Betterment of a displacement retrieval method based on data fitting in a near-half-fringe zone.

Raising the speed and accuracy of displacement retrieval by overcoming the weakness of time-consuming parameter estimation and a complex displacement retrieval algorithm is of key importance in improving the real-time quality of optical feedback self-mixing-based displacement measurement sensor. This paper proposes a high-speed and accurate simultaneous estimation method of displacement, optical feedback factor, and linewidth enhancement factor based on data fitting near a half-fringe cooperating with the fringe-counting method. The displacement measurement accuracy of the proposed method is about 16 nm. The high estimation speed ensured by the principle of the reported method constitutes the main character of the method; besides, the method can be applied to any motion, as well as a harmonic vibration.

Multidisciplinary integrated optimal design process for optomechanical structures.

This paper presents an integrated design process for optomechanical structures based on multidisciplinary optimization. The proposed integrated optimal design process comprises a finite element analysis by ANSYS Workbench, the MATLAB optomechanical transfer program, an optical analysis by ZEMAX, and the multidisciplinary optimization solver by Isight. In ANSYS Workbench, the deformation of optical surfaces, structures, and responses according to the design requirements is calculated in one project. Then, Zernike polynomial coefficients are calculated from surface deformation data of optical surfaces through a MATLAB optomechanical transfer program. In ZEMAX, the Zernike polynomial coefficients are imported into optical surface models of an optical system; then, optical performance parameters, such as the wavefront error, optical aberration, MTF, and OPD, are calculated. In the Isight environment, automatic iterative computations are performed between these three programs and, as a result, the design dimensions of optomechanical structures are determined, satisfying the design requirements and improving the performance of an optical system. By using this integrated optimal design process, the optimal design and analysis for a complete optomechanical structure, as well as individual structure parts, can be performed successfully. In this paper, the optimal design problem for three parts of a Cassegrain telescope, which consists of a primary mirror with an outer diameter of 156 mm and a secondary mirror with an outer diameter of 46 mm, was taken as an example. By using optimal parts, the image wavefront error of the Cassegrain telescope was decreased from 29.9 to 16.1 nm.

Paraconexibacter antarcticus sp. nov., a novel actinobacterium isolated from Antarctic tundra soil.

A Gram-negative, non-motile, aerobic bacterium, named 02-257T, was isolated from Antarctic soil. The cells are surrounded by relatively thin capsules and were catalase-positive and oxidase-negative cocci. Growth of strain 02-257T was observed at 4-35 °C (optimum, 28-30 °C), pH 6.0-8.0 (optimum, pH 6.0) and with 0-1.5% NaCl (optimum, 0 %). Strain 02-257 showed the highest 16S rRNA gene sequence similarity to Paraconexibacter algicola Seoho-28T (95.06 %). Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain 02-257T is a member of a novel species belonging to the clade formed by members of the genus Paraconexibacter in the family Paraconexibacteraceae. The DNA G+C content was 72.9 mol%. Strain 02-257T contained C16 : 0-iso (23.0 %), C18  :  1 ω9c (13.8 %), C16 : 0 (12.5 %) and C17 : 1 ω9c-iso (10.8 %) as major cellular fatty acids and menaquinone MK-7(H4) was detected as the only isoprenoid quinone. Diphosphatidylglycerol, phosphatidylinositol, phosphatidylinositole mannoside, phosphatidylinositole dimannoside, unidentified phosphoglycolipid, unidentified aminophospholipid, two unidentified phospholipids, three unidentified aminolipids and six unidentified lipids were the major polar lipids. meso-Diaminopimelic acids were the diagnostic diamino acids in the cell-wall peptidoglycan. On the basis of phenotypic, chemotaxonomic and phylogenetic data, strain 02-257T is considered to represent a novel species of the genus Paraconexibacter, for which the name Paraconexibacter antarcticus sp. nov. is proposed. The type strain is 02-257T (=CCTCC AB 2021030T=KCTC 49619T).

Normalization-free displacement reconstruction method based on fringe scaling.

The knotty problems in the displacement reconstruction based on the self-mixing (SM) technique are the estimation of the self-mixing interferometry parameters and the normalization of SM signals (SMSs) since they are all very time-consuming and based on complex algorithms. This has an unfavorable effect on the real-time and low-cost natures of the SM displacement sensor. In the paper, we have presented a simple method of displacement retrieval with a high resolution, which does not require the parameter estimation and normalization. The proposed method is based on the scaling of individual fringes in SMSs and speckle noise proof. The simplicity of the method will make a great contribution to lowering the cost of the SM displacement sensor and improving the reliability and resolution of the sensor.

