[Influence of the dentin smear layer trait on the bond strength of the self-adhesive resin cements].

OBJECTIVE: This work aimed to evaluate the influence of smear layer on the bonding effectiveness and durability of the self-adhesive resin cements to dentin. METHODS: A total of 48 fresh caries-free third molars with exposed dentin surface were divided into two groups. The dentin surfaces were treated using a standard grit diamond bur (group A) or further polished using a fine grit diamond bur (group B) and then bonded with either of the two self-adhesive resin cements, namely, Clearfil SA Cement (CSA, Kuraray) and Multilink Speed (MS, Ivoclar Vivadent). After 24 h or 2-year water storage, a microtensile bond strength test was performed. RESULTS: In group A, the dentin surface was rough, the smear layer was thick, and the dentin tubule orifice detritus showed low embolism value. In group B, the dentin surface roughness decreased, the embolism proportion increased, and the smear layer became thin. The initial bonding strengths of CSA and MS in group A were significantly lower than those in group B (P<0.05). The bonding strengths of CSA and MS significantly decreased after two years of water storage (P<0.05). For CSA, the bond strength of group B was significantly lower than that of group A (P<0.05). For MS, the differences in the bonding strength between groups A and B were insignificant (P>0.05). CONCLUSIONS: The properties of the smear layer and the types of self-adhesive resin cement used affected the bond strength and durability.

Consensus scoring model for the molecular docking study of mTOR kinase inhibitor.

The discovery of mammalian target of rapamycin (mTOR) kinase inhibitors has always been a research hotspot of antitumor drugs. Consensus scoring used in the docking study of mTOR kinase inhibitors usually improves hit rate of virtual screening. Herein, we attempt to build a series of consensus scoring models based on a set of the common scoring functions. In this paper, twenty-five kinds of mTOR inhibitors (16 clinical candidate compounds and 9 promising preclinical compounds) are carefully collected, and selected for the molecular docking study used by the Glide docking programs within the standard precise (SP) mode. The predicted poses of these ligands are saved, and revaluated by twenty-six available scoring functions, respectively. Subsequently, consensus scoring models are trained based on the obtained rescoring results by the partial least squares (PLS) method, and validated by Leave-one-out (LOO) method. In addition, three kinds of ligand efficiency indices (BEI, SEI, and LLE) instead of pIC50 as the activity could greatly improve the statistical quality of build models. Two best calculated models 10 and 22 using the same BEI indice have following statistical parameters, respectively: for model 10, training set R2=0.767, Q2=0.647, RMSE=0.024, and for test set R2=0.932, RMSE=0.026; for model 22, raining set R2=0.790, Q2=0.627, RMSE=0.023, and for test set R2=0.955, RMSE=0.020. These two consensus scoring model would be used for the docking virtual screening of novel mTOR inhibitors.

A furoviral replicase recruits host HSP70 to membranes for viral RNA replication.

Many host factors have been identified to be involved in viral infection. However, although furoviruses cause important diseases of cereals worldwide, no host factors have yet been identified that interact with furoviral genes or participate in the viral infection cycle. In this study, both TaHSP70 and NbHSP70 were up-regulated in Chinese wheat mosaic furovirus (CWMV)-infected plants. Their overexpression and inhibition were correlated with the accumulation of viral genomic RNAs, suggesting that the HSP70 genes could be necessary for CWMV infection. The subcellular distributions of TaHSP70 and NbHSP70 were significantly affected by CWMV infection or by infiltration of RNA1 alone. Further assays showed that the viral replicase encoded by CWMV RNA1 interacts with both TaHSP70 and NbHSP70 in vivo and vitro and that its region aa167-333 was responsible for the interaction. Subcellular assays showed that the viral replicase could recruit both TaHSP70 and NbHSP70 from the cytoplasm or nucleus to the granular aggregations or inclusion-like structures on the intracellular membrane system, suggesting that both HSP70s may be recruited into the viral replication complex (VRC) to promote furoviral replication. This is the first host factor identified to be involved in furoviral infection, which extends the list and functional scope of HSP70 chaperones.

