Living Close to Your Neighbors: The Importance of Both Competition and Facilitation in Plant Communities

Recent work has demonstrated that competition and facilitation likely operate jointly in plant communities, but teasing out the relative role of each has proven difficult. Here we address how competition and facilitation vary with seasonal fluctuations in environmental conditions, and how the effects of these fluctuations change with plant ontogeny. We planted three sizes of pine seedlings (Pinus strobus) into an herbaceous diversity experiment and measured pine growth every two weeks for two growing seasons. Both competition and facilitation occurred at different times of year between pines and their neighbors. Facilitation was important for the smallest pines when environmental conditions were severe. This effect decreased as pines got larger. Competition was stronger than facilitation overall and outweighed facilitative effects at annual time scales. Our data suggest that both competition and the counter‐directional effects of facilitation may be more common and more intense than previously considered

Why GPS makes distances bigger than they are

Global Navigation Satellite Systems (GNSS), such as the Global Positioning System (GPS), are among the most important sensors for movement analysis. GPS is widely used to record the trajectories of vehicles, animals and human beings. However, all GPS movement data are affected by both measurement and interpolation error. In this article we show that measurement error causes a systematic bias in distances recorded with a GPS: the distance between two points recorded with a GPS is -- on average -- bigger than the true distance between these points. This systematic `overestimation of distance' becomes relevant if the influence of interpolation error can be neglected, which is the case for movement sampled at high frequencies. We provide a mathematical explanation of this phenomenon and we illustrate that it functionally depends on the autocorrelation of GPS measurement error ($C$). We argue that $C$ can be interpreted as a quality measure for movement data recorded with a GPS. If there is strong autocorrelation any two consecutive position estimates have very similar error. This error cancels out when average speed, distance or direction are calculated along the trajectory. Based on our theoretical findings we introduce a novel approach to determine $C$ in real-world GPS movement data sampled at high frequencies. We apply our approach to a set of pedestrian and a set of car trajectories. We find that the measurement error in the data is strongly spatially and temporally autocorrelated and give a quality estimate of the data. Finally, we want to emphasize that all our findings are not limited to GPS alone. The systematic bias and all its implications are bound to occur in any movement data collected with absolute positioning if interpolation error can be neglected.Comment: 17 pages, 8 figures, submitted to IJGI

Simultaneous microsurgical spermatic vein ligation and sclerotherapy - A combined procedure for the treatment of recurrent or persistent varicocele

Objectives: Microsurgical ligation as well as antegrade sclerotherapy have been established in varicocele treatment. The aim of this study was to evaluate whether a combination of microsurgery. and sclerotherapy can: provide a safe and effective treatment of varicocele recurrence or persistence. Methods. Nine patients with, recurrent or persistent varicoceles were operated by means of the combination method. Under microscopic control varix veins were ligated selectively preserving: lymphatics and arteries. Ectopic veins as a possible source for varicocele persistence or recurrence were also ligated. Finally, an intraoperative venography with subsequent sclerotherapy was, performed through one of the dissected veins. Results. Despite: difficult anatomical situations after previous surgical interventions, the operations were perform, ed successfully without any complications. Clinical controls showed varicocele disappearance without damage of the testis. No varicocele recurrence or persistence was observed. Conclusions. This method combines the advantages of both methods. Precision of the microsurgical technique is combined with velocity of sclerotherapy. Thus, it may represent an Interesting alternative to conventional operation methods especially in the treatment of recurrent or persistent varicoceles. Copyright (C) 2001 S. Karger AG, Basel

Glowing Glass

Defined by the building law in each publicly accessible building (e.g. schools, administration etc.) emergency exit routes have to be marked usually by means of active or passive lightening systems. The use of passive lightening systems require comprehensive components with an independent, battery-powered energy-supply that produces light even in the case of an energy black-out (e.g. disaster situations). The use of powerlines plus the frequently service of battery-powered systems is complicated and expansive. Alternatively after-glowing, phosphorescent signs, attached on walls, wallpapers or doors are an existing alternative. Mostly known to everybody are the green emergency exit signs. Furthermore phosphorescent paints on floors or walls are also used to guide people on the quickest escape way. Used inside of buildings their appearance has mostly a disturbing and negative attitude, even more at premium interior designs. Therefore, the composition of passive lightened systems with premium-quality surfaces leads to a widely usable product phosphorescent glass. This glass consists of laminated glass with a phosphorescent paint application within the glass interlayer. The paper describes the research and development of phosphorescent glass with a strong emphasis on materials testing, application technics and the behavior as laminated safety glass

