Academic literature on the topic 'GELUs activation function'
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Journal articles on the topic "GELUs activation function"
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Li, Chengfan, Yueyu Qi, Xuehai Ding, Junjuan Zhao, Tian Sang, and Matthew Lee. "A Deep Learning Method Approach for Sleep Stage Classification with EEG Spectrogram." International Journal of Environmental Research and Public Health 19, no. 10 (May 23, 2022): 6322. http://dx.doi.org/10.3390/ijerph19106322.
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The classification of sleep stages is an important process. However, this process is time-consuming, subjective, and error-prone. Many automated classification methods use electroencephalogram (EEG) signals for classification. These methods do not classify well enough and perform poorly in the N1 due to unbalanced data. In this paper, we propose a sleep stage classification method using EEG spectrogram. We have designed a deep learning model called EEGSNet based on multi-layer convolutional neural networks (CNNs) to extract time and frequency features from the EEG spectrogram, and two-layer bi-directional long short-term memory networks (Bi-LSTMs) to learn the transition rules between features from adjacent epochs and to perform the classification of sleep stages. In addition, to improve the generalization ability of the model, we have used Gaussian error linear units (GELUs) as the activation function of CNN. The proposed method was evaluated by four public databases, the Sleep-EDFX-8, Sleep-EDFX-20, Sleep-EDFX-78, and SHHS. The accuracy of the method is 94.17%, 86.82%, 83.02% and 85.12%, respectively, for the four datasets, the MF1 is 87.78%, 81.57%, 77.26% and 78.54%, respectively, and the Kappa is 0.91, 0.82, 0.77 and 0.79, respectively. In addition, our proposed method achieved better classification results on N1, with an F1-score of 70.16%, 52.41%, 50.03% and 47.26% for the four datasets.
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Wang, Xuyang, and Yixuan Tong. "Application of an emotional classification model in e-commerce text based on an improved transformer model." PLOS ONE 16, no. 3 (March 5, 2021): e0247984. http://dx.doi.org/10.1371/journal.pone.0247984.
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With the rapid development of the mobile internet, people are becoming more dependent on the internet to express their comments on products or stores; meanwhile, text sentiment classification of these comments has become a research hotspot. In existing methods, it is fairly popular to apply a deep learning method to the text classification task. Aiming at solving information loss, weak context and other problems, this paper makes an improvement based on the transformer model to reduce the difficulty of model training and training time cost and achieve higher overall model recall and accuracy in text sentiment classification. The transformer model replaces the traditional convolutional neural network (CNN) and the recurrent neural network (RNN) and is fully based on the attention mechanism; therefore, the transformer model effectively improves the training speed and reduces training difficulty. This paper selects e-commerce reviews as research objects and applies deep learning theory. First, the text is preprocessed by word vectorization. Then the IN standardized method and the GELUs activation function are applied based on the original model to analyze the emotional tendencies of online users towards stores or products. The experimental results show that our method improves by 9.71%, 6.05%, 5.58% and 5.12% in terms of recall and approaches the peak level of the F1 value in the test model by comparing BiLSTM, Naive Bayesian Model, the serial BiLSTM_CNN model and BiLSTM with an attention mechanism model. Therefore, this finding proves that our method can be used to improve the text sentiment classification accuracy and effectively apply the method to text classification.
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Paul, Ashis, Rajarshi Bandyopadhyay, Jin Hee Yoon, Zong Woo Geem, and Ram Sarkar. "SinLU: Sinu-Sigmoidal Linear Unit." Mathematics 10, no. 3 (January 23, 2022): 337. http://dx.doi.org/10.3390/math10030337.
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Non-linear activation functions are integral parts of deep neural architectures. Given the large and complex dataset of a neural network, its computational complexity and approximation capability can differ significantly based on what activation function is used. Parameterizing an activation function with the introduction of learnable parameters generally improves the performance. Herein, a novel activation function called Sinu-sigmoidal Linear Unit (or SinLU) is proposed. SinLU is formulated as SinLU(x)=(x+asinbx)·σ(x), where σ(x) is the sigmoid function. The proposed function incorporates the sine wave, allowing new functionalities over traditional linear unit activations. Two trainable parameters of this function control the participation of the sinusoidal nature in the function, and help to achieve an easily trainable, and fast converging function. The performance of the proposed SinLU is compared against widely used activation functions, such as ReLU, GELU and SiLU. We showed the robustness of the proposed activation function by conducting experiments in a wide array of domains, using multiple types of neural network-based models on some standard datasets. The use of sine wave with trainable parameters results in a better performance of SinLU than commonly used activation functions.
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Zamora, Julio, Anthony D. Rhodes, and Lama Nachman. "Fractional Adaptive Linear Units." Proceedings of the AAAI Conference on Artificial Intelligence 36, no. 8 (June 28, 2022): 8988–96. http://dx.doi.org/10.1609/aaai.v36i8.20882.