[Polymerization of flowable composite core materials irradiated by super-high intensity light with short time].

PURPOSE: To evaluate the polymerization of dual-cured flowable composite core irradiated by super-high intensity light with short time. METHODS: The light-proof silicon rubber cuboid mold with one end open was syringed and filled by dual-cured flowable resin composite core, then the open end of mold was irradiated directly by a light unit at 1000 mW/cm(2) ×10, ×20 s; or at 3200 mW/cm(2) × 3, ×6 s. The specimens were stored in the light-proof box. After irradiation for 1 h and 24 h, Knoop microhardness was measured along the vertical surfaces of specimens from 1mm to 10 mm depth at 1 mm interval. The data was analyzed by one-way ANOVA with SPSS 16.0 software package. RESULTS: 3200 mW/cm(2) ×3 s light irradiation did not initiate light curing of the specimens. The other three light irradiations could make specimens obtaining higher microhardness than that by pure chemical cure; however, the depth of specimens affected by light irradiation was limited. Within the area affected by light, the microhardness of specimens could be improved by increasing the light irradiation time; after irradiation for 24 h, the microhardness of specimens had no difference between 3200 mW/cm(2) ×6 s and 1000 mW/cm(2) ×20 s light irradiation. CONCLUSIONS: 3200 mW/cm(2) light intensity should be used for irradiation at least for 6 s, which could initiate light curing of flowable composite core to sufficient polymerization.

[Influence of light irradiation mode on microhardness of dual cured resin cements].

PURPOSE: To investigate the influence of different light irradiation modes on microhardness of dual-curing resin cements. METHODS: The cylindrical specimens (1 mm in thickness and 7.5 mm in diameter) of 5 self-adhesive resin cements (Biscem, Clearfil SA Cement, G-CEM LinkAce, Maxcem Elite and RelyX U100) and 2 universal resin cements(DUOLINK and Nexus 3) were irradiated respectively by a continuous mode (light-curing for 20 s) and a delayed mode (light-curing 5 s + auto-curing 60 s + light-curing 20 s), and then they were placed dry in a light-proof thermostat at 37 degrees centigrade. Surface microhardness of specimen was detected at 0.5, 24 h and 4 weeks post-irradiation. After that period of time, all specimens were soaked in ethanol for 24 h, their hardness were detected again, and the percentage of hardness reduction after soaking were calculated. Data were analyzed by SPSS 16.0 software package. RESULTS: The hardness of all resin cements under both irradiation modes increased mainly within 24 h post-irradiation. The irradiation mode did not affect the hardness of all resin cements 4 weeks after irradiation significantly (P>0.05), except for Biscem. However, after ethanol softening, 5 self-adhesive resin cements cured by the continuous mode had higher hardness reduction percentage than that cured by delayed mode (P<0.05); while hardness reduction percentage of 2 universal resin cements had no significant difference between continuous and delayed cure modes (P>0.05). CONCLUSIONS: The self-adhesive resin cements cured by delayed mode had better anti-softening ability. Supported by Nanjing Medical Science and Technology Development Fund (ZKX09035), Nanjing Science and Technology Development Fund (201001083) and Nanjing Medical Science and Technology Development Fund (YKK10125).

Genetic structure and demographic history reveal migration of the diamondback moth Plutella xylostella (Lepidoptera: Plutellidae) from the southern to northern regions of China.

