Kim A. Dora, Dirk van Helden · The Journal of Physiology · 2017
The endothelium isolated as an intact tube of cells offers a powerful approach to study endothelial cell function. The freshly isolated tubes provide significant advantages over isolated endothelial cells or cultured endothelial cells because the cells remain coupled to each other and, as they are native endothelial cells, do not display an altered phenotype. Although in a collapsed state, the constituent endothelial cells retain their spatial arrangement, and remain coupled to each other both physically and electrically. Perhaps most importantly, they are now separated from the surrounding smooth muscle layer. In blood vessels where myo-endothelial gap junctions are present, the flow of current from the smooth muscle otherwise dominates them electrically. All these considerations mean that endothelial cells represent a homocellular population amenable to study with sharp intracellular microelectrodes, and after loading with fluorescent Ca2+ indicators, enable studies of both intra- and intercellular signalling. Furthermore, by pooling sufficient numbers of tubes, a pure population of native microvascular endothelial cells can be prepared for qRT-PCR to detect gene expression – in cells isolated in the same manner for studying their signalling properties and in some examples to date for function in intact arteries and arterioles. All in all, the endothelial tube preparation provides a means to address some key unanswered questions in vascular biology. This novel approach has now been used for the first time to study isolated endothelial cell tubes from lymphatic vessels. It is known that lymphatic smooth muscle cells have a resting membrane potential near −50 mV when unstretched, and with stretch (e.g. in response to luminal pressure) the cells depolarize, which thereby increases the frequency of action potential-like spikes (von der Weid et al. 2014). Smooth muscle contraction is sensitive to blockers of L-type voltage-dependent Ca2+ channels, in a manner not dissimilar to that in resistance arteries and arterioles. It is also known that lymphatic endothelial cells release nitric oxide (NO) to limit contraction of the lymphatic vessels, alongside other roles regarding their permeability (Ohhashi & Takahashi, 1991; von der Weid et al. 1996; Scallan & Davis, 2013). In common with arteries and arterioles, lymphatic vessels are lined by a monolayer of endothelial cells, but they are also intermittently populated with valves, which might be expected to interrupt the endothelial cell monolayer. The segments between valves, termed lymphangions, often behave as autocratic units, exhibiting synchronized contraction and propulsion within, but not necessarily between lymphangions. This is very different from arterioles where myo-endothelial gap junctions between the endothelium and surrounding smooth muscle cells serve to synchronize vasomotor responses, resulting in a functional syncytium along their entire length. An immediate question therefore is: what happens when an endothelial cell tube is isolated from lymphatic vessels, often across a valve? The answer is provided in an article by Behringer et al. (2017) in this issue of The Journal of Physiology. The authors have for the first time isolated intact endothelial cell tubes from lymphatic vessels to study their electrical properties, Ca2+ signalling and gene expression for key membrane ion channels. They present evidence that the lymphatic endothelium of mouse popliteal lymphatics is markedly different from the endothelium of popliteal arteries in that the former lacks expression of Ca2+-activated K+ channels (KCa). These KCa channels underlie the endothelium-dependent hyperpolarization and associated dilatation to many physiological stimuli in resistance arteries and arterioles. Behringer et al. include electrical recordings from the endothelium of intact vessels, supporting findings from guinea pig mesenteric lymphatics that there is no functional electrical connectivity between the endothelium and smooth muscle and that the agonist acetylcholine increases endothelial Ca2+ with resultant dominant depolarization (von der Weid & Van Helden, 1997). Yet, as in arterioles, stimulation with acetylcholine, acting selectively at endothelial cell muscarinic receptors, leads to increases in NO production. The NO serves to reduce contraction of lymphatic vessels (Ohhashi & Takahashi, 1991; von der Weid et al. 1996; Scallan & Davis, 2013). Behringer et al. present evidence that agonist-activated transient receptor potential cation channel subfamily V member 4 (primarily TRPV4) conduct Ca2+ and Na+. While Ca2+ entry is fundamental to NO production (see also von der Weid et al. 1996), the physiological relevance of depolarization remains to be ascertained. Another key observation in the study of Behringer et al. is the hyperpolarized resting membrane potential of the lymphatic endothelial cells, a finding also consistent with the lymphatic endothelium in situ (von der Weid & Van Helden, 1997). This again is very different to arterial endothelial cell tubes, and isolated arterial endothelial cells in general. By way of explanation the current work models lymphatic endothelial cells and predicts a lack of a Cl− current, perhaps due to the absence of the Na+/K+/2Cl− cotransporter. This electroneutral transporter allows Cl− entry into the endothelium, ready to leave when Cl− channels open. Its absence would suggest that the equilibrium potential for Cl− in lymphatic endothelial cells will be more hyperpolarized. The depolarization of lymphatic endothelium following stimulation with acetylcholine or a TRPV4 channel agonist is instead attributed to cations entering the cells. The model proposed by the authors goes some way to explain these processes in lymphatic endothelium, without yet knowing precisely which other ion channels are expressed nor the intracellular concentrations of ions such as Cl−. Nevertheless, this new approach provides another window to our understanding with the unanswered questions providing scope for much future work. None declared. Both authors contributed to conception or design of the work and drafting the work or revising it critically for important intellectual content. Both authors have approved the final version of the manuscript and agree to be accountable for all aspects of the work. All persons designated as authors qualify for authorship, and all those who qualify for authorship are listed. K. A. Dora is funded by the British Heart Foundation (FS/13/16/30199).