Hierarchical imaging of the dynamics during pulsed laser ablation in liquids

Mittels gepulster Laserablation in Flüssigkeiten (Pulsed Laser Ablation in Liquids, PLAL) ist es möglich, Nanopartikel (NP) herzustellen, die direkt in der Flüssigkeit dispergiert und nicht durch verbliebene Tenside oder Reaktanden verunreinigt sind. Nach der Laseranregung des Targets bildet sich eine millimetergroße Kavitationsblase, in der die NP verteilt und größtenteils gefangen sind. In dieser Arbeit werden die fundamentalen Prozesse während PLAL mit einer Reihe von komplementären Messtechniken und hierarchischer in situ Bildgebung untersucht. Die Laser-Materie-Wechselwirkung wird durch optische Abbildung der Kavitationsblase und des gezündeten Plasmas in Kombination mit Absorptionsspektroskopie untersucht. Es wird eine direkte Korrelation zwischen diesen drei Parametern gezeigt, die es erlaubt, indirekte Rückschlüsse auf den Ablationsprozess zu ziehen. Der Inkubationseffekt, der bei unversehrten Targets auftritt, und das Vorhandensein einer Plasma-Schwellfluenz zeigen, dass für eine effiziente Ablation entweder vorbestrahlte Targets oder Fluenzen oberhalb der Schwelle erforderlich sind. Eine Ablation mit geringen Fluenzen auf unversehrten Targets führt zu starken Verlustmechanismen, was in einer stark reduzierte Energielokalisation und damit niedrigen Ablationsrate resultiert. Es wird gezeigt, dass die für eine stabile und effiziente Ablation erforderliche Energiedosis von Materialparametern wie dem Elastizitätsmodul und der für die Materialerwärmung und -verdampfung erforderlichen Enthalpie abhängt. Sobald die PlasmaSchwellfluenz überschritten wird, haben die Materialparameter jedoch nur noch einen geringen Einfluss. Bei der Nanosekunden-Laserablation oberhalb der Schwellfluenz wird der größte Teil der Pulsenergie vom Plasma absorbiert. Unterhalb der Schwellfluenz dominieren die Verlustmechanismen, was zu einer stark reduzierten Ablationseffizienz führt. Für den in situ Nachweis von NP während der Lebensdauer der Kavitationsblase werden Röntgenstreumethoden verwendet. Die NP-Größenverteilung wird mit hoher zeitlicher Auflösung mittels Röntgen-Kleinwinkelstreuung (Small-angle X-ray Scattering, SAXS) untersucht, während RöntgenWeitwinkelstreuung (Wide-angle X-ray Scattering, WAXS) zur Messung der kristallinen Domänengröße verwendet wird. Das frühe Auftreten von großen NP mit großen Kristalldomänengrößen bestätigt die jüngsten Modelle des Ablationsprozesses. Die multimodale NP-Größenverteilung wird direkt durch Filmabhebung und Rayleigh-Instabilitäten auf der flüssigen Metalloberfläche hervorgerufen. Darüber hinaus bestätigt die zeitliche Verteilung der NP, dass sich NP an oder sogar vor der Kavitationsblasengrenze befinden, sowie die nahezu homogene Füllung der Blase mit NP. Zwei verschiedene Mechanismen der Entstehung von großen NP werden ebenfalls identifiziert. Sphärische NP entstehen direkt aus der Schmelze, während die Agglomeration von kleinen NP hauptsächlich während des Blasenkollapses stattfindet. Ein Multiplexing der SAXS-Messungen, um direkt ein 2D-Bild der NP-Verteilung zu erhalten, erfolgt durch Hartmann-Blenden artiger Multikontrast-Bildgebung. Zu diesem Zweck wird ein breiter Röntgenstrahl durch eine maßgeschneiderte Hartmann-Blende beziehungsweise die neu entwickelten gestapelten Röntgenlinsenarrays (Compound Array Refractive Lenses, CARLs) in ein 2D-Array von Teilstrahlen aufgeteilt. Für die hierarchische Abbildung des Ablationsprozesses werden die Kontraste Transmission und Streuung dieser Einzelbild Multikontrast-Bildgebung (Single-Exposure Multi-Contrast Imaging, SEMCI) verwendet. Die in situ Größenreduktion von NP aus Gold mit anorganischen Elektrolyten und makromolekularen Liganden wird untersucht. Es wird gezeigt, dass die Mechanismen der Größenreduktion der beiden Additive unterschiedlich sind. Elektrolyte wirken in situ in der Kavitationsblase, während Liganden dies nicht tun. Durch die Änderung der Streuempfindlichkeit von NP auf den Mikrometerbereich wird die Zusammensetzung der zweiten Blasenoszillation einer Ablation an einem freien Draht geklärt. Diese vom Draht losgelöste zweite Oszillation besteht aus mikrometergroßen Blasen und enthält keine signifikanten Mengen an NP mehr. Die Röntgeneffizienz der SEMCI wird verbessert, indem die üblicherweise verwendeten HartmannBlenden durch Linsenarrays ersetzt werden. Diese CARLs werden durch Prägen von 2D-Arrays mit 100×100 konkaven Linsen in Polymerfolien hergestellt. Die Linsenabstände liegen bei 50 µm und die Scheitelradien der Parabollinsen bei 8 µm. Die Positioniergenauigkeit der Teilstrahlen ist geringer als 1 µm. Durch das Stapeln von bis zu sechs Linsenarray-Folien werden Brennweiten zwischen 60 cm und 125 cm bei Röntgenenergien von 9 keV erreicht. Die maximale Sichtbarkeit beträgt etwa 0,5. Neben der NP-Detektion durch den Streukontrast kann auch die Wellenfrontverzerrung durch Proben oder Röntgenoptiken mit einer Auflösung von 0,2 µrad analysiert werden

