TY - JOUR
AB - The coupling between Ca2+ channels and release sensors is a key factor defining the signaling properties of a synapse. However, the coupling nanotopography at many synapses remains unknown, and it is unclear how it changes during development. To address these questions, we examined coupling at the cerebellar inhibitory basket cell (BC)-Purkinje cell (PC) synapse. Biophysical analysis of transmission by paired recording and intracellular pipette perfusion revealed that the effects of exogenous Ca2+ chelators decreased during development, despite constant reliance of release on P/Q-type Ca2+ channels. Structural analysis by freeze-fracture replica labeling (FRL) and transmission electron microscopy (EM) indicated that presynaptic P/Q-type Ca2+ channels formed nanoclusters throughout development, whereas docked vesicles were only clustered at later developmental stages. Modeling suggested a developmental transformation from a more random to a more clustered coupling nanotopography. Thus, presynaptic signaling developmentally approaches a point-to-point configuration, optimizing speed, reliability, and energy efficiency of synaptic transmission.
AU - Chen, JingJing
AU - Kaufmann, Walter
AU - Chen, Chong
AU - Arai, Itaru
AU - Kim, Olena
AU - Shigemoto, Ryuichi
AU - Jonas, Peter M
ID - 14843
JF - Neuron
SN - 0896-6273
TI - Developmental transformation of Ca2+ channel-vesicle nanotopography at a central GABAergic synapse
ER -
TY - THES
AU - Chen, JingJing
ID - 15101
SN - 2663 - 337X
TI - Developmental transformation of nanodomain coupling between Ca2+ channels and release sensors at a central GABAergic synapse
ER -
TY - JOUR
AB - Quantum computers are increasing in size and quality but are still very noisy. Error mitigation extends the size of the quantum circuits that noisy devices can meaningfully execute. However, state-of-the-art error mitigation methods are hard to implement and the limited qubit connectivity in superconducting qubit devices restricts most applications to the hardware's native topology. Here we show a quantum approximate optimization algorithm (QAOA) on nonplanar random regular graphs with up to 40 nodes enabled by a machine learning-based error mitigation. We use a swap network with careful decision-variable-to-qubit mapping and a feed-forward neural network to optimize a depth-two QAOA on up to 40 qubits. We observe a meaningful parameter optimization for the largest graph which requires running quantum circuits with 958 two-qubit gates. Our paper emphasizes the need to mitigate samples, and not only expectation values, in quantum approximate optimization. These results are a step towards executing quantum approximate optimization at a scale that is not classically simulable. Reaching such system sizes is key to properly understanding the true potential of heuristic algorithms like QAOA.
AU - Sack, Stefan
AU - Egger, Daniel J.
ID - 15122
IS - 1
JF - Physical Review Research
SN - 2643-1564
TI - Large-scale quantum approximate optimization on nonplanar graphs with machine learning noise mitigation
VL - 6
ER -
TY - JOUR
AB - Cell division in all domains of life requires the orchestration of many proteins, but in Archaea most of the machinery remains poorly characterized. Here we investigate the FtsZ-based cell division mechanism in Haloferax volcanii and find proteins containing photosynthetic reaction centre (PRC) barrel domains that play an essential role in archaeal cell division. We rename these proteins cell division protein B 1 (CdpB1) and CdpB2. Depletions and deletions in their respective genes cause severe cell division defects, generating drastically enlarged cells. Fluorescence microscopy of tagged FtsZ1, FtsZ2 and SepF in CdpB1 and CdpB2 mutant strains revealed an unusually disordered divisome that is not organized into a distinct ring-like structure. Biochemical analysis shows that SepF forms a tripartite complex with CdpB1/2 and crystal structures suggest that these two proteins might form filaments, possibly aligning SepF and the FtsZ2 ring during cell division. Overall our results indicate that PRC-domain proteins play essential roles in FtsZ-based cell division in Archaea.
