Primary succession on a seasonal tropical rocky shore: The relative roles of spatial heterogeneity and herbivory

Hong Kong is within the tropics and has a seasonal climate. In winter, shores support patches of ephemeral macroalgae and areas of seemingly bare rock close to crevices where molluscan herbivores are abundant. Using a factorial design of herbivore exclusions in areas far and close to crevices, the development of algal assemblages was monitored in mid-shore, cleared areas, in winter. To estimate the role of herbivore mucus deposition, half the treatments received a mucus application. Algal development was estimated from macroalgal and biofilm development and chlorophyll a levels. In all areas, biofilms (diatoms, unicellular cyanobacteria) developed rapidly in herbivore exclusions followed by ephemeral macroalgae (Enteromorpha spp. and Porphyra suborbiculata). In herbivore access treatments, however, the algal assemblage was influenced by treatment location; few macroalgae developed in areas close to crevices, and the rock was dominated by cyanobacteria. A negative relationship between macroalgae and biofilms suggested that ephemeral algae were competitively dominant. In areas distant from herbivore refuges, ephemeral macroalgae did develop, illustrating that the effectiveness of molluscan herbivores was limited to 50 to 100 cm from these refuges. The absence of large herbivorous fish, and the sparse numbers of herbivorous crabs at this site, means that algae can achieve a spatial escape from consumption, and where this occurs competition between producers is important in assemblage development. Mucus appeared to play a limited role, only sometimes stimulating initial stages of unicellular cyanobacteria and macroalgae. With the onset of summer, macroalgae died back, and rock space became available for colonization. Unicellular cyanobacteria developed rapidly but were replaced in all treatments by the encrusting macroalga, Hapalospongidion gelatinosum, which dominated treatments until the end of the experiment. On seasonal, tropical shores processes influencing community structure can, therefore, be temporally variable and their relative importance, even at the same shore level, can change with season.published_or_final_versio

Cyanobacterial crust in Hong Kong and comments on future research

The existence of cyanobacterial crust in Hong Kong under both experimental and natural conditions was noted. Thirty0three cyanobacterial species were identified from the soil surface at the site of an erosion experiment. Eleven species were unicellular and 22 filamentous. Fourteen were non-heterocystous and 8 heterocystous cyanobacterial species. None of the species were obligate terrestrial species. Species abundance was measured for one year, and clear seasonal and aseasonal groups of species were established. Macro-environmental data were reported, including soil characteristics, rainfall, rainfall variability and pH, both soil and surface runoff. While the crusts appeared to be fairly stable, except at typhoon intensities, further work is needed to establish degrees of temporal and spatial variation. Non-crust forming cyanobacteria grew on the soil surface under grass and fern. We discuss the future research outlining the potential uses of cyanobacteria in substrate remediation both as an aid to aggregate stability on cut slopes and as a means of accelerating natural plant succession on cut and cement plastered slopes.published_or_final_versio

Electrochemically codeposited reduced graphene oxide and palladium nanoparticles: An efficient heterogeneous catalyst for Heck coupling reaction

AbstractThe catalytic activity of electrochemically codeposited reduced graphene oxide and palladium (ERGO-Pd) was examined for Heck coupling reactions. It showed excellent catalytic activity and stability for Heck coupling reaction. The prepared catalyst (ERGO-Pd) can be used up to the 5th cycle with negligible loss in activity

Primary succession on a seasonal tropical rocky shore: The relative roles of spatial heterogeneity and herbivory

Hong Kong is within the tropics and has a seasonal climate. In winter, shores support patches of ephemeral macroalgae and areas of seemingly bare rock close to crevices where molluscan herbivores are abundant. Using a factorial design of herbivore exclusions in areas far and close to crevices, the development of algal assemblages was monitored in mid-shore, cleared areas, in winter. To estimate the role of herbivore mucus deposition, half the treatments received a mucus application. Algal development was estimated from macroalgal and biofilm development and chlorophyll a levels. In all areas, biofilms (diatoms, unicellular cyanobacteria) developed rapidly in herbivore exclusions followed by ephemeral macroalgae (Enteromorpha spp. and Porphyra suborbiculata). In herbivore access treatments, however, the algal assemblage was influenced by treatment location; few macroalgae developed in areas close to crevices, and the rock was dominated by cyanobacteria. A negative relationship between macroalgae and biofilms suggested that ephemeral algae were competitively dominant. In areas distant from herbivore refuges, ephemeral macroalgae did develop, illustrating that the effectiveness of molluscan herbivores was limited to 50 to 100 cm from these refuges. The absence of large herbivorous fish, and the sparse numbers of herbivorous crabs at this site, means that algae can achieve a spatial escape from consumption, and where this occurs competition between producers is important in assemblage development. Mucus appeared to play a limited role, only sometimes stimulating initial stages of unicellular cyanobacteria and macroalgae. With the onset of summer, macroalgae died back, and rock space became available for colonization. Unicellular cyanobacteria developed rapidly but were replaced in all treatments by the encrusting macroalga, Hapalospongidion gelatinosum, which dominated treatments until the end of the experiment. On seasonal, tropical shores processes influencing community structure can, therefore, be temporally variable and their relative importance, even at the same shore level, can change with season.published_or_final_versio

