Experimental phase-space-based optical amplification of scar modes

Waves billiard which are chaotic in the geometrical limit are known to support non-generic spatially localized modes called scar modes. The interaction of the scar modes with gain has been recently investigated in optics in micro-cavity lasers and vertically-cavity surface-emitting lasers. Exploiting the localization properties of scar modes in their wave analogous phase space representation, we report experimental results of scar modes selection by gain in a doped D-shaped optical fiber

Our policy in intraventricular colloid cysts. Experience of 31 operated cases.

The colloid cyst of the third ventricle is abenign tumor situated in the anterior partof the third ventricle. This lesion representsless than 1% of the primary brain tumorbeing more common in young adults.Because of its particular location, thecolloid cyst can obstruct the Monroforamen, producing intermittentintracranian hypertension with headache,vomiting and visual disturbances. Thirtyonecases of colloid cysts have beenoperated using the microsurgical approachin the First Neurosurgical Department ofEmergency Clinical Hospital “Bagdasar-Arseni” between January 1995 andDecember 2008. The age of the patientswas between 17 and 46 years, with amedium age of 31 years. The follow-upperiod was between 9 months and 7 years.In three cases TTA approach has beenperformed. One of the cases developed avenous cerebral infarct after this procedure,but the patient had finally a good outcome.For 28 patients the transcortical approachhas been performed. In all cases the totalresection of the colloid cyst has beenperformed. Of all 31 cases, one casepresented a transitory hemiparesis, twocases showed negativist behavior, and threecases had transitory memory disturbances.There was no intraventricular hemorrhageafter colloid cyst resection in our series. Inconclusion, according to our policy, themicrosurgical approach is the besttreatment for third ventricular colloid cystsbecause of its main advantages comparedwith the endoscopic approach: thepossibility of total resection of the cyst, thegood control of the bleeding source duringthe procedure, and a better exposure of theanatomical landmarks

Broadband integrated beam splitter using spatial adiabatic passage

Light routing and manipulation are important aspects of integrated optics. They essentially rely on beam splitters which are at the heart of interferometric setups and active routing. The most common implementations of beam splitters suffer either from strong dispersive response (directional couplers) or tight fabrication tolerances (multimode interference couplers). In this paper we fabricate a robust and simple broadband integrated beam splitter based on lithium niobate with a splitting ratio achromatic over more than 130 nm. Our architecture is based on spatial adiabatic passage, a technique originally used to transfer entirely an optical beam from a waveguide to another one that has been shown to be remarkably robust against fabrication imperfections and wavelength dispersion. Our device shows a splitting ratio of 0.52$\pm$0.03 and 0.48$\pm$0.03 from 1500\,nm up to 1630\,nm. Furthermore, we show that suitable design enables the splitting in output beams with relative phase 0 or $\pi$. Thanks to their independence to material dispersion, these devices represent simple, elementary components to create achromatic and versatile photonic circuits

Gain-controlled wave chaos in a chaotic optical fibre

International audienceIn this paper, we present a non-standard fibre amplifier specially designed to amplify scar modes of a multimode chaotic optical fibre. More precisely, we introduce Ytterbium in the optical fibre as a gain medium localised on the maximum of intensity of the scar modes. After briefly recalling the relevance of a chaotic optical fibre as a device to visualise quantum chaos, we describe the amplification process of scars. We present some numerical results that demonstrate the selective amplification of scar modes, with an amplification rate proportional to the overlap between these modes and the gain area

Surgical decompression of arachnoid cysts: A study on 44 pediatric patients

Background: There are yet to clarify some aspects regarding the surgical indications and surgical methods that are at choice for treating ACs. The purpose of the study is to contribute to the ongoing debate on the most appropriate treatment. Materials and methods: We included in the study 44 pediatric patients (aged < 18 years), operated for ACs in the Neurosurgery I Department, of the Emergency Clinical Hospital “Bagdasar-Arseni” in Bucharest, during the period January 2003 to December 2012. The surgical methods were either a craniotomy or cyst shunting. The information regarding these patients was retrospectively assessed based on their clinical and imaging records, and cross checked with the OR protocols. Treatment efficiency was evaluated considering postoperative clinical status, imaging appearance and postoperative complications. Results: 84.1% of the patients reported postoperative disappearance or reduction of symptoms, while 13.6 had the same complaints as prior surgery. Only one patient experienced worsening of symptoms. Follow-up imaging showed cyst disappearance in 29.5% patients and cyst reduction in 61.4% patients. 9.1% had no change in cyst volume. Craniotomy correlated with a better imaging appearance (p=0.02). There was no correlation between improved clinical status and cyst fluid reduction (p=0.6). 9 patients (20.4%), all with temporal cysts, experienced postoperative complications, and 7 of them (15, 9%) needed surgery. There was no severe or permanent dysfunction in any of the patients. 42.8% of the cyst shunting patients suffered postoperative complications, whereas only 10% of the craniotomy patients did. Conclusion: Cyst decompression results in significant clinical improvement and it can be performed with little risk for severe complications. Craniotomy seems to be a better surgical treatment option than cystoperitoneal shunt, with a better neuroimaging appearance and a lower complications rate

A rare case of medulloblastoma with excessive nodularity: imagistic features

Medulloblastoma is the most common malignant tumor of childhood. Neuroimaging can play a role in the diagnosis of medulloblastoma, however atypical features do exist [2]. We report the case of a 1 year and 10- month-old infant diagnosed with a medulloblastoma with what we term “excessive” nodularity based on neuroimaging features and confirmed by neuropathology. CT-scan (CT) and magnetic resonance imaging (MRI) examination of the brain revealed a very large posterior fossa tumor attached to tentorium. On T2-weighted and post-gadolinium sequences, the tumor shows an extensive nodular grape-like appearance. Initial the patient was underwent a ventriculo-peritoneal shunt.The second operative procedure was tumour resection. Histology examen revealed a diagnosis of medulloblastoma desmoplastic with extensive nodularity. The neuroradiographic features of this medulloblastoma with what we describe as “excessive” nodularity are important to recognize as these children may be cured with chemotherapy alone

New approach based on biomarkers in acute traumatic spinal cord injury

Spinal cord injury (SCI) is one of the most devastating traumas for an individual because the complete traumatic spinal cord injury leads to paraplegia or tetraplegia. The mechanical injuries directly cause axonal destruction in fiber tracts, destruction of the neurons and of the glial cells, and their destruction releases substances whose presence, quantity and dynamics can be lesional biomarkers. The reactions of partially injured cells simultaneously start and the occurring substances and their quantity may be reaction biomarkers. The lesional biomarkers appear immediately post-injury and after several hours there are both lesional biomarkers and reaction biomarkers. The most important lesional biomarkers are the phosphorylated neurofilament subunits resulting from the axonal neurofilament destruction. The heavy phosphorylated neurofilament subunit (pNF-H) is a predictive lesional biomarker because its values pattern can show the reducing or stopping of the secondary lesions and the favorable outcome. The complete SCI patients with a favorable development had a specific pattern of daily values of pNF-H: a sudden increase up to a maximum value then a progressive decrease to normal. The patients with unfavorable outcome or neurological stabilisation had two patterns: an increase to a plateau of pNF-H values or a progressive increase up to a peak followed by a progressive decrease to quasi-normal values