Spatial and spectral beam characteristics in a terahertz broadband sub-wavelength imaging system using a solid immersion lens.

This study focuses on the spatial and spectral beam characteristics in a terahertz (THz) broadband sub-wavelength imaging system using a solid immersion lens (SIL). Previously, we demonstrated a broadband sub-wavelength THz imaging system by integrating a SIL with a THz time-domain spectrometer (TDS). Key parameters that influence beam characteristics and, consequently, imaging performance, such as SIL misalignment tolerances and beam propagation from the SIL, constitute the primary focus of this investigation. Numerical simulations demonstrate that the system can tolerate millimeter-level transverse and longitudinal SIL position displacements, underscoring its robustness for sub-wavelength imaging in a wide frequency range. Additionally, numerical simulations of beam propagation characteristics reveal that the system achieves sub-wavelength imaging resolution up to 1 mm from the SIL at 0.5 THz, highlighting its potential for non-destructive testing of subsurface structures. These findings gain experimental validation through imaging stacked utility knife blades with sub-wavelength structures ranging from 0.2 to 2 THz.

Investigations on Practical Issues in Solid Immersion Lens Based Sub-Wavelength Terahertz Imaging Technique: System Stability Verification and Interference Pattern Removal.

Terahertz (THz) imaging techniques are attractive for a wide range of applications, such as non-destructive testing, biological sensing, and security imaging. We investigate practical issues in THz imaging systems based on a solid immersion lens (SIL). The system stability in terms of longitudinal misalignment of the SIL is experimentally verified by showing that the diffraction-limited sub-wavelength beam size (0.7 λ) is maintained as long as the SIL is axially located within the depth-of-focus (~13 λ) of the objective lens. The origin of the fringe patterns, which are undesirable but inevitable in THz imaging systems that use continuous waves, is analytically studied, and a method for minimizing the interference patterns is proposed. By combining two THz images obtained at different axial positions of the object and separated by λ/4, the interference patterns are significantly reduced, and the information hidden under the interference patterns is unveiled. The broad applicability of the proposed method is demonstrated by imaging objects with different surface profiles. Our work proves that the resolution of conventional THz imaging systems can easily be enhanced by simply inserting a SIL in front of the object with high tolerance in the longitudinal misalignment and provides a method enabling THz imaging for objects with different surface profiles.

Terahertz continuous wave system using phase shift interferometry for measuring the thickness of sub-100-µm-thick samples without frequency sweep.

A terahertz continuous wave system is demonstrated for thickness measurement using Gouy phase shift interferometry without frequency sweep. One arm of the interferometer utilizes a collimated wave as a reference, and the other arm applies a focused beam for sample investigation. When the optical path difference (OPD) of the arms is zero, a destructive interference pattern is produced. Interference signal intensity changes induced by the OPD changes can be easily predicted by calculations. By minimizing the difference between the measured and the calculated signal against the OPD, the thicknesses of sub-100-µm-thick samples are determined at 625 GHz.

Prophylactic use of probiotic chocolate modulates intestinal physiological functions in constipated rats.

BACKGROUND: This study investigated the in vivo prophylactic effect of probiotic chocolate on constipation. Rats were administered chocolate containing 2.5 × 1010 CFU g-1 of probiotics daily for 4 weeks and treated with loperamide (5 mg kg-1 ) daily at the fourth week of treatment. RESULTS: Probiotic chocolate treatment significantly (P < 0.05) increased the intestinal motility, colon length, fecal moisture content and number of excreted fecal pellets in constipated rats. Moreover, quantitative real-time polymerase chain reaction data and histological images also revealed that both probiotic chocolate LYC and BB12 treatments were capable of upregulating the mRNA expression levels of colonic ZO-1, occludin and AQP8, leading to the maintenance of the defensive barrier function in the constipated rats compared with the negative controls. Interestingly, these treatments also modulated gut bacterial populations by increasing the abundance levels of Lactobacillus and Bifidobacterium, as well as reducing the abundance level of Enterobacteriaceae. CONCLUSION: The present study demonstrated that probiotic chocolate LYC and BB12 could potentially be used as alternative agents for prophylactic constipation. © 2018 Society of Chemical Industry.

