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With a continuously increasing aging population and the improvement of living standards, large demands of biomaterials are expected for a long time to come. Further development of ...novel biomaterials, that are much safer and of much higher quality, in terms of both biomedical and mechanical properties, are therefore of great interest for both the research scientists and clinical surgeons. Compared with the conventional crystalline metallic counterparts, bulk metallic glasses have unique amorphous structures, and thus exhibit higher strength, lower Young’s modulus, improved wear resistance, good fatigue endurance, and excellent corrosion resistance. For this purpose, bulk metallic glasses (BMGs) have recently attracted much attention for biomedical applications. This review discusses and summarizes the recent developments and advances of bulk metallic glasses, including Ti-based, Zr-based, Fe-based, Mg-based, Zn-based, Ca-based and Sr-based alloying systems for biomedical applications. Future research directions will move towards overcoming the brittleness, increasing the glass forming ability (GFA) thus obtaining corresponding bulk metallic glasses with larger sizes, removing/reducing toxic elements, and surface modifications.
Bulk metallic glasses (BMGs), also known as amorphous alloys or liquid metals, are relative newcomers in the field of biomaterials. They have gained increasing attention during the past decades, as they exhibit an excellent combination of properties and processing capabilities desired for versatile biomedical implant applications. The present work reviewed the recent developments and advances of biomedical BMGs, including Ti-based, Zr-based, Fe-based, Mg-based, Zn-based, Ca-based and Sr-based BMG alloying systems. Besides, the critical analysis and in-depth discussion on the current status, challenge and future development of biomedical BMGs are included. The possible solution to the BMG size limitation, the brittleness of BMGs has been proposed.
Underwater vocalizations of frogs are usually inaudible to the human ear and have been poorly documented. Some authors believe that they are more common than currently recognized, yet there have been ...no new records at the genus level for nearly 30 years. I report on the recordings of underwater calling by the ranid species Amolops ricketti (Boulenger, 1899) from a mountain stream in southern China. Males emitted 2.2–3.5 calls per minute under submerged rocks, which were inaudible to the human ear. Most of the recorded calls lasted 0.73–2.09 s and contained a weak initial note with fewer pulses (1–5) and one to three subsequent notes (3–13 pulses each) repeated at a rate of 0.82–1.99 notes·s−1, with an internote interval lasting 0.36–1.19 s. The dominant frequency of calls ranged from 2.1 to 3.0 kHz, and the notes exhibited increasing intensity and slight upward frequency modulation. Comparisons between individuals of different sexes and breeding stages reveal that the loose skin of the flanks and thighs is a male nuptial trait in A. ricketti. The finding extends the phylogenetic distribution of underwater vocalization to a distinct lineage and constitutes another instance of loose‐skin frogs calling underwater, which can also been identified in Pelobates (Pelobatidae), Leptobrachium (Megophryidae), Telmatobius (Telmatobiidae), Rana italica and Rana sakuraii (Ranidae). These independent cases may allow the proposal of an evolutionary correlation of the two traits in anurans, as a large surface/volume ratio facilitates high levels of cutaneous respiration required for the effective performance of underwater calling. An awareness of this possibility may aid in increasing our understanding of the natural history of anurans.
I report on the recordings of underwater calling by the ranid species Amolops ricketti (Boulenger, 1899) from a mountain stream in southern China. The finding extends the phylogenetic distribution of underwater vocalization to a distinct lineage and constitutes another instance of loose‐skin frogs calling underwater, which can also been identified in another five lineages. These independent cases may allow the proposal of an evolutionary correlation of the two traits in anurans, as a large surface/volume ratio facilitates high levels of cutaneous respiration required for the effective performance of underwater calling.
