RESUMO
The exploration of 1D magnetism, frequently portrayed as spin chains, constitutes an actively pursued research field that illuminates fundamental principles in many-body problems and applications in magnonics and spintronics. The inherent reduction in dimensionality often leads to robust spin fluctuations, impacting magnetic ordering and resulting in novel magnetic phenomena. Here, structural, magnetic, and optical properties of highly anisotropic 2D van der Waals antiferromagnets that uniquely host spin chains are explored. First-principle calculations reveal that the weakest interaction is interchain, leading to essentially 1D magnetic behavior in each layer. With the additional degree of freedom arising from its anisotropic structure, the structure is engineered by alloying, varying the 1D spin chain lengths using electron beam irradiation, or twisting for localized patterning, and spin textures are calculated, predicting robust stability of the antiferromagnetic ordering. Comparing with other spin chain magnets, these materials are anticipated to bring fresh perspectives on harvesting low-dimensional magnetism.
RESUMO
OBJECTIVE: To describe the clinicopathological and radiologic features in five cases of primary and secondary orbital aspergillosis. DESIGN: Case series. SETTING: Ophthalmology department of a university hospital. PATIENTS: Five patients over 65 years of age with invasive rhinosino-orbital aspergillosis. RESULTS: Presenting features were abrupt onset of proptosis, ophthalmoplegia and blepharoptosis with precipitous visual loss. All had debilitating periorbital pain or headache, but none had orbital inflammatory signs or appeared "toxic." Predisposing causes included alcoholism, low-dose prednisone therapy and insulin-dependent diabetes mellitus. One patient, suspected of having mucormycosis based on tissue biopsy and results of potassium hydroxide preparations, harboured Aspergillus fumigatus, which grew on culture. Secondary bacterial infections developed in three patients. Three patients died from their disease despite aggressive surgical treatment, including exenteration and sinus extirpation. The one patient with primary orbital aspergillosis survived after exenteration. CONCLUSIONS: Sinonasal aspergillosis with orbital extension and primary orbital aspergillosis have a precipitous clinical course that mimics that of mucormycosis and may be fatal despite early exenteration. Computed tomography and magnetic resonance imaging of the sinuses, orbit and head provide complementary diagnostic signs. While results of potassium hydroxide preparations and tissue biopsy guide treatment of fungal infection, definitive diagnosis requires fungal culture. Relatively good vision may be associated with massive orbital and secondary intracranial extension.