AU - Nußbaum, Phillip
AU - Kureisaite-Ciziene, Danguole
AU - Bellini, Dom
AU - Van Der Does, Chris
AU - Kojic, Marko
AU - Taib, Najwa
AU - Yeates, Anna
AU - Tourte, Maxime
AU - Gribaldo, Simonetta
AU - Loose, Martin
AU - Löwe, Jan
AU - Albers, Sonja Verena
ID - 15118
IS - 3
JF - Nature Microbiology
TI - Proteins containing photosynthetic reaction centre domains modulate FtsZ-based archaeal cell division
VL - 9
ER -
TY - JOUR
AB - In this paper we consider an SPDE where the leading term is a second order operator with periodic boundary conditions, coefficients which are measurable in (t,ω) , and Hölder continuous in space. Assuming stochastic parabolicity conditions, we prove Lp((0,T)×Ω,tκdt;Hσ,q(Td)) -estimates. The main novelty is that we do not require p=q . Moreover, we allow arbitrary σ∈R and weights in time. Such mixed regularity estimates play a crucial role in applications to nonlinear SPDEs which is clear from our previous work. To prove our main results we develop a general perturbation theory for SPDEs. Moreover, we prove a new result on pointwise multiplication in spaces with fractional smoothness.
AU - Agresti, Antonio
AU - Veraar, Mark
ID - 15119
IS - 1
JF - Annales de l'institut Henri Poincare Probability and Statistics
SN - 0246-0203
TI - Stochastic maximal Lp(Lq)-regularity for second order systems with periodic boundary conditions
VL - 60
ER -
TY - JOUR
AB - Entire chromosomes are typically only transmitted vertically from one generation to the next. The horizontal transfer of such chromosomes has long been considered improbable, yet gained recent support in several pathogenic fungi where it may affect the fitness or host specificity. To date, it is unknown how these transfers occur, how common they are and whether they can occur between different species. In this study, we show multiple independent instances of horizontal transfers of the same accessory chromosome between two distinct strains of the asexual entomopathogenic fungusMetarhizium robertsiiduring experimental co-infection of its insect host, the Argentine ant. Notably, only the one chromosome – but no other – was transferred from the donor to the recipient strain. The recipient strain, now harboring the accessory chromosome, exhibited a competitive advantage under certain host conditions. By phylogenetic analysis we further demonstrate that the same accessory chromosome was horizontally transferred in a natural environment betweenM. robertsiiand another congeneric insect pathogen,M. guizhouense. Hence horizontal chromosome transfer is not limited to the observed frequent events within species during experimental infections but also occurs naturally across species. The transferred accessory chromosome contains genes that might be involved in its preferential horizontal transfer, encoding putative histones and histone-modifying enzymes, but also putative virulence factors that may support its establishment. Our study reveals that both intra- and interspecies horizontal transfer of entire chromosomes is more frequent than previously assumed, likely representing a not uncommon mechanism for gene exchange.Significance StatementThe enormous success of bacterial pathogens has been attributed to their ability to exchange genetic material between one another. Similarly, in eukaryotes, horizontal transfer of genetic material allowed the spread of virulence factors across species. The horizontal transfer of whole chromosomes could be an important pathway for such exchange of genetic material, but little is known about the origin of transferable chromosomes and how frequently they are exchanged. Here, we show that the transfer of accessory chromosomes - chromosomes that are non-essential but may provide fitness benefits - is common during fungal co-infections and is even possible between distant pathogenic species, highlighting the importance of horizontal gene transfer via chromosome transfer also for the evolution and function of eukaryotic pathogens.
AU - Habig, Michael
AU - Grasse, Anna V
AU - Müller, Judith
AU - Stukenbrock, Eva H.
