bluuebunny/crossref_metadata_2025 huggingface dataset:
Threshold values and management options for nutrients in a catchment of a temperate estuary with poor ecological status
Authors: Hinsby K. , Markager S. , Kronvang B. , Windolf J. , Sonnenborg T. O. , Thorling L.
Published: February 2012

Abstract. Intensive farming has severe impacts on the chemical status of groundwater and streams and consequently on the ecological status of dependent ecosystems. Eutrophication is a widespread problem in lakes and marine waters. Common problems are hypoxia, algal blooms and fish kills, and loss of water clarity, underwater vegetation, biodiversity, and recreational value. In this paper we evaluate the nitrogen (N) and phosphorus (P) chemistry of groundwater and surface water in a coastal catchment, the loadings and sources of N and P and their effect on the ecological status of an estuary. We calculate the necessary reductions in N and P loadings to the estuary for obtaining a good ecological status, which we define based on the number of days with N and P limitation, and the equivalent stream and groundwater threshold values assuming two different management options. The calculations are performed by the combined use of empirical models and a physically based 3-D integrated hydrological model of the whole catchment. The assessment of the ecological status indicates that the N and P loads to the investigated estuary should be reduced by a factor of 0.52 and 0.56, respectively, to restore good ecological status. Model estimates show that threshold total N concentrations should be in the range of 2.9 to 3.1 mg l−1 in inlet freshwater to Horsens Estuary and 6.0 to 9.3 mg l−1 in shallow aerobic groundwater (∼27–41 mg l−1 of nitrate), depending on the management measures implemented in the catchment. The situation for total P is more complex but data indicate that groundwater threshold values are not needed. The inlet freshwater threshold value for total P to Horsens Estuary for the selected management options is 0.084 mg l−1. Regional climate models project increasing winter precipitation and runoff in the investigated region resulting in increasing runoff and nutrient loads to coastal waters if present land use and farming practices continue. Hence, lower threshold values are required in the future to ensure good status of all water bodies and ecosystems.
Thin-layer effects in glaciological seismic amplitude-versus-angle (AVA) analysis: implications for characterising a subglacial till unit, Russell Glacier, West Greenland
Authors: Booth A. D. , Clark R. A. , Kulessa B. , Murray T. , Hubbard A.
Published: February 2012

Abstract. Seismic amplitude-versus-angle (AVA) methods are a powerful means of interpreting the physical properties of subglacial material, although interpreting an AVA response is complicated in the case of a thinly-layered substrate. A layer thinner than one-quarter of the seismic wavelength is considered seismically "thin", and reflections from its bounding interfaces are perceived as a single event. Since a lodged (non-deforming) subglacial till can capped by a thin (metre-scale) cap of dilatant (deforming) till, serious misinterpretations can result if thin layer considerations are not honoured. AVA responses for layered subglacial tills are simulated: we model dilatant layers of thickness 0.1–3.0 m (up to a quarter-wavelength of our synthetic seismic pulse) overlying a lodged half-space, assigning typical acoustic impedance and Poisson's ratios to each. If thin layer effects are neglected, the AVA response to ultra-thin (<1.0 m) dilatant layers yields incompatible physical properties (acoustic impedance and Poisson's ratio indicating, respectively, a low- and high-porosity unit). We show an interpretative strategy that identifies thin layer effects and accurately quantifies the modelled acoustic impedance of lodged till from the composite AVA response. We apply this method to example seismic AVA data from the Russell Glacier outlet of the West Greenland Ice Sheet, in which characteristics of thin layer responses are evident. We interpret a stratified subglacial deposit, with upper and lower layers of high-porosity (<1.0 m thick, Poisson's ratio >0.492 ± 0.015) and low-porosity (acoustic impedance of 4.20–4.39 × 106 kg m−2 s−1) material, respectively assumed to represent dilatant and lodged tills. Thin layer considerations are strongly advised wherever seismic AVA analyses are used to quantify subglacial material properties.
Risk Factors for Heterotopic Ossification in Primary Total Hip Arthroplasty
Authors: Pavlou George , Salhab Mohammad , Murugesan Log , Jallad Samer , Petsatodis George , West Robert , Tsiridis Eleftherios
Published: February 2012

Heterotopic ossification (HO) is a recognised complication of total hip arthroplasty (THA). This study aims to correlate demographics, surgical approach and type of arthroplasty to the incidence of HO in an attempt to quantify patient risk. A total of 920 primary THAs in 893 patients were performed between 2006 and 2008 in a single arthroplasty centre. Radiographic evaluation was conducted and all cases of HO were classified using the Brooker classification. Age, sex, arthroplasty type and surgical approach were all considered as variables. Arthroplasty type was classified into four groups; total cemented (TC), total uncemented (TU), hybrid (H) and reverse hybrid (RH). Two-level logistic regression analysis was conducted. The overall incidence of HO was 24%. Male sex [OR=3.57, 95% CI (1.79–7.10); p=0.001], lateral approach [OR=2.47, (95% CI 1.23–4.95); p=0.001] and total cemented implants [OR=3.14, (95%CI 1.37–7.23); p=0.007] were significantly associated with HO. The intra-class correlation coefficient was 0.52 [95% CI (0.21, 0.81); p=0.004], demonstrating that patients with previous HO to one THA were very likely to suffer HO in subsequent THA. The results demonstrate very large effects for sex, surgical approach, and implant type on HO incidence. This raises a three arm hypotheses that reaming of the femoral canal for the insertion of cemented implants contaminates the surgical field with bone marrow increasing the risk of HO, whereas modern cementless implants generally employ impaction broaching. In addition surgical insult to the hip abductors during exposure, particularly in males due to higher muscle mass, may also predispose to HO.
Hospital Cost of Treating Early Dislocation following Hip Arthroplasty
Authors: de Palma Luigi , Procaccini Roberto , Soccetti Andrea , Marinelli Mario
Published: February 2012