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This work introduces Fractional Adaptive Linear Units (FALUs), a flexible generalization of adaptive activation functions. Leveraging principles from fractional calculus, FALUs define a diverse family of activation functions (AFs) that encompass many traditional and state-of-the-art activation functions. This family includes the Sigmoid, Gaussian, ReLU, GELU, and Swish functions, as well as a large variety of smooth interpolations between these functions. Our technique requires only a small number of additional trainable parameters, and needs no further specialized optimization or initialization procedures. For this reason, FALUs present a seamless and rich automated solution to the problem of activation function optimization. Through experiments on a variety of conventional tasks and network architectures, we demonstrate the effectiveness of FALUs when compared to traditional and state-of-the-art AFs. To facilitate practical use of this work, we plan to make our code publicly available
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Herrera, Oscar, and Belém Priego. "Wavelets as activation functions in Neural Networks." Journal of Intelligent & Fuzzy Systems 42, no. 5 (March 31, 2022): 4345–55. http://dx.doi.org/10.3233/jifs-219225.
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Traditionally, a few activation functions have been considered in neural networks, including bounded functions such as threshold, sigmoidal and hyperbolic-tangent, as well as unbounded ReLU, GELU, and Soft-plus, among other functions for deep learning, but the search for new activation functions still being an open research area. In this paper, wavelets are reconsidered as activation functions in neural networks and the performance of Gaussian family wavelets (first, second and third derivatives) are studied together with other functions available in Keras-Tensorflow. Experimental results show how the combination of these activation functions can improve the performance and supports the idea of extending the list of activation functions to wavelets which can be available in high performance platforms.
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Randez-Gil, F., N. Bojunga, M. Proft, and K. D. Entian. "Glucose derepression of gluconeogenic enzymes in Saccharomyces cerevisiae correlates with phosphorylation of the gene activator Cat8p." Molecular and Cellular Biology 17, no. 5 (May 1997): 2502–10. http://dx.doi.org/10.1128/mcb.17.5.2502.
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The Cat8p zinc cluster protein is essential for growth of Saccharomyces cerevisiae with nonfermentable carbon sources. Expression of the CAT8 gene is subject to glucose repression mainly caused by Mig1p. Unexpectedly, the deletion of the Mig1p-binding motif within the CAT8 promoter did not increase CAT8 transcription; moreover, it resulted in a loss of CAT8 promoter activation. Insertion experiments with a promoter test plasmid confirmed that this regulatory 20-bp element influences glucose repression and derepression as well. This finding suggests an upstream activating function of this promoter region, which is Mig1p independent, as delta mig1 mutants are still able to derepress the CAT8 promoter. No other putative binding sites such as a Hap2/3/4/5p site and an Abf1p consensus site were functional with respect to glucose-regulated CAT8 expression. Fusions of Cat8p with the Gal4p DNA-binding domain mediated transcriptional activation. This activation capacity was still carbon source regulated and depended on the Cat1p (Snf1p) protein kinase, which indicated that Cat8p needs posttranslational modification to reveal its gene-activating function. Indeed, Western blot analysis on sodium dodecyl sulfate-gels revealed a single band (Cat8pI) with crude extracts from glucose-grown cells, whereas three bands (Cat8pI, -II, and -III) were identified in derepressed cells. Derepression-specific Cat8pII and -III resulted from differential phosphorylation, as shown by phosphatase treatment. Only the most extensively phosphorylated modification (Cat8pIII) depended on the Cat1p (Snf1p) kinase, indicating that another protein kinase is responsible for modification form Cat8pII. The occurrence of Cat8pIII was strongly correlated with the derepression of gluconeogenic enzymes (phosphoenolpyruvate carboxykinase and fructose-1,6-bisphosphatase) and gluconeogenic PCK1 mRNA. Furthermore, glucose triggered the dephosphorylation of Cat8pIII, but this did not depend on the Glc7p (Cid1p) phosphatase previously described as being involved in invertase repression. These results confirm our current model that glucose derepression of gluconeogenic genes needs Cat8p phosphorylation and additionally show that a still unknown transcriptional activator is also involved.
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Einspahr, K. J., R. T. Abraham, C. J. Dick, and P. J. Leibson. "Protein tyrosine phosphorylation and p56lck modification in IL-2 or phorbol ester-activated human natural killer cells." Journal of Immunology 145, no. 5 (September 1, 1990): 1490–97. http://dx.doi.org/10.4049/jimmunol.145.5.1490.
