Maximizing Friend-Making Likelihood for Social Activity Organization

The social presence theory in social psychology suggests that computer-mediated online interactions are inferior to face-to-face, in-person interactions. In this paper, we consider the scenarios of organizing in person friend-making social activities via online social networks (OSNs) and formulate a new research problem, namely, Hop-bounded Maximum Group Friending (HMGF), by modeling both existing friendships and the likelihood of new friend making. To find a set of attendees for socialization activities, HMGF is unique and challenging due to the interplay of the group size, the constraint on existing friendships and the objective function on the likelihood of friend making. We prove that HMGF is NP-Hard, and no approximation algorithm exists unless P = NP. We then propose an error-bounded approximation algorithm to efficiently obtain the solutions very close to the optimal solutions. We conduct a user study to validate our problem formulation and per- form extensive experiments on real datasets to demonstrate the efficiency and effectiveness of our proposed algorithm

Topological Magnetoelectric Effect as Probed by Nanoshell Plasmonic Modes

Axion electrodynamics is applied to study the response of a plasmonic nanoshell with a core made of topological insulator (TI) materials. The electric polarizability of such a system is calculated in the long wavelength limit via the introduction of two scalar potentials satisfying the various appropriate boundary conditions. Our focus is on the topological magneto-electric effect (TME) as manifested in the coupled plasmonic resonances of the nanoshell. It is found that for a TI with broken time-reversal symmetry, such TME will lead to observable red-shifts in the coupled plasmonic modes, with more significant manifestation of such shifts for the bonding modes of a metallic nanoshell. It is speculated that such universal red-shift could be a manifestation of the fundamental dual symmetry as generalized for axion electrodynamics

IS SUICIDE MORTALITY ASSOCIATED WITH METEOROLOGICAL AND SOCIO-ECONOMIC FACTORS? AN ECOLOGICAL STUDY IN A CITY IN TAIWAN WITH A HIGH SUICIDE RATE

Background: Keelung City has the highest suicide rate in Taiwan. This study aimed to determine whether meteorological and socio-economic factors are associated with suicide mortality in Keelung City, by gender and by means of suicide. Subjects and methods: Data on suicides between January 2006 and December 2010 were provided by the Department of Health, Keelung City Government. The suicide victims were categorized into non-violent and violent groups, based on the International Classification of Disease, Ninth Revision. Meteorological data were obtained from the Central Weather Bureau of Taiwan. Socioeconomic data were gathered from the Accounting and Statistics Office, Keelung City Government. Multiple linear regression analysis with backward elimination was performed to determine the model that was most effective in predicting dependent variables. Results: During the 5-year study period, the overall suicide mortality rate was negatively associated with ambient temperature. Male suicide mortality was positively correlated with unemployment, and negatively correlated with ambient temperature, barometric pressure, rainy days, family income and number of holidays. Female suicide mortality and violent suicide mortality were not significantly correlated with any meteorological or socio-economic factors. Non-violent suicide mortality was positively correlated with unemployment, and negatively correlated with ambient temperature, barometric pressure and family income. Conclusions: Suicide is a complex psychopathological phenomenon. Further studies with individual data are warranted to confirm how meteorological and socio-economic conditions influence ones’ suicidal behaviour

New D- A- A- - Configured Small Molecule Donors Employing Conjugation to Red- shift the Absorption for Photovoltaics

