bluuebunny/crossref_metadata_2025 huggingface dataset:
Microwave Fabrication and Magnetic Property of Hierarchical Spherical α-Fe2O3 Nanostructures
Authors: Xue Bin , Liu Run , Xu Zhu-De , Zheng Yi-Fan
Published: September 2008

The hierarchical spherical α-Fe2O3 nanostructures were obtained by polyacrylamide (PAM)-assisted microwave fabrication method. The nanostructures exhibited mesoporous structures with relatively high remanent magnetization and coercivity at 300 K. The PAM was believed to play an important role in the formation of the hierarchical spherical α-Fe2O3 nanostructures.
Leverage Cycles and the Anxious Economy
Authors: Fostel Ana , Geanakoplos John
Published: September 2008

We provide a pricing theory for emerging asset classes, like emerging markets, that are not yet mature enough to be attractive to the general public. We show how leverage cycles can cause contagion, flight to collateral, and issuance rationing in a frequently recurring phase we call the anxious economy. Our model provides an explanation for the volatile access of emerging economies to international financial markets, and for three stylized facts we identify in emerging markets and high yield data since the late 1990s. Our analytical framework is a general equilibrium model with heterogeneous agents, incomplete markets, and endogenous collateral, plus an extension encompassing adverse selection. (JEL D53, G12, G14, G15)
Competition and Price Variation when Consumers Are Loss Averse
Authors: Heidhues Paul , Kőszegi Botond
Published: September 2008

We modify the Salop (1979) model of price competition with differentiated products by assuming that consumers are loss averse relative to a reference point given by their recent expectations about the purchase. Consumers' sensitivity to losses in money increases the price responsiveness of demand—and hence the intensity of competition—at higher relative to lower market prices, reducing or eliminating price variation both within and between products. When firms face common stochastic costs, in any symmetric equilibrium the markup is strictly decreasing in cost. Even when firms face different cost distributions, we identify conditions under which a focal-price equilibrium (where firms always charge the same “focal” price) exists, and conditions under which any equilibrium is focal. (JEL D11, D43, D81, L13)
The Brain as a Hierarchical Organization
Authors: Brocas Isabelle , Carrillo Juan D
Published: September 2008

Based on recent neuroscience evidence, we model the brain as a dual-system organization subject to three conflicts: asymmetric information, temporal horizon, and incentive salience. Under the first and second conflicts, we show that the uninformed system imposes a positive link between consumption and labor at every period. Furthermore, decreasing impatience endogenously emerges as a consequence of these two conflicts. Under the first and third conflicts, it becomes optimal to set a consumption cap. Finally, we discuss the behavioral implications of these rules for choice bracketing and expense tracking, and for consumption over the life cycle. (JEL D11, D74, D82, D87, D91)
How Strong Are Weak Patents?
Authors: Farrell Joseph , Shapiro Carl
Published: September 2008

We study the welfare economics of probabilistic patents that are licensed without a full determination of validity. We examine the social value of instead determining patent validity before licensing to downstream technology users, in terms of deadweight loss (ex post) and innovation incentives (ex ante). We relate the value of such pre-licensing review to the patent's strength, i.e., the probability it would hold up in court, and to the per-unit royalty at which it would be licensed. We then apply these results using a game-theoretic model of licensing to downstream oligopolists, in which we show that determining patent validity prior to licensing is socially beneficial. (JEL D82, K11, L24, O34)
Does Innovation Cause Stock Market Runups? Evidence from the Great Crash
Authors: Nicholas Tom
Published: September 2008

This article examines the stock market's changing valuation of corporate patentable assets between 1910 and 1939. It shows that the value of knowledge capital increased significantly during the 1920s compared to the 1910s as investors responded to the quality of technological inventions. Innovation was an important driver of the late 1920s stock market runup, and the Great Crash did not reflect a significant revaluation of knowledge capital relative to physical capital. Although substantial quantities of influential patents were accumulated during the post-crash recovery, high technology firms did not earn significant excess returns over low technology firms for most of the 1930s. (JEL G14, N12, N22, O30)
The Unequal Effects of Liberalization: Evidence from Dismantling the License Raj in India
Authors: Aghion Philippe , Burgess Robin , Redding Stephen J , Zilibotti Fabrizio
Published: September 2008

We study whether the effects on registered manufacturing output of dismantling the License Raj—a system of central controls regulating entry and production activity in this sector—vary across Indian states with different labor market regulations. The effects are found to be unequal across Indian states with different labor market regulations. In particular, following delicensing, industries located in states with pro-employer labor market institutions grew more quickly than those in pro-worker environments. (JEL J50, L52,L60, O14, O15, O25)
Tracing the Impact of Bank Liquidity Shocks: Evidence from an Emerging Market
Authors: Khwaja Asim Ijaz , Mian Atif
Published: September 2008

