An engineered dual-functional peptide with high affinity to demineralized dentin enhanced remineralization efficacy in vitro and in vivo.

Dental caries continues to be a major global public health problem. Remineralization of demineralized dentin is regarded as one of the hotspots in the current study in the treatment of dental caries. However, traditional remineralization agents, which usually lack the ability to bind to demineralized dentin collagen, are easily removed by the fluids in the oral cavity, thus decreasing the remineralization efficacy. Non-collagenous proteins (NCPs) have significant effects on the biomineralization of dentin due to their dual high binding capacity to the collagen fibers and minerals. But NCPs are hard to extract, store and use directly. Inspired by the biological behavior of NCPs, in this study, we selected two functional sequences of NCPs to develop a novel and engineered dual-functional peptide (which is referred to as CYP) with collagen-binding and mineral-absorbing capability. The binding ability of CYP to collagen fibers and demineralized dentin was investigated, and the results suggested that CYP was endowed with good binding capacity to demineralized dentin, which could resist the washing of the fluid. In addition, we confirmed that CYP exerted formidable remineralization effects in collagen fibers and demineralized dentin following an in vitro remineralization regimen. Furthermore, the dual functions of CYP with good biocompatibility can simultaneously bind collagen and induce nanocrystal precipitation, thereby significantly absorbing calcium and phosphorus ions to form regenerated minerals for reversing the tooth decay process in the rat caries model. Overall, the dual functional peptide CYP fabricated in this study provides an ideal and smart strategy for dentin remineralization and the treatment of caries.

Risk Factors for Glycemic Control in Hospitalized Patients with Type 2 Diabetes Receiving Continuous Subcutaneous Insulin Infusion Therapy.

INTRODUCTION: Patients with diabetes are confronted with numerous obstacles to achieve adequate glycemic control during hospitalization. The aim of this study was to explore the risk factors associated with glycemic control in hospitalized patients with type 2 diabetes mellitus (T2DM) treated with continuous subcutaneous insulin infusion (CSII). METHODS: This cross-sectional study included 5223 patients hospitalized with T2DM in a tertiary hospital in Xiamen (China) between January 2017 and December 2019. All patients were managed according to established protocols for glycemic monitoring and insulin pump treatment regimens. Demographic information and clinical profiles were collected from electronic health records. Multiple linear regression analysis was used to identify the risk factors associated with glycemic control. RESULTS: Among the 5223 hospitalized patients with T2DM receiving CSII therapy, 55.2% achieved their ideal blood glucose level (3.9-10.0 mmol/L), 44.5% experienced hyperglycemia (> 10.0 mmol/L), and 0.3% experienced hypoglycemia (< 3.9 mmol/L) during their hospitalization. Multivariate analyses showed that among inpatients with T2DM, older age, male gender, higher low-density lipoprotein-cholesterol (LDL-C) level, lower C-peptide (C-P) level, lower body mass index (BMI), longer duration of diabetes, previous insulin prescriptions, nephropathy, and retinopathy were factors more likely to be associated with a blood glucose level in the hyperglycemic range (P < 0.05). We also observed that among hospitalized patients with T2DM, those with lower BMI, lower C-P, lower LDL-C, longer disease duration, and previous insulin prescriptions were more likely to correlate with a higher proportion of hypoglycemia range (all P < 0.05). CONCLUSION: Older age, male gender, lower BMI, lower C-P, higher LDL-C, previous insulin prescriptions, longer duration of diabetes, nephropathy, and retinopathy may be risk factors for a higher proportion of hyperglycemic events in hospitalized patients with T2DM under CSII therapy. Furthermore, lower BMI, lower C-P, lower LDL-C, longer duration of diabetes, and previous insulin prescriptions were found to be important factors for a higher proportion of hypoglycemic events. Evaluating the clinical features, comorbidities, and complications of hospitalized patients is essential to achieve reasonable glycemic control.

The correlation between triiodothyronine and the severity of liver fibrosis.

