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Background: Closing the control loop between users and their prostheses by providing artificial sensory feedback is a fundamental step toward the full restoration of lost sensory-motor functions. Methods: We propose a novel approach to provide artificial proprioceptive feedback about two degrees of freedom using a single array of 8 vibration motors (compact solution). The performance afforded by the novel method during an online closed-loop control task was compared to that achieved using the conventional approach, in which the same information was conveyed using two arrays of 8 and 4 vibromotors (one array per degree of freedom), respectively. The new method employed Gaussian interpolation to modulate the intensity profile across a single array of vibration motors (compact feedback) to convey wrist rotation and hand aperture by adjusting the mean and standard deviation of the Gaussian, respectively. Ten able-bodied participants and four transradial amputees performed a target achievement control test by utilizing pattern recognition with compact and conventional vibrotactile feedback to control the Hannes prosthetic hand (test conditions). A second group of ten able-bodied participants performed the same experiment in control conditions with visual and auditory feedback as well as no-feedback. Results: Conventional and compact approaches resulted in similar positioning accuracy, time and path efficiency, and total trial time. The comparison with control condition revealed that vibrational feedback was intuitive and useful, but also underlined the power of incidental feedback sources. Notably, amputee participants achieved similar performance to that of able-bodied participants. Conclusions: The study therefore shows that the novel feedback strategy conveys useful information about prosthesis movements while reducing the number of motors without compromising performance. This is an important step toward the full integration of such an interface into a prosthesis socket for clinical use. [ABSTRACT FROM AUTHOR]

Abstract Background Closing the control loop between users and their prostheses by providing artificial sensory feedback is a fundamental step toward the full restoration of lost sensory-motor functions. Methods We propose a novel approach to provide artificial proprioceptive feedback about two degrees of freedom using a single array of 8 vibration motors (compact solution). The performance afforded by the novel method during an online closed-loop control task was compared to that achieved using the conventional approach, in which the same information was conveyed using two arrays of 8 and 4 vibromotors (one array per degree of freedom), respectively. The new method employed Gaussian interpolation to modulate the intensity profile across a single array of vibration motors (compact feedback) to convey wrist rotation and hand aperture by adjusting the mean and standard deviation of the Gaussian, respectively. Ten able-bodied participants and four transradial amputees performed a target achievement control test by utilizing pattern recognition with compact and conventional vibrotactile feedback to control the Hannes prosthetic hand (test conditions). A second group of ten able-bodied participants performed the same experiment in control conditions with visual and auditory feedback as well as no-feedback. Results Conventional and compact approaches resulted in similar positioning accuracy, time and path efficiency, and total trial time. The comparison with control condition revealed that vibrational feedback was intuitive and useful, but also underlined the power of incidental feedback sources. Notably, amputee participants achieved similar performance to that of able-bodied participants. Conclusions The study therefore shows that the novel feedback strategy conveys useful information about prosthesis movements while reducing the number of motors without compromising performance. This is an important step toward the full integration of such an interface into a prosthesis socket for clinical use.

To fully exploit ultra-short X-ray pulse durations routinely available at X-ray free-electron lasers to follow out-of-equilibrium dynamics, inherent arrival time fluctuations of the X-ray pulse with an external perturbing laser pulse need to be measured. In this work, two methods of arrival time measurement were compared to measure the arrival time jitter of hard X-ray pulses. The methods were photoelectron streaking by a THz field and a transient refractive index change of a semiconductor. The methods were validated by shot-to-shot correction of a pump–probe transient reflectivity measurement. An ultimate shot-to-shot full width at half-maximum error between the devices of 19.2 ± 0.1 fs was measured.

A key challenge in developing diagnosis and treatments for Alzheimer's disease (AD) is to detect abnormal network activity at as early a stage as possible. To date, behavioral and neurophysiological investigations in AD model mice have yet to conduct a longitudinal assessment of cellular pathology, memory deficits, and neurophysiological correlates of neuronal activity. We therefore examined the temporal relationships between pathology, neuronal activities and spatial representation of environments, as well as object location memory deficits across multiple stages of development in the 5xFAD mice model and compared these results to those observed in wild-type mice. We performed longitudinal in vivo calcium imaging with miniscope on hippocampal CA1 neurons in behaving mice. We find that 5xFAD mice show amyloid plaque accumulation, depressed neuronal calcium activity during immobile states, and degenerate and unreliable hippocampal neuron spatial tuning to environmental location at early stages by 4 months of age while their object location memory (OLM) is comparable to WT mice. By 8 months of age, 5xFAD mice show deficits of OLM, which are accompanied by progressive degradation of spatial encoding and, eventually, impaired CA1 neural tuning to object-location pairings. Furthermore, depressed neuronal activity and unreliable spatial encoding at early stage are correlated with impaired performance in OLM at 8-month-old. Our results indicate the close connection between impaired hippocampal tuning to object-location and the presence of OLM deficits. The results also highlight that depressed baseline firing rates in hippocampal neurons during immobile states and unreliable spatial representation precede object memory deficits and predict memory deficits at older age, suggesting potential early opportunities for AD detecting.