We examine the impact of liquidity shocks by exploiting cross-bank liquidity variation induced by unanticipated nuclear tests in Pakistan. We show that for the same firm borrowing from two different banks, its loan from the bank experiencing a 1 percent larger decline in liquidity drops by an additional 0.6 percent. While banks pass their liquidity shocks on to firms, large firms—particularly those with strong business or political ties—completely compensate this loss by additional borrowing through the credit market. Small firms are unable to do so and face large drops in overall borrowing and increased financial distress. (JEL E44, G21, G32, L25)
Restructuring Research: Communication Costs and the Democratization of University Innovation
Authors: Agrawal Ajay , Goldfarb Avi
Published: September 2008

We report evidence that Bitnet adoption facilitated increased research collaboration between US universities. However, not all institutions benefited equally. Using panel data from seven top engineering journals, Bitnet connection records, and institution ranking data, we find that middle-tier universities were the primary beneficiaries; they benefited largely by increasing their collaboration with top-tier schools. Furthermore, we find that the magnitude of this effect is greatest for co-located pairs. Thus, the advent of Bitnet – and likely of subsequent networks – seems to have increased the role of middle-tier universities as producers of new knowledge in the national innovation system. (JEL D85, I23, O31, O33)
The Cycle of Violence? An Empirical Analysis of Fatalities in the Palestinian-Israeli Conflict
Authors: Jaeger David A , Paserman M. Daniele
Published: September 2008

This paper examines the dynamics of violence in the Palestinian-Israeli conflict during the Second Intifada. Using data on the daily number of fatalities between September 2000 and January 2005, we estimate reaction functions for both Israelis and Palestinians and find evidence of Granger causality from Palestinian to Israeli violence, but not vice versa. This finding is consistent using either the incidence or level of fatalities and is robust to the specification of the lag structure and the level of time aggregation. We find no evidence that the Palestinians and Israelis are engaged in a predictable “tit-for-tat” cycle of violence. (JEL D74, H56, O17)
The Relationship between Economic Status and Child Health: Evidence from the United States
Authors: Condliffe Simon , Link Charles R
Published: September 2008

Anne Case et al. (2002), using cross-sectional data, found a positive relationship between children's health and income, with income's protective effect increasing with age. Janet Currie and Mark Stabile (2003), using a panel of Canadian children, found that low- and high-SES children respond similarly to health shocks, but the low-SES children are subject to more shocks as they age. Our study examines this relationship using panel data for US children. We find some support for the latter result of Currie and Stabile, but also evidence that low- and high-SES children respond differently to specific health shocks. (JEL D31, I12, J13)
All-or-Nothing Monitoring
Authors: Zhao Rui R
Published: September 2008

A principal can observe both the output and input of an agent who works at a job involving multiple tasks. We provide a simple theory that explains why it may be optimal for the principal to use only an output-based incentive contract, even though the principal can monitor the agent's actions perfectly in all but one task and knows exactly which action is optimal for each task. (JEL D82, D86, M54)
Commitment and Conflict in Bilateral Bargaining
Authors: Ellingsen Tore , Miettinen Topi
Published: September 2008

Building on previous work by Schelling and Crawford, we study a model of bilateral bargaining in which negotiators can make binding commitments at a low positive cost c. Most of our results concern outcomes that survive iterated strict dominance. If commitment attempts never fail, there are three such outcomes. In two of them, all the surplus goes to one player. In the third, there is a high probability of conflict. If commitment attempts succeed with probability q < 1, the unique outcome that survives iterated strict dominance entails conflict with probability q2. When c = 0, analogous results hold if the requirement of iterated strict dominance is replaced by iterated weak dominance. (JEL C78, D84)
Leveling the Playing Field: Sincere and Sophisticated Players in the Boston Mechanism
Authors: Pathak Parag A , Sönmez Tayfun
Published: September 2008

Empirical and experimental evidence suggests different levels of sophistication among families in the Boston Public School student assignment plan. We analyze the preference revelation game induced by the Boston mechanism with sincere players who report their true preferences and sophisticated players who play a best response. We characterize the set of Nash equilibrium outcomes as the set of stable matchings of a modified economy, where sincere students lose priority to sophisticated students. Any sophisticated student weakly prefers her assignment under the Pareto-dominant Nash equilibrium of the Boston mechanism to her assignment under the recently adopted student-optimal stable mechanism. (JEL D82, I21)
The Limited Influence of Unemployment on the Wage Bargain
Authors: Hall Robert E , Milgrom Paul R
Published: September 2008

When a job-seeker and an employer meet, find a prospective joint surplus, and bargain over the wage, conditions in the outside labor market, including especially unemployment, may have limited influence. The job-seeker's only credible threat during bargaining is to hold out for a better deal. The employer's threat is to delay bargaining. Consequently, the outcome of the bargain depends on the relative costs of delays to the parties, rather than on the payoffs that result from exiting negotiations. Modeling bargaining in this way makes wages less responsive to unemployment. A stochastic model of the labor market with credible bargaining and reasonable parameter values yields larger employment fluctuations than does the standard Mortensen-Pissarides model. (JEL J22, J23, J31, J64)
Trade Policy and Loss Aversion
Authors: Freund Caroline , Özden Çağlar
Published: September 2008

