Automatic selection of optimal Savitzky-Golay smoothing

A method to select the optimal window size of the Savitzky-Golay (SG) algorithm is presented. The approach is based on a comparison of the fitting residuals (i.e., the differences between the input signal and the smoothed signal) with the noise of the instrument. The window size that yields an autocorrelation of the residuals closest to the autocorrelation of the noise of the instrument is considered optimal. The method is applied in two steps. In a first step, the lag-one autocorrelation value of the noise of the instrument is computed through the study of a blank signal. In a second step, the SG algorithm is applied to "smooth" the signal using different window sizes. The method was applied to data from NMR, chromatography, and mass spectrometry and was shown to be robust. It finds the optimal window size for different signal features. This allows the method to be used in an unsupervised way, embedded in a more complex algorithm in which smoothing and/or differentiation of signals is required, provided that the lag-one autocorrelation value of the instrument noise does not change.     

Displacement vector measurement using instantaneous ultrasound signal phase - multidimensional autocorrelation and doppler methods

Two new methods of measuring a multidimensional displacement vector using an instantaneous ultrasound signal phase are described, i.e., the multidimensional autocorrelation method (MAM) and multidimensional Doppler method (MDM). A high measurement accuracy is achieved by combining either method with the lateral Gaussian envelope cosine modulation method (LGECMM) or multidirectional synthetic aperture method (MDSAM). Measurement accuracy is evaluated using simulated noisy echo data. Both methods yield accurate measurements comparable to that of our previously developed cross-spectrum phase gradient method (MCSPGM); however, they require less computational time (the order, MDM < MAM approximate, equals MCSPGM) and would provide realtime measurements. Moreover, comparisons of LGECMM and MDSAM performed by geometrical evaluations clarifies that LGECMM has potentials to yield more accurate measurements with less computational time. Both MAM and MDM can be applied to the measurement of tissue strain, blood flow, sonar data, and other target motions.     

Ultrasonic assessment of cortical bone thickness in vitro and in vivo

In osteoporosis, total bone mass decreases and the thickness of the cortical layer diminishes in the shafts of the long bones. In this study, a simple ultrasonic in vivo method for determining the thickness of the cortical bone layer was applied, and the suitability of two different signal analysis techniques, i.e., envelope and cepstral methods, for measuring cortical thickness was compared. The values of cortical thickness, as determined with both techniques, showed high linear correlations (r ges 0.95) with the thickness values obtained from in vitro measurements with a caliper or in vivo measurements by peripheral quantitative CT (pQCT). No systematic errors that could be related to the cortical thickness were found. The in vivo accuracy of the measurements was 6.6% and 7.0% for the envelope and cepstral methods, respectively. Further, the in vivo precision for the envelope and cepstral methods was 0.26 mm and 0.28 mm, respectively. Although the results are similar for both of the techniques, the simplicity of the envelope method makes it more attractive for clinical applications. In conclusion, a simple ultrasound measurement provides an accurate estimate of the cortical bone thickness. The techniques investigated may have clinical potential for osteoporosis screening and therefore warrant more extensive clinical investigations with healthy and osteoporotic individuals.     

Measured Infrared Spectral Extinction for Aerosolized Bacillus subtilis var. niger Endospores from 3 to 13 mum

We measured spectral extinction in situ for aerosolized Bacillus subtilis var. niger endospores using Fourier-transform infrared spectroscopy from 3.0 to 13.0 mum. Corresponding aerosol size distributions were measured with a commercially available elastic light-scattering probe and verified by direct particle capture and subsequent counting by video microscopy. Aerosol mass density was monitored simultaneously with conventional dosimetry and was used to mass normalize the measured spectral extinction. Mie theory calculations based on measured distributions and available complex indices of refraction agreed well. We also present resultant Mie calculations for the absorption, total scattering, and backscatter. For comparison, measured spectral extinction for three common environmental aerosols is also presented, i.e., for water fog, diesel soot, and Arizona road dust.     

