bluuebunny/crossref_metadata_2025 huggingface dataset:
Examining the Relationship Between Medical Diagnoses and Patterns of Performance on the Modified Dynamic Gait Index
Authors: Matsuda Patricia Noritake , Taylor Catherine , Shumway-Cook Anne
Published: December 2014

Background

In the original and modified Dynamic Gait Index (mDGI), 8 tasks are used to measure mobility; however, disagreement exists regarding whether all tasks are necessary. The relationship between mDGI scores and Centers for Medicare & Medicaid Services (CMS) severity indicators in the mobility domain has not been explored.

Objective

The study objectives were to examine the relationship between medical diagnoses and mDGI scores, to determine whether administration of the mDGI can be shortened on the basis of expected diagnostic patterns of performance, and to create a model in which mDGI scores are mapped to CMS severity modifiers.

Design

This was a cross-sectional, descriptive study.

Methods

The 794 participants included 140 people without impairments (control cohort) and 239 people with stroke, 140 with vestibular dysfunction, 100 with traumatic brain injury, 91 with gait abnormality, and 84 with Parkinson disease. Scores on the mDGI (total, performance facet, and task) for the control cohort were compared with those for the 5 diagnostic groups by use of an analysis of variance. For mapping mDGI scores to 7 CMS impairment categories, an underlying Rasch scale was used to convert raw scores to an interval scale.

Results

There was a main effect of mDGI total, time, and gait pattern scores for the groups. Task-specific score patterns based on medical diagnosis were found, but the range of performance within each group was large. A framework for mapping mDGI total, performance facet, and task scores to 7 CMS impairment categories on the basis of Rasch analysis was created.

Limitations

Limitations included uneven sample sizes in the 6 groups.

Conclusions

Results supported retaining all 8 tasks for the assessment of mobility function in older people and people with neurologic conditions. Mapping mDGI scores to CMS severity indicators should assist clinicians in interpreting mobility performance, including changes in function over time.
Who Enters Teaching? Encouraging Evidence That the Status of Teaching Is Improving
Authors: Lankford Hamilton , Loeb Susanna , McEachin Andrew , Miller Luke C. , Wyckoff James
Published: December 2014

The relatively low status of teaching as a profession is often given as a factor contributing to the difficulty of recruiting teachers, the middling performance of American students on international assessments, and the well-documented decline in the relative academic ability of teachers through the 1990s. Since the turn of the 21st century, however, a number of federal, state, and local teacher accountability policies have been implemented toward improving teacher quality over the objections of some who argue the policies will decrease quality. In this article, we analyze 25 years of data on the academic ability of teachers in New York State and document that since 1999 the academic ability of both individuals certified and those entering teaching has steadily increased. These gains are widespread and have resulted in a substantial narrowing of the differences in teacher academic ability between high- and low-poverty schools and between White and minority teachers. We interpret these gains as evidence that the status of teaching is improving.
Methods for Quantitative Risk Analysis for Travel Demand Model Forecasts
Authors: Adler Thomas , Doherty Michael , Klodzinski Jack , Tillman Raymond
Published: December 2014

Travel demand forecasting models have played a critical role in transportation planning; these models support the evaluation of policies, programs, and projects that involve complex interactions between the activity system and the transportation system. Both the state of the art and the state of the practice in travel demand modeling have advanced considerably during the many decades since the original four-step model structure was conceived. However, the models are not now, and never will be, perfect representations of the systems they represent; so there are inevitably uncertainties about the forecasts that these models generate. Travel demand forecasts are important in many applications, for example, in determining whether a given alternative is financially or technically feasible or meets some benefit threshold. In these applications, uncertainties in model forecasts may translate directly into risks of not accomplishing the objectives related to the decision to implement or not implement the alternative. For projects that involve outside financing, this threshold varies greatly between equity and lender participants because of the differing risk–reward profiles. Several previous papers described the uncertainties associated with travel demand forecasting and recommended ways of improving the state of the practice. Among those recommendations is the application of formal quantitative risk analysis methods. This paper summarizes the existing literature and describes the application of one relatively straightforward but robust approach for conducting quantitative risk analysis with travel demand forecasting models. The formal risk analysis approach described here can assist by providing a more complete evaluation of a project's likelihood of achieving specified objectives. The approach can support the development of traffic and revenue forecasts beyond a most likely scenario to consider any level of risk assumed by a project sponsor, debt provider, or rating agency.
Modeling Demand Elasticity and Route Overlapping in Stochastic User Equilibrium through Paired Combinatorial Logit Model
Authors: Ryu Seungkyu , Chen Anthony , Xu Xiangdong , Choi Keechoo
Published: December 2014

