Surface-enhanced Raman scattering detection of chemical and biological agent simulants

Surface-enhanced Raman scattering spectra of chemical and biological agent simulants, such as dimethyl methylphonate, pinacolyl methylphosphonate, diethyl phosphoramidate, 2-chloroethyl ethylsulfide, bacillus globigii, erwinia herbicola, and bacillus thuringiensis were obtained from silver-oxide film-deposited substrates. Thin AgO films ranging in thickness from 50 to 250 nm were produced by chemical bath deposition onto glass slides. Further Raman intensity enhancements were noticed in UV irradiated surfaces due to photo-induced Ag nanocluster formation, which may provide a possible route to producing highly useful plasmonic sensors for the detection of chemical and biological agents upon visible-light illumination.     

Backscatter signatures of biological aerosols in the infrared

To develop a deeper understanding of the optical signatures of both biological aerosols and potential interferents, we made field measurements of optical cross sections and compared them to model-based predictions. We measured aerosol cross sections by conducting a hard-target calibration of a light detection and ranging system (LIDAR) based on the Frequency Agile Laser (FAL). The elastic backscatter cross sections are estimated at 19 long-wave infrared (LWIR) wavelengths spanning the range from 9.23 to 10.696 μm. The theoretical modeling of the elastic backscatter cross sections is based on the measured refractive index and size distribution of the aerosols, which are used as inputs into Mie calculations. Both model calculations and experimental measurements show good agreement and also indicate the presence of spectral features based on single particle absorption in the backscatter cross sections that can be used as a basis for discrimination for both standoff and point sensors.     

水洗条件对PAN水洗丝条结构和力学性能的影响

研究了水洗条件对聚丙烯腈(PAN)水洗丝条结构和力学性能的影响.用万能材料测试机、XRD、SEM、压汞仪测试纤维的力学性能、晶态结构、表面形态和孔结构,得到结构对力学性能的影响规律.结果表明:随着水洗温度升高,丝束的最大应力和最大载荷降低;水洗温度从55℃增大到90℃,结晶度从64.84%降低到57.73%,晶粒大小从4.034nm变为5.007nm;水洗温度升高,丝表面出现更加明显的纵向沟槽,表面缺陷增多,丝的直径也变得不均匀,孔隙率和孔径变小,微孔逐渐增多;随着结晶度降低、晶粒尺寸变大、表面缺陷增多,丝的力学性能随之下降;相同温度,超声波使纤维的孔径和孔隙率变小,同时使表面缺陷增多,所以超声波对丝的力学性能影响不大.     

Infrared and Raman spectral signatures of aromatic nitration in thermoplastic urethanes

The spectral signatures of nitro attack of the aromatic portion of thermoplastic urethanes (TPU) were determined. Eight fragment molecules were synthesized that represent the nitrated and pristine methylenediphenyl section common to many TPUs. Infrared (IR) and Raman (785 nm illumination) spectra were collected and modeled using the B3LYP/6-31G(d)//B3LYP/6-31G(d) model chemistry. Normal mode animations were used to fully assign the vibrational spectra of each fragment. The vibrational assignment was used to develop a diagnostic method for aromatic nitro attack in thermoplastic urethanes. The symmetric NO(2) stretch coupled out of phase with the C-NO(2) stretch (1330 cm(-1)) was found to be free from spectral interferences. Spectral reference regions that enable correction for physical differences between samples were determined. The carbonyl stretch at 1700 cm(-1) was the best IR reference region, yielding a limit of quantitation (LOQ) of 0.66 +/- 0.02 g N/100 g Estane. Secondary IR reference regions were the N-H stretch at 3330 cm(-1) or the urethane nitrogen deformation at 1065 cm(-1). The reference region in the Raman was a ring stretching mode at 1590 cm(-1), giving an LOQ of 0.69 +/- 0.02 g N/100 g Estane. Raman spectroscopy displayed a larger calibration sensitivity (slope = 0.110 +/- 0.004) than IR spectroscopy (slope = 0.043 +/- 0.001) for nitration determination due to the large nitro Raman cross-section. The full spectral assignment of all eight molecules in the infrared and Raman is presented as supplemental material.     