The diamondback moth Plutella xylostella (Linnaeus) (Lepidoptera: Plutellidae) is one of the most destructive insect pests of cruciferous plants worldwide. Biological, ecological and genetic studies have indicated that this moth is migratory in many regions around the world. Although outbreaks of this pest occur annually in China and cause heavy damage, little is known concerning its migration. To better understand its migration pattern, we investigated the population genetic structure and demographic history of the diamondback moth by analyzing 27 geographical populations across China using four mitochondrial genes and nine microsatellite loci. The results showed that high haplotype diversity and low nucleotide diversity occurred in the diamondback moth populations, a finding that is typical for migratory species. No genetic differentiation among all populations and no correlation between genetic and geographical distance were found. However, pairwise analysis of the mitochondrial genes has indicated that populations from the southern region were more differentiated than those from the northern region. Gene flow analysis revealed that the effective number of migrants per generation into populations of the northern region is very high, whereas that into populations of the southern region is quite low. Neutrality testing, mismatch distribution and Bayesian Skyline Plot analyses based on mitochondrial genes all revealed that deviation from Hardy-Weinberg equilibrium and sudden expansion of the effective population size were present in populations from the northern region but not in those from the southern region. In conclusion, all our analyses strongly demonstrated that the diamondback moth migrates within China from the southern to northern regions with rare effective migration in the reverse direction. Our research provides a successful example of using population genetic approaches to resolve the seasonal migration of insects.

[Effect of curing modes on knoop hardness and microtensile bond strength of two dentin adhesives].

OBJECTIVE: To evaluated the effect of curing modes and light-cure times on knoop hardness (KH) and microtensile bond strength (µTBS) of dentin adhesives in vitro. METHODS: Twenty molars were made into 80 dentin slices (about 1 mm thick). The dentin slices were prepared with an etch&rinse adhesive A (ONE-STEP PLUS) and a self-etch adhesive B (Clearfil SE Bond), and light-cured respectively under fast mode, i.e.1250 mW/cm(2) light intensity for 10 s, 15 s, 20 s, and ramp mode (soft start curing mode), i.e.initial 0 mW/cm(2) gradually increasing to 1250 mW/cm(2) in first 10 s, then steady for the next 10 s. The prepared dentin slices were kept in dark dry room for 24 h at 37°C, and KH were tested. The other 40 molars were flattened to expose coronal dentin, prepared with adhesives as above. Then the prepared teeth were restored with resin composites incrementally and cured under fast mode. The restored teeth were stored in water for 24 h at 37°C, and slowly sectioned to obtain multiple bonded beams. After 7 d water-storage, the samples received microtensile bond test, and the failure models of beams were observed under a stereomicroscope. Data were analyzed by ANOVA and LSD test (α = 0.05). RESULTS: No statistical difference in KH [(28.20 ± 5.36), (29.13 ± 5.60), (28.13 ± 4.40), (27.06 ± 3.77) MPa] and µTBS [(22.30 ± 5.07), (22.73 ± 6.59), (26.32 ± 6.17), (25.67 ± 4.31) MPa] of adhesive A were found between four curing conditions (fast mode for 10 s, 15 s, 20 s and ramp mode for 20 s) (P > 0.05). In adhesive B, KH of Fast 20 s [(28.23 ± 3.67) MPa] were significantly higher than those of Fast 10 s [(14.15 ± 2.24) MPa] and Fast 15 s [(17.63 ± 2.17) MPa] (P < 0.05). The µTBS of Fast 20 s [(42.52 ± 3.59) MPa] were significantly higher than those of Fast 10 s [(24.21 ± 3.60) MPa], Fast 15 s [(22.25 ± 4.16) MPa] and Ramp 20 s [(31.12 ± 5.40) MPa] (P < 0.05). In Fast 20 s and Ramp 20 s modes, there were no statistical difference in KH of adhesive A and B, while µTBS of adhesive B were higher than that of adhesive A(P < 0.05). CONCLUSIONS: As for different type dentin adhesives, the appropriate curing time in fast mode is different, and ramp mode (soft start curing mode) has no advantage over fast mode.

[Effects of sandblasting on surface character and resin bond of zirconia ceramic].