CMOS x-rays detector array based on scintillating light guides

This paper describes a pixel imaging array consisting in 400µm x 400µm photodiodes fabricated in CMOS technology. An array of scintillating CsI:Tl crystals is placed above the photodiodes. These crystals are encapsulated in aluminum walls, forming a light path that guides the visible light produced by the scintillating crystal into the photodiodes. In This way, the x-ray energy is first converted into visible light which is then detected by the photodiode at the end of each light guide. The scintillator is 800 µm thick, absorbing almost all 20keV x-ray photons. Usually, the spatial resolution of the scintillating x-ray detectors is identical to the scintillator thickness. By using the light guides, the scintillator thickness can be increased without decreasing the spatial resolution. The increase of the scintillator thickness is desirable in order to increase the x-rays absorption efficiency. Tests carried out on the system show very promising results near 20keV

Population structure in a Philippines hot spring microbial mat

published_or_final_versio

Methylmercury exposure during early Xenopus laevis development affects cell proliferation and death but not neural progenitor specification

Methylmercury (MeHg) is a widespread environmental toxin that preferentially and adversely affects developing organisms. To investigate the impact of MeHg toxicity on the formation of the vertebrate nervous system at physiologically relevant concentrations, we designed a graded phenotype scale for evaluating Xenopus laevis embryos exposed to MeHg in solution. Embryos displayed a range of abnormalities in response to MeHg, particularly in brain development, which is influenced by both MeHg concentration and the number of embryos per ml of exposure solution. A TC50 of similar to 50 mu g/l and LC50 of similar to 100 mu g/l were found when maintaining embryos at a density of one per ml, and both increased with increasing embryo density. In situ hybridization and microarray analysis showed no significant change in expression of early neural patterning genes including sox2, en2, or delta; however a noticeable decrease was observed in the terminal neural differentiation genes GAD and xGAT, but not xVGlut. PCNA, a marker for proliferating cells, was negatively correlated with MeHg dose, with a significant reduction in cell number in the forebrain and spinal cord of exposed embryos by tadpole stages. Conversely, the number of apoptotic cells in neural regions detected by a TUNEL (terminal deoxynucleotidyl transferase dUTP nick end labeling) assay was significantly increased. These results provide evidence that disruption of embryonic neural development by MeHg may not be directly due to a loss of neural progenitor specification and gene transcription, but to a more general decrease in cell proliferation and increase in cell death throughout the developing nervous system. (C) 2014 The Authors. Published by Elsevier Inc

Free-flap reconstitutions of head and neck defects after oncologic ablation

Background: Head and neck cancers are the sixth most common cancers worldwide. The primary treatment modality for most head and neck cancers is surgery with reconstruction of resultant defects. Reconstruction of these defects is a unique challenge as it has to not only restore integrity but also function and often cosmesis. The objective of this study was to assess the utility of free flaps in the reconstruction of these defects, done in a tertiary care centre in a three-tier city in India. Methodology: We analyzed the computerized medical records of the last 3 years in this retrospective study carried out in the department of head and neck oncology at the cancer centre. The study included cases that had undergone surgery for head and neck cancer and underwent free flap reconstruction. Results: Out of the 1061 cases requiring reconstruction after an oncologic ablation, 201 cases underwent free flap reconstruction. For defects requiring Facio cutaneous reconstruction, the radial forearm was the preferred donor free flap site, while the fibula was the preferred donor site for mandibular reconstructions survival rate was 94.5%, with factors like age and comorbidities like diabetes and hypertension or habits like cigarette smoking or tobacco chewing not affecting survival rates. Twenty cases of minor flap complications were observed. Conclusions: Free flap reconstructions for head and neck defects after oncologic ablation have been a boon with good survival rates and immense flexibility of use, giving good cosmetic and functional outcomes. Our study shows that a significant number of free flap reconstructions can be done in a tertiary care centre in a three-tier city in India with an internationally comparable survival rate

Free-flap reconstitutions of head and neck defects after oncologic ablation

Background: Head and neck cancers are the sixth most common cancers worldwide. The primary treatment modality for most head and neck cancers is surgery with reconstruction of resultant defects. Reconstruction of these defects is a unique challenge as it has to not only restore integrity but also function and often cosmesis. The objective of this study was to assess the utility of free flaps in the reconstruction of these defects, done in a tertiary care centre in a three-tier city in India. Methodology: We analyzed the computerized medical records of the last 3 years in this retrospective study carried out in the department of head and neck oncology at the cancer centre. The study included cases that had undergone surgery for head and neck cancer and underwent free flap reconstruction. Results: Out of the 1061 cases requiring reconstruction after an oncologic ablation, 201 cases underwent free flap reconstruction. For defects requiring Facio cutaneous reconstruction, the radial forearm was the preferred donor free flap site, while the fibula was the preferred donor site for mandibular reconstructions survival rate was 94.5%, with factors like age and comorbidities like diabetes and hypertension or habits like cigarette smoking or tobacco chewing not affecting survival rates. Twenty cases of minor flap complications were observed. Conclusions: Free flap reconstructions for head and neck defects after oncologic ablation have been a boon with good survival rates and immense flexibility of use, giving good cosmetic and functional outcomes. Our study shows that a significant number of free flap reconstructions can be done in a tertiary care centre in a three-tier city in India with an internationally comparable survival rate