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121.
A Soibel SS Banerjee Y Myasoedov ML Rapparort E Zeldov S Ooi T Tamegai 《Pramana》2002,58(5-6):893-898
Using a novel differential magneto-optical imaging technique we investigate the phenomenon of vortex lattice melting in crystals
of Bi2Sr2CaCu2O8 (BSCCO). The images of melting reveal complex patterns in the formation and evolution of the vortex solid-liquid interface
with varying field (H)/temperature (T). We believe that the complex melting patterns are due to a random distribution of material disorder/inhomogeneities across
the sample, which create fluctuations in the local melting temperature or field value. To study the fluctuations in the local
melting temperature/field, we have constructed maps of the melting landscape T
m(H, r), viz., the melting temperature (T
m) at a given location (r) in the sample at a given field (H). A study of these melting landscapes reveals an unexpected feature: the melting landscape is not fixed, but changes rather
dramatically with varying field and temperature along the melting line. It is concluded that the changes in both the scale
and shape of the landscape result from the competing contributions of different types of quenched disorder which have opposite
effects on the local melting transition. 相似文献
122.
A Gurtu P K Malhotra I S Mittra P M Sood SC Gupta VK Gupta GL Kaul LK Mangotra Y Prakash NK Rao ML Sharma 《Pramana》1974,3(5):311-322
This is a continuation of our earlier investigation (Gurtuet al 1974Phys. Lett. 50 B 391) on multiparticle production in proton-nucleus collisions based on an exposure of emulsion stack to 200 GeV/c beam at the NAL. It is found that the ratioR em = 〈n s〉/〈n ch〉, where 〈n ch〉 is the charged particle multiplicity in pp-collisions, increases slowly from about 1 at 10 GeV/c to 1·6 at 68 GeV/c and attains a constant value of 1·71 ± 0·04 in the region 200 to 8000 GeV/c. Furthermore,R em = 1·71 implies an effectiveA-dependence ofR A =A 0.18,i.e., a very weak dependence. Predictions ofR em on various models are discussed and compared with the emulsion data. Data seem to favour models of hadron-nucleon collisions in which production of particles takes place through adouble step mechanism,e.g., diffractive excitation, hydrodynamical and energy flux cascade as opposed to models which envisage instantaneous production. 相似文献
123.
Farré M Asperger D Kantiani L González S Petrovic M Barceló D 《Analytical and bioanalytical chemistry》2008,390(8):1999-2007
In this work, the contributions of triclosan and its metabolite methyl triclosan to the overall acute toxicity of wastewater
were studied using Vibrio fischeri. The protocol used in this paper involved various steps. First, the aquatic toxicities of triclosan and methyl triclosan
were determined for standard substances, and the 50% effective concentrations (EC50) were determined for these compounds. Second, the toxic responses to different mixtures of triclosan, methyl triclosan, and
surfactants were studied in different water matrices, i.e., Milli-Q water, groundwater and wastewater, in order to evaluate
(i) the antagonistic or synergistic effects, and (ii) the influence of the water matrices. Finally, chemical analysis was
used in conjunction with the toxicity results in order to assess the aquatic toxicities of triclosan and its derivative in
wastewaters. In this study, the toxicities of 45 real samples corresponding to the influents and effluents from eight wastewater
treatment works (WWTW) were analyzed. Thirty-one samples were from a wastewater treatment plant (WWTP) equipped with two pilot-scale
membrane bioreactors (MBR), and the influent and the effluent samples after various treatments were characterized via different
chromatographic approaches, including solid-phase extraction (SPE), liquid chromatography coupled to tandem mass spectrometry
(LC–MS/MS), and SPE coupled to gas chromatography–mass spectrometry (GC–MS). The toxicity was determined by measuring the
bioluminescence inhibition of Vibrio fischeri. In order to complete the study and to extrapolate the results to different WWTPs, the toxicity to V. fischeri of samples from seven more plants was analyzed, as were their triclosan and methyl triclosan concentrations. Good agreement
was established between the overall toxicity values and concentrations of the biocides, indicating that triclosan is one of
the major toxic organic pollutants currently found in domestic wastewaters. 相似文献
124.