To fully exploit ultra-short X-ray pulse durations routinely available at X-ray free-electron lasers to follow out-of-equilibrium dynamics, inherent arrival time fluctuations of the X-ray pulse with an external perturbing laser pulse need to be measured. In this work, two methods of arrival time measurement were compared to measure the arrival time jitter of hard X-ray pulses. The methods were photoelectron streaking by a THz field and a transient refractive index change of a semiconductor. The methods were validated by shot-to-shot correction of a pump-probe transient reflectivity measurement. An ultimate shot-to-shot full width at half-maximum error between the devices of 19.2 ± 0.1 fs was measured. [ABSTRACT FROM AUTHOR]

Recent research on transformer-based models have highlighted particular methods for medical image segmentation. Additionally, the majority of transformer-based network designs used in computer vision applications have a significant number of parameters and demand extensive training datasets. Inspired by the success of transformers in recent researches, the unet-transformer approach has become one of the de-facto ideas in overcoming the above challenges. In this manuscript, a novel unet-transformer approach was proposed for heart image segmentation to solve parameters, limited dataset, over segmentation, sensitivity noise and higher training time problems. A framework in which a novel width and height wise axial attention mechanism is incorporated into the design to effectively give positional embeddings and encode spatial flattening. Furthermore, a novel local and global spatial attention mechanism is proposed to effectively learn the local and global interactions between encoder features. Finally, we introduce a mechanism to fuse both contexts for better feature representation and preparation into the decoder. The results demonstrate that our prototype provides a robust novel axial-attention mechanism. [ABSTRACT FROM AUTHOR]

Remote sensing image semantic segmentation plays a crucial role in various fields, such as environmental monitoring, urban planning, and agricultural land classification. However, most current research primarily focuses on utilizing the spatial and spectral information of single-temporal remote sensing images, neglecting the valuable temporal information present in historical image sequences. In fact, historical images often contain valuable phenological variations in land features, which exhibit diverse patterns and can significantly benefit from semantic segmentation tasks. This paper introduces a semantic segmentation framework for satellite image time series (SITS) based on dilated convolution and a Transformer encoder. The framework includes spatial encoding and temporal encoding. Spatial encoding, utilizing dilated convolutions exclusively, mitigates the loss of spatial accuracy and the need for up-sampling, while allowing for the extraction of rich multi-scale features through a combination of different dilation rates and dense connections. Temporal encoding leverages a Transformer encoder to extract temporal features for each pixel in the image. To better capture the annual periodic patterns of phenological phenomena in land features, position encoding is calculated based on the image's acquisition date within the year. To assess the performance of this framework, comparative and ablation experiments were conducted using the PASTIS dataset. The experiments indicate that this framework achieves highly competitive performance with relatively low optimization parameters, resulting in an improvement of 8 percentage points in the mean Intersection over Union (mIoU). [ABSTRACT FROM AUTHOR]

Determining the spatial relation between objects and our location in the surroundings is essential for survival. Vestibular inputs provide key information about the position and movement of our head in the three‐dimensional space, contributing to spatial navigation. Yet, their role in encoding spatial localisation of environmental targets remains to be fully understood. We probed the accuracy and precision of healthy participants' representations of environmental space by measuring their ability to encode the spatial location of visual targets (Experiment 1). Participants were asked to detect a visual light and then walk towards it. Vestibular signalling was artificially disrupted using stochastic galvanic vestibular stimulation (sGVS) applied selectively during encoding targets' location. sGVS impaired the accuracy and precision of locating the environmental visual targets. Importantly, this effect was specific to the visual modality. The location of acoustic targets was not influenced by vestibular alterations (Experiment 2). Our findings indicate that the vestibular system plays a role in localising visual targets in the surrounding environment, suggesting a crucial functional interaction between vestibular and visual signals for the encoding of the spatial relationship between our body position and the surrounding objects. [ABSTRACT FROM AUTHOR]

Remote sensing image semantic segmentation plays a crucial role in various fields, such as environmental monitoring, urban planning, and agricultural land classification. However, most current research primarily focuses on utilizing the spatial and spectral information of single-temporal remote sensing images, neglecting the valuable temporal information present in historical image sequences. In fact, historical images often contain valuable phenological variations in land features, which exhibit diverse patterns and can significantly benefit from semantic segmentation tasks. This paper introduces a semantic segmentation framework for satellite image time series (SITS) based on dilated convolution and a Transformer encoder. The framework includes spatial encoding and temporal encoding. Spatial encoding, utilizing dilated convolutions exclusively, mitigates the loss of spatial accuracy and the need for up-sampling, while allowing for the extraction of rich multi-scale features through a combination of different dilation rates and dense connections. Temporal encoding leverages a Transformer encoder to extract temporal features for each pixel in the image. To better capture the annual periodic patterns of phenological phenomena in land features, position encoding is calculated based on the image’s acquisition date within the year. To assess the performance of this framework, comparative and ablation experiments were conducted using the PASTIS dataset. The experiments indicate that this framework achieves highly competitive performance with relatively low optimization parameters, resulting in an improvement of 8 percentage points in the mean Intersection over Union (mIoU).