In this paper an equivalent mathematical programming formulation is provided for modeling demand elasticity and route overlapping in the stochastic user equilibrium (SUE) problem. The elastic demand establishes the equilibrium between supply function and demand function on the basis of microeconomics. Because the elasticity of demand is an important factor in predicting the future demand pattern and avoiding the potential biased assessment in transportation planning, the elasticity of travel demand must be modeled endogenously. The route overlapping problem is handled by the paired combinatorial logit (PCL) model while retaining the analytical tractability of the logit choice probability function. The PCL SUE model with elastic demand (PCL-SUE-ED) explicitly models the elasticity of travel demand and the effect of route overlapping on travel choice and route choice simultaneously. A path-based partial linearization algorithm is also developed for solving the PCL-SUE-ED model. In addition, a self-regulated averaging line search strategy is incorporated into the algorithm to minimize the computational efforts required to determine a suitable step size that guarantees convergence. Numerical results are provided to examine the features of the PCL-SUE-ED model as well as the efficiency of the path-based partial linearization algorithm.
Incorporation of Escorting Children to School in Modeling Individual Daily Activity Patterns of Household Members
Authors: Gupta Surabhi , Vovsha Peter S. , Livshits Vladimir , Maneva Petya , Jeon Kyunghwi
Published: December 2014

Escorting children to school is a common travel arrangement in a household with schoolchildren. This escorting task affects travel patterns of the adult household members as accommodations are made for dropping children off at school or picking them up or doing both. Approaches to modeling joint travel arrangements between adults and children with respect to escorting have been previously suggested. However, examples of implementing such models in the framework of an operational activity-based model (ABM) are limited. This paper focuses on the explicit modeling of the escorting of children to school by adults and takes into account the possible bundling of escorting tasks in households with multiple children. The developed model is part of the regional ABM system currently being developed for the Maricopa Association of Governments in Arizona. Such a model allows for constraining the travel schedules of workers who tend to escort children on their way to and from work. Escorting has important policy implications because workers who escort children to and from school are very restricted in changing their departure times to and from work and in switching to transit; these restrictions are not evident otherwise. A choice model was formulated and estimated for each household by outbound (to school) and inbound (from school) escorting needs that were dependent on the number of schoolchildren, options of bundling children for escorting on one tour, and number of available chauffeurs in the household.
Effects of Uncertainty in Speed–Flow Curve Parameters on a Large-Scale Model
Authors: Manzo Stefano , Nielsen Otto Anker , Prato Carlo Giacomo
Published: December 2014

Uncertainty is inherent in transport models and prevents the use of a deterministic approach when traffic is modeled. Quantifying uncertainty thus becomes an indispensable step to produce a more informative and reliable output of transport models. In traffic assignment models, volume-delay functions express travel time as a function of traffic flows and the theoretical capacity of the modeled facility. The U.S. Bureau of Public Roads (BPR) formula is one of the most extensively applied volume delay functions in practice. This study investigated uncertainty in the BPR parameters. Initially, BPR parameters were estimated by analyzing observed traffic data related to the Danish highway network. Then, BPR parameter distributions were generated by using the resampling bootstrap technique. Finally, the generated parameter vectors were used to implement sensitivity tests on the four-stage Danish national transport model. The results clearly highlight the importance to modeling purposes of taking into account BPR formula parameter uncertainty, expressed as a distribution of values rather than assumed point values. Indeed, the model output demonstrates a noticeable sensitivity to parameter uncertainty. This aspect is evident particularly for stretches of the network with a high number of competing routes. Model sensitivity was also tested for BPR parameter uncertainty combined with link capacity uncertainty. The resultant increase in model sensitivity demonstrates even further the importance of implementing uncertainty analysis as part of a robust transport modeling process.
Integrated Transport Planning Framework Involving Combined Utility Regret Approach
Authors: Wang Yang , Monzon Andres , Di Ciommo Floridea , Kaplan Sigal
Published: December 2014

Sustainable transport planning requires an integrated approach involving strategic planning, impact analysis, and multicriteria evaluation. This study aimed at relaxing the utility-based decision-making assumption by newly embedding anticipated-regret and combined utility regret decision mechanisms in a framework for integrated transport planning. The framework consisted of a two-round Delphi survey, integrated land use and transport model for Madrid, and multicriteria analysis. Results show that (a) the regret-based ranking has a similar mean but larger variance than the utility-based ranking does, (b) the least-regret scenario forms a compromise between the desired and the expected scenarios, (c) the least-regret scenario can lead to higher user benefits in the short term and lower user benefits in the long term, (d) the utility-based, the regret-based, and the combined utility- and regret-based multicriteria analyses result in different rankings of policy packages, and (e) the combined utility regret ranking is more informative compared with the utility-based or the regret-based ranking.
Joint Modeling of Trip Mode and Departure Time Choices Using Revealed and Stated Preference Data
Authors: Paleti Rajesh , Vovsha Peter S. , Givon Danny , Birotker Yehoshua
Published: December 2014