基于FPGA高速信号采集的多角度动态光散射法纳米粒径测量

根据动态光散射装置测量纳米粒径原理,开发了一套基于现场可编程门阵列(FPGA)的纳米粒径测量系统。该系统通过光电倍增管(PMT)输出光子脉冲信号,利用FPGA实现高速脉冲采集及自相关运算,采用双脉冲计数器实现高精度可控的连续计数,并实现DDR3异步存储以及USB通信交互等接口功能。自研板卡既可实现自相关函数实时采集运算,又可无丢失地保存海量原始数据信号。采用该系统对200nm聚苯乙烯颗粒进行了测量,分析了不同采样时间及延迟时间等参数对粒径测量结果的影响。实验结果表明:自研FPGA采集板卡测量重复性为1.2%,具有很好的稳定性和重复性。     

Method for the Thermal Characterization of PCM Systems in the Volume Range from 100 ml to 1000 ml

The storage of latent heat in phase change materials (PCM) is of great interest in many applications, for example in building applications. However, there is no standard method for the determination of the thermophysical properties of application-sized PCM specimens, i.e., specimens with sizes around 100 ml to 1000 ml. In order to close this metrological gap, a commercially available heat flow meter was modified to perform enthalpy measurements. The feasibility of this method was proven by performing comparative measurements on a stainless steel specimen using both the standard method DSC and the modified heat flow meter. Furthermore, measurements on a gypsum board with microencapsulated PCM were performed with the heat flow meter in order to determine the enthalpy. The coincidence with literature values is within ±4% which demonstrates that this method is a good choice for performing measurements on application-sized PCM specimens.     

Simultaneous determination of species-specific isotopic composition of Hg by gas chromatography coupled to multicollector ICPMS

This work presents the simultaneous online determination of the isotopic composition of different Hg species in a single sample by the hyphenation of gas chromatography (GC) with multicollector-inductively coupled plasma mass spectrometry (MC-ICPMS). With the use of commercially available instrumentation, precise and accurate species-specific Hg isotope delta values (per mil deviation of the Hg isotope ratio in the sample relative to a reference standard) have been obtained online from consecutive GC transient signals. The use of isothermal temperature programs to extend the elution of the Hg species, the proper selection of the peak integration window, as well as the preconcentration of real samples are critical to provide optimal counting statistics. Also, isotope ratio drift during transient signal elution was overcome by introducing a mixed Hg(II) and MeHg standard bracketing scheme and expressing all results using the delta-notation relative to SRM NIST-3133. Using the proposed methodology, we have obtained an external 2SD precision of 0.56 per thousand for delta (202)Hg that is more than 10 times smaller than the overall Hg stable isotope variation thus far observed in terrestrial samples. The measurement of species-specific Hg isotopic composition relative to SRM NIST-3133 has been validated versus two other analytical techniques, i.e., conventional nebulization (CN) of Hg(II) solution and cold vapor (CV) generation of Hg (0) vapor. A good agreement between the species-specific delta values obtained by the different techniques has been obtained in secondary fractionated reference standard (UM-Almaden) and environmental matrixes, i.e., BCR-CRM 464 (tuna fish) and IAEA-085 (human hair). The results show mass-dependent and mass-independent fractionation in environmental samples, i.e., mass-independent fractionation of odd isotopes (199)Hg and (201)Hg in tuna fish was observed. This methodology provides new possibilities for the future study of species-specific stable isotope geochemistry of Hg and other trace metals.     

基于数字锁相环的科氏质量流量计信号处理方法

针对科里奥利质量流量计信号处理中存在的问题 ,即信号频率在小范围内变化和信号易受谐波干扰 ,采用基于数字锁相环的方法处理科氏质量流量计的信息 ,跟踪信号频率的变化 ,计算相位差。对美国专利提出的方法进行了改进 ,做了仿真。仿真结果表明 ,在有谐波干扰的情况下 ,数字锁相环方法可以准确地跟踪信号频率的变化和计算相位差。本文还对计算误差进行了分析     