AU - Leitner, Hanna
AU - Cremer, Sylvia
ID - 14478
IS - 11
JF - Proceedings of the National Academy of Sciences of the United States of America
SN - 0027-8424
TI - Frequent horizontal chromosome transfer between asexual fungal insect pathogens
VL - 121
ER -
TY - JOUR
AB - Given a fixed finite metric space (V,μ), the {\em minimum 0-extension problem}, denoted as 0-Ext[μ], is equivalent to the following optimization problem: minimize function of the form minx∈Vn∑ifi(xi)+∑ijcijμ(xi,xj) where cij,cvi are given nonnegative costs and fi:V→R are functions given by fi(xi)=∑v∈Vcviμ(xi,v). The computational complexity of 0-Ext[μ] has been recently established by Karzanov and by Hirai: if metric μ is {\em orientable modular} then 0-Ext[μ] can be solved in polynomial time, otherwise 0-Ext[μ] is NP-hard. To prove the tractability part, Hirai developed a theory of discrete convex functions on orientable modular graphs generalizing several known classes of functions in discrete convex analysis, such as L♮-convex functions. We consider a more general version of the problem in which unary functions fi(xi) can additionally have terms of the form cuv;iμ(xi,{u,v}) for {u,v}∈F, where set F⊆(V2) is fixed. We extend the complexity classification above by providing an explicit condition on (μ,F) for the problem to be tractable. In order to prove the tractability part, we generalize Hirai's theory and define a larger class of discrete convex functions. It covers, in particular, another well-known class of functions, namely submodular functions on an integer lattice. Finally, we improve the complexity of Hirai's algorithm for solving 0-Ext on orientable modular graphs.
AU - Dvorak, Martin
AU - Kolmogorov, Vladimir
ID - 10045
JF - Mathematical Programming
KW - minimum 0-extension problem
KW - metric labeling problem
KW - discrete metric spaces
KW - metric extensions
KW - computational complexity
KW - valued constraint satisfaction problems
KW - discrete convex analysis
KW - L-convex functions
SN - 0025-5610
TI - Generalized minimum 0-extension problem and discrete convexity
ER -
TY - JOUR
AB - We present an auction algorithm using multiplicative instead of constant weight updates to compute a (1-E)-approximate maximum weight matching (MWM) in a bipartite graph with n vertices and m edges in time 0(mE-1), beating the running time of the fastest known approximation algorithm of Duan and Pettie [JACM ’14] that runs in 0(mE-1 log E-1). Our algorithm is very simple and it can be extended to give a dynamic data structure that maintains a (1-E)-approximate maximum weight matching under (1) one-sided vertex deletions (with incident edges) and (2) one-sided vertex insertions (with incident edges sorted by weight) to the other side. The total time time used is 0(mE-1), where m is the sum of the number of initially existing and inserted edges.
AU - Zheng, Da Wei
AU - Henzinger, Monika H
ID - 15121
JF - Mathematical Programming
SN - 0025-5610
TI - Multiplicative auction algorithm for approximate maximum weight bipartite matching
ER -
TY - JOUR
AB - As a key liquid organic hydrogen carrier, investigating the decomposition of formic acid (HCOOH) on the Pd (1 1 1) transition metal surface is imperative for harnessing hydrogen energy. Despite a multitude of studies, the major mechanisms and key intermediates involved in the dehydrogenation process of formic acid remain a great topic of debate due to ambiguous adsorbate interactions. In this research, we develop an advanced microkinetic model based on first-principles calculations, accounting for adsorbate–adsorbate interactions. Our study unveils a comprehensive mechanism for the Pd (1 1 1) surface, highlighting the significance of coverage effects in formic acid dehydrogenation. Our findings unequivocally demonstrate that H coverage on the Pd (1 1 1) surface renders formic acid more susceptible to decompose into H2 and CO2 through COOH intermediates. Consistent with experimental results, the selectivity of H2 in the decomposition of formic acid on the Pd (1 1 1) surface approaches 100 %. Considering the influence of H coverage, our kinetic analysis aligns perfectly with experimental values at a temperature of 373 K.