Travel choices of mode and trip departure time are closely intertwined because the level-of-service (LOS) attributes for each mode vary substantially across time-of-day (TOD) periods. Most congestion mitigation strategies are intended to alter mode as well as trip departure time choices of travelers. Thus, these two travel dimensions have to be analyzed and modeled jointly. However, it is usually difficult to uncover the trade-offs between different LOS attributes with revealed preference (RP) data, particularly in the context of TOD choice modeling. The objective of the current study was to develop an integrated model of mode and trip departure TOD choices by using both RP and stated preference (SP) data from the large-scale household travel survey undertaken in Jerusalem in 2010. The SP component was designed specifically to compensate for the RP limitations and provide mode and departure time switches as the result of policies such as pricing. The developed model captures the impact of a rich set of socioeconomic factors and is also sensitive to a wide range of policy variables such as toll and parking cost. The developed model also accounts for several important econometric aspects and associated problems that arise during the joint RP-SP analysis while maintaining a model structure that is manageable in model estimation and subsequent application.
Application of Travel Activity Scheduler for Household Agents in a Chinese City
Authors: Deng Yiling , Miller Eric J. , Vaughan James A.
Published: December 2014

The travel activity scheduler for household agents (TASHA) is an operational rule-based model that generates activity schedules and travel patterns for a 24-h typical weekday for all persons in a household. This paper reports the application and validation of the model in Changzhou, China. The data cleaning procedure of the traditional household survey and the verification results of the rules used in the TASHA are presented. After the results of the activity generation and scheduling models were analyzed, an iterative approach was applied to inflating the observed activity rates to calibrate the results. The model was shown to replicate observed activity frequency, tour frequency, and trip start time fairly accurately at the regional level. The activity duration of the model was underestimated by 13.1%, but this underestimate did not add much bias to the shape of the duration distribution by start time. The final model results show that the TASHA is an attractive alternative to conventional modeling systems currently used in Changzhou.
Characterizing Household Vehicle Fleet Composition and Count by Type in Integrated Modeling Framework
Authors: Garikapati Venu M. , Sidharthan Raghuprasad , Pendyala Ram M. , Bhat Chandra R.
Published: December 2014

There has been considerable interest, and consequent progress, in the modeling of household vehicle fleet composition and utilization in the travel behavior research domain. The multiple discrete-continuous extreme value (MDCEV) model is a modeling approach that has been applied frequently to characterize this choice behavior. One key drawback of the MDCEV modeling methodology is that it does not provide an estimate of the count of vehicles in each vehicle type alternative represented in the MDCEV model. Moreover, the classic limitations of the multinomial logit model, such as violations of the independence of irrelevant alternatives property in the presence of correlated alternatives and the inability to account for random taste variations, apply to the MDCEV model as well. A new methodological approach, developed to overcome these limitations, is applied in this paper to model vehicle fleet composition and count in each body type. The modeling methodology involves tying together a multiple discrete-continuous probit (MDCP) model and a multivariate count (MC) model capable of estimating vehicle counts in vehicle type categories considered by the MDCP model. The joint MDCP-MC model system was estimated by using a Greater Phoenix, Arizona, travel survey data set. The joint model system was found to offer behaviorally intuitive results and to provide superior goodness of fit in comparison with an independent model system that ignores the jointness between the MDCP component and the MC component.
Extension of Activity-Based Modeling Approach to Incorporate Supply Side of Activities
Authors: Paul Binny M. , Vovsha Peter S. , Hicks James E. , Livshits Vladimir , Pendyala Ram M.
Published: December 2014

Most of the recent advances in activity-based models (ABMs) have been on the demand side, that is, description of the individual needs for certain types of activities and travel as a function of person, household, and accessibility variables. The supply side of activities that describes characteristics of the locations where a certain activity can be undertaken remains largely unexplored. Two examples of specific activity generators for which the supply side of activity is essential for modeling are major universities and special events. Travel behavior and activity patterns of university students are different from that of the general population, and therefore modeling them with the necessary level of detail enhances the ABM forecasting ability. The same is true about special events such as sporting events. Special events participants can form a substantial part of the overall travel demand in the subarea on the event day, and therefore it is important to model them properly. Although previous studies have acknowledged the importance of modeling university students and special events participants, the challenge remains to integrate them in an ABM framework. This paper describes new practical methods for addressing the supply side of activities (using university students and special events as examples) in the framework of an operational ABM developed for Phoenix and Tucson, Arizona. The paper provides details on the data and methods used to develop university and special events submodels. The methodology and technical approach used to incorporate these models in the ABM framework are presented.
Using Survey Calibration and Statistical Matching to Reweight and Distribute Activity Schedules
Authors: Müller Kirill , Axhausen Kay W.
Published: December 2014

