bluuebunny/crossref_metadata_2025 huggingface dataset:
Modeling photosynthesis of discontinuous plant canopies by linking the Geometric Optical Radiative Transfer model with biochemical processes
Authors: Xin Q. , Gong P. , Li W.
Published: June 2015

Abstract. Modeling vegetation photosynthesis is essential for understanding carbon exchanges between terrestrial ecosystems and the atmosphere. The radiative transfer process within plant canopies is one of the key drivers that regulate canopy photosynthesis. Most vegetation cover consists of discrete plant crowns, of which the physical observation departs from the underlying assumption of a homogenous and uniform medium in classic radiative transfer theory. Here we advance the Geometric Optical Radiative Transfer (GORT) model to simulate photosynthesis activities for discontinuous plant canopies. We separate radiation absorption into two components that are absorbed by sunlit and shaded leaves, and derive analytical solutions by integrating over the canopy layer. To model leaf-level and canopy-level photosynthesis, leaf light absorption is then linked to the biochemical process of gas diffusion through leaf stomata. The canopy gap probability derived from GORT differs from classic radiative transfer theory, especially when the leaf area index is high, due to leaf clumping effects. Tree characteristics such as tree density, crown shape, and canopy length affect leaf clumping and regulate radiation interception. Modeled gross primary production (GPP) for two deciduous forest stands could explain more than 80% of the variance of flux tower measurements at both near hourly and daily timescales. We demonstrate that ambient CO2 concentrations influence daytime vegetation photosynthesis, which needs to be considered in biogeochemical models. The proposed model is complementary to classic radiative transfer theory and shows promise in modeling the radiative transfer process and photosynthetic activities over discontinuous forest canopies.
Observation-based modelling of permafrost carbon fluxes with accounting for deep carbon deposits and thermokarst activity
Authors: Schneider von Deimling T. , Grosse G. , Strauss J. , Schirrmeister L. , Morgenstern A. , Schaphoff S. , Meinshausen M. , Boike J.
Published: June 2015

Abstract. High-latitude soils store vast amounts of perennially frozen and therefore inert organic matter. With rising global temperatures and consequent permafrost degradation, a part of this carbon stock will become available for microbial decay and eventual release to the atmosphere. We have developed a simplified, two-dimensional multi-pool model to estimate the strength and timing of future carbon dioxide (CO2) and methane (CH4) fluxes from newly thawed permafrost carbon (i.e. carbon thawed when temperatures rise above pre-industrial levels). We have especially simulated carbon release from deep deposits in Yedoma regions by describing abrupt thaw under newly formed thermokarst lakes. The computational efficiency of our model allowed us to run large, multi-centennial ensembles under various scenarios of future warming to express uncertainty inherent to simulations of the permafrost carbon feedback. Under moderate warming of the representative concentration pathway (RCP) 2.6 scenario, cumulated CO2 fluxes from newly thawed permafrost carbon amount to 20 to 58 petagrams of carbon (Pg-C) (68% range) by the year 2100 and reach 40 to 98 Pg-C in 2300. The much larger permafrost degradation under strong warming (RCP8.5) results in cumulated CO2 release of 42 to 141 Pg-C and 157 to 313 Pg-C (68% ranges) in the years 2100 and 2300, respectively. Our estimates only consider fluxes from newly thawed permafrost, not from soils already part of the seasonally thawed active layer under pre-industrial climate. Our simulated CH4 fluxes contribute a few percent to total permafrost carbon release yet they can cause up to 40% of total permafrost-affected radiative forcing in the 21st century (upper 68% range). We infer largest CH4 emission rates of about 50 Tg-CH4 per year around the middle of the 21st century when simulated thermokarst lake extent is at its maximum and when abrupt thaw under thermokarst lakes is taken into account. CH4 release from newly thawed carbon in wetland-affected deposits is only discernible in the 22nd and 23rd century because of the absence of abrupt thaw processes. We further show that release from organic matter stored in deep deposits of Yedoma regions crucially affects our simulated circumpolar CH4 fluxes. The additional warming through the release from newly thawed permafrost carbon proved only slightly dependent on the pathway of anthropogenic emission and amounts to about 0.03–0.14 °C (68% ranges) by end of the century. The warming increased further in the 22nd and 23rd century and was most pronounced under the RCP6.0 scenario, adding 0.16 to 0.39 °C (68% range) to simulated global mean surface air temperatures in the year 2300.
Fate of peat-derived carbon and associated CO2 and CO emissions from two Southeast Asian estuaries
Authors: Müller D. , Warneke T. , Rixen T. , Müller M. , Mujahid A. , Bange H. W. , Notholt J.
Published: June 2015

