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Este artigo, partindo da leitura da primeira parte do Teeteto e de passagens do Banquete e do Sofista, busca examinar de que forma Platão interpretou e transpôs o pensamento de Heráclito. O texto sustenta que Platão não transmitiu de Heráclito a imagem de um mobilista radical, nem dissociou a tese do fluxo de outras teses do Efésio, como a tese da unidade dos opostos, mas, ao contrário, distinguiu as teses de Heráclito das opiniões extremadas de seus adeptos e apresentou uma imagem bastante rica, complexa e multifacetada de seu pensamento., This paper, based on the reading of the first part of the Theaetetus, and some passages of the Symposium and the Sophist, explores how Plato interpreted and transposed the thought of Heraclitus. The paper argues that Plato did not transmit an image of Heraclitus as a radical mobilist, nor dissociated the thesis of the flow of other theses of the Ephesian, as in the case of the thesis of the unity of opposites, but rather, he drew a distinction between the thesis of Heraclitus and the extreme views of their supporters, and presented a very rich, complex and multifaceted picture of his thinking.

CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO Uma interpretação muito comum da leitura platônica de Heráclito é aquela segundo a qual Heráclito aparece nos diálogos de Platão, especialmente no Teeteto, como o principal defensor do fluxo extremo e o pensador que trouxe à tona uma interdição incontornável ao conhecimento e à linguagem. Entretanto, se lemos os fragmentos de Heráclito, vemos que a questão do conhecimento foi tematizada expressamente por ele, que a possibilidade do conhecimento e da linguagem foi por ele afirmada, e que o mobilismo por ele defendido não era extremado. Por esta razão, essa interpretação freqüente do Teeteto produz um estranhamento que pode e deve ser convertido num desafio para a leitura de Platão e de Heráclito. Esta tese busca mostrar, a partir principalmente da leitura da primeira parte do Teeteto, como Platão compreendeu e transpôs o pensamento de Heráclito. Algumas conclusões da tese são que Platão, no Teeteto, não transmitiu de Heráclito a imagem exagerada de um mobilista radical, e sim distinguiu as teses mais moderadas de Heráclito das opiniões mais extremadas de seus adeptos. E, se tudo indica que Heráclito nunca dissociou a tese do fluxo universal de outras teses suas, como por exemplo a tese da unidade dos opostos, Platão por sua vez não isolou a tese do fluxo, de modo que não se deve considerar que ele atribuiu a Heráclito uma versão unilateral e empobrecida de sua filosofia. Por fim, ao contrário do que pode parecer à primeira vista, no Teeteto, Platão critica somente o heraclitismo exagerado, dando a entender que está aceitando e considerando respeitável a versão moderada da teoria do fluxo universal, tal como defendida por Heráclito. A current interpretation of Plato’s reading of Heraclitus maintains that Heraclitus appears in Plato’s dialogues, mostly in Theaetetus, as the main defender of the extreme flux and as the philosopher who asserted an irrevocable interdiction of knowledge and language. However, when we read Heraclitus’ fragments, we can see that he expressly considered the theme of knowledge, that he recognized the possibility of knowledge and language, and that the flux he defended was not extreme. For this reason, this frequent interpretation of Theaetetus produces a kind of uneasiness that could and should be turned into a challenge to the reading of Plato and Heraclitus. Basing its arguments mainly of the first part of Theaetetus, this thesis intends to show how Plato understood and translated Heraclitus thought. One of its conclusions is that in Theaetetus Plato did not transmit an exaggerated image of Heraclitus as a radical flux defender, but rather distinguished Heraclitus’ more moderate theories from his followers’ more radical opinions. If most likely Heraclitus never dissociated the universal flux doctrine from other of his theories, as the doctrine of the unity of opposites, and neither Plato did isolate the theory of flux, we should not consider that Plato imputed to Heraclitus an unilateral and impoverished version of heraclitean philosophy. Finally, contrarily to what may seem at first sight, in Theaetetus Plato condemns only exaggerated heraclitism, suggesting that he accepts and respects the moderate version of the theory of universal flux as proposed by Heraclitus himself.

