Reachability in Fixed VASS: Expressiveness and Lower Bounds

The recent years have seen remarkable progress in establishing the complexity of the reachability problem for vector addition systems with states (VASS), equivalently known as Petri nets. Existing work primarily considers the case in which both the VASS as well as the initial and target configurations are part of the input. In this paper, we investigate the reachability problem in the setting where the VASS is fixed and only the initial configuration is variable. We show that fixed VASS fully express arithmetic on initial segments of the natural numbers. It follows that there is a very weak reduction from any fixed such number-theoretic predicate (e.g. primality or square-freeness) to reachability in fixed VASS where configurations are presented in unary. If configurations are given in binary, we show that there is a fixed VASS with five counters whose reachability problem is PSPACE-hard

Rapid dynamics of cell-shape recovery in response to local deformations

It is vital that cells respond rapidly to mechanical cues within their microenvironment through changes in cell shape and volume, which rely upon the mechanical properties of cells’ highly interconnected cytoskeletal networks and intracellular fluid redistributions. While previous research has largely investigated deformation mechanics, we now focus on the immediate cell-shape recovery response following mechanical perturbation by inducing large, local, and reproducible cellular deformations using AFM. By continuous imaging within the plane of deformation, we characterize the membrane and cortical response of HeLa cells to unloading, and model the recovery via overdamped viscoelastic dynamics. Importantly, the majority (90%) of HeLa cells recover their cell shape in o1 s. Despite actin remodelling on this time scale, we show that cell-shape recovery time is not affected by load duration, nor magnitude for untreated cells. To further explore this rapid recovery response, we expose cells to cytoskeletal destabilizers and osmotic shock conditions, which uncovers the interplay between actin and osmotic pressure. We show that the rapid dynamics of recovery depend crucially on intracellular pressure, and provide strong evidence that cortical actin is the key regulator in the cell-shape recovery processes, in both cancerous and non-cancerous epithelial cell

Are the Rates of Dexter Transfer in TADF Hyperfluorescence Systems Optically Accessible?

Seemingly not, but for unexpected reasons. Combining the triplet harvesting properties of TADF materials with the fast emission rates and colour purity of fluorescent emitters is attractive for developing high performance OLEDs. In this “hyperfluorescence” approach, triplet excitons are converted to singlets on the TADF material and transferred to the fluorescent material by long range Förster energy transfer. The primary loss mechanism is assumed to be Dexter energy transfer from the TADF triplet to the non-emissive triplet of the fluorescent emitter. Here we use optical spectroscopy to investigate energy transfer in representative emissive layers. Despite observing kinetics that at first appear consistent with Dexter quenching of the TADF triplet state, transient absorption, photoluminescence quantum yields, and comparison to phosphor-sensitised “hyperphosphorescent” systems reveal that this is not the case. While Dexter quenching by the fluorescent emitter is likely still a key loss mechanism in devices, we demonstrate that – despite initial appearances - it is inoperative under optical excitation. These results reveal a deep limitation of optical spectroscopy in characterizing hyperfluorescent systems

Rapid dynamics of cell-shape recovery in response to local deformations

It is vital that cells respond rapidly to mechanical cues within their microenvironment through changes in cell shape and volume, which rely upon the mechanical properties of cells’ highly interconnected cytoskeletal networks and intracellular fluid redistributions. While previous research has largely investigated deformation mechanics, we now focus on the immediate cell-shape recovery response following mechanical perturbation by inducing large, local, and reproducible cellular deformations using AFM. By continuous imaging within the plane of deformation, we characterize the membrane and cortical response of HeLa cells to unloading, and model the recovery via overdamped viscoelastic dynamics. Importantly, the majority (90%) of HeLa cells recover their cell shape in o1 s. Despite actin remodelling on this time scale, we show that cell-shape recovery time is not affected by load duration, nor magnitude for untreated cells. To further explore this rapid recovery response, we expose cells to cytoskeletal destabilizers and osmotic shock conditions, which uncovers the interplay between actin and osmotic pressure. We show that the rapid dynamics of recovery depend crucially on intracellular pressure, and provide strong evidence that cortical actin is the key regulator in the cell-shape recovery processes, in both cancerous and non-cancerous epithelial cell

Modeling Disk Cracks in Rotors by Utilizing Speed Dependent Eccentricity

This paper discusses the feasibility of vibration-based structural health monitoring for detecting disk cracks in rotor systems. The approach of interest assumes that a crack located on a rotating disk causes a minute change in the system’s center of mass due to the centrifugal force induced opening of the crack. The center of mass shift is expected to reveal itself in the vibration vector (i.e., whirl response; plotted as amplitude and phase versus speed) gathered during a spin-up and/or spin-down test. Here, analysis is accomplished by modeling a Jeffcott rotor that is characterized by analytical, numerical, and experimental data. The model, which has speed dependent eccentricity, is employed in order to better understand the sensitivity of the approach. For the experimental set-up emulated here (i.e., a single disk located mid-span on a flexible shaft), it appears that a rather sizable flaw in the form of a through-thickness notch could be detected by monitoring the damage-induced shift in center of mass. Although, identifying actual disk cracks in complex “real world” environments, where noncritical crack lengths are small and excessive mechanical and/or electrical noise are present, would prove to be rather challenging. Further research is needed in this regard