OBJECTIVE: To evaluate the effect of Al2O3 particles sandblasting on the surface roughness, element composition and resin bond durability of zirconia ceramic. METHODS: Sixty 2.5 mm thick computer aided design and computer aided manufacture (CAD/CAM) zirconia ceramic (Vita Inceram YZ) plates were fired, polished and cleaned. Half of polished ceramic plates was sandblasted with 50 µm alumina particles at 0.3 MPa for 20 s. The surface roughness of polished and sandblasted ceramic surface were measured by 3D-laser scanning microscope, and the surface element weight and atom ratio of the ceramic surface were measured by energy disperse spectroscopy (EDS). Then polished and sandblasted ceramic plates were randomized into six groups. In Group 1 and 2 the polished and sandblasted ceramic plates were bonded irrespectively with conventional resin cement (DUOLINK). In Group 3 and 4 the ceramic plates were bonded with resin cement containing MDP (Panavia F), In Group 5 and 6 the specimens were pretreated with silane coupler acitivated by MDP (Clearfil Ceramic Primer), then bond with Panavia F. The specimens of each test group were then divided into two subgroups, and to received shear test after 0 and 10 000 time thermal cycle. The data was analyzed by one-way ANOVA and independent t test. RESULTS: Comparing with polishing, sandblasting reduced the oxygen atom and weight ratio of zirconia ceramic surface (P < 0.001), and increased the zirconium atom and weight ratio (P < 0.001), meanwhile increased the surface roughness (P < 0.001). The bond strength between ceramic plates and resin cement in all test groups decreased after thermocycling (P < 0.001). All specimen in test group 1 and 2 lost bond, and the bond strength of test group 3 and 5 [(0.59 ± 0.17), (0.89 ± 0.84) MPa] were significantly lower than that of test group 4 and 6 [(14.63 ± 3.03), (16.64 ± 1.90) MPa], and the bond strength of test group 6 were significanlty higher than that of test group 4. CONCLUSIONS: Sandblasting improves durability of bond between zirconia ceramic and resin cement containing MDP, not only by increasing the roughness and area of ceramic surface, but also by changing its surface element composition to obtain more chemical bond.

[The comparative research on resin bond strength and durability of two machinable glass ceramic].

OBJECTIVE: To evaluate the effect of different silane couplers on bond strength and durability of two machinable glass ceramics to resin cement. METHODS: Two machinable glass ceramics (A and B) were silanized by three silane couplers (A, B, C), and were bonded with a resin cement (G-CEM) to form micro-shear test specimens of six groups. The specimens of each group were subdivided into two subgroups, and their micro-shear bond strength was measured before and after 10000 thermal cycles. Bond strength data were analyzed by two-way ANOVA. RESULTS: Before thermal cycles, the bond strength of ceramic A treated by silane coupler A was lower than that of ceramic B (P = 0.002). The bond strength of ceramic A treated by silane coupler C was significantly higher than that treated by silane coupler A and B (P = 0.014, P = 0.019). 10 000 thermal cycles obviously decreased the bond strength of all groups except the group of ceramic A treated by silane coupler B, and no significant difference was found between three silane coupler with either of two ceramic. However the bond strength of ceramic B treated by silane coupler B and C was significantly higher than that of ceramic A (P = 0.003, P = 0.027). CONCLUSION: As well as the types of silane coupler, the type of ceramic could affect their bond strength and durability to resin cement.

[Research on the resin bond durability of glass-infiltrated alumina ceramic].

