bluuebunny/crossref_metadata_2025 huggingface dataset:
Compósitos de cimento Portland com adição de nanotubos de carbono (NTC): Propriedades no estado fresco e resistência à compressão
Authors: Medeiros Marcelo Henrique Farias de , Dranka Francielle , Mattana Alécio Júnior , Costa Marienne do Rocio de Mello Maron da
Published: April 2015

Alguns estudos têm sido desenvolvidos sobre a adição de nanotubos de carbono (NTCs) em compósitos cimentícios e indicam melhorias nas propriedades mecânicas, como aumento da resistência à compressão, à tração e diminuição da porosidade. Com base nessas possíveis melhorias, essa pesquisa foi realizada para analisar a influência dos NTCs na resistência à compressão e fluidez de compósitos de cimento Portland que possam ser usados para reabilitação de estruturas de concreto. Desse modo, foram realizados ensaios de resistência à compressão, squeeze flow, flow table, funil de Marsh e miniabatimento. Foram fixadas uma argamassa e uma pasta de referência (sem adição de nanotubos de carbono), que foram replicadas com mesmo traço e a incorporação de 5 teores de NTCs em relação à massa de cimento: 0,1%, 0,2%, 0,3%, 0,4% e 0,5%. Estes teores foram escolhidos de modo a abranger a faixa de teores mais usadas nas pesquisas sobre NTCs adicionados aos compósitos de cimento Portland. Com relação aos ensaios de medição de fluidez, foi constatado que quanto maior o teor de NTC, mais consistente o compósito cimentício, com indícios de que os teores menores ou iguais a 0,3% são mais adequados para manter a fluidez do compósito de cimento Portland. No caso da resistência à compressão, os resultados indicam que a adição de 0,40% de nanotubos de carbono tende a elevar a resistência em 27%. Por outro lado, a adição de 0,5% de NTC deixou o compósito tão consistente que dificultou a moldagem e a elevação da resistência foi nula comparada a série de referência.
Investigação do processo de corrosão causado pela polpa de bauxita em mineroduto de aço carbono
Authors: Santos Marcelo Costa , Pinheiro Clairon Lima , Filho José Carlos de Araújo Cardoso
Published: April 2015

O tempo de vida útil de um mineroduto depende de diversos fatores, dentre os quais aqueles relacionados ao processo de corrosão provocado pelo escoamento da polpa de minério. Nesse contexto, a corrosão do aço carbono API 5L-X70 foi investigada em meio de água do processo e polpa de bauxita (5% m/v) utilizando técnicas eletroquímicas. Os resultados do potencial de circuito aberto (EOC), polarização e impedância eletroquímica (EIE) mostraram que a presença do minério de bauxita provocou mudanças no comportamento eletroquímico do meio quando comparados aos obtidos em água do processo na ausência do minério. Um aumento na taxa de corrosão do aço carbono foi observado pela presença da bauxita. A análise de superfície nos corpos de prova utilizando microscopia eletrônica de varredura (MEV) mostrou a formação de rachaduras nos óxidos presentes na superfície do metal, sendo esse fenômeno o responsável pelo aumento da corrosão do aço na presença da bauxita. A metodologia utilizada neste trabalho mostrou-se útil para a investigação de processos corrosivos em minerodutos e aplicável a outras situações onde polpas de minérios são escoadas em tubulações de aço.
Avaliação das propriedades físicas de revestimentos cerâmicos produzidos com resíduo da indústria cerâmica (cinza pesada de carvão mineral)
Authors: Skoronski Everton , Souza Diego Hoefling , Santos Samara dos , Cesino Júlio Cesar , Ghislandi Marcos Gomes
Published: April 2015

A cinza resultante da queima do carvão mineral pulverizado é um dos resíduos gerados pelas empresas produtoras de materiais cerâmicas. Quimicamente, é constituída de uma ampla mistura de óxidos, sendo os majoritários Al2O3, SiO2 e Fe2O3 e outros menores como CaO, MgO, sulfatos e outras combinações. Atualmente, em muitas empresas, a cinza produzida é aterrada em áreas licenciadas por órgãos ambientais. Com o ritmo acelerado de produção de revestimentos cerâmicos e em virtude da sua limitada vida útil é necessário a utilização de outros locais, adequados, para deposição das cinzas, medida que provoca um gasto mensal elevado. Diante deste cenário, a adição de cinza à matéria-prima, além de diminuir o impacto ao meio-ambiente, pode propiciar uma redução geral de custos, tanto pelo barateamento da produção, como pela diminuição daquantidade de cinzas a serem aterradas. Desta forma, o objetivo deste trabalho foi avaliar as propriedades físicas de revestimentos cerâmicos produzidos com a adição de cinza pesada de carvão mineral. Para sua realização, corpos de prova foram confeccionados com adição de 1 a 30% de cinza em base mássica. Os corpos de prova foram armazenados dentro de placas refratárias e queimados em forno túnel a uma temperatura de 1084ºC em um ciclo de 29 horas. Foram analisados parâmetros físicos para a barbotina e corpo de prova pós-queima. Os resultados obtidos foram comparados com os padrões estabelecidos pela norma NBR 13818. Foi demonstrado que os experimentos realizados com adição de 1 a 10 % de cinza apresentaram-se dentro dos padrões estipulados pela norma. Para porcentagens de cinza adicionada acima de 4 %, alguns valores estiveram fora dos padrões, sendo a formação de "coração negro" o parâmetro que mais se afastou das exigências da norma em questão.
Argamassas com incorporação de Materiais de Mudança de Fase (PCM): Caracterização física, mecânica e durabilidade
Authors: Cunha Sandra , Aguiar José , Ferreira Victor , Tadeu António
Published: April 2015