We consider multiple-input multiple-output (MIMO) communication systems with adaptive antenna arrays at both ends of the link in which the data transmission is performed via parallel eigenchannels matched to the random spatial channel. The effectiveness of the projection method of space-division multiple access is studied. The method does not require estimation of the arrival directions of signals and is based on orthogonalization of all eigenchannels. Exact analytical expressions are obtained for the bit-error probability during the data transmission via the channel with uncorrelated Rayleigh fading of signals in an MIMO system with an arbitrary number of users and antennas.

Laryngopharyngeal sensation is important in the normal process of swallowing, it is often impaired after neurological events and it has been common practice in such an occurrence to order non-oral tube feeding to prevent aspiration. This study assesses a novel approach to the evaluation of the laryngopharyngeal sensation that allows for improved triage of aspiration risk and more lenience towards oral feeding. This is a case series with follow-up period ranging from 6 to 24 months. Forty patients with neurological deficiencies were tested by a modified laryngopharyngeal sensation study that included evaluation of both supra and infra-glottis. All patients had impaired supra glottic sensation but had good infra glottic sensation that enabled cough protection. All had received oral feeding. Main outcome measure is incident aspiration pneumonia. Twenty-two patients maintained oral feeding without any evidence of aspiration. Eighteen patients had some aspirations associated with cough, and were maintained on modified oral feeding. Out of these 18 patients, four patients (10% of the entire group) developed aspiration pneumonia. The presented procedure identified patients with impaired supraglottic sensation but preserved good infra glottic sensation. This observation enables safe oral feeding in most patients and therefore offers a better quality of life for these individuals.

Summary Objective Laryngeal manifestations of stroke play a significant role in the morbidity and mortality among affected patients. The objective of this article was to describe unique myoclonic vocal fold movement disorder, which is an unusual post-stroke manifestation. Study Design A retrospective case study. Setting The study group included post-stroke patients with dysphagia who were referred to the Swallowing Clinic at Edith Wolfson Medical Center. Subjects and Methods All patients underwent flexible laryngoscopy and flexible endoscopic evaluation of swallowing with sensory testing. The vocal fold movement was analyzed with the Sisson-Ammons video analysis system . Results Three post-pontine stroke patients presented with vocal fold myoclonus (VFM). The myoclonus was spontaneous, unintentional, and irregular (19–420 jerks per minute). Two patients presented with unilateral myoclonus, ipsilateral to the brainstem stroke. One patient, who experienced subsequent pontine strokes, presented with bilateral VFM. When patients were asked to swallow or phonate, the myoclonus disappeared. Conclusion Isolated VFM is an unusual manifestation of pontine injury, resulting in a sudden, involuntary, and non-rhythmic vocal fold movement. This laryngeal pathology is not associated with either dyspnea or dysphonia and most likely not with inefficient swallowing.

We consider multiple-input multiple-output (MIMO) cellular communication systems with antenna arrays at both link ends and data transmission via parallel eigenchannels matched with a random spatial channel. We analyze the effectiveness of the space-division multiple-access (SDMA) method, which does not require estimation of signal-arrival directions and is based on orthogonalization of the parallel channels of all users. We obtained approximate analytical expressions for the mean ratio of the signal power to the noise power and the MIMO system capacity, which are derived for the case of Rayleigh fading of signals. Although the obtained formulas are much simpler than the exact ones, they ensure high accuracy for an arbitrary number of transmitting and receiving antennas and an arbitrary power of transmitter. Our results demonstrate the high effectiveness of the proposed SDMA method.

We consider cellular communication systems with antenna arrays at both link ends, in which the data transmission is performed via parallel eigenchannels under conditions of a scattering medium. To reduce the bit error probability, we propose a method of information transmission based on the use of only part of the eigenchannels with maximum signal-to-noise ratios and ensuring a tradeoff of the data-transmission rate against the bit-error probability. Eigenchannels are separated into energy-strong and energy-weak channels with the help of the threshold technique. Two possible versions of using the proposed method under conditions of a random multipath spatial channel are studied. The results of numerical simulation in the case of Rayleigh fading of signals confirm the high efficiency of the proposed method of information transmission.