OBJECTIVE: To analyze the effect of different silane coupling agents on the resin bond durability of glass-infiltrated alumina ceramic. Methods A glass-infiltrated alumina ceramic was silanized or not by three silane coupling agents. The treated ceramic surfaces were bonded with two resin cements. Their micro-bond strength were measured after 0, 30,000 thermal cycles. RESULTS: Before thermal cycling, resin cement A had lowest bond strength to ceramic, and ceramic treated by silane coupling agent A with two cements had lower bond strength than those treated by silane coupling agent B and C. After thermal cycling, cement A had no bond strength with no treated ceramic, only ceramic treated by silane coupling agent A with two cements had more than 5 MPa bond strength. CONCLUSION: The glass-infiltrated alumina cermaic treated by the silane coupling agent activated by 10-methacryloyloxydecyl-dihydrogen phosphate could obtain better bond durability with different type of resin cements.

[Effect of hydrofluoric acid etching time on the resin bond durability of glass ceramic].

OBJECTIVE: To analyze the effect of hydrofluoric acid (HFA) etching time on the resin bond durability of glass ceramic. METHODS: Three groups of samples of machinable glass ceramic (ProCAD) were etched by 4.8% HFA for 0, 30 and 60 s respectively. The roughness parameters (Ra, Sm, S) and surface area of the samples, were measured with a 3D-laser scanning microscope. Then the ceramic surfaces were bonded with four resin cements (silane coupler/resin cement), which were Monobond S/Variolink II, Clearfil Ceramic Primer/Clearfil Esthetic Cement, GC Ceramic Primer/Linkmax HV, and Porcelain Liner M/SuperBond. The micro-bond strengths between the ceramic and the resin were tested at baseline and after the samples had been treated in 30000 thermal cycles. RESULTS: The Ra [(3.89+/-1.94), (12.53+/-0.80), (13.58+/-1.10) microm] and surface area [(7.81+/-2.96), (30.18+/-2.05), (34.16+/-1.97) mm2] of ceramic increased with the increase of HFA etching time. The thermal cycling test reduced the bond strength of all test groups. The bond strength of Monobond S/Variolink II group [(3.59+/-3.51), (16.18+/-2.62), (20.33+/-2.45) MPa] and Clearfil Ceramic Primer/Clearfil Esthetic Cement group [(4.74+/-2.08), (7.77+/-1.55), (13.45+/-3.75) MPa] increased with the increase of HFA etching time; 30 s HFA etching group of Porcelain Liner M/SuperBond had higher bond strength [(22.00+/-1.64) MPa] than its 0 s HFA etching group [(12.96+/-4.17) MPa], and no significant difference was found between the 30 s and 60 s HFA etching groups of Porcelain Liner M/SuperBond [(20.42+/-3.01) MPa]. HFA etching time had no effect on the bond strength of GC Ceramic Primer/Linkmax HV. CONCLUSIONS: HFA etching can improve the resin bond durability of glass ceramic, and the etching time is not only related to the change of ceramic surface roughness and area, but also to the characteristics of resins.

[Bond durability of self-adhesive resin cement to glass ceramic].

OBJECTIVE: To evaluate the bond durability of glass ceramic to self-adhesive and conventional resin cements. METHODS: Maximum water sorption and solubility of two resin cements (A: self-adhesive type, G-CEM; B: conventional type, Linkmax HV) were measured during 6 week water storage. And their surface Knoop hardness number was measured at 0.5, 24 h and 6 week after irradiation. Sixty-four glass ceramic samples were or were not silanized with one of the three silane coupling agents (A: Monobond S; B: Clearfil Ceramic Primer; C: GC Ceramic Primer), and then cemented with two resin cements. The micro-bond strength between the two cements and glass ceramic were measured at baseline and after 30 000 thermal cycle. RESULTS: Cement A had higher water sorption [(79.62 +/- 5.63) microg/mm³] and solubility [(4.78 +/- 3.33) microg/mm³] than cement B[(35.03 +/- 3.33) microg/mm³, (0.00 +/- 0.00) microg/mm³]. Cement A and B could achieve maximal surface hardness at 24 h after irradiation, and this was maintained during 6 week water storage. After 30 000 thermal cycle, the micro-bond strength between unsilanized glass ceramic and cement A or B was (0.00 +/- 0.00) MPa, and those between cement A and silanized glass ceramic with silane coupling agent A, B and C, were (2.86 +/- 3.25), (12.75 +/- 1.55) and (11.98 +/- 2.35) MPa respectively [for cement B, the data was (5.15 +/- 5.20), (10.94 +/- 3.30) and (14.18 +/- 3.13) MPa]. No significant diffrence was found between the micro-bond strength of cement A and that of cement B with glass ceramic. CONCLUSIONS: Self-adhesive resin cement can achieve similar bond durability to glass ceramic as conventional resin cement does.

