Chemical Engineering

The title compound, (C10H7NH3)[PbI3], crystallizes as an organic-inorganic hybrid. As such, the structure consists of extended chains of [PbI3] units running along the b-axis. Each lead atom is octahedrally coordinated to six iodides, arranged as chains of face-sharing octahedra. These inorganic chains are separated by the isolated organic cations.

The crystal stucture of p-nitroaniline hydrobromide,(O2NC6H4NH3)+.Br- exhibits ionic layers separated by hydrocarbon layers. The hydrocarbon layer stacks head-to-tail but no pi-pi interactions are observed. In the inorganic layer, the ammonium group, bromide anion and nitro group interact to form a three dimensional hydrogen-bonded network. The structure is compared to the related material (O2NC6H4NH3)+.Cl-.

Recently, fault detection and process monitoring using principal component analysis (PCA) were studied intensively and largely applied to industrial process. PCA is the optimal linear transformation with respect to minimizing the mean squared prediction error. If the data have nonlinear dependencies, an important issue is to develop a technique which can take into account this kind of dependencies. Recognizing the shortcomings of PCA, a nonlinear extension of PCA is developed. This paper proposes an application for sensor failure detection and isolation (FDI) to an air quality monitoring network via nonlinear principal component analysis (NLPCA). The NLPCA model is obtained by using two cascade three layer RBF-Networks. For training these two networks separately,
the outputs of the first network are estimated using principal curve algorithm [7] and the problem is transformed as two nonlinear regression problems.

The use of principal component analysis (PCA) for process monitoring applications has attracted much attention recently. PCA is the optimal linear transformation with respect to minimizing the mean square prediction error but it only considers second order statistics. If the data have nonlinear
dependencies, an important issue is to develop a technique
which takes higher order statistics into account and which
can eliminate dependencies not removed by PCA. Recognizing the shortcomings of PCA, a nonlinear extensions of PCA is developed.
The purpose of this paper is to present a non linear generalization of PCA (NLPCA) by combining the principal curves and RBF-Networks. The NLPCA model consists of two RBF networks where the nonlinear transformations of the input
variables (that characterize the nonlinear principal component
analysis) are modelled as a linear sum of radially symmetric
kernel functions by using the first network. The nonlinear principal components, which represents the desired output
of the first network, are obtained by the principal curves
algorithm. The second network tries to perform the inverse
transformation by reproducing the original data. The proposed
approach is illustrated by a simulation example.

The presence of fibrillar protein deposits (amyloid) of human islet amyloid polypeptide (hIAPP) in the pancreatic islets of Langerhans is thought to be related to death of the insulin-producing islet β-cells in type 2 diabetes mellitus (DM2). The mechanism of hIAPP-induced β-cell death is not understood. However, there is growing evidence that hIAPP-induced disruption of β-cell membranes is the cause of hIAPP cytotoxicity. Amyloid cytotoxicity by membrane damage has not only been suggested for hIAPP, but also for peptides and proteins related to other misfolding diseases, like Alzheimer s disease, Parkinson’s disease, and prion diseases. Here we review the interaction of hIAPP with membranes, and discuss recent progress in the field, with a focus on hIAPP structure and on the proposed mechanisms of hIAPP-induced membrane damage in relation to β-cell death in DM2.

There have been increased interests in the research on mechanical and control system of underwater vehicles in the recent past. These ongoing research efforts are motivated by more pervasive applications of such vehicles including seabed oil and gas explorations, scientific deep ocean surveys, military purposes, ecological and waters environmental studies, and also for entertainments. However, the performance of underwater vehicles with screw type propellers is not prospective in terms of its efficiency and maneuverability. The main weaknesses of this kind of propellers are the production of vortices and sudden generation of thrust forces which make the control of the position and motion difficult.
On the other hand, fishes and other aquatic animals are efficient swimmers, posses high maneuverability, are able to follow trajectories, can efficiently stabilize themselves in currents and surges, create less wakes than currently used underwater vehicle, and also have a noiseless propulsion. The fish’s locomotion mechanism is mainly controlled by its caudal fin and paired pectoral fins part. They are classified into BCF (Body and/or Caudal Fin) and MPF (Median and/or paired Pectoral Fins). The study of highly efficient swimming mechanisms of fish can inspire a better underwater vehicles thruster design and its mechanism.
There have not been many studies on underwater vehicles or fish robots using paired pectoral fins as thruster. The work presented in this paper represents a contribution in this area covering study, design and implementation of locomotion mechanisms of paired pectoral fins in a fish robot. The performance and viability of the biomimetic method for underwater vehicles are highlighted through in-water experiment of a robotic fish.

The development and management of fresh groundwater resources in coastal aquifers are seriously constrained by the presence of seawater intrusion. Underutilisation of the available groundwater resource means that valuable fresh water discharges naturally to the sea and is wasted; overdevelopment, on the other hand, mines the resource and will cause a gradual degradation of water quality due to the encroachment of seawater. Over the years, many models have been developed to represent and study the problem of seawater intrusion. They range from relatively simple analytical solutions to complex numerical models. Ernakulam is one of the important ports in west coast of India. Due to increase in population, fast urbanisation and land reforms, the district is facing a number of environment problems such as flooding, groundwater pollution due to discharge of industrial effluents, seawater intrusion etc. There exists an urgent need to study systematically the causes and remedial measures for seawater intrusion. This paper presents the simulation of seawater intrusion in a section of Ernakulam coast through Saturated-Unsaturated TRAnsport (SUTRA) model and examines the impact of increased pumping scenarios on extent of seawater intrusion.

