Narrow Results

Half of the freshwater fish fauna in New Zealand is diadromous (i.e., migrates between the sea and freshwater); unimpeded access to and from the sea is important for the conservation of diadromous fish. The genus Galaxias (Galaxiidae: Osmeriformes) contains five diadromous species that spawn in freshwater, migrate to sea as larvae, and then migrate back into freshwater as 50-55-mm juveniles. Microchemistry of the otolith, a calcified structure in the fish's head, allows an independent test of assumptions about these migrations. Concentric layers of CaCO₃ with some Sr as SrCO₃ comprise the otolith, creating a chronosequence that reflects a fish's migratory history. More Sr accumulates in the otolith when a fish is in seawater than when it is in freshwater. High-resolution nuclear microscopy was used to measure the molar ratios of Sr/Ca in two galaxiid species. Otoliths of inanga (G. maculatus) caught in freshwater all showed a central zone of 100-200 μm in radius with Sr/Ca of 0.008-0.012, indicating early rearing in the sea. Sr/Ca values decreased to 0.001-0.002 as the fish moved into freshwater. Of six adult koaro (G. brevipinnis) caught in a river with sea access and no lakes, five had migrated to sea but one had not, raising questions about the generalized assumptions of migration.

Sr is an indicator used in studies on fish migration. In this study, the Sr profiles of ridges, which are growth lines in fish scales, in Sakhalin taimen (Hucho perryi) were examined by micro-PIXE analysis. Sakhalin taimen were reared under freshwater conditions for six months. The ridges that formed during the rearing experiment were subjected to PIXE spot analysis. This analysis was performed in a 5 X 5 μm² area in the center region of each ridge of the scale section, and the Sr levels were calculated using the thin-section standard. The mean Sr concentration in the ridges was 428± 48 μg/g. The quantitative PIXE spot analysis successfully provided Sr profiles for the scale corresponding to ridge formation.

We evaluated the spatial distributions of cesium and strontium in tea leaves using micro particle-induced X-ray emission (micro-PIXE) analysis to explore the characteristics of the concentrations and translocations of these elements in tea leaves, and the similarities and differences between cesium and potassium and between strontium and calcium. We examined samples of tea [Camellia sinensis (L.) Kuntze] leaves that took up cesium and strontium via foliar absorption. We confirmed that calcium and strontium accumulated in many narrow areas of the leaves, while cesium and potassium were distributed throughout the leaf samples. Almost all of the strontium and calcium accumulated in the same narrow locations in the leaf samples 30 days after foliar absorption.

The sodium alginate extracted from sargassum of South China Sea significantly inhibited the absorption of Sr in human gastrointestinal tract. Because of the identical metabolism dynamics of radioactive Sr and stable Sr, oral medication experiments have been performed by using stable Sr as a tracer. Fifteen adult healthy subjects (10 males and 5 females) were involved and divided into two groups. Concentrations of Sr, Ca, Fe, Cu, and Zn in serum and urine (24 hours) at different times after oral medications were measured by PIXE. It was found from the PIXE results that Sr in serum and in urine were reduced (78 +/− 8.9)% and (78 +/− 11)% respectively by sodium alginate. A reasonable dosage of sodium alginate had little influence to the absorption of Ca, Fe, Cu, and Zn.

The hard tissues of cephalopod, namely statoliths were analyzed with PIXE for the Japanese common squid Todarodes pacificus of the Sea of Japan origin in order to examine the relationship between the amount of trace elements in statoliths and environmental temperature of the squid habitat. Calcium, iron, zinc. copper and strontium were detected in the statoliths. Negative relationship was observed between Sr concentration in statoliths and environmental temperature. On the contrary to Sr, Fe and Zn concentration in statoliths related positively with environmental temperature. These observations revealed that the statoliths would be a useful thermometer for reconstructing the environmental temperature of cephalopod habitat as seen in the hard tissues of other marine organisms.

Trace elements in the squid statoliths were analyzed by PIXE for following seven species distributing at offshore and inshore waters: Family Ommastrephidae, Ommastrephes bartrami, Todarodes pacificus; family Loliginidae, Loligo bleekeri, L. duvaucelii, L. chinensis, L. edulis and Sepioteuthis lessoniana. Statoliths of all seven species contained manganese, iron, capper, zinc and relatively high amount of strontium. Statoliths Sr concentration, an possible index for thermal history of the animal’s habitat, were the highest in O. bartrami that spends their entire life time at pelagic water, and secondly highest in T. pacificus living at the pelagic as well as the coastal waters. On the other hand, statoliths Sr concentration was relatively low in the five species of Loliginidae living at coastal waters, with following order: L. edulis >S. lessoniana >L. duvaucelii >L. bleekeri >L. chinensis. These observations may indicate that quantity of the statoliths trace elements are species specific in squids, thus would be a possible “key” to reconsidering about taxonomy and distribution in squid.