We develop a political economy model where loss aversion and reference dependence are important in shaping people's preferences over trade policy. The policy implications of the augmented model differ in three ways: there is a region of compensating protection, where a decline in the world price leads to an offsetting increase in protection, such that a constant domestic price is maintained; protection following a single negative price shock will be persistent; and irrespective of the extent of lobbying, there will be a deviation from free trade that favors loss-making industries. The augmented model explains protections of the US steel industry since 1980. (JEL F13, F14, L61)
Distorted Gravity: The Intensive and Extensive Margins of International Trade
Authors: Chaney Thomas
Published: September 2008

By considering a model with identical firms, Krugman (1980) predicts that a higher elasticity of substitution between goods magnifies the impact of trade barriers on trade flows. In this paper, I introduce firm heterogeneity in a simple model of international trade. I prove that the extensive margin and the intensive margin are affected by the elasticity of substitution in exact opposite directions. When the distribution of productivity across firms is Pareto, the predictions of the Krugman model with representative firms are overturned: the impact of trade barriers on trade flows is dampened by the elasticity of substitution, and not magnified. (JEL F12, F13)
Trends in the epidemiology and prescribing of medication for allergic rhinitis in England
Authors: Ghouri Nazim , Hippisley-Cox Julia , Newton John , Sheikh Aziz
Published: September 2008

Summary

Objective

To investigate recent trends in the recorded incidence, lifetime prevalence and prescribing of symptom relief medication for allergic rhinitis in England.

Design

Analysis of primary healthcare datasets.

Setting

The UK prevalence of allergic rhinitis has increased very significantly over recent decades. Analysis of primary healthcare datasets offers the possibility to advance understanding about the changing epidemiology and management of allergic rhinitis. QRESEARCH is one of the world's largest national aggregated health databases containing the records of over nine million patients. We extracted data on all patients with a recorded diagnosis of allergic rhinitis and calculated annual age–sex standardized incidence and lifetime period prevalence rates for each year from 2001–2005. We also analysed prescribing trends for antihistamines and drugs used in nasal allergy in those with a recorded diagnosis of allergic rhinitis.

Main outcome measures

Age-sex standardized incidence, lifetime prevalence rates and prescribing trends for symptom relief medication for allergic rhinitis in England.

Results

The age-sex standardized incidence of allergic rhinitis was 5.57 per 1000 person-years in 2001 and increased by 33.0% to 7.41 per 1000 person-years in 2005 ( P<0.001). Lifetime age-sex standardized prevalence of a recorded diagnosis of allergic rhinitis increased by 43.2% from 46.35 per 1000 in 2001 to 66.37 per 1000 in 2005 ( P<0.001). Over this period a 41.7% overall increase in prescriptions for antihistamines and drugs used in nasal allergy was observed (antihistamines 45.5%, drugs used in nasal allergies 35.5%).

Conclusions

Recorded incidence and lifetime prevalence of allergic rhinitis have increased substantially in recent years. A similar increase in prescriptions for antihistamines and drugs used in nasal allergy in patients with allergic rhinitis is also observed.
Challenges in Disability Management of Long-Term Sick Workers
Authors: Hedlund Marianne , Landstad Bodil J. , Wendelborg Christian
Published: September 2008

In Norway various welfare state authorities assist in disability management (DM) of long-term sick workers. This study provides empirical-based knowledge about the Norwegian DM process. The data are based on focus-group interviews with health care providers and case-workers in welfare state authorities. A key issue outlined in this article is that long-term sick workers can easily become ‘stuck’ in the rehabilitation system. The focus is on topics that can explain difficulties of re-employing long-term sick workers. Furthermore, we look at what challenges are typical for DM of these workers in Norway, with respect to re-employment issues.
The Role of the Physician in Disability Management: Assessing Family Physicians' View of Discrepancies Between Practice and Canadian Medical Association Guidelines
Authors: Reynolds Christine A. , Wagner Shannon. L. , Harder Henry. G. , Zimmer Lela
Published: September 2008

Purpose: This research project aimed to explore the views and perspectives of family physicians in regards to fulfilling their role in disability management (DM) — specifically, to examine the discrepancies between physicians' practice in DM and their professional guidelines, with special attention to physicians' experience in collaborating with key stakeholders. Methods: Seven family physicians were interviewed using a semi-structured interview format (8 evidence-based questions and 2 case examples). Interviews were recorded and transcribed. A content analysis of the interview data was conducted in addition to a thematic review of participant responses. Results: Data revealed that in accordance with previous literature, physicians' practice does not typically emulate Canadian Medical Association policy, and the participant physicians described several barriers as the reason for this discrepancy. This study revealed a multitude of frustrations encountered by physicians when interacting with other parties in DM. Participant physicians also reported potential solutions to these frustrations and other related issues. Conclusion: This qualitative study yields valuable insight into barriers, as well as facilitating factors, for physicians in the fulfillment of their DM role. Some practical recommendations for the DM community are presented, while noting that more research should be conducted, including input from key DM stakeholders, to both gain further understanding of physicians' DM function, and to identify viable interventions aimed at optimising their role.
Validation of a kinematic laserscanning system
Authors: Vennegeerts Harald , Martin Jens , Becker Matthias , Kutterer Hansjörg
Published: September 2008

