Time sequence determination of parent–daughter radionuclides using gamma-spectrometry

The acquisition of time-stamped list data provides additional information useful to gamma-spectrometry analysis. A novel technique is described that uses non-linear least-squares fitting and the Levenberg–Marquardt algorithm to simultaneously determine parent-daughter atoms from time sequence measurements of only the daughter radionuclide. This has been demonstrated for the radioactive decay of short-lived radon progeny (²¹⁴Pb/²¹⁴Bi, ²¹²Pb/²¹²Bi) described using the Bateman first-order differential equation. The calculated atoms are in excellent agreement with measured atoms, with a difference of 1.3–4.8% for parent atoms and 2.4–10.4% for daughter atoms. Measurements are also reported with reduced uncertainty. The technique has potential to redefine gamma-spectrometry analysis.

     

An efficient synthesis of epoxydiynes and a key fragment of neocarzinostatin chromophore

[reaction: see text] A key structural feature of the Neocarzinostatin chromophore is a reactive epoxydiyne. We present here a new method for the preparation of epoxydiynes by the addition of an allenyl zinc bromide to a propargylic ketone.     

Bed Bug Aggregation Pheromone Finally Identified

Bed bugs have become a global epidemic and current detection tools are poorly suited for routine surveillance. Despite intense research on bed bug aggregation behavior and the aggregation pheromone, which could be used as a chemical lure, the complete composition of this pheromone has thus far proven elusive. Here, we report that the bed bug aggregation pheromone comprises five volatile components (dimethyl disulfide, dimethyl trisulfide, (E)‐2‐hexenal, (E)‐2‐octenal, 2‐hexanone), which attract bed bugs to safe shelters, and one less‐volatile component (histamine), which causes their arrestment upon contact. In infested premises, a blend of all six components is highly effective at luring bed bugs into traps. The trapping of juvenile and adult bed bugs, with or without recent blood meals, provides strong evidence that this unique pheromone bait could become an effective and inexpensive tool for bed bug detection and potentially their control.     

Basic features of coherent radiation generated by relativistic charge bunches

Abstract

Radiation generated by relativistic charges can be analyzed and described in exquisite detail. One reason that such detailed analysis is possible is because the phases of radiated photons often are determined completely by the initial conditions of the relativistic charges and the radiating system. The phase relationships between the initial charges and the radiated photons represent coherence in the emitted radiation. A previous paper decribed how this coherence could affect the spatial and spectral distributions of radiation generated by a single charge in a periodic radiator. The present paper discusses a complementary issue; namely, how the temporal shape of a relativistic charge bunch can emphasize specific features of the radiation generated at a single interaction site.     

Investigation of distribution of soil antimony using sequential extraction and antimony complexed to soil-derived humic acids molar mass fractions extracted from various depths in a shooting range soil

Trace metal contamination from bullet fragments in shooting ranges is a major environmental concern. In particular, trace metals such as lead, antimony, and copper are toxic and have the potential to enter groundwater supplies and to be absorbed by plants. Soil humic acids can play a critical role in mobilizing some of these released metals through complexation. The purpose of this study is to investigate the antimony complexed to soil-derived humic molar mass fractions extracted from various depths in a shooting range soil and to examine the distribution of antimony in various fractions of shooting range soils using sequential chemical extraction approach. The surface soil and soil core samples from a local shooting range were collected. Soil-derived humic acids were extracted from different depths of the top soil layer and characterized by various spectroscopic methods. Results of sequential chemical extraction demonstrated that Sb was found in shooting range in the upper 30 cm depth of the soil core. Highly elevated Sb is present in the exchangeable and ammonium acetate extracted fractions. Antimony is also present in the residual fraction in both surface and core soil samples, but is most likely present in a lithic phase which may not be readily bio-available. Leached antimony complexed to soil humic acid molar mass fractions was determined by size exclusion chromatography coupled to inductively coupled plasma-mass spectrometry (SEC-ICP-MS). The results demonstrate that Sb is ‘tightly’ bound to humic acid mass molar mass fractions and confined in the top 10 cm of soil-derived humic acids.     

1:1 Complexes of 2,3,5,6‐tetrachloro­benzene‐1,4‐dicarbonitrile with pyrene and phenanthrene: pseudo‐isomorphs

2,3,5,6‐Tetra­chloro­benzene‐1,4‐dicarbonitrile forms alternate π‐stacked 1:1 complexes with pyrene, C₈Cl₄N₂·C₁₆H₁₀, and phenanthrene, C₈Cl₄N₂·C₁₄H₁₀. These complexes are pseudo‐isomorphs. Phenanthrene, disordered about a centre of symmetry, takes the position of the pyrene, which sits exactly on this centre of inversion. The tetra­chloro­benzene­di­car­bo­nitrile mol­ecules in each complex also sit on centres of inversion and are in similar positions within the unit cells in the two structures, except that the orientation of the nitrile groups differs between the two.     

X-ray crystal structure of the 1∶2 triethyleneglycol dimethyl ether (triglyme): Dichloropicric acid adduct

The anhydrous 12 triglyme:Dichloropicric acid adduct is triclinic, space group ; at 24°Ca=8.703(5),b=10.381(4), c=10.404(3) Å, =114.42(3), =99.69(5), =106.40(6)°,D _x=1.656 g cm^–3, V = 776(2)ų,Z=1. Bond lengths and angles are normal except that one C–C–O–C torsion angle in the triglyme is approximately 90° rather than the expected 60 or 180°. Each phenolic OH group hydrogen bonds with a terminal OCH₃ of the polyether. The O...O distance, 2.557(3) Å, is in fair agreement with the 2.52 Å estimated from the single observed IRv (OH) stretch at 1714 cm^–1.     

Magnetic resonance imaging of chemical waves in porous media

Magnetic resonance imaging (MRI) provides a powerful tool for the investigation of chemical structures in optically opaque porous media, in which chemical concentration gradients can be visualized, and diffusion and flow properties are simultaneously determined. In this paper we give an overview of the MRI technique and review theory and experiments on the formation of chemical waves in a tubular packed bed reactor upon the addition of a nonlinear chemical reaction. MR images are presented of reaction-diffusion waves propagating in the three-dimensional (3D) network of channels in the reactor, and the 3D structure of stationary concentration patterns formed via the flow-distributed oscillation mechanism is demonstrated to reflect the local hydrodynamics in the packed bed. Possible future directions regarding the influence of heterogeneities on transport and reaction are discussed.     

High-resolution photoacoustic microscope for rat brain imaging in vivo

<正>A reflection-mode photoacoustic microscope(PAM) for rat brain imaging in vivo is constructed.A pulsed laser is used as an excitation source,and a focused ultrasound transducer is adopted to collect the photoacoustic signal.Raster scanning is applied to acquire three-dimensional(3D) data.The obtained measurements of the lateral and axial resolutions of the microscope are 45 and 15μm,respectively.The imaging depth in the chicken breast tissue is 3.1 mm at a signal-to-noise ratio(SNR) of 20 dB without any signal averaging.The imaging speed is 30 A-line/s.Experimental results in vivo demonstrate the capability of 3D imaging of the brain vessels of the rat after removing the skull.