bluuebunny/crossref_metadata_2025 huggingface dataset:
Utility of neuronavigation and neuromonitoring in epilepsy surgery
Authors: Stone Scellig S. D. , Rutka James T.
Published: August 2008

The management of medically refractory epilepsy poses both a valuable therapeutic opportunity and a formidable technical challenge to epilepsy surgeons. Recent decades have produced significant advancements in the capabilities and availability of adjunctive tools in epilepsy surgery. In particular, image-based neuronavigation and electrophysiological neuromonitoring represent versatile and informative modalities that can assist a surgeon in performing safe and effective resections. In the present article the authors discuss these 2 subjects with reference to how they can be applied and what evidence supports their use. As technologies evolve with demonstrated and potential utility, it is important for all clinicians who deal with epilepsy to understand where neuronavigation and neuromonitoring stand in the present and what avenues for improvement exist for the future.
Advances in intracranial monitoring
Authors: Blount Jeffrey P. , Cormier Jason , Kim Hyunmi , Kankirawatana Pongkiat , Riley Kristen O. , Knowlton Robert C.
Published: August 2008

Intracranial monitoring using electroencephalography (IC-EEG) continues to play a critical role in the assessment of patients with medically intractable localization-related epilepsy. There has been minimal change in grid or electrode design in the last 15–20 years, and the surgical approaches for implantation are unchanged. Intracranial monitoring using EEG allows detailed definition of the region of ictal onset and defines the epileptogenic zone, particularly with regard to adjacent potentially eloquent tissue. Recent developments of IC-EEG include the coregistration of functional imaging data such as magnetoencephalography to the frameless navigation systems. Despite significant inherent limitations that are often overlooked, IC-EEG remains the gold standard for localization of the epileptogenic cortex. Intracranial electrodes take a variety of different forms and may be placed either in the subdural (subdural strips and grids, depth electrodes) or extradural spaces (sphenoidal, peg, and epidural electrodes). Each form has its own advantages and shortcomings but extensive subdural implantation of electrodes is most common and is most comprehensively discussed. The indications for intracranial electrodes are reviewed.
Robotic image-guided depth electrode implantation in the evaluation of medically intractable epilepsy
Authors: Spire William J. , Jobst Barbara C. , Thadani Vijay M. , Williamson Peter D. , Darcey Terrance M. , Roberts David W.
Published: August 2008

Object

The authors describe their experience with a technique for robotic implantation of depth electrodes in patients concurrently undergoing craniotomy and placement of subdural monitoring electrodes for the evaluation of intractable epilepsy.

Methods

Patients included in this study underwent evaluation in the Dartmouth Surgical Epilepsy Program and were recommended for invasive seizure monitoring with depth electrodes between 2006 and the present. In all cases an image-guided robotic system was used during craniotomy for concurrent subdural grid electrode placement. A total of 7 electrodes were placed in 4 patients within the time period.

Results

Three of 4 patients had successful localization of seizure onset, and 2 underwent subsequent resection. Of the patients who underwent resection, 1 is now seizure free, and the second has only auras. There was 1 complication after subpial grid placement but no complications related to the depth electrodes.

Conclusions

Robotic image-guided placement of depth electrodes with concurrent craniotomy is feasible, and the technique is safe, accurate, and efficient.
Pharmacologically intractable epilepsy in children: diagnosis and preoperative evaluation
Authors: Go Cristina , Snead O. Carter
Published: August 2008

It is important to correctly diagnose medically intractable epilepsy in children and to identify those children whose medically refractory, localization-related seizures may be surgically remediable as soon as possible to optimize the surgical outcome. In this paper the authors review the definition of medically intractable seizures and discuss the various causes and risk factors for this disorder in children. They also outline the presurgical diagnostic evaluation process for pharmacologically intractable epilepsy in children who may be candidates for surgical treatment of localization-related seizures. The treatment of children with medically intractable epilepsy is both challenging and rewarding. Surgery has the potential of altering the natural history of epilepsy by improving or eliminating seizures in carefully selected patients.
Novel use of a custom stereotactic frame for placement of depth electrodes for epilepsy monitoring
Authors: Stuart R. Morgan , Goodman Robert R.
Published: August 2008

The authors describe the first reported application of a miniature, customized, one-time use, skull-mounted stereotactic frame for the implantation of depth electrodes for epilepsy monitoring.

Using a platform template, 4 skull fiducial markers were placed 1 week prior to surgery. A brain MR image and a CT scan were subsequently obtained. All planning (longitudinal trajectories into the hippocampi) was done preoperatively using personal computers in the office. No further workstation planning was necessary on the day of the operation. The StarFix microTargeting Platform system was secured to the previously implanted skull fiducial screws. Pin fixation was not required. The platform was used to identify the area of entry for the depth electrodes on the right and left sides. On each side, a 12-contact depth electrode was advanced to the depth of the targets without difficulty. A temporal craniotomy was then performed to place subdural electrodes.