Four new donor- acceptor- acceptor- (D- A- A- )- configured donors, CPNT, DCPNT, CPNBT, and DCPNBT equipped with naphtho[1,2- c:5,6- c- ²]bis([1,2,5]- thiadiazole) (NT) or naphtho[2,3- c][1,2,5]thiadiazole (NBT) as the central acceptor (A) unit bridging triarylamine donor (D) and cyano or dicyanovinylene acceptor (A- ), were synthesized and characterized. All molecules exhibit bathochromic absorption shifts as compared to those of the benzothiadiazole (BT)- based analogues owing to improved electron- withdrawing and quinoidal character of NT and NBT cores that lead to stronger intramolecular charge transfer. Favorable energy level alignments with C70, together with the good thermal stability and the antiparallel dimeric packing render CPNT and DCPNT suitable donors for vacuum- processed organic photovoltaics (OPV)s. OPVs based on DCPNT- :- C70 active layers displayed the best power conversion efficiency (PCE)=8.3%, along with an open circuit voltage of 0.92- V, a short circuit current of 14.5- mA- cm- 2 and a fill factor of 62% under 1 sun intensity, simulated AM1.5G illumination. Importantly, continuous light- soaking with AM 1.5G illumination has verified the durability of the devices based on CPNT:C70 and DCPNT- :- C70 as the active blends. The devices were examined for their feasibility of indoor light harvesting under 500 lux illumination by a TLD- 840 fluorescent lamp, giving PCE=12.8% and 12.6%, respectively. These results indicate that the NT- based D- A- A- - type donors CPNT and DCPNT are potential candidates for high- stability vacuum- processed OPVs suitable for indoor energy harvesting.New donor- acceptor- acceptor- (D- A- A- )- configured small molecule donors with extended Ï - conjugation for red- shifting the absorption were characterized. The OPV comprising the donor DCPNT bearing naphtho[1,2- c:5,6- c- ²]bis([1,2,5]- thiadiazole) (NT) as A, cyano as A- , and acceptor C70 displayed the power conversion efficiency of 8.3% under AM 1.5G and 12.8% under 500 lux of TLD- 840 lamp, indicating the potential for indoor photovoltaics application.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/156487/3/asia202000635.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/156487/2/asia202000635-sup-0001-misc_information.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/156487/1/asia202000635_am.pd

The molecular gas kinematics in the host galaxy of non-repeating FRB 180924B

Fast radio bursts (FRBs) are millisecond-duration transients with large dispersion measures. The origin of FRBs is still mysterious. One of the methods to comprehend FRB origin is to probe the physical environments of FRB host galaxies. Mapping molecular-gas kinematics in FRB host galaxies is critical because it results in star formation that is likely connected to the birth of FRB progenitors. However, most previous works of FRB host galaxies have focused on its stellar component. Therefore, we, for the first time, report the molecular gas kinematics in the host galaxy of the non-repeating FRB 180924B at $z= 0.3216$. Two velocity components of the CO (3-2) emission line are detected in its host galaxy with the Atacama Large Millimeter/submillimeter Array (ALMA): the peak of one component ($-155.40$ km s$^{-1}$) is near the centre of the host galaxy, and another ($-7.76$ km s$^{-1}$) is near the FRB position. The CO (3-2) spectrum shows asymmetric profiles with A$_{\rm peak}$ $=2.03\pm 0.39$, where A$_{\rm peak}$ is the peak flux density ratio between the two velocity components. The CO (3-2) velocity map also indicates an asymmetric velocity gradient from $-180$ km s$^{-1}$ to 8 km s$^{-1}$. These results indicate a disturbed kinetic structure of molecular gas in the host galaxy. Such disturbed kinetic structures are reported for repeating FRB host galaxies using HI emission lines in previous works. Our finding indicates that non-repeating and repeating FRBs could commonly appear in disturbed kinetic environments, suggesting a possible link between the gas kinematics and FRB progenitors.Comment: 5 pages, 4 figures, Accepted for publication in MNRAS, https://www.youtube.com/watch?v=CldxLE7Pdwk&t=1

Tailoring Plasmonic Enhanced Upconversion in Single NaYF4:Yb3+/Er3+ Nanocrystals

By using silver nanoplatelets with a widely tunable localized surface plasmon resonance (LSPR) and their corresponding local field enhancement, here we show large manipulation of plasmonic enhanced upconversion in NaYF4:Yb3+/Er3+ nanocrystals at the single particle level. In particular, we show that when the plasmonic resonance of silver nanolplatelets is tuned to 656 nm, matching the emission wavelength, an upconversion enhancement factor ~5 is obtained. However, when the plasmonic resonance is tuned to 980 nm, matching the nanocrystal absorption wavelength, we achieve an enhancement factor of ~22 folds. The precise geometric arrangement between fluorescent nanoparticles and silver nanoplatelets allows us to make, for the first time, a comparative analysis between experimental results and numerical simulations, yielding a quantitative agreement at the single particle level. Such a comparison lays the foundations for a rational design of hybrid metal-fluorescent nanocrystals to harness the upconversion enhancement for biosensing and light harvesting applications