The processes used to generate a 106-member agent population for a longrange study of 2030 travel in Switzerland are presented in this paper. This study was part of an effort to assess the effects of electric vehicles on the energy production and stability of the electric supply network. The process used well-established statistical methods—survey calibration and statistical matching. Both methods are described, and consistency with known approaches in transportation planning is shown. The paper introduces a new approach that allows exogenous specification of shares of activity types while maintaining the representativeness of the population: survey calibration is applied to satisfy these constraints, and statistical matching allows the joining of data sets with common variables. The discussion of the results for Switzerland focuses on the quality metrics available and highlights the links between the activity schedules and total shares of the activity types. Furthermore, the error introduced by the calibration and matching stages was analyzed and quantified, with special emphasis placed on uncontrolled sociodemographic and travel variables. The specified activity shares could be replicated almost perfectly; the resultant mean error in the uncontrolled variables was within the range of a few percentage points. Therefore, this approach is a viable alternative to a complicated estimation of an activity schedule model that would be necessary otherwise. Finally, two practical issues—data sets describing different populations and biased surveys—and their effect on the outcome were tested by suitably adjusting the input data.
Synthetic Population Generation at Disaggregated Spatial Scales for Land Use and Transportation Microsimulation
Authors: Zhu Yi , Ferreira Joseph
Published: December 2014

The execution of agent-based microsimulation requires an initial set of agents with detailed socioeconomic and demographic attributes to support subsequent behavioral and market models. Data limitations and privacy reasons often restrict the scope and detail with which a synthetic population can be generated by the traditional population synthesis approach. For the accommodation of the growing requirement of microsimulation on spatial resolution and variety, considering new data sources that overcome the data limitations and support population synthesis at more disaggregated levels is necessary. This paper presents a two-stage population synthesis approach not only to improve the accuracy of population generation with imperfect microdata and marginal data, but also to use additional data sets when the spatial details of the synthetic population are interpolated. A general iterative proportional fitting (IPF) method is used in the first stage to estimate the joint distribution of household and individual characteristics under multiple levels of constraints. Additional building information is collected from multiple sources and used to estimate spatial patterns of housing and household characteristics that are then preserved through a second IPF procedure. Preliminary tests of the proposed two-stage IPF-based approach with Singapore data show that the method yields better fitted population realizations at more fine-grained levels than do traditional one-step population synthesis methods.
Model Complexities and Requirements for Multimodal Transport Network Design
Authors: van Eck Gijsbert , Brands Ties , Wismans Luc J. J. , Pel Adam J. , van Nes Rob
Published: December 2014

In the aim for a more sustainable transport system, governments try to stimulate multimodal trip making by facilitating smooth transfers between modes. The assessment of related multimodal policy measures requires transport models that are capable of handling the complex nature of multimodality. This complexity sets requirements for adequate modeling of multimodal travel behavior and can be categorized into three classes that are related to the range and combinatorial complexity of the available alternatives, the mathematical complexity of modeling the choice between them, and the complex effect of demand–supply interactions. Classical modeling approaches typically fail to meet these requirements and state-of-the-practice approaches only partly fulfill them. Therefore, the underlying hypothesis of this study was that the application of such models in network design implied an ill-advised decision-making process. Thus, these modeling approaches, as well as the promising state-of-the-research supernetwork approach, were conceptually compared with each other. Requirements for multimodality were constructed, and all three models were tested on the way in which these requirements can be met. The findings of this conceptual comparison were supported by realistic examples in the real-world transport network of the Amsterdam Metropolitan Area in the Netherlands. The theoretical shortcomings of the classical and state-of-the-practice approach were shown to indeed result in implausible predictions of multimodal travel behavior. The flexibility of the supernetwork approach, however, was very capable of describing the expected effect of supply changes on travel behavior in most situations. This study illustrates the urgency for applying sound multimodal modeling approaches in network design studies.
Impact of body habitus on fluoroscopic radiation emission during minimally invasive spine surgery
Authors: Kukreja Sunil , Haydel Justin , Nanda Anil , Sin Anthony H.
Published: December 2014

OBJECT

Minimally invasive spine surgeries (MISSs) have gained immense popularity in the last few years. Concern about the radiation exposure has also been raised. The purpose of this study was to demonstrate the impact of body habitus on the radiation emission during various MISS procedures. The authors also aim to evaluate the effect the surgeon's experience has on the amount of radiation exposure during MISS especially with regard to patient size.

METHODS

The authors conducted a retrospective analysis of 332 patients who underwent 387 MISS procedures performed at their institution from January 2010 to August 2013 by a single surgeon. The dose of radiation emission available from the fluoroscopic equipment was recorded from the electronic database. The authors analyzed mainly 3 procedure groups: microdiscectomy/decompression (MiDD, n = 211) and transforaminal lumbar interbody fusion (TLIF) either with unilateral instrumentation (UnTLIF, n = 106) or bilateral instrumentation (BiTLIF, n = 70). The patients in each procedure group were divided into 6 categories based on the WHO criteria for obesity: underweight (body mass index [BMI] < 18.50), normal (18.50–24.99), overweight (25.00–29.99), Class 1 obese (30.00–34.99), Class 2 obese (35.00– 39.99), and Class 3 obese (> 40.00).