Gros M Pizzolato TM Petrović M de Alda MJ Barceló D 《Journal of chromatography. A》2008,1189(1-2):374-384
This paper describes the development of an analytical methodology to determine eight beta-blockers in waste waters using molecularly imprinted polymers (MIPs) as extraction and pre-concentration material, followed by liquid chromatography-quadrupole-linear ion trap mass spectrometry (LC-QqLIT MS). The advantages offered by MIPs, in terms of selectivity and specificity, were compared with the most commonly polymeric materials used (the lipophilic-hydrophilic balanced Oasis HLB cartridges). Even though recoveries achieved with both sorbents were similar, ranging from 50 to 110% for sewage treatment plant (STP) effluent and 40-110 for STP influent, respectively, MIPs provided lower method detection limits than Oasis HLB, due to their specificity for target analytes and closely related analogues. Method detection limits (MDL) achieved using MIPs ranged from 0.2 to 6.4 ng/L for STP effluent and from 0.4 to 6.5 ng/L for STP influent. To highlight the advantages of MIPs against conventional polymeric cartridges, a detailed matrix effects study as well as cross reactivity tests were performed. For the latter purpose, the extraction efficiency of some pharmaceuticals and pesticides belonging to different therapeutic classes was assessed. LC-QqLIT MS, used for quantification and confirmation, proved to be a powerful analytical tool, as instrumental detection limits (IDL) achieved ranged from 0.2 to 2.7 pg injected (in multiple reaction monitoring mode (MRM)). In addition the inclusion of high sensitive MS/MS scans for each compound when working in Information Dependent Acquisition mode (IDA) provided extra confirmation for unequivocal identification of target compounds in complex environmental matrices. 相似文献
125.
We work on a model that has succeeded in describing real cases of coexistence of two languages within a closed community of speakers, taking into account bilingualism and incorporating a parameter to measure the distance between languages. The dynamics of this model depend on a characteristic exponent, which weighs the power of the size of a group of speakers to attract new members. So far, this model had been solved only when this characteristic exponent is greater than 1. In this article, we have managed to solve the nature of the stability of all the possible situations for this characteristic exponent, that is, when it is less or equal than 1 and covering also the situations produced when it is 0 or negative. We interpret these new situations and find that, even in such exotic scenarios, there are configurations of the resulting societies where all the languages coexist. © 2014 Wiley Periodicals, Inc. Complexity 21: 86–93, 2016 相似文献
126.
Mira Randahl 《International Journal of Mathematical Education in Science & Technology》2016,47(6):897-916
This paper reports on a study about how the mathematics textbook was perceived and used by the teacher in the context of a calculus part of a basic mathematics course for first-year engineering students. The focus was on the teacher's choices and the use of definitions, examples and exercises in a sequence of lectures introducing the derivative concept. Data were collected during observations of lectures and an interview, and informal talks with the teacher. The introduction and the treatment of the derivative as proposed by the teacher during the lectures were analysed in relation to the results of the content text analysis of the textbook. The teacher's decisions were explored through the lens of intended learning goals for engineering students taking the mathematics course. The results showed that the sequence of concepts and the formal introduction of the derivative as proposed by the textbook were closely followed during the lectures. The examples and tasks offered to the students focused strongly on procedural knowledge. Although the textbook proposes both examples and exercises that promote conceptual knowledge, these opportunities were not fully utilized during the observed lectures. Possible reasons for the teacher's choices and decisions are discussed. 相似文献
127.
Single-molecule spectroscopic investigation of energy migration processes in cyclic porphyrin arrays
Park M Yoon MC Yoon ZS Hori T Peng X Aratani N Hotta J Uji-I H Sliwa M Hofkens J Osuka A Kim D 《Journal of the American Chemical Society》2007,129(12):3539-3544
Covalently linked cyclic porphyrin arrays have been synthesized to mimic natural light-harvesting apparatuses and to investigate the highly efficient energy migration processes occurring in these systems for future applications in molecular photonics. To avoid an ensemble-averaged picture, we performed a single-molecule spectroscopic study on the energy migration processes of cyclic porphyrin arrays and a linear model compound embedded in a rigid polymer matrix by recording fluorescence intensity trajectories, by performing coincidence measurements, and by doing wide-field defocused imaging. Our study demonstrates efficient energy migration within the cyclic porphyrin arrays at the single-molecule level. By comparison with the data of the linear model compound, we could pinpoint the role of the dipole-dipole coupling between diporphyrin subunits and the rigidity of the cyclic structures on the energy transfer processes. 相似文献
128.