The desired location of the electrodes was confirmed on postoperative imaging studies. There were no complications associated with the electrode implantation. The depth electrodes demonstrated symmetrical, robust coverage of each hippocampus, with epileptiform discharges observed bilaterally.

This first application of the StarFix platform for placing depth electrodes for epilepsy monitoring was both safe and feasible. With this technique, the patient does not need to be pinned or placed in a head holder, no imaging or computer planning is required on the day of implantation (which means there is no time pressure when the meticulous target/trajectory planning is done), and with bilateral posterior implants both bur holes can be made simultaneously. For these reasons this system may be preferable to existing methods of depth electrode implantation.
Neuronavigation applied to epilepsy monitoring with subdural electrodes
Authors: Chamoun Roukoz B. , Nayar Vikram V. , Yoshor Daniel
Published: August 2008

Accurate localization of the epileptogenic zone is of paramount importance in epilepsy surgery. Despite the availability of noninvasive structural and functional neuroimaging techniques, invasive monitoring with subdural electrodes is still often indicated in the management of intractable epilepsy. Neuronavigation is widely used to enhance the accuracy of subdural grid placement. It allows accurate implantation of the subdural electrodes based on hypotheses formed as a result of the presurgical workup, and can serve as a helpful tool for resection of the epileptic focus at the time of grid explantation. The authors describe 2 additional simple and practical techniques that extend the usefulness of neuronavigation in patients with epilepsy undergoing monitoring with subdural electrodes. One technique involves using the neuronavigation workstation to merge preimplantation MR images with a postimplantation CT scan to create useful images for accurate localization of electrode locations after implantation. A second technique involves 4 holes drilled at the margins of the craniotomy at the time of grid implantation; these are used as fiducial markers to realign the navigation system to the original registration and allow navigation with the merged image sets at the time of reoperation for grid removal and resection of the epileptic focus. These techniques use widely available commercial navigation systems and do not require additional devices, software, or computer skills. The pitfalls and advantages of these techniques compared to alternatives are discussed.
The bumetanide-sensitive Na-K-2Cl cotransporter NKCC1 as a potential target of a novel mechanism-based treatment strategy for neonatal seizures
Authors: Kahle Kristopher T. , Staley Kevin J.
Published: August 2008

Seizures that occur during the neonatal period do so with a greater frequency than at any other age, have profound consequences for cognitive and motor development, and are difficult to treat with the existing series of antiepileptic drugs. During development, γ-aminobutyric acid (GABA)ergic neurotransmission undergoes a switch from excitatory to inhibitory due to a reversal of neuronal chloride (Cl–) gradients. The intracellular level of chloride ([Cl–]i) in immature neonatal neurons, compared with mature adult neurons, is about 20–40 mM higher due to robust activity of the chloride-importing Na-K-2Cl cotransporter NKCC1, such that the binding of GABA to ligand-gated GABAA receptor-associated Cl– channels triggers Cl– efflux and depolarizing excitation. In adults, NKCC1 expression decreases and the expression of the genetically related chloride-extruding K-Cl cotransporter KCC2 increases, lowering [Cl–]i to a level such that activation of GABAA receptors triggers Cl– influx and inhibitory hyperpolarization. The excitatory action of GABA in neonates, while playing an important role in neuronal development and synaptogenesis, accounts for the decreased seizure threshold, increased seizure propensity, and poor efficacy of GABAergic anticonvulsants in this age group. Bumetanide, a furosemide-related diuretic already used to treat volume overload in neonates, is a specific inhibitor of NKCC1 at low doses, can switch the GABA equilibrium potential of immature neurons from depolarizing to hyperpolarizing, and has recently been shown to inhibit epileptic activity in vitro and in vivo in animal models of neonatal seizures. The fundamental role of NKCC1 in establishing excitatory GABAergic neurotransmission in the neonate makes it a tempting target of a novel mechanism-based anticonvulsant strategy that could utilize the well-known pharmacology of bumetanide to help treat neonatal seizures.
Phase I trial: safety and feasibility of intracranial electroencephalography using hybrid subdural electrodes containing macro- and microelectrode arrays
Authors: Van Gompel Jamie J. , Stead S. Matthew , Giannini Caterina , Meyer Fredric B. , Marsh W. Richard , Fountain Todd , So Elson , Cohen-Gadol Aaron , Lee Kendall H. , Worrell Gregory A.
Published: August 2008

Object

Cerebral cortex electrophysiology is poorly sampled using standard, low spatial resolution clinical intracranial electrodes. Adding microelectrode arrays to the standard clinical macroelectrode arrays increases the spatial resolution and may ultimately improve the clinical utility of intracranial electroencephalography (iEEG). However, the safety of hybrid electrode systems containing standard clinical macroelectrode and microelectrode arrays is not yet known. The authors report on their preliminary experience in 24 patients who underwent implantation of hybrid electrodes.