Abstract. Coastal peatlands in Southeast Asia release large amounts of organic carbon to rivers, which transport it further to the adjacent estuaries. However, little is known about the fate of this terrestrial material in the coastal ocean. Although Southeast Asia is, by area, considered a hotspot of estuarine CO2 emissions, studies in this region are very scarce. We measured dissolved and particulate organic carbon, carbon dioxide (CO2) partial pressure and carbon monoxide (CO) concentrations in two tropical estuaries in Sarawak, Malaysia, whose coastal area is covered by peatlands. We surveyed the estuaries of the rivers Lupar and Saribas during the wet and dry season, respectively. The spatial distribution and the carbon-to-nitrogen ratios of dissolved organic matter (DOM) suggest that peat-draining rivers convey terrestrial organic carbon to the estuaries. We found evidence that a large fraction of this carbon is respired. The median pCO2 in the estuaries ranged between 618 and 5064 μatm with little seasonal variation. CO2 fluxes were determined with a floating chamber and estimated to amount to 14–272 mol m−2 yr−1, which is high compared to other studies from tropical and subtropical sites. In contrast, CO concentrations and fluxes were relatively moderate (0.3–1.4 nmol L−1 and 0.8–1.9 mmol m−2 yr−1) if compared to published data for oceanic or upwelling systems. We attributed this to the large amounts of suspended matter (4–5004 mg L−1), limiting the light penetration depth. However, the diurnal variation of CO suggests that it is photochemically produced, implying that photodegradation might play a role for the removal of DOM from the estuary as well. We concluded that unlike smaller peat-draining tributaries, which tend to transport most carbon downstream, estuaries in this region function as an efficient filter for organic carbon and release large amounts of CO2 to the atmosphere. The Lupar and Saribas mid-estuaries release 0.4 ± 0.2 Tg C yr−1, which corresponds to approximately 80% of the emissions from the aquatic systems in these two catchments.
New insights into the reconstructed temperature in Portugal over the last 400 years
Authors: Santos J. A. , Carneiro M. F. , Correia A. , Alcoforado M. J. , Zorita E. , Gómez-Navarro J. J.
Published: June 2015

Abstract. The consistency of an existing reconstructed annual (December–November) temperature series for the Lisbon region (Portugal) from 1600 onwards, based on a European-wide reconstruction, with (1) five local borehole temperature–depth profiles; (2) synthetic temperature–depth profiles, generated from both reconstructed temperatures and two regional paleoclimate simulations in Portugal; (3) instrumental data sources over the twentieth century; and (4) temperature indices from documentary sources during the late Maunder Minimum (1675–1715) is assessed. The low-frequency variability in the reconstructed temperature in Portugal is not entirely consistent with local borehole temperature–depth profiles and with the simulated response of temperature in two regional paleoclimate simulations driven by reconstructions of various climate forcings. Therefore, the existing reconstructed series is calibrated by adjusting its low-frequency variability to the simulations (first-stage adjustment). The annual reconstructed series is then calibrated in its location and scale parameters, using the instrumental series and a linear regression between them (second-stage adjustment). This calibrated series shows clear footprints of the Maunder and Dalton minima, commonly related to changes in solar activity and explosive volcanic eruptions, and a strong recent-past warming, commonly related to human-driven forcing. Lastly, it is also in overall agreement with annual temperature indices over the late Maunder Minimum in Portugal. The series resulting from this post-reconstruction adjustment can be of foremost relevance to improve the current understanding of the driving mechanisms of climate variability in Portugal.
Technical Note: Approximate solution of transient drawdown for constant-flux pumping at a partially penetrating well in a radial two-zone confined aquifer
Authors: Huang C.-S. , Yang S.-Y. , Yeh H.-D.
Published: June 2015

Abstract. An aquifer consisting of a skin zone and a formation zone is considered as a two-zone aquifer. Existing solutions for the problem of constant-flux pumping in a two-zone confined aquifer involve laborious calculation. This study develops a new approximate solution for the problem based on a mathematical model describing steady-state radial and vertical flows in a two-zone aquifer. Hydraulic parameters in these two zones can be different but are assumed homogeneous in each zone. A partially penetrating well may be treated as the Neumann condition with a known flux along the screened part and zero flux along the unscreened part. The aquifer domain is finite with an outer circle boundary treated as the Dirichlet condition. The steady-state drawdown solution of the model is derived by the finite Fourier cosine transform. Then, an approximate transient solution is developed by replacing the radius of the aquifer domain in the steady-state solution with an analytical expression for a dimensionless time-dependent radius of influence. The approximate solution is capable of predicting good temporal drawdown distributions over the whole pumping period except at the early stage. A quantitative criterion for the validity of neglecting the vertical flow due to a partially penetrating well is also provided. Conventional models considering radial flow without the vertical component for the constant-flux pumping have good accuracy if satisfying the criterion.
Long-term effects of climate and land cover change on freshwater provision in the tropical Andes
Authors: Molina A. , Vanacker V. , Brisson E. , Mora D. , Balthazar V.
Published: June 2015

Abstract. Andean headwater catchments play a pivotal role to supply fresh water for downstream water users. However, few long-term studies exist on the relative importance of climate change and direct anthropogenic perturbations on flow regimes. In this paper, we assess multi-decadal change in freshwater provision based on long time series (1974–2008) of hydrometeorological data and land cover reconstructions for a 282 km2 catchment located in the tropical Andes. Three main land cover change trajectories can be distinguished: (1) rapid decline of native vegetation in montane forest and páramo ecosystems in ~1/5 or 20% of the catchment area, (2) expansion of agricultural land by 14% of the catchment area, (3) afforestation of 12% of native páramo grasslands with exotic tree species in recent years. Given the strong temporal variability of precipitation and streamflow data related to El Niño–Southern Oscillation, we use empirical mode decomposition techniques to detrend the time series. The long-term increasing trend in rainfall is remarkably different from the observed changes in streamflow that exhibit a decreasing trend. Hence, observed changes in streamflow are not the result of long-term climate change but very likely result from direct anthropogenic disturbances after land cover change. Partial water budgets for montane cloud forest and páramo ecosystems suggest that the strongest changes in evaporative water losses are observed in páramo ecosystems, where progressive colonization and afforestation of high alpine grasslands leads to a strong increase in transpiration losses.
User requirements for the snow and land ice services – CryoLand
Authors: Malnes E. , Buanes A. , Nagler T. , Bippus G. , Gustafsson D. , Schiller C. , Metsämäki S. , Pulliainen J. , Luojus K. , Larsen H. E. , Solberg R. , Diamandi A. , Wiesmann A.
Published: June 2015