Multiplexed liquid arrays for simultaneous detection of simulants of biological warfare agents

Liquid array-based multiplexed immunoassays designed for rapid, sensitive, specific, and simultaneous detection of multiple simulants of biological warfare agents have been developed. In both blind and standard laboratory trials, we demonstrate the simultaneous detection of four simulant agents from a single sample. The challenge agents comprise broad classes of pathogens (virus, protein toxins, bacterial spores, vegetative cells). Assay performance of each analyte was optimized, and dose-response curves and the limits of detection (LODs) for individual analytes are presented. Assay performance, including dynamic range, sensitivity, and LODs for liquid arrays and enzyme-linked immunosorbant assay were compared and are shown to be similar. Maximum assay sensitivity is obtained in approximately 1 h, and good sensitivity is achieved in as little as 30 min. Although the sample matrixes are very complex, even for highly multiplexed assays the samples do not exhibit evidence of nonspecific binding, demonstrating that the assays also have high specificity.     

Measured infrared optical cross sections for a variety of chemical and biological aerosol simulants

We conducted a series of spectral extinction measurements on a variety of aerosolized chemical and biological simulants over the spectral range 3-13 microm using conventional Fourier-transform IR (FTIR) aerosol spectroscopy. Samples consist of both aerosolized particulates and atomized liquids. Materials considered include Bacillus subtilis endospores, lyophilized ovalbumin, polyethylene glycol, dimethicone (SF-96), and three common background materials: kaolin clay (hydrated aluminum silicate), Arizona road dust (primarily SiO2), and diesel soot. Aerosol size distributions and mass density were measured simultaneously with the FTIR spectra. As a result, all optical parameters presented here are mass normalized, i.e., in square meters per gram. In an effort to establish the utility of using Mie theory to predict such parameters, we conducted a series of calculations. For materials in which the complex indices of refraction are known, e.g., silicone oil (SF-96) and kaolin, measured size distributions were convolved with Mie theory and the resultant spectral extinction calculated. Where there was good agreement between measured and calculated extinction spectra, absorption, total scattering, and backscatter were also calculated.     

Quantum light signatures and nanosecond spectral diffusion from cavity-embedded carbon nanotubes

Single-walled carbon nanotubes (SWCNTs) are considered for novel optoelectronic and quantum photonic devices, such as single photon sources, but methods must be developed to enhance the light extraction and spectral purity, while simultaneously preventing multiphoton emission as well as spectral diffusion and blinking in dielectric environments of a cavity. Here we demonstrate that utilization of nonpolar polystyrene as a cavity dielectric completely removes spectral diffusion and blinking in individual SWCNTs on the millisecond to multisecond time scale, despite the presence of surfactants. With these cavity-embedded SWCNT samples, providing a 50-fold enhanced exciton emission into the far field, we have been able to carry out photophysical studies for the first time with nanosecond timing resolution. We uncovered that fast spectral diffusion processes (1-3 ns) remain that make significant contributions to the spectral purity, thereby limiting the use of SWCNTs in quantum optical applications requiring indistinguishable photons. Measured quantum light signatures reveal pronounced photon antibunching (g(2)(0) = 0.15) accompanied by side-peak bunching signatures indicative of residual blinking on the submicrosecond time scale. The demonstrated enhanced single photon emission from cavity-embedded SWCNTs is promising for applications in quantum key distribution, while the demonstrated passivation effect of polystyrene with respect to the stability of the optical emission opens a novel pathway toward optoelectronic devices with enhanced performance.     