Magnetic particle imaging (MPI) is a radiation-free vessel- and target-imaging modality that can sensitively detect nanoparticles. A static magnetic gradient field, referred to as a selection field, is required in MPI to provide a field-free region (FFR) for spatial encoding. The image resolution of MPI is closely related to the size of the FFR, which is determined by the selection field gradient amplitude. Because of the limitations of existing gradient coil hardware, the image resolution of MPI cannot satisfy the clinical requirements of human in vivo imaging. Pulsed excitation has been confirmed to improve the image resolution of MPI by breaking down the ‘relaxation wall.’ This work proposes the use of a pulsed waveform magnetic gradient from magnetic resonance imaging to further improve the image resolution of MPI. Through alignment of the gradient direction along the field-free line (FFL), each location on the FFL is able to have a unique excitation field strength that generates a specific relaxation-induced decay signal. Through excitation of nanoparticles on the FFL with many gradient profiles, a high-resolution, one-dimensional (1D) image can be reconstructed on the FFL. For larger magnetic nanoparticles, simulation results revealed that a pulsed excitation field with a greater flat portion generates a 1D bar pattern phantom image with a higher correlation and spatial resolution. With parallel FFL and gradient coil movements, high-resolution, two-dimensional (2D) Shepp–Logan phantom and brain vessel maps were reconstructed through repetition of the spatially resolved measurement of magnetic nanoparticles on the FFL. [ABSTRACT FROM AUTHOR]

A key challenge in developing diagnosis and treatments for Alzheimer's disease (AD) is to detect abnormal network activity at as early a stage as possible. To date, behavioral and neurophysiological investigations in AD model mice have yet to conduct a longitudinal assessment of cellular pathology, memory deficits, and neurophysiological correlates of neuronal activity. We therefore examined the temporal relationships between pathology, neuronal activities and spatial representation of environments, as well as object location memory deficits across multiple stages of development in the 5xFAD mice model and compared these results to those observed in wild-type mice. We performed longitudinal in vivo calcium imaging with miniscope on hippocampal CA1 neurons in behaving mice. We find that 5xFAD mice show amyloid plaque accumulation, depressed neuronal calcium activity during immobile states, and degenerate and unreliable hippocampal neuron spatial tuning to environmental location at early stages by 4 months of age while their object location memory (OLM) is comparable to WT mice. By 8 months of age, 5xFAD mice show deficits of OLM, which are accompanied by progressive degradation of spatial encoding and, eventually, impaired CA1 neural tuning to object-location pairings. Furthermore, depressed neuronal activity and unreliable spatial encoding at early stage are correlated with impaired performance in OLM at 8-month-old. Our results indicate the close connection between impaired hippocampal tuning to object-location and the presence of OLM deficits. The results also highlight that depressed baseline firing rates in hippocampal neurons during immobile states and unreliable spatial representation precede object memory deficits and predict memory deficits at older age, suggesting potential early opportunities for AD detecting.

Peak overlap hampers quantification in one-dimensional (1D) 1H NMR. 2D 1H -13C HSQC spectrum provides resolution superior to 1D 1H NMR. However, quantifying the components in a complex mixture with HSQC is not straightforward as in 1D 1H NMR. Quantification using HSQC could open up new avenues for studying metabolism. The variations in 1H–13C scalar couplings, T1, T2, and pulse imperfections contribute to this problem. Although T1 and T2 can be suitably chosen to minimize their deleterious effects, the differential polarization transfer for different resonances owing to large variations in 1H -13C couplings does not allow the cross-peak intensities to be directly correlated to the quantity of metabolites. Existing approaches are time-consuming. We show that spatial encoding of the polarization transfer delays in HSQC using sweep frequency pulses in the presence of a magnetic field gradient allows one to have a transfer of polarization from 1H to 13C insensitive to variations in 1H -13C couplings improving the quantitative aspect of HSQC. Comparisons to other QHSQC and perfected HSQC variants are also provided.

This is an account of the forms and semantic dimensions of spatial relations in Manange (Tibeto-Burman, Tamangic; Nepal), with comparison to sister language Nar-Phu. Topological relations (“IN/ON/AT/NEAR”) in these languages are encoded by locative enclitics and also by a set of noun-like objects termed as “locational roots.” In Manange, the general locative enclitic is more frequently encountered for a wide range of topological relations, while in Nar-Phu, the opposite pattern is observed, i.e. more frequent use of locational roots. While the linguistic frame of reference system encoded in these forms is primarily relative (i.e. oriented on the speaker’s own viewing perspective), a more extrinsic/absolute system emerges with certain verbs of motion in these languages, with verbs like “come,” “go,” and certain verbs of placement or posture orienting to arbitrary fixed bearings such as slope. This account also provides some examples of cultural or metaphorical extensions of spatial forms as they are encountered in connected speech.

The current volume arose from a one-day pre-meeting workshop entitled “How Grammar Encodes Space in Tibeto-Burman” at the 48th International Conference on Sino-Tibetan Languages and Linguistics, which was held at the University of California, Santa Barbara in August of 2015.

Spatial/locative/directional concepts are sometimes highly grammaticalized in Tibeto-Burman,  notably in the Qiangic languages, which are famous for their systems of “directional prefixes” preposed to verbs to indicate the literal or figurative direction of the verbal event.

