Academia Sinica

About: Academia Sinica is a facility organization based out in Taipei, Taiwan. It is known for research contribution in the topics: Population & Galaxy. The organization has 52086 authors who have published 65998 publications receiving 1728114 citations. The organization is also known as: Central Research Academy.

A Y-like social chromosome causes alternative colony organization in fire ants

Abstract: Intraspecific variability in social organization is common, yet the underlying causes are rarely known. In the fire ant Solenopsis invicta, the existence of two divergent forms of social organization is under the control of a single Mendelian genomic element marked by two variants of an odorant-binding protein gene. Here we characterize the genomic region responsible for this important social polymorphism, and show that it is part of a pair of heteromorphic chromosomes that have many of the key properties of sex chromosomes. The two variants, hereafter referred to as the social B and social b (SB and Sb) chromosomes, are characterized by a large region of approximately 13 megabases (55% of the chromosome) in which recombination is completely suppressed between SB and Sb. Recombination seems to occur normally between the SB chromosomes but not between Sb chromosomes because Sb/Sb individuals are non-viable. Genomic comparisons revealed limited differentiation between SB and Sb, and the vast majority of the 616 genes identified in the non-recombining region are present in the two variants. The lack of recombination over more than half of the two heteromorphic social chromosomes can be explained by at least one large inversion of around 9 megabases, and this absence of recombination has led to the accumulation of deleterious mutations, including repetitive elements in the non-recombining region of Sb compared with the homologous region of SB. Importantly, most of the genes with demonstrated expression differences between individuals of the two social forms reside in the non-recombining region. These findings highlight how genomic rearrangements can maintain divergent adaptive social phenotypes involving many genes acting together by locally limiting recombination.

Mental illness and suicide. A case-control study in east Taiwan.

Abstract: Background: As part of the Taiwan Aboriginal Study Project, a case-control study of suicide among two aboriginal groups and the Han Chinese was carried out in East Taiwan. Methods: Biographical reconstructive interviews were conducted for consecutive suicides from each of the three ethnic groups (a total of 116 suicides), 113 of whom were matched with two controls for age, sex, and area of residence. Results: In all three groups, a high proportion of suicides suffered from mental illness before committing suicide (97% to 100%). The two most prevalent psychiatric disorders were depression and alcoholism, and the most common comorbid pattern was depression with substance use disorders. The risk for suicide was significantly associated with all of these psychiatric conditions, previous suicide attempts, and a family history of suicide and depression. Fifty-one percent of all suicides had consulted medical professionals in the previous month. Conclusion: Despite the widely different rates of depressive illness and alcoholism in different cultures previously reported, the psychiatric antecedents of suicide are the same in the West and the East.

Graphene-based biosensors for detection of bacteria and their metabolic activities

Abstract: Graphene, which is a recently discovered single-atom-thick planar sheet of carbon atoms perfectly arranged in a honeycomb lattice, has great potential in biosensing owing to its extraordinary electrical, physical, and optical properties. In this work, we demonstrate a graphene based biosensor to electrically detect E. coli bacteria with high sensitivity and specificity. The large-sized graphene film was grown by chemical vapor deposition and functionalized with anti-E. coliantibodies and passivation layer. Significant conductance increase of the graphene device was observed after exposure to E. coli bacteria at a concentration as low as 10 cfu/mL, while no significant response was triggered by high concentration of the another bacterial strain. In addition, this biosensor was employed to detect the glucose induced metabolic activities of the bound E. coli bacteria in real time. This simple, fast, sensitive, and label-free nanoelectronic biosensor, in principle, could serve as a high throughput platform for detection of any pathogenic bacteria, and for functional studies or screening of antibacterial drugs.

Orbital analysis of electronic structure and phonon dispersion in MoS 2 , MoSe 2 , WS 2 , and WSe 2 monolayers under strain

Abstract: Structures, electronic properties, and phonon dispersions of monolayer $MX$${}_{2}$ ($M=$ Mo, W; $X=$ S, Se) under various types of mechanical strains are investigated with density functional calculations. By analyzing the orbitals near band gaps, we demonstrate that the $X$-$M$-$X$ bond angle, together with the $X$-$X$ distances, plays one of the most important roles in determining band gaps, as it is directly related to the coupling of $d$ orbitals of the $M$ atoms and $p$ orbitals of the $X$ atoms. It is found that the band gaps of monolayer $MX$${}_{2}$ are more sensitive to biaxial strains. This notion can be attributed to the fact that, under biaxial strains, $MX$${}_{2}$ tends to be stretched more significantly along the out-of-plane direction, resulting in greater changes in bond lengths/angles than uniaxial strains. While most theoretical reports suggested systematic reduction of band gaps under mechanical strains, we found that the direct band gaps can be robustly widened by applying compressive biaxial strains. Our results are of immediate importance for the recent experimental advances in applying compressive strains, which was not applicable before. On the other hand, the anisotropy of $X$-$M$-$X$ bond angles induced by uniaxial strains leads to splitting in the phonon dispersion, and is directly relevant to recent Raman spectroscopy results. As most transition-metal dichalcogenides share the same structural characters, we expect that the notions derived here are applicable to other layered transition-metal oxides/chalcogenides and open up new venues to engineer their properties.