AU - Yao, Zihao
AU - Liu, Xu
AU - Bunting, Rhys
AU - Wang, Jianguo
ID - 15114
JF - Chemical Engineering Science
SN - 0009-2509
TI - Unravelling the reaction mechanism for H2 production via formic acid decomposition over Pd: Coverage-dependent microkinetic modeling
VL - 291
ER -
TY - JOUR
AB - Water is known to play an important role in collagen self-assembly, but it is still largely unclear how water–collagen interactions influence the assembly process and determine the fibril network properties. Here, we use the H2O/D2O isotope effect on the hydrogen-bond strength in water to investigate the role of hydration in collagen self-assembly. We dissolve collagen in H2O and D2O and compare the growth kinetics and the structure of the collagen assemblies formed in these water isotopomers. Surprisingly, collagen assembly occurs ten times faster in D2O than in H2O, and collagen in D2O self-assembles into much thinner fibrils, that form a more inhomogeneous and softer network, with a fourfold reduction in elastic modulus when compared to H2O. Combining spectroscopic measurements with atomistic simulations, we show that collagen in D2O is less hydrated than in H2O. This partial dehydration lowers the enthalpic penalty for water removal and reorganization at the collagen–water interface, increasing the self-assembly rate and the number of nucleation centers, leading to thinner fibrils and a softer network. Coarse-grained simulations show that the acceleration in the initial nucleation rate can be reproduced by the enhancement of electrostatic interactions. These results show that water acts as a mediator between collagen monomers, by modulating their interactions so as to optimize the assembly process and, thus, the final network properties. We believe that isotopically modulating the hydration of proteins can be a valuable method to investigate the role of water in protein structural dynamics and protein self-assembly.
AU - Giubertoni, Giulia
AU - Feng, Liru
AU - Klein, Kevin
AU - Giannetti, Guido
AU - Rutten, Luco
AU - Choi, Yeji
AU - Van Der Net, Anouk
AU - Castro-Linares, Gerard
AU - Caporaletti, Federico
AU - Micha, Dimitra
AU - Hunger, Johannes
AU - Deblais, Antoine
AU - Bonn, Daniel
AU - Sommerdijk, Nico
AU - Šarić, Anđela
AU - Ilie, Ioana M.
AU - Koenderink, Gijsje H.
AU - Woutersen, Sander
ID - 15116
IS - 11
JF - Proceedings of the National Academy of Sciences of the United States of America
SN - 0027-8424
TI - Elucidating the role of water in collagen self-assembly by isotopically modulating collagen hydration
VL - 121
ER -
TY - JOUR
AB - The hippocampal mossy fiber synapse, formed between axons of dentate gyrus granule cells and dendrites of CA3 pyramidal neurons, is a key synapse in the trisynaptic circuitry of the hippocampus. Because of its comparatively large size, this synapse is accessible to direct presynaptic recording, allowing a rigorous investigation of the biophysical mechanisms of synaptic transmission and plasticity. Furthermore, because of its placement in the very center of the hippocampal memory circuit, this synapse seems to be critically involved in several higher network functions, such as learning, memory, pattern separation, and pattern completion. Recent work based on new technologies in both nanoanatomy and nanophysiology, including presynaptic patch-clamp recording, paired recording, super-resolution light microscopy, and freeze-fracture and “flash-and-freeze” electron microscopy, has provided new insights into the structure, biophysics, and network function of this intriguing synapse. This brings us one step closer to answering a fundamental question in neuroscience: how basic synaptic properties shape higher network computations.
AU - Vandael, David H
AU - Jonas, Peter M
ID - 15117
IS - 6687
JF - Science
TI - Structure, biophysics, and circuit function of a "giant" cortical presynaptic terminal
VL - 383
ER -
TY - THES
AB - Point sets, geometric networks, and arrangements of hyperplanes are fundamental objects in
discrete geometry that have captivated mathematicians for centuries, if not millennia. This
thesis seeks to cast new light on these structures by illustrating specific instances where a
topological perspective, specifically through discrete Morse theory and persistent homology,
provides valuable insights.
At first glance, the topology of these geometric objects might seem uneventful: point sets
essentially lack of topology, arrangements of hyperplanes are a decomposition of Rd, which
is a contractible space, and the topology of a network primarily involves the enumeration
of connected components and cycles within the network. However, beneath this apparent
simplicity, there lies an array of intriguing structures, a small subset of which will be uncovered
in this thesis.
