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Total 95 records

#### Modeling for Sensing Behavior of SnO2-CuO Nanostructures toward H2S Gas

, Ph.D. Dissertation Sharif University of Technology ; Ghorbani, Mohammad (Supervisor) ; Moosavi, Ali (Supervisor) ; Mohammadpour, Raheleh (Supervisor)
Abstract

H2S is a toxic and corrosive gas which is detrimental for both human’s health and some of important industries such as oil and gas. Based on different experimental research among various systems, resistive sensors fabricated from SnO2-CuO nanostructures have promising performance toward detection of this gas. High sensitivity and selectivity, response time of order of seconds, recovery times of order of tens of seconds and determining concentration of H2S gas below ppm level are advantages of this system. Unfortunately due to lack of a theoretical model, current experimental researches are excessively based on “trial and error” methodology. In this research some of the basic questions which...

#### Analytical solution for the free vibration analysis of delaminated timoshenko beams

, Article The Scientific World Journal ; Volume 2014 , 2014 ; ISSN: 1537744X ; Abedi, M ; Sharif University of Technology
Abstract

This work presents a method to find the exact solutions for the free vibration analysis of a delaminated beam based on the Timoshenko type with different boundary conditions. The solutions are obtained by the method of Lagrange multipliers in which the free vibration problem is posed as a constrained variational problem. The Legendre orthogonal polynomials are used as the beam eigenfunctions. Natural frequencies and mode shapes of various Timoshenko beams are presented to demonstrate the efficiency of the methodology

#### Experimental design in analytical chemistry -Part I: Theory

, Article Journal of AOAC International ; Vol. 97, issue. 1 , 2014 , pp. 3-11 ; ISSN: 10603271 ; Leardi, R ; Jalali-Heravi, M ; Sharif University of Technology
Abstract

This paper reviews the main concepts of experimental design applicable to the optimization of analytical chemistry techniques. The critical steps and tools for screening, including Plackett-Burman, factorial and fractional factorial designs, and response surface methodology such as central composite, Box-Behnken, and Doehlert designs, are discussed. Some useful routines are also presented for performing the procedures

#### Study on the catalytic activity and theoretical modeling of a novel dual acidic mesoporous silica

, Article RSC Advances ; Volume 4, Issue 32, 2014 , 2014 , Pages 16647-16654 ; ISSN: 20462069 ; Fattahi, A ; Sharif University of Technology
Abstract

A novel mesoporous silica-functionalized dual Brønsted acidic species has been introduced as an efficient catalyst for solvent-free esterification of fatty acids with ethanol. The structure of the catalyst has been characterized by FT-IR spectroscopy, thermal gravimetric analysis (TGA), TEM and N2 adsorption-desorption. TGA of catalyst 1 showed no weight loss before 200 °C, indicating a high degree of hydrophobicity of the surface of the mesoporous silica. TEM images and nitrogen adsorption-desorption showed no noticeable changes to the structure of the catalyst before and after acid treatment. pH metric analysis was performed for the catalyst to determine the loading of the acidic sites....

#### Multi-item multiperiodic inventory control problem with variable demand and discounts: A particle swarm optimization algorithm

, Article Scientific World Journal ; Vol. 2014 , 2014 ; ISSN: 23566140 ; Niaki, S. T. A ; Bahreininejad, A ; Musa, S. N ; Sharif University of Technology
Abstract

A multi-item multiperiod inventory control model is developed for known-deterministic variable demands under limited available budget. Assuming the order quantity is more than the shortage quantity in each period, the shortage in combination of backorder and lost sale is considered. The orders are placed in batch sizes and the decision variables are assumed integer. Moreover, all unit discounts for a number of products and incremental quantity discount for some other items are considered. While the objectives are to minimize both the total inventory cost and the required storage space, the model is formulated into a fuzzy multicriteria decision making (FMCDM) framework and is shown to be a...

#### Crosstalk elimination in the detection of dual-beam optical tweezers by spatial filtering

, Article Review of Scientific Instruments ; Volume 85, Issue 5 , May , 2014 ; ISSN: 00346748 ; Reihani, S. N. S ; Oddershede, L. B ; Sharif University of Technology
Abstract

In dual-beam optical tweezers, the accuracy of position and force measurements is often compromised by crosstalk between the two detected signals, this crosstalk leading to systematic and significant errors on the measured forces and distances. This is true both for dual-beam optical traps where the splitting of the two traps is done by polarization optics and for dual optical traps constructed by other methods, e.g., holographic tweezers. If the two traps are orthogonally polarized, most often crosstalk is minimized by inserting polarization optics in front of the detector; however, this method is not perfect because of the de-polarization of the trapping beam introduced by the required...