Verification of phase measurement error sources in phase-shifting interferometry with four step phase-shifting algorithms.

The phase-shifting technique is one of the most important techniques in interferometry. The measurement accuracy of this technique is affected by several kinds of systematic and random errors like miscalibration, nonlinear response and tilt shift of the phase shifter, nonlinear recording, speckles, fringe fluctuation, etc. In this paper, a method for verification of all of these phase measurement error sources is proposed by introducing a grayscale image. This image is composed from the lattice-site representation determined by a four step phase-shifting algorithm, which represents the distribution of phase-shift angle values. The shape of the grayscale image is definitely more expressive and demonstrative for the kinds of measurement error sources than the black dot distribution in lattice-site representation. So, with this technique, we can recognize the existence of various measurement error sources and roughly estimate their magnitudes before proceeding with experiments. Our method is to be rather qualitative than quantitative. The availability of this method is discussed in a phase-shifting Fizeau interferometer and a fringe projection profilometry. This method is useful in all kinds of interferometric measurements based on the phase-shifting technique.

Joint estimation of self-mixing interferometry parameters and displacement reconstruction based on local normalization.

It is not easy to estimate self-mixing interferometry parameters, namely, the optical feedback factor and the linewidth enhancement factor from the self-mixing signals (SMSs) affected by noise such as speckle. These SMSs call for normalization, which is not only difficult, but also apt to distort the intrinsic information of the signals, thereby resulting in incorrect estimation of the parameters and the displacement reconstruction. In this paper, we present what we believe is a novel normalization method we call "local normalization," which enables more exact and simpler estimation and displacement retrieval compared to previous methods, for it is based on an analytic relation instead of approximation. The method is very noise-proof, and especially speckle-noise-proof as well. The method proposed can be applied to moderate and strong feedback regimes. The simplicity and accuracy of the method will provide a fine tool for a low-cost self-mixing displacement sensor with a high resolution of about 40 nm.

Fast estimation method of feedback factor based on the derivative of the self-mixing signal.

The self-mixing (SM) technique has been a promising optical measurement technique for a few decades. The estimation of the optical feedback factor C is the key to SM displacement measurement with a better resolution than half a wavelength. But this estimation is extremely complex and tricky, and thus leads to its time-consuming nature, which is one of the important causes that increases the cost and labor for the development of a self-mixing sensor. There have been many methods reported for the C estimation, but they are very time consuming, very sensitive to noise, or can only work in a certain feedback regime. This paper presents a novel approach to the C estimation, which is straightforward and can work for all feedback regimes including weak, moderate, and strong. The estimation precision of the proposed method is not only comparable to that of the data fitting technique but also much simpler.

Evaluation method for the optical feedback factor and linewidth enhancement factor using phase discontinuities in self-mixing interferometry signals.

Self-mixing interferometry (SMI) is a reliable method that has been applied to measuring displacements, absolute distances, and velocities of remote targets. Evaluating the optical feedback factor C and the linewidth enhancement factor α is a vital step in calculating laser diode parameters and in processing SMI signals using phase unwrapping. This paper proposes an evaluation method for the optical feedback factor and the linewidth enhancement factor of arbitrary waveforms by investigating the slopes of phase discontinuity distribution in the optical feedback regime of 1

Hymenobacter rutilus sp. nov., isolated from marine sediment in the Arctic.

Strain K2-33028T, which appeared as a brick-red colony on an R2A plate, was isolated from a marine sediment sample from Kings Bay, Svalbard Archipelago, Norway. Phylogenetic analysis based on 16S rRNA gene sequences indicated that K2-33028T represented a member of the genus Hymenobacter. Cells were Gram-reaction-negative, non-spore-forming, aerobic, rod-shaped and without motility. Growth occurred at 4-37 °C (optimum 28 °C) and at pH 6.0-8.0 (optimum pH 7.0). Cells contained menaquinone-7 as the main respiratory quinone and iso-C15 : 0, summed feature 3 (comprising C16 : 1ω7c and/or C16 : 1ω6c), C16 : 1ω5c, summed feature 4 (comprising anteiso-C17 : 1B and/or iso-C17 : 1I) and anteiso-C15 : 0 as the major cellular fatty acids. Phosphatidylethanolamine was predominant in the polar lipid profile. The DNA G+C content was 64.3 mol%. On the basis of phenotypic, chemotaxonomic and phylogenetic data, strain K2-33028T is considered to represent a novel species of the genus Hymenobacter, for which the name Hymenobacterrutilussp. nov. is proposed. The type strain is K2-33028T (=CCTCC AB 2016091T=KCTC 52447T).