Abstract. CryoLand (2011–2015) is a project carried out within the 7th Framework of the European Commission aimed at developing downstream services for monitoring seasonal snow, glaciers and lake/river ice primarily based on satellite remote sensing. The services target private and public users from a wide variety of application areas, and aim to develop sustainable services after the project is completed. The project has performed a thorough user requirement survey in order to derive targeted requirements for the service and provide recommendations for the design and priorities of the service. In this paper we describe the methods used, the major findings in this user survey, and how we used the results to design and specify the CryoLand snow and land ice service. The user requirement analysis shows that a European operational snow and land ice service is required and that there exists developed cryosphere products that can meet the specific needs. The majority of the users were mainly interested not only in the snow services, but also the lake/river ice products and the glacier products were desired.
Los blogs como entornos virtuales de enseñanza y aprendizaje en Educación Superior
Authors: Molina Aventosa Pere , Valenciano Valcárcel Javier , Valencia-Peris Alexandra
Published: June 2015

En la actualidad, existe un interés pedagógico por transformar las tecnologías de la información y comunicación en tecnologías para el aprendizaje y el conocimiento. En este trabajo se presentan una serie de contribuciones didácticas asociadas al uso de blogs en la Educación Superior a partir de una experiencia de innovación educativa por proyectos llevada a cabo por un grupo de profesores universitarios entre los años 2009 y 2013. Tanto el profesorado como el alumnado participante en las asignaturas donde se ha puesto en práctica el edublog, lo verifican como un recurso útil para conformar entornos virtuales de enseñanza y aprendizaje gracias a las múltiples potencialidades que ofrece. Entre ellas se destacan: facilitar el acceso al conocimiento, promover una participación más activa y reflexiva en la construcción de los aprendizajes, amplificar la experiencia social del aprendizaje, proporcionar evidencias sobre el progreso de los estudiantes que ayuden a reorientar el proceso de enseñanza-aprendizaje y estimular el juicio crítico. No obstante, también se identifican problemas relacionados con la participación de los estudiantes y con la gestión de los edublogs por parte del profesorado.
Los mapas conceptuales interactivos como recursos didácticos en el ámbito universitario
Authors: Cabero Almenara Julio , Ballesteros Regaña Cristóbal , López Meneses Eloy
Published: June 2015

En esta investigación describimos las experiencias  desarrolladas en dos universidades andaluzas (Universidad de Sevilla y Pablo de Olavide) con la finalidad de experimentar y conocer las posibilidades de  los mapas conceptuales interactivos como recursos didácticos implementados a través de edublog. Entre las aportaciones más relevantes hay que destacar cómo su diseño y difusión (con la ayuda de las aplicaciones de software social: Mindomo y Blogger)  facilitó la participación activa de los estudiantes en la construcción de su propio y nuevo conocimiento mediante la selección, estructuración e interpretación de las principales características de los dos ámbitos conceptuales trabajados en cada universidad: las posibilidades y limitaciones de las TIC y los ámbitos de intervención del educador y trabajador social.
Las redes sociales aplicadas a la formación
Authors: Vázquez-Martínez Ana Isabel , Cabero-Almenara Julio
Published: June 2015

Abordamos en este artículo la importancia que las redes sociales presentan para su uso como recurso educativo. Relevancia que radica en la posibilidad de implementar nuevos recursos de aprendizaje o aumentar el nivel de conectividad de los participantes, así como el fomento de comunidades de aprendizaje. Igualmente se exponen los riesgos que su empleo entraña, sobre todo para los alumnos con una baja formación tecnológica o excesiva confianza en los medios. Es importante reseñar que el empleo educativo de las redes sociales, no es una simple extensión o traslación del uso para fines lúdicos que generalmente le dan los alumnos, sino que implica un importante cambio en los roles desempeñados tanto por docentes como discentes; de situaciones de aprendizaje acomodaticias y que fomentan la memorización a otras en las que se exige una actitud activa, reflexiva, colaborativa y proactiva, que además precisa del desarrollo/adquisición de habilidades, aptitudes y valores tanto tecnológicos como sociales. Y es destacable como con una implementación y uso adecuados se fomenta no solo el aprendizaje formal, sino también el informal y el no formal.
Academic peer pressure in social media: Experiences from the heavy, the targeted and the restricted user
Authors: Kieslinger Barbara
Published: June 2015