Dislocation is a frequent and costly complication of hip arthroplasty. The purpose of this study was to assess the financial impact on the treating institution of this complication in patients with primary hemiarthroplasty (HA), total hip arthroplasty (THA) and revision surgery (RTHA).

Between October 2001 and August 2009, 2014 consecutive hip arthroplasties were performed at our institution, of which 87 (18 HA, 44 THA and 25 RTHA) dislocated within 6 weeks of the primary operation. The average cost of treating implant dislocation by closed reduction, open reduction or revision was assessed and expressed as a percentage cost increase compared to an uncomplicated procedure.

Of the 87 dislocated implants all needed one or more closed reductions and 52 eventually required revision surgery. An early dislocation increased the cost of HA, THA and RTHA by 472%, 342% and 352%, respectively.
Cultural Effects on Inbound Tourism into the USA: A Gravity Approach
Authors: Vietze Christoph
Published: February 2012

This paper addresses the effects of cultural, and particularly religious, factors on tourist flows into the USA, the world's most popular tourist destination. To estimate this empirically, the author runs an augmented gravity equation. The results provide evidence that cultural proximity between country of origin and country of destination has positive effects on the tourism flows between those countries. In particular, after controlling for a set of geographical variables, more people from countries with the same language (English) and high governmental rankings comparable to that of the USA travel to the USA for holidays than people from other countries. Above all, there is strong evidence that tourists from Christian countries prefer the USA as a holiday destination much more than people from other countries. This finding is stable across model specifications and supports the argument that people wish to go on vacation to countries with similar cultural and political backgrounds to their own.
Research Note: An Error Correction Analysis of Visitor Arrivals in the Bahamas
Authors: Charles Jacky S. , Fullerton Thomas M.
Published: February 2012

Tourism is a major activity for many countries in the Caribbean. Accurate forecasts of visitor arrivals can assist planning efforts in the public and private sectors. This study uses error correction models (ECMs) to analyse visitor arrivals in the Bahamas. Findings suggest that income and habit persistence/word-of-mouth advertising are primary determinants of tourism to the Bahamas, while the cost of travel is generally insignificant. To assess the model reliability further, ECM forecasts are compared to random walk and random walk with drift benchmarks. The ECMs provide fairly reliable forecasts, but are less accurate than the benchmarks.
Modelling International Tourism Demand for the Caribbean
Authors: Onafowora Olugbenga A. , Owoye Oluwole
Published: February 2012

This paper provides models of international tourism demand for four destination countries (the Bahamas, Barbados, Jamaica and St Lucia) in the Caribbean region, where visitor arrivals are mainly from Canada, Germany, the UK and the USA. The authors use a less restrictive econometric technique – the autoregressive distributed lag (ARDL) bounds test – to test for cointegration among the variables in the tourism demand equations. The empirical results from the bounds test indicate the existence of a unique long-run relationship between tourist arrivals, per capita real income, tourism prices and transport costs. The estimated results show that changes in tourists' income, tourism prices, travel costs, the 9/11 2001 terrorist attacks on the USA and the 2003 US–Iraq War significantly affect tourists' travel decisions. The results also show that tourism demand for Caribbean destinations is highly income elastic in both the short run and the long run, but relatively price inelastic in both periods. The price inelasticities suggest that if policy makers and/or tourism stakeholders increase the prices of the tourism products and services, this would not decrease the number of tourist arrivals proportionally but would increase total tourism receipts or revenues. Overall, the CUSUM and CUSUMSQ stability tests reveal that the parameters of the international tourism demand models are stable and, as such, they can be used for policy analysis and forecasting.
Economic Effects of Tourism Tax Changes in Australia: Empirical Evidence from a Computable General Equilibrium Model
Authors: Ihalanayake Ranjith
Published: February 2012

This paper analyses the economic effects of tourism tax changes in Australia. To this end, a tourism tax model (TTM), a computable general equilibrium (CGE) model of the Australian economy, is developed explicitly incorporating two tourism sectors. This is an important improvement in modelling tourism in a CGE context. The tourism sectors are incorporated using the ‘tourism dummy sector approach’, in which both the demand and supply sides of tourism sectors are modelled adequately to reflect the true nature of tourism. This model is used to carry out simulations of abolishing tourism taxes which are financed by an increase in the GST (goods and services tax). The simulation results suggest that the tourism sector expands as a result of tax abolition, while the other sectors contract. The increase in the GST, on the other hand, leads to an increase in commodity prices and thus the economy suffers, as reflected in a reduction in GDP. Overall, the results show that these tax changes are contractionary, as reflected in real consumption and GDP.
Research Note: Recreational Trip Timing and Duration Prediction
Authors: Hailu Atakelty , Gao Lei
Published: February 2012

