Browsing by Author "Laakso, Ilkka"

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3D convolutional neural networksfor classification of magneticresonance images
(2020-08-17) Li, Anqiang
Sähkötekniikan korkeakoulu | Master's thesis
A 50 Hz magnetic field affects hemodynamics, ECG and vascular endothelial function in healthy adults: A pilot randomized controlled trial
(2021-08-05) Okano, Hideyuki; Fujimura, Akikatsu; Kondo, Tsukasa; Laakso, Ilkka; Ishiwatari, Hiromi; Watanuki, Keiichi
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Application of exposure to 50/60 Hz magnetic fields (MFs) has been conducted in the treatment of muscle pain and fatigue mainly in Japan. However, whether MFs could increase blood flow leading to muscle fatigue recovery has not been sufficiently tested. We investigated the acute effects of a 50 Hz sinusoidal MF at Bmax 180 mT on hemodynamics, electrocardiogram, and vascular endothelial function in healthy young men. Three types of regional exposures to a 50 Hz MF, i.e., forearm, upper arm, or neck exposure to MF were performed. Participants who received three types of real MF exposures had significantly increased ulnar arterial blood flow velocity compared to the sham exposures. Furthermore, after muscle loading exercise, MF exposure recovered hemoglobin oxygenation index values faster and higher than sham exposure from the loading condition. Moreover, participants who received real MF exposure in the neck region had significantly increased parasympathetic high-frequency activity relative to the sham exposure. The MF exposure in the upper arm region significantly increased the brachial artery flow-mediated dilation compared to the sham exposure. Computer simulations of induced in situ electric fields indicated that the order-of-magnitude estimates of the peak values were 100-500 mV/m, depending on the exposure conditions. This study provides the first evidence that a 50 Hz MF can activate parasympathetic activity and thereby lead to increase vasodilation and blood flow via a nitric oxide-dependent mechanism.
Accuracy of Optical Heart Rate Measuring on Activity Trackers
(2018-06-18) Nyman, Andreas
Sähkötekniikan korkeakoulu | Master's thesis
Aivojen tasavirtastimulaation mallintaminen – vaikutukset henkilökohtaisiin vasteisiin
(2024-05-26) Häkkänen, Otso
Sähkötekniikan korkeakoulu | Bachelor's thesis
Tavoite: Aivojen tasavirtastimulaation (tDCS) vasteet ovat aiemmassa tutkimuksessa vaihdelleet henkilöiden välillä merkittävästi. Tämä vaikeuttaa tDCS:n kehitystä kaikille henkilöille toimivaksi ja tehokkaaksi hoitomuodoksi. Aiemmassa kirjallisuudessa on pohdittu mahdollista annosvasteyhteyttä sähkökentän ja vasteen välille. Tämän tutkimuksen tavoite on selvittää miten päänsisäiset sähkökentät vaikuttavat terveiden koehenkilöiden vasteisiin verrattuna sham-stimulaatioon. Menetelmät: Tutkimus tehtiin systemaattisena katsauksena kahteen viitetietokantaan (Web of science core collection ja MEDLINE). Löydettiin 116 tutkimusta, jota rajattiin aluksi tiivistelmän perusteella (ulosrajattuja n = 73). Kokotekstin perusteella loppuaineistoon rajattiin 12 sopivaa tutkimusta. Lisäksi muita reittejä tunnistettiin kaksi sopivaa tutkimusta. Tulokset: MEP-vasteissa yhteys oli joko nostava, laskeva tai epälineaarinen. Toiminnallisten yhteyksien ja sähkökentän yhteys oli joko nostava tai ajasta riippuen nostava tai laskeva. Nostava yhteys havaittiin GABA-konsentraation muutoksessa sekä muistitestin reaktioajassa. Yhteyttä ei havaittu sykevaihtelussa tai motorisessa oppimisessa. Pohdinta: Erot tutkimusparametreissä tekevät vertailusta tutkimusten välillä haastavaa. Voimakkain havaittu yhteys oli korkeintaan melko vahva, joten aineiston perusteella sähkökenttä selittää vain osittain henkilökohtaisia vasteita. Tulevaisuudessa alan tutkimuksen kannattaa pyrkiä yhtenäistämään tutkimusmenetelmiä, tutkimaan suurempia ryhmiä sekä laajentamaan tarkastelua epälineaariselle yhteydelle.
