Strong Background Interference Research Articles

1-Naphthylhydrazine hydrochloride: A new matrix for the quantification of glucose and homogentisic acid in real samples by MALDI-TOF MS

BackgroundDue to its strong ultraviolet absorption and low background interference in the low molecular weight region, 1-naphthylhydrazine hydrochloride (NHHC) has been selected as an ideal matrix to detect small molecules by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). ResultsThis salt-tolerant matrix could be applied for the high sensitive glucose analysis with an ultra-low limit of detection of 1amol, and the [glucose+Cl]− signal can be found even in saturated NaCl solution. With NHHC, glucose in serum and the biomarker homogentisic acid in urine were successfully determined by MALDI-TOF MS in negative ion mode. ConclusionThis NHHC-assisted laser desorption/ionization MS method provided a fast and high through-put approach for the small molecule analysis in complex samples, and have a great potential in clinical applications.

Compact Millimeter-Wave Sensor for Remote Monitoring of Vital Signs

A compact millimeter-wave (MMW) sensor has been developed for remote monitoring of human vital signs (heart and respiration rate). The low-power homodyne transceiver operating at 94 GHz was assembled by using solid-state active and passive block-type components and can be battery operated. A description of the MMW system front end and the back-end acquisition hardware and software is presented. Representative test case results on the application of various signal processing and data analysis algorithms developed to extract faint physiological signals of interest in presence of strong background interference are provided. Although the laboratory experiments so far have been limited to standoff distances of up to 15 m, the upper limit of the detection range is expected to be higher. In comparison with its microwave counterparts, the MMW system described here provides higher directivity, increased sensitivity, and longer detection range for measuring subtle mechanical displacements associated with heart and respiration functions. The system may be adapted for use in a wide range of standoff sensing applications including for patient health care, structural health monitoring, nondestructive testing, biometric sensing, and remote vibrometry in general.

太阳对成像型天基激光告警系统的影响

In view of the problem of solar radiation in the imaging space-based laser warning system,the effects of sunlight on the infrared detector of warning system were studied by theoretical analysis and numerical calculation.On the basis of analysis of the different spatial relationship of sun and detector,the influences of direct sunlight and sunlight reflected by earth to the signal to noise ratio(SNR) of infrared image,laser threat detection,the detector safety were investigated respectively.The results show that the sunlight is the mainly background radiation to space-based laser warning system.The sunlight reflected by earth is the main imaging background light of system′s near infrared detector,and the maximum energy density of reflected sunlight exposuring the CCD is 0.97 mJ/cm2.In the reflected sunlight background,the SNR of attack laser image exceeds 103,for the beacon laser is always below 1.While the reflected sunlight has no effect on attack laser detection,but it is strong background interference to the beacon laser detection.The sunlight direct exposure detector is unavoidable to the warning system.As the maximum energy density of the sun imaging spot is about 20 W/cm2,it will lead to the pixel of CCD saturation or even damaged.Since the imaging spot of sun is similar to the laser,direct sunlight will cause serious false alarm.

Non-destructive estimation of wheat leaf chlorophyll content from hyperspectral measurements through analytical model inversion

Optimizing nitrogen (N) fertilization in crop production by in-season measurements of crop N status may improve fertilizer N use efficiency. Hyperspectral measurements may be used to assess crop N status indirectly by estimating leaf and canopy chlorophyll content. This study evaluated the ability of the PROSAIL canopy-level reflectance model to predict leaf chlorophyll content of spring wheat (Triticum aestivum L.) during the growth stages between pre-tillering (Zadoks Growth Stage (ZGS 15)) to booting (ZGS50). Spring wheat was grown under different N fertility rates (0–200 kg N ha−1) in 2002. Canopy reflectance, leaf chlorophyll content, N content and leaf area index (LAI) values were measured. There was a weakly significant trend for the PROSAIL model to over-estimate LAI and under-estimate leaf chlorophyll content. To compensate for this interdependency by the model, a canopy chlorophyll content parameter (the product of leaf chlorophyll content and LAI) was calculated. The estimation accuracy for canopy chlorophyll content was generally low earlier in the growing season. This failure of the PROSAIL model to estimate leaf and canopy variables could be attributed to model sensitivity to canopy architecture. Earlier in the growing season, full canopy closure was not yet achieved, resulting in a non-homogenous canopy and strong soil background interference. The canopy chlorophyll content parameter was predicted more accurately than leaf chlorophyll content alone at booting (ZGS 45). A strong relationship between canopy chlorophyll content and canopy N content at ZGS 45 indicates that the PROSAIL model may be used as a tool to predict wheat N status from canopy reflectance measurements at booting or later.

Weak beacon detection for air-to-ground optical wireless link establishment

In an air-to-ground free-space optical communication system, strong background interference seriously affects the beacon detection, which makes it difficult to establish the optical link. In this paper, we propose a correlation beacon detection scheme under strong background interference conditions. As opposed to traditional beacon detection schemes, the beacon is modulated by an m-sequence at the transmitting terminal with a digital differential matched filter (DDMF) array introduced at the receiving end to detect the modulated beacon. This scheme is capable of suppressing both strong interference and noise by correlation reception of the received image sequence. In addition, the DDMF array enables each pixel of the image sensor to have its own DDMF of the same structure to process its received image sequence in parallel, thus it makes fast beacon detection possible. Theoretical analysis and an outdoor experiment have been demonstrated and show that the proposed scheme can realize fast and effective beacon detection under strong background interference conditions. Consequently, the required beacon transmission power can also be reduced dramatically.