Following Talmy’s classification of world languages in to two-category of verb-framed (V-language) and satellite-framed (S-language) that distinguishes between languages in terms of their encoding patterns of motion events, there has been a lot of investigations on different lexicalization patterns of motion events across spoken languages over the past decades. This paper examines how Persian native speakers lexicalize motion events and what pattern of spatial encoding they follow. To this end, 25 Persian native speakers were asked to watch 12 short animated cartoons representing voluntary motion carried out in vertical and trajectory direction. After recording and transcribing of the participants’ utterances, the analysis of responses indicated that Persian speakers encode manner information mainly in other linguistic means, and they are more willing to describe path of motion in satellites. Based on this pattern of spatial encoding, Persian speakers follow a mixed typology to encode motion events and Persian is categorized in both S- framed and V-framed typologies.

For forensic human identification, one of the most important methods is by opting for protocols of biometrics. The outer human ear, also known as auricle or pinna, has unique characteristics, which are not even the same in identical twins. Thus, considering the uniqueness, reliability, and easy collectability of this trait, herein, a novel method is proposed for human identification namely Automated Ear Pinna Identification (AEPI). The proposed method opts for potentials of deep learning, by creating a unique blend of deep representation from a residual network and a spatial encoding block to identify human ear pinna imagery. The evaluation of the proposed method is also performed by comparing both, same and different ear pinna image pairs. Based on the evaluation, it is observed that the proposed method is 87.207% accurate for classification among classes of the dataset, 97.2% for gender-based classification and 99.0% accurate for identifying humans based on ear pinna images. These scores depict the strong potential and contribution of the proposed method in the field of ear biometrics and it is concluded that AEPI can aid the identification of humans based on ear pinna images in an accurate, effective and efficient manner. AEPI is freely available at (http://zeetu.org/AEPI.html). [ABSTRACT FROM AUTHOR]

Diffusion‐ordered NMR spectroscopy (DOSY NMR) is a widely used method for the analysis of mixtures. It can be used to separate the spectra of a mixture's components and to analyse interactions. The classic implementation of DOSY experiments, based on an incrementation of the diffusion‐encoding gradient area, requires several minutes or more to collect a 2D data set. Spatially‐encoded (SPEN) DOSY makes it possible to collect a complete data set in less than 1 s, by spatial parallelisation of the effective gradient area. While several short descriptions of SPEN DOSY experiments have been reported, a thorough characterisation of its features and its practical use is missing, and this hinders the use of the method. Here, we present the unusual principles and implementation of the SPEN DOSY experiment, an understanding of which is useful to make optimal use of the method. The encoding and acquisition steps are described, and the parameter relations that govern the setup of SPEN DOSY experiments are discussed. The influence of key parameters, including on sensitivity, is illustrated experimentally on mixtures of small molecules. This study should be useful for the setup of SPEN DOSY experiments, which are particularly useful for systems that evolve in time. [ABSTRACT FROM AUTHOR]

Deterministic secure quantum communication (DSQC) is an important primitive of quantum cryptography and has attracted continuous attention. Here, we report the first DSQC protocol based on spatial encoding. The qubit information is encoded in the spatial-mode degree of freedom of photons. A decoy state technique is used to ensure the security of the DSQC protocol. We also analyze the security of the DSQC protocol and show that it is secure against common attacks such as the interception-and-retransmission attack and general entanglement–measurement attack. Without the use of the polarization state of photons, it avoids the degeneration of the states of photons so that it is suitable for long-distance quantum communication. [ABSTRACT FROM AUTHOR]

Objective . The transmit encoding model for synthetic aperture imaging is a robust and flexible framework for understanding the effects of acoustic transmission on ultrasound image reconstruction. Our objective is to use machine learning (ML) to construct scanning sequences, parameterized by time delays and apodization weights, that produce high-quality B-mode images. Approach . We use a custom ML model in PyTorch with simulated RF data from Field II to probe the space of possible encoding sequences for those that minimize a loss function that describes image quality. This approach is made computationally feasible by a novel formulation of the derivative for delay-and-sum beamforming. Main results . When trained for a specified experimental setting (imaging domain, hardware restrictions, etc), our ML model produces optimized encoding sequences that, when deployed in the REFoCUS imaging framework, improve a number of standard quality metrics over conventional sequences including resolution, field of view, and contrast. We demonstrate these results experimentally on both wire targets and a tissue-mimicking phantom. Significance . This work demonstrates that the set of commonly used encoding schemes represent only a narrow subset of those available. Additionally, it demonstrates the value for ML tasks in synthetic transmit aperture imaging to consider the beamformer within the model, instead of purely as a post-processing step., (© 2024 Institute of Physics and Engineering in Medicine.)