Assessment of Human Exposure to Electromagnetic Fields: Review and Future Directions
(2021-10-01) Hirata, Akimasa; Diao, Yinliang; Onishi, Teruo; Sasaki, Kensuke; Ahn, Seungyoung; Colombi, Davide; De Santis, Valerio; Laakso, Ilkka; Giaccone, Luca; Wout, Joseph; Rashed, Essam A.; Kainz, Wolfgang; Chen, Ji
A2 Katsausartikkeli tieteellisessä aikakauslehdessä
This article reviews recent standardization activities and scientific studies related to the assessment of human exposure to electromagnetic fields (EMF). The differences of human exposure standards and assessment of consumer products and medical applications are summarized. First, we reviewed human body modeling and tissue dielectric properties. Then, we explain the rationale of current exposure standards from the viewpoint of EMF and the standardization process for product compliance based on these exposure standards. The assessment of wireless power transfer, as an example of emerging wireless devices, and environmental EMFs in our daily lives are reviewed. Safety in magnetic resonance systems, where the EMF exposure is much larger than from typical consumer devices, is also reviewed. Finally, we summarize future research directions and research needs for EMF safety.
Assessment of the induced electric fields in a carbon-fiber electrical vehicle equipped with a wireless power transfer system
(2018-02-25) De Santis, Valerio; Campi, Tommaso; Cruciani, Silvano; Laakso, Ilkka; Feliziani, Mauro
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
In this study, the electric field induced inside two realistic anatomical models placed near or inside an electric vehicle made of carbon-fiber composite while charging its battery with a wireless power transfer (WPT) system has been investigated. The WPT source consists of two parallel inductive coils operating with a power output of 7.7 kW at two different frequencies of 85 and 150 kHz. Since a misalignment between the primary and the secondary coil creates higher induced fields, a misalignment of 20 cm is also considered as the worst-case exposure condition. The analysis of the obtained results shows that the International Commission on Non-Ionizing Radiation Protection (ICNIRP) basic restrictions are exceeded by 1.3 dB and 4.8 dB for the aligned and misaligned coil positions, respectively. This exceedance is however confined only in a small area of the driver's foot.
Benefits of integrating intelligent video systems with building automation systems
(2018-12-17) Rauhio, Kalle
Sähkötekniikan korkeakoulu | Master's thesis
The world is continually becoming more interconnected and previously separate technical systems are being integrated into now co-operative wholes. The communication revolution that the advent of the Internet produced is now expanding into new fields. The Internet of Things concept is changing the way in which systems communicate with each other within a built environment. This thesis’ main motivation is to examine how the communication and data sharing as well as co-operation between systems works on a more limited scale, between the different technical systems of a building. The main goals of the thesis were to define, what are the possible benefits and uses cases that could be created by integrating intelligent video systems with the technical systems of a building. Additionally, the thesis strived to map out how common integration between different systems was within buildings and how this integration was achieved. The thesis defines the current state of communication protocols and standards within the building automation and intelligent video system fields. Additionally, it describes the basic structures and capabilities of modern building automation and intelligent video systems. One result of the theses was the fact that there is currently very little integration between the different technical systems located within buildings. The few exceptions to this were with systems provided by a single supplier. These systems had a greater level of integration. The main reasons for this low level of integration was found to be the lack of common communication protocols and methods, as well as the organizational divides between the different systems. The main results of the thesis were the articulation of several use cases that system integration would enable as well as proposed additions to the Haystack semantic data model and tagging system.
Can electric fields explain inter-individual variability in transcranial direct current stimulation of the motor cortex?