This paper reports the effect of redox potential (or Fe 3+ /Fe 2+ ratio) on chalcopyrite leaching. The relationship between redox potential and other variables (iron concentration and temperature) is also evaluated. Leaching tests were performed in stirred Erlenmeyer flasks with 0.5 g of pure chalcopyrite and 100 mL of a Fe 3+ /Fe 2+ sulphate solution. The redox potential ranged between 300 and 600 mV Ag/AgCl for the solution at a pH 1.8, 180 rpm, with temperatures at 35°C or 68°C. The results show that although ferric ion is responsible for the oxidation of chalcopyrite, ferrous ion has an important role in that it controls precipitation and nucleation of jarosites, which ultimately causes passivation of this sulphide. Chalcopyrite dissolves through the formation of an intermediary product (covellite, CuS) that is later oxidized by ferric ion, releasing Cu 2+ ions.

The Yankee-Hood dryer is the crucial section of the paper machine due to the consumption of energy. As a consequence of continuously increasing energy costs, determination of the proper operating conditions is essential to operate the tissue machine in the most efficient and economic means while ensuring paper quality. The objective of this study is to evaluate the Yankee-Hood dryer in Ipekkağit' tissue paper factory, set the mass and energy balances and make optimization studies in order to achieve the desired production rate whilst keeping the drying parameters within limits at the minimum energy costs. The approach to solve the problem is to develop a steady state analytical model. The complicated drying system is simplified as the overall and sub systems. Material and energy balances are set up for each system. Data of machine parameters at several paper grades are collected at the factory during production. Material and energy balance equations are solved with the available data for the unknown parameters and for the determination of the drying parameters most effective on energy consumption. The critical drying parameters are air supply velocity, wet- and dry-hood temperatures, steam pressure in cylinder and exhaust humidity. Efficiency, defined as the ratio of energy required to evaporate the water to energy input through the system boundaries, is calculated as 28-30% for different grades of tissue paper production., Steady state rate of heat transfer to the wet sheet is analyzed considering the two-way mechanism, from steam through the cast iron shell and from heated air. The transfer of heat is eased in both mechanisms by the lightweight tissue paper that has a comparatively lower internal thermal resistance with respect to other types of paper products. Steam side is modeled considering different thermal resistances in series: Condensate layer, shell, shell-sheet contact, and paper sheet. These resistances are to the same order of magnitude, cast iron shell being the largest and paper sheet the smallest in value. Sheet-shell contact heat transfer coefficient is strongly dependent on sheet moisture content that is assumed to vary almost linearly due to the angular position on the Yankee. Air side heat transfer is mostly affected by the temperature, humidity and velocity of the air that is blown on to the sheet. Calculations resulted out that rate ofheat transfer from air side is 55-65% while that from steam side is 35-45% of their total indicating the dominance of air side on drying.

For highly entangled linear chains, the mean-square displacement of the primitive chain segments [d(n,t)] 2 (n ) segment index) not including a contribution from a nondiffusive part of the contour length fluctuation (CLF) was analyzed on the basis of the tube concept. The analysis was made by just considering the Gaussian nature of the chains (without detailed assumptions about the chain motion). A simple analytic relationship between this [d(n,t)] 2 and the normalized viscoelastic relaxation function µ(t) was derived in a range of µ(t) > 0.5 and at t longer than the Rouse time τRouse for CLF. This relationship was significantly affected by the dynamic tube dilation (DTD) mechanism. For example, the end segment exhibited d 2 ) 〈R 2 〉(1µ) in the absence of DTD and d 2 = 〈R 2 〉(1µ 1/2 ) in the presence of DTD, with 〈R 2 〉 being the mean-square end-to-end distance of the chain. This difference should enable a test of the DTD picture at short t (but still longer than τ Rouse) through comparison of the viscoelastic and segmental displacement data.

The synthesis, electrochemical and spectroscopic properties of a series of thiophene-substituted 1,3-dithiole-2-ones is described. The derivatives Th-3,3, Th-2,2, Th-2,3, Th-3,3(2,2′-Me), and Th3,3-(2,5,2′,5′-Me), have been successfully polymerized by cyclic voltammetry. From the UV−visible spectra of the neutral films, it was determined that PTh-3,3, PTh-2,2 and PTh-2,3 have a bandgap of 2.04, 2.30, and 2.18 eV, respectively. The voltammetric response of Th-3,3(2,2′-Me) was noticeably different from the other polymers. The SNIFTIRS data suggested that Th-3,3(2,2′-Me) was formed by bonding via the β-positions of the thiophene ring, resulting in a poorly conductive polymer. The in situ solid-state modification of PTh-3,3 to produce a new TTF-derivatized polythiophene was carried out. The cyclic voltammetry of the modified polymer confirmed the inclusion of TTF into the backbone of the film.

