细粒沉积物多组分粒度特征及其成因机制研究

By using high-resolution laser grain size instrument Mastersizer 2000, the grain size distribution of windblown depositions (loess and sandy dunes), aqueous sediments (lake, river, riverside and foreshore sand), weathering crust, sloping materials and other fine-grain sediments are systemically measured. The multimodal characteristics of grain size distribution of these sediments are carefully studied. The standard patterns and their grain size characteristics of various sediments are systemically summarized. The discrepancies of multimodal distribution among windblown depositions, aqueous sediments and other sediments are concluded and the physical mechanisms of grain size multimodal distribution of various sediments are also discussed in this paper. The major conclusions are followed: 1. The multimodal characteristic of grain size distribution is a common feature in all sediments and results from properties of transportation medium, dynamic intensity, transportation manner and other factors. 2. The windblown depositions are controlled by aerodynamic forcing, resulting in that the median size of the predominant mode gradually decreases form sandy dunes to loess. Similarly, the aqueous sediments are impacted by dynamic forces of water currents and the median grain size of the predominant mode decreases gradually from river to lake sediments. Because the kinetic viscidity of air is lower than of water, the grain size of modes of windblown depositions is usually finer than that of corresponding modes of aqueous sediments. Typical characteristics of sediments grain size distribution of various sediments have been summarized in the paper: (1) Suspended particles which diameters are less than 75μm are dominant in loess and dust. There are three modes in loess’ grain size distribution: fine, median and coarse (the median size is <1μm、1-10μm、10-75μm, respectively). The coarse mode which percentage is larger than that of others is controlled by source distance and aerodynamic intensity of dust source areas. Some samples also have a saltation mode which median size is about 300-500μm. Our analysis demonstrates that the interaction of wind, atmospheric turbulence, and dust grain gravity along the dust transportation path results in a multimodal grain size distribution for suspended dust. Changes in the median sizes of the coarse and medium modes are related to variation in aerodynamic forcing (lift force related to vertical wind and turbulence) during dust entrainment in the source area and turbulence intensity in the depositional area. (2) There is a predominant coarse saltation mode in grain size distribution of sandy dunes, which median size is about 100-300μm and the content is larger than that of other modes. The grain size distribution curve is near axis symmetric as a standard logarithm normal function. There are some suspended particles in some samples of sandy dunes, which distribution of the fine part is similar to that of loess. Comparing with sandy samples of river sediments, the sorting property of sandy dunes is better than of river samples although both they are the saltation mode. Thus, the sorting property is a criterion to distinguish dune sands and river sands. (3) There are 5~6 modes (median size are <1μm, 1-10μm, 10-70μm, 70-150μm, 150-400μm, >400μm respectively) in grain size distribution of lacustrine sediments. The former 4 modes are suspensive and others are saltated. Lacustrine sediments can be divided into three types: lake shore facies, transitional facies and central lake facies. The grain size distributions of the three facies are distinctly different and, at the same time, the transition among three modes is also clear. In all these modes, the third mode is a criteria to identify the windblown deposition in the watershed. In lake shore sediments, suspended particles are dominant, a saltation mode sometimes occurs and the fourth mode is the most important mode. In the transitional facies, the percentage of the fourth mode decreases and that of the second mode increases from lake shore to central lake. In the central lake facies, the second mode is dominant. A higher content of the second mode indicates its position more close to the central lake. (4) The grain size distribution of river sediments is the most complex. It consist of suspension, saltation and rolling modes. In most situations, the percentage of the saltation mode is larger than that of other modes. The percentage of suspension modes of river sediments is more than of sandy dunes. The grain size distribution of river sediments indicates dynamic strength of river currents. If the fourth mode is dominant, the dynamic forcing of river is weaker, such as in river floodplain. If the five or sixth mode is dominant, the water dynamic forcing of rivers is strong. (5) Sediments can be changed by later forcing in different degree to form some complicated deposition types. In the paper, the grain size distribution of aqueous sediments of windblown deposition, windblown sediments of aqueous deposition, weathering crust and slope materials are discussed and analyzed. 3. The grain size distribution characteristics of different sediments are concluded: (1) Modal difference: Usually there are suspended and saltation modes in the windblown deposition. The third mode is dominant in loess dust and the fifth mode is predominant in sandy dunes. There are suspended, saltation and rolling particles in aqueous sediments. In lacustrine sediments, the second and fourth mode are predominant for central lake facies or lake shore facies, respectively. In river sediments, the fourth, or fifth, or sixth mode is predominant. Suspended modes: the grain size of suspended particles of windblown depositions usually is less than 75μm. The content of suspended particles is lower or none in sandy dunes. However, suspended particles of aqueous sediments may reach 150μm. Difference in grain size of suspended modes represents difference between transitional mediums and the strength of dynamic forcing. Saltation modes: the median size of saltation mode of sandy dunes fluctuates less than that of river sediments. (2) Loess dust and lacustrine sediment: Their suspended particles are clearly different. There is an obvious pit between the second and the third modes in grain size distribution of lacustrine sediments. The phenomenon doesn’t occur in loess dust. In lacustrine sediments, the second mode can be a dominant mode, such as central lake facies, and contents of the second and the third modes change reversely. However, the percentage of the third mode is always the highest in loess dust. (3) Dune Sand and fluvial sand: In these two depositions, the saltation particles are dominant and the median sizes of their saltation modes overlay in distribution range. The fifth mode of dune sand fluctuates is sorted better than that of fluvial sand. (4) Lacustrine and fluvial sediments: In lacustrine sediments, there are 5-6 modes and suspended particles can be predominant. The second mode is dominant in central lake facies and the third mode is dominant in lake shore facies. Saltation or roll modes occurred in central lake facies may indicate strong precipitation events. In fluvial sediments, saltation particles (or rolling particles) usually dominant. 4. A estimation model of lake depth is firstly established by using contents of the second, the third and the fourth modes. 5. The paleoenvironmental history of the eastern part of SongLiao basin is also discussed by analyzing the grain size distribution of Yushu loess-like sediments in Jilin. It was found that there is a tectonic movement before 40ka B.P. in SongLiao basin. After the movement, loess dust deposited in Yushu area as keerqin desert developed. In recent 2000 years, the climate became drier and more deserts activated in the eastern part of Song-Liao basin.