The increasing data rate of actual laser scanners qualifies these sensors for kinematic applications. In case of surveying static environments the scanner can be integrated into a moving platform system. Therefore two main tasks are outstanding. Position and orientation of the platform have to be registered throughout a freely driven trajectory. The second challenge is to synchronize the scanned spatial data with the time scale of the positioning unit. This paper presents the specification of a mobile mapping system using a phase-based laser scanner with a hybrid INS (Inertial Navigation System)/GPS solution. Among a description of the system structure it includes a software-based method to synchronize the scanned profiles with the trajectory. No extra hardware unit for time registration of scanned profiles is required. After all a spatial comparison of independently observed control points allows the assessment of the system performance.
Line based reconstruction from terrestrial laser scanning data
Authors: Briese Christian , Pfeifer Norbert
Published: September 2008

The methods for reconstructing objects from dense point clouds, typically acquired by terrestrial laser scanning (TLS), are currently unsatisfying, especially from a geodetic perspective, for a number of reasons. Digitization in the point cloud lacks redundancy and no stochastic measures are provided generally. Reconstruction from primitives, e.g., planes, spheres, and cylinders, enforces strong requirements on (large) object parts, which are strictly valid only for very special cases. In this article we propose a new reconstruction technique for terrestrial laser scanning point clouds addressing those issues. In line with photogrammetric restitution, lines, not necessarily straight, are reconstructed in a process providing precision, i.e. internal quality measures. Methods for reconstructing different types of lines will be presented, in particular break lines, form lines, step edges, and boundary lines. The process features a high degree of automation, reducing the manual interaction to supplying one approximate point or one short segment per relevant line. The method will be presented with two examples.
A contribution to construction machine automation
Authors: Gläser Andreas , Möhlenbrink Wolfgang , Schwieger Volker
Published: September 2008

The requirements concerning surveying tasks on modern construction sites have considerably changed. The time slots for assigning and assuring geometric properties get shorter. Thus the surveying tasks change from static to kinematic methods. Nowadays surveying instruments, e.g. robot-tachymeters, can work in real time due to more powerful CPUs and better synchronisation of internal sensors. Therefore it is possible to integrate robot-tachymeters into the construction process using control loops to fulfil the real time positioning task. Accuracy limiting factors like inclined reflector booms on the construction machine, temperature influence as well as synchronisation and dead time problems are pointed out, too.

In this paper a modular toolbox for solution of geometric guidance and control tasks by robot-tachymeters is developed based on a so-called functional analysis and basic aspects of system design. The tachymeters are integrated into the processes to accomplish geometric control tasks of high precision (standard deviation < 1 cm for the position). The exemplary realisation of the modular system is the automatic guidance of a truck model (1:14) on a known trajectory.
Gridline methods for detection of object displacements and rigid body movements
Authors: von Webern Hauke , Kahmen Heribert
Published: September 2008

If measurements are performed without artificial targets, deformation analysis cannot refer to the points on the objects defined at an initial or prior measurement epoch. This paper describes how an arrangement of virtual lines, so-called grid lines (GL), offers a solution. A total station, measuring distances without a reflector, or a theodolite measurement system can be used to make the measurements. The GLs should intersect the object to be measured, as far as possible, at right angles and they can be arranged in such a way that each of them runs through one of the object points chosen for the initial measurements. Subsequently deformations of the object can be described along the GLs.

The general idea behind this method is to track the virtual lines with the optical axis of a theodolite, until it aims at the points where the GLs intersect the surface. Tracking starts where the GLs intersected the surface of the object during the last measurement epoch. However, if the surface moved this point will be no longer an intersection point and the optical axis hits the surface at another point. Consequently there will be a separation of these two points, and if the theodolite starts tracking the GL, a distance function is obtained. This can be used to determine the new intersection point of the GL if that line is tracked until the value of the distance function is zero.

The following sections describe how this process can be iteratively controlled by algorithms for an one-dimensional search space. The algorithms are based on the binary-search-, so-called parabola-, and regula-falsi method. Simulations and practical tests are used to evaluate the different search algorithms. The accuracy of the intersection points and the number of necessary iteration steps, describing the speed of the algorithms, are used as quality assessment parameters. Both quality characteristics depend on the truncation criteria: a distance and a length of an interval.
Tertiary treatment of domestic wastewater using zeolite ceramics and aquatic plants
Authors: Kimochi Y. , Masada T. , Mikami Y. , Tsuneda S. , Sudo R.
Published: September 2008

