3 research outputs found
The Alpha Magnetic Spectrometer (AMS) on the international space station: Part II â Results from the first seven years
The Alpha Magnetic Spectrometer (AMS) is a precision particle physics detector on the International Space Station (ISS) conducting a unique, long-duration mission of fundamental physics research in space. The physics objectives include the precise studies of the origin of dark matter, antimatter, and cosmic rays as well as the exploration of new phenomena. Following a 16-year period of construction and testing, and a precursor flight on the Space Shuttle, AMS was installed on the ISS on May 19, 2011. In this report we present results based on 120 billion charged cosmic ray events up to multi-TeV energies. This includes the fluxes of positrons, electrons, antiprotons, protons, and nuclei. These results provide unexpected information, which cannot be explained by the current theoretical models. The accuracy and characteristics of the data, simultaneously from many different types of cosmic rays, provide unique input to the understanding of origins, acceleration, and propagation of cosmic rays.</p
Molecular engineering of cocktail co-sensitization for efficient panchromatic porphyrin-sensitized solar cells
Co-sensitization of two or more dyes with complementary absorption spectra on a semiconductor film
is an effective approach to enhance the performance of a dye-sensitized solar cell (DSSC). Porphyrin
sensitizer YD2-oC8 showed outstanding photovoltaic performance co-sensitized with an organic dye to
cover the entire visible spectral region, 400â700 nm. To promote the light-harvesting capability beyond
700 nm, a porphyrin dimer (YDD6) was synthesized for a co-sensitized system. We report a systematic
approach for engineering of molecular co-sensitization of TiO2 films in a cocktail solution containing
YD2-oC8, an organic dye (CD4) and YDD6 in a specific molar ratio to optimize the photovoltaic
performance of the device. The resulting device showed panchromatic spectral features in the IPCE
action spectrum in the region 400â700 nm attaining efficiencies of 75â80%; the spectrum is extended to
the near-IR region attaining 40â45% in 700â800 nm region, giving JSC/mA cm
2 Œ 19.28, VOC/mV Œ
753, FF Œ 0.719, and h Œ 10.4% under standard AM 1.5 G one-sun irradiation. This performance is
superior to what is obtained from the individual single-dye devices and the two-dye co-sensitized
systems. The shifts of TiO2 potential upon dye uptake and the kinetics of charge recombination were
examined through measurements of the charge extraction (CE) and intensity-modulated photovoltage
spectroscopy (IMVS), respectively. Five co-sensitized systems were investigated to demonstrate that
suppression of dye aggregation of YDD6 in the co-sensitized film is a key factor to further improve the
device performance
Electrochemical regulation of microbial growth on disposable screen printed carbon electrodes
Herein we report an effective method to enhance microbial immobilization on screen-printed carbon
electrode (SPCE) surface by electrochemical regulation of redox potential. This technique could deliver
a prospective electrode for microbial biofuel cell and other applications. A phototrophic purple nonsulfur
bacterium Rhodopseudomonas palustris CGA009 was selected as a model organism to examine
the proposed approach. Scanning the electrode between
â0.7 to 0.3 V (vs. Ag/AgCl) at 70 mV/s for 50
cycles (âŒ24 min), placed in the growth medium with bacteria, significantly increased microbial adhesion
when compared to SPCE without electrochemical stimulation. The electron-transfer effect between the
adsorbed microorganism and electrode surface was further studied by AC impedance spectroscopy to
confirm the accelerated microbial immobilization. Stable photosynthetic electron transport chain from
immobilized bacteria through SPCE was achieved