Late Holocene palynology and palaeovegetation of tephra-bearing mires at Papamoa and Waihi Beach, western Bay of Plenty, North Island, New Zealand.

The vegetation history of two mires associated with Holocene dunes near the western Bay of Plenty coast, North Island, New Zealand, is deduced from pollen analysis of two cores. Correlation of airfall tephra layers in the peats, and radiocarbon dates, indicate that the mires at Papamoa and Waihi Beach are c. 4600 and c. 2900 conventional radiocarbon years old, respectively. Tephras used to constrain the chronology of the pollen record include Rotomahana (1886 AD), Kaharoa (700 yr B.P.), Taupo (Unit Y; 1850 yr B.P.), Whakaipo (Unit V; 2700 yr B.P.), Stent (Unit Q; 4000 yr B.P.), Hinemaiaia (Unit K; 4600 yr B.P.), and reworked Whakatane (c. 4800 yr B.P.) at Papamoa, and Kaharoa and Taupo at Waihi Beach. Peat accumulation rates at Papamoa from 4600 - 1850 yr B.P. range from 0.94 to 2.64 mm/yr (mean 1.37 mm/yr). At Waihi Beach, from 2900 yr B.P. - present day, they range from 0.11 to 0.21 mm/yr (mean 0.20 mm/yr). Peat accumulation at both sites was slowest from 1850 to 700 yr B.P., suggesting a drier overall climate during this interval. At both sites, the earliest organic sediments, which are underlain by marine or estuarine sands, yield pollen spectra indicating salt marsh or estuarine environments. Coastal vegetation communities declined at both sites, as sea level gradually fell or the coast prograded, and were eventually superseded by a low moor bog at Papamoa, and a mesotrophic swamp forest at Waihi Beach. These differences, and the marked variation in peat accumulation rates, probably reflect local hydrology and are unlikely to have been climatically controlled. The main regional vegetation during this period was mixed northern conifer-angiosperm forest. Kauri (Agathis australis) formed a minor component of these forests, but populations of this tree have apparently not expanded during the late Holocene at these sites, which are near its present southern limit. Occasional shortlived forest disturbances are detectable in these records, in particular immediately following the deposition of Taupo Tephra. However, evidence for forest clearance during the human era is blurred by the downward dislocation of modern adventi ve pollen at these sites, preventing the clear differentiation of the Polynesian and European eras

Re-identification of c. 15 700 cal yr BP tephra bed at Kaipo Bog, eastern North Island: implications for dispersal of Rotorua and Puketarata tephra beds.

A 10 mm thick, c. 15 700 calendar yr BP (c. 13 100 14C yr BP) rhyolitic tephra bed in the well-studied montane Kaipo Bog sequence of eastern North Island was previously correlated with Maroa-derived Puketarata Tephra. We revise this correlation to Okataina-derived Rotorua Tephra based on new compositional data from biotite phenocrysts and glass. The new correlation limits the known dispersal of Puketarata Tephra (sensu stricto, c. 16 800 cal yr BP) and eliminates requirements to either reassess its age or to invoke dual Puketarata eruptive events. Our data show that Rotorua Tephra comprises two glass-shard types: an early-erupted low-K2O type that was dispersed mostly to the northwest, and a high-K2O type dispersed mostly to the south and southeast, contemporary with late-stage lava extrusion. Late-stage Rotorua eruptives contain biotite that is enriched in FeO compared with biotite from Puketarata pyroclastics. The occurrence of Rotorua Tephra in Kaipo Bog (100 km from the source) substantially extends its known distribution to the southeast. Our analyses demonstrate that unrecognised syn-eruption compositional and dispersal changes can cause errors in fingerprinting tephra deposits. However, the compositional complexity, once recognised, provides additional fingerprinting criteria, and also documents magmatic and dispersal processes