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Abstract Protein tyrosine kinases play fundamental roles in the transduction of signals that regulate cell growth, differentiation, and functional responses to a diversity of external stimuli. It is therefore likely that understanding protein tyrosine kinase activity in NK cells will be crucial in further defining the intracellular regulation of their unique and specialized functions. We investigated the role of protein tyrosine phosphorylation in receptor-mediated signal transduction using stimuli known to play major roles in regulating NK cell activation. Immunoblot analyses with antiphosphotyrosine antibodies demonstrated that IL-2, a potent stimulus for NK cell proliferation and an agent that enhances NK cytotoxic function, induced the tyrosine phosphorylation of at least eight proteins in clonal CD16+/CD3-human NK cells. In contrast, IL-4, which modulates NK cell function without inducing proliferation, had no apparent effect on protein tyrosine phosphorylation. Because protein kinase C (PKC) activation plays a prominent, yet distinct role in NK cell-mediated cytolytic reactions, we next investigated whether PKC activation affects NK cell protein tyrosine phosphorylation. Surprisingly, PKC-activating agents, including the phorbol esters 12-O-tetradecanoylphorbol-13-acetate and 4 beta-phorbol 12, 13-didecanoate, as well as the synthetic diacylglycerol,1-oleoyl-2-acetylglycerol, also induced the tyrosine phosphorylation of a distinct set of proteins. The 4 beta-phorbol 12,13-didecanoate homolog, 4 alpha-phorbol 12,13-didecanoate, which does not activate PKC, also failed to induce protein tyrosine phosphorylation. Further, the PKC inhibitor, 1-O-hexadecyl-2-O-methylglycerol blocked tyrosine phosphorylation induced by 1-oleoyl-2-acetylglycerol. In subsequent studies, both CD8+ and CD8- NK clones were found to express the src-family tyrosine kinase, p56lck, which was detected by immunoblot analysis with anti-p56lck antiserum. In both types of clonal NK cell lines, IL-2 and 12-O-tetradecanoyl-phorbol appeared to stimulate the differential phosphorylation of p56lck as evidenced by the appearance of higher molecular mass isoforms on SDS-polyacrylamide gels. Thus, our results identify and characterize a potential role for tyrosine phosphorylation and for the lymphocyte-specific tyrosine kinase p56lck in the signaling events that regulate NK cell activation.
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Tsuchida, Russell, Tim Pearce, Chris Van der Heide, Fred Roosta, and Marcus Gallagher. "Avoiding Kernel Fixed Points: Computing with ELU and GELU Infinite Networks." Proceedings of the AAAI Conference on Artificial Intelligence 35, no. 11 (May 18, 2021): 9967–77. http://dx.doi.org/10.1609/aaai.v35i11.17197.
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Analysing and computing with Gaussian processes arising from infinitely wide neural networks has recently seen a resurgence in popularity. Despite this, many explicit covariance functions of networks with activation functions used in modern networks remain unknown. Furthermore, while the kernels of deep networks can be computed iteratively, theoretical understanding of deep kernels is lacking, particularly with respect to fixed-point dynamics. Firstly, we derive the covariance functions of multi-layer perceptrons (MLPs) with exponential linear units (ELU) and Gaussian error linear units (GELU) and evaluate the performance of the limiting Gaussian processes on some benchmarks. Secondly, and more generally, we analyse the fixed-point dynamics of iterated kernels corresponding to a broad range of activation functions. We find that unlike some previously studied neural network kernels, these new kernels exhibit non-trivial fixed-point dynamics which are mirrored in finite-width neural networks. The fixed point behaviour present in some networks explains a mechanism for implicit regularisation in overparameterised deep models. Our results relate to both the static iid parameter conjugate kernel and the dynamic neural tangent kernel constructions
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Won, Sungyong, Tetsuro Ikegami, C. J. Peters, and Shinji Makino. "NSm Protein of Rift Valley Fever Virus Suppresses Virus-Induced Apoptosis." Journal of Virology 81, no. 24 (October 3, 2007): 13335–45. http://dx.doi.org/10.1128/jvi.01238-07.
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ABSTRACT Rift Valley fever virus (RVFV) is a member of the genus Phlebovirus within the family Bunyaviridae. It can cause severe epidemics among ruminants and fever, myalgia, a hemorrhagic syndrome, and/or encephalitis in humans. The RVFV M segment encodes the NSm and 78-kDa proteins and two major envelope proteins, Gn and Gc. The biological functions of the NSm and 78-kDa proteins are unknown; both proteins are dispensable for viral replication in cell cultures. To determine the biological functions of the NSm and 78-kDa proteins, we generated the mutant virus arMP-12-del21/384, carrying a large deletion in the pre-Gn region of the M segment. Neither NSm nor the 78-kDa protein was synthesized in arMP-12-del21/384-infected cells. Although arMP-12-del21/384 and its parental virus, arMP-12, showed similar growth kinetics and viral RNA and protein accumulation in infected cells, arMP-12-del21/384-infected cells induced extensive cell death and produced larger plaques than did arMP-12-infected cells. arMP-12-del21/384 replication triggered apoptosis, including the cleavage of caspase-3, the cleavage of its downstream substrate, poly(ADP-ribose) polymerase, and activation of the initiator caspases, caspase-8 and -9, earlier in infection than arMP-12. NSm expression in arMP-12-del21/384-infected cells suppressed the severity of caspase-3 activation. Further, NSm protein expression inhibited the staurosporine-induced activation of caspase-8 and -9, demonstrating that other viral proteins were dispensable for NSm's function in inhibiting apoptosis. RVFV NSm protein is the first identified Phlebovirus protein that has an antiapoptotic function.