Focused on three case studies, each addressing one of the mentioned objects, this work
will showcase connections that intertwine topology with diverse fields such as combinatorial
geometry, algorithms and data structures, and emerging applications like spatial biology.
AU - Cultrera di Montesano, Sebastiano
ID - 15094
SN - 2663 - 337X
TI - Persistence and Morse theory for discrete geometric structures
ER -
TY - CONF
AB - We present a dynamic data structure for maintaining the persistent homology of a time series of real numbers. The data structure supports local operations, including the insertion and deletion of an item and the cutting and concatenating of lists, each in time O(log n + k), in which n counts the critical items and k the changes in the augmented persistence diagram. To achieve this, we design a tailor-made tree structure with an unconventional representation, referred to as banana tree, which may be useful in its own right.
AU - Cultrera di Montesano, Sebastiano
AU - Edelsbrunner, Herbert
AU - Henzinger, Monika H
AU - Ost, Lara
ED - Woodruff, David P.
ID - 15093
T2 - Proceedings of the 2024 Annual ACM-SIAM Symposium on Discrete Algorithms (SODA)
TI - Dynamically maintaining the persistent homology of time series
ER -
TY - GEN
AB - Motivated by applications in the medical sciences, we study finite chromatic
sets in Euclidean space from a topological perspective. Based on the persistent
homology for images, kernels and cokernels, we design provably stable
homological quantifiers that describe the geometric micro- and macro-structure
of how the color classes mingle. These can be efficiently computed using
chromatic variants of Delaunay and alpha complexes, and code that does these
computations is provided.
AU - Cultrera di Montesano, Sebastiano
AU - Draganov, Ondrej
AU - Edelsbrunner, Herbert
AU - Saghafian, Morteza
ID - 15091
T2 - arXiv
TI - Chromatic alpha complexes
ER -
TY - JOUR
AB - The brain’s functionality is developed and maintained through synaptic plasticity. As synapses undergo plasticity, they also affect each other. The nature of such ‘co-dependency’ is difficult to disentangle experimentally, because multiple synapses must be monitored simultaneously. To help understand the experimentally observed phenomena, we introduce a framework that formalizes synaptic co-dependency between different connection types. The resulting model explains how inhibition can gate excitatory plasticity while neighboring excitatory–excitatory interactions determine the strength of long-term potentiation. Furthermore, we show how the interplay between excitatory and inhibitory synapses can account for the quick rise and long-term stability of a variety of synaptic weight profiles, such as orientation tuning and dendritic clustering of co-active synapses. In recurrent neuronal networks, co-dependent plasticity produces rich and stable motor cortex-like dynamics with high input sensitivity. Our results suggest an essential role for the neighborly synaptic interaction during learning, connecting micro-level physiology with network-wide phenomena.
AU - Agnes, Everton J.
AU - Vogels, Tim P
ID - 15171
JF - Nature Neuroscience
SN - 1097-6256
TI - Co-dependent excitatory and inhibitory plasticity accounts for quick, stable and long-lasting memories in biological networks
ER -
TY - JOUR
AB - We propose a novel approach to concentration for non-independent random variables. The main idea is to “pretend” that the random variables are independent and pay a multiplicative price measuring how far they are from actually being independent. This price is encapsulated in the Hellinger integral between the joint and the product of the marginals, which is then upper bounded leveraging tensorisation properties. Our bounds represent a natural generalisation of concentration inequalities in the presence of dependence: we recover exactly the classical bounds (McDiarmid’s inequality) when the random variables are independent. Furthermore, in a “large deviations” regime, we obtain the same decay in the probability as for the independent case, even when the random variables display non-trivial dependencies. To show this, we consider a number of applications of interest. First, we provide a bound for Markov chains with finite state space. Then, we consider the Simple Symmetric Random Walk, which is a non-contracting Markov chain, and a non-Markovian setting in which the stochastic process depends on its entire past. To conclude, we propose an application to Markov Chain Monte Carlo methods, where our approach leads to an improved lower bound on the minimum burn-in period required to reach a certain accuracy. In all of these settings, we provide a regime of parameters in which our bound fares better than what the state of the art can provide.