In this study, we examined tertiary treatment of domestic wastewater using zeolite ceramics and aquatic plants, especially reeds, Phragmites australis. The experiment was made at real domestic wastewater treatment facilities, and comparison of treatment performance was made between the method with zeolite ceramics and that with pebble stones as conventional way. SEM observation of the ceramics' surface was also made to examine its possibility as the habitat of bacteria. The results obtained are as follows. Through the tertiary treatment experiment, it was suggested that the water purification system with zeolite ceramics and reeds could keep higher nitrogen removal efficiency for a long time. Zeolite ceramics would be useful when nitrogen compound, NH4-N in particular, in the influent was higher. Under SEM observation, bacteria-like objects were observed on the ceramics' surface. Appropriate operation and maintenance would be needed to keep long-term performance of both the NH4+ absorption and nitrogen removal with use of zeolite ceramics.
Switching small WWTPs from extended to intermittent aeration: process behaviour and performances
Authors: Eusebi Anna Laura , Carletti Giacomo , Cola Emanuela , Fatone Francesco , Battistoni Paolo
Published: September 2008

The paper presents the one year results obtained by a small wastewater treatment plant (WWTP) located in a decentralized area. The plant was organized, reusing current structures, introducing an equalization tank, an anoxic selector and the alternate cycles (AC) as technology in the biological process. The experimentation data processed show the excellent quality of the effluent with high removal efficencies for all the macropollutants. Also, the anoxic selector effect allows, in the critical winter period, the decrease in the filamentous bacteria total number, a net improvement of the settling behaviour with an average solid maximum flux value of 3.8 kgMLSSm−2 h−1 and a good mixed liquor settleability. The alternate cycles process flexibility consents to well manage the high fluctuations of the influent loadings. The costs comparison of AC process and extended aeration confirms the sustainability of the upgrading.
Performance evaluation of various aerobic biological systems for the treatment of domestic wastewater at low temperatures
Authors: Sundaresan N. , Philip L.
Published: September 2008

Studies were undertaken on the performance evaluation of three different types of aerobic reactors, namely, activated sludge process, fluidized bed reactor and submerged bed reactor. Initially synthetic wastewater was used for stabilizing the system and later domestic wastewater of IIT Madras was used as the feed for the biological systems. The hydraulic retention time was maintained as 24 h. The seed sludge was collected from IIT Madras sewage treatment plant. The inlet COD to the reactors with synthetic wastewater was 1,000±20 mg/L and with real wastewater, it was 150 to 350 mg/L. The performance of the reactors was evaluated based on the soluble COD and nitrogen removal efficiency. The pH, temperature, dissolved oxygen (DO) and mixed liquid suspended solid (MLSS) concentration were measured periodically. The reactors were acclimatized at 35°C in batch mode and changed to continuous mode at 30°C. After the systems attained its steady state at a particular temperature, the temperature was reduced from 35°C to 5°C stepwise, with each step of 5°C. The start-up time for submerged bed reactor was slightly more than fluidized and conventional activated sludge process.

The COD removal efficiency of the three reactors was higher with synthetic wastewaters as compared to actual domestic wastewater. Submerged bed reactor was more robust and efficient as compared to activated sludge and fluidized bed reactors. The COD removal efficiency of the reactors was relatively good until the operating temperature was maintained at 15°C or above. At 10°C, submerged bed reactor was able to achieve 40% COD removal efficiency whereas; the fluidized bed and conventional ASP reactors were showing only 20% COD removal efficiency. At 5°C, almost all the systems failed. Submerged bed reactor showed around 20% COD removal efficiency. However, this reactor was able to regain its 90% of original efficiency, once the temperature was raised to 10°C. At higher temperatures, the nitrification efficiency of the reactors was above 80–90%. As the temperature reduced the nitrification efficiency has reduced drastically. In summary, submerged bed reactors seems to be a better option for treating domestic wastewaters at low temperature regions.
Simultaneous removal of N and P in a SBR with production of valuable compounds: application to concentrated wastewaters
Authors: Sperandio M. , Pambrun V. , Paul E.
Published: September 2008

This article examines the optimisation of recovery of phosphorus and nitrogen (via struvite) in small treatment units for high strength wastewaters using biologically assisted precipitation. The particular focus was the synergetic effect between removal of orthophosphate and the biological reactions occurring during nitrogen removal. The most sensitive parameter influencing the phosphate solid forms (HAP, MAP) is pH. Sequencing batch mode helps maintain high gradients in ammonia concentration, which encourages struvite precipitation. Nitrification has a key effect on the precipitation, through its influence on pH and ammonia concentration, determining the remaining soluble phosphorus concentration. Denitrification and CO2 stripping, by increasing pH also improve precipitation of phosphorus. Optimal operating conditions will therefore depend on the chosen strategy: thus nitrification may help to keep phosphorus in a soluble form (as needed in direct urine reuse), whereas if co-precipitation is desired in the biological reactor, nitrification should be controlled in relation with others processes responsible for pH increase.
Dissolved oxygen as a key parameter to aerobic granule formation
Authors: Sturm B. S. McSwain , Irvine R. L.
Published: September 2008