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Yang, Xiaojuan, Surendranath Baliji, R. Cody Buchmann, Hui Wang, John A. Lindbo, Garry Sunter, and David M. Bisaro. "Functional Modulation of the Geminivirus AL2 Transcription Factor and Silencing Suppressor by Self-Interaction." Journal of Virology 81, no. 21 (August 22, 2007): 11972–81. http://dx.doi.org/10.1128/jvi.00617-07.
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ABSTRACT The DNA genomes of geminiviruses have a limited coding capacity that is compensated for by the production of small multifunctional proteins. The AL2 protein encoded by members of the genus Begomovirus (e.g., Tomato golden mosaic virus) is a transcriptional activator, a silencing suppressor, and a suppressor of a basal defense. The related L2 protein of Beet curly top virus (genus Curtovirus) shares the pathogenicity functions of AL2 but lacks transcriptional activation activity. It is known that AL2 and L2 can suppress local silencing by interacting with adenosine kinase (ADK) and can suppress basal defense by interacting with SNF1 kinase. However, how the activities of these viral proteins are regulated remains an unanswered question. Here, we provide some answers by demonstrating that AL2, but not L2, interacts with itself. The zinc finger-like motif (CCHC) is required but is not sufficient for AL2 self-interaction. Alanine substitutions for the invariant cysteine residues that comprise the motif abolish self-interaction or cause aberrant subnuclear localization but do not abolish interaction with ADK and SNF1. Using bimolecular fluorescence complementation, we show that AL2:AL2 complexes accumulate primarily in the nucleus, whereas AL2:ADK and L2:ADK complexes accumulate mainly in the cytoplasm. Further, the cysteine residue mutations impair the ability of AL2 to activate the coat protein promoter but do not affect local silencing suppression. Thus, AL2 self-interaction correlates with nuclear localization and efficient activation of transcription, whereas AL2 and L2 monomers can suppress local silencing by interacting with ADK in the cytoplasm.
Book chapters on the topic "GELUs activation function"
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Toledo, Edmundo, Jose Gonzalez, Mariko Nakano, Daniel Robles, Adrian Hernandez, Hector Perez, Humberto Lanz, and Jorge Cime. "LSTM-Based Mosquito Genus Classification Using Their Wingbeat Sound." In Frontiers in Artificial Intelligence and Applications. IOS Press, 2021. http://dx.doi.org/10.3233/faia210028.
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In this paper, we propose Long-Short Term Memory (LSTM)-based mosquito’s genus classification, in which the time-frequency features are extracted from the wingbeat sound of mosquitos of three genera, Aedes, Anopheles and Culex. The extracted features are fed into the proposed LSTM-based classifier. We evaluated three time-frequency features, which are: Mel Spectrogram, Log-Mel spectrogram, and Mel-frequency Cepstral Coefficients (MFCC). The proposed scheme is composed by two LSTM layers and one Fully Connected layer connected to a SoftMax activation function. The classification accuracies using the three features are 92.97(±0.2)%, 96.71(±0.2)% and 96.65(±0.2)%, respectively. The Area Under Curve (AUC) of the Receiver Operating Characteristics (ROC) for each feature are also obtained, which are 0.9944, 0.9986 and 0.9987, respectively. The proposed classifier requires approximately 62,000 trainable parameters. This number is much smaller than that required for the state-of-arts CNNs, such as AlexNet and Vgg16. This compact configuration of the proposed scheme takes advantage of the mobile and IoT implementation, because the number of trainable parameters is directly proportional to the amount of memory and CPU required.
Conference papers on the topic "GELUs activation function"
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Chun, Young Wook, Joey Barnett, and W. David Merryman. "Aortic Valve Interstitial Cell Activation Does Not Occur at Low Tissue Stiffness During Embryogenesis." In ASME 2012 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/sbc2012-80501.
