Neglecting the naturally existing functional diversity of communities and the resulting potential to respond to altered conditions may strongly reduce the realism and predictive power of ecological ...models. We therefore propose and study a predator-prey model that describes mutual feedback via species shifts in both predator and prey, using a dynamic trait approach. Species compositions of the two trophic levels were described by mean functional traits--prey edibility and predator food-selectivity--and functional diversities by the variances. Altered edibility triggered shifts in food-selectivity so that consumers continuously respond to the present prey composition, and vice versa. This trait-mediated feedback mechanism resulted in a complex dynamic behavior with ongoing oscillations in the mean trait values, reflecting continuous reorganization of the trophic levels. The feedback was only possible if sufficient functional diversity was present in both trophic levels. Functional diversity was internally maintained on the prey level as no niche existed in our system, which was ideal under any composition of the predator level due to the trade-offs between edibility, growth and carrying capacity. The predators were only subject to one trade-off between food-selectivity and grazing ability and in the absence of immigration, one predator type became abundant, i.e., functional diversity declined to zero. In the lack of functional diversity the system showed the same dynamics as conventional models of predator-prey interactions ignoring the potential for shifts in species composition. This way, our study identified the crucial role of trade-offs and their shape in physiological and ecological traits for preserving diversity.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Fourth generation accelerator-based light sources, such as VUV and X-ray Free Electron Lasers (FEL), deliver ultra-brilliant (∼10
12–10
13 photons per bunch) coherent radiation in femtosecond ...(∼10–100
fs) pulses and, thus, require novel focal plane instrumentation in order to fully exploit their unique capabilities. As an additional challenge for detection devices, existing (FLASH, Hamburg) and future FELs (LCLS, Menlo Park; SCSS, Hyogo and the European XFEL, Hamburg) cover a broad range of photon energies from the EUV to the X-ray regime with significantly different bandwidths and pulse structures reaching up to MHz micro-bunch repetition rates. Moreover, hundreds up to trillions of fragment particles, ions, electrons or scattered photons can emerge when a single light flash impinges on matter with intensities up to 10
22
W/cm
2.
In order to meet these challenges, the Max Planck Advanced Study Group (ASG) within the Center for Free Electron Laser Science (CFEL) has designed the CFEL-ASG MultiPurpose (CAMP) chamber. It is equipped with specially developed photon and charged particle detection devices dedicated to cover large solid-angles. A variety of different targets are supported, such as atomic, (aligned) molecular and cluster jets, particle injectors for bio-samples or fixed target arrangements. CAMP houses 4π solid-angle ion and electron momentum imaging spectrometers (“reaction microscope”, REMI, or “velocity map imaging”, VMI) in a unique combination with novel, large-area, broadband (50
eV–25
keV), high-dynamic-range, single-photon-counting and imaging X-ray detectors based on the pnCCDs.
This instrumentation allows a new class of coherent diffraction experiments in which both electron and ion emission from the target may be simultaneously monitored. This permits the investigation of dynamic processes in this new regime of ultra-intense, high-energy radiation—matter interaction. After an introduction into the salient features of the CAMP chamber and the properties of the redesigned REMI/VMI spectrometers, the new 1024×1024 pixel format pnCCD imaging detector system will be described in detail. Results of tests of four smaller format (256×512) devices of identical performance, conducted at FLASH and BESSY, will be presented and the concept as well as the anticipated properties of the full, large-scale system will be elucidated. The data obtained at both radiation sources illustrate the unprecedented performance of the X-ray detectors, which have a voxel size of 75×75×450
μm
3 and a typical read-out noise of 2.5 electrons (rms) at an operating temperature of −50
°C.
Established and recent hard X-ray spectroscopic methods in the form of conventional X-ray absorption near edge structure spectroscopy (XANES) and extended X-ray absorption fine structure spectroscopy ...(EXAFS), and the photon-in/photon-out techniques high energy resolution fluorescence detection XANES and valence-to-core X-ray emission spectroscopy (VtC-XES) provide unique opportunities to study mechanisms in metal-organic reactions. The combination of these techniques allows the determination of the local geometric and electronic structures in the form of the numbers of nearest neighbours, their types and distances around an X-ray absorbing atom and the highest occupied and lowest unoccupied molecular levels. Different sample cells for this purpose, which allow high pressure, electrochemical or multi-spectroscopic measurements under inert conditions, are presented and discussed. The potential of HERFD-XANES and VtC-XES to eliminate limitations of conventional EXAFS spectroscopy is established with case studies on the Hieber anion Fe(CO)
3
(NO)
−
and the iron hydride complex Fe(CO)H(NO)(PPh
3
)
2
. With VtC-XES the formation of an allyl complex by reaction of Fe(CO)
3
(NO)
−
in a catalytic nucleophilic substitution reaction can be followed. Combination of HERFD-XANES and VtC-XES allows the identification and investigation of hydride species, as well as their fate in chemical reactions. On the other hand, in order to investigate the active species formation in iron-catalysed cross coupling reactions, conventional XANES and EXAFS are the method of choice for the moment. For all examples, the advantages and limitations of the hard X-ray toolbox are commented on and the value of the individual methods are compared.