(2019-01-24) Laakso, Ilkka; Mikkonen, Marko; Koyama, Soichiro; Hirata, Akimasa; Tanaka, Satoshi
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
The effects of transcranial direct current stimulation (tDCS) on motor cortical excitability are highly variable between individuals. Inter-individual differences in the electric fields generated in the brain by tDCS might play a role in the variability. Here, we explored whether these fields are related to excitability changes following anodal tDCS of the primary motor cortex (M1). Motor evoked potentials (MEPs) were measured in 28 healthy subjects before and after 20 min sham or 1 mA anodal tDCS of right M1 in a double-blind crossover design. The electric fields were individually modelled based on magnetic resonance images. Statistical analysis indicated that the variability in the MEPs could be partly explained by the electric fields, subjects with the weakest and strongest fields tending to produce opposite changes in excitability. To explain the findings, we hypothesized that the likely locus of action was in the hand area of M1, and the effective electric field component was that in the direction normal to the cortical surface. Our results demonstrate that a large part of inter-individual variability in tDCS may be due to differences in the electric fields. If this is the case, electric field dosimetry could be useful for controlling the neuroplastic effects of tDCS.
Comparison of heart rate variability parameters derived from ballistocardiography and electrocardiography signals
(2020-03-16) Jousjärvi, Eeva
Sähkötekniikan korkeakoulu | Master's thesis
This thesis was performed as a pilot study to evaluate the suitability of the ballistocardiography for the professional use in demanding hospital environment to determine if the method could be exploited in an examination of subjects who are likely to have some sort of disease. The reliability of the ballistocardiography based method for the heart rate variability analysis was assessed by comparing the heart rate variability analysis results computed from ballistocardiography signals to the measures calculated from the concurrently acquired electrocardiography signals. The used input data consisted of six sleep recordings that had been conducted to acute stroke patients. The heart rate variability parameters were derived from the ballistocardiography signals by a custom-made executable heart rate variability analysis script, whereas the analysis of the reference electocardiography signals were carried out using Kubios HRV (Kubios Oy, Finland) software. The agreement between the measurement methods for heart rate variability assessment was evaluated using Bland-Altman analysis technique. The ballistocardiography based measurement method was found to perform well in deriving the root mean square of successive differences (RMSSD) of heartbeats in the patient position “unknown” as well as in defining the normalized low- and high-frequency component powers (LFnu and HFnu) of heart rate variability in the patient positions left and right. In all other combinations of an investigated heart rate variability parameter and a specific patient position or a recording data set, a major systematic error was observed to be present, and the ballistocardiography based method was shown to either significantly under- or over-estimate the values compared to the reference electrocardiography method. The obtained study results indicate that the ballistocardiography based method has a potential to be used for heart rate variability analysis in hospital environment, but further research and validation of the method using a larger and more diverse study population is needed.
Computational 3D Modelling of Electric Fields in Fingrid Oyj’s Electrical Grid
(2017-12-11) Lehtinen, Tuukka
Perustieteiden korkeakoulu | Master's thesis
In this thesis, extremely low frequency external electric fields as well as fields induced into a human body are simulated in various occupational exposure scenarios. The simulated environment is a Fingrid Oyj operated electrical substation. A realistic 3D model of a section of the substation is created and simulations are conducted using software implemented in MATLAB. The software solves the electric fields using finite element method. The human body being exposed to the external electric field is portrayed by a voxel based human phantom model. The results received from the simulations are compared with 2013/35/EU directive safety limits to verify safe working conditions at the studied site. Additionally, the simulated results are compared with data obtained from experimental measurements. This comparison is done to both validate the simulation results and to confirm that the calculations and equations used in conjunction with the experimental measurements produce reliable results. The results obtained show that the EU directive safety limits are not exceeded in the studied occupational scenarios and that the experimental measurement methods previously used by Fingrid work as intended in the majority of cases.