BACKGROUND: The severity of liver fibrosis is an important predictor of death in patients with non-alcoholic fatty liver disease (NAFLD) and type 2 diabetes mellitus (T2DM). However, there is still no definite conclusion on the relationship between triiodothyronine (T3) and the severity of liver fibrosis. Thus, the aim of this study was to analyze the correlation between T3 level and the severity of liver fibrosis. METHODS: We performed a cross-sectional study of 2072 T2DM patients with normal thyroid function from January 2017 to January 2020. NAFLD fibrosis score (NFS), Fibrosis index based on the 4 factors (FIB-4) and BARD score (BARD) were used to assess the severity of fibrosis in T2DM patients, and linear regression analyses were used to determine the factors independently associated with liver fibrosis. Further experiments were performed to assess the impact of low T3 on fibrosis progression in mice model and explore possible mechanisms. RESULTS: Free triiodothyronine (fT3) levels had significantly inverse correlations with NFS and FIB-4, and BARD in T2DM patients (P < 0.05). In multiple linear regression analyses, decreased fT3 level was an independent risk factor for the severity of liver fibrosis of T2DM patients (P < 0.01). Findings from in-vivo experiment using mice model proved that hypothyroidism mice had more severe of liver fibrosis than those mice with normal thyroid function. We also found that T3 could inhibit the profibrotic TREM2+CD9+ macrophage, which had been identified an important player in the progression of liver fibrosis. CONCLUSION: The findings from this study proved an inverse correlation between T3 level and the severity of liver fibrosis, and lower fT3 level within the normal range was an independent risk factor for severe liver fibrosis.

Hypoglycemia unawareness identified by continuous glucose monitoring system is frequent in outpatients with type 2 diabetes without receiving intensive therapeutic interventions.

BACKGROUND: Patients with diabetes are prone to asymptomatic hypoglycemia (AH) due to diminished ability to perceive the onset of hypoglycemia. However, the actual prevalence and influencing factors of AH in outpatients with type 2 diabetes (T2DM) have not been well investigated. METHODS: A total of 351 outpatients with T2DM underwent glucose monitoring by continuous glucose monitoring system (CGMS) for consecutive 72 h without changing their lifestyle and treatment regimens. Hypoglycemia is defined as a blood glucose level less than 3.9 mmol/L, which was further divided into Level 1 hypoglycemia (blood glucose 3.0-3.9 mmol/L) and Level 2 hypoglycemia (blood glucose < 3.0 mmol/L). Univariate and multivariate logistic regression analyses were used to determine the possible risk factors of AH. RESULTS: In all 351 subjects studied, 137 outpatients (39.0%) were captured AH events, in which Level 1 AH and Level 2 AH accounted for 61.3% and 38.7%, respectively. 85 (62.0%) of the AH patients experienced nocturnal asymptomatic hypoglycemia (NAH) and 25 (18.2%) exclusively NAH. Multivariate logistic regression analysis demonstrated that patients with younger age, lower hemoglobin A1c (HbA1c), and higher systolic blood pressure (SBP) levels were associated with increased risk of AH. While after further grading of AH, male sex and Dipeptidylpeptidase-4 inhibitors (DPP4i) regime were shown to be associated with lower risk of Level 2 AH. CONCLUSIONS: Hypoglycemia unawareness could be frequently observed at either daytime or nighttime, although NAH was more common, in outpatients with T2DM. Relative relax HbA1c targets should be considered for patients who are prone to AH.

Case Report: A Rare Case of Coexisting of Autoimmune Polyglandular Syndrome Type 3 and Isolated Gonadotropin-Releasing Hormone Deficiency.

APS (autoimmune polyglandular syndrome) is defined as the coexistence of at least two kinds of endocrine autoimmune diseases. APS type 3 comprises autoimmune thyroid diseases and other autoimmune diseases but does not involve autoimmune Addison's disease. So far, APS-3 combined with isolated gonadotropin-releasing hormone (GnRH) reduction caused by the suspected autoimmune hypothalamic disease has not been reported. We recently received a 43-year-old woman with a one-year history of Graves' disease (GD) and a four-month history of type 1 diabetes presented with hyperthyroidism and hyperglycemia. After the GnRH stimulation test, she was diagnosed with secondary amenorrhea attributed to suspected autoimmune Hypothalamitis and APS type 3 associated with Graves' disease and Latent Autoimmune Diabetes (LADA). According to this case, the hypothalamus cannot be spared from the general autoimmune process. It is recommended to carry out the GnRH stimulation test when encountering APS patients combined with secondary amenorrhea.

Correlation of Serum Cystatin C with Renal Function in Gout Patients with Renal Injury.

