Phase retrieval from single interferogram without carrier using Lissajous ellipse fitting technology.

Phase extraction from single interferogram is of high significance and increasingly interest in optical metrology. In this contribute we propose an advanced Pixel-level Lissajous Ellipse Fitting (APLEF) method to extract the phase from single interferogram without carrier. At each pixel, a Lissajous figure is created by plotting N against D, where N and D are subtractions and additions of intensities of adjacent pixels in a small window. The so created Lissajous figure is already in phase quadrature because of the subtraction and addition process, and the Lissajous Figure is forced to be closed by taking the opposite values of N and D, i.e. -N and -D into account. The closed and in phase quadrature Lissajous Figure is the key point for APLEF to demodulate the single inteferogram without carrier in theoretically. The simulation shows its higher accuracy than existed SPT and Garbusi's method and the experiments finally corroborate its effectiveness.

Influence of Spatial Inhomogeneity of Detector Temporal Responses on the Spectral Fidelity in Continuous Wave Cavity Ringdown Spectroscopy.

Due to their advantages of having a wide bandwidth, low cost, and being easy to obtain, traditional photodetectors (PDs) are being widely applied in measurements of transient signals. The spatial inhomogeneity of such PD temporal responses was measured directly to account for the PD spatial effect of decay rate due to poor alignment in continuous wave cavity ringdown spectroscopy (CW-CRDS) experiments. Based on the measurements of three PDs (i.e., model 1611 (Newport), model 1811 (Newport), and model PDA10CF-EC (Thorlabs)), all the temporal responses followed a tendency of declining first and then rising, and steady platforms existed for the last two PDs. Moreover, as we expected, the closer the PD center was, the faster the response. On the other hand, the initial shut-off amplitude generally reached a larger value for a faster temporal response. As a result, the spatial effect can strongly influence the spectral line shape and value, which will introduce more errors into the precise measurements of spectral parameters using the CRDS technique if this effect is not considered. The defined effective detection area (EDA) of the PDs, which was close to the active area given by manufacturers, was the key parameter that should be paid more attention by researchers. Therefore, the PD should be aligned perfectly to make sure that the EDA covers the laser spot completely.

A novel methodology to directly pre-determine the relative wavelength response of DFB laser in wavelength modulation spectroscopy.

A novel methodology to directly pre-determine the relative wavelength response (RWR) of a DFB laser, in terms of a combined current linearly scanned wavelength response and current modulated wavelength response (CMWR), in wavelength modulation spectroscopy (WMS) is presented. It is shown that the assessed RWR can be used to mimic the measured response with standard deviation of discriminations that are below 3.4 × 10-3cm-1 under a variety of conditions. It is also shown that its performance supersedes two commonly used assessment models of the CMWR but is slightly worse than that of the third model, however with the benefit of solely using a single fitting parameter (the concentration) instead of more. When the novel method is applied to the assessment of CO2 concentration in a Herriot-type multipass cell by using the technique of calibration-free WMS, the results show that there is virtually no difference compared to that by use of the best of the other methods. It is concluded that the novel method is more robust and simplifies the retrieval process of gas concentration.

Precise phase demodulation of single carrier-frequency interferogram by pixel-level Lissajous figure and ellipse fitting.

Phase demodulation from a single carrier-frequency fringe pattern is becoming increasingly important particularly in areas of optical metrology such as dynamic interferometry, deflectometry and profilometry. The Fourier transform (FT) method and the spatial-carrier phase-shifting technique (SCPS) are two popular and well-established approaches to demodulation. However FT has the drawback of significant edge errors because of the Gibbs effect, whilst detuning errors for the local phase shift occur when SCPS is applied. A novel demodulation method based on pixel-level Lissajous figure and ellipse fitting (PLEF) is presented in this paper. Local demodulation in the spatial domain makes PLEF more flexible than the FT method, without spectral leakage. Based on a more adaptable approach, account is taken of variations in illumination and phase distribution over a few neighboring pixels. The mathematic demodulation model is of interest and has been demonstrated via simulation. Theoretical phase extraction error is as low as 10-4 rad. Experiments further corroborate the effectiveness of the proposed method. In conclusion, various influencing factors, e.g. variations of background/modulation, phase amplitude, carrier frequency, additive noise that may affect the precision of PLEF are discussed in detail.

[Determination of anaprazole in human plasma by LC-MS/MS in pharmacokinetic study].

