Capacity of optical wireless communication channels.

Optical wireless communications are realized by modulating the intensity of a light source and detecting intensity fluctuations at the receiver. This mode of operation, known as intensity modulation and direct detection (IM/DD), is simple to implement in practice. However, computing the channel capacity of the underlying channel is not straightforward because of the amplitude constraints that arise due to IM/DD operation. In particular, the transmit signal must be non-negative, while the peak and average amplitudes are constrained due to practical and safety considerations. Though a closed form for the capacity of IM/DD channels is not known, much work has been done to find capacity bounds and asymptotic capacity expressions. In this paper, a description of the IM/DD channel and its physical constraints is presented, followed by a review of recent progress pertaining to the capacity of IM/DD channels. Additionally, capacity-achieving distributions are discussed along with simple constructions that approach capacity. This article is part of the theme issue 'Optical wireless communication'.

Supplementation of Curcuma longa hydrolate improves immunomodulatory response in Nile tilapia reared in a recirculation aquaculture system / [Suplementação de extrato aquoso de Curcuma longa aprimorando a resposta imunomoduladora em tilápias cultivadas em sistema de recirculação em aquicultura]

The objective of this study was to evaluate the effects of dietary supplementation with different doses of Curcuma longa hydrolate on the hematological, immunological and zootechnical parameters of Nile tilapia cultivated in a recirculation system (RAS). Nile tilapia (Oreochromis niloticus) were used, distributed in 16 polyethylene boxes, divided into four treatments: 0.0%; 2.5%; 7.5% and 10.0% of Curcuma longa hydrolate, in quadruplicate. After 45 days of treatment, four fish per experimental unit were anesthetized to remove blood aliquot for hematological and immunological analyzes and dissect the liver to evaluate the hepatosomatic index and final biometry. In the haematological analysis, the fish fed with 2.5% had a higher number of leukocytes, monocytes and lymphocytes than control, while the doses of 7.5% and 10.0% did not differ. Antimicrobial activity showed a significant decrease as the dose of C. longa hydrolate increased. The other hematological, immunological, hepatosomatic index and zootechnical data did not differ between treatments. Thus, supplementation of the hydrolate of Curcuma longa at a dosage of 2.5%, improved and maintained blood-immune homeostasis parameters in these animals, being suggested for further studies.(AU)

O objetivo deste estudo foi avaliar os efeitos da suplementação dietética com diferentes doses de hidrolato de Curcuma longa nos parâmetros hematológicos, imunológicos e zootécnicos da tilápia-do-nilo cultivada em sistema de recirculação. Utilizou-se tilápia- do-nilo (Oreochromis niloticus), distribuída em 16 caixas de polietileno, divididas em quatro tratamentos: 0,0%; 2,5%7,5% e 10,0% de hidrolato de Curcuma longa, em quadruplicata. Após 45 dias de tratamento, quatro peixes por unidade experimental foram anestesiados para remover uma alíquota sanguínea para análises hematológicas e imunológicas, e removeu-se o fígado para avaliar o índice hepatossomático e a biometria final. Na análise hematológica, os peixes alimentados com 2,5% apresentaram maior número de leucócitos, monócitos e linfócitos que no controle, enquanto as doses de 7,5% e 10,0% não diferiram. Por outro lado, a atividade antimicrobiana apresentou uma redução significativa à medida que a dose de hidrolato de C. longa aumentou. Os demais dados hematológicos, imunológicos, hepatossomáticos e zootécnicos não diferiram entre os tratamentos. Assim, a suplementação do hidrolato de Curcuma longa, na dose de 2,5%, melhorou os parâmetros hematoimunológicos e manteve a homeostase nesses animais, sendo sugerida para novos estudos.(AU)

The role of provocative discography in minimally invasive selective endoscopic discectomy.

A discogenic etiology is being widely accepted as a primary source of chronic low-back pain. Even though increasing information is available on the pathophysiology of the degenerated disc, the present MR techniques are still not capable of pin-pointing the source of this pain. In other words, with a non-invasive MR1 study we can still not define which disc is painful and what are the characteristics of discogenic pain from an imaging perspective. Discography remains therefore the only functional test that can delimit both morphologically and by provocation which discs are involved in the patents clinical picture. In combination with endoscopic procedures it helps tailor treatments. We consider that this diagnostic tool should be used routinely and performed by the surgeon himself as part of a screening-therapy protocol in spine surgery. We present our considerations regarding this diagnostic-screening method based on our clinical and surgical experience in patients who have been evaluated and have undergone selective endoscopic disscetomy after the screening.

Utilidad de la discografía en la discectomía endoscópica selectiva mínimamente invasiva / The role of provocative discography in minimally invasive selective endoscopic discectomy

La etiología discogénica se está aceptando cada vez más como la fuente principal del dolor lumbar crónico. Aunque conocemos más y más los mecanismos patofisiológicos del disco intervertebral degenerado, las técnicas diagnósticas mediante RM aún no son capaces de delimitar la fuente de este dolor y cuales son sus características por lo menos en plan morfológico Neurocirugía 2002; 1: 27-31 (imagen). La discografía permanece por lo tanto el único test funcional que puede delimitar morfológicamente y mediante provocación qué disco(s) están involucrados en el cuadro clínico del paciente. En combinación con técnicas endoscópicas nos ayuda a delimitar y planificar los tratamientos.Consideramos que esta técnica diagnóstica debería ser utilizada de rutina y llevada a cabo por el mismo cirujano como parte de un protocolo de screening-terapia en cirugía espinal. Presentamos nuestras consideraciones con respecto a este metodo diagnostico-selectivo basándonos en nuestra experiencia clínica y quirúrgica en pacientes que han sido evaluados y en los cuales se ha llevado a cabo una discectomía endoscópica selectiva (AU)