Synthesis of methyl tert-butyl ether (abbreviated as MTBE) from methanol (MeOH) and tert-butyl alcohol (TBA) in the liquid phase was studied by using Amberlyst 15 in the H+ form as an acid catalyst. Experiments were carried out in a stirred batch reactor at different temperatures (313, 318, and 323 K) under atmospheric pressure.
It was found that catalyst sizes and rotation speeds had no significant effects on reaction rates. Mechanism studies showed that three reactions took place simultaneously. It was also found that dehydration of TBA could not be neglected. The experimental concentration profiles with time could be simulated well by simple kinetics. Finally, rate constants could be expressed by Arrhenius equations.

Thermodynamic work of adhesion, contact angle, wettability and acidbase contributions of the wetting of four North American wood species were determined using the Wilhelmy technique. The wetting angles with water varied from 60 ° for Sitka spruce to 74 ° for Douglas-fir. The wood surfaces had a strong acidic character since the greatest interactions for all the wood pecies occurred with formamide (basic probe) while lesser interactions were obtained withethylene glycol (acidic probe). In addition, dispersive and polar surface free energies of wood, 7 d and 7 p respectively, were determined using Wu's simultaneous equations. In general, 75 to 80% of the total surface free energy of wood was due to dispersion forces. Specific wettabilities of wood and advancing contact angles in thirty various organic liquids were also evaluated.

"The rate and maximum swelling of several North American wood species in 40 organic liquids have been obtained with a computer interfaced linear variable displacement transformer. Since wood swells very fast in some organic liquids, even at room temperature, this apparatus made it possible to obtain
accurate rate data on the swelling of wood in organic liquids. It was found that many similarities existed between wood and cellulose maximum swelling within various solvent chemical classes. Hence, it appears that cellulose is the primary wood polymer responsible for the major amount of swelling of wood. In general, all the liquids, with a molar volume greater than 100 cc or with a small hydrogen bonding parameter, caused very little equilibrium swelling. The logarithm of the rate of wood swelling
(In k) in the liquids was inversely correlated with the solvent molecular weight as well as with the molar volume of the solvent, that is, the larger the solvent molecular size, the slower the rate of swelling. The Ink also was strongly correlated with the maximum tangential swelling of wood. The maximum tangential swelling for all wood species was linearly correlated with the solvent basicity (donor number). Other solvent properties such as volubility parameter, dipole moment, dielectric constant, and surface tension showed very weak correlations with the maximum tangential swelling of wood in organic liquids."

An experiment to assess the influence of commercially available infant formulas on characteristics of feces in a weanling piglet model was conducted. Seven commercial infant formulas [whey, whey + a-lactalbumin Ò , whey + a-lactalbumin + oligofructose, whey + GOS + polyfructose, whey protein concentrate 1 (with 27.3% acid hydrolyzed fat), whey protein concentrate 2 (with 29.4% acid hydrolyzed fat), and enzymatically hydrolyzed whey protein concentrate] were offered to weanling piglets ad libitum for 14 d. Fecal attributes that were assessed include: consistency, color, odor, dry matter, organic matter, pH, biogenic amines, short-and branched-chain fatty acids, phenols, indoles, and ammonia. Overall, there were very few differences among treatment groups in fecal attributes assessed. Minor differences in the concentrations of fecal acetate, valerate, putrescine, and cadaverine were observed in piglets fed GOS + polyfructose-containing formula. However, stool consistency, score, odor, pH, ammonia, phenols, and indoles were similar among treatment groups. Diet had an effect on fecal dry matter percentage, organic matter percentage, color, and 4 week body weights of the piglets. The results obtained in this experiment demonstrate that healthy gut function is prevalent in weanling piglets consuming the experimental treatments.

The project discussed in this paper has been conducted as part of the Autonomatic research cluster based at University College Falmouth. The cluster is focused on research projects that explore the use of digital production technologies within the context of designer maker and craft practice.

My project is concerned with developing more direct control of processes that are typically automated by CAD software and CAM tools. I believe the use of these standardised tools limit the ability of the maker to create unique visual vocabularies.

It is possible to view the aesthetic qualities emerging in the new genre of ‘digital craft’ - such as the use of triangulation and the quality of line produced by generic pre-set machine parameters - as a temporary phase in the digital craft timeline. As more makers adopt digital technologies, we may discover that these visual aesthetic qualities are more attributable to the technology than the maker rather than being understood as unique. The author believes it is therefore important for makers wishing to further their practice in this field to seek ways in which they can gain greater control over the processes and tools they are using.

This paper presents research that explores ways in which programmed mathematical elements in 3D CAD can be deconstructed and manipulated throughout the design and production phases. Employing an iterative designing and making process I have used this ‘hand’ manipulated CAD data to drive CNC machine tools in highly specified ways. This has lead to an in depth understanding of the inter-relationship between CAD and CAM as intrinsic to the development of unique aesthetic qualities. The development of a dialogue between CAD code and CNC tooling has resulted in a greater level of control enabling the realisation of complex and completely controlled patterning on 3D forms that go beyond the restrictions of standard toolsets.

This research has resulted in a range of 3D aluminium sample pieces that I have used to create a visual knowledge bank which documents the relationship between software input, machine parameters and their effects on the visual form. This knowledge has been applied to my working digital design practice enabling me to create aluminium platters and beakers that counter the affects of automation.

