Discrimination of New Zealand stream waters by glass eels of Anguilla australis and Anguilla dieffenbachii

This study tested the hypotheses, using glass eels of longfin eels Anguilla dieffenbachii and shortfin eels Anguilla australis migrating into fresh waters, (1) that both species prefer water from their river of collection to well water, (2) that shortfin eels prefer lowland, pastoral stream water to mainstem river water, (3) that longfin eels are attracted to both waters but do not prefer one to the other, and (4) both prefer water scented with geosmin, a widely occurring metabolite of bacteria and algae, to well water. Glass eels of both species from a river on the west coast of South Island, New Zealand, and shortfin glass eels from an east coast river significantly preferred water from their river of capture to well water. Two to three times as many eels chose their own river water as chose well water. Longfin eels were rare in the east coast river. Shortfin glass eels from the two rivers chose lowland stream water to mainstem river water about two to one in three experiments with different pairs of waters to which they had no prior exposure. Longfin glass eels significantly chose mainstem river water over lowland water in one pair but showed no preference when presented with a different pair. Reactions to solutions of geosmin at concentrations of 10^–5-10^–7 mg 1^–1 were inconclusive, with geosmin being preferred significantly, by shortfin eels, in only one experiment. The interspecific differences in discrimination of natural waters demonstrated in this study, with shortfin eels preferring lowland waters and longfin eels more indifferent to water types, are in broad agreement with both the distribution of adults and observations on their habitat preferences.     

Drosophila ezoana uses an hour‐glass or highly damped circadian clock for measuring night length and inducing diapause

Insects inhabiting the temperate zones measure seasonal changes in day or night length to enter the overwintering diapause. Diapause induction occurs after the duration of the night exceeds a critical night length (CNL). Our understanding of the time measurement mechanisms is continuously evolving subsequent to Bünning's proposal that circadian systems play the clock role in photoperiodic time measurement (Bünning, 1936). Initially, the photoperiodic clocks were considered to be either based on circadian oscillators or on simple hour‐glasses, depending on ‘positive’ or ‘negative’ responses in Nanda–Hamner and Bünsow experiments (Nanda & Hammer, 1958; Bünsow, 1960). However, there are also species whose responses can be regarded as neither ‘positive’, nor as ‘negative’, such as the Northern Drosophila species Drosophila ezoana, which is investigated in the present study. In addition, modelling efforts show that the ‘positive’ and ‘negative’ Nanda–Hamner responses can also be provoked by circadian oscillators that are damped to different degrees: animals with highly sustained circadian clocks will respond ‘positive’ and those with heavily damped circadian clocks will respond ‘negative’. In the present study, an experimental assay is proposed that characterizes the photoperiodic oscillators by determining the effects of non‐24‐h light/dark cycles (T‐cycles) on critical night length. It is predicted that there is (i) a change in the critical night length as a function of T‐cycle period in sustained‐oscillator‐based clocks and (ii) a fixed night‐length measurement (i.e. no change in critical night length) in damped‐oscillator‐based clocks. Drosophila ezoana flies show a critical night length of approximately 7 h irrespective of T‐cycle period, suggesting a damped‐oscillator‐based photoperiodic clock. The conclusion is strengthened by activity recordings revealing that the activity rhythm of D. ezoana flies also dampens in constant darkness.     

How does salinity influence habitat selection and growth in juvenile American eels Anguilla rostrata?

The influence of salinity on habitat selection and growth in juvenile American eels Anguilla rostrata captured in four rivers across eastern Canada was assessed in controlled experiments in 2011 and 2012. Glass eels were first categorized according to their salinity preferences towards fresh (FW), salt (SW) or brackish water (BW) and the growth rate of each group of elvers was subsequently monitored in controlled FW and BW environments for 7 months. Most glass eels (78–89%) did not make a choice, i.e. they remained in BW. Salinity preferences were not influenced by body condition, although a possible role of pigmentation could not be ruled out. Glass eels that did make a choice displayed a similar preference for FW (60–75%) regardless of their geographic origin but glass eels from the St Lawrence Estuary displayed a significantly higher locomotor activity than those from other regions. Neither the salinity preferences showed by glass eels in the first experiment nor the rearing salinities appeared to have much influence on growth during the experiments. Elvers from Nova Scotia, however, reached a significantly higher mass than those from the St Lawrence Estuary thus supporting the hypothesis of genetically (or epigenetically) based differences for growth between A. rostrata from different origins. These results provide important ecological knowledge for the sustained exploitation and conservation of this threatened species.     

Thermoluminescence properties of lithium magnesium borate glasses system doped with dysprosium oxide

We report the impact of dysprosium (Dy³⁺) dopant and magnesium oxide (MgO) modifier on the thermoluminescent properties of lithium borate (LB) glass via two procedures. The thermoluminescence (TL) glow curves reveal a single prominent peak at 190 °C for 0.5 mol% of Dy³⁺. An increase in MgO contents by 10 mol% enhances the TL intensity by a factor of 1.5 times without causing any shift in the maximum temperature. This enhancement is attributed to the occurrence of extra electron traps created via magnesium and the energy transfer to trivalent Dy³⁺ ions. Good linearity in the range of 0.01–4 Gy with a linear correlation coefficient of 0.998, fading as low as 21% over a period of 3 months, excellent reproducibility without oven annealing and tissue equivalent effective atomic numbers ~8.71 are achieved. The trap parameters, including geometric factor (μ_g), activation energy (E) and frequency factor (s) associated with LMB:Dy are also determined. These favorable TL characteristics of prepared glasses may contribute towards the development of Li₂O–MgO–B₂O₃ radiation dosimeters. Copyright © 2015 John Wiley & Sons, Ltd.     