西部黄土高原中新世风尘沉积剖面的磁性地层学和沉积学研究

Observation of the Miocene aeolian dust deposits in Qin'an area provide a long-timescale, almost continuous geological record for understanding significant environmental changes, such as the environmental evolution of Asian monsoons and the inland Asian aridification, and make possible new explorations of global and regional environmental evolutions and other relevant studies. However, the QA-I and QA-II sections that are previously investigated are near to each other, and there is a lack in understanding the spatial characteristics of changes in paleoenvironment. Therefore, new sections of Miocene aeolian dust deposits are needed to complete the present spatial framework. Meanwhile, it is necessary to carry out in-depth studies, which are already belated, on the depositional characteristics of these Miocene aeolian dust deposits.This thesis choose the Miziwan section and Shaogou section that are west to Liupan Mountain for magnetostratigraphic studies, results of which are compared with the QA-I section with respect to the lithology, magnetic susceptibility and paleomagnetic polarity stratigraphy. Quartz-fraction grain size of 300 samples from the QA-I section was analyzed. In addition, 30 out of these samples were determined in terms of the quartz morphological characteristics by using scanning electronic microscopy. On the basis of these data and the correlation with the Xifeng sequence of aeolian dust deposits, the following 3 conclusions are drawn as below:The upper and the lower boundary age of the Miziwan section are 11.6 Ma B.Rand 18.5 Ma B.R, respectively. The Shaogou section spans from 15.1 Ma B.P, to20.8 Ma B.R The lower boundary age of both sections is no older than that of theQA-I section. The Miziwan and the Shaogou sections can be well correlated withthe QA-I section in terms of the field lithological features, magnetic susceptibilityand magnetic polarity stratigraphy.Sedimentological evidence of the QA-I quartz grain size and quartz morphologicalcharacteristics further supports the previous conclusion that the QA-Iloess-paleosol sequence is of aeolian origin, and also verifies the accretionalfeatures in paleosols of this sequence in terms of the grain-size composition.Modifications of the grain-size composition of the original dusts due to later-stageweathering and pedogenesis are common characteristic of Miocene and Quaternary aeolian dust depositions. The above-mentioned processes further rework and refine the bulk grain size, which is more evident in paleosol layers. 3, Like the hipparion Red-Earth and the Quaternary aeolian deposits, the Miocene loess deposits are transported by near-ground winter monsoons. However, the average wind intensity evidenced by the quartz median grain size of Miocene loess, together with the maximum wind intensity by the quartz maximum grain size, is weaker than those of the Quaternary.