Electromagnon with Sensitive Terahertz Magnetochromism in a Room-Temperature Magnetoelectric Hexaferrite.

An electromagnon in the magnetoelectric (ME) hexaferrite Ba_{0.5}Sr_{2.5}Co_{2}Fe_{24}O_{41} (Co_{2}Z-type) single crystal is identified by time-domain terahertz (THz) spectroscopy. The associated THz resonance is active on the electric field (E^{ω}) of the THz light parallel to the c axis (∥ [001]), whose spectral weight develops at a markedly high temperature, coinciding with a transverse conical magnetic order below 410 K. The resonance frequency of 1.03 THz at 20 K changes -8.7% and +5.8% under external magnetic field (H) of 2 kOe along [001] and [120], respectively. A model Hamiltonian describing the conical magnetic order elucidates that the dynamical ME effect arises from antiphase motion of spins which are coupled with modulating electric dipoles through the exchange striction mechanism. Moreover, the calculated frequency shift points to the key role of the Dzyaloshinskii-Moriya interaction that is altered by static electric polarization change under different H.

Validity assessment of quantitative light-induced fluorescence-digital (QLF-D) for the dental plaque scoring system: a cross-sectional study.

BACKGROUND: The aim of this study was to analyze the correlation between the dental plaque indices measured using quantitative light-induced fluorescence-digital (QLF-D) and conventional clinical indices that assess gingival status. METHODS: From among the patients who visited Ewha Womans University Mokdong Hospital, 33 adults in their 20s who had relatively even teeth were selected for full-mouth QLF-D imaging. The images were used to analyze the QLF-D score and the QLF-D ΔR score. As clinical indices, the gingival index (GI), bleeding on probing (BOP), probing pocket depth (PPD), and patient hygiene performance (PHP) index were measured. The correlations between the QLF-D score and QLF-D ΔR score and each clinical index were analyzed. Analyses were performed comparing the indices of maxillary and mandibular teeth, the teeth on right and left sides of the mouth, anterior and posterior teeth, and buccal and lingual surfaces of each tooth. Pearson's correlation analysis was conducted (p < 0.05). RESULTS: The mean full-mouth QLF-D score was highly correlated with the GI, BOP, PPD, PHP index (p < 0.01). The mean full-mouth QLF-D score showed the highest correlation with GI (r = 0.749) and the lowest correlation with PPD (r = 0.683). The correlations between the QLF-D score were higher in the mandible than in the maxilla and in the anterior teeth than in the posterior teeth, while no significant differences were seen between the buccal and lingual surfaces of tooth. CONCLUSIONS: This study concluded that the correlations between the plaque indices measured for each tooth surface area using QLF-D and the clinical indices assessed were significantly high, and it allowed objective determination of the gingival status. Therefore, the plaque index measured using QLF-D may be used as an alternative to supplement the shortcomings of conventional clinical indices for educating patients about plaque control and continued patient oral care.

Improved thickness estimation of liquid water using Kramers-Kronig relations for determination of precise optical parameters in terahertz transmission spectroscopy.

In terahertz transmission spectroscopy, there is a typical problem of thickness uncertainty, which hampers to determine precise optical parameters of samples. In order to resolve this experimental problem, a method optimizing sample thickness using singly subtractive Kramers-Kronig relations is proposed. For tens of micrometers thick water samples, we improved the accuracy of sample thickness by an order of magnitude (up to sub-micrometer) using the algorithm leading to obtain precise optical parameters of water. The broad applicability of the method is demonstrated for measuring various materials in addition to highly absorbing liquid water in the spectral range from 0.3 to 1.6 THz.

Raman spectroscopy for cancer detection and cancer surgery guidance: translation to the clinics.