#### Extension of weighted sum of gray gas data to mathematical simulation of radiative heat transfer in a boiler with gas-soot media

, Article The Scientific World Journal ; Vol. 2014 , 2014 ; ISSN: 1537744X ; Nouri-Borujerdi, A ; Kazi, S. N ; Yarmand, H ; Sharif University of Technology
Abstract

In this study an expression for soot absorption coefficient is introduced to extend the weighted-sum-of-gray gases data to the furnace medium containing gas-soot mixture in a utility boiler 150 MWe. Heat transfer and temperature distribution of walls and within the furnace space are predicted by zone method technique. Analyses have been done considering both cases of presence and absence of soot particles at 100% load. To validate the proposed soot absorption coefficient, the expression is coupled with the Taylor and Foster's data as well as Truelove's data for CO2-H2O mixture and the total emissivities are calculated and compared with the Truelove's parameters for 3-term and 4-term gray...

#### Higher-order four-wave mixing modeling in DWDM networks

, Article Physica Scripta, Belgrade ; Volume T157 , 15 November , 2013 ; 02811847 (ISSN) ; Noshad, M ; Sharif University of Technology
2013

Abstract

In this paper, we derive a theoretical model for the higher-order four-wave mixing (FWM) power in wavelength division multiplexing networks with non-zero dispersion shifted fibers for the first time. We have investigated the higher-order FWM power theoretically and by numerical simulations. Dividing the fiber into a finite number of elements and applying the boundary conditions allow us to derive an expression for the second-order power penalty. At the end of each element, we derive the first-order FWM power for all wavelengths and use these values to calculate the second-order FWM power in the next element. Consequently, for each channel we can compute the total second-order FWM power...

#### Generative model selection using a scalable and size-independent complex network classifier

, Article Chaos ; Volume 23, Issue 4 , 2013 ; 10541500 (ISSN) ; Aliakbary, S ; Habibi, J ; Sharif University of Technology
2013

Abstract

Real networks exhibit nontrivial topological features, such as heavy-tailed degree distribution, high clusteringsmall-worldness. Researchers have developed several generative models for synthesizing artificial networks that are structurally similar to real networks. An important research problem is to identify the generative model that best fits to a target network. In this paper, we investigate this problem and our goal is to select the model that is able to generate graphs similar to a given network instance. By the means of generating synthetic networks with seven outstanding generative models, we have utilized machine learning methods to develop a decision tree for model selection. Our...

#### Thermal conductivity of mixed nanofluids under controlled pH conditions

, Article International Journal of Thermal Sciences ; Volume 74 , 2013 , Pages 63-71 ; 12900729 (ISSN) ; Hamian, S ; Mohammadi, N ; Shafii, M. B ; Sharif University of Technology
2013

Abstract

Just a few investigations have been conducted to study the mixed nanofluids(MNs), which contain more than one type of nanoparticles, despite considerable advances in the field of nanofluids thermal conductivity. In present research, by combining different volume fractions of various nanoparticles, the variation of mixed nanofluids thermal conductivity was considered. The mentioned nanofluids have different fabrication cost. First, the effect of each specific nanoparticle presence in the base fluid on the thermal conductivity of nanofluid was surveyed both experimentally and theoretically. Then, the thermal conductivities of two MNs, one consisted of a metallic nanoparticle (high thermal...