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Elmer Culler, Glen Finch, Edward Girden · American Journal of Physiology-Legacy Content · 1935
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PubMed · 2008
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Bruce Reed, William Jagust · Neurology · 1999
Just over two decades ago, PET emerged from the laboratory as a result of advances in radiochemical synthesis, detector physics, and image reconstruction techniques. The initial use of PET in neurology predominantly involved studies of cerebral blood flow (CBF) and glucose metabolism to define functional abnormalities in disease and map normal cognitive processes. Yet one of the greatest potential strengths of PET imaging is the ability to measure substances in the brain that occur in nanomolar concentrations, such as neurotransmitters and their receptors. A particularly good example of PET neurotransmitter system imaging is the use of [18F]-fluorodopa and related compounds to study PD. Such work has resulted in important insights into the natural history and differential diagnosis of PD, its early detection, and development and monitoring of therapy.1,2 In this issue of Neurology, Kuhl et al.3 provide new data on a PET tracer for the quantitative imaging of brain acetylcholinesterase (AChE) activity, illustrating an analogous use of PET to study the cholinergic system in aging and AD.
The importance of acetylcholine in normal memory function has been appreciated for years, as has the fact that depletion of acetylcholine is the primary neurochemical abnormality in AD. To date, brain acetylcholine measurements in AD have been performed postmortem. Although this method has been sufficient to demonstrate the importance of the cholinergic deficit in AD and, indeed, produced the data that led to the first neurochemically specific and efficacious therapy for AD, it has obvious limitations. For this reason, several laboratories have been investigating PET radiotracer methods for studying the cholinergic system in patients. Three general approaches have been used: 1) presynaptic terminals have been studied with derivatives of vesamicol to label the vesicular …
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Maino, D., Bersanelli, M., Danese, L. et al. · OpenGrey (Institut de l'Information Scientifique et Technique) · 1995
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You Yang (299369), Qiong Liu (299371), Rongrong Ji (299373) et al. · Figshare · 2015
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Mingsai Huan, Baoxi Guo, Yu Tu et al. · 2024
Antenna position errors caused by manufacturing accuracy limits lead to a great difference between the real and ideal models of antenna arrays in extremely high frequency (EHF) band MIMO radar with tiny physical elements and spacings. As the real array is a non-uniform array, the conventional window function fails when applied to non-uniform sampling data, which causes angular ambiguities and seriously degrades the performance of DOA estimation. Based on an advanced analysis of spectral distortion in non-uniform sampling, this paper introduces a method to design a specialized window function for non-uniform MIMO arrays, aiming to minimize the equivalent noise bandwidth (ENBW) while sufficiently suppressing the side-lobe-to-peak ratio of the window function's spectrum. The simulation results show the effectiveness of the optimized window function, which reduces angular ambiguities and thereby improves the performance of DOA estimation for non-uniform MIMO arrays.