Oncological applications of Raman spectroscopy have been contemplated, pursued, and developed at academic level for at least 25 years. Published studies aim to detect pre-malignant lesions, detect cancer in less invasive stages, reduce the number of unnecessary biopsies and guide surgery towards the complete removal of the tumour with adequate tumour resection margins. This review summarizes actual clinical needs in oncology that can be addressed by spontaneous Raman spectroscopy and it provides an overview over the results that have been published between 2007 and 2017. An analysis is made of the current status of translation of these results into clinical practice. Despite many promising results, most of the applications addressed in scientific studies are still far from clinical adoption and commercialization. The main hurdles are identified, which need to be overcome to ensure that in the near future we will see the first Raman spectroscopy-based solutions being used in routine oncologic diagnostic and surgical procedures.

Antioxidant and Anti-Obesity Effects of Juglans mandshurica in 3T3-L1 Cells and High-Fat Diet Obese Rats.

Juglans mandshurica Maxim. walnut (JMW) is well-known for the treatment of dermatosis, cancer, gastritis, diarrhea, and leukorrhea in Korea. However, the molecular mechanism underlying its anti-obesity activity remains unknown. In the current study, we aimed to determine whether JMW can influence adipogenesis in 3T3-L1 preadipocytes and high-fat diet rats and determine the antioxidant activity. The 20% ethanol extract of JMW (JMWE) had a total polyphenol content of 133.33 ± 2.60 mg GAE/g. Considering the antioxidant capacity, the ABTS and DPPH values of 200 µg/ml of JMWE were 95.69 ± 0.94 and 79.38 ± 1.55%, respectively. To assess the anti-obesity activity of JMWE, we analyzed the cell viability, fat accumulation, and adipogenesis-related factors, including CCAAT-enhancer-binding protein alpha (C/EBPα), sterol regulatory element-binding protein-1c (SREBP1c), peroxisome proliferator-activated receptor-gamma (PPARγ), fatty acid synthase (FAS), and acetyl-CoA carboxylase (ACC). We found that total lipid accumulation and triglyceride levels were reduced, and the fat accumulation rate decreased in a dose-dependent manner. Furthermore, JMWE suppressed adipogenesis-related factors C/EBPα, PPARγ, and SREBP1c, as well as FAS and ACC, both related to lipogenesis. Moreover, animal experiments revealed that JMWE could be employed to prevent and treat obesity-related diseases. Hence, JMWE could be developed as a healthy functional food and further explored as an anti-obesity drug.

Photocatalytic degradation of methylene blue over nanosized TiO2 particles prepared using the self-propagating high-temperature synthesis method.

In order to reutilize the spent metallic titanium chips, TiO2 photocatalysts were prepared using the self-propagating high-temperature synthesis (SHS) method, and were characterized by N2 gas adsorption, X-ray diffraction, and scanning electron microscope, particle size distribution. Also, their photocatalytic activities were evaluated using methylene blue as a model organic compound. It was confirmed that the crystal structure of TiO2 prepared by SHS method was relatively homogeneous powder of rutile type. Optimum conditions for photocatalytic degradation of methylene blue under UV-C irradiation were methylene blue 9.5 ppm in solution and at amount of TiO2 added of 0.02 g/L. In addition, it was found that the photocatalytic activity for methylene blue degradation over the prepared TiO2 particles was positively related with BET specific surface area.

Dielectric relaxation change of water upon phase transition of a lipid bilayer probed by terahertz time domain spectroscopy.

We investigate the influence of the 1, 2-ditetradecanoyl-sn-glycero-3-phosphocholine lipid bilayer phases on the water reorientation dynamics with terahertz time domain spectroscopy. The phase of the lipids was controlled by the temperature in the range of 14-35 °C. During the gel-to-fluid phase transition, the hydration water ratio drastically changed from 0.3 to 0.6. The absorption coefficient of the hydration water increased with the temperature in the gel phase and then decreased in the fluid phase. The dielectric relaxation time of the lipid solution decreased initially but then increased after the phase transition. This indicates that the hydration water reorientation dynamics are restricted by lipids and that this phenomenon is pronounced in a biologically relevant fluid phase.

