Secrecy Analysis of a Mu-MIMO LIS-Aided Communication Systems under Nakagami-m Fading Channels.

This study evaluates the performance of large intelligent surface (LIS) technology in the context of a multi-user MIMO mobile communication system (Mu-MIMO) proposed for the sixth generation (6G). LIS employs digitally controlled reflectors to enhance Signal-to-Interference plus Noise Ratio (SINR) and establish line of sight (LoS) connectivity in non-LoS environments, improving transmission security. Analytical expressions are derived to assess LIS performance metrics, including distribution parameters, bit error probability, and secrecy outage probability, considering the presence of eavesdroppers and environmental fading. The study highlights the potential of LIS technology to enhance the confidentiality and reliability of digital communication systems in next-generation networks.

On the Performance of Decode-and-Forward Equal-Gain-Combining Relay Systems over Weibull Fading Channels.

Relay-assisted wireless communications, where both the relay and the final destiny employ diversity-combining techniques, represent a compelling strategy for improving the signal-to-noise ratio (SNR) for mobile terminals, mainly at millimeter-wave (mmWave) frequency bands. In this sense, this work considers a wireless network that employs a dual-hop decode-and-forward (DF) relaying protocol, in which the receivers at the relay and at the base station (BS) use an antenna array. Moreover, it is considered that the received signals are combined at reception using equal-gain-combining (EGC). Recent works have enthusiastically employed the Weibull distribution so as to emulate the small-scale fading behavior in mmWave frequencies, which also motivates its use in the present work. For this scenario, exact and asymptotic expressions for the system's outage probability (OP) and average bit error probability (ABEP) are derived in closed form. Useful insights are gained from these expressions. More precisely, they illustrate how the system and fading parameters affect the performance of the DF-EGC system. Monte Carlo simulations corroborate the accuracy and validity of the derived expressions. Furthermore, the mean achievable rate of the considered system is also evaluated via simulations. Useful insights regarding the system performance are obtained from these numerical results.

A Scheduling Scheme for Improving the Performance and Security of MU-MIMO Systems.

For the receiver of multiple-input multiple-output (MIMO) systems, linear detectors are an interesting option due to their good performance and low complexity. Nevertheless, MIMO systems lose diversity in exchange for eliminating interference when linear detectors are used. Aiming to maintain the system diversity while mitigating interference between users, this work proposes a scheduling scheme for the uplink of multiuser MIMO (MU-MIMO) systems that employ A antennas and the zero-forcing (ZF) detector at the receiver in the base station (BS). The channel model includes Rician fading and additive white Gaussian noise (AWGN) in an imperfect channel estimation scenario. The proposed scheme selects U users from a group of Ut users to transmit simultaneously, so that the signal-to-noise ratio (SNR) is maximized. For this, an exact expression to evaluate the SNR of the users is obtained. With this result, the scheduling strategy is proposed. Results show that as Ut increases, the outage probability (OP), and the bit error rate (BER) decrease as the system diversity increases, even when the system is completely loaded, i.e., when U=A. Moreover, it is shown that the scheduling scheme counteracts the imperfect channel estimation effects as Ut increases. Finally, the proposed scheme is tested in presence of an external eavesdropper trying to decode the information sent by the users. The results show that the presented proposal allows for a reduction of the secrecy-outage-probability (SOP) as Ut increases.

Secrecy Analysis and Error Probability of LIS-Aided Communication Systems under Nakagami-m Fading.

Large intelligent surfaces (LIS) are a new trend to achieve higher spectral efficiency and signal-to-noise ratio in mobile communications. For this reason, this paper proposes metrics to analyze the performance of systems with multiple antennas aided by LIS and derive the spectral efficiency, secrecy outage probability, and bit error probability in an environment with Nakagami-m distributed fading. In addition to an eavesdropper, there is a single-antenna user, an array of antennas at the transmitter side and the possibility of a direct link between transmitter and receiver. This study assumes that the LIS performs non-ideal phase cancellation leading to a residual phase error that follows a Von Mises distribution, and shows that the resulting channel can be accurately approximated by a Gamma distributed SNR whose parameters are analytically derived. From these formulas, it is possible to evaluate the effect of the strength of the line-of-sight link by varying the Nakagami parameter, m.

Unmanned Aerial Vehicle Propagation Channel over Vegetation and Lake Areas: First- and Second-Order Statistical Analysis.