RESULTS

Patients who underwent BiTLIF had the highest median radiation exposure (113 mGy, SD 9.44), whereas microdiscectomy required minimal exposure (12.62 mGy, SD 2.75 mGy). There was a significant correlation between radiation emission and BMI of the patients during all MISS procedures (p < 0.05). The median radiation exposure was substantially greater with larger patients (p ≤ 0.001). In the analyses within the procedure groups, radiation exposure was found to be significantly high in patients who were severely obese (Class 2 and Class 3 obesity). The radiation emission was lower during the surgeries performed in 2013 than during those performed in 2010 especially in obese patients; however, this observation was not statistically significant.

CONCLUSIONS

Body habitus of the patients has a substantial impact on radiation emission during MISS. Severe obesity (BMI ≥ 35) is associated with a significantly greater risk of radiation exposure compared with other weight categories. Surgical experience seems to be associated with lower radiation emission especially in cases in which patients have a higher BMI; however, further studies should be performed to examine this effect.
Hemorrhagic infarction following open fenestration of a large intracranial arachnoid cyst in a pediatric patient
Authors: Auschwitz Tyler , DeCuypere Michael , Khan Nickalus , Einhaus Stephanie
Published: December 2014

Intracranial arachnoid cysts are a rare condition thought to be congenital in nature. Treatment of intracranial arachnoid cysts remains controversial based on their variable presentation. Treatment options include CSF shunting, endoscopic fenestration, or craniotomy and open fenestration for larger cysts. The complications of these procedures can include hydrocephalus, subdural hematomas, hygromas, and—more rarely—intraparenchymal hemorrhage. The authors found very few reports of hemorrhagic infarction as a complication of arachnoid cyst fenestration in the literature. The authors report a case of an 18-year-old female patient who suffered an ipsilateral hemorrhagic infarction after craniotomy for open fenestration of an arachnoid cyst.
Effects of Canola Oil Biodiesel Fuel Blends on Combustion, Performance, and Emissions Reduction in a Common Rail Diesel Engine
Authors: Yoon Sam , Kim Min , Kim Han , Choi Nag
Published: December 2014

In this study, we investigated the effects of canola oil biodiesel (BD) to improve combustion and exhaust emissions in a common rail direct injection (DI) diesel engine using BD fuel blended with diesel. Experiments were conducted with BD blend amounts of 10%, 20%, and 30% on a volume basis under various engine speeds. As the BD blend ratio increased, the combustion pressure and indicated mean effective pressure (IMEP) decreased slightly at the low engine speed of 1500 rpm, while they increased at the middle engine speed of 2500 rpm. The brake specific fuel consumption (BSFC) increased at all engine speeds while the carbon monoxide (CO) and particulate matter (PM) emissions were considerably reduced. On the other hand, the nitrogen oxide (NOx) emissions only increased slightly. When increasing the BD blend ratio at an engine speed of 2000 rpm with exhaust gas recirculation (EGR) rates of 0%, 10%, 20%, and 30%, the combustion pressure and IMEP tended to decrease. The CO and PM emissions decreased in proportion to the BD blend ratio. Also, the NOx emissions decreased considerably as the EGR rate increased whereas the BD blend ratio only slightly influenced the NOx emissions.
The Association between Access to Public Transportation and Self-Reported Active Commuting
Authors: Djurhuus Sune , Hansen Henning , Aadahl Mette , Glümer Charlotte
Published: December 2014

Active commuting provides routine-based regular physical activity which can reduce the risk of chronic diseases. Using public transportation involves some walking or cycling to a transit stop, transfers and a walk to the end location and users of public transportation have been found to accumulate more moderate physical activity than non-users. Understanding how public transportation characteristics are associated with active transportation is thus important from a public health perspective. This study examines the associations between objective measures of access to public transportation and self-reported active commuting. Self-reported time spent either walking or cycling commuting each day and the distance to workplace were obtained for adults aged 16 to 65 in the Danish National Health Survey 2010 (n = 28,928). Access to public transportation measures were computed by combining GIS-based road network distances from home address to public transit stops an integrating their service level. Multilevel logistic regression was used to examine the association between access to public transportation measures and active commuting. Distance to bus stop, density of bus stops, and number of transport modes were all positively associated with being an active commuter and with meeting recommendations of physical activity. No significant association was found between bus services at the nearest stop and active commuting. The results highlight the importance of including detailed measurements of access to public transit in order to identify the characteristics that facilitate the use of public transportation and active commuting.
A GIS Approach to Urban History: Rome in the 18th Century
Authors: Lelo Keti
Published: December 2014