Antioxidant and lipid-reducing effects of Rosa rugosa root extract in 3T3-L1 cell.

Rosa rugosa root is traditionally known to be effective in the treatment of diabetes in Korea. R. rugosa root-specific compounds also show antioxidant effects, and could reduce lipid and fat accumulation, however, the underlying mechanism has not been clarified. In present study, the antioxidant and lipid-reducing effects of a 50% ethanol extract of R. rugosa (REE) were investigated differentiated mouse preadipocytes (3T3-L1 cells). REE showed strong radical scavenging activities and inhibitory effect of total lipid accumulation and triglyceride levels in differentiated 3T3-L1 cells. In addition, REE treatment reduced the mRNA and protein levels of adipogenesis and lipogenesis markers. This REE-promoted lipid reduction was caused by downregulation of peroxisome proliferator activated receptor gamma (PPARγ), CCAAT/enhancer binding protein alpha (C/EBPα), and sterol regulatory element binding protein1 (SREBP1c) and down regulation of ERK expression. Overall, these results demonstrate the potential of REE for development of a drug in the medical treatment of lipid-associated disorders.

Laxative effect of probiotic chocolate on loperamide-induced constipation in rats.

The fecal morphology, defecation frequency, bowel function, intestinal motility, and fecal bacterial composition were evaluated to investigate the laxative effect of probiotic chocolate containing Streptococcus thermophilus MG510 and Lactobacillus plantarum LRCC5193 (LYC) on loperamide-induced constipated rats. Daily oral administration of LYC in constipated rats for two weeks was shown to significantly increase (n = 14) the defecation frequency, fecal moisture content, and relative abundance of fecal Lactobacillus and Faecalibacterium prausnitzii. Moreover, histological analysis of the distal colon of constipated rats revealed that LYC treatment can also increase the thickness of the colonic mucosa and muscle layers, and crypt of Lieberkühn. LYC also significantly increased (n = 5) the intestinal motility and modulated (n = 9) mRNA expression levels of colonic ZO-1 and Cldn-1 in the constipated rats. Altogether, these results demonstrate that probiotic chocolate has potential as a dietary adjunct for the treatment of constipation.

Isolation of thermotolerant yeast Pichia kudriavzevii from nuruk.

Thermotolerant yeast strains were isolated from nuruk, a traditional Korean fermentation starter in which variety of microorganisms are present. Among the isolates, the MBY1358 identified as yeast Pichia kudriavzevii showed significantly higher growth rate (0.59 ± 0.00 1/h) at 44 °C than other strains. Maximum ethanol concentration of 8.35 ± 0.03 g/L was obtained from 20 g/L glucose with yield of 0.44 ± 0.01 g/g at 44 °C, which is 1.14 times ethanol production of the control strain of P. kudriavzevii. The MBY1358, which was significantly more thermotolerant than the control strain and fermented 200 g/L glucose to 107.33 ± 5.03 g/L ethanol at 44 °C, was deposited to Korean Collection for Type Cultures (KCTC) under the accession number 27654.

Reference line-pair values of panoramic radiographs using an arch-form phantom stand to assess clinical image quality.

PURPOSE: This study was performed to suggest reference line-pair values of panoramic images with clinically desirable qualities using an arch-form phantom stand. MATERIALS AND METHODS: The line-pair test phantom was chosen. A real skull model was selected for setting the arch-form model of the phantom stand. The phantom stand had slits in four regions (incisor, premolar, molar, TMJ). Four raw images of the test phantom in each region and one raw image of the real skull were converted into 50 test phantom images and 50 skull phantom images with various line-pair values. 50 post-processed real skull phantom images were divided into 4 groups and were randomly submitted to 14 evaluators. Image quality was graded on a 4 point scale (1. good, 2. normal, 3. poor but interpretable, and 4. not interpretable). The reference line pair was determined as the first line-pair value scored less than 2 points. RESULT: The mean scores tended to decrease as the line-pair values increased. The reference line-pair values were 3.19 LP/mm in the incisor, 2.32 LP/mm in the premolar and TMJ, and 1.88 LP/mm in the molar region. CONCLUSION: Image quality evaluation methods and criteria should be able to assess various regions considering the characteristics of panoramic systems. This study suggested overall and regional reference line-pair values and established a set of standard values for them.

