Development and method validation of a sampling technique for a reproducible detection of synthetic cannabinoids in exhaled breath using an in vitro pig lung model.

Alternative matrices, especially exhaled breath (EB), have gained increasing attention for a few years. To interpret toxicological findings, knowledge on the toxicokinetic (TK) properties of a substance in EB is indispensable. Whilst such data are already accessible for various drugs (e.g. Δ9-tetrahydrocannabinol), they are still not available for new psychoactive substances, particularly synthetic cannabinoids (SCs). As SCs raise a high public health concern, the aim of this study was to assess these data in future TK studies in pigs. For this purpose, an in vitro sampling technique of EB was initially developed, being prospectively applied to anesthetized and ventilated pigs for the detection of SCs in a controlled and reproducible manner as exemplified by cumyl-5F-P7AICA. Furthermore, a method for the qualitative and quantitative detection of cumyl-5F-P7AICA in EB using glass fiber filters (GFF) was established und fully validated. Therefore, cumyl-5F-P7AICA (0.5 mg/mL in ethanol abs.) was initially nebulized using a ventilation machine and a breathing tube, as they are also used in surgeries. The aerosol was delivered into a simulated pig lung. To collect EB, a pump was connected to that part of the breathing tube, that contains EB (expiratory limb), and sampling was performed repeatedly (n=6) for 15 min (2 L EB/min) each using GFF. For extraction of the substance, the GFF were macerated with acetone and the remaining experimental components were rinsed with ethanol. After sample preparation, the extracts were analyzed by LC-MS/MS. In the complete experimental setup, about 40% of the initially nebulized cumyl-5F-P7AICA dose was found with 3.6 ± 1.3% being detected in the GFF. Regarding the comparably high loss of substance, the open ventilation system and a conceivable adsorption of the SC in the ventilator have to be considered. However, the herein introduced approach is promising to determine the TK properties of cumyl-5F-P7AICA in EB.

Invasive fractional-flow-reserve prediction by coronary CT angiography using artificial intelligence vs. computational fluid dynamics software in intermediate-grade stenosis.

Coronary computed angiography (CCTA) with non-invasive fractional flow reserve (FFR) calculates lesion-specific ischemia when compared with invasive FFR and can be considered for patients with stable chest pain and intermediate-grade stenoses according to recent guidelines. The objective of this study was to compare a new CCTA-based artificial-intelligence deep-learning model for FFR prediction (FFRAI) to computational fluid dynamics CT-derived FFR (FFRCT) in patients with intermediate-grade coronary stenoses with FFR as reference standard. The FFRAI model was trained with curved multiplanar-reconstruction CCTA images of 500 stenotic vessels in 413 patients, using FFR measurements as the ground truth. We included 37 patients with 39 intermediate-grade stenoses on CCTA and invasive coronary angiography, and with FFRCT and FFR measurements in this retrospective proof of concept study. FFRAI was compared with FFRCT regarding the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and diagnostic accuracy for predicting FFR ≤ 0.80. Sensitivity, specificity, PPV, NPV, and diagnostic accuracy of FFRAI in predicting FFR ≤ 0.80 were 91% (10/11), 82% (23/28), 67% (10/15), 96% (23/24), and 85% (33/39), respectively. Corresponding values for FFRCT were 82% (9/11), 75% (21/28), 56% (9/16), 91% (21/23), and 77% (30/39), respectively. Diagnostic accuracy did not differ significantly between FFRAI and FFRCT (p = 0.12). FFRAI performed similarly to FFRCT for predicting intermediate-grade coronary stenoses with FFR ≤ 0.80. These findings suggest FFRAI as a potential non-invasive imaging tool for guiding therapeutic management in these stenoses.

Human-centred physical neuromorphics with visual brain-computer interfaces.