This paper presents models that predict two recreational fishing trip parameters: the length of a trip and the timing of a trip within a year. A discrete choice (logit) model – linking the choice of trip timing to calendar events, the demographic characteristics of anglers and the nature of the trip – is estimated econometrically. A Tobit model is used to evaluate the effects on fishing trip length of personal and trip characteristics. The results indicate that timing choice and trip length can be explained well in terms of observable personal and trip variables. Knowledge of these relationships is a useful input to tourism/recreational fishing management, as well as to the development of tourism/fishing activity simulation models.
IV Estimation of a Panel Threshold Model of Tourism Specialization and Economic Development
Authors: Chang Chia-Lin , Khamkaew Thanchanok , McAleer Michael
Published: February 2012

The significant impact of international tourism in stimulating economic growth is especially important from a policy perspective. For this reason, the relationship between international tourism and economic growth would seem to be an interesting and topical empirical issue. The paper investigates whether tourism specialization was important for economic development in 159 countries over the period 1989–2008. The results from panel threshold regressions show a positive relationship between economic growth and tourism. Instrumental variable estimation of a threshold regression is used to quantify the contributions of tourism specialization to economic growth, while correcting for endogeneity between the regressors and error term. The significant impact of tourism specialization on economic growth in most regressions is robust to different specifications of tourism specialization, as well as to differences in real GDP measurement. However, the coefficients of the tourism specialization variables in the two regimes are significantly different, with a higher impact of tourism on economic growth found in the low regime. These findings do not alter with changes in the threshold variables. The empirical results suggest that tourism growth does not always lead to substantial economic growth.
Risks and Benefits of Outsourcing Hotel Operations: A Comparison between Scotland and Taiwan
Authors: Espino-Rodríguez Tomás F. , Lai Pei Chun , Baum Tom
Published: February 2012

This paper examines the use of outsourcing in the activities comprising hotel operations in Scotland and Taiwan. Outsourcing is a key process integrated into the design of the supply chain management. The research also focuses on empirically identifying the role of the outsourcing strategy in hotels. To this end, the authors propose two hypotheses to study the relationship between the benefits and risks of outsourcing and the tendency to use third-party organizations. These hypotheses are analysed and tested in the two regions. The study was conducted on a representative sample of 118 hotels in Scotland and Taiwan. A questionnaire was used to obtain the findings. The results indicate that the principal candidates for outsourcing are the activities requiring technical skills and those services not involving direct contact with guests. No significant differences were found between the current levels of outsourcing in Scottish and Taiwanese hotels. The findings indicate that a stronger perception of the risks and benefits of outsourcing has a greater influence on outsourcing strategy. Furthermore, in the case of Scottish hotels, it is the benefits that determine the level of outsourcing, while it is the risks that do so in Taiwanese hotels. This work contributes to the literature on outsourcing from a services perspective.
Nationality as a Segmentation Criterion in Tourism Research: The Case of International Tourists' Expenditures While on Trips in Norway
Authors: Thrane Christer , Farstad Eivind
Published: February 2012

The practice of using nationality or its equivalents as a segmentation criterion in tourism research has been both warned against and advocated among tourism scholars. Whenever a nationality, country-of-residence, country-of-origin or similar variable has been included in multivariate statistical modelling, however, its role has tended to be that of one of many control variables. The main purpose of this paper is to quantify and describe more comprehensively than in past research how variations in expenditure levels are associated with the nationality of foreign tourists in Norway during the summers of 2007 and 2009. The results show that nationality has both gross and net (unadjusted and ceteris paribus) effects on expenditures, and that this variable solely accounts for over 35% of the overall explained variance in tourism expenditures. The implications of the results are discussed.
Occlusal Plane Determination Using Custom Made Broadrick Occlusal Plane Analyser: A Case Control Study
Authors: Manvi Supriya , Miglani Shaveta , Rajeswari C. L. , Srivatsa G. , Arora Sarvesh
Published: February 2012

Proper occlusal plane is an essential consideration when multiple long span posterior restorations are designed. The determination of the occlusal plane can have a profound effect on the short and long term success of a restorative case. Purpose of Study. (1) To determine the appropriate occlusal curve for individual patients. (2) To compare the deviation of the clinical occlusal curve with the ideal ones. Materials and Methods. A total of 20 subjects were examined and study models were made of their maxillary and mandibular dentition. Inter-occlusal records were made and the casts were articulated in semiadjustable articulator. An ideal occlusal plane was created. The distance of the farthest cusp tip from the Broadrick curve was measured along the long axis of the tooth for each individual. Paired t-tests were used to compare the findings between subjects and controls. Results. A statistically significant difference P<0.05 was found in the deviation from the Broadrick curve between patients who have lost posterior teeth and the control group who had a full dentition with no missing teeth. Conclusion. Proper utilization of the broadrick flag on a semi-adjustable articulator will allow for a correct determination of the occlusal plane.
Liquid Chromatographic Determination of Quinolones in Water and Human Urine Samples After Microextraction by Packed Sorbent
Authors: Rani Susheela , Kumar Ashwini , Malik Ashok Kumar , Singh Baldev
Published: February 2012