The use of unmanned aerial vehicles (UAV) to provide services such as the Internet, goods delivery, and air taxis has become a reality in recent years. The use of these aircraft requires a secure communication between the control station and the UAV, which demands the characterization of the communication channel. This paper aims to present a measurement setup using an unmanned aircraft to acquire data for the characterization of the radio frequency channel in a propagation environment with particular vegetation (Caatinga) and a lake. This paper presents the following contributions: identification of the communication channel model that best describes the characteristics of communication; characterization of the effects of large-scale fading, such as path loss and log-normal shadowing; characterization of small-scale fading (multipath and Doppler); and estimation of the aircraft speed from the identified Doppler frequency.

Large Intelligent Surfaces Communicating Through Massive MIMO Rayleigh Fading Channels.

Large intelligent surfaces (LIS) promises not only to improve the signal to noise ratio, and spectral efficiency but also to reduce the energy consumption during the transmission. We consider a base station equipped with an antenna array using the maximum ratio transmission (MRT), and a large reflector array sending signals to a single user. Each subchannel is affected by the Rayleigh flat fading, and the reflecting elements perform non-perfect phase correction which introduces a Von Mises distributed phase error. Based on the central limit theorem (CLT), we conclude that the overall channel has an equivalent Gamma fading whose parameters are derived from the moments of the channel fading between the antenna array and LIS, and also from the LIS to the single user. Assuming that the equivalent channel can be modeled as a Gamma distribution, we propose very accurate closed-form expressions for the bit error probability and a very tight upper bound. For the case where the LIS is not able to perform perfect phase cancellation, that is, under phase errors, it is possible to analyze the system performance considering the analytical approximations and the simulated results obtained using the well known Monte Carlo method. The analytical expressions for the parameters of the Gamma distribution are very difficult to be obtained due to the complexity of the nonlinear transformations of random variables with non-zero mean and correlated terms. Even with perfect phase cancellation, all the fading coefficients are complex due to the link between the user and the base station that is not neglected in this paper.

A relação do fading affect bias com o humor e a memória episódica / The relation between the fading affect bias, mood and episodic memory / La relación del fading affect bias con el humor y la memoria episódica

O fading affect bias (FAB) atua na memória autobiográfica humana, favorecendo a manutenção das emoções positivas em detrimento das negativas. Este trabalho questionou se esse mecanismo poderia ser influenciado pela depressão e se seria encontrado na memória episódica. Cinquenta e cinco voluntários registraram eventos autobiográficos positivos e negativos durante uma semana. Eles preencheram o Inventário de Depressão de Beck e realizaram um teste de memória com palavras de conotação positiva, negativa e neutra. Os resultados sugeriram que o humor deprimido pode interferir no funcionamento do FAB e prejudicar a manutenção das emoções positivas na memória. Os efeitos na memória episódica foram menos conclusivos.

The fading affect bias (FAB) works in human autobiographical memory in favour of the maintenance of positive emotions over negative ones. This study questioned whether this mechanism could be influenced by depression and if it could also be found in episodic memory. 55 volunteers registered personal positive and negative life events for a week, filled the Beck Depression Inventory and performed a recognition memory test with positive, neutral and negative words. The results suggested the depressed mood could influence the well functioning of the FAB and damage the maintenance of positive emotions in memory. The effects on the episodic memory were less conclusive.

El fading affect bias (FAB) actúa sobre la memoria autobiográfica humana favoreciendo el mantenimiento de las emociones positivas sobre las negativas. Este trabajo cuestionó si este mecanismo podría estar influenciado por la depresión y si se encontraría en la memoria episódica. 55 voluntarios registraron eventos autobiográficos positivos y negativos durante una semana, completaron el Inventario de depresión de Beck y se sometieron a una prueba de memoria con connotaciones positivas, negativas y neutrales. Los resultados sugirieron que el estado de ánimo deprimido puede interferir con el funcionamiento del FAB y afectar el mantenimiento de las emociones positivas en la memoria. Los efectos sobre la memoria episódica fueron menos concluyentes.

Cooperative Spectrum Sensing with Coded and Uncoded Decision Fusion under Correlated Shadowed Fading Report Channels.

