Investigation of the diameter-dependent piezoelectric response of semiconducting ZnO nanowires by Piezoresponse Force Microscopy and FEM simulations.

Semiconducting piezoelectric nanowires (NWs) are promising candidates to develop highly efficient mechanical energy transducers made of biocompatible and non-critical materials. The increasing interest in mechanical energy harvesting makes the investigation of the competition between piezoelectricity, free carrier screening and depletion in semiconducting NWs essential. To date, this topic has been scarcely investigated because of the experimental challenges raised by the characterization of the direct piezoelectric effect in these nanostructures. Here we get rid of these limitations using the piezoresponse force microscopy technique in DataCube mode and measuring the effective piezoelectric coefficient through the converse piezoelectric effect. We demonstrate a sharp increase in the effective piezoelectric coefficient of vertically aligned ZnO NWs as their radius decreases. We also present a numerical model which quantitatively explains this behavior by taking into account both the dopants and the surface traps. These results have a strong impact on the characterization and optimization of mechanical energy transducers based on vertically aligned semiconducting NWs.

Photomobile Polymer-Piezoelectric Composite for Enhanced Actuation and Energy Generation.

In this study, we present an innovative approach to increase the quantum yield and wavelength sensitivity of photomobile polymer (PMP) films based on azobenzene by doping the polymer matrix with noble metal nanoparticles. These doped PMP films showed faster and more significant bending under both UV as well as visible and near-infrared light regardless of whether it was coherent, incoherent, polarized, or unpolarized irradiation, expanding the potential of PMP-based actuators. To illustrate their practical implications, we created a proof-of-concept model of power generation by coupling it to flexible piezoelectric materials under simulated sunlight. This model has been tested under real operating conditions, thus demonstrating the possibility of generating electricity with variable light exposure. Additionally, our synthetic protocol is solvent-free, which is another benefit of environmental relevance. Our research lays the groundwork for the development of sunlight-sensitive devices, such as photomechanical actuators and advanced photovoltaic modules, which may break ground in the thriving field of smart materials. We are confident that the presented findings will contribute to the ongoing discourse in the field and inspire additional advances in renewable energy applications.

Dimensional Roadmap for Maximizing the Piezoelectrical Response of ZnO Nanowire-Based Transducers: Impact of Growth Method.

ZnO nanowires are excellent candidates for energy harvesters, mechanical sensors, piezotronic and piezophototronic devices. The key parameters governing the general performance of the integrated devices include the dimensions of the ZnO nanowires used, their doping level, and surface trap density. However, although the method used to grow these nanowires has a strong impact on these parameters, its influence on the performance of the devices has been neither elucidated nor optimized yet. In this paper, we implement numerical simulations based on the finite element method combining the mechanical, piezoelectric, and semiconducting characteristic of the devices to reveal the influence of the growth method of ZnO nanowires. The electrical response of vertically integrated piezoelectric nanogenerators (VING) based on ZnO nanowire arrays operating in compression mode is investigated in detail. The properties of ZnO nanowires grown by the most widely used methods are taken into account on the basis of a thorough and comprehensive analysis of the experimental data found in the literature. Our results show that the performance of VING devices should be drastically affected by growth method. Important optimization guidelines are found. In particular, the optimal nanowire radius that would lead to best device performance is deduced for each growth method.

Low-Temperature Growth of ZnO Nanowires from Gravure-Printed ZnO Nanoparticle Seed Layers for Flexible Piezoelectric Devices.