The gout-induced continuous deposition of urate in the kidney tissues is the main cause of renal injury, for which cystatin C (Cys C) is an important indicator. This research analyzed the correlation between general renal injury indicators and serum Cys C level, and further investigated the potential of Cys C in renal injury diagnosis. A total of 140 gout patients with renal injury (GRI) were recruited and grouped by their glomerular filtration rate (GFR). Urea nitrogen, uric acid, creatinine, and Cys C levels in the serum were evaluated. The diagnostic efficacy of serum Cys C was evaluated by the nonparametric receiver operating characteristic analysis. Serum Cys C level was increased with decreased GFR in GRI. Urea nitrogen, uric acid, and creatinine levels in the serum showed positive correlations with Cys C level. The area under the curve for serum Cys C was 0.8589 (P < 0.001). In conclusion, this research demonstrated that the serum Cys C level was a precise diagnostic marker for GFR and renal damage evaluation, and showed a significant diagnostic value for renal injury in patients with gout.

Lipid accumulation product (LAP) was independently associatedwith obstructive sleep apnea in patients with type 2 diabetes mellitus.

BACKGROUND: Lipid accumulation product (LAP) is a new index based on a combination of waist circumference (WC) and serum triglycerides (TG) reflecting lipid accumulation. In this cross-sectional study, we aimed to explore whether LAP was independently associated with obstructive sleep apnea (OSA) in Type 2 diabetes mellitus (T2DM) patients. METHODS: A cross-sectional study of 317 T2DM patients who underwent overnight polysomnography (PSG) tests was conducted. The clinical data between non-OSA group and OSA group were compared. Multivariable linear regression and multivariable logistic regression analyses were performed to determine associations of LAP, with apnea-hypopnea index (AHI) and OSA. RESULTS: Among 317 patients, 219 (69.1%) were men, and the mean ages (±SD) were 51.4 (±13.5) years for men and 54.6 (±15.1) years for women (p = 0.067). The prevalence rates of OSA were 63.0% for men and 68.4% for women (p = 0.357). LAP (log-transformed) was significantly correlated with AHI (log-transformed), with the Pearson's correlation coefficient of 0.170 (p = 0.002). With adjustment for potential confounding factors, multivariate linear regression analyses showed the association of LAP with AHI was not statistically significant, with the adjusted linear regression coefficients (95% CI) of per SD increase of LAP for AHI (log-transformed) was 0.092 (- 0.011-0.194, p = 0.080). Multivariate logistic regression analyses showed LAP was significantly associated with increased risk of OSA, with the adjusted OR (95%CI) of per SD increase of LAP of 1.639 (1.032-2.604, p = 0.036). However, as constituents of LAP, neither TG nor WC was significantly associated with AHI and OSA. CONCLUSION: LAP was independently associated with OSA and might be used as a potential OSA risk marker in T2DM patients, beyond the general index of obesity.

Sex-specific associations between prenatal antibiotics exposure and offspring's body mass index.

OBJECTIVE: Animal studies and epidemiological studies have shown that there is potential sex-specific sensitivity to the intrauterine environment in relation to the developmental programming of obesity. The objective of this study was to assess the sex-specific association between prenatal antibiotics exposure and body mass index (BMI) in offspring from 1 to 4 years. METHODS: A total of 10,163 mother-child pairs from the Medical Birth Registry in Xiamen, China, were included in this prospective cohort study. Data on prenatal antibiotics exposure were collected from the prescription database. RESULTS: A total of 4909 (48.3%) offspring had prenatal antibiotics exposure. The associations between prenatal antibiotics exposure and offspring's BMI were significantly different among female offspring and male offspring (P for interaction: 0.034 at 1 year of age; 0.033 at 2 years of age; 0.020 at 3 years of age; and 0.021 at 4 years of age). In female offspring, prenatal antibiotic use was significantly associated with a higher BMI Z-score from 1 to 4 years old (difference in BMI Z-score: 0.11 [95% CI: 0.05-0.17] at 1 years of age; 0.10 [95% CI: 0.05-0.16] at 2 years of age; 0.14 [95% CI: 0.09-0.21] at 3 years of age; and 0.13 [95% CI: 0.07-0.19] at 4 years of age) after adjustment for confounder. Prenatal antibiotics use was not associated with offspring BMI Z-score from 1 to 4 years in male offspring. CONCLUSIONS: The association of prenatal antibiotics exposure and BMI Z-score from 1 to 4 years old may differ by sex of offspring.

