We have performed for the first time the simultaneous measurement of the two-body and threebody photodisintegration cross-sections of 4 He in the energy range from 21.8 to 29.8 MeV using monoenergetic pulsed photons and a 4π time projection chamber containing 4 He gas as an active target in an event-by-event mode. The photon beam was produced via the Compton backscattering of laser photons with high-energy electrons. The 4 He(γ,p) 3 H and 4 He(γ,n) 3 He cross sections were found to increase monotonically with energy up to 29.8 MeV, in contrast to the result of a recent theoretical calculation based on the Lorentz integral transform method which predicted a pronounced peak at around 26−27 MeV. The energy dependence of the obtained 4 He(γ,n) 3 He cross section up to 26.5 MeV is marginally consistent with a Faddeev-type calculation predicting a flat pattern of the excitation function. The cross-section ratio of 4 He(γ,p) 3 H to 4 He(γ,n) 3 He is found to be consistent with the expected value for charge symmetry of the strong interaction within the experimental uncertainty in the measured energy range. The present results for the total and two-body crosssections of the photodisintegration of 4 He are compared to previous experimental data and recent theoretical calculations.

Simultaneous control of the size and chemical composition is an advantageous strategy to obtain the desired photochemical properties of multinary semiconductor nanocrystals, ZnS-AgInS2 solid solution ((AgIn) x Zn2(1–x)S2, ZAIS) nanocrystals (NCs), being different from conventional binary nanocrystals. The energy gap (E g) of ZAIS NCs was enlarged with a decrease in particle size due to the quantum size effect or with an increase in ZnS content in the ZAIS solid solution. The levels of the conduction band edge and valence band edge, determined by photoelectron spectroscopy in air, were shifted more negatively and more positively, respectively, with an increase in E g. A volcano-type dependence was observed between the PL quantum yield (QY) and the size of ZAIS NCs, in which the optimal PL QY for each x value was obtained at a similar particle size around 5–6 nm, except for x = 1.0, and maximum QY was recorded to be 79% for ZAIS NCs prepared with x = 0.5. The photocatalytic activity for H2 evolution was also greatly dependent on both the size and the chemical composition of ZAIS NCs, and then the highest activity was observed for ZAIS NCs having an average diameter of about 4.2–5.5 nm and E g of 2.3–2.4 eV. This can be reasonably explained by the enlargement of the driving force to reduce protons in the solution with a negative shift of the conduction band edge of ZAIS NCs and by the quenching of photoexcited ZAIS NCs with an increase in the amount of surface defect sites and/or with the formation of deeper trap sites along with a decrease in the particle size.

The iron storage protein ferritin contains threefold and fourfold symmetric channels that are thought to provide pathways for the transfer of Fe(2+) ions in and out of the protein. Using the known crystal structure of the ferritin protein, we perform electrostatic potential energy calculations to elucidate the functional properties of these channels. The threefold channel is shown to be responsible for the transit of Fe(2+) ions. Monovalent ions can also diffuse through the threefold channel but presence of divalent ions in the pore retards this process leading to a selectivity mechanism similar to the one observed in calcium channels. The fourfold channel is found to be impermeant to all cations with the possible exception of protons. Because proton transfer is essential to maintain the electroneutrality of the protein during iron deposition, we suggest that the function of the fourfold channel is to form a "proton wire" that facilitates their transfer in and out of ferritin.

We investigated the effect of anchoring group position on the formation and electric conductance of single molecule junctions for benzenedithiol and benzenediamine by the scanning tunneling microscope break junction technique. The conductances of the single 1,4-benzenedithiol, 1,3-benzenedithiol, 1,4-benzenediamine, and 1,3-benzenediamine molecules were 0.005 (±0.001) G 0 (G 0 = 2e 2/h), 0.004 (±0.001) G 0, 0.01 (±0.003) G 0, and 0.005 (±0.002) G 0, respectively. No 1,2-disubstituted benzene molecules formed junctions. While the 1,4-position provided larger conductance than the 1,3-position for both anchoring groups, the effect of the anchoring position on conductance was clearer for benzenediamine than benzenedithiol. The resulting anchoring position and its stability are discussed in consideration of the formation of the single molecular junction. The relationship between conductance and anchoring group (position) was analyzed based on ab initio transport calculations. The deformation and change of the energy alignment of the “conductive” molecular orbital give clearer insight to the anchoring position effect than to quantum interference.