Computational errors of the induced electric field in voxelized and tetrahedral anatomical head models exposed to spatially uniform and localized magnetic fields
(2020-01-10) Soldati, Marco; Laakso, Ilkka
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
At low and intermediate frequencies, the strength of the induced electric field is used as dosimetric quantity for human protection in the International Commission on Non-Ionizing Radiation Protection (ICNIRP) guidelines. To compute the induced electric field, numerical methods based on anatomically realistic voxel models are commonly used. However, grid-based models introduce staircase approximation errors when curved surfaces are discretized with voxels, particularly in correspondence of boundaries with large differences in electrical conductivity. By contrast, those kind of artefacts are absent in tetrahedral meshes. Here, we investigate the computational errors that affect voxelized and tetrahedral head models when exposed to uniform magnetic fields at 50 Hz, and localized exposure due to transcranial magnetic stimulation. Five subjects were considered, and for each of them four voxel grids and four tetrahedral meshes were reconstructed with different resolutions. The differences in the results were characterized by comparing the induced electric fields computed using those meshes/grids. The results showed modest discrepancies in the overall electric field distributions between the various grids and meshes. However, the peak electric field strengths were erroneous for both tetrahedral and voxel models. Therefore, post-processing techniques are needed to suppress those numerical artefacts. For this purpose, the 99.99th, or lower, percentile of the electric field strength was found to remove the numerical errors. In addition, we found that spatially averaging the electric fields over 2 mm cubical volumes, as described by the ICNIRP, was effective in removing most of the spuriously large electric fields. When spatial averaging was used, relative coarse head models consisting of approximately 1 mm voxels or tetrahedral meshes with 2 mm average side length were sufficient to mitigate the artefacts. Nonetheless, the additional percentile filtering might still be needed to suppress the erroneous values completely.
Computational uncertainty of finite-difference time-domain method in electromagnetic dosimetry
(2009) Laakso, Ilkka
Helsinki University of Technology | Licentiate thesis
Electromagnetic dosimetry studies the absorption of electromagnetic fields inside the human body. For radio-frequency fields, the dose metric is specific absorption rate (SAR) which is linked to possible adverse thermal effects of electromagnetic power absorption. As the geometry of the human body is complex and heterogeneous, accurate analysis of SAR values needs to be done by numerical methods. In the recent years, finite-difference time-domain (FDTD) method has become the method of choice for computational dosimetry. The emphasis of this thesis is to study how reliably the SAR values are assessed by FDTD method, and which factors affect the accuracy and uncertainty of the results. In addition to SAR values, also the temperature rise due to electromagnetic power absorption and its modelling by the bioheat equation is studied.
Cost of focality in TDCS: Interindividual variability in electric fields
(2020) Mikkonen, Marko; Laakso, Ilkka; Tanaka, Satoshi; Hirata, Akimasa
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Background: In transcranial direct current stimulation (TDCS), electric current is applied via two large electrodes to modulate brain activity. Computational models have shown that large electrodes produce diffuse electric fields (EFs) in the brain, which depends on individual head and brain anatomy. Recently, smaller electrodes as well as novel electrode arrangements, including high-definition TDCS (HD-TDCS) montages, have been introduced to improve the focality of EFs. Here, we investigated whether the EFs of focal montages are more susceptible to interindividual anatomical differences. Methods: Thirteen TDCS montages, including conventional M1-contralateral forehead montages with different stimulating electrode sizes as well as 4 × 1 HD and bipolar HD montages, producing varying EF focalities were modeled using the finite element method in 77 subjects, with individual anatomically realistic models based on magnetic resonance images. Results: Interindividual variability of predicted EFs increased with EF focality for conventional M1-contralateral forehead and 4 × 1 HD montages. 4 × 1 HD-TDCS was found to have the highest EF focality and greatest variability. Bipolar HD montages targeting the region between two small electrodes did not follow this pattern, but produced EF magnitudes comparable to those of 4× 1 HD-TDCS, with a minor decrease in focality and lower interindividual variability. Conclusions: EF focality in TDCS was achieved at the cost of increased interindividual variability. Hence, individual modeling is required to plan EF doses when focal montages are used. Among the studied montages, bipolar HD montages provided a compromise between inter-individual variability, focality and magnitude of the predicted EFs.
Design and implementation of embedded temperature and voltage control software for a medical device gas sensor
(2024-05-20) Nguyen, Danh
Sähkötekniikan korkeakoulu | Master's thesis
Excessive heat production resulting from the overuse of power supply poses a significant challenge in embedded systems, with heightened concerns in medical devices. In the medical field, this issue becomes even more critical, as overheating can pose dangers to patients and, in severe cases, lead to serious consequences. Therefore, this master's thesis is dedicated to design and implement temperature and voltage control software for a medical device in order not to provide too much heat because of using highly inappropriate voltage. The software's primary objective is to efficiently manage and regulate the operating voltage, current, and power supply across various components, aiming to enhance the gas sensor's performance and achieve optimal efficiency. The research encompasses both the design aspects of the software and its practical implementation, involving rigorous testing to assess the system's reliability. Additionally, additional testings between the software with the PID control and the one without PID control will be conducted to identify and address potential issues in this new control system. The goal of this research is to mitigate temperature-related risks associated with prolonged operation and overpowering of the sensor. The proposed control loops aim to ensure that the gas sensor's surface temperature remains within the optimal range as required by the International Electrotechnical Commission (IEC) standards, thereby enhancing the overall safety and performance of the same medical device.