This paper aims to offer other makers methods which allow the potential for 'hacking' into code in order to expand the possibilities for control and creative engagement with digital tools and thereby offering more unique opportunities for developing visual vocabularies than using standard toolsets alone.

The surface behavior of avidin and two polymers, formed by affinity polymerization from two different stoichiometric mixtures ofavidin and the bifunctional ligand bisbiotin, has been investigated at the air/ water interface. Strong hysteresis in the pressure-area isotherms is attributed to mechanical distortion of the molecules. When subjected to a step change in pressure! the monolayer area relaxes to a new equilibrium value following first-order dynamics, the time constant being of the order of minutes for a pressure change of 5 mN m '. Equilibrium isotherms for the fully relaxed monolayers are linear over most of the pressure range, with both compression and expansion isotherms exactly coincident. Monolayers ofthe avidin/bisbiotin polymer were deposited onto electron microscope grids by the LB technique and imaged in a TEM. The area per repeat unit was estimated to be ca. 30 nm2 in good agreemenr with previous estimates, but much smaller than the area per molecule obtained by extrapolating the pressurearea isotherm to zero pressure. Finally it is shown that spreading solvents containing a high percentage ofchlorolorm cause avidin to denature at the air/water inteface, this manilesting itselfas a large molecular area at low surface pressure. However, it appears that denaturation may De reversed almost completely when the monolayer is compressed. The investigation suggests that it may be feasible to fabricate molecular electronic networks based on affinitv polvmerization. o r99l Academic press. Inc.

The influence of polymer concentration, going from the dilute through the overlap into the concentrated regime, during drop on demand inkjet printing is investigated for a range of cellulose ester (CE) polymers from visual examination of ligament stretching as a function of applied wave form. The physical behaviour of the polymer fluids in drop formation is indicative of the dominance of viscoelastic effects within the timescale of the process, in preventing ligament breakup at the pinch point compared with a water-glycerol-isopropanol blend Newtonian fluid of similar viscosity. This has previously been described in terms of the polymer chain undergoing a coil-stretch transition at the strain rates experienced in the inkjet process. When formulated at the coil overlap concentration all polymers showed qualitatively similar behaviour with respect to time and length of ligament at rupture irrespective of polymer molecular weight. Beyond the overlap concentration the ligament rupture time continues to increase with increasing elasticity of the solution but the ligament rupture length decreases rapidly. In this regime chain entanglement becomes important, dramatically increasing the elastic nature of the ligament. Additionally it is proposed that in the case of weakly associating polymers such as cellulose esters, the effective relaxation time is further increased due to the possibility that on chain extension intramolecular H-bonds are broken and may reform as intermolecular associations whilst the polymer chains are extended. These intermolecular associations act as physical crosslinks, thereby creating a transient network structure. This network structure is capable of having a finite large viscosity. Once the strain is removed the network will decay as the chains return to the more thermodynamically stable coil state.

. Total reflection X-ray fluorescence analysis excited with synchrotron radiation SR-TXRF has been used for rainwater trace element analysis. The samples were collected from four different sites at Campinas City, SP, Brazil. Standard solutions with gallium as internal standard were prepared for the calibration system. Rainwater samples of 10 l were added to Perspex reflector disks, dried under vacuum and analyzed for 100 s measuring time. The detection limits obtained for K-shell lines varied from 29 ng ml y1 for sulfur to 1.3 ng ml y1 for zinc and copper, while for L-shell the values were 4.5 ng ml y1 for mercury and 7.0 ng ml y1 for lead. ᮊ

This study aims to apply the ultrasound technique in the
field of clean technology to protect environment. The principle
of ultrasound was conducted here to study the effect of applying
high frequency of ultrasound waves. Four kinds of water
namely; Seawater from Aqaba gulf, Red Sea, brackish from
Maan desert southern part of Jordan, hot spring from northern
part of Jordan and tap water (Amman City) were selected to
study the effect of ultrasound on its physical properties. High
ultrasound frequency device with 1.7 MHz was applied to
study the effect of ultrasound waves. All conducted experiments
were fixed at room temperature. The effect of liquid volume
while applying a constant ultrasound waves on the water properties
were investigated here. Exposing time of ultrasound
waves was fixed at 0.5, 1.0 and 1.5 h. The experimental
results showed that ultrasonic wave irradiation for different
samples of water at different period of time has its significant
impacts on physical and chemical properties of water such as
pH, total dissolved solids and consequently the conductivity.
Key Words: High frequency ultrasound, Total dissolved
solids, Water desalination, Water treatment, Environmental
protection, Physical properties.

Separation of proteins from whey; namely α – Lactoglobulin and β – Lactalbumin was
obtained using the bubble foam column technique. Two types of whey were conducted in this study;
yogurt whey and cheese whey. The effect of gas flow-rate and the height of the whey (liquid holdup)
inside the column were studied at room temperature and at constant pH of whey. Whey used here
obtained from local dairy factory as waste, and was used to investigate the performance ability of
bubble column to extract very low concentration portion from waste. Enrichment ratio showed that the
possibility of extracting protein from whey was high. Results showed that enrichment ration was
higher for yogurt whey from that of cheese whey. The results also showed that the efficiency of
separation of these proteins increased with decreasing both the air flow-rate, and wheys volume inside
the column. The maximum amount of protein obtained at air flow-rate = 0.2 Liter/ min at experimental
condition.