AU - Esposito, Amedeo Roberto
AU - Mondelli, Marco
ID - 15172
JF - IEEE Transactions on Information Theory
SN - 0018-9448
TI - Concentration without independence via information measures
ER -
TY - JOUR
AB - The James Webb Space Telescope is revealing a new population of dust-reddened broad-line active galactic nuclei (AGN) at redshifts z ≳ 5. Here we present deep NIRSpec/Prism spectroscopy from the Cycle 1 Treasury program Ultradeep NIRSpec and NIRCam ObserVations before the Epoch of Reionization (UNCOVER) of 15 AGN candidates selected to be compact, with red continua in the rest-frame optical but with blue slopes in the UV. From NIRCam photometry alone, they could have been dominated by dusty star formation or an AGN. Here we show that the majority of the compact red sources in UNCOVER are dust-reddened AGN: 60% show definitive evidence for broad-line Hα with a FWHM > 2000 km s −1, 20% of the current data are inconclusive, and 20% are brown dwarf stars. We propose an updated photometric criterion to select red z > 5 AGN that excludes brown dwarfs and is expected to yield >80% AGN. Remarkably, among all zphot > 5 galaxies with F277W – F444W > 1 in UNCOVER at least 33% are AGN regardless of compactness, climbing to at least 80% AGN for sources with F277W – F444W > 1.6. The confirmed AGN have black hole masses of 107–109M⊙. While their UV luminosities (−16 > MUV > −20 AB mag) are low compared to UV-selected AGN at these epochs, consistent with percent-level scattered AGN light or low levels of unobscured star formation, the inferred bolometric luminosities are typical of 107–109M⊙ black holes radiating at ∼10%–40% the Eddington limit. The number densities are surprisingly high at ∼10−5 Mpc−3 mag−1, 100 times more common than the faintest UV-selected quasars, while accounting for ∼1% of the UV-selected galaxies. While their UV faintness suggests they may not contribute strongly to reionization, their ubiquity poses challenges to models of black hole growth.
AU - Greene, Jenny E.
AU - Labbe, Ivo
AU - Goulding, Andy D.
AU - Furtak, Lukas J.
AU - Chemerynska, Iryna
AU - Kokorev, Vasily
AU - Dayal, Pratika
AU - Volonteri, Marta
AU - Williams, Christina C.
AU - Wang, Bingjie
AU - Setton, David J.
AU - Burgasser, Adam J.
AU - Bezanson, Rachel
AU - Atek, Hakim
AU - Brammer, Gabriel
AU - Cutler, Sam E.
AU - Feldmann, Robert
AU - Fujimoto, Seiji
AU - Glazebrook, Karl
AU - De Graaff, Anna
AU - Khullar, Gourav
AU - Leja, Joel
AU - Marchesini, Danilo
AU - Maseda, Michael V.
AU - Matthee, Jorryt J
AU - Miller, Tim B.
AU - Naidu, Rohan P.
AU - Nanayakkara, Themiya
AU - Oesch, Pascal A.
AU - Pan, Richard
AU - Papovich, Casey
AU - Price, Sedona H.
AU - Van Dokkum, Pieter
AU - Weaver, John R.
AU - Whitaker, Katherine E.
AU - Zitrin, Adi
ID - 15170
JF - Astrophysical Journal
SN - 0004-637X
TI - UNCOVER spectroscopy confirms the surprising ubiquity of active galactic nuclei in red sources at z > 5
VL - 964
ER -
TY - CONF
AB - A linearly ordered (LO) k-colouring of a hypergraph is a colouring of its vertices with colours 1, … , k such that each edge contains a unique maximal colour. Deciding whether an input hypergraph admits LO k-colouring with a fixed number of colours is NP-complete (and in the special case of graphs, LO colouring coincides with the usual graph colouring). Here, we investigate the complexity of approximating the "linearly ordered chromatic number" of a hypergraph. We prove that the following promise problem is NP-complete: Given a 3-uniform hypergraph, distinguish between the case that it is LO 3-colourable, and the case that it is not even LO 4-colourable. We prove this result by a combination of algebraic, topological, and combinatorial methods, building on and extending a topological approach for studying approximate graph colouring introduced by Krokhin, Opršal, Wrochna, and Živný (2023).