Atomic layer deposition of copper for CMOS interconnects

This work concerns the atomic layer deposition (ALD) of copper. ALD is a technique that allows conformal coating of difficult topographies such as narrow trenches and holes or even shadowed regions. However, the deposition of pure metals has so far been less successful than the deposition of oxides except for a few exceptions. Challenges include difficulties associated with the reduction of the metal centre of the precursor at reasonable temperatures and the tendency of metals to agglomerate during the growth process. Cu is a metal of special technical interest as it is widely used for interconnects on CMOS devices. These interconnects are usually fabricated by electroplating, which requires the deposition of thin Cu seed layers onto the trenches and vias. Here, ALD is regarded as potential candidate for replacing the current PVD technique, which is expected to reach its limitations as the critical dimensions continue to shrink. This work is separated into two parts. In the first part, a laboratory-scale ALD reactor was constructed and used for the thermal ALD of Cu. In the second part, the potentials of the application of Cu ALD on industry scale fabrication were examined in a joint project with Applied Materials and Intel. Within this project precursors developed by industrial partners were evaluated on a 300 mm Applied Materials metal-ALD chamber modified with a direct RF-plasma source. A feature that makes ALD a popular technique among researchers is the possibility to produce high- level thin film coatings for micro-electronics and nano-technology with relatively simple laboratory- scale reactors. The advanced materials and surfaces group (AMSG) at Tyndall National Institute operates a range of home-built ALD reactors. In order to carry out Cu ALD experiments, modifications to the normal reactor design had to be made. For example a carrier gas mechanism was necessary to facilitate the transport of the low-volatile Cu precursors. Precursors evaluated included the readily available Cu(II)-diketonates Cu-bis(acetylacetonate), Cu-bis(2,2,6,6-tetramethyl-hepta-3,5-dionate) and Cu-bis(1,1,1,5,5,5-hexafluoacetylacetonate) as well as the Cu-ketoiminate Cu-bis(4N-ethylamino- pent-3-en-2-onate), which is also known under the trade name AbaCus (Air Liquide), and the Cu(I)- silylamide 1,3-diisopropyl-imidazolin-2-ylidene Cu(I) hexamethyldisilazide ([NHC]Cu(hmds)), which was developed at Carleton University Ottawa. Forming gas (10 % H2 in Ar) was used as reducing agent except in early experiments where formalin was used. With all precursors an extreme surface selectivity of the deposition process was observed and significant growth was only achieved on platinum-group metals. Improvements in the Cu deposition process were obtained with [NHC]Cu(hmds) compared with the Cu(II) complexes. A possible reason is the reduced oxidation state of the metal centre. Continuous Cu films were obtained on Pd and indications for saturated growth with a rate of about 0.4 Å/cycle were found for deposition at 220 °C. Deposits obtained on Ru consisted of separated islands. Although no continuous films could be obtained in this work the relatively high density of Cu islands obtained was a clear improvement as compared to the deposits grown with Cu(II) complexes. When ultra-thin Pd films were used as substrates, island growth was also observed. A likely reason for this extreme difference to the Cu films obtained on thicker Pd films is the lack of stress compensation within the thin films. The most likely source of stress compensation in the thicker Pd films is the formation of a graded interlayer between Pd and Cu by inter-diffusion. To obtain continuous Cu films on more materials, reduction of the growth temperature was required. This was achieved in the plasma assisted ALD experiments discussed in the second part of this work. The precursors evaluated included the AbaCus compound and CTA-1, an aliphatic Cu-bis(aminoalkoxide), which was supplied by Adeka Corp.. Depositions could be carried out at very low temperatures (60 °C Abacus, 30 °C CTA-1). Metallic Cu could be obtained on all substrate materials investigated, but the shape of the deposits varied significantly between the substrate materials. On most materials (Si, TaN, Al2O3, CDO) Cu grew in isolated nearly spherical islands even at temperatures as low as 30 °C. It was observed that the reason for the island formation is the coalescence of the initial islands to larger, spherical islands instead of forming a continuous film. On the other hand, the formation of nearly two-dimensional islands was observed on Ru. These islands grew together forming a conductive film after a reasonably small number of cycles. The resulting Cu films were of excellent crystal quality and had good electrical properties; e.g. a resistivity of 2.39 µΩ cm was measured for a 47 nm thick film. Moreover, conformal coating of narrow trenches (1 µm deep 100/1 aspect ratio) was demonstrated showing the feasibility of the ALD process.