#### Mesoporous silica-functionalized dual Brønsted acidic ionic liquid as an efficient catalyst for thioacetalization of carbonyl compounds in water

, Article Catalysis Communications ; Volume 41 , 2013 , Pages 96-100 ; 15667367 (ISSN) ; Dizicheh, Z. B ; Hashemi, M. M ; Sharif University of Technology
2013

Abstract

A novel silica-functionalized dual Brønsted acidic ionic liquid (ionic liquid with two Brønsted acidic species) has been reported as a highly efficient catalyst for thioacetalization of carbonyl compounds. The reaction was efficiently performed in water as an environmentally benign solvent with good to high yields. Thermal gravimetric analysis showed that the catalyst is stable at least up to 350 C. Furthermore, the catalyst can be recycled and reused for six runs of reaction without appreciable loss of activity. The structure of the catalyst is modelized to gain more realistic structural insight about the functionalized ionic liquid

#### Symmetric bursting behaviors in the generalized FitzHugh-Nagumo model

, Article Biological Cybernetics ; Volume 107, Issue 4 , 2013 , Pages 465-476 ; 03401200 (ISSN) ; Fallah, H ; Razvan, M. R ; Sharif University of Technology
2013

Abstract

In the current paper, we have investigated the generalized FitzHugh-Nagumo model. We have shown that symmetric bursting behaviors of different types could be observed in this model with an appropriate recovery term. A modified version of this system is used to construct bursting activities. Furthermore, we have shown some numerical examples of delayed Hopf bifurcation and canard phenomenon in the symmetric bursting of super-Hopf/homoclinic type near its super-Hopf and homoclinic bifurcations, respectively

#### Predicting hourly air pollutant levels using artificial neural networks coupled with uncertainty analysis by Monte Carlo simulations

, Article Environmental Science and Pollution Research ; Volume 20, Issue 7 , 2013 , Pages 4777-4789 ; 09441344 (ISSN) ; Kamali, N ; Rajabi, M. M ; Sharif University of Technology
2013

Abstract

Recent progress in developing artificial neural network (ANN) metamodels has paved the way for reliable use of these models in the prediction of air pollutant concentrations in urban atmosphere. However, improvement of prediction performance, proper selection of input parameters and model architecture, and quantification of model uncertainties remain key challenges to their practical use. This study has three main objectives: to select an ensemble of input parameters for ANN metamodels consisting of meteorological variables that are predictable by conventional weather forecast models and variables that properly describe the complex nature of pollutant source conditions in a major city, to...

#### Soft computing method for prediction of co2 corrosion in flow lines based on neural network approach

, Article Chemical Engineering Communications ; Volume 200, Issue 6 , 2013 , Pages 731-747 ; 00986445 (ISSN) ; Nareh'ei, M. A ; Chamkalani, R ; Zargari, M. H ; Dehestani Ardakani, M. R ; Farzam, M ; Sharif University of Technology
2013

Abstract

An important aspect of corrosion prediction for oil/gas wells and pipelines is to obtain a realistic estimate of the corrosion rate. Corrosion rate prediction involves developing a predictive model that utilizes commonly available operational parameters, existing lab/field data, and theoretical models to obtain realistic assessments of corrosion rates. This study presents a new model to predict corrosion rates by using artificial neural network (ANN) systems. The values of pH, velocity, temperature, and partial pressure of the CO2 are input variables of the network and the rate of corrosion has been set as the network output. Among the 718 data sets, 503 of the data were implemented to find...

#### Theoretical modeling of generation of hat-top intensity profile from Gaussian beam by means of a two-stage beam shaper

, Article Optics Communications ; Volume 294 , 2013 , Pages 182-187 ; 00304018 (ISSN) ; Golnabi, H ; Sharif University of Technology
2013

Abstract

Both theoretical and experimental results of an optical beam shaping system are investigated in this report. The described system is a two-stage beam shaping device including a fiber-bundle and a prism-duct. A source light is used to illuminate the fiber-bundle and the image of output beam is captured by a CCD camera. The fiber-bundle output beam shape shows a linear arrangement of circular spots lights, which are placed in a rectangular cross section of about 21.37 mm×2.44 mm. In another study, the photograph picture of the prism output beam is taken by a digital camera. The prism output beam cross section is a square shape with a dimension of about 4×4 mm2. According to the experimental...

