Systems hosting flat bands offer a powerful platform for exploring strong correlation physics.Theoretically,topological degeneracy arising in systems with non-trivial topological orders on periodic manifolds of non-ze...Systems hosting flat bands offer a powerful platform for exploring strong correlation physics.Theoretically,topological degeneracy arising in systems with non-trivial topological orders on periodic manifolds of non-zero genus can generate ideal flat bands.However,experimental realization of such geometrically engineered systems is very difficult.In this work,we demonstrate that flat planes with strategically patterned hole defects can engineer ideal flat bands.We construct two families of models:singular flat band systems where degeneracy is stabilized by non-contractible loop excitations tied to hole defects and perfectly nested van Hove systems where degeneracy arises from line excitations in momentum space.These models circumvent the need for exotic manifolds while retaining the essential features of topological flat bands.By directly linking defect engineering to degeneracy mechanisms,our results establish a scalable framework for experimentally accessible flat band design.展开更多
Background: Macular holes are the common cause of visual impairment especially in the elderly and have a variety of etiological factors. The advances in the management of macular holes are encouraging and are now avai...Background: Macular holes are the common cause of visual impairment especially in the elderly and have a variety of etiological factors. The advances in the management of macular holes are encouraging and are now available in developing countries although scarce, where hitherto;patients seek attention outside their country. The need to understand this disease has therefore become pertinent in all retina clinics. Objective: To evaluate the pattern of presentation of macular holes and its management in a retina clinic in South South Nigeria. Methods: A 5 year retrospective, non comparative review of 24 consecutive cases presenting to a retinal clinic was carried out. Relevant information was extracted from the medical records and analyzed. Results: Three hundred and sixty four cases were seen between January 2009 and December 2013. Twenty four cases had macular holes and ten (41.7%) had bilateral presentation with a total of 34 eyes. The incidence of macular holes was 6.6%. The mean age was 46 years (SD ± 13.42) with a female preponderance, 5:1. Idiopathic holes formed the bulk of the cases 14(58.3%);others were trauma 4(16.7%), posterior uveitis 2, (8.3%), chemotherapy 2 (8.3%), Solar retinopathy and retinitis pigmentosa 1 (4.2%). Nineteen (55.9%) of the 34 eyes were visually impaired (BCVA <6/18). Nineteen eyes had full thickness holes (55.9%) requiring surgery, however only 3(12.5%) of these could afford to have surgery with one reoperation. Four patients (16.7%) had complications in form of retinal detachments at presentation. Conclusion: This study has shown that the incidence of macular holes in the developing world is significant and resources to manage these cases are grossly lacking. Specialist training, with government subsidizing costs will alleviate these difficulties and reduce visual loss from macular holes.展开更多
In this study, we demonstrate a novel method for fabricating polythiophene patterns, i.e., cylindrical holes and cylinders, through blending of a thermally curable polythiophene carrying with tertiary ester groups(PT-...In this study, we demonstrate a novel method for fabricating polythiophene patterns, i.e., cylindrical holes and cylinders, through blending of a thermally curable polythiophene carrying with tertiary ester groups(PT-tert-ESTER) and poly(methyl methacrylate)(PMMA), followed by thermal conversion of the PT-tert-ESTER to an insoluble polythiophene via low-temperature cleavage of the tertiary ester groups and removal of the PMMA component via ultraviolet degradation. We show that the surface polarity of substrates, the mass ratio of PT-tert-ESTER to PMMA in the blend solutions as well as the concentration of the blend solutions strongly influence the formation of the polythiophene patterns. Cylindrical holes are more readily formed on less polar substrates when a PT-tert-ESTER dominated blend solution is used, while cylinders are more readily formed on more polar substrates when a PMMA dominated blend solution is used. Moreover, the diameters of both the cylindrical holes and the cylinders decrease as the PT-tert-ESTER concentration is increased in the respective ranges of the PT-tert-ESTER/PMMA ratios where the patterns are formed. Grazing incident X-ray diffraction data have indicated that the patterning of the PT-tert-ESTER component in the blend films improves the crystallinity of PT-tert-ESTER as well as the molecular packing of the insoluble polythiophene in the resultant patterned polythiophene films.展开更多
基金supported by the Ministry of Science and Technology(Grant No.2022YFA1403901)the National Natural Science Foundation of China(Grant Nos.12494594,11888101,12174428,and 12504192)+2 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB28000000)the New Cornerstone Investigator Program,the Chinese Academy of Sciences through the Youth Innovation Promotion Association(Grant No.2022YSBR-048)the Shanghai Science and Technology Innovation Action Plan(Grant No.24LZ1400800).