A method for the simultaneous determination of quinolones in water and urine samples by microextraction in a sorbent-packed syringe (MEPS) with LC is described. MEPS is a new miniaturized SPE technique that can be used with chromatographic instruments without any modifications. In MEPS, approximately 1 mg of the solid packing material is inserted into a syringe (100–250 μL) as a plug. Sample preparation takes place on the packed bed. The new method is promising, easy to use, economical, and rapid. The determination of quinolones in groundwater and urine was performed using MEPS as a sample preparation method with LC-UV determination. Four quinolone antibiotics—enrofloxacin, enoxacin, danofloxacin, and nalidixic acid—in groundwater and urine samples were used as analytes. The extraction recovery was found to be between 64.9 and 98.9%. The results showed high correlation coefficients (R2 > 0.992) for all of the analytes within the calibration range. The LOQ was between 0.091 and 0.315 ng/mL.
Multiplex, Construct-Specific, and Real-Time PCR-Based Analytical Methods for Bt Rice with cry1Ac Gene
Authors: Randhawa Gurinder Jit , Singh Monika
Published: February 2012

Qualitative and quantitative analytical methods based on PCR for Bacillus thuringiensis (Bt) rice hybrid, namely, MRP 5401 Bt expressing a modified version of the Bt cry1Ac gene, are reported here. Multiplex PCR assays were developed to target the cry1Ac transgene, Cauliflower mosaic virus (CaMV) 35S promoter, Agrobacterium tumefaciens nopaline synthase (nos) terminator, the neomycin phosphotransferase II (nptII) marker gene, and an endogenous α-tubulin (TubA) gene in Bt rice. The 3.178 kb region of inserted gene construct comprising the region of the CaMV 35S promoter and cry1Ac gene was amplified, and the construct integrity was confirmed by the nested PCR. The LOD for cry1Ac gene-specific simplex PCR was 0.01%, as established using Bt rice DNA dilutions with 100, 10, 1.0, 0.1, 0.05, 0.01, and 0.001% genetically modified trait. A real-time PCR assay was also developed to quantify the cry1Ac gene. The method performance of the reported real-time PCR assay was in line with the acceptance criteria of Codex Alimentarius Commission ALINORM 10/33/23, with LOD and LOQ values of 0.05%. The reliable PCR assays prior to commercial release of Bt rice would facilitate efficient regulatory compliance for identification of genetic trait, labeling requirements, and effective risk assessment and management. They could also address consumers' concerns and legal disputes that may arise.
Enumeration Methods and Production of Enterotoxins in Food-Derived Staphylococcus aureus
Authors: Zhang Chi , Zhang Deqin , Yang Jun , Zhou Jungui , Hu Qilong , Ling Rui , Dong Mingsheng
Published: February 2012

Staphylococcal food poisoning is one of the most common foodborne diseases worldwide; it results from the ingestion of staphylococcal enterotoxins (SEs) in food, mainly Staphylococcus aureus. This study investigated the statistical relationships among morphological enumerations of food-derived S. aureus and production of SEs using different methodologies. Food samples naturally contaminated with coagulase-positive S. aureus were submitted for enumeration on Baird-Parker (BP) agar, Rabbit Plasma Fibrinogen agar (RPFA), and PetrifilmTM Staph Express count system (STX), and the morphologically typical colonies were isolated for VIDAS and real-time (RT) PCR tests. RPFA and STX displayed better performance for the enumeration of SE-positive S. aureus when compared with BP, including higher frequencies of SE-positive isolates and better correlation indices between typical and SE-positive counts. Among all the evaluated culture media, no significant difference (P > 0.05) was shown on the frequencies of typical colonies that carried 11 individual se genes. In addition, results for SE identification between VIDAS and RT-PCR assay were unparalleled. These data will be valuable for the selection of methods for inspection of food-derived S. aureus.
Refinement of AOAC Official MethodSM 2005.06 Liquid Chromatography-Fluorescence Detection Method to Improve Performance Characteristics for the Determination of Paralytic Shellfish Toxins in King and Queen Scallops
Authors: Turner Andrew D , Hatfield Robert G
Published: February 2012