#### Theoretical modeling and simulation of higher order FWM crosstalks in multichannel WDM optical communication systems

, Article Advanced Materials Research, Xiamen ; Volume 660 , 2013 , Pages 130-134 ; 10226680 (ISSN) ; 9783037856413 (ISBN) ; Noshad, M ; Farrokhi, A ; Sharif University of Technology
2013

Abstract

In this paper, we derive a theoretical model for the higher order FWM power in WDM networks with NZDSF fibers for the first time. We have investigated the higher order FWM power theoretically and by numerical simulations. Dividing the fiber into finite number of elements and applying the boundary conditions, allow us derive an expression for second order power penalty. At the end of each element we derive the first order FWM power for all wavelengths and use these values to calculate the second order FWM power in the next element. Consequently, for each channel we can compute the total second order FWM power penalty at the end of the fiber

#### Theoretical investigation on antioxidant activity of bromophenols from the marine red alga Rhodomela confervoides: H-atom vs electron transfer mechanism

, Article Journal of Agricultural and Food Chemistry ; Volume 61, Issue 7 , 2013 , Pages 1534-1541 ; 00218561 (ISSN) ; Javan, M. J ; Tehrani, Z. A ; Sharif University of Technology
2013

Abstract

Bromophenols are known as antioxidant radical scavengers for some biomolecules such as those in marine red alga. Full understanding of the role played by bromophenols requires detailed knowledge of the radical scavenging activities in probable pathways, a focus of ongoing research. To gain detailed insight into two suggested pathways, H-atom transfer and electron transfer, theoretical studies employing first principle quantum mechanical calculations have been carried out on selected bromophenols. Detailed investigation of the aforementioned routes revealed that upon H-atom abstraction or the electron transfer process, bromophenols cause an increase in radical species in which the unpaired...

#### Coarsening dynamics of nanodroplets on topographically structured substrates

, Article Journal of Physics Condensed Matter ; Volume 25, Issue 4 , 2013 ; 09538984 (ISSN) ; Moosavi, A ; Sharif University of Technology
2013

Abstract

Employing a biharmonic boundary integral method with linear elements, coarsening dynamics of nanodroplets on topographical step heterogeneity is investigated. It is shown that the step height and droplet configuration have an influential effect on the dynamics. Increasing the step height slows down the process while locating the droplets close to the step boosts the coarsening rate. Considering a slip boundary condition enhances the dynamics and reveals a transition in the droplet migration direction. Our results reveal that increasing the surface wettability weakens the dynamics. Various types of the disjoining pressure over the step are also considered and their effects on the coarsening...