This article addresses the impact of forward error correction when applied to the report channel transmissions of a centralized decision fusion cooperative spectrum sensing scheme designed to detect idle ofdma subchannels. The ofdma signal is transmitted over slow frequency-selective multipath Rayleigh fading channels and sensed using the maximum eigenvalue detection test statistic. The decisions on the OFDMA subchannel occupancy are transmitted to a fusion center over report channels represented by a shadowed fading model combining a three-dimensional spatially correlated shadowing with a slow and flat multipath Rayleigh fading. Binary bch and Repetition codes are used to protect these decisions. Results show that shadowing correlation severely deteriorates the overall spectrum sensing performance and that error correction may not be able to protect the report channel transmissions. It can be even worse with respect to the system performance especially at low signal-to-noise regimes. In the situations in which error correction is effective, the Repetition code is capable of outperforming the BCH, meaning that the diversity gain may be more relevant than the coding gain when the spectrum sensing decisions are subjected to correlated shadowing.

Synthesis and luminescence studies of Tb-doped MgO-MgAl2O4-Mg2SiO4 ceramic for use in radiation dosimetry.

In the present work, MgO ceramic samples with different terbium concentrations were produced and the Thermoluminescence (TL) and Optically Stimulated Luminescence (OSL) properties analyzed and discussed, aiming the use in radiation dosimetry. The samples were produced using MgO, Mg(NO3)2·6H2O, Al2O3, SiO2 and Tb(NO3)3·6H2O precursors in stoichiometric concentrations with five different terbium concentrations between 0.1 and 0.5 mol% and after, heat-treated at high temperature ~1500 °C. X-ray diffraction measurements on samples showed the formation of MgO as principal phase, and others in low concentration due to MgAl2O4, Mg2SiO4 and Tb4O7 phases. The TL glow curve of samples showed an intense and well-defined peak having the maximum at ~210 °C and other less intense at ~350 °C. The sample with 0.1 mol% of terbium concentration presented highest luminescence peak when compared to the other samples. The relationship between 210 °C TL peak intensity and dose was linear to doses between 1 and 20 Gy and the minimum detectable dose obtained by interpolation taking into account three times the standard deviation of the zero dose reading, was ~40 µGy. A fading of ~20% during the first 5 hours after irradiation of 210 °C peak was observed. TL emission spectra showed strong emission lines due to Tb3+ ion. The OSL signal presented a linear behavior to doses between 1 and 10 Gy using 532 nm wavelength stimulation.

Adaptive Wavelet Coding Applied in a Wireless Control System.

Wireless control systems can sense, control and act on the information exchanged between the wireless sensor nodes in a control loop. However, the exchanged information becomes susceptible to the degenerative effects produced by the multipath propagation. In order to minimize the destructive effects characteristic of wireless channels, several techniques have been investigated recently. Among them, wavelet coding is a good alternative for wireless communications for its robustness to the effects of multipath and its low computational complexity. This work proposes an adaptive wavelet coding whose parameters of code rate and signal constellation can vary according to the fading level and evaluates the use of this transmission system in a control loop implemented by wireless sensor nodes. The performance of the adaptive system was evaluated in terms of bit error rate (BER) versus E b / N 0 and spectral efficiency, considering a time-varying channel with flat Rayleigh fading, and in terms of processing overhead on a control system with wireless communication. The results obtained through computational simulations and experimental tests show performance gains obtained by insertion of the adaptive wavelet coding in a control loop with nodes interconnected by wireless link. These results enable the use of this technique in a wireless link control loop.

An Empirical Study of the Transmission Power Setting for Bluetooth-Based Indoor Localization Mechanisms.

Nowadays, there is a great interest in developing accurate wireless indoor localization mechanisms enabling the implementation of many consumer-oriented services. Among the many proposals, wireless indoor localization mechanisms based on the Received Signal Strength Indication (RSSI) are being widely explored. Most studies have focused on the evaluation of the capabilities of different mobile device brands and wireless network technologies. Furthermore, different parameters and algorithms have been proposed as a means of improving the accuracy of wireless-based localization mechanisms. In this paper, we focus on the tuning of the RSSI fingerprint to be used in the implementation of a Bluetooth Low Energy 4.0 (BLE4.0) Bluetooth localization mechanism. Following a holistic approach, we start by assessing the capabilities of two Bluetooth sensor/receiver devices. We then evaluate the relevance of the RSSI fingerprint reported by each BLE4.0 beacon operating at various transmission power levels using feature selection techniques. Based on our findings, we use two classification algorithms in order to improve the setting of the transmission power levels of each of the BLE4.0 beacons. Our main findings show that our proposal can greatly improve the localization accuracy by setting a custom transmission power level for each BLE4.0 beacon.

