Titania nanowires as substrates for sensing and photocatalysis of common textile industry effluents

Sensing and photocatalysis of textile industry effluents such as dyes using mesoporous anatase titania nanowires are discussed here.Spectroscopic investigations show that the titania nanowires preferentially sense cationic (e.g. Methylene Blue, Rhodamine B) over anionic (e.g. Orange G, Remazol Brilliant Blue R) dyes. The adsorbed dye concentration on titania nanowires increased with increase in nanowire dimensions and dye solution pH. Electrochemical sensing directly corroborated spectroscopic findings. Electrochemical detection sensitivity for Methylene Blue increased by more than two times in magnitude with tripling of nanowire average length. Photodegradation of Methylene Blue using titania nanowires is also more efficient than the commercial P25-TiO2 nanopowders. Keeping illumination protocol and observation times constant, the Methylene Blue concentration in solution decreased by only 50% in case of P25-TiO2 nanoparticles compared to a 100% decrease for titania nanowires. Photodegradation was also found to be function of exposure times and dye solution pH.Excellent sensing ability and photocatalytic activity of the titania nanowires is attributed to increased effective reaction area of the controlled nanostructured morphology. (C) 2010 Elsevier B.V. All rights reserved.

Common past, divided memories: historical memory of the Polish minority members in Lithuania

The Master’s thesis examines historical memory of the Polish minority members in Lithuania with regard to how their interpretation of the common Polish-Lithuanian history reiterates or differs from the official Polish and Lithuanian narratives conveyed by the school textbooks. History teaching in high schools carries a crucial state-supported role of “identity building policies” – it maintains a national narrative of memory, which might be exclusive to minorities and their peculiar understanding of history. Lithuanians Poles, in this regard, represent a national minority, which is exposed to two conflicting national narratives of the common past – Polish and Lithuanian. As members of the Polish nation, their understanding of the common Polish-Lithuanian history is conditioned by the Polish historical narrative, acquired as part of the collective memory of the family and/or different minority organizations. On the other hand, they encounter Lithuanian historical narrative of the Polish-Lithuanian past throughout the secondary school history education, where the curriculum, even if taught in Polish, largely represents the Lithuanian point of view. The concept of collective memory is utilized to refer to collective representations of national memory (i.e. publicly articulated narratives and images of collective past in history textbooks) as well as to socially framed individual memories (i.e. historical memory of minority members, where individual remembering is framed by the social context of their identity). The thesis compares the official national historical narratives in Lithuania and Poland, as conveyed by the Polish and Lithuanian history textbooks. The consequent analysis of qualitative interviews with the Polish minority members in Lithuania offers insights into historical memory of Lithuanian Poles and its relation to the official Polish and Lithuanian national narratives of the common past. Qualitative content analysis is applied in both parts of the analysis. The narratives which emerge from the interview data could be broadly grouped into two segments. First, a more pronounced view on the past combines the following elements: i) emphasis on the value of multicultural and diverse past of Lithuania, ii) contestation of “Lithuanocentricity” of the Lithuanian narrative and iii) rejection of the term “occupation”, based on the cultural presuppositions – the dominant position of Polish culture and language in the Vilnius region, symbolic belonging and “Lithuanianness” of the local Poles. While the opposition to the term of “occupation” is in accord with the official Polish narrative conveyed by the textbooks, the former two elements do not neatly adhere to either Polish or Lithuanian textbook narratives. They should rather be considered as an expression of claims for inclusion of plural pasts into Lithuanian collective memory and hence as claims for symbolic enfranchisement into the Lithuanian “imagined community”. The second strand of views, on the other hand, does not exclude assertions about the historically dominant position of Polish culture in Lithuania, but at the same time places more emphasis on the political and historical continuity of the Lithuanian state and highlights a long-standing symbolic connectedness of Vilnius and Lithuania, thus, striking a middle way between the Polish and Lithuanian interpretations of the past.

Design of clutter-rejecting compact pulse bursts with amplitude modulation and frequency-shift keying

A method is presented for the design of compact pulse burst signals, with amplitude and frequency stepping between individual pulses, for optimum rejection of radar clutter distributed arbitrarily in range. The method is illustrated by an example. It is shown that amplitude stepping plays a useful role only when the reciprocal of the individual pulse width is not insignificant compared to the bandwidth permitted to the signal. As an important and useful subclass of the amplitude-and-frequency-stepped signals, constant amplitude FSK bursts are studied and the extent of loss of clutter performance due to amplitude flattening is evaluated.