Effect of surface-mannose modification on aerosolized liposomal delivery to alveolar macrophages

Purpose: The effect of surface-mannose modification on aerosolized liposomal delivery to alveolar macrophages (AMs) was evaluated in vitro and in vivo. Method: 4-Aminophenyl-α-D-mannopyranoside (Man) was used for surface-mannose modification, and mannosylated liposomes with various mannosylation rates (particle size: 1000 nm) were prepared. Results: In the in vitro uptake experiments, the uptake of mannosylated liposomes by AMs was increased with the increase in the mannosylation rate over the range 2.4–9.1 mol% Man and became constant at over 9.1%. Thus, the most efficient mannosylation rate was 9.1 mol% Man. Furthermore, free mannose inhibited the uptake of mannosylated liposomes by AMs. This indicates that the uptake mechanism of mannosylated liposomes by AMs is mannose receptor-mediated endocytosis. In the in vivo animal experiments, the mannosylated liposomes (mannosylation rate, 9.1 mol% Man) were more efficiently delivered to AMs after pulmonary aerosolization to rats than nonmodified liposomes and did not harm lung tissues. Conclusion: These results indicate that surface-mannose modification is useful for efficient aerosolized liposomal delivery to AMs.     

生物媒质中声学参量与温度的关系研究

1引言 目前,高强度聚焦超声(HIFU)在临床应用中已有很大的发展,但还远没有能大规模的推广应用.究其原因,主要是还没有能找到实时、无损的检测因使用高强度聚焦超声而引起的生物组织温度变化的方法.一个成功的超声治疗系统应该不仅能够提供清晰的超声图象,而且能实时提供生物组织内部的温度分布,以便准确的进行超声治疗,切除病变部分而不对正常组织造成任何伤害.研究表明,声速等声参量虽也可反映组织的温度变化,但变化率却不大.非线性参量B/A不仅对生物组织的成分和结构的变化很敏感[1],而且还能反映一些流体随温度的变化.本文利用有限振幅插入取代法测量了在生物组织中声学参量随温度的变化.     

Classification of chemical and biological warfare agent simulants by surface-enhanced Raman spectroscopy and multivariate statistical techniques

Initial results demonstrating the ability to classify surface-enhanced Raman (SERS) spectra of chemical and biological warfare agent simulants are presented. The spectra of two endospores (B. subtilis and B. atrophaeus), two chemical agent simulants (dimethyl methylphosphonate (DMMP) and diethyl methylphosphonate (DEMP)), and two toxin simulants (ovalbumin and horseradish peroxidase) were studied on multiple substrates fabricated from colloidal gold adsorbed onto a silanized quartz surface. The use of principal component analysis (PCA) and hierarchical clustering were used to evaluate the efficacy of identifying potential threat agents from their spectra collected on a single substrate. The use of partial least squares-discriminate analysis (PLS-DA) and soft independent modeling of class analogies (SIMCA) on a compilation of data from separate substrates, fabricated under identical conditions, demonstrates both the feasibility and the limitations of this technique for the identification of known but previously unclassified spectra.     

Genuine and pseudo-thermophysical properties of biological media

There is an increasing demand for data on the thermophysical properties of biological materials, in response to the rapid progress of bioengineering and technology. However, there have been only limited sources of reliable data. A state-of-the-art review is presented on the measurement of thermophysical properties of biological media, mainly focusing attention on the difficulties in measuring techniques and the complicated characteristics of living organs and tissues. Some recent results are introduced in the hope of drawing increased attention to the interdisciplinary area of thermophysical properties research.Paper presented at the Japan-United States Joint Seminar on Thermophysical Properties, October 24–26, 1983, Tokyo, Japan.     

On the noise power spectral density of particulate recording media

The ac-noise power spectrum is investigated. Because of the interaction forces between the particles, the structure of the particulate layer has a dominant influence. This structure is quantified by means of the dc-noise power spectrum. Depending on the dispersion and coating technique the duster structure appears to vary. The ac-noise power is described by a mechanism of negative and positive interactions which occur simultaneously. Flux-closuring particles are near to each other at distances less than 0.1 μm, whereas magnetic strings appear to extend over tens of microns.     

Autonomous detection of aerosolized biological agents by multiplexed immunoassay with polymerase chain reaction confirmation

The autonomous pathogen detection system (APDS) is an automated, podium-sized instrument that continuously monitors the air for biological threat agents (bacteria, viruses, and toxins). The system has been developed to warn of a biological attack in critical or high-traffic facilities and at special events. The APDS performs continuous aerosol collection, sample preparation, and detection using multiplexed immunoassay followed by confirmatory PCR using real-time TaqMan assays. We have integrated completely reusable flow-through devices that perform DNA extraction and PCR amplification. The fully integrated system was challenged with aerosolized Bacillus anthracis, Yersinia pestis, Bacillus globigii, and botulinum toxoid. By coupling highly selective antibody- and DNA-based assays, the probability of an APDS reporting a false positive is extremely low.     