Methods

In this study, 24 consecutive patients underwent long-term iEEG monitoring with implanted hybrid depth and subdural grid and strip electrodes; both clinical macroelectrodes and research microelectrodes were used. The patients included 18 women and 6 men with an average age of 35 ± 12 years (range 21–65). The mean hospital stay was 11 ± 4 days (range 5–20), with mean duration of implantation 7.0 ± 3.2 days (range 3–15). Data from the 198 consecutive craniotomies for standard clinical subdural grid insertion (prior to surgery in the 24 patients described here) were used for comparison to investigate the relative risk of complications.

Results

Focal seizure identification and subsequent resection was performed in 20 patients. One patient underwent a subsequent operation after neurological deterioration secondary to cerebral swelling and a 5-mm subdural hematoma. There were no infections. The overall complication rate was 4.2% (only 1 patient had a complication), which did not significantly differ from the complication rate previously reported by the authors of 6.6% when standard subdural and depth intracranial electrodes were used. There were no deaths or permanent neurological deficits related to electrode implantation.

Conclusions

The authors demonstrate the use of hybrid subdural strip and grid electrodes containing high-density microwire arrays and standard clinical macroelectrodes. Hybrid electrodes provide high spatial resolution electrophysiology of the neocortex that is impossible with standard clinical iEEG. In this initial study in 24 patients, the complication rate is acceptable, and there does not appear to be increased risk associated with the use of hybrid electrodes compared with standard subdural and depth iEEG electrodes. More research is required to show whether hybrid electrode recordings will improve localization of epileptic foci and tracking the generation of neocortical seizures.
The role of optical spectroscopy in epilepsy surgery in children
Authors: Bhatia Sanjiv , Ragheb John , Johnson Mahlon , Oh Sanghoon , Sandberg David I. , Lin Wei-Chiang
Published: August 2008

Object

Surgery is an important therapeutic modality for pediatric patients with intractable epilepsy. However, existing imaging and diagnostic technologies such as MR imaging and electrocochleography (ECoG) do not always effectively delineate the true resection margin of an epileptic cortical lesion because of limitations in their sensitivity. Optical spectroscopic techniques such as fluorescence and diffuse reflectance spectroscopy provide a nondestructive means of gauging the physiological features of the brain in vivo, including hemodynamics and metabolism. In this study, the authors investigate the feasibility of using combined fluorescence and diffuse reflectance spectroscopy to assist epilepsy surgery in children.

Methods

In vivo static fluorescence and diffuse reflectance spectra were acquired from the brain in children undergoing epilepsy surgery. Spectral measurements were obtained using a portable spectroscopic system in conjunction with a fiber optic probe. The optical investigations were conducted at the normal and abnormal cortex as defined by intraoperative ECoG and preoperative imaging studies. Biopsy samples were taken from the investigated sites located within the zone of resection. The optical spectra were classified into multiple subsets in accordance with the ECoG and histological study results. The authors used statistical comparisons between 2 given data subsets to identify unique spectral features. Empirical discrimination algorithms were developed using the identified spectral features to determine if the objective of the study was achieved.

Results

Fifteen pediatric patients were enrolled in this pilot study. Elevated diffuse reflectance signals between 500 and 600 nm and/or between 650 and 850 nm were observed commonly in the investigated sites with abnormal ECoG and/or histological features in 10 patients. The appearance of a fluorescent peak at 400 nm was observed in both normal and abnormal cortex of 5 patients. These spectral alterations were attributed to changes in morphological and/or biochemical characteristics of the epileptic cortex. The sensitivities and specificities of the empirical discrimination algorithms, which were constructed using the identified spectral features, were all > 90%.

Conclusions

The results of this study demonstrate the feasibility of using static fluorescence and diffuse reflectance spectroscopy to differentiate normal from abnormal cortex on the basis of intraoperative assessment of ECoG and histological features. It is therefore possible to use fluorescence and diffuse reflectance spectroscopy as an aid in epilepsy surgery.
Selective amygdalohippocampectomy: the trans-middle temporal gyrus approach
Authors: Wheatley B. Matt
Published: August 2008

The most common surgical procedure for the mesial temporal lobe is the standard anterior temporal resection or what is commonly called the anterior temporal lobectomy. There are, however, a number of other more selective procedures for removal of the mesial temporal lobe structures (amygdala, hippocampus, and parahippocampal gyrus) that spare much of the lateral temporal neocortex. Included in these procedures collectively referred to as selective amygdalohippocampectomy are the transsylvian, subtemporal, and transcortical (trans-middle temporal gyrus) selective amygdalohippocampectomy. In this manuscript the author reviews some of the surgical details of the trans-middle temporal gyrus approach to the mesial temporal structures.
Selective amygdalohippocampectomy via the transsylvian approach
Authors: Adada Badih
Published: August 2008

Surgery is an established treatment for temporal lobe epilepsy refractory to medication. Several surgical approaches have been used to treat this condition including temporal lobectomy, transcortical selective amygdalohippocampectomy, subtemporal amygdalohippocampectomy, and transsylvian amygdalohippocampectomy. In this article the author reviews the transsylvian amygdalohyppocampectomy and pertinent anatomy. He also discusses the procedure's results with regard to seizure control, neuropsychological outcome, and visual field preservation.
Surgical treatment of intractable epilepsy associated with focal cortical dysplasia
Authors: Diaz Roberto Jose , Sherman Elisabeth M. S. , Hader Walter J.
Published: August 2008