Steady-state visual evoked potentials (SSVEPs) are widely used for brain-computer interfaces (BCIs) as they provide a stable and efficient means to connect the computer to the brain with a simple flickering light. Previous studies focused on low-density frequency division multiplexing techniques, i.e. typically employing one or two light-modulation frequencies during a single flickering light stimulation. Here we show that it is possible to encode information in SSVEPs excited by high-density frequency division multiplexing, involving hundreds of frequencies. We then demonstrate the ability to transmit entire images from the computer to the brain/EEG read-out in relatively short times. High-density frequency multiplexing also allows to implement a photonic neural network utilizing SSVEPs, that is applied to simple classification tasks and exhibits promising scalability properties by connecting multiple brains in series. Our findings open up new possibilities for the field of neural interfaces, holding potential for various applications, including assistive technologies and cognitive enhancements, to further improve human-machine interactions.

Massively parallel combination screen reveals small molecule sensitization of antibiotic-resistant Gram-negative ESKAPE pathogens.

Antibiotic resistance, especially in multidrug-resistant ESKAPE pathogens, remains a worldwide problem. Combination antimicrobial therapies may be an important strategy to overcome resistance and broaden the spectrum of existing antibiotics. However, this strategy is limited by the ability to efficiently screen large combinatorial chemical spaces. Here, we deployed a high-throughput combinatorial screening platform, DropArray, to evaluate the interactions of over 30,000 compounds with up to 22 antibiotics and 6 strains of Gram-negative ESKAPE pathogens, totaling to over 1.3 million unique strain-antibiotic-compound combinations. In this dataset, compounds more frequently exhibited synergy with known antibiotics than single-agent activity. We identified a compound, P2-56, and developed a more potent analog, P2-56-3, which potentiated rifampin (RIF) activity against Acinetobacter baumannii and Klebsiella pneumoniae. Using phenotypic assays, we showed P2-56-3 disrupts the outer membrane of A. baumannii. To identify pathways involved in the mechanism of synergy between P2-56-3 and RIF, we performed genetic screens in A. baumannii. CRISPRi-induced partial depletion of lipooligosaccharide transport genes (lptA-D, lptFG) resulted in hypersensitivity to P2-56-3/RIF treatment, demonstrating the genetic dependency of P2-56-3 activity and RIF sensitization on lpt genes in A. baumannii. Consistent with outer membrane homeostasis being an important determinant of P2-56-3/RIF tolerance, knockout of maintenance of lipid asymmetry complex genes and overexpression of certain resistance-nodulation-division efflux pumps - a phenotype associated with multidrug-resistance - resulted in hypersensitivity to P2-56-3. These findings demonstrate the immense scale of phenotypic antibiotic combination screens using DropArray and the potential for such approaches to discover new small molecule synergies against multidrug-resistant ESKAPE strains.

External cues improve visual working memory encoding in the presence of salient distractors in schizophrenia.

BACKGROUND: People with schizophrenia (PSZ) are impaired in attentional prioritization of non-salient but relevant stimuli over salient distractors during visual working memory (VWM) encoding. Conversely, guidance of top-down attention by external predictive cues is intact. Yet, it is unknown whether this preserved ability can help PSZ encode more information in the presence of salient distractors. METHODS: We employed a visuospatial change-detection task using four Gabor patches with differing orientations in 66 PSZ and 74 healthy controls (HCS). Two Gabor patches flickered which were designated either as targets or distractors and either a predictive or a non-predictive cue was displayed to manipulate top-down attention, resulting in four conditions. RESULTS: We observed significant effects of group, salience and cue as well as significant interactions of salience by cue, group by salience and group by cue. Across all conditions, PSZ stored significantly less information in VWM than HCS. PSZ stored significantly less non-flickering than flickering information with a non-predictive cue. However, PSZ stored significantly more flickering and non-flickering information with a predictive cue. CONCLUSIONS: Our findings indicate that control of attentional selection is impaired in schizophrenia. We demonstrate that additional top-down information significantly improves performance in PSZ. The observed deficit in attentional control suggests a disturbance of GABAergic inhibition in early visual areas. Moreover, our findings are indicative of a mechanism for enhancing attentional control in PSZ, which could be utilized by pro-cognitive interventions. Thus, the current paradigm is suitable to reveal both preserved and compromised cognitive component processes in schizophrenia.

Can neural networks benefit from objectives that encourage iterative convergent computations? A case study of ResNets and object classification.

