AMOLF Institutional Repository
Not a member yet
1351 research outputs found
Sort by
Controlling the Self-Assembly of Hierarchical PS-b-P4VP Structures Prepared by Dip-Coating and Emulsion Breath Figure Techniques
Get PDFThe breath figure (BF) method is a common laboratory-scale pathway for fabricating porous structures. The emulsion BF approach, one of the BF variations, has attracted increasing attention since it bypasses the high humidity requirement, which is characteristic for the conventional BF method. In this paper, we used the emulsion BF technique with PS-b-P4VP block copolymer (BCP) and SiO2 nanoparticles (NPs) as the stabilizers for water droplets. We combined this with the dip-coating technique to obtain a hierarchical structure consisting of BF pores and BCP nanodomains. By altering the dip-coating speeds and the NPs’ surface wetting properties and size, the average diameters of BF pores could be controlled. Notably, we were able to achieve both nano and microscale BF pores in the network. The effect of NPs for stabilization and dip-coating parameters on BF pores and BCP nanodomains formation was established, extending the comprehension of this underdeveloped subject
Cavity Quantum Optomechanical Nonlinearities and Position Measurement beyond the Breakdown of the Linearized Approximation
Get PDFSeveral optomechanics experiments are now entering the highly sought nonlinear regime where optomechanical interactions are large even for low light levels. Within this regime, new quantum phenomena and improved performance may be achieved; however, a corresponding theoretical formalism of cavity quantum optomechanics that captures the nonlinearities of both the radiation-pressure interaction and the cavity response is needed to unlock these capabilities. Here, we develop such a nonlinear cavity quantum optomechanical framework, which we then utilize to propose how position measurement can be performed beyond the breakdown of the linearized approximation. Our proposal utilizes optical general-dyne detection, ranging from single to dual homodyne, to obtain mechanical position information imprinted onto both the optical amplitude and phase quadratures and enables both pulsed and continuous modes of operation. These cavity optomechanical nonlinearities are now being confronted in a growing number of experiments, and our framework will allow a range of advances to be made in, e.g., quantum metrology, explorations of the standard quantum limit, and quantum measurement and control
Synchronous replication initiation of multiple origins
Get PDFInitiating replication synchronously at multiple origins of replication allows the bacterium Escherichia coli to divide even faster than the time it takes to replicate the entire chromosome in nutrient-rich environments. What mechanisms give rise to synchronous replication initiation remains however poorly understood. Via mathematical modelling, we identify four distinct synchronization regimes depending on two quantities: the duration of the so-called licensing period during which the initiation potential in the cell remains high after the first origin has fired and the duration of the blocking period during which already initiated origins remain blocked. For synchronous replication initiation, the licensing period must be long enough such that all origins can be initiated, but shorter than the blocking period to prevent reinitiation of origins that that the delay between the firing of the first and the last origin scales with the coefficient of variation (CV) of the initiation volume. Matching these to the values measured experimentally shows that the firing rate must rise with the cell volume with an effective Hill coefficient that is at least 20; the probability that all origins fire before the blocking period is over is then at least 92%. Our analysis thus that the low CV of the initiation volume is a consequence of synchronous replication initiation. Finally, we show that the previously presented molecular model for the regulation of replication initiation in {E. coli} can give rise to synchronous replication initiation for biologically realistic parameters
Photon superbunching in cathodoluminescence of excitons in WS2 monolayer
Get PDFCathodoluminescence spectroscopy in conjunction with second-order auto-correlation measurements of g 2 ( τ ) allows to extensively study the synchronization of photon emitters in low-dimensional structures. Co-existing excitons in two-dimensional transition metal dichalcogenide monolayers provide a great source of identical photon emitters which can be simultaneously excited by an electron. Here, we demonstrate large photon bunching with g 2 ( 0 ) up to 156 ± 16 of a tungsten disulfide monolayer (WS2), exhibiting a strong dependence on the electron-beam current. To further improve the excitation synchronization and the electron-emitter interaction, we show exemplary that the careful selection of a simple and compact geometry—a thin, monocrystalline gold nanodisk—can be used to realize a record-high bunching g 2 ( 0 ) of up to 2152 ± 236 . This approach to control the electron excitation of excitons in a WS2 monolayer allows for the synchronization of photon emitters in an ensemble, which is important to further advance light information and computing technologies
Rapid deracemization through solvent cycling: proof-of-concept using a racemizable conglomerate clopidogrel precursor
Get PDFWe demonstrate that a conglomerate-forming clopidogrel precursor undergoing solution phase racemization can be deracemized through cyclic solvent removal and re-addition. We establish that the combination of slow growth and fast dissolution of crystals is ideal for rapid deracemization, which we achieve by repurposing a Soxhlet apparatus to realize the slow removal and fast re-addition of solvent autonomously