杜氏盐藻玻璃珠新型转化方法的建立

首次采用玻璃珠法成功转化了杜氏盐藻(以下简称盐藻),转化细胞经染色后呈现蓝色,表明外源报告基因GUS得到了成功的表达。同时还进行了转化时间、转速、PEG和质粒DNA浓度等因素对转化影响的分析,优化了转化条件。结果显示最佳的转化条件为:在800μL盐藻(106个细胞/mL)中加入150μLPEG和90μL质粒,在300mg玻璃珠存在的条件下,于转速2400r/min涡旋12s能够得到较为理想的转化结果。该方法与已报道的转化方法相比,具有操作简便、省时快捷、不需要昂贵消耗试剂和仪器设备、比较经济等优点。此方法的建立为深入研究盐藻基因工程提供了有力的工具。     

Effect of curing on water diffusivities in acrylate free films as measured via a sorption technique

Studies were performed to investigate the effect of curing on the diffusion coefficients of water, as measured via the sorption technique, in acrylate polymeric films. The mathematical model selected for obtaining diffusion constants from the vapor-phase sorption studies was derived from the longtime Fourier equation used for diffusion into a planar sheet. For Eudragit NE films, the diffusion coefficients of water decreased continuously until a constant minimum value was reached. Diffusion coefficients in Eudragit RS films decreased initially but increased beyond 4 hours of curing at 70δC and 90°C. This latter result suggested the possible evaporation of plasticizer, which also results in a more dramatic increase in glass transition temperature with curing for the Eudragit RS free film in comparison to the Eudragit NE free film. Such loss of plasticizer could also lead to the formation of molecular-scale channels within the films, which would result in increased film permeability. To verify this proposed explanation, the amounts of triethyl citrate plasticizer in Eudragit RS free films were determined using Fourier-transform infrared spectrophotometry. An optimal curing condition was predicted for Eudragit NE and Eudragit RS films based upon the curing conditions at which a minimum value of the diffusion coefficient was reached. Published: August 31, 2007     

Ketoprofen poly(lactide-co-glycolide) physical interaction

The aim of this work was to provide an understanding of the interaction occurring between ketoprofen and poly(lacticco-glycodic acid) (PLGA) that leads to polymer plasticization. Experimental glass transition temperature (Tg) values were fitted with the theoretical ones predicted by the Fox and Gordon-Taylor/Kelley-Bueche equations. PLGA films containing different amounts of ketoprofen (KET) were prepared by solvent casting and characterized by scanning electron microscopy, differential scanning calorimetry, and Fourier transform infrared spectroscopy (FTIR). Differential scanning calorimetry evidenced that KET acted as a plasticizer in a similar biphasic way in both end-capped and uncapped PLGA. At KET contents of 20% to 35%, depending on the investigated polymer, the Tg was around 23°C. Higher KET amounts did not lower further the Tg, and the excess of drug was found to crystallize into the polymeric matrix. Experimental Tg's deviated negatively from the predicted ones probably because of hydrogen bonding. The FTIR spectra of the films, loaded with different amounts of KET, showed a shift to higher wavenumbers for the peaks at 1697 and 1655 cm⁻¹ confirming the presence of some interactions, probably hydrogen bonds between the ketoprofen carboxylic group and the PLGA carbonyl groups along the polymer backbone. The hydrogen bonding between KET and PLGA is probably responsible for KET plasticizing effect. KET behaving as a lubricant may disrupt polymer chain-chain interactions, removing additional barriers to bond rotation and chain mobility. Published: May 11, 2007     

Biomaterials of PVA and PVP in medical and pharmaceutical applications: Perspectives and challenges

Poly(vinyl alcohol) (PVA) has attracted considerable research interest and is recognized among the largest volume of synthetic polymers that have been produced worldwide for almost one century. This is due to its exceptional properties which dictated its extensive use in a wide variety of applications, especially in medical and pharmaceutical fields. However, studies revealed that PVA-based biomaterials present some limitations that can restrict their use or performances. To overcome these limitations, various methods have been reported, among which blending with poly(vinylpyrrolidone) (PVP) showed promising results. Thus, our aim was to offer a systematic overview on the current state concerning the preparation, properties and various applications of biomaterials based on synergistic effect of mixtures between PVA and PVP. Future trends towards where the biomaterials research is headed were discussed, showing the promising opportunities that PVA and PVP can offer.     

Thermoluminescence glow curve deconvolution and kinetic parameter determination of samarium-doped lithium borosilicate glass

Thermoluminescence glow curves of gamma-irradiated samarium-doped lithium borosilicate glass were investigated. The number of overlapping peaks was determined using the repeated initial rise method. The glow curves were deconvoluted into four overlapping peaks. The trapping parameters such as activation energy E, frequency factor (s), and kinetic order (b) for each peak were determined. The obtained results indicated that the lithium borosilicate glass doped with samarium had four electron trap levels with the average activation energies of 0.82, 1.01, 1.21, and 1.31 eV. Thermal fading analysis of the individual peaks based on the deconvolution data was performed. The obtained results showed high thermal fading of the first peak, but high thermal stability of the second and third peaks compared with the other peaks. These results could be used to explain some observed properties such as high thermal fading and light sensitivity for this thermoluminescent material. Moreover, the obtained results may be helpful in minimizing fading corrections in dosimetric applications.