Two different fly ashes (FAs) have been tested for their ability to give synthetic zeolitic products. Polish bituminous (PB) and South African (SA) coal fly ash (FA) samples derived from pilot-scale circulated fluidized bed (CFB) combustion facilities have been utilized as raw material. The two FAs underwent a hydrothermal activation with 1M NaOH solution at 90 °C for 24 h. Two different FA/NaOH solution/ratios (50, 100 g/L) were examined for each FA. For lower FA/NaOH solution ratios, the excess of NaOH seems to be prohibitive for the zeolite growth while for a ratio higher than 100 g/L the NaOH quantity seems to be insufficient for the effective activation of the FAs. The experimental products were characterized by means of X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) while X-Ray Fluorescence (XRF) was applied for the determination of their chemical composition and the trace elements concentration. Regarding the PB-CFB FA, the following zeolitic materials were formed: Na-Al-Si Zeolite A (Na), K-Al-Si Zeolite A (K) and Erionite. For the SA-CFB FA, the zeolitic materials formed were: ZSM-18, K-Ca-Al-Si-Hydrate Unnamed Zeolite, Erionite and Linde (L). The zeolitic products were also evaluated in terms of their cation exchange capacity (CEC), specific surface area (SSA), specific gravity (SG), particle size distribution (PSD), pH and the range of their micro- and macroporosity. The products were characterized by finer particle size concerning SA-CFB FA, while PB-CFB FA showed an increase of the percentage of the fine particles. The pH value of FAs before and after the hydrothermal activation for all the proportions is 11.3 to 11.9 and a condensation occurs by nucleophilic attack of OH-. The values of CEC, SSA along with the efficiency of pores were higher for FA/NaOH = 100 g/L. The current work focuses on testing the synthesized zeolitic materials of the aforementioned zeolification process for their potential of retaining heavy metals from a contaminated soil.   

Keywords:  CFB fly ash; synthetic zeolites; alkaline activation; bituminous coal

In this paper the fly ash, which is the finest residue of the lignite combustion entrapped by electrostatic filters at the electrical power stations, is examined, in order to determine the possibility of its usage in the production of concrete. It is implemented by testing concrete models in actual scale. Mineralogical, petrographical and chemical analyses of the fly ash as well as of the produced concrete are presented. The concrete that was produced by cement, sand, water, aggregates and fly ash (in various percentages) showed micro-cracks in its structure, due to the reduced interconnection of the fly ash with the aggregates. Nevertheless, the fly ash may act as adhesive material, as well as the material that fills the cracks of the concrete. Tests of the strength on models made by this concrete have shown comparable results in strength with reference concrete produced without ash. It is concluded that the mixing of fly ash in concrete does not affect its strength and sometimes it fills the cracks of the concrete mass.

Μελέτη της δυνατότητας χρήσης ιπτάμενης τέφρας στο σκυρόδεμα.

Paper in the Ash Library (http://www.flyash.info/) in the web http://www.flyash.info/2005/15kou.pdf .

The aim of this work is to define the chemical and mineralogical composition of the fuel gas desulphurization (FGD) gypsum produced from the Meliti thermal power plant in the region of Florina in North West Greece, in order to investigate potential uses in the cement industry. Mineralogical and microprobe analyses were carried out on FGD gypsum samples collected from the Meliti 330 MW lignite-fired power plant.
Results show that the main component of the FGD gypsum is pure mineral gypsum (CaSO4·2H2O). The particle size of the gypsum ranges from 5 to 50 µm and the crystals are mainly of rhomboid shape. Microprobe analysis shows that the concentration of CaO and SO3, which are the main components, range from 31.9%-32.5% and from 45.90-46.40%, respectively. 
This FGD gypsum can easily substitute the natural gypsum used in the production of cement. Copyright © 2007 Society of Chemical Industry

Ορυκτολογική και ορυκτοχημική μελέτη της γύψου που προκύπτει ως παραπροϊόν κατά τη διαδικασία της αποθείωσης των καυσαερίων στο λιγνητικό σταθμό της Φλώρινα. Δυνατοότητες αξιοποίησής της στην τσιμεντοβιομηχανία.

Trivalent chromium (Cr(III)) is considered to be essential for the human metabolism, whilst hexavalent (Cr(VI)) is very toxic and soluble in water and can be migrated into the direction of the groundwater. Using the GFAAS and ICP-MS for total chromium, diphenylcarbazide-Cr(VI)-complex colorimetric method for hexavalent chromium, and flame-AAS and ICP-MS for other elements, their concentrations were determined in 63 surface and groundwater samples from the Thiva – Tanagra – Malakasa basin, Eastern Sterea Hellas, Greece.
In that area, which is notorious for the industrial activities during the last 40 years, significant chromium concentrations were determined in the urban water supply of Oropos (up to 80 μg/L Cr(VI)) and Inofyta (up to 53 μg/L Cr(VI)). High concentrations of Cr(VI), ranging from 5 to 33 μg/L Cr(VI), were also found in the groundwater that is used for the urban water supply of the town of Thiva (NW).  High As content (up to 34 μg/L As) among with Cr(VI) (up to 40 μg/L) were detected in the urban water supply of Schimatari. In the Asopos River, although total chromium values are up to 13 μg/L, hexavalent chromium less than 5 mg/L and other toxic elements were relatively low, during our research, their values suggest a connection with the industrial activity in the area.
The pollution of groundwater by Cr(VI) in the majority of water wells in the Thiva – Tanagra – Malakasa basin, is related to the widespread industrial activity, the usage of hexavalent chromium in various processes and the discharges of Cr-bearing wastes.