Patterns of de novo allo B cells and antibody formation in chronic cardiac allograft rejection after alemtuzumab treatment.

Even though the etiology of chronic rejection (CR) is multifactorial, donor specific antibody (DSA) is considered to have a causal effect on CR development. Currently the antibody-mediated mechanisms during CR are poorly understood due to lack of proper animal models and tools. In a clinical setting, we previously demonstrated that induction therapy by lymphocyte depletion, using alemtuzumab (anti-human CD52), is associated with an increased incidence of serum alloantibody, C4d deposition and antibody-mediated rejection in human patients. In this study, the effects of T cell depletion in the development of antibody-mediated rejection were examined using human CD52 transgenic (CD52Tg) mice treated with alemtuzumab. Fully mismatched cardiac allografts were transplanted into alemtuzumab treated CD52Tg mice and showed no acute rejection while untreated recipients acutely rejected their grafts. However, approximately half of long-term recipients showed increased degree of vasculopathy, fibrosis and perivascular C3d depositions at posttransplant day 100. The development of CR correlated with DSA and C3d deposition in the graft. Using novel tracking tools to monitor donor-specific B cells, alloreactive B cells were shown to increase in accordance with DSA detection. The current animal model could provide a means of testing strategies to understand mechanisms and developing therapeutic approaches to prevent chronic rejection.

Estimation of atmospheric nutrient inputs to the Atlantic Ocean from 50°N to 50°S based on large-scale field sampling: Iron and other dust-associated elements

Atmospheric inputs of mineral dust supply iron and other trace metals to the remote ocean and can influence the marine carbon cycle due to iron's role as a potentially limiting micronutrient. Dust generation, transport, and deposition are highly heterogeneous, and there are very few remote marine locations where dust concentrations and chemistry (e.g., iron solubility) are routinely monitored. Here we use aerosol and rainwater samples collected during 10 large-scale research cruises to estimate the atmospheric input of iron, aluminum, and manganese to four broad regions of the Atlantic Ocean over two 3 month periods for the years 2001–2005. We estimate total inputs of these metals to our study regions to be 4.2, 17, and 0.27 Gmol in April–June and 4.9, 14, and 0.19 Gmol in September–November, respectively. Inputs were highest in regions of high rainfall (the intertropical convergence zone and South Atlantic storm track), and rainfall contributed higher proportions of total input to wetter regions. By combining input estimates for total and soluble metals for these time periods, we calculated overall percentage solubilities for each metal that account for the contributions from both wet and dry depositions and the relative contributions from different aerosol types. Calculated solubilities were in the range 2.4%–9.1% for iron, 6.1%–15% for aluminum, and 54%–73% for manganese. We discuss sources of uncertainty in our estimates and compare our results to some recent estimates of atmospheric iron input to the Atlantic.

An Investigation into the Optimum Thickness of Titanium Dioxide Thin Films Synthesized by Using Atmospheric Pressure Chemical Vapour Deposition for Use in Photocatalytic Water Oxidation

Twenty eight films of titanium dioxide of varying thickness were synthesised by using atmospheric pressure chemical vapour deposition (CVD) of titanium(IV) chloride and ethyl acetate onto glass and titanium substrates. Fixed reaction conditions at a substrate temperature of 660 degrees C were used for all depositions, with varying deposition times of 5-60 seconds used to control the thickness of the samples. A sacrificial electron acceptor system composed of alkaline sodium persulfate was used to determine the rate at which these films could photo-oxidise water in the presence of 365 nm light. The results of this work showed that the optimum thickness for CVD films on titanium substrates for the purposes of water oxidation was approximate to 200 nm, and that a platinum coating on the reverse of such samples leads to a five-fold increase in the observed rate of water oxidation.

