwell time in the dots are calculated by a time-dependent mode-matching method. Under high-frequency modulation, the traversing electrons are found to exhibit three types of resonant scatterings. They are intersideband scatterings: into quasibound states in the dots, into true bound states in the dots, and into quasibound states just beneath the subband threshold in the leads. Dip structures or fano structures in $G$ are their signatures. Our results show structures due to 2$\hbar\omega$ intersideband processes. At the above scattering resonances, we have estimated, according to our dwell time calculation, the number of round-trip scatterings that the traversing electrons undertake between the two dot openings.Comment: 8 pages, 5 figure

Recent advancement in water quality indicators for eutrophication in global freshwater lakes

Eutrophication is a major global concern in lakes, caused by excessive nutrient loadings (nitrogen and phosphorus) from human activities and likely exacerbated by climate change. Present use of indicators to monitor and assess lake eutrophication is restricted to water quality constituents (e.g. total phosphorus, total nitrogen) and does not necessarily represent global environmental changes and the anthropogenic influences within the lake's drainage basin. Nutrients interact in multiple ways with climate, basin conditions (e.g. socio-economic development, point-source, diffuse source pollutants), and lake systems. It is therefore essential to account for complex feedback mechanisms and non-linear interactions that exist between nutrients and lake ecosystems in eutrophication assessments. However, the lack of a set of water quality indicators that represent a holistic understanding of lake eutrophication challenges such assessments, in addition to the limited water quality monitoring data available. In this review, we synthesize the main indicators of eutrophication for global freshwater lake basins that not only include the water quality constituents but also the sources, biogeochemical pathways and responses of nutrient emissions. We develop a new causal network (i.e. multiple links of indicators) using the DPSIR (drivers-pressure-state-impact-response) framework that highlights complex interrelationships among the indicators and provides a holistic perspective of eutrophication dynamics in freshwater lake basins. We further review the 30 key indicators of drivers and pressures using seven cross-cutting themes: (i) hydro-climatology, (ii) socio-economy, (iii) land use, (iv) lake characteristics, (v) crop farming and livestock, (vi) hydrology and water management, and (vii) fishing and aquaculture. This study indicates a need for more comprehensive indicators that represent the complex mechanisms of eutrophication in lake systems, to guide the global expansion of water quality monitoring networks, and support integrated assessments to manage eutrophication. Finally, the indicators proposed in this study can be used by managers and decision-makers to monitor water quality and set realistic targets for sustainable water quality management to achieve clean water for all, in line with Sustainable Development Goal 6

Immunolocalization of chloride transporters to gill epithelia of euryhaline teleosts with opposite salinity-induced Na+/K+-ATPase responses

Opposite patterns of branchial Na+/K+-ATPase (NKA) responses were found in euryhaline milkfish (Chanos chanos) and pufferfish (Tetraodon nigroviridis) upon salinity challenge. Because the electrochemical gradient established by NKA is thought to be the driving force for transcellular Cl- transport in fish gills, the aim of this study was to explore whether the differential patterns of NKA responses found in milkfish and pufferfish would lead to distinct distribution of Cl- transporters in their gill epithelial cells indicating different Cl- transport mechanisms. In this study, immunolocalization of various Cl- transport proteins, including Na+/K+/2Cl(-) cotransporter (NKCC), cystic fibrosis transmembrane conductance regulator (CFTR), anion exchanger 1 (AE1), and chloride channel 3 (ClC-3), were double stained with NKA, the basolateral marker of branchial mitochondrion-rich cells (MRCs), to reveal the localization of these transporter proteins in gill MRC of FW- or SW-acclimated milkfish and pufferfish. Confocal microscopic observations showed that the localization of these transport proteins in the gill MRCs of the two studied species were similar. However, the number of gill NKA-immunoreactive (IR) cells in milkfish and pufferfish exhibited to vary with environmental salinities. An increase in the number of NKA-IR cells should lead to the elevation of NKA activity in FW milkfish and SW pufferfish. Taken together, the opposite branchial NKA responses observed in milkfish and pufferfish upon salinity challenge could be attributed to alterations in the number of NKA-IR cells. Furthermore, the localization of these Cl- transporters in gill MRCs of the two studied species was identical. It depicted the two studied euryhaline species possess the similar Cl- transport mechanisms in gills

Elevated Na+/K+-ATPase responses and its potential role in triggering ion reabsorption in kidneys for homeostasis of marine euryhaline milkfish (Chanos chanos) when acclimated to hypotonic fresh water