Trace elements in squid statoliths were analyzed by PIXE for the following fourteen species in five families of different habitat origin: Ommastrephidae, Ommastrephes bartrami, Dosidicus gigas, Sthenoteuthis oualaniensis; Gonatidae, Gonatopsis makko, G. borealis, Berryteuthis magister; Loliginidae, Loligo bleekeri, L. duvaucelii, L. chinensis, L. edulis and Sepioteuthis lessoniana; Sepiidae, Sepia aculeata and Sepiella inermis; Sepiolidae, Rossia pacifica, Manganese, iron, copper, zinc and strontium were detected from statoliths of all species examined. Among these trace elements, Sr is the highest in concentration. Variation of statoliths Sr concentration reflects taxonomic position and the habitat of specimens. In Ommastrephids and Gonatids, that have oceanic habitat, statoliths Sr concentration is relatively high whereas that of Loliginids and Sepiids, that have coastal habitat, is comparatively low. This fact supports our previous report on this subject. R. pacifica exceptionally shows high statoliths Sr concentration although this species inhabits in coastal water.

Japanese sea bass (Lateolabrax japonicus) is a typical euryhaline marine fish and frequently migrates from salt to freshwater environments during early life stages. We hypothesized that strontium concentrations in the otolith could be a useful index to examine freshwater entry because of its lower concentration in freshwater. Otoliths of Japanese sea bass juveniles collected in the Chikugo river and estuary were analyzed by Particle Induced X-ray Emission (PIXE) to see relationship between strontium concentration and ambient salinity. Strontium concentrations in otoliths of sea bass juveniles are significantly lower in the river samples than in brackish water samples.

Trace elements in shells of short necked clams were analyzed with PIXE. Two groups of the shells ware sampled from high salinity and low salinity. Strontium (Sr) and Iron (Fe) concentration ware significantly different between the two groups. Although water temperature and salinity may affect Sr concentration in the shells, the Sr concentration was higher in better growth clams.

Trace elements in a cuttlebone, a buoyant calcified tissue developing simultaneously with the individual growth, of an adult giant cuttlefish originating from the water of Ishigaki Island were measured by PIXE to examine the ontogenetic change of the element concentration. Beside calcium (major element), iron, zinc, manganese, copper, bromine and relatively large amounts of strontium were detected in the cuttlebone. Strontium concentration varied with position along the cuttlebone: it was high near the spine (the portion that deposited at the paralarval stage), then showed some variations at the middle portion of the cuttlebone (the portion that deposited from young stage to sub-adult stage) and became the highest near the locus (the portion that deposited near the catch date, i.e., adult stage). This variation was compared to migration of this species between inshore and offshore waters.

In this work, various nano-sized samples of Y₂O₃, Y₂O₃:Eu and Y₂O₃:Eu, Sr were prepared by urea solution combustion method. Then the resultant nanopowders were investigated by means of X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FTIR) and photo-luminescence emission spectra. Furthermore, the CIE color coordinate of samples were calculated from photoluminescence emission spectra. Results showed that by doping of strontium, the photoluminescence intensity and chromaticity of Y₂ O₃:Eu phosphor was enhanced while crystallite size was decreased.

A Sr-incorporated Na–Ti–O nano-network with a lateral pore size of 20–300 nm was developed on titanium (Ti) substrate using one-step alkali etching in a mixed solution of NaOH and Sr(OH)₂. The pore size of coating increases with Sr content, implying the proper amount of Sr in the electrolyte accelerates nanowire aggregation. The Sr(OH)₂ particle precipitation has no significant effect on the coating morphology. Moreover, biological experiments suggest the prepared coating exhibits good cytocompatibility, and the amount of Sr under 0.7 at.% has no noticeable promoting effect on the cytocompatibility.

Ti6Al4V alloy of titanium is a significant biomaterial due to its biocompatible nature, but it lacks required bioactivity to make it mimic properties to a human bone. Thus, hydroxyl-apatite (HAp), an inorganic compound found in human bones, is generally coated onto Ti6Al4V substrates to improve their bio-characteristics. But, HAp itself lacks certain bio-functionalities, such as allowing tissue bone regeneration and poor binding to the Ti6Al4V substrate, which results in osteoporosis and reduced bioactivity of the bio-implant, respectively. The proposed way out for this is the further doping of HAp with Strontium (Sr) for enabling tissue bone regeneration as well as addition of Polydopamine (PDA) for improved adhesion of HAp-based coatings with the substrate. Moreover, PDA results in increased drug delivery area and thus can be used as a material for enhancing resistance to bacterial growth. The present study demonstrates an experimental work on deposition of HAp, HAp with PDA and HAp with PDA and Sr coatings deposited onto Ti6Al4V alloy by means of biomimetic coating technique. Initially the pure HAp coatings were deposited using 10 SBF (simulated body fluid) solution and optimized in terms of time duration for desired coating uniformity. Then, for the optimized coating duration, the PDA pretreated Ti6Al4V substrates were coated, utilizing HAp, and Sr (at two different compositions) combinations were deposited through modified 10 SBF solutions. The characterization involving microstructural analysis and phase detection was performed for all these coatings using Scanned Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and X-Ray Diffraction (XRD) of the coated substrates and adhesion strength was calculated using a standard pull out adhesion test ISO 13779–4. The study showed an effective and comparatively cheap method of depositing organic coatings using biomimetic technique to obtain improved bio-functionalities in metallic implants at low temperatures.