Sedimentation in an artificial lake -Lake Matahina, Bay of Plenty

Lake Matahina, an 8 km long hydroelectric storage reservoir, is a small (2.5 km2), 50 m deep, warm monomictic, gorge-type lake whose internal circulation is controlled by the inflowing Rangitaiki River which drains a greywacke and acid volcanic catchment. Three major proximal to distal subenvironments are defined for the lake on the basis of surficial sediment character and dominant depositional process: (a) fluvial-glassy, quartzofeld-spathic, and lithic gravel-sand mixtures deposited from contact and saltation loads in less than 3 m depth; (b) (pro-)deltaic-quartzofeldspathic and glassy sand-silt mixtures deposited from graded and uniform suspension loads in 3-20 m depth; and (c) basinal-diatomaceous, argillaceous, and glassy silt-clay mixtures deposited from uniform and pelagic suspension loads in 20-50 m depth. The delta face has been prograding into the lake at a rate of 35-40 m/year and vertical accretion rates in pro-delta areas are 15-20 cm/year. Basinal deposits are fed mainly from river plume dispersion involving overflows, interflows, and underflows, and by pelagic settling, and sedimentation rates behind the dam have averaged about 2 cm/year. Occasional fine sand layers in muds of basinal cores attest to density currents or underflows generated during river flooding flowing the length of the lake along a sublacustrine channel marking the position of the now submerged channel of the Rangitaiki River

A comparison of bioactive glass scaffolds fabricated by robocasting from powders made by sol-gel and melt-quenching methods

Bioactive glass scaffolds are used in bone and tissue biomedical implants, and there is great interest in their fabrication by additive manufacturing/3D printing techniques, such as robocasting. Scaffolds need to be macroporous with voids ≥100 μm to allow cell growth and vascularization, biocompatible and bioactive, with mechanical properties matching the host tissue (cancellous bone for bone implants), and able to dissolve/resorb over time. Most bioactive glasses are based on silica to form the glass network, with calcium and phosphorous content for new bone growth, and a glass modifier such as sodium, the best known being 45S5 Bioglass®. 45S5 scaffolds were first robocast in 2013 from melt-quenched glass powder. Sol-gel-synthesized bioactive glasses have potential advantages over melt-produced glasses (e.g., greater porosity and bioactivity), but until recently were never robocast as scaffolds, due to inherent problems, until 2019 when high-silica-content sol-gel bioactive glasses (HSSGG) were robocast for the first time. In this review, we look at the sintering, porosity, bioactivity, biocompatibility, and mechanical properties of robocast sol-gel bioactive glass scaffolds and compare them to the reported results for robocast melt-quench-synthesized 45S5 Bioglass® scaffolds. The discussion includes formulation of the printing paste/ink and the effects of variations in scaffold morphology and inorganic additives/dopants

Chlorine Dioxide Is a Size-Selective Antimicrobial Agent

Background / Aims: ClO2, the so-called "ideal biocide", could also be applied as an antiseptic if it was understood why the solution killing microbes rapidly does not cause any harm to humans or to animals. Our aim was to find the source of that selectivity by studying its reaction-diffusion mechanism both theoretically and experimentally. Methods: ClO2 permeation measurements through protein membranes were performed and the time delay of ClO2 transport due to reaction and diffusion was determined. To calculate ClO2 penetration depths and estimate bacterial killing times, approximate solutions of the reaction-diffusion equation were derived. In these calculations evaporation rates of ClO2 were also measured and taken into account. Results: The rate law of the reaction-diffusion model predicts that the killing time is proportional to the square of the characteristic size (e. g. diameter) of a body, thus, small ones will be killed extremely fast. For example, the killing time for a bacterium is on the order of milliseconds in a 300 ppm ClO2 solution. Thus, a few minutes of contact time (limited by the volatility of ClO2) is quite enough to kill all bacteria, but short enough to keep ClO2 penetration into the living tissues of a greater organism safely below 0.1 mm, minimizing cytotoxic effects when applying it as an antiseptic. Additional properties of ClO2, advantageous for an antiseptic, are also discussed. Most importantly, that bacteria are not able to develop resistance against ClO2 as it reacts with biological thiols which play a vital role in all living organisms. Conclusion: Selectivity of ClO2 between humans and bacteria is based not on their different biochemistry, but on their different size. We hope initiating clinical applications of this promising local antiseptic