We study the influence of the discreteness of information about the channel state, which is transmitted over the receiver–transmitter return line, on the effeiciency of MIMO systems. It is shown that such a discreteness results in energy losses and appearance of crosstalk in parallel eigenchannels of the MIMO system. We propose a method of crosstalk suppression, which ensures a pronounced decrease in the energy losses and restores the nondependence of eigenchannels with respect to transmitted symbols but leads to the correlation of output internal noise. Expressions for a maximum likely estimate of received signals are derived with allowance for the noise correlation. Mathematical simulation results showing the high efficiency of the proposed method are presented for the case of Rayleigh fading of signals.

We consider adaptive spatial signal processing in antenna arrays under conditions of multipath propagation. It is shown that estimation of the elements of the matrix of multichannel impulse response (MCIR) in the receiving channels of antenna arrays is not sufficient for performing such a processing, and we should also determine the MCIR-matrix rank, which is equal to the minimum number of adaptive spatial channels for reception of a multipath signal. We propose a threshold method for estimating the rank of the MCIR matrix on the basis of the statistical properties of maximum-likelihood estimation of the elements of this matrix and a priori information on the properties of internal noise in the receiving channels of the system. The weight vectors of the beamformer processor ensuring adaptive spatial signal processing are estimated.

We study multiple-input multiple-output (MIMO) cellular communication systems with antenna arrays at both link ends and parallel channels for data transmission. These channels (the so-called eigenchannels) are formed with the help of adaptive transmitting and receiving beamformer processors matched with a random fading environment. To increase the capacity of MIMO systems, we propose a space-division multiple-access (SDMA) method, which does not require estimation of signal-arrival directions and is based on orthogonalization of the parallel channels of all users. We find the signal-to-noise ratios at the eigenchannel outputs and the total capacity of a MIMO system in the case of simultaneous servicing of an arbitrary number of users. We present numerical results for the case of Rayleigh fading of signals, which confirm the high effectiveness of the proposed SDMA method.

We carry out a comparative analysis of performances of a cellular communication system with adaptive modulation and coding (AMC) and a system with power control (PC). It is shown that the performance of an AMC system is higher than the performance of a PC system for an arbitrary probability density function of the signal fading. To achieve identical throughputs of the two systems, the mean transmitted power for PC must be greater than that for AMC. For identical mean transmitted powers, the throughput of an AMC system is always greater than that of a PC system. We consider code division multiple-access (CDMA) systems with arbitrary numbers of fading time-taps (paths), having a statistically independent Rayleigh fading of signals from path to path. The influence of self-interference on AMC and PC performance is studied. This self-interference results from the nonideal path separation in the receiver.

We propose a method for estimating signal parameters and the weight vector in adaptive antenna arrays (AA) based on estimation of the parameters of a minimum polynomial of a sample correlation matrix (CM) of the input process. Being highly efficient, this method allows us to estimate signal parameters with accuracies that are close to the Cramer-Rao limits.

Methods are proposed for determination of the weight vector in adaptive antenna arrays (AA) in the case of a short input-process sample, when the number of sampled vectors is smaller than the number of AA elements and an inverted correlation matrix of the interference in the AA receiving channels does not exist.

The efficiency of adaptive spatial signal processing in arrays providing the maximum signal/noise ratio is studied for the case when the number of sample vectors is less than the number of elements of the adaptive array (AA) and there is no inverse correlation matrix of a jammer in the AA receiving channels. Three methods for defining the stable solution for the weight vector in the AA, which are based on supplementing a posteriori information on the jammer with a priori data on them, are studied. These methods are almost equally highly efficient, but the latter method requires considerably less calculation. Results of mathematical simulation of the efficiency of the suggested methods are given.

A concept of using MIMO technology in millimeter range wireless communications systems with orthogonal frequency division multiplexing is considered. The concept is based on dividing transmitting and receiving multi-element antenna arrays into separate sub-arrays with analogue radiation pattern shaping and on using two most powerful space sub-channels for information transmission. Sequence and structure of transmitted packets between transceivers are suggested that allow for obtaining information on communications channel based on additional training sequences without feedback channel. Modeling results of communications system’s operation in conditions of multipath frequency-selective fading channel are presented.