The hard X-ray spectroscopy methods XAS, valence-to-core XES and higher solution XANES offer unique insights into organometallic reaction mechanisms.
Potential induced degradation (PID) of solar cells can severely reduce a PV module's performance. In case of bifacial solar cells, the rear side is another source of PID as was found for industrially ...produced bifacial PERC solar cells from three different manufacturers. It is shown that a rear-side PID test can lead to more than 12% power degradation. The observed PID mechanisms are not completely recoverable implying long-term losses under field operation. This new, non-recoverable PID effects are characterized by a locally increased recombination at the rear side of the cells. From nano-scale analytics by means of transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and energy-dispersive X-ray spectroscopy (EDXS) are performed and PID related defects are traced back to a local Si corrosion and delamination of the passivation layers. At the Si passivation interface an increased amount of SiOx, Na and further impurities are found that indicate an electrochemically driven corrosion process under cathodic conditions.
Surface-modified porous silica is a well-established composite material. To improve its embedding and application behavior, adsorption studies of various probe molecules have been performed using the ...technique of inverse gas chromatography (IGC). For this purpose, IGC experiments were carried out in the infinite dilution mode on macro-porous micro glass spheres before and after surface modification with (3-mercaptopropyl)trimethoxysilane. To provide information about the polar interactions between probe molecules and the silica surface, in particular, eleven polar molecules have been injected. In summary, the free surface energy for pristine silica (
= 229 mJ/m
) and for (3-mercaptopropyl)trimethoxysilane-modified silica (
= 135 mJ/m
) indicates a reduced wettability after surface modification. This is due to the reduction of the polar component of the free surface energy (
) from 191 mJ/m
to 105 mJ/m
. Simultaneously, with the reduction of surface silanol groups caused by surface modification of silica and, therefore, the decrease in polar interactions, a substantial loss of Lewis acidity was observed by various IGC approaches. Experiments with all silica materials have been conducted at temperatures in the range from 90°C to 120°C to determine the thermodynamic parameters, such as adsorption enthalpy (
) and adsorption entropy (
), using the Arrhenius regression procedure evaluating the IGC data. With the help of the enthalpy-entropy compensation, two types of adsorption complexes are assumed between polar probe molecules and the silica surface because of different isokinetic temperatures. Identical adsorption complexes with an isokinetic temperature of 370°C have been assigned to alkanes and weakly interacting polar probes such as benzene, toluene, dichloromethane, and chloroform. Polar probe molecules with typical functional groups such as OH, CO, and CN, having the ability to form hydrogen bonds to the silica surface, exhibit a lower isokinetic temperature of 60°C. Quantum chemical calculations of the probe molecules on a non-hydroxylated and hydroxylated silica cluster supported the formation of hydrogen bonds in the case of a strong polar adsorption complex with a bonding distance of 1.7 nm-1.9 nm to the silica surface.
For an excitonic photovoltaic (PV) device to perform efficiently, photogenerated excitons in the charge donor need to be dissociated through charge transfer (CT) to the acceptor rapidly after their ...photogeneration and remain separated for a longer time to allow the collection of charges. To improve the efficiency of these steps, several combinations of materials have been examined. Due to their excellent optical properties, two-dimensional transition-metal dichalcogenides (2D-TMDs) have recently been explored. Another promising class of materials to platform efficient PVs is organic–inorganic perovskites. Here, we report on the ultrafast exciton dissociation through electron transfer from a 2D tungsten disulfide (WS2) monolayer to a thin layer of methylammonium lead iodide (CH3NH3PbI3) perovskites. Photoluminescence measurements showed that when the 2D-WS2 monolayer was covered with perovskites, its emission completely quenched, suggesting that the CT process is highly efficient. Despite that pump–probe spectroscopy measurements were carried out with a ∼45 fs temporal resolution, the CT dynamics were not captured. A comparison of the ultrafast dynamics of the two band-edge excitons of the charge donor (2D-WS2) suggested that electron transfer is the dominant pathway of CT. Furthermore, these pump–probe measurements indicated that a small fraction of transferred electrons remained in the perovskites up to almost 2 ns. These findings may open a new horizon for understanding the dissociation of photogenerated excitons in 2D-TMDs through hybridization with another class of nanomaterials.
FSGS recurrence after kidney transplantation is a major risk factor for graft loss. However, the natural history, clinical predictors, and response to treatment remain unclear because of small sample ...sizes and poor generalizability of single-center studies, and disease misclassification in registry-based studies. We therefore aimed to determine the incidence, predictors, and treatment response of recurrent FSGS in a large cohort of kidney transplant recipients.
The Post-Transplant Glomerular Disease (TANGO) project is an observational, multicenter, international cohort study that aims to investigate glomerular disease recurrence post-transplantation. Transplant recipients were screened for the diagnosis of idiopathic FSGS between 2005 and 2015 and details were recorded about the transplant, clinical outcomes, treatments, and other risk factors.