Design Concepts for Pediatric Magnetic Resonance Imaging Receiver Coils
(2018-06-18) Pradere-Koskiahde, Aleksi
Sähkötekniikan korkeakoulu | Master's thesis
Design of three axis bi-planar surface mount gradient coils for Magnetic Resonance Imaging device.
(2020-10-19) Sanchayan, Rajeetharan
Sähkötekniikan korkeakoulu | Master's thesis
Building very low ﬁeld strength and an open patient access MRI device is the project goal. In pre-gradient coil design construction phase, permanent magnet is chosen as static magnetic ﬁeld source and modeled as two pole open patient access structure. To support this structure gradient coils needed to be bi-planar and surface mountable. By applying Biot-Savart law for an inﬁnite current carrying straight coil a pattern between magnetic ﬁeld and the distance between calculated point to the wire is identiﬁed. Utilizing particular pattern and through COMSOL simulation software’s parametric sweep function the best gradient characteristic delivering coil geometry is deﬁned and chosen as the design for the x and y-gradient coil. Maxwell pair is used to produce z-gradient in conventional devices; it is also used in this design. The designed three axis gradient coils are modelled to the previous design and integrated in the previous design model and the superposition of the results are analyzed. Some further issues related to the improvement of the design are also proposed.
Development and analysis of a data acquisition system for a magnetic resonance imaging system
(2024-08-29) Pétas, Oskari
School of Electrical Engineering | Master's thesis
Magnetic Resonance Imaging (MRI) is a widely used and crucial method for clinical diagnosis. MRI images of the head are a critical diagnosis tool for serious conditions such as a brain stroke. MRI is safe, but also an expensive method due to various factors such as the need for cryogenics and high-power electronics in high and ultra-high field strength superconducting MRI devices. A possible solution to overcome the cost and safety issues of high-field MRI devices is to use a low magnetic field. However, lower magnetic fields result in a reduced signal-to-noise ratio leading to a lower resolution as well as artifacts and distortions in the images. The aim of this thesis is to develop a data acquisition system for a prototype low-field MRI device and characterize its main properties. This work involved designing and developing a management console program and integrating a remotely controllable oscilloscope into an existing system. The shimming of the magnet as well as tuning of the acquisition electronics were iteratively adjusted, and programming of sequences and image formation post-processing were developed. The integrated system and subsystems of the prototype were tested to verify functionality. Through iterative tuning of imaging sequence parameters, reasonably strong Free Induction Decay (FID) signals as well as spin echo signals were acquired. A complete imaging sequence using spin echo was developed, and a k-space was obtained through demodulation, filtering, and downsampling. An MRI image of a simple phantom of a syringe filled with tap water was successfully obtained using the inverse Fourier transform. The image had a low resolution and a low signal-to-noise ratio. This thesis demonstrates the feasibility of developing a low-field MRI device and highlights the challenges in achieving adequate image quality.