Focal cortical dysplasias (FCDs) are congenital malformations of cortical development that are a frequent cause of refractory epilepsy in both children and adults. With advances in structural and functional neuroimaging, these lesions are increasingly being identified as a cause of intractable epilepsy in patients undergoing surgical management for intractable epilepsy. Comprehensive histological classification of FCDs with the establishment of uniform terminology and reproducible pathological features has aided in our understanding of FCDs as an epilepsy substrate. Complete resection of FCDs and the associated epileptogenic zone can result in a good surgical outcome in the majority of patients.
Corpus callosotomy in children with intractable epilepsy using frameless stereotactic neuronavigation: 12-year experience at The Hospital for Sick Children in Toronto
Authors: Jea Andrew , Vachhrajani Shobhan , Johnson Keyne K. , Rutka James T.
Published: August 2008

Object

Although corpus callosotomy has been used effectively since the late 1930s to treat severe, medically intractable seizure disorders, particularly atonic or drop-attack seizures, controversy remains as to when, how, and how much surgery should be performed. Intraoperative determination of the extent of callosotomy, the need to stage the procedure, and the side of the interhemispheric approach represent technical issues that remain debatable. The authors report the 12-year experience of the senior author as well as surgical outcomes with corpus callosotomy using a frameless stereotactic neuronavigation system (ISG View Wand and BrainLab).

Methods

Thirteen consecutive children at The Hospital for Sick Children underwent single-stage corpus callosotomy for medically intractable seizures. The mean age was 10.3 years. Five children underwent partial callosotomy, and 8 underwent complete callosotomy. The side of operative approach to avoid large parasagittal bridging veins was determined by preoperative study of 3D MR imaging/MR venography reconstructed by the neuronavigation system. The extent of callosotomy was determined using intraoperative feedback from the neuronavigation system and postoperative MR imaging.

Results

The extent of callosotomy determined by intraoperative neuronavigation and postoperative MR imaging correlated closely in all cases. There were no operative deaths. There was no significant postoperative morbidity related to venous infarction. Four of 5 patients in the partial callosotomy cohort and 7 of 8 patients in the complete callosotomy cohort showed significant improvement in seizure control.

Conclusions

The use of frameless stereotactic neuronavigation is a safe, effective, and important surgical adjunct in the planning and execution of successful corpus callosotomy in children with intractable epilepsy.
Vagus nerve stimulation: current concepts
Authors: Mapstone Timothy B.
Published: August 2008

Vagus nerve stimulation (VNS) has become an accepted treatment option for pharmacologically resistant epilepsy. Although initially approved for adults, it increasingly has gained acceptance in children. In this article the author reviews the current state of knowledge of VNS therapy and discusses its potential utility.
Visitor Value Perception of a Heritage Tourism Site Development: A Case Study
Authors: Taylor Ruth , Shanka Tekle
Published: August 2008

Successful tourism attraction site development includes the ability to design and deliver unique, authentic products, services, and experiences for visitors. Value perception is an important strategic imperative for management and a decision imperative for visitors in that it represents both short-term and long-term benefits and sacrifices to both attraction and visitor. This research study discusses visitor value perception, and investigates the expectations of visitors to a proposed development associated with a prime tourism attraction site development. A total of 960 useable questionnaires were analyzed to provide the findings of this study. It was identified that while a range of product offerings were available at the site, the core identity valued by visitors was that of heritage. The research project found that overall the proposed development of the tunnels project was thought to enhance this element of the site, while allowing additional services to be developed in the form of an adventure experience. Results are discussed and implications for the project development are identified.
Sweepstakes Promotions to Build Database for Promoting International Tourism Destinations
Authors: Pinar Musa , Ozgur Ceyhun
Published: August 2008

This article discusses the importance of a tourism-oriented database to promote tourism destinations and how sweepstakes promotions can be utilized in developing a sophisticated database for more effective destination marketing. The article presents various ways databases can be utilized
by domestic and international destination marketers. Sweepstakes promotions can be effective in promoting international tourism and attracting potential tourists to desired destinations of the sponsoring countries. In addition, they can also be used to develop a sophisticated database from
sweepstakes entrants. Such a database could be used to design more effective relationship marketing strategies. Finally, the article presents several managerial implications for building a more effective database from targeted sweepstakes.
Millennial Students, Movies, and Tourism
Authors: Hahm Jeeyeon , Upchurch Randall , Wang Youcheng
Published: August 2008

This study examines the degree to which the leisure activity of "going to a movie film" influences an individual's image formation process, and therefore desire to visit the portrayed tourist destination. The results of this single case study are twofold. First, demographic differences occur between pretest and posttest measures of destination attributes as the result of exposure to a destination specific movie, and second, the desire to visit the film locations as expressed in the movie significantly vary by gender, age, and ethnicity.
Aircraft Contrails Contribute to Climate Change: Whole Tourism Systems are Appropriate Contexts for Research on Sustainable Tourism
Authors: Leiper Neil , Braithwaite R. W. , Witsel Mieke
Published: August 2008

