Search for light dark matter in XENON10 data

We report results of a search for light (?10 GeV) particle dark matter with the XENON10 detector. The event trigger was sensitive to a single electron, with the analysis threshold of 5 electrons corresponding to 1.4 keV nuclear recoil energy. Considering spin-independent dark matter-nucleon scattering, we exclude cross sections σ(n)>7×10(-42) cm(2), for a dark matter particle mass m(χ)=7 GeV. We find that our data strongly constrain recent elastic dark matter interpretations of excess low-energy events observed by CoGeNT and CRESST-II, as well as the DAMA annual modulation signal.     

On a Neumann boundary value problem for the Painlevé II equation in two-ion electro-diffusion

A two-point Neumann boundary value problem for a two-ion electro-diffusion model reducible to the Painlevé II equation is investigated. The problem is unconventional in that the model equation involves yet-to-be-determined boundary values of the solution. In prior work by Thompson, the existence of a solution was established subject to an inequality on the physical parameters. Here, a two-dimensional shooting method is used to show that this restriction may be removed. A practical algorithm for the solution of the boundary value problem is presented in an appendix.     

ESI-MS quantitation of iron as its 4-(2-pyridylazo)resorcinol (PAR) complex: application to pharmaceutical tablets containing iron oxide pigment

Quantitation of iron oxide (Fe(2)O(3)) in pharmaceutical formulations using electrospray ionization mass spectrometry (ESI-MS) following iron complexation with 4-(2-pyridylazo)resorcinol (PAR) was evaluated. Complexation of Fe(III) with PAR was found to produce an intense mass spectral signal at low pH compared to the free ligand. Using the selected-ion-monitoring mode of a triple-quadrupole mass spectrometer, the signal at m/z 484 arising from the singly charged [Fe(III)(PAR)(2)](+) complex gave a limit of detection of ~2 μM for total iron. The linear range of the calibration curve was found to be 2-43 μM total iron. Trace iron interference was decreased to submicromolar levels by performing an optimized labware cleaning protocol and instrument replumbing using Polyetheretherketone (PEEK) tubing. The validation parameters of this ESI-MS total iron analysis (specificity, linearity, precision, accuracy, robustness and stability) are within the acceptance criteria listed in the validation guidelines developed by the Food and Drug Administration for industry. Recovery of 93% of the added iron indicated a satisfactory extraction procedure for tablets containing Fe(2)O(3) pigment. There was no statistical difference between the results obtained by ESI-MS and the common elemental method, inductively coupled plasma-optical emission spectroscopy. Since the proposed ESI-MS method can be performed on a mass spectrometer equipped with an ESI source, which is standard instrumentation in the pharmaceutical industry, the method validated here provides an alternate method for metal ion analysis by ESI-MS.     

Oxygen evolution from BF3/MnO4-

MnO(4)(-) is activated by BF(3) to undergo intramolecular coupling of two oxo ligands to generate O(2). DFT calculations suggest that there should be a spin intercrossing between the singlet and triplet potential energy surfaces on going from the active intermediate [MnO(2)(OBF(3))(2)](-) to the O···O coupling transition state.     

纸质活性炭纤维的制备及性能表征

通过KOH活化纸巾制备活性炭纤维, 比表面积高达1388 m²/g. 用制得的活性炭纤维作为吸附剂进行亚甲基蓝吸附实验研究,用Langmuir和Freundlich吸附模型分析实验数据,并研究pH值对活性炭纤维吸附亚甲基蓝影响. 活性炭纤维吸附速率更适于Pseudo-second-order动力学模型,相关系数高达0.998. 整个浓度变化区间Langmuir吸附等温线比Freundlich吸附等温线更适合实验数据. 所制备活性炭纤维对亚甲基蓝最大平衡吸附量为520 mg/g,实验发现,pH值越高活性炭纤维对亚甲基蓝吸附量越大.     

Coordination properties of axially unfixed chiral dipyridine ligands towards metal and ammonium ions

New chiral dipyridine ligands with an axially unfixed 1,1′-biphenyl bridge were prepared via homocoupling of bromophenyl pyridines. The conformeric ratios of the free ligands in solution and their coordination properties towards metal ions were studied by NMR spectroscopy. X-Ray crystallography of the silver(I) and copper(I) complexes showed 1:1 metal to ligand complexes and S planar chirality. Interestingly, the biphenyl ligands show a 1:2 stepwise binding towards most ammonium ions tested with strong fluorescence enhancement, but a selectively 1:1 binding towards l-ornithine methyl ester hydrochloride with no fluorescence enhancement.     

Transverse optical patterns for ultra‐low‐light‐level all‐optical switching

We review recent theoretical and experimental efforts toward developing an all‐optical switch based on transverse optical patterns. Transverse optical patterns are formed when counterpropagating laser beams interact with a nonlinear medium. A perturbation, in the form of a weak switch beam injected into the nonlinear medium, controls the orientation of the generated patterns. Each state of the pattern orientation is associated with a state of the switch. That is, information is stored in the orientation state. A realization of this switch using a warm rubidium vapor shows that it can be actuated by as few as 600 ± 40 photons with a response time of 5 µs. Models of nonlinear optical interactions in semiconductor quantum wells and microresonators suggest these systems are also suitable for use as fast all‐optical switches using this same conceptual design, albeit at higher switching powers.