O despertar da consciência ambiental pela sociedade, tem levantado problemas até então ignorados tais como os consumos energéticos. Numa sociedade com um elevado ritmo de crescimento e padrões de conforto cada vez maiores, surge a necessidade de minimizar os elevados consumos energéticos, tirando partido de fontes de energia renováveis. As argamassas com incorporação de materiais de mudança de fase (PCM) possuem a capacidade de regular a temperatura no interior dos edifícios, contribuindo desta forma para o aumento do nível de conforto térmico e diminuição do recurso a equipamentos de climatização, apenas com recurso à energia solar. Contudo, a incorporação de materiais de mudança de fase em argamassas modifica algumas das suas principais características. Portanto, o principal objetivo deste estudo consistiu na caracterização física e mecânica de argamassas aditivadas com PCM, assim como na avaliação da sua durabilidade. Para tal foram desenvolvidas 12 composições distintas, à base de diferentes ligantes e dopadas com 40% de PCM. Tendo sido possível observar que a incorporação de PCM provoca diferenças significativas em propriedades tais como a trabalhabilidade, resistência à compressão, resistência à flexão, aderência, absorção de água por capilaridade, absorção de água por imersão e resistência a ações de gelo-degelo. Contudo, foi possível concluir que a incorporação de PCM nas argamassas pode ser realizada com sucesso. Sendo que, as alterações verificadas nas argamassas podem ser contornadas através da incorporação de uma maior dosagem de ligante, superplastificante e até mesmo a inclusão de fibras. Apesar dos resultados desta investigação serem promissores é importante referir que outras investigações devem ser realizadas com o intuito de observar a influência do PCM em argamassas constituídas por outros materiais.
O movimento LGBT e as políticas de educação de gênero e diversidade sexual: perdas, ganhos e desafios
Authors: Vianna Cláudia Pereira
Published: April 2015

Este artigo explora a relação entre Estado e movimentos sociais na produção de políticas públicas de educação voltadas para o gênero e para a diversidade sexual. Esta reflexão toma como fontes principais duas investigações mais recentes voltadas para a compreensão da introdução do gênero e da diversidade sexual nas políticas públicas de educação no Brasil, no governo de Luiz Inácio Lula da Silva: uma tese de livre docência (VIANNA, 2011) e outro trabalho que verificou como as políticas voltadas para o currículo foram compreendidas, apropriadas e implementadas por professoras e professores de escolas públicas do estado de São Paulo (VIANNA, 2012). A intenção deste artigo foi olhar a produção dessas políticas a partir das tensões presentes na interlocução do governo Lula com demandas sociais por diminuição da desigualdade e construção de direitos sociais advindas do movimento LGBT (Lésbicas, Gays, Bissexuais, Transexuais e Transgêneros). Ao discutir ganhos, perdas e desafios futuros, o texto destaca as contradições presentes no processo de interlocução entre o governo e o movimento LGBT. Quando o governo introduz demandas de gênero e diversidade sexual na educação, parece querer valorizar o tema sem considerar as relações de poder que determinam os parâmetros tradicionais que sustentam as relações de gênero e as identidades docentes no cotidiano escolar.
Influence of initial stress distribution on liquefaction-induced settlement of shallow foundations
Authors: Bertalot D. , Brennan A.J.
Published: April 2015

During earthquakes, saturated sandy soils may generate significant excess pore pressures and approach a state of liquefaction. Structures founded on shallow foundations above such soils may consequently undergo large settlements. Recent case history analysis has shown that the stress imposed by the foundation is a key factor in the estimation of such settlements. However, the case history data showed that although increasing bearing pressure caused an increase in settlements as expected, this was only true up to a point, and that very heavy structures appeared to settle less than some lighter structures. This work aims to investigate these counter-intuitive results by means of controlled experimental testing using a geotechnical centrifuge. Results of the centrifuge tests show that the trend derived from case histories is correct and that liquefaction-induced settlements peak for a given bearing stress (90 kPa for the models tested) and reduce for greater applied stresses. Further, by analysis of excess pore pressure distributions beneath the foundations it is shown that the main factor inhibiting pore pressure generation beneath the footings is not so much the confining pressure as the in-situ static shear stress around the edge of the foundation. This is supported by element test data from the literature. When this initial static shear stress is so high that the applied cyclic shear stress cannot exceed it (i.e. the direction of shear stress does not reverse) then pore pressure generation is greatly reduced, thus causing the observed reduction in expected settlements.
Effect of floated sludge recycling on phosphorus removal in dissolved air flotation
Authors: Kwak Dong-Heui , Lee Ki-Cheol
Published: April 2015