Terrimonas crocea sp. nov., isolated from the till of a high Arctic glacier.

A yellow-pigmented bacterial strain, designated M1-33108T, was isolated from the till of high Arctic glacier Midtre Lovénbreen near Ny-Ålesund, in the West Svalbard Archipelago, Norway. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain M1-33108T belonged to the genus Terrimonas and its closest neighbour was Terrimonas arctica R9-86T with 96.12 % 16S rRNA gene sequence similarity. Cells of strain M1-33108T were Gram-reaction-negative, aerobic, non-spore-forming, rod-shaped bacteria that lacked motility. Cells contained iso-C15 : 1 G, iso-C15 : 0, iso-C17 : 0 3-OH, C16 : 0 and summed feature 3 (comprising C16 : 1ω7c and/or C16 : 1ω6c) as its major cellular fatty acids and menaquinone-7 as the sole respiratory quinone. The polar lipid profile of strain M1-33108T consisted of phosphatidylethanolamine, two unknown aminophospholipids, eight unknown aminolipids, an unknown glycolipid and three unknown polar lipids. The DNA G+C content was 45.0 mol%. On the basis of phenotypic, chemotaxonomic and phylogenetic data, strain M1-33108T is considered to represent a novel species in the genus Terrimonas, for which the name Terrimonas crocea sp. nov. is proposed. The type strain is M1-33108T (=CCTCC AB 2016103T=KCTC 52448T).

Development of late blight resistant potatoes by cisgene stacking.

BACKGROUND: Phytophthora infestans, causing late blight in potato, remains one of the most devastating pathogens in potato production and late blight resistance is a top priority in potato breeding. The introduction of multiple resistance (R) genes with different spectra from crossable species into potato varieties is required. Cisgenesis is a promising approach that introduces native genes from the crops own gene pool using GM technology, thereby retaining favourable characteristics of established varieties. RESULTS: We pursued a cisgenesis approach to introduce two broad spectrum potato late blight R genes, Rpi-sto1 and Rpi-vnt1.1 from the crossable species Solanum stoloniferum and Solanum venturii, respectively, into three different potato varieties. First, single R gene-containing transgenic plants were produced for all varieties to be used as references for the resistance levels and spectra to be expected in the respective genetic backgrounds. Next, a construct containing both cisgenic late blight R genes (Rpi-vnt1.1 and Rpi-sto1), but lacking the bacterial kanamycin resistance selection marker (NPTII) was transformed to the three selected potato varieties using Agrobacterium-mediated transformation. Gene transfer events were selected by PCR among regenerated shoots. Through further analyses involving morphological evaluations in the greenhouse, responsiveness to Avr genes and late blight resistance in detached leaf assays, the selection was narrowed down to eight independent events. These cisgenic events were selected because they showed broad spectrum late blight resistance due to the activity of both introduced R genes. The marker-free transformation was compared to kanamycin resistance assisted transformation in terms of T-DNA and vector backbone integration frequency. Also, differences in regeneration time and genotype dependency were evaluated. CONCLUSIONS: We developed a marker-free transformation pipeline to select potato plants functionally expressing a stack of late blight R genes. Marker-free transformation is less genotype dependent and less prone to vector backbone integration as compared to marker-assisted transformation. Thereby, this study provides an important tool for the successful deployment of R genes in agriculture and contributes to the production of potentially durable late blight resistant potatoes.

Negative-balance isolated pelvic perfusion in patients with incurable symptomatic rectal cancer: results and drug dose correlation to adverse events.