The development of the theory of adaptive arrays (AAs) is proposed based on the representation of the inverse covariance matrix (CM) of a noise in the AA channels as a finite power series expansion using the direct CM and by representation of a weight vector of the AA as a finite series expansion of the power vectors. The dimension of the power CM basis is equal to the power of the minimum polynomial of the CM. In the case when the number of external interference sources is less than the number of AA channels, such polynomials have the same fundamental role as the characteristic polynomial of the CM in an opposite case. Proofs for the existence of the above mentioned polynomials of the CM are given. A new method for the calculation of the polynomial coefficients is presented, and the physical properties of the power vector basis are studied. It is shown that the power vectors are correlated and that there are two stages of AA signal processing.

Publication in the conference proceedings of EUSIPCO, Antalya, Turkey, 2005

The effects of non-ideal channel estimation in multiple-input-multiple-output (MIMO) wireless communication systems using the eigenchannel technique for the independent symbol transmission are investigated in this paper. Analytical expression is derived for the Shannon capacity for arbitrary signal-to-noise ratio (SNR), training sequence length (TSL), transmit and receive antenna numbers. The weight error loss (WEL) that quantifies the increase in signal-to-noise ratio (SNR) required to meet a given capacity target due to weight jitter are investigated.

The multiple-input-multiple-output (MIMO) communication systems using an adaptive beamformer processor (BFP) in a receive antenna array and a fixed (non- adaptive) BFP in a transmit antenna array are considered. The transmitter does not have channel knowledge in such systems. Different variants of the adaptive BFP are proposed. The maximum likelihood (ML) detector and the simplified algorithms of the independent symbol detection are investigated. In the case of the Rayleigh fading environment the simulation results for the bit error rate (BER) are given.

A novel technique to calculate the BER of a q-branch coherent receiver is described. The assumed system consists of an antipodal binary-modulated transmitted signal, with independent Rician fading on each received branch. The method allows simplification of a (q+1)-dimensional integral down to a 1-dimensional integral (Id), which is readily amenable to numerical evaluation.

This prospective study was designed to (1) test the hypothesis that the majority of families of newly dead infants in a tertiary neonatal intensive care unit would consent to their infants' being intubated for teaching purposes, (2) determine factors related to family consent, and (3) determine the effects of participation on resident physicians and respiratory therapists. Family consent for intubation was requested following 44 (80%) of the 55 deaths that occurred during the 10-month study period. Of these requests, 32 (73%) were granted. Proportionately more white than black families consented and consent was positively related to autopsy permission. Fifty-three (75%) of 71 trainees completed a mailed questionnaire after their first intubation experience. Although each respondent found the experience helpful, many reported mixed feelings categorized as doubt about participating, apprehension and discomfort, respect for the body, appreciation for the opportunity, a sense of achievement, and feelings of comfort knowing that consent had been obtained. These findings confirm our initial hypothesis and suggest that (1) newly dead infants can be a valuable resource for teaching intubation skills, and (2) others considering a similar approach need to be aware of and sensitive to trainees' feelings.

Acute epiglottitis in the child is an emergency, well known to pediatricians, that requires rapid diagnosis and treatment. Aggressive treatment in recent years has markedly decreased mortality (17). Acute epiglottitis in adults has been thought to be rare, but lately numerous studies have shown an increase in the disease. We present 19 older patients, aged 13-72 (mean 44.7 years), with acute epiglottitis. A most important finding was the relatively long time from onset of symptoms until diagnosis, averaging 2.5 days. All the blood and throat cultures were negative, except for a single throat culture which yielded Pseudomonas aeruginosa. The most common presenting symptoms were severe sore-throat and dysphagia; half presented with some respiratory distress. Diagnosis was usually made on indirect laryngoscopy, but lateral X-ray of the soft tissues of the neck was found to be highly reliable. Treatment was usually conservative, including antibiotics, rehydration and steroids to alleviate edema. All patients were under strict observation for the first 48 hours, but only 1 required intubation. There were no deaths.