- Greek Abstract

Η παρούσα είναι η πρώτη ερευνητική εργασία που δημοσιεύτηκε σε επιστημονικό περιοδικό, με κριτές, σχετικά με το πρόβλημα της ρύπανσης από εξασθενές χρώμιο στην ευρύτερη περιοχή του Ασωπού ποταμού.

ΤΟ ΕΞΑΣΘΕΝΕΣ ΧΡΩΜΙΟ ΚΑΙ ΑΛΛΑ ΤΟΞΙΚΑ ΣΤΟΙΧΕΙΑ ΣΤΑ ΥΠΟΓΕΙΑ ΚΑΙ ΤΑ ΕΠΙΦΑΝΕΙΑΚΑ ΥΔΑΤΑ ΤΗΣ ΠΕΡΙΟΧΗΣ ΘΗΒΑΣ -ΤΑΝΑΓΡΑΣ - ΜΑΛΑΚΑΣΑΣ.

ΠΕΡΙΛΗΨΗ

Το τρισθενές χρώμιο (Cr(III)) θεωρείται απαραίτητο στον ανθρώπινο μεταβολισμό, ενώ το εξασθενές (Cr(VI)) είναι ιδιαίτερα τοξικό και ευδιάλυτο στο νερό και μπορεί να μεταφέρεται στο υπόγειο και επιφανειακό νερό. Οι συγκεντρώσεις εξασθενούς χρωμίου, ολικού χρωμίου, καθώς και άλλων τοξικών στοιχείων προσδιορίστηκαν σε 63 δείγματα επιφανειακών και υπογείων νερών από την Κεντρική Εύβοια και την λεκάνη Θήβας –Τανάγρας–Μαλακάσας της Ανατολικής Στερεάς Ελλάδος. Οι αναλύσεις έγιναν με χρήση GFAAS και ICP-MS για το ολικό χρώμιο, flame-AAS και ICP-MS για τον προσδιορισμό των υπόλοιπων στοιχείων και χρωματομετρίας με τη χρήση του συμπλόκου diphenylcarbazide-Cr(VI) για το εξασθενές χρώμιο. 
Στην λεκάνη της Θήβας –Τανάγρας–Μαλακάσας, γνωστή για τη βιομηχανική δραστηριότητα τα τελευταία 40 χρόνια, προσδιορίστηκαν σημαντικές συγκεντρώσεις χρωμίου στο νερό του δικτύου υδροδότησης του Ωρωπού  (μέχρι 80 μg/L Cr(VI)) και των Οινοφύτων (μέχρι 53 μg/L Cr(VI)). Υψηλές συγκεντρώσεις εξασθενούς χρωμίου, κυμαινόμενες από 5 έως 33 μg/L, προσδιορίστηκαν και στο υπόγειο νερό, το οποίο τροφοδοτεί το δίκτυο υδροδότησης της πόλης των Θηβών (ΒΔ). Υψηλές περιεκτικότητες σε αρσενικπ (As) [μέχρι 34 μg/L As] μαζί με Cr(VI) [μέχρι 40 μg/L] προσδιορίστηκαν στο δίκτυο υδροδότησης του Σχηματαρίου.
Στον ποταμό Ασωπό, αν και το ολικό χρώμιο φθάνει τα  13 μg/L, το εξασθενές χρώμιο είναι λιγότερο από 5 mg/L. Γενικά, οι συγκεντρώσεις  των  τοξικών στοιχείων στον Ασωπό ήταν σχετικά χαμηλές κατά τη διάρκεια της μελέτης μας, αλλά οι τιμές τους υποδηλώνουν την σχέση τους με τη βιομηχανική δραστηριότητα της περιοχής.
Η ρύπανση του υδροφόρου ορίζοντα από Cr(VI), που προσδιορίσθηκε στην πλειονότητα των γεωτρήσεων στην λεκάνη Θήβας–Τανάγρας–Μαλακάσας, σχετίζεται με τη χρήση του εξασθενούς χρωμίου και άλλων τοξικών μετάλλων σε ποικίλες διεργασίες και την υπεδάφια απόρριψη χρωμιούχων βιομηχανικών αποβλήτων.

Asopos River, Attika, Viotia
Ποταμός Ασωπός, Αττική, Βοιωτία

A nonlinear full-order observer is synthesized for a class of complex nonlinear time-delay systems of the retarded type. The system under consideration is subject to delayed states, delayed output, known nonlinear disturbances and unknown perturbations. The known nonlinearities are assumed to satisfy global Lipschitz conditions and, for the unknown perturbations, bounding information, dependent upon the output and controls, is assumed. Each delay system, in the class considered, contains multiple, time-varying, discrete and distributed delays. The problem addressed is the design of full-order, state observers such that, under the dynamics of the observation error system, the zero state is globally uniformly exponentially stable.