Ensino de Relações Espaciais de Esquerda e Direita a Participantes com Autismo e Deficiência Intelectual / Teaching Left-right Spatial Relations to Individuals with Autism and Intellectual Disability

RESUMO O reconhecimento dos conceitos de direita-esquerda é uma evidência do desenvolvimento da noção do corpo e faz parte de um processo de lateralização simbólica. Nesse sentido, o objetivo foi ensinar respostas de ouvinte para relações espaciais de direita-esquerda envolvendo partes do corpo e verificar o uso dessas relações em um contexto diferente. Foram conduzidos dois experimentos, que se diferenciaram em função da idade e repertório de entrada dos participantes e do delineamento experimental. No primeiro, foi utilizado um delineamento do tipo A-B e os participantes foram um menino com autismo e dois jovens com deficiência intelectual. No segundo, foi utilizado o delineamento de linha de base múltipla entre participantes, que foram quatro meninos com autismo. O ensino envolveu o uso de um procedimento de instrução com múltiplos exemplares e esvanecimento de dicas (imitação, dicas gestuais, verbais e físicas). Os resultados indicaram aprendizagem das relações ensinadas e uso dessas relações em um contexto diferente (generalização). O uso de múltiplos exemplares e de esvanecimento mostraram-se promissores no ensino de relações espaciais a participantes com pouco repertório verbal.

ABSTRACT The recognition of the left-right concept is an evidence of the body notion development and is part of a process of symbolic lateralization. In this sense, the goal of the present study was to teach listener responses to left-right spatial relations involving body parts and to verify the use of these relations in a different context. Two experiments were conducted, which differed in terms of the age and the input repertoire of the participants and and in terms of experimental design. In the first, an A-B design was used and the participants were a boy with autism and two adolescents with intellectual disabilities. In the second, a concurrent multiple baseline design across participants was used and the participants were four boys with autism. The teaching phase involved the use of a multiple exemplar instruction (MEI) and prompt fading (imitation, gestural, verbal and physical prompts) procedure. The results indicated that the participants learned the taught relations and used those relations in a different context (generalization). The use of MEI and fading showed to be promising in teaching left-right spatial relations to participants with a small verbal repertoire.

Melancolía y desvanecimiento del yo en el poema “El húsar” (1953) de Álvaro Mutis / Melancholy and fading in Álvaro Mutis's poem El Húsar [The Hussar] (1953)

En este artículo proponemos una lectura analítica del problema del fading o desvanecimiento del yo como una característica de la melancolía en el poema “El húsar” (1953) del poeta colombiano Àlvaro Mutis. Planteamos para ello un análisis basado en la aplicación del método psicoanalítico propuesto por Jacques Lacan, el cual ofrece una perspectiva hermenéutica original en el estudio de la literatura. En esta lectura proponemos que existe un proceso de transformación progresivo de la figura del héroe a partir del cual las fronteras entre el sujeto y el objeto se van perdiendo. Este proceso se conoce como fading o desvanecimiento del yo según el cual el objeto y el sujeto se funden para dar paso al puro real de la muerte y la posterior desaparición del héroe mutisiano.

In this article we analyze in Álvaro Mutis's poem El húsar [The Hussar] (1953) the theoretical problem of fading of the I as a characteristic of melancholy theorized in Lacan´s psychoanalytical theory. We demonstrate how the psychoanalytical method could be applied to literary analysis as an original hermeneutical tool that offers a valuable approach in the study of literature. Our main argument in this article is that in the poem El húsar the hero's self is set in an ongoing process of fading where the frontier between subject and object tend to disappear. At the end of this semantic process the signifier loses its symbolic value and the real of death is what lasts.

Cet article a pour but d'examiner le problème du fading ou effacement du moi en tant que caractéristique de la mélancolie dans le poème "Le hussard" (1953) du poète colombien Álvaro Mutis. Pour ce faire, une lecture basée sur l'application de la méthode psychanalytique de Jacques Lacan est proposée. Cette analyse démontrera que la psychanalyse offre une perspective herméneutique originale dans l'étude de la littérature. Dans ce poème il existe un processus de transformation progressive du personnage du héros: les frontières du sujet et de l'objet se fondent dans un processus de fading dans lequel le signifiant perd graduellement sa valeur symbolique pour donner lieu au réel de la mort et à l'ultérieure disparition du héros.