AOAC Official MethodSM 2005.06 LC-fluorescence detection (FLD) method is an official alternative to the mouse bioassay for the determination of paralytic shellfish poisoning (PSP) toxins in bivalve shellfish. To validate the method for species of relevance to the UK official control monitoring program, the method performance characteristics were tested for whole king and queen scallops. Validation showed that, while the performance was generally acceptable for the quantitation of non-N-hydroxylated toxins, poor toxin recovery and sensitivity was evident for the analysis of N-hydroxylated toxins following periodate oxidation. These effects occurred in a range of scallop samples with variable temporal and spatial sources. The effects were also noted in other laboratories following a small interlaboratory study. As a result, the method was refined to improve the recovery and sensitivity of analysis following the periodate oxidation step in the PSP method for scallops. Performance improved through alterations to the preparation of the periodate oxidant, use of higher volumes for C18 cleanup, and injection volumes in combination with the use of a king scallop matrix modifier for oxidation of N-hydroxylated toxin calibration standards. A single-laboratory validation of the refined method showed that the selectivity, linearity, sensitivity, recovery, and precision were acceptable and similar to values reported previously for AOAC Official Method 2005.06 in other bivalve species. Results showed the method to be rugged for all parameters investigated, including small changes to the composition of the new periodate reagent utilized in the refined method. The refined scallops LC method was subsequently compared with the European reference method. PSP-positive scallops showed an excellent agreement between the methods for queen and Atlantic scallops, with a small level of positive bias in the LC results for whole king scallops. These differences were related solely to the use of the highest toxicity equivalence factors for toxin epimeric pairs, with gonyautoxin (GTX)1,4 and GTX2,3 in particular present at high concentrations in the king scallops. Overall, the refined LC-FLD method improved the performance characteristics of AOAC Official Method 2005.06 for the determination of PSP toxins in whole king and queen scallops, and showed a good overall agreement between the official methodologies. It is, therefore, recommended as a more appropriate option for the routine monitoring of PSP toxins in these species.
Nationwide assessment of nitrosamine occurrence and trends
Authors: Russell Caroline G. , Blute Nicole K. , Via Steve , Wu Xueying , Chowdhury Zaid
Published: February 2012

Nitrosamine data reported from the first rounds of samples collected under the second Unregulated Contaminants Monitoring Rule (UCMR2) and the Ontario Drinking Water Surveillance Program were reviewed to assess the frequency and magnitude of occurrence and the effect of disinfectant type and other treatment factors on reported nitrosamine concentrations. Initial monitoring data reveal that N‐nitrosodimethylamine (NDMA) was detected in drinking water at concentrations higher than the UCMR2 minimum reporting level (MRL) of 2 ng/L in 1 of every 10 samples. Other nitrosamines (e.g., N‐nitrosodiethylamine, N‐nitroso‐di‐n‐butylamine, N‐nitrosopyrrolidine, and N‐nitroso‐methylethylamine) were rarely detected at levels above their MRLs. NDMA was primarily detected in systems using chloramines, with more than two thirds of all chloraminated water systems detecting NDMA in at least one sample. Follow‐up survey results from 45 water systems participating in UCMR2 and 6 water systems from Ontario, Canada, generally followed expected trends based on the literature. NDMA occurrence was more frequent and concentrations were higher in water systems having long contact times with chloramines. A comparison of maximum‐residence‐time distribution system samples with entry point samples indicates that NDMA concentrations may increase in a chloraminated distribution system if precursors have not fully reacted at the entry point.
Effect of changing water quality on galvanic coupling
Authors: Boyd Glen R. , Reiber Steven H. , McFadden Matthew S. , Korshin Gregory V.
Published: February 2012

Two galvanic pipe‐loop couples (lead‐copper and lead–bronze) were exposed to controlled changes in water quality (disinfectant, pH, alkalinity, and phosphate) and monitored for changes in lead and copper release. In addition open circuit potential (OCP) profiles were measured along the junction of dissimilar metals to determine the extent of the zone affected by galvanic coupling. Grab sampling results showed changes in water quality caused transient (short‐lived) increases in lead and decreases in copper that corresponded to the galvanic action of lead on the other coupled metal. OCP measurements indicated that the galvanic effect on corrosion potential can induce a shift of up to 600 mV. The extent of the galvanically affected zone was limited, penetrating no more than a few inches from the juncture along the surface of each pipe. Additional testing confirmed strong effects of external versus internal coupling on the OCP profiles in the galvanically affected zone.
Occurrence of trace inorganic contaminants in drinking water distribution systems
Authors: Peng Ching‐Yu , Hill Andrew S. , Friedman Melinda J. , Valentine Richard L. , Larson Gregory S. , Romero Angela M.Y. , Reiber Steve H. , Korshin Gregory V.
Published: February 2012

Many trace inorganic contaminants (e.g., lead, arsenic, nickel, vanadium, uranium) can accumulate on the surface of or be occluded within corrosion scales formed in drinking water distribution systems (DWDSs). However, few data are available on the actual concentrations of these contaminants beyond system entry points. An investigation was conducted to determine the occurrence levels and patterns of 11 trace inorganic contaminants in DWDSs. Among the trace inorganic contaminants that were found in practically all studied samples of intact corrosion scales and solids mobilized during hydrant flushing, barium was the most concentrated on a mass basis, followed by, in decreasing order, lead, nickel, vanadium, arsenic, chromium, uranium, cadmium, antimony, selenium, and thallium.
Basic and Applied Cognitive Research in a Country Discovering Psychology
Authors: Cornoldi Cesare
Published: February 2012

The paper illustrates how the author started research in the field of applied cognitive psychology. The paper describes the obstacles and opportunities associated with living in a country where Psychology was underdeveloped. Copyright © 2012 John Wiley & Sons, Ltd.
Unfalsified adaptive control: Controller switching algorithms for nonmonotone cost functions
Authors: Jin H. , Safonov M.G.
Published: February 2012