The prevailing model for the variety in drug responses is that different drugs stabilize distinct active states of their G protein-coupled receptor (GPCR) targets, allowing coupling to different effectors. However, whether the same ligand generates different GPCR active states based on the immediate environment of receptors is not known. Here we address this question using spatially resolved imaging of conformational biosensors that read out distinct active conformations of the δ-opioid receptor (DOR), a physiologically relevant GPCR localized to Golgi and the surface in neuronal cells. We have shown that Golgi and surface pools of DOR both inhibit cAMP, but engage distinct conformational biosensors in response to the same ligand in rat neuroendocrine cells. Further, DOR recruits arrestins on the surface but not on the Golgi. Our results suggest that the local environment determines the active states of receptors for any given drug, allowing GPCRs to couple to different effectors at different subcellular locations.

Objectives: Because of the fast growing acquisition of real‑time spatiotemporal data for various applications such as smart city or real‑time air‑quality monitoring, the traditional database technologies can‑ not satisfy the higher standards for large‑scale data indexing, querying, and storing operations. As the viable alternative, NoSQL databases that are scalable and possess fast input/output capabilities offer potential solutions to accommodate the needs. Methods: We propose a Hilbert curve and Cassandra technologies based approach for efficient indexing and storing of large‑scale spatiotemporal datasets aiming to provide an effective framework for processing, querying, and analyzing large amount of data with spatial and temporal features. For example, the dataset of vehicle trajectories contains valuable spatial and temporal features those are being employed in the real world. The collected spatiotemporal datasets are preprocessed in order to fit the proposed structures for different applications. Specifically, two types of query applications commonly used in the real world are the spatiotemporal range query and query upon vehicle IDs respectively. Two corresponding indexing structures are designed and implemented in order to accommodate the requests. S2 Geometry Library open sourced by Google is utilized to divide the earth surface into grids, and data points fall in grids are assigned with the specific IDs as the keys. The keys and columns are so designed by applying the Hilbert curve and Cassandra techniques that the resultant structures will physically store the spatially neighboring data points close to each other, and they are more suitable for large‑scale spatiotemporal data querying and analyzing applications. Results: The datasets acquired from the real applications are used to conduct the computational experiments to validate the efficiency of the proposed approach. The query efficiency and the time consumed to store large amount of spatiotemporal data are investigated and bench‑ marked against some existing database technologies. Conclusions: The computational experiments reveal the superiority of the proposed approach comparing to the existing methodologies, the required time to store (insert) data in the database is reduced by 6 times while the time needed to query data is decreased by at least 10 times. The efficiency of the proposed methodology is validate further by applying it to query the vehicle trajectories gathering the real‑time air quality data. [ABSTRACT FROM AUTHOR]

Purpose: To achieve rapid, low specific absorption rate (SAR) super‐resolution imaging by exploiting the characteristic magnetization off‐resonance profile in SSFP. Theory and Methods: In the presented technique, low flip angle unbalanced SSFP imaging is used to acquire a series of images at a low nominal resolution that are then combined in a super‐resolution strategy analogous to non‐linear structured illumination microscopy. This is demonstrated in principle via Bloch simulations and synthetic phantoms, and the performance is quantified in terms of point‐spread function (PSF) and SNR for gray and white matter from field strengths of 0.35T to 9.4T. A k‐space reconstruction approach is proposed to account for B0 effects. This was applied to reconstruct super‐resolution images from a test object at 9.4T. Results: Artifact‐free super‐resolution images were produced after incorporating sufficient preparation time for the magnetization to approach the steady state. High‐resolution images of a test object were obtained at 9.4T, in the presence of considerable B0 inhomogeneity. For gray matter, the highest achievable resolution ranges from 3% of the acquired voxel dimension at 0.35T, to 9% at 9.4T. For white matter, this corresponds to 3% and 10%, respectively. Compared to an equivalent segmented gradient echo acquisition at the optimal flip angle, with a fixed TR of 8 ms, gray matter has up to 34% of the SNR at 9.4T while using a ×10 smaller flip angle. For white matter, this corresponds to 29% with a ×11 smaller flip angle. Conclusion: This approach achieves high degrees of super‐resolution enhancement with minimal RF power requirements. [ABSTRACT FROM AUTHOR]

Converging evidence has established that positive concepts presented on a computer screen are associated with upper regions of space, and negative concepts with a lower region of space. One explanation for this is that understanding positive or negative concepts requires the re-experiencing of direction, whereby “happy is up” and “sad is down.” However, it is unclear how the regions of space are encoded in these paradigms, space can be encoded in relation to oneself (egocentrically) or in object centred coordinates that are independent of oneself (exocentrically). The current study compares exocentric and egocentric coding of space, using a variation of the Meier and Robinson (2004) paradigm. Participants were asked to evaluate valenced concepts in either the upper or lower half of the screen. Spatial primes were used such that the concepts were preceded by either an upwards or a downwards eye movement. Exocentric coding of space in this paradigm was the computer screen, whilst egocentric coding was the eye movement used to access the top or bottom of the screen. It was proposed that egocentric coding of space, being coded in the body, provides evidence of a stronger relationship between the original bodily state of ‘up’ or ‘down’ and subsequent simulation. However, significant results supported an exocentric coding of space, with faster responses to positive concepts in the upper half of the screen, and to negative concepts in the lower half, irrespective of the direction of the eye movement preceding it. The implications of this for embodied cognition are discussed.