Anaprazole is a proton pump inhibitor clinically used for curing peptic ulcer. A rapid, sensitive and convenient LC-MS/MS method was first established for the determination of anaprazole in human plasma. d(3), (13)C-anaprazole was used as internal standard (IS). After extraction from human plasma by protein precipitation with acetonitrile, all components were separated on an Extend C(18) column (100 mm × 4.6 mm, 3.5 µm). The assay was linear over the concentration range of 5.00-3 000 ng·m L(-1) (r(2) > 0.995). The method was successfully applied to a pharmacokinetic study of 40 mg anaprazole enteric-coated tablets in 14 Chinese healthy volunteers under fasting or high fat diet conditions. C(max) was (1 020 ± 435) ng·m L(-1) and AUC(0-t) was (2 370 ±754) h·ng·m L(-1) under fasting condition. And C(max) was (538 ± 395) ng·m L(-1) and AUC(0-t) was (1 610 ± 650) h·ng·m L(-1) under high fat diet condition. The plasma results suggest that the exposure of anaprazole is reduced by the high fat diet.

Phase shifting interferometry from two normalized interferograms with random tilt phase-shift.

We propose a novel phase shifting interferometry from two normalized interferograms with random tilt phase-shift. The determination of tilt phase-shift is performed by extracting the tilted phase-shift plane from the phase difference of two normalized interferograms, and with the calculated tilt phase-shift value the phase distribution can be retrieved from the two normalized frames. By analyzing the distribution of phase difference and utilizing special points fitting method, the tilted phase-shift plane is extracted in three different cases, which relate to different magnitudes of tilts. Proposed method has been applied to simulations and experiments successfully and the satisfactory results manifest that proposed method is of high accuracy and high speed compared with the three step iterative method. Additionally, both open and closed fringe can be analyzed with proposed method. What's more, it cannot only eliminate the small tilt-shift error caused by slight vibration in phase-shifting interferometry, but also detect the large tilt phase-shift in phase-tilting interferometry. Thus, it will relaxes the requirements on the accuracy of phase shifter, and the costly phase shifter may even be useless by applying proposed method in high amplitude vibrated circumstance to achieve high-precision analysis.

Correction of phase extraction error in phase-shifting interferometry based on Lissajous figure and ellipse fitting technology.

The accuracy of phase-shifting interferometers (PSI) is crippled by nonlinearity of the phase shifter and instability of the environment such as vibration and air turbulence. A general algorithm, utilizing Lissajous figures and ellipse fitting, of correcting the phase extraction error in the phase shifting interferometry is described in this paper. By plotting N against D, where N and D represent the numerator and denominator terms of the phase extraction function (i.e. an arctangent function) respectively, a Lissajous ellipse is created. Once the parameters of the ellipse are determined by ellipse fitting, one can transform the ellipse to a unit circle (ETC). Through this process the phase extraction error caused by random phase shift errors can be corrected successfully. Proposed method is non-iterated, adapts to all phase shifting algorithms (PSAs), and has high accuracy. Some factors that may affect the performance of proposed method are discussed in numerical simulations. Optical experiments are implemented to validate the effectiveness of proposed algorithm.

Influence study of solving correction forces caused by fitting errors for thin meniscus mirror.

The actuator influence functions of a thin meniscus mirror can be expanded in Zernike polynomials. And the correctness of influence functions has a great effect on solving the correction forces. The Zernike coefficients are applied as parameters in the all-floating support system. We analyze the main interferential factors when different deformation modes are corrected. The influence caused by fitting errors is studied in this paper. A preferable result can be obtained after eliminating the interferential factors. The method can obtain useful correction forces. Comparing the peak-to-valley and root mean square values among the results calculated by different accuracy influence functions, we find that there is a limited convergence property when the accuracy increases.

Theoretical and experimental study of a catadioptric compensator for an aspheric surface.

A new type of catadioptric compensator is established. The tolerance values of lens spacing, lens thickness, and tilt in mounting are about three times higher than that of the Offner compensator. They overcome the localization of the Offner compensator, improve the test validity, and reduce the test risk of system detection by cross-validation with existing means. The performance of the catadioptric compensator is verified in experiments and theoretically.

Microwave-assisted synthesis of N,N'-diaryl cyanoguanidines.

[reaction: see text] A mild, efficient, and high-yielding method for the synthesis of N,N'-diaryl cyanoguanidines from their corresponding thioureas under microwave-assisted conditions is described. A series of cyanoguanidines were synthesized containing both electron-donating and electron-withdrawing substituents. The reactions were facilitated by the use of polar solvents along with moderate temperatures.