BACKGROUND: Drug leakage and lack of a drug-removal system have prevented clinical application of isolated pelvic perfusion (IPP). These barriers were overcome with negative-balance IPP (NIPP) in experimental pig models. Here, a phase 1 clinical study of NIPP was performed in patients with incurable symptomatic rectal cancer. PURPOSE: To establish a safe regimen of high-dose regional chemotherapy with NIPP using cisplatin in patients with incurable rectal cancer. MATERIAL AND METHODS: Between June 2004 and January 2007, NIPP therapy was performed for 23 patients (11 women, 12 men; mean age, 58 years). NIPP was routinely performed twice over a 4-week interval. Dose-limiting toxicities (DLTs) were defined using a 5 + 3 design, and cisplatin doses were escalated from 170 mg/m(2), with a fixed 5-fluorouracil dose of 1000 mg/m(2). The grade of adverse events (AEs) at the first and second sessions of NIPP therapy, pharmacokinetics, and antitumor response were evaluated. RESULTS: No DLTs were observed during the first session of NIPP. However, at the second session, two patients experienced the DLT of neuropathy after administration of 200 mg/m(2) cisplatin. Therefore, 190 mg/m(2) cisplatin was indicated as the maximum tolerated dose (MTD). The plasma pelvic-to-systemic exposure ratio was 18.4 based on the maximum concentration and 19.0 based on the concentration-time curve. Solid tumor responses included complete response in two patients, partial response in five patients, stable disease in 15 patients, and progressive disease in one patient. CONCLUSION: NIPP may offer the safe delivery of high-dose regional chemotherapy (MTD of 190 mg/m(2) cisplatin) with negligible AEs and effective control of tumor growth in patients with incurable rectal cancer.

Improvement of the recombinant phytase expression by intermittent feeding of glucose during the induction phase of methylotrophic yeast Pichia pastoris.

PURPOSE: For growth of methylotrophic yeast, glycerol is usually used as a carbon source. Glucose is used in some cases, but not widely consumed due to strong repressive effect on AOX1 promoter. However, glucose is still considered as a carbon source of choice since it has low production cost and guarantees growth rate comparable to glycerol. RESULTS: In flask cultivation of the recombinant yeast, Pichia pastoris GS115(pPIC9K-appA38M), while methanol induction point(OD600) and methanol concentration significantly affected the phytase expression, glucose addition in induction phase could enhance phytase expression. The optimal flask cultivation conditions illustrated by Response Surface Methodology were 10.37 OD600 induction point, 2.02 h before methanol feeding, 1.16% methanol concentration and 40.36µL glucose feeding amount(for 20 mL culture volume) in which the expressed phytase activity was 613.4 ± 10.2U/mL, the highest activity in flask cultivation. In bioreactor fermentation, the intermittent glucose feeding showed several advantageous results such as 68 h longer activity increment, 149.2% higher cell density and 200.1% higher activity compared to the sole methanol feeding method. These results implied that remaining glucose at induction point might exhibit a positive effect on the phytase expression. CONCLUSION: Glucose intermittent feeding could be exploited for economic phytase production and the other recombinant protein expression by P. pastoris GS115.

Lateral position does not cause an interhemicerebral difference of cerebral hemodynamic in healthy adult volunteers.

Cerebral perfusion is maintained at a consistent value irrespective of changes in systemic blood pressure or disease-induced changes in general physical condition. This regulatory mechanism is effective despite postural changes, working even during changes in posture, such as those from sitting to standing or from the head-down to the head-up position. However, no study has addressed changes in perfusion separately in the left and right cerebral hemispheres, and there has been no specific investigation of the effect of the lateral decubitus position on perfusion in each hemisphere. Surgery, particularly respiratory surgery, is often performed with the patient in the lateral decubitus position, and since intraoperative anesthesia may also have an effect, it is important to ascertain the effect of the lateral decubitus position on perfusion in the left and right cerebral hemispheres in the absence of anesthesia. The effects of the lateral decubitus position on heart rate, blood pressure, and hemodynamic in the left and right cerebral hemispheres assessed by regional saturation of oxygen measured by near-infrared spectroscopy were investigated in healthy adult volunteers. Although the lateral decubitus position causes systemic circulatory changes, it may not cause any difference in hemodynamic between the left and right cerebral hemispheres.

Characteristics and Effectiveness of Mobile- and Web-Based Tele-Emergency Consultation System between Rural and Urban Hospitals in South Korea: A National-Wide Observation Study.