Behaviour of adipose-derived canine mesenchymal stem cells after superparamagnetic iron oxide nanoparticles labelling for magnetic resonance imaging

Background: Therapy with mesenchymal stem cells (MSCs) has been reported to provide beneficial effects in the treatment of neurological and orthopaedic disorders in dogs. The exact mechanism of action is poorly understood. Magnetic resonance imaging (MRI) gives the opportunity to observe MSCs after clinical administration. To visualise MSCs with the help of MRI, labelling with an MRI contrast agent is necessary. However, it must be clarified whether there is any negative influence on cell function and viability after labelling prior to clinical administration. Results: For the purpose of the study, seven samples with canine adipose-derived stem cells were incubated with superparamagnetic iron oxide nanoparticles (SPIO: 319.2 µg/mL Fe) for 24 h. The internalisation of the iron particles occurred via endocytosis. SPIO particles were localized as free clusters in the cytoplasm or within lysosomes depending on the time of investigation. The efficiency of the labelling was investigated using Prussian blue staining and MACS assay. After 3 weeks the percentage of SPIO labelled canine stem cells decreased. Phalloidin staining showed no negative effect on the cytoskeleton. Labelled cells underwent osteogenic and adipogenic differentiation. Chondrogenic differentiation occurred to a lesser extent compared with a control sample. MTT-Test and wound healing assay showed no influence of labelling on the proliferation. The duration of SPIO labelling was assessed using a 1 Tesla clinical MRI scanner and T2 weighted turbo spin echo and T2 weighted gradient echo MRI sequences 1, 2 and 3 weeks after labelling. The hypointensity caused by SPIO lasted for 3 weeks in both sequences. Conclusions: An Endorem labelling concentration of 319.2 µg/mL Fe (448 µg/mL SPIO) had no adverse effects on the viability of canine ASCs. Therefore, this contrast agent could be used as a model for iron oxide labelling agents. However, the tracking ability in vivo has to be evaluated in further studies

Effect of immediate all-digital restoration of single posterior implants: The SafetyCrown concept on patient-reported outcome measures, accuracy, and treatment time-A randomized clinical trial.