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An estimated 2.5 percent of the American population has heart valve (HV) disease and more than 100,000 US patients require a prosthetic valve replacement each year [1]. However, prosthetic valves can cause accelerated calcification leading to recurrence of HV disease in patients [2]. Thus, the development of a suitable tissue-engineered heart valve (TEHV) would greatly benefit patients with HV disease. Aortic valve interstitial cells (AVICs) play a crucial role in the progression of aortic valve disease as well as the maintenance of normal valve. Therefore, in order to design a suitable TEHV, these specialized cells need to be better understood. AVICs are known to synthesize ECM and express matrix degrading enzymes and their inhibitors that mediate and regulate remodeling of ECM components [3]. Interestingly, it was recently established that AVICs sense the stiffness of their surrounding ECM in vivo and are phenotypically responsive to mechanical cues with AVICs differentiating into myofibroblasts or osteoblasts, which are pathologic markers. Specifically, soft collagen gels (∼34kPa) caused less differentiation of AVICs than stiffer collagen gel (∼100kPa) [4]. However, for these experiments the AVICs were cultured on tissue culture polystyrene (TCPS) for at least one passage, and it is likely that AVICs cultured on TCPS might retain modified characteristics of AVICs in tissue prior to seed them on soft gels because of the memory to rigid substrate stiffness. Therefore, in this study, we examined the phenotype and function of AVICs on substrates that mimic ECM stiffness of adult leaflet as well as of developing embryo. In addition, we examine the effects of transforming growth factor-β1 (TGF-β1) which has been the most extensively studied cytokine initiator of fibrotic response of AVICs.
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Knupp, C. L. "STUDIES OF A HIGH AFFINITY, STABLE PLATELET-THROMBIN COMPLEX FORMED DURING PLATELET ACTIVATION. A POSSIBLE MECHANISM FOR TRANSMEMBRANE SIGNAL GENERATION." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1644472.
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The precise mechanism of signal transmission from the platelet surface to the interior required for thrombin-induced platelet activation is not known. A stable complex between Iodo-[125l]-thrombin and platelets has been noted previously on SDS polyacrylamide gels. This 77,000 dalton complex was thought to represent the high affinity binding found in binding studies. The complex is inhibited by excess native thrombin but not by excess active site-modified thrombin. Thus, it displays the characteristics of the crucial thrombin-platelet interaction needed for platelet activation. My studies using similar methods for analysis were performed to determine if this interaction might have a role in signal generation for thrombin-induced platelet activation. Thrombin concentration studies with 3 minute incubations demonstrated that formation of the complex occurred only at thrombin doses which result in platelet activation (above 0.1 U/ml). The amount of the complex increased as the thrombin dose increased. Time course studies with thrombin 1 U/ml revealed that the reaction was rapid and was present on platelets after only 5 seconds of incubation. The complex was noted in supernatants but not until 30 seconds. This interaction was not present on platelets chilled to 4°C and was markedly diminished on platelets exposed to the metabolic inhibitors, antimycin A and 2-deoxyglu-cose. The specific thrombin inhibitors, hirudin and dansylargin-ine N-(3-ethyl-l,5-pentanediyl) amide, prevented the complex formation. Addition of either inhibitor after formation of the complex reversed its formation up to 1 minute after the addition of thrombin but not beyond this time. Treatment with trypsin but not chymotrypsin removed this complex from the platelet. It is concluded that this reaction is not simply a binding event as it requires functional platelets and is only formed at thrombin doses which activate platelets. It is an early, specific, surface reaction which requires thrombin binding and active-site domains for its formation. Formation of this complex is consistent with observation of "receptor processing" noted with specific thrombin binding. Therefore, this reaction could have an important function in the signal processing mechanism for thrombin-induced platelet activation.
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Fox, J. E. B., C. C. Reynolds, J. K. Boyles, R. A. Abel, and M. M. Johnson. "IDENTIFICATION OF GLYCOPROTEIN Ib8 AS THE Mr = 24,000 PLATELET POLYPEPTIDE PHOSPHORYLATED BY AGENTS THAT ELEVATE CYCLIC AMP." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1642926.