The total phosphorus (TP) content allowed in effluent water in many countries has been reduced to below 0·1 mg/l, which is about one tenth of the TP concentration in effluent water discharged from plants using conventional biological processes. Research and advanced treatment processes are being actively applied to remove phosphorus from municipal wastewater, with most research focusing on stable and efficient chemical treatments. To enhance the removal of phosphorus, a series of experiments was conducted based on a pilot plant of the dissolved air flotation (DAF) process using effluent from a municipal wastewater treatment plant, which applies a biological process for nutrient removal. Specifically, this study evaluated the effect of floated sludge recycling in the DAF process in addition to the treatment conditions for TP removal. The applied treatment led to rapid TP removal with [Al]/[P] molecular ratios of less than 2·0. Slight TP removal occurred with [Al]/[P] ratios greater than 2·0, indicating the inrush of the equilibrium control stage. When the floated sludge was recycled, increased removal of TP was achieved. The recycling of floated sludge thus improved the quality of the treated water and reduced the coagulant dosage, generating an efficient process for TP removal.
Determination of appropriate dimensions of submerged vanes
Authors: Seyed Mirzaei Seyed Hessam , Firoozfar Ali Reza , Ayyoubzadeh Seyed Ali
Published: April 2015

Utilisation of submerged vanes in front of intake ports is an effective approach to address sedimentation in lateral intakes from rivers. Strategically installed, these flow-training structures could increase the mid-depth and near surface flows into the intake, and simultaneously prevent bed-load transport from entering the intake channels. The effectiveness of submerged vanes depends on their number, shape, dimensions and configuration. Determination of optimum values for dimensions or configuration of the vanes is very challenging as the effect of many parameters, which are effective in sedimentation in the intake zone, must be investigated. In this study, effort has been made to determine appropriate dimensions of submerged vanes that are installed in front of a 90° intake from a straight channel. Fuzzy TOPSIS, a multi-objective optimisation method, has been utilised for the optimisation process by considering ten parameters. The simulations have been conducted for three discharge ratios of 0·11, 0·16 and 0·21. The results show that a height of 0·2 times the flow depth, and a length of four times the vane height are the appropriate dimensions for utilisation of submerged vanes in front of the lateral intakes from straight channels.
Downside Variance Risk Premium
Authors: Feunou Bruno , Okou Cedric , Jahan-Parvar Mohammad R.
Published: April 2015

We propose a new decomposition of the variance risk premium in terms of upside and downside variance risk premia. The difference between upside and downside variance risk premia is a measure of skewness risk premium. We establish that the downside variance risk premium is the main component of the variance risk premium, and that the skewness risk premium is a priced factor with significant prediction power for aggregate excess returns. Our empirical investigation highlights the positive and significant link between the downside variance risk premium and the equity premium, as well as a positive and significant relation between the skewness risk premium and the equity premium. Finally, we document the fact that the skewness risk premium fills the time gap between one quarter ahead predictability, delivered by the variance risk premium as a short term predictor of excess returns and traditional long term predictors such as price-dividend or price-earning ratios. Our results are supported by a simple equilibrium consumption-based asset pricing model.
Phenological synchronization drives demographic rates of populations
Authors: Rasmussen Nick L. , Rudolf Volker H. W.
Published: April 2015

Phenology is increasingly recognized as an important factor structuring communities because it determines when and at what life stage organisms interact. Previous work indicates that changes in first or mean timing of a phenological event can affect populations and communities, but little is known about the consequences of changes in the distribution (e.g., synchrony) of a phenological event. We conducted an experiment using an anuran study system to determine how synchrony of reproduction and egg hatching affects offspring performance, whether the effects are density dependent, and how hatching synchrony influences the synchrony of a subsequent phenological event (metamorphosis). Changes in hatching synchrony altered survival, development rates, and body size at metamorphosis, which can affect post‐metamorphosis performance. The degree of synchrony at hatching also affected the degree of synchrony at metamorphosis, indicating that timing of one stage can carry over to affect that of later ones. Importantly, these effects were all density dependent, likely because decreasing hatching synchrony switched intraspecific interactions from scramble to contest competition. This study demonstrates that phenological synchrony has important consequences for ecological interactions and population dynamics, emphasizing the need to develop a comprehensive understanding of how shifts in phenological distributions affect communities.
A Compositional Model for CO2 Floods Including CO2 Solubility in Water
Authors: Chang Yih-Bor , Coats Brian K. , Nolen James S.
Published: April 2015

Abstracts

This paper presents a three-dimensional, three-phase compositional model for simulating CO2 flooding including C02 solubility in water. Both fully implicit and IMPES formulations are included. In this model, C02 is allowed to dissolve in the aqueous phase while all other components except water exist in the oil and gas phases. Oil- and gas-phase densities and fugacities are modeled by a cubic equation of state. The aqueous phase properties are functions of the amount of dissolved C02. C02 solubility is computed using a C02 fugacity coefficient table that is converted internally from input C02 solubility data as a function of pressure at reservoir temperature. Correlations for computing the solubility of C02 in water and other properties of C02 saturated water are presented. Results for simulation runs with and without C02 solubility in water are shown for comparison.
Closing the Divide between Human Nutrition and Plant Breeding
Authors: Diepenbrock Christine H. , Gore Michael A.
Published: April 2015

