Advances towards using finger/toenail dosimetry to triage a large population after potential exposure to ionizing radiation

Rapid and accurate retrospective dosimetry is of critical importance and strategic value for the emergency medical response to a large-scale radiological/nuclear event. One technique that has the potential for rapid and accurate dosimetry measurements is electron paramagnetic resonance (EPR) spectroscopy of relatively stable radiation-induced signals (RIS) in fingernails and toenails. Two approaches are being developed for EPR nail dosimetry. In the approach using ex vivo measurements on nail clippings, accurate estimation of the dose-dependent amplitude of the RIS is complicated by the presence of mechanically-induced signals (MIS) that are generated during the nail clipping. Recent developments in ex vivo nail dosimetry, including a thorough characterization of the MIS and an appreciation of the role of hydration and the development of effective analytic techniques, have led to improvements in the accuracy and precision of this approach. An in vivo nail dosimetry approach is also very promising, as it eliminates the problems of MIS from the clipping and it has the potential to be an effective and efficient approach for field deployment. Two types of EPR resonators are being developed for in vivo measurements of fingernails and toenails.     

Acoustic timescale characterisation of symmetric and asymmetric multidimensional hot spots

In this work, two-dimensional hot spots are modelled by combining a linear temperature gradient with a constant temperature plateau. This approach retains the simplicity of a linear temperature gradient, but captures the effects of a local temperature maximum of finite size. Symmetric and asymmetric plateau regions are modelled using both rectangular and elliptical geometries. A one-step Arrhenius reaction for H₂–air is used to model the reactive mixture. Plateaus with different ratios of excitation to acoustic timescales, spanning two orders of magnitude, are simulated. Even with clear differences in behaviour between one and two dimensions, the a priori prescribed hot spot timescale ratio is shown to characterise the 2-D gasdynamic response. The relationship between one and two dimensions is explored using asymmetric plateau regions. It is shown that 1-D behaviour is recovered over a finite time. Furthermore, the duration of this 1-D behaviour is directly related to the asymmetry of the plateau.     

Observation of persistent α‐helical content and discrete types of backbone disorder during a molten globule to ordered peptide transition via deep‐UV resonance Raman spectroscopy

The molten globule (MG) state can aid in the folding of a protein to a functional structure and is loosely defined as an increase in structural disorder with conservation of the ensemble secondary structure content. Simultaneous observation of persistent secondary structure content with increased disorder has remained experimentally problematic. As a consequence, modeling how the MG state remains stable and how it facilitates proper folding remains difficult due to a lack of amenable spectroscopic techniques to characterize this class of partially unfolded proteins. Previously, deep‐UV resonance Raman (dUVRR) spectroscopy has proven useful in the resolution of global and local structural fluctuations in the secondary structure of proteins. In this work, dUVRR was employed to study the MG to ordered transition of a model four‐helix bundle protein, HP7. Both the average ensemble secondary structure and types of local disorder were monitored, without perturbation of the solvent, pH, or temperature. The MG to ordered transition is induced by stepwise coordination of two heme molecules. Persistent dUVRR spectral features in the amide III region at 1295–1301 and 1335–1338 cm⁻¹ confirm previous observations that HP7 remains predominantly helical in the MG versus the fully ordered state. Additionally, these spectra represent the first demonstration of conserved helical content in a MG protein. With successive heme binding, significant losses are observed in the spectral intensity of the amide III₃ and S regions (1230–1260 and 1390 cm⁻¹, respectively), which are known to be sensitive to local disorder. These observations indicate that there is a decrease in the structural populations able to explore various extended conformations with successive heme binding events. DUVRR spectra indicate that the first heme coordination between two helical segments diminishes exploration of more elongated backbone structural conformations in the inter‐helical regions. A second heme coordination by the remaining two helices further restricts protein motion. Copyright © 2013 John Wiley & Sons, Ltd.     

小尺寸铕(Ⅲ)配合物荧光纳米颗粒的制备

利用再沉淀法分别制备出了小尺寸(~10nm)纯相和杂相的Eu³⁺配合物荧光纳米颗粒。所制备的纯相的荧光纳米颗粒在水溶液中容易聚集,并且荧光猝灭严重。相比较而言,掺有适量疏水性硅烷的杂相纳米颗粒则具有较强的荧光、均匀的尺寸和良好的分散性。硅烷在碱性环境下(pH=9)迅速地水解,而后在纳米微粒的表面形成二氧化硅薄层。亲水的二氧化硅薄层消除了Eu³⁺配合物纳米颗粒间的疏水相互作用,进而防止了纳米颗粒的聚集,从而导致了杂相荧光纳米颗粒发光性能的提高。     

A Particle-Mesh Method for the Shallow Water Equations Near Geostrophic Balance

In this paper we outline a new particle-mesh method for rapidly rotating shallow water flows based on a set of regularized equations of motion. The time-stepping method uses an operator splitting of the equations into an Eulerian gravity wave part and a Lagrangian advection part. An essential ingredient is the advection of absolute vorticity by means of translated radial basis functions. We show that this implies exact conservation of enstrophy. The method is tested on two model problems based on the qualitative features of the solutions obtained (i.e., dispersion or smoothness of potential vorticity contours) as well as on the increase in mean divergence level.     