Effect of spectral correlations on spectral switches in the diffraction of partially coherent light

The subject is the spectral characteristics of partially coherent light whose spectral degree of coherence satisfies or violates the scaling law in diffraction by a circular aperture. Three kinds of spectral correlations of the incident light are considered. It is shown that no matter whether the partially coherent light satisfies or violates the scaling law, a spectral switch defined as a rapid transition of spectral shifts is always found in the diffraction field. Different spectral correlations of the incident field in the aperture result in different points at which the spectral switch occurs. With an increment in the correlations, the position at which the spectral switch takes place moves toward the point at which the phase of the center frequency component omega0 becomes singular for illumination by spatially fully coherent light. For light that satisfies the scaling law, the spectral switch is attributed to the diffraction-induced spectral changes; for partially coherent light that violates the scaling law, the spectral switch is attributed to both the diffraction-induced spectral changes and the correlation-induced spectral changes.     

Effect of diffraction on early-arriving photons during femtosecond laser transillumination of highly scattering media of biological significance

Early-arriving photons of 100-fs laser pulses transmitted through highly scattering media have been detected by a streak camera. Because of their partial spatial coherence, they are affected by diffraction from small hidden discontinuities. The experimental data of the patterns are analyzed with Fresnel diffraction theory and then corrected accordingly. Submillimeter hidden objects were scanned and imaged. Diffraction correction resulted in a significantly improved contrast in the hidden object's image.     

Noise, clutter, and determinism in infrared spectral signatures under varying meteorological conditions

Infrared remote detection of chemical and biological agents in a complex environment depends on the ability to recognize threat signatures and differentiate them from the signatures of innocuous materials. In this paper, we addressed the methods of producing the constraint spectra needed to ensure reliable operation in a meteorologically changing environment. We collected arrays of background spectra of ground, woods, and low-angle sky on an irregular basis over a period of a year. Based on the hypothesis that the concentration fluctuations of species in the sensor's field of view can be exploited to form signatures, the standard deviations of the array (the result is characteristic of all fluctuations) and the difference array (the result is characteristic of sensor fluctuations) were computed. Subtracting these two spectra and filtering the result produced a spectrum, which is a measure of the IR fluctuations in the scene. The resulting set of scene spectra were processed into aberrant noise, and deterministic groups by numerical filtering and statistical methods.     

BEM analysis of spectral response from finite pole-length heads on perpendicular media

The Boundary Element Method (BEM) is used to solve for the fields from high-permeability, finite pole-tip gapped heads, with and without a permeable layer beneath the recording medium. The underlayer enhances the recording and playback performance for perpendicular magnetization by increasing both perpendicular fields and field gradients. Reciprocity is used to find the spectral (frequency) response for both sine-wave and square-wave perpendicular magnetizations. Regions of low spectral response, geometrically induced by the finite pole-tips, are more pronounced with the underlayer than without, and are explored for various pole-lengths.     

Effect of milling and acid washing on the pozzolanic activity of incinerator sewage sludge ash

Incinerator sewage sludge ash (ISSA) is a problematic waste that contains significant levels of phosphates, primarily in the form of whitlockite (Ca₃(PO₄)₂). Phosphate is a valuable finite resource, and a number of studies have shown that it can be extracted from ISSA by acid washing. This produces an acid washed residue that has potential to be used in construction products. The effects of milling and acid washing on the pozzolanic activity of ISSA have been evaluated using the strength activity index (SAI) test and the Frattini test. Coal fly ash (FA), metakaolin (MK) and quartz sand were also tested for comparison. Milling improved the pozzolanic activity of FA and ISSA according to both the SAI and Frattini tests. If ISSA is acid washed to recover phosphate, the process is likely to produce an acid insoluble material with little or no pozzolanic activity. The Frattini test is considered a more suitable method for directly assessing pozzolanic activity as a range of factors can affect SAI test results.