文摘Systems hosting flat bands offer a powerful platform for exploring strong correlation physics.Theoretically,topological degeneracy arising in systems with non-trivial topological orders on periodic manifolds of non-zero genus can generate ideal flat bands.However,experimental realization of such geometrically engineered systems is very difficult.In this work,we demonstrate that flat planes with strategically patterned hole defects can engineer ideal flat bands.We construct two families of models:singular flat band systems where degeneracy is stabilized by non-contractible loop excitations tied to hole defects and perfectly nested van Hove systems where degeneracy arises from line excitations in momentum space.These models circumvent the need for exotic manifolds while retaining the essential features of topological flat bands.By directly linking defect engineering to degeneracy mechanisms,our results establish a scalable framework for experimentally accessible flat band design.
文摘Background: Macular holes are the common cause of visual impairment especially in the elderly and have a variety of etiological factors. The advances in the management of macular holes are encouraging and are now available in developing countries although scarce, where hitherto;patients seek attention outside their country. The need to understand this disease has therefore become pertinent in all retina clinics. Objective: To evaluate the pattern of presentation of macular holes and its management in a retina clinic in South South Nigeria. Methods: A 5 year retrospective, non comparative review of 24 consecutive cases presenting to a retinal clinic was carried out. Relevant information was extracted from the medical records and analyzed. Results: Three hundred and sixty four cases were seen between January 2009 and December 2013. Twenty four cases had macular holes and ten (41.7%) had bilateral presentation with a total of 34 eyes. The incidence of macular holes was 6.6%. The mean age was 46 years (SD ± 13.42) with a female preponderance, 5:1. Idiopathic holes formed the bulk of the cases 14(58.3%);others were trauma 4(16.7%), posterior uveitis 2, (8.3%), chemotherapy 2 (8.3%), Solar retinopathy and retinitis pigmentosa 1 (4.2%). Nineteen (55.9%) of the 34 eyes were visually impaired (BCVA <6/18). Nineteen eyes had full thickness holes (55.9%) requiring surgery, however only 3(12.5%) of these could afford to have surgery with one reoperation. Four patients (16.7%) had complications in form of retinal detachments at presentation. Conclusion: This study has shown that the incidence of macular holes in the developing world is significant and resources to manage these cases are grossly lacking. Specialist training, with government subsidizing costs will alleviate these difficulties and reduce visual loss from macular holes.
基金financially supported by the National Natural Science Foundation of China(Nos.21274158 and 91333114)the National Research Laboratory Program of the Korea Science and Engineering Foundation(KOSEF)+1 种基金the World Class University Program(No.R32-2008-000-10142-0)the Center for Nanoscale Mechatronics&Manufacturing(08K140100414,CNMM)
文摘In this study, we demonstrate a novel method for fabricating polythiophene patterns, i.e., cylindrical holes and cylinders, through blending of a thermally curable polythiophene carrying with tertiary ester groups(PT-tert-ESTER) and poly(methyl methacrylate)(PMMA), followed by thermal conversion of the PT-tert-ESTER to an insoluble polythiophene via low-temperature cleavage of the tertiary ester groups and removal of the PMMA component via ultraviolet degradation. We show that the surface polarity of substrates, the mass ratio of PT-tert-ESTER to PMMA in the blend solutions as well as the concentration of the blend solutions strongly influence the formation of the polythiophene patterns. Cylindrical holes are more readily formed on less polar substrates when a PT-tert-ESTER dominated blend solution is used, while cylinders are more readily formed on more polar substrates when a PMMA dominated blend solution is used. Moreover, the diameters of both the cylindrical holes and the cylinders decrease as the PT-tert-ESTER concentration is increased in the respective ranges of the PT-tert-ESTER/PMMA ratios where the patterns are formed. Grazing incident X-ray diffraction data have indicated that the patterning of the PT-tert-ESTER component in the blend films improves the crystallinity of PT-tert-ESTER as well as the molecular packing of the insoluble polythiophene in the resultant patterned polythiophene films.