The degree of social media uptake in research practice differs greatly, across and within disciplines. This qualitative study explores the use of social media within a specific target group of researchers working in the field of technology-enhanced learning. The individual cases reveal a range from heavy use, leading to addiction, to very restricted or no use of social media. One of the main implications of social media penetration in academia is the emergence of peer pressure. People adopt different strategies and different digital identities to cope with the perceived pressure. Based on individual cases, this qualitative study gives insights into current transformation processes related to the scholarly uptake of social media and leads to the establishment of further challenging research questions.
The Role of Microfinance for Empowerment of Poor Women in Yemen
Authors: Alshebami Ali Saleh , Khandare D. M.
Published: June 2015

The objective of this paper is to identify the challenges facing the empowerment of women in Yemen. This paper is mainly based on the secondary data collected from the records of the Yemeni Government programmes viz., Social Fund for Development, Microfinance books, websites, official reports and other sources related to the research subject. The mentioned study covers the period from 1997 to 2013 and the area for the study is Yemen. The result of the study reported that there are multiple factors affecting the empowerment of women in Yemen through microfinance such as customs and traditions, high interest rate, financial literacy, wrong religious perceptions, demanded collaterals. However, despite the difficulties and challenges facing women empowerment in Yemen, it is believed that women who are connected to microfinance programs have been positively affected with their households in various aspects as many studies revealed that.
Variability of Different Reference Bodies in Normal, Keratoconus, and Collagen Crosslinked Corneas
Authors: Labiris Georgios , Giarmoukakis Athanassios , Rampotas Alexandros , Symeou Maria , Bougatsou Panagiota , Sideroudi Haris , Kozobolis Vassilios P.
Published: June 2015

Purpose

To evaluate the reproducibility of different Scheimpflug imaging–derived reference bodies in normal, keratoconus (KC), and crosslinked (CXL) eyes.

Methods

In this prospective, observational study, 40 participants populated the control group (CG), while 33 and 34 patients formed the KC group and the CXL group, respectively. One eye was randomly selected when both were eligible. Elevation measurements were obtained using Scheimpflug camera, by applying the following reference bodies: the best fit sphere (BFS), the best fit toric ellipsoid (BFTE), the best fit toric ellipsoid with fixed eccentricity of 0.4 (BFTEF), the best fit ellipsoid (BFE), and the best fit torus, by 2 operators in 2 sessions. The variability of different reference bodies’ parameters was assessed using intraclass correlation coefficient (ICC).

Results

Differences between operators were nonsignificant for all reference bodies’ parameters in all study groups (p>0.1). Regarding CG, BFS for both operators and BFTE for operator 1 presented the best intrasession repeatability (majority of ICCs >0.90), while average interobserver reliability was recorded for the majority of reference bodies’ parameters. Regarding KC and CXL groups, BFS, BFTEF, and BFE reference bodies demonstrated the best intrasession and interobserver reproducibility (majority of ICCs >0.90) for both groups. Steep and flat radius parameters presented the best overall reproducibility, with the majority of ICCs for all reference bodies ranging above 0.90, in all study groups.

Conclusions

High variability was encountered for most reference surfaces. Ellipsotoric surfaces presented acceptable repeatability in KC and post-CXL corneas.
Intravitreal Autologous Plasmin Prepared by Urokinase for Vitreolysis: A Pilot Study
Authors: Maleki Alireza , Tohidi-Zand Seyed-Reza , Amirizadeh Naser , Dehghan-Haghighi Javid , Zanjani Habibollah , Arish Mohammad , Salari Amir-Masoud , Mirhosseini Seyed Mohammad , Abrishami Mojtaba
Published: June 2015

Purpose

To evaluate the effects of intravitreal autologous plasmin injection (IVAP) on vitreoretinal diseases and vitreolysis.

Methods

In this interventional, prospective, case series pilot study, 8 eyes were assigned to IVAP. Plasminogen as centrifuged from the patients’ plasma was converted to plasmin by adding urokinase. A total of 0.2 mL extracted plasmin was injected intravitreally. Posterior vitreous detachment (PVD) and potential injection-related complications at week 4 were the primary outcome measures. Secondary outcomes included changes in best-corrected visual acuity (VA) (logMAR) and central macular thickness (CMT).

Results

Mean age of the patients was 54.35 years. Two patients had complete PVD and 3 patients had partial PVD. Four patients had decrease in CMT. The VA was not changed in 6 patients, improved in 1 patient, and decreased in 1 patient. No uveitis, endophthalmitis, or postinjection vitreous hemorrhage was observed.

Conclusions

This pilot study demonstrated the efficacy of urokinase-prepared IVAP injection on releasing vitreomacular traction and inducing vitreolysis.
Ranibizumab Prefilled Syringes: Benefits of Reduced Syringe Preparation Times and Less Complex Preparation Procedures
Authors: Souied Eric , Nghiem-Buffet Sylvia , Leteneux Claudia , Bayer Sascha , Derveloy Audrey , Sagkriotis Alexandros , Becker Guido , Cohen Salomon-Yves
Published: June 2015

Purpose

A recently developed ranibizumab prefilled syringe (PFS) eliminates several preparatory steps versus the standard vial-based method, and is expected to reduce syringe preparation time (SPT) and enhance procedural simplicity for intravitreal injections.