This article explores the integration of GIS technology with urban historical studies, focusing on one case study from the 18th century, the project Historical atlas of the modern Rome. The methodology employed in this project allows for effectiveness and accuracy in historical data acquisition and integration, which enables refined analyses of socioeconomic and environmental phenomena. The approach outlined in this article allowed researchers from different disciplines—city historians, archaeologists, demographists, economists, and so on—to interpret urban phenomenologies according to different thematic keys. These interpretations were derived from archival sources that complement each other and offer diversified insights into the urban context. The techniques described in the article are based on methods of data acquisition and spatial analysis developed in a GIS environment by exploiting the effectiveness of this technology in the quantitative treatment of cartographic and documentary sources.
Polymer Coated CaAl-Layered Double Hydroxide Nanomaterials for Potential Calcium Supplement
Authors: Kim Tae-Hyun , Lee Jeong-A , Choi Soo-Jin , Oh Jae-Min
Published: December 2014

We have successfully prepared layered double hydroxide (LDH) nanomaterials containing calcium and aluminum ions in the framework (CaAl-LDH). The surface of CaAl-LDH was coated with enteric polymer, Eudragit®L 100 in order to protect nanomaterials from fast dissolution under gastric condition of pH 1.2. The X-ray diffraction patterns, Fourier transform infrared spectroscopy, scanning electron and transmission electron microscopy revealed that the pristine LDH was well prepared having hydrocalumite structure, and that the polymer effectively coated the surface of LDH without disturbing structure. From thermal analysis, it was determined that only a small amount (less than 1%) of polymer was coated on the LDH surface. Metal dissolution from LDH nanomaterials was significantly reduced upon Eudragit®L 100 coating at pH 1.2, 6.8 and 7.4, which simulates gastric, enteric and plasma conditions, respectively, and the dissolution effect was the most suppressed at pH 1.2. The LDH nanomaterials did not exhibit any significant cytotoxicity up to 1000 μg/mL and intracellular calcium concentration significantly increased in LDH-treated human intestinal cells. Pharmacokinetic study demonstrated absorption efficiency of Eudragit®L 100 coated LDH following oral administration to rats. Moreover, the LDH nanomaterials did not cause acute toxic effect in vivo. All the results suggest the great potential of CaAl-LDH nanomaterials as a calcium supplement.
Synthesis, Docking and Biological Activities of Novel Hybrids Celecoxib and Anthraquinone Analogs as Potent Cytotoxic Agents
Authors: Almutairi Maha , Hegazy Gehan , Haiba Mogedda , Ali Hamed , Khalifa Nagy , Soliman Abd
Published: December 2014

Herein, novel hybrid compounds of celecoxib and 2-aminoanthraquinone derivatives have been synthesized using condensation reactions of celecoxib with 2-aminoanthraquinone derivatives or 2-aminoanthraquinon with celecoxib derivatives. Celecoxib was reacted with different acid chlorides, 2-chloroethylisocyanate and bis (2-chloroethyl) amine hydrochloride. These intermediates were then reacted with 2-aminoanthraquinone. Also the same different acid chlorides and 2-chloroethylisocyanate were reacted with 2-aminoanthraquinone and the resulting intermediates were reacted with celecoxib to give isomers for the previous compounds. The antitumor activities against hepatic carcinoma tumor cell line (HEPG2) have been investigated in vitro, and all these compounds showed promising activities, especially compound 3c, 7, and 12. Flexible docking studies involving AutoDock 4.2 was investigated to identify the potential binding affinities and the mode of interaction of the hybrid compounds into two protein tyrosine kinases namely, SRC (Pp60v-src) and platelet-derived growth factor receptor, PDGFR (c-Kit). The compounds in this study have a preferential affinity for the c-Kit PDGFR PTK over the non-receptor tyrosine kinase SRC (Pp60v-src).
Marine Origin Collagens and Its Potential Applications
Authors: Silva Tiago , Moreira-Silva Joana , Marques Ana , Domingues Alberta , Bayon Yves , Reis Rui
Published: December 2014

Collagens are the most abundant high molecular weight proteins in both invertebrate and vertebrate organisms, including mammals, and possess mainly a structural role, existing different types according with their specific organization in distinct tissues. From this, they have been elected as one of the key biological materials in tissue regeneration approaches. Also, industry is constantly searching for new natural sources of collagen and upgraded methodologies for their production. The most common sources are from bovine and porcine origin, but other ways are making their route, such as recombinant production, but also extraction from marine organisms like fish. Different organisms have been proposed and explored for collagen extraction, allowing the sustainable production of different types of collagens, with properties depending on the kind of organism (and their natural environment) and extraction methodology. Such variety of collagen properties has been further investigated in different ways to render a wide range of applications. The present review aims to shed some light on the contribution of marine collagens for the scientific and technological development of this sector, stressing the opportunities and challenges that they are and most probably will be facing to assume a role as an alternative source for industrial exploitation.
Titanium Implant Osseointegration Problems with Alternate Solutions Using Epoxy/Carbon-Fiber-Reinforced Composite
Authors: Petersen Richard
Published: December 2014