Hypereutectic Al-Si alloys are widely utilized in the automotive industry due to their high strength-to-weight ratio, minimal thermal expansion, and superior castability. The downside of hypereutectic Al-Si alloys is the formation of coarse primary silicon particles. The primary Si phases were controlled by the growth-hindering agents, phosphorus (refiner), and strontium (modifier) by using a conventional stir casting technique at room temperature. The microstructural changes were observed through an optical microscope and SEM analysis. The additions of 0.08% P have ensured the formation of the uniformly distributed fine-grained particles in the alloy. The primary silicon particle size was reduced from 220$\mu$m to 150$\mu$m as compared to the untreated alloy. The tensile and yield properties of the treated alloy were increased by 12.7% when compared to the untreated alloy with a hardness of 131 BHN. The treated alloy imparted better impact toughness, ensuring a ductile mode of failure through the fractography studies. The influence of the microstructure on the machinability of the alloy was investigated in a dry environment with uncoated and coated inserts (code: CCGT 09T304 FL K10) by varying the process parameters, i.e. speed, feed rate, and depth of cut (DoC). Modification of the primary and eutectic Si phases of an Al-20Si hypereutectic alloy increases machinability with coated inserts as well as its mechanical properties.

Samarium (Sm)-doped calcium–strontium–hydroxyapatite (Ca–Sr–HA:Sm) materials were designed and prepared, and the influence of Sr-introduction on the structure, photoluminescence (PL) and cytotoxicity of samples was revealed. The Sr-doping deduces the shift of some diffraction peaks to smaller angles and enlarges the particle size of samples. The typical red– orange emissions and corresponding luminescence quenching of Sm${}^{3+}$ were observed, and the optimal luminescence performance appeared when $i$(Sr) = 7(Sr/Ca = 7/3) and quenching concentration closes to $x$(Sm) = 0.8 mol.%. The non-radiative transitions and energy transfers due to the dipole–dipole interactions between ions with different symmetry are essential to the luminescence and quenching of Sm${}^{3+}$. Furthermore, the viability values of human HepG2 cells are calculated larger than 90%, and the red–orange color emission was observed when the particles are incubated with cells.

La_2−xSr_xNiO₄ shows a maximum in the c/a ratio around x = 0.6 up to which composition the concentration of holes is equal to that expected theoretically. The material becomes a degenerate semiconductor above a certain temperature up to x = 0.8, but is metallic at room temperature when x ≥ 1.0. All the compositions with x ≥ 0.05 are paramagnetic in the 15 - 300K range. Based on these measurements, an electronic phase diagram is tentatively proposed. It is noteworthy that the antiferromagnetic order disappears at low doping levels in both La_2−xSr_xNiO₄ and La_2−xSr_xCuO₄, but metallicity is seen at 300K only at a much higher x value in the former system.

Strontium hexaferrite powder synthesised conventionally has been treated in nitrogen atmosphere and subsequently calcined in air (Nitrogen Treatment and Re-calcination : NTR Process). The phase identification studies by means of X-ray diffraction (XRD) showed decomposition of strontium hexaferrite and reduction of the resultant iron oxide (Fe₂O₃) during the reaction with nitrogen. According to high resolution scanning electron microscopy (HRSEM) studies, reduction during nitrogenation, resulted in the division of some big grains into much finer sub-grains, strontium hexaferrite, Fe₃O₄ and Sr₇Fe₁₀O₂₂ were the main phases obtained after reduction. The hexaferrite phase reformed on subsequent calcination. The magnetic measurements indicated a significant decrease in the intrinsic coercivity during nitrogenation due to the formation of Fe₃O₄. However, after a re-calcination process, the remanence and maximum magnetisation (i.e. magnetisation at 1100 kA/m ) exhibited values close to the initial values before treatment but the value of the intrinsic coercivity was higher than that prior to nitrogenation. The microstructure showed that this could be attributed to very fine grains which originated from the fine sub-grains formed during nitrogenation.

The selected temperature was 950°C for nitrogenation and 1000°C for re-calcination. The time and initial pressure were selected to be 5 hours and 1 bar respectively. The highest coercivity obtained after re-calcination was 340 kA/m.

We review the recent progress at LNE-SYRTE on an optical lattice clock using Sr atoms. We discuss the required lattice depth to cancel motional effects in such a clock and show that a relatively small lattice depth is sufficient provided the lattice is oriented vertically. We also demonstrate an accurate frequency measurement of the Sr clock transition with accuracy in the low 10^-15 range. Finally, we describe a new non-destructive method to detect the atoms in the clock and discuss the expected associated improvement in the frequency stability of the clock.