Recent work has suggested that feedforward residual neural networks (ResNets) approximate iterative recurrent computations. Iterative computations are useful in many domains, so they might provide good solutions for neural networks to learn. However, principled methods for measuring and manipulating iterative convergence in neural networks remain lacking. Here we address this gap by 1) quantifying the degree to which ResNets learn iterative solutions and 2) introducing a regularization approach that encourages the learning of iterative solutions. Iterative methods are characterized by two properties: iteration and convergence. To quantify these properties, we define three indices of iterative convergence. Consistent with previous work, we show that, even though ResNets can express iterative solutions, they do not learn them when trained conventionally on computer-vision tasks. We then introduce regularizations to encourage iterative convergent computation and test whether this provides a useful inductive bias. To make the networks more iterative, we manipulate the degree of weight sharing across layers using soft gradient coupling. This new method provides a form of recurrence regularization and can interpolate smoothly between an ordinary ResNet and a "recurrent" ResNet (i.e., one that uses identical weights across layers and thus could be physically implemented with a recurrent network computing the successive stages iteratively across time). To make the networks more convergent we impose a Lipschitz constraint on the residual functions using spectral normalization. The three indices of iterative convergence reveal that the gradient coupling and the Lipschitz constraint succeed at making the networks iterative and convergent, respectively. To showcase the practicality of our approach, we study how iterative convergence impacts generalization on standard visual recognition tasks (MNIST, CIFAR-10, CIFAR-100) or challenging recognition tasks with partial occlusions (Digitclutter). We find that iterative convergent computation, in these tasks, does not provide a useful inductive bias for ResNets. Importantly, our approach may be useful for investigating other network architectures and tasks as well and we hope that our study provides a useful starting point for investigating the broader question of whether iterative convergence can help neural networks in their generalization.

How does the primate brain combine generative and discriminative computations in vision?

Vision is widely understood as an inference problem. However, two contrasting conceptions of the inference process have each been influential in research on biological vision as well as the engineering of machine vision. The first emphasizes bottom-up signal flow, describing vision as a largely feedforward, discriminative inference process that filters and transforms the visual information to remove irrelevant variation and represent behaviorally relevant information in a format suitable for downstream functions of cognition and behavioral control. In this conception, vision is driven by the sensory data, and perception is direct because the processing proceeds from the data to the latent variables of interest. The notion of "inference" in this conception is that of the engineering literature on neural networks, where feedforward convolutional neural networks processing images are said to perform inference. The alternative conception is that of vision as an inference process in Helmholtz's sense, where the sensory evidence is evaluated in the context of a generative model of the causal processes that give rise to it. In this conception, vision inverts a generative model through an interrogation of the sensory evidence in a process often thought to involve top-down predictions of sensory data to evaluate the likelihood of alternative hypotheses. The authors include scientists rooted in roughly equal numbers in each of the conceptions and motivated to overcome what might be a false dichotomy between them and engage the other perspective in the realm of theory and experiment. The primate brain employs an unknown algorithm that may combine the advantages of both conceptions. We explain and clarify the terminology, review the key empirical evidence, and propose an empirical research program that transcends the dichotomy and sets the stage for revealing the mysterious hybrid algorithm of primate vision.

Deep neural networks are not a single hypothesis but a language for expressing computational hypotheses.

An ideal vision model accounts for behavior and neurophysiology in both naturalistic conditions and designed lab experiments. Unlike psychological theories, artificial neural networks (ANNs) actually perform visual tasks and generate testable predictions for arbitrary inputs. These advantages enable ANNs to engage the entire spectrum of the evidence. Failures of particular models drive progress in a vibrant ANN research program of human vision.

Exercise-induced myocardial T1 increase and right ventricular dysfunction in recreational cyclists: a CMR study.