Cox-2, tenascin, CRP, and ingraft chimerism in a model of post-transplant obliterative bronchiolitis

Chronic rejection in the form of obliterative bronchiolitis (OB) is the major cause of death 5 years after lung transplantation. The exact mechanism of OB remains unclear. This study focused on the role of cyclo-oxygenase (COX) -2, tenascin, and C-reactive protein (CRP) expression, and the occurrence of ingraft chimerism (= cells from two genetically distinct individuals in a same individual) in post-transplant OB development. In our porcine model, OB developed invariably in allografts, while autografts stayed patent. The histological changes were similar to those seen in human OB. In order to delay or prevent obliteration, animals were medicated according to certain protocol. In the beginning of the bronchial allograft reaction, COX-2 induction occurred in airway epithelial cells prior to luminal obliteration. COX-2 expression in macrophages and fibroblasts paralleled the onset of inflammation and fibroblast proliferation. This study demonstrated for the first time, that COX-2 expression is associated with the early stage of post- transplant obliterative airway disease. Tenascin expression in the respiratory epithelium appeared to be predictive of histologic features observed in human OB, and influx of immune cells. Expression in the bronchial wall and in the early obliterative lesions coincided with the onset of onset of fibroblast and inflammatory cell proliferation in the early stage of OB and was predictive of further influx of inflammatory and immune cells. CRP expression in the bronchial wall coincided with the remodelling process. High grade of bronchial wall CRP staining intensity predicted inflammation, accelerated fibroproliferation, and luminal obliteration, which are all features of OB. In the early obliterative plaque, majority of cells expressed CRP, but in mature, collagen-rich plaque, expression declined. Local CRP expression might be a response to inflammation and it might promote the development of OB. Early appearance of chimeric (= recipient-derived) cells in the graft airway epithelium predicted epithelial cell injury and obliteration of the bronchial lumen, which both are features of OB. Chimeric cells appeared in the airway epithelium after repair following transplantation-induced ischemic injury. Ingraft chimerism might be a mechanism to repair alloimmune-mediated tissue injury and to protect allografts from rejection after transplantation. The results of this study indicate, that COX-2, tenascin, CRP, and ingraft chimerism have a role in OB development. These findings increase the understanding of the mechanisms of OB, which may be beneficial in further development of diagnostic options.

Raman induced phase conjugation spectroscopy

Raman induced phase conjugation (RIPC) spectroscopy is a relatively new coherent Raman spectroscopic (CRS) technique using optical phase conjugation (OPC), with which complete Raman spectra of transparent media can be obtained. It is a non-degenerate four-wave mixing technique in which two pulsed laser beams at Ω1 and Ω1 ± Δ where A corresponds to a vibrational frequency of a nonlinear medium mix with a third laser beam at Ω1 to generate a fourth beam Ω1 ± Δ, which is nearly phase conjugate to one of the beams at Ω1. With this technique one can measure the ratio of the resonant and nonresonant components of the third-order nonlinear susceptibilities of the nonlinear media. We have used this technique to get Raman spectra of well-known organic solvents like benzene etc., using pulsed Nd: YAG -dye laser systems. We have also studied the effect of delaying one of the interacting beams with respect to the others and the phase conjugate property of RIPC signals.

Characterization of biaxial crystals for tangentially phase-matched frequency conversion

Ultraviolet radiation has been generated by tangentially phase-matched sum-frequency mixing in biaxial L-arginine phosphate (LAP) crystal for the first time using Nd:YAG output at 1064 nm and Rh 6G dye laser output at 560 nm as the two input sources. Characterization has also been made of such a cheap, biaxial crystal for its possible use in devices for tangentially phase-matched short wavelength generation. If the crystal is of proper cut, thickness and quality so that its maximum capability can be exploited it can replace the potassium dihydrogen phosphate (KDP) group of crystals for various applications.

Interferometry with a novel composite material

An interesting application of optical phase conjugation is phase conjugate interferometry. We report here a new approach to real-time interferometry which combines the high phase conjugate efficiency of photorefractive crystals and the fast response times offered by dye-doped polymer films by using a composite structure. The ability of this material to generate two independent but overlapping phase conjugate waves. which can interfere to reveal the phase changes in a test object, is discussed and demonstrated with a specific example.