An investigation of clustered radiation-induced lesions in DNA

Recent track structure modelling studies indicate that radiation induced damage to DNA consists of a spectrum of different lesions of varying complexity. There is considerable evidence to suggest that, in repair-proficient systems, it is only the small proportion of more complex forms that is responsible for most of the biological effect. The complex lesions induced consist initially of clustered radical sites and a knowledge of their special chemistry is important in modelling how they react to form the more stable products that are processed by the repair systems. However, much of the current understanding of the chemical stage of radiation has developed from single-radical systems and there is a need to translate this to the more complex reactions that are likely to occur at the important multiple radical sites. With low LET radiation, DNA dsb may derive either from single-radical attack that damages both strands by a transfer mechanism, or from pairs of radical sites induced in close proximity, with one or more radical on each strand. With high LET radiation, modelling studies indicate that there is an increased probability of dsb arising from sites with more than two radical centres, leading to a greater frequency of more complex types of break. The spectrum of these lesions depends on the overall outcome of consecutive physical and chemical processes. The initial pattern of radical damage is determined by the energy depositions on and around the DNA, according to the type of radiation. This pattern is then modified by scavengers that inhibit the formation of radicals on the DNA, and by agents that either chemically repair (e.g. thiols) or fix (e.g. oxygen) a large fraction of these radicals. The reaction kinetics associated with clustered radical sites will differ from those of single sites: (1) because of the opportunities for interactions between the radicals themselves; and (2) because certain endpoints, e.g. a dsb, may require a combination of the products of two or more radicals. Fast response techniques using pulsed low and high LET irradiation have been established to measure the reactions of radical sites on pBR322 plasmid DNA with oxygen and thiols with a view to obtaining information about cluster size. This paper describes experimental approaches to explore the role of the chemical stage of the radiation effect in relation to lesion complexity.

Magnetisation of 2.6T in Gadolinium Thin Films

There is renewed interest in rare-earth elements and gadolinium in particular for a range of studies in coupling physics and applications. However, it is still apparent that synthesis impacts understanding of the intrinsic magnetic properties of thin gadolinium films, particularly for thicknesses of topicality. We report studies on 50nm thick nanogranular polycrystalline gadolinium thin films on SiO2 wafers that demonstrate single-crystal like behavior. The maximum in-plane saturation magnetization at 4K was found to be 4pMS4K = (2.61±0.26)T with a coercivity of HC4K = (160±5)Oe. A maximum Curie point of TC = (293±2)K was measured via zero-field-cooled - field-cooled magnetization measurements in close agreement with values reported in bulk single crystals. Our measurements revealed magnetic transitions at T1 = (12±2)K (as deposited samples) and T2 = (22±2)K (depositions on heated substrates) possibly arising from the interaction of paramagnetic fcc grains with their ferromagnetic hcp counterparts.

Línguas em Timor-Leste: que gestão escolar do plurilinguismo?