PURPOSE: Although cardiac troponin I (cTnI) increase following strenuous exercise has been observed, the development of exercise-induced myocardial edema remains unclear. Cardiac magnetic resonance (CMR) native T1/T2 mapping is sensitive to the pathological increase of myocardial water content. Therefore, we evaluated exercise-induced acute myocardial changes in recreational cyclists by incorporating biomarkers, echocardiography and CMR. METHODS: Nineteen male recreational participants (age: 48 ± 5 years) cycled the 'L'étape du tour de France" (EDT) 2021' (175 km, 3600 altimeters). One week before the race, a maximal graded cycling test was conducted to determine individual heart rate (HR) training zones. One day before and 3-6 h post-exercise 3 T CMR and echocardiography were performed to assess myocardial native T1/T2 relaxation times and cardiac function, and blood samples were collected. All participants were asked to cycle 2 h around their anaerobic gas exchange threshold (HR zone 4). RESULTS: Eighteen participants completed the EDT stage in 537 ± 58 min, including 154 ± 61 min of cycling time in HR zone 4. Post-race right ventricular (RV) dysfunction with reduced strain and increased volumes (p < 0.05) and borderline significant left ventricular global longitudinal strain reduction (p = 0.05) were observed. Post-exercise cTnI (0.75 ± 5.1 ng/l to 69.9 ± 41.6 ng/l; p < 0.001) and T1 relaxation times (1133 ± 48 ms to 1182 ± 46 ms, p < 0.001) increased significantly with no significant change in T2 (p = 0.474). cTnI release correlated with increase in T1 relaxation time (p = 0.002; r = 0.703), post-race RV dysfunction (p < 0.05; r = 0.562) and longer cycling in HR zone 4 (p < 0.05; r = 0.607). CONCLUSION: Strenuous exercise causes early post-race cTnI increase, increased T1 relaxation time and RV dysfunction in recreational cyclists, which showed interdependent correlation. The long-term clinical significance of these changes needs further investigation. TRIAL REGISTRATION NUMBERS AND DATE: NCT04940650 06/18/2021. NCT05138003 06/18/2021.

The effects of caffeine and d-amphetamine on spatial span task in healthy participants.

Studies that examined the effect of amphetamine or caffeine on spatial working memory (SWM) and verbal working memory (VWM) have used various tasks. However, there are no studies that have used spatial span tasks (SSTs) to assess the SWM effect of amphetamine and caffeine, although some studies have used digit span tasks (DST) to assess VWM. Previous reports also showed that increasing dopamine increases psychosis-like experiences (PLE, or schizotypy) scores which are in turn negatively associated with WM performance in people with high schizotypy and people with schizophrenia. Therefore, the present study aimed to examine the influence of d-amphetamine (0.45 mg/kg, PO), a dopamine releasing stimulant, on SST, DST, and on PLE in healthy volunteers. In a separate study, we examined the effect of caffeine, a nonspecific adenosine receptor antagonist with stimulant properties, on similar tasks. METHODS: Healthy participants (N = 40) took part in two randomized, double-blind, counter-balanced placebo-controlled cross-over pilot studies: The first group (N = 20) with d-amphetamine (0.45 mg/kg, PO) and the second group (N = 20) with caffeine (200 mg, PO). Spatial span and digit span were examined under four delay conditions (0, 2, 4, 8 s). PLE were assessed using several scales measuring various aspects of psychosis and schizotypy. RESULTS: We failed to find an effect of d-amphetamine or caffeine on SWM or VWM, relative to placebo. However, d-amphetamine increased a composite score of psychosis-like experiences (p = 0.0005), specifically: Scores on Brief Psychiatric Rating Scale, Perceptual Aberrations Scale, and Magical Ideation Scale were increased following d-amphetamine. The degree of change in PLE following d-amphetamine negatively and significantly correlated with changes in SWM, mainly at the longest delay condition of 8 s (r = -0.58, p = 0.006). CONCLUSION: The present results showed that moderate-high dose of d-amphetamine and moderate dose of caffeine do not directly affect performances on DST or SST. However, the results indicate that d-amphetamine indirectly influences SWM, through its effect on psychosis-like experiences. CLINICAL TRIAL REGISTRATION NUMBER: CT-2018-CTN-02561 (Therapeutic Goods Administration Clinical Trial Registry) and ACTRN12618001292268 (The Australian New Zealand Clinical Trials Registry) for caffeine study, and ACTRN12608000610336 for d-amphetamine study.