Ecg localization method based on volume conductor model and kalman filtering
(2021-06-22) Nakano, Yuki; Rashed, Essam A.; Nakane, Tatsuhito; Laakso, Ilkka; Hirata, Akimasa
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
The 12-lead electrocardiogram was invented more than 100 years ago and is still used as an essential tool in the early detection of heart disease. By estimating the time-varying source of the electrical activity from the potential changes, several types of heart disease can be noninvasively identified. However, most previous studies are based on signal processing, and thus an approach that includes physics modeling would be helpful for source localization problems. This study proposes a localization method for cardiac sources by combining an electrical analysis with a volume conductor model of the human body as a forward problem and a sparse reconstruction method as an inverse problem. Our formulation estimates not only the current source location but also the current direction. For a 12-lead electrocardiogram system, a sensitivity analysis of the localization to cardiac volume, tilted angle, and model inhomogeneity was evaluated. Finally, the estimated source location is corrected by Kalman filter, considering the estimated electrocardiogram source as time-sequence data. For a high signal-to-noise ratio (greater than 20 dB), the dominant error sources were the model inhomogeneity, which is mainly attributable to the high conductivity of the blood in the heart. The average localization error of the electric dipole sources in the heart was 12.6 mm, which is comparable to that in previous studies, where a less detailed anatomical structure was considered. A time-series source localization with Kalman filtering indicated that source mislocalization could be compensated, suggesting the effectiveness of the source estimation using the current direction and location simultaneously. For the electrocardiogram R-wave, the mean distance error was reduced to less than 7.3 mm using the proposed method. Considering the physical properties of the human body with Kalman filtering enables highly accurate estimation of the cardiac electric signal source location and direction. This proposal is also applicable to electrode configuration, such as ECG sensing systems.
The Effect of Dual-Hemisphere Transcranial Direct Current Stimulation Over the Parietal Operculum on Tactile Orientation Discrimination
(2017-09-20) Fujimoto, Shuhei; Tanaka, Satoshi; Laakso, Ilkka; Yamaguchi, Tomofumi; Kon, Noriko; Nakayama, Takeo; Kondo, Kunitsugu; Kitada, Ryo
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
The parietal operculum (PO) often shows ipsilateral activation during tactile object perception in neuroimaging experiments. However, the relative contribution of the PO to tactile judgment remains unclear. Here, we examined the effect of transcranial direct current stimulation (tDCS) over bilateral PO to test the relative contributions of the ipsilateral PO to tactile object processing. Ten healthy adults participated in this study, which had a double-blind, sham-controlled, cross-over design. Participants discriminated grating orientation during three tDCS and sham conditions. In the dual-hemisphere tDCS conditions, anodal and cathodal electrodes were placed over the left and right PO. In the uni-hemisphere tDCS condition, anodal and cathodal electrodes were applied over the left PO and contralateral orbit, respectively. In the tDCS and sham conditions, we applied 2 mA for 15 min and for 15 s, respectively. Computational models of electric fields (EFs) during tDCS indicated that the strongest electric fields were located in regions in and around the PO. Compared with the sham condition, dual-hemisphere tDCS improved the discrimination threshold of the index finger contralateral to the anodal electrode. Importantly, dual-hemisphere tDCS with the anodal electrode over the left PO yielded a decreased threshold in the right finger compared with the uni-hemisphere tDCS condition. These results suggest that the ipsilateral PO inhibits tactile processing of grating orientation, indicating interhemispheric inhibition (IHI) of the PO.
Effect of electrical conductivity uncertainty in the assessment of the electric fields induced in the brain by exposure to uniform magnetic fields at 50 Hz
(2020-12-09) Soldati, Marco; Laakso, Ilkka
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
International exposure standard/guidelines establish limits for external electromagnetic field strengths. At low frequencies, these maximum allowable exposure levels are derived from the limits defined for internal electric field strengths which have been set to avoid adverse health effects. In the IEEE International Committee on Electromagnetic Safety standard, the relationship between internal and external fields was obtained through homogeneous elliptical models without considering the dielectric properties of tissues. However, the International Commission on Non-Ionizing Radiation Protection guidelines were established using computational dosimetry on realistic anatomical models. In this case, variability in the electrical conductivity of the tissues represents a major source of uncertainty when deriving allowable external field strengths. Here we characterized this uncertainty by studying the effect of different tissue conductivity values on the variability of the peak electric field strengths induced in the brain of twenty-five individuals exposed to uniform magnetic fields at 50 Hz. Results showed that the maximum electric field strengths computed with new estimations of brain tissue conductivities were significantly lower than those obtained with commonly used values in low-frequency dosimetry. The lower strengths were due to the new brain conductivity values being considerably higher than those usually adopted in dosimetry modeling studies. A sensitivity analysis also revealed that variations in the electrical conductivities of the grey and white matter had a major effect on the peak electric field strengths in the brain. Our findings are intended to lessen dosimetric uncertainty in the evaluation of the electric field strengths due to electrical properties of the biological tissues.