Fiber-optic probes for in vivo Raman spectroscopy in the high-wavenumber region

In vivo Raman spectroscopy, using fiber-optic probes is hindered by the intense background signal, which is generated in the fused-silica fibers, in the fingerprint region of the Raman spectrum (approximately 0-2000 cm(-1)). Optical filtering is necessary to obtain tissue spectra of sufficient quality. The complexity of fiber-optic probes for fingerprint Raman spectroscopy, in combination with size constraints and flexibility requirements for in vivo use have been a major obstacle in the development of in vivo diagnostic tools based on Raman spectroscopy. A setup for remote Raman spectroscopic tissue characterization in the high-wavenumber region ( approximately 2400-3800 cm(-1)) is presented. It makes use of a single, unfiltered, optical fiber for guiding laser light to the sample and for collecting scattered light and guiding it back to a spectrometer. Such a simple configuration is possible because the fused-silica core and cladding of the fiber present almost no Raman background signal at these wavenumbers. Several commercially available optical fibers were tested with respect to Raman signal background, to determine their suitability for in vivo Raman spectroscopy measurements in the high-wavenumber region. Different fiber core, cladding, and coating materials were tested. Silica core-silica clad fibers, with an acrylate coating and a black nylon jacket, proved to be one of the best candidates. In vitro measurements on brain tissue of a 6-month-old pig were obtained with a remote high-wavenumber Raman setup. They illustrate the low background signal generated in the setup and the signal quality obtained with a collection time of 1 s.     

Precise Measurement of Isotope Ratios with a Double-Focusing Magnetic Sector ICP Mass Spectrometer

The potential of a commercially available double-focusing magnetic sector ICP mass spectrometer (Element, Finnigan MAT, Bremen, Germany) for precise isotope ratio measurement at the low-resolution setting (R = 300) was evaluated. Optimization of scanning conditions led to a relative standard deviation for a set of 10 consecutive 2 min measurements of ～0.1% ((206)Pb(+)/(207)Pb(+)) at signal intensities of ～200?000 counts/s (peak height). This compares favorably with the best values ever reported for quadrupole ICPMS and barely exceeds the theoretical value (counting statistics). Increasing the signal intensity to values ≥500?000 counts/s (peak height) resulted in a further reduction of the RSDs obtained (for both (25)Mg(+)/(26)Mg(+) and (206)Pb(+)/(207)Pb(+)) to typically 0.04%. These figures are remarkably better than those reported for commercially available quadrupole ICPMS systems. This improvement significantly reduces the difference between isotope ratio precision of ICPMS on one hand and those of thermal ionization mass spectrometry and plasma source multiple collector mass spectrometry on the other.     

The effects of some physico-chemical factors and pharmaceutical excipients on the bioavailability of nitrofurantoin oily and aqueous suspensions in rats

The effects of some physico-chemical factors and various excipients, i.e., sucrose, aluminum stearate, hydrogenated castor oil, Cab-o-sil, and lecithin, either alone or in combination, from suspensions in fractionated coconut oil and distilled water have been investigated. In vitro drug release studies were performed according to the flask-stirrer method. In addition to adsorption and solubility studies, determination of partition coefficients and rheological measurements have been carried out. The experimental design was based on an 8×8 latin square using rats as the test animals. The results of the study showed that the rate and extent of absorption of nitrofurantoin are decreased significantly by the use of an oily rather than an aqueous vehicle. In vitro drug release data showed some correlation with in vivo parameters, and also with the apparent viscosity of the vehicles. However, no correlation was detectable between in vivo parameters and the apparent viscosity of the vehicles.     

Image quality evaluation with a new phase rotation beamformer

Over the last few decades, dynamic focusing based on digital receive beamforming (DRBF) has led to significant improvements in image quality. However, it is computationally very demanding due to its requirement for multiple lowpass filters (e.g., a complex filter for each receive channel in quadrature demodulation-based phase rotation beamformers (QD-PRBF)). We recently developed a novel phase rotation beamformer with reduced complexity, which can lower: 1) the number of lowpass filters using 2-stage demodulation (TSD) and 2) the number of beamforming points using adap tive field-of-view (AFOV) imaging. In TSD, dynamic focusing is performed on the mixed signals, while sampling frequency of the beamformed signal (i.e., beamforming frequency) is adjusted based on the displayed field-of-view (FOV) size in AFOV imaging. In this paper, the image quality of the developed beamformer (i.e., TSD-AFOV-PRBF) has been quantitatively evaluated using phantom and in vivo data. From the phantom study, it was found that TSD-AFOV-PRBF with only 1024 beamforming points provides comparable image quality to QD-PRBF. We obtained a median contrast resolution (CR) degradation of 7.6% for the FOV size of 160 mm. Image quality steadily improves with FOV size reduction (e.g., 2.3% CR degradation at 85 mm). Similar results were also obtained from an in vivo study. Thus, TSD-AFOV-PRBF could provide comparable image quality to conventional beamformers at considerably reduced computational cost.     