Patterning Complex Line Motifs in Thin Films Using Immersion Controlled Reaction‐Diffusion
Get PDFThe discovery of self-organization principles that enable scalable routes towards complex functional materials has proven to be a persistent challenge. Here reaction-diffusion driven, immersion controlled patterning (R-DIP) is introduced, a self-organization strategy using immersion controlled reaction-diffusion for targeted line patterning in thin films. By modulating immersion speeds, the movement of a reaction-diffusion front over gel films is controlled, which induces precipitation of highly uniform lines at the reaction front. A balance between the immersion speed and diffusion provides both hands-on tunability of the line spacing (d = 10 − 300 µm) as well as error-correction against defects. This immersion-driven patterning strategy is widely applicable, which is demonstrated by producing line patterns of silver/silver oxide nanoparticles, silver chromate, silver dichromate, and lead carbonate. Through combinatorial stacking of different line patterns, hybrid materials with multi-dimensional patterns such as square-, diamond-, rectangle- and triangle-shaped motifs are fabricated. The functionality potential and scalability is demonstrated by producing both wafer-scale diffraction gratings with user-defined features as well as an opto-mechanical sensor based on Moiré patterning
Cytosolic Interactome Protects Against Protein Unfolding in a Single Molecule Experiment
Get PDFSingle molecule techniques are particularly well suited for investigating the processes of protein folding and chaperone assistance. However, current assays provide only a limited perspective on the various ways in which the cellular environment can influence the folding pathway of a protein. In this study, a single molecule mechanical interrogation assay is developed and used to monitor protein unfolding and refolding within a cytosolic solution. This allows to test the cumulative topological effect of the cytoplasmic interactome on the folding process. The results reveal a stabilization against forced unfolding for partial folds, which are attributed to the protective effect of the cytoplasmic environment against unfolding and aggregation. This research opens the possibility of conducting single molecule molecular folding experiments in quasi-biological environments
Nanomaterial Transformations Captured by Atomic Resolution 3D Electron Microscopy
Get PDFElectron tomography is a powerful tool to explore the morphology, 3D structure, and composition of a broad range of (nano)materials. Although these experiments are already at the state-of-the-art, several open questions remain. These questions are often related to the fact that 3D characterization by TEM is typically performed using the conventional conditions of a TEM: ultrahigh vacuum and room temperature. Since it is known that the morphology and consequently, the activity of nanomaterials will transform at higher temperatures or pressures, this poses a fundamental limitation. It is therefore not surprising that much effort has been devoted to monitoring nanoparticle transformations upon application of external stimuli by TEM
Minimizing cell number fluctuations in self-renewing tissues with a stem-cell niche
Get PDFSelf-renewing tissues require that a constant number of proliferating cells is maintained over time. This maintenance can be ensured at the single-cell level or the population level. Maintenance at the population level leads to fluctuations in the number of proliferating cells over time. Often, it is assumed that those fluctuations can be reduced by increasing the number of asymmetric divisions, i.e., divisions where only one of the daughter cells remains proliferative. Here, we study a model of cell proliferation that incorporates a stem-cell niche of fixed size, and explicitly model the cells inside and outside the niche. We find that in this model, fluctuations are minimized when the difference in growth rate between the niche and the rest of the tissue is maximized and all divisions are symmetric divisions, producing either two proliferating or two nonproliferating daughters. We show that this optimal state leaves visible signatures in clone size distributions and could thus be detected experimentally
Optimal inference of molecular interaction dynamics in FRET microscopy
Get PDFIntensity-based time-lapse fluorescence resonance energy transfer (FRET) microscopy has been a major tool for investigating cellular processes, converting otherwise unob-servable molecular interactions into fluorescence time series. However, inferring the molecular interaction dynamics from the observables remains a challenging inverse problem, particularly when measurement noise and photobleaching are nonnegli-gible-a common situation in single-cell analysis. The conventional approach is to process the time-series data algebraically, but such methods inevitably accumulate the measurement noise and reduce the signal-to-noise ratio (SNR), limiting the scope of FRET microscopy. Here, we introduce an alternative probabilistic approach, B-FRET, generally applicable to standard 3-cube FRET-imaging data. Based on Bayesian filtering theory, B-FRET implements a statistically optimal way to infer molecular interactions and thus drastically improves the SNR. We validate B-FRET using simulated data and then apply it to real data, including the notoriously noisy in vivo FRET time series from individual bacterial cells to reveal signaling dynamics otherwise hidden in the noise