Ensino sem erro e aprendizagem de discriminação / Errorless learning and discrimination learning / Aprendizaje sin error y la discriminación aprendizaje

O termo aprendizagem sem erro tem sido utilizado para se referir, de maneira ampla, à programação de contingências de ensino que resultam em desempenhos precisos ou com pouco erro. A ocorrência de erros durante a aprendizagem tem sido considerada uma parte importante e necessária à aprendizagem na cultura e no meio acadêmico. Na Análise do Comportamento os erros e suas implicações para a aprendizagem são investigados em estudos sobre controle de estímulos e os resultados indicam que erros podem interferir na precisão de desempenhos já aprendidos, gerar comportamentos emocionais, esquiva da tarefa e/ou do professor. Neste estudo, são apresentados diferentes procedimentos de modificação gradual de estímulos para ensinar discriminações, que podem gerar aprendizagem sem erro, e os fatores que afetam a eficácia dessas contingências de ensino. Esses procedimentos necessitam ser mais amplamente divulgados, por serem contribuições importantes da Análise do Comportamento para contextos aplicados, especialmente para o desenvolvimento de tecnologias de ensino quando métodos tradicionais fracassam.

The term errorless learning is largely used to refer to programming teaching contingencies which result in accurate performances or learning without errors. The occurrence of errors during learning has been considered an important and necessary part of learning in cultural and academic contexts. Errors and their implications for learning are investigated in behavioral analytic studies on stimuli control and their results indicate that errors can affect the accuracy of an already established performance, generate emotional behaviors, and avoidance of the task or teacher. The present study describes different procedures with gradual stimulus change, to teach discrimination skills with none or few errors, and the factors that affect the efficacy of those discriminative training. Such procedures are a relevant contribution from behavior analysis to applied contexts, especially for the development of educational technologies when traditional methods fail.

El término aprendizaje sin error se ha utilizado para referirse, en general, la programación de contingencias de enseñanza que se traducen en rendimientos precisos o con poco errores. La ocurrencia de errores durante el aprendizaje se ha considerado importante y necesario para el aprendizaje en la cultura y en la academia. En el Análisis de la Conducta errores y sus implicaciones para el aprendizaje son investigados en los estudios sobre control de estímulos y los resultados indican que errores puede afectar la precisión de rendimiento ya aprendido, generar comportamientos emocionales, evitación de la tarea o del maestro. En este texto, se presentarán diferentes procedimientos de modificación gradual de estímulos para enseñar la discriminación, que puede generar el aprendizaje sin error y los factores que afectan la efectividad de estas contingencias. Estos procedimientos deben difundirse más ampliamente, constituyen importantes contribuciones para contextos de análisis aplicado del comportamiento, especialmente para el desarrollo de tecnologías educativas cuando fallan los métodos tradicionales.

Assessing Nonverbal Same/Different Judgments of Auditory Stimuli in Individuals with Intellectual Disabilities: A Methodological Investigation.

This methodological paper reports an initial attempt to evaluate the feasibility and utility of a nonverbal task for assessing generalized same/different judgments of auditory stimuli in individuals who have intellectual disabilities. Study 1 asked whether participants could readily acquire a baseline of auditory same/different, go-left/go-right performance with minimal prompting. Sample stimuli consisted of pairs of successively presented sine-wave tones. If the tones were identical, participants were reinforced for selections of a visual stimulus on the left side of the computer screen; if the two stimuli were different, selections of the visual stimulus on the right were reinforced. Two of five participants readily acquired the task, generalized performance to other stimuli and completed a rudimentary protocol for examining auditory discriminations that are potentially more difficult than those used to establish the initial task. In Study 2, two participants who could not perform the go-left/go-right task with tone stimuli, but could do so with spoken-word stimuli, successfully transferred control by spoken words to tones via an auditory superimposition-and-fading procedure. The findings support the feasibility of using the task as a general-purpose auditory discrimination assessment.

