Electrotunable nanoplasmonics for amplified surface enhanced Raman spectroscopy

Tuning the properties of optical metamaterials in real time is one of the grand challenges of photonics. Being able to do so will enable a new class of photonic materials for use in applications such as surface enhanced Raman spectroscopy and reflectors/absorbers. One strategy to achieving this goal is based on the electrovariable self-assembly and disassembly of two-dimensional nanoparticle arrays at a metal liquid interface. As expected the structure results in plasmonic coupling between NPs in the array but perhaps as importantly between the array and the metal surface. In such a system the density of the nanoparticle array can be controlled by the variation of electrode potential. Due to the additive effect, we show that less than 1 V variation of electrode potential can give rise to a dramatic simultaneous change in optical reflectivity from ~93 % to ~1 % and the amplification of the SERS signal by up to 5 orders of magnitude. The process allows for reversible tunability. These concepts are demonstrated in this manuscript, using a platform based on the voltage-controlled assembly of 40 nm Au-nanoparticle arrays at a TiN/Ag electrode in contact with an aqueous electrolyte. We show that all the physics underpinning the behaviour of this platform works precisely as suggested by the proposed theory, setting the electrochemical nanoplasmonics as a promising new direction in photonics research

A tunable nanoplasmonic mirror at an electrochemical interface

Designing tunable optical metamaterials is one of the great challenges in photonics. Strategies for reversible tuning of nanoengineered devices are currently being sought through electromagnetic or piezo effects. For example, bottom-up self-assembly of nanoparticles at solid | liquid or liquid | liquid interfaces can be used to tune optical responses by varying their structure either chemically or through applied voltage. Here, we report on a fully reversible tunable-color mirror based on a TiN-coated Ag substrate immersed in an aqueous solution of negatively charged Au-nanoparticles (NPs). Switching electrode potential can be used to fully control the assembly/disassembly of NPs at the electrode | electrolyte interface within a 0.6 V wide electrochemical window. The plasmon coupling between the electrode and the adsorbed NP array at high positive potentials produces a dip in the optical reflectance spectrum, creating the "absorber" state. Desorption of NPs at low potentials eliminates the dip, returning the system to the reflective "mirror" state. The intensity and wavelength of the dip can be finely tuned through electrode-potential and electrolyte concentration. The excellent match between the experimental data and the theory of optical response for such system allows us to extract valuable information on equilibrium and kinetic properties of NP-assembly/disassembly. Together with modeling of the latter, this study promotes optimization of such meta-surfaces for building electrotunable reflector devices

Determinants of female fecundity in a simultaneous hermaphrodite: the role of polyandry and food availability

Classical sexual selection theory assumes that the reproductive success of females is primarily limited by the resources available for egg production rather than by the number of mating partners. However, there is now accumulating evidence that multiple mating can entail fitness costs or benefits for females. In this study we investigated the effect of polyandry (i.e., the mating with different mating partners) and food availability on the reproductive output of the female sex function in an outcrossing simultaneous hermaphrodite, the free-living flatworm Macrostomum lignano. We exposed virgin worms to different group sizes, a treatment that has previously been shown to affect the level of polyandry in this species. Moreover, we manipulated the food availability throughout the subsequent egg laying period, during which the worms were kept in isolation. The number of offspring produced was used as an estimate of female fecundity. We found that food availability, but not group size, had a significant effect on female fecundity. Additionally, female fecundity was positively correlated with the number of stored sperm in the female sperm-storage organ at the time of isolation, but it was not correlated with body or ovary size of the worms. Our results suggest that female fecundity in M. lignano is primarily determined by the resources available for egg production, and not by the level of polyandry, confirming classic sexual selection theory for simultaneous hermaphrodites

Resección de hemivértebra con técnica de eggshell en cifoescoliosis congénita: resultados en niños entre uno y siete años Ressecção de hemivertébra com a técnica de eggshell em cifoescoliose congênita: resultados em crianças com idade entre um e sete anos Hemivertebrae resection with eggshell procedure for congenital kyphoscoliosis: results in children aged from one to seven years