Environmental activists and concerned scientists have suggested since the 1970s that jet aircrafts' contrails, also known as vapor trails, might be having undesirable effects on the environment. In 2001, an unusual but scientifically rigorous research project, testing this hypothesis,
found that contrails do have an environment impact. On busy routes the effects are significant and serious, similar to the effects of greenhouse gases, resulting in climate change. The present article discusses implications of this for sustainable tourism and ecotourism. Almost all research
to date on these linked topics has focused exclusively on destinations. Knowledge about the effects of contrails adds weight to the evidence and belief that sustainable tourism and ecotourism cannot be achieved by attempts to sustain destinations if other elements in whole tourism systems
are being damaged by tourism. A comprehensive understanding of tourism's environmental impacts and research on sustainability requires, as the unit of analysis, whole tourism systems.
Exploring Wine Tourism in New Zealand: The Visitors' Points of Views
Authors: Alonso Abel D. , Fraser Rick A. , Cohen David A.
Published: August 2008

With the remarkable growth of New Zealand's wine industry in the last decade, the concept of wine tourism has been gaining in popularity among different groups of travelers to rural areas. Numerous factors can impact individuals' decision to visit wineries. Many consumer-related studies
emphasize the consumers' perceived value of the consumption experience, as well as how to deliver a satisfying experience to consumers. This also applies to wineries seeking to attract visitors and benefit commercially in the process in the form of wine and food sales. This study conducted
among New Zealand wineries explores several aspects related to visitors' winery experience. These aspects include the most relevant factors impacting on visitors' decision to travel to wineries, how visitors discover their chosen winery, the value they place on elements of their winery experience,
and their overall satisfaction. The findings suggest the critical importance of word-of-mouth advertising in influencing winery choice. The results also indicate that a rather large number of visitors travel to wineries for reasons other than the wine, including their proximity of the winery,
passing by, or on route to another destination. The overall results could have important implications for wineries, particularly in their efforts to market their businesses.
Impact of Weather Variability on Golfing Activity and Implications of Climate Change
Authors: Nicholls Sarah , Holecek Donald F. , Noh Jeonghee
Published: August 2008

Despite the obvious influence of weather conditions on golfing activity, the relationships between participation in golf and specific weather variations have rarely been considered in the empirical literature. Given the increasing evidence to support global climate change, quantification
of historical relationships between participation and weather conditions is a vital prerequisite to modeling the potential implications of changing weather patterns for participation in outdoor activities such as golf. The purpose of this article was to determine the influence of weather variations
on daily golfing activity at three golf courses in Michigan. Multiple regression analysis revealed that variations in maximum temperature and precipitation had statistically significant influences on daily golfing activity in all the models developed. Fluctuations in other variables, including
minimum temperature, public holidays, consumer confidence, and the price of gas, also emerged as significant, but not consistently so across all the models. The results presented highlight both the problems and opportunities associated with modeling the relationships between outdoor activity
participation and weather conditions. While the models constructed do identify interesting relationships between the variables tested, they also illuminate the difficulties in accounting for the myriad of influences on outdoor activity participation in a quantitative setting. Nevertheless,
the analyses should be of immense utility to outdoor recreation and tourism planners and managers for both the short- and long-term planning and management of their enterprises. Models of present-day relationships between activity participation and variability in climatic, economic, and other
relevant factors could aid in short-term decisions regarding issues such as purchasing and staffing requirements. When combined with scenarios of future climatic, economic, and other conditions, they could also be used to inform choices regarding the expansion of existing facilities and diversification
into new geographic and/or activity domains.
Convention Center Management—Influencing the Attendee Experience: The Case of Charleston Convention Center
Authors: Ryan Chris , Crotts John , Litvin Steven
Published: August 2008

This article suggests that convention center management has a direct ability to influence attendee experiences in only limited ways, while possibly having indirect or stakeholder influences in other directions. The issue for such center management is whether the areas in which it holds direct responsibility, such as signposting, décor, and ambience, are of sufficient importance to impact upon the delegate experience given the importance of other variables such as destination attractiveness and program content. The study reports findings from a sample of 256 attendees at a cross section of events at the Charleston Convention Center. The findings suggest that cleanliness of toilets and staff interactions are important to attendees. Overall satisfaction also correlated with ease of finding the car park entrance, the quality of sound systems, overall event layout, the friendliness of staff, and ease of access to downtown Charleston. Some of these factors lie within the direct control of management.
Estimating the Determinants of Tourist Spending: A Comparison of Four Models
Authors: Kozak Metin , Gokovali Ummuhan , Bahar Ozan
Published: August 2008