Among 11,742 kidney transplant recipients screened for FSGS, 176 had a diagnosis of idiopathic FSGS and were included. FSGS recurred in 57 patients (32%; 95% confidence interval 95% CI, 25% to 39%) and 39% of them lost their graft over a median of 5 (interquartile range, 3.0-8.1) years. Multivariable Cox regression revealed a higher risk for recurrence with older age at native kidney disease onset (hazard ratio HR, 1.37 per decade; 95% CI, 1.09 to 1.56). Other predictors were white race (HR, 2.14; 95% CI, 1.08 to 4.22), body mass index at transplant (HR, 0.89 per kg/m
; 95% CI, 0.83 to 0.95), and native kidney nephrectomies (HR, 2.76; 95% CI, 1.16 to 6.57). Plasmapheresis and rituximab were the most frequent treatments (81%). Partial or complete remission occurred in 57% of patients and was associated with better graft survival.
Idiopathic FSGS recurs post-transplant in one third of cases and is associated with a five-fold higher risk of graft loss. Response to treatment is associated with significantly better outcomes but is achieved in only half of the cases.
Malnutrition risk is identified in over one-third of inpatients; reliance on dietetics-delivered nutrition care for all “at-risk” patients is unsustainable, inefficient, and ineffective. This study ...aimed to identify and prioritise low-value malnutrition care activities for de-implementation and articulate systematised interdisciplinary opportunities. Nine workshops, at eight purposively sampled hospitals, were undertaken using the nominal group technique. Participants were asked “What highly individualised malnutrition care activities do you think we could replace with systematised, interdisciplinary malnutrition care?” and “What systematised, interdisciplinary opportunities do you think we should do to provide more effective and efficient nutrition care in our ward/hospital?” Sixty-three participants were provided five votes per question. The most voted de-implementation activities were low-value nutrition reviews (32); education by dietitian (28); assessments by dietitian for patients with malnutrition screening tool score of two (22); assistants duplicating malnutrition screening (19); and comprehensive, individualised nutrition assessments where unlikely to add value (15). The top voted alternative opportunities were delegated/skill shared interventions (55), delegated/skill shared education (24), abbreviated malnutrition care processes where clinically appropriate (23), delegated/skill shared supportive food/fluids (14), and mealtime assistance (13). Findings highlight opportunities to de-implement perceived low-value malnutrition care activities and replace them with systems and skill shared alternatives across hospital settings.
Entorrhiza is a small fungal genus comprising 14 species that all cause galls on roots of Cyperaceae and Juncaceae. Although this genus was established 130 years ago, crucial questions on the ...phylogenetic relationships and biology of this enigmatic taxon are still unanswered. In order to infer a robust hypothesis about the phylogenetic position of Entorrhiza and to evaluate evolutionary trends, multiple gene sequences and morphological characteristics of Entorrhiza were analyzed and compared with respective findings in Fungi. In our comprehensive five-gene analyses Entorrhiza appeared as a highly supported monophyletic lineage representing the sister group to the rest of the Dikarya, a phylogenetic placement that received but moderate maximum likelihood and maximum parsimony bootstrap support. An alternative maximum likelihood tree with the constraint that Entorrhiza forms a monophyletic group with Basidiomycota could not be rejected. According to the first phylogenetic hypothesis, the teliospore tetrads of Entorrhiza represent the prototype of the dikaryan meiosporangium. The alternative hypothesis is supported by similarities in septal pore structure, cell wall and spindle pole bodies. Based on the isolated phylogenetic position of Entorrhiza and its peculiar combination of features related to ultrastructure and reproduction mode, we propose a new phylum Entorrhizomycota, for the genus Entorrhiza, which represents an apparently widespread group of inconspicuous fungi.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A luminescent Pt2Fe spin crossover complex Schäfer, Bernhard; Bauer, Thomas; Faus, Isabelle ...
Dalton transactions : an international journal of inorganic chemistry,
2017, Letnik:
46, Številka:
7
Journal Article
Recenzirano
A heterotrinuclear Pt2Fe spin crossover (SCO) complex was developed and synthesized employing a ditopic bridging bpp-alkynyl ligand L and alkynyl coordinated PtII terpy units: FeII(L-PtII)22(BF4)2 ...(1). We identified two different types of crystals of 1 which differ in their molecular packing and the number of co-crystallized solvent molecules: 1H (1·3.5CH2Cl2 in P1combining macron) and 1L (1·10CH2Cl2 in C2/c); while 1L shows a reversible SCO with a transition temperature of 268 K, the analogous compound 1H does not show any SCO and remains blocked in the HS state. The temperature-dependent magnetic properties of 1H and 1L were complementarily studied by Mössbauer spectroscopy. It has been shown that 1L performs thermal spin crossover and that 1L can be excited to a LIESST state. The vibrational properties of 1 were investigated by experimental nuclear resonance vibrational spectroscopy. The experimentally determined partial density of vibrational states (pDOS) was compared to a DFT-based simulation of the pDOS. The vibrational modes of the different components were assigned and visualized. In addition, the photophysical properties of 1 and L-Pt were investigated in the solid state and in solution. The ultrafast transient absorption spectroscopy of 1 in solution was carried out to study the PL quenching channel via energy transfer from photoexcited PtII terpy units to the FeII-moiety.
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