Methods

Syringe preparation times for the ranibizumab PFS and vial were recorded during standard treatment sessions at 2 centers, without randomization. The duration of each step in preparing the syringe was recorded. At each center, total SPT (mean total duration of all syringe preparation steps) for each method was compared using a 2-tailed t test.

Results

In total, 97 SPTs were analyzed across both centers. Center 1 SPTs were 46 seconds (PFS) versus 75 seconds (vial; difference, 29 seconds; p<0.001). Center 2 SPTs were 46 seconds (PFS) versus 63 seconds (vial; difference, 17 seconds; p<0.001). This equates to a 27%-39% reduction in SPT when using the PFS rather than the vial, resulting mostly from the reduced number of syringe preparation steps associated with the PFS.

Conclusions

Syringe preparation times for ranibizumab intravitreal injections are significantly shorter with the PFS than with the vial. The time saved by using the PFS may benefit physicians and nurses, and the simplicity of the injection preparation process with the PFS is advantageous.
Foveal Pit Morphology Evaluation during Optical Biometry Measurements using a Full-Eye-Length Swept-Source OCT Scan Biometer Prototype
Authors: Bertelmann Thomas , Blum Marcus , Kunert Kathleen , Haigis Wolfgang , Messerschmidt-Roth Anke , Peter Monika , Buehren Tobias , Sekundo Walter
Published: June 2015

Purpose

To assess the scan quality of foveal pit morphology (FPM) and to quantify central retinal thickness (CRT) during routine optical biometry measurements with a full-eye-length swept-source optical coherence tomography (SS-OCT) scan biometer prototype (IOLMaster700) and to compare these results with standard examinations using spectral-domain optical coherence tomography (SD-OCT) technique (Cirrus4000 SD-OCT).

Methods

As part of a SS-OCT scan protocol to measure biometric parameters for intraocular lens power calculation, central horizontal 1 mm retinal B scans were taken from phakic (group I) and pseudophakic (group II) nonvitrectomized eyes. To evaluate FPM, macular scans of either examination technique were subjectively analyzed and compared. Repeated CRT measurements were performed to analyze repeatability and consistency of IOLMaster700 recordings. These results were compared with CRT evaluations using SD-OCT.

Results

Overall, 146 eyes of 146 patients were included in this series. The subjective assessments of FPM are illustrated. Repeated CRT measurements (repeatability) with the IOLMaster700 disclosed an overall intraclass correlation of 0.57 (group I: 0.48; group II: 0.89). Overall coefficient of variation (accuracy) was calculated to be 12.43% (group I: 14.21%; group II: 5.66%). The comparison of CRT measurements between both devices showed significant differences in group I (p = 0.006).

Conclusions

Compared with SD-OCT, resolution of the 1 mm retinal B scan of SS-OCT scan biometry was lower. However, advanced pathologic characteristics were clearly discernible. Repeatability and accuracy of CRT measurements were acceptable though lower than with the standard SD-OCT technique. The CRT differed significantly in eyes of particular interest (group I) between both devices. The new scan could provide useful information for subsequent patient examination and further treatment planning for cataract surgery.
The Seasonality of Slipped Upper Femoral Epiphysis - Meta-Analysis: A Possible Association with Vitamin D
Authors: Farrier Adam J. , Ihediwa Ugwunna , Khan Shoaib , Kumar Ameet , Gulati Vivek , Uzoigwe Chika E. , Choudhury Muhammed Z.
Published: June 2015

We performed a meta-analysis of studies evaluating the seasonality of slipped upper femoral epiphysis (SUFE). In addition we compared the monthly incidences of SUFE at latitudes greater than 40° with the established serum 25-hydroxyvitamin levels for children resident at a comparative latitude.

In total 11 relevant studies were identified, involving 7451 cases of SUFE. There was significant variation in the month of onset of SUFE. The degree of variability increased with increasing latitude. The modal month of symptomatic onset was dependent upon latitude. At latitudes greater than 40°, the most common month of onset was August. At latitudes between 20° and 40°, this was earlier in the calendar year, around April. The seasonal variability was statistically significant (p<0.0001 and p<0.005 for latitudes >40° and 20°-40° respectively).

The pattern of monthly fluctuation in onset of SUFE very closely mirrored the monthly pattern of variation for serum 25-hydroxyvitamin D3. There was a very strong positive correlation (Spearman rank rho = + 0.8, p = 0.001). There is a monthly variation in incidence of SUFE. The degree of variability increases with increasing latitude. There may be an association with vitamin D. We hypothesise that elevated serum 25-hydroxyvitamin D3 accelerates growth thus rendering the growth plate vulnerable to slippage in analogous manner to the pubertal growth spurt.
Fixation of a Fractured Femoral Head through a Medial Hip Approach: An Original Approach to the Femoral Head
Authors: Cavaignac Etienne , Laumond Grégoire , Régis Pailhé , Murgier Jérôme , Reina Nicolas , Chiron Philippe
Published: June 2015

The decision to treat a femoral head fracture conservatively or surgically is the subject of ongoing debate. Several surgical approaches have been proposed for the open reduction and internal fixation of femoral head fractures. To our knowledge, fixation through a minimally invasive medial approach has not been described until now. The novel medial hip approach passes between the adductor muscle bellies posteriorly and their aponeuroses anteriorly. It provides direct access to the fracture site and allows for fixation by compression, without needing to dislocate the hip or detach the muscles. Any loose bodies in the joint that cannot be fixed can also be removed during the procedure. These features make the medial hip approach a clinically-relevant treatment option for the surgical management of femoral head fractures.
Preoperative Predictors of Outcome in the Arthroscopic Treatment of Femoroacetabular Impingement
Authors: Nabavi Arash , Olwill Caroline M. , Harris Ian A.
Published: June 2015

Aims

The aim of this study was to establish preoperative factors associated with a good outcome in the surgical treatment of femoroacetabular impingement.