The aim of the article is to present recent developments in material research with bisphenyl-polymer/carbon-fiber-reinforced composite that have produced highly influential results toward improving upon current titanium bone implant clinical osseointegration success. Titanium is now the standard intra-oral tooth root/bone implant material with biocompatible interface relationships that confer potential osseointegration. Titanium produces a TiO2 oxide surface layer reactively that can provide chemical bonding through various electron interactions as a possible explanation for biocompatibility. Nevertheless, titanium alloy implants produce corrosion particles and fail by mechanisms generally related to surface interaction on bone to promote an inflammation with fibrous aseptic loosening or infection that can require implant removal. Further, lowered oxygen concentrations from poor vasculature at a foreign metal surface interface promote a build-up of host-cell-related electrons as free radicals and proton acid that can encourage infection and inflammation to greatly influence implant failure. To provide improved osseointegration many different coating processes and alternate polymer matrix composite (PMC) solutions have been considered that supply new designing potential to possibly overcome problems with titanium bone implants. Now for important consideration, PMCs have decisive biofunctional fabrication possibilities while maintaining mechanical properties from addition of high-strengthening varied fiber-reinforcement and complex fillers/additives to include hydroxyapatite or antimicrobial incorporation through thermoset polymers that cure at low temperatures. Topics/issues reviewed in this manuscript include titanium corrosion, implant infection, coatings and the new epoxy/carbon-fiber implant results discussing osseointegration with biocompatibility related to nonpolar molecular attractions with secondary bonding, carbon fiber in vivo properties, electrical semiconductors, stress transfer, additives with low thermal PMC processing and new coating possibilities.
Are Vicilins Another Major Class of Legume Lectins?
Authors: Ribeiro Ana , Monteiro Sara , Carrapiço Belmira , Ferreira Ricardo
Published: December 2014

Legume lectins comprise a structurally related, Ca/Mn-dependent, widespread, abundant and well characterized lectin family when compared to the large number of lectins from other sources described in the literature. Strangely enough, no specific function has been assigned to them aside from a possible role in storage and/or defense. Using a recent and fine-tuned methodology capable of specific lectin identification, β-conglutin, Vicia faba vicilin and β-lathyrin, the vicilin storage globulins from Lupinus albus, V. faba and Lathyrus sativus, respectively, were shown to be capable of affinity binding to thoroughly washed erythrocyte membranes and of specific elution with appropriate sugars. Based on this evidence and on sparse data published in the literature, a second family of legume lectins is proposed: the 7S family of storage proteins from leguminous seeds, or family II of legume lectins. These lectins are also structurally related, widespread and well characterized. In addition, they self-aggregate in a Ca/Mg, electrostatic dependent manner and are even more abundant than the family I of legume lectins. Using the same evidence, reserve and defense roles may be attributed to family II of legume lectins.
Monitoring Active Volcanos Using Aerial Images and the Orthoview Tool
Authors: Marsella Maria , Nardinocchi Carla , Proietti Cristina , Daga Leonardo , Coltelli Mauro
Published: December 2014

In volcanic areas, where it can be difficult to perform direct surveys, digital photogrammetry techniques are rarely adopted for routine volcano monitoring. Nevertheless, they have remarkable potentialities for observing active volcanic features (e.g., fissures, lava flows) and the connected deformation processes. The ability to obtain accurate quantitative data of definite accuracy in short time spans makes digital photogrammetry a suitable method for controlling the evolution of rapidly changing large-area volcanic phenomena. The systematic acquisition of airborne photogrammetric datasets can be adopted for implementing a more effective procedure aimed at long-term volcano monitoring and hazard assessment. In addition, during the volcanic crisis, the frequent acquisition of oblique digital images from helicopter allows for quasi-real-time monitoring to support mitigation actions by civil protection. These images are commonly used to update existing maps through a photo-interpretation approach that provide data of unknown accuracy. This work presents a scientific tool (Orthoview) that implements a straightforward photogrammetric approach to generate digital orthophotos from single-view oblique images provided that at least four Ground Control Points (GCP) and current Digital Elevation Models (DEM) are available. The influence of the view geometry, of sparse and not-signalized GCP and DEM inaccuracies is analyzed for evaluating the performance of the developed tool in comparison with other remote sensing techniques. Results obtained with datasets from Etna and Stromboli volcanoes demonstrate that 2D features measured on the produced orthophotos can reach sub-meter-level accuracy.
Online Fault Detection of Permanent Magnet Demagnetization for IPMSMs by Nonsingular Fast Terminal-Sliding-Mode Observer
Authors: Zhao Kai-Hui , Chen Te-Fang , Zhang Chang-Fan , He Jing , Huang Gang
Published: December 2014

