177,716 research outputs found
Alcune considerazioni sui rapporti Tiraboschi-Lanzi
No full textIl contributo ricostruisce le relazioni letterarie e personali mantenute fra Girolamo Tiraboschi e Luigi Lanzi, storici della letteratura e dell'arte. Metodologicamente affini, i due letterati mantennero anche un rapporto epistolare, testimoniato fra l'altro dalle sei lettere del Tiraboschi al Lanzi riferite in Appendice al saggio
A Time Averaged Semiclassical Approach to IR Spectroscopy
No full textSemiclassical vibrational spectroscopy is based on the evolution of classical trajectories and is able to reproduce quantum effects with good accuracy at the cost of a reasonable computational effort. [1-5] Nevertheless, semiclassical vibrational power spectra do not simulate all the features of the experimental IR spectra, since intensities in power spectra are not directly related to IR absorptions. Therefore, we
developed a new semiclassical approach to the calculation of molecular IR spectra by employing the time average technique upon symmetrization of the quantum dipole-dipole autocorrelation function. [6,7] We tested the accuracy of this new method on a few simple analytical systems and small molecules in the gas phase. In particular, spectra in the limit of infinite or zero temperature were investigated. Overall the method features excellent accuracy in calculating absorption intensities and provides estimates for the frequencies of vibrations in agreement with the corresponding power spectra.
[1] R. Conte, A. Aspuru-Guzik, and M. Ceotto, J. Phys. Chem. Lett. 4, 3407 (2013).
[2] G. Bertaina, G. Di Liberto, and M. Ceotto, J. Chem. Phys. 151, 114307 (2019).
[3] C. Aieta, M. Micciarelli, G. Bertaina, and M. Ceotto, Nat. Comm. 11, 4384 (2020).
[4] A. Rognoni, R. Conte, and M. Ceotto, Chem. Sci. 12, 2060 (2021).
[5] R. Conte, C. Aieta, G. Botti, M. Cazzaniga, M. Gandolfi, C. Lanzi, G. Mandelli, D. Moscato, and M. Ceotto, Theor. Chem. Acc. 142, 53 (2023).
[6] A. L. Kaledin and W. H. Miller, J. Chem. Phys. 118, 7174 (2003).
[7] A. L. Kaledin and W. H. Miller, J. Chem. Phys. 119, 3078 (2003)
An extended semiclassical initial value representation approach to IR spectroscopy
No full textRecently—Lanzi et al., J. Chem. Phys. 160, 214107 (2024)—we introduced a time averaged approach to infrared (IR) spectroscopy. The pivotal advance in that paper was represented by the possibility to get accurate semiclassical estimates of the IR absorption intensities and associated transition frequencies from a single calculation. However, the method relies on the convergence of Monte Carlo integrations based on the generation of thousands of pairs of semiclassical trajectories. This makes the approach highly accurate but limited to small, few-atom molecules. Here, we build on the theoretical grounds of that work to extend the application of the method to larger molecules. The goal is achieved by moving to tailored single-pair trajectory calculations and introducing a partially time-independent approximation to the real part of the coherent state overlap. Upon testing the level of accuracy on small molecules such as water, formaldehyde, and methane, we
calculate IR spectra for ethanol and glycine. Vibrational intensities and frequencies are found to be fairly accurate, and the method can be straightforwardly applied to larger molecular systems
Local pentoxifylline administration decreases the formalin induced fos expression in rat spinal cord
No full textPro-inflammatory cytokines play a key role in the inflammatory response and contributing to producing local hyperalgesia. It is known that pentoxifylline inhibits inflammatory cytokine production. Therefore, the aim of this study was to find out, using a behavioural test and neuronal Fos expression, if this drug had some antinociceptive effect decreasing nociresponsive neuron activation in the spinal cord after nociceptive inflammation (injection of formalin in the hind paw). Our data showed that formalin induced a great number of Fos-positive neurons in the dorsal horn of the lumbar spinal cord mainly in the ipsilateral I and II laminae. The local pre-treatment with pentoxifylline before the formalin injection, decreased the nociceptive response in the formalin test and the number of Fos positive neurons in the spinal cord. This finding suggests that pentoxifylline is involved in decreasing the activation of nociresponsive neurons in the spinal cord playing a role in local anti-nociception
Semiclassical vibrational spectroscopy from small molecules to solvated biomolecules
No full textThe hallmark of semiclassical dynamics is the ability to get quantum effects starting from classical
trajectories.[1] Therefore, the main challenge semiclassical methods have to face is to demonstrate
their accuracy and possibility to be applied even to large and complex systems.[2]
I will show that semiclassical dynamics can be straightforwardly interfaced to different descriptions
of the potential energy surface (PES), ranging from ab initio PESs[3-5] to force fields[6,7] and
QM/MM schemes. This allows one to apply semiclassical spectroscopy to the calculation of the
quantum vibrational features of very different systems, including not only small molecules
characterized by elusive Fermi resonances, like ethanol, or hard-to-assign experimental spectra, like
proline, but also large systems like solvated biomolecules. Finally, ongoing efforts to reproduce also
the intensity of absorption in the framework of semiclassical dynamics will be illustrated.[8]
[1] W. H. Miller The semiclassical initial value representation: A potentially practical way for
adding quantum effects to classical molecular dynamics J. Phys. Chem. A 105, 2942 (2001).