Much research has asserted that high shear forces are necessary for the formation of aerobic granular sludge in Sequencing Batch Reactors (SBRs). In order to distinguish the role of shear and dissolved oxygen on granule formation, two separate experiments were conducted with three bench-scale SBRs. In the first experiment, an SBR was operated with five sequentially decreasing superficial upflow gas velocities ranging from 1.2 to 0.4 cm s−1. When less than 1 cm s−1 shear was applied to the reactor, aerobic granules disintegrated into flocs, with corresponding increases in SVI and effluent suspended solids. However, the dissolved oxygen also decreased from 8 mg L−1 to 5 mg L−1, affecting the Feast/Famine regime in the SBR and the substrate removal kinetics. A second experiment operated two SBRs with an identical shear force of 1.2 cm s−1, but two dissolved oxygen concentrations. Even when supplied a high shear force, aerobic granules could not form at a dissolved oxygen less than 5 mg L−1, with a Static Fill. These results indicate that the substrate removal kinetics and dissolved oxygen are more significant to granule formation than shear force.
Simultaneous storage and utilization of polyhydroxyalkanoates and glycogen under aerobic conditions
Authors: Karahan Ozlem , Orhon Derin , van Loosdrecht Mark C. M.
Published: September 2008

This study aims to investigate the storage response of an activated sludge system in the presence of two different substrates which are stored as two different polymers. The objective of the study was to determine the changes in the response of an activated sludge system when two different storage mechanisms could occur simultaneously. Acetic acid (HAc) and soluble starch (SolS) were selected as model substrates and three different feeding conditions, namely (i) when both HAc and SolS were initially present in the reactor, (ii) only HAc was present, and (iii) only SolS was present in the substrate solution. The batch reactors were monitored for acetic acid, polyhydroxyalkanoates (PHA), poly-glucose (glycogen like substances) and oxygen uptake rate (OUR). The experiments have shown that, while the main portion of hydrolyzed starch was stored as poly-glucose, which was further used for heterotrophic growth, the rest was utilized for direct growth. However, acetic acid was totally stored as PHA and the stored PHA was used for biomass growth under the presented experimental conditions. When the system was fed with the substrate mixture, the storage mechanism was not significantly affected. Both PHA and poly-glucose storage took place simultaneously with the same stoichiometry and kinetics defined for single substrate utilization.
Performance of a fungal based SBR under pH extreme and shock phenolic exposure
Authors: D'Urso A. , Gapes D. , Bravi M.
Published: September 2008

An investigation was performed to explore the capabilities of a filamentous fungal biomass to grow non-aseptically in a glucose-fed Sequencing Batch Reactor system in very extreme environment (pH 3.5) conditions. Trichoderma viride Pers: Fr. Isolate 8/90 was used as inoculum. Microscopic investigations were carried out to confirm fungal dominance in the open culture. In batch tests, the fungal biomass showed a significant ability to grow and remove the applied organic load (2000 mgGlucose L−1 d−1), with high biomass yields. Furthermore, the biomass showed an ability to resist gallic acid toxicity at high concentraions (1 g L−1) without any pre- exposure acclimation of the biomass. The biomass (about 2.5 gVSS L−1) demonstrated significant aerobic removal of gallic acid in a timeframe of 20 h from initial exposure. The robust characteristics of this SBR system demonstrate potential for future development of fungal based treatment for recalcitrant feedstocks or operation under extreme environmental conditions.
Theoretical analysis and enhanced nitrogen removal performance of step-feed SBR
Authors: Guo Jianhua , Peng Yongzhen , Yang Qing , Wang Shuying , Chen Ying , Zhao Chenhong
Published: September 2008

To achieve high nitrification and denitrification rates, step-feed SBR with multiple aerobic and anoxic phases was adopted to study nitrogen removal performance. Theoretical analysis of step-feed SBR was presented first, from which feeding steps and C/N ratio had significant influences on nitrogen removal performance. Total nitrogen removal efficiency would increase with increasing of feeding steps, while the increasing extent was not distinct with feeding steps above 4. At a given feeding step, nitrogen removal efficiency would also increase with increasing of C/N ratio. Experimental work was conducted in a lab-scale SBR to investigate practical effects of these critical factors, using real municipal wastewater. The results showed when C/N ratio was appropriately decreasing influent flow mode could achieve enhanced nitrogen removal with less adding of external carbon source, compared with equal influent flow mode. Three-step equal influent flow mode was recommended to treat common municipal wastewater in view of operation complexity. Non steady-state experiments over about three months confirmed step-feed SBR was an enhanced nitrogen removal process with high efficiency. Total nitrogen in the effluent was under 2 mg/L, the average removal efficiency achieved for TN was over 97% just adding a little external carbon source, and good sludge settleability was obtained.
Biological aerated filter treated textile washing wastewater for reuse after ozonation pre-treatment
Authors: Wang X. J. , Chen S. L. , Gu X. Y. , Wang K. Y. , Qian Y. Z.
Published: September 2008