Based on the Vlasov–Maxwell equations describing self-consistent nonlinear beam dynamics and collective processes, the evolution of an intense sheet beam propagating through a periodic focusing field has been studied. It has been shown that in the case of a beam with uniform phase-space density, the Vlasov–Maxwell equations can be replaced exactly by the hydrodynamic equations with a triple adiabatic pressure law coupled with the Maxwell equations. We further demonstrate that starting from the system of hydrodynamic and Maxwell equations, a set of coupled nonlinear Schrödinger equations for the slowly varying amplitudes of density waves can be derived. In the case where a parametric resonance between a certain mode of density waves and the external focusing occurs, the slow evolution of the resonant amplitudes in the cold-beam limit is shown to be governed by a system of coupled Gross–Pitaevskii equations. Properties of the nonlinear Schrödinger equation as well as properties of the Gross–Pitaevskii equation are discussed, together with soliton and condensate formation in intense particle beams.

This note provides explicit algebraic stabilizing formulas for clf 's when controls are restricted to certain Minkowski balls in Euclidean space. Feedbacks of this kind are known to exist by a theorem of Artstein, but the proof of Artstein's theorem is nonconstructive. The formulas are obtained from a general feedback stabilization technique and are used to construct approximation solutions to some stabilization problems.

A new notion of input-to-state stability involving infinity norms of input derivatives up to a finite order k is introduced and characterized. An example shows that this notion of stability is indeed weaker than the usual iss. Applications to the study of global asymptotic stability of cascaded non-linear systems are discussed. A function F : S ! R is positive definite if F ðxÞ > 0; 8x 2 S; x=0 and F ð0Þ ¼ 0: A function g : R 50 ! R 50 is of class K if it is continuous, positive definite, and strictly increasing. It is of class K 1 if it is also unbounded. Finally, b : R 50  R 50 ! R 50 is of class KL if for each fixed t50; bðÁ; tÞ is of class K and for each fixed s > 0; bðs; tÞ decreases to 0 as t ! 1: An important fact concerning K 1 functions which will often be used in the following sections is the socalled 'weak triangular inequality' gða þ bÞ4gð2aÞ þ gð2bÞ for all a; b50:

We are often uncertain about the identity of objects. This phenomenon appears in theories of object persistence in early childhood; in the well-known Morning Star/Evening Star example; in tracking and data association systems for radar; in security systems based on personal identification; and in many aspects of our everyday lives. The paper presents a formal probabilistic approach to reasoning about identity under uncertainty in the framework of first-order logics of probability, with application to wide-area freeway traffic monitoring.

Many problems in applied mathematics, physics, and engineering require the solution of the heat equation in unbounded domains. Integral equation methods are particularly appropriate in this setting for several reasons: they are unconditionally stable, they are insensitive to the complexity of the geometry, and they do not require the artificial truncation of the computational domain as do finite difference and finite element techniques. Methods of this type, however, have not become widespread due to the high cost of evaluating heat potentials. When m points are used in the discretization of the initial data, M points are used in the discretization of the boundary, and N time steps are computed, an amount of work of the order O(N 2 M 2 + NMm) has traditionally been required. In this paper, we present an algorithm which requires an amount of work of the order O(NM log M + m log m) and which is based on the evolution of the continuous spectrum of the solution. The method generalizes an earlier technique developed by Greengard and Strain (1990, Comm. Pure Appl. Math. 43, 949) for evaluating layer potentials in bounded domains.

The complexation of the anions of Methyl Orange (MO
¡) (1) and Indomethacin (Ind¡) (2) by the
¯-cyclodextrin dimer (3) has been studied by means of high-performance liquid chromatography. The
cyclodextrin annuli are shown to jointly act as a single binding site for complexation of MO
¡ (1).
Thus the association constants of (3 ¢3§0¢ 3)£103 and (220§20)£103 dm3 mol¡1 for the 1 : 1 complexes
with ¯-cyclodextrin and the dimer (3), respectively, indicate very strong cooperative binding by the
annuli of the linked species. By contrast, the complexation of Ind¡ (2) by the cyclodextrin dimer (3)
is characterized by two independent binding sites. This lack of cooperative binding is re°ected in the
association constant for the 1 : 1 complex in each binding site, which at (1¢3§0¢ 1)£103 dm3 mol¡1 is
little greater than that of (0¢7§0¢05)£103 dm3 mol¡1 for the complex with ¯-cyclodextrin.

A new theory of exact solutions is presented for the problem of the slow viscous Stokes flow of a plane, doubly connected annular viscous blob driven by surface tension. The formulation reveals the existence of an infinite number of conserved quantities associated with the flow for a certain general class of initial conditions. These conserved quantities are associated with a class of exact solutions. This work is believed to provide the first exact solutions for the evolution of a doubly connected fluid region evolving under Stokes flow with surface tension.