Improvement of crop nutritional quality through breeding, termed biofortification, is a strategy being used to address micronutrient deficiencies worldwide. These efforts stand to benefit tremendously from recent advances across the plant sciences, from flourishing germplasm and genomic resources and phenotyping tools to improved characterization at the levels of physiology, cell biology, and gene expression. Next steps in crop biofortification in this decade and beyond include adapting high‐throughput phenotyping platforms for measurement of nutritional quality traits, testing genome‐wide and other DNA marker‐based selection strategies that can mine parsimonious answers from large data sets, and further characterizing genotype × environment interactions and post‐harvest effects on end nutrition. Also necessary are accompanying considerations of yield and other agronomic traits—in particular, the non‐uniform responses of both these and quality traits to climate change across crops, environments, and farming management systems. These integrative analyses from genotype to phenotype and planting to consumption can minimize trade‐offs between yield and nutrition and maximize the range, magnitude, and longevity of the benefits of biofortified varieties to human health and nutrition.
Whistleblowing in Audit Firms: Do Explicit Protections from Retaliation Activate Implicit Threats of Reprisal?
Authors: Wainberg James , Perreault Stephen
Published: April 2015

Despite the increasing number of statutory protections now provided to whistleblowers, fear of reprisal remains a primary reason why individuals fail to report misconduct. In order to alleviate such fears and encourage reporting, hotline policies often describe explicit whistleblower protections from specific types of retaliation (e.g., harassment, threats or intimidation, loss of job, etc.). However, we posit that such vivid descriptions may actually achieve the opposite of their intended effect by increasing the salience of retaliatory threats, thereby discouraging whistleblower reporting. We conduct an experiment and find evidence that when explicit protections are added to an audit firm's whistleblower hotline policy, auditors assess the risk of reporting as higher and, as a result, are less likely to indicate that the misconduct will be reported through the hotline. To our knowledge, our study is the first to demonstrate that offering explicit protections to whistleblowers can have these unintended and counter-intuitive consequences.
Discordance Between Distance Ambulated as Part of Usual Care and Functional Exercise Capacity in Survivors of Critical Illness Upon Intensive Care Discharge: Observational Study
Authors: Waters Angela , Hill Kylie , Jenkins Sue , Johnston Catherine , Mackney Jennifer
Published: April 2015

Background

People who have had a prolonged admission to an intensive care unit (ICU) commonly have profound debilitation and weakness. For the delivery of effective exercise training, an accurate assessment of exercise capacity is essential.

Objective

The study objectives were to investigate how much ground-based walking is undertaken by inpatients recovering from critical illness within 1 week of discharge from an ICU and to evaluate the feasibility and safety of the Six-Minute Walk Test (6MWT) for this population.

Design

This was an observational study.

Methods

Within 1 week of discharge from the ICU, functional exercise capacity was measured with the 6MWT. The maximum distance ambulated on the ward in a single session as part of usual clinical management was extracted from the medical notes. The distance achieved during the 6MWT and the maximum distance ambulated on the ward were compared.

Results

The participants (N=23) were survivors of a critical illness; their mean age was 57 years (SD=11). The median length of ICU stay was 11 days (interquartile range [IQR]=7). The mean 6-minute walk distance (6MWD) was 179 m (SD=101), and the maximum distance ambulated on the ward was 30 m (IQR=65). There was a moderate association between the distance participants ambulated on the ward and the 6MWD (r=.54). The maximum distance ambulated on the ward, expressed as a percentage of the 6MWD, was 29% (IQR=34%). Five participants (22%) experienced oxygen desaturation (oxygen saturation of <85%) and recovered within 1 minute of resting.

Limitations

The maximum distance ambulated on the ward was estimated with premeasured distances.

Conclusions

Most participants ambulated at a low percentage of their measured exercise capacity. The 6MWT appears to be a safe and useful test for inpatients recently discharged from the ICU.
Lester J. Cappon and the Publishing of Modern Documentary Editions
Authors: Cox Richard J.
Published: April 2015

Documentary editing is a well-developed field connected to the historical and archival professions. It was not always so well established, as a study of Lester J. Cappon's career suggests. Between his work at the Institute of Early American History and Culture starting in the 1950s and his final years as a fellow at the Newberry Library, Cappon played an important role in nurturing documentary editing as a profession.
Multiple Pie Charts: Unreadable, Inefficient, and Over-Used
Authors: Kozak Marcin , Hartley James , Wnuk Agnieszka , Tartanus Małgorzata
Published: April 2015

A pie chart is a common way of presenting simple statistics—for example, the amount of time devoted to teaching, researching, and administration by the faculty can be illustrated by dividing a circle (‘pie’) into three appropriately sized segments. There has been much discussion about the strengths and weaknesses of such pie charts for a long time, and it is not likely to end soon. 3D pie charts show the same statistics, but in three dimensions. Multiple pie charts can be found where the data for groups to be compared are presented in adjacent pies. Here we argue that, even if a simple pie chart may have some advantages, the same cannot be said for multiple pie charts. Multiple pie charts are difficult to analyze and interpret, especially when comparing adjacent pies.
Utility of dynamic computed tomography angiography in the preoperative evaluation of skull base tumors
Authors: Bi Wenya Linda , Brown Patrick A. , Abolfotoh Mohammad , Al-Mefty Ossama , Mukundan Srinivasan , Dunn Ian F.
Published: April 2015

OBJECT

The anatomical complexity of skull base tumors mandates detailed preoperative planning for safe resection. In particular, the location of critical vascular and bony structures can influence the surgical approach. Traditional methods, such as MRI, MR angiography and/or venography (MRA/MRV), CT angiography and/or venography (CTA/CTV), and digital subtraction angiography, each have their limitations. One alternative that combines the benefits of both detailed anatomy compatible with intraoperative image guidance and visualization of the vascular flow is the 320–detector row dynamic volume CTA/CTV. The authors investigated this technique’s impact on the surgical approach used in a series of complex intracranial tumors.