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Michael P. Whyte · Elsevier eBooks · 2002
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Alkhanishvili, Davit, Porciani, Cristiano, Sefusatti, Emiliano · arXiv (Cornell University) · 2022
Traditional estimators of the galaxy power spectrum and bispectrum are sensitive to the survey geometry. They yield spectra that differ from the true underlying signal since they are convolved with the window function of the survey. For the current and future generations of experiments, this bias is statistically significant on large scales. It is thus imperative that the effect of the window function on the summary statistics of the galaxy distribution is accurately modelled. Moreover, this operation must be computationally efficient in order to allow sampling posterior probabilities while performing Bayesian estimation of the cosmological parameters. In order to satisfy these requirements, we built a deep neural network model that emulates the convolution with the window function, and we show that it provides fast and accurate predictions. We trained (tested) the network using a suite of 2000 (200) cosmological models within the cold dark matter scenario, and demonstrate that its performance is agnostic to the precise values of the cosmological parameters. In all cases, the deep neural network provides models for the power spectra and the bispectrum that are accurate to better than 0.1 per cent on a timescale of 10 $μ$s.
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Wooshik Kim · Optics Letters · 2001
Two-dimensional phase retrieval by use of a window function is considered. First the uniqueness and the reconstruction of a two-dimensional signal from the Fourier intensities of the three signals, an original signal, the signal windowed by a window w(m, n) , and the signal windowed by its complementary window w(c)(m, n) = 1 - w(m, n) , are addressed. Then phase retrieval without a complementary window is considered. Conditions under which a signal can be uniquely specified from the Fourier intensities of the original signal and the windowed signal by w(m, n) are developed, and a reconstruction algorithm is presented.
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Alan D. Friedman · Blood · 2005
Comment on Theilgaard-Monch et al, page [1785][1]
This study provides a detailed analysis of gene expression patterns during granulocytic maturation and in so doing provides novel insights into myeloid cell development and activities.
As part of the innate immune system, granulocytes are
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J. C. Phillips, Richard Kerner · The Journal of Chemical Physics · 2008
Window glass is a ternary mixture, while Pyrex (after window glass, the most common form of commercial glass) is a quaternary. Here, we investigate the chemical, physical, and mathematical factors that determine the compositions of these optimized glasses. Previously, we succeeded in deriving exactly the composition of window glass (sodium calcium silicate) without adjustable parameters. Borosilicates are a much more challenging problem, and Pyrex (sodium aluminum borosilicate) requires a different approach. Our analysis shows that mean-field (or global) models (networks without significant clustering) are sufficient for window glass and probably most other commercial silicate glasses. However, it appears that the most important property of pyrex, its ability to resist mechanical shocks, requires a cluster model (large medium range order). We propose such a model, and argue that it also follows from hierarchical principles. Our model is strongly supported by specific experiments, and we suggest further experiments to test the principles underlying commercial glasses.
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Tsz Kin Tam, Kam K.H. Ng · Journal of the Air Transport Research Society · 2026
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D. Alkhanishvili, C. Porciani, E. Sefusatti · Astronomy and Astrophysics · 2022
Traditional estimators of the galaxy power spectrum and bispectrum are sensitive to the survey geometry. They yield spectra that differ from the true underlying signal since they are convolved with the window function of the survey. For the current and future generations of experiments, this bias is statistically significant on large scales. It is thus imperative that the effect of the window function on the summary statistics of the galaxy distribution is accurately modelled. Moreover, this operation must be computationally efficient in order to allow sampling posterior probabilities while performing Bayesian estimation of the cosmological parameters. In order to satisfy these requirements, we built a deep neural network model that emulates the convolution with the window function, and we show that it provides fast and accurate predictions. We trained (tested) the network using a suite of 2000 (200) cosmological models within the cold dark matter scenario, and demonstrate that its performance is agnostic to the precise values of the cosmological parameters. In all cases, the deep neural network provides models for the power spectra and the bispectrum that are accurate to better than 0.1% on a timescale of 10 μs.
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Peter Widmayer (hrsg, Schweizer Informatikertag, Peter Brusilovsky et al. · 1995
Abstract: Existing intelligent learning environments for programming step towards represent comprehensive adaptive a learning environments that support in all learning programming. activities In most of these systems, however, only the component is tutoring adaptive. The user interface usually looks the for same for the novice the advanced and learner, while the student's knowledge of the subject changes matter strongly from the beginning to the end of a course. We argue that a next adaptive step towards learning environments is to make all its components adaptive. In we discuss this paper, some problems of creating adaptive environment intelligent components learning for environments and present our current work into this direction.