The combination of chemical and biological treatment processes is a promising technique to reduce refractory organics from wastewater. Ozonation can achieve high color removal, enhance biodegradability, and reduce the chemical oxygen demand (COD). The biological technique can further decrease COD of wastewater after ozonation as a pre-treatment. In this study the ozonizing-biological aerated filter processes were used to treat textile washing wastewater for reuse after conventional treatment. The result showed that when the influent qualities were COD about 80 mg/L, color 16 degree and turbidity about 8 NTU, using the combination processes with the dosages of ozone at 30–45 mg/L with the hydraulic retention time (HRT) of biological aerated filter (BAF) at 3–4 hours respectively, gave effluent qualities of COD less than 30 mg/L, color 2 degree and turbidity less than 1NTU. The cost of treatment was less than one yuan/t wastewater, and these processes could enable high quality washing water reuse in textile industry.
Effect of pH on Fenton process using estimation of hydroxyl radical with salicylic acid as trapping reagent
Authors: Chang Chen-Yu , Hsieh Yung-Hsu , Cheng Kai-Yuan , Hsieh Ling-Ling , Cheng Ta-Chih , Yao Kuo-Shan
Published: September 2008

This study estimates the yield of hydroxyl radical using salicylic acid as the trapping reagent and investigates the relationship between hydroxyl radical and pH value. The formation and variation of hydroxyl radical under different pH values were evaluated using reaction products, 2,3-DHBA, 2,5-DHBA, and catechol. The formation rate of hydroxyl radical was dependent on the ratio of ferrous ion to hydrogen peroxide and pH values. The difference between various pH values was explored. The kinetics and mechanisms of hydroxyl radical reactions were established in the Fenton process. Experimental results showed that the best reaction conditions were 8.5 mM H2O2, 1.25 mM Fe2 + , Fe2 + /H2O2=0.147 at pH 3 and the formation rate constant of hydroxyl radical was 1.12 × 1011 M−1 s−1.
Escherichia coli in household drinking water and diarrheal disease risk: evidence from Cambodia
Authors: Brown J. M. , Proum S. , Sobsey M. D.
Published: September 2008

Escherichia coli counts in household drinking water may or may not reliably indicate the presence of diarrheogenic pathogens originating in feces. The extent to which a bacterial indicator like E. coli predicts risks from all classes of pathogens (viruses and parasites as well as bacteria), especially in tropical waters, is uncertain. To investigate the association between E. coli in household drinking water and diarrheal diseases in Cambodia, we conducted a 22 week cohort study in a rural village in Kandal Province. Episodes of diarrhea (all) and bloody diarrhea (dysentery), water quality, water sources, and other covariates were monitored biweekly in 180 households. Households used a variety of water treatment, storage, and handling practices.

Results suggest a weak but positive association between E. coli counts in household drinking water and diarrhea and for diarrhea with blood (dysentery), after adjusting for clustering within households and within individuals over time. Compared to households with <1 E. coli/100 ml in drinking water, there was no observed increased risk for having 1–10 E. coli/100 ml (LPR = 0.98, 95% CI 0.81–1.2 for diarrheal disease; LPR = 0.75, 95% CI 0.36–1.6 for dysentery). Households with measured E. coli of 11–100/100 ml did report increased diarrhea (LPR = 1.2, 95% CI 1.1–1.3 for diarrheal disease; LPR = 1.4, 95% CI 1.0–1.8 for dysentery), as did those with 101–1,000 E. coli/100 ml (LPR = 1.2, 95% CI 1.2–1.3 for diarrheal disease; LPR = 1.2, 95% CI 1.0–1.4 for dysentery) and those with >1,000 E. coli per 100 ml sample (LPR = 1.2, 95% CI 1.1–1.2 for diarrheal disease; LPR = 1.2, 95% CI 1.0–1.3 for dysentery). Unlike the results of some previous studies, diarrheal disease risks did not increase progressively in magnitude with increasing concentration of E. coli in drinking water.
Evaluation of catalysts and membranes for high yield biohydrogen production via electrohydrogenesis in microbial electrolysis cells (MECs)
Authors: Cheng Shaoan , Logan Bruce E.
Published: September 2008

Hydrogen gas can be produced from fermentation end products such as acetic acid through the electrohydrogenesis process in microbial electrolysis cells (MECs). In many MEC reactors, precious metal catalysts and expensive cation exchange membranes are often used. Here we examine Co- and FeCo-based alternatives to Pt, and compare the performance of an anion exchange membrane with that of a cation exchange membrane (Nafion™ 117). It is found that these alternative catalysts have 40–80% better performance than uncatalysed surfaces, but they do not equal the performance of Pt based on our electrochemical tests using cyclic voltammetry. It was also found that the anion exchange membrane (AEM) performance was equal to that of cation exchange membrane (CEM) at applied voltages of 600 mV or less in MEC tests, but that it exceeded performance of the CEM at voltages above 600 mV. These results demonstrate choosing catalysts will require both analysis of performance and materials costs, but that performance is improved for producing H2 gas in MECs using AEMs.
Feasibility of disinfection kinetics and minimum inhibitory concentration determination on bacterial cultures using flow cytometry
Authors: Cunningham J. H. , Cunningham C. , Van Aken B. , Lin L.-S.
Published: September 2008