Synthesis and photocatalytic properties of AgLi1/3Ru2/3]O-2: A new delafossite oxide

A new delafossite oxide, AgLi1/3Ru2/3]O-2, synthesized by ion-exchanging interlayer-Li+ with Ag+ in layered Li2RuO3, is reported. The transformation of layered Li2RuO3 (monoclinic, space group C2/c) to AgLi1/3Ru2/3]O-2 possessing a delafossite structure (space group R (3) over barm) has been established with powder X-ray diffraction. The successful conversion of LiLi1/3Ru2/3]O-2 to AgLi1/3Ru2/3]O-2 is further confirmed by EDAX analysis. The diffuse reflectance spectrum of AgLi1/3Ru2/3]O-2 shows broad absorption in the UV-visible region suggesting its use as a photocatalyst. The photocatalytic activity of AgLi1/3Ru2/3]O-2 has been investigated by degrading various dyes. It showed significant photocatalytic activity for dye degradation both under UV and solar radiation. (C) 2010 Elsevier B.V. All rights reserved.

Vesicle and Stable Monolayer Formation from Simple ``Click'' Chemistry Adducts in Water

Click chemistry has been successfully extended into the field of molecular design of novel amphiphatic adducts. After their syntheses and characterizations, we have studied their aggregation properties in aqueous medium. Each of these adducts forms stable suspensions in water. These suspensions have been characterized by dynamic light scattering (DLS) studies and transmission electron microscopy (TEM). The presence of inner aqueous compartments in such aggregates has been demonstrated using dye (methylene blue) entrapment studies. These aggregates have been further characterized using X-ray diffraction (XRD), which indicates the existence of bilayer structures in them. Therefore, the resulting aggregates could be described as vesicles. The temperature-induced order-to-disorder transitions of the vesicular aggregates and the accompanying changes in their packing and hydration have been examined using high-sensitivity differential scanning calorimetry, fluorescence anisotropy, and generalized polarization measurements using appropriate membrane-soluble probe, 1,6-diphenylhexatriene, and Paldan, respectively. The findings of these studies are consistent with each other in terms of the apparent phase transition temperatures. Langmuir monolayer studies confirmed that these click adducts also form stable monolayers on buffered aqueous subphase at the air-water interface.

Role of lattice defects and crystallite morphology in the UV and visible-light-induced photo-catalytic properties of combustion-prepared TiO2

The physico-chemical, photo-physical and micro-structural properties responsible for the strikingly different photocatalytic behavior of combustion-prepared TiO2 (c.TiO2) and Degussa P25 (d.TiO2) samples are elucidated in this study. Electron microscopy and selected area electron diffraction micrographs revealed that the two samples exhibited different morphologies. The grains of c.TiO2 were spherical and comprised of 5-6 nm size primary particle. On the other hand, d.TiO2 consisted of large (0.5-3.0 mu m) size and irregular shape aggregates having primary particles of 15-40 nm cross-sectional diameter. The ESR study revealed that the presence of certain defect states in c.TiO2 helped in stabilization of O-. and Ti3+-OH type species during room-temperature UV-irradiation. No such paramagnetic species were however formed over d.TiO2 under similar conditions. C1s and Ti 2p XPS spectra provide evidence for the presence of some lattice vacancies in c.TiO2 and also for the bulk Ti4+ -> Ti3+ conversion during its UV-irradiation. Compared to d.TiO2, c.TiO2 displayed considerably higher activity for discoloration of methyl orange but very poor activity for splitting of water, both under UV and visible light radiations. This is attributed to enhanced surface adsorption of dye molecules over c.TiO2, because of its textural features and also the presence of photo-active ion-radicals. On the other hand, the poor activity of c.TiO2 for water splitting is related to certain defect-induced inter-band charge trapping states in the close vicinity of valence and conduction bands of c.TiO2, as revealed by thermoluminescence spectroscopy. Further, the dispersion of nanosize gold particles gave rise to augmented activity of both the catalysts, particularly for water splitting. This is explained by the promotional role of Au-0 or Au-0/TiO2 interfacial sites in the adsorption and charge-adsorbate interaction processes. (C) 2011 Elsevier B.V. All rights reserved.

Rapid Synthesis of Ultrahigh Adsorption Capacity Zirconia by a Solution Combustion Technique

Tetragonal ZrO2 was synthesized by the solution combustion technique using glycine as the fuel. The compound was characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, infrared spectroscopy, and BET surface area analysis. The ability of this compound to adsorb dyes was investigated, and the compound had a higher adsorption capacity than commercially activated carbon. Infrared spectroscopic observations were used to determine the various interactions and the groups responsible for the adsorption activity of the compound. The effects of the initial concentration of the dye, temperature, adsorbent concentration, and pH of the solution were studied. The kinetics of adsorption was described as a first-order process, and the relative magnitudes of internal and external mass transfer processes were determined. The equilibrium adsorption was also determined and modeled by a composite Langmuir-Freundlich isotherm.