O presente estudo tem por objetivo compreender, no contexto geopolítico de Timor-Leste, quais as imagens, funções e estatutos das línguas que aí circulam e, simultaneamente, percecionar de que modo a Escola gere essa pluralidade linguística. Para o efeito, tivemos em conta as representações/imagens relativamente às línguas, às suas funções e estatutos, não só dos alunos e dos diferentes atores educativos (professores, diretores de escola e formadores do 1.º e 2.º ciclo), mas também aquelas que circulam em contexto social alargado, onde incluímos os intervenientes e os responsáveis pelas políticas educativas e outros elementos da população. Foi deste modo que procurámos perceber de que forma tais representações se influenciam reciprocamente e se refletem na Escola. O estudo realizado foi de cariz etnográfico. Assim, o investigadorobservador, colocado no terreno, foi produzindo um diário do observador e recolhendo informação etnográfica, através da sua convivência com a sociedade timorense (escritos do quotidiano, questionário à polícia, observação de aula, entre outros), auscultando as “vozes” quer dos alunos (por meio de biografias linguísticas e desenhos), quer dos atores educativos (através de biografias linguísticas e entrevistas), quer ainda dos intervenientes nas políticas educativas (com recurso a entrevistas) e de alguns jovens timorenses, recorrendo de novo às entrevistas. Simultaneamente, foi feita uma recolha documental, ao longo de todo o período em que o estudo decorreu, que integrou fontes escritas (documentos oficiais, como sejam os documentos reguladores das políticas linguísticas e os manuais, fontes não oficiais, incluindo documentos vários e testemunhos e fontes estatísticas, como os Censos) e fontes não escritas (imagens e sons registados, estes posteriormente transcritos). Todos estes dados foram classificados em dados primários e secundários, em função da sua relevância para o estudo. Para a sua análise socorremo-nos da análise de conteúdo para as biografias, as entrevistas e os manuais de língua portuguesa, estes no quadro de uma abordagem para a diversidade linguística e cultural, de uma análise documental para os documentos reguladores do Sistema Educativa e outros documentos oficiais relativos às línguas e, finalmente, recorremos a uma análise biográfica (Molinié, 2011) para os desenhos realizados pelos alunos. Os resultados obtidos vieram evidenciar o multilinguismo social e escolar que se vive no país, as imagens e as funções que as línguas desempenham nestes dois contextos, o escolar e o da sociedade alargada, permitindo-nos compreender que a Escola não é apenas um microcosmos dentro da sociedade, mas um espaço de encontro, por vezes de confronto, entre diversas línguas, culturas e identidades. Ela é também espaço onde as questões do plurilinguismo são mais desafiantes na medida em que as línguas não são apenas objeto de ensino aprendizagem, mas desempenham igualmente funções importantes na aquisição dos saberes escolares, na interação social e no desenvolvimento cognitivo dos alunos. Nestes contextos, ocorrem duas situações relevantes, uma é o facto de a Escola ser um lugar onde os repertórios linguísticos plurilingues dos alunos entram em contacto com as línguas de escolarização, o português, o tétum e o malaio indonésio e outra é que saberes escolares e saberes culturais utilizam línguas diferentes, isto é, os primeiros são veiculados em tétum e português, eventualmente em malaio indonésio, mas os saberes culturais são expressos nas línguas autóctones, ameaçadas, porém, por uma crescente expansão do tétum. Contudo, estas línguas criam também espaços privados, identitários e de coesão social dentro da grande cidade que é Díli. São línguas “secretas” e “de defesa.” Por fim, referiremos a urgência para que se tomem medidas no sentido de se criar um consenso sobre a normalização do tétum, que conduza à sua aplicação em contexto educativo e ao seu desenvolvimento funcional, isto é, que leve à planificação do seu estatuto. Visa-se, com este estudo, contribuir para que os atores, acima referidos, possam «repensar» a Escola, em Timor Leste, e, em particular, no que diz respeito à gestão das línguas que nela circulam, através de uma política linguística (educativa) que beneficie o Sistema Educativo, com eventuais repercussões no âmbito do currículo, da produção de materiais e da formação de professores. Face aos resultados obtidos, ainda que consideremos este estudo como parcelar, pelo facto de ter decorrido, sobretudo, na capital timorense, permitimo-nos sugerir a necessidade de esbater fronteiras entre o espaço escolar e as realidades dos alunos, encontrando uma gestão escolar deste plurilinguismo que crie um currículo mais integrador dos saberes linguísticos dos alunos.

Monsenhor Airosa - pedagogo - empresário : história do colégio de regeneração de Braga : (1869-1931)

Tese de doutoramento, Educação (História da Educação), Universidade de Lisboa, Instituto de Educação, 2015

Estate of S.D. Woodruff in Account with H.H. Collier

The estate of S.D. Woodruff in account with H.H. Collier. This contains 1 1/2 printed pages listing expenses to be paid to Johnson Clench for copy of depositions, 1906-1907.