Discovery of a cis-regulatory element SaeM involved in dynamic regulation of synergid-specific MYB98.

MYB98 is a key regulator of the genetic network behind pollen tube attraction toward the female gametophyte. MYB98 is specifically expressed in the synergid cells (SCs), a female gametophyte component cells specialized for pollen tube attraction. However, it had not been clear how exactly MYB98 achieves this specific expression pattern. In the current study, we have determined that a normal SC-specific expression of MYB98 is dependent on a 16-bp-long cis-regulatory element, CATTTACACATTAAAA, freshly named as the "S ynergid-specific A ctivation E lement of M YB98" (SaeM). An 84 bp fragment harboring SaeM in the middle was sufficient to drive exclusively SC-specific expression. The element was present in a significantly large proportion of SC-specific gene promoters and in the promoter of MYB98 homologous genes in the Brassicaceae (pMYB98s). Significance of such family-wide SaeM-like element conservation in exclusive SC-specific expression was confirmed by the Arabidopsis-like activation feature of Brassica oleracea-derived pMYB98 and absence of such feature of pMYB98 derived from a non-Brassicaceae member Prunus persica. Additionally, the yeast-one-hybrid assay showed that the SaeM can be recognized by ANTHOCYANINLESS2 (ANL2) and DAP-seq data further suggested for additional three ANL2 homologs targeting the similar cis-element. Overall, our study has concluded that SaeM plays a crucial role in driving exclusively SC-specific expression of MYB98 and strongly suggests for the involvement of ANL2 and its homologs in its dynamic regulation in planta. Future study on the transcription factors is expected to shed more light on the mechanism behind the process.

Interference between items stored for distinct tasks in visual working memory.

The action perspective on working memory suggests that memory representations are coded according to their specific temporal and behavioral task demands. This stands in contrast to theories that assume representations are stored in a task-agnostic format within a "common workspace". Here, we tested whether visual items that are memorized for different tasks are stored separately from one another or show evidence of inter-item interference during concurrent maintenance, indicating a common storage. In two experiments, we combined a framing memory task (memorize a motion direction for continuous direction report) with an embedded memory task (memorize a motion direction for a binary direction discrimination) that was placed within the retention period of the framing task. Even though the temporal and action demands were item specific, we observed two types of interference effects between the items: The embedded motion direction was (1) repulsed away and (2) degraded in precision by the motion direction of the item in the framing task. Repulsion and precision degradation increased with item similarity when both items were concurrently held in working memory. In contrast, perceptual and iconic memory control conditions revealed weaker repulsion overall and no interference effect on precision during the stimulus processing stages prior to working memory consolidation. Thus, additional inter-item interference arose uniquely within working memory. Together, our results present evidence that items that are stored for distinct tasks to be performed at distinct points in time, reside in a common workspace in working memory.

Improved correspondence of fMRI visual field localizer data after cortex-based macroanatomical alignment.

Studying the visual system with fMRI often requires using localizer paradigms to define regions of interest (ROIs). However, the considerable interindividual variability of the cerebral cortex represents a crucial confound for group-level analyses. Cortex-based alignment (CBA) techniques reliably reduce interindividual macroanatomical variability. Yet, their utility has not been assessed for visual field localizer paradigms, which map specific parts of the visual field within retinotopically organized visual areas. We evaluated CBA for an attention-enhanced visual field localizer, mapping homologous parts of each visual quadrant in 50 participants. We compared CBA with volume-based alignment and a surface-based analysis, which did not include macroanatomical alignment. CBA led to the strongest increase in the probability of activation overlap (up to 86%). At the group level, CBA led to the most consistent increase in ROI size while preserving vertical ROI symmetry. Overall, our results indicate that in addition to the increased signal-to-noise ratio of a surface-based analysis, macroanatomical alignment considerably improves statistical power. These findings confirm and extend the utility of CBA for the study of the visual system in the context of group analyses. CBA should be particularly relevant when studying neuropsychiatric disorders with abnormally increased interindividual macroanatomical variability.