#### Study of the dijet mass spectrum in pp→W+jets events at √s=7 TeV

, Article Physical Review Letters ; Volume 109, Issue 25 , December , 2012 ; 00319007 (ISSN) ; Khachatryan, V ; Sirunyan, A. M ; Tumasyan, A ; Adam, W ; Aguilo, E ; Bergauer, T ; Dragicevic, M ; Erö, J ; Fabjan, C ; Friedl, M ; Frühwirth, R ; Ghete, V. M ; Hammer, J ; Hörmann, N ; Hrubec, J ; Jeitler, M ; Kiesenhofer, W ; Knünz, V ; Krammer, M ; Krätschmer, I ; Liko, D ; Mikulec, I ; Pernicka, M ; Rahbaran, B ; Rohringer, C ; Rohringer, H ; Schöfbeck, R ; Strauss, J ; Taurok, A ; Waltenberger, W ; Walzel, G ; Widl, E ; Wulz, C.-E ; Mossolov, V ; Shumeiko, N ; Suarez Gonzalez, J ; Bansal, M ; Bansal, S ; Cornelis, T ; De Wolf, E. A ; Janssen, X ; Luyckx, S ; Mucibello, L ; Ochesanu, S ; Roland, B ; Rougny, R ; Selvaggi, M ; Staykova, Z ; Van Haevermaet, H ; Van Mechelen, P ; Van Remortel, N ; Van Spilbeeck, A ; Blekman, F ; Blyweert, S ; D'hondt, J ; Gonzalez Suarez, R ; Kalogeropoulos, A ; Maes, M ; Olbrechts, A ; Van Doninck, W ; Van Mulders, P ; Van Onsem, G.P ; Villella, I ; Clerbaux, B ; De Lentdecker, G ; Dero, V ; Gay, A. P. R ; Hreus, T ; Léonard, A ; Marage, P. E ; Reis, T ; Thomas, L ; Vander Marcken, G ; Vander Velde, C ; Vanlaer, P ; Wang, J ; Adler, V ; Beernaert, K ; Cimmino, A ; Costantini, S ; Garcia, G ; Grunewald, M ; Klein, B ; Lellouch, J ; Marinov, A ; Mccartin, J ; Ocampo Rios, A. A ; Ryckbosch, D ; Strobbe, N ; Thyssen, F ; Tytgat, M ; Verwilligen, P ; Walsh, S ; Yazgan, E ; Zaganidis, N ; Basegmez, S ; Bruno, G ; Castello, R ; Ceard, L ; Delaere, C ; Du Pree, T ; Favart, D ; Forthomme, L ; Giammanco, A ; Hollar, J ; Lemaitre, V ; Liao, J ; Militaru, O ; Nuttens, C ; Pagano, D ; Pin, A ; Piotrzkowski, K ; Schul, N ; Vizan Garcia, J. M ; Beliy, N ; Caebergs, T ; Daubie, E ; Hammad, G. H ; Alves, G. A ; Correa Martins Junior, M ; De Jesus Damiao, D ; Martins, T ; Pol, M. E ; Souza, M. H. G ; Aldá Júnior, W. L ; Carvalho, W ; Custódio, A ; Da Costa, E. M ; De Oliveira Martins, C ; Fonseca De Souza, S ; Matos Figueiredo, D ; Mundim, L ; Nogima, H ; Oguri, V ; Prado Da Silva, W. L ; Santoro, A ; Soares Jorge, L ; Sznajder, A ; Anjos, T. S ; Bernardes, C. A ; Dias, F. A ; Fernandez Perez Tomei, T. R ; Gregores, E. M ; Lagana, C ; Marinho, F ; Mercadante, P. G ; Novaes, S. F ; Padula, S. S ; Genchev, V ; Iaydjiev, P ; Piperov, S ; Rodozov, M ; Stoykova, S ; Sultanov, G ; Tcholakov, V ; Trayanov, R ; Vutova, M ; Dimitrov, A ; Hadjiiska, R ; Kozhuharov, V ; Litov, L ; Pavlov, B ; Petkov, P ; Bian, J. G ; Chen, G. M ; Chen, H. S ; Jiang, C. H ; Liang, D ; Liang, S ; Meng, X ; Tao, J ; Wang, J ; Wang, X ; Wang, Z ; Xiao, H ; Xu, M ; Zang, J ; Zhang, Z ; Asawatangtrakuldee, C ; Ban, Y ; Guo, S ; Guo, Y ; Li, W ; Liu, S ; Mao, Y ; Qian, S. J ; Teng, H ; Wang, D ; Zhang, L ; Zhu, B ; Zou, W ; Avila, C ; Gomez, J. P ; Gomez Moreno, B ; Osorio Oliveros, A. F ; Sanabria, J. C ; Godinovic, N ; Lelas, D ; Plestina, R ; Polic, D ; Puljak, I ; Antunovic, Z ; Kovac, M ; Brigljevic, V ; Duric, S ; Kadija, K ; Luetic, J ; Morovic, S ; Attikis, A ; Galanti, M ; Mavromanolakis, G ; Mousa, J ; Nicolaou, C ; Ptochos, F ; Razis, P. A ; Finger, M ; Finger, M ; Assran, Y ; Elgammal, S ; Ellithi Kamel, A ; Khalil, S ; Mahmoud, M. A ; Radi, A ; Kadastik, M ; Müntel, M ; Raidal, M ; Rebane, L ; Tiko, A ; Eerola, P ; Fedi, G ; Voutilainen, M ; Härkönen, J ; Heikkinen, A ; Karimäki, V ; Kinnunen, R ; Kortelainen, M. J ; Lampén, T ; Lassila-Perini, K ; Lehti, S ; Lindén, T ; Luukka, P ; Mäenpää, T ; Peltola, T ; Tuominen, E ; Tuominiemi, J ; Tuovinen, E ; Ungaro, D ; Wendland, L ; Banzuzi, K ; Karjalainen, A ; Korpela, A ; Tuuva, T ; Besancon, M ; Choudhury, S ; Dejardin, M ; Denegri, D ; Fabbro, B ; Faure, J. L ; Ferri, F ; Ganjour, S ; Givernaud, A ; Gras, P ; Hamel De Monchenault, G ; Jarry, P ; Locci, E ; Malcles, J ; Millischer, L ; Nayak, A ; Rander, J ; Rosowsky, A ; Shreyber, I ; Titov, M ; Baffioni, S ; Beaudette, F ; Benhabib, L ; Bianchini, L ; Bluj, M ; Broutin, C ; Busson, P ; Charlot, C ; Daci, N ; Dahms, T ; Dobrzynski, L ; Granier De Cassagnac, R ; Haguenauer, M ; Miné, P ; Mironov, C ; Naranjo, I. N ; Nguyen, M ; Ochando, C ; Paganini, P ; Sabes, D ; Salerno, R ; Sirois, Y ; Veelken, C ; Zabi, A ; Agram, J. L ; Andrea, J ; Bloch, D ; Bodin, D ; Brom, J. M ; Cardaci, M ; Chabert, E. C ; Collard, C ; Conte, E ; Drouhin, F ; Ferro, C ; Fontaine, J. C ; Gelé, D ; Goerlach, U ; Juillot, P ; Le Bihan, A. C ; Van Hove, P ; Fassi, F ; Mercier, D ; Beauceron, S ; Beaupere, N ; Bondu, O ; Boudoul, G ; Chasserat, J ; Chierici, R ; Contardo, D ; Depasse, P ; El Mamouni, H ; Fay, J ; Gascon, S ; Gouzevitch, M ; Ille, B ; Kurca, T ; Lethuillier, M ; Mirabito, L ; Perries, S ; Sordini, V ; Tschudi, Y ; Verdier, P ; Viret, S ; Tsamalaidze, Z ; Anagnostou, G ; Beranek, S ; Edelhoff, M ; Feld, L ; Heracleous, N ; Hindrichs, O ; Jussen, R ; Klein, K ; Merz, J ; Ostapchuk, A ; Perieanu, A ; Raupach, F ; Sammet, J ; Schael, S ; Sprenger, D ; Weber, H ; Wittmer, B ; Zhukov, V ; Ata, M ; Caudron, J ; Dietz-Laursonn, E ; Duchardt, D ; Erdmann, M ; Fischer, R ; Güth, A ; Hebbeker, T ; Heidemann, C ; Hoepfner, K ; Klingebiel, D ; Kreuzer, P ; Magass, C ; Merschmeyer, M ; Meyer, A ; Olschewski, M ; Papacz, P ; Pieta, H ; Reithler, H ; Schmitz, S. A ; Sonnenschein, L ; Steggemann, J ; Teyssier, D ; Weber, M ; Bontenackels, M ; Cherepanov, V ; Erdogan, Y ; Flügge, G ; Geenen, H ; Geisler, M ; Haj Ahmad, W ; Hoehle, F ; Kargoll, B ; Kress, T ; Kuessel, Y ; Nowack, A ; Perchalla, L ; Pooth, O ; Sauerland, P ; Stahl, A ; Aldaya Martin, M ; Behr, J ; Behrenhoff, W ; Behrens, U ; Sharif University of Technology
2012