Spray Pyrolysed Zinc Oxide Thin Films : Effects of Doping and Ion Beam Irradiation

In recent years scientists have made rapid and significant advances in the field of semiconductor physics. One of the most important fields of current interest in materials science is the fundamental aspects and applications of conducting transparent oxide thin films (TCO). The characteristic properties of such coatings are low electrical resistivity and high transparency in the visible region. The first semitransparent and electrically conducting CdO film was reported as early as in 1907 [1]. Though early work on these films was performed out of purely scientific interest, substantial technological advances in such films were made after 1940. The technological interest in the study of transparent semiconducting films was generated mainly due to the potential applications of these materials both in industry and research. Such films demonstrated their utility as transparent electrical heaters for windscreens in the aircraft industry. However, during the last decade, these conducting transparent films have been widely used in a variety of other applications such as gas sensors [2], solar cells [3], heat reflectors [4], light emitting devices [5] and laser damage resistant coatings in high power laser technology [6]. Just a few materials dominate the current TCO industry and the two dominant markets for TCO’s are in architectural applications and flat panel displays. The architectural use of TCO is for energy efficient windows. Fluorine doped tin oxide (FTO), deposited using a pyrolysis process is the TCO usually finds maximum application. SnO2 also finds application ad coatings for windows, which are efficient in preventing radiative heat loss, due to low emissivity (0.16). Pyrolitic tin oxide is used in PV modules, touch screens and plasma displays. However indium tin oxide (ITO) is mostly used in the majority of flat panel display (FPD) applications. In FPDs, the basic function of ITO is as transparent electrodes. The volume of FPD’s produced, and hence the volume of ITO coatings produced, continues to grow rapidly. But the current increase in the cost of indium and the scarcity of this material created the difficulty in obtaining low cost TCOs. Hence search for alternative TCO materials has been a topic of active research for the last few decades. This resulted in the development of binary materials like ZnO, SnO2, CdO and ternary materials like II Zn2SnO4, CdSb2O6:Y, ZnSO3, GaInO3 etc. The use of multicomponent oxide materials makes it possible to have TCO films suitable for specialized applications because by altering their chemical compositions, one can control the electrical, optical, chemical and physical properties. But the advantages of using binary materials are the easiness to control the chemical compositions and depositions conditions. Recently, there were reports claiming the deposition of CdO:In films with a resistivity of the order of 10-5 ohm cm for flat panel displays and solar cells. However they find limited use because of Cd-Toxicity. In this regard, ZnO films developed in 1980s, are very useful as these use Zn, an abundant, inexpensive and nontoxic material. Resistivity of this material is still not very low, but can be reduced through doping with group-III elements like In, Al or Ga or with F [6]. Hence there is a great interest in ZnO as an alternative of ITO. In the present study, we prepared and characterized transparent and conducting ZnO thin films, using a cost effective technique viz Chemical Spray Pyrolysis (CSP). This technique is also suitable for large area film deposition. It involves spraying a solution, (usually aqueous) containing soluble salts of the constituents of the desired compound, onto a heated substrate.