AU - Filakovský, Marek
AU - Nakajima, Tamio Vesa
AU - Opršal, Jakub
AU - Tasinato, Gianluca
AU - Wagner, Uli
ID - 15168
SN - 9783959773119
T2 - 41st International Symposium on Theoretical Aspects of Computer Science
TI - Hardness of linearly ordered 4-colouring of 3-colourable 3-uniform hypergraphs
VL - 289
ER -
TY - JOUR
AB - Primary implant stability, which refers to the stability of the implant during the initial healing period is a crucial factor in determining the long-term success of the implant and lays the foundation for secondary implant stability achieved through osseointegration. Factors affecting primary stability include implant design, surgical technique, and patient-specific factors like bone quality and morphology. In vivo, the cyclic nature of anatomical loading puts osteosynthesis locking screws under dynamic loads, which can lead to the formation of micro cracks and defects that slowly degrade the mechanical connection between the bone and screw, thus compromising the initial stability and secondary stability of the implant. Monotonic quasi-static loading used for testing the holding capacity of implanted screws is not well suited to capture this behavior since it cannot capture the progressive deterioration of peri‑implant bone at small displacements. In order to address this issue, this study aims to determine a critical point of loss of primary implant stability in osteosynthesis locking screws under cyclic overloading by investigating the evolution of damage, dissipated energy, and permanent deformation. A custom-made test setup was used to test implanted 2.5 mm locking screws under cyclic overloading test. For each loading cycle, maximum forces and displacement were recorded as well as initial and final cycle displacements and used to calculate damage and energy dissipation evolution. The results of this study demonstrate that for axial, shear, and mixed loading significant damage and energy dissipation can be observed at approximately 20 % of the failure force. Additionally, at this load level, permanent deformations on the screw-bone interface were found to be in the range of 50 to 150 mm which promotes osseointegration and secondary implant stability. This research can assist surgeons in making informed preoperative decisions by providing a better understanding of the critical point of loss of primary implant stability, thus improving the long-term success of the implant and overall patient satisfaction.
AU - Silva-Henao, Juan D.
AU - Schober, Sophie
AU - Pahr, Dieter H.
AU - Reisinger, Andreas G.
ID - 15164
JF - Medical Engineering and Physics
SN - 1350-4533
TI - Critical loss of primary implant stability in osteosynthesis locking screws under cyclic overloading
VL - 126
ER -
TY - JOUR
AB - Interpretation of extracellular recordings can be challenging due to the long range of electric field. This challenge can be mitigated by estimating the current source density (CSD). Here we introduce kCSD-python, an open Python package implementing Kernel Current Source Density (kCSD) method and related tools to facilitate CSD analysis of experimental data and the interpretation of results. We show how to counter the limitations imposed by noise and assumptions in the method itself. kCSD-python allows CSD estimation for an arbitrary distribution of electrodes in 1D, 2D, and 3D, assuming distributions of sources in tissue, a slice, or in a single cell, and includes a range of diagnostic aids. We demonstrate its features in a Jupyter Notebook tutorial which illustrates a typical analytical workflow and main functionalities useful in validating analysis results.
AU - Chintaluri, Chaitanya
AU - Bejtka, Marta
AU - Sredniawa, Wladyslaw
AU - Czerwinski, Michal
AU - Dzik, Jakub M.
AU - Jedrzejewska-Szmek, Joanna
AU - Wojciki, Daniel K.
ID - 15169
IS - 3
JF - PLoS Computational Biology
SN - 1553-734X
TI - kCSD-python, reliable current source density estimation with quality control
VL - 20
ER -