Efficacy of Vildagliptin Added to Continuous Subcutaneous Insulin Infusion (CSII) in Hospitalized Patients with Type 2 Diabetes.

INTRODUCTION: The aim of this study was to compare the efficacy of vildagliptin as add-on therapy to short-term continuous subcutaneous insulin infusion (CSII) with CSII monotherapy in hospitalized patients with type 2 diabetes mellitus (T2DM). METHODS: A total of 200 hospitalized patients with inadequately controlled T2DM were randomized into groups, with one group receiving CSII monotherapy (CSII group, n =100) and the other group receiving CSII plus vildagliptin as add-on (CSII + Vig group, n = 100). Of these, 191 completed the 7-day trial (CSII group, n = 99; CSII + Vig group, n = 92) and included in the analysis. The glycemic control and variability of the patients were measured using all-day capillary blood glucose (BG) monitoring. Weight and fasting C-peptide levels were evaluated before and after the interventions. RESULTS: Mean BG concentrations during the whole treatment period were lower and the time to reach target BG was reduced in the CSII + Vig group compared with the CSII group (9.89 ± 3.37 vs. 9.46 ± 3.23 mmol/L, P < 0.01; 129 ± 4 vs. 94 ± 5 h, P < 0.01, respectively). Similarly, the indicators of glycemic variability, namely the standard deviation of BG and the largest amplitude of glycemic excursion, were significantly decreased in the CSII + Vig group compared with the CSII group (2.68 ± 1.05 vs. 2.39 ± 1.00 mmol/L, P < 0.01; 7.19 ± 2.86 vs. 6.23 ± 2.73 mmol/L, P < 0.01, respectively). CONCLUSIONS: Short-term CSII with vildagliptin as add-on therapy may be an optimized treatment for hospitalized patients with T2DM compared with short-term CSII monotherapy.

Associations of apnea hypopnea index and educational attainments with microvascular complications in patients with T2DM.

PURPOSE: The relationship between obstructive sleep apnea (OSA) and diabetic microvascular complications (DMC) are controversial. Whether low education is associated with increased risk of DMC independently of poor lifestyles are currently unknown. The aim of this study is to explore the independent associations of different PSG index and educational attainment with risks of DR, DKD, and DPN. METHODS: A cross-sectional study of 330 patients with T2DM who underwent overnight polysomnography (PSG) tests. Multivariable logistic regression analysis was performed to determine the associations of PSG index and educational attainments with DR, DKD, and DPN. RESULTS: The prevalence rates of DMC were 30.6% for DR, 24.9% for DKD, and 64.6% for DPN. All PSG index (AHI, REM-AHI, NREM-AHI, the severity of OSAS, ODI, MAI, and lowest SaO2) were not significantly associated with risks of DR, DKD, or DPN with adjustment for potential confounding factors. Subjects with increasing educational attainments showed significantly decreased prevalence rates of DR (42.6, 27.3, and 21.3%, p = 0.005), DKD (31.7, 25.3, and 14.7%, p = 0.035) and DPN (74.3, 63.6, and 53.3%, p = 0.015), respectively. Logistic regression analyses showed that educational attainment of primary or below showed significantly increased risks of DR (OR (95% CIs): 3.596 (1.453-8.899, p = 0.006)) and DKD (OR (95% CIs): 3.201 (1.244-8.242, p = 0.016)) as compared with that of college or above. There were significant trends of lower educational attainment with increased risks of DR and DKD (p values < 0.05). CONCLUSION: PSG index were not significantly associated with DMC. But lower education was significantly associated with increased risks of DR and DKD, and strategies to prevent DMC for those with low education should be strengthened.

Circular RNA hsa_circ_0001178 facilitates the invasion and metastasis of colorectal cancer through upregulating ZEB1 via sponging multiple miRNAs.

Metastasis is the main cause of increasing cancer morbidity and mortality. However, the underlying mechanism of cancer metastasis remains largely unknown. In the present study, we identified one circular RNA (circRNA) closely related to the metastasis of colorectal cancer (CRC), namely hsa_circ_0001178. CRC patients with high hsa_circ_0001178 were more prone to have metastatic clinical features, advanced TNM stage and adverse prognosis. Stable knockdown of hsa_circ_0001178 significantly weakened CRC cell migratory and invasive capabilities in vitro as well as lung and liver metastases in vivo. Mechanistic study revealed that hsa_circ_0001178 acted as a competing endogenous RNA (ceRNA) for miR-382/587/616 to upregulate ZEB1 (a key trigger of epithelial-to-mesenchymal transition), thereby promoting CRC metastatic dissemination. Of note, ZEB1 could also increase hsa_circ_0001178 expression via physically binding to hsa_circ_0001178 promoter region. Collectively, our data uncover the crucial role of hsa_circ_0001178 in CRC metastasis, and targeted therapy based on this positive feedback ceRNA axis may be a promising treatment for metastatic CRC patients.