INTRODUCCIÓN: La hemivértebra es la causa de 50% de las cifoescoliosis congénitas y en general requiere tratamiento quirúrgico. OBJETIVO: evaluar los resultados clínicos y radiológicos de la resección de hemivértebra con técnica de eggshell en niños entre uno y siete años. DISEÑO DEL ESTUDIO: análisis retrospectivo de pacientes sometidos a resección de hemivértebra con técnica de eggshell. MÉTODOS: entre Enero del 2006 y Junio del 2008, siete hemivértebras fueron resecadas en siete pacientes consecutivos, entre uno y siete años de edad. Se revisó retrospectivamente las fichas clínicas y radiografías. La edad promedio al momento de la cirugía fue 3,2 años (rango de uno a siete años) y el seguimiento promedio fue de 17 meses (rango 7 a 35 meses). Se registró ángulo de Cobb de la escoliosis y cifosis en el preoperatorio y al término del seguimiento, tiempo operatorio, transfusión de glóbulos rojos y complicaciones. RESULTADOS: el ángulo preoperatorio promedio de la escoliosis fue 35° y 19° al término del seguimiento, con un 40% de corrección. El ángulo preoperatorio promedio de la cifosis fue 42° y 25° al término del seguimiento, con un 33% de corrección. Cuatro pacientes necesitaron transfusión de glóbulos rojos, promedio 1,25 unidades. El tiempo quirúrgico promedio fue 225 minutos. Dos pacientes presentaron complicaciones, una rotura dural y una fractura pedicular. No se presentaron complicaciones neurológicas. Todos los pacientes presentaban fusión sólida al término del seguimiento. CONCLUSIÓN: la resección de hemivértebra con técnica de eggshell es un procedimiento seguro, que permite una excelente e inmediata corrección de la cifoescoliosis congénita, la que se mantiene en el corto plazo.<br>INTRODUÇÃO: A hemivértebra associa-se a 50% das cifoescolioses congênitas e geralmente requer tratamento cirúrgico. OBJETIVO: avaliar os resultados clínicos e radiológicos da ressecção da hemivértebra, utilizando a técnica de eggshell em crianças entre um e sete anos. FORMA DO ESTUDO: análise retrospectiva dos pacientes submetidos à ressecção de hemivértebra com a técnica eggshell. MÉTODOS: Entre Janeiro de 2006 e Junho de 2008, sete hemivértebras foram ressecadas em sete pacientes consecutivos, entre um e sete anos de idade. Realizou-se análise retrospectiva dos prontuários e exames radiográficos. A média de idade no momento da cirurgia foi de 3,2 anos (variação entre um a sete anos) e o seguimento médio foi de 17 meses (variação de 7 a 35 meses). Registrou-se ângulo de Cobb na escoliose e cifose no pré-operatório e no término do seguimento, o tempo operatório, transfusão de glóbulos vermelhos e complicações. RESULTADOS: o ângulo pré-operatório médio da escoliose foi de 35° e 19° no término do seguimento, com um 40% de correção. O ângulo pré-operatório médio da cifose foi de 42° e 25° no término do seguimento, com 33% de correção. Quatro pacientes precisaram de transfusão de glóbulos vermelhos, 1,25 unidades como média. O tempo cirúrgico médio foi de 225 minutos. Dois pacientes apresentaram complicações, uma rotura dural e uma fratura pedicular. Não houve complicações neurológicas. Todos os pacientes apresentaram sólida fusão no término do seguimento. CONCLUSÃO: a ressecção de hemivértebra utilizando a técnica de eggshell é um procedimento seguro que permite uma excelente e imediata correção da cifoescoliose congênita, a qual é mantida no curto prazo.<br>INTRODUCTION: Hemivertebrae is associated with 50% of the congenital kyphoscoliosis and surgical treatment is usually required. OBJECTIVE: to evaluate clinical and radiographic results of hemivertebra resection with an eggshell procedure in children aged from one to seven years old. STUDY DESIGN: retrospective review of patients who underwent hemivertebrae resection with an eggshell procedure. METHODS: from January 2006 to June 2008, seven hemivertebrae were resected in seven consecutive patients aged one to seven years old. A retrospective chart and a radiographic review were performed. The mean age at surgery was 3,2 years (range from one to seven years). The mean follow-up was 17 months (range from 7 to 35 months). Cobb's angle in the coronal and sagittal planes preoperative and at follow-up, operating time, transfusion requirements and complications were analyzed. RESULTS: the mean pre-operative scoliosis Cobb's angle was 35° and the average at follow-up was 19°. The mean correction at follow-up was 40%. The average of the pre-operative kyphosis Cobb's angle was 42° and average at follow-up was 25°. Rate of correction at follow-up was 33%. Four patients required transfusion, with an average of 1,25 blood units. The average of operating time was 225 minutes. Complications were encountered in two patients; one dural tear and one pedicular fracture. No neurological complications. All patients achieved solid fusion at follow-up. CONCLUSION: hemivertebra resection with the eggshell procedure is a safe surgical technique and provides an excellent and immediate correction of congenital kyphoscoliosis at short term follow-up