Controller switching algorithms used for adaptive control are investigated. The concept of interfalsification, a generalization of the existing ϵ‐hysteresis algorithm, is defined; a new concept of self‐falsification is introduced, and the two concepts are compared. On the basis of the idea of self‐falsification, new controller switching algorithms are designed and two new convergence theorems are proved. These new results allow for removal of the assumption that the cost function associated with each controller be monotonically nondecreasing in time, thus opening the possibility of safe data‐driven adaptive control designs with fading‐memory cost functions. Theoretical analysis and simulations illustrate that the self‐falsification algorithms can also decrease insertions of destabilizing controllers and improve the transient properties. Copyright © 2012 John Wiley & Sons, Ltd.
An adaptive control strategy for wound rotor synchronous machines
Authors: El Magri A. , Giri F. , El Fadili A. , Chaoui F.Z.
Published: February 2012

This paper addresses the problem of controlling wound rotor synchronous motors in association with their power conversion components, i.e. AC/DC rectifiers and DC/AC inverters. Considering the whole association, ‘converter‐motor’ makes it possible to account, in addition to motor speed regulation, four other important control objectives such as power factor correction with respect to the supply net and DC link voltage regulation. To achieve these objectives, an adaptive control strategy is developed, based on a nonlinear model of the whole ‘converter‐motor’ association. Adaptation is motivated by the uncertain nature of some motor characteristics, especially the mechanical parameters. The closed‐loop system stability and performances are formally described using averaging theory. Copyright © 2012 John Wiley & Sons, Ltd.
Stability and stabilization in switched discrete‐time systems
Authors: Zhang Hui , Shi Yang , Mehr Aryan Saadat
Published: February 2012

In this paper, we investigate the stability and stabilization problem for discrete‐time switched systems. We consider a probabilistic case where the system is switched among different subsystems, and the probability of each subsystem being active is defined as its occurrence probability. The relationship between the developed model of the switched system and the Markovian jump system is analyzed. For a switched system with a known subsystem occurrence probabilities, we give a stochastic stability criterion in terms of a linear matrix inequality. Then, we extend the results to a more practical case where the subsystem occurrence probabilities of switching are known to be constant, but their specific values are only known with some uncertainty. A new iterative approach is employed to choose the switching law between the subsystems. For unstable switched systems, mode‐dependent state feedback and static output feedback controllers are developed to achieve the stabilization objective. Finally, several simulation examples are presented to show the efficacy of the proposed criteria and methods. Copyright © 2012 John Wiley & Sons, Ltd.
Biofunctional Silk/Neuron Interfaces
Authors: Benfenati Valentina , Stahl Katja , Gomis‐Perez Carolina , Toffanin Stefano , Sagnella Anna , Torp Reidun , Kaplan David L. , Ruani Giampiero , Omenetto Fiorenzo G. , Zamboni Roberto , Muccini Michele
Published: February 2012

Silk fibroin (SF) is a biocompatible and slowly biodegradable material with excellent mechanical properties and huge potential for use as biofunctional interface in electronic devices that aim to stimulate and control neural network activity and peripheral nerve repair. It is shown that SF films act as material interfaces that support the adherence and neurite outgrowth of dorsal root ganglion (DRG) neurons and preserve neuronal functions. Silk films preserve the capability of neuronal cells to fire and DRG neurons on silk films retain the intracellular free Ca2+ concentration ([Ca2+]i) response to capsaicin, a typical noxious stimulus for this neuronal culture model. It is also demonstrated that nerve growth factor (NGF)‐functionalized silk films promote neurite outgrowth and modulate functional properties of DRG neurons. The results show that silk preserves DRG neuronal physiology and is a promising biomaterial platform for the future development of devices with goals including functional recovery of injured neurons, neurite functional outgrowth in vitro, or functional electrostimulation in vivo.
Enhanced Energy Storage in Nanocomposite Capacitors through Aligned PZT Nanowires by Uniaxial Strain Assembly
Authors: Tang Haixiong , Lin Yirong , Sodano Henry A.
Published: February 2012

The design of nanocomposite capacitors poses certain challenges due to the reduced dielectric strength resulting from the integration of typically high dielectric fillers into the polymer. In prior efforts it was demonstrated that increasing of the filler could lead to energy‐storage densities up to 19.3% above the neat polymer. To further enhance the energy density, a novel strategy is developed to align nanowires in a thermoplastic matrix by uniaxial stretching assembly. It is demonstrated that the energy‐storage capability of the nanocomposite can be enhanced through the alignment of lead zirconate titanate (PZT) nanowires (NWs) in the direction of the applied electric field compared to randomly oriented samples. The maximum energy density of the nanocomposites is as high as 1.28 J cm−3 at a volume fraction of 40% PZT NWs (aspect ratio around 14) with axis of alignment in the direction of the electric field. The findings of this research could lead to broader interest due to development of the piezoceramic nanocomposites with enhanced dielectric properties for use in next‐generation energy‐storage and conversion devices.
Properties of strong off‐shore Borneo vortices: a composite analysis of flow pattern and composition as captured by ERA‐Interim
Authors: Braesicke Peter , See Hai Ooi , Abu Samah Azizan
Published: February 2012