Abstract

We report an investigation of the invariant mass spectrum of the two jets with highest transverse momentum in pp→W+2-jet and W+3-jet events to look for resonant enhancement. The data sample corresponds to an integrated luminosity of 5.0 fb-1 collected with the CMS detector at √s=7 TeV. We find no evidence for the anomalous structure reported by the CDF Collaboration, and establish an upper limit of 5.0 pb at 95% confidence level on the production cross section for a generic Gaussian signal with mass near 150 GeV. Additionally, we exclude two theoretical models that predict a CDF-like dijet resonance near 150 GeV

#### Properties of functional brain networks correlate frequency of psychogenic non-epileptic seizures

, Article Frontiers in Human Neuroscience ; Issue DEC , 2012 ; 16625161 (ISSN) ; Joudaki, A ; Jalili, M ; Rossetti, A. O ; Frackowiak, R. S ; Knyazeva, M. G ; Sharif University of Technology
Frontiers Media S. A
2012

Abstract

Abnormalities in the topology of brain networks may be an important feature and etiological factor for psychogenic non-epileptic seizures (PNES). To explore this possibility, we applied a graph theoretical approach to functional networks based on resting state EEGs from 13 PNES patients and 13 age- and gender-matched controls. The networks were extracted from Laplacian-transformed time-series by a cross-correlation method. PNES patients showed close to normal local and global connectivity and small-world structure, estimated with clustering coefficient, modularity, global efficiency, and small-worldness metrics, respectively. Yet the number of PNES attacks per month correlated with a...