METHODS

All patients with complex intracranial tumors who had undergone preoperative dynamic CTA/CTV as well as MRI in the period from July 2010 to June 2012 were retrospectively reviewed. Those in whom only routine CTA/CTV sequences had been obtained were excluded. Clinical records, including imaging studies, operative reports, and hospital course, were reviewed. Ease in detecting specific major arterial and venous tributaries using dynamic CTA/CTV was graded for each case. Furthermore, 2 skull base neurosurgeons projected a desired surgical approach for each tumor based on MRI studies, independent of the CTA/CTV sequences. The projected approach was then compared with the ultimately chosen surgical approach to determine whether preoperative awareness of vasculature patterns altered the actual operative approach.

RESULTS

Sixty-four patients were eligible for analysis. Dynamic CTA/CTV successfully demonstrated circle of Willis arteries, major draining sinuses, and deep internal venous drainage in all cases examined. The superior petrosal sinus, vein of Labbé, tentorial veins, and middle fossa veins were also identified in a majority of cases, which played an important role in preoperative planning. Visualization of critical vascular—especially venous—anatomy influenced the surgical approach in 39% (25 of 64) of the cases.

CONCLUSIONS

Dynamic CTA/CTV has been applied to few neurosurgical disease pathologies to date. This noninvasive technology offers insight into vascular flow patterns as well as 3D anatomical relationships and provides thin-cut sequences for intraoperative navigation. The authors propose dynamic CTA as an addition to the preoperative planning for complex skull base tumors.
Improvement in venous outflow following superior sagittal sinus decompression after a gunshot wound to the head: case report
Authors: Birk Daniel M. , Tobin Matthew K. , Moss Heather E. , Feinstein Eric , Charbel Fady T. , Alaraj Ali
Published: April 2015

The most commonly described indications for surgical management of closed depressed skull fractures are hematoma evacuation and repair of extensive cosmetic deformity. Venous sinus injury, which occurs in a subset of depressed skull fractures, is not typically listed as an indication for surgical treatment due to the potential for major venous hemorrhage associated with surgery near these structures. However, if patients exhibit signs and symptoms of intracranial hypertension and radiographic findings demonstrate sinus compromise, surgical elevation of the depressed skull fragments is indicated. The authors present the case of a 25-year-old woman with a depressed skull fracture secondary to a gunshot wound with symptomatic compromise in venous outflow of the posterior one-third of the superior sagittal sinus. The patient was treated with surgical decompression via bilateral craniectomy along with intracranial pressure–lowering medical therapy and had almost full resolution of her presenting symptoms with documented improvement in flow through the superior sagittal sinus. While the use of surgical treatment for these types of injuries is highly debated, the authors demonstrate here that safe, effective surgical management of these patients is possible and that surgical decompression should always be considered in the case of symptomatic venous sinus flow obstruction.
Preparedness of neurosurgery graduates for neuroendovascular fellowship: a national survey of fellowship programs
Authors: Chalouhi Nohra , Zanaty Mario , Tjoumakaris Stavropoula , Manasseh Philip , Hasan David , Bulsara Ketan R. , Starke Robert M. , Lawson Kevin , Rosenwasser Robert , Jabbour Pascal
Published: April 2015

OBJECT

Endovascular interventions have become an essential part of a neurosurgeon’s practice. Whether endovascular procedures have been effectively integrated into residency curricula, however, remains uncertain. The purpose of this study was to assess the preparedness of US neurosurgery graduate trainees for neuroendovascular fellowship.

METHODS

A multidomain, global assessment survey was sent to all directors/faculty of neuroendovascular fellowship programs involved in training of US neurosurgery graduates. Surveyees were asked to assess trainees as they entered fellowship.

RESULTS

The response rate was 78% (25/32). Of respondent program directors, 38% reported that new fellows did not know the history and imaging of the patient and 50% were unable to formulate an appropriate treatment plan. As many as 79% of fellows were unfamiliar with endovascular devices and 75% were unfamiliar with angiographic equipment. Furthermore, 58% of fellows were unable to perform femoral access, 54% were unable to perform femoral closure, 79% were unable to catheterize a major vessel, 86% were unable to perform a 4-vessel angiogram, and 100% were unable to catheterize an aneurysm. Additionally, program directors reported that over 50% of fellows could not recognize neurovascular anatomy and 54% could not recognize/classify vascular abnormalities. There was an overall agreement that fellows demonstrated professionalism and interest in research and had good communication/clinical skills.

CONCLUSIONS

The results of this study suggest potential gaps in the training of neurosurgery residents with regard to endovascular neurosurgery. In an era of minimally invasive therapies, changes in residency curricula may be needed to keep pace with the ever-changing field of neurosurgery.
The predictive value of magnetic resonance imaging in evaluating intracranial arteriovenous malformation obliteration after stereotactic radiosurgery
Authors: Lee Cheng-Chia , Reardon Michael A. , Ball Benjamin Z. , Chen Ching-Jen , Yen Chun-Po , Xu Zhiyuan , Wintermark Max , Sheehan Jason
Published: April 2015

OBJECT

The current gold standard for diagnosing arteriovenous malformation (AVM) and assessing its obliteration after stereotactic radiosurgery (SRS) is digital subtraction angiography (DSA). Recently, MRI and MR angiography (MRA) have become increasingly popular imaging modalities for the follow-up of patients with an AVM because of their convenient setup and noninvasiveness. In this study, the authors assessed the sensitivity and specificity of MRI/MRA in evaluating AVM nidus obliteration as assessed by DSA.