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Mahrokh G. Shayesteh, Mahdi Mottaghi-Kashtiban · 2009
We present a new simple form window function with application to FIR filter design, which has superior performance compared to the several commonly used windows. The new window is almost equi-ripple. For sufficiently high orders, the proposed window has the main lobe width of roughly equal to that of the commonly used Hamming window, while featuring 5.6 ~ 12 dB smaller side lobe peak. For lower window lengths, the performance of Hamming window is degraded, while the new window maintains its maximum side lobe peak about -48 ~ -49.5 dB compared to -37 ~ -39 dB of Hamming window, and at the same time offers smaller main lobe width. Our results also show substantial performance improvement of the proposed window compared to the Gaussian, Kaiser, and Lanczos windows. A performance comparison of the proposed and Dolph-Chebyshev windows is also presented. The designed FIR filters confirm the efficiency of the new window.
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Md Abdus Samad, Jia Uddin, Md. Razu Ahmed · Advanced materials research · 2012
Attenuated side lobe peak in the range of around ~-45dB is required in many applications of signal processing and measurements. However, the problem is usual window based FIR filter design lies in its side lobes amplitudes that are higher than the requirement of application. We propose a modified Lanczos window function by heuristic by examining the Lanczos window, which has better performance like equiripple, minimum side lobe compared to the several commonly used windows. The proposed window has slightly larger main lobe width of the commonly used Hamming window, while featuring 5.1~18.5 dB smaller side lobe peak. The proposed modified Lanczos window maintains its maximum side lobe peak about -55.2~-51.9 dB compared to -39~-36.7 dB of Hamming window for M=10~14, while offering roughly equal main lobe width. Our simulated results also show significant performance upgrading of the proposed modified Lanczos window compared to the Kaiser, Gaussian, and Lanczos windows. The proposed modified Lanczos window also shows better performance than Dolph-Chebyshev window. Finally, the example of designed low pass FIR filter confirms the efficiency of the proposed modified Lanczos window.
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Lynne Spencer, Daniel D. Traficante · Applied Spectroscopy · 1998
An apodization function, the sinc-TRAF function (S-TRAF), has been developed for application to exponentially decaying data sets where the acquisition times ( AT) is less than or equal to one time constant, T 2 . For heavily truncated time-domain signals, S-TRAF is able to remove sinc ripple with only minor losses in linewidth (LW) and signal-to-noise ratio (S/N). Ripple removal achieved with the application of S-TRAF rivals that observed from use of the “ultimate ripple-free resolution enhancement” function (URFRE) for AT as low as 0.3 T 2 *. S-TRAF maintains LW and S/N better than URFRE for all acquisition times examined.
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Jian Qiu Zhang, S.J. Ovaska · IEEE Transactions on Instrumentation and Measurement · 2000
An adaptive window function for distorted power measurement is introduced in this paper. It can automatically provide the optimal window function according to the measured signal. Thus, the applied window function is always optimal in the sense of the zeros of its frequency response corresponding to the undesired measured signal spectrum components which will result in the harmful truncation errors. As a result, the harmful truncation errors of asynchronous sampling and the influence of interharmonics in the measured signal spectrum can be totally eliminated. The correctness, accuracy, and applicability of the proposed method have been verified both theoretically and by extensive simulations.
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Radim Bača · Proceedings of the VLDB Endowment · 2024
Window function expressions (WFEs) became part of the SQL:2003 standard, and since then, they have often been implemented in database systems (DBS). They are especially essential to OLAP DBSs, and people use them daily. Even though WFEs are a heavily used part of the SQL language, the amount of research done on their optimization in the last two decades is not significant. WFE does not extend the expressive power of the SQL language, but it makes writing SQL queries easier and more transparent. DBSs always compile SQL queries with WFE using a sequence of partition-sort-compute operators, which we call a linear strategy. Plans resulting from the linear strategy are robust and, in many cases, efficient. This article introduces an alternative strategy using a self-join, which is not considered in the current DBSs. We call it the self-join strategy, and it is based on an SQL query transformation where the result query uses a self-join query plan to compute WFE. One output of this work is a tool that can automatically perform such SQL query transformations. We created a microbenchmark showing that the self-join strategy is more effective than the linear strategy in many cases. We also performed a cost-based experiment to evaluate the query optimizers' ability to select an appropriate strategy. The article's main aim is to show that usage of the self-join strategy for queries with WFE is beneficial if selected in a cost-based manner.
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