Studies on the meteriological aspects of air pollution over Cochin

Pollutants that once enter into the earth’s atmosphere become part of the atmosphere and hence their dispersion, dilution, direction of transportation etc. are governed by the meteorological conditions. The thesis deals with the study of the atmospheric dispersion capacity, wind climatology, atmospheric stability, pollutant distribution by means of a model and the suggestions for a comprehensive planning for the industrially developing city, Cochin. The definition, sources, types and effects of air pollution have been dealt with briefly. The influence of various meteorological parameters such as vector wind, temperature and its vertical structure and atmospheric stability in relation to pollutant dispersal have been studied. The importance of inversions, mixing heights, ventilation coefficients were brought out. The spatial variation of mixing heights studies for the first time on a microscale region, serves to delineate the regions of good and poor dispersal capacity. A study of wind direction fluctuation, σθ and its relation to stability and mixing heights were shown to be much useful. It was shown that there is a necessity to look into the method of σθ computation. The development of Gausssian Plume Model along with the application for multiple sources was presented. The pollutant chosen was sulphur dioxide and industrial sources alone were considered. The percentage frequency of occurrence of inversions and isothermals are found to be low in all months during the year. The spatial variation of mixing heights revealed that a single mixing height cannot be taken as a representative for the whole city have low mixing heights and monsoonal months showed lowest mixing heights. The study of ventilation co-efficients showed values less than the required optimum value 6000m2/5. However, the low values may be due to the consideration of surface wind alone instead of the vertically averaged wind. Relatively more calm conditions and light winds during night and strong winds during day time were observed. During the most of the year westerlies during day time and northeasterlies during night time are the dominant winds. Unstable conditions with high values of σθ during day time and stable conditions with lower values of σθ during night time are the prominent features. Monsoonal months showed neutral stability for most of the time. A study σθ of and Pasquill Stability category has revealed the difficulty in giving a unique value of for each stability category. For the first time regression equations have been developed relating mixing heights and σθ. A closer examination of σθ revealed that half of the range of wind direction fluctuations is to be taken, instead of one by sixth, to compute σθ. The spatial distribution of SO2 showed a more or less uniform distribution with a slight intrusion towards south. Winter months showed low concentrations contrary to the expectations. The variations of the concentration is found to be influenced more by the mixing height and the stack height rather than wind speed. In the densely populated areas the concentration is more than the threshold limit value. However, the values reported appear to be high, because no depletion of the material is assumed through dry or wet depositions and also because of the inclusion of calm conditions with a very light wind speed. A reduction of emission during night time with a consequent rise during day time would bring down the levels of pollution. The probable locations for the new industries could be the extreme southeast parts because the concentration towards the north falls off very quickly resulting low concentrations. In such a case pollutant spread would be towards south and west, thus keeping the city interior relatively free from pollution. A more detailed examination of the pollutant spread by means of models that would take the dry and wet depositions may be necessary. Nevertheless, the present model serves to give the trend of the distribution of pollutant concentration with which one can suggest the optimum locations for the new industries

Layer-by-layer electrostatic entrapment of protein molecules on superparamagnetic nanoparticle: new strategy to enhance adsorption capacity and maintain biological activity

There is a recent interest to use inorganic-based magnetic nanoparticles as a vehicle to carry biomolecules for various biophysical applications, but direct attachment of the molecules is known to alter their conformation leading to attenuation in activity. In addition, surface immobilization has been limited to monolayer coverage. It is shown that alternate depositions of negatively charged protein molecules, typically bovine serum albumin (BSA) with a positively charged aminocarbohydrate template such as glycol chitosan (GC) on magnetic iron oxide nanoparticle surface as a colloid, are carried out under pH 7.4. Circular dichroism (CD) clearly reveals that the secondary structure of the entrapped BSA sequential depositions in this manner remains totally unaltered which is in sharp contrast to previous attempts. Probing the binding properties of the entrapped BSA using small molecules (Site I and Site II drug compounds) confirms for the first time the full retention of its biological activity as compared with native BSA, which also implies the ready accessibility of the entrapped protein molecules through the porous overlayers. This work clearly suggests a new method to immobilize and store protein molecules beyond monolayer adsorption on a magnetic nanoparticle surface without much structural alteration. This may find applications in magnetic recoverable enzymes or protein delivery.

Polymer-mediated disruption of drug crystallinity

Ibuprofen (IB), a BCS Class II compound, is a highly crystalline substance with poor solubility properties. Here we report on the disruption of this crystalline structure upon intimate contact with the polymeric carrier cross-linked polyvinylpyrrolidone (PVP-CL) facilitated by low energy simple mixing. Whilst strong molecular interactions between APIs and carriers within delivery systems would be expected on melting or through solvent depositions, this is not the case with less energetic mixing. Simple mixing of the two compounds resulted in a significant decrease in the differential scanning calorimetry (DSC) melting enthalpy for IB, indicating that approximately 30% of the crystalline content was disordered. This structural change was confirmed by broadening and intensity diminution of characteristic IB X-ray powder diffractometry (PXRD) peaks. Unexpectedly, the crystalline content of the drug continued to decrease upon storage under ambient conditions. The molecular environment of the mixture was further investigated using Fourier transform infrared (FT-IR) and Fourier transform Raman (FT-Raman) spectroscopy. These data suggest that the primary interaction between these components of the physical mix is hydrogen bonding, with a secondary mechanism involving electrostatic/hydrophobic interactions through the IB benzene ring. Such interactions and subsequent loss of crystallinity could confer a dissolution rate advantage for IB. (C) 2006 Elsevier B.V. All rights reserved.