Methods

A prospective study including 253 consecutive patients (280 hips) was carried out. We defined a “good” score as one which had either a 20 point improvement from preoperative to 12 months postoperative follow-up, or a score of over 80 points at 12-month follow-up in either the Non Arthritic Hip Score (NAHS) or Modified Harris Hip Score (MHHS). We analysed 9 potential predictors of 12-month postoperative outcome: patient age, gender, BMI, surgery type (primary/revision), preoperative anxiety level, preoperative labro-chondral damage, operative side, patients belonging to the armed forces and patients being treated under the workers compensation scheme. We used logistic regression (multivariable, adjusted) and, Fisher's exact test and student t test (bivariate, unadjusted) to analyse the data.

Results

A strong association between workers’ compensation status and not achieving a good outcome following arthroscopic surgery for femoroacetabular impingement (odds ratio 3.84, 95% CI, 0.13-0.51, P<0.0001) was found. A negative effect on postoperative outcome was also observed with increased BMI, although this association was modest (odds ratio 1.06, 95% CI, 0.87-0.99 p = 0.03). Patients with a higher preoperative score did better at 12 months than the rest of the cohort.

Conclusions

The data from this study may be useful for both patient and physician to consider when deciding on a suitable treatment in potential surgical candidates suffering from femoroacetabular impingement.
Diagnosis of Infected Total Hip Arthroplasty
Authors: Enayatollahi Mohammad A. , Parvizi Javad
Published: June 2015

Despite the battery of available tests, the diagnosis of periprosthetic joint infection (PJI) remains a challenge. A comprehensive medical history and physical examination with appropriate radiographs followed by erythrocyte sedimentation rate and serum C-reactive protein are the first-line screening test for patients with suspected hip PJI. The second line of investigation of patients with abnormal serology or a strong suspicion for PJI, is joint aspiration. Aspirates should be sent for assessment of white blood cell count, polymorphonuclear percentage, leukocyte esterase strip test, and microbiology. If the first attempt fails, the joint should be re-aspirated at a different time. The International Consensus recommends against infiltration of saline or other fluids into a “dry” joint. In patients not planned for surgery but need further evaluation for PJI, a nuclear imaging study may help. In others with a planned revision surgery, intraoperative samples for frozen section and culture study are the best measures available. Treatment strategies for PJI are well established in the literature. Poor surgical candidates receive oral suppressive antibiotic therapy alone. Acute PJI, presenting within 4 weeks of the index surgery, or as a result of bacteraemia, may be treated with irrigation and debridement and implant retention. Chronic PJI, occurring more than 4 weeks after initial surgery, is treated with 1-stage or 2-stage revision arthroplasty. In some persistent infections or patients who refuse to undergo revision surgery, salvage procedures may be needed.
The Biological Approach in Acetabular Revision Surgery: Impaction Bone Grafting and a Cemented Cup
Authors: Colo Ena , Rijnen Wim H.C. , Schreurs Berend Willem
Published: June 2015

Acetabular impaction bone grafting (IBG) in combination with a cemented cup in revision total hip arthroplasty (THA) is a proven and well-recognised technique which has been used in clinical practice for more than 35 years. Nowadays, with cemented prostheses tending to lose a larger part of the THA market every year in primary and revision cases, and many young surgeons being only trained in implanting uncemented prostheses, this technique is considered by many as technically demanding and time consuming, making its use less appealing. Despite this image and many new innovative techniques using uncemented implants in acetabular revisions over the last 25 years, IBG with a cemented cup is still one of the few techniques that really can reconstitute bone and respects human biology. In this era of many biologically-based breakthroughs in medicine, it is hard to explain that the solution of most orthopaedic surgeons for the extensive bone defects as frequently seen during acetabular revision surgery, consists of implanting bigger and larger metal implants. This review aims to put the IBG method into a historical perspective, to describe the surgical technique and present the clinical results.
Pelvic Discontinuity: Modern Techniques and Outcomes for Treating Pelvic Disassociation
Authors: Schwarzkopf Ran , Ihn Hansel E. , Ries Michael D.
Published: June 2015

Pelvic discontinuity is an uncommon condition that usually presents in the revision total hip arthroplasty population. However, its incidence will most likely increase due to the increasing number of primary and revision total hip arthroplasties (THA) done in recent years. Pelvic discontinuity (acetabular disassociation) is perhaps one of the more challenging cases for the hip arthroplasty surgeon to manage. Historically, the management of pelvic discontinuity has been wrought with many challenges. What follows is a review of the current techniques and outcomes for acetabular reconstruction in patients with acetabular disassociation including: porous metal components, internal fixation with acetabular reconstruction, acetabular distraction with jumbo cups, cup and cage construct, and the use of custom triflange.