[Effect of irradiation intensity on dual-cured resin/ceramic bond durability].

OBJECTIVE: To evaluate the effect of light irradiation intensity on bond durability of dual-cured resin luting agents to silanized ceramics. METHODS: Linkmax HV (LMHV), Nexus 2 (NX2), Variolink II HV (VL II HV) as dual-cured resin luting agents were bonded to silanized GN-I glass ceramics, and irradiated by 800, 310 and 80 mW x cm(-2) light intensity to form micro-shear test specimens. After 1, 90 d water storage, micro-shear bond strength of silanized resin/ceramic luting agent were measured. Data of each resin luting agent were analyzed by one-way ANOVA. RESULTS: 90 d water storage decreased significantly the bond strength of all test groups, and the weak of irradiation intensity did not deteriorate this reduction of bond strength of luting resin/cermaic, oppositely in which LMHV irradiated by 310 mW x cm(-2) light intensity and NX2 irradiated by 80 mW x cm(-2) showed the higher bond strength than that irradiated by 800 mW x cm(-2). CONCLUSION: The weak of irradiation intensity does not affect the bond durability of dual-cured resin luting agents to silanized ceramics.

Characterization of midgut trypsinogen-like cDNA and enzymatic activity in Plutella xylostella parasitized by Cotesia vestalis or Diadegma semiclausum.

Protein digestion in insects is a result of the action of a complex of proteinases present in the midgut. In this report we describe the cloning and sequencing of a trypsin cDNA from larvae of the lepidopteran herbivore Plutella xylostella. We investigated the expression of this gene and enzymatic activity of its translation product with N-a-benzoyl-l-arginine p-nitroanilide (BApNA) as substrate in P. xylostella larvae that were either unparasitized or parasitized by Cotesia vestalis or Diadegma semiclausum parasitoids. The full cDNA sequence consisted of an open reading frame (ORF) encoding 273 amino acid residues including 23 residues of a signal peptide, and the predicted mature trypsinogen-like enzyme had a molecular mass of 26.5 kDa. The amino acid sequence of this trypsinogen-like enzyme protein and phylogenetic relationship with other published trypsin enzyme proteins suggested that it may be a new proteinase in the trypsin protein family. Parasitism of D. semiclausum did not significantly change the mRNA transcript level or BApNAase activity in host larvae. By contrast, parasitization by C. vestalis induced higher transcript levels coupled with a higher level of BApNAase activity. The BApNAase activity in the midgut of nonparasitized or parasitized P. xylostella larvae increased to a maximum level at pH 12, and the parasitism by both C. vestalis and D. semiclausum increased sensitivity of the enzyme to pH values ranging from 2 to 9.5. These parasitoid-induced changes may represent host manipulation by the developing parasitoid larva.

Population genetic structure of Chilo suppressalis (Walker) (Lepidoptera: Crambidae): strong subdivision in China inferred from microsatellite markers and mtDNA gene sequences.