To prevent irreversible demagnetization of a permanent magnet (PM) for interior permanent magnet synchronous motors (IPMSMs) by flux-weakening control, a robust PM flux-linkage nonsingular fast terminal-sliding-mode observer (NFTSMO) is proposed to detect demagnetization faults. First, the IPMSM mathematical model of demagnetization is presented. Second, the construction of the NFTSMO to estimate PM demagnetization faults in IPMSM is described, and a proof of observer stability is given. The fault decision criteria and fault-processing method are also presented. Finally, the proposed scheme was simulated using MATLAB/Simulink and implemented on the RT-LABplatform. A number of robustness tests have been carried out. The scheme shows good performance in spite of speed fluctuations, torque ripples and the uncertainties of stator resistance.
Correlated Spatio-Temporal Data Collection in Wireless Sensor Networks Based on Low Rank Matrix Approximation and Optimized Node Sampling
Authors: Piao Xinglin , Hu Yongli , Sun Yanfeng , Yin Baocai , Gao Junbin
Published: December 2014

The emerging low rank matrix approximation (LRMA) method provides an energy efficient scheme for data collection in wireless sensor networks (WSNs) by randomly sampling a subset of sensor nodes for data sensing. However, the existing LRMA based methods generally underutilize the spatial or temporal correlation of the sensing data, resulting in uneven energy consumption and thus shortening the network lifetime. In this paper, we propose a correlated spatio-temporal data collection method for WSNs based on LRMA. In the proposed method, both the temporal consistence and the spatial correlation of the sensing data are simultaneously integrated under a new LRMA model. Moreover, the network energy consumption issue is considered in the node sampling procedure. We use Gini index to measure both the spatial distribution of the selected nodes and the evenness of the network energy status, then formulate and resolve an optimization problem to achieve optimized node sampling. The proposed method is evaluated on both the simulated and real wireless networks and compared with state-of-the-art methods. The experimental results show the proposed method efficiently reduces the energy consumption of network and prolongs the network lifetime with high data recovery accuracy and good stability.
Investigation on Blind Tip Reconstruction Errors Caused by Sample Features
Authors: Wan Jiahuan , Xu Linyan , Wu Sen , Hu Xiaodong
Published: December 2014

Precision measurements of a nanoscale sample surface using an atomic force microscope (AFM) require a precise quantitative knowledge of the 3D tip shape. Blind tip reconstruction (BTR), established by Villarrubia, gives an outer bound with larger errors if the tip characterizer is not appropriate. In order to explore the errors of BTR, a series of simulation experiments based on a conical model were carried out. The results show that, to reconstruct the tip precisely, the cone angle of the tip characterizer must be smaller than that of the tip. Furthermore, the errors decrease as a function of the tip cone angle and increase linearly with the sample radius of curvature, irrespective of the tip radius of curvature. In particular, for sharp (20 nm radius) and blunt (80 nm radius) tips, the radius of curvature of the tip characterizer must be smaller than 5 nm. Based on these simulation results, a local error model of BTR was established. The maximum deviation between the errors derived from the model and the simulated experiments is 1.22 nm. Compared with the lateral resolution used in the above simulated experiments (4 nm/pixel), it is valid to ignore the deviations and consider the local error model of BTR is indeed in quantitative agreement with the simulation results. Finally, two simulated ideal structures are proposed here, together with their corresponding real samples. The simulation results show they are suitable for BTR.
Delay Tracking of Spread-Spectrum Signals for Indoor Optical Ranging
Authors: Salido-Monzú David , Martín-Gorostiza Ernesto , Lázaro-Galilea José , Martos-Naya Eduardo , Wieser Andreas
Published: December 2014

Delay tracking of spread-spectrum signals is widely used for ranging in radio frequency based navigation. Its use in non-coherent optical ranging, however, has not been extensively studied since optical channels are less subject to narrowband interference situations where these techniques become more useful. In this work, an early-late delay-locked loop adapted to indoor optical ranging is presented and analyzed. The specific constraints of free-space infrared channels in this context substantially differ from those typically considered in radio frequency applications. The tracking stage is part of an infrared differential range measuring system with application to mobile target indoor localization. Spread-spectrum signals are used in this context to provide accurate ranging while reducing the effect of multipath interferences. The performance of the stage regarding noise and dynamic errors is analyzed and validated, providing expressions that allow an adequate selection of the design parameters depending on the expected input signal characteristics. The behavior of the stage in a general multipath scenario is also addressed to estimate the multipath error bounds. The results, evaluated under realistic conditions corresponding to an 870 nm link with 25 MHz chip-rate, built with low-cost up-to-date devices, show that an overall error below 6% of a chip time can be achieved.