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Platelet function is inhibited by agents that elevate intracellular cyclic AMP concentrations, presumably as a result of the cyclic AMP-stimulated phosphorylation of intracellular proteins. Polypeptides that become phosphorylated are of Mr = 250,000, Mr = 51.000 (P51), Mr = 36,000 (P36), Mr = 24,000 (P24), and Mr = 22.000 (P22). The Mr = 250,000 polypeptide is actin-binding protein, but the identity of the other polypeptides 1s unknown. In the present study, we identified the P24 polypeptide. Platelets were radiolabeled with [32P]P1 and then Incubated for 2-5 min in the presence or absence of 5 μM prostaglandin E1 (PGE1). The PGE1-induced phosphorylation of P24 was detected on autoradiograms of SDS-gels. Since P24 has been shown to be membrane-associated, its molecular weight was compared with those of known membrane proteins. P24 comigrated with the β-chain of purified GP Ib on reduced gels (Mr = 24,000) and also on nonreduced gels (when GP Ibβ is disulfide-linked to GP Ibα and migrates with Mr = 170,000). Like GP Ibβ, P24 was associated with actin filaments in Triton X-100 lysates. Both GP Ibβ and P24 were selectively associated with filaments of the membrane skeleton and were released from filaments when the Ca2+-dependent protease was active. Antibodies against GP Ib immunoprecipitated P24 from platelet lysates. Finally, exposure of Bernard-Soulier platelets (that lacked GP Ib) to PGE1 resulted in phosphorylation of actin-binding protein, P51, P36, and P22, but not P24. We conclude that P24 is GP Ibβ. To determine whether phosphorylation of GP Ibβ is responsible for the inhibitory effects of PGE1 on platelets, we compared the action of PGE1 on control platelets with that on Bernard-Soulier platelets. One of the ways in which PGE1 inhibits platelet activation is by inhibiting the polymerization of actin. While PGE1 inhibited actin polymerization in control platelets, it did not in Bernard-Soulier platelets. We conclude that GP Ibβ is phosphorylated by agents that elevate cyclic AMP and that phosphorylation of this glycoprotein results in inhibition of platelet function.
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Wasi, S., S. Juodvalkis, P. Alles, and J. E. Aubin. "STUDIES ON THE DIRECT PROTEOLYTIC ACTION OF HUMAN TISSUE PLASMINOGEN ACTIVATOR ON HUMAN FIBRONECTIN AND VITRONECTIN." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1644376.
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The ability of cells to make or break specific attachments to extracellular matrix (ECM) and other cells is important in cell migration, proliferation and wound repair. Specific attachment proteins believed to be involved in mediating these interactions comprise functional domains joined by protease sensitive segments. Proteases can conceivably modulate cellular interactions by releasing functional domains from parent molecules. Tissue plasminogen activator (t-pA) is known to participate in various pathophysiological processes. That t-pA may also act directly on structural proteins has not been investigated. We have studied the direct proteolytic action of melanoma t-pA on fibronectin (FN), vitronectin (VN) and laminin (LN). These were incubated with t-pA for 0 to 48 h in 50 mM Tris HCi, pH 7.4. The cleavage products were separated on polyacrylamide slab gels and blotted onto nitrocellulose strips. FN and VN fragments with cell attachment properties were identified by incubating the strips with human gingiva fibroblasts and staining with Amido black. Monoclonal antibodies to FN were used to identify heparin, cell and gelatin binding fragments. VN was converted to a major 55 Kd product as a function of time. Lower molecular weight species migrating at 45 Kd, 30 Kd and 15 Kd positions were also identified. Most of these fragments possessed cell attachment properties. LN became susceptible to t-pA digestion after dénaturation with H2O2. The catalytic activity of t-pA could be inhibited in the presence of nitrophenyl-p-guinidino benzoate (a synthetic inhibitor of plasminogen activator), whereas O-phenanthroline (a metalloprotease inhibitor), α 2-antiplasmin and trasylol had no effect. A monoclonal IgG preparation (HI 72 A1, kindly provided by Dr. David J. Loskutoff) that specifically inhibits t-pA also inhibited the protelyotic action of t-pA on FN. These data suggest that direct proteolytic action of t-pA on adhesive proteins may modulate cellular behaviour in various normal and pathological conditions which involve dynamic interactions between cells and ECM and where plasminogen activator levels are elevated either transiently or permanently, for example during tissue remodelling, wound-related repair and thrombolytic therapy.
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Tariq, Zeeshan, Murtada Saleh Aljawad, Mobeen Murtaza, Mohamed Mahmoud, Dhafer Al-Shehri, and Abdulazeez Abdulraheem. "A Data-Driven Approach to Predict the Breakdown Pressure of the Tight and Unconventional Formation." In SPE Annual Technical Conference and Exhibition. SPE, 2021. http://dx.doi.org/10.2118/206136-ms.