The milkfish (Chanos chanos) is an economic species in Southeast Asia. In Taiwan, the milkfish are commercially cultured in environments of various salinities. Na+/K+-ATPase (NKA) is a key enzyme for fish iono- and osmoregulation. When compared with gills, NKA and its potential role were less examined by different approaches in the other osmoregulatory organs (e.g., kidney) of euryhaline teleosts. The objective of this study was to investigate the correlation between osmoregulatory plasticity and renal NKA in this euryhaline species. Muscle water contents (MWC), plasma, and urine osmolality, kidney histology, as well as distribution, expression (mRNA and protein), and specific activity of renal NKA were examined in juvenile milkfish acclimated to fresh water (FW), seawater (SW 35aEuro degrees), and hypersaline water (HSW 60aEuro degrees) for at least two weeks before experiments. MWC showed no significant difference among all groups. Plasma osmolality was maintained within the range of physiological homeostasis in milkfish acclimated to different salinities, while, urine osmolality of FW-acclimated fish was evidently lower than SW- and HSW-acclimated individuals. The renal tubules were identified by staining with periodic acid Schiff's reagent and hematoxylin. Moreover, immunohistochemical staining showed that NKA was distributed in the epithelial cells of proximal tubules, distal tubules, and collecting tubules, but not in glomeruli, of milkfish exposed to different ambient salinities. The highest abundance of relative NKA alpha subunit mRNA was found in FW-acclimated milkfish rather than SW- and HSW-acclimated individuals. Furthermore, relative protein amounts of renal NKA alpha and beta subunits as well as NKA-specific activity were also found to be higher in the FW group than SW and the HSW groups. This study integrated diverse levels (i.e., histological distribution, gene, protein, and specific activity) of renal NKA expression and illustrated the potential role of NKA in triggering ion reabsorption in kidneys of the marine euryhaline milkfish when acclimated to a hypotonic FW environment

Elevated Na+/K+-ATPase responses and its potential role in triggering ion reabsorption in kidneys for homeostasis of marine euryhaline milkfish (Chanos chanos) when acclimated to hypotonic fresh water

The milkfish (Chanos chanos) is an economic species in Southeast Asia. In Taiwan, the milkfish are commercially cultured in environments of various salinities. Na+/K+-ATPase (NKA) is a key enzyme for fish iono- and osmoregulation. When compared with gills, NKA and its potential role were less examined by different approaches in the other osmoregulatory organs (e.g., kidney) of euryhaline teleosts. The objective of this study was to investigate the correlation between osmoregulatory plasticity and renal NKA in this euryhaline species. Muscle water contents (MWC), plasma, and urine osmolality, kidney histology, as well as distribution, expression (mRNA and protein), and specific activity of renal NKA were examined in juvenile milkfish acclimated to fresh water (FW), seawater (SW 35aEuro degrees), and hypersaline water (HSW 60aEuro degrees) for at least two weeks before experiments. MWC showed no significant difference among all groups. Plasma osmolality was maintained within the range of physiological homeostasis in milkfish acclimated to different salinities, while, urine osmolality of FW-acclimated fish was evidently lower than SW- and HSW-acclimated individuals. The renal tubules were identified by staining with periodic acid Schiff's reagent and hematoxylin. Moreover, immunohistochemical staining showed that NKA was distributed in the epithelial cells of proximal tubules, distal tubules, and collecting tubules, but not in glomeruli, of milkfish exposed to different ambient salinities. The highest abundance of relative NKA alpha subunit mRNA was found in FW-acclimated milkfish rather than SW- and HSW-acclimated individuals. Furthermore, relative protein amounts of renal NKA alpha and beta subunits as well as NKA-specific activity were also found to be higher in the FW group than SW and the HSW groups. This study integrated diverse levels (i.e., histological distribution, gene, protein, and specific activity) of renal NKA expression and illustrated the potential role of NKA in triggering ion reabsorption in kidneys of the marine euryhaline milkfish when acclimated to a hypotonic FW environment

Particle Probe of Horava-Lifshitz Gravity

Kehagias-Sfetsos black hole in Ho\v{r}ava-Lifshitz gravity is probed through particle geodesics. Gravitational force of KS black hole becomes weaker than that of Schwarzschild around horizon and interior space. Particles can be always scattered or trapped in new closed orbits, unlike those falling forever in Schwarzschild black. The properties of null and timelike geodesics are classified with values of coupling constants. The precession rates of the orbits are evaluated. The time trajectories are also classified under different values of coupling constants for both null and timelike geodesics. Physical phenomena that may be observable are discussed.Comment: 10 pages, 8 figure

Protons in near earth orbit

The proton spectrum in the kinetic energy range 0.1 to 200 GeV was measured by the Alpha Magnetic Spectrometer (AMS) during space shuttle flight STS-91 at an altitude of 380 km. Above the geomagnetic cutoff the observed spectrum is parameterized by a power law. Below the geomagnetic cutoff a substantial second spectrum was observed concentrated at equatorial latitudes with a flux ~ 70 m^-2 sec^-1 sr^-1. Most of these second spectrum protons follow a complicated trajectory and originate from a restricted geographic region.Comment: 19 pages, Latex, 7 .eps figure

Search for antihelium in cosmic rays

The Alpha Magnetic Spectrometer (AMS) was flown on the space shuttle Discovery during flight STS-91 in a 51.7 degree orbit at altitudes between 320 and 390 km. A total of 2.86 * 10^6 helium nuclei were observed in the rigidity range 1 to 140 GV. No antihelium nuclei were detected at any rigidity. An upper limit on the flux ratio of antihelium to helium of < 1.1 * 10^-6 is obtained.Comment: 18 pages, Latex, 9 .eps figure