Disinfection kinetics has been well established for selected antimicrobial agents on isolated bacterial strains. Due to the difficulties of culturing most bacteria, the majority of these studies have been limited to readily cultivable microorganisms of a single type or family. This study explores the feasibility of using flow cytometry for characterising the disinfection kinetics and minimum inhibitory concentration (MIC) of an Escherichia coli culture and a microbial consortium. The proposed method relies on fluorescent dye molecules to indicate the morphological and physiological status of numerous individual cells. Biocides of varying effectiveness and inactivation mechanisms (chlorine, iodine, and silver) were used to evaluate this novel application. Using pseudo-first-order kinetics, the coefficients of specific lethality of chlorine and iodine on Escherichia coli were 4.71 and 3.78×10−3 L mg−1 min−1 and MIC of silver ion was between 60 and 80 μg L−1. The coefficients of specific lethality of chlorine and iodine on the microbial consortium were 4.96 and 8.89×10−3 L mg−1 min−1 and MIC of silver ion was between 40 and 60 μg L−1. This method can be used to provide a rapid and consistent way of determining disinfection kinetics and MICs for pure and mixed bacterial cultures and can potentially be used to examine water and wastewater disinfection efficiency. However, caution should be used to ensure that the physiological and morphological status characterised by cytodyes is a result of the inactivation mechanisms of the disinfectants evaluated.
Improving access to water supply and sanitation in urban India: microfinance for water and sanitation infrastructure development
Authors: Davis Jenna , White Gary , Damodaron Said , Thorsten Rich
Published: September 2008

This article summarises initial findings of a study to explore the potential of providing micro-financing for low-income households wishing to invest in improved water supply and sanitation services. Through in-depth interviews with more than 800 households in the city of Hyderabad in India, we conclude that, even if provided with market (not concessional) rates of financing, a substantial proportion of poor households would invest in water and sewer network connections.
Treatment of succinonitrile wastewater by immobilized high efficiency microorganism strains
Authors: Zhou X. F. , Zhang Y. L. , Xu D. Q. , Cao W. H. , Dai C. M. , Qiang Z. M. , Yang Z. , Zhao J. F.
Published: September 2008

Using succinonitrile as a sole source of carbon and nitrogen, two bacterium strains named as J-1-3 and J-13-1 were isolated and screened out from the treatment facilities of Shanghai petrochemical wastewater treatment plant treating acrylic fiber production wastewater. The optimal growth conditions of the two strains in the degradation of succinonitrile with varied initial concentrations were determined through flask tests as follows: temperature 30°C, shaker rotary speed of 250 r/min, inoculum percentage 0.1%, and initial pH 6. Results indicate that the two strains, especially J-13-1, exhibited a high efficiency for succinonitrile degradation. Thereafter, the bacterium strains were immobilized separately by sodium alginate and polyvinyl alcohol 1750±50, and applied to succinonitrile degradation again. Results show that in a very broad range of the initial succinonitrile concentration, i.e., 30–5,000 mg/L, the sodium alginate immobilized grains could degrade more than 80% of succinonitrile after 24 h under the experimental conditions of 30°C, pH 6.5, and shaker rotary speed of 250 r/min. However, the polyvinyl alcohol immobilized grains tended to inflate and break down due to a weak mechanical strength.
Influence of irradiation crosslinking on the self‐heating and conduction of an acetylene carbon black filled high‐density polyethylene composite in the electric–thermal equilibrium state
Authors: Song Yihu , Zheng Qiang
Published: September 2008

The electric self‐heating and conduction behaviors of a high‐density polyethylene/acetylene carbon black composite crosslinked with electron‐beam irradiation are studied with respect to the electric field and ambient temperature. On the basis of scaling arguments, the critical fields and current densities for the onsets of self‐heating and global electrical breakdown are discussed with respect to the intrinsic resistivity at a given ambient temperature as well as the irradiation dosage. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
A convenient approach to synthesize stable silver nanoparticles and silver/polystyrene nanocomposite particles
Authors: Wang Desong , An Jing , Luo Qingzhi , Li Xueyan , Li Minna
Published: September 2008

In this study, silver nanoparticles were prepared by the reduction of silver nitrate in SDS+ isopentanol/styrene/H2O reverse microemulsion system using sodium citrate as reducing agent. The Ag/PS nanocomposite particles were prepared by in situ emulsion polymerization of the styrene system containing silver nanoparticles that did not separate from the reaction solution. The polymerization dynamic characteristic was studied, at the same time, silver nanparticles and the encapsulation of composite particles were characterized by Fourier‐transform‐infrared spectroscopy (FTIR), transmission electron microscopy (TEM), X‐ray diffraction (XRD) measurement, UV–vis diffuse reflectance spectroscopy, and X‐ray photoelectron spectroscopy (XPS). The results of TEM and UV–vis absorption spectra showed that well‐dispersed silver nanoparticles have a narrow size distribution. XRD showed that Ag and Ag/PS nanocomposite particles were less than 10 and 20 nm in size, which is similar to those observed by TEM. The results of XPS spectra revealed that the microemulsion system can stabilize the silver nanoparticles from aggregation and provided supporting evidence for the polystyrene encapsulated silver nanoparticle structure. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008.