Clinical image quality evaluation for panoramic radiography in Korean dental clinics.

PURPOSE: The purpose of this study was to investigate the level of clinical image quality of panoramic radiographs and to analyze the parameters that influence the overall image quality. MATERIALS AND METHODS: Korean dental clinics were asked to provide three randomly selected panoramic radiographs. An oral and maxillofacial radiology specialist evaluated those images using our self-developed Clinical Image Quality Evaluation Chart. Three evaluators classified the overall image quality of the panoramic radiographs and evaluated the causes of imaging errors. RESULTS: A total of 297 panoramic radiographs were collected from 99 dental hospitals and clinics. The mean of the scores according to the Clinical Image Quality Evaluation Chart was 79.9. In the classification of the overall image quality, 17 images were deemed 'optimal for obtaining diagnostic information,' 153 were 'adequate for diagnosis,' 109 were 'poor but diagnosable,' and nine were 'unrecognizable and too poor for diagnosis'. The results of the analysis of the causes of the errors in all the images are as follows: 139 errors in the positioning, 135 in the processing, 50 from the radiographic unit, and 13 due to anatomic abnormality. CONCLUSION: Panoramic radiographs taken at local dental clinics generally have a normal or higher-level image quality. Principal factors affecting image quality were positioning of the patient and image density, sharpness, and contrast. Therefore, when images are taken, the patient position should be adjusted with great care. Also, standardizing objective criteria of image density, sharpness, and contrast is required to evaluate image quality effectively.

Effect of bit depth and kVp of digital radiography for detection of subtle differences.

OBJECTIVES: The purpose of this study is to investigate the effects of different bit depths and kilovoltage peak (kVp) values used in intraoral digital radiography on observer performance in detecting subtle radiographic density differences. STUDY DESIGN: Using an intraoral CCD sensor set at 8- or 12-bit depth, kVp set at 60 or 70, and 14 different exposure times, digital radiographs were acquired of a specially designed aluminum step-wedge phantom with small holes of different depths in each step. Ten observers examined all images. RESULTS: The observers counted more holes with the 12-bit images compared with the 8-bit images, particularly at 60 kVp. Significantly more holes were also counted with images taken at 70 kVp compared with those taken at 60 kVp. CONCLUSION: Regarding the detection of subtle radiographic density differences, 12-bit images and 70 kVp were superior to 8-bit images and 60 kVp.

Methylpyrazole-capped two-dimensional supramolecular M(II) (M = Mn, Ni, Co) assemblies constructed by covalent and noncovalent interactions: uncommon coordination modes of methylpyrazoles and magnetic properties.

Two mononuclear complexes [Mn(5-methylpyrazole)4(N3)2] (1) and [Ni(5-methylpyrazole)4(N3)2] (2), as well as a novel one-dimensional coordination polymer [Co(3-methylpyrazole)2(5-methylpyrazole)2(tp)]n (3) (tp = terephthalate), were characterized. The isostructural complexes, 1 and 2, display two-dimensional supramolecular networks formed by hydrogen bonds between the N-H groups of 5-methylpyrazoles and the end N atoms of the azide ligands and additional face-to-face pi-pi interactions of the 5-methylpyrazoles. For 3, tp-bridged one-dimensional chains assisted by intrachain hydrogen bonds among the N-H groups of methylpyrazoles and carboxylate oxygens are connected with the help of interchain C-H...O hydrogen bonds, leading to a two-dimensional structure. The intra- and interchain hydrogen bonds account for the coexistence of two unique coordination forms (5-methylpyrazole and 3-methylpyrazole) of methylpyrazoles in the same coordination sphere. Weak antiferromagnetic interactions coupled with the spin-orbit coupling effect are operative in 3 through the tp ligands.