(1) Background: The government of South Korea has established a nationwide web- and mobile-based emergency teleconsultation network by designating urban and rural hospitals. The purpose of this study is to analyze the characteristics and effectiveness of the tele-emergency system in South Korea. (2) Methods: Tele-emergency consultation cases from May 2015 to December 2018 were analyzed in the present study. The definition of a tele-emergency in the present study is an emergency consultation between doctors in rural and urban hospitals via a web- and mobile-based remote emergency consultation system (RECS). Consultations through an RECS are grouped into three categories: medical procedure or treatment guidance, image interpretation, and transportation requests. The present study analyzed the characteristics of the tele-emergency system and the reduction in unnecessary transportation (RUT). (3) Results: A total of 2604 cases were analyzed in the present study from 2985 tele-emergency consultation cases. A total of 381 cases were excluded for missing data. Consultations for image interpretation were the most common in trauma cases (71.3%), while transfer requests were the most common in non-trauma cases (50.3%). Trauma patients were more frequently admitted to rural hospitals or discharged and followed up with at rural hospitals (20.3% vs. 40.5%) after consultations. In terms of disease severity, non-severe cases were statistically higher in trauma cases (80.6% vs. 59.4%; p < 0.001). The RUT was statistically highly associated with trauma cases (60.8% vs. 42.8%; p < 0.001). In an analysis that categorized cases by region, a statistically higher proportion of transportation was used in island regions (69.9% vs. 49.5%; p < 0.003). More RUT was associated with non-island regions (30.1% vs. 50.5%; p = 0.001). (4) Conclusions: The tele-emergency system had a great role in reducing unnecessary patient transportation in non-severe trauma cases and non-island rural area emergency cases. Further research is needed for a cost/benefit analysis and clinical outcomes.

Effects of cloth face masks on physical and cognitive performance during maximal exercise testing.

Wearing a cloth face mask has been shown to impair exercise performance; it is essential to understand the impact wearing a cloth face mask may have on cognitive performance. Participants completed two maximal cardiopulmonary exercise tests on a cycle ergometer (with and without a cloth face mask) with a concurrent cognitive task. Blood pressure, heart rate, oxygen saturation, perceived exertion, shortness of breath, accuracy, and reaction time were measured at rest, during each exercise stage, and following a 4-minute recovery period. The final sample included 35 adults (age = 26.1 ± 5.8 years; 12 female/23 male). Wearing a cloth face mask was associated with significant decreases in exercise duration (-2:00 ± 3:40 min, P = 0.003), peak measures of maximal oxygen uptake (-818.9 ± 473.3 mL/min, -19.0 ± 48 mL·min-1·kg-1, P < 0.001), respiratory exchange ratio (-0.04 ± 0.08, P = 0.005), minute ventilation (-36.9 ± 18 L/min), oxygen pulse (-3.9 ± 2.3, P < 0.001), heart rate (-7.9 ± 12.6 bpm, P < 0.001), oxygen saturation (-1.5 ± 2.8%, P = 0.004), and blood lactate (-1.7 ± 2.5 mmol/L, P < 0.001). While wearing a cloth face mask significantly impaired exercise performance during maximal exercise testing, cognitive performance was unaffected in this selected group of young, active adults.

Low-dose dexmedetomidine facilitates the carotid body response to low oxygen tension in vitro via α2-adrenergic receptor activation in rabbits.

CONTEXT: Some anaesthetics exert an inhibitory effect on the response of the carotid body to low oxygen tension. However, the effect of dexmedetomidine on the carotid body response has not been reported. OBJECTIVE: To investigate the effect of dexmedetomidine on carotid body activity. The hypothesis is that dexmedetomidine does not have an inhibitory effect on the response of the carotid body to low oxygen tension. DESIGN: Animal experimental study in vitro. Ten carotid bodies surgically removed from male New Zealand white rabbits were tested. SETTING: Research laboratory of Nippon Medical School, Tokyo, Japan, from July 2008 to February 2010. INTERVENTION: The carotid body was perfused with three different concentrations of dexmedetomidine (0.1, 1.0 and 10 nmol l). The contribution of α2-adrenergic receptors was evaluated by addition of 1.0 nmol l yohimbine, an α2-adrenergic receptor antagonist. MAIN OUTCOME MEASURES: The differences in carotid sinus nerve activity between high oxygen tension (baseline) and low oxygen tension (peak) were analysed. RESULTS: At all three concentrations, dexmedetomidine did not depress the baseline and peak activity of the carotid body, whereas 0.1 nmol l dexmedetomidine facilitated the response to low oxygen tension stimulation. The differences in carotid sinus nerve activity between baseline (pO2 80.4 ± 9.1 kPa) and peak (pO2 22.1 ± 2.6 kPa) were 140 ± 70 Hz in controls and 266 ± 116 Hz with 0.1 nM dexmedetomidine (P < 0.05). This increase was not shown in the presence of 1.0 nmol l yohimbine. CONCLUSION: Dexmedetomidine does not depress the activity of the carotid body under high oxygen tension or the response to low oxygen tension, whereas 0.1 nmol l dexmedetomidine facilitates this response via α2-adrenergic receptor activation.