Spatial navigation relies on various types of neurons to form an internal representation in the brain of the external world. Among them, grid cells are generally believed to serve as an invariant metric system by their spatially periodic firing fields. But how this metrical coordinate system is organized in three-dimensional (3-D) real world remains a mystery, since most researches merely concerned the encoding scheme on the horizontal plane. We computationally explored the activity pattern of grid cell in the medial entorhinal cortex of crawling animal in 3-D space. By including the presumably referring signals of gravity and animal's body plane, grid cell firing fields on curved surfaces were produced based on the novel gravity-modulated oscillatory model. The results can account for the known experimental recordings and predict a mosaic-type grid code consisting of dynamically rotated planar arrangements. We further analyzed the path integration mechanism and derived the condition to ensure the invariant grid fields on any curved surface in 3-D space. It turns out that if the grid code is indeed not fully volumetric, it may become trajectory-dependent in 3-D space. And thus for crawling animals, 3-D grid fields could be degenerated and impaired, causing the path integration and distance measurement inaccurate. Besides, the volumetric firing fields were also discussed, although it is more suitable for flying or aquatic animals. This work can help us understand the intrinsically different spatial codes and navigating abilities among species with various locomotion modes and provide new insights of how the actual physical world is represented in the brain. [ABSTRACT FROM AUTHOR]

G protein-coupled receptors (GPCRs) are the largest family of cell surface receptors and a critical class of regulators of mammalian physiology. Also known as seven transmembrane receptors (7TMs), GPCRs are ubiquitously expressed and versatile, detecting a diverse set of endogenous stimuli, including odorants, neurotransmitters, hormones, peptides, and lipids. Accordingly, GPCRs have emerged as the largest class of drug targets, accounting for upward of 30% of all prescription drugs. The view that ligand-induced GPCR responses originate exclusively from the cell surface has evolved to reflect accumulating evidence that receptors can elicit additional waves of signaling from intracellular compartments. These events in turn shape unique cellular and physiological outcomes. Here, we discuss our current understanding of the roles and regulation of compartmentalized GPCR signaling., Competing Interests: Conflict of interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Deliberation is thought to involve the internal simulation of the outcomes of candidate actions, the valuation of those outcomes, and the selection of the actions with the highest expected value. While it is known that deliberation involves prefrontal cortical areas, specifically the dorsomedial prefrontal cortex (dmPFC), as well as the hippocampus (HPC) and other brain regions, how these areas process prospective information and select actions is not well understood. We recorded simultaneously from ensembles in dmPFC and CA1 of dorsal HPC in rats during performance of a spatial contingency switching task, and examined the relationships between spatial and reward encoding in these two areas during deliberation at the choice point. We found that CA1 and dmPFC represented either goal locations or the current position simultaneously, but that when goal locations were encoded, HPC and dmPFC did not always represent the same goal location. Ensemble activity in dmPFC predicted when HPC would represent goal locations, but on a broad timescale on the order of seconds. Also, reward encoding in dmPFC increased during hippocampal theta cycles where CA1 ensembles represented the goal location. These results suggest that dmPFC and HPC share prospective information during deliberation, that dmPFC may influence whether HPC represents prospective information, and that information recalled about goal locations by HPC may be integrated into dmPFC reward representations on fast timescales. [ABSTRACT FROM AUTHOR]

Optische Messverfahren nach dem Prinzip der strukturierten Beleuchtung bedienen sich oftmals der Kombination eines Phasenschiebeverfahrens mit einem geeigneten Entfaltungsverfahren, um eine im Messbereich eindeutige Ortskodierung vorzunehmen. Ein leistungsfähiges Verfahren aus dieser Klasse stellt das Heterodyn-Phasenschiebeverfahren dar, welches auf der sequenziellen Registrierung mehrerer Phasenschiebesequenzen mit geringfügig unterschiedlicher Periodenlänge und Auswertung der synthetischen Schwebungssignale zwischen diesen basiert. Die geeignete Auswahl der hierfür zu kombinierenden Periodenlängen hat entscheidenden Einfluss sowohl auf die Robustheit des Entfaltungsverfahrens als auch auf die statistische Unsicherheit der resultierenden Ortskodierung. In dem vorliegenden Beitrag wird eine vorteilhafte Ausführungsform des Heterodynverfahrens vorgestellt und einer detaillierten Analyse im Hinblick auf seine statistischen Eigenschaften unterzogen. Im Ergebnis werden Kriterien zur Bestimmung geeigneter Periodenlängen formuliert, die eine Maximierung der Robustheit des Entfaltungsvorgangs und eine Minimierung der Unsicherheit der Ortskodierung ermöglichen. Optical measuring methods according to the principle of structured illumination often use the combination of a phase shift method with a suitable deconvolution method in order to carry out a spatial coding which is unequivocal within the measuring range. A powerful method of this class is the heterodyne phase shift method, which is based on the sequential registration of multiple phase shift sequences with slightly different period lengths and evaluation of the synthetic beat signals between them. The appropriate choice of the period lengths to be combined has a decisive influence both on the robustness of the deconvolution method and on the statistical uncertainty of the resulting spatial encoding. In the present article, an advantageous realization of the heterodyne method is presented and subjected to a detailed analysis with regard to its statistical properties. As a result, criteria for determining appropriate period lengths are formulated that allow for maximizing the robustness of the deployment process and minimizing the uncertainty of spatial coding. [ABSTRACT FROM AUTHOR]