Although the issue of tourist spending estimation has long been of considerable interest to many researchers, there has been no consensus yet about its definition as the dependent variable. This study attempts to estimate determinants of tourist spending by utilizing a self-generated
survey data and the Ordinary Least Squares (OLS) method. The distinction of this study is that it develops four different models to test the accuracy of the determinants of tourist spending and it considers not only the demand side but also the supply side. Dependent variables for different
models are defined as total vacation spending (MODEL#1), daily spending per group (MODEL#2), daily spending per person (MODEL#3), and total spending per person (MODEL#4). The analysis was accomplished through the use of dummy variables such as sociodemographics and vacation-taking behavior
of tourists, as suggested in the literature. All four estimation results indicated that some of the explanatory variables are consistent determinants of tourist spending, regardless of the type of models defined. Moreover, this study compares and contrasts the findings to suggest the best
acceptable model for estimating the determinants of tourist spending. Both managerial and theoretical implications are also discussed.
Uniform Rattle‐type Hollow Magnetic Mesoporous Spheres as Drug Delivery Carriers and their Sustained‐Release Property
Authors: Zhao Wenru , Chen Hangrong , Li Yongsheng , Li Liang , Lang Meidong , Shi Jianlin
Published: September 2008

A novel kind of rattle‐type hollow magnetic mesoporous sphere (HMMS) with Fe3O4 particles encapsulated in the cores of mesoporous silica microspheres has been successfully fabricated by sol–gel reactions on hematite particles followed by cavity generation with hydrothermal treatment and H2 reduction. Such a structure has the merits of both enhanced drug‐loading capacity and a significant magnetization strength. The prepared HMMSs realize a relatively high storage capacity up to 302 mg g−1 when ibuprofen is used as a model drug, and the IBU–HMMS system has a sustained‐release property, which follows a Fick's law.
Hierarchical Inorganic–Organic Nanocomposites Possessing Amphiphilic and Morphological Complexities: Influence of Nanofiller Dispersion on Mechanical Performance
Authors: Xu Jinqi , Bartels Jeremy W. , Bohnsack David A. , Tseng Tzu‐Chia , Mackay Michael E. , Wooley Karen L.
Published: September 2008

Novel nanocomposites possessing ternary compositions and complex morphologies have been prepared from amphiphilic crosslinked hyperbranched fluoropolymer–poly(ethylene glycol) (HBFP–PEG) in the presence of pristine and chemically functionalized nanoscopic fillers, single‐walled carbon nanotubes (SWNTs) and silica nanoparticles (SiO2). Both SWNTs and SiO2 were engineered specifically to become phase‐designated reinforcing functional materials, SWNT‐g‐PEG and SiO2‐g‐HBFP, which (1) improved the dispersion of fillers, nanotubes, or spherical nanoparticles in the amphiphilic matrices, (2) enhanced the non‐covalent interactions between nanofillers and polymers, and more importantly, (3) maintained reactive functionalities to be further covalently integrated into the complex networks. Tensile moduli (Edry) for these as‐prepared SWNT‐containing composites increased by up to 430% relative to the unfilled material, while those incorporated with SiO2 had a 420% increase of Edry. After swelling in water, the water absorption within the micro‐ and nanochannels of PEG‐rich domains rigidified or softened the entire crosslinked network, as determined by the amount of PEG.
The Role of the Interface in CO Oxidation on Au/CeO2 Multilayer Nanotowers
Authors: Zhou Zheng , Kooi Steven , Flytzani‐Stephanopoulos Maria , Saltsburg Howard
Published: September 2008

The CO oxidation reaction is studied in this work using a controlled structure consisting of Au/CeO2 multilayers, in the form of towers of 10 × 10 µm2 base, with layer thicknesses in the nanometer range. This structure is prepared on a 3″ Si wafer using reverse photolithography and vapor deposition in an e‐beam chamber. The thickness of each layer is of nanometer dimensions and only the edges of the Au and CeO2 layers are exposed to the reaction gas mixture. The CO oxidation reaction rate is found to scale with the total length of the Au/CeO2 interfaces for nanotowers with the same total Au and CeO2 surface areas. TEM and X‐ray diffraction (XRD) analyses reveal highly stressed gold films in the nanotowers, the lattice strain being temperature and film thickness dependent. Deactivation with time‐on‐stream is commensurate with relaxation of the gold films, as measured by a drop in their lattice strain.
Evaluation of Digitally Encoded Layer‐by‐layer Coated Microparticles as Cell Carriers
Authors: Fayazpour Farzaneh , Lucas Bart , Vandenbroucke Roosmarijn E. , Derveaux Stefaan , Tavernier Jan , Lievens Sam , Demeester Joseph , De Smedt Stefaan C.
Published: September 2008