The complexity of pelvic discontinuity and with the myriad of options available to the hip arthroplasty surgeon to address this particular issue, pre-operative planning becomes all the more essential.
Hip Arthroscopy: A Focus on the Future
Authors: Divecha Hiren M. , Rajpura Asim , Board Tim N.
Published: June 2015

The indications for hip arthroscopy over the last decade have increased rapidly, driven by technical and technological advances aimed at hip joint preservation. This article reviews the current indications and supporting evidence for hip arthroscopy, explores some newer techniques/technologies and discusses the future directions in this rapidly evolving and expanding field.
The Prevention and Treatment of Dislocation following Total Hip Arthroplasty: Efforts to Date and Future Strategies
Authors: Jones Stephen A.
Published: June 2015

Dislocation continues as one of the common complications following primary Total Hip Arthroplasty (THA). Considering revision THA, dislocation is also one of the leading causes of failure and the subsequent need for rerevision surgery. This article aims to highlight the efforts to date that surgeons have utilised together with the implants employed to both prevent and treat THA dislocation. A fundamental principal in the management of THA instability is identification of the risk factors for dislocation and these are considered in 5 subgroups; patient factors, surgeon factors, implant design, implant orientation and soft tissue factors. Risk stratification is proposed as a future method of deciding upon best treatment for those patients most at danger of THA dislocation and subsequent continued instability.
Extracorporeal Membrane Oxygenation and Severe Portopulmonary Hypertension following Liver Transplantation: Brief Report
Authors: Chan-Dominy Amy C. , Rahiman Sarfaraz N. , Anders Marc , Butt Warwick
Published: June 2015

Background

Patients with severe portopulmonary hypertension (PoPH) responsive to medical therapy may be considered for liver transplantation. We present a case of extracorporeal membrane oxygenation (ECMO) resuscitation for PoPH crisis in a child following liver transplantation (LT), and review the literature on management of this challenging setting.

Case report

A 7-year-old girl, with previous Kasai portoenterostomy and subsequent severe PoPH responsive to pulmonary vasodilator therapy, underwent orthotopic LT. Five days following surgery, she had an asystolic arrest with suprasystemic pulmonary hypertension, and was resuscitated with ECMO therapy. Multi-modal strategies included sildenafil, ambrisentan, nitric oxide, intravenous Epoprostenol infusion, levosimendan, and atrial septostomy. Ten days after her LT, exploration for bleeding was necessary following abdominal drain removal. By 10 days of ECMO support, she was reviewed and considered for lung transplantation. Unfortunately, she deteriorated precipitously with abdominal compartment syndrome and multi-organ failure; sadly, life support was withdrawn 23 days after transplantation.

Discussion

Patients with severe PoPH may need combined thoracic organ and liver transplantation either at single or serial events. Case reports on ECMO use include resuscitation after massive pulmonary embolism during liver transplantation, bridge until the goal of vasodilatory therapy was reached in worsening PoPH following LT, and bridge to lung or repeat liver transplantation for severe pulmonary hypertension.

Conclusions

ECMO resuscitation and support may be deployed as rescue therapy around the period of liver transplantation. We highlight the importance of patient selection and high risk of complications during ECMO therapy as a bridge to PoPH control.
Thermal and Photo Stability of Glutathione-Capped Cadmium Telluride Quantum Dots
Authors: Wansapura Poorna T. , Díaz-Vásquez Waldo A. , Vásquez Claudio C. , Pérez-Donoso José M. , Chasteen Thomas G.
Published: June 2015

Background

Nanoparticles (NPs) are increasingly being used in a number of applications that include biomedicine, biological labeling and cancer marker targeting, and their successful storage is important to preserve their viability. A systematic investigation of the thermal and photo stability of chemically stabilized cadmium telluride (CdTe) quantum dots (QDs) under various storage conditions either in solution or as dried nanoparticles has not been published. Here we report experiments involving chemically synthesized glutathione-capped CdTe QDs whose photoluminescence spectra were examined initially and then periodically during storage times up to 76 days.

Methods

Samples of dried QDs or QDs in solution (water or buffered) were examined under different light conditions including complete darkness, constant 12,000 lux incident light, and under diurnal sunlight; at temperatures ranging from -80°C to room temperature.

Results

Though QDs stored in solution in the dark at -80°C lost only 50% of peak fluorescence (FL510) within 2 weeks, solution-stored QDs exposed to sunlight at room temperature showed FL510 drops of 85% in the first 24 hours. In contrast, QDs precipitated from aqueous solution, dried and stored in time course experiments in the presence of atmospheric oxygen – when resuspended in water – lost an average of only 12% FL510 over 76 days under all conditions tested, even in direct sunlight.

Conclusions

Glutathione-capped CdTe particles can be stored as dried nanoparticles for extended periods of time, enhancing their viability in biomedicine, biological labeling and cancer marker targeting.
Sealing Capability of Implant-Abutment Junction under Cyclic Loading: A Toluidine Blue in Vitro Study
Authors: Scarano Antonio , Perrotti Vittoria , Piattelli Adriano , Iaculli Flavia , Iezzi Giovanna
Published: June 2015

Purpose

The aim of the present in vitro study was to evaluate the leakage observed in external hexagon (EH) and cone Morse (CM) tapered implant-abutment connections, using toluidine blue.