Kinetic performance comparison of superficially porous, fully porous and monolithic reversed-phase columns by gradient kinetic plots for the separation of protein biopharmaceuticals.

To find the best performing column for the analysis of protein-based biopharmaceuticals is a significant challenge as meanwhile numerous modern columns with distinct stationary phase morphologies are available for reversed-phase liquid chromatography. Especially when besides morphology also several other column factors are different, it is hard to decide about the best performing column a priori. To cope with this problem, in the present work 13 different reversed-phase columns dedicated for protein separations were systematically tested by the gradient kinetic plot method. A comprehensive comparison of columns with different morphologies (monolithic, fully porous and superficially porous particle columns), particle sizes and pore diameters as well as column length was performed. Specific consideration was also given to various monolithic columns which recently shifted a bit out of the prime focus in the scientific literature. The test proteins ranged from small proteins starting from 12 kDa, to medium sized proteins (antibody subunits obtained after IdeS-digestion and disulphide reduction) and an intact antibody. The small proteins cytochrome c, lysozyme and ß-lactoglobulin could be analysed with similar performance by the best columns of all three column morphologies while for the antibody fragments specific fully porous and superficially porous particle columns were superior. A 450 Å 3,5 µm superficially porous particle column showed the best performance for the intact antibody while a 1.7 µm fully porous particle column with 300 Å showed equivalent performance to the best superficially porous column with thin shell and 400 Å pore size for proteins between 12 and 25 kDa. While the majority of the columns had C4 bonding chemistry, the silica monolith with C18 bonding and 300 Å mesopore size approximated the best performing particle columns and outperformed a C4 300 Å wide-pore monolith. The current work can support the preferred choice for the most suitable reversed-phase column for protein separations.

Thromboembolic complications of recreational nitrous oxide (ab)use: a systematic review.

The recreatinal use of nitrous oxide has become more common in recent years, especially in adolescents and young adults. It has been mainly associated with medical conditions like megaloblastic anemia and (myelo)neuropathy. We report on the thromboembolic complications, a less known side effect, associated with recreational inhalation of nitrous oxide. An extensive literature search was performed for publications reporting on the thromboembolic complications associated with recreational nitrous oxide abuse. Data about sex, age, location of thrombosis, laboratory findings, therapy and outcome were collected. A total of 13 case reports or case series were identified comprising a total of 14 patients. The reported thromboembolic side effects included deep venous thrombosis, pulmonary embolism, mesenterial-, portal and splenic vein thrombosis, cerebral sinus thrombosis, cortical vein thrombosis, stroke, acute myocardial infarction and peripheral artery thromboembolism. These side effects are possibly mediated by the interaction of nitrous oxide with vitamin B12, a cofactor of the methionine synthase complex, which eventually results in elevation of plasma levels of homocysteine. Despite being a known risk factor for cardiovascular disease, the exact pathophysiological mechanism remains unclear. Cessation of nitrous oxide inhalation is necessary to prevent recurrent thrombosis. Nitrous oxide abuse may thus result in a wide spectrum of thromboembolic complications. One should be aware of this etiology, especially in a young person with no obvious risk factors for cardiovascular disease. Spreading awareness is important to inform people about the potentially serious side effects associated with nitrous oxide inhalation.

Monolithic Papain-Immobilized Enzyme Reactors for Automated Structural Characterization of Monoclonal Antibodies.