To obtain more biologically relevant data there is a growing interest in the use of living cells for assaying the biological activity of unknown chemical compounds. Density ‘multiplex’ cell‐based assays, where different cell types are mixed in one well and simultaneously investigated upon exposure to a certain compound are beginning to emerge. To be able to identify the cells they should be attached to microscopic carriers that are encoded. This paper investigates how digitally encoded microparticles can be loaded with cells while keeping the digital code in the microcarriers readable. It turns out that coating the surface of the encoded microcarriers with polyelectrolytes using the layer‐by‐layer (LbL) approach provides the microcarriers with a ‘highly functional’ surface. The polyelectrolyte layer allows the growth of the cells, allows the orientation of the cell loaded microcarriers in a magnetic field, and does not hamper the reading of the code. It has further been shown that the cells growing on the polyelectrolyte layer can become transduced by adenoviral particles hosted by the polyelectrolyte layer. It is concluded that the digitally encoded microparticles are promising materials for use in biomedical and pharmaceutical in‐vitro research where cells are used as tools.
Solution‐Processible Red Iridium Dendrimers based on Oligocarbazole Host Dendrons: Synthesis, Properties, and their Applications in Organic Light‐Emitting Diodes
Authors: Ding Junqiao , Lü Jianhong , Cheng Yanxiang , Xie Zhiyuan , Wang Lixiang , Jing Xiabin , Wang Fosong
Published: September 2008

A series of novel red‐emitting iridium dendrimers functionalized with oligocarbazole host dendrons up to the third generation (red‐G3) have been synthesized by a convergent method, and their photophysical, electrochemical, and electroluminescent properties have been investigated. In addition to controlling the intermolecular interactions, oligocarbazole‐based dendrons could also participate in the electrochemical and charge‐transporting process. As a result, highly efficient electrophosphorescent devices can be fabricated by spin‐coating from chlorobenzene solution in different device configurations. The maximum external quantum efficiency (EQE) based on the non‐doped device configuration increases monotonically with increasing dendron generation. An EQE as high as 6.3% was obtained as for the third generation dendrimer red‐G3, which is about 30 times higher than that of the prototype red‐G0. Further optimization of the device configuration gave an EQE of 11.8% (13.0 cd A−1, 7.2 lm W−1) at 100 cd m−2 with CIE coordinates of (0.65, 0.35). The state‐of‐the‐art performance indicated the potential of these oligocarbazole‐based red iridium dendrimers as solution processible emissive materials for organic light‐emitting diode applications.
Platinum Lead Nanostructures: Formation, Phase Behavior, and Electrocatalytic Properties
Authors: Yang Shengchun , Peng Zhenmeng , Yang Hong
Published: September 2008

This paper describes the synthesis and crystal phase behavior of platinum lead nanorods. Both face‐centered cubic (fcc) Pt100−xPbx (x < 50) and hexagonally close‐packed (hcp) Pt50Pb50 nanostructures are synthesized at mild reaction temperatures (180–200 °C). The crystal phase and composition of these PtPb nanorods can be controlled by changing the reaction time and temperature. A mechanism for the formation of either kinetically or thermodynamically stable PtPb nanorods is discussed. The approach developed for controlling crystal phases at fairly low temperatures can be important for the design of alloy or intermetallic nanostructures for a broader range of applications.
Bulk Synthesis and Surface Patterning of Nanoporous Metals and Alloys from Supraspherical Nanoparticle Aggregates
Authors: Klajn Rafal , Gray Timothy P. , Wesson Paul J. , Myers Benjamin D. , Dravid Vinayak P. , Smoukov Stoyan K. , Grzybowski Bartosz A.
Published: September 2008

Supraspheres (SS) composed of hundreds to thousands of metal nanoparticles (NPs) and crosslinked by dithiol linkers are assembled into larger structures, which are subsequently converted into nanoporous metals (NMs). Conversion is achieved by heating which removes organic molecules stabilizing the NPs and allows for NP fusion. Heating of SS solutions leads to NMs of overall macroscopic dimensions; localized radiation using collimated electron beam is used to prepare metallized surface micropatterns. Depending on the composition of supraspherical precursors, nanoporous materials composed of up to three metals can be obtained. Strategies for controlling pore size and nanoscale surface roughness of these materials are discussed.
Traversing the Metal‐Insulator Transition in a Zintl Phase: Rational Enhancement of Thermoelectric Efficiency in Yb14Mn1−xAlxSb11
Authors: Toberer Eric S. , Cox Catherine A. , Brown Shawna R. , Ikeda Teruyuki , May Andrew F. , Kauzlarich Susan M. , Snyder G. Jeffrey
Published: September 2008

For high temperature thermoelectric applications, Yb14MnSb11 has a maximum thermoelectric figure of merit (zT) of ∼1.0 at 1273 K. Such a high zT is found despite a carrier concentration that is higher than typical thermoelectric materials. Here, we reduce the carrier concentration with the discovery of a continuous transition between metallic Yb14MnSb11 and semiconducting Yb14AlSb11. Yb14Mn1‐xAlxSb11 forms a solid solution where the free carrier concentration gradually changes as expected from the Zintl valence formalism. Throughout this transition the electronic properties are found to obey a rigid band model with a band gap of 0.5 eV and an effective mass of 3 me. As the carrier concentration decreases, an increase in the Seebeck coefficient is observed at the expense of an increased electrical resistivity. At the optimum carrier concentration, a maximum zT of 1.3 at 1223 K is obtained, which is more than twice that of the state‐of‐the‐art Si0.8Ge0.2 flown by NASA.
Luminescent Tags on Fullerenes: Eu3+ Complexes with Pendant Fullerenes
Authors: Fuchsbauer Anita , Troshina Olesya A. , Troshin Pavel A. , Koeppe Robert , Lyubovskaya Rimma N. , Sariciftci Niyazi Serdar
Published: September 2008