Khalid A. M. Salih Mohammed F. Hamza Hamed Mira Yuezhou Wei Feng Gao Ayman M. Atta Toyohisa Fujita Eric Guibal 《Molecules (Basel, Switzerland)》2021,26(4)
The strong demand for rare-earth elements (REEs) is driven by their wide use in high-tech devices. New processes have to be developed for valorizing low-grade ores or alternative metal sources (such as wastes and spent materials). The present work contributed to the development of new sorbents for the recovery of rare earth ions from aqueous solutions. Functionalized mesoporous silica composite was synthesized by grafting diethylenetriamine onto composite support. The physical and chemical properties of the new sorbent are characterized using BET, TGA, elemental analysis, titration, FTIR, and XPS spectroscopies to identify the reactive groups (amine groups: 3.25 mmol N g−1 and 3.41 by EA and titration, respectively) and their mode of interaction with Nd(III) and Gd(III). The sorption capacity at the optimum pH (i.e., 4) reaches 0.9 mmol Nd g−1 and 1 mmol Gd g−1. Uptake kinetics are modeled by the pseudo-first-order rate equation (equilibrium time: 30–40 min). At pH close to 4–5, the sorbent shows high selectivity for rare-earth elements against alkali-earth elements. This selectivity is confirmed by the efficient recovery of REEs from acidic leachates of gibbsite ore. After elution (using 0.5 M HCl solutions), selective precipitation (using oxalate solutions), and calcination, pure rare earth oxides were obtained. The sorbent shows promising perspective due to its high and fast sorption properties for REEs, good recycling, and high selectivity. 相似文献
129.
Oh M Liu X Park M Kim D Moon D Lah MS 《Dalton transactions (Cambridge, England : 2003)》2011,40(21):5720-5727
The self-assembly of a polyprotic pentadentate ligand, N-cyclopentanoylaminobenzoylhydrazide (H(4)L(4)), and an In(III) nitrate hydrate in methanol led to a strained hexanuclear indium metal-organic macrocycle (In-MOM), [In(III)(6)(H(2)L(4))(6)(NO(3))(x)(solvent)(6-x)](NO(3))(6-x) (where, the solvent is either methanol or a water molecule and x is the number of the nitrate anions ligated). The ligand in the doubly deprotonated state serves as an unsymmetric linear ditopic donor and the alternating indium ions in two different chelation modes serve as two different bent ditopic metal acceptors, which led to a D(3)-symmetric hexanuclear In-MOM. Although the hexanuclear In-MOM is enthalpically unfavorable because of the ring strain, the combination of the soft coordination characteristic of the indium ion and the slight ligand deformation from the conjugated planar conformation allows the formation of the entropically favored hexanuclear In-MOM rather than the enthalpically favored octanuclear In-MOM. While the hexanuclear In-MOM is stable in acetonitrile, it partially dissociates into its components in dimethylsulfoxide, and then slowly reaches a new equilibrium state with several different indium species yet to be identified in addition to the free ligand. 相似文献
130.
Ivetic V Trivic S Pogancev MK Popovic M Zlinská J 《Molecules (Basel, Switzerland)》2011,16(9):8062-8075
The purpose of this study was to investigate the effects of treatment with water, n-butanol and ether extracts of Hypercom perforatum L. on epileptogenesis in rabbits. Animals from the control group received solvent-ethanol, and the kindling model of epilepsy was used. Epileptic focus was induced in Chinchilla rabbits by stimulation of the hippocampus. The following parameters were determined: the minimum current strength necessary to induce after-discharge (AD) - discharges appearing after cessation of stimulation; AD duration; the number of stimulations necessary to induce spontaneous kindling; and the latency time for the development of full kindling. The results obtained indicate that epileptogenesis is influenced by Hypericum perforatum L. extract treatment. Animals treated with an ether extract of Hypericum perforatum L. required significantly weaker minimum current strengths for the development of epileptogenic focus, and displayed longer AD times, while the number of electro-stimulations necessary for full kindling was less. In contrast, animals treated with water and n-butanol extracts required increased electro-stimulations for the development of epileptic discharge, and displayed shortened AD durations versus controls. 相似文献