A differential laser Doppler velocimeter using 48-channel spatial encoded measurement points is proposed for dense cross-sectional velocity distribution measurements. An asymmetrical push–pull configuration and multiple photodiodes are employed to increase the number of the measurement points. The functionality of the proposed structure is experimentally demonstrated. The results indicate that a cross-sectional velocity distribution is successfully measured with the proposed structure. [ABSTRACT FROM AUTHOR]

• Optimized implementation of spatial/spectral encoding in ultrafast 2D NMR. • Excitation profile of spatial/spectral pulses includes additional sidebands. • Method for efficient suppression of unwanted sidebands by interleaved excitation. • Better flexibility in the design of ultrafast experiments. • Application to ultrafast TOCSY and HSQC experiments. The possibility to record a full 2D spectrum in less than a second using ultrafast 2D NMR (UF2DNMR) is beneficial in many applications. However, the spatial encoding process on which UF2DNMR is based sets specific constraints on the spectral width and resolution of the resulting spectra. To overcome these limitations, a tailored encoding method using spatial/spectral pulses (SPSP) can be employed as an alternative to the traditional linear spatial encoding of interactions. Here we analyze and further develop this alternative spatial encoding strategy. We first carry out numerical simulations to describe the features of bidimensional SPSP pulses. Sidebands are identified along the spectral dimension of the excitation profile. An interleaved excitation scheme is then developed and implemented experimentally to suppress the unwanted signals that arise from these harmonic sidebands. Two examples are shown to illustrate the potential of the proposed approach. An ultrafast selective TOCSY spectrum is recorded to access sub-spectra and fully assign 1H NMR resonances of individual residues of cyclosporin A. An ultrafast HSQC spectrum of a mixture of metabolites is recorded with an optimized spectral width in the spatially encoded dimension. [ABSTRACT FROM AUTHOR]

• A brief review of experiments involving direct detection of multiple FIDs in liquid- and solid-state NMR is provided. • This includes experiments with homonuclear and multinuclear detection. • Applications to small molecules and biomolecules are described. • Such experiments provide more information in a single measurement as compared to the conventional techniques. Pulse schemes with direct observation of multiple free induction decays (FIDs) offer a dramatic increase in the spectral information content of NMR experiments and often yield substantial improvement in measurement sensitivity per unit time. Availability of multiple receivers on the state-of-the-art commercial spectrometers allows spectra from different nuclear species to be recorded in parallel routinely. Experiments with multi-FID detection have been designed with both, homonuclear and multinuclear acquisition. We provide a brief overview of such techniques designed for applications in liquid- and solid- state NMR as well as in hyperpolarized samples. Here we show how these techniques have led to design of experiments that allow structure elucidation of small molecules and resonance assignment in proteins from a single measurement. Probes with multiple RF micro-coils routed to multiple NMR receivers provide an alternative way of increasing the throughput of modern NMR systems. Solid-state NMR experiments have also benefited immensely from both parallel and simultaneous FID acquisition in a variety of multi-dimensional pulse schemes. We believe that multi-FID detection will become an essential component of the future NMR methodologies effectively increasing the information content of NMR experiments and reducing the cost of NMR analysis. [ABSTRACT FROM AUTHOR]

Purpose: Acquisition of high‐resolution imaging data using multiple excitations without the sensitivity to fluctuations of the transverse magnetization phase, which is a major problem of multi‐shot MRI. Theory and Methods: The concept of superresolution MRI based on microscopic tagging is analyzed using an analogy with the optical method of structured illumination. Sinusoidal tagging is shown to provide subpixel resolution by mixing of neighboring spatial frequency (k‐space) bands. It represents a phaseless modulation added on top of the standard Fourier encoding, which allows the phase fluctuations to be discarded at an intermediate reconstruction step. Improvements are proposed to correct for tag distortions due to magnetic field inhomogeneity and to avoid the propagation of Gibbs ringing from intermediate low‐resolution images to the final image. The method was applied to diffusion‐weighted EPI. Results: Artifact‐free superresolution images can be obtained despite a finite duration of the tagging sequence and related pattern distortions by a field map based phase correction of band‐wise reconstructed images. The ringing effect present in the intermediate images can be suppressed by partial overlapping of the mixed k‐space bands in combination with an adapted filter. High‐resolution diffusion‐weighted images of the human head were obtained with a three‐shot EPI sequence despite motion‐related phase fluctuations between the shots. Conclusion: Due to its phaseless character, tagging‐based sub‐pixel encoding is an alternative to k‐space segmenting in the presence of unknown phase fluctuations, in particular those due to motion under strong diffusion gradients. Proposed improvements render the method practicable in realistic conditions. [ABSTRACT FROM AUTHOR]