Chilo suppressalis (Walker) displays significant geographical differences in ecological preference that may be congruent with patterns of molecular variation. To test this, we collected and analysed 381 individuals of this species from cultivated rice at 18 localities in China during the rice-growing season of 2005-2006. We used four microsatellite DNA markers and four mitochondrial DNA gene fragments. We found that this species is highly differentiated, coupled with an estimated population expansion date of at least 60 000 bp. Phylogenetic analyses, Bayesian clustering, and phylogeographical analyses of statistical parsimony haplotype network consistently divided the populations into three clades: a central China (CC) clade, a northern plus northeastern China (NN) clade and a southwestern China (SW) clade. Analysis of molecular variance indicated a high level of geographical differentiation at different hierarchical levels [F(ST) for microsatellite markers, COI, COII, 16S and ND1 is 0.06004 (P < 0.0001), 0.27607 (P < 0.0001), 0.22949 (P < 0.0001), 0.19485 (P < 0.0001) and 0.29285 (P < 0.0001), respectively]. Isolation by distance appeared among the samples from within China (r = 0.404, P = 0.0002); N(e)m values estimated using a coalescent-based method were small (< 2 migrants per generation), suggesting that the observed levels of differentiation are a result of migration-drift equilibrium. Our results imply that the genetic differentiation of this borer, which is approximately in accordance with its observed number of generations per year in different Chinese geographical regions, is probably attributed to climatic and/or geological events (e.g. the last glacial maximum) and subsequently strengthened by the domestication of rice.

Digital color image watermarking based on phase-shifting interferometry and neighboring pixel value subtraction algorithm in the discrete-cosine-transform domain.

A novel single-channel color-image watermarking with digital-optics means based on phase-shifting interferometry (PSI) and a neighboring pixel value subtraction algorithm in the discrete-cosine-transform (DCT) domain is proposed. The converted two-dimensional indexed image matrix from an original color image is encrypted to four interferograms by a PSI and double random-phase encoding technique. Then the interferograms are embedded in one chosen channel of an enlarged color host image in the DCT domain. The hidden color image can be retrieved by DCT, the improved neighboring pixel value subtraction algorithm, an inverse encryption process, and color image format conversion. The feasibility of this method and its robustness against some types of distortion and attacks from the superposed image with different weighting factors are verified and analyzed by computer simulations. This approach can avoid the cross-talk noise due to direct information superposition, enhance the imperceptibility of hidden data, and improve the efficiency of data transmission.

Information security system by iterative multiple-phase retrieval and pixel random permutation.

A novel information security system based on multiple-phase retrieval by an iterative Fresnel-transform algorithm and pixel random permutation (PRP) technique is proposed. In this method a series of phase masks cascaded in free space are employed and the phase distributions of all the masks are adjusted simultaneously in each iteration. It can achieve faster convergence and better quality of the recovered image compared with double-phase encoding and a similar approach in the spatial-frequency domain with the same number of phase masks and can provide a higher degree of freedom in key space with more geometric parameters as supplementary keys. Furthermore, the security level of this method is greatly improved by the introduction of the PRP technique. The feasibility of this method and its robustness against occlusion and additional noise attacks are verified by computer simulations. The performance of this technique for different numbers of phase masks and quantized phase levels is investigated systematically with the correlation coefficient and mean square error as convergence criterions.

Experimental demonstrations of the digital correction of complex wave errors caused by arbitrary phase-shift errors in phase-shifting interferometry.

In previous papers we proposed a digital method of correcting both amplitude and phase distortions caused by arbitrary phase-shift errors in standard four-frame phase-shifting interferometry (PSI), then extended it to the most generalized PSI, and showed the validity of this technique by computer simulations. Here some new simulations and a series of optical experiments with a plane wave, a spherical wave, and a piece of glass as objects are reported. The experimental results have further proved the correctness of our theoretical analysis and confirmed that our method is able to suppress double-frequency fringes in the retrieved amplitude map and the distortions in the phase map that are introduced by phase-shift errors such as to effectively eliminate the wave ripples and wall-like structures that are present in the unwrapped phase map owing to these errors. In addition, our technique can reduce the density of invalid pixels, which are barriers in phase unwrapping. Therefore the accuracy of both amplitude and phase measurements can be considerably improved.