The Borneo vortex (BV) is an important source of extreme weather for Malaysia. We describe climatological properties of strong off‐shore BVs using a potential vorticity (PV) threshold analysis of ERA‐Interim data. The composite BV at the location of most likely high PV occurrence has a warm core with enhanced specific humidity between 800 and 200 hPa, and a dry layer above. Two effects contribute to this structure: Air is vertically transported upwards in the BV whilst precipitating and the large scale flow in which the BV is embedded advect dry, ozone‐rich air from the equatorial tropical tropopause layer towards higher latitudes. Copyright © 2012 Royal Meteorological Society
Blocking roads to increase the evacuation efficiency
Authors: Huibregtse Olga , Hegyi Andreas , Hoogendoorn Serge
Published: February 2012

In order to evacuate as many people as possible in case of an approaching disaster, evacuation plans have to be made in advance. These plans usually consist of optimized traffic flows. Theoretically, these flows lead to an efficient evacuation, but in practice evacuees will most probably not behave like these flows without any intervention. This difference is partly caused by evacuees using roads that are unused in the optimized traffic flows case. In this paper, a new approach is investigated that can be applied to approach these flows during an evacuation: blocking the roads (i.e., making the roads inaccessible) that have a flow equal to zero in the optimal traffic flows. This approach is expected to be effective because the people are forced to behave in the direction of the optimized traffic flows. In a case study, this approach turns out to be effective. For two different cases, the efficiency of the evacuation (a function of the arrivals) improves with respectively 10.0% and 13.4% when the zero‐flow links are blocked compared with an evacuation without any intervention. Copyright © 2012 John Wiley & Sons, Ltd.
A probability model and sampling algorithm for the inter‐day stochastic traffic assignment problem
Authors: Wei Chong , Asakura Yasuo , Iryo Takamasa
Published: February 2012

In this study, we consider that inter‐day traffic flow fluctuations in a network are caused by stochastic travel behavior. We treat route traffic flows at each time interval as random variables. Therefore, the solution of the stochastic assignment problem should be the conditional joint probability distribution of the route flows given that the network is in stochastic user equilibrium. We formulate the conditional joint distribution and develop a Gibbs sampler to draw samples from the conditional joint distribution. The characteristics of the route flows at each time interval during the time horizon can be estimated on the basis of the simulated samples. Copyright © 2012 John Wiley & Sons, Ltd.
Trip generation modeling using data collected in single and repeated cross‐sectional surveys
Authors: Mwakalonge Judith L. , Badoe Daniel A.
Published: February 2012

The majority of US metropolitan regions still use the four‐step urban transportation modeling system to develop their travel forecasts. Trip generation, the first step of this system, has as objective of predicting the expected total travel demand in a region. The commonly used methods in planning practice for predicting this expected total travel demand typically use only the most recent cross‐sectional data available from a study region for model development, which ties the resulting travel‐forecast model to the economic environment prevailing at the time of data collection. Applying such models to generate forecasts of travel in economic environments significantly different from those embodied in the estimated model parameters could result in greater errors than would otherwise be the case.

To address the aforementioned problem, this paper proposes the development of trip generation models estimated on multiple independent cross‐sectional datasets collected in the same urban region but at different times representing different economic environments. Data used in the research were collected in cross‐sectional household travel behavior surveys undertaken in the Greater Toronto Area, Canada in 1986, 1996, 2001, and 2006.

The results lead to the conclusion that well‐specified models, estimated on pooled multiple cross‐sectional datasets, yield travel predictions in the base and horizon years, respectively, that have smaller error compared with corresponding travel predictions generated with single cross‐sectional models. Copyright © 2012 John Wiley & Sons, Ltd.
Identification of the First Known Inhibitors of O‐Acetylpeptidoglycan Esterase: A Potential New Antibacterial Target
Authors: Pfeffer John M. , Clarke Anthony J.
Published: February 2012

The O‐acetylation of peptidoglycan (PG) is now known to occur in 53 species, including numerous human pathogens such as, Staphylococcus aureus, Bacillus anthracis, species of Enterococcus, Campylobacter jejuni, Helicobacter pylori, Neisseria gonorrhoeae and N. meningitidis. This modification, which occurs at the C‐6 hydroxyl of N‐acetylmuramoyl residues within PG, serves to regulate autolytic activity during PG metabolism and contributes to pathogenesis and persistence within a host. O‐Acetylpeptidoglycan esterase (Ape) was recently discovered as an enzyme responsible for the removal of O‐acetyl groups from PG, thus permitting the continued maintenance and metabolism of the sacculus. Recombinant Ape1 from N. gonorrhoeae was purified to apparent homogeneity and optimal storage conditions for the enzyme were determined. Using 4‐methylumbelliferyl acetate as substrate, a fluorogenic assay amenable for the high‐throughput screening for potential inhibitors was developed and Ape1 was screened against a subset of compounds of the Canadian Compound Collection. The overall Z′ score for the screen was 0.62, indicative of a well‐suited assay with a sufficient signal window, and the threshold was set at 65 %. After eliminating a number of false‐positives, seven compounds were identified as true inhibitors of Ape1, the first to be identified for this class of enzyme. Dose–response curves were generated leading to the identification of five of these compounds with IC50 values ranging between 0.3 and 23 μM. Of these, purpurin was selected for further analysis and it was found to inhibit the growth of both Gram‐positive and Gram‐negative bacteria that produce both O‐acetylated PG and Ape.
Structure–Activity Relationships of Organofluorine Inhibitors of β‐Amyloid Self‐Assembly
Authors: Török Béla , Sood Abha , Bag Seema , Kulkarni Aditya , Borkin Dmitry , Lawler Elizabeth , Dasgupta Sujaya , Landge Shainaz , Abid Mohammed , Zhou Weihong , Foster Michelle , LeVine Harry , Török Marianna
Published: February 2012