METHODS

The authors study a consecutive series of 136 patients who underwent SRS between January 2000 and December 2012 and who underwent regular clinical examinations, several MRI studies, and at least 1 post-SRS DSA follow- up evaluation at the University of Virginia. The average follow-up time was 47.3 months (range 10.1–165.2 months). Two blinded observers were enrolled to interpret the results of MRI/MRA compared with those of DSA. The sensitivity, specificity, positive predictive value, and negative predictive value for the obliteration of AVM were reported.

RESULTS

On the basis of DSA, 73 patients (53.7%) achieved final angiographic obliteration in a median of 28.8 months. The sensitivity (the probability of finding obliteration on MRI/MRA among those for whom complete obliteration was shown on DSA) was 84.9% for one observer (Observer 1) and 76.7% for the other (Observer 2). The specificity was 88.9% and 95.2%, respectively. The false-negative interpretations were significantly related to the presence of draining veins, perinidal edema on T2-weighted images, and the interval between the MRI/MRA and DSA studies.

CONCLUSIONS

MRI/MRA predicted AVM obliteration after SRS in most patients and can be used in their follow-up. However, because the specificity of MRI/MRA is not perfect, DSA should still be performed to confirm AVM nidus obliteration after SRS.
Endoscopic endonasal transsphenoidal surgery in elderly patients with pituitary adenomas
Authors: Gondim Jackson A. , Almeida João Paulo , de Albuquerque Lucas Alverne F. , Gomes Erika , Schops Michele , Mota Jose Italo
Published: April 2015

OBJECT

With the increase in the average life expectancy, medical care of elderly patients with symptomatic pituitary adenoma (PA) will continue to grow. Little information exists in the literature about the surgical treatment of these patients. The aim of this study was to present the results of a single pituitary center in the surgical treatment of PAs in patients > 70 years of age.

METHODS

In this retrospective study, 55 consecutive elderly patients (age ≥ 70 years) with nonfunctioning PAs underwent endoscopic transsphenoidal surgery at the General Hospital of Fortaleza, Brazil, between May 2000 and December 2012. The clinical and radiological results in this group were compared with 2 groups of younger patients: < 60 years (n = 289) and 60–69 years old (n = 30).

RESULTS

Fifty-five patients ≥ 70 years of age (average age 72.5 years, range 70–84 years) underwent endoscopic surgery for treatment of PAs. The mean follow-up period was 50 months (range 12–144 months). The most common symptoms were visual impairment in 38 (69%) patients, headache in 16 (29%) patients, and complete ophthalmoplegia in 6 (10.9%). Elderly patients presented a higher incidence of ophthalmoplegia (p = 0.032) and a lower frequency of pituitary apoplexy before surgery (p < 0.05). Tumors with cavernous sinus invasion were treated surgically less frequently than in younger patients. Although patients with an American Society of Anesthesiologists score of 3 were more common in the elderly group (p < 0.05), no significant difference regarding surgical time, extent of resection, and hospitalization were observed. Elderly patients presented with more complications than patients < 60 years (32.7% vs 10%, p < 0.05). Complications observed in the elderly group included 5 CSF leaks (9%), 2 permanent diabetes insipidus cases (3.6%), 4 postoperative refractory hypertension cases (7.2%), 1 myocardial ischemia (1.8%), and 1 death (1.8%). Postoperative new anterior pituitary deficit was more common in the younger group (< 60 years old: 17.7%) than in the elderly (≥ 70 years old: 12.7%); however, there was no statistical difference.

CONCLUSIONS

Endoscopic transsphenoidal surgery for elderly patients with PAs may be associated with higher complication rates, especially secondary to early transitory complications, when compared with surgery performed in younger patients. Although the worst preoperative clinical status might be observed in this group, age alone is not associated with a worst final prognosis after endoscopic removal of nonfunctioning PAs.
Unplanned reoperation after lumbopelvic fixation with S-2 alar-iliac screws or iliac bolts
Authors: Mazur Marcus D. , Ravindra Vijay M. , Schmidt Meic H. , Brodke Darrel S. , Lawrence Brandon D. , Riva-Cambrin Jay , Dailey Andrew T.
Published: April 2015

OBJECT

S-2 alar-iliac (S2AI) screws are an attractive alternative to conventional fixation with iliac bolts because they are lower profile, require less muscle dissection, and have greater pullout strength. Few studies, however, compare outcomes between these techniques.

METHODS

The authors conducted a retrospective cohort study of consecutive adult patients at a single institution from December 2009 to March 2012 who underwent lumbopelvic fixation using S2AI screws or iliac bolts. Medical records were reviewed for patients with clinical failure, defined as an unplanned reoperation because of instrumentation failure and/or wound-related complications. Univariate, multivariate, and survival analyses were used to compare patients who required reoperation with those who did not. Method of pelvic fixation was the main predictor variable of interest, and the authors adjusted for potential confounding risk factors.