Serum Uric Acid Is Independently Associated with Risk of Obstructive Sleep Apnea-Hypopnea Syndrome in Chinese Patients with Type 2 Diabetes.

PURPOSE: We aimed to investigate the association between serum uric acid (SUA) levels and obstructive sleep apnea-hypopnea syndrome (OSAHS) in patients with type 2 diabetes. METHODS: A cross-sectional study of 212 type 2 diabetes mellitus (T2DM) patients was conducted in Xiamen, China. All patients underwent polysomnography (PSG) recordings for OSAHS diagnosis. Patients were grouped according to the apnea-hypopnea index (AHI) as mild (5-14.9), moderate (15-29.9), and severe (≧30) OSAHS. Patients with AHI ≤ 4.9 served as the control group. Weight, body mass index (BMI), SUA, liver function, renal function, blood pressure, lipid profiles, and glycemic parameters were measured. RESULTS: A total of 158 patients (101 men and 57 women) with complete data were analyzed in this study. 127 patients were identified as OSAHS. Among the 127 patients with OSAHS, 56 (44.1%), 37 (29.1%), and 34 (26.8%) had mild, moderate, and severe OSAHS, respectively. Correlation analyses showed that the SUA level was significantly related to the apnea-hypopnea index (AHI) (r = 0.194, p = 0.016). The level of SUA was significantly higher among OSAHS patients compared to the control group (control group: 333.14 ± 80.52 µmol/L, mild group: 345.50 ± 90.27 µmol/L, moderate group: 363.59 ± 134.26 µmol/L, and severe group: 428.37 ± 123.58 µmol/L and p = 0.029). Multivariable logistic regression analyses showed that SUA was the independent risk factor for OSAHS (OR: 1.006, 95% CI: 1.001-1.011, p = 0.020). CONCLUSIONS: The SUA level is significantly associated with the severity of OSAHS and should be controlled when managing OSAHS.

Age at menarche and risk of gestational diabetes mellitus: a population-based study in Xiamen, China.

BACKGROUND: It has been reported that earlier age at menarche is associated with a higher risk for type 2 diabetes mellitus. However, the relationship between age at menarche and gestational diabetes mellitus is inconsistent across studies. We hypothesized that an earlier age at menarche would predict the gestational diabetes mellitus risk. METHODS: This was a population-based, retrospective cohort study of 70,041 women aged 18 to 53 years old, conducted between 2011 and 2018. The subjects were recruited from the Medical Birth Registry in Xiamen, China. Age at menarche was categorized as 8-12, 13, 14, 15, 16-19 years old. Logistic regression analysis and spline analysis was used to assess the risk of the menarche age group for gestational diabetes mellitus. Linear regression analysis was performed to evaluate independent associations between age at menarche and fasting plasma glucose and blood glucose 1 hour and 2 hours after a 75-g of glucose load between 24 and 28 weeks' gestation. RESULTS: The overall prevalence of GDM was 17.6%. After adjustment for family history of diabetes, earlier age at menarche (8-12, and 13 years old) was associated with increased odds for GDM (OR, 1.08; 95% CI, 1.02-1.15, and OR, 1.07; 95% CI, 1.03-1.14, respectively) compared with average age at menarche (14 years old). With further adjustment for pre-pregnancy body mass index, blood pressure, educational level, age at delivery, and hepatitis B surface antigen status, this association was attenuated (OR, 0.93, and OR, 1.02, respectively). Multivariable-adjusted spline regression models showed a linear dose-response association between age at menarche and GDM (P for nonlinearity, 0.203; P for linearity, 0.006). On linear regression analysis, earlier age at menarche was significantly associated with increased blood glucose one and 2 hours after a glucose load but not with the fasting plasma glucose. CONCLUSIONS: As expected, early age at menarche was found to be associated with an increased risk of gestational diabetes mellitus. However, this association may be mediated by potential confounding factors other than age. An additional finding was that earlier menarche was significantly related with elevated pregnancy glucose concentrations after a glucose load.