Zinc oxide (ZnO) nanowires (NWs) are excellent candidates for the fabrication of energy harvesters, mechanical sensors, and piezotronic and piezophototronic devices. In order to integrate ZnO NWs into flexible devices, low-temperature fabrication methods are required that do not damage the plastic substrate. To date, the deposition of patterned ceramic thin films on flexible substrates is a difficult task to perform under vacuum-free conditions. Printing methods to deposit functional thin films offer many advantages, such as a low cost, low temperature, high throughput, and patterning at the same stage of deposition. Among printing techniques, gravure-based techniques are among the most attractive due to their ability to produce high quality results at high speeds and perform deposition over a large area. In this paper, we explore gravure printing as a cost-effective high-quality method to deposit thin ZnO seed layers on flexible polymer substrates. For the first time, we show that by following a chemical bath deposition (CBD) process, ZnO nanowires may be grown over gravure-printed ZnO nanoparticle seed layers. Piezo-response force microscopy (PFM) reveals the presence of a homogeneous distribution of Zn-polar domains in the NWs, and, by use of the data, the piezoelectric coefficient is estimated to be close to 4 pm/V. The overall results demonstrate that gravure printing is an appropriate method to deposit seed layers at a low temperature and to undertake the direct fabrication of flexible piezoelectric transducers that are based on ZnO nanowires. This work opens the possibility of manufacturing completely vacuum-free solution-based flexible piezoelectric devices.

Morphology Transition of ZnO from Thin Film to Nanowires on Silicon and its Correlated Enhanced Zinc Polarity Uniformity and Piezoelectric Responses.

ZnO thin films and nanostructures have received increasing interest in the field of piezoelectricity over the last decade, but their formation mechanisms on silicon when using pulsed-liquid injection metal-organic chemical vapor deposition (PLI-MOCVD) are still open to a large extent. Also, the effects of their morphology, dimensions, polarity, and electrical properties on their piezoelectric properties have not been completely decoupled yet. By only tuning the growth temperature from 400 to 750 °C while fixing the other growth conditions, the morphology transition of ZnO deposits on silicon from stacked thin films to nanowires through columnar thin films is shown. A detailed analysis of their formation mechanisms is further provided. The present transition is associated with strong enhancement of their crystallinity and growth texture along the c-axis together with a massive relaxation of the strain in nanowires. It is also related to a prevailed zinc polarity, for which its uniformity is strongly improved in nanowires. The nucleation of basal-plane stacking faults of I1-type in nanowires is also revealed and related to an emission line at about 3.326 eV in cathodoluminescence spectra, further exhibiting fairly low phonon coupling. Interestingly, the transition is additionally associated with a significant improvement of the piezoelectric amplitude, as determined by piezoresponse force microscopy measurements. The Zn-polar domains exhibit a larger piezoelectric amplitude than the O-polar domains, showing the importance of controlling the polarity in these deposits as a prerequisite to enhance the performances of piezoelectric devices. The present findings demonstrate the high potential in using the PLI-MOCVD system to form ZnO with different morphologies and polarity uniformity on silicon. They further reveal unambiguously the superiority of nanowires over thin films for piezoelectric devices.

Epidural abscesses of the CNS.

Epidural abcessess can involve the intercranial or spinal compartments and can result in potentially devastating neurological injuries. Although rare, incidence of spinal epidural abscesses (SEAs) is increasing as predisposing factors such as injected-drug use, chronic immunosuppression, and spinal surgery become more common. Whereas symptoms of SEAs can include fever, back pain, and neurological dysfunction, the presentation of intracranial epidural abscesses (ICEAs) is less well defined. Neuroimaging narrows the potential diagnoses and enables prompt empirical therapy until specific microbiological diagnosis is made. Surgical intervention is an integral part of treatment for epidural abscesses in patients with neurological symptoms or who have not responded to medical management. Prognosis for both SEAs and ICEAs is typically poor because of delayed diagnosis and intervention and is dependent on the neurological status at the time of diagnosis. Increased clinical awareness can greatly improve outcomes by helping to diagnose patients earlier.

Mercury chronic toxicity might be associated to some cases of hydrocephalus in adult humans?