RESULTS

Of the 60 patients included, 23 received S2AI screws. Seventeen patients (28%) underwent an osteotomy. The mean follow-up was 22 months. A Kaplan-Meier survival model was used to evaluate the time to reoperation from the initial placement of lumbopelvic instrumentation. The failure-free rate was 96.6% at 6 months, 87.0% at 1 year, and 73.5% at 2 years. Reoperation was more common in patients with iliac bolts than in those with S2AI screws (13 vs 2; p = 0.031). Univariate analysis identified potential risk factors for unplanned reoperation, including use of iliac bolts (p = 0.031), absence of L5–S1 interbody graft (p = 0.048), previous lumbar fusion (p = 0.034), and pathology other than degenerative disease or scoliosis (p = 0.034). After adjusting for other risk factors, multivariate analysis revealed that the use of S2AI screws (OR 8.1 [1.5–73.5]; p = 0.030) was the only independent predictor for preventing unplanned reoperation.

CONCLUSIONS

Both S2AI screws and iliac bolts were effective at improving fusion rates at the lumbosacral junction. The use of S2AI screws, however, was independently associated with fewer unplanned reoperations for wound-related complications and instrumentation failures than the use of iliac bolts.
Syrinx location and size according to etiology: identification of Chiari-associated syrinx
Authors: Strahle Jennifer , Muraszko Karin M. , Garton Hugh J. L. , Smith Brandon W. , Starr Jordan , Kapurch Joseph R. , Maher Cormac O.
Published: April 2015

OBJECT

Syrinx size and location within the spinal cord may differ based on etiology or associated conditions of the brain and spine. These differences have not been clearly defined.

METHODS

All patients with a syrinx were identified from 14,118 patients undergoing brain or cervical spine imaging at a single institution over an 11-year interval. Syrinx width, length, and location in the spinal cord were recorded. Patients were grouped according to associated brain and spine conditions including Chiari malformation Type I (CM-I), secondary CM (2°CM), Chiari malformation Type 0 (CM-0), tethered cord, other closed dysraphism, and spinal tumors. Syringes not associated with any known brain or spinal cord condition were considered idiopathic. Syrinx characteristics were compared between groups.

RESULTS

A total of 271 patients with a syrinx were identified. The most common associated condition was CM-I (occurring in 117 patients [43.2%]), followed by spinal dysraphism (20 [7.4%]), tumor (15 [5.5%]), and tethered cord (13 [4.8%]). Eighty-three patients (30.6%) did not have any associated condition of the brain or spinal cord and their syringes were considered idiopathic. Syringes in patients with CM-I were wide (7.8 ± 3.9 mm) compared with idiopathic syringes (3.9 ± 1.0, p < 0.0001) and those associated with tethered cord (4.2 ± 0.9, p < 0.01). When considering CM-I–associated and idiopathic syringes, the authors found that CM-I–associated syringes were more likely to have their cranial extent in the cervical spine (88%), compared with idiopathic syringes (43%; p < 0.0001). The combination of syrinx width greater than 5 mm and cranial extent in the cervical spine had 99% specificity (95% CI 0.92–0.99) for CM-I–associated syrinx.

CONCLUSIONS

Syrinx morphology differs according to syrinx etiology. The combination of width greater than 5 mm and cranial extent in the cervical spine is highly specific for CM-I–associated syringes. This may have relevance when determining the clinical significance of syringes in patients with low cerebellar tonsil position.
Congenital neurocristic tumor presenting as an isolated calvarial defect in an infant: case report
Authors: Hadley Caroline , Mohila Carrie A. , Luerssen Thomas G. , Lam Sandi
Published: April 2015

In infants, the presence of a cranial defect may be due to a variety of traumatic, inflammatory, neoplastic, and congenital abnormalities. Differentiation between these possible etiologies is facilitated by clinical presentation, patient history, and physical examination. Congenital cutaneous neural crest–derived lesions are unlikely to be considered in a patient presenting with an asymptomatic cranial defect without overlying mass or skin pigmentation. The authors present an unusual case of a 2-month-old infant with an asymptomatic calvarial defect with normal overlying skin. Pathology of the excised tissue showed features consistent with a congenital neurocristic tumor: a pigmented, neural crest–derived hamartomatous tumor that typically presents as a melanotic skin lesion.
Encephaloduroarteriosynangiosis and encephalomyoarteriosynangiosis for treatment of moyamoya syndrome in pediatric patients with sickle cell disease
Authors: Griessenauer Christoph J. , Lebensburger Jeffrey D. , Chua Michelle H. , Fisher Winfield S. , Hilliard Lee , Bemrich-Stolz Christina J. , Howard Thomas H. , Johnston James M.
Published: April 2015

OBJECT

Pediatric patients with sickle cell disease (SCD) and moyamoya syndrome (MMS) are at significant risk for cerebrovascular accidents despite chronic transfusion therapy. Encephaloduroarteriosynangiosis (EDAS) and encephalomyoarteriosynangiosis (EMAS) are additional therapeutic options for these patients. To date, the incidence of complications after and efficacy of EDAS and EMAS in stroke prevention in this population have been described in several institutional case series reports, but no randomized prospective trials have been reported.

METHODS

The authors retrospectively reviewed the cases of all pediatric patients at the University of Alabama at Birmingham with a history of homozygous hemoglobin S (HbS) and sickle cell/β-thalassemia (SB0 thalassemia) and on chronic transfusion therapy, including 14 patients with MMS who underwent EDAS or EMAS.