The cardiac surgery–associated neutrophil gelatinase-associated lipocalin (CSA-NGAL) score: A potential tool to monitor acute tubular damage

AbstractAcute kidney injury (AKI), defined as a rise in serum creatinine (functional AKI), is a frequent complication after cardiac surgery. The expression pattern of acute tubular damage biomarkers such as neutrophil gelatinase–associated lipocalin (NGAL) has been shown to precede functional AKI and, therefore, may be useful to identify very early tubular damage. The term subclinical AKI represents acute tubular damage in the absence of functional AKI (biomarker positivity without a rise in serum creatinine) and affects hard outcome measures. This potentiates an tubular-damage–based identification of renal injury, which may guide clinical management, allowing for very early preventive-protective strategies. The aim of this paper was to review the current available evidence on NGAL applicability in adult cardiac surgery patients and combine this knowledge with the expert consensus of the authors to generate an NGAL based tubular damage score: The cardiac surgery–associated NGAL Score (CSA-NGAL score). The CSA-NGAL score might be the tool needed to improve awareness and enable interventions to possibly modify these detrimental outcomes. In boldly doing so, it is intended to introduce a different approach in study designs, which will undoubtedly expand our knowledge and will hopefully move the AKI biomarker field forward

Vibration Based Crack Detection in a Rotating Disk

This paper describes the experimental results concerning the detection of a crack in a rotating disk. The goal was to utilize blade tip clearance and shaft vibration measurements to monitor changes in the system's center of mass and/or blade deformation behaviors. The concept of the approach is based on the fact that the development of a disk crack results in a distorted strain field within the component. As a result, a minute deformation in the disk's geometry as well as a change in the system's center of mass occurs. Here, a notch was used to simulate an actual crack. The vibration based experimental results failed to identify the existence of a notch when utilizing the approach described above, even with a rather large, circumferential notch (l.2 in.) located approximately mid-span on the disk (disk radius = 4.63 in. with notch at r = 2.12 in.). This was somewhat expected, since the finite element based results in Part 1 of this study predicted changes in blade tip clearance as well as center of mass shifts due to a notch to be less than 0.001 in. Therefore, the small changes incurred by the notch could not be differentiated from the mechanical and electrical noise of the rotor system. Although the crack detection technique of interest failed to identify the existence ofthe notch, the vibration data produced and captured here will be utilized in upcoming studies that will focus on different data mining techniques concerning damage detection in a disk

Разработка способа очистки газовой среды в процессе выращивания полупроводниковых монокристаллов

An individual’s zinc status has a significant impact on the immune system, and zinc deficiency, as well as supplementation, modulates immune function. To investigate the effects of zinc on different leukocyte subsets, we used microarray technology to analyze and compare the changes in mRNA expression in cell culture models of monocytes (THP-1), T cells (Jurkat), and B cells (Raji), in response to supplementation for 40 h with 50 μM zinc or 2.5 μM of the membrane-permeant zinc chelator TPEN [N,N,N′,N′-tetrakis-(2-pyridyl-methyl)ethylenediamine], respectively. In each cell type, several hundred genes were identified to be zinc sensitive, but only a total of seven genes were commonly regulated in all three cell lines. The majority of those genes were involved in zinc homeostasis, and none in immune function. Nevertheless, further analysis revealed that zinc affects entire functional networks of genes that are related to proinflammatory cytokines and cellular survival. Although the zinc-regulated activities are similar throughout the gene networks, the specific genes that are affected vary significantly between different cell types, a situation that helps to elucidate the disparity of the effects that zinc has on different leukocyte populations

Bending the Rules: Widefield Microscopy and the Abbe Limit of Resolution

One of the most fundamental concepts of microscopy is that of resolution–the ability to clearly distinguish two objects as separate. Recent advances such as structured illumination microscopy (SIM) and point localization techniques including photoactivated localization microscopy (PALM), and stochastic optical reconstruction microscopy (STORM) strive to overcome the inherent limits of resolution of the modern light microscope. These techniques, however, are not always feasible or optimal for live cell imaging. Thus, in this review, we explore three techniques for extracting high resolution data from images acquired on a widefield microscope–deconvolution, model convolution, and Gaussian fitting. Deconvolution is a powerful tool for restoring a blurred image using knowledge of the point spread function (PSF) describing the blurring of light by the microscope, although care must be taken to ensure accuracy of subsequent quantitative analysis. The process of model convolution also requires knowledge of the PSF to blur a simulated image which can then be compared to the experimentally acquired data to reach conclusions regarding its geometry and fluorophore distribution. Gaussian fitting is the basis for point localization microscopy, and can also be applied to tracking spot motion over time or measuring spot shape and size. All together, these three methods serve as powerful tools for high-resolution imaging using widefield microscopy

Bub1 Kinase and Sgo1 Modulate Pericentric Chromatin in Response to Altered Microtubule Dynamics

Tension sensing of bi-oriented chromosomes is essential for the fidelity of chromosome segregation. The spindle assembly checkpoint (SAC) conveys lack of tension or attachment to the anaphase promoting complex. Components of the SAC (Bub1) phosphorylate histone H2A (S121) and recruit the protector of cohesin, Shugoshin (Sgo1) to the inner centromere. How the chromatin structural modifications of the inner centromere are integrated into the tension sensing mechanisms and the checkpoint are not known