Novel fullerene‐containing Eu (III) complexes are obtained by mixing a fullerene derivative bearing chelating pyridinyl groups with an Eu (III) complex possessing three coordinated 4,4,4,‐trifluoro‐1‐(2‐naphtyl)‐1,3‐butanedione residues and two water molecules. One of the complexes designed is formed in water using a water‐soluble fullerene derivative as a precursor material. We investigate the photophysical properties of this new type of highly soluble self‐assembled fullerene‐derivative Eu3+ coordination compounds. A strong emission line of the Eu3+ 4f–4f transition is recorded under excitation with UV irradiation. The behaviour of the complexes in organic matrices and water is studied as the first steps towards luminescence tagged fullerene derivatives for use in biomedicine and optoelectronics.
Light‐Emission Performance of Silicon Nanocrystals Deduced from Single Quantum Dot Spectroscopy
Authors: Valenta Jan , Fucikova Anna , Vácha František , Adamec František , Humpolíčková Jana , Hof Martin , Pelant Ivan , Kůsová Kateřina , Dohnalová Kateřina , Linnros Jan
Published: September 2008

Spectra of individual silicon nanocrystals within porous Si grains are studied by the wide‐field imaging microspectroscopy and their ON–OFF blinking is detected by the confocal single‐photon‐counting microscopy. Observed spectral and blinking properties comprise all features reported before in differently prepared single Si nanocrystals (SiNCs). Former apparently contradictory results are shown to be due to different experimental conditions. When the effect of dark periods (OFF switching) is removed the common ultimate photoluminescence properties of SiO2 passivated SiNCs are found, namely the quantum efficiency (QE) of about 10–20% up to the pumping rate corresponding to one exciton average excitation per quantum dot. At higher pump rates the QE is slowly decreasing as the 0.7th power of excitation. This is most likely due to Auger recombination which, however, seems to be weakened compared with measurements of nanocrystal assemblies. We conclude that SiNCs may be pumped above one exciton occupancy to yield a higher light emission, being advantageous for applications.
Tailor‐made Polymeric Membranes based on Segmented Block Copolymers for CO2 Separation
Authors: Car Anja , Stropnik Chrtomir , Yave Wilfredo , Peinemann Klaus‐Viktor
Published: September 2008

This paper reports the design of a tailor made polymeric membrane by using poly(ethylene oxide)–poly(butylene terephthalate) (PEO‐PBT) multi‐block copolymers. Their properties are controlled by the fraction of the PEO phase and its molecular weight. To explain the effect of structural changes in copolymer membranes, transport properties of four gases (CO2, H2, N2, and CH4) are discussed. After characterization, the two best copolymers are selected in order to prepare tailor made blends by adding poly(ethylene glycol) (PEG). The best selected copolymer that contained 55 wt. % of 4000 g mol−1 PEO produced a blend with high CO2 permeability (∼190 barrer), which is twice the permeability of the pure copolymer. At the same time, an enhancement of CO2/H2 selectivity is observed (∼13). These results suggest that the morphology of PEO‐PBT can be well controlled by the addition of low‐molecular‐weight PEG, and consequently the gas transport properties can be tuned.
Effect of Oligothienyl Chain Length on Tuning the Solar Cell Performance in Fluorene‐Based Polyplatinynes
Authors: Liu Li , Ho Cheuk‐Lam , Wong Wai‐Yeung , Cheung Kai‐Yin , Fung Man‐Kin , Lam Wai‐Ting , Djurišić Aleksandra B. , Chan Wai‐Kin
Published: September 2008

A series of solution‐processable and strongly visible‐light absorbing polyplatinynes containing oligothienyl–fluorene ring hybrids were synthesized and characterized. These rigid‐rod organometallic materials are soluble in polar organic solvents and show intense absorptions in the visible spectral region, rendering them excellent candidates for bulk heterojunction polymer solar cells. The photovoltaic behavior depends significantly on the number of thienyl rings along the polymer chain, and some of these polymer solar cells show high power conversion efficiencies (PCEs) of up to 2.9% and a peak external quantum efficiency to 83% under AM1.5 simulated solar illumination. The effect of oligothienyl chain length on improving the polymer solar cell efficiency and on their optical and charge transport properties is elucidated in detail. At the same blend ratio of 1:5, the light‐harvesting capability and PCE increase markedly with increasing number of thienyl rings. The power dependencies of the solar cell parameters (including the short‐circuit current density, open‐circuit voltage, fill‐factor, and PCE) were also examined. The present work opens up an attractive avenue to developing conjugated metallopolymers with broad and strong solar energy absorptions and tunable solar cell efficiency and supports the potential of metalated conjugated polymers for efficient power generation.