Treatment of giant pharyngoesophageal diverticulum by video-assisted thoracoscopy.

A 67-year-old woman presented with a giant pharyngoesophageal diverticulum (Zenker's diverticulum) that extended deep into the chest. Surgery, using either an open or endoscopic approach, was difficult. We stapled the common wall between the diverticulum and the esophagus using video-assisted thoracoscopic surgery. The patient exhibited good anatomic and functional results at 6 months' follow-up.

9-(3-Methoxy-phen-yl)-6,6-dimethyl-4-phenyl-2,3,5,6,7,9-hexa-hydro-thieno[3,2-b]quinolin-8(4H)-one 1,1-dioxide.

The title compound, C(26)H(27)NO(4)S, with a thiophene ring fused to a quinoline ring, was synthesized via the condensation of dihydro-thio-phen-3(2H)-one 1,1-dioxide, 5,5-dimethyl-3-(phenyl-amino)cyclo-hex-2-enone and 3-methoxy-benzaldehyde in refluxing ethanol. In the crystal structure, the thiophene dioxide ring and the pyridine ring adopt envelope conformations. The connection of the pyridine ring to the phenyl and benzene rings can be described by the C-C-C-C and C-N-C-C torsion angles of 45.5 (2) and 88.7 (2)°, respectively. The cyclo-hex-2-enone ring is in a half-chair conformation. The crystal packing is stabilized by non-classical inter-molecular C-H⋯O hydrogen bonds with the carbonyl O and sulfone O atoms acting as acceptors.

5'-Amino-1,3-dioxo-2',3'-di-hydro-7'H-spiro-[indane-2,7'-thieno[3,2-b]pyran]-6'-carbonitrile 1',1'-dioxide.

The title compound, C(16)H(10)N(2)O(5)S, was synthesized via the condesation of dihydro-thio-phen-3(2H)-one 1,1-dioxide, 1H-indene-1,2,3-trione and malononitrile in ethanol. The 2,3-dihydro-thio-phene 1,1-dioxide and pyran rings adopt envelope conformations. The mean planes through the planar part of the pyran ring and the benzene ring are nearly perpendicular, forming a dihedral angle of 88.40 (7)°. The crystal packing is stabilized by inter-molecular N-H⋯O and N-H⋯N hydrogen bonds with the sulfone O atom and the cyano N atom acting as acceptors.

Efficient all solid-state continuous-wave yellow-orange light source.

We present highly efficient sum-frequency generation between two CW IR lasers using periodically poled KTP. The system is based on the 1064 and 1342 nm laser-lines of two Nd:YVO4 lasers. This is an all solid-state light source in the yellow-orange spectral range. The system is optimized in terms of efficiency as well as stability. We compare the performance of a singly and a doubly resonant system, and find that the stability of the singly resonant system is superior to that of the doubly resonant system. We find that the overall conversion efficiency of the single resonant system is higher than for the doubly resonant configuration.

Compact 492-nm light source based on sum-frequency mixing.

More than 27 mW of 492-nm power was generated in a compact design, using intra-cavity sum frequency mixing of a laser diode and a diode-pumped solid-state laser in a periodically-poled KTiOPO4 crystal.

Generation of turquoise light by sum frequency mixing of a diode-pumped solid-state laser and a laser diode in periodically poled KTP.

We report a simple and efficient method to achieve visible light by sum-frequency mixing radiation from a diode-pumped solid-state laser and a laser diode in a periodically poled KTiOPO4 crystal. Since high-power laser diodes are available at a wide range of wavelengths, it is thereby possible to obtain essentially any wavelength in the visible spectrum by appropriate choice of lasers. For demonstration we choose to construct a light source in the blue-green region. A turquoise output power of 4.0 mW was achieved.

Three-dimensional characterization of the effective second-order nonlinearity in periodically poled crystals.

A novel technique for characterization of the second-order nonlinearity in nonlinear crystals is presented. It utilizes group-velocity walk-off between femtosecond pulses in type II SHG to achieve three-dimensional resolution of the nonlinearity. The longitudinal and transversal spatial resolution can be set independently. The technique is especially useful for characterizing quasi-phase-matched nonlinear crystals, and it is demonstrated in potassium titanyl phosphate.