Synthesis and neurotrophic activity of nonimmunosuppressant cyclosporin A derivatives.

In order to exploit cyclophilin as a potential target for neurological drug design, we demonstrate in this presentation that several nonimmunosuppressant analogues of cyclosporin A, modified at the various positions in the 'effector' domain, are equipotent nerve growth agents compared to cyclosporin A. Our results suggest that neurotrophic activity of cyclosporin A and its derivatives resides in the binding domain, and binding to cyclophilin and/or inhibiting rotamase activity may be a necessity for neurotrophic effects of cyclophilin ligands.

Synthesis, molecular modeling and biological evaluation of aza-proline and aza-pipecolic derivatives as FKBP12 ligands and their in vivo neuroprotective effects.

Nonimmunosuppressant ligands, exemplified by GPI 1046 (1), for the peptidyl-prolyl isomerase FKBP12 have been found to unexpectedly possess powerful neuroprotective and neuroregenerative effects in vitro and in vivo. We have extensively explored the therapeutic utility of FKBP12 ligands based on analogues of proline and pipecolic acid. As part of our ongoing program to explore novel structural classes of FKBP12 ligands, we herein wish to report a new class of FKBP12 ligands containing aza-proline and aza-pipecolic acid analogues. Details of the synthetic studies, together with biological activity will be presented.

Synthesis and evaluation of chiral bicyclic proline FKBP12 ligands.

As part of our ongoing program to explore novel structural classes of FKBP12 ligands, we herein wish to report a new class of FKBP12 ligands containing chiral bicyclic proline analogues. Details of the synthetic routes, together with preliminary biological activity, will be presented.

Synthesis and biological evaluation of non-peptidic cyclophilin ligands.

Peptidylprolyl isomerase cyclophilins play critical roles in a variety of biological processes. Recent findings that cyclophilins are present at high levels in the CNS and that cyclosporin A may possess neuroprotective/neurotrophic effects have prompted us to search for nonimmunosuppressant small molecule cyclophilin ligands. To this end, we report the lead identification through "virtual screening" and the synthesis of our first series of non-peptidic cyclophilin ligands, along with the preliminary biological results.

Direct synthesis of guanidines using di(imidazole-1-yl)methanimine.

A direct synthetic approach to guanidine compounds is reported here using di(imidazole-1-yl)methanimine and di(imidazole-1-yl)cyanomethanimine as guanylating reagents.

Synthesis of N-glyoxyl prolyl and pipecolyl amides and thioesters and evaluation of their in vitro and in vivo nerve regenerative effects.

The recent discovery that small molecule ligands for the peptidyl-prolyl isomerase (PPIase) FKBP12 possess powerful neuroprotective and neuroregenerative properties in vitro and in vivo suggests therapeutic utility for such compounds in neurodegenerative disease. The neurotrophic effects of these compounds are independent of the immunosuppressive pathways by which drugs such as FK506 and rapamycin operate. Previous work by ourselves and other groups exploring the structure-activity relationships (SAR) of small molecules that mimic only the FKBP binding domain portion of FK506 has focused on esters of proline and pipecolic acid. We have explored amide and thioester analogues of these earlier structures and found that they too are extremely potent in promoting recovery of lesioned dopaminergic pathways in a mouse model of Parkinson's disease. Several compounds were shown to be highly effective upon oral administration after lesioning of the dopaminergic pathway, providing further evidence of the potential clinical utility of a variety of structural classes of FKBP12 ligands.

Synthesis of ketone analogues of prolyl and pipecolyl ester FKBP12 ligands.

The recently discovered small-molecule ligands for the peptidyl and prolyl isomerases (PPIase) of FKBP12 have been shown to possess powerful neuroprotective and neuroregenerative effects. Ketone analogues of the prolyl and pipecolyl esters, which mimic only the FKBP binding domain portion of FK506, are proposed and an efficient synthetic strategy is presented in this report, along with the preliminary results of in vitro and in vivo biological studies.

Use of parallel-synthesis combinatorial libraries for rapid identification of potent FKBP12 inhibitors.

Using simple, inexpensive equipment, we have used solution-phase parallel synthesis to rapidly prepare hundreds of sulfonamide- and urea-containing FKBP inhibitors, resulting in rapid identification of extremely potent compounds in these series.