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Abstract Unconventional reservoirs are characterized by their extremely low permeabilities surrounded by huge in-situ stresses. Hydraulic fracturing is a most commonly used stimulation technique to produce from such reservoirs. Due to high in situ stresses, breakdown pressure of the rock can be too difficult to achieve despite of reaching maximum pumping capacity. In this study, a new model is proposed to predict the breakdown pressures of the rock. An extensive experimental study was carried out on different cylindrical specimens and the hydraulic fracturing stimulation was performed with different fracturing fluids. Stimulation was carried out to record the rock breakdown pressure. Different types of fracturing fluids such as slick water, linear gel, cross-linked gels, guar gum, and heavy oil were tested. The experiments were carried out on different types of rock samples such as shales, sandstone, and tight carbonates. An extensive rock mechanical study was conducted to measure the elastic and failure parameters of the rock samples tested. An artificial neural network was used to correlate the breakdown pressure of the rock as a function of fracturing fluids, experimental conditions, and rock properties. Fracturing fluid properties included injection rate and fluid viscosity. Rock properties included were tensile strength, unconfined compressive strength, Young's Modulus, Poisson's ratio, porosity, permeability, and bulk density. In the process of data training, we analyzed and optimized the parameters of the neural network, including activation function, number of hidden layers, number of neurons in each layer, training times, data set division, and obtained the optimal model suitable for prediction of breakdown pressure. With the optimal setting of the neural network, we were successfully able to predict the breakdown pressure of the unconventional formation with an accuracy of 95%. The proposed method can greatly reduce the prediction cost of rock breakdown pressure before the fracturing operation of new wells and provides an optional method for the evaluation of tight oil reservoirs.
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Kalgaonkar, Rajendra A., Qasim Sahu, and Nour Baqader. "Novel In-Situ Gelled Acid System Based on Inorganic Nanoparticles." In SPE International Hydraulic Fracturing Technology Conference & Exhibition. SPE, 2022. http://dx.doi.org/10.2118/205336-ms.
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Abstract Gelled acid systems based upon gelation of hydrochloric acid (HCl) are widely used in in both matrix acidizing and fracture acidizing treatments to prevent acidizing fluid leak-off into high permeable zones of a reservoir. The gelled up fluid system helps retard the acid reaction to allow deeper acid penetration for hydrocarbon productivity enhancement. The in-situ gelation is typically achieved by using crosslinked polymers with the acid. Conventional in-situ crosslinked gelled acid systems are made up of polyacrylamide gelling agent, iron based crosslinker and a breaker chemical in addition to other additives, with the acid as the base fluid. However, the polymer-based systems can lead to damaging the formation due to a variety of reasons including unbroken polymer residue. Additionally, the iron-based crosslinker systems can lead to scaling, precipitation and or sludge formation after the acid reacts with the formation, resulting in formation damage and lowering of hydrocarbon productivity. In this paper we showcase a new nanoparticles based gelled acid system that overcomes the inherent challenges faced by conventional in-situ crosslinked gelled acid systems. The new system can work in 5 to 20 % HCl up to 300°F. The new system does not contain any polymer or iron based crosslinker that can potentially damage the formation. It comprises nanoparticles, a gelation activator, acidizing treatment additives along with HCl. The new in-situ gelled acid system has low viscosity at surface making it easy to pump. It gels up at elevated temperatures and pH of 1 to 4, which helps with diverting the tail end acid to tighter or damaged zones of the formation. We demonstrate that the viscosification and eventual gelation of the new system can be achieved as the acid reacts with a carbonate formation and the pH rises above 1. As the acid further reacts and continues to spend there by increasing the pH beyond 4, the gel demonstrates reduction of viscosity. This assists in a better cleanup post the acidizing treatment. Various experimental techniques were used to showcase the development of the nanoparticle based acid diversion fluid. Static and dynamic gelation studies as a function of time, temperature and pH are reported. The gelation performance of the new system was evaluated at temperatures up to 300°F and discussed in the paper. Comparative performance of different types of gelation activators on the gelation profile of the nanoparticles is evaluated. It is also shown that the gelation and viscosity reduction is entirely a pH dependent phenomenon and does not require any additional breaker chemistry, and therefore provides more control over the system performance. The novelty of the new gelled acid system is that it is based upon nanoparticles making it less prone to formation damage as compared to a crosslinked polymer based system.
Reports on the topic "GELUs activation function"
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Heifetz, Yael, and Michael Bender. Success and failure in insect fertilization and reproduction - the role of the female accessory glands. United States Department of Agriculture, December 2006. http://dx.doi.org/10.32747/2006.7695586.bard.