Safety and efficacy of oral rehydration therapy until 2 h before surgery: a multicenter randomized controlled trial.

PURPOSE: In many countries, patients are generally allowed to have clear fluids until 2-3 h before surgery. In Japan, long preoperative fasting is still common practice. To shorten the preoperative fasting period in Japan, we tested the safety and efficacy of oral rehydration therapy until 2 h before surgery. METHODS: Three hundred low-risk patients scheduled for morning surgery in six university-affiliated hospitals were randomly assigned to an oral rehydration solution (ORS) group or to a fasting group. Patients in the ORS group consumed up to 1,000 ml of ORS containing balanced glucose and electrolytes: 500 ml between 2100 the night before surgery and the time they woke up the next morning and 500 ml during the morning of surgery until 2 h before surgery. Patients in the fasting group started fasting at 2100 the night before surgery. Primary endpoints were gastric fluid volume and pH immediately after anesthesia induction. Several physiological measures of hydration and electrolytes including the fractional excretion of sodium (FENa) and the fractional excretion of urea nitrogen (FEUN) were also evaluated. RESULTS: Mean (SD) gastric fluid volume immediately after anesthesia induction was 15.1 (14.0) ml in the ORS group and 17.5 (23.2) ml in the fasting group (P = 0.30). The mean difference between the ORS group and fasting group was -2.5 ml. The 95% confidence interval ranged from -7.1 to +2.2 ml and did not include the noninferior limit of +8 ml. Mean (SD) gastric fluid pH was 2.1 (1.9) in the ORS group and 2.2 (2.0) in the fasting group (P = 0.59). In the ORS group, mean FENa and FEUN immediately after anesthesia induction were both significantly greater than those in the fasting group (P < 0.001 for both variables). The ORS group reported they had been less thirsty and hungry before surgery (P < 0.001, 0.01). CONCLUSIONS: Oral rehydration therapy until 2 h before surgery is safe and feasible in the low-risk Japanese surgical population. Physicians are encouraged to use this practice to maintain the amount of water in the body and electrolytes and to improve the patient's comfort.

Preventive effect of subacidic 1% NaF-HF gel on dental caries in 6- to 7-year-old schoolchildren: a randomized controlled trial.

Objective: This study aimed to examine and compare the anti-caries effects of slightly acidic 1% NaF-HF gel when applied once or twice (7-day or 6-month interval) to mandibular first molars in 6- to 7-year-old children. Method and materials: This was a 1-year, multi-arm, placebo-controlled, double-blind, parallel-group randomized trial. In total, 1,077 schoolchildren from eight primary schools were allocated to one of the four study groups (group 1, single application; group 2, two applications with a 7-day interval; group 3, two applications with a 6-month interval; group 4, placebo control). The occlusal surfaces of permanent mandibular first molars were examined by three calibrated examiners who were blind to the group allocation at baseline and the end of the study. Caries reduction and prevented fraction was assessed. Results: A total of 986 children completed the study. There was a statistically significant difference in the mean D1MFT increment across the groups (P < .001). The mean D1MFT increment was 0.37 in group 1 (single application), 0.18 in group 2 (two applications with a 7-day interval), 0.21 in group 3 (two applications with a 6-month interval), and 0.56 in the control group. The mean D2MFT increments (0.22 in group 1, 0.06 in group 2, 0.18 in group 3, and 0.50 in the control group) also showed a statistically significant difference across the groups (P < .001). Conclusion: Subacidic 1% NaF-HF gel exerts a high preventive effect on caries (more than 40%) when applied twice at a 7-day interval in 6- to 7-year-old schoolchildren who do not use fluoride toothpaste in areas where drinking water is not fluoridated.

The wavevector star channel and symmetry group.

The concepts of `wavevector star channel' and `wavevector star channel group' are newly defined, which allow the effective study of phase transitions considering directly the translational symmetry breaking in crystals. A method is suggested by which the wavevector star channels can be found using the image of the representation of the translational group. According to this method, the wavevector star channels are found for the 80 Lifschitz stars in the reciprocal lattice. The wavevector star channel group is defined as the set of symmetry elements of the parent phase which leave the star channel invariant, and the wavevector star channel groups with one, two, three and four arms are calculated. It is shown that the complicated symmetry changes in the pyroelectric crystal Pb1-xCaxTiO3 (PCT) can be described using the new five-component reducible order parameter transformed according to the representation of the wavevector star channel group, rather than the nine-component one based on the theory of the full irreducible representation of the space group.