Synergistic interaction of phosphate nanoparticles from fish by-products and phosphate-solubilizing bacterial consortium on maize growth and phosphorus cycling

Phosphate nanomaterials, such as hydroxyapatite/β-tricalcium nanoparticles (nHAs) derived from food industry by-products, offer a sustainable alternative to enhance P-use efficiency in agriculture. However, their limited solubility remains a challenge. This study first investigated the mechanisms of P solubilization of salmon and tuna bones (SnHAs and TnHAs) in fifteen strains of phosphate-solubilizing bacteria (PSB) by an in vitro system. Then, best-performing strains were assembled in a consortium and tested in vivo on maize. We hypothesized that combining nHAs and the PSB consortium inoculated as seed coating (SC) outperforms single treatments alone in promoting plant growth and P cycling, and ensures the establishment in plant-soil system without a bacterial reinforcement (BR) by an additional inoculum suspension. The synergistic effect of nHAs and PSB was proved, improving maize root (+22 %) and total plant biomass (+29 %), as well as P (+32 %) and K (66 %) uptake compared to single treatments. With nHAs and SC, P-use efficiency and recovery increased by 25 % and three-fold, respectively, compared to nHAs alone or with bacterial reinforcement. Consistently, root and substrate bacterial biomass were associated with nHAs plus SC, while nHAs alone or with PSB upregulated PHT1;1 and PHT1;2 transporter genes in maize. Finally, linking the in vitro and in vivo system, we demonstrated that propionic acid production and P-solubilization efficiency of PSB co-applied with nHAs are key drivers of maize growth and P uptake. Our findings indicated that co-applying nHAs and PSB through SC offers a sustainable strategy to improve maize P-use efficiency

The role of calcium (source & content) on the in vitro behaviour of sol–gel quaternary glass series

To highlight the effect of salt precursors on the final properties, bioactivity and biocompatibility, five quaternary (Si–Ca–P–Na) glass compositions were successfully prepared through two distinct rapid sol–gel routes; one using acetate salt precursors (A) catalysed by nitric acid, and the other using nitrate salts (N) and citric acid as a catalyst. The sols dried rapidly, and stabilised at 550 & 800 °C to be characterised by X–ray diffraction (XRD), Magic angle spinning–Nuclear magnetic resonance (29Si MAS–NMR) and Fourier transform infra–red spectroscopy (FTIR). Upon immersion in simulated body fluid (SBF), hydroxyapatite (HAp) formation was initially enhanced by increasing Ca–content up to 40 mol%, but the formation of calcite was favoured with further increments of Ca to 45 and 48 mol%. The A–glasses exhibited lower density and lower network connectivity compared with N–glasses. The chemical surface modifications after 4 h in SBF were more evident for N–glasses in comparison to A–glasses. The biocompatibility is favoured for the samples treated at 800 °C and for the samples of the higher silica contents

Enhanced bioactivity of a rapidly-dried sol-gel derived quaternary bioglass

Novel quaternary (67Si-24Ca-10Na-8P) glass powders were successfully synthesised by sol-gel followed by two alternative drying schedules, conventional drying (CD) and an innovative fast drying (FD) process (200 times quicker). The glasses were thermally stabilised at 550 °C, and then characterised by different complementary techniques. The samples showed very similar silica network structures, with the FD one having slightly lower degree of polymerisation than the CD sample. This less polymerised, more open, network structure exhibited an improved bioactivity in simulated body fluid (SBF), probably also due to the apparent presence of poorly crystalline HAp in the stabilised glass powder. In contrast, the CD glass exhibited an unwanted secondary crystalline silica phase. Both glasses showed excellent biomineralisation upon immersion in SBF, being more pronounced in the case of FD with clear evidence of HAp formation after 4 h, while equivalent signs in the CD samples were only noticed after longer immersion periods between 8 h and 1 week.publishe