[2] M. Ceotto, G. Di Liberto, R. Conte Semiclassical “divide-and-conquer” method for
spectroscopic calculations of high dimensional molecular systems Phys. Rev. Lett. 119, 010401
(2017).
[3] R. Conte, A. Nandi, C. Qu, Q. Yu, P. L. Houston, and J. M. Bowman Semiclassical and
VSCF/VCI calculations of the vibrational energies of trans- and gauche-ethanol using a CCSD(T)
potential energy surface J. Phys. Chem. A 126, 7709 (2022).
[4] A. Rognoni, R. Conte, M. Ceotto Caldeira-Leggett model vs ab initio potential: A vibrational
spectroscopy test of water solvation J. Chem. Phys. 154, 094106 (2021).
[5] G. Botti, C. Aieta, R. Conte The complex vibrational spectrum of proline explained through the
adiabatically switched semiclassical initial value representation J. Chem. Phys. 156, 164303 (2022).
[6] F. Gabas, R. Conte, M. Ceotto Quantum vibrational spectroscopy of explicitly solvated
thymidine in semiclassical approximation J. Phys. Chem. Lett. 13, 1350 (2022).
[7] D. Moscato, F. Gabas, R. Conte, M. Ceotto Vibrational spectroscopy simulation of solvation
effects on a G-quadruplex J. Biomol. Struct. Dyn. doi:10.1080/07391102.2023.2180435 (2023).
[8] C. Lanzi, C. Aieta, M. Ceotto, R. Conte A semiclassical approach to IR spectroscopy, being
prepared
Chronic exposure to aluminium decreases NADPH-diaphorase positive neurons in the rat cerebral cortex
No full textAluminium (Al) exposure is neurotoxic and is considered a possible etiological factor for many neurodegenerative disorders. Since it is known that Al impairs the glutamate-nitric oxide-cGMP pathway in neurons, this study was carried out to monitor the expression of NADPH-d in some central nervous system areas of rats after chronic administration of Al in drinking water. We tested three different nervous areas known to contain NADPH-diaphorase positive neurons: two cortical area (somatosensory cerebral cortex and cerebral cortex), a deep brain area (dorsolateral periaqueductal gray matter) and a spinal area (lumbar enlargement of the spinal cord). Our data showed that Al significantly decreased NADPH-d positive neurons in the cerebral cortex and the NADPH-d staining of many granular neurons in the cerebellum. We also found that Al did not cause neuron loss or apoptosis in the cerebral cortex. These findings suggest that the cortical nitroxidergic neurons and granule cells were a specific target of Al neurotoxicity
Classification of packed executables for accurate computer virus detection
No full textExecutable packing is the most common technique used by computer virus writers to obfuscate malicious code and evade detection by anti-virus software. Universal unpackers have been proposed that can detect and extract encrypted code from packed executables, therefore potentially revealing hidden viruses that can then be detected by traditional signature-based anti-virus software. However, universal unpackers are computationally expensive and scanning large collections of executables looking for virus infections may take several hours or even days. In this paper we apply pattern recognition techniques for fast detection of packed executables. The objective is to efficiently and accurately distinguish between packed and non-packed executables, so that only executables detected as packed will be sent to an universal unpacker, thus saving a significant amount of processing time. We show that our system achieves very high detection accuracy of packed executables with a low average processing time
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
McBoost: Boosting scalability in malware collection and analysis using statistical classification of executables
No full textIn this work, we propose Malware Collection Booster (McBoost), a fast statistical malware detection tool that is intended to improve the scalability of existing malware collection and analysis approaches. Given a large collection of binaries that may contain both hitherto unknown malware and benign executables, McBoost reduces the overall time of analysis by classifying and filtering out the least suspicious binaries and passing only the most suspicious ones to a detailed binary analysis process for signature extraction. The McBoost framework consists of a classifier specialized in detecting whether an executable is packed or not, a universal unpacker based on dynamic binary analysis, and a classifier specialized in distinguishing between malicious or benign code. We developed a proof-of-concept version of McBoost and evaluated it on 5,586 malware and 2,258 benign programs. McBoost has an accuracy of 87.3%, and an Area Under the ROC curve (AUC) equal to 0.977. Our evaluation also shows that McBoost reduces the overall time of analysis to only a fraction (e.g., 13.4%) of the computation time that would otherwise be required to analyze large sets of mixed malicious and benign executables
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