Face‐to‐face communication: Electron transport through single‐molecule π stacks was directly measured between gold nanogap electrodes by using STM (see scheme). Self‐assembled coordination cages containing π‐stacked aromatic molecules are conductive (right), whereas the empty cage is not (left).

High temporal and spatial resolution measurements in the boundary of the DIII-D tokamak show that edge-localized modes ͑ELMs͒ are produced in the low field side, are poloidally localized and are composed of fast bursts ͑ϳ20 to 40 s long͒ of hot, dense plasma on a background of less dense, colder plasma ͑ϳ5 ϫ 10 18 m −3 , 50 eV͒ possibly created by the bursts themselves. The ELMs travel radially in the scrape-off layer ͑SOL͒, starting at the separatrix at ϳ450 m / s, and slow down to ϳ150 m / s near the wall, convecting particles and energy to the SOL and walls. The temperature and density in the ELM plasma initially correspond to those at the top of the density pedestal but quickly decay with radius in the SOL. The temperature decay length ͑ϳ1.2 to 1.5 cm͒ is much shorter than the density decay length ͑ϳ3 to 8 cm͒, and the latter decreases with increasing pedestal ͑and SOL͒ density. The local particle and energy flux ͑assuming T i = T e ͒ at the midplane wall during the bursts are 10% to 50% ͑ϳ1 to 2ϫ 10 21 m −2 s −1 ͒ and 1% to 2% ͑ϳ20 to 30 kW/ m 2 ͒, respectively, of the LCFS fluxes, indicating that particles are transported radially much more efficiently than heat. Evidence is presented suggesting toroidal rotation of the ELM plasma in the SOL. The ELM plasma density and temperature increase linearly with discharge/pedestal density up to a Greenwald fraction of ϳ0.6, and then decrease resulting in more benign ͑grassier͒ ELMs.

In order to examine the electrostatic forces in globular proteins, pKa values and their ionic strength dependence of His residues of hen egg white lysozyme (HEWL) and human lysozyme (HUML) were measured, and they were compared with those calculated numerically. pKa values of His residues in HEWL, HUML, and short oligopeptides were determined from chemical shift changes of His side chains by 1H-nmr measurements. The associated changes in pKa values in HEWL and HUML were calculated by solving the Poisson-Boltzmann equations numerically for macroscopic dielectric models. The calculated pKa changes and their ionic strength dependence agreed fairly well with the observed ones. The contribution from each residue of each alpha-helix dipole to the pKa values and their ionic strength dependence was analyzed using Green's reciprocity theorem. The results indicate that (1) the pKa of His residues are largely affected by surrounding ionized and polar groups; (2) the ionic strength dependence of the pKa values is determined by the overall charge distributions and their accessibilities to solvent; and (3) alpha-helix dipoles make a significant contribution to the pKa, when the His residue is close to the helix terminus and not fully exposed to the solvent.

We investigated the single 1,4-benzenediamine molecule bridging between Au or Pt electrodes. The conductances of the molecular junctions with the Au−NH2 and Pt−NH2 bonds (Au−NH2 and Pt−NH2 molecular junctions) were 1 × 10−2 G 0 (2e 2/h) and 5 × 10−3 G 0, respectively. The stretching lengths of the Au−NH2 and Pt−NH2 molecular junctions were 0.03 and 0.07 nm, respectively. The conductance value of the Au−NH2 molecular junction was unexpectedly larger than the value evaluated with the density of states of the metal electrodes and the molecule−metal bond strength, which have been discussed before. The large conductance value could be explained by the small energy difference between metal and molecular orbitals (ΔE) and the high degree of π-conjugation (P) of the Au−NH2 molecular junction, which would be unique characteristics of the Au−NH2 bond. The present study showed the importance of these two factors (ΔE, P) in studying the conductance of the single molecular junction.