The use of stirred tank crystallizers (STCs) for the separation and purification of crystals has recently garnered increased attention. Previous research on the crystallization of potassium ...dihydrogen phosphate (KDP) has primarily concentrated on process efficiency and thermodynamics, with less emphasis on kinetics. In this study, we employ STC technology to delve into the crystallization process of KDP. We explored the mechanisms underlying crystal formation by continuously withdrawing a suspension containing target crystals of a specific size distribution. Our investigation of the KDP crystallization process focuses on key parameters—suspension density (
M
T
), solution supersaturation (Δ
C
), and stirring rate (
N
P
) that influence crystal growth and the nucleation process. We propose and validate two crystallization kinetic models for crystal growth and nucleation rates against STC data. By employing multivariate nonlinear regression analysis, we extract crystallization kinetics parameters using the crystallization kinetics model. We also conduct comparative studies of two crystallization kinetic rates. Our findings reveal that the parameters provided by the kinetic mathematical model align well with the experimental data. Furthermore, the discrepancy between experimental and calculated values is maintained within an acceptable range.
Abstract Hot Neptunes are extrasolar planets that are similar in size to Neptune in our solar system but are much closer to their host stars, completing an orbit in 10 days or less. The origin of hot ...Neptunes is not fully understood. A potential large third body at a distance can lead to the migration of long-period planets to become much closer to the host star, and such a dynamical process helps explain the origin of hot Jupiters. We investigate whether hot Neptunes could share a similar origin by analyzing radial velocity data from multiple sources for a sample of 34 hot Neptune systems. Hot Neptune systems appear to have similar values of linear trend to hot Jupiter systems. We perform a maximum likelihood analysis to constrain the mass and distance distribution of the putative third body. The overall fraction of hot Neptune systems with third bodies is consistent with unity, higher than 71% at the 2 σ level. On average, the mass and distance distribution of the third bodies for hot Neptune systems is consistent with that for hot Jupiter systems. Our results suggest that hot-Neptune systems share the same origin mechanism as hot Jupiters, e.g., through the gravitational effect of third bodies.
Several types of multiphase solid (MS) inclusions are identified in garnet from ultrahigh‐pressure (UHP) eclogite in the Dabie orogen. The mineralogy of MS inclusions ranges from pure K‐feldspar to ...pure quartz, with predominance of intermediate types consisting of K‐feldspar + quartz ± silicate (plagioclase or epidote) ± barite. The typical MS inclusions are usually surrounded with radial cracks in the host garnet, similar to where garnet contains relict coesite. Barite aggregates display significant heterogeneity in major element composition, with total contents of only 57–73% and highly variable SiO2 contents of 0.32–25.85% that are positively correlated with BaO and SO3 contents. The occurrence of MS inclusions provides petrographic evidence for partial melting in the UHP metamorphic rock. The occurrence of barite aggregates with variably high SiO2 contents suggests the coexistence of aqueous fluid with hydrous melt under HP eclogite facies conditions. Thus, local dehydration melting is inferred to take place inside the UHP metamorphic slice during continental collision. This is ascribed to phengite breakdown during ‘hot’ exhumation of the deeply subducted continental crust. As a consequence, the aqueous fluid is internally buffered in chemical composition and its local sink is a basic trigger to the partial melting during the continental subduction‐zone metamorphism.
► Electrochemical estimate coincided with mass loss during the initial immersion. ► Electrochemistry did not coincide with mass loss after long-term immersion. ► Reduction of rust layers increase the ...electrochemical results. ► Electrochemistry coincided with mass loss after calibration.
Corrosion rates of mild steel for long-term immersion were estimated by electrochemical and weight-loss methods. The results showed that application of electrochemical methods yielded erroneous values. The main reason was that, β-FeOOH, produced after long-term immersion with high electrochemical activity in the inner rust layer, exerted significant influence. In electrochemical tests, even small polarization can make β-FeOOH participate in cathodic reaction, which leads to overestimating corrosion rate. In order to confirm it, electrochemical behaviour was studied in aerated and deaerated conditions to investigate the effect of rust layers on reduction reaction. After calibration, the electrochemical measurement result was coincided with the weight loss.