A broad group of structurally diverse small organofluorine compounds were synthesized and evaluated as inhibitors of β‐amyloid (Aβ) self‐assembly. The main goal was to generate a diverse library of compounds with the same functional group and to observe general structural features that characterize inhibitors of Aβ oligomer and fibril formation, ultimately identifying structures for further focused inhibitor design. The common structural motifs in these compounds are CF3‐C‐OH and CF3‐C‐NH groups that were proposed to be binding units in our previous studies. A broad range of potential small‐molecule inhibitors were synthesized by combining various carbocyclic and heteroaromatic rings with an array of substituents, generating a total of 106 molecules. The compounds were tested by standard methods such as thioflavin‐T fluorescence spectroscopy for monitoring fibril formation, biotinyl Aβ1–42 single‐site streptavidin‐based assays for observing oligomer formation, and atomic force microscopy for morphological studies. These assays revealed a number of structures that show significant inhibition against either Aβ fibril or oligomer formation. A detailed analysis of the structure–activity relationship of anti‐fibril and ‐oligomer properties is provided. These data present further experimental evidence for the distinct nature of fibril versus oligomer formation and indicate that the interaction of the Aβ peptide with chiral small molecules is not stereospecific in nature.
Arc mRNA docks precisely at the base of individual dendritic spines indicating the existence of a specialized microdomain for synapse‐specific mRNA translation
Authors: Dynes Joseph L. , Steward Oswald
Published: February 2012

Arc (aka Arg 3.1) is induced by neural activity and learning experience. Arc mRNA is rapidly exported into dendrites where it localizes near activated synapses. By imaging green fluorescent protein (GFP)‐tagged mRNA in living neurons in culture, we show that fusion transcripts containing the Arc 3′UTR (untranslated region) localize with remarkable precision in a microdomain at the base of dendritic spines. Transcripts with the Arc 3′UTR that encode a reporter protein rather than Arc show precise localization. Localization persists in the presence of translation inhibitors, indicating that localization does not require ongoing translation. Similarly, polyribosome complexes remained stably positioned at spine bases in brain tissue treated with the translation inhibitor (puromycin) that releases ribosomes from mRNA. Single particle tracking revealed that Arc mRNA particles positioned at spine bases exhibited highly constrained submicron movements. These observations imply the existence of a microdomain at the spine base where Arc mRNA docks in association with a previously unknown mRNA‐binding structural element. J. Comp. Neurol., 520:3105–3119, 2012. © 2012 Wiley Periodicals, Inc.
A multilevel fault model for integrated parallel fault‐tolerant systems
Authors: Fechner Bernhard
Published: February 2012

The appearance of multithreaded, multicore, and manycore systems has led to a performance leap. Such systems are denoted as integrated, when there are electrical and physical dependencies between different functional units, that is, multiple cores integrated on a single die. Typically, such systems have a common, shared interface to the outside world, bearing the potential of a single point of failure. In this work, several questions concerning fault propagation shall be tackled. First, if one component within a core fails, how likely is a faulty behavior of other components on the same or other cores? Second, what is the overall reliability of such a system? It is important to answer these questions prior to an implementation, because the total costs of a reliable product shall be as small as possible. Our approach combines different abstraction levels in one multilevel fault model. The first stage is the physical level, covering the physical effects of a fault. Validation on this level can be omitted, if the modeling is precise enough. The second stage is a component and routing model where current is represented as logic value. The last level is the behavioral modeling of components by finite state machines. Because of the different number and nature of existing parallel systems, a theoretical approach is followed. The model can cover the whole range of parallel devices from field programmable gate arrays to multicore CPUs and manycore graphics processing units. Therefore, it can help to improve the reliability of current and future parallel fault‐tolerant systems by identifying the underlying bottlenecks. The function of the model is exemplarily shown by applying it to a field programmable gate array, identifying switchboxes as the main reliability bottleneck. Copyright © 2012 John Wiley & Sons, Ltd.
Lattice‐based signcryption
Authors: Li Fagen , Bin Muhaya Fahad T. , Khan Muhammad Khurram , Takagi Tsuyoshi
Published: February 2012

Signcryption is a cryptographic primitive that performs simultaneously both the functions of digital signature and public‐key encryption, at a cost significantly lower than that required by the traditional signature‐ then‐encryption approach. In this paper, we provide a positive answer to the question of if it is possible to construct signcryption based on lattice problems. More precisely, we design an efficient signcryption scheme that can send a message of length l one time. We prove that the proposed scheme has the indistinguishability against adaptive chosen ciphertext attacks under the learning with errors assumption and strong unforgeability against adaptive chosen messages attacks under the inhomogeneous small integer solution assumption in the random oracle model. Copyright © 2012 John Wiley & Sons, Ltd.