RESULTS

Sixty-two patients with SCD and on chronic transfusion therapy were identified. After exclusion of patients on chronic transfusion therapy for indications other than stroke prevention, 48 patients (77.4%) remained. Of those patients, 14 (29.1%) underwent EDAS or EMAS. Nine (18.8%) and 25 (52.1%) patients were on chronic transfusion therapy for primary or secondary stroke prevention, respectively, but did not undergo EDAS or EMAS. The 14 patients with SCD and radiological evidence of MMS and on chronic transfusion therapy for primary or secondary stroke prevention underwent 21 EDAS or EMAS procedures for progressive vascular disease (92.9% of patients), stroke (71.4%), and/or seizure (7.1%). The mean (± SD) time from initiation of chronic transfusion therapy to EDAS or EMAS was 76.8 ± 58.8 months. Complications included 1 perioperative stroke, 1 symptomatic subdural hygroma, 1 postoperative seizure, and 1 case of intraoperative cerebral edema that required subsequent cranioplasty. Before EDAS or EMAS, the stroke rate was calculated to be 1 stroke per 7.8 patient-years. One additional stroke occurred during the follow-up period (mean follow-up time 33.7 ± 19.6 months), resulting in a post-EDAS/EMAS stroke rate of 1 stroke per 39.3 patient-years, a 5-fold reduction compared with that in the pre-EDAS/EMAS period. The patients’ mean pre-EDAS/EMAS HbS level of 29.5% ± 6.4% was comparable to the mean post-EDAS/EMAS HbS level of 25.5% ± 6.1% (p = 0.104).

CONCLUSIONS

The results of this retrospective case series in a large cohort of pediatric patients with SCD and MMS suggest that EDAS/EMAS provides a stroke-prevention benefit with an acceptably low morbidity rate. Given the combined experience with EDAS and EMAS for this indication at this and other institutions, a prospective clinical trial to assess their efficacy compared with that of chronic transfusion therapy alone is warranted.
Development and characterization of EST‐SSR markers in Bombax ceiba (Malvaceae)
Authors: Ju Miao‐Miao , Ma Huan‐Cheng , Xin Pei‐Yao , Zhou Zhi‐Li , Tian Bin
Published: April 2015

Premise of the study:

Bombax ceiba (Malvaceae), commonly known as silk cotton tree, is a multipurpose tree species of tropical forests. Novel expressed sequence tag–simple sequence repeat (EST‐SSR) markers were developed and characterized for the species using transcriptome analysis.

Methods and Results:

A total of 33 new EST‐SSR markers were developed for B. ceiba, of which 13 showed polymorphisms across the 24 individuals from four distant populations tested in the study. The results showed that the number of alleles per polymorphic locus ranged from two to four, and the expected heterozygosity and observed heterozygosity per locus varied from 0.043 to 0.654 and from 0 to 0.609, respectively.

Conclusions:

These newly developed EST‐SSR markers can be used in phylogeographic and population genetic studies to investigate the origin of B. ceiba populations. Furthermore, these EST‐SSR markers could also greatly promote the development of molecular breeding studies pertaining to silk cotton tree.
Une Europe des jungles
Authors: Wannesson Philippe
Published: April 2015

L’Europe se barricade derrière des frontières rendues toujours plus infranchissables. Ces barrières n’ont jamais dissuadé les migrant·e·s de poursuivre leur parcours migratoire. Reste qu’aux points de blocage, des jungles se forment à la périphérie des villes, qui rendent visibles la présence de ces exilé·e·s en attente de passage. Et partout en Europe, elles suscitent les mêmes réactions.
Muscle microvascular adaptation and angiogenic gene induction in response to exercise training are attenuated in middle-aged rats
Authors: Suzuki J.
Published: April 2015

This study was designed to investigate exercise-induced changes in muscle capillarisation, the mRNA expression of angiogenic genes, and microRNA levels in young and middle-aged rats. Rats in the training groups were subjected to treadmill running 5 days a week for 3 weeks. The exercise protocol for the young (12-week old) group was 20-25 m/min, 40-60 min/day with a gradient of 15%, and for the middle-aged (12-month old) group was 18-20 m/min, 40-60 min/day with a gradient of 5%. The enzyme histochemical identification of capillary profiles was performed on cross-sections of gastrocnemius muscle. Total RNA was isolated, reverse transcription was performed, and mRNA and microRNA levels were determined by real-time PCR. The capillary-to-fibre ratio was significantly increased by exercise training in the young group (by 10%), but only slightly in the middle-aged (by 5%) group. Vascular endothecial growth factor (VEGF) mRNA levels were at significantly higher values after acute exercise (1.6-fold) and the 3-week training protocol (1.9-fold) in the young group, but not in the middle-aged group. VEGF protein expression levels were significantly increased after training in the young group only. Endothelial nitric oxide synthase, VEGF-R2 and thrombospondin-1 mRNA levels were significantly lower in the middle-aged group than in the young group. Anti-angiogenic miR-195 levels were significantly enhanced by exercise training in the middle-aged group only. These results indicated that the exercise-induced adaptation of muscle capillarity was attenuated in middle-aged rats, possibly by the lower induction of VEGF and up-regulation of anti-angiogenic miRNA expression.