Mercury accumulates in nervous tissue causing neurological and psychiatric manifestations. Numerous clinical findings have been described in patients that suffered chronic mercury intoxication. Some findings, such as hydrocephalus, have been described only in experimental studies. Following, we present a case of 50 year-old man with a 3-month history of severe frontal headache episodes and vision loss together with a history of asthenia, anorexia, muscle pain, fatigue and neuropsychiatric symptoms. The magnetic resonance imaging showed hydrocephalus and stenosis of aqueduct of Sylvius. This patient reported that he worked as laboratory metallurgic auxiliary for over 30 years. During this time, he had been chronically exposed to elemental mercury. The metals whole blood test was normal, except by his blood mercury level that was 61.5 µg/L (normal ~1 µg/L). In our best knowledge, hydrocephalus and stenosis of aqueduct of Sylvius have been described only in animals exposed to methylmercury during their gestation. We think that this case of hydrocephalus might be associated with the chronic mercury exposure and therefore this etiology must be taken in account in a patient with hydrocephalus of unknown etiology.

[Study of neurological diseases prevalence in Aratoca, a rural area of eastern Colombia]. / Estudio neuroepidemiológico en Aratoca, una área rural del oriente colombiano.

BACKGROUND: Current health statistics on the prevalence of neurological diseases, in Colombia, are still lacking. AIM: To determine the prevalence of migraine, cerebrovascular disease, movement disorders, peripheral neuropathies, mental retardation and developmental disorders, epilepsy, dementia and sequels of cranial trauma in a rural population of Colombia. MATERIALS AND METHODS: We evaluated 544 subjects in Aratoca, a rural place of Santander, placed at 400 kilometers from Bogota. The world health organization (WHO) protocol for neuroepidemiological studies modified by our group, a survey to determine sequels of cranial trauma and the mini mental state examination were used as instruments. People 12 years-old or more and suspected to have a neurological disease was evaluated by adult neurologists and those less than 12 years-old were evaluated by a neuropediatrician. RESULTS: 223 out of 544 subjects surveyed were evaluated by the clinicians of which 135 had a neurological disorder. The prevalence of neurological diseases, per thousand inhabitants were as follows: migraine 189.3; epilepsy 33; febrile seizures 25.6; peripheral neuropathy 22.1; mental retardation 18.4; developmental and language disorders 11; dementia 10.5; cerebrovascular disease 4.7; and movement disorders 3.7. CONCLUSIONS: These results will allow to define appropriate control measures, as well as to prevent and treat these prevalent neurological disorders in rural places of Colombia as Aratoca and the like.

Cefalea en urgencias: diagnóstico y tratamiento de las cefaleas primarias / Headache emergencies: diagnosis and treatment of primary cephaleas

La mayoría de los pacientes que llegan a los servicios de urgencias presentan cefalea primaria, migraña, cefalea tensional, o cefalea en salvas. Sin embargo, hasta la tercera parte de las consultas son por una enfermedad que puede ser invalidante o potencialmente mortal; por esa razón el médico en urgencias debe conocer e identificar los signos de alarma. Es fundamental hacer un buen diagnóstico a través de una historia clínica y un examen físico y neurológico completo, aliviar el dolor y los síntomas asociados, e investigar la causa y tratarla. En el presente artículo se hace una revisión de los signos y síntomas de los diferentes tipos de cefalea, y los aspectos diagnósticos y terapéuticos.

Most patients visiting the emergency services have a primary headache such as tension-type headache, or cluster headache. However, about 30 percent of the consultations are due of a disease that can be disabling or life-threathening. For this reason, the physician in the emergency deparment should recognize the signs of alarm. It is essential to make a good diagnosis through a clinical history and a complete physical and neurological examination, to relieve the pain and associated symptoms, and to investigate the cause and treat it. This review describes the signs and symptoms of different types of headaches and the therapeutic and diagnostic aspects.