光纤式质量流量计的研究

研究出一种光纤传感器与电磁涡流传感器相结合的新型质量流量计,并给出理论模型和实际系统结构。该流量计对旋涡发生体进行了独特设计,即将光纤嵌入到旋涡发生体内部构成光纤式升力检测器。利用光纤的微弯损耗特性,检测出流体流经旋涡发生体时产生的变动升力大小,结合信号电极测量出的涡流频率,由单片机计算出流体质量流量。与其它质量流量计相比,光纤式质量流量计结构简单,抗干扰能力强。以水为被测对象的实验证明,其测量结果的相对误差在1%以内。     

Safety considerations for sample analysis using a near-infrared (785 nm) Raman laser source

Raman spectroscopy is often considered a nondestructive analytical technique; however, this is not always the case. The 300-mW 785-nm near-infrared (NIR) laser source used with many commercially available instruments has sufficient power to burn samples. This destructive potential is of special concern if the sample is irreplaceable (e.g., fine art, forensic evidence, or for in vivo medical diagnostics) or a hazardous energetic material (explosive or pyrophoric samples). This study quantifies the heat resulting from illuminating an extensive color array with a 785-nm NIR laser and relates these values to the hazards associated with Raman analysis. In general, darker colors were found to be more problematic. Since visible colors are not ideally correlated with absorptive characteristics at 785 nm, predictions based on thermography are not perfect; however, this approximation gives a useful method for predicting the thermal response of unknown samples to NIR exposure. Additionally, experimental studies evaluated the analysis of flammable organic solvents, propellants, military explosives, mixtures containing military explosives, shock-sensitive explosives, and gunpowders (i.e., smokeless, black, and Pyrodex powders). Safety guidelines for analysis are presented.     

Simultaneous measurement of velocity and length of moving surfaces by a speckle velocimeter with two self-mixing laser diodes

A novel laser speckle velocimeter with two self-mixing laser diodes (SM-LD's) for velocity and length measurements of moving surfaces is reported. The mean frequency of the speckle signal obtained in the measurement system depends on the surface path illuminated by the SM-LD. This behavior of the speckle signal in the SM-LD's is exploited to detect the front and the end edges of a target surface by sampling continuously the number of intensity changes in a speckle signal waveform. Once the edges are determined, the velocity and the length of the surface are calculated easily. The error for length and velocity measurements of a target with a homogeneous rough plane surface of 60-mm length, moving at a velocity of 200 mm/s, can be as low as 2.1% and 1.75%, respectively.     

Compensation of the bias caused by the wall filter on the mean Doppler frequency

In the presence of noise, any wall filter induces a bias on the mean Doppler frequency estimated by the algorithm based on the calculation of the phase of the autocorrelation function at lag 1. In this paper, it is shown that the bias results from the nonzero value of the autocorrelation function of the filtered noise at lag 1. A general method for compensating the bias was then deduced. It consists of a preliminary estimation of the filtered noise contribution and its subtraction from the autocorrelation function of the Doppler signal. The method is independent of the nature of the noise and wall filter. An evaluation of this method on simulated Doppler signals and on measurements from a moving-string phantom showed that effective compensation of the bias was obtained, but at the expense of a higher variance. Taking into account both the bias and the variance, however, it was shown that this method offers an improvement over the noncompensated method. Finally, the performance of this method was demonstrated using in vivo measurements taken from a human aorta.     