O treinamento do lance livre no basquetebol / Free throw training in basketball / Entrenamiento de tiro libre en baloncesto

Apesar da importância do lance livre, as médias de acertos nestas situações tem sido inferiores a 70 por cento, apenas alguns jogadores atingem médias superiores. Neste trabalho apresentamos um novo método de treinamento de lances livres através das técnicas de mudança gradual e progressiva das alterações nas especificações dos materiais utilizados nos treinos (no caso, o diâmetro do aro da cesta e a altura da cesta). Foram participantes desta pesquisa 12 atletas, com idade entre 13 e 14 anos. Estes foram submetidos a duas fases na linha de base. Após esta etapa, os atletas foram divididos em dois grupos: o grupo 1 foi submetido à intervenção relacionada a dimensão diâmetro da cesta; e o grupo 2 à intervenção relacionada a dimensão altura da cesta. O procedimento de fading ou esvanecimento foi idêntico para ambos os grupos que passaram pelo delineamento de linha base múltipla entre participantes. A etapa seguimento foi idêntica à etapa de linha de base e tinha como objetivo avaliar se os resultados produzidos na última fase da intervenção se mantinham após a retirada do tratamento. Nos resultados, percebemos que a repetição do ato de arremessar não produziu melhoras no desempenho dos atletas avaliados. O procedimento de fading promoveu melhoras durante a intervenção que se mantiveram durante o seguimento.(AU)

Despite its importance, average free throw accuracy has been below 70 percent; only a few players have managed to achieve a higher average. In this paper a new method of free throw training is presented by progressive and gradual techniques aimed towards specifications changes in materials used in training (in this case, the diameter of the basketball rim and its height). In this research, 12 athletes aged from 13 to 14 years old were chosen to participate in it. They were submitted to two stages at the baseline condition. After this stage, the athletes were divided into two groups: group 1 was submitted to an intervention related to the diameter of the basket and group 2, to an intervention related to the height of the basket. The fading procedure was identical for both groups that went through the multielement baseline design. The next stage was identical to the baseline condition and had the purpose of evaluating whether the results achieved in the last modified stage would last once the treatment was removed. Analyzing the results, it is made clear that practicing shots through repetition did not produce the results expected in the selected group. The fading procedure has brought improvements to the level of accuracy of the evaluated athletes during the treatment, and these results were almost the same in the next stage, identical to the baseline condition.(AU)

A pesar de su importancia, los promedios de aciertos en estas situaciones han sido inferiores a 70 por ciento, sólo algunos jugadores alcanzan promedios superiores. En este trabajo presentamos un nuevo método de entrenamiento de lances libres a través de las técnicas de cambio gradual y progresivo de las alteraciones en las especificaciones de los materiales utilizados en los entrenamientos (en este caso, el diámetro del aro de la cesta y la altura de la cesta). Fueron participantes de este estudio 12 atletas, con edad entre 13 y 14 años, integrantes de un equipo competitivo de básquetbol. Estos fueron sometidos a dos fases en la línea de base. Tras esta etapa, los atletas fueron divididos en dos grupos: el grupo 1 fue sometido a la intervención relacionada a la dimensión diámetro de la cesta; y el grupo 2 a la intervención relacionada a la dimensión altura de la cesta. El procedimiento de fading o desvanecimiento fue idéntico para ambos grupos que pasaron por el delineamiento de línea base múltiple entre participantes. La etapa seguimiento fue idéntica a la etapa de línea de base y tenía como objetivo evaluar si los resultados producidos en la última fase de la intervención se mantenían tras la retirada del tratamiento. En los resultados, percibimos que la repetición del acto de lanzar no produjo mejorías en el desempeño de los atletas evaluados. El procedimiento de fading promovió mejorías durante la intervención que se mantuvieron durante el seguimiento.(AU)

Relationship between DAPI-fluorescence fading and nuclear DNA content: An alternative method to DNA quantification?

In observations by confocal or conventional fluorescence microscopy, important factors should be considered in order to obtain accurate images. One of them, such as the fluorescence bleaching from highest intensity to lowest signal of fluorescence is a common problem with several DNA fluorochromes and especially for DAPI stain. The fluorescence of DAPI fades rapidly when it is exposed to UV light, under optimal conditions of observation. Although the fading process can be retarded using a mounting medium with antifading reagents, the photochemical process underlying the fluorescence decay has not yet been fully explained. In addition, no relationship between fluorescence fading and nuclear DNA content has been tested. In order to test this relationship, we measured by means of image analysis the DAPI-fluorescence intensity in several cellular types (spermatozoa, erythrocytes and haemocytes) during their fluorescence bleaching. An algorithm specifically built in MATLAB software was used for this approach. The correlation coefficient between nuclear DNA content and DAPI-fluorescence fading was found equal to 99 percent. This study demonstrates the feasibility to measure nuclear DNA content by fluorescence fading quantification, as an alternative method concurrently with image analysis procedures.