Dilación, dilatación e inclinación en hidrocefalia de presión normal / Delay, Dilation, and Bending in Normal Pressure Hydrocephalus

Introducción: La hidrocefalia idiopática de presión normal es una entidad conformada por una triada de signos clínicos que incluyen alteraciones de la marcha, de la cognición y del control de esfínteres urinarios, concomitantes con un aumento de líquido cefalorraquídeo con presión normal, hidrocefalia y atrofia cortical, sin causa identificable. Métodos y resultados: Reporte de caso. Paciente colombiano, de género masculino y 26 años de edad, con un cuadro clínico de tres años de evolución: presentaba los criterios clínicos descritos anteriormente, además de una notoria afectación extrapiramidal, caracterizada por distonía focal, incluyendo pleurotonos. Sumado a lo anterior, presentó labilidad emocional, alteraciones de memoria, personalidad que pasó de introvertida a compulsiva, trastornos del sueño, aislamiento y disminución de la reacción al peligro. Inicialmente se diagnosticó depresión, y luego, esquizofrenia paranoide. Recibió olanzapina sin mejoría de su cuadro neuropsiquiátrico. Algunos de estos signos y síntomas mejoraron luego de punción lumbar, la cual tuvo una presión normal, confirmándose así el diagnóstico clínico, con posibilidades terapéuticas promisorias. Conclusión: La hidrocefalia de presión normal se debe considerar en personas jóvenes, cuya sintomatología y exámenes de neurolaboratorio no cumplan con los fundamentos de la psiquiatría basada en la evidencia.

Introduction: Normal pressure hydrocephalus is a clinical entity characterized by a triad of clinical signs including gait abnormalities, cognitive disorders and sphincter dysfunction. It parallels an increased cerebrospinal fluid pressure, hydrocephalus and brain cortical atrophy. No detectable cause is a must. Methods and results: Case report. This is a Colombian male patient, 26 years-old, who had the clinical findings commented above starting three years before our evaluation. He also presented notorious extrapyramidal involvement, mostly focal dystonia including pleorotonus. Besides this, mood lability, memory disorders, personality changes turning from introverted to compulsive, sleep disorders, isolation and fearlessness were also present. Initially, depression was diagnosed and then paranoid schizophrenia was considered. Olanzapine was given with no benefits on his neuropsychiatric disorder. Some of these signs and symptoms improved after a lumbar puncture which had a normal pressure. It confirmed the diagnosis and offered very promising therapeutic possibilities. Conclusion: Normal pressure hydrocephalus must be considered in young people who have clinical symptoms and neurolaboratory findings out of the range of those commonly considered to be part of evidence-based psychiatry.

Estudio de correlación entre marcadores de inflamación y grosor íntima media carotídeo, en pacientes con ataque cerebrovascular isquémico / An analytical cross-sectional study to determine the association between intimae media

Introducción. El estudio de factores emergentes de riesgo para enfermedad cerebrovascular ha cobrado importancia, especialmente el de las infecciones y los estados inflamatorios. Nuestro grupo ha postulado que en nuestra población dietas inapropiadas y la baja infraestructura sanitaria, puede generar un estado de inflamación crónica. Objetivo. Determinar la asociación entre el grosor de íntima media carotideo (GIM) y los niveles de marcadores inflamación. Métodos. Estudio transversal analítico de 34 pacientes con enfermedad cerebrovascular isquémica y 34 sujetos sanos pareados por edad, género y procedencia geográfica. La población de estudio es una submuestra del estudio multicéntrico nacional de factores de riesgo para enfermedad cerebrovascular isquémica (FREC-VI). Se tomaron muestras sanguíneas para determinación de factor de necrosis tumoral alpha, interleucina 6 y proteína C reactiva (FNT, IL6, PCR), fibrinógeno y eco doppler color carotídeo. Resultados. Los niveles de PCR e IL6 se encontraron significativamente más elevados en los sujetos casos comparados con los controles, p=0.001 y p=0.0001 respectivamente. El fibrinógeno y el FNT no mostraron diferencias significativas. No se encontraron diferencias en los valores del grosor íntima media en las arterias carótidas comunes e internas. El OR para PCR fue de 8.39 (IC95 por ciento:1.38-50.65), para IL6 de 1.45 (IC95 por ciento:1.07-1.95), y para FNT 1.11 (IC95 por ciento: 0.99-1.23). La PCR y la IL6 presentaron correlaciones significativas con el grosor íntima media de la carótida externa derecha. Conclusiones. La IL6 y la PCR son los marcadores inflamatorios asociados al ataque cerebrovascular isquémico. Los niveles elevados de PCR e IL6 se correlacionan directamente con el grosor íntima media de la arteria carótida externa derecha. No se encontró asociación del FNT y el fibrinógeno con GIM