The characterization of monoclonal antibodies (mAbs) requires laborious and time-consuming sample preparation steps before the liquid chromatography-mass spectrometry (LC-MS) analysis. Middle-up approaches entailing the use of specific proteases (papain, IdeS, etc.) emerged as practical and informative methods for mAb characterization. This work reports the development of immobilized enzyme reactors (IMERs) based on papain able to support mAb analytical characterization. Two monolithic IMERs were prepared by the covalent immobilization of papain on different supports, both functionalized via epoxy groups: a Chromolith® WP 300 Epoxy silica column from Merck KGaA and a polymerized high internal phase emulsion (polyHIPE) material synthesized by our research group. The two bioreactors were included in an in-flow system and characterized in terms of immobilization yield, kinetics, activity, and stability using Nα-benzoyl-L-arginine ethyl ester (BAEE) as a standard substrate. Moreover, the two bioreactors were tested toward a standard mAb, namely, rituximab (RTX). An on-line platform for mAb sample preparation and analysis with minimal operator manipulation was developed with both IMERs, allowing to reduce enzyme consumption and to improve repeatability compared to in-batch reactions. The site-specificity of papain was maintained after its immobilization on silica and polyHIPE monolithic supports, and the two IMERs were successfully applied to RTX digestion for its structural characterization by LC-MS. The main pros and cons of the two supports for the present application were described.

Interactions of Truncated Menaquinones in Lipid Monolayers and Bilayers.

Menaquinones (MK) are hydrophobic molecules that consist of a naphthoquinone headgroup and a repeating isoprenyl side chain and are cofactors used in bacterial electron transport systems to generate cellular energy. We have previously demonstrated that the folded conformation of truncated MK homologues, MK-1 and MK-2, in both solution and reverse micelle microemulsions depended on environment. There is little information on how MKs associate with phospholipids in a model membrane system and how MKs affect phospholipid organization. In this manuscript, we used a combination of Langmuir monolayer studies and molecular dynamics (MD) simulations to probe these questions on truncated MK homologues, MK-1 through MK-4 within a model membrane. We observed that truncated MKs reside farther away from the interfacial water than ubiquinones are are located closer to the phospholipid tails. We also observed that phospholipid packing does not change at physiological pressure in the presence of truncated MKs, though a difference in phospholipid packing has been observed in the presence of ubiquinones. We found through MD simulations that for truncated MKs, the folded conformation varied, but MKs location and association with the bilayer remained unchanged at physiological conditions regardless of side chain length. Combined, this manuscript provides fundamental information, both experimental and computational, on the location, association, and conformation of truncated MK homologues in model membrane environments relevant to bacterial energy production.

Capturing the objects of vision with neural networks.

Human visual perception carves a scene at its physical joints, decomposing the world into objects, which are selectively attended, tracked and predicted as we engage our surroundings. Object representations emancipate perception from the sensory input, enabling us to keep in mind that which is out of sight and to use perceptual content as a basis for action and symbolic cognition. Human behavioural studies have documented how object representations emerge through grouping, amodal completion, proto-objects and object files. By contrast, deep neural network models of visual object recognition remain largely tethered to sensory input, despite achieving human-level performance at labelling objects. Here, we review related work in both fields and examine how these fields can help each other. The cognitive literature provides a starting point for the development of new experimental tasks that reveal mechanisms of human object perception and serve as benchmarks driving the development of deep neural network models that will put the object into object recognition.

Perception of effort during an isometric contraction is influenced by prior muscle lengthening or shortening.

PURPOSE: Following a shortening or lengthening muscle contraction, torque produced in the isometric steady state is lower (residual torque depression; rTD) or higher (residual torque enhancement; rTE), respectively, compared to a purely isometric contraction at the same final muscle length and level of activation. This is referred to as the history dependence of force. When matching a given torque level, there is greater muscle activation (electromyography; EMG) following shortening and less activation following lengthening. Owing to these differences in neuromuscular activation, it is unclear whether perception of effort is altered by the history dependence of force during plantar-flexion. METHODS: Experiment 1 tested whether perception of effort differed between the rTD and rTE state when torque was matched. Experiment 2 tested whether perception of effort differed between the rTD and rTE state when EMG was matched. Finally, experiment 3 tested whether EMG differed between the rTD and rTE state when perception of effort was matched. RESULTS: When torque was matched, both EMG and perception of effort were higher in the rTD compared to rTE state. When EMG was matched, torque was lower in the rTD compared to rTE state while perception of effort did not differ between the two states. When perception of effort was matched, torque was lower in the rTD compared to rTE state and EMG did not differ between the two states. CONCLUSION: The combined results from these experiments indicate that the history dependence of force alters one's perception of effort, dependent on the level of motor command.