A methodology for auto-monitoring of internal contamination by 131I in nuclear medicine workers

The manipulation of 131I in Nuclear Medicine involves significant risks of internal contamination of the staff. In the event of an accidental contamination, or when the Radiological Protection Program includes routine individual monitoring of internal contamination, it is necessary to implement internal dose estimation through in vivo and in vitro bioassay techniques. Due to the huge extension of the Brazilian country, this type of monitoring becomes unfeasible if all measurements have to be performed at the institutes of the CNEN. Thus, if the Nuclear Medicine Centres (NMC) become able to conduct the monitoring of their employees, this skill would be of great significance. The methodology proposed in this work consists in a simple and inexpensive protocol for auto-monitoring the internal contamination by 131I, using the resources available at the NMC. In order to verify the influence of the phantom in the calibration factor for the measurement of 131I in thyroid, it was performed a comparison among a variety of phantoms commercially available, including the Neck-Thyroid Phantom developed in IRD. A protocol for performing in vivo and in vitro measurements by the NMC was established. The applicability of the individual monitoring techniques was also evaluated by comparing the detection limits with the derived limits associated with the annual dose limits for workers.     

Ultrasensitive nonlinear measurements of femtosecond pulses in the telecommunications band by aperiodically poled LiNbO3 waveguides

We have used aperiodically poled lithium niobate waveguides to perform intensity autocorrelation and frequency-resolved optical gating (FROG) measurements for ultraweak femtosecond pulses at 1.5 microm wavelength. The required pulse energies for intensity autocorrelation and FROG are as low as 52 aJ and 124 aJ, respectively. The corresponding sensitivities are 3.2 x 10(-7) mW(2) and 2.7 x 10(-6) mW(2), about 3-5 orders of magnitude better than the previous records. The high nonlinear conversion efficiency is attributed to the long waveguide structure, and the needed broad phase-matching bandwidth is realized by chirping the poling period. We discuss the theory of intensity autocorrelation and FROG measurements in the presence of different phase-matching bandwidths, and we show, for the first time to our knowledge, that the distorted intensity autocorrelation trace due to a delta-like phase-matching spectrum is described by a modified field autocorrelation function. We also report new experimental results comparing autocorrelation traces measured with chirped and unchirped waveguide samples and demonstrating high-quality FROG measurements for cubic phase waveforms generated in a programmable pulse shaper.     

In vivo and noninvasive measurement of a songbird head's optical properties

By assessing the cerebral blood volume and the hemoglobin oxygen saturation level, near-infrared spectroscopy (NIRS) probes brain oxygenation, which reflects cerebral activity. To develop a noninvasive method monitoring the brain of a songbird, we use an original NIRS device, i.e., a white laser coupled with an ultrafast spectrotemporal detector of optical signals without wavelength scanning. We perform in vivo measurements of the absorption coefficient and the reduced scattering coefficient of the caudal nidopallium area of the head of a songbird (the zebra finch).     

In vivo time-resolved reflectance spectroscopy of the human forehead

We present an in vivo broadband spectroscopic characterization of the human forehead. Absorption and scattering properties are measured on five healthy volunteers at five different interfiber distances, using time-resolved diffuse spectroscopy and interpreting data with a model of the diffusion equation for a homogeneous semi-infinite medium. A wavelength-tunable mode-locked laser and time-correlated single-photon counting detection are employed, enabling fully spectroscopic measurements in the range of 700-1000 nm. The results show a large variation in the absorption and scattering properties of the head depending on the subject, whereas intrasubject variations, assessed at different interfiber distances, appear less relevant, particularly for what concerns the absorption coefficient. The high intersubject variability observed indicates that a unique set of optical properties for modeling the human head cannot be used correctly. To better interpret the results of the analysis of in vivo measurements, we performed a set of four-layer model Monte Carlo simulations based on different data sets for the optical properties of the human head, partially derived from the literature. The analysis indicated that, when simulated time-resolved curves are fitted with a homogeneous model for the photon migration, the retrieved absorption and reduced scattering coefficients are much closer to superficial layer values (i.e., scalp and skull) than to deeper layer ones (white and gray matter). In particular, for the shorter interfiber distances, the recovered values can be assumed as a good estimate of the optical properties of the first layer.