Estudio neuroepidemiológico en Aratoca, un área rural del oriente colombiano / Prevalence of neurological diseases in Aratoca, a rural area of eastern Colombia

Background: Current health statistics on the prevalence of neurological diseases, in Colombia, are still lacking. Aim: To determine the prevalence of migraine, cerebrovascular disease, movement disorders, peripheral neuropathies, mental retardation and developmental disorders, epilepsy, dementia and sequels of cranial trauma in a rural population of Colombia. Materials and methods: We evaluated 544 subjects in Aratoca, a rural place of Santander, placed at 400 kilometers from Bogota. The world health organization (WHO) protocol for neuroepidemiological studies modified by our group, a survey to determine sequels of cranial trauma and the mini mental state examination were used as instruments. People 12 years-old or more and suspected to have a neurological disease was evaluated by adult neurologists and those less than 12 years-old were evaluated by a neuropediatrician. Results: 223 out of 544 subjects surveyed were evaluated by the clinicians of which 135 had a neurological disorder. The prevalence of neurological diseases, per thousand inhabitants were as follows: migraine 189.3; epilepsy 33; febrile seizures 25.6; peripheral neuropathy 22.1; mental retardation 18.4; developmental and language disorders 11; dementia 10.5; cerebrovascular disease 4.7; and movement disorders 3.7. Conclusions: These results will allow to define appropriate control measures, as well as to prevent and treat these prevalent neurological disorders in rural places of Colombia as Aratoca and the like

Neurotoxicologia clinica: los plaguicidas / Clinical neurotoxicology: pesticides

Los plaguicidas son compuestos quimicos de gran utilidad principalmente en la agriculatura. Su uso incorrecto e indiscriminado ha llevado a cuadros clinicos de neurotoxicidad importantes, en especial de Encefalopatia y Neuropatia Periferica. Se actualizan las diversas manifestaciones clinicas neurologicas en las intoxicaciones por Organofosforados, Organoclorados, Carbonatos, herbicidas como el Paraquat y los Repelentes de insectos

Paraparesia espastica tropical asociada al HTLV-I en Santander / Tropical spastic paraparesis associated with HTLV-I in Santander

La paraparesia espastica tropical (PET) ha sido descrita como una enfermedad neurologica, endemica cronica, restringida a grupos raciales de ancestro africano en comunidades tropicales costeras. Recientemente se ha establecido que es causada por un Retrovirus denominado HTLV-I y que afecta diversos grupos raciales con descripciones cada vez mas numerosas en diversos paises, incluyendo zonas no tropicales. La OMS ha recomendado el nombre de PET/HAM (paraparesia espastica tropical/mielopatia asociada a HTLV-I) para destacar no solo el compromiso anatomico principal sino su etiologia. En Colombia la mayoria de los casos se han informado en la zona sur-occidental y es nuestro proposito presentar dos casos de PET con anticuerpos positivos contra el HTLV-I en suero y LCR, en hombres residentes en el oriente colombiano uno de ellos de raza negra y otro mestizo. Se actualizan algunos conceptos sobre la PET

Degeneracion hepatolenticular (Enfermedad de Wilson) / Hepatolenticular degeneration (Wilson's Disease)

Se presenta el caso de una nina de 13 anos con Enfermedad de Wilson y se hace un resumen de los aspectos mas importantes de la enfermedad hepatolenticular una de las afecciones "degenerativas", cuyo trastorno del metabolismo del cobre se origina en defectos enzimaticos de la ceruloplasmina. Un hallazgo importante en este caso fueron los depositos de cobre en las encias. La escanografia mostro atrofia cerebral y cavitaciones paraventriculares.