Full textAbstract:
The research problem. Understanding of insect reproduction has been critical to the design of insect pest control strategies including disruptions of mate-finding, courtship and sperm transfer by male insects. It is well known that males transfer proteins to females during mating that profoundly affect female reproductive physiology, but little is known about the molecular basis of female mating response and no attempts have yet been made to interfere with female post-mating responses that directly bear on the efficacy of fertilization. The female reproductive tract provides a crucial environment for the events of fertilization yet thus far those events and the role of the female tract in influencing them are poorly understood. For this project, we have chosen to focus on the lower reproductive tract because it is the site of two processes critical to reproduction: sperm management (storage, maintenance, and release from storage) and fertilization. E,fforts during this project period centered on the elucidation of mating responses in the female lower reproductive tract The central goals of this project were: 1. To identify mating-responsive genes in the female lower reproductive tract using DNA microarray technology. 2. In parallel, to identify mating-responsive genes in these tissues using proteomic assays (2D gels and LC-MS/MS techniques). 3. To integrate proteomic and genomic analyses of reproductive tract gene expression to identify significant genes for functional analysis. Our main achievements were: 1. Identification of mating-responsive genes in the female lower reproductive tract. We identified 539 mating-responsive genes using genomic and proteomic approaches. This analysis revealed a shift from gene silencing to gene activation soon after mating and a peak in differential gene expression at 6 hours post-mating. In addition, comparison of the two datasets revealed an expression pattern consistent with the model that important reproductive proteins are pre-programmed for synthesis prior to mating. This work was published in Mack et al. (2006). Validation experiments using real-time PCR techniques suggest that microarray assays provide a conservativestimate of the true transcriptional activity in reproductive tissues. 2.lntegration of proteomics and genomics data sets. We compared the expression profiles from DNA microarray data with the proteins identified in our proteomic experiments. Although comparing the two data sets poses analyical challenges, it provides a more complete view of gene expression as well as insights into how specific genes may be regulated. This work was published in Mack et al. (2006). 3. Development of primary reproductive tract cell cultures. We developed primary cell cultures of dispersed reproductive tract cell types and determined conditions for organ culture of the entire reproductive tract. This work will allow us to rapidly screen mating-responsive genes for a variety of reproductive-tract specifi c functions. Scientific and agricultural significance. Together, these studies have defined the genetic response to mating in a part of the female reproductive tract that is critical for successful fertllization and have identified alarge set of mating-responsive genes. This work is the first to combine both genomic and proteomic approaches in determining female mating response in these tissues and has provided important insights into insect reproductive behavior.
2
Lurie, Susan, John Labavitch, Ruth Ben-Arie, and Ken Shackel. Woolliness in Peaches and Nectarines. United States Department of Agriculture, 1995. http://dx.doi.org/10.32747/1995.7570557.bard.
Full textAbstract:
The overall goal of the research was to understand the processes involved in the development of woolliness in peaches and nectarines. Four specific hypotheses were proposed and in the course of the research evidence was gathered t support two of them and to not support two others. The hypotheses and a summary of the evidence are outlined below. 1. That woolliness arises from an imbalance between the activities of the cell wall pectin degrading enzymes. Using 'Flavortop' nectarines and 'Hermoza' peaches as model systems, storage regimes were manipulated to induce or prevent woolliness. The expression (mRNA abundance), protein content (Western blotting), and activity of polygalacturonase (PG) and pectin esterase (PE) were followed. Expression of the enzymes was not different, but activity and the ratio between PG and PE activities were quite different in fruits developing woolliness or ripening normally. This was also examined by looking at the substrate, the pectin moiety of the cell wall, and i woolly fruit there were more high molecular weight pectins with regions of non-methylated galacturonic acid residues. Taking an in vitro approach it was found a) that PE activity was stable at 0oC while PG activity decreased; b) incubating the calcium pectate fraction of the cell wall with PE extracted from peaches caused the polymers to form a gel characteristic of the visual woolly symptoms in peaches. 2. That continued cell wall synthesis occurs during storage and contributes to structural changes i cell walls and improper dissolution and softening after storage. We tried to adapt our technique of adding 13C-glucose to fruit discs, which was used successfully to follow cell wall synthesis during tomato ripening. However, the difference in sugar content between the two fruits (4% in tomato and 12% in peach) meant that the 13C-glucose was much more diluted within the general metabolite pool. We were unable to see any cell wall synthesis which meant that either the dilution factor was too great, or that synthesis was not occurring. 3. That controlled atmosphere (CA) prevents woolliness by lowering all enzyme activities. CA was found to greatly reduce mRNA abundance of the cell wall enzymes compared to regular air storage. However, their synthesis and activity recovered during ripening after CA storage and did not after regular air storage. Therefore, CA prevented the inhibition of enzyme activation found in regular air storage. 4. That changes in cell wall turgor and membrane function are important events in the development of woolliness. Using a micro pressure probe, turgor was measured in cells of individual 'O'Henry' and 'CalRed' peaches which were woolly or healthy. The relationship between firmness and turgor was the same in both fruit conditions. These data indicate that the development and expression of woolliness are not associated with differences in membrane function, at least with regard to the factors that determine cell turgor pressure. In addition, during the period of the grant additional areas were explored. Encoglucanase, and enzyme metabolizing hemicellulose, was found to be highly expressed air stored, but not in unstored or CA stored fruit. Activity gels showed higher activity in air stored fruit as well. This is the first indication that other components of the cell wall may be involved in woolliness. The role of ethylene in woolliness development was also investigated at it was found a) that woolly fruits had decreased ability to produce ethylene, b) storing fruits in the presence of ethylene delayed the appearance of woolliness. This latter finding has implication for an inexpensive strategy for storing peaches and nectarines.