25 research outputs found
DNA-based Self-Assembly of Chiral Plasmonic Nanostructures with Tailored Optical Response
Surface plasmon resonances generated in metallic nanostructures can be
utilized to tailor electromagnetic fields. The precise spatial arrangement of
such structures can result in surprising optical properties that are not found
in any naturally occurring material. Here, the designed activity emerges from
collective effects of singular components equipped with limited individual
functionality. Top-down fabrication of plasmonic materials with a predesigned
optical response in the visible range by conventional lithographic methods has
remained challenging due to their limited resolution, the complexity of
scaling, and the difficulty to extend these techniques to three-dimensional
architectures. Molecular self-assembly provides an alternative route to create
such materials which is not bound by the above limitations. We demonstrate how
the DNA origami method can be used to produce plasmonic materials with a
tailored optical response at visible wavelengths. Harnessing the assembly power
of 3D DNA origami, we arranged metal nanoparticles with a spatial accuracy of 2
nm into nanoscale helices. The helical structures assemble in solution in a
massively parallel fashion and with near quantitative yields. As a designed
optical response, we generated giant circular dichroism and optical rotary
dispersion in the visible range that originates from the collective
plasmon-plasmon interactions within the nanohelices. We also show that the
optical response can be tuned through the visible spectrum by changing the
composition of the metal nanoparticles. The observed effects are independent of
the direction of the incident light and can be switched by design between left-
and right-handed orientation. Our work demonstrates the production of complex
bulk materials from precisely designed nanoscopic assemblies and highlights the
potential of DNA self-assembly for the fabrication of plasmonic nanostructures.Comment: 5 pages, 4 figure
Cervical intramedullary schwannoma: a case report and review of the literature
Intramedullary schwannomas unrelated with neurofibromatosis are uncommon tumors, but if correctly diagnosed and properly treated they may have a good prognosis
Stent e angioplastica dei vasi epiaortici. L’esperienza del neuroradiologo interventista
Tuberculoma of the anterior optic pathways. Case report
A tuberculoma, encasing the anterior optic pathways in a neoplastiform growth, was found in a 25-year-old man complaining of severe visual loss, diabetes insipidus, and sexual impotence following tuberculous meningitis. Following biopsy and anti-tuberculosis treatment, a satisfactory restoration of sight in one eye allowed the patient to resume an almost normal life
Abnormal N-heterocyclic carbenes as ligands in catalytic transfer hydrogenation and as central modules in heterobimetallic complexes
Posttraumatic intraventricular haemorrhages
Of a series of 350 patients studied for blunt head trauma by CT scan 10 were found to have an intraventricular haemorrhage (IVH); in 8 cases we could find concomitant CT abnormalities as well as intracerebral contusion or haemorrhage, and in two cases no other CT abnormality was noted. CT scan represents the first reliable and non-surgical tool for identifying this process. Two possible mechanisms that govern the formation of an IVH are postulated: a) an erosion of the ventricular wall by an intracerebral haemorrhage; b) the rupture of subependymal veins deformed by the negative pressure following dilatation of the ventricular wall. The prognosis in our cases is severe
Gliomas of the optic nerve and chiasm. A clinical review
A series of 24 children with anterior optic gliomas, observed and for the most part operated upon in a neurosurgical service, is reviewed. A low incidence of unilateral nerve tumors and of associated neurofibromatosis, and a rather high frequency of precocious or pseudoprecocious puberty were noted in comparison with other series. Most tumors were low-grade growths. The results of surgical treatment reflect a good prognosis for unilateral tumors and an increasing prognostic ominousness for the posterior neoplastic development. Cerebrospinal fluid shunts and radiation treatment do have a role as adjuncts to surgical exploration and biopsy, which are generally indicated since no preoperative test seems to grant an absolute diagnosis. The opinion that chiasmal tumors should not be treated at all is not shared. When the treatment of an illness falls as far short of the ultimate, as does the therapy of neoplastic disease, then it is necessary to reconsider frequently the principles upon which it is based and the results it achieves. These results are two-fold, curative and palliative and, while our efforts are directed toward the former, we realize only too frequently that the best results will sometimes lie in palliation. The disappointment in accepting this lesser goal must not allow us to underestimate its importance or neglect the help it may give