Noise-enhanced human balance control

Noise can enhance the detection and transmission of weak signals in certain nonlinear systems, via a mechanism known as stochastic resonance. Here we show that input noise can be used to improve motor control in humans. Specifically, we show that the postural sway of both young and elderly individuals during quiet standing can be significantly reduced by applying subsensory mechanical noise to the feet. We further demonstrate with input noise a trend towards the reduction of postural sway in elderly subjects to the level of young subjects. These results suggest that noise-based devices, such as randomly vibrating shoe inserts, may enable people to overcome functional difficulties due to age-related sensory loss.     

Application of the ISO 13472-1 in situ technique for measuring the acoustic absorption coefficient of grass and artificial turf surfaces

This paper presents the applicability of an in situ technique based on ISO 13472-1 standard for measuring the acoustic absorption coefficient of grass and artificial turf surfaces for normal incidence from a sound source. The in situ method is based on acoustic impulse response measurement of the material surface. A maximum length sequence (MLS) signal is played through a loudspeaker and the acoustic response from the surface is recorded using a single microphone. The fast Hadamard transform and fast Fourier transform based digital signal post-processing algorithm provides the acoustic absorption coefficient of the surface under test. The normal incidence acoustic absorption coefficient of a commercial artificial quash surface of Dow Co. obtained from this method was compared with the results from the ASTM E1050 impedance tube method for the same surface. The acoustic absorption coefficients of a test-site grass surfaces were measured for 30 mm and 100 mm length of grass blades in wet and dry soil conditions. Substantial difference in the acoustic absorption coefficient was observed for a similar grass-like artificial surface used for estimating sound power of commercial garden equipments and lawnmowers. The advantage of the in situ method lies in its ability to measure the normal incident acoustic absorption coefficient of any planar surface as installed or in situ. Additionally a quick testing time of less than a minute with the use of a laptop sound card based inexpensive data acquisition system is the main feature of this robust method.     

Nylon and nylon blend nanotubes and nanorods

Nylon nanorods and nanotubes (200 nm diameter) were fabricated by the membrane wetting technique (solvent and melt wetting) from a range of nylons (6; 6,6; 6,9; 6,10; 6,12; 11; 12, 6(3)T) and nylon blended with different dyes (Nylon Cast Blue, Nylon 6/6 Black) or with molybdenum disulfide (Nylon cast MDS). The 65-μm long nylon nanotubes and nanorods were characterized by scanning electron microscopy. The nanoscale nylon 6,6 served as an effective high surface area alternative to a nylon membrane as a solid support in a chemiluminescent assay for nylon-bound biotinylated nucleic acids based on streptavidin- alkaline phosphatase and chemiluminescent detection of the bound alkaline phosphatase label with the dioxetane substrate, CDP-Star. Layer-by-layer deposition of the cationic polymer (Sapphire-II™; Tropix) onto the nylon 6,6 nanostructures prior to UV-cross-linking with biotinylated DNA resulted in further enhancement of binding and detection of biotinylated DNA.     

基于均值距离测度的医学图像配准

针对互信息测度在配准医学图像时易陷入局部极值、速度慢的缺点,提出了基于均值不等式的均值距离测度.首先根据均值不等式推导出5种均值距离测度：方根-算术均值距离(SAM)、方根-几何均值距离(SGM)、方根-调和均值距离(SHM)、算术-几何均值距离(AGM)、算术-调和均值距离(AHM).然后通过人体脑部CT/MR和MR-T1/PD图像的刚体配准实验,从函数曲线、配准精度、计算时间和收敛性能方面,对互信息与5种均值距离信息测度进行了比较与分析.实验结果表明,在不损失配准精度的前提下,AHM和SAM测度可以获得更快的配准速度,对噪声有很强的鲁棒性.     

Pulsed EPR spectrometer with injection-locked UCSB free-electron laser

We describe the first free-electron laser (FEL)-based pulsed electron paramagnetic resonance (EPR) system designed to study spin dynamics and structure changes of proteins in aqueous solution with nano-second of time resolution. This novel approach opens up the possibility for high-power sub-THz and THz pulsed EPR spectroscopy.