Methods

A total of 60 implants, 30 with a screw-retained EH abutment and 30 with a CM taper internal connection, were used. Toluidine blue was placed into the deepest portion of the internal compartment of the 2 different implant systems, and cyclic loading was applied for each group as follows: 10 samples underwent 1 × 106 loading cycles, 10 samples underwent 3 × 106 cyclic loading and the least 10 samples underwent 6 × 106 cyclic loading.

Results

No signiﬁcant differences between the EH and CM groups were detected when the lowest loading cycles were applied (p = 0.2624), while differences were found when the samples were loaded with 3 x 106 and 6 x 106 cycles (p = 0.00124), with signiﬁcantly lower toluidine leakage in CM group.

Conclusions

In conclusion, the results of the present in vitro study demonstrated that flow of the toluidine blue to the external portion of the implant-abutment assembly occurred in both types of implant-abutment connections, with very different percentages. Indeed, the CM taper internal connection seems to be more resistant to the leakage of dyes when compared with EH connections.
Ultrasound-guided brachiocephalic vein catheterization in infants weighing less than five kilograms
Authors: Aytekin Cüneyt , Özyer Umut , Harman Ali , Boyvat Fatih
Published: June 2015

Purpose

To describe our experience with the use of ultrasound-guided supraclavicular brachiocephalic vein approach for central vein catheterization in infants weighing less than 5 kg.

Methods

A retrospective review was performed for infants who underwent ultrasound-guided central vein catheterization from January 2012 to November 2014. Infants weighing less than 5 kg with supraclavicular brachiocephalic vein access were included in the study. Indications for central venous access, venous access side, catheter type and complications were evaluated.

Results

Thirty-four catheterizations in 34 infants weighing from 1.5 to 4.9 kg (median 3.48 kg) were included in the study (aged 11 days to 7 months and 10 days, weight range 1.5 to 4.9 kg). Technical success rate was 97% (33 of 34 infants). No technical or clinical major complications were observed.

Conclusions

Ultrasound-guided supraclavicular brachiocephalic vein access is a favorable alternative for central venous catheterization in low-weight infants with regard to high technical success rate and absence of major complications.
The use of the early cannulation prosthetic graft (Acuseal™) for angioaccess for haemodialysis
Authors: Maytham Gary G.D , Sran H.K. , Chemla Eric S.
Published: June 2015

Objectives

Autogenous arteriovenous (AV) accesses are the preferred choice for the delivery of haemodialysis (HD). With an increase in the prevalence of end-stage renal disease and in the life expectancy of these patients, the quality and availability of superficial vessels can be limited and reduced with time. The use of prosthetic AV accesses may therefore become necessary for the delivery of HD. A new early cannulation vascular prosthesis (GORE® ACUSEAL Vascular Graft) has been introduced, developed to hinder suture line and cannulation needle bleeding. The authors report their experience with this new conduit at a London teaching hospital.

Methods

Between May 2011 and June 2013, 52 patients underwent 55 procedures where the ACUSEAL® prosthetic AV access was utilized to facilitate HD. The majority of procedures involved the placement of prosthetic brachio-axillary accesses or prosthetic axillo-axillary chest accesses.

Results

The 1-year primary and secondary patency was found to be 46% and 61%, respectively. Successful cannulation of the newly placed AV access was performed with 24 hours of surgery in 40 patients (73%). Tunnelled vascular catheters were required in only 10 (18%) patients. Six (11%) of the patients in the study suffered early complications, and 9 (16%) patients developed AV access infection.

Conclusions

These results show that, while providing patency results that compare favourably to those published for other types of regular prosthetic accesses, the conduits are amenable to very early cannulation with few cannulation-related complications. This leads to a dramatic reduction in the need for temporary or tunnelled catheters.
True aneurysm in autologous hemodialysis fistulae: definitions, classification and indications for treatment
Authors: Balaz Peter , Björck Martin
Published: June 2015

Introduction

Definition, etiology, classification and indication for treatment of the arteriovenous access (AVA) aneurysm are poorly described in medical literature. The objectives of the paper are to complete this information gap according to the extensive review of the literature.

Methods

A literature search was performed of the articles published between April 1, 1967, and March 1, 2014. The databases searched included Medline and the Cochrane Database of Systematic Reviews. The eligibility criteria in this review studies the need to assess the association of aneurysms and pseudoaneurysms with autologous AVA. Aneurysms and pseudoaneurysms involving prosthetic AVA were not included in this literature review. From a total of 327 papers, 54 non-English papers, 40 case reports and 167 papers which did not meet the eligibility criteria were removed. The remaining 66 papers were reviewed.

Results

Based on the literature the indication for the treatment of an AVA aneurysm is its clinical presentation related to the patient's discomfort, bleeding prevention and inadequate access flow. A new classification system of AVA aneurysm, which divides it into the four types, was also suggested.

Conclusions

AVA aneurysm is characterized by an enlargement of all three vessel layers with a diameter of more than 18 mm and can be presented in four types according to the presence of stenosis and/or thrombosis. The management of an AVA aneurysm depends on several factors including skin condition, clinical symptoms, ease of cannulation and access flow. The diameter of the AVA aneurysm as a solo parameter is not an indication for the treatment.