Petrological evidence is provided for anatexis of ultrahigh‐pressure (UHP) metamorphic quartzite in the Sulu orogen. Some feldspar grains exhibit elongated, highly cuspate shapes or occur as ...interstitial, cuspate phases constituting interconnected networks along grain boundaries. Elongated veinlets composed of plagioclase + quartz ± K‐feldspar also occur in grain boundaries. These features provide compelling evidence for anatexis of the UHP quartzite. Zircon grains from impure quartzite are all metamorphic growth with highly irregular shape. They contain inclusions of coesite, jadeite, rutile and lower pressure minerals, including multiphase solid inclusions that are composed of two or more phases of muscovite, quartz, K‐feldspar and plagioclase. All zircon grains exhibit steep REE patterns, similar U–Pb ages and Hf isotope compositions with a weighted mean of 218 ± 2 Ma. Most grains have similar δ18O values of −0.6 to 0.1‰, but a few fall in the range −5.2 to −4.3‰. Thus, these grains would have grown from anatectic melts at various pressures. Zircon O isotope differences indicate that anatectic melts were derived from different sources with contrasting O isotopes, but similar Hf isotopes, that is, one from the quartzite itself and the other probably from the country‐rock granitic gneiss. Zircon grains from pure quartzite contain relict magmatic cores and significant metamorphic overgrowths. Domains that contain eclogite facies minerals exhibit flat HREE patterns, no Eu anomalies and concordant U–Pb ages of c. 220 Ma. Similar U–Pb ages are also obtained for domains that contain lower pressure minerals and exhibit steep REE patterns and marked negative Eu anomalies. These observations indicate that zircon records subsolidus overgrowth at eclogite facies conditions but suprasolidus growth at lower pressures. Zircon enclosed by garnet gave consistent U–Pb ages of c. 214 Ma. Such garnet is interpreted as a peritectic product of the anatectic reaction that involves felsic minerals and possibly amphibole and titanite. The REE patterns of epidote and titanite also record multistage growth and metasomatism by anatectic melts. Therefore, the anatexis of UHP metamorphic rocks is evident during continental collision in the Triassic.
Biodegradable metals Zheng, Y.F.; Gu, X.N.; Witte, F.
Materials science & engineering. R, Reports : a review journal,
03/2014, Letnik:
77
Journal Article
Recenzirano
After decades of developing strategies to minimize the corrosion of metallic biomaterials, there is now an increasing interest to use corrodible metals in a number of medical device applications. The ...term “biodegradable metal” (BM) has been used worldwide to describe these new kinds of degradable metallic biomaterials for medical applications and there were many new findings reported over the last decade. In this paper, the definition of BM and its classification are given for the first time, along with the summary of the degradation mechanisms of BMs and its environmental influencing factors, which includes the degeneration of mechanical integrity and the metabolism of the degradation products. The recently-developed representative Mg-based BMs (pure Mg, Mg–Ca alloy, Mg–Zn alloy, etc.), Fe-based BMs (pure Fe, Fe–Mn-based alloys, etc.) and other BMs (pure W, pure Zn and its alloys, Ca-based and Sr-based bulk metallic glasses, etc.) were comprehensively reviewed with emphases on their microstructures, mechanical properties and degradation behaviors, in vitro and in vivo performances, pre-clinical and clinical trials. Moreover, current approaches to control their biodegradation rates to match the healing rates of the host tissues with various surface modification techniques and novel structural designs are summarized. Finally, this paper comprehensively discusses the directions of future development and the challenges of transitioning BMs from raw materials to semi-products to final medical devices. All in all, BM belongs to “bioactive” biomaterials and its future research and development direction should lean towards “third-generation biomedical materials” with “multifunctional capabilities” in a controllable manner to benefit the local tissue reconstruction.
Consumption of food crops contaminated with heavy metals is a major food chain route for human exposure. We studied the health risks of heavy metals in contaminated food crops irrigated with ...wastewater. Results indicate that there is a substantial buildup of heavy metals in wastewater-irrigated soils, collected from Beijing, China. Heavy metal concentrations in plants grown in wastewater-irrigated soils were significantly higher (
P
≤
0.001) than in plants grown in the reference soil, and exceeded the permissible limits set by the State Environmental Protection Administration (SEPA) in China and the World Health Organization (WHO). Furthermore, this study highlights that both adults and children consuming food crops grown in wastewater-irrigated soils ingest significant amount of the metals studied. However, health risk index values of less than 1 indicate a relative absence of health risks associated with the ingestion of contaminated vegetables.
Long-term wastewater irrigation leads to buildup of heavy metals in soils and food crops.
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