First-Order Hyperpolarizabilities of Sulfophthalein Dyes

In this paper we report the first hyperpolarizabilities (beta) of 12, sulfophthalein dyes. Since these dyes are ionic in nature, their second-order nonlinearities were measured by the hyper-Rayleigh scattering technique in solution. The measured beta values are large and highly solvent dependent. Inclusion of solvent polarity in ab initio estimates of static second-order polarizability does not fully account for the experimental beta values. Contributions from the dissociated forms of the dye in different solvents seem to play an important role in enhancing beta in these systems.

Optimal control of arrivals to queues with delayed queue length information

We consider discrete-time versions of two classical problems in the optimal control of admission to a queueing system: i) optimal routing of arrivals to two parallel queues and ii) optimal acceptance/rejection of arrivals to a single queue. We extend the formulation of these problems to permit a k step delay in the observation of the queue lengths by the controller. For geometric inter-arrival times and geometric service times the problems are formulated as controlled Markov chains with expected total discounted cost as the minimization objective. For problem i) we show that when k = 1, the optimal policy is to allocate an arrival to the queue with the smaller expected queue length (JSEQ: Join the Shortest Expected Queue). We also show that for this problem, for k greater than or equal to 2, JSEQ is not optimal. For problem ii) we show that when k = 1, the optimal policy is a threshold policy. There are, however, two thresholds m(0) greater than or equal to m(1) > 0, such that mo is used when the previous action was to reject, and mi is used when the previous action was to accept.

The Folding Mechanism of Barstar: Evidence for Multiple Pathways and Multiple Intermediates

The mechanism of folding of the small protein barstar in the pre-transition zone at pH 7, 25 degrees C has been characterized using rapid mixing techniques. Earlier studies had established the validity of the three-state U-S reversible arrow U-F reversible arrow N mechanism for folding and unfolding in the presence of guanidine hydrochloride (GdnHCl) at concentrations greater than 2.0 M, where U-S and U-F are the slow-refolding and fast-refolding unfolded forms, respectively, and N is the fully folded form. It is now shown that early intermediates, I-S1 and I-S2 as well as a late native-like intermediate, I-N, are present on the folding pathways of U-S, and an early intermediate I-F1 on the folding pathway of U-F, when bars tar is refolded in concentrations of GdnHCl below 2.0 M. The rates of formation and disappearance of I-N, and the rates of formation of N at three different concentrations of GdnHCl in the pre-transition zone have been measured. The data indicate that in 1.5 M GdnHCl, I-N is not fully populated on the U-S --> I-S1 --> I-N --> N pathway because the rate of its formation is so slow that the U-S reversible arrow U-F reversible arrow N pathway can effectively compete with that pathway. In 1.0 M GdnHCl, the U-S --> I-S1 --> I-N transition is so fast that I-N is fully populated. In 0.6 M GdnHCl, I-N appears not to be fully populated because an alternative folding pathway, U-S --> I-S2 --> N, becomes available for the folding of U-S, in addition to the U-S --> I-S1 --> I-N --> N pathway Measurement of the binding of the hydrophobic dye 1-anilino-8-naphthalenesulphonate (ANS) during folding indicates that ANS binds to two distinct intermediates, I-M1 and I-M2, that form within 2 ms on the U-S --> I-M1 --> I-S1 --> I-N --> N and U-S --> I-M2 --> I-S2 --> N pathways. There is no evidence for the accumulation of intermediates that can bind ANS on the folding pathway of U-F.

Translational velocity oscillations of piston generated vortex rings

Experimental results are presented that show that the translational velocities of piston generated vortex rings often undergo oscillations, similar to those recently discovered for drop generated rings. An attempt has been made to minimize uncertainties by utilizing both dye and hydrogen bubbles for visualization and carefully repeating measurements on the same ring and on different realizations under the same nominal piston conditions. The results unambiguously show that under most conditions, both for laminar and turbulent rings and for rings generated from pipes and orifices, the oscillations are present. The present results, together with the earlier results on drop generated rings, give support to the view that translational velocity oscillations are probably an inherent feature of translating vortex ring fields. (C) 1995 American Institute of Physics.