Motivated by the viscous sintering of amorphous materials in the presence of a distribution of rigid platelet inclusions added to increase the strength of the final sintered medium, a simple model for the shrinkage of compressible pores close to a wall in Stokes flow is proposed. The model assumes that the pore remains elliptical/ellipsoidal in shape at all times. The model is expected to be valid provided the pore is not too far from spherical and not too close to the wall. It relies on a separation of the flow into 'inner' and 'outer' problems. The inner problem is to assume that the ellipsoid evolves in a linear ambient flow given by the first two terms in a local expansion of an outer flow produced by the image singularity distribution of a point-sink near a planar no-slip boundary. The focus of the present paper is to test the viability of the model in the planar case. Using a spectral method based on analytic functions and conformal mappings, the results of a full numerical simulation are compared with the predictions of the planar model. The effects of the proximity of the pore to the wall, the anisotropy in the pore shape and its relative orientation to the wall are all examined. It is observed that, as they shrink, pores drift towards the wall becoming elongated in the direction perpendicular to the wall.

In the symmetric rendezvous search game played on K n (the completely connected graph on n vertices) two players are initially placed at two distinct vertices (called locations). The game is played in discrete steps and at each step each player can either stay where he is or move to a different location. The players share no common labelling of the locations. They wish to minimize the expected number of steps until they first meet. Rendezvous search games of this type were first proposed by Steve Alpern in 1976. They are simple to describe, and have received considerable attention in the popular press as they model problems that are familiar in real life. They are notoriously difficult to analyse. Our solution of the symmetric rendezvous game on K 3 makes this the first interesting game of its type to be solved, and establishes the long-standing conjecture that the Anderson-Weber strategy is optimal.

Live bacterial vaccines have great promise both as vaccines against enteric pathogens and as heterologous antigen vectors against diverse diseases. Ideally, room temperature stable dry formulations of live bacterial vaccines will allow oral vaccination without cold-chain storage or injections. Attenuated Salmonella can cross the intestinal wall and deliver replicating antigen plus innate immune activation signals directly to the intestinal immune tissues; however, the ingested bacteria must survive firstly gastric acid and secondly the antimicrobial defences of the small intestine. We found that the way in which cells are grown prior to formulation markedly affects sensitivity to acid and bile. Using a previously published stable storage formulation that maintained over 10% viability after 56 days storage at room temperature, we found dried samples of an attenuated Salmonella serovar Typhimurium vaccine lost acid and bile resistance compared to the same bacteria taken from fresh culture. The stable formulation utilised osmotic pre-conditioning in defined medium plus elevated salt concentration to induce intracellular trehalose accumulation before drying. Dried bacteria grown in rich media without osmotic pre-conditioning showed more resistance to bile, but less stability during storage, suggesting a trade-off between bile resistance and stability. Further optimisation is needed to produce the ultimate room temperature stable oral live bacterial vaccine formulation.

Numerical simulations reveal the formation of singular structures in the polymer stress field of a viscoelastic fluid modeled by the Oldroyd-B equations driven by a simple body force. These singularities emerge exponentially in time at hyperbolic stagnation points in the flow and their algebraic structure depends critically on the Weissenberg number. Beyond a first critical Weissenberg number the stress field approaches a cusp singularity, and beyond a second critical Weissenberg number the stress becomes unbounded exponentially in time. A local approximation to the solution at the hyperbolic point is derived from a simple ansatz, and there is excellent agreement between the local solution and the simulations. Although the stress field becomes unbounded for a sufficiently large Weissenberg number, the resultant forces of stress grow subexponentially. Enforcing finite polymer chain lengths via a FENE-P penalization appears to keep the stress bounded, but a cusp singularity is still approached exponentially in time.

Using slender-body hydrodynamics, we study the flow-induced deformation of a high-aspect-ratio elastic filament. For a filament of zero rest curvature rotating in a viscous linear shear flow, our model predicts a bifurcation to shape instabilities due to compression by the flow, in agreement with experimental observations. Further, nonlinear simulations of this shape instability show that in dilute solutions, flexibility of the fibers causes both increased shear thinning as well as significant nonzero first-normalstress differences. These stress differences are positive for small-to-moderate deformations, but negative for large-amplitude flexing of the fibers.

square vessel would also generate antivortices in order to comply with the imposed symmetry. By proper arrangement of the laser ®elds, the vortex patterns in Bose±Einstein condensates con®ned by triangular or square traps could also reveal symmetry-induced antivortices.

A mechanism by which smooth initial conditions evolve towards a topological reconfiguration of fluid interfaces is studied in the context of Darcy's law. In the case of thin fluid layers, nonlinear PDEs for the local thickness are derived from an asymptotic limit of the vortex sheet representation. A particular example considered is the Rayleigh-Taylor instability of stratified fluid layers, where the instability of the system is controlled by a Bond number B. It is proved that, for a range of B and initial data ''subharmonic'' to it, interface pinching must occur in at least infinite time. Numerical simulations suggest that ''pinching'' singularities occur generically when the system is unstable, and in particular immediately above a bifurcation point to instability. Near this bifurcation point an approximate analytical method describing the approach to a finite-time singularity is developed. The method exploits the separation of time scales that exists close to the first instability in a system of finite extent, with a discrete spectrum of modes. In this limit, slowly growing long-wavelength modes entrain faster short-wavelength modes, and thereby, allow the derivation of a nonlinear evolution equation for the amplitudes of the slow modes. The initial-value problem is solved in this slaved dynamics, yielding the time and analytical structure of a singularity that is associated with the motion of zeros in the complex plane, suggesting a general mechanism of singularity formation in this system. The discussion emphasizes the significance of several variational principles, and comparisons are made between the numerical simulations and the approximate theory.