OBJECTIVE The SafetyCrown workflow facilitates the immediate restoration of posterior single sites with the one-abutment/one-time concept. This randomized clinical trial aimed to assess the direct effect of immediate restoration on dental patient-reported outcomes (dPROs), feasibility, implant accuracy, and time. MATERIALS AND METHODS Participants with a single posterior edentulous site for late implant placement underwent optical impressions, shade selection, and cone beam computed tomography. After virtual treatment planning, they were randomized into the test group and the control group. For the test group, individual definitive hybrid abutments were prefabricated. The next step was a fully guided surgery with printed guides. After the implant was placed using guided surgery, the abutment was inserted. A chairside CAD/CAM workflow was used to provide the patient with a provisional restoration. Implants in the control group were left submerged to heal. Oral health-related quality of life (OHRQoL) was assessed using the OHIP-G14, and dPRO was measured using a 10-item visual analog scale (VAS) questionnaire. Additional measurements of implant accuracy and time were performed. Follow-up was performed 7 to 10 days after implant placement. RESULTS Thirty-nine participants with 45 restorations were included (test group: 23, control: 22). Immediate restoration was successful in 21 out of 23 implants (91.3%) in the test group. Both groups exhibited decreased OHRQoL without significant intergroup differences, while patient satisfaction was high overall. Test group participants perceived higher benefits and satisfaction with immediate loading than participants in the control group. Implant accuracy averaged 0.60 mm at the shoulder and 0.95 mm at the apex. Operative time was longer in the immediate loading group (61.9 min) than in the control group (32.1 min) (p < 0.001). CONCLUSIONS Considering the limitations, the immediate restoration of late placed posterior implants using the described workflow proved feasible in 21 out of 23 cases. Both groups achieved high patient satisfaction with no differences in OHRQoL during the first week. Patients who received immediate loading rated the benefits very highly and were satisfied with the provisional restoration during the healing period

A Shack-Hartmann sensor for single-shot multi-contrast imaging with hard X-rays

An array of compound refractive X-ray lenses (CRL) with 20x20 lenslets, a focal distance of 20 cm and a visibility of 0.93 is presented. It can be used as a Shack-Hartmann sensor for hard X-rays (SHARX) for wavefront sensing and permits for true single-shot multi-contrast imaging the dynamics of materials with a spatial resolution in the micrometer range, sensitivity on nanosized structures and temporal resolution on the microsecond scale. The object's absorption and its induced wavefront shift can be assessed simultaneously together with information from diffraction channels. This enables the imaging of hierarchical materials. In contrast to the established Hartmann sensors the SHARX has an increased flux efficiency through focusing of the beam rather than blocking parts of it. We investigated the spatiotemporal behavior of a cavitation bubble induced by laser pulses. Furthermore, we validated the SHARX by measuring refraction angles of a single diamond CRL, where we obtained an angular resolution better than 4 microrad

In situ structural kinetics of picosecond laser-induced heating and fragmentation of colloidal gold spheres

Fragmentation of colloidal 54 nm gold nanoparticles by picosecond laser pulses is recorded by timeresolved X-ray scattering, giving access to structural dynamics down to a 80 ps resolution. Lattice temperature and energy dissipation have been quantified to verify that the maximum applied fluence of 1800 J m$^{-2}$ heats up the particles close to boiling. Already within 30 ns, particles with significantly lower particle sizes of 2 to 3 nm are detected, which hints towards an ultrafast process either by a thermal phase explosion or Coulomb instability. An arrested growth is observed on a microsecond time scale resulting in a final particle size of 3–4 nm with high yield. In this context, the fragmentation in a NaCl/NaOH solution seems to limit growth by electrostatic stabilization of fragments, whereas it does not modify the initial product sizes. The laser-induced fragmentation process is identified as a single-step, instantaneous reaction

Bulk morphology of porous materials at submicrometer scale studied by dark-field x-ray imaging with Hartmann masks

We present the quantitative investigation of the submicron structure in the bulk of porous graphite by using the dark-field x-ray imaging with Hartmann masks. By scanning the correlation length and measuring the mask visibility reduction, we obtain the average pore size, relative pore fraction, fractal dimension, and Hurst exponent of the structure in a simple and flexible setup with relaxed requirements on beam coherence. Profiting from the dimensionality of the mask, we obtain scattering signals in two orthogonal directions, which reveals the anisotropy of pore sizes