Objective: A method is proposed to obtain high-resolution 2-D $J$-resolved nuclear magnetic resonance (NMR) spectra in inhomogeneous magnetic fields. Methods: The proposed experiment enables the acquisition of an entire 2-D spectrum in a single scan by utilizing intermolecular double-quantum coherences and the spatial encoding of NMR observables. Results: Chemical shifts, $J$ coupling constants, and multiplet patterns are recovered even when field inhomogeneities are severe enough to completely obscure conventional NMR spectra. After intentional deshimming to yield inhomogeneous magnetic fields, the method was demonstrated on ethyl 3-bromoproprionate in acetone and on a complex mixture of organic compounds. To illustrate the technique's applicability to biological samples with intrinsic magnetic field inhomogeneities arising from macroscopic magnetic susceptibility variations, we performed the experiment on a pig bone marrow sample. Conclusion: Our results show that the new method is a fast and effective tool for studying complex chemical mixtures and biological tissues. Significance: The method could potentially be useful for real-time in vivo NMR studies. [ABSTRACT FROM AUTHOR]

Purpose Fourier encoded MRI signal is complex and, therefore, sensitive to uncontrolled phase variations caused, e.g., by object motion. An alternative encoding is proposed which leads to phaseless (positive real) signals and allows the phase fluctuations to be removed by simple magnitude calculation before the Fourier transform. Theory and Methods Phaseless encoding uses harmonic modulation of the longitudinal magnetization with different frequencies and phases before excitation. It can be combined with Fourier encoding of complementary dimensions to produce, e.g., a 3D version of echo planar imaging insensitive to intershot phase variations. It can also be mixed with Fourier encoding of the same dimension allowing a high-resolution image to be obtained from magnitude-reconstructed low-resolution components. The latter is a generalization of the super-resolution MRI with microscopic tagging proposed recently. Improved reconstruction for this technique was adopted from its optical analogue, harmonic excitation light microscopy (HELM). Results Artifact free images were obtained despite phase fluctuations caused by random receiver reference and object motion during diffusion weighting. Proposed reconstruction of mixed-encoded data reaches higher resolution than the original super-resolution method. Conclusion Spatial information can be encoded in the magnitude of the MR signal rendering the experiment insensitive to phase fluctuations. Magn Reson Med 78:1029-1037, 2017. © 2016 International Society for Magnetic Resonance in Medicine [ABSTRACT FROM AUTHOR]

The spin-lattice relaxation time ( T 1 ) plays a crucial role in the study of spin dynamics, signal optimization and data quantification. However, the measurement of chemical shift-specific T 1 constants is hampered by the magnetic field inhomogeneity due to poorly shimmed external magnetic fields or intrinsic magnetic susceptibility heterogeneity in samples. In this study, we present a new protocol to determine chemical shift-specific T 1 constants in inhomogeneous fields. Based on intermolecular double-quantum coherences, the new method can resolve overlapped peaks in inhomogeneous fields. The measurement results are in consistent with the measurements in homogeneous fields using the conventional method. Since spatial encoding technique is involved, the experimental time for the new method is very close to that for the conventional method. With the aid of T 1 knowledge, some concealed information can be exploited by T 1 weighting experiments. [ABSTRACT FROM AUTHOR]

We introduce a new approach for resolving the NMR spectra of mixtures that relies on the mutual diffusion of dissolved species when a concentration gradient is established within the NMR tube. This is achieved by cooling down a biphasic mixture of triethylamine and deuterated water below its mixing temperature, where a single phase is expected. Until equilibrium is reached, a gradient of concentration, from 'pure' triethylamine to 'pure' water, establishes within the tube. The amount of time required to reach this equilibrium is controlled by the mutual diffusion coefficient of both species. Moreover, a gradient of concentration exists for each additional compound dissolved in this system, related to the partition coefficient for that compound in the original biphasic state. Using slice selective experiments, it was possible to measure these concentration gradients and use them to separate signals from all the present species. We show the results acquired for a mixture composed of n-octanol, methanol, acetonitrile and benzene and compare them with those obtained by pulse field gradient NMR. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Standard diffusion NMR measurements require the repetition of the experiment multiple times with varying gradient strength or diffusion delay. This makes the experiment time-consuming and restricts the use of hyperpolarized substances to boost sensitivity. We propose a novel single-scan diffusion experiment, which is based on spatial encoding of two-dimensional data, employing the spin-echoes created by two successive adiabatic frequency-swept chirp π pulses. The experiment is called ultrafast pulsed-field-gradient spin-echo (UF-PGSE). We present a rigorous derivation of the echo amplitude in the UF-PGSE experiment, justifying the theoretical basis of the method. The theory reveals also that the standard analysis of experimental data leads to a diffusion coefficient value overestimated by a few per cent. Although the overestimation is of the order of experimental error and thus insignificant in many practical applications, we propose that it can be compensated by a bipolar gradient version of the experiment, UF-BP-PGSE, or by corresponding stimulated-echo experiment, UF-BP-pulsed-field-gradient stimulated-echo. The latter also removes the effect of uniform background gradients. The experiments offer significant prospects for monitoring fast processes in real time as well as for increasing the sensitivity of experiments by several orders of magnitude by nuclear spin hyperpolarization. Furthermore, they can be applied as basic blocks in various ultrafast multidimensional Laplace NMR experiments. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]